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Lodi•Quarterly Groundwater Monitoring Page 3 !' TABLE 1: Static Water Levels . November 1991 and April 1992 I I �+��I• �iRg .�.:.:......::.}}: :.:.:?•;::::.• ........ ��{'�J./1: {guy -. .,. •:ti Static Water Level 51.15 51.40 51.50 49.75 50.0 50.17 Well Depth 65 60 59 65 60 59 I Screened Interval 50- 65 45 -60 44 - 59 50 -65 45 - 60 44- 59 NOTES: Static Water Levels Measured from top of well casing using a Solinst Water Level Indicator. Using the above information, the groundwater gradient was determined ra through an orthographic g p construction known as a 3-point Problem (Davis, G.H., 1984, Structural Geology of Rocks and s Regions: John Wiley & Sons, pp 210). Solving a 3-point Problem requires elevation control for a least three points that lie on a common plane, in this case the groundwater surface. The elevation control was obtained by subtracting the static water levels (measured form the top of well casings) from the elevations of the well heads (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). It should be noted that the groundwater elevations varied by only a few hundredths of a foot. With this in mind, the groundwater gradient trends N27.5°E, with a nearly horizontal gradient. 4.0 GROUNDWATER SAMPLING Three additional well casing volumes were purged from well SRK-MWI and SRK-MW3 before analytical samples were collected. Monitoring well SRK-MW2 was bailed dry after one casing volume was removed. This well was allowed to recharge for approximately one hour, then sampled. The analytical samples were collected from wells SRK-MW1 and SRK-MW3 after the pH, temperature, and conductivity had stabilized. "Stabilized" is defined as three consecutive readings within 15% of one another. Copies of the Field Groundwater Purging/Sampling Logs are provided in Appendix A. Copies of the Geologic Logs and Monitoring Well Construction Diagrams are provided in Appendix B. Three pre-cleaned dedicated teflon bailers and dedicated nylon rope were used to retrieve the ' water samples. The water samples were carefully poured into laboratory grade sample containers equipped with teflon lined lids, then placed in an iced cooler. The analytical groundwater parameters include volatile hydrocarbons, benzene, toluene, ethylbenzene, and xylene (BTEX) (EPA Methods 50301801518020); and total lead (EPA Method 7421). Ethylenebromide (EDB)was not included in the suite of analytes, because EDB degrades in soil very rapidly (EDB is converted almost completely within 2 months to ethylene) and also in water, Steffen Robertson and Kirsten