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Record of Decision System (RODS)

HANFORD 100-AREA (USDOE)

Abstract

Site Name:  HANFORD 100-AREA (USDOE)
Address:  100 AREA 
City & State:  BENTON COUNTY  WA  99352
County:  BENTON
 
EPA ID:  WA3890090076
EPA Region:  10
 
NPL Status:  Currently on the Final NPL
 
ROD Type:  Record of Decision
ROD ID:  EPA/541/R-99/039
ROD Date:  07/15/1999
Operable Unit(s):  27
 
Media:  Debris, Groundwater, Soil
 
Contaminant:  Base Neutral Acids, Metals, PAH, PCBs, Radioactive
 
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

The Hanford Site was established during World War II as part of the "Manhattan Project" to produce plutonium for nuclear weapons. Hanford Site operations began in 1943, with USDOE facilities located throughout the Site and the City of Richland. Certain portions of the Site are known to have cultural significance and may be eligible for listing in the National Register of Historical Places.

In 1988, the Hanford Site was scored using EPA's Hazard Ranking System. As a result of the scoring, the Hanford Site was added to the National Priorities List (NPL) in November 1989 as four sites (the 100 Area, the 200 Area, the 300 Area, and the 1100 Area). Each of these areas was further divided into operable units. The 100 Area NPL site consists of the following operable units for contaminated sources such as soils, structures, debris, and burial grounds: 100-BC-1, 100-BC-2, 100-KR-1, 100-KR-2, 100-NR-1, 100-DR-1, 100-DR-2, 100-HR-1, 100-HR-2, 100-FR-1, 100-FR-2,100-IU-1, 100-IU-2, 100-IU-3, 100-IU-4 and 100-IU-5; for contaminated groundwater: 100-BC-5, 100-KR-4, 100-NR-2, 100-HR-3, and 100-FR-3.

In anticipation of the NPL listing, the Department of Energy (DOE), EPA, and the Washington State Department of Ecology (Ecology) entered into a Federal Facility Agreement and Consent Order in May 1989 known as the Tri-Party Agreement. This agreement established a procedural framework and schedule for developing, implementing, and monitoring remedial response actions at Hanford. The agreement also addressed Resource Conservation and Recovery Act (RCRA) compliance and permitting.

In 1992, the Hanford Future Site working Group evaluated four future land use options for the site and recommended cleanup of sources and contaminated groundwater flow into the Columbia River as an "immediate priority." This recommendation was a key consideration in the selection of high priority liquid radioactive disposal sites for interim remedial actions. The recommendations also expressed a desire for ultimately achieving "unrestricted use" for the air, surface, subsurface, and groundwater, with the exception of the B Reactor as a museum option. That option would place the reactor itself in a "restricted" status.

The Final River Conservation Study and the Environmental Impact Statement for the Hanford Reach of the Columbia River (National Park Service 1994) proposed that the Hanford Reach of the Columbia River and approximately 102,000 acres of adjacent lands be designated as a National Wild and Scenic River and a National Wildlife Refuge, respectively.

On September 27, 1995, the Interim Record of Decision was signed for this site.

DOE performed a 100 area wide phase 1 and 2 Feasibility Study (FS) and operable unit specific Limited Field Investigations for the 100-BC-1, 100-DR-1 and 100-HR-1 operable units. A 100 area-wide Phase 3 Source Waste Site FS and 100 Area operable unit specific Focused FS also were conducted to evaluate specific waste site remedial action goals, objectives and technologies.

100-IU-1
The Riverland Rail Yard (100-IU-1 OU) supported Hanford construction and operations activities from 1943 until 1954, while decontamination of radioactive rail cars continued until 1956. Included in this site are a 2,4-D pesticide container site, a rail yard maintenance facility, and two former military installations with associated demolition debris.

In June 1993 an Action Memorandum, signed by the Tri-Parties, the USDOE agreed to perform an expedited response action for the cleanup of the Riverland Rail Yard Maintenance Facility and pesticide container sites, and closure of an empty munitions cache hole. Diesel contaminated concrete and soil from the rail yard and pesticide sites were removed from the site for bioremediation. The remaining contaminants in the soil were at levels which were below Model Toxics Control Act (MTCA) residential standards. Radioactive decontamination of the facility occurred around 1963, after which the maintenance facilities were dismantled and sold. Follow-up radiological surveys were performed in 1977, 1978, and 1993, revealing only natural background levels.

100-IU-3
This area was acquired for use as a military buffer zone against potential hostile attacks on the 100 Area reactors. Several Anti-Aircraft Artillery Batteries and three Nike Missile Sites were located on the Wahluke Slope. These sites were decommissioned in 1960-1961, and demolished in 1974.

