Laserfiche WebLink
:CVvATC r <br /> A S S O C I A T E S I N C . <br /> 5.1.2 Soil Volume Calculations <br /> Using the analytical results from the subsurface investigations mentioned in Section 3.0, ATC <br /> estimated the lateral extent of TPHg, benzene, and MTBE from 40 to 60 feet bgs and from 60.5 <br /> ' to 75 feet bgs in the vadose zone beneath the site as depicted on Figures 7 through 12. The <br /> isoconcentration contours shown on Figures 9 and 10 were used to estimate the volume of <br /> petroleum impacted soil from 40 to 60 feet bgs and from 60 to 75 feet bgs, respectively. The total <br /> ' volume of petroleum impacted vadose zone soil is estimated to be approximately 92,284 cubic <br /> feet. MTBE mass balance calculations were not completed due to an insufficient number of data <br /> points. Soil volume calculations and assumptions are included in Appendix A. <br /> ' 5.1.3 Pre-Remediation Mass Balance Calculations- Soil <br /> ' Using the analytical results from the subsurface investigations mentioned in Section 3.0, ATC <br /> estimated the lateral extent of TPHg and benzene concentrations in the vadose zone beneath the <br /> site as depicted on Figures 7 through 10. The estimated lateral extent of TPHg and benzene from <br /> 40 feet bgs to 60 feet bgs is generally similar, and the estimated lateral extent of TPHg and <br /> benzene from 60.5 feet bgs to 75 feet bgs is generally similar, with the estimated lateral extent of <br /> benzene being slightly larger in both depth intervals. Consequently, the isoconcentration shown <br /> ' on Figure 9 was used by ATC to perform mass balance calculations to estimate the area of TPHg <br /> and benzene in soil from 40 feet bgs to 60 feet bgs, and the isoconcentration shown on Figure 10 <br /> was used by ATC to perform mass balance calculations to estimate the area of TPHg and <br /> ' benzene in soil from 60 feet bgs to 75 feet bgs. The total mass of TPHg in the soil from 40 feet <br /> bgs to 75 feet bgs was estimated to be approximately 1,878 kilograms. The total mass of <br /> benzene in the soil from 40 feet bgs to 75 feet bgs was estimated to be approximately 14 <br /> kilograms. Mass balance calculations are included in Appendix A. <br /> ' 5.1.4 Pre-Remediation Mass Balance Calculations-Groundwater <br /> Mass balance calculations for groundwater were not performed because the lateral extent of <br /> ' impacted groundwater has not been defined. <br /> 5.1.5 Estimated Length of Operation and Final Constituent Concentrations <br /> Because this is only an interim remediation system, the length of operation and final constituent <br /> concentrations can not be estimated at this time. Once the lateral extent of impacted groundwater <br /> has been defined, ATC will submit a Final Remediation Plan that will include the estimated <br /> length of operation of the system and final constituent concentrations. <br /> 1 <br /> t <br /> s:\emironmental\212911,eporl lirp.doc 5 <br />