PB96-964603
                                EPA/ROD/R10-96/134
                                May 1996
EPA Superfund
      Record of Decision:
       Hanford 100 Area (USDOE),
       O.U. 100-HR-3 and 100-KR-4,
       Hanford Site, Benton County, WA
       3/26/96

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                 DECLARATION OF THE RECORD OF DECISION
SITE NAME AND LOCATION

USDOE Hanford 100 Area
100-HR-3 and 100-KR-4 Operable Units
Hanford Site
Benton County, Washington

STATEMENT OF BASIS AND PURPOSE

This decision document presents the selected interim remedial actions for portions of the
USDOE Hanford 100 Area, Hanford Site, Benton County, Washington, which were chosen in
accordance with the Comprehensive Environmental Response, Compensation, and Liability Act
of 1980 (CERCLA), as amended by the Superfund Amendments and Reauthorization Act of
1986 (SARA), and to the extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). This decision is based on the administrative record for
this site.

The Washington State Department of Ecology (Ecology) concurs on the selected remedy.

ASSESSMENT OF THE  SITE

Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing  the response action selected in this Record of Decision (ROD), may present an
imminent and  substantial endangerment to public health, welfare, or the environment.

DESCRIPTION OF THE SELECTED REMEDY

The selected remedy is an interim action that involves removing hexavalent chromium from
ground water that discharges into the Columbia River.  To intercept the chromium plumes,
groundwater will be pumped from  approximately 30 wells located along and inland from the
river shoreline.  The water will then be treated using an ion exchange treatment technology to
remove chromium.  The treated effluent will then be returned to the aquifer using injection
wells located upgradient of the existing chromium plumes.  The interim action includes
monitoring of the groundwater near the river and the effluent from the treatment system to
determine system performance in meeting the remedial action objectives for protection of the
Columbia River.  The interim action also involves institutional controls to protect human
health from groundwater contaminants.

DECLARATION

This interim action is protective of human health and the environment, complies with Federal
and State applicable or relevant and appropriate requirements directly associated with this

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action, and is cost-effective. This action utilizes permanent solutions and alternative treatment
technologies to the maximum extent practicable, given the limited scope of the action.  This
remedial action complies with the statutory preference for remedies that employ treatment that
reduces toxicity, mobility, or volume of contaminants as a principal element. Subsequent
actions are planned to fully address the threats posed by these operable units.

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. Because this is an interim action Record of Decision  (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 National Priority
List (NPL) site.
                                           11

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                                                                   028957

Signature sheet for the Record of Decision for the USDOE Hanford 100-HR-3 and 100-KR-4
Operable Units Interim Remedial Actions between the United States Department of Energy and
the United States Environmental Protection Agency, with concurrence by the Washington State
Department of Ecology.
                                             y// 1 ft
  5hnD. Wagoner   /j                                   Date
r Manager, Richland Operations
United States Department of Energy
                                       in

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Signature sheet for the Record of Decision for the USDOE Hanford 100-HR-3 and 100-KR-4
Operable Units Interim Remedial Actions between the United States Department of Energy and
the United States Environmental Protection Agency, with concurrence by the Washington State
Department of Ecology.
                                                4
Chuck Clarke     ^                                Date"
Regional Administrator, Region 10
United States Environmental Protection Agency
                                         IV

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Signature sheet for the Record of Decision for the USDOE Hanford 100-HR-3 and 100-KR-4
Operable Units Interim Remedial Actions between the United States Department of Energy and
the United States Environmental Protection Agency, with concurrence by the Washington State
Department of Ecology.
      d. Wilson                                            Date
Program Manager, Nuclear and Mixed Waste Program
Washington State Department of Ecology

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                           TABLE OF CONTENTS

DECLARATION OF THE RECORD OF DECISION	i

                           DECISION SUMMARY

SITE NAME, LOCATION, AND DESCRIPTION 	1
SITE HISTORY AND ENFORCEMENT ACTIVITIES	2
HIGHLIGHTS OF COMMUNITY PARTICIPATION	8
SCOPE AND ROLE OF RESPONSE ACTION WITHIN SITE STRATEGY	10
SUMMARY OF SITE CHARACTERISTICS	11
SUMMARY OF SITE RISKS	25
REMEDIAL ACTION OBJECTIVES	33
DESCRIPTION OF ALTERNATIVES	34
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES	37
SELECTED REMEDY	42
STATUTORY DETERMINATIONS  	49
DOCUMENTATION OF SIGNIFICANT CHANGES  	53

                                 FIGURES

1.     Hanford Site	3
2.     100-HR-3 Operable Unit  	4
3.     100-KR-4 Operable Unit	5
4.     Well Location Map for the 100-HR-3 Operable Unit	15
5.     Well Location Map for the 100-KR-4 Operable Unit	16
6.     Columbia River Flood Plain  	17

                                 TABLES

1.     Maximum Concentration Summary for Contaminants of
      Potential Concern in the 100-D/DR Area	18
2.     Maximum Concentration Summary for Contaminants of
      Potential Concern in the 100-H Area	19
3.     Maximum Concentration Summary for Contaminants of
      Potential Concern in the 600 Area Between the 100-D/DR and 100-H Areas	20
4.     Maximum Concentration Summary for Contaminants of
      Potential Concern in the 100-K Area	21
5.     Threatened and Endangered Species Potentially Found on the Hanford Site	22
6.     Fish Species in the Hanford Reach of the Columbia River  	23
7.     Ecological Risk Summary for Radionuclide Contaminants of
      Potential Concern in the 100-HR-3 Operable Unit	27
8.     Ecological Risk Summary for Nonradionuclide Contaminants of Potential
      Concern in the 100-HR-3 Operable Unit	28
                                    VI

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9.     Ecological Risk Summary for Radiological Contaminants of Potential
      Concern in the 100-KR-4 Operable Unit	31
10.    Ecological Risk Summary for Nonradionuclide
      Contaminants of Potential Concern in the 100-KR-4 Operable Unit	32

                                  APPENDIX A

RESPONSIVENESS SUMMARY	54
                                       vn

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                               DECISION SUMMARY
                  I. SITE NAME, LOCATION, AND DESCRIPTION

The U.S. Department of Energy's Hanford Site was listed on the National Priorities List
(NPL) in November 1989 under the Comprehensive Environmental Response,  Compensation,
and Liability Act of 1980 (CERCLA) as amended by the Superfund Amendments and
Reauthorization Act of 1986 (SARA).  The Hanford Site was divided and listed as four NPL
Sites: the 100 Area, the 200 Area, the 300 Area, and the 1100 Area.

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) and surrounding communities in Benton, Franklin, and Grant counties
(figure 1).  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.

The 100 Area, which encompasses approximately 68 km2 (26 mi ) bordering the south shore
of the Columbia River, is the site of nine retired plutonium production reactors.  The
groundwater impacted by operations associated with those 9 reactors has been  divided into five
operable units.  Two of the five groundwater operable units are addressed in this Record of
Decision.

Pre-1943 land use at Hanford was primarily grazing and agriculture with some traditional use
by Native Americans.  Historically groundwater use included domestic consumption, as well
as other needs for the small agricultural communities, and by Native Americans.  Currently
groundwater is not used but is monitored  to assess contaminant conditions. Existing land use
in the 100 Area includes facilities support, waste management, and undeveloped land.
Facilities 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 known as "past-practice waste sites" located
throughout the 100 Area. Lastly, there are undeveloped lands located throughout the 100 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 Hanford Reach of the Columbia River is the last free-flowing portion of the Columbia
River in the United States above Bonneville Dam.  The river contains the only remaining
spawning habitat for native salmon on the main  stem of the Columbia River in the United
States. The river and associated riparian  and upland areas are valued ecological  and
recreational resources. The Hanford Reach along the 100-HR-3 and 100-KR-4 Operable Units
is currently being used for activities such  as hunting, fishing, and water skiing.  The Hanford
Reach of the Columbia River: Comprehensive River Conservation Study and Environmental
Impact Statement has identified much of Hanford Reach,  including the 100 Area, for
consideration as a designated recreational river under the Wild and Scenic Rivers Act.

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               H. SITE HISTORY AND ENFORCEMENT ACTIVITIES

In anticipation of the NPL listing, DOE, EPA, and 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 addresses Resource
Conservation and Recovery Act (RCRA) compliance and permitting.

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 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 (a grouping of individual waste units based primarily on geographic
area and common waste sources).  The 100 Area NPL site consists of the following operable
units for contaminated  sources such as soils, structures,  debris, and burial grounds: 100-BC-l,
100-BC-2, 100-KR-l,  100-KR-2,  100-NR-l, 100-DR-l, 100-DR-2, 100-HR-l, 100-HR-2,
100-FR-l, 100-FR-2, 100-IU-l, 2, 3, 4, 5, and 6; and for contaminated groundwater:
100-BC-5, 100-KR-4,  100-NR-2,  100-HR-3, and  100-FR-3.  This ROD addresses the
chromium contaminated plumes in the 100-HR-3 and 100-KR-4 Operable Units.

The 100-HR-3 Operable Unit 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 (figure 2). 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 Operable Unit 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-l and 100-KR-2 Operable Units (figure 3).  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.

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              Figure 1. Hanford Site.
                                                      Seattle    ^          Spokane
                                                         Washington
                     100-N

              /     100-K
                100-B,C
                                                            / Hanford
                                                          #   Site
      200-West
        Area
                              200-East
                                Area
                                                        Supply
                                                        System
02468  10 kilometers
                                                        11007
                                                      3000 Area
i   i  i   i  i  i
01234  Smiles

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                      Figure 2. 100-HR-3 Operable Unit.
                                                                  100-HR-3
                                                                  Operable Unit
                                                                  Boundary
1 kilometer

       1 mile
                                          100-HR-1
                                          Operable Unit
                              100-HR-3
                          OPERABLE UNIT
                                           183-H Solar
                                           Evaporation
                                           Basins
                                                          100-HR-2
                                                          Operable Unit
                                             100-IU-4
                                             Operable Unit
                      100-DR-1
                      Operable Unit
                       100-DR-2
                       Operable Unit
Area of chromium contamination in
groundwater to be addressed by
interim remedial measure
NOTE: Most chromium is believed to be the
hexavalent form, with only minor trivalent
chromium present.
                  Hanford Site
                  Boundary
                                                  ~  ^Environmental
                                                     Restoration
                                                     Disposal
                                                     Facility
           Seattle   f         Spokane

              Washington

                         Hanford Site
                                                                      5 miles

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                               Figure 3. 100-KR-4 Operable Unit.
                                                                                      100-KR-4
                                                                                      Operable Unit
                                                                                      Boundary
                                                                                  116-K-2 Trench
                                                                                  (Mile-Long Trench)
       300 Meters
       •
      1000 Feet
                                                                      100-KR-4
                                                                      OPERABLE UNIT
                                    100-KR-1
                                    Operable
                                     nit
                                                                   118-K-2
                                                                   Sludge Burial
                                                                   Ground
                                                                 100-K East Reactor
100-K West Reactor
             100-KR-2
             Operable
             Unit
     Approximate area of chromium
   < contamination in groundwater to be
     addressed by interim remedial measure
Hanford Site
Boundary
     NOTE: Most chromium is believed to be the
     hexavalent form, with only minor trivalent
     chromium present.
                                                                      ^   *""*" Areas
                                                                     "^v Environmental /
                                                                        Restoration
                                                                        Disposal
                                                                        Facility
                Washington

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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 programs set up
by DOE Order 5400.1.  These include the Operational Monitoring program conducted by the
Maintenance and Operations contractor for the Site, and the Sitewide Environmental
Surveillance program, which is conducted by Pacific Northwest National Laboratory.  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.  The following three paragraphs identify reactor-area specific activities
that add to the data available from these site wide programs.

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 unmonitored 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

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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 ion exchange treatment system to remove hexavalent chromium from
groundwater.  Through July 1995, this pump-and-treat system has extracted more than 4
million gallons (15 million liters) of groundwater and has 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.

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              m.  HIGHLIGHTS OF COMMUNITY PARTICIPATION

The DOE, Ecology, and EPA developed a Community Relations Plan in April 1990 as part of
the overall Hanford Site restoration. The Plan was designed to promote public awareness of
the investigations and public involvement in the decision-making process.  The Plan
summarizes known concerns based on community interviews. Since that time 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 100 Area Focused Feasibility Study  Document and Proposed Plans for 100-HR-3 and
100-KR-4 were made available to the public in both the Administrative Record and the
Information Repositories maintained at the locations listed below. These documents underwent
a 45 day public comment period from September 11,  1995 to October 25,  1995.
      ADMINISTRATIVE RECORD (Contains all project documents)

             U.S. Department of Energy
             Richland Field Office
             Administrative Record Center
             740 Stevens Center
             Richland, Washington 99352

             EPA Region 10
             Superfund Record Center
             1200 Sixth Avenue
             Park Place Building, 7th Floor
             Seattle, Washington 98101

             Washington State Department of Ecology
             Administrative Record
             300 Desmond Drive
             Lacey, Washington 98503-1138
      INFORMATION REPOSITORIES (Contain limited documentation)

             University of Washington
             Suzzallo Library
             Government Publications Room
             Mail Stop FM-25
             Seattle, Washington 98195

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             Gonzaga University
             Foley Center
             E. 502 Boone
             Spokane, Washington 99258

             Portland State University
             Branford Price Millar Library
             Science and Engineering Floor
             SW Harrison and Park
             P.O.Box 1151
             Portland, Oregon 97207

             DOE Richland Public Reading Room
             Washington State University, Tri-Cities
             100 Sprout Road, Room 130
             Richland, Washington 99352
Notice of the public comment period and availability of documents for review was published in
the Seattle Pi/Times, the Spokesman Review-Chronicle, the Tri-City Herald, and the
Oregonian on September 10 and 11, 1995. The notice also ran throughout the week of
September 10 in the various papers published by the Hood River News. In addition a 2-page
focus sheet that summarized the Proposed Plans was mailed to an "interested in Hanford"
mailing list of about 4,700.  That mailing list included the members of the Hanford Advisory
Board (a  citizen / stakeholder cleanup advisory board), Native American Tribes with reserved
treaty rights  to Hanford-related resources, and Natural Resource Trustees. The Proposed
Plans were faxed to participants in the Hanford Natural Resource Trustee Council (which
includes the  Tribes) on August 21-22, 1995.  Focus sheets and Proposed Plans were mailed to
a number of individuals in response to requests during the comment period.  The Proposed
Plans and focus sheet identified that a public meeting would be held upon  request.  Such a
request was received from the Columbia River United citizen  stakeholder group located in
Hood River, Oregon. Per their request, a meeting was held October 18, 1995 that discussed
the proposed actions relative to other Hanford ground water and Columbia River issues.  At the
meeting,  representatives from DOE, EPA and Ecology provided information about this and
related projects and answered questions about the projects.  A response to the comments
received during the public comment period is included in the Responsiveness Summary,  which
is attached as Appendix A to this ROD.  This decision document presents  the selected interim
remedial  action for the groundwater at the 100-HR-3 and 100-KR-4 Operable Units at the
Hanford Site in Richland, Washington. 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.