During 1989 and 1990, an investigation of the Wahluke Slope was performed to asses potential health, safety, and environmental concerns raised by Ecology and the public. Based on the investigation, three of the Wahluke Slope sites; the H-06-L Nike missile launch site, H-06-C Nike missile control site, and the 2,4-D pesticide disposal site, were identified and included as part of the 100-IU-3 OU. During the investigation of this OU, 36 additional sites were identified. Soil contamination in these areas resulted from historic use of petroleum products and pesticides by the military.

USDOE prepared an engineering evaluation and cost analysis, North Slope (Wahluke Slope) Expedited Response Action Cleanup Plan in 1993, regarding cleanup options applicable to the Wahluke Slope sites. The Tri-Parties signed an Action Memorandum in 1994, requiring removal of hazardous substances and proper abandonment of water wells. During 1994, a CERCLA expedited response action was performed to remove any hazardous substances that remained in the 39 sites on the Wahluke Slope. Soil contaminated with the pesticide DDT and its associated breakdown products was disposed of at a hazardous waste landfill in Arlington, OR. Petroleum contaminated soil (PCS) was transported to a PCS treatment facility in Pasco, WA, for bioremediation. Several 55-gallon drums of miscellaneous and hazardous substances were sent to appropriate handling facilities. Non-hazardous trash, debris, and concrete were either returned to their excavations or recycled. The remaining contaminants in the 100-IU-3 OU were measured at levels below MTCA residential cleanup standards. Water wells were decommissioned in accordance with WAC 173-160 regulations (Minimum Standards for Construction and Maintenance of Wells) to eliminate this potential contamination path to groundwater, and to prevent interconnection of aquifers. No groundwater contamination has been associated with the 100-IU-3 OU.

100-IU-4
Little historical documentation of the site is available. The landfill was used during the years of reactor operation for disposal of crushed, empty Sodium Dichromate barrels.

In 1992, Ecology and EPA recommended an expedited response action be performed at the Sodium Dichromate Barrel Landfill, after which USDOE prepared an engineering evaluation and cost analysis regarding remediation alternatives applicable to this unit. The Tri-Parties signed an Action Memorandum in 1993, requiring full excavation and removal of all buried materials from the landfill.

Excavation, removal, and disposal activities took place between March and July, 1993. Approximately 5,000 crushed drums were removed from the site, along with minor amounts of asbestos-containing materials, two 5-gallon roofing tar cans, and a small amount of used oil and grease. Soil sampling results indicated levels below MTCA residential cleanup standards were achieved.

100-IU-5
The White Bluffs Pickling Acid Cribs Site is the only site identified in the 100-IU-5 Operable Unit. This area was the location of construction activities from about 1943 - 1959. Little historical information is known about this site. It is believed that the cribs received waste streams from a pipe fabrication facility operating sometime between 1943 and 1959.

In EPA and Ecology recommended that USDOE perform an expedited response action for this site. Characterization activities indicated contaminants of concern were at levels below MTCA residential cleanup standards. No investigation of ground water was completed for this unit due to its close proximity to other 100 Area operable units. No radioactive contamination has been associated with this unit.

OU2: (100-HR-3 and 100-KR-4)(EPA/ROD/R1O-96/134)
Prior to starting the "Limited Field Investigation" in 1992 in the 100-KR-4 and 100-HR-3 Operable Units, groundwater monitoring consisted of periodic sampling under DOE Order 5400.1. A limited record exists for groundwater conditions during the reactor operating years. Riverbank seepage monitoring was completed in 1984 and 1988 as part of the Sitewide Environmental Surveillance program.

At the 100-K Area, groundwater sampling was associated with operations at the 100-K East and 100-K West fuel storage basins. Some post-1959 data from several wells are available to describe conditions downgradient of the 116-K-2 trench used for liquid effluent disposal that included chromium.

For the 100-D/DR reactor area, (100-HR-3 Operable Unit), historical data describing conditions during reactor operations are limited to several wells that were constructed in 1960. Quarterly sampling was started in 1991 under the RCRA/Operational program for monitoring liquid effluent discharge to 100-D Ponds. An infiltration experiment was conducted in 1967 that created a groundwater mound in the vicinity of the coolant water retention basins. The results may provide an analog for the un-monitored conditions that prevailed during reactor operating years.

A similar database exists for the 100-H Area (100-HR-3 Operable Unit). Monitoring of the 183-H Solar Evaporation Basins facility occurred between 1973 and 1985, when monitoring was substantially increased under the RCRA/Operational program. A comprehensive database exists to describe the contaminant plume, which includes chromium, associated with the 183-H facility for years after 1985.

