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R. Mitchell - S. M. Stoller Corporation
M. Roddy, T. Wood - Bechtel/BWXT Idaho, LLC
L. Knobel - United States Geological Survey
M. Finnerty - Argonne National Laboratory-West
S. Lowry - Naval Reactors Facility
One potential pathway for exposure from contaminants released at the Idaho National Environmental and Engineering Laboratory (INEEL) is through the water pathway (surface water, drinking water, and groundwater). The Management and Operating contractor monitors groundwater, as well as liquid effluents, drinking water, and storm water runoff at the INEEL to comply with applicable laws and regulations, U.S. Department of Energy orders, and Wastewater Land Application Permit requirements. Argonne National Laboratory-West and the Naval Reactors Facility conduct their own groundwater, effluent, and drinking water monitoring. The U.S. Geological Survey (USGS) INEEL Project Office performs groundwater monitoring, analyses, and studies of the Eastern Snake River Plain Aquifer (ESRPA) under and adjacent to the INEEL. The Environmental Surveillance, Education and Research program contractor monitors drinking water and surface water at offsite locations.
Historic waste disposal practices have produced localized areas of chemical and radiochemical contamination in the ESRPA beneath the INEEL. These contaminated areas are monitored by the above-mentioned organizations as well as various other organizations.
Results from a number of special studies conducted by the USGS of the properties of the aquifer were published during 2004. Several purgeable organic compounds continue to be found in monitoring wells, including drinking water wells at the INEEL. Concentrations of organic compounds were below the U.S. Environmental Protection Agency maximum contaminant levels and state of Idaho groundwater primary and secondary concentration standards for these constituents.
Groundwater surveillance monitoring required in area specific Records of Decisions under the Comprehensive Environmental Response, Compensation, and Liability Act was performed in 2004. No contaminant concentrations exceeded expected or historical concentrations.
Semiannual drinking water samples were collected from 14 locations off the INEEL. One sample from Idaho Falls had measurable gross alpha activity. Eleven samples had measurable tritium, and 21 samples had detectable gross beta activity. None of the samples exceeded the EPA MCL for these constituents.
A total of 11 offsite surface water samples were collected from five locations along the Snake River. Most of the samples had measurable gross beta activity, while only one sample had measurable tritium. Detectable gross alpha activity was not found in any sample. None of these constituents were above regulatory limits.
Operations at facilities located on the Idaho National Engineering and Environmental Laboratory (INEEL) release radioactive and nonradioactive constituents into the environment. These releases are in compliance with regulations, and monitoring of the releases ensures protection of the public and environment. Historic waste disposal practices have produced localized areas of chemical and radiochemical contamination in the Eastern Snake River Plain Aquifer (ESRPA) beneath the INEEL. These contaminated areas are monitored by various organizations.
This chapter presents results from both radiological and nonradiological surveillance sampling and Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) sampling of groundwater and surface water samples taken at both onsite and offsite locations. Results from sampling conducted by the Management and Operating (M&O) contractor; Argonne National Laboratory-West (ANL-W); the U.S. Geological Survey (USGS); and the Environmental Surveillance, Education and Research Program (ESER) contractor are presented here. Results are compared to the state of Idaho groundwater primary and secondary constituents standards (PCS/SCS) of IDAPA 58.01.11 (IDAPA 58.01.11) and the U.S. Environmental Protection Agency (EPA) health-based maximum contaminant levels (MCL) for drinking water and/or the U.S. Department of Energy (DOE) Derived Concentration Guide (DCG) for ingestion of water.
This chapter begins with a general overview of the various organizations monitoring groundwater at the INEEL in Section 6.1. Sections 6.2 and 6.3 present discussions of the hydrogeology of the INEEL and hydrogeologic data management, respectively. Section 6.4 describes aquifer studies related to the INEEL and ESRPA. Radiological and nonradiological monitoring of groundwater at the INEEL are discussed in Sections 6.5 and 6.6, respectively. Section 6.7 outlines the CERCLA groundwater activities performed in 2004. Section 6.8 describes offsite drinking and surface water monitoring.
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The USGS INEEL Project Office performs groundwater monitoring, analyses, and studies of the ESRPA under and adjacent to the INEEL. This is done through an extensive network of strategically placed monitoring wells on the INEEL (Figure 6-1 and Figure 6-2) and at locations throughout the Eastern Snake River Plain (ESRP). Chapter 3, Section 3.1, summarizes the USGS routine groundwater surveillance program. In 2004, USGS personnel collected over 1,000 samples for radionuclides and inorganic constituents including trace elements and approximately 30 samples for purgeable organic compounds.
In addition to the above duties, the USGS performs groundwater monitoring activities for the Naval Reactors Facility (NRF) through an interagency agreement. As part of the 2004 NRF sampling program, the USGS performed sampling three times from nine NRF wells and four USGS wells, collecting a total of 45 samples. Samples were analyzed for radionuclides, inorganic constituents, and purgeable organic compounds.
ANL-W performs semiannual groundwater monitoring at one upgradient monitoring well, three downgradient monitoring wells, and one production well. Samples are analyzed for gross activity (alpha and beta), uranium isotopes, tritium, inorganics, and water quality parameters.
