HR: 1330h
AN: H43C-04    [Abstracts]
TI: Evaluating Conceptual Site Models with Multicomponent Reactive Transport Modeling
AU: * Dai, Z
EM: zdai@alltel.net
AF: Advanced Environmental Solutions, LLC, 407 West Main Street , Lexington, SC 29072 United States
AU: Heffner, D
EM: dheffner@advenvsoln.com
AF: Advanced Environmental Solutions, LLC, 407 West Main Street , Lexington, SC 29072 United States
AU: Price, V
EM: vprice1@alltel.net
AF: Advanced Environmental Solutions, LLC, 407 West Main Street , Lexington, SC 29072 United States
AU: Temples, T J
EM: ttemples@sc.rr.com
AF: Advanced Environmental Solutions, LLC, 407 West Main Street , Lexington, SC 29072 United States
AU: Nicholson, T J
EM: tjn@nrc.gov
AF: United States Nuclear Regulatory Commission, 11545 Rockville Pike, Rockville, MD 20852 United States
AB: Modeling ground-water flow and multicomponent reactive chemical transport is a useful approach for testing conceptual site models and assessing the design of monitoring networks. A graded approach with three conceptual site models is presented here with a field case of tetrachloroethene (PCE) transport and biodegradation near Charleston, SC. The first model assumed a one-layer homogeneous aquifer structure with semi-infinite boundary conditions, in which an analytical solution of the reactive solute transport can be obtained with BIOCHLOR (Aziz et al., 1999). Due to the over-simplification of the aquifer structure, this simulation cannot reproduce the monitoring data. In the second approach we used GMS to develop the conceptual site model, a layer-cake multi-aquifer system, and applied a numerical module (MODFLOW and RT3D within GMS) to solve the flow and reactive transport problem. The results were better than the first approach but still did not fit the plume well because the geological structures were still inadequately defined. In the third approach we developed a complex conceptual site model by interpreting log and seismic survey data with Petra and PetraSeis. We detected a major channel and a younger channel, through the PCE source area. These channels control the local ground-water flow direction and provide a preferential chemical transport pathway. Results using the third conceptual site model agree well with the monitoring concentration data. This study confirms that the bias and uncertainty from inadequate conceptual models are much larger than those introduced from an inadequate choice of model parameter values (Neuman and Wierenga, 2003; Meyer et al., 2004). Numerical modeling in this case provides key insight into the hydrogeology and geochemistry of the field site for predicting contaminant transport in the future. Finally, critical monitoring points and performance indicator parameters are selected for future monitoring to confirm system performance.
UR: http://www.advenvsoln.com/agu05H08a.htm
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2005 Joint Assembly