Superfund Record of Decision Weldon Spring Quarry Plant Pitts USDOE St Charles MO


                                    EPA/ROD/R07-98/166
                                    1998
EPA Superfund
     Record of Decision:
     WELDON SPRING QUARRY/PLANT/PITS
     (USDOE/ARMY)
     EPA ID: MO3210090004
     OU05
     ST. CHARLES COUNTY, MO
     09/30/1998

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EPA 541-R98-166

RECORD OF DECISION: DOE/OR/21548-725
                                  Record of Decision for Remedial Action
                                  for the,  Quarry Residuals  Operable  Unit
                                        at the Weldon Spring Site,
                                         Weldon Spring,  Missouri

                                              September 1998

                                                prepared by
    U.S.  Department of Energy,  Oak Ridge  Operations  Office,  Weldon Spring  Site  Remedial Action Project,
                                         Weldon Spring,  Missouri

                                  U.S.  Department of Energy
                                  Weldon Spring Site Remedial Action Project
                                  Weldon Spring,  Missouri

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RECORD OF DECISION: DOE/OR/21548-725
                                  Record of Decision for Remedial Action
                                  for the Quarry Residuals Operable Unit
                                        at the Weldon Spring Site,
                                          Weldon Spring,  Missouri

                                              September 1998
                                                prepared by
    U.S.  Department of Energy,  Oak Ridge Operations Office,  Weldon Spring Site Remedial Action Project,
                                          Weldon Spring,  Missouri

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DECLARATION STATEMENT

Site Name and Location

Weldon Spring Quarry
St. Charles County, Missouri

Statement of Basis and Purpose

This Record of Decision (ROD) presents the selected remedial action for the Quarry Residuals Operable
Unit (QROU) of the U.S. Department of Energy's Weldon Spring Site in St. Charles County, Missouri. This
action was selected following reguirements of the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA), as amended, and, to the extent practicable, the National Oil and Hazardous
Substances Pollution Contingency Plan. National Environmental Policy Act (NEPA) issues related to the
guarry area have also been addressed and have been integrated into the CERCLA decision-making process for
the QROU.

This decision is based on the Administrative Record for the QROU. Major documents include the (1) RI/FS
Work Plan, (2) Remedial Investigation and Baseline Risk Assessment Reports, (3) Feasibility Study Report,
and (4) Proposed Plan. Public comments received during the review period for the Proposed Plan were
considered and have been incorporated into this decision.

The State of Missouri concurs with the selected remedy.

Assessment of the Site

The response action selected by this ROD addresses actual or threatened releases of hazardous substances
from this site that were not addressed under previous response actions.

Description of the Select Action

The QROU is the second of two operable units established for the guarry area of the Weldon Spring site.
The first operable unit, the Quarry Bulk Waste Operable Unit, addressed the excavation and relocation of
the source materials located in the guarry proper. This operable unit addresses residual conditions at
the guarry, including contaminated groundwater and surface water. Based on exposure assessments under
current and reasonably anticipated land uses, no further action is necessary to protect human health and
the environment. However, because contamination will remain on-site, long-term monitoring will be
undertaken as described below.

The major components of the selected remedy are:

• Monitor long term to verify that conditions at the guarry area and the St. Charles County
well field remain protective of human health and the environment;

• Implement institutional controls to prevent uses inconsistent with recreational use or uses
that would adversely affect contaminant migration.

Further sampling activities are planned for two purposes. Given the presence of significant levels of
contamination in guarry groundwater north of the slough, which is in close proximity to the St. Charles
County well field, and the reliance on natural systems to limit potential exposure, a field test will be
performed to further evaluate the effectiveness of groundwater remediation. This activity will include
the operation of a pilot-scale extraction trench. Sampling will also be performed to establish the extent
of contamination for the two soil areas (i.e., the northeast slope and the ditch area near the transfer
station) within the guarry proper. Preliminary sampling has indicated the presence of radiological
contamination. A complete characterization of these areas could not be performed because access to these
areas is limited. If contaminant levels are found to be unacceptable following a risk evaluation, these
areas will be addressed under a subseguent response action.

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Statutory Determinations

The selected action is protective of human health and the environment,  complies with applicable or
relevant and appropriate requirements,  and is cost effective. This remedy utilizes permanent solutions
and alternative treatment technologies to the maximum extent practicable for this site. This remedy does
not satisfy the statutory preference for treatment as a principal element of the remedy.

Because groundwater contamination will remain at the guarry at levels that exceed those for unlimited
land use and unrestricted exposure,  a review will be conducted within five years after commencement of
the action to evaluate conditions at the guarry area and to ensure that the remedy continues to provide
adeguate protection of human health and the environment. The five-year reviews will be developed in
consultation with the U.S. Environmental Protection Agency and the Missouri Department of Natural
Resources and will be made available to the public for review and comment.

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                                                 CONTENTS

DECLARATION STATEMENT 	 iii

NOTATION 	  ix

1  SITE HISTORY 	   1

2  SCOPE AND ROLE OF REMEDIAL ACTION 	   5

3  COMMUNITY PARTICIPATION 	   7

4  SITE CHARACTERISTICS 	   9

   4.1  Soil and Geology 	   9
   4.2  Hydrogeology/Groundwater 	   9
   4.3  Biotic Resources 	  11
   4.4  Nature and Extent of Contamination 	  12
        4.4.1  Soil 	  12
         4.4.2  Femme Osage Slough and Creeks 	  15
         4.4.3  Groundwater 	  15

5  SUMMARY OF SITE RISKS 	  19

   5.1  Human Health 	  19
   5.2  Ecological Assessment 	  20

6  DESCRIPTION OF REMEDIAL ALTERNATIVES 	  23

   6.1  Alternative 1:  No Action 	  23
   6.2  Alternative 2:  Monitoring with No Active Remediation	  23
   6.3  Alternative 6:  Groundwater Removal at Selected Areas,
         with On-Site Treatment	  25

7  SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES	  27

8  SELECTED ACTION 	  31

   8.1   Quarry Groundwater Monitoring 	  32
   8.2   Quarry Proper Restoration 	  33
   8 .3   Well Field Contingency Plan 	  33
   8.4   Additional Data Needs 	  35
          8.4.1  Field Test 	  35
          8.4.2  Soil Sampling at the Northeast Slope and Ditch Area 	  36

9  STATUTORY DETERMINATIONS 	  39

   9.1   Protection of Human Health and the Environment 	  39
   9.2   Compliance with Applicable or Relevant and Appropriate Reguirements 	  39
         9.2.1  Chemical-Specific ARARs 	  40
          9.2.2  Chemical-Specific TBCs 	  40
          9.2.3  Action-Specific ARARs 	  41
   9.3   Cost-Effectiveness 	  42
   9.4   Utilization of Permanent Solutions and Alternative Treatment Technologies
          to the Maximum Extent Practicable 	  43
   9.5   Preference for Treatment as a Principal Element 	  43
   9.6   Irreversible and Irretrievable Commitment of Resources 	  43
   9.7   Significant Changes 	  43

10  REFERENCES 	  45

APPENDIX A: Responsiveness Summary 	  47

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                                                  TABLES

1  Summary of Contaminant Data Collected for the QROU 	  13
2  Summary of Human Health Risk Estimates for the Quarry Area 	  21
3  Comparative Analysis of Alternatives 	  29

                                                  FIGURES

1  Location of the Weldon Spring Site 	   2
2  Area near the Weldon Spring Quarry 	   3
3  Cross Section through the Quarry Area 	  10
4  Locations of Background Wells, DOE Wells, and St. Charles County Wells 	  16
5  Predicted Percentage of the Mass of Uranium Remaining in the Groundwater
   in the Area of the Contaminated Alluvium North of the Femme Osage Slough
   during Remediation 	  26
6  Preliminary Monitoring System for Quarry Area Groundwater 	  34
7  Areas with Suspected Contamination to be Fully Characterized
   during Quarry Restoration 	  37

                                                 NOTATION

       The following is a list of the acronyms,  initialisms, and abbreviation (including units of
measure) used in this document. Acronyms and abbreviations used only in tables and figures are defined in
the respective tables and figure captions.

                                 ACRONYMS, INITIALISMS, AND ABBREVIATIONS

ARAR          applicable or relevant and appropriate reguirement
BRA           baseline risk assessment
CERCLA        Comprehensive Environmental  Response,  Compensation,  and Liability Act
CFR           Code of Federal Regulations
COPC          contaminant of potential concern
CSR           Code of State Regulations
1,3-DNB       1,3-dinitrobenzene
2,4-DNT       2,4-dinitrotoluene
DOE           U.S. Department of Energy
EPA           U.S. Environmental Protection Agency
FS            feasibility study
MCL           maximum contaminant level
MDNR          Missouri Department of Natural Resources
MDOH          Missouri Department of Health
NCP           National Oil and Hazardous Substances Pollution Contingency Plan
NPDES         National Pollutant Discharge Elimination System
NPL           National Priorities List
O&M           operation and maintenance
pp            proposed plan
QROU          guarry residuals operable unit
RD/RA         remedial design/remedial action
RI            remedial investigation
RI/FS         remedial investigation/feasibility study
ROD           Record of Decision
TBC           to-be-considered (reguirement)
WSCC          Weldon Spring Citizens Commission
WSSRAP        Weldon Spring Site Remedial Action Project

                                             Units of Measure
cm
ft
g
gal
gpm
ha
km
L
centimeter(s)              m
foot (feet.)                m  3
gram(s)                     Ig
gallon(s)                   mi
gallon(s)  per minute       mL
hectare(s)                 pCi
kilometer(s)                ppm
liter(s)                    s
                           yd3
meter(s)
cubic meter(s)
microgram  (s)
mile (s)
milliliter(s)
picocurie(s)
part(s) per million
second(s)
cubic yard(s)

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                                  RECORD OF DECISION FOR REMEDIAL ACTION
                                  FOR THE QUARRY RESIDUALS OPERABLE UNIT
                                        AT THE WELDON SPRING SITE,
                                          WELDON SPRING MISSOURI

                                              1 SITE HISTORY

       The Weldon Spring Quarry is one of two noncontiguous areas that constitute the U.S. Department of
Energy's  (DOE) Weldon Spring site. The main area of the site is the chemical plant. Both areas are
located in St. Charles County, Missouri, about 48 km (30 mi) west of St. Louis  (Figure 1). The U.S.
Environmental Protection Agency  (EPA) listed the guarry on the National Priorities List  (NPL) in 1987,
and the chemical plant area was added to the list in 1989. The guarry is about  6.4 km  (4 mi)
south-southwest of the chemical plant area, it is accessible from State Route 94 and is currently fenced
and closed to the public  (Figure 2). The guarry is approximately 300 m  (1.000 ft) long by 140 m  (450 ft)
wide and covers an area of approximately 3.6 ha (9 acres). The guarry was used  by the Army for disposal
of chemically contaminated (explosive) materials in the 1940s and was later used for the disposal of
radioactively contaminated material by the Atomic Energy Commission  (AEC) in the 1960s.

       Approximately 110,000 m 3 (144,000 yd 3)  of soil and waste material was  removed from the guarry
and transported to the chemical plant area as part of completing the remedial action stipulated in the
Record of Decision (ROD) for the Quarry Bulk Waste Operable Unit  (DOE 1990). Bulk waste removal was
completed in October 1995. These wastes have been placed in the disposal cell at the chemical plant.
Prior to bulk waste removal,  contaminated water contained in the guarry pond was also removed;
approximately 170 million L  (44 million gal) has been treated as of March 1998.


