United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R07-93/067
September 1993
PB94-964302
&EPA Superfund
Record of Decision
Weldon Spring Quarry/Plant/
Pits (USDOE), MO
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA/ROD/R07-93/067
3. Recipient's Accession No.
THIS and Subtitle
SUPERFUND RECORD OF DECISION
Weldon Spring Quarry/Plant/Pits (USDOE), MO
Second Remedial Action
& Report Date
09/28/93
7. Authors)
a Performing Organization Rapt. No.
ft Performing Organization Nanw and Address
10 Project Taskwork Untt No.
11. Contract(C) or Grant(G) No.
(Q
(G)
So.
ring Organization Narm and Address
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
13. Type of Report* Period Covered
800/800
14.
15. Supplementary Notes
PB94-964302
1& Abatraet (Umtt: 200 words)
The 223-acre Weldon Spring Quarry/Plant/Pits (USDOE) is an inactive chemical plant and
lime quarry located in St. Charles County, Missouri. The site consists of 40
buildings, the 26-acre raffinate pits, the 11-acre Ash Pond, the 0.7-acre Frog Pond,
two former dump areas, a. woodlands area, and a wetlands area. Land use in the area is
predominantly agricultural, with two conservation and wildlife areas and a U.S. Army
Reserve and National Guard Training Center located adjacent to the site. There are two
aquifers, a shallow and a deep aquifer, underlying the site, and a small northern
portion of the site lies within the 100-year floodplain of Schote Creek. Ah estimated
850 people reside two miles from the site. From 1941 to 1946, the U.S. Army operated
the Weldon Springs Ordnance Works onsite, producing explosives such as TNT and DNT. In
1949, 15,000 acres were transferred to the State and the University of Missouri for use
as a wildlife area and agricultural land. In 1955, the U.S. Atomic Energy Commission
(AEC), a predecessor to USDOE, acquired 205 acres of the site from the Army to
construct a uranium feed materials plant. From 1957 to 1966, the AEC processed uranium
and thorium ore concentrates at the plant and disposed of radioactive- and chemically-
contaminated waste, such as uranium, metals, and PCBs, onsite in the fourth raffinate
(See Attached Page)
17. Documant Analysis a. Descriptor*
Record of Decision - Weldon Spring Quarry/Plant/Pits (USDOE), MQ
Second Remedial Action
Contaminated Media: soil, sediment, sludge, debris
Key Contaminants: organics (PAHs, PCBs), metals (arsenic, chromium, lead), other
inorganics (asbestos), radioactive materials
b. Idertlfiers/Open-Ended Terms
COSATI Held/Group
ia Availability Statement
1ft Saeurity Class (This Report)
None
20. Saeurity Class (This Page)
None
2i: No. of Pages
138
22. Price
(SeeANS4-Z38.1B)
See Inttrvctlont on R»v»n»
OPTIONAL FORM 272(4-77)
(Formerly NTB-35)
Department of Commerce
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EPA/ROD/R07-93/067
Weldon Spring Quarry/Plant/Pits (USDOE), MO
Second Remedial Action
Abstract (Continued)
pit and the quarry. The four raffinate pits were excavated from existing soil during the
operation period of the chemical plant to receive waste slurry from the processing
operations. These pits constitute the most heavily contaminated area of the site and
contain approximately 200,000 yd3 of sludge and 57,000,000 gallons of water. Plant
operations generated several chemical and radioactive waste streams, including raffinates
from the refinery operation and washed slag from the uranium recovery process. Waste
slurries were piped to the raffinate pits, where the solids settled to the bottom and the
supernatant liquids were decanted to the plant process sewer, which drained offsite into
the Missouri River. In 1967, the Army reacquired the chemical plant property and began
decontaminating and dismantling operations to prepare the facility for herbicide
production. In 1969, this project was canceled, and the plant has remained unused since
that time. In 1971, the Army returned the raffinate pits portion of the chemical plant
area to the AEC, and the remainder of the property to USDOE in 1985. In 1986, USDOE
initiated cleanup activities, including several interim response actions. A 1990 ROD
addressed the removal and temporary storage of the quarry bulk wastes onsite. This
interim ROD addresses the contaminated source area at the chemical plant and the disposal
of the material that may be generated by upcoming actions. The primary contaminants of
concern affecting the soil, sediment, debris, and sludge are other organics, including
PAHs and PCBs; metals, including arsenic, chromium, and lead; other inorganics, including
asbestos; and radioactive materials.
The selected interim remedial action for this site includes constructing a new sludge
processing facility, a volume reduction facility, and an engineered disposal facility
onsite; excavating or dredging approximately 339,000 yd3 of contaminated soil, 119,800 yd3
of contaminated sediment, and 220,000 yd3 of contaminated sludge and transporting them to
the onsite treatment facility; treating the contaminated soil, sediment, and sludge onsite
using solidification/stabilization in the sludge processing facility and disposing- of the
resultant material onsite; performing volume reduction operations; backfilling, regrading,
and vegetating the excavated areas with clean soil; disposing of the excavated material
not targeted for onsite treatment in the onsite disposal facility; treating approximately
30,650 yd3 of contaminated vegetation onsite using biodegradation, followed by onsite
disposal; treating approximately 3,960 yd3 of containerized process chemicals onsite in
the sludge processing facility using stabilization or neutralization, or incinerating them
offsite; decontaminating approximately 169,600 yd3 of structural debris onsite, with on-
or offsite disposal; conducting pilot-scale, bench-scale, and leachability tests; using
grout material from the mixing of raffinate sludge for grouting voids in debris at the
onsite disposal cell for the sludge treatment process; capping the engineered disposal
facility with a long-term RCRA cover and a leachate collection system; providing for a
contingency remedy using vitrification of the contaminated sludge, soil, and sediment, if
solidification/stabilization proves to be ineffective during pilot-scale testing; and
monitoring the ground water, surface water, and air to facilitate protection of the
general public and the environment. The estimated present worth cost for this remedial
action is $78,500,000, which includes an estimated total O&M cost of $23,900,000 for 30
years. The estimated present worth cost for the contingency remedy is $96,900,000, which
includes an estimated total O&M cost of $23,900,000 for 30 years.
PERFORMANCE STANDARDS OR GOALS:
Soil,.sediment, sludge, and debris cleanup goals are based on State and Federal ARARs and
an excess incremental cancer risk level of 10~^. Chemical-specific soil cleanup goals
include Ra~226 6.2 pCi/g; Ra~228 6.2 pCi/g; Th~230 6.2 pCi/g; Th~232 6.2 pCi/g; u~238 120
pCi/g; arsenic 75 mg/kg; chromium (total) 110 mg/kg; chromium VI 100 mg/kg; lead 450
mg/kg; thallium 20 mg/kg; benz(a)anthracene 5.6 mg/kg; benzo(b)fluoranthene 5.6 mg/kg;
benzo(k)fluoranthene 5.6 mg/kg; benzo(a)pyrene 5.6 mg/kg; chrysene 5.6 mg/kg;
indeno(l,2,3-cd)pyrene 5.6 mg/kg; PCBs 8 mg/kg; and TNT 140 mg/kg. While these levels were
developed to ensure that cleanup is successful, the remedial action will aim to reach
levels as low as reasonably achievable (ALARA) during field excavation activities.
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EPA/ROD/R07-93/067
Weldon Spring Quarry/Plant/Pits (USDOE), MO
Second Remedial Action
Abstract (Continued)
Certain State and Federal regulatory requirements under NESHAPs, RCRA, and TSCA were
waived under CERCLA, Section 121 (d)(4)(A-D). ALARA goals include Ra~226 5 pCi/g; Ra~228
5 pCi/g; Th~23C) 5 pCi/g; Th~232 5 pCi/g; and u~238 30 pCi/g; arsenic 45 mg/kg; chromium
(total) 90 mg/kg; chromium VI 90 mg/kg; lead 240 mg/kg; thallium 16 mg/kg; PAHs 0.44
mg/kg; PCBs 0.65 mg/kg; and TNT 14 mg/kg. Chemical-specific sediment, sludge, and debris
cleanup goals were not provided.
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RECORD OF DECISION: DOE/OR/21548-376
Record of Decision for Remedial Action at the Chemical
Plant Area of the Weldon Spring Site
September 1993
prepared by
U.S. Department of Energy, Oak Ridge Field Office, Weldon Spring Site Remedial Action
Project
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DECLARATION
SITE NAME AND LOCATION
Weldon Spring Site
St. Charles County, Missouri 63304
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for the chemical plant area
of the Weldon Spring site in St. Charles County, Missouri. This remedial action was selected
in accordance with 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 (NCP), 40 CFR Part 300.
In making this decision, it is the U.S. Department of Energy's (DOE's) policy to
integrate National Environmental Policy Act (NEPA) values into the CERCLA remedial action
process; however, it is not the intent of the DOE to make a statement on the legal applicability
of the NEPA to CERCLA actions. This single document is intended to serve as the DOE's
Record of Decision (ROD) under both the CERCLA and the NEPA.
The decision presented herein is based on the information available in the Administrative
Record maintained in accordance with the CERCLA. The decision is also based on the issuance
of the Proposed Plan for Remedial Action at the Chemical Plant Area of the Weldon Spring Site
(DOE 1992a), holding a public meeting to receive comments on the Proposed Plan, and
completion of the Remedial Investigation/Feasiblity Study-Final Environmental Impact Statement
(RI/FS-Final EIS). In addition', the DOE has considered all comments received on the Proposed
Plan and the RI/FS-Final EIS documents in the preparation of the ROD.
As the lead agency for the State of Missouri regarding the Weldon Spring Site Remedial
Action Project, the Missouri Department of Natural Resources concurs that Alternative 6a:
Removal, Chemical Stabilization/Solidification and Disposal On Site is the preferred remedy for
the chemical plant area of the Weldon Spring site, and also concurs with applicable and/or
relevant and appropriate requirements (ARARs) and waivers.
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ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from this site, if not addressed by
implementing the response action selected in the ROD, may present a threat to human health and
the environment.
DESCRIPTION OF THE REMEDY
The chemical plant operable unit remedial action is the third of five major response
actions planned for the chemical plant area. Previous response actions included a removal action
involving the decontamination and dismantlement of site structures with short-term storage of
the material on site until selection of a disposal option in this ROD and a removal action to treat
impounded surface water. In addition, bulk waste material from the Weldon Spring Quarry is
being placed in temporary storage on site until the selection of a disposal option.
This operable unit addresses the various sources of contamination at the chemical plant
area including soils, sludge, sediment, and materials placed in short-term storage as a result of
previous response actions.
This remedial action uses treatment to address the principal threat remaining at the site,
(e.g., raffinate pit sludges and certain soil from the quarry). The major components of this
remedy are:
• Dredge sludge from the raffinate pits, excavate sediment from Frog Pond and
Ash Pond and three off-site lakes, and excavate soil from specific locations
(including two former dump areas, locations adjacent to the chemical plant
buildings On site, and 10 vicinity properties off site) using standard
construction equipment and procedures. .
• Remove material stored at the temporary facilities on site (including bulk waste
excavated from the quarry, treatment residuals from the water treatment plants at the
quarry and the chemical plant area, and building material from the chemical plant
area) using standard construction equipment and procedures.
• Certain contaminated materials such as the raffinate pit sludges and portions
of quarry soil will be treated on site by chemical stabilization/solidification.
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Treated and untreated materials will be disposed of on site in a facility
designed and constructed specifically for the Weldon Spring site wastes.
• Continued evaluation of vitrification as a contingency treatment option.
In reaching the decision to implement this remedial alternative, DOE evaluated three
other alternatives in addition to no action. The other alternatives are: (1) Removal,
Vitrification, and Disposal On-site; (2) Removal, Vitrification, and Disposal at the Envirocare
Facility; and (3) Removal Vitrification, and Disposal at the Hanford Reservation Facility. A
description of the alternatives is provided in the Decision Summary of the ROD (attached), and
is available in the Administrative Record. CERCLA's nine criteria (two threshold, five primary
balancing, and two modifying criteria) set out in the NCP were used to evaluate the alternatives.
The selected remedy and the contingency treatment option represent the best balance of key
factors with respect to these criteria and are the environmentally preferable alternatives.
Short-term effectiveness, implementability, and cost are the key factors for selection of
the preferred alternative. The short-term effectiveness of the selected remedy is greater than for
the two alternatives that involve transportation of the waste to off-site locations. The selected
remedial action is the most implementable of all the alternatives evaluated in detail because the
chemical stabilization/solidification technology has been utilized at other sites and would use
readily available resources. Finally, the selected remedy is the most cost effective of those
alternatives evaluated.
STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the environment; it complies with
Federal and State of Missouri requirements that are legally applicable or relevant and appropriate
to the remedial action, except as specifically waived pursuant to CERCLA, as set forth below,
and is cost effective. This remedy utilizes permanent solutions and alternative treatment (or
resource recovery) technologies to the maximum extent practicable, and satisfies the CERCLA
statutory preference for remedies that employ treatment that reduces toxicity, mobility, or
volume as a principal element.
The following Federal and State of Missouri requirements are waived under this Record
of Decision:
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19 CSR 20-10.040 - Stale Rn-222 limit of 1 pCi/1 above background in uncontrolled
areas. CERCLA provision for waiver: Section 121(d)(4)(C).
40 CFR Part 268. Subpart E - Land Disposal Restrictions (LDR) storage limitations.
CERCLA provision for waiver: Section 121(d)(4)(C).
40 CFR Part 268. Subpart C - LDR placement restrictions. CERCLA provision for
waiver: Section 121(d)(4)(A).
10 CSR 25. S-262f21fOl - packaging, marking, and labeling requirements. CERCLA
provision for waiver Section 121(d)(4)(A) and Section 121(d)(4)(B).
• 40 CFR 761 .TSftrtGI - Toxic Substance Control Act (TSCA) requirements for bottom
landfill liner. CERCLA provision for waiver: Section 121(d)(4)(D).
• 40 CFR 264.314(f) - restrictions regarding free liquids in CSS grout placed in the
disposal facility for purposes of disposing of CSS treated wastes and to fill voids of
dismantlement debris. CERCLA provisions for waiver: Section 121(d)(4)(B) and
Section 121(d)(4)(D).
• 40 CFR Part 268.42. Subpart D - LDR treatment standards based upon use of a
specified technology. CERCLA provision for waiver: Section 121(d)(4)(D).
• 40 CFR 61. Subpart M - National Emission Standards for Hazardous Air Pollutants
(NESHAPs) requirements for asbestos storage. CERCLA provision for waiver:
Section 121(d)(4)(B).
• 40 CFR 76 1.65 (a) - TSCA requirement for PCB storage and disposal. CERCLA
provision for waiver: Section 121(d)(4)(A).
Because both the selected and contingency remedies would result in hazardous substances
remaining on site above health-based levels (within the engineered disposal facility), a review
will be conducted within five years after this remedial action is complete in accordance with
CERCLA to ensure that the remedy continues to provide adequate protection of human health
and the environment.
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All practicable means to avoid or minimize environmental harm from implementation of
the selected remedy have been adopted. Excavation of contaminated soil in an area extending
into the Schote Creek 100-year floodplain will be conducted using sediment controls to minimize
off-site transport of contaminated materials and no net change in flood potential is expected due
to these actions. A mitigation action plan will be prepared for dredging and excavation activities
in areas considered to be wetlands to minimize adverse impacts. Final site layout and design
will include all practicable means (e.g., sound engineering practices and proper construction
practices) to minimize environmental impacts.
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Regional Administrator,
U.S. Environmental Protection Agency Region VII
Date
Assisj£ntxSecretary for Environmental Restoration
and Waste Management
U.S. Department of Energy
Date
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TABLE OF CONTENTS
NUMBER PAGE
1 SITE NAME, LOCATION, AND DESCRIPTION 1
2 SITE HISTORY 8
3 HIGHLIGHTS OF COMMUNITY PARTICIPATION . . ............. 10
4 SCOPE AND ROLE OF REMEDIAL ACTION ............ . . ......... 12
5 SITE CHARACTERISTICS . 15
6 SUMMARY OF SITE RISKS 25
6.1 Contaminants of Concern 25
6.2 Exposure Assessment 25
6.2.1 Contaminant Fate and Transport 25
6.2.2 Exposure Scenarios 26
6.2.3 Exposure Point Concentrations 32
6.3 Toxicity Assessment 34
6.4 Summary of the Human Health Risk Characterization 35
6.5 Ecological Assessment 42
6.6 Conclusion 44
7 DESCRIPTION OF ALTERNATIVES 46
7.1 Alternative 1: No Action '. .-.-.. . . 47
7.2 Alternative 6a: Removal, Chemical Stabilization/Solidification and Disposal On
Site 47
7.2.1 Applicable or Relevant and Appropriate Requirements 53
7.3 Alternative 7a: Removal, Vitrification, and Disposal On Site 57
7.3.1 Applicable or Relevant and Appropriate Requirements 60
7.4 Alternative 7b: Removal, Vitrification, and Disposal at the Envirocare Facility 60
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TABLE OF CONTENTS (Continued)
NUMBER PAGE
7.4.1 Applicable or Relevant and Appropriate Requirements 62
7.5 Alternative 7c: Removal, Vitrification, and Disposal at the Hanford Reservation
Facility . . ... . . . .'..62
7.5.1 Applicable or Relevant and Appropriate Requirements 63
8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES 64
8.1 Threshold Criteria 65
8.1.1 Overall Protection of Human Health and the Environment 65
8.1.2 Compliance with ARARs 66
8.2 Primary Balancing Criteria 68
8.2.1 Long-Term Effectiveness and Permanence 68
8.2.2 Reduction in Toxicity, Mobility, and Volume through Treatment .... 68
8.2.3 Short-Term Effectiveness 69
8.2.4 Implementability 70
8.2.5 Cost 71
8,3 Modifying Criteria . . . .'.. . . . ...,. 71
8.3.1 State Acceptance 71
8.3.2 Community Acceptance 72
9 SELECTED REMEDY 73
9.1 Key Components 73
9.2 Cleanup Criteria 78
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TABLE OF CONTENTS (Continued)
NUMBER PAGE
9.2.1 Radioactive Contaminants 83
9.2.2 Chemical Contaminants 84
9.2.3 Post-Cleanup Assessment 86
10 STATUTORY DETERMINATIONS
10.1 Protection of Human Health and the Environment
10.2 Compliance with Applicable or Relevant and Appropriate Requirements
10.2.1 Location-Specific ARARs 89
10.2.2 Contaminant-Specific ARARs 93
10.2.3 Action-Specific ARARs 95
10.2.3.1 Storage .96
10.2.3.2 Excavation 98
10.2.3.3 Treatment 99
10.2.3.4 Disposal 101
10.3 Cost-Effectiveness 109
10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the
Maximum Extent Practicable 110
10.5 Preference for Treatment as a Principal Element 112
10.6 Irreversible and Irretrievable Commitment of Resources 112
10.7 Significant Changes 113
11 REFERENCES 114
12 ACRONYMS 118
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TABLE OF CONTENTS (Continued)
NUMBER PAGE
APPENDIXES
A Responsiveness Summary
B Comment Letters on the Draft Remedial Investigation/Feasibility Study-Environmental Impact
Statement
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LIST OF FIGURES
FIGURE PAGE
1-1 Location of the Weldon Spring Site 2
1-2 General Layout of the Chemical Plant Area 3
1-3 Surface Water Drainages Near the Weldon Spring Site ................. 5
1-4 Surface Features Near the Weldon Spring Site . ... .'. . . ... .... 7
4-1 Components of Site Remediation 13
6-1 Location of Contaminated Vicinity Properties in the Area of the Weldon Spring
Site 43
9-1 Waste Media Flowpath 74
9-2 Areas of Soil Identified for Remediation Based on Cleanup Criteria 79
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LIST OF TABLES
5-1 Sources of Contamination at the Weldon Spring Site .................. 16
5-2 Estimated Areas and Volumes of Contaminated Media ................. 19
5-3 Concentration Ranges of Radioactive Contaminants of Concern ............ 20
5-4 Concentration Ranges of Chemical Contaminants of Concern ............ . 21
6-1 Scenario Descriptions for On-Site Receptors Under Current and Future
Conditions ............................................ 27
6-2 Scenario Descriptions for Of£Site Receptors Under Current and Future
Conditions .................. .......................... 30
6-3 Oral and Inhalation Slope Factors .............................. 36
6-4 Oral and Inhalation Reference Doses ............................ 37
6-5 Estimated Carcinogenic Risks for On-Site Receptors under the Baseline
Configuration .......................................... 40
6-6 Estimated Hazard Indexes for On-Site Receptors under the Baseline
Configuration .......................................... 40
6-7 Estimated Carcinogenic Risks and Hazard Indexes for Exposures to Soil and Air
under the Modified Site Configuration ........................... 41
6-8 Estimated Carcinogenic Risks and Hazard Indexes for a Recreational Visitor at
Off-Site Areas .......................................... 44
6-9 Description of Vicinity Properties in the Area of the Weldon Spring Site ...... 45
9-1 Cost Estimate for Alternative 6a ............................... 76
9-2 Cost Estimate for Alternative 7a ............................... 77
9-3 Estimated Radiological Risks for the Recreational Visitor, Ranger, and Resident
Associated with the Soil Cleanup Criteria ...... ........ , ....... .. . . 80
9-4 Estimated Chemical Health Effects for the Recreational Visitor, Ranger, and
Resident Associated with the Soil Cleanup Criteria ................... 81
10-1 Disposal Facility Design ARARs ............................. 102
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DECISION SUMMARY
1 SITE NAME, LOCATION, AND DESCRIPTION
The Weldon Spring site is located in St. Charles County, Missouri, about 48 km (30 mi)
west of St. Louis (Figure 1-1). The site consists of two geographically distinct areas: the88-ha
(217-acre) chemical plant area, which is about 3.2 km (2 mi) southwest of the junction of
Missouri (State) Route 94 and U.S. Route 40/61, and a 3.6-ha (9-acre) limestone quarry, which
is about 6.4 km (4 mi) south-southwest of the chemical plant area. The chemical plant area and
the quarry are accessible from State Route 94, and both are fenced and closed to the public.
This remedial action addresses sources of contamination at the chemical plant area, hereafter
referred to as "the site," and its vicinity. This action also represents the selected disposal option
for contaminated bulk waste material from the quarry and vicinity areas.
The site was initially used by the Army during the 1940s to produce the explosives
trinitrotoluene (TNT) and dinitrotoluene (DNT). After extensive demolition, decontamination,
and regrading, the chemical plant was built by the U.S. Atomic Energy Commission (AEC, a
predecessor of the U.S. Department of Energy [DOE]) to process uranium and thorium ore
concentrates during the 1950s and 1960s. Radioactively and chemically contaminated waste was
disposed of at the site during this period, and waste was disposed of in the quarry by both the
Army and the AEC from the 1940s through the 1960s. Radioactive contaminants are primarily
radionuclides of the natural uranium and Th-232 decay series; chemical contaminants include
naturally occurring metals and inorganic anions, as well as organic compounds such as
polychlorinated biphenyls (PCBs) and nitroaromatic compounds.
Site features include about 40 buildings (currently being dismantled), four raffmate pits,
two ponds (Ash Pond and Frog Pond), and two former dump areas (north dump and south
dump) (Figure 1-2). Most of the land surface around the buildings is paved or covered with
gravel; the remainder of the site contains a variety of grasses and scattered small shrubs and
trees. Much of the site is routinely mowed, and little undisturbed and/or natural habitat exists
except in the northern quadrant. Soil in the two dump areas and at scattered locations
throughout the chemical plant is radioactively contaminated; discrete locations also contain
elevated concentrations of certain metals and a few organic compounds. Portions of the site are
classified as prime farmland soil by the U.S. Soil Conservation Service on the basis of soil type,
slope, and drainage.
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WENTZVILLE
ST. CHARLES
ST.
CHARLES , ,/,
' r ST. LOUIS
COUNTY
MISSISSIPPI RIVER
LAKE ST. LOUIS
ST. PETERS
MISSOURI /' • /'
WELDON
SPRING
WELDON SPRING
CHEMICAL PLANT
AND
RAFFINATE PITS
WELDON SPRING !|!
HEIGHTS ||
WELDON SPRING
QUARRY
MISSOURI RIVER
LOUIS
COUNTY
MADISON
COUNTY
COUNTY LINE
LOCATION OF THE WELDON SPRING SITE
FIGURE 1-1
A/VP/013/0293
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MATERIAL
STAGING
AREA
DOE
PROPERTY
FENCE
ASBESTOS'--'--^ POND ^'=o,
CONTAINER Vgs=saa=...r --\X
STAGING ^Crvr^^^-T'-- X
STATE
ROUTE
94
STAGING
AREA
FORMER
COAL
STORAGE ;-
RAFFINATE:;
PiTNO.1 \\ .WATERTREATMENT PLANT
DOE
PROPERTY
FENCE
RETENTION POND
TEMPORARY
STORAGE
AREA
YRAFFINATE
PIT NO.2
iY'T|,i:: HlD'Iph •.' EFFLUENT PONDS (FUTURE)
.7<.'V.' EQUALIZATION BASIN
EFFLUENT PONDS
BUILDING 434
**
DECONTAMINATION PAD
- QUARRY HAUL ROAD
LEGEND
CONTAMINATED SOURCE AREAS
FACILITIES BEING CONSTRUCTED
STRUCTURES BEING DISMANTLED
500
S
152.4
SCALE
1000 R
304.8 M
GENERAL LAYOUT OF
THE CHEMICAL PLANT AREA
FIGURE 1-2
REPORT NO.:
EXHIBIT NO:
A/CP/01 7/0293
JAB
DRAWN BY:
GLN
2/93
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The raffinate pits cover about 10 ha (26 acres) in the southwestern portion of the site.
They were excavated from existing soil during the operational period of the chemical plant to
receive waste slurry from the processing operations. These pits constitute the most heavily
contaminated area and contain about 150,000 m3 (200,000 yd3) of sludge and a combined
average 216,000 m3 (57,000,000 gal) of water. In addition, some drums and rubble from the
Army's earlier decontamination activities at the chemical plant were disposed of primarily in the
fourth pit.
Ash Pond covers about 4.5 ha (11 acres) in the northwestern portion of the site. This
area received fly ash from the steam plant during the operational period. Frog Pond covers
about 0.3 ha (0.7 acres) in the northeastern part of the site and served as a settling basin for
flows from the pilot plant. The combined volume of surface water in these ponds averages
about 8,700 m3 (2,300,000 gal). The four pits and two ponds combined cover about 15 ha
(38 acres) and are included on the Wetlands Inventory Map produced by the U.S. Department
of the Interior.
The site is transected by a surface water divide (Figure 1-3), and the natural land surface
is gently sloping. Surface runoff from the southern portion of the site flows south toward the
Missouri River via a 2.4-km (1.5-mi) natural channel referred to as the Southeast Drainage;
runoff from the remainder of the site flows north toward the Mississippi River. Soil in the
Southeast Drainage is radioactively contaminated as a result of past discharges, and intermittent
flows continue to carry contaminants off site from surface runoff down the channel. A small
portion (about 0.5 ha [1.3 acres]) of the northern area of the site along the drainage leading off
site from Ash Pond is within the 100-year floodplain of Schote Creek, a perennial stream west
and north of the site. The affected area represents a very small fraction (<0.01%) of that
floodplain. Contaminant levels in site runoff have recently decreased as a result of interim
actions to divert surface flow around contaminated soil areas such as the south dump and to
remove suspended solids using a siltation pond, straw, and vegetative cover.
The site is also situated atop a groundwater divide. Groundwater in the shallow
Burlington Keokuk Limestone aquifer south of the divide flows toward the Missouri River, and
groundwater north of the divide flows north toward the Mississippi River. Groundwater in this
shallow aquifer beneath the site and the nearby area (e.g., the Army property) is contaminated
with nitrates, sulfates, nitroaromatic compounds, some heavy metals, and uranium. No
drinking-water wells are currently completed in this aquifer, either on site or in the immediate
vicinity. The limited data available for the deep, productive St. Peter Sandstone indicate that
groundwater in this aquifer is not contaminated.
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STATE
ROUTE K „
/ US. ROUTE
URGERMEISTE
:; AUGUST A. BUSCH
CONSERVATION AREA
HAMPTON
MEMORIAL
FRANCIS .--
t - HOWELL
• HIGH t T
• SCHOOL/ '
:" STATE
•-' ROUTED .•-'^ f.
RAFFINATE PITS
SPRING
CHEMICAL
PLANT
\ SOUTH-
'^.EAST '.
^DRAINAGE
\ WELDON SPRING-
CONSERVATION AREA
.LJTTLE '•
FEMME
OSAGE
. CREEK
'-•~.\
LEGEND
- SURFACE WATER DIVIDE BETWEEN
MISSISSIPPI RIVER AND MISSOURI RIVER
— CREEK OR SURFACE DRAINAGE
— CREEK OR SURFACE DRAINAGE
0 POND OR LAKE
0
SCALE
1.6 KM
SURFACE WATER DRAINAGES
NEAR THE WSS
FIGURE 1-3
HE»ORTNO.
BMBlT NC :
o*0""™ JAB |D"AWN*Y: GLN
A/VP/027/0393
DATE
6/9/93
-------
About 22 ha (SS acnes) in the northern quadrant of the site have been relatively
undisturbed and are essentially grassland/old-field habitat with some secondary forest growth.
A wide variety of species occurs on site, especially in this northern portion. Deer, rabbits,
raccoons, squirrels, turtles, frogs, wild turkeys, geese, and ducks have been observed. The site
does not provide critical habitats for any Federal-listed threatened or endangered species, and
no Federally listed species have been sighted in the chemical plant area. Two State-listed
species, the pied-billed grebe (a State rare species) and the Swainson's hawk (a State endangered
species) have been reported for the site, although there is no evidence that either species breeds
on or uses the site year-round.
