An assessment of drinking-water supplies on the Hanford Site: an evaluation conducted at a federal nuclear facility in southeastern Washington State.

Introduction

The U.S. Department of Energy's (DOE's) Hanford Site was established in southeastern Washington State (Figure 1) in 1943 to house facilities for producing and processing nuclear materials for the U.S. government. Nine plutonium production reactors were constructed on the site between 1944 and 1954, along with facilities to separate and purify reactor products into desirable forms (Gray, 1993). Eight of the nine production reactors were shut down by the early 1970s. One remained operational until 1987.

Decades-long nuclear-fuel processing activities on the site generated an estimated 1.4 billion cubic meters of chemical and radioactive waste in liquid, gaseous, and solid forms (U.S. Environmental Protection Agency [U.S. EPA], 1987a, 1987b, 1987c, 1987d). These materials were released to the air, soil column, and surface water, or stored in 177 underground tanks with capacities ranging up to 3.8 million liters (Gerber, 1992). The current DOE mission at Hanford emphasizes cleaning up the tank, the former waste disposal locations, and the groundwater underlying the site, with the intent to limit the movement of persistent contaminants from the soil column (vadose zone) to groundwater and to reduce the transfer of groundwater contaminants to the adjacent Hanford Reach of the Columbia River. Numerous groundwater discharges are known to enter the Columbia River along the Hanford Site shoreline (McCormack & Carlile, 1984; Dirkes, 1990), and Hanford-produced contaminants are measurable in river water near and downstream from the site (Poston, Hanf, Dirkes, & Morasch, 2003).

Hanford is an EPA Region 10 Superfund site with a cleanup budget that was approximately 1.9 billion dollars in fiscal year 2003. Activities associated with this classification have, in recent years, attracted many new workers to the site. Anticipated non-DOE uses of cleaned-up Hanford lands may bring in even more workers in future years. Because of the large amount of nuclear and chemical waste still present at Hanford, there is concern about potential health impacts to workers and the public from exposure to remaining contaminants. One area of concern has been the possibility that harmful materials may be present in on-site drinking water. The objective of the study reported here was to characterize drinking water at Hanford Site DOE facilities and to compare current levels of contaminants to state and federal standards for water quality. This information may be relevant to site workers and to planners involved with determining future use of the site.

[FIGURE 1 OMITTED]

Regulatory Oversight

Under the federal Safe Drinking Water Act (SDWA) and its 1986 and 1996 amendments, U.S. EPA set legal limits on the levels of certain contaminants in drinking water. U.S. EPA also established water-testing schedules and methods that water system owners must follow. The state governments, through their health departments and environmental agencies, were expected to accept the major responsibility for the administration and enforcement of the regulations set by U.S. EPA. In the state of Washington, the federal drinking-water laws are implemented by the Washington State Department of Health (WDOH) through state administrative codes (Washington Administrative Codes [WAC]). All water systems on the Hanford Site are designated by Washington State as public water systems and are operated in accordance with the requirements contained in the applicable state codes. Water quality at Hanford is monitored according to written contaminant-specific plans that are in keeping with both state and federal drinking-water laws and are acceptable to WDOH.

Description of Hanford Site Drinking-Water Systems

The Hanford Site historically was divided into operational areas (Marceau et al., 2002) (Figure 1). The six 100 Areas (B/C, KE/KW, N, D, H, and F) on the shore of the Columbia River are where the nine retired plutonium production reactors are located. The 200-East and 200-West areas include facilities that processed the irradiated materials from the reactors. Fuel rods for the reactors were manufactured in the 300 Area, near the city of Richland. The 400 Area is the location of the Fast Flux Test Facility (FFTF), a liquid-sodium-cooled test reactor built by DOE in the 1970s to test equipment and fuel for the Liquid Metal Fast Breeder Reactor Program. The remainder of the site, the 600 Area, houses facilities that serve the entire site or more than one specific production area, and includes several non-DOE commercial and research facilities.

Four principal drinking-water pumping facilities were used on the site in 2001 and 2002 (Figure 1). Most site workers were provided with drinking water pumped from the Columbia River. The 100-B Area pump house served as the primary Columbia River pumping station, and the pump house in the 100-D Area functioned as its emergency backup. Together these two facilities potentially supplied water to an average of 4,184 people per workday in the 100, 200-East, 200-West, and 600 areas. Water for the 100-K Area was obtained via its own river pump house and was potentially served to an average of 631 people per day. Drinking water in the 400 Area was pumped from three wells of varying depths located within the 400 Area complex. Generally, only one of the three wells is operated at a time, but water from more than one well can be commingled in a holding tank prior to dissemination through the distribution system. An estimated 389 people were potentially served each workday from these wells. In the 300 Area, an average of 1,805 people were served each day, but the water for this area was supplied by the city of Richland.

