Environmental Monitoring Information
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Environmental Monitoring Information |
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Environmental monitoring of the Hanford Site consists of 1) effluent monitoring, and 2) environmental surveillance, including groundwater monitoring. Effluent monitoring is performed as appropriate by the operators at the facility or at the point of release to the environment. Additional monitoring is conducted in the environment near facilities that discharge, or have discharged, effluents. Environmental surveillance consists of sampling and analyzing environmental media on and off the site to detect and quantify potential contaminants and to assess their environmental and human health significance.
The overall objectives of the monitoring and surveillance programs are to demonstrate compliance with applicable federal, state, and local regulations; confirm adherence to DOE environmental protection policies; and support environmental management decisions.
Effluent monitoring includes facility effluent monitoring (monitoring effluents at the point of release to the environment) and near-facility environmental monitoring (monitoring the environment near operating facilities).
Liquid and gaseous effluents that may contain radioactive and hazardous constituents are continually monitored at the Hanford Site. Facility operators monitor effluents mainly through analyzing samples collected near points of release into the environment. Effluent monitoring data are evaluated to determine their degree of compliance with applicable federal, state, and local regulations and permits.
Measuring devices are used to quantify most facility effluent flows, with a smaller number of flows calculated using process information. Liquid and gaseous effluents with a potential to contain radioactivity at prescribed threshold levels are monitored for total alpha and total beta activity and, as warranted, specific gamma-emitting radionuclides. Nonradioactive hazardous constituents are also monitored, as applicable.
Radioactive effluents from many onsite facilities are approaching levels practically indistinguishable from the naturally occurring radioactivity present everywhere. This decrease translates to a very small offsite radiation dose attributable to site activities. The new site mission of environmental restoration rather than nuclear materials production is largely responsible for this trend. Consistent with these conditions of diminishing releases, totals of radionuclides in effluents released at the site in 1996 are not significantly different from totals in 1995.
The near-facility environmental monitoring program is designed to protect the environment adjacent to facilities and ensure compliance with federal, state, and local regulations. Specifically, in 1996, this program monitored new and existing sites, processes, and facilities for potential impacts and releases; fugitive emissions and diffuse sources from contaminated areas; and surplus facilities before decontamination or decommissioning. Air, surface water and springs, surface contamination, vadose zone monitoring, soil and vegetation, external radiation, and investigative sampling (which can include wildlife) were sampled. Some parameters typically monitored are pH, radionuclide concentrations, radiation exposure levels, and concentrations of selected hazardous chemicals. Samples are collected from known or expected effluent pathways. These pathways are generally downwind of potential or actual airborne releases and downgradient of liquid discharges.
Near-Facility Air Monitoring. Radioactivity in air was sampled by a network of continuously operating samplers at 58 locations near nuclear facilities: 4 located in the 100-N Area, 4 in the 100-K Area, 38 in the 200 Areas, 3 at the Environmental Restoration Disposal Facility, 4 at the 100-D,DR Area, 3 at the 100-B,C Area, 1 near the 300 Area Treated Effluent Disposal Facility, and 1 collocated with sam-plers operated by the Pacific Northwest National Laboratory and the Washington State Department of Health at the Wye Barricade. Air samplers were primarily located within approximately 500 meters (1,500 feet) of sites and/or facilities having the potential for, or history of, environmental releases, with an emphasis on the prevailing downwind directions. Of the radionuclide analyses performed, strontium-90, cesium-137, plutonium-239,240, and uranium were consistently detectable in the 100-N and 200 Areas. Cobalt-60 was consistently detectable in the 100-N Area. Air concentrations for these radionuclides were elevated near facilities compared to the concentrations measured offsite by Pacific Northwest National Laboratory.
