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Project No 40186VIS / Storm Nexus Study Proposal 5_ 7_25.docx May 9, 2025
Katherine Woodhull-Fuget
City of Visalia
Engineering and Building Department
315 E Acequia Ave.
Visalia, CA 93291
Subject: Storm System Nexus Study
Dear Katherine:
Enclosed is a Scope and Fee prepared by Carollo Eng ineers, Inc. (Carollo), to provide an updated master plan, nexus study, and rate study for the City of Visalia (City) Storm system. In addition to rate study analysis, updates to the storm master plan will be incorporated. The following sections outline our project team, scope, and fee for this work.
Project Team
We have selected a team that is both familiar with the City of Visalia and can provide specialized expertise in stormwater systems. Our team will provide the City with a technically sound and comprehensive plan to guide future project cost to support the required storm improvements. Ryan Sellman is the proposed principal-in- charge and will lead resource management for the pr oject team. Reace Fisher , who will be responsible for day- to-day communication with the City and the project team. Reace will be supported by a team of qualified staff essential to meeting the project goals. Isalah Barnes , who has been supporting the City on the collection system rate study and has over 16 years of related financial experience, will serve as the project’s financial technical advisor. She has not only served the City of Visalia, but numerous clients with rate study/nexus study projects throughout California. Ryan Orgill will lead the planning efforts team. Ryan has over 20 years of hydraulic modeling support and helped the City on their last two master plan updates.
Scope of Work
The following scope of work is our interpretation of the City’s base scope of work provided and our understanding of the desired changes after City rev iew. There are sub-tasks included in this scope of work without associated sub-task fees in the detailed co st schedule simplified for billing purposes. These tasks are described in detail to provide clarity on the overall completion of the project per City direction.
Storm Drain Tasks
Task SD-1 – Model Review
After some discrepancies with the initial models de veloped by CWE were identified, particularly in comparison with the City’s adopted Storm Master Plan and Engin eering Standards, City staff utilized the models provided by CWE to conduct additional research and explore desi gn alternatives. This included some extensive modification to CWE’s models.
Katherine Woodhull-Fuget
City of Visalia
Now that the City has explored design alternatives and settled on revised design parameters to utilize moving forward, the City intends to provide Carollo with the revised models and associated documentation. Und er this task, Carollo will:
Validate the City-revised existing and future conditions models. Review the revised models and associa ted documentation for flaws in approach, methodology, a ssumptions, and engineering judgement. Bring any identified flaws and proposed improvements or solut ions to the attention of City staff for discussion. Based on discussions with City staff, further modify the models as needed for sound engineering practi ce.
Deliverables:
Memorandum summarizing findings of model review
Carollo-validated (and revised if necessary) Existing Conditions and Future Conditions SWMM models GIS deliverables (packaged geodatabase with layers/ shapefiles for SWMM elements) Task SD-2 – Master Plan Redevelopment
Carollo will revise the draft Storm Master Plan as part of this task. The revised Storm Master Plan will be updated to:
Provide direction for development
» Identify tributary areas
» Propose pipe sizes and depths
» Identify (potential) basin locations
» Propose basin capacities (and dimensions)
» Clearly define design criteria
Level of Protection for different types of infrastructure Minimum pipe sizes, slopes, and velocities
Accepted calculation methods
– Establish runoff coefficients and other constants
Provide a basis for updating the storm impact fees
» Outline Master Plan CIPs with defensible cost estimates (include discussion of cost estimate methodology)
» Clearly define included and excluded costs (what is covered by the impact fee) Provide a high level basis for updating the storm service charges » Outline Master Plan CIPs to address existing deficiencies Articulate design criteria used to evaluate the existing system Provide defensible cost estimates for CIPs for iden tified deficiencies Provide placeholder/generalized CIPs for MS4 Compli ance deficiencies » Include a recommendation of further evaluation of the conveyance capacity of the waterways, and for further regional flood control efforts
Katherine Woodhull-Fuget
City of Visalia
Discuss value/drawbacks of integrated modeling of the waterways » Estimate R&R needs based on estimated age of existi ng system Provide rough order of magnitude estimates for repl acement of aging/failing infrastructure, including culverts
» Estimate operation and maintenance costs given proj ected growth and maintaining an acceptable level of service
Articulate how the design criteria were established
» Discuss how the City’s design methodology, philosop hy, and criteria have changed over time Ex: shift from detention to retention
» Discuss the differences between the continuous mode ling approach and the rational method, and the steps taken to converge the two
Discuss overlap between storm master plan and MS4 compliance » MS4 hydromodification requirements (development pea k runoff cannot exceed pre-development peak runoff of 2-year 24-hour design storm)
Under this task, Carollo will revise the draft Storm Master Plan draft prepared by CWE to meet the nee ds outlined above. Modifications to specific sections of the draft are outlined below. Executive Summary – update
1. Introduction – update to discuss previous efforts in more depth, as appropriate 2. Existing Conditions – revise to add more descrip tion of the existing drainage system design and less detail into the ditch agreements
3. Basis of Design – update
» 3.1. Level of Protection – elaborate on the listed level of protection. Provide the additional context of the modeling method used in 1994 in comparison with the Rational method used to check incoming development. Explain what the estimated level of protection provided by existing infrastructure is (e.g., roughly 2-year).
