Print this pageContamination Potential Mapping Using Geographic Information Systems (GIS) within the Savannah River Site (SRS), South Carolina
BENNETT, CHRIS, JAMES BOLLINGER, JOHN REED, ELZBIETA COVINGTON, JAMES RINE, JOHN SHAFER, RICHARD BERG
Methodology utilizing GIS technology was developed to evaluate and map the "contamination potential" of the upper groundwater flow system (above the shallowest, regional confining zone) at the General Separations Area (GSA) within DOE's SRS. The methodology involves mapping the geology in 3D while closely defining aquifer vs. confining units, soil properties, and area hydrology. Integration of these data is best accomplished using a stack-unit map. A stack-unit map shows successions of geologic materials in their order of vertical occurrence, to a specified depth or boundary. Each discrete map area represents a unique succession differentiated on the basis of lithology, thickness of individual units, hydraulic conductivity, or other material properties. The stack-unit map for the GSA consists of multiples of 79 unique combinations of stack-unit successions within 470 polygons. For the GSA, contamination potential is mapped primarily by considering the variability of hydraulic conductivities of the stack-unit successions, rank ordering them, and then overlaying soil properties. For example, an aquifer mapped within an area of high contamination potential is overlain by the thickest accumulations of sand and gravel, minimal or no fine-grained layers, and by surface soils with low organic matter (low attenuation potential) and high hydraulic conductivities. An aquifer mapped with a low contamination potential is protected by overlying fine-grained deposits and surface soils with higher organic matter. This resultant map is easy to revise with GIS technology.