The technical information baseline for the RI/FS associated with each operable unit was augmented substantially in 1992 with the installation of new monitoring wells and subsequent quarterly sampling as part of the limited field investigation. A comprehensive riverbank seepage sampling project was completed in late 1991, which helped relate contamination along the shoreline to groundwater contamination underlying the reactor areas. RI/FS characterization activities that followed the four quarters of sampling conducted during the limited field investigation consist of semiannual well sampling, annual riverbank seepage sampling and periodic Columbia River substrate sampling. Water table elevations were measured at periodic intervals to show the seasonal ranges in flow direction and gradients.

As a result of the discharge of groundwater from the operable units into the river, chromium, a metal that is toxic to aquatic organisms in low concentrations, poses a risk to aquatic organisms in the Columbia River adjacent to the 100-D/DR, 100-H and 100-K Areas. The most toxic form of chromium, hexavalent chromium, readily dissolves in water and, therefore, moves freely with groundwater. Hexavalent chromium has been detected in groundwater and in the groundwater/river interface where groundwater upwells into the river. Once discharged to the river, it is easily assimilated by aquatic organisms, some of which are adversely affected. Trivalent chromium is less soluble and less toxic, and is not easily transported by groundwater. Most chromium in groundwater at the Hanford Site is hexavalent chromium, because of the original sources and prevailing geochemical conditions.

In August 1994, a pilot-scale treatability test began at the 100-D/DR Area, to assess the effectiveness of an iron exchange treatment system to remove hexavalent chromium from groundwater. Through July 1995, this pump-and-treat system had extracted more than 4 million gallons (15 million liters) of groundwater and had removed more than 38 pounds (17 kilograms) of chromium. This system is successful in removing chromium from extracted groundwater at 100-D/DR, and indicates that an ion exchange treatment system can be a successful groundwater treatment technology for chromium in the 100 Area.

The DOE, Washington State Department of Ecology and EPA developed a Community Relations Plan in April 1990 that was designed to promote public awareness of investigations and public involvement in the decision-making process. The plan summarizes the known concerns based on community interviews. Several public meetings have been held and numerous fact sheets have been distributed in an effort to keep the public informed about Hanford cleanup issues. The Plan was updated in 1993 to enhance public involvement and is currently undergoing an additional update.

The Focused Feasibility Study Document and Proposed Plans were made available to the public in both the Administrative Record and several libraries. These documents underwent a 45 day public comment period from September 11, 1995 to October 25, 1995. Notice of this comment period was published in four State and Local papers on September 10 and 11, 1995. Separate mailings went to about 4, 700 "interested in Hanford" citizens. A meeting was held on October 18, 1995 that discussed the proposed actions relative to other Hanford groundwater and Columbia River issues.

The selected interim remedy is chosen in accordance with CERCLA, as amended by SARA, and to the extent practicable, the National Contingency Plan (NCP). The decision for these operable units is based on the Administrative Record.

The interim action is expected to provide adequate protection of human health and ecological receptors in the Columbia River and will continue until implementation of the final remedy for the 100-HR-3 and 100-KR-4 groundwater operable units, or until such time that the DOE demonstrates to the State and the EPA that no further interim action is required. This interim action is expected to become part of the final remedial action.
Because this is an interim action ROD, review of these operable units and the remedy will be ongoing as the Tri-Parties continue to develop and implement final remedial alternatives for the operable units and the 100 Area NPL site. Because this remedy will result in hazardous substances remaining on-site above health-based levels, a review will be conducted within five years after commencement of remedial action to ensure that the remedy continues to provide adequate protection of human health and the environment.

The Proposed Plan for 100-IU-1, 100-IU-3, 100-IU-4 and 100-IU-5 was made available to the public in both the Administrative Record and in Information Repositories on June 26, 1995. The public comment period was held from June 26, 1995 - August 9,1995.

The Hanford Site is a 560-square mile Federal Facility located in southeastern Washington along the Columbia River. The region includes the incorporated cities of Richland, Pasco, and Kennewick (Tri-Cities) located approximately 17 miles southeast of the 100 Area. The Tri-Cities area consists of approximately 100,000 residents. There are also surrounding communities in Benton, Franklin, and Grant counties. Land use in the surrounding areas includes urban and industrial development, irrigated and dry-land farming, grazing and wildlife refuges. Certain portions of the site are known to have cultural and historical significance and may be eligible for listing in the National Register of Historic Places. The site was established in 1943 and was used to produce plutonium for nuclear weapons as part of the Manhattan Project during World War II. There are nine retired plutonium production reactors located on the Hanford Site. The site boundary includes several subdivisions, entitled Areas 100, 200, 300, 400, 600, 1100, and 3000.

To the west, north, and east, the 100 Area are bounded by sparsely populated farming and ranching communities. To the south is the rest of the contiguous Hanford Site.

