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RICHLAND, Wa. — In the 1950s, large cask trucks, heavily shielded to provide protection against radiation, drove north from near Richland with loads of highly radioactive waste that Hanford officials did not want buried too close to town.

At a site along the main Hanford highway six miles north of the city, they would back into position to dump their loads down pipes deep into the ground.

In between loads, each layer of waste would be topped with soil or grout to reduce the radiation emanating from the pipe.

More waste was buried directly in the soil at the 7.5 acre 618-10 Burial Ground.

One of the most hazardous burial ground cleanup projects along the Columbia River at Hanford, it was left as one of the last waste sites to be tackled.

But this week, after a decade of work to figure out what was buried there and then safely dig it up, the site is quiet.

Late last week crews finished replanting the area with 76,000 shrubs plus grasses and other native plants.

“It’s nice to see the area match the surrounding terrain and get back to what it used to look like,” said Mike Kruzic, the site’s revegetation project manager for Department of Energy contractor CH2M Hill Plateau Remediation Co.

Radioactive lab waste

From 1954 to 1963 the burial ground was used for some of the worst waste generated at the Hanford nuclear reservation’s 300 Area just north of Richland.

At the 300 Area uranium fuel was fabricated to be irradiated at Hanford’s reactors to produce plutonium for the nation’s nuclear weapons, and the area was used to research many of the processes used to produce plutonium, creating highly radioactive and chemically contaminated waste.

Much of the worst of the laboratory waste created over nearly a decade was disposed of at the 618-10 Burial Ground.

Cans, ranging from the size of juice cans to paint cans, were dropped down 94 vertically buried pipes. Other waste was buried directly in the ground.

Workers dug down to 30 feet to retrieve about 2,200 drums and other miscellaneous containers of waste, including a 20,000-pound chamber once used to decontaminate equipment in the 300 Area. It had to be lifted out with a crane.

But the most challenging work was removal of the vertically buried pipes in one corner of the burial ground, which were suspected of having some of the most radioactive waste at the site.

Unusual burial

“There were a number of people who thought this project, the remediation, couldn’t be done safely,” Kruzic said.

But former contractor Washington Closure Hanford came up with a method to remove the waste in the pipes that reached about 20 feet deep, while protecting workers. CH2M took over when Washington Closure’s contract expired, with most environmental cleanup along the Columbia River completed.

Most of the pipes were made of corrugated piping or five 55-gallon drums welded into a pipe.

Crews drove an overcasing vertically into the soil to surround them and then used an auger to chew through the pipes.

The soil within the overcasing, bits of pipe and the radioactive waste were mixed together, scooped out and incorporated in concrete-like grout for disposal.

The remaining 14 pipes were made of heavy-gauge steel, a surprise not recorded in the historical records that nuclear reservation workers had searched before starting cleanup.

Because the auger was not tough enough to chew through them, workers dug up the soil around each of the pipes until the top four or five feet of the pipe were exposed.

Then an open box with a hole in the bottom was fitted over each steel pipe.

A soupy grout mixture was poured into the box and a hydraulic shear on the end of an excavator was lowered into the grout to munch up the steel pipe and waste contained in the mixture.

Between the time cleanup started in April 2011 and was completed in late 2017, some 528,000 tons of contaminated soil and debris were removed, said Lorna Dittmer, environmental director for CH2M’s river risk management project.

Waste was taken to a lined, central Hanford landfill miles from the Columbia River for disposal.

2 more sites

The work included two nearby waste sites that were too close to address until 618-10 was completed.

One was a small site where testing was done using a radioactive tracer material to track soil contamination.

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But the second was used to dispose of liquid contaminated with uranium and fossil fuels by dumping them into the ground.

CH2M workers excavated the dump site down to groundwater, about 68 feet deep.

With the huge holes dug for the liquid disposal site and the 618-10 Burial Ground, space for infrastructure for the cleanup and space to pile up clean soil removed during excavation, the disturbed area stretched over about 120 acres. That’s the size of about 90 football fields.

The final step was returning the land to what it looked like more than 60 years ago, Kruzic said.

Returning to nature

Subcontractor Environmental Assessment Services of Richland workers spent the summer driving around Hanford and hand collecting seeds from native plants they spotted.

“The intent is to have locally derived seeds that are adapted to the weather, the environment, so they are more likely to be successful growing,” Kruzic said.

Seeds from 40 species were collected. Shrubs like big sagebrush, antelope bitterbrush and snow buckwheat were grown in nurseries, with plants just a couple inches tall hand planted in the sandy soil north of Richland.

Some of the species were requested by the tribes, including coyote tobacco, a wild tobacco that grew in the area of the 618-10 Burial Ground.

Few seeds were available for certain species, like mariposa lilies and yellowbell. They were planted in groupings, from which they are expected to spread.

Native grass seeds, including Sandberg’s bluegrass and Indian ricegrass, were purchased from local providers.

Some seed was broadcast onto the ground and then covered with straw, which will help protect young plants from the cold and keep birds from eating the seed.

Planting started in mid November to take advantage of the rainfall from then until February.

Roots will grow and seeds will start to germinate in the winter, Kruzic said.

The plantings will be evaluated annually to determine how different plant species are faring, said John Neath, the DOE river corridor closure supervisor for field remediation.

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