EPA Superfund Record of Decision: Mather Air Force Base (AC&W Disposal Site) EPA ID: CA8570024143 OU 01 Mather CA


                                    EPA/ROD/R09-96/149
                                    1996
EPA Superfund
     Record of Decision:
     MATHER AIR FORCE BASE (AC&W DISPOSAL SITE)
     EPA ID: CA8570024143
     OU01
     MATHER, CA
     06/21/1996

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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 Sites	2-1
              2.1.4 Description of the  Selected Remedy	2-2
              2.1.5 Statutory Determinations   	 2-4
              Decision Summary for Soil  OU Sites Selected for  Remedial Action	2-4
                    Site Names, Location, and Description 	 2-4
                    Site History and Enforcement Activities	2-4
                    Highlights  of Community Participation 	 2-6
                    Scope  and Role of Response Action	2-6
                    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

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Table of Contents (Continued)
2.2.5.6
2.2.5.7
2.2.5.8
2.2.5.9
2.2.3.10
2.2.5.11
2.2.5.12
2.2.6 Summary of
2.2.6.1
2.2.7Description
2.2.7.1
2.2.7.2
2.2.7.3
2.2.7.4
2.2.7.5
2.2.7.6
2.2.7.7
2.2.7.8
2.2.7.9
2.2.7.10
2.2.7.11
2.2.7.12
Site 56 - Oil/Water Separator 2989 	
Site 57 - Oil/Water Separator 7019 	
Site 59 - Oil/Water Separator 4251 	
Site 60 - Oil/Water Separator 6900 	
Site 62 - OWS 7110 and Jet Engine Test Cell
Site 65 Oil/Water Separator 6910 	
Site 69 - Open Burn Detonation Area 	
Site Risks 	
Human Health Risks 	
of Alternatives 	
Site 7/11 Remedial Alternative 	
Site 13 Remedial Alternatives 	
Site 15 Remedial Alternatives 	
Site 20 Remedial Alternatives 	
Site 37/39/54 Remedial Alternative 	
Site 56 Remedial Alternatives 	
Site 57 Remedial Alternatives 	
Site 59 Remedial Alternatives 	
Site 60 Remedial Alternatives 	
Site 62 Remedial Alternatives 	
Site 65 Remedial Alternatives 	
Site 69 Remedial Alternatives 	
Summary of Comparison Analysis of Alternatives 	
2.2.8.1

2.2.8.2
2.2.8.3
2.2.8.4
2.2.8.5
2.2.8.6
2.2.8.7
2.2.8.8
Overall Protection of Human Health and the
Environment 	
Compliance with ARARs 	
Long-Term Effectiveness and Permanence . . . .
Reduction of Toxicity, Mobility, or Volume . .
Short-Term Effectiveness 	
Implementability 	
Cost 	
State/Support Agency Acceptance 	
.... 2-12
.... 2-13
.... 2-13
.... 2-13
.... 2-14
.... 2-14
.... 2-14
.... 2-15
.... 2-15
. . . . 2-21
.... 2-21
.... 2-21
.... 2-22
.... 2-22
.... 2-23
.... 2-23
.... 2-24
.... 2-24
.... 2-25
.... 2-25
.... 2-26
.... 2-26
. 2-26

.... 2-27
.... 2-27
.... 2-28
.... 2-28
.... 2-28
.... 2-28
.... 2-28
.... 2-28

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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
                         3.2          Site 13 - Drainage Ditch Number 1	2-33
                         3.3          Site 15 - Drainage Ditch Number 3	2-36
                         3.4          Site 20 Sewage Treatment Plan	2-38
                         3.5          Site 37/39/54 - Building 3389/Hazardous Waste
                                             Control Storage  	 2-39
                         3.6          Site 56 - Oil/Water Separator 2989	2-42
                         3.7          Site 57 - Oil/Water Separator 7019	2-43
                         3.8          Site 59 - Oil/Water Separator 4251	2-45
                         3.9          Site 60 - Oil/Water Separator 6900	2-46
                         3.10         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
              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

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Table of Contents (Continued)

                     3.2.4.1
              3.2.5
Summary of Site
3.2.5.1 Site
3.2.5.2 Site
3.2.5.3 Site
3.2.5.4 Site
3.2.5.5 Site
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.2
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.5,
.6
.7
.7
.9
.10
.11
.12
.13
.14
.15
.16
.17
.18
.19
.20
.21
.22
.23
.24
.25
.26
.27
.28
.29
.30
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Site
Characteristics 	
9 - Fire Department Training Area Number 2
10 - Fire Department Training Area Number 3
14 - Drainage Ditch Number 2 	
16 - Electron Tube Burial Site 	
21 - Asphalt Rubble Storage Site 	
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
- Asphalt Rubble
- 1983 JP-4
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- Building
- OWS 7038
- OWS 4771
- OWS 6905
- OWS 3321
- OWS 4120
Spill
10072,
10060,
16100,
10090,
3308,
3388
3875,
2995,
2898,
10150,
8540,
7003,
8158,
10410,
10450,
10030,
10400,
18501,



Storage Site 	
and
One
One
One
One
Six

One
Two
One
Two
One
One
One
Two
One
One
One
One



Refueling Apron
Abandoned UST . .
Abandoned UST . .
Abandoned UST . .
Abandoned UST . .
Abandoned USTs . .

UST 	
USTs 	
UST 	
Abandoned USTs . .
UST 	
UST 	
UST 	
Abandoned USTs . .
UST 	
UST 	
UST 	
UST 	



and Two USTs 	



... 3-4
... 3-4
... 3-6
... 3-6
. . . 3-6
. . . 3-6
. . . 3-6
. . . 3-7
. . . 3-7
. . . 3-7
. . . 3-7
. . . 3-7
... 3-8
... 3-8
... 3-8
... 3-8
... 3-9
... 3-9
... 3-9
... 3-9
. . . 3-9
. . . 3-9
. . . 3-10
. . . 3-10
. . . 3-10
. . . 3-10
. . . 3-10
. . . 3-10
. . . 3-11
. . . 3-11
. . . 3-11

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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
                        .5.35    Site  F	3-12
                        .5.36    Site  G	3-12
                     3.2.5.37    Site  H	3-13
                     3.2.5.38    Site
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

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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/SAC  Industrial Area Groundwater Plume
                                   Remedial Alternatives  	  5-9
                     5.2.7.2          Site 7 Groundwater Plume Remedial Alternatives ....  5-9

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Table of Contents (Continued)
                     5.2.7.3          Northeast Groundwater Plume Remedial
                                       Alternatives   	 5-10
5.2.8










5.2.9




5.2.10







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

5-12
. . . 5-12
. . . 5-12
. . . 5-12
. . . 5-12
. . . 5-12
. . . 5-13
. . . 5-13
. . . 5-13
. . . 5-13

. . . 5-13
. . . 5-15
. . . 5-17
. . . 5-18
. . . 5-18
. . . 5-18
. . . 5-19
. . . 5-19
. . . 5-20
. . . 5-20
. . . 5-22
. . . 5-23
. . . 5-24
6.0    List of Applicable or Relevant and Appropriate Reguirements and
              To-Be-Considereds 	   6-1
       6.1    Chemical-Specific ARARs and TBCs	6-2

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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 Reguirements  for Ex Situ Soil Bioremediation
                               Facility	6-40


7.0    Responsiveness Summary  	   7-1

8.0    References	8-1

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List of Figures

Figure

1-1
2-1
3-1
4-1
5-1
Title
Page
Site Vicinity Map 1-3
Soil OU Sites Selected for Remedial Action 2-5
Soil OU Sites Selected for No Further Action 3-3
Soil OU "Petroleum Only" Sites 4-3
Groundwater OU Plumes 5-5
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 Groundwater 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
Estimated Areas and Volumes - Sediments 2-8
Estimated Areas and Volumes - Surface Soils 2-8
Estimated Areas and Volumes - Subsurface Soils 2-8
Site 7/11 Remedial Alternatives 2-21
Site 13 Remedial Alternatives 2-22
Site 15 Remedial Alternatives 2-22
Site 20 Remedial Alternatives 2-22
Site 37/39/54 Remedial Alternatives 2-23
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
Table
2-3.
2-4.
2-5.
2-6.
2-7.
2-8.
2-9.
2-10
2-11
2-12
2-13
2-14
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
Site 56 Remedial Alternatives
Site 57 Remedial Alternatives
Site 59 Remedial Alternatives
Site 60 Remedial Alternatives
Site 62 Remedial Alternatives
Site 65 Remedial Alternatives
Site 69 Remedial Alternatives
.2-23
.2-24
.2-24
.2-25
.2-25
.2-26
2-26
Comparative Analysis of Soil Operable Unit Remedial Alternatives 2-29
Site 7/11 Cleanup Levels 2-33
Site 13 Cleanup Levels 2-34
Site 15 Cleanup Levels 2-36
Site 20 Cleanup Levels 2-39
Sites 37/39/54 Cleanup Levels 2-41
Site 56 Cleanup Levels 2-42
Site 57 Cleanup Level 2-45

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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 2-49
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 Groundwater 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 Leachable Constituent Concentrations 6-43

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List of Appendices


       Appendix

       A



List of Acronyms
Title

Administrative Record Index for Soil Operable
Unit Sites and Groundwater Operable Unit Plumes,
Mather Air Force Base, Sacramento County, California
Page
         A-l
AC&W          Aircraft Control and Warning
AFB           Air Force Base
AGE           Aerospace Ground Eguipment
ARAR          Applicable or Relevant and Appropriate Reguirement
ASC           Additional Site Characterization
AST           aboveground storage tank
ATC           Air Training Command
AWQC          Ambient Water Quality Criteria
bis           below land surface
BTEX          benzene,  toluene,  ethylbenzene,  and xylenes
CCR           California Code of Regulations
CERCLA               Comprehensive Environmental  Response,  Compensation,  and  Liability
              Act of 1980
CFR           Code of Federal Regulations
COG           contaminant of concern
COPC          contaminant of potential concern
CVR           Central Valley Region
CVRWQCB              Central Valley Regional Water Quality  Control  Board
D.I.          deionized
DCE           dichloroethene
DLM           Designated Level Methodology
DTSC          Department of Toxic Substances Control
DWR           Department of Water Resources
BSD           Explanation of Significant Difference
FFS           Focused Feasibility Study
FR            Federal Register
FS            feasibility study
gpm           gallons per minute
HWCL          Hazardous Waste Control Law
IRP           Installation Restoration Program
JETC          jet engine testing cell
JP-4          jet propellant fuel
LCRS          leachate collection and removal  systems

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

List of Acronyms  (Continued)
UST
WDR
WET
WQG
yd3
underground storage tank
Waste Discharge Reguirement
waste extraction test
water guality goal
cubic yards

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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 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 qroundwater 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.

