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U Ms. Lori Duncan,REHS Page 4 of 8 San Joaquin Environmental Health Department June 9, 2005 PROPOSED SCOPE OF WORK Well Destruction Based on construction drawings for the planned carwash (Figure 2), monitoring well MW4 must be abandoned before construction activities begin. MW-4 will be destroyed properly by a licensed drilling contractor at the direction of a URS geologist. MW-4 will be destroyed by presSur outing and then overdrilling the top 5 feet with 10-inch, outside- diameter (OD), hollow-stem augers (HSAs) and filling with a Portland cement grout containing <5% bentonite powder(grout)to the surface. _ SVE/AS System Installation Task 1 —SVE/AS System Design Before beginning field activities, URS will obtain necessary permits for the installation of this SVE/AS system from the City of Stockton. Permits will also be obtained from the San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) prior to remediation system equipment installation. The Remedial system design plans, including remedial piping layouts and equipment specifications, will be completed and forwarded to SJVUAPCD and SJCEHD. The SVE system will be used to control possible vapor migration induced by the AS system and to enhance airflow and subsequent hydrocarbon destruction in the shallow water-bearing zone, capillary fringe, and vadose zone. The SVE/AS system will use! ells (AS-1/EW-1 through AS-21/EW-21) (Figure 2). URS also will drill and install three additional shallow monitoring wells (MW-9 through MW-11) to monitor downgradient groundwater concentrations and evaluate the effectiveness of the SVE/AS remediation system (Figure 2). URS will prepare a site-specific Health and Safety Plan (HASP) prior to field activities. The HASP will be reviewed by field staff and contractors and will be present on site during field activities. A site plan showing proposed well locations and piping runs is included as Figure 2. Task 2—SVE/AS Well Installation Remediation wells will be combination wells set in a single borehole. Borings will be drilled using a 10- inch OD HAS-equipped drill rig to accommodate a 1-inch OD AS well and a 2-inch OD SVE well in each borehole. The wells will be installed so that the AS wells are screened from approximately 6 to 38 feet bgs in the silt zone, where the contaminant mass is located. URS will ensure that the wells are not screened in the silty sand zone located beneath the silt to ensure that lateral migration of petroleum does not occur. The SVE wells will be screened above and below groundwater to capture the vapors from the sparging. Soil samples will be collected at 5-foot intervals during drilling of the borings using a modified California split-spoon sampler. Soil samples will be used for lithology and screened with a photoionization detector (PID) for possible laboratory analysis. One sample from each boring will be submitted for laboratory analysis. A URS geologist will log the soils according to the Unified Soil K:\Wprmess\J5 BP ARCO\02168\2005 System Installation\SVE-AS Workplan.dm