2011-12-28 – Supplemental Feasibility Study Radiological-Impacted Material Excavation Alternatives Analysis West Lake Landfill Operable Unit-1

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Supplemental Feasibility Study
Radiological-Impacted Material Excavation Alternatives Analysis West Lake Landfill Operable Unit-1
Prepared for
The United States Environmental Protection Agency Region VII

Prepared on behalf of
The West Lake Landfill OU-1 Respondents

Prepared by
Engineering Management Support, Inc. 7220 West Jefferson Avenue, Suite 406 Lakewood, Colorado 80235

In association with
Feezor Engineering, Inc. 406 E. Walnut Street Chatham, Illinois 62629
and
Auxier & Associates, Inc. 9821 Cogdill Road, Suite 1 Knoxville, Tennessee 37932
September 30, 2011 Revised December 16, 2011 Final December 28, 2011

Table of Contents
1 Introduction …………………………………………………………………………………………………………….. 1

1.1
Scope of the SFS ………………………………………………………………………………. 1

1.2
SFS Approach ………………………………………………………………………………….. 3

1.3
Report Organization …………………………………………………………………………..

2 Site Conditions………………………………………………………………………………………………………… 7

2.1
Site Location and Surrounding Area……………………………………………………. 7

2.1.1
Historic Landfill Operations and Disposal Areas ………………………………….. 8

2.1.2
Superfund Operable Units………………………………………………………………….. 9

2.1.3
Current Site Uses……………………………………………………………………………..

2.1.4
Site Zoning, Use Restrictions, and Easements…………………………………….. 11

2.1.5
Surrounding Land Uses……………………………………………………………………. 12

2.1.6
Missouri River Floodplain ……………………………………………………………….. 12

2.2
Nature and Extent of Radionuclide and Chemical Occurrences in OU-1… 14
2.2.1
Source of the Radionuclides………………………………………………………………

2.2.2
General Locations and Lateral Extent of RIM Occurrences in Areas 1 and 2 ……………………………………………………………………………………………………… 16
2.2.3
Vertical Extent of RIM Occurrences in Areas 1 and 2 …………………………. 17

2.2.4
Estimated Volume of RIM……………………………………………………………….. 17

2.2.5
Radiological Occurrences on the Buffer Zone and Crossroad Property….. 19
2.2.6
Radiological Characterization of the RIM …………………………………………..

2.2.7
Radionuclide Decay and Ingrowth…………………………………………………….. 22

2.2.8
Principal Threat Wastes …………………………………………………………………… 22

2.2.9
Occurrences of Non-Radiological Chemical Constituents in Soil/Waste… 22
2.2.9.1.1 Trace Metal Occurrences in Soil……………………………………………………….. 23

2.2.9.1.2 Total Petroleum Hydrocarbons in Soil……………………………………………….. 23

2.2.9.1.3 Volatile Organic Compounds in Soil …………………………………………………. 23

2.2.9.1.4 Semi-Volatile Organic Compounds in Soil…………………………………………. 24

2.2.9.1.5 Pesticides and Polychlorinated Biphenyls in Soil………………………………… 24

2.2.9.1.6 Potential for Occurrences of Hazardous Wastes…………………………………..

2.2.9.1.7 Asbestos Containing Materials in Soil/Waste……………………………………… 25

2.3
Radionuclide Occurrences in Air………………………………………………………. 26

2.4
Groundwater Conditions ………………………………………………………………….. 26

2.4.1
Geology…………………………………………………………………………………………. 27

2.4.2
Hydrogeology…………………………………………………………………………………. 27

2.4.3
Occurrences of Radionuclides in Groundwater …………………………………… 29

2.4.4
Occurrences of Chemical Constituents in Groundwater………………………..

2.5
Baseline Risk Assessment………………………………………………………………… 31

2.5.1
Human Health Risk Assessment ……………………………………………………….. 31

2.5.2
Ecological Risk Assessment …………………………………………………………….. 33

3 Potential ARARs and Remedial action Objectives………………………………………………………

3.1
Potential Applicable or Relevant and Appropriate Requirements ………….. 35

3.1.1
Potential Chemical-Specific ARARs …………………………………………………. 35

i

Table of Contents (continued)

3.1.1.1
Health and Environmental Protection Standards for Uranium and Thorium Mill Tailings…………………………………………………………………………………… 35
3.1.1.2
Standards for Cleanup of Contaminated Land – 40 CFR 192.12(a)……….. 36

3.1.1.3
Radon Emissions Standards – 40 CFR 192.02(b)………………………………… 38

3.1.1.4
Groundwater Protection Standards – 40 CFR 192 Subparts A and B……… 39

3.1.1.5
Other Potential Chemical-Specific ARARs ………………………………………… 40

3.1.1.6
National Emissions Standards for Hazardous Air Pollutants…………………. 40

3.1.1.7
Missouri Radiation Regulations for Protection Against Ionizing Radiation ……………………………………………………………………………………………………… 40
3.1.1.8
Missouri Maximum Contaminant Levels……………………………………………. 41

3.1.2 Potential Location-Specific ARARs ………………………………………………….. 41

3.1.2.1 Floodplain Management…………………………………………………………………… 42

3.1.2.2 Missouri Solid Waste Management Regulations – Site Selection………….. 43

3.1.2.3 Missouri Solid Waste Regulations – Airport Safety…………………………….. 44

3.1.2.4 Missouri Solid Waste Management Regulations – Floodplains …………….. 45

3.1.2.5 Missouri Solid Waste Management Regulations – Wetlands………………… 45

3.1.2.6 Missouri Solid Waste Management Regulations – Seismic Impact Zones. 45
3.1.2.7 Missouri Solid Waste Management Regulations – Unstable Areas………… 46

3.1.2.8 Missouri Solid Waste Management Regulations – Plans ……………………… 46

3.1.2.9
Missouri Solid Waste Management Regulations – Base of Landfill ………. 47

3.1.2.10
FAA Guidance ……………………………………………………………………………….. 47

3.1.2.11
Airport Negative Easement and Restrictive Covenants………………………… 49

3.1.3 Potential Action-Specific ARARs……………………………………………………… 51

3.1.3.1
Health and Environmental Protection Standards for Uranium and Thorium Mill Tailings…………………………………………………………………………………… 52
3.1.3.2
Missouri Solid Waste Management Regulations …………………………………. 52

