PB97-964507
EPA/541/R-97/129
January 1998
EPA Superfund
Record of Decision:
Moffett Naval Air Station, OU 1
Sunnyvale, CA
8/14/1997
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MOFFETT FEDERAL AIRFIELD
FINAL OPERABLE UNIT 1
RECORD OF DECISION
(Pursuant to the Comprehensive Environmental Response,
Compensation, and Liability Act)
August 1, 1997
Issued By:
U.S. Department of the Navy - Engineering Field Activity West
Naval Facilities Engineering Command
and
U.S. Environmental Protection Agency
Region 9 - San Francisco, California
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PRC Environmental Management, Inc.
1099 18th Street
Suite 1960
Denver, CO 80202
303-295-1101
Fax 303-295-2818
nnc
August 25, 1997
Mr. Stephen Chao/Mr. Hubert Chan
Department of the Navy
Engineering Field Activity West
Naval Facilities Engineering Command
900 Commodore Drive, Building 210
San Bruno, California 94066-5006
CLEAN Contract Number N62474-88-D-5086
Contract Task Order 0236
Subject: Final Operable Unit 1 Record of Decision, Moffett Federal Airfield
Dear Messrs. Chao and Chan:
Enclosed is the final version of the Final Operable Unit 1 Record of Decision (ROD) prepared
by PRC Environmental Management, Inc. (PRC) for your records. Copies have been
distributed to the regulatory agencies, project staff, and other interested parties.
If you have any questions, please call me at (303) 312-8874.
Sincerely,
TimotbylJ. Mower
Project Manager
TEM/jem
Enclosures
cc: Distribution List
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FINAL OPERABLE UNIT 1
RECORD OF DECISION
MOFFETT FEDERAL AIRFIELD
DISTRIBUTION LIST
Contact Number of Copies
Mr. Stephen Chao/Mr. Hubert Chan, EFA West 3
Mr. Marvin Norman, EFA West 1
Mr. Michael Gill, EPA 2
Ms. Danita Yocom, EPA 1
Mr. Joseph Chou, DTSC 2
Ms. Frances McChesney, DTSC 1
Mr. Michael Rochette, RWQCB 1
Mr. Glenn Young, IWMB 1
Mr. Don Chuck, MFA 1
Ms. Deb Judy, PRC 1
Mr. Bill Westerfield, PRC 1
Mr. Kenneth Eichstaedt, URS 1
Ms. Sandy Olliges, NASA 1
Ms. Tina Pelley, SAIC 1
Mr. Peter Strauss 1
Mr. Ted Smith, SVTC (letter only)
Mr. Alex Terrazas, City of Mountain View 1
Mr. Stewart McGee, City of Sunnyvale 1
Dr. James McClure, HLA 1
Ms. Ingrid Chen, Raytheon 1
Mr. Dennis Curran, Locus 1
Mr. V. Thomas Jones, Schlumberger 1
Mr. David Glick, RAB Co-chair 1
RAB THE Committee (c/o Dr. James McClure) 5
Administrative Record 2
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CONTENTS
Section Page
1.0 DECLARATION STATEMENT FOR OPERABLE UNIT 1 1
2.0 DECISION SUMMARY FOR OPERABLE UNIT 1 6
2.1 SITE NAME, LOCATION, AND DESCRIPTION 6
2.2 SITE HISTORY 9
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION 12
2.4 SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY 15
2.5 SITE CHARACTERIZATION 15
2.5.1' Site 1 Characteristics 16
2.5.2 Site 2 Characteristics 18
2.5.2.1 Summary of Site 2 Characteristics Based on OU1 RI/FS
Activities 19
2.5.2.2 Summary of Site 2 Characteristics Based on New Information 21
2.6 SUMMARY OF SITE RISKS 22
2.6.1 Human Health Risk Assessment; 22
2.6.2 Ecological Assessment Summary 25
2.7 DESCRIPTION OF THE ALTERNATIVES 28
2.7.1 Description of Alternatives Presented in the FS 28
2.7.1.1 Alternative 1: No Action 28
2.7.1.2 Alternative 2: Native Soil Cap, Trench Vent 29
2.7.1.3 Alternative 3: Multilayer Cap, Trench Vent 35
2.7.2 Description of Consolidation Alternative 37
2.8 SUMMARY OF COMPARATIVE ANALYSIS 39
2.8.1 Remedial Alternatives Evaluation Criteria 39
2.8.1.1 Threshold Criteria 39
2.8.1.2 Balancing Criteria 39
2.8.1.3 Modifying Criteria 40
2.8.2 Comparative Analysis of Site 1 Alternatives 40
2.8.2.1 Site 1 Alternatives and the Threshold Criteria 40
2.8.2.2 Site 1 Alternatives and the Balancing Criteria 41
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CONTENTS (Continued)
Section gage
2.8.2.3 Site 1 and the Modifying Criteria 44
2.8.2.4 Results of Site 1 Comparative Analysis 45
2.8.3 Comparative Analysis of Site 2 Alternatives 46
2.8.3.1 Site 2 Alternatives and the Threshold Criteria 46
2.8.3.2 Site 2 Alternatives and the Balancing Criteria 46
2.8.3.3 Site 2 Alternatives and the Modifying Criteria 50
2.8.3.4 Site 2 Comparative Analysis Results 51
2.9 DOCUMENTATION OF SIGNIFICANT CHANGES 52
2.9.1 Significant Changes to Alternative 2 Cap Design 52
2.9.2 Significant Change from Capping to Consolidation for Site 2 55
2.10 SELECTED REMEDY 55
2.11 STATUTORY DETERMINATIONS 57
2.11.1 Protection of Human Health and the Environment 59
2.11.2 Compliance with ARARs -. 60
2.11.2.1 Chemical-Specific ARARs 66
2.11.2.2 Location-Specific ARARs 66
2.11.2.3 Action-Specific ARARs 71
2.11.2.4 CAMU Designation Criteria and Specific Information 75
2.11.3 Cost-Effectiveness 82
2.11.4 Utilization of Permanent Solutions 82
2.11.5 Preference for Treatment 82
3.0 RESPONSIVENESS SUMMARY 83
3.1 JUNE 1995 PUBLIC MEETING COMMENTS AND RESPONSES 84
3.2 JUNE 1995 WRITTEN COMMENTS AND RESPONSES 91
3.2.1 Comments from the City of Sunnyvale 91
3.2.2 Comments from the City of Mountain View 107
3.2.3 Comments from the RAB Cost Committee, compiled by Christina Scon,
Committee Chairperson 107
3.2.4 Comments from the RAB Technical, Historical, and Educational
Committee, compiled by Jim McClure, Committee Chairperson 110
3.2.5 Comments from the Santa Clara Valley Water District, compiled by
Thomas I. Iwamura, Engineering Geologist 121
3.2.6 Comments from RAB Members 128
3.2.7 Comments from the League of Women Voters 137
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CONTENTS (Continued)
Section Page
3.2.8 Comments from the Silicon Valley Toxics Coalition 147
3.2.9 Comments from Santa Clara County Environmental Resources Agency 164
3.2.10 Comments from the National Aeronautics and Space Administration 166
3.2.11 Comments from California Integrated Waste Management Board 167
3.2.12 Other Written Comments 173
3.3 JANUARY 1996 PUBLIC MEETING COMMENTS AND RESPONSES 178
3.4 JANUARY 1996 WRITTEN COMMENTS AND RESPONSES 182
3.4.1 Comments from the City of Mountain View 182
3.4.2- Comments from California Integrated Waste Management Board 183
3.5 MARCH 1997 PUBLIC MEETING COMMENTS AND RESPONSES 184
3.6 MARCH 1997 WRITTEN COMMENTS AND RESPONSES 184
3.6.1 Comments from the City of Mountain View 184
3.6.2 Comments from Mr. Thomas Iwamura, SCVWD 186
4.0 REFERENCES 187
HI
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CONTENTS (Continued)
FIGURES
Figure Page
1 REGIONAL LOCATION MAP 7
2 RI/FS SITES 13
3 SITE 2 LOCATION MAP 23
4 CONCEPTUAL DIAGRAM OF ALTERNATIVE 2 31
5 GAS AND GROUNDWATER COLLECTION TRENCHES 33
6 CONCEPTUAL DIAGRAM OF ALTERNATIVE 3 36
7 REVISED CAP CONFIGURATION 54
8 SITE 1 CAMU LOCATION MAP 70
TABLES
Table Page
1 ARARS FOR SELECTED ALTERNATIVE 62
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ACRONYMS AND ABBREVIATIONS
ARAR Applicable or relevant and appropriate requirement
AWQC Ambient water quality criteria
BCDC Bay Conservation and Development Commission
bis Below land surface
BRAC Base realignment and closure
Caltrans California Department of Transportation
Cal/EPA California Environmental Protection Agency
CAMU Corrective Action Management Unit
CBCEC California Base Closure Environmental Committee
CCR California Code of Regulations
CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
CFR Code of Federal Regulations
CIWMB California Integrated Waste Management Board
CLEAN Comprehensive Long-term Environmental Action Navy
cm/sec Centimeters per second
COE U.S. Army Corps of Engineers
COPC Chemical of potential concern
CPT Cone penetrometer test
CRC Coastal Resources Coordination
CRP Community relations plan
DFG State of California Department of Fish and Game
DoD Department of Defense
DTSC California EPA Department of Toxic Substances Control
EFA West Engineering Field Activity West
EPA U.S. Environmental Protection Agency
ESD Explanation of significant differences
FFA Federal Facilities Agreement
FS Feasibility study
FWS U.S. Fish and Wildlife Service
i
HELP Hydrologic Evaluation of Landfill Performance
HLA Harding Lawson Associates
HP HydroPunch
HTA heavier-than-air
IAS Initial Assessment Study
IRP Installation Restoration Program
IT International Technology Corporation
LDR Land disposal restriction
LEA Local enforcement agency
LEL Lower explosive limit
LGCW Landfill gas characterization well
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ACRONYMS AND ABBREVIATIONS (Continued)
LGMW Landfill gas monitoring well
LTA Lighter-than-air
LWV League of Women Voters
MCL Maximum contaminant level
MEK Methyl ethyl ketone (2-butanone)
MEW Middlefield, Ellis, and Whisman
Tg/kg Micrograms per kilogram
Tg/L Micrograms per liter
mg/kg Milligrams per kilogram
mg/L Milligrams per liter
MOU Memorandum of understanding
msl Mean'sea level
MTR Minimum technology requirement
NAS Naval air station
NASA National Aeronautics and Space Administration
NAVFAC Naval Facilities Engineering Command
NBA North base area
NCP National Oil and Hazardous Substances Pollution Contingency Plan
NEESA Naval Energy and Environmental Support Activity
NEPA National Environmental Policy Act
NEX Naval exchange
NOAA National Oceanic and Atmospheric Administration
NMOC Nonmethane organic compound
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
NWP Nationwide Permit
O&M Operation and maintenance
OU Operable unit
PAH Polynuclear aromatic hydrocarbon
ppb Parts per billion
PCB Polychlorinated biphenyl
PG&E Pacific Gas and Electric Company
POTW Publicly owned treatment works
PPE Personal protective equipment
PRC PRC Environmental Management, Inc.
QA/QC Quality assurance and quality control
RAB Restoration advisory board
RAO Remedial action objective
RCRA Resource Conservation and Recovery Act
RD/RA Remedial design and remedial action
RI/FS Remedial investigation and feasibility study
ROD Record of decision
RWQCB California Regional Water Quality Control Board, San Francisco Bay Region
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ACRONYMS AND ABBREVIATIONS (Continued)
SARA Superftmd Amendments and Reauthorization Act
SCVWD Santa Clara Valley Water District
SMHM Salt marsh harvest mouse
SVOC Semivolatile organic compound
SVTC Silicon Valley Toxics Coalition
SWAT Solid Waste Assessment Test
SWRCB State Water Resources Control Board
SWRP Stormwater retention pond
TAG Technical assistance grant
TCE Trichloroethene
TDS Total dissolved solids
T&E Threatened and endangered
THE Technical, Historical, and Educational
TPH Total petroleum hydrocarbons
TRC Technical Review Committee
USC United States Code
USCS Unified Soil Classification System
UST Underground storage tank
VOC Volatile organic compound
WQPS Water quality protection standard
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1.0 DECLARATION STATEMENT FOR OPERABLE UNIT 1
Site Name and Location
Moffett Federal Airfield (formerly Naval Air Station Moffett Field) Mountain View, California
This federal facility is on the National Priorities List (NPL). Moffett Federal Airfield (Moffett Field)
has been closed as an active military facility under the Base Realignment and Closure (BRAC)
program. Control of base operations was transferred to the National Aeronautics and Space
Administration (NASA) on July 1, 1994.
Statement of Basis and Purpose
This decision document presents the selected remedial action for Operable Unit 1 (OU1) at Moffett
Field. OU1 consists of two landfills (Sites 1 and 2); the selected remedial action for Site 2 is
consolidation of waste from Site 2 to Site 1 and groundwater monitoring and for Site 1 is capping, gas
and groundwater collection trenches, and gas and groundwater monitoring. The remedial action (RA)
was chosen in accordance with the Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA), as amended by the Superfund Amendments and Reauthorization Act
(SARA), and to the extent practicable with the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is supported by information contained in the administrative
record for OU1. The U.S. Environmental Protection Agency (EPA) and the State of California
Environmental Protection Agency concur with the selected remedy.
Assessment of Site
Actual or threatened releases of hazardous substances from OU1, if not addressed by implementing the
response action selected in this record of decision (ROD), may present a current or potential threat to
public health, welfare, or the environment.
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Description of the Selected Remedy
The selected response action addresses the principal threat posed by the site through consolidation and
containment of wastes. The major components of the selected response action include:
1. Consolidating wastes from the Site 2 landfill to the Site 1 landfill in accordance with
substantive provisions of Title 23 California Code of Regulations (CCR) Chapter 15,
backfilling and restoring Site 2, and designating the Site 1 landfill as a corrective action
management unit (CAMU) in accordance with 22 CCR, Division 4.5, Chapter 14,
Article 15.5, Section 66264.552. Containers of hazardous wastes excavated at Sites 1
and 2 will be characterized and shipped off site for disposal.
2. Capping the Site 1 landfill hi accordance with California Solid Waste Management
Regulations, in CCR, Title 14 - Natural Resources, Division 7, Chapter 3, Article 7.8
- Disposal Site Standards, Closure and Postclosure (14 CCR) and 23 CCR Chapter 15
or federal regulations in 40 Code of Federal Regulations (CFR) 258.60, whichever are
more stringent.
3. Conducting groundwater monitoring at Sites 1 and 2 in accordance with provisions of
14 CCR and 23 CCR Chapter 15. Conducting groundwater monitoring at Site 2 for a
minimum period of 3 years after Site 2 waste is consolidated at Site 1 to ensure
groundwater at Site 2 is not adversely affected. Pursuant to 23 CCR, Chapter 15,
Article 5, Section 2550.4, the Navy will derive and propose concentration limits for
each constituent of concern. Federal ambient water quality criteria (AWQC) and
RWQCB Basin Plan water quality objectives will be considered in deriving the
concentration limits.
4. Installing a subsurface groundwater collection trench along the northern border of
Site 1 to intercept potential future leachate migration before it reaches surface water, if
necessary. If groundwater monitoring data exceed the criteria derived in accordance
with 23 CCR Chapter 15, Article 5 (item 3 above), the Navy will immediately notify
the regulatory agencies and will evaluate the groundwater contamination in accordance
with CERCLA, and will obtain concurrence from EPA and the State on remediation
decisions.
5. Conducting landfill gas monitoring at Site 1 in accordance with applicable provisions of
14 CCR and 23 CCR Chapter 15.
6. Installing a passive gas venting trench along the western boundary of Site 1 to prevent
off-site, subsurface migration of landfill gases.
7. Conducting postclosure maintenance activities at Site 1 in accordance with applicable
provisions of 14 CCR and 23 CCR Chapter 15 or 40 CFR 258.61, whichever is more
stringent.
8. Institutional controls - Fencing, signs, operation and maintenance (O&M) of Building
191 pump station and drain/subdrain system, and restrictions on cap disturbances. The
Navy will resolve any issues with NASA regarding the process to develop appropriate
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restrictive provisions to ensure continued O&M of the Building 191 pump station and
to maintain the integrity of the Site 1 cap. The Navy will enter into an agreement with
NASA or develop another appropriate vehicle to accomplish this task. The Navy will
resolve any issues concerning the necessary restrictive provisions within 1 year of the
date of this ROD.
OU1 remedy selection is consistent with overall remedial investigation and feasibility study (RI/FS)
activities at Moffett Field. The selected response actions described in this ROD will address the source
of contamination by containing on-site wastes. The response action will reduce Sites 1 and 2 as
sources to groundwater contamination by consolidating the waste material located above and below the
water table at Site 2 to Site 1 and by capping Site 1. Consolidation and capping also reduce the risk
associated with exposure to contaminated materials. In addition, because of the proximity of surface
water to the northern boundary of the Site 1 landfill, the selected remedy also includes construction of
a groundwater collection trench as a contingency measure to provide immediate protection to this
adjacent surface water (component 4 above). Qualified professionals will be used to conduct the work
required by this ROD.
Groundwater within the subsurface collection trench will be monitored at the same frequency as at the
Site 1 groundwater monitoring wells. If chemical concentrations exceeding concentration limits set
pursuant to 23 CCR Chapter 15 Article 5 are observed, the Navy will immediately notify the
regulatory agencies and will evaluate the groundwater contamination in accordance with CERCLA, and
will obtain concurrence from EPA and the State on remediation decisions. Potential actions may
include additional or more frequent sampling or groundwater extraction and treatment, depending on
the nature and levels of the chemicals detected.
The collection trench can be activated if, based on the monitoring data and the consultation process
described above, the groundwater poses a threat to ecological receptors. OU1 includes surrounding
groundwater, however, the remedy does not include active leachate extraction or active groundwater
remediation. Groundwater monitoring will be conducted at Site 2 in accordance with provisions of 23
CCR Chapter 15. Monitoring will occur for a minimum of 3 years to confirm that groundwater
contamination is no longer a concern and to provide data to support discontinuation of groundwater
monitoring at Site 2. Groundwater monitoring will continue at Site 1 during the postclosure period
and, should groundwater become contaminated by the landfill in the future and require remediation, the
collection trench can be activated as an initial, immediate response. Implementing the collection trench
will protect surface water while allowing time to implement a more permanent remedy, if necessary.
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Any groundwater contamination exceeding federal AWQC or RWQCB basin plan water quality
objectives will be evaluated in accordance with CERCLA.
If it becomes necessary to collect, treat, and discharge leachate, any means of discharge must comply
with the substantive requirements of applicable or relevant and appropriate requirements (ARARs) if
the discharge is on site (such as to Marriage Road Ditch, North Patrol Road Ditch, or the stormwater
retention pond), or be subject to a permit if the discharge is off site (such as to a publicly owned
treatment works [POTW]). An explanation of significant differences (BSD) or ROD amendment will
be prepared, as appropriate, for the collection, treatment, and discharge of leachate. Prior to adoption
of the BSD or ROD amendment, the Navy will solicit federal and state ARARs and will comply with
CERCLA public participation requirements. The Navy will obtain concurrence from EPA and the
State on remediation decisions.
The OU1 remedy includes O&M of the Building 191 pump station and drain/subdrain system. This
pump station and associated drainage system support the Moffett Federal Airfield storm drainage
system. Currently, pumping at Building 191 influences groundwater gradients, as the drainage system
that feeds the pump station is below the water table in some areas. At Site 1, the regional groundwater
gradient is reversed by Building 191 pumping, as the groundwater flows from north to south (away
from San Francisco Bay). At Site 2, the groundwater gradient is south to north, which is normal. The
gradient is steeper, however, as a result of pumping at Building 191. Should Building 191 O&M
discontinue, the northern portion of Moffett Federal Airfield (including OU1) may be prone to
flooding. Therefore, O&M of the pump station was included as a component of the remedy to prevent
potential flooding of the OU1 landfill areas. The need for continued Building 191 O&M will be
referenced in appropriate land use documents and federal real property records, along with restrictive
provisions to maintain the integrity of the Site 1 cap. The Navy will resolve any issues with NASA
regarding the process to develop appropriate restrictive provisions to ensure continued O&M of the
Building 191 pump station and to maintain the integrity of the Site 1 cap. The Navy will enter into an
agreement with NASA or develop another appropriate vehicle to accomplish this task. The Navy will
resolve any issues concerning the necessary restrictive provisions within 1 year of the date of this
ROD.
This OU is one of four active OUs at Moffett Field. Other OUs where concurrent RI/FS activities have
occurred include OU2-East (soils at Sites 3, 4, 6, 7, 10, 11, and 13), OU5 (east-side aquifers), and
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OU6 (wetland areas). A station-wide RI/FS which addresses all sites is also underway. Other activities
are being conducted as source control measures for the west-side aquifers and soils and through
corrective measures for petroleum sites. All investigations, remedial designs, and schedules are
coordinated to provide an overall basewide management strategy for cleanup.
Statutory Determinations
The selected remedy is protective of human health and the environment, complies with federal and state
requirements that are applicable or relevant and appropriate to the remedial action, and is cost-
effective. This remedy uses permanent solutions and alternative treatment technologies to the
maximum extent practicable for this OU. However, because treatment of the principal threats of the
OU was not found to be practicable, this remedy does not satisfy the statutory preference for treatment
as a principal element of the remedy. A remedy in which contaminants could be treated effectively has
been precluded because of the size of the Site 1 landfill and because there are no known homogeneous
hot spots that represent the major sources of contamination at Sites 1 or 2. Therefore, in accordance
with EPA's 1993 presumptive remedy for CERCLA municipal landfill sites guidance, a containment
technology was selected.
Because this remedy will result in hazardous substances remaining on site, a review will be conducted
within 5 years after implementation to ensure that the remedy continues to meet objectives.
^^2£-
ao Date '
ironmental Coordinator, Navy EFA West
A
Daniel Opalski Date
I' Director Federal Facilities Cleanup Office, EPA Region 9
*
J.Lan<$,
Antfibny J. Landjs, Pfi. ^ Date
Chief
Northern California Operations
Office of Military Facilities
California Department of Toxi&£ubstances Control
tl/^
K. tfarsamian" Date '
Executive Officer, California Regional Water Quality
Control Board, San Francisco Bay Region
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2.0 DECISION SUMMARY FOR OPERABLE UNIT 1
This section contains information regarding site description and history, community participation,
scope and role of OU1, site characteristics and risks, FS evaluations, the selected remedy, significant
changes, and statutory determinations.
2.1 SITE NAME, LOCATION, AND DESCRIPTION
Moffett Field is located near the southwestern edge of San Francisco Bay in Santa Clara County,
California (Figure 1).'
The address of the facility is:
Moffett Federal Airfield
Moffett Field, California 94035
Moffett Field is bounded by saltwater evaporation ponds to the north, Stevens Creek to the west,
U.S. Highway 101 to the south, and Lockheed Missile and Space Company's Lockheed Aerospace
Center (Lockheed) to the east. Moffett Field also borders the cities of Mountain View and Sunnyvale,
California. The City of Sunnyvale is located east of Mountain View and both are adjacent to the
southern portion of Moffett Field. NASA's Ames Research Center is located to the west and north of
the runways.
Ground surface elevations at Moffett Field range from approximately 36 feet above mean sea level
(msl) to 2 feet below msl. A sizable portion of Moffett Field is situated on previously submerged land
or marshlands that have been filled to their existing elevations with backfill material.
Wetlands located along the northern portion of Moffett Field are the only natural surface water features
at the station. The wetlands on Moffett Field are approximately 40 acres in size; all of the wetland
area is below sea level. An area of wetlands consisting of approximately 80 acres lies between Moffett
Federal Airfield and Stevens Creek. About half of this area is below sea level. The portion above sea
level is a critical habitat for a variety of mammals and birds. Approximately 1 mile beyond the
northern boundary of Moffett Field is the San Francisco Bay. Coyote Creek and Guadalupe Slough
drain into San Francisco Bay to the east of Moffett Field, and Stevens Creek drains into the San
Francisco Bay to the west.
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SAN PABLO
BAY
BENICIA' °
MARTINE
BO
^x
RICHMOND
o WALNUT CREEK
SAN
FRANCISCO
BAY
SAN
FRANCISCO
REDWOOD
CITY
MOFFETT FEDERAL AIRFIELD
FIGURE 1
MOFFETT FEDERAL AIRFIELD
REGIONAL LOCATION MAP
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San Francisco Bay is California's largest estuary. Historically, tidal salt marsh and mud flats covered
extensive areas of the southern portion of the bay; however, most of these wetlands have been
eliminated or greatly altered. A large area to the north and northeast of Moffett Field was diked and is
now used as commercial saltwater evaporation ponds. There are no streams on Moffett Field, although
several streams are present to the east and west. No other surface water features are present at Moffett
Field, with the exceptions of several small ponds maintained on the Moffett Field golf course as water
hazards, stormwater drainage ditches and retention ponds, standing water after floodings or rainfall,
and the wetlands described above.
The northern Santa Clara Valley groundwater basin is part of the down-dropped structural trough lying
between the San Andreas and Hayward faults. The erosion of the uplifted Santa Cruz Mountains has
contributed sediment that has been transported by northward-flowing streams. Moffett Field lies on the
San Jose alluvial plain near the toe of alluvial fans emanating from the Santa Cruz Mountains. On a
regional scale, the overall sediment grain size becomes finer northward away from the mountains. On
a local scale, alluvial processes have juxtaposed clay, silt, sand, and gravel in adjacent depositional
environments.
The hydrogeologic setting at Moffett Field consists of alluvial sand aquifers or sand and grave] aquifers
separated by low permeability silt and clay aquitards. In the interior part of the Santa Clara Valley, the
numerous aquifers have been divided into two broad zones or sequences: the upper-aquifer sequence
(A and B aquifers) and the lower-aquifer sequence (C aquifer) (PRC 1992). The distinction between
the two aquifer sequences is that the upper-aquifer sequence is generally unconfined, although in places
it is semiconfuied. The lower-aquifer sequence is confined under a laterally extensive clay aquitard at
depths of 140 to 200 feet below land surface (bis). Aquifers in the upper zone are generally thin and
discontinuous. Aquifer materials range from silty to fine sand to coarse gravel. The A and B aquifers
are not presently used. NASA uses one C-aquifer well for agricultural supply at Moffett Field. The C
aquifer, however, is used as a source of municipal drinking water for the nearby communities of
Mountain View and Sunnyvale.
The water table at Moffett Field is not a static boundary, but fluctuates in response to changes in
evaporation, precipitation, and groundwater pumping. The water table at Moffett Field ranges from
approximately 5 to 15 feet bis. Tidal influence on the water table elevation is negligib'e.
044XJ236«236\fnlrod.
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Current and potential beneficial uses applicable to the main groundwater basins in the San Francisco
Bay region are outlined in the San Francisco Bay Region Water Quality Control Plan (basin plan) and
include municipal supply, industrial service, industrial process water supply, and agricultural supply.
With the exception of the northern portion of the A aquifer (including Sites 1 and 2), the aquifers at
Moffett Field (A, B, and C aquifer zones) meet the state standards for yield (200 gallons per day) and
total dissolved solids (TDS) (less than 3,000 milligrams per liter [mg/L]). Therefore, under State
Water Resources Control Board (SWRCB) Resolution 88-63, the A, B, and C aquifers are considered
potential drinking water sources (except northern areas of the A aquifer). Surface water
replenishment, provided by the upper aquifers, helps maintain wildlife habitats associated with the
nearby wetlands.
2.2 SITE HISTORY
Moffett Field has been continuously operated by the U.S. government or military since it was
commissioned in 1933 to support the West Coast dirigibles (blimps) of the lighter-than-air (LTA)
program. In 1935, the station was transferred to the U.S. Army Air Corps, which used it for training
purposes. In 1939, a permit was granted to Ames Aeronautical Laboratory to use part of the station.
In 1942, the station was returned to Navy control and was named Naval Air Station Moffett Field. In
late 1942, the heavier-than-air (HTA) program was initiated and began to take precedence over the
LTA program. In 1945, the HTA program was moved to Half Moon Bay Field and Moffett Field was
used as a major overhaul and repair base. The LTA program was discontinued at Moffett Field in
1947. In 1949, the station became home to the Military Air Transport Service Squadron.
By 1950, Moffett Field was the largest naval air transport base on the West Coast and became the first
all-weather naval air station. In 1953, the station became home to all Navy fixed-wing, land-based
antisubmarine efforts. A weapons department was formed on the base in 1954, and in February 1966
the base activated its high-speed refueling facilities. During the station reorganization in 1973, it
became the headquarters of the Commander Patrol Wings, U.S. Pacific Fleet.
During the 1980s and early 1990s, the mission of Moffett Field was to support antisubmarine warfare
training and patrol squadrons. The station supported more than 70 tenant units, including the
Commander Patrol Wings, U.S. Pacific Fleet, and the California Air National Guard. Moffett Field
n 044-0036milfi\s:Vwpdocs\usiavyVinofrea\ao^n36\fnlrad.doc\8-l-97\jeni
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was the largest P-3 Orion patrol aircraft base in the world, with nearly 100 aircraft. These aircraft
j
were assigned to nine squadrons supported by 5,500 military. 1,500 civilian, and 1,000 reservist
personnel. No heavy manufacturing or major aircraft maintenance were conducted at Moffett Field,
but a significant amount of unit- and intermediate-level maintenance occurred.
In April 1991, Moffett Field was designated for closure as an active military base under the
Department of Defense (DoD) BRAC program. On July 1, 1994, control of the base was transferred
to NASA, which operates the Ames Research Center on the northwestern side of Moffett Field. The
Navy and NASA signed a memorandum of understanding (MOU) on December 22, 1992 concerning
environmental activities at the station. Under the MOU, the Navy will continue with environmental
restoration activities and remain responsible for remediating Navy contaminant sources. NASA is
responsible for nonenvironmental operations and ongoing environmental compliance activities.
Wastes have been generated at Moffett Field through maintenance operations, fuel management, and
fire training since the early 1930s. Chemicals of potential concern (COPCs) include waste oils and jet
fuels; solvents and cleaners; washing compounds; and lesser amounts of gasoline, hydraulic fluids,
asbestos, paints, pesticides, battery acid, and polychlorinated biphenyls (PCBs). Wastes were disposed
of in unlined landfills, drained through drainage ditches and unpaved areas, and stored temporarily in
unlined wastewater ponds. In addition, some underground storage tanks (USTs) and sumps (many of
them now removed) were found to have leaked petroleum hydrocarbons and fuels, and lesser amounts
of waste oils and solvents.