All drinking water obtained from the Columbia River was filtered and chlorinated at treatment plants on the site. Active river water treatment plants were located in the 100-K, 100-N, and 200-West areas. Multiple treatment processes were provided in series to remove turbidity and microorganisms, and then to inactivate or remove a specific percentage of Giardia cysts or other pathogenic organisms. At a minimum, filtration was provided at each river water treatment plant to achieve the required reduction in turbidity. Turbidity was monitored continuously to maintain performance expectations. Water from the 400 Area wells was chlorinated but not filtered. Drinking water in the 300 Area was delivered to consumers via a DOE-owned and -operated distribution system and was chlorinated on site when needed even though the water had already been treated by the city of Richland.

Sampling and Analysis Information

Hanford Site drinking-water systems have been classified by the state of Washington as Group A public water systems. Group A systems can be either community or noncommunity systems. The systems at Hanford are defined as nontransient, noncommunity systems. State and federal laws requiring the monitoring of radiological contaminants in drinking water apply to community systems and therefore are not directly applicable to the Hanford Site. Radionuclides in DOE systems at Hanford are, however, monitored to community system requirements to comply with the requirements of DOE Order 5400.5, a DOE Directive (DOE, 1990). Monitoring includes collecting and analyzing samples and comparing analytical results with established state and federal drinking-water standards and guidelines.

Radiological Sampling

Drinking-water samples for radiological analysis were collected and analyzed quarterly in 2001 and 2002. Untreated river water samples were collected at the pump houses in the 100-B, 100-D, and 100-K areas in 2001. Well water samples collected during 2001 in the 400 Area consisted of treated water collected at a consumer-accessible sink. In 2002, in compliance with recently revised drinking-water regulations, all samples were collected after the water was treated but before it was distributed to the consumer. Collection sites in 2002 included treatment plants in the 100-N, 100-K, 200-West, and 400 areas. A state-certified analytical laboratory in Richland, Washington, analyzed all samples during both years for gross alpha, gross beta, tritium, and strontium-90. Gross alpha and gross beta measurements are general indicators of radiological contamination. Tritium (12.3-year half-life) and strontium-90 (28.8-year half-life) are materials that were produced in large quantities at Hanford and are also components of atmospheric fallout from worldwide nuclear-weapons testing. Tritium also is produced naturally in the atmosphere.

To comply with revised regulations, one sample from each water supply in 2002 also was analyzed for iodine-131, radium-226, and radium-228. Iodine-131 is a manmade isotope produced by the detonation of nuclear weapons and by nuclear-reactor operations. Because iodine-131 has a short half-life (eight days), it is not likely that it would be measurable in Hanford Site drinking water obtained from either river water or groundwater sources. Both radium-226 (1,599-year half-life) and radium-228 (5.8-year half-life) are isotopes that result from the decay of naturally occurring uranium-238 and thorium-232, respectively (Eisenbud, 1987). Radium should be measurable in both surface and groundwater at Hanford, but U.S. surface waters such as the Columbia River usually have low radium levels (Hess, Michel, Horton, Prichard, & Coniglio, 1985).

A continuing program of internal laboratory quality control, participation in inter-laboratory crosschecks, replicate sampling and analysis, submission of blind standard samples and blanks, and splitting of samples with other laboratories verified the quality of radiological results. These verifications in 2001 and 2002 were summarized and published in the Hanford Site's annual environmental reports (Poston, Hanf, Dirkes, & Morasch, 2002; Poston, Hanf, Dirkes, & Morasch, 2003).

Radiological Results

Thirty-two drinking-water samples were analyzed for gross alpha in 2001 and 2002 and alpha activity was detected only in one sample (Table 1). This river water sample was collected in 2001 at the 100-D Area pump house.

Gross beta was detected in one of 24 river water samples analyzed during 2001 and 2002 and the measured concentration was about 8.4 percent of the U.S. EPA screening level of 1.85 becquerels per liter (Bq/L) (Table 1). This sample was collected at the 100-N Area water treatment plant, which gets water from either the 100-B Area pump house or the 100-D Area pump house. All eight drinking-water samples from the 400 Area (groundwater) analyzed during 2001 and 2002 were positive for gross beta, with the highest concentration measured during 2001 (Table 1).