The site is bordered by the August A. Busch Conservation Area to the north, the Weldon
Spring Conservation Area to the south and east, and the U.S. Army Reserve and National Guard
Training Area to the west (Figure 1-4). The two wildlife areas are managed by the Missouri
Department of Conservation and are open throughout the year for recreational uses; together,
these areas receive about 1,200,000 visitors each year. Army reserve troops had previously used
the Army property each year, primarily for weekend training exercises. This Army property
and portions of the wildlife areas constitute the balance of the former ordnance works and are
also listed on the National Priorities List (NPL). Soil at several small locations on the Army
property and in the two wildlife areas contains generally low levels of radioactivity as a result
of previous site activities. Three lakes in the Busch Conservation Area also contain low levels
of radioactivity as a result of surface runoff. These lakes also show elevated levels of lead,
barium, and arsenic, although there is no known source from the site.
A State of Missouri highway maintenance facility is located on State Route 94, just
northeast of the site entry gate, and Francis Howell High School is located about 1 km (0.6 mi)
east of the site (Figure 1-4). The maintenance facility employs nine staff and one mechanic.
The school employs about 160 faculty and staff, and about 1,600 students currently attend. The
two closest communities to the site are Weldon Spring and Weldon Spring Heights; they are
.located about 3.2 km (2 mi) east of the site and have a combined population of about 850.
Three residences are located within this 3.2 km (2 mi) distance from the site, the closest of
which is a trailer occupied by the janitor at the high school. The largest city in the county is
St. Charles; it is located about 24 km (15 mi) northeast of the site and has a population of about
50,000.
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U.S. ROUTE
40/61
DARDENNE
CREEK
STATE
ROUTE K
SCHOTE ,
CREEK
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2 SITE HISTORY
In April 1941, the U.S. Department of the Army acquired about 7,000 ha (17,000 acres)
of land in St. Charles County, Missouri, to construct the Weldon Spring Ordnance Works — a
production facility for trinitrotoluene (TNT) and dinitrotoluene (DNT) explosives. The facility
began operations in 1941 and closed in 1946. By 1949, all but about 810 ha (2,000 acres) of
the ordnance works property had been transferred to the State of Missouri and the University
of Missouri for use as wildlife area and agricultural land. Except for several small parcels
transferred to St. Charles County, the remaining property became the chemical plant area of the
Weldon Spring site and the adjacent U.S. Army Reserve and National Guard Training Area.
In May 1955, the U.S. Atomic Energy Commission (AEC) acquired 83 ha (205 acres)
of the property from the Army for construction of a uranium feed materials plant. An additional
6 ha (15 acres) was later transferred to the AEC for expansion of waste storage capacity; i.e.,
to construct the fourth raffinate pit. Considerable explosives decontamination and regrading
activities were conducted prior to constructing the chemical plant. Uranium and thorium ore
concentrates were processed at the plant from 1957 to 1966.
Plant operations generated several chemical and radioactive waste streams, including
raffinates from the refinery operation and washed slag from the uranium recovery process.
Waste slurries were piped to the raffinate pits, where the solids settled to the bottom and the
supernatant liquids were decanted to the plant process sewer. This sewer drained off site to the
Missouri River via the Southeast Drainage. Some solid waste was also disposed of on site
during the plant's operational period. The quarry, which had been used by the Army since the
early 1940s to dispose of chemically contaminated waste, was transferred to the AEC in July
1960. Radioactively contaminated wastes such as uranium and thorium residues, building
rubble, and process equipment were disposed of in the quarry through 1969.
The Army reacquired the chemical plant property in 1967 and began decontamination and
dismantling operations to prepare the facility for herbicide production. Much of the resultant
debris was placed in the quarry; a small amount was also placed in the fourth raffinate pit. The
project was canceled in 1969 prior to any production, and the plant has remained essentially
unused and in caretaker status since that time. The Army returned the raffinate pits portion of
the chemical plant area to the AEC in 1971 and the remainder of the property to the U.S.
Department of Energy (DOE) in 1985. Prior to that transfer, the Army conducted building
repair and additional decontamination activities in 1984. The DOE established a project office
m:\users\jof\blg\rod\rod_txt.s-2.h10
-------
at the site in 1986 to support cleanup activities, and several interim response actions have been
developed and implemented since that time.
The U.S. Environmental Protection Agency (EPA) listed the quarry on the National
Priorities List (NPL) in 1987, and the chemical plant area was added to this listing in 1989. The
balance of the former Weldon Spring Ordnance Works property, which is adjacent to the DOE
portion of the property and for which the Army has responsibility, was added to the NPL as a
separate listing in 1990.
A Record of Decision was prepared for management of the Weldon Spring quarry bulk
wastes in 1990. The selected remedy entailed removal of the bulk wastes from the quarry,
transportation along a dedicated haul road to the chemical plant area, and interim storage in the
temporary storage area south of the raffinate pits. This work is presently underway.
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3 HIGHLIGHTS OF COMMUNITY PARTICIPATION
A Remedial Investigation/Feasibility Study (RI/FS) process was conducted for the Weldon
Spring site in accordance with the requirements of the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA), as amended, to document the proposed management
of the chemical plant area as an operable unit for overall site remediation and to support the
comprehensive disposal options for the entire cleanup. Documents developed during the RI/FS
process included the Remedial Investigation (DOE 1992b), a Baseline Assessment
-------
A report of this hearing was featured in the site's publication, WSSRAP Update, copies
of which were distributed to about 70,000 residences in St. Charles County on February 7,
1993.
A detailed response to the comments received during the public comment period for this
remedial action was developed as a separate document and may be found in the Administrative
Record and the information repositories. A responsiveness summary that addresses the major
issues raised during the public comment period is attached to this Record of Decision. This
decision document presents the selected remedial action for managing the chemical plant area
of the Weldon Spring site in accordance with the CERCLA, as amended, and to the extent
practicable, the National Contingency Plan (NCP). The decision for this site is based on the
Administrative Record.
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4 SCOPE AND ROLE OF REMEDIAL ACTION
This proposed remedial action is the major component of overall site cleanup
(Figure 4-1), and addresses comprehensive disposal decisions for the project. The primary focus
of this action is contaminated material at the chemical plant area, including that generated as a
result of previous response actions. However, the scope also includes the disposition of material
that may be generated by upcoming actions (e.g., at the Southeast Drainage and the quarry).
Although cleanup decisions for other components of site remediation are not included in the
scope of this action, the contaminated material that could be generated by future response actions
is being considered to facilitate an integrated disposal decision. The types of material that could
result from future actions are the same as those being addressed in this action; i.e., soil,
sediment, vegetation, and containerized process waste from the water treatment plants.
As used in this Record of Decision (ROD) and associated site documents, the use of the
term "on site" refers to all areas, contaminated or otherwise, that exist within the physical
boundaries of the Weldon Spring Chemical Plant (WSCP) and the Weldon Spring Quarry. The
quarry and the chemical plant areas are reasonably close in proximity, and are compatible with
regard to remediation approach. Therefore, they are considered one Comprehensive
Environmental Response, Compensation and Liability Act (CERCLA) site for purposes of this
remedial action. "Off site" refers to those adjacent or nearby properties not located within the
physical boundaries of the WSCP.
Several interim response actions have been selected for both the chemical plant area and
the quarry and are currently being designed and/or implemented. The primary interim actions
are summarized as follows:
• Excavation of solid wastes from the quarry, with transport to the chemical
plant area for controlled storage in a temporary storage area (TSA) pending
the disposal decision presented in this ROD.
• Removal and treatment of ponded water from the quarry, with transport of the
treatment residuals to the chemical plant area for controlled storage as above.
• Removal and treatment of ponded water from surface water impoundments at
the chemical plant area, with controlled storage of the treatment residuals as
above.
m:\users\jof\blg\rod\rod_txt.s-4.h10 12
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WELOON SPRING SITE
QUARRY
CHEMICAL PLANT AREA
INTERIM RESPONSE ACTIONS J
INTERIM RESPONSE ACTIONS
VKMTY SEDIMENT
(SOUTHEAST DRAINAGE)
NOTE • THE BOXES REPRESENT CONTAMINATED MEDIA ADDRESSED BY THE PROJECTS CLEANUP
ACTIONS FOR THE CHEMICAL PLANT AREA AND THE QUARRY. AND THEY ARE CONNECTED BY
SOLID LINES TO THE APPROBATE PHASE OF SITE CLEANUP. DASHED UNES IDENTIFY WASTE
STORED AT THE CHEMICAL PLANT AREA AS A RESULT OF THE INTERIM ACTIONS. THE MEDIA
FOR WHICH SPECIFIC TREATMENT AND DISPOSAL DECISIONS WILL BE MADE AS A PART OF
THE CURRENT REMEDIAL ACTION ARE INDICATED BY SHADING.
* -REMOVALACTION
** -REMEDIALACTION
COMPONENTS OF SITE REMEDIATION
FIGURE 4-1
flEPOOTNO.;
JAB
BMCTMO.:
AyPl/027/0293
GLN
8/9/93
-------
• Consolidation and containerization of abandoned chemicals and process wastes.
• Decontamination and dismantlement of site structures, with controlled storage
in the material staging area (MSA) and/or the TSA as above.
These removal actions have been (and are being) conducted to respond to contaminant
releases and to mitigate health and safety threats in accordance with CERCLA requirements.
The actions have also been conducted in accordance with Council on Environmental Quality
regulations for implementing the procedural provisions of the National Environmental Policy Act
(NEPA).
The role of this proposed remedial action is to establish appropriate responses and final
conditions for solid material at the chemical plant area and to identify an appropriate disposal
decision for waste generated by project cleanup activities. The action addresses management
of the following materials to minimize potential releases and related exposures:
• Sludge, sediment and soil from the raffmate pits and ponds; site-wide soil
(e.g., from past dump and spill areas); and soil and sediment from vicinity
properties.
• Structural debris in storage at the MSA.
» Solid material excavated from the quarry — including soil, sediment, process
residues, rock, building rubble and equipment, and vegetation — and in
storage at the TSA.
• Containerized wastes, including residuals generated by the two water
treatment plants and in storage at Building 434, the TSA, or other engineered
facilities.
Cleanup decisions for sediment and soil in the Southeast Drainage, groundwater beneath
the chemical plant area, and material remaining at the quarry following bulk waste removal
(including groundwater) are not included in the scope of the current remedial action. Separate
environmental documentation will be prepared within the next several years to support cleanup
decisions for those locations and media. These documents will be developed in consultation with
the U.S. Environmental Protection Agency (EPA) Region VII and the State of Missouri.
m:\usors\jof\blg\rod\rod_txt.s-4.h10 14
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5 SITE CHARACTERISTICS
The site has been extensively studied to determine the nature and extent of contamination
in various media. These studies have produced thousands of data records for soil, surface water,
sludge, sediment, and building material and other debris. Groundwater has also been sampled,
and limited biota sampling has been conducted. This information has been used to identify areas
and media for cleanup. The results of these studies are presented in the Remedial Investigation
for the Chemical Plant Area of the Weldon Spring Site (RI) (DOE 1992b). A general description
of the environmental setting at the Weldon Spring site is presented in Section 1, including a
discussion of key source areas and general contaminant information.
The primary source areas and key contaminants that have been identified at the site are
summarized in Table 5-1. The estimated areas and volumes of contaminated media addressed
by the disposal decision under this action are summarized in Table 5-2. The concentration
ranges of the major radioactive and chemical contaminants at the site are listed in Tables 5-3 and
5-4. A discussion on background levels of these contaminants is presented in Section 2 of the
Feasibility Study (FS) (DOE 1992d).
The RI information was used to assess human health and ecological risks for the site to
determine if adverse effects could result from possible exposures. Site characteristics were
evaluated for this assessment in order to identify the primary mechanisms of contaminant release
and pathways by which site contaminants could be transported to potential receptors (humans and
biota). The primary mechanisms and transport pathways identified for the site are:
• Surface runoff from on-site areas to off-site drainage soil and surface water.
• Surface water loss to groundwater via losing streams off site.
• Groundwater discharge to surface water via gaining streams off site.
• Leaching from contaminated surface and/or subsurface soil, sediment, or
sludge to groundwater.
• External gamma radiation from radioactively contaminated surfaces, including
building material and soil.
• Atmospheric dispersion of radon from radium-contaminated soil.
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TABLE 5-1 Sources of Contamination at the Weldon Spring Site
Area/Medium
Comments'*'
Pltmwy On-Sit» Source*
Raffinate pits
Surface water
Sludge
Soil
Structural debris
Frog Pond
Surface water
Sediment
Soil
Ash Pond
Surface water
Sediment
Soil
Building debris
Soil and building
debris from site
removal actions
The four raffinaw pits previously received process waste from the chemical plant and constitute
the moat heavily contaminated source area at the site.
Although currently present in the pits, this water is targeted for removal and treatment under an
interim action. Contaminants: uranium, radium, arsenic, manganese, selenium, cyanide,
nitrate, and fluoride.
Precipitates of waste slurries from uranium- and thorium-processing operations have settled to
the bottom of each pit. Contaminants: uranium, thorium, radium, arsenic, molybdenum,
vanadium, and aulfate.
Contamination in banns and beneath the pits is a result of contact with, and leaching from, the
sludge and surface water. Characterization of this soil is limited because of difficulty in
sampling under current conditions; additional characterization will be conducted as the surface
water and sludge are removed. Contaminants: radionuclide and metal precipitates (see
sludge), and nitrate.
A small amount of debris consisting of concrete, tanks, piping, drums, and structural material is
present in Raffinate Pit 4. These materials were placed in Pit 4 during closure of the chemical
plant when the Army began converting the plant for herbicide production. Contaminants:
uranium, thorium, radium, PCBs. and metals.
Frog Pond previously received flow from storm and sanitary sewers at the pilot chemical plant
and currently receives overland flow from the northeastern portion of the site.
Although currently present in the pond, this water is targeted for removal and treatment under
an interim action. Contaminants: uranium and chloride.
The sediment contains transported solids and precipitates from the surface water.
Contaminant: uranium.
Soil around the pond could be contaminated as a result of leaching from the surface water and
sediment. Contaminant: uranium.
Ash Pond previously received fly ash slurry from the power plant and currently receives • .
overland flow from the northwestern portion of the site. Soil and building debris from site
removal actions are being stored here.
Although currently present in the pond, this water is targeted for removal and treatment under
an interim action. Contaminants: uranium and nitrate.
The sediment contains transported solids and precipitates from the surface water.
Contaminants: uranium and nitrate.
Soil around the pond is contaminated as a result of runoff from the South Dump. Contaminant:
uranium.
Debris resulting from site removal actions: Uranium and nonfriable asbestos.
Contaminants: uranium, thorium, and radium.
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16
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TABLE 5-1 Sources of Contamination at the Weldon Spring Site (Continued)
Area/Medium
Comments'*'
North dump and south
dump
Soil
Metal building and
•quipmant debris
Material staging area
(MSA)
Metal building and
equipment debris
Decontamination
debris
Temporary storage area
(TSA)
Metal building and
equipment debris
Concrete building
debris end rock
Soil
Sludge and sediment
Containerized
process wastes from
the two water
treatment plants
Residual soil and
sediment from the
quarry area
These dump areas were previously used to store and dispose of radioactive material.
Contaminants: uranium, thorium, .and radium.
Contaminants: uranium, thorium, and radium.
The MSA is located in the northwestern portion of the site and provides a staging area for
radiologically contaminated material resulting from dismantlement activities. The MSA includes
a 3-ha (8-acre) gravel pad staging area with an engineered runoff collection system and
retention pond.
Contaminants: uranium, thorium, and radium.
Contaminants: uranium, thorium, and radium.
The TSA is being constructed to store bulk quarry waste which will be excavated under an
interim action.
Contaminants: uranium, thorium, and radium.
Contaminants: uranium, thorium, and radium.
Contaminants: uranium, thorium, radium, arsenic, lead, nickel, and selenium; also, in some
spots, PCBs. polycyclic lor polynuclear) aromatic hydrocarbons (PAHs), and nitroaromatic
compounds such as TNT. 2,4-DNT. 2.6-DNT, NB, and TNB.
Contaminants: uranium, thorium, radium, arsenic, and 2,4-DNT.
Contaminants: uranium, thorium, radium, arsenic, fluoride, and nitroaromatic compounds.
This material could be temporarily stored at the TSA if it were determined to require removal.
The contaminated material that could result from future actions will be addressed in separate
environmental documentation supporting cleanup decisions for this location. Contaminants:
same as the bulk waste soil and sediment.
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17
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TABLE 5-1 Sources of Contamination at the Weldon Spring Site (Continued)
Area/Medium
Comments1*1
Building 434
Containerized
chemicals
BuDding 434 was remodeled to use for storage of containerized material resulting from previous
interim response actions. (As a contingency, this building might be used to store containerized
process wastes from the water treatment plants.) Contaminants include nitric, sulfuric, and
hydrofluoric acids; sodium hydroxide; PCBs; heavy metals; and paint solvents. Two tanks of
tributyl phosphate have been drummed and transferred to Building 434.
Asbestos Storage Area Containerized, tegg«d asbestos.
Scmttmnd On-Sft» Sources
Soil in areas adjacent
to the chemical plant
buildings
Soil in areas adjacent
to the raffinate pits
Vegetation
Off-Site Source*
Burgermeister Spring
and Lakes 34, 35, and
36 in the Busch Wildlife
Aree
Surface water
Sediment
Soil at vicinity
properties
These area* were previously used to unload and store process material and to house electrical
equipment. Contaminants: uranium, thorium, radium, sulfate, nitrate, PCBs. and PAHs.
These areas were previously impacted by spills or overland flow. Contaminants: uranium,
thorium, radium, fluoride, sulfate. and nitrate.
Vegetation could be contaminated as a result of biouptake.
These areas are contaminated by surface runoff and groundwater discharge from contaminated
areas on site.
Contaminants: uranium and nitrate.
Contaminant: uranium.
These areas were previously impacted by transport and storage activities. Contaminants:
uranium, thorium, and radium.
'*' Only primary contaminants ere indicated in this table; additional in-place source area data are provided in the Rl
(DOE 1992c). Notation: TNB, 1.3,5-trinitrobenzene; 2,4-DNT, 2.4-dinitrotoluene; 2,6-DNT, 2,6-dinitrotoluene; TNT,
2,4,6-Trinitrotoluene; NB, nitrobenzene; PAHs, polycyclic aromatic hydrocarbons; PCBs. polychlnrinated biphenyls.
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18
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TABLE 5-2 Estimated Areas and Volumes of Contaminated Media
Contaminated Media end Locations
Sludge
Raffinate pits
Sediment
A*h Pond
Frog. Pond
TSA
Lakes 34. 35, and 36
Femme Osage Slough
Total sediment1*'
Soil
North Dump
South Dump
Other cite-wide coil
TSA
Raffinate pits
Soil at subsurface piping
Off site (vicinity properties)
Total soil1*1
Structural material
Concrete at TSA
Steel at TSA
Rubble/concrete at MSA
Steel at MSA
Debris at MSA
Asbestos
Building 434
Total structural material
Process chemicals
Treatment plant process waste
Consolidated chemicals
Total process chemicals
Vegetation :
From quarry • .
From building demolition
From site-wide areas
Total vegetation
Total volume
Area
(hectares)
10.4
3.5
0.7
6.4
45.7
1.4
51.8
0.8
1.7
8.1
0.8
10.4
1.8
0.5
24.1
0.9
0.3
1.0
1.0
0.2
0.2 .
0.2
3.9
0.2
0.2
0.4
0.2
0.04
1.5
1.7
(acres)
25.8
86
1.9
1.0
113.0
3.5
128.0
1.9
4.2
20.0
2.0
25.8
4.5
1.2
59.6
2.3
0.8
2.5
2.5
0.5
0.5
0.5
9.6
0.5
0.5
1.0
0.4
0.1
3.8
4.3
Id
Volume
(m3)
168.212
6.269
5.352
3.134
15.292
61.550
91.599
5,810
12,921
65.296
39,759
117,366
15,292
2,752
259.199
23,090
8,028
45,111
39.300
2.829
7.493
3,823
129,676
2,752
275
3,027
4,969
573
17.891
23.434
675.141
(yd3)
220,000
8,200
7.000
4.100
20.000
80,500
119.800*'
7,600
16.9OO
85.400
52.000
153,500
20,000
3,600
339,000
30,200
10,500
59,000
51.400
3,700
9.800
5,000
169.600
3,600
360
3,960
6,500
750
23.400
30.650
883,000
'*' Volumes for sediment and soil are based on the ALARA goals shown in Tables 9-3 and 9-4.
(bl Total sediment material includes an engineering approximation of contaminated soil which may require removal as part of
the quarry residuals operable unit.
(cl A value for total area would not be indicative of the total area impacted because some areas are counted more than once
(e.g., the sludge and soil in the raffinate pits).
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TABLE 5-3 Concentration Ranges of Radioactive Contaminants of Concern
On-Site
Concentration Range1*'
Contaminant
Ac-227ticl
Pb-210(el
Pa-231lel
Ra-226
Ra-228
Rn-220w
Rn-222|fl
Th-230
Th-232'o'
0-235^'
U-238
Soil
(pCi/o)
O.O06-44
O.4-450
O.O1-87
0.4-4 5O
0.4-150
.
-
0.3-97
0.4-150
0.01-110
O.3-2.30O
Surface
Water
(pCi/l)
-Ml
.
• '
3.4-130
1.5-25
.
-
1.4-760
0.2-7.6
1 .3-60
28-1.300
Raffinate Pit
Sludge
(pCi/g)
2.8-990
1.0-1.700
3.6-1.200
1.0-1.700
4.0-1.400
-
-
8.0-34.000
3.0-1.400
0.2-78
4.9-1,700
Off-Site
Concentration Range"*'
Surface
Water
(pCi/l)
•
'
ND'd>
ND
.
-
1 .0-8.0
ND
0.09-27
2.0-590
Sediment
(pCi/g)
.
' . •
0.7-220
0.4-480
.
-
1.5-10,000
0.7-2.5
0.02-33
0.5-720
'*' The concentration range is for detected values only; a single value is given if the contaminant was detected in only one
•ample. For surface water, combined values for the raffinate pits and NPDES sampling locations NP-0002. NP-OO03, and
NP-OOO4. For sludge, reported as wet weights (the sludge contains about 73% water by weight).
lbl The concentration range is for detected values only; a single value is given if the contaminant was detected in only one
sample. Combined values for Lakes 34. 35, and 36; Burgermeister Spring; and the Southeast Drainage. For sediment,
reported as dry weights.
lcl The concentrations of Ac-227, Pb-210. and Pa-231 for site soil and raffinate-pit sludge were determined from the
radiological source term analysis.
'*" A hyphen indicates that the contaminant was not measured nor calculated from the radiological source term analysis; ND
= not detected.
(•I
Rn-220 is a contaminant of concern only for the chemical plant buildings.
Rn-222 is a contaminant of concern for the chemical plant buildings and outdoor air. The concentration of Rn-222 and its
• short-lived decay products in outdoor air was calculated from the concentration of Ra-226 in soil.
'9) Consistent with the radiological source term analysis, Th-232 was assumed to be in secular equilibrium with Ra-228 for
•ite soil.
N The ratio of U-238:U-235:U-234 in surface water, sludge, and sediment was assumed to be 1:0.046:1.
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TABLE 5-4 Concentration Ranges of Chemical Contaminants of Concern
On-Site
Concentration Range'*1
Contaminant
Metals
Antimony
Arsenic
Barium
Beryllium
Cadmium
Chromium III
Chromium VI
Cobalt
Copper
Lead
Lithium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Thallium
Uranium, total
Vanadium
Zinc
Inorganic anions
Fluoride
Nitrate
Nitrite
Asbestos1*1
PAHS'"
• Acenaphthene
Anthracene
• Benz(a)anthracene
Benzo(b)fluoranthene
Benzo(k)fiuoranthene
Benzo(g.h,i)perylene
Benzo(a)pyrene
Chrysene
Ruoranthene
Fluorene
lndeno(1 ,2,3-cd)pyrene
2-Methytnaphthalene
Naphthalene
Phenanthrene
Pyrene
Soil
(mg/kg)
6.4-110
1.3-130
25-5.200
0.51-5.5
0.51-11
2.0-280
0.22-31
2.8-110
3.6-460
1.3-1.900"'
S.3-71
3.3-13.000
0.11-2.1
4.1-120
5.6-270
0.63-47
0.92-13
1 .0-80
0.9-6,900
7.2-380
6.1-1,100
1 .3-45
0.54-3,800
1 .5-29
ND
1.9
3.4
0.41-8.2 .
4.6
3.9
2.1
5.1
0.39-8.0
0.58-11
1.6
3.2
0.52-4.6
1.8
0.42-11
0.35-19
Surface
Water
U/g/l)
65-400
12-120
ND
7.0-9.0
37
28-170
3.1-19
NO
30-45
22-450
61-4,500
16-33
0.29-0.36
690-4,100
47-170
7.5-220
25-40
ND
4.4-5,200
90-2,100
26-60
230-19,000
190-7.200.000
-
-
-
••. -
'
-
-
-
-
-
-
-
-
-
-
-
Raffinate Pit
Sludge
(mg/kg)
6.0-87
3.1-1.100
20-7.700
0.59-25
0.94-14
4.5-150
0.50-17
5.1-44
3.7-510
2.1-640
5.0-120
25-3,000
0.10-15
16-1.600
3.3-8,800
2.7-81
1.0-5.0
1.1-58
15-5.100
26-8,700
7.9-1.600
3.2-170
0.6-160.000
1.0-1,600
-
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Off-Site
Concentration Range'6'
Surface
Water
U/g/l)
70-76
12-29
78-110
ND
ND
13-23
1.4-2.6
ND
ND
9.5-15
ND
18-870
0.35-1.3
22-42
ND
ND
4.0-6.0
33
6.0-1,800
ND
21-78
170-600
300-260.000
-
-
-
-
•
-
-
-
-
-
-
-
-
-
-
-
-
Sediment
(mg/kg)
ND|C'
3.0^19
10O-330
ND
ND
6.3-23
0.70-2.5
7.0-37
5.O-170
9.0-48
Jel
280-6,500
ND
-
8.0-66
ND
ND
ND
1.6-2,200
14-75
24-220
-
-
-
-
ND
ND
ND
ND
ND
. ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
PCBs
Nitroaromatic compounds
0.18-12
0.15-11
ND
0.2
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TABLE 5-4 Concentration Ranges of Chemical Contaminants of Concern (Continued)
On-Site
Concentration Range
Contaminant
Soil
Surface
Water
Raffinate Pit
Sludge
(mg/kg)
Off-Site
Concentration Range
Surface
Water Sediment
. (mg/kg)
DNB
2.4-DNT
2.6-DNT
NB
TNB
TNT
1 .0-3.8
0 .83-6.3
1.6-3.5
1.6-3.8
O.63-5.7
t.3-32<«>
ND
NO
ND
ND
0.04-1.4
0.80-7.5
ND
ND
ND
ND
ND
ND
0.18-O.81
0.3-1 1
0.19-18
0.87
0.02-0.84
0.05-110
ND
ND
ND
ND
ND
ND
'** The concentration range is for detected values only; a single value is given if the contaminant was measured in only one
•ample. For surface water, the combined value for the raffinate pits and NPDES sampling locations NP-O002, NP-O003.
•nd NP-O004. For sludge,.reported as wet weights (the sludge contains about 73% water by weight).
(bl The concentration range is for detected values only; a single value is given if the contaminant was measured in only one
•ample. For surface water and Mdiment, the combined value for Lakes 34, 35, and 36; Burgermeister Spring; and the
Southeast Drainage. For sediment, reported as dry weights.
'c' ND « not detected; a hyphen indicates that the contaminant was not assayed.
'* One high sample was measured at 43,000 mg/kg.
'*' Asbestos is a contaminant of concern only for the chemical plant buildings.
"' Although not technically considered PAHs, 2-methylnaphthalene and naphthalene are included in this category for
presentational purposes.
tol One high sample was measured at 650,000 mg/kg.
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• Atmospheric dispersion of fugitive dust containing uranium, thorium, and radium.
In addition to areas of contamination on site, several off-site locations are contaminated
as a result of releases that occurred during the operational period of the chemical plant (such as
the release of raffinate pit surface water to the Southeast Drainage) in addition to ongoing
releases (e.g., via surface runoff over contaminated soil and leaching of contaminants from the
raffinate pits to groundwater). These off-site locations include Burgermeister Spring and three
lakes in the Busch Conservation Area and 10 vicinity properties, one of which is the Southeast
Drainage (which includes intermittent flow that is lost underground and reemerges downstream
through a series of springs).
In order to develop specific cleanup decisions, a variety of information was used to
estimate possible human health and ecological risks associated with the site. This information
includes contaminant data from the extensive site characterization effort, fate and transport
considerations, possible receptors, different types of exposures that could occur, and
lexicological data developed by the U.S. Environmental Protection Agency (EPA) from the
scientific literature. The risk estimates focus on the media and locations addressed by this
remedial action. Section 6 discusses the receptors and routes of exposure, and also summarizes
the risk assessment results.
Several key factors are relevant to the fate and transport of site contaminants and the
potential for human and ecological exposures. First, certain interim actions at the site have not
yet been completed — including dismantlement of all buildings and removal and treatment of
water from the raffinate pits. (The latter is to be coordinated with raffinate sludge removal.)