As detailed in Chapter 3, CERCLA activities at the INEEL are divided into ten Waste Area Groups (WAGs) (Figure 3-3). Each of these WAGs is addressing groundwater for its particular contaminants. WAG 10 has been designated as the site-wide WAG and addresses the combined impact of the individual contaminant plumes. As individual Records of Decision (RODs) are approved for each WAG, many of the groundwater monitoring activities are administratively turned over to the Long-Term Stewardship (LTS) program as an effort to consolidate monitoring activities.
The ESER contractor monitors offsite drinking and surface water. There were 30 drinking water and 11 surface water samples collected for analyses in 2004.
The INEEL Oversight Program collects split samples with the M&O and other INEEL contractors of groundwater from both compliance (discussed in Chapter 5) and surveillance wells. Results of the Oversight programs monitoring are presented in annual reports prepared by that organization and are not reported here.
Table 6-1 presents the various groundwater and surface water monitoring activities performed on and around the INEEL.
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The INEEL occupies 2300 km2 (890 mi2) of the northwest side of the ESRP. The ESRP is a northeast-southwest oriented structural basin approximately 435 km (270 miles) long and 80 to 113 km (50 to 70 miles) wide. The ESRP is bounded by typical Basin and Range fault block mountains and valleys along the north edge and downwarping and faulting along the southern edge. Over time, the ESRP has been filled with basaltic and rhyolitic volcanic rocks related to the passage of the North American tectonic plate over the Yellowstone hotspot.
Sequences of basaltic rocks make up approximately the upper 550-1500 m (1800-4000 ft) of the fill material within the ESRP. Basalts were erupted over well defined cycles separated by long periods of no volcanic activity. Individual basalt flows range from 1.5 to 15 m (5 to 50 ft) in thickness and can cover tens of square miles. As newer basalt flows were erupted, they spread out across the landscape, covering previous basalt surfaces or accumulated soils which now form interflow zones and interbeds, respectively. Moving through these interflow zones is the water of the ESRPA.
The ESRPA is one of the largest, most productive aquifers in the United States. It has been estimated that there are 200 to 300 million acre-feet of water contained within the ESRPA. Presently, the aquifer is tapped to meet the demands of agriculture, industry, and the more than 280,000 people who live on and around the ESRPA. In 1990, the ESRPA was classified as a "sole-source aquifer" by the EPA. More recently the state of Idaho has implemented protections for the ESRPA under its groundwater quality regulations.
The water of the ESRPA originates as recharge from river waters of the upper Snake River Plain, such as the Henry's Fork, the south fork of the Snake River, and the Big and Little Lost Rivers (Figure 6-3). Other sources of recharge water include the flow of groundwater out of the surrounding mountain valleys (Birch Creek, Medicine Lodge Creek, Camas Creek), leakage from irrigation canals and ponds, and infiltration from precipitation and irrigation.
Once in the ESRPA, the water moves to the southwest at rates ranging from 1.5 to 6.1 m per day (5 to 20 ft per day). This is much faster than most aquifers and is attributed to the high permeability of the interflow zones.
Groundwater is removed from the ESRPA through pumping and as spring flows along the Snake River in the area between Twin Falls and Hagerman. Because of the high flow velocities, estimated travel time from the INEEL to the Snake River through the ESRPA varies from 50 to 100 years.
Beyond the regional controls on flow in the ESRPA, the hydrogeology of the INEEL is controlled locally by surface water flows in the Big Lost River. Periods of high flow in the river have been shown to create temporary shifts in the local flow direction from northeast-southwest to north-south. The effect of these local changes has been to spread contamination related to INEEL operations over a larger area than would be expected. Other impacts of INEEL operations to the subsurface hydrogeology have been the formation of numerous perched water zones beneath waste ponds as a result of the seepage of pond water into the soils and the introduction of contaminants both directly (through injection) and indirectly (through vertical movement of water beneath ponds and facilities) to the ESRPA.
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Over time, hydrogeologic data at the INEEL has been collected by a number of organizations, including the USGS, the M&O, and other site contractors. One of the functions of the INEEL Hydrogeologic Data Repository (HDR) is to maintain and make the data generated by these varied groups available to users and researchers. The HDR was established as a central location for the storage and retrieval of hydrologic and geologic information at the INEEL. The HDR is used to maintain reports, data files, maps, historic records, subcontractor reports, engineering design files, letter reports, subsurface information, and other data in many formats. This information is related to the hydrology and geology of the INEEL, the ESRP, and the ESRPA beneath the INEEL. The HDR is also used to maintain the INEEL Comprehensive Well Inventory, with records of well construction, modification, abandonment, and logging. The HDR also maintains databases of historic and current water analysis, water levels, and special studies. Information from the HDR is available by request. A web site is being constructed that will allow open access to much of this information.
