Go with the Flow: Investing in Multi-Benefit Urban Stormwater Capture and Use

The field of stormwater harvesting is evolving and expanding as utilities and communities consider viable alternatives to increase water supplies, improve resiliency of their water resources, and find multi-benefit and innovative approaches to addressing regulatory and stormwater quality challenges. In many cases communities turn to stormwater harvesting with a specific driver in mind, from water quality and local flood reduction to heat island mitigation. After further evaluation they often uncover many other benefits, many being of direct value to the community. Stormwater capture and use (SCU) projects can come in all shapes and sizes, as does the quality of the water when it gets to these stormwater harvesting projects. Current research in stormwater harvesting and the technologies fueling this sector's growth will be discussed in terms of their applicability and 'fit-for-purpose.' This presentation will highlight several significant projects and programs including the County of Los Angeles' Safe Clean Water Program, the City of San Diego's dry-weather diversion program to Pure Water, the Long Beach Municipal Urban Stormwater Treatment Project (LB-MUST), the City of Santa Monica's Sustainable Water Infrastructure Project (SWIP) and others. Key programs/projects include: County of Los Angeles' Safe Clean Water Program — In 2018 voters in Los Angeles County passed a parcel tax on impervious areas. The Program generates nearly $300M/year for capital projects; operations and maintenance; and technical studies. Most of the funding is distributed base on populations served by the agencies within the County. Approximately 40 percent of the funding is competitively awarded as Regional Projects based on load reduction, water supply benefits, community benefits and other criteria. Since capture and use projects score very highly with load reduction and water supply benefits, they often dominate the funding for Regional Projects. City of Long Beach's LB MUST — The LB MUST Project in Long Beach that captures and treats flows from 12,300 acres of urban watershed. With LB MUST the primary goal is to treat urban runoff (dry weather flow) and polluted stormwater (85th percentile average annual precipitation) to comply with the City's NPDES permit, which incorporates TMDLs. The project is expected to be complete in early 2024 and is a great example of a multi-benefit SCU project. Treatment processes including ceramic ultrafiltration and UV oxidation are used to produce non-potable water supply for various municipal and environmental demands. LEED recognized the project last year with Platinum Certification City of Santa Monica's SWIP — Santa Monica is densely populated beach community also within the County of Los Angeles. Beach water quality issues drove the City to create the SMURRF in the 2000s. Santa Monica also has significant groundwater and a goal to be self-sustainable with respect to water supply. Recent additions to the SMURRF (storage and advanced treatment) allow the City to capture and use more water. SWIP include facilities where pretreated stormwater is blended with wastewater for purification. Managed blending of stormwater with wastewater for treatment to non-potable reuse is quite popular in SoCal as deep droughts and conservation measures result in lower wastewater flows than many recycling facilities had planned for. Managed addition of stormwater and dry weather flows help to make up for this. City of San Diego's Planning for Stormwater to Pure Water — The City of San Diego's Pure Water Program is a phased, multi-year program aimed at providing additional local supply through expanded water reclamation and advanced water purification. The program will be implemented in several phases to eventually provide one-third of the area's drinking water needs by 2035. As currently planned, wastewater flows will be diverted to either new or existing water reclamation facilities to produce recycled water that will undergo additional treatment at a Pure Water facility. The resulting purified water will be stored in existing reservoirs and blended with imported and local water supplies. The water will be treated at existing drinking water treatment plants for distribution through the City's existing potable water supply system. Phase 1 of the Pure Water Program will be the first potable reuse project permitted in California for reservoir augmentation and future phases of the Program will likely rely on a similar approach. Local elected officials and NGOs have pressed for increased urban stormwater water capture and use options to enhance water supply and water quality in the Region. In addition, conservation measures and drought have resulted in reduced overall sewer flows for many agencies. As a result, the City is carefully evaluating the feasibility of capturing stormwater for diversion to the existing sewer system for use as an additional water supply. We will share how these projects were developed considering the required water quality for each application — from irrigation and recreational, to environmental demands. This presentation will also look at current research needs in stormwater harvesting. The presentation will conclude with a discussion of stormwater harvesting lessons learned and the application of a proven planning process can be valuable, and transferable, to other locations in North America.