City of Merced
Wastewater
Collection
System Master
Plan
January 18, 2023
City Council
Presentation
1 2
Agenda
• Previous Studies
• Wastewater Unit Rate Update
• Updated Wastewater Flow Projections
• Existing System
• Interim System
• Buildout System
• CIPs & Recommendations
2022 Master Plan Update Built on Previous Work
• 2017 Wastewater Collection System Master Plan Draft
¾Recommended expansion of existing WWTF instead of building new wastewater treatment plant in North Merced
¾Looked at two buildout sewer trunk options for collection system but no Interim Solution
• 2020 Wastewater Collection System Hydraulic Model Conversion & South Trunk Sewer Service Alternatives Analysis
¾Model was converted from ICM to PCSWMM using new flow monitoring data
¾Buildout solutions were revaluated for South Merced
BACKGROUND
3 Per-Capita Flow
Analysis
WASTEWATER UNIT RATE UPDATE
4 Parameter
Updated Unit Rate
Values
Previous Planning
Values
Average Per Capita Flow (gpcd) 60 (1)
85Factor of Safety (gpcd) 5
Recommended Per Capita Flow
(gpcd) 65
EDU Density (persons per
household) 3.20
(2) 3.02 (3)
Unit Wastewater Generation Rate
(gpd/EDU) 208 257
1. Average per capita flow based on 2021 fl ow monitoring efforts, as shown in Table 4-3.
2. The per-capita density of single-family housing units from the City’s Financing Plan and Impact Fee Update Report (December 2021) prepared by Economic & Planning Systems, Inc.
3. The 2030 General Plan defines the average residential dens ity within the City’s SUDP as 3.02 persons/unit. 5 Updated
Wastewater
Flow
Projections
Service Area Total Area
(Acres)
Total
EDUs ADWF (MGD)
Existing Service Area (1) 6,497 33,029 6.88
x UC Merced (2) 200 0.14
Total Existing 6,697 33,029 7.02
Interim Service Area
x General Plan Land Use Parcels 2,737 19,669 4.09
x City Specified Land Use Parcels 82 788 0.16
x Single Lot Parcels/ 1 EDU 407 2,129 0.44
x Specific Development Plan Parcels 311 2,417 0.50
x UC Merced (committed ADWF exceeding existing, 0.13 MGD) (2) 380 - 0.13 x Pre-Annexation Areas (5) 155 5,480 1.15
Subtotal Interim 4,072 30,483 6.47
Buildout Service Area
x Pre-Annexation Areas (Remaining) 1,555 12,432 2.59
x Remaining Parcels within SUDP (General Plan) Boundary (3) 9,313 49,642 10.33 x Campus Community (planning ADWF estimate, 0.84 MGD) (4) 1,106 - 0.84 Subtotal Buildout 11,974 62,074 13.76
Total Interim Service Area 10,769 63,512 13.49
Total Buildout Service Area 22,743 125,586 27.25
1. The existing total EDU estimate is approximate and was provided by the City; existing system flows are based on flow monitoring data independent of actual EDUs.
2. UC Merced wastewater flow equates to the projections provided in the 2020 UC Merced Long Range Development Plan Recirculated Draft Subsequent Environmental Impact Report, (December 2019). The existing flow is approximately 0.14 MGD with an addition of
0.13 MGD projected under future conditions resulting in a total flow of approximately 0.27 MGD.
3. The area and EDU estimate of parcels bisected by the City’s S UDP boundary are limited to the portion that exists within the City’s planning area.
4. ADWF estimate from Table 2.0-8 of the UC Merced and University Community Project Final EIS/EIR (March 2009), scaled to reflec t changes to the wastewater unit rate (208/257). See Section 4.1 of this report.
5. After model completion, the amount of available capacity fo r pre-annexation areas, after implementation of proposed improvements, was considered. These available EDUs and flow capacity are listed here.
