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Supper Center Mart - 3 - October 24, 2011 <br /> Site History/Assessments <br /> In February 1998, soil contamination was identified during the removal of USTs. To date, 15 <br /> monitoring wells have been installed and monitored regularly. A Site map showing the location <br /> of the former USTs and monitoring wells is provided at the end of this five year summary. <br /> Remediation Summary <br /> • Free Product: No free product was documented throughout the life of this case <br /> • Soil Excavation: An unknown volume of impacted soil was removed and disposed <br /> offsite in 1997 <br /> • In-Situ Soil/ Groundwater Remediation: Dual phase extraction, conducted from January <br /> 2011 and present, has extracted 197,510 gallons of groundwater and 2,212 pounds of <br /> TPHg. The rate of TPHg removal in June 2011 was approximately 12 pounds per day <br /> General Site Conditions <br /> • Geology and Hydrogeology: The Site is underlain by interbedded and intermixed sand, <br /> silt, clay, and gravel, with some cemented sand lenses. The depth to groundwater is <br /> approximately 27 feet bgs and the groundwater gradient is northeast <br /> • Groundwater Trends: There are more than 12 years of groundwater monitoring data for <br /> this Site. Benzene trends are shown below, source area shallow (MW-3 and MW-9A) <br /> and source area deep (MW-9B) <br /> BENZENE Results for MW3 <br /> 120000 <br /> 100000 <br /> 90000 <br /> Q <br /> � 60000 <br /> K <br /> 40000 - <br /> 20000 <br /> /rte^Y�-►-.a <br /> 0 <br /> dr O~ 110, <br /> --BENZENE -Tr.n <br /> BENZENE Results for MW9A <br /> 9000 <br /> 9000 <br /> 7.00 <br /> 4000 <br /> 3000 <br /> 2000 <br /> 1000 <br /> 0 e w <br /> -—BENZENE ---T-0 <br /> BENZENE Results for MW98 <br /> 6000 <br /> 7000 <br /> 6000 ---- -1501111 <br /> -- <br /> 4000 - <br /> 3000 <br /> 2000 <br /> 1000 - - � <br /> BBN=N6 ---T—d <br /> i I <br />