Therefore, although exposures to these areas are expected to be reduced within the next several
years as these actions are implemented, related estimates (those health risk assessments
performed for the building and raffina'te-pit areas) were included in the Baseline Assessment
(DOE 1992c) for the site. Second, surface water in the raffinate pits currently limits the
emanation of radon, external gamma radiation and wind dispersion of the fine-grained sludge.
If, in a future scenario, no site controls were in place and the surface water in the raffinate pits
drained away (e.g., from a break in the dikes), air pathways could become an important
exposure consideration for nearby individuals. Except in such a case, the air pathway does not
play a role in contaminant transport because of the nature of surface features (including
vegetation) and local meteorological conditions.
Local geology and geochemistry also play a role in contaminant transport. Solution
features are present in the vicinity of the site, although the site itself is not considered to be
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situated in an area of significant collapse potential. Site geology and surface water and
groundwater flow were studied in coordination with the State of Missouri Department of Natural
Resources, Division of Geology and Land Survey. This testing did not detect void space in the
overburden or soil material, and voids in the limestone bedrock were few and small (with 90%
of the void space within the upper 3 m [10 ft] of bedrock). No open subsurface networks were
identified on site.
In addition, all surface water drainages on the chemical plant site are classified as
gaining. Dye trace tests indicate that small voids do exist (e.g., in the weathered portion of the
limestone bedrock), but results suggest that they are isolated. Thus, although contaminants that
leach to groundwater (or are lost to the subsurface via nearby losing streams off site) could be
further transported through solution channels rather than by diffuse flow, study results indicate
that such transport at the site would be limited. In addition, clays in the overburden present low
hydraulic conductivity and considerable attenuation capacity for contaminants that may leach
from contaminated areas. (The site geology and flow characteristics continue to be evaluated
in support of future documents and decisions for the groundwater operable unit. These
documents will include an evaluation of potential exposure to groundwater.)
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6 SUMMARY OF SITE RISKS
Potential human health effects associated with the chemical plant area of the Weldon
Spring site and nearby off-site locations were assessed by estimating the radiological and
chemical doses and associated health risks that could result from exposure to site contaminants.
The assessment, which considered both current and future site conditions, is given in the
Baseline Assessment for the Oiemical Plant Area of the Weldon Spring Site (BA) (DOE 1992c)
and in an updated rebaseline assessment in Appendix E of the Feasibility Study for the Chemical
Plant Area of the Weldon Spring Site (FS) (DOE 1992d). Impacts to environmental resources
are also addressed in the Baseline Assessment.
6.1 Contaminants of Concern
Radioactive and chemical contaminants and their concentrations in affected media are
listed in Tables 5-3 and 5-4. The contaminants of concern for the human health assessment were
identified from those detected in site soil, surface water, sediment, sludge, and buildings, and
they represent the major chemical classes present at the site. These contaminants include
radionuclides, metals, inorganic anions, nitroaromatic compounds, polycyclic (or polynuclear)
aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and asbestos. Selection of
the contaminants of concern was based on both the history of site operations and an evaluation
of characterization data with respect to the distribution and concentration of contaminants in the
various media at the site and the potential contribution of individual contaminants to overall
health effects.
6.2 Exposure Assessment
6.2.1 Contaminant .Fate and Transport
The fate and transport of contaminants released into the environment at the site were
evaluated to determine potential exposure points. Human exposures evaluated were those
resulting from potential contact with sources and affected media within the site boundary and
contaminated media at off-site areas impacted by transport from the site.
The principal source areas and contaminated media identified at the site are (1) chemical
plant buildings; (2) surface water and sludge at the four raffinate pits; (3) surface water and
sediment at Frog Pond and Ash Pond (conservatively represented by the raffinate pits in this
assessment because the contaminant levels are much higher in the pits); (4) contaminated soil
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at the north dump, at the south dump, at the coal storage area, around certain chemical plant
buildings, and at other scattered locations; (5) groundwater in the upper aquifer in the
Burlington-Keokuk Limestone; and (6) containerized chemicals in storage in Building 434.
Off-site locations and media that have been impacted by contaminant transport from these
source areas include surface water and sediment in the Southeast Drainage (Weldon Spring
Wildlife Area) and in Burgermeister Spring and Lakes 34, 35, and 36 (Busch Conservation
Area). Soil at discrete areas, referred to as soil vicinity properties, is also contaminated as a
result of past operations (Table 5-1).
The major pathways that have resulted in contaminant transport to these off-site locations
are surface water runoff, surface water loss to groundwater (via losing streams), groundwater
discharge to surface water (via gaining streams), and leaching from surface and/or subsurface
material to groundwater.
6.2.2 Exposure Scenarios
To address the changing site configurations, five assessments were conducted for the
chemical plant area that considered time, institutional controls, and land use. A sixth assessment
was conducted for the off-site areas impacted by site releases. The receptors, areas and media
contacted, and routes of exposure evaluated for these assessments are summarized in Tables 6-1
and 6-2 and are described as follows.
For the first assessment, the site configuration as of early 1992 was evaluated to identify
potential health effects under baseline conditions. These conditions include the presence of the
raffinate pits and buildings but not the temporary facilities such as the temporary storage area
(TSA), material staging area (MSA), and water treatment plant that will be completed to support
interim actions. About 200 workers are currently on site, and public access is controlled by a
perimeter fence and security guards. The potential on-site receptors identified for these
conditions are a site maintenance worker and a trespasser. A swimmer was also evaluated to
address the possibility that an intruder might swim in the raffinate pits.
The same baseline site configuration was evaluated for the second assessment as for the
first assessment, but it was hypothetically assumed that U.S. Department of Energy (DOE) and
other workers were no longer at the site and access was no longer controlled. This assessment
permits an evaluation of long-term impacts that might occur in the absence of any further
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TABLE 6-1 Scenario Descriptions for On-Site Receptors Under Current and Future Conditions
Site Condition* and
Receptor Description • On-8lte Area Medium Route* of Exposure
Baseline situ configuration, with access restrictions
Maintenance Worker An Individual conducts routine -maintenance Site wide Soil External gamma Irradiation,
activities eight hours a day, 200 days a year, Ingestlon. dermal contact.
for 10 years.
Air Inhalation.
Trespasser An individual enters the site five times per Site wide Soil External gamma Irradiation,
year, one hour per visit, for 10 years. ingastion, dermal contact.
Air Inhalation.
Raffinate pits Surface water Ingestlon.
Sludge External gamma Irradiation,
Ingestion. .
• : Buildings Residues External gamma Irradiation,
ingestion, dermal contact.
Air Inhalation.
Swimmer1'1 An individual swims in the raffinate pits for Raffinate pits Surface water Incidental Ingestion, dermal
one hour, once per year, for 10 years.
Sludge External gamma Irradiation,
ingestion, dermal contact.
Air Inhalation.
Recreational visitor An individual visits the site 20 times per year. Site wide Soil External gamma Irradiation,
four hours per visit, for 30 years. ingestion, dermal contact.
Air Inhalation.
Raffinate pits Surface water Ingestlon.
Sludge Incidental ingestion.
Buildings Residues External gamma irradiation,
Ingestion, dermal contact.
Air Inhalation.
Incidental
incidental
incidental
Incidental
contact.
Incidental
incidental
Incidental
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TABLE 6-1 Scenario Descriptions for On-Site Receptors Under Current and Future Conditions (Continued)
Site Condition* and
Receptor Description C
Sportsman An Individual hunt* at the site 1 5 days par
year, four hours per day, 'for 30 years.
>n-6tt« Area Medium Route* of Expoaur*
Site wide Soil External gamma Irradiation, incidental
Ingaation, dermal contact.
Air Inhalation.
Game Ingestion.
Interim site configuration, with access restrictions
Maintenance An Individual conducts maintenance activities Site wide Soil External gamma Irradiation, Inoldenta)
worker"3' eight hours per day, 200 days per year, for Ingsation, dermal contact,
10 years.
Air Inhalation.
TSA and MSA Waste/debris External gemma Irradiation.
Trespasser An Individual enters the. site five times per
year, one hour per visit, for 10 years.
Site wide Soil External gamma Irradiation, Incidental
Ingeetion, dermal contact.
Air Inhalation.
Interim site configuration, with no access restrictions
Recreational Visitor An individual visits the site 20 times per year, Site wide Soil External gamma Irradiation, incidental
four hours per visit, for 30 years. Ingestion, dermal contact.
Air Inhalation.
Raffinate pits Surface water Ingestion;
Sludge Incidental Ingestion.
TSA and MSA Waste/debris External gamma Irradiation.
Modified site configuration, with no access restrictions
Recreational Visitor An individual visits the site 20 times per year,
four hours per visit, for 30 years.
Site wide Soil External gamma irradiation, incidental
ingestion. dermal contact.
Air Inhalation.
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TABLE 6-1 Scenario Descriptions for On-Site Receptors Under Current and Future Conditions (Continued)
Site Condition* and
Receptor
Ranger
Resident1'1
Farmer10'
Description On-SIt
An Individual works outdoors and in an on- Site
site ranger station eight hours per day,
250 days per year, for 25 years.
An individual lives in a house on site 24 hours Site
per day, 350 days per year, for 30 years.
• Area Medium
wide Soil
Air
wide Soil
Air
An individual lives on a farm on site 24 hours Ash Pond Soil
per day, 350 days per year, for 30 years.
Air
Fruits, vegetables,
beef, dairy products
Route* of Expo*ur*
External gamma irradiation, incidental
tngeation, dermal contact.
Inhalation.
External gamma irradiation, incidental
ingestion, dermal contact.
Inhalation.
External gamma Irradiation, incidental
ingestion, dermal contact.
Inhalation.
Ingestion.
'*' Conditions for
(bl
this receptor also represent those, for a swimmer under the baseline configuration with no access restrictions.
Exposures were assessed for a worker performing routine maintenance activities such as mowing and fence repair (as for the worker under the baseline configuration) and
elso for a worker performing maintenance activities at the TSA and MSA debris staging areas.
|cl Although ingestion of groundwater was evaluated for this receptor, the results are not included in this summary because of the preliminary nature of the assessment (see
Appendix E, Section E.4).
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TABLE 6-2 Scenario Descriptions for Off-Site Receptors Under Current and Future Conditions
Receptor Description : Off-Site Area
Recreational Visitor An Individual visits the off-site location 20 Vicinity
times per year, four hours per visit, for properties'1'
30 years.
Southeast Drainage
Burgermaister Spring
Lakes 34, 35 end 36
Swimmer An individual swims in Lake 34, 35, and 36 Lakes 34, 35 and 36
for one hour, once per year, for 10 years.
Sportsman An individual fishes at Lakes 34, 35, and 36 Lakes 34, 35 and 36
seven days per year, four hours per day, for
30 years.
Medium
Soil
Surface water
Sediment/soil
Surface water
Surface water
Sediment/soil
Surface water
Sediment/soil
Surface water
Sediment/soil
Fish
Route* of Exposure
External gamma Irradiation, Incidental
ingestion.
Ingestlon.
External gamma Irradiation, Incidental
Ingestion.
Ingestlon.
Ingestlon,
External gamma Irradiation, Incidental
Ingestlon, dermal contact,
Incidental Ingeitlon, dermal contact.
External gamma Irradiation, Incidental
Ingestlon, dermal contact.
Ingeetlon.
External gamma Irradiation, Incidentel
ingestion, dermal contact.
Ingestion.
Soil vicinity properties except the Southeast Drainage, which is addressed separately.
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cleanup. Under these conditions, land use on site was assumed to be recreational because the
site is adjacent to two wildlife areas where recreational use is expected to continue into the
reasonably foreseeable future. Consequently, a recreational visitor was identified as the future
on-site receptor. To address possible exposures to contaminated game, a sportsman who was
assumed to hunt on site was also evaluated. Because a sportsman might also fish at the off-site
lakes, on-site and off-site exposures were combined for this receptor. Potential exposures were
also assessed for an individual (youth) who was assumed to swim in the raffinate pits. The first
and second assessments are presented in the BA (DOE 1992c).
For the third and fourth assessments, which are presented in Appendix £ of the FS
(DOE 1992d), the site configuration was assumed to reflect conditions associated with recent
interim actions that are in various stages of planning and implementation. These actions include
dismantling the chemical plant buildings and storing the material at the MSA, storing the bulk
wastes excavated from the quarry at the TSA, and removing and treating water from the
raffinate pits (Section 4). The purpose of these two assessments was to identify impacts that
could occur if no further cleanup actions were taken at the site beyond those that have already
been initiated, and assuming they are completed. These actions will result in interim or
transitional site conditions because they represent only a partial completion of overall cleanup
plans, pending implementation of the remedial actions identified in this Record of Decision
(ROD).
Both short-term and long-term assessments were conducted for the interim site
configuration. The short-term assessment evaluated possible health effects from the transitional
site conditions for the reasonable scenario under which the DOE remains on site and existing
institutional controls (e.g., access restrictions) are maintained; the maintenance worker and
trespasser were the receptors evaluated. The long-term assessment of the interim site
configuration evaluated exposures that could occur in the more extended future (e.g., after
100 years), hypothetically assuming that the DOE is no longer present and access to the site is
unrestricted. Under these conditions, the most likely land use is recreational; therefore, the
receptor evaluated was a recreational visitor.
The fifth assessment was conducted to focus the development of preliminary cleanup
criteria for site soil. Soil is the only medium for which criteria were developed within the scope
of the current remedial action because the other media have been addressed by interim actions.
Therefore, a modified site configuration was evaluated by focusing on soil areas and not
including the raffinate pits, buildings, and temporary facilities. For this assessment, which is
presented in Appendix E of the FS (DOE 1992d), it was hypothetically assumed that the DOE
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is no longer present, that access is unrestricted, and that land use in the area might change in
the extended long term (e-g., after 100 to 200 years and beyond). Four receptors were
evaluated for this long-term assessment of the modified site configuration: a recreational visitor,
a ranger, a resident, and a fanner.
For the sixth assessment, off-site exposures were evaluated for a member of the general
public at Burgermeister Spring; Lakes 34,35, and 36; the Southeast Drainage; and specific soil
vicinity properties. Although most of these areas are located in the Weldon Spring and Busch
conservation areas, several vicinity properties are located on the adjacent Army land to which
access is currently restricted. Recreational use of the conservation areas is expected to continue
for the reasonably foreseeable future; hence, this assessment estimated exposures to the con-
taminated areas for a recreational visitor. (Ongoing and likely future exposures on the Army
land would be bounded by those associated with recreational use because use of this land by
Army personnel is less frequent. To be conservative, recreational use of those vicinity
properties was evaluated for both the current and future assessments.) A swimmer was also
evaluated for the off-site lakes.
Contaminant levels at the off-site locations are expected to remain the same or be
somewhat lower in the future because interim actions are mitigating site releases. Therefore,
one assessment was conducted for both current and future exposures that extend to 100 or
200 years and beyond. This assessment is presented in the BA (DOE I992c).
Current data for the Southeast Drainage are limited, so exposures associated with this
location will be reevaluated in greater detail within the next several years after more data
become available. For the remaining vicinity properties, the results of the long-term assessment
of the modified site configuration that considered nonrecreational land uses for on-site soil are
incorporated into decisions for off-site soil. This addresses the possibility that local land use
might change in the extended future.
6.2.3 Exposure Point Concentrations
Exposure point concentrations for the various media addressed in the exposure assessment
were determined on the basis of data availability and the objective of the analysis. For the
radioactive contaminants, not all contaminants of concern were directly measured. To address
this issue, information from the radiological source term analysis for site soil and raffmate-pit
sludge was used to infer concentrations of radionuclides not directly measured. Extensive data
were available for soil, and contaminant heterogeneity was addressed by conducting both a site-
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wide and a location-specific analysis for all receptors except the farmer. For the site-wide
analysis, the 95% upper confidence limit of the arithmetic average (UL^) value was used as the
exposure point concentration for each contaminant. For the location-specific analysis, actual
measurements from each sample location were used as the exposure point concentrations. For
the farmer analysis, the 4-ha (10-acre) Ash Pond area was the basis for exposure point
concentrations. It was recognized that a larger area is required to support a family farm, and
this area was chosen because it is the most radioactively contaminated and contains most of the
chemical contaminants of concern. The farmer-area approach consisted of two methods: for
chemical contaminants, the UL^ of the arithmetic average from borehole measurements in the
Ash Pond area was used; for radionuclides, the contour-weighted value was used. This value
was determined using a statistical technique (kriging).
For the assessments evaluating current site conditions, exposure point concentrations for
air were modeled from UL^ values for the southern portion of the site, which is considered the
most likely source of fugitive dust under baseline conditions. This modeling approach was used
because measurements are not available for all airborne contaminants. Under future conditions,
where the site configuration has changed, exposure point concentrations for the recreational
visitor, ranger, and resident were modeled from soil UL^ values for the entire site. For the
farmer, exposure point concentrations were modeled from soil concentrations consistent with the
other pathways. For sludge, sediment, and surface water, maximum concentrations were used
as the exposure point concentrations (with one exception), because screening-level analyses were
conducted for these media and certain limitations exist for the available data. The exception is
uranium in surface water at the Southeast Drainage, in which water flows intermittently and
measured concentrations vary widely over time with runoff conditions; half the maximum
measured concentration was used to represent this exposure point concentration over the 30-year
exposure period.
For radioactive contamination in the buildings, average concentrations from Building 403,
a former process building that is heavily contaminated, were used to represent exposure point
concentrations for all buildings. The UL^ value was used for residual PCB contamination from
information for Building 408, and airborne concentrations of asbestos were determined from
UL95 values for Building 201. Cleanup decisions have already been made for buildings and
surface water, so results of these conservative analyses are considered as screening-level
information.
On the basis of the types of contaminants present at the site (i.e., most are relatively
immobile and resistant to biodegradation) and the implementation of release controls to prevent
m:\users\jof\blg\rod\rod_txt.s-6.h10 33
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further off-site releases, the contaminant levels at on-site and off-site areas are assumed to be
similar to current conditions. Given that processing operations at the site ceased approximately
40 years ago, this is expected to be a reasonable but conservative assumption, with one
exception. Ingrowth of Rn-222 from uranium would produce a peak concentration
approximately 200,000 years in the future. This factor has been considered in the development
of cleanup criteria. In general, other contaminant levels would be expected to decrease over
time as a result of natural processes. Hence, the exposure point concentrations for the receptors
evaluated under possible future ate conditions were the same as those evaluated for current
on-site receptors, and similarly, the exposure point concentrations for a future recreational visitor
off site were assumed to be the same as those assessed for the current off-site recreational
visitor. Because the exposure parameters for the off-site recreational visitor would also be the
same under current and future conditions, only one assessment was conducted for this receptor.
6.3 Toxicity Assessment
Cancer and chemical toxicity are the two general health-effect end points from exposure
to site contaminants. Cancer induction is the primary health effect associated with radionuclides
at the site, and 17 of the chemical contaminants of concern are classified as potential
carcinogens. Four of the 17 are classified as Group A carcinogens (arsenic, chromium VI,
nickel, and asbestos), for which strong evidence exists for human carcinogenic!ty.
A number of toxic effects are linked with exposure to noncarcinogenic contaminants.
Uranium is the most significant contributor to noncarcinogenic health effects associated with site
soil, and the chemical toxicity associated with human exposure to uranium is kidney damage.
The PCBs inside the chemical plant buildings, and at a few soil locations, also contribute
significantly to potential chemical carcinogenic!ty and toxicity, which is characterized by skin
effects and liver damage.
Potential carcinogenic risks from exposures to radiation were estimated using a two-phase
evaluation. For the first phase, radiation doses were calculated for all relevant radionuclides and
pathways using dose conversion factors (DCFs) based on dosimetry models developed by the
International Commission on Radiation Protection. Radiological risks were calculated by
multiplying the doses by a risk factor which represents an age-averaged lifetime excess cancer
incidence per unit intake (and per unit external exposure). Three separate risk factors were
used: (1) a risk factor of 3.5 x 10"4/working-level month (WLM) was used for inhalation of
Rn-222 and its short-lived decay products; (2) a risk factor of 1.2 x lO^/WLM was used for
m:\users\jof\blg\rod\rod_txt.s-6.h10 34
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inhalation of Rn-220 and its short-lived decay products; and (3) a risk factor of 6 x 10~7/mrem
was used for all other exposure routes.
The potential for carcinogenic and noncarcinogenic effects of human exposure to
chemicals was quantified with slope factors and reference doses (RfDs). Cancer slope factors
have been developed by the U.S. Environmental Protection Agency (EPA) for estimating
incremental lifetime cancer risks associated with exposure to potentially carcinogenic chemicals.
The slope factors, which are expressed in units of (mg/kg-d)*1, are multiplied by the estimated
intake of a carcinogen, in mg/kg-d, to provide an upper-bound estimate of the incremental
lifetime cancer risk. These risk estimates are considered to be conservative because the slope
factors are derived as upper-bound estimates such that the true risk to humans is not likely to
exceed the risk estimate and, in fact, may be lower. Slope factors are derived from the results
of human epidemiological studies or chronic animal bioassays. Slope factors derived on the
basis of animal studies are adjusted to account for extrapolation from animals to humans.
Reference doses have been developed by the EPA for indicating the potential for adverse
health effects from exposure to chemicals inducing noncarcinogenic effects. The RfDs, which
are expressed in units of mg/kg-d, are estimates of the lifetime daily exposure level for humans,
including sensitive subpopulations, that are likely to be without an appreciable risk of adverse
effects during a lifetime. The potential for adverse health effects is estimated by comparing
contaminant intakes, in mg/kg-d, to the RfD. The RfDs are derived from the results of human
epidemiological studies or animal studies, to which uncertainty factors have been applied. These
uncertainty factors help ensure that the RfDs do not underestimate the potential for the
occurrence of adverse noncarcinogenic effects.
The slope factors and RfDs are specific to the chemical, the route of exposure, and, for
RfDs, the duration over which the exposure occurs. For all scenarios evaluated, the exposure
duration exceeded a period of seven years; hence, chronic RfDs were applied to the assessment.
The slope factors and RfDs used in the assessment are listed in Tables 6-3 and 6-4, respectively.
6.4 Summary of the Human Health Risk Characterization
Potential carcinogenic risks from radiological and chemical exposures were estimated for
the human health assessment in terms of the increased probability that an exposed individual
could develop cancer over the course of a lifetime. According to the NCP, an acceptable excess
lifetime cancer risk to an individual from exposure to site contaminants is between 1 x 10"4 to
m:\users\jof\blg\rod\rod_txt.s-6.h1 0 35
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TABLE 6-3 Oral and Inhalation Slope Factors
Contaminant
Metals
Arsenic
Beryllium
Lead
Asbestos
PAHs'0'
PCBs
Nitroaromatic
compounds
2.4-DNT
2.6-DNT
TNT
Oral
Slope Factor
(Img/kg-dr1)
1.8
4.3
NA»>
NA
11.5
7.7
0.68W
0.68lfl
0.03
Weight-of-
Evidenca1*1
A
B2
B2
A
62
62
B2
82
C
Contaminant
Metals
Arsenic
Beryllium .
Cadmium
Chromium VI
Lead
Nickel
Asbestos
PAHsle- •'
PCBs
Nitroaromatic
compounds
2.4-DNT
2.6-DNT
TNT
Inhalation
Slope Factor
(|mg/kg-dr1)
15
8.4
6.1
41
NA
1.7
0.23'd>
6.1
NA
NA
NA
NA
Carcinogenic
Weight-of-
Evidence1*1
A
B2
61
A
82
A
A
82
62
B2
B2
C
'*' Carcinogenic weight-of-eyidence is a qualitative designation for potential carcinogens: A, human carcinogen; B1 and B2,
probable human carcinogen; C, possible human carcinogen.
Ib)
NA indicates not available.
— asbestos, metals, nitroaromatic compounds. PCBs; (Appendix B) end EPA (1991b) — PAHs.
m:\users\jof\blg\rod\rod_txt.s-6.h10
36
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TABLE 6-4 Oral and Inhalation Reference Doses
Contaminant
Metals
Antimony
Arsenic
Barium
Beryllium
Cadmium (in water)
Cadmium (in food)
Chromium III
Chromium VI
Cobalt
Copper1"
Lead
Lithium
Manganese
Mercury, inorganic
Molybdenum
Nickel
Selenium
Silver
Thallium, soluble salts
Uranium, soluble salts
Vanadium
Zinc
Inorganic onions
Fluoride, soluble
Nitrate
Nitrite
Contaminant •.
Metals
Barium
Cadmium'*1
Chromium III
Chromium VI
Manganese
Mercury
Oral Reference
Dose, Chronic
(mg/kg-d)
4 x 1CT4
3 x 1CT4
7 x 10'2
5 x 10'3
5 x 10-*
1 x 10'3
1
s x icr3
NAlbl
4 x 10'2
NA
2 x 1C'2
1 x 10°
3 x Itr4
4 x 10'3
2 x 10'2
5 x 10'3
5 x 10'3
7 x 10'5
3 x 10'3
7 x TO'3
2 x 10'1
6 x 10'2
1.6
1 x 10'1
Inhalation
Reference
Dose. Chronic
(mg/kg-d)
1 x 10"*
2 x 10'*
6 x 10'7
6 x 10'7
1 x 10"*
9 x 10'5
Oral Reference
Dose, Chronic
Contaminant
Asbestos
PAHs
Acenaphthene
. Anthracene
Benz(a)anthracenel*'
Benzo(b)fluoranthene'''
Benzo(k)f!uoranthene'*'
Benzo(g,h,i)perylene|gl
• Benzo(a)pyrene(*'
Chrysene'11
Fluoranthene
Ruorene
IndenoU ,2,3-cd)pyrenelal
2-Methvlnaphthaleneldl
Naphthalene
Phenenthrene'*1
Pyrene
PCBs
Nitroaromatic
compounds
DNB
2.4-DNT
2.6-DNT
MB
TNB
TNT
(mg/kg-d)
NA .
6 x 10'2
3 x 10' '
3 x Ifr2
3 x 10'2
3 x 10'2
3 x 10'2
3 x 10'2
3 x 10'2
4 x 10-2
4 x 10'2
3 x 10'2
4 x 10-3
4 x 10'3
3 x ID'2
3 x ID'2
1 x 10-4
1 x lO^4
2 x 10"*
4 x 10-3
5 x ID"4
5 x 10'5
5 x 10"4
Inhalation
Reference
Dose, Chronic
. Contaminant
Nitroaromatic
compound
NB
(mg/kg-d)
6 x 10'*
'*' In the absence of an RfD from Integrated Risk Information System or Health Effects Assessment Summary Tables, the RfD
for pyrene was used for this compound.
|bl NA indicates not available.
(cl RfD calculated from the current drinking water standard of 1.3 mg/l.
m:\users\jof\blg\rod\rod_txt.s-6 .hi 0
37
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wl In the absence of an RfD from IRtS or HEAST. the RfO for naphthalene was used for this compound.
'*' RfD derived from a minimum ristttewel of 7 x 10"* mg/m3.
Sources: EPA (1991c) — barium (inhalation), chromium (inhalation), copper, mercury, molybdenum, NB (inhalation), thallium.
vanadium, zinc; EPA (1991b) — antimony, arsenic, barium (oral), beryllium, cadmium (oral), chromium (oral), manganese, nickel,
selenium, silver, thallium, uranium, fluoride, nitrate, nitrite, PAHs, DNB, NB (oral), TNB, TNT; Hurst (1990) — lithium; ATSDR
(1989a) - cadmium (inhalation); ATSDR (1989b) - 2.4-DNT, 2,6-DNT; ATSDR (1989c) - PCBs.
1 x 1CT6 — or 1 in 10,000 to lin 1 million (EPA 1990). This range is referred to as the target
risk range in this discussion, and it provides a point of reference for the site-specific risks
presented in the BA and FS. To put this range in the context of the background cancer rate,
about one in three Americans wfll develop cancer from all sources, and it is estimated that 60%
of cancers are fatal (American Cancer Society 1992). These estimates translate to a fatality
cancer risk of about 2 x 10*1, or 1 in 5. The individual lifetime risk of fatal cancer associated
with background radiation, primarily from naturally occurring radon, is estimated to be about
1 X 10'2, or 1 in 100 (EPA 1989b).
Radiological risks were calculated by multiplying the estimated radiological doses by
specific risk factors to estimate the probability of cancer induction per unit dose. Chemical risks
were calculated by multiplying the estimated average daily intake by the chemical-specific slope
factors.
The potential for adverse effects other than cancer from exposure to a single contaminant
was assessed by estimating the hazard quotient — the ratio of the daily intake (averaged over
the exposure period) to the RfD. The individual hazard quotients determined for each
contaminant and medium to which a given receptor may be exposed were then summed to
determine the hazard index; a hazard index of less than 1 was considered to indicate a
nonhazardous situation. Conversely, if the total hazard index was greater than 1, a potential
concern may be indicated.
To determine whether cleanup is warranted at NPL sites, the EPA considers incremental
risks relative to the target risk range of 1 x 10"6 to 1 x 10"4, in combination with other site-
specific factors (Appendix B). In the following summary of the risk results, estimates are
presented as total risks unless otherwise specified. Potential incremental risks from exposures
to site contaminants were assessed in developing cleanup criteria for site soil, which are
discussed in Section 9 of this ROD.
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The estimated risks and hazard indexes evaluated for exposures at the site under the
baseline, interim, and modified future site configurations, as described in Section 6.2.2, are
summarized in Tables 6-5 through 6-7. As appropriate to the site configuration and receptor,
intakes and risks were estimated for exposures associated with (1) site-wide soil and air,
(2) raffinate pit surface water and sludge, and (3) building air and residues. The significant
findings of the risk assessment are summarized below and discussed with respect to their
relationship to the need for remedial action; detailed discussions of the results of the risk
characterization results are presented in the BA and in Section 1.6 and Appendix E of the FS.
