Colma Creek, San Bruno Creek, and Navigable Slough are connected waterways within the cities of South San Francisco and San Bruno that are prone to flooding, especially during high tide levels in the San Francisco Bay. Colma Creek and San Bruno Creek comprise two of the three long-standing active flood zones that the OneShoreline inherited from the former San Mateo County Flood Control District (the third is San Francisquito Creek).

Along Colma Creek, this assessment of future priorities is being completed in close coordination with the City of South San Francisco’s planning efforts. The District has met with City of South San Francisco (City) planning staff and consultants to discuss opportunities to improve Colma Creek in concert with the City’s update to its General Plan, slated to be completed in 2022. These discussions are focused on flood-prone sites adjacent to the Creek or within Creek right-of-way where either the City or District has land rights, where the City has interest or proposed land use changes, and/or where new private developments are proposed. The District’s goal is to identify sites of interest that will increase the region’s resilience to long-term sea level rise and help transform Colma Creek into an environmental and recreational asset to the surrounding community.

Along San Bruno Creek, complexity of ownership has led to disaggregated data and stalled solutions. Many neighborhoods that drain to the Creek, particularly the Belle Air neighborhood, have faced chronic and substantial localized flooding for years. This frequent flooding will only get worse as climate changes, and long-time residents have reported that recent storms resulted in the worst flooding they have seen in 40 years. OneShoreline is building upon past studies and local expertise to scope a regional project tying into SFO’s Shoreline Protection Program to the south and South San Francisco’s efforts to protect its Water Quality Control Plant from flooding to the north. 

Three potential project components have been identified that could address the significant flooding issues observed in this region:

1. A pump station that would carry the excess flows around the existing tide gate where the San Bruno Creek meets the San Francisco Bay, along with a backup generator to ensure continued function during a storm event;
   
2. The rehabilitation of two existing pump stations, built in the 1960s and owned/operated by OneShoreline, that facilitate stormwater drainage from San Bruno to the San Francisco Bay;
   
3. The design and construction of a detention basin at an existing low elevation site along 7^th Avenue to increase capacity at the site to store water during high-intensity rainfall events, especially those that occur during high tide.