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    IV.  SCOPE AND ROLE OF RESPONSE ACTION WITHIN SITE STRATEGY

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 ground water operable units, or until such time that the DOE
demonstrates to Ecology and the EPA that no further interim action is required.  This interim
action is expected to become part of the final remedial action for the 100-HR-3 and  100-KR-4
Operable Units.  As with the remedy selection for interim action, final remedy selection will
occur only after taking public comment into consideration.

In addition to this action for the 100-HR-3 and 100-KR-4 Operable Units, plans are underway
to address waste sites that are the historic  sources of ground water contamination.  Surface
waste sites that are within operable units 100-DR-l, 100-DR-2, 100-HR-l, 100-HR-2,
100-KR-l and 100-KR-2 received wastes during previous operation of the reactors and their
support facilities.  Cleanup of high priority liquid effluent waste sites in the 100-DR-l and
100-HR-l Operable Units were addressed in a September  1995 interim action Record of
Decision. The 100-DR-2, 100-HR-2, 100-KR-l  and 100-KR-2 Operable Units will be the
subject of future response actions.  The 100-IU-4 Operable Unit upgradient of 100-HR-3
includes the former Sodium Dichromate Barrel Landfill, which was previously used to dispose
of empty crushed barrels.  The 100-IU-4 Operable Unit was remediated in April 1992 through
an Expedited Response Action and a no further action final ROD was signed in February
1996.

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.
                                         10

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                    V.  SUMMARY OF SITE CHARACTERISTICS

5.1 Site Geology and Hydrogeology

The Hanford Site is located in the Pasco Basin, a topographic and structural basin situated in
the northern portion of the Columbia Plateau.  The plateau is divided into three general
structural subprovinces:  the Blue Mountains; the Palouse; and, the Yakima Fold Belt.  The
Hanford Site is located in the eastern portion of the Yakima Fold Belt.

5.1.1 Geology
The 100 Area is located in the northern portion of the Hanford Site, adjacent to the Columbia
River. The geology of the 100 Area is similar to much of the rest of the Hanford Site, which
generally consists of three distinct geologic formations.  The oldest and deepest formation
consists of a thick series of basalt flows and interbeds that have been warped and folded.  The
top of the basalt in the 100 Area ranges in elevation from 46 m (150 ft) near the 100 H Area to
64 m  (210 ft) below sea level west of the 100 K Area.  The Ringold Formation overlies the
Columbia River Basalts and is up to 185 m (about 600 ft) thick in the Pasco basin. The
Ringold Formation is made up of sedimentary deposits which consist of interbedded clay, silt,
fine to coarse sand, and gravel.  The uppermost formation is referred to as the Hanford
Formation.  It consists of sand and gravel deposited by catastrophic floods during the last
glacial episode. In the 100 Area, the Hanford Formation consists primarily of the Pasco
Gravel Facies, with local occurrences of the sand-dominated or slackwater deposits.

The 100 K Area differs geologically from the surrounding area because the Ringold Formation
is exposed along the bank of the Columbia River and up to 366 m (1200 ft) inland. Coyote
Rapids, immediately upstream of the 100 K Area consists of cemented Ringold material.  The
contact between the Hanford Formation and the Ringold Formation is generally noted by  an
iron staining and an increase in cementation. The Hanford Formation underlying the 100 K
Area is a wedge that increases in thickness away from the Columbia River.  It varies in
thickness from 0 to about 37 m (120 ft) near the southwest corner of the K Area. The Hanford
Formation in the vicinity of the 100  K Area consists mainly of gravels.

Underlying the 100 H & D Areas, a lacustrine mud unit up to 30 m (100 ft) thick forms the
base of the Ringold Formation.  Overlying  the mud unit, fluvial sands and gravels interbedded
with overbank and lacustrine sediments comprise the remaining Ringold Formation. The
Ringold/Hanford contact is highest west of the 100 H Area and slopes toward the Columbia
River to the east.  The Hanford Formation thickness ranges from near 0 to 24 m (80 ft).  The
unit is thickest in the west central portion of the 100 HR-3 Operable Unit.  In this area the
Hanford Formation consists of unconsolidated gravels in a matrix of fine to coarse sand.

5.1.2  Hydrogeology
Underlying the 100 Area the uppermost aquifer is referred to as the unconfmed aquifer.  This
aquifer is open to the vadose zone and is hydraulically connected to the Columbia River.
Below the unconfmed  aquifer there exists multiple confined aquifers.  The confined aquifers to
date have received very little contamination due to an upward hydraulic gradient.

                                          11

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The unconfined aquifer system underlying the 100 K and D Areas is comprised exclusively of
Ringold Formation fluvial sand and gravel. Ground water flow direction is north-northwest
towards the Columbia River.  The mean hydraulic conductivity of the Ringold Formation is
about 32 ft/day.  Ground water elevation across the K Area ranges from about elev. 382 to
elev. 392 ft.  Across the D Area groundwater elevation ranges from about elev. 381 to elev.
386 ft.  In the 100 H Area the unconfined aquifer occurs predominantly in the Hanford
Formation. Groundwater elevation ranges from about elev. 374 to elev. 377 ft. The saturated
portion of the Hanford Formation is about 13 to 24 ft thick across this area.  Flow direction is
northeast towards the Columbia River. The mean  hydraulic conductivity for the H Area is
about 100 ft/day.

5.2 Columbia River Water Quality

Surface water at the 100 Areas of the Hanford Site is limited to the  Columbia River and
springs along the riverbank.  The Columbia River is the second largest river in North America
and the dominant surface-water body  on the Hanford Site.  The existence of the Hanford Site
has precluded development of this section of river for irrigation and power, and the  Hanford
Reach  (the free flowing section of the Columbia River beginning  at Priest Rapids  Dam and
ending at Lake Wallula) is now being considered for designation as  a National Wild and Scenic
River as a result of congressional action in  1988 (Public law 100-605).

Washington State has classified the stretch of the Columbia River from Grand  Coulee to the
Washington-Oregon border, which includes the Hanford Reach, as Class A, Excellent. Class
A waters are to be suitable for essentially all uses, including raw drinking water, recreation,
and wildlife habitat.

The seepage of groundwater, or springs, into the Columbia River has been known to occur for
many years.  These relatively small springs flow intermittently, apparently influenced
primarily by changes in river level. Hanford-origin contaminants have been documented in
these groundwater discharges along the Hanford Reach.

5.3 Groundwater System

Groundwater in the unconfined aquifer at the Hanford Site generally flows from recharge areas
in the elevated region near the western boundary of the Hanford Site toward the Columbia
River on the eastern and northern boundaries.  The Columbia River is the primary discharge
area for the unconfined aquifer. Natural areal recharge from precipitation across the entire
Hanford Site is thought to range from almost 0 to  10 cm (0 to 4 in.) per year,  but is probably
less than 2.5 cm (1 in.) per year.  Since 1944, the artificial recharge from Hanford Site
wastewater disposal operations has been significantly greater than the natural recharge. An
estimated 1.68 x 10    L (4.4 x 1011 gallons) of liquid was discharged to disposal ponds,
trenches, and cribs.  Now that liquid discharges from reactor processes has stopped,
groundwater flow has  since returned to its pre-Hanford flow direction and gradient in the
100-HR-3 and 100-KR-4 Operable Units.
                                          12

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5.4  Groundwater Data Summary

The primary purpose of the limited field investigation at the Operable Units was to collect
sufficient data to determine if the groundwater is contaminated to the extent that an interim
remedial action was warranted.  The limited field investigation was designed to augment
existing historical groundwater data mentioned in Section II. The data gathered during the
limited field investigation were also used to conduct a qualitative risk assessment for human
and ecological receptors, and to evaluate remedial alternatives.

As part of the limited field investigation, 22 new groundwater wells were installed (in addition
to the existing 42 wells) in the 100-HR-3 Operable Unit and 7 new groundwater wells were
installed  (in addition to the existing 12 wells) in the 100-KR-4 Operable Unit.  These wells
were constructed to help define groundwater quality in areas downgradient of the priority
waste sites  in the area that are sources of the contaminants, and estimate groundwater quality
at locations where human and ecological receptors may be exposed to groundwater.

Groundwater samples were  collected from these new wells and existing monitoring wells
(100-HR-3, figure 4; 100-KR-4, figure 5). A total of 262 samples from  100-HR-3 and  82
samples from 100-KR-4, exclusive of duplicates and splits, were collected over four  rounds of
sampling (September 1992 to June 1993 for 100-KR-4, and May 1992  to March 1993 for
100-HR-3). These samples were analyzed for organic, inorganic, and  radioactive constituents.
Soil samples were collected during well-drilling activities and analyzed for physical properties.
Tables 1  through 3 (100-HR-3), and table 4 (100-KR-4) present the maximum concentrations
of radiological and nonradiological chemicals in groundwater, in springs  and seeps, and in the
Columbia River within and  adjacent to these areas.  These maximum concentrations were used
to evaluate  risks to receptors. Data from near-river wells were used to evaluate ecological
risk, and data from all wells were used to evaluate human health risk.

During March of 1995 pore water samples were collected in the river substrate adjacent to the
100-H Area.  Results indicated that chromium is present in the river substrate at levels of
concern.  Similar data are being collected at other reactor areas.  Additionally,  sampling points
are being successfully installed along  the shoreline to evaluate the river-groundwater  interface.
These new  data will support the Remedial Design Report/Remedial Action  Work Plan
(RDR/RAWP).

5.5  Ecological Description

An 18 mile stretch of the Columbia River is located within the 100 Area.  The Columbia River
corridor is  a valued ecological area within the Hanford Site.  Semi-arid land with a sparse
covering of cold desert shrubs and drought-resistant grasses dominates  the Hanford landscape.
Forty percent of the area's annual average of six and one quarter inches of rain occurs between
November  and January. Numerous ecological studies have characterized the biological
resources of the Hanford Site, including the terrestrial, riparian, and aquatic habitats.
                                          13

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Because this interim action involves activities located on upland habitat, adjacent to riparian
and aquatic areas, and affects the chemical and hydrological regime in the near-river
environment, the potential list of species that could be affected includes potentially all species
associated with the Hanford site, both resident and migratory.  Table 5 lists species of concern
found or potentially occurring on the Hanford Site, and table 6 lists known fish species in the
Hanford Reach of the Columbia River. Portions of the 100-HR-3 and 100-KR-4 lie within the
100-year flood plain (figure 6).  There is a band of wetland habitat adjacent to the Columbia
River that varies from very thin in 100-KR-4 to very wide in portions of 100-HR-3.

5.6 Cultural Resources Review

Both 100-HR-3 and 100-KR-4 are in areas rich with cultural resources.  The 100-K Area
contains a number of archaeological and ethnohistoric sites that range in age from 9,000 years
ago to the mid-nineteenth century.  The 100-K area is considered extremely sensitive as a
Native American-related cultural resource.  Two individual sites within the 100-K Area are
individually eligible for the National Register of Historic Places while others are included in
the Ryegrass Archaeological District.  Along the rapids associated with the 100-K Area,
Smohalla, Prophet of the Wanapum people performed the first washat, the dance ceremony
that has become central to the Seven Drums or Dreamer religion. This religion spread to
many neighboring Tribes and is currently practiced in some form throughout the interior
Northwest. Furthermore, a Wanapum cemetery exists in the 100-K Area.