Strontium-90 was measured in 23 of the 24 samples from river water sources analyzed during 2001 and 2002. The highest concentration, about 0.7 percent of the U.S. EPA limit of 0.296 Bq/L (Table 1), was seen in water from the 100-D Area pump house in 2001. The 100-D Area intake is located downstream of the 100-B, 100-K, and 100-N areas, where groundwater containing strontium-90 is found near the river. Strontium-90 was not detected in any of the 400 Area well water samples in either year.

Tritium was detected in five of 11 river water samples analyzed in 2001 and in two of nine river water samples analyzed in 2002. The highest concentration (~1.2 percent of the U.S. EPA annual average limit [Table 1]) was measured in water from the 100-B Area pump house. This drinking-water intake is the one farthest upstream at the site (Figure 1) and the one least likely to be influenced by Hanford contaminated effluents entering the river.

The highest tritium concentration measured in drinking water on the site in 2001 and 2002 was found in a groundwater sample from the 400 Area. This concentration was 19 percent of the U.S. EPA annual average limit for tritium in drinking water and was slightly more than 16 times greater than the highest level measured in river water samples (Table 1). Annual average tritium concentrations in 400 Area drinking water in 2001 and 2002 were 117 Bq/L and 128 Bq/L, respectively. A groundwater tritium plume originating from the former plutonium-processing facilities in the 200 areas is known to affect well water in the 400 Area (Hartman, Morasch, & Webber, 2003), and tritium levels in 400 Area drinking water can fluctuate depending on which of three drinking-water wells is being used. Tritium concentrations are usually lowest in the deepest well (Somers, 1987), which is considered the primary supply well. Tritium concentrations above the annual average U.S. EPA limit of 740 Bq/L have been measured in the two shallowest wells in recent years (Poston, Hanf, & Dirkes, 2000), and the annual average level in 400 Area drinking water could potentially exceed the U.S. EPA standard if either of these two wells were used as the primary water source for most of the year. Neither of these wells was used in 2001 and 2002, however, and when water from one of these wells is needed, the current DOE policy is to use the well with the lowest tritium level as demonstrated by sampling and analysis.

Iodine-131, radium-226, and radium-228 were monitored once at all four sampling locations in 2002. As expected, iodine-131 was not detected in any samples. Radium-226 was, however, found in all four samples analyzed during the year. The maximum radium-226 concentration (Table 1) was measured in Columbia River water from the 200-West Area treatment plant.

Radium-228 was found in two of three river water samples but not in the 400 Area well water sample. The highest detectable radium-228 level (Table 1) was found in water sampled at the 100-N Area treatment plant. As stated earlier, both the 100-N Area and 200-West Area treatment plants obtain water from the 100-B Area pump house or from the 100-D Area pump house if the 100-B Area facility is off line. There are no established drinking-water limits for radium-226 and radium-228 individually, but U.S. EPA has established a limit for the two combined. The highest concentration of radium-226 and radium-228 combined was measured in two river water samples and was only 2.2 percent of the MCL of 0.185 Bq/L.

Nonradiological Sampling

Drinking-water samples collected for non-radiological analyses were obtained in accordance with the WDOH-approved plans and procedures of the Hanford Site. Samples for coliform analyses were collected each month at representative locations around the site (primarily building sinks) by qualified personnel and transported to the analytical laboratory at the Benton-Franklin Health District office in Richland, Washington, for analysis. Disinfection requirements for all water sources included ensuring sufficient water and disinfectant contact times, maintaining a free-chlorine residual at each treatment plant prior to supplying consumers, and maintaining a detectable free-chlorine residual within each distribution system. The chlorine residual was monitored continuously at the water treatment plants, and samples were collected daily from each distribution system. Monthly samples were collected in the 100-K, 100-N, 200-East, 200-West, 400, and 300 areas for coliform and total organic carbon analyses (surface-water systems only), and quarterly or annually (400 Area) at several locations within each distribution system to monitor levels of undesirable halogenated organic by-products (trihalomethanes [THMs] and haloacetic acids [HAA5s]).

Inorganic- and organic-chemical monitoring of Hanford water systems was performed in accordance with federal and state monitoring schedules. Samples for a suite of volatile-organic-compound (VOC) analyses were collected annually from the 100-N, 100-K, and 200-West areas, and once every three years from the 400 Area. Semivolatile organic compounds (SOCs) were monitored every year at the 200-West, 100-N, and 100-K areas and every three years in the 400 Area. Both the VOC and SOC samples were monitored for a wide variety of U.S. EPA-regulated and state-unregulated materials. Inorganic contaminants, including nitrate, fluoride, arsenic, and selected metals, were monitored annually in the 100-N, 100-K, 200-West, and 400 areas. Samples for lead and copper analyses were collected every three years at the above locations and in the 300 Area, but were not collected during 2001 and 2002.