Environmental studies began at Moffett Field in 1984. The Navy initiated these environmental
restoration activities as part of the Installation Restoration Program (IRP). The Navy conducted an
initial assessment study (IAS) in 1984 to gather data on the past use and disposal of hazardous
materials at Moffett Field (NEESA 1984). Nineteen sites were identified as potential sources of
wastes, including nine sites identified in the IAS and 10 sites added during subsequent investigations.
EPA proposed Moffett Field as an NPL site in June 1986 and placed it on the NPL in 1987.
Placement on the NPL initiated the RI/FS process under CERCLA. Data collected during the initial
studies were used to plan the RI/FS. The RI/FS work is coordinated through the August 1990 federal
facilities agreement (FFA) with EPA and the California Environmental Protection Agency (Cal/EPA)
(including the Department of Toxic Substances Control [DTSC] and the Regional Water Quality
Control Board, San Francisco Bay Region [RWQCB]).
JQ (H4-0236irulfi\»:\wp(loa\mnavy\nwffec\cU)-OZ>6\fnlrod.doc\8-l-97\(em
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The RI was implemented in two phases. During Phase I, the types and concentrations of chemical
contaminants at 19 sites were identified. The Phase I characterization was completed in August 1990.
The Phase II investigations were initiated in 1990 to provide more detailed, site-specific data. Phase II
investigations revealed a need to organize the RI/FS process into six separate OUs. Subsequently,
Moffett Field was divided into six OUs to help expedite the RI/FS process.
OU1 • Soils and groundwater at Sites 1 and 2 landfills
OU2 - Soils at Sites 3 through 11, 13, 14, and 16 through 19
OU3 - Soils at Sites 12 and 15
OU4 - Aquifers on the western side of Moffett Field
OU5 - Aquifers on the eastern side of Moffett Field
OU6 - Wetland areas
In October 1992, however, EPA determined that the aquifers on the western side of Moffett Field were
affected by a regional volatile organic compound (VOC) plume emanating from the Middlefield-Ellis-
Whisman (MEW) Superfund site south of Moffett Field. EPA determined that these aquifers were
subject to the 1989 ROD already written for the MEW site. Consequently, OU4 was deleted and OUS
was modified to include all aquifers not part of the regional VOC plume. OU2 was separated into
OU2-West (Sites 8, 16, 17, 18, and the western portion of Site 10, which overlie the regional VOC
plume) and OU2-East (Sites 3, 4, 6, 7, 11, 13, and the eastern portion of Site 10, which do not overlie
the regional VOC plume).
In February 1993, the Navy recommended to the regulatory agencies that all sites containing petroleum
and petroleum constituents be removed from the CERCLA process (CERCLA contains an exclusion
for petroleum and petroleum constituents). The Navy also recommended that these sites be addressed
in a manner consistent with the Resource Conservation and Recovery Act (RCRA) Subtitle I and
appropriate state regulations for underground storage tanks. The agencies agreed to the modification
and corrective actions at petroleum sites are underway. Therefore, OU3 (which contained petroleum
contaminated Sites 12 and 15) was removed, and Sites 5, 9, 14, and 19, which also contain petroleum-
contamination, have been deferred to the IRP petroleum sites program and will not be addressed
through RODs. Five additional sites have been identified; the current OU definitions and study areas
are listed below.
11 044XlZ36irolft\i:\wp(locj\uiinvy\moffcn\c«o-0236\fnlrod.
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OU1 - Soils and groundwater at Sites 1 and 2 landfills
OU2-East - Soils at Sites 3, 4, 6, 7, 10 (runways), 11, 13,
OU2-West - Soils at Sites 8, 10 (Chase Park), 14-North, 16, 17, and 18
OU5 - Aquifers on the eastern side of Moffett Field
OU6 - Wetland areas
Petroleum Sites - Sites 5, 9, 12, 14-South, IS, 19, 20, and 24
Station-wide Sites - Sites 21, 22, 23, Weapons Storage Bunkers, Industrial
Wastewater Flux Ponds, and Potential Runway Wetland
Figure 2 depicts all the RI/FS site locations at Moffett Field. This ROD addresses the OU1 landfill
refuse, leachate, surrounding groundwater, adjacent surface water, and landfill gases. Site-specific
information for the sites included in OU1 are provided in the OU1 RI report (IT 1993a), the OU5 RI
report (IT 1993b), the OU1 FS report (PRC 1995), and Section 2.5 of this ROD. Figure 2 depicts the
locations of the OU1 sites at Moffett Field.
2.3 HIGHLIGHTS OF COMMUNITY PARTICIPATION
In May 1989, the Navy developed a Moffett Field community relations plan (CRP). The CRP outlined
specific activities based on concerns voiced by the community. Since 1993, the EPA has provided a
technical assistance grant (TAG) to the Silicon Valley Toxics Coalition (SVTC), a local environmental
group. The TAG allowed SVTC to hire a consultant to assist in reviewing Moffett Field environmental
documents. In addition, the Navy formed a technical review committee (TRC), which met quarterly to
discuss environmental progress at the site. The TRC evolved into what is now known as the
restoration advisory board (RAB). The RAB is made up of members of the TRC and community and
holds regular public meetings to discuss environmental progress at Moffett Field.
The OU1 RI report was released in March 1993 (IT 1993a). The FS report and proposed plan for
OU1 were released to the public hi May 1995 (PRC 1995). The RI report, FS report, and proposed
plan were made available to the public through both the administrative record and the information
repository. The notice of availability for the proposed plan and related documents was published in the
San Jose Mercury News and San Francisco Chronicle on May 29, 1995. A public comment period
was held from May 30, 1995, through August 30, 1995. A public meeting was held on Thursday,
12
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LEGEND
— — — NASA/AUES RESEARCH CENTCH BOUNDARY
Wjffh n/rs sues
x »— FENCE
I]
500' 0 500' 1000'
SCALE: I' - 1000'
SITE MO- RJEL FARM (PtrwxtUU sires)
10 CHASE PARK AREA (OU2-WEST)
AND RUNWAYS (OU2-CAST)
II ENCWC TEST STAND AREA
(OU2-CAST)
12 FiKEFIGHTMG TRAMMC AREA
(PETROUUU SITES)
1} COUPICNT PARKING AREA
(OU2-CAST)
U TANKS Ifc 20, «7. AMD 68
(REMOVED) (PETROUUU SITES)
:15 NMC SUMPS AND OIL/WATER
SEPARATORS (PETROLEUM SITES)
1> PW STEAM RACK SUUP NO. 60
(REMOVED) (002-WEST)
17 PAINT SHOP SUUP NO. 81
(REMOVED) (OU2-WEST)
18 DRY CLEANERS SUUP NO. M
(REMOVED) (OU2-WCST)
19 TANKS 1 U. «. AND U
(REMOVED) (PETROLEUM SITES)
ZOOX ROAD FUEL SPILL
21 PATROL ROAD DITCH
:COIF COURSE LANDFILL *2
GOLF COURSE LANDFILL *]
ACTIVI PETROLEUM SITES
(MSRF. FUEL PIER.
HANGAR 1 PITS)
FIGURE 2
MOFFETT FEDERAL AIRFIELD
OU1 ROD
RI/FS SITES
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June 15, 1995. At this meeting, representatives from the Navy, EPA, and the State of California
answered questions about OU1 and supplied the basis for proposing the selected response action for
Sites 1 and 2. A response to the comments received during this public meeting and the public comment
period is included in Sections 3.1 and 3.2 of the responsiveness summary (Section 3.0).
Following the first public comment period, the Navy modified the preferred alternative based on public
and regulatory agency comments. As a result, a revised proposed plan was released to the public in
December 1995. The revised proposed plan was made available to the public through both the
administrative record and the information repository. The notice of availability for the revised
proposed plan and related documents was published in the San Jose Mercury News on January 4, 1996.
A second public comment period was held from January 4, 1996, through February 5, 1996. A second
public meeting was held on Tuesday, January 16, 1996. At this meeting, representatives from the
Navy, EPA, and the State of California answered questions about OU1 and supplied the basis for
revising the original proposal and presented the modified response action for Sites 1 and 2. A response
to the comments received during the second public meeting and public comment period is included in
Sections 3.3 and 3.4 of the responsiveness summary (Section 3.0).
New information collected as part of OU1 remedial design (RD) efforts indicated that the Site 2 landfill
is much smaller than initially estimated. Consequently, the Navy proposed a change in the preferred
alternative for OU1. The change involves excavating the waste at the Site 2 landfill and consolidating
that waste at the Site 1 landfill. The Site 1 landfill would be designated as a CAMU and capped. The
Navy issued a revised proposed plan describing the consolidation and capping preferred alternative for
OU1 and published a notice of availability of the consolidation and capping proposed plan in the San
Jose Mercury News and Sunnyvale Sun on March 10, 1997. The public comment period was held from
March 7, 1997 to April 11, 1997. A public meeting was held on March 20, 1997. A response to
comments received during the public meeting and public comment period for the consolidation and
capping preferred alternative is included in Sections 3.5 and 3.6 of the responsiveness summary
(Section 3.0).
These community participation activities fulfill the requirements of Sections 113(k)(2)(B)(i-v)
and 117(a)(2) of CERCLA.
14 0444O3«inilCi\5AwpdocsVusnavy\inofrea\cio-0236\fti]iod.docV8-l-97\)ein
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2.4 SCOPE AND ROLE OF OPERABLE UNIT WITHIN SITE STRATEGY
The selected response actions described in this ROD will address the source of the contamination by
containing wastes on-site and reducing the risk associated with exposure to contaminated materials. In
addition, the response action will limit Sites 1 and 2 as sources to groundwater contamination by
removing waste from Site 2 and consolidating it a Site 1 and by incorporating low-permeability cap
layers.
Selection of the remedy for OU1 is consistent with overall RI/FS activities at Moffett Field. Moffett
Field is a large federal facility containing numerous potential sources of contamination. As discussed
in Section 2.2, 24 sites at Moffett Field have been identified to date and are in some phase of the
assessment process. In addition to OU1, OUs addressed by RODs are as follows:
OU Designation OU Description ROD Schedule
OU2-East Sites 3, 4, 6, 7, 11, and 13 December 1994
OUS East Side Aquifers June 1996
OU6 Wetland Areas Covered by Station-wide ROD
Station-wide Station-wide July 1998
The installation management strategy is to accelerate actions at the OUs while identifying and closing
out assessment activities at sites not requiring action. This strategy, which uses no-action RODs,
allows resources to be concentrated on the OUs requiring action.
2.5 SITE CHARACTERIZATION
Based on experience, EPA has developed presumptive remedies to accelerate cleanup for certain types
of sites. Presumptive remedies are preferred technologies based on an evaluation of performance data
from previous technology implementation. EPA has established the expectation that engineering
controls, such as containment, will be used for wastes that pose a relatively low, long-term threat or
where treatment is impracticable (40 CFR 300.430(a)(l)(iii)(B)). EPA's September 1993 guidance,
Presumptive Remedy for CERCLA Municipal Landfill Sites and the preamble to the National Oil and
Hazardous Substances Pollution Contingency Plan (NCP) published in the Federal Register on
March 8, 1990, identify landfills as areas where treatment may be impracticable because of the size
and heterogeneity of municipal waste (EPA 1993). OU1 field investigations during the RI/FS
044-OU6irulfi\»:\wpdocf\uuMV7\n»fiiM\ao-0236\ftUrod.doc\8-l-97\jem
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incorporated this presumptive remedy approach. In accordance with EPA's February 1991 guidance,
Conducting Remedial Investigations/Feasibility Studies for CERCLA Municipal Landfill Sites,
complete characterization of the landfill refuse is not necessary because containment, which is often the
most practical technology for landfills, does not require such information (EPA 1991). In addition, the
heterogeneity of contaminant distribution and concentrations typically associated with landfills make
accurate characterization of landfill refuse impractical and virtually impossible. As a result, OU1
RI/FS field investigations focused on OU1 hydrogeology, ground water chemistry, surface water
chemistry, and landfill gas composition to evaluate whether contamination from the landfills was
migrating past landfill boundaries into the surroundings. Additional groundwater investigations at Site
1 and radiological surveys at Sites 1 and 2 were conducted in September 1996. The radiological
survey did not detect radioactive materials above background concentrations. The groundwater
investigation did not indicate conditions significantly different than those reported in the OU1 RI and
FS reports. The results of the additional investigations are presented in the Draft Final OU1 Field
Investigation Technical Memorandum (PRO 1997). The following two subsections discuss Site 1 and
Site 2 general characteristics, hydrogeology, and summarize the general nature and extent of
contamination. More detailed site-specific information for the sites can be found in the OU1 RI report
(IT 1993a), the OU5 RI report (IT 1993b), and the OU1 FS report (PRC 1995).
2.5.1 Site 1 Characteristics
The Runway Landfill (Site 1) is located in the northernmost portion of Moffett Field at the end of the
runways between Zook Road and the Cargill Salt Company evaporation ponds (Figure 2). This site
encompasses an area of approximately 12 acres. The surface of Site 1 is covered with weeds, gravel,
and minor amounts of debris. Surface elevations range from approximately 3 feet below msl near the
perimeter to approximately 23 feet above msl toward the center of the landfill. Site 1 was operated
from 1965 until the late 1970s as a landfill. Subsequently, the site was used as a pistol range.
Unexploded ordnance was removed from the site prior to the RI in 1988. Any contamination
associated with pistol range operations will be addressed by the landfill remedy.
Detailed operation records for the Runway Landfill were not maintained; however, a solid waste
facility permit was obtained from Santa Clara County in 1979. This permit states that the landfill
operated as a sanitary landfill and that the landfill received wastes such as cardboard, lawn cuttings,
prunings, wood waste, and asbestos insulation wrapped in double plastic bags. According to civilian
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and military personnel interviews, the landfill received domestic refuse as well as waste from
maintenance and military operations, such as refuse, scrap equipment, paint and paint thinners,
solvents, lacquer, ash, asbestos, jet fuels, waste oil, fuel filters (containing fuel sludge, lead
compounds, and rust), transformer oil, transformer filters, and PCB-contaminated sawdust. However,
data collected during field investigations support the information found in the permit and indicate that
the Site 1 landfill was operated much like a solid waste landfill. Low contaminant concentrations were
found in leachate and surface debris and subsurface borehole logs show that demolition and
construction debris was disposed of in the landfill (PRC 1995).
Information obtained from civilian and military personnel interviews indicate that refuse was placed in
an excavation that typically ranged from 8 to 12 feet below msl. The refuse material was then covered
with soil that ranged from 0.6 to 7 feet in thickness. Although no disposal records for the landfill
exist, a conservative maximum estimate of the total volume of refuse at Site 1 is approximately
423,000 cubic yards. The refuse has not been fully characterized. The heterogeneity of contaminant
distribution and concentrations typically associated with landfills makes accurate characterization of
landfill refuse impractical. Accurate characterization is generally not necessary because containment,
which is often the most practicable technology, does not require such information (EPA 1991).
Portions of refuse are located below the water table and are saturated at Site 1. Approximately the
bottom one-third of the refuse at Site 1 is saturated. Refuse saturation (or refuse subsidence relative to
the water table) may have been caused by past regional aquifer pumping coupled with excavating prior
to placing wastes. Borehole logs indicate that a silty clay aquitard several feet thick exists below the
landfill and above the uppermost aquifer zone. The thickness of this aquitard varies, and the hydraulic
conductivity has been measured in the 1 x 10"8 centimeters per second (cm/sec) range. It is not known
conclusively whether this aquitard is continuous beneath the landfill.
Beneath the aquitard, the A-aquifer exists and consists of silty sand or sand and gravel deposits
separated by low-permeability silts and clays. The A-aquifer zone extends from approximately 15 to
65 feet below msl and has been divided into two zones, the A1-aquifer and the A2-aquifer zones. In
general, groundwater in the A1-aquifer zone beneath the landfill (the uppermost aquifer) flows north to
south. The regional gradient is south to north toward San Francisco Bay. The southward gradient at
Site 1 is opposite from the regional gradient due to active pumping of the storm drainage system.
Pumping occurs at the Building 191 pump station (located south of Site 1, but just north of Site 2 [see
044-0236iml (t\i:\wpdoct\usnavy\moffenVatMa36\ftUro
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Figure 2]). The pump station influences groundwater gradients because the drainage system that feeds
the pump station is below the water table in some areas. Should pumping at Building 191 cease, the
northern area of Moffett Federal Airfield, including Site 1, may be prone to flooding.
Four water bodies or zones are associated with Site 1: the leachate zone, surrounding groundwater,
the man-made ephemeral stormwater retention pond (SWRP) to the north, and the saltwater
evaporation pond (termed Jagel Slough) to the east. It appears that low-permeability barriers exist
between the four water bodies in the area (measured hydraulic conductivities are 1 x 10"8 cm/sec). The
barriers limit water movement between each body. As a result, head differences are maintained
between each water body. Since the Site 1 landfill is relatively isolated from the other water bodies by
low-permeability barriers, elevated water levels are maintained. Potential for flow from the landfill to
the other bodies exists, but actual flow is limited or constrained by these barriers.
Chemical data from groundwater samples collected to date at the landfill perimeter show that the
landfill is not significantly impacting groundwater. Some chemicals have been detected infrequently
and at low concentrations in samples collected from surrounding groundwater monitoring wells (PRC
1995). However, the data do not show any consistent patterns or trends that would indicate the
presence of any leachate plumes emanating from the landfill. No contaminants have been detected
consecutively from the same well except acetone and carbon disulfide. Furthermore, no compounds
were consecutively detected above detection limits in any one well or in any two consecutive rounds.
The bay muds surrounding the landfill appear to be retarding contaminant migration outside landfill
boundaries. At Site 1, there is a clay layer below the refuse with a laboratory-tested hydraulic
conductivity of 1 x 10' cm/sec. It is not known if the layer is completely continuous, but it is present
in all borehole logs from Site 1. The low hydraulic conductivity, high organic content associated with
the clays, and low contaminant source concentrations combine to restrict flow and limit contaminant
migration.
2.5.2 Site 2 Characteristics
Several investigations and studies have been conducted to characterize Site 2. Section 2.5.2.1
summarizes the characteristics of Site 2 evaluated as part of the OU1 RI/FS activities. Section 2.5.2.2
summarizes the new Site 2 characteristics discovered during OU1 design efforts that resulted in the
consolidation alternative for Site 2. These data indicate that the volume of waste at Site 2 is much
smaller than was estimated during the RI/FS.
Jg 044-0236injlft\i:\wpdoci\uuuvy\moffcn\ochO23MftUrod.doc\S-l-97Veni
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2.5.2.1 Summary of Site 2 Characteristics Based on OU1 RI/FS Activities
The Golf Course Landfill (Site 2) is located in the northern portion of the base just west of the golf
course and adjacent to a saltwater evaporation pond (Figure 2). It is bordered by Zook Road on the
west, Macon Road on the south, Patrol Road on the north, and Building 561 and its enclosure on the
east. The site covers an area of approximately 5 acres and is approximately 1,600 feet from Site 1
(see Figure 2) and has a similar habitat.
Site 2 is flanked by the golf course which is landscaped and maintained. Ornamental pines, acacia, and
eucalyptus are typical" landscape trees present in this area. Salt grass is the predominant turf in many
areas of the golf course. Landscaped areas were observed to support opportunistic species common to
suburban and park settings.
Site 2 appeared as a shallow excavation in aerial photographs of the site taken in 1947. An aerial
photograph dated July 23, 1952 shows the Site 2 area as flat with no debris piles and indicates the end
of disposal activities. The photograph shows the site is covered by vegetation and no activities are
occurring at the site. A burn pit in the present golf course landfill area was used for disposal of
outdated flares and cartridge-activated devices until 1971. Later photographs also show operation of a
small arms range from the early 1960s to about 1976. Surface dumping of construction debris appears
in a 1983 photograph, but no excavation activity is evident. No activities at Site 2 are indicated by a
photograph dated November 3, 1987. In summary, analysis of aerial photographs indicates that waste
disposal at Site 2 ended in 1952.
Site 2 is relatively flat, overgrown with vegetation, contains several mounded areas where debris is
occasionally visible, and has a perimeter fence. Earthen fill and refuse placed at the site generally
extend from 1 to 7 feet below msl. The area is graded for flood control to drain surface water runoff
into local drainage ditches which convey runoff to the North Patrol Road Ditch (formerly the Navy
Channel) along the northern boundary of the station. Water is then pumped from this perimeter
channel to the Northern Channel that eventually discharges to Guadalupe Slough.
Because records of the landfill operations were not maintained, the history of the landfill was
researched by studying aerial photographs and previous reports and by interviewing pust and present
base personnel. Site 2 was operated from the 1940s until approximately 1952. The landfill received
1 044X3236imlf$V«:\wpdoa\usnavy\inoffen\£M)-0236\fti]rod.doc\8-l-97\jem
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domestic refuse as well as waste from maintenance and military operations, such as refuse, scrap
equipment, paint and paint thinners, solvents, lacquer, oil, fuel filters, and sawdust contaminated with
PCBs. The limited characterization data collected during field investigations indicate that the Site 2
landfill was operated much like a solid waste landfill (see Section 2.5.1) and that Site 2 was used in a
similar manner as Site 1. Personnel interviews indicated that this site was used by the same shops as
the more recent Site 1 landfill.
Although no disposal records for the landfill exist, the FS report conservatively estimated that the total
maximum volume of refuse at Site 2 is approximately 169,400 cubic yards. This estimate assumed
waste was 20 feet thick over an area of 5 acres. The refuse has not been fully characterized.
Complete characterization of landfill refuse is impractical because of the heterogeneity of contaminant
distribution and concentrations that are typically associated with landfills. Accurate characterization is
generally not necessary because containment, which is often the most practicable technology, does not
require such information (EPA 1991).
Stratigraphic units penetrated by borings at Site 2 are representative of estuarine environments and
changes in an estuarine/alluvial boundary resulting from sea-level fluctuations. Saturated zones of silty
sand and sandy clay below the uppermost clay layers make up the upper Al-aquifer zone. Similar to
Site 1 soils, test results indicated low hydraulic conductivity values on the order of 1x107 cm/sec for
soils below and surrounding Site 2.
Groundwater elevations at Site 2 are below msl because of diking and the existing Moffett Field storm
drain system. Water levels in monitoring wells at the site range from 4 to 7 feet below msl.
Groundwater flow patterns in the vicinity of Site 2 are influenced by the storm sewer lift station
(Building 191). The groundwater at Site 2 flows to the north toward San Francisco Bay. The gradient
is slightly steeper due to active pumping of the storm drainage system. Pumping occurs at the Building
191 pump station (located just north of Site 2 [see Figure 2]). The pump station influences
groundwater gradients because the drainage system that feeds the pump station is below the water table
in some areas. Should pumping at Building 191 cease, the northern area of Moffett Federal Airfield,
including Site 2, may be prone to flooding.
The majority of landfill refuse at Site 2 appears to be above the water table (PRC 1993). Eight borings
have been drilled inside the boundaries of the landfill and borehole logs from seven show no refuse
2Q 0*4-0236irulft\$:\wpdoc«\um2vy\mofTetl\ao-0236\lhlrod.doc\»-l-97\)eni
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below the water table. One borehole log, however, indicates that some refuse is below the water table.
In addition, borehole logs show that there is inert fill (gravels and sand) devoid of refuse located below
the water table within landfill boundaries.
Chemicals from leachate have been detected infrequently and at low concentrations in samples from
downgradient ground water monitoring wells (PRC 1995). However, the data do not indicate consistent
patterns or trends for any organic contaminant plumes emanating from the landfill. The low-level
detections are random in nature. No compounds were consecutively detected above detection limits in
any one well or in any two consecutive rounds. Plumes of leachate are not migrating past Site 2
boundaries even though Site 2 does not have a documented, engineered barrier between the landfill and
surrounding groundwater. Low source contaminant concentrations and low hydraulic conductivity
soils surrounding the landfill are reasons for the absence of migrating contaminants.
2.5.2.2 Summary of Site 2 Characteristics Based on New Information
The new information regarding Site 2 is discussed in more detail in the Final Operable Unit 1
Alternatives Analysis Technical Memorandum dated April 14, 1997. This section summarizes the
information presented in the April 14, 1997 technical memorandum.
Since early studies began at the site, the Navy has acknowledged the presence of an underground
natural gas pipeline at Site 2. The gas pipeline is a 36-inch diameter, high pressure main operated by
Pacific Gas and Electric Company (PG&E) and one of three pipelines that provides primary service to
the City of San Francisco. However, detailed utility investigations conducted for the cap design
uncovered significant new information. The Navy excavated four test pits along the pipeline alignment
at Site 2 during July 1996 and confirmed the location and depth of the pipeline. The pipeline is located
above the water table and does not function as a horizontal migration pathway.
Since completion of the OU1 RI/FS, several investigations have been conducted to better define the
extent of waste material at Site 2. Trenching conducted by the Navy during April 1996 to define more
accurately the landfill boundary showed the presence of inert fill and construction debris, but not large
amounts of waste materials. Two test pits excavated during the pipeline investigation in July 1996
indicated the presence of only inert materials such as construction debris. In September 1996, the
Navy excavated eight additional trenches in the northern half of Site 2 to obtain additional information
concerning visual waste identification, the location of waste relative to the water table, and the overall
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volume of waste at Site 2. Municipal-type wastes were found to be isolated in a specific waste area
and were easily distinguished from inert construction debris (above and surrounding the waste area) or
native clays (beneath the waste area). The eastern limit of the waste area was found during excavation
activities (see Figure 3). The other boundaries can be estimated based on previous trenches excavated
during investigation of the natural gas pipeline and historical aerial photographs. Trenching indicates
that portions of the waste are saturated, as expected.
Based on the trenching results, the volume of waste at Site 2 is likely much smaller than earlier
estimates. Trenching results indicate that the area used for waste disposal probably was less than 1
acre and waste thicknesses appear to be less than 10 feet at most locations. Therefore, the in-place
volume of waste at Site 2 is likely less than 20,000 cubic yards. Furthermore, based on field
observations, only minimal, if any, hazardous waste is likely to be present at Site 2.
2.6 SUMMARY OF SITE RISKS
The following subsections discuss the human health risk assessment and the ecological assessment
conducted forOUl.
2.6.1 Human Health Risk Assessment
A quantitative human health risk assessment has limited use in evaluating whether landfill refuse
requires remediation. The decision to remediate (cap) a landfill is typically not dependent on risk
assessment results. In fact, EPA presumptive remedy guidance does not advocate performing
quantitative risk assessments for landfill refuse. Quantifying risks from landfill refuse has little
practical use because an underlying assumption has to be made that the landfill content is well
characterized, which is a questionable assumption at best. The heterogeneity of contaminant
distribution and concentrations makes characterization of landfill content an impractical and virtually
impossible task. Characterizing landfill content is also a health and safety hazard for field crews.
Because of these circumstances, EPA has developed a strategy to address landfills that is based on
containment of contaminants. Containment is known as the presumptive remedy for landfills and does
not require accurate characterization of landfill content or a quantified assessment of associated risks.
The Navy has employed the presumptive remedy strategy for Site 1. Even though a human health risk
assessment has limited use, one was conducted and is contained in the OU1 remedial investigation
report (IT 1993a).
22 044^O36imlfs\s:\wpdacj\UHUvy\moffrtt\ctt)-OZ36\fhlrod.doc\8-]-97\jen)
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II
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APPROXIMATE "WASTE LOCATION
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FIGURE 3
MOFFETT FEDERAL AIRFIELD
OUI ROD
SITE 2 LOCATION MAP
23
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As stated above, quantified risk assessment results have limited use for landfills. Qualitatively
however, the following exposure pathways are associated with constituents in refuse and landfill gas
and the remedial alternatives were developed considering these hazards:
• Ingestion of and dermal contact with surface soils
• Inhalation of paniculate matter from wind-eroded surface soils
• Inhalation or explosion of landfill gas
For groundwater, exposure pathways associated with human health are incomplete because the
groundwater is not a current drinking water supply and it is not reasonably expected to be a drinking
water supply in the future. The groundwater has high TDS (greater than 20,000 mg/L) which limits its
use. Water with a TDS level greater than 3,000 mg/L is not considered a potential source of drinking
water under California State Water Resources Control Board (SWRCB) Resolution 88-63. TDS
concentrations at Sites 1 and 2 exceed these limits.
In addition to the groundwater being nonpotable, groundwater surrounding OU1 will not likely be
extracted for future beneficial use because of previous problems that occurred while pumping
groundwater. During a period extending from 1915 to about 1965 (California Department of Water
Resources Bulletin 118-1, 1968), shallow groundwater was used to irrigate farmlands and for public
supply (IT 1989). Groundwater pumping from shallow aquifers subsequently caused salt water from
the San Francisco Bay to flow into shallow aquifers in the region. As pumping increased, saltwater
intrusion spread inland.
Another adverse side effect of shallow groundwater extraction was related to land subsidence. At
Moffett Field, subsidence was about 2 to 8 feet, and as much as 12 to 13 feet at San Jose (IT 1989).
The subsidence caused changes in drainage patterns, inundation of coastal areas, and additional salt
water intrusion into shallow aquifers.
A rigid basin-wide groundwater management plan, consisting in part of pumping controls, was
implemented to prevent additional destructive effects of overpumping. Since about 1970, there has
been no increased salt water intrusion and land subsidence. The stabilization is related to a decline in
pumping, which is attributed to both groundwater basin management and land use factors that
discourage groundwater pumping (IT 1989). The Santa Clara Valley Water District (SCVWD)
24
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requires a 50-foot deep seal on any extraction well to prevent downward vertical migration of shallow
groundwater (SCVWD 1989).
For the above reasons, groundwater surrounding Sites 1 and 2 will not likely be used as a water supply
and therefore, exposure pathways to leachate and groundwater are incomplete.
2.6.2 Ecological Assessment Summary
Ecological receptors could be potentially exposed to OU1 contaminants through the following
mechanisms:
i
• Contact with surface refuse
• Contact with subsurface refuse via burrowing
• Chemical uptake into plant root systems
• Contact with landfill gas
• Leachate migration into adjacent surface waters
Containment is the presumptive remedy for landfills, and capping the waste will minimize the potential
for ecological receptors to come in contact with surface refuse. In addition, landfill caps can be
designed to deter animals from burrowing into the landfill, thereby reducing the potential for contact
with subsurface refuse. Similarly, landfill caps can be designed to prevent plant roots from extending
beyond a certain depth, which reduces the potential for chemical uptake into root systems. Finally, a
landfill cap can include gas vents to reroute subsurface gases and reduce the potential for contact with
landfill gas. Because the presumptive remedy addresses four of the above-mentioned pathways,
attempts have not been made to quantify ecological risks from refuse. This information is not
necessary because containment, the most practical technology, does not require such information (EPA
1991).
