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7C Page 47 marina bottom sedimen#s and would creafe temporary water quality impacfs, resulting in a potentially significant impact. Mitigation 8-3: Require the following mitigation measures to reduce water quality impacts associated with propased project flushing channels dredging and marina filling operations: 1. As a condition of project approval, require the app[icant ta apply to the U.S. Corps of Engineers (Corps)for an Individual Department of Army Fill Permit, and abide by any conditions imposed by the Corps and its sister agencies of the Dredged Materiais Management OfFice (DMMO) pertaining to the disposal of dredged sediments. 2. Cantract with a water quality and sediment testing Eaboratory certified by the State of California to conduct an updated testing of marina and flushing channei sediments. Flushing channel sediments wiI( have to be drawn as core logs during a pre-project, pre-excavatian testing program. Results of the updated testing shall be submitted along with the Department of Army Permit application to the Carps, and the 401 Water Quality Certification request to the RWQCB. 3. impkement the dredging aperations utilizing a suction dredge#hat minimally disturbs adjacent sediments (see Mitigatron 8-1 herein). Confer with the Corps to determine the appropriate method for the site conditions (e.g., sedirr�ent characteristics)and the feast environmentally damaging rr►ethod for sheet pile/hulkhead installation and warksite segregation from Bay waters. Findings: lmpiementation of these measures would reduce the impacts of flushing channel dredging and marina filling operations to a less-than-significanf level. D. Marina and Creek Sedimentation and Associated Creek/Bav Water Qualitv Impacts Potential tm�act 9-4: Project implementation, including an approximately 9.50- acre reduction in marina open water area, would reduce the tidal prism (the water volume exchanged between higher high and lower low waters} which functions to scour tidal sediments from the marina entrances and from the iower reach�s of �edwoad Creek. Rates of siitatian in these water bodies wou{d increase. Future dredging and spoils disposal could be required at higher than existing frequencies, resulting in more frequenf wafer quality disturbances antf higher costs to the City. This constitutes a pofentia!!y sign�cant impact. M'rfiigation 9-4: Require the follawing mitigation measures#o reduce potential siltation impacts on the marina inlet channels and the praject reach of Redwood Creek {extending to the Smith Slough confluence), carresponding dredging needs, and associated water quality impac�s: 1. Require the applicant to conduct additional hydraulic analyses to verify to the satisfaction of the City Engineer that the marina iniets will operate a# close to a sel#-scouring condition. ff the anaEyses do nof verify probabie maintenance of such a candition, the project design shall be adjusted accordingly. AttylResa/Reso.i 772 2g 1213Q7