Surface-Water Disposal Units and 100-N Springs Monitoring. Samples collected from surface-water disposal units included water, sediment, and aquatic vegetation. Only water samples were taken at 100-N shoreline springs. Radiological analyses of water samples from surface-water disposal units included strontium-90, plutonium-238, plutonium-239,240, uranium, tritium, and gamma-emitting radionuclides. Radiological analyses of sediment and aquatic vegetation samples were performed for strontium-90, plutonium-239,240, uranium, and gamma-emitting radionuclides (Figure 9). Nonradiological analyses were performed for pH, temperature, and nitrates.
Figure 9. Thousands of environmental samples are analyzed annually.
Radiological analytical results for liquid samples from surface-water disposal units (i.e., ponds and ditches) located in the 200 Areas were less than the DOE-derived concentration guides, and in most cases, were equal to or less than the analytical detection limits. Although some elevated levels were seen in both aquatic vegetation and sediment, in all cases, the radiological analytical results were much less than the standards used for radiological control. The results for pH were well within the 2.0 to 12.5 pH standard for liquid effluent discharges based on the discharge limits listed in the Resource Conservation and Recovery Act. The analytical results for nitrates were all less than the 45-milligram per liter EPA drinking water standard for public water supplies.
Groundwater springs along the 100-N Area shoreline are sampled annually to verify the reported radionuclide releases to the Columbia River from past N Reactor operations. By characterizing the radionuclide concentrations in the springs along the shoreline, the results can be compared to the concentrations measured at the facility effluent monitoring well. In 1996, the concentrations detected in shoreline springs samples were highest in springs nearest the effluent monitoring well.
Near-Facility Radiological Surveys. In 1996, there were approximately 4,016 hectares (9,923 acres) of posted outdoor contamination areas and 1,025 hectares (2,532 acres) of posted underground radioactive materials areas, not including active facilities, at the Hanford Site. These areas were typically associated with burial grounds, covered ditches, cribs, and tank farms. The posted contamination areas vary between years because of an ongoing effort to clean, stabilize, and remediate areas of known contamination. During this time, new areas of contamination were being identified. It was estimated that the external dose rate at 80% of the identified outdoor contamination areas was less than 1 millirem per hour measured at 1 meter (3.28 feet), though direct dose rate readings from isolated radioactive specks (a diameter less than 0.6 centimeter [0.25 inch]) could have been considerably higher. Contamination levels of this magnitude did not significantly add to dose rates for the public or Hanford Site workers in 1996.
Vadose Zone Monitoring. The inactive liquid effluent facilities vadose zone monitoring program tracks the movement of radioactive contaminants that were discharged to the soil. There are over 300 liquid waste disposal sites at Hanford that have received over 53 billion liters (14 billion gallons) of waste, excluding the 1,620 billion liters (430 billion gallons) that were discharged at the surface to ponds and ditches. During 1996, approximately 70 boreholes were logged around these facilities for radioactive plume identification and tracking. In addition, approximately 35 wells scheduled for decommissioning onsite were surveyed for gamma-ray radiation to ensure the wells were not contaminated and for moisture and geologic data to help determine moisture migration pathways. The environmental restoration program also was supported by the collection of approximately 40 borehole logs for delineating subsurface radioactive contamination.
Soil and Vegetation Sampling from Operational Areas. Soil and vegetation samples were collected on or adjacent to waste disposal units and from locations downwind and near or within the boundaries of the operating facilities. Samples were collected to detect potential migration and deposition of facility effluents. Special samples were also taken where physical or biological transport problems were identified. Migration can occur as the result of resuspension from radioactively contaminated surface areas, absorption of radionuclides by the roots of vegetation growing on or near underground and surface-water disposal units, or by waste site intrusion by animals. Soil and vegetation sample concentrations for some radionuclides were elevated near facilities when compared to concentrations measured offsite. The concentra- tions show a large degree of variance; in general, samples collected on or adjacent to waste disposal facilities had significantly higher concentrations than those collected farther away. The number of sampling locations at the 100-N Area was reduced by approximately 50% in 1996.
