Upper Yosemite Creek Daylighting Project
|Sponsoring Agency||San Francisco Public Utilities Commission|
|Public or private land?||()|
|Location (lat/lon)||37.723353, -122.413308|
|Location Description||The project is located in the Yosemite watershed, on the southeastern side of San Francisco. Green infrastruture components will be placed within and around MacLaren Park. The properties surrounding the project site are zoned as residential housing with one unit per lot and the surrounding neighborhood is considered a socio-economically disadvantaged community.|
This project will utilize green infrastructure to improve stormwater management in the historic Upper Yosemite Creek area of San Francisco. The main goals of the project are stormwater volume reduction and peak flow attenuation. Bioretention structures and creek daylighting are some of the techniques that will be used to reach these goals. This project will contribute to development of performance, maintenance and design standards for future green infrastructure projects.
Part 2 - Detail
The Upper Yosemite Creek Daylighting project will daylight the headwaters of the historic Yosemite Creek to manage stormwater runoff from 110 acres of McLaren Park. This San Francisco Public Utilities Commission (SFPUC) project will feature storage and infiltration facilities, as well as a creek channel to convey stormwater and alleviate localized flooding issues. This is the first creek daylighting project initiated by the City, and it has the added benefit of reintroducing natural habitat and providing opportunities for community learning and beautification.
Currently, stormwater from the area drains into Yosemite Marsh and McNab Lake. When the water levels in Yosemite Marsh and McNab Lake reach the outlet elevations, water spills into the combined sewer system. San Francisco’s combined sewer system collects, transports, and treats both wastewater and stormwater. During severe wet weather events, the combined sewer system can become overwhelmed, sometimes causing combined sewer discharges (CSD) at permitted CSD outfalls in the Pacific Ocean and the San Francisco Bay.
The Yosemite Creek Daylighting project is one of eight Early Implementation Projects (EIPs) that the SFPUC is planning to construct as part of its Sewer System Improvement Program (SSIP). The common goal of the EIPs is to demonstrate the use of performance-based green infrastructure technologies to remove stormwater from the combined sewer system and attenuate peak flows. However, the Upper Yosemite Creek Daylighting Project is unique in that it is the only EIP featuring creek daylighting. The information and expertise gained will be used to support the future of green infrastructure within the City of San Francisco.
The proposed scope for the Yosemite Creek Daylighting project includes a creek channel that will flow along the northern edge of McLaren Park from Yosemite Marsh, the southern edge of the soccer field, and the northern, eastern and southern edges of the softball fields. Overflow structures will be modified at Yosemite Marsh and McNab Lake to divert excess water to the new creek channel. To control flow velocity and increase habitat space, bioretention facilities will be incorporated at various points along the creek. Subsurface stormwater storage tanks will be installed at the northwestern edge of the softball fields. These subsurface tanks will be used to store stormwater and manage flow volumes heading for the combined sewer system. In addition, opportunities to reuse captured stormwater to irrigate the soccer field or the creek channel are being investigated.
The project team has been working closely with the SF Recreation and Parks Department to integrate the creek into existing park uses. The project area is surrounded by a socio-economically disadvantaged community called Portola Valley. During the planning phase of this project, public workshops and multiple small community group meetings were held to solicit public input and feedback. Two online surveys were provided for additional public feedback on the project. Public input has been used to refine the scope and aesthetic of the project. The project will feature an outdoor classroom to provide opportunities to learn about San Francisco's historic creeks and the benefits of natural systems to treat and manage stormwater. The proposed scope incorporates design features to create habitat and biodiversity, increase education and public involvement regarding water resource management, promote neighborhood greening, and enhance interagency project synergies. Additional agencies that the Project Team worked with to refine and gain project approvals are the San Francisco Municipal Transportation Agency, San Francisco Fire Department, and the San Francisco Department of Public Works.
These early implementation projects are critical to gain public support for the SSIP Green Infrastructure Program, inform the cost/benefit as utility assets, and meet the goals for the City and County of San Francisco to revitalize public streets, create green jobs and improve wildlife habitat.
Previous studies conducted by the SFPUC identified needs for flood and stormwater management in the Yosemite watershed. This project will decrease localized flooding and increase groundwater infiltration by capturing stormwater runoff and directing it to a new unlined creek channel, bioretention facilities, and subsurface storage tanks. In addition to watershed needs, the project considered synergy opportunities and social and environmental factors. Proposed enhancements to McLaren Park include improved drainage of athletic fields and construction of a new pedestrian path that would provide safer access the park. The project will feature an outdoor classroom to provide opportunities to learn about San Francisco's historic creeks and the benefits of treating and managing stormwater with natural systems. The headwater reach of the historic Yosemite creek will be restored and bioretention facilities will create potential habitat using native plant species. Subsurface storage tanks will be installed to retain excess stormwater, and potential reuse for irrigation of McLaren Park athletic fields or the creek channel will be investigated.
The green infrastructure technologies included in the current scope of the preferred project alternative can manage stormwater from approximately 110 acres of McLaren Park. The creek channel and inline bioretention areas are estimated to remove approximately 1 million gallons of stormwater per year from the combined sewer system (in a typical rainfall year). The underground storage facility is estimated to remove approximately 6.5 million gallons of stormwater per year. The reduction in peak flow resulting from a “Level of Service” storm (1.3 inches in three hours) is estimated to be approximately 1.2 million gallons per event. These are initial estimates based on unit green infrastructure performance metrics developed using numerous citywide Sewer System Master Plan and SSIP modeling analyses conducted using the City and County of San Francisco Hydrologic and Hydraulic model10. These values will be refined through project-specific modeling during conceptual engineering and design. Based on this preliminary estimate of annual stormwater volume removed and the estimated annualized life cycle cost, the costs of the Yosemite Creek Daylighting Project is approximately $0.114 per gallon of stormwater removed.
As one of SFPUC’s Early Implementation Projects, information obtained from this project will be used to develop plans for future installations of green infrastructure.