PB96-964507
                                 EPA/ROD/R09-96/149
                                 August 1996
EPA  Superfund
       Record of Decision:
       Mather Air Force Base, Soil and Groundwater
       Operable Units, Sacramento, CA
       6/21/1996

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      Superfund Record of Decision
                 Final

Soil Operable Unit Sites and Groundwater
         Operable Unit Plumes

         Mather Air Force Base
     Sacramento  County, California

            April 29, 1996

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 Table of Contents.
List of Figures  	x
List of Tables	  xi
List of Appendices	  xiii
List of Acronyms	  xiv

1.0    Introduction  	  1-1
       1.1     Site Background	  1-2
              1.1.1    Soil OU Sites Selected for No Further Action 	  1-5
              1.1.2    Petroleum Only Sites Selected for No Further Action Under
                       CERCLA (but remain to be closed under other regulations) ...  1-7
       1.2     Signatures	  1-9

2.0    Soil Operable Unit Sites Selected for Remedial Action	  2-1
       2.1     Declaration for the Soil Operable Unit Sites Selected for Remedial Action .  2-1
              2.1.1    Site  Name and Location	  2-1
              2.1.2    Statement of Basis and Purpose  	  2-1
              2,1.3    Assessment of the  Sites	  2-1
              2.1.4    Description of the  Selected Remedy	  2-2
              2.1.5    Statutory Determinations	  2-4
       2.2     Decision Summary for Soil OU Sites Selected for Remedial Action  .....  2-4
              2.2.1    Site  Names, Location, and Description	  2-4
              2.2.2    Site  History and Enforcement Activities	  2-4
              2.2.3    Highlights of Community Participation	  2-6
              2.2.4    Scope and Role of Response Action	  2-6
              2.2.5    Summary of Site Characteristics	  2-6
                      2.2.5.1     Site 7/11 - "7100 Area" Disposal Site/Existing Fire
                                        Protection Training Area 	  2-9
                      2.2.5.2     Site 13 - Drainage Ditch Number 1  	2-10
                      2.2.5.3     Site 15 - Drainage Ditch No. 3	2-10
                      2.2.5.4     Site 20 - Sewage Treatment Plant	2-11
                      2.2.5.5     Site 37/39/54 - Building 3389/Hazardous Waste
                                        Central Storage  	2-11
RL/2-16-96/ES/1260005.AWS
                                           11

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 Table of Contents  (Continued)
                     2.2.5.6     Site 56 - Oil/Water Separator 2989	2-12
                     2.2.5.7     Site 57 - Oil/Water Separator 7019	2-13
                     2.2.5.8     Site 59 - Oil/Water Separator 4251	2-13
                     2.2.5.9     Site 60 - Oil/Water Separator 6900	2-13
                     2.2.5.10    Site 62 - OWS 7110 and Jet Engine Test Cell	2-14
                     2.2.5.11    Site 65 Oil/Water Separator 6910	2-14
                     2.2.5.12    Site 69 - Open Burn Detonation Area	2-14
             2.2.6   Summary of Site Risks	2-15
                     2.2.6.1     Human Health Risks	2-15
             2.2.7   Description of Alternatives 	2-21
                     2.2.7.1     Site 7/11 Remedial Alternative  	2-21
                     2.2.7.2     Site 13 Remedial Alternatives	2-21
                     2.2.7.3     Site 15 Remedial Alternatives	2-22
                     2.2.7.4     Site 20 Remedial Alternatives	2-22
                     2.2.7.5     Site 37/39/54 Remedial Alternative  	2-23
                     2.2.7.6     Site 56 Remedial Alternatives	2-23
                     2.2.7.7     Site 57 Remedial Alternatives	2-24
                     2.2.7.8     Site 59 Remedial Alternatives	2-24
                     2.2.7.9     Site 60 Remedial Alternatives	2-25
                     2.2.7.10    Site 62 Remedial Alternatives	2-25
                     2.2.7.11    Site 65 Remedial Alternatives	2-26
                     2.2.7.12    Site 69 Remedial Alternatives	2-26
             2.2.8   Summary of Comparison Analysis of Alternatives  	2-26
                     2.2.8.1     Overall Protection of Human Health and the
                                       Environment	2-27
                     2.2.8.2     Compliance with ARARs	2-27
                     2.2.8.3     Long-Term Effectiveness and Permanence	2-28
                     2.2.8.4     Reduction of Toxicity, Mobility, or Volume  	2-28
                     2.2.8.5     Short-Term Effectiveness	2-28
                     2.2.8.6     Implementability  	2-28
                     2.2.8.7     Cost  	2-28
                     2.2.8.8     State/Support Agency Acceptance   	2-28
RL/2-16-96/ES/1260005.AWS                          U1

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Table of Contents (Continued)
                     2.2.8.9     Community Acceptance	2-31
             2.2.9   The Selected Remedies	2-31
                     2.2.9.1     Site 7/11 - "7100 Area" Disposal Site/Existing Fire
                                        Protection Training Area  	2-31
                     2.2.9.2     Site 13 - Drainage Ditch Number 1   	2-33
                     2.2.9.3     Site 15 - Drainage Ditch Number 3   	2-36
                     2.2.9.4     Site 20 Sewage Treatment Plant	2-38
                     2.2.9.5     Site 37/39/54 - Building 3389/Hazardous Waste
                                        Control Storage  	2-39
                     2.2.9.6     Site 56 - Oil/Water Separator 2989	2-42
                     2.2.9.7     Site 57 - Oil/Water Separator 7019	2-43
                     2.2.9.8     Site 59 - Oil/Water Separator 4251	2-45
                     2.2.9.9     Site 60 - Oil/Water Separator 6900	2-46
                     2.2.9.10    Site 62 - Oil/Water Separator 7110 and
                                 Jet Engine Test Cell (Facility 7099)	2-46
                     2.2.9.11    Site 65 - Oil/Water Separator 6910	2-48
                     2.2.9.12    Site 69 - Open Burn/Open Detonation Area	2-49
             2.2.10  Statutory Determinations	2-51

3.0    Soil Operable Unit Sites Selected for No Further Action	  3-1
       3.1    Declaration for the Soil Operable Unit Sites Selected for
             No Further Action  	  3-1
             3.1.1   Site Name and Location	  3-1
             3.1.2   Statement of Basis and Purpose  	  3-1
             3.1.3   Description of the No Further Action Decision  	  3-2
             3.1.4   Summary of Site Risks	  3-2
                     3.1.4.1     Human Health Risks	  3-2
       3.2    Decision Summary for Soil OU Sites Selected for No Further Action ....  3-2
             3.2.1   Site Name, Location, and Description	  3-2
             3.2.2   Site History  and Enforcement Activities	  3-4
             3.2.3   Highlights of Community Participation	  3-4
             3.2.4 Scope and Role of Response Action	  3-4
RL/2-16-96/ES/1260005.AWS                          1V

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 Table of Contents (Continued)
                     3.2.4.1 Description of the "No Action" Alternative	 3-4
             3.2.5   Summary of Site Characteristics	 3-4
                     3.2.5.1     Site 9 - Fire Department Training Area Number 2 .  . 3-4
                     3.2.5.2     Site 10 - Fire Department Training Area Number 3  . 3-6
                     3.2.5.3     Site 14 - Drainage Ditch Number 2  	 3-6
                     3.2.5.4     Site 16 - Electron Tube Burial Site	 3-6
                     3.2.5.5     Site 21 - Asphalt Rubble Storage Site	 3-6
                     3.2.5.6     Site 22 - Asphalt Rubble Storage Site	 3-6
                     3.2.5.7     Site 24 - 1983 JP-4 Spill and Refueling Apron  .... 3-7
                     3.2.5.8     Site 26 - Building 10072, One Abandoned UST  ... 3-7
                     3.2.5.9     Site 27 - Building 10060, One Abandoned UST  ... 3-7
                     3.2.5.10    Site 28 - Building 16100, One Abandoned UST  ... 3-7
                     3.2.5.11    Site 31 - Building 10090, One Abandoned UST  ... 3-7
                     3.2.5.12    Site 33 - Building 3308, Six Abandoned USTs	 3-8
                     3.2.5.13    Site 38 - Building 3388	 3-8
                     3.2.5.14    Site 40 - Building 3875, One UST	 3-8
                     3.2.5.15    Site 41 - Building 2995, Two USTs	 3-8
                     3.2.5.16    Site 42 - Building 2898, One UST	 3-9
                     3.2.5.17    Site 43 - Building 10150, Two Abandoned USTs  .. 3-9
                     3.2.5.18    Site 44 - Building 8540, One UST	 3-9
                     3.2.5.19    Site 45 - Building 7003, One UST	 3-9
                     3.2.5.20    Site 46 - Building 8158, One UST	 3-9
                     3.2.5.21    Site 48 - Building 10410, Two Abandoned USTs  . . 3-9
                     3.2.5.22    Site 49 - Building 10450, One UST  	3-10
                     3.2.5.23    Site 51 - Building 10030, One UST	3-10
                     3.2.5.24    Site 52 - Building 10400, One UST  	3-10
                     3.2.5.25    Site 53 - Building 18501, One UST	3-10
                     3.2.5.26    Site 55 - OWS 7038  	3-10
                     3.2.5.27    Site 58 - OWS 4771  	3-10
                     3.2.5.28    Site 61 - OWS 6905  	3-11
                     3.2.5.29    Site 63 - OWS 3321 and Two USTs	3-11
                     3.2.5.30    Site 64 - OWS 4120  	3-11
RL/2-16-96/ES/1260005.AWS

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 Table of Contents (Continued)
                     3.2.5.31    Site 66 - OWS 6915  	3-11
                     3.2.5.32    Site A  	3-12
                     3.2.5.33    Site C  	3-12
                     3.2.5.34    Site E  	3-12
                     3.2.5.35    Site F  	3-12
                     3.2.5.36    Site G  	3-12
                     3.2.5.37    Site H  	3-13
                     3.2.5.38    Site I	3-13

4.0    Soil Operable Unit "Petroleum Only" Sites Selected for No Action Under
       CERCLA (but which remain to be closed under other regulations)   	  4-1
       4.1    Declaration for the Soil Operable Unit Petroleum Only Sites
             Selected for No Action	  4-1
             4.1.1   Site Name and Location	  4-1
             4.1.2   Statement of Basis and Purpose  	  4-1
             4.1.3   Description of the Selected Remedy	  4-2
             4.1.4   Declaration Statement	  4-2
       4.2    Decision Summary for Soil OU "Petroleum Only" Sites Selected
             for No Action Under CERCLA (but which remain to be closed
             under other regulations)	  4-2
             4.2.1   Site Name, Location, and Description	  4-2
             4.2.2   Site History and Enforcement Activities	  4-4
             4.2.3   Highlights of Community Participation	  4-4
             4.2.4   Scope and Role of Response Action	  4-5
             4.2.5   Summary of Site Characteristics	  4-5
                     4.2.5.1      Site 19 - Fuel Tank Sludge Burial Site  	  4-5
                     4.2.5.2      Site 29/B - Fuel Spill at Petroleum Oil and  ,
                                 Lubricant Yard Number 4	  4-6
                     4.2.5.3      Site 32 - Fuel Spill at Army/Air Force Exchange
                                 Services Service Station	  4-6
                     4.2.5.4      Site 34 - Fuel Spill at Family Housing Army/
                                 Air Force Exchange Services Service Station	  4-7
RL/2-16-96/ES/1260005.AWS                          V1

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 Table  of Contents (Continued)
                     4.2.5.5      Site 35 - Building 3226 - Four Abandoned USTs ...  4-7
                     4.2.5.6      Site 36 - Building 3286	  4-7
             4.2.6   Summary of Site Risks	  4-7
                     4.2.6.1      Human Health Risks	  4-8
             4.2.7   Statutory Authority Finding	  4-8

5.0    Groundwater Operable Unit Plumes Selected for Remedial Action  	  5-1
       5.1    Declaration for the Groundwater Operable Unit Plumes Selected for
                     Remedial Action	  5-1
             5.1.1   Plume Name and Location	  5-1
             5.1.2   Statement of Basis and Purpose   	  5-1
             5.1.3   Assessment of the Plume	  5-1
             5.1.4   Description of Selected Remedy	  5-2
             5.1.5   Statutory Determinations	  5-3
       5.2    Decision Summary  for Groundwater OU Plumes Selected for
                     Remedial Action	  5-4
             5.2.1   Plume Name, Location,  and Description	  5-4
             5.2.2   Site History and Enforcement Activities	  5-4
             5.2.3   Highlights of Community Participation	  5-4
             5.2.4   Scope and  Role of Response Action	  5-6
             5.2.5   Summary of Site Characteristics	  5-6
                     5.2.5.1      Main Base/SAC Industrial Area Groundwater
                          Plumes  	  5-6
                     5.2.5.2      Site 7 Groundwater Plume	  5-8
                     5.2.5.3      Northeast Groundwater Plume  	  5-8
             5.2.6   Summary of Site Risks	  5-8
             5.2.7   Description of Alternatives	  5-9
                     5.2.7.1     Main Base/S AC Industrial Area Groundwater Plume
                                       Remedial Alternatives  	  5-9
                     5.2.7.2      Site 7 Groundwater Plume Remedial Alternatives  . .  5-9
RL/2-16-96/ES/1260005.AWS                         V11

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 Table of Contents (Continued)
                     5.2.7.3      Northeast Ground water Plume Remedial
                                       Alternatives	5-10
             5.2.8   Summary of Comparison Analysis of Alternatives  	5-10
                     5.2.8.1      Overall Protection of Human Health and
                                       the Environment	5-12
                     5.2.8.2      Compliance with ARARs	5-12
                     5.2.8.3      Long-Term Effectiveness and Permanence	5-12
                     5.2.8.4      Reduction of Toxicity, Mobility, or Volume  	5-12
                     5.2.8.5      Short-Term Effectiveness	5-12
                     5.2.8.6      Implementability  	5-12
                     5.2.8.7      Cost  	5-13
                     5.2.8.8      State/Support Agency Acceptance  	5-13
                     5.2.8.9      Community Acceptance	5-13
             5.2.9   The Selected Remedies	5-13
                     5.2.9.1      Main Base/SAC Industrial Area
                                       Groundwater Plume  	5-13
                     5.2.9.2      Site 7 Groundwater Plume	5-15
                     5.2.9.3      Northeast Groundwater Plume  	5-17
             5.2.10  Description of the Selected Remedies	5-18
                     5.2.10.1     Extraction Wells	 . 5-18
                     5.2.10.2     Pre-Treatment Unit	5-18
                     5.2.10.3     Air Stripping Tower and Blower	5-19
                     5.2.10.4     Post-Treatment Unit	5-19
                     5.2.10.5     Vapor Phase Carbon Adsorption System	5-20
                     5.2.10.6     Discharge of Treated Water	5-20
                     5.2.10.7     Affected Water Supply Wells	5-22
             5.2.11  Performance Evaluations	.-	5-23
             5.2.12  Statutory Determinations	5-24

6.0   List of Applicable or Relevant and Appropriate Requirements and
             To-Be-Considereds	  6-1
      6.1    Chemical-Specific ARARs and TBCs 	  6-2
RL/2-16-96/ES/1260005.AWS
                                         Vlll

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Table of Contents (Continued)
             6.1.1   Federal Chemical-Specific ARARs and TBCs  	  6-2
                    6.1.1.1      Soils	  6-2
                    6.1.1.2      Surface Waters  	  6-3
                    6.1.1.3      Groundwater	  6-3
             6.1.2   State Chemical-Specific ARARs and TBCs	  6-4
                    6.1.2.1      Soils	  6-4
                    6.1.2.2      Surface Waters	  6-4
                    6.1.2.3      Groundwater	  6-4
      6.2    Location-Specific ARARs and TBCs	  6-9
             6.2.1   Federal Location-Specific ARARs	6-10
             6.2.2   State Location-Specific ARARs  	6-10
      6.3    Action-Specific ARARs and TBCs	6-12
             6.3.1   Federal ARARs  	6-12
                    6.3.1.1      Other Federal Regulations  	6-33
             6.3.2   State ARARs and TBCs   	6-33
                    6.3.2.1      State Air ARARs	6-33
                    6.3.2.2      State Groundwater and Soil ARARs	6-34
                    6.3.2.3      State Solid Waste ARARs  	6-38
                    6.3.2.4      Other State Regulations	6-39
                    6.3.2.5      State Requirements for Ex  Situ Soil Bioremediation
                                Facility  	6-40

7.0   Responsiveness Summary	  7-1

8.0   References  	  8-1
RL/2-16-96/ES/1260005.AWS
                                        IX

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List of Figures.
       Figure                    Title                                          Page

       1-1                 Site Vicinity Map	1-3
       2-1                 Soil OU Sites Selected for Remedial Action	2-5
       3-1                 Soil OU Sites Selected for No Further Action	3-3
       4-1                 Soil OU "Petroleum Only" Sites	4-3
       5-1                 Groundwater OU Plumes	5-5
RL/2-16-96/ES/1260005.AWS

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List of Tables.
       Table                     Title                                            Page

Table 1-1. Selected Remedial Alternatives for the Soil Operable Unit Sites
       Selected for Remedial Action  	  1-6
Table 1-2. Selected Remedial Alternatives for the Ground water Operable Unit Plumes .  .  1-7
Table 2-1. Remedial Alternatives for the Soil Operable Unit Sites Selected
              for Remedial Action  	  2-2
Table 2-2. Previous Investigations at the Soil Operable Unit Sites Selected
              for Remedial Action  	  2-7
Table 2-3. Estimated Areas and Volumes - Sediments	  .  2-8
Table 2-4. Estimated Areas and Volumes - Surface Soils	  2-8
Table 2-5. Estimated Areas and Volumes - Subsurface Soils	  2-8
Table 2-6. Site 7/11 Remedial Alternatives	2-21
Table 2-7. Site 13 Remedial Alternatives	2-22
Table 2-8. Site 15 Remedial Alternatives	2-22
Table 2-9. Site 20 Remedial Alternatives	2-22
Table 2-10.  Site 37/39/54 Remedial Alternatives	2-23
Table 2-11.  Site 56 Remedial Alternatives 	2-23
Table 2-12.  Site 57 Remedial Alternatives 	2-24
Table 2-13.  Site 59 Remedial Alternatives	 2-24
Table 2-14.  Site 60 Remedial Alternatives 	2-25
Table 2-15.  Site 62 Remedial Alternatives 	2-25
Table 2-16.  Site 65 Remedial Alternatives 	2-26
Table 2-17.  Site 69 Remedial Alternatives 	2-26
Table 2-18.  Comparative Analysis of Soil Operable Unit Remedial Alternatives	2-29
Table 2-19.  Site 7/11 Cleanup Levels  	2-33
Table 2-20.  Site 13 Cleanup Levels	2-34
Table 2-21.  Site 15 Cleanup Levels	2-36
Table 2-22.  Site 20 Cleanup Levels	2-39
Table 2-23.  Sites 37/39/54 Cleanup Levels	2-41
Table 2-24.  Site 56 Cleanup Levels	2-42
Table 2-25.  Site 57 Cleanup Level  	2-45
RL/2-16-96/ES/1260005. AWS
                                           XI

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Table 2-26.  Site 59 Cleanup Levels	2-45
Table 2-27.  Site 60 Cleanup Levels	2-46
Table 2-28.  Site 62 Cleanup Levels	2-47
Table 2-29.  Site 65 Cleanup Levels	2^9
Table 2-30.  Site 69 Cleanup Levels	2-50
Table 3-1. Previous Investigations at the No Further Action Sites  	  3-5
Table 4-1. Previous Investigations at the Soil Operable Unit "Petroleum Only" Sites ...  4-4
Table 4-2. Estimated Areas and Volumes - Subsurface Soils	  4-6
Table 5-1. Selected Remedial Alternatives for the Ground water OU Plumes	  5-3
Table 5-2. Previous Investigations at the Groundwater Operable Unit Sites  	  5-4
Table 5-3. Estimates of Volume - Groundwater	  5-7
Table 5-4. Main Base/SAC Industrial Plume Remedial Alternatives  	  5-9
Table 5-5. Site 7 Plume Remedial Alternatives    	5-10
Table 5-6. Northeast Plume Remedial Alternatives  	5-10
Table 5-7. Comparative Analysis of Groundwater Remedial Alternatives   	5-11
Table 5-8. Main Base/SAC Industrial Area Plume Cleanup Levels	5-15
Table 5-9. Site 7 Plume Cleanup Levels	5-16
Table 5-10.  Northeast Plume Cleanup Levels  	5-18
Table 6-1. Chemical-Specific TBCs for Surface Water  	  6-3
Table 6-2. Chemical-Specific ARARs and TBCs for Sediments  	  6-5
Table 6-3. Chemical-Specific TBCs for Surface Soils	  6-6
Table 6-4. Chemical-Specific TBCs for Subsurface Soils  	  6-8
Table 6-5. Chemical-Specific ARARs and TBCs for Drinking and Groundwater	  6-9
Table 6-6. Action Specific ARARs	6-13
Table 6-7. Groundwater Discharge Treatment Standards	6-36
Table 6-8. Maximum Total or Leachable Constituent Concentrations	6-43
RL/2-16-96/ES/1260005.AWS
                                         Xll

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List of Appendices
      Appendix     Title                                                    Page

      A            Administrative Record Index for Soil Operable
                    Unit Sites and Groundwater Operable Unit Plumes,
                    Mather Air Force Base, Sacramento County, California	A-1
RL/2- 16-96/ES/1260005. A WS
                                       xm

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 List of Acronyms.
 AC&W
 AFB
 AGE
 ARAR
 ASC
 AST
 ATC
 AWQC
 bis
 BTEX
 CCR
 CERCLA

 CFR
 COC
 COPC
 CVR
 CVRWQCB
 D.I.
 DCE
 DLM
 DISC
 DWR
 ESD
 FFS
 FR
 FS
 gpm
 HWCL
 IRP
JETC
JP-4
LCRS
 Aircraft Control and Warning
 Air Force Base
 Aerospace Ground Equipment
 Applicable or Relevant and Appropriate Requirement
 Additional Site Characterization
 aboveground storage tank
 Air Training Command
 Ambient Water Quality Criteria
 below land surface
 benzene, toluene, ethylbenzene, and xylenes
 California Code of Regulations
 Comprehensive Environmental Response, Compensation, and Liability
 Act of 1980
 Code of Federal Regulations
 contaminant of concern
 contaminant of potential concern
 Central Valley Region
 Central Valley Regional Water Quality Control Board
 deionized
 dichloroethene
 Designated Level Methodology
 Department of Toxic Substances Control
 Department of Water Resources
 Explanation of Significant Difference
 Focused Feasibility Study
 Federal Register
 feasibility study
 gallons per minute
 Hazardous Waste Control Law
 Installation Restoration Program
jet engine testing cell
jet propellant fuel
leachate collection and removal systems
RU10-95/ES/1260005.AWS
                                       XIV

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 List of Acronyms (Continued).
 MBRA
 MCL
 mg/kg
 mg/L
 NCP
 NPL
 OU
 OWS
 PAH
 PCB
 PCE
 POL
 POTW
 ppm
 PTU
 PVC
 RCRA
 RI
 ROD
 SAC
 SARA
 SIP
 SMAQMD
 SVE
 SWRCB
 TBC
 TCE
 TDL
 TPH
 TSCA
 UCL
 USAF
 USEPA
 Mather Baseline Risk Assessment
 maximum contaminant level
 milligrams per kilogram
 milligrams per liter
 National Contingency Plan
 National Priorities List
 operable unit
 oil/water separator
 polycyclic aromatic hydrocarbon
 polychlorinated biphenyl
 perchloroethene (tetrachloroethene)
 petroleum,  oil, and lubricant
 publicly owned treatment works
 parts per million
 post-treatment unit
 polyvinyl chloride
 Resource Conservation and Recovery Act
 remedial investigation
 Record of Decision
 Strategic Air Command
 Superfund Amendments and Reauthorization Act of 1986
 State Implementation Plan
 Sacramento Metropolitan Air Quality Management District
 soil vapor extraction
 State Water Resources Control Board
 to-be-considered
 trichloroethene
 total designated level
 total petroleum hydrocarbons
Toxic Substance Control Act
upper confidence level
United States Air Force
United States Environmental Protection Agency
RL/10-95/ES/1260005.AWS
                    XV

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 List of Acronyms (Continued).
 UST              underground storage tank
 WDR             Waste Discharge Requirement
 WET              waste extraction test
 WQG             water quality goal
 yd3                cubic yards
KL/10-95/ES/1260005.AWS                        XVI

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 1.0   Introduction
This decision document presents the selected remedial actions for the Soil Operable Unit (OU)
Sites and Groundwater OU Plumes, at the formerly active Mather Air Force Base (AFB),
Sacramento County, California. The selected remedial actions were developed in accordance
with the Comprehensive Environmental Response, Compensation, and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthorization Act of 1986
(SARA) and, to the extent practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP).  These decisions, documented herein, are based on the information
contained in the Administrative Record File for the subject sites and plumes. The
Administrative Record Index (Appendix A) identifies documents that were considered or relied
upon to make these decisions.

The purpose of this Record of Decision (ROD) is to decide the appropriate level of
remediation necessary to protect human health and the environment, and determine what
requirements are applicable or relevant and appropriate requirements (ARARs) based on the
groundwater beneficial use designation and site-specific conditions.

This ROD has been divided into seven sections which specifically address the range of selected
remedial  actions for the Soil OU sites and Groundwater OU plumes.  These seven sections
are:
             Section 1.0 - Introduction:
                    This section presents a summary of the selected remedial alternatives, as
                    well as signatures of concurrence by the United States Air Force
                    (USAF), United States Environmental Protection Agency (USEPA), and
                    the State of California.

             Section 2.0 - Soil OU Sites Selected for Remedial Action:
                    This section of the ROD documents the remedial actions selected for soil
                    sites where cleanup is warranted.

             Section 3.0 - Soil OU Sites Selected for No Further Action:
                    This section of the ROD documents the decision that no action is
                    warranted at these soil sites since conditions pose no current or potential
                    threat to human health or the environment.
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       •      Section 4.0 - Soil OU "Petroleum Only" Sites Selected for No Action Under
             CERCLA (but remain to be closed under other regulations):
                    This section of the ROD documents the decision that no action is
                    warranted under CERCLA. since CERCLA does not provide the
                    appropriate legal authority to undertake a remedial action at these soil
                    sites. The no action decision does  not constitute a finding that adequate
                    protection has been achieved at the sites.  Cleanup alternatives have been
                    developed and will be implemented under the Resource Conservation
                    and Recovery Act (RCRA) Subtitle I, other appropriate State of
                    California regulations, and the Defense Environmental Restoration
                    Program.

       •      Section 5.0 - Groundwater OU Plumes Selected for Remedial Action:
                    This section of the ROD documents the remedial actions for the
                    groundwater plumes.

       •      Section 6.0 - Listing of ARARs:
                    This section describes all federal and state ARARs required to be
                    complied with under this ROD.

       •      Section 7.0 - Responsiveness Summary:
                    This section contains comments received during the public comment
                    period and responses to these comments.


Each section is addressed in its entirety in this ROD.  The Soil OU sites  and Groundwater OU
plumes selected for remedial action (Sections 2.0 and 5.0) are the main focus of this ROD.
This ROD addresses all compliance requirements under CERCLA. Any CERCLA sites at
Mather AFB not addressed in this ROD, or previous Mather AFB RODs, will be addressed in
the Final OU ROD.


1.1    Site Background
The formerly active Mather AFB is located in the Central Valley region of northern California
hi Sacramento County, approximately ten miles east of downtown Sacramento, California and
due south of unincorporated Rancho Cordova, California, as shown on Figure 1-1.
Figure 1-1. The base is due south of U.S. Highway 50, a major highway connecting
Sacramento and South Lake Tahoe. The formerly active  base encompassed approximately
5,845  acres at the time of closure (129 acres of easements) in an unsurveyed part of Township
8 North, Ranges 6 East and 7 East. Mather AFB was constructed in 1918 and its primary
mission was as a flight training school.  The base was decommissioned under the Base Closure
and Realignment Act on September 30, 1993.
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                                                        Figure  1-1.  Site Vicinity Map

                                                               PREPARED FOR
                                                         MATHER AIR  FORCE  BASE
                                                        SACRAMENTO. CALIFORNIA
                                                                    INTERNATIONAL
                                                                    TECHNOLOGY
                                                                    CORPORATION
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Contamination exists at Soil OU sites and Groundwater OU plumes as a result of past USAF
operations conducted between 1918 and 1993.  The Soil OU is comprised of contaminated
soils associated with waste disposal pits, oil/water separators (OWS), gas stations,
underground storage tanks (USTs), fire training areas, and other miscellaneous sites.  The
Groundwater OU consists of contaminated groundwater plumes beneath and within the
immediate vicinity of the base with the exception of the Aircraft Control and Warning
(AC&W) OU plume.  The main sources of contamination at the Soil OU sites and
Groundwater OU plumes include industrial activities, equipment maintenance, fire suppression
training, and fuels storage and delivery.

Installation Restoration Program (IRP) activities at the formerly active base have been
conducted since 1982. These previous investigations  have confirmed the presence of volatile
organic compounds and other hydrocarbons at several of the IRP sites.  Based on this, the
entire base was proposed for listing on the Superfund (CERCLA) National Priorities List
(NPL) in July  1989, and was placed on the NPL on November 21, 1989. In July 1989, the
USAF, the USEPA, and the State of California signed a Federal Facility Agreement under
CERCLA Section 120 to ensure that environmental impacts from past and present operations
are thoroughly investigated  and appropriate cleanup actions are taken to protect human health,
welfare,  and the environment. The Federal Facility Agreement sets enforceable deadlines for
documents, defines roles and responsibilities of each signatory party, and provides a vehicle
for dispute resolution.  The USAF is the owner of the site, the principal responsible party, and
lead agency for conducting investigative and  cleanup activities. There have been no CERCLA
enforcement actions at the Soil OU sites or Groundwater OU plumes.

The Group 2 Sites Remedial Investigation (RI) Report [IT 1992a], the Group 3 Sites Technical
Memorandum [IT 1993a], and the Additional Field Investigation Report [IT 1994a] became
available to the public  at the Mather Environmental Management Office in 1993  and 1994.
The Groundwater OU  and Soil OU Focused Feasibility Study (FFS) Report [IT 1995a] became
available to the public  in 1995.  Each of these documents and the Proposed Plan for the
Groundwater OU Plumes and Soil OU Sites [IT  1995b] are part of the Administrative Record
File and are available for review at the following information repositories:

       •      the Environmental Management Office, Mather AFB;
       •      the Sacramento Central Library; and
       •      the Rancho Cordova Community Library.
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 Formal request for public comment on the Proposed Plan [IT 1995b] and FFS Report [IT 1995a]
 was published in the Sacramento Bee on May 1, 1995.

 The public comment period extended from May 8, 1995 through June 7, 1995, to afford the public
 a chance to comment on the Proposed Plan and the supporting RI/Feasibility Study (FS) reports.
 A public meeting was held at Mather AFB (Building 2460) on May 18, 1995.  Representatives
 from the USAF, the USEPA Region IX, the California Regional Water Quality Control Board,
 and the California Department of Toxic Substances Control (DTSC) were present at the meeting.
 Representatives from the USAF and regulatory agencies answered questions  about the Soil OU
 sites and  Groundwater  OU plumes and  the remedial alternatives under  consideration.   The
 Responsiveness Summary, Section 7.0 of this ROD, contains comments received during the public
 comment period and responses to these  comments.

 An informal dispute was  invoked concerning the  cleanup of VOCs  in the vadose  zone.   The
 parties to the FFA  resolved the dispute as reflected in Sections 2.2.9.1 (Site 7/11), 2.2.9.5 (Site
 37/39/54), and 2.2.9.7 (Site 57).  The resolutions are negotiated solutions that are not generally
 applicable to other sites  except those at  this facility.

 The USAF, the USEPA  Region IX, and  the State of California concur with the selected remedial
 actions (which are presented in Tables 1-1 and 1-2 and detailed in Sections 1.1.1 and 1.1.2) and
 statutory determinations for each of the separate sections of this ROD.  Concurrence by the parties
 is indicated by the signatures in Section 1.2 of this ROD.

 1.1.1  Soil OU Sites Selected for No Further Action
 Cleanup options were not developed for sites which were previously clean-closed or recommended
 for clean-closure by  Sacramento  County  (i.e.,  USTs  already  removed)  or for which no
 contaminants of concern  (COCs) were identified. Based on the human health risk assessment, all
the sites have cancer risks within  or below the acceptable  range of  1 x  10^ to 1 x 10"6 and
non-cancer risks less than a hazard index of 1.0 in their current state. Therefore, cleanup or
further investigative activities is not warranted. These no further action sites include:  Sites 9,
 10, 14, 16, 21, 22, 24, 26, 27, 28, 31,  33, 38, 40, 41, 42, 43, 44, 45, 46, 48, 49,  51, 52, 53,
55, 58, 61, 63, 64, 66, A, C, E, F, G, H, and I.
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          Table 1-1.  Selected Remedial Alternatives for the Soil Operable Unit Sites
                                    Selected for Remedial Action
       Selected
      Remedial
     Alternative
                                  Description
         7.3*
 Filling in the depression at Site 7 to grade with on-base soils; hi situ bioremediation
 and possibly soil vapor extraction (SVE) of the contaminated shallow and deep soils at
 Sites 7 and 11; installation of a landfill cover at Site 7 as appropriate, and groundwater
 monitoring if contamination remains at the site that threatens groundwater quality.
         13.3
Excavation and transportation of the contaminated ditch sediments and surface soils to
the on-base ex situ bioremediation facility for treatment and on-base disposal as
appropriate after treatment and groundwater monitoring if contamination remains at the
site that threatens groundwater quality.	
         15.3
Excavation and transportation of the contaminated ditch sediments to the on-base
ex situ bioremediation facility for treatment and on-base disposal as appropriate after
treatment and surface water monitoring if contamination remains at the site that
threatens surface water quality.	
         20.2
Excavation and transportation of the contaminated shallow subsurface soils to the on-
base ex situ bioremediation facility for treatment and on-base disposal as appropriate
after treatment and groundwater monitoring if contamination remains at the site that
threatens groundwater quality.	
        37.2**
Excavation and transportation of the contaminated surface soils to the on-base ex situ
bioremediation facility for treatment and on-base disposal as appropriate after
treatment; in situ bioremediation and possibly SVE of the contaminated shallow and
deep subsurface soils at Sites 37, 39, and 54; and groundwater monitoring if
contamination remains at the site that threatens groundwater quality.	
         56.3
Excavation and transportation of the contaminated surface soils and shallow subsurface
soils to the on-base ex situ bioremediation facility for treatment and on-base disposal as
appropriate after treatment and groundwater monitoring if contamination remains at the
site that threatens groundwater quality.	
         57.3
SVE of the contaminated shallow and deep subsurface soils and groundwater
monitoring if contamination remains at the site that threatens groundwater quality.
         59.2
Excavation and transportation of the contaminated shallow subsurface soils to the on-
base ex situ bioremediation facility for treatment and on-base disposal as appropriate
after treatment and groundwater monitoring if contamination remains at the site that
threatens groundwater quality.	
         60.2
Excavation and transportation of the contaminated shallow subsurface soils to the on-
base ex situ bioremediation facility for treatment and on-base disposal as appropriate
after treatment and groundwater monitoring if contamination remains at the site that
threatens groundwater quality.	
         62.3
Excavation and transportation of the contaminated surface soils and shallow subsurface
soils to the ex situ bioremediation facility for treatment and on-base disposal as
appropriate after treatment and groundwater monitoring if contamination remains at the
sites that threatens groundwater quality.	
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            Table 1-1. Selected Remedial Alternatives for the Soil Operable Unit
                        Sites Selected for Remedial Action (Continued)
      Selected
     Remedial
    Alternative
                                Description
         65.3
 Excavation and transportation of the contaminated surface soils to an approved off-base
 facility for disposal; excavation and transportation of the contaminated shallow
 subsurface soils to the on-base ex situ bioremediation facility for treatment and on-base
 disposal as appropriate after treatment and groundwater monitoring if contamination
 remains at the site that threatens groundwater quality.       	
        69.2
 Excavation and transportation of the contaminated sediments and surface soils for on-
 base disposal as appropriate and surface water monitoring as appropriate if
 contamination remains at the site that threatens surface water quality.	
        This remedial alternative applies to Sites 7/11.
        This remedial alternative applies to Sites 37/39/54.
  Table 1-2.  Selected Remedial Alternatives for the Groundwater Operable Unit Plumes
     Selected
     Remedial
    Alternative
                                Description
    Main/SAC.2
Extraction of the contaminated groundwater with treatment by air stripping and injection
of the treated groundwater back into the aquifer (alternative means of groundwater
discharge may be implemented) and groundwater monitoring. In addition, carbon will
be utilized to adsorb and treat the off-gas from the air stripper, if appropriate.	
       SP7.2
Extraction of the contaminated groundwater with treatment by air stripping and injection
of the treated groundwater back into the aquifer (alternative means of groundwater
discharge may be implemented) and groundwater monitoring. In addition, carbon will
be utilized to adsorb and treat the off-gas from the air stripper, if appropriate.	
      Selected
     Alternative
Long-Term Groundwater Monitoring and Land-Use Restrictions
1.1.2 Petroleum Only Sites Selected for No Further Action Under CERCLA (but remain
       to be closed under other regulations)


A "no action" decision is the selected remedy for the "petroleum only" sites based on the lack
of statutory authority under CERCLA.  The "petroleum only" sites include:  Sites 19, 29/B,
32, 34, 35, and 36.  Additionally,  based on the human health risk assessment, all cancer risks
are within or below the acceptable range of 1 x 10^ to 1 x 10"6 and a non-cancer risk less than
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a hazard index of 1.0 in their current state.  However, these sites do not meet criteria for
closure under RCRA Subtitle I and other applicable State of California regulations.
Regulatory oversight will be provided by CVRWQCB and possibly Sacramento County.
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 1.2   Signatures
                                                                             /
Alan K. Olsen                                                     /       Date
Director,  Air Force Base Conversion Agency
U.S. Air Force
Julie Anderson                                                             Date
Director, Federal Facilities Cleanup Office, Region IX
U.S. Environmental Protection Agency
                 •  //
Anthony J. LanQis, CP. E.                                                     Date
Chief, Northern California Operations
Office of Military Facilities
Department of Toxic Substances Control
California Environmental Protection Agency
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2.0  Soil Operable Unit Sites Selected for Remedial Action

2.1    Declaration for the Soil Operable Unit Sites Selected for Remedial Action

                         Statutory Preference for Treatment as a
                               Principal Element is Met
                  and a Five-year Review is Required at those Soil OU
                   Sites Selected for Remedial Action Under CERCLA

2.7. 7  Site Name and Location
Soil OU Sites (IRP Sites) Selected for Remedial Action
Mather AFB (a NPL Site)
Sacramento County, California

2. 7.2  Statement of Basis and Purpose
The Soil OU sites were investigated under the Mather IRP and are described and evaluated in
the RI/FS documents. This decision document presents the selected remedial actions for the
Soil OU sites for which remedial action is warranted at the formerly active Mather AFB.
These sites include: Sites 7/11 - "7100 Area" Disposal Site/Existing Pure Protection Training
Area, Site 13 - Drainage Ditch Number 1, Site 15 - Drainage Ditch Number 3, Site 20 -
Sewage Treatment Plant, Sites 37/39/54 - Building 3389/Hazardous Waste  Control Storage
Facility, Site 56 - OWS 2989, Site 57 - OWS 7019, Site 59 - OWS 4251, Site 60 - OWS 6900,
Site 62 - Jet Engine Test Cell (Facility 7099) and OWS 7110, Site 65 - OWS  6910, and Site 69
- Open Burn/Open Detonation Area.  These remedial actions were chosen in accordance with
CERCLA, as amended by SARA, and to the extent practicable, the NCP. These decisions are
based on the Administrative Record File for these sites.

The USEPA Region IX and the State of California concur with the selection of remedial
alternatives for each of the Soil OU sites.

2.7.3  Assessment of the Sites
Contamination exists at these Soil OU sites as a result of past US AF operations conducted
between 1918 and 1993.
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Actual or threatened releases of hazardous substances from these sites, if not addressed by
implementing the response actions selected in this section of the ROD, may present an
imminent and substantial endangerment to human health, welfare, or the environment.