Another organization was also created at the INEEL to handle all laboratory analytical requests. The INEEL Sample and Analysis Management (SAM) Program was established to provide, consolidated environmental sampling activities and analytical data management. The SAM provides a single point of contact for obtaining analytical laboratory services and managing cradle-to-grave analytical data records. The SAM develops statement(s) of work, procedures, and guidance documents to establish and maintain analytical and validation contracts. The consolidated approach is based on the need for Site-wide reporting compliance, comprehensive technical analyses, and increased consistency in the manner in which analytical data are managed at the INEEL. The SAM also participates in monitoring laboratory performance and annual onsite laboratory audits to ensure quality and compliance.
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The ESRPA, which underlies the ESRP and the INEEL, serves as the primary source for drinking water and crop irrigation in the Upper Snake River Basin. A description of the hydrogeology of the INEEL and the movement of water in the ESRPA is given in Section 6.2. Further information may be found in numerous publications of the USGS. Copies of these publications can be requested from the USGS INEEL Project Office by calling 208-526-2438. During 2004, personnel of the USGS INEEL project office published 11 documents covering hydrogeologic conditions at the INEEL, on the Eastern Snake River Plain and in other areas of interest around the world. The abstracts to each of these reports are presented in Appendix C.
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Historic waste disposal practices have produced localized areas of radiochemical contamination in the ESRPA beneath the INEEL. The Idaho Nuclear Technology and Engineering Center (INTEC) facility used direct injection as a disposal method up to 1984. This wastewater contained high concentrations of both tritium and strontium-90 (90Sr) and iodine-129 (129I). Injection at the INTEC was discontinued in 1984 and the injection well sealed in 1990. When direct injection ceased, wastewater from INTEC was directed to a pair of shallow percolation ponds, where the water infiltrates into the subsurface. Disposal of low- and intermediate-level radioactive waste solutions to the percolation ponds ceased in 1993 with the installation of the Liquid Effluent Treatment and Disposal Facility. The old percolation ponds were taken out of service to be clean closed, and the new INTEC percolation ponds went into operation in August 2002. Test Reactor Area (TRA) also discharged contaminated wastewater to a shallow percolation pond. The TRA pond was replaced in 1993 by a flexible plastic (hypalon) lined evaporative pond, which stopped the input of tritium to groundwater.
The average combined rate of tritium wastewater disposal at the TRA and INTEC was highest between 1952 to 1983 (910 Ci/yr), decreased during 1984 to 1991 (280 Ci/yr), and continued to decrease during 1992 to 1995 (107 Ci/yr). From 1952 to 1998, the INEEL disposed about 93 Ci of 90Sr at TRA and about 57 Ci at INTEC. Wastewater containing 90Sr was never directly discharged to the ESRPA at TRA; however, at INTEC a portion of the 90Sr was injected directly to the ESRPA. From 1996 to 1998, the INEEL disposed about 0.03 Ci of 90Sr to the INTEC infiltration ponds (Bartholomay et al. 2000).
Presently, only 90Sr continues to be detected by the M&O contractor and the USGS at levels above the Primary Constituent Standard (PCS) value in some surveillance wells between INTEC and Central Facilities Area (CFA). Other radionuclides (i.e., gross alpha) have been detected above their PCS values in wells monitored by individual WAGs.
U.S. Geological Survey
Tritium - Because tritium is equivalent in chemical behavior to hydrogen, a key component of water, it has formed the largest plume of any of the radiochemical pollutants. The configuration and extent of the tritium contamination area, based on the most recent published data (1998), are shown in Figure 6-4 (Bartholomay et al. 2000). The area of contamination within the 0.5 pCi/L contour line decreased from about 103 km2 (40 mi2) in 1991 to about 52 km2 (approximately 20 mi2) in 1998.
Concentrations of tritium in the area of contamination have continued to decrease. The area of elevated concentrations near CFA likely represents water originating at INTEC some years earlier when larger amounts of tritium were disposed. This is further supported by the fact that there are no known sources of tritium contamination to groundwater at CFA.
Two monitoring wells downgradient of TRA (Well 65) and INTEC (Well 77) (see Figure 6-2) have continually shown high tritium activities in the aquifer over time. For this reason, these two wells are considered representative of maximum concentration trends in the rest of the aquifer near TRA. The average tritium concentration in Well 65 near TRA decreased, from (9.4 ± 0.5) x 103 pCi/L in 2003 to (8.3 ± 0.6) x 103 pCi/L in 2004; the tritium concentration in Well 77 south of INTEC also showed a slight decrease, (13.4 ± 0.3) x 103 pCi/L in 2003 to (12.9 ± 1.2) x 103 pCi/L in 2004.
The Idaho groundwater PCS for tritium is the same as the EPA MCL for tritium in drinking water of 20,000 pCi/L. The values in both Well 65 and Well 77 dropped below this limit in 1997 as a result of radioactive decay (tritium has a half-life of 12.3 years), a cessation of tritium disposal, advective dispersion, and dilution within the ESRPA (See Figure 6-5).
Strontium-90 - The configuration and extent of 90Sr in groundwater, based on the latest published USGS data, are shown in Figure 6-6 (Bartholomay et al. 2000). The contamination originates from INTEC as a remnant of the earlier injection of wastewater. No 90Sr in groundwater has been detected in the vicinity of TRA. All 90Sr at TRA was disposed to infiltration ponds in contrast to the direct injection that occurred at the INTEC. At TRA, 90Sr is retained in surficial sedimentary deposits, interbeds, and in the perched groundwater zones. The area of the 90Sr contamination from INTEC is approximately the same as it was in 1991.
