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Lower San Diego Creek Tributary Urban Runoff Diversions Alternative Feasibility Study Irvine, CA The Irvine Ranch Water District (IRWD) began treating urban runoff in 1997 by constructing wetlands at the San Joaquin Marsh and Wildlife Sanctuary in Irvine located adjacent to Riparian View between Michelson Drive and Campus Drive. A large portion of urban runoff from San Diego Creek, Orange County Flood Control District (OCFCD), Facility No. F05, is diverted/pumped into a system of man made ponds or wetland detention facilities where it is detained/ treated between 10-20 days then the "polished" or treated water is diverted back into San Diego Creek for discharge into the Newport Bay estuary system. Bacteria, Nitrogen, Phosphorus and other pollutants are removed from the urban runoff by flowing through the wetlands and interacting with the plants, soils, and exposure to ultraviolet radiation/ sunlight. Between 2015 and 2017, IRWD in partnership with City of Irvine, City of Tustin, Caltrans, County of Orange, and OCFCD constructed the Peters Canyon Channel Water Capture and Reuse Pipeline project. This project diverted dry -weather, urban runoff, and groundwater flows from the tributaries to a new urban runoff diversion pipeline facility to an Orange County Sanitary District (OCSD) sewer main line. The Peters Canyon Channel water Capture and Reuse Pipeline project created a need for additional dry -weather flows to feed the San Joaquin Marsh wetlands. Coupled with the desire to reduce pollution from San Diego Creek and the Newport Bay Estuary system, IRWD identified three tributaries within the lower San Diego Creek watershed for study to determine the feasibility of diverting their dry -weather flows to the San Joaquin Marsh. The three tributaries were identified as: Bonita Canyon Creek, UCI Storm Drain and San Canyon Channel. Stantec reviewed the constituent and flow rate data for the three tributaries and determined that the tributary dry -weather flows could be introduced without significant consequence to the Marsh 's health and function. Furthermore, given the high concentration of some constituents, Stantec concluded that dilution with existing Marsh inflow and treatment within the San Joaquin Marsh itself would result in an enhancement of water quality in reaches of San Diego Creek located downstream of the Marsh. Stantec performed feasibility assessment and alternative analyses for all the three tributaries streams to construct diversion pipelines to intercept and capture the dry - weather flows prior to discharge into the San Diego Creek and convey to the San Joaquin Marsh. The assessment included location and type of diversion structures, types and alignment of the conveyances, preliminary engineers opinion of probable construction cost and alternatives ranking. Key Elements • Review water quality sampling data • Review of the constituents from each tributary system • Assess feasibility meeting water quality objective • Develop conceptual diversion locations • Develop conceptual diversion conveyances alternatives • Evaluate and ranking the alternatives Prepare preliminary cost estimate Team Members • Roger Chung, PE, CFM, QSD/P, F. ASCE—Stantec • Phil Jones PE, QSD/P—Stantec • Dan Hayes, PE—Stantec Project Dates 2017-2019 Reference Ian Swift Natural Resources Manager Irvine Ranch Water District 3512 Michelson Drive Irvine, CA 92612 T: 949-453-5864 E: Swift@irwd.com ® Stantec • Proposal for On -Call Storarwater Project Design Services