                                    2 SCOPE AND ROLE OF REMEDIAL ACTION

       The Quarry Residuals Operable Unit (QROU)  the second of two Operable units established for the
guarry area of the Weldon Spring Site. The first operable unit, referred to as  the Quarry Bulk Waste
Operable Unit, addressed the excavation and relocation of the source materials  within the guarry to
temporary storage at the chemical plant area. Bulk waste excavation was carried out in conjunction with a
removal action to extract, treat, and discharge contaminated water from the guarry sump. This operable
unit addresses residual conditions at the guarry,  including  (1)residual contamination at the guarry
proper, (2) the Femme Osage Slough and nearby creeks, and  (3) contaminated groundwater located north of
the Femme Osage Slough.

       The Weldon Spring site consists of two distinct geographical areas (1)  the guarry area, which is
the subject of this ROD, and  (2) the chemical plant area. Under the chemical plant ROD, wastes and
contaminated media from the chemical plant area and the guarry area will be disposed of in an on-site
cell. The only remaining remedial decision to be made for the Weldon Spring site concerns the management
of contaminated groundwater at the chemical plant area.

                                         3 COMMUNITY PARTICIPATION

       A remedial investigation/feasibility study (RI/FS) process was conducted for the QROU of the
Weldon Spring site in accordance with the reguirements of the Comprehensive Environmental Response,
Compensation, and Liability Act  (CERCLA), as amended, to document the proposed  management of the guarry
proper, the Femme Osage Slough and nearby creeks,  and guarry groundwater north  of the Femme Osage Slough
as components of the QROU Documents developed during the RI/FS process included the Remedial
Investigation (DOE 1998d) , Baseline Risk Assessment  (BRA) (DOE 1998a), Feasibility Study  (DOE 1998b), and
Proposed Plan (PP) (DOE 1998c) . Together, the RI,  BRA,  FS, and PP constitute the reguired primary
documents, consistent with the provisions of the First Amended Federal Facility Agreement entered into
between DOE and the EPA. In accordance with Section 117 of CERCLA, copies of these final documents were
released to the public on March 18, 1998.

       The RI, BRA,  FS, and PP,  along with other documents in the Administrative Record, have been made
available for public review at the Weldon Spring site.  Copies also have been made available to the public
in information repositories at Francis Howell High School and at four branches  of the St. Charles
City/County Library:  Kathryn M. Linneman, Spencer Creek, Middendorf-Kradell, and Kisker Road. A notice of
availability of these documents was published in the St. Charles Journal on March 22 and April 5, 1998.

       A public comment period for this remedial action was held from March 18, 1998,  through May 21,
1998. A public hearing was held on April 16, 1998, at the Administration Building of the Weldon Spring
Site Remedial Action Project  (WSSRAP) as a part of the public participation process. This public hearing

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was advertised in the newspaper cited above. At this meeting, representatives from DOE and EPA Region VII
received comments from the public about the site and the remedial alternatives under consideration.
Transcripts of the public meeting are included as part of the Administrative Record for this operable
unit remedial action. The Administrative Record includes the information considered in deciding on the
selected action. All public comments, oral and written, were considered in the decision-making process
for determining the selected action (see Appendix A).

4 SITE CHARACTERISTICS
4.1 SOIL AND GEOLOGY

Unconsolidated surficial materials are present in the area of the Weldon Spring guarry: loess
deposits and residual soils cover the upland regions, and alluvium occurs along the stream and river
valleys. Coarse-grained deposits constitute the bottom 6 to 24 m (20 to 80 ft) of the Missouri River
floodplain. Fine-grained deposits constitute the upper 4.6 to 7.6 m ( 15 to 25 ft) of the Missouri River
floodplain and the full thickness of Little Femme Osage Creek and the Femme Osage Creek alluvium (DOE
1998d).

The uppermost bedrock unit in the vicinity of the guarry is the Kimmswick Limestone. The Kimmswick
Limestone is underlain in descending order by the Decorah Group, Plattin Limestone, Joachim Dolomite, and
St. Peter Sandstone (see Figure 3). The sides of the guarry expose the Kimmswick Limestone, whereas the
bedrock floor of the guarry lies in the upper portion of the Decorah Group. The contact between the
Kimmswick Limestone and Decorah Group, which may provide the primary pathways for contaminant migration
from the guarry area, is in contact with fine-grained soils, silty clay, and organic silt and clay north
of Femme Osage Slough (DOE 1998d).

4.2 HYDROGEOLOGY/GROUNDWATER

Groundwater in the vicinity of the guarry occurs in alluvium, fractured limestone, and Sandstone
(Berkeley Geosciences Associates 1984). The uppermost groundwater unit is composed of carbonate rocks
near the guarry, tributary alluvium near little Femme Osage Creek, and Missouri River alluvium between
the guarry bluff and the Missouri River. Water table (unconfined) conditions typically occur in the
alluvium; confined to semiconfined conditions occur in the bedrock and alluvium where layers of varying
permeability are present. The St. Peter Sandstone, approximately 90 m (300 ft) below the floor of the
guarry, constitutes the deeper aguifer.

In the vicinity of the guarry, groundwater flows primarily from north to south, and a westward
gradient runs from the guarry to Little Femme Osage Creek. South of the guarry rim, the direction of the
groundwater flow is generally south to southeast toward the Femme Osage Slough. In the alluvium south of
the slough, groundwater is within 3 m (10 ft) of the ground surface, although the depth to water varies
with seasonal pumping demands in the nearby St. Charles County well field and with water levels in the
Missouri River.

For the purposes of this action, alluvial aguifer in the vicinity of the guarry is composed of two
horizons: the overlying fine-grained deposits and the underlying coarse-grained deposits referred to as
the Missouri River alluvium. The deep bedrock aguifers underlying, the alluvial deposits are considered
outside the area of potential impacts from this site.

FIGURE 3 Cross Section through the Quarry Area

The upper horizon is fine grained and has low, yet spatially variable, hydraulic conductivity
because of the heterogeneous nature of the clay and silty clay materials composing this unit. In a
marginal zone that lies between the bluff and the slough, the full seguence of materials consists of the
fine-grained deposits. Only in two bedrock lows, which extend into this area, do coarser materials (silt
and fine sand) occur. Groundwater impact from guarry contaminants is generally confined to the
fine-grained materials. Well yields in this area typically range from less than 0.03 to 0.16 L/s (0.5 -
2.5 gpm); these yields are not sustainable for any length of time, and the wells typically dewater. The
lower yields occur in the low conductivity clay and silty clay materials, whereas the higher yields occur
in the wells situated in the previously described bedrock lows. Consistent with the EPA's guidelines for
groundwater classification, groundwater in this zone is not considered a potential source of drinking
water because yields are insufficient to sustain any routine production sufficient for household use.

The Missouri River alluvial aguifer in which the St. Charles County well field is located is the
principal aguifer in the area. The alluvial aguifer thins to the north, away from the river, until it is
truncated by the risin2 bedrock and the overlaying fine-grained unit. The alluvial aguifer is
characterized by to 24 m (20 - 80 ft) of coarse-grained deposits consisting of fine- to medium-grained

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sand with some silt that grades with depth to coarse-grained sand with cobbles and boulders. These
deposits are overlain by 5 to 8 in (15 -25 ft) of fine-grained deposits. Recharge to the coarse grained
materials occurs primarily from the Missouri River, intermittent surface flooding, infiltration of
precipitation, and discharge from the underlying bedrock.

The hydraulic gradient between the bluff and the slough is generally southward toward the slough.
In general, the groundwater elevation data indicate a southeasterly gradient across the slough. At most
locations, the slough is a source of recharge to the shallow groundwater. However, at some locations
north of the slough, groundwater levels are higher, which indicates discharge to the slough (DOE 1998d).

A notable decrease of uranium (from 3,400 to lOpCi/L) occurs over a short distance (30 to 91 m
[100 - 300 ft]) north of the slough, which indicates that processes other than dilution are reducing the
amount of dissolved uranium in groundwater. These processes include sorption onto the aguifer matrix and
organics and precipitation of dissolved uranium from the groundwater. Uranium migration in the
groundwater will be limited to some extent by sorption onto the aguifer materials. Site-specific
distribution coefficient estimates range from 5 to 50 m.L/g for materials north of the slough.
Contaminant removal from groundwater via precipitation of solid phases typically results from changes in
geochemical conditions in the aguifer system. In the shallow aguifer north of the slough, uranium
activity decreases abruptly near the northern margin of the slough in response to a sudden decrease in
the oxidation potential, which is coincident to a reduction of dissolved uranium in groundwater. The
sharp decrease in uranium levels indicates that sorption, which typically generates more diffuse
boundaries, is not the only process attenuating the uranium in groundwater.

4.3 BIOTIC RESOURCES

Much of the land surrounding the guarry consists of state-owned conservation areas containing
second-growth forest. Nonfcrested areas, which cover much of St. Charles County, are largely used for
crop production and pasture or are old-field habitat.

Aguatic habitats in the vicinity of the guarry include the Missouri River, Little Femme Osage
Creek, Femme Osage Slough, and numerous small, unnamed creeks, drainages, and ponds throughout the Weldon
Spring Conservation Area. In addition, the nearby August A. Busch Memorial Conservation Area contains
more than 35 ponds and lakes; however, these ponds and lakes are in the Mississippi River drainage and
are not influenced by the guarry area.

The U.S. Fish and Wildlife Service (Frazer 1995; DOE 1998d) has identified the potential for five
federal-listed threatened or endangered species to occur in the vicinity of the guarry area: three birds
(bald eagle, peregrine falcon, and interior least tern), one fish (pallid sturgeon), and one plant
(decurrent false aster). The Fish and Wildlife Service has also identified several candidate species as
possibly occurring in the area. The Missouri Department of Conservation has identified 13 state
endangered and 19 state rare species for St. Charles County (Dickneite 1995). However, many of these
species are not expected to occur at the guarry area; some only pass through the area during migration.
For other species, suitable habitat is absent from the guarry. To date, only the bald eagle has been
observed in the vicinity of the guarry area (DOE 1998d) ; all of those birds were sighted near the
Missouri River and away from the guarry proper.

4.4 NATURE AND EXTENT OF CONTAMINATION

The nature and extent of contamination at the QROU are discussed in detail in the RI (DOE 1998d).
Contaminated media at the QROU can be generally categorized into three separate entities: (1) residual
contamination at the guarry proper, (2) the Femme Osage Slough and nearby creeks (Little Femme Osage
Creek and Femme Osage Creek), and (3) guarry groundwater north of the Femme Osage Slough. A summary of
the data collected to support the RI is presented in Table 1. Samples were also collected for each medium
of concern to delineate naturally occurring levels of chemical and radiological constituents (i.e.,
background levels) from those levels that may have resulted from site activities.

4.4.1 Soil

At the guarry proper, soil was sampled from the rims and slopes, and sediment was sampled from
wall and floor fractures and from the ramp and floor of the guarry sump. Potential contaminants
identified in soil samples from the rims and slopes included several metals, radionuclides, nitroaromatic
compounds, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). In disturbed
soil on the rim and knoll of the guarry, only selenium, silver, zinc, radium-226, thorium-230, and
uranium-238 were detected at concentrations significantly higher than background levels. In samples from
the guarry fractures, lower levels of contamination were found in the wall fractures than in floor
fractures. Radium, thorium, and uranium isotopes, and aluminum, selenium, and silver were detected at

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some fractures at concentrations exceeding background levels. Samples collected from the sump area were
primarily contaminated with radium-226, thorium-230, uranium, and low levels of PAHs.

Outside the quarry proper, surface and subsurface soil samples were collected, with a focus on the
area south of the guarry between the Katy Trail and Femme Osage Slough. The area sampled included
Vicinity Property 9, which was remediated in 1996. Low concentrations (but higher than background levels)
of uranium are sorbed onto soils located between the guarry and the slough. Lead and zinc were detected
at low levels above background in shallow soils south and east of the guarry. Low levels of nitroaromatic
compounds (i.e.. <1.7 ppm) were detected in soils to the east, west, and south of the guarry.

