SITE INFORMATION AND CORRESPONDENCE_FILE 1

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JUL 9 '98 16:59 FROM GETT' cR-RYAN INC TO 12094683433 PAGE .005/eio work Pias for wafer wall bxtroction-Toxo BP 76 Branded F=ility No. 11195 July 9. 1998 WATM WEM CONSTRUCTION The following construction details are based on observations and measurements coRected on site and during the samara survey. The water well is constructed with eight-inch inner-diameter steel casing which extends to approximately 94.5 feet below ground surface(bgs). The well extends to a tozal depth of approximately 99.5 feet bps. The bottom five feet of the well is un-casod opzn borehole. Static depth-to-groundwater was measured at approximately 8.5 feet bgs on June 5, 1998. PDI did not observe any obvious perforations or holes during their review of the camera survey video. Although the using ends at approximately 94.5 feet below grade, it is uncertain if the casing originally ended, or"landed", at that depth or whether it has deteriorated below that depth. However, PDI did observe a cavity at approximately 95.5 feet bgs which appears to represent an aquifer. Above this cavity, the borehole is circular and well defined, which may represent an overlying aquitard above the depth of 95.5 feet bgs. Based on discussions with PDI, it appears that the water well may be a driven well, installed using the cable tool drilling metbod. This method is commonly used in the Lathrop area to install water wells of this depth. The cable tool well driller would typically advance the boring and drive the well casing simultaneously until the desired depth was attained. The driller would often find a suitable water producing aquifer and terminate or'land" the using in a competent clay layer above the aquifer. SCOPE OF WOME GR, in conjunction with PDI, has developed the following scope of work for destruction of the water well. A letter from PDI outlining the proposed =pa of work is attached to this worts plan. The proposed scepa of work is designed to properly destroy the well without creating any opportunities for contaminant migration as a result of the well destruction process. GR proposes the following tasks: Tads 1: Groutkg3 of Ogarn Wed Boring GR is proposing to grout the open borehole portion of the water well with Portland cement. This step is dcsj Y to malas certain that the aquifer below the total depth of the well casing is scaled off from the well prior to casing perforation. The Portland cement grout will b2 pumped from thz bottom of the Nell to approximately 80 feet bgs by the use of a tremie pipe and grout pump. All groundwater expelled during the grouting opzration will be contained in DOT approved, 55-gallon drums, which will be stored on site pending proper disposal. 2