Near-Facility External Radiation. External radiation fields were measured near facilities and waste handling, storage, and disposal sites to measure, assess, and control the impacts of operations.
A hand-held micro-rem meter (to measure low-level radiation exposure) was used to survey points along the N Springs area (Figure 10). The radiation rates measured in the N Springs area continued to decline in 1996, reflecting discontinued discharges to the 1301-N Liquid Waste Disposal Facility and the continuing decay of its radionuclide inventory.
The 1996 thermoluminescent dosimeter results indicate that direct radiation levels are highest near facilities that had contained or received liquid effluent from N Reactor. These facilities primarily include the 1301-N and 1325-N Liquid Waste Disposal Facilities. Because the results for these two facilities were noticeably higher than those for other 100-N Area thermoluminescent dosimeter locations, they were approximately 9% lower than exposure levels measured at these locations in 1995.
This is the fourth year that thermoluminescent dosimeters have been placed in the 100-K Area, surrounding the 105-K East and 105-K West Fuel Storage Basins and adjacent reactor buildings. Three of the thermoluminescent dosimeters have consistently shown elevated readings as a result of their proximity to radioactive waste storage areas or stored radioactive rail equipment.
Five new thermoluminescent dosimeter locations were established in the 100-D,DR Area during the fourth quarter of 1996 to evaluate environmental restoration activities at the 116-D-7 and 116-DR-9 Liquid Waste Disposal Facilities. Although no comparative data are available because of the recent placement of these dosimeters, the fourth quarter analyses indicate readings comparable to offsite background levels.
The highest dose rates in the 200/600 Areas were measured near waste handling facilities such as tank farms. The highest dose rate was measured at the 241-A Tank Farm complex located in the 200-East Area. The average annual dose rate measured in 1996 by thermoluminescent dosimeters was 120 millirem per year, which equaled the average dose rate measured in 1995.
Two new thermoluminescent dosimeter locations were established at the Environmental Restoration Disposal Facility during the fourth quarter of 1996 to evaluate the disposal activities currently in progress. Although no comparative data are available because of the recent placement of these dosimeters, the fourth quarter analyses indicate readings comparable to offsite background levels.
The highest dose rates in the 300 Area were measured near waste handling facilities such as the 340 Waste Handling Facility. The average annual dose rate measured in the 300 Area in 1996 was 120 millirem per year. This represents a decrease of 14% compared to the average dose rate of 140 millirem per year measured in 1995. The average annual dose rate at the 300 Area Treated Effluent Disposal Facility in 1996 was 85 millirem per year, which represents an increase of 5% compared to the average dose rate of 81 millirem per year measured in 1995.
The average annual dose rate measured in the 400 Area in 1996 was 83 millirem per year, which represents an increase of 8% compared to the average dose rate of 77 millirem per year measured in 1995.
Investigative Sampling. Investigative sampling was conducted in the operations areas to confirm the absence or presence of radioactive or hazardous contaminants. Investigative sampling took place near facilities such as storage and disposal sites for at least one of the following reasons:
Environmental surveillance of the Hanford Site and the surrounding region is conducted to demonstrate compliance with environmental regulations, confirm adherence to DOE environmental protection policies, support DOE environmental management decisions, and provide information to the public.
Environmental surveillance includes sampling environmental media on and off the Hanford Site for potential chemical and radiological contaminants originating from site operations. The media sampled in 1996 included air, surface water and sediment, drinking water, food and farm products, fish and wildlife, soil and vegetation, external radiation levels, and groundwater.
The primary pathways for movement of radioactive materials and chemicals from the site to the public are the atmosphere and surface water. Figure 11 illustrates these potential routes and exposure pathways to humans.