Surveys for 100-HR-3 have located 25 prehistoric sites and 58 historic sites.  Six of the
prehistoric sites have been evaluated for and found eligible for listing to the National Register
of Historic Places.
                                           14

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                                                                                                        I         I
                                                                                                                         I         I         I         I


                                                                                                                           100-HR-3  Operable Unit
                                                                                                                           Monitoring Well  Locations

                                                                                                                              •*•   Groundwoter  Monitoring Well
                                                                                                                              I   Riverbonk Seepage
                                                                                                                                  Well Prefix 199-  or 699-
                                                                                                                                  Stote Plane Coordinotes
                                                                                                                                  (Meters)
                                                                                                                                                                                1
                                                                                                                                                                                 £t
                                                                                                                                                                                 o
                                                                                                                                                                                 B
                                                                                                                                                                                ID
                                                                                                                                                                                 O
                                                                                                                                                                                 9
                                                                                                                                                                                 O
                                                                                                                                                                                 d
 E572500
_J	
                                                                                88-41
E573000   E573500   E574000   E574500    E575000    E575500    E576000   E576500    E577000^  E577500   E578000   E578500    E579000
   I         I         I         I        I         I         I         I         I         I         I

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       Figure 5. Well Location Map for the 100-KR-4 Operable Unit.
     I
    -N-
0   150  300  METERS
0   500  100 FEET
                                              LEGEND
                                          	GROUNDWATER OPERABLE UNIT BOUNDARY
                                          100-KR-4
                                             4-  GROUNDWATER MONITORING WELL
                                                                      ITH:JJA:PC411-A3
                                    16

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                           Figure 6. Columbia River Flood Plain.
BPA Midway   »
 Substation
                                                                               Adams Co.
                                                                              Franklin Co.
                 Benton
                   Co.
                                                        Old Hanford
                                                          Townsite
                                                                       Washington
                                                                       Public Power
                                                                      Supply System
Rattlesnake
 Springs
                                                                    300 Area PNL &
                                                                     Westinghouse
                                                                          Hanford
                                                                        Advanced
                                                                     Nuclear Fuels
            Hanford Site  -i^
            Boundary
                                                            West Richland
                         10 kilometers
                         •

                      5 miles
                                                17

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             Table 1.  Maximum Concentration Summary for Contaminants of
                          Potential Concern in the 100-D/DR Area.
Groundwater
Contaminants
All
Groundwater
Wells
Near-River
Groundwater
Wells
D/DR
Area
Springs
D/DR
Area
Columbia
River
MCL
(pCi/L or
mg/L)
Radionuclides (pCi/L)
Tritium
Strontium-90
Uranium 233/234
Uranium 238
78,000
41(J)
1.5
1.4
19,000
7.6
1.1
1.1
3,100
4.5
1.0°
1.0C
<200
<1
0.33C
0.33C
20,000a
8a
NA
NA
Inorganics (mg/L)
Barium
Chromium
Iron
Manganese
Vanadium
0.164
2.09
0.550
0.19
0.020
0.092
0.44(J)
0.550
0.056
0.020
0.055
0.12
0.072
0.004(B)
0.005
0.026
0.009(U)
0.102
0.007(U)
(U)
2.0a
O.la'b
NA
NA
NA
Organics (mg/L)
Bis(2-ethylhexyl)phthalate
0.003
0.003
(U)
(U)
NA
Anions (mg/L)
Ammonia as N
Nitrate as N
Sulfide
0.75
32.7
1
0.26
14.1
1
0.1(J)
0.68
(U)
<0.5(UJ)
(U)
(U)
NA
10a
NA
a 40 CFR 141 (Primary MCL). MCLs presented for comparison purposes.
Qo-m-rvlo \/alii£> -tvai-wi-ff dt\ 10 •fir»t* f/ifal r»Vi-twnniTinn ~\K.C^\ 10 fr\r VIOYQ\/CI I^nf" r»ntVMT"inim
0      Sample Value reported is for total uranium.
(J)     Estimated value.
(B)     Analyte detected at a concentration below the contract required detection limit, but above the instrument
       detection limit.
(U)     Undetected.
NA     Not applicable.
Near-River wells were: 199-D5-20, -D8-4, -D8-5, -D8-53, -D8-54A, -D8-55.
                                               18

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             Table 2.  Maximum Concentration Summary for Contaminants of
                             Potential Concern in the 100-H Area.

Groundwater
Contaminants
All
Groundwater
Wells
Near-River
Groundwater
Wells

HArea
Springs
HArea
Columbia
River
MCL
(pCi/L or
mg/L)
Radionuclides (pCi/L)
Tritium
Carbon- 14
Strontium-90
Technetium-99
Uranium-233/234
Uranium 235
Uranium-238
Americium-241
11,000
72
33
2,270
26.8
2.43
18.6
0.28(J)
7,100
72
33
500
26.8
2.43
18.6
0.28(J)
3,800(J)
NA
12.7
12
NA
1.22C
1.22°
NA
400(J)
NA
0.7(J)
3.4
NA
0.53C
0.53C
NA
20,000a
2,000d
8a
900e
NA
NA
NA
NA
Inorganics (mg/L)
Barium
Chromium
Iron
Manganese
0.14
0.49
5.4
0.18
0.10
0.49
1.5
0.002(B)
0.054
0.052
0.924
0.038
0.031
0.006(U)
0.183
0.012(3)
2.0a
O.la>b
NA
NA
Organics (mg/L)
Chloroform
0.053
0.031
NA
NA
NA
Anions (mg/L)
Ammonia as N
Fluoride
Nitrate as N
Sulfide
0.29
1.3
170
1
0.29
0.21
32
1
(U)
0.21
1.01
(U)
(U)
0.45
0.12
(U)
NA
4.0a
10a
NA
a 40 CFR 141 (Primary MCL). MCLs presented for comparison purposes.
Sample Value reported is for total chromium. MCL is for hexavalent chromium.
c Value reported is for total Uranium.
f~* a\r*\i\Qtc*r\ V*ac/ar1 <~»ti otrniiol ox/£»**arrA r»/~»fi/'»
-------
          Table 3.  Maximum Concentration Summary for Contaminants of
     Potential Concern in the 600 Area Between the 100-D/DR and 100-H Areas.
Groundwater
Contaminants
All
Groundwater
Wells
Near-River
Groundwater
Wells
600 Area
Springs
600 Area
Columbia
River
MCL
(pCi/L or
mg/L)
Radionuclides (pCi/L)
Tritium
11,000
NA
NA
NA
20,000a
Inorganics (mg/L)
Arsenic
Chromium
0.012
0.17
NA
NA
NA
NA
NA
NA
0.05a
O.la»b
a
b
NA
40 CFR 141 (Primary MCL). MCLs presented for comparison purposes.
Sample value reported is for total chromium. MCL is for hexavalent chromium.
Not Available
                                        20

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             Table 4.  Maximum Concentration Summary for Contaminants of
                             Potential Concern in the 100-K Area.

Groundwater
Contaminants
All
Groundwater
Wells
Near-River
Groundwater
Wells

KArea
Springs
KArea
Columbia
River
MCL
(pCi/L or
mg/L)
Radionuclides (pCi/L)
Tritium
Carbon- 14
Strontium-90
Technetium-99
Uranium-233/234
Uranium-235
Uranium-238
1,900,000
23,000
36
46
3.3
0.3
2.6
35,000
16,000
36
11(R)
2.3
0.2(J)
1.9
8,900
NA
8.8
5.2
NA
NA
l.lc
ND
NA
0.7(J)
2.0
NA
NA
0.5C
20,000a
2,000a
8a
900d
NA
NA
NA
Inorganics (mg/L)
Aluminum
Arsenic
Cadmium
Chromium
Iron
Lead
Manganese
Nickel
Silver
Vanadium
Zinc
0.844(J)
0.010
0.002
1.95
5.43(J)
0.008
0.070
0.019
0.007(B)
0.024(B)
0.461(B)
0.072(B)
0.007(B)
0.002(B)
0.261
1.23
0.006(J)
0.070
0.010
0.005(B)
0.019(B)
0.461(B)
0.225
NA
ND
0.069
0.243
NA
0.009(B)
ND
0.006(B)
0.011(3)
ND
ND
NA
ND
ND
0.171
NA
0.020
ND
ND
ND
0.006(B)
NA
0.05a
0.005a
o.ia-b
NA
0.015e
NA
NA
0.10a
NA
NA
Organics (mg/L)
Chloroform
Trichloroethene
0.017
0.019
0.017
0.019
NA
NA
NA
NA
NA
0.005a
Anions (mg/L)
Chloride
Nitrate/Nitrite
21.6
26
21.6
26
6.01
1.47(J)
0.86
0.5(J)
NA
10a
a 40 CFR 141 (Primary MCL). MCLs presented for comparison purposes.
Qa-miVlA 1/aliiA -re*r\f\irt£*r\ 10 •f!r»f f/~»fol r»Vi-tv»-rr»iTim
c    Value for total uranium reported.
     Calculated based on annual average concentration yielding 4 mrem/yr for 2 liter/day daily intake
     Interim Primary Drinking Water Regulations).
e    Action level per 40 CFR 141, Subpart I.
(B)   Concentration below the contract required detection limit but above the instrument detection limit.
(J)   Estimated value.
(R)   Rejected during data validation due to frequency of instrument calibration.
NA  Not Available or Not Applicable.
ND  Not detected.
Near-River wells were: 199-K-13, -K-18, -K-19, -K-20, -K-21,  -K-22, -K-31, -K-32A, -K-33, -K-34, -K-37.
                                                 21

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Table 5. Threatened and Endangered Species Potentially Found on the Hanford Site
Species
Notes
Endangered Vascular Plants
Persistentsepal yellowcress
(Rorippa columbiae)
Northern Wormwood
(Artemisia campertris ssp borealis var
workskioldii)
Known to have a scattered distribution because of specialized habitat
requirements or habitat loss; generally occurs in marshy places; known to
inhabit wet shoreline of Hanford Reach in Benton County.
Rare, local endemic species near the river; not known from Hanford but
reported just to the north near Beverly, Grant County.
Threatened Vascular Plants
Columbia milk-vetch
(Astragalus columbianus)
Dwarf Evening Primrose
(Camissonia (= Oenothera) pygmaea)
Hoover's desert parsley
(Lomatium tuberosum)
Locally endemic to area near Priest Rapids Dam; could potentially occur in
Northwest portion of Hanford along the Columbia River.
Has been found at Hanford on mechanically disturbed areas.
Locally endemic to south-central Washington, including Benton County;
known to inhabit rocky hillsides.
Endangered Birds
Aleutian Canada goose
(Branta canadensis leucopareia)
American white pelican
(Pelecanus erythrorhynchus)
Peregrine falcon
(Falco peregrinus)
Sandhill crane
(Grits canadensis)
Only incidental occurrence at Hanford.
Flocks have recently become common in the Columbia Basin during all
seasons foraging on fish, amphibians, and crustaceans, and roosting on
islands.
Breeds and winters in eastern Washington, inhabiting open marshes, river
shorelines, wide meadows, and farmlands; nests on undisturbed cliff faces; an
erratic visitor to Hanford.
Inhabits open prairies, grainfields, shallow lakes, marshes, and ponds;
common migrant during spring and fall in Washington; some known and
suspected nesting sites in eastern Washington; an occasional visitor at
Hanford.
Threatened Birds
Bald eagle
(Haliaeetus leucocephalus)
Ferruginous hawk
(Buteo regalis)
Regular winter visitor to the Columbia River, feeding on spawned-out salmon
and waterfowl; they roost in the 100 Areas and nest (unsuccessfully to date)
along the Hanford Reach.
Inhabits open prairies and sagebrush plains, usually with rocky outcrops or
scattered trees; known to nest in Benton and Franklin Counties, including
Hanford; rarely winter in Washington, but are known to occasionally forage
on small mammals, birds, and reptiles on sagebrush plains of Hanford.
Threatened Mammals
Pygmy rabbit
(Sylvilagus idahoensis)
Inhabits undisturbed areas of sagebrush with soils soft enough to permit
burrows; once known to exist at Hanford west of the 200 Areas plateau.
1 Indicates both state and federal designation.
                                    22

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Table 6.  Fish Species in the Hanford Reach of the Columbia River.
                         (Page 1 of 2)
Common Name
American Shad
Black bullhead
Black crappie
Bluegill
Bridgelip sucker
Brown bullhead
Burbot
Carp
Channel catfish
Chinook salmon
Chiselmouth
Coho salmon
Cutthroat trout
Dolly Varden
Lake whitefish
Largemouth bass
Largemouth sucker
Leopard dace
Longnose dace
Mottled sculpin
Mountain sucker
Mountain whitefish
Northern squawfish
Pacific lamprey
Peamouth
Scientific Name
Alosa sapidissima
Ictalurus melas
Pomoxis nigromaculatus
Lepomis macrochirus
Catostomus columbianus
Ictalurus nebulosus
Lota lota
Cyprinus carpio
Ictalurus punctatus
Oncorhynchus tshawytscha
Acrocheilus alutaceus
Oncorhynchus kisutch
Oncorhynchus clarki
Salvelinus malma
Coregonus clupeaformis
Micropterus salmoides
Catostomus macrocheilus
Rhinichthys falcatus
Rhinichthys cataractae
Cottus bairdi
Catostomus platyrhynchus
Prosopium williamsoni
Ptychocheilus oregonensis
Entosphenus tridentatus
Mylocheilus caurinus
                             23

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Table 6.  Fish Species in the Hanford Reach of the Columbia River.
                         (Page 2 of 2)
Common Name
Piute sculpin
Prickley sculpin
Pumpkinseed
Rainbow trout (steelhead)
Redside shiner
Reticulate sculpin
River lamprey
Sand roller
Smallmouth bass
Sockeye salmon
Speckled dace
Tench
Threespike stickleback
Torrent sculpin
Walleye
White crappie
White sturgeon
Yellow perch
Yellow bullhead
Scientific Name
Cottus beldingi
Cottus asper
Lepomis gibbosus
Oncorhynchus mykiss
Richardsonius balteatus
Cottus perplexus
Lampetra ayresi
Percopsis transmontana
Micropterus dolomieui
Oncorhynchus nerka
Rhinichthys osculus
Tinea tinea
Gasterosteus aculeatus
Cottus rotheus
Stizostedion vitreum vitreum
Pomoxis annularis
Acipenser transmontanus
Perca flavescens
Ictalurus natalis
                             24

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                           VI.  SUMMARY OF SITE RISKS

6.1  Qualitative Risk Assessment

A qualitative risk assessment was performed as part of the limited field investigation, and
determined the principal risk drivers at the 100-HR-3 Operable Unit and the 100-KR-4
Operable Unit. Another purpose of the qualitative risk assessment was to qualitatively
evaluate human health and environmental risks to help determine if the operable units were a
candidate for an interim remedial action.  The qualitative risk assessment evaluated risks for a
predefined set of human and environmental exposure scenarios.  If the estimated risks
exceeded certain thresholds, interim remedial actions were considered necessary to reduce the
risks posed by the contaminants. The qualitative risk assessment is not intended to replace or
be a substitute for the baseline risk assessment that will be conducted in association with
determining the final action for  these  operable units. The qualitative risk assessment used the
groundwater data from the first  four rounds of the limited field investigation sampling.  The
data were evaluated for consistency and compliance with EPA data management guidance.

6.1.1 Human Health  Risks
Human health risks were evaluated for the 100-HR-3 and 100-KR-4 Operable Units to
determine whether interim remedial actions were required.  The 100-HR-3 and 100-KR-4
Operable Unit Focused Feasibility Studies concluded that there were no current unacceptable
human health risks from contaminants in the groundwater, primarily because exposure to
groundwater contaminants is precluded by DOE  site controls. The interim action is expected
to provide adequate protection of human health via institutional controls, and the interim
remedial action itself will not  pose any unacceptable risks to human health.

6.1.2 Ecological Risks
Ecological risks were evaluated  based on the exposure of biological receptors that live in or
near the Columbia River to contaminants in surface water, as a result of contaminated
groundwater migrating into the river.   Plants and animals can also be exposed to contaminants
where groundwater surfaces in springs and seeps or where plant roots reach to contaminated
groundwater.  Most contaminants are also transferred through the food web.