! 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 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 in Sacramento
County, approximately ten miles east of downtown Sacramento, California and due south of unincorporated
Rancho Cordova, California, as shown in 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.



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 investigate 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.

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 10-4 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 investigate 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


                                                              Description
 Selected
  Remedial
Alternative
          7.3*             Filling in the depression at Site 7  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  guality.

          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 guality.

          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  guality.

          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 guality.

         7.2**             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 guality.

          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 guality.

          57.3             SVE of the contaminated shallow  and  deep  subsurface  soils  and groundwater
                     monitoring if contamination remains at  the  site  that  threatens groundwater  guality.

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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


                                                              Description
 Selected
  Remedial
Alternative
          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  guality.

          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 guality.

              This  remedial  alternative  applies  to  Site 7/11.
              This  remedial  alternative  applies  to  Sites 37/39/54.

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Table 1-2. Selected Remedial Alternatives for the Groundwater Operable Unit Plumes
Selected
Remedial
Alternative
Description
Main/SAC.2
SP7.2
Selected
Alternative
Extraction of the contaminated groundwater with treatment by air stripping and injection
of the treated groundwater back into the aguifer (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.

Extraction of the contaminated groundwater with treatment by air stripping and injection
of the treated groundwater back into the aguifer (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.

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 included: 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 10-4 to 1 x 10-6 and a non-cancer risk less than
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

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

2.1.1 Site Name and Location

Soil OU Sites (IRP Sites) Selected for Remedial Action
Mather AFB (a NPL Site)
Sacramento County, California

2.1.2 Statement of Basis and Purpose

The Soil OU sites were investigated under the Mather IRP and are described and evaluated in the RI/FS
ocuments. This decision presents the selected remedial actions for the Soil OU sites for which remedial
ction is warranted at the formerly active Mather AFB. These sites include: Sites 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, 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.

2.1.3 Assessment of the Sites

Contamination exists at these Soil OU sites as a result of past USAF operations conducted between 1918 and
1993.

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 related to contaminants 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 10-4. 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

          7.3*
          13.3
          15.3
        20.2**
                                  Description
       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 guality.

       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 guality.

       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 guality.

       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 guality.

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Table 2-1.  Remedial Alternatives for the Soil Operable Unit Sites Selected for Remedial Action (Continued)
        Selected
        Remedial                                       Description
       Alternative
       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  guality.

          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  guality.

          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 guality.

          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  guality.

          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  guality.

          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 guality.

          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  guality.

        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 guality.

*      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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2.1.5 Statutory Determinations

The selected remedies satisfy the statutory requirements of Section 121(b) of CERCLA, as amended by SARA, in
that the following 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 Soil 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 in 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 in Table 2-2.

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 place Mather AFB on the NPL (or "Superfund" list) in 1989. In order
to organized 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 1194b].
Any sites not addressed in the ROD will be addressed in an upcoming Final Basewide OU ROD.

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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                              Applicable  Investigation

                        7/11                                   1, 2, 4, 5,  6,  7,  8,  9,  10,  13,  14,  15
                         13                                       1, 3, 5,  7,  9,  10,  11,  13,  14,  15
                         15                                      1,  2, 4, 5,  7,  9,  10,  11,  13,  14,  15
                         20                                          1, 3,  5,  7,  9,  10, 14, 15
                      37/39/54                                  7, 11, 12,  13,  14,  15
                         56                                               5,  7,  11,  14, 15
                         57                                                  7,  11,  14,  15
                         59                                                  7,  11,  14,  15
                         60                                                   11,  14, 15
                         62                                                  11,  13,  14, 15
                         65                                                  7,  11,  14,  15
                         69                                                 7,  11, 13, 14,  15

1.     Installation Restoration   (IRP) Records Search for Mather Air Force  Base,  Phase  1  [CH2M-H111,  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     Contaminant  of  Concern
           13
           15
           69
                4,7
             2,4,5,6,7
                 1
Area  (square feet)

       2.4 x 104
       5.8 x 104
       1.1 x 103
Volume  (cubic feet)

      4.8  x  104
      1.2  x  105
      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
Contaminant of Concern
                                                              Area (square feet)
                         Volumea  (cubic feet)
11
13
20
39
56
62
65
69

3


2,
2
3

1
,4
4
5
3,
,4
,4
1

,5


4,5
,5
,5

1.
1.
5.
3.
1.
5.
2.
1.
9
1
4
0
5
4
2
2
x
x
X
X
X
X
X
X
105
103
104
103
103
103
103
105
3.
2.
1.
6.
2.
1.
4.
2.
8
2
1
0
9
1
3
3
x
x
X
X
X
X
X
X
105
103
105
103
103
104
103
105
a = two foot depth assumed for calculatinq volumes

Contaminant of Concern = 1-Dioxins and Furans,  2-Polycyclic aromatic hydrocarbons, 3-Oil and qrease, 4-Metals, and 5-Total petroleum hydrocarbons.

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Table 2-3.   Estimated Areas and Volumes - Subsurface Soils
Site Number Contaminant of Concern
7* TPH-D
TPH-G
Thallium
20 TPH-D
37 Benzene
Oil and Grease
TPH-D
TPH-G
39 Benzene
TPH-D
TPH-G
Area (square feet)
1.9 x 105
2.0 x 105
1.3 x 103
1.2 x 103
(a)
3.1 x 102
3.1 x 102
5.1 x 103
6.0 x 104
(b)
4.1 x 104
Volume
2.9 x 106
3.0 x 106
6.0 x 104
1.5 x 104
(a)
3.5 x 103
3.5 x 103
1.3 x 105
1.5 x 106
(b)
1.7 x 106

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       Site Number     Contaminant  of  Concern          Area (square feet)                Volume  (cubic feet)

           54               Benzene                           (a)                         (a)
                             TPH-G                           8.0 x 102              2.0 x 104

           56             Oil and Grease
                             Lead
                             TPH-D                           8.9 x 102              1.3 x 104
                             TPH-G                           8.8 x 102              1.3 x 104

           57              Trichloroethane                     4.9 x 104              2.6 x 106

           59                TPH-D                           6.7 x 102              1.4 x 104
                             TPH-G                           1.6 x 103              3.2 x 104

           60                TPH-G                           6.6 x 102              9,9 x 103

           62                TPH-D                           2.3 x 102              2.5 x 103

           65                TPH-D                           2.0 x 102              3.1 x 103
                             TPH-G                           1.6 x 103              2.4 x 104

* Site 11 contains some contaminants adjacent to Site 7 that will be remedied 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

= 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

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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.

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. Contaminants at Site 11 has been identified in 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 groundwater
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 guality, and surface
water guality.

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 in 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.

Contamination at the site has been identified in 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 guality.

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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 in 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
in 1995, according to a Removal Action Memorandum dated September 1994. Recent sampling determined that the
sludge contains hazardous waste 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 i has been
characterized for disposal; portions have been found to contain hazardous concentrations of mercury (as is
reported in 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 in 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 COG identified at the UST site is diesel.
The bases for cleanup are protection of ecological receptors and groundwater guality.

2.2.5.5 Site 37/39/54 - Building 3389/Hazardous Waste Central 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 northeast 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 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 guality.

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.

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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 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 COG identified at
the site is trichloroethene (TCE). The basis for cleanup is protection of groundwater quality.

2.2.5.8 Site 59 - Oil/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
wastewater 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 t 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.

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 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

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identified at the site are chromium, diesel, gasoline, lead, and oil and grease. The basis for cleanup is
protection of groundwater quality.

2.2.5.12 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.

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 10-4). 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 III, 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 COG 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.

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]:

! 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.

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! 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 subseguent steps in the COG 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 Surface 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 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 in 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 guantitation limit for each
corresponding analytical method. In some cases, the 95 percent UCL was less than the guantitation 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 gualified as not detected (i.e., ND) to be included in the
database at a value of one-half the guantitation limit. Although such an approach is compatible with the
conservative nature of risk assessment, associated results are freguently of limited value in an engineering
context. Accordingly, if the 95 percent UCL was less than the guantitation 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 (WOG) 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
possible 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.

! Determine a Leachability Factor - The leachability 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 leachability 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.

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              !       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.

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 1995].  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 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 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 Ix
10-4 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.

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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.

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 eguipment.  Deep soils  (30 feet bis to the water table) are not considered
feasible or appropriate to excavate.  The no action alternative, as reguired 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.

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Table 2-6.  Site 7/11 Remedial Alternatives

       ALTERNATIVE                                   DESCRIPTION

           7.1       No Action

           7.2       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).

           7.3       Filling in the depression at site 7 to grade; in situ bioremediation and possible 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.

Table 2-7.  Site 13 Remedial Alternatives

ALTERNATIVE                                   DESCRIPTION

   13.1       No Action

   13.2       Excavation (sediments and surface soils)  with off-base disposal and groundwater
              monitoring (if contamination that threatens groundwater quality remains at the site)

   13.3       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                                   DESCRIPTION

   15.1       No Action

   15.2       Excavation (sediments)  with off-base disposal and surface water monitoring (if
              contamination that threatens surface water quality remains at the site)

   15.3       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)

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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       No Action
                                              DESCRIPTION
   20.2       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 guality remains at the site)

   20.3       In situ bioremediation (shallow soils)  and groundwater monitoring (if contamination
              that threatens groundwater guality remains at the site)

2.2.7.5       Site 37/39/54 Remedial Alternatives

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

              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 guality 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));  in situ bioremediation
              and possibly SVE,  (deep soils); and groundwater monitoring (if contamination that
              threatens groundwater guality 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.
37.3

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Table 2-11.  Site 56 Remedial Alternatives
ALTERNATIVE

56.1

56.2
                                              DESCRIPTION
              No Action
56.3
2.2.7.7
              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 guality
              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 guality remains at the site)

                    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                                   DESCRIPTION
57.1

57.2


57.3


2.2.1.1
              No Action

              In situ bioremediation (shallow and deep soils)  and groundwater monitoring (if
              contamination that threatens groundwater guality remains at the site)

              In situ vapor extraction (shallow and deep soils)  and groundwater monitoring (if
              contamination that threatens groundwater guality remains at the site)
                     Site 59 Remedial Alternatives

Table 2-13 presents three remedial alternatives that have developed for possible application at Site 59.