3.1.4 RCRA Subtitle C Regulations…………………………………………………………… 54

3.2
Additional Requirements Associated with Off-site Disposal ………………… 55

3.2.1 CERCLA Off-site Rule……………………………………………………………………. 55

3.2.2 Off-site Transportation Requirements………………………………………………… 56

3.2.3 Waste Acceptance Criteria for Off-site Disposal…………………………………. 57

3.2.3.1
U.S. Ecology, Grandview, Idaho ………………………………………………………. 57

3.2.3.2
Clean Harbors, Deer Trail, Colorado …………………………………………………. 58

3.2.3.3
EnergySolutions, Clive Utah…………………………………………………………….. 59

3.2.3.4
Other Off-site Disposal Facilities………………………………………………………. 60

3.3
Remedial Action Objectives …………………………………………………………….. 60

3.4
Cleanup Levels……………………………………………………………………………….. 61

4 Technology Screening ……………………………………………………………………………………………. 66

4.1
Technologies Evaluated in the FS Report…………………………………………… 67

4.2
Additional Technology Evaluations/Revisit Previously Eliminated Technologies ………………………………………………………………………………….. 69
4.3
Descriptions of Additional Technologies……………………………………………. 71

4.3.1 Monitoring……………………………………………………………………………………… 71

ii

Table of Contents (continued)

4.3.1.1 Long-term Performance Monitoring………………………………………………….. 71

4.3.1.2 Short-term Monitoring During Construction ………………………………………. 71

4.3.2 Containment …………………………………………………………………………………… 72

4.3.2.1 Capping and Covers ………………………………………………………………………… 73

4.3.2.2 Land Encapsulation…………………………………………………………………………. 73

4.3.2.2.1 On-Site: New Cell…………………………………………………………………………… 73

4.3.2.2.2 Off-Site Licensed Facility………………………………………………………………… 73

4.3.2.3
Cryogenic Barriers ………………………………………………………………………….. 76

4.3.2.4
Vertical Barriers ……………………………………………………………………………… 77

4.3.2.4.1 Slurry Wall…………………………………………………………………………………….. 77

4.3.2.4.2 Grout Curtain …………………………………………………………………………………. 77

4.3.2.4.3 Sheet Pile Cutoff Wall …………………………………………………………………….. 77

4.3.3 Physical/Chemical Treatment …………………………………………………………… 78

4.3.3.1 Solidification/Stabilization……………………………………………………………….. 78

4.3.3.2 Chemical Separation ……………………………………………………………………….. 79

4.3.3.3 Physical Separation …………………………………………………………………………. 80

4.3.3.3.1 Dry Soil Separation…………………………………………………………………………. 80

4.3.3.3.2 Soil Washing ………………………………………………………………………………….. 82

4.3.3.3.3 Flotation ………………………………………………………………………………………… 82

4.3.3.4
Vitrification……………………………………………………………………………………. 83

4.3.4 Biological Treatment……………………………………………………………………….. 84

4.3.5 Removal ………………………………………………………………………………………… 84

4.3.5.1
Excavation……………………………………………………………………………………… 85

4.3.5.2
Storm Water Management ……………………………………………………………….. 85

4.3.5.3
Bird Nuisance Mitigation…………………………………………………………………. 86

4.3.6 Transportation ………………………………………………………………………………… 87

4.3.6.1
Hauling of Wastes and Construction Materials – On-site, Off-road and Off-site, On-road Trucks………………………………………………………………………… 87
4.3.6.2
Hauling of Waste Material -Rail ………………………………………………………. 88

4.4
Implementability Screening of Remediation Technologies and Process Options ………………………………………………………………………………………….. 89
4.4.1 Dry Soil Separation…………………………………………………………………………. 89

4.4.2 Temporary Structure to Enclose an Excavation…………………………………… 91

4.5
Evaluation of Remediation Technologies and Process Options …………….. 92

5 Remedial Action Alternatives………………………………………………………………………………….. 93

5.1
Remedial Alternatives Evaluated in FS ……………………………………………… 93

5.2
ROD-Selected Remedy ……………………………………………………………………. 94

5.2.1 Engineering Components of the ROD-Selected Remedy ……………………… 97

5.2.1.1
Regrading of the Landfill Surface for the ROD-Selected Remedy…………. 98

5.2.1.2
Removal of Radiologically-Impacted Soil from the Buffer Zone/Crossroad Property……………………………………………………………………………………….. 102
5.2.1.3
Engineered Landfill Cover for the ROD-Selected Remedy…………………. 103

5.2.1.4
Rock Armoring/Flood Protection of the Toe of the Landfill ……………….. 104

iii

Table of Contents (continued)

5.2.1.5 Stormwater Management/Surface Water Runoff Control……………………. 105

5.2.1.6 Landfill Gas Monitoring and Control ………………………………………………. 107

5.2.1.7 Management of Subsurface Liquids During Construction …………………… 108

5.2.1.8 Regulated Materials Management During Construction……………………… 108

5.2.1.9 Long-Term Operations and Maintenance for the ROD-Selected Remedy109
5.2.1.10 Environmental Monitoring for the ROD-Selected Remedy…………………. 110

5.2.2 Non-Engineered Components of the ROD-Selected Remedy ……………… 111

5.2.2.1
Institutional Controls Included in the ROD-Selected Remedy…………….. 111

5.2.2.2
Five Year Reviews ………………………………………………………………………… 112

5.3
Additional “Complete Rad Removal” Remedial Action Alternatives…… 113
5.3.1 RIM Occurrences, Extents and Volumes………………………………………….. 113

5.3.2 RIM Excavation and Associated Activities ………………………………………. 114

5.3.2.1 RIM Excavation Procedure and Sequencing……………………………………… 115

5.3.2.2 Material Handling …………………………………………………………………………. 116

5.3.2.3 Material Stockpiling………………………………………………………………………. 117

5.3.2.4
Radiological Surveys during RIM Excavation ………………………………….. 119

5.3.2.5
Application of Daily Soil Cover ……………………………………………………… 120

5.3.2.6
Removal of Radiologically-Impacted Soil from the Buffer Zone/Crossroad Property……………………………………………………………………………………….. 121
5.3.2.7
Management of Subsurface Liquids During RIM Excavation ……………… 121

5.3.2.8
Regulated Materials Management During RIM Excavation………………… 121

5.3.2.9
Radiological Surveys after RIM Excavation……………………………………… 122

5.3.2.10
Stormwater and Landfill Gas Monitoring and Control……………………….. 122

5.3.2.11
Baseline Monitoring for “Complete Rad Removal” Alternatives…………. 123

5.3.2.12
Long-Term Operations, Maintenance and Monitoring and Non-Engineered Components………………………………………………………………………………….. 123
5.3.3 “Complete Rad Removal” with Off-site Disposal Alternative …………….. 124

