ARCHIVED REPORTS_XR0003968 - Laserfiche WebLink

Home Browse Search

After drilling and soil sampling was completed, 2-inch diameter PVC monitoring wells were constructed within the boreholes through the hollow stem of the augers. The wells were constructed of 2-inch diameter Schedule 40 PVC casing with flush-threaded connections and PVC well screens with 0.020-inch slots. Well screens extended 11 to 12 feet below the water table surface and 3 to 4 feet above the water table surface. A graded sand pack (#2112)was placed adjacent to the entire length of the well screen and extended two feet above the top of the screen. A two feet bentonite pellet seal was placed above the sand pack and hydrated with potable water. Levels of the sand pack and bentonite pellets were confirmed during placement by sounding with a weighted tape. The ' annular space above the bentonite pellet seal was filled to the ground surface with neat cement containing approximately 5 percent bentonite. The wells were completed at grade in traffic-rated utility vaults with a locking water-tight cap. Well construction details are presented in Table 1 and shown graphically on the boring logs included in Appendix B. 2.2 WELL SURVEY AND WATER LEVEL MEASUREMENTS The two newly-installed wells (MW-2 and MW-3) and the existing well (MW-1A)were surveyed by a California licensed surveyor for ground-level and top of PVC casing elevations. The reference datum for all elevations is the City of Lodi Bench Mark #849 (elevation 47.49 feet MSL). Static water levels were measured to the nearest 0.01 foot in each well on January 15, 1993 using an electronic water level indicator. Well survey results, depth to groundwater and groundwater elevations are shown on Table 1. 2.3 WELL DEVELOPMENT AND GROUNDWATER SAMPLING The newly-installed wells (MW-2 and MW-3) were developed and sampled on January 15, 1993. Well development was accomplished by bailing with a clean PVC bailer to remove fine sand and suspended sediment from the well. Approximately 15 well casing volumes (25 gallons)of water were removed from MW-2 and MW-3 during development. During development, the discharge water was measured for pH, temperature, and specific conductance. Stabilization of these physical parameters was used to indicate that fresh formation water was entering the wellbore. Following completion of development, groundwater samples from wells MW-2 and MW-3 were collected using a clean stainless steel bailer. Existing well MW-lA was purged and sampled on January 15, 1993. Prior to sampling, approximately 3 well casing volumes of water was evacuated from the well using a clean PVC bailer. During evacuation, pH, temperature, and specific conductance measurements were recorded as described above. Following purging, a groundwater sample was collected using a clean stainless steel bailer. Field sampling data sheets for each monitoring well are included as Appendix C. Water samples were transferred directly from the bailer into laboratory supplied glassware and labeled to designate sample location, sample number, and date and time collected. Sample containers were stored in a cooler containing ice. Water samples were delivered to Superior and analyzed for TPHg and BTEX in accordance with EPA methods modified 8015 and 602,respectively. ( MARDEERPT 50014-003-01 MD04 6