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Preliminary Design Report Addendum No.2 <br />1.0 INTRODUCTION <br />1.1 BACKGROUND <br />The City of Santa Ana, in association with the Cities of Newport Beach and Costa Mesa, is currently <br />developing a conceptual engineering plan for a proposed urban runoff diversion facility. The proposed <br />Delhi Channel Diversion Facility is located in the downstream portion of the Santa Ana Delhi Channel <br />system near the intersection of Mesa Drive and Irvine Avenue adjacent to the Newport Beach Golf <br />Course. The proposed project is intended to collect non - stormwater discharges from the Delhi Channel <br />and divert the flow to the sanitary sewer system for further treatment, or to the on -site golf course <br />reservoir to be used for irrigation purposes. <br />The proposed project addresses the potential urban surface water quality issues associated with discharges <br />to the Upper Newport Bay. The proposed diversion facility will comprise an in- channel flow diversion <br />structure, an intake and bypass outlet structures, a primary treatment facility including coarse screen, fine <br />screen, gravity sedimentation, sub - surface storage facilities, and a lift station and force main (FM) to <br />convey the harvested flow from the discharge storage chamber to the existing drainage sewer for further <br />treatment in the regional wastewater treatment plant. The goal of the proposed project is to divert non- <br />stormwater during dry weather condition to eliminate the potential threat of selenium exceeding the <br />current Total Maximum Daily Loads (TMDLs) (Santa Ana Delhi Channel Diversion Project Preliminary <br />Design Report, Sept. 2012, Addendum No. 1 August, 2013). <br />Key drivers for the project are: <br />• Removing environmental impacts: the project will provide a treatment system that will remove <br />pollutants from dry- weather /stormwater discharges from the regional drainage system complying <br />with current and future TMDL concerns from local watersheds; <br />• Removing local cities for wastewater treatment: The costs are too high for local cities to invest <br />capital to operate and maintain a wastewater treatment facility to address TMDL challenges; <br />• Harvested water is a valuable resource: dry - weather discharges and stormwater is becoming a <br />valuable resource and will be in demand for local golf course irrigation needs. <br />Engineering and environmental evaluation of alternative force main routes has been completed, along <br />with the design of the diversion facility. <br />1.2 FACILITY DESCRIPTION <br />Preliminary Design Report (PDR) Addendum No. 1 (August 2013) revised the conceptual design PDR <br />(July 2012) to include a three -stage clarifier system with bar screen, sediment removal and fine screen to <br />capture floatables. The flow capacity of the system will treat the front end portion of the first flush storm <br />water quality event to a maximum flow capacity of 100 cfs and all of the dry- weather discharges within <br />the Santa Ana Delhi Watershed. The proposed channel diversion would be accomplished through the use <br />of an in- channel flow diversion structure and discharge into a side inlet incorporated into the original <br />flood control channel. The existing channel would be removed and replaced approximately thirty feet <br />upstream and fifty feet downstream from the in- channel structure for structural purposes. The existing <br />channel will be modified with inlet and bypass outlet structures as part of the proposed diversion facility. <br />URS >I <br />25F -133 <br />