Table 2-13.  Site 59 Remedial Alternatives

ALTERNATIVE                                   DESCRIPTION
59.1

59.2
59.3
2.2.7.9
              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 guality remains at the site)

              In situ bioremediation (shallow soils)  and groundwater monitoring (if contamination
              that threatens groundwater guality remains at the site)

                     Site 60 Remedial Alternatives
Table 2-14 presents four remedial alternatives that have been developed for possible application at Site 60.

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Table 2-14.

ALTERNATIVE

60.1

60.2
60.3
60.4
             Site 60 Remedial Alternatives
No Action
                                 DESCRIPTION
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 guality remains at the site)

In situ vapor extraction  (shallow soils) and groundwater monitoring  (if contamination
that threatens groundwater guality remains at the site)

In situ bioremediation (shallow soils) and groundwater monitoring  (if contamination that
threatens groundwater guality 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                                   DESCRIPTION
62.1
62.2
62.3
2.2.7.11
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 guality 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 guality remains at the site)

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                                   DESCRIPTION

65 .1          No Action

65.2          Excavation (surface soils)  with off-base disposal;  in situ bioremediation (shallow soils);
              and groundwater monitoring (if contamination that threatens groundwater guality remains
              at the site)

65.3          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 guality remains at the site)

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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 DESCRIPTION

69.1 No Action

69.2 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 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.
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

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

The relatively 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 Toxicity, 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 guantity 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 administration 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.

2.2.8.7              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 eguipment salvage value, zero percent inflation, and a five percent
discount factor so that each option could be egually compared in 1994 dollars.  A detailed cost analysis was
performed for each of the alternative 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.

-------
Table 2-18.  Comparative Analysis of Soil Operable Unit Remedial Alternatives

         Evaluation         Site                  7/11                   13                  15                   20                  37/39/54              56
          Criteria          Number

                         Alternative     7.1    7.2    7.3*   13.1   13.2    13.3*  15.1   15.2   15.3*  20.1   20.2*   20.3   37.1   37.2*  37.3   56.1   56.2   56.3*

       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)

* 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
Yes
NA**
G
P
F
G
0.018
Yes
Yes
B
B
B
G
4.21
Yes
Yes
B
B
G
B
3.69
Yes Yes
NA** Yes
G B
P G
G B
B G
0.15 0.88
Yes Yes
Yes NA**
B F
B P
B G
G B
0.279 0.51
Yes
Yes
B
G
B
G
2.20
Yes Yes
Yes NA**
B F
B P
B F
G B
0.827 0.28
Yes
Yes
B
B
B
G
0.33
Yes
Yes
B
B
G
B
0.62
Yes
NA**
F
P
G
B
0
Yes
Yes
B
B
B
G
1.75
Yes
Yes
B
B
B
G
3.38
Yes Yes
NA** Yes
G B
P G
F G
B G
0 0.71
Yes
Yes
B
B
B
G
0.0

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Table 2-18.  Comparative Analysis of Soil Operable Unit Remedial Alternatives  (Continued)

         Evaluation         Site                  57                     59                     60                      62                     65              69
          Criteria          Number

                          Alternative        57.1       57.2   57.3*  59.1    59.2*  59.3   60.1   60.2*  60.3   60.4   62.1    62.2    62.3*  65.1   65.2   65.3*  69.1   69.2*

       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
Yes Yes
NA** Yes
F B
Yes
Yes
B
Yes Yes
NA** Yes
F B
Yes Yes
Yes NA**
B F
Yes
Yes
B
Yes
Yes
B
Yes
Yes
B
Yes Yes
NA** Yes
F B
Yes
Yes
B
Yes Yes
NA** Yes
F B
Yes
Yes
B
Yes Yes
NA** Yes
F B
G
B
0
B
G
0.57
B
G
1.01
F
B
0
B
G
0.87
G
G
0.63
P B
B G
0.003 0.033
G
G
0.26
F F G
GBG
0.63 0.011 0.21
B G
G B
0.049 0.
B
G
,004 0.186
B G B
G B B
0.134 0.081 0
       Present Worth Cost
       ($ millions)

* 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
                                                                                                                                                                      0.45

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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 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.

2.2.9.1              Site  7/11 -  "7100  Area"  Disposal  Site/Existing  Fire  Protection 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 deep  soils  at Site 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
                     groundwater  quality nor  generational 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 prescription landfill cover
pursuant to Article 8 of 23 California Code of 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 of 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 common unit (e.g., cost to remove a pound of TCE), provided that the underlying
groundwater has not reached aguifer 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 reguired 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
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 reguired 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 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 guality for its beneficial use. Table
2-19 presents the Site 7/11 cleanup levels.

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Table 2-19. Site 7/11 Cleanup Levels

Contaminant of Concern Cleanup Level (ppm)

Subsurface Soils

TPH as Diesel 10
TPH as Gasoline 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;

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

! treating the excavated soils by in 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 guality remains
at the site, and monitoring surface water if contamination that threatens surface water
guality 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 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 guality, surface water guality, and ecological
receptors. Table 2-20 presents the Site 13 cleanup levels.

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                          Table  2-20.   Site  12  Cleanup  Levels

       Contaminant of Concern            Cleanup Level  (ppm)

Surface Water

Aluminum                                 6.28
Chromium                                 1.1 x 10-2
Lead                                     9.4 x 10-3
Manganese                                1.0 x 10-1
Silver                                   1.6 x 10-2
Zinc                                     5.4 x 10-2

Sediment

Arsenic                                  16
Chromium                                 176
Chromium VI                              ND  (0.1)
Cobalt                                   35
Copper                                   104
Lead                                     81
Mercury                                  ND  (0.23)

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                            Table  2-20.   Site  12  Cleanup Levels  (Continued)

       Contaminant of Concern                   Cleanup Level (ppm)

       Nickel                                          81
       Vanadium                                        153
       Zinc                                            116
       4,4-DDD                                         1.9
       4,4-DDE                                         1.3
       4,4-DDT                                         1.3

       Sediment (Continued)

       alpha-Chlordane                                 3.4 x 10-1
       Dieldrin                                        2.8 x 10-2
       gamma-Chlordane                                 3.4 x 10-1

       Surface Soil

       Arsenic                                         16
       Benzo(a)anthracene                              3.3 x 10-1
       Benzo(g,h,i)perylene                            3.3 x 10-1
       Fluoranthene                                    3.3 x 10-1
       Indeno(1,2,3-cd)pyrene                          3.3 x 10-1
       Mercury                                         ND (0.2)
       Naphthalene                                     3.3 x 10-1
       Oil and Grease                                  430
       Pyrene                                          3.3 x 10-1
       TPH as Diesel                                   100
       Zinc                                            1559

ppm = parts per million                         ND = not detected
TPH = total petroleum hydrocarbon               ODD = dichlorodiphenyldichloroethane
DDT = dichlorodiphenyltrichloroethane           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 guality
remains at the site.

Capital costs 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 guality 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 1.1 x 10-2
Lead 9.4 x 10-3
Manganese 1.0 x 10-1
Vanadium 1.0 x 10-1
Zinc 5.4 x 10-2

Sediment

Barium 1300
Cadmium 1.4

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Table 2-20.  Site 15 Cleanup Levels (Continued)

       Contaminant of Concern                   Cleanup Level (ppm)

       Sediment (Continued)

       Chromium                                 176
       Chromium VI                              ND  (0.1)
       Copper                                   104
       Lead                                     81
       Mercury                                  ND  (0.2)
       Zinc                                     116
       Acenaphthene                             3.3 x 10-1
       Acenaphthylene                           3.3 x 10-1
       alpha-Chlordane                          3.4 x 10-1
       Anthracene                               3.3 x 10-1
       Aroclor 1248                             6.6 x 10-2
       Aroclor 1254                             6.6 x 10-2
       Aroclor 1260                             6.6 x 10-2
       Benzo(a)anthracene                       3.3 x 10-1
       Benzo(a)pyrene                           3.3 x 10-1
       benzo(b)fluoranthene                     3.3 x 10-1
       Benzo(g,h,i)perylene                     3.3 x 10-1
       Benzo(k)fluoranthene                     3.3 x 10-1
       Chrysene                                 3.3 x 10-1
       Dibenzo(a,h)antharcene                   3.3 x 10-1
       Dieldrin                                 2.8 x 10-2
       Fluoranthene                             3.3 x 10-1
       Fluorene                                 3.3 x 10-1
       gamma-Chlordane                          3.4 x 10-1
       Indeno(1,2,3-cd)pyrene                   3.3 x 10-1
       Naphthalene                              3.3 x 10-1
       Oil and Grease                           430

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Table 2-21. Site 15 Cleanup Levels (Continued)

Contaminant of Concern Cleanup Level (ppm)

Sediment (Continued)

Phenanthrene 3.3 x 10-1
Pyrene 3.3 x 10-1
TPH as Diesel 10
TPH as Gasoline 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;

! treated the excavated soils by ex situ bioremediation as appropriate;

! transporting the treated soils to, and consolidating them with landfill cap foundation
on 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 guality 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 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.

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Table 2-22. Site 20 Cleanup Levels

Contaminant of Concern Cleanup Level (ppm)

Surface Soil (sludge location)

Lead 130
Mercury 20
Zinc 1559

Subsurface Soil (diesel spill location)

TPH as Diesel 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 guality 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 is the leachate to exceed the aguifer 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 aguifer 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 reguired 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 guality.  Table 2-23 presents the Site 37/39/54 cleanup
levels.

