El Centro City Council
January 20, 2026

• Lift stations with structural, electrical, and safety deficiencies that affect reliability and compliance with modern standards
• Aging sewer pipelines and manholes experiencing deterioration from hydrogen sulfide (H₂S) exposure, requiring lining and rehabilitation
• Wastewater Treatment Plant components with failing concrete, corroded equipment, and outdated processes
• Primary clarifiers operating over capacity during wet weather conditions • Digesters dating back to the 1950s that require major maintenance and rehabilitation The largest overall need identified in the sewer system is investment in Wastewater Treatment Plant rehabilitation and lift station improvements to ensure long-term operational reliability.

Capital Improvement Program (CIP) and Financial Coordination Based on the findings, the master plans recommend a 20-year Capital Improvement Program totaling approximately $169.6 million, consisting of:
• Approximately $76.9 million for water system improvements • Approximately $92.7 million for sewer system improvements Projects are prioritized and phased, with the highest-risk and highest-need improvements targeted within the first five years. The master plans are intended to directly inform the City’s capital budgeting and are being coordinated with the City’s water and sewer rate study to align infrastructure needs with long-term financial planning.

CEQA
Adoption of the Water Master Plan and Sewer Master Plan is exempt from the California Environmental Quality Act (CEQA) pursuant to CEQA Guidelines Section 15262 (Feasibility and Planning Studies), as the plans are long-range planning documents and do not approve or authorize any specific projects. Any individual projects identified in the master plans will be subject to separate CEQA review prior to approval or construction.

CONCLUSION:

Adopt the Water Master Plan and Sewer Master Plan as presented, and authorize staff to utilize the plans as guiding documents for future capital improvement planning, budgeting, grant applications, and coordination with the City’s water and sewer rate study.

ATTACHMENTS:

1. Sewer Master Plan FINAL

2. Water Master Plan FINAL

Sewer Master Plan Update
City of El Centro
JANUARY 2026
Prepared for:
307 W Brighton Avenue
El Centro, California 92243
Contact: Abraham Campos, Public Works Director / City Engineer Prepared by:
687 S. Coast Highway 101, Suite 110
Encinitas, California 92024
Contact: Elizabeth Caliva, Project Manager

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Table of Contents
SECTION PAGE NO.

Acknowledgements.......................................................................................................................................................... vii Acronyms and Abbreviations............................................................................................................................................ ix Executive Summary .......................................................................................................................................................... xi ES-1 Key Project Objectives........................................................................................................................... xi ES-2 Service Area and System Overview..................................................................................................... xii ES-3 Future Flow Projections........................................................................................................................ xii ES-4 Hydraulic Model Development and Calibration................................................................................. xiv ES-5 Collection System Capacity Analysis .................................................................................................. xiv ES-6 Collection System Condition Assessment........................................................................................... xv ES-7 CIP Project Recommendations ............................................................................................................ xv 1 Introduction ..........................................................................................................................................................1

1.1 Project Objectives and Overview ...........................................................................................................1

1.2 Previous Master Plan .............................................................................................................................2

1.3 Service Area Overview............................................................................................................................3

1.4 Report Organization ...............................................................................................................................7 2 Existing System Summary ...................................................................................................................................9

2.1 Gravity Mains..........................................................................................................................................9

2.2 Inverted Siphons.................................................................................................................................. 12

2.3 Diversion Manholes............................................................................................................................. 12

2.4 Sewer Lift Stations and Force Mains ................................................................................................. 15

2.5 Wastewater Treatment Plant.............................................................................................................. 18 3 Existing and Future Dry Weather Flows ........................................................................................................... 21

3.1 Existing Flow Summary ....................................................................................................................... 21

3.1.1 Existing Land Use Summary.................................................................................................. 22

3.2 Population and Planned Developments Summary............................................................................ 24

3.2.1 Population Summary ............................................................................................................. 24

3.2.2 Near-Term (2035) Developments......................................................................................... 25

3.2.3 Ultimate (2045) Developments ............................................................................................ 27

3.3 Future Flow Summary ......................................................................................................................... 27

3.3.1 Unit Sewer Flow Generation Factors .................................................................................... 27

3.3.2 Near-Term (2035) Scenario Flow Projections...................................................................... 28

3.3.3 Ultimate (2045) Scenario Flow Projections ......................................................................... 28

3.4 Existing and Future Dry Weather Flow Summary .............................................................................. 29

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4 Sewer Model Development and Calibration.................................................................................................... 31

4.1 March 2025 Flow Monitoring Program.............................................................................................. 31

4.1.1 Sewersheds and Flow Schematic ......................................................................................... 31

4.1.2 Flow Monitoring Results Summary ....................................................................................... 34

4.1.3 Dry Weather Time Patterns ................................................................................................... 34

4.2 Sewer Model Development................................................................................................................. 37

4.2.1 Manhole Field Survey ............................................................................................................ 37

4.2.2 Trunk Model Network Generation......................................................................................... 40

4.2.3 As-Built Record Drawing Updates ......................................................................................... 40

4.3 Existing Dry Weather Flow Allocation ................................................................................................. 41

4.3.1 Dry Weather Scenario Calibration Results ........................................................................... 41

4.4 Existing Wet Weather Flow Allocation ................................................................................................ 42

4.4.1 Wet Weather Model Calibration Results .............................................................................. 46 5 Collection System Capacity Analysis................................................................................................................ 47

5.1 System Design Criteria........................................................................................................................ 47

5.1.1 Gravity Main Design Criteria.................................................................................................. 47

5.1.2 Lift Station and Force Main Design Criteria ......................................................................... 48

5.2 System Deficiency Criteria .................................................................................................................. 49

5.2.1 Gravity Main Deficiency Criteria............................................................................................ 49

5.2.2 Lift Station and Force Main Deficiency Criteria ................................................................... 50

5.3 Dry Weather Capacity Analysis ........................................................................................................... 50

5.3.1 Existing (2025) Dry Weather Flow ........................................................................................ 50

5.3.2 Near-Term (2035) Dry Weather Flow.................................................................................... 50

5.3.3 Ultimate (2045) Dry Weather Flow....................................................................................... 51

5.4 Wet Weather Capacity Analysis .......................................................................................................... 54

5.4.1 Existing (2025) Wet Weather Flow ....................................................................................... 54

5.4.2 Near-Term (2035) Wet Weather Flow .................................................................................. 56

5.4.3 Ultimate (2045) Wet Weather Flow...................................................................................... 58

5.5 Lift Station and Force Main Capacity Analysis................................................................................... 60

5.5.1 Lift Station No. 3.................................................................................................................... 60

5.5.2 Main Lift Station..................................................................................................................... 61

5.5.3 Alder Canal – Villa Ave Lift Station........................................................................................ 62

5.5.4 4th & Wake Lift Station ......................................................................................................... 63

5.5.5 Lift Station No. 2.................................................................................................................... 64

5.5.6 Eastside Lift Station............................................................................................................... 65

5.5.7 Lift Station Optimization Analysis ......................................................................................... 66

5.6 Capacity Analysis Summary ................................................................................................................ 66 6 Collection System Condition Assessment and Improvements....................................................................... 69

6.1 Lift Station Condition Assessment Summary .................................................................................... 69

6.1.1 Methodology........................................................................................................................... 71

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6.1.2 Results and Recommendations............................................................................................ 71

6.2 Gravity Main Condition Assessment Summary.................................................................................. 75

6.2.1 Methodology........................................................................................................................... 77

6.2.2 Results and Recommendations............................................................................................ 78

6.3 Manhole Condition Assessment Summary ........................................................................................ 84

6.4 WWTP Condition Assessment Summary ............................................................................................ 84

6.4.1 Methodology........................................................................................................................... 85

6.4.2 Results and Recommendations............................................................................................ 85 7 Capital Improvements Program ....................................................................................................................... 91

7.1 Pipeline Capacity Improvement Projects ........................................................................................... 91

7.2 Pipeline Condition Improvement Projects.......................................................................................... 94

7.3 Manhole Condition Improvement Projects ........................................................................................ 94

7.4 Lift Station Improvement Projects...................................................................................................... 94

7.5 WWTP Improvement Projects ............................................................................................................. 98

7.6 Staffing Plan ......................................................................................................................................101

7.7 Additional Recommendations...........................................................................................................102

7.8 Recommended CIP Projects Cost Summary....................................................................................102

7.9 Potential Funding Sources................................................................................................................109 TABLES
ES.1 20-Year Sewer CIP Projects Cost Summary.....................................................................................................xvii

1.1 2008 Sewer Master Plan CIP Status – 2025 Update........................................................................................2

2.1 Gravity Main Summary by Diameter and Material1 ...........................................................................................9

2.2 Gravity Main Summary by Installation Year1 ................................................................................................... 10

2.3 Existing Diversion Manholes in Trunk Sewer Model1 ..................................................................................... 12

2.4 Existing Sewer Lift Station and Force Main Summary .................................................................................... 16

3.1 Land Use Summary........................................................................................................................................... 22

3.2 Existing and Projected Population Estimates1 ................................................................................................ 24

3.3 Unit Sewer Flow Generation Factors by Land Use Type ................................................................................. 27

3.4 Estimated ADWF from Planned Near-Term Developments ............................................................................ 28

3.5 Existing and Future ADWF Summary ............................................................................................................... 29

4.1 System Improvements Not in Sewer GIS – Updated in Trunk Sewer Model................................................. 40

4.2 Model Calibration Results – Existing (2025) Dry Weather Flow.................................................................... 42

4.3 Annual Average and Peak Influent Flows to Plant (2015 – 2025)................................................................ 44

4.4 Model Calibration Results – Existing (September 2022) Wet Weather Flow................................................ 46

5.1 Recommended Design Criteria – Gravity Mains ............................................................................................. 47

5.2 Recommended Design Criteria – Lift Stations & Force Mains....................................................................... 49

5.3 2025 Update Deficiency Criteria – Gravity Mains........................................................................................... 49

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5.4 2025 Update Deficiency Criteria – Lift Stations & Force Mains .................................................................... 50

5.5 Existing (2025) System Pipeline Capacity Deficiencies – PWWF .................................................................. 54

5.6 Near-Term (2035) System Pipeline Capacity Deficiencies – PWWF.............................................................. 56

5.7 Ultimate (2045) System Pipeline Capacity Deficiencies – PWWF ................................................................. 58

5.8 Lift Station No. 3 Capacity Analysis – PWWF .................................................................................................. 60

5.9 Lift Station No. 3 Wet Well Emergency Storage Analysis – ADWF ................................................................. 61

5.10 Main Lift Station Capacity Analysis – PWWF................................................................................................... 61

5.11 Main Lift Station Wet Well Emergency Storage Analysis – ADWF.................................................................. 62

5.12 Alder Canal – Villa Ave Lift Station Capacity Analysis – PWWF...................................................................... 62

5.13 Alder Canal – Villa Ave Lift Station Wet Well Emergency Storage Analysis – ADWF.................................... 63

5.14 4th & Wake Lift Station Capacity Analysis – PWWF........................................................................................ 63

5.15 4th & Wake Lift Station Wet Well Emergency Storage Analysis – ADWF ...................................................... 64

5.16 Lift Station No. 2 Capacity Analysis – PWWF .................................................................................................. 64

5.17 Lift Station No. 2 Wet Well Emergency Storage Analysis – ADWF ................................................................. 64

5.18 Eastside Lift Station Capacity Analysis – PWWF............................................................................................. 65

5.19 Eastside Lift Station Wet Well Emergency Storage Analysis – ADWF............................................................ 65

5.20 Existing and Future Sewer Flows in Trunk Sewer Model ................................................................................ 67

6.1 Lift Station Condition Assessment Summary .................................................................................................. 75

6.2 Pipeline Assessment Certification Program (PACP) Codes............................................................................. 77

6.3 Pipeline Condition Grades ................................................................................................................................ 78

6.4 Gravity Main Condition Assessment Recommendations Summary............................................................... 81

6.5 TDS Grab Samples Results............................................................................................................................... 83

6.6 WWTP Condition Assessment Recommendations Summary ......................................................................... 88

7.1 Recommended Pipeline Capacity Improvement Projects Summary.............................................................. 92

7.2 Recommended Pipeline Condition Improvement Projects Summary ............................................................ 94

7.3 Recommended Pipeline Condition Improvement Projects Summary ............................................................ 94

7.4 Recommended Lift Station Improvement Projects Summary ........................................................................ 95

7.5 Recommended Wastewater Treatment Plant Improvement Projects Summary .......................................... 98

7.6 Summary of Total Recommended Full Time Employee (FTEs).....................................................................101

7.7 Recommended Additional Improvement Projects Summary .......................................................................102

7.8 Cost Multiplier Summary ................................................................................................................................102

7.9 Recommended Pipeline Improvement Projects Cost Summary ..................................................................105

7.10 Recommended Manhole Improvement Projects Cost Summary .................................................................105

7.11 Recommended Lift Station Improvement Projects Cost Summary..............................................................106

7.12 Recommended Wastewater Treatment Plant Improvements Projects Cost Summary ..............................107

7.13 Recommended Additional Improvements Projects Cost Summary .............................................................107

7.14 Annual CIP Project Summary Table by Improvement Type...........................................................................107

7.15 Potential Funding Sources .............................................................................................................................109

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FIGURES
ES.1 Sewer Collection System. ................................................................................................................................. xiii

1.1 Regional Map. ......................................................................................................................................................5

1.2 Sewer Service Area and Collection System........................................................................................................6

1.3 El Centro Monthly Climate Normals (1981-2010).............................................................................................7

2.1 Existing Gravity Mains by Diameter.................................................................................................................. 11

2.2 Existing Modeled Diversion Manholes............................................................................................................. 13

2.3 Existing Modeled Diversion Manholes - Continued......................................................................................... 14

2.4 Existing and Planned Near-Term Sewer Lift Stations and Force Mains. ....................................................... 17

2.5 Existing Wastewater Treatment Plant Site Overview. ..................................................................................... 19

3.1 Average Influent Dry Weather Flow to Wastewater Treatment Plant (March 2025). ................................... 21

3.2 Existing Land Use Summary............................................................................................................................. 23

3.3 Planned Near-Term Developments.................................................................................................................. 26

4.1 March 2025 Flow Monitor Locations and Sewersheds.................................................................................. 32

4.2 Existing System Flow Schematic...................................................................................................................... 33

4.3 Existing Dry Weather Hourly Time Patterns (Weekday and Weekend). ......................................................... 36

4.4 March 2025 Manhole Survey Locations. ........................................................................................................ 39

4.5 Average Monthly and Peak Daily Influent Flow to Wastewater Treatment Plant (January 2015 – July 2025)............................................................................................................................. 43

4.6 Diurnal Wet Weather Pattern for Defect Flow. ................................................................................................ 45

5.1 Existing (2025) Dry Weather Flow Capacity Analysis Results – Maximum Pipeline d/D.............................. 52

5.2 Near-Term (2035) Dry Weather Flow Capacity Analysis Results – Maximum Pipeline d/D......................... 53

5.3 Existing (2025) Wet Weather Flow Capacity Analysis Results – Maximum Pipeline d/D. ........................... 55

5.4 Near-Term (2035) Wet Weather Flow Capacity Analysis Results – Maximum Pipeline d/D........................ 57

5.5 Ultimate (2045) Wet Weather Flow Capacity Analysis Results – Maximum Pipeline d/D. .......................... 59

6.1 Lift Station Condition Assessment Locations.................................................................................................. 70

6.2 Main Lift Station Bar Screen Structure Grating Deterioration........................................................................ 72

6.3 Alder Canal Villa Ave Lift Station Infiltration Damage in Dry Well. ................................................................. 72

6.4 Eastside Lift Station Level Transducer Cable.................................................................................................. 73

6.5 Countryside Lift Station Failing Wet Well Liner. .............................................................................................. 73

6.6 Gravity Main Condition Assessment Locations. .............................................................................................. 76

6.7 Severe Root Intrusion (Adams Ave) – Trim Intrusion & CIPP Lining............................................................... 79

6.8 Broken Pipe with Soil Visible (State St) – Excavation Point Repair. .............................................................. 79

6.9 Crack Longitudinal (Imperial Ave) – CIPP Lining. ............................................................................................ 80

6.10 Debris in Pipe (Imperial Ave) – Heavy Cleaning & Debris Removal. .............................................................. 80

6.11 Gravity Main Condition Assessment Recommendations................................................................................ 82

6.12 Missing Supports and Covers at Primary Clarifier Gallery. ............................................................................. 84

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6.13 Missing Supports and Covers at Primary Clarifier Gallery. ............................................................................. 86

6.14 Cracked Concrete and Exposed Rebar at Aeration Basins. ........................................................................... 86

6.15 Delaminated Coating and Unsealed Cover at Digester Tank. ........................................................................ 87

6.16 Corrosion and Rusting at Belt Press Access Ladder....................................................................................... 87

7.1 Recommended Pipeline Capacity Improvement Projects............................................................................... 93

APPENDICES
A Sewer Lift Station Condition Assessment Technical Memorandum B Wastewater Treatment Plant Condition Assessment Technical Memorandum C Planned Near-Term Developments Table
D City of El Centro Temporary Sewer Flow Metering Report E Dry Weather Model Calibration Results
F Pipeline Condition Assessment Data & Recommendations Log G Staffing Plan Technical Memorandum
H Detailed Engineer’s Opinion of Probable Costs for Recommended CIP Projects

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Acknowledgements
Dudek thanks the City of El Centro for their support in the development of this 2025 Sewer Master Plan Update. In particular, the assistance and expertise of the following Public Works staff were invaluable during the preparation of this report:

City of El Centro
Abraham Campos, PE, Public Works Director/City Engineer Liz Zarate, Public Works Analyst I
David Gracia, Wastewater Plant Supervisor
Marcos Tarazon, Wastewater Plant Chief Operator
Marco Canchola, Streets & Utilities Supervisor
Felix DeLeon Jr, PE, Principal Engineer
Gabriel Martinez, Project Manager
Catherine Gutierrez, Public Works Analyst I
The following Dudek staff members were principally involved in the development and preparation of this 2025 Sewer Master Plan Update:

Dudek
Russ Bergholz, PE, Principal-in-Charge
Elizabeth Caliva, PE, Project Manager
Greg Ripperger, PE, Deputy Project Manager
Brandon Lacap, PE, Lift Station Condition Assessment Lead Joe Schneider, PE, Electrical Condition Assessment Lead Shannon Brown, PE, Pipeline Condition Assessment Lead
Jenny Li, PE, Senior Engineer/Lead Modeler
Kenneth Muntz, EIT, Senior Engineer
Chris O’Connor, PE, Senior Engineer
Katerina Jowid, Project Engineer
Ted Dhanes, EIT, Project Engineer
Julie Arvizu, Project Engineer
Talulah Patch, Project Engineer

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Acronyms and Abbreviations
Acronym/Abbreviation Definition
ABS Acrylonitrile butadiene styrene
Ac Acre
ADF Average daily flow
ADWF Average dry weather flow
ATS Automatic transfer switch
AWWF Average wet weather flow
CCTV Closed circuit television
CDBG Community Development Block Grant
CIP Capital Improvement Program
CIPP Cured in place pipe
City City of El Centro
CIWQS California Integrated Water Quality System
COG Council of Governments
CWSRF Clean Water State Revolving Fund
d/D Depth to diameter ratio
DU or du Dwelling unit(s)
DU/acre Dwelling units per acre
EA or ea Each
EPA U.S. Environmental Protection Agency
ES Executive Summary
FM Flow monitor
GIS Geographic Information System
GPD or gpd Gallons per day
gpd/acre Gallons per day per acre
gpd/DU Gallons per day per dwelling unit
GPM or gpm Gallons per minute
HCD Department of Housing and Community Development
HDPE High density polyethylene
HDR High density residential
HP Horsepower
HUD Department of Housing & Urban Development
HVAC Heating, ventilation, and air conditioning
i.e. That is
I&I Inflow and infiltration
IBank California Infrastructure and Economic Development Bank ISRF Infrastructure State Revolving Fund
KGRA Known Geothermal Resource Area
LDR Low density residential
LED Light-emitting diode
LF Lineal feet

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Acronym/Abbreviation Definition
LS Lift station
LVSP Lithium Valley Specific Plan
MCC Motor control center
MDR Medium density residential
MG Million gallons
MGD Million gallons per day
NEC National Electrical Code
NEMA National Electrical Manufacturers Association
NFPA National Fire Protection Association
No. Number
PACP Pipeline Assessment Certification Program
PDWF Peak dry weather flow
PF Peaking factor
PLC Programmable Logic Controller
PMF Peak monthly flow
PVC Polyvinyl chloride
PWWF Peak wet weather flow
RDII Rainfall dependent inflow and infiltration
RG Rain gauge
RHNA Regional Housing Needs Allocation
RR Rural residential
RTU Remote Terminal Unit
SCADA Supervisory Control and Data Acquisition
SCAG Southern California Association of Government’s
SSMP Sewer System Management Plan
SWRCB California State Water Resources Control Board
TDH Total dynamic head
TDS Total dissolved solids
UNK Unknown
UV Ultraviolet
UWMP Urban Water Management Plan
VCP Vitrified clay pipe
VFD Variable frequency drive
WDR Waste Discharge Requirements
WIFIA Water Infrastructure Finance and Innovation Act
WW Wastewater
WWTP Wastewater treatment plant

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Executive Summary
The Executive Summary provides highlights from the 2025 Sewer Master Plan Update for the City of El Centro by summarizing the key findings and recommendations from each section of the report. The Executive Summary is organized into the following:
▪ Key Project Objectives
▪ Service Area and System Overview
▪ Future Flow Projections
▪ Collection System Hydraulic Model Development and Calibration ▪ Collection System Capacity Analysis
▪ Collection System Condition Assessment
▪ Capital Improvement Program (CIP) Recommendations
ES-1 Key Project Objectives
A comprehensive study of the City’s sewer system was last completed in March 2008 and published as the 2008 Sewer Master Plan. The 2025 Update achieves the following key objectives:

1. Data Review and Gap Analysis: Assess available data pertaining to the existing sewer system and identify deficiencies within the City's sewer GIS database.

2. Field Survey: Conduct a rim and invert elevation survey of approximately 100 strategically selected manholes located along trunk sewer mains (12-inch diameter or greater) for greater confidence in the modeled capacity analysis results.

3. Model Development: Construct a new hydraulic model of the trunk system using GIS and field survey data.

4. Flow Monitoring: Perform sewer flow monitoring at nine (9) locations to identify flow patterns for creation of land use based sewer flow generation patterns, applying existing sewer inflows into the model and system calibration.

5. Generation Factors: Develop unit sewer generation factors for common land use types within the City.

6. Flow Projections: Update dry weather flow projections to reflect current and anticipated future conditions within the service area.

7. Model Calibration: Calibrate the trunk sewer model to within 10% or better accuracy.

8. Capacity Evaluation: Analyze the capacity of the modeled trunk system under peak dry and wet weather flow conditions for Existing (2025), Near-Term (2035) and Ultimate (2045) scenarios.

9. Condition Assessment: Conduct a condition assessment of selected gravity mains and field inspection of all 15 lift stations and the wastewater treatment plant.

10. Lift Station Optimization: Assess the feasibility of decommissioning any of the existing lift stations and redirecting tributary flows to the gravity system.

11. Capital Improvement Plan Development: Identify and prioritize capital improvement projects to address capacity and condition- and age-related deficiencies identified throughout the collection system.

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12. Cost Estimation: Prepare planning-level engineer’s cost opinions for each recommended project and integrate into a multi-year CIP for implementation by the City.

ES-2 Service Area and System Overview
The City of El Centro is the largest in Imperial Valley, covering approximately 11 square miles and supporting a population of 44,000. The City’s sewer collection system features 123 miles of gravity main, with a significant portion over 50 years old and some brick sewers dating back to the early 20th century. The system also includes 15 lift stations, three of which are slated for abandonment within the next five years.

All sewer flow generated within the City’s service area is treated at a single wastewater treatment plant, which has a permitted capacity of 8.0 MGD and discharges to the Salton Sea. The City’s existing sewer collection system is depicted in Figure ES.1.

ES-3 Future Flow Projections
Flow monitoring data from March 2025 was used to estimate existing dry weather flows throughout the City’s collection system. Future system flows were developed based on projected population growth and planned developments.

Population Summary: The City’s current estimated population is 44,230, according to the U.S. Census Bureau.

Population projections from the Southern California Association of Governments (SCAG) and the City’s Urban Water Management Plan (UWMP) suggest a steady growth rate of 1.1% annually, with the population expected to reach 58,753 by 2045. However, SCAG’s Regional Housing Needs Allocation (RHNA) process anticipates the need for 3,442 new housing units by 2029, which could accelerate population growth to 57,360 by 2030 or a 26% increase from 2020. While zoning is in place to support this growth, City staff do not expect full development of these units by 2029 due to historically slow growth trends.

Existing Dry Weather Flows: The 2025 flow monitoring data provides partial estimates of current dry weather flows.

The data, in combination with influent flow data from the City’s wastewater treatment plant, indicates an average dry weather flow (ADWF) of 3.52 MGD across the system. This data helps establish a baseline for understanding the system's capacity and planning future improvements.

Future Dry Weather Flows: Two future scenarios, Near-Term (2035) and Ultimate (2045), were developed based on the Existing (2025) scenario. The Near-Term scenario includes known planned developments, projecting an additional 0.60 MGD in ADWF. The Ultimate scenario was created by applying a system-wide multiplier based on population growth to the Near-Term, resulting in a total ADWF of 4.58 MGD by 2045. These projections help the City plan for sewer system improvements to accommodate future demand.

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Figure ES.1 Sewer Collection System

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ES-4 Hydraulic Model Development and Calibration
A new hydraulic model of the City’s existing trunk sewer system was constructed using data from a 2025 field survey of 100 representative manholes, which provided current invert elevations and pipe diameters. Flow monitoring and treatment plant influent flow data were used to calibrate the newly created model to existing dry and wet weather flow conditions, forming the basis for future model scenarios and capacity analysis. 2025 Flow Monitoring Program: A temporary flow monitoring program was implemented in 2025, featuring nine strategically placed flow monitors to measure sewer flows within designated sewersheds. The data collected from these monitors was used to develop unique dry weather hourly time patterns for each sewershed, reflecting typical daily variations in sewer flow. This flow monitoring data was used to calibrate the Existing dry weather scenario of the hydraulic model.