4.4.2 Femme Osage Slough and Creeks

Surface water and sediment samples from the upper and lower reaches of the Femme Osage Slough,
Little Femme Osage Creek, and downstream portion of Femme Osage Creek have been characterized for
radiological and chemical contamination. Contaminants identified as contaminants of potential concern
(COPCs) for surface water and sediment included several metals and uranium (see Table 1). Nitroaromatic
compounds were also identified as COPCs for surface water, but were only detected at low concentrations
in the Little Femme Osage Creek upgradient of the guarry. The source of this contamination is believed to
be runoff from the Weldon Springs Ordnance Works (WSOW) area. In general contaminant concentrations were
lower in the creek than in the slough. Plausible sources of contamination in the slough include
groundwater seepage, runoff from Vicinity Property 9 prior to remediation, and mixing with Missouri River
water. Several metals that were elevated in the creek and slough were also elevated in the Missouri
River.

Fish from Femme Osage Slough were collected and analyzed to investigate any potential impacts from
site contaminants. Species sampled from the slough included white and black crappie, largemouth bass,
sunfish, and several bottom feeders such as bigmouth buffalo, yellow bullhead, and common carp. Fish
samples were analyzed for uranium, radium, thorium, arsenic, lead, and mercury. Samples were prepared as
fillets, fish cakes, and whole body samples. Analyses indicated low-level concentrations of metals (i.e.,
lead, arsenic, and mercury) and uranium, similar to concentrations detected in the background samples
collected from Busch Lakes 33 and 37. Radium and thorium isotopes were not detected in any samples.

4.4.3 Groundwater

Contamination of groundwater underlying the guarry area has been characterized from data collected
from a network of monitoring wells. This network includes 19 wells that monitor groundwater in the
bedrock system and 26 wells that monitor groundwater in the alluvium. Four additional alluvium wells are
owned by St. Charles County (see Figure 4). Data over a 10-year period were evaluated in determining the
nature and extent of contamination. The primary contaminants in guarry groundwater north of the slough
are uranium and nitroaromatic compounds. These contaminants were likely derived from contaminated bulk
wastes that were previously disposed of in the guarry. Although other contaminants were present in guarry
bulk wastes, uranium and nitroaromatic compounds are more soluble and were leached from the bulk wastes
into the shallow groundwater.

The extent of the uranium contamination is limited to the area north of the slough. The highest
concentrations of uranium were detected in wells along the southern rim of the guarry and southward in
the alluvium near Vicinity Property 9. South of the slough, slightly elevated uranium levels with respect
to the statistically determined background value (i.e., 2.8 pCi/L) were detected at RMW-2. However, the
maximum uranium concentration detected at RMW-2 (i.e., 10 pCi/L) is within the range of concentrations
detected in the background wells. Uranium concentrations in the remaining wells south of the slough have
been in the background range.

Prior to removal of the bulk wastes from the guarry, nitroaromatic compounds were also detected
at concentrations greater than 1 Ig/L in four shallow bedrock wells and two alluvial wells located north
of the slough. Between 1996 and 1997, a 40% reduction in TNT and an 18% reduction in DNT concentrations
have been observed.

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5 SUMMARY OF SITE RISKS

Potential impacts to humans, biota, and other environmental resources that might occur at the
quarry area if no remedial action is conducted were assessed as part of the process for selecting an
appropriate remedial action. Current and future land use conditions were considered in the assessment
presented in the Baseline Risk Assessment report (DOE 1998a) prepared for the QROU. Key results of the
human health and ecological assessment are summarized in Sections 5.1 and 5.2.

5.1 HUMAN HEALTH

Potential carcinogenic risks for both radiological and chemical exposures were assessed in terms
of the increased probability that an individual would develop cancer over a lifetime. The U.S.
Environmental Protection Agency (EPA) has indicated that for known or suspected carcinogens, the
acceptable exposure levels for the general public at sites on the NPL are generally concentrations
that represent an excess upper-bound lifetime cancer risk to an individual of between 1 x 10 -6 and 1 x
10 -4 (i.e., 1 in 1,000,000 to 1 in 10,000 [EPA 1989]). This "acceptable range" is used as a point of
reference for discussing the results of the carcinogenic risk assessment for the QROU.

Potential health effects other than cancer from exposure to chemical contaminants were also
assessed. The quantitative measure of noncarcinogenic health effects is the hazard index. The EPA has
defined a hazard index of greater than 1 as the level of concern for noncarcinogenic health effects.

A recreational visitor scenario was used to project human exposures to contaminants identified in
the RI for the quarry area (DOE 1998d) on the basis of current and assumed future land uses. This
scenario is consistent with current land use at the quarry area (primarily north of the slough and the
slough itself); future land use is expected to remain similar to current use. Groundwater is used for
residential purposes at the county well field; however, monitoring data indicate that concentrations at
the county well field are consistent with background, and this is not expected to change in the future.

In this case, reasonable maximum exposure is not considered to include residential or other
scenarios that include direct, long-term consumption of localized contaminated groundwater. Because of
the localized nature of the contamination and physical constraints, such as low groundwater yields and
unsustainable production of these low yields, the surficial nature of the groundwater, and the location
of the area within the Missouri River floodplain, which makes the area susceptible to routine flooding,
such scenarios are not considered plausible.

Exposure pathways and associated risk estimates evaluated for the quarry proper and Femme Osage
Slough and nearby creeks are summarized in Table 2. Exposure pathways evaluated for the quarry proper
included external irradiation, incidental ingestion and dermal contact with soil, inhalation of air
particulates, and ingestion of surface water from the quarry pond. Exposure pathways evaluated for the
slough and creeks included ingestion of surface water, sediment, and fish; dermal contact with surface
water and sediment; and inhalation of air particulates. The recreational visitor was assumed to visit
each area for 4 hours, 20 times per year, over a period of 20 years.

The results of the risk calculations for the recreational visitor at the quarry proper and Femme
Osage Slough indicate that radiological and chemical risks are below to within the EPA's acceptable risk
range of 1 X 10 -6 to 1 x 10 -4 (EPA 1989). Hazard indices are also less than 1, which indicates that
noncarcinogenic health effects are not a concern. The estimated radiological risk is 3 x 10 -5 for the
recreational visitor exposed to contaminants at the various locations (i.e., cumulative risk from
exposure to contaminants at the quarry proper and at Femme Osage Slough and creeks); this estimate
incorporates multiple contaminants, multiple media, and multiple pathways. The estimated chemical
carcinogenic risk and hazard index for this recreational visitor are 4 x 10 -6 and 0.05, respectively.

The estimated risks are within the acceptable risk range and do not indicate the need for further
remediation of the quarry proper, the Femme Osage Slough and nearby creeks, or the quarry groundwater
north of the Femme Osage Slough.

The available hydrological and geochemical information, as well as long-term environmental
monitoring data, support the conclusion that site contaminants will not measurably affect the Missouri
River alluvial aquifer. However, given the reliance on natural systems to preclude potential significant
impacts to the aquifer, alternatives addressing groundwater remediation were evaluated in the FS (DOE
1998b).

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5.2
ECOLOGICAL ASSESSMENT
Femme Osage Slough and Little Femme Osage Creek are the principal habitats at the QROU where biota
could be exposed to quarry-related contaminants. A screening level assessment employing very conservative
exposure scenarios was conducted for these habitats. This assessment identified current levels of
aluminum, barium, manganese, and uranium in the surface water of Femme Osage Slough and Little Femme
Osage Creek as posing a potential risk to aguatic biota using these habitats. Risk estimates or quotients
for these contaminants were greater than 1, indicating the potential for risk and a need for further
ecological evaluations of the aquatic habitats in the slough and creek. These ecological evaluations were
conducted, and the results are discussed below. For other contaminants in surface water at the quarry
area, no or low risks were identified. Arsenic, cadmium, lead, manganese, mercury, nickel, and zinc are
present in sediments at concentrations estimated to result in low risk to aquatic biota. No risks from
nitroaromatic compounds were indicated in either surface water or sediment. Modeling results indicated no
risks to modeled terrestrial wildlife receptors foraging in Femme Osage Slough or drinking from Little
Femme Osage Creek.

TABLE 2 Summary of Human Health Risk Estimates for the Quarry Area
Quarry proper
Soil
External irradiation
Ingestion
Dermal
Inhalation
Fractures b
External irradiation
Ingestion
Inhalation
Femme Osage Slough c
Surface water
Ingestion
Dermal
Sediment
Ingestion
Dermal
Inhalation
Fish
Ingestion
Total d,e,f
Overall carcinogenic risk g
a NA = not applicable.
b Dermal contact with soils in the fractures is assumed to be unlikely.
c Estimates for Femme Osage Slough are representative of those for Little Femme Osage and
Femme Osage Creeks.
d These totals represent risks and the hazard index for the multiple pathways exposure
scenario, which projects a recreational visitor who is exposed to contaminants present at the
quarry area (including at the quarry proper and Femme Osage Slough).
e Ingestion of groundwater is unlikely because there is no access for a recreational visitor to
the quarry groundwater. However, calculations were performed for potential risk to a
hypothetical resident from ingestion of and dermal contact with groundwater (see
Section 5.2.3 of the BRA [DOE 1998a)) for informational purposes only.
f External irradiation for quarry proper soil and fractures was not summed because it is not
appropriate to do so; the higher of the two risks was used to calculate the total.
g The sum of chemical and radiological carcinogenic risks rounded to one significant figure.
Because screening risk estimates for several metals indicated potential risks, as discussed above,
further ecological evaluations or surveys of aguatic and terrestrial biota were conducted at the guarry
area to further evaluate actual impacts. The survey results indicate that the existing aguatic and
terrestrial communities consist of species that would be expected to occur in the area. No impacts to
abundance or species diversity of aguatic invertebrates were detected. Internal and external examinations
of small mammals collected from the site showed no abnormalities that might indicate adverse effects from
exposure to site contaminants. Analyses of tissue from fish and small mammals indicated uranium
concentrations within the range reported in the literature for North America for which no adverse effects
have been observed. Concentrations of radionuclides in the tissues of small mammals collected from the

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quarry area were comparable to levels detected in specimens from reference sites.

In summary, the current levels of contamination in surface water and sediments from
Femme Osage Slough and Little Femme Osage Creek do not appear to be affecting ecological
resources at these habitats and do not pose a future risk to biota at the site. This conclusion is
supported by the absence of any observable adverse effects to aguatic or terrestrial biota, the generally
low levels of potential risk estimated for aguatic biota, and the lack of risks estimated for terrestrial
biota. Thus, remediation of these habitats is not indicated on the basis of potential ecological
concerns.
6 DESCRIPTION OF REMEDIAL ALTERNATIVES

Six preliminary alternatives for addressing groundwater contamination were assembled from
combinations of technologies and associated management strategies that were retained following, a
screening and evaluation process. Potential remedial action alternatives were screened to eliminate those
alternatives determined too difficult to implement on the basis of unproven technologies, those
determined not sufficient to remediate the site within a reasonable time period, or those determined to
have limited application for specific contaminant or site conditions. Details of these evaluations are
presented in the Feasibility Study report (DOE 1998b) prepared for the QROU. The three final alternatives
retained for detailed analysis are described in Sections 6.1 to 6.3.

6.1 ALTERNATIVE 1: NO ACTION

Under Alternative 1, no further action would be taken at the QROU, CERCLA requires consideration
of a "No Action" alternative. No containment, removal, treatment, or other mitigative measures would be
implemented. This alternative does not include groundwater monitoring or any active or passive
institutional controls (e.g., physical barriers, deed restrictions). Under this alternative, it was
assumed that all existing activities, including monitoring by DOE, would be discontinued. Existing land
use and natural conditions and processes are expected to continue and provide continued protection to the
downgradient well field. However, this alternative does not provide for the collection of data that would
verify the continued protectiveness of future conditions.

