20B - AA - COOP AGMT - DIVERSION PROJ

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l:� Response: Comment noted. The project will require temporary closure of the trail during construction of the channel diversion facilities for approximately 120 days. After construction, the trail will be restored to existing conditions using decomposed granite. The City of Santa Ana will seek approval of the trail reconstruction plans from OCPW prior to the start of work. 2.2 COMMENTS FROM SANTA ANA REGIONAL WATER QUALITY CONTROL BOARD — FEBRUARY 25, 2016 1. Comment: The Project design should consider the impacts of removing all low flows at the diversion structure to downstream aquatic ecosystems, including a freshwater emergent wetland that exists in the section of the Santa Ana -Delhi Channel downstream of the Mesa Street Bridge. In this location, freshwater pools form above the tidal influence that wildlife utilizes. Species observed in this location include western pond turtle and California least tern, a California species of special concern and federally - listed endangered species, respectively. As such, Project proponents should determine avoidance, minimization or mitigation resulting from Project impacts to the listed and other freshwater marsh species established in the areas downstream of the project site. United States Fish and Wildlife Service staff expressed concern over the reduction of channel flows into Upper Newport Bay that would result from the project and possible impact to the salt -water marsh located downstream of the channel confluence with the Bay. The Project proponents should respond to the USFWS concern prior to implementing the Project and consider Project options to avoid potential adverse impacts to the downstream salt marsh. Response: Portions of Final Design for the Project were based off of recommendations made by the Santa Ana Regional Water Quality Control Board in the Santa Ana Delhi Channel Watershed Water Quality Summary (Shibberu, 2009). This sunnuary rcconnnended that the channel low -flow notch be blocked during the dry season (See Table 16 of Section 5.0). Final Design of the project included blocking the trapezoidal low -flow "notch" during all weather events via a cross - channel weir. Up to 20 cubic feet per second (cfs) of flows blocked by the proposed diversion structure will be screened via an inclined screen (Coanda) type BMP to remove trash and debris. Up to 3 cfs may be pumped from a Transfer (Bypass) Culvert to be discharged into the regional sewer collection system; all flows exceeding this capacity will be returned to channel. The Bypass Culvert is designed such that up to 20 cfs of annual flows will be returned to channel after receiving screening treatment to remove trash and other debris. Also, flows in the channel downstream of the Project (e.g. below the Mesa Street Bridge) will not be affected by the Project and will continue to flow in this downstream channel reach. These flows enter the channel from local storm drain inlets that include at least (1) 36 ", (2) 42 ", and (3) 18" storm drain system inlets and contribute to channel flows downstream of the Proj ect. To address USFWS' concern regarding reduction of channel flows into Upper Newport Bay, operation of the Project pumps to divert flows to the regional sewer collection system 209 -14