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Report regarding a resolution approving and authorizing the City Manager to execute a Cooperative Implementation Agreement No. D43CIASF0002 with Caltrans for the Phase II Orange Memorial Park Storm Water Capture Project. (Bianca Liu, Associate Engineer, Robert Dusenbury, Lotus Water)
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RECOMMENDATION
Recommendation
It is recommended that the City Council adopt a resolution approving and authorizing the City Manager to execute Cooperative Implementation Agreement No. D43CIASF0002 with Caltrans for the Phase II Orange Memorial Park Storm Water Capture Project.
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BACKGROUND/DISCUSSION
The City of South San Francisco is a member of the San Mateo Countywide Water Pollution Prevention Program (SMCWPPP), a program of the City/County Association of Governments of San Mateo County (C/CAG). C/CAG is a joint powers agency whose members are the County and the 20 incorporated cities and towns in San Mateo County. SMCWPPP supports C/CAG’s member agencies in complying with requirements contained in the second five-year term of the Municipal Regional Permit (MRP) issued by the San Francisco Bay Regional Water Board. Four important components SMCWPPP is implementing to assist member agencies include green infrastructure planning, stormwater resource planning, mercury/polychlorinated biphenyl (PCB) load reduction, and trash load reductions.
The MRP requires San Mateo County permittees to reduce PCBs by 370 grams per year by June 30, 2020, with an interim reduction of 60 grams per year required by June 30, 2018, with a minimum of 15 grams per year of the total be achieved via green infrastructure. San Mateo County permittees also need to demonstrate they have reduced mercury by six grams per year via green infrastructure by June 30, 2020. These reduction rates are required by the MRP as part of the process to achieve compliance with the mercury and the PCBs total maximum daily load (TMDL) for San Francisco Bay. San Mateo County permittees are also required to reduce trash discharges to the Bay from municipal storm drain systems. This requirement began with the issuance of the first MRP in 2009, with a 40% reduction required in 2014. Under the current MRP term, 70% reduction is required in 2017, 80% reduction in 2019, and zero impact on receiving waters from trash by 2022.
These reductions will largely be accomplished through the implementation of green infrastructure, including stormwater capture and use and/or infiltration to groundwater. SMCWPPP developed a countywide Storm Water Resource Plan (SWRP) that focuses primarily on storm water capture with a multi-benefit approach to overall water resources planning, including water quality. This plan is being followed by local Green Infrastructure Plans (GI Plans) to meet MRP requirements. Development of the GI Plans will be a multi-year effort that includes preparation of a reasonable assurance analysis (RAA) to demonstrate long-term GI Plan implementation by all MRP permittees will reduce PCB loads by three kilograms per year by 2040.
Effective on April 26, 2017, the California Department of Transportation (Caltrans) agreed to fund $9,500,000 to the City’s Orange Memorial Storm Water Capture Project (Original Project) through Cooperative Implementation Agreement No. D43CIASF0001. The Original Project is currently at 60% design. The design includes a drop inlet diversion structure to re-direct all dry-weather urban runoff and up to approximately 15 cubic feet per second of the first flush of wet-weather runoff from the Colma Creek channel through pre-treatment structures to remove trash, debris, and sediment before conveying the water into a subsurface multi-chambered storage reservoir with an overall storage capacity of approximately 1,250,000 gallons. A portion (approximately 250,000) of the storage functions as a cistern holding water that will receive water quality polishing and disinfection for eventual non-potable irrigation use in and around the park, and the remainder (approximately 1,000,000) functions as an infiltration chamber. When storage capacity is exceeded, diverted water that has been screened for full trash capture and has been through pretreatment for removal of floatables and settleables overflows back into the channel.
The RAA model estimates that the current 60% design will capture and treat approximately eight (8) percent of the average annual drainage volume from 6,570 acres of tributary watershed areas in the City of South San Francisco, Town of Colma, the City of Daly City, a portion of unincorporated San Mateo County, and two small portions of Pacifica and San Bruno. Caltrans right-of-way constitutes 234 acres of the tributary area, including 7.08 miles of State Highway 82 (El Camino Real), 8.43 miles of Interstate 280, and 3.34 miles of State Highway 35 (Skyline Blvd). The Original Project has multiple benefits in addition to water quality improvements, including flood reduction and beneficial use of treated water for irrigation and groundwater recharge.
The City now seeks to expand the Original Project with the proposed Phase II Orange Memorial Park Storm Water Capture Project (Phase II Project). The Phase II Project will allow the City to increase the scale of the Original Project and effectively double the water quality treatment provided in terms of diversion, pretreatment, and infiltration capacity. The Phase II Project will include a water capture facility at this site with 30 cubic feet per second diversion and over 2 million gallons of storage, which will capture and treat approximately sixteen (16) percent of the average annual drainage volume in Colma Creek at the Project site, per the RAA model.
The Phase II Project involves additional engineering and geotechnical assessment for the expanded footprint, detailed design, and construction of a larger capture and treatment system, including a larger instream drop inlet, pretreatment structures, conveyance pipes, flow splitter, and infiltration gallery.
The City of South San Francisco, as lead agency, will enter into a second Cooperative Implementation Agreement, No. D43CIASF0002, with Caltrans for a total amount of $6 million to continue funding for these projects.
FISCAL IMPACT
The Project construction costs will be fully funded through the Cooperative Implementation Agreement No. D43CIASF0002 with no matching funds required from the City. Caltrans has set aside funds over the next four fiscal years to pay for the total project costs (estimated at $6 million), contingent on City Council authorization. Once funds have been allocated for a fiscal year, the City will have three years to spend the funds. This allocation schedule will work with the City’s current schedule to begin construction spring of 2020.
RELATIONSHIP TO STRATEGIC PLAN
Approval of this action will contribute to the City’s Strategic Plan outcome of improved Quality of Life by providing green infrastructure and improving water quality.
CONCLUSION
Staff recommends that the City Council adopt a resolution approving the Cooperative Implementation Agreement No. D43CIASF0002 between the City and Caltrans, and authorizing the City Manager to execute the agreement.
Attachment:
Exhibit A - Draft Cooperative Implementation Agreement No. D43CIASF0002