The 1994 MP did not run a 10-day duration storm, it ran a 1-day storm for both the 2-year and the 10-year events. All of the in-town regional basins outlined in the 1994 MP were designed as detention, not retention. The 1994 MP only identified the waterways and the Goshen Drain as “Major Drains” subject to the 10-year level of protection, with everything else identified as Minor (Collector) Drains sized for no less than the 2-year level of protection (in many cases a value somewhere between the 2-year and the 10-year was selected).
Incoming development has been evaluated using the R ational method and only held to a 2-year level of protection for conveyance. Basins have bee n sized using the rational coefficients and so provide capacity less than that required by modelin g a continuous 10-year, 10-day storm.
Katherine Woodhull-Fuget
City of Visalia
» 3.2. Low Impact Development – elaborate on implications of MS4 compliance on storm drain infrastructure and master planning. Describe the im pact, if any, increased LID implementation will have on the functionality of the overall system
4. Hydrologic Analysis – update based on City’s mod eling efforts » 4.1. Modeling Approach – update, note removal of se epage from sizing of storage units » 4.2. Scenarios – update design storms
» 4.3. Subcatchment Delineation – update figures
» 4.4. Rainfall – elaborate on NOAA Atlas 14 data usage. Include discussion of variability across the City and defend the use of a single set of values city-wide
» 4.5. Infiltration – provide source information for the curve numbers and land cover data (or tie back to section 4.1). Add a comparison of mapped hydrologic groups with those in the 1994 master plan (the dominant soil type in the 1994 MP was type C but the updated soil survey has the dominant type as type B) and discuss the implications on model results.
» 4.6. Runoff – update to reflect removal of percent imperviousness because it is already accounted for in the CN. Note that subcatchments with zero slope wer e estimated based on neighboring catchments to ensure their runoff was accounted for.
5. Hydraulic Analysis of Waterways – Add a disclaimer to this section regarding the limited usefulness and accuracy associated with the 2006 LiDAR data used b y CWE, which was modified based on the assumption that there was ponded water or vegetation. The disc laimer would also apply to the associated model results. » 5.1. Modeling Approach – explain the rationale of the selected modeling approach of using HEC-RAS models for the waterways, rather than a single mode l in SWMM5 » 5.2. Stormwater Outfall Flows – Update based on City’s modeling efforts. Clarify, as appropriate, how the outfall peak flows were derived from the model(s) and discuss the uncertainty involved in comparing the sum of outfall discharges distributed along a waterway with the channel capacity of point cross-sections. » 5.3. Analysis and Results – discuss, as appropriate, the use of 2006 LiDAR data and the assumptions involved in modifying cross-sections. Describe what flows were applied to the HEC-RAS models and where, and clearly articulate under what circumstances (and design storm) bank overtopping occurs. 6. Hydraulic Analysis of Basins, Pumps, & Pipe Network » 6.1. Modeling Approach – Elaborate on the dynamic w ave method vs kinematic wave method. At a minimum, note that the 1994 MP used the kinematic w ave method and explain why the dynamic wave method was used instead.
