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KEEINFELDER For the protection of the field crew, the PID was also used to measure the total ionizable concentration in the breathing zone prior to and while drilling the borings No consistent readings were noted in the breathing zone above 1 ppmv 4.3 Monitoring Well Development and Sampling On March 31, 1994, the three monitoring wells (MW-1, MW-2, and MW-3) were developed by swabbing and bailing to remove sediment laden water from the wells, set the filter packs, and increase the effective hydraulic radius of the wells A minimum of 10 well volumes were removed from each well The well development and sampling procedures are explained in Appendix B, Kleinfelder Field Procedures On April 4, 1994, monitoring wells MW-1, MW-2, and MW-3 were purged and sampled by bailing Prior to purging the wells, each well was checked for floating product with a clean disposable bailer Monitoring wells MW-1 and MW-2 did not have a product layer or sheen but did have a gasoline odor Monitoring well MW-3 did not have a product layer, sheen or odor Water samples (sample #84299 from MW-1, sample #84291 from MW-2, and sample #94267 from MW-3) were collected in containers supplied by the analytical laboratory Well sampling procedures are described in Appendix B, Kleinfelder Field Procedures The Purge Characterization and Sample Logs are included in Appendix D 4.4 Monitoring Well Elevation Survey Relative elevations and the "x, y" coordinates for the north side of the top of each 2-inch PVC well casing were surveyed by Thompson-Hysell Associates from Modesto, California (California Licensed Land Surveyor) on April 20, 1994 The coordinates were tied to a bench mark located near Charter Way and U S Interstate 5 The survey map provided by MThompson-Hysell is included in Appendix F ' The depth to groundwater was measured from a set location at the top of each casing on April 4, 1994 The depth to water was then subtracted from the corresponding casing elevation to provide a groundwater surface elevation in each well The well casing elevations, depth-to-water measurements, and calculated groundwater surface elevations relative to mean sea level are presented on Table 3 The water surface elevations are used to estimate the groundwater gradient direction ETH and WC194 Copyright 1994 Kleinfelder Inc Page 7 of 11