As stated above, there is a potential for leachate to migrate into adjacent surface waters and
subsequently impact aquatic or ecological receptors which inhabit surface waters. The SWRP is
located downgradient from the leachate zone at Site 1 and the North Patrol Road Ditch is downgradient
from Site 2. To evaluate whether ecological impacts have occurred from the landfills, groundwater
data were compared to AWQC for the protection of aquatic life. If these levels are exceeded in
25 044-0236iiul ft\i:\wpdoa\uaavy\moffea\cu»0236\fnlrod.(locV8- l-97\jcm
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groundwater, ecological receptors in surface water could potentially be affected since groundwater
recharges surface water in the SWRP near Site 1 and the North Patrol Road Ditch at Site 2. This
evaluation is conservative because groundwater concentrations do not represent the resulting
concentrations in surface water from leachate migration. Groundwater contaminants will likely dilute
and disperse as contamination migrates toward surface water bodies. These characteristics must be
taken into consideration during evaluation monitoring and any corrective action that is implemented.
This evaluation concluded that OU1 perimeter groundwater constituent concentrations are either below
AWQC or similar to .constituent concentrations found in north base area (NBA) groundwater
monitoring wells. Data from the groundwater monitoring wells located between the landfills and
surface water bodies do not show that leachate plumes are migrating from the landfills.
As stated above, the exposure pathways for ecological receptors are incomplete based on containment
of the OU1 wastes through use of the presumptive remedy and groundwater data. Therefore, the
ecological assessment for OU1 was streamlined. The purpose of the ecological assessment was to
evaluate potential impacts to the habitats and surrounding environments resulting from capping at OU1.
The potential ecological impacts from consolidation of the Site 2 wastes to Site 1 are similar to those
associated with capping Site 2, except that long-term impacts from exposure to subsurface waste at Site
2 are no longer a concern.
During this evaluation, the Navy found that Sites 1 and 2 consist of disturbed, low-value habitats that
support predominantly non-native plant and animal species (PRC 1994). This habitat will be destroyed
during consolidation of wastes from Site 2 to Site 1 and capping, and some changes will occur during
re-establishment. These detrimental impacts to the habitat are expected to be short term and it is
reasonable to assume that the landfill habitat will recover rapidly following consolidation and capping
activities. In addition, consolidation and capping are protective of the long-term welfare of the
environment.
During the streamlined ecological assessment, field survey results found that no threatened and
endangered (T&E) species or special status species are known to currently inhabit these sites.
Two species were of special concern since they are known to inhabit other areas of Moffett Field.
These two species are the burrowing owl and the salt marsh harvest mouse (SMHM). OU1 does not
provide suitable habitat for the burrowing owl and it has not been observed at the sites. However,
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potential SMHM habitat exists adjacent to Site 1. Stands of pickleweed have been observed and
potentially represents habitat for the SMHM, which is a federal T&E species. These stands of
pickleweed are isolated. Corridors do not exist between these stands and nearby wetland areas,
indicating that it is unlikely that the SMHM inhabits Site 1.
Because results are often inconclusive, extensive trapping has not been done in these areas to confirm
or deny the presence of the SMHM. In addition, the U.S. Fish and Wildlife Service (FWS) indicated
that there is reasonable chance that the SMHM may exist adjacent to Site 1. Therefore, FWS
recommended that the Navy assume that the SMHM exists and prepare a replacement plan, which
would address each acre of lost habitat. The draft replacement plan is scheduled for delivery in mid-
1997.
The proposed landfill capping will affect potential wetlands in the vicinity of Site 1. Wetland areas
were delineated in accordance with U.S. Army Corps of Engineers (COE) criteria, and the results are
contained in the Final Phase I Site-wide Ecological Assessment Report (PRC and MW 1995).
Specifically, three limited potential wetlands are near Site 1. These areas include 1.25 acres southwest
of Site 1 within the fenced landfill area, 0.4 acres on the northern border of Site 1 along the fringe of
the stormwater retention pond, and 0.1 acres in the central portion of Site 1. However, the Navy and
regulatory agencies have determined that a landfill cap is necessary to protect the environment. Filling
small segments of potential wetlands will be required to cap the Site 1 landfill. Therefore, the Navy
will meet the substantive requirements of Nationwide Permit (NWP) 38 through the U.S. Army Corps
of Engineers (COE). This permit allows for fill to be placed in wetlands if filling is associated with the
remediation of hazardous and toxic waste. The Navy has determined that NWP 38 and Section 404 of
the Clean Water Act (CWA) are applicable to the action at Site 1. The Navy has further determined
that the planned activities at OU1 will meet all the substantive requirements of NWP 38 and CWA
Section 404 except the requirement concerning mitigation. Mitigation of wetlands destroyed during
activities at OU1 will be addressed in the stationwide ROD. The Navy will consult with RWQCB to
review the wetland areas affected by Site 1 activities and obtain concurrence to determine potential
mitigation requirements.
27 044-02J6inilfj\s;\wpdoci\uauvy\nKfrea\ao-0236\fhlrt)d.(loc\8-l-97Vnii
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2.7 DESCRIPTION OF THE ALTERNATIVES
Alternatives for OU1 have been developed and evaluated in two documents. The OU1 FS report
evaluated three alternatives each for Site 1 and Site 2. Section 2.7.1 describes these alternatives. The
alternatives analysis technical memorandum developed and evaluated an additional alternative for
Site 2, the consolidation alternative. Section 2.7.2 describes the consolidation alternative.
2.7.1 Description of Alternatives Presented in the FS
The alternatives assembled in the FS for Site 1 are as follows:
• Alternative 1: No action, Groundwater and Gas Monitoring, Institutional Controls
• Alternative 2: Native Soil Cap, Groundwater Collection Trench, Gas Vent Trench,
Groundwater and Gas Monitoring, Institutional Controls
• Alternative 3: Multilayer Cap, Groundwater Collection Trench, Gas Vent Trench,
Groundwater and Gas Monitoring, Institutional Controls
The alternatives assembled in the FS for Site 2 are as follows:
• Alternative 1: No action, Groundwater and Gas Monitoring, Institutional Controls
• Alternative 2: Native Soil Cap, Groundwater and Gas Monitoring, Institutional
Controls
• Alternative 3: Multilayer Cap, Groundwater and Gas Monitoring, Institutional
Controls
The following subsections describe the remedial alternatives in more detail.
2.7.1.1 Alternative 1: No Action
Under the no-action alternative, no remedial actions would be implemented. Only gas and
groundwater monitoring would be conducted. The no-action alternative is identified to provide a
baseline against which other alternatives can be compared.
0*MX236inilfs\s:\wpdo«Uisnavy\moffen\cu)-0236\IhJrod.doc\8-l-97\jem
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2.7.1.2 Alternative 2: Native Soil Cap, Trench Vent
Alternative 2 consists of institutional controls, a native soil cap, a trench vent (Site 1 only), and gas and
groundwater monitoring. The following paragraphs describe these components.
2.7.1.2.1 Institutional Controls
Institutional controls would be implemented as part of Alternative 2 to protect human health. Access to
the sites would be restricted by fences with posted signs. Sites 1 and 2 are currently fenced in with a
locked gate. Both landfills are on government property and are not accessible by the general public.
The need for continued Building 191 O&M will be referenced in appropriate land use documents and
federal real property records, along with restrictive provisions to maintain the integrity of the Site 1
cap.
O&M of the Building 191 pump station and drain/subdrain system would be included as an institutional
control under Alternative 2. This pump station and associated drainage system support the Moffett
Federal Airfield storm drainage system. Currently, pumping at Building 191 influences groundwater
gradients, as the drainage system that feeds the pump station is below the water table in some areas.
At Site 1, the regional groundwater gradient is reversed by Building 191 pumping, as the groundwater
flows from north to south (away from San Francisco Bay). At Site 2, the groundwater gradient is
south to north, which is normal. The gradient is relatively steeper, however, as a result of pumping at
Building 191. Should Building 191 O&M discontinue, the northern portion of Moffett Federal Airfield
(including OU1) may be prone to flooding. Therefore, O&M of the pump station was included as a
component of the remedy to prevent potential flooding of the OU1 landfill areas. Restrictive
provisions and notice requirements concerning the continued O&M of the Building 191 pump station
and the associated drain system continues would be placed in land use planning documents and federal
real property records. The Navy will resolve any issues with NASA regarding the process to develop
appropriate restrictive provisions to ensure continued O&M of the Building 191 pump station and to
maintain the integrity of the Site 1 cap. The Navy will enter into an agreement with NASA or develop
another appropriate vehicle to accomplish this task. The Navy will resolve any issues concerning the
necessary restrictive provisions within 1 year of the date of this ROD.
The Navy will coordinate with NASA, as the federal property holding agency, to notify the California
Integrated Waste Management Board (CIWMB) and local enforcement agency in the event of property
29 (mX)236iruHs\j:\wpdoc5\uauvy\moffeo\cto-0236Vnlrod.doe\8-l-97\jem
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transfer or land use change at Site 1 so that issues related to postclosure land use at Site 1 are managed
appropriately.
2.7.1.2.2 Native Soil Cap
A native soil cap would be implemented under this alternative to isolate landfill refuse, eliminate direct
contact with surface refuse, and reduce erosion, infiltration, and surface contaminant migration. A biotic
barrier and gas vents would also be installed to minimize plant root uptake of chemicals and reduce
inhalation exposures for burrowing animals. The soil cap would consist of a 3-foot layer of soil. The cap
would be sloped so rainwater will drain off the landfill to a perimeter ditch or the SWRP. The cap would
be designed to minimize erosion, thereby reducing the potential for surface contaminant migration. The
native soil cap would also reduce infiltration into the landfills and reduce the formation of leachate by
promoting vegetation, evapotranspiration, and runoff. The purpose of the soil cap is to prevent direct
contact, minimize erosion, and reduce infiltration. Gases generated beneath the soil cap under Alternative
2 would be allowed to escape upward through the cap, as no low-permeability layer exists in the cap to
impede gas flow. Figure 4 is a conceptual diagram of the cap under Alternative 2.
2.7.1.2.3 Groundwater Monitoring
The groundwater monitoring program would be in accordance with provisions of Title 23 CCR, Chapter
15, Articles, which have been identified as applicable for Sites 1 and 2. The groundwater monitoring
program would be contained in an appropriate remedial design document. The groundwater monitoring
program development will consider the March 1994 Long-term Ground Water Monitoring Program
Guidance (CBCEC 1994), which was prepared for the California Base Closure Environmental Committee
(CBCEC). For groundwater monitoring, detection monitoring and, if needed, evaluation monitoring
would be implemented based on substantive requirements in Title 23 CCR and contained in an appropriate
remedial design document. As part of detection monitoring, groundwater constituent concentrations would
be monitored, and, if chemical concentrations exceeding concentration limits set pursuant to 23 CCR
Chapter 15 Article 5 are observed, the Navy will immediately notify the regulatory agencies and will
evaluate the groundwater contamination in accordance with CERCLA, and will obtain concurrence from
EPA and the State on remediation decisions. Potential response action could include hydraulic control of
the groundwater and leachate through pump and treat methods.
30
044-0236iru I ($\a: \fnlrod .doc\8-12-97\jem
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SOIL CAP
FILTER
FABRIO
BIOTIC BARRIER
LOCAL-
WATER
TABLE
-GAS VENTING
TRENCH (FOR
WESTERN END
OF SITE 1 ONLY)
EXTENT OF
LANDFILL
i
i
I
LEGEND
LANDFILL GAS
MIGRATION
VEGETATION
FIGURE 4
MOFFETT FEDERAL AIRFIELD
OU1 ROD
CONCEPTUAL DIAGRAM
OF ALTERNATIVE 2
31
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A contingency measure would be implemented as part of Alternative 2 at Site 1 and would be in place
in the event nearby surface water is threatened. The contingency measure is proposed at Site 1 due to
the proximity and potential impact of landfill contamination to ecological receptors and habitats in the
adjacent northern area. The contingency measure includes enhancing the containment provided by the
bay muds at Site 1 with a vertical subsurface barrier and collection trench along the northern boundary
of Site 1. Figure 5 shows a conceptual design of the subsurface collection trench and vertical barrier.
Groundwater within the subsurface collection trench would be monitored at the same frequency as at
the Site 1 groundwater monitoring wells. If chemical concentrations exceeding concentration limits set
pursuant to 23 CCR Chapter 15 Article 5 are observed, the Navy will immediately notify the
regulatory agencies and will evaluate the groundwater contamination in accordance with CERCLA, and
will obtain concurrence from EPA and the State on remediation decisions. Potential actions may
include additional or more frequent sampling or groundwater extraction and treatment, depending on
the nature and levels of the chemicals detected.
The subsurface collection trench would be designed to intercept any leachate that may migrate into
shallow groundwater and protect the SWRP receptors while a more permanent remedy could be
evaluated. Initially, collected leachate can be stored in tanks. The leachate can then be sampled,
treated (if necessary), and disposed of. The available treatment and disposal options will depend on the
nature and volume of contaminated leachate. If treatment is necessary, the Navy will first evaluate
using existing on-site treatment systems, such as the OUS treatment system or the west-side aquifers
treatment system. Again, depending on the volume and nature of the release, the Navy may also
consider using a package treatment system to reduce contaminant concentrations prior to discharge or
directly discharging the water to the local publicly owned treatment works (POTW). Other possible
discharge options include reuse at the Moffett Field golf course or discharge to surface waters under a
National Pollutant Discharge Elimination System (NPDES) permit. Leachate migration has not
occurred at Site 1 and is not expected to in the future (PRC 1995). However, the contingency measure
would protect against the possibility of any buried waste mobilizing and migrating off site in the future.
The Navy will obtain concurrence from EPA and the State on remediation decisions regarding
leachate.
Only the northern boundary of Site 1 is selected for additional containment because leachate is
upgradient to a sensitive ecosystem. Releases along other borders could be addressed by hydraulic
control with downhole pumps, if needed. A contingency measure is not considered for Site 2 since
hydraulic control could be readily achieved, as demonstrated by the pumping at the Building 191 lift
station.
22 CM4-0236inj]fj\s:\wpdoci\usiuvy\moffea\cio-0236\fhJrod.doc\8-l-97\jem
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SUBSURFACE
eXpUNDWATER
COLLECTION
OAS VENT
-LANDFLL
CAP
I
SUflROUNtNNO
CLAYS
COLLECTION PUUP\PtPING
6RAVEI-
COLLECTWN
TRENCH
UNER
SECTION A - A
LECEND
- LEACHATE GRADIENT
NOT TO SCALE
FIGURE 5
MOFFETT FEDERAL AIRFIELD
OU1 ROD
GAS AND GROUNDWATER
COLLECTION TRENCHES
33
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2.7.1.2.4 Gas Monitoring
Gas monitoring would be conducted under Alternative 2. The gas monitoring program would be in
accordance with substantive provisions of Title 14 CCR, Chapter 3, Article 7.8, or 40 CFR
258.61(a)(4), whichever is more stringent, which have been identified as applicable for OU1. Methane
concentrations would be monitored and if the lower explosive limit (LEL) (concentration of 5 percent
by volume in air) is exceeded at site boundaries, a corrective action program would be implemented
according to applicable requirements. An example of a corrective action includes extending the gas
collection trench (described below). According to San Francisco Bay Area Air Quality Management
District (BAAQMD) regulation 8-34-111.1, landfills smaller than 1 million tons are exempt from
BAAQMD requirements for landfill gas monitoring and collection. Sites 1 and 2 are both smaller than
1 million tons. However, landfill gas monitoring is required by federal and state landfill closure
regulations.
At Site 2, methane has not been detected inside or at the perimeter. If this trend continues, the need
for gas monitoring would be re-evaluated and may no longer be required at Site 2.
2.7.1.2.5 Gas Trench Vent
Methane gas was detected at the western end of Site 1 in landfill gas monitoring well (LGMW) 1-3 at a
concentration of 31 percent by volume and was potentially migrating westward during the air solid
waste assessment test (SWAT) (IT 1992). Under Alternative 2, a gas collection trench has been
included at Site 1 to intercept and vent gas to the atmosphere before it migrates off site. The north-
south trench would extend along the western end of the landfill for approximately 300 feet, and tie into
the east-west groundwater collection gravel trench. The trench vent depth would extend to the water
table (roughly 5 feet) and vertical riser vents would be included to allow accumulated gases to escape
from the trench to the surface. The trench is located near the runway extension to minimize impacts to
the wetland area to the west of the landfill. A trench vent is not included for Site 2 because no
methane migration was detected during the air SWAT (IT 1992).
34 044-0236injlft\$:\wpdoct\uinavyVjnoffen\£to-0236\fnlrod.doc\8-l-97\jem
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2.7.1.3 Alternative 3: Multilayer Cap, Trench Vent
Alternative 3 consists of similar features as Alternative 2 (institutional controls, gas and groundwater
collection trenches, and gas and groundwater monitoring) with the addition of a multilayer cap.
Previous sections discussed institutional controls, collection trenches, and monitoring. Therefore, the
multilayer cap will be the only component of Alternative 3 discussed below.
A multilayer cap would be implemented under this alternative to isolate landfill refuse, eliminate direct
contact of surface soils, reduce erosion, reduce surface contaminant migration, and limit infiltration.
The function of the multilayer cap is the same as the native soil cap function identified in Alternative 2.
The main difference is that the multilayer cap is specifically designed to reduce infiltration. The
multilayer cap includes a low-permeability layer of material in the cap. The other layers mainly
function to protect this low-permeability layer and maintain its function. Above the low-permeability
layer (or barrier layer), a drainage layer may be required to transport water away from the barrier
layer. This drainage layer reduces the hydraulic head on top of the barrier layer and therefore limits
the driving force of vertical migration. Above the drainage layer, a soil layer which supports
vegetation is typically installed. This layer mainly functions to protect the barrier layer by reducing
erosion and desiccation. A biotic barrier can also be included to prevent burrowing animals from
destroying the integrity of the barrier layer. Lastly, to support the barrier layer and provide a
foundation for its construction, a layer of soil is placed before the barrier layer. Figure 6 is a
conceptual diagram of Alternative 3.
At Site 1, methane was detected at significant levels inside landfill boundaries. Low-permeability caps
placed over landfills generating gas can cause gas pressure to build up. The increase in gas pressure
can damage the cap and increase horizontal migration. Therefore, passive gas control has been
included under this alternative for Site 1 to protect the integrity of the low-permeability cap and to
mitigate any increase in horizontal migration caused by the low-permeability cap.
Passive gas control would consist of gas vents incorporated into the multilayer cap at Site 1. The gas
vents would be placed beneath the barrier layer and would provide a low resistance path for the gas.
Gas vent riser pipes would be located around the perimeter or within the landfill to passively carry gas
to the surface (see Figure 6). Gas vents are not required for the multilayer cap proposed for Site 2
because gases are not being generated.
35 0444)236iniirs\s:\v^ocs\iaiuvy\inoffea\cu>-0236\ftilrad.doc\8-l-97\jem
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FILTER
FABRIC
LOCAL-
WATER
TABLE
-GAS VENTING
TRENCH (FOR
WESTERN END
OF SITE 1 ONLY)
FILTER FABRIC
TWO PLACES
EXTENT OF
LANDFILL
s
VEGETATION LAYER
j DRAINAGE LAYER
t_-_-. BARRIER LAYER
GAS VENTING LAYER
(SITE 1 ONLY)
FOUNDATION LAYER
LANDFILL GAS
MIGRATION
VEGETATION
FIGURE 6
MOFFETT FEDERAL AIRFIELD
OU1 ROD
CONCEPTUAL DIAGRAM
OF ALTERNATIVE 3
36
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2.7.2 Description of Consolidation Alternative
Based on new information discovered during OU1 design activities; the volume of waste in Site 2 is
much less than estimated in the OU1 FS report. The OU1 FS estimated that Site 2 contained about 5
acres and about 169,000 cubic yards of waste. The new information indicates that wastes at Site 2
cover about 1 acre and are about 20,000 cubic yards in volume. The new information indicates that
the presumptive remedy of capping for Site 2 should be re-evaluated. In consideration of these new
data and EPA's December 1996 guidance Application of the CERCLA Municipal Landfill Remedy to
Military Landfills, the Navy re-evaluated the Site 2 remedial approach. The guidance considers the
practical application of excavation as a key factor in the decision process and suggests that landfills
smaller than 100,000 cubic yards may under some circumstances be suitable for excavation. Based on
this information, the Navy, in consultation with EPA, DTSC, and RWQCB, has developed a
consolidation alternative as described below:
• Excavation of waste from Site 2 and consolidation of the wastes at Site 1
• Backfill and restoration of the land surface at Site 2
• Groundwater monitoring at Site 2
The wastes from Site 2 would be contained within the cap already planned for the Site 1 landfill.
Provisions for cap construction, groundwater and landfill gas monitoring, and postclosure maintenance
at Site 1 would be the same as described in Section 2.7.1.
Excavation activities at Site 2 would begin near the location of wells W2-10 and W2-8 where waste
materials were identified during previous investigations. These well locations and the estimated extent
of the waste to be excavated are shown on Figure 3. The excavation would continue radially from
each well until visual screening indicates that all waste materials have been removed. The Navy plans
to remove all waste materials to the fullest extent technically and economically feasible. Prior to
backfilling the excavation, the Navy will collect and analyze confirmatory horizontal and vertical soil
samples after all waste identified by visual screening has been removed. The Navy will consult with
the regulatory agencies to select the number and locations of these samples. The Navy will consult
with the regulatory agencies to determine the final limits of the excavation based on the sample results.
If concurrence is not reached, further evaluation of the nature and extent of the Site 2 landfill
contamination will be required and further remediation may be necessary. Inert materials, such as
7 044-0236irulft\s:\wpdacs\iisnavy\nx>ffenVcto-0236\fhlrod.doc\g-l-97\jeni
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construction debris, would remain at Site 2 but would be covered by a least 12 inches of clean fill to
minimize safety hazards from protruding debris.
The Navy will not place containers of hazardous waste excavated from Site 2 at Site 1. Furthermore,
free liquids observed in the Site 2 excavation that are clearly not groundwater (for example, free-phase
paints, oils, or solvents) will be removed and not placed at Site 1. Similarly, containers of hazardous
waste encountered during activities at Site 1 will be removed. These containers will be tested and
disposed of appropriately off site. Freely mobile waste materials will not be placed or allowed to
remain at Site 1 but will be shipped off site to an appropriate disposal facility.
Wastes from Site 2 are expected to be solid (nonhazardous) wastes. Waste classification requirements
in Title 23 CCR, Chapter 15, Article 2 are applicable for wastes excavated at Site 2. The Navy, with
the concurrence of the regulatory agencies, will use visual screening methods to meet these
requirements. However, because some characteristic hazardous wastes may be associated with the
solid wastes at Site 2, the Navy proposes that Site 1 be designated a CAMU, which allows on-site
handling of remediation wastes without triggering RCRA land disposal restrictions (LDRs) and
minimum technology requirements (MTRs). Designation of Site 1 as a CAMU will not exempt the
Navy from taking the steps described above for handling mobile, liquid wastes. The cap planned for
Site 1 contains the same components as the cap originally envisioned for Site 2 so waste from Site 2
will be equally protected by the Site 1 cap. In addition, formerly saturated wastes from Site 2 will be
placed above the water table at Site 1, reducing the potential for leachate formation.
Active groundwater remediation is not part of the consolidation alternative. However, excavation
activities at Site 2 will likely require dewatering to allow removal of saturated wastes. This
groundwater will be used for dust control at the site if sampling indicates that the water does not
contain substances exceeding federal AWQC for aquatic life or RWQCB water quality objectives.
Water will be applied at Site 1 only within a bermed area 10 feet interior to the foot print of the landfill
cap and in accordance with pertinent occupational health and safety requirements. Groundwater data
indicate that the Site 2 wastes are not affecting surrounding groundwater quality and removal of the
wastes is expected to further reduce this potential effect. However, the Navy will monitor
downgradient groundwater quality for a minimum of 3 years to confirm that groundwater quality is not
affected. Groundwater monitoring at Site 2 will follow the substantive regulations in 23 CCR, Chapter
15, Article 5. The groundwater monitoring program will be contained in an appropriate remedial
design document.
3 0444)236iniir(\>:VwpdocsVuaavyVinofren\cto-0236\fnlrad.docV8-l-97\jeni
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2.8 SUMMARY OF COMPARATIVE ANALYSIS
This section presents a comparative analysis of the alternatives against the nine evaluation criteria set
forth in the NCP (40 CFR Part 300.430(e)(9)(iii)). Section 2.8.1 describes the evaluation criteria.
Section 2.8.2 presents the comparative analysis of Site 1 alternatives as described in the OU1 FS.
Section 2.8.3 presents the comparative analysis for the Site 2 alternatives described in the FS and for
the consolidation alternative.
2.8.1 Remedial Alternatives Evaluation Criteria
The NCP requires that each alternative that undergo a detailed analysis be evaluated against nine
evaluation criteria. The nine evaluation criteria fall into three categories, threshold criteria, balancing
criteria, and modifying criteria. Sections 2.8.1.1. through 2.8.1.3 below describe the individual criteria
evaluated under each of the three categories.
2.8.1.1 Threshold Criteria
For any alternative to be eligible for selection, it must meet certain threshold criteria. The two
threshold criteria are overall protection of human health and the environment and compliance with
applicable or relevant and appropriate requirements (ARARs).
2.8.1.2 Balancing Criteria
After the comparison with threshold criteria, five additional criteria are used to analyze differences
among alternatives. The following five criteria are used for comparative analysis:
• Long-term Effectiveness and Permanence
• Reduction in Toxicity, Mobility, and Volume
• Short-Term Effectiveness
• Implementability
• Cost
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2.8.1.3 Modifying Criteria
Modifying criteria include state agency and community acceptance. These assessments evaluate issues
and concerns of both the state agencies and the public and are evaluated following the release of the
proposed plan.
2.8.2 Comparative Analysis of Site 1 Alternatives
This section presents the comparative analysis of the Site 1 alternatives for the three categories of
evaluation criteria. Section 2.8.2.1 through 2.8.2.3 present the comparative analysis of the alternatives
for die threshold, balancing, and modifying criteria. Section 2.8.4 presents the results of the Site 1
comparative analysis.
2.8.2.1 Site 1 Alternatives and the Threshold Criteria
Alternative 1 does not meet the threshold criteria of overall protection of human health and the
environment and compliance with ARARs for Site 1. If no action is taken, site conditions would be
unpredictable and uncontrolled, which could result in future erosion and exposure to human and
ecological receptors. Leaving Site 1 uncontrolled would not likely provide continual overall
protectiveness from hazards.
Since Alternative 1 does not meet the threshold criteria for Site 1, this alternative is not eligible for
selection. However, Alternative 1 provides a basis for comparison for Alternatives 2 and 3.
Alternatives 2 and 3 meet the threshold criteria for Site 1. Both alternatives provide protection to
human health and die environment by isolating the contamination with a cap and protecting die integrity
of die cap with supporting technologies. Both alternatives monitor groundwater. Gas migration
control and monitoring would be conducted to promote control of hazards associated with methane
migration. In addition, die FS evaluation indicated that both alternatives would meet ARARs.
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2.8.2.2 Site 1 Alternatives and the Balancing Criteria
The OU1 FS evaluated each of the Site 1 alternatives against the five balancing criteria and then
compared the alternatives to one another in relation to the balancing criteria. Sections 2.8.2.2.1
through Sections 2.8.2.2.5 summarize the comparative analysis of the Site 1 alternatives.
2.8.2.2.1 Site 1 Alternatives and Long-term Effectiveness and Permanence
Alternatives 2 and 3 both provide long-term effectiveness and permanence for Site 1 but would require
occasional O&M to promote long-term effectiveness and permanence. The only difference between
Alternative 2 and Alternative 3 is that Alternative 3 employs a multilayer cap instead of a single layer
soil cap. The function of the multilayer cap is the same as the native soil cap's function, which is to
isolate landfill refuse, eliminate exposure to surface soils, reduce erosion, and limit infiltration. The
functional difference between the alternatives is that Alternative 3 employs a low-permeability layer
and drainage layer that specifically function to reduce infiltration. These layers may reduce the amount
of leachate generated, which should reduce leachate migration. For the soil cap in Alternative 2,
evapotranspiration, soil storage capacity, and runoff processes act to limit infiltration.
The comparative alternative evaluation in the FS proposed that the native soil cap would have similar
effectiveness compared to the multilayer, clay (or clay equivalent) cap for Site 1. This analysis was
based on (1) cap performance, (2) site conditions, (3) the ability to maintain cap integrity, and (4) the
potential for increased gas migration. The analysis of these factors is discussed in detail in the FS
report (PRC 1995).
Alternatives 2 and 3 provide greater long-term effectiveness and permanence than Alternative 1. Over
the long-term, Site 1 conditions under Alternative 1 would be unpredictable and uncontrolled which
could result in future erosion and exposure to human and ecological receptors. Although implementing
Alternative 2 or 3 would destroy any current habitats at Site 1, these are expected to be short-term
impacts. The area is expected to recover in less than 5 years (see Section 2.8.2.3) (PRC 1994).
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2.8.2.2.2 Site 1 Alternatives and the Reduction in Toxicity, Mobility, and Volume
None of the Site 1 alternatives reduce the toxicity, mobility, or volume of contaminants through the use
of treatment because treatment is not a component of any of the Site 1 alternatives. The objective of
the Site 1 alternatives is to reduce mobility of contamination by isolation. In accordance with EPA
presumptive remedy guidance (EPA 1993), reductions hi toxicity, mobility, and volume are not
addressed by any alternatives considered because such treatment is impractical for landfill sites.
Alternatives 2 and 3 are more effective in reducing the mobility of contamination than Alternative 1.
Alternatives 2 and 3 reduce mobility of refuse by containment, whereas Alternative 1 does not reduce
contaminant mobility.
2.8.2.2.3 Site 1 Alternatives and Short-term Effectiveness
Alternative 1 provides greater short-term effectiveness than Alternatives 2 and 3 because no remedial
action would be implemented. No workers would be exposed and no increase in truck traffic would
occur. Alternative 1 also provides greater short-term effectiveness because it minimizes impacts to the
current habitat and associated residents.
Site 1 consists of disturbed, low-value habitat that supports predominantly non-native plant and animal
species. Under Alternatives 2 and 3, heavy machinery and soil used to cap the Site 1 landfill would
destroy the existing vegetative community and would kill or displace species inhabiting the site.