Mean concentrations of 90Sr in wells have remained at about the same concentrations since 1989. The annual average concentration in well 65 decreased between 2003 (2.55 ± 0.58 pCi/L) and 2004 (1.0 ± 2.0 pCi/L). Concentrations in Well 77 remained the same at 1.8 ± 0.7 pCi/L in 2003 and 1.8 ± 0.4 pCi/L in 2004. The PCS and MCL for 90Sr in drinking water is 8 pCi/L.
The trend of 90Sr over the past ten years is shown in Figure 6-7. Although the trend is increasing, the statistical fit is weak (3 percent for Well 65 and 10 percent for Well 77). The uncertainties associated with 90Sr are also larger. This increase over the last five years is thought to be due, in part, to a lack of recharge from the Big Lost River that would act to dilute the 90Sr. Other reasons may also include an increase in the disposal of other chemicals into the INTEC percolation ponds that may have changed the affinity of 90Sr on soil and rock surfaces, causing it to become more mobile (Bartholomay et al. 2000).
Naval Reactors Facility
Groundwater samples around NRF are collected by the USGS under an interagency agreement. Groundwater monitoring did not detect any gross alpha or gross beta activity in excess of natural background concentrations. Measurements of tritium were at least a factor of 100 below PCS values. No 90Sr or programmatic gamma-emitters were detected. For more information, see Bechtel Bettis 2004.
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U.S. Geological Survey
Sampling for purgeable (volatile) organic compounds in groundwater was conducted by the USGS at the INEEL during 2004. Water samples from an onsite production well and seven groundwater monitoring wells were collected and submitted to the USGS National Water Quality Laboratory in Lakewood, Colorado, for analysis of 28 purgeable organic compounds. USGS reports describe the methods used to collect the water samples and ensure sampling and analytical quality (Mann 1996, Bartholomay et al. 2003). Ten purgeable organic compounds were detected at concentrations above the laboratory reporting level of 0.2 or 0.1 µg/L in at least one well on the INEEL (Table 6-2). None of the measured constituents were above their respective PCS.
The Radioactive Waste Management Complex (RWMC) production well contained detectable concentrations of eight of these purgeable organic compounds. Annual average concentrations of these compounds in this well remained essentially unchanged from those observed in 2003, however, the 2004 average concentration for trichloroethene (2.66 µg/L) was slightly above the average concentration of 2003 (2.48 µg/L).
Naval Reactors Facility
Groundwater samples around NRF are collected by the USGS under an interagency agreement. Most volatile organic compounds, inorganic analytes, and water quality parameters were below the minimum detection levels. All of the target nonradiological constituent concentrations averaged below Idaho PCS/SCS and EPA MCLs, with the exception of chromium in well NRF-13. The high average value for chromium in NRF-13 is from a single anomalous value that appears to be the result of high suspended solids in the well. Groundwater monitoring wells are not used for drinking water supply. For more information, see Bechtel Bettis 2004.
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CERCLA activities at the INEEL are divided into WAGs that roughly correspond to the major facilities at the site plus the site-wide WAG 10 (Figure 6-8). The boundaries of the various WAGs are found on Figure 6-8. In 2004, a total of 192 aquifer monitoring wells were sampled to satisfy CERCLA requirements. The following sub-sections provide an overview of ground water sampling results. More detailed discussions of the CERCLA driven sampling can be found in the WAG specific monitoring reports.
Summary of WAG 1 Groundwater Monitoring Results
The objective of the operable unit (OU) 1 07B remedial action is to contain and restore the contaminated groundwater at Test Area North (TAN). The groundwater at TAN is contaminated with trichloroethene (TCE), tetrachloroethene (PCE), and dichloroethene (DCE). To facilitate this remedial action, the contaminated groundwater was divided into three zones. The locations of wells used in the definition of each zone are shown in Figure 6-9. The boundaries of each zone of the plume were based on TCE concentrations. The three zones are defined as follows:
Hot Spot Zone (TCE concentrations exceeding 20,000 µg/L) - In situ bioremediation (ISB) is used in the hot spot to promote bacterial growth by supplying essential nutrients to bacteria that occur naturally in the aquifer and are able to break down contaminants. An amendment (such as whey or sodium lactate) is injected into well TSF-05 or other wells in the immediate vicinity. Amendment injections increase the rate at which the microbes break down the organic compounds into harmless compounds by supplying needed nutrients. The amendment supply is distributed, as needed, and the treatment system operates year-round.
In general, activities performed during 2004 included periodic amendment injections (sodium lactate and whey), groundwater sampling and analysis, well-drilling activities, construction activities, and Alternate Electron Donor (AED) laboratory studies. Seven amendments were injected during the year, five into well TSF-05 and two into well TAN-1859. Whey powder was used for the last amendment during FY04. All other amendment injections were made with sodium lactate. Groundwater samples were collected monthly from 17 sampling locations in the treatment cell to track the progress of ISB in the hot spot zone.
