SITE INFORMATION AND CORRESPONDENCE

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.� Aline M. Farr, Ph.D. Mevc S"tva March 21. 1995 It is my undersianding, that the County requested that additional soil samptcs be collected. due to the detection levels for BTEX for the sail samples collected from the tank excavations being higher than required by the County. Two borings were drilled in Noverrlbet 1993 to address; this concern of the County. One of the borings (B-t) was locxted at the foirnerr location of Waste Oil Tank WO-1. The second boring (B-2) was locattd in the vicinity of the three other USTs. As summarized in Table 1, TPH , ethylbGnxene, and xylenes, wert detected in one of the gull samples tollecled from $-1 at a depth of 8 feet The boring log for this sample indicates -that there were no hydrocarbon odors below a depth of 9Y2 feet The absence of petroleum hydrumbons below this depth was confirmed by analyzing a sample from boring B-1 at a depth of IS feet. This sail sample had non-detectablt concentrations of TPH and RTEX Rv�ew of Saiy�SrotwDles licsul As specified by the Tri-Regional Guidelines, one soil boring was installed at the former location of the 500-g2llon UST The results from this boring were reviewed relative to the methodology specified in the LLTFT Manual. Applyin the leaching potential analysis outlined in the LVFT Manual results in a Sale rating of 4+4. Based on this rating` and the concentration of xylenes altd TFIH2 detected in one sample from Boring B-1, the LUFT manual states that a "General Kish Appraisal" needs to be perforated. Further, the LUFT Manual states that "the gerteiral risk eppraisal is more sophisticated than the leaching potential analysce' (LUFT. p 29) and that the eppraisai "is based on a technical foundation which conservatively accounts for influences on pollutant migrarion." (1rUFT, p.28) Using the Gmeratl Risk Appraisal, as recommended by the LUFT Manual., the acceptable cumulative soil contarninxtion levels for protection of groundwater at the Brannon Tam Site are as follows }. I ppm Benzene, 100 ppm toluene, 200 ppm xylenes, and 300 ppm ethlybenxene. As summarized in Table 1, of these four compounds, only xylenes and ethylbenzwe have been detected The rnaxiMuM cumulative soil cordamirlf ice levels fol thest two compounds ar the Brannon Tire Site aac. 2.7 ppm far xylentrs and 0.49 ppm for ethylbenitene These soil concentrations are significantly less than rhe acceptable cumulaitve soil contamination levels specified by the General Risk Appraisal. In fact, the concentrations detected would be acceptable if the distance to highest groundwater was only 5 feet ` Ybc NOMbers speraried tlt Table 2-1 providr "a ximPlibcd way 10 M91%the possiNc lbmar to giouiud water froze uopaaminativo Wits, Alternate elvowup levels, based on additional sitr-specirk aualysim, would sapctatde lite initirj atlowatir levels." (LUFT, p.207. As sided in etre LtrFi'Maui, the omcftraadions fat TP,4 tisled 9n 11•c Leaching lkaeatiar't•ablc weir appi*Xituolvd by using; rht ascaeptable 13'iX&L-levels divided try their pet—at_Mpuniliort in gasotl"r, ' Hasid ea t tneam #w-4 piceipils4oa of 24.4 imches(Mtuured ter 'S"wAlon Firc Stairva 94)sod s diolmot eta Highest V0'W4wz1cr fM sail sample of 35-40[t