For the purposes of the qualitative risk assessment, maximum concentrations of the
contaminants from near-river  well samples were  used to represent concentrations potentially
available to aquatic receptors at  the ground water-river water interface. To estimate ecological
risks, the total daily doses to animals  in aquatic and riparian habitats from radiological
contaminants were estimated using the CRITR2 computer code.  These doses were then
compared to the DOE benchmark of 1 rad/day (DOE Order 5400.5). For the inorganic and
organic contaminants, the maximum representative groundwater concentrations from four
rounds of limited  field investigation sampling were compared to EPA's acute and chronic
Ambient Water Quality Criteria (AWQC) for the protection of aquatic organisms.  (The EPA's
AWQC for hexavalent chromium are  numerically equal to the State of Washington's Ambient
Water Quality Standards used as an ARAR for this ROD.)  If groundwater concentrations
                                          25

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exceeded the 1 rad/day benchmark or the AWQC, an ecological risk was presumed to be
present.

6.1.2.1 100-HR-3
The ecological risk analyses for 100-HR-3 indicated that none of the ecological receptors
living in or near the Columbia River that were addressed in the qualitative risk assessment
(plant, fish , crustacean, plant-eating duck, fish-eating duck, heron) will receive a radiological
dose in excess of the 1  rad/day benchmark (table 7). The ecological risk assessment, however,
identified inorganic and organic contaminants that exceeded the risk threshold (table 8). These
included chromium, sulfide, and bis(2-ethylhexyl)phthalate in the 100-D/DR Area and
chromium, iron, and sulfide in the 100-H Area.  There are no near-river well data for the 600
Area so comparable analyses are not available (table 3), however extrapolation from
surrounding groundwater data does not indicate an ecological risk. Chromium is the most
toxic with respect to aquatic receptors, and is the contaminant that has been consistently
observed in groundwater in the 100-HR-3 Operable Unit.  Chromium (particularly the soluble
mobile hexavalent form of chromium) is the most toxic of these four contaminants with respect
to aquatic receptors, notably embryonic salmon. Most chromium in groundwater at the
Hanford Site is hexavalent chromium, because of the original sources and prevailing
geochemical conditions.

The sulfide concentration in most of the groundwater samples were at or below the 1 mg/L
level of detection.  One sample had a concentration of 26 mg/L, but was determined to be
inconsistent with the remaining samples and eliminated from the data set in the limited field
investigation. Of 107 samples analyzed for sulfides, 74 were qualified as nondetected.  The
remaining data were at or below the level of detection.  Therefore sulfides are not considered a
contaminant of concern.

Analysis of the data for bis(2-ethylhexyl)phthalate indicate that the erratic values  that were
occasionally obtained for this chemical result from laboratory contamination rather than a
contaminant condition in the aquifer.  This material, a plasticer, is a common artifact of the
sampling/analysis process and is not believed to be a Hanford contaminant.

For iron, only three of the samples collected  during 1993-1994 had concentrations above the
chronic AWQC of 1,000 Mg/L.  Each  sample was  taken from wells constructed with carbon
steel casings. After the first few rounds  of sampling from these wells, concentrations dropped
to several hundred Mg/L-  The several high concentrations of iron are believe to be an artifact
of well construction material.
                                          26

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          Table 7. Ecological Risk Summary for Radionuclide Contaminants of
                    Potential Concern in the 100-HR-3 Operable Unit.
Organism
Plant
Fish
Crustaceans
Plant-Eating Ducks
Fish-Eating Ducks
Heron
Total Dose to Aquatic and Riparian Receptors,
Using Data From Near-River Wells (rad/day)
100-D Area
0.002
0.00005
0.0001
0.01
0.0005
0.0003
100-H Area
0.03
0.002
0.003
0.06
0.008
0.005
Doses are calculated using the sum of all radionuclide concentrations for each area.
All doses are less than the DOE's risk benchmark of 1.0 rad/day.
                                            27

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Table 8.  Ecological Risk Summary for Nonradionuclide Contaminants of Potential
                   Concern in the 100-HR-3 Operable Unit.
                               (Page 1 of 2)

                                100-D Area
Analyte
Bis(2-ethylhexyl)
phthalate
Barium
Chromium (VI)
Nitrate as N
Manganese
Sulfide
Vanadium
Ammonia as N
Near River Wells
Maximum
Concentration
(unfiltered, jig/L)
3
91.7
443
14100
56
1000
19.6
260
AWQC
(unfiltered, /ig/L)
Acute


16
NA
NA

NA

Chronic


11
NA
NA

NA

Exceeds
Risk
Threshold
yesa

yes


yesa


                                    28

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    Table 8. Ecological Risk Summary for Nonradionuclide Contaminants of Potential
                         Concern in the 100-HR-3 Operable Unit.
                                       (Page 2 of 2)

                                        100-H Area
Analyte
Barium
Chromium (VI)
Flouride
Iron
Nitrate as N
Sulfide
Ammonia as N
Chloroform
Near River Wells
Maximum
Concentration
(unfiltered, in
Mg/L)
100
490
80
1500
32000
1000
29
31
AWQC
(unfiltered, jig/L)
Acute

16

1000



28900
Chronic

11





1240
Exceeds
Risk
Threshold

yes

yesa

yesa


       NA - No data available
       AWQC - Ambient Water Quality Criteria for Protection of Aquatic Life
(B)     Concentration below the contract required detection limit but above the instrument detection limit.
(J)     Estimated value.
a      Appears to be an artifact of well construction, sampling, or analysis.
Contaminants of potential concern are contaminants that were detected at concentrations above sitewide background.

6.1.2.2  100-KR-4
The ecological risk analyses for 100-KR-4 indicated that one of the ecological receptors (Table
9, fish-eating ducks) living in or near the Columbia River that were addressed in the
qualitative risk assessment will receive a radiological dose in excess of the 1 rad/day
benchmark (DOE Order 5400.5). The dose was primarily due to carbon-14.  Carbon-14
appears in three 100-K Area wells at elevated concentrations.  None of these wells are located
within the chromium plume that is the target of the interim action.  The source of the elevated
carbon-14 appears to be the french drains  that received condensate from the inert gas used in
100-K West and 100-K East reactor operations.  These contaminant sources will be addressed
in the ROD for the 100-KR-2 Operable Unit. The ecological assessment also identified
                                            29

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inorganic contaminants that exceeded the AWQC (Table 10).  These included cadmium,
chromium, iron, lead, silver and zinc.

Only two samples from one well, 199-K-18, had cadmium concentrations greater than the
concentrations associated with the lowest observed effect levels reported in the literature.
Several of the samples exceeded EPA1 s AWQC. These data are believed to be artifacts of the
well construction.

One of 25 samples collected from near-river wells during the March 1993 to January 1994
period exceeded EPA's AWQC for iron of 1000 ^g/L.  The rest of the detectable
concentrations were well below this level with many nondetects.

Lead concentrations were all below 5.9 Mg/L and appear to represent a background level more
than a contaminant plume.  Fifteen out of a total 20 samples were below the detection limit.
The five detectable concentrations ranged  from 3.1 to 5.9 //g/L.

Only one out of 26 samples had  a detectable concentration of silver during the January 1993
through January 1994 period.

Zinc is present at a level exceeding the EPA AWQC of 110 //g/L in well 199-K-22 (figure 5).
This well is located within the chromium plume that is the target of this interim action.
Elevated concentration of zinc in this well are believed to result from a galvanized screen (zinc
plated) that was installed in this well, and  thus is not representative of a zinc plume.

6.1.3  Risk Summary for 100-HR-3 / 100-KR-4
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in this ROD, may present an imminent and
substantial endangerment to public health, welfare, or the environment.  Groundwater
contaminated with chromium is identified  in the three reactor areas at concentrations in excess
of ecological-based risk thresholds. This ground water discharges to the Columbia River
primarily via upwelling through  the river bottom, an environment known to be critical to
sensitive ecological receptors such as embryonic salmon.  In addition, concentrations of
several contaminants exist in groundwater at these operable units that exceed human health
levels.
                                          30

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    Table 9. Ecological Risk Summary for Radiological Contaminants of Potential
                       Concern in the 100-KR-4 Operable Unit.
Receptor
Plant
Fish
Crustacean
Plant-eating Duck
Fish-eating Duck
Heron
Estimated Total Dose
(rad/day)
0.19
0.37
0.37
0.33
l.la
0.70
Major Contributor
Carbon- 14
Carbon- 14
Carbon- 14
Carbon- 14
Carbon- 14
Carbon- 14
Estimated total dose exceeds DOE benchmark of 1 rad/day
                                        31

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                  Table 10.  Ecological Risk Summary for Nonradionuclide
            Contaminants of Potential Concern in the 100-KR-4 Operable Unit.
Analyte
Aluminum
Cadmium
Chloride (mg/L)
Chromium (VI)
Iron
Lead
Manganese
Nickel
Nitrate/Nitrite (mg/L)
Silver
Vanadium
Zinc
Trichloroethene
Chloroform
Near River Wells
Maximum
Concentration
(unfiltered, in
/ig/L)
72.1(B)
2.2(B)
21.6
261
1230
5.8(J)
69.6
9.9
26
5.2(B)
19.1(B)
461(B)
19
17
AWQC
(unfiltered, /ig/L)
Acute

3.9
860
16
1000
82

1400

4.1

120a
45000
28900
Chronic

1.1
230
11

3.2

160

0.12

110a
21900
1240
Exceeds
Risk
Threshold

yesb

yes
yesb
yesb



yesb

yes


a       Actual value is hardness dependent. Approximate value using typical Columbia River hardness of 100 mg/1
        hardness is provided for comparison purposes.
        Appears to be an artifact of well construction, sampling, or analysis.
NA     No data available
AWQC  Ambient Water Quality Criteria for Protection of Aquatic  Life
(B)      Concentration below the contract required detection limit but above the instrument detection limit.
(J)      Estimated value.
Contaminants of potential concern are contaminants that were detected at concentrations above site wide background.
                                                32

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                      VII.  REMEDIAL ACTION OBJECTIVES

Remedial action objectives to protect human health and the environment include the following
3 components:

*      Protection of aquatic receptors in the river bottom substrate from contaminants in
       groundwater entering the Columbia River.
*      Protection of human health by preventing exposure to contaminants in the groundwater.
*      Provide information that will lead to the final remedy.

These three components are detailed below.

PROTECTION OF AQUATIC RECEPTORS

The first remedial action objective for the 100-HR-3 and 100-KR-4 Operable Units is to
prevent the discharge of hexavalent chromium to the Columbia River substrate at
concentrations exceeding those that are considered protective of aquatic life in the River and
riverbed sediments.  Prioritization of areas to be addressed by the remedial action will be
based on suitable salmon habitat.  The aquatic receptor exposure point of concern is within the
river substrate at depths up to  18 inches (46 centimeters), where embryonic salmon and fry
could be present during parts of the year. The relevant standard is the State of Washington's
chronic Ambient Water Quality Standard for Protection of Freshwater Aquatic Life for
hexavalent chromium of 11 parts per billion (WAC 173-201A-040). Monitoring will be
performed to assess the effectiveness of the remedial action in meeting the Ambient Water
Quality Standard. Remedial actions should improve water quality in the aquifer by removing
contaminants, reducing mobility or toxicity.

Protection of Human Health From Exposure to Groundwater

A second remedial action objective for these operable units is to continue to protect the public
such that there is no exposure  to contaminants above health based levels. This objective can
be achieved by preventing exposure to contaminated groundwater or reduction of contaminants
to health based levels as a result of actions taken to protect ecological receptors.

Provide Information That Will Lead to the Final Remedy

Additional information will be obtained during the interim action prior to the development and
implementation of a final action.  Effectiveness of the interim action will be evaluated based
on site-specific data.  This evaluation should include:  treatment cost, efficiency, evaluation of
other technologies, hydraulic impacts, and effectiveness of contaminant removal from the
aquifer.
                                          33

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                      Vm.  DESCRIPTION OF ALTERNATIVES

The 100 Area Feasibility Study, Phases 1 and 2 provided a list of six generic groundwater
alternatives that could be applied to the groundwater operable units in the 100 Areas.  Of the
six alternatives, only five were applicable to groundwater remediation at the 100-HR-3 and
100-KR-4 Operable Units:

•      Alternative 1: No Action

•      Alternative 2: Institutional Control/Continued Current Actions

•      Alternative 3: Containment

•      Alternative 4: Removal/Reverse Osmosis Treatment/Disposal

•      Alternative 5: Removal/Ion Exchange Treatment/ Disposal.

The treatment of groundwater contaminants in situ was evaluated and dropped from the 100
Area Feasibility Study,  Phases 1 and 2? as an appropriate alternative for the 100-HR-3 and
100-KR-4 Operable Units because insufficient information was available on in situ treatment
methods.  However, more recently DOE has conducted tests of reduction/oxidation in situ
treatment technology and will consider this technology for implementation of future remedial
actions at the 100-HR-3 and 100-KR-4 Operable Units.

8.1 Common Elements.

All five alternatives, except the no action alternative, evaluated for the 100-HR-3 and
100-KR-4 Operable Units include controls to prevent human access to groundwater and to
require that groundwater concentrations will be tested.  In addition to continued access
restrictions, the present network of groundwater monitoring wells will be maintained, and
samples will be collected to monitor chromium concentrations in groundwater. Monitoring
will also aid in determining when these controls are no longer necessary.  To provide a
common basis for comparative purposes, costs, as shown below for each alternative were
developed for the first 5-year period.  A 5  percent annual discount rate was applied to calculate
present worth.  This 5-year cost-planning period is not a basis for cessation of the pump-and-
treat action at the end of that period. As required by CERCLA, this remedy will be reviewed
at least as often as every 5 years.

8.2 Remedial Alternatives Evaluated

Alternative 1:  No Action - Evaluation of this alternative is required by CERCLA to compare
the no action alternative with the different  action alternatives, and to consider taking no action
if appropriate.  Under the no action alternative, no CERCLA groundwater monitoring would
be required.  Although  the  DOE would retain control of the site throughout the interim period,


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no institutional controls would be implemented specifically for the no action alternative.
Additional monitoring and restrictions would not be implemented, and contamination in the
groundwater would flush into the Columbia River.

