Stormwater poses flooding and pollution in metropolitan areas, and impacts of unclean urban stormwater have given rise to green stormwater infrastructure (GSI). The City of Los Angeles' (City) Los Angeles Sanitation (LASAN) has spent over $600 M for the past 15 years applying GSI for stormwater treatment/capture/infiltration/reuse. These GSI project types comprise natural treatment systems, mechanical process systems, and passive systems in public sites (e.g., right-of-ways, alleys, lakes, parks, parking lots). After construction of GSI projects, the optimization of these projects was initiated to ensure that the individual project elements are functioning as a system in an optimal manner to assist in meeting water quality requirements and maintaining long-term project sustainability. The optimization of GSI will cover all the aspects of using GSI and the lessons learned from the design, construction, optimization phases, and from water quality and quantity characteristics achieved. After the optimization period, the GSI projects will proceed to operations and maintenance (O&M) phase of the project. Uses of GSI are to capture, slow, infiltrate, and retain stormwater on site, employing systems that include catch basin intercepts, dry well chambers, wetlands, cisterns, replacing asphalt with permeable surfaces, percolating stormwater through infiltration, rain gardens, bioswales, providing underground storage for reuse, treating stormwater runoff before it enters water bodies. GSI projects' performances during storm events rendering water quality and water-supply benefits and achieving total maximum daily loads (TMDLs) that must be met. Optimization of GSI have other benefits for the community, including fewer beach closures, cleaner communities, healthier environments, lowered health risks, enhanced recreational opportunities, and lower demand for potable water.
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