» 6.2. Existing Conditions Model Components – update based on City’s modeling efforts » 6.3. Existing Conditions Deficiencies - update base d on City's modeling efforts » 6.4. Future Conditions Model Components - update ba sed on City's modeling efforts 6.4.1. Storage Basins – elaborate on design of future storage basins. Include discussion of water depths in park-basin facilities
7. Stormwater Management Alternatives
Katherine Woodhull-Fuget
City of Visalia
» 7.1. Level of Protection – provide an evaluation of the current and alternative levels of protection. Discuss the implications of changing the level of protection and make a recommendation. » 7.2. Stormwater Storage – elaborate on the current approach to stormwater storage and how it differs from the historical approach. Discuss alternative a pproaches to stormwater storage (detention vs retention, shared-use vs single-use facilities, etc.) and make a recommendation. » 7.3. Stormwater Conveyance – elaborate on methods o f conveyance and their implications. 8. Proposed Improvements
» 8.1. CIP Cost Estimates – provide more information as to the cost estimate methodology, including contingencies and unit costs.
» 8.2. Existing Conditions CIPs – update based on Cit y modeling efforts. Add discussion of the need for MS4 compliance CIPs, CIPs for waterway capacity def iciencies, regional flood protection projects, and localized flooding projects. CWE ECIP #11 will be kept, but it will be rewritten » 8.3. Future Conditions CIPs – update based on City modeling efforts 9. Water Quality Measures – discuss overlap between storm master plan and MS4 compliance Appendices
» Appendix A: Photographs of Flooded City Areas – Pho tographs of flooding not addressed by any proposed projects will be excluded in the document
» Appendix B: Basins, Pumps, and Pipe Network Map – p rovide a larger map with more detailed information, if appropriate
» Appendix C: Existing Conditions CIPs – update/redo based on City modeling efforts. Anticipate 1 to 2 new/revised sheets
» Appendix D: Matrix Ranking of Existing Conditions C IPs - update/redo based on City modeling efforts » Appendix E: Future Conditions CIPs - update/redo ba sed on City modeling efforts. Anticipate 33 new or revised sheets
» Appendix F: Matrix Ranking of Future Conditions CIP s - update/redo based on City modeling efforts New Chapters/Sections to add:
» Design Criteria for Master Plan Implementation
Clearly articulate design criteria and methodology to be used by development Include methodology for upsizing and criteria for r eimbursement of lines not explicitly included in master plan (for pipe oversizing)
– Develop a high-level estimate for pipe oversizing for incorporation in CIP. This could be based on a high-level percentage assumption.
» Recommendations for Future Studies
Deliverables:
Draft Revised Storm Master Plan (in both Microsoft Word and PDF formats) Final Storm Master Plan (in both Microsoft Word and PDF formats) Katherine Woodhull-Fuget
City of Visalia
Task SD-3 – CEQA Assistance – Optional or Not-to-Exceed The City has procured the environmental consulting firm Dudek to fulfill the CEQA compliance requireme nts of adopting the Storm and Sewer Master Plans. At this time, the Storm Master Plan is expected to require an Initial Study and Programmatic Environmental Impact Report. Under this optional task, Carollo would provide the City with assistance in providing information to Dudek d uring the CEQA process. Additionally, should the environmental review process trigger the need to modify projects in the Storm Master Plan, Carollo would revise the Storm Master Plan under this task.
Deliverables:
Exhibits if requested (native files preferred)
Revised Storm Master Plan if necessary (in both Microsoft Word and PDF formats) Task SD-4 – Storm Nexus Study Additional Work
Carollo will update the Storm Rate Study from the original Task 4 Nexus Study. This update will include incorporating the most recent financial, capital, and customer billing data from the City into the previously developed models.
Task 4.1: Project Initiation
A kickoff meeting will be used to formalize lines o f communication between Carollo and the City’s team, finalize the project schedule, and ensure project goals and objectives are clearly defined, delineated, and understood by all parties. Additionally, milestones for project deliverables will be established.
Carollo will prepare a data request list and submit it to the City staff upon Notice to Proceed. As data is received, we will review each data item for completeness and clarity so we can follow up with additional requests or questions if needed. Some data may have previously been sent to Carollo, but we may need most up to date data.
Task 4.1 Deliverables
Kick-off meeting workshop with City staff.
Data request list for Nexus Study.
Task 4.2 : Calculate Storm Impact Fees
Carollo will review and confirm the previously agre ed upon impact methodology for appropriateness. Carollo will utilize the model developed in the original Task 4 Study. The recommended impact fee will be in line with industry best practices and in compliance with California legislation.
Task 4.2 Deliverables
Identify impact fee methodology.
Calculate impact fee.
Meeting to discuss results (web-based).
Katherine Woodhull-Fuget
City of Visalia
Task 4.3 : Storm Impact Fees Documentation and Presentation Carollo will present preliminary findings and recom mendations in successive drafts for review and comment by City staff (up to 2 revisions of each report before authorization to produce final). The report will include the aspects identified in the California Department of Housing and Community Development Impact Fee Nexus Studies Template. Carollo will incorporate City comments and revisions into the Final Nexus Study Report.
