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6-26-1998 2: 10PM FROM ADVANCED GEOENVIRONM 209 467 1118 P. 3 <br /> SCOPE OF WORK <br /> Additional Soil and Ground Water Assessment <br /> Sierra Lumber <br /> 375 West Hazelton Avenue,Stockton,California <br /> In August 1988,one 1,000-gallon gasoline UST was removed from inside the eastern warehouse(see <br /> Figure 1). Upon removal of the UST,two samples were collected from the floor of the excavation: <br /> UST-1 was collected from a depth of 9 feet below surface grade(bsg); UST-2 was collected from <br /> a depth of 15 feet bsg. <br /> Total petroleum hydrocarbons quantified as gasoline were detected in UST-t and UST-2 at <br /> concentrations of 790 and 1,200 ppm, respectively. <br /> Between June and October 1994, four soil borings and three ground water monitoring wells were <br /> drilled and installed at the site.TPH-g was detected in soil samples at concentrations ranging from <br /> 1.2 ppm to 14,000 ppm. BTEX were detected in soil samples at concentrations up to 1,200 ppm. <br /> Ground water samples were collected from the monitoring wells on nine occasions between October <br /> 1994 and November 1997.TPH-g has been detected in samples from each well at concentrations as <br /> high as 200,000 ppb; BTEX have been detected in each well at concentrations up to 31,000 ppb; <br /> MTBE has been detected in wells MW-1 and MW-2 at concentrations as high as 1.700 ppb. <br /> The San Joaquin County Public Health Services -Environmental Health Division(PHS-EHD)is <br /> requiring additional investigation to assess the lateral and vertical extent of hydrocarbon-impacted <br /> soil and ground water. A work plan addendum has been submitted to and approved by the PHS- <br /> EHD. The following is the proposed scope of work: <br /> 1. Preparation of a drilling permit and permit fee. <br /> 2. Preparation of a site specific health and safety plan. <br /> 3. Drilling and installation of one ground water monitoring well south of the former UST <br /> excavation,between MW-1 and MW-2. This well should be drilled to a depth of at least 50 <br /> feet,continuously sampled and should be dual-completed with two PVC casings to monitor <br /> both first-encountered ground water(approximately 25 feet bsg)and deeper ground water <br /> (estimated at to be 45 feet bsg). <br /> 4. Drilling and installation of ground water monitoring wells northeast of the former UST area <br /> (near boring B-2, inside the warehouse);west of the former UST area;and southwest of the <br /> former UST area. Sampling should be performed at five-foot intervals. <br /> 5. Development of wells. <br /> 6. Surveying of wells. Wells should be surveyed by a licensed professional. <br /> 7. Analysis of ten (10) soil samples for TPH-g, BTEX and VOCs (including oxygenated <br /> compounds)in accordance with EPA methods 8015, 8020 and 8260. <br /> 8. Collection and analysis of eight(8)ground water samples.Ground water samples should be <br />