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FINAL SITE 47 SOIL SAMPLING WORK PLAN <br /> PORT OF STOCKTON-ROUGH AND READY ISLAND,CALIFORNIA <br /> time. More recently, the Naval Computer and Telecommunications Station San Diego <br /> Detachment Stockton (NCTS Stockton) managed the depot until July 2002 when Navy <br /> operations ceased.The Navy divided RRI into four areas based on general land use:the Landfill <br /> Area, Administrative Area, Warehouse Area, and Agricultural Area. Rough and Ready Island <br /> is now under the administration of the Port of Stockton. The Site covers portions of the <br /> Agricultural Area. <br /> 2.2 DESCRIPTION OF SITE 47 <br /> 2.2.1 Site Lithology and Hydrogeology <br /> Rough and Ready Island is located in the delta area formed by the Sacramento River and San <br /> Joaquin River along the western margin of the Central Valley of California. The shallow soils <br /> that underlie the Site fall into three general categories: native alluvium, peat, and artificial fill. <br /> The native alluvial deposits range from coarse sand to clay and silt,with rapid changes in grain <br /> size and texture both laterally and vertically. The peat is formed from decay and compaction of <br /> dead plant matter. It ranges from very woody and undecomposed to very fine, soft organic silt. <br /> Artificial fill at the Site is highly variable, and can consist of rubble from demolitions, native <br /> alluvium relocated from other portions of RRI, dredge spoils, and imported gravel. <br /> Ground water at the Site is encountered at depths ranging from 3 to 10 feet below ground <br /> surface (bgs). All shallow ground water discharge at the Site is routed through the existing <br /> drainage system to the pumping facility located near the southwest corner of the island. <br /> 2.2.2 Environmental Conditions and Chemicals of Concern <br /> Site 47 is an area where arsenic is present in soil at concentrations that exceed the US EPA Risk <br /> Based Screening Level(RSL) for industrial exposures, as well as other applicable standards.The <br /> source of this arsenic is unknown but the concentrations exceed the background levels <br /> developed for RRI and some individual samples have exceeded 500 milligrams per kilogram <br /> (mg/kg) arsenic. Because of the potential for high arsenic in soil, soil within the boundaries of <br /> Site 47 will be subject to special handling requirements as described in the SMP. The SMP also <br /> outlines procedures for protecting existing monitoring wells located near the proposed work <br /> site. <br /> Ground water at Site 47 contains arsenic at concentrations exceeding applicable screening <br /> levels. The most recent sampling event at Site 47 was completed on March 12, 2015. The <br /> concentration of arsenic in ground water was 350 micrograms per liter, and the depth to water <br /> was 3.24 feet bgs. <br /> March 2015 2 Environmental Risk Services <br /> Corporation s <br />