KARST
2006 EPA WIPP FACT SHEET No. 6
Karst in the Area of the WIPP
Some stakeholders bel ieve that the geologic characterization
of the subsurface surrounding the WIPP repository does not
adequately identify the presence of karst. Asa result of these
concerns, EPA agreed to re-evaluate the potential for the pres-
ence of karst at WIPP and the possible impacts of the long-
term containment of wastefor the 2004 WIPP Recertification.
Duringthe 1998 certification, EPA reviewed existing informa-
tion to understand the issue of karst around the Wl PP site. As
a result of that review, EPA agreed that there a re karst features
in the vicinity of the WIPP site, but that karst feature develop-
ment will not impact the containment capabilities of the WIPP
for at least the 10,000-year regulatory period.
As part of the 2004 recertification process, EPA con-
ducted the following activities to further investigate any
potential for karst near the WIPP site.
• EPA examined the geophysical methods suggested by
stakeholders to locate karst.
• EPA conducted a thorough review of the geologic and
hydrologic information related to karst.
• EPA conducted a field trip to re-examine the evidence
of karst around the WIPP site.
• EPA considered all pertinent information that was de-
veloped since EPA's 1998 certification decision.
• EPA reviewed the DOE/Sandia National Laboratory
analysis of the potential for karst.
• EPA also considered public comments on karst.
What is Karst?
Karst is a type of topography in which there are
numerous sinkholes and large voids, such as caves.
Karst is caused when soluble rocks dissolve. Karst
may form when rainwater, reacting with carbon dioxide
from the air and forming carbonic acid, seeps through
the soil into the rock. Soluble rock includes limestone
and evaporite rocks, such as halite (salt) and gypsum.
If substantial and abundant karst features were pres-
ent at WIPP, this could increase the speed at which
releases of radionuclides travel away from the reposi-
tory through the subsurface.
As a result of this in-depth review of the potential for karst
at the WIPP site, EPA again concludes that the WIPP site
does not exhibit evidence of karst; it is highly unlikely that
reactive water could reach and dissolve the Rustler dolo-
mites; and the hydrologic regime at WIPP is adequately
modeled without modeling karst features.
For more information on EPA's karst evaluation go to EPA's
WIPP website or docket, to the Compliance Application
Review Documents, Section 15, and EPA's Technical Sup-
port Document for Section 194.14: Evaluation of Karst at
the WIPP Site.
Fact Sheets in this Series:
Recertification Fact Sheet No. 1
Public Involvement Fact Sheet No. 2
Performance Assessment Fact Sheet No. 3
TRU Waste Inventory Fact Sheet No. 4
Groundwater Fact Sheet No. 5
Karst
Fact Sheet No. 6
United States Environmental Protection Agency I Office of Air and Radiation (6608J) I EPA402-F-06-011 I March 2006
www.epa.gov/radiation/wipp
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