Purpose: To ensure that development projects are designed to reduce pollutants commonly found in urban runoff, and lessen the intensity of wet weather events on combined sewer systems.

The San Francisco Public Utilities Commission and the Port of San Francisco developed Stormwater Design Guidelines to show new development and redevelopment project applicants how to achieve on-site stormwater management using low-impact design strategies. Required by ordinance, every application for a development project over 5,000 sq. ft. must be accompanied by a stormwater control plan that meets the criteria set by the Stormwater Design Guidelines.

In compliance with the Clean Water Act’s National Pollutant Discharge Elimination System (NPDES) permit, the City and County of San Francisco must review design strategies that impact separate sewer systems (which comprise ~10% of city sewers). The City and County broadened the reach of these regulations by requiring development projects that rely on combined sewer systems (which comprise ~90% of city sewers) to adhere to the Guidelines as well.

The Stormwater Design Guidelines were designed to look beyond the minimum design standards required by the NPDES permit to encourage stormwater control plans that are uniquely appropriate for San Francisco’s climate, geography and development patterns. The Guidelines emphasize plant- and soil-based stormwater controls that enhance urban habitat and provide aesthetic benefits in addition to providing core stormwater management functions. Technical requirements concerning the efficiency of stormwater controls are equivalent to LEED Sustainable Sites standards. The EPA recognizes the 5,000 sq. ft. threshold as the generally accepted standard for enforcement.

An extensive 34-month outreach strategy was developed to inform the public about the Guidelines and the proposed review process. Engineers, planners and design professionals were targeted to gather technical feedback on the Draft Guidelines. A variety of civic groups knowledgeable in matters related to sustainability were also solicited. Further, the Public Utilities Commission and the Port provided technical assistance to 15 large projects that were under construction during the outreach period. All of these efforts resulted overwhelming public support for the Design Guidelines.

Projects complying with the Guidelines will improve the water quality of the San Francisco Bay and Pacific Ocean, help restore hydrologic function and wildlife habitat to San Francisco’s urban watershed and reduce the burden on the City and County’s combined sewer system.

The expenditure of staff time to review submitted stormwater control plans is the primary cost associated with the Stormwater Design Guidelines. The Public Utilities Commission worked in conjunction with the Department of Building Inspection to integrate stormwater control plan review into the existing review process. Environmental review accounts for ~3% of the budget for a separate Public Utilities Commission program that installs the same stormwater controls required of developers under the Guidelines. Mandating the Guidelines is economical because developers take on the other ~97% of costs (planning, design, construction and maintenance) associated with the stormwater controls.

Additionally, stormwater controls generally decrease costs associated with maintaining the combined sewer system. The savings are a result of reducing the total volume and amount of pollutants processed by the wastewater treatment plants.