The topography of the 100 Area is marked by Saddle Mountains to the north, and Gable Mountain/Gable Butte to the South, and is transected by the Columbia River. The geologic structure beneath the 100 Area consists of three distinct levels of soil formations. The deepest of these is a thick series of basalt flows that have been warped and folded, resulting in protrusions cropping out as rock ridges in some areas. Layers of silt, gravel, and sand known as the Ringold formation form the middle level. The uppermost level is known as the Hanford formation and consists of gravel and sands deposited by catastrophic floods during glacial retreat.
There are several unconfined aquifers at the site. Some of these are connected hydraulically to the Columbia River. Groundwater flow direction is north-northwest towards the Columbia River. Under the unconfined aquifers are several confined aquifers. The groundwater is not currently used but is monitored to assess contaminant conditions.

Surface water is limited to the Columbia River which is the dominant surface-water body on the Hanford Site. Small springs flow intermittently, apparently influenced by changes in river level. The Hanford Reach is the last free-flowing portion of the Columbia River above Bonneville Dam. The Columbia River contains the only remaining spawning habitat for native salmon on the main stem of the river in the United States. Portions of the river's shoreline in the 100 Area are within the probable maximum 100 year plain of the Columbia River. Due to irrigation practices, and in part to natural conditions, three wetland areas are contained within the Wahluke slope.

Existing land use in the 100 Area includes facilities support, waste management, and undeveloped land. Facility support activities include operations such as water treatment and maintenance of the reactor buildings. The waste management land use designation results from former uncontrolled disposal activities in areas now know as "past practice waste sites" located mostly in the reactor areas.

There are undeveloped lands located throughout the area that are the least disturbed and contain minimal infrastructure.

An 18 mile stretch of the Columbia River is located within the 100 Area. The shoreline of the Columbia River is a valued ecological area within the Hanford Site. Approximately 25% of the Wahluke Slope Area (north of the Columbia River) is permitted to the U.S. Fish and Wildlife Service, and is managed as the Saddle Mountain Refuge, with limited public access. The remaining 75% is permitted to the Washington State Department of Wildlife, and is operated as a State Wildlife Recreation Area. Semi-arid land with a sparse covering of cold desert shrubs and drought-resistant grasses dominates the Hanford landscape. Forty percent of the areas annual average of six and one quarter inches of rain occurs between November and January.

The 100 Area, which encompasses approximately 68 km squared bordering the south shore of the Columbia River, is the site of nine retired plutonium production reactors. Two of the reactors (K-East and K-West) reside in the 100-KR-2 Operable Unit in the 100-K Area. Adjacent to each of these reactors is a spent nuclear fuel (SNF) storage basin. The contents of those basins are addressed in this record of decision (ROD).
The K Basins are currently being used to store irradiated (spent) nuclear fuel from past operations. The basins are located inside the reactor building and hold 1.3 million gallons of water each. The water provides a radiation shield, as well as a thermal sink for heat generated by the stored SNF. The SNF consists of metallic uranium clad in either a Zircaloy or aluminum jacket. The cladding on some of the SNF has been damaged, allowing contact between the irradiated uranium and the basin water. Corrosion of the damaged fuel results in transfer of radiounuclides to the basin water and produces contaminated sludge.

The purpose of the K Basins CERCLA interim remedial action is to mitigate the potential to release hazardous substances from the K Basins. Within this scope is removal of the SNF, sludge, water, and debris from the basins, pretreatment of the water, basin deactivation. Other activities covered in the K Basins EIS and ROD, namely the stabilization and interim storage of the SNF, are not addressed by this interim remedial action. Stabilization and interim storage of the SNF continue to be conducted under the authority of the Atomic Energy Act of 1954 as analyzed via the NEPA process. The SNF Cold Vacuum Drying (CVD) and Canister Storage Building (CSB) facilities are being constructed to be equivalent to current Nuclear Regulatory Commission (NRC) standards and operating procedures being developed such that SNF management beyond the scope of this CERCLA action does not present an endangerment to public health, welfare, or the environment. The NEPA analysis of environmental impacts associated with removing SNF, sludge, water, and debris from the K Basins and pretreating the water were used in the CERCLA process. Sludge treatment processes were not analyzed in the NEPA process, but were analyzed in the CERCLA feasibility study.

The area north of the Columbia River, known as the Wahluke Slope, covers approximately 364 square km (140 sq. mi.), and is separated from the rest of the site by the river. The Wahluke Slope is the location of 39 waste sites which make up the 100-IU-3 OU. The 100 Area south of the Columbia River includes the other three units addressed in this ROD (EPA/ROD/RIO-96/134). The Riverland Rail Yard (100-IU-1 OU) is 34 sq. km. (13 sq. mi.) and is bordered by Washington State Highway 24 to the south and east, the Columbia River to the north, and the Hanford Site boundary to the west. The Sodium Dichromate Barrel landfill (100-IU-4 OU) is 10.6 acres in size, and is located between the 100-D and 100-H reactor areas. The White Bluffs Pickling acid Cribs (100-IU-5 OU) are cumulatively one-half acre in size, and are located about 2 km. (1.2 mi.) west of the 100-F reactor.