5.3.4 “Complete Rad Removal” with On-site Disposal Alternative……………… 128

5.3.4.1 Siting of On-site Cell …………………………………………………………………….. 129

5.3.4.2
General Configuration of On-site Cell……………………………………………… 131

5.3.4.3
Liner Construction – On-site Cell……………………………………………………. 133

5.3.4.4
Filling of On-site Cell with RIM……………………………………………………… 135

5.3.4.5
Cover Construction – On-site Cell…………………………………………………… 136

5.3.4.6
OM&M Components – On-site Disposal in Engineered Cell Alternative 137

5.3.5 Closure Construction -Remaining Solid Waste Areas of Areas 1 and 2.. 138
6 Detailed Analysis of Alternatives …………………………………………………………………………… 139

6.1
Description of Evaluation Criteria …………………………………………………… 140

6.1.1 Overall Protection of Human Health and the Environment …………………. 140

6.1.2 Compliance with ARARs……………………………………………………………….. 140

6.1.3 Long-Term Effectiveness and Permanence ………………………………………. 141

6.1.4 Reduction of Toxicity, Mobility or Volume through Treatment ………….. 142

6.1.5 Short-Term Effectiveness……………………………………………………………….. 143

6.1.6 Implementability …………………………………………………………………………… 144

iv

Table of Contents (continued)

6.1.7 Cost …………………………………………………………………………………………….. 145

6.1.7.1 Capital and Operation, Maintenance, and Monitoring Costs……………….. 146

6.1.7.2 Contingency Costs ………………………………………………………………………… 148

6.1.7.3 Present Worth and Non-discounted Constant Dollar Costs …………………. 151

6.1.8
State Acceptance …………………………………………………………………………… 151

6.1.9
Community Acceptance …………………………………………………………………. 152

Detailed Analysis of Alternatives ……………………………………………………. 152

6.2.1
Regrading and Enhanced Capping (ROD-Selected Remedy)………………. 152

6.2.1.1 Overall Protection of Human Health and the Environment …………………. 154

6.2.1.2 Compliance with ARARs……………………………………………………………….. 155

6.2.1.2.1
Missouri Solid Waste Rules for Sanitary Landfills…………………………….. 155

6.2.1.2.2
Environmental Protection Standards for Uranium and Thorium Mill Tailings………………………………………………………………………………………… 156
6.2.1.2.3
National Emissions Standards for Hazardous Air Pollutants (NESHAPs)158
6.2.1.2.4
Clean Water Act……………………………………………………………………………. 158

6.2.1.2.5
Safe Drinking Water Act………………………………………………………………… 158

6.2.1.2.6
Missouri Radiation Regulations for Protection Against Ionizing Radiation ……………………………………………………………………………………………………. 158
6.2.1.2.7
Missouri Well Construction Code……………………………………………………. 158

6.2.1.2.8
Missouri Storm Water Regulations………………………………………………….. 159

6.2.1.3 Long-Term Effectiveness and Permanence ………………………………………. 159

6.2.1.3.1 Magnitude of Residual Risks ………………………………………………………….. 159

6.2.1.3.2 Adequacy and Reliability of Controls………………………………………………. 160

6.2.1.4 Reduction of Toxicity, Mobility or Volume through Treatment ………….. 161

6.2.1.5 Short-Term Effectiveness……………………………………………………………….. 162

6.2.1.5.1 Protectiveness of the Community During Remedial Actions ………………. 162

6.2.1.5.2 Protectiveness of Workers During Remedial Actions ………………………… 163

6.2.1.5.3 Environmental Impacts ………………………………………………………………….. 163

6.2.1.5.4 Ability to Monitor Effectiveness……………………………………………………… 164

6.2.1.5.5 Time Until Remedial Action Objectives are Achieved……………………….. 164

6.2.1.6 Implementability …………………………………………………………………………… 164

6.2.1.6.1 Ability to Construct and Operate the Technology ……………………………… 165

6.2.1.6.2 Reliability of the Technology………………………………………………………….. 165

6.2.1.6.3 Ease of Undertaking Additional Remedial Actions, if Necessary ………… 166

6.2.1.6.4
Ability to Monitor Effectiveness of Remedy…………………………………….. 167

6.2.1.6.5
Ability to Obtain Approvals from Other Agencies …………………………….. 167

6.2.1.6.6
Coordination with Other Agencies…………………………………………………… 167

6.2.1.6.7
Availability of Off-site Treatment, Storage and Disposal Services and Capacity……………………………………………………………………………………….. 169
6.2.1.6.8
Availability of Necessary Equipment and Specialists ………………………… 169

6.2.1.6.9
Availability of Prospective Technologies …………………………………………. 169

6.2.1.7 Cost …………………………………………………………………………………………….. 169

6.2.2 “Complete Rad Removal” with Off-site Disposal Alternative …………….. 170

6.2.2.1 Overall Protection of Human Health and the Environment …………………. 172

v

Table of Contents (continued)

6.2.2.2 Compliance with ARARs……………………………………………………………….. 173

6.2.2.2.1 CERCLA Off-site Rule………………………………………………………………….. 173

6.2.2.2.2 Off-site Transportation Requirements………………………………………………. 173

6.2.2.2.3 Waste Acceptance Criteria (WAC) for Off-site Disposal……………………. 174

6.2.2.2.4 Missouri Solid Waste Rules for Sanitary Landfills…………………………….. 174

6.2.2.2.5
Clean Water Act……………………………………………………………………………. 175

6.2.2.2.6
Safe Drinking Water Act………………………………………………………………… 175

6.2.2.2.7
Missouri Radiation Regulations for Protection Against Ionizing Radiation ……………………………………………………………………………………………………. 175
6.2.2.2.8
Missouri Well Construction Code……………………………………………………. 175