Medial Zone (TCE concentrations between 1000 and 20,000 µg/L) - Pump-and-treat is used in the medial zone. This process involves extraction of contaminated groundwater, treatment through air strippers, and reinjection of treated groundwater. Air stripping is a process that brings clean air into close contact with contaminated liquid, allowing the volatile organic contaminants to pass from the liquid into the air.
During 2004, all contaminant concentrations in water and air effluents from the New Pump and Treat Facility (NPTF) were below discharge limits and the influent contaminant concentrations continued to decrease. Water levels in several monitoring wells responded to extraction well startup (that is, pumping from extraction wells caused drawdown at these monitoring wells). Drawdown in wells TAN-19, -32, -33, and -36 indicates that the required plume capture width is achieved and that the NPTF is meeting its operational requirement to keep contaminated groundwater from migrating further downgradient.
Distal Zone (TCE concentrations between 5 and 1000 µg/L) - Monitored natural attenuation (MNA) has been selected as the treatment of choice for the distal zone of the plume. This process is the sum of the physical, chemical, and biological processes that act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in groundwater.
Engineering and administrative controls are in place to protect current and future users from health risks associated with groundwater contamination. During the early part of the restoration timeframe, the contaminant plume may continue to increase slowly in size until the natural attenuation process overtakes it.
The primary MNA activities performed during 2004 were groundwater sampling and data analysis. Groundwater samples were collected for volatile organic compounds (VOCs) and radiological parameters from 17 monitoring wells. Several of these locations were equipped with FLUTe™ systems and were sampled at multiple discrete depths below land surface. TCE concentration data and other data related to TCE degradation indicate that MNA will meet the remedial action objectives for the distal zone of the plume. Radionuclide groundwater monitoring in 2004 indicates that the natural attenuation mechanisms, as defined in the MNA Remedial Action Work Plan for the radionuclides tritium, cesium-137 (137Cs), 90Sr, and uranium-234 (234U), continue to be functional within the contaminant plume (DOE-ID 2003a). Groundwater monitoring in 2004 has shown no alarming increases in radionuclides, and future groundwater monitoring, as outlined in the MNA Operations, Monitoring, and Maintenance Plan, will be sufficient to track the progress of the MNA remedy for radionuclides at TAN OU 1-07B (DOE-ID 2003b).
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Summary of WAG 2 Groundwater Monitoring Results
Groundwater samples were collected from seven aquifer wells for WAG 2 during the calendar year 2004. The locations of the wells are shown on Figure 6-9, except for Highway 3 well, which is shown on Figure 6-16 for WAG 10. Six of the wells were sampled in both March and October of 2004, while Middle-1823 was only sampled in October 2004. Aquifer samples were analyzed for chromium (filtered and unfiltered), strontium-90, gamma spectroscopy, and tritium. The data for the March 2004 sampling event can be found in the FY04 Annual Report for WAG 2 (ICP 2004), and the data for the October 2004 sampling can be found in the FY05 annual report for WAG 2 (ICP 2005a). The data for the March 2004 and October 2004 sampling events are summarized in Table 6-3. Chromium was the only constituent detected above its MCL. Chromium concentrations in wells TRA-07, and USGS-065 were greater than the 100 mg/L MCL, with a maximum concentration of 136 mg/L in TRA-07 (Figure 6-10). Except for Highway-3, chromium concentrations were above background at all other aquifer wells sampled in WAG 2. The concentrations of chromium are declining in both USGS-065 and TRA-07.
Summary of WAG 3 Groundwater Monitoring Results
Groundwater samples (aquifer) were collected from 16 wells under CERCLA at WAG 3 in April, 2004 (DOE-ID 2005). Groundwater samples were analyzed for tritium, 90Sr, Iodine-129 (129I), uranium isotopes, plutonium isotopes, americium-241 (241Am), mercury, gamma spectrometry, neptunium-237 (237Np), technetium-99 (99Tc), and gross alpha/beta activities. The sampling results are summarized in Table 6-4. Groundwater monitoring results for 2004 confirm previous observations that the concentrations of most radionuclides in groundwater continue to decline over time. One exception may be 99Tc, whose concentrations appear to be slowly increasing at several monitoring well locations.
Strontium-90, 99Tc, and gross alpha were detected in some wells above their respective MCLs. Tritium, 129I, plutonium, uranium, and 137Cs were also detected, but concentrations were below EPA maximum contaminant levels. Activities of 233/234U and 238U isotopes were similar to background concentrations. Uranium-235 was detected in groundwater samples from three wells at levels slightly above natural background, but the concentrations were close to the detection limit and appear similar to those reported previously.
Strontium-90 concentrations are above the MCL (8 pCi/L) at nine of the 16 monitoring wells sampled in 2004 (Figure 6-11). However, 90Sr levels have declined at most locations from the concentrations that were observed in 2001 and 2003. Strontium-90 was above its maximum contaminant level of 8 pCi/L in several wells near INTEC but was below its maximum contaminant level in the downgradient direction in wells at the CFA landfills. Tritium and 129I concentrations were below MCLs in all wells sampled during 2003 and 2004. Iodine-129 concentrations increased slightly in several wells since 2001, but trends are inconclusive.