2.1.4 Description of the Selected Remedy
This section of the ROD  addresses remedies related to contamination of the soils at Sites 7/11,
13,  15, 20, 37/39/54, 56, 57, 59, 60, 62, 65, and 69.


Based on the human health risk assessment, all cancer risks  are within or below the acceptable
range of 1 x 10"4 to 1 x 10"6 and all non-cancer risks have a hazard index of less than 1.0 in
their current state,  except for Sites 56,  62, and 69 which have an estimated current and future
cancer risk greater than 1 x 10^.  In addition, an ecological  risk exists at Sites 13,  15, 20, 62,
and 69.  The selected remedies at the Soil OU sites will be instituted to reduce risk to human
health, and/or reduce the risk to ecological receptors, and/or for the protection of
groundwater/surface water quality.


Table 2-1 provides the major components of the selected remedy for each of the Soil OU sites.
        Table 2-1.  Remedial Alternatives for the Soil Operable Unit Sites Selected
                                     for Remedial Action
     Selected
    Remedial
   Alternative
                                Description
       7.3*
Filling the Site 7 depression to grade with on-base soils; in situ bioremediation and
possibly soil vapor extraction (SVE) of the contaminated shallow and deep soils at Sites 7
and 11; installation of a landfill cover at Site 7 as appropriate, and groundwater
monitoring if contamination remains at the site that threatens groundwater quality.	
       13.3
Excavation and transportation of the contaminated ditch sediments and surface soils to the
on-base ex situ bioremediation facility for treatment and on-base disposal as appropriate
after treatment and groundwater monitoring if contamination remains at the site that
threatens groundwater quality.	
       15.3
Excavation and transportation of the contaminated ditch sediments to the on-base ex situ
bioremediation facility for treatment and on-base disposal as appropriate after treatment
and surface water monitoring if contamination remains at the site that threatens surface
water quality.	 	    	
      20.2**
Excavation and transportation of the contaminated shallow subsurface soils to the on-base
ex situ bioremediation facility for treatment and on-base disposal as appropriate after
treatment and groundwater monitoring if contamination remains at the site that threatens
groundwater quality.
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         Table 2-1.  Remedial Alternatives for the Soil Operable Unit Sites Selected
                                 for Remedial Action (Continued)
     Selected
    Remedial
   Alternative
                                               Description
      37.2***
            Excavation and transportation of the contaminated surface soils to the on-base ex situ
            bioremediation facility for treatment and on-base disposal as appropriate after treatment;
            in situ bioremediation and possibly SVE of the contaminated shallow and deep subsurface
            soils at Sites 37, 39, and 54; and groundwater monitoring if contamination remains at the
            site that threatens groundwater quality.    		
        56.3
            Excavation and transportation of the contaminated surface soils and shallow subsurface
            soils to the on-base ex situ bioremediation facility for treatment and on-base disposal as
            appropriate after treatment and groundwater monitoring if contamination remains at the
            site that threatens groundwater quality .	
        57.3
            Soil vapor extraction of the contaminated shallow and deep subsurface soils and
            groundwater monitoring if contamination remains at the site that threatens groundwater
            quality.	
       59.2
            Excavation and transportation of the contaminated shallow subsurface soils to the on-base
            ex situ bioremediation facility for treatment and on-base disposal as appropriate after
            treatment and groundwater monitoring if contamination remains at the site , that threatens
            groundwater quality.	
        60.2
            Excavation and transportation of the contaminated shallow subsurface soils to the on-base
            ex situ bioremediation facility for treatment and on-base disposal as appropriate after
            treatment and groundwater monitoring if contamination remains at the site , that threatens
            groundwater quality.
       62.3
            Excavation and transportation of the contaminated surface soils and shallow subsurface
            soils to the ex situ bioremediation facility for treatment and on-base disposal as
            appropriate after treatment and groundwater monitoring if contamination remains at the
            sites that threatens groundwater quality.	
       65.3
            Excavation and transportation of the contaminated surface soils to an approved off-base
            facility for disposal; excavation and transportation of the contaminated shallow subsurface
            soils to the on-base ex situ bioremediation facility for treatment and on-base disposal as
            appropriate after treatment and groundwater monitoring if contamination remains at the
            site that threatens groundwater quality.	
      69.2**
            Excavation and transportation of the contaminated sediments and surface soils for on-base
            disposal as appropriate and surface water monitoring as appropriate if contamination
            remains at the site that threatens surface water quality.
*
**
***
This remedial alternative applies to Sites 7/11.
Soils do not overlay a contaminated groundwater plume , Main Base Groundwater Plume, Strategic Air
Command Industrial Groundwater Plume, Site 7 Groundwater Plume, Northeast Groundwater Plume).
This remedial alternative applies to Sites 37/39/54.
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2. 7.5 Statutory Determinations
The selected remedies satisfy the statutory requirements of Section 121(b) of CERCLA, as
amended by SARA, in that the following mandates are attained:

       •     the selected remedies are protective of human health and the environment;

       •     the selected remedies comply with federal and state requirements that are legally
             applicable or relevant and appropriate to the remedial actions;

       •     the selected remedies are cost-effective; and

       •     the selected remedies utilize permanent solutions and alternative treatment
             technologies, or resource recovery technologies, to the maximum extent
             practicable.

These remedies will result in hazardous substances remaining at some sites (i.e., Sites 56, 62,
and 69) above levels that threaten human health or the environment during the remedial action.
In addition, any of the remedial actions may result in contaminants remaining at the site above
levels that allow for unlimited use.  Therefore, a review will be conducted no less often than
every five years after commencement of the selected remedial actions to ensure that the
remedies continue to provide adequate protection of human health and the environment, and
protect groundwater quality for its beneficial uses.

2.2   Decision Summary for So/I OU Sites Selected for Remedial Action

2.2.1  Site Names,  Location, and Description
The Soil OU sites selected for remedial action at the formerly active Mather AFB are
presented in Figure 2-1 and include:  Site 7/11 - "7100 Area" Disposal Site/Existing Fire
Protection Training Area, Site 13 - Drainage Ditch Number 1, Site 15 - Drainage Ditch
Number 3, Site 20 - Sewage Treatment Plant, Site 37/39/54 - Building 3389/Hazardous Waste
Central Storage Facility, Site 56 - OWS 2989, Site 57 - OWS 7019, Site 59  - OWS 4251, Site
60 - OWS 6900, Site 62 - Jet Engine Test Cell (Facility 7099) and OWS 7110,  Site  65  - OWS
6910, and Site 69 - Open Burn/Open Detonation Area. More detailed site maps are presented
hi the Groundwater OU and Soil OU FFS Report [IT 1995a].

2.2.2  Site History and Enforcement Activities
Previous investigations have been conducted at the Soil OU sites selected for remedial action
as part of the USAF IRP and are summarized hi Table 2-2.
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                                                                   Sunrise Btvd.
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2.2.3 Highlights of Community Participation
The public participation requirement of CERCLA Sections 113(k)(2)(B)(I-v) and 117 were met
through a public comment period (held May 8 through June 7, 1995) and public meeting (held
May 18, 1995) to address the Proposed Plan and content of supporting RI/FS documents.

2.2.4 Scope and Role of Response Action
Environmental studies were initiated by the USAF in 1982 to investigate soil contamination
resulting from past operations at the base.  The USEPA placed Mather AFB on the NPL (or
"Superfund" list) in 1989.  In order to organize cleanup efforts, the base was divided into five
OUs.  This has allowed sites  with similar sources of contamination and site conditions to be
grouped together. The following section of this ROD discusses the cleanup options for one of
the OUs, the Soil OU.  Section 5.0 of this ROD presents cleanup options for the Groundwater
OU. Previous RODs presented cleanup options for the AC&W OU  [IT 1993e] (where
contaminated groundwater is  now being extracted and treated by air  stripping) and the Landfill
OU [IT 1994b].  Any sites not addressed in the ROD will be addressed in an upcoming Final
Basewide OU ROD.

2.2.5 Summary of Site Characteristics
Contamination exists at the Soil OU sites as a result of past USAF operations conducted
between 1918 and 1993. The Soil OU is comprised of contaminated soils  associated with
waste disposal pits, OWSs, gas stations,  USTs, fire training areas, and other miscellaneous
sites.  Any impact to the groundwater underlying these sites is addressed in the Groundwater
OU section of this ROD (Section 5.0).

Previous RIs have been conducted at Soil OU sites as part of the USAF IRP.  A brief
description of each of the Soil OU sites recommended for remedial action, including
summaries of hazardous material releases and the nature and extent of contamination is
provided in the following sections (contamination area and volume estimates for the sediments,
surface soils, and subsurface  soils are presented in Tables 2-3 through 2-5).
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         Table 2-2.  Previous Investigations at the Soil Operable Unit Sites Selected
                                       for Remedial Action
Site Number
7/11
13
15
20
37/39/54
56
57
59
60
62
65
69
Applicable Investigation
1, 2, 4, 5, 6, 7, 8, 9, 10, 13, 14, 15
1,3,5,7,9, 10, 11, 13, 14, 15
1,2,4,5,7, 9, 10, 11, 13, 14, 15
1, 3, 5, 7, 9, 10, 14, 15
7, 11, 12, 13, 14, 15
5,7, 11, 14, 15
7, 11, 14, 15
7, 11, 14, 15
11, 14, 15
11, 13, 14, 15
7, 11, 14, 15
7, 11, 13, 14, 15
1.      Installation Restoration Program (IRP) Records Search for Mather Air Force Base, Phase I [CH2M-Hill,
        Inc. 1982];
2.      IRP Phase II, Stage 1 Investigation [Weston 1986];
3.      IRP Phase II, Stage 2 Investigation [AeroVironment 1987];
4.      IRP Phase II, Stage 3 Investigation [AeroVironment 1988];
5.      Well Redevelopment and Sampling Plan [IT 1988a];
6.      Solid Waste Assessment Test Report [IT 1993b];
7.      Quarterly Routine Groundwater Sampling [IT 1995c] and [EA 1990a-c];
8.      Landfill Gas Testing Report [IT 1988b];
9.      Site Inspection Report [IT 1990a];
10.     Group 2 Sites Remedial Investigation Report [IT 1992a];
11.     Group 3 Sites Technical Memorandum [IT 1993a];
12.     Underground Storage Tank Closure Reports [IT 1990b and IT 1993c-d];
13.     Soil Operable Unit (OU) and Groundwater OU Additional Field Investigation Report [IT 1994a];
14.     Groundwater OU and Soil OU FFS Report [IT 1995a]; and
15.     Mather Baseline Risk Assessment Report [IT 1995d].
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                      Table 2-3.  Estimated Areas and Volumes - Sediments
Site Number
13
15
69
Contaminant of Concern
4,7
2,4,5,6,7
1
Area (square feet)
2.4 x 10"
5.8 x 104
l.lx 103
Volume" (cubic feet)
4.8 x 104
1.2 xlO5
2.2 x 103
a = two foot depth assumed for sediment contamination
Contaminant of Concern = 1-Dioxins and Furans, 2-Polycyclic aromatic hydrocarbons, 4-Metals, 5-Total petroleum hydrocarbons,
6-Polychlorinated biphenyls, and 7-Pesticides.
                    Table 2-4.  Estimated Areas and Volumes - Surface Soils
Site Number
11
13
20
39
56
62
65
69
Contaminant of Concern
1
3,4,5
4
5
2,3,4,5
2,4,5
3,4,5
1
Area (square feet)
1.9xl05
l.lxlO3
5.4 x 104
3.0 x 103
1.5 x 103
5.4 x 103
2.2 x 103
1.2x 10s
Volume" (cubic feet)
3.8x 105
2.2 x 103
1.1 x 105
6.0 x 103
2.9 x 103
1.1 x 104
4.3 x 103
2.3 x 105
a = two foot depth assumed for calculating volumes
Contaminant of Concern = 1-Dioxins and Furans, 2-Polycyclic aromatic hydrocarbons, 3-Oil and grease, 4-Metals, and 5-TotaI petroleum
hydrocarbons.


                  Table 2-5.  Estimated Areas and Volumes - Subsurface Soils
Site Number
r
20
37
39
Contaminant of Concern
TPH-D
TPH-G
Thallium
TPH-D
Benzene
Oil and Grease
TPH-D
TPH-G
Benzene
TPH-D
TPH-G
Area (square feet)
1.9 x 105
2.0 x 105
1.3 x 103
1.2x 103
(a)
3.1 x 102
3.1 x 102
5.1 xlO3
6.0 x 10"
(b)
4.1 xlO4
Volume (cubic feet)
2.9 x 106
3.0 x 106
6.0 x 104
1.5x 104
(a)
3.5 x 103
3.5 x 103
1.3 x 10s
1.5 xlO6
(b)
1.7 xlO6
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Site Number
54
56
57
59
60
62
65
Contaminant of Concern
Benzene
TPH-G
Oil and Grease
Lead
TPH-D
TPH-G
Trichloroethene
TPH-D
TPH-G
TPH-G
TPH-D
TPH-D
TPH-G
Area (square feet)
(a)
8.0 x 102
©
©
8.9 x 102
8.8 x 102
4.9 x 104
6.7 x 102
1.6x 103
6.6 x 102
2.3 x 102
2.0 x 102
1.6x 103
Volume (cubic feet)
(a)
2.0 x 104
©
©
1.3 x 104
1.3x10"
2.6 x 106
1.4x 104
3.2 x 104
9.9 x 103
2.5 x 103
3.1xl03
2.4 x 104
* Site 11 contains some contamination adjacent to Site 7 that will be remediated under the Site 7 alternative. The area and volume estimates
  will likely increase during remedial design.
(a) = included with the area, volume, and mass of Site 39
(b) = diesel detections are sporadic and coincide with higher concentration gasoline detections
0 = three detections above background, detections coincide with gasoline and diesel detections
TPH-D = Total petroleum hydrocarbons as diesel
TPH-G = Total petroleum hydrocarbons as gasoline

2.2.5. 1      Site 7/11 - "7100 Area" Disposal Site/Existing Fire Protection  Training
               Area
For purposes of remediation, Sites 7 and 11 were grouped together based on proximity and
common contaminants.
Site 7 is located in the southwest corner of the base and has been used as a disposal area since
1953. The site was originally a gravel borrow pit excavated to a depth of approximately
40 feet.  From  1953 until approximately 1966, this site was a major disposal area for
petroleum, oil,  and lubricant (POL) wastes.  Other waste reportedly disposed of includes
empty drums, sludge from plating-shop dip tanks, absorbent sand used for cleaning oil and
solvent spills, paint chips, waste paint and thinners, and  at least one load of transformer oil
that may have contained polychlorinated biphenyls (PCBs).

Site 11 is located south of the Sewage Treatment Plant and adjacent to Site 7.  Fire training
exercises were conducted there from  1958 until 1993.  Two jet propellant fuel (JP-4)
aboveground storage  tanks (ASTs) were installed in 1974; these have since been replaced.
The facility was upgraded to include a lined burn pit in the mid-1980's.
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Contamination at Site 7 has been identified in the shallow and deep subsurface soils. The
COCs identified at the site are diesel, gasoline, lead, and thallium. Contamination at Site 11
has been identified hi the surface soils.  The COCs identified at Site 11 are dioxins and furans.
These are not selected for remediation, but will be excavated as part of the Site 7 cleanup, and
incorporated into the foundation for the cap at Site 7.  This decision is based on dioxin
detections below the cleanup standards set in response to regulatory comments on the risk
assessment.  Site 7 is  the apparent historic source for ground water contamination (see Section
5.2.5.2); although there have been no significant detections of chlorinated solvents in the Site
7/11 soils, soil gas will be monitored during remedial design per Section 2.2.9.1.  The bases
for cleanup are compliance with ARARs for waste disposal sites, mitigating a likely source of
groundwater contamination, and protection of groundwater for its beneficial uses.

2.2.5.2      Site 13 - Drainage Ditch Number 1
Site 13 is located just north of the northeast end of runways,  and is part of the surface  drainage
system for the base.  Oil/water separator 3990 was installed  at the site in 1968, and received
runoff from two aircraft wash pads via area drains and piping.  Prior to installation of  OWS
3990, the waste may have been poured directly into the drainage ditch and/or a nearby shallow
excavation.

Contamination at the site has been identified in the surface water, sediments, and surface soils.
The COCs identified at the site are metals, pesticides, polycyclic aromatic hydrocarbons
(PAHs), diesel, and oil and grease. The basis  for cleanup  is  protection of ecological receptors
and groundwater quality, and surface water quality.

2.2.5.3      Site 15 - Drainage Ditch No. 3
Site 15 covers the portion  of the West Ditch that trends north-south along the western
boundary of the base,  1,500 feet east of Happy Lane Boulevard and directly west of the former
Strategic Air Command (SAC) portion of the base.  The ditch is unlined and received surface
runoff from the Main  Base area, including the Air Training Command (ATC) and former SAC
shops. Until about 1971, floor drains in the shops were connected to the storm sewer system
which emptied into the West Ditch.

Oil/water separator 7039 is located at the southern end of the West Ditch and was installed hi
1967.  Waste oils and solvents were reportedly dumped directly into the separator system and
occasionally overflowed into the West Ditch. Prior  to construction of OWS 7039, waste oil
was reportedly dumped into a below ground metal container  or tank near the present location
of the OWS.
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Contamination at the site has been identified hi the surface waters and sediments.  The COCs
identified at the site are metals, pesticides, PAHs, PCBs, gasoline, diesel, and oil and grease.
The basis for cleanup is protection of ecological receptors and surface water quality.

2.2.5.4      Site 20 -  Sewage Treatment Plant
Site 20 is located in the southwest portion of the base.  This site contained a 150-gallon diesel
UST that was excavated and removed hi 1985. An estimated 700 gallons of diesel fuel leaked
from the tank. Some sludge from the former waste water treatment at Site 20 remains  on the
site adjacent to the sludge drying beds, not associated with the diesel spill location. This
sludge was planned for an expedited removal action hi  1995, according to a Removal Action
Memorandum dated September 1994. Recent sampling determined that the  sludge contains
hazardous waste and non-designated waste, and current plans are to dispose of any non-
hazardous and non-designated sludge into Site 4 during landfill closure.  This removal  was
delayed until 1996 because of budgetary constraints.  Additional 'new' sludge was removed
from digester tanks at Site 20 during demolition of these tanks in 1995,  This 'new' sludge has
remained isolated on site  while it has been characterized for disposal; portions have been
found to contain hazardous concentrations of mercury (as is reported hi the Draft Additional
Site Characterization Remedial Investigation Report,  IT Corp., 1996). This sludge will be
disposed of as hazardous  waste, or stabilized as planned for lead-bearing sludge hi the  1994
Removal Action Memorandum (IT, 1994c) to  render it non-hazardous and non-designated for
on-base disposal. In response to the detection of mercury in the 'new'  sludge, a cleanup level
for mercury at Site 20 has been added to this ROD, and will apply to all sludge and shallow
soils.

The COCs  identified at the sludge site are metals, while the only COC identified at the UST
site is diesel. The bases for cleanup are protection of ecological receptors and groundwater
quality.

2.2.5.5      Site 37/39/54 - Building 3389/Hazardous Waste Centra/ Storage
For purposes of remediation, Sites 37, 39, and 54 were grouped together based on proximity
and common contaminants.

Site 37 is located in the northwest portion of the base and is associated with five steel USTs at
Building 3389.  Four of the USTs had a capacity of 12,000 gallons and stored diesel fuel, lube
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oil, and waste oil. The fifth UST had a capacity of 550 gallons and stored kerosene and
solvents.

Site 39 operated from 1988 to 1993 as a hazardous waste storage facility permitted under the
RCRA. Site 39 is a fenced compound located in the Main Base area consisting of a
gravel-covered storage yard that contains several concrete pads and buildings.  A variety of
hazardous wastes were stored at this site.  The site contained eight 25,000 gallon USTs used to
store waste fuels and aviation gasoline, as well as one waste oil and one waste jet fuel AST.
The USTs and ASTs were removed in 1993.

Site 54 is a RCRA facility and was a 90-day holding yard comprised of a large, fenced,
asphalt-paved yard. The asphalt-paved yard is extensively cracked, and sealant applied to the
cracks has eroded in many places.  Bowsers and drums of waste hydraulic fluids, PD-680 (a
commercial variety of Stoddard solvent), and Citrikleen (a petroleum-based solvent that
contains no chlorinated or aromatic solvents) were stored at the site at least since 1982.

Contamination at the combined sites has been identified in the surface  soils, shallow
subsurface soils, and deep subsurface soils.  The COCs identified at the site are benzene,
toluene, ethylbenzene, and xylenes (BTEX), diesel, gasoline, lead, and oil and grease.  In
addition, chlorinated solvents were detected at the combined Site 37/39/54 during the
Additional Site Characterization (IT Corp., 1996).  These contaminants will be evaluated in
the feasibility study for the Final Operable Unit, and incorporated as appropriate in the
remedial action for these sites as described in Section 2.2.9.5.  The basis  for cleanup is
protection of groundwater quality.
2.2.5.6     Site 56 - Oil/Water Separator 2989
Site 56 consists of OWS 2989 located in the eastern portion of the Main Base and two former
OWS facilities. Oil/water separator 2989 was used to receive wastewater generated at the Old
Motor Pool washrack, which were treated and discharged to the sanitary sewer system.  The
following materials were reportedly contained in the wastewater: fuels, oil and grease,
antifreeze, and possibly cleaning fluids.

Contamination has been identified in  the surface soils and shallow subsurface soils. The COCs
identified at the site are diesel, gasoline, metals, PAHs, and oil and grease.  A current cancer
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risk to humans (3.3 x 10"4) and a potential future cancer risk to humans (8.0 x 10"4 ) have been
identified.  The basis for cleanup is protection of human health and groundwater quality.
2.2.5.7      Site 57 - Oil/Water Separator 7019
Site 57 consists of OWS 7019 and is located in the central portion of the SAC area.  This
OWS was used to separate oils, fuels,  hydraulic fluids, and PD-680 from the Aerospace
Ground Equipment (AGE) Shop washwaters, and discharge the waters to the sanitary sewer
system.

Contamination at the site has been identified in the shallow subsurface soils. The only COC
identified at the site is trichloroethene  (TCE).  The basis for cleanup is protection of
groundwater quality.

2.2.5.8      Site 59 -  O/7/Water Separator 4251
Site 59 consists of OWS 4251 and is located in the southern portion of the Main Base at the
ATC washrack, approximately ten feet south of Building 4252. Oil/water separator 4251 was
constructed in 1969 and received waste water generated from the ATC washrack.  The
wastewater reportedly contained fuels, oil and grease, hydraulic fluid, and antifreeze.

Contamination at the site has been identified in the shallow subsurface soils. The COCs
identified at the site are diesel and gasoline. The basis for cleanup is protection of
groundwater quality.

2.2.5.9      Site 60 - Oil/Water Separator 6900
Site 60 consists of OWS 6900 which is located in the SAC area and supported Building 7005.
Building 7005 was an aircraft maintenance hanger used for aircraft fuel-system maintenance.
A large floor (trench) drain within the  hanger was used to collect fuel that emptied from an
aircraft, which then emptied into underground vaults immediately outside the building.  A
conduit in the bottom of the vault led to the OWS.  It is reported that TCE, perchloroethene
(tetrachloroethene) (PCE), methyl ethyl ketone,  and other solvents were used in Building
7005.

Contamination at the site has been identified in the shallow subsurface soils. The COCs at the
site are gasoline and xylenes.  The basis for cleanup  is protection of groundwater quality.
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 2.2.5.10    Site 62 - OWS 7110 and Jet Engine Test Cell
 Site 62 is located in the southwest portion of the base and consists of an abandoned Jet Engine
 Testing Cell (JETC) and adjoining OWS 7110, built in 1961. The JETC consisted of asphalt
 and concrete pads, Building 7098,  a groundwater production well,  and a water storage and
 treatment system.  The site was used to test the operation of jet engines.  Oils, fuels,  and
 solvents may have been used at the site.  Runoff from the JETC drained onto the surrounding
 soils. The OWS drained into a ditch running west near Building 7099.

 Contamination at the site has been  identified in the surface soils and shallow subsurface soils.
 The COCs identified at the site are diesel, metals, and PAHs.  A future cancer risk to humans
 (1.5 x 10"4) has been identified. The basis for cleanup is protection of human health,
 ecological receptors, and groundwater quality.
2.2.5.11    Site 65 Oil/Water Separator 6910
Site 65 consists of OWS 6910 and is located in the north section of the SAC area at the old
AGE Shop, approximately 35 feet northeast of Building 7009. Oil/water separator 6910 was
constructed in the mid-1960s and received wastewater containing fuels, oils, hydraulic fluids,
and antifreeze generated from Building 7009.  Effluent lines from OWS 6910 were reportedly
connected to the sanitary sewer system in 1972.

Contamination at the site has been identified in the surface soils and shallow subsurface soils.
The COCs identified at the site are chromium, diesel, gasoline, lead, and oil and grease.  The
basis for cleanup is protection of groundwater quality.
2.2.5. 72    Site 69 - Open Burn Detonation Area
Site 69 is an excavated area in the southeastern portion of the base, reportedly used for
destruction of unwanted small ordnance, classified aircraft parts, and other materials. At the
south end is a burn pit approximately four feet deep and ten feet in diameter. The excavation
is unpaved and unlined, and drains southwest to join an unnamed ephemeral tributary.  At the
northern end of the site are two small bunkers,  a personnel bunker and a popping furnace,
which were in use since the 1950s until 1993.
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Contamination at the site has been identified in the surface water, sediments, and surface soils.
The COCs identified at the site are metals and dioxins and furans.  A potential future cancer
risk to humans has been identified (1.1 x 10"*). The basis for cleanup is protection of human
health, ecological receptors, and surface water quality.
2.2.6 Summary of Site Risks
Remedial investigation activities at Mather AFB included fate and transport modeling and a
baseline risk assessment (e.g., Mather Baseline Risk Assessment [MBRA]) [IT 1995d].  The
data collected and utilized in the RIs and FFS were of USEPA quality Level ffl, IV, or V, or
equivalent [USEPA 1987].  Formal data validation of the RI- and FFS-generated data was
performed to ensure that data were of the quality commensurate with their intended use.

Although a majority of the Soil OU sites are currently controlled by the USAF, Mather AFB
was decommissioned on September 30, 1993.  Future land use is either residential or
industrial, depending on the individual site. The following sections describe the criteria used
to screen contaminants of potential concern (COPCs).
2.2.6.1     Human Health Risks
Analytes detected in the course of the RI activities (e.g., COPCs) at Mather AFB were
subjected to a multi-step screening process to determine COCs.  This screening process is
presented in the following sections.  The following steps were employed in the COC
determination process for the Soil OU sites.

       •     initial screening methods prescribed by USEPA guidance;
       •     comparison to background;
       •     comparison to ARARs;
       •     comparison to analytical method quantitation limit;
       •     evaluation of operational history (i.e., process knowledge); and
       •     evaluation of estimated risk to human and ecological receptors.
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2.2.6.1.1    Initial Screening
Remedial investigation data collected at the Soil OU sites were used to identify the initial
COPCs.  The list of initial COPCs was reduced using the following methods as prescribed by
USEPA guidance [USEPA 1989a]:

       •       Quality Control Blank Contamination - As part of the data validation process, a
              chemical was not considered further if the maximum sample concentration did
              not exceed ten times the highest blank for all common laboratory contaminants
              (2-butanone, acetone, methylene chloride, phthalates, and toluene) or five times
              the highest blank for other chemicals. This screening action reduced the
              inclusion of chemicals that are most likely sampling or analytical artifacts.

       •       Frequency of Detection - Chemicals were eliminated if they were detected in
              five percent or less of the samples for a site. Infrequently detected chemicals
              may be artifacts of sampling, analytical, or other problems.

       •       Essential Nutrients - Calcium, carbonates, iron, magnesium, phosphorus,
              potassium, sodium, and sulfates are essential nutrients.  These constituents are
              generally toxic only at very high doses  and were eliminated because they were
              detected at levels below toxic concentrations.

All analytes which passed this initial screening, and associated chemical results were compiled
on a site-specific basis to calculate the 95 percent upper confidence limit (UCL) on the mean
concentration for each chemical.  The 95 percent UCL for each COPC was used during
subsequent steps in the COC determination process. The results of the initial screening and
compilation are presented in the Group 2 Sites RI [IT  1992a] and the MBRA [IT  1995d].

2.2.6.1.2    Comparison to Background
A comparison of COPC concentrations to Mather AFB background concentrations was
performed to determine if detections in environmental samples were due to naturally occurring
constituents.  This comparison utilized data from the "Background Inorganic Soils for Mather
Air Force Base" report [IT 1993f].

2.2.6.1.2.1  Surf ace Water
For inorganics (only), deionized (D.I.) water waste extraction tests (WET) were performed on
background surface soil/sediment samples.  The associated results indicated the concentrations
of metals which may be present in surface waters as a result of leaching from background
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surface soils/sediments. Accordingly, the D.I. WET results are indicative of naturally
occurring (background) concentrations of metals in surface waters in the area of Mather AFB.

Inorganic COPC concentrations in surface water were compared to the background soil
D.I. WET results; COPCs for which maximum concentrations were less than associated
D.I. WET results were eliminated from further consideration.  Inorganics for which D.I. WET
data were not available, and for all organics, background concentrations in surface water were
assumed to be zero.

2.2.6.1.2.2  Soils and Sediments
For inorganics and oil and grease, the associated 95 percent UCLs for each COPC were
compared to documented background levels [IT 1993g],

The COPCs for which the 95  percent UCL were within background concentrations/ranges,
were eliminated from further consideration. For inorganics for which background data were
not available, and for all organics with the exception of oil and grease, background
concentrations were assumed to be zero.

The results of this comparison are presented in the MBRA [IT  1995d] and are reiterated hi the
FFS Report [IT 1995a].

2.2.6.1.3    Comparison to Analytical Method Quantitation Limit
For solid media, the calculated 95 percent UCLs were compared to the quantitation limit for
each corresponding analytical method.  In some cases, the 95 percent UCL was less than the
quantitation limit as follows.

The initial data compilation was performed in accordance with USEPA risk assessment
guidance [USEPA 1989a].   Such guidance mandates the inclusion of data qualified as not
detected (i.e., ND) to be included in the database at a value of one-half the quantitation limit.
Although such an approach is compatible with the conservative nature of risk assessment,
associated results are frequently of limited value in an engineering context. Accordingly, if
the 95 percent UCL was less than the quantitation limit the associated COPC was considered
"not detected."
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2.2.6.1.4   Comparison to Applicable or Relevant and Appropriate
             Requirements/To-Be-Considered
Chemical-specific ARARs were identified for surface water and soils and are further described
in Section 6.0.  There were no chemical-specific ARARs identified for air; however, the
action-specific ARARs will control the release of pollutants to the air from the soils during
remediation activities. Federal and state water regulation primary maximum contaminant
levels (MCLs) were used for comparison to surface water and groundwater.

2.2.6.1.4.1 Surface Water
Contaminant of potential concern concentrations in surface waters were compared to
appropriate to-be-considered materials (TBC), in most cases USEPA Ambient Water Quality
Criteria (AWQC).  The COCs for which the 95 percent UCL was less than the corresponding
TBC were eliminated from further consideration.

2.2.6.1.4.2 Soils
Contaminant of potential concern concentrations in sediments and soils were compared to total
designated levels (TDLs) calculated using the Designated Level Methodology (DLM)
[CVRWQCB  1989].

The DLM was used to evaluate or estimate potential impact to the groundwater from COPCs
in the surface and subsurface soils. The DLM was also used to screen COPCs in sediments to
evaluate potential impacts to surface water.  The application of this methodology consisted of
the following  steps:

      •      Determine the desired water quality goal (WQG) for each constituent -
             Promulgated regulations and standards were used where available.
             Contaminants in the surface soils and subsurface soils have a potential to impact
             groundwater (i.e., source of drinking water); therefore, the MCL was used as
             the WQG.  Contaminants in the sediments could possibly impact surface waters;
             therefore, AWQC were used as the WQG. In the absence of promulgated
             regulations, contaminant goals, health advisories, or risk-based values were
             used as WQGs.

      •      Determine the Environmental Attenuation Factor for each constituent - This
             factor is used to transform WQGs into site-specific designated levels
             (concentrations of constituents in the wastes that have the potential to degrade
             water quality by migrating from the reference location).
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              Determine a Leachability Factor - The teachability factor is the ratio of total to
              soluble concentrations of the chemical constituent.  Where available, actual
              deionized solubilities determined using the California Waste Extraction Text
              protocol were used to assess the threat to water quality.  Where measured
              solubilities were unavailable, a theoretical leachibility factor was used.  This
              factor was used to determine the fraction of the total constituent concentration
              available for leaching from the waste. The remaining portion of the constituent
              is immobile or unavailable for leaching due to encapsulation in the waste matrix
              or chemical bonding. A leachability factor of 100 was used for inorganic
              constituents and 10 for organic constituents as prescribed in the DLM guidance
              [CVRWQCB 1989], subject to agency review and professional judgement
              during document review.

              Determine a Total Designated Level - The TDL represents the concentration of
              a constituent in a solid waste which, if exceeded, may threaten the water

                                TDL  =  WQG x  EAF x LF
              quality.  The TDL is calculated by the following equation:

              where:       TDL  = total designated level
                           WQG = water quality goal
                           EAF  = environmental attenuation factor
                           LF = leachability factor


The COPCs for which the 95 percent UCL was less than the associated TDL were eliminated
from further consideration, subject to reinstatement as COPCs if warranted by comment
resolution or professional judgement during document review.


2.2.6.1.5    Process Knowledge Evaluation
Operational and disposal histories for the Soil OU sites were reviewed to evaluate the
likelihood that past operations or disposal practices may have impacted the proximate
environment.  Results of the process knowledge evaluation were developed in accordance with
the following definitions:


       Yes:          documented,  reported, or observed evidence (e.g., floating-product in an
                    excavation) of a release for that COPC;

       Possible:      evidence or documentation that the COPC was used or stored at the site;

       No:          no evidence that the COPC was stored, used, and/or released at the site.

                                          9  1Q
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 Process knowledge was not used as sole justification, but was used in conjunction with the
 other screening criteria, to aid in the elimination of constituents from the list of COPCs.

 2.2.6.1.6   Risk Assessment Results
 Estimates of potential risks/hazards to human and ecological receptors were obtained from the
 MBRA [IT 1995d].  Recent revisions include the use of surrogate toxicity values, an updated
 dermal exposure model, revised dermal absorption values, and an aggregate mining scenario
 [IT 1995b]. Additional ecological risk assessment activities were conducted in Spring 1995.
 These activities included further evaluation of the potential toxicity of surface water, sediment,
 and surface soil contaminants at three local habitat types and respective reference sites through
 toxicity testing and residue analysis. The house mouse exposure pathway was also
 re-evaluated utilizing an assumption of an omnivorous mouse.  The initial list of COPCs
 (presented in the FFS Report [IT 1995a]) which were identified on the basis of potential
 ecological risk/hazard have not changed appreciably due to  these additional activities.

 From an ecological perspective, COPCs for which concentrations exceeded background
 screening values or for which associated estimates of potential ecological hazard index
 exceeded 1.0 were also identified as COCs.  An ecological risk exists at Sites 13, 15, 20, 62,
 and 69.  Therefore, the selected remedies at these sites will be instituted for the protection of
 ecological receptors and/or surface water quality.

 From a human health perspective,  COPCs for which the estimated incremental lifetime cancer
 risk exceeded  1 x 10"6, or the hazard quotient exceeded 1.0, on an individual pathway basis,
 were identified as COCs.

 Based on the human health risk assessment, all cancer risks were within or below the
 acceptable range of 1 x 10^ to 1 x  10~6 in their current state, except for Sites 56, 62, and 69
 which have a current and future cancer risk greater than 1 x 10"4.  Therefore, the selected
remedies at Sites 56, 62, and 69 will be instituted to reduce human health risks and/or for
protection of groundwater quality.

Actual or threatened releases of hazardous substances, if not addressed by implementing the
response actions selected in the ROD, may present an imminent and substantial endangerment
to public health, welfare, or the environment.
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 2.2.7 Description of Alternatives
 A total of 36 remedial alternatives (including the no action alternative) for the twelve Soil OU
 sites which warrant remedial action were developed for detailed analysis in the FFS Report [IT
 1995a].  Soil is the affected medium at these sites. Any contamination of the groundwater
 underlying the soil sites is addressed in the Groundwater OU section of this ROD (Section
 5.0).

 In developing the alternatives, it was assumed that the sediments (maximum two foot deep),
 surface soils (zero to two feet below land surface  [bis]), and shallow soils (2 to 30 feet bis) are
 capable of being excavated without specialized equipment.  Deep soils (30 feet bis to the water
 table) are not considered feasible or appropriate to excavate.  The no action alternative, as
 required by CERCLA, has been included for each site to provide a baseline.
2.2.7.1      Site 7/11 Remedial Alternative
Table 2-6 presents three remedial alternatives that have been developed for possible application
at Site 7/11.
                       Table 2-6.  Site 7/11 Remedial Alternatives
ALTERNATIVE
7.1
7.2
7.3
DESCRIPTION
No Action
Excavation (shallow soils) with ex situ bioremediation and on-base disposal (or off-
base disposal if the excavated material is classified as hazardous waste or would be
classified as designated waste at the on-base disposal site(s)); in situ bioremediation
and possibly soil vapor extraction (SVE) (deep soils); capping (as appropriate); and
groundwater monitoring (if contamination that threatens groundwater quality remains
at the site).
Filling hi the depression at site 7 to grade; in situ bioremediation and possibly SVE
(shallow and deep soils at sites 7 and 11); capping (as appropriate); and groundwater
monitoring (if contamination that threatens groundwater quality remains at the site).
2.2.7.2      Site 13 Remedial Alternatives
Table 2-7 presents three remedial alternatives that have been developed for possible application
at Site 13.
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                        Table 2-7.  Site 13 Remedial Alternatives
ALTERNATIVE
13.1
13.2
13.3
DESCRIPTION
No Action
Excavation (sediments and surface soils) with off-base disposal and groundwater
monitoring (if contamination that threatens groundwater quality remains at the site)
Excavation (sediments and surface soils) with ex situ bioremediation and on-base disposal
(or off-base disposal if the excavated material is classified as hazardous waste or would
be classified as designated waste at the on-base disposal site(s)); and groundwater
monitoring (if contamination that threatens groundwater quality remains at the site)
2.2.7.3      Site 15 Remedial Alternatives
Table 2-8 presents three alternatives that have been developed for possible application at
Site 15.
                        Table 2-8. Site 15 Remedial Alternatives
ALTERNATIVE
15.1
15.2
15.3
DESCRIPTION
No Action
Excavation (sediments) with off-base disposal and surface water monitoring (if
contamination that threatens surface water quality remains at the site)
Excavation (sediments) with ex situ bioremediation and on-base disposal (or off-base
disposal if the excavated material is classified as hazardous waste or would be classified
as designated waste at the on-base disposal site(s)); and surface water monitoring (if
contamination that threatens surface water quality remains at the site)
2.2.7.4      Site 20 Remedial Alternatives
Table 2-9 presents three alternatives that have been developed for possible application at
Site 20.
                        Table 2-9. Site 20 Remedial Alternatives
ALTERNATIVE
20.1
- 20.2
20.3
DESCRIPTION
No Action
Excavation (shallow soils) with ex situ bioremediation and on-base disposal (or off-base
disposal if the excavated material is classified as hazardous waste or would be classified
as designated waste at the on-base disposal site(s)); and groundwater monitoring (if
contamination that threatens groundwater quality remains at the site)
In situ bioremediation (shallow soils) and groundwater monitoring (if contamination
that threatens groundwater quality remains at the site)
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2.2.7.5      Site 37/39/54 Remedial Alternative
Table 2-10 presents three remedial alternatives that have been developed for possible
application at Site 37/39/54.
                       Table 2-10.  Site 37/39/54 Remedial Alternatives
  ALTERNATIVE
                                DESCRIPTION
        37.1
No Action
        37.2
Excavation (surface soils) with ex situ bioremediation and on-base disposal (or off-base
disposal if the excavated material is classified as hazardous waste or would be classified
as designated waste at the on-base disposal site(s)); in situ bioremediation and possibly
soil vapor extraction (SVE) (shallow and deep soils); and groundwater monitoring (if
contamination that threatens groundwater quality remains at the site)	
        37.3
Excavation (surface and shallow soils) with ex situ bioremediation and on-base disposal
(or off-base disposal if the excavated material is classified as hazardous waste or would
be classified as designated waste at the on-base disposal site(s)); in situ bioremediation
and possibly SVE, (deep soils); and groundwater monitoring (if contamination that
threatens groundwater quality remains at the site)	
2.2.7.6      Site 56 Remedial Alternatives
Table 2-11 presents three remedial alternatives that have been developed for possible
application at Site 56.
                          Table 2-11.  Site 56 Remedial Alternatives
ALTERNATIVE
56.1
56.2
56.3
DESCRIPTION
No Action
Excavation (surface soils) with ex situ bioremediation and on-base disposal (or off-base
disposal if the excavated material is classified as hazardous waste or would be classified
as designated waste at the on-base disposal site(s)); in situ bioremediation (shallow
soils); and groundwater monitoring (if contamination that threatens groundwater quality
remains at the site)
Excavation (surface and shallow soils) with ex situ bioremediation and on-base disposal
(or off-base disposal if the excavated material is classified as hazardous waste or would
be classified as designated waste at the on-base disposal site(s)); and groundwater
monitoring (if contamination that threatens groundwater quality remains at the site)
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2.2.7.7      Site 57 Remedial Alternatives
Table 2-12 presents three remedial alternatives that have been developed for possible
application at Site 57.

