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Diamond Lodi,CA-June 1993 Groundwater Monitoring Page 7 Because lead levels were detected above State of California drinking water standards in unfiltered waters collected during earlier monitoring events, additional water samples were collected from each well, which were filtered the same day of collection and submitted to a California licensed laboratory for lead analyses. Unfiltered groundwater samples were also submitted for total lead analyses. Analytical results have been evaluated by Dr. Karen Hagelstein, CIH, as to their significance. 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 City of Lodi Bench-Mark 710, Brass Cap at the southeast corner of Stockton Street and Locust Street: Elevation 49.74 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 one hour before the groundwater levels were measured and recorded. Static water level data has been collected from each of the three monitoring wells during quarterly sampling events (performed by SRK) on November 25, 1991, April 7, 1992, September 1, 1992, February 4, 1993, and June 28, 1993 using a Solinst water level meter. Table I contains static water level information collected to date by SRK, and most recent data qualify earlier results. TABLE 1: Static Water Levels Nov 25, 1991 Apr 7,1992 Sep 1, 1992 Feb 4. 1993 Jun 28,1993 (feet) (feat) (feet) (feet) (feet) ff-MW3 65' Screened Interval (50' -65') 51.15 49.75 53.95 50.05 49.65 60' Screened Interval (45' -60') 51.40 50.00 54.15 50.30 49.90 59' Screened Interval (44' -59') 51.50 50.17 54.30 50.40 49.90 NOTES: Static water levels measured from top of well casing using a Solinst Water Level Indicator Top of well casing elevations referenced to City of Lodi MB#710 ' The static water level elevations collected June 28, 1993, were on the average 0.4 feet lower than the previous sampling event (February 4, 1993), and approximately 4 feet higher than the September 1, 1992 sampling event. SRK contacted the Western Regional Climate Center to obtain precipitation data for the Lodi area. Precipitation data was obtained from the Lodi weather station (Station Number 045032). A copy of this information gathered from 1985 through 1992, is provided in Appendix A. The SRK series monitoring wells were installed during November 1991 under the direct guidance of PHS/EHD when the Lodi area received a monthly accumulation of 0.48 inches of precipitation. "I'll 2J133- y.Lod Steffen Robertson and Kirsten