Model Network Generation: The trunk sewer model network was developed using a combination of the existing sewer GIS data, field survey information, and as-built record drawings. Invert elevations were collected for approximately 100 manholes, with interpolations made for intermediate manholes.

Flow Allocation and Calibration: Dry weather flows were allocated to the model based on average measured flows from the 2025 flow monitoring program. Eight (8) of the nine sewersheds were calibrated using weekday flows, while FM 09 (a predominately industrial and commercial sewershed) was calibrated using weekend flows. The model was calibrated once both average and peak dry weather flows were within 10% of the measured values. An Existing wet weather scenario was developed and calibrated using a defect flow pattern and allocations developed to simulate the average and peak wet weather flows recorded during a significant historical wet weather event.

ES-5 Collection System Capacity Analysis
The capacity of the City’s modeled trunk sewer system was evaluated under both dry and wet weather flow conditions in the Existing, Near-Term, and Ultimate planning scenarios. The capacity analysis results are used to identify potential deficiencies within the existing collection system based on recommended deficiency criteria reviewed and accepted by the City.

Design and Deficiency Criteria: Design and deficiency criteria for the gravity mains, lift stations, and force mains in the City’s collection system were reviewed and finalized with City staff prior to adoption The chapter establishes design criteria for sewer pipelines, including minimum diameters, velocities, and Manning's roughness coefficient.

These criteria ensure that new and existing pipelines can handle peak dry weather flows (PDWF) and allow for potential wet weather flows. The criteria also include a maximum depth-to-diameter ratio (d/D) to prevent pipelines from flowing full, which could increase the risk of sanitary sewer spills.

Dry Weather Capacity Analysis: The capacity of the City's modeled trunk system was analyzed in the Existing, NearTerm, and Ultimate dry weather flow scenarios. The results of the analysis indicate that no modeled trunk mains are anticipated to exceed the City’s deficiency criteria in any planning scenario under dry weather flow conditions.

Wet Weather Capacity Analysis: The capacity of the City's modeled trunk system was also analyzed in the Existing, Near-Term, and Ultimate wet weather flow scenarios. Modeled capacity analysis results indicate that potential deficiencies may result from the outsized influence of defect flow entering the system at specific sewersheds within the service area.

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ES-6 Collection System Condition Assessment
Condition assessment was performed on the City’s existing lift stations, selected gravity mains, manholes, and the wastewater treatment plant.

Lift Station Condition Assessment: Condition assessment was performed on the City’s 15 active lift stations. Of the 15 lift stations, nine were determined to require a comprehensive site visit and field investigation due to age or criticality. The remaining six received a visual wet well inspection only.

Gravity Main Condition Assessment: Closed Circuit Television (CCTV) inspection reports for 40 gravity main segments, totaling approximately 1.7 miles, were reviewed to determine an appropriate rehabilitation or repair method intended to address observed structural and other physical defects. The methodology involved reviewing CCTV reports, recording defects, and identifying suitable repair methods.

Manhole Condition Assessment: The City performed field inspections on manholes in Imperial Avenue between Danenburg Avenue to McCabe Road. All manholes were found by the City to need significant rehabilitation. Based on discussions with City staff, the manhole rehabilitation method recommended included a combination of mortar repair with corrosion resistant geopolymer mortar and cured-in-place (CIP) PVC composite manhole liners (CIPM liner) for all 11 manholes
Wastewater Treatment Plant Condition Assessment: A comprehensive site investigation of the City’s wastewater treatment plant was completed. The assessment identified potential improvements for the influent distribution structure, the primary clarifiers, and the sludge digesters at the City’s treatment plant.

ES-7 CIP Project Recommendations
Capital Improvement Program (CIP) project recommendations and planning level engineer’s cost opinions include recommended pipeline improvement projects to address both capacity and condition deficiencies in the City's sewer collection network. Two capacity-related projects are recommended, including an I&I study. Two condition-related projects are recommended to correct structural deficiencies found in sewer pipelines.

Additionally, separate condition assessment technical memorandums were developed for the City’s lift stations and wastewater treatment plant. Twenty lift station and 8 treatment plant improvement projects were recommended based on the findings presented in the technical memorandums. Additional long-term studies, including a cybersecurity vulnerability assessment, are recommended The sewer CIP projects and estimated costs are presented in Table ES-1. All cost estimates are based on an Engineering News Record (ENR) Construction Cost Index (CCI) of 15,993.96 for September 2025, with a 4% annual escalation factor applied to reflect fiscal year cost projections.

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Table ES.1. 20-Year Sewer CIP Projects Cost Summary

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1 Introduction
The following section summarizes the objectives of the 2025 Sewer Master Plan Update (2025 Update) for the City of El Centro (City). The section includes an overview of the City’s previous master planning efforts and existing sewer service area to provide context for the evaluation and recommendations provided in the 2025 Update. The section also outlines the structure of the report with a brief description of each section as a guide for understanding the development and findings of the 2025 Update.

1.1 Project Objectives and Overview
The 2025 Update analyzes the capacity and condition of the City’s collection system and culminates in a new CIP schedule intended to meet existing and future development needs. Since adoption of the last sewer master plan in 2008, development and population growth within the City's service area have progressed at a slower pace than originally projected, resulting in certain sewer facilities operating consistently below their design capacities.

Additionally, several key assets, including lift stations and critical components of the wastewater treatment plant, are approaching the end of their service life and will soon require replacement or significant rehabilitation. Public Works staff have cited these considerations as the primary motives for completion of the 2025 Update.

The 2025 Update achieves the following key objectives:

1. Data Review and Gap Analysis: Assess available data pertaining to the existing sewer system and identify deficiencies within the City's sewer GIS database.

2. Field Survey: Conduct a rim and invert elevation survey of approximately 100 strategically selected manholes located along trunk sewer mains (12-inch diameter or greater) for greater confidence in the modeled capacity analysis results.

3. Model Development: Construct a new hydraulic model of the trunk system using GIS and field survey data.

4. Flow Monitoring: Perform sewer flow monitoring at nine (9) locations to identify flow patterns for creation of land use based sewer flow generation patterns, applying existing sewer inflows into the model and system calibration.

5. Generation Factors: Develop unit sewer generation factors for common land use types within the City.

6. Flow Projections: Update dry weather flow projections to reflect current and anticipated future conditions within the service area.

7. Model Calibration: Calibrate the trunk sewer model to within 10% or better accuracy.

8. Capacity Evaluation: Analyze the capacity of the modeled trunk system under peak dry and wet weather flow conditions for Existing (2025), Near-Term (2035) and Ultimate (2045) scenarios.

9. Condition Assessment: Conduct a condition assessment of selected gravity mains and field inspection of all 15 lift stations and the wastewater treatment plant.

10. Lift Station Optimization: Assess the feasibility of decommissioning any of the existing lift stations and redirecting tributary flows to the gravity system.

11. Capital Improvement Plan Development: Identify and prioritize capital improvement projects to address capacity and condition-related deficiencies identified throughout the collection system.

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12. Cost Estimation: Prepare planning-level engineer’s cost opinions for each recommended project and integrate into a multi-year CIP for implementation by the City.

1.2 Previous Master Plan
The 2008 Sewer Master Plan included a hydraulic model of the City’s trunk system, developed using H2OMap Sewer Suite 8.0 by MWHSoft. The model was calibrated to dry weather flow monitoring data collected in March 2007. However, the model was not available for use or reference during preparation of the 2025 Update.

The 2008 Sewer Master Plan assessed the trunk system’s capacity under Existing (2008), 2015, and Build-Out peak dry and wet weather flow conditions. Build-Out was defined as complete development of the City’s existing Sphere of Influence (SOI). Peak wet weather flow was estimated as the highest recorded influent flow to the wastewater treatment plant over a six-year period (January 2001 to December 2006). The results of the capacity analysis indicated that a total of approximately one mile of the City’s trunk system is deficient in all scenarios.

Additional capacity and lift station deficiencies would need to be addressed at Build-Out.

To address the identified deficiencies, the 2008 Sewer Master Plan recommended a series of improvement projects, including:
▪ Five pipeline capacity improvement projects to be completed prior to Build-Out, consisting of approximately 5,030 linear feet (LF) of gravity main replacement (ranging from 8-inch to 18-inch diameter) and 1,900 LF of new 6-inch force main.
▪ One additional pipeline project and three lift station upgrades to be implemented at Build-Out. ▪ Ten improvement projects targeting existing wastewater treatment plant processes and facilities.

The estimated costs of the improvement projects in 2008 were as follows:
▪ Gravity main replacements: $2.86 million
▪ Force main extension: $0.37 million
▪ Lift station upgrades: $15.7 million
▪ Treatment plant upgrades: $6.81 million
As summarized in Table 1.1, by the time of the 2025 Update, the City had completed seven of the recommended projects from the 2008 Sewer Master Plan. The completed projects included two lift station (Alder Canal – Villa Ave and Lift Station No. 3) and five treatment plant upgrades.

Table 1.1. 2008 Sewer Master Plan CIP Status – 2025 Update Project Description Location Length (LF) 2025 Status
Upsize existing 12-inch gravity
main to 15-inch
Imperial Ave from Holt Ave to Main St 1,848 Not Completed Upsize existing 14-inch gravity
main to 18-inch
4th St from Brighton Ave to State St 926 Not Completed
Upsize existing 8-inch and 10-
inch gravity main to 12-inch
3rd St from State St to Commercial Ave 1,125 Not Completed

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Table 1.1. 2008 Sewer Master Plan CIP Status – 2025 Update Project Description Location Length (LF) 2025 Status
Upsize existing 6-inch gravity
main to 8-inch
8th St from Westwind Dr to Ross Ave 1,132 Not Completed New 6-inch force main
extension and pump upgrades
From Dogwood Rd to Fairfield Ave
between Holt and Heil Ave / Heil and
Dogwood LS
1,900 Not Completed
Upsize existing 8-inch gravity
main to 12-inch (at Build Out)
Plank Drive from Ross Ave to Hamilton
Ave
1,306 Not Completed
Upgrade and replace pumps
and wet wells (at Build Out)
Alder Canal – Villa Ave LS — Completed
Upgrade and replace pumps
and wet wells (at Build Out)
Lift Station No. 3 — Completed
Construction of new Northern
lift station (at Build Out)
Dogwood Rd and Cruickshank Rd — Not Completed
Preliminary Treatment
(Headworks and Grit Removal)
Wastewater Treatment Plant — Completed
Primary Clarifier Concrete Crack
Repair (2 Clarifiers)
Wastewater Treatment Plant — Completed
Aeration Basin Aerator Platform
Demolition (Basins 1 - 6)
Wastewater Treatment Plant — Not Completed
Aeration Basin Ceramic Disk
Replacement - (Basins 1 - 4
with 663 disks)
Wastewater Treatment Plant — Ongoing
Aeration Basin Ceramic Disk
Replacement - (Basins 5 - 6
with 810 disks)
Wastewater Treatment Plant — Ongoing
Aeration Basin Stainless Steel
Gate Replacement
Wastewater Treatment Plant — Completed
Aeration Basin Concrete Spall
Repair
Wastewater Treatment Plant — Ongoing
Aeration Basin South Walkway
Replacement
Wastewater Treatment Plant — Completed
Boiler/Heat Exchanger Wastewater Treatment Plant — Completed Plant Water Pump Station Wastewater Treatment Plant — Not Completed

1.3 Service Area Overview
The City of El Centro was incorporated in 1908 and is located approximately 120 miles east of San Diego, 250 miles west of Phoenix, and 10 miles north of the United States–Mexico border. With a population of 44,000, El Centro is the most populous city in the Imperial Valley and serves as the county seat of Imperial County. El Centro is primarily accessible via State Routes 86 and 111 and Interstate 8. Figure 1.1 presents a regional map highlighting the City’s location in southern California and Imperial County.

El Centro encompasses an area of 11 square miles and lies entirely below sea level, with an average elevation of - 42 feet. The City is surrounded by thousands of acres of agricultural land that support robust crop production

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throughout the Imperial Valley. Over the past four decades, government services and commercial trade have emerged as the City’s leading employment sectors. Agriculture continues to play a vital role in the local economy, with crop production generating over $2 billion of gross value in 2023 for Imperial County (Source: 2023 Imperial County Agricultural Crop & Livestock Report).

El Centro’s sewer collection system and wastewater treatment plant are operated and maintained by the City’s Public Works Department. The collection system includes approximately 123 miles of gravity pipeline, 15 sewer lift stations, and five miles of force main. The sewer service area and collection system are depicted in Figure 1.2.

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Figure 1.1 Regional Map

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Figure 1.2 Sewer Service Area and Collection System

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El Centro has a hot desert climate characterized by long, hot summers and mild winters. The average annual low and high temperatures are approximately 59°F and 88°F, respectively. The City receives an average of 2.85 inches of rainfall per year, with most precipitation occurring between December and February. While generally arid, El Centro is occasionally subject to intense thunderstorms resulting from the remnants of tropical storms or hurricanes traveling across the surrounding desert. Notable recent storm events include Tropical Storm Kay in September 2022 and Hurricane Hilary in August 2023, both of which brought above-average rainfall to the area.

Figure 1.3 presents the monthly climate normals (i.e., average of data collected over 30 years) recorded at the El Centro Naval Air Facility, located approximately seven miles northwest of the City center (Source: U.S. Climate Data, https://www.usclimatedata.com/climate/el-centro/california/united-states/usca0332).

Figure 1.3 El Centro Monthly Climate Normals (1981-2010)

1.4 Report Organization
The 2025 Update is organized into the following sections:
▪ Section 1 – Introduction provides an overview of the background, scope, and objectives of the 2025 Update. Includes a summary of key characteristics of the City’s sewer collection system and service area. ▪ Section 2 – Existing System Summary describes the components of the City’s existing sewer system, including gravity mains, diversion manholes, lift stations, force mains, and the wastewater treatment plant.

Includes a summary of the current distribution of land use types within the City.

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▪ Section 3 – Existing and Future Dry Weather Flows estimates current dry weather flows and projected future flows based on known development activity. Describes the development of unit sewer generation factors for major land use types
▪ Section 4 – Sewer Model Development and Calibration summarizes the flow monitoring program, manhole field survey, development of a new trunk sewer model, allocation of existing dry and wet weather flows, and model calibration results.
▪ Section 5 – Collection System Capacity Analysis presents the results of the capacity analysis for the modeled trunk system under existing, near-term, and ultimate dry and wet weather flow conditions.

Evaluates the feasibility of consolidating, decommissioning, or otherwise optimizing the performance of certain lift stations as identified by Public Works staff. ▪ Section 6 – Collection System Condition Assessment and Improvements summarizes the methodology and results of the condition assessment performed on the City’s gravity mains, lift stations, and wastewater treatment plant.
▪ Section 7 – Capital Improvement Program provides a prioritized list of recommended improvement projects intended to address identified capacity and condition deficiencies. Includes planning-level cost opinions and a multi-year implementation schedule.

The following documents are included as Appendices to this report:
▪ Appendix A Sewer Lift Station Condition Assessment Technical Memorandum ▪ Appendix B Wastewater Treatment Plan Condition Assessment Technical Memorandum ▪ Appendix C Planned Near-Term Developments Table
▪ Appendix D City of El Centro Temporary Sewer Flow Metering Report ▪ Appendix E Dry Weather Model Calibration Results
▪ Appendix F Pipeline Condition Assessment Data & Recommendations Log ▪ Appendix G City of El Centro Staffing Plan Technical Memorandum ▪ Appendix H Detailed Engineer’s Opinion of Probable Costs for Recommended CIP Projects

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2 Existing System Summary
The following Existing System Summary section summarizes existing features of the City’s sewer collection system.

The section describes major components of the collection system, including gravity mains, diversion manholes, lift stations and associated force mains, and the wastewater treatment plant.

A comprehensive understanding of the City’s existing sewer system is essential for capacity evaluation, condition assessment, and CIP development. In characterizing key elements of the collection system, the Existing System Summary provides a basis for subsequent analyses and empowers the City to make well-informed decisions regarding system improvements or modifications.

2.1 Gravity Mains
The City’s existing sewer collection system includes approximately 123 miles of gravity pipeline, with diameters ranging from 4-inch to 36-inch as summarized in Table 2.1. Approximately 73% of the collection system is 8-inch or smaller in diameter.

Approximately 74% of all gravity mains in the City’s system are constructed of vitrified clay pipe (VCP), while the remaining pipelines are composed of polyvinyl chloride (PVC), brick, or other materials.

Pipeline installation years range from 1931 to 2020, with approximately half of the system estimated to be over 50 years old as summarized in Table 2.2. Installation year information is missing from the City’s GIS database for approximately one-third of the collection system, including segments identified as brick material through inspection videos recorded in January 2025. The City’s brick pipelines likely date back to the early 20th century, a period in which brick was commonly used to construct sewer pipelines prior to the adoption of modern building methods.

Figure 2.1 depicts the existing gravity mains in the City’s collection system, classified by diameter.

Table 2.1. Gravity Main Summary by Diameter and Material1 Diameter
(inch)
Length of Pipe (LF)
VCP PVC Other % of Total
2 Subtotals
4 1,856 611 330 2,797 0.4%
6 14,771 7,531 — 22,302 3.4%
8 356,967 92,714 — 449,681 69.2%
10 10,721 7,235 — 17,956 2.8%
12 39,607 31,329 — 70,936 10.9%
14 3,882 - — 3,882 0.6%
15 15,923 613 — 16,536 2.5%
18 7,570 8,964 131 16,666 2.5%
20 — 17 — 17 0.0%
21 — 473 — 473 0.1%
22 423 — — 423 0.1%
24 4,332 5,556 — 9,889 1.5%

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Table 2.1. Gravity Main Summary by Diameter and Material1 Diameter
(inch)
Length of Pipe (LF)
VCP PVC Other % of Total
2 Subtotals
27 20,435 5,580 — 26,015 4.0%
30 4,080 — — 4,080 0.6%
36 126 8,117 — 8,244 1.3%
Subtotals 482,346 167,091 461 Total 649,897
% of Total 74.2% 25.7% 0.1%
Notes:
1 Source: City of El Centro sewer GIS database provided by City of El Centro Public Works staff in September 2024. 2 “Other” pipeline materials include cast iron, Acrylonitrile butadiene styrene (ABS), brick, and those not defined in the City’s GIS database. No pipe segments were identified as brick in the GIS database, but Public Works staff believe brick pipelines exist within Villa Ave. Additionally, inspection videos from January 2025 show brick pipelines within Adams Ave and 4th St.

Table 2.2. Gravity Main Summary by Installation Year1
Installation Year Length of Pipe (LF) % of Total
Unknown2 231,669 35.6%
1931-1939 15,726 2.4%
1940-1949 3,330 0.5%
1950-1959 49,024 7.5%
1960-1969 41,405 6.4%
1970-1979 62,317 9.6%
1980-1989 75,377 11.6%
1990-1999 40,763 6.3%
2000-2009 121,048 18.6%
2010-2020 9,240 1.4%
Total 649,897 100.0%
Notes:
1 Source: City of El Centro sewer GIS database provided by City Public Works staff in September 2024. 2 Any gravity main in the GIS database missing installation year data was assumed to be more than fifty years old (i.e., constructed prior to 1975). Brick pipelines are assumed to have been constructed between 1931 and 1939.

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Figure 2.1 Existing Gravity Mains by Diameter

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2.2 Inverted Siphons
An inverted siphon is a pipeline designed to cross underneath existing features such as storm drain channels, bodies of water (e.g., streams or creeks), utility lines, or other overlying structures. Inverted siphons are designed to operate below the hydraulic grade line and therefore always flowing full or under pressure.

Inverted siphons are typically classified as either single or double barrel systems. A double barrel siphon consists of two parallel pipelines, usually of identical diameter. In a double barrel siphon, one pipeline serves as the primary conveyance line while the second functions as a backup, available for use in the event of maintenance or failure of the primary line.

According to Public Works staff, the City’s existing sewer collection system does not contain any inverted siphons.

2.3 Diversion Manholes
Diversion manholes are specialized structures within a collection system that direct sewer flow through two or more outlet pipes oriented in different directions. Diversion manholes often incorporate stoplogs to intentionally block one outlet and divert flow into a preferred downstream route. In some configurations, a weir is installed at the upstream invert of the secondary (overflow) pipe to prioritize flow through the primary outlet. During periods of elevated flow such as a significant wet weather event, water may rise above the weir and enter the overflow pipe, thereby relieving potential capacity constraints in the main line.

The accurate representation of flow through diversion manholes is essential during capacity evaluation of the City’s sewer system. Four diversion manholes were identified within the existing collection system, as summarized in Table 2.3 and shown in Figures 2.2 and 2.3. All four were surveyed in March 2025 and incorporated into the trunk sewer model as detailed in Section 4.2.1.

Table 2.3. Existing Diversion Manholes in Trunk Sewer Model1 City
Manhole
ID Location
DS Invert
Elevation
Difference
(ft)
Main
Invert
Elevation
(ft)
Main Invert
Diameter
(inch) and
Cardinal
Direction
Overflow
Invert
Elevation
(ft)
Overflow
Invert
Diameter
(inch) and
Cardinal
Direction
22-14-136 W Commercial
Ave and N 4th St

4.6 42.20 18, West 46.80 18, Northwest
22-15-114 W Commercial
Ave & N 3rd St

0.14 44.67 10, West 44.81 8, Southwest
19-14-126 Ross Ave & S 4th
St

2.80 51.80 8, North 54.60 8, East
20-13-102 Holt Ave & Alley
west of 8th St

0.23 53.24 12, West 53.47 8, North
Notes:
1 The invert elevations in this table were adjusted by +100 ft to account for the negative invert elevations present throughout the City’s collection system. For example, an invert elevation of 42.16 ft in this table corresponds to an invert elevation of -57.84 ft when measured in the field.

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Figure 2.2 Existing Modeled Diversion Manholes

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Figure 2.3 Existing Modeled Diversion Manholes - Continued

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2.4 Sewer Lift Stations and Force Mains
The City operates and maintains 15 sewer lift stations within its collection system, as summarized in Table 2.4 and depicted in Figure 2.4.

The 2025 Update includes field inspection and condition assessment of each active lift station in the City’s service area. Nine of the 15 lift stations received comprehensive site investigations due to their age or critical role within the sewer system. The remaining six stations received visual inspections of the wet wells only.

During the inspection process, Public Works staff indicated that the 4th and Wake, Legacy, and Countryside lift stations are scheduled to be abandoned within the next five years. Flow currently tributary to these stations will be redirected via gravity pipeline to the new Southern Lift Station, located at the intersection of W Danenberg Dr and Farnsworth Ln. Although the City approved construction plans for the Southern Lift Station in April 2024, construction had not commenced at the time of the 2025 Update.

Detailed descriptions of the condition assessment performed at each lift station, including site layouts, hydraulic and pump characteristics, inspection results, and recommended improvements, are documented in a separate technical memorandum included in Appendix A.

Due to limitations in force main inspection techniques, the 2025 Update does not include an assessment of the physical condition of the force mains associated with each lift station. Instead, a desktop hydraulic evaluation of each force main based on existing diameter, flow rate, and allowable velocity is presented in Section 5.

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Table 2.4. Existing Sewer Lift Station and Force Main Summary Name Location
Number
of
Pumps
Installation
Year1
Design
Capacity2 (gpm/
ft TDH)

Force
Main
Diameter
(inch)
Force Main
Length (ft)/
Material
Lift Station No. 3 2255 N La Brucherie Rd (El Centro WWTP) 3 2006 3,000 / 37 24 400 / DI Gios Southeast corner of Gio’s Mobile Home
Estates, west of N Waterman Ave
2 2016 250 / 20 4 Unknown
Main 1587 W Pico Ave 3 2007 2,535 / 39 30 6000 / PVC
Countryside East of Hwy 86, approximately 120 ft north
of Willow Bend Dr
2 2002 550 / 45 6 429/ HDPE;
PVC
Legacy (Southern
Countryside)
Valor Ln between Farnsworth Ln and Rubert
Franks Dr
2 2011 250 / 20 6 1,925 / PVC
Alder Canal – Villa Ave Southeast corner of E Villa Rd and Villa Ln 2 2005 Unknown 20 12,235 / PVC 3rd and Ross W Ross Ave between 2nd St and S 3rd St 2 2016 – 2017
325 / 27 4 225 / ABS
4th and Wake Northeast corner of Wake Ave and S 4th St 2 1985 200 / UNK 4 335 / PVC 8th and Wake Northeast corner of Wake Ave and S 8th St 2 2006 200 / 35 6 140 / PVC Lift Station No. 2 Northwest corner of Wake Ave and S La Brucherie Rd
2 2016 850 / 30 12 980 / PVC
Orange Ave W Orange Ave between Lotus Ave and
Haskell Rd
2 2005 400 / 46 4 60 / PVC
Lift Station No. 1 W McCabe Rd, approximately 200 ft east of Date Drain
2 1975 400 / 14.6 6 180 / PVC
Buena Vista Imperial Ave, approximately 140 ft south of Manuel Ortiz Ave
2 2006 369 / 27 8 130 / PVC
Eastside Southeast corner of W Commercial Ave and
N 3rd St
3 2007 1,132 / 26 10 70 / PVC
Heil and Dogwood Northeast corner of E Heil Ave and S
Dogwood Rd
2 1998 250 / 25 6 175 / PVC
Notes:
1 Installation Year refers to the latest known year that pumps were installed or replaced at each lift station, per Sewer Lift Station Condition Assessment Draft Technical Memorandum dated June 2025.
2 Design Capacity is defined as the pumping capacity of each lift station with its largest pump out of service. For example, the pump design capacity of Lift Station No. 3 is 3,000 gpm at 37 ft TDH (Total Dynamic Head).

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Figure 2.4 Existing and Planned Near-Term Sewer Lift Stations and Force Mains

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2.5 Wastewater Treatment Plant
All sewer flow generated within the City’s service area is conveyed to the El Centro Wastewater Treatment Plant (WWTP), located at 2255 N La Brucherie Road in the northwest corner of the City. The treatment plant is a conventional primary and secondary treatment plant with ultraviolet (UV) disinfection facilities. Wastewater treated at the plant is discharged into the Central Drain, which ultimately flows into an outfall at the Salton Sea located approximately 50 miles northwest of the City. Currently, the City’s treatment plant is not equipped to produce recycled water.