Animals that would be displaced during cap implementation include the red fox, black-tailed hare,
vagrant shrew, California vole, harvest mice, birds, and lizards. However, the detrimental impacts to
the habitat are expected to be short term. Based on the OU1 ecological assessment, the landfill habitat
is expected to recover rapidly as a result of the following site-specific conditions (PRC 1994):
• The ability of the animal species to emigrate from the site during cap construction and
then re-establish territories in the following season
• The abundance of similar species in surrounding habitats (PRC 1994)
• The overall high reproductive rate of commonly occurring species such as shrews,
voles, and ground squirrels due to short gestation and large litter size (PRC 1994)
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• Revegetation
Aerial photographs of Site 1 taken in 1987 show a general lack of vegetative cover. Much of the
landfill surface is bare, burned, matted, or covered with stockpiled drums and scrap equipment.
However, photos of the same area taken in 1992 indicate vegetative recolonization with approximately
75 percent vegetative cover. Areas not sustaining vegetation are hard-packed, gravelly areas to the
west and south of the pistol range area.
Due to the past recovery rate of the area, it is reasonable to assume that the area would again recover
in less than 5 years after the landfill has been capped. The recovered habitat would not likely be
identical to the current habitat, but it would be similar. Revegetation using regionally native plants
may enhance the recovery rate.
Alternative 2 would be more effective than Alternative 3 in the short term. Although both alternatives
are expected to be constructed relatively quickly (6 to 12 months). Alternative 3 would require more
time to implement due to larger volumes of material required and more complex installation. Over
three times more material would be required for Alternative 3. Truck traffic would be greater and
increase the potential for vehicle accidents and disturbances and exposure to workers could be
prolonged. In addition, for Alternative 3, refuse may need to be disturbed to achieve more stringent
grades required due to the multiple layers and to minimize material requirements. Disturbing refuse
would increase exposure and risk to workers.
2.8.2.2.4 Site 1 Alternatives and Implementability
Alternative 1 would be easier to implement than Alternatives 2 and 3. Except for the monitoring wells,
no construction is required for Alternative 1. Monitoring is readily implementable. For Alternatives 2
and 3, greater technical and administrative effort would be required to construct the caps, collection
trenches, and institutional controls at Site 1.
Alternative 2 would be simpler to implement than Alternative 3 due to the addition of multiple layers in
Alternative 3. For the additional layers, additional construction materials include gravel from borrow
sources, sand, and clay. In addition, slopes needed to maintain layer stability may require more
precontouring and therefore increase the possibility of disturbing landfill contents. Also, construction
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of the low-permeability layer would require specialized quality assurance and quality control (QA/QC)
testing.
2.8.2.2.5 Site 1 Alternatives and Cost
The following is a list of the capital and present worth O&M (based on 30 years and an 8 percent
discount rate) costs for Alternatives 1 through 3 at Site 1:
• Alternative 1: $1,068,000
• Alternative 2: $2,306,900
• Alternative 3: $5,091,400
Alternative 2 does not include multiple layers and consequently has lower capital and construction
costs. O&M costs are similar. Estimated costs for monitoring, institutional controls, and collection
trenches are identical for Alternatives 2 and 3. Alternative 1 has a lower cost than Alternatives 2 and 3
since no remedial action would be implemented under Alternative 1.
2.8.2.3 Site 1 and the Modifying Criteria
The state and community acceptance of the Site 1 alternatives are compared below.
2.8.2.3.1 Site 1 Alternatives and State Acceptance
DTSC, RWQCB, and EPA agreed on Alternative 2 as the preferred alternative for landfill containment
for Site 1. DTSC and RWQCB participated in the development of the FS and the initial proposed plan.
However, following the June 1995 public comment period, CIWMB noted several deficiencies with
Alternative 2 and did not recommend selecting Alternative 2 for Site 1.
2.8.2.3.2 Site 1 Alternatives and Community Acceptance
A public comment period was held from May 30, 1995 to July 31, 1995 on the three alternatives
presented in the FS and the June 1995 proposed plan. In addition, a public meeting was held on
June 15, 1995. During this meeting, the Navy presented the proposed plan for OU1 and answered
44
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questions. The community had concerns regarding regulatory compliance, overall protection to human
health and the environment, and site characterization. Responses to community comments are
presented in Section 3.1 and 3.2 of the responsiveness summary (Section 3.0).
2.8.2.4 Results of Site 1 Comparative Analysis
The results from the comparative analysis indicated Alternative 2 (monitoring, soil cap, and trench
vent) was the most feasible for Site 1. Alternative 2 was easier to implement, had greater short-term
effectiveness, and was believed to have equal long-term effectiveness with lower costs as compared to
Alternative 3- Alternative 3 incorporated additional layers to directly address infiltration. The
increased layers reduce implementability and increase costs. In addition, for Site 1, Alternative 3 did
not offer greater effectiveness, as described in the FS report (PRC 1995). Alternative 2 was initially
recommended as more feasible also when compared to Alternative 1 because it meets the threshold
criteria and is more attractive based on several factors. Although Alternative 1 is easiest to implement,
has the lowest cost, and minimizes impacts to the current habitat and current receptors, it is not
recommended over Alternative 2. The short-term impacts from habitat destruction are not significant
(PRC 1994). Alternative 2 eliminates the exposures to human and ecological receptors by (1)
minimizing direct contact with landfill contents, (2) minimizing infiltration, (3) preventing inhalation of
contaminated dust, and (4) minimizing erosion and runoff through revegetation and grading. In
addition, in-place containment of landfill contents minimizes the potential spread of contaminants off
site into the nearby wetlands. Alternative 1 achieves none of these results. Neither capping nor
limited capping of the landfill would leave these potential pathways intact, and would provide no
protection against off-site contaminant migration. Erosion and runoff would continue to occur,
potentially spreading contaminants off site.
In summary, Alternative 2 was recommended in the initial proposed plan because the Navy believed it
met ARARs and provided a cost-effective means to achieve long-term protectiveness. However, based
on comments received during the public comment period, the Navy issued a new proposed plan in
December 1995 that proposed implementation of a modified Alternative 2. This modifications to
Alternative 2 are discussed in more detail in Sections 2.9 and 2.10.
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2.8.3 Comparative Analysis of Site 2 Alternatives
The comparative analysis of Site 2 Alternatives is presented below. The analysis is presented for each
of the three categories of criteria in Sections 2.8.3.1 through 2.8.3.3 and the results of die analysis are
summarized in Section 2.8.3.4.
2.8.3.1 Site 2 Alternatives and the Threshold Criteria
Alternative 1 does not meet the threshold criteria of overall protection of human health and the
environment and compliance with ARARs for Site 2. If no action is taken, site conditions would be
unpredictable and uncontrolled which could result in future erosion and exposure to human and
ecological receptors. Leaving Site 2 uncontrolled would not likely provide continual overall
protectiveness from hazards.
Since Alternative 1 does not meet the threshold criteria for Site 2, this alternative is not eligible for
selection. However, Alternative 1 provides a basis for comparison for Alternatives 2 and 3 and the
consolidation alternative.
Alternatives 2 and 3 and the consolidation alternative meet the threshold criteria for Site 2.
Alternatives 2 and 3 provide protection to human health and the environment by isolating the
contamination with a cap and protecting the integrity of the cap with supporting technologies. The
consolidation alternative would provide overall protectiveness at Site 2 by removing the waste from
Site 2 and consolidating it at Site 1. Under the consolidation alternative, wastes from the saturated
zone at Site 2 would be placed above the water table at Site 1 and provide an extra measure of
protectiveness for groundwater at Site 2.
In addition, the FS evaluation and the April 1997 alternatives analysis technical memorandum indicated
that Alternatives 2 and 3 and the consolidation alternative would meet ARARs.
2.8.3.2 Site 2 Alternatives and the Balancing Criteria
Sections 2.8.3.2.1 though 2.8.3.2.5 below present the comparative analysis of Site 2 alternatives for
the five balancing criteria.
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2.8.3.2.1 Site 2 Alternatives and Long-Term Effectiveness and Permanence
The consolidation alternative would provide the greatest degree of long-term effectiveness and
permanence. Removing wastes from Site 2 would remove potential exposures to wastes at the site.
Placement of previously saturated wastes from Site 2 above the water table at Site 1 would further
reduce the potential for contaminant migration and enhance the long-term effectiveness of this
alternative. The consolidation alternative would require less O&M than Alternatives 2 and 3 because
Site 2 would not need to be capped.
Alternatives 2 and 3 both provide long-term effectiveness and permanence for Site 2 but would require
occasional O&M to promote long-term effectiveness and permanence. The only difference between
Alternative 2 and Alternative 3 is that Alternative 3 employs a multilayer cap instead of a single layer
soil cap. The function of the multilayer cap is the same as the native soil cap's function, which is to
isolate landfill refuse, eliminate exposure to surface soils, reduce erosion, and limit infiltration. The
functional difference between Alternatives 2 and 3 is that Alternative 3 employs a low-permeability
layer and an optional drainage layer that specifically function to reduce infiltration. These layers may
reduce the amount of leachate generated, which should reduce leachate migration. For the soil cap in
Alternative 2, evapotranspiration, soil storage capacity, and runoff processes act to limit infiltration.
The comparative alternative evaluation in the FS proposed that the native soil cap would have similar
effectiveness compared to the multilayer, clay (or clay equivalent) cap for the OU1 landfills. This
analysis was based on (1) cap performance, (2) site conditions, (3) the ability to maintain cap integrity,
and (4) the potential for increased gas migration. The analysis of these factors is discussed in detail in
the FS report (PRC 1995).
Alternatives 2 and 3 provide greater long-term effectiveness and permanence than Alternative 1 but
less long-term effectiveness and permanence than the consolidation alternative. Over the long-term,
site conditions under Alternative 1 would be unpredictable and uncontrolled which could result in
future erosion and exposure to human and ecological receptors. Although implementing Alternative 2
or 3 or the consolidation alternative would destroy any current habitats at Site 2, these are expected to
be short-term impacts. The area is expected to recover in less than 5 years (see Section 2.8.2.3) (PRC
1994).
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2.8.3.2.2 Site 2 Alternatives and the Reduction in Toxicity, Mobility, and Volume
None of the Site 2 alternatives reduce the toxicity, mobility, or volume of contaminants through the use
of treatment because treatment is not a component of any of the Site 2 alternatives. The objective of
the Site 2 alternatives is to reduce mobility of contamination by isolation. In accordance with EPA
presumptive remedy guidance, reductions in toxicity, mobility, and volume are not addressed by any
alternatives considered because such treatment is unpractical for landfill sites. However, consolidation
will result in the placement of previously saturated wastes in the unsaturated zone at Site 1 and
potential contaminant migration will be reduced.
2.8.3.2.3 Site 2 Alternatives and Short-term Effectiveness
Alternative 1 provides greater short-term effectiveness than Alternatives 2 and 3 and the consolidation
alternative because no remedial action would be implemented. No workers would be exposed and no
increase in truck traffic would occur. Alternative 1 also provides greater short-term effectiveness
because it minimizes impacts to the current habitat and associated residents.
Site 2 consists of disturbed, low-value habitat that supports predominantly non-native plant and animal
species. Heavy machinery and soil used to cap Site 2 (Alternatives 2 and 3) and to excavate waste
from Site 2 (consolidation alternative) would destroy the existing vegetative community and would kill
or displace species inhabiting the site. Animals that would be displaced during waste excavation and
cap implementation include the red fox, black-tailed hare, vagrant shrew, California vole, harvest
mice, birds, and lizards. However, the detrimental impacts to the habitat are expected to be short
term. Based on the OU1 ecological assessment, the landfill habitat is expected to recover rapidly as a
result of the following site-specific conditions (PRC 1994):
• The ability of die animal species to emigrate from the site during cap construction and
then reestablish territories in the following season
• The abundance of similar species in surrounding habitats (PRC 1994)
• The overall high reproductive rate of commonly occurring species such as shrews,
voles, and ground squirrels due to short gestation and large litter size (PRC 1994)
• Revegetation
The following discussion is pertinent to Site 2 because ecological conditions at Site 2 and Site 1 are
very similar. Aerial photographs of Site 1 taken in 1987 show a general lack of vegetative cover.
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Much of the landfill surface is bare, burned, matted, or covered with stockpiled drums and scrap
equipment. However, photos of the same area taken in 1992 indicate vegetative recolonization with
approximately 75 percent vegetative cover. Areas not sustaining vegetation are hard-packed, gravelly
areas to the west and south of the pistol range area.
Due to the past recovery rate of the Site 1 area, it is reasonable to assume that the Site 2 area would
recover in less than 5 years after Site 2 has been capped (Alternatives 2 and 3) or excavated
(consolidation alternative). The recovered habitat would not likely be identical to the current habitat,
but it would be similar. Revegetation using regionally native plants may enhance the recovery rate.
Alternative 2 would be more effective than Alternative 3 and the consolidation alternative in the short
term. Alternatives 2 and 3 are expected to be constructed relatively quickly (6 to 12 months), although
Alternative 3 would require more time to implement due to larger volumes of material required and
more complex installation. Over three times more material would be required for Alternative 3.
Truck traffic would be greater and increase the potential for vehicle accidents and disturbances and
exposure to workers could be prolonged. In addition, for Alternative 3, refuse may need to be
disturbed to achieve more stringent grades required due to the multiple layers and to minimize material
requirements. Disturbing refuse would increase exposure and risk to workers. The consolidation
alternative would be the least effective in the short-term because short-term risks to workers would be
potentially increased during the excavation and consolidation of wastes from Site 2 to Site 1. Worker
risks associated with excavation and consolidation of wastes could be minimized through
implementation of appropriate health and safety precautions. The consolidation alternative would take
less time to implement (3 months) than Alternatives 2 and 3 (6 to 12 months).
2.8.3.2.4 Site 2 Alternatives and Implementability
Alternative 1 would be easier to implement than Alternatives 2 and 3 and the consolidation alternative.
Except for the monitoring wells, no construction is required for Alternative 1. Monitoring is readily
implementable. For Alternatives 2 and 3 and the consolidation alternative, greater technical and
administrative effort would be required to excavate and consolidate wastes and construct the caps,
collection trenches, and institutional controls at Site 2.
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The consolidation alternative would be simpler to implement than Alternatives 2 and 3 because it
involves excavation of waste from Site 2 and does not require construction of a cap at Site 2.
Alternatives 2 and 3 would both require construction of caps at Site 2. Alternative 2 would be simpler
to implement than Alternative 3 due to the addition of multiple layers in Alternative 3. For the
additional layers, additional construction materials include gravel from borrow sources, sand, and clay.
In addition, slopes needed to maintain layer stability may require more precontouring and therefore
increase the possibility of disturbing landfill contents. Also, construction of the low-permeability layer
would require specialized QA/QC testing.
2.8.3.2.5 Site 2 Alternatives and Cost
The following is a list of the capital and present worth O&M (based on 30 years and an 8 percent
discount rate) costs for Alternatives 1 through 3 and .the consolidation alternative at Site 2:
• Alternative 1: $ 366,200
• Alternative 2: $ 850,700
• Alternative 3: $1,372,700
• Consolidation Alternative: $1,091,700
Alternative 2 is less costly than the consolidation alternative and Alternative 3 because it does not
include excavation and consolidation of waste or multiple cap layers and consequently has lower capital
and construction costs. The consolidation alternative costs less than Alternative 3 because capital costs
of excavation and consolidation are less than those of capping with a multiple layer cap and because of
the reduced O&M requirements. O&M costs are similar for Alternatives 2 and 3 but less for the
consolidation alternative. Estimated costs for monitoring, institutional controls, and collection trenches
are identical for Alternatives 2 and 3. Alternative 1 has a lower cost than Alternatives 2 and 3 and the
consolidation alternative since no remedial action would be implemented under Alternative 1.
2.8.3.3 Site 2 Alternatives and the Modifying Criteria
The state and community acceptance of the Site 2 alternatives are presented below.
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2.8.3.3.1 Site 2 Alternatives and State Acceptance
DTSC, RWQCB, and EPA, agreed on Alternative 2 as the preferred alternative for landfill
containment for Site 2. All three agencies participated in the development of the FS and the initial
proposed plan. However, following the June 1995 public comment period, CIWMB noted several
deficiencies with Alternative 2 and did not recommend selecting Alternative 2 for Site 2. In March
1997, the Navy proposed a new plan for the remedial action at Site 2, the consolidation alternative.
DTSC, RWQCB, and CIWMB agreed with the development, evaluation, and recommendation of the
consolidation alternative at Site 2.
2.8.3.3.2 Site 2 Alternatives and Community Acceptance
A public comment period was held from May 30, 1995 to July 31, 1995 on the three alternatives
presented in the FS and the June 1995 proposed plan. In addition, a public meeting was held on
June 15, 1995. During this meeting, the Navy presented.the proposed plan for OU1 and answered
questions. The community had concerns regarding regulatory compliance, overall protection to human
health and the environment, and site characterization. Responses to community comments are
presented in Section 3.1 and 3.2 of the responsiveness summary (Section 3.0). The community also
submitted comments on the proposal to consolidate wastes from Site 2 to Site 1 as presented in the
March 1997 proposed plan. In general, the community accepts the consolidation alternative for Site 2.
Responses to community comments received on the March 1997 proposed plan to consolidate Site 2
wastes at Site 1 are presented in Sections 3.5 and 3.6 of the responsiveness summary (Section 3.0).
2.8.3.4 Site 2 Comparative Analysis Results
The results of the comparative analysis presented in the OU1 FS for Alternatives 1 through 3 at Site 2
is the same as the analysis discussed above in Section 2.8.2.4. However, the results of the
comparative analysis for Site 2 are now changed by die evaluation of the proposed consolidation
alternative. The consolidation alternative compares more favorably than Alternatives 1 through 3
because it would: (1) provide greater long-term effectiveness and permanence by reducing the mobility
of the Site 2 waste, (2) be easier to implement, and (3) take less time to implement. Excavation of
wastes from Site 2 and consolidation with the wastes at Site 1 offers several additiona1 advantages over
capping wastes at Site 2. One advantage would be the gain of the Site 2 area for a wider range of land
51 044-0236injlfsU:\wpdocJ\uauvy\moffea\cu>O236\fnlrod.doc\g-l-97\jem
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uses in the future than would be allowed if Site 2 was capped. Another advantage would be the
significant reduction in long-term O&M costs associated with a cap at Site 2. If groundwater
monitoring is not required beyond 3 years, no further O&M expenditures would be needed for Site 2.
Finally, placing the formerly saturated wastes from Site 2 above the water table at Site 1 would
increase the protection of groundwater and the surrounding environment by reducing the potential for
leachate formation in those wastes.
In summary, Alternative 2 was recommended in the initial proposed plan because the Navy believed it
met ARARs and provided a cost-effective means to achieve long-term protectiveness. However, based
on the new information regarding the volume of waste at Site 2 and the development and analysis of the
consolidation alternative, the Navy believes that the consolidation alternative provides the best balance
among the alternatives analyzed for Site 2.
2.9 DOCUMENTATION OF SIGNIFICANT CHANGES
Two significant changes to the OU1 preferred alternative have been proposed since the initial proposed
plan dated June 1995. Section 2.9.1 below discusses the proposed modification of Alternative 2 (the
preferred alternative identified in the June 1995 proposed plan) for Sites 1 and 2. Section 2.9.2 below
discusses the proposed change from preference of Alternative 2 to preference of the consolidation
alternative for Site 2.
2.9.1 Significant Changes to Alternative 2 Cap Design
The initial proposed plan dated June 1995 recommended Alternative 2 (soil cap. groundwater and gas
collection trenches at Site 1, monitoring, and maintenance) as the preferred alternative for Sites 1 and 2
based on the analysis presented in the RI/FS reports and summarized in Section 2.8. A proposed plan
was presented to solicit public comments and facilitate the evaluation of the two modifying criteria:
state acceptance and community acceptance.
During the June 1995 public comment period, state, county, and local regulatory agencies indicated
that it is unlikely that the original proposal (Alternative 2) would meet performance standards contained
in the landfill closure regulations. As a result, the Navy agreed to revise the proposed plan based on a
prescribed, state pre-approved configuration for the two landfill caps at OU1. The responsiveness
summary contains specific comments and responses regarding this issue. The revised cap
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configuration uses design concepts from both Alternatives 2 and 3 and is somewhat of a hybrid of the
two FS alternatives. Instead of 3-foot thick soil caps, the landfill caps will, at a minimum, contain 1
foot of topsoil overlying a low-permeability layer. These layers will be built on a 2-foot foundation
layer. In addition to this minimum requirement, the Navy will include a biotic barrier and possibly a
drainage layer between the low-permeability layer and topsoil to protect the integrity of the low-
permeability layer and drain percolated water off the cap. The biotic barrier will prevent burrowing
animals and deep plant roots from puncturing this layer. The drainage layer may be added to provide a
pathway for percolation to flow from the cap. Several factors will be considered when evaluating the
need for a drainage layer. These include slope stability, standard accepted practices in the area, and
experience at other landfills. Inclusion of the drainage layer will be evaluated further during the
design. Lastly, the Site 1 cap will include gas venting beneath the impermeable layer to prevent gas
pressure buildup and horizontal subsurface gas migration. The revised cap configuration is very
similar to Alternative 3 except for layer thicknesses and construction materials. Figure 7 depicts the
revised cap configuration. Construction materials and cap dimensions will be specified during the
remedial design.
The Navy held a second public comment period and public meeting to disseminate information
regarding the revised proposal and to allow any interested parties to voice additional concerns.
Although this second public meeting and public comment period were held, the modifications are not
major changes from the originally proposed strategy. The original strategy included landfill caps, a
groundwater collection trench, gas venting, monitoring, and postclosure maintenance and these features
remain as part of the proposed remedy. The second proposed plan was made available to the public in
December 1995. No significant comments were received during the second public comment period,
and no significant changes have been made to the proposed changes to Alternative 2 as a result of
public comments. The December 1995 proposed plan contained an error concerning the hydraulic
conductivity of the low-permeability layer. The proposed plan stated that the conductivity of this layer
would be 10s cm/sec but should have stated that the conductivity would be less than 10"* cm/sec. A
conductivity of 10"* cm/sec is in accordance with the substantive landfill cap regulations. Section 2.10
describes the landfill cap and contains the correct hydraulic conductivity value (10"6 cm/sec) for the
low-permeability layer.
ei 044XJ236injlfs\i:\wpdoej\usnavy\moffen\cu>-0236\ft>lrod.(loc\£-l-97\jen)
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BIOTIC
BARRIER
GAS VENT
12-INCH VEGETATION LAYER
24-INCH FOUNDATION LAYER
inoooooooni
REFUSE
I
§
MINIMUM DIMENSIONS SHOWN
NOT TO SCALE
FIGURE 7
MOFFETT FEDERAL AIRFIELD
OU1 ROD
REVISED CAP CONFIGURATION
54
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2.9.2 Significant Change from Capping to Consolidation for Site 2
As of January 1996, the preferred alternative was a modified version of Alternative 2 as described in
Section 2.9.1 above. However, based on new information collected as part of OU1 design activities,
the volume of wastes at Site 2 is much less than estimated in the OU1 FS report. Consequently, the
Navy developed and evaluated an additional alternative for Site 2, the consolidation alternative. The
consolidation alternative was developed and analyzed in an April 1997 technical memorandum.
Because the consolidation alternative is considered a major change in the remediation strategy for
Site 2, the Navy issued a proposed plan in March 1997 recommending the selection of the
consolidation alternative for Site 2 instead of the modified Alternative 2.
2.10 SELECTED REMEDY
The initial proposed plan dated June 1995 recommended Alternative 2 (soil cap, groundwater collection
trench at Site 1, trench vent at Site 1, monitoring, and maintenance) as the preferred alternative based
on the analysis presented in the RI/FS reports. After the June 1995 public comment period ended, the
Navy re-evaluated the proposal, modified the preferred alternative based on comments received, issued
a revised proposed plan, and held a second public comment period and public meeting. Based on new
information that indicates that the volume of waste in Site 2 is much less than that estimated in the OU1
FS, the Navy developed and analyzed the consolidation alternative for Site 2. The Navy issued a
proposed plan in March 1997 that recommended selection of the consolidation alternative for Site 2. A
public comment period and public meeting were held to discuss the recommendation of the
consolidation alternative for Site 2. Based on the comments received on the three proposed plans for
OU1, the final remedial action has been selected.
The final remedial action for OU1 consists of:
Site 1
• Landfill cap, including:
12-inch minimum vegetation layer (potentially using recycled soils)
and revegetation using regionally native plants
Biotic barrier
Drainage layer (optional)
Low-permeability layer (10"* cm/sec minimum)
Gas vents
24-inch minimum foundation layer
55 0444XQ6ifulf$\s:\wp(too\uauvy\iix)ffea\ct(><^6\fh]rod.doc\8-l-97\jein
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• Gas venting trench
• Subsurface groundwater collection trench
• Groundwater and gas monitoring
• Institutional controls - Fencing, signs, O&M of Building 191 pump station and
drain/subdrain system, and restrictions on cap disturbances. The Navy will resolve
any issues with NASA regarding the process to develop appropriate restrictive
provisions to ensure continued O&M of the Building 191 pump station and to maintain
the integrity of the Site 1 cap. The Navy will enter into an agreement with NASA or
develop another appropriate vehicle to accomplish this task. The Navy will resolve any
issues concerning the necessary restrictive provisions within 1 year of the date of this
ROD.
• Postclosure maintenance
The selected remedial action for Site 1 is identical to the originally proposed alternative
(Alternative 2 in the FS) except that it includes a modified cap configuration. The cap
configuration was modified to address regulatory concerns.
Site 2
• Excavation of municipal-type wastes from Site 2
• Transport to and consolidation of Site 2 wastes at Site 1
• Backfilling and restoration of excavated area at Site 2
and revegetation using regionally native plants
• Groundwater monitoring for a minimum of 3 years
• Designation of Site 1 as CAMU through issuance of this ROD
Because of the proximity of surface water to the northern boundary of the Site 1 landfill, the selected
remedy includes construction of a groundwater collection trench as a contingency measure to provide
immediate protection to this adjacent surface water. This in-place collection trench can be activated in
the future if groundwater becomes contaminated by the Site 1 landfill and migrates toward this surface
water to the north.
Groundwater within the subsurface collection trench would be monitored at the same frequency as at
the Site 1 groundwater monitoring wells. If chemical concentrations exceeding concentration limits set
pursuant to 23 CCR Chapter 15 Article 5 are observed, the Navy will immediately notify the
regulatory agencies and will obtain concurrence from EPA and the State regarding appropriate actions.
Jg OOX)236imlft\s.\wpdocsUisnavy\moffen\cttH0236\fnlrcd.doc\8-l-97\jem
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Potential actions may include additional or more frequent sampling or groundwater extraction and
treatment, depending on the nature and levels of the chemicals detected.
The remedy, however, does not include active leachate extraction or active groundwater remediation at
this time. Groundwater monitoring at Site 1 will continue throughout the postclosure period and,
should groundwater become contaminated by Site 1 in the future and require remediation, the
collection trench can be activated as an initial, immediate response. Implementing the collection trench
at Site 1 will protect surface water while allowing time to implement a more permanent remedy, if
necessary. Groundwater monitoring at Site 2 will continue for a minimum of 3 years to confirm that
groundwater quality is not adversely affected. Groundwater monitoring at Sites 1 and 2 will comply
with the substantive regulations in 23 CCR, Chapter 15, Article 5. The Navy will evaluate the
groundwater contamination in accordance with CERCLA, and will obtain concurrence from EPA and
the State on remediation decisions. The cost estimate for the selected remedial alternative is provided
in Section 2.8.3.2.5.
The OU1 remedy also includes institutional controls. These controls include restrictions on cap
disturbances and O&M of the Building 191 pump station and drain/subdrain system. O&M of the
pump station was included as a component of the remedy to prevent potential flooding of OU1. The
necessity of these restrictions and actions will be noted in the land use planning documents and real
property records. The Navy will resolve any issues with NASA regarding the process to develop
appropriate restrictive provisions to ensure continued O&M of the Building 191 pump station and to
maintain the integrity of the Site 1 cap. The Navy will enter into an agreement with NASA or develop
another appropriate vehicle to accomplish this task. The Navy will resolve any issues concerning the
necessary restrictive provisions within 1 year of the date of this ROD. In the event of a future
conveyance of the property, the necessity of pump station O&M and use restrictions at Site 1, will be
addressed by appropriate notices and land use covenants; however, subsequent landowners may
propose remedy modifications to the Navy and, if appropriate, the remedy may be modified in
accordance with CERCLA Section 120 and the NCP.
2.11 STATUTORY DETERMINATIONS
Because of the proximity of surface water to the northern boundary of the Site 1 landfill, the selected
remedy includes construction of a groundwater collection trench as a contingency measure to provide
immediate protection to this adjacent surface water. This in-place collection trench can be activated in
57 OU-(GJ6inilftU:\wpdoct\usnavy\moffeo\ao-0236\Jhlrod.doc\8-l-97\jcn)
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the future if groundwater becomes contaminated by the Site 1 landfill and migrates toward this surface
water to the north. Groundwater within the subsurface collection trench would be monitored at the
same frequency as at the Site 1 groundwater monitoring wells. If chemical concentrations exceeding
concentration limits set pursuant to 23 CCR Chapter IS Article 5 are observed, the Navy will
immediately notify the regulatory agencies and will obtain concurrence from EPA and the State
regarding appropriate actions. Potential actions may include additional or more frequent sampling or
groundwater extraction, depending on the nature and levels of the chemicals detected. The remedy,
however, does not include active leachate extraction or active groundwater remediation at this time.
Groundwater monitoring at Site 1 will continue throughout the postclosure period and, should
groundwater become contaminated by Site 1 in the future and require remediation, the collection trench
can be activated as an initial, immediate response. Implementing the collection trench at Site 1 will
protect surface water while allowing time to implement a more permanent remedy, if necessary.
Groundwater monitoring at Site 2 will continue for a minimum of 3 years to confirm that groundwater
quality is not adversely affected. The Navy will evaluate the groundwater contamination in accordance
with CERCLA, and will obtain concurrence from EPA and the State on remediation decisions. The
cost estimate for the selected remedial alternative is provided in Section 2.8.3.2.5.
The OU1 remedy also includes institutional controls. These controls include restrictions on cap
disturbances and O&M of the Building 191 pump station and drain/subdrain system. O&M of the
pump station was included as a component of the remedy to prevent potential flooding of OU1. The
necessity of these restrictions and actions will be noted in the land use planning documents and real
property records. In the event of a future conveyance of the property, the necessity of pump station
O&M and use restrictions at Site 1, will be addressed by appropriate notices and land use covenants;
however, subsequent landowners may propose remedy modifications to the Navy and, if appropriate,
the remedy may be modified in accordance with CERCLA Section 120 and the NCP.
