Tuesday, January 12, 2010
Metals in Groundwater and RACER
In this post I follow up on a question introduced earlier; viz., how likely is it that RACER will help the citizens of Northern New Mexico to check up on LANL's stewardship of the local environment?
In attempting again to answer this question, I first reproduce here a history of high metal concentrations in the groundwater at LANL's Technical Area 49 (TA-49), as revealed by the Water Quality Data Base. Although this history was presented in the fall of 2008 at meetings of the Northern New Mexico Citizens Advisory Board, no formal response by LANL to the problems revealed here has ever been offered.
In two earlier white-papers I discussed (in the summer of 2008) data excerpted from the Radionuclides in Groundwater section of LANL’s online Water Quality Data Base (WQDB). These short papers were intended to serve as non-technical introductions to the WQDB for members of the Northern New Mexico Citizens Advisory Board (NNMCAB).
In this latest of an ongoing series, I describe data from the Metals in Groundwater section of the WQDB. After a few general remarks, I discuss the high levels of chromium(3) being measured in Regional Well 28 (R-28), and then react to a recent study, by geologist Bob Gilkeson, in which past high levels of lead(4) in deep wells at TA-49 were considered.
The data tabulated in the Metals in Groundwater section of LANL’s online Water Quality Data Base describe the results of measurements of the concentrations of approximately 24 non-radioactive metals, made at about 430 locations distributed over the DOE/LANL site, and in its immediate vicinity, during the past 40 years.
These data are a record of the concentrations of metals, measured at wells or springs, in units of mg/l (micrograms per liter). In contrast to the case of Radionuclides in Groundwater, discussed earlier(1,2), uncertainties in the measured values of metal concentrations in groundwater are not tabulated, nor are values for the estimated Minimum Detectable Amount (MDA). Even so, measured concentrations are often accompanied by a < sign, perhaps denoting that the data recorded is, in some sense, a “non-detect”(5). However, in no case do values of measured concentrations appear with a minus sign, which would indicate that the sample value was less than the value of a corresponding blank(6). In the following, we will not refer to tabulated data, if it is preceded by a < sign.
A user of the WQDB might wonder how measured values for the concentrations of individual metals translate into estimations of health risks.
In order to address this question, we consulted the EPA’s online standard for metals in drinking water, and found the following EPA benchmark information relating to health risks; i.e., the Primary Drinking water Standards(7), for metals in groundwater. These standards set values for the Maximum Contaminant Level (MCL) as:
Metal MCL (mg/L) ...... Metal MCL(mg/L)
Antimony 6 ............... Copper 1300
Arsenic 10 ................. Lead 15
Barium 2000 ............. Mercury 2
Beryllium 4 ................ Selenium 50
Cadmium 5 ................ Thallium 2
Chromium 100 ........... Uranium 30
Also, EPA’s Secondary Drinking Water Standards(8) for metals in groundwater are:
Metal MCL (mg/L) ...... Metal MCL(mg/L)
Aluminum 50 ............. Manganese 50
Copper 1000 .............. Silver 100
Iron 300 ................... Zinc 5000
The subject of chromium in groundwater at LANL is interesting because it appears to be almost unique. It seems that chromium may be one of only a few substances contaminating the aquifer beneath the Pajarito Plateau, for which LANL aggressively assigns itself the blame(3, 9-11). Moreover, until recently, it seems that this contamination had been found to exist, primarily, in only one deep well.
The well in question, R-28, was drilled into the regional aquifer below Mortandad Canyon at the end of 2003, and a single well-screen was installed(12). This screen was intended to sample the groundwater at depths between 934 ft and 958 ft bgs, near the top of the underlying aquifer.
The first data from this well(13) was collected on 5-20-05 and, while showing essentially normal values for the concentrations of most metals, showed a dissolved chromium (Cr(VI)) concentration of 375 mg/L, which was roughly four times the EPA’s MCL. Previously, at other deep wells located all over LANL, levels of dissolved chromium were usually no more than ~5 mg/L, and had never been found to exceed ~20 mg/L. Evidently, this data from R-28 was a very surprising circumstance, since it led, seven months later, to a report from LANL to NMED, and ten months later to a LANL(9) public announcement.