The 2025 Update includes a comprehensive site visit, condition assessment, and capacity evaluation of the wastewater treatment plant. Field observations, evaluation methodology, and recommended improvements for the treatment plant are documented in a separate technical memorandum included in Appendix B.

The plant is permitted to treat up to 8.0 MGD over any 30-day reporting period. In March 2025, the average influent flow was recorded at 3.52 MGD, with a peak hourly flow of 4.93 MGD occurring on the evening of March 10, 2025.

However, the historical peak wet weather flow observed by Public Works staff at the treatment plant was 9.0 MGD during one hour of a significant wet weather event. As detailed in Appendix B, the primary clarifiers do not have adequate capacity to meet the observed peak wet weather flow of 9.0 MGD.

Figure 2.5 presents an overview of the existing plant and associated treatment facilities.

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Figure 2.5 Existing Wastewater Treatment Plant Site Overview

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3 Existing and Future Dry Weather Flows
The following section summarizes the current and projected sewer flows within the City’s service area based on population, land use, and planned future developments. The section presents unit sewer flow generation factors for individual land use types, which serve as the basis for estimating future dry weather flows from planned developments.

The accurate representation of existing and future dry weather flows is critical for capacity evaluation of the sewer collection system under various planning scenarios. By relating flow projections to forecasted population growth and development, the Existing and Future Dry Weather Flows section will support the City in aligning future system improvements to anticipated service needs throughout the collection system.

3.1 Existing Flow Summary
Hourly influent flow data collected at the wastewater treatment plant in March 2025 indicates the existing average dry weather flow (ADWF) is approximately 3.52 MGD. Figure 3.1 depicts the daily average influent flow to the treatment plant from March 1 through March 31, 2025. Average influent flow is approximately 5% higher on weekdays than on weekends.

For comparison, the average influent flow to the treatment plant as reported in the 2008 Sewer Master Plan was

3.65 MGD, based on data collected in March 2007. In nearly 20 years, the total flow generated within the City’s sewer service area has decreased by only 3.4%. The relatively stable overall flow rate suggests the City has experienced little to no population growth since 2007, or that the impact of any growth on the sewer system has been offset by regional and statewide water conservation efforts.

Figure 3.1 Average Influent Dry Weather Flow to Wastewater Treatment Plant (March 2025)

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3.1.1 Existing Land Use Summary
Residential land use accounts for nearly half of the City’s total area, with low-density residential being the predominant land use type. The density of each residential land use type, expressed in dwelling units per acre, is defined in Section 3.3.1.

Commercial and industrial land use each comprise approximately 20% of the City’s total area. Including Public Facilities, non-residential land use types make up more than half of the service area. The prevalence of nonresidential land use, especially in the eastern portion of the City, may contribute to the higher sewer flows observed at the treatment plant during the traditional work week.

Table 3.1 and Figure 3.2 summarize the existing distribution of land use types within the City, based on 2020 data obtained from the Southern California Association of Governments’ (SCAG) online database.

Table 3.1. Land Use Summary
Land Use Type Area (Acres) % of Total City Area
Rural Residential (RR) 111 1.8%
Low Density Residential (LDR) 2,228 35.1%
Medium Density Residential (MDR) 248 3.9%
High Density Residential (HDR) 433 6.8%
Civic1 60 0.9%
Commercial (includes Downtown, General, and
Tourist Commercial)
1,246 19.6%
Industrial (includes General and Planned Industrial) 1,242 19.6% Public Facility2 782 12.3%
Totals 6,349 100%
Notes:
1 Civic land use is defined as local government offices, state and federal facilities, professional offices, financial institutions, and other businesses located within the City’s civic center along Main St. 2 Public Facility land use is defined as all land owned by the City, Imperial Irrigation District, or El Centro Regional Medical Center.

This land use category also includes public school districts, police and fire stations, parks and recreation facilities, and water and sewer facilities (e.g., treatment plants).

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Figure 3.2 Existing Land Use Summary

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3.2 Population and Planned Developments Summary
Projected population growth and planned development data are the primary resources used to estimate future dry weather flows within the City’s sewer service area. The following summarizes the forecasted population of the City through the planning horizon covered by the 2025 Update (Ultimate or 2045) and all known future developments based on information provided by the City’s Planning and Zoning Division.

3.2.1 Population Summary
The following summarizes the City’s existing population as well as anticipated population growth through 2045.

3.2.1.1 Existing Population
According to the City’s 2020 Urban Water Management Plan (UWMP) completed in May 2021, the population of the City was 45,657 in 2020. The 2020 UWMP also documented SCAG’s population projections for the City from 2025 through 2045. SCAG estimated that the City’s population in 2025 will be 48,208, or a 5.6% increase from 2020.

SCAG’s projected population of 48,208 in 2025 is higher than the City’s estimated population of 44,230 according to the U.S. Census Bureau at the time of writing the 2025 Update (Source:
https://www.census.gov/quickfacts/fact/table/elcentrocitycalifornia/PST045223).

3.2.1.2 Projected Population
According to SCAG’s population projections as documented in the 2020 UWMP, the City’s population will increase

28.7% over a 25-year period, from 45,657 in 2020 to 58,753 in 2045. SCAG’s projections result in an average population growth rate of approximately 1.1% per year.

To derive more accurate population estimates for the 2025 Update, the City’s current population of 44,230 in 2025 was used as the basis for projections up to 2045. Anticipated growth rates from Table 3-1 of the 2020 UWMP were used to calculate revised estimates for the population of the City at each five-year interval (e.g., 2030, 2035, 2040, etc.).

Table 3.2 summarizes the City’s anticipated population from 2025 to 2045 in five-year increments, assuming the current population of 44,230 in 2025 and growth rates from the 2020 UWMP.

Table 3.2. Existing and Projected Population Estimates1 Year 2025 2030 2035 2040 2045
Population 44,230 46,570 48,642 51,273 53,903
Notes:
1 Five-year growth rates calculated using population estimates in Table 3-1 of the City of El Centro 2020 Urban Water Management Plan (UWMP) dated May 2021.

Under California law, local governments are required to plan for adequate development of housing units to accommodate projected population growth across the state. The California Department of Housing and Community

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Development (HCD) determines the regional housing need for each Council of Governments (COG). SCAG is a COG encompassing six counties and 191 cities in southern California, including the City of El Centro.

SCAG allocates housing planning goals to each city through the Regional Housing Needs Allocation (RHNA) process, as authorized by the California Government Code. According to SCAG’s estimates, the City must identify adequate vacant and non-vacant sites to support the development of 3,442 new dwelling units by 2029.

If all 3,442 units are constructed and occupied by 2029, with an average household size of 3.4 persons per unit (Source: Section V of SCAG’s Pre-Certified Local Housing Data for El Centro, April 2021), the City’s population is anticipated to increase to approximately 57,360 in 2030 based on a population of 45,657 in 2020. The population increase represents a projected growth rate of approximately 26% between 2020 and 2030, more than double the rate estimated in the 2020 UWMP for the same period.

However, the RHNA process does not require all dwelling units to be constructed and fully occupied by 2029. Rather, each city must complete any necessary zoning changes to allow for residential development should the local housing demand increase. The City has already designated zoning to support development of its allocated units.

3.2.2 Near-Term (2035) Developments
According to data provided by the City’s Planning and Zoning Division, 52 developments are expected to complete construction and contribute additional sewer flows to the City’s collection system by 2035 (i.e., Near-Term). Based on planning documents filed with the City, the 52 near-term developments include:
▪ Seven low or medium density residential subdivisions (i.e., tract developments), totaling 1,675 new single family residential dwelling units
▪ Six high-medium or high density residential developments (i.e., multi-family or apartment buildings), totaling 827 new dwelling units
▪ One state-funded septic to sewer conversion project in the vicinity of Villa Ave and Cross Rd, resulting in 32 existing low density residential units connecting to the gravity collection system ▪ Twenty-eight commercial developments, including restaurants, self-storage facilities, medical offices, and hotels
▪ Three industrial developments, including development of approximately 500 acres in the Ross and Dogwood Area.
▪ Two public or institutional facilities, including a new police station and highway patrol station ▪ Three public parks with public restrooms
▪ Annexation of Dogwood and Villa site, assumed to be developed up to 50% by 2035 with the remaining 50% developed by 2045. Development is dependent on the progression of the Lithium Valley Specific Plan (refer to Section 3.2.3 for additional information).

Details for each of the 52 planned near-term developments are tabulated in Appendix C. Figure 3.3 depicts the approximate location of each near-term development.

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Figure 3.3 Planned Near-Term Developments

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3.2.3 Ultimate (2045) Developments
At the time of the 2025 Update, no known developments were anticipated to complete construction after 2035 and prior to 2045 (i.e., Ultimate). The only exception is the partial annexation of Dogwood and Villa as described in Section 3.2.2. However, the City may experience additional growth following implementation of the Lithium Valley Specific Plan (LVSP). In February 2025, Imperial County prepared a draft of the LVSP defining future land use and zoning changes to support the county in its efforts to capitalize on the vast lithium deposits identified within the Salton Sea Known Geothermal Resource Area (KGRA).

The timing and extent of county-wide development as presented in the LVSP and subsequent impact on the City’s service area are not yet clearly defined. In addition, there is a likelihood that the overall specific plan will not move forward as planned. Public Works staff anticipate a 1% rate of growth per year between 2035 and 2045, for an overall growth rate of 10% between Near-Term and Ultimate. The assumed 10% growth rate is consistent with the City’s projected population increase of 5,735 people from 53,018 in 2035 to 58,753 in 2045, or a 10.8% increase.

3.3 Future Flow Summary
Two future dry weather flow scenarios, Near-Term (2035) and Ultimate (2045), were developed in the trunk sewer model as part of the 2025 Update. The Near-Term scenario is based on information (e.g., proposed number of dwelling units, land use type, etc.) concerning planned developments that are anticipated to finish construction and require sewer service by 2035. The Ultimate scenario uses the City’s projected population growth to estimate an overall increase in sewer flows throughout the collection system by 2045.

The following summarizes the methodology used to develop the Near-Term (2035) and Ultimate (2045) dry weather flow scenarios.

3.3.1 Unit Sewer Flow Generation Factors
Unit sewer flow generation factors for each land use type in the City’s service area were developed based on 2025 flow monitoring data, unit water demand factors from the 2025 Water Master Plan Update (under separate cover), and potential future state water conservation requirements.

The unit generation factors summarized in Table 3.3 are used to allocate existing dry weather flows throughout the City’s trunk sewer model and estimate the ADWF generated by planned developments as described in Section 3.3.2. The dry weather flow allocation process is described in Section 4.

Table 3.3. Unit Sewer Flow Generation Factors by Land Use Type Land Use Type
Unit Generation Factor
gpd/DU DU/acre gpd/acre
High Density Residential 120 20 2,400
Medium Density Residential 175 10 1,750
Low Density Residential1 175 4 700
Community Commercial — — 1,200
General Commercial — — 1,200

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Table 3.3. Unit Sewer Flow Generation Factors by Land Use Type Land Use Type
Unit Generation Factor
gpd/DU DU/acre gpd/acre
Tourist Commercial — — 1,200
Downtown Commercial — — 1,200
General Industrial — — 200
Planned Industrial — — 400
Public Facility / Civic — — 800
Public Park — — 175
Notes:
1 Low Density Residential includes parcels categorized as Rural Residential.

3.3.2 Near-Term (2035) Scenario Flow Projections
Unit sewer factors were used to estimate the ADWF generated by each near-term development listed in Appendix C.

Table 3.4 summarizes the anticipated increase in ADWF due to the 52 developments, based on their proposed land use types. The calculated ADWF of each planned development was applied to the nearest modeled manhole in the trunk sewer model to develop the Near-Term dry weather flow scenario.

Table 3.4. Estimated ADWF from Planned Near-Term Developments Proposed Land Use Type ADWF (MGD)
Low or Medium Density Residential 0.30
High Density Residential 0.11
Commercial 0.05
Industrial 0.13
Other (e.g., Public Facility) 0.01
Total Increase in ADWF from Near-Term Developments 0.60 Assuming all 52 developments are constructed and connected to the City’s collection system by 2035, the total ADWF in the Near-Term scenario is estimated at 4.13 MGD.

3.3.3 Ultimate (2045) Scenario Flow Projections
The City’s projected population growth rate between 2035 and 2045 was used to determine a global multiplier intended to represent the increase in sewer flows in the Ultimate dry weather scenario. The change in dry weather flow from the Near-Term to the Ultimate scenario can be represented as an increase of approximately 10.8%. A global multiplier of 1.108 was applied to dry weather flows in the Near-Term scenario to create the Ultimate scenario and simulate overall densification throughout the City, as outlined below:

Ultimate Scenario ADWF = Population Multiplier x Near-Term Scenario ADWF Ultimate Scenario ADWF = 1.108 x 4.13 MGD

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The total ADWF in the Ultimate scenario is estimated to be 4.58 MGD. Should implementation of the LVSP accelerate within the next 5-10 years, it is recommended that the 2025 Update be revised to incorporate any significant new developments within the City’s service area. Public Works staff anticipate that development related to the LVSP will occur primarily in the northeast region of the City, with residential developments intended to support new employment opportunities generated by the KGRA to be constructed first.

3.4 Existing and Future Dry Weather Flow Summary
Table 3.5 summarizes the estimated ADWF generated within the City’s collection system for the Existing (2025) as well as the anticipated Near-Term (2035) and Ultimate (2045) dry weather flow scenarios.

Table 3.5. Existing and Future ADWF Summary
Planning Scenario (Year) Projected ADWF Increase (MGD) Total Estimated ADWF (MGD) Existing (2025) — 3.52
Near-Term (2035) 0.60 4.12
Ultimate (2045) 0.45 4.57

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4 Sewer Model Development
and Calibration
The following section summarizes the creation and calibration of a new trunk sewer model to represent the majority of flow through the City’s collection system. The section includes a description of the sewer flow monitoring program, manhole survey, and additional data collection efforts necessary for development of an accurate hydraulic model.

Once calibrated to existing dry and wet weather flow conditions, the trunk sewer model can be used to approximate the range of plausible flows that may be observed throughout the system. The calibrated sewer model is used as the basis for development and capacity evaluation of future flow scenarios, including the Near-Term and Ultimate.

4.1 March 2025 Flow Monitoring Program
Data collected by flow monitors is used to develop unit generation factors when the upstream sewershed is of uniform land use, allocate flows within the sewershed, and ultimately calibrate the model to existing conditions as measured in the field.

A 10-year or greater storm is ideal for measuring wet weather flows through a collection system. Defect flow (rainfall derived inflow and infiltration or RDII) is characterized by comparing the observed wet weather flows to typical ADWF throughout the system. A 10-year storm has a 10% chance of occurring in any given year, resulting in the average time between storms of such size as 10 years. Most likely, a temporary flow monitoring program will not capture a 10-year or greater storm. Therefore, historical flow information collected by existing monitors or at the treatment plant is often the best source of data for estimating defect flow in a collection system.

For the 2025 Update, nine flow monitors were installed within gravity mains throughout the City’s collection system.

One rain gauge was installed on the roof of the Public Works building at 307 W Brighton Avenue. Data collection occurred over a two-week period, from March 6 through March 19, 2025.

A flow monitoring report is included in Appendix D. The report summarizes the equipment, installation process, observed site conditions, and hydrograph reports for each flow monitor.

4.1.1 Sewersheds and Flow Schematic
Eight of the nine flow monitors were installed at the same locations as those evaluated in the 2008 Sewer Master Plan. Flow monitoring sites remained consistent to compare changes in dry weather flow over time and replicate the trunk model developed in 2008. FM 09 was added for the 2025 Update to measure flows entering the Alder Canal – Villa Ave Lift Station. Public Works staff have long suspected that the gravity main upstream and force main downstream of the lift station are significantly oversized for the tributary dry weather flow.

Figure 4.1 depicts the locations of all nine flow monitors and the extents of their upstream sewersheds. The active modeled trunk mains in each sewershed are highlighted.

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Figure 4.1 March 2025 Flow Monitor Locations and Sewersheds

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The portion of the City’s collection system from approximately Adams Ave or Villa Ave north to the wastewater treatment plant was not measured by any of the temporary flow monitors in March 2025. However, the flow generated in this area can be estimated as the difference between the influent flow to the treatment plant and the total flow measured by the downstream flow monitors (i.e., FM 01, FM 02, FM 07, and FM 09). Therefore, this area was designated as the “WWTP” sewershed since the treatment plant effectively serves as its permanent flow monitor.

Smaller sewersheds, such as FM 03 and FM 08, are expected to generate less flow than those located farther downstream that may collect flow from multiple upstream sewersheds in the system. The flow schematic in Figure 4.2 illustrates how flows generated in one area of the City’s collection system can be conveyed through various sewersheds, lift stations, or diversion manholes to reach the treatment plant. Where basins are arranged in series, the flow schematic can assist in validating the subtraction of upstream sewersheds to determine each individual sewershed’s contribution to overall flow through the system.

Figure 4.2 Existing System Flow Schematic

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4.1.2 Flow Monitoring Results Summary
The following observations are based on review of the flow monitoring data collected in March 2025:
▪ FM 06 is downstream of the primary direction of flow of a diversion manhole located at W Holt Ave and the alley west of S 8th St. During a typical dry weather flow period, all flow through the diversion manhole is assumed to be conveyed west into the 12-inch gravity main in Holt Ave (and therefore measured by FM 06). ▪ Two gravity mains run parallel in S 4th St, from Ross Ave north to State St. FM 05 measures flow through the 14-inch main on the west (i.e., southbound) side of S 4th St. During a typical dry weather flow period, the only flow assumed to be measured by FM 05 are local flows generated by the residences west of S 4th St, south of State St, and north of Ross Ave.
▪ FM 02 is located downstream of FM 03, FM 04, FM 05, and the overflow of the diversion manhole at W Holt Ave and S 8th St. The average flow recorded by FM 02 was 0.86 MGD. Based on the unit sewer generation factors developed in Section 3 and average flows through FM 03, FM 04, and FM05, the average flow at FM 02 should be approximately double the measured value of 0.86 MGD. ▪ Influent flow to Main Lift Station and the wastewater treatment plant (both downstream of FM 02) correspond to the expectation for higher measured flow at FM 02. Therefore, data collected by the temporary flow monitor at FM 02 was not used to calibrate the FM 02 sewershed. Instead, influent flow to Main Lift Station in March 2025 was used to calibrate the upstream system based on the relationship depicted in Figure 4.2.

The rain gauge recorded two minor precipitation events during the 2-week flow monitoring period:
▪ The total rainfall depth as measured by the rain gauge was 0.5 inches across both wet weather events. ▪ The wet weather events occurred on March 11 and March 13, 2025. Each event corresponded to a oneyear or lower frequency storm (Source: NOAA Atlas 14 Point Precipitation Frequency Estimates).

Since a 10-year storm did not occur during the flow monitoring period, historical influent flow data recorded at the wastewater treatment plant was used to calibrate the model to wet weather flow conditions as described in Section 4.4.

4.1.3 Dry Weather Time Patterns
March 2025 flow monitoring data was used to develop unique dry weather hourly time patterns for each sewershed.

An hourly time pattern is a series of 24 multipliers, one for each hour of the day, that is applied to the average dry weather flow value to approximate the observed daily fluctuations in flow within a sewershed. The multiplier assigned to each hour is also known as a peaking factor. Hourly patterns are created by normalizing measured sewer flows over a 24-hour (diurnal) period, such that the average of all peaking factors is 1.0.

The highest peaking factor in an hourly pattern represents the peak dry weather flow measured at the outlet of the sewershed, as summarized by the following formula:

Peak Dry Weather Flow (PDWF) = Maximum Peaking Factor (PF) x Average Dry Weather Flow (ADWF)

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As detailed in Section 4.3, the model calibration process involves the validation of both average and peak dry weather flows. The development of hourly patterns based on measured data facilitates the accurate representation of diurnal flow variations throughout the sewer model.

All but one (FM 09) of the nine flow monitors recorded higher ADWF on weekdays than weekends. PDWF recorded by FM 01 through FM 08 was approximately equal (within 3% difference) between weekdays and weekends, with peak flow occurring later in the day (i.e., after 7:00 PM) on weekdays. Therefore, most of the modeled trunk system was calibrated to weekday dry weather flow data. Only the FM 09 sewershed was calibrated to weekend dry weather flows.

Figure 4.3 depicts the diurnal dry weather patterns for FM 01 through FM 08 over a typical weekday. The weekend diurnal pattern for FM 09 is also included. Generally, smaller sewersheds exhibit a more significant peaking response (i.e., higher maximum peaking factor) due to the concentrated effect of fewer individual dischargers. The average weekday maximum peaking factor of FM 01 through FM 08 is 1.28.

The most significant sources of sewer flow in the FM 09 sewershed are the Imperial Valley Mall and The Plaza shopping center, both large commercial developments that are more heavily trafficked on weekends. The weekend maximum peaking factor of the FM 09 sewershed is 1.36.

The average of all weekday diurnal patterns for FM 01 through FM 08 was applied to the WWTP sewershed.

Weekday patterns were used since most of the collection system exhibits higher flows on weekdays compared to weekends. The ADWF of the WWTP sewershed was calculated as the difference between the influent flow to the treatment plant and the sum of average flows measured at the upstream sewersheds.

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Figure 4.3 Existing Dry Weather Hourly Time Patterns (Weekday and Weekend)

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4.2 Sewer Model Development
The principal tool used to analyze the capacity of a sewer collection system is a hydraulic model of the system. A sewer model is a digital representation of the physical collection network capable of simulating both dry and wet weather flow conditions across a range of planning scenarios (e.g., Existing, Near-Term, or Ultimate).

A new hydraulic model of the City’s collection system was developed using Aquanuity’s AquaTwin Sewer software.

AquaTwin Sewer runs as an extension to ArcGIS Pro, facilitating the seamless integration of existing GIS data during development and analysis of a sewer model.

A trunk model was developed for the 2025 Update due to missing or unverified GIS data on crucial attributes of the City’s collection system, including manhole invert elevations. The trunk model consists primarily of 12-inch or greater diameter sewer mains, in-line lift stations and associated force mains, and a single system outfall (i.e., wastewater treatment plant).

In general, larger diameter pipelines are more likely to experience capacity limitations as they convey flow from greater tributary areas. Therefore, a trunk model is an efficient means of representing the most important elements of a collection system for capacity analysis of the system. The following summarizes the data collected and used to create the trunk model.

4.2.1 Manhole Field Survey
According to Public Works staff, the City’s sewer GIS database is generally accurate in terms of existing pipeline diameter and connectivity. However, approximately 15% of the manholes in the GIS database are missing rim and invert elevation data. Manholes populated with elevation data have not been field verified and are of low confidence, per Public Works staff.

A hydraulic sewer model requires accurate pipe slopes to calculate the capacity of each gravity main segment.

Manhole invert elevations and the distance between manholes (i.e., pipe length) determine the slope of a gravity main. Therefore, any uncertainty in existing manhole invert elevation data may result in a lack of confidence in the modeled capacity results.

Based on discussions with Public Works staff, a field survey of existing manholes was deemed necessary to achieve confidence in the results of the 2025 Update. Given the significant cost associated with surveying every manhole in the system, it was determined that a survey of 100 manholes is adequate to develop a model of the primary trunk sewer pipelines that support the entire collection system. Such an abbreviated representation of the collection system is known as a skeletonized or trunk sewer model.

The 100 manhole survey was completed in March 2025 by a licensed surveyor, who collected rim and invert elevation data necessary for development of a trunk sewer model. Manholes were selected to maximize the modeled extents of each measured sewershed described in Section 4.1.1. Similarly, manholes along the trunk (i.e., 12-inch or greater) mains, at potential diversion sites, or at major street intersections with multiple sewer manholes were prioritized for survey to construct an accurate trunk sewer model. Figure 4.4 depicts the locations of the surveyed manholes.

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Since the City’s service area lies entirely below sea level, all surveyed rim and invert elevations were adjusted by 100 ft to avoid the use of negative values throughout the trunk sewer model. For example, a manhole rim and invert elevation of -45 ft and -53 ft as surveyed in the field are converted to 55 ft and 47 ft respectively, for inclusion in the sewer model.

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Figure 4.4 March 2025 Manhole Survey Locations

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4.2.2 Trunk Model Network Generation
A trunk model of the City’s sewer collection system was generated as follows:
▪ The City’s sewer GIS network was imported into AquaTwin Sewer as the basis of the new trunk sewer model. - Most 10-inch and smaller collection mains, especially those located within residential neighborhoods or on the outskirts of the City, were deactivated in the sewer model (i.e., not included in existing or future capacity analysis).
▪ Invert elevations for existing manholes located between survey points were interpolated using AquaTwin Sewer’s Calculate Inverts tool, which can assume a constant slope between two junctions (i.e., manholes) with known invert elevations.
- Of the 123 miles of gravity main in the City’s collection system, approximately 22 miles were included in the trunk sewer model.
▪ Six of the City’s 15 existing lift stations were included in the sewer model due to their location within the trunk system. All flow through the collection system is conveyed through at least one if not several of these lift stations.
- Wet well dimensions, influent gravity main invert elevations, pumping capacities, and other hydraulic characteristics for the six lift stations were obtained from Appendix A and incorporated into the trunk sewer model.

4.2.3 As-Built Record Drawing Updates
During development of the trunk sewer model, it was observed that several modifications or improvements to the collection network had not been incorporated into the City’s GIS database. As summarized in Table 4.1, Public Works staff provided as-built record drawings or other documentation for each improvement project. Only improvements pertaining to the modeled trunk system are included, as they may affect the capacity analysis presented in Section 5.

