5.  Potential Sources of Contamination Already in the Study Area

There are two potential sources of radioactive contaminants in the study area, the NTS and US Ecology’s hazardous waste treatment and disposal facility. If the proposed Yucca Mountain nuclear waste repository opens, it will also be a potential source of radioactive contaminants.

5.1  The Nevada Test Site

The NTS is north-northeast of the study area (See Figure 4.0.2). It occupies 1,375 square miles[1]. Nuclear devices have been tested (detonated) at the NTS since the early 1950s[2]. Both above ground and underground tests were conducted until 1962. Since then, all tests have been conducted in underground shafts and tunnels[3]. A total of 828 underground tests, (consisting of 921 weapons detonations) were conducted between 1951 and 1992[4]. Approximately one third of those tests were conducted near or below the water table[5]. Most of the tests were conducted in the valley fill and volcanic rock units[6]. The last nuclear explosion at the NTS occurred in 1992[7]. The DOE currently conducts subcritical nuclear tests at the NTS [8].

 

The tests generated large amounts of tritium[9] as well as other radioactive contaminants. Groundwater samples collected from eight wells installed in and near detonation cavities[10] have displayed tritium activities between 113,000 pCi/L and 160,000,000 pCi/L[11]. These activities are extremely high[12]. The areas where the high tritium activities have been detected are in the northwest portion (Pahute Mesa) and the east-central portion (Yucca Flat) of the NTS[13].

 

Lower tritium activities have been found in groundwater on other parts of the NTS, as well as in groundwater down-gradient of (in the direction of flow from) the NTS. These areas include Pahute Mesa, both within the NTS and just west of the NTS boundary[14], the central portion of the NTS, the northeastern portion (Yucca Flat), and the southeastern portion (Frenchman Flat). Tritium activities in these areas ranged from 20 pCi/L to 564 pCi/L[15]. These tritium activities could be the result of the atmospheric testing of nuclear weapons rather than underground testing (see Appendix 12.2). However, their proximity to underground nuclear detonation sites makes it likely that they are associated with these detonations.

 

In addition to tritium, gross alpha and gross beta activities have been detected in samples from wells on and near the NTS. These activities may be due either to the decay of naturally occurring radionuclides, or radionuclides produced by nuclear testing. It is likely that testing caused some of the higher activities[16].

 

Contaminated groundwater also occurs around the E-tunnel in the north-central portion of the NTS.  The tunnel was the site of nuclear tests. Groundwater seeps out of the tunnel and the seepage is collected in five basins down slope of the tunnel portal[17].  Tunnel seepage contains high tritium activities as well as strontium-90, cesium-137, plutonium-238, plutonium-239/240, and americium-241[18].

 

Groundwater beneath the NTS flows to the south or southwest toward natural discharge areas[19] and the study area (see Figure 4.1.1).  At Yucca Flat, data indicate that groundwater in the valley fill and volcanic units flows downward to the Lower Carbonate Aquifer, and then southwestward[20].

 

Is it possible for contaminants from the NTS to have reached the study area?  Yes.  According to Laczniak groundwater from the Yucca Flat portion of the NTS may flow through the Lower Carbonate Aquifer to Ash Meadows[21].  Yucca Flat is approximately 40 miles from Ash Meadows[22] and groundwater at Yucca Flat is contaminated with tritium.  Groundwater flow rates in the Lower Carbonate Aquifer may are rapid, possibly more than 36,000 ft/yr.  Therefore, contaminated groundwater from Yucca Flats could have reached the springs at Ash Meadows in less than ten years.  However, there is no evidence (i.e., elevated tritium activities[23]) that this has occurred (see Section 10).

 

There are also two predictions that place tritium contamination already in Oasis Valley, 12 miles from the NTS boundary, coming off the underground test area of Pahute mesa[24].  The Purvance study has shown that the leading edge of a radioactive plume can migrate up to 25 times faster than the center of mass of the plume, which means that contamination could arrive soon in Oasis Valley.  This concerns people as far away as California as well, since upwelling springs in the Oasis Valley are an important water source for the southward flowing Amargosa River.[25]  A good summary of the groundwater characteristics of the NTS can be found in the Technical Peer Review Report:  Strategy for Remediation of Groundwater Contamination at the NTS. [26]

 

Area 3 and Area 5 of the NTS are also used as shallow burial disposal sites for imported low-level nuclear waste materials, shipped by truck from other DOE weapons complex facilities involved in a cleanup process around the United States. Some transuranic wastes over and above the 1600 barrels recently shipped from the NTS to the Waste Isolation Pilot Plant (WIPP) in Carlsbad NM are also being considered for shallow burial also at this time.[27]