Groundwater from monitoring well ICPP-MON-A-230 located north of the INTEC tank farm contained elevated 99Tc concentrations that exceeded the MCL (900 pCi/L) by a factor of approximately three. This was the only well that exceeded the 99Tc MCL during 2004. The occurrence of elevated 99Tc at this location is believed to be the result of past leaks from underground pipelines and valve boxes at the INTEC tank farm. Tc-99 concentrations in groundwater appear to have increased slightly at several locations downgradient of INTEC (DOE-ID 2004).
Gross beta results generally mirrored the results for 90Sr and 99Tc. Gross alpha activity in groundwater exceeded the MCL (15 pCi/L) in two wells located within INTEC. Gross alpha levels in wells located downgradient of INTEC were all below the MCL.
Cesium-137 was present in groundwater samples from two of the monitoring wells near the former injection well, but the concentrations were far below the MCL of 200 pCi/L.
Plutonium-241 was the only plutonium isotope detected in WAG 3 aquifer samples during 2004, and was detected in just one well (USGS-48; 20.6 pCi/L). This concentration was below the derived MCL (300 pCi/L). Americium-241 was not detected in any of the samples, and 237Np was only detected in a single well at a concentration close to the detection limit.
Mercury was detected in two wells during 2004, but the concentrations were below the MCL of 2 µg/L. Nitrate concentrations in groundwater slightly exceeded the MCL at two of the wells within INTEC. The elevated nitrate levels probably result from vadose zone sources. Elevated chloride concentrations that persist in wells near to and downgradient of the former percolation ponds are attributed to the elevated salinity of the service waste previously discharged to the percolation ponds.
Summary of WAG 4 Groundwater Monitoring Results
Groundwater monitoring for the CFA landfills consisted of sampling eleven wells for volatile organic compounds, metals, and anions. The locations of the wells sampled are shown on
Figure 6-12. Because of falling water levels in the aquifer, only seven wells had sufficient water for sampling. Groundwater samples were not collected from LF2-08, LF2-09, LF2-11 and LF3-10. Analytes detected in groundwater are compared to regulatory levels in Table 6-5. A full description of the groundwater sampling and results is contained in ICP 2005b. The groundwater data indicated that nitrate was the only analyte above a maximum contaminant level. Nitrate was detected above its maximum contaminant level of 10 mg/L in well CFA-MON-A-002
(15.3 mg/L). Although previously above the MCL, the nitrate concentration in CFA-MON-A-03 (8.3 mg/L) dropped below the MCL in 2004. Nitrate concentrations in CFA-MON-A-002 and 003 dropped in 2004, but these concentrations are still within their historic ranges. Groundwater gradients and groundwater flow directions indicate that nitrate concentrations will not migrate to the Central Facilities Area production wells.
Iron was detected above its secondary maximum contaminant level of 300 µg/L in four samples, and aluminum was detected above its secondary maximum contaminant level of 200 µg/L in one sample. Because the pH of the groundwater is between 7 and 8 and has a high dissolved oxygen content, both the iron and aluminum are probably due to suspended particulates.
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Summary of WAG 5 Groundwater Monitoring Results
WAG 5 FY-05 Groundwater monitoring was completed during October 2004 in accordance with the requirements delineated in the WAG 5 ROD (DOE-ID 2000a) and the Groundwater Monitoring Plan (DOE-ID 2000b). Nine wells were sampled, and the locations of these wells are shown on Figure 6-13. Samples were analyzed for volatile organic compounds, select metals, anions and radionuclides. Specific metals requested included arsenic, barium, cadmium, chromium, lead, mercury, selenium, and silver. Radionuclide analyses included gross alpha and beta, gamma spectrometry, tritium, and 129I. The results are summarized below, and the complete listing of results can be found in ICP (2005d).
All constituents analyzed from the October 2004 sampling event were below MCLs. The data are summarized in Table 6-6. There were three detections of toluene and one detection of trichloroethene. Toluene was detected in three wells at concentrations less than 1 µg/L up to 76.1 µg/L, with the highest concentration occurring at ARA-MON-A-004. Other BTEX (benzene, toluene, ethyl benzene, and xylene) components or hydrocarbon TICs (tentatively identified compounds) were not associated with toluene at the three locations where toluene was detected. The source of the toluene detections is uncertain, but the lack of other hydrocarbons at the locations of the toluene detections is not consistent with fuel migration. The occurrence of toluene may be a laboratory artifact. All detections were well below the toluene MCL of 1,000 µg/L. Trichloroethene were detected at a concentration less than 1 µg/L and well below its MCL of 5 µg/L. Lead concentrations, which had been above its action level of 15 µg/L in several wells in the past, were all below the action level in October 2004. Replacement of galvanized riser pipe with stainless steel riser pipe appears to have removed the source of lead in the wells. Consequently, lead concentrations have declined to background concentrations.
