WIPP ENVIRONMENTAL MONITORING PROJECT
(Aerial view of the WIPP Site)
Project Concept
As defined in the original grant language, the purpose of the WIPP EM project is to establish and maintain independent environmental research and monitoring in the vicinity of the WIPP and to make the results easily accessible to all interested parties. This project began implementation during the WIPP pre-disposal phase, and is continuing during the operational (disposal) phase. The WIPP EM project is organized and carried out independent of direct oversight by DOE, and the project does not provide data to any regulatory body to meet the compliance demonstration requirements applicable to the WIPP.
Study Design for the WIPP EM
A primary objective of the WIPP EM pre-disposal baseline phase was to quantify the background environmental levels of the radionuclides and inorganic non-radioactive constituents that are known or expected to occur in the wastes deposited at the WIPP. These data serve as a basis for comparison against data collected for the same constituents after the WIPP began operation, and extending into the post-operational phase. A true quantification requires application of specialized methods, particularly in radiochemistry, to produce data that are free of non-detect values.
It is also important to note that the objective requires sampling designs that provide data to characterize the spatial variation in the analytes of interest across the natural landscape in the vicinity of the WIPP, and the temporal variation in the analytes of interest with respect to seasonal and interannual ecosystem fluctuations. For example, the background concentrations of Pu in aerosols in the vicinity of the WIPP span a range of values that may be dependent on such factors as localized soil type and seasonal weather variations that impact resuspension.
The WIPP EM incorporates analyses of a variety of inorganic substances as part of the routine monitoring design. According to information contained in the waste acceptance criteria for the WIPP (DOE/WIPP-069, November 8, 1999), the mixed waste to be placed at the WIPP may contain arsenic, barium, beryllium (powder), cadmium, chromium, copper, lead, mercury,nickel, selenium, and silver. These constituents are naturally-occurring elements, and are also produced as contaminants from other anthropogenic sources, so quantification of pre-operational levels in the WIPP region was needed to evaluate potential future releases. Some of these trace elements are of concern due to possible toxicological effects for humans and ecosystems. From a practical standpoint, they are also very important and useful in the WIPP EM project as chemical tracers. The sources for these metals are reasonably well known, even on global scales (Nriagu, J. O. and J. M. Pacyna, 1988, Nature, 333:134), and they are readily determined in various types of environmental media.
If contaminant releases from the WIPP were known or suspected, it would become critical to predict the movements of the contaminants within the ecosystem. A second major objective of the WIPP EM baseline studies was to gather information concerning the basic structural/chemical composition of environmental media and ecosystem processes that could be applied in such predictive modeling. Concurrent analyses of naturally occurring radionuclides, non-radioactive elements, and target ions (such as nitrate and sulfate), provide an understanding of the complex and interlocking biogeochemical cycles that characterize the WIPP surface environment. Such characterization provides the basis for modeling of ecosystem processes that determine the fate and transport of contaminants of concern.
The following sections present a brief description of the basic sampling design for each major environmental medium in the WIPP EM, including some primary considerations that serve as the basis of the design. In addition to the core sampling and analyses, information is provided on ancillary studies that are planned or in progress.
Aerosols
 (Aerosol sampling station near WIPP) |
Aerosols are considered a prime environmental medium of concern with respect to potential future releases by the WIPP because airborne contaminants can rapidly disperse, can be transported over long distances, and represent a significant mode for uptake by humans and other organisms. CEMRC studies of aerosols focus on both man-made and naturally-occurring radionuclides (including those known or expected to occur in the wastes to be deposited at the WIPP) and selected non-radioactive, inorganic constituents. |
Aerosol sampling is conducted at four locations as part of the WIPP EM, with samplers operating continuously at each location. The locations include a port inside the WIPP exhaust shaft, a site approximately 0.1 km northwest (downwind) of the WIPP exhaust shaft (On Site station), a site approximately 1 km northwest (downwind) of the WIPP (Near Field station), and a site approximately 19 km southeast (upwind) of the WIPP (Cactus Flats station) (see Fig.2 of the 2000 Annual Report). The sites were selected on the basis of the prevailing wind directions at the WIPP. In designing aerosol studies, it is widely recognized that there is seldom a satisfactorily defined "control" location that is far enough from a source to ensure isolation from aerosol releases, while adequately replicating key ecological features of aerosol composition, soil, topography, biota and weather conditions. The Cactus Flats location represents a reasonable compromise to approximate a control location for surface parameters, based on average conditions.
