SITE INFORMATION AND CORRESPONDENCE_1987-1992

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Section 10-1 Construction Details Well Destruction Specifications Special Page 2 of 3 to be 60 percent plugged at 215 feet bgs, 30 percent plugged at 223 feet bgs, and 10 percent plugged at,240 feet bgs . The borehole was open from 260 feet to 276 feet . Additionally, a video log indicated that possible holes in the casing occurred at a depth of 136 feet bgs . This well was sampled in December 1990 or January 1991, and the sample contained 47 µg/1 PCE, 8 . 5 gg/1 TCE, and 5 . 8 µg/1 cis-1, 2 DCE. Later in 1991, the well was noted to have caved to 118 feet bgs . The well was videotaped again in February 1992 in an attempt to determine the cause of the caving. The well depth had decreased to 100 feet bgs, but the cause and character of the caving could not be determined. The caving may be related to the holes noticed in the casing at a depth of 136 feet, or to the reduction in the casing diameter at 128 feet. Well LVMD4--Hiatory and Description LVMD4 was installed in 1980 using cable tool equipment. The well was drilled to a depth of approximately 205 feet . It was completed with 14-inch diameter 14 gage steel casing from 0 to 70 bgs, with a sanitary seal to 70 feet bgs . From 0 to 130 feet, 10- inch-diameter 10 gage steel casing was installed. The water well drillers report states that the depth of the completed well is 195 feet. No casing perforated zones were noted. This well is not thought to contain PCE and is being destroyed because of the occurrence of iron and manganese in the water. Well LVMD6--History and Description LVMD6 was installed in 1958 using cable tool equipment. This well was drilled to a total depth of 266 feet and was constructed of 14-inch diameter 7 gage steel casing, with vertical perforations from 210 to 262 feet. A sanitary seal was placed from 0 to 40 feet. In 1984, the well was lined with 8-inch diameter PVC casing to mitigate a sand production problem. The invoice from this work indicates that the PVC casing is solid from 0 to 162 feet bgs and from 242 to 262 feet bgs . This well was videotaped in 1990. It was noted that vertical slots were present from 85 to 115 feet bgs and from 145 to 160 feet bgs . Horizontal perforations were noted at 160 feet and 210 feet with some scum on the casing at 190 feet. The bottom of the well was reported to be at 254 feet . The discrepancy between the perforated intervals reported on the video log and the invoice data has not been resolved. Field inspection of the PVC liner indicated that it was not secure, which may allow water to enter this well . This well was sampled in December 1990 or January 1992 and contained 26 gg/1 PCE. 10-1 . 2 PERMITS Well destruction permits, encroachment permits, and building permits shall be obtained by the contractor from the appropriate San Joaquin County agencies prior to the start of work at no additional cost to the Owner. 6691\SPECS\SEC7I0N.101