The significance of each pathway was determined from measurements and calculations that estimated the amount of radioactive material or chemical transported along each pathway and by comparing the concentrations or potential doses to environmental and public health protection standards or guides. Pathways were also evaluated based on prior studies and observations of radionuclide and chemical movement through the environment and food chains. Calculations based on effluent data showed the expected concentrations off the Hanford Site to be low for all Hanford-produced radionuclides and chemicals and to be frequently below the level that could be detected by monitoring technology. To ensure that radiological and chemical analyses of samples were sufficiently sensitive, minimum detectable concentrations of key radionuclides and chemicals were established at levels well below applicable health standards.
Radioactive materials in air were sampled continuously at 40 locations onsite, at the site perimeter, and in nearby and distant communities. Nine of these locations were community-operated environmental surveillance stations that were managed and operated by local school teachers (Figure 12). At all locations, particulates were filtered from the air and analyzed for radionuclides. Air was sampled and analyzed for selected gaseous radionuclides at key locations. Several radionuclides released at the site are also found worldwide from two other sources: naturally occurring radionuclides and radioactive fallout from historical nuclear activities not associated with Hanford. The potential influence of emissions from site activities on local radionuclide concentrations was evaluated by comparing differences between concentrations measured at distant locations within the region and concentrations measured at the site perimeter.
For 1996, no differences were observed between the annual average total beta air concentrations measured at the site perimeter and those measured at distant community locations. Air concentrations of total alpha were slightly elevated at the site perimeter compared to the distant stations; however, the concentrations were within the range of historical values. Numerous specific radionuclides in quarterly composite samples were analyzed using gamma scan analysis; however, no radionuclides of Hanford origin were detected consistently.
Tritium concentrations for 1996 were slightly elevated at the site perimeter compared to the distant station; however, the difference was not statistically significant.
Iodine-129 concentrations were statistically elevated at the site perimeter compared to the distant locations, indicating a measurable Hanford source (Figure 13); however, the average concentration at the site perimeter was only 0.000003% of the DOE- derived concentration guide of 70 picocuries per cubic meter. The DOE-derived concentration guide is the air concentration that would result in a radiation dose equal to the DOE public dose limit (100 millirems per year).
Strontium-90 was detected in 8 of the 15 onsite air samples, with the maximum concentration at 0.002% of the DOE-derived concentration guide of 9 picocuries per cubic meter. Strontium-90 was also detected at three of the seven perimeter locations and at two of the six distant locations. The maximum concentration at the perimeter location was less than 0.0004% of the DOE-derived concentration guide and at the distant location less than 0.0002% of the DOE-derived concentration guide.
Plutonium-239,240 concentrations were similar for air samples collected at the site perimeter and the distant locations. The maximum plutonium-239,240 air concentration was 0.06% of the DOE-derived concentration guide of 0.02 picocuries per cubic meter.
Uranium isotopic concentrations (uranium-234, uranium-235, and uranium-238) were similar onsite, at the perimeter, and at the distant locations for 1996. The uranium concentrations were 0.03% of the 0.1-picocurie per cubic meter DOE-derived concentration guide.
No samples were collected in 1996 to test for nonradionuclides.
The Columbia River was one of the primary environmental exposure pathways to the public during 1996 as a result of past operations at the Hanford Site. Radiological and chemical contaminants entered the river along the Hanford Reach primarily through seepage of contaminated groundwater. Water samples were collected from the river at various locations throughout the year to determine compliance with applicable standards.
Although radionuclides associated with Hanford operations continued to be identified routinely in Columbia River water during the year (Figure 14), concentrations remained extremely low at all locations and were well below standards. The concentration of tritium was significantly higher (5% significance level) at the Richland Pumphouse (downstream from the site) than at Priest Rapids Dam (upstream from the site), indicating contribution along the Hanford Reach (Figure 15).
Figure 14. Water Sampling from the Columbia River Shoreline
Transect sampling in 1996 revealed elevated tritium concentrations along the Benton County shoreline near the 100-N Area, Old Hanford Townsite, 300 Area, and Richland Pumphouse. Total uranium concentrations were elevated along the shorelines of both Benton and Franklin counties near the 300 Area and Richland Pumphouse. The highest total uranium concentration was measured near the Franklin County shoreline of the Richland Pumphouse transect and likely resulted from groundwater seepage and irrigation return canals on the east shore of the river.
