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1444 MARIPOSA ROAD <br /> WKA No 2938 05 <br /> August 26, 1999 <br /> ' Page 16 <br /> wells somewhere between February and August of 1996 Though this site condition poses a <br /> ' difficulty with regard to absolute perfect data, it is our opinion that the data prior to screened <br /> interval submersion supports our ultimate conclusions and recommendations <br /> ' To underscore this point, the data string from well MW1 running from October of 1993 to <br /> August of 1996 (submersion date) shows a relatively consistent decline in gasoline and benzene <br /> ' concentration This declining trend is mirrored in well MW2 for the period running from <br /> October 1993 to August of 1995 (submersion date) Because only one hit was recorded for <br /> ' gasoline and two hits for benzene in well MW3 no real trend is readily apparent in this well with <br /> regard to the submersion of the screened interval <br /> The inactive onsite domestic well located at the southeast side of theropertY between wells <br /> p <br /> ' MW3 and MW6 was sampled on May 2, 1996 Results of laboratory analysis revealed no <br /> detectable concentrations of TPH as gasoline, diesel, motor oil, BTEX, or MTBE Maintenance <br /> records for this well indicate that the total depth of the well is 191 feet bsg <br /> Based on the removal of the former USTs, removal of contaminated soil, historical gradient data <br /> ' and concentrations of petroleum hydrocarbons in the perimeter wells, and the attenuation of <br /> dissolved-phase petroleum hydrocarbons in groundwater, potential sensitive receptors in the <br /> ' form of offsite wells will likely not be impacted by contaminated groundwater beneath the site <br /> i <br /> Based on field observations and results of laboratory analysis, it is our opinion that a majority of <br /> the contaminated soil has been removed from the former UST excavation, aerated and placed <br /> back in the excavation, thus posing no significant threat to groundwater quality Additionally, <br /> because the contaminant release occurred prior to the 1992 tank removal and only trace <br /> concentrations of contaminants are present in groundwater directly beneath the former <br /> ' excavation and at the property boundaries, it appears that a certain degree of natural attenuation <br /> is working to degrade the problem and limit the lateral migration of any remaining petroleum <br /> ' hydrocarbons <br /> ' Given the relatively low concentrations of contamination remaining in the soil beneath the site, <br /> . the trace concentrations of TPH, BTEX and MTBE reported in groundwater samples from seven <br /> WALLACE KUHL <br /> Recycled paper &ASSOCIATES INC. <br />