TA-16 at Los Alamos National Laboratory is where Royal Demolition Explosive (RDX) was used for some 45 years. Courtesy image
BY MAIRE O’NEILL
Los Alamos County residents and public officials are beginning to ask more questions about hexahydro-1,3,5-trinitro-1,3,5-triazine, RDX, also known as Royal Demolition Explosive, cyclonite, hexogen and T4.
The issue of RDX in the regional aquifer came up during an Oct. 16 presentation by Los Alamos National Laboratory Environmental Management Field Office Manager Doug Hintze and N3B Regulatory and Stakeholder Interface Manager Frazer Lockhart to the Los Alamos County Council. Councilor Antonio Maggiore appeared to be surprised when Hintze referred to RDX being in the regional groundwater aquifer.
EM-LA officials say the distance from the nearest Los Alamos County drinking water well (PM-5) to the one location, R-68 in the uppermost regional aquifer, where concentrations of RDX in excess of the New Mexico Environment Department screening level have been found is more than three miles.
The NMED screening level is 7.02 ug/L for tap water and in May 2017, samples at the R-68 well tested at 15 ppb (parts per billion). Screening levels are used to determine if remediation is necessary and are not cleanup requirements of themselves.
RDX has been present at LANL since the 1950s. Building 260 at TA-16 was the Lab’s conventional high explosive (HE) machining facility during much of the Cold War. From 1951 to 1996, 13 sumps discharged HE-contaminated wastewater through the TA-16-260 outfall. Identified potential release sites which have been remediated include the sumps and drain lines that lead to the outfall, as well as the outfall itself, a pond, and a drainage channel. The RDX site is the Lab’s first corrective measures study/corrective measures implementation project.
The Environmental Protection Agency says RDX is one of the most powerful high explosives available. It is often mixed with other explosives, oils or waxes to make military munitions and other products. RDX is commonly found at hand grenade ranges, anti-tank rocket ranges, bombing ranges, artillery ranges, munitions testing sites, explosives washout lagoons, demolition areas and open burn/open detonation sites.
RDX is classified as a Group C (possible human) carcinogen. The EPA says it can damage the nervous system if inhaled or ingested and that it plans to update its toxicity benchmarks and health risk assessment. Potential treatment technologies listed by the EPA include in situ bioremediation, granular activated carbon treatment, composting, phytoremediation and incineration.
The EPA says potential exposure to RDX could occur by dermal contact or inhalation exposure; however, the most likely route of exposure at or near hazardous waste sites is ingestion of contaminated drinking water or agricultural crops irrigated with contaminated water. The EPA classified it as a Group C carcinogen based on the presence of hepatocellular adenomas and carcinomas in female mice that were exposed it. The EPA says RDX targets the nervous system and can cause seizures in humans and animals when large amounts are inhaled or ingested.
At that Oct. 16 County Council workshop, Councilor Maggiore said he has asked before about RDX and that this was the first time it has openly been acknowledged that there’s an RDX plume. He asked how long have RDX has been used at the Lab.
Hintze replied that RDX has been used for many decades and that the plume was actually identified some time ago and was included as a separate campaign in the Consent Order between DOE and NMED. The Consent Order, revised in 2016, is a document which sets forth a process for characterizing the nature and extent of contaminant releases, characterizing the risks to human health and the environment from these releases and mitigating unacceptable risks.
“When we work on the Consent Order we go through Appendix C as the prioritized order. Even though this may be the first time it’s been identified and it’s been in our scope and our lifecycle, it’s been identified for years,” Hintze said.
Councilor Maggiore noted that it has been almost 15 years since starting work on the chromium plume and asked if there is a similar timeline for “really effectively starting the RDX plume”. Hintze responded that for RDX, the initial campaign involved drilling a well, R68 a couple of years ago.
“From that initial characterization of the plume itself, there was belief that the plume was in the perched aquifer. When we drilled R-68 a couple of years ago it was identified that there was actually RDX down in the regional aquifer,” he said.
Hintze said as part of the Consent Order, another well, R69 is currently being completed and that samples will be available from that well in November.
“Then we can go back to the New Mexico Environment Department and figure out exactly what is the remedy necessary for the RDX. We don’t have the answer because we don’t have the well drilled to figure out what the extent of the plume is. It’s still in the characterization phase for the RDX,” he said. Asked by Councilor Maggiore if RDX is in the regional aquifer, Hintze said, “It’s in the regional aquifer. That’s what R-68 told us”.
Councilor Maggiore appeared to be upset at Hintze’s statement and went on to ask questions.
“RDX is pretty nasty stuff, isn’t it? It’s an explosive, it’s a carcinogen isn’t it? And you’ve let it get to the regional aquifer. Does it behave as far as treatment options, is it something you can do the hydrostatic nonsense that you’re talking about for the chromium plume? Is it a pump and treat? Are we pumping and treating now from the regional aquifer? How fast does it move in the water?,” he asked.
Hintze replied that the pump treat is only for the chromium and that the remedy will be decided once the extent of the RDX is known from the drilling of R-69.
