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Supplemental Investigation Report,Problem Assessment Report and Work Plan Cleanup and Abatement Order No 5-00-707 „�_ PATTY,,. No 1232 5,0 FIELD SAMPLING PLAN Based on the information currently available for the Wards and Unocal sites, and the RIW • Chemicals of concern are gasoline and it constituents, i e , BTEX Fuel oxygenates, e g , MTBE, TBA, DIPE, ETBE, TAME, EDB, ethanol and methanol, are not chemicals of concern • EAI is recommending that additional assessment work be completed to better define the extent of petroleum hydrocarbons in soil and ground water The two areas targeted for further investigation are the Unocal site and the area around the RIW 5.1 Unocal Site Three additional wells are proposed for the Unocal site as approximately shown on Figure 19 Wells MW-23S and MW-23D (the "S" standards for shallow with the well to be terminated at 50 feet bgs, and slotted between 30 and 50 feet bgs, and the "D" stands for deep with the well to be terminated at 70 feet bgs, and slotted between 50 and 70 feet bgs), are proposed for the area between the existing marquis and building on the site, which is also within the former source area excavated by Unocal in 1988 These wells are needed because there are no current ground water data between existing well MW-11 and the former source areas, i e , USTs and fuel islands Also, it is proposed that soil samples be collected and tested during installation of these wells to determine if any residual hydrocarbons are present in the soil used to backfill the area excavated in 1988 (see Section 2 3 2) One deep well (MW-18D) is proposed to be located adjacent to existing well MW-18 (see Figure 19) This well is proposed because without pumping of the RIW the ground flow water direction will be easterly, and there is no deep well in this direction Other Unocal wells, e g , MW-13, MW-14 and MW-16 are all deep wells and have no significant hydrocarbon impact This well will ensure that they are sufficient data points to monitor the extent of impact, without operation of the RIW 5 1 1 Drilling and Soil Sampling The borings will be drilled by a State of California licensed C-57 Water Well Driller The borings will be drilled using 10-inch diameter continuous flight hollow stem augers Soil samples will be obtained from each boring at approximately five feet bgs and at five-foot intervals thereafter The soil samples will be collected using six 2 5-inch diameter by three- inch long brass tubes mounted within a 2 5-inch inside diameter split-spoon drive sampler employed in advance of the augers After sample recovery, the ends of the lower most tube will be covered with aluminum fail and plastic caps 'aped over the ends The samples will be labeled with a sample point identification, depth interval, EAI project number, time and date, individually sealed in "Ziploc" plastic bags, and immediately placed into an ice chest The samples will be kept chilled until delivered to the laboratory for analytical testing All samples _ will be logged on a chain of custody record form BS 1232P IRw_WP -13- ENVIRONMENTAL AUDIT,iNC.,,