R-25 Monitoring Well Project

• Summary
• Location
• Background
• Findings
• Additional Information
• Ongoing and Planned Laboratory Actions

Summary
Los Alamos National Laboratory has detected high explosives residues in deep groundwater beneath the southwest edge of the Laboratory. The discovery was made in a monitoring well that is currently being drilled. The high explosives come from past experimental work at Los Alamos. Wells that supply drinking water to Los Alamos residents are at least 3.5 miles away. These wells show no signs of high explosives, and no threat to human health is present.

Los Alamos National Laboratory is taking this finding seriously and, in cooperation with regulatory agencies, will drill additional wells to define the extent of the contamination and ensure that drinking water supplies are protected. In the past few years, the Laboratory has eliminated or reduced potential sources of the high explosives pollution.

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Location
Monitoring well R-25 is located in the Los Alamos National Laboratory's Technical Area 16 on the south rim of Cañon de Valle. Technical Area 16 operations include high explosives research, development, testing, and manufacturing activities.

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Background
R-25 is the third of 32 planned deep wells that the Laboratory will install as part of a seven-year groundwater study. The study, known as the Hydrogeologic Workplan, has been approved by the New Mexico Environment Department and is being carried out in coordination with the Department. The goal is to develop better understanding of the geology, groundwater flow, and geochemistry beneath the 43 square mile Laboratory, and to assess impacts that Laboratory activities have had on groundwater quality.

R-25 is designed to provide information about hydrological, geochemical, and geological conditions beneath the relatively unstudied southwest part of the Laboratory. This will be the first well to penetrate the regional aquifer in the TA-16 area.

Drilling activities began in late July 1998 and were completed in late February 1999. Although originally planned for a depth of 1550 ft, the borehole was drilled to a depth of 1942 ft because of the HE issues identified during drilling operations. Geologic core and water samples collected during the drilling operations are being analyzed for chemical and radioactive constituents at defined intervals. Geologic core will also be analyzed to understand how water moves through the rocks.

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Findings
The hole was drilled through dry volcanic rock before encountering groundwater at a depth of 747 ft. Water was present continuously from 747 ft to 1132 ft. From 1132 ft to a depth of 1286 ft, there are alternating zones of wet and dry rock. It can not yet be determined whether the thick upper groundwater body is perched or part of the regional aquifer. Below 1286 ft saturation occurred continuously to the total depth of 1942 ft. The top of the regional aquifer may lie at about 1286 ft, but this is uncertain.

Groundwater samples were collected at depths ranging from 747 ft to 1942 ft. These samples were sent to an independent laboratory and analyzed for potential contaminants, including high explosives, metals, inorganic compounds, organics, and radionuclides.

High explosives and chemicals associated with their breakdown were present in most of the samples down to a depth of 1607 ft. High explosive contaminants found include hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazine (HMX), 2,4,6-trinitrotoluene (TNT), 4-amino-2,6 dinitrotoluene (4-A-DNT), 2-amino-4,6 dinitrotoluene (2-A-DNT), and 1,3,5-trinitrobenzene (TNB). Analytical results for deeper groundwater samples are pending.

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Additional Information
The Laboratory believes that discharges from past high explosive manufacturing activities at Technical Area 16 are the source of high explosive constituents found in the groundwater at R-25. The manufacturing activities and discharges have occurred since the 1940s. The only safe way to work with high explosives is to keep them wet - water is used to cool and wet high explosives during machining, for example.

Groundwater at TA-16 is not used for drinking water. The closest water supply well is located 3.5 miles east of R-25. The groundwater travel time between R-25 and the nearest water supply well is probably between 50 and 200 years.

As a result of the findings at R-25, the nearest six water supply production wells on Laboratory property were tested for the presence of high explosives. Samples from these wells contained no high explosives or high explosive degradation products.

The Laboratory has already taken steps to reduce the discharge of high explosives processing water in the TA-16 area. The Laboratory recognized in the early 1990s that high explosives wastewater discharges at TA-16 would not meet new State stream standards, and began to reduce discharges and improve discharge water quality. These changes were completed in September of 1997 and included a new high explosives wastewater treatment plant. In addition, installation of new vacuum pumps at TA-16 high explosives processing facilities improved reuse of wastewater and reduced flow to the wastewater treatment plant. Other changes eliminated 19 of the 21 high explosive wastewater outfalls.

Before 1997 the Laboratory discharged more than 12 million gallons of high explosives-contaminated wastewater a year at TA-16. Since the new treatment plant was installed and the wastewater outfalls were eliminated, the Laboratory discharges only about 1% of the previous amounts (120,000 gallons per year).

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Ongoing and Planned Laboratory Actions
TA-16 is one of the Laboratory's highest priority clean up sites under the Environmental Restoration Project. Removal of high explosives from contaminated soils near recently eliminated wastewater outfalls will begin this year.

The Laboratory is now constructing the R-25 well with nine sampling ports distributed throughout the upper and lower zones of saturation. Once completed, the additional samples will be collected on a periodic basis to define the distribution of high explosive concentrations in groundwater and to detect changes in the quality of the groundwater over time.

The Laboratory is accelerating the schedule for installation of a new regional aquifer monitoring well that will be located between R-25 and the nearest water supply wells. The new well will show whether contaminants have moved away from TA-16, and provide information to assist the Laboratory efforts to ensure that drinking water supplies are protected.

The Laboratory is planning additional investigations in the TA-16 area to better understand the nature and extent of groundwater contamination identified by the R-25 drilling effort.

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