RDX Plume Characterization

Ensure contamination doesn’t threaten human and environmental health

Royal Demolition Explosive (RDX) Plume Characterization Overview

Building 260 at LANL’s Technical Area 16 was the conventional, high explosive machining facility. From 1951-1996, 13 sumps discharged liquid containing high explosive compounds (RDX, HMX and TNT) and barium through the building outfall and into Cañon de Valle. Soils, surface water and groundwater beneath Cañon de Valle were contaminated. RDX  in groundwater was first identified in the late 1990s and discovered in the regional aquifer in 2005.

RDX Documents

Goal

Ensure contamination from past LANL operations does not threaten human and environmental health

Description

Characterize groundwater movement and RDX concentrations, perform risk assessment, and issue a corrective measures evaluation, if needed

RDX Characterization and the 2016 Consent Order

The 2016 Consent Order between DOE and New Mexico Environment Department (NMED) divides cleanup work into 16 campaigns. One of the campaigns is RDX Characterization. Recent and upcoming work includes:

✔ Submit two annual reports to NMED in FY21: the Investigation Report and Risk Assessment Report.
✔ Continue sampling from well R-69, placed in service in FY19. The well provides important information about how RDX has reached the groundwater.
✔ Submitted to NMED the The Investigation Report for Royal Demolition Explosive in Deep Groundwater (FY19 milestone). The report presents the results of hydrology, geology, and geochemistry studies, nature and extent of RDX, updates the Conceptual Site Model and the screening of potential risk. The report can be read here.
✔ Submitted to NMED the Annual Long-Term Monitoring and Maintenance Report for the Corrective Measures Implementation at Former 260 Outfall Area. The report can be read here.
✔ Submitted to NMED the Fate and Transport Modeling and Risk Assessment Report for RDX Contamination in Deep Groundwater. The report evaluated the risk to human health from exposure to RDX in groundwater. The report concluded there is no risk to human health and that long-term groundwater monitoring is protective. The report can be read here.

If further remediation is necessary to protect groundwater, DOE Office of Environmental Management Los Alamos Field Office will submit to NMED a CME for RDX in the deep groundwater.

RDX at a Glance

✔ RDX was used widely in World War II and remains common in military applications.
✔ RDX is an organic, man-made product that does not occur in nature.
✔ RDX has a low water solubility but does not bind significantly to soils, so it can leach into groundwater.
✔ The state’s tap water screening level is based on a 150-pound person drinking one liter of contaminated water per day, 350 days a year, for 26 years. That person’s increased risk over 70 years would be 1 in 100,000.
✔ The risk assessment analyzed current risk and future risk, and determined that there is no risk to human health and that long-term groundwater monitoring is protective.

Recent studies show the RDX plume will migrate only 2,500 feet toward water supply wells in the next 50 years. Results of the fate and transport model evaluated risk to human health of RDX in the groundwater and concluded there is no risk to human health and long-term groundwater monitoring is protective.

Latest Status

✔ No drinking water is at risk

✔ Analysis of groundwater hydrology and RDX movement continue

✔ Nine wells monitor RDX concentrations in groundwater

✔ Wells R-68 and R-69 exceed the state’s tap water screening level of 9.66 parts per billion

Regulating Water Quality

The New Mexico Water Quality Control Commission’s  tap water screening level of 9.66 parts per billion is based on the Environmental Protection Agency screening levels.

Area Hydrology

Scientists are working to refine their understanding of how RDX migrated through the subsurface at LANL. Conceptual models based on multi-year studies indicate the primary RDX migration pathway is via surface water moving down Cañon de Valle and seeping downward through the rock layers into the underlying groundwater zones, shallow to deep. Monitoring wells located in each of the groundwater zones provide information on the hydrologic connections and changes over time.

The RDX Monitoring Network

No RDX has been detected in wells that supply water for Los Alamos County (LAC).

Nine wells in TA-16 and TA-9 are used to monitor groundwater in the regional aquifer that provides water for LAC. Groundwater samples from monitoring wells, R-68 and R-69, which are more than three miles from the LAC water supply wells, show RDX levels of contamination above the New Mexico tap water screening level of 9.66 parts per billion.

Results of the fate and transport model evaluated risk to human health of RDX in the groundwater and concluded there is no risk to human health and long-term groundwater monitoring is protective.

Cleanup Work Conducted To Date

Surface soil cleanup in 2000-2001 and in 2009-2010 removed and properly disposed of about 1,500 cubic yards of high explosive-contaminated soil from the outfall area. Residual RDX remains in the subsurface groundwater. Long-term monitoring and maintenance is conducted to evaluate the effectiveness of the corrective measure and provide information for the conceptual site model for RDX movement through surface water, springs and groundwater.