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N i ` 30 January 2014 AGE Project No . 99-0682 Page 11 of 28 (50 to 90 feet bsg) samples collected from wells MW-7 and MW-8 and from borings CPT-1 , CPT4 and CPT-7 (Figures 10, 11 and 13) . Based on groundwater data collected from site wells and grab groundwater samples ' collected during historical investigations the , the lateral and vertical extent of the dissolved hydrocarbon plume is marginally defined at the site . The shallow plume appears defined to the north by MW-3 to the east by borings P-521 - 1 through 3 and MW-4 , to the west by well MW-2 . The shallow dissolved plume is not defined to the south ( Figure 12 ) . For intermediate level wells , the plume is defined to the east by boring B-5, to the west by well MW-9 and to the south by boring CPT-5 . The plume is undefined to the north and elevated �tl} � concentrations have been reported in well MW-11 during the active investigation . However, y � l (releases deeper assessment has not been performed at the adjacent site located at 630 North ray ' , California Street and it is possible that elevated concentrations resulting from samples p�� ycollected at well MW- 11 are a result of releases from this tank site in combination with from the Stallworth Auto Sales site . 6.3 . MASS OF REMAINING DISSOLVED PETROLEUM HYDROCARBONS Figures 10 and 11 depict the estimated extent of the dissolved hydrocarbon plume in cross sectional views ; Figures 12 and 13 depict the shallow and intermediate extent of the dissolved hydrocarbon plumes in plane view. Utilizing the above figures , the mass of dissolved TPH-g in groundwaterwas determined by splitting the groundwater plume into different isocontours based on concentrations reported during the March 2013 groundwater monitoring event and grab groundwater samples collected throughout the investigation . Furtherthe mass was split into two different depth discrete zones (20 to 50 feet bsg and 50 to 90 feet bsg) . The volume of each was determined by the following formula : V = Area (A) multiplied by the height (h) A= Area as determined using computer area inquiry function h = thickness (as determined utilizing Figures 10 and 11 ) Using the above calculations and the analytical results for groundwater samples collected during historical investigations and the groundwater monitoring event performed in March 2013 , approximately 49 lbs. (equivalent to 7. 8 gallons) of TPH-g impact is estimated to be dissolved in groundwater at the site . The assumptions for the calculations of hydrocarbon mass in groundwater is presented in Appendix D . Advanced GeoEnvironmental, Inc.