                        Table 2-12. Site 57 Remedial Alternatives
ALTERNATIVE
57.1
57.2
57.3
DESCRIPTION
No Action
In situ bioremediation (shallow and deep soils) and groundwater monitoring (if
contamination that threatens groundwater quality remains at the site)
In situ soil vapor extraction (shallow and deep soils) and groundwater monitoring
contamination that threatens groundwater quality remains at the site)
(if
2.2.7.8      Site 59 Remedial Alternatives
Table 2-13 presents three remedial alternatives that have been developed for possible
application at Site 59.

                        Table 2-13. Site 59 Remedial Alternatives
ALTERNATIVE
59.1
59.2
59.3
DESCRIPTION
No Action
Excavation (shallow soils) with ex situ bioremediation and on-base disposal (or off-
base disposal if the excavated material is classified as hazardous waste or would be
classified as designated waste at the on-base disposal site(s)); and groundwater
monitoring (if contamination that threatens groundwater quality remains at the site)
In situ bioremediation (shallow soils) and groundwater monitoring (if contamination
that threatens groundwater quality remains at the site)
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                                          2-24

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2.2.7.9      Site 60 Remedial Alternatives
Table 2-14 presents four remedial alternatives that have been developed for possible
application at Site 60.
                        Table 2-14. Site 60 Remedial Alternatives
ALTERNATIVE
60.1
60.2
60.3
60.4
DESCRIPTION
No Action
Excavation (shallow soils) with ex situ bioremediation and on-base disposal (or off-base
disposal if the excavated material is classified as hazardous waste or would be classified
as designated waste at the on-base disposal site(s)); and groundwater monitoring (if
contamination that threatens groundwater quality remains at the site)
In situ soil vapor extraction (shallow soils) and groundwater monitoring (if contamination
that threatens groundwater quality remains at the site)
In situ bioremediation (shallow soils) and groundwater monitoring (if contamination that
threatens groundwater quality remains at the site)
2.2.7.10     Site 62 Remedial Alternatives
Table 2-15 presents three remedial alternatives that have been developed for possible
application at Site 62.
                       Table 2-15.  Site 62 Remedial Alternatives
ALTERNATIVE
62.1
62.2
62.3
DESCRIPTION
No Action
Excavation (surface soils) with ex situ bioremediation and on-base disposal (or off-base
disposal if the excavated material is classified as hazardous waste or would be classified
as designated waste at the on-base disposal site(s)); in situ bioremediation (shallow soils);
and groundwater monitoring (if contamination that threatens groundwater quality remains
at the site)
Excavation (surface and shallow soils) with ex situ bioremediation and on-base disposal
(or off-base disposal if the excavated material is classified as hazardous waste or would
be classified as designated waste at the on-base disposal site(s)); and groundwater
monitoring (if contamination that threatens groundwater quality remains at the site)
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                                          2-25

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2.2.7.11     Site 65 Remedial Alternatives
Table 2-16 presents three remedial alternatives that have been developed for possible
application at Site 65.

                       Table 2-16.  Site 65 Remedial Alternatives
ALTERNATIVE
65.1
65.2
65.3
DESCRIPTION
No Action
Excavation (surface soils) with off-base disposal; in situ bioremediation (shallow soils);
and groundwater monitoring (if contamination that threatens groundwater quality remains
at the site)
Excavation (surface soils) with off-base disposal; excavation (shallow soils) with ex situ
bioremediation and on-base disposal (or off-base disposal if the excavated material is
classified as hazardous waste or would be classified as designated waste at the on-base
disposal site(s)); and groundwater monitoring (if contamination that threatens
groundwater quality remains at the site)
2.2.7.12    Site 69 Remedial Alternatives
Table 2-17 presents two remedial alternatives that have been developed for possible application
at Site 69.
                       Table 2-17.  Site 69 Remedial Alternatives
ALTERNATIVE
69.1
69.2
DESCRIPTION
No Action
Excavation (sediments and surface soils) with on-base disposal (or off-base disposal if the
excavated material is classified as hazardous waste or would be classified as designated
waste at the on-site disposal area), and surface water monitoring as appropriate if
contamination remains on site that threatens surface water quality.
2.2.8 Summary of Comparison Analysis of Alternatives
The remedial alternatives developed in the FFS Report [IT 1995a] were analyzed hi detail
using the nine evaluation criteria required by the NCP (Section 300.430(e)(7)). These criteria
are classified as threshold, primary balancing, and modifying criteria. In order for a remedial
alternative to be selected, it must at a minimum, meet the threshold criteria.
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Threshold criteria are:
              overall protection of human health and the environment; and
              compliance with ARARs.
Primary balancing criteria are:
       •      long-term effectiveness and permanence;
       •      reduction of toxicity, mobility, or volume through treatment;
       •      short-term effectiveness;
       •      implementability; and
       •      cost.

Modifying criteria are:

       •      state/support agency acceptance; and
       •      community acceptance.

The relative ability of each alternative to meet each of the nine criteria were weighed to
identify the alternative providing the best tradeoffs for each site. The following sections
summarize the nine criteria.  Table 2-18 presents the results of the comparative analysis.

2.2.8.1      Overall Protection of Human Health and the Environment
Overall protection of human health and the environment addresses whether or not a cleanup
option provides adequate protection.  It also describes how risks, posed through each exposure
route, are eliminated,  reduced, or controlled through treatment, engineering controls, or
institutional controls.

2.2.8.2      Compliance with ARARs
Compliance with ARARs addresses whether a cleanup option will meet all ARARs or federal
and state environmental statues and/or provide grounds for invoking a waiver.  Details of the
ARARs analysis are described in Section 6.0 of this ROD.
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2.2.8.3      Long- Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a cleanup option to maintain
reliable protection of human health and the environment over time, once cleanup goals have been
met.

2.2.8.4      Reduction of Toxlcity, Mobility, or Volume
Reduction of toxicity, mobility, or volume refers to the anticipated ability of a cleanup option to
reduce health hazards, contaminant migration,  or quantity of contaminants at the site through
treatment.

2.2.8.5      Short-Term Effectiveness
Short-term effectiveness refers to the period of time in which the remedy achieves protection,  as
well as the remedy's potential to prevent adverse impacts on human health and the environment
that may result during the excavation, construction, or implementation period until the cleanup
goals are achieved.

2.2.8.6      Implementability
Implementability refers to the technical and administrative feasibility of a remedy, including the
availability of materials and services needed to carry out a particular remedy.  It also includes
coordination of federal, state,  and local governments in  cleanup of the site.

2.2.5.7      Cost
This criterion examines the estimated cost for each remedial alternative.  For comparison, capital
and annual operation and maintenance costs were used to calculate a present worth cost for each
alternative. The present worth cost estimates assume zero equipment salvage value, zero percent
inflation, and a five  percent discount factor so that each option could be equally compared in
1994 dollars.  A detailed cost analysis was performed for each of the alternatives proposed in the
FFS Report [IT 1995a].

2.2.8.8      State/Support Agency Acceptance
This indicates whether,  based on review of the  RI Report [IT 1992a], FFS Report [IT 1995a],
and Proposed Plan [IT 1995b], the state concurs with the preferred cleanup options.  The State of
California is represented by the California Environmental Protection Agency, DTSC  as a support
agency under the Federal Facility Agreement for Mather AFB; DTSC coordinates review
comments from other state agencies, such as the Central Valley Regional Water Quality Control
Board (CVRWQCB) and the Integrated Waste Management Board.
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                                          2-28

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                                            Table  2-18.  Comparative Analysis of Soil Operable Unit Remedial Alternatives
Evaluation
Criteria
Site
Number
Alternative
Overall Protection of Human
Health and the Environment
Compliance with
ARARs
Long-Term Effectiveness and
Permanence
Reduction of Toxicity,
Mobility, and Volume
Short-Term Effectiveness
Implementability
Present Worth Cost
($ millions)
7/11
7.1
Yes
NA**
G
P
F
G
0.018
7.2
Yes
Yes
B
B
B
G
4.21
7.3'
Yes
Yes
B
B
G
B
3.69
13
13.1
Yes
NA**
G
P
G
B
0.15
13.2
Yes
Yes
B
G
B
G
0.88
13.3'
Yes
Yes
B
B
B
G
0.279
15
15.1
Yes
NA**
F
P
G
B
0.51
15.2
Yes
Yes
B
G
B
G
2.20
15.3'
Yes
Yes
B
B
B
G
0.827
20
20.1
Yes
NA**
F
P
F
B
0.28
20.2'
Yes
Yes
B
B
B
G
0.33
20.3
Yes
Yes
B
B
G
B
0.62
37/39/54
37.1
Yes
NA**
F
P
G
B
0
37.2*
Yes
Yes
B
B
B
G
1.75
37.3
Yes
Yes
B
B
B
G
3.38
56
56.1
Yes
NA**
G
P
F
B
0
56.2
Yes
Yes
B
G
G
G
0.71
56.3'
Yes
Yes
B
B
B
G
0.048
to
bo
         * The State of California and the community concur on the selected remedial alternative asterisked for each of the Soil Operable Unit sites.
         ** ARARs do not have to be met unless a remedial action is taken.

         P = Poor
         F = Fair
         G = Good
         B = Best
         NA = not applicable
         ARAR = applicable or relevant and appropriate requirement

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                                   Table 2-18.  Comparative Analysis of Soil Operable Unit Remedial Alternatives (continued)
Evaluation
Criteria
Site
Number
Alternative
Overall Protection of Human
Health and the Environment
Compliance with ARARs
Long-Term Effectiveness and
Permanence
Reduction of Toiucity,
Mobility, and Volume
Short-Term Effectiveness
Implementabil ty
Present Worth Cost
($ millions)
57
57.1
Yes
NA*»
F
P
G
B
0
57.2
Yes
Yes
B
G
B
G
0.57
57.3'
Yes
Yes
B
B
B
G
1.01
59
59.1
Yes
NA**
F
P
F
B
0
59.21
Yes
Yes
B
B
B
G
0.087
59.3
Yes
Yes
B
B
G
G
0.63
60
60.1
Yes
NA**
F
P
P
B
0.003
60.2*
Yes
Yes
B
B
B
G
0.033
60.3
Yes
Yes
B
B
G
G
0.26
60.4
Yes
Yes
B
B
F
G
0.63
62
62.1
Yes
NA**
F
P
F
B
0.011
62.2
Yes
Yes
B
B
G
G
0.21
62.3'
Yes
Yes
B
B
B
G
0.049
65
65.1
Yes
NA**
F
P
G
B
0.004
65.2
Yes
Yes
B
B
B
G
0.186
65.3'
Yes
Yes
B
B
B
G
0.134
69
69.1
Yes
NA**
F
P
G
B
0.081
69.2'
Yes
Yes
B
B
B
B
0.45
to
u>
o
        * The State of California and the community concur on the selected remedial alternative asterisked for each of the Soil Operable Unit sites.
        ** ARARs do not have to be met unless a remedial action is taken.

        P = Poor
        F = Fair
        G = Good
        B = Best
        NA = not applicable
        ARAR = applicable or relevant and appropriate requirement

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2.2.8.9      Community Acceptance
This is an assessment of the general public response to the Proposed Plan following review of
the public comments received on the RI Reports and FFS Report, during the public comment
period (from May 8 through June 7, 1995) and open community meeting (held on May 18,
1995). Section 7.0 of this ROD documents the community acceptance of the selected
remedies, as presented in the Responsiveness Summary.

2.2.9 The Selected Remedies
This section presents the remedies selected by the USAF, with concurrence by the USEPA and
the State of California, for each of the Soil OU sites which warrant cleanup. The selected
remedies were chosen based on the results of the comparative analysis of the alternatives
presented in Table 2-18 and provide the best trade-offs with respect to the nine evaluation
criteria.  All design and construction of the selected remedial actions will be conducted by
certified professionals or under the supervision of certified professionals, as appropriate.

2.2.9. 7     Site 7/11 -  "7100 Area" Disposal Site/Existing Fire Protect/on Training
             Area
Alternative 7.3 was selected by the USAF, with concurrence by the USEPA and the State of
California, as the remedy for Site 7/11. The major components of this remedy include:

       •      filling in the  depression at Site 7 with inert fill

       •      treating the contaminated shallow and deep soils at Sites 7 and 11  by in situ
             bioremediation and possibly soil vapor extraction (SVE). The in situ
             bioremediation system could be converted to a SVE system if significant
             amounts of solvents are encountered, in order to speed up remediation;

       •      installing a prescriptive  landfill cover over the Site 7 impacted area if site
             conditions indicates it is appropriate, or a vegetative cover if there is no threat
             to ground water quality nor generation of landfill gases, using inert soils and/or
             non-designated soils to construct the foundation for the cap/cover; and

       •      monitoring the groundwater (if contamination remains in place that threatens
             groundwater  quality).

Remediation at Site 7/11 will be implemented in a phased approach, whereby SVE,
bioventing, and soil gas monitoring will be implemented prior to a final determination on the
need for a prescription landfill  cover pursuant to Article 8 of 23 California Code of

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       Regulations (CCR), Division 3, Chapter 15.  Once the SVE/bioventing system has been
       operated until it has met cleanup standards, or design goals as appropriate, or has otherwise
       reached technical or economic limitations, a determination will be made whether a continuing
       source of methane or trace gases exist, and whether a significant threat to groundwater quality
       exists.

       The Air Force will conduct further soil gas sampling at this site to define the extent of VOC
       contamination, as part of the remedial design work.  The feasibility of SVE will be evaluated
       when it is demonstrated that soil contaminants may cause concentrations in the leachate to
       exceed the aquifer cleanup levels, based on an interpretation of soil gas data using VLEACH
       or another appropriate vadose zone model.

       The actual decision on whether to build and operate an SVE system will depend on the degree
       to which the contamination presents a threat to ground water and whether  site characteristics
       are suitable for the SVE technology.  It is generally  preferable from a technical and cost
       perspective to clean up contamination in the vadose zone before it reaches the ground water.
       The feasibility analysis will be prepared by the Air Force as a primary document.  The
       decision will be made by the signatory parties to the FFA and will be based, at a minimum, on
       the following factors:

           a.  the cost and time associated with the predicted additional groundwater remediation if
              no SVE is implemented;

           b.  the cost of implementing the SVE system to meet the SVE soil cleanup standard;

           c.  the incremental cost over time of vadose zone remediation compared to the incremental
              cost of groundwater remediation, on the basis of a common unit (e.g., cost to remove a
              pound of TCE), provided that the underlying groundwater has not reached aquifer
              cleanup levels;

           d.  the results of VLEACH or another appropriate vadose zone model, in conjunction with
              a groundwater fate and transport model to predict the resulting concentration from the
              vadose zone contamination in the nearest groundwater wells monitoring the  site;

           e.  the results of VLEACH or another appropriate vadose zone model, that interprets soil
              gas data, to predict the mass and concentration of discharges from the vadose zone to
              the groundwater;
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This demonstration is to be made prior to operation of the bioventing system in areas
considered for SVE (to prevent interference from bioventing).  Once SVE is initiated, it will
be terminated in accordance with the demonstration required for Site 57 (Section 2.2.9.7).
The need to implement the bioventing remedy will be reevaluated when SVE is terminated.

Initial site grading will be accomplished in conjunction with drilling in order to allow site
access for the drill rigs; the Site 7 depression may or may not be filled above grade at this
time.  Further grading may be accomplished to minimize infiltration of surface water into Site
7 during SVE and bioventing. Final site construction will be accomplished at the completion
of SVE and bioventing consistent with the determination of the type of cap or cover that is
required at Site 7.

Capital  cost estimates for this remedy are projected at approximately $2.7 million, operation
and maintenance costs are estimated at $2.0 million. Total cost, represented as a net present
worth using a five percent discount rate, is calculated at $3.69 million.

The basis for cleanup at Site 7/11 is compliance with ARARs for waste disposal sites,
mitigating a likely source of groundwater contamination, and protection of groundwater
quality for its beneficial use.  Table 2-19 presents the Site 7/11 cleanup levels.

                          Table 2-19. Site 7/11  Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Subsurface Soils
TPH as Diesel
TPH as Gasoline
10
1
TPH = total petroleum hydrocarbon
ppm = parts per million
2.2.9.2     Site  13 - Drainage Ditch Number 1
Alternative 13.3 was selected by the USAF, with concurrence by the USEPA and State of
California as the remedy for Site 13.  The major components of this remedy include:
             removing surface water, if present, by pumping and discharging to the publicly
             owned treatment works (POTW);

             excavating approximately 1,900 cubic yards (yd3) of contaminated sediments
             and surface soils to remove all contamination above acceptable levels;

                                          2-33

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       •      transporting the excavated soils to the on-base ex situ bioremediation facility;

       •      treating the excavated soils by ex situ bioremediation as appropriate;

       •      transporting the treated soils to, and consolidating them with landfill cap
              foundation materials at Site  7, as appropriate; and

       •      monitoring the groundwater if contamination that threatens groundwater quality
              remains at the site, and monitoring surface water if contamination that threatens
              surface water quality remains at the site.

Capital cost estimates for this remedy are projected at approximately $100,000, operation and
maintenance costs are estimated at $212,000.  Total cost, represented as a net present worth
using a five percent discount rate, is calculated at $279,000.

The basis for cleanup at Site  13 is protection of groundwater quality, surface water quality,
and ecological receptors.  Table 2-20 presents the Site 13 cleanup levels.

                           Table 2-20. Site 13 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Water
Aluminum
Chromium
Lead
Manganese
Silver
Zinc
Sediment
Arsenic
Chromium
Chromium VI
Cobalt
Copper
Lead
Mercury
6.28
l.lx ID'2
9.4 x ID'3
l.OxlO-1
1.6 x 10-2
5.4 x 10-2

16
176
ND(O.l)
35
104
81
ND (0.2)

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                       Table 2-20.  Site 13 Cleanup Levels (Continued)
Contaminant of Concern
Nickel
Vanadium
Zinc
4,4-DDD
4,4-DDE
4,4-DDT
Cleanup Level (ppm)
81
153
116
1.9
1.3
1.3
Sediment (Continued)
alpha-Chlordane
Dieldrin
gamma-Chlordane
3.4 x 10-'
2.8 x 10-2
3.4 x 10-'
Surface Soil
Arsenic
Benzo(a)anthracene
Benzo(g,h,i)perylene
Fluoranthene
Indeno(l ,2,3-cd)pyrene
Mercury
Naphthalene
Oil and Grease
Pyrene
TPH as Diesel
Zinc
16
3.3 x 10-'
3.3 x ID'1
3.3 x 10-1
3.3 x lO'1
ND (0.2)
3.3 x 10-'
430
3.3 x ID'1
100
1559
ppm = parts per million
TPH = total petroleum hydrocarbon
DDT = dichlorodiphenyltrichloroethane
ND = not detected
ODD = dichlorodiphenyldichloroethane
DDE = dichlorodiphenyldichloroethene

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2.2.9.3      Site 15 - Drainage Ditch Number 3
Alternative 15.3 was selected by the USAF, with concurrence by the USEPA and State of
California as the remedy for Site 15.  The major components of this remedy include:

       •      removing surface water, if present, by pumping and discharging to the POTW;

       •      excavating approximately 4,300 yd3 of contaminated  sediments to remove all
              contamination above acceptable levels;

       •      transporting the sediments to the on-base ex situ bioremediation facility;

       •      treating the excavated sediments by ex situ bioremediation as appropriate;

       •      transporting the treated sediments to, and consolidating them with landfill cap
              foundation materials at Site 7, as appropriate; and

       •      monitoring the surface water if contamination that threatens surface water
              quality remains at the site.

Capital cost estimates for this remedy are projected at approximately $229,000, operation and
maintenance costs are estimated at $682,000.  Total cost, represented as a net present worth
using a five percent discount rate, is calculated at $827,000.

The basis for cleanup is protection of groundwater/surface water quality and ecological
receptors.  Table 2-21 presents the  Site 15 cleanup levels.

                          Table 2-21. Site 15 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Water
Chromium
Lead
Manganese
Vanadium
Zinc
Sediment
Barium
Cadmium
l.lxlO-2
9.4 x 10-3
1.0x10-'
1.0x10-'
5.4 x 10-2

1300
1.4
                                         2-36

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Table 2-21.  Site 15 Cleanup Levels (Continued)
Contaminant of Concern
Cleanup Level (ppm)
Sediment (Continued)
Chromium
Chromium VI
Copper
Lead
Mercury
Zinc
Acenaphthene
Acenaphthylene
alpha-Chlordane
Anthracene
Aroclor 1248
Aroclor 1254
Aroclor 1260
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(g , h , i)pery lene
Benzo(k)fluoranthene
Chrysene
Dibenzo(a,h)anthracene
Dieldrin
Fluoranthene
Fluorene
gamma-Chlordane
Indeno(l,2,3-cd)pyrene
Naphthalene
Oil and Grease
176
ND(O.l)
104
81
ND (0.2)
116
3.3 x 1C'1
3.3 x ID'1
3.4 x 10-'
3.3 x 10-'
6.6 x lO'2
6.6 x ID'2
6.6 x ID'2
3.3 x 10-'
3.3 x 10-'
3.3 x 10-'
3.3 x 10-'
3.3 x 10-'
3.3 x 10-'
3.3 x 10-'
2.8 x 10-2
3.3 x 10-'
3.3 x 10-'
3.4 x 10-'
3.3 x 10-'
3.3 x 10''
430
                    2-37

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                     Table 2-21. Site 15 Cleanup Levels (Continued)
Contaminant of Concern
Cleanup Level (ppm)
Sediment (Continued)
Phenanthrene
Pyrene
TPH as Diesel
TPH as Gasoline
3.3 x 10-'
3.3 x 10'1
10
1
TPH = total petroleum hydrocarbon      ppm = parts per million
ND = not detected
2.2.9.4      Site 20 Sewage  Treatment Plant
Alternative 20.2 was selected by the USAF, with concurrence by the USEPA and State of
California as the remedy for Site 20.  The major components of this remedy include:


       •      excavating approximately 550 yd3 of TPH-contaminated shallow soils to remove
              all contamination above acceptable levels;

       •      transporting the excavated soils to the on-base ex situ bioremediation facility;

       •      treating the excavated soils by ex situ bioremediation as appropriate;

       •      transporting the treated soils to, and consolidating them with landfill cap
              foundation materials at Site 7, as appropriate;

       •      removing sludge and disposing as appropriate in accordance with 1994 RAM
              for Site 20 (i.e. either disposal as hazardous waste,  or treatment to render it
              non-hazardous and non-designated for on-base disposal); and

       •      monitoring the groundwater if contamination that threatens groundwater quality
              remains at the site.


Capital cost estimates for this remedy are projected at approximately $31,700, operation and
maintenance costs are estimated at $338,000.  Total cost, represented as a net present worth
using a five percent discount rate, is calculated at $325,000.


The basis for cleanup of TPH-d is protection of groundwater quality; the basis for cleanup of
sludge is protection of human and ecological health. Table  2-22 presents the Site 20 cleanup
levels.
                                          2-38

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                                  Table 2-22.  Site 20 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Soil (sludge location)
Lead
Mercury
Zinc
Subsurface Soil (diesel spill location)
TPH as Diesel
130
20
1559

10
       TPH = total petroleum hydrocarbon
ppm = parts per million
       2.2.9.5     Site 37/39/54 - Building 3389/Hazardous Waste Control Storage
       Alternative 37.2 was selected by the USAF, with concurrence by the USEPA and the State of
       California as the remedy for Site 37/39/54.  The major components of this remedy include:


              •      excavating approximately 220 yd3 of contaminated surface soils to remove all
                    contamination above acceptable levels;

              •      transporting the excavated soils to the on-base ex situ bioremediation facility;

              •      treating the excavated soils by ex situ bioremediation as appropriate;

              •      transporting the treated soils to, and consolidating them with landfill cap
                    foundation materials at Site 7, as appropriate;

              •      treating the contaminated shallow and deep soils by in situ bioremediation and
                    possible SVE. The in situ bioremediation system could be converted if
                    appropriate, to an SVE system if significant amounts of solvents are
                    encountered in order to speed up remediation; and

              •      monitoring the groundwater if contamination that threatens groundwater quality
                    remains at the site.


       The Air Force will conduct further soil gas sampling at this site to define the extent of VOC
       contamination, as part of the remedial design work. The feasibility of SVE will be evaluated
       when it is demonstrated that soil contaminants may cause concentrations in the leachate to
       exceed  the aquifer cleanup levels, based on an interpretation of soil gas data using VLEACH
       or another appropriate vadose zone model.
RL/10-95/ES/1260005.AWS
                                                2-39

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       The actual decision on whether to build and operate an SVE system will depend on the degree
       to which the contamination presents a threat to ground water and whether site characteristics
       are suitable for the SVE technology.  It is generally preferable from a technical and cost
       perspective to clean up contamination in the vadose zone before it reaches the ground water.
       The feasibility analysis will be prepared by the Air Force as a primary document.  The
       decision will be made by the signatory parties to the FFA and will be based, at a minimum, on
       the following factors:

           a.  the cost and time associated with the predicted additional groundwater remediation if
              no SVE is implemented;

           b.  the cost of implementing the SVE system to meet the SVE soil cleanup standard;

           c.  the incremental cost over time of vadose zone remediation compared to the incremental
              cost of groundwater remediation, on the basis of a common unit (e.g., cost to remove a
              pound of TCE), provided that the underlying groundwater has not reached aquifer
              cleanup levels;

           d.  the results of VLEACH or  another appropriate vadose zone model, in conjunction with
              a groundwater fate and transport model to predict the resulting concentration from the
              vadose zone contamination in the nearest groundwater wells monitoring the site;

           e.  the results of VLEACH or  another appropriate vadose zone model, that interprets soil
              gas data, to predict the mass and concentration of discharges from the vadose zone to
              the groundwater;

       This demonstration is to be made prior to operation of the bioventing  system in areas
       considered for SVE (to prevent interference from bioventing).  Once SVE is initiated, it will
       be terminated in accordance with the demonstration required for Site 57 (Section 2.2.9.7).
       The need to implement the bioventing remedy will be reevaluated when SVE is terminated.

       Capital cost estimates for this remedy are projected at approximately $509,000 operation and
       maintenance costs are estimated at  $1,709,000.  Total cost, represented  as a net present worth
       using a five percent discount rate, is calculated at $1,757,000.

       The basis for cleanup is protection of groundwater quality. Table 2-23 presents the
       Site 37/39/54 cleanup levels.
RL/10-95/ES/1260005.AWS
                                                2-40

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                            Table 2-23.  Sites 37/39/54 Cleanup Levels
Contaminant of Concern*
Cleanup Level (ppm)
SITE 37
Subsurface Soil
Oil and Grease
TPH as Diesel
TPH as Gasoline
430
10
1
SITE 39
Surface Soil
Oil and Grease
TPH as Diesel
Subsurface Soil
Benzene
Ethylbenzene
Toluene
TPH as Diesel
TPH as Gasoline
Xylene
430
100

1 x 10'1
2.9
4.2
10
1
1.7
SITE 54
Subsurface Soil
Benzene
TPH as Gasoline
1 x 10-'
1
TPH = total petroleum hydrocarbon
ppm = parts per million
        During the Additional Site Characterization field effort (IT Corp., 1996) chlorinated solvents were
        detected hi the soil samples.  However, these constituents and their corresponding cleanup goals are not
        presented hi this Record of Decision. Any additional contaminants of concern and associated cleanup
        levels will be incorporated into the remedial design per Section 2.2.9.5 and documented hi the Feasibility
        Study Report and  Record of Decision for the Final Operable Unit.

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2.2.9.6      Site 56 - Oil/Water Separator 2989
Alternative 56.3 was selected by the USAF, with concurrence by the USEPA and the State of
California as the remedy for Site 56. The major components of this remedy include:

       •      excavating approximately 1,110 yd3 of contaminated surface and shallow soils
              to remove all contamination above acceptable levels;

       •      transporting the excavated soils to the on-base ex situ bioremediation facility;

       •      treating the excavated soils by ex situ bioremediation as appropriate;

       •      transporting the treated soils to, and consolidating them with landfill cap
              foundation materials at Site 4 or Site 7, as appropriate; and

       •      monitoring the groundwater if contamination that threatens groundwater quality
              remains at the site.
Capital cost estimates for this remedy are projected at approximately $36,000, operation and
maintenance costs are estimated at $12,000.  Total cost, represented as a net present worth
using a five percent discount rate, is calculated at $48,000.

The basis for cleanup is protection of human health and groundwater quality. Table 2-24
presents the Site 56 cleanup levels.
                           Table 2-24.  Site 56 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Soil
Arsenic
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Chrysene
Dibenzo(a,h)anthracene
Lead
Oil and Grease
TPH as Diesel
22
3.3 x lO'1
3.3 x 10-'
3.3 x ID'1
3.3 x 10-'
3.3 x lO'1
130
430
100

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Contaminant of Concern
Cleanup Level (ppm)
Subsurface Soil
Oil and Grease
TPH as Diesel
TPH as Gasoline
430
100
5
TPH = total petroleum hydrocarbon
ppm = parts per million
2.2.9.7     Site 57 - Oil/Water Separator 7019
Alternative 57.3 was selected by the USAF, with concurrence by the USEPA and the State of
California as the remedy for Site 57.  The major components of this remedy include:

       •      treating the contaminated shallow and deep soils by hi situ SVE; and

       •      monitoring the groundwater if contamination that threatens groundwater quality
             remains at the site.

The goal of cleaning up the vadose zone is to minimize further degradation of the groundwater
by the contaminants hi the soil.  It is generally preferable from a technical and cost perspective
to clean up contamination in the vadose zone before it reaches the groundwater.  The soil
cleanup standard will be achieved when the residual vadose zone contaminants will not cause
the groundwater cleanup standard, as measured in groundwater wells monitoring the plume, to
be exceeded after the cessation of the groundwater remediation. The Air Force will make the
demonstration that the standard has been met through contaminant fate and transport modeling,
trend analysis, mass balance, and/or other means.  This demonstration will include
examination of the effects of the residual vadose zone contamination in the groundwater using
VLEACH or another appropriate vadose zone model, hi conjunction with a groundwater fate
and transport model, to predict the resulting concentration from this residual vadose zone
contamination hi the nearest groundwater wells monitoring the site.  This demonstration can be
made prior to the cessation of groundwater remediation.  The Ah" Force  shall provide
verification, through actual data, that the above standard has been met.  The signatory parties
to this Record of Decision (ROD) will jointly make the decision that the  soil cleanup standard
has been met.

The Air Force shall operate the SVE system until it makes the demonstration that the cleanup
standard, set forth above, has been met. The Air Force shall continue to operate the SVE
system if appropriate, after considering the following factors:

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 a)     Whether the predicted concentration of the leachate from the vadose zone (using
       VLEACH or another appropriate vadose zone model that interprets soil gas data) will
       exceed the ground water cleanup standard;

 b)     Whether the mass removal rate is approaching asymptotic levels after temporary
       shutdown periods and appropriate optimization of the SVE system;

 c)     The additional cost of continuing to operate the SVE system at concentrations
       approaching asymptotic mass levels;

 d)     The predicted effectiveness and cost of further enhancements to the SVE system (e.g.,
       additional vapor extraction wells);

 e)     Whether the cost of groundwater remediation will be significantly more if the residual
       vadose zone contamination is not addressed;

 f)     Whether residual mass  in the vadose zone will significantly prolong the time to attain
       the ground watercleanup standard; and

 g)     The incremental cost over time of vadose zone remediation compared to the
       incremental cost over time for groundwater remediation on the basis of a common unit
       (e.g., cost of pound of TCE removed) provided that the underlying groundwater has
       not reached aquifer cleanup levels.

 The signatory parties agree that the Air Force may cycle the SVE system on and  off in order
 to optimize the SVE operation  and/or to evaluate the factors listed above.

 The signatory parties to this ROD will jointly make the decision that the SVE system may be
 shut off.  If the parties cannot reach  a joint resolution, any party may invoke dispute
 resolution. This ROD does not resolve the ARAR  status of State requirements regarding the
establishment of soil cleanup levels.  The parties agree that hi the event of a dispute regarding
 SVE shutoff, the State may argue its authority to require soil cleanup (including soil cleanup
 standards) as the basis for continuing operation of  the SVE system, based on the above factors.

Capital cost estimates for this remedy are projected at approximately $852,000, operation and
maintenance costs are estimated at $168,000.  Total cost, represented as a net present worth
using a five percent discount rate, is calculated at $1,012,000.
                                           AA

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 The basis for cleanup is protection of groundwater quality.

                            Table 2-25.  Site 57 Cleanup Level
            Contaminant of Concern
               Cleanup Level
  Subsurface Soil
  Trichloroethene
See text in Section 2.2.9.7
2.2.9.8      Site 59 - Oil/Water Separator 4251
Alternative 59.2 was selected by the USAF, with concurrence by the USEPA and the State of
California as the remedy for Site 59.  The major components of this remedy include:

       •      excavating approximately 1,200 yd3 of contaminated shallow soils to remove all
              contamination above acceptable levels;

       •      transporting the excavated soils to the on-base ex situ bioremediation facility;

       •      treating the excavated soils by ex situ bioremediation as appropriate;

       •      transporting the treated soils to, and consolidating them with landfill cap
              foundation materials at Site 4 or Site 7, as appropriate; and

       •      monitoring the groundwater if contamination that threatens groundwater quality
              remains at the site.

Capital cost estimates for this remedy are projected at approximately $64,000, operation and
maintenance costs are estimated at $24,000.  Total cost, represented as a net present worth
using a five percent discount rate,  is calculated at $87,000.

The basis for cleanup is protection of groundwater quality. Table 2-26 presents the Site 59
cleanup levels.

                           Table 2-26.  Site 59 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Subsurface Soil
TPH as Diesel
TPH as Gasoline
10
1
TPH = total petroleum hydrocarbon      ppm = parts per million

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         2.2.9.9      Site 60 - Oil/Water Separator 6900
I        Alternative 60.2 was selected by the USAF, with concurrence by the USEPA and the State of
         California as the remedy for Site 60.  The major components of this remedy include:


                •      excavating approximately 350 yd3 of contaminated shallow soils to remove all
                       contamination above acceptable levels;

                •      transporting the excavated soils to the on-base ex situ bioremediation facility;

                •      treating the excavated soils by ex situ bioremediation as appropriate;

                •      transporting the treated soils to, and consolidating them with landfill cap
                       foundation materials at Site 4 or Site 7, as appropriate; and

                •      monitoring the groundwater if contamination that threatens groundwater quality
                       remains at the site.


         Capital cost estimates for this remedy are projected at approximately $23,000, operation and
         maintenance costs are estimated at $11,000. Total cost, represented as a net present worth
         using a five percent discount rate, is calculated at $33,000.


         The basis for cleanup is protection of groundwater quality.  Table 2-27 presents the Site 60
         cleanup levels.
                                    Table 2-27. Site 60 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Subsurface Soil
TPH as Gasoline
Xylenes
5*
17
         TPH = total petroleum hydrocarbon             ppm = parts per million
          * If contamination is found to exist below the limits excavation, the remedial action and cleanup level will be
         reevaluated.
         2.2.9.10     Site 62 - Oil/Water Separator 7110 and Jet Engine Test Cell
                       (Facility 7099)
         Alternative 62.3 was selected by the USAF, in concurrence by the USEPA and the State of
         California as the remedy for Site 62.  The major components of the remedy include:
                                                   2-46

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       •      excavating approximately 500 yd3 of contaminated surface and shallow soils to
              remove all contamination above acceptable levels;

       •      transporting the excavated soils to the on-base ex situ bioremediation facility;

       •      treating the excavated soils by ex situ bioremediation as appropriate;

       •      transporting the treated soils to, and consolidating them with landfill cap
              foundation materials at Site 4 or Site 7, as appropriate; and

       •      monitoring the groundwater if contamination that threatens groundwater quality
              remains at the site.

Capital cost estimates for this remedy are projected at approximately $29,000, operation and
maintenance costs are estimated at $23,000.  Total cost, represented as a net present worth
using a five percent discount rate,  is calculated at $49,000.
The basis for cleanup is protection of ecological receptors, human health, and groundwater
quality.  Table 2-28 presents the Site 62 cleanup levels.

                           Table 2-28.  Site 62 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Soil
Benzo(k)fluoranthene
Cadmium
Fluoranthene
Lead
Naphthalene
Pyrene
TPH as Diesel
Zinc
3.3 x lO'1
9
3.3 x lO'1
130
3.3 x 10-'
3.3 x ID'1
10
1559
                                          9.-47

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                            Table 2-28. Site 62 Cleanup Levels (Continued)
Contaminant of Concern
Cleanup Level (ppm)
Subsurface Soil
Benzo(a)pyrene
TPH as Diesel
3.3 x 10-'
10
       TPH = total petroleum hydrocarbon
ppm = parts per million
       2.2.9.11     Site 65 - Oil/Water Separator 6910
       Alternative 65.3 was selected by the USAF, in concurrence by the USEPA and the State of
       California as the remedy for Site 65. The major components of the remedy include:


              •       excavating approximately 900 yd3 of contaminated surface and shallow soils to
                     remove all contamination above acceptable levels;

              •       transporting the excavated surface soils to an off-base disposal facility;

              •       transporting the excavated shallow soils to the on-base ex situ bioremediation
                     facility;

              •       treating the excavated shallow soils by ex situ bioremediation  as appropriate;

              •       transporting the treated soils, and consolidating them with landfill cap
                     foundation materials at Site 4 or Site 7, as appropriate; and

              •       monitoring the groundwater if contamination that threatens groundwater quality
                     remains at the site.


       Capital cost estimates for this remedy are projected at approximately $114,000, operation and
       maintenance costs are estimated at $22,000.  Total cost, represented as a net present worth
       using a five percent discount rate, is calculated at $134,000.


       The basis for cleanup is  protection of groundwater quality.  Table 2-29 presents the Site 65
       cleanup levels.
RL/10-95/ES/1260005.AWS
                                                 2-48

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                           Table 2-29. Site 65 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Soil
Chromium
Lead
Oil and Grease
TPH as Diesel
Subsurface Soil
TPH as Diesel
TPH as Gasoline
210
130
430
10

10
1
TPH = total petroleum hydrocarbon
ppm = parts per million
2.2.9. 72     Site 69 - Open Burn/Open Detonation Area
Alternative 69.2 was selected by the USAF, in concurrence by the USEPA and the State of
California as the remedy for Site 69.  The major components of the remedy include:

       •       removing surface water, if present, by pumping and discharging to the POTW;

       •       excavating approximately 8,680 yd3 of contaminated sediments and surface soils
              to remove all contamination above acceptable levels;

       •       transporting the excavated sediments and surface soils to, and consolidating
              them with landfill cap foundation materials at Site 4, as appropriate; and

       •       monitoring surface water as appropriate if contamination remains at the site that
              threatens  surface water quality.

Capital cost estimates for this remedy are projected at approximately $370,000, operation and
maintenance costs are estimated at $93,000.  Total cost,  represented as a net present worth
using a five percent discount rate, is calculated at $451,000.

