Is San Diego Ready for the Next Atmospheric River? Designing San Diego's Pump Station Network with Resiliency in Mind

The 'heart' of the City of San Diego's stormwater drainage system is its network of stormwater pump stations. While much of the City's stormwater system is hidden underground or obscured from public view, this infrastructure system is essential to San Diegans' quality of life, health, and safety. Many of the City's 14 stormwater pump stations built in the 1940s are past their prime, yet remain working hard well beyond their projected useful life. In some cases, these pump stations require emergency structural repairs; are unsafe for operators to access, operate, and maintain; and are comprised of deficient mechanical and electrical equipment pieced together throughout the years. Many of the pump stations lack sufficient capacity to pump flows from the increased barrage of climate change induced extreme rainfall events and their limited function is compounded by expansive urbanization generating increased runoff. All of these factors have placed San Diegan's safety and property at risk from flooding. To address this, the City of San Diego's visionary 'Think Blue' Infrastructure Program is leveraging funding from its $733 million Water Infrastructure Finance and Innovation Act (WIFIA) loan with the EPA to embark on a pump station replacement program. A huge and complicated undertaking, the City has determined this to be the best course of action in-lieu of rehabilitating the aged and undersized infrastructure. With a project of this size, the City will employ innovative solutions that go beyond the primary goal of providing a 'Flood Safe Community.' This modernization of stormwater infrastructure will also ensure clean water and clean beaches and allow the Stormwater Department, and community, to reap the many potential benefits of using stormwater as a resource. To initiate this monumental pump station replacement program, the City and Stantec developed a Pump Station Design Guide (PSDG). The PSDG recommends the minimum acceptable design and plan submittal requirements for stormwater pump stations. While there are many resources that describe how to design pumping systems, most focus on either very general or very specific pumping applications. Additionally, they reflect the authors' experiences and opinions, but do not apply to the City's specific applications. To combat this the PSDG focuses on the City of San Diego operations' staff preferences and localized experience to enhance reliability, ease of operation, maintenance, efficiency, and costs. The new pump stations will incorporate advanced technology to repurpose the dry weather low flow polluted water, as well capture trash. Conformance with these new guidelines will expedite the design, review, and acceptance of plans, and ensure uniformity of design concepts, procedures, construction materials, types of equipment, and quality of work products. The PSDG summarizes and outlines relevant City policies, applicable codes, as well as engineering and operational practices and procedures that have been developed to establish cost-effective, reliable, and safe stormwater pump stations. Equipment and materials specified in the PSDG were selected to be long-lasting and, in general, employ designs that have a long record of success. The PSDG design criteria will result in pumping systems that are simple, reliable, and as maintenance free as possible. Unique to the PSDG are specific hydrologic and hydraulic criteria to account for the changing climate. The criteria advances the City's posture by providing more resilient design and construction principles to reshape the City's built environment. This includes criteria for engineers to plan and design for increased rainfall intensity from extreme rainfall events and sea level rise. The PSDG will also include protocols and standards to integrate low flow diversions within the pump stations. As a result, future pump stations will not only be designed to address increased stormwater runoff, but also serve to help improve water quality and the health of the downstream receiving water. The low flow diversions could also potentially capture and divert urban runoff and stormwater to the City's PURE Water system where it can be used to supply clean drinking water back to the public. For decades, San Diego has been at the global forefront implementing environmental forward programs and this stormwater initiative is no different. This next generation of pump stations is not only safeguarding the City's residents and property, but taking proactive steps to stop pollution before it gets into storm drains. The Pump Station Design Guide is advancing the science and practice of stormwater capture and reuse, and another example of how the City of San Diego is leading the future of water.