For the baseline case, i.e., the current site configuration with continued access controls,
the combined incremental risks from exposure to radioactive and chemical contaminants for the
two hypothetical receptors evaluated — the maintenance worker and trespasser — exceed the
upper end of the target range; i.e., the risks are greater than 1 x 10"4 (Table 6-5). Risks are
also greater than the target range for the hypothetical recreational visitor under the modified
(future) case, for which it is assumed, for purposes of analysis, that institutional controls are
lost. The hazard index exceeds 1 for both the trespasser and recreational visitor. For the
worker, inhalation of radon (estimated from conservative assumptions for radium in site soil)
accounts for most of this risk. For the trespasser and recreational visitor, the elevated risks are
associated with exposures at the raffinate pits and buildings; the hazard index above 1 is
associated with exposures at the buildings.
The reasonable maximum exposure (RME) for the raffinate pits and buildings would be
incurred by the trespasser under current conditions and by the recreational visitor under
hypothetical future conditions. The risks from exposures at the raffinate pits result primarily
from exposure to radioactive contamination in the sludge; for the buildings, the risks are from
combined exposures to radon, dust, and residues for the radioactive contaminants and from
exposures to residues (PCBs) for the chemical contaminants.
Decisions have already been made for interim actions at the site to dismantle the
buildings and remove surface water from the pits. For the buildings, that action will effectively
remove all potential risks currently associated with indoor exposures. For the raffinate pits,
removal of surface water under the interim action and excavation, treatment, and placement of
raffinate pit sludge in the disposal cell under the current remedial action (see Section 9.1) will
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TABLE 6-5 Estimated Carcinogenic Risks for On-Site Receptors under the Baseline
Configuration'3*
Area and Medium
Maintenance Worker
Radiological Chemical
Trespasser16' Recreational Visitor*1
Radiological Chemical Radiological Chemical
She-wide toil and air
Raffinate-pit surface water
S x 10-* 1 x 10'5
MQM NQ
2 x 10-e
2 x 10-*
2 x 10-7
9 x 10'6
6 x 10'5
3 x 10'3
3 x 10*
1 x 10"4
and sludge
Building air and residues NQ
Combined risk S x 10"
NQ 1 x W4 4 x W4 1 x 10'3 3 x 10'3
1 x 10'5 9 x 10-5 1 x W* 1 x TO'3 1 x 10'3
*** The maintenance worker and trespasser were evaluated for the baseline configuration under which existing site controls
were assumed to be maintained; the recreational visitor was evaluated for the baseline configuration under which controls
were assumed to no longer exist. The risk to the sportsman, which includes both on-site and off-site exposures, is given
in the text.
lb| The individual risks correspond to the reasonable maximum exposures, which were estimated by assuming that the entire
exposure occurs at the indicated area and medium. The combined risks correspond to exposures that were assumed to
be equally distributed among site-wide soil and air, raffinate-pit surface water and sludge, and building air and residues.
For a swimmer, the estimated radiological and chemical risks from exposures to raffinate-pit surface water and sludge and
site-wide air are 2 x 1CT4 and S x 10'6.
-------
TABLE 6-7 Estimated Carcinogenic Risks and Hazard Indexes for Exposures to Soil
and Air under the Modified Site Configuration
Receptor
Recreational visitor
Ranger
Range'*'
Median
Resident
Range
Median
Farmer'"
Carcinogenic Risk
Radiological
6 x
6 x 10-*
7 x
1 x 10-6
2 x
1 x
io-5
- 1 x 10'2
1C"4
-9 x 10'2 3 x
10-*
ID'2
Chemical
2 x
2 x
2 x
lO'6
3 x
2 x
10'6
10'5
10'5
- 6 x W*
ID'5
10-4
Health Hazard
Index for
Noncarcinogenic
Effects
0.02
0.3 - 0.5
0,4
0.09 - 9
0.6
11
'*' For chemical risks, because the variation is small and the results are rounded to one significant figure, the range and median
are represented by the same value in this table.
lbl Results for the farmer include the contribution from ingesting food grown on contaminated soil. Considerable uncertainty
is associated with the methodology used to estimate intakes for this pathway, and the chemical risk and hazard index
estimated from a parallel analysis for a nearby background location are comparable to those estimated for the on-site farmer
location. Excluding the contribution from this pathway, the estimated radiological and chemical risks for the farmer are
1 x IO'2 and 5 x 10'5, and the hazard index is 2.
eliminate the associated risks. Cleanup criteria have not been specifically developed for the
waste sludge; rather criteria developed for site soil (as addressed in the following discussions
and in Section 9.2) will be applied to determine the extent of excavation required at the pits.
The risks and hazard indexes estimated for the four future land-use scenarios under the
modified site configuration are summarized in Table 6-7. These analyses focused on exposures
related to soil contaminants (i.e., incidental ingestion of soil and inhalation of soil-generated
airborne contaminants), and the results shown in the tables represent the range of values
estimated from data for several hundred individual locations across the site, as discussed in
Section 6.2.3. For the ranger, resident, and farmer, the estimated radiological risks exceed the
target risk range at most locations, primarily from inhalation of radon. The estimated chemical
risks and hazard indexes for the resident each exceed the target levels (1 x 10"4 and 1,
respectively) at 14 locations across the site. The potential noncarcinogenic effects are associated
with incidental ingestion of soil, and the primary contributors are arsenic, PCBs, and uranium.
Future residential land use is considered to represent the RME scenario for the purpose
of developing soil cleanup criteria protective of human health. Because the extent of exposure
for a resident is greater than that associated with a worker (the RME scenario under current
m:\users\jof\blg\rod\rod_txt.s-6.h10 41
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conditions), development of cleanup criteria on the basis of the more conservative residential
scenario will also be protective of the worker. The development of cleanup criteria for site soil
and the results of a "post-cleanup" assessment of residual risks for the RME and other scenarios
are presented in Section 9.2.
For the off-site locations, exposures incurred by a recreational visitor represent the RME
scenario. The hazard indexes for this receptor at these areas are less than 1, and the estimated
risks are shown in Table 6-8. The radiological and chemical risks are less than 1 x 10"5 at
Burgermeister Spring and Lakes 34, 35, and 36, and hence fall within the target risk range. The
radiological risks for the soil vicinity properties are also within or below the target risk range
except for vicinity property B4 (Figure 6-1). The risk estimated for repeated exposures at this
remote location in the Weldon Spring Wildlife Area (now referred to as the Conservation Area)
is 3 x 10"4. The radiological risk estimated for similar exposures at the Southeast Drainage is
2 x 10"4, which also exceeds the target range.
Except for the Southeast Drainage, the DOE is planning to clean up all vicinity properties
for which it has responsibility as part of the current remedial action. The same criteria
developed for on-site soil (see Section 9.2) will be used for these areas. Specific cleanup
decisions for the Southeast Drainage, which currently receives contaminated runoff from the site,
are not included in the scope of the current remedial action (see Section 4); these will be
addressed in separate environmental documentation prepared during the next several years to
support final decisions for that area.
6.5 Ecological Assessment
The Weldon Spring site is located adjacent to two State conservation areas and more than
200 species of plants and animals are expected to occur on site. Several State- and Federal-listed
threatened and endangered species have been identified in this area. Studies to date have not
reported these species at the site, although the pied-billed grebe, a State rare species, has been
observed at the raffmate pits. Soil contaminants at certain discrete locations that present a
potential impact to exposed biota include arsenic, cadmium, copper, lead, zinc, mercury,
uranium, and selenium. Possible effects reported in scientific literature include decreased
biomass and diversity.
m:\users\jof\blg\rod\rod_txt.s-6.h10 42
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U.S. ROUTE-
40/61
DARDENNE
CREEK
A.
(
r -"
>'t%''~LAKE33
- STATE
ROUTE K
KRAUT
RUN
AUGUST A. BUSCH
CONSERVATION AREA
LAKE 34
SCHOTE J)
CREEK P'
B10
STATE
ROUTED
BURGERMEISTER—rA
SPRING / /-LAKE 35 .
v
WELDON
SPRING
/•~
B3
y
^ u.s. ARMY'RESERVE
\ ^ PROPERTY
X.
*v X
"" \
SURFACE WATER
DIVIDE
FRANCIS HOWELL
HIGH SCHOOL
LAKE 36 V
I / WELDON
B1 €T*y SPRING
. HEIGHTS
UNIV. OF MO
- MO HWY. DEPT. RESEARCH-
V. /"PARK
/ -, 'WELDON SPRING
i /^^ BS* CHEMICAL PLANT ^
STATE
ROUTE
94
DRAINAGE
WELDON SPRING CONSERVATION AREA I ^^
WELDON \ ™^// ^^
STATE •••-.. CSDOIMP \ V' ,-^MISSOURI RIVER
ROUTE DD ""•;. SPRING >
/ LITTLE FEMME^ ".-'QUARRY
If
'
LITTLE FEMME'
OSAGE CREEK
/
STATE
ROUTE F
\
AS
ST. CHARLES \ /
COUNTY i '
WELL FIELD / ,'
/ )
" FEMME
OSAGE
SLOUGH
FEMME
OSAGE
CREEK
LEGEND
O REMEDIATED PROPERTY
• CONTAMINATED PROPERTY
A ARMY PROPERTY
B BUSCH WILDLIFE AREA,
WELDON SPRING WILDLIFE AREA
SCALE
LOCATION OF CONTAMINATED
VICINITY PROPERTIES IN THE AREA
OF THE WELDON SPRING SITE
FIGURE 6-1
I DO-OBIT NC.:
A/VP/015/0293
OtSlUATOR
JAB
DATE.
8/9/93
-------
TABLE 6-8 Estimated Carcinogenic Risks and Hazard Indexes for a Recreational
Visitor at Off-Site Areas(al
Area and Medium
Lakes 34, 35, and 36 surface water
and sediment
Burgermeister Spring surface water
Southeast Drainage surface water
and sediment
Radiological
Risk
8 x 1
-------
TABLE 6-9 Description of Vicinity Properties in the Area of the Weldon Spring Site
Vicinity
Property
A1
A2
A3
A4
AS
A6
A7
B1
B2
B3
64
B5
B6
B7
B8
B9
BIO
'Description
Soil covered mound, 1 .2 m wide ditch and drainage
ditch flowing northwest.
Rectangular area of soil, 21.4 m (70 ft.) by 79.3 m
(260 ft) adjacent to railroad track.
Wooden loading dock.
Short segment of Southeast Drainage.
Surface drainage ditch leading west from raffinate
pits.
Length of drainage ditch from Ash Pond 201 m
(660 ft).
Isolated area measuring 2.1 m (7 ft) by 1 .5 m (5 ft).
Area of soil 167 m2 (1800 ft2).
Small piece of pipe near Highway 94.
Two small isolated areas of soil, 2.7 m (9 ft) by
2.4 m (8 ft) and.2.1 m (7 ft) by 1 .8 m (6 ft).
Mound of soil, miscellaneous wood, metal and other
debris.
Abandoned drums and adjacent soil.
Isolated area of soil, 91 cm (3 ft) by 91 cm (3 ft).
Southeast Drainage.
Three isolated areas of soil, one measuring 61 cm
(2 ft) by 91 cm (3 ft), two measuring 91 cm (3 ft) by
91 cm (3 ft).
Area of contaminated soil - will be fully characterized
following quarry bulk waste removal.
Isolated area of soil, estimated to be 0.15 m3
(0.2 yd3). ' ,
Status
Contaminated
Contaminated
Contaminated
Contaminated
Contaminated
Contaminated
Remediated
Remediated
Remediated
Contaminated
Contaminated
Contaminated
Contaminated
Contaminated
Remediated
Contaminated
Contaminated
A full description of each property and extent of contamination is found in the Rl (DOE 1992b)
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45
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7 DESCRIPTION OF ALTERNATIVES
Alternative remedial actions for the site were developed as part of the Feasibility Study
(FS) (DOE 1992d) by identifying remedial technologies and process options that are potentially
applicable to the various contaminated media associated with the site. Potentially applicable
technologies were incorporated into seven preliminary alternatives, and these alternatives were
screened on the basis of effectiveness, implementability, and cost. From the screening analysis
of the preliminary alternatives, the following final alternatives were retained for detailed
evaluation:
• Alternative 1: No action.
• Alternative 6a: Removal, chemical stabilization/solidification, and disposal on
site.
• Alternative 7a: Removal, vitrification, and disposal on site.
• Alternative 7b: Removal, vitrification, and disposal at the Envirocare facility.
• Alternative 7c: Removal, vitrification, and disposal at the Hanford Reservation
facility.
These alternatives are described in Sections 7.1 through 7.5 on the basis of preliminary
conceptual engineering information. The no-action alternative was retained for this evaluation
in accordance with the Comprehensive Environmental Response, Compensation and Liability Act
(CERCLA), as amended, and National Environmental Policy Act (NEPA) processes to provide
a baseline for comparison with the final action alternatives.
The technology process options discussed herein (e.g., for chemical stabilization/
solidification and vitrification) are considered representative of the general technologies that
define the alternatives. The actual processes applied for site cleanup activities will be
determined as part of the detailed design stage for this remedial action after the remedy is
selected. Similarly, other representative components that have been evaluated for this analysis,
such as the types of equipment and material and the treatment rates, will be specified as part of
detailed design. The major regulatory requirements associated with each of these alternatives
are discussed within the subsection for each alternative.
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7.1 Alternative 1: No Action
The National Contingency Plan (NCP) requires that the "no-action" alternative be
evaluated at every site to establish a baseline for comparison. Under Alternative 1, no further
action would be taken at the site. Certain interim response actions for which decisions have
already been finalized are assumed to be in effect, as follows: (1) the bulk waste excavated
from the quarry would be in short-term storage at the temporary storage area (TSA); (2) the
water treatment plants at the quarry and the chemical plant area would be operational; (3) the
buildings and other structures would be dismantled, and the resulting material would be in short-
term storage at the material staging area (MSA), debris staging area, and asbestos-container
staging area; and (4) the containerized chemicals would remain in storage at Building 434.
Contaminated soil, sludge, and sediment would remain in their current conditions, with
continued potential for off-site releases during the short term and into the future. Site
ownership, access restrictions, and monitoring would continue into the foreseeable future.
Annual costs to maintain the site under this alternative are estimated to be approximately
$1.2 million, with increases likely to address contamination that might be released in the absence
of further source control or migration control measures.
Alternative 1 would not meet all applicable or relevant and appropriate requirements
(ARARs).
7.2 Alternative 6a: Removal, Chemical Stabilization/Solidification and Disposal On
Site
Under Alternative 6a, about 675,000 m3 (883,000 yd3) of contaminated sludge, soil,
sediment, structural material, vegetation, and process waste from the two water treatment plants
would be removed from the source areas and on-site storage areas. Approximately 342,000 m3
(447,000 yd3) of that material would be treated by chemical stabilization/solidification or volume
reduction, as appropriate, and about 772,000m3 (1,010,000yd3) of treated and untreated
material would be placed in an engineered disposal facility on site.
It is expected that the remedial action activities could be completed within about
10 years after the Record of Decision (ROD) for this action. For this and all other alternatives,
substantial, continuous, physical on-site remedial action could commence within 15 months after
signature of the chemical plant ROD. Remedial actions could include removal of foundations
and contaminated soils to cleanup levels; construction of retention/detention basins; or treatment
of wastes currently stored in Building 434. A 15 month schedule would not be sufficient time
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in which to commence disposal cell construction, due to design and procurement requirements,
nor could a treatment facility (for CSS or vitrification) be operational in this time frame, due
to the necessity to perform additional treatment studies and pilot testing to implement full scale
design and operation.
About one year would be required for pilot-scale testing; 3.5 to 4.5 years for design,
construction, and start-up of the chemical stabilization/solidification (CSS) process plant; and
4.5 years for operating the CSS facility. Construction and operation of the. disposal facility
would require about 6.5 years. (Some of these activities would overlap.) Groundwater, surface
water, and air would be monitored at the site and at specific off-site areas throughout the cleanup
and maintenance period to facilitate protection of the general public and the environment.
Because waste would remain on site under this alternative (in the disposal facility), the U.S.
Department of Energy (DOE) would review the effectiveness of the remedy at least every
five years following the mitigation of the remedial action in accordance with the provisions of
Section 121(c) of CERCLA, as amended.
Treatment would be used as a principal element of the response, primarily to reduce
the mobility of contaminants in raffinate-pit sludge, process waste, and certain soils. Standard
equipment and readily available resources would be used to implement Alternative 6a, and the
total cost is estimated to be about $157 million. The representative technical components of this
alternative are described in the following paragraphs.
Standard construction equipment and procedures would be used to remove contaminated
sludge and soil from the raffinate pits; sediment from ponds and lakes; solid material (including
structural material and debris, process equipment, rock, vegetation, and soil) from the MSA and
TSA; underground pipes; and soil from dump areas, scattered locations across the site, and
vicinity properties. Good engineering practices and other mitigative measures would be appb'ed
to minimize potential releases; for example, the size of the area being disturbed would be
minimized and erodible material would be misted with water during excavation and transport.
Sludge would be removed from the raffinate pits with a floating dredge and then
pumped as a slurry to an adjacent treatment facility. (Although much of the surface water in
these pits would have been previously removed and treated under a separate action, a small
amount of water would be left in the pits to cover the sludge and prevent radon and paniculate
emissions.) After the sludge had been removed, the more highly contaminated soil forming the
berms and pit bottoms would be removed with conventional earth-moving equipment (such as
bulldozers and front-end loaders) and transported by truck to the treatment facility. Similar
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equipment would be used to excavate sediment from other surface water impoundments after the
water was removed and to excavate soil from across the site and vicinity properties. The
excavated material not targeted for treatment would be transported by truck directly to the
disposal facility.
Structural material, debris, and soil from the MSA and TSA would be removed and
transported to the appropriate treatment facility or the disposal facility. In addition, a mobile
chipper would be used intermittently to reduce the volume of woody material at the site; the
resultant chips may be composted on site to reduce the waste volume. Containerized process
chemicals stored in Building 434 would be either transported off site to a permitted incinerator
or treated in the on-site sludge processing facility with stabilization or by chemical
neutralization.
Excavated areas would be backfilled with clean soil material, regraded to natural
contours matching the surrounding topography, and vegetated to support final site restoration.
Much of the backfill could be obtained nearby; e.g., from a 81-ha (200-acre) parcel of land
owned by the Missouri Department of Conservation located on State Route 94 across from
Francis Howell High School. Additional fill such as gravel, sand, and topsoil may be obtained
from local vendors.
Two new facilities would be constructed on site to support this alternative: one for CSS
(the sludge processing facility) and another for physical treatment (the volume reduction facility).
Each facility would be equipped with emission control systems to limit potential releases (e.g.,
a baghouse or high-efficiency paniculate air [HEPA] filter system). A mulch pile would also
be constructed on site to enhance the biodegradation of wooden debris and vegetation.
The volume of vegetation would be reduced and biodegradation facilitated by chipping
vegetation in a mobile unit and then placing it in a composting facility (mulch pile) at the
northern portion of the site. This pile would be maintained in an area of between 0.4 and 1.6 ha
(1 and 4 acres) until material placement in the disposal cell could begin. The pile would be
actively managed to enhance the biodegradation process, and this composting could result in a
volume reduction of 80 to 90% (MKF and JEG 1992). The end product of the process would
be placed in the on-site disposal cell. Materials such as railroad ties and utility poles would
probably not be composted because they would have been treated with chemicals to inhibit
biodegradation. These materials would be chipped and placed in the disposal cell.
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The two criteria applied to determine what material will be treated by chemical
stabilization/solidification are (1) whether treatment is needed to provide a structurally stable
material, or (2) whether treatment is needed to eliminate the characteristic that would otherwise
make the waste subject to the RCRA land disposal restrictions. Material expected to be treated
includes the raffinate pit sludges (which are not structurally stable) and certain soil excavated
from the quarry and in short-term storage at the TSA (which may be RCRA characteristic
waste). Other material that may be treated includes process residuals from the water treatment
plants and soil beneath the raffinale pits. Material treated by chemical stabilization/solidification
would increase in volume by about 32%, and the overall volume for combined waste disposal
would increase by about 12%. To minimize emissions during material transport to the sludge
processing facility, the sludge would be pumped directly to the treatment facility as a slurry, and
loose soil material would be wetted during transport over the short distances from the staging
areas or pits.
The CSS treatment facility would be situated on approximately a 0.8 ha (2 acre) area
located near the raffinate pits. Following dredging, settling, and thickening, the raffmate sludge
would be conveyed to the CSS treatment plant by pumping or other continuous conveyance
system. The thickened sludge would be placed in a storage tank and feed parameters (e.g.,
density and moisture content) checked before the sludge is metered into a mixing unit with
binder agents. Binders that through bench scale testing have proven effective in immobilizing
contaminants in the raffinate sludge and site and quarry soils are fly ash and Portland cement.
The CSS grout material resulting from the mixing of raffinate sludge and binder agents
would be tested for quality control parameters and either be transported by truck to the disposal
facility for grouting of voids in dismantlement debris or be further mixed with contaminated soils
to produce a CSS soil-like product. These quality control parameters will be determined during
pilotrscale testing of the CSS grout material. The batch material from the pilot scale program
will be tested using the toxicity characteristic leaching procedure (TCLP). Results of TCLP
testing will then be utilized to develop the quality control parameters for the grout material
produced in the full-scale CSS facility. The mixing of CSS grout with soils would either be
performed in the same mixer (e.g., high shear mixer) used to initially produce the CSS grout
or, if necessary, another mixer (e.g., pug mill) which may be more suitable for producing a CSS
soil-like material. This determination will be part of the CSS pilot testing program.
Other equipment components involved in the CSS treatment process such as tanks,
pumps, compressors, valves, and piping for the preparation, storage, and conveyance of feed
materials are readily available and widely used in the construction, mining, and hazardous waste
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remediation industries. The operating parameters of the CSS treatment facility will be refined
and the CSS grout and soil-like formulas optimized to meet performance and placement criteria
during pilot testing.
Volume reduction operations would include the use of material-sizing equipment such
as a shear, an impact crusher, a rotary shear shredder, and an in-drum compactor to treat
structural material, rock, and containerized debris such as used personal protective equipment.
The volume of material processed by these methods would be reduced from 10% to 50%,
depending on the specific material type. A decontamination unit would also be provided to treat
selected structural materials for which release and reuse is practicable. Such material could be
treated with a wet or dry abrasive blast process; the equipment and facility would contain
emission control systems. Any structural material determined to be unreleasable would be
transported to the disposal facility.
Other facilities already present on site for interim actions would continue to be used for
this remedial action, including the MSA, water treatment plant, and decontamination pad.
Support facilities would also be maintained on site to provide electrical power, potable water,
showers, portable sanitary facilities, offices for the construction management staff, and staging
for excavation and construction activities. Most of these facilities are already in place, and they
could be expanded to address incremental requirements associated with increased activity on site.
Additional staging facilities would be constructed to support the heavy equipment needed for
cleanup activities and to provide for stockpiling of material.
The various treatment and support facilities would be dismantled at the end of the
remedial action period and either decontaminated for reuse (e.g., at another DOE facility) or,
assuming reuse is not feasible or cost effective, treated by volume reduction and placed in the
disposal facility. Following closure of the water treatment plant, a mobile water treatment unit
may be utilized to support final site-closure activities.
An engineered disposal facility would be constructed at the chemical plant area within
a specifically designated portion of the site that has undergone numerous subsurface
investigations to confirm the suitability of the area for disposal of site wastes. The scope and
range of the waste materials would cover an area of about 17 ha (42 acres) while the entire
facility including the perimeter encapsulation dikes, would cover about 28 ha (70 acres). The
design volume of material that would be placed in the cell is estimated to be about
1.1 million m3 (1.5 million yd3). This value includes incremental swell factors associated with
excavation and treatment, and a contingency of about 10% to address the potential contribution
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from subsurface and off-site material that has not yet been adequately characterized, including
material that may be generated by future cleanup activities at the quarry and the Southeast
Drainage.
The base of the disposal facility would consist of a double liner/leachate collection
system. The lower leachate collection system would also serve as a leachate detection system
and would facilitate the monitoring of cell performance during operation of the cell and the
active leachate management period. The liners would be designed to minimize transport of any
leachate from the contaminated material that would be contained in the cell. The multilayer cell
cover would include an infiltration/radon attenuation barrier, a biointrusion layer, a frost
protection layer, and an erosion protection layer. This cover would serve as a barrier to radon
release and would protect against the potential effects of freeze-thaw cycles, intrusion by plant
roots or burrowing animals, and erosion (including that associated with extreme precipitation
events). The cell would be seismically engineered to withstand damage from potential
earthquakes. The cell would be maintained and its performance would be monitored for the long
term.
The cell would be constructed in stages to provide timely receiving capacity for waste
generated by various concurrent cleanup activities (e.g., building dismantlement and volume
reduction). This staged construction would minimize both the need for temporary storage and
the potential for construction impacts by limiting the active work area. The cell would be
maintained and its performance monitored for the long term, and its effectiveness would be
reviewed every five years. The monitoring program would include visual inspection of the cell
and regular testing of air, surface water, and groundwater. The surface water and groundwater
monitoring program would comply with 40 CFR 264 Subpart F and 10 CSR 25-7.264(2)(f) as
described in Section 10. This monitoring would be frequent (e.g., quarterly to annually) during
the near term, and the frequency of monitoring would be evaluated within the five-year schedule,
after the site entered long-term caretaker .status and reduced, if appropriate.
Site-specific operational arid contingency plans would be prepared to support the
remedial action. These plans would specify (1) safe work practices, engineering controls, and
worker protective equipment to reduce occupational exposures and/or contaminant releases;
(2) monitoring techniques and frequencies; and (3) contingencies for a variety of possible
occurrences (e.g., an accident, increased contaminant levels measured by monitoring systems,
or an environmental disturbance such as a heavy rainstorm, tornado, or earthquake).
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Under Alternative 6a, the DOE would continue to maintain custody of and
accountability for the disposal area, but the remainder of the site could be released for other use.
For example, the property outside the disposal location could be transferred back to the Army
for incorporation into the adjacent Army Reserve Training Area, or it could be released for
incorporation into the adjacent wildlife areas. Planning discussions would be held with parties
interested in the future use of this property after the remedy is selected for the current remedial
action. However, the final disposition of the site will not be determined until after the final
remedy is selected for the chemical plant area; i.e., until after the decision is made for the
groundwater operable unit within the next several years. Any institutional controls pertinent to
the future use of this property, such as restrictions on the use of land or groundwater, would be
identified at that time.
7.2.1 Applicable or Relevant and Appropriate Requirements
Federal and State environmental laws were evaluated for their applicability or relevance
and appropriateness to the circumstances of the releases and threatened releases at the site. The
applicable or relevant and appropriate requirements are discussed below.
Subtitle C of the Resource Conservation and Recovery Act (RCRA), as amended by the
Federal Facilities Compliance Act (FFCA), regulates the generation, transportation, treatment,
storage, and disposal of hazardous wastes as defined in 40 CFR 261. The determination on the
applicability of RCRA Subtitle C requirements to the various response alternatives included an
evaluation of whether any RCRA-listed or characteristic hazardous wastes were present at the
site.
Based on current information (e.g., site records, the likely sources of contaminants),
there are no known listed hazardous wastes present in any of the source areas on site. Three
drums of containerized chemicals stored in Building 434 may be sufficiently similar to discarded
commercial chemical products (listed wastes), which would make Subtitle C requirements
relevant and appropriate to their management. However, it is not planned to manage these
drums in the on-site treatment or disposal facilities. Further characterization of these drums is
underway to assist in determining treatment/disposal options at a commercial facility. Pending
a decision on treatment and disposal options for this waste, the drums are being stored on site
in accordance with the RCRA.
A relatively small volume of materials fails the TCLP test and must be considered a
characteristic hazardous waste. The management of these materials must comply with RCRA
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(as amended by the FFCA) Subtitle C requirements, until they are treated to remove the
characteristics and successfully test to be nonhazardous. The analysis of action-specific ARARs
addressing relevant and appropriate RCRA hazardous waste rules is presented in Section 10.
Past bench scale tests have shown that the chemical stabilization/solidification product
will pass the TCLP test and that decant or free liquid from the product would very likely also
pass. Ongoing studies are being conducted to confirm that the free liquid will pass the TCLP
test. This issue will also be addressed during CSS pilot scale testing. If needed, specialized
addititives or reagents will be added to the CSS mixture to reduce any potential for the free
liquid to fail the TCLP test. Although only small amounts of free liquid are expected to be
generated from the CSS product, it will be managed through placement techniques as described
in Section 10.2.3.4, Other Disposal Requirements.
All surface water discharges at the site are controlled through a surface water
management program carried out in accordance with National Pollutant Discharge Elimination
System (NPDES) permits issued under Section 402 of the Clean Water Act (CWA). Any
changes in surface water discharges during construction of the disposal cell would be addressed
through the NPDES permit.
The National Emission Standards for Hazardous Air Pollutants (NESHAP) are set forth
under the Clean Air Act (CAA). The NESHAP standards have been set for those contaminants
present in site wastes (i.e., radionuclides and asbestos) which may be released into the air during
excavation/construction activities.
The following standards for radionuclides in 40 CFR 61 are applicable to remedial
actions under consideration. Subpart H regulates emissions of radionuclides other than radon
from DOE facilities. Emissions of these radionuclides to the ambient air shall not exceed
amounts that would cause any member of the public to receive an effective dose equivalent of
10 mrem per year. Subpart H is applicable to the protection of the public during implementation
of the remedial action as the Weldon Spring site is a DOE facility.
