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Diamond Manteca CA June 1993 Groundwater Momtonng Page 2 • Purging and sampling the wells according to PHS/EHD guidelines • Shipping the groundwater samples under correct chain-of-custody procedures to a California licensed laboratory for analyses • Reporting the analytical results and supplying comparisons between these results and those from earlier monitoring events • Estimating the localized groundwater gradient r 3.0 GROUNDWATER GRADIENT Prior to the April 1992 quarterly monitoring event, SRK retained the services of a registered California ' Land Surveyor to provide elevations at the top of well heads relative to a known datum (referenced to the USGS Bench-Mark D-83, Brass Cap on top step of Legion Hall, South side of Yosemite Avenue Elevation 38 051 feet), and the locations of the wells relative to on-site structures This information is provided on ' Figure 1 The locking caps were removed from each monitoring well and the static water levels were allowed to equilibrate approximately 1-hour before the groundwater levels were measured Static water levels were measured to the monitoring wells installed by SRK on November 24, 1991, April 6, 1992, August 31, 1992, February 5, 1993, and June 29-30, 1993, using a solinst water level meter Water levels were also measured in the BEI monitoring wells on October 15, 191, August 31, 1992, February 5, 1993, and June 29-30, 1993, using a Solinst water Ievel meter Table 1 contains static water level information collected to date by SRK ' TABLE I• Static Water Levels ' Oct 15, Nov 25, April 7, Aug 31, E'eb 5, Jun 29-30 1:991 (ft) 1991 (ft) 1992(ft) 1992 (ft) 1993(ft) 1993(ft) SRK-MW 1 ' Well Depth=38' Screened Interval (23' -38') NI 2345 2120 2545 2125 2255 SRK-MW2 Well Depth=39 Screened Interval(24' -39') Ni 23 75 2152 2580 21 55 2285 SRK-MW3 ' Well Depth=39' Screened interval (24' -39') NI 2375 22 10 2570 2145 2276 BEI -MW4(Assumed to be MW2 in BEI Reports) Well Depth=30 Screened Interval(15' -30') 2567 NS NS 2555 21 4 2260 BEI -MW5 (Assumed to be MW3 in BEI Reports) Well Depth=30 Screened Interval(15' -30) 2508 NS NS 2590 2155 2300 BEI -MW (Assumed to be MW 1 in BEI Reports) Well Depth=30' Screened Interval (15' -30') 2508_ NS NS 25 85 21 55 2300 ' NOTES Static water levels measured from top of well casing using a Solinst Water Level Indicator Top of casing elevations referenced to the USGS bench mark D-83 which is a brass cap on the top step of Legion Hall south side of Yosemite Avenue Elevation 38 051 feet NI=No sample collected because monitoring well had not yet been installed NS =No sample collected �s�aa".QLiyM_ Steffen Robertson and Kirsten