  100-HR-3    Capitol Cost:                                         $0
              Operation and Maintenance Cost (5-year period):         $0
              Present Worth (5-year period):                         $0
              Estimated Time to Implement:        ,                 0 Months
  100-KR-4    Capitol Cost:                                         $0
              Operation and Maintenance Cost (5-year period):         $0
              Present Worth (5-year period):                         $0
              Estimated Time to Implement:                         0 Months

Alternative 2:  Institutional Controls/Continued Current Actions - This alternative involves
commitment to continued groundwater monitoring and institutional controls. Institutional
controls would include, but may not be limited to, access and land-use restrictions, and site
security. Groundwater monitoring would be used to continually evaluate the effectiveness of
this interim action, and to support decisions to continue the action or implement other interim
remedial actions (including the no action alternative). This alternative would also utilize the
data from ongoing studies to evaluate this interim action, complete the groundwater conceptual
model, and generate additional technology performance data.

100-HR-3     Capital Cost:                                         $0
              Operation and Maintenance Cost (5-year period):         $1,200,000
              Present Worth (5-year period):                         $ 1,000,000
              Estimated Time to Implement:                         0 Months
100-KR-4     Capital Cost:                                         $0
              Operation and Maintenance Cost (5-year period):          $600,000
              Present Worth (5-year period):                          $500,000
              Estimated Time to Implement:                         0 Months

Alternative 3:  Containment - For this alternative, cutoff walls would be installed next to the
Columbia River to isolate the existing groundwater chromium plume.  A cutoff wall is a
subsurface vertical barrier designed to prevent the migration of contaminants, divert
uncontaminated groundwater around contaminant plumes, or completely surround contaminant
plumes.  A network of extraction and injection wells, termed hydraulic control, would be
installed to intercept and control the contaminated groundwater plume and enhance the
effectiveness of the cutoff wall.  The objective of the containment alternative would be to
eliminate receptor pathways by preventing migration of contaminated groundwater to
environmental receptors, such as those in the Columbia River.

100-HR-3     Capital Cost:                                         $12,200,000
              Operation and Maintenance Cost (5-year period):         $15,300,000
              Present Worth (5-year period):                         $25,400,000
              Estimated Time to Implement:                         15 Months


                                          35

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100-KR-4    Capital Cost:                                         $32,200,000
             Operation and Maintenance Cost (5-year period):         $32,200,000
             Present Worth (5-year period):                         $60,100,000
             Estimated Time to Implement:                         15 Months

Alternative 4: Removal/Reverse Osmosis Treatment/ Disposal - Groundwater would be
removed through a series of extraction wells placed within the groundwater plume.  Reverse
osmosis would be used to remove hexavalent chromium to the maximum extent practicable to
speed the remedy, and in no event shall the effluent concentration exceed 50 Mg/L.  Reverse
osmosis uses a membrane that  allows water to pass, but will not pass chromium and most co-
contaminants.  Contaminants removed from the groundwater would be treated as needed to
meet requirements for transportation to and disposal in  an appropriate on-site facility such as
the Environmental Restoration Disposal Facility. Treated groundwater would be reinjected to
the aquifer. The objectives of this option would be to prevent migration of groundwater
containing chromium above  the AWQC into the Columbia River, to prevent  migration outside
the operable unit, and to minimize source-to-receptor pathways by removal, treatment, and
disposal of groundwater contaminants. Costs below are based on treating 8.6 x 10  gallons at
100-HR-3 and 5.8 x 108 gallons at 100-KR-4.

100-HR-3    Capital Cost:                                         $7,400,000
             Operation and Maintenance Cost (5-year period):         $24,600,000
             Present Worth (5-year period):                         $28,800,000
             Estimated Time to Implement:                         15 Months
100-KR-4    Capital Cost:                                         $4,700,000
             Operation and Maintenance Cost (5-year period):         $13,800,000
             Present Worth (5-year period):                         $16,700,000
             Estimated Time to Implement:                         15 Months

Alternative 5: Removal/Ion Exchange Treatment/ Disposal - Groundwater will be removed
through a series of extraction wells placed within the groundwater plume.  Hexavalent
chromium will be removed by  ion exchange treatment to the maximum extent practicable to
speed the remedy, and in no event shall the effluent concentration exceed 50 ///L.  The ion
exchange media, when exhausted, would be replaced with new media. Exhausted media will
be disposed at the Environmental Restoration Disposal Facility in the Hanford 200 Area.  The
objectives of this alternative are the same as for Alternative 4.

100-HR-3    Capital Cost:                                         $6,600,000
             Operation and Maintenance Cost (5-year period):         $13,700,000
             Present Worth (5-year period):                         $18,600,000
             Estimated Time to Implement:                         15 Months
100-KR-4    Capital Cost:                                         $4,200,000
             Operation and Maintenance Cost (5-year period):         $8,100,000
             Present Worth (5-year period):                         $ 11,200,000
             Estimated Time to Implement:                         15 Months
                                         36

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       IX.  SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES

9.1 CERCLA Nine Criteria

This section summarizes the relative performance of each of the alternatives with respect to the
nine criteria identified in the NCP. These criteria fall into three categories: The first two
(Overall Protection of Human Health and the Environment and Compliance with ARARs) are
considered threshold criteria and must be met. The next five are considered balancing criteria
and are used to compare technical and cost aspects of alternatives.  The final two criteria (State
and Community Acceptance) are considered modifying criteria. Modifications to remedial
actions may be made based upon state and local comments and concerns.  These were
evaluated after all public comments were received.

A description of the nine evaluation criteria contained in the NCP, and a brief analysis of each
alternative against the criteria is presented in the box below.  The five alternatives are
evaluated against these criteria to select the remedy.  Only criteria pertinent to the selection of
an interim action have been addressed in detail.
                                         37

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               EXPLANATION OF CERCLA EVALUATION CRITERIA

Threshold Criteria:

1.     Overall Protection of Human Health and the Environment - How well does the
       alternative protect human health and the environment, both during and after
       construction?

2.     Compliance with Applicable or Relevant and Appropriate Requirements - Does the
       alternative meet all federal and state applicable or relevant and appropriate
       requirements (ARARs)?

Balancing Criteria:

3.     Long-Term Effectiveness and Permanence - How well does the alternative protect
       human health and the environment after completion of cleanup?  What, if any,
       risks will remain at the site?

4.     Reduction ofToxicity, Mobility, or Volume Through Treatment - Does the
       alternative effectively treat the contamination to significantly reduce the toxicity,
       mobility, and volume of the hazardous substances?

5.     Short-Term Effectiveness - Are there potential adverse effects to either human
       health or the environment during construction or implementation of the
       alternative. How quickly does the alternative reach the cleanup goals?

6.     Implementability - Is the alternative both technically and administratively feasible?
       Has the technology been used successfully on other similar sites?

7.     Cost - What are the estimated costs of the alternative?

Modifying Criteria:

8.     State Acceptance - What are the state's comments or concerns  about the
       alternatives considered and about EPA's preferred alternative? Does the state
       support or oppose the preferred alternative?

9.     Community Acceptance - What are the community's comments  or concerns about
       the preferred alternative? Does the community generally support or oppose the
       preferred alternative?
                                        38

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9.1.1 Overall Protection of Human Health and the Environment - All remedial
alternatives except the No Action Alternative would protect human health because institutional
controls limit direct exposure to groundwater.  Alternative 3 (Containment), 4 (Reverse
Osmosis), and 5 (Ion Exchange) would provide the best protection of the environment by
reducing chromium  concentrations and exposure of ecological receptors to chromium.

9.1.2 Compliance  with Applicable or Relevant and Appropriate Requirements - The
ARARs identified for the five alternatives include the State of Washington's Chronic Ambient
Water Quality Standard for Protection  of Freshwater Aquatic Life for hexavalent chromium
(WAC 173-201A-040); state Underground Injection Standards (WAC 173-218) for chromium,
for the injection of treated groundwater; and state dangerous waste management standards
(WAC 173-303) for management and disposal  of those treatment resins determined to be
dangerous wastes.

Alternative 1 (No Action) would not invoke ARARs that would need to be satisfied.
Alternative 1 (No Action) and Alternative 2 (Institutional Controls/Continued Current Actions)
will not meet the water quality standards in the Columbia River, as these alternatives would
allow hexavalent chromium to continue to exist in the river at levels above the ambient water
quality standards.

Alternatives 3 (Containment), 4 (Reverse Osmosis), and 5 (Ion Exchange) would be designed
with the intent of achieving ambient water quality standards for hexavalent chromium in the
river substrate either by retarding (alternative 3)  the flow of groundwater or by removing
(alternatives 4 and 5) hexavalent chromium in groundwater before it discharges to the river.

The interim remedial action selected, is protective of human  health and the environment, and
complies with Federal and State applicable or relevant and appropriate requirements directly
associated with  this  action (by preventing human exposure to contaminated groundwater, and
preventing chromium exceedances of the AWQC in the Columbia River substrate).  Ambient
water quality standards, and state injection standards for contaminants other  than chromium
may not be met. Specifically, discharge of strontium-90, tritium, and nitrate are anticipated  to
be above standards.  The  interim remedial action addresses chromium and is part of a final
remedial action  that will satisfy ARAR requirements when completed.

9.1.3 Long-Term Effectiveness and Permanence - The ion exchange treatment alternative
will be the most effective and permanent in reducing long-term risk, including risk of exposure
to ecological receptors, and the system could be expanded.  The reverse osmosis treatment
alternative would be more difficult to expand should increased groundwater recovery rates be
required.  The containment alternative  would provide protection  of the river by limiting the
migration of contaminants into the river, but there would  be no reduction in  the mass of
contaminants in the  aquifer, except by  natural processes.  Under the containment alternative,
contaminants would eventually migrate past a barrier wall and into the river.  Alternatives 1
(No Action) and 2 (Institutional Controls/  Continued Current Actions) do not provide
significant long-term effectiveness.
                                          39

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9.1.4 Reduction of Toxicity, Mobility, or Volume Through Treatment - Through
treatment, the ion exchange and reverse osmosis treatment alternatives would provide the most
reduction in toxicity, mobility, and volume of chromium in the groundwater. The remaining
alternatives contain no treatment.

9.1.5 Short-Term Effectiveness - Of the  three alternatives judged most likely to meet the
remedial action goal (Alternatives 3,4, and 5), short-term effectiveness is met by reducing
chromium exposure to ecological receptors. Alternative 3 (Containment) would causes the
most short-term impacts to the riparian and terrestrial habitat and their inhabitants, as well as
to cultural resources. Alternatives 4 and 5 (Reverse Osmosis and Ion Exchange) would cause
lesser short-term impacts.  These impacts would be mitigated, to the extent practicable, during
construction. The Alternatives 1 (No Action) and 2 (Institutional Controls/Continued Current
Actions) will not be effective in the short term. Alternative 4 (Reverse Osmosis) generates the
greatest amount of sludge and thus the greatest sludge-disposal impact.  Alternative 5 (Ion
Exchange) generates less sludge volume whereas Alternatives 1,2, and 3 generate no sludge
and hence have no secondary disposal impacts.

9.1.6 Implementability - Alternative 2 (Institutional Controls/Continued Current Actions)
would require administrative actions to implement restrictions and current monitoring.  The
technology for Alternative 5 (Ion Exchange) is well established and easily implemented.
Alternative 4 (Reverse Osmosis) is somewhat more difficult to implement due to maintenance
necessary to keep the membrane system functioning and the large capacity treatment system
needed for the secondary waste slurry. Alternative 3 (Containment) using vertical barrier
technology is difficult to implement because of geologic conditions such  as large boulders.
The hydraulic barrier technology is relatively easy to implement.

Implementation of any of the remedial alternatives would require close coordination with state
and federal resource agencies, Native American Tribes, and Natural Resource Trustees to
avoid or minimize further impacts to ecological receptors while conducting remedial activities.

9.1.7 Cost - Of the three alternatives judged most likely to meet the interim remedial action
goal (Alternatives 3, 4, and 5), the lowest present worth costs are for Alternative 5 (Ion
Exchange): $29,800,000, and Alternative 4 (Reverse Osmosis): $45,500,000. The highest
present worth cost is for the Alternative 3 (Containment): $85,500,000.  Alternatives 1 (No
Action)  and 2 (Institutional Controls/Continued Current Actions) would not require capital
investment.  The capital, operation and maintenance, and present worth costs of each
alternative are presented in the alternative descriptions above.  Costs presented are
preliminary, and are presented for comparison purposes only.  A definitive cost estimate for
the selected remedy will be prepared as part of remedial design.

9.1.8 State Acceptance - The State of Washington concurs with the selected alternative.

9.1.9 Community Acceptance - Appendix A of this ROD is a responsiveness summary to
comments received during the 45 day public comment.  Written comments supported taking a
cleanup  action at these operable units.  Generally  the comments received during the public


                                          40

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meeting in Hood River (see Section III), although general in nature, were supportive of
pump-and-treat actions to prevent the spread of groundwater contamination and to protect the
Columbia River.

9.2 EVALUATION OF POTENTIAL ENVIRONMENTAL IMPACTS

The environmental consequences of implementing the remedial alternatives, including potential
short-term direct and indirect impacts, have been evaluated in Section 6.0, Detailed Analysis
of Alternatives, in 10Q-HR-3 Operable Unit Focused Feasibility Study and 100-KR-4 Operable
Unit Focused Feasibility Study.  Impacts are expected to be limited to potential exposure of
remediation workers to hazardous or radioactive substances, short-term indirect impact to
wildlife from construction noise, and disturbance of the land area designated for wells,
equipment, and facilities.  Removal of groundwater contamination  is expected to improve
rather than degrade ecological conditions in the river. The cumulative impact of implementing
reasonable foreseeable remedial actions in 100 Area operable units  is expected to generally
improve ecological conditions in the 100 Areas in the long term.

