The chemicals - from high explosives - have not been detected in wells that supply drinking water.
The Laboratory is working closely with the New Mexico Environment Department, which took independent samples from the well.
"The Laboratory is committed to doing all it can to protect the health and safety of our neighbors and our workers," said Charlie Nylander, leader of the Laboratory's Monitoring Well Installation Project. "We are working to find ways to determine whether this contamination may pose a threat to drinking water supplies in the future and how we might mitigate the situation."
Laboratory researchers took the samples from characterization well R-25, the third of 32 monitoring wells sponsored by Los Alamos' Defense Program and Environmental Management Program that will help scientists better understand hydrologic and geochemical processes on the Pajarito Plateau, and whether Laboratory-derived contaminants or other substances have made their way into local ground water bodies. This ground water characterization and monitoring effort is scheduled to continue at least until 2005 and cost nearly $50 million.
Scientists collected samples at progressively lower depths within the monitoring well, located within Laboratory Technical Area 16. Most water samples tested positive for high explosives and explosives byproducts that had become dissolved in the water. Many water samples contained at least one high explosive constituent in concentrations above what Environmental Protection Agency Health Advisories say are safe for drinking water.
"Once we confirmed the presence of these chemicals at R-25, we immediately took samples from water supply wells located on Laboratory property," said Nylander. "Results of tests showed that the contamination is not in our community drinking water. We are taking action to determine whether the chemicals will affect drinking water in the future, and we will continue to monitor drinking water wells for these contaminants."
The R-25 monitoring well is located near the southwestern edge of the Laboratory on the south rim of Cañon de Valle within TA-16. Activities conducted at TA-16 include high explosives research and development, and high explosives testing and processing. Researchers have worked with high explosives at the site since the 1940s.
In order to work safely with these explosive materials, technicians must run water over them during machining, milling and other operations. The water virtually eliminates the chances for accidental detonation and is a necessary safety precaution. Waste water contaminated with explosive residue was discharged in many areas within TA-16 for years.
Even before the contamination was discovered, the Laboratory had significantly reduced discharges of the chemicals; it has eliminated 19 out of a total of 21 explosives waste water outfalls in the area.
One of the two remaining outfalls is a new High-Explosives Waste Water Treatment Facility that went on line in September 1997. The state-of-the-art plant significantly improved the quality of discharged waste water. Also, installation of waste water recycling facilities at TA-16 has reduced by 100 times the volume of high explosive-contaminated waste. In the past, high-explosives work resulted in the discharge of more than 12 million gallons of waste water a year; discharges from the treatment plant are about 120,000 gallons a year.
The remaining source of waste water contaminated with high explosives is located at a concrete pad where researchers detonate the materials. After these experiments, crews wash the pad into a settling tank from which waste water is discharged. These discharges are infrequent.
Because of the historic discharges at TA-16, researchers expected to see some high explosives contamination in ground water bodies, but they weren't sure how much. Consequently, the R-25 well was a priority for Laboratory ground water surveillance activities and the Environmental Restoration Project. R-25 is the first well to be drilled into the regional aquifer in the southwestern portion of the Laboratory.
Based on past data and information gained through other drilling projects in the Los Alamos area, Laboratory hydrologists expected to encounter the regional aquifer - an underground reservoir that is used as the community water supply - at around 1,350 feet below the surface. In addition, hydrologists believed there was a possibility that drilling might reveal one or more perched aquifers, subsurface water zones that lie above and are segregated from the regional aquifer.
At R-25, the drilling team encountered ground water at 747 feet below the surface; this ground water zone continued to a depth of 1,132 feet. The researchers then encountered a zone of alternating wet and dry rock between 1,132 feet and 1,286 feet. They encountered at 1,286 feet another saturated zone that extends to the current depth of 1,507 feet. Crews plan to continue drilling to a depth of 1,800 feet.
Laboratory researchers took samples of the water at varying depths and analyzed them for natural and man-made contaminants, including metals, organic and inorganic chemicals, and radionuclides. Data indicate that no man-made contaminants other than the high explosive chemicals have entered water systems below TA-16.
High explosive contaminants found in water samples include: RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), which stands for Royal Demolition Explosive, widely used at TA-16; HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), which stands for High Melting Explosive, also widely used at TA-16; TNT (2,4,6-trinitrotoluene), a common explosive; 4-A-DNT (4-amino-2,6-dinitrotoluene), a degradation byproduct of TNT; 2-A-DNT (2-amino-4,6-dinitrotoluene), a degradation byproduct of TNT; and TNB (1,3,5-trinitrobenzene), an impurity often found in TNT.
- RDX was found in water samples taken at 747 feet, 867 feet, 1,047 feet, 1,137 feet and 1,181 feet. For those samples, RDX was found in concentrations of 12 parts per billion (micrograms per liter), 63 parts per billion, 84 parts per billion, 50 parts per billion and 4.2 parts per billion.
- HMX contamination was found at 867 feet, 1,047 feet and 1,137 feet. Concentrations for those samples were 8.3 parts per billion, 12 parts per billion and 9.2 parts per billion.
- TNT was found 867 feet and 1,047 feet at concentrations of 19 parts per billion and 5.3 parts per billion, respectively.
- Small concentrations of 4-A-DNT and 2-A-DNT were found at 747 feet, 867 feet, 1,047 feet and 1,137 feet.
- TNB in a concentration of 2.2 parts per billion was found at 867 feet.
Laboratory researchers have not yet validated test results from deeper water samples.
The Environmental Protection Agency has established health advisory guidelines for some of the chemicals. The EPA advisory guideline for RDX concentrations in drinking water is 2 parts per billion; the guideline for HMX is 400 parts per billion; and the guideline for TNT is 2 parts per billion.
Laboratory officials point out that the chemicals have not been detected in wells that supply Los Alamos with drinking water.
An independent, outside laboratory analyzed the water samples. Lab scientists have validated data for the water samples. Researchers will continue to take samples at intervals all the way to 1,800 feet. The New Mexico Environment Department also has taken water samples from the well.
Because of the complex hydrology at the R-25 site, Laboratory researchers at this time are uncertain whether all of the contamination is found in a perched aquifer or whether the chemicals are in water that makes up a portion of the regional aquifer.
The nearest drinking water supply well is about 3 miles east of R-25. Earlier hydrology studies of the deep aquifer indicate that the ground water moves laterally at a rate of between 95 and 345 feet per year, but the exact rate still remains unknown. Hydrologists believe that ground water in the R-25 area moves to the east-southeast.
Nylander said a new characterization well will be located to the southeast of R-25 to help hydrologists and geochemists determine the extent of the contamination and the direction it is moving. In addition, Los Alamos researchers are developing computer models of ground water flow and geochemistry in the area to give hydrologists further insight into what is happening below the surface.
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