Table 4.1. System Improvements Not in Sewer GIS – Updated in Trunk Sewer Model As-Built
Drawing Set Location Description – Per As-Builts
Install
Year
10636 Wake Ave / Lift Station No. 2 Force
Main
All flow going into the gravity mains at
the Date Drain and Wake Ave
intersection was sent West on Wake Ave
and into LS 2
2016
10411,
10439
Holt Ave between 9th St Alley and at
Imperial Ave
Re-route flows from 9th St West into
Hold Ave, and from Holt Ave into the 12”
sewer on Imperial Ave
1952
10407,
10477
Wake Ave between Imperial Ave and
at La Brucherie
Re-route Imperial & Wake flows West to
LS 2
1993
March 2025
Survey
Ocotillo Dr between La Brucherie Rd
and Imperial Ave
Re-route flows on Ocotillo Dr East to the
12” sewer on Imperial Ave
N/A
Conversations
with City
Main Lift Station Force Main Removed abandoned force main coming from Main Lift Station into the Date
Approx.
1957

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Table 4.1. System Improvements Not in Sewer GIS – Updated in Trunk Sewer Model As-Built
Drawing Set Location Description – Per As-Builts
Install
Year
Canal, and route all flows through the
new force main into the treatment plant
8/10/2009
Construction
Plans
8th St and Fairfield Dr Pipeline
Replacement Project
Upsize 6-in VCP line on 8th St, between
Ross Ave and Southwind Dr with new 8-
in PVC line, and relocate MHs
2009

4.3 Existing Dry Weather Flow Allocation
Following development of the trunk sewer model network, average dry weather flows were allocated to each modeled manhole to create the existing dry weather flow scenario as follows:
▪ Generate Thiessen polygons around the modeled manholes using ArcGIS Pro spatial analysis tools - Each Thiessen polygon is uniquely associated with only one modeled manhole. - Thiessen polygons are used to estimate the number of individual parcels that may contribute sewer flows to the trunk system at each modeled manhole.
▪ Assign each parcel a unit sewer generation factor corresponding to its existing land use type (per Table 3.2 in Section 3.2.1)
▪ Calculate and allocate the ADWF to each modeled manhole as the sum of the ADWF generated by all existing parcels within its respective Thiessen polygon. This process was automated using AquaTwin Sewer’s Inflow Builder wizard.
▪ Assign each modeled manhole a diurnal dry weather pattern corresponding to the measured sewershed in which it resides.

The total dry weather flow assigned to each manhole was calculated based on unit sewer generation factors, existing land use, and area or dwelling units of the tributary parcels. Once ADWF and diurnal patterns were allocated throughout the trunk sewer model, the existing dry weather scenario was calibrated to measured flow data and used to develop wet weather and future flow scenarios.

4.3.1 Dry Weather Scenario Calibration Results
The existing dry weather flow scenario was calibrated by comparing the modeled average and peak flows through each sewershed to their measured counterparts and adjusting time patterns or ADWF allocations until the modeled and measured flow values are within 10% difference.

Table 4.2 presents the modeled average and peak dry weather flows and their measured equivalents for each sewershed identified in the 2025 Update. Most sewersheds were calibrated in the model to less than 5% difference of measured data.

Diurnal graphs of modeled and measured flows through each calibrated sewershed are included in Appendix E.

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Table 4.2. Model Calibration Results – Existing (2025) Dry Weather Flow Sewershed/
Flow
Monitor ID
Average Dry Weather Flow Peak Dry Weather Flow
Measured
(MGD)
Modeled
(MGD) % Difference
Measured
(MGD)
Modeled
(MGD) % Difference
FM 01 0.973 0.945 2.9% 1.205 1.163 3.5%
FM 021 0.856 1.138 33.0% 1.034 1.465 41.6%
FM 03 0.091 0.089 2.2% 0.111 0.109 2.3%
FM 04 0.383 0.377 1.5% 0.472 0.464 1.6%
FM 05 0.199 0.203 2.4% 0.263 0.270 2.4%
FM 06 0.547 0.530 3.1% 0.706 0.682 3.5%
FM 07 0.762 0.780 2.3% 1.039 1.038 0.04%
FM 08 0.191 0.194 1.8% 0.264 0.268 1.3%
FM 09 0.259 0.248 4.2% 0.354 0.361 2.1%
Notes:
1 FM 02 was calibrated to influent flow to Main Lift Station in March 2025. Data recorded by the temporary flow monitor at FM 02 was determined to be of unreliable quality for model calibration as detailed in Section 4.1.2.

4.4 Existing Wet Weather Flow Allocation
No significant wet weather event occurred in March 2025 during the flow monitoring program. Instead, historical daily influent flow data collected at the wastewater treatment plant was used to characterize the collection system’s response to RDII and develop an existing wet weather flow scenario.

Figure 4.5 depicts the average monthly and peak daily influent flows recorded at the treatment plant from January 2015 through July 2025. Average monthly flow is the average flow observed entering the treatment plant each month (i.e., average of 30 or 31 days), while peak daily flow is the maximum influent flow recorded on a single day each month. The absolute peak daily flow occurred on September 9, 2022, and coincided with Tropical Storm Kay sweeping across the City’s service area.

Table 4.3 summarizes the average and peak influent flow through the treatment plant from 2015 through 2025.

The various flow designations are defined as follows:
▪ Average Annual Flow: Average influent flow recorded at the treatment plant each year (i.e., average of 365 days)
▪ Peak Monthly Flow: Average influent flow for the month with the highest observed flow each year (e.g., in 2022, the peak monthly flow is attributed to September 2022) ▪ Peak Daily Flow: Maximum influent flow recorded on a single day each year (typically occurs during the month with the peak monthly flow)
▪ Peak Month Factor (PMF): Ratio of the peak monthly flow to the average annual flow. ▪ Peak Day Factor (PDF): Ratio of the peak daily flow to the average annual flow.

The maximum PDF observed at the treatment plant over the past decade was 1.62 and occurred in September 2022. Therefore, the wet weather flow scenario in the trunk sewer model was based on peak influent flow data from September 2022.

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Figure 4.5 Average Monthly and Peak Daily Influent Flow to Wastewater Treatment Plant (January 2015 – July 2025)

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Table 4.3. Annual Average and Peak Influent Flows to Plant (2015 – 2025) Year
Average Annual
Flow (MGD)
Peak Monthly
Flow (MGD)
Peak Month
Factor / PMF
Peak Daily
Flow (MGD)
Peak Day
Factor / PDF
2015 2.97 3.03 1.02 3.50 1.18
2016 3.14 3.46 1.10 3.60 1.15
2017 3.41 3.46 1.02 4.40 1.29
2018 3.42 3.53 1.03 5.00 1.46
2019 3.36 3.51 1.04 4.70 1.40
2020 3.25 3.39 1.04 4.90 1.51
2021 3.38 3.46 1.02 4.20 1.24
2022 3.46 3.69 1.07 5.60 1.62
2023 3.51 3.71 1.06 4.73 1.35
2024 3.55 3.67 1.03 5.05 1.42
2025 3.52 3.58 1.02 3.76 1.07
Average PDF 1.33
Maximum PDF (Year 2022) 1.62
Existing flow allocations from the dry weather scenario were inherited in the new wet weather scenario. In the wet weather scenario, defect flow or RDII was allocated throughout the modeled trunk system and estimated as the following:

Defect Flow = Average Wet Weather Flow (AWWF) - Average Dry Weather Flow (ADWF) In the above, AWWF and ADWF are equivalent to the Peak Daily Flow and Average Annual Flow presented in Table 4.3, respectively. Using an AWWF of 5.60 MGD and ADWF of 3.46 MGD, the total defect flow estimated as entering the collection system in the September 2022 wet weather event is 2.14 MGD.

Following discussions with Public Works staff, the 2.14 MGD of defect flow was distributed in the following manner across the trunk sewer model:
▪ 0.85 MGD or 40% of the total defect flow was allocated to the trunk system tributary to Eastside Lift Station (or FM 05 sewershed)
▪ 0.85 MGD or 40% of the total defect flow was allocated to the trunk system tributary to Alder Canal – Villa Ave Lift Station (or FM 09 sewershed)
▪ 0.43 MGD or 20% of the total defect flow was allocated to the remainder of the trunk system The “40/40/20” defect flow allocation method is based on SCADA data at Lift Station No. 3 and Eastside Lift Station in September 2022. Eastside Lift Station recorded a significant increase in influent flow during the wet weather event relative to its average influent dry weather flow.

Similarly, Lift Station No. 3 also experienced a sudden influx of flow. The primary lift stations tributary to Lift Station No. 3 are Lift Station No. 2, Orange, and Alder Canal – Villa Ave Lift Station. SCADA data at Lift Station No. 2 and Orange Lift Station exhibited minimal variation between dry weather days and Tropical Storm Kay. Therefore, most

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defect flow into Lift Station No. 3 was assumed to originate from the collection system upstream of Alder Canal – Villa Ave Lift Station.

Since the treatment plant only records influent flow daily (i.e., one data entry per day), hourly flow data was not readily available to generate a diurnal wet weather pattern for calibration of the trunk model to observed wet weather flow conditions. According to Public Works staff, the maximum instantaneous peak flow observed entering the treatment plant was approximately 9.0 MGD.

The following relationship was used to derive a maximum peaking factor for the September 2022 wet weather calibration event:

Peak Wet Weather Flow (PWWF) = Maximum Wet Weather Peaking Factor (WW PF) x Average Dry Weather Flow (ADWF) Assuming a PWWF of 9.0 MGD and ADWF of approximately 3.46 MGD, the maximum wet weather peaking factor for the overall collection system is 2.6. Figure 4.6 depicts the diurnal wet weather pattern applied uniformly to the defect flow allocated throughout the trunk model:

Figure 4.6 Diurnal Wet Weather Pattern for Defect Flow

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4.4.1 Wet Weather Model Calibration Results
The existing wet weather flow scenario was calibrated by comparing the modeled average and peak flows into the treatment plant to their measured counterparts from September 2022 and adjusting the diurnal wet weather pattern until modeled and measured flow values are within 10% difference.

Table 4.4 presents the modeled average and peak wet weather flows and their measured equivalents recorded at the treatment plant.

Table 4.4. Model Calibration Results – Existing (September 2022) Wet Weather Flow Outfall
Average Wet Weather Flow Peak Wet Weather Flow
Measured
(MGD)
Modeled
(MGD) % Difference
Measured
(MGD)
Modeled
(MGD) % Difference
WWTP 5.60 5.64 0.70% 9.00 9.22 2.4%

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5 Collection System Capacity Analysis
The following section summarizes the recommended design and deficiency criteria used to implement new sewer improvements and evaluate the capacity of the City’s existing collection system. The section presents the capacity analysis results for the modeled trunk system in the Existing, Near-Term, and Ultimate planning scenarios under dry and wet weather flow conditions. Lastly, the section evaluates the pumping and storage capacity of each modeled lift station and analyzes the feasibility of removing any existing lift stations from service or optimizing their performance.

The results of the modeled capacity analysis are used to identify existing constraints and anticipate future areas of concern due to projected growth or development within the collection system. Each potential capacity deficiency is evaluated on an individual basis and may result in a recommended improvement project for incorporation into the City’s CIP.

5.1 System Design Criteria
System design criteria are used to design and implement new facilities intended to improve the existing level of service or accommodate projected future flows within the collection system. Following discussions with Public Works staff, it was determined that no modifications need to be made to the recommended design criteria presented in the 2008 Sewer Master Plan.

5.1.1 Gravity Main Design Criteria
Table 5.1 summarizes the recommended gravity main design criteria from the 2008 Sewer Master Plan. The following criteria should be used to determine the diameter and other design parameters of proposed new gravity mains within the City’s collection system.

Table 5.1. Recommended Design Criteria – Gravity Mains
General Criteria Minimum Diameter 8 inch
Minimum Velocity when Pipeline is Flowing Half Full 2.0 fps Minimum Velocity at PDWF for Inverted Siphons1 3.0 fps
Manning’s Roughness Coefficient “n” 0.013
Maximum d/D2 at PDWF Diameter < 12-inch 0.50
Diameter ≥ 12-inch 0.75
Maximum d/D at PWWF All Diameters 0.9
Notes:
1 According to Public Works staff, there are no siphons within the City’s existing collection system. A recommended minimum velocity is provided should siphons be required during future improvement projects. 2 d/D refers to the ratio of water depth to pipeline diameter in a gravity main.

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The capacity within a gravity sewer depends upon its pipeline diameter, roughness, allowable flow depth, and slope as determined by Manning’s Equation:

𝑸 = 𝟏. 𝟒𝟖𝟔 × 𝑨 × 𝑹
𝟐/𝟑 × 𝑺𝟏/𝟐 × 𝒏−𝟏
Where:

𝑄 = Volumetric flow rate (cubic feet per second)
𝐴 = Cross-section area of flow (square feet)
𝑅 = Hydraulic radius (feet)
𝑆 = Pipe slope (feet per feet)
𝑛 = Manning’s roughness coefficient
Where:

𝑅 = 𝐴/𝑃
𝑃 = Wetted perimeter (feet)
The maximum depth over diameter ratio (d/D) of a pipeline can be derived using Manning’s Equation and is the primary value used to evaluate the available capacity of an existing or proposed gravity main.

In general, gravity mains are not intended to flow full (i.e., maximum d/D of 1.0), as unoccupied space at the top of the pipe is required to accommodate sewer gases as well as a measure of inflow and infiltration (I&I) entering the system during wet weather events. In a standard sewer collection system, gravity mains that are constantly flowing at or near full capacity may be at increased risk of spills during a significant wet weather event.

The Manning’s roughness coefficient (“n”) of pipelines varies with material and age. A roughness coefficient of

0.013 is commonly used to evaluate existing pipeline capacity and assess future system needs. Studies have indicated that a roughness coefficient of 0.013 is a conservative estimate of the average friction factor of typical sewer gravity mains over their useful lifespan.

5.1.2 Lift Station and Force Main Design Criteria
Table 5.2 summarizes the recommended lift station and force main design criteria for the City’s collection system.

The force main design criteria are the same as those presented in the 2008 Sewer Master Plan. Low force main velocities can result in solids deposition within the pipeline and generate long-term maintenance issues for Public Works staff. Conversely, excessively high velocities can damage the force main through abrasion and prompt early replacement or rehabilitation of the pipeline.

The 2008 Sewer Master Plan recommended that lift stations be designed to accommodate peak wet weather flow with one standby pump. A standard lift station is equipped with at least two pump units, duty and standby. The design capacity of the standby pump should be the same as that of the largest duty pump unit.

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Additional lift station design criteria introduced in the 2025 Update include a source of emergency backup power, provided via on-site generators or provisions for a portable generator connection. Lastly, the lift station wet well structure should have adequate capacity to store at least six hours of average dry weather flow during an emergency event. Emergency storage capacity is taken as the volume between the lag pump on level setting and high water level of the wet well.

Table 5.2. Recommended Design Criteria – Lift Stations & Force Mains Lift Station Criteria Minimum Number of Pumps 2
Minimum Rated Capacity of Pump Duty pump capable of handling peak flow
Standby Pump Capacity 100% of the largest pump
capacity
Emergency Storage Capacity 6 hours of ADWF
Emergency Backup Power Required
Force Main Criteria Minimum Diameter 6 inch
Minimum Velocity 2.0 fps
Maximum Velocity 8.0 fps
Hazen-Williams Coefficient “C” 120

5.2 System Deficiency Criteria
While design criteria should be incorporated in the planning and construction of new sewer facilities, separate and distinct deficiency criteria are used to determine when existing infrastructure should be replaced with a larger diameter pipeline or higher capacity lift station to mitigate the risk of a spill or other service interruption. Such deficiency criteria are also referred to as “trigger” criteria because they result in a recommendation for an improvement project.

5.2.1 Gravity Main Deficiency Criteria
Table 5.3 summarizes the gravity main deficiency criteria used to evaluate the capacity of the City’s existing gravity collection system. Following discussions with Public Works staff, it was determined that a maximum d/D of 1.0 (i.e., pipe flowing full) will be used as the sole deficiency criteria when evaluating the capacity of existing gravity mains under both dry and wet weather flow conditions, regardless of pipeline diameter.

Within each model scenario, any existing gravity mains in the City’s trunk sewer model with a maximum d/D of 1.0 will be recommended for upsizing or an alternative improvement project (e.g., flow diversion, etc.).

Table 5.3. 2025 Update Deficiency Criteria – Gravity Mains Maximum d/D at PDWF All Diameters 1.0
Maximum d/D at PWWF All Diameters 1.0

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5.2.2 Lift Station and Force Main Deficiency Criteria
Table 5.4 summarizes the deficiency criteria used to evaluate the capacity of existing lift stations in the City’s collection system. Deficiency criteria for force main velocity and lift station pumping capacity are identical to their design counterparts. However, the storage capacity and presence of emergency backup power at existing lift stations shall be evaluated on a case-by-case basis.

Certain lift stations may be constrained by the physical limitations of their existing site, which render a significant wet well expansion or on-site generator storage infeasible.

Table 5.4. 2025 Update Deficiency Criteria – Lift Stations & Force Mains Lift Station Criteria Minimum Rated Capacity of Pump Duty pump capable of handling peak flow
Standby Pump Capacity 100% of the largest pump
capacity
Emergency Storage Capacity Case-by-case basis
Emergency Backup Power Case-by-case basis
Force Main Criteria Minimum Velocity 2.0 fps
Maximum Velocity 8.0 fps

5.3 Dry Weather Capacity Analysis
The following sections present the results of the capacity analysis on the trunk sewer model under Existing (2025), Near-Term (2035), and Ultimate (2045) dry weather flow conditions.

5.3.1 Existing (2025) Dry Weather Flow
The City’s trunk sewer model was analyzed in the Existing dry weather flow scenario. Maximum d/D of all modeled gravity mains over a representative 24-hour period were compared to the deficiency criteria presented in Section 5.2.1.

As shown in Figure 5.1, no modeled gravity mains are anticipated to exceed the deficiency criteria under Existing dry weather flow conditions.

5.3.2 Near-Term (2035) Dry Weather Flow
The City’s trunk sewer model was analyzed in the Near-Term dry weather flow scenario. In addition to the planned near-term developments defined in Section 3.2.2, the Near-Term scenario incorporates the City’s planned abandonment of the 4th and Wake, Legacy, and Countryside lift stations and construction of the Southern lift station at the intersection of W Danenberg Dr and Farnsworth Ln. All dry weather flow tributary to the three soonto-be abandoned lift stations was reallocated to the assumed gravity discharge manhole of the Southern lift station at E Danenberg Dr and S Dogwood Rd in the Near-Term scenario.

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Maximum d/D of all modeled gravity mains over a representative 24-hour period were compared to the deficiency criteria presented in Section 5.2.1. As with the Existing scenario, no modeled gravity mains are anticipated to exceed the deficiency criteria under Near-Term dry weather flow conditions. Figure 5.2 depicts the results of the capacity analysis in the Near-Term scenario.

5.3.3 Ultimate (2045) Dry Weather Flow
The City’s trunk sewer model was analyzed in the Ultimate dry weather flow scenario. Maximum d/D of all modeled gravity mains over a representative 24-hour period were compared to the deficiency criteria presented in Section 5.2.1.

As with the Existing and Near-Term scenarios, no modeled gravity mains are anticipated to exceed the deficiency criteria under Ultimate dry weather flow conditions. The results of the capacity analysis closely resemble those shown in Figure 5.2.

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Figure 5.1 Existing (2025) Dry Weather Flow Capacity Analysis Results – Maximum Pipeline d/D

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Figure 5.2 Near-Term (2035) Dry Weather Flow Capacity Analysis Results – Maximum Pipeline d/D

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5.4 Wet Weather Capacity Analysis
The following sections present the results of the capacity analysis on the trunk sewer model under Existing (2025), Near-Term (2035), and Ultimate (2045) wet weather flow conditions.

5.4.1 Existing (2025) Wet Weather Flow
The City’s trunk sewer model was analyzed in the Existing wet weather flow scenario. Maximum d/D of all modeled gravity mains over a representative 24-hour period were compared to the deficiency criteria presented in Section 5.2.1.

Table 5.5 summarizes the two potential capacity deficiencies identified under Existing peak wet weather flow conditions. The locations of the deficiencies are depicted in Figure 5.3.

Table 5.5. Existing (2025) System Pipeline Capacity Deficiencies – PWWF Deficiency
ID Location
Ex. Diameter
(inch)
Ex. Worst
Condition Length (LF)
EX-1 N 8th St at Villa Ave 8 Max d/D = 1.0 460
EX-2 Fairfield Dr from Hamilton Ave north to
Commercial Ave; Commercial Ave from
Fairfield Dr west to Eastside lift station
15; 18 Max d/D = 1.0 5,800
Total 6,260
Deficiency EX-1 arises from backwater effects observed within the existing 8-inch main in N 8th St, which connects directly to the 27-inch trunk main in Villa Ave. The tributary area of the 8-inch main in N 8th St is limited, with no planned near-term developments upstream. Considering the depth of the trunk main in Villa Ave at N 8th St (i.e., at least 18.5 ft deep) and less than 6 inches of anticipated surcharge over the top of pipe crown in the 8-inch gravity main, EX-1 will not be recommended for upsizing in the 2025 Update.

Deficiency EX-2 results from the high defect flow allocated to the FM 04 sewershed during development of the wet weather scenario in Section 4.4. The FM 04 sewershed is tributary to the Eastside lift station, which recorded significantly elevated influent flow during the wet weather calibration event. Therefore, EX-2 may not be due to undersized pipelines but instead a higher than average rate of RDII throughout the Eastside lift station’s tributary area. To address EX-2, an alternative to a traditional pipeline upsizing project is recommended and detailed in Section 7.1.

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Figure 5.3 Existing (2025) Wet Weather Flow Capacity Analysis Results – Maximum Pipeline d/D

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5.4.2 Near-Term (2035) Wet Weather Flow
The City’s trunk sewer model was analyzed in the Near-Term wet weather flow scenario. Maximum d/D of all modeled gravity mains over a representative 24-hour period were compared to the deficiency criteria presented in Section 5.2.1.

As summarized in Table 5.6 and depicted in Figure 5.4, the two potential capacity deficiencies identified in the Existing wet weather flow scenario are anticipated to persist in the Near-Term. The maximum d/D of modeled gravity mains in 4th St downstream of the abandoned 4th and Wake lift station are anticipated to improve following the redirection of tributary flow to the Southern lift station.

Table 5.6. Near-Term (2035) System Pipeline Capacity Deficiencies – PWWF Deficiency
ID Location
Ex. Diameter
(inch)
Ex. Worst
Condition Length (LF)
EX-1 N 8th St at Villa Ave 8 Max d/D = 1.0 460
EX-2 Fairfield Dr from Hamilton Ave north to
Commercial Ave; Commercial Ave from
Fairfield Dr west to Eastside lift station
15; 18 Max d/D = 1.0 5,800
Total 6,260

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Figure 5.4 Near-Term (2035) Wet Weather Flow Capacity Analysis Results – Maximum Pipeline d/D

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5.4.3 Ultimate (2045) Wet Weather Flow
The City’s trunk sewer model was analyzed in the Ultimate wet weather flow scenario. Maximum d/D of all modeled gravity mains over a representative 24-hour period were compared to the deficiency criteria presented in Section 5.2.1.

As summarized in Table 5.7 and depicted in Figure 5.5, the two potential capacity deficiencies identified in the Existing and Near-Term wet weather flow scenarios are anticipated to persist in the Ultimate system.

Table 5.7. Ultimate (2045) System Pipeline Capacity Deficiencies – PWWF Deficiency
ID Location
Ex. Diameter
(inch)
Ex. Worst
Condition Length (LF)
EX-1 N 8th St at Villa Ave 8 Max d/D = 1.0 460
EX-2 Fairfield Dr from Hamilton Ave north to
Commercial Ave; Commercial Ave from
Fairfield Dr west to Eastside lift station
15; 18 Max d/D = 1.0 5,800
Total 6,260

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Figure 5.5 Ultimate (2045) Wet Weather Flow Capacity Analysis Results – Maximum Pipeline d/D

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5.5 Lift Station and Force Main Capacity Analysis
Six of the City’s existing 15 lift stations and their force mains were included in the trunk sewer model. A pumping capacity analysis was completed by comparing the firm capacity of each modeled lift station to its peak influent flow in the calibrated trunk model. The firm capacity of a lift station is its capacity with the largest pump taken out of service.

An emergency storage capacity analysis was also completed for each modeled lift station. The storage analysis results provide an estimate of the total time in hours that may elapse before the volume of sewage in the wet well exceeds the high water level during a power outage or other emergency event. During this time, Public Works staff can establish a source of emergency backup power for the impacted lift station via on-site or portable generators.

The storage analysis completed for each lift station does not include potential storage within the upstream gravity collection system. High water level settings were generally unavailable for the City’s lift stations; therefore, the high water level of each lift station was assumed to be the invert elevation of the influent gravity main per as-built record drawings. The following terms are used when evaluating the emergency storage capacity of a lift station:
▪ Total Wet Well Volume: The volume (in MG) of the wet well assuming the height dimension is the difference between the high water level setting and the wet well floor elevation. ▪ Operational Volume: The volume (in MG) of the wet well assuming the heigh dimension is the difference between the lag pump on level setting and the wet well floor elevation. ▪ Emergency Volume: The difference between the Total Wet Well Volume and Operational Volume as defined above. Equivalent to the volume (in MG) of the wet well assuming the heigh dimension is the difference between the lag pump on and high water level settings.
▪ Recommended Emergency Volume: The volume (in MG) equivalent to six hours of modeled ADWF through each lift station.

5.5.1 Lift Station No. 3
Lift Station No. 3 is comprised of three 40 hp pumps and a 32 ft x 10 ft x 31.3 ft rectangular wet well. Two of the pumps are soft starts (converted from VFD), with the third pump remaining on VFD. Tables 5.8 and 5.9 summarize the results of the pumping and emergency storage capacity analysis for Lift Station No. 3.

Table 5.8. Lift Station No. 3 Capacity Analysis – PWWF
Planning
Scenario
(Year)
Capacity (gpm) Total
Capacity
(gpm /
MGD)
Firm
Capacity
(gpm / MGD)
PWWF
(MGD)
Deficient?
Pump 1 Pump 2 Pump 3 (Yes/No)
Existing (2025) 3,000 3,000 3,000 9,000 / 13.0 6,000 / 8.64 3.93 No Near-Term
(2035)
3,000 3,000 3,000 9,000 / 13.0 6,000 / 8.64 4.46 No
Ultimate (2045) 3,000 3,000 3,000 9,000 / 13.0 6,000 / 8.64 4.63 No

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All three pumps at Lift Station No. 3 have a design capacity of 3,000 gpm at 37 ft of TDH. Table 5.8 demonstrates that with any one pump out of service, Lift Station No. 3 has adequate firm capacity to pump the modeled peak influent flow under wet weather conditions in each planning scenario.