5.2  US Ecology’s[28] Hazardous Waste Facility

US Ecology’s hazardous waste facility is near the Amargosa River, approximately ten miles upstream from the study area (see Figure 4.0.2).  It began accepting low-level nuclear wastes in 1962[29].  The low-level waste facility appears to have been poorly run.  Some of the nuclear wastes disposed at the facility were liquid, even though the disposal of liquid wastes was prohibited by the facility’s license[30].  Liquid wastes were drained directly from tanker trucks into unlined trenches[31].  Some of US Ecology’s employees stole materials intended for disposal and used them for personal purposes or sold them to others[32].  US Ecology also forgot where it buried some of the wastes.  When it later constructed a fence around the disposal facility, one of its disposal trenches was left outside of the fence[33].  In 1992 the nuclear waste portion of the facility was closed by order of the Governor of Nevada[34].  The facility still receives hazardous wastes[35].

 

The US Ecology facility was excavated into the alluvium along the Amargosa River.  This alluvium is part of the valley fill aquifer. Groundwater in the valley fill aquifer is approximately 360 feet below ground surface[36].  US Ecology has contaminated unsaturated alluvium and groundwater with tritium.

 

Water vapor in the unsaturated alluvium between land surface and the water table contains high tritium concentrations.  In a test hole approximately 300 feet south of the facility, tritium activities range from about 50,000 pCi/L near the surface (depth approximately 5 feet) to about 5600 pCi/L just above the water table (depth approximately 357 feet)[37].  Tritium activities in the unsaturated zone near the facility increased significantly between 1994 and 1997[38].  The reason for the increase is unknown.

 

In 1982, high tritium activities (410,000 pCi/L) were found in a well near the southern boundary of the facility[39].  Tritium activities decreased over a period of about two years until tritium was no longer detected[40].  Since that time, groundwater from several wells on and near the facility has been sampled but little tritium has been detected[41].  The high initial tritium concentrations would not have decayed to undetectable levels in a few years[42].  The most likely explanation for the disappearance of the tritium is that it was transported down-gradient by the groundwater.  Hydraulic gradients in the alluvium along the Amargosa River are not available.  However, in hydrologic settings such as this it is common for groundwater to flow roughly parallel to the stream channel, in the downstream direction.  If this were the case, the tritium from the US Ecology facility would be moving toward the study area.

 

Is it possible for contaminants from US Ecology’s facility to have reached the study area?  Yes.  The facility is approximately ten miles from the study area and it is likely that groundwater flows from the facility toward the study area.  The facility is known to have contaminated groundwater in the valley fill aquifer with tritium.  Groundwater in the aquifer may travel as fast as 3500 ft/yr.  Since 1962, the contaminated groundwater could have traveled more than 25 miles.  Therefore, contaminants from US Ecology’s facility could have reached the study area.  However, there is no evidence (i.e., elevated tritium activities[43]) that this has occurred (see Section 10).


 

[1] U.S. Dept. of Energy, 2005, page 1-1.

[2] U.S. Dept. of Energy, 2005, page 1-5.

[3] Laczniak et al., 1996, page 3.

[4] U.S. Dept. of Energy, 2005, page 1-5.

[5] U.S. Dept. of Energy, 2005, page 1-5.

[6] Laczniak et al., 1996, page 26; and DOE, 2005, page A-16.

[7] Laczniak et al., 1996, page 3.

[8] U.S. Dept. of Energy, 2005, page 1-5. Subcritical tests do not result in nuclear explosions (U.S. Dept. of Energy, 2004, page D-7).

[9] U.S. Dept. of Energy, 2003, Nevada Test Site Environmental Report 2002, October 2003. page 8-6.

[10] The nuclear explosions melt the surrounding rock, creating subsurface cavities. The diameters of these cavities range from about 100 feet to more than 700 feet (Laczniak et al., 1996, page 21).

[11] U.S. Dept. of Energy 2005, page 4-19; and DOE, 2004, page 3-17.

[12] The U.S. EPA drinking water standard for tritium is 20,000 pCi/L (DOE, 2005, page 4-15).

[13] U.S. Dept. of Energy 2005, page 4-19 and figure 4-12.

[14] 20 pCi/L tritium was detected in well PM-3, approximately 2 miles west of the boundary (DOE, 2005, page 4-8 and figure 4-2). No tritium was detected in a duplicate sample from this well.

[15] U.S. Dept. of Energy 2003, table 8.2; and DOE 2005, pages 4-8, 4-12, and 4-15.

[16] This is the case for well U-19 BH on Pahute Mesa. It contained 66 pCi/L gross alpha and 99 pCi/L gross beta. The U.S. EPA drinking water standard for gross alpha is 15 pCi/L and the EPA ‘level of concern’ for gross beta is 50 pCi/L. Tritium has also been detected in this well (32 pCi/L) (U.S. Dept. of Energy, 2005, page 4-15).