The basis for cleanup is protection of human health, ecological receptors, and surface water
quality. Table 2-30 presents the Site 69 cleanup levels.
                                          2-49

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                                    Table 2-30.  Site 69 Cleanup Levels
Contaminant of Concern
Cleanup Level (ppm)
Surface Water
Barium
Manganese
Sediment
OCDD
OCDF
Total HPCDD
Total HPCDF
Total HXCDD
Total HXCDF
Total PCDD
Total PCDF
Total TCDF
1
1.0x10-'

5 x lO'6
total 2,3,7,8-TCDD equivalent
Surface Soil
Barium
Manganese
Zinc
1754
(A)
1559
DI /in OC/CC/11JWYK
                                                   2-50

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                      Table 2-30.  Site 69 Cleanup Levels (Continued)
Contaminant of Concern
Cleanup Level (ppm)
Surface Soil (continued)
OCDD
OCDF
Total HPCDD
Total HPCDF
Total HXCDD
Total HXCDF
Total PCDD
Total PCDF
Total TCDF
2x10-"
total 2,3,7,8-TCDD equivalent
(A) Manganese was a contaminant of concern (COC) in the Focused Feasibility Study Report; however, revised
natural background concentration is 5720 ppm.  The maximum concentration detected was 1430 ppm; therefore,
manganese is no longer a COC.
ppm = parts per million                       HPCDD = heptachlorodibenzo-p-dioxin
HPCDF = heptachlorodibenzofuran             HXCDD = hexachlorodibenzo-p-dioxin
HXCDF = hexachlorodibenzofuran             OCDD  = octachlorodibenzo-p-dioxin
OCDF = octachlorodibenzofuran               TCDD  = tetrachlorodibenzo-p-dioxin
TCDF = tetrachlorodibenzofuran               PCDD  = pentachlorodibenzo-p-dioxin
PCDF = pentachlorodibenzofuran


2.2.10       Statutory Determinations

The selected remedies satisfy the statutory requirements in CERCLA Section 121(b), as

amended by SARA, in that the following mandates are attained:
              the selected remedies are protective of human health and the environment, will
              decrease site risks, and will not create short-term risks nor have cross-media
              consequences;

              the selected remedies comply with federal and state requirements that are
              applicable, or relevant and appropriate, to the remedial actions;

              the selected remedies are cost-effective in their fulfillment of the nine CERCLA
              evaluation criteria; and

              the selected remedies utilize permanent solutions to the maximum extent
              practicable.

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 3.0  Soil Operable Unit Sites Selected for No Further Action
3.1   Declaration for the Soil Operable Unit Sites Selected for No Further Action
                       No Further Action is Necessary to Ensure
                    Protection of Human Health and the Environment
3.1.1 Site Name and Location
Soil OU Sites (IRP Sites) Selected for No Further Action
Mather AFB (a NPL Site),
Sacramento County, California

3.1.2 Statement of Basis and Purpose
The Soil OU sites for which no further action was chosen at the formerly active Mather AFB
were investigated under the Mather AFB IRP and are described and evaluated in the RI/FS
documents. These sites include:  Site 9 - Fire Department Training Area Number 2, Site 10 -
Fire Department Training Area Number 3, Site 14 - Drainage Ditch Number 2, Site 16 -
Electron Tube Burial Site, Site 21 - Asphalt Rubble Storage Site, Site 22 - Asphalt Rubble
Storage Site, Site 24 - JP-4 Spill Site/Refueling Apron, Site 26 - Building 10072 UST, Site 27
- Building 10060 UST,  Site 28 - Building  16100 UST, Site 31 - Building 10090 UST, Site 33 -
Building 3308 USTs, Site 38 - Building 3388, Site 40 - Building 3875 UST, Site 41 -  Building
2995 USTs, Site 42 - Building 2898 UST, Site 43 - Building 10150 USTs, Site 44 - Building
8540 UST, Site 45 - Building 7003 UST, Site 46 - Building 8158 UST, Site 48 - Building
10410 USTs, Site 49 - Building 10450 UST, Site 51 - Building 10030 UST, Site 52 -  Building
10400 UST, Site 53 - Building 18501 UST, Site 55 - OWS 7038, Site 58 - OWS 4771, Site 61
- OWS 6905, Site 63 - OWS 3221 and USTs, Site 64 - OWS 4120, Site 66 - OWS 6915, Site
A - Building 1226 UST, Site C - Building 3975 UST, Site E - Building 10015 UST, Site F -
Building 10065 UST, Site G - Building 18018 UST, Site H - Building 18020 UST and
Building 18011 UST, and Site I - Building 4853 UST.  These remedial actions were chosen in
accordance with CERCLA, as amended by SARA, and to  the extent practicable, the NCP.
These decisions are based on the Administrative Record for these sites.

The USEPA Region IX and the State of California concur that no action is necessary at these
sites to ensure protection of human health and the environment.

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 3.1.3 Description of the No Further Action Decision
 Cleanup options were not developed for sites which were previously clean-closed or
 recommended for clean-closure by Sacramento County (i.e., USTs already removed) or for
 which no COCs were identified. Based on the human health risk assessment, all cancer risks
 are within or below the acceptable range of 1 x 10^ to 1 x 10"6 and all non-cancer risks have a
 hazard index of less than 1.0 in their current state. Therefore, the USAF is not proposing
 cleanup or further investigative activities.  These no further action sites include: Sites 9, 10,
 14, 16,  21, 22, 24, 26, 27, 28, 31, 33, 38, 40, 41, 42, 43, 44, 45, 46, 48, 49, 51, 52, 53, 55,
 58, 61,  63, 64, 66, A, C, E, F, G, H, and I.

 3.1.4 Summary of Site Risks
 Remedial investigation activities at Mather AFB included fate  and transport modeling and the
 MBRA  [IT 1995d].  The data collected and utilized in the RIs  and FFS were of USEPA
 quality Level HI, IV, or V, or equivalent [USEPA 1987]. Formal data validation of the
 RI- and  FFS-generated data was performed to ensure that data were of the quality
 commensurate with their intended use.

 Based on the human health risk assessment, all cancer risks for the sites described in this no
 further action section are within or below the acceptable range of 1 x 10"4 to  1 x 10"6, and all
 non-cancer risks have a hazard index less than 1.0 in their current state.

 3.1.4.1     Human Health  Risks
 Analytes detected in the course of the RI activities at Mather AFB were subjected to a
 multi-step screening process to determine COCs.  The following steps were employed in the
 COC determination process for the Soil OU sites and are described in Section 2.2.6.1.

      •     initial screening  methods prescribed by USEPA guidance;
      •     comparison to background;
      •     comparison to ARARs;
      •     comparison to analytical method quantitation limit;
      •     evaluation of operational history (i.e., process knowledge); and
      •     evaluation of estimated risk to human and ecological receptors.

3.2   Decision Summary for Soil OU Sites Selected for No Further Action

3.2.1 Site Name, Location,  and Description
The Soil OU sites selected for no further action at the formerly active base are presented in
Figure 3-1 and in Section 3.1.2.

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Rgure  3-1.   Soil Operable Unit Sites  Selected  for No  Further Action
                                                                            SCALE
       SOIL OPERABLE UNIT SITE SELECTED FOR NO FURTHER ACTION
0
3000      6000 FEET

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 3.2.2 Site History and Enforcement Activities
 Previous investigations have been conducted at the Soil OU sites selected for no further action
 as part of the USAF IRP and are presented in Table 3-1.

 3.2.3 Highlights of Community Participation
 The public participation requirement of CERCLA Sections 113(k)(2)(B)(I-v) and 117 were met
 through a public comment period (held May 8 through June 7, 1995) and a public meeting
 (held on May 18, 1995) to address the Proposed Plan and content of supporting RI/FS
 documents  in the selection of the no further action sites.

 3.2.4 Scope and Role of Response Action
 Since these sites have been clean-closed or recommended to Sacramento County for
 clean-closure, or no COCs were identified, this section of the ROD presents the no further
 action alternative as the planned response action.  No unacceptable risk to human health or the
 environment exists at these sites.

 3.2.4. 7 Description of the  "No Action" Alternative
 Cleanup options were not developed for sites which were previously clean-closed by
 Sacramento County or recommended for clean-closure (i.e., UST already removed to
 Sacramento County),  or for which no COCs were identified.  Since no risk to human health or
 the environment exists at these  sites, the USAF is not proposing cleanup or further
 investigative activities.  The no action alternative will not involve any long-term monitoring.

 3.2.5 Summary of Site Characteristics
 A brief description of each of the no further action sites is provided in the following  sections.

 3.2.5.1      Site 9 - Fire Department  Training Area  Number 2
 Site 9 was used  as a fire-training area between 1945 and 1947 and is reportedly located west of
 the Base Operations Building, underneath the aircraft parking ramp. Exercises were
 conducted daily  in a cleared area within an earthen berm.  Approximately 50 to 250 gallons of
POL waste were reportedly used per exercise, with some solvents being possibly commingled
with the POL waste.  The location of Site 9 has not been found on historic air photographs,
nor has any other evidence indicated where this site was situated.  Consequently, no  sampling
has been conducted. Because the site cannot be located, no further action will be conducted
under CERCLA.

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                        Table 3-1.  Previous Investigations at the No Further Action Sites
SITE NUMBER
9
10
14
16
21
22
24
26
27
28
31
33
38
40
41
42
43
44
45
46
48
49
51
52
53
55
58
61
63
64
66
A
C
E
F
G
H
I
APPLICABLE INVESTIGATION
1, 11, 12
1,2,4,5,6, 11, 12
1,2,3,4,5,6,7, 10, 11, 12
1,4,5,7, 11, 12
1,4, 11, 12
1, 11, 12
4,5,7,11,12
1,4,5,6,7,9, 11, 12
1,7, 11, 12
1,7, 11, 12
9, 11, 12
9, 11, 12
9, 11, 12
9, 11, 12
9, 11, 12
9, 11, 12
9, 10, 11, 12
9, 11, 12
11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
5,8, 11, 12
5,8, 11, 12
8, 11, 12
5,8,9, 10, 11, 12
5,8, 11, 12
5,8, 11, 12
9, 10, 11, 12
7,9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
9, 10, 11, 12
        1.       Installation Restoration Program (IRP) Records Search for Mather Air Force Base, Phase I [CH2M-HiIl, Inc. 1982];
        2.       IRP Phase II, Stage 2 Investigation [AeroVironment 1987];
        3.       IRP Phase II, Stage 3 Investigation [AeroVironment 1988];
        4.       Well Redevelopment and Sampling Plan [IT 1988a];
        5.       Quarterly Routine Groundwater Sampling [IT 1993g] and [EA 1990a-c];
        6.       Site Inspection Report [IT 1990a];
        7.       Group 2 Sites Remedial Investigation Report [IT 1992a];
        8.       Group 3 Sites Technical Memorandum [IT 1993a];
        9.       Underground Storage Tank Closure Reports [IT 1990b and IT 1993c-d];
        10.      Soil Operable Unit (OU) and Groundwater OU Additional Field Investigation Report [IT 1994a];
        11.      Mather Baseline Risk Assessment Report [IT 1995d]; and
        12.      Groundwater OU and Soil OU Focused Feasibility Study Report [IT 1995a].
RL/10-95/ES/1260005.AWS
                                                             3-5

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       3.2.5.2      Site  10 - Fire Department Training Area Number 3
       Site 10 is the assumed location of a fire-training area used between 1947 and 1958, and is
       located under the SAC refueling tanker loading apron. Approximately 100 to 500 gallons of
       POL waste, possibly commingled with solvents, were used per exercise.  Investigations of this
       site have revealed no COCs.  However, another location, just north of the former refueling
       apron, was found in 1994, and is now thought to be the actual location of the fire-training
       area.  The new location, called Site IOC, was investigated in 1995 and will be included in the
       Final  OU.

       3.2.5.3      Site  14 - Drainage Ditch Number 2
       Site 14 is an unlined drainage ditch located in the north-central portion of the base between
       Building 2950 and the former motor pool area. During the late 1960s, waste oils and solvents
       were reportedly dumped directly into the ditch.  The ditch drains off-base and feeds a
       south-trending ditch that reenters the base at Site  13.  Investigations have revealed no COCs.

       3.2.5.4      Site  16 - Electron Tube Burial Site
       Site 16 is located in the SAC area, directly under Building 8170.  In the late 1950s,
       approximately sixty low-level radioactive electron tubes were reportedly buried in 15-foot
       auger  holes. The electron tubes were placed inside one-gallon containers and encased in
       concrete. Investigations have revealed no radiation at the surface above background levels,
       nor in nearby groundwater from Well MAFB-18. There is no significant health risk due to
       exposure to the intact concrete containing the electron tubes.  Future landowners or lessees
       will be notified that  any excavation at the site should proceed with caution to avoid inadvertent
       exposure to broken concrete containers and/or electron tubes.

       3.2.5.5     Site 21 - Asphalt Rubble Storage Site
       Site 21 is located in two discrete areas northeast of Site 20. Asphalt and concrete rubble were
       stored on the ground in the two areas within the site.  Site 21 did not reportedly receive any
       hazardous waste. Known disposal practices indicated no disposal of contaminants, and visual
       inspections were consistent with disposal of inert construction rubble only.

       3.2.5.6     Site 22 - Asphalt Rubble Storage Site
       Site 22 is located east of the sewage treatment plant. Asphalt and concrete rubble were stored
       on the ground at the site.  Site 22 reportedly did not receive any hazardous waste. Known
RL/IO-95/ES/1260005.AWS                                  3-6

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       disposal practices indicated no disposal of contaminants, and visual inspections were consistent
       with disposal of inert construction rubble only.

       3.2.5.7      Site 24 - 1983 JP-4 Spill and Refueling Apron
       Site 24 consists of the SAC aircraft refueling tanker loading apron and an adjacent low, grassy
       area located south and west of the loading area. In 1983, approximately 8,000 gallons of JP-4
       were spilled on the concrete tanker loading area during refueling operations.  Some of the fuel
       was reportedly washed by rainwater onto adjacent unpaved areas. Investigations have revealed
       no COCs.

       3.2.5.8      Site 26 - Building 10072, One Abandoned UST
       Site 26 is located in the extreme southwest corner of the base.  The site had a 250-gallon UST
       which  stored motor gasoline.  The tank and its associated piping were installed in 1956 and
       removed in 1987.  Investigations have revealed no COCs. This site has been recommended to
       Sacramento County for clean-closure.

       3.2.5.9      Site 27 - Building 10060, One Abandoned UST
       Site 27 is located in an ungraded, grassy area between the runways and the former base
       housing. A steel 379-gallon diesel fuel UST was installed at the site in 1954  and removed in
       1987.  Investigations have revealed no COCs.  This site has been recommended to Sacramento
       County for clean-closure.

       3.2.5.10     Site 28 - Building 16100, One Abandoned UST
       Site 28 is located on the western edge of an open area between the former Wherry and
       Capehart housing, adjacent to base housing well FH-6. The site had a steel 218-gallon motor
       gasoline UST which was installed in 1968 and removed in 1987. Investigations have revealed
       no COCs. This site has been clean-closed by Sacramento County.

       3.2.5. 7 7     Site 31  - Building 10090, One Abandoned UST
       Site 31 is approximately 2,000 feet east of Site 7.  This site contained a 250-gallon steel UST
       that stored motor gasoline for emergency  power generation.  The tank was installed in 1954
       and removed in December 1987.  During excavation, a strong hydrocarbon odor was noted,
       and a "black scum" and "film of gasoline" were observed on the surface of water seeping into
       the excavation. Water was encountered 2 to 3 feet bis  during excavation.  The water
       encountered in the excavation was probably perched-water above a low permeability soil

                                               7 7
RL/10-95/ES/1260005.AWS                                 J '

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       horizon.  The quantity of fuel lost at the site is unknown.  This site has been recommended to
       Sacramento County for clean-closure. The Air Force intends to excavate limited soil at this
       site to remove easily removable contaminated soils.

       3.2.5.12    Site 33 - Building 3308, Six Abandoned USTs
       This site is located in the Main Base area, approximately 900 feet southwest of Site 32. This
       site contained one 3,600-gallon and five 1,500-gallon USTs that were used to store gasoline
       and mineral spirits. The tanks were installed in 1942.  The tanks were reportedly taken out of
       service in 1961 and were removed in December 1988.  During excavation, strong solvent
       odors were noted, and one of the tanks contained residual hydrocarbons.

       Prior to completing the excavation,  the hydrocarbons (approximately 540 gallons) were
       removed from the tank and transported to a recycling facility.  Approximately 400 cubic yards
       of contaminated soil were removed from the site, incinerated, and disposed of on-base.  The
       excavation was backfilled with clean crushed rock and then covered with four-inch thick
       asphalt paving.  Potentially contaminated soil next to existing structures and buildings was not
       removed due to limited access; the Air Force will consider  excavating additional soil under the
       building awning if consistent with building use or property  transfer.

       3.2.5.13    Site 38 -  Building 3388
       Site 38 consists of Building 3388 located near the intersection of Fourth Street and Air Corps
       Way.  Two steel 5,000-gallon tanks (Tanks 3390 and 3391) were used to store gasoline,
       diesel, and alcohols from 1945 to  1977.  This site has been recommended to Sacramento
       County for clean-closure.

       3.2.5.14    Site 40 -  Building 3875, One UST
       Site 40 is at Building 3875 near the intersection of Stratotanker Avenue and Femoyer Street.
       A steel 570-gallon diesel  fuel UST was installed in 1958 and removed hi 1988.  Investigations
       have revealed no COCs.  This site has been clean-closed by Sacramento County.

       3.2.5.15     Site 41 -  Bui/ding 2995, Two USTs
       Site 41  is at Building 2995 near Femoyer Street at the Old Motor Pool facility.  This site had
       two, steel 10,500-gallon USTs which stored gasoline and diesel from 1965 to 1977.
       Investigations have revealed no COCs.  The USTs were removed in 1989 and the site has been
       clean-closed by Sacramento County.
RL/10-95/ES/1260005.AWS
                                                3-8

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       3.2.5.16    Site 42 - Building 2898, One UST
       Site 42 is at Building 2898 located on Femoyer Street.  This site had a steel 500-gallon UST
       which stored aviation gasoline from 1967 until 1974-1975.  Investigations have revealed no
       COCs. The UST was removed in 1988 and the site has been clean-closed by Sacramento
       County.

       3.2.5.7 7    Site 43 - Building 10150, Two Abandoned USTs
       Site 43 is located in the east-central portion of the base near the AC&W site. One tank was
       removed in 1988 and the area clean-closed by Sacramento County.  The second tank was
       removed in 1993 and the site recommended to Sacramento County for clean-closure.
       Investigations have revealed no COCs.

       3.2.5.18    Site 44 - Building 8540,  One UST
       Site 44 consisted of a concrete 1,800-gallon UST located at Building 8540.  The tank was used
       to store oil and water starting in 1942 and was removed in 1988.  This site has been
       clean-closed by Sacramento County.  Investigations have revealed no COCs.

       3.2.5.19    Site 45 - Bui/ding 7003, One UST
       Site 45 is  at Building 7003 located at the old missile fueling facility.  The tank was used to
       store ammonia from the early 1960s until 1978 and was removed in 1988. This site has been
       clean-closed by Sacramento County.  Investigations have revealed no COCs.

       3.2.5.20   Site 46 - Bui/ding 8158, One UST
       Site 46 is  at Building 8158 located in the northeast portion of the base, in the SAC Alert
       Facility and consisted of a steel 250-gallon diesel  fuel UST.  The UST and its associated
       piping were removed in 1993 and the site has been recommended to Sacramento County for
       clean-closure.  Investigations have revealed no COCs.

       3.2.5.27    Site 48 - Building 10410, Two Abandoned USTs
       Site 48 is at Building 10410 located in the east-central portion of the base  near the AC&W
       site. Site drawings indicate the presence of two USTs;  however, a site inspection found only
       one tank.  The existing tank which contained gear oil and diesel fuel was removed in 1993 and
       has been recommended to Sacramento County for clean-closure. Investigations have revealed
       no COCs.
                                               i o
RL/10-95/ES/I260005.AWS                                 J~y

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       3.2.5.22    Site 49 - Building 10450, One UST
       Site 49 is located hi the east-central portion of the base near the AC&W facility.  The site
       consisted of a steel 8,500-gallon UST which contained gasoline and diesel.  This tank was
       removed hi 1993 and the site has been recommended to Sacramento County for clean-closure.
       Investigations have revealed no COCs.

       3.2.5.23    Site 51 - Building 10030, One UST
       Site 51 is located hi the north-central portion of the base near the northeast end of
       Runway 22L. The site consisted of a 275-gallon diesel fuel UST.  The UST was  removed in
       1993 and the site has been recommended to Sacramento County for clean-closure.
       Investigations have revealed no COCs.

       3.2.5.24    Site 52 - Building 10400, One UST
       Site 52 is located hi the east-central portion of Building 10400.  The site was covered by
       gravel, grass, and railroad-tie landscape border.  The site consisted of a steel 4,000-gallon
       diesel fuel UST.  The UST was removed in 1993 and the site has been recommended to
       Sacramento County for clean-closure. Investigations have revealed no COCs.

       3.2.5.25    Site 53 - Building 18501, One UST
       Site 53 is located in the southeast portion of the base, near Sites G  and H and within the
       former Weapons Storage Facility area. The site consisted of a 200-gallon diesel fuel UST.
       The UST was removed hi 1993 and the site has been recommended to Sacramento County for
       clean-closure. Investigations have revealed no COCs.

       3.2.5.26    Site 55 - OWS 7038
       Site 55 consisted of OWS 7038, located hi the western portion of the SAC area, approximately
       120 feet west of Building 7035.  Oil/water separator 7038 is a belt-type skimmer which
       received aircraft washwater and discharges to the base sanitary sewer system.  Prior to 1971,
       OWS 7038 reportedly received TCE, PCE, antifreeze, methyl ethyl ketone,  and methylene
       chloride produced during maintenance operations. Investigations have revealed no COCs.

       3.2.5.27    Site 58 - OWS 4771
       Site 58 consists of OWS 4771 and is located hi the southeast portion of the Main Base at the
       Army Helicopter washrack, approximately 450 feet east of Building 4677.  Oil/water separator
       4771 is a belt-type skimmer, constructed hi 1969, that received wastewater generated from the

                                               ^ 10
RL/IO-95/ES/1260005.AWS                                 J lu

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       washrack. The waste water reportedly contained fuels, oil and grease, hydraulic fluid,
       PD-680, and antifreeze.  Effluent from the OWS was discharged directly to the sanitary sewer
       system.  Investigations have revealed no COCs.

       5.2.5.25    Site 61 - OWS 6905
       Site 61 consists of an OWS that supports Building 7005, located in the SAC area.
       Building 7005 was an aircraft maintenance hangar (referred to as the Fuel Cell), used for
       aircraft fuel-system maintenance, which drained to OWS 6905.  The OWS discharged directly
       to the storm sewer system.  It was reported that TCE, PCE, methyl ethyl ketone, and other
       solvents were used hi Building 7005 in the 1960s and 1970s. Investigations have revealed no
       COCs.

       3.2.5.29    Site 63 - OWS 3321 and Two USTs
       Site 63 is located in the northwest portion of the base and consisted of OWS 3321 at the South
       Hobby Shop, northeast of Building 3320.  Oil/water separator 3321 is a sump-type OWS that
       received wastewater from the Automotive Hobby Shop and adjoining automotive component
       steam-cleaning pad at Building 3320.  The wastewater may have contained fuels, oils,
       hydraulic fluid, antifreeze, cleaning fluids (containing trichloroethane, TCE, and methyl ethyl
       ketone), and paint strippers (containing phenols and methyl chloride). Underground storage
       tank 3320A was a 250-gallon waste oil tank, while UST 3320B was a 1,000 gallon waste oil
       tank. The tanks were removed in 1993 and the tank sites have been recommended to
       Sacramento County for clean-closure.  Investigations have revealed no COCs.

       3.2.5.30   Site 64 - OWS 4120
       Site 64 consists of OWS 4120 and is located hi the far west portion of the Main Base at the
       fuel tanker yard, approximately 240 feet northeast of Building 4120.  Oil/water separator 4120
       was a sump-type OWS that was constructed in the 1960s and received wastewater generated
       from the fuel truck washrack yard.  These wastewater contained fuels, oils, hydraulic fluids,
       and antifreeze.  Effluent from the OWS was discharged to the sanitary sewer system.
       Investigations have revealed no COCs.

       3.2.5.31    Site 66 - OWS 6915
       Site 66 consists of OWS 6915 and is located in the central portion of the SAC  area at the jet
       engine repair shop, approximately 10  feet north of Building 7024.  Oil/water separator 6915 is
       a sump-type OWS, constructed in the  early 1960s, which received wastewater from the jet
RUIO-95/ES/1260005.AWS
                                               3-11

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       engine repair shop.  This wastewater contained fuels, oils, hydraulic fluid, and antifreeze.
       Effluent from this OWS was discharged directly to the storm drain system.  Investigations
       have revealed no COCs.  This site has been clean-closed by Sacramento County.

       3.2.5.32    Site A
       Building 1226 is the former Sierra Dining Hall located in the northwest portion of the base on
       Lower Placerville Road.  Tank 1226 was located on the southeast side of the building and was
       reported to be a 4,000-gallon diesel fuel tank. Investigations have revealed no COCs.  The
       tank was removed hi 1993 and the site recommended to Sacramento County for clean-closure.

       3.2.5.33    Site C
       Building 3975 is located in the north-central portion of the base and is part of the Water
       Treatment Plant. Tank 3965 was reported to be a 550-gallon diesel fuel tank.  The tank
       passed a leak test hi 1988 and was removed in 1993.  Investigations have revealed no COCs.
       The site has been recommended to Sacramento County for clean-closure.

       3.2.5.34    Site E
       Tank 10015 was located in the north-central portion of the base on Alert Road near the
       approach end of the Runway 22. It supported the Instrument Landing  System Facility at
       Building 10015. The tank was reported to be a 1,000-gallon diesel fuel tank.  The tank passed
       a leak test in 1988 and was removed hi 1993.  Investigations have revealed no COCs. The site
       has been recommended to Sacramento County for clean-closure.

       3.2.5.35    SiteF
       Site F is located in the  center of the base on Perimeter Road between Runway 22 and the air
       traffic control tower. The site consisted of Tank  10065, located west of Building 10065.  The
       UST was a 1,000-gallon diesel fuel tank.  Investigations have revealed no COCs. The UST
       was removed hi 1993 and the site has been recommended to Sacramento County for
       clean-closure.

       3.2.5.36    Site G
       Site G is located in the southeast portion of the base near Sites H and 53. The site is south of
       Building  18018 and consists of a fiberglass 6,000-gallon diesel fuel tank. Investigations have
       revealed no COCs. The UST was removed in 1993 and the site has been recommended to
       Sacramento County for clean-closure.
RL/10-95/ES/1260005.AWS
                                               3-12

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       3.2.5.37    SiteH
       Site H is located in the southeast portion of the base near Sites G and 53. It consisted of a
       steel 750-gallon diesel fuel tank located at the northeast corner of Building 18020.
       Investigations have revealed no COCs.  The UST was removed hi 1993 and the site has been
       recommended to Sacramento County for clean-closure.

       3.2.5.38    Site I
       Site I consists of Tank 4853 and is located hi the north-central portion of the base,
       approximately 60 feet east of the helicopter washrack.  The steel 550-gallon UST reportedly
       stored unleaded gasoline. The UST passed a leak test hi 1988 and was removed hi 1993.
       Investigations have revealed no COCs.  The site has been recommended to Sacramento County
       for clean-closure.
RL/10-95/ES/1260005.AWS
                                                3-13

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      4.0  Soil Operable Unit "Petroleum Only" Sites Selected for No
             Action Under CERCLA (but which remain to be closed
             under other regulations)

      4.1    Declaration for the Soil Operable Unit Petroleum Only Sites Selected for No
             Action

                                  No Action is Necessary Based
                         on the Lack of Statutory Authority under CERCLA

      4.1.1  Site Name and Location
      Soil OU "Petroleum Only" Sites Selected for No Action Under CERCLA (but which remain to
      be closed under other regulations)
      Mather AFB (a NPL Site),
      Sacramento County, California

      4.1.2  Statement of Basis and Purpose
      The "petroleum only" sites were investigated under the Mather AFB IRP and are described
      and evaluated in previous RI/FS documents. However, there is no CERCLA authority to take
      action at these sites. Therefore, they will be cleaned up under RCRA Subtitle I and other
      applicable State of California regulations with regulatory oversight by the CVRWQCB, and
      Sacramento County as appropriate. The IRP Soil OU "petroleum only" sites for which the no
      action remedial alternative was developed at the formerly active Mather AFB include: Site 19
      -Fuel Tank Sludge Burial Site, Site 29/B - Fuel Spill at POL Yard Number 4, Site 32 - Fuel
      Spill at Army/Air Force Exchange Services Station, Site 34 - Fuel Spill at Family Housing
      Army/Air Force Exchange Services Station, Site 35 - Building 3326, and Site 36  -
      Building 3286.  These sites consist of only petroleum contamination and have not been
      remediated, with the exception of Site 32 which was remediated hi late 1995 through soil
      excavation and is expected to be closed by the Regional Water Quality Control Board.  Section
      3.0 of this ROD discusses sites which consist of only petroleum contamination. These sites
      have been clean-closed or recommend for clean-closure by Sacramento County.  These
      decisions  are based on the Administrative Record for these sites.

      The USEPA Region IX and the State of California concur on the lack of statutory authority
      under CERCLA to examine remedial actions for the "petroleum only" sites; therefore, those
RL/10-95/ES/1260005.AWS

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       sites will be remediated under the Defense Environmental Restoration Program, RCRA
       Subtitle I and other applicable State of California regulations.

       4.1.3 Description of the Selected Remedy
       The COCs at the "petroleum only" sites are exempt from remedial action under CERCLA.
       Therefore, a "no action" decision is the selected remedy for the "petroleum only" sites based
       on the lack of statutory authority under CERCLA.  The "petroleum only" sites include:  Sites
       19, 29/B, 32, 34, 35, and 36. Based on the human health risk assessment, all cancer risks are
       within or below the acceptable range of 1 x 10"* to  1 x 10"6 and all non-cancer risks have a
       hazard index of less than 1.0 in their current state.

       4.1.4 Declaration Statement
       The USEPA does not have authority under CERCLA Section 104 to address the "petroleum
       only" sites.  The "no action" decision does not constitute a finding that adequate protection has
       been achieved at the sites.  Cleanup alternatives have been developed and documented in the
       FFS Report [IT 1995a] and these sites will be addressed under RCRA Subtitle I and other
       applicable State of California regulations, with regulatory oversight by the CVRWQCB, and
       Sacramento County as appropriate.  Cleanup activities at the "petroleum only" sites are not
       subject to the same requirements as the CERCLA sites, i.e., "petroleum only" sites do not
       require a CERCLA five-year review, are not subject to the 15 month requirement to begin
       remedial activities, etc. However, permits will be required for remedial activities.

       4.2   Decision Summary for Soil OU "Petroleum Only" Sites  Selected for No
             Action Under CERCLA (but which remain to be closed under other
             regulations)

       4.2.1 Site Name, Location, and Description
       Locations of the Soil OU "petroleum only" sites at the formerly active Mather AFB are
       presented in Figure 4-1 and include:  Site 19 - Fuel Tank Sludge Burial Site, Site 29/B - Fuel
       Spill at POL Yard Number 4, Site 32 - Fuel Spill at Army/Air Force  Exchange Services
       Station, Site 34 - Fuel Spill at Family Housing Army/Air Force Exchange Services Station,
       Site 35 - Building 3326, and Site 36 - Building 3286.
RL/10-95/ES/1260005.AWS                                4-2

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Rgure  4-1.   Soil Operable Unit  "Petroleum  Only" Sites
      SOIL OU PETROLEUM ONLY SFTES
                                                                       3000
6000  FEET

-------
       4.2.2 Site History and Enforcement Activities
       Cleanup options were developed for the "petroleum only" sites and are presented in the FFS
       Report [IT 1995a]; however, the USEPA does not have authority under CERCLA to address
       these sites.  Therefore, the no action decision is documented as the selected remedy in this
       section of the ROD.


       Previous investigations have been conducted at the Soil OU "petroleum only" sites as part of
       the USAFIRP and are summarized hi Table 4-1.


          Table 4-1. Previous Investigations at the Soil Operable Unit "Petroleum Only" Sites
SITE NUMBER
19
29/B
32
34
35
36
APPLICABLE INVESTIGATION
1,2,3,4,5,6,9,10,11
1,6,8,9, 10, 11
1,4,6,7, 10, 11
1, 8, 9, 10, 11
8,9, 10, 11
8,9,10,11
       1.      Installation Restoration Program (IRP) Records Search for Mather Air Force Base, Phase I [CH2M-Hill,
              Inc. 1982];
       2.      IRP Phase II, Stage 2 Investigation [AeroVironment 1987];
       3.      Well Redevelopment and Sampling Plan [IT 1988a];
       4.      Quarterly Routine Groundwater Sampling [IT 1995c] and [EA 1990a-c];
       5.      Site Inspection Report [IT 1990a];
       6.      Group 2 Sites Remedial Investigation Report [IT 1992a];
       7.      Group 3 Sites Technical Memorandum [IT 1993a];
       8.      Underground Storage Tank Closure Reports [IT 1990b and IT 1993c-d];
       9.      Soil Operable Unit (OU) and Groundwater OU Additional Field Investigation Report [IT 1994a];
       10.     Groundwater OU and Soil OU FFS Report [IT 1995a]; and
       11.     Mather Baseline Risk Assessment Report [IT 1995d].

       4.2.3 Highlights of Community Participation

       The public participation requirement of CERCLA  Sections 113(k)(2)(B)(I-v) and 117 do not

       apply to these sites; however, these sites were included hi the Proposed Plan, and the public

       comment period (held from May 8 through June 7, 1995) and public meeting (held

       May 18, 1995) to address the Proposed Plan and content of supporting RI/FS documents.
RL/10-95/ES/I260005.AWS                                   4-4

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       4.2.4 Scope and Role of Response Action
       Since there is no CERCLA authority to take action at these sites, this section of the ROD
       presents the no action alternative to indicate that no action will occur at these sites under
       CERCLA authority as the planned response action.

       4.2.5 Summary of Site Characteristics
       The Soil OU is comprised of contaminated soils associated with OWSs, gas stations, and other
       miscellaneous sites.  A summary of hazardous material releases is provided in the following
       section along with a summary of nature and extent of contamination on a site-by-site basis.
       The sources of contamination are fuels storage and delivery.  The objective of this section of
       the ROD is to address the primary concerns at the Soil OU "petroleum only" sites posed by
       soil contamination.

       Environmental studies were initiated by the USAF in 1982 to investigate soil contamination
       resulting from past base operations. The USEPA placed Mather AFB on the NPL (or
       "Superfund" list) in 1989. In order to organize cleanup efforts, the base is divided into five
       OUs. This has allowed sites  with similar sources of contamination and site conditions to be
       grouped  together.  This section of the ROD discusses potential cleanup options for one of the
       OUs, the Soil OU.  Previous  RODs presented cleanup options for the AC&W OU [IT 1993e]
       (where groundwater contamination is now being extracted and treated by air stripping)  and the
       Landfill OU, while the Groundwater OU is presented hi Section 5.0 of this ROD.  Any
       remaining sites will be addressed hi the Final Basewide OU.

       Previous PJs have  been conducted at the Soil OU "petroleum only" sites as part of the USAF
       IRP.  A brief description of the nature and extent of contamination at each of the Soil OU
       "petroleum only" sites is provided hi the following sections and Table 4-2.

       4.2.5.7      Site 19 - Fuel Tank Sludge Burial Site
       Site 19 is located hi the northwest portion of the base inside a diked area containing two JP-4
       ASTs. It was reported that the site may have continued small quantities of weathered sludge
       from  fuel tank cleaning operations.  Contamination was identified hi the shallow subsurface
       soils. The only COC at this site is gasoline. The COC is not related to the marked disposal
       site, but apparently is related  to the operation of the ASTs, and associated USTs and piping.
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                      Table 4-2.  Estimated Areas and Volumes - Subsurface Soils
Site Number
19
29/B
32*
34
35
36
Contaminant of
Concern
TPH-G
TPH-D
TPH-G
Benzene
TPH-G
TPH-G
TPH-G
TPH-G
Area
(square feet)
5.4 x 104
(a)
1.4 xlO5
8.0 x 104
1.6xl03
1.3 x 10"
6.9 x 103
2.6 x 104
Volume
(cubic feet)
5.4 x 105
(a)
6.3 x 106
4.1xl06
1.7 x 104
3.0 x 105
7.6 x 104
1.2xl06
              (a) = diesel detections are sporadic and coincide with higher concentration gasoline detections
              TPH-D = Total petroleum hydrocarbons as diesel          TPH-G = Total petroleum hydrocarbons as gasoline
              *Contaminated soil was excavated in late 1995. Site 32 is expected to be closed by the Regional Water Quality Control Board.
       4.2.5.2      S/te 29/B - Fuel Spill at Petroleum Oil and Lubricant Yard Number 4
       Site 29 is situated near the western end of the Main Base and was used as a service station and
       POL yard from 1958 until 1988. The site consisted of four 25,000-gallon aviation gasoline
       USTs which were removed in 1984 and replaced with four fiberglass 20,000-gallon USTs
       which were removed in 1994. Site B is located adjacent to Site 29 and consisted of four
       25,000-gallon USTs and one empty steel 550-gallon tank used for storing waste fuel. The
       USTs were removed in 1993. Contamination was identified in the shallow and deep
       subsurface soils. The COCs identified at the site are benzene, diesel, ethylbenzene, and
       xylenes.  This site is currently being remediated by bio venting with SVE at "hot spots".

       4.2.5.3      S/te 32 - Fuel Spill at Army/Air Force Exchange Services Service
                     Station
       Site 32 is located in the north central portion of the base, in the Main Base administration and
       operations area.  Between 1960 and 1973, a total of five, steel 10,000-gallon USTs were
       installed  at this site. Three of the USTs and associated piping were removed hi 1988.  The
       two remaining USTs were removed hi 1994.  In addition, a 550-gallon waste oil tank was
       removed from the site in 1994.  Contamination was identified hi the shallow subsurface soils.
       The only COC identified at the site is gasoline. This site has been remediated through
       excavation of the soil hi late 1995. It is expected that the site will be closed by the Regional
       Water Quality Control Board.
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       4.2.5.4      Site 34 - Fuel Spill at Family Housing Army/Air Force Exchange
                    Services Service Station
       Site 34 is located in the south central portion of the base, approximately 1,500 feet northeast
       of the south gate and adjacent to the former Family Housing Area.  Building 21030 was
       constructed in 1968 and operated as an Army/Air Force Exchange Services Service Station
       until its closure  in February 1988.  Three, steel 10,000-gallon USTs located immediately
       northeast of Building 21030 were installed in 1968 to store unleaded premium, unleaded
       regular, and leaded regular gasoline. Additionally, two 250-gallon waste oil USTs are located
       at the southwest corner of the stations property.  Contamination was identified in the shallow
       subsurface soils. The COCs identified at the site are benzene, gasoline, and xylenes.

       4.2.5.5      Site 35 - Building 3226 - Four Abandoned USTs
       Site 35 is located in the western portion of the Main Base and is the former location of four
       25,000-gallon steel USTs.  The USTs stored aviation gasoline from 1945 until approximately
       1965. The USTs were removed in 1989. Contamination was identified in the deep subsurface
       soils.  The only  COC identified at the site is gasoline.

       4.2.5.6      Site 36 - Building 3286
       Site 36 is located in the western portion of the Main Base and is the former location of four
       25,000-gallon steel USTs.  The USTs stored motor gasoline from 1945 until approximately
       1965. The USTs were removed in 1988. Contamination was identified in the shallow  and
       deep subsurface  soils. The only COC identified at the site is gasoline.

       4.2.6 Summary of Site Risks
       Remedial investigation activities at Mather AFB included fate and transport modeling and a
       MBRA [IT 1995d]. The data collected and utilized in the RIs and FFS were of USEPA
       quality Level HI, IV, or V, or equivalent [USEPA 1987].  Formal data validation of the
       RI- and FFS-generated data was performed to ensure that data were of the quality
       commensurate with their intended use.

