Resolution 2879 - Laserfiche WebLink

During a major earthquake, there could be a localized loss of foundation support, settlement or slope distortion. If a major slope failure were to occur upslope from RADCAD, the slump could disturb the disposal area with additional deltaic silt. Placement of the berm will reduce potential impacts of slumping that might occur as a result of a major slope failure. 2. Dredging procedures (WDOE Water Quality Certification, page 3 and Draft Record of Decision, page 1) The work will involve the dredging and excavation of approximately 3,305,000 cubic yards (cy) of material (1 ,428,000 cy of clamshell and the remainder by hydraulic dredge or by clamshell dredge with disposal through a pumpout barge) . The clamshelledmaterial will consist of approximately 928,000 cy of contaminated material and 500,000 cy of relatively uncontaminated material. This material will be deposited by bottom-dump scow at an open-water disposal site near the Snohomish River Delta. The remaining 1 ,877,000 cy of hydraulically dredged material, or material to be clamshelled with disposal through a pumpout barge, will be used to cap the contaminated material. Approximately 33,000 cy of the excavated material (wood refuse) and 52,000 tons of debris from the East Waterway on Port Gardner Bay will be removed and disposed at an approved upland disposal site. The dredging will be performed in two annual phases. During the first year (Phase I) , 500,000 cy of clamshell dredge materials will be disposed to create a downslope mound. Then, approximately 97,000 cy of clamshell dredged contaminated material will be discharged by bottom-dump barge to be followed by approximately 239,000 cy of hydraulic dredged uncontaminated material for capping. During the second year (Phase II) , approximately 831 ,000 cy of contaminated material will be discharged and then covered by approximately 1 ,638,000 cy of hydraulic dredged capping material. Approximately 1 , 189,000 cy of fill material will be placed to construct a breakwater, moles and for bank protection. Timing: For Phase I, no dredging or disposal of contaminated dredge material shall take place between December 1 and July 15 and no dredging of clean material shall occur between January 15 and June 15. Pile driving or rock breakwater construction shall not occur from March 15 to June 15. The Department of Ecology in consultation with the Department of Fisheries, where necessary, may grant a reasonable extension of time for dredging and dumping of clean material. For Phase II dredging, the period allowable for dredging and disposal will be adjusted by taking into consideration the data and information from Phase I dredging. Such information will include, but not be limited to, water quality and aquatic life data and information. The "fish windows" or project-timing still pertain to the program. The program is projected to begin in 1988. Length of the program is dependent on Congressional funding and could involve application for a second permit were it to exceed the 5 + 1 years length of the permit now provided. 3. Spoils disposal area. The RADCAD site would cover approximately 400 acres and range in depths between -310 and -430 feet (MLLW) . It is located approximately 9000 feet southwest of the dredge and Homeport site. -13-