Laserfiche WebLink
1 <br /> ✓ice=` Geomatrix <br /> 1 <br /> • the lateral migration of vapor containing gasoline constituents in the unsaturated <br />' zone would be difficult to control and might pose potential health and safety <br /> risks to Site workers or operations <br /> • Excavation of the affected soil for off-site disposal and dewatering would be <br /> cost prohibitive due to the lateral and vertical extent of the affected soil and <br /> groundwater at the Site Expensive engineering systems would be required to <br />' protect existing structures and ongoing operations at the Site <br /> • Soil vapor extraction would not be effective in removing residual petroleum <br />' hydrocarbons in the saturated zone or in fine-grained sediments <br /> The other remedial approach that has been considered for similar sites is <br />' implementation of institutional controls Under this remedial approach, a Site <br /> Management Plan (SMF) would be developed to provide guidelines for the proper <br /> management of impacted soil and groundwater when intrusive activities are <br /> t conducted at the Site The SMP would include a description of subsurface <br /> conditions, guidelines on soil handling, soil disposal, and construction dewatering, <br /> as well as the responsibilities for implementation of the SMP The SMP would also <br /> require additional evaluation of Site conditions should Site uses change in the <br /> future <br /> Based on the Site conditions, the best available remedial approach for the Site is <br /> institutional controls <br /> 15 Estimated Mass The residual mass of TPHg in affected soil and groundwater at <br /> the Site was estimated using data included on site maps (Figures 2 and 8) and on <br /> geologic cross sections (Figures 9, 10, 11, and 12) <br />' TPHg Mass in Sod <br /> Soil samples were collected from the Site between 1998 and 2002 The TPHg mass <br />' remaining in the soil beneath the Site since 2002 likely has decreased as a result of <br /> natural attenuation processes, including biological, physical, and chemical <br /> mechanisms Dimensions of affected soil are estimated to be approximately 17 feet <br />' thick, 100 feet wide, and 180 feet long Approximate contours of equal TPHg <br /> concentration in affected soil using logarithmic contour intervals are presented on <br /> Figures 8, 9, and 10 <br />' To calculate the residual mass of TPHg in soil, the affected soil volume is divided <br /> into two zones one with TPHg concentrations greater than 100 milligrams per <br /> tkilogram (mg/kg) and one with concentrations less than 100 mg/kg Assuming a <br /> soil density of 100 pounds (45 kg) per cubic foot, the total mass of affected soil is <br /> about 1 4 x 107 kg with approximately 2 2 x 106 kg of affected soil with TPHg <br /> concentration greater than 100 mg/kg and 1 2 x 107 kg of affected soil with TPHg <br /> concentration less than 100 mg/kg <br />' 116000s16437 00MArchrve16437-041 doc 4 <br />