       Based on the human health risk assessment, all cancer risks are within or below the acceptable
       range of 1 x lO'4 to 1 x 10"6 and all non-cancer risks have a hazard index of less than 1.0,
       respectively.
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       4.2.6.1      Human Health Risks
       Analytes detected in the course of the RI activities at Mather AFB were subjected to a
       multi-step screening process to determine COCs. This screening process is presented in
       Section 2.2.6.1.  The following steps were employed in the COC determination process for the
       Soil OU sites and are discussed hi Section 2.2.6.1.


              •      initial screening methods prescribed by USEPA guidance;
              •      comparison to background;
              •      comparison to ARARs;
              •      comparison to analytical method quantitation limit;
              •      evaluation of operational history (i.e., process knowledge); and
              •      evaluation of estimated risk to human and ecological receptors.


       4.2.7  Statutory Authority Finding
       The no action finding is selected based on the petroleum exclusion in CERCLA.
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       5.0  Groundwater Operable  Unit Plumes Selected for Remedial
             Action
       5.1   Declaration for the Groundwater Operable Unit Plumes Selected for Remedial
             Action

                              Statutory Preference for Treatment as a
                                    Principal Element is Met
                              and a Five-Year Review is Required for
                    the Main Base/SAC Industrial and Site 7 Groundwater Plumes
                              Statutory Preference for Treatment as a
                                  Principal Element is Not Met
                              and a Five-Year Review is Required for
                                the Northeast Groundwater Plume
      5.1.1 Plume Name and Location
      Groundwater OU Plumes Selected for Remedial Action
      Mather AFB (a NPL Site),
      Sacramento County, California

      5.1.2 Statement of Basis and Purpose
      The Groundwater OU plumes were investigated under the Mather AFB IRP and are described and
      evaluated in the RI/FS documents.  This decision document presents the selected remedial actions
      which were developed for the Groundwater OU plumes at the formerly active Mather AFB.
      These plumes include: the Main Base/SAC Industrial Area, the Site 7, and the Northeast. These
      remedial actions were chosen in accordance with CERCLA, as amended by SARA, and to the
      extent practicable, the NCP. These decisions are based on the Administrative Record for these
      plumes.

      The USEPA Region IX and the State of California concur on the selected remedial alternatives
      for each of the Groundwater OU plumes.

      5.1.3 Assessment of the Plume
      Contamination exists at the Groundwater OU plumes as  a result of past USAF operations
      conducted between  1918  and  1993.   The Groundwater OU  encompasses the contaminated
      groundwater beneath and  within the immediate vicinity of the base with the exception of the
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       AC&W OU plume, which is addressed in a separate ROD (IT, 1993).  The main sources of
       contamination include industrial activities, equipment maintenance, landfill disposal, other waste
       disposal activities (i.e., Site 7), and fuels storage and delivery.

       Investigation of numerous IRP sites has identified several sources of groundwater contamination,
       most notably Site 57, where chlorinated solvents have been detected in soil and soil gas over a broad
       area. Site 18 may also be a source; an SVE pilot test was conducted as part of the Additional Site
       Characterization Remedial Investigation (ASC RJ) in 1995 (IT Corp, 1996a). The location of'hot
       spots' of contamination at the water table indicates the likelihood of nearby sources of contamination
       in the overlying soil or perhaps  in  the upgradient  direction (i.e. the direction from which the
       contamination would be carried by the moving groundwater). Examples are near Site 37/39/54 and
       near Site 56. These sources must have existed in the past, and many probably still exist today, even
       though the use of the chemicals at Mather has been eliminated for years.  Additional continuing
       sources of groundwater contamination were investigated in 1995 during the ASC RI (IT Corp.,
       1996b). Portions of the sanitary sewer system that overlie groundwater contamination at the water
       table were targeted for flushing, sampling and soil gas measurements.

       Known vadose-zone sources are addressed as part of the Soil OU (this  ROD) or will be addressed
       in the Final OU ROD.   Additional characterization may be necessary to evaluate potentially
       significant sources of groundwater contamination.  Any remedial actions for additional source
       areas will be addressed as part of a future decision document.

       Actual or threatened releases  of  hazardous substances from these plumes, if not addressed by
       implementing the response actions selected in this section of the ROD, may present an imminent
       and substantial endangerment to public health, welfare,  or the environment.

       5.1.4 Description of Selected Remedy
       This section of the ROD  addresses remedies related to contamination of the  groundwater
       underlying the Main Base/SAC Industrial Area, the Site 7 Area, and the Northeast Area Landfill
       Sites.  Any contamination of the  soil overlying the groundwater plumes has been addressed in
       separate sections of this ROD  (Sections 2.0 and 4.0).

       Based on the human health  risk assessment, all cancer risks are within or below the acceptable
       range of  1  x  10"4 to  1  x 10"6 and all  non-cancer risks have a hazard index  of less than 1.0,
       respectively, in their current state, except for the Main Base/SAC Industrial Area Groundwater
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       Plume which has a cancer risk greater than 1 x 10"4 associated with the highest concentration
       detected in the groundwater plume.  Therefore, the selected remedies will be instituted to reduce
       risk to human health and the environment and to comply with the requirements that are ARARs
       based on the beneficial use of the groundwater and the specific conditions of the site.


       Table 5-1 provides the major components of the selected remedy for each of the Groundwater OU
       plumes.


              Table 5-1. Selected Remedial Alternatives for the Groundwater OU Plumes
Selected Remedial Alternative
Main/SAC.2
SP7.2
NE.l
Description
Groundwater extraction, air stripping with off-gas treatment (carbon
adsorption), and groundwater injection*; and groundwater monitoring
Groundwater extraction, air stripping with off-gas treatment (carbon
adsorption), and groundwater injection*; and groundwater monitoring
Long-term groundwater monitoring
       * Alternative discharge options may be implemented for discharge of treated groundwater. Examples of alternate
       means of discharge are:  injection into a deeper aquifer; recharge through the vadose zone; surface water discharge;
       provision of water to industrial/agricultural user(s); and provision of water for municipal supply.
       SAC = Strategic Air Command         NE = Northeast       OU = operable unit     SP7 = Site 7


       5.1.5  Statutory Determinations

       The selected remedies satisfy the statutory requirements of Section 121(b) of CERCLA, as

       amended by SARA, in that the following four  mandates are attained:


              •      the selected remedies are protective of human health and the environment;

              •      the selected remedies comply with federal and state requirements that are legally
                    applicable or relevant and appropriate to the remedial actions;

              •      the selected remedies are cost-effective; and

              •      the selected remedies utilize  permanent solutions and  alternative treatment
                    technologies,  or  resource  recovery technologies,  to  the maximum extent
                    practicable.


       These remedies will  result in hazardous substances remaining onsite at some of the groundwater

       plumes above health-based levels during the remedial action.  Therefore, a review will be

       conducted within five years after commencement  of the remedial actions to ensure  that the
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       remedies continue to provide adequate protection of human health and the environment, and
       protect groundwater quality.


       5.2    Decision Summary for Groundwater OU Plumes Selected for Remedial Action


       5.2.1  Plume Name, Location, and Description
       The Groundwater OU plumes selected for remedial action at the formerly active Mather AFB are
       presented in Figure 5-1 and include the: Main Base/SAC Industrial Area Groundwater Plume,
       the Site 7 Groundwater Plume, and the Northeast Groundwater Plume.


       5.2.2  Site History and Enforcement Activities
       Previous  investigations have been conducted at the Groundwater OU plumes as part of the US AF
       IRP and are summarized in Table 5-2.


       5.2.3  Highlights of Community Participation
       The public  participation requirement of CERCLA Sections 113(k)(2)(B)(I-v) and 117 were met
       through a public comment period (held May 8 through June 7, 1995) and public meeting (held
       May 18,  1995) to address the Proposed Plan and content of supporting RI/FS documents.


              Table 5-2.   Previous Investigations at the Groundwater Operable Unit Sites
Groundwater Plume
Main Base/Strategic Air Command
Industrial Area
Site 7
Northeast
Applicable Investigation
1,2,3,4,5,6,7,8,9,10,11

1,2,3,4,5,6,7,8,9,10,11
1,2,3,4,5,6,7,8,9,10,11
       1.     Installation Restoration Program (IRP) Phase II, Stage 1 Investigation [Weston 1986];
       2.     IRP Phase II, Stage 2 Investigation [AeroVironment 1987];
       3.     IRP Phase II, Stage 3 Investigation [AeroVironment 1988];
       4.     Well Redevelopment and Sampling Plan [IT 1988a];
       5.     Quarterly Routine Groundwater Sampling [IT 1995c] and [EA 1990a-c];
       6.     Site Inspection Report [IT 1990a];
       7.     Group 2 Sites Remedial Investigation Report [IT 1992a];
       8.     Group 3 Sites Technical Memorandum [IT 1993a];
       9.     Soil Operable Unit (OU) and Groundwater OU Additional Field Investigation Report [IT 1994a];
       10.    Mather Baseline Risk Assessment Report [IT 1995d]; and
       11.    Groundwater OU and Soil OU Focused Feasibility Study Report [IT 1995a].
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                                                                   MAIN BASE/SAC INDUSTRIAL X**"
                                                                    *~ AREA PLUMES        /
                                                                                                                    NORTHEAST
                                                                                                                    PLUME
Figure 5-1.   Groundwater Operable  Unit  Plumes

 LEGEND

 NOTE:  (DARK) SOLID LINE INDICATES APPROXIMATE EXTENT
       OF GROUNOWATER PLUME
3000
6000 FEET

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       5.2.4 Scope and Role of Response Action
       Environmental studies were initiated by the USAF in 1982 to investigate contamination
       resulting from past operations at the base.  The USEPA placed Mather AFB on the NPL hi
       1989.  In order to organize cleanup efforts, the base was divided into five OUs. This has
       allowed contaminated sites and plumes with similar sources of contamination and
       characteristics to be grouped together.  The following sections of the ROD discuss the cleanup
       options for one of those OUs, the Groundwater OU. The AC&W  OU ROD presented cleanup
       options for the AC&W plume [IT 1993e], while Sections 2.0, 3.0, and 4.0 of this ROD
       presents the cleanup options for the Soil OU sites, many of which overlay the contaminated
       groundwater plumes.

       5.2.5 Summary of Site Characteristics
       Contamination exists at the Groundwater OU plumes as a result of past USAF operations
       conducted from 1918 through 1993. The Groundwater OU plumes encompass the
       contaminated groundwater beneath and within the immediate vicinity of the base with the
       exception of the AC&W OU plume. The main sources of contamination include industrial
       activities, equipment  maintenance, fire suppression training, landfill disposal, other disposal
       activities (i.e., Site 7), and fuels storage and delivery.

       The objective of this  section of the ROD is to address the primary contamination concerns at
       the Groundwater OU plumes. Previous RIs have been conducted at the Groundwater OU
       plumes as part of the USAF IRP. A brief description of each of the Groundwater OU plumes
       recommended for remedial action, including nature and extent of contamination (volume
       estimates are presented in Table 5-3), is provided in the following sections.  Any impact to the
       soil overlying these plumes were addressed in separate sections of this ROD  (Sections 2.0,
       3.0, and 4.0).

       5.2.5.1      Main Base/SA C Industrial Area Groundwater Plumes
       The SAC Industrial Area Groundwater Plume and the Mam Base Groundwater Plume have
       been grouped together for the purpose  of remediation based on proximity,  common
       contaminants, and commingling. The Group 2 Sites RI [IT  1992a] and Group 3 Sites
       Technical Memorandum [IT 1993a] identified a widespread chlorinated hydrocarbon plume
       underlying the Main Base area (Figure 5-1) which extends off-base to the west. The Mam
       Base portion of the plume consists of several commingled plumes at the water table which
       have merged together in deeper hydrogeologic units and is characterized by high
       concentrations of PCE and lower TCE and carbon tetrachloride concentrations. Additionally,
       the Group 2 Sites RI and Group 3 Sites Technical Memorandum identified a dissolved-phase
       chlorinated hydrocarbon plume underlying the SAC area (Figure 5-1) extending from the
       vicinity of Site 57 off-base to the southwest [IT 1992a and IT 1993a].  The SAC Industrial
       area portion of the plume is characterized by high concentrations of TCE and lower PCE and
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       cis-l,2-dichloroethene (DCE) concentrations.  The Main Base/SAC Industrial area plume is
       oriented northeast-southwest following the general basewide groundwater flow direction. The
       COCs identified are 1,1-DCE, 1,2-dichloroethane, benzene, carbon tetrachloride,
       chloromethane, cis-l,2-DCE, diesel, gasoline, lead,  TCE, PCE, and xylenes.  A cancer risk to
       humans has been estimated at 3.7 x  10"3 for exposure to groundwater from the SAC Industrial
       Area Plume and 9.3 x 10"4 for exposure to groundwater from the Main Base Plume.  The basis
       for cleanup is protection of human health and groundwater quality.

                             Table 5-3. Estimates of Volume - Groundwater
Major
COC
TCE
PCE
CC14
Hydrogeologic
Unit
A
Bu
B
D
Total
A
Bu
B
D
Total
A
Bu
B
D
Total
Groundwater Plume
Main Base"
Volume*
(cubic feet)
1.4x 10s
5.4 x 107
4.8 x 108
5.3 x 106
6.8 x 108
1.1 x 108
9.5 x 107
l.Ox 10"
3.9x 108
1.6 x 109
3.6 x 107
1.9x 107
1.3 x 109(2)
1.2 xlO8
1.5 x 10'
SAC
Industrial"
Volume*
(cubic feet)
2.9 x 108
2.2 x 108
1.3x 109
NA
1.8 x 109
1.2x 108
2.4 x 108
5.5 x 108
NA
9.1 x 108
2.3 x 107
4.4. x 107
NA
NA
6.7 x 107
Northeast(l)
Volume*
(cubic feet)
US
NP
NA
NA
NA
US
NP
9.9 x 106
NA
9.9 x 106
US
NP
4.6 x 106
NA
4.5 x 106
Site?
Volume*
(cubic feet)
6.8 x 107
NP
l.SxlO8
NA
2.2 x 10"
5.1 x 107
NP
7.6 x 107
NA
1.3 x 108
NA
NP
NA
NA
NA
              TCE = Trichloroethene             COC = contaminant of concern PCE = Tetrachloroethene
              SAC = Strategic Air Command CCL, = Carbon Tetrachloride         NP = Unit Not Present
              US = Unit Unsaturated             NA = Not Applicable
              (1) Hydrogeologic Unit C - PCE Contamination Volume = 9.6 x 101 cubic feet.
              (2) Main Base Plume and SAC Industrial Plume volumes are reported under Main Base Plume.
              * Estimates of plume size as of 1993.
              ** Revised estimates will be provided in the Additional Site Characterization RI Report.
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       5.2.5.2     Site 7 Groundwater Plume
       The Group 2 Sites RI identified a chlorinated hydrocarbon plume underlying the Site 7 area
       (Figure 5-1) and extending off-base to the southwest [IT 1992a]. The plume is characterized
       by high concentrations of TCE and lower PCE and cis-l,2-DCE concentrations.

       The groundwater COCs identified at the Site 7 Plume are 1,1-DCE, 1,2-dichloroethane,
       1,4-dichlorobenzene, benzene, chloromemane, cis-l,2-DCE, diesel, PCE, TCE, and vinyl
       chloride. A cancer risk to humans has been estimated at 9.7 x 10"5 from exposure to the
       groundwater.  Even though the cancer risk is within the acceptable range, active remediation is
       proposed because the risk is near the 1 x 10"4 threshold, and the plume extends approximately
       one mile off-base in the direction of drinking water wells.  The basis for the cleanup is
       protection of groundwater quality and human health.
       5.2.5.3      Northeast Groundwater Plume
       The Group 2 Sites RI identified a chlorinated hydrocarbon plume underlying the Northeast
       Landfill area (Figure 5-1) [IT 1992a]. This plume is located in the northeast corner of the
       base, underlying Sites 3,4, and 5, and appears to have merged with the Main Base/SAC
       Industrial Area Plume (see Section 5.2.5.1).

       The groundwater COCs identified at the Northeast Plume area are 1,2-dichloropropane,
       carbon tetrachloride, chloromethane, cis-l,2-DCE, and PCE. The primary source of
       contamination appears to be from Landfill Site Number 4. The risk assessment, using
       conservative assumptions and maximum concentrations,  estimated the excess cancer risk for
       exposure to the groundwater to be 2.4 xlO~5.  The excess cancer risk is within the acceptable
       range (i.e.,  1 x 10"6 to 1 x 10"4) and there is no current pathway by which contaminants could
       endanger human health or the environment. Additionally, contaminant concentrations are
       expected to decrease over time.
      5.2.6 Summary of Site Risks
      Based on the human health risk assessment, all cancer risks are within or below the acceptable
      range of 1 x 10"4 to  1 x 10~6 and all non-cancer risks less than a hazard index of 1.0 hi their
      current state, except for a localized portion of the Main Base/SAC Industrial Area Plumes.
      Therefore, the selected remedy will be instituted to reduce risk to human health and the
      environment to comply with the requirements that are ARARs based on the beneficial use of
      the groundwater and the site-specific conditions.

      Actual or threatened releases of hazardous  substances, if not addressed by implementing the
      response actions selected in the ROD, may present an imminent and substantial endangerment
      to public health, welfare, or the environment.
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       5.2.7 Description of Alternatives
       Two or three remedial alternatives (including the no action alternative) were developed for
       each of the three Groundwater OU plumes for detailed analysis in the FFS Report [IT  1995a].
       Groundwater is the affected medium; any contamination in the soil overlying the groundwater
       plumes has been addressed as part of the Soil OU sections of this ROD (Sections 2.0, 3.0,
       and 4.0).  Under the no action alternative, groundwater monitoring would continue under the
       existing basewide monitoring program.
       5.2.7.1     Main Base/SAC Industrial Area Groundwater Plume Remedial
                   Alternatives
       Table 5-4 presents three remedial alternatives developed for application at the Main Base/SAC
       Industrial Area Groundwater Plume.
                Table 5-4. Main Base/SAC Industrial Plume Remedial Alternatives
ALTERNATIVE
Main/SAC.l
Main/SAC.2
Main/SAC.3
DESCRIPTION
No Action (includes groundwater monitoring)
Extraction of the contaminated groundwater with treatment by air stripping and
injection of the treated groundwater into the aquifer (alternative means of discharge of
treated groundwater may be implemented), and groundwater monitoring. In addition,
carbon will be utilized to adsorb and treat the off-gas from the air stripper, if
appropriate.
Extraction of the contaminated groundwater with treatment by ultraviolet oxidation
and injection of the treated groundwater into the aquifer (alternative means of
discharge of treated groundwater may be implemented), and groundwater monitoring.
      SAC = Strategic Air Command
      5.2.7.2     Site 7 Groundwater Plume Remedial Alternatives
      Table 5-5 presents three remedial alternatives developed for application at the Site "7
      Groundwater Plume.
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                           Table 5-5.  Site 7 Plume Remedial Alternatives
ALTERNATIVE
SP7.1
SP7.2
SP7.3
DESCRIPTION
No Action (includes groundwater monitoring)
Extraction of the contaminated groundwater with treatment by air stripping and
injection of the treated groundwater into the aquifer (alternative means of discharge
of treated groundwater may be implemented), and groundwater monitoring. In
addition, carbon and will be utilized to adsorb and treat the off-gas from the air
stripper, if appropriate.
Extraction of the contaminated groundwater with treatment by ultraviolet oxidation
and injection of the treated groundwater into the aquifer (alternative means of
discharge of treated groundwater may be implemented), and groundwater
monitoring.
       SP = Site 7


       5.2.7.3      Northeast Groundwater Plume Remedial Alternatives
       Table 5-6 presents two remedial alternatives developed for application at the Northeast
       Groundwater Plume.  (See Section 5.2.9.3 for discussion of the selected alternative).

                          Table 5-6.  Northeast Plume Remedial Alternatives
ALTERNATIVE
NE.l
NE.2
Selected Alternative
DESCRIPTION
No Action (includes groundwater monitoring)
Extraction of the contaminated groundwater with treatment by air stripping and
injection of the treated groundwater into the aquifer (alternative means of
discharge of treated groundwater may be implemented), and groundwater
monitoring.
Long term groundwater monitoring and land use restrictions.
       NE = Northeast
       5.2.8 Summary of Comparison Analysis of Alternatives
       The remedial alternatives developed in the FFS Report [IT 1995a] were analyzed in detail using
       the nine evaluation criteria required by the NCP (Section 300.430(e)(7)).  These criteria are
       classified as threshold, primary balancing, and modifying criteria. In order for a remedial
       alternative to be selected, it must at a minimum, meet the threshold criteria.
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       Threshold criteria are:
                      overall protection of human health and the environment; and
                      compliance with ARARs.
        Primary balancing criteria are:
                      long-term effectiveness and permanence;
                      reduction of toxicity, mobility, or volume through treatment;
                      short-term effectiveness;
                      implementability; and
                      cost.
       Modifying criteria are:
               •       state/support agency acceptance; and
               •       community acceptance.

       The relative ability of each alternative to meet each of the nine criteria were weighed to
       identify the alternative providing the best tradeoffs for each site.  The following sections
       summarize the nine criteria.  Table 5-7 presents the results of the comparative analysis.

                Table 5-7. Comparative Analysis of Groundwater Remedial Alternatives
Evaluation
Criteria
Plume
Alternative
Overall Protection of
Human Health and the
Environment
Compliance with ARARs
Long-Term Effectiveness
and Permanence
Reduction of Toxicity,
Mobility, and Volume
Short-Term Effectiveness
Implementability
Present Worth Cost
($ millions)
Main Base/SAC Industrial Groundwater Plume
Main/SAC.l
No
NA**
P
P
F
G
7.72
Main/SAC.2"
Yes
Yes
B
B
G
B
20.31
Main/SAC.3
Yes
Yes
B
B
B
B
22.77
Site 7 Groundwater Plume
SP7.1
No
NA**
G
P
G
G
1.12
SP7.2"
Yes
Yes
B
B
G
B
3.21
SP7.3
Yes
Yes
B
B
B
B
5.35
Northeast
Groundwater
Plume
NE.T
No
NA**
G
.P
G
G
0.28
NE.2
Yes
Yes
B
B
G
B
1.91
       The State of California and the community concur on the selected remedial alternative* for each of the Groundwater Operable Unit plumes.
       ** ARARs do not have to be met unless a remedial action is taken.
       P = Poor        F = Fair        G = Good       B = Best         SP7 = Site 7      NA = not applicable
       SAC = Strategic Air Command NE = Northeast           ARAR = applicable or relevant and appropriate requirements
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       5.2.8.1      Overall Protection of Human Health and the Environment
       Overall protection of human health and the environment addresses whether or not a cleanup
       option provides adequate protection, and it describes how risks, posed through each exposure
       route, are eliminated, reduced, or controlled through treatment, engineering controls, or
       institutional controls.

       5.2.8.2      Compliance with ARARs
       Addresses whether a cleanup option will meet all ARARs or federal and state environmental
       statutes and/or provide grounds for invoking a waiver. Applicable or relevant and appropriate
       requirements include cleanup and protection of groundwater quality for its beneficial use.
       Details of the ARARs analysis are described in Section 6.0 of this ROD.

       5.2.8.3      Long- Term Effectiveness and Permanence
       Long-term effectiveness and permanence refers to the ability of a  cleanup option to maintain
       reliable protection of human health and the environment over time, once cleanup goals have
       been met.

       5.2.8.4      Reduction of Toxicity, Mobility, or Volume
       Reduction of toxicity, mobility, or volume refers to the preference for a cleanup option that
       uses treatment to reduce health hazards, contaminant migration, or quantity of contaminants at
       the site.

       5.2.8.5      Short-Term Effectiveness
       Short-term effectiveness refers to the period of time in which the remedy achieves protection,
       as well as the remedy's potential to create adverse impacts on human health and the
       environment that may result during the construction and implementation period until the
       cleanup goals are achieved.

       5.2.8.6      Implementability
       Implementability refers to the technical and administrative feasibility of a remedy, including
       the availability of materials and services needed to carry out a particular remedy. It also
       includes coordination of federal, state, and local governments in cleanup of the site.
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       5.2.8.7     Cost
       This criterion examines the estimated cost for each remedial alternative.  For comparison,
       capital and annual operation and maintenance costs were used to calculate a present worth cost
       for each alternative. The present worth cost estimates assume zero equipment salvage value,
       zero percent inflation, and a five percent discount factor.  A detailed cost analysis was
       performed for each of the alternatives proposed in the FFS Report [IT 1995a].

       5.2.8.8     State/Support Agency Acceptance
       This indicates whether, based on its review of the RI Report [IT 1992a],  FFS Report
       [IT  1995a],  and Proposed Plan [IT 1995b], the state concurs with the preferred cleanup
       options.  The USAF, as the lead agency, has involved the USEPA and State of California.

       5.2.8.9     Community Acceptance
       This is an assessment of the general public response following review of the public comments
       received on the RI Reports, FFS Report, and Proposed Plan during the public comment period
       (held May 8 through June 7, 1995) and public meeting (held May 18, 1995). Section 7.0 of
       this  ROD contains comments received during the public comment period  and responses to
       these comments.

       5.2.9 The  Selected Remedies
       This section presents the remedies selected by the USAF, with concurrence by the USEPA and
       the State of  California for each of the Groundwater OU plumes.  The selected remedies  were
       chosen based on the results of the comparative analysis of the alternatives presented in Table
       5-7 and provide the best of trade-offs with respect to the nine evaluation criteria.  All design
       and  construction of the selected remedial actions will be conducted by certified professionals
       or under the supervision of certified professionals, as appropriate.

       5.2.9.1     Main Base/SAC Industrial Area  Groundwater Plume
       Alternative Main/SAC.2 was selected by the USAF, with concurrence by the USEPA and the
       State of California as the remedy for the Main/SAC Industrial Area Groundwater Plume. The
       major components of this remedy include:

             •      a phased implementation program;

             •      groundwater extraction,  to achieve aquifer cleanup standards, estimated but not
                   limited to a total rate of 1,300 gallons per minute (gpm);
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              •      treatment of the extracted groundwater through air stripping with off-gas
                     treatment (i.e., carbon adsorption) to achieve aquifer cleanup standards MCLs
                     (see Table 5-8), and to achieve discharge standards;

              •      groundwater injection per standards in Table 6-7; in combination with other
                     discharge options that are (a) consistent with attainment of cleanup standards,
                     and (b) cost-effective.

              •      land-use restrictions will be implemented on USAF property as appropriate, in
                     order to preclude installation of groundwater wells that would not be compatible
                     with  protection of public health and the environment; and

              •      monitoring the groundwater.


       Alternative discharge options will be evaluated during remedial design.  The design will
       incorporate reinjection of treated groundwater and other discharge options that are (a)
       consistent with attainment of cleanup standards, and (b) cost-effective.  The design will include
       contingency planning to avoid or minimize disruption of treatment operations should the
       primary discharge options be compromised (i.e. if reinjection capacity declines).  Any means
       of discharge must meet substantive requirements of ARARs if onsite or be permitted as
       required offsite, and would be preceded by public notice and solicitation of public comment as
       appropriate. Examples of alternative means of discharge are:


              •      injection to a deeper aquifer;
              •      recharge through the vadose zone;
              •      irrigation;
              •      surface water discharge;
              •      provision of water to industrial/agricultural user(s); and
              •      provision of water for municipal supply.


       Capital cost estimates for this remedy are projected at approximately $5.88 million and
       operation and maintenance costs are estimated at $62.72 million.  Total cost, represented as a
       net present worth using a five percent discount rate, is calculated at $20.31 million.


       The Main Base/SAC Industrial Area Groundwater Plume cleanup levels are presented in Table
       5-8.
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                   Table 5-8. Main Base/SAC Industrial Area Plume Cleanup Levels
Contaminant of Concern
1,2-DCA
cis-l,2-DCE
Benzene
CC14
Xylenes
1,1-DCE
Chloromethane
TCE
PCE
TPH as Gasoline
TPH as Diesel
Lead
Cleanup Level (mg/L)
5.0 x 10*
6.0 x 10-3
l.OxlO'3
5.0 x 10"4
1.7xlO-2
6.0 x 10'3
3.0 x 10-3
5.0 x ID'3
5.0 x 10°
5.0 x 10-2
1.0x10-'
l.SxlO'2
PRG Basis
CA MCL, PQL
CAMCL
CAMCL
CA MCL, PQL
T&O
CAMCL
SNARL
FMCL
FMCL
PQL
USEPA HA
FMCL
       DCA = dichloroethane         CC14 = carbon tetrachloride
       TCE = trichloroethene         PCE = tetrachloroethene
       mg/L = milligrams per liter     SAC = Strategic Air Command
       CA MCL = California Maximum Contaminant Level
DCE = dichloroethene
TPH = total petroleum hydrocarbon
T&O = taste and odor
PQL = Practical Quantitation Limit
       SNARL = suggested no adverse response level    FMCL = Federal Maximum Contaminant Level
       USEPA HA = United States Environmental Protection Agency health advisory
       5.2.9.2     Site 7 Groundwater Plume
       Alternative SP7.2 was selected by the USAF, with concurrence by the USEPA and the State of
       California as the remedy for the Site 7 Groundwater Plume. The major components of this
       remedy include:


             •      ground water extraction at a rate of approximately 250 gpm;

             •      treatment of the extracted groundwater through air stripping with off-gas
                    treatment (i.e., carbon adsorption) to achieve aquifer cleanup standards  (see
                    Table 5-9),  and to achieve discharge standards;

             •      groundwater injection per standards in Table 6-7; in combination with other
                    discharge options that are (a) consistent with attainment of cleanup standards,
                    and  (b) cost-effective;

             •      land-use restrictions will be implemented on USAF property as appropriate, in
                    order to preclude installation of groundwater wells that would not be compatible
                    with protection of public health and the environment; and

             •      monitoring the groundwater.
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       Alternative discharge options will be evaluated during remedial design.  The design will
       incorporate reinjection of treated groundwater and other discharge options that are (a)
       consistent with attainment of cleanup standards, and (b) cost-effective.  The design will include
       contingency planning to avoid or minimize disruption of treatment operations should the
       primary discharge options be compromised (i.e. if reinjection capacity declines).  Any means
       of discharge must meet substantive requirements of ARARs if onsite or be permitted as
       required offsite, and would be preceded by public notice and solicitation of public comment as
       appropriate.  Examples of alternative means of discharge are:
                     injection to a deeper aquifer;
                     recharge through the vadose zone;
                     surface water discharge;
                     irrigation;
                     provision of water to industrial/agricultural user(s); and
                     provision of water for municipal supply.
       Capital cost estimates for this remedy are projected at approximately $738,309 and operation
       and maintenance costs are estimated at $3.8 million. Total cost, represented as a net present
       worth using a five percent discount rate, is calculated at $3.2 million.


       The Site 7 Groundwater Plume cleanup levels are presented in Table 5-9.
                                Table 5-9.  Site 7 Plume Cleanup Levels
Contaminant of Concern
1,1-DCE
1,2-DCA
cis-l,2-DCE
Benzene
1,4-DCB
Chloromethane
Vinyl Chloride
TCE
PCE
TPH as Diesel
Cleanup Level (mg/L)
6.0 x lO'3
5.0 x 10-"
6.0 x 10-3
l.OxlO-3
5.0 x 10-3
3.0 x 10-3
5.0 x 10-4
5.0 x lO'3
5.0 x lO'3
1.0x10-'
PRG Basis
CAMCL
CA MCL, PQL
CAMCL
CAMCL
CAMCL
SNARL
CA MCL, PQL
FMCL
FMCL
USEPA HA
       TPH = total petroleum hydrocarbon
       DCE = dichloroethene
       mg/L = milligrams per liter
       PCE = tetrachloroethene
       CA MCL = California Maximum Contaminant Level
       SNARL = suggested no adverse response level
DCA = dichloroethane
DCB = dichlorobenzene
TCE = trichloroethene

PQL = Practical Quantitation Limit
FMCL = Federal Maximum Contaminant Level
       USEPA HA = United States Environmental Protection Agency health advisory
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       5.2.9.3     Northeast Groundwater Plume
       The USAF, with concurrence by the USEPA and the State of California, has decided that
       active remediation of the Northeast Groundwater Plume is not warranted at this time because
       action is being taken to remediate the source (Landfill Site 4), and because removing the
       low-concentration contaminants from the groundwater would provide little benefit while
       incurring high costs. However, because several of the contaminants are above the primary
       drinking water standards, institutional controls (such as deed restrictions) will be applied to
       prohibit the installation of groundwater supply wells on Mather AFB that would jeopardize
       public health or the environment from the Northeast Groundwater Plume area. If off-base
       groundwater wells are proposed or constructed that could result in exposure to contaminated
       groundwater from the Northeast Plume, the need for active cleanup or other action will be
       revisited. Additionally, long-term groundwater monitoring will be continued and modified as
       necessary to monitor contaminant concentrations. Monitoring will be conducted pursuant to
       Title 23, CCR, Section 2550.10 (Corrective Action Monitoring) for  at least one year from the
       date that the levels in Table 5-10 are attained.  After that time, monitoring will, as required by
       the Landfill ROD, be conducted pursuant to Title 23, CCR,  Section  2550.8 (Detection
       Monitoring), in order to detect potential future releases from Landfill Site 4.  Contaminant
       concentration levels  in the groundwater will be re-evaluated annually.  If the contamination
       concentrations drop below the levels in Table 5-10 for one year, any institutional controls may
       be removed. Prior to the first CERCLA five-year review, additional predictive modeling will
       be conducted in order to assess whether the contaminants will meet the levels in Table 5-10
       within a reasonable time.  The results of that modeling will be published in an appropriate
       document or an Explanation of Significant Difference (BSD), if necessary.  If, at any time
       monitoring or modeling indicates that the contaminants will not meet the levels in Table 5-10
       within a reasonable time, or at least forty years from the date of this ROD, or that significant
       migration of the contaminants may occur at levels above those in Table 5-10 which impacts
       public health or the environment, active remediation will be reconsidered.

       No capital costs are associated with this remedy, operation and maintenance costs for
       long-term monitoring are estimated at $322,399. Total cost, represented as a net present
       worth using a five percent discount rate, is calculated at $279,159.

       The Northeast Groundwater Plume cleanup levels are presented in Table 5-10.
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                            Table 5-10.  Northeast Plume Cleanup Levels
Contaminant of Concern
cis-l,2-DCE
CC14
Chloromethane
1 ,2-dichloropropane
PCE
Cleanup Level (mg/L)
6.0 x 10-3
5.0 x 10"
3.0 x lO'3
5.0 x 10'3
5.0 x lO'3
PRG Basis
CAMCL
CA MCL, PQL
SNARL
FMCL
FMCL
       DCE = dichloroethene                              PCE = tetrachloroethene
       CC14 = carbon tetrachloride                          mg/L = milligrams per liter
       CA MCL = California Maximum Contaminant Level       PQL = Practical Quantitation Limit
       SNARL = suggested no adverse response level           FMCL = Federal Maximum Contaminant Level

       5.2.10       Description  of the Selected Remedies
       This section is a description of the conceptual engineering features and operation of the
       selected  remedy for the Main Base/SAC Industrial Groundwater Plume and the Site 7
       Groundwater Plume.  The specific design details will be determined during the remedial
       design phase, and hence, may differ slightly from those indicated and discussed below.

       5.2.10.1    Extraction Wells
       The contaminated groundwater would be pumped from the zone of interest from production
       wells using down-hole submersible pumps.  These wells would have a combined production
       rate of approximately 1,300 gpm (Main Base/SAC Industrial Plume) and 250 gpm (Site 7
       Plume).  The influent water would flow through buried poly vinyl chloride (PVC) piping to a
       pre-treatment filtration unit.

       5.2.10.2    Pre-Treatment Unit
       The pre-treatment unit would consist of a bag-type filter.  The filter bag would be capable of
       removing particles from the influent water that are as small as one micron. Actual
       specifications for the pre-treatment unit will be developed during the remedial design phase.

       After passing through the pre-treatment unit, the influent would be pumped to the top of the
       air stripping tower. A description of the major components of the air stripping treatment unit
       is presented below.
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       5.2.10.3    Air Stripping Tower and Blower
       The ah" stripping tower would be of a cylindrical, vertical design which will allow air flow
       countercurrent to the liquid flow through packing. Components of a typical ah" stripping tower
       include:
                    Spray Nozzle - Spray nozzles are used to uniformly distribute the liquid influent
                    over the packing to avoid channeling and dry spots.

                    Mist Eliminator - The mist eliminator is a relatively thin bed of packing or
                    wire mesh material.  It is situated above the main packing and spray nozzles and
                    is used to remove entrained water droplets from the exiting air stream.

                    Packing System - Within the column of polypropylene packing material, the
                    liquid and countercurrent air contact each other, stripping contaminants from
                    the liquid. Over time, the packing material can become encrusted with solids
                    suspended in the liquid influent or can be fouled with biological growth,
                    necessitating removal and disposal.  This fouling would cause gradual reduced
                    efficiency in the removal of contaminants, as well as increasing the pressure
                    drop through the packing resulting in decreased air flow from the blower. It is
                    anticipated that the removal and refill of the packing material would need to be
                    carried out only once per year.  The used packing would be classified as
                    non-hazardous waste and could  be disposed in a sanitary landfill. The treated
                    water would exit the tower and  be forced by an effluent pump along the effluent
                    line to the post-treatment infiltration unit.

                    Blower - The supply air for the air stripping tower is provided by the blower.
                    After contacting the liquid, the air flows out the top of the stripping tower.
                    Here the off-gas is warmed by a heater.  The heater is used to reduce the
                    relative humidity in the air stream which increases the effectiveness of the vapor
                    phase carbon adsorption process and reduces carbon consumption
       5.2.10.4    Post-Treatment Unit
       Specifications of post-treatment unit (PTU), if needed, will be developed during the remedial
       design phase. Purposes of the PTU will be to remove any particulates which may have formed
       in the treatment process, and to maintain effluent chemical properties to mitigate potential
       chemical, physical, or biological fouling of the aquifer and injection wells.  The effluent will
       be pumped from the PTU to the injection wells through buried PVC pipelines.
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       5.2.10.5     Vapor Phase Carbon Adsorption System
       Vapor phase carbon adsorption is included as part of the selected remedy to maintain capture
       efficiency of the contaminants present in the off-gas.  There are two main types of vapor phase
       carbon adsorption systems which may be used in conjunction with the air stripper to remove
       contaminants  from the off-gas stream. The first type consists of self-contained, portable
       activated carbon canisters.  These canisters are filled with regenerated granular carbon which
       remove impurities from the stripper off-gas and are typically designed for installation on a
       concrete pad.   The only installation needed is to connect the inlet from the stripper tower
       outlet port. The canisters can be connected in a series lead-lag configuration for increased
       contact times, or parallel  configuration for high flowrates.  The useful life of the carbon is
       dependent upon the concentration of the organic compounds in the gas stream, flowrate, and
       temperature.  When the carbon becomes saturated with contaminants, the canister would be
       detached, sealed, and shipped for regeneration.  The carbon vendor would provide shipping
       and regeneration as a service.

       The second type of carbon system is a permanent skid-mounted structure in which single or
       dual beds of granular activated carbon are arranged. The system employs the same principles
       as the carbon  canisters, however, maintenance is more involved, but because of the size
       difference in the carbon canister versus carbon bed, maintenance is nowhere near as frequent.
       Maintenance consists of removal and transport of the spent carbon to a regeneration facility,
       cleaning the vessel and  filling the vessel with regenerated carbon.  The shipping and
       regeneration service would be provided by the carbon vendor.

       After carbon treatment, the treated vapor would be discharged to the atmosphere. The off-gas
       would be analyzed continuously to monitor the level of releases of organic gases to the
       atmosphere.

       Selection of the type of carbon system will be made after further analysis in the design phase.

       5.2.10.6    Discharge of Treated Water
       Detailed specifications for the injection wells, including location and selection of well screen
       intervals, will be developed during the remedial design phase.   Treated effluent will be
       injected into the formation using  wells screened in the hydrogeologic unit of interest. Based
       on experience at the AC&W Site, it was found that a 2:1 ratio of injection to extraction wells
       is necessary for optimization of the system.
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       Alternative discharge options will be evaluated during remedial design. The design will
       incorporate reinjection of treated groundwater and evaluate reinjection in conjunction with
       other discharge options that are (a) consistent with attainment of cleanup standards, and (b)
       cost-effective.  The design will include contingency planning to avoid or minimize disruption
       of treatment operations should the primary discharge options be compromised (i.e.  if
       reinjection capacity declines). Any means of discharge must meet substantive requirements of
       ARARs if onsite or be permitted  as required offsite, and would be preceded by public notice
       and solicitation of public comment as appropriate. Examples of alternative means of discharge
       are:

              •      injection to a deeper aquifer;
              •      recharge through the vadose zone using injection wells,  infiltration ponds, or
                     infiltration galleries;
              •      surface water discharge (i.e., storm water drainage);
              •      provisions of water to industrial/agricultural users;
              •      provisions of water for municipal supply; and
              •      irrigation (golf course, parks, wetlands).