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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                           430
       TPH as Diesel                            10
       TPH as Gasoline                          1

                                              Site 39

       Surface Soil

       Oil and Grease                           430
       TPH as Diesel                            100

       Subsurface Soil

       Benzene                                  1 x 10-1
       Ethylbenzene                             2 . 9
       Toluene                                  4 .2
       TPH as Diesel                            10
       TPH as Gasoline                          1
       Xylene                                   1.7

                                              Site 54

       Subsurface Soil

       Benzene                                  1 x 10-1
       TPH as Gasoline                          1

TPH = total petroleum hydrocarbon ppm = parts per million

*      During the Additional Site Characterization field effort (IT Corp.,  1996)  chlorinated solvents were
detected in the soil samples.  However,  these constituents and their corresponding cleanup goals are not
presented in 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 in 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;

! 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 guality 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 22
Benzo(a)anthracene 3.3 x 10-1
Benzo(a)pyrene 3.3 x 10-1
Benzo(b)fluoranthene 3.3 x 10-1
Chrysene 3.3 x 10-1
Dibenzo(a,h)anthracene 3.3 x 10-1
Lead 130
Oil and Grease 430
TPH as Diesel 100

Contaminant of Concern Cleanup Level (ppm)

Subsurface Soil

Oil and Grease 430
TPH as Diesel 100
TPH as Gasoline 5

TPH = total petroleum hydrocarbon ppm = parts per million

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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 in situ SVE;  and

              !       monitoring the  groundwater if contamination that  threatens  groundwater  guality remains
                     at the  site.

The goal of cleaning up the vadose zone is to minimize further degradation of the groundwater by the
contaminants in 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, in conjunction with a groundwater fate and transport model, to
predict the resulting concentration from this residual vadose zone contamination in the nearest groundwater
wells monitoring the site.  This demonstration can be made prior to the cessation of groundwater remediation.
The Air 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:

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 groundwater 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 of 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

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that in the event of a dispute regarding SVE shutoff, the State may argue its authority to reguire 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.

The basis for cleanup is protection of groundwater guality.

Table 2-25. Site 57 Cleanup Levels

Contaminant of Concern Cleanup Level (ppm)

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 guality remains
at the site.

Capital costs 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 guality. 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 10
TPH as Gasoline 1

TPH = total petroleum hydrocarbon ppm = parts per million

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2.2.9.9 Site 60 - Oil/Water Separator 6900

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 on 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 guality 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 guality. 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 5*
Xylenes 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:

! 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 guality remains
at the site.

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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 guality. 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 3.3 x 10-1
Cadmium 9
Fluoranthene 3.3 x 10-1
Lead 130
Naphthalene 3.3 x 10-1
Pyrene 3.3 x 10-1
TPH as Diesel 10
Zinc 1559

Table 2-28. Site 62 Cleanup Levels

Contaminant of Concern Cleanup Level (ppm)

Subsurface Soil

Benzo(a)pyrene 3.3 x 10-1
TPH as Diesel 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 the 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 guality 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.

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The basis for cleanup is protection of groundwater quality. Table 2-29 presents the Site 65 cleanup levels.

Table 2-29. Site 65 Cleanup Levels

Contaminant of Concern Cleanup Level (ppm)

Surface Soil

Chromium 210
Lead 130
Oil and Grease 430
TPH as Diesel 10

Subsurface Soil

TPH as Diesel 10
TPH as Gasoline 1

TPH - total petroleum hydrocarbon ppm = parts per million

2.2.9.12 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.

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Table 2-30.  Site 69 Cleanup Levels

       Contaminant of Concern

       Surface Water

       Barium
       Manganese

       Sediment

       OCDD
       OCDF
       Total
       Total
       Total
       Total
       Total
       Total
       Total
HPCDD
HPCDF
HXCDD
HXCDF
PCDD
PCDF
TCDF
       Surface Soil

       Barium
       Manganese
       Zinc
                            Cleanup Level  (ppm)
                                   1.0 x 10-1
                                                5 x 10-6
                                                total 2,3,7,8-TCDD equivalent
                                   1754
                                   (A)
                                   1559

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Table 2-30.  Site 69 Cleanup Levels

       Contaminant of Concern                   Cleanup Level (ppm)

       Surface Soil (Continued)

       OCDD                                     2 x 10-4
                                                total 2,3,7,8-TCDD equivalent
       OCDF
       Total HPCDD
       Total HPCDF
       Total HXCDD
       Total HXCDF
       Total PCDD
       Total PCDF
       Total TCDF

(A) Manganese was a contaminant of concern (COG)  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 COG.

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.

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 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

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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 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.

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 10-4 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 guality Level III, IV, or V, or eguivalent
[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 COG 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 guantitation limit;
! evaluation of operational history (i.e., process knowledge); and
! evaluation of estimated risk to human and ecological receptors.

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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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Table 3-1. Previous Investigations at the No Further Action Sites

SITE NUMBER APPLICABLE INVESTIGATION

9 1, 11, 12
10 1, 2, 4, 5, 6, 11, 12
14 1, 2, 3, 4, 5, 6, 7, 10, 11, 12
16 1, 4, 5, 7, 11, 12
21 1, 4, 11, 12
22 1, 11, 12
24 4, 5, 7, 11, 12
26 1, 4, 5, 6, 7, 9, 11, 12
27 1, 7, 11, 12
28 1, 7, 11, 12
31 9, 11, 12
33 9, 11, 12
38 9, 11, 12
40 9, 11, 12
41 9, 11, 12
42 9, 11, 12
43 9, 10, 11, 12
44 9, 11, 12
45 11, 12
46 9, 10, 11, 12
48 9, 10, 11, 12
49 9, 10, 11, 12
51 9, 10, 11, 12
52 9, 10, 11, 12
53 9, 10, 11, 12
55 5, 8, 11, 12
58 5, 8, 11, 12
61 8, 11, 12
63 5, 8, 9, 10, 11, 12
64 5, 8, 11, 12
66 5, 8, 11, 12
A 9, 10, 11, 12
C 7, 9, 10, 11, 12
E 9, 10, 11, 12
F 9, 10, 11, 12
G 9, 10, 11, 12
H 9, 10, 11, 12
I 9, 10, 11, 12

1. Installation Restoration Program (IRP) Records Search for Mather Air Force Base, Phase I [CH2M-H111,
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].
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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 a 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 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 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
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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.

3.2.5.11 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
horizon. The guantity 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 in 1988. Investigations have revealed no COCs.
This site has been clean-closed by Sacramento County.

3.2.5.15 Site 41 - Building 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.

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
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1988 and the site has been clean-closed by Sacramento County.

3.2.5.17 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 - Building 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. The site has been clean-closed by Sacramento
County. Investigations have revealed no COCs.

3.2.5.20 Site 46 - Building 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 duel 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.

3.2.5.21 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.

3.2.5.22 Site 49 - Building 10450, One UST

Site 49 is located in 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 in 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 in 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 in 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 in 1993 and
the site has been recommended to Sacramento County for clean-closure. Investigations have revealed no COCs.
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3.2.5.26 Site 55 - OWS 7038

Site 55 consisted of OWS 7038, located in 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 in the southeast portion of the Main Base at the Army Helicopters
washrack, approximately 450 feet east of Building 4677. Oil/water separator 4771 is a belt-type skimmer,
constructed in 1969, that received wastewater generated from the washrack. The wastewater 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.

3.2.5.28 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 in 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 in 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 contains 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 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 northeast 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 in 1993 and the
site recommended to Sacramento County for clean-closure.
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3.2.5.33 Site C

Buildings 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 in 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 in 1993.
Investigations have revealed no COCs. The site has been recommended to Sacramento County for clean-closure.

3.2.5.35 Site F

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 in 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 Site 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.

3.2.5.37 Site H

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 in 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 in 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 in 1988 and was removed in 1993. Investigations have revealed no COCs. The site has been
recommended to Sacramento County for clean-closure.

4.0 Soil Operable Unit "Petroleum Only" Sites Selected for No Action Under CERCLA (but which remain to be
closed under the 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
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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 in
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 recommended 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 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 10-4 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 adeguate 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 reguirements as the CERCLA sites, i.e., "petroleum only" sites do not
reguire a CERCLA five-year review, are not subject to the 15 month reguirement to begin remedial activities,
etc. However, permits, will be reguired 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 - Building 3286.

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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 USAF IRP and
are summarized in Table 4-1.

Table 4-1. Previous Investigations at the Soil Operable Unit "Petroleum Only" Sites

SITE NUMBER APPLICABLE INVESTIGATION

19 1, 2, 3, 4, 5, 6, 9, 10, 11
29/B 1, 6, 8, 9, 10, 11
32 1, 4, 6, 7, 10, 11
34 1, 8, 9, 10, 11
35 8, 9, 10, 11
36 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 reguirement of CERCLA Sections 113(k)(2)(B)(I-v) and 117 do not apply to these
sites; however, these sites were included in 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.

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.
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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 in Section 5.0 of this ROD. Any remaining sites will be addressed
in the Final Basewide OU.

Previous RIs 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 in the following sections and Table 4-2.

4.2.5.1 Site 19 - Fuel Tank Sludge Burial Site

Site 19 is located in 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 guantities of weathered sludge from fuel tank cleaning
operations. Contamination was identified in the shallow surface soils. The only COG at this site is
gasoline. The COG 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

Contaminant of Area Volume
Site Number Concern (square feet) (cubic feet)
19 TPH-G 5.4 x 104 5.4 x 105
29/B TPH-D (a) (a)
TPH-G 1.4 x 105 6.3 x 106
Benzene 8.0 x 104 4.1 x 106
32* TPH-G 1.6 x 103 1.7 x 104
34 TPH-G 1.3 x 104 3.0 x 105
35 TPH-G 6.9 x 103 7.6 x 104
36 TPH-G 2.6 x 104 1.2 x 106

(a) = diesel detections are sporadic and coincide with higher concentration gasoline detections
TPH-D = Total petroleum hydrocarbons as diesel
TPH-G = 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 Site 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 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 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 bioventing with SVE at "hot spots".