Gross alpha and gross beta concentrations were similar to background. Antimony-125 (125Sb)was detected in Well PBF-MON-A-001 at a concentration of 16.8 ± 0.984 pCi/L, but this result is near the minimum detectable activity of 13.7 pCi/L for this analysis. Ruthenium-106 (106Ru) was detected in PBF-MON-A-004 at 38.1 pCi/L but was flagged "J" during validation and was less than the minimum detectable activity of 41.4 pCi/L. In addition, these results are questionable for three other reasons. First, no other gamma-emitting radionuclides were reported in the samples, especially cobalt-60 and 137Cs, which would be expected in the presence of the two isotopes in question. Second, both 125Sb and 106Ru have short half-lives (2.77 and 1.01 years, respectively) and if actually present would indicate a short travel time to the well from the source. However, no activities have taken place in the vicinity of the Auxiliary Reactor Area or the Critical Infrastructure Test Range in the last 20 years that could have contributed to the presence of these isotopes in the environment. Third, neither of these isotopes have been detected historically in samples from these two wells.
Summary of WAG 7 Groundwater Monitoring Results
Fifteen aquifer-monitoring wells were sampled under OU 7-13/14 and analyzed for a variety of radionuclide, inorganic, and organic contaminants (ICP, 2005c). Historically, aquifer samples have been collected quarterly; however, because years of monitoring data continued to show consistently low and unchanging detection rates of contaminants, the monitoring frequency was reduced to semiannually in August 2004. In addition to the wells monitored by OU 7-13/14, the USGS routinely samples eight wells in the vicinity of the RWMC. Figure 6-14 shows the location of the aquifer monitoring wells sampled at the RWMC.
During analyses of WAG 7 groundwater samples, carbon tetrachloride, tritium,
chromium, and nitrate (as nitrogen) are consistently detected above aquifer
background levels in some wells.
Contaminants detected in the aquifer beneath the RWMC in 2004 are summarized below:
Tritium was detected in the vadose zone and aquifer beneath the RWMC, but significant detections also occurred upgradient of the RWMC. It is speculated that some of the tritium is from upgradient facilities, primarily TRA; however, it is also likely that some of the tritium beneath the RWMC comes from sources in the SDA. Uranium detections in aquifer wells located around the RWMC are representative of natural uranium; however, indications of very low concentrations of anthropogenic uranium were found in two upgradient RWMC wells. The environmental data appear to warrant further investigation.
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Summary of WAG 9 Groundwater Monitoring Results
ANL-W samples five wells (four monitoring and one production) (Figure 6-15) twice a year for selected radionuclides, metals, total organic carbon, total organic halogens, and water quality parameters as required under the WAG 9 ROD (ANL-W, 1998). Gross alpha, gross beta, and certain uranium isotopes were measured in groundwater during 2004. Uranium isotopes (i.e., natural uranium, uranium-235, uranium-238), and gross alpha and gross beta activity have been measured in these wells in the past. The concentrations are consistent with concentrations attributable to natural sources of uranium- and thorium-series radionuclides and the concentrations are statistically the same for both upgradient and downgradient wells, implying a natural source for this radioactivity. Table 6-7 gives the values for the measured radionuclides.
The common metals aluminum, calcium, iron, magnesium, potassium, and sodium were detected at levels consistent with past years. Barium, chromium, copper, manganese, vanadium, and zinc also were measured (Table 6-7). Anions and water quality parameters were within ranges of past values.
Summary of WAG 10 Groundwater Monitoring Results
The WAG 10 2004 groundwater sampling consisted of a sampling event in June-July, 2004. Twenty-two wells were sampled in June-July 2004. The wells were sampled for volatile organic compounds, metals (filtered), anions (including bicarbonate), and radionuclides (129I, tritium, 99Tc, gross alpha, gross beta, gamma spec, uranium-isotopes, and 90Sr). The locations of the wells are shown in Figure 6-16. The results are summarized on Table 6-8 and briefly described below. The complete results can be found in DOE-ID 2005.
Methylene chloride was detected above the MCL in one well, but its occurrence is doubtful since this compound is a common laboratory contaminant and it was also detected in the laboratory blank. Other detected VOCs include trichloroethene, carbon tetrachloride, bromomethane, and carbon disulfide.
None of the metals were measured above their respective MCL. Nitrate is elevated in USGS-004 relative to other WAG 10 wells and probably represents off-site agricultural influences upgradient of the INEEL. Off-site influence was also indicated by elevated specific conductivity values for USGS-004 and USGS-27.
Tritium, gross alpha, gross beta, and uranium isotopes were the primary radiological analytes detected. Gross alpha, gross beta, and uranium isotopes were at background concentrations. Tritium was detected in two wells at concentrations less than 1,000 pCi/L or well below the MCL of 20,000 pCi/L.
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Drinking Water Sampling
As part of the offsite monitoring performed by the ESER contractor, radiological analyses are performed on drinking water samples taken at offsite locations. In 2004, the ESER contractor collected 30 drinking water samples from 14 offsite locations.
Gross alpha activity was detected in one sample from Idaho Falls. The measured concentration of 4.58 ± 1.46 pCi/L was significantly below the EPA MCL of 15 pCi/L.