At that time, it was said that the probable source of this contamination was effluent water from a cooling tower, attached to a power plant, formerly situated at the head of Sandia Canyon. It seems that this water had contained dissolved chromate (Cr(VI)), added as a corrosion inhibitor, which had somehow found its way into groundwater at the newly drilled R-28. It was estimated that during the period of time from the 1950’s to the 1970’s, between 58,000 and 230,000 lbs of dissolved chromium had been dumped(10) into Sandia Canyon.
This view was supported somewhat by the fact that a number of alluvial (shallow) wells in Sandia, Pueblo, Los Alamos, and Pajarito Canyons had shown a record of sporadic high levels of chromium in filtered(14) groundwater samples. For example, in the Pueblo Canyon alluvial well APCO-1, chromium concentrations were as high as 5300 mg/L, on 3-29-95; in the Los Alamos Canyon alluvial LAO-2 the concentration was 400 mg/L, on 12-21-93; and in the Pajarito Canyon alluvial PCO-3 the concentration was 740 mg/L, on 6-7-93, all in filtered samples. However, it was also true that these high levels of chromium were neither persistent in time, nor were they spread out in space; i.e., they existed for periods of time of no more than a few months, usually did not recur, and they were observed only at isolated locations. Other nearby alluvial wells did not show these sharp chromium concentration spikes. Perhaps most importantly, in no case had such high chromium concentrations been measured in alluvial wells during the past five years.
However, it may have seemed odd that no other deep wells in the vicinity of R-28 had ever shown signs of elevated chromium levels; e.g., the old test well TW-3, in Los Alamos Canyon, had never registered high levels of chromium. Also, none of the Los Alamos County water supply wells, PM-1, PM-2, and PM-3, in place since 1977, and PM-4 and PM-5, in place since 1988, had ever shown signs of elevated chromium. These water supply wells are, in no case, more than two miles from R-28, and surround it. PM-1 and PM-3 are in Sandia Canyon itself, PM-4 is in Cañada del Buey, PM-5 sits between Tenmile Canyon and Cañada del Buey, while PM-2 is in Pajarito Canyon. These last three wells are all to the south of Mortandad Canyon.
Finally, it may have seemed odd too that no intermediate depth wells had ever shown elevated chromium levels; e.g., MCOI-8, MCOI-4, and MCOBT-4.4, all in Mortandad Canyon, and all located within 1 ½ miles upstream of R-28, had no history of high chromium concentration.
Subsequently, many studies have been performed, based on computer simulations, in an attempt to better understand this situation. LANL scientists now believe that there is a plume of groundwater, contaminated by high levels of dissolved chromium (~400 mg/L (+/-) 25 mg/L), confined to an area centered on R-28, and extending no more than one-half mile in any direction; see Fig. 4.2-1 of ref. 3. It is problematic as to how these high levels of Cr(VI) have been maintained, essentially without change, for at least the past three years.
Based upon these observations, it is reasonable to speculate that there is a large source of chromium located somewhere upstream of R-28. And, in fact, a source of sedimentary chromium is known to exist in a wetland at the head of Sandia Canyon, adjacent to, and downstream from, the site of the old power plant cooling tower; see Fig. 1.0-1 of ref. 3.
Presumably, this chromium is in its reduced state, Cr(III), which is largely insoluble in water, for values of pH near neutral. Further, evidence exists that this source of chromium is being mobilized by outfalls from a large sewage treatment plant which sweep regularly through the wetland(15).
In order to further test this hypothesis, LANL has planned for several new wells to be drilled in the immediate vicinity of R-28. The latest news(14) is that, in the first of these wells to be completed, SCI-2, perched water has been detected at a depth of 509 ft bgs, and a filtered sample of this water shows a chromium concentration of ~500 mg/L.
The subject of lead in groundwater at LANL is also of some interest. During the period 1959-1961 LANL conducted underground weapons tests at MDA-AB (TA-49). These were the so-called hydronuclear tests, described by Bob Thorn(16). Residues of these tests included a variety of toxic materials(17), among which was an estimated 200,000lbs of elemental lead (Pb).
The tests were conducted in unlined earthen shafts, dug to depths of between 30 and 100 ft. These shafts were disrupted by the test explosions and, one assumes, toxic residues were mixed into the adjacent tufa and soil. What has become of these residues, the mobility of which has been unrestricted by any artificial barrier, over the past 50 years? I alluded to this subject in a previous publication(1). This subject has also been discussed by Bob Gilkeson, in a recent study(4).
