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Mr. Jim Lancaster -2 - 30 June 2000 2. Table 1 of the report provides groundwater elevation and free product thickness measurements. However, the report does not present the total volume of free product removed from the wells. Woolsey needs to include a table with the total amount of free product removed during the monitoring period and a cumulative total of product removed. 3. Table 2 of the report shows that sampling of MW-1 has not occurred since 1995 because the well is either dry or has insufficient water volume to sample. This well should be abandoned to ensure that it does not provide a conduit for infiltration of surface water and potential contaminants to groundwater. According to the figures in the reports, MW-8 is directly adjacent to the well and has supplied groundwater data consistently. Therefore, Woolsey needs to provide a work plan for well abandonment of MW- 1. 4. In the second quarter 2000 report, GZA states, "A comparison of historic groundwater elevations in well MW9 and concentrations of gasoline hydrocarbons in groundwater indicates there is little if any correlation between the two. However, a clear correlation exists between falling water levels and increasing hydrocarbon concentrations and vice versa." These statements seem contradictory and need to be clarified. 5. Groundwater is degraded along the southern edge of the property boundary, directly downgradient from the tank farm, loading area, and transfer block. Staff is concerned that MW-10 is actually crossgradient from these areas, providing no downgradient delineation of the plume. Woolsey needs to prepare a work plan to delineate the downgradient contaminant plume. The work plan needs to include a time schedule to evaluate remedial alternatives to expedite cleanup, once plume delineation is complete. 6. The reports do not provide well construction information, so it is unclear whether any wells onsite monitor the lower water-bearing zone beneath the site. Also, the report does not state whether any past investigations have delineated the vertical extent of contaminants beneath the site. Woolsey needs to prepare a work plan to determine the vertical extent of the contaminant plume. By 17 July 2000, please submit responses to comments. We plan to prepare a new draft monitoring and reporting program (MRP), which we will send for your review and comment under separate cover. By 2 August 2000, we request Woolsey submit a work plan that includes the following: ❑ Delineation of the downgradient and vertical extent of the plume; ❑ A time schedule for a remedial alternative evaluation; and ❑ Abandonment of MW-1. If you have any questions, you may contact me at (916) 255-3119. J SSICA gineering Geologist 1 cc: Mr. Patrick Riddle, Law Offices of Patrick D. Riddle, Acampo 1 J,��-= �1TLL-�11L111A111Gi, 1 Joaquin County Public Health Services, Stockton lr/I/ Mr. Greg Stahl, Ground Zero Analytical, Inc., Escalon