Subpart Q sets forth the standard for radon emissions. The standard states that no
source at a DOE facility shall emit more than 20 pCi/m2s of Rn-222 into the air as an average
for the entire source. This standard is applicable at completion of the final remedial action as
the Weldon Spring site is a DOE facility.
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Regulation 40 CFR 61 Subpart T is considered relevant and appropriate to final site
conditions because the site contains material sufficiently similar to uranium mill tailings.
Subpart T states that Rn-222 emissions to ambient air from uranium mill tailings piles which are
no longer operational should not exceed 20 pCi/m2s.
The asbestos standard in 40 CFR 61 Subpart M requiring no visible emissions is
considered to be applicable to some of the remedial actions under consideration. Various other
requirements pertaining to asbestos abatement projects are promulgated in 40 CFR 61,
Subpart M. These requirements address asbestos removal, demolition, and renovation
operations. Because the Weldon Spring site remedial action includes asbestos abatement
activities, these standards and requirements are applicable to the remedial alternatives under
consideration. Removed asbestos is being stored on an interim basis pending final disposal. The
NESHAP disposal requirements for asbestos are applicable at the time of final waste disposal.
Regulation 40 CFR 192.02(b), which addresses releases of radon from tailings disposal
piles, is considered to be relevant and appropriate to those aspects of the remedial alternatives
which involve waste disposal. At completion, the disposal facility will have to meet the Rn-222
flux standards specified in 40 CFR 192.02(b). This standard requires reasonable assurance that
Rn-222 from residual radioactive material will not (1) exceed an average release rate of
20 pCi/m2s, or (2) increase the annual average concentration of Rn-222 in air at or above any
location outside the site perimeter by more than 0.5 pCi/1. This regulation is relevant and
appropriate as the Weldon Spring waste is considered sufficiently similar to uranium mill
tailings.
Subpart D of the Uranium Mill Tailings Remedial Action (UMTRA) regulations sets
forth standards for the management of uranium by-product materials. Regulation 40 CFR
192.32(b) sets forth closure standards and is considered applicable to the remedial action at the
Weldon Spring site, as the radioactively contaminated material has been classified as by-product
material as defined in the Atomic Energy Act, as amended.
The State of Missouri has adopted the National Ambient Air Quality Standards
(NAAQS) criteria specified in the CAA through the State Implementation Plan and has
promulgated ambient concentration standards under 10 CSR 10-6.010. Implementation of some
of the remedial alternatives could result in emissions of several of the criteria pollutants,
including paniculate matter (50 ng/m? annual average or 150 ^g/m3 over a 24-hour period) and
lead (1.5 /xg/m3 quarterly average). Although ambient standards for these contaminants are not
ARARs, the standards provide a sound technical basis for ensuring protection of public health
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and welfare during implementation and will be considered for components of the remedial action
involving potential air releases.
Paniculate standards promulgated under 10 CSR 10-5.180 (Missouri Air Pollution
Control Regulations) for internal combustion engines (no release for more than 10 seconds at
one time) are applicable to paniculate release from any internal combustion engines used during
implementation of the action.
The Missouri Department of Health has issued standards for Protection Against Ionizing
Radiation in 19 CSR 20, which include a Rn-222 concentration limit of 1 pCi/L above
background (quarterly average) in uncontrolled areas. This requirement is applicable to
protection of the public during remedial action activities. The remaining requirements are
similar to those identified in the DOE Orders for radiation protection of individuals and the
environment, and the remedial action will also comply with the applicable provisions of those
Orders.
Missouri has adopted by reference the RCRA Subtitle C hazardous waste management
regulations. These State requirements are the same as the Federal requirements (the State
requirements are not more stringent), which are considered ARARs. However, Missouri has
also adopted additional rules, which include landfill siting requirements, that are considered
legally applicable to the disposal of hazardous waste in the State. These requirements are
discussed separately, with the action-specific ARARs identified in Section 10.
Atomic Energy Act (AEA) requirements for DOE's radioactive waste management and
radiation exposure standards are incorporated into DOE Orders developed under DOE's AEA
authority. These Orders are generally consistent with, and typically include, equivalent technical
Nuclear Regulatory Commission (NRC) requirements that are appropriate for DOE operations
and waste management. DOE Order requirements are -"to-be-considered" (TBC) requirements,
which when included in a DOE CERCLA Record of Decision (ROD) are enforceable cleanup
standards under the CERCLA. Limited sections of NRC requirements can be "Relevant and
Appropriate" or TBC only when DOE Orders do not clearly address a specific condition or
particulars of the site, and supplemental requirements from NRC requirements are needed to
facilitate protection of human health and the environment.
Key environmental requirements promulgated by the NRC were assessed to determine
their potential as relevant and appropriate or to-be-considered (TBC) requirements for the
Weldon Spring Site Remedial Action Project. Radiation exposure standards are promulgated in
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10 CFR 20. These standards are not applicable because they apply only to NRC licensees.
Neither are these standards both relevant and appropriate based on the circumstances of the
action relative to the type of facility for which similar, equally protective standards have been
established in DOE Orders 5400.5, Radiation Protection of the Public and the Environment', and
5480.11, Radiation Protection for Occupational Workers, for radiation protection. The remedial
action will be conducted in accordance with DOE Order 5400.5, Chapter II, "Requirements for
Radiation Protection of the Public and the Environment" and Chapter HI, "Derived
Concentration Guides for Air and Water." The remedial action will also follow DOE Order
5480.11.
Standards published under 10 CFR 61 address the disposal of low-level radioactive
waste. These requirements are not applicable because the definition of wastes covered under this
part specifically excludes 1 le(2) byproduct materials. Neither are the requirements of 10 CFR
61 both relevant and appropriate because the design standards address near-surface disposal, for
which the disposal unit is typically a trench, and release for unrestricted use could be considered
after 500 years on the basis of assumed radioactive decay and migration. These requirements
are not technically appropriate to the long-lived, radon-generating, alpha-emitting materials
present at the Weldon Spring site. The remedial action will be conducted in accordance with
DOE Order 5820.2A, Radioactive Waste Management, Chapter III, "Management of Low-Level
Waste" and Chapter IV, "Management of Waste Containing Byproduct Material and Naturally
Occurring and Accelerator Produced Radioactive Material."
7.3 Alternative 7a: Removal, Vitrification, and Disposal On Site
Alternative 7a is similar to Alternative 6a except that vitrification would be the
treatment method for the sludge, the more highly contaminated soil and sediment, and the
containerized process waste. Under Alternative 7a, about 675,000m3 (883,000yd3) of
contaminated sludge, soil, sediment, structural material, and water treatment plant process
wastes would be removed from the source areas and on-site storage areas. About 342,000 m3
(447,000 yd3) of that material would be treated by vitrification or volume reduction, as
appropriate, and about 522,000 m3 (683,000 yd3) of treated and untreated material would be
placed in an engineered disposal facility on site.
It is projected that remedial action activities could be completed in 10 years following
the ROD, if no difficulties were encountered during testing, start-up, or operation. It is
estimated that 2.5 to three years are estimated to be required for bench-scale and pilot-scale
testing; five to seven years for design, construction, and start-up of the vitrification facility; and
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four years for operation. As construction and operation of the disposal facility would require
about 6.5 years, some of these activities could overlap. However, the total time required for
these activities could be longer because of the innovative nature of this technology. As in
Alternative 6a, releases would be controlled with good engineering practices and mitigative
measures, and monitoring would be conducted throughout the cleanup and maintenance period
to address protection of the general public and the environment. Similarly, the DOE would
review the effectiveness of the remedy every 5 years.
Treatment would be a principal element of Alternative 7a, and vitrification would
reduce the toxicity of certain contaminants (e.g., nitrate and nitroaromatic compounds); the
toxicity of radiation from the site waste would not be affected by vitrification (or any other
treatment method). Vitrification would also reduce the mobility of contaminants in soil and
sludge and the disposal volumes of these media; this treatment method would result in a volume
reduction of about 68% for the treated material and an overall volume reduction of 24% for the
combined waste. The volume of other material, such as structural debris and vegetation, would
be reduced as described for Alternative 6a.
Standard equipment and readily available resources would be used for the excavation
and nonthermal treatment operations. However, equipment and resources are not readily
available for vitrification. Use of the vitrification technology for large-scale operations is
innovative and would require further bench-scale and pilot-scale testing followed by engineering
scale-up before implementation at the Weldon Spring site. The total cost of implementing
Alternative 7a is estimated to be about $182 million. The representative technical components
of removal and much of the treatment and disposal components are the same as described for
Alternative 6a. Those components of Alternative 7a that differ from Alternative 6a are
described in the following paragraphs.
The vitrification unit within the sludge processing facility would be expected to consist
of two melters operating in parallel to provide system flexibility. The contaminated material that
would be treated in these melters is the same material that would be chemically treated under
Alternative 6a. Feed preparation (sludge dewatering and material sizing) would be required
before vitrification. In addition, the sludge and soil would have to be mixed in an optimized
blend ratio to produce a glassy product. The vitrification process would operate continuously
(24 hours per day throughout the year), and would consume a considerable amount of energy.
The vitrified product would be irregularly shaped 0.32- to 0.64-cm (1/8- to 1/4-in.)
pieces of glass-like fritted material; it would be collected in a hopper and transferred to bins for
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truck transport directly to the disposal facility or to an adjacent staging area. Emissions from
the vitrification process would be treated before release to the atmosphere. The specific off-gas
treatment system would be developed following bench-scale and pilot-scale testing and
optimization, but it would likely consist of a heat removal system, a primary quench scrubber,
a submicron aerosol scrubber, a nitrogen oxide gas removal system, and a final filtration system,
as required. Off-gas treatment requirements under this alternative would result in additional
technical complexity, and delays could occur if inadequate controls were achieved during testing.
The location of the disposal area would be similar to that identified for Alternative 6a.
However, for Alternative 7a, it was assumed that two cells could be constructed over the same
general surface area. The first would be the same as that described for Alternative 6a, only
smaller, and would receive all but the vitrified material. The design volume for nonvitrified
material is about 591,000 m3 (773,000 yd3) with contingency. This disposal facility would
cover about 12 ha (30 acres). A second cell could be constructed for the vitrified material, and
it could have less stringent engineering controls if pilot testing demonstrated that the product
would resist leaching. That is, although this cell would contain a cap similar to that described
for Alternative 6a and a compacted natural clay liner, it would not include a leachate collection
system because the material is expected to withstand leaching into the long term. The design
volume of this cell is about 86,400 m3 (113,000 yd3) with contingency, and it would cover an
area of about 5 ha (12 acres). The vitrified material would be cohesionless and would be placed
in the cell in alternate layers with a binder such as clay to promote waste compaction and
increase cell stability. The cell would be maintained and its performance monitored for the long
term. As described for Alternative 6a, site-specific operational and contingency plans would be
prepared to support the remedial action phase of this project, and institutional controls would
be maintained for the long term.
On the basis of continuing engineering evaluations and pending further analyses to be
developed during the detailed design phase, this approach might be modified to parallel the
scenario described under Alternative 6a. The result would be a single disposal facility, designed
to contain both the vitrified and untreated waste, which would incorporate the same features
described under Alternative 6a. The major difference would be the smaller size of the cell
because of volume reduction achieved during vitrification. The analyses for the representative
case in the FS are expected to bound potential impacts that would be associated with cell
operations (including construction, waste placement, and closure) under the modified approach
if Alternative 7a were selected.
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7.3.1 Applicable or Relevant and Appropriate Requirements
ARARs for this alternative are similar to the ones discussed for Alternative 6a.
Additional emission standards for Alternative 7a are discussed below.
Regulation 40 CFR 266, Subpart H provides RCRA emissions standards for hazardous
waste burned in boilers and industrial furnaces. This requirement is considered applicable to the
vitrification alternative, as the fossil-fuel heated melter proposed for the vitrification facility is
an industrial furnace that will process hazardous wastes. Part 266.104 states that the furnace
must achieve a destruction and removal efficiency of 99.99% for each principal organic
hazardous constituent. Concentrations of carbon monoxide (CO) in the off-gas must not exceed
100 ppmv (parts per million by volume) over a 60 minute moving average. Particulate emissions
must not exceed 180 mg/dscm (dry standard cubic meter) or 0.008 gr/dscf (dry standard cubic
foot) when corrected to 7% oxygen in the stack gas. In addition, Part 266.102 states that CO,
oxygen, and possibly total hyrocarbons must be monitored continously at a point downstream
of the combustion zone and prior to release into the atmosphere. The monitoring must conform
with performance specifications found in Appendix IX of 40 CFR 266.
Regulation 10 CSR 10-5.030 limits paniculate matter emissions from new indirect
heating sources. Regulation 10 CSR 10-5.050 limits paniculate matter from any industrial source
to less than 0.030 grain/standard ft3 of exhaust gas. Regulation 10 CSR 10-5.090 limits the
opacity of the exit gas to 20%. The regulations are considered applicable to the vitrification
process as the fossil-fuel heated melter is considered an industrial furnace which emits exit
gases.
7.4 Alternative 7b: Removal, Vitrification, and Disposal at the Envirocare Facility
Alternative 7b is similar to Alternative 7a except that the treated and untreated material
would be transported to the Envirocare facility near Clive, Utah, for disposal. It is expected that
the removal and treatment activities at the Weldon Spring site could be completed within the
same time frame as Alternative 7a; however, the environmental compliance process associated
with obtaining the necessary license to dispose of the large volume of by-product material at the
Envirocare facility could delay implementation of this alternative. Release controls and
monitoring would also be the same as previously described. Under this alternative, the same
material targeted for treatment under Alternative 7a would be vitrified at the Weldon Spring site
before off-site transport for disposal. The total cost of implementing Alternative 7b is estimated
to be about $351 million.
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The Weldon Spring waste is classified as 1 le(2) by-product material as defined in the
Atomic Energy Act, as amended. The DOE can transfer this type of material only to organiza-
tions licensed to receive it by the U.S. Nuclear Regulatory Commission (NRC). This
requirement would apply to the disposal of waste from the Weldon Spring site at the Envirocare
site. The Envirocare site has been permitted by the State of Utah to accept mixed hazardous
waste and naturally occurring radioactive material. However, a disposal facility is not currently
available at the site to receive material from the Weldon Spring site (i.e., lle(2) by-product
material). Envirocare of Utah, Inc., has submitted an application to the NRC for a license to
allow for disposal of lle(2) by-product material, and the NRC is currently preparing an
Environmental Impact Statement (EIS) to support the license application. Because of the nature
of the regulatory compliance process associated with the proposed Envirocare facility, the
Weldon Spring site cleanup might be delayed for several years under this alternative, depending
on the length of time it takes the NRC and the Envirocare owners to complete the environmental
review process.
The technologies and activities that would be used to construct, operate, and maintain
a disposal facility for the Weldon Spring waste at the Envirocare site would most likely be
similar to those identified for Alternative 7a. Although implementation of Alternative 7b would
allow for release of the entire Weldon Spring site for future uses, the site will be evaluated every
five years to evaluate the effectiveness of the cleanup. The long-term institutional controls
appropriate for the Weldon Spring site would be determined on the basis of final site conditions,
which will depend on the remedy selected for the groundwater operable unit, as described for
Alternative 6a.
To support off-site disposal, the treatment facilities planned for the Weldon Spring site
would have to be modified to include a staging area for loading the waste product into containers
and onto trucks for off-site transport. These trucks would then transport contaminated material
from the Weldon Spring site to a rail siding transfer station in Wentzville, Missouri, that would
be either leased or newly constructed to support this action. About 38,600 trips would be
required to transport the material to the siding over a combined one-way haul distance of
932,000 truck-km (579,000 truck-mi). The material would then be transferred to railcars for
subsequent shipment along a commercial rail line to Clive, Utah. The transportation component
of this alternative would probably extend over seven years. On the basis of an estimated
515 required train trips, Alternative 7b would involve transportation over about
1,240,000 rail-km (773,000 rail-mi).
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Transport of waste for off-site disposal at the Envirocare facility would result in an
increased risk of transportation accidents, with the potential for exposing workers and the
general public to radioactive and chemically hazardous substances. On the basis of current
statistics for highway and rail accident rates and the distance that would be traveled by transport
vehicles, a total of about six transportation accidents would be expected to occur. About half
of these would be truck accidents, largely as a result of truck transport of the waste to the rail
siding transfer station in Wentzville. The remaining three transportation accidents would involve
railcars transporting the waste to Clive. Based on statistics, no fatalities would be expected,
although several injuries could occur as a result of these accidents.
7.4.1 Applicable or Relevant and Appropriate Requirements
Compliance with ARARs under Alternative 7b would be the same as for Alternative 7a.
In addition, applicable requirements for transportation of radioactive and chemically hazardous
material to the Envirocare facility would be met.
7.5 Alternative 7c: Removal, Vitrification, and Disposal at the Hanford Reservation
Facility
Alternative 7c is similar to Alternative 7b except that the contaminated material would
be transported to the Hanford Reservation facility near Richland, Washington, for disposal.
Removal and treatment considerations would be the same as described for Alternative 7b, and
the basic components of off-site disposal would be similar.
Under Alternative 7c, cleanup activities at the Weldon Spring site could be delayed
many years because an appropriate disposal facility is not currently available at the Hanford
facility to receive site waste and no such facility is planned. The technologies and activities that
would be used to construct, operate, and maintain a disposal facility at the Hanford site would
likely be similar to those identified for Alternative 7a. The total cost of implementing
Alternative 7c is estimated to be about $304 million. This cost is based on an estimate of
$130/m3 ($100/yd3) to dispose of the large volume of waste from the Weldon Spring site. The
cost estimate for this alternative assumes that long-term monitoring and maintenance at the
Hanford site would cost the same as at the Weldon Spring site. A detailed cost analysis would
be performed to develop a firm price for disposal at the Hanford site, if this were a component
of the remedy selected for the Weldon Spring site.
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Transport of contaminated material to the Hanford site for disposal would involve the
same considerations identified for Alternative 7b, but Alternative 7c would require transporting
the material along a commercial rail line to Richland, Washington, and transferring it to a
dedicated rail line for transport to the Hanford site. On the basis of an estimated SIS train trips,
Alternative 7c would involve transportation over about 1.7 million rail-km (1.1 million rail-mi)
during an estimated seven-year period. A total of about eight transportation accidents would be
expected, three involving trucks and five involving railcars. (More railcar accidents are
expected for Alternative 7c than 7b because of the longer transport distance.) Statistically, no
fatalities would be expected, although several injuries could occur as a result of these accidents.
7.5.1 Applicable or Relevant and Appropriate Requirements
Compliance with ARARs under Alternative 7c would be the same as for Alternative 7a.
In addition, applicable requirements for transportation of radioactive and chemically hazardous
material to the Hanford Reservation facility would be met.
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8 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
The U.S. Environmental Protection Agency (EPA) has identified nine evaluation criteria
against which final remedial action alternatives are to be evaluated. These criteria are derived
from statutory requirements in Section 121 of the Comprehensive Environmental Response,
Compensation and Liability Act (CERCLA), as amended, as well as other additional technical
and policy considerations that have proven to be important for selecting remedial alternatives.
A balancing of these criteria is used to determine the most appropriate solution for the specific
problems at each site. These statutory mandates, which any selected remedy must meet, include
protection of human health and the environment, compliance with applicable or relevant and
appropriate requirements (ARARs), cost effectiveness and use of a permanent solution and
alternate treatment or resource recovery technologies to the maximum extent practicable. The
nine criteria are:
1. Overall protection of human health and the environment. Addresses
protection from unacceptable risks in both the short term and the long term
by minimizing exposures.
2. Compliance with ARARs. Addresses compliance with Federal and State
environmental requirements and State facility siting requirements, unless a
waiver condition applies.
3. Long-term effectiveness and permanence. Addresses residual risks, focusing
on the magnitude and nature of risks associated with untreated waste and/or
treatment residuals. This criterion includes a consideration of the adequacy
and reliability of any associated institutional or engineering controls, such as
monitoring and maintenance requirements.
4. Reduction of contaminant toxicity, mobility, or volume through treatment.
Addresses the degree to which treatment is used to address the principal
hazards of the site; the amount of material treated; the magnitude,
significance, and irreversibility of specific reductions; and the nature and
quantity of treatment residuals.
5. Short-term effectiveness. Addresses the effect of implementing the alternative
relative to potential risks to the general public during the action period,
potential impacts to workers and the environment during the action period, the
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effectiveness and reliability of mitigative measures, and the time required to
achieve protection of workers and the environment.
6. Implementability. Addresses technical feasibility, including the availability
and reliability of required resources (such as specific material and equipment,
facility capacities, and availability of skilled workers); the ease of
implementation; and the ability to monitor effectiveness. This criterion also
addresses administrative feasibility, e.g., coordination with other agencies and
the need for approvals or permits for off-site actions as appropriate to the
alternative.
7. Cost. Addresses both capital costs and operation and maintenance costs, as
well as the combined net present worth.
8. State acceptance. Addresses formal comments made by the State of Missouri
on the consideration of alternatives and identification of the preferred
alternative.
9. Community acceptance. Addresses the formal comments made by the
community on the alternatives under consideration.
The first two criteria are considered threshold criteria and must be met by the final
remedial action alternatives for a site (unless a waiver condition applies to the second criterion).
The next five criteria are considered primary balancing criteria and are evaluated together to
identify the advantages and disadvantages in terms of effectiveness and cost among the
alternatives. The last two are considered modifying criteria and are evaluated after the Remedial
Investigation/Feasibility Study (RI/FS) has been reviewed.
8.1 Threshold Criteria
8.1.1 Overall Protection of Human Health and the Environment
All of the final alternatives except Alternative 1 (no action) would provide overall
protection for human health and the environment. This protection could not be ensured for the
extended future, if no action were taken, because over time contaminants could migrate via
groundwater to off-site receptors, resulting in possible impacts. For each of the action
alternatives, human and environmental exposures would be reduced by removing the sources of
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contamination, treating the waste that contributes to the principal hazards at the site, and
managing low-risk contaminated materials not requiring treatment by permanently containing
these untreated materials with the treated waste product in an engineered disposal facility
designed to prevent the release of contaminants into the environment for at least 200 to
1,000 years.
8.1.2 Compliance with ARARs
Alternative 1 (no action) would not comply with all Federal and State ARARs.
Alternative 6a would meet all location, action, and contaminant-specific ARARs with the
exceptions of:
• The State of Missouri's Rn-222 limit of 1 pCi/1 above background in uncontrolled
areas (19 CSR 20-10.040) may not be achieved during implementation: Absolute
compliance with requirement during all phases of remedy implementation is
technically impracticable from an engineering perspective (Section 121(d)(4)(C) of
the CERCLA).
• Regulation 40 CFR 61, Subpart M presents National Emission Standards for
Hazardous Air Pollutants (NESHAP) requirements for asbestos handling. Due to
technical impracticability and potential increased exposure to personnel, the small
pieces of asbestos found in the quarry bulk wastes (smaller than 0.6 m x 0.6 m x
0.05 m [2 ft x 2 ft x 2 in.]) will not be segregated from the soils. As this material
is moved from the temporary storage area (TSA), the NESHAPs requirements will
be waived under Section 121(d)(4)(B) of the CERCLA.
• Regulation 40 CFR 268, Subpart E specifies the land disposal restrictions (LDRs).
The LDRs prohibit the storage of restricted wastes unless storage is solely for the
purpose of accumulating sufficient quantities of wastes to facilitate proper treatment,
recovery, or disposal. The limitations on storage time are waived under Section
121(d)(4)(C) of the CERCLA.
• Regulation 40 CFR 268, Subpart C specifies LDR restrictions on hazardous waste
placement. This requirement is waived under Section 121(d)(4)(A) of the CERCLA.
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• Regulation 40 CFR 268, Subpart D specifies treatment standards which must be
attained prior to land disposal of the hazardous waste. The treatment standard based
upon use of a specified technology is waived under Section 121(d)(4)(D) of the
CERCLA.
• Regulation 10 CSR 25.5-262(2)(C)l sets forth the State regulation that hazardous
wastes stored prior to off-site shipment shall comply with U.S. Department of
Transportation (DOT) regulations regarding packaging, marking, and labeling.
Meeting new packaging requirements for storage set forth in the DOT requirement
HM-181 (in 49 CFR) could potentially result in unnecessary personnel exposure.
Therefore, this requirement is waived under Section 121(d)(4)(A) and Section
121(d)(4)(B) of the CERCLA.
• Regulation 40 CFR 761 -65(a) requires that any polychlorinated biphenyl (PCB) article
or container be removed from storage and disposed of within one year from the date
when it was first placed in storage. This requirement is waived under Section
121(d)(4)(A) of the CERCLA.
• Regulation 40 CFR 761.75(b)(3) of the Toxic Substance Control Act (TSCA) states
that the bottom landfill liner system or natural in-place soil barrier shall be at least
17 m (50 ft) from the historical high-water table. This requirement is waived under
Section 121(d)(4)(D) of the CERCLA.
• Regulation 40 CFR 264.314(f) sets forth restrictions on the placement of waste
containing free liquids in a landfill. This requirement is waived in accordance with
Section 121(d)(4)(B) and Section 121(d)(4)(D) of the CERCLA.
Alternative 7a would meet all location, action, and contaminant-specific ARARs.
The exceptions to this alternative meeting all ARARs, and waivers for these exceptions,
are the same as those discussed under Alternative 6a. The waiver for 40 CFR 264.314(a), (b),
(c), and (d) regarding placement of free liquids in a landfill is not applicable to Alternative 7a,
as vitrification produces a glass-like product with no liquids.
Compliance with location, contaminant, and on-site action-specific requirements for
Alternative 7b would be similar to that described for Alternative 7a. Applicable requirements
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for transportation of radioactive and chemically hazardous material to the Envirocare facility
would be met under this alternative.
Compliance with ARARs under Alternative 7c would be similar to that described for
Alternative 7b.
8.2 Primary Balancing Criteria
8.2.1 Long-Term Effectiveness and Permanence
The long-term effectiveness of chemical stabilization/solidification generally is considered
to be less than for vitrification (i.e., wastes that are vitrified could be expected to resist leaching
for a longer time [thousands of years] compared with the chemically stabilized form [hundreds
of years]. However, the uncertainties with regard to the performance and implementability of
vitrification steered the decision toward a more demonstrated technology. In fact, it was this
combination of performance uncertainty and potential for greater long-term effectiveness that led
to the decision to further evaluate vitrification as a contingency treatment option in the selected
remedy. The important point is that residual risks at the site would be reduced to near
background levels regardless of which technology is used. The required monitoring and five-
year reviews will provide an effective precaution against any future potential release going
undetected and resulting in actual exposure. In addition, long-term effectiveness and permanence
of the disposal facility is affected by the loss of institutional controls. The likelihood that
institutional controls would be lost is the same for Alternatives 6a and 7a. However,
continuation of institutional controls into the extended long term at a commercial facility
(Alternative 7b) might be more difficult to ensure than at a Federally owned facility (Alternatives
6a, 7a, and 7c).
8.2.2 Reduction in Toxicity, Mobility, and Volume through Treatment
Greater reduction in toxicity, mobility, or volume through treatment would be achieved
for Alternatives 7a, 7b, and 7c (vitrification), as compared with Alternative 6a, chemical
stabilization/solidification (CSS). The volume of structural material, vegetation, and wooden
debris would be similarly reduced under each alternative; however, for the sludge and soil that
would be treated by vitrification, some contaminants (e.g., the limited organic compounds)
would be destroyed, the others would be immobilized in a glass-like matrix, and the overall
disposal volume would decrease by about 24%. Alternative 6a would also significantly reduce
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contaminant mobility by incorporating contaminants into a cement-like matrix, but contaminant
toxicity would not change and the overall waste disposal volume would increase by about 12%.
8.2.3 Short-Term Effectiveness
The short-term effectiveness of Alternatives 6a and 7a would be essentially the same.
Potential short-term impact concerns from the implementation of Alternative 7b or 7c would be
substantially greater than for Alternative 6a or 7a, due to the increased handling of waste
material and the transportation of the waste to the off-site locations.
The two key differences among the final action alternatives are the treatment method and
the disposal location (which includes a transportation component for the off-site disposal
alternatives). Therefore, impacts to workers and the general public from removal activities
during the remedial action period would be similar for each alternative because the same areas
would be excavated or dredged. Incremental impacts to workers and the public from treatment
activities could result from differences between the chemical treatment and vitrification
operations, i.e., additional emissions are associated with vitrification, as compared with CSS,
because contaminants would be released from the stack of the vitrification facility. However,
these emissions are expected to be controlled by an extensive air pollution control system within
the facility, so related impacts would be small to none.
Potential health impacts for members of the general public during the cleanup period
would be below the EPA target limits for protecting human health for each of the action alterna-
tives. Impacts would be relatively higher for Alternatives 7b and 7c than for Alternative 6a or
7a because of the increased likelihood of exposures and accidents during the waste handling and
transportation activities for off-site disposal. The potential for risk to workers would be higher
under the vitrification alternatives because this process would require more workers and
additional accidents could result from the hazards of high operating temperatures and limited
field experience.
Environmental impacts could potentially result from excavating and dredging
contaminated material, constructing access roads, staging areas, and other support facilities;
constructing and operating the disposal facility (either on site or off site); and excavating borrow
soil from a location near the Weldon Spring site to provide backfill for the remediated areas on
site and to construct the cell under Alternatives 6a and 7a. Additional impacts could be
associated with activities at the rail siding in Wentzville and other transportation operations
under Alternatives 7b and 7c. Except for the permanent loss of habitat at the disposal facility
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area and possibly at the off-site borrow location (depending on the location selected during
detailed design), any potential impact would be short term and likely could be mitigated by
various standard practices, e.g., engineering controls to limit erosion and siltation. A mitigation
action plan will be developed that will outline specific measures to be implemented for
environmental controls or to address contingency response actions.