The selected remedy meets the statutory requirements of Section 121 of CERCLA. The statute
requires that remedial actions undertaken at Superfund sites:
• Be protective of human health and the environment
• Comply with ARARs unless a statutory waiver is justified
• Be cost effective
• Utilize permanent solutions and alternate treatment technologies or resource recovery
technologies to the maximum extent practical
50 044-0236inilfs\i:\wpdou\UHUvy\mofrea\ct(v0236\ftUrod.doc\8-I-97\jem
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• Satisfy the preference for treatment that reduces toxicity, mobility, or volume as a
principal element, or provide an explanation as to why this preference is not satisfied
A brief description of how the selected remedy satisfies each of the statutory requirements is provided
in the following subsections.
2.11.1 Protection of Human Health and the Environment
The selected remedial alternative provides protection to human health and the environment by
consolidating Site 2 wastes at Site 1 and by encapsulating the contamination in the Site 1 landfill with a
cap. Site 2 municipal-type wastes will be removed and transported to Site 1 for consolidation. Site 2
wastes will be consolidated at Site 1 in accordance with federal and State of California regulations
regarding sanitary landfill operations, including waste compaction standards and interim cover
requirements. Liquid waste and containerized waste will be disposed of off site at an appropriate
facility.
Inert materials, such as construction debris, will remain at Site 2. The excavated areas at Site 2 will be
backfilled with clean material and restored with vegetation. Groundwater monitoring will be conducted
for at least 3 years to ensure Site 2 is not adversely impacting groundwater quality. This ROD
designates Site 1 as a CAMU. Additional information on the CAMU designation is provided in this
section.
The Site 1 cap will isolate landfill refuse, eliminate direct contact with surface refuse, reduce erosion,
and minimize infiltration and surface contamination migration. A biotic barrier will be installed to
minimize burrowing animal exposure and plant root uptake of chemicals. In addition, gas vents will be
installed at Site 1 to prevent gas pressure from building up beneath the cap and increasing horizontal
migration. The gas vents will also provide controlled venting of landfill gases. Riser pipes will be
installed to vent the gases to the atmosphere. The riser pipe outlets will be positioned so that any
potential gas inhalation hazards are mitigated.
The cap will be sloped so rainwater will drain off the landfill to a perimeter ditch or the SWRP. The
cap will be designed to minimize erosion, thereby reducing the potential for surface contaminant
migration. The cap will also limit infiltration into the landfills and reduce the formation of leachate by
incorporating a low-permeability layer.
59 044-0236iiulfs\s:Vwpdocs\usnavyVniofreu\cu>0236\folFad.()oc\8-l'97\jem
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The selected remedial alternative also includes groundwater monitoring at both sites and a corrective
action contingency measure at Site 1 to protect aquatic receptors at the SWRP, if necessary. The
contingency measure will be implemented at Site 1 due to the proximity and potential impact of landfill
contamination to ecological receptors and habitats in the adjacent northern area.
Gas migration will be controlled at Site 1 with a collection trench, gas vents, and gas monitoring will
be conducted at Site 1 to promote control of hazards associated with methane migration. Methane
concentrations will be monitored and if the LEL (concentration of 5 percent by volume in air) is
exceeded at site boundaries, a corrective action program will be implemented according to 14 CCR
requirements. At Site 2, methane has not been detected inside or at the perimeter of the landfill.
2.11.2 Compliance with ARARs
The selected remedial alternative complies with ARARs. Section 121 (d) of CERCLA, as amended by
the SARA, states that remedial actions must attain or exceed ARARs. ARARs may include
regulations, standards, criteria, or limitations promulgated under federal or state laws. ARARs apply
to on-site response actions; response actions which take place off-site must comply with all laws,
including both administrative and substantive requirements. An ARAR may be either "applicable," or
"relevant and appropriate," but not both. The NCP (40 Code of Federal Regulations [CFR] Part 300)
defines "applicable," "relevant and appropriate," and "to be considered" as follows:
• "Applicable requirements are those cleanup standards, standards of control, and other
substantive environmental protection requirements, criteria, or limitations promulgated
under federal or state environmental or facility siting law that specifically address a
hazardous substance, pollutant, contaminant, remedial action, location, or other
circumstance found at a CERCLA site. Only those state standards that are identified by
a state in a timely manner and that are more stringent than federal requirements may be
applicable."
• "Relevant and appropriate requirements are those cleanup standards, standards of
control, and other substantive environmental protection requirements, criteria, or
limitations promulgated under federal or state environmental or facility siting law that,
while not "applicable" to a hazardous substance, pollutant, contaminant, remedial
action, location, or other circumstance found at a CERCLA site, address problems or
situations sufficiently similar to those encountered at the CERCLA site that their use is
well suited to the particular site. Only those state standards that are identified by a state
in a timely manner and that are more stringent than federal requirements may be
relevant and appropriate."
044-0236injlft\i:VwpdocJ\usnavy\moffen\cio-0236\ftiJrod.doc\8-l-97\jem
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The preliminary identification of ARARs involves considering a number of site-specific factors
including potential remedial actions, compounds at the site, physical characteristics of the site, and site
location. A requirement is applicable if it specifically addresses or regulates the hazardous substance,
pollutant, contaminant, action being taken, or other circumstances at the site. To determine whether a
particular requirement would be legally applicable, it is necessary to evaluate specific jurisdictional
prerequisites of the statute or regulation. All jurisdictional prerequisites must be met for the
requirement to be applicable. Jurisdictional prerequisites include:
• Who, as specified by the regulation, is subject to its authority
• The types of substances and activities listed as falling under the authority of the
regulation
• The time period for which the regulation is in effect
• The types of activities the regulation requires, limits, or prohibits
If jurisdictional requirements are met, the requirement is applicable. If not, the next step is to consider
whether the requirement is relevant and appropriate (EPA 1988).
The basic considerations when determining whether a requirement is relevant and appropriate include
evaluating whether the requirement (1) regulates or addresses problems sufficiently similar to those
encountered at the CERCLA site (that is, relevance) and (2) is appropriate to the circumstances of the
release, such that its use is well suited to the particular site. Determining whether a requirement is
relevant and appropriate is site specific and must be based on best professional judgment (EPA 1988).
A requirement may be relevant but not appropriate for the specific site. Only those requirements that
are determined to be both relevant and appropriate must be complied with. Portions of a requirement
may be relevant and appropriate even if a requirement in its entirety is not (EPA 1988).
ARARs identified for remedial actions are based on anticipated chemicals present, the location of the
site, and possible remedial actions for the site. The following sections discuss how the final alternative
complies with the major chemical-specific, location-specific, and action-specific ARARs. Table 1 lists
ARARs for the selected alternative.
044X)236i[uir(\i:\wpdoc<\uaavyVnioRea\cto-0236\fnlrod.doc\8-l-97\jnn
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TABLE 1
MOFFETT FEDERAL AIRFIELD OU1 ROD
ARARS FOR SELECTED ALTERNATIVE*
Citatioii
Description
• Classification;
40CFR258.il
A facility in a 100-year flood plain must be
designed, constructed, operated, and maintained
to avoid washout.
Location specific
Relevant and appropriate
Northern MFA may experience tidal
flooding.
Endangered Species Act of 1973
(16 USC 1536(a)(2)
50 CFR Part 200
Requires federal agencies to ensure actions will
not jeopardize threatened and endangered (T&E)
species or cause destruction or adverse
modification to habitat. Action must conserve
T&E species because a critical habitat is present
or T&E species exist.
Location specific
Applicable
A T&E species potentially resides near
OU1.
California Fish and Game Code
Section 2080
Actions should be taken to conserve T&E
species.
Location specific
Applicable
A T&E species potentially resides near
OU1.
Executive Order 11990,
Protection of Wetlands
(40 CFR 6, Appendix A)
CWA Section 404;
40 CFR 6.302
San Francisco Bay Basin Plan,
1995, Sec. 4 (Implementation
Plan)
Water Code 513142.5 and CA
Executive Order W-59-93
Because wetlands exist, actions must minimize
the degradation of wetlands.
Location specific
Applicable
Parts of northern MFA are considered
wetlands.
Water Code 13142.5 and
Executive Order W-59-93
are to be considered criteria
Coastal Zone Management Act
(16 HSC §1456(c); 40 CFR
6.302)
California Coastal Act of 1976
(14 CCR §13001 - 13600)
San Francisco Bay Plan
(McAteer-Petris Act of 1965)
If within a coastal zone, activities must be
consistent with approved state management
programs.
Location specific
Applicable
OU1 is in a coastal zone.
OM-02361m I f5\s:\wpd
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TABLE 1 (Continued)
MOFFETT FEDERAL AIRFIELD OU1 ROD
ARARS FOR SELECTED ALTERNATIVE*
/Classification"
14 CCR 17767; 17772;
17773(b)/40 CFR 258.60(a)/
These are requirements for landfill cap design
and closure.
Action specific (capping)
Applicable
17776; 17777(a)(b); 17778(a) (c)-
0); 40 CFR 258.26
17779 (a)-(c) (eMh)
Subtitle D of RCRA and Title 14 are both
identified as ARARs for Site 1. Subtitle D
requirements will be followed unless state
requirements are more stringent.
These are requirements for waste management
units and cap requirements for units that may
affect water quality.
23 CCR 2580(d)(e);
23 CCR2581(a)(b)/
40 CFR 258.60(a)
Action specific (capping)
Applicable
Title 23 CCR requirements are applicable
for landfill closure as the regulations
complement 14 CCR Article 7.8.
23 CCR 2596 and 2597
These are requirements regarding operations
plan and closure and postclosure maintenance
plans.
Action specific (closure and
postclosure)
Applicable
The substantive portions of these provisions
are applicable to the selected remedy for
Site 1. The Navy will provide the required
information in an appropriate RD document.
14 CCR 17788(a)(lK2)(3)(5);
40 CFR 258.61(a)(l);
17796(a)(c)(d);
23 CCR 2581(c)(l)(3)(4)(5)
These are general and landfill-specific
requirements for postclosure at solid waste
landfills.
Action specific
(postclosure maintenance)
Applicable
Postclosure requirements in 14 CCR and 23
CCR are applicable for Site 1 for the
reasons discussed under capping.
14 CCR 17782(a)(b); 40 CFR
258.61(a)(3); 23 CCR
2550.1(a)(l)(2)(3); .2(a); .3;
These are groundwater monitoring program
requirements following closure.
Action specific
(groundwater monitoring)
Applicable
(e)(4 - 15); .8(a-i), .9
40Cm258.51(a)(c)(d);
40 CFR 258.53(a)-(0; 40 CFR
258.54(a)(b)
San Francisco Bay Basin Plan,
1995, Sec.2 (Beneficial Uses) and
3 (Water Quality Objectives)
The substantive portions of the groundwater
monitoring requirements in 14 CCR and 23
CCR are applicable for Sites 1 and 2 for the
reasons discussed under capping. The Navy
will provide the required information in an
appropriate RD document.
63
044^236iralh\j:\wpdocf\u$mvy\mofTtti\et
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TABLE 1 (Continued)
MOFFETT FEDERAL AIRFIELD OU1 ROD
ARARS FOR SELECTED ALTERNATIVE*
Citation
14 CCR 17783(a)(2), (a)(3). (d);
.3; .5(a)(l), (b). (c), (d)(l)(2);
.9; .ll;40CFR258.61(a)(4)
BAAQMD Regulation 8, Rule 34
14 CCR 17766(a)
14 CCR 17677
14 CCR 17678
14 CCR 17680
14 CCR 17684
14 CCR 17706
14 CCR 17707
40 CFR 258.22
14 CCR 17708
14 CCR 17709
Description
These are requirements for gas monitoring and
control during closure and postclosure.
This requirement concerns, the emergency
response plan
Spreading and Compacting: Requires spreading
and compacting refuse in layers.
Slopes and Cuts: Slope of working face to be
maintained to allow effective compaction.
Stockpiling: Requires that stockpiles of cover
material not interfere with unloading, spreading,
or compacting waste or other pertinent safety
and drainage factors.
Intermediate Cover: Requires cover on fill
where no additional refuse will be placed within
180 days.
Dust Control: Operator shall take adequate
steps to minimize creation of dust.
Vector and Bird Control: Operator shall take
adequate steps to control flies, rodents, and
other vectors and to minimize bird problems.
Drainage and Erosion Control: Adequate
drainage shall be provided. Effects of erosion
shall be promptly repaired and steps taken to
prevent further occurrence.
Contact with Water: Waste shall not be placed
in direct contact with surface water or
groundwater.
•• '. • • AKAfl .• '••• ','
••..' Classification
Action specific
(methane gas monitoring
and emissions)
Applicable
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Siv^/JigcSsii^^;"';
Requirements in 14 CCR are applicable for
the reasons discussed under capping and
closure. The landfills are exempt from
Regulation 8 requirements based on the size
of the landfills.
Information about potential hazards and
procedures to minimize them will be
included in an appropriate RD document.
This requirement affects placement of Site 2
refuse.
This requirement affects placement of Site 2
refuse.
This requirement affects the placement and
use of cover material during the
construction of the Site 1 cap.
This regulation sets requirement for interim
cover of Site 2 refuse prior to Site 1 cap
construction.
This requirement affects operating practices
for consolidation of Site 2 materials.
This requirement affects operating practices
for consolidation of Site 2 materials.
This requirement affects operating practices
for consolidation of Site 2 materials.
This requirement may affect placement of
wastes at Site 1.
044X)236injlfs\s:\wpdoc»\ujijavy\moffcn\ao«23«\ftihbl.doc\7.| I
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TABLE 1 (Continued)
MOFFETT FEDERAL AIRFIELD OU1 ROD
ARARS FOR SELECTED ALTERNATIVE*
••,&:>;;;... v:: Citation^ •- .-v'%
14 CCR 17710
14 CCR 17713
^4 CCR 17743
40 CFR 258.28
23 CCR, Chapter 15, Article 2
23 CCR 2547(a)
(Class III portion only)
22 CCR 66261. 1-.4; . 10; .20-
.24
22 CCR 66261 .30, .100, .101
22 CCR 66262. 10 -.12
22 CCR 66262.30 - .34
22 CCR 66264.552
22 CCR 66268.1 -.9. .30, .32,
.40-.50
. •.'.'. i1 "•;;. • \ '•'. •.".'" .• m •'. ,: i- '..-,•:, •?. ; •'. ;••'•.'•• " ' . .
..,..'.,' . '';•'•.''. ' ' ;' • • • • • ' '
^.^/•iXr^^i-ii.Descriptioh'1^-- O'^":;-: ••/; '%
Grading of Fill Surface: Covered surfaces shall
be graded to promote runoff of precipitation.
Odor Control: The disposal site shall not be a
source of odor nuisances.
Requirements prohibit placement of bulk or
containerized liquid wastes.
These are requirements for waste classification
and management.
These are requirements for seismic
considerations for landfill design.
These are requirements for identification and
characterization of hazardous waste.
These are requirements for generators of
hazardous waste.
This concerns corrective action management
units.
These sections include requirements for
evaluating whether land disposal restrictions
(LDRs) are applicable.
iv. ^;v:':ARAR:;,;;?v\;;;£!f
•• '---I - Clai^ficaiidn S$
•v :,-..-, ... • . . • ";• J>j,'-'...
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Relevant and appropriate
Action specific
Applicable
Action specific
Relevant and appropriate
Action specific
Applicable
Actions specific
Applicable
Location specific
Relevant and appropriate
Action specific
Applicable
£t£-K»;:ti*5]j^
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This regulation sets requirements for slope
of interim cover.
This requirement affects operating practices
for consolidation of Site 2 materials.
Liquid wastes from Site 2 will not be placed
at Site 1.
This requirement affects consolidation of
Site 2 materials.
Landfill components will be designed to
withstand the maximum probable
earthquake without damage.
Liquid, containerized (such as drums) waste
excavated from Site 2 and any such
materials encountered during capping of
Site 1 will be analyzed to determine if they
must be managed as hazardous wastes.
The substantive generator requirements
apply to the on-site handling of hazardous
waste excavated from Site 2 and shipped off
site.
This requirement allows placement of
remediation waste excavated from Site 2 at
Site 1.
These requirements are applicable for waste
destined for off-site disposal.
To the extent that the cited provisions contain administrative requirements, those requirements are not ARARs; only the substantive provisions
within the requirements are ARARs.
BAAQMD Bay Area Air Quality Management District
CCR California Code of Regulations
CFR Code of Federal Regulations
LDR
RD
T&E
use
Land disposal restriction
Remedial design
Threatened and endangered
United States Code
65
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2.11.2.1 Chemical-Specific ARARs
Chemical-specific ARARs are health- or risk-based numerical values or methodologies that, when
applied to site-specific conditions, establish the acceptable amount or concentration of a chemical that
may be found in, or discharged to, the ambient environment. If a chemical has more that one cleanup
level, the most stringent level will be identified as an ARAR for this remedial action.
Chemical-specific ARARs do not exist for landfill refuse or soils. Site 2 municipal-type waste will be
removed from Site 2 using visual identification. Waste classification requirements in Tide 23 CCR,
Chapter IS, Article 2 are ARARs for wastes excavated at Site 2. The Navy, with the concurrence of
the regulatory agencies, will use visual screening methods to meet these requirements. Based on the
trenching conducted in Site 2 during 1996, it is easy to visually discern between the municipal-type
waste, construction debris, and native soil material at Site 2. Sampling of soil from the excavation area
after excavation of the wastes will be conducted. The soil sampling analytical results will aid in
assessing ground water quality at Site 2 after the 3 years of groundwater monitoring are concluded.
Chemical-specific ARARs will be met for landfill gas at Site 1 through implementing the trench vent,
installing gas vents in the cap, and through a gas monitoring program.
Because this action does not include active groundwater remediation, no chemical-specific ARARs are
identified. Rather, chemical-specific ARARs will be identified in accordance with CERCLA if,
through the monitoring program, remediation is found to be necessary. As part of the groundwater
monitoring program, analytical results will be compared to federal AWQC. The Basin Plan water
quality objectives and beneficial use designations will be considered, as appropriate, in developing the
groundwater monitoring program. Moreover, if additional response actions are necessary, potential
chemical-specific ARARs could include the Basin Plan and AWQC. Groundwater monitoring at
Sites 1 and 2 will comply with the substantive regulations in 23 CCR, Chapter 15, Article 5.
2.11.2.2 Location-Specific ARARs
Location-specific ARARs are restrictions placed on the concentration of hazardous substances or the
conduct of activities due to characteristics of the site or its immediate environment. For example,
location of the site or proposed RA in a flood plain, wetlands, historic place, or sensitive ecosystem
may trigger location-specific ARARs. Any RA that would affect special locations must comply with
044-023£iru I fs\J:\wpdoct\uinavy\mofTeti\cco-0236\fhlrod.(loc\8-1 -97\Jem
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Che regulations. The following paragraphs discuss how the selected remedial alternative complies with
the location-specific ARARs identified in Table 1.
Flood Plains (Location Standards) 40 CFR 258.11
This regulation is relevant and appropriate because northern Moffert Field may experience tidal
flooding. This regulation states that any facility must be designed, constructed, and operated to avoid
washout. The landfill cap will be designed to avoid washout from tidal flooding. The northern
boundary of Site 1 will include a perimeter road with a shoulder protected with riprap. The road and
riprap will extend to a height to accommodate seasonal water level fluctuations. In addition, if washout
does occur at Site 1, it will be repaired during post-closure O&M.
Endangered Species Act/California Fish and Game Code
This act is an ARAR because a T&E species are found near OU1. The statutory interpretation of the
term "jeopardize the continued existence of..." language contained in Section 7 of the Endangered
Species Act of 1973 means "... to engage in an action that reasonably would be expected, directly or
indirectly, to reduce appreciably the likelihood of both the survival and recovery of a listed species in
the wild by reducing the reproduction, numbers, or distribution of that species" (Littell 1992).
California Department of Fish and Game (DFG) Code Section 2080, which prohibits the taking of
threatened or endangered species, is also an ARAR.
Based on the OU1 ecological assessment, capping of Site 1 and excavation of waste at Site 2 are not
reasonably expected to appreciably reduce the likelihood of the survival and the recovery of any T&E
species (PRC 1994). The Site 1 and Site 2 surfaces are not a critical habitat upon which any T&E
species depend (PRC 1994). However, stands of pickleweed have been observed adjacent to Site 1.
This pickleweed represents potential habitat for the SMHM, which is a federal T&E species. A band
of pickleweed about 7 feet wide borders the northern perimeter of Site 1 along the SWRP basin. The
eastern border along Jagel Slough has a narrow border of pickleweed about 3 feet wide. Another stand
of pickleweed is found along the southern border next to the fence line. This area is approximately 10
feet by 12 feet with a vehicle path dividing it in half. These stands of pickleweed are isolated.
Corridors do not exist between these stands and nearby wetland areas. Therefore, it is unlikely that the
SMHM inhabits Site 1.
f.-i 0*44)236Jni)rs\t:\wpdoctVusiuvyVn»fTen\c(o-0236\fiilrod.
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Because results are often inconclusive, extensive trapping has not been done in these areas to confirm
or deny the presence of the SMHM at Site 1. According to the FWS, there is reasonable chance that
the SMHM may exist at Site 1. Therefore, FWS recommended that the Navy prepare a replacement
plan, which would address each acre of lost habitat. The replacement plan will provide the specific
procedures and details of the restoration.
Also, Section 7 of the Endangered Species Act of 1973 forbids agency action that is likely to "result in
the destruction or adverse modification of habitat." The regulations define the term "destruction or
adverse modification" as meaning "... a direct or indirect alteration that appreciably diminishes the
value of critical habitat for both the survival and recovery of a listed species. Such alterations include,
but are not limited to, alterations adversely modifying any of those physical or biological features that
were the basis for determining the habitat to be critical" (Littell 1992).
Although potential habitat exists for the SMHM near Site 1, the habitat is not believed to be critical and
lost habitat will be addressed. The stands of pickle weed are small and isolated. Corridors between
these stands and nearby wetland areas do not exist. Therefore, it is unlikely that the habitat is critical
for species survival.
In addition, actions taken under the selected remedial alternative will conserve T&E species that may
use the SWRP as a habitat, including future pickleweed habitat. The landfill cap will protect the
SWRP habitat by reducing erosion and wash out that could accelerate contaminant migration into the
pond. The design of the cap will also include a perimeter road and shoulder with associated drainage
to minimize sediment loading generated from hillside runoff. Capping the landfill will eliminate
exposure pathways resulting from erosion of the landfill surface. The groundwater monitoring and
corrective action contingency measures will protect the SWRP habitat from contaminants resulting
from potential leachate migration from the landfill.
Executive Order 11990. Protection of Wetlands. 40 CFR 6.302
This executive order requires federal agencies to avoid, to the extent possible, the adverse impacts
associated with the destruction or loss of wetlands and to avoid support of new construction in
wetlands, if a practicable alternative exists. Wetlands are defined in Executive Order 11990 as those
areas inundated by surface or groundwater with a frequency sufficient to support under normal
044-OZ36iniUs\s:\wpdoa\usnavy\inoflenVcto-0236\ftilrad.doc\8-l-97\)em
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circumstances a prevalence of vegetative or aquatic life that requires saturated or seasonally saturated
conditions for growth or reproduction. Wetlands generally include swamps, marshes, bogs, and
similar areas such as sloughs, potholes, wet meadows, river overflows, mud flats, and natural ponds.
The Navy delineated three potential wetland areas near OU1 based on the delineation criteria found in
the 1987 COE wetlands delineation manual (see Figure 8). The first area (Area 1) is approximately
1.25 acres and is southwest of the Site 1 landfill. This area is within the Site 1 fenced area, but is not
located on the landfill surface. This area was found to be a wetland with hydrophytic vegetation,
appropriate hydrology, and hydric soils. Since the outer edge of this area abuts the landfill, the edge
will require fill during-capping.
The second area is the SWRP. The majority of this site is not vegetated, except for the fringe of
vegetation along the pond edges (Area 2). The southern fringe of the SWRP adjacent to the landfill
(approximately 0.4 acres) will require filling to construct the subsurface collection trench and cap
shoulder. The rest of the fringe will not be affected. The vegetated SWRP fringe may qualify under
the technical criteria as a wetland. A third area of approximately 0.1 acres exists in the central portion
of Site 1 near the former pistol range berm.
The landfill capping will affect the two wetlands in the vicinity of Site 1. However, the Navy and
regulatory agencies have determined that a landfill cap is necessary to protect the environment.
Because filling small segments of wetlands will be required to cap the Site 1 landfill, the substantive
requirements of NWP 38 will be met as part of the remedial design. This permit allows for fill to be
placed in wetlands if filling is associated with the remediation of hazardous and toxic waste. The Navy
has determined that NWP 38 and CWA Section 404 are applicable to the action at Site 1. The Navy
has further determined that the planned activities at OU1 will meet all the substantive requirements of
NWP 38 and CWA Section 404 except the requirement concerning mitigation. Mitigation of wetlands
destroyed during activities at OU1 will be addressed in the stationwide ROD. The Navy will consult
with RWQCB to review the wetland areas affected by Site 1 activities and reach concurrence to
determine potential mitigation requirements.
Proposed actions under the selected alternative will minimize the degradation of OU1 wetlands. The
landfill cap will protect the adjacent wetlands by reducing erosion and wash out that could accelerate
contaminant migration into these wetlands. The design of the cap will also include a perimeter road
and shoulder with associated drainage to minimize sediment loading generated from hillside runoff.
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-CAMU LOCATION
arm
(23 PROBABLE WETLAND AREAS
QUESTIONABLE WETLAND AREAS
NOTE: "PROBABLE' WETLAND AREAS (STORMWATER RETENTION POND) PROVIDE DRY SEASON BRACKISH SURfACE WATER HABITAT OF MODERATE QUALITY.
'QUESTIONABLE' WETLAND AREAS OFFER LIMITED FEEDING AND FORAGING OPPORTUNITIES. POOR COVER VALUE. AND GENERALLY POOR HABITAT QUALITY.
SOURCE: FINAL PHASE I SITE-WIDE ECOLOGICAL ASSESSMENT REPORT (PRC^ND MW 1885).
FIGURE 8
MOFFETT FEDERAL AIRFIELD
OUI ROD
CAMU LOCATION
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Coastal Zone Management Act. California Coastal Act of 1976
The Coastal Barriers Resources Act (16 United States Code [USCJ Section 1456(c)) requires that all
activities must be conducted in a manner consistent with approved state management programs. This
statute is potentially applicable to OU1 because the OU1 sites are located in a coastal zone. The
California Coastal Act of 1976 governs the state management program for coastal areas including the
northern portion of Moffett Field. The California Coastal Act states that the basic goals of the state for
the coastal zone are to protect, maintain, and where feasible, enhance and restore the overall quality of
the coastal zone environment and its natural and artificial resources. Implementing the OU1 remedial
alternative will be consistent with this goal. Within the San Francisco Bay area, the local coastal zone
management program is described in the San Francisco Bay Plan, enacted pursuant to the McAteer-
Petris Act of 1965. The San Francisco Bay Conservation and Development Commission (BCDC)
implements this plan. The San Francisco Bay Plan contains requirements that are applicable to the
actions at OU1.
2.11.2.3 Action-Specific ARARs
Action-specific ARARs are technology- or activity-based requirements or limitations for remedial
activities. These requirements are triggered by the particular remedial activities conducted at the site
and indicate how a selected remedial alternative should be achieved. For OU1, waste consolidation,
landfill capping, groundwater and gas monitoring, and postclosure O&M are the remedial activities for
which action-specific ARARs have been selected. State and federal hazardous and solid waste
regulations were evaluated as potential activity based requirements for OU1. Federal and California
solid waste regulations, whichever are more stringent, were selected as ARARs for the Site 1 cap. The
rationale for this selection is provided below.
Landfill ARARs
State and federal hazardous waste regulations (Subtitle C of RCRA [40 CFR Pan 264.310] and Title 22
CCR Section 66264.310) for capping landfills are not applicable since documentation does not exist to
confirm that hazardous waste disposal occurred at either landfill. Some of the wastes disposed of at the
OU1 landfills may have been hazardous constituents; however, this circumstance is common to all
solid waste and CERCLA landfills. Further, low contaminant concentrations in leachate show that a
7| 044-02J«imlft\i:\wp(k»\unuvy\moffea\cu><)2J6\ihJrod.doc\8-l-97\}eni
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minimal threat from hazardous substances exists at OU1. In addition, documentation received from
CIWMB indicates that Site 1 was operated as a solid waste facility. The Navy was issued a Solid
Waste Facilities Permit for Site 1 by Santa Clara County. The permit states that the types of waste
received at the site included cardboard, lawn cuttings, primings, wood waste, and asbestos insulation
wrapped in double plastic bags. The permit also states that disposal of hazardous waste was to be
prohibited at the facility. This further supports the assumption that OU1 landfills were operated as
solid waste landfills and received similar types of wastes (solid waste with small amounts of hazardous
waste). Also, visible surface debris includes obvious construction and demolition debris, such as
concrete rubble with reinforcing steel, asphalt chunks, wire, wood chips, glass, and mounds of dirt
overgrown with weeds (possibly street sweepings), which are similar to solid waste landfill waste. For
these reasons, the Navy identified solid waste closure regulations as most appropriate for Site 1.
CIWMB concurred with these conclusions and determined that California landfill closure and
monitoring requirements contained in 14 CCR and 23 CCR are applicable for OU1 remedial actions
(CIWMB 1995). However, federal regulations adopted pursuant to Subtitle D of RCRA and found in
40 CFR Part 258 are also applicable to this action. The Navy will follow whichever regulation is more
stringent.
The Site 2 selected remedy requires designation of Site 1 as a CAMU, which is accomplished with this
ROD. Site 1 is designated a CAMU in accordance with the designation criteria established in Title 22
CCR 66264.552(c). The way in which Site 1 meets the CAMU designation criteria is discussed in
Section 2.11.2.4 below. The description of the selected remedial action for Site 1 provides specific
information about the CAMU, including its areal configuration; remediation waste management design
and operation; groundwater monitoring and reporting requirements; and closure and post-closure
requirements. This specific information is summarized in Section 2.11.2.4.
Waste classification requirements in Title 23 CCR, Chapter 15, Article 2 are ARARs for wastes
excavated at Site 2. The Navy, with the concurrence of the regulatory agencies, will use visual
screening methods to meet these requirements. The Navy does not intend to consolidate any wastes at
Site 1 other than wastes excavated from Site 2. Soils currently stockpiled at the bioremediation pad
will, however, be used as fill in the foundation layer beneath the Site 1 cap. Surplus soils from the
light rail project under construction along the southern boundary of the facility may also be used at
OU1 after review and approval by the regulatory agencies. Construction of the permanent landfill cap
at Site 1 is scheduled to follow immediately after completion of excavation and consolidation. The
72 (M441236iiulft\s:\wpdocs\usnavy\niof>en\cto-0236\ftilrod.doc\8-l-97\jern
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Navy will not place containers of hazardous waste excavated from Site 2 at Site 1. Furthermore, free
liquids observed in the Site 2 excavation that are clearly not groundwater (for example, free-phase
paints, oils, or solvents) will be removed and not placed at Site 1. Similarly, containers of hazardous
waste encountered during activities at Site 1 will be removed. These containers will be tested and
disposed of appropriately off site. Freely mobile waste will not be placed or allowed to remain at Site
1 but will be shipped off site to an appropriate disposal facility.
