OPERABLE UNIT E RECORD OF DECISION RECORD OF DECISION OPERABLE UNIT E FORT RICHARDSON ANCHORAGE, ALASKA September 2005 CERCLIS ID: AK6214522157 ANC//050320046 i OPERABLE UNIT E RECORD OF DECISION Table of Contents Section Page Abbreviations ................................................................................................................................ viii Part I - Declaration Statement 1.0 Site Name and Location............................................................................................................ 1 1.1 Statement of Basis and Purpose .........................................................................1 1.2 Assessment of the Site .........................................................................................1 1.3 Description of Selected Remedy ........................................................................2 1.4 Statutory Determination .....................................................................................2 1.5 ROD Data Certification Checklist......................................................................3 1.6 U.S. Army Authorizing Signature .....................................................................4 1.7 EPA Authorizing Signature................................................................................5 1.8 State of Alaska (ADEC) Authorizing Signature ..............................................6 Part II - The Decision Summary 1.0 Site Name, Location, and Description .................................................................................... 7 1.1 Armored Vehicle Maintenance Area...............................................................10 1.2 Building 35-752 Area .........................................................................................10 1.3 Building 955-Sludge Bin....................................................................................11 1.4 Building 796-Battery Shop ................................................................................11 2.0 Site History and Enforcement Activities ............................................................................. 12 2.1 Action Sites .........................................................................................................12 2.1.1 Armored Vehicle Maintenance Area (AVMA) ..............................12 2.1.2 Investigations at the AVMA ............................................................13 2.2 No Further Action Sites.....................................................................................14 2.2.1 Building 35-752 Area.........................................................................14 2.2.2 Investigations and Actions at the Building 35-752 .......................21 2.2.3 Building 955-Sludge Bin ...................................................................23 2.2.4 Building 796-Battery Shop................................................................24 3.0 Highlights of Community Participation ............................................................................. 26 4.0 Scope and Role of Operable Units ....................................................................................... 28 5.0 Summary of Source Area Characteristics ............................................................................ 30 5.1 Conceptual Site Model ......................................................................................30 5.2 Overview of AVMA Area .................................................................................30 5.3 Geology and Hydrology of the AVMA ..........................................................31 ANC//050320046 iii OPERABLE UNIT E RECORD OF DECISION 5.4 Sampling Strategy ..............................................................................................32 5.5 Nature and Extent of Contamination at the AVMA .....................................33 5.5.1 Soil .......................................................................................................34 5.5.2 Groundwater ......................................................................................38 6.0 Land and Resource Uses ......................................................................................................... 44 6.1 Land Use..............................................................................................................44 6.1.1 Fort Richardson..................................................................................44 6.1.2 AVMA .................................................................................................44 6.2 Groundwater Beneficial Use ............................................................................44 6.2.1 AVMA .................................................................................................45 7.0 Summary of Site Risks............................................................................................................ 46 7.1 Summary of Human Health Risk Assessment ..............................................46 7.1.1 Exposure Assessment .......................................................................46 7.1.2 Toxicity Assessment..........................................................................49 7.1.3 Risk Characterization........................................................................50 7.1.4 Summary of Risk Estimates for the Armored Vehicle Maintenance Area........................................................................................52 7.1.5 Identification of Chemicals of Concern..........................................56 7.2 Baseline Ecological Risk Assessment ..............................................................57 7.2.1 Potentially Complete Ecological Exposure Pathways .................58 7.2.2 Ecological Management Goals, Assessment Endpoints, and Measures .......................................................................................................58 7.2.3 Representative Species......................................................................60 7.2.4 Exposure Assessment .......................................................................60 7.2.5 Ecological Effects Assessment .........................................................61 7.2.6 Summary of Risk Estimates .............................................................61 7.3 Postwide Risk Assessments..............................................................................63 7.3.1 Postwide Human Health Risk Assessment ...................................63 7.3.2 Postwide Ecological Risk Assessments ..........................................63 7.4 Uncertainties .......................................................................................................64 7.4.1 HHRA..................................................................................................64 7.4.2 Baseline ERA ......................................................................................66 8.0 Description of Alternatives.................................................................................................... 68 8.1 Need for Remedial Action ................................................................................68 8.2 Remedial Action Objectives..............................................................................68 8.3 Significant Applicable or Relevant and Appropriate Requirements .........70 8.4 Development of Remedial Alternatives .........................................................70 8.5 Remedy Components ........................................................................................71 8.6 Remedial Alternatives .......................................................................................71 8.6.1 Background Information ..................................................................71 8.6.2 AVMA Groundwater ........................................................................72 ANC//050320046 iv OPERABLE UNIT E RECORD OF DECISION 9.0 Summary of Comparative Analysis of Remedial Alternatives ........................................ 77 9.1 Threshold Criteria ..............................................................................................79 9.1.1 Overall Protection of Human Health and the Environment.......79 9.1.2 Compliance with Applicable or Relevant and Appropriate Requirements ...............................................................................................79 9.2 Balancing Criteria...............................................................................................80 9.2.1 Long-term Effectiveness and Permanence.....................................80 9.2.2 Reduction of Toxicity, Mobility, and Volume Through Treatment......................................................................................................81 9.2.3 Short-term Effectiveness...................................................................81 9.2.4 Implementability ...............................................................................82 9.2.5 Cost ......................................................................................................82 9.3 Modifying Criteria .............................................................................................83 9.3.1 State Acceptance ................................................................................83 9.3.2 Community Acceptance ...................................................................83 10.0 Principal Threat Wastes .......................................................................................................