The INL and the Snake River Plain Aquifer
A recent study by the U.S. Geological Survey of the Snake River
Plain Aquifer below the Idaho National Laboratory may have caused
some public concern about what we are doing to protect the aquifer.
Following is an updated fact sheet about the INL and the aquifer
which we hope will answer questions you may have about this topic.
If you have other questions or need more information, please contact
Brad Bugger, U.S. DOE public affairs officer, at (208) 526-0833.
This unit is one of several that is used to "vacuum" volatile organic contaminants from the zone beneath the buried waste, removing them before they migrate into the Snake River Plain Aquifer below.
The Snake River Plain Aquifer underneath the Idaho National
Laboratory is one of the most productive groundwater resources in
the U.S. Each year about 2 million acre-feet of water is drawn from
the aquifer. Approximately 95 percent of the water withdrawn from
the aquifer is used for irrigation, 3 percent for domestic water,
and 2 percent for industrial purposes. The aquifer is the primary
water source for more than 280,000 people in southeastern Idaho.
Although not the only source of contamination, historic activities at
the Idaho National Laboratory have affected the quality of the aquifer
water. In the past, the INL employed industrial waste disposal practices
common at the time that included injecting contaminated waste water
directly into the aquifer. Some of these practices led to contamination
of the groundwater below some areas of the INL with heavy metals,
chemicals and radioactive elements. These waste disposal practices are
no longer used and are prohibited under current environmental
regulations. Other waste disposal practices, including burying materials
contaminated with radioactive and hazardous materials, have also
contributed to aquifer contamination in the past.
For more than two decades, the U.S. Department of Energy, governed by
federal and state laws, has been cleaning up the aquifer below the INL
and taking actions to protect it from additional contamination. While
some of the groundwater below the INL is still contaminated, in more
than 50 years of groundwater monitoring no contaminants have been
detected near or outside the INL boundary in concentrations exceeding
federal safe drinking water standards.
Recent monitoring by the U.S. Geological Survey, Idaho Department of
Environmental Quality, and INL site contractors in wells near the
southern boundary of the INL found concentrations of the wastewater
constituent tritium, a radioactive form of hydrogen, at detectable
concentrations. These concentration levels were above what is normally
considered �background levels,� in deep layers of the aquifer. Previous
monitoring at the INL did not allow for collection of samples at the
depths these constituents were found. But it is important to note that
the concentrations of these newly-discovered contaminants were still
well below federal safe drinking water standards.
Over the past two decades, DOE and its regulating agencies, the U.S.
Environmental Protection Agency and the Idaho Department of
Environmental Quality, have undertaken scientific studies at the nine
facility areas at INL to understand the extent to which past activities
contaminated the groundwater. The studies required under the federal
Superfund law were to determine if cleanup was needed to reduce risks to
within legally acceptable limits, and if so, what cleanup measures were
The agencies determined that past activities at Test Area North, the
Advanced Test Reactor Complex (formerly called the Test Reactor Area),
the Radioactive Waste Management Complex, the Idaho Nuclear Technology
and Engineering Center (formerly known as the Idaho Chemical Processing
Plant) and the Central Facilities Area contributed contaminants to the
aquifer in concentrations requiring cleanup of the aquifer and/or of
sources of the contamination. Those cleanups are either under way and
progressing well, or are complete and undergoing monitoring to confirm
Studies showed that the aquifer didn�t require remedial actions at
the four other facilities: the Naval Reactors Facility, Experimental
Breeder Reactor-1, the Power Burst Facility/Auxiliary Reactor Area, and
the Materials and Fuels Complex (formerly called Argonne National
A Remedial Investigation/Baseline Risk Assessment for the Radioactive
Waste Management Complex � where radioactive and hazardous waste has
been disposed over several decades -- was completed and made public in
May of 2006. The study found that a small portion of the aquifer near
the facility had been contaminated, and predicted that additional
contaminants would reach the aquifer if no protective action were taken.