Several metals and anions were detected both upstream and downstream of the Hanford Site. Nitrate concentrations were elevated along the Franklin County shoreline of the Old Hanford Townsite, 300 Area, and Richland Pumphouse transects and likely resulted from groundwater seepage associated with extensive irrigation north and east of the Columbia River.
With the exception of aluminum, iron, and nitrate which had the higher average quarterly concentration at the Richland Pumphouse, no consistent differences were found between average quarterly contaminant concentrations in the Vernita Bridge and Richland Pumphouse transect samples. All metal and anion concentrations in Columbia River water collected in 1996 were less than Washington State ambient surface water quality criteria levels for acute toxicity, except for silver and cadmium that both exceeded the criteria for a few samples. The chronic toxicity levels for lead and selenium were occasionally exceeded in Columbia River transect samples. Volatile organic compounds (chloroform, toluene, and trichloroethylene) were occasionally detected in Columbia River water in 1996.
Samples of Columbia River surface sediments were collected in 1996 from permanently flooded monitoring sites above McNary Dam (downstream of the site), above Priest Rapids Dam (upstream of the site), and along the Hanford Reach. Strontium-90 was the only radionuclide to exhibit consistently higher median concentrations at McNary Dam compared to the other locations. The median concentration of cobalt-60 was highest in sediment collected along the Hanford Reach. Sediment samples were also collected from five periodically inundated riverbank springs in 1996. The concentrations of radionuclides in sediment collected from riverbank springs were similar at all locations and were comparable to sediment collected behind Priest Rapids Dam.
Detectable concentrations of most metals were found in all Columbia River sediment samples with the exception of silver, which was below the detection limit for all samples. Median concentrations of most metals were highest in McNary Dam sediments. The highest median concentration of chromium was found in riverbank spring sediment.
Water samples were collected from six Columbia River shoreline springs in 1996. All radiological contaminant concentrations measured in riverbank spring water in 1996 were less than the DOE- derived concentration guides. However, tritium concentrations in the 100-B Area and Old Hanford Townsite riverbank springs (Figure 16) exceeded the Washington State ambient surface water quality criteria levels. There are currently no ambient surface water quality criteria levels directly applicable to uranium. However, total uranium exceeded the site-specific proposed EPA drinking water standard in the 300 Area riverbank spring. All other radionuclides were below the Washington State ambient surface water quality criteria.
All nonradiological contaminants measured in riverbank springs located on the Hanford shoreline in 1996 were below the Washington State ambient surface water acute toxicity levels with the exception of cadmium in the 100-F Area spring; chromium(IV) in springs in the 100-B, 100-D, and 100-F Areas; and copper in the 100-F and 300 Areas springs. The Washington State ambient surface water chronic toxicity levels for cadmium, chromium, selenium, and zinc were exceeded at some locations. Riverbank spring sampling protocols do not lend themselves to a direct comparison of most metal concentrations measured in riverbank springs to ambient surface water acute and chronic toxicity levels. The standards are used instead as a point of reference. Nitrate concentrations were the highest in the 100-D Area and the Old Hanford Townsite springs. Concentrations of volatile organic compounds were similar to previous years with most compounds below the detection limits. Chloroform (100-B and 100-D Areas), tetrahydrofuran (100-B Area), and trichloroethylene (100-B Area) were the only volatile organic compounds detected.
Water was collected from three onsite ponds located near operational areas in 1996. Although the ponds were not accessible to the public and did not constitute a direct offsite environmental impact during 1996, they were accessible to migratory waterfowl and other animals. As a result, a potential biological pathway existed for the removal and dispersal of onsite pond contaminants. With the exception of uranium-234 and uranium-238 in water samples from West Lake, radionuclide concentrations in the onsite pond water were below the DOE-derived concentration guides. The average annual total beta concentration in West Lake exceeded the ambient surface water quality criteria level.
