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LL Fuller Mobile Home AW 365 E. Louise Ave.,Lathrop, California September 18, 1995 Phase III Remediation Workplan pager 2 from each boring through a stainless steel screen inside the augers. B-5 soil samples were ND (None Detected), but the groundwater sample had BTEX contamination. B-6 was ND for both soil and water. Monitoring well MW-4 was installed in the sidewalk of Bizzibe Street in the apparent down-gradient direction. Laboratory soil samples were obtained at five, ten and twenty-five feet below ground level (Tables 1 & 2). i. On December 21, 1991, after receiving the analytical results from the previous borings, WHF drilled and installed three monitoring wells, MW-5, 6 and 7. Each was 25 feet deep and soil samples were taken at five and ten feet. All soil samples tested "ND" (Table 1). Monthly depth to water!readings are being recorded and the groundwater gradient calculated for each month' The past gradients have been irregular, probably due to the fact that the gradient is extremely flat and the litholoSY is probably affecting stabilization of the minor fluctuations across the site(Appendix A). 3.0 Workplan 3.1 Well destruction -- i WHF shall obtain a well destruction permit for the abandoned drinking water well, and destroy the well by overdrilling the existing borehole. The total depth of the overdrilling will be; determined by the professional judgment of the licensed C-57 contractor during the drilling operation. The entire boring shall be backfilled with cement grout to within two (2) feet of the surface to allow development of the property. The remaining two (2) feet shall be backfilled with native soil to ground level. f i 3.2 Pump & Treat i Excavation of the remaining contaminated sail in the former underground storage tank excavation would prove to be difficult. The excavation is located on the shoulder of a six foot deep storm water containment pond and adjacent to a property line fence)(Figure 2). There is also a City of Lathrop sanitary sewer line parallel to and inside the fence. f h !tank excavation and installation of M%V-1 2 & 3 At the time o the to e a vation , , the water table was at 12 and 9 feet below ground level, respectively. This was during an eight year drought period that has since ended. The water table has risen to 5-7 feet below grade and has inundated the soil contamination interval. There is essentially no soil contamination above the water table to excavate (Table 1 & 3). i