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0 <br /> C-SHADRIFS91.6/G W PP.4 <br /> 01/22/92 <br /> such as packing materials, sludges, solvents, and contaminants likely introduced <br /> to help the wastes bum) and/or several ground-stained areas onsite. <br /> Groundwater contamination also has been detected in the Central Area. The <br /> metals arsenic and selenium have been detected sporadically in groundwater <br /> samples taken during various environmental studies. These metals are primarily <br /> confined to the shallow water-bearing zone and do not appear to be migrating <br /> toward potable wells. The sources for arsenic and selenium are not apparent and <br /> may include natural and offsite contributions as well as onsite sources. During <br /> the RI studies, no observable pattern for arsenic in groundwater was noted. The <br /> pesticide bromacil (known to result from application onsite) also has been <br /> detected sporadically in the groundwater. <br /> Soil and groundwater studies were performed at SHARPE to assess the extent of <br /> groundwater contamination. The general objectives of these studies have been <br /> to identify the lateral and vertical extent of groundwater contamination, <br /> determine the rate of VOC contaminant migration, define underlying <br /> groundwater and stratigraphic characteristics, and evaluate methods for <br /> groundwater remediation and disposal. Results of these studies showed that past <br /> soil contamination was still contributing to groundwater quality degradation, and <br /> additional efforts were proposed in 1986 to identify precisely the contaminant <br /> source locations. <br /> Under the direction of USATHAMA, the RI effort began in 1982. The multi-year <br /> RI process has been conducted in phases, resulting in a substantial environmental <br /> database. More than 200 groundwater monitor and extraction wells have been <br /> installed at SHARPE. Over 3,500 groundwater samples have been collected and <br /> analyzed, most of them for at least 30 individual chemical compounds. <br /> Approximately 1,800 soil gas, 500 soil, and 200 air samples have been collected <br /> 5 <br />