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05 August 2015 <br /> AGE Project No. 06-1463 <br /> Page 4 of 5 <br /> The volume of each isocontour was determined by the following formula: <br /> V = Area (A) multiplied by the height (h) <br /> A= Area as determined using computer area inquiry function <br /> h = thickness (well screening interval equal to 20 feet) <br /> Using the above calculations approximately 47.05 lbs. (equivalent to 7.53 gallons) of <br /> TPH-g impact was estimated to be dissolved in groundwater at the site prior to <br /> performance of corrective action. The assumptions for the calculations of hydrocarbon <br /> mass in groundwater are presented in Appendix C. <br /> POST-REMEDIATION MASS OF DISSOLVED PETROLEUM HYDROCARBONS <br /> Figure 6 depicts the estimated extent of the post-remediation dissolved hydrocarbon <br /> plume in plane view. Utilizing this figure, the mass of dissolved TPH-g in groundwater <br /> was determined by splitting the groundwater plume into different isocontours based on <br /> concentrations reported during the most recent post-corrective action monitoring event. <br /> Further, the mass was calculated using the screening depth of wells installed at the site <br /> (height equal to 20 feet). <br /> The volume of each was determined by the following formula: <br /> V = Area (A) multiplied by the height (h) <br /> A= Area as determined using computer area inquiry function <br /> h = thickness (well screening interval equal to 20 feet) <br /> Using the above calculations, approximately 10.24 lbs. (equivalent to 1.63 gallons) of <br /> TPH-g impact is estimated to be remaining dissolved in groundwater at the site. The <br /> assumptions for the calculations of hydrocarbon mass in groundwater are presented in <br /> Appendix C. <br /> Based on the estimates of dissolved petroleum hydrocarbon mass pre- and post- <br /> remediation, approximately 78% of the initial dissolved mass at the site has been <br /> mitigated. <br /> DISSOLVED HYDROCARBON TREND ANALYSIS: <br /> Based on plots of TPH-g versus time, using historically petroleum-impacted wells at the <br /> site, (Appendix D), a definitive trend of decreasing dissolved concentrations is evident in <br /> all of the sites wells. Additionally, based on the plots of TPH-g concentrations versus <br /> time, a linear trend line was utilized to project the time in which currently impacted <br /> Adianced GcoEii%-ironmcntal,Inc. <br />