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' former Manna Pio Site Page 3 Ruarteily Gioundwater Monitoiing Report &Monitoring Well Construction Ptoject No 207 2 June 2, 2000 t 2.0 DEEP MONITORING WELL CONSTRUCTION ' 2 1 Field Work - Monitoring Well Drilling & Construction ' Manna Pro was directed by the regulatory oversight agency, the San Joaquin County Department of Public Health - Environmental Health Division, to submit a work plan to further investigate the vertical distribution of gasoline ' range hydrocarbons The Work Plan was submitted on August 16, 1999 This document also covered a proposed remedial action pilot and feasibility study ' The Work Plan was approved by the PHS-EHD on September 22, 1999 and cost pre-approval was granted by the State UST Clean-up Fund on February 18 2000 ' 2.1 1 Monitoring Well Drilling ' On April 17, 2000 a BK-81 drilling rig, owned and operated by V&W Drilling Co (C-57 #710678), was used to drill a boring later converted into a deep monitoring well which is designated MW-11 (see Figure 6 for schematic diagram) In order I� to reduce the possibility of cross-contamination of deeper soils in the boring from what was anticipated to be high levels of gasoline contamination from shallower intervals in the same boring, the drilling was performed in two steps First, on ' April 17, 2000, 15-inch diameter augers were used to drill MW-11 to a depth of 50 feet Soil samples were collected during the drilling process to document ' geologic characteristics and for possible laboratory analysis After the boring was completed to 50 feet, 8 5/8 inch 1 d steel casing was set and cemented by tremae pipe to total depth The casing was equipped with a wood, end-plug to ' prevent cement from entering the casing After the cement was allowed to cure, on April 19, 2000 the rig was converted to operate mud rotary drilling tools The top-drive rotary table was equipped with a swivel to handle drill pipe and a steel mud pit was installed to contain the drilling mud and cuttings A bland, gel-water drilling mud was mixed and Icirculated down the inside of the drill pipe and back up thorough the casing annulus A 6 inch o d tri-cone, mill-toothed drilling bit was affixed to the drill pipe assembly and the wooden base plug of the 8 518 inch conductor casing was drilled out The boring was then advanced to a total depth of 97 feet using the rotary bit During drilling, SimulProbe direct push sampling equipment was used to obtain samples of soil and groundwater at several intervals An on-site analytical laboratory was present to evaluate samples as they were obtained i I2937 Veneman Ave ,#B240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293 I