ARCHIVED REPORTS XR0000129 - Laserfiche WebLink

Home Browse Search

significantly due to seasonal recharge and local pumping influences Groundwater appears to also exist below the base of the sandy zone within the silt and clay deposits 2.2.2 Municipal Supply Wells ' In order to specifically assess the possible hydraulic influences to Site groundwater conditions, SECOR personnel contacted the water purveyor for this area, the California Water Service Company Mr Mike Stevens, General Superintendent, provided SECOR with a map showing the ' distribution of active municipal supply wells in the vicinity of the Site Two wells, No 71 and No 77 are located within approximately one-half mile distance from the Site Well No 77 is less than ' 2,000 feet from the former Mayor Mart property A third well, No 21, is the next closest well, located approximately six-tenths of a mile from the Site No information was available from the California Water Service Company regarding the location of private domestic, agricultural or industrial water supply wells Information regarding the approximate location of and operating characteristics for wells No 21, 71 and 77 are presented in Table 1 The locations for these three wells are shown on Figure 5 as presented on the purveyor's map A copy of a portion of this map and relevant subsurface iinformation on these wells is provided in Appendix C According to Mr Stevens, the well water quality is monitored by the California Water Service Company for the analytes required by State and Federal regulations for municipal water purveyors on a semi-annual frequency basis or as required i2.2.3 Regional Groundwater Level Fluctuations ' In addition to the service area map, SECOR was also provided a copy of the fourteen-year historical hydrograph for the Stockton area, and well sounding 1991 records for all Company wells This hydrograph, as shown in Figure 6, illustrates the average change in static water levels in Stockton iarea wells since 1980 On the basis of this hydrograph and a review of the well soundings, the following groundwater level characteristics can be observed is The greatest increase in water levels typically occurs from February through April, and the highest average groundwater levels in 1986 and 1987 were approximately 35 0 feet below igrade (or -15 0 feet below sea level) • The greatest reduction in water levels typically occurs from August through October, and the lowest average groundwater levels in 1992 were recorded at approximately 80 0 feet below grade (or -60 0 feet below sea level) 19 ' SECOR IntemaUonal Inc (SECOR�) CRC Environmental Risk Management,Inc 6 November 30 1994 N0026 001 01 add i