Sampling in the WIPP exhaust shaft (Station A) consists of collection of one or more filters daily (Monday through Friday) from a Fixed Air Sampler (FAS), that is operated with an average air flow of 56 L min-1. The daily FAS samples are subjected to gross alpha/beta counting individually. The five daily (Monday - Friday) samples from each week are composited for weekly gamma counting and all weekly composites are combined each calendar quarter for analyses of Pu and Am by alpha spectrometry. This sampling is a workplace monitor thatprovides a gross check of emissions on a short resolution time-scale (for daily and weekly samples), with a higher sensitivity check for cumulative emissions over a three-month time scale. (Collection of FAS samples by the CEMRC began in December 1998).
At the other three stations, aerosol samples for radionuclide analyses are collected using high-volume samplers (approximately 1.13 m3 min-1). These samplers are operated to maximize particulate loading without impacting air flow, so individual samples are collected for periods ranging from three to six weeks, depending on levels of particulate deposition. By focusing on high particulate loading, this sampling allows collection of sufficient mass for quantitative determination of the manmade alpha-emitting radionuclides (Pu and Am) at background levels via alpha spectrometry, which was of particular interest in baseline studies. Low-volume samplers (10 L min-1) are operated for collection of samples for analyses of non-radioactive, inorganic constituents (trace metals and selected ionic compounds). Analytical methods for inorganic constituents do not require large sample concentrations, so low-volume sampling includes two 2-day samples, and one 3-day sample weekly. All three stations support one high-volume sampler collecting total suspended particulate (TSP) matter and one low-volume sampler collecting TSP. The Near Field and Cactus Flats stations also support a second high-volume sampler collecting particulate matter less than 10 mm aerodynamic equivalent diameter (PM10).
Since November 1998, dichotomous low-volume samplers have been operated at the Near Field and Cactus Flats stations. The dichotomous sampler is an EPA-equivalent reference method for sequential measurement of both PM10 and PM2.5. With respect to human health, PM10 and PM2.5 are the particulate classes that are generally recognized as the most significant of the respirable aerosol components, and it is important to characterize the natural temporal and spatial variation in these components that would impact potential uptakes of WIPP contaminants by humans.
Soils
Soils are of high interest to the WIPP EM because aerosol releases of contaminants would eventually be deposited in surface soils, which then can serve as a source for continuing contaminant exposure and uptake via direct contact, food chain pathways, and re-suspension. From this perspective, soil is an integrating medium of primary concern in predictive ecosystem and contaminant transport modeling, that requires good information about the dispersion of analytes of concern across the landscape.
The soil sampling design for the WIPP EM baseline and monitoring studies is organized to address analyte variability on three spatial scales. First, soil sampling is conducted within a 166 km2 area centered on the WIPP operations facility, and at a comparable area encompassing the Cactus Flats aerosol sampling station. Within each of these two areas, samples are collected at 16 locations positioned in concentric rectangular grids (see Fig 2 of the 2000 Annual Report). For baseline studies, at each of the 16 locations in each area, samples were collected at three randomly selected sites within 25-m of the location's reference point. Individual sampling sites are selected on the basis of relatively flat topography and minimum surface erosion or disturbance due to human or livestock activity. The resulting data provided for estimation of variability at the small-scale (between samples within a .0025 km2 area), medium-scale (among locations within each 166 km2 area), and large-scale (between the two sampling areas located approximately 19 km apart). This type of design has been applied in other experimental studies focusing on analyte dispersion patterns in soils (Gilbert, R.O., 1987, Statistical Methods for Environmental Pollution Monitoring, Van Nostrand Reinhold Co., New York).
During baseline studies, samples for pilot projects were collected at various times in 1996 and 1997 using this spatial design. In 1998 and 1999, the full suite of 96 samples were collected. In 2000 and subsequent years, one sample at each of the 16 locations in each area (32 total) are being collected annually. The limitation of soil sampling to one period annually is based on the assumption that any input of contaminants to surface soils from WIPP releases would occur via aerosol deposition, and since aerosol sampling is conducted continuously, more frequent soil sampling is not warranted unless there was evidence of a contaminant increase in aerosols.
Surface Water and Sediments
The WIPP EM incorporates studies at three reservoirs on the Pecos River, which is the major perennial fresh water system closest to the WIPP that has extensive human usage. The three reservoirs are: Brantley Lake, located approximately 40 miles northwest of the WIPP; Lake Carlsbad, located in Carlsbad and approximately 25 miles northwest of the WIPP; and Red Bluff Lake, located approximately 30 miles southwest of the WIPP. Surface and underground drainage from the area of the WIPP is to the southwest, and Red Bluff Lake is downstream of the area where drainage from the WIPP area enters the Pecos River. Brantley Lake and Lake Carlsbad are both upstream of the WIPP area drainage, and thus would be unlikely to receive contaminants via drainage from the vicinity of the WIPP but could be contaminated by atmospheric deposition. In addition to their proximity to the WIPP, these three reservoirs were selected because of the potential exposure of human populations to contaminants through use by the local population for sport fishing and recreation, and through use of Pecos River water for agricultural irrigation in a large region of the river floodplain throughout New Mexico and Texas.
