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Clasure Appeal, • • <br /> Page4 <br /> 'of 5 h"On,6421 Capitol Avenue,Lodi,Califomia <br /> 3) The mass of MTBE remaining in groundwater was incorrectly calculated and the <br /> was sult <br /> a gross underestimation of MTBE remaining in groundwater at the site. <br /> underestimated mass calculation was used in the risk model to close the Subject Property.r <br /> The Closure SummaryThis <br /> MTBE remaining in <br /> Report Prepared b <br /> groundwater at the Sub Subject Propertyated <br /> 31, 2005 calculates the <br /> are multiple problems with this mass calculation. p y at 1.75 o mass of <br /> Pounds (Appendix M). There <br /> AGE uses a contaminated aquifer thickness of 20 feet <br /> the aquifer) and uses the equation for a conical shape to estimate the volume of the disco <br /> phase MTBE <br /> Plume remaining at the Subject property(b-10 feet where b is half the thickness of <br /> Summary Report illustrates lved <br /> the dissolved However, Figure 14 in the Closure <br /> under the Subject Property. The thickness Phase MTBE plume thickness at 80 feet consistently <br /> amount of dissolved base and shape errors in the calculation would increase the <br /> noted that only 13.33 Pounds Of MTBE was remediated fromundWater from the site.5 <br /> Pounds to 14 pounds. It should be <br /> Apex recommends correcting the mass of MTBE still remaining in groundwater <br /> under the <br /> Subject Property and rerunning the risk model. <br /> 4) The Closure Summary Report prepared b <br /> y AGE natural groundwater flow direction s consistently o he north northeast. This direction is <br /> towards Gilbert and Eileen Moore's Flag City Shell well August northeast. <br /> This states that <br /> detection of MTBE and suggests the Flag City Chevron plume may bewmigratingntly had a <br /> Apex prepared a Workplan for Monitoring Well Installations dated Apri124, 2006 for the Gilbert <br /> and Eileen Moore's Flag City Shell site which was approved by the San Joaquin County <br /> Environmental Health Department on May 9, 2006. The workplan proposes that two wells are <br /> installed just to the northeast of the Subject Property. These wells should provide additional data <br /> on the migration of the dissolved phase plume. It would be premature to consider the Subject <br /> Property for closure until the new wells are installed and more information is acquired about the <br /> source of MTBE in well MW-613. <br />