The act of consolidating remediation waste from Site 2 to the CAMU (Site 1) does not constitute land
disposal of hazardous .waste and, therefore, does not trigger Title 22 CCR, Division 4.5, Chapter 14
regulations regarding minimum technology requirements for transfer, treatment, storage, and disposal
facilities or Chapter 18 regulations regarding land disposal restrictions, in accordance with the CAMU
regulation. Therefore, these regulations are not ARARs for consolidation of the Site 2 remediation
wastes to Site 1. However, certain requirements in 40 CFR Part 258 and Title 14 CCR Article 7.5,
whichever are more stringent, are ARARs for the consolidation component of the remedy. These
requirements include dust control, grading, and vector control. The relevant requirements are listed on
Table 1.
The specific provisions of Title 14 CCR Article 7.8 and 40 CFR 258.60, whichever are more
stringent, listed in Table 1 are ARARs for the closure of Site 1. Title 14 CCR 17760 (scope and
applicability of Article 7.8) states that Article 7.8 applies to "solid waste disposal sites that did not
commence complete closure prior to August 18, 1989, which is fully implemented by November 18,
1990, in accordance with all applicable requirements." Through Article 7.8 regulations, prescriptive
standards for capping contained in 23 CCR 2546, 2581, and 2595 are referenced. The components
that make up the selected remedial alternative have been included so that landfill closure regulations
specified in 14 CCR Article 7.8 and 40 CFR 258.60, whichever are more stringent, listed on Table 1,
will be met. The Site 1 landfill cap configuration is based on a prescribed, state pre-approved
arrangement for landfill caps. The cap design standards in 14 CCR Article 7.8 for closure of a
nonhazardous solid waste landfill consist of (from top to bottom): a 12-inch topsoil layer, a 12-inch
low-permeability (clay or synthetic membrane liner) layer, and a 24-inch minimum foundation layer.
Information required by these regulations will be contained in an appropriate remedial design
document.
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Groundwater monitoring regulations in 23 CCR, Chapter 15, Article 5 or 40 CFR 258 Subpart E that
are listed in Table 1 are applicable to Sites 1 and 2. Pursuant to 23 CCR, Chapter 15, Article 5,
Section 2550.4, the Navy will derive and propose concentration limits for each constituent of concern.
Federal AWQC and RWQCB Basin Plan water quality objectives will be considered in deriving the
concentration limits.
The unsaturated zone monitoring provisions in 23 CCR 2550.7(d) cannot be conducted in accordance
with 23 CCR 2550.7(d)(5), which states that unsaturated zone monitoring is required unless it can be
demonstrated that there is not unsaturated zone monitoring device or method designed to operate under
the subsurface conditions existent at the waste management unit. Such is the case at Site 1. The Site 1
wastes are located within the saturated zone; no unsaturated zone exists between the bottom of the Site
1 wastes and the saturated zone.
The groundwater and gas monitoring program will be designed in accordance with the substantive
provisions of 23 CCR or 40 CFR 258.61(a)(3) regulations and 14 CCR or 40 CFR 258.61(a)(4)
regulations, respectively, whichever are more stringent, as listed on Table 1. Any groundwater
response actions needed in the future will be carried out in accordance with CERCLA after
concurrence is obtained from EPA and the State, and after modification of this ROD where necessary.
At Site 1, the gas vents and gas venting trench will be installed to control gas concentrations at the
landfill boundary to below the lower explosive limit in accordance with 14 CCR or 40 CFR
258.61(a)(4). To further meet the requirements of 14 CCR or 40 CFR 258.61(a)(4), the combination
of the low-permeability layer, the gas vents, and riser pipes will function to provide controlled venting
at Site 1 to mitigate any potential inhalation hazards associated with trace gases.
Because leachate collection, treatment, and discharge is not part of the selected remedy, ARARs for
leachate collection, treatment, and discharge are not identified in this ROD. However, leachate
collection and treatment may be required in the future if monitoring indicates that it is necessary.
Groundwater within the subsurface collection trench will be monitored at the same frequency as at the
Site 1 groundwater monitoring wells. If chemical concentrations exceeding concentration limits set
pursuant to 23 CCR Chapter 15 Article 5 are observed, the Navy will immediately notify the
regulatory agencies and will evaluate the groundwater contamination in accordance with CERCLA, and
will obtain concurrence from EPA and the State on remediation decisions. Potential actions may
include additional or more frequent sampling or groundwater extraction and treatment, depending on
the nature and levels of the chemicals detected.
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An in-place leachate collection trench is being installed as part of the Site 1 capping system. If it
becomes necessary to collect, treat, and discharge leachate, any means of discharge must comply with
substantive requirements of ARARs if the discharge is on site (such as to Marriage Road Ditch, North
Patrol Road Ditch, or the stormwater retention pond), or be subject to a permit if the discharge is off
site (such as to a POTW). An explanation of significant differences (BSD) or ROD amendment will be
prepared, as appropriate, for the collection, treatment, and discharge of leachate. Prior to adoption of
the ESD or ROD amendment, the Navy will solicit federal and state ARARs and will comply with
CERCLA public participation requirements. The Navy will obtain concurrence from EPA and the
State on remediation decisions.
The substantive provision of certain reports under Title 14 and 40 CHI 258 are considered ARARs for
the landfill cap. Specifically, the requirements for operations plans in 23 CCR 2596, for closure and
postclosure maintenance plans in 23 CCR 2597, and for emergency response plans in 14 CCR 17766
are relevant and appropriate. The substantive requirements of these provisions will be included in an
appropriate remedial design document.
Hazardous Waste ARARs
Only nonhazardous solid waste is intended for consolidation at Site 1. The substantive hazardous waste
identification regulations in Title 22 CCR Division 4.5, Chapter 11, Articles 1, 2, 3, and 5 and Title
23 CCR Division 3 Chapter 15 Article 2 are applicable to the characterization of liquid waste and
containerized wastes excavated from Site 2 and any such materials encountered during the capping of
Site 1. Hazardous wastes excavated from Site 2 and encountered at Site 1 will be characterized hi
accordance with these applicable regulations, and if they are hazardous, they will be disposed of off
site at appropriate facilities in accordance with all applicable laws and regulations.
2.11.2.4 CAMU Designation Criteria and Specific Information
This section discusses the definition of a CAMU, how Site 1 satisfies the CAMU designation criteria,
and specific information for the Site 1 CAMU. Even though Site 1 has been designated a CAMU, the
Navy does not intend to consolidate any wastes at Site 1 other than wastes excavated from Site 2. Soils
currently stockpiled at the bioremediation pad will, however, be used as fill in the foundation layer
beneath the Site 1 cap. Surplus soils from the light rail project under construction along the southern
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boundary of the facility may also be used at OU1 after review and approval by the regulatory agencies.
Waste classification requirements in Title 23 CCR, Chapter 15, Article 2 are ARARs for wastes
excavated at Site 2. The Navy, with the concurrence of the regulatory agencies, will use visual
screening methods to meet these requirements. Construction of the permanent landfill cap at Site 1 is
scheduled to follow immediately after completion of excavation and consolidation. The Navy will not
place containers of hazardous waste excavated from Site 2 at Site 1. Furthermore, free liquids
observed in the Site 2 excavation that are clearly not groundwater (for example, free-phase paints, oils,
or solvents) will be removed and not placed at Site 1. Similarly, containers of hazardous wastes
encountered during activities at Site 1 will be removed. These containers will be tested and disposed of
appropriately off site. Freely mobile waste materials will not be placed or allowed to remain at Site 1
but will be shipped off site to an appropriate disposal facility.
2.11.2.4.1 Definition of a CAMU
As defined in 22 CCR 66260.10, a CAMU is a facility or area within a facility designated for the
purpose of implementing corrective action requirements under 22 CCR 66264.101 and RCRA Section
3008(h). Wastes placed at a CAMU must be remediation wastes. Title 22 CCR 66260.10 defines
remediation waste as all solid and hazardous wastes and all media (including groundwater, surface
water, soils, and sediments) and debris, that contain listed hazardous wastes or that themselves exhibit
a hazardous waste characteristic. The substantive requirements for CAMUs under RCRA are ARARs
for CERCLA actions.
Placement of remediation waste in a CAMU does not constitute land disposal. Seven criteria are
included in the regulations for evaluating the appropriateness of a CAMU:
• The CAMU facilitates the implementation of reliable, effective, protective, and cost-
effective remedial actions.
• Waste management activities associated with the CAMU do not create unacceptable risks
to human health and the environment.
• The CAMU incorporates uncontaminated areas only if the inclusion of such areas is more
protective than using contaminated areas at a facility.
• Areas within the CAMU, where wastes remain in place after closure of the CAMU, are
managed and contained to minimize the potential for future releases, to the extent <
practicable.
0444)236ini1fs\s:\wp(locsVuinavy\inoflen\cu>4)236\fnlrod.doc\8-l-97\jem
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• The CAMU expedites the implementation of the remedial activity, when appropriate and
practicable.
• The CAMU enables the use of treatment technologies, when appropriate, to enhance the
long-term effectiveness of remedial actions by reducing the toxicity, mobility, or volume
of wastes that will remain in place after closure of the CAMU.
• The CAMU minimizes the land area where wastes will remain in place after closure of
the CAMU, to the extent practicable.
The following section discusses how Site 1 satisfies the CAMU designation criteria.
2.11.2.4.2 CAMU Criteria Evaluation
Designation of Site 1 as a CAMU satisfies the CAMU designation criteria in 22 CCR 66264.552(c) as
explained below.
Facilitate Reliable, Effective, Protective and Cost-Effective Remedies. As shown in this ROD,
consolidation of wastes from the Site 2 landfill into Site 1 will provide a reliable remedy that is
effective, protective, and cost-effective. Excavation and surface grading are well developed and
reliable technologies. Standard construction techniques and earthmoving equipment will be used.
Costs for consolidation are anticipated to be less than for construction of a cap at Site 2. Consolidation
of Site 2 wastes to Site 1 will be more effective than capping the Site 2 wastes in place. Site 2 wastes
now in the saturated zone at Site 2 will be moved and consolidated above the water table at Site 1,
reducing the likelihood that these wastes will contaminate groundwater.
Do Not Create Unacceptable Risks. Exposures to construction workers could occur during the
excavation and consolidation activities. Excavation of landfill wastes is a potentially hazardous
activity. Effective implementation of a health and safety plan, however, will minimize the risk of
exposure during excavation and consolidation activities. The Navy will test liquid waste and
containerized hazardous waste found during excavation and dispose of such waste at an appropriate
disposal facility hi compliance with the offsite policy rule.
Use Uncontaminated Areas Only if More Protective. The Site 1 landfill is a contaminated area.
Uncontaminated areas will not be needed for the CAMU.
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Minimize Potential for Future Releases. Consolidation of wastes from Site 2 to Site 1 will reduce the
overall area occupied by landfill wastes at Moffett Field and so reduce the subsequent potential for
exposure. In addition, saturated wastes from Site 2 will be placed in the unsaturated zone at Site 1 to
further reduce the potential for leachate formation. Engineering controls, such as capping, to isolate
the wastes at Site 1 will minimize the potential for exposure to landfill contaminants. Consolidation of
wastes to one location allows monitoring efforts to be concentrated at a single site.
Expedite Remedy Implementation. Excavation and consolidations of wastes into a CAMU will
require less time than cap construction. The construction techniques involved in consolidation also are
simpler and easier to implement than those needed for cap construction. Liquid waste and
containerized hazardous waste will be tested to determine if they are hazardous and will be disposed of
off site in compliance with the off site policy rule.
Enhance Long-Term Effectiveness. Consolidation of wastes from Site 2 to a CAMU at Site 1 will
reduce the overall area occupied by landfill wastes at Moffett Field, reduce the subsequent potential for
exposure, and enhance the long-term effectiveness of the remedial action. Neither consolidation nor
capping involves treatment; therefore, neither could substantially reduce the toxicity or volume of
wastes. However, consolidation will result in the placement of previously saturated wastes in the
unsaturated zone at Site 1 and contaminant mobility will be reduced. Consolidation has the potential to
slightly reduce waste toxicity and volume to the extent that liquid waste and containerized hazardous
wastes uncovered during excavation will be disposed of off site.
Minimize Land Areas Where Wastes Remain After Closure. Consolidation of wastes from Site 2 to
a CAMU at Site 1 will reduce the land area where wastes remain in place and will allow future reuse
of the Site 2 area that would not be possible if Site 2 wastes were capped in place.
Summary of Designation Criteria. Designation of Site 1 as a CAMU satisfies the CAMU designation
'criteria. Key aspects of the evaluation include (1) the increased reliability of containing the waste at
the Site 1 area rather than at the Site 2 area, (2) the increase in long-term effectiveness gained by
placing formerly saturated wastes in the unsaturated zone, (3) the reduction in total contaminated land
area at Moffett Field, and (4) the decrease in remediation cost.
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2.11.2.4.3 Specific Information for the Site 1 CAMU
The CAMU regulations require that specific information about the CAMU be provided. This specific
information includes:
• The areal configuration of the CAMU
• Requirements for remediation waste management including design and operation
• Groundwater monitoring and reporting requirements
• Closure'and postclosure requirements
The following discussion addresses these requirements.
Areal Configuration. Figure 8 indicates the location of the Site 1 CAMU. This area is the same
general area proposed to be covered by the Site 1 cap. Minor modifications to the area may be
necessary during remedial design of the Site 1 cap depending on various engineering design factors,
airfield height restrictions, and property boundary constraints. Any modifications to wetland areas at
Site 1 will be coordinated with the natural resource trustees.
Remediation Waste Management Requirements. Remediation waste management requirements
include specification of the appropriate design and operation methods. Design of the Site 1 cap will
meet the prescriptive solid waste landfill closure standards in the applicable substantive portions of
CCR Title 14 and 40 CFR 258.60, whichever are more stringent. The cap design standards specified
by 14 CCR Article 7.8 (listed in 23 CCR 2581) include, from top to bottom: 12-inch topsoil layer, 12-
inch low-permeability clay layer, and 24-inch foundation layer. CIWMB has indicated that an
appropriate synthetic geomembrane may be an acceptable substitute for the clay low-permeability
layer. Additions to the above minimum requirements, such as thicker layers or addition of a drainage
layer, may be necessary based on engineering design considerations to meet the applicable substantive
portions of the 14 CCR regulations.
In addition to the cap requirements, two other waste management features will be incorporated at
Site 1. An underground groundwater collection trench will be installed below grade along the northern
border of Site 1 to intercept potential future leachate migration before it reaches the surface water.
This measure will provide immediate protection of the adjacent surface water. The second feature is a
79 044-0236iiulft\s:\wpdacs\usnavyVmon'eU\c<
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passive gas venting trench that will be installed along the western boundary of Site 1 to prevent off-
site, subsurface migration of landfill gases.
Operations at Site 1 during consolidation activities would be in accordance with requirements that are
relevant and appropriate for solid waste landfill operations. These requirements are listed in Table 1 of
this ROD and include items such as requirements for spreading and compacting waste, drainage and
erosion control, surface grading, and intermediate cover.
Groundwater Monitoring Requirements. According to 22 CCR 66264.552(e)(3), groundwater
monitoring at a CAMU must be sufficient to "(a) continue to detect and characterize the nature, extent,
concentration, direction, and movement of existing releases of hazardous constituents in groundwater
from sources located within the CAMU and (B) detect and subsequently characterize releases of
hazardous constituents to groundwater that may occur from areas of the CAMU in which wastes will
remain in place after closure of the CAMU." Groundwater monitoring is already required for closure
of the Site 1 landfill and these regulations would satisfy the requirements listed for use and closure of a
CAMU. Groundwater monitoring requirements are specified in substantive portions of 14 CCR and 23
CCR and 40 CFR 258.61(a)(3) and include detailed requirements for evaluating the items described in
22 CCR 66264.552(e)(3). Specific ARARs for groundwater monitoring at Site 1 are contained in
Table 1.
Closure and Postclosure Requirements. Closure of a CAMU must be conducted to (1) minimize the
need for maintenance, and (2) minimize the potential for off-site migration of contaminants, to the
extent necessary to protect human health and the environment. For the Site 1 CAMU, these
requirements focus on capping requirements (closure) and operation and maintenance requirements
(postclosure). Title 22 66264.5S2(e)(4)(C) directs the state to consider the following factors in
establishing closure requirements: (1) CAMU characteristics, (2) volume of waste in place after
closure, (3) physical and chemical characteristics of the waste, (4) hydrogeological and relevant
environmental conditions that may influence the migration of potential releases, and (5) potential risks
to human health and environmental receptors if a release were to occur. Similarly, postclosure
requirements must be established to protect human health and the environment. For example,
monitoring and maintenance activities must be conducted to ensure the integrity of the cap.
OQ
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The design of the Site 1 cap will follow the solid waste landfill closure standards listed in CCR Title 14
and 40 CFR 258.60, whichever are more stringent. The objectives of the Title 14 and RCRA Subtitle
D requirements are the same as those for closure of a CAMU: protection of human health and the
environment by minimizing the potential for off-site migration of contaminants and minimization of
ongoing maintenance needs. The landfill closure standards of Title 14 and RCRA Subtitle D consider
similar factors in establishing the closure requirements as are required for CAMU closure. Factors
considered for CAMU closure including waste volume, waste characteristics, hydrogeological
conditions, and potential risks from a release are all addressed by the Title 14 and 40 CFR 258.60
requirements. Likewise, postclosure requirements for CAMUs such as monitoring and maintenance
are contained within the Title 14 and RCRA Subtitle D standards. In addition to the protection
provided by the cap, the northern border ground water interceptor trench and the western boundary
passive gas venting trench will provide controls for potential future releases at Site 1. Specific ARARs
for landfill closure and postclosure activities at Site 1 are contained Table 1. By satisfying the Title 14
and 40 CFR 258.60 standards, whichever are more stringent, CAMU closure and postclosure
requirements will be addressed. Satisfying Title 22 requirements will also address CAMU closure
requirements.
Summary of Specific Information. Requirements for design, operation, closure, and postclosure
already incorporated into the landfill cap remedial action at Site 1 will meet the requirements for
design, operation, closure, and postclosure of a CAMU at Site 1. Table 1 lists the ARARs for these
activities. In achieving the substantive standards of CCR Tide 14 and 40 CFR 258.60, whichever are
more stringent, the requirements for a CAMU will be met. Designating Site 1 as a CAMU will be
protective of human health and the environment by minimizing the potential for off-site migration of
contaminants and will comply with ARARs. Therefore, Site 1 satisfies the criteria and requirements
for CAMU designation.
Designation. By concurring on the ROD, EPA and the state designate as a CAMU the area designated
for a landfill under the selected remedial alternative as shown on Figure 8. The CAMU regulation is
an ARAR as discussed in Section 2.11 of this ROD. This ROD documents the CAMU designation
pursuant to 40 CFR 264.552(0 as implemented through the California EPA, Department of Toxic
Substances Control, Hazardous Waste Regulations, Title 22, Chapter 14, 66264.552. The proposed
plan for this ROD shall satisfy public notice requirements under the CAMU regulations. In designating
the CAMU, EPA and the state have considered the criteria set forth in Section 66264.552 and
determined that the CAMU satisfies each of these criteria.
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2.11.3 Cost-Effectiveness
Research has shown that the most cost-effective solutions to landfills are based on containing wastes
and monitoring at the landfill perimeter for any migration from the landfill. If contaminant migration
is detected, it can be addressed through corrective actions such as subsurface collection trenches. EPA
has developed the presumptive remedy strategy of containment for landfills in the 1993 Presumptive
Remedy For CERCLA Municipal Landfill Sites and the OU1 RI/FS employed this strategy. The
specific remedy for Site 1 was selected based on the presumptive remedy strategy and ARARs. The
remedy for Site 2 balanced the considerations of removal of the waste with health and safety concerns
and long-term operation and maintenance requirements. Because of the relatively small volume of
waste at Site 2, excavation of the Site 2 wastes and consolidation of the wastes at Site 1 is a cost-
effective action.
2.11.4 Utilization of Permanent Solutions
The statutory requirements of Section 121 of CERCLA require that remedial actions undertaken at
Superfund sites use permanent solutions and alternate treatment technologies or resource recovery
technologies to the maximum extent practical. The OU1 remedy utilizes permanent solutions and
alternative treatment technologies to the maximum extent practical. The selected alternative is a
permanent means to mitigate hazards associated with the OU1 landfills and complies with ARARs.
Consolidation of Site 2 wastes at Site 1 will permanently remove the threats associated with Site 2.
The Site 1 landfill cap will isolate landfill refuse, eliminate exposure to refuse, reduce erosion, and
limit infiltration. The cap layers may reduce the amount of leachate generated, which should reduce
the potential for leachate migration. The subsurface collection trench and gas vents will mitigate
hazards associated with contaminant migration from the landfills.
2.11.5 Preference for Treatment
The statutory requirements of Section 121 of CERCLA require that remedial actions undertaken at
Superfund sites satisfy the preference for treatment that reduces toxicity, mobility, or volume as a
principal element, or provide an explanation as to why this preference is not satisfied. This preference
is not satisfied at OU1 because treatment of the principal threat was not found to be practical.
Research has shown that treatment of refuse is generally not practical. The heterogeneity of
contaminant distribution and concentrations typically associated with landfills makes treatment of
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landfill refuse costly and difficult to implement. In addition, because landfills are heterogeneous,
excavation followed by treatment or in-place treatment can create hazardous working conditions for
field crews. A remedy in which contaminants could be treated effectively is also precluded because of
the large size of Site 1 and because there are no known homogeneous hot spots that represent the
major sources of contamination and that would be amenable to treatment at Sites 1 and 2. Typically,
treatment is only considered for landfills less that 1 acre in size or have documented, homogeneous
areas.
3.0 RESPONSIVENESS SUMMARY
This responsiveness summary has been prepared by the Navy to document public comments and
questions regarding the proposed plan for OU1 at Moffett Field. The responsiveness summary
contains comments received during the public comment period (May 30, 1995, through August 30,
1995) for the original OU1 proposed plan dated June 1995. Comments were also received on the
proposed plan during the OU1 public meeting held on June 15, 1995.
Following the first public comment period, the Navy modified the preferred alternative based on public
and regulatory agency comments. As a result, a revised proposed plan was released to the public in
January 1996. A second public comment period was held from January 4, 1996, through February 5,
1996. A second public meeting was held on January 16, 1995.
Following the second public comment period, the Navy modified the preferred alternative based on
regulatory agency comments. As a result, a revised proposed plan was released to the public in March
1997. A third public comment period was held from March 7, 1997, through April 11, 1997. A third
public meeting was held on March 20, 1997.
This section provides responses to comment received during all three public comment periods and from
all three public meetings.
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Comments were provided by many different entities, including the following:
• Members of the general public
• Moffett Field RAB
• SVTC
CIWMB
• City of Sunnyvale
• City of Mountain View
SCVWD
• League of Women Voters (LWV)
• NASA
• Santa Clara County Environmental Resources Agency
In addition to the written comments, a written transcript of the public meetings was used to identify
additional comments and concerns. The Navy has provided written responses to all comments (oral
and written) received. However, the Navy has summarized and edited the comments or questions
when it was necessary to provide a better understanding of each specific issue. The complete written
transcript for the OU1 public meetings can be found in the information repository.
3.1 JUNE 1995 PUBLIC MEETING COMMENTS AND RESPONSES
Comment 1: A member of the public did not understand why the implementdbility of Alternative 2
and Alternative 3 was not the same. In addition, the justification for short-term
effectiveness ranking was not clear.
Response: Alternative 3 was considered more difficult to implement because more stringent
specifications would be required and more materials would be handled during
construction. Alternative 2 was considered to have greater short-term effectiveness
because it would not take as long to build as Alternative 3. In addition, fewer
truckloads of materials would require shipment. Consequently, risks to workers and
the public during construction would be less.
Comment 2: A member of the public asked whether landfill excavation and removal had been
considered.
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Response: Excavation and removal were considered but were not presented in the FS report.
Extreme costs and hazardous working conditions make landfill excavation and
redisposal impractical.
Comment 3: A member of the public asked whether dioxins had been tested for in the landfills and
about detection levels.
Response: Dioxins have not been tested for in landfill refuse. Dioxin contamination inside either
landfill has not been characterized because this information is not needed to implement
capping at the landfills. During cap construction, heavy equipment could generate
fugitive dust emissions. Construction workers will mitigate any potential hazards by
using personal protective equipment (PPE) such as respirators. In addition, dust
suppression strategies such as wind speed alarms can be implemented to reduce fugitive
dust emissions during capping.
Dioxins have not been tested for in groundwater surrounding the landfills. The
occurrence of dioxin in groundwater is expected to be minimal based on strong
sorption to soils. In addition, dioxins have not been a concern since they have very
low water solubility and vapor pressure. Dioxins could dissolve into organic
compounds in leachate and potentially migrate with leachate; however, leachate does
not appear to be migrating from the landfills based on current monitoring data. The
Navy will conduct field work to further investigate contaminant migration at Site 1.
Comment 4: Mr. Paul Fisher from the City of Sunnyvale raised several concerns.
Response: The City of Sunnyvale submitted written comments to reiterate concerns expressed
during the public meeting. Please see Section 3.2.1 for specific written comments and
responses.
Comment 5: A member of the public asked what happens after the 30-year postclosure maintenance
period ends.
Response: If, after 30 years, the site still poses a threat to human health and the environment, the
Navy will continue to conduct postclosure O&M.
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Comment 6: A member of the public asked whether Alternative 2 complies with the law and has been
approved by the RWQCB.
Response: Following submittal of the FS report, Alternative 2 was approved by EPA, DTSC, and
RWQCB. During the public comment period, CIWMB stated that Alternative 2 does
not meet performance standards. Therefore, the Navy is revising the proposed plan
and soliciting additional public comments.
Comment 7: A member of the public asked when the cleanup will be sufficient to allow development
on the landfill.
Response: Placing structures on the landfill may be limited by deed restrictions. However, the
capped landfills could be used for outdoor recreation.
Comment 8: A member of the public asked whether the Navy would retain jurisdiction over the
landfills and monitoring systems for 30 years or more.
Response: The Navy will retain responsibility for meeting environmental requirements for at least
30 years. If, at the end of 30 years of postclosure maintenance, the Navy demonstrates
to the satisfaction of the local enforcement agency (LEA) and RWQCB that, based on
site geology, design characteristics, and collected field data, the site poses no threat to
public health or the environment, then the postclosure maintenance period may be
terminated.
Comment 9: A member of the public asked for clarification regarding the purpose of the
groundwater collection trench.
Response: The purpose of the groundwater collection trench is to intercept potentially migrating
contamination from the landfill before it reaches the SWRP. It will be constructed as a
contingency in the unlikely event leachate contamination migrates towards the pond.
Comment 10: A member of the public asked what the biotic barrier would be made of and asked
about its thickness.
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Response: The biotic barrier will be constructed out of a material that a burrowing animal could
not penetrate. Materials such as compacted gravel or cobbles have been used. The
type of material and layer thickness will be specified during the detailed design phase.
Comment 11: A member of the public asked whether the biotic barrier would be a barrier to
infiltration.
Response: The biotic barrier will not be designed to limit infiltration.
Comment 12: A member of the public asked for a discussion about the anecdotal evidence found
during the site investigations.
Response: During the initial stages of the investigation, information regarding types and quantities
of waste disposed of at the landfills was obtained by personal communications with
current or former staff at Moffett Field. These initial estimates indicated that large
amounts of solvents, paints thinners, and oils could have been disposed of in the
landfill. Confirming the accuracy of this anecdotal information is extremely difficult at
OU1. No documentation or disposal records were kept for the landfills and it is
impossible to verify much of the information obtained from the interviews. Leachate
data do not indicate that the anecdotal information was accurate.
Comment 13: Jim McClure of Harding Lawson Associates (HLA) asked about previous discussions
that indicated construction debris had been disposed of at the site as recently as the last
year or two.
Response: The RAB submitted written comments that included this concern. Please see
Section 3.2.4 for specific written comments and responses.
Comment 14: A member of the public asked for clarification regarding the type of liner beneath the
landfill.
Response: Existing physical evidence shows that there are native bay muds beneath the landfill
and that man-made liners do not exist.
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Comment 15: A member of the public asked for clarification regarding the depth of the groundwaier
collection trench.
Response: The collection trench will be installed to extend to below the basin of the SWRP.
Comment 16: A member of the public asked about groundwaier monitoring system gaps, specifically,
the gap between monitoring wells Wl-14 and W1-J5.
Response: This issue has been raised in numerous written comments. Please see the comments
and responses in Section 3.2.
Comment 17: A member of the public requested clarification regarding the applicability of 14 CCR.
Response: Title 14 CCR has been identified as applicable for OU1 landfill closure.
Comment 18: A member of the public asked about the permeability of the bay muds at Site 1 and how
it compares to the permeability of landfill liners.
Response: The permeability of bay muds has been measured at about 10'' cm/sec at the locations
sampled. However, only limited areas have been sampled. Permeability requirements
for landfill liners typically range from 1x10"* cm/sec to IxlO'7 cm/sec.
Comment 19: A member of the public asked whether sand layers have been found in the bay muds at
Site 1.
Response: An aquifer consisting of silty sands is located approximately 12 to IS feet below sea
level at Site 1. Other small sand lenses may exist within shallow bay muds above the
aquifer.
Comment 20: A member of the public asked how many wells were placed in the sand layer at Site 1.
Response: There are ten aquifer monitoring wells at Site 1.
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Comment 21: Ms. Leslie Byster ofSVTC asked whether the Navy had investigated the remedies
implemented at similar sites surrounding the bay.
Response: Information was received about Oyster Point, Third Avenue Landfill, and the old
Stinson Beach Landfill. The following paragraphs summarize information obtained
and discuss its applicability to OU1.
CIWMB was contacted for information regarding Oyster Point. The remedy was
selected to prevent leachate migration and included a single-layer, low-permeability cap
and a slurry wall. The cap was constructed solely with bay muds. The landfill was
closed in the early 1970s and the area is now a marina. It is not known whether
leachate migration was occurring, however, a slurry wall was constructed. Since it is
not known whether leachate migration was occurring, it is difficult to compare these
circumstances and associated remedy to OU1.
CIWMB was also contacted for information regarding the Third Avenue Landfill.