“I hope the moment you have further information, that you are back before the Council talking to us because this is everyone’s water supply and not just locally. It is regional – your words, not mine and it is unacceptable. Absolutely not acceptable,” Maggiore said before he was prevented from further comment by Council Chair David Izraelevitz who interrupted him and continued the meeting.
Council Vice Chair and liaison to the Los Alamos Board of Public Utilities told that board Oct. 17 of the discussion at the Council Meeting.The Los Alamos Board of Public Utilities. Utilities Manager Tim Glasco said he would certainly check into the latest information.
“We get the groundwater data from the Lab as a courtesy before it is released to the public and they notify us when there is anything of note and we have not been notified of any issues with RDX in the aquifer. So my assumption based on that is that this is older data that we were already aware. We know there is RDX contamination in the area around S Site south of any of our County wellfields. That is what I am presuming this is about. This has been known for some time. We have not been notified of anything in proximity to any of our drinking water wells but we will check into that,” Glasco said.
The board asked Glasco to present a staff report at its November meeting. DPU public information officer Julie Williams-Hill said Friday that as far as DPU knows, the Los Alamos drinking water wells are not in immediate risk of being contaminated. She said the last time DPU was briefed about RDX was about two years ago. She pointed out that DPU coordinates and communicates with DOE and LANL regularly.
“We meet with them monthly to discuss items related to water – the sampling schedule, test results and items of concern such as the chromium plume,” Williams-Hill said. She said Glasco has reached out to Hintze’s office to set up a meeting with him to discuss the issue.
Research into a 546-page compendium of technical reports related to the deep groundwater aquifer published in March for the RDX Project reveals details of what has been happening with the RDX issue since the mid-2000s. In 2007 DOE and LANL submitted a corrective measures valuation for intermediate and regional groundwater which NMED disapproved. NMED then requested additional characterization to evaluate the feasibility of the remedial alternatives proposed and to assess the extent of contamination on perched-intermediate groundwater and in the regional aquifer. In response, the Lab installed additional wells, conducted single-well and multi-well aquifer tests and tracer tests as well as geochemical, bioremediation and natural attenuation studies.
The recommendations for the new regional wells R-68 and R-69 referred to by Hintze were based on continuing increases in RDX concentrations in an earlier well – R-18 – along with unique ratios of high explosives-degradation products, indicating contamination in R-18 could originate from a source other than the TA-16-260 outfall, with one possibility being historical releases from TA-09. Other objectives for R-68 and R-69 include refining the nature and extent of RDX in the regional aquifer, constraining the regional water table north of Canon de Valle and characterization of the extent of RDX in the perched-intermediate groundwater.
A thick, high-RDX zone was found at a depth of ~650 to ~900 ft, indicating a significant zone of contaminated perched-intermediate groundwater north of Cañon de Valle. Drilling of R-68 was completed at the end of February 2017 to a total depth of 1422 feet below ground surface. The zone of contamination was estimated based on non-representative groundwater samples collected during the development of the CdV-9-1(i). Representative samples collected from CdV-9-1(i) have RDX at concentrations an order of magnitude lower.
Regional groundwater characterization samples were collected from R-68 in March, June, July and on Sept. 6, 2017, and analyzed off-site for a full suite of constituents including HE compounds and degradation products, volatile organic and semi-volatile organic compounds, metals, low-level tritium, and general inorganics. The analytical results from R-68 were screened against the lowest applicable screening value, and RDX was detected above the NMED tap water screening level of 7.02 µg/L. RDX was detected at concentrations ranging from 8.08 µg/L to 17.1 µg/L, with the highest value measured in the Sept. 6, 2017 sample. Of the eight wells that currently monitor regional groundwater, only R-68 has RDX above NMED screening level.
In 2016 and 2017, the estimated RDX inventory in the subsurface was re-evaluated based on RDX concentrations measured in groundwater samples from monitoring wells and borehole screening data, including data from new wells completed in perched-intermediate zones and in the regional aquifer. The updated evaluation estimates mass of RDX in the subsurface ranges from 1533 to 3608 kg, with approximately 19 to 52 percent of the inventory in deep perched and regional groundwater.
The revised inventory assessment indicates that the total mass of RDX in the subsurface environment is approximately 85 percent less than originally estimated in the 2005 study. It also indicates that most of the RDX in groundwater resides within the deep perched-intermediate zone and that there is less RDX in the perched-intermediate and regional aquifer groundwater than originally estimated in 2005.
“Overall, the updated reevaluation of the RDX mass represents a substantial improvement in our understanding of the RDX contaminant distribution within the subsurface environment and is consistent with the site conceptual model, as well as our model predictions on the transport of RDX from surface and near-surface sources to deeper aquifers,” the compendium report states. “The lower mass of RDX in the updated inventory assessment reflects a better constrained data set to develop inventory estimates, with more wells providing RDX data from the perched-intermediate zones and the regional aquifer, as well as RDX data derived from screening samples collected in the vadose zone during drilling. This significantly improved data set has resulted in a more accurate estimate of the RDX mass distribution in the VZ and the groundwater system.”