The Department of Energy is proposing digging up an additional 14 million cubic yards of sand and gravel at Hanford to use as fill material.
It has prepared a draft study proposing expanding nine existing borrow pits closest to where the fill will be needed and adding one new borrow pit. Together they would provide sand and gravel over 10 years. The study does not address borrow pits for silt and soil.
The additional fill material is needed because environmental cleanup work, primarily near the Columbia River, has turned up previously unknown contaminated areas. In addition, other areas have had more contamination that expected.
Near the former C Reactor, soil has been dug up as deep as 85 feet to remove chromium, a chemical once added to reactor cooling water to prevent corrosion.
Contaminated soil is taken to the Environmental Restoration Disposal Facility, a lined landfill in central Hanford for waste contaminated with hazardous chemical or low-level radioactive waste. The clean fill material is needed to backfill the excavations and to allow native vegetation to be replanted.
By expanding multiple borrow pits, the distance sand and gravel would have to be hauled would be reduced and greenhouse gas emissions would be minimized, according to the report.
The borrow pits will be recontoured to "blend stably and naturally with adjacent areas in a pattern that is both aesthetically pleasing and that would support healthy establishment of native (plant) communities" when they are closed, the report stated.
Among the largest expansions would be 35 additional acres of borrow pit up to 121 feet deep near the 100 D Reactor, where chromium-contaminated soil in the area is expected to be dug up to near groundwater. The borrow pit there now covers 64 acres.
The new borrow pit would be between the K and N reactors and would cover 30 acres and be up to 124 feet deep.
The additional area added among all the borrow pits would total 187 acres, bringing the total borrow pit area to 704 acres.
The study, an environmental assessment, is posted at www.hanford.gov. Comments may be sent until Jan. 14 to borrowareaEA@rl.com or Paula Call, NEPA Document Manager, Borrow Area Expansion EA, Department of Energy, P.O. Box 550, Mailstop A2-15, Richland, WA 99352.