Bob quotes data(13) taken from the WQDB, describing the history of Pb concentrations measured in the old test wells DT-5A, DT-9, and DT-10, located at MDA-AB. He points out the very large excursion in the record of Pb concentrations recorded at DT-5A, during the period 1992-1995; i.e., to a level of ~9000 mg/L, which is 90 times the MCL. It seems that DT-5A is located in the middle of a cluster of five shafts, once used for hydronuclear tests, and is no farther than 1000 ft from any one of those shafts.
Bob notes also that, during this same period, excursions were recorded in Pb concentrations from DT-9 and DT-10, although to values of less than 100 mg/L. But, those two wells are both located outside of the cluster of shafts, and at a distance of several thousand feet from the nearest shaft. Meanwhile, at the old test well TW-3, located in Los Alamos Canyon, approximately five miles distant from MDA-AB, no excursion in Pb concentration was ever seen.
Enquiring minds ask for an explanation of these phenomena. After all, if what was measured at DT-5A, DT-9, and DT-10 were Pb residues from old hydronuclear tests, residues which had somehow become mobile for a period of a few years during the early 1990’s, then such residues could become mobile again, at some future time.
It appears that LANL may actually favor an explanation of these facts based on a theory(18, 19) of “ … well sampling and well construction issues rather than from LANL contamination.” This appears to be a peculiar theory, on the one hand, because it assumes something which is not much in evidence; viz., that either the drilling fluids, or the well casing and/or the well screening materials used in the construction of DT-5A were rich in Pb, but not so for DT-9 and DT-10, and not at all so for TW-3. On the other hand, this theory is also peculiar since it does not attempt to account for the pronounced time-history of the Pb concentrations that have been observed. At the same time, LANL personnel deny the presence in groundwater of Pb residues from old hydronuclear tests at MDA-AB(19).
However, it is also true that LANL’s point of view finds support in other data found in the WQDB. These data are the records of the concentrations of other common metals, found in the groundwater at these four wells. In Figs. 1, 2, 3, and 4, I plot the histories of measured concentrations for iron (Fe), zinc (Zn), and lead (Pb), at the old test wells DT-5A, DT-9, DT-10, and TW-3, respectively.
Interestingly, excursions in Pb concentration, appearing during the 1993-1994 time period, are accompanied by excursions in both the concentrations of Fe and Zn. Moreover, at DT-9 and DT-10, the excursion in Pb concentration is much smaller than the excursions in both the concentrations of Fe and Zn. At TW-3, concentration histories show a series of fluctuations, but do not show a dominant excursion in the concentration of any metal during the 1993-1994 time period(20).
It may be relevant that LANL will report, in its soon to be released Environmental Surveillance Report for 2007(21), that elevated levels of Pb, and several other metals, have been detected recently in Water Canyon and Threemile Canyon surface water. Water Canyon borders on MDA-AB, and Threemile Canyon borders on Water Canyon. Anon!
We have seen that the subject of metals in groundwater at LANL is one of minor mystery; and we have seen two examples of such mystery.
The story of the high levels of chromium in the groundwater beneath Mortandad Canyon is at least curious. Hard evidence to support the prevailing theory, that the original source of chromium contamination was the old water cooling tower at the head of Los Alamos Canyon, is only now beginning to emerge(3). Earlier, the evidence seemed to be just circumstantial. Certainly, a power plant cooling tower did dump lots of chromium into Sandia Canyon, and that chromium had to go somewhere. But, the connection between that cooling tower in Sandia Canyon, and R-28 in Mortandad Canyon, was tenuous, and seemed to be confined to the histories of chromium contamination measured in samples from select alluvial wells, mostly, but not exclusively, upstream of R-28. Also, these histories showed, for the most part, an isolated excursion in chromium concentration during the period 1993-1995; and this excursion did not recur. At the same time, similar excursions did not occur in other nearby alluvial wells.
But wait! The story of the high levels of Pb, Fe, and Zn measured in groundwater beneath TA-49 is similarly strange. This is because the histories of these three contaminants, in the three deep wells DT-5A, DT-9 , and DT-10, are ones that themselves show sharp excursions in concentration during the 1993-1995 time period, which failed to recur; see Figs. 1-4.