No cost is associated with the performance of this alternative. No net present worth, capital
costs, or annual operation and maintenance (O&M) costs are associated because no activities would be
undertaken.

6.2 ALTERNATIVE 2: MONITORING WITH NO ACTIVE REMEDIATION

Under Alternative 2, long-term monitoring of groundwater in the quarry area would be performed;
results would be evaluated at five-year review periods as required by CERCLA. Contaminant concentrations
in the groundwater north of Femme Osage Slough are expected to decrease with time as a result of (1)
adsorption of uranium onto the fine-grained aquifer materials and (2) precipitation., in the area of the
slough where decaying organic matter maintains a reducing condition. These reducing conditions convert
uranium to the +4 state, thus forming uranium dioxide UO 2), which is highly insoluble. Continued
migration of very small concentrations of uranium in the groundwater to the St. Charles County well field
is probable; however, concentrations greater than the background range have not been detected. In
addition, concentrations are not expected to increase because of the removal of the bulk waste source
materials. Monitoring data collected for the past 10 years from wells south of the slough and at the
production wells have indicated uranium concentrations to be consistent with the statistically derived
background level of approximately 2.8 pCi/L. Contaminated groundwater migrating south of the slough would
be significantly diluted with uncontaminated water from the Missouri River. Groundwater originating from
the quarry area contributes less than 1% of the groundwater available to the production wells.
Infiltration from rainwater, runoff, and sporadic local flooding, could also dilute the groundwater at
the quarry area north of the slough (DOE 1998d).

Groundwater monitoring would be conducted in the existing well network, as appropriate. This
network would be expanded or reduced, depending on the results of future efforts to optimize the network
for long-term monitoring. Optimization efforts would evaluate contaminant distribution, groundwater flow
paths, and geochemical constraints that govern contaminant fate and transport in the aquifer system. The
network of wells to be monitored as part of this alternative would be formulated from the existing
network to include monitoring of the area west of RMW-2. The exact monitoring network and details
regarding frequency of sampling and parameters analyzed would be identified in subsequent remedial
design/remedial action (RD/RA) reports for the QROU.

Under Alternative 2, the monitoring response would continue in perpetuity or until judged
unnecessary based on a review of the data. A judgment to discontinue monitoring would be developed in
consultation with the EPA and the Missouri Department of Natural Resources. Because contamination would

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remain on-site above levels that allow for unlimited use and unrestricted exposure, reviews would be
conducted at least every five years to ensure that the remedy continued to provide adequate protection of
human health and the environment.

Costs for this alternative would be associated with performing periodic monitoring of an optimized
monitoring network to provide data for verifying that conditions in the guarry area and the well field
remain protective of human health and the environment. Routine sampling and analysis of uranium and
nitroaromatic compound concentrations would be performed, as well as data collection to verify the
continued effects of natural processes on contaminant concentrations within the area.

The annual O&M cost for the monitoring effort is estimated to be no greater than $0.6 million.
This estimate is an upper bound because the sampling, frequency and number of wells assumed were based on
the current network and frequency of sampling. The final monitoring network is expected to be smaller and
would be sampled at a lower frequency. The capital cost for this alternative is estimated to be
approximately $0.15 million for the construction of up to seven additional groundwater monitoring wells.

6.3 ALTERNATIVE 6: GROUNDWATER REMOVAL AT SELECTED AREAS, WITH ON-SITE TREATMENT

Under Alternative 6, an interceptor trench would be installed north of the Femme Osage Slough in a
selected area bounded by and encompassing monitoring wells MW-1014 and MW-1016 (approximately 340 m
[1,100 ft]). This trench would be installed in the unconsolidated materials to the top of bedrock. The
purpose of the trench would be to create a high-permeability channel through the native soil so that more
groundwater could be recovered. Extracted groundwater would be treated, as necessary, to meet discharge
limits.

Groundwater modeling using, analytical methods indicates that the effect of the extraction system
may reduce the mass of uranium within the alluvial aquifer by 8 to 10% over a two-year operating period
(see Figure 5). This constitutes a relatively small reduction and does not provide a measurable increase
in protectiveness over the foreseeable future.

The capital cost is estimated to be between $1 and $2 million for construction of the interceptor
trench. The O&M costs for a two-year testing period are estimated to be between $1 and $2 million. The
O&M costs are primarily for treatment of the extracted groundwater (which ranges from $0.4 to $0.5
million per year), if treatment is necessary to meet discharge limits.

The costs associated with the long-term monitoring portion of this alternative would be identical
to those discussed in Section 6.2. The monitoring approach for this alternative would not be
significantly different from that designed for Alternative 2: Monitoring With No Active Remediation.

7 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES

A comparison of the final remedial action alternatives for the QROU was conducted by categorizing
the nine evaluation criteria of the National Oil and Hazardous Substances Pollution Contingency Plan
(NCP) (EPA 1990) into the following three groups: threshold criteria, primary balancing criteria, and
modifying criteria.

The threshold category contains the two criteria that each alternative must meet in order to be
eligible for selection:

• Overall protection of human health and the environment; and
• Compliance with applicable or relevant and appropriate requirements (ARARs), unless a waiver
condition applies.

These threshold criteria ensure that the remedial action selected will be protective of human health and
the environment, and that the action will either attain the ARARs identified at the time of the ROD or
provide grounds for obtaining a waiver.

The primary balancing category contains the five criteria that are used to assess the relative
advantages and disadvantages of each alternative to determine which is most appropriate:

• Long-term effectiveness and permanence;
• Reduction of toxicity, mobility, or volume through treatment;
• Short-term effectiveness;
• Implementability; and
Cost.

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The first two criteria consider the preference for treatment as a principal element and the bias against
off-site land disposal of untreated waste. Cost-effectiveness is determined by evaluating the following
three of the five balancing criteria: long-term effectiveness and permanence; reduction of toxicity,
mobility, or, volume through treatment; and short-term effectiveness. Overall effectiveness is then
compared with cost to ensure that the costs are proportional to the overall effectiveness of a remedial
action.

       The modifying,  category consists of two criteria that are considered in remedy selection and that
are addressed in the responsiveness summary (see Appendix A) of this ROD:

       •      State acceptance and
       •      Community acceptance.

Table 3 summarizes the analysis performed for the first seven criteria.

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                                                                                                 TABIiE 3 Comparative Analysis  of Alternatives
Evaluation Criteria
                                    Alternative  1:
                                No Action
              Alternative 2:
Monitoring with No Active Remediation
                                                                                Would provide protection similar to
                                                                                Alternatives 1 and 6.  Monitoring data would be
                                                                                collected to verify that conditions continue to be
                                                                                protective of human health and the environment
                                                                    Would  provide  protection similar to Alternatives 1
                                                                    alternative  would remove and treat a percentage of
                                                                    contaminated volume  of groundwater north the sloug]
                                                                    would  lead to  a slight reduction in the amount of i
                                                                    could  potentially migrate south of the slough towa.
                                                                    St.  Charles  County well field.  However, the additi<
                                                                    reduction would not  result in greater protectivene:
                                                                    Alternatives 1 and 2 .  This alternative would also i
Compliance with ARARs
                                Future  conditions  are  expected to be at
                                least similar  to current,  if not  better.
                                Continued  slow decreases  in
                                contaminant  concentrations are
                                expected as  a  result  of  source removal
                                and  naturally  occurring  processes.

                                No immediate reduction of toxicity.
                                mobility,  or volume because  no
                                treatment  would be performed
                                However, slow  reduction  of
                                contaminant  concentrations is expected
                                as a result  of natural processes
Similar to Alternative 1.  In addition, data would
be available to verify that conditions at the guarry
area continue to be protective of human health
and the environment.
Would be similar if not slightly better than that i
and 2 because of the reduction in the amount of ur<
could potentially migrate south of the Femmie Osagi
toward the St. Charles County well field. However,
slight reduction would not result in greater prote<
Alternatives 1 and 2.

Would satis fy the statutory preference for treatme]
element of remediation and would provide reduction
toxicity, mobility, or volume of a small portion o
contaminated groundwater through treatment. The ef
extraction system may reduce the mass of uranium w.
alluvial aguifer by 8 to 10 % relative to the basel.
                                No  potential  impacts  on  workers  or  the
                                environment,  because  no  activities
                                would  be  undertaken.
Expected to be low, with less than one case of
occupational inj ury and no occupational fatalities
during proposed monitoring well construction.
Any potential short-term environmental impacts
would be limited to the immediate vicinity of the
guarry area, and mitigative measures would be
applied to minimize potential impacts
Similar to Alternative 2.  Expected to be low, with
cases of occupational injury and no occupational f<
proposed construction activities.
Implementability
                                                                                Few implementability concerns because of the
                                                                                limited actions taken.  Monitoring would be
                                                                                performed with the use  of readily available resources.
                                                                    Few implementability concerns.  Groundwater extract.
                                                                    treatment  are  we11-developed technologies.  Further
                                                                    of  these technologies would not be reguired
                                                                                Is  cost-effective because it would provide overall
                                                                                protection of human health and the environment
                                                                                for a reasonable cost.  Costs are associated with
                                                                                continuing the existing environmental monitoring
                                                                                program,  potential construction and operation of
                                                                                additional monitoring wells, and conducting a
                                                                                performance review at least every five years.
                                                                                Could be  implemented with existing resources
                                                                                and maintained at a relatively low cost.
                                                                    Not  cost-effective  compared with Alternatives 1 an
                                                                    the  expenditure  of  funds  for removal of a minimal
                                                                    contamination would not  be cost effective.

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8 SEIiECTED ACTION

DOE's selected action for the QROU is Alternative 2: Long-Term Monitoring. This decision was based
on the reguirements of CERCLA, the detailed analysis of alternatives using the nine NCP criteria, and
input received during the public comment period. The selected action will ensure continued protection of
groundwater resources within the St. Charles County well field over the long term.

On the basis of the exposure assessment discussed in Section 5, no further remediation is
necessary to protect human health and the environment. Because source removal was accomplished under a
previous action, no new migration of contaminants to the groundwater system should occur. However,
because of the presence of significant levels of uranium in guarry groundwater north of the slough, which
is in close proximity to the St. Charles County well field, it was considered prudent to continue to
evaluate the need for and effectiveness of reducing or removing the uranium from guarry groundwater and
to confirm the behavior of natural processes occurring at the guarry area. These natural processes are
expected to mitigate any potential migration of the uranium toward the well field.

The FS evaluations (DOE 1998b) indicate that available engineering technologies could
achieve only a very small and slow reduction of the uranium in guarry groundwater at high costs without
achieving increased protection. Accordingly, the selected action for the QROU has the following
components that the DOE will implement:

1. A long-term groundwater monitoring strategy will be implemented to confirm expectations that
significant impacts to the Missouri River alluvial aguifer will not occur and that conditions at
the guarry area will continue to be protective of human health and the environment.

2. Institutional controls will be necessary to prevent uses inconsistent with recreational use, or
uses that would adversely affect contaminant migration. DOE will continue to coordinate with the
Missouri Department of Conservation and the Missouri Department of Natural Resources-Parks to
establish a written agreement, such as a license agreement, memorandum of understanding, or deed
attachment, outlining and agreeing to the terms of the institutional controls. Terms may include
limiting access to groundwater north of the slough for the following uses: irrigation,
consumption, or as a surface water source. The terms of the agreement will be evaluated at each
five-year review, at which time changes or deletions to the terms would be made, as appropriate.
The Well Field Contingency Plan (DOE 1998e) provides for ongoing availability of a safe water
supply.

3. The guarry will be restored through backfilling with soil to reduce fall hazards, stabilize the
highwalls, eliminate ponding of surface water, and minimize infiltration through the inner
guarry area to the groundwater.

