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Diamond Lumber-Lodi Quarterly Groundwater Monitoring Page 2 During this field exercise, other activities included spreading non-hazardous drummed soil cuttings resulting from SRK's subsurface soil and groundwater investigation (December 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 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 (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 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, and February ' 4, 1993 using a Solinst water level meter. Table 1 contains static water level information collected to date by SRK. TABLE 1: Static Water Levels cyst 7, 19xL Sc t, 1942 I~eb 4 1M SRK - MWI Well Depth = 65' Screened Interval (50' - 65') 51.15 49.75 53.95 50.05 1 SRK - MW2 Well Depth = 60' Screened Interval (45' - 60') 51.40 50.00 54.15 50.30 SRK - MW3 Well Depth = 59' Screened Interval (44' - 59') 51.50 50.17 54.30 50.40 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 February 4, 1993, were on the average 4 feet higher than the previous sampling event (August 1992). 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 the PHS/EHD when the Lodi area received a monthly accumulation of 0.48 inches of precipitation. An estimate of the groundwater gradient was made by using the most recent static water elevations to complete an orthographic construction known as a 3-point problem (Davis, G.H., 1984, Structural Geology of Rocks and Regions: John Wiley & Sons, pp 210). Solving a 3-paint problem requires 32SO4s4\4_atrly.loa Steffen Robertson and Kirsten