During 1996-97, pilot studies were conducted to identify shallow, mid-and deep-basin areas of each reservoir and to characterize the physical and chemical nature of the sediments at the various depths. The deep basin areas now serve as the focus for sediment sampling because radioactive contaminants (and other inorganic contaminants) are known to concentrate in zones featuring fine-grained sediments, which are highest in the deepest waters. The sediment sampling consists of collection of one sample from each of four randomly selected locations within the deep basins at each reservoir. Each sample analyzed is a composite of two to four grab samples taken from the top 5-10 cm of the sediment surface. Two samples of water (one at the surface and one approximately 0.5 to 1 m above the sediment bed) are also collected at one deep basin site at each reservoir. During 1997-1999, sediment and surface water samples were collected once during the spring, once in winter, and twice in the summer. Because of the distance between the WIPP site and these reservoirs, the potential risk of direct contamination of the reservoirs by releases from the WIPP is relatively low compared to other media, and sampling is now conducted once annually in the summer.
Drinking Water
The WIPP EM studies of ground water focus on the major drinking water supplies used by communities in the WIPP region because these are often perceived by the public as a potential route for contaminants to reach humans. However, studies of the hydrogeology of the region suggest (1) that the risk is low for contaminants from the WIPP to reach the various regional underground aquifers that are used as sources of drinking water, and (2) the movement of contaminants into these aquifers, if it occurred, would be extremely slow (DOE, 1997, Waste Isolation Pilot Plant Disposal Phase Final Supplemental Environmental Impact Statement, DOE/EIS-0026-S-2). Five community supplies of drinking water (representing three major regional aquifers) are included in routine sampling, including Carlsbad, Loving/Malaga, Otis, Hobbs, and a secondary source for Carlsbad. One private water well (representing a fourth aquifer) that is located within ten miles of the WIPP is also sampled because it is the only private well in close proximity to the WIPP that is known to have been used for human consumption in recent years, and because it draws from the aquifer considered most likely to be contaminated by releases from the WIPP into ground water, (DOE, 1990, Final Supplemental Environmental Impact Statement, DOE/EIS-0026-FS).
Studies of the drinking water sources utilize samples collected at locations in the drinking water systems that are considered to be representative of the overall supply to the system's user group. Many of the systems draw from several wells simultaneously or on a rotating basis, and routinely sampling all of the dozens of individual wells is not justified. Instead, samples for municipal systems are drawn from the primary reservoir vessels downstream of the well sources, which are more representative of the overall water supply than samples from individual wells. Likewise, for municipal supplies, samples are not taken from individual user taps because of the potential contamination introduced via the residential segments of the system, which would have no demonstrable relationship to contaminants from the WIPP. Recharge of the target aquifers is not known to be strongly linked to seasonal cycles (except in a few cases where an indirect linkage via hydraulic head pressure is suspected). Therefore, there is little basis to expect any significant seasonality in drinking water contaminants of concern, and the WIPP EM sampling design for drinking water does not incorporate a seasonal component.
During initial baseline studies in 1996-1998, the drinking water samples were subjected to a suite of analyses for over 150 analytes, including those that are regulated under the Safe Drinking Water Act, and contaminants known or suspected to be present in the WIPP wastes. In addition to serving as a baseline for future comparisons, these analyses provided information that was considered to be of general interest to the public. Knowledge of the basic chemical composition of the water supplies is also useful in radioanalytical studies, where chemical processes can be strongly affected by non-radioactive components.
In relation to the core objectives of the WIPP EM, radioanalyses of drinking water conducted during 1997-1998 were unable to detect Pu or Am in any of the samples collected. The analyses applied to the samples consisted of traditional alpha spectrometry. Samples of drinking water were also submitted for thermal ionization mass spectrometry (TIMS) (a more sensitive radioanalytical technique). The TIMS analyses did not detect any of the manmade actinides of interest. Each of the six drinking water supplies are now sampled once annually for selected radiological and inorganic testing.
Biota
Studies of biota for the WIPP EM have focused on native vegetation because the vegetation is consumed by beef cattle, and consumption of beef from cattle pastured in the vicinity of the WIPP could serve as an exposure pathway to humans for contaminants released from the WIPP. While it would seem more desirable to monitor the presence of contaminants in the beef directly, the livestock industry in the region routinely uses supplemental feeding for range cattle during some portion of most years. This means that the cattle are potentially exposed to contaminants from distant sources via the supplemental feeding, thereby confounding the interpretation of any direct analyses of range cattle tissues. Secondarily, if the occurrence of radioactive contaminants in major food plants is known, the potential uptake of radioactive contaminants by range cattle can be effectively predicted from existing data on livestock diets, consumption rates, and absorption ratios.