6.2.2.2.9
Missouri Storm Water Regulations………………………………………………….. 175

6.2.2.3 Long-Term Effectiveness and Permanence ………………………………………. 176

6.2.2.3.1 Magnitude of residual risk ……………………………………………………………… 176

6.2.2.3.2 Adequacy and reliability of controls………………………………………………… 177

6.2.2.4 Reduction of Toxicity, Mobility or Volume through Treatment ………….. 178

6.2.2.5 Short-Term Effectiveness……………………………………………………………….. 180

6.2.2.5.1 Protection of the Community During Remedial Actions…………………….. 180

6.2.2.5.2 Protection of Workers During Remedial Actions ………………………………. 182

6.2.2.5.3 Environmental Impacts ………………………………………………………………….. 183

6.2.2.5.4 Ability to Monitor Effectiveness……………………………………………………… 183

6.2.2.5.5 Time Until Remedial Action Objectives are Achieved……………………….. 184

6.2.2.6 Implementability …………………………………………………………………………… 185

6.2.2.6.1 Ability to Construct and Operate the Technology ……………………………… 186

6.2.2.6.2 Reliability of the Technology………………………………………………………….. 188

6.2.2.6.3 Ease of Undertaking Additional Remedial Actions, if Necessary ………… 189

6.2.2.6.4 Ability to Monitor Effectiveness of Remedy…………………………………….. 190

6.2.2.6.5 Ability to Obtain Approvals from Other Agencies …………………………….. 190

6.2.2.6.6 Coordination with Other Agencies…………………………………………………… 192

6.2.2.6.7 Availability of Off-site Treatment, Storage and Disposal Services and … 194
6.2.2.6.8 Availability of Necessary Equipment and Specialists ………………………… 195

6.2.2.6.9 Availability of Prospective Technologies …………………………………………. 195

6.2.2.7 Cost …………………………………………………………………………………………….. 196

6.2.3 “Complete Rad Removal” with On-site Disposal Alternative……………… 197

6.2.3.1 Overall Protection of Human Health and the Environment …………………. 199

6.2.3.2 Compliance with ARARs……………………………………………………………….. 199

6.2.3.3 Long-Term Effectiveness and Permanence ………………………………………. 200

6.2.3.3.1 Magnitude of residual risk ……………………………………………………………… 200

6.2.3.3.2 Adequacy and reliability of controls………………………………………………… 201

6.2.3.4 Reduction of Toxicity, Mobility or Volume through Treatment ………….. 202

6.2.3.5 Short-Term Effectiveness……………………………………………………………….. 203

6.2.3.5.1 Protection of the Community During Remedial Actions…………………….. 203

6.2.3.5.2 Protection of Workers During Remedial Actions ………………………………. 205

6.2.3.5.3 Environmental Impacts ………………………………………………………………….. 205

6.2.3.5.4 Ability to Monitor Effectiveness……………………………………………………… 206

vi

Table of Contents (continued)
6.2.3.5.5
Time Until Remedial Action Objectives are Achieved……………………….. 206

6.2.3.6 Implementability …………………………………………………………………………… 207

6.2.3.6.1
Ability to Construct and Operate the Technology ……………………………… 209

6.2.3.6.2
Reliability of the Technology………………………………………………………….. 212

6.2.3.6.3
Ease of Undertaking Additional Remedial Actions, if Necessary ………… 213

6.2.3.6.4
Ability to Monitor Effectiveness of Remedy…………………………………….. 214

6.2.3.6.5
Ability to Obtain Approvals from Other Agencies …………………………….. 214

6.2.3.6.6
Coordination with Other Agencies…………………………………………………… 216

6.2.3.6.7
Availability of Off-site Treatment, Storage and Disposal Services and Capacity……………………………………………………………………………………….. 218
6.2.3.6.8
Availability of Necessary Equipment and Specialists ………………………… 218

6.2.3.6.9
Availability of Prospective Technologies …………………………………………. 219

6.2.3.7 Cost …………………………………………………………………………………………….. 219

7 Comparative Analysis of Alternatives…………………………………………………………………….. 221

7.1
Threshold Criteria …………………………………………………………………………. 221

7.1.1 Overall Protection of Human Health and the Environment …………………. 221

7.1.2 Compliance with ARARs……………………………………………………………….. 222

7.1.2.1 Chemical-Specific ARARs. ……………………………………………………………. 222

7.1.2.2 Location-Specific ARARs. …………………………………………………………….. 223

7.1.2.3 Action-Specific ARARs…………………………………………………………………. 224

7.1.2.4 Remedy Selection Absent ARAR Compliance………………………………….. 225

7.2
Primary Balancing Criteria …………………………………………………………….. 226

7.2.1 Long-Term Effectiveness and Permanence ………………………………………. 226

7.2.2 Reduction of Toxicity, Mobility or Volume through Treatment ………….. 228

7.2.3 Short-Term Effectiveness……………………………………………………………….. 229

7.2.3.1 Protection of the Community………………………………………………………….. 229

7.2.3.2 Worker Protection …………………………………………………………………………. 231

7.2.3.3 Environmental Impacts ………………………………………………………………….. 231

7.2.3.4 Time to Achieve Remedial Action Objectives (RAOs)………………………. 232

7.2.4 Implementability …………………………………………………………………………… 233

7.2.5 Cost …………………………………………………………………………………………….. 239

7.3
Modifying Criteria ………………………………………………………………………… 242

8 References…………………………………………………………………………………………………………… 243

vii

Table of Contents (continued)
Appendices
A. Existing Institutional Controls, City of St. Louis -Negative Easement and Restrictive Covenant on West Lake Landfill, and FAA ROD, MOU, and Advisories
B. Identification and Quantification of the Volume of RIM above Cleanup Levels
C. Off-site Disposal Facilities – Waste Acceptance Criteria
D. Evaluation of Trench Shoring Applicability
E. Evaluation of Regrading Options for ROD-Selected Remedy
F. Required Cover Thicknesses Calculations
G. Conceptual Environmental Monitoring Plan
H. Evaluation of Potential Risks Associated with the Proposed Remedial Alternatives
I. Estimated Greenhouse Gas Emissions Associated with the Alternatives
J. Estimated Project Schedules for the Remedial Alternatives
K. Estimated Costs for the Remedial Alternatives
List of Tables
1.
Summary Comparison of Results from Proximately Located RI and NRC Soil Borings

2.
Summary of Thorium-230 Decay and Radium-226 In-Growth Over Time

3.
Summary Comparison of Soil Sample Results to RCRA Toxicity Characteristic Regulatory Levels

4.
Summary of Calculated Risks for Current and Future Potential Receptors

5.
Preliminary Identification of Potential Chemical-Specific ARARs and TBC Criteria

6.
Preliminary Identification of Potential Location-Specific ARARs and TBC Criteria

7.
Preliminary Identification of Potential Action-Specific ARARs and TBC Criteria

8.
Comparison of USEI Waste Acceptance Criteria (WAC) to Projected OU-1 RIM Concentrations

9.
Summary of Estimated Costs

10.
Comparative Analysis of Alternatives

List of Figures
1.
General Location Map

2.
Site Area

3.
Site Features

4.
Site Topography

5.
Site and Adjacent Property Ownership

6.
Landfill and Adjacent Property Zoning

7.
Existing Environmental Easements and Land-Use Covenants

8.
Setback from Airport Runway

9.
Geologic Map

10.
Extent of Geomorphic Flood Plain

11.
Extent of Radiologically-Impacted Materials

viii

Table of Contents (continued)
List of Figures (cont.)
12.
Comparison of Areal Extent of RIM from NRC, RI and SFS Studies

