Because the existence of a chromium plume in the regional aquifer below Sandia and Mortendad Canyons has been a source of concern for citizens of northern New Mexico, Voices of Los Alamos asked experts to discuss the problem at a Nov. 27 meeting.
Danny Katzman is the Technical Program Director for LANL’s chromium project and a hydrogeologist. Katzman began by saying that he was working on a way to explain the complicated technical project, putting together FAQs (frequently asked questions) for the DOE website. This is now posted here.
Katzman explained that chromium occurs in two forms: chromium-3 or trivalent, which is harmless, and chromium-6 or hexavalent, which is toxic to humans. The hexavalent form, which dissolves in water, is used for chrome plating. At the Lab it was used to prevent corrosion in the power plant cooling towers from 1956 to 1972. During that time about 160,000 pounds of excessive concentrations were released into Sandia Canyon.
In 1972 the plant operators switched to a different corrosion inhibitor after chromium showed up in surface water below the area where the chromium was being released. The chromium plume was discovered in 2005; it is approximately one mile by one-half mile in size, approximately 1,000 feet below ground level, and 50-60 feet thick. It floats near the top of the aquifer below Laboratory property, south of East Jemez Road and extending to the Laboratory’s border with San Ildefonso. It is migrating in an easterly direction. Since the county’s drinking water wells draw from almost a thousand feet deeper in the aquifer, they are safe from contamination at present.
Currently DOE and the Laboratory are working to prevent migration and reduce the size of the plume through a process of extracting, treating and reinjecting. Through a series of extraction wells, the contaminated groundwater is pumped above ground and treated using a method called ion exchange. The clean water is then transported through a series of buried pipes to injection wells. These wells were installed at the eastern edge of the plume so that when the clean water is reinjected into the aquifer it results in a mounding of the water table (a speed bump). This mound pushes the contaminated water back toward the center of the plume. Also, any contaminated water that may manage to pass through the mound is greatly diluted. Katzman mentioned that the DOE has spent $50 million installing this infrastructure and was sensitive to cultural sites and environmental issues. He indicated that the infrastructure is barely visible.
Studies are underway to evaluate a permanent remedy to clean the concentrated plume. DOE and LANL have looked at pump-and-treat remediation; however, they believe a more promising solution is to convert the hexavalent chromium to trivalent by injecting the plume with either molasses or sodium dithionite.
James Alarid, Department of Public Utilities (DPU) Deputy Utility Manager, explained that no drinking water wells have been contaminated by the chromium plume. DOE has drilled two sentinel wells between the chromium plume and PM3 well, the closest drinking water well, which is a quarter mile away from the plume. The sentry wells measure the water at the level of the water table and at the level of withdrawal and will provide an early warning of a contamination risk for drinking water. Should one of the sentinel wells indicate contamination from the chromium plume, the County would have plenty of time to react before it reaches drinking water well PM3.
Extensive testing is conducted on all of the county’s drinking water wells for total chromium. NMED conducts tests every three years. LANL and DPU test yearly. In addition, LANL and DPU test the four drinking wells closest to the plume quarterly for total chromium. Alarid noted that some chromium occurs naturally in our drinking water, and has ranged over the years from non-detectable to 13 parts per billion. The state maximum for drinking water is 50 parts per billion.
Should a well become contaminated, DPU can take the well off-line. Alarid confirmed that the county also has an insurance policy that will pay to either replace a well or treat the drinking water to safe standards. DPU will not provide water to its customers that doesn’t meet safe federal and state drinking water standards.
Lastly, Alarid pointed out that not only is Los Alamos drinking water safe, but it is excellent quality water. The DPU held an informal blind taste test at an Earth Day event in 2005. Various Los Alamos residents were asked to identify the tap water among various bottled waters. The majority identified the Fiji bottled water as Los Alamos County’s tap water! A comparison of our tap water with the Fiji brand water revealed that the mineral constituents were very similar, including the high levels of silica. DPU Manager Tim Glasco pointed out that Fiji water, packed in plastic bottles and shipped from the antipodes, has 250,000 times the carbon footprint.