Work to keep uranium from leaching into the Columbia River at Hanford just north of Richland is being expanded after a test showed good results.
Wells are being drilled now to inject a solution into the ground to bind the uranium contaminating the ground to the soil and prevent it from migrating into the groundwater and then into the river.
Much of the soil contaminated with uranium at the Hanford 300 Area has been dug up down to 15 feet, removing the majority of the contamination that could reach the groundwater.
Hanford officials had hoped that would take care of the issue.
The plan was to then let the contamination in the groundwater dissipate over time, improving the groundwater quality to drinking water standards.
Instead, the groundwater has been repeatedly recontaminated. As the Columbia River rises, so does the groundwater, continually rewetting soil and allowing more uranium to dissolve into the groundwater.
Of particular concern is a three-acre area contaminated by an old waste site. At certain times of the year, monitoring has shown places in the acreage where the contamination has spiked to three times the drinking water standard.
During World War II and the Cold War when plutonium was made at Hanford for the nation’s nuclear weapons program, the 300 Area just north of Richland was used to make uranium into fuel for reactors.
As a byproduct of the process, 60 tons of dissolved uranium was released into the ground in disposal ponds and trenches.
During World War II and the Cold War when plutonium was made at Hanford for the nation’s nuclear weapons program, the 300 Area just north of Richland was used to make uranium into fuel for reactors. As a byproduct of the process, 60 tons of dissolved uranium was released into the ground in disposal ponds and trenches.
Hanford contractor CH2M Hill Plateau Remediation Co. conducted a test project for the Department of Energy last year, injecting phosphate into the ground.
The expectation was that it would combine with uranium in a carbonate form to make autunite, a uranium phosphate mineral that’s bright yellow and flaky. It’s a stable mineral that does not readily dissolve when hit by water, keeping it in the soil instead of in the water.
“It did very well,” said Marty Doornbos, CH2M director of the soil and groundwater project at Hanford.
After the river rose, three monitoring wells showed groundwater meeting drinking water standards in areas where groundwater historically had too much uranium, he said.
The test, done on three-quarters of an acre, also showed that the best way to get the phosphate into the soil just above the groundwater was through injection wells rather than the other method attempted, a drip system with hoses buried about six feet under the soil.
24 monitoring wells will be drilled
48 injection wells will be drilled
As the weather began to improve in recent weeks, work began to drill wells for the expanded project.
Two dozen wells are being added for monitoring and four dozen wells to inject phosphate in the remaining 2.25 acres. It will be injected in a zone from about 25 feet deep to 35 feet deep just above groundwater.
Each well can spread phosphate in a 40 foot radius, and some overlap of phosphate zones are planned between wells to make sure that the entire area is treated.
The phosphate starts binding up the uranium immediately, but the effect becomes stronger over time, Doornbos said.
The injection of the phosphate in the new wells will be done in August and September when the river is low so as much soil as possible can be saturated with the phosphate, said Mike Cline, DOE director for the Hanford soil and groundwater division.
DOE is continuing to follow the plan of natural dissipation of uranium in the 300 Area groundwater, with the treatment of the three-acre area enhancing it, he said.
The uranium reaching the Columbia River from Hanford is only adding to other sources also contaminating the river.
About 10 times as much uranium from fertilizer and uranium that is naturally in the ground enters the river from three irrigation outlets on the Franklin County side of the river. The Yakima River also has been estimated to add 25 times as much uranium to the Columbia River.