DATE: MARCH 11, 2025
DEPARTMENT: PUBLIC WORKS
FROM: DAVID JACOBS, DIRECTOR
BY: HEIDI NIGGEMEYER, NPDES PROGRAM MANAGER
TITLE: ADOPTION OF THE STORMWATER MASTER PLAN (SWMP) UPDATE RECOMMENDED MOTION:
A motion to approve a resolution adopting the Salinas Stormwater Master Plan Update and related Appendices.
EXECUTIVE SUMMARY:
The Salinas Stormwater Master Plan Update presents the findings from the development of a hydrology and hydraulics model to create a Stormwater Capital Improvement Program (CIP). This program will assist the City in prioritizing both existing and future stormwater system needs through repair, rehabilitation, replacement, or new stormwater facilities.
BACKGROUND:
The City of Salinas owns and operates a municipal separate storm sewer system (MS4) that collects and conveys stormwater runoff throughout the City. The City periodically conducts studies to plan for current and future stormwater drainage needs. The approval of the Economic Development Element and other proposed developments (like the Future Growth Area Specific Plans) require the Stormwater Master Plan (SWMP) be updated to determine how and whether the storm drainage system can accommodate these changes. Additionally, the updated SWMP would identify potential infrastructure projects that need to be implemented to reduce flooding and accommodate increased development; these project costs can be incorporated into the development of a new stormwater utility fee as they affect the overall cost of the stormwater program.
In December 2021, the City authorized a professional services agreement with Wallace Group to perform the Salinas Stormwater Master Plan update (Resolution No. 22269). This report presents an overview of the findings from the SWMP update which is a comprehensive update to the City’s 2004 SWMP.
The City’s current stormwater system conveys stormwater via over 145 miles of pipes, culverts, and channels to local receiving waters that ultimately flow to the Monterey Bay. Major receiving waters include the Reclamation Ditch, Gabilan Creek, Natividad Creek, Santa Rita Creek, Alisal Creeks, and the Salinas River, which are all 303(d) listed1 (impaired waterbodies). The preparation of the SWMP update included document review and data collection, field survey of 1,150 storm drain manholes and 55 storm drain outfalls, comprehensive hydrology assessment including rainfall projections for potential climate change conditions, development of a hydraulic stormwater model to identify system deficiencies for existing and future build-out conditions, and development of a Stormwater Capital Improvement Program (CIP).
Stormwater Capital Improvement Program
The Stormwater Capital Improvement Program is separated into recommended existing and future projects. The existing projects are based on system hydraulic deficiencies, operation and maintenance repairs identified by City staff, and focused studies to address more complex flooding issues. These 63 projects range from $1 million to $29 million and include 27 projects identified as necessary to address hydraulic deficiencies, 25 operation and maintenance repair projects, five (5) focused studies, and six (6) projects to improve stormwater collection basins. These projects address known flooding and maintenance issues in 92 locations throughout the City, as identified by City staff. Projects are ranked based on flooding frequency, flooding severity, climate resiliency, and public safety considerations such as flood impacts to critical facilities, evacuation routes, or freeways and other major roadways.
Future stormwater projects were identified based on potential impact of future developments per the City’s General Plan. Twenty-six (26) projects were identified to address hydraulic deficiencies resulting from future development and potential climate impacts. The timing of these future projects is dependent on when future developments connect to the City’s storm drain system. These improvements are recommended to be completed prior to or as part of a development project that comes online. In addition, future maintenance projects were identified based on pipes that currently have limited or marginally deficient hydraulic capacity. These pipes are recommended to be upsized with larger diameter pipes when that are slated for replacement due to age and material deficiencies (i.e. when they have reached very high probability of failure). A total of 127 future maintenance projects were identified for hydraulic upgrades. Total potential cost for future projects exceeds $1 billion.
Mapping and GIS Integration
Data collected through field surveys and developed through the hydraulic model under the SWMP update has been incorporated into the City’s GIS-based stormwater information management system, 2NForm, for asset management. Through this GIS integration the SWMP update will support the City’s ongoing stormwater permit compliance activities. 1 303(d) listed refers to a listing by the State Water Resources Control Board identifying a water body as impaired based on the California Clean Water Act Section 303(d). The State and Regional Water Boards assess water quality data for California’s waters every two years to determine if they contain pollutants at levels that exceed water quality criteria and standards.
One Water Roadmap
In a separate but related project the City has entered a contract with Carollo to develop a one water plan for the City. The objective of the plan is to improve water reliability and identify sustainable ways to manage the water resources that are available. Carollo will work with City staff to brainstorm and develop an initial list of current and potential new projects or programs that help address the City's water management challenges, such as growth, industrial wastewater treatment plant expansion, and stormwater reuse. A trigger-based roadmap will consist of a visual that lists the project opportunities, including key triggers, such growth (demands or flows), new regulations, and/or inter-agency agreements.
CEQA CONSIDERATION:
The City of Salinas has determined that the proposed action is not a project as defined by the California Environmental Quality Act (CEQA) Guidelines Section 15378.
CALIFORNIA GOVERNMENT CODE §84308 APPLIES:
No
STRATEGIC PLAN INITIATIVE:
The proposed project and agreement meet the City Council’s Strategic Plan Initiatives of Investment Strategies/Risk Management and Operational Efficiencies.
DEPARTMENTAL COORDINATION:
Preparation of the SWMP update has relied on coordination between the Stormwater (NPDES), Development Engineering, GIS, and Wastewater/Environmental Maintenance Divisions in Public Works. The NPDES Division has coordinated the overall execution of the SWMP update, with GIS supporting database updates and Wastewater/Maintenance Services providing valuable input to the SWMP update from an operations perspective.
FISCAL AND SUSTAINABILITY IMPACT:
Fund
Appropriation
Appropriation
Name
Total Appropriation
Amount for recommendation
FY 24-25 Operating Budget Page
Last Budget Action (Date, Resolution)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
There is no direct fiscal impact associated with adopting this report. Through prior Council adoption, funds were appropriated and expended for the preparation of the SWMP update. Implementation of the recommended capital improvement projects listed in the SWMP update, which address existing deficiencies, total $321 million. Of this total, $12 million are high priority projects recommended and should be completed as soon as funding is available. The current capital reserves available in CIP 9735 – Storm Sewer Infrastructure Improvements total approximately $1.4 million, which is insufficient to cover projects of this magnitude.
ATTACHMENTS:
Resolution
Final Draft - Salinas Stormwater Master Plan Update
Appendices - Salinas Stormwater Master Plan Update
Salinas SWMP Update Presentation
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