[17] U.S. Dept. of Energy 2005, page 4-16 and figure 4-3.

[18] Highest measured activities (pCi/L): tritium = 946,000, strontium-90 = 1.49, cesium-137 = 62.7, plutonium-238 = 0.44, plutonium-239/240 = 4.96, americium-241 = 0.26 (U.S. Dept. of Energy, 2003, pages 5-41 – 5-42; U.S. Dept. of Energy, 2004, page 3-14, and U.S. Dept. of Energy 2005, pages 4-16 and 4-17).

[19] Laczniak et al., 1999, page 2; U.S. Dept. of Energy, 2005, page A-9.

[20] Laczniak et al., 1996, page 26.

[21] Laczniak et al., 1996, page 26.

[22] Laczniak et al., 1996, figure 1.

[24] Daniels, J.I., Editor, Pilot Study Risk Assessment for Selected Problems at the Nevada Test Site, UCRL-LR-113891, Lawence Livermore National Laboratory, June 1993;  Purvance, David T., Travel times of non-local dispersion and their geoelectric approximation in Nevada’s fractured welded tuffs, Water Resources Research, Vol. 37, No. 12, p. 2915, 2001. 2001.

[25] Christian, Bill, “The Amargosa River Conservancy Effort,” Nature Conservancy presentation to Devil’s Hole Workshop, Death Valley National Park, April 27, 2006.

[26] American Society of Mechanical Engineers, Technical Peer Review Report:  Strategy for Remediation of Groundwater Contamination at the Nevada Test Site, November 2001.

[27] NTS Citizen’s Advisory Board Public Meeting, January 8, 2006, Bob Ruud Community Center, Pahrump NV.

[28] US Ecology was formerly known as the Nuclear Engineering Company (NECO) (GAO, 1998, page 34).

[29] Prudic, D.E., D.A. Stonestrom, and R.G. Striegl, 1997, Tritium, Deuterium, and Oxygen-18 in Water Collected From Unsaturated Sediments Near a Low-Level Radioactive Waste Burial Site South of Beatty, Nevada, U.S. Geological Survey Water-Resources Investigations Report 97-4062, page 4. Although this was a low-level nuclear waste facility, some materials not generally considered by the public to be low-level waste (although considered as such by regulatory agencies) were disposed at the facility. This includes 47 pounds of plutonium (GAO, 1998, page 53).

[30] U.S. General Accounting Office (GAO), 1998, Letter to Senator Barbara Boxer and Representative George Miller, Radioactive Waste: Answers to Questions Related to the Proposed Ward Valley Low-Level Radioactive Waste Disposal Facility, May 22, 1998, page 5. URL: http://www.nirs.org/radwaste/llw/gaoqsonwdvalley1998seepp49521606911.pdf.

[31] U.S. General Accounting Office, 1998, pages 34 and 46.

[32] U.S. General Accounting Office, 1998, pages 7 and 49.

[33] U.S. General Accounting Office (GAO), 1999, GAO Report to the Chairman, Committee on Energy and Natural Resources, U.S. Senate Low-Level Radioactive Wastes, States Are Not Developing Disposal Facilities, GAO/RCED-99-238 September 1999. pages 7, 8, and 49.

[34] U.S. General Accounting Office, 1999, page 16.

[35] American Ecology, 2006, Beatty, NV – Hazardous Waste Treatment & Disposal Facility, URL: http://www.americanecology.com/locations/beatty/INDEX.ASP

[37] Striegl, R.G., R.W. Healy, R.L. Michel, and D.E. Prudic, 1997, Tritium in Unsaturated Zone Gases and Air at the Amargosa Desert Research Site, and in Spring and River Water, Near Beatty, Nevada, USGS Open-File Report 97-778, May 1997, page 11.

[38] Striegl et al., 1997, figure 4. The last available tritium data were collected in 1997.

[39] U.S. General Accounting Office, 1998, page 48.

[40] U.S. General Accounting Office, 1998, page 48. A sample collected three months after the initial sample had a tritium activity of 48,900 pCi/L. Eighteen months later the tritium activity was 2100 pCi/L. After 27 months (January 1985) tritium was below the detection limit.

[41] Prudic et al., 1997, page 11 and table 5. Since January 1985 the highest measured tritium activity in groundwater was 3.8 pCi/L.

[42] The half-life of tritium, that is the amount of time required for one half of the tritium present to decay, is 12.36 years (U.S. Dept of Energy, 2005, page C-2).

[43] In the vicinity of the study area, elevated tritium activities are defined as activities greater than 1400 pCi/L (see Appendix 12.4).