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LEEOSHILL•HEPKENHOFF. INC. <br /> Between these two zones is primarily a clay to sandy clay matrix with at <br /> ' least two thin, apparently continuous sand layers. Figure 2.4 illus- <br /> trates an idealized cross section beneath LVC using the geologic logs <br /> from LVMD wells #1, #2, and #6. <br /> ' 2.4.3 Restoration of LVMD Well #1 <br /> ' In December 1984, in compliance with mandated AB1803 water quality <br /> testing, water samples from LVMD wells #1 and #6 showed detectable <br /> ' levels of tetrachloroethene (PCE) and trichloroethene (TCE) . The con- <br /> centrations detected in LVMD well #1 were 120 ppb and 14.3 ppb for PCE <br /> and TCE, respectively. The state action levels for PCE and TCE are 4.0 <br /> ' ppb and 5.0 ppb, respectively. After the problem was detected, San <br /> Joaquin County Public Works began a procedure of pumping to waste LVMD <br /> ' well #1, then allowing the well to recover. After periods of extended <br /> pumping, the' levels of PCE in LVMD well #1 would drop to acceptable <br /> levels, then the levels would rise after the pump was shut down and <br /> ' water levels allowed to recover. <br /> In the spring of 1985, the pump in LVMD well #1 was removed and a video <br /> ' inspection was made of the integrity of the 14- and 12-inch casings. A <br /> major casing separation was detected at a depth of 42 feet from the <br /> surface. At this depth, water was seen to be entering the well through <br /> ' a fracture in the casing. Although water was entering the well at a <br /> depth of approximately 42 feet, the static water level was measured to <br /> ' be approximately 48 feet below grade. To eliminate this cascading water <br /> in LVMD #1, the 14-inch casing was perforated and a 10-3/4-inch PVC <br /> liner was installed to a depth of 80 feet and pressure grouted into <br /> place to provide a sanitary seal . According to available construction <br /> ' details, the presence of an annular cement seal at LVMD #1 prior to <br /> installation of the aforementioned liner could neither be confirmed nor <br /> ' denied. <br /> After the remedial sanitary seal was placed in LVMD well #1, the PCE and <br /> ' TCE concentrations were dramatically reduced. This well was placed back <br /> in service with the approval of DOHS in the spring of 1986 and, since <br /> the fall of 1986, PCE levels in this well have been non-detect. <br /> ' 2-8 <br />