4.2.5.3 Site 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 in 1988. The two remaining USTs were removed in 1994. In
addition, a 550-gallon waste oil tank was removed from the site in 1994. Contamination was identified in the
shallow subsurface soils. The only COG identified at the site is gasoline. This site has been remediated
through excavation of the soil in late 1995. It is expected that the site will be closed by the Regional
Water Quality Control Board.

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 COG identified at the site is
gasoline.
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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 COG 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 guality Level III, IV, or V, or eguivalent
[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.

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 COG determination process for the Soil OU sites and are discussed in Section 2.2.6.1.

4.2.7 Statutory Authority Finding

The no action finding is selected based on the petroleum exclusion in CERCLA.

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
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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 AC&W OU plume, which is addressed in a separate ROD (IT,
1993). The main sources of contamination include industrial activities, eguipment 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 RI) 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 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 reguirements that are ARARs based on the beneficial use of the groundwater and the specific conditions of
the site.
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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 Description

Main/SAC.2 Groundwater extraction, air stripping with off-gas treatment (carbon
adsorption), and groundwater injection*; and groundwater monitoring

SP7.2 Groundwater extraction, air stripping with off-gas treatment (carbon
adsorption), and groundwater injection*; and groundwater monitoring

NE.l 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 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 USAF IRP and are
summarized in Table 5-2.
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5.2.3 Highlights of Community Participation

The public participation reguirement of CERCLA Sections 113(k)(2)(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 Applicable Investigation

Main Base/Strategic Air Command 1,2,3,4,5,6,7,8,9,10,11
Industrial Area

Site 7 1,2,3,4,5,6,7,8,9,10,11

Northeast 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].

5.2.4 Scope and Role of Response Action

Environmental studies were initiated by the USAF to investigate contamination resulting from past operations
at the base. The USEPA placed Mather AFB on the NPL in 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, eguipment 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/SAC Industrial Area Groundwater Plumes

The SAC Industrial Area Groundwater Plume and the Main 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 are (Figure 5-1) which extends off-base to the west. The Main 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 cis-1,2-dichloroethene (DCE)
concentrations. The Main Base/SAC Industrial area plume is oriented northeast-southeast following the
general basewide groundwater flow direction. The COCs identified are 1,1-DCE, 1,2-dichloroethane, benzene,
carbon tetrachloride, chloromethane, cis-1,2-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 guality.
-------
Table 5-3. Estimates of Volume - Groundwater
Groundwater Plume
Major
COG
Main Base** SAC
Hydrogeologic Industrial**
Unit
Volume* Volume*
(cubic
TCE

PCE

CCI4

A
Bu
B
D
Total
A
Bu
B
D
Total
A
Bu
B
D
Total
1.
5.
4.
5.
6.
1.
9.
1.
3.
1.
3.
1.
1.
1.
1.
4
4
8
3
8
1
5
0
9
6
6
9
3
2
5
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
feet)
108
107
108
106
108
108
107
109
108
109
107
107
109(2)
108
109
(cubic feet)
2.
2.
1.

1.
1.
2.
5.

9.
2.
4.

6.
9 x
2 x
3 x
NA
8 x
2 x
4 x
5 x
NA
1 x
3 x
4 x
NA
NA
7 x
108
108
109

109
108
108
108

108
107
107

107
Northeast (1)
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 7
Volume*
(cubic feet)
6.8 x
NP
1.5 x
NA
2.2 x
5.1 x
NP
7.6 x
NA
1.3 x
NA
NP
NA
NA
NA
107

108

108
107

107

108

TCE = Trichloroethene
SAC = Strategic Air Command
US - Unit Unsaturated
COG = contaminant of concern
CGI4 = Carbon Tetrachloride
NA = Not Applicable
PCE = Tetrachloroethene
NP = Unit Not Present
(1) Hydrogeologic Unit C - PCE Contamination Volume = 9.6 x 107 cubic feet.

(2) Main Base Plume and SAC Industrial Plume volumes are reported under Main Base Plume.

* Estimates of plumes size as of 1993.

**Revised estimates will be provided in the Additional Site Characterization RI Report.
-------
5.2.5.2 Site 7 Groundwater Plume

The Group 2 Sites 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, chloromethane, 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 guality 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 x 10-5. 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 in 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 reguirements 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.

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, 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 DESCRIPTION

Main/SAC.l No Action (includes groundwater monitoring)

Main/SAC.2 Extraction of the contaminated groundwater with treatment by air stripping and
injection of the treated groundwater into the aguifer (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.

Main/SAC.3 Extraction of the contaminated groundwater with treatment by ultraviolet oxidation
and injection of the treated groundwater into the aguifer (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.
-------
Table 5-5. Site 7 Plume Remedial Alternatives

ALTERNATIVE DESCRIPTION

SP7.1 No Action (includes groundwater monitoring)

SP7.2 Extraction of the contaminated groundwater with treatment by air stripping and
injection of the treated groundwater into the aguifer (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.

SP7.3 Extraction of the contaminated groundwater with treatment by ultraviolet oxidation
and injection of the treated groundwater into the aguifer (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 DESCRIPTION

NE.l No Action (includes groundwater monitoring)

NE.2 Extraction of the contaminated groundwater with treatment by air stripping and
injection of the treated groundwater into the aguifer (alternative means of
discharge of treated groundwater may be implemented), and groundwater monitoring.

Selected Alternative 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 reguired by the NCP (Section 300.430 (e) (7)). These criteria are classified as threshold,
primary balance, and modifying criteria. In order for a remedial alternative to be selected, it must at a
minimum, meet the threshold criteria.
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

Plume Main Base/SAC Industrial Groundwater Plume
Evaluation
Criteria
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)
Alternative Main/SAC.1
No

NA**

P
Yes

Yes

B
F

7.72
G

20.31
Main/SAC.2* Main/SAC.3 SP7.1
Yes

Yes

B
No

NA**

G
22.77
G

1.12
Site 7 Groundwater Plume
Groundwater
Plume
SP7.2* SP7.3
Yes

Yes

B
Yes

Yes

B
B

5.35
No

NA**

G
G

0.28
Northeast
NE.l*

Yes

B
1.91
NE.2
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 ot 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 reguirements
-------
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.

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);

! treatment of the extracted groundwater through air stripping with off-gas treatment
(i.e., carbon adsorption) to achieve aguifer 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 a 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.
-------
5.
6.
1.
5.
1.
6.
3.
5.
5.
5.
1.
1.
,0
,0
,0
,0
,7
,0
,0
,0
,0
,0
,0
,5
X
X
X
X
X
X
X
X
X
X
X
X
10-4
10-3
10-3
10-4
10-2
10-3
10-3
10-3
10-3
10-2
10-1
10-2
Table 5-8. Main Base/SAC Industrial Area Plume Cleanup Levels

Contaminant of Concern Cleanup Level (mg/L)

1,2-DCA
cis-l,2-DCE
Benzene
CC14
Xylenes
1,1-DCE
Chioromethane
TCE
PCE
TPH as Gasoline
TPH as Diesel
Lead

DCA = dichloroethane CC1 = carbon tetrachloride
TCE = trichloroethene PCE = tetrachloroethene
mg/L = milligrams per liter SAC = Strategic Air Command
CA MCL = California Maximum Contaminant Level
SNARL = suggested no adverse response 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:

! groundwater 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 aguifer 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;

CA MCL, PQL
CA MCL
CA MCL
CA MCL, PQL
T&O
CA MCL
SNARL
FMCL
FMCL
PQL
USEPA HA
FMCL

DCE = dichloroethene
TPH = total petroleum hydrocarbon
T&O = taste and odor
PQL = Practical Quantitation Limit
FMCL = Federal Maximum Contaminant
Level
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 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
Chioromethane
Vinyl Chloride
TCE
PCE
TPH as Diesel
Cleanup Level (mg/L)

6.0 x 10-3
5.0 x 10-4
6.0 x 10-3
1.0 x 10-3
5.0 x 10-3
3.0 x 10-3
5.0 x 10-4
5.0 x 10-3
5.0 x 10-3
1.0 x 10-1
PRG Basis

CA MCL
CA MCL, PQL
CA MCL
CA MCL
CA MCL
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 = dichloroethene
DCB = dichlorobenzene
TCE = trichloroethene

PQL = Practical Quantitation Limit
FMCL = Federal Maximum Contaminant Level
USEPA HA = United States Environmental Protection Agency health advisory
-------
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 levels in Table 5-10 are attained. After that time, monitoring will, as reguired 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 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.
-------
Table 5-10. Northeast Plume Cleanup Levels

Contaminant of Concern Cleanup Level (mg/L) PRG Basis

cis-l,2-DCE 6.0 x 10-3 CA MCL
CC14 5.0 x 10-4 CA MCL, PQL
Chloromethane 3.0 x 10-3 SNARL
1,2-dichloropropane 5.0 x 10-3 FMCL
PCE 5.0 x 10-3 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
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
polyvinyl 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 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.

5.2.10.3 Air Stripping Tower and Blower

The air stripping tower would be of a cylindrical, vertical design which will allow air flow countercurrent
to the liguid flow through packing. Components of a typical air stripping tower include:

! Spray Nozzle - Spray nozzles are used to uniformly distribute the liguid 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 liguid and
countercurrent air contact each other, stripping contaminants from the liguid. Over
time, the packing material can become encrusted with solids suspended in the liguid
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 liguid, 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
aguifer and injection wells. The effluent will be pumped from the PTU to the injection wells through buried
PVC pipelines.

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 freguent. 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.

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 deadlines). 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 discharqe
are:

! injection to a deeper aquifer;
! recharqe throuqh the vadose zone usinq injection wells, infiltration ponds, or
infiltration qalleries;
! surface water discharqe (i.e., storm water drainaqe);
! provisions of water to industrial/aqricultural users;
! provisions of water for municipal supply; and
! irriqation (qolf course, parks wetlands).

All disposal alternatives will comply with discharqe 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
discharqe to injection of treated water unless (a) additional or alternative discharqe is done under
applicable permit or (b) additional or alternative discharqe meets the substantive requirements of applicable
or relevant and appropriate requlations as aqreed 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 receivinq waters.

