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Beacon Station No 419 August 2, 1996 <br /> Stockton, California Assessment Report <br /> Wellhead Elevation Survey <br /> On June 6, 1996, the wellheads for all the groundwater monitoring wells at the site were <br /> surveyed to a local National Geodetic Vertical Datum benchmark by a licensed land <br /> surveyor (Ron Archer Civil Engineering Inc ) The results of this wellhead survey data are <br /> included in Appendix D <br /> Monitoring Well Development and Sampling <br /> On May 29, 1996 Horizon personnel were onsite to perform well development and <br /> groundwater sampling of the groundwater monitoring wells MW-4 through MW-6 The <br /> wells were developed, purged, and sampled as described in Appendix B Depth to <br /> groundwater levels were taken before and after development and purging of the wells <br /> Groundwater samples were contained in cooled storage for transport to the laboratory for the <br /> requested analyses <br /> LABORATORY METHODS AND RESULTS <br /> Soil Samples <br /> Soil samples collected from S13-4, SB-5, and MW-4 through MW-6 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 55 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 borings SB-4, and MW-4 through MW-6 except for a trace concentration of <br /> 0 0057 parts per million (ppm) total xylenes detected in the soil sample collected at 50 feet <br />• 1419 11-RPT 5 HORIZON ENVIRONMENTAL INC <br />