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Mr Kyle Christie Project 0805-146 03 <br /> August 2, 1995 <br /> Page 5 <br />' HVOC analyses be performed on a senuannual basis (during the first and third quarters of <br /> each year) Concentrations of TPHG and benzene are shown on Figure 2 <br /> ACTIVITIES PERFORMED DURING THE SECOND QUARTER <br /> • Performed quarterly groundwater sampling <br /> Assembled the results of the file search and aerial photograph study in an <br />' Evaluation of Off-Site Sources Report The off-site evaluation report was <br /> submitted to the SJCPHS on May 5, 1995 <br />' • Prepared and subrrutted a workplan to drill additional soil borings to assess <br /> hydrocarbons beneath the USTs In May 1995, EMCON drilled one angle boring <br /> and installed two vapor extraction wells <br /> ANTICIPATED WORK <br /> o ARCO will continue to perform quarterly groundwater monitoring The next <br /> sampling event is tentatively scheduled for August 1995. Because wells MW-2 <br />' and MW-5 are located within the dissolved hydrocarbon plume and other nearby <br /> monitoring wells provide lateral definition, EMCON recommends these wells be <br /> discontinued from quarterly sampling <br />' * Groundwater samples will be analyzed for TPHG, BTEX and halogenated <br /> P Y g <br /> volatile organic compounds In addition, samples collected from well MW-6 will <br />' be analyzed for TOG <br />' CONCLUSIONS <br /> Based on results of the subsurface investigation, TPHG was detected only in the historical <br />' capillary fringe zone (25 feet bgs and at a concentration of 6 0 ppm) BTEX constituents were <br /> detected in all borings at low concentrations. Based on soil samples collected at the ARCO <br /> Station during several drilling operations conducted at and adjacent to the site, residual <br />' hydrocarbons appear to be present primarily within the histoncal capillary fringe zone. <br /> However, based on soil collected from the Texaco Service Station and from borings located <br /> adjacent to the Transmission Store, residual hydrocarbons are present above the histoncal <br /> capillary fringe zone <br />' SAC\N TIM80510805I460 3SL-951pas 3 <br />