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WORK PLAN 0 • <br /> FOR GROUND WATER WELL INSTALLATION AND MONITORING <br /> PORT OF STOCKTON-ROUGH AND READY ISLAND,CALIFORNIA <br /> Wells and borings advanced at and near Site 47 reveal water bearing silty sands <br /> between 10 and 15 feet bgs. An underlying sandy water bearing layer was also <br /> encountered at about 25 feet bgs, with a clay layer separating the two sandy zones. Two <br /> borings did not encounter a water bearing zone within 30 feet of ground surface. <br /> Ground water elevations in RRI wells indicate the ground water flows generally <br /> west-northwestward across Site 47. <br /> 2.3.3Q Y ualit of Shallow Soil <br /> Background soil conditions were characterized throughout RRI in 1997, and are <br /> documented in the Technical Memorandum, Background Soil Concentration for Metals and <br /> Pesticides, NCS Stockton (PRC, 1997c). The PRC study developed background screening <br /> level concentrations (BSLs) for various constituents in soil at RRI. The study concluded <br /> that there are no reportable BSLs of volatile organic compounds (VOCs), semi-volatile <br /> organic compounds (SVOCs), or polynuclear aromatic hydrocarbons (PAHs) in soil. <br /> However, the study did not consider documentation by others (e.g., USEPA, EPRI) that <br /> allow for natural and ambient anthropogenic sources of PAHs to soil from various <br /> sources, including fire, widespread use of crude oil based asphalt, and historical <br /> industrial emissions. <br /> The study developed BSLs for inorganics and organochlorine pesticides (OCPs) in the <br /> three dominant geologic media: sand, silt and mineral clay, and organic clay. The <br /> background presence of OCPs was attributed to the extensive agricultural activities in <br /> the Central Valley and Delta. Comparing total BSLs for inorganics and OCPs with <br /> Regional Screening Levels (RSLs, USEPA Region 9, 2009) for residential and industrial <br /> land use scenarios, the BSLs for arsenic and vanadium exceed the RSLs under an <br /> industrial land use scenario. <br /> The study also developed BSLs for water soluble constituents in soil using the <br /> California Waste Extraction Test and deionized water (DI WET). Comparing the water <br /> soluble BSLs with the lowest water quality objective listed in A Compilation of Water <br /> Quality Goals (Regional Board, 2008), the water soluble BSL exceeds the water quality <br /> objective for aluminum, arsenic, cadmium, iron, lead, manganese, molybdenum, nickel, <br /> thallium, and vanadium. Although this comparison excludes an evaluation of the <br /> attenuation capacity of vadose zone soil, the water soluble fraction in background soil is <br /> likely to be a significant contributing factor to the ground water BSLs that also exceed <br /> water quality objectives. <br /> September 2014 Environmental Risk Services <br /> Corporation <br />