In addition, further data collection will be performed by DOE to support ongoing evaluations regarding
the need for and effectiveness of groundwater remediation. This activity will include a pilot study
involving the construction of a trench. Soil sampling at the guarry proper will also be conducted to
delineate the full extent of radiological contamination at the northeast slope and ditch area within the
guarry proper.

8.1 QUARRY GROUNDWATER MONITORING

The selected action addresses groundwater contamination by monitoring to provide data for
verifying that conditions in the guarry area and the well field remain protective of human health and
the environment. These data will also indicate the continued effects of natural processes on contaminant
concentrations within the area. Routine sampling and analysis of uranium and nitraromatic compound
concentrations in groundwater will be performed. It is anticipated that existing patterns of contaminant
migration will persist over time. However, if long-term monitoring identifies a trend or change resulting
in increased levels of contaminants south of the slough approaching a trigger level of 30 pCi/L, the
potential for significant impacts to the well field and the alluvial aguifer will be reevaluated. This
reevaluation will include a risk evaluation consistent with CERCLA, identification of ARARs, and a
determination of need of any groundwater remediation. The trigger level of 30 pCi/L is sufficiently
above the established natural variation (nondetect to 16 pCi/L) of uranium in the aguifer to be a useful
indicator of currently unanticipated migration from the site. In addition, this level is considered
protective under hypothetical exposure assessments and is consistent with the standard in Title 40, Part
192.02, of the Code of Federal Regulations (40 CFR 192.02).

Remedial design activities will define an optimal monitoring network, identify appropriate
freguencies and parameters for monitoring, and provide for interpretations of the results that will
determine the criteria for continuation or ultimate conclusion of monitoring activities as part of the

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QROU ROD. The decision to continue or conclude monitoring activities will be made at the initial
five-year review period and during each subseguent five-year review, as appropriate.

To optimize logistics, monitoring activities stipulated in this ROD may be correlated with those
for the Well Field Contingency Plan (DOE 1998e) . The option to combine these two monitoring reguirements
will also be evaluated before initiation of monitoring activities for this ROD.

A network of wells to be monitored as part of the action in this ROD will be designed to provide
for long-term monitoring of groundwater, including the groundwater in the area west of RMW-2. The final
design of the optimized network will be presented in the RD/RA reports. Existing wells that are likely to
be included in the post-ROD monitoring network are shown in Figure 6. These wells were selected on the
basis of the following preliminary selection criteria; distribution of contamination; the hydrological,
geochemical, and contaminant fate and transport models; and the location and screening interval of each
well. This preliminary network includes existing wells located north of the slough that would monitor
changes in the horizontal and vertical distribution of contaminants. On the basis of the hydrological
conceptual model depicting groundwater flow from the north of the slough to the south of the slough,
existing wells that monitor groundwater along the base of the alluvium could also be selected and
included in the monitoring network. The existing RMW wells will also be included to monitor the portion
of the alluvial aguifer that supplies the well field.

8.2 QUARRY PROPER RESTORATION

The current restoration design plan includes backfilling the guarry with soil to reduce fall
hazards, to stabilize the north and south highwalls, and to eliminate ponding of surface water. The floor
and benches of the guarry would be covered by the backfill. The backfill would reduce the potential for
mobilization of any potential residual contaminants into the groundwater. Restoration would be designed
to force groundwater flow around the inner guarry area by backfilling with a relatively low permeability
material. Infiltration would be reduced through the installation of a low permeability cover. More
definitive specifications for the backfill would be included in subseguent RD/RA reports.

The design would also effectively prevent any potential residual contaminants in the cracks and
fissures (i.e., flakes of yellowcake) from mobilizing to the surface through erosion and/or freeze/thaw
action, thus reducing the already low potential risks associated with external gamma radiation and
ingestion. Mobilization of contaminants into the groundwater would not be likely because the benches are
in the unsaturated portions of the bedrock, and infiltration of precipitation would be prevented by the
final grading designed to promote sheetflow and to return the area to conditions that are as close as
possible to natural contours. Dismantlement of facilities utilized during bulk waste removal activities
would also be performed during this time. Haul road restoration is expected to be minimal. Restoration
activities are currently planned for the fall of 1999.

8.3 WELL FIELD CONTINGENCY PLAN

The Well Field Contingency Plan (DOE 1998e) was developed by DOE to ensure the continued
availability of a safe and reliable public water supply for St. Charles County during bulk waste removal
activities. This plan provides for groundwater monitoring to detect any contaminant migration beyond the
presently known boundaries, defines action levels, and identifies response actions that could be taken in
the unlikely event of elevated contaminant levels at the well field. To date, no impacts to the well
field have been observed, and none are expected in the future. The Well Field Contingency Plan (DOE
1998e) also discusses the preparation of hydrogeological characterization plans to support development of
criteria for the design and construction of a replacement well field in the unlikely event that should
prove necessary.

In developing the approach contained in the Well Field Contingency Plan (DOE 1998e), data from
south of the slough were evaluated to identify trends or changes indicative of impacts to the Missouri
River alluvium from the guarry. The level adapted as a trigger for reevaluation of the conditions in the
Missouri River alluvium has been established at 30 pCi/L in a RMW-series well. Should such a level occur,
DOE would initiate a more rigorous monitoring effort to investigate the cause and source of this impact.
On the basis of conservative modeling performed in this portion of the aguifer, impacts to the production
wells would not occur within the 100-year modeling period if levels of 30 pCi/L were indicated in a
RMW-series well.

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8.4 ADDITIONAL DATA NEEDS

DOE will conduct further data collection for two purposes: (1) to gather data to continue the
evaluation to determine the effectiveness of groundwater remediation and (2) to define the extent of
radiological soil contamination at the northeast slope and ditch area at the guarry proper.

8.4.1 Field Test

Given the presence of significant levels of uranium in guarry groundwater north of the slough,
which is in close proximity to the St. Charles County well field, and the reliance on the natural systems
to limit potential exposure, evaluation to determine the effectiveness of groundwater remediation will be
continued, and field data related to uranium recovery in guarry groundwater will be collected. This field
test, conducted to verify predictive models that were presented in the FS (DOE 1998b) relating to
groundwater remediation, will be essentially a scaled down version of the approach evaluated under
Alternative 6. Alternative 6 is considered to be the most effective approach to groundwater extraction.
Groundwater removal will be facilitated with the use of a trench sufficiently large to intercept a
representative cross section of alluvial material and optimally located to extract groundwater in areas
with high uranium contamination. The system will be evaluated and monitored for up to two years, and the
data collected will be compared with a set of predetermined performance goals. These performance goals
will be identified on the basis of the predictive model shown in Figure 5. This predictive model
indicates that this trench could only reduce the uranium mass by no more than 10% for the two-year
operational period. The evaluations in the FS also indicate that the time frame for remediation of
uranium-contaminated groundwater north of the slough would be greater than 100 years. If performance of
the trench system exceeds the performance goals, the need for and effectiveness of groundwater
remediation will be reevaluated. Conversely, if the performance of the removal system is less effective
or within the specified performance goals, further evaluation of groundwater will not be necessary. The
determination of the performance goals for the removal system and details pertaining to structure, size,
location, and sampling parameters will be presented in the RD/RA work plan developed in consultation with
the EPA and the Missouri Department of Natural Resources.

The determination of the effectiveness of active groundwater remediation will include
consideration of factors consistent with those presented in Office of Solid Waste and Emergency Response
(OSWER) Directive 9234.2-25, "Guidance for Evaluating the Technical Impracticability of Groundwater
Restoration."

Field tests will be conducted in the marginal alluvium north of the slough to provide
site-specific estimates for parameters (i.e., hydraulic conductivity, distribution coefficients, and
oxidation potential) that demonstrate the engineering feasibility and reliability of groundwater
remediation in the area of uranium impact. These tests will also ascertain the variability of these
parameters because of the heterogeneity of the aguifer materials. This information will be used to
supplement the present hydrological, geochemical, and contaminant fate and transport models for the
guarry area north of the slough for evaluating the need for and effectiveness of groundwater remediation.

Data have been previously compiled that indicate the distribution of uranium and fate and
transport mechanisms in the aguifer system both north and south of the slough (see Chapter 4). These
data indicate that the hydrogeologic and geochemical systems in the guarry area are complex and result in
a system with a limited capability of effectively remediating groundwater.

8.4.2 Soil Sampling at the Northeast Slope and Ditch Area

At the guarry proper, additional sampling is planned at the northeast slope and the ditch area
near the transfer station (see Figure 7). Only a few samples were collected from these two areas during
the RI phase because access was difficult. The samples collected indicate the presence of radiological
contamination; however, additional samples need to be collected to sufficiently define the extent of
contamination. Risk calculations will be performed consistent with the approach presented in the Baseline
Risk Assessment report (DOE 1998a), to include these additional data points. If response action is
necessary, the cleanup criteria for radionuclides presented in the chemical plant ROD (DOE 1993) will be
applied. This response action would involve removal of contaminated soil from the northeast slope and the
ditch area. Finally, DOE intends for the extent of any soil removal at the northeast slope to be
protective of human health and the environment, but not to include the relocation of State Route 94.

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9 STATUTORY DETERMINATIONS

In accordance with the statutory requirements of Section 121 of CERCLA, as amended, remedial
actions shall be selected that:

• Are protective of human health and the environment.
Comply with ARARs;
• Are cost-effective; and
• Utilize permanent solutions and alternative treatment technologies to the maximum extent
practicable.

The selected action is discussed below in relation to how it fulfills the requirements. In
addition, CERCLA Section 121's preference for treatment as a principal element is discussed.

9.1 PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT

The selected action will be protective of human health and the environment. Because source removal
has been accomplished under a previous action, no new migration of contaminants to the groundwater system
should occur. Long-term monitoring will be used to confirm expectations that uranium located between the
quarry and the Femme Osage Slough will not significantly affect the Missouri River alluvial aquifer or
the St. Charles County well field.

9.2 COMPLIANCE WITH APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS

A comprehensive list of potential chemical- and action-specific ARARs and to-be considered
requirements (TBCs) for the selected action are presented in Appendix A of the FS (DOE 1998b). The listed
ARARs were identified according to the NCP and procedures outlined in the most recent EPA guidance. The
selected action would comply with the following ARARs, as required by Section 121(d) of CERCLA.

9.2.1 Chemical-Specific ARARs

Chemical ARARs set concentration limits or ranges in various environmental media for specific
hazardous substances, pollutants, or contaminants of concern. Missouri water quality standards in
groundwater for nitrobenzene (17 Ig/L),2,4-dinitrotoluene (2,4-DNT) (0.11 I/L) , and 1,3-dinitrobenzene
(1,3-DNB)(l.Olg/L) are chemical-specific ARARs for quarry groundwater. The limit for 1,3-DNB is a health
advisory level that is used to establish a groundwater cleanup criterion until additional data become
available to support alternative criteria or until other standards are established.

Currently, only a few data points marginally exceed the Missouri water quality standards for
groundwater. It is projected that these ARARs are likely to be met within a reasonable period of time
(i.e., several years) after implementation of the selected action for this ROD (see Section 8).
Appropriate action will be taken either to meet or obtain a waiver of the ARARs in the event the selected
action fails to meet them. However, at this time it is expected that the selected action will meet ARARs.

The FS (DOE 1998b) and the PP (DOE 1998c) considered whether the 40 CFR 192.02 standard for
uranium is a potential ARAR for this action. The quarry groundwater north of the slough is impacted;
however, it is not considered to be a usable groundwater source. Conversely, the Missouri River alluvium
south of the slough, which includes the well field, is currently not impacted and is presently being used
as a potable water source. Because quarry groundwater north of the slough is not a usable source, 40 CFR
192.02 is not considered an ARAR for that groundwater. However, 40 CFR 192.02 would likely be an ARAR
for any remedial action considered for the usable groundwater source south of the slough in the unlikely
event of contaminant migration from north of the slough. While 40 CFR 192.02 currently appears to be the
only groundwater standard that would be considered as a potential ARAR for any future remedial action to
address contamination of usable groundwater, other standards in place at the time of the future action
would also be considered in the ARAR analysis.