The 100-BC-1 OU is one of the three OUs associated with the 100 B/C Area at the Hanford Site. The 100-BC-1 and 100-BC-2 OUs address contaminant sources while the 100-BC-5 OU addresses contamination present in the underlying groundwater. The 100-BC-1 OU encompasses approximately 1.8 square kilometers and is located immediately adjacent to the Columbia River Shoreline. In general, it contains waste units associated with the original plant facilities constructed to support B Reactor operation, as well as the cooling water retention basin systems for both B and C Reactors. The B Reactor, constructed in 1943, operated from 1944 through 1968, when it was retired from service. The C Reactor, constructed in 1951, operated from 1952 until 1969, when it also was retired from service. Currently, the only active facilities in the 100-BC-1 OU are those that extract and treat water from the Columbia River and transport that water to other 100 Area and 200 Area facilities.
The 100-DR-1 OU is one of three OUs associated with the 100D/DR Area at the Hanford Site. The 100-DR-1 and 100-DR-2 are source OUs. The third OU, 100-HR-3 is the groundwater OU for D/DR and H Areas. The 100 D/DR Area contains two reactors; the D reactor associated with the 100-DR-1 OU, and the DR Reactor associated with the 100-DR-2 OU. The D Reactor operated from 1944 to 1967 when it was retired. The DR reactor operated form 1950 to 1964 when it was retired. The 100-DR-1 OU encompasses approximately 1.5 square kilometers and is immediately adjacent to the Columbia River. Currently, sanitary and fire protection water is provided to the 100-H and 100-F Areas from the 100-D Area.

The 100-HR-1 Source OU is one of two source OUs associated with the 100-H Area at the Hanford Site. The 100-HR-1 and 100-HR-2 Source OUs address contaminant sources while the 100-HR-3 Groundwater OU addresses contamination in the underlying groundwater. The 100-HR-1 Source OU encompasses approximately 0.41 square kilometers and is located immediately adjacent to the Columbia River shoreline. The OU contains waste units associated with the original plant facilities constructed to support the H Reactor. The area also contains evaporation basins which received liquid process wastes and non-routine deposits of chemical wastes from the 300 Area, where fuel elements for the N Reactor were produced. These solar evaporation basins received wastes from 1973 through 1985 and are regulated under RCRA as treatment, storage, and disposal facilities. The H Reactor complex was constructed after World War II to produce Plutonium for use in military weapons. The H Reactor operated from 1949 to 1965, when it was retired. Currently there are no active facilities, operations, or liquid discharges within the 100-HR-1 Source OU.

Groundwater in the 100-B/C Area flows in a northerly direction towards the Columbia River. The depth to groundwater at high river stage ranges from 22.89 m in well 199-B4-4, located near the B Reactor, to 15.06 m in well 199-B3-47, located due north of the 166-B-14 sludge disposal trench. Groundwater in the 100-D/DR Area flows in a north/northwest direction towards the Columbia River. Groundwater in the 100-H Area generally flows in a northeasterly direction towards the Columbia River. The groundwater table elevation (above mean sea level) at normal to low river stage ranges from 114.9 m in the southwest corner to approximately 113.9m near the river. The groundwater gradient is approximately 0.0006.

OU 2: (100-HR-3 and 100-KR-4)
The CERCLIS 3 OU2 for the Hanford Site concerns groundwater in two segments of the Area. These segments are referred to as 100-HR-3 OU and 100-KR-4 OU.
The 100-HR-3 OU is located in the north-central part of the Hanford Site along the Columbia River. This operable unit includes the groundwater underlying the 100-D/DR and 100-H Reactor Areas and a portion of the 600 Area. The 100-D/DR Area is the site of two deactivated reactors: the 100-D Reactor, which operated from 1944 to 1967 and the 100-DR Reactor, which operated from 1950 to 1965. The 100-H reactor operated from 1949 to 1965.

The 100-KR-4 OU is also located in the north-central part of the Hanford Site, upriver of 100-HR-3. The 100-KR-4 Operable Unit includes the groundwater underlying the 100-KR-1 and 100-KR-2 Operable Units. The 100-K Area is the site of two deactivated reactors: the 100-K East Reactor, which operated from 1955 to 1971, and the 100-K West Reactor, which operated from 1955 to 1970.

During the years of reactor operations, large volumes of reactor coolant water containing chromium and radionuclides were discharged to retention basins for ultimate disposal in the Columbia River through outfall pipelines. Liquid wastes, containing significant quantities of chromium from reactor operations, were also discharged to the soil column at cribs, trenches, and french drains. Contaminant plumes in groundwater resulted from these former waste disposal practices. Groundwater contaminated with chromium is present beneath the 100-D/DR, 100-H and 100-K Reactor areas and is migrating toward and discharging into, the Columbia River. The groundwater upwells into the river through the riverbed with minor contributions from riverbank seepage.

