Frequently Asked Questions

Answers to some of the most frequently asked questions related to the Groundwater Remediation Project are provided on this page. If you would like to ask a question, please send an e-mail to Karin Nickola.

What is the Central Plateau and where is it located?

The Central Plateau is a 75-square-mile area near the middle of the Hanford Site that includes the 200 East and West Areas. Numerous facilities formerly used for producing nuclear materials, as well as Hanford's 177 underground tanks for storing high-level radioactive waste, are located in the 200 Areas.

What is the vadose zone?

The vadose zone is the soil and rock between the ground surface and the water table. In the vadose zone, spaces between soil and rock are filled with air and water. At the water table, these spaces become entirely filled with water.

How much contaminated groundwater is there at Hanford?

As a result of past disposal practices, about 80 square miles (207 square kilometers) of Hanford's groundwater has contaminant levels greater than federal and state drinking water standards. The contaminated groundwater does not threaten drinking water supplies, but some contaminated groundwater has reached the Columbia River.

What contaminants are present in groundwater at Hanford?

The major chemical contaminants present in Hanford groundwater include carbon tetrachloride, chromium, and nitrate. Major radioactive contaminants include iodine-129, strontium-90, technetium-99, tritium, and uranium.

How much liquid waste was disposed to the ground at Hanford?

According to estimates, almost 450 billion gallons (more than 1.7 trillion liters) of liquid waste, some containing radionuclides and hazardous chemicals, have been released to the ground on the Hanford Site since 1944. Many of the large volume discharges have reached the groundwater, while the more concentrated low-volume liquid wastes have yet to reach the water table.

What is the difference between the groundwater and the aquifer?

Groundwater is the water that fills the pores or cracks between grains in a layer of sediment or rock. Groundwater from the Hanford Site can reach the Columbia River in days, months, or years, depending on the geology and how far it has to travel. During this time, many of the contaminants are decreased by natural decay.

An aquifer is a geologic layer that allows water to pass through easily, with all of its pores saturated with water.

The water table at Hanford ranges from less than about 3 feet (1 meter) near the Columbia River to more than 328 feet (100 meters) in the center of the Site. The water table is the top of an unconfined aquifer.

An unconfined aquifer is an area of water that moves easily through the ground. Depending on the geology of the area, groundwater may rise to the surface through springs or seeps, flow laterally into nearby rivers, streams, or ponds, or sink deeper into the earth. At Hanford, the unconfined aquifer is in a sequence of sandy, gravelly sediment.

A confined aquifer is an area of water contained between solid layers of soil. Confined aquifers at Hanford occur beneath clay or basalt layers. Layers of dense, impermeable basalt rock prevent Hanford's groundwater contaminants from entering deep confined aquifers beneath the site. However, in some places the top impermeable layer of basalt is absent.

What is a groundwater plume and how many are there at Hanford?

A plume is a volume of air, soil, or water containing contaminants. Remediation technologies are being used to treat plumes containing carbon tetrachloride, chromium, strontium-90, technetium-99, and uranium.

What are the risks to public health and the environment from Hanford's groundwater?

Contaminated groundwater beneath the Hanford Site is not a primary source of drinking water and is not used for irrigation. Therefore, it does not represent a significant risk to human health. From an environmental perspective, chromium contaminated groundwater entering the Columbia River through spring and seeps may represent a risk to salmon. Remedial actions to address these risk have been underway since 1996.

How many waste sites exist at Hanford?

More than 800 waste sites have been identified at Hanford. During nuclear materials production, solid and liquid wastes in barrels were buried in pits, burial trenches, and landfills. Cooling and waste water was stored in cribs, ponds, trenches, and French drains, while some facilities disposed waste directly to the soil. In addition, there are 177 underground tanks used to store high-level radioactive waste at Hanford. These tanks contain more than 53 million gallons (more than 200 million liters) of high-level and low-level waste.

What are the risks to public health and the environment from Hanford's waste sites?

These waste sites represent a direct exposure risk from ionizing radiation to Hanford Site workers, but represent no significant risk to the off-site public. The risk from the waste sites lies in contaminant migration into the groundwater that may ultimately flow into the Columbia River. Numerous activities are underway to characterize and remediate waste sites to prevent contaminants from entering the groundwater. An extensive environmental sampling program has been ongoing at Hanford to evaluate the potential risk to plants and animals, and although some elevated levels of radioactive contamination have been found in waste sites, no impacts have been observed that threaten the health of the natural environment.

What is the science & technology roadmap?

The science & technology roadmap is a process enabling problem holders -- such as DOE, regulators, tribal governments, stakeholders, and remediation contractors -- to come together with problem solvers -- such as scientists and engineers from universities and DOE's national laboratories -- to define problems and establish paths for solutions.

What is the System Assessment Capability?

The System Assessment Capability is an assessment tool that enables users to model the movement of contaminants from all waste sites at Hanford through the vadose zone (the soil between the earth's surface and groundwater), groundwater, and the Columbia River and estimate the impact of contaminants on human health, ecology, local cultures, and the local economy.

What is a pump-and-treat?

A pump-and-treat system is used to pump contaminated groundwater from an extraction well to the surface where contaminants are removed. Treated water is returned to the groundwater upstream, helping flush contaminated water toward the pump-and-treat system for further extraction.

Pump-and-treats reduce the amount of contamination entering the Columbia River until a final cleanup solution is in place. Five pump-and-treat systems are currently in use at Hanford to remove carbon tetrachloride, chromium, strontium-90, technetium-99, and uranium from the groundwater.

What is In-Situ Redox Manipulation?

In-Situ Redox Manipulation (ISRM) treats groundwater using a chemically reactive treatment zone established within the groundwater itself. As groundwater naturally flows through this zone on its way to the Columbia River, toxic chromium is chemically converted to a non-toxic form. The treated groundwater then continues to flow through the zone and discharges into the river.

How many underground waste tanks are there at Hanford?

There are 149 single-shelled and 28 double-shelled tanks at the Hanford Site used for storing high-level radioactive waste from past defense production activities. The tanks are located in the Central Plateau's 200 Areas. The Central Plateau is a 75-square-mile area near the middle of the Hanford Site.

How many wells are monitored regularly at Hanford?

More than 700 groundwater-monitoring wells were sampled in FY 2002. In addition, monitoring was performed at 24 Resource Conservation and Recovery Act (RCRA) sites, 5 liquid or solid waste sites, and 11 Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) sites. The federal government (U.S. Department of Energy and its predecessors) has monitored groundwater on the Hanford Site since the 1940s to help determine what chemical and radiological contaminants have made their way into the vadose zone and groundwater.

What is CERCLA?

CERCLA, or the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, is a federal law enacted in 1980 and amended in 1986 to include cleanup of federal facilities. CERCLA governs the cleanup and restoration of inactive waste sites containing hazardous, toxic, and/or radioactive substances.

What is RCRA?

RCRA, or the Resource Conservation and Recovery Act of 1976, is a federal law enacted in 1976 to address the treatment, storage, and disposal of hazardous waste. In 1985, RCRA was amended to include hazardous wastes and constituents containing radioactive and hazardous mixed wastes.