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CLEAkRATER <br /> £reueronn:enfaf Services <br /> Confirmation borings in March 2000 indicated that only a limited residual volume of soil <br /> contamination remains in the area of MW-2 It was estimated that approximately 37 lbs of sorbed-phase <br /> TPHg are now present beneath the site The maximum TPHg concentration in this area was 240 mg/kg <br /> Based on these data, it appears the SVE/AS system removed over 99% of the TPHg present before <br /> remediation It is likely that the limited mass of residual gasoline in the soil will naturally degrade <br /> over time, and will not pose an ongoing threat to groundwater, as evidenced by ongoing groundwater <br /> monitoring results <br /> Groundwater contaminants have also decreased in dramatic fashion since site remediation occurred <br /> Maximum post-remediation TPHg, benzene, and MTBE concentrations are currently 560 pg/L, 2 6 pg/L, <br /> and 78 pg/L, respectively Residual dissolved-phase contaminants are restricted to the uppermost 10 <br /> feet of water column, based on non-detect results for the sparge wells, and do not extend laterally much <br /> beyond their well locations Additionally, no other Fuel Oxygenates (TBA, ETBE, DIPE, TAME) or Lead <br /> Scavengers (1,2-DCA, EDB) were detected in the groundwater beneath the site It is likely that these low <br /> residual dissolved-phase contaminant concentrations will naturally attenuate below detectable limits <br /> within short period of time <br /> Samples from the on-site dornestic well continue to be free of any petroleum contaminants <br /> ® Consideiing the well was riot impacted by Elevated contaminants levels prior to remediation, it seems � <br /> appears that the well is not threatened by the minimal peat-remediation contaminant levels now <br /> presem In the soil and shallow groundwater beneath the site <br /> Based on all hlstotical site information, it appears that soil and groundwater beneath the site have been <br /> effectively remediated to the extent practicable, and residual contaminants do not appear to pose a <br /> threat to any nearby receptors Accordingly Clearwater recommends that the site receive regulatory <br /> closure Following closure, all investigation/remediation wells should be properly= abandoned and all <br /> subsurface remediation conduits shoulc be removed and properly backfilled/compacted <br /> ZB107C Conf Borings /CWTAR 1Q00 7 March 27 2000 <br />