The 100 Area Land Uses included Native American use and agriculture before Hanford. The waste management land use designation results from former uncontrolled disposal activities in areas now know as past practice waste sites located throughout the 100 Area. There are undeveloped lands located throughout the area that comprise approximately 90 percent of the land area within the 100 Area. These areas are the least disturbed and contain minimal infrastructure. The shoreline of the Columbia River is a valued ecological area within the Hanford Site. Wetlands along the Columbia River are contained within the boundaries of the 100 Area National Priorities List (NPL) site.

OU 27
US Department of Energy Hanford 100 Area, which encompasses approximately 68 km squared bordering the south shore of the Columbia River, is the site of the nine retired plutonium-production reactors. The waste sites being considered for remediation in this Interim Action Record of Decision (IAROD) are in the 100-BC-1, 100-BC-2, 100-DR-2, 100-FR-1, 100-FR-2, 100-HR-1, 100-HR-2, 100-KR-1, 100-KR-2, 100-IU-2, 100-IU-6, and 200-CW-3 OUs and contaminated equipment and debris from the 105-B, 105-KW, 105-KE, 105-H and 105-D Reactor Buildings. The 100-IU-2 and 100-IU-6 OUs are former locations of temporary housing and support facilities for the Manhattan Project and include the former town sites of White bluffs and Hanford. Because of their process history, the DOE, the US. Environmental Protection Agency (EPA), and the State have determined that the waste sites of the 200-SW-3 waste site group are similar to liquid waste disposal sites in the 100 Area and will, therefore, be considered as part of the 100 Area Remaining Sites. These waste sites received cooling water and sludge from 100 Area reactor operations The remainder of the above operable units include waste sites around the 100 Area production reactors where liquid and solid radioactive wastes and industrial chemicals were disposed to the soil.

Pre-Hanford uses included Native American usage and agriculture. Existing land use in the 100 Area includes facilities support, waste management, and undeveloped land. Facility support activities include operations such as water treatment and maintenance of the reactor buildings. The contaminated waste site land area resulted from former uncontrolled disposal activities in areas know as "past-practice waste sites" which are located throughout the 100 Area. Lastly, there are undeveloped lands that comprise approximately 90% of the land area within the 100 Area. The undeveloped areas are the least disturbed and contain minimal infrastructure. A 20-km stretch of the Columbia River is located within the 100 Area. The shoreline of the Columbia River is a valued ecological area within Hanford Site. Portions of the shoreline with a sparse covering of cold desert shrubs and drought-resistant grasses dominates the Hanford Site's landscape. Wetlands along the Columbia River are contained within the boundaries of the 100 Area NPL site.

In 1992, the Hanford Future Site Uses Working Group recommended that 100 Area be considered for the following four future land-use options: Native American uses, Limited recreation, recreation-related commercial use, and wildlife use; 105-B Reactor as a museum and visitor center and wild life and recreational use.
For the purposes of this interim action, the RAOs are for "unrestricted use," consistent with the previous 100 Area soil cleanup decisions.

The 100-B/C Area (the 105-B Reactor) was constructed in 1943 and operated from 1944 through 1968. The 105-Reactor, constructed in 1951, operated from 1952 until 1969, when it also was retired from service. Currently, the only active facilities in the 100-BC-1 OU are those that extract and treat water from the Columbia River and transport that water to other 100 Area and 200 Area facilities. The 100-BC-1 and 100-BC-2 OUs, located in 100-B/C Area, include contaminant sources, and the 100-BC-5 OU includes contamination present in the underlying groundwater. The 100-BC-1 OU encompasses approximately 1.8 km squared and is located immediately adjacent to the Columbia River shoreline. In general, the OU contains waste units associated with the original plant facilities constructed to support B Reactor operation, as well as the cooling water retention basin systems for both B and C Reactors.

The 100-D area encompassed the 105-DR Reactor which operated from 1950 to 1964, when it was retired from service. Currently, sanitary and fire protection water is provided to the 100-H and 100-F Areas from the 100-D Area. The 100-DR-1 and 100-DR-2 are source OUs in the 100-D Area. The 100-HR-3 is the groundwater OU for the 100-D/DR Area contains two reactors: the 105 D Reactor associated with the 100-DR-1 OU, and the 105-DR Reactor associated with the 100-DR-2 OU. The D reactor operated from 1944 to 1967, when it was retired.
The 100-H Area comprised of the 105-H Reactor complex. It was constructed after World War II to product plutonium for use in military weapons. The H Reactor operated from 1949 to 965, when it was retired from service. Currently, there are no active facilities, operations or liquid discharges within the 100-HR-1 source OU. The 100-HR-1 and the 100-HR-2 source OUs, located in the 100-H Area, include contaminant sources, and the 100-HR-3 groundwater OU includes contamination present in the underlying groundwater. The OU contains waste units associated with the original plant facilities constructed to support the H Reactor. The are also contains evaporation basins that received liquid process wastes and non-routine deposits of chemical wastes from the 300 Area (where fuel elements for the 105-N Reactor were produced). These solar evaporation basins received wastes from 1973 through 1985 and are regulated under the Resource Conservation and Recovery Act of 1976 as treatment, storage and disposal facilities.