Concentrations of most radionuclides in water collected from all three ponds during 1996 were similar to those observed during past years. However, tritium concentrations in the 1996 samples from the Fast Flux Test Facility pond were lower than those observed in 1995. The elevated concentrations in 1995 most likely resulted from the use of a backup water supply in the 400 Area during June and July 1995. The primary source of water to the Fast Flux Test Facility pond is 400 Area sanitary water.
Irrigation water from the Riverview canal was sampled three times in 1996 to determine radionuclide concentrations. The radionuclide concentrations in offsite irrigation water were below the derived concentration guides and ambient surface water quality criteria levels.
Surveillance of Hanford Site drinking water was conducted to verify the quality of water supplied by site drinking water systems and to comply with regulatory requirements. Radiological monitoring was performed by the Pacific Northwest National Laboratory and DE&S Hanford, Inc.; nonradiological monitoring was conducted by DynCorp Tri-Cities Services, Inc. These results are discussed here; nonradiological results are reported directly to the Washington State Department of Health.
During 1996, radionuclide concentrations in site drinking water were similar to those observed in recent years and were in compliance with Washington State Department of Health and EPA annual average drinking water standards.
The Hanford Site is situated in a large agricultural area that produces a wide variety of food products and alfalfa. Milk, vegetables, fruit, and wine were collected from areas around the site and were analyzed for cobalt-60, strontium-90, iodine-129, cesium-137, and tritium.
Most farm products sampled did not contain measurable concentrations of these radionuclides (Figure 17). Iodine-129 was found at slightly elevated levels in milk samples from downwind locations. The levels were low, they have been decreasing over the past 6 years, and they are now indistinguishable between upwind and downwind locations. Tritium concentrations in wine have been reported in the past at levels higher than could be confirmed at other analytical laboratories (split samples). Recently, it was discovered that these high concentrations were caused by alcohol in the initial sample distillate; the alcohol produced spuriously high results. The problem was eliminated by removing the alcohol from the sample before analysis.
Figure 17. Food and farm products are sampled in agricultural areas surrounding the Hanford Site.
Analyses of fish and wildlife samples for radionuclides in 1996 indicated that some species had accumulated radionuclides at concentrations greater than background levels. Strontium-90 was detected in the offal (i.e., carcass without most of the muscle and viscera) of Columbia River bass and carp at levels slightly exceeding those found in fish collected upstream of Hanford in the Priest Rapids Dam reservoir.
There was no apparent difference between concentrations of strontium-90 in Hanford Reach carp and background carp collected in 1996. Cesium-137 was detected in one bass fillet sample; all other fish and wildlife muscle samples did not have measurable concentrations of cesium-137. Strontium-90 was detected in all deer bone samples analyzed in 1996. Concentrations were similar to levels observed in prior years and did not indicate exposure to elevated levels of strontium in the environment. The mean concentration of strontium-90 (0.07 ± 0.005 picocuries per gram, wet weight) in pheasant bone was similar to levels observed over the preceding 5 years and exceeded concentrations observed in background samples collected from 1991 through 1995 by a factor of two. Collectively, the levels of radionuclides measured in Hanford fish and wildlife indicated accumulations of small amounts of specific radionuclides that possibly originated either from historic fallout or Hanford Site activities.
Soil and vegetation samples were not collected in 1996. Sampling will be conducted periodically in the future consistent with ongoing site cleanup activities.
Radiological dose rates were measured at both onsite and offsite locations using thermoluminescent dosimeters. Radionuclides contributing to these measured doses were of natural and artificial origin. In 1996, terrestrial dose rates did not change significantly from those measured in 1995. The annual average background dose rate measured in distant communities was 71 ± 1 millirem per year compared to the 1995 average measurement of 72 ± 8 millirem per year (Figure 18).