Could all of these isolated concentration excursions, occurring at different locations, but at roughly the same time, be just a coincidence? Or was there some, as yet, unaccounted for influence on the measurements of metal concentrations made at wells distributed over a wide area on the Pajarito Plateau, during 1993-1995?
1) “Summary [with Commentary] of ‘Radionuclides in Groundwater’ from LANL’s ‘Water Quality Data Base’ I.”, Ken LaGattuta NNMCAB, 7-18-08.
2) “Summary [with Commentary] of ‘Radionuclides in Groundwater’ from LANL’s ‘Water Quality Data Base’ II: History of Tritium Activities”, Ken LaGattuta NNMCAB, 8-30-08.
3) D. Katzman, “Chromium Fate and Transport for Chromium Contamination from Sandia Canyon”, LA-UR-08-4702. The story of the contamination of groundwater beneath Sandia Canyon by chromium is extensive and ongoing.
4) “Comment on the Large Plume of Lead in the Groundwater Below the LANL Legacy Waste Disposal Site MDA AB and the Deficiencies in the LANL Protection Practices …” , Robert H. Gilkeson, 8-25-08.
5) See remarks in ref. 2, relating to the proper use of the MDA.
6) See remarks in ref. 2, relating to (-) Result values.
7) Office of Water (4606M), EPA 816-F-03-016, www.epa.gov/safewater, June, 2003. The Primary Drinking Water Standard defines values of the MCL beyond which serious health effects could ensue, for the general population. It should be clear that applying a drinking water standard to groundwater, which may not be used for regular drinking, is a conservative approach.
8) Ibid. The Secondary Drinking Water Standard defines values of the MCL beyond which noticeable minor health effects could ensue, for the general population.
9) “Los Alamos National Laboratory News”, James E. Rickman, March 17, 2006.
10) “Los Alamos National Laboratory News”, James E. Rickman, December 7, 2006.
11) “Los Alamos National Laboratory News”, James E. Rickman, May 3, 2007. Quoting from this news release: “Personnel in the Lab's Water Stewardship Project recently began construction of monitoring well R-35 in lower Sandia Canyon. This regional-aquifer-monitoring well is being constructed upgradient and near Los Alamos County drinking-water-supply well PM-3. The R-35 well will act as a ‘sentinel’ that can determine whether a plume of hexavalent chromium—a component of a corrosion inhibitor used from the 1950s to the 1970s—is approaching the county’s PM-3 well.” However, R-28 was installed(12) in 2003, and the discovery of high levels of dissolved chromium in this well was made(13) in May, 2005.
12) (www.wqdbworld.lanl.gov / Chemistry/ Characterization Wells/ Completion Reports.
13) (www.wqdbworld.lanl.gov / Chemistry/ Metals/ Groundwater.
14) D. Katzman (LANL), in talk presented to the NNMCAB’s EMSR Committee, Sept. 10, 2008. He emphasized the importance of obtaining filtered water samples, when attempting to measure the concentration of Cr(VI) in groundwater. Presumably, unfiltered samples would include sediments onto which insoluble Cr(III) could be adsorbed.
15) Ibid. Katzman reported that the nitrogen detected in groundwater at R-28 is in the form of nitrate, suggesting that its origin is in sewage.
16) R. N. Thorn and D. R. Westervelt, “Hydronuclear Experiments”, LA-10902-MS, Feb., 1987.
17) D. G. Levitt, etal , “Site Characterization and Monitoring of TA-49 at LANL”, in Proceedings of Waste Management ‘03 Conference, Tucson, AZ, Feb. 23-27, 2003.
18) Environmental Surveillance at Los Alamos during 2006, LA-14341-ENV.
19) Terry Morgan (LANL), during a discussion of EM issues at LANL, Aug., 2008. Present were T. Morgan, A. Simmons, L. Bonds-Lopez, and myself.
20) Unfortunately, all entries in the WQDB for metals in groundwater, prior to 1993, are for unfiltered samples; entries for filtered samples, begin in 1993. Although in Figs. 1-4, for data prior to 1993, I have recorded the values measured for unfiltered samples, beginning with 1993-1994 the recorded values are largely for filtered samples. Most importantly, the peaks appearing circa 1993-1994 are for filtered samples.
21) Environmental Surveillance at Los Alamos during 2007, (DRAFT) Executive Summary, Table ES-4, Sept., 2008.