Non-Potable Reuse and Stormwater Ordinance Synergy: San Francisco’s Approach
The San Francisco Stormwater Design Guidelines (Guidelines) were adopted by the SFPUC in January, 2010. The Guidelines are the implementing arm of the Stormwater Management Ordinance (SMO) which requires that all projects disturbing 5,000 square feet or more of the ground surface manage part of their stormwater on-site, including the reuse of stormwater to meet non-potable demands.
In July 2015, the Board of Supervisors unanimously approved an amendment to Health Code Article 12C, often referred to as the San Francisco Non-Potable Ordinance (NPO), requiring new development in the City of more than 250,000 square feet to incorporate alternative water supply and reuse systems to offset their non-potable water demands.
The SFPUC has been studying the nexus between the Non-potable Ordinance (NPO) and the Stormwater Management Ordinance (SMO) for the purpose of developing guidance on strategies and solutions for new developments that are required to comply with both ordinances. The purpose of this study is to create technical guidance and advance policy to facilitate the efficient compliance with both ordinances. A primary objective of the SMO is to reduce the volume of water entering the City’s sewer systems during storm events, while the intent of the NPO is to offset the use of potable water for non-potable demands year-round. As a result, the two ordinances, when evaluated in combination, both fundamentally involve rainwater harvesting and the reduction of flows to the sewer. This presentation includes analytical results and conclusions from identifying potential interactions and synergies between the two ordinances with the goal of identifying how development projects with mandated NPO compliance can employ rainwater harvesting to create an efficient integrated water reuse system that also complies with SMO.
One outcome of the study is a public facing document for developers and engineers identifying and presenting design solutions and concepts that should be considered by development applicants that could facilitate compliance with both ordinances with a single solution or system. Design solutions are organized by land use/project type and presented in a multi-page handout and online publication that the SFPUC provides to applicants to inform their designers and engineers about recommended approaches or policies for dual compliance. The document contains narratives, specifics of the ordinances, schematic process diagrams, tables, and other methods of conveying concept design or operation solutions for compliance with both ordinances. Solutions investigated include physical design solutions (e.g., dual tank approach), real time controls, seasonal operation (e.g. tank level requirements differ in rainy season versus dry season), and other details about how to reduce cost and optimize configurations while still achieving the intended benefits of both ordinances.
Results of the study show that the NPO and the SMO have the highest potential for beneficial synergy in any of the following building scenarios:
• Buildings with high non-potable demand (>3,000 gpd/acre of impervious site area); or
• Commercial/Office buildings where rainwater capture is required to meet NPO Demand; or
• Buildings granted Modified Compliance in the combined sewer service area; or
• Buildings where Foundation Drainage is available but the production rate is less than total NPO Demand
In other building scenarios that do not need rainwater to meet NPO Demand (e.g., most residential buildings) and choose to meet SMO compliance by other means, a non-potable runoff reduction equivalency program has the potential to be implemented to reduce the SMO requirement by the volume reused for NPO compliance.
The speakers will engage the audience from a program development perspective as well as a detailed technical perspective. This presentation highlights a one water approach and bridge between water quality and water resource policies.
Eric Zickler is a principal at Lotus Water, a progressive water resource engineering firm based in San Francisco focused on pursing a one water approach to all of their projects. He has over 17 years of experience working in water infrastructure design, water resource planning, and regulatory policy for both public and private sector clients. Mr. Zickler has a BS and MS in Civil Engineer and is a registered professional engineer in the State of California.
Taylor Chang is a water resources analyst for the San Francisco Public Utilities Commission (SFPUC). She works on San Francisco's Non-potable Water Program by providing technical assistance to projects that are installing onsite non-potable water systems and administering the SFPUC’s grant assistance program. She is also working with the National Blue Ribbon Commission to advance the field of onsite reuse by providing policy and technical support.
Sarah Minick manages the Urban Watershed Management Program at the San Francisco Public Utilities Commission. Through planning, policy development, regulation, and capital work, her team works toward green infrastructure that enhances the function of San Francisco's sewer system, manages stormwater as a water resource, restores ecological function to the city’s urban watersheds, and brings beauty and habitat value to the public realm. Sarah led the development and implementation of San Francisco’s Stormwater Management Ordinance, Urban Watershed Stewardship Grant Program, and Rainwater Harvesting Program, and is the client representative for the SFPUC’s green infrastructure capital projects. Sarah holds a bachelor of science from Stanford University and two masters degrees from UC Berkeley in City and Regional Planning and Environmental Planning.