20B - AA - COOP AGMT - DIVERSION PROJ

Home Browse Search

Santa Ana Delhi Diversion Project - 2 - February 25, 2016 easily observed when on -site, a freshwater emergent wetland exists in the section of the Santa Ana -Delhi Channel (channel) downstream of the Mesa Street Bridge and the proposed Project site. In this location, fresh water pools form above the tidal influence that wildlife utilizes. California Department of Fish and Wildlife species of special concern and Federal Endangered Species Act listed species have been reported utilizing the freshwater marsh. The United States Geologic Survey biological survey team and others have periodically identified western pond turtle (Actinemys rnarmorata palllda), a California Department of Fish and Wildlife species of special concern, in this section of the channel. The California least tern (Sternula antillarum brown), federally listed as endangered, feeds in the freshwater sections of the channel as reported in the 1993 EIR and by local wildlife experts. As such, the 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. In addition, United States Fish and Wildlife Service (USFWS) staff expressed concerns over the reduction of channel flows into Upper Newport Bay that would result from the implementation of this Project, and possible impacts to the salt- water marsh located downstream of the channel confluence with the Bay. Recently, USFWS staff provided Regional Board staff with a documene that describes the benefits of adequate nutrients to a healthy salt -water marsh. The Project proponents should respond to USFWS' concern prior to implementing the Project, and consider Project options to avoid potential adverse impacts to the downstream salt marsh. The implementation of the Project could result in increased erosion in the earthen downstream sections of the channel. Implementation of the Project would remove sediment from dry weather flows along the earthen section of the channel from Mesa Street to the Bay. The lack of sediment deposition could encourage greater scouring during wet weather flows, but the MND does not discuss this possibility. Board staff recommends conducting a hydraulic study of the channel examining sediment transport prior to determining whether to construct the Project. The MND states that during wet weather, water may be allowed to pool several feet deep behind the diversion structure before it is released downstream. The Project proponents should consider the effects of these wet weather releases to the downstream sections of channel and the habitat. In addition, the Project proponents should evaluate whether allowing routine smaller releases versus Personal communication with USFWS staff Chris Medak. z Zedler, 1993, "Canopy Architecture of Natural and Planted Cord grass Marshes: Selecting Habitat Evaluation Criteria ". 20B -24