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13 December 1995 AGE-NC Project No. 95-0109 Page 2 of 8 remediation, in April and June 1993; Also included in Attachment A is a figure showing benzene concentrations in September 1995, approximately one-year after inoculation. Although the lateral extent of impacted ground water has not decreased, it appears that overall concentrations have decreased considerably. Of course, because of the rise in ground water elevation over the past two years (approximately 5 to 6 feet), concentrations of hydrocarbons (including benzene) in ground water have oscillated in many wells. 3.0. SCOPE OF WORK 3.1. INSTALLATION OF GROUND WATER MONITORING WELL During the meeting on 27 October 1995, the need for an additional ground water monitoring well south of MW-9 was discussed. Presently, the down-gradient extent of dissolved hydrocarbons is defined by wells MW-12 and MW-13; wells MW-8 and MW-9 are still impacted by hydrocarbons. However,MW-13 is approximately 215 feet south of MW-8 and MW-12 is approximately 225 feet south of MW-9. A well placed south of MW-9, near Cherokee Lane, would provide a more precise indication of the down-gradient extent of hydrocarbons. Therefore, AGE proposes to drill, sample and install one ground water monitoring well south of MW-9. Monitoring well MW-15 will be installed approximately 90 feet south of MW-9, within the City of Lodi right-of-way. The well will be drilled to a depth of 73 feet below surface grade (bsg) using a truck-mounted drill rig equipped with hollow-stem augers. Soil samples will be collected at five-foot intervals beginning at a depth of 20 feet bsg using a California split-spoon sampler and brass sleeves. The sampler will be driven by dropping a 140- pound weight from a height of 30 inches. The number of blows required to drive each 6-inch length of the sampler (blow counts) will be recorded on the boring logs by an AGE staff geologist. Upon sample retrieval, the middle brass sleeve will be removed from the sampler. The ends of the sleeve will be immediately covered with Teflon or aluminum sheets, sealed with plastic end caps, secured with tape and immediately placed in a chilled container for transportation to a State-certified laboratory. Each sample sleeve will be labeled with the following: boring location, depth, time, date and sampler's initials. All sampling tools and brass sleeves used for sample collection will be thoroughly rinsed with clean water after washing with a solution of Alconox. All hollow stem augers will be steam-cleaned prior to advancement in each borehole. After completion, the well will be developed using a submersible pump. No sooner than 72 hours after completion and development, a ground water sample will be collected from the well in accordance with standard ground water protocol for the site.