State-approved site water purveyor procedures were followed for the collection and timely transport of the samples. Chain-of-custody control provided further insurance that the requirements were met for documenting and maintaining custody of the samples from their point of origin to receipt at the laboratory.

Nonradiological Monitoring Results

In 2001 and 2002, all of the river water treatment plants effectively removed or inactivated 99.9 percent of Giardia lamblia and 99.99 percent of viruses. None of the Hanford Site drinking-water samples analyzed for total coliform bacteria in 2001 and 2002 were found to be coliform positive.

Concentrations of natural organic matter (disinfectant by-product precursors) in drinking-water samples were in compliance with regulatory requirements. Sampling also showed that annual average concentrations of undesirable halogenated organic by-products (HAA5s and THMs) were below their respective MCLs of 60 [micro]g/L and 80 [micro]g/L (Table 2) (U.S. EPA, 2001). No U.S. EPA-regulated VOCs were detected by the analytical lab in either year.

Scans for SOCs in surface water and groundwater systems were conducted in early 2002, and results were reported for 85 regulated and unregulated materials. Only one contaminant (Dalapon [2,2-dichloropropanoic acid]) was detected, and it was seen in water from the Columbia River. The highest amount detected (0.97 [micro]g/L) was far below the MCL of 200 [micro]g/L established by U.S. EPA (U.S. EPA, 2002). Dalapon is a herbicide that is used to control grasses in a wide variety of crops. It is also used in noncrop applications in lawns, in drainage ditches, along railroad tracks, and in industrial areas. This chemical was used on the site in the mid- to late-1990s, but it is believed that the concentration measured in 2002 is related to applications of the chemical to orchards and farmlands located upstream of the site.

Potential inorganic contaminants monitored at the site in 2001 and 2002 included 27 state- and U.S. EPA-regulated materials and parameters. Analytical results indicated that the concentrations of all regulated metals and other inorganic contaminants in site drinking-water samples collected in both years were below their respective maximum concentration limits.

Sanitary surveys of Hanford's Group A water systems were performed by the Washington State Department of Health in June 2001. Each survey included an on-site review of the water source, facilities, equipment, operation, and maintenance of the water systems to evaluate their ability to reliably produce and distribute safe drinking water. All systems were found to be well operated and maintained, and monitoring program plans were satisfactory.

Discussion

Concentrations of all radionuclides in drinking water supplied to Hanford Site facilities by DOE were below state and federal regulatory limits in 2001 and 2002. Tritium and gross beta levels in 400 Area drinking-water wells were elevated relative to other water sources on the site, and tritium concentrations in the two shallowest wells can potentially be high enough to exceed the 740 Bq/L annual average drinking-water standard. DOE's practice of using the two shallow wells only when needed and then using the well with the lowest tritium level as determined by sampling and analysis would, however, keep the annual average concentration below the regulatory limit for community systems.

Because of its upstream location, water pumped from the river at the 100-B Area pump house is not likely to contain contaminants from the fugitive groundwater discharges entering the river along the Hanford Reach shoreline. Water pumped from the river at the 100-K, 100-N, and 100-D areas could potentially contain contaminants from shoreline groundwater discharges that occur in or near each of the upstream reactor areas. Studies have shown, however, that the highest contaminant concentrations are localized near shoreline discharge points (McCormack & Carlile, 1984; Dirkes, 1990) and that concentrations in river water samples collected outside the immediate discharge zones are below the limits set by state and federal drinking-water standards (e.g., Poston et al., 2003). Estimated groundwater discharge volumes throughout the Hanford Reach are small (~0.77 [m.sup.3] per second [Dirkes, Hanf, & Poston, 1999]) compared with the total flow of the river (annual average river flow in 2002 was 3,340 [m.sup.3] per second [Poston et al., 2003]), and shoreline contaminant concentrations are quickly diluted to very low levels.

