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Diamond Lumber Manteca Quarterly Groundwater Monrtonng Page 2 • Performing a records search of registered wells located within 2,000 feet of the site • Estimating the localized groundwater gradient Duringthis field exercise other activities included ded spreading non-hazardous drummed soil cuttings resulting from SRK's subsurface soil and groundwater investigation(De(,ember 1991) on-site according to verbal authorization from PHS/EHD 3.0 GROUNDWATER GRADIENT Prior to the April 1992 quarterly groundwater 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 (located in the pocket at the back of this report) 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 in the monitoring wells installed by SRK on November 24, 1991, April 6, 1992,August 31, 1992, and February 5, 1993 using a Solinst water level meter Water levels were also measured in the BEI monitoring wells on October 15, 1991, August 31, 1992, and February 5, 1993 using a Solinst water level meter Table 1 contains static water level information collected to date by SRK TABLE 1 Static Water Levels OcL 15, Mar.25, Apnl 7, Ari&31, Feb 5, 1991 (feet) i94£ (feet) 1992(fEet) 1992(feet) 1993(feet) SRK- MW1 Well Depth = 38' Screened Interval (23' -38') NI 2345 2120 2545 2125 SRK- MW2 Well Depth = 39' Screened Interval (24' -39') NI 2375 2152 2580 2155 SRK - MW3 ' Well Depth = 39' Screened Interval (24' - 39') NI 2375 2210 2570 2145 BEI - MW4 (Assumed to be MW2 in BEI Reports) Well Depth = 30' Screened Interval (15' -30') 2-567 NS NS 2555 214 BEI - MW5 (Assumed to be MW3 in BEI Reports) Well Depth = 30' Screened Interval (15' -30') 2508 NS NS 2-590 2155 BEI -MW6(Assumed to be MW1 in BEI Reports) Well Depth = 30' Screened Interral ('15' -30') 2508 NS 1.11, 2585 2155 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 l 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 Steffen Robertson and Kirsten