       All disposal alternatives will comply with discharge permit requirements, and will be
       documented in an BSD, if appropriate.

       The selected remedy (1) prohibits the bypass or overflow of untreated or partially treated
       waste; (2) limits discharge to injection of treated water unless (a) additional or alternative
       discharge  is done under applicable permit or (b) additional or alternative discharge meets the
       substantive requirements of applicable or relevant and appropriate regulations as agreed by the
       FFA parties; (3) requires that the pH of any treated water shall  be between 6.5 and  8.5 or
       equivalent to the receiving waters.

       Initial background concentration of all potential pollutants shall  be determined for each water-
       bearing zone in which reinjection will occur. These constituents will be monitored during RA
       until it can be determined that there is no condition of pollution occurring as a result of the
       discharge.  If the results necessitate the establishment of reinjection standards for additional
       constituents in order to meet ARARs, an amendment to the ROD or other appropriate decision
       procedure will be considered by the U.S. Air Force, U.S. EPA, and Cal EPA.

       The selected remedy does not contemplate on-site disposal of hazardous wastes or wastes
       derived from the remedial action.   Therefore no action-specific ARARs were selected.  If
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       hazardous or other wastes are derived from the remedial action, such as waste water,
       screenings, sludges and other solids generated during construction, operation and maintenance
       of the treatment system, these will be disposed of off-site in accordance with applicable
       federal, state, and local laws, regulations, and ordinances.  However, these requirements
       would not be considered ARARs under CERCLA, as ARARs apply only to on-site activities.

       5.2.10.7    Affected Water Supply Wells

       The Main Base/SAC Industrial Area Groundwater Plume has reached at least one water supply
       well beyond the base boundary and potentially could reach other wells beyond the base
       boundary. The current levels of contaminant constituents in the affected well are below the
       maximum contaminant level (MCL) safe drinking water standards promulgated by USEPA and
       the Slate hut arc near the one-in-a-million cancer risk level.

       To address the human health threat posed by the Plume to  affected water supply wells and wells
       that may be affected in the future due to plume migration,  and to address plume migration as a
       result of supply wells, the USAF will develop a Mather-specific off-base Water Supply
       Contingency Plan in consultation with the State, USEPA, and local water agencies. The
       proposed Water Supply Contingency Plan will be subject to public review and comment. The
       USAF will submit a Draft Water Supply Contingency Plan by June 27, 1996,  to the agencies and
       the local water agencies for review and comment. The USAFs commitment to submit a draft
       Contingency Plan to the other ROD signatory parties is a schedule deadline enforceable under
       the Mather AFB Federal Facility Agreement (FFA).

       The proposed plan will address the following for each affected well or potentially affected well:

       (1)    Determine which wells will likely be affected;

       (2)    Provide an ongoing monitoring plan of supply wells and their guard wells, including
             increased frequency of sampling once a constituent from the Plume has been detected;

       (3)    Determine the impact of supply well pumping on the plume and recommend action(s) to
             minimize plume migration;
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       (4)     Evaluate the short term and long term options for providing alternate water supplies (the
              evaluation shall consider the technical effectiveness in dealing with the health threat,
              implementation time frame, cost, and acceptability to the water purveyor);

       (5)     Propose a preferred alternative, including an implementation time schedule, which should
              address the sequencing of alternate remedies if the final solution is to include short-term
              and long-term solutions);

       (6)     Develop a trigger for ascertaining when an option(s) should be implemented;

       (7)     Propose measures and an implementation schedule to mitigate the vertical migration of
              contaminants to deeper aquifer zones for each well likely to be impacted by the plume;
              and

       (8)     Determine when the monitoring plan can be terminated.
       USAF development of the off-base Water Supply Contingency Plan shall be subject to the
       consultation provisions and requirements of Section 7 of the Mather AFB FFA, effective 21 July
       1989, among USEPA, the State, and the USAF.  For purposes of Section 7 of the Mather AFB
       FFA, the Contingency Plan shall be considered a primary document.

       The State reserves any rights it would otherwise have, absent this ROD or the Mather FFA, with
       respect to the impact of the plume on any affected well or other likely affected wells.  This
       reservation of rights expires upon concurrence with the final contingency plan.  The Air Force
       intends, aside from this ROD and within any necessary constraints of the Federal Tort Claims
       Act, to work with affected parties, Sacramento County, and the State regarding immediate needs
       to abate impacts of the plume.  Nothing stated in this ROD shall be construed as an admission by
       the Air Force of tort liability.

       5.2.11       Performance Evaluations
       The Air Force will develop monitoring, reporting, and notification programs during the RD/RA
       phase. The monitoring program shall include sufficient monitoring (both in terms of location,
       frequency, and test methods) to evaluate the effectiveness of the RA and ensure that discharge
       standards for effluent reinjection or other approved discharge are being met.
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       Periodic performance evaluation reports will present groundwater monitoring data. The
       evaluation reports shall demonstrate that the capture zones of the extraction wells are consistent
       with attainment of the aquifer cleanup standards, and that the injection of treated groundwater
       does not degrade the receiving water quality.

       In addition to operational monitoring  of influent and air emissions, routine sampling of the
       groundwater will be conducted to monitor the migration of the contaminated plumes and
       decreases in the concentrations. Specific sampling, analysis, and monitoring requirements will
       be established during the remedial design.  This data will be utilized to evaluate the need for
       institutional control as well as to periodically evaluate the performance of the remedial system.

       Five-Year Site Reviews and periodic performance evaluations, as recommended by USEPA,
       are to be included as a component of the selected remedy. The specific schedule for periodic
       performance evaluations will be determined during the remedial design phase. However,
       USEPA recommends an initial evaluation to be conducted one to two years after the remedy is
       operational and functional, in order to determine whether modifications to the restoration
       action are necessary.  The USEPA also recommends that more extensive performance
       evaluations be conducted at least every five years [55 Federal Register (FR) 8740]. The
       purpose of the evaluations is to determine whether  cleanup levels have been, or will be,
       achieved in the desired time frame. After the evaluations are  completed, the following options
       should be considered:

             •      discontinue operations;

             •      upgrade or replace the remedial action to achieve the original remedial action
                    objectives or modified remedial action objectives; and/or

             •      modify the  remedial action objectives and continue remediation, if appropriate
                    [55 FR 8740].

       5.2.12      Statutory Determinations
       The selected remedies satisfy the statutory requirements  in CERCLA Section 121(b), as
       amended by SARA, in that the following mandates are attained:

             •      the selected remedies are protective of human health and the environment, will
                    decrease site risks, and will not create short-term risks nor have cross-media
                    consequences;
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              •      the selected remedies comply with federal and state requirements that are
                     applicable, or relevant and appropriate, to the remedial actions;

              •      the selected remedies are cost-effective in their fulfillment of the nine CERCLA
                     evaluation criteria; and

              •      the selected remedies utilize permanent solutions to the maximum extent
                     practicable.
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       6.0  List of Applicable or Relevant and Appropriate
             Requirements and  To-Be-Considereds	

       Pursuant to Section 121(d)(l) of CERCLA, remedial actions must attain a degree of cleanup
       which assures protection of human health and the environment. Additionally, remedial actions
       that leave hazardous substances, pollutants, or contaminants onsite must meet standards,
       requirements, limitations, or criteria that are ARARs.  Federal ARARs include requirements
       under any federal environmental laws, while state ARARs include promulgated requirements
       under state environmental or facility-siting laws that are more stringent than federal ARARs,
       and that have been identified to USEPA by the State of California in a timely manner.

       Applicable requirements are those cleanup standards, control standards, and other substantive
       environmental protection requirements, criteria, or limitations promulgated under federal or
       state law that specifically address a hazardous substance, pollutant, contaminant, remedial
       action, location, or other circumstance at a CERCLA site.  In general, onsite actions need
       comply only with the substantive aspects of ARARs, not with corresponding administrative
       requirements (such as, but not limited to, permits, recordkeeping, and reporting).

       Relevant and appropriate requirements include those that, while not "applicable" to a
       hazardous substance, pollutant, contaminant, remedial action, location, or other circumstance
       at a CERCLA site, nevertheless address problems or situations sufficiently similar to those
       encountered at the CERCLA site to indicate their use is well-suited to the particular site. A
       requirement must be either applicable or both relevant and appropriate to be an ARAR.  If no
       ARAR addresses a particular situation, or if an ARAR is insufficient to protect human health
       or the environment, then nonpromulgated standards, criteria, guidance, and TBC advisories
       may be used to develop a protective remedy.

       Applicable or relevant and appropriate requirements are identified on a site-specific basis from
       information about site-specific chemicals, specific actions that are being considered as
       remedies, and specific features of the site location.  There are three categories of ARARs:

             •      Chemical-specific ARARs are numerical values or methodologies  which, when
                   applied to site-specific conditions, result in the establishment of numerical
                   values.  They are used to determine acceptable concentrations of specific
                   hazardous substances, pollutants,  and contaminants in the environment;
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              •      Location-specific ARARs are restrictions placed on the concentration of hazardous
                    substances or the conduct of activities solely because the site occurs in, or may
                    affect, a special location, such as a wetland or floodplain; and

              •      Action-specific ARARs are technology- or activity-based requirements or
                    limitations on actions taken with respect to hazardous waste.

       The ARARs and TBCs were developed using the following guidelines and documents: CERCLA
       Compliance with Other Laws Manual, Part I:  Interim Final [USEPA 1988]; "CERCLA
       Compliance with Other Laws Manual, Part II: Clean Water Act and Other Environmental
       Statutes and State Requirements" [USEPA 1989b]; and "California State Water Resources
       Control Board ARARs Under CERCLA"  [SWRCB 1992]. The following sections outline the
       ARARs and other information considered for the Soil OU sites where remedial actions will be
       initiated (listed in Section 2.0 of this ROD) and Groundwater OU plumes (listed in Section 5.0 of
       (his ROD).

       The following sections present the federal and state regulations and guidance under each
       appropriate ARAR category (i.e. chemical-, location-, and action-specific). Chemical-specific
       ARARs and TBCs are listed in Section 6.1,  location-specific ARARs and TBCs are listed in
       Section 6.2, and action-specific ARARs and TBCs are listed in Section 6.3.

       6. 7    Chemical-Specific ARARs and  TBCs
       Chemicals of concern for the Soil OU sites and Groundwater OU plumes are listed in the
       following sections. These COCs were identified for soils (i.e., sediments, surface soils, and
       subsurface soils), surface water, and groundwater.  The chemical-specific ARARs and TBCs for
       these COCs are presented based on whether they are ARARs or TBCs, the type of
       contamination, and applicable media.

       6.1.1  Federal Chemical-Specific ARARs and TBCs
       The following federal chemical-specific ARARs and TBCs have been identified for the Soil OU
       sites and Groundwater OU plumes.

       6.1.1.1      Soils
       The only federal ARAR is USEPA Toxic Substance Control Act (TSCA), implemented through
       40 Code of Federal Regulations (CFR) Part 761.120-135, which applies to sites where the soil
       contains greater than 50 mg/kg total PCB and the spill occurred after February 17, 1978. The
       TSCA is a TBC for the Site 15 contaminated sediments, because PCB concentrations do not
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       not exceed 50 mg/kg. The date(s) the PCBs were released to the soils at Mather AFB is not
       known, so these requirements are considered relevant and appropriate for establishing
       chemical-specific COC limits.  40 CFR Part 761 is also identified in Section 6.3.1.1 as a
       chemical-specific TBC for Site 15 soils.


       6.1.1.2     Surface Waters
       Sites 13, 15, and 69  have identified surface waters at which the following TBCs would apply.
       Federal AWQC for the protection of freshwater aquatic life and human health were used for
       the development of cleanup standards for on-base surface waters (Table 6-1).  These sites
       consist of ditches  which are tributaries to the Sacramento River,  which have beneficial use
       designation of municipal water supply and aquatic habitat.


                         Table 6-1.  Chemical-Specific TBCs for Surface Water
Chemical
Aluminum
Barium
Chromium
Lead
Manganese
Silver
Vanadium
Zinc
Concentration (mg/L)
8.7 x 102 (1)
l.Ox 10° (2)
1.1 x 10'2 (1)
9.9 x 10'4 (1)
5.0 x 10'2 (3)
1.2x 10 4 (1)
l.Ox 10' (4)
4.9 x 102 (1)
Site Number
13
69
13, 15
13, 15
13, 15,69
13
15
13, 15
       TBC = to-be-considered materials
mg/L = milligrams per liter
       (1)     U. S. Environmental Protection Agency National Ambient Water Quality Criteria, Freshwater Aquatic
              Life Protection, Recommended Criteria, Continuous Concentration (four-day average).
       (2)     U. S. Environmental Protection Agency National Ambient Water Quality Criteria, Health and Welfare
              Protection, Non-Cancer Public Health Effects.
       (3)     U. S. Environmental Protection Agency National Ambient Water Quality Criteria, Health and Welfare
              Protection, Taste and Odor or Welfare.
       (4)     Agricultural Water Quality Goals

       California Regional Water Quality Control Board Central Valley Region (CVRWQB), 1993, "A Compilation of
       Water Quality Goals," Sacramento, California.


       6.1.1.3      Groundwater

       Section 121 of CERCLA indicates that remedial actions shall attain federal WQG or AWQC

       where they are relevant and appropriate.  National Primary Drinking Water regulation,

       40 CFR Part 141, established MCLs and MCL goals for organic and inorganic constituents as

       ARARs.
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       6.1.2 State Chemical-Specific ARARs and TBCs
      , The following State of California chemical-specific ARARs and TBCs have been identified.

       6.7.2.7      Soils
       There are no state chemical-specific ARARs for COCs found in the soils for the Soil OU sites.
       To assure protection of human health and the environment chemical-specific TBCs were
       developed from WQGs [CVRWQCB 1993].  The WQG was used as the regulatory factor for
       each COC identified at a site.  The WQG was multiplied by a teachability factor and an
       environmental attenuation factor which are based on site-specific characteristics to develop  a
       TDL for each site-specific COC.  The TDL methodology is described in the DLM guidance
       document [CVRWQCB 1989].  The TBCs established for sediments, surface soils, and
       subsurface soils are listed in Tables 6-2 through 6-4, respectively.

       6.1.2.2      Surface Waters
       There are no state chemical-specific ARARs or TBCs identified for surface waters. The
       federal TBCs  listed in Section 6.1.1.2,  Table 6-1 were the most stringent requirements
       identified for surface waters.

       The beneficial uses of Mather Lake and Morrison Creek are not designated in the Basin Plan
       specifically.  However, the Basin Plan indicates that the beneficial use of these surface water
       bodies should be municipal supply.  Further, as a tributary of the Sacramento River, Morrison
       Creek is assumed to have the same uses as the river (that is, municipal, agricultural,
       recreational, and aquatic habitat). Based on this use-analysis, narrative standards for taste and
       odor thresholds are considered TBC requirements.

       6.1.2.3      Groundwater
       The Porter-Cologne Water Quality Control Act is one of  the statutory bases for remediation of
       contaminants that threaten water quality in California.  It establishes the authority of the State
       Water Resources Control Board (SWRCB) and the CVRWQCB to protect the quality of
       surface water and groundwater in California.

       State Water  Resources  Control Board Resolution 68-16 has been identified as an applicable
       requirement for the protection of surface water and groundwater  of the state.  The USAF and
       the state do not agree on the full applicability of all the substantive requirements contained
       within the resolution and the impact on the remedial activities needed to cleanup Mather AFB.
       The USAF disagrees with the State's contention that the narrative language establishes
       chemical-specific ARARs for both soil and groundwater,  and  that discharges subject to the
       resolution include post-1968 migration of hi situ contamination from the vadose zone to
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                   Table 6-2. Chemical-Specific ARARs and TBCs for Sediments
Chemical
Concentration (rag/kg)
Site Number
ARAR
PCBs (Aroclor 1248, 1254, and 1260)
5.0 x 10'
15
TBC*
Acenaphthene
Acenaphthylene
Anthracene
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(g,h,i)perylene
Benzo(k)fluoranthene
Chlordane (alpha and gamma)
Chrysene
4,4-DDD
4,4-DDE
4,4-DDT
Dibenzo(a,h)anthracene
Dieldrin
Diesel
Fluoranthene
Fluorene
Gasoline
Indeno(l ,2,3-cd)pyrene
Naphthalene
Phenanthrene
Pyrene
2,3,7,8-TCDD equivalent
5.2 x 10°
2.8 x lO'5
2.8 x lO'5
2.8 x lO'5
2.8 x 10-5
2.8 x 10-5
2.8 x lO'5
2.8 x 10'5
5.7 x lO'6
2.8 x 10-5
8.3 x 10-5
5.9 x lO'5
5.9 x 10-5
2.8 x 10'5
1.4x 10'6
1.0x10°
3.7 x 10°
2.8 x 10'5
5.0 x 10-2
2.8 x 10-5
6.2 x 10°
6.3 x 10'2
9.6 x 10°
(1)
15
15
15
15
15
15
15
15
13, 15
15
13
13
13
15
13, 15
15
15
15
15
15
15
15
15
69
TBC*
Arsenic
Barium
Cadmium
Chromium VI •
Chromium, Total
Cobalt
Copper
l.SxlO-3
l.OxlO2
5.5 x lO'2
1.1x10°
1.1x10°
5.0 x 10°
1.3 x 103
13
15
15
13, 15
13, 15
13
13, 15
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                Table 6-2. Chemical-Specific ARARs and TBCs for Sediments (Continued)
Chemical
Concentration (mg/kg)
Site Number
TBC* (Continued)
Lead
Mercury
Nickel
Vanadium
Zinc

9.9 x lO'2
1.2xlO-3
7.3 x 10°
l.Ox 10'
4.9 x 10'
4.9 x 10°
13, 15
13, 15
13
13
13
15
        TBC  = to-be-considered material
        PCB  = polychlorinated biphenyls
        ODD = Dichlorodiphenyldichloroethane
        DDT = Dichlorodiphenyltrichloroethane
ARAR = applicable or relevant and appropriate requirement
TCDD = tetrachlorodibenzo-p-dioxin
DDE = Dichlorodiphenyldichloroethene
mg/kg  = milligrams per kilogram
        (1) A Leachability Factor was not assigned and the total designated level was not calculated.

        California Regional Water Quality Control Board Central Valley Region (CVRWQB), "A Compilation of Water
        Quality Goals," 1993, Sacramento,  California.

        *       Designated Level Methodology (DLM) value varies with site conditions (e.g., depth to groundwater) and
               appropriate water quality objective.  Appendix E of the Groundwater Operable Unit and Soil Operable
               Unit Focused Feasibility Study Report [IT 1995a] shows how the site-specific DLM-based values were
               derived, using appropriate  teachability and environmental attenuation factors.

                            Table 6-3. Chemical-Specific TBCs for Surface Soils
Chemical
Concentration (mg/kg)
Site Number
TBC*
Benzo(a)anthracene
Benzo(a)pyrene
Benzo(b)fluoranthene
Benzo(g,h, i)perylene
Benzo(k)fluoranthene
Chrysene
Dibenzo(a,h)anthracene
Fluoranthene
Indeno(l ,2,3-cd)pyrene
Naphthalene
Pyrene
2,3,7,8-TCDD equivalent, total
Trichloroethene
Diesel
l.Ox ID'1
2.0 x 10'1
2.0 x 10-'
2.8 x 10'3
2.0 x 10-'
2.0 x lO'1
3.0 x 10-'
4.2 x 10' (2)
4.0 x 10-'
2.0 x 10'
9.6 x 102 (2)
(1)
5.0 x 10°
l.Ox 102
13, 56 .
56
56
13
62
56
56
13,62
13
13,62
13,62
11, 69
57
13, 39, 56, 62, 65
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                     Table 6-3. Chemical-Specific TBCs for Surface Soils (Continued)
Chemical
Arsenic
Barium
Cadmium
Chromium, Total
Lead
Manganese
Mercury
Zinc
Concentration (mg/kg)
5.0 x 102
l.Ox 104
5.0 x 10'
5.0 x 102
1.5xl02
5.0 x 102
2.0 x 10'
5.0 x 10s
Site Number
13,56
69
62
65
13, 20, 39, 56, 62, 65
69
13, 20
13, 20, 62, 69
       TBC = to-be-considered material
       mg/kg = milligrams per kilogram
TCDD = tetrachlorodibenzo-p-dioxin
       *      The Designated Level Methodology (DLM) value varies with site conditions (e.g., depth to groundwater)
              and appropriate water quality objective. Appendix E of the Groundwater Operable Unit and Soil
              Operable Unit l
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        constituents that adversely affect its beneficial use.  Table 6-5 lists the ARARs and TBCs for
        drinking water and groundwater.


                           Table 6-4. Chemical-Specific TBCs for Subsurface Soils
Chemical

Concentration
(mg/kg)
Site Number

TBC*
Benzene
Benzo(a)pyrene
Chlordane (alpha and gamma)
4,4-DDE
4,4-DDT
Diesel
Ethylbenzene
Fluoranthene
Gasoline
Pyrene
Toluene
Trichloroethene
Xylenes
Cadmium
Lead

Mercury
Thallium
1.0x10-'
2.0 x 10-2
l.OxlO-2
l.OxlO'1
1.0x10°
l.OxlO1
l.OxlO2
2.9 x 10°
1.4xl03
5.0 x 10-'
5.0 x 10°
l.OSxlO2
4.2 x 10°
5.0 x 10-2
1.7 x 10°
1.7x10'
5.0 x 10°
1.5x10'
1.5 x 102
2.0 x 10°
2.0 x 10'
2.0 x 10°
39,54
62
13
13
13
7, 13, 20, 37, 39, 59, 62, 65
15,56
39
62
7, 39, 54, 59, 65
56,60
62
39
57
39
60
62
7, 13, 37, 65
56
13
15
7
       TBC = to-be-considered material
       DDT = dichlorodiphenyltrichloroethane
DDE = dichlorodiphenyldichloroethene
mg/kg  = milligrams per kilogram
       California Regional Water Quality Control Board Central Valley Region (CVRWQB),  "A Compilation of Water
       Quality Goals," 1993, Sacramento, California.

       *       Designated level methodology value varies with site conditions (e.g., depth to groundwater) and
               appropriate water quality objective.  Appendix E of the Groundwater Operable Unit and Soil Operable
               Unit Focused Feasibility Study Report [IT 1995a] for how the site-specific DLM-based values were
               derived, using leachability and environmental attenuation factors.
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             Table 6-5. Chemical-Specific ARARs and TBCs for Drinking and Groundwater
Chemical
Concentration (mg/L)
Plumes
ARAR
Benzene
Carbon Tetrachloride
1 ,4-Dichlorobenzene
1 ,2-Dichloroethane
1,1-Dichloroethene
cis-1 ,2-Dichloroethene
1 ,2-Dichloropropane
Tetrachloroethene
Trichloroethene
Vinyl Chloride
Xylenes
Lead
l.OxlO-3 (1)
5.0 x 10^ (1)
5.0 x 10-3 (1)
5.0 x 1Q-4 (1)
6.0 xlO'3 (1)
6.0 x 10-3 (1)
5.0 x 10'3 (2)
5.0 x lO'3 (2)
5.0 x 10-3 (2)
5.0 x IQ-4 (1)
1.75x10° (1)
1.5 xlO-2 (2)
MB/SAC, 7
MB/SAC, NE
7
MB/SAC, 7
MB/SAC, 7
MB/SAC, 7, NE
NE
MB/SAC, 7, NE
MB/SAC, 7
7
MB/SAC
MB/SAC
TBC
Chloromethane
TPH as Diesel '
TPH as Gasoline
3.0 x lO'3 (4)
l.OxlO'1 (3)
5.0 x lO'3 (3)
MB/SAC, 7, NE
MB/SAC, 7
MB/SAC
       TBC = to-be-considered material
       mg/L = milligrams per liter
       SAC = Strategic Air Command
       MB = Main Base
7 = Site 7
NE = Northeast
TPH = total petroleum hydrocarbon
ARAR = applicable or relevant and appropriate requirement
       (1)     Drinking Water Standards (California and Federal) Maximum Contaminant Levels (MCL), California
              Department of Health and Services, Primary MCL.
       (2)     Drinking Water Standards (California and Federal) MCL, U.S. Environmental Protection Agency
              (USEPA), Primary MCL.
       (3)     Other Taste and Odor Thresholds.
       (4)     Health Advisories or Suggested No-Adverse-Response Levels for toxicity other than cancer risk,
              USEPA.

       California Regional Water Quality Control Board Central Valley Region (CVRWQB), "A Compilation of Water
       Quality Goals," 1993, Sacramento, California.


       6.2   Location-Specific ARARs and TBCs
       Location-specific ARARs and TBCs are requirements that place restrictions on the

       concentration of a COC or the conduct of activities because of the presence of unique site
       features such as surface waters and wetlands.  The location of the Soil OU sites were analyzed

       for unique site features to identify location-specific ARARs.  The unique site
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       features considered were:

              •      surface water;
              •      floodplain and wetlands;
              •      habitats of rare, threatened, endangered, and special status species;
              •      earthquake faults;
              •      historically or culturally significant properties;
              •      wilderness areas;
              •      wild and scenic rivers; and
              •      coastal zones.

       Of these unique site features, surface water occurs at or near:  Site 13 (Drainage Ditch
       Number 1), Site 15 (Drainage Ditch Number 3), and Site 69 (Open Burn Pit).  Portions of Site
       7 may be located within the 100-year floodplain of Morrison Creek.  Vernal pools and
       seasonal wetlands, some of which are known to contain endangered species, have been
       identified at Mather AFB.  However, currently there has been no documentation that there are
       wetlands likely to harbor endangered species at or near any of the remedial actions selected by
       this ROD. The existence of wetlands and endangered species will be considered during
       remedial design to avoid or minimize impact during activities such as location of electrical
       conduit and water pipes associated with groundwater treatment systems. No other unique site
       features were identified.

       6.2.1  Federal Location-Specific ARARs
       The Endangered Species Act and implementing regulations at 50 CFR 17, 222, 226, 227,
       and 402, apply to some of the remedial actions at Mather AFB, if they impact endangered
       wildlife.  These impacts may be identified by a final biological assessment finding that the
       vernal pools on Mather AFB, do contain an endangered species. No vernal pools have been
       identified hi the vicinity of any of the Soil OU sites, for which remedial action is selected in
       this ROD. The direct cleanup activities are not expected to impact any endangered species;
       however, associated cleanup activities (i.e., construction of pipelines for groundwater
       injection) may impact habitat or critical resources. All activities must ensure that regulatory
       requirements are followed and impacts avoided or mitigated.

       6.2.2  State Location-Specific ARARs
       The Fish and Game Code Section 1600 requires that any work within the 100-year floodplain
       (consisting of, but not limited to, diversion or obstruction of the natural flow or changes  in the
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       channel, bed, or bank of any river, stream or lake) will involve mitigation measures to avoid
       or minimize impacts on natural resources. Portions of Site 7 may be located within the
       100-year floodplain; certain provisions of the Fish and Game Code Section 1600 would be
       relevant and appropriate for this site if the site is actually located in the 100-year floodplain.
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       6.3   Action-Specific ARARs and TBCs
       Action-specific ARARs are technology or activity-based requirements or limitations on actions
       taken with respect to the hazardous waste.  The following sections describe the state and
       federal action-specific ARARs and TBCs.  All ARARs are listed in Table 6-6 with each
       substantive requirement identified as either applicable or relevant and appropriate.  Several of
       the requirements are marked with a footnote giving clarification to either their ARAR status or
       the legal interpretation of why they are considered ARARs for a particular site or remedial
       action.  The TBCs are presented at the federal or state level in Sections 6.3.1.1 and 6.3.2.4.
       Sections 6.3.1 and 6.3.2 include a description of the sources of the action-specific ARAR
       regulations and the regulatory authority the agencies have  to enforce these requirements. In
       addition, the USAF  position on substantive requirements of ARARs and how they apply to the
       selected remedial actions are described.

       6.3.1 Federal ARARs
       The following federal action-specific ARARs and TBCs have been identified. The  federal
       action-specific ARARs are listed in Table 6-6, TBCs are listed in Sections 6.3.1.1 and 6.3.2.4
       and a brief description of the sources of action-specific ARARs are provided in this section.

       The Federal Safe Drinking Water Act regulates the injection of waste into injection wells.
       These wells are identified by unique characteristics such as depth, location of drinking water
       source, and material injected.   Forty CFR 144 - Underground Injection Control Program is the
       regulation  listing the requirements for the operation and use of injection wells.

       The California DTSC regulations promulgated under the Hazardous Waste Control  Law
       (HWCL) are applicable to RCRA-permitted storage facilities and proper characterization of
       hazardous  waste, and storage and disposal of such waste.  There is only one RCRA permitted
       facility (Site 37/39/54 - Building 3389/Hazardous Waste Central Storage Facility) being closed
       under the remedial actions and there is no intention of building any to support the cleanup
       activities.  If any hazardous waste is identified, it will be disposed of and handled under the
       permit by rule provisions of RCRA with treatment to render non-hazardous or disposed
       offsite.  Other HWCL provisions are relevant and appropriate to treatment systems, such as ex
       situ bioremediation treatment cells, where soils are managed.  Many of the HWCL  provisions
       are both relevant and appropriate because they describe requirements for the safe  handling of
       contaminated materials and precautions for preventing further contamination.
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C
9
                                                                         Table 6-6.  Action Specific ARARs
                 Source
Standard, Requirement, Criterion, or
              Limitation
                                                                           ARAR Status
                             Description of Applicable or Relevant and Appropriate Requirements
                                                                                           Fedei-ai AKARs
             Federal Safe
             Drinking Water
             Act
40 CFR 144 - Underground Injection
Control Program
 Applicable
USEPA established substantive requirements for actions that involve injection of fluids into
subsurface through wells.  The injection can not cause a violation of primary MCLs, must be
maintained, must be monitored, and injection can not take place until the well construction is
complete.

This regulation applies to the technology selected for the cleanup of Main/SAC and Site 7
ground water plumes.	    	
              California
              Hazardous
              Waste Control
              Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 12
(Standards Applicable to Generators of
Hazardous Waste), Article 1
(Applicability)	
Subsection(s)
  as Listed
   Below
Establishes standards for generators of hazardous waste located in California.  Only applicable if the
wastes from excavated sites or treatment processes are classified as hazardous or non-RCRA
hazardous waste, and the remedial action constitutes treatment, storage, or disposal of hazardous
waste.
                                 22CCR66262.il
                                            Applicable
              California
              Hazardous
              Waste Control
              Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 14
(Standards for Owners and Operators of
Hazardous Waste Transfer, Treatment,
Storage, and Disposal Facilities), Article
6 (Water Quality Monitoring and
Response Programs for Permitted
Facilities)	
Subsection(s)
  as Listed
   Below
                                 22 CCR 66264.94(a)
                                            Applicable
                                 22 CCR 66264.96°
                                            Applicable
These standards are applicable to permitted hazardous waste facilities.  Owners or operators of
permitted hazardous waste facilities must monitor the groundwater during the closure and
post-closure periods.  Groundwater Monitoring Requirements (22 CCR 66264.97):  Groundwater
needs to be monitored during the closure and post-closure periods at permitted RCRA/HWCL
facilities. Corrective  action monitoring (22 CCR 66264.100) is conducted if there is a corrective
action.
The concentration limit (22 CCR 66264.94(a)) may be background or established based on threats to
human health and the environment. If all of the wastes and contaminated materials are removed
from a waste  management unit, monitoring should be continued until the groundwater results
indicate that all water levels are in compliance with the water quality standard for three consecutive
years (22 CCR 66264.96(c)).

These regulation sections are applicable to any RCRA corrective action at the treatment facility,
Site 39, which was the Hazardous Waste Central Storage Facility,  which was permitted under
RCRA.
                                 22 CCR 66264.97
                                            Applicable
                                 22 CCR 66264.100
                                            Applicable

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TO
f
                                                                Table 6-6. Action-Specific ARARs (continued)
                 Source
Standard, Requirement, Criterion, or
             Limitation
ARAR Status
            Description of Applicable or Relevant and Appropriate Requirements
            California
            Hazardous
            Waste Control
            Law
 ON
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 14
(Standards for Owners and Operators of
Hazardous Waste Transfer, Treatment,
Storage, and Disposal Facilities), Article
7 (Closure and Post-Closures)	
Subsection(s)
  as Listed
    Below
                                22 CCR 66264.111
                                                                            Applicable
                                22 CCR 66264.112(b)
                                           Applicable
                                22 CCR 66264.114
                                            Applicable
Closure Performance Standard (22 CCR 66264. Ill): Closure of a permitted hazardous waste
facility should minimize the need for maintenance of the facility, and control, minimize, or
eliminate emissions of hazardous chemicals into the environment.

Content of Closure Plan (22 66264.112(b)):  All substantive steps required for closure of the facility
should be planned prior to beginning site activities.  The time required for each step should be
estimated. Disposal or Decontamination of Equipment, Structure and Soils (22 CCR 662624.114):
All contaminated equipment, structures, and soils shall be properly disposed of or decontaminated.
Post-Closure Care and  Use of Property (22 CCR 66264.117):  Unless the contamination is totally
removed, monitoring and maintenance of the facility must be continued. Post-closure uses shall
never disturb containment systems or monitoring equipment.

These regulation sections are applicable to the corrective action under taken for facility closure at
the treatment facility, Site 39, which was the Hazardous Waste Central Storage Facility, which was
permitted under RCRA.
                                22 CCR 66264.117
                                            Applicable
             California
             Hazardous
             Waste Control
             Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 14
(Standards for Owners and Operators of
Hazardous Waste Transfer, Treatment,
Storage, and Disposal Facilities), Article
9 (Use and Management of Containers)
 Subsection(s)
  as Listed
    Below
                                 22 CCR 66264.171
                                            Applicable
                                22 CCR 66264.172
                                            Applicable
                                 22 CCR 66264.173
                                            Applicable
                                22 CCR 66264.174
                                            Applicable
The chemicals recovered from the sediments, surface soils, subsurface soils, or groundwater may
need to be managed as either a RCRA or non-RCRA hazardous waste. The treatment, storage, and
disposal requirements for these wastes are either applicable or relevant and appropriate (depending
upon the classification of the waste material) and they include: using containers to store the
recovered product that are compatible with this material (22 CCR 66264.172); using containers that
are in good condition (22 CCR 66264.171); segregating the waste from incompatible wastes (22
CCR 66264.177); inspect the containers (22 CCR 66264.174); isolating the waste from sources of
ignition (if the material is ignitable) and (22 CCR 66264.176); providing adequate secondary
containment for the waste stored (22 CCR 66264.175); containers must be closed during transfer
(22 CCR 66264.173); and all hazardous material must be removed at closure (22 CCR 66264.178).

If during excavation, treatment processes, or cleanup activities hazardous waste is identified through
the proper characterization process, the hazardous waste will be managed in accordance with the
standards stated in these sections of the regulation.
                                 22 CCR 66264.175
                                            Applicable
                                 22 CCR 66264.176
                                            Applicable
                                 22 CCR 66264.177
                                            Applicable
                                 22 CCR 66264.178
                                            Applicable

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                                                   Table 6-6. Action-Specific ARARs (continued)
    Source
Standard, Requirement, Criterion, or
             Limitation
                                                             ARAR Status
                             Description of Applicable or Relevant and Appropriate Requirements
California
Hazardous
Waste Control
Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 14
(Standards for Owners and Operators of
Hazardous Waste Transfer, Treatment,
Storage, and Disposal Facilities), Article
12 (Waste Piles)           	
Subsection(s)
  as Listed
   below
                    22 CCR 66264.251
                                           Applicable
                    22 CCR 66264.254
                                           Applicable
Delineates requirements for the management of waste piles for hazardous waste. This regulation is
applicable to sites where excavated materials are classified as hazardous wastes and managed in
waste piles.  The titles of the regulations are Section 66264.251.  Design and Operating
Requirements; Section 66264.254. Monitoring and Inspection; Section 66264.256. Special
Requirements for Ignitable or Reactive Waste; Section 66264.257.  Special Requirements for
Incompatible Wastes; Section 66264.258.  Closure and Post-Closure Care; and Section 66264.259.
Special Requirements for Hazardous Wastes F020, F021,  F022, F023, F026, and F027.

If during excavation, treatment processes, or cleanup activities, hazardous waste is identified
through the proper characterization process, and will be managed in waste piles, the hazardous
waste will be managed in accordance with the standards stated in these sections of the regulation.
                    22 CCR 66264.256
                                           Applicable
                    22 CCR 66264.257
                                            Applicable
                    22 CCR 66264.258
                                            Applicable
                    22 CCR 66264.259
                                            Applicable
California
Hazardous
Waste Control
Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 14
(Standards for Owners and Operators of
Hazardous Waste Transfer, Treatment,
Storage, and Disposal Facilities), Article
19 (Corrective Action for Waste
Management Units)	
Subsection(s)
  as Listed
   Below
                    22 CCR 66264.552
                                           Relevant and
                                           Appropriate
                    22 CCR 66264.553
                                           Relevant and
                                           Appropriate
CAMU:  Placement, consolidation, and treatment of soils and wastes being generated as part of a
corrective action under RCRA will not be considered a new disposal to land as long as the materials
are handled in designated CAMUs. Land disposal restrictions (22 CCR 66268) are not invoked
when remediation wastes are managed at a CAMU.  A CAMU can only be used for the
management of remediation wastes pursuant to implementing corrective actions at the facility.

USEPA intended that the Federal CAMU rule be considered for the management of wastes
generated at CERCLA sites.  Excavation of wastes from the discharge and disposal sites might be
managed at a CAMU for on-base disposal, or ex situ bioremediation.

A CAMU is an area within a facility for the purpose of implementing corrective actions.
Uncontaminated areas are allowed to be designated as part of a CAMU when they are necessary to
achieve the overall goals for the facility and will enhance the protectiveness  of the remedial action.
The CAMU rule allows consolidation and treatment of wastes in a single unit, from other areas of
the facility, without triggering minimum technology requirements and LDR found in other
provisions of RCRA and HWCL:  that is, placement of wastes into a CAMU is not considered land
disposal and redeposition of treated wastes into the CAMU does not trigger the  LDRs.
Groundwater must be monitored at the CAMU in order to detect and characterize a release.

If during excavation, treatment processes, or cleanup activities hazardous waste is identified through
the proper characterization process, and will be managed in waste piles, the hazardous waste will be
managed in accordance with the standards stated in these sections of the regulation.

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9
a
                                Table 6-6. Action-Specific ARARs  (continued)
                 Source
Standard, Requirement, Criterion, or
             Limitation
ARAR Status
            Description of Applicable or Relevant and Appropriate Requirements
             California
             Hazardous
             Waste Control
             Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 18 (Land
Disposal Restrictions), Article 1
(General)	       	
 Subsection(s)
  as Listed
    Below
                                 22 CCR 66268.3
                                            Applicable
                                 22 CCR 66268.7(a) & (b)
                                            Applicable
Provides the purpose, scope, and applicability of LDRs. The tide of the sections of the regulations
are; Section 66268.3. Dilution Prohibited As a Substitute for Treatment; Section 66268.7. Waste
Analysis and Record keeping; and Section 66268.9. Special Rules Regarding Wastes That Exhibit a
Characteristic.

If during excavation, treatment processes, or cleanup activities hazardous waste is identified through
the proper characterization process, and will be managed in waste piles, the hazardous waste will be
managed in accordance with the standards stated in these sections of the regulation.  Only applicable
if hazardous wastes are disposed of or treated in an area not designated as a CAMU or disposed of
or treated beyond the area of contamination.
                                 22 CCR 66268.9
                                            Applicable
             California
             Hazardous
             Waste Control
             Law
 ON
 i—»
 O\
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 18 (Land
Disposal Restrictions), Article 3
(Prohibitions on Land Disposal)	
Subsection (s)
  as Listed
    Below
                                 22 CCR 66268.30
                                            Applicable
                                 22 CCR 66268.31
                                            Applicable
                                 22 CCR 66268.32
                                            Applicable
These standards are applicable to sites where excavated material is classified as hazardous waste
and is disposed of or treated in an area not designated as a CAMU.  Provides waste-specific LDRs
for Section 66268.30.  Waste Specific Prohibitions-Solvent Wastes; Section 66268.31. Waste
Specific Prohibitions-Dioxin-Containing Wastes; Section 66268.32. Waste Specific
Prohibitions-California List Wastes; Section 66268.33. Waste Specific Prohibitions-First Third
Wastes; Section 66268.34. Waste Specific Prohibitions-Second Third Waste; and
Section 66268.35.  Waste Specific Prohibitions-Third Third Waste.

