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Results of CPT Investigation and Work Plan Cleanup and Abatement Order No 5-00-707 EAI Project No 1232 3.0 FIELD SAMPLING PLAN Based on the information currently available for the Wards and Unocal sites, and the RTW 0 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 • The vertical extent of contamination around the RTW does not exceed 100 feet bgs v Additional assessment work is required to define the extent of petroleum hydrocarbons beneath the Unocal site • Additional assessment work is required to define the vertical extent of petroleum hydrocarbons in ground water beneath the Wards site Additionally, RWQCB staff also have requested that a deep well be installed near the R1W for future monitoring purposes The protocols to be used to develop, survey, purge and sample the wells, decontaminate equipment, label and handle sample containers, document field work, manage wastes, and quality assurance and quality control measures are described in Section 5 0 of the SIRNAR Report Health and safety procedures will be in accordance with EAI's Health and Safety Plan for this project dated September 28, 2000 (see EAI 2000A) ' 3.1 Unocal Site To provide better data on the source of hydrocarbon impacted ground water at the Unocal site, two wells (MW-25S and MW-25D) will be installed near the former excavation, and one deep well (MW-18D) will be installed down gradient (easterly) from the site (see Figure 2) Seethe STR/PAR Report for specifics regarding the need for these wells See Appendix D for proposed well construction details One nested well (MW-23 SID) will be installed near existing well MW-11 to provide better data on the vertical extent of contamination below the Unocal site (see Figure 2 and Appendix D) The nested well will be constructed with one two inch PVC well screened from 85 to 90 feet and a second two inch well screened from approximately 100 to 105 feet The boring will be continuously sampled from 85 to 105 feet to assure that a silt or clay layer of approximately five feet is present between the two-screened intervals A centralizer will be used on the shallower well to assure the two wells are not in contact and that a good seal is achieved above the two casings Finally, the wells will be tremmie grouted to within two feet of the surface and flush mounted well boxes installed A non-ethanol containing bentonite will be used for the well seal See Appendix D for proposed well construction details BS 1232P WELLS_WP -5- ENVXRON14ENTAL AUDIT, INC.,