Concentrations of the specific radionuclides monitored in Hanford Site drinking water obtained from the Columbia River in 2001 and 2002 were similar to concentrations measured in river water samples collected downstream of the site at the city of Richland's drinking water pump house (City of Richland, 2002). In most cases, measured contaminant levels in river water samples were very low, and in all cases they were below state and federal annual average drinking-water limits (Poston et al., 2003)

The authors' monitoring results indicated that current filtering systems and disinfectant applications are effectively controlling populations of potentially harmful microorganisms and that most VOC, SOC, and inorganic contaminants do not affect drinking water supplied to Hanford Site facilities. Proper operation and maintenance of the distribution systems is one factor that protects Hanford Site drinking-water consumers from microbiological contaminants. Personnel operating the water treatment plants and distribution systems are required to be certified by WDOH as being knowledgeable about water treatment processes and technologies and to have proven themselves, by examination, capable of effectively and safely operating the water system. All public water systems on the Hanford Site, both production and distribution, are operated by WDOH-certified Water Works Operators who maintain certifications at levels commensurate with the complexity of the systems.

Most nonradiological contaminants detected in Hanford Site drinking water were by-products of the disinfection (chlorination) process. An unrelated chemical contaminant noted in 2001 and 2002 was Dalapon, an herbicide used for agricultural weed control off the site. Concentrations of this chemical were well below the MCL established by U.S. EPA for this material.

With the closing of the production reactors and associated plutonium separation facilities at Hanford, the federal government began focusing on waste cleanup, waste management, and environmental remediation and restoration (Gray & Becker, 1993). Current DOE goals include reducing the size of the Hanford Site from 1,517 [km.sup.2] to 194 [km.sup.2] by 2012 and preparing portions of the cleaned-up site for other DOE missions, non-DOE federal missions, and other public and private sector uses (DOE, 2002). A recent Presidential Proclamation (Establishment of the Hanford Reach National Monument, 2000) placed ~800 [km.sup.2] of the site in the Hanford Reach National Monument under management by DOE and the U.S. Fish and Wildlife Service (Figure 1). The authors' results indicate that safe, high-quality drinking water will be available at the tap as long as Hanford-specific procedures and standard industry practices acceptable to WDOH continue to be followed

TABLE 1 Maximum Radiological-Contaminant Levels (Bq/L) (a) in Hanford
Site Drinking-Water Samples, 2001 and 2002

Contaminant                          Water Source
                          Columbia                400 Area
                         River Water              Well Water

Gross alpha           0.072 [+ or -] 0.044      ND (c)
Gross beta            0.156 [+ or -] 0.067      0.51 [+ or -] 0.11
Strontium-90          0.0041 [+ or -] 0.0015    ND
Tritium               8.7 [+ or -] 4.8        141 [+ or -] 10.4
Iodine-131            ND                        ND
Radium-226            0.003 [+ or -] 0.007      0.001 [+ or -] 0.0004
Radium-228            0.025 [+ or -] 0.011      ND
Combined radium-226,  0.026                     0.001
  -228

Contaminant                  Maximum
                      Contaminant  Level
                          (MCL) (b)

Gross alpha             0.555
Gross beta              1.85 (d)
Strontium-90            0.296 (e)
Tritium               740 (e)
Iodine-131            __ (f)
Radium-226            __ (f)
Radium-228            __ (f)
Combined radium-226,    0.185
  -228

(a) [+ or -] 2 times the total propagated analytical error.
(b) From Radionuclides Rule (U.S. Environmental Protection Agency)
(2000).
(c) Not detected.
(d) A screening level rather than an MCL.
(e) Average annual concentrations assumed to produce a total body or
organ dose of 40 micro-sieverts per year.
(f) No established MCL.

TABLE 2 Annual Average Concentrations ([micro]g/L) of Undesirable
Halogenated Organic By-products in Hanford Site Drinking Water, 2001
and 2002

Drinking-Water Systems   Trihalomethanes  Haloacetic Acids
                          2001    2002     2001    2002

300 Area                  36.4     27.7    14.1     21.3
400 Area                  10.7      7.96    0        0
100-K Area                19.9     21.9    19.5     35.1
100-N Area                27.4     65.7    15.6     35.3
200-W Area                27.7     31.1    16.3     47.5
200-E Area                30.9     37.1    15.8     46.8
U.S. EPA MCL              80       80      60       60

Acknowledgements: The authors appreciate the insightful reviews, encouragement, and support they received from Dr. D.D. Dauble, Dr. G.W. Patton, Mr. T.M. Poston, Mr. K.R. Price, and Dr. W.H. Rickard, all of the Pacific Northwest National Laboratory. Special thanks are due to Ms. G.P. O'Connor, who advocated for a writers' group at the laboratory, selected the group, and assisted its members throughout the process, including editing and preparation of this article for publication.

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Corresponding Author: R.W. Hanf, Pacific Northwest National Laboratory, P.O. Box 99, K6-75, Richland, WA 99352. E-mail: [e-mail].