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City of Santa Ana On -Call Stormwater Project Design Services RFP No.: 20-102 the City has made in implementing a stormwater program and regional projects, such as those at Maybury and Raitt & Myrtle Parks, which demonstrate the City's commitment to improving water quality and meeting regulatory requirements. Approximately 37% of the City is considered DAC, 65% of which is within the Newport Bay Watershed. This will allow the City to go after funding with little to no match for multi -benefit projects. We are excited to share details of many programs, even those targeted to address economic impacts of the pandemic, with the City so that multi -benefit projects that help address regulatory requirements can be implemented at little to no cost to the City. Due to proposal length limitations, we look forward to discussing these with you in person or virtually! Stormwater Solutions There is a demand to improve water quality throughout the region and within the City, especially within the Newport Bay Watershed, which covers 60% of the City's area and is subject to a variety of TMDLs. The most effective solution, in terms of pollutant removal and cost, truly depends on the site, field conditions, and goals. CWE does not take a cookie cutter approach when assisting in the development and design of compliance projects. We carefully craft a project that fits into the location, aligns with field conditions, meets water quality goals, fits into funding programs, and can be operated and maintained based on the City's preferences. Some of the most popular regional stormwater solutions (or Best Management Practices [BMPs]) are summarized below to demonstrate our understanding and approach. Subsurface Infiltration Systems Subsurface infiltration systems can come in many shapes, sizes, and materials. Many of the projects highlighted as part of our experience utilized a form of subsurface infiltration, including precast concrete vaults, High Density Polyethylene (HDPE) chambers, and drywells. We understand the Raitt & Myrtle Park Stormwater Project being implemented by the City was to include a subsurface infiltration system. Infiltration is typically the most successful and cost- effective solution for addressing pollutants, as all pollutants in the captured runoff are removed from the downstream receiving water. Infiltration also provides other benefits, such as groundwater recharge. We understand the groundwater levels in the City are expected to be shallow (less than 50 feet). If the groundwater is too shallow, such that ten feet of separation cannot be provided between the system invert and the groundwater level, then infiltration may not be feasible. Areas identified as being susceptible to liquefaction also exist in the City and can influence infiltration feasibility. We recommend implementing site specific geotechnical explorations early in the concept development process to better understand if infiltration will be suitable. Table 1 Common Subsurface Infiltration System Challenges and Constraints High groundwater levels Shallow infiltration will be evaluated (to provide 10 feet of separation) or alternative strategies will be explored (options WE CWE7