ARCHIVED REPORTS XR0006032 - Laserfiche WebLink

Home Browse Search

II ' QUARTERLY GROUNDWATER MONITORING FEMRT 1399 East Yosemite Avenue Manteca,CalfforrM Aegis began a program of groundwater monitoring in February 1991 Monthly monitoring ' of groundwater levels and quarterly sampling of groundwater was continued until May 1992 On June 20, 1991, Aegis installed monitoring wells MW-1 B, MW-4, and MW-5 on the site Wells MW-4 and MW-5 were completed with 4-inch-diameter casing to a ' depth of 35 feet below grade Well MW-1B was completed with 6-inch-diameter casing by 'over-coring" the former MW-1 A Quarterly monitoring has continued since then ' 4.0 GROUNDWATER MONITORING ' 41 Groundwater On October 21, 1992, Aegis personnel collected measurements of the depths to liquids ' in wells MW-1 B, MW-2, MW-3, MW-4, and MW-5 Since July 27, 1992, groundwater levels have fallen in all wells (Figure 3) an average of approximately 0 98-feet (Table 1) On the bass of the October 21, 1992 measurements, groundwater is estimated to flow to the rnorthwest (Figure 4) at an average gradient of approximately 0 002 ft/ft For April 9, 1992, the flow direction was estimated to be to the northwest Previous groundwater levels are summarized in Table 1 All groundwater elevation measurements were conducted according to the Aegis standard operating procedures (SOP) included as Appendix A 4 2 Water Sampling and Analysis ' On October 21, 1992, Aegis personnel collected groundwater samples from four of the five monitoring wells at the project site Well MW-16 was not sampled due to the free , presence of floating liquid hydrocarbons The samples were collected according to the Proms c Aegis SOP included in Appendix A, and delivered under chain-of-custody to NET Pacific, Inc , of Santa Rosa, California, a state-certified analytical laboratory ' The samples were analyzed for concentrations of ' total petroleum hydrocarbons (TPH), as gasoline, by GC-FID/EPA Methods 5030/8015, and, ' benzene, toluene, ethylbenzene, and total xylenes by EPA Method 8020 Groundwater analytical results obtained to date, including data reported by previous ' consultants, are summarized in Table 2 Concentrations of TPH, as gasoline, and benzene reported for samples collected on October 21, 1992, are also shown on Figure 5 Copes of the laboratory analytical reports and chain-of-custody form are included in Appendix B 90-098C QMR 2-