If during excavation, treatment processes, or cleanup activities hazardous waste is identified through
the proper characterization process, and will be managed in waste piles, the hazardous waste will be
managed in accordance with the standards stated in these sections of the regulation.
                                 22 CCR 66268.33
                                            Applicable
                                 22 CCR 66268.34
                                            Applicable
                                 22 CCR 66268.35
                                            Applicable
             California
             Hazardous
             Waste Control
             Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 18 (Land
Disposal Restrictions), Article 4
(Treatment Standards)	
 Subsection(s)
   as Listed
    Below
                                 22 CCR 66268.41
                                                                             Applicable
                                 22 CCR 66268.42
                                                                             Applicable
These standards are applicable to sites where excavated materials are classified as hazardous waste
and are disposed of or treated in an area not designated as a CAMU.  Provides treatment standards
expressed in contaminant concentrations in Section 66268.41.  Treatment Standards Expressed As
Concentrations in Waste Extract; Section 66268.42.  Treatment Standards Expressed As Specified
Technologies; and Section 66268.43. Treatment Standards Expressed As Waste Concentrations.

These standards provide waste specific LDRs for solvent wastes, dioxin-containing wastes, and
California Listed Wastes.

If during excavation, treatment processes, or cleanup activities hazardous waste is identified through
the proper characterization process, and will be managed in waste piles,  the hazardous waste will be
managed in accordance with the standards stated in these sections of the  regulation.
                                 22 CCR 66268.43
                                                                             Applicable

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1
                                Table 6-6. Action-Specific ARARs (continued)
                 Source
Standard, Requirement, Criterion, or
             Limitation
                                                                          ARAR Status
                              Description of Applicable or Relevant and Appropriate Requirements
             California
             Hazardous
             Waste Control
             Law
Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 18 (Land
Disposal Restrictions), Article 5
(Prohibitions on Storage)	
Subsection(s)
  as Listed
   Below
                                 22 CCR 66268.50
                                           Applicable
This standard is applicable to sites where excavated material is classified as hazardous waste.  The
standard provides prohibitions on storage of restricted wastes.

If during excavation, treatment processes, or cleanup activities hazardous waste is identified through
the proper characterization process, and will be managed in waste piles, the hazardous waste will be
managed in accordance with the standards stated in these sections of the regulation.
                                                                                    Slate of California Air ARARi
             California
             Clean Air Act
 O\
 t—»
 -J
SMAQMD, Rule 202, Section 301
 Applicable
This section of the rule requires the installation of BACT to a new emissions unit or modification of
an existing emissions unit that will result in an emission of ROG,  NOx, SOx, PM10, or CO.

Best Available Control Technology for any emission unit is the most stringent of the following:

The most effective emission control device, emission limit, or technique, singly or in combination,
which has been required or used for the type of equipment comprising such an emissions unit unless
the applicant demonstrates to the satisfaction of the SMAQMD that such limitations required on
other sources have not been demonstrated to be achievable. For this type of process, a control
efficiency (effluent/influent) of 95 percent is considered BACT.

Top-down analysis process is the selection of any alternative basic equipment, fuel, process,
emission control device, or technique, singly or in combination, determined to be technically
feasible and cost-effective by the SMAQMD.

In making a BACT determination for each affected pollutant the district may consider the overall
effect on other affected pollutants.

This regulation will apply to the treatment processes that release or cause to be released the
pollutants listed in the regulation.  The remedial alternatives utilizing air strippers, soil  vapor
extraction and ex situ bioremediation must ensure BACT is used to control emissions in excess of
levels specified in the rule.	

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9
a
m
                                 Table  6-6. Action-Specific ARARs (continued)
                 Source
Standard, Requirement, Criterion, or
              Limitation
ARAR Status
                                                                                                          Description of Applicable or Relevant and Appropriate Requirements
             California
             Clean Air Act
SMAQMD, Rule 202, Section 302
  Applicable
This section of the rule requires an applicant to provide offsets for any stationary source with the
potential to emit any pollutant in excess of the levels shown below.

          ROG	1501bs/day
          NOx	1501bs/day
          SOx	1501bs/day
          PM10....801bs/day
          CO	5501bs/day

Offsets for CO shall not be required if the applicant can demonstrate that ambient air quality
standards will not be violated in the affected areas, and will not cause or contribute to a violation of
the ambient air quality standard. All emissions increases in excess of the levels specified  above
need to be offset for the same calendar quarter.

Emissions are determined by using actual stack test data, emission factors, engineering calculations,
or other methods approved by the district in accordance with Section 411 of Rule 202.

This regulation will apply to the treatment processes that release or cause to be released the
pollutants listed in the regulation. The remedial alternatives utilizing air strippers, soil vapor
extraction and ex situ bioremediation must ensure offsets are used for emissions in excess of levels
specified in the  rule.
             California
             Clean Air Act
SMAQMD, Rule 401
  Applicable
This rule prohibits the discharge of air contaminants which obscure visibility by more than
20 percent for a period of more than three minutes in any one hour.

This regulation is applicable to any remedial action activity, which may cause a visible emission.
             California
             Clean Air Act
SMAQMD, Rule 402
  Applicable
This rule prohibits the discharge of air contaminants in quantities which cause injury, detriment,
nuisance, or annoyance to any considerable number of persons or which endangers the comfort,
response, health, or safety of any such person or which causes or has natural tendency to cause
injury or damage to business or property.

This regulation is applicable to any remedial action activity, which may discharge air contaminants
as defined by the rule.	
             California
             Clean Air Act
SMAQMD, Rule 403
  Applicable
This rule requires a person to take every reasonable precaution not to cause or allow emissions of
fugitive dusts from being airborne beyond the property line from which the emissions originated.

This regulation is applicable to any remedial action activity, which may cause the release of fugitive
dust.
             California
             Clean Air Act
SMAQMD, Rule 404
  Applicable
This rule prohibits the discharge of paniculate matter from any source in excess of 0.1 grains per
standard cubic foot.

This regulation is applicable to any remedial action activity , which may cause the release of
paniculate matter.        	

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                                                                Table 6-6.  Action-Specific ARARs  (continued)
                 Source
Standard, Requirement, Criterion, or
             Limitation
                                                                           ARAR Status
                                                                                                         Description of Applicable or Relevant and Appropriate Requirements
             California
             Clean Air Act
SMAQMD, Rule 405
 Applicable
This rule controls the discharge of dust and condensed fumes into the atmosphere by establishing
emission rates based on process weight.

This regulation is applicable to any remedial action activity, which may cause the release of dust or
condensed fumes.
                                                                            State of California Groundwater and Soil ARARs
             Federal Clean
             Water Act
40 CFR 122 - USEPA Administered
Permit Programs: The National
Discharge Elimination System
                                 40 CFR 122.26
Subsections(s)
  as Listed
    Below
                                            Applicable
Requirements to ensure storm-water discharges from Mather AFB remedial action activities do not
contribute to a violation of surface water quality standards.
ON
H-i
VO
             Federal Clean
             Water Act
40 CFR 122 - USEPA Administered
Permit Programs: The National
Discharge Elimination System	
Subsections(s)
  as Listed
    Below
                                 40 CFR 122.41 (d)
                                            Applicable
40 CFR 122.41(e)
  Applicable
All reasonable steps must be taken to minimize or prevent discharges which have a reasonable
likelihood of causing adverse impacts on surface water quality (40 CFR 122.41(d)).  All equipment
and facilities must be properly operated and maintained, including adequate laboratory controls and
appropriate quality assurance procedures (40 CFR 122.41(e)).  Discharges into surface water must
achieve federal and state water quality standards (40 CFR 122.44(d)).

These sections of the regulation governing impacts to water quality apply to the groundwater
during/after treatment at the Main/SAC and Site 7 groundwater plumes.
                                 40 CFR 122.44 (d)
                                            Applicable
                                 State Water Resources Board
                                 Order 92-08-DWQ
                                            Applicable
                  Must identify the sources of sediment and other pollutants that affect the quality of storm-water
                  discharges and implement practices to reduce these discharges.

                  Storm-water discharges from construction sites must meet pollutant limits and standards.  The
                  narrative effluent standard includes the requirements to implement BMPs and/or appropriate
                  pollution prevention control practices.

                  Inspections of the construction site prior to anticipated storm events and after actual storm events
                  need to be conducted to identify areas contributing to storm-water discharge and evaluated for the
                  effectiveness of BMPs and other control practices.

                  Applies to construction sites fives acres or greater in size.  It also applies to smaller sites that are
                  part of a larger common plan of development or sale.

                  The remedial actions at the groundwater sites are  being conducted as part of the overall remedial
                  actions for Mather AFB.  Excavation, grubbing, clearing, and other activities may be required for
                  installation of a groundwater extraction and treatment system.	

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9
                                                                Table 6-6.  Action-Specific ARARs (continued)
                Source
Standard, Requirement, Criterion, or
             Limitation
ARAR Status
            Description of Applicable or Relevant and Appropriate Requirements
                                State Water Resources Board
                                Order 92-13-DWQ (as amended by
                                Order number 92-12-DWQ)
                                            Applicable
                  Storm-water discharges must meet the narrative standard of the permit, this standard includes
                  implementing BMPs and prohibits the discharge of non-storm-water.  Discharges should identify the
                  sources of pollutants to the storm-water. BMPs for these sources can include treatment of storm-
                  water discharge and source reduction. Non-storm-water sources of pollutants include improper
                  dumping, spills, and leaks.

                  Monitoring must be conducted to demonstrate compliance and measure the effectiveness of BMPs.
                  Monitoring includes performing visual inspections during the dry and wet seasons, conducting
                  annual inspections, and sampling and analysis for specific analytical parameters.

                  Applies to landfills, land application sites, and disposal sites (Site 7) that have received industrial
                  wastes, and other industrial areas.
            Porter-Cologne
            Water Quality
            Control Act
            (California
            Water Code
            Sections 13000,
             13140, 13240)
                                CVR Basin Plan
                                            Applicable
                  Establishes water quality objectives, including narrative and numerical standards, that protect the
                  beneficial uses of surface and groundwater in the region. The designated beneficial uses are
                  municipal and domestic; agricultural; and industrial supply.

                  Specific applicable portions of the Basin Plan include beneficial uses of affected water bodies and
                  water quality objectives to protect those uses.
             Porter-Cologne
             Water Quality
             Control Act
             (California
             Water Code
             Sections 13000,
             13140, 13240)
                                SWRCB Resolution 68-16
                                            Applicable
                  The resolution establish requirements for activities involving discharges of contamination directly
                  into surface waters or groundwater (e.g. quality of pump and treat effluent into surface waters or
                  groundwater).

                  Substantive requirements established by the resolution include use of "best practicable treatment or
                  control" for discharging the effluent.

                  This regulation applies to remedial action activities that cause active discharges to surface waters or
                  groundwater.	
             Porter-Cologne
             Water Quality
             Control Act
             (California
             Water Code
             Sections 13000,
             13140, 13240)
SWRCB Resolution 88-63
  Applicable
Specifies that, with certain exceptions, all ground and surface waters have the beneficial use of
municipal or domestic water supply.  Applies in determining beneficial uses for waters that may be
affected by discharges of waste.

SWRCB Resolution 88-63 applies to all sites that may be affected by discharges of waste to
groundwater or surface water. The resolution specifies that, with certain exceptions, all
groundwater and surface waters have beneficial use of municipal or domestic water supply.
Consequently, California State primary MCLs are relevant and appropriate, however the most
stringent federal or state standard will be the ARAR for  the remedial action. California standards
which may be ARARs for the site(s) are found in 22 CCR 66435, 22 CCR 64444.5, and 22 CCR
64473.                                                                	  	

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                                                                Table 6-6.  Action-Specific ARARs (continued)
                 Source
                    Standard, Requirement, Criterion, or
                                 Limitation
                                                                          ARAR Status
                                                                       Description of Applicable or Relevant and Appropriate Requirements
             Porter-Cologne
             Water Quality
             Control Act
             (California
             Water Code
             Sections 13140,
             13240, 13260,
             13263, 13267,
             13300, 13304,
             13307)
                   SWRCB Resolution 92-49
                   (as amended April 21, 1994)
                   Subparagraph IIIG
                                          Relevant and
                                           Appropriate
                 Section IIIG directs the Water Boards to ensure dischargers clean up and abate the "effects" of
                 discharges in a manner promoting attainment of either background water quality or the best
                 reasonable water quality if background quality is not feasible (feasibility determined by factors listed
                 in Section IIIG and 23 CCR Chapter 15, Section 2550.4).  Minimum water standards must be
                 protective of beneficial use.

                 Section IIIG directs the Water Board to apply 23 CCR Chapter 15, Section 2550.4 in approving any
                 alternative cleanup levels less stringent than background quality and to apply 23 CCR Chapter 16,
                 Section 2725 for alternatives cleanup levels for remediation of releases from USTs.

                 The requirement to obtain the Water Board's approval is not an ARAR; however, the Air Force will
                 consult with the Water Board and USEPA in applying the State's criteria to establish alternative
                 cleanup levels.

                 Subject to the limitations described above, this requirement is relevant and appropriate for
                 establishing levels for effects to surface and groundwater quality caused by releases of
                 contaminants.
O\
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260,
13263, 13267,
13304)
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 1 (General)
Subsection(s)
  as Listed
   Below
                                 23 CCR 2510(g)'
                                          Relevant and
                                           Appropriate
                                 23CCR2511(d)
                                                              Applicable or
                                                              Relevant and
                                                              Appropriate2
23 CCR 2510(g) states persons responsible for discharges at waste management units which are
closed, abandoned, or inactive on the effective date of these regulations may be required to develop
and implement a monitoring program in accordance with Article 5 of this Chapter. If water quality
impairment is found, such persons may be required to develop and implement a corrective action
program based on the provisions of this subchapter.

23 CCR 2511 (d) states actions taken by or at the direction of public agencies to cleanup or abate
conditions of pollution or nuisance resulting from unintentional or unauthorized releases of waste or
pollutants to the environment; provided that wastes, pollutants, or contaminated materials removed
from the immediate place of release shall be discharged according to Article 2 of this Chapter; and
further provided that remedial actions intended to contain such wastes at the place of release shall
implement applicable provisions of this subchapter to the extent feasible.

This regulation applies2 to waste management units located at Sites 7, 56, 57, 59, 60, 62, 65, and
69.

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                                        Table 6-6. Action-Specific ARARs (continued)
Source
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260,
13263, 13267,
13304)
Standard, Requirement, Criterion, or
Limitation
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article '2 (Waste Classification
and Management)
23 CCR 2520(a)
23 CCR 2520(b)
23 CCR 2520(c)
23 CCR 2520(d)
ARAR Status
Applicable or
Relevant and
Appropriate3'4
(See Sections
Listed Below)
Applicable to
Site 7
Applicable to
Site?
Applicable to
Site?
Applicable to
Site?
Description of Applicable or Relevant and Appropriate Requirements
Waste Classification: Wastes must be classified as either: hazardous waste (23 CCR 2521),
designated waste (23 CCR 2522), nonhazardous solid waste (23 CCR 2523), or inert waste
(23 CCR 2524). A hazardous waste can only be discharged to a Class I facility (unless a variance is
applicable under Title 22 regulations). A designated waste can be discharged to a Class I or Class
II facility. A nonhazardous solid waste can be discharged to a Class I, II, or III facility. Inert
wastes do not need to be sent to a classified facility.
Some of the sites have alternatives that involve excavation of the contaminated soil. At the
conclusion of on-base treatment, the soils are proposed for use hi the foundation layer of the landfill
cap at Site 4. It is expected based on engineering judgement that most of the sites excavated will
yield designated and not yield hazardous waste. However, until sampling is performed on the
material at time of excavation, a final determination cannot be made. The excavated waste must be
discharged to the appropriate facility pursuant to Article 2.
Requires that wastes identified as hazardous, designated, or nonhazardous solid waste (sections
2521, 2522 and 2523 of Article 2) be allowed only at waste management units which have been
approved and classified.
Prohibits the discharge of wastes which have the potential to reduce or impair the integrity of
containment structures or which, if commingled with other wastes in the unit, could produce violent
reaction, heat or pressure, fire or explosion, toxic by-products, or reaction products which in turn:
a. require a higher level of containment than provided by the unit;
b. are restricted 'hazardous wastes'; or
c. impair the integrity of containment structures.
Requires accurate characterization of waste.
Requires management of liquids at classified waste management units.
o\
N>

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                                        Table 6-6. Action-Specific ARARs (continued)
Source
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260,
13263, 13267,
13304)
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260,
13263, 13267,
13304)
Standard, Requirement, Criterion, or
Limitation
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 3 (Waste Management
Unit Classification and Siting)
23 CCR 2530(c)
23 CCR 2530 (d)
23 CCR 2532
23 CCR 2533(c)
Tide 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 4 (Construction
Standards)
23CCR2541(c)
23 CCR 254 l(d)
23 CCR 2546(a) & 2546(c) to (f)
ARAR Status
Subsection(s)
as Listed
Below
Applicable4'5
Applicable4'5
Applicable4'5
Relevant and
Appropriate to
Site?
Subsection(s)
as Listed
Below3
Relevant and
Appropriate to
Site?
Applicable to
Site?
Applicable to
Site?
Description of Applicable or Relevant and Appropriate Requirements
Classification and Siting Criteria (23 CCR 2530(c & d)): New waste piles shall be designed,
constructed, and operated to ensure that wastes will be a minimum of five feet above the highest
groundwater elevation. All containment structures at the unit shall have a foundation or base
capable of supporting the structures and capable of withstanding hydraulic pressure gradients.
Class II (23 CCR 2532): Waste Management Units for Designated Waste: Waste management units
will be isolated from the waters of the state through either natural or engineered barriers. The unit
needs to be able to withstand flooding without washout, ground rupture, and rapid geological
change.
Relevant to the ex situ bioremediation alternatives. Excavated wastes from various sites will be
spread in lifts in a bioremediation cell. Treatment might include nutrient addition, irrigation, and
aeration. This treatment is considered similar to a waste pile.
Soils containing petroleum hydrocarbons are not anticipated to be classified as hazardous, but may
be classified as designated wastes. Thus Class II requirements are considered most relevant.
Requires that landfills be designed, constructed, operated, and maintained to prevent inundation or
washout due to floods with a 100-year return period.

Requires hydraulic conductivities determined through laboratory methods be confirmed by
appropriate field testing.
Requires earthen materials used in containment structures consist of a mixture of clay and other
suitable fine- grained soils which have specified characteristics, and which can be compacted to
attain the required permeability when installed.
Requires management of precipitation and drainage control
ON

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70
C
                                                                  Table 6-6. Action-Specific ARARs (continued)
                  Source
Standard, Requirement, Criterion, or
              Limitation
                                                                            ARAR Status
                              Description of Applicable or Relevant and Appropriate Requirements
              Porter-Cologne
              Water Quality
              Control Act
              (California
              Water Code
              Sections
              13140-13147,
              13172,  13260,
              13263,  13267,
              13304)
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 5 (Water Quality
Monitoring and Response Programs for
Waste Management Units)	
23 CCR 2550.1
                                  23 CCR 2550.4
 ON
 to
23 CCR 2550.6
                                  23 CCR 2550.7
                                  23 CCR 2550.9
                                  23 CCR 2550.10
Subsection(s)
  as Listed
   Below3
                                           Relevant and
                                           Appropriate
                                                                             Relevant and
                                                                             Appropriate6
                                           Relevant and
                                           Appropriate
                                           Relevant and
                                            Appropriate
                                                                             Relevant and
                                                                             Appropriate
                                                                             Relevant and
                                                                              Appropriate
These provisions of Chapter 15 address remediation of contamination at waste management units
and monitoring of groundwater quality during the remedial action.  The corrective action program
requires that the cleanup objectives be met at the designated monitoring points and that they be met
throughout the zone that is affected. Further, demonstration of the effectiveness of the remediation
requires showing the concentrations at each monitoring point are at or below the cleanup levels for
one year following completion of the corrective action(s).  The evaluation monitoring program
provides further substantive requirements regarding the designation of monitoring parameters and
monitoring frequency.

Section 23 CCR Part 2550.1 describes the three types of groundwater monitoring programs;
detection, statistical evaluation, and physical evaluation monitoring. Section 23 CCR Part 2550.10
(Corrective Action Program)  requires that a groundwater monitoring program be implemented in
conjunction with a corrective action to demonstrate the effectiveness of the remedial  technologies.
Both monitoring programs must meet the requirements outlined in Section 2550.7 which state:
-there is a sufficient number of monitoring points, including background points; and
-the monitoring points should be located at appropriate locations and screened in the  zones of
concern.

Cleanup levels must be  set at background concentration levels  or, if background levels are not
technologically and economically feasible, then at the lowest levels that are economically and
technologically feasible. Specific factors must be  considered in setting cleanup levels above
background levels. Cleanup levels above background levels shall be evaluated every five years. If
the actual concentration of a constituent is lower than its associated cleanup level, the cleanup level
shall be lowered to reflect existing water quality (23 CCR 2550.4).  It has been determined that
cleanup to background is not economically feasible and therefore not relevant and appropriate to
aquifer cleanup standards.

Requires monitoring for compliance with remedial action objectives for three years from the date of
achieving cleanup levels (23 CCR 2550.6).

Requires general soil, surface water, and groundwater monitoring (23 CCR 2550.7)

Requires an assessment of the nature and extent of the release, including a determination of the
spatial distribution and concentration of each constituent (23 CCR 2550.9).

Requires implementation of corrective action measures that ensure that cleanup levels are achieved
throughout the zone affected by the release by removing the waste constituents or treating them in
place.  Source control may be required. Also requires monitoring to determine  the effectiveness of
corrective actions. To demonstrate cleanup, the concentration of each COC in the groundwater
must be equal to, or less than, the cleanup goal for at least one year following suspension of the
corrective action (23 CCR 2550.10).

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73
r^


9
                                        Table 6-6. Action-Specific ARARs (continued)
Source
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260,
13263, 13267,
13304)
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260,
13263, 13267,
13304)
Standard, Requirement, Criterion, or
Limitation
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 8 (Closure and
Post-Closure Maintenance)
23 CCR 2580(a)
23 CCR 2580(d)
23 CCR 2580(e)
23 CCR 2581
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 9 (Compliance
Procedures)
23 CCR 2596(b)
23 CCR 2597
ARAR Status
Subsections as
Listed Below3
Applicable
Relevant and
Appropriate
Relevant and
Appropriate
Applicable to
Site?
Subsections as
Listed Below3
Applicable to
Site?
Applicable to
Site?
Description of Applicable or Relevant and Appropriate Requirements
General Closure Requirements: partial or final closure of classified waste management units must
include continued maintenance of waste containment, precipitation, drainage controls, and
groundwater monitoring throughout the closure and post-closure periods (23 CCR 2580(a)). At
least two permanent monuments must be installed to allow the elevations of wastes, containment
structures, and monitoring facilities to be determined (23 CCR 2580(d)). Vegetation cover for a
closed waste management unit shall require minimum irrigation and maintenance, and shall not
impair the integrity of any containment structure (23 CCR 2580(e)).
The post-closure maintenance period will extend as long as wastes pose a threat to water quality.
This regulation applies to Site 7.
Requires a final cover constructed in accordance with specific prescriptive standards, to be
maintained as long as wastes pose a threat to water quality.
Regulation applies to closing solid waste disposal sites.
Procedures related to routine operations and emergency conditions must be developed for the waste
disposal activities.
Procedures for closure and post-closure maintenance must be developed. The magnitude of
settlement due to waste decompsition and compaction and subsidence of the underlying natural
geologic materials must be estimated. If the post-closure use is not non-irrigated open space, the
water balance for the site must be estimated and adverse impacts on the final cover anticipated.
State of California Solid Waste ARARs
California Inte-
grated Waste
Management
Act of 1989
PRC 40502,
43020,43021
and 43030
Title 14 (Natural Resources), Division 7
(California Integrated Waste
Management Board), Chapter 3
(Minimum Standards for Solid Waste
Handling and Disposal), Article 7.3
(Disposal Site Records)
14 CCR 17636
14 CCR 17637
Subsections as
Listed Below
Applicable
Applicable
This regulation is applicable to solid waste disposal sites as defined by Public Resources Code
Section 40122, i.e. for waste consolidation at Site 7.
Weight/Volume Records: the weight or volume of waste accepted must be determined to an
accuracy of ±10%
Subsurface Records: the length and depth of any cut(s) made in natural terrain where fill will be
placed and the depth to groundwater must be determined and documented.

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73
c
9
S
m
Table 6-6. Action-Specific ARARs (continued)
Source
California Inte-
grated Waste
Management
Act of 1989
PRC 40502,
43020,43021
and 43030
California Inte-
grated Waste
Management
Act of 1989
PRC 40502,
43020, 43021
and 43030
Standard, Requirement, Criterion, or
Limitation
Title 14 (Natural Resources), Division 7
(California Integrated Waste
Management Board), Chapter 3
(Minimum Standards for Solid Waste
Handling and Disposal), Article 7.4
(Disposal Site Improvements)
14 CCR 17658
14CCR 17659
Title 14 (Natural Resources), Division 7
(California Integrated Waste
Management Board), Chapter 3
(Minimum Standards for Solid Waste
Handling and Disposal), Article 7.5
(Disposal Site Operations)
14 CCR 17676
14 CCR 17677
14 CCR 17678
14 CCR 17680
14 CCR 17684
14 CCR 17686
14 CCR 17687
14 CCR 17688
14 CCR 17689
14 CCR 17690
14 CCR 17691
14 CCR 17692
ARAR Status
Subsections as
Listed Below
Applicable
Applicable
Subsections as
Listed Below
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Description of Applicable or Relevant and Appropriate Requirements
This regulation is applicable to solid waste disposal sites as defined by Public Resources Code
Section 40122, i.e. for waste consolidation at Site 7.
Site Security: the perimeter of the landfill must be secured either through barriers or topographic
constraints to discourage unauthorized entry.
Access Roads: landfill roads must be reasonably smooth to minimize dust and tracking of materials
onto public roads.
This regulation is applicable to solid waste disposal sites as defined by Public Resources Code
Section 40122, i.e. for waste consolidation at Site 7.
Confined Unloading: Requires limiting unloading area, controlling windblown materials, and
deposition at toe of fill.
Spreading and Compacting: Requires spreading and compacting of refuse in layers.
Slopes and Cuts: The slope of the working face shall be maintained at a ratio which will allow
effective compaction of the wastes. The depth of cuts and slopes of trench sides shall not exceed
specified horizontal to vertical ratios.
Stockpiling: Requires stockpiled cover material and unacceptable native materials to be placed so as
not to cause problems or interference with site operations.
Intermediate Cover: Requires cover on fill where no additional refuse will be deposited within 180
days.
Scavenging: Scavenging is prohibited.
Salvaging Permitted: Salvaging is permitted in a planned and controlled manner.
Volume Reduction and Energy Recovery: Volume reduction and energy recovery are permitted in
planned and controlled manners.
Processing Area: Processing area shall be confined to greatest degree practicable.
Storage of Salvage: Salvage material must be safely isolated for storage.
Removal: Storage time for salvage materials shall be limited to a safe duration.
Non-Salvageable Items: Items capable of impairing public health shall not be salvaged without
approval by Enforcement Agency and local health entity.

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                                        Table 6-6. Action-Specific ARARs (continued)
Source
California Inte-
grated Waste
Management
Act of 1989
PRC 40502,
43020,43021
and 43030
Standard, Requirement, Criterion, or
Limitation
Title 14 (Natural Resources), Division 7
(California IWMB), Chapter 3
(Minimum Standards for Solid Waste
Handling and Disposal), Article 7.6
(Disposal Site Controls)
14 CCR 17701
14CCR 17704
14 CCR 17705
14 CCR 17706
14 CCR 17707
14 CCR 17708
14 CCR 17709
14 CCR 17710
14 CCR 17711
14 CCR 17713
14 CCR 17741
ARAR Status
Subsections as
Listed Below
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Applicable
Description of Applicable or Relevant and Appropriate Requirements
This regulation is applicable to solid waste disposal sites as defined by Public Resources Code
Section 40122, i.e. for waste consolidation at Site 7.
Nuisance Control: Each site shall be operated and maintained so as not to create a public nuisance.
Leachate Control: The operator shall take adequate steps to monitor, collect, treat, and effectively
dispose of leachates.
Gas Control: Landfill gas control may be required based on the monitoring results.
Dust Control: The operator shall take adequate measures to minimize the creation of dust.
Vector and Bird Control: The operator shall control or prevent the propagation, harborage, or
attraction of flies, rodents, or other vectors, and to minimize bird problems.
Drainage And Erosion Control: Adequate drainage shall be provided. Effects of erosion shall be
promptly repaired and steps taken to prevent further occurrence.
Contact with Water: No solid waste shall be deposited in direct contact with surface water.
Grading of Fill Surface: Covered surfaces of the disposal area shall be graded to promote run-off and prevent
ponding, accounting for future settlement
Litter Control: Litter and loose materials shall be routinely collected and disposed of properly.
Odor Control: The disposal site shall not be a source of odor nuisances.
Burning Wastes: Burning wastes shall be extinguished.
ON

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                                                                Table 6-6. Action-Specific ARARs (continued)
                 Source
Standard, Requirement, Criterion, or
             Limitation
                                                                          ARAR Status
                             Description of Applicable or Relevant and Appropriate Requirements
ON
Ni
oo
             California
             Integrated
             Waste
             Management
             Act of 1989
             Public
             Resources Code
             Sections 40502
             and 43020
Title 14 (Natural Resources), Division 7
(California Integrated Waste
Management Board), Chapter 3
(Minimum Standards for Solid Waste
Handling and Disposal), Article 7.8
(Disposal Site Closure and Post-Closure
Maintenance)
Subsection(s)
  as Listed
   Below
The regulation is applicable to solid waste sites that closed after August 1988.  Although never
classified as a landfill under California regulations, Site 7 was used for the disposal of POL and
other industrial wastes.  The wastes discarded at Site 7 are likely to be classified as designated
wastes using the criteria in effect in 1994 (23 CCR 2520-2523). Because of the similarity of
historical activities and site conditions at Site 7 to a landfill, Article 7.8 regulations are considered
relevant and appropriate.
14 CCR 17766
                                           Relevant and
                                           Appropriate
                  ERP:  Potential emergency conditions that may exceed the design of the site and could endanger the
                  public health or environment must be anticipated.  Procedures for mitigation of these conditions
                  should be developed (14 CCR 17766).
                                 14 CCR 17767
                                           Relevant and
                                           Appropriate
                  Security at Closed Sites:  All points of access to the site must be restricted, except permitted entry
                  points.  All monitoring, control, and recovery systems shall be protected from unauthorized access
                  (14 CCR 17767).
                                 14 CCR 17773(b)
                                           Relevant and
                                           Appropriate
                                 14 CCR 17773(c)
                                           Relevant and
                                           Appropriate
                  Final Cover: The design and construction of the final cover must meet specific prescriptive
                  standards (references 23 CCR 2581(a)).  These include minimum thickness and quality of the
                  construction material (14 CCR 17773 (b) and (e)).  If the prescriptive standards are not feasible,
                  engineered alternatives can be approved provided that they are consistent with the performance
                  goals and afford equivalent protection against water quality impact (14 CCR 17773 (b, c, d, e)).
                                 14 CCR 17773(d)
                                           Relevant and
                                           Appropriate
                                 14 CCR 17773(e)
                                           Relevant and
                                           Appropriate

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71
C
9
                                                               Table 6-6. Action-Specific ARARs (continued)
                 Source
Standard, Requirement, Criterion, or
             Limitation
                                                                         ARAR Status
                            Description of Applicable or Relevant and Appropriate Requirements
             California
             Integrated
             Waste
             Management
             Act of 1989
             Public
             Resources Code
             Sections 40502
             and 43020
14 CCR 17774(a)
14 CCR 17774(C)
14 CCR 17774(d)
                                14 CCR 17774(e)
                                14 CCR 17774 (f)
                                14 CCR 17774(g)
                                14 CCR 17774(h)
                                14 CCR 17776(a)
                                14 CCR 17776(c)
                                14 CCR 17776(e)
                                14 CCR 17776(f)
                                14 CCR 17777(a)
                                14 CCR 17777(b)
                                14 CCR 17777(c)[portions]
Relevant and
Appropriate
Relevant and
Appropriate
CQA: A CQA program must be designed and implemented. It must include specific parameters
(and for some components specific testing methods) for each component of the final cover (14 CCR
17774(a, c - h)).
Relevant and
Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                         Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                 Final Grading:  The final grades for the covered landfill must meet grading standards provided in
                 23 CCR 2581(b), they must be appropriate to control runoff and erosion.  Two monuments must be
                 installed to assess changes in the grade pursuant to 23 CCR 2581(d) (14 CCR 17776(a, c, e, f)).
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                                         Relevant and
                                          Appropriate
                 Final Site Face:  The design of the final site face must provide for the integrity of the final cover
                 under both static and dynamic conditions.  The design of the final face must achieve a safety factor
                 of 1.5 under dynamic conditions.  This evaluation must consider the critical slope, the engineering
                 properties of the foundation materials, refuse, and other layers making up the site, the maximum
                 expected horizontal acceleration in rock, and other seismic shaking parameters (14 CCR 17777(a, b,
                 cfportions])).

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XJ
c
                                         Table 6-6. Action-Specific ARARs (continued)
Source

Standard, Requirement, Criterion, or
Limitation
14 CCR 17778(a)
14 CCR 17778(c)
14 CCR 17778(d)
14 CCR 17778(e)
14 CCR 17778(0
14 CCR 17778(g)
14 CCR 17778(h)
14 CCR 17778(i)
14 CCR 17778(j)
14 CCR 17779
14 CCR 17781
14 CCR 17783
14 CCR 17788
ARAR Status
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
Description of Applicable or Relevant and Appropriate Requirements
Final Drainage: The design of the final cover must control runon and runoff produced by a
100-year, 24-hour storm event and must be prepared according to CQA requirements. The runon
and runoff control systems must be designed and constructed in accordance with 23 CCR 2546(c)
and (d). The runoff collection and holding facilities must perform pursuant to requirements in
23 CCR 2546(d) (14 CCR 17778(a, c -j).
Slope Protection and Erosion Control: The design and construction of the slopes must protect the
integrity of the final cover and minimize soil erosion (14 CCR 17779).
Leachate Control During Closure and Post-Closure: Leachate must be monitored, collected,
treated, and discarded appropriately. The state does not intend that subsurface leachate monitoring
and collection systems need to be added to existing landfills unless leachate production and/or
accumulation is evident (14 CCR 17781).
Gas Monitoring and Control During Closure and Post-Closure: Landfill gases must be collected and
analyzed; the concentration of combustible gas at the landfill boundary must be five percent or less,
and trace gases must not be at levels that cause adverse health or environmental impacts.
Monitoring should be conducted for 30 years or until authorized to be discontinued by showing that
methane is no longer produced. Methane was not detected in the landfill gas survey conducted in
1988. Measurable (ppb to ppm) levels of benzene and chlorinated hydrocarbons were found in the
soil gas (14 CCR 17783).
Post-Closure Maintenance: The landfill must be maintained and monitored for no less than 30 years
following closure. Monitoring would continue for 30 years following closure unless it can be
demonstrated that the landfill does not pose a threat to public health and safety or to the
environment. If the threat has been eliminated, post-closure maintenance can be discontinued
(14 CCR 17788).
ON
UJ
o

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                                                    Table 6-6. Action-Specific ARARs  (continued)
    Source
Standard, Requirement, Criterion, or
             Limitation
                                                              ARAR Status
                             Description of Applicable or Relevant and Appropriate Requirements
                    14 CCR 17796(c)
                                           Relevant and
                                           Appropriate
                    14 CCR 17796(d)
                                           Relevant and
                                           Appropriate
                  Post-Closure Land Use:  Site closure design shall show one or more proposed uses of the closed site
                  or show development that is compatible with open space (14 CCR 17796(c, d, f))-

                  Construction improvements will be compatible with closure and post-closure requirements and any
                  new activities must not increase the potential threat to public health and safety.
                    14 CCR 17796(f)
                                           Relevant and
                                           Appropriate
                    14 CCR 17796(c)
                                           Relevant and
                                           Appropriate
                    14 CCR 17796(d)
                                           Relevant and
                                           Appropriate
                  Post-Closure Land Use: Site closure design shall show one or more proposed uses of the closed site
                  or show development that is compatible with open space (14 CCR 17796(c, d, f))-

                  Construction improvements will be compatible with closure and post-closure requirements and any
                  new activities must not increase the potential threat to public health and safety.
                    14 CCR 17796(f)
                                           Relevant and
                                           Appropriate
California
Integrated
Waste
Management
Act of 1989
Public
Resources Code
Sections 40502
and 43509
Title 14 (Natural Resources), Division 7
(California Integrated Waste
Management Board), Chapter 5
(Enforcement of Solid Waste Standards
and Administration of Solid Waste
Facilities Permits; Loan Guarantees),
Article 3.2 (Reports of Facility
Information)
Subsection(s)
  as Listed
   Below
Provides the minimum standards for closure of a solid waste disposal site (Section 18262.3.
Contents of the Final Closure Plan and Section 18265.3. Contents of the Final Post-Closure
Maintenance Plan). Applies to solid waste disposal sites that received waste after January 1, 1988.
                    14 CCR 18222
                                           Relevant and
                                           Appropriate
                  Report of Disposal Site Information:  The planning and procedural requirements necessary to ensure that solid
                  waste is handled and disposed in manners that protect public health and safety and the environment must be
                  conducted.
California
Integrated
Waste
Management
Act of 1989
Public
Resources Code
Sections 40502
and 43509
Title 14 (Natural Resources), Division 7
(California Integrated Waste
Management Board), Chapter 5
(Enforcement of Solid Waste Standards
and Administration of Solid Waste
Facilities Permits; Loan Guarantees),
Article 3.4 (Application and Approval of
Closure and Post-Closure Maintenance
Plans)
Subsection(s)
  as Listed
   Below
Provides the minimum standards for closure of a solid waste disposal site (Section 18262.3.
Contents of the Final Closure Plan and Section 18265.3.  Contents of the Final Post-Closure
Maintenance Plan). Applies to solid waste disposal sites that received waste after January  1, 1988.
                    14 CCR 18262.3
                                                               Relevant and
                                                               Appropriate
                    14 CCR 18265.3
                                                               Relevant and
                                                               Appropriate

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                                                            Table 6-6.  Action-Specific ARARs (continued)
Source
Standard, Requirement, Criterion, or
Limitation
ARAR Status
Description of Applicable or Relevant and Appropriate Requirements
Other Stale of California ARARs V; : :
40 CFR 122
122.26
Fish and Game Code
Sections 5650
Section 5652
Subsection(s)
as Listed
Below
Relevant and
Appropriate
Relevant and
Appropriate
It is unlawful to deposit in, permit to pass into, or place where it can pass into the waters of this
slate any material listed in Fisli and Game Code Sections 5650 and 5652.
Os
U)
to
CCR = California Code of Regulation
ERP = Emergency Response Plan
ROG = reactive organic gas
CO = carbon monoxide
CFR = Code of Federal Regulation
RCRA = Resource Conservation and Recovery Act
AFB = Air Force Base
CAMU = Corrective Action Management Unit
USEPA = United States Environmental Protection Agency
                                             HWCL = Hazardous Waste Control Law
                                             POL = petroleum, oil, and lubricant
                                             NOx = nitrogen oxide
                                             CVR = Central Valley Region
                                             MCL = maximum contaminant level
                           BMP = Best Management Practice       CQA = Construction Quality Assurance
                           UST = underground storage tanks        LDR = land disposal restrictions
                           SOx = sulfur oxide                    PM10 = paniculate matter
                           ppm = parts per million                ppb  = parts per billion
                           COC = contaminant of concern SAC = Strategic Air Command
ARAR = applicable or relevant and appropriate requirement    BACT = Best Available Control Technology
DWQ = Department of Water Quality                       SWRCB = State Water Resource Control Board
SMAQMD = Sacramento Metropolitan Air Quality Management District
CERCLA = Comprehensive Environmental Response, Compensation, and Liability Act
        1. Only as invoked through 23 CCR 2511(d) for action intended to contain waste in place.
        2. 23 CCR 251 l(d) is applicable to waste management units in operation after November 27, 1984, and relevant and appropriate for units whose operations ceased prior to November 27, 1984.
        3. Only as invoked by 23 CCR 2511 (d).
        4. The regulation is applicable to waste removed from waste management units and relevant and appropriate for waste removed from other sites/units.
        5. Only as invoked through 23 CCR 251 l(d) and 23 CCR 2520(a)(2).
        6. Only as invoked by 92-49 IIIG.