Ecological review of the operable units indicates that the sites to be impacted by the interim
remedial action are located within areas previously disturbed by pre-Hanford Site agricultural
activities and by previous reactor operations at the Hanford Site.  Because of the  previous
disturbance, ecological or cultural resources are not expected to be significantly impacted by
the interim remedial action.  However, Cultural and Natural Resource Reviews will be
conducted before siting each well, pipeline, or treatment facility to determine the potential
impacts associated with specific actions. Mitigation measures will  include actions to minimize
dust, use of protective equipment to minimize worker exposures, seasonal scheduling of site
work to minimize disturbance to wildlife, archeological monitoring and/or data recovery, as
appropriate, and revegetation of the site following interim action.
                                          41

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                              X. SELECTED REMEDY

The selected remedy shall satisfy ARARs and meet the remedial action objectives set forth in
Section VII and includes the following:

•     Groundwater Extraction
      Groundwater will be extracted from wells primarily located along the river in each of
      the three reactor areas. Extraction wells should be located at a sufficient distance
      inland from the river to minimize withdrawal of river water.  Extraction wells shall be
      located such that the plume is captured to meet the remedial action objectives. Based
      on preliminary modeling accomplished for the operable unit focused feasibility studies,
      the following extraction well design was estimated as sufficient to capture the
      chromium plume to meet the chromium remedial action objectives:

             100-K Area: Eleven extraction wells spaced approximately 240 m (786 ft) apart
             with a composite withdrawal rate of 220 gpm.
             100-H Area: Nine extraction wells spaced approximately 160 m (515 ft) apart
             with a composite withdrawal rate of 225 gpm.
             100-D Area: Ten extraction wells spaced approximately 160 m (515 ft) apart
             with a composite withdrawal rate of 100 gpm.

      During remedial design, estimates will be improved based on the incorporation of the
      results of ongoing river pore water sampling and  shoreline drive point sampling, recent
      groundwater sampling data, and other pertinent data collected since the completion of
      the focused  feasibility study.  The groundwater extraction system shall be designed in
      accordance with the Remedial Design Report/Remedial Action Work Plan
      (RDR/RAWP) as approved by EPA and Ecology.

•     Groundwater Treatment and Discharge Standards - Hexavalent Chromium
      10Q-Dr lQO-Hr and 100-K Areas:  The groundwater treatment systems will reduce the
      effluent chromium concentrations to the maximum extent practicable.  However,
      groundwater above 50 Mg/L chromium will not be discharged. The average chromium
      concentrations in the effluent are expected to be below this standard.  This will be
      performed using ion exchange resins such as a weak base anionic resin with a high
      selectivity toward chromate anions (hexavalent chromium).

•     Groundwater Treatment - Other Contaminants
      Because this interim action is designed to reduce levels of hexavalent chromium in the
      groundwater and the river substrate, there is a potential for other groundwater co-
      contaminants to be present in the reinjected effluent at concentrations above the
      drinking water standards set for those contaminants. Potential co-contaminants include
      nitrate, strontium-90, tritium, uranium, and technicium-99.  The ion exchange system
      required to remove chromium will also reduce concentrations of other anionic
      contaminants such as nitrate, technicium-99, and  uranium-238.  Strontium-90 exists in
      groundwater as a cation and is not expected to be removed in the ion exchange system.


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Tritium is also not expected to be removed by the treatment system. In addition to
chromium at both operable units, other potential co-contaminants include:

       100-HR-3: nitrate, strontium-90, tritium, uranium, and technetium-99.
       100-KR-4: tritium and strontium-90.

These other co-contaminants do not exceed the ecological risk criteria, and institutional
controls (detailed elsewhere) limit human exposure.

Ground water Reinfection
After treatment,  water will be reinjected into the upper aquifer, using injection wells
located upgradient of the existing chromium plume in the 100-HR-3 and 100-KR-4
Operable Units respectively. Based on preliminary modeling accomplished for the
operable unit Focused Feasibility Studies, the number of wells needed to accomplish
this was estimated to be:

       1QQ-D Area: Five injection wells.
       10Q-H Area: Three injection wells.
       1QO-K Area: Two injection wells.

During the remedial design process, more precise estimates are expected to be
developed based on the collection and incorporation of well and site-specific data. The
ground water treatment and reinjection system shall be designed in accordance with the
RDR/RAWP as approved by EPA and Ecology.

Compliance Monitoring - River Protection
The data analysis and evaluation procedures used to evaluate compliance with cleanup
levels shall be defined in a compliance monitoring plan as part of the RDR/RAWP and
prepared in accordance with WAC 173-340-720(8) and/or as approved by EPA and
Ecology.

The aquatic receptor exposure point of concern is within the river substrate at depths up
to 18 inches (46  centimeters), where embryonic salmon and fry could be present during
parts of the year. Since it is impractical to routinely monitor the  river substrate,
groundwater will be monitored at near-river on-shore locations above the common high
river mark.  Monitoring shall be conducted at sufficient locations to evaluate the
performance of the remedial action.  The siting and design of the compliance
monitoring system shall be in accordance with the RDR/RAWP as approved by EPA
and Ecology. To account for dilution within the aquifer between  the monitoring
location on-shore and the aquatic receptor exposure point of concern within the river
substrate, a preliminary dilution factor of 1:1 has been selected based  on the available
data (i.e.,  22 Mg/L hexavalent chromium in on-shore near-river well points is
considered equivalent to 11 Mg/L hexavalent chromium in the  river substrate).  It will
take a period of time for the extraction system to have an effect on groundwater quality
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adjacent to the Columbia River.  Concentrations in excess of 22 Mg/L may be observed
in the compliance wells during the early stages of operation.

Groundwater sampling will be conducted when dilution by river water at the
compliance monitoring points is minimal. The details of the ground water quality
monitoring program will be described in the RDR/RAWP. Chromium compliance
monitoring will be conducted at multiple depth intervals.   Baseline sampling will be
conducted prior to the start of the interim action.

Sampling will be conducted monthly for at least three months following start-up of the
extraction system. Subsequently, there may be substantial reductions in frequency,
number of stations, and depths sampled, if demonstrated  to be appropriate, and
approved by EPA and Ecology.  A network of piezometers (or comparable technique)
will be installed and monitored such that the capture zone around the extraction wells
can be estimated.

In the event of special conditions such as an unusual flood event or prolonged down-
time of the pump-and-treat system, extra monitoring, at the direction of EPA or
Ecology shall be conducted.

The analyte list will be defined during remedial design; it shall include:

      Hexavalent chromium (or total chromium assumed to be hexavalent). The
      method detection limit and  quantitation limit of the selected test method shall be
      sufficiently low to allow comparison with the remedial action goals.
      Conductivity or comparable measurements  adequate to indicate ratio of
      river-derived versus groundwater-derived water.
      On an infrequent basis, likely co-contaminants will be monitored as part of
      on-going Tri-Party Agreement activities to  assess  protectiveness of human
      health and the environment.

Compliance monitoring will include analysis of results in a timely manner to support
modifications to the treatment system in order to meet the remedial action objectives.
Significant system modifications as identified in the RDR/RAWP are subject to EPA
and Ecology approval.

Compliance Monitoring  - Effluent for Reinjection
The data analysis and evaluation procedures used to evaluate compliance with cleanup
levels shall be defined in the RDR/RAWP and prepared using with WAC
173-340-720(8) and approved by EPA and Ecology.

Construction Requirements
Construction requirements shall be scoped as part of the RDR/RAWP with guidance
provided by and as approved by EPA and Ecology. This Work Plan shall include at
least the following elements:
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       Construction is expected to comply with appropriate worker safety
       requirements.
       In coordination with wildlife and other resource management agencies, activities
       should avoid or minimize disruption to local wildlife and other natural resources
       to the extent practicable.
       Design should provide for flexibility following  startup to accommodate changes
       in plume characteristics, or different understandings of actual or perceived
       responses of the aquifer/plume to the pump-and-treat system. When the actual
       response of the aquifer is known, the pump and treat systems may be altered as
       needed,  and approved by EPA and Ecology to meet the remedial action
       objectives.
       For areas that are disturbed during construction and operation,  it is expected
       that the land will be revegetated following construction in those areas that are
       not needed for operation and maintenance of the treatment system and where the
       land is also not expected to be re-disturbed within the next few years by other
       site activities.  Following completion of the interim action,  it is expected that
       rectification of the habitat affected by this activity will be conducted and
       coordinated with activities in the source operable units (100-DR-l, 100-DR-2,
       100-HR-l,  100-HR-2, 100-KR-l, and 100-KR-2).
       To the extent practicable, facilities are expected to be designed and located in a
       manner that minimizes interference with and interference by remedial actions
       for the source waste sites.
       Sites with cultural resource significance should  be avoided during remedial
       activities if avoidance is possible.  Where avoidance is not possible, a data
       recovery/mitigation plan must be prepared in consultation with the affected
       resource trustee and carried out for each site impacted by remedial activities.

Schedule
Draft A of the RDR/RAWP is due to EPA and Ecology 120 calendar days after the
ROD is signed.

Phase 1: Two pump-and-treat systems designed in accordance with this ROD in two of
the three reactor areas are to be operating as per the RDR/RAWP within  15 months of
this ROD. Operating is defined as continuous removal  and treatment of water at rates
defined in the RDR/RAWP. Some limited testing needed to optimize  the system is
expected.
Phase 2: The third pump-and-treat system in the third reactor area shall be operating as
per the RDR/RAWP within 18 months of this ROD.

The RDR/RAWP will establish a schedule including  Tri-Party Agreement milestones
for this interim remedial action.  This Work Plan including the schedule is subject to
EPA and Ecology approval.

Resin Disposal
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Waste generated during the remedial action, principally exhausted resins, will be
disposed of at the Environmental Restoration Disposal Facility (ERDF) or at other
on-site facilities as appropriate.  Resins will be stabilized prior to disposal such that:

       The Chromium concentration in leachate generated using the Toxicity
       Characteristic Leachate Procedure (TCLP) is less than 5.0 mg/1
       ERDF waste acceptance criteria are met for disposal at ERDF.

In the event that some materials cannot be disposed to ERDF or other on-site facilities,
and require disposal at an off-site facility, such a facility must be in compliance with
EPA's Offsite Rule (40 CFR 300.440) concerning off-site disposal of wastes.  If during
the design or conduct of the remedial action it is determined that regeneration of resins
is appropriate, that option may be implemented with any waste disposed as described
for resins in this paragraph.

Human Access Institutional Controls
Institutional controls are required to prevent human exposure to groundwater.  The
DOE is responsible for establishing and maintaining land use and access restrictions
until MCLs and risk-based criteria are met or the final remedy is selected. Institutional
controls include placing written notification of  the remedial action in the facility land
use master plan. The DOE will prohibit any activities that would interfere with the
remedial activity without EPA  and Ecology concurrence.  In addition, measures
necessary to ensure the continuation of these  restrictions will be taken in the event of
any transfer or lease of the property before a final remedy is selected. A copy of the
notification will be given to any prospective purchaser/transferee before any transfer or
lease.  The DOE will provide EPA and Ecology with written verification that these
restrictions have been put in place.

Up-time requirements
Operating pump-and-treat systems as described in this ROD and the subsequent
RDR/RAWP will achieve substantial treatment for this interim action. The extraction
and treatment system shall be designed to run on  an essentially continuous basis such
that routine procedures such as resin changes and mechanical maintenance can be
conducted with  minimal impact to system operations.

The system should be winterized such that winter weather or preparation for winter
weather does not cause extended shut-down of the system and compromise the remedial
action objectives. The system  shall be designed such that if one or several of the wells
are down (such  as due to a mechanical problem, or a well pump needs to be replaced),
the rest of the system can continue operating. In the event of a partial or total  system
shutdown EPA  or Ecology may impose additional near-river compliance sampling
requirements. EPA and Ecology may also authorize short-term intentional shutdowns
for the purposes of observing aquifer response or for other purposes as deemed
appropriate.  The provisions of this paragraph do not apply at the conclusion of the
interim action.
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Investigation-Derived Waste
Remedial investigation at 100-HR-3 and 100-KR-4 generated investigation-derived
waste consisting of soil and slurries from monitoring well installation, and purge water
generated during development and monitoring of the wells.  This waste is stored in the
respective reactor areas in drums.  Soil will be disposed to ERDF, as will slurries
following dewatering in accordance with ERDF  waste acceptance criteria. Water may
be processed via the ion exchange treatment system installed for groundwater under this
ROD.

Impacts to RCRA Monitoring
Two RCRA treatment, storage, and disposal (TSD) units, 100-D Pond and the 183-H
Solar Evaporation Basins, are located within the boundaries of the 100 HR-3 Operable
Unit. The  183-H basins are anticipated to be remediated and closed under RCRA, and
the 100-D Pond is currently an inactive unit. The implementation of the remedial
actions under this Interim Action ROD are believed likely to impact the current RCRA
groundwater sampling program around both of these facilities.  For any RCRA unit
whose monitoring compliance program is impacted,  Ecology may approve
modifications to the monitoring program as appropriate.  Potential alternative
compliance actions include monitoring  other existing wells (including remediation
wells) for appropriate RCRA constituents during the period when the groundwater is
affected by the remedial action.

Operational Requirements
The pump and treat portion of the interim remedial action will continue until the
selection of a final action or it is demonstrated to EPA's and Ecology's  satisfaction that
termination (or intermittent operation) is appropriate because: (A) sampling indicates
that hexavalent chromium is below the  compliance value, and site data indicate it will
remain below the compliance value; or (B) based on an evaluation of the following
criteria:

       The effectiveness of the treatment technology does not justify further operation.
       An alternate treatment technique, such as in situ chemical reduction or other
       improved treatment technique is evaluated and proves to be more effective,
       and/or less costly, and is consistent with  the remedial action objectives.

Wetlands and Flood Plains
The interim action will be implemented such that to the extent practicable disturbance
to wetlands will be avoided and system components except monitoring points will be
located away  from wetlands.   System components will be located such  that they will
not increase deleterious effects of flooding.

Protectiveness
The interim action is expected to provide adequate protection of human  health and
ecological receptors in the Columbia River until  implementation of the final  remedy for
the 100-HR-3 and 100-KR-4 groundwater operable units, or until such time that the
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      DOE demonstrates to Ecology and the EPA that no further interim action is required.
      Contaminated soil overlying these operable units are or will be addressed in separate
      remedial actions.