Carollo will attend and present the draft and final Rate Study Report at one (1) City Council meeting.
Task 4.3 Deliverables
Draft Storm Impact Fee Nexus Report (in Microsoft Word and PDF format) with up to 2 revision cycles. Final Storm Impact Fee Nexus Report (in Microsoft Word and PDF format). Attendance and presentation (in Microsoft PowerPoint and PDF format) of Final Sewer Rate Study Report at one City Council meeting.
Task 4.4 : Community Outreach
Carollo will facilitate with City staff up to two community meetings to present study updates and find ings. We will assist City staff to prepare presentation materials prior to each meeting. Some community members may not be familiar with cost of service and rate design, so m uch of the material may be focused on educating members about cost of service and rate design principles an d methodologies. We will help ensure that the attendees understand the process and calculations that result in our recommendations.
Task 4.4 Deliverables
Facilitate two community outreach meetings (in-pers on) to be combined with the Rate Study meeting. Minutes for each meeting.
Task SD-5 – Storm Rate Study Additional Work
Carollo will update the Storm Rate Study from the original Task 4. This update will include incorporating the most recent financial, capital, and customer billing data from the City into the previously developed models.
Task 5.1: Project Initiation
A kickoff meeting will be used to formalize lines o f communication between Carollo and the City’s team, finalize the project schedule, and ensure project goals and objectives are clearly defined, delineated, and understood by all parties. Additionally, milestones for project deliverables will be established. Some data may have previously been sent to Carollo, but we may need most up to da te data.
Carollo will prepare a data request list and submit it to the City staff upon Notice to Proceed. As data is received, we will review each data item for completeness and clarity so we can follow up with additional requests or questions if needed. Some data may have previously been sent to Carollo, but we may need most up to date data.
Depending on the City’s desired start for Task SD-4 and SD-5, the kickoff meeting for these two tasks can be one meeting.
Katherine Woodhull-Fuget
City of Visalia
Task 5.1 Deliverables
Kick-off meeting workshop with City staff.
Data request list for Rate Study
Task 5.2: Storm Rate Study Revenue Requirements (Funds 222 and 481) Carollo will analyze the short- and long-term sufficiency of the fund’s existing revenues against exis ting and forecasted operational and capital expenditures, including potential repair and replacement needs that have been identified in the City’s capital improvement program. The revenue requirements analysis will be undertaken in close collaboration with City staff. Future changes in expenditures due to regulatory requirements, including both capital and level of service objectives, can be evaluated and incorporated into the forecast.
A multi-year financial plan will be prepared with projections of expenses, revenues, and reserves. The se expense projections will focus on providing adequate funding for operating and capital expenses. Carollo will consider up to two capital planning horizon scenarios. The multi-year financial plans will indicate the annual revenue increases needed to fund the project expenses and t o maintain adequate reserves.
As part of this task, Carollo will develop capital deficiencies based on Task SD-1 and discussions with City staff.
Task 5.2 Deliverables
10-year capital deficiencies.
10-Year revenue requirement forecast (two planning horizons). Two workshops with City staff (web-based).
Task 5.3: Cost of Service Analysis
The cost of service analysis will justify and allocate the revenue requirements among customer classes . A cost of service analysis will be conducted, beginning with updating the functional and cost component allocati ons.
Separate allocations for O&M and capital costs will be developed. Carollo uses methodologies endorsed by AWWA and WEF to allocate costs to functional catego ries, cost components, and customer classes.
Task 5.3 Deliverables
Costs by customer class.
Task 5.4: Service Charge s Calculation
Where the cost of service analysis determines the allocation of costs between various functions, the service charge calculation is used to ensure each customer, within a class, is paying their appropriate and reasonable share. We will develop a five-year service charge plan to transition the City from your existing rates to cost-based rates by Year 5. Any proposed charges will be in co mpliance with City ordinances and voter-approved propositions, and state and federal regulations and requirements.
Task 5.4 Deliverables
5-year rate schedule.
Katherine Woodhull-Fuget
City of Visalia
Bill impacts.
Task 5.5: Community Outreach
Carollo will facilitate with City staff up to two community meetings to present study updates and find ings. We will assist City staff to prepare presentation materials prior to each meetings. Some community members may not be familiar with cost of service and rate design, so m uch of the material may be focused on educating members about cost of service and rate design principles an d methodologies. We will help ensure that the attendees understand the process and calculations that result in our recommendations.