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       The following chapters of Title 22, Division 4.5 Environmental Health Standards for
       Management of Hazardous Waste, have been identified as ARARs for remedial action sites at
       Mather AFB: Chapter 12 - Standards Applicable to Generators of Hazardous Waste, Article 1
       - Applicability;  Chapter 14 - Standards for Owners and Operators of Hazardous Waste
       Transfer, Treatment, Storage, and Disposal Facilities; Article 6 - Water Quality Monitoring
       and Response Programs for Permitted Facilities; Article 7 - Closure and Post Closure; Article
       9 - Use and Management  of Containers; Article 12 - Waste  Piles; Article 19 - Corrective
       Action for Waste Management Units; Chapter 18 - Land Disposal Restrictions, Article 1 -
       General; Article 3 - Prohibitions on Land Disposal; Article  4 - Treatment Standards; and
       Article 5 - Prohibitions on Storage.

       6.3.1.1      Other Federal Regulations
       The TSCA delineates the  requirements for excavation of PCBs and  sampling activities
       associated  with PCB removal through 40 CFR Part 761. These requirements are TBCs for the
       excavation and removal of PCB contaminated soils. This guidance  is used to establish
       minimum depths and  area for cleanup as outlined in the regulation.  Site 15 is the only site
       where PCBs are COCs, and the material is below the 50 ppm level  specified in the regulation.
       The identified alternative  will excavate the material and dispose of it at Site 4 or Site 7, as
       appropriate, as foundation material for a landfill cap.

       6.3.2 State ARARs and TBCs
       The following California statutes, laws, and regulations have been identified as ARARs and
       TBCs. The following subsections  list the ARARs and TBCs in the  following order:  air,
       water, waste, and other state regulations.  The state action-specific ARARs are  listed in
       Table 6-6,  TBCs are listed in the text under other regulations and a brief description of the
       source of the ARARs are  listed along with the regulations derived under the source.  Also
       presented is the  USAF position on substantive requirements  of these ARARs and how they
       apply to the selected remedial actions.

       6.3.2.1      State Air ARARs
       The California Clean  Air Act, under the Federal Clean Air Act and 1990 Amendments,
       authorizes the State of California to develop a State Implementation Plan (SIP) to enforce clean
       air regulations and laws.  The SIP, developed through state  legislation, divided the state into
       local air control districts and allowed each district to enforce the requirements of the federal
       and state Clean Air Acts.  Mather AFB is  located in the Sacramento Metropolitan Air Quality
       Management District  (SMAQMD); state air regulations are  the most stringent
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        ARARs.  The SMAQMD applicable regulations are:  Rule 202, Section 301 - Best Available
       Control Technology; Section 302 - Offsets; Rule 401 - Visible Emissions; Rule 402 -
       Nuisance; Rule 403 - Fugitive Dust; Rule 404 - Particular Matter; and Rule 405 - Dust and
       Condensed Fumes.  Table 6-6 contains the applicable or relevant and appropriate sections of
       these regulations identifying the ARAR status and a brief description of the substantive
       requirements and applicability to either the site, remedial action, or technology used to cleanup
       the site and contaminated material.

       6.3.2.2      State Groundwater and Soil ARARs
       The Federal Clean Water Act regulates discharge to surface waters and groundwater. Under
       this statute is the 40 CFR 122 - USEPA Administrative Permit Program: National Discharge
       Elimination System regulation for  stormwater and other discharges to surface waters. This
       program is delegated to the state under the statute and therefore  is  considered a state ARAR.

       The SWRCB has issued two general orders under the federal statute, Clean Water Act, that
       provides the substantive requirements for stormwater management at industrial sites
       (SWRCB Order 92-13-DWQ) and construction sites  (SWRCB Order 92-08-DWQ).  The
       substantive requirements for industrial sites are meeting the narrative water quality standards,
       implementing best management practices, identifying and monitoring sources of stormwater
       pollutants, and eliminating non-stormwater sources of pollutants.  The substantive requirements
       associated with construction activities such as excavation and grading include application of
       engineering measures and best management practices to control stormwater runoff.

       The Porter-Cologne Water Quality Control Act is one of the statutory bases  for regulation of
       discharges of waste to land that could impair either surface water or groundwater quality in
       California. It establishes the authority of the SWRCB and the CVRWQCB to protect the
       quality of surface water and groundwater.  The California Water Code sections used as a
       source for action-specific ARARs and TBCs are presented in Table 6-6 along with the
       associated regulatory citations.  Under the Porter-Cologne Act the  following regulations or
       resolutions regulating and protecting the waters of the state are considered relevant and
       appropriate and are therefore ARARs:  Central Valley Region (CVR) Basin Plan; SWRCB
       Resolution 68-16;  SWRCB Resolution 88-63; and SWRCB Resolution 92-49; California
       Title 23, Chapter 3,  SWRCB, Subchapter 15 - Discharges of Waste to Land, Article 1 -
       General; Article 2 - Waste Classification and Management; Article 3 - Waste Management
       Unit Classification and Siting; Article 5 - Water Quality Monitoring and Response Programs
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        for Waste Management Units; Article 8 - Closure and Post-Closure Maintenance; and
       Article 9 - Compliance Procedures.  Table 6-6 contains the applicable or relevant and
       appropriate sections of these regulations identifying the ARAR status and a brief description of
       the substantive requirements and applicability to either the site, remedial action, or technology
       used to clean up the site and contaminated material.

       State Water Resources Control Board Resolution 68-16 has been identified as an applicable
       requirement for the protection of surface waters  and groundwater of the state.  The USAF and
       the state do not agree on the full substantive requirements of this resolution and  the impacts on
       the remedial action activities need to cleanup Mather AFB.  The USAF disagrees with the
       state's contention that the narrative language establishes chemical-specific ARARs for both
       soils and groundwater, and that discharges subject to the resolution include post-1968
       migration of in situ contamination from the vadose zone to groundwater. The USAF believes
       that discharges only encompass remedial activities that actively discharge to surface water and
       groundwater of the state.

       According to the decision of the USEPA Administrator, SWRCB Resolution 68-16, the water
       anti-degradation policy, is a state ARAR for the  establishment of numerical limits for the
       reinjection of treated groundwater into clean areas (i.e., high quality waters) of the aquifer,
       (i.e., outside of the contaminated plume). The numerical limits established on a monthly
       median and on a daily maximum basis to meet the requirements of SWRCB Resolution 68-16
       are set forth in Table 6-7. With respect to the injection of treated groundwater within the
       contaminated plume, treatment shall be such that the concentration level of the contaminant in
       the groundwater must not exceed the concentration in the groundwater at the point of injection
       measured on a monthly median basis and also not exceed the federal and state ARAR. With
       respect to injection of treated groundwater outside the contaminated plume, the effluent is
       required to meet daily and 30-day median concentrations for each COC as shown in Table 6-7.
       To meet the requirement that the selected remedy be protective of human health  and the
       environment, the USAF shall maintain hydraulic control of the plume while  extracting
       contaminated groundwater, and reinjecting treated groundwater into the contaminant  plume or
       the clean portion of the aquifer.
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                               Table 6-7.  Groundwater Discharge Treatment Standards


Constituent




Main Base/SAC Ind. Plume
Benzene
CCi,
Chloromethane
1,2-DCA
1,1 -DCE
Cis-l,2-DCE
Lead
PCE
TPH-G
TPH-D
TCE
Xylene
Site 7 Plume
Benzene
Chloromethane
1,2-DCA
1.1-DCE
Cis-1.2-DCE
1,4-DCB
PCE
TPH-D
TCE
Vinyl Chloride

Standard for Injection into
Noncontaminated Portions of the
Aquifer Based on State Board
Resolution 68-16 0*g/l)

30 Day Median

0.5
0.5
0.5
0.5
0.5
0.5
Background
0.5
50.0
50.0
0.5
0.5

0.5
0.5
0.5
0.5
0.5
0.5
0.5
50.0
0.5
0.5

Daily Maximum

0.5(1)
0.5 (2)
3.0
0.5 (3)
6.0
6.0
15.0
0.7 (4)
50.0
100.0
2.3 (5)
17.0

0.5(1)
3.0
0.5 (3)
6.0
6.0
0.88 (7)
0.7 (4)
100.0
2.3 (5)
0.5 (6)
Standards for Injection in the Contaminated Portions
of the Aquifer Based on the more Stringent of
(a)MCL's (State or Federal) whichever is more
stringent or (b)In Situ Groundwater Concentrations at
the Point of Injection as 30 Day Median (j*g/l)

Class of Carcinogens

A
B2
C
B2
C
D
-
B2
-
-
B2
D

A
C
B2
C
D
C
B2
-
B2
C
Slate or Federal MCLs
Daily Maximum

1.0 (CA-MCL)
0.5 (CA-MCL PQL)
3.0 (SNARL)
0.5 (CA-MCL PQL)
6.0 (CA-MCL)
6.0 (CA-MCL)
15.0 (FMCL)
S.O(FMCL)
50.0 (PQL)
100.0 (US EPA HA)
5.0 (FMCL)
17.0 (TO)

1.0 (CA-MCL)
3.0 (SNARL)
0.5 (CA-MCL PQL)
6.0 (CA-MCL)
6.0 (CA-MCL)
5.0 (CA MCL)
5.0 (FMCL)
100.0 (US EPA HA)
5.0 (FMCL)
0.5 (CA MCL PQL)
         (1)       California Environmental Protection Agency (CA EPA), Cancer Potency Factor as a Water Quality Criterion = 0.35 ^g/1, U. S.
                  Environmental Protection Agency (USEPA) Integrated Risk Information System (IRIS) =  1.0 /^g/l
         (2)       CA EPA. Cancer Potency Factor as a Water Quality Criterion = 0.23 Mg/1. USEPA IRIS  = 0.3 ^g/1
         (3)       CA EPA. Cancer Potency Factor as a Water Quality Criterion = 0.5 Mg/1, USEPA IRIS = 0.4 ^tg/1
         (4)       CA EPA. Cancer Potency Factor as a Water Quality Criterion = 0.69 j/g/i, USEPA IRIS  = 0.7 ^g/1
         i5)       CA EPA. Cancer Potency Factor as a Water Quality Criterion = 2.3 ng/l, USEPA IRIS = 3.0 ^g/l
         (6)       CA EPA, Cancer Potency Factor as a Water Quality Criterion = 0.13 /^g/i. USEPA IRIS  = 0.015 ng/l
         (7)       CA EPA, Cancer Potency Factor = 0.88 Mg/1
         California Regional Water Quality Control Board Central Valley Region (CVRWQB),
         Sacramento, California.
'A Compilation of Water Quality Goals,"  1993,
         CA-MCL = Drinking Water Standards, California Department of Health Services, Primary Maximum Contaminant Level (MCL)
         SNARL = Health Advisory or Suggested No-Adverse-Response Levels for Toxicity other than cancer risk
         FMCL = Drinking Water Standards, U. S. Environmental Protection Agency, Primary MCL
         US EPA HA = Health Advisories or SNARLs for toxicity other than cancer risk, U. S. Environmental Protection Agency
         TO = Other Taste & Odor Thresholds              PQL = Practical Quantitation Limit       CC\t = carbon tetrachloride
         PCE  = tetrachloroethene       TCE = trichloroethene        DCA = dichloroethane         DCE = dichloroethene
         TPH-G = total petroleum hydrocarbons as gasoline   TPH-D = total petroleum hydrocarbons as diesel     ng/1 = micrograms per liter
         A =  Known human carcinogen; sufficient epidemiologic evidence in humans.        B2 = Probable human carcinogen; limited
         epidemiologic evidence in humans.                  C = Possible human carcinogen; limited evidence from animal studies; no human data.
                                     D = Not classified as to human carcinogenity; no data or inadequate evidence.
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       The USAF is currently studying the potential relevance and appropriateness of SWRCB
       Resolution 92-49 as it pertains to USAF IRP activities within the state.  The only section with
       substantive requirements appears to be Section IIIG.  Section IIIG is the only provision of
       SWRCB Resolution 92-49 that arguably is relevant and appropriate in establishing
       water-related cleanup levels under limited circumstances yet to be determined.  The portion of
       Section IIIG, through incorporation of certain provisions in Titles 22 and 23 CCR, that creates
       a presumption of media cleanup  resulting in background groundwater concentration levels is
       not generally a relevant and appropriate requirement for groundwater or vadose zone cleanup
       levels.  The USAF hopes to eventually resolve the ARAR status of SWRCB Resolution 92-49
       through ongoing discussions with its U.S. Department of Defense counterparts, USEPA, and
       the state.  For purposes of this ROD, the USAF believes that if vadose zone contamination
       overlies a groundwater plume, that remediation of the COCs in the groundwater satisfies the
       requirement of Section IIIG to abate the effects of discharge. In that situation, Section IIIG is
       not a relevant and appropriate requirement for the remediation of the vadose zone, even
       though technical considerations,  risk, cost-effectiveness, and other remedy-selection factors
       may warrant concurrent remediation  of the vadose zone to promote the groundwater
       remediation.  If these factors warrant concurrent vadose zone remediation, the USAF will
       conduct such remediation but not based on the premise that Section IIIG requires such action.

       The state's position is that SWRCB Resolution 92-49 is an applicable requirement for remedial
       actions in the vadose zone where there is an impact, or a threat of an impact, to the beneficial
       uses of the groundwater or  surface waters.  In such a case the state contends, SWRCB
       Resolution 92-49  requires remediation of the vadose zone to the lowest concentration  levels of
       constituents technically and economically feasible, which must at least protect the beneficial
       uses of groundwater and  surface  waters, but need not be more stringent than is necessary to
       achieve background levels of the constituents in surface water and groundwater.

       Many of the requirements for the proper handling and disposal of designated waste (23 CCR,
       Division 3, Chapter 15) have been incorporated through the use of the on-base ex situ
       bioremediation facility.  This facility will first handle RCRA and/or designated waste from
       petroleum-only contaminated sites. These sites are, by definition, excluded from CERCLA
       but included within the Defense Environmental Restoration Program conducted pursuant  to 10
       U.S.  Code Section 2701 et. seq.  These provisions require that Defense Environmental
       Restoration Program response actions be conducted consistent with CERCLA Section 120 and
       guidelines, rules,  and regulations (e.g., NCP), and criteria established by the USEPA. The
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       "petroleum only" contaminated sites were included in the RI, FFS, and Proposed Plan in a
       manner consistent with the Federal Facility Agreement and Defense Environmental Restoration
       Program.  The SRWCB identified Waste Discharge Requirements (WDRs) for the operation of
       the ex situ bioremediation site due to the use of the site for treatment of contaminated media
       from the petroleum-only contaminated sites.  Substantive WDRs have been developed in order
       to implement the portions of WDRs that are substantive requirements for treating CERCLA
       wastes at the ex situ bioremediation facility.  Under these circumstances, the WDRs served as,
       a means of identifying the Regional Water Quality Control Board's substantive requirements
       for the ex situ bioremediation facility.  This expedient reference to the WDRs to identify
       substantive requirements is not intended to suggest that WDRs or any other form of permit are
       requirements for this ROD or any other CERCLA onsite response actions.  The  substantive
       WDRs are listed in Section 6.3.2.5.

       6.3.2.3      State Solid Waste ARARs
       The California Integrated Waste Management Act of 1989 is intended to reduce, recycle, and
       reuse solid waste generated in the state to the maximum extent feasible in  an efficient and
       cost-effective manner to conserve water, energy, and other natural resources, to  protect the
       environment, and to improve the regulations for solid waste management.   Sections of the
       Public Resource Code which were used as a source for action-specific ARARs are presented in
       Table 6-6, along with the associated regulatory citations.

       California Title 14:  Natural Resources. Division 7, Integrated Waste Management Board;
       Chapter 3 - Minimum Standards for Solid Waste Management Handling and Disposal,
       Article 7.8 - Disposal Site Closure and Post-Closure Maintenance.  Table  6-6 contains  the
       applicable or relevant and appropriate sections of these regulations identifying the ARAR
       status and a brief description of the substantive requirements and applicability to either the
       sites, remedial  action, or technology used to cleanup the site and contaminated material.

       The requirements in 14 CCR 17788, ("the landfill is to be maintained and monitored for a
       period of not less than 30 years after completion of closure pursuant to Chapter 5, Article 3.4,
       Section 18265") will be applied with consideration.to the facts that Site 7:

             •      has been dormant and inactive for approximately 30 years;
             •      was closed in accordance with requirements in effect at the  time; and
             •      currently poses no threat to human health and the environment.
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       The requirements of 14 CCR 17788 will be met as described in the following manner.

       The USAF will cap, if appropriate, the impacted area in accordance with all ARARs listed in
       Table 6-6. After the cap is in place the USAF will maintain and monitor the cap in
       accordance with 14 CCR 17788(a)(l - 5) as long as the site presents an unacceptable risk to
       human health and the environment. 14 CCR 17796(c) requires that any construction
       improvements on the landfill sites will maintain the integrity and functioning of the landfill
       containment and monitoring system, and that any new activities at the site will not increase the
       potential threat to health, safety, and the environment.

       6.3.2.4      Other State Regulations
       The State Fish and Game Code regulates to protect aquatic life living in the waters of the state.
       All remedial activities that have the potential of causing a discharge to any stream lake or
       other body of water must comply with the requirements of the code.

       Regional Water Quality Control Board, CVR Basin Plan "Disposal of Wastewater on Land
       Policy."  This plan is a TBC to any activity that may affect water quality.  The Basin Plan
       requires that land disposal be considered an alternative to discharges to surface waters.

       Tri-Regional Board Staff Recommendations for Preliminary Evaluation and Investigation of
       Underground Tank Sites - this action-specific TBC recommends that soil samples from UST
       sites be analyzed for total petroleum hydrocarbon (TPH) as gasoline or diesel (depending upon
       the fuel) and BTEX. The appendix to this guideline recommends that a  final remedial plan
       include a verification sampling program.

       California Well Standards (California Department of Water Resources [DWR], Bulletin 74-90,
       June 1991) and Sacramento County Code,  Title 6, Chapter 6.28 - The California Water Code
       (Chapters 1152, 1373, and 13801)  requires the DWR to establish standards for the
       construction, operation, and abandonment  of water wells, monitoring wells,  and cathodic
       protection wells.  Sacramento County has developed well construction regulations based on
       authority granted to the county through enforcement of the state standards.  These standards
       should be considered as TBCs for construction of groundwater wells (injection, extraction, and
       monitoring).

       In addition to these well standards, the guidelines provided by the California Base Closure.
       Environmental Committee (March  1994) in "Long-Term Groundwater Monitoring Guidance"
       are TBCs for:
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              •      establishing background ground water quality;
              •      frequency of water level measurements;
              •      suite of constituents in the monitoring program;
              •      sampling frequency; and
              •      inspection and well maintenance.

       Several of the California regulations require certification by a professional geologist or
       engineer, registered or certified by the State of California.  These portions of the regulations
       are considered procedural rather than substantive requirements.  However, to the degree that
       federal contractors perform and/or supervise the engineering and geotechnical work, they will
       be certified professional or under the supervision of certified professionals as appropriate.

       6.3.2.5      State Requirements for Ex Situ Soil Bioremediation Facility
       As discussed in Section 2.2.9 of this document, the USAF will operate an ex situ soil
       bioremediation facility onsite to treat excavated soils from Sites 56, 59, 60, 62, and 65, and
       other suitable sites with CERCLA contamination.  Approximately 5,000 yd3 of soil from these
       sites are expected to be treated at the bioremediation facility. The USAF also expects to use
       the ex situ soil bioremediation facility for the treatment of petroleum-contaminated soils
       excavated from  sites described in Section 4.0 that are not being addressed under the CERCLA
       process. Use of the bioremediation facility for the Section 4.0 sites is hereafter referred to as
       "Phase I operation" since this soil treatment is expected to occur prior to treatment of  soils
       excavated from  the CERCLA sites.

       The bioremediation facility will consist of a single lined bioremediation cell and  soil
       processing area. During operation of the facility during Phase I, the USAF will comply with
       the WDRs specified in CVRWQCB Order No.  95-221.  The WDRs were derived from
       Title 23 CCR, Division 3, Chapter 15.

       Operation of the bioremediation facility for CERCLA-related response actions (e.g., treatment
       and disposal of treated soils from the sites discussed in Section 2.2.9), the USAF will  comply
       with the intent of the substantive requirements for Class II Waste Piles found in or  derived
       from Chapter 15.  Substantive requirements for this particular soil bioremediation facility and
       optional conditions the USAF agrees to comply with,  include the following:

              •      The design of the bioremediation cell unit  will consist of the following
                    components from top to bottom: four to six inch cover, consisting of least

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                     contaminated soil; six inch sand layer, or a three inch sand layer and
                     three inches of recycled drainage rock; geotextile fabric; 30 mil PVC liner;
                     geotextile fabric over a mostly asphalt base with some areas of native soil.

                     Materials used to construct liners will have appropriate physical and chemical
                     properties to ensure containment of discharged wastes over the operating life
                     and closure of the bioremediation cell. All visible portions of synthetic liners
                     will be inspected on a weekly basis.

                     Materials used to construct leachate collection and removal systems (LCRSs)
                     will have appropriate physical and chemical properties to ensure the
                     transmission of leachate over the life  of the bioremediation cell and the closure
                     period. Leachate collection and removal systems will be designed, constructed,
                     and maintained to collect twice the anticipated daily volume of leachate
                     generated by the unit and to prevent buildup of hydraulic head on the
                     underlying liner or underlying natural geologic materials of low hydraulic
                     conductivity at any time.  The depth of fluid in any LCRS sump will be kept at
                     the minimum necessary for safe pump operation.  The LCRS sump will be
                     inspected three tunes per week for leachate generation.

                     The bioremediation facility will be designed, constructed, and operated to
                     prevent inundation or washout due to 100-year floods.  The waste  containment
                     facilities and precipitation and drainage controls will be properly maintained
                     until clean closure has been achieved.

                     Waste destined for treatment will only be discharged into, and shall be confined
                     to, the soil processing area, the bioremediation cell, or tanks specifically
                     designed for waste containment.

                     All wells within 500 feet of the unit will  have sanitary seals meeting the
                     requirements of the Sacramento County Environmental Health Management
                     Department or will be properly abandoned.

                     Accept only soils that are not classified as  "hazardous waste" using the criteria
                     in Title 22 CCR, Division 4.5, Chapter 11, for discharge to the bioremediation
                     facility, subject to variances from hazardous waste management requirements
                     established by the DTSC.  Additionally, wastes that could potentially impair the
                     integrity of containment structures, require a higher level of containment than
                     provided by the unit, or which are restricted hazardous wastes will not be
                     discharged to the bioremediation facility.

                     Other than the minimum amount of water necessary for dust control and
                     operation of the bioremediation process, the USAF will not discharge liquid,
                     semi-solid waste (waste containing less than 50 percent solids), or  solid waste
                     containing free liquid or moisture in excess of the waste's moisture holding
                     capacity to the bioremediation cell.
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                     The discharge of designated solid or liquid waste or leachate to surface water,
                     surface water drainage courses, ponded water, or ground water that would cause
                     impairment to water quality is prohibited.

                     Leachate and runoff from the bioremediation cell will flow into a sump where it
                     will be pumped to a Baker tank.  From storage in the Baker tank, the liquid will
                     be used to supplement the moisture content soils that do not have sufficient
                     moisture to support the bioremediation process.

                     Waste or waste  constituents from the bioremediation facility will not be
                     discharged to natural geologic materials, groundwater, or surface waters at,
                     beneath, or adjacent to the waste management units.  This includes ponded
                     water and areas within 100  feet of surface waters.

                     Treated soils may be disposed of as  "inert waste" if the following criteria are
                     met:

                           the treated soil is not a hazardous waste as determined by criteria in
                           22 CCR Division 4, Chapter 11, including toxicity, ignitability,
                           reactivity, and corrosivity;
                           TPH as gasoline and aromatic volatile organics (BTEX) are not
                           detectable in representative samples of treated soil;
                           the leachable TPH as diesel concentration is less than 10 ug/L;
                           the metal concentrations are less than the 95 percent UCL of the
                           background concentration calculated in the "Background Inorganic Soils
                           Report for Mather AFB"  [IT 1993f]; and
                           PAHs  will not be discharged where they will be subject to erosion and
                           transport to surface waters.

                     Soil taken from  the bioremediation facility  and used as foundation material at
                     Landfill Sites 3  and 4 will have total or leachable constituent concentrations
                     equal to or less than those presented in Table 6-8.  Soil not achieving these
                     levels will be  disposed at an offsite Class II Waste Disposal Facility or treated
                     and disposed in  an appropriate manner.
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                Table 6-8. Maximum Total or Leachable Constituent Concentrations
         Constituent
Concentration
        TPH-D
        TPH-G

        Oil and Grease

        Aromatic Hydrocarbons
        Benzene

        Ethylbenzene

        Toluene

        Xylene
Img/L
Median Concentration is non-detect
Maximum Concentration is 5 mg/kg
430 mg/kg
Median Concentration is non-detect
Maximum Concentration is 0.01 mg/kg
Median Concentration is non-detect
Maximum Concentration is 0.29 mg/kg
Median Concentration is non-detect
Maximum Concentration is 0.42 mg/kg
Median Concentration is non-detect
Maximum Concentration is 0.17 mg/kg
        Polycyclic Aromatic Hydrocarbons
        Benzo(a)Anthracene
        Benzo(a)Pyrene
        Benzo(b)Fluoranthene
        Benzo(k)Fluoranthene
        Chrysene
0.01 mg/L
0.02 mg/L
0.02 mg/L
0.02 mg/L
0.02 mg/L
        Toxic Metals
        Lead
        Organic Lead
        Manganese
        Chromium
1.5 mg/L
0.5 mg/kg
0.5 mg/L
0.5 mg/L
      TPH-D = total petroleum hydrocarbon as diesel
      TPH-G = total petroleum hydrocarbon as gasoline
        mg/kg = milligrams per kilogram
        mg/L = milligrams per liter
                   If soil is not inert, and for discharge to a location other than Landfill Site 3
                   or 4,  the following cleanup levels prior to removal of treated soils from the
                   bioremediation cell will be implemented:

                          Total petroleum hydrocarbon as diesel, nonvolatiles, PAHs, lead, and/or
                          other metals will not be present in representative samples of treated soil
                          in soluble concentrations that will impact either surface or groundwater
                          as determined by the DLM or an appropriate fate and transport
                          predictive model.  Soluble concentrations will  be measured using the
                          deionized water (DI) WET Method.
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                            Aromatic volatile organic compounds will not be detectable using
                            analytical detection limits as close to USEPA Method Detection Limits
                            as practicable.

                     The bioremediation facility will be clean-closed after completion of use in
                     accordance with the closure plan.  At closure, all residual wastes, including
                     liquids, sludge, precipitates, settled solids, and liner materials and adjacent
                     natural geologic materials contaminated by wastes will be completely removed
                     and discharged to an appropriate waste management unit.
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       7.0  Responsiveness Summary
       The public comment period for the "Proposed Plan for the Groundwater Operable Unit Plumes
       and Soil Operable Unit Sites" [IT 1995b] at Mather AFB, began on May 8, 1995 and ended on
       June 7, 1995.  A public meeting was held on May 18, 1995, at which the Proposed Plan was
       summarized, and questions and public comments solicited.  The transcript from the public
       meeting is included in the Administrative Record File and reproduced here. The public
       submitted four formal written comments on the Proposed Plan. The written comments were
       from the USEPA and County of Sacramento and are included in the Administrative Record.
       No other comments were received during the public comment period.


       Note:  Sites 19, 29/B, 32, 34, 35, and 36 are sites with only petroleum contamination and are
       excluded from regulation under CERCLA. The USAF is not responding to comments on these
       sites in this ROD. Public comments on "petroleum only" sites will be considered by the
       CVRWQCB in approving cleanup activities at these sites.


       Comment 1 and Response:


       Comment:


             The County is very concerned that inadequate cleanup budget, including possible
             cutbacks, will seriously delay environmental investigation and cleanup and in turn
             seriously impact productive economic reuse of the base property. The USAF must
             proceed diligently to assure funding for environmental cleanup and compliance within
             the time frames necessary for reuse.  The work described in the Proposed Plan must
             proceed on a timely basis, or successful reuse may be jeopardized.


       Response:


             The USAF has and will continue to seek adequate funding for cleanup at Mather AFB
             for the protection of human health and the environment, and to support base reuse
             objectives to the best of the USAF's resources and ability consistent with USAF policy.
             Presently, all identified remediation requirements at Mather AFB are scheduled to
             receive sufficient funding necessary to implement planned remedial response actions in
             accordance with the ROD for the Soil OU sites and Groundwater OU plumes.
RL/10-95/ES/1260005.AWS                                 '"*

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       Comment 2 and Response:


       Comment:
              Particularly, funding should be prioritized for high priority reuse projects identified
              by the County.  An initial list of such high priority County projects has previously
              been distributed and discussed with the USAF and environmental regulators. This list
              is attached to this letter as Exhibit A.
       Response:


              The USAF has reviewed the list of high priority County projects, and in the future
              will consider the County reuse priorities during project planning and  funding
              prioritization. It is USAF policy to give funding priority to projects that promote
              rescue, after human health concerns and regulatory compliance requirements have
              been addressed.   However, with the expectation of the County Department of Public
              Works Roadway Improvement and Relocation Program, the projects identified on the
              County Priority  List have no association with any of the remedial actions proposed in
              this Soil OU sites and Groundwater  OU plumes ROD. The Roadway Improvement
              and Relocation Program proposes  new road construction, road realignments, and road
              widening which  may conflict or interfere with planned remedial actions.  The USAF
              is working with  County officials to coordinate compatible remedial actions.  In some
              instances road realignment may need to be delayed until remedial actions have been
              concluded.  In other instances remedial actions may be designed  and  scheduled to
              allow work on roads to proceed in a timely manner.


       Comment 3 and Response:


       Comment:
             The County is currently initiating several development projects, including demolition
             of existing structures, construction of new structures, utility line reallocations, and
             roadway improvements and relocation.  New areas of contamination may be
             discovered as part of the County's reuse efforts. In large part due to budget issues,
             the County and USAF must investigate entering into a memorandum of understanding
             or similar arrangement,  whereby the County could assist the USAF in performing site
             investigations/assessments and minor cleanups,  to be reimbursed by the USAF. Such
             a relationship should be discussed and  included in the Proposed Plan, and the County
             and USAF should continue to explore this possibility.
RiyiO-95/ES/1260005.AWS                                 7-2

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       Response:
              The comment proposes using a memorandum of understanding that would allow
              Sacramento County to assist in investigating and performing minor cleanups at newly
              discovered areas of contamination.  The comment does not address itself to any of the
              proposed remedial alternatives in the Proposed Plan.  This comment is being
              discussed directly with Sacramento County.
RL/10-9S/ES/1260005.AWS                                 7-3

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       8.0  References
       Aerovironment, Inc., 1987, "Installation Restoration Program Phase II -
       Confirmation/Quantification Stage 2 Final Report, September 1985 to June 1987," Volumes 1
       and 2, Aerovironment, Inc., Monrovia, California.

       Aerovironment, Inc., 1988, "Installation Restoration Program Phase II -
       Confirmation/Quantification Stage 3 Final Report, July 1986 to March 1987," Volumes 1
       and 2, Aerovironment, Inc., Monrovia, California.

       California State Water Resources Control Board (SWRCB), 1992, "California State Water
       Resources Control Board ARARs Under CERCLA," Sacramento, California.

       CH2M-HU1, Inc., 1982, "Installation Restoration  Program Records Search (Phase 1),"
       CH2M-Hill, Inc., Gainesville, Florida.

       Central Valley Regional Water Quality Control Board (CVRWQCB), 1989, "The Designated
       Level Methodology for Waste Characterization and Cleanup Level Determination,"  California
       Regional Water Quality Control Board, Central Valley Region Staff Report, October 1986
       (updated June 1989).

       Central Valley Regional Water Quality Control Board (CVRWQCB), 1993, "A Compilation of
       Water Quality Goals," Central Valley Regional Water Quality Control Board, Sacramento,
       California.

       Central Valley Regional Water Quality Control Board (CVRWQCB), 1995, "Basin Plan for
       Sacramento-San Joaquin Basin," California Regional Water Quality Control Board,
       Sacramento, California.

       EA Engineering, Science,  and Technology (EA), 1990a, "Quarterly Groundwater Sampling at
       Mather Air Force Base, May-June 1990," Volume 1-Report;  Volume 2-Appendix A,
       Appendix B, Appendix C, Pt. 1; Volume 3-Appendix C, Pt. 2; EA Engineering, Science, and
       Technology Corporation, Lafayette, California.
RL/IO-95/ES/1260005.AWS
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       EA Engineering, Science, and Technology (EA), 1990b, "Quarterly Groundwater Sampling at
       Mather Air Force Base, August 1990," Volume 1-Report; Volume 2-Appendix A, Appendix
       B, Appendix C, Pt. 1; Volume 3-Appendix C, Pt. 2; EA Engineering, Science, and
       Technology Corporation, Lafayette, California.

       EA Engineering, Science, and Technology (EA), 1990c, "Quarterly Groundwater Sampling at
       Mather Air Force Base, November-December 1990," Volume 1-Report; Volume  2-Appendix
       A, Appendix B, Appendix C, Pt. 1; Volume 3-Appendix C, Pt. 2; EA Engineering, Science,
       and Technology Corporation, Lafayette, California.

       IT Corporation (IT), 1988a,  "Well Redevelopment and Sampling Plan for Mather Air Force
       Base, California," Prepared by IT Corporation for HAZWRAP, July 1988.

       IT Corporation (IT), 1988b,  "U.S. Air Force Installation Restoration Program, Phase IV-A
       Activities at Mather Air Force Base, California, Landfill Gas Testing Report for Eight Sites at
       Mather Air Force Base, California", Prepared by IT Corporation for Hazardous Waste
       Remedial Actions Program.

       IT Corporation (IT), 1990a,  "U.S. Air Force Installation Restoration Program, Phase IV-A
       Activities at Mather Air Force Base, California, Final Site Inspection Report", IT
       Corporation, Knoxville, Tennessee.

       IT Corporation (IT), 1990b,  "Underground Storage Tank Closure Report, Mather Air Force
       Base, California".

       IT Corporation (IT), 1992a,  "Final Remedial Investigation for Group 2  Sites, Mather Air
       Force Base, California", Prepared by IT Corporation for Environmental Management
       Operations.

       IT Corporation (IT), 1993a,  "U.S. Air Force Installation Restoration Program, Final
       Technical Memorandum for Group 3 Sites for Mather Air Force Base, California", Prepared
       by IT Corporation for Environmental Management Operations.
RL/10-95/ES/1260005.AWS
                                               8-2

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       IT Corporation (IT), 1993b, "U.S. Air Force Installation Restoration Program, Final Solid
       Waste Assessment Test Report for Mather Air Force Base, California", Prepared by IT
       Corporation for Environmental Management Operations.

       IT Corporation (IT), 1993c, Subsurface Soil Investigation (Project C) Underground Storage
       Tank Removal Project, Mather Air Force Base, California, Prepared by IT Corporation for
       U.S. Corps of Engineers.

       IT Corporation (IT), 1993d, Closure Reports, Underground Storage Tank Removal Project,
       Mather Air Force Base, California, Prepared by IT Corporation for U.S. Corps of Engineers.

       IT Corporation (IT), 1993e, "Superfund Record of Decision:  Aircraft Control and Warning
       Site, Mather Air Force Base, Sacramento County, California", December 1993, Prepared by
       IT Corporation for Environmental Management Operations.

       IT Corporation (IT), 1993f,  "Background Inorganic Soils for Mather Air Force Base,"
       IT Corporation, Albuquerque, New Mexico and Richland, Washington.

       IT Corporation (IT), 1993g, "Quarterly Groundwater Monitoring Report - Third Quarter 1993
       for Mather Air Force Base, California," IT Corporation, Martinez, California.

       IT Corporation (IT), 1994a, "Final Soils and Groundwater Operable Unit Additional Field
       Investigation Remedial Investigation Report for Mather Air Force Base, California," Prepared
       by IT Corporation for Air Force Center for Environmental Excellence, Brooks Air Force
       Base, Texas.

       IT Corporation (IT), 1994b, "Superfund Draft Final Record of Decision, Landfill Operable
       Unit Sites, Mather Air Force Base, Sacramento County California," Prepared by IT
       Corporation for Air Force Center for Environmental Excellence, Brooks Air Force Base,
       Texas, December 12, 1994.

       IT Corporation (IT), 1994c,  "Removal Action Memorandum for Sites 20, 29, and 32, Mather
       Air Force Base, California," Prepared by IT Corporation for Battelle Environmental Services
       Organization, September, 1994.
RL/10-95/ES/1260005.AWS

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       IT Corporation (IT), 1995a, "Groundwater Operable Unit and Soil Operable Unit Focused
       Feasibility Study Report for Mather Air Force Base, California," Prepared by IT Corporation
       for Air Force Center for Environmental Excellence, Brooks Air Force Base, Texas.

       IT Corporation (IT), 1995b, "Proposed Plan for Environmental Cleanup at the Groundwater
       Operable Unit Plumes and Soil Operable Unit Sites," Prepared by IT Corporation for U.S. Air
       Force Base Conversion Agency, Mather Air Force Base, California.

       IT Corporation (IT), 1995c, "Quarterly Monitoring Report - Third Quarter 1995 for Mather
       Air Force Base, California," IT Corporation, Martinez, California.

       IT Corporation (IT), 1995d, "Final Mather Baseline Risk Assessment (MBRA) Mather Air
       Force Base,  California," Prepared by IT Corporation for Air Force Center for Environmental
       Excellence, Brooks Air Force Base, Texas, December  19, 1995.

       IT Corporation, 1996a, "Draft Technical Information Report on Soil Vapro Extraction Pilot
       Testing at Installation Restoration Program Sites 18, 39, and 57,  " Prepared by IT Corporation
       for Air Force Center for Environmental Excellence, Brooks Air Force Base, Texas, March 12,
       1996.

       IT Corporation, 1996b, "Draft Additional  Site Characterization and Final  Basewinde Operable
       Unit Remedail Investigation Report," Prepared by IT Corporation for Air Force Center for
       Environmental Excellence, Brooks Air Force Base, Texas, March 19,  1996.

       U.S. Environmental Protection Agency (USEPA), 1987,  "Data Quality Objectives for
       Remedial Response Activities: Development Process, March 1987," EPA/540/G-87/003,
       Washington, D.C.

       U.S. Environmental Protection Agency (USEPA), 1988,  "CERCLA Compliance with Other
       Laws Manual, Part I: Interim Final, August 1988," EPA/540/G-89/006, Washington, D.C.

       U.S. Environmental Protection Agency (USEPA), 1989a, "Risk Assessment Guidance for
       Superfund, Volume I, Human  Health Evaluation Manual, Interim Final, December, 1989,"
       EPA/540/1-89/002, Washington, D.C.
                                               8 4
RL/10-95/ES/1260005.AWS                                 °"^

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       U.S. Environmental Protection Agency (USEPA), 1989b, "CERCLA Compliance with Other
       Laws Manual, Part II: Clean Air Act and Other Environmental Statues and State
       Requirements," EPA/540/G-89/009, Washington, D.C., August 1989.

       Weston, Roy F., Inc. (Weston), 1986, "Installation Restoration Program Phase n -
       Confirmation/Quantification Stage 1 Final Report," Volumes 1 and 2, Roy F. Weston, Inc.,
       West Chester.
RL/10-95/ES/1260005.AWS
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