Modeled flow through the 24-inch force main achieves a velocity of 3.2 fps and 9.1 fps under Existing PDWF and Ultimate PWWF conditions, respectively. The anticipated force main velocity of 9.1 fps is slightly greater than

8.0 fps; however, no improvements are currently recommended due to the uncertainty of development associated with the Ultimate scenario.

Table 5.9. Lift Station No. 3 Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operationa
l Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/ No)
Existing
(2025)

0.012 0.016 0.00 1.65 0.41 0.41 0.00 Yes
Near-Term
(2035)

0.012 0.016 0.00 2.31 0.58 0.58 0.00 Yes
Ultimate
(2045)

0.012 0.016 0.00 2.61 0.65 0.65 0.00 Yes
The wet well’s lag pump on level and high water level settings are 6.5 ft and 5 ft, respectively. Since the pump on level is greater than the high water level, there is assumed to be no emergency storage within the Lift Station No. 3 wet well. Table 5.9 demonstrates that in each planning scenario, the wet well does not contain any emergency storage for the modeled ADWF through Lift Station No. 3.

5.5.2 Main Lift Station
The Main Lift Station is comprised of three 50 hp VFD pumps and a 32 ft deep circular wet well with a diameter of 24 ft. Tables 5.10 and 5.11 summarize the results of the pumping and emergency storage capacity analysis for Main Lift Station.

Table 5.10. Main Lift Station Capacity Analysis – PWWF
Planning
Scenario
(Year)
Capacity (gpm) Total
Capacity
(gpm /
MGD)
Firm
Capacity
(gpm / MGD)
PWWF
(MGD)
Deficient?
Pump 1 Pump 2 Pump 3 (Yes/No)
Existing (2025) 2,535 2,535 2,535 7,605 / 11.0 5,070 / 7.30 5.29 No Near-Term
(2035)
2,535 2,535 2,535 7,605 / 11.0 5,070 / 7.30 5.35 No
Ultimate (2045) 2,535 2,535 2,535 7,605 / 11.0 5,070 / 7.30 5.62 No

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All three pumps at Main Lift Station have a design capacity of 2,535 gpm at 39 ft of TDH. Table 5.10 demonstrates that with any one pump out of service, Main Lift Station has adequate firm capacity to pump the modeled peak influent flow under wet weather conditions in each planning scenario.

Modeled flow through the 30-inch force main achieves a velocity of 1.6 fps and 2.5 fps under Existing PDWF and Ultimate PWWF conditions, respectively. The modeled force main velocity of 1.6 fps is slightly less than 2.0 fps; however, no improvements are recommended as influent flow to Main Lift Station will increase during a wet weather event and produce higher force main velocities.

Table 5.11. Main Lift Station Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operational
Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/ No)
Existing
(2025)

0.034 0.010 0.024 3.10 0.77 0.75 0.18 Yes
Near-Term
(2035)

0.034 0.010 0.024 3.21 0.80 0.78 0.18 Yes
Ultimate
(2045)

0.034 0.010 0.024 3.55 0.89 0.86 0.16 Yes
The wet well’s lag pump on level and high water level settings are 3 ft and 10 ft, respectively. Table 5.11 demonstrates that in each planning scenario, the wet well contains approximately ten minutes or less of emergency storage for the modeled ADWF through Main Lift Station.

5.5.3 Alder Canal – Villa Ave Lift Station
The Alder Canal – Villa Ave Lift Station is comprised of two 60 hp VFD pumps and a 16.3 ft x 27 ft x 32 ft rectangular wet well. Tables 5.12 and 5.13 summarize the results of the pumping and emergency storage capacity analysis for Alder Canal – Villa Ave Lift Station.

Table 5.12. Alder Canal – Villa Ave Lift Station Capacity Analysis – PWWF Planning Scenario
(Year)
Capacity (gpm)
Total Capacity
(gpm / MGD)
Firm Capacity
(gpm / MGD)
PWWF
(MGD)
Deficient?
(Yes/No)
Pump
1 Pump
2 Existing (2025) 1,908 1,908 3,816 / 5.50 1,908 / 2.75 1.16 No Near-Term (2035) 1,908 1,908 3,816 / 5.50 1,908 / 2.75 1.48 No Ultimate (2045) 1,908 1,908 3,816 / 5.50 1,908 / 2.75 1.59 No Both pumps at Alder Canal – Villa Ave Lift Station have a design capacity of 1,908 gpm at 76.6 ft of TDH. Table 5.12 demonstrates that with one pump out of service, Alder Canal – Villa Ave Lift Station has adequate firm capacity to pump the modeled peak influent flow under wet weather conditions in each planning scenario.

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Modeled flow through the 20-inch force main achieves a velocity of 1.1 fps and 1.2 fps under Existing PDWF and Ultimate PWWF conditions, respectively. The force main velocity is less than 2.0 fps in all flow scenarios due to the large diameter of the force main and relatively low influent flow to the lift station.

Table 5.13. Alder Canal – Villa Ave Lift Station Wet Well Emergency Storage Analysis – ADWF
Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operational
Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/ No)
Existing
(2025)

0.050 0.023 0.026 0.37 0.09 0.07 1.71 Yes
Near-Term
(2035)

0.050 0.023 0.026 0.67 0.17 0.14 0.96 Yes
Ultimate
(2045)

0.050 0.023 0.026 0.77 0.19 0.17 0.82 Yes
The wet well’s lag pump on level and high water level settings are 7 ft and 15 ft, respectively. Table 5.13 demonstrates that in the Existing scenario, the wet well contains more than 90 minutes of emergency storage for the modeled ADWF through Alder Canal – Villa Ave Lift Station. The emergency storage duration decreases significantly in future scenarios as additional flow from the new Southern Lift Station is routed into the existing lift station.

5.5.4 4th & Wake Lift Station
The 4th & Wake Lift Station is comprised of two 10 hp constant speed pumps and a 19.9 ft deep circular wet well with a diameter of 5.5 ft. Tables 5.14 and 5.15 summarize the results of the pumping and emergency storage capacity analysis for 4th & Wake Lift Station. The 4th & Wake Lift Station was only analyzed in the Existing scenario, as it is one of three lift stations that will be abandoned and replaced with the new Southern Lift Station prior to the Near-Term.

Table 5.14. 4th & Wake Lift Station Capacity Analysis – PWWF Planning Scenario
(Year)
Capacity (gpm)
Total Capacity
(gpm / MGD)
Firm Capacity
(gpm / MGD)
PWWF
(MGD)
Deficient?
(Yes/No)
Pump
1 Pump
2 Existing (2025) 200 200 400 / 0.58 200 / 0.29 0.09 No Both pumps at 4th & Wake Lift Station have a design capacity of 200 gpm at an unknown TDH. Table 5.14 demonstrates that with one pump out of service, 4th & Wake Lift Station has adequate firm capacity to pump the modeled peak influent flow under wet weather conditions in the Existing scenario. Modeled flow through the 4-inch force main achieves a maximum velocity of 3.2 fps under Existing PDWF conditions.

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Table 5.15. 4th & Wake Lift Station Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operationa
l Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/No)
Existing
(2025)

0.0014 0.0011 0.0003 0.085 0.0212 0.0209 0.085 Yes
The wet well’s lag pump on level and high water level settings are 6.3 ft and 8 ft, respectively. Table 5.15 demonstrates that in the Existing scenario, the wet well contains only 5 minutes of emergency storage for the modeled ADWF through 4th & Wake Lift Station.

5.5.5 Lift Station No. 2
Lift Station No. 2 is comprised of two 15 hp constant speed pumps and a 26.4 ft deep circular wet well with a diameter of 10 ft. Tables 5.16 and 5.17 summarize the results of the pumping and emergency storage capacity analysis for Lift Station No. 2.

Table 5.16. Lift Station No. 2 Capacity Analysis – PWWF Planning Scenario
(Year)
Capacity (gpm)
Total Capacity
(gpm / MGD)
Firm Capacity
(gpm / MGD)
PWWF
(MGD)
Deficient?
(Yes/No)
Pump
1 Pump
2 Existing (2025) 850 850 1,700 / 2.45 850 / 1.22 0.71 No Near-Term (2035) 850 850 1,700 / 2.45 850 / 1.22 0.63 No Ultimate (2045) 850 850 1,700 / 2.45 850 / 1.22 0.67 No Both pumps at Lift Station No. 2 have a design capacity of 850 gpm at 30 ft of TDH. Table 5.16 demonstrates that with one pump out of service, Lift Station No. 2 has adequate firm capacity to pump the modeled peak influent flow under wet weather conditions in each planning scenario. The peak influent flow decreases in future scenarios as a portion of the collection system that is currently tributary to Lift Station No. 2 will be routed east into the new Southern Lift Station. Modeled flow through the 12-inch force main achieves a velocity of 3.2 fps and 3.3 fps under Existing PDWF and Ultimate PWWF conditions, respectively.

Table 5.17. Lift Station No. 2 Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operational
Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/No)
Existing
(2025)

0.0041 0.0041 0.00 0.58 0.14 0.14 0.00 Yes

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Table 5.17. Lift Station No. 2 Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operational
Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/No)
Near-Term
(2035)

0.0041 0.0041 0.00 0.49 0.12 0.12 0.00 Yes
Ultimate
(2045)

0.0041 0.0041 0.00 0.55 0.14 0.14 0.00 Yes
The wet well’s lag pump on level and high water level settings are both 7 ft. Since the pump on level is equal to the high water level, there is assumed to be no emergency storage within the Lift Station No. 2 wet well. Table 5.17 demonstrates that in each planning scenario, the wet well does not contain any emergency storage for the modeled ADWF through Lift Station No. 2.

5.5.6 Eastside Lift Station
The Eastside Lift Station is comprised of two 15 hp constant speed pumps and a 27.4 ft deep circular wet well with a diameter of 10 ft. Tables 5.18 and 5.19 summarize the results of the pumping and emergency storage capacity analysis for Eastside Lift Station.

Table 5.18. Eastside Lift Station Capacity Analysis – PWWF Planning Scenario
(Year)
Capacity (gpm)
Total Capacity
(gpm / MGD)
Firm Capacity
(gpm / MGD)
PWWF
(MGD)
Deficient?
(Yes/No)
Pump
1 Pump
2 Existing (2025) 1,132 1,132 2,264 / 3.26 1,132 / 1.63 3.21 Yes Near-Term (2035) 1,132 1,132 2,264 / 3.26 1,132 / 1.63 2.68 Yes Ultimate (2045) 1,132 1,132 2,264 / 3.26 1,132 / 1.63 2.58 Yes Both pumps at Eastside Lift Station have a design capacity of 1,132 gpm at 26 ft of TDH. Table 5.18 demonstrates that with one pump out of service, Eastside Lift Station does not have adequate firm capacity to pump the modeled peak influent flow under wet weather conditions in each planning scenario. Modeled flow through the 10-inch force main achieves a velocity of 6.1 fps and 6.2 fps under Existing PDWF and Ultimate PWWF conditions, respectively.

Table 5.19. Eastside Lift Station Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operational
Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/No)
Existing
(2025)

0.0041 0.0041 0.00 0.46 0.12 0.12 0.00 Yes

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Table 5.19. Eastside Lift Station Wet Well Emergency Storage Analysis – ADWF Planning
Scenario
(Year)
Total
Wet
Well
Volume
(MG)
Operational
Volume
(MG)
Emergency
Volume
(MG)
ADWF
(MGD)
Recommended
Emergency
Volume (MG)
Emergency
Volume
Deficiency
(MG)
Emergency
Storage
Duration
(hrs)
Deficient?
(Yes/No)
Near-Term
(2035)

0.0041 0.0041 0.00 0.53 0.13 0.13 0.00 Yes
Ultimate
(2045)

0.0041 0.0041 0.00 0.59 0.15 0.15 0.00 Yes
The wet well’s lag pump on level and high water level settings are both 7 ft. Since the pump on level is equal to the high water level, there is assumed to be no emergency storage within the Eastside Lift Station wet well. Table 5.19 demonstrates that in each planning scenario, the wet well does not contain any emergency storage for the modeled ADWF through Eastside Lift Station.

5.5.7 Lift Station Optimization Analysis
As depicted in Figure 5.2 and others, once constructed the Southern Lift Station will convey flow through the easternmost trunk main of the collection system to Alder Canal – Villa Ave Lift Station. By the Near-Term scenario, the Southern Lift Station will replace the existing 4th & Wake, Countryside, and Legacy lift stations, resulting in noticeably higher flows through Alder Canal – Villa Ave Lift Station. However, as demonstrated in Sections 5.4 and

5.5.3, the gravity main upstream of Alder Canal – Villa Ave Lift Station and the pumping units have adequate capacity to accommodate additional flows from Southern Lift Station under both dry and wet weather conditions.

Similarly, Public Works staff have considered decommissioning the Heil & Dogwood and Eastside lift stations and rerouting all tributary flow east to leverage the significant remaining available capacity at Alder Canal – Villa Ave Lift Station. However, the topography of Heil Ave and Commercial Ave is not conducive to uninterrupted gravity flow from the Heil & Dogwood and Eastside lift stations to Alder Canal – Villa Ave. New lift stations will be required to route the tributary flows east, negating any benefits of eliminating the existing lift stations.

Lastly, the Main Lift Station receives flow from trunk mains within Villa Ave and Imperial Ave, which converge at a single manhole at the intersection of Villa and Imperial Ave. From this manhole, a single gravity line conveys flow into Main Lift Station. Public Works staff recognize the manhole may be a critical point of failure within the collection system due to its prominent location upstream of Main Lift Station and lack of redundancy.

To establish separate influent lines to Main Lift Station from the east and south, a reconfiguration of the single manhole at Villa and Imperial Ave was evaluated in the Ultimate wet weather flow scenario. No new capacity deficiencies were identified due to the modification, which will improve the reliability and hydraulic performance of the existing system.

5.6 Capacity Analysis Summary
The Existing dry and wet weather flow scenarios evaluated in the preceding capacity analyses are based on the calibrated conditions described in Sections 4.3 and 4.4, respectively.

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The Near-Term dry weather scenario is based on the calibrated Existing dry weather scenario, with the ADWF from each planned near-term development applied to the nearest modeled trunk sewer manhole. Finally, the Ultimate dry weather scenario is based on the Near-Term with a global multiplier of 1.108 applied to each ADWF loading.

Similarly, the Near-Term wet weather scenario is based on the calibrated Existing wet weather scenario, with the ADWF from each planned near-term development applied to the nearest modeled trunk sewer manhole. The Ultimate wet weather scenario is based on the Near-Term with a global multiplier of 1.108 applied to each ADWF loading. The defect flows developed in the Existing wet weather scenario were unmodified in the Near-Term and Ultimate.

Table 5.20 summarizes the existing and future modeled ADWF and PWWF for each planning scenario.

Table 5.20. Existing and Future Sewer Flows in Trunk Sewer Model Planning Scenario (Year) ADWF (MGD) PWWF (MGD)
Existing (2025) 3.78 9.22
Near-Term (2035) 4.39 9.80
Ultimate (2045) 4.88 10.3

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INTENTIONALLY LEFT BLANK

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6 Collection System Condition
Assessment and Improvements
The following section summarizes the condition assessment performed on the City’s existing lift stations, selected gravity mains, and wastewater treatment plant as part of the 2025 Update. Site investigations were conducted at each lift station and the treatment plant to assess the structural, mechanical, electrical, and other relevant characteristics of the existing facilities. Closed Circuit Television (CCTV) inspection reports were reviewed to evaluate the existing physical condition of selected gravity main segments.

Routine condition assessment helps ensure the City remains in compliance with the Statewide Sanitary Sewer Systems General Order (WQ 2022-0103-DWQ). The General Order requires condition assessment and proactive maintenance as part of a sewer service provider’s Sanitary Sewer Management Plan (SSMP).

This section also summarizes recommended improvements to the lift stations, inspected gravity mains, and wastewater treatment plant. The recommendations are intended to improve the overall performance, safety, reliability, and day-to-day operations of critical collection and treatment facilities throughout the City’s sewer system.

A comprehensive list of condition-related recommended improvement projects is included in Section 7.

6.1 Lift Station Condition Assessment Summary
Field inspection of the City’s 15 existing lift stations was completed in February 2025. Of the 15 operational lift stations, nine were subject to a comprehensive site visit and evaluation due to their advanced age or importance to the overall system. The remaining six lift stations received a wet well inspection only. Figure 6.1 depicts the location of each inspected lift station in the City’s collection system.

Detailed descriptions of the condition assessment performed at each lift station, including site layouts, hydraulic and pump characteristics, inspection results, and recommended improvements, are documented in a separate technical memorandum included in Appendix A.

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Figure 6.1 Lift Station Condition Assessment Locations

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6.1.1 Methodology
Condition assessment of each lift station proceeded as follows:
▪ Conduct a field inspection to observe the existing condition of the following asset disciplines:
- Site: Civil components including grading, paving, perimeter fencing, access, and utilities. - Mechanical: Pumps, piping, valves, odor control and mechanical equipment, and any HVAC within the lift station facility.
- Structural: Access hatches and covers, below-grade concrete structures, and structural components relating to the wet well, lift station, vaults, and any applicable superstructures. - Electrical & Instrumentation: Electrical service equipment, emergency power equipment, motor controls, instruments, and control panels.
- Climate Change Vulnerability: Potential impacts from flooding, electrical outages, heat waves, and other extreme weather events.
▪ Assess the condition of each asset discipline based on field observations, data review, and discussions with Public Works staff
▪ Assign each asset discipline a condition designation (Excellent, Good, Fair, or Poor) ▪ Identify recommended improvements based on each asset discipline’s condition designation ▪ Prepare a planning-level engineer’s opinion of construction costs for each recommended improvement (included in Section 7)

6.1.2 Results and Recommendations
Numerous structural and electrical defects were observed during field inspection of the City’s lift stations.

Representative examples of defects are depicted in Figures 6.2 through 6.5. Detailed observations recorded at each lift station are documented and categorized by asset discipline in Appendix A.

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Figure 6.2 Main Lift Station Bar Screen Structure Grating Deterioration Figure 6.3 Alder Canal Villa Ave Lift Station Infiltration Damage in Dry Well

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Figure 6.4 Eastside Lift Station Level Transducer Cable Figure 6.5 Countryside Lift Station Failing Wet Well Liner

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Table 6.1 summarizes the condition designations of the asset disciplines of each lift station. The following improvements are generally recommended for implementation across all existing lift stations to enhance safety and operational reliability:
▪ Replacement of access hatches/covers and doors/doorways ▪ Structural and electrical upgrades required to conform to the latest national fire protection and electrical codes (i.e., NFPA 820 and NEC 500)
▪ Perform third-party testing on all electrical equipment and breakers ▪ Improve cellular connectivity and signal on site
▪ Ensure proper mounting of all ultrasonic level elements within wet well structures - At most lift stations, it was observed that the ultrasonic level sensors are attached via manufacturer’s cable, which can cause strain and premature failure
▪ Perform a power system study including short circuit analysis, coordination, and arc flash analysis - Install Arc flash stickers on all electrical equipment ▪ Relocate all electrical and controls equipment outside of hazardous envelopes ▪ Install sealing fittings (seal-offs) on all conduits exiting wet wells and hazardous envelopes - Unsealed conduits are a safety hazard due to the possibility of hydrogen sulfide (H2S) gas leaking into and accumulating within electrical panels or enclosures containing combustible equipment ▪ Relocate conduit penetrations for float switches and level sensors outside of equipment enclosures that contain electrical and controls equipment (alternatively, relocate all electrical and controls equipment out of pump enclosure and/or hazardous envelope)
▪ Install on-site water connection to provide a permanent water supply for site wash-down ▪ Install bypass connections for all sites that do not currently have one Recommended improvement projects were ranked as High, Medium and Low priority corresponding to the planning scenario (Existing, Near-Term, or Ultimate) in which they should be completed. Detailed descriptions and prioritization of each improvement project are included in Section 7 and Appendix A. All system surveys, studies, and asset replacement projects necessary to meet current code requirements are categorized as High priority and scheduled for completion within the next ten years (Fiscal Year 2026 to 2035).

The High priority projects include:
▪ Structures, Hatches / Doors, and Bypass Connection Program ▪ Arch Flash / Short Circuit Study Program
▪ Testing and Studies Program
▪ Instrumentation and Controls Program
▪ Force Main Program
▪ Power and Generator Program
▪ Pumps, Piping, Supports, and HVAC Program
▪ Main Lift Station Rehabilitation Project
▪ Eastside Lift Station Rehabilitation Project
▪ Buena Vista Lift Station Rehabilitation Project

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▪ Legacy Lift Station Decommissioning Project
▪ 4th & Wake Lift Station Decommissioning Project
Table 6.1. Lift Station Condition Assessment Summary
Lift Station Site Civil Mechanical Structural
Electrical &
Instrumentation
Climate
Vulnerability
Lift Station No. 3 Excellent Fair to Good Poor Poor to Fair Poor Gios Excellent Fair to Good Poor Poor to Fair Poor
Main Excellent Fair to Good Fair Poor Good
Countryside Excellent Fair Poor to Fair Poor to Fair Fair to Good Legacy (Southern
Countryside)
Excellent Fair Good Good Good
Alder Canal – Villa
Ave
Excellent Fair Fair Fair Good to Fair
3rd and Ross Excellent Fair Poor Fair Poor
4th and Wake Good to
Excellent
Good Poor Fair Fair
8th and Wake N/A Fair Poor N/A N/A
Lift Station No. 2 N/A Fair to Good Excellent N/A N/A
Orange Ave N/A Good Poor N/A N/A
Lift Station No. 1 Excellent Fair to Good Fair to Good Good N/A Buena Vista N/A Good Fair to Good N/A N/A
Eastside N/A Fair Good N/A N/A
Heil and Dogwood N/A Poor to Fair Fair to Good N/A N/A

6.2 Gravity Main Condition Assessment Summary
CCTV inspection reports for 40 gravity pipeline segments, totaling approximately 1.7 miles, were reviewed as part of the 2025 Update. Each inspection report documented the structural and other physical defects within each pipe segment as identified by the camera operator. The locations of the 40 segments are depicted in Figure 6.6.

A suitable rehabilitation or repair method was recommended for each pipe segment. Pipeline rehabilitation and repair methods range from the in-situ (i.e., trenchless), such as trimming intrusions and lining with Cured-In-Place Pipe (CIPP), to the more complex including excavation point repairs and complete replacement.

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Figure 6.6 Gravity Main Condition Assessment Locations

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6.2.1 Methodology
Condition assessment of each gravity main segment proceeded as follows:
▪ Review of CCTV inspection report provided by Public Works staff, including pictures and video where applicable
▪ Log all relevant gravity main and lateral data and observed defects as noted within report ▪ Identify an appropriate rehabilitation or repair method for the pipe segment, with less intrusive methods favored whenever suitable
▪ Prepare a planning-level engineer’s opinion of construction costs for each recommended repair method (included in Section 7)
CCTV inspections of the reviewed pipe segments were completed between 2014 and 2025. The inspection reports were prepared in accordance with the National Association of Sewer Service Companies (NASSCO) Pipeline Assessment Certification Program (PACP) standards.

The PACP standards define a uniform set of codes used to easily categorize any frequently encountered structural defects, faults and imperfections, or other physical observations within an inspected pipe segment. Table 6.2 summarizes the most common defects and observations noted during condition assessment of the City’s gravity mains and their corresponding PACP code.

Table 6.2. Pipeline Assessment Certification Program (PACP) Codes PACP Code Definition
B Broken
BSV/BVV Broken Soils/Void Visible
CC/CL/CM Crack Circumferential/Longitudinal/Multiple
DAE/DAGS Deposits Attached Encrustation/Grease
DSC/DSZ Deposits Settled Hard (Compacted)/Other
FC/FL/FM Fracture Circumferential/Longitudinal/Multiple H Hole
JOL/JOM Joint Offset Large/Medium
MCU Miscellaneous Camera Underwater
MSA Miscellaneous Survey Abandoned
MWL/MWM Miscellaneous Water Level/Mark
MWLS Miscellaneous Water Level Sag
OBI/OBZ Obstruction through Wall/Other
RBL/RML Roots Ball/Medium Lateral
RFJ/RMJ Roots Fine Joint/Medium Joint
TBA/TBI Tap Break In Active/Intruding
TFA/TFC/TFD Tap Factory Active/Capped/Defective
X Collapse

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NASSCO PACP standards require all observed structural defects to be assigned a condition grade from 1 to 5. The condition grades noted in each inspection report can be used to quickly determine the presence and quantity of major defects in a pipe segment. As summarized in Table 6.3, a higher condition grade corresponds to a more severe defect, with the most critical assigned a grade of 4 or 5. In general, a pipe segment with a single Grade 5 structural defect is considered significantly more likely to fail and therefore requires immediate attention, compared to a segment with several Grade 1 or 2 defects that may remain in good condition for years to come.

Table 6.3. Pipeline Condition Grades
Grade Description Estimated Time to Failure
1 Excellent Unlikely
2 Good 20+ years
3 Fair 10-20 years
4 Poor 5-10 years
5 Immediate Action Has failed or could fail within 5 years

6.2.2 Results and Recommendations
The following repair methods were considered for each pipe segment after review of the inspection reports:
▪ CIPP Lining: Cured-In-Place Pipe (CIPP) lining of entire segment from manhole to manhole. CIPP lining effectively constructs a new pipeline within an existing line, using the existing pipe as a mold. The liner is a resin-saturated felt tube that is inverted into the existing pipe segment between two manholes and cured in place using steam or hot water. The resultant new pipeline is as strong as the original “host” pipe segment and has an expected useful life of more than 50 years. ▪ Replace in Place: Excavation and replacement of the entire segment from manhole to manhole. ▪ In-situ Point Repair: Trenchless/in-situ repair of a single defect, typically 4-feet in length or less, using a CIPP short liner.
▪ Excavation Point Repair: Replacement of a short segment of pipe by open trench construction to address a severe defect. Dresser style couplings for connections to the existing pipe are recommended to reduce the potential for differential settlement. May also include replacement of lateral connection(s) to the sewer main.
▪ Trim Intrusion: Laterals or other objects that intrude into the gravity main can catch debris and restrict sewer flow. Such intruding elements can be trimmed by a small robotic device traversing through the main.

In-situ (i.e., trenchless) methods were recommended whenever appropriate to reduce repair costs and potential impacts to the public and environment. Representative examples of observed defects with their corresponding recommended repair method are depicted in Figures 6.7 through 6.10.

