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Work Plan For a Limited Subsurface Investigation - Former Chevron Service Station !#9-5775 November 24, 1998 To implement the proposed scope of work, GR proposes the following seven tasks: Task 1. Well Survey GR will conduct a survey to locate domestic and municipal wells within a %-mile radius of the subject site. This search will consist of a review of files at the California Department of Water Resources and the City of Lodi Water Department. Where possible, GR will obtain the construction and operational details (pumping rates volumes, etc.) for these wells. Task 2. Pre -field Activities GR will update the site safety plan, and will obtain the necessary well installation and soil boring permit from SJCPHS. USA will be notified at least 48 hours prior to initiating work. A private line locator will be contracted to clear the on-site boring locations. Task 3. Well Installation GR will install four groundwater monitoring wells (MW -1 through MW -4) and advance one exploratory soil boring (SB -1) at the locations shown on Figure 2. Drilling and well construction will be performed by V & W Drilling (C57 #720904). A GR geologist will monitor the drilling activities and prepare a log of the boring. All borings will be drilled with 8 -inch diameter hollow -stem augers to approximately 15 feet into first encountered groundwater or 65 feet bgs, whichever is deeper. Well borings MW -1, MW -2 and MW -3 and exploratory soil boring SB -1 will be continuously logged to the total depth explored. Well boring MW -4 will be sampled on at 5 -foot intervals, as a minimum. Soil samples for possible chemical analysis will be obtained from each of the borings. Soil samples for chemical analysis will be collected at changes in lithology and where photoionization detector (PID) screening readings are greater than 100 parts per million vapor (ppmv). At lease two soil samples for chemical analysis will be collected from the saturated zone. Selected soil samples will be submitted for chemical analysis as described in Task 5. Upon completion of drilling exploratory soil boring SB -1 will be backfilled to ground surface with neat cement containing approximately 5% bentonite powder using a tremie and pump. The groundwater monitoring well will be constructed with 2 -inch diameter Schedule 40 polyvinyl chloride (PVC) well casing and 0.02 -inch machine slotted well screen. The wells will be constructed with 20 feet of screen, extending from 30 to 50 feet bgs. The actual screen interval will depend on the groundwater depth and lithologic conditions encountered during drilling. Well borings will be backfilled from 65 to 50 feet bgs with bentonite. Proposed well construction details are shown of Figure 3. Drill cuttings will be stored at the site pending receipt of chemical analytical data for disposal. The drill cuttings will be stockpiled on and covered with plastic sheeting. Four discrete soil samples will be collected from the drill cuttings for disposal characterization. These samples will be submitted to the laboratory for compositing and analysis will be collected as described 346341.04-1 3