CWE developed design PS&Es for the City of Torrance for the Walnut Stormwater Capture and Groundwater Replenishment Basin project.  This Walnut Basin Project diverts a minimum of 23 acre-feet of stormwater per year collected from the LACFCD storm drain back in the existing Walnut Basin, as per the Machado Lake Enhanced Watershed Management Program (EWMP).  Located in a residential neighborhood in southeast Torrance, this project called for the installation of a diversion structure in storm drain adjacent to the basin.  The diversion structure was sized to take dry-weather runoff and stormwater runoff from storms up to the 85^th percentile storm event, while allowing runoff from larger storm events to continue down the storm drain unimpeded.  The diversion structure routes runoff to a hydrodynamic separator pre-treatment unit, where debris and sediments with medium-to-large grain sizes are removed.  After passing through the pre-treatment unit, runoff enters a 48-inch reinforced concrete pipe, which was jacked into place in a narrow easement between two houses, that conveys water to Walnut Basin.  Riprap was installed at the entrance to Walnut Basin to reduce the velocity of the runoff and prevent erosion.  The project will accomplish most of the required reduction from the critical baseline load for most pollutants, including nutrients, pesticides, polychlorinated biphenyls (PCBs), bacteria, and lead.  Diverting the water back to the existing basin improves the storm drain system capacity, increase local water supplies, and reduce energy consumption.  Stormwater is collected from a 56-acre residential area surrounding Walnut Basin.  Tasks included: PS&Es for the diversion structure, piping, street resurfacing, catch basins, and jack-and-bore installation; preparing storm drain, erosion control, traffic control, and demolition plans; street resurfacing; providing details for hydraulic structures; project management; data collection and site evaluation; preparation of a Monitoring and Reporting Plan (MRP) and a Project Assessment and Evaluation Plan (PAEP), implementation of a Quality Assurance Project Plan (QAPP) including physical, chemical, and biological monitoring of any surface water; geotechnical analysis; topographic survey; utility research and notification; utility potholing and coordination; acquisition of the storm drain connection permit; and bilingual public outreach and education