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Figure 6.7 Severe Root Intrusion (Adams Ave) – Trim Intrusion & CIPP Lining Figure 6.8 Broken Pipe with Soil Visible (State St) – Excavation Point Repair

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Figure 6.9 Crack Longitudinal (Imperial Ave) – CIPP Lining Figure 6.10 Debris in Pipe (Imperial Ave) – Heavy Cleaning & Debris Removal Of the 40 reviewed pipe segments, 25 were recommended for at least one method of rehabilitation or repair. A log of the reviewed pipe segments, including gravity main diameter, length, number of laterals, observed defects, and recommended repairs are included in Appendix F. Table 6.4 summarizes the recommended repair methods and their respective quantities (lineal feet or number of segments). Figure 6.11 depicts the locations of the recommended repairs.

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Public Works staff noted that CIPP liner was installed within certain segments of the 27-inch trunk main in Villa Ave based on findings from inspection reports completed in 2015. Therefore, the trunk main in Villa Ave should be reinspected prior to implementation of any lining project to verify if and where pipeline rehabilitation is still necessary.

Furthermore, field survey of the trunk main in Villa Ave indicated extensive sagging throughout the pipeline. Public Works staff have observed misalignment of gravity main inverts at various locations throughout the collection system and attribute
Table 6.4. Gravity Main Condition Assessment Recommendations Summary Recommended Repair / Rehabilitation Method
Number of Pipe
Segments Quantity (LF or EA)
CIPP Lining (8-, 12-, 22-, or 27-inch Pipe) 22 3,866 LF Excavation Point Repair (8- or 12-inch Pipe) 3 EA

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Figure 6.11 Gravity Main Condition Assessment Recommendations

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6.2.2.1 Total Dissolved Solids (TDS) Concentrations
At the outset of the flow monitoring program summarized in Section 4.1, Public Works staff collected grab samples to measure the concentration of total dissolved solids (TDS) at each flow monitoring location. Table 6.5 summarizes the measured TDS concentration at each flow monitoring location in March 2025.

Table 6.5. TDS Grab Samples Results
FM Location TDS (mg/L)
FM 01 1,400
FM 02 2,300
FM 03 1,400
FM 04 3,200
FM 05 1,200
FM 06 1,400
FM 07 1,700
FM 08 1,500
FM 09 2,200
The average TDS concentration in the City’s potable water supply is approximately 700 mg/L. The TDS concentration in domestic wastewater is typically 200 to 500 mg/L higher than its potable water equivalent.

Industrial and commercial customers can significantly increase the TDS concentration in wastewater, depending on the on-site activities and quality of discharge involved.

Several of the grab sample collection sites, including FM 02, FM 04, and FM 09, resulted in notably high TDS concentrations that are not typically observed within a municipal sewer system primarily serving residential customers. Due to the predominance of agricultural land use throughout Imperial Valley, groundwater TDS concentrations often range from 1,000 to over 3,000 mg/L, depending on aquifer depth and proximity to agricultural activities (Source: California Water Library). Certain wells near sources of agricultural return flows have recorded TDS concentrations of up to 5,000 mg/L. City staff have detected TDS concentrations as high as 25,000 mg/L at a depth of approximately 20 ft in groundwater samples.

Elevated TDS concentrations within the City’s sewer collection system may result from persistent groundwater infiltration via cracks and fractures in gravity mains. For example, a significant increase in defect flow was observed within the FM 04 and FM 09 sewersheds relative to their physical area during the wet weather calibration event described in Section 4.4. The high defect flows and TDS concentrations observed at FM 04 and FM 09 indicate the condition of the upstream gravity mains may be poor and require additional physical maintenance or repair. It is recommended that the City complete a focused I&I study within the FM 04 sewershed to identify specific locations that may be significant sources of defect flow or high TDS concentrations. Such sources may be individual commercial or industrial dischargers, or certain pipe segments with structural defects that allow for groundwater infiltration.

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6.3 Manhole Condition Assessment Summary
The City performed field inspections on manholes in Imperial Avenue between Danenburg Avenue to McCabe Road, as shown in Figure 6.12. The City provided the list of manholes to Dudek for inclusion in the CIP project recommendations for this master plan. All manholes were found by the City to need significant rehabilitation. Based on discussions with City staff, the manhole rehabilitation method recommended included a combination of mortar repair with corrosion resistant geopolymer mortar and cured-in-place (CIP) PVC composite manhole liners (CIPM liner) for all 11 manholes.

Figure 6.12 Missing Supports and Covers at Primary Clarifier Gallery

6.4 WWTP Condition Assessment Summary
A site investigation and capacity evaluation of the City’s wastewater treatment plant was completed in July 2025 as part of the 2025 Update. The wastewater treatment plant was originally constructed in 1957 to treat sewer flows generated within the City before discharge into the Central Drain and ultimately Salton Sea. The most recent plant expansion was completed by the City in 1994 and included additional aeration basins, secondary clarifiers, a gas mixing system, and numerous other improvements and upgrades.

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The treatment plant is permitted by the state of California to treat an average flow of 8.0 MGD. Generally, the plant operates well below its rated capacity as the average recorded influent flow is only 3.52 MGD. In addition, certain treatment processes within the plant limit its overall ability to accept the permitted flow rate.

Detailed descriptions of each existing wastewater treatment facility, condition assessment, capacity analysis, and recommended improvements are documented in a separate technical memorandum included in Appendix B.

6.4.1 Methodology
Condition assessment of the wastewater treatment plant proceeded as follows:
▪ Conduct a field inspection to observe the existing condition of each treatment facility or component. ▪ Assess the condition of each treatment facility based on field observations, data review, and discussions with Public Works staff
▪ Complete a desktop capacity evaluation of the plant’s main treatment processes (i.e., primary clarifiers, aeration basins, and secondary clarifiers) under both existing and future flow conditions. ▪ Identify recommended improvements based on each treatment facility’s condition and/or capacity deficiencies.
▪ Prepare a planning-level engineer’s opinion of construction costs for each recommended improvement (included in Section 7)

6.4.2 Results and Recommendations
Numerous structural, mechanical, and electrical defects were observed during field inspection of the City’s wastewater treatment plant. Representative examples of defects are depicted in Figures 6.13 through 6.16.

Table 6.6 summarizes the recommended improvements for each major facility at the wastewater treatment plant, categorized by replacement, repair, new installation, and/or removal.

Detailed observations recorded at each facility are documented in Appendix B.

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Figure 6.13 Missing Supports and Covers at Primary Clarifier Gallery Figure 6.14 Cracked Concrete and Exposed Rebar at Aeration Basins

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Figure 6.15 Delaminated Coating and Unsealed Cover at Digester Tank Figure 6.16 Corrosion and Rusting at Belt Press Access Ladder

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Table 6.6. WWTP Condition Assessment Recommendations Summary Treatment
Facility Replacement Repair / Rehabilitation New Installation Removal Headworks
(Primary
Treatment)
Bar screen structure; channel grating
hardware; all piping that is 6-inch or less
and all related valves and appurtenances in
the primary clarifier gallery; temporary
piping connected to primary sludge pumps;
five sluice gates and metallic safety
components in the primary clarifier gallery
Floor drain at staircase landing;
bar screen structure at lowerlevel entrance; recoat and inspect 24-inch influent line;
clean and inspect interior and
exterior of the influent
distribution structure
Shade structure over
primary sludge pump;
permanent supports for
influent line
All unused piping and
related appurtenances in
primary clarifier gallery;
temporary supports for
influent line
Aeration
Basins
(Secondary
Treatment)
Diffusers and piping; 36 sluice gates Concrete; inspect interior and exterior of basins
N/A Mechanical mixer
concrete pads
Secondary
Clarifiers and
Ancillary
Pumps
(Secondary
Treatment)
West splitter box and sluice gates; sluice
gates for central splitter box; roof deck of
plant water pump station; concrete pads for
WAS Pumps No. 1 and 2
Concrete for northwest access
hatch of sludge pump room;
concrete curb surrounding
southwest aluminum hatch;
inspect interior and exterior of
plant water pump station; plant
water pumps, piping, and
appurtenances
Cover to the wet well in
the sludge pump room
N/A
Digester
Tanks (Solids
Treatment)
Exterior coating of Tanks No. 2 and 3;
concrete flatwork around tanks; floating
cover for Tank No. 3; gas mixing systems for
Tanks No. 1 and 2 with new pump-type
mixing systems; all sludge piping, plug
valves, and appurtenances; all waste gas
piping and appurtenances for each
digester; collapsed storm drain between the
digesters and the primary clarifier gallery
Line tanks; recoat spiral
stairway and remove lower
sections and platforms by Tanks
No. 2 and 3; relocate stairway
by Tanks No. 1 and 2
N/A Old digester sludge pump
and replace with new
rotary lobe pump on a
permanent equipment
pad; unused process
piping, including digester
supernatant piping, for
each digester
Gravity Belt
Thickeners
(Solids
Treatment)
GBTs and related piping and
appurtenances; air compressors; temporary
polymer piping with permanent piping;
Polymer Feed Pump No. 2 and outlet
connection joint
Concrete slabs; existing shade
Structure
Shade structure over
polymer totes that reach
over the belt presses
and cover polymer totes
with plastic covering; a
N/A

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Table 6.6. WWTP Condition Assessment Recommendations Summary Treatment
Facility Replacement Repair / Rehabilitation New Installation Removal permanent mount for
TWAS Pumps No. 1 and
2 Dewatering
(Solids
Treatment)
Belt Press No. 1; concrete pads under both
belt presses; access ladders for both belt
presses
N/A Shade structure over
both belt presses; new
209-feet x 209-feet x 6-
inch sludge drying bed
north of the existing
sludge drying bed
N/A
Operations
Building
N/A Exterior of electrical room.

Americans with Disability Act
(ADA)-compliance.

New main office building
Northeast of the existing
building.

Used electrical equipment
from the blower building
electrical room (MCC No.
3)

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7 Capital Improvements Program
The following section summarizes the recommended capacity and condition improvement projects developed to address the pipeline, lift station, and wastewater treatment plant deficiencies identified in Sections 5 and 6.

Additional recommendations include a staffing plan and other long-term initiatives to enhance the operational efficiency and resiliency of the City’s sewer system. Lastly, the section presents planning-level engineer’s cost opinions for each recommended project as well as potential funding sources for City staff to pursue.

The recommended projects and associated cost opinions are compiled into a multi-year sewer CIP for implementation by the City. The sewer CIP is a culmination of the results and recommendations developed in the 2025 Update.

Completion of the projects defined in the CIP will improve the existing level of service, ensure regulatory compliance, and address future growth throughout the City’s sewer system.

7.1 Pipeline Capacity Improvement Projects
Based on the results of the capacity analysis in Section 5, two pipeline improvement projects are recommended to address existing and anticipated capacity deficiencies under Existing and Ultimate PWWF conditions.

In addition to the two projects, a targeted Infiltration Study utilizing TDS sampling is recommended to better understand and mitigate groundwater infiltration into the sanitary sewer system. This approach will:
▪ Identify sewer sub-basins with elevated TDS levels indicative of groundwater intrusion; ▪ Prioritize areas for further CCTV inspection and rehabilitation; ▪ Support data-driven decisions for inflow and infiltration (I&I) reduction; ▪ Enhance system capacity and reduce treatment costs.

This infiltration study also aligns with the emphasis of the Sanitary Sewer Systems General Order (WQ 2022-0103-DWQ) on condition assessment and proactive maintenance planning, which is required as part of an agency’s SSMP.

The following Table 7.1 summarizes the two recommended pipeline capacity improvement projects, while Figure 7.1 depicts the locations of the projects within the City’s collection system.

As PCAP-1 is based on deficiencies identified in the Existing planning scenario, it is recommended that the City complete the project prior to the Near-Term scenario, or within the next 10 years. PCAP-2, the reconfiguration of the Main LS influent gravity sewers, is also recommended for completion prior to the Near-Term scenario.

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Table 7.1. Recommended Pipeline Capacity Improvement Projects Summary Project
ID
Deficiency
ID
Planning
Scenario Project Description Justification
PCAP-1 EX-2 Existing
(2025)
Focused I&I study of the
Eastside LS tributary area as
well as TDS sampling
systemwide to identify sources
of I&I; includes CCTV inspection
and smoke testing of areas of
suspected high I&I.

System flow data indicates high
defect flow entering this basin
and high TDS in the Eastside LS
tributary area.

PCAP-2 N/A Existing
(2025)
Reconfigure influent sewer into
the Main LS wet well and
construct separate gravity lines
from Villa and Imperial Ave
Establish a second influent pipe
into Main Lift Station for
redundancy / reliability due to
failure of existing single
convergence manhole during
wet weather event

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Figure 7.1 Recommended Pipeline Capacity Improvement Projects

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7.2 Pipeline Condition Improvement Projects
The following Table 7.2 summarizes the recommended condition improvement projects identified during condition assessment of the City’s pipelines. The locations of the pipeline replacement projects are shown in Section 6.2.

Table 7.2. Recommended Pipeline Condition Improvement Projects Summary Project ID Description Justification
PCON-1 Excavation point repair on the following gravity segments: Two 8-inch mains; One 12-inch main
Pipeline segments have one significant
structural defect or encrusted/compacted
deposits that severely impact normal sewer
flow.

PCON-2 CIPP lining of 22 gravity segments, from manhole to manhole: 1,047 LF of 8-inch main; 1,087 LF of
12-inch main; 432 LF of 22-inch main; 1,300 LF
27-inch main. Heavy cleaning prior to CIPP lining.

Pipeline segments have multiple cracks or
fractures
PCON-3 $1M Annual CIPP Lining Program from Year 11
through 20 (FY36-37 through FY45-46).

Continued rehabilitation of aging pipeline
infrastructure to ensure system reliability.

7.3 Manhole Condition Improvement Projects
The following Table 7.3 summarizes the recommended condition improvement projects identified during condition assessment of the City’s manhole inspection data. The locations of the manhole rehabilitation projects are shown in Section 6.3.

Table 7.3. Recommended Pipeline Condition Improvement Projects Summary Project ID Description Justification
MH-1 Manhole Mortar Repair and CIPM Lining of 11
manholes on Imperial Ave between Danenburg
Ave to McCabe Rd.

Rehabilitation of manholes in poor
condition.

MH-2 Ongoing $200,000 per year Manhole
Rehabilitation Program from Year 6 through Year
20 (FY31-32 to FY45-46).

Continued rehabilitation of aging manhole
infrastructure to ensure system reliability.

7.4 Lift Station Improvement Projects
The following Table 7.4 provides a summary of recommended capital improvement projects for each of the evaluated lift stations. These recommended improvements projects are focused on mitigating existing operational and safety risks, while utilizing the remaining useful life left in each lift station asset. Each station is provided with recommended improvements involving rehabilitation of the lift station assets to address immediate concerns, potential catastrophic failure of existing structures, code violations, safety risks, security risks, bypass capability, and increased reliability.

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Table 7.4. Recommended Lift Station Improvement Projects Summary Project ID Project Name Description and Justification
LSCON-1 Structures,
Hatches / Doors,
and Bypass
Connection
Program – Phase
1 Structures – This program will address rehabilitation and replacement of structural components at lift stations to improve safety, reliability, and long-term performance. Improvements include rehabilitation of wet wells, replacement of wet well piping and pipe supports, rehabilitation of wet well liners, replacement of access stairs, replacement of wet well access covers, and wall penetration patching and related structural improvements. The specific scope will vary by facility based on condition assessments, but implementation of this program will extend service life of key structures, improve maintainability, and ensure compliance with safety standards.

Hatches / Doors – This program will replace aging wet well access covers, hatches, and vault doors at lift stations to improve safety, security, and reliability. The specific improvements will vary by facility but will generally address deteriorated or non-standard access points that no longer meet current operational or safety requirements.

Implementation of this program will enhance worker safety, improve site security, and ensure that facilities comply with applicable access and safety standards.

Bypass Connection – This program involves installing permanent bypass pumping connections at all lift stations that currently lack this critical feature. The bypass assemblies will provide quick and reliable access points for temporary pumps during planned maintenance or emergency events, minimizing the risk of sanitary sewer overflows and service disruptions. Improvements will include new suction and discharge fittings, associated valving, and site modifications as needed to ensure safe and efficient pump setup. Implementation of this program will enhance system resiliency, improve operational flexibility, and support regulatory compliance across the wastewater collection system.

LSCON-2 Arc Flash / Short
Circuit Study
Program
This program will improve electrical safety at lift stations through the completion of power system studies and the application of updated arc flash labeling. The work will include short circuit and coordination analyses to confirm system protection settings, along with installation of arc flash hazard warning stickers at eight lift stations.

Implementation of this program will enhance worker safety, ensure compliance with electrical safety standards, and reduce risks associated with maintenance and emergency response activities.

LSCON-3 Testing and
Studies Program
This program will complete specialized evaluations and third-party testing to improve safety and reliability of lift station facilities. Planned work includes a dry well seismic evaluation at one facility to assess structural resilience and independent testing of motor control centers (MCCs) and breakers at three facilities to verify electrical safety and performance. Implementation of this program will provide critical data to guide future improvements, reduce operational risks, and ensure compliance with applicable safety and reliability standards.

LSCON-4 Instrumentation
and Control
Program – Phase
1 This program will replace and upgrade critical electrical and control systems at lift stations, including programmable logic controllers (PLCs), motor control centers (MCCs), automatic transfer switches (ATSs), variable frequency drives (VFDs), electrical panels, conduits, site lighting, instrumentation, and control panels. The specific improvements will vary by facility based on existing conditions and operational needs, but will generally focus on standardizing equipment, improving reliability, and extending service life. Implementation of this program will enhance operational efficiency, expand remote monitoring and control capabilities, and ensure compliance with current electrical and safety standards across the collection system.

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Table 7.4. Recommended Lift Station Improvement Projects Summary Project ID Project Name Description and Justification
LSCON-5 Force Main
Program – Phase
1 This program will replace downstream force mains from Orange LS and Lift Station No. 3 to address existing operational challenges and capacity limitations. The work will include installation of new force mains designed to accommodate current and projected flows, along with all associated bypass pumping required to maintain service during construction. Implementation of this program will resolve hydraulic constraints, improve system reliability, and ensure the collection system can continue to operate effectively under future demand conditions.

LSCON-6 Power and
Generator
Program
This program will improve the reliability of lift station power systems through installation of permanent backup generators and portable generator connectors with transfer switches. Additional improvements include replacement of corroded generator piping, replacement of utility power poles, and replacement of main breakers. The specific scope will vary by facility based on condition assessments, but implementation of this program will enhance system resiliency, reduce the risk of service interruptions, and ensure compliance with electrical and safety standards.

LSCON-7 Structures,
Hatches / Doors,
and Bypass
Connection
Program – Phase
2 See LS.01 for detailed descriptions.

LSCON-8 Instrumentation
and Control
Program – Phase
2 See LS.04 for detailed descriptions.

LSCON-9 Pumps, Piping,
Supports, and
HVAC Program
This program will address mechanical and ventilation improvements at lift stations to enhance reliability, safety, and operability. Improvements include installation of emergency eye wash stations, replacement of force mains within wet wells, replacement of sump pumps and associated discharge piping, repair of forced air ventilation systems, replacement of pump bases, installation of chemical injection ports, replacement of suction piping in wet wells, and installation of discharge flow meters. The specific scope will vary by facility based on condition and operational needs, but implementation of this program will improve worker safety, extend equipment life, and ensure reliable system performance.

LSCON-10 Main Lift Station
Rehabilitation
Project
This project will rehabilitate key electrical, structural, and mechanical systems at the lift station to improve safety, reliability, and long-term performance. Planned improvements include upgrades to site and emergency lighting, replacement of the generator and flow meter, structural repairs to the bar screen vault (including floor grating and access stairs), and enhancements to safety and ventilation systems. Collectively, these improvements will extend facility service life, improve maintainability, and ensure continued reliable operation.

LSCON-11 East Side Lift
Station
This project will rehabilitate critical components within the wet well to improve reliability and maintainability. Planned improvements include installation of a backup level element, replacement of suction piping, and rehabilitation of the

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Table 7.4. Recommended Lift Station Improvement Projects Summary Project ID Project Name Description and Justification
Rehabilitation
Project
wet well liner, along with associated bypass pumping to support construction activities. Together, these upgrades will extend the service life of the wet well, reduce operational risk, and ensure continued reliable performance of the lift station.

LSCON-12 Buena Vista Lift
Station
Rehabilitation
Project
This project will address security, structural, and operational needs at the lift station. Planned improvements include installation of intrusion switches to enhance site security, replacement of wet well access covers to improve safety and maintainability, and spot repairs to the wet well liner to extend structural service life. The project will also include bypass pumping to support construction activities. Together, these improvements will reduce operational risks, improve safety, and ensure reliable facility performance.

LSCON-13 Legacy Lift Station
Decommissioning
Project
This project will decommission the existing lift station that will no longer required for system operation. Planned work will include permanent disconnection of electrical and mechanical equipment, abandonment or removal of wet well piping, and demolition or filling of below-grade structures as required. Additional work may include site restoration and minor utility rerouting to ensure continuity of service. Collectively, these improvements will safely retire the facility, eliminate ongoing maintenance costs, and reduce long-term operational risk.

LSCON-14 4th & Wake Lift
Station
Decommissioning
Project
This project will decommission the existing lift station that will no longer required for system operation. Planned work will include permanent disconnection of electrical and mechanical equipment, abandonment or removal of wet well piping, and demolition or filling of below-grade structures as required. Additional work may include site restoration and minor utility rerouting to ensure continuity of service. Collectively, these improvements will safely retire the facility, eliminate ongoing maintenance costs, and reduce long-term operational risk.

LSCON-15 Force Main
Program – Phase
2 This program will replace approximately 12,300 linear feet of downstream force main of Alder Villa LS to address the existing oversized force main. The project will include installation of new piping designed to accommodate current and future flows, along with bypass pumping to maintain service during construction. Implementation of this program will resolve hydraulic constraints, improve reliability, and ensure the collection system continues to perform effectively under future demand conditions.

LSCON-16 Gios Lift Station
Rehabilitation
Project
This project will implement targeted upgrades to improve safety, reliability, and maintainability at the lift station.

Planned improvements include installation of an emergency eye wash to improve worker safety, replacement of water service piping to ensure dependable utility connections, and installation of pump lifting chains to facilitate safer and more efficient pump maintenance. Collectively, these improvements will enhance operational safety, reduce risks, and support reliable long-term performance of the facility.

LSCON-17 Lift Station No. 3
Rehabilitation
Project
This project will rehabilitate key electrical, structural, and mechanical components of the lift station to improve safety, reliability, and performance. Planned improvements include replacement of wet well lighting, installation of a discharge flow meter with a new vault, site grading to improve drainage and access, and installation of a permanent fixed access ladder for the bar screen motor. Additional work will include replacement of existing 40-HP pumping units, replacement of wet well access hatches, and provision of bypass pumping to support construction activities.

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Table 7.4. Recommended Lift Station Improvement Projects Summary Project ID Project Name Description and Justification
Collectively, these improvements will extend the service life of the facility, enhance worker safety, and ensure continued reliable operation.

LSCON-18 8th & Wake Lift
Station
Rehabilitation
Project
This project will replace the existing 5-HP pumps to improve reliability and maintainability of the lift station. The pump replacement will extend equipment service life, reduce the risk of unplanned failures, and ensure continued reliable operation of the facility.

LSCON-19 Alder Canal - Villa
Ave Lift Station
Rehabilitation
Project
This project will rehabilitate key electrical, structural, and site components of the lift station to improve safety, reliability, and performance. Planned improvements include verification of the drywell flood alarm and integration with the RTU, redesign and installation of LED lighting in the drywell, and drainage and grading improvements to prevent water infiltration. Additional work will include installation of outdoor lighting at the chemical area, replacement of exterior and interior lighting at the electrical building, installation of a discharge flow meter with a new vault, and site grading improvements. Station bypass pumping will be provided to support construction activities.

Collectively, these improvements will extend the service life of the facility, enhance worker safety, and ensure continued reliable operation.

LSCON-20 3rd & Ross Lift
Station
Rehabilitation
Project
This project will implement targeted upgrades to improve safety, reliability, and maintainability of the lift station.

Planned improvements include installation of new site task lighting and provision of an on-site water connection to support facility operations and maintenance. Collectively, these improvements will enhance worker safety, improve operational efficiency, and ensure continued reliable performance of the facility.

7.5 WWTP Improvement Projects
Recommended improvements to the City’s wastewater treatment plant are listed in Table 7.5 to address the condition and capacity deficiencies described in Appendix B. These improvements are broken down into treatment processes.

Table 7.5. Recommended Wastewater Treatment Plant Improvement Projects Summary Project ID
Project
Name Description and Justification
WWTP-1 Headworks Bar screen structure - replace entrance door hardware and intrusion switch. Repair floor drain at staircase landing, bar screen structure lower-level entrance. Replace channel grating hardware, bar screen structure. Recoat and inspect 24- inch influent line and replace temporary wooden supports with permanent concrete or steel supports Empty, clean, and

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Table 7.5. Recommended Wastewater Treatment Plant Improvement Projects Summary Project ID
Project
Name Description and Justification
have a structural engineer inspect the interior and exterior of the influent distribution structure to determine proposed structural improvements.

WWTP-2 Primary
Clarifiers
Replace existing clarifiers with two larger clarifiers (Alternative B). Install shade structure over primary sludge pumps.

Replace all piping that is 6- inches or less, scum piping, plug valves, and all other related valves and appurtenances in the primary clarifier gallery. Remove all unused piping and related appurtenances in primary clarifier gallery. Replace temporary piping connected to primary sludge pumps with permanent piping in primary clarifier gallery. Replace the five sluice gates and metallic safety components including the grating, handrail, light pole, shade structure, and sampling shed platform in the primary clarifier gallery
WWTP-3 Aeration
Basins
Empty, clean, and inspect interior and exterior of each basin. Rehabilitate concrete. Remove mechanical mixer concrete pads. Replace diffusers and piping. Replace 36 sluice gates.

WWTP-4 Secondary
Clarifiers
Replace west splitter box and sluice gates. Replace sluice gates for central splitter box. Inspect interior and exterior of plant water pump station. Replace roof deck of plant water pump station. Inspect plant water pumps, piping, and appurtenances. Refurbish concrete for northwest access hatch of sludge pump room and rehabilitate concrete curb surrounding southwest aluminum hatch. Replace concrete pads for WAS Pumps No. 1 and No. 2. Install cover to the wet well in the sludge pump room.