•     Disposal to ERDF and Lead Regulatory Agency
      The 100-HR-3 Operable Unit was initially designated as a Resource Conservation and
      Recovery Act (RCRA) Past Practice unit. The Tri-Parties have decided to redesignate
      this operable unit as a CERCLA Past Practice unit in order to facilitate the disposal of
      contaminated materials at the CERCLA Environmental Restoration Disposal Facility
      (ERDF).  Section 5.4 of the Hanford Federal Facility Agreement and Consent Order
      signed by the DOE, EPA, and Ecology  (and hence termed the Tri-Party Agreement)
      describes the process that was followed  to initially designate operable units as RCRA
      Past Practice or CERCLA Past Practice, and indicates that the remedial actions selected
      for operable units under either designation would be comprehensive to satisfy the
      technical requirements of both statutory authorities.  Ecology will remain the lead
      regulatory agency for 100-HR-3 following redesignation.
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                       XI.  STATUTORY DETERMINATIONS

Under CERCLA Section 121,  selected remedies must be protective of human health and the
environment, comply with ARARs, be cost effective, and utilize permanent solutions and
alternative treatment technologies or resource recovery technologies to the maximum extent
practical.  In addition, CERCLA includes a preference for remedies that employ treatment that
significantly and permanently reduces the volume, toxicity, or mobility of hazardous
substances as their principal element. This section discusses how the selected remedy meets
these statutory requirements.

The selected remedy provides the best balance of tradeoffs among the  alternatives with respect
to evaluation criteria that are used to evaluate remedies under CERCLA.  The selected remedy
will protect human health with institutional controls and protect the environment by reducing
the discharge of contaminants to the river. It will comply with ARARs for hexavalent
chromium directly associated with this action,  is cost effective, and will utilize permanent
solutions to the maximum extent practicable.  The selected alternative satisfies the CERCLA
preference for treatment as  a principal element.
11.1 Protection of Human Health and the Environment

Site institutional controls will continue during the interim remedial action period. These
controls limit human access to the groundwater and thereby limit human exposure to
acceptable risk levels.  The ecological risk resulting from the groundwater flow into the river
is addressed by the pump-and-treat component of the action identified in this ROD.  The
pump-and-treat will reduce the concentration of chromium  to Ambient Water Quality
Standards within the river bottom substrate.  Implementation  of this remedial action will not
pose unacceptable short-term risks toward site workers that cannot be mitigated through
acceptable remediation practices.

11.2 Compliance with ARARs

The selected remedy will comply with the federal and state ARARs identified below.  This
interim remedial action addresses chromium in the groundwater (by preventing human
exposure to contaminated groundwater,  and preventing chromium exceedances of AWQC in
the Columbia River substrate)  and is only part of a final remedial action that will satisfy other
ARAR requirements when completed. The ARARs identified for the action identified in this
ROD are the following:

11.2.1  Chemical-Specific ARARs

•     Underground Injection  Standards (WAC 173-218) and Underground Injection Control
      Program (40 CFR 144, Subpart B) for chromium are applicable to reinjection of treated
      groundwater.
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•      Clean Water Act, Ambient Water Quality Criteria for Protection of Aquatic Life
       (50 FR 30788, 40 CFR 131) for chromium are relevant and appropriate for establishing
       cleanup goals that are protective of the Columbia River.

•      Water Quality Standards for Waters of the State of Washington, (WAC 173-201A-040)
       for chromium are relevant and appropriate for establishing cleanup goals that are
       protective of the Columbia River.

11.2.2 Action-Specific ARARs

•      State of Washington Dangerous Waste Regulations, (WAC 173-303) are applicable for
       the identification, treatment, storage, and land disposal of wastes determined to be
       dangerous wastes.

•      Land Disposal Restrictions (40 CFR 268) are applicable to the land disposal of wastes
       determined to be hazardous wastes.

•      Minimum Standards for Construction and Maintenance of Wells (WAC 173-160 and
       162) are applicable regulations for the location, design, construction, and abandonment
       of groundwater  extraction, reinjection, and monitoring wells.

•      Dangerous Waste Standards for Tank System  Units (WAC 173-303-640).  The
       substantive requirements of this are relevant and appropriate to the construction,
       operation, maintenance and closure of any tanks and associated components (e.g.
       piping) that contain dangerous waste associated with both the water treatment system
       and the resin stabilization system.

11.2.3 Location-Specific ARARs

•      National Archeological and Historical Preservation Act (16 USC Section 469); 36 CFR
       Part 65, is applicable to recover and preserve artifacts in areas where an action may
       cause irreparable harm, loss, or destruction of significant artifacts.

•      National Historic Preservation Act (16 USC 470, et. seq.)\ 36 CFR Part 800, is
       applicable to actions in order to preserve historic properties controlled by a federal
       agency.

•      Public Law 100-605, To Authorize a Study of the Hanford Reach of the Columbia River
       and for Other Purposes is applicable to planning, designing, and locating activities in a
       manner that minimizes direct and adverse effects on the values for which the river is
       under study.   The location of any facilities within 1/4 mile of the river will be
       coordinated with the National Park Service.

•      Endangered Species Act of 1973 is applicable to protection of endangered or threatened
       species. Consultation with the U.S. Department of the Interior will occur as needed.


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•      Migratory Bird Treaty Act is relevant and appropriate to protection of migratory birds
       in the areas. Consultation with the U.S. Fish and Wildlife Service will occur as
       needed.

•      Bald and Golden Eagle Protection Act of 1985 is applicable due to the known roosting
       of bald eagles in the general vicinity of potential extraction wells.  Consultation with
       the U.S. Department of Interior will occur as needed.

11.2.4 Other Criteria, Advisories, or Guidance to be Considered for this Remedial
       Action (TBCs)

•      Floodplain Management Executive Order (E.O.  11988) and Protection of Wetlands
       Executive Order (E.O. 11990) are relevant and appropriate to activities within the
       floodplains  and wetlands.  To the extent practicable, actions should avoid or minimize
       the impact to floodplains and wetlands, and minimize loss due to floods.

•      Environmental Restoration Disposal Facility (ERDF) Waste Acceptance Criteria
       (BHI-00139, Rev. 0, October 1995) delineates primary requirements including
       regulatory requirements, specific isotopic constituents and contamination levels, the
       dangerous/hazardous constituents and  concentrations, and the physical/chemical waste
       characteristics that are acceptable for disposal of wastes at ERDF.

11.3  Cost Effectiveness

The selected remedy was the most cost effective of the  three remedies evaluated that achieved
the remedial action objective.

11.4  Utilization of Permanent Solutions and Alternative Treatment Technologies to the
      Maximum Extent Possible

The selected remedy utilizes permanent solutions.  Pump-and-treat using ion-exchange is not
an innovative technology.

11.5  Preference for Treatment as a Principal Element

The selected remedy utilizes treatment to concentrate the chromium into a small volume of
resin relative to the large volume of treated groundwater. The resin is then solidified into
cement. This process reduces the volume, mobility, and toxicity of the chromium.

11.6 CERCLA Section 104(d)(4) Determination

The CERCLA Section 104(d)(4)  states where two or more non-contiguous facilities are
reasonably related on the basis  of geography, or on the basis of the threat or potential  threat to
the public health or welfare or  the environment, the President may, at his discretion, treat
these  facilities as one for the purposes of this section.

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The preamble to the NCP indicates that when non-contiguous facilities are reasonably close to
one another and wastes at these sites are compatible for a selected treatment or disposal
approach, CERCLA Section 104(d)(4) allows the lead agency to treat these related facilities as
one site for response purposes and, therefore, allows waste transfer between such
non-contiguous facilities without having to obtain a permit. The  100-HR-3 and 100-KR-4
Operable Units and the ERDF are all contained within the Hanford Site, and are subject to the
Tri-Party Agreement.  They are reasonably related based on geography, on the basis of the
threat or potential threat to the public health, welfare or the environment,  and therefore are
being treated as a single site for response purposes under this ROD.  This is consistent with the
determination made in the January 20, 1995 ROD for the ERDF that stated... "Therefore, the
ERDF and the 100, 200, and 300 Area NPL sites are considered to be a single site for
response purposes under this ROD."
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              XII.  DOCUMENTATION OF SIGNIFICANT CHANGES

The DOE, EPA, and Ecology reviewed all written and verbal comments submitted during the
public comment period.  Upon review of these comments, it was determined that no significant
changes to the selected remedy, as originally identified in the Proposed Plans, were necessary.
The Proposed Plan for 100-KR-4 identified two contaminants (zinc and carbon-14) for
remedial action, that upon more detailed analysis do not warrant inclusion in the interim
action.
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                   APPENDIX A - RESPONSIVENESS SUMMARY

Public comments reflected overwhelming support for taking an active pump-and-treat
action to prevent plumes from entering the Columbia River. Most of the comments
regarded the choice of treatment technique: ion-exchange resin verses other techniques.
Regarding the other techniques, comments revolved around reverse osmosis relative to
co-contaminants and also other new treatment techniques available by identified vendors.

       Ion exchange verses reverse osmosis treatment techniques are discussed in the
       following comment response.  Other treatment techniques are discussed in subsequent
       comment responses.

Why is the "ion exchange system" method  of cleanup preferred to "reverse osmosis"?
What are the benefits and advantages of the former over the latter?

       First, a brief description of these two methods.  Ion exchange requires pumping water
       through large tanks filled with  a resin. Resins are a material to which chemicals tend
       to stick.  Resins are designed to have  a tremendous quantity of binding ("sticky") sites.
       As tanks of resins approach their capacity for contaminants, a progressively higher
       amount of contaminants pass through  without being captured.  Generally a number  of
       these ion exchange tanks are plumbed together so that progressively cleaner water can
       be obtained at each stage.  After several treatment steps, the contaminants  may be
       essentially all removed, so large numbers of additional columns provide no added
       benefit.  When contaminants "break-through" the first column, all the binding sites are
       not yet used. Continued use will eventually nearly saturate the binding sites, resulting
       in maximal use of the resin.  By the time contaminant saturation of the resin in the  first
       tank is nearly saturated, most of the contaminant input is breaking through to the
       second treatment tank. At that point,  resin from the first tank is removed and
       regenerated for re-use, or disposed. The tank is then cleaned and refilled with fresh
       resin, and now becomes the final "polisher" tank. The  choice of resin determines
       which contaminants are removed.  It is anticipated that a weak base anionic resin bed
       will be used to capture chromium.  Co-contaminants with similar chemical properties
       would also be retained by this resin (for example: uranium and nitrate).
       Co-contaminants such as strontium-90 and tritium would not be retained.

       Reverse osmosis uses hydraulic pressure to push water through a membrane that is
       permeable to water but not to the contaminant.  Clean water is drawn off from the
       clean side of the membrane. Water on the "dirty" side  of the membrane becomes
       concentrated with particulate and dissolved contaminants and minerals, and its osmotic
       pressure rises. Water from the clean side of the membrane is inclined to pass back
       through the membrane to the dirty side in response to the osmotic pressure, but is held
       back by the hydraulic pressure applied to the clean  side. Ever increasing hydraulic
       pressure is needed to overcome ever increasing osmotic pressure until the point of
       diminishing returns indicates that it is time to flush out the slurry on the dirty side of
       the membrane. The osmotic pressure is reduced and the system again operates


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       productively.  In practice, a continuous flow system is usually used rather than the
       "batch mode" just described.

       A major advantage of ion exchange over reverse osmosis is substantially less secondary
       wastes.  With ion exchange, very small volumes of waste resins (relative to the volume
       of treated water) are generated.  With reverse osmosis, relatively large volumes of
       contaminated liquid are generated.  The expense associated with purchase, handling,
       and disposal of resins is small relative to the treatment and disposal of the solution
       generated with reverse osmosis.  An additional advantage of the ion exchange is that it
       is a very reliable process. Having a treatment system with minimal down-time is  an
       important element of being protective.

Are the various cleanup sites discrete, or are they interconnected by the same aquifers
and affected by the same plumes?

       When the three reactor areas covered by this ROD were in operation, they discharged
       large amounts of water that formed a mound on the former water table.  This mound of
       water flowed in  all directions, including upgradient (away from the river) against  the
       natural groundwater flow direction. Thus ground water in all directions from the
       reactor areas were initially contaminated with chromium.  Following shutdown of the
       reactors, and an end to the discharge of the liquids, the mound dissipated and
       groundwater flows have returned to their  natural directions.  Wells upgradient of the
       reactors generally still have slightly elevated levels of chromium.  In the 100-K and
       100-H Areas,  the residual chromium remaining  in the upgradient portions of the aquifer
       should gradually be flushed back through the reactor area.  However the 100-D Area is
       unique.

       Chromium from the 100-D area  that was pushed inland from the historic groundwater
       mound has in part been pushed into areas that naturally were upgradient of 100-H
       Area. With the return of groundwater flow to its natural direction,  this chromium is in
       part flushing out towards the 100-H area. With this sketch of the process at work in
       the 100-D and 100-H Area, the net effect of all  the processes at work result in the
       100-D and 100-H discharges have mutually affected their mutual "upgradient" area
       resulting in the whole area having moderately elevated levels of chromium. Within the
       100-D and 100-H area are discrete significantly  elevated chromium plumes that result
       in the ecological risk that this ROD addresses. 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.

What is the target date of beginning this project?

       Design can begin in earnest upon signature of this ROD.  Well drilling will begin soon
       after the ROD.  Groundwater extraction and treatment systems at two reactor areas will
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       be operational within 15 months of signature of this ROD. The system at the third
       reactor area will be operational within 18 months after signature of this ROD.

Once underway, what is the suspected length (time) of the project to completion.

       More than a few years. The pump and treat portion of the interim remedial action will
       continue until the selection of a final action or it is demonstrated to EPA's and
       Ecology's satisfaction that termination (or intermittent operation)  is appropriate
       because: (a) sampling indicates that hexavalent chromium is below the compliance
       value, and site data indicate it will remain below the compliance value, or (b) based on
       an evaluation of the following criteria:

              The effectiveness of the treatment technology does not justify further operation.
              An alternate treatment technique, such as in situ chemical  reduction or other
              improved treatment technique is evaluated and proves to be more effective,
              and/or less costly, and is consistent with the remedial action objectives.