8.2.4 Implementability
The implementation of Alternative 6a would be the most straightforward of the final
action alternatives because the chemical stabilization/solidification technology has been utilized
at other sites and would use readily available resources. Implementation of chemical
stabilization/solidification at the Weldon Spring site (testing, design, construction, and start-up)
is estimated to require a maximum of five years. Implementation of Alternative 7a, 7b, or 7c
would require further engineering scale-up of the vitrification system and application of that
innovative technology to a large waste volume. Although the results of bench-scale testing have
shown that the Weldon Spring wastes can be successfully vitrified, they also indicate the need
for further testing to evaluate treatment of waste materials representing the extremes in chemical
variability, and to test treatment equipment that would be similar in type and function to that
required in full-scale operations. Implementation of vitrification at the Weldon Spring site
(testing, design, construction, and start-up) is estimated to require about 7 years. However,
there is greater uncertainty with this estimate due to the innovative nature of the technology.
Alternative 7b or 7c would require coordination of licensing, regulatory compliance, and
establishment of administrative procedures (as appropriate) in order to dispose of the Weldon
Spring waste at either off-site facility.
Difficulty in implementing either Alternative 7b or 7c would include such factors as
permitting of the facilities and transportation of the wastes to the off-site facilities. While the
Envirocare facility is permitted to accept mixed hazardous waste and naturally occurring
radioactive material, there is no permitted disposal facility currently on the site that may receive
lle(2) by-product material. Envirocare has submitted an application to the NRC for a license
to dispose of lle(2) by-product material. The Hanford facility (Alternative 7c) does not
currently have an appropriate disposal facility to receive Weldon Spring site waste. Construction
of such a disposal facility at Hanford could delay cleanup activities at the Weldon Spring site
for several years.
Transportation concerns include constructing the necessary rail siding transfer station in
Wentzville, Missouri, and the increased risk of transportation accidents.
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8.2.5 Cost
Description of Alternatives Approximate Costs fin millions)
Alternative 1: No Action $1.2 (annual)
Alternative 6a: Removal, Chemical $157 (total)
Stabilization/Solidification, and
Disposal On Site
Alternative 7a: Removal, $182 (total)
Vitrification, and Disposal On Site
Alternative 7b: Removal, $351 (total)
Vitrification, and Disposal at
Envirocare Site near Clive, Utah
Alternative 7c: Removal, $304 (total)
Vitrification, and Disposal at the
Hanford Reservation Site near
Richland, Washington
8.3 Modifying Criteria
8.3.1 State Acceptance
The State of Missouri has requested that the DOE agree to certain stipulations as a
condition for obtaining State concurrence. These stipulations are:
• No wastes from other sites shall be disposed of at the Weldon Spring site.
• An on-site disposal facility shall meet the substantive siting and design requirements
of State and Federal hazardous waste laws and regulations.
• The selected remedial alternative shall be protective of human health and the
environment.
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• Cleanup procedures, design, and standards shall meet all State and Federal ARARs.
• Human radiation exposures must be reduced to a level that is as low as reasonably
achievable (ALARA).
• The DOE shall commit to cleaning up the contaminated vicinity properties. These
properties include several small locations on the adjacent Army area, August A.
Busch Conservation Area, and Weldon Spring Conservation Area.
• Natural barriers and engineered materials, methods, and designs shall be used to the
maximum extent possible in order to achieve a protective and permanent waste
disposal solution, and institutional control measures shall be minimized.
• The U.S. Department of Energy (DOE) shall retain ownership and control of the
disposal facility.
• The DOE shall commit to long-term monitoring and maintenance of the disposal
facility.
8.3.2 Community Acceptance
In general, the comments received from the public indicate acceptance of Alternative 6a
as a selected remedy for the Weldon Spring site. The main concerns that were raised involved
a commitment by the DOE that the on-site disposal facility be used solely for Weldon Spring
wastes, and that no off-site wastes be accepted for disposal on site. There were also concerns
for safeguards to the Francis Howell High School population.
As stated in this Record of Decision (ROD), no off-site wastes will be accepted for
disposal at the Weldon Spring site. In addition, measures taken to facilitate the safety of
personnel at Francis Howell High School have been described in the Remedial Investigation/
Feasibility Study-Final Environmental Impact Statement (RI/FS-Final EIS) package.
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9 SELECTED REMEDY
On the basis of the evaluation of final alternatives, Alternative 6a (removal, chemical
stabilization/solidification, and disposal on site) has been identified as the selected remedy for
remedial action at the chemical plant area of the Weldon Spring site. The key components of
the remedy are described in Section 9.1, and the cleanup criteria developed for this remedy are
presented in Section 9.2.
9.1 Key Components
Material will be removed from contaminated areas, treated as appropriate by chemical
stabilization/solidification, and disposed of in an engineered disposal facility constructed on site
(Figure 9-1). The treatment method specified in the selected remedy will substantially reduce
the risks associated with those waste materials that represent the principal hazard at the site.
This remedy will also provide for the safe management of less contaminated site wastes. This
alternative will reduce risks and provide protection of human health and the environment in less
time and at a lower cost than the other action alternatives. Chemical stabilization/solidification
is an established technology that uses readily available resources and has been utilized at other
sites, and disposal in an on-site engineered facility would also use readily available resources
and standard technologies.
Chemical stabilization/solidification will be the treatment method used for contaminated
sludge, certain quarry soil and sediment, and certain other contaminated soil from the site (such
as soil taken from beneath the raffmate pits). Material treated by chemical stabilization/
solidification will undergo an increase in volume of about 32%. Volume reduction operations
will be used to treat structural material, rock, and containerized debris (e.g., used personal
protective equipment): The average volume of material processed by these methods will be
reduced by between 10% and 50% depending upon the specific material type. Volume reduction
operations will include a decontamination unit that can be used to treat selected structural
materials for which release and reuse is practicable.
An engineered disposal facility will be constructed in the area of the chemical plant
within a specifically designated portion of the site that has undergone numerous subsurface
investigations to confirm the suitability of the area for disposal of site waste. The design volume
of material that would be placed in the cell is estimated to be about 1.1 million m3
(1.5 million yd3). The base of the disposal facility will be designed to minimize the downward
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- OPTIONS FOR REMEDIATION
WASTE MEDIA FLOWPATH
FIGURE 9-1
REPORT NO.:
OflKSIHMDR
BMMTNO.:
JAB
DRAWN ft.
GLN
A/PI/053/0393
* 3/93
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transport of any leachate from the contaminated material that will be contained in the cell. The
long-term multilayer cell cover will serve as a barrier to infiltration and radon release and will
protect against the potential effects of freeze-thaw cycles, intrusion by plant roots or burrowing
animals, and erosion (including that associated with extreme precipitation events). In addition,
the cell will be seismically engineered to withstand damage from potential earthquakes. The
disposal facility will be maintained and its performance will be monitored for the long term.
Table 9-1 presents the estimated costs of the selected remedy. These costs are based on
preliminary conceptual design information. Some changes may be made to the remedy as a
result of the remedial design and construction processes. Such changes reflect modifications
resulting from the engineering design process and could increase the cost estimates identified in
this table.
Vitrification of the contaminated sludge, soil, and sediment (instead of chemical
stabilization/solidification) is being retained as a contingency treatment option. Vitrification is
being carried forward into the conceptual design phase so the effectiveness of this technology
and the uncertainties associated with its implementability can continue to be evaluated.
Estimated costs for this contingency remedy (Alternative 7a) are presented in Table 9-2.
If it becomes necessary to implement the contingency treatment option (vitrification and
disposal on site) because chemical stabilization/solidification does not perform adequately during
pilot-scale testing (i.e., if engineering limitations prevent treatment of the waste or if it is not
possible to consistently produce a waste product which passes the toxicity characteristic leaching
procedure [TCLP] test), an Explanation of Significant Differences from the selected action in
this ROD will be developed in accordance with U.S. Environmental Protection Agency (EPA)
guidance for post-ROD changes and this document will be made available to the public.
Since both chemical stabilization/solidification and vitrification processes involve the
addition of soils, a practical approach is to use site soils with higher levels of radioactivity, such
as those from Ash Pond and the north dump. These soils will be mixed preferentially with
raffinate sludge and quarry bulk waste. If additional soil mixing material is needed, other site
soils with still lower concentrations of radioactivity will be used preferentially over
uncontaminated borrow soils.
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TABLE 9-1 Cost Estimate for Alternative 6a
Estimated Cost
Activity (million $)
Removal
Raffinate pits remediation 11.9
Chemical plant area preparation*0' 2.8
Building foundation and underground pipe removal10' 5.9
Soil and sediment excavation 1.7
Building 434 waste removal'0' 0.6
Vicinity properties remediation1*
Army properties 1, 2, 3 and Busch properties 3, 4, 5(cl 0.4
Busch Lakes 34. 35, and 36(cl 0.4
Army properties 5 and 6lei 0.3
Removal subtotal 24.0
Treatment
Bench-and pilot-scale testing 2.1
Sludge processing facility construction 3.1
Sludge processing facility operations 14.7
Volume reduction facility construction'0' 2.9
Volume reduction facility operations'0' 2.5
Construction of second treatment train (distillation)
of water treatment facility'0' 1.2
Water treatment plant operations 3.5
Treatment subtotal 30.0
Disposal
Disposal facility construction material tests 0.9
Disposal facility construction 47.6
Disposal facility operations 7.2
Disposal subtotal 55.7
Other
Material hauling 9.7
TSA operations'0' 2.0
MSA operations'0' 5.2
Decontamination station operations'0' 1.2
Facilities removal'0' 1.8
Site restoration 3.4
Long-term maintenance'"' 23.9
Other subtotal 47.2
Total 156.9
Present worth 78.5
'°' Items that are part of Alternative 6a and for which the cost estimate does not differ between this alternative and the
contingency remedy (Alternative 7a).
(dl Includes both excavation and restoration costs.
'*' For a 30-year period; includes environmental monitoring.
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TABLE 9-2 Cost Estimate for Alternative 7a
Estimated Cost
Activity (million $)
Removal
Common removal costs (see Table 14) 10.4
Raffinete pits remediation 14.4
Soil and sediment excavation . 1.7
Removal subtotal 26.5
Treatment
Common treatment costs (see Table 14) 6.6
Bench- and pilot-scale testing 8.2
Sludge processing facility construction 25.6
Sludge processing facility operations 20.5
Water treatment plant operations 3.5
Treatment subtotal 64.4
Disposal
Disposal facility construction material tests 0.9
Disposal facility construction 37.1
Disposal facility operations 6.7
Disposal subtotal 44.7
Other
Common other costs (see Table 14) 10.2
Material hauling 9.3
Site restoration 3.4
Long-term maintenance1*1 23.9
Other subtotal 46.8
Total 182.4
Present worth 96.9
'*' For a 30-year period; includes environmental monitoring.
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9.2 Cleanup Criteria
Interim actions have addressed cleanup criteria for surface water at the Weldon Spring
site, and groundwater will be addressed as a separate operable unit in the future. Thus, soil is
the focus of cleanup criteria for the current remedial action (as discussed in Section 2 of the FS).
Cleanup criteria for the key contaminants in site soil were developed from available
environmental regulations and guidelines in combination with the results of the site-specific risk
assessments. As part of the latter, a site-specific analysis was conducted to address the reduction
of residual risks to levels as low as reasonably achievable (ALARA), as described in Section 2
of the FS. For the purpose of developing these criteria from risk information, the RME was
identified as the residential scenario described in Section 6.2.2, under which exposures to soil
were evaluated for inhalation and incidental ingestion combined. In accordance with the NCP,
the initial point of departure for the development of the cleanup criteria was an incremental risk
level of 1 x 10"6 for carcinogens. A hazard index of 1 was the target for the noncarcinogens.
However, for many of the contaminants at the Weldon Spring site, the point of departure for
incremental risks could not reasonably serve as the endpoint for site cleanup criteria. That is,
background concentrations of certain naturally occurring metals (including the radionuclides
present at the site) correspond to risks more than 100 to 1,000 times greater than this level.
Thus, it is very difficult to distinguish incremental contamination from variability in background
concentrations that correspond to a fractional increment of 1 x 10"6. For this reason, the site-
specific risk assessments addressed reducing residual risks to ALARA levels, as described in
Section 2 of the FS.
The soil areas identified for remediation on the basis of the risk-based criteria determined
from these assessments are shown in Figure 9-2. Concentration-based criteria were also
developed for each primary contaminant of concern to provide a means for ensuring that cleanup
has been.achieved, i.e., by verification sampling across the site. These criteria are listed in
Tables 9-3 and 9-4 and represent the total concentrations (i.e., including background) above
which site soil would be removed; the ALARA goals represent lower levels that the remedial
action would aim to achieve during field excavation activities.
If soils with contaminant concentrations exceeding natural background are released off
site, further risk assessments must be performed using parameters specific to the intended use
or disposition of the soils. Concrete rubble will be treated like soil and will likewise not be
released off site. The criteria contained in DOE Order 5400.5 will be used for materials (such
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400
800 Fee:
_J
100
I
200 Meters
E3
©
O
o
0
©
€
©
•
e
e
Structures Being Dismantled
Radiological Targe:
Radiological ALARA Goa1
Arsenic Targe:
Arsenic ALARA Goa
Chromium ALARA Goa'
Lead Targe:
Lead ALARA Goa'
Thallium ALARA Goa:
Nitromavc Compounds ALARA Goa'
PAH Targe:
PCB Targe:
PCB ALARA Goal
AREAS OF SOIL IDENTIFIED FOR
REMEDIATION BASED ON
CLEANUP CRITERIA
FIGURE 9-2
REPORT NO.:
DOEADFV2154S-376
ORIQINATOA:
JB
IXHIIIT NO.:
A/CP/077/0893
SRS
DATE.
8/23/93
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TABLE 9-3 Estimated Radiological Risks for the Recreational Visitor, Ranger, and
Resident Associated with the Soil Cleanup Criteria
Radionuclide/
Criterion1*1
Ra-226
Cleanup criteria
ALARA goal
Background
Ra-228
Cleanup criteria
ALARA goal
Background
Th-230
Cleanup criteria
ALARA goal
Background
Th-232
Cleanup criteria
ALARA goal
Background
U-238
Cleanup criteria
ALARA goal
Background
SoH
Concentration
(pCVg)lb)
6.2
5
1.2
6.2
5
1.2
6.2
5
1.2
6.2
5
1.2
120
30
1.2
Recreational
Visitor
5 x TO'5
4 x 10'5
9 x 10'6
2 x 10'5
1 x 1O-S
3 x 10'6
3 x 10'7
2 x 10-7
6 x 10'8
2 x 10-6
1 x 10'6
3 x 10'7
2 x 10'5
4 x 10'6
2 x ID'7
Risk to Hypothetical Receptor
Ranger
8 x 10*
6 x 10*
2 x 10"*
2 x 10-*
2 x 10*
5 x 10'5
4 x 10'6
3 x 10'6 .
8 x 10'7
2 x 10-5
2 x 10'5
4 x 10-6
2 x 10*
5 x 10'5
3 x 10'6
Resident
2 x 10"2
8 x 10'3
2 x 10-3
1 x 10'3
8 x 10"4
2 x ID"4
8 x 10'6
6 x 10'6
2 x 10'6
4 x 10'5
3 x 10'5
7 x 10-6
5 x 10*
1 x 10*
8 x 10'6
'•' The radiological risks associated with all radionuclides in the U-238, U-235, and Th-232 decay series were included in the
human health assessments. Cleanup criteria were developed for the five radionuclides listed in this table on the basis of
a site-specific analysis of the relative concentrations of radionuclides present in site soil. The contributions of the other
radionuclides in the three decay series are incorporated into the risk estimates reported for these five radionuclides, as
described in Chapter 2 of the FS. Data for local background are presented for comparison; the background soil
concentration of 1.2. pCi/g represents the average concentration measured for each of the listed radionuclides at off-site
locations that have not been affected by site releases.
' ' The cleanup criteria for the individual radium and thorium isotopes represent the surface concentrations; the subsurface
concentration is 16.2 pCi/g. The ALARA goal of 5 pCi/g applies to both surface and subsurface contamination. The listed
cleanup criteria and ALARA goals for these individual isotopes include the background concentration of 1.2 pCi/g.
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TABLE 9-4 Estimated Chemical Health Effects for the Recreational Visitor, Ranger, and Resident Associated with the
Soil Cleanup Criteria
Chemical/
Criterion11"1
Metals
Arsenic
Cleanup criterion
ALARA goal
Background
Chromium (total)
Cleanup criterion
ALARA goal
Background
. Chromium (VI)
Cleanup criterion
ALARA goal
Lead
Cleanup criterion
ALARA goal
Background
Thallium
Cleanup criterion
ALARA goal
Background
PAHs1'1
Cleanup criterion
ALARA goal
PCBs1"
Cleanup criterion
ALARA goat
Soil
Concentration
(mg/kg)
75
45
26
110
90
36
100
90
450
240
34
20
16
16
5.6
0.44
8
0.65
Recreational
Visitor
6 x 10'6
3 x 10'6
2 x 10'6
NA|C)
NA
NA
3 x 10'7
3 x 10'7
_WI
'
—
NA
NA
NA
3 x 10-e
2 x 10'7
2 x 10'9
2 x 10'7
Risk
Ranger
7 x TO'5
3 x 10'5
2 x 10-5
NA
NA
NA
6 x 10'6
5 x 106
-
-
—
NA
NA
NA
3 x 10'5
2 x 10'6
3 x 10'5
2 x 10'6
Resident
2 x 10-4
1 x 104
7 x 10'5
NA
NA
NA
1 x 10'5
9 x 10'6
-
-
—
NA
NA
NA
1 x 10'4
8 x 10'6
1 x 10'4
8 x 10'9
Recreational
Visitor
0.02
0.01
0.008
0.03
0.02
0.01
0.03
0.02
-
—
—
0.03
0.02
0.02
0.00002
0.000001
0.008
0.0006
Hazard Quotient1*1
Ranger
0.3
0.2
0.1
0.6
0.4
0.1
0.6
0.4
-
- —
—
0.3
0.3
0.3
0.0002
0.00002
0.09
0.008
Resident
0.9
0.5
0.3
1
0.8
0.3
1
0.8
-
—
—
1
0.8
0.8
0.0007
0.00005
0.3
0.02
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TABLE 9-4 Estimated Chemical Health Effects for the Recreational Visitor, Ranger, and Resident Associated with the
Soil Cleanup Criteria (Continued)
Risk Hazard Quotient1*1
Chemical/
Criterion""1
Soil
Concentration .
(nig/kg)
Recreational
Visitor
Ranger
Recreational
Resident Visitor
Ranger
Resident
Trinitrotoluene
Cleanup criterion
ALARA goal
140
14
2 x 10'7
2 x 10'8
2 x 10'6
2 x 10'7
7 x 10'8
7 x 10'7
0.03
0.003
0.3
0.03
1
0.1
'•' The hazard quotient shown for each contaminant represents the sum of the contributions from Inhalation and Ingestlon, as appropriate.
-------
as metal scrap) with solid exterior surfaces. These criteria are compatible with standards used
throughout the nuclear industry.
9.2.1 Radioactive Contaminants
Cleanup criteria for the radionuclides of concern at the Weldon Spring site — i.e.,
Ra-226, Ra-228, Th-230, Th-232, and U-238 — were determined from available standards and
guidelines in combination with risk assessment information. These cleanup criteria address all
radionuclides that may be present at the site, using results of a site-specific radionuclide source
term analysis. The procedures used to develop these criteria are described in Section 2.2 and
Section 2.4 of the FS. The criteria for Ra-226 and Ra-228 were adopted from EPA standards
given in 40 CFR 192 that were determined to be relevant and appropriate to the conditions at
the Weldon Spring site (see Section 10.2). Cleanup criteria for Th-230 and Th-232, which were
adopted from DOE Order 5400.5, were included to protect from future exposures to Ra-226 and
Ra-228 (and Rn-222 and Rn-220) as a result of radionuclide ingrowth. If both Th-230 and
Ra-226, or both Th-232 and Ra-228, are present and not in secular equilibrium, the cleanup
criteria apply for the radionuclide with the higher concentration. At locations where both
Ra-226 and Ra-228 are present, the cleanup criteria of 5 pCi/g (above background) in the top
15 cm (6 in.) of soil, and 15 pCi/g (above background) in each 15-cm (6-in.) layer of soil more
than 15 cm (6 in.) below the surface, applies to the sum of the concentrations of these two
radionuclides. For U-238, no general standards are available. Hence, the cleanup criterion was
developed on the basis of the site-specific risk assessment alone; this criterion is 120 pCi/g.
In accordance with the both the CERCLA process and DOE Order 5400.5, results of the
site-specific risk assessment were then applied to determine the ALARA goals for each
radionuclide. The ALARA goal represents the level that can reasonably be achieved during field
implementation within existing constraints, as indicated by site-specific conditions. As discussed
in Section 2 of the FS, the constraints for developing ALARA goals for radionuclides at the
Weldon Spring site are the ability to measure the contaminants in the field, distinguish
contamination from background, and verify that cleanup has been achieved. The ALARA goals
for Ra-226, Ra-228, Th-230, and Th-232 at all depths are each 5 pCi/g, including background.
As described above for the cleanup criteria, the ALARA goal for the radium isotopes applies
to the sum of the concentrations of Ra-226 and Ra-228 at locations where both contaminants are
present. For surface soil, the ALARA goal is 5 pCi/g combined, including background; for
subsurface soil, the ALARA goal is 5 pCi/g combined, above background. The ALARA goal
for U-238 at all depths is 30 pCi/g, including background.
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9.23 Chemical Contaminants
The chemical contaminants of concern for which final cleanup criteria were developed
are arsenic, chromium, lead, thallium, PAHs, PCBs, and TNT. Some ARAR and TBC
information is available for lead and PCBs, and these standards and guidelines were used as the
starting point to develop cleanup criteria, in combination with the site-specific risk assessments.
For lead, the EPA has established interim guidance that considers the natural presence of lead
in soil and recommends a cleanup level of 500 to 1000 mg/kg, as determined by site-specific
conditions (EPA 1989a). The EPA has also developed an uptake/biokinetic model to estimate
blood lead levels in children, who represent the most sensitive subpopulation for the residential
scenario. The health-based criterion developed for lead on the basis of site-specific input to this
model is 450 mg/kg.
For PCBs, regulations in the Toxic Substances Control Act that address cleanup of soil
following a spill of PCB-contaminated material were considered relevant and appropriate to site
conditions (see Section 10.2). The standard indicates that soil in areas of unrestricted access at
which a spill occurs should be decontaminated to 10 mg/kg by weight, and this served as the
starting point of the analysis. A health-based criterion of 8 mg/kg was determined on the basis
of the risk assessment and other site-specific considerations, as discussed in Section 2.4.2.6 of
the FS. ARARs are not currently available for the remaining chemical contaminants, so the
cleanup criteria were developed solely on the basis of the site-specific risk assessments.
Cleanup criteria were developed for those contaminants at the Weldon Spring site that
contribute significantly to site risks or hazard indexes on the basis of contaminant levels
measured during extensive site characterization activities. Several nitroaromatic compounds —
DNB, 2,4-DNT, 2,6-DNT, NB, TNB, and TNT — have been detected in site soil at a few
discrete locations, but the results of the site-specific risk assessments indicate that the
concentrations of these compounds are below levels of concern, except for TNT. For this
reason, a final criterion has been developed only for TNT. For the remaining nitroaromatic
compounds, the preliminary target levels presented in Section 2.5 of the FS will serve as the
starting point for addressing these contaminants, if detected during field activities at levels higher
than those currently identified in site characterization activities. Sampling during and after soil
remediation will be conducted to ensure that residual risks associated with these compounds do
not exceed the target range and that the hazard indexes are below 1 (see Section 4 of the
Proposed Plan and Section 9.2.3 of this ROD).
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Soil contamination at the Weldon Spring site is heterogeneous, i.e., contaminants are
located in different combinations at different areas of the site. For the chemical contaminants,
the areas that will be excavated were identified on the basis of actual measurements from the
location-specific assessment and the results of the risk assessment (Figure 9-2). This risk-based
approach allows the identification of areas for remediation resulting from the presence of
multiple contaminants.
The concentration-based cleanup criteria were also developed from the site-specific risk
assessment, considering information on the known patterns of contamination (Table 9-4). In
general, the chemical contaminants contributing significantly to health effects near or above
target levels are not present together; hence, additivity was generally not an issue in developing
the cleanup criteria. The few areas at which multiple contaminants are present were identified
for remediation on the basis of the location-specific risk assessment. However, to address the
possibility that additional contaminant co-location may be found during field activities, lower
ALARA goals were also established for all chemical contaminants. As indicated above,
remediation of site soil will be designed to meet these ALARA goals. For lead, PAHs, PCBs,
and TNT, the ALARA goals are the levels that had been proposed for statewide consideration
by the Missouri Department of Health (1992) for soil in residential settings; the levels were
withdrawn subsequent to the preparation of the FS. Many of these health-based levels were
consistent with the ALARA process, so they have been retained. However, the draft State levels
for arsenic and thallium were considerably below local background concentrations, and the levels
for chromium were higher than those derived from the site-specific assessment. Hence, the draft
State levels (subsequently withdrawn) were not adopted as ALARA goals for those three
contaminants.
It is expected that contaminant levels remaining in soil across the site after remediation
will range between the cleanup criteria and the ALARA goals, reaching the goals in most cases.
Excavating soil to achieve these levels is expected to reduce risks to within or below the target
risk range and to reduce hazard indexes below 1. Even lower criteria will be applied on a
location-specific basis, if areas are identified during field work at which multiple contaminants
are present. These criteria will be determined by combining the appropriate information from
the target risk tables in Section 2.5 of the FS to ensure that health-protective concentrations have
been achieved.
The cleanup criteria for chemical contaminants in subsurface soil at the site were
addressed by separate analyses to ensure that levels remaining would be protective under future
scenarios that could involve exposure to contaminants that are currently buried. For the purpose
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of site cleanup, subsurface is defined as soil deeper than 15 cm (6 in.) below the surface. As
discussed in Section 2.4.2 of the FS, the lower potential for exposures to subsurface material
compared with surface material — i.e., from redistribution of this soil on the surface and
leaching of contaminants to groundwater — resulted in the selection of subsurface criteria for
chemicals that are 10 times the surface criteria. In no case will the subsurface residual levels
exceed the subsurface cleanup criteria. The ALARA goals for subsurface soil are the same as
the cleanup criteria for surface soil, averaged over a 3 m (10 ft) depth. The plans for site
remediation will be designed to achieve subsurface ALARA goals. Thus, based on the known
patterns and locations of contamination, subsurface cleanup is expected to attain the subsurface
ALARA goals.
9.2.3 Post-Cleanup Assessment
Excavating soil to meet the cleanup targets for chemicals at the site would result in an
incremental chemical risk at or below the EPA's target range for all scenarios, and the hazard
index would be well below the level of concern. However, this is not the case for the
radiological cleanup criteria, because incremental radiological risks exceed the target range at
certain locations under a residential scenario. (The radiological risk at an uncontaminated area
is about 3 x 10~3, which indicates the difficulty in distinguishing an incremental risk of
1 X 10"4 from contamination versus natural variability.) Therefore, an additional "post-cleanup"
assessment was conducted for the radionuclides. For this assessment, areas with soil concen-
trations that exceed the ALARA goals were assumed to be excavated and backfilled with
uncontaminated soil from a nearby background area. The results of this evaluation were also
used to assess compliance with environmental standards and guidelines.
Results indicate that the incremental radiological risk across the site for the resident,
following soil excavation and backfill would range from 0 (i.e., background) to 6 x 10~3, with
a median of 8 x 10"6. Locations where the risk would exceed 1 x 10"4 are generally those
areas where the radium concentration in soil slightly exceeds the background concentration of
1.2 pCi/g; a small increment of 0.075 pCi/g corresponds to a risk of 1 x 10"4. (This highlights
the issue associated with meeting the EPA's target.) In addition, an annual dose of 25 mrem/yr
above background could not be achieved for residential use at about 10% of the soil areas. The
elevated risk estimates for those areas result almost entirely from exposures to the estimated
levels of indoor radon, which would be generated by the residual radium in soil (entering
through the basement or foundation slab). However, the target risk range was not specifically
developed on the basis of exposures to radionuclides, and the EPA has separately identified an
acceptable level for indoor radon of 4 pCi/L (EPA 1992a). The indoor radon concentrations
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associated with the cleanup target and goal for radium are expected to be at or below this level
at all site locations.
For outdoor air, the incremental radon concentration is estimated to be less than
0.1 pCi/L, and the annual dose from inhalation of airborne particulates generated from site soil
is estimated to be less than 10 mrem/yr at all locations. Hence, standards for the radiological
dose from exposure to outdoor air would be met by the cleanup targets for site soil. Potential
leaching to groundwater, for radionuclides from soil, was also assessed for post-remedial action
conditions to provide an initial indication of the potential impact to future receptors, in the event
that groundwater in the shallow aquifer at the site was used for drinking. The results indicate
that the proposed cleanup targets for soil are expected to be protective of groundwater. (This
pathway will be evaluated further in the upcoming, final assessment of the chemical plant area.)
The incremental risk estimated for the ranger from sitewide exposures following
remediation varies from 2 x 10~5 to 2 x 10"4, with a median of 2 x 10"5- The median and low
end of the range are the same, because outdoor exposures from site-wide activities dominate the
combined risk from indoor and outdoor exposures for this hypothetical receptor at most
locations. For the recreational visitor, the incremental risk is estimated to be 7 x 10"6. Thus,
the incremental radiological risks associated with future recreational land use at the site are
within the target range.
