Laserfiche WebLink
1 <br /> • 7-Eleven/Stockton 4 <br />' March 1991 <br /> • Sampled groundwater from domestic wells TMG, 1912, 1927, 8%8, 9140, 9156, and <br />' 9172 on three occasions <br />' • Sampled the groundwater-treatment system influent and effluent in October, 1990 <br />' GROUNDWATER MONITORING <br />' Monitoring of the groundwater elevation in the monitoring wells was conducted three times <br /> during the reporting period, on October 23, November 27, and December 28, 19W These monitoring <br /> data are presented in Appendix A Groundwater monitoring was performed in accordance with <br /> Groundwater Technology Standard Operating Procedure (SOP) 8 (Appendix B) <br />' Analysis of the groundwater monitoring data indicates that groundwater elevations have <br /> . decreased about 0 5- to 3 0-feet in the monitoring wells during this three-month reporting period The <br />' majority of the wells decreased between 0 5 and 1 0-foot in elevation from September 24, 1990 to <br /> December 28, 1990 This continued drop in water level elevations is most likely due to the drought <br /> conditions continuing into the winter months of 1990 The depth-to-groundwater at the site is <br /> approximately 47- to 49-feet below ground surface The groundwater-table elevation is approximately <br /> 36- to 38-feet below mean sea level (msl) <br /> f <br /> I Since the groundwater monitoring wells were first monitored in May, 1986, the local <br /> groundwater-table elevation has declined steadily The decline in the groundwater levels is depicted in <br /> the hydrograph for monitoring wells MW-7. MW-8, and MW-9 (Figure 3) Monitoring wells MW-7 and <br /> MW-8 are representative of the majority of the wells at the site The one exception to the general water- <br /> level decline was the data from MW-9 which reflected a mounding of the groundwater surface due to a <br /> leaking water pipe at the rear of the 7-Eleven Store In April, 1989, this leaking water pipe was repaired <br /> and the mounding condition was corrected <br /> According to National Weather Service local climatological data for the Stockton area, below- <br /> normal annual precipitation has been recorded for the past five years However, in 1982 and 1983, just <br /> prior to this drought period, annual precipitation was almost twice normal Therefore, the steady decline <br /> in the groundwater-table elevation may be in response to prolonged drought conditions combined with <br /> an abnormally-elevated groundwater level at the beginning of the monitoring period <br /> [z GROI ND%%-NTFR <br /> TECH\OE nGl INC <br />