Nuclear Decommissioning Report - Hanford’s “Big Dig”: Unique Challenges and Requirements

Nuclear Decommissioning Report

March 2012 Issue

Hexavalent chromium. For most of the world, people think of a carcinogen made famous by Erin Brockovich. But those two words in the remediation world produce respect and careful planning. Hexavalent chromium is well-known in the environmental remediation industry for its ability to travel freely through the soil with water, creating areas of deep contamination in the soil column, while spreading in unpredictable directions based on the type of soils in the area and the obstructions it encounters. Because of the nature of legacy waste sites, although a good idea of what will be encountered is possible through thorough research and planning, it is impossible to predict every problem that will need to be solved. At Hanford’s 100-C-7 and 100-C-7:1 Waste Sites Remediation Project, also known as “The Big Dig” for its size and depth, the properties of hexavalent chromium are challenging the team of Washington Closure Hanford (WCH) and the small businesses on the ground, Sage Tec and Federal Engineers and Constructors (FE&C), to work together and keep the project on track. The team has found that communication is key when the hex chrome plumes are, like much of Hanford, different than what is expected.

History

The Hanford Nuclear Reservation is located in southeast Washington State. It encompasses 586 square miles and is considered by many to be the largest, most complex cleanup effort in the world. It was created during WWII to produce plutonium as part of the country’s nuclear weapons program. Over the next few decades, it was home to nine nuclear reactors spread out along the Columbia River and five chemical processing facilities. Washington Closure Hanford is the prime contractor to the U.S. Department of Energy’s Richland Operations Office for the $2.3 billion River Corridor Closure Project, which includes the land bordering the Columbia River. Within it, cleanup projects are intended to remove contaminants that could enter the river.

The 100-C-7 and 100-C-7:1 waste sites are located approximately 1,115 feet west of the C Reactor building and are associated with the decommissioned water treatment facilities, including the sedimentation basins, clearwells and pump house. The 100-C-7 waste site consists of residual sodium dichromate contamination associated with the filter building/pump room of the reactor. The 100-C-7:1 site is the stained surface soil adjacent to the sedimentation basins found in 2002. More significantly, these waste sites are less than a mile from the Columbia River.

Remedial actions initiated in 2004 found chromium staining at a depth of 15 feet at the 100-C-7:1 subsite, which prompted characterization boreholes and test pits to determine the lateral and vertical extent of the contamination. Subsequent analytical results indicated significant concentrations of chromium throughout the vadose zone (the soil between the surface and groundwater) beneath the site. WCH subcontracted this work out to small business, to the team of Sage Tec and FE&C who began field work in 2011. Sage Tec is a local, woman-owned small disadvantaged business and FE&C is a small business with a decade’s worth of experience at Hanford and other DOE sites. Both subcontractors perform general contractor work in D&D, remediation and construction and have senior personnel with decades of experience in working at nuclear sites, especially in the DOE complex, including design, construction, D&D and environmental cleanup.

Project Scope

The project’s objective is to excavate and properly remove soils contaminated with hexavalent chromium and other types of contamination, piping, metal debris and asbestos, and handle stockpiling and staging of Above Cleanup Level (ACL) and Below Cleanup Level (BCL) materials. Contaminated soils are being packaged in special containers and shipped to Hanford’s Environmental Restoration Disposal Facility (ERDF), a massive landfill well away from the river regulated by the U.S. Environmental Protection Agency that accepts low-level radioactive, hazardous and mixed wastes that are generated during the cleanup activities of the site.

When the project began, Dean Strom, WCH’s project manager for C-7, knew this would be a massive undertaking. “We expect 600,000 tons of the total material will be contaminated and have to be shipped to ERDF. Of that, we expect 40,000 tons will require treatment,” he said. [1]

Once the project began, it was clear that the estimated amounts and complexity of the job would be more than expected. The project presents a number of challenges and both WCH and the Sage Tec/FE&C team had to work closely together, and with other groups and agencies, in implementing solutions that worked for all parties.