9.2.2 Chemical-Specific TBCs

The proposed maximum contaminant level (MCL) of 20 Ig/L for uranium identified in the Proposed
National Primary Drinking Water Regulations (Volume 56, page 33050, of the Federal Register [56 FR 33050]
[July 18, 1991]) is treated as a TBC because it does, not meet the requirements to be considered an ARAR
(20 Ig/L for uranium corresponds to 13.6 pCi/L for the distribution of uranium isotopes present in
groundwater at the quarry area.). This standard is not an ARAR because it is a proposed regulation and is
not promulgated. Section 121 (d) of CERCLA does not require compliance with TBCs. Although TBC, the
proposed MCL is not useful for evaluating groundwater impact at this site, because it falls within the
range of natural background concentrations of uranium in groundwater in this area. A more appropriate

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level of 30 pCi/L has been selected as a trigger level for reevaluating the decisions made regarding the
QROU. The trigger level of 30 pCi/L total uranium is considered to be sufficiently above the natural
variation of uranium in the aguifer to be indicative of site impact and is a level considered to be
protective under hypothetical exposure assessment.

9.2.3 Action-Specific ARARs

Action-specific ARARs are standards that restrict or control specific remedial activities related
to the management of hazardous substances or pollutants for a variety of media. These reguirements are
triggered by a particular activity, not by specific chemicals or the location of the activity. Several
action-specific ARARs may exist for any specific action. These action-specific ARARs do not in themselves
determine the appropriate remedial alternative, but indicate performance levels to be achieved for the
activities performed under the selected action. On-site actions must comply, with all substantive
provisions of an ARAR, but not with related administrative and procedural reguirements (e.g., filing
reports or obtaining a permit). The term "on-site" includes the areal extent of contamination and all
suitable areas in very close proximity to the contamination necessary to implement the response action.
No permit applications would be necessary for any on-site activities. The selected action would comply
with all pertinent action-specific ARARs, which are listed in Appendix A of the FS (DOE 1998b) and
summarized below.

All activities that may result in the disturbance of media contaminated with radionuclides (e.g.,
well construction) would conform to the operational standards for uranium and thorium mill tailings
promulgated by the EPA (Title 40, Part 192, Subparts D and E of the Code of Federal Regulations [40 CFR
192, Subparts D and E]) that establish certain annual dose limitations for exposure to radiation.
Although not applicable to Weldon Spring site activities, these reguirements are relevant and appropriate
to these activities because they specifically address exposures of workers to radiation associated with
the same radionuclides during remediation activities. Similarly, radiation exposure limits for the public
established in Missouri Radiation Regulations, Protection Against Ionizing Radiation (Title 19, Part
20-10.040, et al., of the Code of State Regulations [19 CSR 20-10.040, et al. ] ) , as they apply to
nonoccupational exposures, are ARARs with which the selected action will comply.

A National Pollutant Discharge Elimination System (NPDES) permit for construction or
operation (including discharge) of a water treatment facility is not reguired under Section 121 (e)(1) of
CERCLA codified at 40 CFR 300.400 (e)(1). Use of an existing NPDES permitted facility is an option for
groundwater treatment. Discharge contaminant concentrations will be consistent with those of the existing
facility.

In addition, any release of radionuclides to the ambient air during soil excavation activities
will comply with the limitations set forth in the EPA's National Emission Standards for Hazardous Air
Pollutants (40 CFR 61, Subpart H). Similarly, the release of particulate matter during other
earth-disturbing activities must comply with Missouri Air Pollution Control Regulations (10 CSR 10-5.180
and 10-6.170). Missouri reguirements for well construction would be an ARAR for any newly installed wells
or for the plugging of wells under the selected action (10 CSR 23-4.050).

Appendix A of the FS (DOE 1998b) also lists several regulations that set occupational exposure
limits for activities involving media contaminated with radionuclides, including the Missouri Radiation
Regulations, Protection Against Ionizing Radiation (19 CSR 20-10.040 et al.); Occupational Safety and
Health Administration (OSHA) Occupational Safety and Health and Environmental Controls (29 CFR 1910,
Subpart G); and DOE Occupational Radiation Protection (10 CFR 835). These regulations are not ARARs
because they are not environmental or siting regulations; however, as employee protection regulations,
these reguirements must be complied with by employees working with contaminated media or in contaminated
areas.

DOE Order 5400.5, "Radiation Protection of the Public and the Environment," has been established
as a TBC. Because DOE Orders are not promulgated regulations, they are not ARARs but are considered as
TBCs. The selected action will comply with all DOE Orders.

9. 3 COST-EFFECTIVENESS

The selected action would be cost-effective because it provides overall protection of human health
and the environment at a reasonable cost. Costs are associated primarily with activities associated with
long-term monitoring of groundwater (see Section 6.2).

The annual O&M cost for long-term monitoring is estimated to be no greater than $0.6 million. The
capital cost is estimated to be approximately $0.15 million for potential construction of up to seven
additional monitoring wells. Costs associated with the field tests and additional soil sampling would be

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identified in the RD/RA work plan. Preliminary estimates indicate that the cost for the additional field
tests and additional soil sampling at the quarry proper would be approximately $0.4 million. Costs for
construction of a trench are estimated to be between $1 and $2 million. The O&M costs for a two-year
testing period are estimated to be between $1 and $2 million. The annual O&M costs would be primarily for
treatment of extracted groundwater (which ranges from $0.4 to $0.5 million per year), if treatment is
necessary to meet discharge limits.

9.4 UTILIZATION OF PERMANENT SOLUTIONS AND ALTERNATIVE TREATMENT TECHNOLOGIES TO THE MAXIMUM EXTENT
PRACTICABLE

The selected action does not involve alternative treatment technologies, but it is expected to
provide permanent protectiveness.

9.5 PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT

This remedy does not satisfy the statutory preference for treatment as a principal element. The
selected action involves long-term monitoring. Treatment was not included because it was not a necessary
element in achieving protectiveness.

9.6 IRREVERSIBLE AND IRRETRIEVABLE COMMITMENT OF RESOURCES

The implementation of the selected action would not result in permanent commitment of land at the
guarry area. Current and future land use at the guarry area would not have to change as a result of the
implementation of this action.

9.7 SIGNIFICANT CHANGES

The selected action differs from that of the preferred alternative presented in the Proposed Plan
(DOE 1998c) in that it does not include the construction of a trench. The selected action calls for
long-term monitoring to ensure protectiveness of human health and the environment. However, as part of
additional sampling activities to be conducted by DOE, a pilot-scale study would be conducted involving
construction of a trench to collect data that would support ongoing evaluations regarding the need for
and effectiveness of groundwater remediation (see Section 8). This decision was reached after further
discussions with the EPA and the Missouri Department of Natural Resources and in consideration of the
overall concern for the effectiveness of the removal system. This concern was also expressed by the
Weldon Spring Citizens Commission (WSCC).

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10 REFERENCES

Berkeley Geosciences Associates. 1984, Characterization and Assessment for the Weldon Spring Quarry
Low-Level Radioactive Waste Storage Site, prepared by Berkeley Geosciences Associates, Berkeley, Calif.,
for Oak Ridge National Laboratory. Oak Ridge. Tenn., Sept.

Dickneite, D.F., 1995, letter from Dickneite (Environmental Administrator, Missouri Department of
Conservation, Jefferson City, Mo.) to S. McCracken (Project Manager, Weldon Spring Site) with enclosure,
Oct. 19.

DOE: see U.S. Department of Energy.

EPA: see U.S. Environmental Protection Agency.

Frazer, G.D., 1995, letter from Frazer (Field Supervisor, U.S. Fish and Wildlife Service, Columbia Field
Office, Columbia, Mo.) to S.H. McCracken (U.S. Department of Energy, Weldon Spring Site Remedial Action
Project, St. Charles, Mo.), May 12.

U.S. Department of Energy, 1990, Record of Decision for the Management of the Bulk Wastes at the Weldon
Spring Quarry, Rev. 0, DOE/OR/21548-317, St. Charles, Mo. Sept.

U.S. Department of Energy, 1993, Record of Decision for Remedial Action at the Chemical Plant Area of the
Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-376, prepared by Argonne National Laboratory,
Argonne, III., for U.S. Department of Energy. Oak Ridge Operations Office, Weldon Spring Site Remedial
Action Project, Weldon Spring, Mo., Sept.

U.S. Department of Energy, 1998a. Baseline Risk Assessment for the Quarry Residuals Operable Unit of the
Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-594, prepared by Argonne National Laboratory,
Argonne, III., for U.S. Department of Energy, Oak Ridge Operations Office, Weldon Spring Site Remedial
Action Project, Weldon Spring, Mo., Feb.

U.S. Department of Energy, 1998b, Feasibility Study for Remedial Action for the Quarry Residuals Operable
Unit at the Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-595, prepared by Argonne National
Laboratory, Argonne, III., for U.S. Department of Energy, Oak Ridge Operations Office, Weldon Spring Site
Remedial Action Project. Weldon Spring, Mo., March.

U.S. Department of Energy, 1998c, Proposed Plan for Remedial Action at the Quarry Residuals Operable Unit
of the Weldon Spring Site, prepared by Argonne National Laboratory, Argonne, III., for U.S. Department of
Energy, Oak Ridge Operations Office, Weldon Spring Site Remedial Action Project, Weldon Spring. Mo.,
March.

U.S. Department of Energy, 1998d, Remedial Investigation for the Quarry Residuals Operable Unit of the
Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-587, prepared by MK-Ferguson Company and Jacobs
Engineering Group, Weldon Spring, Mo., for U.S. Department of Energy. Oak Ridge Operations Office, Weldon
Spring Site Remedial Action Project, Weldon Spring, Mo., Feb.

U.S. Department of Energy, 1998e, Well Field Contingency Plan, Draft, prepared by MK-Ferguson Company and
Jacobs Engineering Group, Weldon Spring, Mo., for U.S. Department of Energy, Oak Ridge Operations Office,
Weldon Spring Site Remedial Action Project, Weldon Spring, Mo.

U.S. Environmental Protection Agency, 1989, Risk Assessment Guidance for Superfund, Volume I: Human
Health Evaluation Manual (Part A), Interim Final, EPA/540/1-89/002, Office of Emergency and Remedial
Response, Washington, D.C., Dec.

U.S. Environmental Protection Agency, 1990, "National Oil and Hazardous Substances Pollution Contingency
Plan; Final Rule (40 CFR Part 300)," Federal Register, 55(46) : 8666-8865, March 8.

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                                                APPENDIX A:

                                          RESPONSIVENESS SUMMARY

       The Proposed Plan (DOE 1998b)  for the Quarry Residuals Operable Unit (QROU)  was issued to the
public for review and comment on March 18, 1998. The U.S. Department of Energy  (DOE) and the U.S.
Environmental Protection Agency  (EPA) held a public meeting to discuss the proposed action on April 16,
1998, at the Administration Building of the Weldon Spring Site Remedial Action Project  (WSSRAP) located
at 7295 Highway 94 South, St. Charles, Missouri. Representatives of the State of Missouri were also in
attendance. The DOE and the EPA responded to oral comments made on the Proposed Plan  (DOE 1998b) at this
meeting; those responses are included in the meeting transcript. The meeting transcript is part of the
Administrative Record for the QROU and is on file at the information repositories for the WSSRAP. The
repositories are located in the project office reading room at Francis Howell High School and at four
branches of the St. Charles City/County Library as listed in Section 3 of this Record of Decision  (ROD).

