IDAHO FALLS, Idaho – EM and cleanup contractor Fluor Idaho recently finished capping most of the Idaho Site tank farm with asphalt to reduce or eliminate the movement of water through contaminated soil to the Snake River Plain Aquifer 475 feet below the Idaho Nuclear Technology and Engineering Center (INTEC).
The asphalt paving will prevent precipitation from reaching a contaminated body of water about 130-140 feet beneath INTEC. It resulted from historic leaks in piping and valve boxes at the tank farm, which accepted millions of gallons of liquid waste from spent nuclear fuel reprocessing until the early 1990s. Known as a perched water zone, the body of water was created when facility discharges and precipitation percolated into the ground, accumulating above a sedimentary layer of ground.
“The asphalt mix design along with a surface seal coat that we used for this project prevents water infiltration, and combined with additional surface water controls in and around the tank farm, we hope to eventually dry up the underlying body of contaminated water,” said Fluor Idaho Project Engineer Dean Shanklin.
Workers paved about two-thirds of the 5-acre tank farm in 2017. Once EM finishes emptying three more tanks and treats the liquid waste they contain, crews will clean and grout all remaining tanks under the Resource Conservation and Recovery Act. Ultimately, EM will install an engineered soil cover several feet thick over the entire tank farm and close the area under the Comprehensive Environmental Response, Compensation, and Liability Act.
Crews installed about a mile of lined drainage ditches to collect rain and snowmelt and divert it to a lined evaporation pond east of INTEC. Shanklin said Fluor Idaho’s Environmental Restoration Program monitors INTEC for leaks from underground piping and buildings, primarily through the use of the perched water monitoring well network. Over the last 10 years, the program has eliminated over 80 water discharges from the 65-year-old facility.
“The asphalt cap over the tank farm, although an interim measure, is an important step in not just minimizing the infiltration of water in the area, but also getting to the final closure of the tank farm,” Shanklin said.
The aquifer is the primary drinking and irrigation water source for more than 300,000 Idahoans.