The remedy was a multilayer clay cap and shoreline reconstruction. Waste is located
below the water table, however, leachate migration was not occurring. No remedy was
implemented to restrict potential leachate migration. This circumstance is similar to
Site 1, but, at Site 1 a groundwater interceptor trench is proposed to protect surface
water from potential future leachate migration.
The California Department of Transportation (Caltrans) was contacted for information
regarding the Stinson Beach Landfill. The remedy was excavation, dewatering,
segregation of hazardous and nonhazardous wastes, disposal, and restoration.
Leachate migration was a concern at the Stinson site, but it was not occurring. This
remedy was completed as a mitigation project to restore intertidal mudflat habitat
destroyed during reconstruction of Route 1. The remedy was apparently not pursued
to control leachate migration.
CIWMB stated that apparently several old landfills around the bay have waste below
the water table. However, leachate migration is generally not a problem.
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Comment 22: Ms. Leslie Byster ofSVTC was concerned about dioxins dissolving into leachate and
migrating outside landfill boundaries.
Response: Dioxins have not been tested for in groundwater surrounding the landfills and specific
dioxin tests are not planned in the future. The occurrence of dioxin in groundwater is
expected to be minimal based on strong sorption to soils. In addition, dioxins have not
been a concern since they have very low water solubility and vapor pressure. Dioxins
could dissolve into organic compounds in leachate and potentially migrate with
leachate; however, leachate does not appear to be migrating from the landfills based on
current monitoring data. The Navy will conduct field work to further investigate
contaminant migration at Site 1.
Comment 23: Ms. Leslie Byster of the SVTC raised concerns about the accuracy of the anecdotal
information that described what has been disposed at OU1.
Response: This issue has been raised in numerous written comments. Please see the comments
and responses in Section 3.2.
Comment 24: Mr. Peter Strauss of the SVTC raised concerns about corrective action triggering
levels. Building 191 's role in the OU1 cleanup, and wetlands protection and
enhancement.
Response: Mr. Strauss submitted written comments expressing SVTC concerns. Please see the
comments and responses in Section 3.2.8.
Comment 25: Ms. Cynthia Sievers expressed concern that the Navy was taking a minimal approach to
cleanup at OUI and was not following the same standards as local entities.
Response: The Navy must comply with the same landfill closure regulations as local landfills.
CIWMB has identified 14 CCR solid waste landfill closure regulations as applicable for
OUI. During the public comment period, CIWMB stated that the Navy's proposed
alternative would not meet specified performance standards in 14 CCR. As a result,
the Navy has agreed to revise the proposed plan based on a prescribed, state pre-
approved configuration for the two landfill caps at OUI. Additional public comments
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were solicited from December 8, 1995 to January 22, 1996 on the revised proposal. In
addition, a public meeting was held January 11, 1996 regarding the revised proposal.
Comment 26: RAB Technical, Historical, and Educational (THE) committee chairperson Jim
McClure raised several concerns.
Response: The THE committee reiterated and expanded oral comments by also submitting written
comments. Please see Section 3.2.4 for specific written comments and responses.
Comment 27: NASA-raised concerns regarding consistency with the Bay plan.
Response: NASA submitted written comments expressing their concerns. Please see the
comments and responses in Section 3.2.10.
Comment 28: Ms. Mary Vrabel read a statement on behalf of the LWV.
Response: The LWV submitted written comments. Please see Section 3.2.7 for specific written
comments and responses.
Comment 29: RAB member Mr. David Click expressed several concerns, similar to THE committee
concerns.
Response: Mr. Click submitted written comments. Please see Section 3.2.6 for specific written
comments and responses.
3.2 JUNE 1995 WRITTEN COMMENTS AND RESPONSES
3.2.1 Comments from the City of Sunnyvale
Comment 1: Section 1.3.2. Site 1 Hvdroeeolonv. The report states that landfill liners typically have
a conductivity of1x10* cm/sec and that native soils under the site have an average
conductivity of 1x10* cm/sec. There are also areas under the site with very high
permeabilities (that is, sand lenses). From the limited data on hand the report
presumes that an uninterrupted layer of low-permeability soil underlies the site.
However, it is common in the south bay for high-permeability sand lenses to disrupt the
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continuity of such a layer. These sand lenses are found onfy after exhaustive study or
actual excavation of the site. The report implies that the natural soils beneath the site
exceed standards for landfill liners. To use the conductivity for naturally occurring
soils is unreliable, and it is unreasonable to assume that native unengineered soils are
superior to properly engineered and constructed liners.
Response: The Navy agrees that exhaustive sampling or excavation would be required if it was
necessary to completely characterize the soil beneath the landfill. However, this
information is not necessary and it is not assumed that the clay layers beneath the
landfills are continuous and superior to an engineered liner. Information from the
limited soil investigations offered a possible explanation for the lack of evidence of any
contaminant migration. Additional field work will be conducted to further investigate
whether contaminant migration is occurring. In addition, groundwater will continue to
be monitored.
Comment 2: Section 1.3.2. Site 1 Hvdropeologv. Perched leachate in the landfill is said to be
caused by placing refuse in lifts. Common landfill practice is to build landfills in lifts
and most landfills do not develop perched groundwater or leachate. Those that do, do
not generally attribute the perched leachate to placing the waste in lifts. Thus, your
conclusion regarding the cause of the perched leachate at these sites does not appear to
be well supported.
Response: Perched moisture (above the saturated waste [leachate] zone) was reportedly observed
during the OU1 RI. Placing waste in lifts was identified as a possible cause.
However, the reasons for these perched areas of moisture have very little bearing on
landfill remedial alternatives.
Comment 3: Section 1.3.2. Site 1 Hvdrogeologv. The description of groundwater "barriers" is
misleading and not consistent with previous groundwater work in the south San
Francisco Bay. Generally in the south bay there are a number of transmissive zones
and naturally occurring "groundwater barriers" are not believed to exist close to the
surface.
Response: As stated in the response to Comment 1, it would be difficult to prove conclusively that
naturally occurring barriers to contaminant movement exist. However, groundwater
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analytical data and groundwater elevations presented in the FS indicate that they exist.
Continual groundwater monitoring is proposed because their existence cannot be
proven conclusively. Additional field work will be conducted to further investigate
potential contaminant migration.
Comment 4: Section 1.3.3.1. Summary of Data Collected. The report states that Wl-04 was
damaged and will be abandoned properly during the RA. It is generally accepted
practice that damaged wells are abandoned as soon as practical to avoid groundwater
contamination.
Response: The Wl-4 location is currently inaccessible as a result of dredging. The roads to be
constructed during the RA will remedy this situation.
Comment 5: Section 1.3.3.1. Summary of Data Collected. While a limited amount of data on
detections is provided in the appendices it would be helpful to identify what tests were
done and will be done and at what frequency.
Response: All detections were included in the appendices. In addition, Tables 2 and 6
summarized the groundwater sampling and analyses. Also, Tables 16 and 17 described
a proposed groundwater monitoring program for OU1. A detailed long-term
monitoring program will be developed during the RD.
Comment 6: Section 7.3.5.5. Groundwater Surrounding the Landfill, "as a conservative approach,
all perimeter A1-aquifer wells at Site 7 ... are considered downgradient. ' This
assumption may not be conservative, has a very high likelihood of leading to incorrect
conclusions, and may allow a plan that will do more harm than good. It is possible
that the site is being affected by other sources or that the site has a single hot spot that
is contaminating all other areas of the site. Applying this simple assumption to a
possibly complex situation will not allow proper analysis of these and other
possibilities.
Response: The approach that considers all perimeter monitoring wells as downgradient from the
landfill will not be harmful. It was adopted on the basis of the leachate mounding
observed at Site 1. The leachate mound results in a radially outward potential for flow.
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Therefore, it was sensible to consider perimeter monitoring wells as downgradient. If
groundwater monitoring wells indicate that perimeter ground water is being impacted, a
verification monitoring phase would be implemented. Under verification phase
monitoring, the Navy would further delineate any groundwater contamination plume
and attempt to uncover any potential, unforeseen complex circumstances. For
example, if delineation efforts discovered that groundwater concentrations increased
with distance from the landfill, it would be evident that the landfill was not the source
of contamination and appropriate action would be taken.
Comment 7: Section 1,3.3.5. Groundwater Surrounding the Landfill. In addition, the assumption
that all groundwater monitoring wells are downgradient has led to lumping all
"downgradient wells" together and has artificially made the number of detections of
contaminates seem small. Upon review of individual wells for organic contaminates it
is very likely that some wells will show consistent contamination while others are
consistently "clean."
Response: The Navy has carefully reviewed organic detections in each well to determine whether
any patterns or consistent detections are evident. Tables 2 and 6 in the FS report (PRC
1995) list the number of consecutive detections and addresses them in accompanying
text. For example, at Site 1 the Navy found that only three chemicals were detected
during consecutive quarters in the same well. In May and August 1989, acetone was
detected in monitoring well Wl-5 at concentrations of 10 micrograms per liter (|ig/L)
and 6 jig/L, respectively. Since then, acetone has not been detected in the six samples
collected from Wl-5. In September and December 1993, carbon disulfide was
detected in Wl-14 at a concentration of 0.2 ng/L. Carbon disulfide has not been
detected since in Wl-14. Also in September and December of 1993, an unknown.
light total petroleum hydrocarbons (TPH) component was detected in W1-17 at
concentrations of 110 \igfL and 7 |ig/L, respectively. Since then, light TPH
components have not been detected in Wl-17.
Comments: Section 1.3.3.5. Groundwater Surrounding the Landfill. From the limited information
present it appears that groundwater is flowing beneath the site and that contamination
is occurring, but there is insufficient information presented in an acceptable manner to
reach the same conclusions as in the report. It is also alarming to see the number of
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references to laboratory error and inaccurate data analysis in the report. The report
does not speak well of the reliability of the groundwater data, while on the other hand it
uses the same data to draw broad conclusions and to gamble on a skimpy closure
method.
Response: Approximately 613 groundwater samples were collected and analyzed to support the
OU1 RI/FS. All organic and inorganic detections in groundwater since 1988 have
been provided either in FS report tables or in appendices in the FS report (PRC 1995).
The data have been sorted by monitoring well and by compound so that any patterns or
trends could be identified. AH the data were presented objectively and the data were
reviewed. The conclusion presented in the report and substantiated by data is that
groundwater remediation is not necessary at OU1. Evidence has not been presented
that indicates otherwise.
Groundwater has been sampled and analyzed in accordance with rigorous
QA/QC protocol and it is reliable. The FS report indicates that acetone and
bis(2-ethylhexyl)phthalate results are questionable since they are known to be common
lab contaminants and detections were ubiquitous during the RI. However, these
problems have not been evident during the nine groundwater sampling rounds
conducted since the RI.
Comment 9: Section 1.3.3.5. Groundwater Surrounding the Landfill. The conclusion section does
not consider seasonal variability of groundwater and leachate elevations. Groundwater
and leachate levels generally play a role when considering 'consecutive* detections.
Without accounting for seasonal variations, the analysis is incomplete and fails to
justify the stated conclusions.
Response: Seasonal variability is accounted for in the analysis. As of March 1995 at Site 1,
12 organic compounds had been detected more than once. Of these 12 organic
compounds, four compounds had been detected more than once in the same well. Of
these four spatially consistent detections, one well (Wl-5) had detections occur during
the same season. A light, unknown TPH component was detected in December 1992
and December 1993 at extremely low levels (1 |ig/L and 5 ng/L). No light
TPH compound was detected in December 1994. There are no apparent patterns or
trends that indicate contaminant plumes are migrating either continuously or seasonally.
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Comment 10: Section 2.3.3.5. Groundwater Surrounding the Landfill. Analysis of groundwater
required by 23 CCR should be reviewed. The statement "requires that two consecutive
detections above a WQPS (typically background concentrations)" is not necessarily
true. The selection of WQPS requires a scientific analysis of existing conditions as well
as potential long term goals and uses of water at the site. There must be a justification
for the WQPS that is identified. There is no justification presented. Until WQPS are
established the conclusion drawn is not appropriate.
Response: The selection of background concentrations as WQPS is justified by 23 CCR 2550.4,
Concentration Limits, which states that the concentration limit should not exceed the
background value of that constituent. This section also states that concentration limits
greater than background can be proposed for a corrective action phase. However, the
Navy is currently in the detection monitoring phase.
Comment 11: Section 1.3.3.5. Groundwater Surrounding the Landfill. The statement that "however.
the landfill is the likely source of organic leachate chemicals that have been
infrequently detected in groundwater samples" argues that the landfill is a source of
groundwater contamination. If the site is a source of groundwater contamination the
site should have a corrective action plan to mitigate any adverse environmental
impacts.
Response: The landfill is probably the source of the detections; however, corrective action is not
necessary. Corrective action would not be considered until chemicals were consistently
detected in groundwater above water quality objectives developed for the protection of
aquatic life. Tables 2 and 6 show that only very low, infrequent detections have
occurred.
There are three phases of activities associated with groundwater monitoring under
23 CCR: detection monitoring, evaluation monitoring, and corrective action programs.
As part of detection monitoring, groundwater constituent concentrations would be
monitored, and, if a concentration level statistically exceeded its background
concentration, evaluation monitoring would begin. The evaluation monitoring phase is
used to assess the nature and extent of the violation (exceedance in WQPS). During
evaluation monitoring, additional wells may be installed and sampled to verify leakage
from the landfill as indicated by detection monitoring. The groundwater monitoring
system, monitoring frequency, and sampling and analysis may be altered. In addition,
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data needed to complete a corrective action program would be developed during
evaluation monitoring.
Corrective action programs require activities to achieve compliance with standards,
initiating and completing corrective actions within a reasonable period of time
considering extent of pollution, and establishing and implementing a monitoring
program to demonstrate effectiveness of the corrective action program (may be based
on the evaluation monitoring program). Corrective action would likely include
hydraulic control of the groundwater and leachate through pump and treat methods. A
contingency measure is proposed for Site 1 and would be in place if corrective action is
required along the northern boundary. A contingency measure is proposed at the Site 1
northern boundary because of the proximity and potential impact of landfill
contamination on ecological receptors and habitats in the adjacent SWRP. The
contingency measure includes enhancing the containment provided by the bay muds at
Site 1 with a vertical subsurface barrier and collection trench along the northern
boundary of Site 1. The subsurface collection trench will be designed to intercept any
contaminants that may migrate into shallow groundwater and protect the SWRP
receptors. The collected leachate can then be pumped to a treatment system designed
to address the contaminant that has migrated. In addition to pumping the trench,
leachate can also be extracted from within the landfill through the leachate monitoring
wells as part of corrective action.
Leachate migration requiring corrective action is not necessary at this time or expected
to be in the future. However, the contingency measure will protect against the
possibility of any buried, drummed waste mobilizing and migrating off site in the
future. Only the northern boundary of Site 1 is presently selected for additional
containment because it is upgradient to surface water and associated receptors.
Additional field work will be conducted to investigate contaminant migration at the
southwestern border. Releases along the other borders can also be addressed by
containment and hydraulic control, if needed. Site 2 is not considered for the
additional containment since hydraulic control can be easily maintained near the site as
demonstrated by the Building 191 lift station and associated runway drainage system.
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Comment 12: Section 1.3.3.5. Groundwater Surrounding the Landfill. Based on the landfill cross
sections provided (Figures 5, 6, and 7), well WJ-6 is the onfy well shown with a
screened interval that is in a high-permeability lens. Other wells are generally
screened in bay muds. This greatly limits these wells' ability to be used as monitoring
wells. New wells should be constructed in highly permeable layers to that accurate
data can be obtained and analyzed. All boring logs should be made pan of the report.
Response: With the exception of W1-16, all of the groundwater monitoring wells at Site 1 are
screened across the most permeable sediments observed while drilling. Many of the
wells are also partially screened in bay muds; however, they will still function as
intended and do not need to be replaced. Additional field work will be conducted that
will enhance the current monitoring network.
Comment 13: Section 1.3.3.5. Groundwater Surrounding the Landfill. Under the inorganic
constituent discussion it is stated that there is a potential for flow from the leachate
zone to the aquifer zone. The immediately preceding paragraph implies that it is highly
unlikely that there is a potential for flow from the landfill to groundwater. These
statements are highly contradictory and should be reviewed for consistency.
Response: The paragraphs are not contradictory. Potential for flow (or a gradient) does exist
between leachate and groundwater; however, low hydraulic conductivity soils, high
organic content associated with the clays, and low source contaminant concentrations
are likely to combine to restrict flow and limit contaminant migration. This conclusion
is supported by the analytical data collected during the investigations.
Comment 14: Section 1.3.3.5. Groundwater Surrounding the Landfill. The next paragraph describes
that wells with high TDS are used for comparison to determine groundwater
contamination. The reason for using the high TDS wells is clear; these wells are most
obviously from the area around the site. The wells are typed, either up or down
gradient, and then the well's results are compared to determine the extent of
contamination. Earlier in the report discussion was centered on samples with high
matrix interference that could likely lead to erroneous results. Matrix interference is
often caused by high TDS in the samples. These statements therefore also seem
contradictory and should be reviewed for consistency.
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Response: High TDS concentrations often cause matrix interference. Samples having matrix
interference may result in elevated detection limits and qualified data. The laboratory
attempts to minimize the effects of matrix interference while maintaining the integrity
of the sample with accepted and proven procedures. A sample's integrity is protected
by QC procedures such as the use of matrix spikes. If QC procedures indicate that
matrix interference is present, additional procedures may be used to eliminate the
interference. However, it may be impossible to eliminate some matrix interference and
the resulting data are qualified accordingly.
In addition to the laboratory procedures, all of the analytical data for Moffett Field
undergo external, third-party validation which verifies that the laboratories performed
the testing with an acceptable amount of QC. Third party data validation procedures
may result in additional data qualification and possibly the elimination of some results.
Data that are qualified with an "R" are not acceptable for any purpose and are
considered erroneous, data qualified with a "J" qualifier are usable and estimate the
true value.
Comment 15: Section 1.3.3.5. Groundwater Surrounding the Landfill. The North Base Wells that
were chosen for background comparison are not identified. Their locations and boring
logs should be provided.
Response: The Navy will send the City of Sunnyvale a map showing these well locations and
borehole logs.
Comment 16: Section 1.3.3.5. Groundwater Surrounding the Landfill. The conclusion that the
source of TPH in Jagel Slough is not a result of Site 1 may be in error. It is true that
wells Wl-1 and Wl-16 are between Jagel Sough and Site 1, but both are screened
through clay. Clay is not a very permeable material and contamination from Site 1
may be reaching the slough through a sand lens that is not currently being monitored.
Response: Monitoring well Wl-16 is mainly screened through clay; however, Wl-1, Wl-8,
and Wl-5 are screened through permeable sediments and are located between the Jagel
Slough and the Site 1 landfill. TPH migration into Jagel Slough has not been indicated
by samples collected from these wells. In addition, hydrographs show that Jagel
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Slough is upgradient from surrounding groundwater. Therefore, it is unlikely that
Jagel Slough has been impacted by TPH from the landfill.
Comment 17: Section 1.3.5. Site 2 Hvdrogeologv. Figure 20 shows that the site is being dewatered
by the drainage pumping house Building 191. The pump discharge should be analyzed
for contamination.
Response: The pump discharge has been analyzed for contamination and low levels of chlorinated
solvents have been detected in the past. However, recent samples have not indicated
contamination. Building 191 receives drainage from many areas at Moffett Field and it
is difficult to identify the source of the detections at the pump discharge. However,
there are two monitoring wells located between Building 191 and Site 2. Sampling
results from these wells indicate that the chlorinated solvents detected at Building 191
did not originate from Site 2.
Comment 18: Section 1.3.6.1. Summary of Data Collected. Monitoring well W2-12 is not considered
an upgradient well, but it seems that it should be based on its location and screened
interval.
Response: Monitoring well W2-12 was installed as an upgradient well and has been analyzed as
upgradient.
Comment 19: Section 1.3.6.3. Groundwater Surrounding the Landfill. The conclusions drawn for
Site 2 are the same as for Site 1. The conclusions are drawn partly from a peculiar
analysis of 23 CCR and the conclusions are based on monitoring data that are not
presented in the report. As with Site 1, the conclusions are based on monitoring data
that have been obtained from groundwater wells that appear to be screened primarily
in clay.
Response: All inorganic and organic detections in groundwater since 1988 have been provided
either hi FS report tables or in appendices in the FS report. The conclusions in the
report are based solely on groundwater monitoring data presented in the report. All the
perimeter groundwater monitoring wells at Site 2 are screened across the most
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permeable sediments observed while drilling. Many of the wells are also partially
screened in silts and clays; however, they still have functioned as intended.
Comment 20: Section 1.3.6.3. Inorganic Constituents. The conclusions drawn for Site 2 are nearly
identical to Site 1 and are subject to the same potential flaws as discussed for Site 1.
Response: Please see the response to previous comments.
Comment 21: Section 1.3.6.6. Surface Water. Samples were collected, but there is no description of
how many samples were taken, how often the samples were taken, and what tests were
done on each sample.
Response: The information requested is beyond the scope of an FS report. The information listed
can be found in RI reports (IT 1993a, IT 1993b), the field investigation technical
memorandum (PRC 1993), and the site-wide ecological assessment report (PRC and
MW 1995) which are located at the information repository.
Comment 22: Section 1.3.6.6. Surface Water. The conclusion that Site 2 is not leaking into surface
water because contaminants should be consistently detected should be reviewed.
Leakage from a landfill can be based on many variables but, in general, landfills are
most likely to leak after major storm events. The data on leakage should be reviewed
to determine if detections of surface water contaminants are occurring at some regular
interval or if leakage is related to some physical phenomenon.
Response: It would be extremely difficult to correlate groundwater and, consequently, surface
water chemistry with storm events. However, the landfills will be capped and
infiltration will be minimized to reduce any effects storm events have on groundwater
or surface water chemistry.
Comment 23: Section 1.3.6.7. Landfill Gas. The frequency of testing should be discussed and should
conform to 14 CCR. Physical structures within 1,000 feet of a landfill should be
monitored.
Response: The proposed gas monitoring program was developed according to 14 CCR. At Sites 1
and 2, gas concentrations are monitored quarterly. At Site 1, no physical structures
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are located within 1,000 feet. At Site 2, landfill gas is not being generated. Gas has
not been detected inside or outside landfill boundaries and gas monitoring at Site 2 will
likely be discontinued.
Continent 24: Section 1.3.7.3. Leachate Migration into Surrounding Growdwater. Areas around the
margin of South San Francisco Bay exhibit highly variable permeability, with areas of
bay mud (low permeability) containing lenses of other materials such as sand (high
permeability) in a highly unpredictable fashion. These sand lenses often act as
conduits for movement ofleachate and landfill gas. Therefore, using the average K
values for bay mud beneath the site is questionable. By using the K values presented
the higher permeability of portions of the strata beneath the sites is ignored. Further,
the sample preparation that was used to find the stated K values in the laboratory
probably does not replicate the condition of the clay beneath the sites when the sites
were first used.
Response: The information in this section was provided to offer a possible explanation for the lack
of evidence of contaminant migration. No sand lenses have been discovered that
provide a conduit for migration. The Navy will conduct additional field work to
further investigate whether contaminant migration is occurring at the southern end of
Site 1 (between monitoring wells Wl-14 and Wl-15).
The landfill closure strategy accounts for the possibility that the bay muds are not
continuous. The groundwater interceptor trench will protect the SWRP from any
contamination migrating through smaller sand lenses. Continual A1-aquifer monitoring
results will monitor landfill impacts on surrounding groundwater and will monitor
whether sand lenses are transporting contamination into more permeable sediments.
Comment 25: Section 1.5. Applicable or Relevant and Appropriate Requirements. This report does
not appear to take into account the requirements of 14 CCRfor closure of a landfill.
Most of the discussion seems to be ignorant of 14 CCR. The report should also
consider 23 CCR requirements for groundwater monitoring and leachate management.
Specifically the report does not address the "five foot separation criteria "for waste
and groundwater and does not adequately address 23 CCR Chapter 15, Article 5
monitoring requirements.
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Response: The FS report identifies 14 CCR and 23 CCR as the two major applicable regulations
that will guide OU1 remedial actions. The report identifies these regulations in detail
in Appendix J, which lists all applicable requirements from both 14 CCR and 23 CCR.
Comment 26: Section 1J>.^Applicable or Relevant and Appropriate Requirements. It is true that these
regulations apply to nonhazardous municipal landfills and that Sites 1 and 2 are
hazardous waste sites, but it seems logical that Sites 1 and 2 should not be held to a
lesser standard than sites that have never knowingly received hazardous waste.
Response: Some .of the wastes at the OU1 landfills are potentially hazardous constituents;
however, this circumstance is common to all solid waste and CERCLA landfills.
Compliance with solid waste monitoring and closure regulations will provide protection
for human health and the environment. Further, low contaminant concentrations in
leachate show that a minimal threat from hazardous substances exists at OU1.
Maximum detected concentrations are below maximum concentrations given for the
toxicity characteristic in 40 CFR 261.24. In addition, documentation received from
CIWMB indicates that Site 1 was operated as a solid waste facility. The Navy was
issued a Solid Waste Facilities Permit for Site 1 by Santa Clara County Environmental
Agency. The permit states that the types of waste received at the site include
cardboard, lawn cuttings, primings, wood waste, and asbestos insulation wrapped in
double plastic bags. The permit also states that the disposal of hazardous waste was to
be prohibited at the facility. This further supports the assumption that OUl landfills
were operated as solid waste landfills and received similar types of wastes (solid waste
with small amounts of hazardous waste). Also, visible surface debris includes obvious
construction and demolition debris, such as concrete rubble with reinforcing steel,
asphalt chunks, wire, wood chips, glass, and mounds of dirt overgrown with weeds
(possibly street sweepings), which are similar to solid waste landfill waste. For these
reasons, the Navy identified 23 CCR groundwater monitoring requirements and 14
CCR closure regulations as most appropriate for OUl. CIWMB concurs with these
conclusions.
Comment 27: Section 1.5. Applicable or Relevant and Appropriate Requirements. Table 9 states that
14 CCR closure requirements are applicable. Title 14 CCR requires that a landfill be
closed according to 23 CCR, Chapter 15. This chapter specifically requires a
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minimum of 12 inches of low permeability clay as well as two feet of foundation soil
beneath the clay and one foot of vegetative cover to protect the clay layer.
Response: The Navy has agreed to revise the cap design and base the design on the
aforementioned prescriptive standard at a cost increase of $1,772,000. The Navy's
revised cap design includes the same layers that are specified as minimum requirements
in 23 CCR. Three components have been added to the standard configuration in 23
CCR.
As stated in the comment, the 23 CCR cap standard consists of a 2-foot-thick
foundation layer beneath a 1-foot low-permeability clay layer, which is under a 1-foot
layer of cover soil. In addition, the Navy has included a gas venting layer at Site 1.
This layer will prevent gas pressure from building up beneath the low-permeability
layer and causing horizontal gas migration. The Navy has added a biotic barrier and
may also add a drainage layer above the low-permeability layer. The drainage layer
would be installed above the barrier layer to (1) prevent hydraulic head build-up, (2)
prevent associated seepage through the layer, and (3) prevent plant-root saturation.
Inclusion of a drainage layer will be further evaluated during the RD. The biotic
barrier will protect the low-permeability layer from burrowing animals. The cap
described above is similar to Alternative 3 in the FS report.
Comment 28: Section 6.2. The Hydrologic Evaluation of Landfill Performance (HELP) Model results
seem flawed. Intuitively, a site within 3 feet of loamy soil should allow much greater
storm water infiltration than a site with 3 feet of loamy soil over 2 feet of clay. To
assist in explaining this concept the following sketch (see attachment) illustrating the
report's comparison of Alternatives 2 and 3 is provided.
It is likely that one or more of the assumptions fed into the HELP model, such as soil
characteristics, plant characteristics or evaporative zone/climatological data are
flawed. These should be reviewed.
Response: Alternatives 2 and 3 have roughly equivalent performance because the upper 3-foot
layers on both caps equally reduce the already low annual precipitation observed at
Moffett Field. Approximately 90 percent of the 13 inches of annual rainfall is lost
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through evapotranspiration. The remaining 1 inch of precipitation is inconsequential,
especially when contaminant migration is not currently evident.
Comment 29: Section 4.0. The report seems flawed in its consideration of closure by Alternatives 1
and 2. Alternatives 1 and 2 would not even be considered by regulatory agencies
under ordinary circumstances (that is, if the site were not on the Superfund list and
subject to CERCLA).
Response: OU1 activities are regulated under CERCLA and the report was prepared accordingly.
Alternative 1 was included as a baseline for comparison and Alternative 2 received
significant consideration from regulatory agencies.
Comment 30: Section 1.5. Applicable or Relevant and Appropriate Requirements. The report does
not address leachate management as required by 23 CCR. It seems appropriate to at
least review the concept of pumping and treating existing leachate. The report
indicates that the waste mass is hydraulicalfy separated from groundwater by a very
low-permeability natural clay liner. If this is truly the case, it seems that pumping the
leachate from the waste mound should be a very easy and effective procedure.
Combining pumping with the very low intrusion of surface water that is predicted by the
HELP model (if it has been correctly applied in this report) after the site is closed
should result in very little leachate being generated in the future.
Response: Appendix J addressed leachate management as required by 14 CCR and 23 CCR. Title
14 CCR states that leachate control shall cease after the landfill operator demonstrates
to the local enforcement agency that leachate is no longer produced or the discharge of
leachate will have no effect on water quality. At Site 1, refuse is below the water table
and, as a-result, leachate will always be produced. The FS has demonstrated to
enforcement agencies that the leachate produced has no effect on water quality. The
Navy will, however, conduct additional field work to investigate contaminant
migration. Therefore, the conclusion reached in the FS may change based on results of
this investigation.
Comment 31: Section 1,5, Applicable or Relevant and Appropriate Requirements. All current
regulations for municipal solid waste landfills have requirements for post closure
maintenance funds and for long-term monitoring. The OUI report may not be the
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proper forum to address these issues, but these issues should be discussed before any
final closure method is chosen. A postclosure maintenance plan should be prepared
prior to closure of the sites.
Response: The Navy will prepare a postclosure maintenance plan during the RD.
Comment 32: The location of the two sites, adjacent to the bay and possibly upgradient of the
Sunnyvale Landfill, is a concern because, if the Moffett Field sites are not closed
property, contaminant plumes could cause environmental degradation to a large area.
In addition, by not properly closing these sites today, future problems that could have
been reduced or prevented may occur. I urge you to re-evaluate the report and
existing regulations to confirm that your plan is both feasible and proper given the
existing conditions.
Response: OU1 landfills are not upgradient of the Sunnyvale Landfill. With proper and continual
groundwater monitoring and corrective action contingency plans, the Navy can address
any environmental degradation in a timely manner.