         The public comment period for the Proposed Plan (DOE 1998b) was initially scheduled
to end on April 18, 1998. However, the period was extended by 30 days to accommodate reguests
from the Weldon Spring Citizens Commission  (WSCC) and the State of Missouri. The comment period formally
ended on May 21, 1998. In addition to oral comments received and responded to at the public meeting,
comment letters were received from the Missouri Department of Health  (MDOH), the Missouri Department of
Natural Resources  (MDNR), and the WSCC. These letters are also part of the Administrative Record for the
QROU. In this responsiveness summary, the comment letters are referred to by an alphabetical identifier
determined by the order in which they were received by the project office. Each comment letter has been
reproduced to provide detailed responses to comments or issues raised in the individual letters.

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March 23, 1998

Stephen McCracken
Project Manager
Department of Energy
7295 Highway 94 South
St. Charles, MO 63304

RE: Weldon Spring Quarry Proposed Plan

Dear Mr. McCracken:

The Department of Health (MDOH) has reviewed the Proposed Plan and associated documents for the Weldon
Springs Quarry Site in Weldon Spring, Mo. MDOH is encouraged by the decision of the US Department of
Energy to take a proactive approach to reduce contamination north of the slough. Alternative 3,
Groundwater Removal at Selected Areas, with On-Site Treatment, is acceptable to our office if the well
contingency plan is determined to be protective of the St. Charles County water supply. A-l MDOH reguests
the opportunity to review this plan before it's approval. As MDOH has stated in the past, our concern is
for the continued protection of the St. Charles County well field, therefore, our office would like to be
assured that there will be appropriate monitoring, action levels set, and a response plan in place to
address any threat to the public water supply in the event of contamination progressing south of the
slough.

We appreciate the opportunity to participate in this matter. If you have any guestions, please contact
Pam Holley at (573) 751-6111.

dr/sc/ph

cc: Larry Erickson, MDNR

Response A-l

The DOE recognizes the importance of the monitoring effort described in the Well Field Contingency Plan
(DOE 1998d) for protecting the well field. This plan has been made available for review and comment. All
input or comments will be considered to make this plan protective of the St. Charles County well field.
It is our intent that the contingency plan provides for adeguate monitoring, action levels, and
appropriate actions ranging from increased monitoring to the relocation of the well field if indicated by
the data.

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Steve McCracken
Project Manager
U.S. Department of Energy
Weldon Spring Site Remedial Action Project
7295 Highway 94 South
St. Charles, MO 63303

Re: Feasibility Study for Remedial Action for the Quarry Residuals Operable Unit at
the Weldon Spring Site, Weldon Spring, Missouri, March 1998; and Proposed
Plan for Remedial Action for the Quarry Residuals Operable Unit at the Weldon
Spring Site, Weldon Spring, Missouri, March 1998

Dear Mr. McCracken:

We have reviewed the above referenced reports and cannot yet concur with the
proposed remedial alternative as described therein.

The Department of Energy (DOE) has stated that complete cleanup of groundwater at
the Weldon Spring guarry is not warranted by the likelihood of radioactive and chemical
B-l contamination reaching the St. Charles County wellfield, and that subsurface
hydrogeological conditions make such cleanup technically practicable. The Missouri
Department of Natural Resources (MDNR) believes that the data and their uncertainties
warrant active remediation of contaminated groundwater to achieve groundwater
cleanup standards and disagrees with an approach that calls for monitoring only.
B-2 MDNR does agree that a demonstration to determine practicality of a groundwater
cleanup is necessary; however, we disagree that the existing data shows this to be
impractical.

Complying with groundwater cleanup standards (i.e., the Applicable or Relevant and
Appropriate Reguirements (ARARs)) is not contingent on demonstrating the cleanup is
practicable. The demonstration of technical impracticability should not be the only
B-3 or even primary goal of the proposed remedy. Rather, the first goal of the proposed
remedial alternative must be achieving the groundwater cleanup standards. If after a
good faith attempt to implement the remedy, achieving the cleanup standards is not
practicable, then those standards may be waived.

B-4 The proposed remedy does not appear to have as its goal achieving the groundwater
cleanup standards. The proposed remedial alternative clearly is intended to provide the
necessary data to demonstrate technical impracticability and waive the groundwater
cleanup standards. MDNR does not object to further investigations in this area, and we
reiterate our offer to work with DOE to define a set of performance-based criteria
necessary and sufficient to justify the granting of such a waiver if supported by data
from the field.

To the extent the Proposed Plan is not explicit on the goal of achieving groundwater
cleanup standards, the Proposed Plan should be revised to state:

1) The goal of the proposed remedial alternative is achieving groundwater cleanup
standards,
B-5
2) How the proposed remedial alternative will achieve that goal, and

3) The implementation of the remedial alternative will continue until ARARs are
attained or until waived.

B-6 We do not object to the Proposed Plan including as an additional goal the collection
of data intended to demonstrate technical impracticability.

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Mr. McCracken
Page two

Specifically, several significant issues remain unresolved:

The Proposed remedy will not attain ARARs. The National Contingency Plan at 40 CFR
430(f)(1)(ii)(B) reguires that "On-site remedial actions selected in a ROD must attain those
ARARs that are identified at the time of [Record of Decision (ROD)] signature or provide
grounds for invoking a waiver. The proposed remedy will not attain ARARs for uranium
B-7 or for some nitroaromatics. If DOE does not plan to attain ARARs, a waiver of the ARAR
should be obtained before the ROD is signed. MDNR reiterates its offer to work with DOE to
define a set of criteria necessary and sufficient to justify granting a Technical
Impracticability waiver of ARARs.

• The Proposed remedy leaves the cleanup of the guarry incomplete. Currently, there
are no cleanup levels provided for the remaining contaminated material in the
guarry proper. Contamination, including flakes of yellowcake, remains in cracks and
B-8 crevices of the guarry floor and walls. This residual material is a concern because
it is a source of contamination to groundwater and because it involves a risk from
direct exposure. DOE continues to postpone a final remedial action for
contamination in the guarry proper to final restoration of the guarry.

• The Proposed remedy omits appropriate remediation goals. DOE rejects
containment as a remediation goal. DOE responds, "[T]he current goal of achieving
B-9 as much reduction as possible of the uranium present north of the slough is
appropriate and adeguate." *[A]chieving as much reduction as possible is not an
appropriate remediation goal. The NCP at 40 CFR 430(f)(1)(ii)(B) reguires that

B-10 "On-site remedial actions selected in a ROD must attain those ARARs that are
identified at the time of ROD signature or provide grounds for invoking a waiver."

Plume containment should be included as a remediation goal. DOE states, "The
primary remediation goal for the QROU is to reduce the amount of uranium in guarry
groundwater north of the slough, thereby reducing the amount of uranium that could
migrate to the St. Charles County well field." Plume containment could be effected
under the proposed alternative by either active means (e.g., continued water
extraction from the trench after groundwater cleanup standards are achieved) or
passive means (e.g., grouting the trench after active measures are completed).

B-ll Including plume containment as a remediation goal is appropriate since 1) as stated
in the Proposed Plan, "migration of uranium to the county well field is possible and
could be occurring (probably at very low rates)" (MDNR believes the Draft Final
Proposed Plan describes the situation more accurately, i.e., migration of uranium "is
most likely occurring (albeit at very low rates)."); 2) any contamination which
migrates into the alluvium south of the Femme Osage Slough cannot leave the
alluvium other than through the public wells (QROU Remedial Investigation, Figure
8-19 at p. 8-33); 3) current DOE plans leave residual contamination in the guarry
proper which is a source of further groundwater contamination; and 4) migration of
any contamination into the public water supply should be avoided.

* Groundwater cleanup levels are not achieved throughout the area outside the guarry
proper. Groundwater contamination outside the guarry proper and north of the
Femme Osage Slough exceeds groundwater cleanup standards. DOE proposes
that the area south of the Femme Osage Slough (i.e., the "RMW" monitoring wells)
B-12 as the point of compliance, for demonstrating compliance with groundwater cleanup
standards. This conflicts with EPA guidance that "groundwater cleanup standards
should generally be attained throughout the contaminated plume, or at and beyond
the edge of the waste management area, when the waste is left in place." Since the
proposed remedy leaves waste within the guarry proper that must be managed, the
guarry proper constitutes a waste management area outside of which cleanup levels
must be achieved.

* A two-year implementation period is inappropriate. DOE specifies only a two-year
"implementation period" for the remedial action "to gauge the performance of this
proposed action" and to reevaluate the need for waivers of the nitroaromatic ARARs.
MDNR does not object to periodic reviews of the remedy's performance. However,
in response to our comment that no fixed time period would be appropriate, DOE

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Mr. McCracken
Page three

B-13 stated, "if the reduction achieved [in two years] is as estimated or greater, the goal
of providing as much reduction as possible would have already been achieved. The
implementation of the action beyond the two-year period proposed would not be
cost-effective in light of the acceptable and protective conditions that exist in the
well field and the contingencies already planned for the wellfield via the Wellfield
Contingency Plan."

An understanding or clarification needs to be given that explains how the remedial
action can go forward, beyond the two-year period, if the effectiveness exceeds
estimates. It is unclear how the Department of Energy can deem an action as "not
B-14 cost-effective" at the time, even though future actual performance data may exceed
modeling estimates. It would appear that if actual contamination reductions are
greater than model estimates, this would support the decision to continue active
remediation until ARARs are achieved.

Review of the Wellfield Contingency Plan is not complete. The 1988 draft version of
the Wellfield Contingency Plan referenced in the Proposed Plan was received after
the Feasibility Study and Proposed Plan were submitted for public comment. The
Proposed Plan takes credit for the Wellfield Contingency Plan, which describes
B-15 groundwater monitoring, action levels, and planned responses to ensure the safety
of drinking water supplied to residents of St. Charles County from this wellfield.
Concurrence with the Proposed Plan is not possible until a review of the Wellfield
Contingency Plan is complete.

Natural resources damages are not assessed. The Director, Missouri Department of
Natural Resources, is the State of Missouri's trustee for natural resources. Pursuant
to Section 107(f) of CERCLA or Section 311(f) (5) of the Clean Water Act, the state
trustee for natural resources may act on behalf of the public to assess and recover
B-16 damages to natural resources. The proposed remedial alternative will leave
contaminated groundwater to continue to threaten the St. Charles County wellfield
and may limit the ability to expand production of the wellfield to provide drinking
water to residents in this rapidly growing area. Natural resources damages have not
yet been assessed. This may need to be in the Record of Decision.

Response B-l

Evaluations based on over 10 years of monitoring data and various field studies supporting the
remedial investigation (RI)(DOE 1998c) indicate that impact from guarry contamination is limited to north
of the Femme Osage Slough. Data collected from the well field indicate conditions consistent with the
naturally occurring conditions in the upgradient Darst Bottoms. Further, the tightness of the aguifer,
affinity of the soil for uranium, and redox conditions present in the guarry area north of the slough
contribute to the relatively small and slow migration of uranium to the well field; these very same
features, in turn, do not allow for effective removal of the uranium from the system.

Response B-2

Ample data are available to indicate that current conditions at the well field are protective of
human health and the environment. The selected action calls for long-term monitoring. However, additional
data will be collected via a pilot-scale trench to evaluate the need for and effectiveness of groundwater
remediation. The data collected will be used to verify predictive models relating to groundwater
remediation and support the hydrological, geochemical, and contaminant fate and transport models for the
guarry area.

Response B-3

The goal of the selected action is to ensure protection of human health and the environment. The
selected action complies with Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA), as amended, reguirements. It is expected that the selected action will meet all ARARs
identified in the ROD. Establishing technical impracticability would only be necessary in the event the
selected action was not able to meet a particular applicable or relevant and appropriate reguirement
(ARAR) .