During baseline studies, vegetation samples were collected from a total of six species of plants that serve as preferred forage species for cattle during at least some portion of the year. These include fall witchgrass (Leptoloma cognatum), sand paspalum (Paspalum setaceum), spike dropseed (Sporobolus contractus), mesa dropseed (S. flexuosus), honey mesquite (Prosopus glandulosa), and shinnery oak (Quercus havardii). The sampling included collection of discrete samples of each species, because relevant published work indicates that plant species can vary significantly in both uptake of radionuclides into plant tissues and in adherence of radiation-contaminated soil particles to external plant surfaces.
Vegetation is sampled either once or twice annually, depending on rainfall conditions, during the two major periods of new growth for native vegetation (March-May and August-October). Not all of the same species can be sampled at each period because some of the species only produce major new growth during one season, and because the abundance of the species varies among years depending on weather patterns. Six samples of each of three species (contingent on availability) are collected during each sampling period from selected sites on the sampling grid surrounding the WIPP (which encompasses the Near Field aerosol sampling station). The vegetation samples are analyzed for selected radionuclides only. Collecting samples at the same locations used for soils allows for a direct comparison between radionuclide levels measured in soils and vegetation. Vegetation sampling has currently been suspended until analytical results are obtained from baseline studies.
Additional studies are in progress to evaluate the effectiveness of expanding the biota sampling for radionuclides to include arthropods. In many desert ecosystems, total arthropod biomass has been shown to equal or exceed total biomass for any other consumer component, and arthropod communities encompass primary, secondary and tertiary consumers, as well as detritivores and necrovores. As such, arthropods could be used to study the movement of radionuclides through natural ecosystem food chains. Arthropods were collected during 1998 and 1999, and collection may be repeated in future years, pending analytical results.
Human Population
The "Lie Down and Be Counted" project serves as a component of the WIPP EM that directly addresses the general concern about personal exposure to contaminants shared by residents who live near many DOE sites. Although this aspect of the project could be viewed as using local residents as monitors of contaminant release from the WIPP, the design of wide-scale monitoring of other media ensures (as much as reasonably possible) that contaminant releases would be detected in the environment long before significant contact with human residents. It is important to note that an individual who is determined to have internally deposited radioactive materials after the WIPP begins operation, could not use the results of this study to suggest that the uptake occurred as a result of exposure to materials at the WIPP unless that individual had been subject to an in vivo bioassay a priori, with negative results.
As in other aspects of the WIPP EM, in vivo bioassay testing has been used to establish a baseline profile of internally-deposited radionuclides in a sample of local residents. The sampling design included solicitation of volunteers from all segments of the community, with sample sizes sufficient to meet or exceed a 15% range margin of error for comparisons between major population ethnicity and gender categories as identified in the 1990 census. The minimum sample size threshold was achieved for the major categories early in 1998, and is as low as 8% margin of error range for some categories. Since the WIPP began operation, bioassays of the original volunteer cohort is repeated on a schedule of once every two years, and additional new volunteers are incorporated each year to create replacements for attrition from the original cohort.
Meteorological Monitoring
Fully automated meteorological stations are operated by the CEMRC at the Near Field aerosol station and the Cactus Flats aerosol station. Details concerning the sensors and operation of the equipment are presented in the 2000 Annual Report section on meteorology. The data derived from these stations is essential to interpreting results from other parts of the project, particularly the aerosol studies. For example, notable short-term changes in aerosol compositions can be evaluated against wind direction to determine if there were a possible difference in source terms.
Analyses and Release of Data
The scheduling and management of sample analyses collected in the WIPP EM project is based on (1) priorities for providing information to the public in a timely manner, (2) relative risks of human exposure to contaminants among the various media sampled, (3) needs for stringent data validation and verification prior to release, and (4) time constraints resulting from sample preparation and analysis procedures. Based on this, and as noted previously, analyses of daily and weekly composite FAS aerosol samples provide gross data on radiation at a location immediately adjacent to the waste-handling and deposition activities. These analytical results are made available within a few weeks of sample collection, and the data (along with quarterly composite data) are posted on the CEMRC web page weekly. This is a routine, quick turnaround monitoring strategy that focuses on detection of potential short-term, large-scale radioactive contaminant release via the medium likely of most risk for worker and public exposure (aerosols).
Results of analyses of other (non-FAS) aerosol sampling are carried out with quarterly batches of filters, with results posted on the web page approximately 45 days after the end of each quarter. For samples of soils, sediments, surface water, drinking water and biota, collection is annual or semi-annual (as previously described), and the period of time required for completion of analyses varies with each medium. As for aerosols, analytical results for these media areas will generally be posted to the web site within two months after sample collection. A schedule of sample collection and posting of results for the current year is provided at Recent Data for WIPP Environmental Monitoring.
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