Initial backqround concentration of all potential pollutants shall be determined for each water-bearinq zone
in which reinjection will occur. These constituents will be monitored durinq RA until it can be determined
that there is no condition of pollution occurrinq as a result of the discharqe. 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 waste or wastes derived from the
remedial action. Therefore no action-specific ARARs were selected. If hazardous or other wastes are derived
from the remedial action, such as waste water, screeninqs, sludqes and other solids qenerated durinq
construction, operation and maintenance of the treatment system, these will be disposed of off-site in
accordance with applicable federal, state, and local laws, requlations, 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 wells beyond the base boundary. The current levels of contaminant
constituents in the affected wells are below the maximum contaminant level (MCL) safe drinkinq water
standards promulqated by USEPA and the State but are 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 miqration, and to address plume miqration as a result of supply wells,
the USAF will develop a Mather-specific off-base Water Supply Continqency Plan in consultation with the
State, USEPA, and local water aqencies. The proposed Water Supply Continqency Plan will be subject to public
review and comment. The USAF will submit a Draft Water Supply Continqency Plan by June 27, 1996, to the
aqencies and the local water aqencies for review and comment. The USAFs commitment to submit a draft
Continqency Plan to the other ROD siqnatory parties is a schedule deadline enforceable under the Mather AFB
Federal Facility Aqreement (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 freguency of sampling once a constituent from the Plume has been detected;

(3) Determine the impact of supply well pumping on the plume and recommended action(s) to
minimize plume migration;

(4) Evaluate the short term and long term options for providing alternate water supplies (the
evaluate 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 seguencing 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 aguifer 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 reguirements 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, freguency, 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.

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
aguifer cleanup standards, and that the injection of treated groundwater does not degrade the receiving water
guality.

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 reguirements will be established during the remedial design.
This data will be utilized to evaluate the need for institutional control as well as 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 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 reguirements 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 conseguences;

! the selected remedies comply with federal and state reguirements 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.

6.0 List of Applicable or Relevant and Appropriate
Reguirements and To-Be-Considereds

Pursuant to Section 121(d)(1) 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, reguirements, limitations, or criteria
that are ARARs. Federal ARARs include reguirements under any federal environmental laws, while state ARARs
include promulgated reguirements 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 reguirements are those cleanup standards, control standards, and other substantive environmental
protection reguirements, 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. Ln general, onsite actions need comply only with the substantive aspects of ARARs, not with
corresponding administrative reguirements (such as, but not limited to, permits, recordkeeping, and
reporting).

Relevant and appropriate reguirements 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 reguirement must be either applicable or both relevant and
appropriate to be an ARAR. Lf 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 reguirements 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;

! 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 reguirements 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 Reguirements" [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 this 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.

6.1 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 not exceed 50 mg/kg. The date(s) the PCBs were released to the
soils at Mather AFB is not known, so these reguirements are considered relevant and appropriate for
establishing chemical-specific COG 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 aguatic 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 aguatic habitat.
-------
Table 6-1. Chemical-Specific TBCs for Surface Water

Chemical Concentration (mg/L) Site Number

Aluminum 8.7 x 10-2 (1) 13
Barium 1.0 x 100 (2) 69
Chromium 1.1 x 10-2 (1) 13, 15
Lead 9.9 x 10-4 (1) 13, 15
Manganese 5.0 x 10-2 (3) 13, 15, 69
Silver 1.2 x 10-4 (1) 13
Vanadium 1.0 x 10-1 (4) 15
Zinc 4.9 x 10-2 (1) 13, 15

TBC = to-be-considered mg/L = milligrams per liter

(1) U.S. Environmental Protection Agency National Ambient Water Quality Criteria, Freshwater Aguatic
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.

6.1.2 State Chemical-Specific ARARs and TBCs

The following State of California chemical-specific ARARs and TBCs have been identified.

6.1.2.1 Soils

There are no state chemical-specific ARARs and 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 993].
The WQG was used as the regulatory factor for each COG identified at a site. The WQG was multiplied by a
leachability factor and an environmental attenuation factor which are based on site-specific characteristics
to develop a TDL for each site-specific COG. 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 reguirements 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 aguatic habitat). Based on this use-analysis,
narrative standards for taste and odor thresholds are considered TBC reguirements.
-------
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 qroundwater 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 in situ contamination from the vadose zone to
groundwater. The USAF believes that only active discharges directly to surface water or groundwater of the
state are subject to the provisions of SWRCB Resolution 68-16.
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Table 6-2. Chemical-Specific ARARs and TBCs for Sediments

Chemical Concentration (mg/L)

ARAR

PCBs (Aroclor 1248, 1254, and 1260) 5.0 x 101

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(1,2,3-cd)pyrene
Naphthalene
Phenanthrene
Pyrene
2,3,4,8-TCDD eguivalent
Arsenic
Barium
Cadmium
Chromium VI
Chromium, Total
Cobalt
Copper
5
2
2
2
2
2
2
2
5
2
8
5
5
2
1
1
3
2
5
2
6
6
9
.2
.8
.8
.8
.8
.8
.8
.8
.7
.8
.3
.9
.9
.8
.4
.0
.7
.8
.0
.8
.2
.3
.6
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
100
10-5
10-5
10-5
10-5
10-5
10-5
10-5
10-6
10-5
10-5
10-5
10-5
10-5
10-6
100
100
10-5
10-2
10-5
100
10-2
100
(1)
TBC*
1
1
5
1
1
5
.8
.0
.5
.1
.1
.0
X
X
X
X
X
X
10-3
102
10-2
100
100
100
1.3 x 103
Site Number
15
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
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/L)

TBC* (Continued)
Lead
Mercury
Nickel
Vanadium
Zinc
TBH = to-be-considered material
PCB = polychlorinated biphenyls
DDD = Dichlorodiphenyldichloroethane
DDT = Dichlorodiphenyltrichloroethane
9.9 x 10-2
1.2 x 10-3
7
3 x 100
1.
4.
4.9 x
.0 x 101
.9 x 101
100
Site Number
13, 15
13, 15
13
13
13
15
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 leachability and environmental attenuation factors.
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Table 6-3. Chemical-Specific TBCs for Surface Soils

Chemical Concentration (mg/L) Site Number
TBC*

Benzo(a)anthracene 1.0 x 10-1 13, 56
Benzo(a)pyrene 2.0 x 10-1 56
Benzo(b)fluoranthene 2.0 x 10-1 56
Benzo(g,h,i)perylene 2.8 x 10-3 13
Benzo(k)fluoranthene 2.0 x 10-1 62
Chrysene 2.0 x 10-1 56
Dibenzo(a,h)anthracene 3.0 x 10-1 56
Fluoranthene 4.2 x 101 (2) 13, 62
Indeno(l,2,3-cd)pyrene 4.0 x 10-1 13
Naphthalene 2.0 x 101 13, 62
Pyrene 9.6 x 102 (2) 13, 62
2,3,7,8-TCDD equivalent, total (1) 11, 69
Trichloroethene 5.0 x 100 57
Diesel 1.0 x 102 13, 39, 56, 62, 65
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Table 6-3. Chemical-Specific TBCs for Surface Soils (Continued)

Chemical Concentration (mg/L)
Arsenic
Barium
Cadmium
Chromium, Total
Lead

Manganese
Mercury
Zinc

TBC = to-be-considered material
mg/kg = milligrams per kilogram
Site Number

5.0 x 102 13, 56
1.0 x 104 69
5.0 x 101 62
5.0 x 102 65
1.5 x 102 13, 20, 39, 56, 62, 65

5.0 x 102 69
2.0 x 101 13, 20
5.0 x 105 13, 20, 62, 69

TCDD = tetrachlorodibenzo-p-dioxin
* The Designated Level Methodology (DLM) value varies with site conditions (e.g., depth to groundwater)
and appropriate water guality 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 leachability and environmental attenuation factors.

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

(1) A leachability factor was not assigned and the total designated level was not calculated.
(2) Water guality goal number for fluoranthene is 42 Og/1, California Inland Surface Waters Plan Numerical
Water Quality Objectives, Human Health Protection (30-day average) Sources of Drinking Water; pyrene
is 960 Og/1, United States Environmental Protection Agency Ambient Water Quality Criteria, Health and
Welfare Protection, Non-Cancer Public Health Effects.

The CVRWQCB Basin Plan [CVRWQCB 1995] for Sacramento-San Joaguin Basin contains chemical-specific
reguirements that pertain to the Mather AFB area. The Basin Plan [CVRWQCB 1995] designates the beneficial
uses of the groundwater in the Mather AFB area as domestic, municipal, irrigation, stock water, process, and
service supply waters. Based on these uses, narrative standards for taste and odor thresholds are ARARs, but
associated numerical goals are TBCs for these ARARs. The Basin Plan also establishes the following
gualitative chemical-specific ARARs based on the designated use(s) of the groundwater; the domestic or
municipal water supply shall not contain concentrations of chemical in excess of state reguired MCLs; and the
agricultural water supply shall not contain concentrations of constituents that adversely affect its
beneficial use. Table 6-5 lists the ARARs and TBCs for drinking water and groundwater.
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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
1.0 x 10-1
2.0 x 10-2
1.0 x 10-2
1.0 x 10-1
1.0 x 100
1.0 x 101

1.0 x 102
2.9 x 100
1.4 x 103
5.0 x 10-1

5.0 x 100
1.0 x 102
4,
5,
1,
1,
5,
1,
1,
2,
2,
.2
.0
.7
.7
.0
.5
.5
.0
.0
x
x
X
X
X
X
X
X
X
100
10-2
100
101
100
101
102
100
101
2.0 x 100
39, 54
62
13
13
13
7, 13, 20, 37, 39, 59, 62, 65

15, 56
39
62
7, 39, 54, 59, 65

59, 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 guality 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.
-------
Table 6-5. Chemical-Specific ARARs and TBCs for Drinking and Groundwater

Chemical Concentration (mg/L)

ARAR
Plumes
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
1.0 x 10-3
5.0 x 10-4
.0 x 10-3
.0 x 10-4
.0 x 10-3
.0 x 10-3
.0 x 10-3
.0 x 10-3
.0 x 10-3
.0 x 10-4
1.75 x 100
1.5 x 10-2
(1)
(1)
(1)
(1)
(1)
(1)
(2)
(2)
(2)
(1)
(1)
(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
Chioromethane
TPH as Diesel
TPH as Gasoline
TBC

3.0 x 10-3 (4)
1.0 x 10-1 (3)
5.0 x 10-3 (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 reguirement
(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.
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6.2 Location-Specific ARARs and TBCs

Location-specific ARARs and TBCs are requirements that place restrictions on the concentration of a COG 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 features considered were:

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

Of these unique site features, surface water occurs at or near: Site 13 (Drainaqe Ditch Number 1), Site 15
(Drainaqe 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 endanqered species, have been identified at Mather AFB. However, currently there has been no
documentation that there are wetlands likely to harbor endanqered species at or near any of the remedial
actions selected by this ROD. The existence of wetlands and endanqered species will be considered durinq
remedial desiqn to avoid or minimize impact durinq activities such as location of electrical conduit and
water pipes associated with qroundwater treatment systems. No other unique site features were identified.