The 1996 annual average perimeter dose rate was 88 ±10 millirem per year; in 1995, the average measured was 86 ± 8 millirem per year at the same locations. All onsite dosimeters averaged 86 ±5 millirem per year in 1996; in 1995, the onsite average was 86 ± 4 millirem per year. Thermoluminescent dosimeters along the Columbia River shoreline had an annual average of 89 ± 7 millirem per year in 1996; in 1995, the average was 103 ± 12 millirem per year. On average, the dose rate along the 100-N Area shoreline (129 ± 30 millirem per year) was approximately 50% higher than the typical shoreline dose rate (82 ± 3 millirem per year).
Two key elements of the strategy to protect groundwater at the Hanford Site are to 1) protect the unconfined aquifer from further contamination, and 2) monitor the extent of groundwater contamination. The groundwater monitoring program at the Hanford Site documents groundwater quality to meet these needs.
The monitoring program is designed to detect new contaminant plumes and to document the distribution and movement of existing groundwater contamination (Figure 19). Monitoring provides the historical baseline for evaluating current and future risk from exposure to groundwater contamination and for deciding on remedial options. Because the geology and hydrology of the Hanford Site control the movement of contaminants in groundwater, hydrogeologic studies are an integral part of the monitoring program.
In 1996, monitoring of radiological and chemical constituents in groundwater at the Hanford Site was performed to characterize physical and chemical trends in the flow system, establish groundwater quality baselines, assess groundwater remediation, and identify new or existing groundwater problems. Groundwater monitoring was also performed to verify compliance with applicable environmental laws and regulations and to fulfill commitments made in official DOE documents.
Samples were collected from approximately 800 wells to determine the distributions of radiological and chemical constituents in Hanford Site groundwater. In addition, hydrogeologic characterization and modeling of the groundwater flow system were used to assess the monitoring network and to evaluate potential impacts of groundwater contamination.
During 1996, groundwater surveillance and monitoring activities were restructured into the Groundwater Monitoring Project. This project incorporates sitewide groundwater monitoring mandated by DOE Orders with near-field groundwater monitoring conducted to ensure that operations in and around specific waste disposal facilities comply with applicable regulations. Groundwater monitoring required at 26 waste treatment, storage, and disposal units is summarized below.
To assess the quality of groundwater, concentrations measured in samples were compared with the EPA drinking water standards and the DOE- derived concentration guides. Groundwater is used for drinking at three locations on the Hanford Site. In addition, water supply wells for the city of Richland are located near the southern boundary of the Hanford Site. Radiological constituents including cobalt-60, strontium-90, technetium-99, iodine-129, cesium-137, plutonium, tritium, uranium, total alpha, and total beta were detected at levels greater than the drinking water standard in one or more onsite wells. Concentrations of strontium-90, plutonium, tritium, and uranium were detected at levels greater than the derived concentration guides.
Extensive tritium plumes extend from the 200-East and 200-West Areas into the 600 Area (Figure 20). The plume from the 200-East Area extends east and southeast, discharging to the Columbia River. This plume has impacted tritium concentrations in the 300 Area at levels of more than one-half the EPA drinking water standard. The spread of this plume farther south than the 300 Area is restricted by the groundwater flow away from the Yakima River and the recharge ponds associated with the north Richland well field. Groundwater with tritium at levels above the drinking water standard also discharges to the Columbia River at the 100-N Area. A small but high concentration tritium plume near the 100-K East Reactor also may discharge to the river. Tritium at levels greater than the drinking water standard was also found in the 100-B, 100-D, and 100-F Areas.
The strontium-90 plume in the 100-N Area, which contains concentrations greater than the DOE- derived concentration guide, discharges to the Columbia River. Localized areas in both the 100-K and 200-East Areas also contain strontium-90 at levels greater than the derived concentration guide. Strontium-90 is found at levels greater than the EPA drinking water standard in the 100-B, 100-D, 100-F, 100-H, 100-K, and 200-West Areas and the 600 Area in the former Gable Mountain Pond area.