WWTP-5 Digesters Reline each digester. Replace exterior coating on Digesters No. 2 and No. 3. Replace floating cover on Digester No. 3.

Remove old digested sludge pump and replace it with new rotary lobe pump on a permanent equipment pad. Add one digested sludge pump. Replace gas mixing system with new pump-type mixing system for Digesters No. 1 and No. 2.

Replace all sludge piping, plug valves, and appurtenances between the digesters and primary clarifiers and between the digesters and the belt presses. Replace all waste gas piping and appurtenances for each digester. Remove unused piping, including the digester supernatant piping, for each digester. Recoat spiral stairway and remove lower section by Digester No. 2 and No. 3. Relocate stairway by Digester No. 1 and No. 2. Recoat the platforms for Digesters No. 2 and No. 3. Replace storm drain between digesters and primary clarifier gallery. Replace concrete flatwork for each digester.

WWTP-6 Gravity Belt
Thickeners
Replace GBTs and related piping and appurtenances. Replace air compressors. Rehabilitate concrete slabs. Replace temporary polymer piping with permanent piping. Replace Polymer Feed Pump No. 2 and outlet connection joint. Install shade structure over polymer totes that reach over the belt presses and cover polymer totes with plastic covering.

Rehabilitate existing shade structure.

Permanently mount TWAS Pumps No. 1 and No. 2. Replace temporary piping for TWAS Pump No. 1 with permanent piping and install permanent piping for TWAS Pump No. 2.

WWTP-7 Dewatering Replace Belt Press No. 1. Replace concrete pads under both belt presses. Replace access ladders for both belt presses.

Install shade structure over both belt presses. Install new 209-feet x 209-feet x 6-inch sludge drying bed north of the existing sludge drying bed.

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Table 7.5. Recommended Wastewater Treatment Plant Improvement Projects Summary Project ID
Project
Name Description and Justification
WWTP-8 Operations
Building
Construct a new main office building Northeast of the existing building. Remove used electrical equipment from the blower building electrical room (MCC No. 3) and refurbish the exterior of the electrical room WWTP-9 Operations
Building ADA
Compliance
Bring current Operations Building up to ADA basic compliance, including ramp installation, adjusted threshold and door clearances, accessible route from parking to entrance, widen doors to 32" clear opening, replacing knobs with lever-style handles, adjusting closing force and door swing clearance. Modifying restrooms to include grab bars, ADA-compliant stall and sink (heights, faucet controls, turning radius). Providing at least one van accessible space and installing compliant signage and striping. Lowering light switches, thermostats and other controls to 48" max height, adjusting counters to provide auxiliary surfaces at 34" height.

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7.6 Staffing Plan
To ensure that all current and future needs of the sewer system are met, and to support its long-term resilience and regulatory compliance, it is essential to have a robust staffing plan. As part of the 2025 Update, a staffing study was prepared to estimate the additional personnel required to support the City’s goals for effective sewer system management. The study is included in Appendix G of this report. Work effort incorporated within this staffing study includes routine maintenance activities such as cleaning, lift station inspections, CCTV inspections, infrastructure rehabilitation or replacement, and treatment plant operations and maintenance.

To conduct the study, the following documents were reviewed:
▪ Organizational charts from various districts
▪ Staffing plans from various districts
▪ El Centro’s Sewer System Management Plan
▪ El Centro’s ongoing Water and Sewer Master Plan
▪ Notes from interviews with City staff
A staffing plan was then developed based on the reviewed documents. The methodology for developing a staffing plan began with a review of organizational charts and staffing plans from multiple water/sewer service districts and cities to identify common workforce structures. Ratios relative to service area or service volume served as a reference for shaping the City of El Centro’s workforce structure. Data from El Centro’s Sewer System Management Plan and Sewer Master Plan were then incorporated into the analysis. These metrics were used as scaling factors and were applied to peer agency staffing ratios to estimate El Centro’s full-time equivalent staffing requirements.

Table 7.6 summarizes the total number of full-time employees needed to maintain both the sewer collection system and the WWTP, based on the analysis in Appendix G. Based on the analysis of the sewer collection system maintenance requirements and the organizational charts for the WWTP staff, it is recommended that the City staff a total of 13 employees for the WWTP, five to six operators for sewer collection system maintenance, and one dedicated WWTP Instrumentation Electrical Technician. Alongside that, it is recommended that the City hire one to five additional engineering staff, as well as one to two additional administrative staff to be shared between the Sewer and Water maintenance efforts.

Table 7.6. Summary of Total Recommended Full Time Employee (FTEs) Department
Current Number of
FTTs
Recommended
Additional FTEs
Recommended
Total FTEs
WWTP Staff 13 1 14
Instrumentation Electrical Technician 0.5 0.5 1
Underground Utilities Staff (Sewer
Operators)
3 2 to 3 5 to 6
Engineering1 5 1 to 5 6 to 10
Administration1 (excluding Fleet staff) 6 1 to 2 7 to 8 Notes:
1 Recommendations for Engineering and Administration staff are shared between the Sewer and Water Systems.

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7.7 Additional Recommendations
To enhance system integrity, operational security, and environmental compliance, the following capital and programmatic initiatives summarized in Table 7.7 are recommended:

Table 7.7. Recommended Additional Improvement Projects Summary Project
ID Project Description Justification
AD-1 Brick Sewer Study - Focused study program to investigate all the brick sewer pipes in the system. Conduct CCTV
inspections of all suspected brick segments, particularly those located parallel to the Union Pacific Railroad
between Adams Avenue and Villa Avenue. Brick sewers,
due to their age and material composition, are highly
susceptible to structural failure, including sudden
collapse, root intrusion, and infiltration.

Extend the service life of legacy
infrastructure; reduce the risk of
sanitary sewer spills; improve
hydraulic performance and structural
integrity; comply with the General
Order’s requirements for asset
management and risk mitigation.

AD-2 Cybersecurity Vulnerability Assessment - Evaluate the vulnerability of the City’s wastewater treatment facilities, SCADA systems, and data networks to unauthorized
access, ransomware, and other cyber threats.

Safeguard public health, ensure
regulatory compliance, and protect
the City’s operational continuity.

AD-3 Sewer Collection System Survey – Perform full sewer collection system survey of all 1,981 manholes over 5-
year period and update City sewer GIS.

Build a complete, accurate GIS of the
sewer collection system, including
manhole inverts, ground surface
elevations, and confirmed pipeline
diameters.

7.8 Recommended CIP Projects Cost Summary
Estimated project costs were developed using planning-level assumptions informed by recent bid data, industrystandard unit costs, and engineering judgment. For pipeline rehabilitation and replacement, costs were calculated on a per-linear-foot basis and adjusted for variables such as pipe diameter, installation depth, and surface restoration requirements. Lift station rehabilitation costs reflect the anticipated scope of mechanical, electrical, and structural improvements necessary to restore or enhance operational reliability. Wastewater treatment plant rehabilitation estimates are based on preliminary assessments of process upgrades, equipment replacement, and structural repairs. Costs for additional studies, including condition assessments and flow evaluations, were estimated based on expected level of effort and professional labor rates. All estimates include allowances for contingencies, permitting, and construction management to provide the City with a realistic and comprehensive foundation for capital planning. Table 7.8 provides a breakdown of the cost multiplier assumptions.

Table 7.8. Cost Multiplier Summary
Cost Multiplier Value
General Requirements 10%
Contingency 30 – 40%
Engineering 10 – 30% depending on project size
Construction Management 10 – 15% depending on project size

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Table 7.8. Cost Multiplier Summary
Cost Multiplier Value
Engineering Services during Construction 2%
Environmental 2%
Administration 2%
Projects identified in the master plan were prioritized based on the severity of observed deficiencies and an assessment of overall system risk. This prioritization framework ensures that resources are allocated to the most critical needs, or those with the highest potential for service disruption, environmental impact, or regulatory non-compliance.

Tables 7.9 through 7.14 summarize the probable construction and total project costs associated with each recommended CIP project. Detailed cost breakdowns for individual projects are provided in Appendix H. All cost estimates are based on an Engineering News Record (ENR) Construction Cost Index (CCI) of 15,993.96 for September 2025, with a 4% annual escalation factor applied to reflect fiscal year cost projections.

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Table 7.9. Recommended Pipeline Improvement Projects Cost Summary Table 7.10. Recommended Manhole Improvement Projects Cost Summary

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Table 7.11. Recommended Lift Station Improvement Projects Cost Summary

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Table 7.12. Recommended Wastewater Treatment Plant Improvements Projects Cost Summary Table 7.13. Recommended Additional Improvements Projects Cost Summary Table 7.14. Annual CIP Project Summary Table by Improvement Type

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7.9 Potential Funding Sources
Table 7.15 presents descriptions of potential State and Federal funding sources the City may want to consider for the sewer CIP.

Table 7.15. Potential Funding Sources
Funding
Source Program Description Type
Typical Range
of Funding
Estimated
Time to
Acquire Funds
California State
Water
Resources
Control Board
(SWRCB)1
Clean Water
State Revolving
Fund (CWSRF)
Provides low-interest
loans for water quality
improvement projects,
including sewer system
upgrades.

State $1 million to
$100 million
6-12 months
California
Infrastructure
and Economic
Development
Bank (IBank)
Infrastructure
State Revolving
Fund (ISRF)
Program
Offers low-cost
financing to public
agencies for various
infrastructure projects,
including sewer
systems.

State $1 million to
$65 million
6-12 months
Department of
Housing &
Urban
Development
(HUD)
Community
Development
Block Grants
(CDBG)2
Administered by HUD,
these grants can be
used for infrastructure
projects in low- to
moderate-income
communities.

Federal Varies, typically
$500,000 to $5
million
6-18 months
U.S.

Environmental
Protection
Agency (EPA)
Water
Infrastructure
Finance and
Innovation Act
(WIFIA)
Provides long-term,
low-cost supplemental
loans for significant
water and wastewater
projects.

Federal $20 million to
$7.5 billion
12-24 months
Federal
Emergency
Management
Agency (FEMA)
Building
Resilient
Infrastructure
and
Communities
(BRIC)
Funds infrastructure
resilience projects,
including water/
wastewater systems.

Federal $500,000 to
$50 million
12–24 months
California
Department of
Water
Resources
(DWR)
Integrated
Regional Water
Management
(IRWM) Grants
Funds regional water
management projects,
including wastewater
and stormwater.

State $1 million to
$10 million
6–18 months

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Appendix A
Sewer Lift Station Condition Assessment
Technical Memorandum

Sewer Lift Station Condition Assessment
Technical Memorandum
Sewer Master Plan and Rate Study
OCTOBER 2025
Prepared for:
1275 W. Main Street
El Centro, CA 92243
Contact: Abraham Campos, P.E.

Prepared by:
687 South Coast Highway Suite 101
Encinitas, CA 92024
Contact: Brandon Lacap, P.E.

Printed on 30% post-consumer recycled material.

INTENTIONALLY LEFT BLANK

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 i OCTOBER 2025
Table of Contents
SECTION PAGE NO.

Acronyms and Abbreviations.......................................................................................................................................... xiv 1 Introduction ..........................................................................................................................................................1 2 Project Background and Approach .....................................................................................................................4

2.1 Objective .................................................................................................................................................4

2.2 Field Investigation Overview ..................................................................................................................4

2.3 Condition Assessment Methodology .....................................................................................................5

2.4 Summary of Condition Assessment Results...................................................................................... 15 3 Lift Station Assessments .................................................................................................................................. 17

3.1 Lift Station No. 3.................................................................................................................................. 17

3.1.1 Location and Layout .............................................................................................................. 17

3.1.2 System Characteristics.......................................................................................................... 18

3.1.3 Inspection Summary.............................................................................................................. 19

3.1.4 Hydraulic Assessment ........................................................................................................... 25

3.1.5 Recommended Improvements.............................................................................................. 26

3.2 Gios Lift Station ................................................................................................................................... 30

3.2.1 Location and Layout .............................................................................................................. 30

3.2.2 System Characteristics.......................................................................................................... 31

3.2.3 Inspection Summary.............................................................................................................. 32

3.2.4 Hydraulic Assessment ........................................................................................................... 36

3.2.5 Recommended Improvements.............................................................................................. 37

3.3 Main Lift Station .................................................................................................................................. 39

3.3.1 Location and Layout .............................................................................................................. 39

3.3.2 System Characteristics.......................................................................................................... 41

3.3.3 Inspection Summary.............................................................................................................. 42

3.3.4 Hydraulic Assessment ........................................................................................................... 61

3.3.5 Recommended Improvements.............................................................................................. 61

3.4 Countryside Lift Station....................................................................................................................... 67

3.4.1 Location and Layout .............................................................................................................. 67

3.4.2 System Characteristics.......................................................................................................... 69

3.4.3 Inspection Summary.............................................................................................................. 70

3.4.4 Hydraulic Assessment ........................................................................................................... 76

3.4.5 Recommended Improvements.............................................................................................. 76

3.5 Legacy Lift Station............................................................................................................................... 77

3.5.1 Location and Layout .............................................................................................................. 77

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 ii OCTOBER 2025

3.5.2 System Characteristics.......................................................................................................... 77

3.5.3 Inspection Summary.............................................................................................................. 78

3.5.4 Hydraulic Assessment ........................................................................................................... 82

3.5.5 Recommended Improvements.............................................................................................. 83

3.6 Alder Canal - Villa Ave Lift Station ...................................................................................................... 86

3.6.1 Location and Layout .............................................................................................................. 86

3.6.2 System Characteristics.......................................................................................................... 88

3.6.3 Inspection Summary.............................................................................................................. 89

3.6.4 Hydraulic Assessment .........................................................................................................105

3.6.5 Recommended Improvements............................................................................................106

3.7 3rd & Ross Lift Station......................................................................................................................111

3.7.1 Location and Layout ............................................................................................................111

3.7.2 System Characteristics........................................................................................................113

3.7.3 Inspection Summary............................................................................................................114

3.7.4 Hydraulic Assessment .........................................................................................................118

3.7.5 Recommended Improvements............................................................................................119

3.8 4th & Wake Lift Station.....................................................................................................................122

3.8.1 Location and Layout ............................................................................................................122

3.8.2 System Characteristics........................................................................................................124

3.8.3 Inspection Summary............................................................................................................125

3.8.4 Hydraulic Assessment .........................................................................................................130

3.8.5 Recommended Improvements............................................................................................131

3.9 8th & Wake Lift Station.....................................................................................................................134

3.9.1 Location and Layout ............................................................................................................134

3.9.2 System Characteristics........................................................................................................135

3.9.3 Inspection Summary............................................................................................................136

3.9.4 Hydraulic Assessment .........................................................................................................138

3.9.5 Recommended Improvements............................................................................................138

3.10 Lift Station No. 2................................................................................................................................140

3.10.1 Location and Layout ............................................................................................................140

3.10.2 System Characteristics........................................................................................................141

3.10.3 Inspection Summary............................................................................................................142

3.10.4 Hydraulic Assessment .........................................................................................................142

3.10.5 Recommended Improvements............................................................................................143

3.11 Orange Lift Station ............................................................................................................................144

3.11.1 Location and Layout ............................................................................................................144

3.11.2 System Characteristics........................................................................................................145

3.11.3 Inspection Summary............................................................................................................146

3.11.4 Hydraulic Assessment .........................................................................................................147

3.11.5 Recommended Improvements............................................................................................148

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 iii OCTOBER 2025

3.12 Lift Station No. 1................................................................................................................................149

3.12.1 Location and Layout ............................................................................................................149

3.12.2 System Characteristics........................................................................................................150

3.12.3 Inspection Summary............................................................................................................151

3.12.4 Hydraulic Assessment .........................................................................................................156

3.12.5 Recommended Improvements............................................................................................157

3.13 Buena Vista Lift Station ....................................................................................................................157

3.13.1 Location and Layout ............................................................................................................157

3.13.2 System Characteristics........................................................................................................158

3.13.3 Inspection Summary............................................................................................................159

3.13.4 Hydraulic Assessment .........................................................................................................160

3.13.5 Recommended Improvements............................................................................................161

3.14 East Side Lift Station.........................................................................................................................162

3.14.1 Location................................................................................................................................162

3.14.2 System Characteristics........................................................................................................164

3.14.3 Inspection Summary............................................................................................................165

3.14.4 Hydraulic Assessment .........................................................................................................166

3.14.5 Recommended Improvements............................................................................................167

3.15 Heil & Dogwood Lift Station..............................................................................................................167

3.15.1 Location................................................................................................................................167

3.15.2 System Characteristics.......................................................................................................168

3.15.3 Inspection Summary............................................................................................................169

3.15.4 Hydraulic Assessment .........................................................................................................170

3.15.5 Recommended Improvements............................................................................................171 4 Recommended Improvement Projects ..........................................................................................................173

4.1 Scheduled Lift Station Improvements and Operational Changes ..................................................173

4.2 General Recommended Improvements...........................................................................................173

4.3 Lift Station CIP Projects.....................................................................................................................174

4.3.1 Project Prioritization ............................................................................................................177

4.3.2 Project Cost Estimation .......................................................................................................179

4.3.3 Project Cost Distribution......................................................................................................180

4.3.4 Summary of Projects ...........................................................................................................181 TABLES
Table 1. Existing Lift Station Characteristics Summary...................................................................................................2 Table 2. Condition Assessment Designations Descriptions............................................................................................5 Table 3. Condition Assessment Designation Examples ..................................................................................................7 Table 4. General Evaluation Summary for Lift Stations by Asset Discipline ............................................................... 16 Table 5. Lift Station No. 3 Pumping Units ..................................................................................................................... 18

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 iv OCTOBER 2025
Table 6. Lift Station No. 3 Structures and Force Main Characteristics....................................................................... 19 Table 7. Lift Station No. 3 Inspection Summary ........................................................................................................... 20 Table 8. Lift Station No. 3 Recommended Improvements........................................................................................... 27 Table 9. Gios Lift Station Pumping Units....................................................................................................................... 31 Table 10. Gios Lift Station Structures and Force Main Characteristics ...................................................................... 31 Table 11. Gios Lift Station Inspection Summary .......................................................................................................... 32 Table 12. Gios Lift Station Recommended Improvements................................................................................... 37 Table 13. Main Lift Station Pumping Units ................................................................................................................... 41 Table 14. Main Lift Station Structures and Force Main Characteristics ..................................................................... 41 Table 15. Main Lift Station Inspection Summary .................................................................................................... 42 Table 16. Main Lift Station Recommended Improvements.................................................................................. 61 Table 17. Countryside Lift Station Pumping Units........................................................................................................ 69 Table 18. Countryside Lift Station Structures and Force Main Characteristics.......................................................... 69 Table 19. Countryside Lift Station Inspection Summary.............................................................................................. 71 Table 20. Legacy Lift Station Pumping Units ................................................................................................................ 78 Table 21. Legacy Lift Station Structures and Force Main Characteristics .................................................................. 78 Table 22. Legacy Lift Station Inspection Summary ...................................................................................................... 79 Table 23. Legacy Lift Station Recommended Improvements...................................................................................... 83 Table 24. Alder Canal – Villa Ave Lift Station Pumping Units ...................................................................................... 88 Table 25. Alder Canal – Villa Ave Lift Station Structures and Force Main Characteristics ........................................ 88 Table 26. Alder Canal - Villa Ave Lift Station Inspection Summary.............................................................................. 89 Table 27. Alder Canal - Villa Ave Lift Station Recommended Improvements ...........................................................106 Table 28. 3rd & Ross Lift Station Pumping Units .......................................................................................................113 Table 29. 3rd & Ross Lift Station Structures and Force Main Characteristics.........................................................114 Table 30. 3rd & Ross Lift Station Inspection Summary .............................................................................................115 Table 31. 3rd & Ross Lift Station Recommended Improvements.............................................................................119 Table 32. 4th & Wake Lift Station Pumping Units ......................................................................................................124 Table 33. 4th & Wake Lift Station Structures and Force Main Characteristics........................................................124 Table 34. 4th & Wake Lift Station Inspection Summary ............................................................................................125 Table 35. 4th & Wake Lift Station Recommended Improvements............................................................................131 Table 36. 8th & Wake Lift Station Pumping Units ......................................................................................................135 Table 37. 8th & Wake Lift Station Structures and Force Main Characteristics........................................................136 Table 38. 8th & Wake Lift Station Inspection Summary ............................................................................................137 Table 39. 8th & Wake Lift Station Recommended Improvements....................................................................139 Table 40. Lift Station No. 2 Pumping Units.................................................................................................................141 Table 41. Lift Station No. 2 Structures and Force Main Characteristics...................................................................141 Table 42. Lift Station No. 2 Inspection Summary.......................................................................................................142

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707
v OCTOBER 2025
Table 43. Lift Station No. 2 Recommended Improvements ......................................................................................143 Table 44. Orange Lift Station Pumping Units..............................................................................................................145 Table 45. Orange Lift Station Structures and Force Main Characteristics ...............................................................145 Table 46. Orange Lift Station Inspection Summary .............................................................................................146 Table 47. Orange Lift Station Recommended Improvements ...................................................................................148 Table 48. Lift Station No. 1 Pumping Units.................................................................................................................150 Table 49. Lift Station No. 1 Structures and Force Main Characteristics...................................................................150 Table 50. Lift Station No. 1 Inspection Summary .................................................................................................151 Table 51. Buena Vista Lift Station Pumping Units......................................................................................................158 Table 52. Buena Vista Lift Station Structures and Force Main Characteristics .......................................................159 Table 53. Buena Vista Lift Station Inspection Summary............................................................................................160 Table 54. East Side Lift Station Recommended Improvements ........................................................................162 Table 55. East Side Lift Station Pumping Units ..........................................................................................................164 Table 56. East Side Lift Station Structures and Force Main Characteristics............................................................164 Table 57. East Side Lift Station Inspection Summary ................................................................................................165 Table 58. East Side Lift Station Recommended Improvements................................................................................167 Table 59. Heil & Dogwood Lift Station Pumping Units ...............................................................................................169 Table 60. Heil & Dogwood Lift Station Structures and Force Main Characteristics .................................................169 Table 61. Heil & Dogwood Lift Station Inspection Summary .....................................................................................170 Table 62. Heil & Dogwood Lift Station Recommended Improvements...........................................................171 Table 63. Scheduled Lift Station Improvements and Operational Changes.............................................................173 Table 64. Recommended Lift Station CIP Projects.....................................................................................................175 Table 65. Lift Station CIP Projects Soft Cost Markup as Percent of Construction Costs .........................................180 Table 66. Lift Station CIP Projects List........................................................................................................................182

FIGURES
Figure 1. Lift Station Vicinity Map.....................................................................................................................................3 Figure 2: Lift Station No. 3 Location.............................................................................................................................. 17 Figure 3: Lift Station No. 3 Layout ................................................................................................................................ 18 Figure 4: Lift Station No. 3 Site Grading and Access.................................................................................................... 20 Figure 5: Lift Station No. 3 Site Safety .......................................................................................................................... 20 Figure 6: Lift Station No. 3 Dry Well Pumps.................................................................................................................. 21 Figure 7: Lift Station No. 3 Bar Screen (Side View) ...................................................................................................... 21 Figure 8: Lift Station No. 3 Piping and Valves............................................................................................................... 22 Figure 9: Lift Station No. 3 Forced Air Ventilation ........................................................................................................ 22 Figure 10: Lift Station No. 3 Dry well structure............................................................................................................. 22 Figure 11: Lift Station No. 3 H2S Sensor...................................................................................................................... 22

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 vi OCTOBER 2025
Figure 12: Lift Station No. 3 Wet Well Liner Delamination .......................................................................................... 23 Figure 13: Lift Station No. 3 Wet Well Raised Walkway............................................................................................... 23 Figure 14: Lift Station No. 3 Panel Enclosure Building ................................................................................................ 23 Figure 15: Lift Station No. 3 Electrical Building............................................................................................................ 23 Figure 16: Lift Station No. 3 Level Sensor Mounting with No Conduit Sealing Fitting. .............................................. 24 Figure 17: Lift Station No. 3 Conduit............................................................................................................................. 25 Figure 18: Gios Lift Station Location.............................................................................................................................. 30 Figure 19: Gios Lift Station Layout................................................................................................................................. 30 Figure 20: Gios Lift Station Facility Site ........................................................................................................................ 32 Figure 21: Gios Lift Station Water Service Backflow Preventor................................................................................... 32 Figure 22: Gios Lift Station Submersible Pumps.......................................................................................................... 33 Figure 23: Gios Lift Station Piping, Valves, and Pipe Supports ................................................................................... 33 Figure 24: Gios Lift Station Wet Well Concrete Condition............................................................................................ 34 Figure 25: Gios Lift Station Wet Well Spalling .............................................................................................................. 34 Figure 26: Gios Lift Station Open Wet Well, Adjacent Electrical Equipment, Electrical Rack .................................... 34 Figure 27: Gios Lift Station Non-Hazardous Rated Electrical Meter & J-Boxes at Wet Well ...................................... 35 Figure 28: Gios Lift Station Galvanized Pipe Used as Electrical Conduit & Electrical Equipment Safety Concern & Equipment Condition Example....................................................................................................................................... 35 Figure 29: Main Lift Station Location ............................................................................................................................ 40 Figure 30: Main Lift Station Layout ............................................................................................................................... 40 Figure 31: Main Lift Station Facility Access Road and Sliding Entrance Gate............................................................ 42 Figure 32: Main Lift Station Facility Sliding Entrance................................................................................................... 43 Figure 33: Main Lift Station Dry Well Access Stairs and Handrails ............................................................................. 43 Figure 34: Main Lift Station Bar Screen Structure Grating .......................................................................................... 43 Figure 35: Main Lift Station Wet Well Access Hatch .................................................................................................... 44 Figure 36: Main Lift Station Electrical Room Lighting ................................................................................................. 44 Figure 37: Main Lift Station Dry Well Pumps and Pump Bases................................................................................... 44 Figure 38: Main Lift Station Dry Well Submersible Sump Pumps ............................................................................... 45 Figure 39: Main Lift Station Bar Screen System........................................................................................................... 45 Figure 40: Main Lift Station Bar Screen System........................................................................................................... 45 Figure 41: Main Lift Station Bypass Connection Assembly.......................................................................................... 46 Figure 42: Main Lift Station Discharge Flow Meter...................................................................................................... 46 Figure 43: Main Lift Station Pump Discharge Valves ................................................................................................... 46 Figure 44: Main Lift Station Sump Pump Discharge Valves and Fittings.................................................................... 47 Figure 45: Main Lift Station Odor Exhaust Standpipe.................................................................................................. 47 Figure 46: Main Lift Station Swamp Cooler Air Inlet Duct within Electrical Building/Dry Well .................................. 47 Figure 47: Main Lift Station Bioxide Injection Station.................................................................................................. 48 Figure 48: Main Lift Station Low-Flow Water Supply System and Surge Tanks ......................................................... 48

