Low-Level Waste Disposal Facility, Oak Ridge (TN, USA)

DSI provided hydrologic, hydraulic and environmental engineering support for the development of the Conceptual Design Report (CDR) for the Low-Level Waste Disposal Facility (LLWDF). Two disposal facilities are proposed to be constructed, a Class I Disposal Facility located on West Chestnut Ridge, and a Class II Disposal Facility located in West Bear Creek Valley. The Class I facility consists of impermeable synthetically lined trenches with approximately one year of disposal capacity for each trench. The Class II facility utilizes the Tumulus concept of above-grade concrete pads with waste encapsulated in concrete vaults.

Conducted water balance studies to determine the impact of post-development runoff on surface waters with respect to water quantity, water quality, and sediment transport. Conceptually designed the final covers and in-trench run-on/run-off controls to cost effectively minimize the waters which require treatment. The Leachate Treatment Facility (LTF) and associated equalization/holding tanks were sized through a detailed routing, storage and trench filling analyses. The HELP 2.0 model was modified to obtain detailed daily flow rates which were input to a DSI water budget program. A 30-well monitoring network was designed. Nested wells were used to assess vertical movement of potential contamination. Intra-trench runoff and run-on pumps were sized via complete hydrograph routing.

Hydrologic and groundwater modeling was conducted to size the leachate collection system pumps and the below-liner pumps, respectively. The groundwater model FEMWATER was used to determine the storm flow and unsaturated zone flows into the below-liner sumps. Hydrogeologic characterization data for West Chestnut Ridge site was utilized in the modeling studies.

Aerial view of LLWDF (courtesy DOE, Oak Ridge)