What is the total amount of water that needs to be pumped?

       Water will be pumped at a rate sufficient to capture the chromium plume to an adequate
       degree to meet the remedial action objectives  (see next comment). The total amount of
       water that will be pumped depends on how long the pump-and-treat system runs (see
       the previous and next comment).

How much will it cost.

       Costs were estimated as part of the feasibility study for this interim action.  If the
       systems were to run for 5 years, the total costs were estimated by DOE to be about
       29.8 million dollars.  Ecology and EPA believe the project could be designed,
       operated, and maintained for substantially less than that estimate.  Actual costs for the
       project will be monitored.

What will be the residual levels of contamination at the conclusion of the project; and
that would those levels mean in relation to human use or contact with the groundwater.

       Residual levels of contamination will be such  that the remedial action  objectives are
       met.  The remedial action objective for the pump-and-treat aspect of this is to protect
       ecological receptors in the Columbia River. Protection of human health under this
       interim action, however, is specifically addressed through institutional controls to limit
       human access to the ground water.

Is hexavalent chromium the only contaminant being targeted in this project?

       As far as active remedial actions, yes.  Site institutional controls will continue during
       the interim remedial action period.  These controls limit human access to the


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       groundwater and thereby limit human exposure to groundwater that exceeds drinking
       water MCLs for a number of contaminants in addition to chromium.

Where will new wells be dug?

       New wells will be located within the chromium plumes of the three reactor areas.  It is
       anticipated that these primarily will be located along and inland from the river shore
       where the main portion of the chromium discharges.  A combination of existing and
       new wells will be used to create a capture zone.

What is the goal of the project? What is clean, and what level of clean is the objective?
Are there parameters that define what is safe for salmon eggs and fry, and if so is that
the goal?  What are EPA's standards for the protection of aquatic life, and are those the
goal?

       The goal of the pump-and-treat systems is to prevent discharge of hexavalent chromium
       at levels exceeding concentrations that are considered protective of aquatic life in the
       Columbia River and riverbed sediments. The aquatic receptor exposure point is within
       the river substrate at depths up to 18 inches (46 centimeters), where embryonic salmon
       and fry are present during parts of the year. The relevant standard is the State of
       Washington's Chronic Ambient Water Quality Standard for Protection of Freshwater
       Aquatic Life for hexavalent chromium of 11 parts per billion.

Development of site-specific toxicity information on the impacts of chromium to salmon
eggs, larvae, and juveniles  to support development of site-specific criteria to ensure
protectiveness was suggested.

       The EPA's AWQC for chromium of 11 ///L was based largely on toxicity information
       for embryonic salmon and fry. The EPA's AWQC were used by the State of
       Washington to establish Water Quality Standards for Surface Waters of the State of
       Washington. Thus the legal threshold used in this ROD to define protectiveness,
       although not site-specific, has a species-specific basis.  From the remedial action
       perspective, at this time, DOE, EPA, and Ecology do not consider site-specific toxicity
       information  cost effective in light of other known cleanup needs that would go
       unfunded if additional bioassays were conducted.  (See next comment for the natural
       resource damage perspective.)

Development of site-specific toxicity information is important for another reason.
Impacts from  chromium discharges into salmon redds are likely to be  one of the more
quantifiable injuries to natural resources, and are likely to be a major focus of a damage
assessment.  The commentor encourages prompt and accurate assessment and mitigation
of these potential injuries as advocated by DOE guidance (DOE/EH-0192,  page 12) and
as required under  CERCLA 107(f)(2)(A). The U.S. Fish and Wildlife Service expressed a
desire to participate in impact assessment and mitigation planning.
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       For fiscal year 1996 (FY 96) DOE has initiated an initial scoping level risk assessment
       in support of the Columbia River Comprehensive Impact Assessment (CRCIA).  The
       FY 96 effort also includes identifying remaining work believed to be needed by the
       CRCIA management team (comprised of DOE, EPA, Ecology, Tribal, Hanford
       Advisory Board, and State of Oregon representatives) to perform a "comprehensive"
       assessment of the Columbia River.  The scoping level risk assessment involves
       determining exposure of a variety of species to a number of Hanford's contaminants in
       the Columbia River. The contaminants include chromium and the species include
       salmon.  The assessment, the scope of which was agreed to by the CRCIA management
       team follows EPA guidelines for ecological risk assessment and is designated to support
       development of interim remedial actions. Based on the FY 96 work, any required
       mitigation and/or additional assessment needs will be determined. The U.S. Fish and
       Wildlife Service and other interested parties are encouraged  to participate with the
       CRCIA management team in this assessment and any required mitigation activities.

Construction of extraction wells adjacent to the river has the potential to disturb roosting
bald eagles, waterfowl, and terrestrial birds.  To minimize impacts of the project,
construction activities should be timed to avoid peak periods of bird activity. The U.S.
Fish and Wildlife Service indicated a  willingness to provide consultation of the most
appropriate timing for construction activities.

       The DOE will provide the Natural Resource Trustees an opportunity to comment on
       timing for in-field activities  that are potentially disruptive to wildlife. The DOE will
       consult with the U.S. Department of the Interior and the U.S. Fish and Wildlife
       Service as appropriate.

The U.S.  Fish and Wildlife offered to provide technical support to ensure that
revegetation efforts, following the interim action, are technically feasible, appropriately
restore disturbed natural resources, and would be compatible with designation of this
area as a Wild and Scenic River corridor.  It was requested that all the Natural Resource
Trustees be consulted early in the revegetation planning.  A description of pre-project
conditions is necessary if appropriate revegetation is to occur.

       Surface disturbance and ultimate restoration associated with these groundwater actions
       is largely co-located and similar in nature to what will be occurring with the surface
       waste sites.  Revegetation/restoration of surface disturbance  associated with actions
       from this ROD will be addressed as part of the revegetation/restoration of the source
       operable unit.  Natural Resource Trustees will be included in those planning efforts.
       For areas that are disturbed  during construction and operation, it is expected that the
       area will be revegetated following construction in those areas that are not needed for
       operation and maintenance of the treatment system and is also not expected to be re-
       disturbed within the next few years by other site activities.  Following completion of
       the interim action, it is expected that rectification of the habitat affected by this activity
       will be conducted and coordinated with comparable activities for the source operable
       units (100-DR-l, 100-DR-2, 100-HR-l, 100-HR-2, 100-KR-l, and  100-KR-2).


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Planning of pipeline locations should take into account and attempt to avoid higher
quality habitat and other important natural resource features.

       The ground surface on which these remedial activities will take place is primarily
       disturbed habitat, due to agriculture and defense related activities. To  the extent
       practicable, areas of higher quality habitat will be avoided or impacts will be
       minimized.

A number of comments were received from business vendors or technical  experts
identifying themselves as competent to conduct the work as described in the proposed
plan, or to identify innovative techniques that may be better or more cost effective, or to
suggest alternate methods to achieve remedial action objectives.

       Commitment to a pump-and-treat is a long-term expensive proposition. The Tri-Parties
       endorse the most cost effective remedial approach consistent with the CERCLA 9
       criteria and the remedial action objectives. Evaluation of technologies is an ongoing
       process with incorporation as deemed appropriate.  If in the future a substantially
       different remedial  action approach is considered, public comment will  be solicited
       before a decision to implement it is made.  Treatability tests may be conducted without
       public comment.

There were comments regarding the fact that the proposed plans did not include any
action directed at removal of the chromium that is already in the river sediments.

       Hexavalent chromium is very soluble in water.  Most of the hexavalent chromium is
       dissolved into and  moving with the water.  Thus the river bottom sediments to not
       accumulate hexavalent chromium.  When hexavalent chromium is reduced to trivalent
       chromium, it becomes much less soluble and hence has the potential to accumulate in
       sediments.  However it is also less toxic. Because it is less toxic and in paniculate (not
       dissolved) form, it is generally less bioavailable, and therefore, less of an
       environmental threat.

A commentor noted his previous experience  with ion exchange resins as not being cost
effective, part of the problem being that the chromium destroyed the resins.  Alternatives
such as precipitation were suggested.

       There has been considerable experience using resins to treat chromium that have been
       successful, including a treatability test at 100-HR-3.  The resins have not been
       destroyed by chromium.  Precipitation can be cost-effective with very high
       concentrations of chromium.  Generally speaking, precipitation methods are not
       cost-effective for lower concentrations of chromium, and do not achieve the low
       concentrations required for this remedial action.

       Currently, we plan to dispose of the resins after one use,  however if resin regeneration
       is determined to be practicable, then regeneration may be utilized.


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A commentor identified their company's electrocoagulation and electrochemical
flocculation process as a remedial alternative.

       This process was evaluated in the 100 Area Feasibility Study, Phases 1 and 2 against
       the following criteria and was eliminated:

             Effectiveness
             Implementability - Technical Feasibility
             Implementability - Administrative Feasibility
             Cost.

A commentor identified that the pump-and-treat system does not capture all the plume,
and the treatment train does not remove all the chromium. It was stated that this "does
not seem very effective".

       It is correct that: (1) plume capture will be partial, and (2) treatment of the water will
       be partial.  But the remedial action objective of this interim action is not to totally
       prevent chromium from entering the river.  The remedial action is intended to capture
       and treat enough of the chromium that residuals that enter the river are at or below
       concentrations considered to be protective of the aquatic organisms that inhabit the
       Columbia River bottom.

A commentor identified that this interim action addresses part of the contaminated
groundwater but does not address the remaining groundwater contamination.

       Ecological risk is addressed by the pump-and-treat action for the single contaminant
       that exceeds the ecological-risk based threshold — hexavalent chromium.  Potential
       human health risks associated with exposure to remaining contaminants are addressed
       by institutional controls.  Thus for the interim period addressed by this interim action,
       this action  should be protective of human health and the environment.  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.

Commentors also reiterated another facet of the problem is the previously contaminated
soil and the risk that these contaminants pose to surface exposure as well as a continuing
to the groundwater.

       In addition to the cleanup plan for the 100-HR-3 and 100-KR-4 groundwater operable
       units, action is being taken to address waste sites that are the historic sources of
       groundwater contamination.  Surface waste sites that are within the 100-DR-l,
       100-DR-2, 100-HR-l,  100-HR-2,  100-KR-l and 100-KR-2 Operable Units received
       wastes during previous operation of the  reactors and their support facilities. Cleanup of
       waste sites in the 100-DR-l and 100-HR-l  Operable Units have been addressed in a
       September 1995 interim action Record of Decision.  The 100-DR-2, 100-HR-2,


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       100-KR-l and 100-KR-2 Operable Units will be the subject of future Proposed Plans.
       The 100-IU-4 Operable Unit upgradient of 100-HR-3 includes the former Sodium
       Bichromate Barrel Landfill, which contained empty crushed barrels that had been used
       to store sodium dichromate.  The 100-IU-4 Operable Unit was remediated in April
       1992 through an Expedited Response Action and has been addressed in a previous
       proposed plan.

While many comments identified that protection of salmon is an effort worthy of this
action, it was noted that adverse effects to other wildlife must be considered in this plan.

       Aquatic toxicity tests for chromium have been conducted for a wide variety of species,
       and embryonic salmon and fry are among  the most sensitive to hexavalent chromium.
       The chronic exposure standard used for this remedial action of 11 M/L hexavalent
       chromium was established to be protective of aquatic life in general, not just embryonic
       salmon and fry.  Field activities will be conducted in a manner to minimize adverse
       impacts to wildlife.

The issue of bioaccumulation of hexavalent  chromium was identified as a concern.

       The criteria and standards  for chromium have been established such that the
       bioconcentration or bioaccumulation of hexavalent chromium that occurs at those
       concentrations does not endanger aquatic life.

There were comments regarding the disposal of resins contaminated with chromium and
other contaminants and the ultimate migration of these contaminants resulting in a
future replay of the current problems.

       The resins will be treated prior to disposal if necessary to meet the waste acceptance
       criteria for the Environmental Restoration  Disposal Facility. This treatment is intended
       to reduce the mobility of the contaminants. Hexavalent chromium reacts with the
       resins resulting in conversion to the less toxic and less mobile trivalent form.

The Nez Perce Tribe comments expressed a  request and interest in future involvement in
many technical aspects of the conduct of this interim action.

       The Tri-Parties intend to continue our policy to consult with affected Native American
       Indian Tribes on a government-to-government basis.  The Tri-Parties will also continue
       to consult with the Tribes as well as the other Natural Resource Trustees regarding
       natural resource issues associated with  this remedial action.

A number of comments addressed costs associated with the remedial action.  Several
addressed choosing the most cost effective remedy while others indicated that one cannot
put a price tag on the importance of protecting the Columbia River.
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       This ROD addresses both concerns. The ion-exchange pump-and-treat was identified
       as the most cost effective remedial action that is protective of human health and the
       environment.  As planned,  it also reduces chromium to concentrations that should
       protect the health of the aquatic system,  including embryonic salmon and fry in nests in
       the river bottom gravels.

A commentor noted that the initial modeling  to support remedial design were identified
as not to be construed as quantitatively accurate or reliable as indicators  of effectiveness
or efficiency. This suggests the interim remedial action should be accomplished with
design contingency, in order to assure successful remediation.

       During remedial design,  initial modeling will be refined to better estimate appropriate
       well positioning for plume  capture. Also, as the system comes on line, operational and
       compliance monitoring will be conducted.  When the actual response of the aquifer is
       known, the design may be altered as needed and approved/directed by EPA and
       Ecology to meet the remedial action objectives.  Contingency in the initial design
       capacity will be included based on uncertainty in design assumptions.

Interest was  expressed in some of the alternate technology testing that was identified in
the Proposed Plans for information purposes  (are not specifically mandated by this
ROD).

       Cost effective remedial technologies for  groundwater remediation is an active area of
       practical research. Chromium and other toxic metals are a common problem and are
       frequently the target of such research effort.  Several techniques identified in the
       Proposed Plans and others not specifically mentioned have been and are under way at
       Hanford. Many other techniques are being developed and tested at other areas. Should
       a different technique show promise as a  substitute for the ion-exchange pump-and-treat,
       the Tri-Parties may convert to this method.  If this change is fundamentally different
       than described in this ROD, an opportunity for public comment will be provided.
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