13.
Locations of NRC and RI Soil Borings

14.
Buffer Zone/Crossroad Property Sampling Locations

15.
Ingrowth of Radium Over Time

16.
Groundwater and Surface Water Dissolved Radium Results

17.
Groundwater and Surface Water Total Radium Results

18.
Groundwater and Surface Water Dissolved Arsenic Results

19.
Groundwater and Surface Water Total Arsenic Results

20.
Groundwater and Surface Water Dissolved Lead Results

21.
Groundwater and Surface Water Total Lead Results

22.
Groundwater and Surface Water Benzene Results

23.
Groundwater and Surface Water Total Chlorobenzene Results

24.
Technology Implementability Screening of Remediation Technologies and Process Options

25.
Locations of Potential Off-Site Disposal Facilities and Rail Points

26.
Waste Volume/Size Reduction and Separation Equipment

27.
Evaluation of Remediation Technologies and Process Options

28.
Conceptual Cross-section of the ROD Remedy

29.
Potential Material Stockpile Areas

30.
On-Site Treatment of Contact Stormwater and Leachate

31.
RIM Excavation Sequencing

32.
Conceptual Alignment of On-Site Rail Spur

33.
Proposed Location New On-Site Cell

34.
Profile of On-site Disposal Cell Liner and Cover

35.
Final Closed Topography Areas 1 and 2

36.
Area 2 Waste Excavation Intersection with OU-2 Boundaries

37.
Profile of Area 2 Waste Excavation Intersection with OU-2 Boundaries

ix

List of Acronyms

AC Advisory Circular
ACM asbestos containing materials
AEC Atomic Energy Commission
amsl above mean sea level
AOA air operations area
AOC Administrative Order on Consent
ARAR Applicable or Relevant and Appropriate Requirements
ARRA American Recovery and Reinvestment Act
ASTM American Society of Testing Materials
bcy bank cubic yard
BDAT Best Demonstrated Available Technology
bgs below ground surface
Bi Bismuth
BMP Best Management Practices
BRA Baseline Risk Assessment
C&D Construction and demolition
CERCLA Comprehensive Environmental Recovery, Compensation, and Liability Act
cf cubic feet
CFR Code of Federal Regulations
cm centimeter
CM Construction Manager
cm/sec centimeter per second
COCs Chemicals of concern
COD Chemical Oxygen Demand
CoPC constituent of potential concern
CQA construction quality assurance
CSR Code of State Regulations
cy, or cu yd cubic yard
DAF Dilution-Attenuation Factor
DCGL Derived concentration guideline
DOD Department of Defense
DOE United States Department of Energy
DOT United States Department of Transportation
DQO data quality objective
dtrs daughters
ea each
ecy embankment cubic yards
EDTA ethylenediaminetetraacetic acid
EMSI Engineering Management Support, Inc.
ENR CCI Engineering News Record Construction Cost Index
EPA United States Environmental Protection Agency
EPC Exposure point concentration
ERA Ecological Risk Assessment
x

List of Acronyms (continued)

FAA Federal Aviation Administration FEMA Federal Emergency Management Agency FIRM Flood Insurance Rate Map FRTR Federal Remediation Technologies Roundtable FS Feasibility Study FUSRAP Formerly Utilized Sites Remedial Action Program ft feet gm, or g gram GM Geiger Mueller gpm gallons per minute GRA General Response Action HAZMAT hazardous materials HDPE high density polyethylene HHRA Human Health Risk Assessment HI Hazard Index HP health physics hr hour IC Institutional Control IP industrial packaging IRIS Integrated Risk Information System K Potassium kg kilogram L liter LAACC Large Area Activated Charcoal Canisters lbs pounds lcy loose cubic yard LDPE low density polyethylene LDR Land disposal restrictions LEL lower explosive limit lf linear foot LFMR Landfill mining and reclamation Li Lithium LLRW Low level radioactive waste LoMR Letter of Map Revision LPGAC Liquid Phase Granular Activated Carbon LSA low specific activity MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual MCA Multi-channel analyzer MCL Maximum contaminant level MCLG Maximum contaminant level goal MDA Minimum detectable activity MDOT Missouri Department of Transportation MDNR Missouri Department of Natural Resources MECA Missouri Environmental Covenants Act
xi

List of Acronyms (continued)

m meter MeV Million electron volts mg milligram mm millimeter mo ` month MOU Memorandum of Understanding mrem millirem msf thousand square feet MSD Metropolitan St. Louis Sewer District MSWLF Municipal Solid Waste Landfill MTG Migration to Groundwater Na Sodium NARM Naturally-Occurring and Accelerator-Produced Radioactive Material NCP National Oil and Hazardous Substance Pollution Contingency Plan NEPA National Environmental Policy Act NESHAPs National Emissions Standards for Hazardous Air Pollutants NOAA National Oceanic and Atmospheric Administration NPDES National Pollutant Discharge Elimination System NRC Nuclear Regulatory Commission NORM Naturally occurring radioactive material NPL National Priorities List O Oxygen O&M operation and maintenance OM&M operation, maintenance, and monitoring OMB Office of Management and Budget OSHA Occupational Safety and Health Administration OSR Off-site Rule OSTRI Office of Superfund Technology Research and Innovation OSWER Office of Solid Waste and Emergency Response OU Operable Unit Pa Protactinium PAH Poly-nuclear aromatic hydrocarbon Pb Lead PCB Poly-chlorinated biphenyl pCi pico Curie PFLT Paint filter liquids test Po Polonium POTW Publicly-Owned Treatment Works PPE personal protective equipment ppm Parts per million PRG Preliminary Remediation Goal PUF Poly-urethane foam R Roentgen RD Remedial design
xii

List of Acronyms (continued)