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 vii OCTOBER 2025
Figure 49: Main Lift Station Standby Generator Exterior Piping.................................................................................. 49 Figure 50: Main Lift Station Pad-Mounted Emergency ................................................................................................ 49 Figure 51: Main Lift Station Pump Discharge Supports............................................................................................... 49 Figure 52: Main Lift Station Dry Well Structure ............................................................................................................ 50 Figure 53: Main Lift Station Minor Cracking of Dry Well Walls .................................................................................... 50 Figure 54: Main Lift Station Cracking of Concrete Floor.............................................................................................. 50 Figure 55: Main Lift Station Wet Well Top Slab ............................................................................................................ 51 Figure 56: Main Lift Station Wet Well Access Hatches ................................................................................................ 51 Figure 57: Main Lift Station Concrete Wet Well Structure Interior.............................................................................. 52 Figure 58: Main Lift Station Deteriorating Wet Well Liner ........................................................................................... 52 Figure 59: Main Lift Station Compromised Wet Well Liner.......................................................................................... 52 Figure 60: Main Lift Station Electrical/Controls Building............................................................................................. 53 Figure 61: Main Lift Station Interior of the.................................................................................................................... 53 Figure 62: Main Lift Station Access Stairs to Bar Screen Vault................................................................................... 53 Figure 63: Main Lift Station Bar Screen Vault Access Door Frame............................................................................. 54 Figure 64: Main Lift Station Pipe Clamp within Bar Screen Vault ............................................................................... 54 Figure 65: Main Lift Station Concrete Degradation of ................................................................................................. 54 Figure 66: Corroded Generator Piping (Left), Leaning Utility Pole (Right)................................................................... 55 Figure 67: Main Lift Station Standby Natural ............................................................................................................... 55 Figure 68: Main Lift Station Electrical Enclosure Conduits.......................................................................................... 56 Figure 69: Main Lift Station Existing Utility Meter SES,................................................................................................ 56 Figure 70: Main Lift Station Newer ATS & Controller Inside Old ATS’s MCC Section Behind Door ........................... 57 Figure 71: Main Lift Station VFD Enclosure with .......................................................................................................... 57 Figure 72: Main Lift Station Control Panel with 33 Contactors (Four are in Use) ...................................................... 58 Figure 73: Example of Height of Existing Middle Level Lighting.................................................................................. 58 Figure 74: Main Lift Station Existing Drywell Sump Pump Control Panels................................................................. 58 Figure 75: Main Lift Station Large Gaps Around Bar Screen....................................................................................... 59 Figure 76: Main Lift Station Electrical, Screen Control Panel, Conduits, Light (Not Hazardous-Rated).................... 59 Figure 77: Main Lift Station Broken Conduits: At Electrical Building (Left), At Bar Screen (Right)............................ 59 Figure 78: Main Lift Station Typical Bar Screen Vault Light Fixture ............................................................................ 60 Figure 79: Main Lift Station Water Line on Wall Indicating.......................................................................................... 60 Figure 80: Countryside Lift Station Location................................................................................................................ 68 Figure 81: Countryside Lift Station Layout.................................................................................................................... 68 Figure 82: Countryside Lift Station Site ........................................................................................................................ 71 Figure 83: Countryside Lift Station Water Backflow Preventer.................................................................................... 71 Figure 84: Countryside Lift Station Self-Priming Pump and Motors............................................................................ 71 Figure 85: Countryside Lift Station Piping and Valves ................................................................................................. 72

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 viii OCTOBER 2025
Figure 86: Countryside Lift Station Wet Well Access.................................................................................................... 72 Figure 87: Countryside Lift Station Failing Wet Well Liner........................................................................................... 72 Figure 88: Countryside Lift Station Conduit Penetration ............................................................................................. 73 Figure 89: Countryside Lift Station Junction Box with Conduits Directly to Wet Well and Unbolted Cover............... 73 Figure 90: Countryside Lift Station Level Sensor Mounting and Opening to Wet Well .............................................. 74 Figure 91: Countryside Lift Station Broken Power Conduit from Utility Meter as it Enters the Green Fiberglass Enclosure......................................................................................................................................................................... 74 Figure 92: Legacy Lift Station Location......................................................................................................................... 77 Figure 93: Legacy Lift Station Layout............................................................................................................................ 77 Figure 94: Legacy Lift Station Facility Site .................................................................................................................... 79 Figure 95: Legacy Lift Station Submersible Pumps and Guide Rails .......................................................................... 79 Figure 96: Legacy Lift Station Piping and Valves.......................................................................................................... 80 Figure 97: Legacy Lift Station Wet Well Access and Root Intrusion............................................................................ 80 Figure 98: Legacy Lift Station Grease Accumulation in ............................................................................................... 81 Figure 99: Legacy Lift Station New Pump ..................................................................................................................... 81 Figure 100: Legacy Lift Station New Junction Box Intercepting Wet Well Conduits................................................... 81 Figure 101: Legacy Lift Station Missing Sealing Fittings on Conduits from Wet Well................................................ 82 Figure 102: Legacy Lift Station Existing Level Transducer Hanging from its Cable ................................................... 82 Figure 103: Villa Lift Station Location ........................................................................................................................... 86 Figure 104: Villa Lift Station Layout .............................................................................................................................. 87 Figure 105: Villa Lift Station Facility Access Road and Entrance Gate ....................................................................... 89 Figure 106: Villa Lift Station Site Security Fencing ...................................................................................................... 89 Figure 107: Villa Lift Station Dry Well Access Stairs..................................................................................................... 90 Figure 108: Villa Lift Station Above Grade Tripping Hazards Near Wet Well .............................................................. 90 Figure 109: Villa Lift Station Depressed Area Near...................................................................................................... 90 Figure 110: Villa Lift Station Dry Well Light Switch....................................................................................................... 90 Figure 111: Villa Lift Station Inoperable Lighting ......................................................................................................... 91 Figure 112: Villa Lift Station Inoperable Lighting within Electrical Building ............................................................... 91 Figure 113: Villa Lift Station Influent Manhole Lid at the Bottom of Manhole........................................................... 91 Figure 114: Villa Lift Station Dry Pit Pumping Units and Discharge Piping................................................................. 92 Figure 115: Villa Lift Station Dry Pit Pumping Units and.............................................................................................. 92 Figure 116: Villa Lift Station Future Pump.................................................................................................................... 92 Figure 117: Villa Lift Station Dry Pit Pump Motor......................................................................................................... 92 Figure 118: Villa Lift Station Pump Suction Body and Suction Elbow......................................................................... 93 Figure 119: Villa Lift Station Pump Discharge.............................................................................................................. 93 Figure 120: Villa Lift Station Pump Discharge Piping, Valves, and Force Main.......................................................... 93 Figure 121: Villa Lift Station Floor-Mounted Pipe Supports......................................................................................... 94 Figure 122: Villa Lift Station Wall-Mounted Pipe Struts............................................................................................... 94

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 ix OCTOBER 2025
Figure 123: Villa Lift Station Sump Pump Discharge Piping........................................................................................ 94 Figure 124: Villa Lift Station Wet Well Suction Piping.................................................................................................. 94 Figure 125: Villa Lift Station Dry Well Supply Air Ducting ............................................................................................ 95 Figure 126: Villa Lift Station Dry Well Ventilation Ducting ........................................................................................... 95 Figure 127: Villa Lift Station Ventilation Air Exhaust Blowers...................................................................................... 95 Figure 128: Villa Lift Station Air Intake Filter Bank and Supply Blower Motors.......................................................... 95 Figure 129: Villa Lift Station Electrical Building Heater and Exhaust Units................................................................ 96 Figure 130: Villa Lift Station Electrical Building Heater and Exhaust Vents ............................................................... 96 Figure 131: Villa Lift Station Dry Well Access Ladder .................................................................................................. 96 Figure 132: Villa Lift Station Infiltration ........................................................................................................................ 97 Figure 133: Villa Lift Station Dry Well Access Stairs..................................................................................................... 97 Figure 134: Villa Lift Station Pipe Penetration.............................................................................................................. 97 Figure 135: Villa Lift Station Dry Well Roof Equipment Hatch..................................................................................... 98 Figure 136: Villa Lift Station Wet Well Structure .......................................................................................................... 98 Figure 137: Villa Lift Station Wet Well Structure .......................................................................................................... 98 Figure 138: Villa Lift Station Wet Well Ceiling/Top Slab (Facing East)........................................................................ 99 Figure 139: Villa Lift Station Wet Well Ceiling/Top Slab (Facing West) ...................................................................... 99 Figure 140: Villa Lift Station Wet Well Bottom and ...................................................................................................... 99 Figure 141: Villa Lift Station Wet well Access............................................................................................................... 99 Figure 142: Villa Lift Station Influent Manhole Cone Section and Liner...................................................................100 Figure 143: Villa Lift Station Influent Manhole Bench and Chemical Buildup..........................................................100 Figure 144: Villa Lift Station Influent Manhole Bench and Chemical Buildup..........................................................100 Figure 145: Villa Lift Station Manhole.........................................................................................................................100 Figure 146: Villa Lift Station Electrical Building..........................................................................................................101 Figure 147: Villa Lift Station MCC Condition and Four Holes in MCC Face for Pump #1 ........................................101 Figure 148: Villa Lift Station Partially Inoperable Lighting in Electrical Building ......................................................101 Figure 149: Villa Lift Station Existing Discontinued PLC............................................................................................102 Figure 150: Villa Lift Station Level Transmitter Junction Box (Left), Float Switch Junction Box (Right)..................102 Figure 151: Villa Lift Station SES Main .......................................................................................................................103 Figure 152: Villa Lift Station Corroded Exhaust..........................................................................................................103 Figure 153: Villa Lift Station Drywell Conduit, Lighting and Instrument Corrosion ..................................................103 Figure 154: Villa Lift Station Water Infiltration (Severe Conduit Corrosion Where Conduits Penetrate Wall) ........104 Figure 155: 3rd & Ross Lift Station Location..............................................................................................................112 Figure 156: 3rd & Ross Lift Station Layout.................................................................................................................113 Figure 157: 3rd & Ross Lift Station Facility Site.........................................................................................................115 Figure 158: 3rd & Ross Lift Station Self-Priming........................................................................................................115 Figure 159: 3rd & Ross Lift Station Piping and Valves ..............................................................................................115

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707
x OCTOBER 2025
Figure 160: 3rd & Ross Lift Station Wet Well .............................................................................................................116 Figure 161: 3rd & Ross Lift Station Wet .....................................................................................................................116 Figure 162: 3rd & Ross Lift Station Conduit Penetration ..........................................................................................116 Figure 163: 3rd & Ross Lift Station Fiberglass Enclosure with Equipment, Level Sensor Penetration and Manhole in Close Proximity..............................................................................................................................................................117 Figure 164: 3rd & Ross Lift Station Uncapped...........................................................................................................117 Figure 165: 3rd & Ross Lift Station Float Switch Cable Outside Enclosure (Between Enclosure and Wet Well, Not in Conduit).........................................................................................................................................................................117 Figure 166: 3rd & Ross Lift Station Utility Meter and Main Breaker Condition........................................................118 Figure 167: 4th & Wake Lift Station Location ............................................................................................................123 Figure 168: 4th & Wake Lift Station Layout................................................................................................................123 Figure 169: 4th & Wake Lift Station Concrete Pad (Left), Water Meter Backflow Preventer (Right) ......................125 Figure 170: 4th & Wake Lift Station Suction and Discharge Piping Above Grade ...................................................126 Figure 171: 4th & Wake Lift Station Suction and Discharge Piping Within Wet Well ..............................................126 Figure 172: 4th & Wake Lift Station Self-Priming Pumps..........................................................................................126 Figure 173: 4th & Wake Lift Station Wet Well............................................................................................................127 Figure 174: 4th & Wake Lift Station Wet Well Top Slab ............................................................................................127 Figure 175: 4th & Wake Lift Station Wet Well............................................................................................................127 Figure 176: 4th & Wake Lift Station Fiberglass Enclosure with Equipment, Level Penetration Inside and Manhole in Proximity........................................................................................................................................................................128 Figure 177: 4th & Wake Lift Station Level Transducer Penetration Inside the Fiberglass Enclosure ....................128 Figure 178: 4th & Wake Lift Station Example of Gap/Opening to Wet Well.............................................................128 Figure 179: 4th & Wake Lift Station Receptacle and Swich (Left), Exposed Wires and Terminations (Right) .......129 Figure 180: 4th & Wake Lift Station Electrical Utility Meter and Main Breaker Enclosure......................................129 Figure 181: 4th & Wake Lift Station Broken...............................................................................................................129 Figure 182: 8th & Wake Lift Station Location ............................................................................................................134 Figure 183: 8th & Wake Lift Station Layout................................................................................................................135 Figure 184: 8th & Wake Lift Station Wet Well Concrete at Access Manhole ...........................................................137 Figure 185: 8th & Wake Lift Station Wet Well Walls..................................................................................................137 Figure 186: 8th & Wake Lift Station Wet Well Liner...................................................................................................137 Figure 187: 8th & Wake Lift Station Transducer Penetration and Wet Well Access................................................138 Figure 188: Lift Station No. 2 Location .......................................................................................................................140 Figure 189: Lift Station No. 2 Layout ..........................................................................................................................140 Figure 190: Lift Station No. 2 Access Hatch (Above) and Wet Well (Below).............................................................142 Figure 191: Orange Lift Station Location....................................................................................................................144 Figure 192: Orange Lift Station Layout .......................................................................................................................144 Figure 193: Orange Lift Station Wet Well Structure ...................................................................................................146

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 xi OCTOBER 2025
Figure 194: Orange Lift Station Wet Well Manhole Cover (Top Left), Wet Well Access Manhole (Top Right), Level Sensor Penetration (Bottom) .......................................................................................................................................146 Figure 195: Lift Station No. 1 Location .......................................................................................................................149 Figure 196: Lift Station No. 1 Layout ..........................................................................................................................149 Figure 197: Lift Station No. 1 Facility Site ..................................................................................................................151 Figure 198: Lift Station No. 1 Dry Well Access ...........................................................................................................151 Figure 199: Lift Station No. 1 Self-Priming Pump and Motors .................................................................................152 Figure 200: Lift Station No. 1 Piping and Valves........................................................................................................152 Figure 201: Lift Station No. 1 Wet Well Riser .............................................................................................................153 Figure 202: Lift Station No. 1 Wet Well Structure and Suction Elbow ......................................................................153 Figure 203: Lift Station No. 1 Broken Conduits Due to..............................................................................................154 Figure 204: Lift Station No. 1 Broken Conduit at LB and ..........................................................................................154 Figure 205: Lift Station No. 1 Exposed Fan Wiring and Wire Terminations in Drywell.............................................155 Figure 206: Lift Station No. 1 Utility Meter, Main Disconnect, and Conduits on Utility Pole ...................................155 Figure 207: Buena Vista Lift Station Location............................................................................................................157 Figure 208: Buena Vista Lift Station Layout ...............................................................................................................158 Figure 209: Buena Vista Lift Station Wet Well............................................................................................................160 Figure 210: Buena Vista Lift Station Wet Well Access ...............................................................................................160 Figure 211: East Side Lift Station Location ................................................................................................................163 Figure 212: East Side Lift Station Layour ..................................................................................................................163 Figure 213: East Side Lift Station Wet Well................................................................................................................165 Figure 214: East Side Lift Station Wet Well Access Hatch.........................................................................................165 Figure 215: Heil & Dogwood Lift Station Location.....................................................................................................168 Figure 216: Heil & Dogwood Lift Station Layout.........................................................................................................168 Figure 217: Heil and Dogwood Lift Station Wet Well .................................................................................................170 Figure 218: Heil and Dogwood Lift Station .................................................................................................................170 Figure 219. Lift Station CIP Project .............................................................................................................................177 Figure 220: Lift Station CIP Total Project Cost Distribution .......................................................................................181

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 xii OCTOBER 2025

ATTACHMENTS
Attachment A: Lift Station CIP Project Cutsheets

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 xiii OCTOBER 2025

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CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 xiv OCTOBER 2025
Acronyms and Abbreviations
Acronym/Abbreviation Definition
AC Asphalt Concrete
ATS Automatic Transfer Switch
CEC California Electrical Code
CIP Capital Improvement Plan
CMU Concrete Masonry Unit
DIP Ductile Iron Pipe
EI&C Electrical, Instrumentation, and Controls
FOG Fats, Oils and Grease
ft/s Feet Per Second
FY Fiscal Year
gpm Gallons Per Minute
H2S (H2S) Hydrogen Sulfide
HI Hydraulic Institute
HP Horsepower
HWL High Water Line
IID Imperial Irrigation District (electrical utility)
LS Lift Station
MTS Manual Transfer Switch
MCC Motor Control Center
NA or N/A Not Accessible or Not Applicable
NEC National Electrical Code
NEMA National Electric Manufacturers Association
NFPA National Fire Protection Association
OSHA Occupational Health and Safety Administration
PLC Programmable Logic Controller
RFP Request For Proposals
RTU Remote Telemetry Unit
SES Service Entrance Section
SMP/SSMP Sewer [System] Master Plan
SSO Sanitary Sewer Overflow
TDH Total Dynamic Head
UPS Uninterruptible Power Supply
UWMP Urban Water Management Plan
VFD Variable Frequency Drive
WRF Water Reclamation Facility
WWTP Waste Water Treatment Plant

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707
xv OCTOBER 2025

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CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 1 OCTOBER 2025
1 Introduction
The City of El Centro (City) contracted Dudek to prepare a Sewer Master Plan Update that incorporates Condition Assessments and Capital Improvement Plans for the City’s wastewater system that will guide strategic planning and investments for the City’s collection and treatment programs.

The following technical memorandum provides desktop analysis and assessment/evaluation of all fifteen (15) lift stations. Dudek and the City have determined that a comprehensive field investigation is only necessary for select older and critical lift stations. Nine (9) out of the City’s fifteen (15) active lift stations will receive a comprehensive condition assessment. A wet well assessment was performed on remaining six (6) active lift stations. In addition, this technical memorandum provides a list of recommended Capital Improvement Plan (CIP) projects with estimated associated planning-level construction value for the associated improvements of each lift station.

Table 1 displays summarized record information for the City’s fifteen (15) existing sewer lift stations and Figure 1 includes a vicinity map displaying the general location of each lift station. The lift station characteristics were compiled from available record drawings, information provided by City operations staff, and the City’s 2008 Sewer System Master Plan (SSMP). Where possible, asset characteristics were visually confirmed during field inspections.

Note that in some instances equipment identification labels/nameplates were not accessible or were found to no longer exist during field inspections; therefore, characteristics of some equipment shown on record drawings could not be verified during field investigations.

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 2 OCTOBER 2025
Table 1. Existing Lift Station Characteristics Summary
Lift
Stati
on
No.

Lift
Station
Site
Year of Install
or Modification
Facility Type Firm Capacity
Scope of Condition Assessment
Comprehensive Wet Well Only

1 Lift
Station
No. 3
2006 Wet Well/Dry Well 3,000 gpm @

37.4’ TDH X
2 Gios 1976 Submersible Wet Well 250 gpm@ 20’
TDH X
3 Main
1933
2007
(Rehabilitation)
Wet Well/Dry Well 2,535 gpm @
39’ TDH X
4 Countrysi
de 2002
Above Grade
Packaged Pump
Station
550 gpm @ 45’
TDH X
5 Legacy 2006 Submersible Wet Well 250 gpm @ 20’ X
6 Alder
Canal/
Villa Ave
2005 Wet Well/Dry Well Unknown X
7 3rd &
Ross 1988
Above Grade
Packaged Pump
Station
325 gpm @ 27
TDH’ X
8 4th &
Wake 1985
Above Grade
Packaged Pump
Station
200 gpm @
Unknown TDH X
9 8th &
Wake 2006
Above Grade
Packaged Pump
Station
200 gpm @ 35’
TDH X
10 Lift
Station
No. 2
1975
2016
(Relocated)
Submersible Wet Well 850 gpm @ 30’
TDH X
11 Orange
Ave 2005
Above Grade
Packaged Pump
Station
400 gpm @ 46’
TDH X
12 Lift
Station
No. 1
1975 Wet Well/Dry Well 400 gpm @

14.6 TDH X
13 Buena
Vista 2006
Above Grade
Packaged Pump
Station
369 gpm @ 27’
TDH X
14 East Side
1913
2007
(Rehabilitation)
Submersible Wet Well 1,000 gpm @
26’ TDH X
15 Heil &
Dogwood 1993
Above Grade
Packaged Pump
Station
250 gpm @ 25’
TDH X

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 3 OCTOBER 2025
Figure 1. Lift Station Vicinity Map

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 4 OCTOBER 2025
2 Project Background and Approach
The City of El Centro’s sewage collection system is currently comprised of fifteen (15) lift station (LS) sites and associated force mains, 125 miles of gravity pipe and one (1) Wastewater Treatment Plant (WWTP). The age of the assessed lift stations varies from 19 to 112 years old, though some have been modified or rehabilitated since. The system serves an approximate population of 44,000 (2020 Urban Water Management Plan, Psomas) and the continued operation and expansion of the system is a critical factor in the City’s success. Dudek was tasked with completing condition assessments of major elements of the City’s sewer infrastructure and providing CIP recommendations as part of an updated Sewer Master Plan.

The new Southern Lift Station is currently under construction and is intended to replace the 4th & Wake, Legacy, and Countryside Lift Stations within the next five years. Flow from these three lift stations will be redirected to the new Southern Lift Station wet well. Accordingly, each of the three lift stations can be decommissioned once flows have been redirected to the new Southern Lift Station. Additionally, the City informed Dudek that Imperial County (County) has secured a grant to replace Lift Station No. 1. The lift station replacement project is currently under design and is scheduled to be replaced. This facility is owned and operated by the City but serves the County and is outside the City’s limits.

The City cited odor problems as a key issue within the collection system. The City currently spends about $300,000 per year on chemical dosing and injection to control odor problems, but this approach has limited success. Odor problems due to hydrogen sulfide gas generated within the collection system are mainly caused by oversized lift stations and force mains (i.e., excess capacity), which lead to long detention times and anaerobic conditions. A key contributor to the odor problems is the Alder Canal – Villa Avenue Lift Station force main, which is a 20-inch PVC pipe that is approximately 12,000 feet long. The hydraulic efficiencies and corresponding recommendations for improvement are discussed in Section 3.6.

2.1 Objective
The objective of this task is to perform condition assessments for fifteen (15) of the City’s active lift stations, identify asset deficiencies, and develop prioritized improvement recommendations for rehabilitation or replacement of assets at each lift station. Six (6) of these active lift stations will only have their wet wells assessed. Recommended improvements are to be grouped and prioritized based on factors including existing conditions, failure risks, and accommodation for anticipated growth.

2.2 Field Investigation Overview
Dudek staff performed condition assessment field investigations on February 11, 12, and 13 of 2025 to observe and assess the condition of existing site/civil, mechanical, structural, and electrical, instrumentation and controls (EI&C) assets at the City’s lift stations. The condition assessment team featured registered professional engineers in civil engineering and electrical engineering with in engineers-in-training (EIT) playing a supporting role. City staff assisted with the investigations by providing access to facilities and providing insight relating to the operational performance and history of various facilities and equipment, including maintenance and emergency access

CITY OF EL CENTRO SEWER LIFT STATION CONDITION ASSESSMENT TECHNICAL MEMORANDUM 16707 5 OCTOBER 2025
concerns. The condition assessment team that performed the site investigations are hereinafter referred to as “inspector.”

2.3 Condition Assessment Methodology
The approach to the comprehensive condition assessment of the lift stations will identify specific site civil, mechanical, structural, EI&C improvements that extend the useful life and provide increased operational reliability of each lift station. Additionally, evaluation of safety, emergency features, access, and impact to the surrounding environment suggests improvements that will reduce risk of injury, risk of sewer spill, and prevent negative impacts to the community.

The condition assessment field investigation consisted of visual inspection for rust, corrosion, cracking, leaks, abnormal noise, and other indications suggesting wear to gauge the relative condition of the facility. In some cases, the City staff provided information regarding the condition of mechanical and electrical equipment which the inspector would not otherwise see or detect, such as historical failures, reoccurring issues, prior rehabilitation and/or replacement, and/or retrofits. This information from City staff is included in the observations for each facility as applicable. Assets at each lift station were organized into one of four specific disciplines. Facility asset disciplines were organized according to the following:
• Site/Civil: Civil elements including grading, paving, perimeter fencing, access, and utilities. • Mechanical: Pumps, piping, valves, odor control and mechanical equipment, and any HVAC within the lift station.
• Structural: Access hatches and covers, facility structures including below-grade concrete structures, wet well, lift station, vaults, and superstructures, as applicable. • Electrical & Instrumentation: Electrical service equipment, emergency power equipment, motor controls, instruments, and control panel.

An additional evaluation was performed to characterize the climate change vulnerability at lift stations where a comprehensive assessment was completed. This included assessing the potential impacts from flooding, electrical outages, and extreme heat.

Following the field inspection, equipment, structures, and electrical gear were assigned one of four condition designations to describe relative condition. The general condition designations are explained in Table 2.

Table 2. Condition Assessment Designations Descriptions Condition Description
Excellent
Observed to be new or like new. No corrosion, rust, coating deterioration or structural deficiencies detected during inspection. Wear and maintenance of the facility is appropriate for age and use intensity. City staff do not report any operations or maintenance deficiencies or concerns such as excessive noise, vibration, or leaks.

Good
Observed to be operating as intended with minimal corrosion, rust, painting deterioration, and no structural deficiencies. Normal wear and maintenance of the facility or components is observed but does not appear to be inhibiting performance. City staff does not report any significant operations or maintenance deficiencies or concerns.