6.2.1 Federal Location-Specific ARARs

The Endanqered Species Act and implementinq requlations at 50 CFR 17, 222, 226, 227, and 402, apply to some
of the remedial actions at Mather AFB, if they impact endanqered wildlife. These impacts may be identified
by a final bioloqical assessment findinq that the vernal pools on Mather AFB, do contain an endanqered
species. No vernal pools have been identified in 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
endanqered species; however, associated cleanup activities (i.e., construction of pipelines for qroundwater
injection) may impact habitat or critical resources. All activities must ensure that requlatory requirements
are followed and impacts avoided or mitiqated.

6.2.2 State Location-Specific ARARs

The Fish and Game Code Section 1600 requires that any work within the 100-year floodplain (consistinq of, but
not limited to, diversion or obstruction of the natural flow or chanqes in the channel, bed, or bank of any
river, stream or lake) will involve mitiqation 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.

6.3 Action-Specific ARARs and TBCs

Action-specific ARARs are technoloqy or activity-based requirements or limitations on actions taken with
respect to the hazardous waste. The followinq 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 qivinq
clarification to either their ARAR status or the leqal 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
requlations and the requlatory authority the aqencies 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 unigue characteristics such as depth, location of drinking water source, and material injected.
Forty CFR 144 - Underground Injection Control Program is the regulation listing the reguirements 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 reguirements for the safe handling of contaminated materials and precautions for
preventing further contamination.
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ARAR Status
Applicable
Applicable

Applicable
Federal ARARs
Applicable
US EPA established substantive requirements for actions that involve inj ection of fluids into
subsurface through wells. The injection can not cause a violation of primary MCLs, must be
maintained, must be monitored, and inj ection can not take place until the well construction is
complete.
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.
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)

22 CCR 66264.94(a)
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.
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ARAR Status
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)
6264 .117

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)

22 CCR 66264 .171

22 CCR 66264 .172

22 CCR 66264 .173

22 CCR 66264.174

22 CCR 66264 .175

22 CCR 66264 .176

22 CCR 66264 .177

22 CCR 66264 .178
Applicable
Applicable

Applicable
Applicable

Applicable

Applicable
Content of Closure Plan (22 66264.112(b)): All substantive steps reguired for closure of the facility
should be planned prior to beginning site activities. The time reguired for each step should be
estimated. Disposal or Decontamination of Eguipment, Structure and Soils (22 CCR 662624.114):
All contaminated eguipment, 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 eguipment.

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.
The chemicals removed 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 reguirements 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 adeguate secondary
containment for the waste stored (22 CCR 66264.175); containers must be closed during trans fer
(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.
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ARAR Status
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)
Delineates reguirements 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
Reguirements; Section 66264 . 254 . Monitoring and Inspection; Section 66264.256. Special
Reguirements for Ignitable or Reactive Waste; Section 66264.257. Special Reguirements for
Incompatible Wastes; Section 66264.258. Closure and Post-Closure Care; and Section 66264.259.
Special Reguirements for Hazardous Wastes F020, F021, F022, F023, F026, and F027.
22 CCR 66264.251

22 CCR 66264.254

22 CCR 66264.256

22 CCR 66264.257

22 CCR 66264.258

22 CCR 66264.259
Applicable

Applicable

Applicable
If during excavation, treatment processes, or cleanup activities, hazardous wastes 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.
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)

22 CCR 66264 .552
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
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 reguirements 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.

Applicable

Applicable
Provides the purpose, scope, and applicability of LDRs. The title 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 .

22 CCR 66268.30
22 CCR

Title 22, Division 4.5 (Environmental
Health Standards for Management of
Hazardous Waste), Chapter 18 (Land
Disposal Restrictions), Article 4
(Treatment Standards)
Applicable

Applicable

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-sped fie 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 662 68.34. 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.
These standards are applicable to sites where excavated materials are classified as hazardous waste
and are disposed or treated in an area not designated as a CAMU. Provides treatment standards
expressed in contaminant concentrations in Section 662 68.41. 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.
Applicable
If during excavation, treatment processes, or cleanup activities hazardous wastes 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.
Applicable
-------
ARAR Status
Health Standards for Management of
Hazardous Waste), Chapter 18 (Land
Disposal Restrictions), Article 5
(Prohibitions on Storage)
as Listed
Below
Applicable
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.
State of California Air ARARs
Applicable
The most effective mission control device, emission limit, or technigue, singly or in combination.
which has been reguired or used for the type of eguipment comprising such an emissions unit unles;
the applicant demonstrates to the satisfaction of the SMAQMD that such limitations reguired 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 eguipment, fuel process,
emission control device, or technigue, singly or in combination, determined to be technically
feasible and cost-effective by the SMAQMD.
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.
-------
ARAR Status
ROG 150 Ibs/day
NOx 150 Ibs/day
SOx 150 Ibs/day
PM10 80 Ibs/day
CO 550 Ibs/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.
This requlation will apply to the treatment processes that release or cause to be released the
pollutants listed in the requlation. The remedial alternatives utilizinq 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
California
Clean Air Act
Applicable
This rule prohibits the discharqe of air contaminants in quantities which cause inj ury, detriment,
nuisance, or annoyance to any considerable number of persons or which endanqers the comfort,
response, health, or safety of any such person or which causes or has natural tendency to cause
inj ury or damaqe to business or property.
SMAQMD, Rule 403
Applicable
California
Clean Air Act
Applicable
-------
ARAR Status
Applicable
Federal Clean
Water Act
Federal Clean
Water Act
40 CFR 122 - USEPA Administered
Permit Programs: The National
Discharge Elimination System
40 CFR 122 - USEPA Administered
Permit Programs: The National
Discharge Elimination System

40 CFR 122.41(d)

40 CFR 122.41(e)

40 CFR 122.44 (d)
Applicable

Applicable

Applicable
All reasonable steps must be taken to minimize or prevent discharges which have a reasonable
likelihood of causing adverse impacts on surface water guality (40 CFR 122.41(d)). All eguipment
and facilities must be properly operated and maintained, including adeguate laboratory controls and
appropriate guality assurance procedures (40 CFR 122.41(e)). Discharges into surface water must
achieve federal and state water guality standards (40 CFR 122.44(d)).
Storm-water discharges from construction sites must meet pollutant limits and standards. The
narrative effluent standard includes the reguirements 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.
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 reguired for
installation of a groundwater extraction and treatment system.
-------
ARAR Status
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 proper
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.
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections 13000,
13140, 13240)
Applicable
Establishes water guality obj ectives, 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.
Control Act
(California
Water Code
Sections 13000 ,
13140, 13240)
Applicable
The resolution establish reguirements for activities involving discharges of contamination directly
into surface waters or groundwater (e.g. guality of pump and treat effluent into surface waters or
groundwater).
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.
Conseguently, 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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ARAR Status
(California
Water Code
SWRCB Resolution 92-49
(as amended April 21, 1994)
Subparagraph IIIG
Section IIIG directs the Water Boards to ensure discharges clean up and abate the "effects" of
discharges in a manner promoting attainment of either background water guality of the best
reasonable water guality if background guality 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 15, Section 2550.4 in approving any
alternative cleanup levels less stringent than background guality and to apply 23 CCR Chapter 16,
Section 2725 for alternatives cleanup levels for remediation of releases from USTs.
The reguirement to obtain the Water Board's approval is not an ARAR; however, the Air Force will
consult with the Water Board and US EPA in applying the State's criteria to establish alternative
cleanup levels.
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)
Relevant and
Appropriate
Subj ect to the limitations described above, this reguirement is relevant and appropriate for
establishing levels for effects to surface and groundwater guality caused by releases of
contaminants.

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 reguired to develop
and implement a monitoring program in accordance with Article 5 of this Chapter. If water guality
impairment is found, such persons may be reguired 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.
Appropriate 2
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ARAR Status
(California
Water Code
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 2 (Waste Classification
and Management)
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 in 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.
Applicable to
Site 7
Reguires 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 ro 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. reguire a higher level of containment than provided by the unit;
b. are restricted 'hazardous wastes'; or
c. impair the integrity of containment structures.
Reguires management of liguids at classified waste management units.
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ARAR Status
(California
Water Code
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)
Applicable4,5
Applicable4,£
Classification and Siting Criteria (23 CCR 2530 (c & d) ) : New waste piles should 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.
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 4 (Construction
Standards)
Relevant and
Appropriate to
Reguires 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 reguired permeability when installed.
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ARAR Status
(California
Water Code
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
These provisions of Chapter 15 address remediation of contamination at waste management units
and monitoring of groundwater guality during the remedial action. The corrective action program
reguires that the cleanup obj ectives 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
reguires showing that 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 reguirements regarding the designation of monitoring parameters and
monitoring freguency.

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) reguires that a groundwater monitoring program be implemented in
conj unction with a corrective action to demonstrate the effectiveness of the remedial technologies.
Both monitoring programs must meet the reguirements 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 guality (23 CCR 2550.4). It has been determined that
cleanup to background is not economically feasible and therefore not relevant and appropriate to
aguifer cleanup standards.
Reguires 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 reguired. Also reguires monitoring to determine the effectiveness of
corrective actions. To demonstrate cleanup, the concentration of each COC in the groundwater
must be egual 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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ARAR Status
(California
Water Code
Title 23 (Waters), Division 3 (State
Water Resources Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 8 (Closure and
Post-Closure Maintenance)
Applicable
General Closure Requirements; partial or final closure of classified waste management units must
include continued maintenance of waste contaminant, 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 reguire 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 guality.

