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Also, the highest concentrations at the site occur between depths of 15 and 20 feet <br /> below the ground surface while the highest historical groundwater level in the area <br /> occurred at a depth of 38 feet This suggests that there exists approximately 20 feet of <br /> "clean soil" and that the groundwater contamination is unrelated to the contamination <br /> in the soil But groundwater samples from MW2 and MW5 located downgradient <br /> within the site indicate elevated levels of hydrocarbons <br /> 3.0 WORK TO BE CONDUCTED <br /> The San Joaquin Department of Health Services has directed all Principal Responsible <br /> Parties associated with this site to further define the groundwater contamination plume <br /> downgradient and provide remedial alternatives to mitigate offsite migration of the <br /> contaminated groundwater plume.To accomplish this, additional monitoring wells <br /> need to be installed to replace those that are now dry and remediation alternatives will <br /> be explored to mitigate the contamination in the groundwater and prevent the further <br /> migration of the plume off-site <br /> 3.1 Additional Work Towards Phase 2 Investigation <br /> Based upon investigations conducted by LH and KJC,petroleum hydrocarbon <br /> concentrations in groundwater are higher on the west(upgradient) side of the property <br /> than on the east side (downgradient) The Phase 2 investigation suggests that there <br /> exists an offsite source to this contamination of groundwater Hence, additional - <br /> investigation to fully define the groundwater plume and identify the source of <br /> contamination needs to be conducted <br /> The following subsections, 3.1 1 and 3 12 describe the activities to investigate the <br /> source and extent of groundwater contamination. <br /> 3.1.1 Groundwater Monitoring Wells Installation <br /> Four additional wells will be installed on- and offsite to define the extent of <br /> groundwater contamination We will install these monitoring wells to a depth of <br /> approximately 60 feet Two wells will be installed downgradient of the site and two <br /> upgradient <br /> 3.1.2 Groundwater Sampling and Analysis <br /> r 6 <br />