RICHLAND — Hanford workers are deliberately contaminating the groundwater at the nuclear reservation.
It’s part of a test project to see if driving chromium that’s already contaminating the soil deeper down to the groundwater would speed cleanup of the remaining pollution along the Columbia River.
“We’re flushing contamination out of the soil that would take decades to slowly come down (to groundwater),” said Mike Cline, the Department of Energy Hanford project director for soil and groundwater.
The contaminated water is then pumped up and cleaned before the groundwater can migrate to the nearby Columbia River.
The initial results of the test, done near the defunct K East and K West reactors, have been “quite spectacular,” said Bill Barrett, vice president of soil and groundwater remediation for DOE contractor CH2M Hill Plateau Remediation.
Chromium can cause cancer in people — it was the drinking-water contaminant addressed in the lawsuit that led to the movie “Erin Brockovich.”
It is particularly harmful to salmon and other aquatic life in the Columbia River, even at levels that meet drinking water standards.
A form of the chemical was widely used at Hanford reactors north of Richland that produced plutonium for the nation’s nuclear weapons program through the Cold War.
Sodium dichromate was added as a corrosion inhibitor to river water that was used to cool Hanford reactors. Soil was contaminated from disposed reactor water and from spills of the chemical and leaking pipes.
The Department of Energy has been tackling hexavalent chromium-contaminated groundwater at Hanford in two ways.
It has been digging up contaminated soil, sometimes down to groundwater in the most heavily contaminated areas near the Columbia River, to prevent chromium from migrating deeper into the soil to groundwater.
In places that groundwater is contaminated, “pump and treat” plants use wells to pump up contaminated groundwater. The chromium is stripped from the water and the clean water is reinjected into the ground.
The three pump and treat plants being used to treat groundwater near the K East and K West reactors along the Columbia River have been working well.
By 2015 the plants had cleaned up most of the plume near the two reactors and were shut down.
But continued checks of monitoring wells in the area showed that chromium in the soil was recontaminating the water, with the chromium again at high levels.
When the Columbia River would rise, the groundwater in the area also would rise and flush more contamination from the soil.
The pump and treat plants were put back into use, again removing most of the groundwater contamination.
But Hanford officials wanted a more permanent fix.
They came up with the idea to see if deliberately driving contaminants into the water could allow cleanup of the contaminated plume once and for all.
Workers installed a system of pipes about 2 feet underground to sprinkle water into the soil over an area of almost an acre above where contamination continued to reappear.
The water goes down through the soil, picking up chromium, until it reaches groundwater about 80 feet deep.
The watering system was turned on in May.
“We saw spikes in contamination at our [groundwater] extraction wells faster than we anticipated,” Barrett said. “But the containment has been good. We have driven down the contamination to near drinking water standards.”
Chrome levels spiked up to as high as 1,650 parts per billion. Drinking-water standards for Washington state are 48 parts per billion and the goal to protect fish is to dilute contamination to even lower levels where the site’s groundwater enters the river.
Soil flushing tests
By mid-August, 27 million gallons of water had been flushed through the contamination zone.
“We’re not getting anymore out,” Cline said on Aug. 13 as the flushing system was shut down.
“Right now it looks very successful,” he said.
But he cautioned it was a test project and groundwater will be closely monitored to see if any contamination comes back. The test likely will be done a second time even if additional chromium is not detected to see if contamination spikes again.
In a typical month before the test, half a kilogram of chromium was removed from groundwater for treatment.
But in June, the soil flushing testing allowed 7 kilograms to be removed, or a little more than a year’s worth, said Ellwood Glossbrenner, the DOE soil and groundwater project lead.
If the results are as good as they initially appear at the K reactors area, the project could be expanded to other reactor areas at Hanford along the Columbia River.
The technology could save decades of cleanup work, with chromium no longer slowly trickling down to groundwater and driving up contamination levels to above drinking water standards, Cline said.