FINAL Record of Decision January 2016 Revision 03 Fort Riley Sherman Heights Small Arms Range Impact Slope Junction City, Kansas Military Munitions Response Program U.S. Army Corps of Engineers, Omaha District Contract W9128F-09-D-0059, Task Order 0009 FINAL CONTRACT W9128F-09-D-0059 TASK ORDER 0009 MMRP RECORD OF DECISION FORT RILEY SHERMAN HEIGHTS SMALL ARMS RANGE IMPACT SLOPE JUNCTION CITY, KANSAS Prepared for: U.S. ARMY Fort Riley Prepared by: U.S. ARMY CORPS OF ENGINEERS Omaha District January 2016 Revision 03 Record of Decision Sherman Heights Small Arms Range Impact Slope Fort Riley, Kansas Table of Contents 1.0 DECLARATION ............................................................................................................. 1-1 1.1 Site Name and Location .............................................................................................. 1-1 1.2 Statement of Basis and Purpose ................................................................................. 1-1 1.3 Assessment of Site ...................................................................................................... 1-1 1.4 Description of Selected Remedy ................................................................................. 1-1 1.5 Statutory Determinations ............................................................................................. 1-2 1.5.1 Part 1: Statutory Requirements .......................................................................... 1-2 1.5.2 Part 2: Statutory Preference for Treatment ........................................................ 1-2 1.5.3 Part 3: Five-Year Review Requirement .............................................................. 1-2 1.6 ROD Data Certification Checklist ................................................................................ 1-2 1.7 Authorizing Signatures ................................................................................................ 1-3 2.0 DECISION SUMMARY .................................................................................................. 2-1 2.1 Site Name, Location, and Brief Description ................................................................. 2-1 2.2 Site History and Enforcement Activities ....................................................................... 2-1 2.3 Community Participation .............................................................................................. 2-4 2.4 Scope and Role of MRS or Response Action .............................................................. 2-6 2.5 Site Characteristics ...................................................................................................... 2-6 2.5.1 Topography ........................................................................................................ 2-6 2.5.2 Climate ............................................................................................................... 2-6 2.5.3 Geology and Hydrology ...................................................................................... 2-7 2.5.4 Hydrogeology ..................................................................................................... 2-7 2.5.5 Hydrology ........................................................................................................... 2-8 2.5.6 Vegetation .......................................................................................................... 2-8 2.5.7 Ecology ............................................................................................................... 2-9 2.5.8 Nature and Extent of Contamination .................................................................. 2-9 2.6 Current and Potential Future Land Use and Resource Uses .................................... 2-13 2.6.1 Conceptual Site Model ..................................................................................... 2-13 2.7 Summary of Site Risks .............................................................................................. 2-16 2.7.1 Summary of the Human Health Risk Assessment ............................................ 2-16 2.7.2 Summary of the Ecological Risk Assessment .................................................. 2-20 2.7.3 Basis for Taking Action ..................................................................................... 2-24 2.8 Remedial Action Objectives ....................................................................................... 2-24 2.9 Description of Alternatives ......................................................................................... 2-25 2.9.1 Alternative 1: No Action .................................................................................... 2-26 2.9.2 Alternative 2: LUCs .......................................................................................... 2-26 2.9.3 Alternative 3: Excavation and Off-Site Disposal ............................................... 2-27 2.9.4 Alternative 4: Soil Cover ................................................................................... 2-28 2.10 Comparative Analysis of Alternatives ........................................................................ 2-28 2.10.1 Overall Protection of Human Health and the Environment ............................... 2-29 2.10.2 Compliance with Applicable or Relevant and Appropriate Requirements ........ 2-30 2.10.3 Long-Term Effectiveness and Permanence ..................................................... 2-30 2.10.4 Reduction of Toxicity, Mobility, or Volume Through Treatment ........................ 2-31 2.10.5 Short-Term Effectiveness ................................................................................. 2-31 2.10.6 Implementability ............................................................................................... 2-31 2.10.7 Cost .................................................................................................................. 2-32 W9128F-09-D-0059, TO 0009 i January 2016 BWJ130451 Revision 03 Record of Decision Sherman Heights Small Arms Range Impact Slope Fort Riley, Kansas 2.10.8 Regulatory Acceptance .................................................................................... 2-33 2.10.9 Community Acceptance ................................................................................... 2-33 2.11 Principal Threat Wastes ............................................................................................ 2-34 2.12 Selected Remedy ...................................................................................................... 2-34 2.12.1 Summary of the Rationale for the Selected Remedy ....................................... 2-34 2.12.2 Summary of Estimated Remedy Costs ............................................................. 2-34 2.12.3 Expected Outcomes of Selected Remedy ........................................................ 2-35 2.13 Statutory Determinations ........................................................................................... 2-35 2.13.1 Protection of Human Health and the Environment ........................................... 2-35 2.13.2 Compliance with ARARs .................................................................................. 2-35 2.13.3 Cost Effectiveness ............................................................................................ 2-35 2.13.4 Utilization of Permanent Solutions and Alternative Treatment Technologies to the Maximum Extent Practicable .................................................................. 2-36 2.13.5 Preference for Treatment as a Principal Element ............................................. 2-36 2.13.6 Five-Year Review Requirements ...................................................................... 2-36 2.14 Documentation of Significant Changes ..................................................................... 2-36 3.0 RESPONSIVENESS SUMMARY .................................................................................. 3-1 3.1 Stakeholder Comments and Lead Agency Responses ............................................... 3-1 3.2 Community Participation .............................................................................................. 3-1 3.1 Summary of Comments Received during the Public Comment Period and Agency Responses .................................................................................................................. 3-1 3.1.1 Comments Received During the Public Meeting ................................................ 3-1 3.1.2 Written Comments Received During the Comment Period ................................ 3-2 3.3 Technical and Legal Issues ......................................................................................... 3-2 4.0 REFERENCES ............................................................................................................... 4-1 W9128F-09-D-0059, TO 0009 ii January 2016 BWJ130451 Revision 03 Record of Decision Sherman Heights Small Arms Range Impact Slope Fort Riley, Kansas List of Tables Table 1-1 ROD Data Certification Checklist ......................................................................... 1-2 Table 2-1 MEC Summary ..................................................................................................... 2-3 Table 2-2 Public Notification of Document Availability ......................................................... 2-5 Table 2-3 Public Comment Period Requirements ................................................................ 2-5 Table 2-4 Previous MRS Characterization