Hanford, a 586-square-mile (1,520-square-kilometer) nuclear site located in southeast Washington U.S., is considered by many to be the largest, most complex cleanup effort in the world. The Department of Energy and CH2M HILL continue to search for new technologies to address Hanford’s contaminants. The main challenge is developing systems, such as the 200 West Pump and Treat System, that are cost-effective and able to reduce contamination to to meet regulatory standards.
Created in 1943 to support the production of plutonium for the country’s nuclear weapons program, the Hanford Site was integral to the United States defense mission for decades. The site included nine nuclear reactors along the Columbia River and five chemical processing facilities in the center, connected by a system of roads and railways. Then in 1989, as the Cold War ended, production operations ceased and the Hanford Site mission shifted from plutonium production to environmental cleanup.
During more than 30 years of production, approximately 475 billion gallons (1.8 trillion liters) of contaminated liquids were discharged directly into the soil through evaporation ponds and infiltration structures. The result was more than 43 million cubic yards (33 million cubic meters) of radioactive waste and over over 130 million cubic yards (100 million cubic meters) of contaminated soil. The waste generated by years of production has led to contamination of the aquifer. The U.S. Department of Energy (DOE) and its main contractor for groundwater remediation, CH2M HILL Plateau Remediation Company (CH2M HILL), are working together to develop innovative strategies to address the contamination and return the groundwater to drinking water standards.
Urgency – Why the Rush?
Design, Build, and Operation
CH2M HILL has delivered some of the largest water, environmental and infrastructure programs in the world. The DOE contracted CH2M HILL to design, construct, test and operate a new pump and treat facility to keep contaminated groundwater beneath the center of the Hanford Site from reaching the Columbia River. “The treatment system will eventually clean up the groundwater to meet the drinking water standard,” said Foss.
The new facility will be the largest pump and treat facility on the Hanford Site, capable of treating groundwater at a nominal rate of 2,000 gallons per minute or three million gallons per day—enough to supply drinking water for a city of 10,000 people. In terms of treatment stringency, specialized processes remove particles to the parts-per-billion level. The facility will play an integral role in cleaning up one of Hanford’s largest contaminated plumes located in an area near Hanford’s former plutonium processing plant called the “Central Plateau,” a 75-square-mile area near the center of the site. The DOE, CH2M HILL and other site contractors are on target for shrinking Hanford’s active area of cleanup to 10 square miles on the Central Plateau by the year 2015.
“When people think of cleanup at Hanford they usually think of demolishing structures, or removing dangerous wastes,” said Kent Dorr, CH2M HILL vice president of engineering, projects and construction. “But there’s also a lot that needs to be built in order to shrink the site cleanup footprint.” Hundreds of miles of pipelines, pump and transfer stations and a new generation of treatment facilities are now in place that will clean up groundwater on-site for the next 25 years. “That’s an investment that will pay back future generations not just for years, but for lifetimes to come,” said Dorr.
The purpose of the facility, including its construction, is to protect the environment. CH2M HILL is designing the facility to achieve Leadership in Engineering and Environmental Design (LEED) Gold Certification, one of the highest benchmarks set by the U.S. Green Building Council for high-performance green buildings, and the first building to achieve Gold Certification on the Hanford Site.
Meeting the stringent requirements for Gold Certification requires the use of specific materials, and waste handling and construction practices. During construction, for example, the building site must be tightly confined to minimize site disturbance. At least 30 percent of construction materials must be composed of recycled or reclaimed content and more than 50 percent of construction waste must be diverted from landfill disposal. The facility’s design, construction and operation will also meet new DOE-mandated green building standards that address site sustainability, water efficiency, renewable energy, conservation of materials and resources, and indoor environmental quality. This will be all in an effort to leave the Hanford site in a safe state, and clean natural habitats for wildlife and for future generations.
The facility will utilize a two-pronged strategy of plume containment and treatment. First, CH2M HILL will remove the contaminant sources to the extent possible via removal of contaminated structures and excavation of contaminated soils. The 200 West Pump and Treat system will then treat contaminated groundwater and inject it back into the ground. Several integrated approaches must happen as part of this strategy, including an ion exchange system, a series of biological processes, and an air stripper process.
The ion exchange system removes radionuclides from the groundwater. Most systems on the Hanford Site primarily use ion exchange columns to remove contamination. The media in an ion exchange system is designed to attract specific contaminants like Technetium-99 and Iodine-129 and essentially strip the contaminants from groundwater. The ion exchange system is followed by a fluidized bed bioreactor that uses microorganisms to break down contaminants in the water (similar to public drinking water systems that have been used for decades) and to remove nitrate, metals, and some of the volatile compounds like carbon tetrachloride.
A membrane bioreactor system follows the fluidized bed reactor system stripping out more of the volatile compounds; it acts like a filter system to strip out the sludge material produced in the fluidized bed bioreactor. The groundwater then goes on to an air stripper system to remove any remaining volatile compounds.
Finally, the treated water is sent to injection wells that place the water into the ground to replenish the aquifer.
CH2M HILL installed a new network of 15 extraction wells and nine injection wells to help extract contaminated groundwater and re-inject treated water into the ground. Extraction wells, drilled and constructed through a complex mix of boulders, cobble, sand and clay, were as much as 525 feet deep (160 meters) – twice as deep as the average well on Hanford.
Some of the wells are miles from the facility, requiring long-distance monitoring of temperature, pressure and flow changes from each well to signal freezing pipelines or other problems such as pump failure. Three transfer buildings and approximately 35 miles (56 kilometers) of high density polypropylene piping are used to route water from extraction wells to the treatment facility; two more transfer buildings route water from the treatment facility to injection wells.
Hanford Groundwater Future and Impacts
Once the 200 West Pump and Treat System goes online there will be a total of six pump and treat systems operating on the Hanford Site. Combined, their capacity will be 168 million gallons (636 million liters) per month. That is estimated to be 168 municipal water towers. During the next 25 years, the 200 West Pump and Treat Facility alone will treat nominally 24 billion gallons (90.85 billion liters) of groundwater and remove an estimated 110,000 pounds (50,000 kilograms) of carbon tetrachloride, cleaning up the aquifer for future generations. For years after operations cease, the groundwater will continue to be monitored to ensure protection of the aquifer.
“We’re making unprecedented progress in cleaning up the groundwater contaminants along the Columbia River,” said Foss. “We’re working closely with the DOE and using our experience at other projects to meet this exciting challenge, developing methods that are both cost-effective and meet regulatory standards.”
For decades, the chemicals and radiological contaminants percolating in the groundwater created an environmental challenge, threatening not only the site, but the Columbia River.
But that’s soon going to change. “Thanks largely to the state-of-the-art water treatment plant we’re building,” says Foss, “Hanford’s long-term groundwater contamination problem will soon be contained.”
CLICK HERE to watch a short video on Hanford’s groundwater project.
About the Author:
Tania Reyes-Mills is a project communications lead for the Soil and Groundwater Remediation Project with CH2MHILL Plateau Remediation Company.
CH2MHILL is one of the largest contractors on the Hanford Site in charge of remediation. Reyes-Mills establishes avenues of communication within the corporation between senior staff and the workforce. She is also involved in external media relations and public involvement. Prior to working in corporate communications she worked for ABC News in Las Vegas, Nevada. As a journalist, Reyes-Mills shed light on many issues, including stories on Hanford and Yucca Mountain.
She graduated from San Diego State University with a major in Media Management and a minor in Spanish.