The only widespread contaminants from the complex to be found in the
aquifer are volatile organic contaminants � particularly carbon
tetrachloride (�carbon tet�). The carbon tet found in the aquifer is
attributed to waste buried at the disposal site because it has not been
discovered in the aquifer upgradient from the Radioactive Waste
Beginning in 1996, vapor vacuum extraction from the �vadose zone�
(the area between the surface of the waste disposal area and the
aquifer, which is about 600 feet down) has been used to reduce the
amount and concentrations of carbon tet that reaches the aquifer.
Historically, concentrations of carbon tet that exceeded safe drinking
water standards were found in seven different monitoring wells on the
INL Site. After continuous treatment with vapor vacuum extraction and
the beginning of the excavation of waste containing carbon tet, the
latest aquifer monitoring in May, 2010 showed levels exceeding safe
drinking water standards in only one monitoring well.
In 2008, DOE and its regulators agreed on a comprehensive cleanup
strategy for the Radioactive Waste Management Complex. The selected
remedy controls the source of contamination through retrieval of buried
waste, as well as using in situ grouting (using a grout mixture to
stabilize potentially mobile contaminants), continued vapor vacuum
extraction of carbon tet, and eventually, a barrier over the surface of
the remaining buried waste. The effectiveness of these measures will be
monitored long-term, and access and control of the area will be
controlled over time.
Retrieving waste reduces inventories of carbon tet. In situ grouting
reduces mobility of two potential contaminants � technetium-99 and
iodine-129 -- which are found in the waste buried there. Operating the
existing vapor vacuum extraction and treatment system continues to
remove and treat carbon tet � and other volatile organic compounds � in
the vadose zone. The extraction and treatment system, coupled with waste
retrieval, addresses the greatest and most imminent threat to
Meanwhile, a record of decision was completed in May 2007 for the
Idaho Nuclear Technology and Engineering Center�s tank farm contaminated
soil and contaminated groundwater. The record of decision was based on a
study completed in 2006 that determined the nature and extent of
contamination, assessed risks to people and the environment, and
concluded that action was necessary to protect workers and the Snake
River Plain Aquifer.
Multiple approaches will be used to reduce infiltration of waster
through the contaminated tank farm soils and to the shallow �perched
water� (a zone of water about 110 below the tank farm), where most of
the contaminants of concern to the aquifer reside. This will include
various water control measures, such as installation of an asphalt cover
over the tank farm and surrounding area; monitoring of perched water
levels as an early detection system for underground pipe leaks; and more
intensive storm water management. Once the INTEC facility is closed, a
final, thick soil cover will be installed that is designed to accept and
dispense moisture to plants at the surface, while limiting water
infiltration to the underlying cover layers. Controlling water at this
site will help eliminate a potential �driver� of surface and sub-surface
contaminants into the aquifer below.
In 2009, a record of decision was signed for site-wide groundwater at
the INL. The record of decision was based on a multi-year environmental
investigation of the aquifer beneath the site, and concluded that
groundwater leaving the INL site boundary will continue to be safe for
domestic and agricultural uses. This investigation was responsible for
regional aquifer concerns related to the INL that could not be addressed
on an area-specific basis, or any other areas at the INL that were not
covered by other investigations.
Based on decades of sampling by several agencies and institutions,
and on computer modeling results, the DOE and its regulatory agencies
agreed that water leaving the INL boundary currently meets established
drinking water standards and will continue to do so in the foreseeable
future. That is why the three agencies � the U.S. DOE, U.S.
Environmental Protection Agency and the Idaho Department of
Environmental Quality � selected a �no action� approach that will
include ongoing monitoring to assure water quality remains high over
Finally, DOE is required to complete five-year reviews as long as
contaminants remain in place above risk-based levels to ensure the
selected remedies continue to protect workers, the public and the
environment. DOE will monitor the groundwater over the long-term to
assure the accuracy of computer modeling which predicts the water
leaving site boundaries will be safe to use, and that contaminants do
not migrate off the INL site at levels of concern.
Editorial Date September 23, 2010
By Brad Bugger