Challenge One: Contamination Depths Greater than Expected

During the excavation, the depth of hex chrome was greater than pre-project tests had indicated, as well as the direction of the plumes of contamination which were different relative to their suspected source locations. These findings have resulted in several challenges. “Increasing the depth of the excavations increased the size of the excavation at ground level,” said Shane Bigham, Sage Tec’s project manager onsite. “Because there were additional concrete foundations in these new areas, they had to be abated and removed. These foundations contained piping with asbestos insulation.” The expanded remediation site also contained overhead power lines and poles, which needed to be relocated. This necessitated approvals with other federal agencies and coordinating with another prime contractor.
When these differences in work scope were discovered, the WCH/Sage Tec /FE&C team immediately began working together to find a judicious and safe path forward, as outlined in the general conditions of the contract.

“Having a clear process in place by the prime contractor for what to do when differing site conditions are identified enables our companies to work seamlessly together to get the work done, even if the scope changes,” said Laura Shikashio, president of Sage Tec. “We proceeded with work as soon as the required paperwork was filed and approved. It helps to have companies working together that respect each other and have a mutual understanding of what needs to be done to succeed.”

Because the extent of the chromium contamination grew, so did the tons of remediation. To date, approximately 950,000 bank cubic meters of soils have been excavated, sorted and stockpiled per its waste category, and over 400,000 tons of material has been shipped to ERDF. As of today, excavation is 100 percent complete at C-7 and 83 percent complete at C-7:1, which does not include the volume which will expand to the west after power lines are moved. That volume is not yet known.

Challenge Two: Chromium Concentration Greater than Expected

In addition to the depth of contamination, the levels and concentration of hexavalent chromium were also higher than expected, which also presents challenges during excavation and disposal at ERDF. During excavations, this material requires additional sorting and segregation as well as special packaging and shipping. At ERDF, this material is classified as Land Disposal Restricted (LDR), which means it has to undergo further complex and time consuming treatment prior to final disposal.

Challenge Three: Recycling of Scrap Materials

There has been the recycling or reuse of large quantities of scrap metal and concrete under this project. “We were able to recycle 630 tons of scrap metal,” said Strom. “Recycling of materials is something not easily done, but it is worth it.” [1] The scrap metal included piping, rebar, grating and structural steel. It was subjected to a robust radiological survey screen to ensure no contamination entered the debris stream. The recycling created many benefits including:

  • It saved WCH nearly $300,000 in disposal costs;
  • It provided a local recycler with work;
  • It will save space in the ERDF landfill; and
  • The metal will be used again.

“Everybody wins,” said Strom. [1] WCH also directed 212,000 tons of clean concrete rubble from C-7 to U Plant, to be used as fill material during cleanup of the former processing facility.

Recycling and the general stockpile areas for a job this large did come with its own challenges. The areas needed to comply with the Native American Graves Protection Act, which under law requires federal agencies and institutions that receive federal funding to return Native American cultural items to their respective peoples. This process created necessary delays while WCH worked with DOE and the five neighboring tribes to put a plan together on how to proceed and obtain the required approvals.

And the Dig Continues

The “Big Dig,” one of many cleanup projects at the Hanford Site under Washington Closure Hanford, is a good example of the challenges inherent in legacy waste sites. Additionally, the Big Dig is one of the most expansive in terms of land mass and material that must be removed, disposed of and treated. Through clear communication and a thorough understanding of the work involved, WCH has worked side-by-side with its small business partners Sage Tec and FE&C. The crew has handled the work with no lost days to injury and accident and has been part of WCH’s recently attaining six million hours without a lost workday injury. Even given the challenges, the campaign is successfully removing massive amounts of the elusive hexavalent chromium along Hanford’s river corridor.

References:
[1] “Earth is Moving at 100-C-7.” The Current. August 2011: 2.

About the Author:


Kristina French is Communications Manager for Federal Engineers and Constructors (FE&C). She has 17 years of experience working in marketing and communications in the scientific disciplines, including working for several engineering, architecture, agricultural and software firms. French has a bachelor’s degree from Washington State University and lives in Richland, Washington, U.S.