RA Remedial action
Ra Radium
RACM Regulated asbestos-containing material
RAECOM Radiation Attenuation Effectiveness and Cover Optimization with Moisture Effects computer program
RAO Remedial Action Objective
RCRA Resource Conservation and Recovery Act
RD Remedial Design
RDWP Remedial Design Work Plan
rem roentgen equivalent in man
RESRAD RESRAD – CHEM: A computer code for chemical risk assessment
RI Remedial Investigation
RIM Radiologically Impacted Material
RMC Radiation Management Corporation
RML radioactive material license
ROD Record of Decision
RSMo Revised Statutes of Missouri
SAP Sampling and Analysis Plan
sec, or s second
sf or sq ft square feet
SFS Supplemental Feasibility Study
Si Silocon
SLAPS St. Louis Airport Site
SLDS St. Louis Downtown Site
STLAA St. Louis Airport Authority
SOW Statement of Work
SVOC Semi-Volatile Organic Compound
SWMP Solid Waste Management Program
SWPP Stormwater Pollution Prevention Plan
t ton
TBC To Be Considered
TCLP Toxicity Characteristic Leaching Procedure
TENORM Technologically Enhanced Naturally Occurring Radioactive Materials
Th Thorium
TS Transfer Station
TSDF Treatment, storage, and disposal facility
TSS Total Dissolved Solids
U Uranium
ug microgram
UMTRCA Uranium Mill Tailings Radiation Control Act
uR microRoentgen
U.S.C. United States Code USACOE United States Army Corps of Engineers USCS Unified Soil Classification System
xiii

List of Acronyms (continued)
USDA United States Department of Agriculture USEI US Ecology Idaho UTS Universal treatment standards VOCs Volatile Organic Compounds VCA Verification of current acceptability WAC Waste Acceptance Criteria WL Working Level yr Year
xiv

1 INTRODUCTION
As a result of internal deliberations by the United States Environmental Protection Agency (EPA) and its further consideration of certain comments provided by interested community members, EPA determined that a Supplemental Feasibility Study (SFS) is warranted. This SFS will be added to the Administrative Record for this Site.
1.1 Scope of the SFS
This SFS has been performed to provide additional evaluation of a select group of potential remedial alternatives for Operable Unit 1 (OU-1) at the West Lake Landfill Site. EPA determined that additional work was necessary to accomplish the objectives of the RI/FS for OU.
1. Specifically, EPA requested the OU-1 Respondents to perform an SFS consisting of an engineering and cost analysis of the ROD-selected remedy, and two remedial alternatives that would remove all material containing radionuclides at levels greater than those that would allow for unrestricted use (relative to the presence of radionuclides) of the radiologically-contaminated areas (Areas 1 and 2 and the Buffer Zone/Crossroad properties) in OU-1; referred to by EPA as “complete rad removal”.
The ROD-selected containment remedy for OU-1 would protect human health and the environment by providing source control and institutional controls for the landfilled waste materials. A description of and reasons for selection of this remedy are presented in EPA’s Record of Decision (ROD) for OU-1 (EPA, 2008a). The source control and institutional control methods prevent human receptors from contacting the waste material. The source control method mitigates contaminant migration to air and restricts infiltration of precipitation into the landfill, which contributes to protection of groundwater quality. The description and basis for the selected remedy was documented in the ROD. The components of the ROD-selected remedy include the following:
1.
Install landfill cover meeting the Missouri closure and post-closure care requirements for sanitary landfills, including enhancements consistent with the standards for uranium mill tailing sites, i.e., armoring layer and radon barrier;

2.
Consolidation of radiologically contaminated surface soil from the Buffer Zone/Crossroad Property to the containment area;.

3.
Apply groundwater monitoring and protection standards consistent with requirements for uranium mill tailing sites and sanitary landfills;.

4.
Surface water runoff control;

5.
Gas monitoring and control including radon and decomposition gas as necessary;

6.
Institutional controls to prevent land and resource uses that are inconsistent with a closed sanitary landfill site containing long-lived redionuclides; and

7.
Long-term surveillance and maintenance of the remedy.

Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 1
Performance standards for each of the remedy components are specified in the ROD. As a result of subsequent discussions between EPA Region 7 and EPA’s Office of Superfund Remediation and Technology Innovation (OSRTI), the following additional performance standards were identified for the ROD-selected remedy:

The proposed cap should meet UMTRCA guidance for a 1,000-year design period
including an additional thickness to prevent radiation emissions.


Air monitoring stations for radioactive materials should be installed at both on-site and off-site locations.


Groundwater monitoring should be implemented at the waste management unit boundary and also at off-site locations. The groundwater monitoring program needs to be designed so that it can be determined whether contaminants from the landfill have migrated across the waste management unit boundary in concentrations that exceed drinking water Maximum Contaminant Levels. The groundwater monitoring program needs to measure for both contaminants that have historically been detected in concentrations above MCLs (e.g., benzene, chlorobenzene, dissolved lead, total lead, dissolved arsenic, total arsenic, dissolved radium and total radium) and broader indicators of contamination (e.g., redox potential, alkalinity, carbonates, pH and sulfates/sulfides).


Flood control measures at the site should meet or exceed design standards for a 500-year storm event under the assumption that the existing levee system is breached.

This SFS analysis incorporates those additional performance standards and refines the description and evaluation of the containment remedy that was selected in the ROD.
In a January 11, 2010, letter (EPA, 2010a) and Statement of Work (SOW) (EPA, 2010b) requesting that the Respondents perform this SFS, EPA identified the two “complete rad removal” alternatives that EPA directed be developed and evaluated in addition to the ROD-selected remedy:
1.
Excavation of radioactive materials with off-site commercial disposal of the excavated materials (referred to as “complete rad removal” with off-site disposal alternative in this SFS); and

2.
Excavation of radioactive materials with on-site disposal of the excavated materials in an on-site engineered disposal cell with a liner and cap if a suitable location outside the geomorphic flood plain can be identified (referred to as “complete rad removal” with on-site disposal alternative in this SFS).

EPA indicated (EPA, 2010a) that “complete rad removal” was defined to mean attainment of risk-based radiological cleanup levels specified in OSWER Directives 9200.4-25 and 9200.4-18. Although these new alternatives have been termed “complete rad removal,” it must be
Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 2
recognized that implementation of either of these alternatives would not result in complete removal of all radionuclides from the landfill, but instead would remove radionuclides from Areas 1 and 2 to the degree feasible such that additional engineering and institutional controls would not be required based on the radiological content of these areas. Because these areas would still contain solid wastes after removal of the radiologically-impacted materials, regrading, capping and establishment of institutional controls related to the presence of solid wastes would still be required.
As described in the SOW (EPA, 2010b), EPA required the two “complete rad removal” alternatives to be evaluated along with the ROD-selected remedy. The two “complete rad removal” alternatives along with the ROD-selected remedy were evaluated using the threshold and primary balancing criteria set forth in the National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 CFR § 300.430 (EPA, 2009a). These criteria include the following:

Threshold Criteria: -Overall Protection of Human Health and the Environment; -Compliance with applicable or relevant and appropriate requirements of other

regulations (ARARs).


