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CLEARWATER ' G R O U P I N C • Environmental Servues ' environmental laboratorylocated in Sunnyvale, California Samples were analyzed for TPHg by EPA Y�' Method 8015 (modified) and BTEX with methyl tert-butyl ether (MTBE) by EPA Method 8020 ' 2 2 Monitoring Well Installation EA The three borings were converted into monitoring wells (MW-X, -Z and 3)constructed of 2-inch diameter schedule 40 PVC flushed-threaded well material Fifteen feet of 0 020-inch slot well screen ' extends from the bottom of each well at 20 feet bgs to 5 feet bgs A filter pack of#3 sand was placed ui the annular space against the screen and extends from the bottom of each well to one foot above the well ' screen The filter pack is overlain by a two-foot thick bentonite seal The remaining annular space was sealed with neat grout Wells are protected at the surface by locking expansion plugs and flush ' mounted traffic rated well boxes Well construction details are included on the Boring Logs in Appendix B ' 2 3 Monitoring Well Development and Surveying The monitoring wells MW-4, MW-5 and MW-6 were developed by alternate surging and bailing on '• January 20, 1999 Prior to developing or sampling, the depth to water was measured to the nearest 0 01 feet,from the top of the well casing, using an electric water sounder At least ten well casing volumes of water were purged from the well for development Temperature,conductivity, and pH measurements of the purge water were collected during well development ' On January 20, 1999, top of casing elevations of each new well were surveyed by Clearwater, to the nearest 0 01 feet relative to a project datum Field data sheets which include gauging, development, ' sampling, and survey data are included m Appendix C ' 2 4 Monitoring Well Sampling Wells MW-4, MW-5 and MW-6 were sampled on January 20, 1999, after the development activities ' described above Monitoring wells MW-1, MW-2 and MW-3 were sampled on March 23, 1999 At least three well casing volumes of water were purged from wells MW-1,MW-2 and MW-3 prior to sampling ' Temperature,conductivity, and pH measurements of removed water were collected dunng well purging After groundwater in the wells recovered to 80% of the pre-purged volume, a polyethylene sampling bailer was dedicated to the well and used to collect a groundwater sample Water samples were Itransferred to laboratory supplied sample bottles and labeled with appropriate well designations • Samples were documented on a chain of custody form and placed in a cooler for shipment to Entech All 1 C-178 WELLINST RPT 3 May 7, 1999