Challenge

The US Department of Energy (DOE) created the Idaho Cleanup Project in order to safely close and dispose of nuclear and radioactive waste at a former nuclear base in Idaho. The Subsurface Disposal Area (SDA) within the Radioactive Waste Management Complex in particular needed to be closed and covered, but the cover needed to meet a required 1,000-year performance period and all state and regulatory requirements for radioactive and hazardous waste.

Solutions

The prime contractor for the project, contracted GLA to complete the engineering design for the final evapotranspiration (ET) cover at the SDA. Our team began by summarizing and categorizing the regulatory and other requirements in a technical and function requirements document. GLA then completed site investigations to produce a cover design that is site-specific to climate, soils, nutrients, and seeding conditions.

Based on the regulatory and site-specific requirements, our team produced a cover design that achieves the best possible performance for the 97-acre landfill. This completed design documents include our team’s design for the cover, including construction plans, technical specifications, and a design report. The primary cover layer is an ET soil cover underlain by a grading layer of construction debris and general fill material. Our design also included provisions for monitoring, including a lysimeter moisture collection system, a climate station, and an automated data recording system. The cover design was reviewed and approved by the DOE, the U.S. Environmental Protection Agency, and the Idaho Department of Environmental Quality, meeting all required state and federal regulations.

Results

GLA’s cover design achieves the best possible performance for a number of goals. The cover is designed to minimize moisture seepage to equal or outperform standard regulatory designs and to minimize wind damage. It provides the necessary barrier to radioactivity and intrusion prevention performance while maximizing design life to meet a 1,000-year performance period. The design is soundly engineered, constructible, and cost-effective, providing a wide range of benefits to our client while also ensuring protection from radioactivity to the environmental and human health.