Primary Balancing Criteria:
-Long-term Effectiveness and Permanence;
-Reduction of Toxicity, Mobility, or Volume through Treatment;
-Short-term Effectiveness;
-Implementability; and
-Cost.

Additional descriptions of these criteria are presented in Section 6 of this SFS.
The NCP also requires remedial alternatives to be evaluated in terms of Modifying Criteria which include State and community acceptance. State and community acceptance will be evaluated by EPA as part of any decision process that may be undertaken by EPA after completion of the SFS and are not considered in this document.
1.2 SFS Approach
This SFS has been developed pursuant to a January 11, 2010, letter from EPA to the OU-1 Respondents (EPA, 2010a), an EPA-developed Statement of Work (SOW) (EPA SOW, 2010b) attached to the January 11 letter, and the EPA-approved Work Plan for the Supplemental Feasibility Study (SFS Work Plan) (EMSI, 2010a).
The engineering and cost analyses of the “complete rad removal” alternatives and the ROD-selected remedy performed for this SFS are based primarily on existing information provided in the Remedial Investigation (RI) (EMSI, 2000), Baseline Risk Assessment (BRA) (Auxier, 2000), Feasibility Study (FS) (EMSI, 2006), and the ROD for OU-1. These analyses also consider the
Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 3
results of a supplemental evaluation prepared by EPA subsequent to the ROD (TetraTech, 2009). Additionally, information was obtained from representatives of the United States Army Corps of Engineers (USACE), the United States Department of Energy (DOE), and various vendors of equipment, materials and services as necessary to develop and evaluate the potential effectiveness, implementability and cost of the “complete rad removal” alternatives. Additional field investigations or laboratory testing were not included in the scope of this effort and were not performed.
This report has been prepared to address the requirements of the SOW, EPA-approved Work Plan, and the NCP, in accordance with EPA’s Guidance for Conducting Remedial Investigations and Feasibility Studies Under CERCLA (EPA, 1988a) and other EPA FS-related guidance documents (e.g., EPA, 1991a; EPA, 2000). This SFS:

provides a summary discussion of site conditions and other information presented in the RI for OU-1 (EMSI, 2000);


addresses findings in United States Nuclear Regulatory Commission (NRC) reports that evaluated the radiological disposal areas at the West Lake Landfill site;


provides additional characterization of the dimensions of radiologically impacted materials in the two radiological disposal areas;


summarizes the characterization of potential site risks presented in the BRA for OU-1 (Auxier, 2000);


provides further information and evaluation pertaining to a negative easement on the property held by the City of St. Louis, and its potential impacts on remedy implementation for OU-1;


provides additional information about environmental monitoring during remedy implementation and long-term maintenance and operations;


evaluates potential treatment technologies for the radiologically impacted materials; and


evaluates potential ARARs and remedial technologies, and descriptions of the remedial alternatives previously presented and evaluated in the site FS (EMSI, 2006).

Where necessary for the evaluation of the “complete rad removal” alternatives, or as otherwise
appropriate for completion of the SFS, brief summaries or tabulations of the results of prior site
evaluations are provided; however, the prior reports should be reviewed or consulted for
additional details and specific information relative to those evaluations.
Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 4
1.3 Report Organization
This report is organized as follows:
Section 1: Introduction – Presents information regarding the scope and approach used to complete the SFS.
Section 2: Site Conditions – Summarizes information regarding site conditions as they relate to the alternatives evaluated in the SFS. Detailed information about site conditions was presented in the RI report for OU-1 (EMSI, 2000) and a summary discussion of site conditions related to the development and evaluation of remedial alternatives was presented in the FS report for OU-1 (EMSI, 2006). This section provides a description of occurrences of radionuclides in soil/waste, air and groundwater at the site. In addition, this section describes the nature, general locations, and overall lateral and vertical extent of Radiologically-Impacted Materials (RIM). This section also provides a summary of the occurrences of chemical constituents in soil/waste and groundwater. Lastly, this section provides a brief summary of the results of the Baseline Risk Assessment (Auxier, 2000).
Section 3: ARARs – Summarizes information regarding potential ARARs and remedial action objectives (RAOs) as they relate to the additional alternatives evaluated in the SFS. Additional, detailed information about potential ARARs and RAOs was presented in the FS report for OU-1 (EMSI, 2006).
Section 4: Remedial Technologies – Summarizes information regarding additional remedial technologies that may be potentially applicable to the “Complete Rad Removal” alternatives evaluated in the SFS. Additional, detailed information about potentially applicable technologies was presented in the FS report for OU-1 (EMSI, 2006).
Section 5: Remedial Alternatives – Provides descriptions of the ROD-selected remedy and the “complete rad removal” alternatives that are the subject of the detailed evaluations presented in Sections 6 and 7. Descriptions of other remedial alternatives previously developed and evaluated for OU-1 were presented in the FS report for OU-1 (EMSI, 2006) and are not repeated in this SFS report.
Section 6: Detailed Analysis of Alternatives – Presents a detailed analysis of the ROD-selected remedy and the “complete rad removal” alternatives relative to the threshold and balancing criteria defined by the NCP.
Section 7: Comparative Analysis of Alternatives – Presents a summary comparison of the ROD-selected remedy and the two “complete rad removal” alternatives in terms of the threshold and balancing criteria defined by the NCP.
Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 5
Section 8: References – Provides a list of references cited in this report.
This SFS also includes the following appendices:
Appendix A: Existing Institutional Controls affecting the Site, the City of St. Louis Negative Easement and Restrictive Covenant on West Lake Landfill, and FAA ROD, MOU and Advisory Circulars
Appendix B: Identification and Quantification of the Volume of RIM above
Cleanup Levels Appendix C: Off-site Disposal Facilities – Waste Acceptance Criteria Appendix D: Evaluation of Potential Application of Shoring Technology Appendix E: Evaluation of Area 1 and 2 Regrading Options Appendix F: Required Cover Thicknesses Calculations Appendix G: Conceptual Environmental Monitoring Plan Appendix H: Evaluation of Potential Risks Associated with the Proposed
Remedial Alternatives
Appendix I: Estimated Greenhouse Gas Emissions Associated with the

Alternatives Appendix J: Estimated Project Schedules for the Remedial Alternatives Appendix K: Estimated Costs for the Remedial Alternatives.
Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 6
2 SITE CONDITIONS
The purpose of this Section 2 is to provide information necessary to support the evaluation of remedial technologies and alternatives presented in Sections 4, 6, and 7. Therefore, this section summarizes certain site-specific information from the existing Administrative Record in order to present a summary of the site conditions at the West Lake Landfill.
This Section 2 is divided into five subsections:

Section 2.1 provides information regarding the West Lake landfill and the surrounding area including discussions and/or descriptions of historical landfill operations and disposal areas; Superfund Operable Units (OUs) on the site; current site uses; site zoning, use restrictions and easements; surrounding land uses; and potential impacts or consequences from the landfill’s proximity to the Missouri River floodplain.