Existing System Results
The existing model was used to
evaluate the extent of hydraulic
deficiencies within system under peak
flow conditions. The model simulates
an ADWF of 7.02 MGD and predicts a
PWWF of 19.5 MGD will occur at the
WWTF under 10-year, 24-hour design
storm conditions.
The existing system has sufficient
capacity to convey PWWF flows and
meet level of service (LOS) guidelines
with no significant surcharging
. 6
Interim System Results
The results of the interim system model
predicts LOS failures and capacity
deficiencies in several reaches of the
trunk system, including the G Street,
Rascal, North Merced West Ave, and
48-inch Interceptor trunk sewers.
Despite surcharging and capacity
limitations, no sewer system overflows
(SSOs) are predicted to occur within the
system under interim conditions.
7 Interim System
Improvements
x CIP 1: BRPS FM Discharge Change: Operational modifications to FM discharge location.
Adds Additional 3,000 EDUs, limited to the G Street trunk sewer x CIP 2: Parallel Sewer & Creek Crossing: New 48-inch parallel sewer and creek crossing.
Adds Additional 48,500 EDUs, limited by upstream capacity & CIP 3 & 4 x CIP 3 & 4: West Ave. & 48-inch Interceptor: Replace and expand the 48-inch Interceptor and West Ave sewers to 60-inch.
Adds Additional 48,500 EDUs, limite d by upstream capacity and CIP 2 x CIP 5: Yosemite Sewer Extension & Creek Crossing: A new 27-inch extension of the Yosemite Avenue sewer west connecting G Street, R Street, and the Highway 59 Pump Station (H59PS) sewer shed.
Adds Additional 5,480 EDUs, limited by upstream capacity and H59PS 8 9EXISTING INFLUENT TRUNK SEWER
9 Influent Trunk – Existing
Condition
Buildout System
Approach
Size Interim Improvements for Build-out and Upsize
Highway 59 Pump Station.
BUILDOUT SYSTEM
10 CIP No Name
Existing
Pipe Size (in)
Slope (ft/ft) Length (ft)
Interim
Pipe Size (in)
Buildout
Pipe Size (in)
1 BRPS FM
Discharge
Change (1)
NA NA NA NA NA
2 Parallel Sewer
& Creek
Crossing
NA 0.00067 6,491 36 48
3 West Ave. 42 Current: 0.0007
New: 0.0006 1,900 48
Current Slope:
60 New Slope: 60
4 48-inch
Interceptor 48 Current: 0.0003
New: 0.0006 14,695 48 (2)
Current Slope:
66 New Slope: 60
5 Yosemite Sewer
Extension NA 0.00047 7,660 27 27
1. CIP No. 1 includes changing the discharge of the Bellevue Ranch Pump Station to utilize its existing alternative force main which discharges flow to the gravity sewer along R Street.
2. A new 48-inch pipe with a roughness (n) of 0.013 has capacit y to convey interim flow at the existing slope. The existing 48-inch pipe is known to have a much higher roughness value and would require replacement.
3. CIPs 3 and 4 are recommended to be constructed together at the new specified slope, dropping the invert at the influent junction box at the WWTF
NORTH MERCED BUILDOUT IMPROVEMENTS
11 Proposed
Buildout
System
Improvement
Projects
(South
Merced)
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SOUTH MERCED BUILDOUT IMPROVEMENTS
12 Proposed
Buildout
System
Improvement
Projects
(South
Merced)
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COSTS SUMMARY
13 Item Area of Improvements Total Cost
1 Interim System Improvements $30,310,000
2 North Merced Major Improvements $58,906,000
3 South Merced Major Improvements $18,182,000
Subtotal Major Improvements $107,398,000
4 North Merced Minor Improvements $12,536,000
5 South Merced Minor Improvements $4,456,000
Subtotal Minor Improvements $16,992,000
Total Improvements Cost $124,390,000
•Costs based on ENRCCI (20 Cities Index) = 13,175, October 2022.