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Workplan for Limited Subsurface Investigation Moore Balk Petroleum Plant,5491 F Street,Banta,San Joaquin County,California results of all soil and water sampling were documented in the report Tank Closure Results and Recommendations Report dated December 23, 1998. On April 8 and 9, 1999, Apex personnel supervised the advancement of eight soil borings at the subject property (Figure 2). The results of all soil and water sampling were documented in the report Results Report for Subsurface Investigation and Second Ottarter 1999 Grozmdr eater Moidtori77g dated June 1, 1999. PROPOSED INVESTIGATION Apex proposes to drill four soil borings on-site and convert the four borings into groundwater monitoring wells MW-4A, MW-7, MW-8 and MW-9, (Figure 2). The four proposed soil borings will be drilled to an anticipated total depth of 20 feet below grade (bg) with the use of a hollow stem auger drill rig. Soil samples will be collected at five-foot intervals, obvious lithologic changes, or obvious hydrocarbon odors from each of the borings. All fieldwork will be conducted according to the Apex Standard Operating Procedures (SOP) included in Appendix B. The proposed locations of groundwater monitoring wells MW-7 through MW-9 are to define the lateral extent of petroleum impacted groundwater. The four proposed groundwater monitoring wells will be constructed as two-inch diameter wells and screened set from 5 to 20 feet bg (Figure +�.. 3). Prior to drilling, the underground utility notification network, USA, will be contacted for identification of buried utilities at or entering the project site from the public right-of-way. As a further precaution against drilling into or through potential buried obstructions, the first five feet of the boring will be augured by hand. All five proposed drilling locations will require concrete boring or cutting prior to drilling with a hollow stem auger drill rig. SOIL SAMPLING Soil samples will be collected a five-foot intervals and at obvious lithologic changes. Soil samples will also be collected below the water table from each of the four proposed borings. The groundwater table is approximately 10 feet below grade. All soil samples will be screened in the field with the use of a PID. The soil sample with the highest PID reading, one soil sample at the 15 foot interval, and the base soil sample from each boring (25 foot sample) will be submitted, under chain-of-custody,to a state-certified laboratory for analysis of a)TPH, as gasoline; TPH, as diesel by modified EPA Method 8015; b) BTEX and MTBE by EPA Method 8020; and c) five oxygenates by EPA Method 8260. A minimum of three soil samples from each soil boring will be submitted for analysis (total of 12 soil samples). Soil samples will be collected beneath the water table to determine the vertical extent of petroleum hydrocarbons. All drill cuttings will be temporarily stockpiled on site, under and on plastic sheeting, pending receipt of the analytical results. 3