The nature and extent of radionuclide occurrences in OU-1 are discussed in Section 2.2 including the source of the radionuclides; general locations and lateral extent of radiologically-impacted materials (RIM); vertical extent of RIM occurrences in Areas 1 and 2; estimated volume of RIM; radiological occurrences on the Buffer Zone and Crossroad Property; radiological characterization of the RIM in Areas 1 and 2; projected radionuclide decay and ingrowth of the RIM; and the evaluation of principal threat wastes. Section 2.2 also includes information regarding the occurrence of non-radiological hazardous substances (trace metals, petroleum hydrocarbons, volatile and semi-volatile organics, pesticides and PCBs) in soil samples collected from Areas 1 and 2 as well as discussions regarding the potential for occurrences of hazardous wastes and asbestos-containing materials in the landfill matrix.


The presence of radionuclides in air is discussed in Section 2.3.


Brief descriptions of the site geology and hydrogeology and the nature and extent of radionuclide and chemical occurrences in groundwater near Areas 1 and 2 are provided in Section 2.4.


Finally, Section 2.5 includes summaries and conclusions from the baseline human health and screening-level ecological risk assessments.

2.1 Site Location and Surrounding Area
The West Lake Landfill is located within the western portion of the St. Louis metropolitan area on the east side of the Missouri River floodplain approximately two miles east of the river (Figure 1). The landfill is located approximately one mile north of the intersection of Interstate 70 and Interstate 270 within the city limits of the City of Bridgeton in northwestern St. Louis County.
Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 7
The site is bounded to the east and northeast by St. Charles Rock Road (State Highway 115) (Figure 2). Commercial and industrial properties bound the site immediately to the north, across St. Charles Rock Road to the north and east, and to the south. The site is bounded on the west by Old St. Charles Rock Road (vacated) and the Earth City Industrial Park (Earth City) stormwater/flood control pond. The Earth City commercial and industrial complex continues to the west and north of the stormwater/flood control pond and extends from the site to the Missouri River. Earth City is separated from the river by an engineered levee system owned and maintained by the Earth City Flood Control District.
2.1.1 Historic Landfill Operations and Disposal Areas
The West Lake Landfill is an approximately 200-acre parcel containing multiple areas of past operations. The site was used agriculturally until a limestone quarrying and crushing operation began in 1939. The quarrying operation continued until 1988 and resulted in two quarry pits, the North Quarry Pit and the South Quarry Pit (Figure 3), which were excavated to maximum depth of 240 feet below ground surface (bgs) (Herst & Associates, 2005).
The West Lake Landfill is the site of several areas where solid wastes have been disposed. Beginning in the early 1950s or perhaps the later 1940s, portions of the quarried areas and adjacent areas were used for landfilling municipal refuse, industrial solid wastes, and construction/demolition debris. These operations predated state laws and regulations governing such operations. Landfill activities conducted after 1974 within the quarry areas were subject to permits obtained from the Missouri Department of Natural Resources (MDNR). In 1974 landfilling began in the portion of the site described as the North Quarry Pit. Landfilling continued in this area until 1985 when the landfill underwent expansion to the southwest into the area described as the South Quarry Pit (Herst & Associates, 2005). In August 2005, the Bridgeton Sanitary Landfill stopped receiving waste pursuant to an agreement with the City of St. Louis to reduce the potential for birds to interfere with airport operations. The Bridgeton Sanitary Landfill is inactive and closure and post-closure activities are proceeding under MDNR supervision.
In addition to the Bridgeton Sanitary Landfill north and south quarry pits currently in the process of closure/post-closure, the West Lake Landfill property contains four other areas where solid wastes were disposed (Figure 3):

Area 1 where solid wastes and radiologically-impacted materials were disposed;


Area 2 where solid wastes and radiologically-impacted materials were disposed;


A closed demolition landfill; and


An inactive sanitary landfill.

Supplemental Feasibility Study Report West Lake Landfill OU-1 12/16/2011 Page 8
2.1.2 Superfund Operable Units
Superfund-program remedial action at the site is divided into two operable units (OUs). OU-1 is comprised of the solid wastes and RIM disposed in Areas 1 and 2 and portions of an adjacent property, formerly described as the Ford Property and now called the Buffer Zone/Crossroad Property. OU-2 consists of the other landfill areas that are not impacted by radionuclides and includes the inactive sanitary landfill located adjacent to Area 2, the closed demolition landfill, and the Bridgeton Sanitary Landfill located in the North and South Quarry Pits. The closed demolition landfill and the Bridgeton Sanitary Landfill, while designated as part of OU-2, are regulated by the MDNR pursuant to State of Missouri solid waste regulations and are not being actively addressed by the Superfund program. To the extent that the presence of or activities associated with these OU-2 areas potentially impact OU-1 and the remedial alternatives considered by this SFS, those impacts are discussed in the appropriate SFS section.
OU-1 Area 1 is situated on the northern and western slopes of a topographic high within the overall West Lake landfill property. Ground surface elevation in Area 1 varies from 490 feet above mean sea level (AMSL) on the south to 452 feet AMSL at the roadway near the transfer station entrance (Figure 4). OU-1 Area 2 is situated between a topographic high of landfilled materials on the south and east, and the Buffer Zone/Crossroad Property on the west. The highest topographic level in Area 2 is about 500 feet AMSL on the southwest side of Area 2, sloping to approximately 470 feet AMSL near the top of the landfill berm (Figure 4). The upper surface of the berm along the western edge of Area 2 is located approximately 20 to 30 feet above the adjacent Buffer Zone/Crossroad Property and approximately 30 to 40 feet higher than the water surface in the flood control channel located to the south-west of Area 2. A berm on the northern portions of Area 2 controls runoff to the adjacent properties.
No contemporaneous reports, drawings or other records from the former site operators exist regarding the construction of the disposal units or the overall types and amounts of wastes that were disposed in the Area 1 and Area 2 landfills during their operation. Based on the RI investigations, it appears that these areas were filled using an “area-fill” approach whereby waste materials consisting primarily of munic