Laserfiche WebLink
h Ge010glcal7"eclsatcs Inc. Page 13 <br /> Site Conceptual Model <br /> Project No. 989.2 <br /> December 17,2003 <br /> ' Here is an overview: <br /> • Benzene reduction of 99.3% <br /> • Toluene reduction of 99.9% <br /> • Ethylbenzene reduction of 87.4% <br /> • Total xylene reduction of 99.5% <br /> ' • TPH-gasoline reduction of 87.1% <br /> 6. Groundwater data, gathered from quarterly groundwater-monitoring events, support the <br /> hypothesis of active intrinsic bioremediation. Downgradient monitoring wells show the <br /> absence of or a decrease in the above-mentioned constituents over time. <br /> 7. Groundwater parameters are such that aerobic biodegradation is likely at the site. <br /> 8. The site is located in the sediments of the Central Valley region. The water table wells <br /> ' are set in a silty clay layer, which should impede the vertical migration of the plume. The <br /> blue clay located at approximately 30 feet bgs may have a high cation exchange capacity <br /> (CEC). The ionic attraction may slow the lateral migration of contaminates sorbed in the <br /> soil. The organic content of a soil can contribute substantially to the CEC. <br /> 9. The current and potential threat to human health and safety is minimal. <br /> 10. The current and potential threat to the environment is minimal. <br /> Site Characteristics <br /> • The plume is defined vertically by MW-101 and laterally by MW-2, MW-3, MW-7, MW- <br /> 8 and MW-9. <br /> • The clay layer at 30 feet bgs provides a significant barrier to vertical plume migration. <br /> • Groundwater slope is gradual (<0.007 ft/ft), which minimizes the convective flow and <br /> impedes the migration of the plume. <br /> • Measurements of dissolved oxygen in the shallow monitoring wells range between 0.3 <br /> ' and 3.9 ppm. <br /> • MW-1 is at the heart of the TPH-G plume. <br /> • MW-6 is at the heart of the MtBE plume. <br /> 1 <br /> 1 <br />