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Mr. McCracken
Page four

Response B-4

See responses B-2 and B-3. The MDNR will have the opportunity to provide input to define
additional field measurements that would supplement the current database and increase confidence in the
evaluations that support the decisions for the QROU.

Response B-5

The Proposed Plan (DOE 1998b) that was released for public comment was a final document and will
not be revised per CERCLA protocols. With respect to groundwater standards, see responses B-3 and B-7.

Response B-6

See response B-2.

Response B-7

The selected action will meet ARARs; no ARARs have been identified for uranium in groundwater. For
a detailed discussion of ARARs, see Section 9.2. of this ROD.

Response B-8

As part of the selected action described in Section 8 of this ROD, the DOE has proposed additional
characterization at the northeast slope and drainage ditch area within the guarry proper. These data
would then be used to perform risk calculations consistent with the approach presented in the BRA (DOE
1998a) for the QROU. If calculations indicate risks to be greater than the EPA's acceptable risk range of
10 -6 to 10 -4 for a recreational scenario, soil removal would be undertaken to meet cleanup criteria
presented in the chemical plant ROD (DOE 1993) for radionuclides.

In addition, guarry restoration by backfilling with soil is planned; this will prevent further
infiltration to groundwater of any residual yellowcake or flakes in cracks and crevices that may be
present.

Response B-9

Evaluations indicate already protective conditions at the guarry area and the well field. The
implementation of engineering methods to provide containment of the plume of contamination is not
warranted. In fact, current hydrological and geochemical models indicate contamination to be confined to
the guarry area north of the slough. In addition, no ARARs have been identified that reguire containment.

Response B-10

See response B-3.

Response B-ll

See response B-9.

Response B-12

See Response B-7 and Section 8 of this ROD.

Response B-13

Data collection involving a trench will be conducted for up to two years: at which time, data
collected will be compared with a predetermined set of performance goals. If performance of the removal
system exceeds the performance goals, the need for and effectiveness of groundwater remediation will be
reevaluated. However, if the performance is less effective or within the specified performance goals,
then further evaluation of groundwater remediation will not be necessary (see Section 8 of this ROD).

Response B-14

See Response B-13.

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Response B-15

       The most recent draft of the Well Field Contingency Plan was distributed for agency review on
March 17, 1998. As stated in response A-l, input and comments provided on this plan will continue to be
considered and incorporated, as appropriate, to ensure that protection of the well field is as
comprehensive as possible.

Response B-16

       The assessment to address natural resource damages does not occur as part of the remedy selection
process. These issues are addressed following performance of remedial activities.

We look forward to working with you to resolve these issues and executing a Record of Decision which is
protective of human health and the environment and attains all applicable or relevant and appropriate
laws and regulations. If you have any guestions, please contact Larry Erickson at  (573) 751-6838.

Sincerely,

DIVISION OF ENVIRONMENTAL QUALITY

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Weldon Spring Citizens Commission
100 N. Third Street
St. Charles, MO 63301
May 21, 1998
Mr. Stephen H. McCracken, Project Manager
U.S. Department of Energy
Weldon Spring Site Remedial Action Project Office
7295 Highway 94 South
St. Charles, Missouri 63304

Dear Mr. McCracken:

This letter is to serve as public comment from the Weldon Spring Citizens
Commission on the Proposed Plan for Remedial Action at the Quarry Residuals Operable
Unit of the Weldon Spring Site, March 1998, DOE/OR/21548-724. This response is in
fulfillment of the Commission's primary goal which is "To ensure that the public has a
voice in the safe and timely completion of the Weldon Spring project." One of the primary
stated objectives that guided the Commission in formulating their response was "to
maximize the guality of the cleanup while minimizing the impact to the surrounding
environment and the public." Our written responses to the proposal described above are
intended to reflect the collective perceptions, considered opinions, and concerns of
informed local Citizens who have a demonstrated interest in both short term and long
term conseguences of the remediation efforts of the WSSRAP

The Commission unanimously supports the Department of Energy's "alternative #
2" (monitoring with no active remediation) as described in the Proposed Plan for Remedial
Action at the Quarry Residuals Operable Unit of the Weldon Spring Site, March 1998.
C-l The decision was reached after an exhaustive review of information evaluated over the
last five months including independent technical review provided to the Commission. Our
comments first address the guarry proper followed by comments regarding the
groundwater remediation.

We believe that restoration of the guarry is essential and should be restored to
eliminate physical and radiological exposure. This should be done by filling and capping
C-2 the guarry with suitable material and taking whatever measures necessary to ensure that
any residual contaminants do not migrate from the site. The Commission expects to be
involved in the Remedial Design and Remedial Action Work Plan.

Response C-l

The DOE acknowledges the preference of the WSCC for Alternative 2 (monitoring with no active
remediation) described in the Proposed Plan (DOE 1998b).

Response C-2

The DOE is planning to perform guarry restoration by backfilling with soil as discussed in
previous sections of this ROD. The WSCC will continue to be given the opportunity to review and provide
input on subseguent reports or documents prepared in support of the QROU, as well as other Weldon Spring
site activities.

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Mr. Stephen McCracken 2 May 21, 1998

With respect to the groundwater, the Commission believes that the first line of
defense to an unforeseen event which would contaminate the drinking water is continued
monitoring backed up by an updated Well Field Contingency Plan. We believe that data
from continuous review of alternative #2 can accomplish our goals. This would include
data from existing monitoring wells as well as new strategic monitoring wells. This will
C-3 insure that the integrity of the well field is not compromised by a change in the existing plume
and will allow us to make appropriate responses if the integrity is compromised. The
Commission will review the data for the existing and proposed monitoring wells within a
year of the completion of the Quarry Restoration. This will allow the Commission to
decide whether there should be a change in the scope and/or frequency of future
monitoring.

With respect to the Well Field Contingency Plan, the Commission believes that the
plan is the only action to safeguard the drinking water if the monitoring proposed in
alternative #2 shows migration of the plume toward the St. Charles County well field.
This plan needs to be strengthened. The plan must state:
C-4 1. who will be responsible and update the implementation of the plan;
2. who will be involved in communicating the monitoring results if there is an
increased presence of uranium in the water supply wells;
3. what will be the public involvement in the review and the evaluation of the
plan.

The essential difference between alternative #2 and alternative #6 in the Proposed
Plan for Remedial Action at the Quarry Residuals Operable Unit of the Weldon Spring
Site, March 1998, was the construction of a trench to capture and remove residual
groundwater contaminants. However, from the information provided to the Commission,
there were serious doubts that the trench would be successful in reducing measurable
amounts of contaminants. As stated, the best prediction called for only an 8-10% reduction
in the mass of uranium over a two year period. With the stated length of operation of two
years, this predicted amount of reduction does not, in our opinion, support the possible
unforeseen risks of the disturbance of the natural barrier. In addition, possible other
negative effects are: the chaining of the slough with increased contaminant concentrations,
creating unknown pathways for the contaminants, breaking the natural barrier, and other
technical reason as stated in the Feasibility Study for Remedial Action for the Quarry
Residuals Operable Unit at the Weldon Spring Site, Weldon Spring Missouri, March 1998,
DOE/OR/121548-595, page 4-17.

Response C-3

Under the selected action described in this ROD, monitoring would be performed to ensure that
conditions continue to be protective of human health and the environment at the well field. The specific
process to be undertaken regarding review of data will be defined in post-ROD remedial design/remedial
action reports. The WSCC will have the opportunity to provide input into this process and associated
reports.

Response C-4

The March 1998 version of the Well Field Contingency Plan (DOE 1998d) will be revised to
incorporate comments received from various stakeholders. The DOE is responsible for updating and
implementing this plan. Specific information requested in this comment will be provided in the revised
version of the report, as appropriate.

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        Mr. Stephen McCracken                  3                           May 21, 1998

               We cite the August 21, 1997 Department of Energy's response to the Weldon
        Spring Citizens Commission's Comment #6 on the Remedial Investigation for the Quarry
        Residuals Operable Unit of the Weldon Spring Site, Weldon Spring, Missouri: "A risk   to
C-5     downgradient groundwater from concentrating uranium in soils in this area  [north of the
        slough] could be the introduction of materials or a significant change in the natural system
       which might significantly alter the reducing nature of this area.  Any change to a more oxidizing
       system would allow the precipitated uranium in the soil to become  mobilized
        in the dissolved phase and migrate south of the slough."

               In summary, the Commission unanimously supports alternative #2 and strongly
        urges the DOE to incorporate the recommendations submitted in this document in the final record
       of decision.  The Commission would like to extend their gratitude to the Department
        of Energy for their candor and openness in providing the Commission with information as
C-6     well as responding to our numerous reguests for clarification and explanations associated with
       this proposal.  This type of cooperation has allowed the Commission to maintain its objectivity
       and impartiality.  We hope this level of honest and open dialog will continue in the future and we
       appreciate the opportunity to offer a community perspective on this ongoing remediation effort.




        cc: Karen Reed, DOE
            Dan Wall,  EPA
            Jim Garr,  MDC
            John Young, MDNR
            Robert Geller, MDNR
            Larry Erickson, MDNR
            Glenn Carlson, MDNR

Response C-5

       Construction of the trench should have little to no impact on the  natural processes (adsorption
and precipitation) presently mitigating the rudgration of uranium south of the slough. The high levels of
uranium are present in an oxidizing portion of the aguifer; therefore, the trench would also be located
in this portion of the aguifer. Because the trench will behave as a collection system, the groundwater
will be pulled to this location. It is expected that the groundwater capture zone for this trench will
not be large because of the fine-grained nature of the Soils. South of the trench, a reducing zone is
present that allows for the precipitation of uranium from the groundwater. The operation of the trench
will not result in oxidizing groundwater invading the reducing zone and resulting in its degradation or
remobilization of uranium because of the small area of influence the trench will have in comparison to
the size of the reducing area. Also, the installation of the trench will  not impact the capacity of the
existing soils to adsorb uranium.

Response C-6

       The selected action described in this ROD was reached after consideration of all comments
received, including those from the WSCC. The process for exchange of information and communication
between the DOE and the WSCC is expected to continue as it has.

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REFERENCES FOR APPENDIX A

U.S. Department of Energy, 1993, Record of Decision for Remedial Action at the Chemical Plant Area of the
Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-376, prepared by Argonne National Laboratory,
Argonne, 111., for U.S. Department of Energy, Oak Ridge Operations Office, Weldon Spring Site Remedial
Action Project, Weldon Spring, Mo., Sept.

U.S. Department of Energy, 1998a, Feasibility Study for Remedial Action for the Quarry Residuals Operable
Unit at the Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-595, prepared by Argonne National
Laboratory, Argonne, 111., for U.S. Department of Energy, Oak Ridge Operations Office, Weldon Spring Site
Remedial Action Project, Weldon Spring, Mo., March.

U.S. Department of Energy, 1998b, Proposed Plan for Remedial Action at the Quarry Residuals Operable Unit
of the Weldon Spring Site, prepared by Argonne National Laboratory, Argonne 111., for U.S. Department of
Energy, Oak Ridge Operations Office, Weldon Spring Site Remedial Action Project, Weldon Spring, Mo.,
March.

U.S. Department of Energy, 1998c, Remedial Investigation for the Quarry Residuals Operable Unit of the
Weldon Spring Site, Weldon Spring, Missouri, DOE/OR/21548-587, prepared by MK-Ferguson Company and Jacobs
Engineering Group, Weldon Spring, Mo., for U.S. Department of Energy, Oak Ridge Operations Office, Weldon
Spring Site Remedial Action Project, Weldon Spring, Mo., Feb.

U.S. Department of Energy, 1998d, Well Field Contingency Plan, Draft, prepared by MK-Ferguson Company and
Jacobs Engineering Group, Weldon Spring, Mo., for U.S. Department of Energy, Oak Ridge Operations Office,
Weldon Spring Site Remedial Action Project, Weldon Spring, Mo.

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