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29 January 2002 t AGE-NC Project No. 98-0466 Page 24 of 25 ' the property, potential sources for additional releases no longer at the areas of concern identified in this report. ' 6.0. RECOMMENDATIONS ' Based on the results of this and previous investigations, AGE recomm ds: ' • No fin-ther investigation at the former south steam cleaning are the former truck parking area, the west ditch and the former Cover Plant. As discussed in Section 5.0., the detected TPH-d in the grab ground water sample collected from boring P 3 is quite likely the down- gradient margin of the hydrocarbon-impactedgroundwater plume related to an unauthorized release from a former diesel UST. Furthermore, the TPH-d, TPH-mo, lead, zinc and chromium detected in the western ditch area appears to be of limited mass and extent and ' does not seem likely to significantly impact ground water outside the immediate area. • No further investigation of the detected concentrations of formadehyde in the grab ground water samples collected from borings PB 10 (44 x 120 Building sump), PB 11 (north bum pit area) and PB 12 (north storm water basin). The detected concentr tions are slightly above the AL of 100 µg/1, low concentrations of formaldehyde have beer detected in analyzed soil ' samples and no source for additional releases currently exists at the site. In addition, no formaldehyde "hot spots" have been detected during any phase of investigation at the site. • Further investigation of the detected concentrations of TPH-d and TPH-mo in the grab ' ground water sample collected from boring PBB (former wash-d areanorth of Millwork Building) to identify a possible source area. However, the low obility, low toxicity and relatively low concentrations detected do not appear to pose a sign cant risk to groundwater tquality. • Additional investigation of the chromium and lead, TPH-d and,formaldehyde detected in ' grab ground water samples collected from borings advanced near the burn pit/north storm water basin area(PB 11 and PB 12). The concentrations of chro and/or lead detected in the water samples were slightly above the MCL for chromium and the AL for lead and ' formaldehyde. • Completion of an updated, expanded sensitive receptor survey tc identify wells in the area. ' • Preparation of a work plan, upon designation of an oversight agency, for excavation and backfilling of the bum pits and former teepee incinerator and for characterization of the soil piles for treatment, if needed, and future use on site. 1 Advanced Geo Environmental,Inc. 1