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A <br /> Project Descriptions AddanBrown <br /> REGULATORY COMPLIANCE, UTAH <br /> AdrianBrown was retained to evaluate landfill design criteria at a low-level radioactive waste and <br /> mixed waste disposal facility in Utah. The disposal facility is monitored under strict state and federal <br /> regulatory authority that must meet stringent engineering designs and specifications. AdrianBrown <br /> used several sophisticated hydrologic models to demonstrate that the landfill design would be effective <br /> in minimizing environmental impacts and to ensure that human health and the environment would be <br /> adequately protected. AdrianBrown also evaluated the effectiveness of the facility monitoring well <br /> network to detect potential contaminant releases from the disposal cell. <br /> AdrianBrown evaluated the performance of a proposed landfill design in terms of the ability of the <br /> structure to contain contaminated landfill leachate from reaching the water table at levels elevated above <br /> the Utah Ground Water Protection Limits established for the site. AdrianBrown used a three phased <br /> approach to model potential leachate migration from the landfill. The first phase included modeling the <br /> pseudo-steady state infiltration through the landfill using the HELP model. For the second phase, the <br /> infiltration rates predicted by HELP were input into the UNSAT-H model to simulate moisture contents <br /> and advective transport rates through the vadose zone. The third phase involved the vertical transport <br /> through the vadose zone and horizontal transport in groundwater. This was accomplished by using the <br /> PATHRAE transport model which was modified by AdrianBrown to include both the vertical and <br /> horizontal transport components. The modeling results showed that radionuclide and hazardous waste <br /> constituents would be within acceptable risk-based standards at the compliance monitoring wells. This <br /> modeling exercise was instrumental in acquiring the groundwater discharge permit for the facility. <br /> AdrianBrown also conducted extensive plume migration studies to determine the effectiveness of the <br /> current monitoring well network to detect offsite migration of contaminants in the event of potential <br /> liner failure. The proficiency of the facility monitoring well network was quantified using the <br /> Monitoring Efficiency Model (MEMO). The MEMO model incorporates the characteristics of the site <br /> hydrogeology, fate and transport characteristics of a specified contaminant, site and source geometry, <br /> configuration of the monitoring well network, and plume geometry to arrive at a quantified well <br /> efficiency value. Several modeling simulations were performed to evaluate potential impacts under <br /> various hydrologic conditions. The predictive modeling demonstrated that the current monitoring well <br /> network was adequate for early plume detection from random point sources within cell disposal area. <br /> These results provided justification for not adding additional monitoring well coverage, which <br /> subsequently saved the facility thousands of dollars in additional sampling and analysis costs. <br /> I <br /> I <br />