As in years past, measurable gross beta activity was present in most offsite drinking water samples (21 of the 30 samples). Detectable concentrations ranged from 2.99 ± 0.98 pCi/L to 7.85 ± 1.06 pCi/L (Table 6-9). The upper value of this range is below the EPA screening level for drinking water of 50 pCi/L. Concentrations in this range are normal and cannot be differentiated from the natural decay products of thorium and uranium that dissolve into water as the water passes through the basalt terrain of the Snake River Plain.
Tritium was measured in ten drinking water samples during 2004, ranging from 78.0 ± 25.1 pCi/L at Taber in May to 142.0 ± 30.2 at Aberdeen and Howe in November (Table 6-9). The maximum level is still well below the DOE's DCG of 2.0 x 106 pCi/L and the EPA MCL of 20,000 pCi/L for tritium in water. These levels can be explained by natural variability.
Offsite Surface Water Sampling
As part of the offsite monitoring performed by the ESER contractor, radiological analyses are performed on surface water samples taken at offsite locations. Locations outside of the INEEL boundary are sampled twice a year for gross alpha, gross beta, and tritium. In 2004, the ESER contractor collected 11 surface water samples from five offsite locations.
Gross alpha activity was not detected in any sample during 2004.
Tritium was detected in one offsite surface water sample during 2004. The November surface water sample collected in the Hagerman area had a concentration of 86.8 ± 35.8 pCi/L (Table 6-10).
This sample was well below the PCS and EPA MCL of 20,000 pCi/L. These levels can be attributed to natural variability.
Gross beta activity was measured in 8 of the 11 offsite surface water samples. Detectable concentrations ranged from 2.90 ± 0.92 pCi/L to 7.14 ± 0.98 pCi/L at Hagerman and Bliss, respectively (Table 6-10). The maximum concentration is well below the EPA screening level for gross beta in drinking water of 50 pCi/L. Concentrations in this range are consistent with those measured in the past and cannot be differentiated from natural decay products of thorium and uranium that dissolve into water as the water passes through the surrounding basalts of the Snake River Plain.
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Argonne National Laboratory-West (ANL-W), 1998, Final Record of Decision for Argonne National Laboratory-West, W7500-000-ES-04, September 1998.
Bartholomay, R.C., Knobel, L.L, and Rousseau, J.P., 2003, Field Methods and Quality-Assurance Plan for Quality-of-Water Activities, U.S. Geological Survey, Idaho National Engineering Laboratory, Idaho, U.S. Geological Survey Open-File Report 03-42, DOE/ID 22182.
Bartholomay, R.C., Tucker, B.J., Davis, L.C., and Greene, M.R., 2000, Hydrogeologic Conditions and Distribution of Selected Constituents in Water, Snake River Plain Aquifer, Idaho National Engineering and Environmental Laboratory, Idaho, 1996 Through 1998, Water-Resources Investigation Report 00-4192, DOE/ID 22167, September.
Bechtel Bettis, 2004, 2004 Environmental Monitoring Report for the Naval Reactor Facility, NRFRC-EE-0012.
ICP, 2004, Annual Groundwater Monitoring Status Report for Waste Area Group 2 for Fiscal Year 2004, ICP/EXT-04-00369, Rev. 0, September 2004.
ICP, 2005a, Annual Groundwater Monitoring Status Report for Waste Area Group 2 for Fiscal Year 2005, ICP/EXT-05-00967, Rev. 0, August 2005.
ICP, 2005b, Central Facilities Area Landfills I, II, and III Annual Monitoring Report (2004), ICP/EXT-05-00915, Rev. A, June 2005.
ICP, 2005c, Fiscal Year 2004 OU 7-13/14 Environmental Monitoring Report for the Radioactive Waste Management Complex, ICP/EXT-05-00795, May 2005.
ICP, 2005d, Annual Groundwater Monitoring Status Report for Waste Area Group 5 Fiscal Year 2005, INEEL/EXT-05-00901, Rev. 0, June 2005.
IDAPA 58.01.11, "Ground Water Quality Rules," State of Idaho Department of Health and Welfare, current revision.
Mann, L.J., 1996, Quality-Assurance Plan and Field Methods for Quality-of-Water Activities, U.S. Geological Survey, Idaho National Engineering Laboratory, Idaho, U.S. Geological Survey Open-File Report 96-615, DOE/ID-22132.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2000a, Final Record of Decision for Power Burst Facility and Auxiliary Reactor Area, DOE/ID-10700.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2000b, Groundwater Monitoring Plan for the Waste Area Group 5, Remedial Action, DOE/ID-10779, Revision 0.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2003a, Monitored Natural Attenuation Remedial Action Work Plan for Test Area North Final Groundwater Remediation, Operable Unit 1-07B, DOE/ID-11055, Revision 0.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2003b, Monitored Natural Attenuation Operations, Monitoring, and Maintenance Plan for Test Area North, Operable Unit 1-07B, DOE/ID-11066, Revision 0.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2004, Annual INTEC groundwater monitoring report for Group 5-Snake River Plain Aquifer (2004), DOE/ID-11222, Rev 0. May 2005.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2005, Waste Area Group 10, Operable Unit 10-08, Remedial Investigation/Feasibility Study Annual report (FY-2004), DOE/ID-11198, Rev 0. March 2005.
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