Following completion of site cleanup activities, an assessment of the residual risks based
on actual site conditions, including measured concentrations of site contaminants, will be
performed to determine the need for any future land use restrictions. This assessment will
consider the presence of the on-site disposal cell, the buffer zone, the adjacent Army site, and
any other relevant factors necessary to ensure that appropriate measures are taken to protect
human health and the environment for the long term. The remedy selected in this ROD will be
re-examined at least every five years to ensure that it is protective.
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10 STATUTORY DETERMINATIONS
In accordance with the statutory requirements of Section 121 of the Comprehensive
Environmental Response, Compensation and Liability Act (CERCLA), as amended, remedial
actions shall be selected that:
• Are protective of human health and the environment.
• Comply with applicable or relevant and appropriate requirements (ARARs).
• Are cost effective.
• Utilize permanent solutions and alternative treatment technologies to the
maximum extent practicable.
• Satisfy the preference for treatment which, as a principle element, reduces
toxicity, mobility, or volume.
The manner in which the Weldon Spring Chemical Plant remedial action satisfies these
five requirements is discussed in the following sections.
10.1 Protection of Human Health and the Environment
The selected remedy is protective of human health and the environment by (1) removing
the sources of contamination, (2) treating the materials giving rise to the principal threats at the
site to reduce contaminant mobility, and (3) containing treated and untreated materials in an
engineered disposal facility designed to prevent migration of contaminants into the environment.
The contingency remedy would also be protective of human health and the environment for the
same reasons, with additional protection provided by treating contaminated materials to reduce
toxicity and volume.
10.2 Compliance with Applicable or Relevant and Appropriate Requirements
Both the selected remedy and the contingency remedy will comply with ARARs, unless
those requirements have been properly waived in accordance with CERCLA, and will be
performed in accordance with all pertinent U.S. Department of Energy (DOE) Orders. The
ARARs are presented below according to location-specific, contaminant-specific, and action-
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specific requirements. Removal, treatment, transportation, and disposal of the contaminated
material for both the selected remedy and the contingency remedy are on-site actions and must
comply with the substantive requirements of Federal and State environmental laws that are
ARARs.
ARAR waivers that are appropriate to this action are discussed in the following sections.
10.2.1 location-Specific ARARs
Location-specific ARARs are restrictions placed on the concentration of hazardous
substances or the conduct of activities solely because they are in a specific location. The
analysis of location-specific ARARs included a review of the Resource Conservation and
Recovery Act (RCRA), the Missouri Hazardous Waste Management Laws, the Antiquities Act,
the Historic Sites Act, the National Historic Preservation Act, the Archeological and Historic
Preservation Act, the Archeological Resources Protection Act, the Endangered Species Act, the
Missouri Wildlife Code, the Fish and Wildlife Coordination Act, the Clean Water Act (CWA),
and the Farmland Protection Policy Act.
Federal Executive Order 11988 and Missouri Governor's Executive Order 82-19 require
that adverse impacts associated with activities in a floodplain be avoided to the maximum extent
practicable. These requirements are considered applicable to the Weldon Spring remedial action.
It is noted, however, that a portion of the Schote Creek 100-year floodplain extends onto the site
in an area where excavation of contaminated soil is planned. The excavation of these materials
will not increase the potential for off-site transport due to flooding; in fact, these remedial
actions will result in the removal of these materials from within the 100-year floodplain.
No long-term impacts to flood storage capacity are anticipated from the remediation of
the Ash Pond drainage and vicinity property A6. Potential short-term impacts, resulting
primarily from vegetation clearing and excavation activities, would be mitigated by using good
engineering practices and implementing the following mitigative measures: (1) erosion and
sediment control measures, such as berms and silt fences, will be used during all excavation,
fill, and contouring activities; contaminated soil and sediment will be excavated only when the
Ash Pond drainage channel is dry; only clean fill will be used; excavated areas will be filled as
soon as practicable after excavation and graded to original contours as much as possible; and
revegetation activities will be implemented as soon as possible following recontouring of the
refilled areas.
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Executive Order 11990 requires Federal agencies to avoid, to the extent possible, any
adverse impacts to wetland areas. This order is considered applicable since there are several
areas on site (such as the pits) that are considered wetlands. There is no practicable alternative
but to remove the contaminated material from these areas. The potential off-site soil borrow
area also contains wetlands. Mitigative measures are being coordinated with the State of
Missouri and will be defined in the mitigation action plan. A Clean Water Act Section 404
permit will be obtained from the U.S. Army Corps of Engineeers due to activities that may
impact the wetland at the borrow area.
The DOE has initiated consultations with the U.S. Fish and Wildlife Service (FWS)
regarding the need for mitigation of the on-site wetlands that would be lost as a result of
remedial activities at the site. The FWS has recommended that the DOE consider wetland
creation as a means of mitigating the wetlands loss. The DOE has initiated surveys of wetlands
that could be affected by site activities to document their size, type, and biotic composition.
Upon completion of these surveys and additional consultations with the FWS and the Missouri
Department of Conservation, the DOE will develop a wetlands mitigation plan for the site that
is expected to include wetlands creation. Mitigative measures will be taken at the off-site
borrow area, such as contouring to ensure that downgradient wetlands are not indirectly
impacted.
The Farmland Protection Policy Act (7 CFR 658; 40 CFR 6.302[c]) requires Federal
agencies to assess the adverse impacts of Federal programs on farmland preservation and to
consider alternative actions to lessen the adverse effects. This requirement is considered
applicable for the potential off-site soil borrow area, as the borrow area has been classified as
prime or unique farmland. A separate environmental assessment is planned for the borrow area
to assess possible environmental impacts. Mitigation measures and restoration activities would
be conducted at the off-site borrow area, as necessary, to minimize any adverse impacts to
farmland. •
Because the potential soil borrow area is off site, the requirements, including
administrative requirements, of the following acts are applicable: the Archaeological and
Historic Preservation Act, the Archaeological Resources Protection Act, and Section 404 of the
Clean Water Act. The Archaeological and Historic Preservation Act requires that data recovery
and preservation activities be conducted if prehistoric, historical, and archaeological data might
be destroyed as a result of a Federal activity. A permit is required for excavation or removal
of any archaeological resources on Federal lands under the Archaeological Resources Protection
Act. Studies are being performed to determine if any archaeological sites or resources will be
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affected in the borrow area, and whether any resources would be removed before soil is
excavated. A permit would be obtained for removal of any archaeological resources in the
borrow area.
Location standards are specified under RCRA (40 CFR 264.18) that address the siting
of new hazardous waste treatment, storage, and disposal facilities. These requirements are
considered to be applicable to the siting of the treatment facility (chemical stabilization/
solidification or vitrification), since the unit is expected to treat hazardous wastes. However,
the treatment process will render the characteristic wastes nonhazardous; therefore, these
standards are not applicable to the disposal facility. No listed wastes will be managed in the
treatment system or the disposal facility. Certain of these requirements, as well as the
companion requirements in the Missouri Hazardous Waste Management Laws, may be relevant
and appropriate to the disposal facility as described below:
• Regulation 40 CFR 264.18(a) restricts locating hazardous waste management facilities
within 200 ft of a fault that has been displaced in Holocene time. This requirement
is intended to minimize the chances of a catastrophic failure resulting from an
earthquake and is both relevant and appropriate to the disposal facility due to
sufficient similarity of wastes and the purpose of the requirements.
• Regulation 40 CFR 264.18(b) restricts locating hazardous waste management facilities
within a 100-year floodplain. This requirement is intended to prevent the spreading
of contaminants during extreme flooding conditions and is both relevant and
appropriate to the disposal facility due to sufficient similarity of wastes and the
purpose of the requirements.
• Regulation 10 CSR 25-7.264(2)(N)l.A provides siting criteria for new hazardous
waste landfills that identify a requirement for 9 m (30 ft) of soil or other material
with a permeability of 1 x 10-7 cm/s or an equivalent protection based on at least 6
m (20 ft) of naturally occurring material for a landfill that receives only waste
generated by its operator. Site characterization has demonstrated that present site
conditions will meet the above criteria and it is, therefore, reasonable that such
conditions be retained. An explanation is presented below on how this condition will
be retained once the disposal cell is constructed.
The on-site disposal facility will be constructed and maintained to provide equivalent
protection. Much of the site overburden has already been considerably disturbed as a result of
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the extensive excavation, backfilling, and regrading activities that were conducted during plant
construction many years ago. Thus, the existing overburden material, although naturally
occurring, will not be the original, in-place material at the site. Therefore, the soil beneath the
cell will be compacted to achieve a permeability at least as low a 1 x 10-7 cm/s over a depth of
6 m (20 ft). Compaction and permeability criteria are based on data collected during field
permeability testing of in situ site soils using a two-stage borehole (TSB) procedure. As
determined in the TSB testing, travel time and permittivity calculations were used to demonstrate
that the soil units (Ferrelview Formation and clay till) comprising the foundation of the disposal
facility will provide a level of protection superior to the State requirement 10 CSR 25-
7.264(2)(N)1.A. The tests also determined that the soil units will satisfy the minimum soil
performance requirement relative to the movement of hazardous constituents.
The intent of the overburden requirement is to provide a material that would retard
contaminant migration so that groundwater would be protected from any impacts that could
result from future leaching. The overburden soil, as explained above, will meet or exceed the
permeability of 1 x 10-7. Other protective factors to groundwater include the cell components
(i.e., the cover and liner) which will be engineered to limit infiltration and ensure that cell
performance can be monitored, and post-closure monitoring which will detect any potential
lapses in the integrity of the disposal cell facility.
• Regulation 10 CSR 25-7.264(2)(N)l.A(IV)(e) provides siting criteria for hazardous
waste landfills which restrict locating new facilities in an area subject to catastrophic
collapse. This requirement is intended to ensure long-term protection and is both
relevant and appropriate to this action due to sufficient similarity of the regulated
conditions. Previous studies have identified an area within the site boundary that
complies with this standard. The cell will be located such that all waste materials are
kept within that area. These studies are detailed in the Site Suitability Data Report
(MKF and JEG 1991).
• Regulation 10 CSR 25-7.264(2)(N)2.D provides siting criteria for hazardous waste
landfills which specify a 91 m (300 ft) buffer zone between the property line of the
disposal facility and the actual landfill. The buffer zone provides an area which will
be used only for monitoring and maintenance activities. This regulation is considered
relevant and appropriate as discussed in Section 10.2.3.4.
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In addition, Missouri Solid Waste Management Law 10 CSR 80-3.010(5)(C)(2) specifies
a buffer zone of SO ft (15 m) for landfills units. This regulation is considered relevant and
appropriate as discussed in Section 10.2.3.4.
The proposed action will not impact historic, archeological, or cultural resources,
sensitive ecosystems, or any threatened or endangered species.
As determined in the Feasibility Study (FS) (DOE 1992d), no other location-specific
requirements were found to be either applicable or relevant and appropriate.
10.2.2 Contaminant-Specific ARARs
Contaminant-specific ARARs are health- or risk-based numerical values that establish the
acceptable amount or concentration of a chemical that may be found in, or discharged to, the
environment. Contaminant-specific ARARs were analyzed to identify each environmental law
or regulation pertinent to the types of contaminants that will be encountered during the remedial
action. This analysis included a review of the health and environmental protection standards for
Uranium and Thorium Mill Tailings Actions (UMTRA), the Resource Conservation and
Recovery Act (RCRA), the Missouri Radiation Regulations, the National Emission Standards for
Hazardous Air Pollutants (NESHAP), the Clean Air Act, the Missouri Air Quality Standards,
the Missouri Air Pollution Control Regulations, the Toxic Substance Control Act (TSCA), and
the Clean Water Act. Several of the following standards were incorporated into the
determination of cleanup criteria for contaminated soil at the Weldon Spring site (as explained
in Section 2 of the FS).
NESHAP requirements for radionuclides (given in 40 CFR 61 Subparts H and Q) and
asbestos (given in Subpart M) are applicable to the protection of the public during
implementation of the remedial action. The NESHAP requirement for Rn-222 emissions
(Subpart T) are relevant and appropriate as the site contains material sufficiently similar to
uranium mill tailings, and the release requirements are well suited to final site conditions.
The NESHAP standards in 40 CFR 61 Subpart N set forth requirements for arsenic
emissions. While this requirement is not considered a ARAR, because glass manufacturing is
not part of the remedial action and commercial arsenic would not be used as a raw material, the
requirement will be addressed in controlling emissions during implementation.
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State air-quality standards found in 10 CSR 10-5.180, paniculate standards for internal
combustion engines, and 10 CSR 10-6.170, restriction of paniculate matter to the ambient air
are applicable to the implementation phase (including the excavation of borrow material) and will
be met.
UMTRA 40 CFR 192.32(b)(l)(ii) addresses releases of radon from disposal areas after
the closure period. These standards will be applicable after the bulk wastes have been placed
in the disposal facility and the cover has been completed. At that time, the disposal area will
meet the Rn-222 flux standards specified in 40 CFR 192.32(b)(l)(ii). These standards require
reasonable assurance that Rn-222 releases will not exceed an average release rate of
20 pCi/m2 sec.
Regulation 40 CFR 192, Subpart B addresses residual concentration levels of Ra-226 in
soil. Residual levels should not exceed background by more than 5 pCi/g in the top 15 cm of
soil or 15 pCi/g in each 15 cm layer below the top layer, averaged over an area of 100 m2.
This standard applies to residual radium in soil at designated uranium processing sites. Because
the Weldon Spring site is not a designated site, the standard is not applicable to this remedial
action. However, it is relevant and appropriate because the contamination patterns at the
Weldon Spring site are similar to those at the mill tailings sites. That is, there are no large
volumes of subsurface radium-contaminated material with concentrations between 5 pCi/g and
15 pCi/g.
Regulation 40 CFR 192, Subpart E, specifies annual dose equivalent exposures to
uranium and thorium by-product material as a result of planned discharges of radioactive
material to the general environment. While the remedial action does not include a planned
discharge of radioactive material, the requirements are relevant and appropriate to protection of
the public during implementation of the action because the waste types are considered
sufficiently similar. Subpart E also provides residual concentration limits for Ra-228 in soil.
These levels, which are numerically identical to those given in Subpart B for Ra-226, are
considered to be relevant and appropriate to site conditions for the same reasons as described
above.
The State quarterly Rn-222 limit of 1 x 10"9 /xCi/ml (1 pCi/1) above background in
uncontrolled areas published in 19 CSR 20-10.040, Missouri Radiation Regulations, cannot be
achieved during implementation of this action. It is possible that activities might result in
temporary exceedances of the standard during the cleanup period. These activities are
intermediate in nature, and are part of an overall remedial action that would attain compliance
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with this standard upon completion. Protection will be achieved by limiting exposure to
workers. Because compliance with the requirement during remedial implementation is
technically impracticable, this standard is waived under the provisions of Section 121(d)(4)(C)
of the CERCLA during implementation: compliance with such requirements is technically
impracticable from an engineering perspective.
Regulation 19 CSR 20-10.040 also specifies maximum permissible exposure limits for
persons outside a controlled area. This requirement is applicable to the protection of the public
during the implementation phase and will be met.
Regulation 40 CFR 261 includes levels for identification of hazardous wastes which are
subject to hazardous waste regulations. Regulation 40 CFR 268 outlines the treatment standards
for wastes restricted from land disposal. These regulations are applicable to the identification
and disposal of listed or characteristic hazardous wastes.
Regulation 40 CFR 761, Subpart G deals with spills of materials contaminated with
greater than 50 ppm polychlorinated biphenyls (PCBs). The standard specifies a soil
decontamination level of 10 ppm PCBs. While any spills at the site would have preceded the
effective date of the regulations, the recommended level of 10 ppm by weight was considered
in developing cleanup criteria for PCBs in site soil.
If the vitrification alternative were to be implemented, the following standards would also
be relevant and appropriate. Missouri air quality standards (10 CSR 10-6.060) specify de
minimus emission levels for specific pollutants that the vitrification system would have to meet.
Regulation 10 CSR 10-5.030 places restrictions on emissions of paniculate matter from fuel-
burning equipment used for indirect heating. While such equipment would be used for direct
heating of wastes in the vitrification system, this requirement would be relevant and appropriate
based upon similarity of conditions.
10.2.3 Action-Specific ARARs
Action-specific ARARs are technology- or activity-based requirements or limitations on
actions taken that are triggered by the particular remedial activities selected to accomplish the
remedy. The analysis of action-specific ARARs addressed the following tasks for the selected
remedy:
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• Storage. Various contaminated materials are currently in storage at the chemical
plant area as a result of interim response actions.
• Excavation. Removal of the contaminated sludge, soil, sediment, and
vegetation from the chemical plant area and vicinity properties, and removal
of the quarry bulk wastes and structural materials from the temporary storage
areas at the chemical plant area.
• Treatment. Treatment of the raffmate-pit sludge and some soil and sediment
by chemical stabilization/solidification and the structural materials by
size/volume reduction.
• Disposal. Placement of all treated and untreated materials in an engineered
disposal facility on site.
The analysis of action-specific ARARs for the contingency remedy addressed the same tasks,
except that the treatment method for the sludge and soil was vitrification.
The ARARs for these activities are discussed in Sections 10.2.3.1 through 10.2.3.4.
10.2.3.1 Storage. As interim response actions prior to implementation of the final
remedy, various wastes have been collected and placed in storage to prevent potential releases
into the environment. Containerized chemical wastes (including PCB containerized waste) are
stored in Building 434, and quarry bulk wastes will be stored at the TSA prior to placement in
the on-site disposal facility. Building 434 contains approximately 2,500 drums of containerized
wastes. It is estimated that 20% of the drums contain RCRA characteristic wastes, which
includes approximately 190 drums of tributyl phosphate (TBP) waste. The TBP, which contains
PCBs, mercury, uranium, and thorium, is being stored in Building 434 on an interim basis until
proper treatment and disposal is determined. All RCRA and TSCA wastes are being stored in
accordance with the RCRA and TSCA regulations (e.g., labeling, adequate roof and walls), with
the exception of the storage limitation requirement discussed below. At the present time, no off-
site treatment and disposal facilities have been identified that can or will accept the Weldon
Spring site mixed waste. State and Federal ARARs that regulate the storage and management
of these wastes are discussed below.
The facilities that manage or store RCRA wastes, or were designed to meet RCRA
standards, will be closed in accordance with the substantive RCRA requirements (40 CFR 264,
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Subpart G). The RCRA requirements are applicable to the following facilities as they are used
to treat, store, or dispose of RCRA wastes or were designed in accordance with RCRA
requirements and were constructed after 1980: the chemical plant and quarry water treatment
plant equalization basins; the temporary storage area; Building 434; and the chemical
stabilization/solidification facility.
The Land Disposal Restrictions (LDRs) specified under RCRA prohibit the storage of
restricted wastes (40 CFR 268 Subpart E) unless storage is solely for the purpose of
accumulating sufficient quantities of wastes to facilitate proper treatment, recovery, or disposal.
The EPA has issued two guidance documents that address the application of the LDR storage
prohibitions to cleanup actions:
• Overview of the RCRA LDRs, Office of Solid Waste and Emergency Response
(OSWER) Directive 9347.3-0IPS, July 1989.
• Guide to Management of Investigation-Derived Wastes, OSWER Publication
9345.3-03FS, April 1992.
Both documents recognize that LDR wastes may be generated during cleanup actions and
stored pending selection and implementation of the final remedy, and state that such storage is
allowable under the LDR storage prohibition. Therefore, the limitations on storage time are
waived under the provisions of Section 121(d)(4)(C) of CERCLA: compliance with such
requirements is technically impracticable from an engineering perspective.
Management of the quarry bulk wastes to be stored at the TSA is required to meet the
NESHAP requirements for asbestos (40 CFR 61, Subpart M) as defined in the Record of
Decision (ROD) for that action. During bulk waste removal, it is planned to place large
asbestos-containing material (ACM) pieces (larger than 0.6 m x 0.6 m x 0.05 m [2 ft x 2 ft x
2 in.]) in appropriate bags and to place the bags in wind-tight, leak-tight metal boxes which will
be transported to the asbestos storage area. Small pieces of asbestos, however, will be handled
with the fine-grained soils. These small pieces that cannot practically be removed will be placed
with the fine-grained soils at the TSA. This pile will be covered or sprayed with a foam to
provide a wind-tight seal.
The smaller pieces that cannot be removed safely will not be segregated from the soil.
Segregation is not technically feasible and could potentially increase exposure to personnel.
Therefore, under this action, as this material is removed from the TSA, the NESHAP
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requirements are waived under the provisions of Section 121(d)(4)(B) of CERCLA: compliance
with the requirement will result in greater risk to human health and the environment than the
action that is proposed.
In accordance with the Missouri State Code of Regulations 10 CSR 25.5-262(2)(C)l,
hazardous wastes stored prior to off-site shipment shall be in compliance with the packaging,
marking, and labeling requirements of the Department of Transportation (DOT) regulations
delineated in 49 CFR during the entire on-site storage period. The wastes stored on site are
packaged, labeled, and marked in accordance with the regulations effective at the time of
containerization. Recently promulgated and future changes to the DOT regulations could greatly
impact the operation of the on-site storage area by requiring a large quantity of containers to be
repackaged (relabeling and remarking are administrative requirements). Continuing the efforts
to maintain compliance with the transportation requirements for storage is not merited, primarily
because these materials are not expected to be transported off site in the near term. Also,
repackaging the waste in accordance with new DOT requirements (HM-181) could result in
unnecessary personnel exposure. Prior to off-site shipment, the wastes will be re-packaged in
accordance with applicable DOT requirements; therefore, the regulation 10 CSR 25.5-262(2)(C)l
is waived under provisions of Section 121(d)(4)(A) and Section 121(d)(4)(B) of CERCLA: the
alternative is an interim measure and will become part of a total remedial action that will attain
the applicable or relevant and appropriate Federal or State requirement and compliance with the
requirement will result in greater risk to human health and the environment than the action that
is proposed.
Regulation 40 CFR 761.65(a) requires that any PCB article or container be removed from
storage and disposed of within one year from the date when it was first placed in storage.
Under this action, PCB wastes will be stored in an adequate PCB .storage facility (meeting the
requirements of 40 CFR 761.65[b]) until final disposition of the PCB wastes can be
accomplished. This requirement is waived under provisions of Section 121(d)(4)(A) of the
CERCLA: this component is an interim measure and will become a part of a total remedial
action that will attain the applicable or relevant and appropriate Federal or State requirement.
This requirement could also be waived on the basis of impracticability since the PCB-
contaminated waste is also radioactively contaminated and a disposal facility is not currently
available for this type of waste.
10.2.3.2 Excavation. Excavation of contaminated areas will include removal of the
contaminated sludge, soil, sediment, and vegetation from the chemical plant area and vicinity
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properties, and removal of the quarry bulk wastes and structural materials from the TSA at the
chemical plant area.
Although most of the raffinate pit sludge does not exhibit RCRA characteristics, certain
isolated pockets of the raffinate pit sludge have failed the TCLP test. Since it does not appear
to be feasible to excavate the sludge in a manner that would separate the RCRA pockets from
the non-RCRA material, the raffinate pit sludge will be managed as a characteristic waste for
treatment purposes. After the raffinate pit sludge is removed, the clay bottom and soils beneath
will be excavated to the soil cleanup criteria defined in Section 9.2. If the clay bottom and soils
are determined to be characteristic hazardous waste, they will be treated in the CSS treatment
plant. Other soil, sediments, past dump and spill areas are not considered RCRA wastes. These
areas will be excavated to the extent of contamination, verified "clean" based upon the cleanup
criteria and backfilled with uncontaminated soils.
The LDRs (40 CFR 268 Subpart C) place specific restrictions (e.g., treatment of waste
to concentration levels) on characteristic RCRA hazardous waste prior to its placement in land
disposal units. Certain activities carried out under the remedial action may constitute placement;
for example, placing sludge or sediment into a sedimentation tank and then redepositing the
material back into the source area, or the movement of waste from one on-site area to another
prior to treatment. These wastes will eventually be treated to the applicable specified treatment
standards prior to placement in the disposal cell. Therefore, the LDRs are waived for these
actions under the provisions of Section 121(d)(4)(A) of CERCLA; i.e., the alternative is an
interim measure and will become part of a total remedial action that will attain the applicable
or relevant Federal or State requirement.
10.2.3.3 Treatment. For the selected remedy, the hazardous waste treatment
requirements specified in 40 CFR 264 and 10 CSR 25-7.264 are applicable. These include
general facility standards, preparedness and prevention standards, and standards for closure upon
completion of the remedial action. All treated material must pass the toxicity characteristic
leachate procedure (TCLP) test which will ensure adequate treatment. In addition, 40 CFR 264,
Subpart X requirements for miscellaneous units are also applicable.
The LDRs (40 CFR 268 Subpart D) specify treatment standards which must be attained
before LDR wastes or treatment residuals may be land disposed. LDR wastes fall into one of
two categories; those wastes subject to concentration-based treatment standards (described in
40 CFR 268.43), and those wastes subject to specific technology treatment standards (described
in 40 CFR 268.42). Compliance with a concentration-based treatment standard requires only
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that the treatment level be achieved. Once achieved, the waste may be land disposed. Most of
the LDR wastes generated and stored at the Weldon Spring Site Remedial Action Project
(WSSRAP) are subject to concentration-based treatment standards. These standards will be
attained prior to land disposal.
The second type of treatment standard is based on the use of a specified technology. In
these circumstances, a specific technology is required for the wastes, and as long as the wastes
are treated .by this technology, the treatment residuals are assumed to meet the treatment
standards. Technologies other than those specified may be used to treat wastes subject to this
type of treatment standard; however, it must be demonstrated to the appropriate regulatory
agency that the alternative treatment method can achieve a measure of performance equivalent
to that achievable by the specified technology. A limited amount of LDR wastes at the
WSSRAP is subject to specified technology treatment standards. Given the limited national
capacity for managing mixed waste, the specified technology may not be available.
A comprehensive site treatment plan as required by the Federal Facilities Compliance Act
(FFCA), will be developed and implemented to evaluate and verify specified and alternative
treatment technologies for the WSSRAP waste types. The plan will be consistent with the
overall remedial action as controlled by the CERCLA process.
If it is determined that the specified technology treatment is not available for the LDR
waste, the alternative treatment method would be implemented. In this case, the LDR treatment
standard is waived under the provisions of CERCLA 121(d) (4) (D); however, the alternative
must attain a standard of performance equivalent to that required under the specified technology
treatment standard. The effectiveness of the alternative technologies will be demonstrated by
TCLP assurance testing prior to disposal. WSSRAP waste types and specified and alternative
treatment technologies as described in the LDR standards are listed below:
1. TYPE OF WASTE: DOOl-High Total Organic Carbon (TOC) Non-wastewater
SPECIFIED TECHNOLOGY: Incineration, fuel substitution, or recovery
ALTERNATIVE TECHNOLOGY: Oxidation
2. TYPE OF WASTE: California List-Liquid hazardous wastes containing greater than
or equal to 50 ppm PCBs
SPECIFIED TECHNOLOGY: Incineration in accordance with 40 CFR 761.70 or
burning in a high efficiency boiler in accordance with 40 CFR 761.60
ALTERNATIVE TECHNOLOGY: Oxidation followed by stabilization
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3. TYPE OF WASTE: D008-Lead Batteries
SPECIFIED TECHNOLOGY: Thermal recovery in a lead smelter
ALTERNATIVE TECHNOLOGY: Stabilization
4. TYPE OF WASTE: D008-Radioactive Lead Solids
SPECIFIED TECHNOLOGY: Macroencapsulation
ALTERNATIVE TECHNOLOGY: Stabilization
5. TYPE OF WASTE: D009-Elemental Mercury Contaminated with Radioactive
Materials
SPECIFIED TECHNOLOGY: Amalgamation
ALTERNATIVE TECHNOLOGY: Amalgamation followed by stabilization
The Best Demonstrated Available Technology (BDAT) for D008-non-wastewater wastes
that are subject to a concentration-based treatment standard is stabilization.
Compliance with ARARs for the contingency (vitrification) remedy would be similar to
that identified above, except that additional emission regulations requirements would be relevant
and appropriate to the off gas from the vitrification facility. These requirements include
Missouri air pollution control regulations for maximum allowable emissions of paniculate matter
from fuel-burning equipment used for indirect heating, restrictions for emissions of visible air
contaminants, and restriction for emissions of paniculate matter from industrial processes. State
ambient air quality standards are also considered relevant and appropriate for Alternative 7a,
insofar as the vitrification process would have a potential to emit pollutants above the de
minimus emission levels specified in these regulations. Emission requirements for hazardous
waste incineration under RCRA, as well as emission requirements for burning hazardous waste
in boilers or industrial furnaces, are also relevant and appropriate for treatment of characteristic
waste, because vitrification is considered similar to an industrial furnace (melting furnace). The
substantive requirements will be met with emissions from the vitrification unit; however, actual
permits are not required since this is an on-site CERCLA action.
