Reso 2004-069 - Laserfiche WebLink

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DMMS SITE DESCRIPTION AND EXISTING CONDITIONS The DMMS has been in use since 1973 by the City and the Corps, when materials from the San Leandro Marina were first deposited on the site. This area received the materials resulting from the demolition and replacement of portions of the existing San Leandro Marina and associated dredge materials. The site is oriented in a north-south direction with an internal dike separating the two main dredge basins (Figuxe 3). The DMMS area is hydrologically connected to North Marsh of the San Leandro Marshlands to the south through a culvert in the southern levee in the West Basin, and experiences muted tidal flooding (estimated at 0.5 feet of tidal flux). The DMMS is sparsely vegetated and primarily consists of large patches of bare ground and ponded water. The surface elevation of the DMMS area is estimated at 1.0 foot Mean Sea Level (MSL), with surrounding levee heights of +10 ft MSL. The DMMS receives tidal action and standing water routinely covers 30-80 percent of the site with remaining areas consisting of dry mud, upland grasslands, and sparsely vegetated islands. The 100-acre DMMS contains both wetland and upland habitat and has been managed since 1973 primarily for dredge disposal activities. The D1~1NIS is managed to provide shorebird habitat during the years between dredging cycles. The site receives tidal water from the. adjacent Shoreline Marshlands area to provide a food source for the large numbers of shorebirds that use the San Leandro shoreline area. REMOVAL OF STORED DREDGED MATERIAL The City is considering different grading scenarios for the DMMS following offhaul of material. The general grading concept is to remove material from the East and West basins to an approximate elevation of +3 feet MSL in the south to +1.5 feet MSL approximately 500 feet north of the southern levee. Based on grading scenario calculations, it is estimated that approximately 00,000 to 80.000 cubic yards of dried dredged material will be excavated from the site for offhaul (this includes an assumed desiccation crack volume range of 30 to 40 percent). Upon excavation and loading into trucks, it is estimated that the material will have a loose volume of 80,000 to 100,000 cubic yards. The dredged material would he hauled to Oyster Bay Regional Shoreline Park, located approximately 1.5 nines north of the DMMS. Oyster Bay Regional Shoreline Park consists of approximately 200-acres along San Francisco Bay at the westerly end of Davis Street and was formerly used as a sanitary landfill. The site is planned as a future park and is covered by waste discharge requirements as mandated by the RWQCB, and has received excavated material from the City of San Leandro in the past. ~ The amount of shrinkage in volume that occurs in the dredged material due to drying out. San Leandro DMYIS 5 March / 2004 Sediment Removal Project