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V ADDMONAL ASSESSMENT WORKPLAN COLBERG BOAT WORKS APRIL 2001 The well will be sealed from the top of the bentonite to within 1-foot of ground surface with a LN neat cement/bentonite (<5%) grout. To protect the integrity of the well, the top of the wellhead assembly will be enclosed at the surface in a traffic-rated, flush-mounted well box. All work will be performed in accordance with the County regulations, California Code of Regulations, Title 'r 23, Section 2647 and 2648 and California Department of Water Resources Bulletins 74-81 and 74-90. Final well monitoring well location and design will be determined based on the geoprobe data and consultation with the County. Selected soil samples collected during the well installations will be analyzed for TPH G, BTEX, 1,2-DCA, EDB, and fuel oxygenates using EPA methods 8015M, 8020 and 8260B, respectively. It is anticipated that a minimum of one soil sample from each boring will be analyzed. Organic vapor emissions from the soil samples will be monitored in the field using a PID or FID. �. Soil cuttings will be placed into DOT approved 55-gallon drums and stored on-site until the soil is profiled for disposal. Disposal of the cuttings will be completed by GHH. Well Development +r The groundwater monitoring wells will be developed using a surge block and/or submersible pump to remove fines and develop the sand pack and aquifer materials. Turbidity will be monitored to check the effectiveness of development. Development and purge water will be put into DOT approved 55-gallon drums and labeled accordingly. As with the cuttings, the drums will be left on-site pending laboratory analyses and selection of appropriate disposal, which will be completed by GHH. V Groundwater Purging The newly developed wells will be allowed to equilibrate for a minimum of 48-hours prior to purging for sampling. Prior to purging, depths to groundwater in all wells will be measured to the ,r nearest 0.01-foot. A minimum of three casing volumes of groundwater will then be pumped from each well prior to groundwater sampling. Specific conductance,pH, temperature and turbidity will be measured during the purging process. When these parameters stabilize the wells will be L. allowed to recharge before sampling. Groundwater Sampling Groundwater samples will be collected from monitoring wells MW-1, MW-2, MW-3 and the new monitoring wells after the wells have sufficiently recovered to the static groundwater levels, or in `r the event that the well is pumped dry during purging, when the water level recovers to at least 80% of the original water level. In the event that the wells are not sampled within 24-hours of purging, each well will be re-purged until at least three well volumes have been removed prior to `+ sampling- 5