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i <br /> In January 1987, four additional ground water monitoring <br /> wells were installed to define the lateral extent of <br /> dissolved hydrocarbon constituents in the ground water. One <br /> of the wells was installed onsite while the other three <br /> wells were installed offsite. Analysis of the water samples <br /> collected from the monitoring wells indicated the presence of <br /> detectable concentrations of dissolved hydrocarbons in the <br /> shallow ground water at the site. Because of the close <br /> proximity of the site to two other potential sources of <br /> hydrocarbon fuel contamination, the extent and nature of <br /> ground water contamination could not be defined at that time. <br /> Periodic ground water monitoring and sampling conducted from <br /> April 1987 to October 1988 indicated the continued presence <br /> of dissolved hydrocarbon constituents in the shallow ground <br /> water beneath the site. Review of the results of the October <br /> 1988 sampling event indicates that the extent of onsite <br /> ground water contamination is limited to the northern and <br /> eastern portion of the site. The presence of detectable <br /> levels of dissolved hydrocarbon constituents in the offsite <br /> ground water samples, however, may indicate that either the <br /> contamination plume has migrated downgradient towards the <br /> north/northeast or the other nearby service stations may have <br /> similar subsurface contamination problems. <br /> SCOPE OF PROPOSED WORK <br /> The proposed subsurface investigation study will be conducted <br /> in accordance with applicable regulations and guidelines of <br /> the San Joaquin County Public Health Services-Environmental <br /> Health Division (SJCEHD) and the Central Valley Regional <br /> Water Quality Control Board (RWQCB) . To properly address the <br /> potential ground water contamination problem at the site, the <br /> proposed scope of work has been divided into two parts : <br /> Part 1 - Supplemental Subsurface Investigation/ <br /> Remedial Planning Study <br /> Part 2 - Ground water Monitoring and Sampling <br /> The tasks included under each part of the proposed scope of <br /> work are described below. <br /> RT 1 - SUPPLEMENTAL -S-UBSURFACE INVE TI ATI DIAL <br /> PLANNING T D <br /> Part 1 will involve supplemental subsurface investigative <br /> work to define the nature and extent of ground water <br /> contamination, and a remedial planning study. The tasks <br /> proposed herein also include detailed review of available <br /> information and reports on any past or ongoing subsurface <br /> investigations at the nearby sites . <br /> 2 <br />