24 March 2004

Hydrogeologic Analysis of Bedrock Systems: UNLV and Yucca Mountain

Hard Hats Required” was read on a sign by workshop attendees entering into the Yucca Mountain Proposed Radioactive Waste Repository at the Nevada Test Site last month. Attendees from twenty-one states participated during the three-day workshop at UNLV conducted by the Midwest GeoSciences Group. The workshop featured a field trip to the Nevada Test Site which is located about 100 miles north of Las Vegas.

The workshop Advances in Hydrogeologic Analysis of Fractured Bedrock Systems was conducted this year at the University of Nevada Las Vegas in order to tour inside Yucca Mountain. “For a limited time, non-project-related professionals are allowed access into Yucca Mountain Project tunnel pending Department of Energy approval,” stated Tim Kemmis, one of the workshop coordinators. Kemmis added “The field trip illustrates many of the principles taught during the first day of classroom sessions.”

Rob Hoey of the Maine Department of Environmental Protection observing the absence of seepage and feeling the low humidity shared “…this tunnel is much drier than I expected”. Rob’s comment was indicative of many attendees’ observations due to the depth of the water table exceeding 1,500 feet below the tunnel entrance. The main criterium for storage of high-level nuclear waste at Yucca Mountian is that the facility be secure for 10,000 years. A major concern, however, is rock fracturing and how that would affect ground water seeping into the facility and to the water table. As a consequence, Yucca Mountain is perhaps the most extensively studied fractured rock site in the world.

Field trip leaders from the US Department of Energy pointed out the subvertical faults along the tunnel walls and explained how individual joints and fractures were mapped throughout the proposed tunnel area. Another concern about the site is the timing and magnitude of faulting bounding the Yucca Mountain area. Field trip participants observed trenches where extensive investigations were made of the age and displacement of nearby faults. Other concerns about the site were discussed by Yucca Mountain Project staff, including prediction of long-term climatic change and the effects of rock heating and cooling related to long-term storage of the nuclear waste.

Ken Bradbury and Maureen Muldoon from Wisconsin, Willard Murray and Glenn Duffield from the east coast, and John Peck from Las Vegas were the primary course instructors. The course focused on combining fundamental approaches with recent advances in hydrogeologic site characterization of fractured bedrock settings. Rob Hoey reported that site characterization and aquifer testing topics are much more comprehensive than other courses dedicated to the subject of fractured bedrock.

This Midwest GeoSciences Group recently announced that they are offering the same course again next year at the Desert Research Institute at UNLV with a field trip into Yucca Mountain again.