Task 5.5 Deliverables
Facilitate two community outreach meetings (in-pers on) to be combined with the Nexus Study meetings. Minutes for each meeting.
Task SD-6 – Project Management
Project management activities associated with tasks SD-1 through SD-5 will be conducted as part of this task, including day-to-day administration, communication with the City, coordination, and progress meetings. Carollo will administer the project to maintain project schedule and budget. The project progress and budget status will be included in monthly progress reports that will b e attached to billing invoices.
Additionally, monthly progress reports shall include a list of work completed for the time period and meeting minutes for all meetings held during the time perio d.
Biweekly informal project status meetings/calls between the project team and the City will also be conducted as a part of this task. It is assumed that up to 20 bi-weekly calls (30-minutes or less) will be conducted throughout the project duration. Carollo will be responsible for providing meeting agendas and minutes for each meeti ng.
Meeting agendas shall be provided to the City prior to the meeting and meeting minutes shall be provided to the City within 2 working days after the meeting. These agendas and minutes shall clearly outline any needs from the City and dates when the information is needed b y.
Katherine Woodhull-Fuget
City of Visalia
Fee Proposal
The following proposed fee schedule (Attachment A) is included to provide a lump sum effort change ord er of $115,700 to complete the above-described scope of work. Work will be completed on a Lump Sum basis and billed by percent complete for each task provided o n the fee schedule.
Schedule
Based on our experience with similar studies and discussions with City staff, we estimate a project timeline of approximately fourteen (14) months to complete all tasks and perform council presentations/workshops. See Attachment B for the Schedule task breakdown.
We look forward to working with you on this project . Please feel free to contact Reace Fisher (559)-696-4961 for questions, comments, or changes.
Sincerely,
CAROLLO ENGINEERS, INC.
Ryan Sellman, PE Reace Fisher, PE
Principal-in-Charge Project Manager
RS:ib
Principal-in-
Charge
Project
Manager
Technical
Advisor
Project
Engineer
Staff
Analyst
Engineering
Support
Document
Processing/
QC
Task Task Description
Remaining
Budget
$311 $291 $325 $240 $154 $291 $142
SD-1 2 6 8 28 58 34 4 140 $31,082 $2,600 $0 $33,700
SD-2 Master Plan Redevelopment 2 12 6 52 166 24 16 278 $53,36 4 $4,700 $0 $58,100 SD-3 CEQA Assistance, Optional 0 4 2 8 10 6 0 54 $7,020 $900 $0 $8,000 SD-4 Storm Nexus Study Additional Work 1 24 2 0 24 6 1 58 $13 ,529 $1,000 $7,348 $7,200 SD-5 Storm Rate Study Additonal Work 1 24 2 0 32 2 1 62 $13,5 97 $5,000 $18,600 $0 SD-6 Storm Project Management 0 20 0 10 0 0 0 30 $8,220 $500 $0 $8,700 6 90 20 98 290 72 22 622
$1,866 $26,190 $6,500 $23,520 $44,660 $20,952 $3,124 $126,812 $14,700 $25,948 $115,700 Notes:
2. Budget is based on a 14-month overall project completion schedule. Additional time over 14-months will incur additional cost.
3. Other Direct Costs include project equipment/communication, workshop materials, expert necessary travel.
1. Budget is based on an estimated level of effort based on our interpretation of the project requirements based our discussions with the Owner.
Model Review
Storm Total:
May 9, 2025
Storm Total Hours:
Storm Project
Carollo Labor
Total
Hours
Labor
Cost
Total Change
Order (1,2)
Nexus Study Support
Attachment A - Fee Schedule
CITY OF VISALIA
Total ODC
Cost (3)
Task Task Description
June July Aug Sep Oct Nov Dec Feb Mar Apr May Jun July Aug SD-1
SD-2 Master Plan Redevelopment
SD-3 CEQA Assistance, Optional
SD-4 Storm Nexus Study Additional Work
SD-5 Storm Rate Study Additonal Work
SD-6 Storm Project Management 14-Month Duration Min
Storm Project
Model Review
Task
Assumes 6 months - May Vary
To Start at end of CEQA Process
To Start at end of CEQA Process
Attachment B - Schedule
Nexus Study Support
CITY OF VISALIA
May 9, 2025