This regulation applies to Site 7.
Porter-Cologne
Water Quality
Control Act
(California
Water Code
Sections
13140-13147,
13172, 13260
13263, 13267,
13304)
Title 23 (Waters), Division 3 (State
Water Resource Control Board),
Chapter 15 (Discharges of Waste to
Land), Article 9 (Compliance
Procedures)
Applicable to
Site 7
Applicable to
Site 7
Procedures for closure and post-closure maintenance must be developed. The magnitude of
settlement due to waste decomposition 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.
California Inte-
grated Waste
Management
Act of 1989
PRC 40502,
43020, 43021
and 43030
Title 14 (Natural Resources), Division
(California Integrated Waste
Management Board), Chapter 3
(Minimum Standards for Solid Waste
Handling and Disposal), Article 7.3
(Disposal Site Records)

14 CCR 17646
Applicable
Applicable
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ARAR Status
California Inte-
grated Waste
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 7.4
(Disposal Site Improvements)
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 176
14 CCR 17684
14 CCR 17689

14 CCR 17690

14 CCR 17691

14 CCR 17692
Applicable

Applicable

Applicable
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.
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ARAR Status
California Inte-
grated Waste
Management
Act of 1989
PRC 40502,
43020, 43021
and 43030
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 17711

14 CCR 17713

14 CCR 17741
Applicable

Applicable

Applicable
Liter 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.
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ARAR Status
California
Integrated
Waste
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)

14 CCR 17766
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 as considered
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).
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).
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 guality of the
construction material (14 CCR 1773 (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 eguivalent protection against water guality impact (14 CCR 17773 (b, c, d, e)).
-------
ARAR Status
California
Integrated
Waste
CQA: A CQA program must be designed and implemented. It must
(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
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,
c[portions])).
-------
ARAR Status
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 reguirements. 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 reguirements j
23 CCR 2546(d) (14 CCR 17778(a, c-j).
Relevant and
Appropriate
Relevant and
Appropriate
Relevant and
Appropriate
14 CCR 17781
Relevant and
Appropriate
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) .
Relevant and
Appropriate
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 closures 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).
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ARAR Status
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)

14 CCR 18222
Relevant and
Appropriate
Provides the minimum standards for closure of a solid waste disposal site (Section 182 62.3.
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.
Report of Disposal Site Information: The planning and procedural reguirements necessary to ensure that solid
waste is handled and disposed in manners that protect public health and safety and the environment must be
conducted.
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)
Provides the minimum standards for closure of a solid waste disposal site (Section 182 62.3.
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, 988.
-------
ARAR Status
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
ARAR = applicable or relevant and appropriate reguirement
DWQ = Department of Water Quality
SMAQMD = Sacramento Metropolitan Air Quality Management District
CERCLA = Comprehensive Environmental Response, Compensation, and Liability Act
BMP = Best Management Practice
UST = underground storage tanks
SOx = sulfur oxide
ppm = parts per million
COC = contaminant of concern SAC = Strategic Air Command
BACT = Best Available Control Technology
SWRCB = State Water Resource Control Board
CQA = Construction Quality Assurance
LDR = land disposal restrictions
PM10 = particulate matter
ppb = parts per billion
1. Only as invoked through 23 CCR 2511 (d) for action intended to contain waste in place.
2. 23 CCR 2511 (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 2"
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 2511 (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 for 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 - Prohibition
on Land Disposal; Article 4 - Treatment Standards; and Article 5 - Prohibitions on Storage.

6.3.1.1 Other Federal Regulations

The TSCA delineates the reguirements for excavation of PCBs and sampling activities associated with PCB
removal through 40 CFR Part 761. These reguirements 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
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 reguirements 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 reguirements 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 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 reguirements 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 reguirements for stormwater management at industrial sites (SWRCB Order 92-13-DWQ) and
construction sites (SWRCB Order 92-08-DWQ). The substantive reguirements for industrial sites are meeting
the narrative water guality standards, implementing best management practices, identifying and monitoring
sources of stormwater pollutants, and eliminating non-stormwater sources of pollutants. The substantive
reguirements 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 qroundwater. The
California Water Code sections used as a source for action-specific ARARs and TBCs are presented in Table 6-6
alonq 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 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 stated 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 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 COG 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
Standard for Injection into
Noncontaminated Portions of the
Aquifer Based on State Board
Resolution 68-16 (Og/1)
Daily Maximum
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 (Og/1)

State or Federal MCLs
Daily Maximum
Main Base/SAC Ind. Plume
Benzene
CC14
Chioromethane
1,2-DCA
1,1-DCE
Cis-l,2-DCE
Lead
PCE
TPH-G
TPH-D
TCE
Xylene
A 1.0 (CA-MCL)
B2 0.5 (CA-MCL-PQL)
C 3.0 (SNARL)
B2 0.5 (CA-MCL PQL)
C 6.0 (CA-MCL)
D 6.0 (CA-MCL)
15.0 (FMCL)
B2 5.0 (FMCL)
50.0 (PQL)
100.0 (US EPA HA)
B2 5.0 (FMCL)
D 17.0 (TO)
Site 7 Plume
Benzene
Chioromethane
1,2-DCA
1,1-DCE
Cis-l,2-DCE
1,4 - DCB
PCE
TPH-D
TCE
Vinyl Chloride
6)
C
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 (FCML)
100.0 (US EPA HA)
5.0 (FMCL)
0.5 (CA MCL PQL)
California Environmental Protection Agency (CA EPA), Cancer Potency Factor as a Water Quality Criterion =
CA EPA, Cancer Potency Factor as a Water Quality Criterion = 0.23 Og/1, USEPA IRIS = 0.3 Og/1
CA EPA, Cancer Potency Factor as a Water Quality Criterion = 0.5 Og/1, USEPA IRIS = 0.4 Og/1
CA EPA, Cancer Potency Factor as a Water Quality Criterion = 0.69 Og/1, USEPA IRIS = 0.7 Og/1
CA EPA, Cancer Potency Factor as a Water Quality Criterion = 2.3 Og/1, USEPA IRIS = 3.0 Og/1
CA EPA, Cancer Potency Factor as a Water Quality Criterion =0.13 Og/1, USEPA IRIS = 0.015 Og/1
CA EPA, Cancer Potency Factor = 0.88 Og/1
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 CC14 = carbon tetrachloride
PCE = tetrachloroethene TCE = trichloroethene DCA = dichloroethane DDE = dichloroethene
TPH-G = total petroleum hydrocarbons as gasoline TPH-D = total petroleum hydrocarbons as diesel Og/1 = micrograms per liter
A = Known human carcinogen; sufficient epidemiologic evidence in humans. B2 = Probable human carcinogen; limited epidemiologic evidence in humans.
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 92049 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 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 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 of 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 of 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 "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 SWRCB
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.
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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, Integrate 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 reguirements and applicability to either the sites, remedial action, or
technology used to cleanup the site and contaminated material.

The reguirements 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 reguirements in effect at the time; and
! currently poses no threat to human health and the environment

The reguirements 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) (1-5) as long as the site presents an unacceptable risk to human health and
the environment. 14 CCR 17796(c) reguires 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 and Fish Game Code regulates to protect aguatic 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 reguirements 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 guality. The Basin Plan reguires 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:

! establishing background groundwater 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 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
contaminated soil; six inch sand layer, or a three inch sand layer and
three inches of recycled drainage rock; geotextile fabric; 30 mil PVC
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liner; geotextile fabric over 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 times 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
reguirements 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 reguirements established by the DTSC. Additionally, wastes that
could potentially impair the integrity of containment structures, reguire 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
liguid, semi-solid waste (waste containing less than 50 percent solids), or
solid waste containing free liguid or moisture in excess of the waste's
moisture holding capacity to the bioremediation cell.

The discharge of designated solid or liguid waste or leachate to surface
water, surface water drainage courses, ponded water, or groundwater that
would cause impairment to water guality is prohibited.
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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,
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 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 egual 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
1 mg/L
Median Concentration is non-detect
Maximum Concentration is 5 mg/kg
430 mg/kg
Armoatic Hydrocarbons
Benzene

Ethylbenzene

Toluene

Xylene
Polycyclic Aromatic Hydrocarbons
Benzo(a)Anthracene
Benzo(a)Pyrene
Benzo(b)Fluoranthene
Benzo(k)Fluoranthene
Chrysene

Toxic Metals
Lead
Organic Lead
Manganese
Chromium

TPH-D = total petroleum hydrocarbon as diesel
TPH-G = total petroleum hydrocarbon as gasoline
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
0.01 mg/L
0.02 mg/L
0.02 mg/L
0.02 mg/L
0.02 mg/L
1.5 mg/L
0.5 mg/kg
0.5 mg/L
0.5 mg/L

mg/kg = milligrams per kilogram
mg/L = milligrams per liter
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! 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.

• 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 liguids, 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.

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 8, 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 necessary to implement planned remedial response actions in accordance with
the ROD for the Soil OU sites and Groundwater OU plumes.

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
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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 reguirements
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 alignments, 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.

Response:

The comment proposes using a memorandum of understanding that would allow Sacramento County to assist in
investigation 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.
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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-H111, Inc., 1982, "Installation Restoration Program Records Search (Phase 1)," CH2M-H111, Inc.,
Gainesville, Florida.

Central Valley Region 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 Joaguin
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.

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) , 1990b, "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.

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
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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 Corporations.

IT Corporation (IT), 1993f, "Background Inorganic Soils for Mather Air Force Base," IT Corporation,
Albuquergue, 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.

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 (IT), 1996a, "Draft Technical Information Report on Soil Vapor 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 (IT), 1996b, "Draft Additional Site Characterization and Final Basewinde Operable Unit
Remedial 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.
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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.

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

Weston, Roy F. , Inc. (Weston), 1986, "Installation Restoration Program Phase II - Confirmation/Quantification
Stage 1 Final Report," Volumes 1 and 2, Roy F. Weston, Inc., West Chester.
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