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FINAL DRAFT CONFIDENTLAL ATTORNEY/CLIENT WORK PRODUCT The results of analysis (and previous soil analyses) are summarized in Table 1. ' With the exception of 0.050 parts per million xylenes detected at a depth of 20 feet in CB-7 no.analytes were detected in borings-CB I through CB7. ' TPHG along with toluene, ethylbenzene, and xylenes was found to be present in detectable concentrations in orings CB-8 and CB-9. No benzene was detected in an borin Laboratory data sheets are included in Attachment 1 as are boring logs. The locations of the borings are depicted on Figure 2. Based on the levels of contaminants detected in borings CB-8 and CB-9,'and the County's stated r.: position that non-detectable levels will be required for closure it has become apparent that vapor extraction by itself will not be sufficient to:secure soil closure in a':timely manner. The ability of vapor extraction to reduce all soil contaminant 'concentrations to non-detectable levels in a heterogeneous soil profile is questionable. Therefore excavation of impacted soil is being considered as a remedy at this time. Due to' the significant financial outlay associated with excavation, however, it is desirable that a clear:'understanding be set forth concerning the nature of the workscope along with a commitment by the County to close the soil investigation upon completion of the workscope. REVISED SOII. CLOSURE PLAN We seek County concurrence with. the .following proposed elements of the workscope and acknowledgment that completion of the vi orkscbpe will result in soil closure. Rationale for the proposed elements are also provided below. This outline provides only the principal features of the proposed plan. Should these particulars be acceptable we will prepare a detailed workplan for County approval which will include the;specifics of proposed'soil disposal, transportation, sampling methodology, backfilling procedures, etc. 1) Contaminated soil will be excavated-:within, but not outside, the boundaries of'the area outlined and labeled "limits of soil contamination" on Figure 3. Explanation: Figure 3 depicts the lateral extent of soil contamination as TPHG based on soil samples from the 30 borings/wells that,have been drilled at the site. Borings in which no TPHG was detected are highlighted. These borings provide a perimeter of non-detectable TPHG concentrations around the east central portion of the former tank'pit. The area within this perimeter is to be excavated and the soil removed. Prior,to the recent drilling of the nine confirmation borings, scattered detections-of low levels of various aromatic hydrocarbons were reported in soil samples outside the boundary of-contamination depicted on Figure 3. Sampling of the confirmation borings following .vapors; extraction indicates that these low levels of aromatics are no longer present outside the area.contaminated with detectable TPHG. The minor contamination detected in soil boring ASB -1 southeast of the(former tank pit has presumably been addressed by vapor extraction from-'well VP4. Futher, no contamination was detected in