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June 30, 1992 �AWALAFAAM . Unocal Station No. 6981, Stockton, California RECOMMENDATIONS Based on the results of this and previous work, we recommend o Evaluating the lateral extent of dissolved hydrocarbons in ground water using a Hydropunch system at locations west, north, and east of the site. Results will be used to select locations for additional monitoring wells. The proposed Hydropunch sample locations are shown on PIate 23. o Installing monitoring wells north, east, west, and south of the site after the dissolved plume is delineated with the Hydropunch The proposed location where wells will be installed is shown on Plates 23 and 24 (Proposed Well Location Map), however, the actual locations of the bonngs will be based on the result of the Hydropunch sampling o Performing an aquifer pumping test to evaluate the transmissrvmty, storativity, and other aquifer characteristics The proposed location of the pumping-test well is shown on Plate 2 ADDENDUM TO WORK PLAN RESNA will conduct the following work after the appropriate permits have been obtained TASK 1: Delineation of Dissolved Hydrocarbons and Installation of PumRing Test Well 11 Use a Hydropunch system at three offsite locations shown on Plate 23 to collect water samples for laboratory analyses. Submit one water sample from each hydropunch location to a State-certified laboratory for analysis of TPHg using EPA Method 8015 with EPA extraction Method 5030 and for BTEX using EPA Method 602 1.2 Dnll four 8-inch-diameter soil borings offsite to approximately 70 feet below surface grade and construct 2-inch-diameter groundwater morutonng wells in the borings. Proposed locations of the bonngs are shown on Plate 23, however, the actual locations may change if hydrocarbons are detected during the hydropunch sampling 0302-7 380332-7 5