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i <br /> GROUNDWATER ASSESSMENT REPORT <br /> 16 Provide assumptions,parameters, calculations and the model used in any risk <br /> assessments <br /> Concentrations of contaminates in the soil or groundwater were, for the most part,not <br /> ' detected and certainly not detected at levels that warrant risk assessment Remediation was <br /> not necessary for this site nor have remediation activities been implemented This item <br /> does not apply to this site and case <br /> 17. Provide assumptions,parameters, calculations and the model used in fate and transport <br /> modeling. <br /> iRemedial methods were not necessary for this site No remedial activities have been <br /> implemented <br /> 18. Provide a rationale why the conditions remaining at the site will not adversely impact <br /> water quality, human health,and safety, or other beneficial uses. The rationale for <br /> 1 closure must include a findtng about present and future water use, and risks the site may <br /> stall represent to human health and safety, and water quality <br /> The rationale for closure is based on the following <br /> • A mass of MTBE-impacted soil was not identified through soil sampling and <br /> analysis Residual concentrations localized near the former UST excavation do not <br /> represent a significant mass capable of migrating vertically downward through the <br /> soil <br /> ' . Analyses detected only 15 ug/L of MTBE in the groundwater in monitoring well <br /> MW-3 in January 2002 Three subsequent sampling events did not show <br /> concentrations of MTBE in MW-3 or the other monitoring wells <br /> • There is no indication that MTBE has migrated laterally or vertically beyond the <br /> ' areas of detected soil impact <br /> • The geology and hydrogeology does not appear conducive to initiating the future <br /> ' migration of MTBE from the former UST excavation <br /> • Public groundwater sources are located at substantial distances both laterally and <br /> ' vertically from the former UST location and migration of MTBE detected from <br /> the site to those sources is remote <br /> + Laboratory analyses did not detect total petroleum hydrocarbons as gasoline, <br /> benzene,toluene, ethylbenzene,and xylenes during the UST removal activities or <br /> subsequent soil and groundwater investigations or groundwater monitoring <br /> ' 1n summary,residual contamination, if any, at the site is extremely localized The various <br /> . soil and groundwater investigations have not detected concentrations of MTBE or other <br /> ' Groundwater Morutonng and Sampling Report- F-5 ESA/200252 <br /> Request for No Further Action December 2003 <br />