The 100-F Area is situated in the north-central part of the Hanford Site along the southern shoreline of the Columbia River, approximately 32 km northwest of the city of Richland, Washington. The 105-F Reactor was constructed from 1943 to 1945 and operated from 1945 to 1965. Most of the facilities associated with the F Reactor, other than the biological research facilities, were also retired in 1965. The 100-FR-1 and 100-FR-2 source OUs, located in the 100-F Area, include contaminant sources, and the 100-FR-3 groundwater OU includes contamination in the underlying groundwater. The OUs contain waste units associated with the original plant facilities constructed to support F Reactor operation, as well as the cooling water retention basin systems for the F Reactor and biological laboratories for studying the effects of radiation on plants and animals.
The 100-IU-2 and 100IU-6 OUs are the former locations of temporary housing and support facilities for the Manhattan Project and include the former town sites of White Bluffs and Hanford. Waste sites in these OUs primarily consist of construction debris.

OU 15:
Operations in the 200 North Area were mainly related to irradiated nuclear fuel storage. The purpose of the facilities in this area was to provide a storage site for the fuel while the radioisotope decay processes for many of the short-lived radioisotopes were occurring. The area is located approximately 7 to 12 km south of the 100 Areas and immediately north of the 200 Areas. The 200-CW-3 waste site group includes contaminant sources resulting from the release of cooling water from the fuel storage basins.

OU8:
The 100-NR-1 OU encompasses an area of approximately 405 hectares (over 1,000 acres) and contains the N Reactor, the Hanford Generating Plant (HGP), and adjacent support facilities. Reactor operations and former waste-handling practices have caused contamination in the soil around the N Reactor, the HGP, and the adjacent support facilities, and in the 100-NR-2-OU.

The 100-NR-2 OU encompasses the contaminated groundwater underlying the 100-N Area. During the years of reactor operations until shortly after reactor shutdown, large volumes of reactor coolant wastewater containing activation and fission products, as well as small quantities of corrosive liquids and laboratory chemicals generated by various N Reactor operations, were discharged to the soil through cribs and trenches. A groundwater pump and treat system has been in operation since September 1995 as part of on expedited response action at the 100-NR-2 OU. This system provides removal of strontium-90 from extracted groundwater, treatment of strontium-90 by ion exchange, and return of treated groundwater to the unconfined aquifer using upgradient injection wells.

Throughout the operational history of the N Reactor, significant spills were documented in unplanned release reports. The unplanned release reports were used for reporting and tracking the activities associated with each spill. Spills in the 100-N Area consisted of three basic types: radioactive, corrosive, and petroleum. Response to unplanned releases or spills depended on the location of the spill, the constituents involved, and the potential impact to worker safety and the environment. Spills that were likely to have an impact on humans or the Columbia River were remediated, to the extent possible, at the time of the spill to mitigate potential impacts.
The Department of Energy, Environmental Protection Agency, and the Washington State Department of Ecology, also known as the Tri-Parties, entered into the Federal Facility Agreement and Consent Order in May 1989. The 100-NR-1 and 100-NR-2 OUs were designated as units subject to Resource Conservation and Recovery Act (RCRA) corrective action. In 1998, DOE published the results of a Corrective Measures Study, that was conducted to gather information to support selection of a remedial alternative to address contamination at the 100-NR-1 and 100-NR-2 OUs. In a addition, a qualitative risk assessment (QRA), comprised of both human health and ecological risk assessments, was conducted to evaluate current and potential effects of contaminants in the 100-NR-1 OU on human health and the environment.

The structures and buildings associated with the 100-NR-1 OU have a Superfund Removal Action Memorandum issued in January 1999 to authorize cleanup of the sites.

A Record of Decision addressing OU8 was completed in September 1999.
 
Remedy:  The selected remedy for both 100 and 200 Areas waste sites will include the following activities:

DOE is required to submit the remedial design report, remedial action work plan, an sampling and analysis plan as primary documents. These documents and associated documents concerning the planning and implementation of remedial design and remedial action shall be submitted to EPA and Ecology for approval prior to the initiation of remediation. The current remedial design report and remedial action work plan may be revised as an alternative to submitting new documents.