10.2.3.4 Disposal. The primary environmental regulations that pertain to the design and
operation of a newly constructed disposal facility are the Solid Waste Disposal Act, the RCRA,
the TSCA, the Missouri hazardous and solid waste management laws, and the UMTRA. None
of these regulations are applicable to the combination of wastes to be disposed of; however,
aspects from each may be relevant and appropriate to activities included in the design,
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TABLE 10-1 Disposal Facility Design ARARs
Location
Buffer Zone
Cover
Liners
Solid Waste
Disposal Act
(SWDAI
(dl
40 CFR 241.209-1
Resource Conservation
and Recovery Act
(RCRA)
40 CFR 264.18(a)
|a|
40 CFR 264.18(b)
Ib)
40 CFR 264.310(a)
la)
40 CFR 264.301(c)(1)
Toxic Substances
Control Act
(TSCA)
(a)
40 CFR 761.75(b)(2)
Missouri Code of State
Regulations
Hazardous Waste
Ib)
10 CSR 25-
7.264(2)(N)1.A(III)(8)
Ic)
10 CSR 25-
7.264(2)(N)1.A(IV)(b)
(c)
10 CSR 25-
7.264(2)(N)1.A(IV)(c)
(a)
10 CSR 25-
7.264(2)(N)1.A(IV)(e)
10 CSR 25-7.264(2)(N)2.D
Id
10CSR25-7.264(2)(N)2.A
Missouri Code of State
Regulations
Solid Wast*
la)
10CSR80-3.010(5)(C)(2)
Id)
10 CSR 80-3.010(1 3)(A)
Id)
10CSR80-3.010(13)(B)
(el
10 CSR 80-
3.010(7)(B)1.(G)
Uranium Mill Tailings
Radiation Control
Act
(UMTRCA)
(a)
40 CFR
192.32(b)( )(n)
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TABLE 10-1 Disposal Facility Design ARARs (Continued)
Leachate
Collection
Systems
Groundwater
Monitoring
Post-Closure
Monitoring and
Maintenance
Solid Waste
Disposal Act
ISWDA)
40 CFR 241.204-
3
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construction, and operation of the disposal facility. Table 10-1 shows the various requirements
from each of these regulations and establishes whether it is relevant or appropriate and the
rationale for the determination. Many requirements within the various regulations are similar
or redundant and, in such an instance, the requirement that is considered more stringent is
designated.
Although RCRA hazardous wastes regulations would be applicable to the excavation and
treatment of hazardous wastes, the successful treatment to below RCRA characteristic levels
would relieve these same wastes from any further jurisdiction as hazardous. While the RCRA
requirements are not considered to be applicable to disposal operations, many are considered to
be relevant and appropriate based primarily on the purpose of the requirements and the nature
of the actions. The disposal facility shall comply with the substantive requirements of the TSCA
with the exception of 40 CFR 761.75(b)(3). This requirement states the bottom landfill liner
system or natural in-place soil barrier shall be at least 50 ft (17 m) from the historical high-water
table. The volumes of TSCA wastes are expected to be limited, and any wastes containing
greater than 50 ppm of PCBs will either be managed separately or the above requirement will
be waived to allow disposal in the cell. This waiver is justified under the provisions of
CERCLA 121(d)(4)(D), which states that the alternative will attain a standard of performance
that is equivalent to that required under the otherwise applicable standard, requirement, or
limitation through use of another method or approach. Consequently, the RCRA requirements
and the UMTRA requirements, which regulate the disposal of low-level radioactive wastes, are
the primary ARARs for cell construction and operation activities.
For purposes of analysis, the disposal requirements of these laws and their corresponding
regulations can be grouped into the following categories: buffer-zone requirements, siting
requirements, cover requirements, liner/leachate collection system requirements, and monitoring
requirements.
As there are no buffer-zone requirements in the Federal regulations, the State of Missouri
solid waste and hazardous waste regulations were reviewed for applicability or relevance and
appropriateness to the on-site disposal facility. The Missouri solid waste regulation for a buffer
zone (10 CSR 80-3.010[5][C][2]) requires a buffer zone of 15 m (50 ft) between the disposal
facility and the property boundary. Given the nature of the site wastes, the need for monitoring
and maintenance, and the impact on the integrity of the disposal facility, the Missouri solid
waste requirement of a 15 m (50 ft) buffer zone is considered relevant and appropriate.
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The Missouri hazardous waste regulation (10 CSR 25-7.264[2][N]2.D) specifies a 91 m
(300 ft) buffer zone between the disposal facility and the property boundary. The Missouri
Hazardous Waste requirement of a 91 m (300 ft) buffer zone is not applicable but is relevant and
appropriate.
The intent of the buffer zone, in addition to ensuring that the public will not come in
contact with the facility or its contents, is to allow adequate easement for operations,
maintenance, and monitoring. Assuming a typical side slope of 3:1 for the covering of the waste
cell, the buffer zone between the toe of the 3:1 dike (the area where the side slope meets the
ground) and the property boundary will be at least 91 m (300 ft). However, for greater long-
term integrity of the facility and enhancement of cell stability, additional clean-fill-dike material
will be utilized at a flatter 5:1 slope. This extra clean-fill dike will not impinge on any
operations, maintenance or monitoring of the disposal facility, and will provide better protection
to the public.
In addition, in an effort to provide an additional safeguard, the DOE will attempt to
acquire a small parcel of adjacent land from the Missouri Department of Conservation to extend
the buffer zone to the degree practicable.
Siting. Siting criteria are discussed in the analysis of location-specific ARARs.
Cover. Requirements are specified in the various laws for disposal facility covers. As
discussed above, the optimal cover, on the basis of the wastes to be disposed of, is a hybrid
cover that consists of the major features of a RCRA cover plus the features of an UMTRA cover
aimed at long-term control of radon. The UMTRA standard in 40 CFR 192.32(b)(l) refers to
the RCRA closure standard in 40 CFR 264.111 for nonradiological hazards. The UMTRA
requirements in 40 CFR Part 192, Subpart D (which limit releases of Rn-222 so as not to exceed
20 pCi/m2s and which specify that the cover be effective for 1,000 years to the extent reasonably
achievable, and in any case, for at least 200 years), are applicable because these requirements
address by-product wastes as defined in the regulations. The RCRA design requirements in
40 CFR 264.310(a) are relevant and appropriate because they address similar actions.
Liner/Leachate Collection System. Design standards for liners and leachate collection
systems are specified in the Missouri Code of State Regulations, the TSCA, and the RCRA;
there are none in the UMTRA. Missouri solid waste regulations require at least 0.6 m (2 ft) of
compacted soil with a hydraulic conductivity no greater than 10"6 cm/s. Both the Missouri
hazardous waste regulations and the RCRA specify a double-liner, double-leachate collection
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system for hazardous waste landfills. The TSCA requirements, which are broader and take into
consideration the nature of the wastes and protectiveness of the overburden materials, require
a liner consisting of 0.9 m (3 ft) of compacted soil with a permeability equal to or less than
1 x 10~7 cm/s, or a synthetic membrane liner. The TSCA also provides for three different
leachate collection systems: (1) simple leachate collection, (2) compound leachate collection,
and (3) suction lysimeters.
Each of these three laws contains elements that should be considered relevant and.
appropriate; consequently, a hybrid system was selected on the basis of the following
considerations: (1) all wastes to be disposed of are solid, nonhazardous wastes that are expected
to generate only minimal leachate; (2) the site is underlain by thick, unsaturated, low-
permeability soils; and (3) it is prudent in the short term to remove precipitation, construction
water, and transient drainage using a leachate collection system.
On the basis of the above, the hybrid system would consist of a single leachate collection
system underlain by a composite liner. There are, however, other circumstances which affect
the preferred design of the hybrid system by adding a secondary redundant liner and leachate
collection system. These circumstances include site-specific considerations such as the presence
of pre-existing groundwater contamination in the area. Although a single leachate collection and
removal system could be designed to remove leachate and prevent migration through the liner,
there is no way to ensure that 100% of the leachate will be collected. Considering that the
redundant leachate collection and removal system can also serve as a leak detection system, this
second system is desirable, since it could establish whether or not elevated contaminant levels
in the groundwater can be attributed to cell failure.
Other considerations include the fact that RCRA wastes are present at the site. It is
planned that all RCRA characteristic wastes will be treated to below RCRA standards, and listed
wastes would be managed off site. However, utilizing a cell design which is consistent with
RCRA (double liner/leachate collection and removal system) may provide flexibility for the
potential situation where RCRA wastes would be placed in the cell. (If this were to happen, an
Explanation of Significant Difference would be prepared in accordance with EPA guidance for
post-ROD changes.)
For these reasons, the RCRA requirements for a double liner/leachate collection system
are considered relevant and appropriate.
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A response action plan will be developed during the remedial design phase, which will
specify response actions that will occur if excessive quantities of leachate are observed (i.e.,
during monitoring/maintenance or repair of the cap). Active management of the leachate
collection system will continue until such time as it is agreed by the DOE and the regulatory
agencies that it is no longer required.
Borrow source area activities will consist of the excavation and transfer along a dedicated
.haul road of approximately 1.9 million m3 (2.5 million yd3) of clay material, which will be used
for the construction of the disposal cell. Certain action-specific ARARs apply to these borrow
source area activities. These ARARs contain administrative requirements that are applicable to
the borrow area activity. Off-site actions must comply with all legally applicable requirements,
both substantive and administrative.
The Land Reclamation Act (10 CSR 40-10.010) require obtaining a Land Reclamation
Permit from the Land Reclamation Commission prior to surface mining of industrial minerals,
including clay. However, a permit is not required of a governmental agency whose operations
comply with the reclamation standards in RSMo. 444.774 and who registers with the Land
Reclamation Commission prior to operations. The borrow area action will comply with the
reclamation standards and will register with the commission.
The Clean Water Act requires a NPDES Permit for storm water discharges associated
with industrial activities from construction sites involving the excavation or grading of five or
more acres. This requirement is considered applicable to the borrow area because the extent of
excavation at the borrow area is estimated at approximately 95 acres. Included as part of the
permit process is a Water Pollution Prevention Plan, which will be prepared for the borrow area
and which will include preventative measures for erosion control.
Monitoring and Maintenance. Requirements for post-closure monitoring and
maintenance are specified in the RCRA and the UMTRA. The TSCA does not define specific
post-closure requirements for a chemical waste landfill. Requirements under the RCRA specify
a 30-year post-closure care period for maintenance of the cover, the leachate collection system,
and the groundwater monitoring system. Ground water monitoring requirements are set forth in
the RCRA and the Missouri Code of State Regulations. The RCRA groundwater protection
standard (40 CFR 264 Subpart F) sets forth general monitoring requirements. A groundwater
monitoring program should provide representative samples of background water quality, as well
as the quality of the groundwater passing the point of compliance. The sampling should allow
for the detection of contaminant migration into the uppermost aquifer. State regulation
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10 CSR 25-7.264(2)(f) sets forth surface water monitoring requirements to detect impacts from
groundwater contamination. A sampling plan should provide representative background surface
water quality (upgradient) samples as well as representative downgradient surface water quality
samples. The initial values should be established for biological activity, chemical indicator
parameters, and hazardous constituents by conducting quarterly sampling for one year. The
surface water quality should be determined at least semiannually, and at those times when
contaminant migration is greatest from the shallow groundwater to surface water. This
monitoring should be conducted through the post-closure care period.
Post-closure standards under the UMTRA require the control of radiological hazards to
(1) be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at
least 200 years; and (2) limit releases of Rn-222 so as not to exceed an average release rate of
20 pCi/m2s.
These UMTRA standards are relevant and appropriate because they address similar waste
materials and a disposal scenario similar to the WSSRAP. The UMTRA requirements also
directly reference the RCRA requirements of 40 CFR 264.111 with respect to the closure
performance standard for nonradiological hazards. Therefore, 40 CFR 264. Ill and 264.310 are
also relevant and appropriate. Since the hazardous waste monitoring/maintenance requirements
are more stringent than the solid waste requirements, the latter are not considered as ARARs.
Other Disposal Requirements. Other waste disposal issues include the restriction on
the placement of waste containing free liquids in a landfill and a recommended minimum
unconfmed strength (UCS) for grout-like stabilized wastes. As required by 40 CFR 264.314
placement of wastes containing free liquids as defined by EPA Method 9095 (paint filter test)
is restricted. Also, for grout-like materials resulting from the stabilization/solidification of
wastes, a minimum UGS of 50 psi in place is recommended by EPA (EPA 1986 .and EPA
1992b).
The free liquids restriction is not considered relevant with respect to CSS grout. Based
on CSS testing of WSSRAP wastes, the free liquids restriction would likely prevent meeting
waste placement objectives related to the proposed remedial action under Alternative 6a.
Although the CSS grout resulting from the stabilization of. raffmate sludge or contaminated soils
may fail the paint filter test as a result of maintaining the needed fluidity for effective placement,
long term benefits with respect to performance of the disposal facility would be realized.
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First, the grout resulting from the treatment of raffinate sludge or more highly
contaminated soils will be used to fill voids in the materials from the dismantlement of buildings
and foundations. With hardening of the grout to a minimum UCS of 50 psi, the stability of
placed waste will be increased and long-term subsidence of the cell cover will be minimized.
Second, by filling voids of dismantlement debris with a treated waste, the overall size of the cell
is reduced by making use of the void space.
To compensate for free liquids in the grout that allows the grout to flow into voids of
dismantlement debris, grout placement techniques can be developed and specified so that free
liquids are effectively removed by the leachate collection system. Grout placement techniques
could include thin enough lifts of grouted debris which will promote drainage of liquids and
temporary sumps for collection and removal of liquids from the cell. Such measures could be
demonstrated so that the requirements of 40 CFR 264.314(f) are achieved.
The restriction of free liquids from materials placed in the disposal cell, as specified in
40 CFR 264.314(f), is therefore waived only with respect to grout used in filling voids of
dismantlement debris. It will be determined during pilot-scale testing that any free liquids
generated during solidification process will pass TCLP. The free liquids will be randomly tested
during full scale operations to ensure that they pass TCLP. Also, all grout-like material will
achieve a minimum UCS of 50 psi in place at 28 days as documented through bench and pilot
scale testing. Placement methods (e.g., compaction) that minimize long-term subsidence of the
cell cover will be used for non-grout materials.
10.3 Cost-Effectiveness
The selected remedy is estimated to cost about $157 million and is estimated to require
about 10 years to complete. These figures, however, are based on preliminary conceptual design
estimates and are likely to increase as engineering design is completed. The contingency
treatment option is estimated to cost about $182 million and would also require about 10 years
to complete. However, because the treatment technology employed in the contingency treatment
option (vitrification) is an innovative technology, these estimates have greater uncertainty than
those for the selected remedy; implementation of the contingency remedy is dependent upon the
results of ongoing testing. The selected remedy is cost effective because it would achieve
required objectives for the least cost and would use an established treatment technology. Thus,
the potential for schedule delays and the resultant increased costs would be less for this remedy
than for the other alternatives. The contingency treatment option would also be cost effective,
assuming that results of ongoing and future bench-scale and pilot-scale testing demonstrate that
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this option could be implemented at a cost and in a period of time comparable to that identified
for the selected remedy. The increased cost of the vitrification technology would be somewhat
offset by the increase in long-term protectiveness gained by the reduction in contaminant toxicity
and volume.
Both the selected remedy and the contingency remedy would support comprehensive
remediation of the Weldon Spring site by removal of the sources of contamination at the site and
providing for disposal of all contaminated material generated from remediation of the site.
10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the
Maximum Extent Practicable
The selected remedy represents the maximum extent to which the permanent solutions
and treatment technologies can be utilized in a cost-effective manner. The selected remedy will
result in the permanent removal of contaminated sludge, soil, sediment, and vegetation from the
source areas and treatment of the material posing the principal threats to the maximum extent
practicable. Of those alternatives that are protective of human health and the environment and
that comply with ARARs, the selected remedy provides the best balance among the alternatives
in terms of long-term effectiveness and permanence; reduction in toxicity, mobility, or volume
through treatment; short-term effectiveness; implementability; and cost. The selected remedy
also meets the statutory preference for treatment as a principal element, and meets State and
community acceptance.
The selected remedy will significantly reduce the hazards posed by the contaminated
media through stabilization/solidification of contaminants such that the treated product will
significantly reduce contaminant mobility. The treated and untreated material will both be
placed in an engineered disposal facility designed to contain the materials over the long term.
Because the more highly contaminated material will be treated to reduce contaminant mobility,
the impact on human health and the environment would be minimal if the containment system
were to fail.
The contingency treatment option would also provide for significant reductions in risk.
Vitrification would be expected to provide somewhat greater long-term effectiveness because
organic contaminants and some inorganic contaminants would be destroyed, and the contaminants
in the treated waste form would be more thoroughly immobilized. However, larger uncertainties
are associated with the implementability of vitrification compared with chemical stabilization/
solidification, and thus could lead to project delays and increased costs. Vitrification is being
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carried forward as a contingency treatment option so the effectiveness of this technology can
continue to be evaluated in terms of current uncertainties associated with its implementability.
The selected remedy treats the material posing the principal threats at the site, achieving
significant reduction in contaminant mobility. Chemical stabilization/solidification and disposal
on site is more effective in the short term, requiring up to five years to implement the treatment
operations and 10 years to complete remedial action at the site. In comparison, vitrification will
require about seven years for implementation, provided engineering scale-up and design are not
delayed because of the innovative nature of this technology. The off-site disposal alternatives
could require significantly more time to implement due to the increased administrative
requirements for transport and disposal of the wastes at the off-site facilities.
The off-site disposal alternatives do not offer an increase in effectiveness over the on-site
disposal alternatives that can justify the greatly increased costs (two to 10 times the cost of the
selected remedy). The long-term effectiveness of the off-site alternatives would be somewhat
greater at the Weldon Spring site due to the removal of contaminated material from the site, and
potential long-term impacts at the off-site locations would be less than those expected at the
Weldon Spring site for on-site disposal, because of the arid climate and distance to potential
receptors. However, short-term impacts would be greater due to the increased handling of
contaminated materials and the transportation of those materials to the off-site locations. In
addition, implementation of these alternatives would require coordination of licensing,
permitting, regulatory compliance, and establishment of administrative procedures (as
appropriate) in order to dispose of the Weldon Spring waste at either off-site facility.
The major balancing criteria that provide the basis for selection of the preferred
alternative are short-term effectiveness, implementability, and cost. The selected remedy can
be implemented more quickly, with less difficulty, and at less cost than the other alternatives and
is therefore determined to be the most appropriate method. The contingency treatment option
is being retained to facilitate implementation of an alternate treatment technology in the event
that chemical stabilization/solidification does not perform adequately. Both technology types will
be reevaluated against the balancing criteria during conceptual design and bench-scale and pilot-
scale testing. If the contingency treatment option (vitrification and disposal on site) were
selected pursuant to this continuing evaluation, an Explanation of Significant Differences from
the selected remedy would be made available to the public, and public input would be soli cited.
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10.5 Preference for Treatment as a Principal Element
The selected remedy satisfies the preference for treatment as a principal element by
treating the materials giving rise to the principal hazards at the site (the raffmate-pit sludge and
the more highly contaminated fraction of soil, sand, and sediment) by chemical stabilization/
solidification. This treatment method will significantly reduce contaminant mobility. The
contingency remedy would also satisfy the preference for treatment as a principal element by
treating these same materials by vitrification. Vitrification would also significantly reduce
contaminant mobility. In addition, vitrification would reduce contaminant toxicity by destruction
of organic contaminants and some inorganic contaminants, and waste volume would be reduced
through the elimination of water and void spaces during the melting process.
10.6 Irreversible and Irretrievable Commitment of Resources
Implementing the selected remedy will result in the permanent commitment of land at the
Weldon Spring site for waste disposal. This commitment of land for the disposal facility is
consistent with current land use at the site. The Weldon Spring site is a contaminated, inactive
industrial complex under the custody of the DOE, and it contains waste pits from past disposal
practices; it is adjacent to a similar contaminated site owned by the Army.
The disposal cell proper is expected to cover about 17 ha (42 acres), but the total amount
of committed land would be larger (e.g., double the waste containment area) because a buffer
zone will be established around the cell. No other area of the Weldon Spring site would sustain
a long-term impact or injury as a result of this permanent remedy. Perpetual care will be taken
of the committed land because the waste would retain its toxicity for thousands of years. For
example, the cover will be visually inspected, groundwater will be monitored, and the
effectiveness of the overall system at the Weldon Spring site will be reviewed at least every
five years.
Consumptive use of geological resources (e.g., quarried rock, sand, and-gravel) and
petroleum products (e.g., diesel fuel and gasoline) will be required for the removal,
construction, and disposal activities. Adequate supplies of these materials are readily available
in the Weldon Spring area. The treatment process will also require the consumptive use of
materials (including cement and fly ash) and energy. Cement and fly ash are readily available
locally in the quantities required, and natural gas can be obtained from the local utility.
Implementing the selected remedy is not constrained by the availability of resources or supplies
beyond those currently available in the St. Louis area.
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10.7 Significant Changes
The Proposed Plan for the Weldon Spring site was released for public comment in
November 1992. The Proposed Plan identified Alternative 6a, Removal, Chemical Stabilization/
Solidification and Disposal On Site, as the preferred alternative. The DOE reviewed all written
and verbal comments submitted during the public comment period. Upon review of these
comments, it was determined that no significant changes to the remedy, as it was originally
identified in the Proposed Plan, were necessary.
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11 REFERENCES
Agency for Toxic Substances and Disease Registry, 1989a. Toxicological Profile for Cadmium.
ATSDR/TP-88/08. Prepared by Life Systems, Inc. March.
Agency for Toxic Substances and Disease Registry, 1989b. Toxicological Profile for 2,4-
Dinitrotoluene, 2,6-Dinitrotoluene. ATSDR/TP-89/13. Prepared by Clement Associates.
December.
Agency for Toxic Substances and Disease Registry, 1989c. Toxicological Profile for Selected
PCBs (Aroclor-1260, -1254, -1248, -1242, -1232, -1221, and -1016). ATSDR/TP-
888/21. Prepared by Syracuse Research Corporation. June.
American Cancer Society, 1992. Cancer Facts & Figures — 1992. Atlanta, GA.
ATSDR, see Agency for Toxic Substances and Disease Registry.
DOE, see U.S. Department of Energy.
EPA, see U.S. Environmental Protection Agency.
Missouri Department of Health, 1992. Any-Use Soil Levels for Residential Settings; Proposed
Rule (19CSR 20-9.020). Missouri Register, 17(17): 1299-1304. September 1.
MK-Ferguson Company and Jacobs Engineering Group, 1991. Site Suitability Data on Potential
Location of a Disposal Facility: Collapse Potential and Permeability, Rev. 2.
DQE/OR/21548-102. Prepared for the U.S. Department of Energy, Oak Ridge
Operations Office, Weldon Spring Site Remedial Action Project. St. Charles, MO.
September.
MK-Ferguson Company and Jacobs Engineering Group, 1992. Engineering Analysis of
Remedial Action Alternatives, Phase 7, Rev. 0. DOE/OR/21548-269. Prepared for the
U.S. Department of Energy, Oak Ridge Operations Office, Weldon Spring Site Remedial
Action Project. St. Charles, MO. November.
U.S. Department of Energy, 1992a. Proposed Plan for Remedial Action at the Chemical Plant
Area of the Weldon Spring Site. DOE/OR/21548-160. November.
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U.S. Department of Energy, I992b. Remedial Investigation for the Chemical Plant Area of the
Weldon Spring Site, Rev. 0. DOE/OR/21548-074. Prepared by MK-Ferguson Company
and Jacobs Engineering Group for U.S. Department of Energy, Oak Ridge Field Office,
Weldon Spring Site Remedial Action Project. St. Charles, MO. November.
U.S. Department of Energy, 1992c. Baseline Assessment for the Chemical Plant Area of the
Weldon Spring Site, Rev. 0. DOE/OR/21548-091. Prepared for the U.S. Department
of Energy, Oak Ridge Operations Office, Weldon Spring Site Remedial Action Project,
by Environmental Assessment and Information Sciences Division, Argonne National
Laboratory. November.
U.S. Department of Energy, 1992d. Feasibility Study for Remedial Action at the Chemical
Plant Area of the Weldon Spring Sire, Rev. 0. DOE/OR/21548-148. Prepared by
Environmental Assessment and Information Sciences Division, Argonne National
Laboratory for the U.S. Department of Energy, Oak Ridge Field Office, Weldon Spring
Site Remedial Action Project. St. Charles, MO. November.
U.S. Environmental Protection Agency, 1986. U.S. EPA Guidance for the Prohibition on the
Placement of Bulk Liquid Hazardous Waste in Landfills. OSWER Policy Directive No.
9487.00-2A EPA 530-SW-86-016.
U.S. Environmental Protection Agency, 1989a. Interim Guidance, on Establishing Soil Cleanup
Levels at Superfund Sites. SOWER 9355.4-02. Office of Solid Waste and Emergency
Response, Washington, D.C. September.
U.S. Environmental Protection Agency, 1989b. National Emissions Standards for Hazardous
Air Pollutants; Radionuclides, Final Rule and Notice, of Reconsideration (40 CFR Pan
61). Federal Register, 54(240):51654-51715. December 15.
U.S. Environmental Protection Agency, 1990. National Oil and Hazardous Substances
Pollution Contingency Plan; Final Rule (40 CFR Pan 300). Federal Register,
55(46):8666-8865, March 8.
U.S. Environmental Protection Agency, 199la. Integrated Risk Information System. Office of
Research and Development, database, accessed December.
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U.S. Environmental Protection Agency, 1991b. Health Effects Assessment Summary Tables.
OERR 9200.6-303(91-1). Office of Emergency and Remedial Response, Annual, FY-
1991. January.
U.S. Environmental Protection Agency, 1992a. A Citizen's Guide to Radon, 2nd Ed. Office
of Air and Radiation, Washington, D.C. May.
U.S. Environmental Protection Agency, 1992b. Federal Register November 18, 1992, 40 CFR
Parts 260 et al., Hazardous Waste Management. Liquids in Landfills. Rule.
Federal Regulations
7 CFR 658 USDA SCS Farmland Protection Policy
10 CFR 20 Standards for Protection Against Radiation
29 CFR 1910 OSHA Standards
40 CFR 6 Appendix A EPA Regulations for Implementing EO 11990 (Wetlands) and EO
11988 (Floodplains)
40 CFR 61 EPA NESHAPs National Emissions Radionuclides
40 CFR 190 Environmental Radiation Protection Standards for Nuclear Power Operations
40 CFR 192 UMTRA Standards
40 CFR 241 EPA Solid Waste Guidelines
40 CFR 261 EPA Identification and Listing of Hazardous Waste
40 CFR 264 EPA Standards for o/o of Hazardous Waste. Treatment, Storage, and Disposal
Facilities
40 CFR 268 EPA Land Disposal Restrictions
40 CFR 300 CEQ National Oil and Hazardous Substances Pollution Contingency Plan
40 CFR 761 EPA PCB Regulations
. 40 CFR 763 EPA TSCA Asbestos Regulations
49 CFR 170-177 Department of Transportation Hazardous Transportation Regulations
DOE Orders
5480.11 Radiation Protection for Occupational Workers
5400.5 Radiation Protection of the Public and the Environment
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Federal Executive Order
11988 Floodplain Management
11990 Protection of Wetlands
Missouri State Regulations
10 CSR 10-5.030 Maximum Allowable Emission of Paniculate Matter from Fuel Burning
Equipment Used for Indirect Heating
10 CSR 10-5.050 Restriction of Emission of Paniculate Matter from Industrial Processes
10 CSR 10-5.090 Restriction of Emission of Visible Air Contaminants
10 CSR 10-5.180 Emission of Visible Air Contaminants from Internal Combustion Engine
10 CSR 10-6.010 Ambient Air Quality Standards
10 CSR 10-6.060 Permits Required
10 CSR 10-6.170 Restriction of Paniculate Matter to the Ambient Air Beyond the Premises
of Origin
10 CSR 25-7.264 Missouri Hazardous Waste Treatment, Storage and Disposal Requirements
19 CSR 20-10.040 Missouri Radiation Regulations
Missouri Register, September 1, 1992; Vol. 17, No. 17.
Missouri Register, November 2, 1992; Vol. 17, No. 21.
Other Orders
Missouri Governor's Executive Order 82-19 on Flood Plain Management
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12 ACRONYMS
AEA Atomic Energy Act
AEC U.S. Atomic Energy Commission
ALARA as low as reasonably achievable
ARAR applicable or relevant and appropriate requirements
BA baseline assessment
BOAT best demonstrated available technology
CAA Clean Air Act
CERCLA Comprehensive Environmental Response, Compensation and Liability Act
CSS chemical stabilization/solidification
CWA Clean Water Act
DAC derived air concentration
DCF dose conversion factor
DCG derived concentration guideline
DNB dinitrobenzene
DNT dinitrotoluene
DOE U.S. Department of Energy
EIS Environmental Impact Statement
EPA U.S. Environmental Protection Agency
ERDA Energy Research and Development Adminstration
FS feasibility study
LDR Land Disposal Restrictions
MCL maximum contaminant level
MCLG maximum contaminant level goals
MSA material staging area
NAAQS National Ambient Air Quality Standards
NB nitrobenzene
NCP National Contingency Plan
NEPA National Environmental Policy Act
NESHAP National Emission Standards for Hazardous Air Pollutants
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
NRC Nuclear Regulatory Commission
OSHA Occupational Safety and Health Administration
OSWER Office of Solid Waste and Emergency Response
PAH polycyclicpolynuclear) aromatic hydrocarbons
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PCB polychlorinated biphenyl
PP Proposed Plan
RCRA Resource Conservation Recovery Act
RfD reference dose
RI remedial investigation
RI/FS Remedial Investigation/Feasibility Study
RI/FS-EIS Remedial Investigation/Feasibility Study-Environmental Impact Statement
ROD Record of Decision
SDWA Safe Drinking Water Act
SWDA Solid Waste Disposal Act
TCLP toxicity characteristic leaching procedure
TNB trinitrobenzene
TNT trinitrotoluene
TSA temporary storage area
TSCA Toxic Substance Control Act
UMTRA Uranium Mill Tailings Remedial Action
UMTRCA Uranium Mill Tailings Radiation Control Act of 1978
WLM working-level month
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