Technetium-99 concentrations greater than the EPA drinking water standard were found in the northwestern part of the 200-East Area and adjacent 600 Area. Technetium-99 was also detected at levels greater than the drinking water standard in the 100-H and 200-West Areas and adjacent 600 Area. Groundwater in one well completed in the upper basalt-confined aquifer in the northern part of the 200-East Area had technetium-99 concentrations above the drinking water standard. Increases in technetium-99 concentrations at wells near the S-SX and T Tank Farms are being evaluated as possible indications of groundwater contamination from tank leaks.
Iodine-129 was detected at levels greater than the EPA drinking water standard in the 200-East Area and in an extensive part of the 600 Area to the east and southeast. The iodine-129 and tritium plumes share common sources. Iodine-129 at levels greater than the drinking water standard also extends into the 600 Area to the northwest of the 200-East Area. Iodine-129 was also found at concentrations above the drinking water standard in the southern part of the 200-West Area and extending into the 600 Area. There is a smaller iodine-129 plume in the northcentral part of the 200-West Area.
Cobalt-60 was detected above the EPA drinking water standard in the 600 Area north of the 200-East Area in one well completed in the unconfined aquifer and in one well completed in the confined aquifer. Cesium-137 was detected in one well in the 200-East Area and one well in the 200-West Area. Concentrations at the 200-East Area well were greater than the EPA drinking water standard.
Uranium was detected at levels greater than the EPA drinking water standard in wells in the 100-F, 100-H, 200-East, 200-West, 300, and 600 Areas. Groundwater with uranium concentrations greater than the drinking water standard appears to be discharging to the Columbia River from the 300 Area. Wells near U Plant in the 200-West Area had concentrations greater than the DOE- derived concentration guide.
Plutonium was detected in groundwater samples from two wells in the 200-East Area. The level in one of these wells exceeded the DOE-derived concentration guide.
Certain nonradioactive chemicals regulated by the EPA and Washington State were also present in Hanford Site groundwater. These were carbon tetrachloride, chloroform, chromium, cyanide, fluoride, nitrate, tetrachloroethylene, and trichloroethylene.
An extensive plume of carbon tetrachloride at levels greater than the EPA drinking water standard was found in groundwater at the 200-West Area and extends into the 600 Area. A less-extensive plume of chloroform, which may be a degradation product of the carbon tetrachloride, is associated with the carbon tetrachloride plume. Maximum chloroform levels are also greater than the drinking water standard.
Chromium was found at levels greater than the EPA drinking water standard in the 100-B, 100-D, 100-F, 100-H, 100-K, 100-N, 200-East, 200-West, and 600 Areas.
Cyanide was detected above the EPA drinking water standard in one 600 Area well north of the 200-East Area.
Fluoride was measured at levels greater than the EPA primary drinking water standard in the 200-West Area.
Nitrate concentrations exceeded the EPA drinking water standard at locations in all 100 Areas, with the exception of the 100-B Area. Those plumes discharge to the Columbia River. Nitrate from the 200-East Area extends east and southeast in the same area as the tritium plume. Nitrate from sources in the northwestern part of the 200-East Area is present in the adjacent 600 Area at levels greater than the drinking water standard. Nitrate is also present at levels greater than the drinking water standard in the 200-West Area and adjoining 600 Area. Some nitrate in the 600, 1100, and north Richland areas is believed to result from offsite sources.
Tetrachloroethylene was detected at levels below the EPA drinking water standard. Trichloroethylene was found at levels greater than the EPA drinking water standard in the 100-F Area and the 600 Area. Trichloroethylene was also detected at levels greater than the drinking water standard in the 100-K, 200-West, and 300 Areas and near the Horn Rapids Landfill.
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