Removing and stockpiling any necessary uncontaminated overburden will involve, to the extent practicable, that this material will be used for backfilling excavated areas.

Excavation activities will follow standard construction practices for excavation and transportation of hazardous materials and will follow as low as reasonable achievable (ALARA) practices for remediation workers. Dust suppression during excavation, transportation, and disposal will be required, as necessary.

Treatment, as necessary to meet ERDF waste acceptance criteria will be performed in the 100 Area or at the ERDF prior to disposal. Recycling of treated materials and re-use of treated materials for backfilling excavated areas are expected to reduce remedial action costs. Materials that are transported to ERDF for disposal must meet disposal acceptance criteria, including treatment provisions, for that facility.

The extent of remediation of the waste sites will take into account certain site-specific factors. The waste sites are represented by the following two general categories and the primary factors for consideration are discussed for each:

For shallow sites were the entire engineered structure, soil, or debris contamination is present within the top 4.6 m (15ft), remedial action objectives (RAOs) will be achieved when contaminant levels are demonstrated to be at or below MTCA Method B for inorganics or organics for residential exposure and the 15 mrem/year residential dose level and are at levels that provide protection of groundwater and the Columbia River.

For sites where the engineered structure, and/or contaminated soil and debris begins above 4.6 m (15ft) and extends to below 4.6 m (15ft), the engineered structure (at a minimum) will be remediated to achieve RAOs so the contaminant levels are demonstrated to be at or below MTCA Method B levels for metals and organics for exposure and the 15 mrem/yr. residential dose level and are at levels that provide protection of groundwater and the Columbia River. Any residual contamination present below the engineered structure and is greater than 4.6 m (15ft) in depth shall be subject to several factors in determining the extent of remediation including reduction of risk by decay of short-lived radionuclides protection of human health and the environment, remediation costs, sizing the ERDF, worker safety, presence of ecological and cultural resources, the use of institutional controls and long-term monitoring costs. The extent of remediation must ensure that contaminant levels remaining in the soil are protective of groundwater at levels equal to or less than the 00 times the groundwater cleanup levels established in accordance with WAC 173-340-720. If residual concentrations exceed cleanup levels, site specific modeling will be performed to provide refinement on contaminants found to simulate actual conditions at the waste site. For radionuclides, groundwater and river protection will be demonstrated through a technical evaluation using the computer model Residual Radioactivity (RESDAD).

After the site has been demonstrated to have achieved cleanup levels and RAOs, the site will be backfilled with clean materials and revegetated in accordance with approved plans. Revegetation plans will be developed as part of remedial design activities with input from affected stakeholders such as Natural Resource Trustees and Native American Tribes. Revegetation efforts will attempt to establish a viable habitat at the remediated areas and will emphasize the use of native seed stock.

Institutional Controls and long-term monitoring will be required for sites where wastes are left in place and preclude an unrestricted land use. Institutional controls selected as part of this remedy are designed consistent with the interim action nature of their ROD. Additional measures may be necessary to ensure long-term viability of institution controls fi the final remedial actions selected for the 100 Area does not allow for unrestricted land use. Any additional controls will be specified as part of the final remedy. The following institutional controls are required as part of this interim action:

DOE will continue to use a badging program to control access to the associated sites for the duration of the interim action. Visitors entering any of the sites associated with this Interim Action ROD are required to be escorted at all times.

DOE will utilize the onsite excavation permit process to control land use (e.g., well drilling or excavation of soil) within the 100 Area OUs.

DOE will maintain existing signs prohibiting public access.

DOE will provide notification to EPA and Ecology upon discovery of any trespass incidents.

Trespass incidents will be reported to the Sheriff's office for investigation and evaluation for possible prosecution.

DOE will take the necessary precautions to add access restriction language to any land transfer, sale or lease of property that the U.S. Government considers appropriate while institutional controls are compulsory.

Until final remedy selection, DOE shall not delete or terminate any institutional control requirement established in this Interim Action ROD unless EPA and Ecology have provided written concurrence on the deletion or termination and appropriate documentation has been placed in the Administrative Record.

DOE will evaluate the implementation and effectiveness of institutional controls for the 100 Area OUs on an annual basis. The DOE shall submit a report to EPA and Ecology by March 30 of each year summarizing the results of the evaluation for the preceding calendar year. At a minimum, the report shall contain an evaluation of whether or not the institutional control requirements continue to be met and a description of any deficiencies discovered and measures taken to correct problems.

Because this is an interim action and wastes will continue to be present in the 100 Area until such time as a final ROD is issued and final remedial objectives are achieved, a 5-year review will be required.

Estimate Capital Cost: Not provided
Estimated Annual O&M Cost: Not provided
Estimated Total O&M Cost: Not provided
Estimated Present Worth Cost: $18,000,000
Other: Estimated Cost of Sampling: $12,288,024
 
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