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I� <br /> Beacon Station No.474 August 2, 1996 <br /> Stockton,Califomia Assessment Report <br /> Monitorine Well Development and Sam lin <br /> On May 29, 1996 Horizon personnel were onsite to perform well development and on May <br /> 30, 1996 Horizon personnel were onsite to perform groundwater sampling of the <br /> groundwater monitoring wells MW-4 and MW-5. The wells were developed, purged, and <br /> sampled as described in Appendix B. Depth to groundwater levels were taken before and <br /> after development and purging of the wells. Groundwater samples were contained in cooled <br /> storage for transport to the laboratory for the requested analyses. <br /> LABORATORY METHODS AND RESULTS <br /> Soil Samples <br /> Soil samples collected from B-1 through B-4, MW-4, and MW-5 were submitted under <br /> Chain of Custody (COC) to West Analytical Laboratory (WEST) in Davis, California <br /> (Certification No. 1346). Soil samples selected for analysis were the samples collected from <br /> depths ranging from approximately 10 to 75 feet bgs in each of the above mentioned <br /> borings. The samples were analyzed for total petroleum hydrocarbons as gasoline (TPHg) <br /> and for the gasoline constituents benzene, toluene, ethylbenzene, xylene (BTEX), and <br /> methyl-t-butyl ether (MTBE) by modified EPA Methods 30501801518020. Gasoline <br /> hydrocarbons were not present above the laboratory reporting limits in any of the samples <br /> analyzed from the borings except for a concentration of 0.055 parts per million (ppm) <br /> benzene, 0.012 ppm toluene, and 0.010 ppm total xylenes detected in the soil sample <br /> collected at 70 feet bgs in boring B-2. MTBE was not present above the laboratory reporting <br /> limits in any of the soil samples analyzed. Laboratory results are summarized in Table 1. <br /> Laboratory analytical reports and.COC forms are included in Appendix.E. . <br /> i 5 <br /> 1474.11-RPT HORIZON ENVIRONMENTAL INC. <br />