Hanford crews, with the help of bacteria, are attacking an 80,000-gallon spill of diesel fuel near the Columbia River at Hanford.
It's part of the final phase of environmental cleanup at Hanford's N Reactor, where 900,000 tons of contaminated soil and building rubble have been hauled to a lined landfill in central Hanford.
Eight of Hanford's nine plutonium-production reactors that lined the Columbia River depended on coal-fired plants for auxiliary power.
But N Reactor relied on fuel oil and diesel for auxiliary power and to run a series of pumps and facilities near the reactor. N Reactor was Hanford's most modern and longest-running reactor, operating from 1963-87.
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Washington Closure Hanford subcontractor TerranearPMC, based in Irving, Texas, recently started work to dig up fuel oil- and diesel-contaminated soil to about 15 feet deep in several places near the reactor.
Enough contamination lingers in the soil that the smell of diesel hangs in the air.
Workers have unearthed pipes buried five to six feet deep that are blackened with fuel oil. The pipes corroded and leaked. In some cases, spilled fuel would travel along the outside of the underground pipes.
"A lot of dirt is being moved. A lot of trucks are going out," said Rob Meyer, a Washington Closure field engineer, as he stood near a 20-foot-high pile of contaminated dirt yet to be loaded onto trucks to be taken to a Hanford landfill.
"This was flat just a couple weeks ago," he said.
But where the largest spill occurred from transfer pipes and storage tanks, most of the diesel fuel is sitting about 65 to 75 feet deep above the groundwater.
In the past, a trench was dug between the spill area and the Columbia River to intercept contaminated groundwater. Diesel floated on top of the water and, periodically during the '60s and '70s, the fuel would be burned off, said Mark Buckmaster, Washington Closure program manager for field remediation.
Rather than digging up deep contamination at the spill site, Washington Closure plans to use a process called bioventing.
Bacteria feed on the fuel, producing water and carbon dioxide as byproducts. But for the bacteria to flourish and consume the fuel, there must be adequate oxygen available. Bacteria at the large spill site already have used most of the oxygen in the soil.
But last year, during a six-month pilot project, Washington Closure increased the oxygen level in the soil. The project bolstered the bacteria colonies in the soil and reduced the diesel in the soil, Buckmaster said.
The test produced enough success that Washington Closure plans to start a bioventing project in December to clean up contaminated deep soil.
A series of blowers will push oxygen into two injection wells. The oxygen is expected to spread out to a 250-foot radius from each well in the porous ground.
Bioventing is expected to continue for several years. More will be known about the schedule when work is completed to determine how fast the bacteria are consuming the contamination.
Washington Closure estimates Terranear will need to remove about 275,000 tons of contaminated waste, including soil tainted with fuel or other contaminants and miscellaneous pipeline in the final phase of cleanup near N Reactor, excluding some continuing groundwater cleanup.
Crews have walked over about three square miles around the reactor to identify any remaining waste, such as piles of debris.
Historical documents also have been searched. The goal is to restore the area to the way it looked before Hanford was taken over by the federal government during World War II to produce plutonium for the nation's weapons program then and through the Cold War.
When cleanup began, 113 structures stood around the reactor and it had 149 sites where the soil had been contaminated by spills, releases and discharges. They ranged from 10-gallon spills from pipelines to large trenches where cooling water from the reactor was discharged into the soil.
These days, the land around the reactor is a patchwork of dig sites where contaminated soil has been removed, with digs at about 40 sites still planned. The site has about six miles of buried pipeline ranging from a few inches in diameter to up to nine feet in diameter.
The last of the sites are expected to be dug up by Terranear by December 2013. Disturbed sites not replanted this winter will be replanted in late 2014 and early 2015 to take advantage of winter moisture.
-- Annette Cary: 582-1533; firstname.lastname@example.org