ARCHIVED REPORTS_XR0007742 - Laserfiche WebLink

Home Browse Search

HYDROGEOLOGY At the time of WCC's investigation in 1988, groundwater was encountered beneath the site at approximately 50 feet bgs within the silty clay sediments Well MW3 was installed to 50 feet bgs and wells MW 1 and MW2 were installed to approximately 60 feet bgs Because only two wells contained significant groundwater quantities, the hydraulic gradient could not be measured at that time During drilling in November 1992, groundwater was encountered at 80 feet bgs, suggesting a significant drop in the local water table Because of this decrease in groundwater elevation, shallow monitoring wells MW1, MW2, and MW3 currently contain no groundwater The static groundwater in the new monitoring wells (MW3R, MW4, MW5, and MW6) was measured at approximately 75 feet bgs, or,lust below the sand layer mentioned previously The hydraulic gradient was measured to be 0 003 to the northeast using the four deeper wells on November 20, 1992 Figure 4 shows this most recent groundwater measurement Appendix B contains the survey data including depth to water measurements, relative well head elevations, and groundwater elevations SITE INVESTIGATION On November 18 and 19, 1992, the drilling, well installation, and soil sampling program was performed The investigation consisted of installation of four groundwater monitoring wells, two vadose wells (VW1 and VW2), and a soil boring (B5) Wells MW3R, MW4, MW5, and MW6 were installed near the perimeter of the site to define the extent of groundwater contamination Well MW3R was intended to replace well MW3 which was originally installed to too shallow a depth for effective groundwater monitoring The groundwater wells were installed to greater depths than initially anticipated to accommodate the deeper groundwater level Vadose wells VW1 and VW2 were installed immediately adjacent to the underground tanks to define the extent Page 3