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Soil Boring and Monitoring Well Installation Report Page 4 Ranch Market Riverbank CA September G 2000 • 4.4 Monitoring Well Installation Groundwater monitoring wells were installed in borings MW-5, MW-6, MW-7, MW-8, and MW-9 using 2-inch-diameter, schedule 40 PVC blank casing and 0 020-inch-slot well screen with flush threads set from 30 to 40 feet bgs A #3-sand filter pack was installed in the annulus from the bottom of each boring to at least 2 feet above the top of the well screen, followed by a well seal consisting of a 2-foot-thick hydrated bentonite layer overlain by neat cement to ground surface The bentonite layer was constructed above the water table with bentonite chips MW-5d was installed using 2-inch-diameter, schedule 40 PVC blank casing and 0 020-inch-slot well screen with flush threads set from 65 to 70 feet bgs A#3-sand filter pack was installed in the annulus from the bottom of each boring to at least 2 feet above the top of the well screen, followed by a transition sand approximately 2-feet thick A bentonite slurry was mixed using bentonite powder and pumped through tremie pipe to the appropriate depth forming a 2-foot thick seal The boring was then grouted using neat cement pumped through tremae up to grade Each well was secured by a locking expandable well cap and fitted with a traffic-rated well box set in concrete Well surging was conducted following the installation of the sand filter pack and prior to the installation of the bentonite seal Well completion details for the six newly installed wells are presented in Table 1 and illustrated on the appropriate boring logs (Appendix B) Morrow Surveying, a certified surveyor for the State of California, surveyed the locations of the ten groundwater monitoring wells, four domestic wells, and eight soil borings The elevation of the top of casing and well box of ten groundwater monitoring wells and three domestic wells were surveyed to within 0 01 feet relative to mean sea level (Appendix D) 4.5 Quarterly Groundwater Monitoring and Sampling Groundwater sampling was conducted for DW-1 on May 3, June 1, and July 25, 2000 Results are presented on Table 2 In addition, Groundwater monitonng and sampling was conducted for the ten monitoring wells and the three operational domestic wells (DW-1, DW-3, and DW-4) now at the Site and at properties adjacent to the Site (Figure 2) on August 16, 2000 Procedures for the monitoring and sampling are summarized below 4.5.1 Groundwater Monitoring On August 16, 2000, SECOR personnel measured the depth to water in each of the site related groundwater monitoring wells (see Field Notes, Appendix C) Depth to water was measured using a water level meter to the nearest 0 01 foot in each well Due to slow recharge in the deep monitoring well (MW-5d), groundwater elevations were again measured in MW-5d on August 21, 2000 to assess conditions after development MW-5 was also measured at that time for comparison purposes A groundwater elevation contour map was prepared from the data collected on August 16, 2000 (Figure 7) No separate-phase petroleum hydrocarbons were reported in the monitoring wells at the site Groundwater monitoring data are summarized in Table 3 Pile R-Welllnstall&M&S rpt doc SECOR International Incorporated