The basic strategy of (1) capping the landfills, (2) installing a gas interceptor trench,
(3) installing a groundwater collection trench, and (4) continuing groundwater and gas
monitoring (with corrective action contingencies) is an adequate, cost-effective
solution. During the public comment period, the Navy learned that state, county, and
local regulatory agencies do not believe that the original proposed alternative is in
compliance with applicable landfill closure regulations. As a result, the Navy has
agreed to revise the proposed plan based on a prescribed, state pre-approved
configuration for the two landfill caps at OU1 at an additional cost of $1,772,000.
Therefore, instead of 3-foot, single-layer soil caps, the landfill caps will, at a
minimum, contain 1 foot of topsoil overlying an impermeable layer. These layers will
be built on a 2-foot foundation layer. In addition to this minimum requirement, the
Navy will include a biotic barrier and possibly a drainage layer between the
impermeable layer and topsoil to protect the integrity of the impermeable layer and
drain percolated water from the cap. The biotic barrier will prevent barrowing animals
and deep plant roots from puncturing this layer. The drainage layer provides a
pathway for percolation to flow off the cap. Inclusion of the drainage layer will be
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evaluated during the RD. The Navy will include gas venting beneath the impermeable
layer to prevent gas pressure build-up and horizontal subsurface gas migration.
3.2.2 Comments from the City of Mountain View
Comment 1: As the host city to Moffett Field, we wish to bring out concerns regarding the closure of
OU1 to your attention. We have discussed the proposed closure methodology with
CIWMB, RWQCB, and the Santa Clara County Health Department, Toxic Substances
Division. These agencies have all indicated the proposed closure method,
Alternative 2, either does not meet their approval or is inferior to the prescriptive
closure methods stipulated in state and federal regulations. We find this disappointing,
and encourage you to re-evaluate your proposed closure method to comply with the
recommendations of these agencies and the regulations which they enforce.
Response: During the public comment period, the Navy learned that state, county, and local
regulatory agencies do not believe that the original proposed alternative is in
compliance with applicable landfill closure regulations. As a result, the Navy has
agreed to revise the proposed plan based on a prescribed, state pre-approved
configuration for the two landfill caps at OU1 at a cost increase of $1,772,000.
3.2.3 Comments from the RAB Cost Committee, compiled by Christina Scott, Committee
Chairperson
Comment 1: Will the soil cap in Alternative 2 be constructed to meet the specifications in 23 CCR,
Section 2581?
Response: A revised proposal includes landfill caps that will be constructed to meet the
, specifications in 23 CCR Section 2581. Originally, Alternative 2 was proposed as an
engineered alternative to the cap design specified in 23 CCR 2581. However, during
the public comment period, the Navy learned that state, county, and local regulatory
agencies do not believe that Alternative 2 is in compliance with applicable landfill
closure regulations. As a result, the Navy has agreed to revise the proposed plan based
on a prescribed, state pre-approved configuration for the two landfill caps at OU1 at a
cost increase of $1,772,000. Therefore, instead of 3-foot, single-layer soil caps, the
landfill caps will, at a minimum, contain 1 foot of topsoil overlying an impermeable
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layer. These layers will be built on a 2-foot foundation layer. In addition to this
minimum requirement, the Navy will include a biotic barrier and possibly a drainage
layer between the impermeable layer and topsoil to protect the integrity of the
impermeable layer and drain percolated water off the cap. The biotic barrier will
prevent burrowing animals and deep plant roots from puncturing this layer. The
drainage layer would provide a pathway for percolation to flow from the cap.
Inclusion of the drainage layer will be evaluated further during the RD. Lastly, the
Navy will include gas venting beneath the impermeable layer to prevent gas pressure
build-up and horizontal subsurface gas migration.
Comment 2: How will the quality of the borrow material be assured?
Response: The specific construction QA/QC procedures have not been formally compiled.
However, in general, a civil or geological engineer will specify the type of soil
required for each layer of the cap. At the borrow source, soil tests will be conducted
to evaluate whether the soil meets specifications. In addition, during layer
construction, periodic tests will be conducted to ensure that the final configuration is in
accordance with specifications.
Comment 3: What degree of compaction will be required for the cap ?
Response: The low-permeability layer is required to have a hydraulic conductivity less than
1x106 cm/sec or at least as low as underlying soil. The vegetation layer will not be
compacted.
Comment 4: Do the O&M cost estimates for the postclosure period include any provisions forfeiture
corrective actions?
Response: Cost opinions have not been prepared for any future corrective actions. It is difficult to
predict the extent of any future corrective action that may be needed.
Comment 5: How will future major O&M or corrective actions be funded?
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Response: These activities will be funded through annual DoD environmental restoration budgets.
These budgets are proposed by Naval Facilities Engineering Command (NAVFAC)
headquarters in Washington D.C. and are approved as part of a total budget package
each year by Congress and the President. While congressional actions cannot be
anticipated, it is NAVFAC's responsibility to request the necessary money for the
upcoming fiscal year's environmental restoration.
Comment 6: Will a bond be posted or an insurance policy enstated?
Response: These activities are not anticipated at this time.
Comment 7: The FS does not contain any provision for the continued operation of the pumping
system at Building 191. It appears that this pumping is critical to maintaining year-
round access to the sites, O&M costs should be included in the estimates for the
alternatives.
Response: Operation of the Building 191 pump station and drain/subdrain system will be part of
the Navy's OU1 remedy as an institutional control. Detailed provisions for system
O&M are not included in die OU1 FS or the ROD because the pump station must be
operated and maintained by NASA as part of their current land use. A review of the
remedy and lift station operation will be conducted periodically to ensure that the
remedy continues to provide adequate protection of human health and the environment.
Comment 8: What happens to the OU1 landfills after the 30-year postclosure period? Who will
maintain the sites? If your assumption is that at that time the landfills will become part
of the natural landscape of the area, do you anticipate initiating wetlands restoration?
Whether the postclosure status needs to be considered and funding set aside by the U.S.
Navy.
Response: The federal government will be obligated to provide for postclosure maintenance for at
least 30 years. The federal government is not released from its responsibilities after 30
years if data indicate that the landfills still pose a threat to human health or the
environment. Funding is based on annual budgets (please see the response to
Comment 5).
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3.2.4 Comments from the RAB Technical, Historical, and Educational Committee, compiled by
Jim McClure, Committee Chairperson
Introduction
The THE Committee of the RAB for Mqffett Field has reviewed the May 15, 1995, Final FSfor OU1 at
Moffett Field, OU1 consists of two landfills, called Sites 1 and 2 by the Navy.
During the THE Committee review of the OUJ FS, several questions and concerns have been identified.
This presentation summarizes concerns previously documented in the THE Committee's July 19, 1995,
report. That report was distributed to RAB members with the Navy's July 26, 1995, minutes of the July
13, 1995, RAB meeting. This presentation has been modified from the July 19 report, to better classify
concerns and to present some additional concerns identified by the THE Committee members.
Recommendation
On the basis of the identified concerns, it is recommended that the May 15, 1995, OU1 FS either be
rejected or withdrawn, and that it be revised to adequately address these concerns.
The Committee Concerns
OU1 FS concerns identified by the THE Committee can be grouped into the following five general
areas:
• Adequacy of Site Investigation
• Assumptions About Current Conditions
• Assumptions About Future Conditions
• Design Assumptions
• Regulatory Compliance and Financial Security
Adequacy of Site Investigation
Comment 1: Lead contamination associated with the operation of the pistol firing range at Site 1 has
not been investigated.
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Response: Lead contamination at the landfill surface has not been characterized because this
information is not needed to implement capping at the landfills. During cap
construction, heavy equipment could generate fugitive dust emissions. Construction
workers will mitigate any potential hazards by using PPE such as respirators. In
addition, dust suppression strategies such as wind speed alarms can be implemented to
reduce fugitive dust emissions during capping.
Comment 2: The OUJ FS descriptions of hazardous wastes disposed in the landfills differ from those
presented in relevant sections of the RI report. The result is that the possible extent of
hazardous waste disposal in OU1 is obscured in the OUJ FS.
Response: The hazardous waste descriptions in the RI report were originally presented in the IAS.
All of the information regarding types and quantities of waste disposed at the landfills
were obtained by personal communications with current or previous staff at Moffett
Field. Confirming the accuracy of this anecdotal information is extremely difficult at
OU1. No documentation or disposal records were kept for the landfills and it is
impossible to verify any information obtained .from interviews without actively
excavating the landfills. A fate and transport analysis would have little value since the
waste could have been disposed of in drums.
To address this concern, the Navy has (1) reviewed the IAS (NEESA 1984) and
examined the basis for the assumptions regarding disposal, (2) identified approaches in
EPA presumptive remedy guidance documents (EPA 1991, 1993) regarding similar
circumstances since these circumstances are common to many landfills, and (3)
considered additional remediation strategies that regard anecdotal information as
potentially accurate.
One explanation for the differing information in the IAS and collected data is that the
LAS is not accurate. To evaluate this further, the following paragraphs contain a
summary of the LAS and places emphasis on the basis for assumptions made.
The LAS contains a cursory, qualitative survey of waste generation rat^s and disposal
practices at Moffett Field from the 1930s to the early 1980s. The information is based
on record searches, on-site surveys, and civilian and military personnel interviews.
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The IAS presents waste generation rates from different groups that have resided at
Moffett Field, most notably Public Works, P-3 Orion patrol squadrons and jet
squadrons, aircraft intermediate maintenance departments, and general operations (such
as the fire department, photography lab, and naval exchange [NEX] gas station). Of
these groups, Public Works and the squadrons reportedly used the landfills for waste
disposal. Waste disposal at the landfills from Public Works and the squadrons are
summarized below from the IAS (NEESA 1984).
Public Works operated, maintained, and repaired buildings, structures, and other
facilities at Moffett Field. Public Works is comprised of metal and welding shops,
paint shops, utilities shops, electrical shops, pipe shops, the steam plant, the building
trades shop, the transportation division, and the pesticide shop. Of these shops and
divisions, the paint shop, the electrical shop, the pipe shop, and utilities shop disposed
of waste at the landfills.
According to the IAS, the paint shop had an area of Site 2 reserved for paint shop
waste. Paints and thinners were disposed in cans, as it was easier to dispose of wastes
in barrels at the shop rather than on the ground. The paint shop staff never observed
pools of liquid or chemical smells at the landfills.
The electrical shop reportedly used paper elements to filter oil from transformers. The
crews used about seven to eight filters in a filter press and filtered about two to three
20- to 30-gallon capacity transformers per month hi the summer. The shop generated a
few dozen filters per year, as well as small amounts of sawdust used to soak up spilled
transformer oil. The filtering was done on site and the filters were dried in an oven.
The electrical shop reportedly used the landfills only for disposal of paper transformer
oil filters.
Jet squadrons operated at Moffett Field from 1950 until 1962. According to personnel
interviewed, most oily and solvent wastes were collected hi 55-gallon barrels and
stored beside hangars. The outside corners of the hangars reportedly were used to
store barrels of waste materials. According to the IAS, the barrels were either hauled
to the runway landfill (Site 1) by station personnel or disposed of down storm sewers
around the hangars, or off the edge of die aprons. The amount of liquid wastes taken
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to Site 1 is not known; however, the IAS estimates that a total of 1.5 million gallons
were generated and assumes 5 to 10 percent of the 1.5 million gallons generated were
disposed at the landfills. The basis for this assumption is unknown.
Seven P-3 Orion squadrons have been stationed at Moffett Field since 1962, which was
near the time that Site 1 began operations and Site 2 ceased operations. Disposal
methods reportedly varied. In the early 1960s, much of the solvents were poured
down deck drains, around the hangars, and around the aprons, or placed in barrels and
stored around the hangars. Personnel interviews indicated that some of the waste
containerized in 55-gallon drums was hauled to Site 1 in the early 1960s. The amounts
are not known.
The IAS reports of disposal practices contain several inconsistencies. The IAS
indicates that barrels were disposed of at Site 1 from 1950 to 1962, however, the Site 1
landfill did not exist before 1962. In addition, the IAS states that 1.5 million gallons of
liquid waste were generated by the Orion squadrons from 1962 to 1978 (that is, during
the operating period of Site 1). However, the report tables indicate that 687,000
gallons of liquid waste were generated. The IAS then assumes that 5 to 10 percent of
the 1.5 million gallons was disposed at Site 1. Both the 5 to 10 percent estimate and
the 1.5-million-gallon estimate are arbitrary. The LAS also states that 1.5 million
gallons of liquid waste were generated during the jet era at Moffett Field, however,
report tables indicate that 528,000 gallons were generated. The report again arbitrarily
assumes that 5 to 10 percent of the 1.5 million gallons (1,363 to 2,727 55-gallon
drums) were disposed at Site 2. The estimates appear to be arbitrary and speculative,
and are inconsistent with other estimates in the IAS report.
Another explanation for the differing information in the LAS and collected data is that
the collected data do not adequately depict landfill content. There is no question that
the landfill content is not characterized and it is not known what was disposed in the
landfills. Notably, this circumstance is not unique to Moffett Field. Many Superfund
landfills have the potential to contain a wide variety of wastes, including drums of
waste. EPA guidance (EPA 1991, 1993) is very clear on how to address these sites.
Landfill characterization is not recommended and containment is the best remedy
unless (1) the location of the drums is known, (2) the location is easily accessible, and
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(3) removal will reduce the principal threat. At Moffett Field, geophysical surveys do
not show any drum disposal within Site 1. Leachate and groundwater data show low
concentrations. Lastly, information presented in the IAS regarding waste disposal is
questionable. The stated assumptions appear to have very little basis and are difficult
to verify.
The Navy's strategy has been to evaluate containing the refuse through capping and,
most importantly, to recognize that if any previously drummed waste begins to migrate
from the landfill, the monitoring program will detect the release and corrective action
will be implemented.
An additional strategy to protect against the possibility of buried, drummed waste
mobilizing and migrating off-site was also evaluated. This strategy includes enhancing
containment with a subsurface interceptor trench with a vertical barrier along the
northern boundary of Site 1. This trench has been added as a corrective action
contingency measure and will be in place if contamination migrates. The interceptor
trench, in conjunction with capping and monitoring, will protect adjacent surface
water. Only the northern boundary of Site 1 is presently selected for the possible
additional containment because this area is upgradient to the SWRP ecosystem.
Releases along other borders will not affect sensitive ecosystems and additional
containment is not warranted. Additional field work will be conducted to investigate
contaminant migration along the southwestern border. Any releases along these
borders could be addressed by containment or hydraulic control if needed. Site 2 is not
considered for the additional containment since hydraulic control can be easily
maintained near the site as demonstrated by the Building 191 lift station and associated
runway drainage system.
The reason for omitting the RI (actually IAS) estimates of the quantities of waste from
the FS is that evidence collected during field investigations does not support the
estimates. The Navy did not intend to misrepresent or suppress information. Chemical
data from leachate wells do not support the estimates that hundreds of thousands of
gallons of liquid waste were dumped in the landfill.
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Comment 3: The existing ground-water monitoring network does not adequately characterize
leachate or groundwaterflow.
Response: A field investigation will be conducted to further characterize contaminant migration
and ground water flow.
Comment 4: The OU1FS does not appear to have reliably established the lateral and vertical extent
of the landfills. In particular, available information indicates that at Site 1, refuse may
have been placed into underlying aquifer material, but this is not indicated on the cross
sections.
Response: To establish the lateral extent of the landfills, the Navy will dig trenches. Trenching
data will further refine and confirm initial estimates of landfill boundary locations. To
depict the vertical extent of refuse, cross-sections were constructed based on borehole
logs. Borehole logs did not indicate that refuse had been placed into the aquifer.
No records were kept regarding the initial depth of any excavations at Site 1. The
information included in the text was obtained from interviewing base personnel during
the IAS. The physical evidence collected during the OU1 RL/FS does not confirm that
refuse extends into the aquifer at Site 1. The physical evidence regarding landfill depth
is summarized below.
Nine borings have been extended through Site 1 landfill refuse. The maximum
refuse depth has been measured at 12.9 feet below msl at boring Wl-11(F).
In addition to borings through the landfill, the Navy conducted an electrical
resistivity survey to locate the base of the landfill. The survey did not support
the more reliable borehole logs. Survey results indicated that the landfill base
is approximately 5 to 10 feet shallower than found in borings. The electrical
resistivity information was not mentioned in the FS report since it did not
accurately depict boundaries relative to soil boring information. However, the
RI report discusses the results in detail (IT 1993a).
If refuse extended 21 feet below msl, data indicate that the leachate zone would
be in direct contact and communication with the A1-aquifer zone. If these two
water bodies were in direct communication, sustained leachate mounding would
not be observed. Water elevation data indicate that leachate elevations are
above groundwater elevations and that leachate is "mounded." If the leachate
zone was in direct contact with the A1-aquifer, mounding would not likely
occur.
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• Perimeter groundwater data collected to date do not indicate that contamination
is migrating into the A1-aquifer at the landfill boundary. If the aquitard
between the A1-aquifer zone and leachate zone was significantly breached,
contaminant migration may be more likely. However, the Navy has agreed
that additional field work is needed to support or disprove this point.
The physical evidence indicates that the information obtained from interviews may not
be completely accurate. However, there is no practical or reliable method that can be
used to verify or disprove anecdotal information. Therefore, the Navy will continue to
monitor perimeter groundwater for releases of contamination from the landfills.
Assumptions About Current Conditions
Comment 5: The OU1 FS understates soil hydraulic conductivity measurements from the RI report
by factors of up to approximately 10. Therefore, leakage out of the landfills could be
10 times greater than assumed.
Response: Leakage out of the landfill has been evaluated by analyzing groundwater chemistry data
collected from monitoring wells. The information presented regarding measured
hydraulic conductivity of surrounding soils was presented as a possible explanation for
the lack of contaminant migration.
The underlying soil hydraulic conductivity has not been accurately characterized and
the selected remedy accounts for this uncertainty. The groundwater interceptor trench
will be designed to protect the SWRP from any migrating contamination. Continual
A1-aquifer monitoring data will measure landfill impacts on surrounding groundwater
and will monitor whether contamination is being transported into saturated permeable
sediments.
The claim that the OU1 FS "understates soil hydraulic conductivity measurements from
the RI report by factors of up to approximately 10" is unsubstantiated. Pages 14 and 18
of the FS state:
"The cross sections indicate that silty clays exist between the lower
boundary of the landfill refuse and the first water bearing unit
(A 1-aquifer zone). Twenty-three samples from die landfill borings
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were collected and logged from native clays below and surrounding the
landfill. Twelve of these samples were tested for porosity and
hydraulic conductivity in the laboratory using geotechnical tests.
These data are presented in the OU1 RI report (IT 1993a). Seven
locations exhibited conductivities in the 1x10** cm/sec range. Three
locations measured 1x10"* cm/sec, one location was 1x10"'cm/sec at 21
feet below ground surface (bgs) and another taken at 50 feet bgs (from
the A2-aquifer zone) was measured at 1x103 cm/sec. The conductivity
of soil underneath and surrounding the landfill was also evaluated
through soil classification during borehole drilling using the Unified
Soil Classification System (USCS).
The soil and groundwater data show that significant clays exists around
the landfill. The results indicate that clays below the landfill and above
. the A1-aquifer zone generally have hydraulic conductivity values in the
IxlO8 cm/sec range (IT 1993a)."
A review of Table 3.4-1 and paragraph two on page 3-7 in the OU1 RI report
(IT 1993a) that summarizes Site 1 geotechnical test results shows that the FS report
accurately provides the laboratory data and does not distort RI information.
Comment 6: Available data, presented in the OU1 FS, indicate that both the Site 1 and Site 2
landfills are leaking. Despite these data, the OU1 FS proposes remedial alternatives
that are based on the assumption that the landfills are not leaking.
Response: Field work will be conducted to further investigate the possibility that contamination is
migrating between monitoring wells Wl-14 and Wl-15 at Site 1.
Chemical data from surrounding perimeter groundwater monitoring wells at Sites 1 and
2 do not indicate remedial alternatives are needed for groundwater. The landfill is
most likely the source of infrequent and low detections in perimeter groundwater;
however, corrective action is not necessary. Corrective action would not be considered
until chemicals were consistently detected in groundwater above water quality
objectives developed for the protection of aquatic life. Tables 2 and 6 show that only
very low, infrequent detections have occurred.
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Assumptions About Future Conditions
Comment 7: The OU1 FS essentially ignores the importance of the continued operation of the aging
Moffett Field subdrain and storm drain system, including the active pumping required
at the Building 191 pump station. The proposed remedial alternatives appear to
depend on continued operation of the drainage system, but no provision for system
operation and maintenance is included in the alternatives.
Response: Please see the response to Comment 7 in Section 3.2.3.
Design Assumptions
Comment 8: The OU1 FS does not consider the probable lower cost and better performance that
might be obtained by constructing landfill caps that incorporate synthetic
"impermeable" membrane layers. Such caps are routinely constructed for landfill
closures. Omission of such caps from consideration may result in an unrealistic
assessment of the cost-effectiveness of a single-layer soil cap.
Response: The FS report evaluates the need for low-permeability caps, with the understanding
that there are several configurations of layer type and design available. Single-layer
caps were found to be more feasible for OU1 than low-permeability caps, regardless of
their materials of construction. Rationale for selecting a single layer cap rather than
the cap depicted in 23 CCR Chapter IS (or equivalent) included:
1. A native, single-layer cap reduces infiltration to rates similar to rates achieved
by a low-permeability layer due to Moffett Field's climate.
2. Contaminant plumes do not exist and, based on modeling, are not expected to
occur in the future. Therefore, minimizing infiltration is not a controlling
factor.
3. Employing a low-permeability cap has the potential for increasing horizontal
subsurface gas migration.
4. A multilayer, low-permeability cap would be more difficult to construct.
5. A multilayer, low-permeability cap would be more costly.
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6. At Site 1, leachate will exist regardless of cap type because refuse is below the
water table. In addition, since waste is saturated below the water table, other
technologies would be required to mitigate contaminant migration. If
contaminant plumes migrate, a multilayer cap would not enhance the
effectiveness of hydraulic control or significantly decrease the amount of water
requiring extraction and treatment.
7. If hydraulic control is implemented, leachate extraction would increase refuse
decomposition, gas generation, and settlement since waste is saturated.
Settlement can compromise the integrity of the barrier layer.
However, as a result of regulatory agency review during the public comment period,
the Navy has agreed to revise the proposed plan to incorporate landfill caps that more
clearly meet established state standards and are more consistent with local landfill caps.
Comment 9: The OU1FS appears to understate typical minimum requirements for landfill cap
hydraulic conductivities by a factor of JO to 100, depending on which criteria are used
to determine the appropriate cap characteristics. Therefore, the proposed caps may
leak more than some minimum standard caps.
Response: The Navy has agreed to include low-permeability caps constructed with a hydraulic
conductivity at least as low as native soils beneath the landfills.
Comment 10: The OU1 FS indicates that there is little difference between the performance of a single-
layer soil cap and a multilayer cap designed to meet hazardous waste site closure
requirements. However, review of the specifications of the multilayer cap used in the
comparison modeling reveals that the proposed multilayer cap incorporates unrealistic
design assumptions, such as an inadequate internal drainage layer, and does not meet
typical minimum requirements for such caps.
Response: Regulatory agency review during the public comment period has resulted in the Navy
revising the proposed plan to incorporate landfill caps that more clearly meet
established state standards, at a cost increase of $1,772,000.
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Regulatory Compliance and Financial Security Assumptions
Comment 11: The OU1FS does not appear to provide expressly for the continued funding of remedial
activities such as Moffett Field drainage system operation and maintenance. This is
important in light of recent Navy statements implying limits on the Navy's ability or
willingness to ensure fitture funding.
Response: The Navy does not have direct control over long-term funding for environmental
restoration at Moffett Field. Budgets are proposed by NAVFAC headquarters in
Washington D.C. and are approved as part of a total budget package each year by
Congress and the President. While congressional actions cannot be anticipated,
NAVFAC will uphold their responsibility to request the necessary money for the
upcoming fiscal year's environmental restoration work.
Comment 12: The proposed landfill caps do not meet typical minimum requirements for hazardous
waste landfills. The FS proposes to treat the landfills as nonhazardous, despite
information indicating substantial hazardous waste disposal in the landfills, and with
only a minimal field sampling program to verify refuse, leachate, and groundwater
quality.
Response: Hazardous waste landfill closure regulations are not applicable to OU1. Title 14 CCR
solid waste landfill closure regulations have been identified as applicable by CIWMB.
Documentation received from CIWMB indicates that Site 1 was operated as a solid
waste facility. The Navy was issued a Solid Waste Facilities Permit for Site 1 by Santa
Clara County Environmental Agency. The permit states that the types of waste
received at the site include cardboard, lawn cuttings, prunings, wood waste, and
asbestos insulation wrapped in double plastic bags. The permit also states that the
disposal of hazardous waste was to be prohibited at the facility.
Some of the wastes at the OU1 landfills may contain hazardous constituents; however,
this circumstance is common to all solid waste and CERCLA landfills. Compliance
with solid waste monitoring and closure regulations will protect human health and the
environment. Further, low contaminant concentrations in leachate show that a minimal
threat from hazardous substances exists at OU1. Maximum detected concentrations are
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below maximum concentrations given for the toxicity characteristic in 40 CFR Part
261.24. This further supports the assumption that OU1 landfills were operated like
solid waste landfills and received similar types of wastes (solid waste with small
amounts of hazardous constituents). Also, visible surface debris includes obvious
construction and demolition debris, such as concrete rubble with reinforcing steel,
asphalt chunks, wire, wood chips, glass, and mounds of dirt overgrown with weeds
(possibly street sweepings), which are similar to solid waste landfill waste. For these
reasons, the Navy identified 23 CCR groundwater monitoring requirements and 14
CCR closure regulations as most appropriate for OU1. CIWMB concurred that these
regulations are applicable for OU1 closure.
Comment 13: Evidence presented at the OU1FS public meeting indicated that Site 2 still may be
receiving waste.
Response: In July 1995, the Navy investigated recent waste disposal at Site 2 and found that soil
piles (presumably from dredging activity) and landscaping debris (such as tree limbs)
have been recently dumped at Site 2 by the current landowner. The Navy has
undertaken administrative action to prevent this from occurring in the future.
Summary
The THE Committee supports Navy and regulatory agency efforts to close the OU1 landfills
expeditiously, cost-effectively, and in an environmentally protective manner. However, to achieve these
goals, the concerns described above should be addressed.
3.2.5 Comments from the Santa Clara Valley Water District, compiled by Thomas I. Iwamura,
Engineering Geologist
Comment 1: Site Characterization of Site 1. On page 14 under Site 1 Hydrogeology, the statement
that water level elevations within the landfill indicate that refuse is saturated is
contradicted by the following sentence which says approximately the bottom one-third
of Site 1 is saturated.
Response: The sentence about the bottom one-third of Site 1 is saturated is correct.
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Comment 2: Site Characterization of Site 1: The discussion under Hydrogeology, page /& and
under Leachate Migration, page 74, indicate soil and groundwater data show that
significant clays exist around the landfill. This combined with laboratory permeability
tests on "undisturbed" soil samples, differences in potentialpiezometric heads within
the different components of the groundwater bodies delineated by restrictive flow, and
finding limited evidence of lateral migration ofleachates lead to the conclusion that
there appears to be no leachate migration from the Site 1 landfill. This conclusion has
not been substantiated, as:
Comment 2a: The cross section presented as Figures 5, 6, and 7 show aquifers within the clay
deposits have separations through clay beds at the site as little as 4 feet to the Al
aquifer. The occurrence of the next deeper aquifer layer (A2 aquifer) was not explored
as borings depth was terminated a few feet below the Al aquifer.
Response: The 4-foot thickness could act as an aquitard and effectively separate the leachate zone
from the A1-aquifer. This separation may not be complete, but based on information
obtained from the current groundwater monitoring network, the existence of these clays
may partially explain the lack of contaminant migration observed at Site 1. The
existence of these clays, the low source concentrations, and contaminant retardation
may be responsible for the lack of contaminant migration. The Navy will conduct
additional field work to further investigate potential contaminant migration at Site 1.
An extensive investigation into the groundwater quality of the A2-aquifer beneath
Site 1 has not been conducted because of information obtained from the A1-aquifer.
Groundwater quality data from the A1-aquifer do not indicate that the A1-aquifer
requires remediation. Therefore, it is assumed that the A2-aquifer, B-aquifer, and
C-aquifer also do not require remediation as a result of Site 1. However, should future
monitoring data or future field investigations indicate the A1-aquifer requires
remediation, then potential impacts to the A2-aquifer will be investigated.
Comment 2b: Laboratory permeability determinations of clay samples usually understate the true
permeability as the samples become compacted during the sampling process.
Furthermore, they represent very small sampling within a vast system, often
overlooking potential natural "defects" within a block of soil.
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Response: The permeability of underlying soils has not been fully characterized. Extensive
sampling or excavation would be required if it was necessary to completely
characterize the soil beneath the landfill. However, this information is not necessary
and the Navy does not assume that clay layers beneath the landfills are continuous.
The information from the limited soil investigations offered a possible explanation for
the lack of evidence of contaminant migration. However, it would be difficult to prove
conclusively that naturally occurring barriers to groundwater movement exist.
Therefore, because it is not known conclusively, continual groundwater monitoring is
proposed. In addition, the Navy will conduct more field work to further investigate
potential contaminant migration.
Comment 2c: The delineation of two separate groundwater bodies as depicted on Figures 12,
leachate potentiometric surface, and 13, Al aquifer potentiometric surface, has not
been substantiated. The leachate potentiometric surface map was interpreted by using
wells constructed within the landfill and theAl aquifer potentiometric map was
interpreted by using wells only along the edges of the landfill. The distinction of the
two groundwater bodies cannot be made without constructing a monitoring well within
the Al aquifer beneath the landfill to determine if a common groundwater body exists
with a groundwater mound occurring within the landfill, as an alternative scenario.
Such an alternative common aquifer scenario is depicted in Figures 5, 6, 7, and 11,
showing a common connected groundwater body with a mound within the landfill. This
would imply the clay deposits are leaky.
Aquifer tests conducted for the OU5 RI indicated this clay cap overlying the Al aquifer
in the general site area to be leaky. The Santa Clara Valley Water District (District)
had also performed aquifer tests in the Palo Alto flood basin area (a similar Bay
estuarine area) and also found the clay cap and the next lower aquitard to be leaky.
Studies of contaminant discharges in Silicon Valley and in areas bordering the
baylands have also indicated the clay cap and the next intervening aquitard to be leaky.
Response: Conclusions regarding the integrity of the aquitard between the leachate zone and the
A1-aquifer have not been substantiated and the aquitard may leak. However,
groundwater analytical data and groundwater elevations presented in the FS indicate
that the aquitard does not significantly leak and contaminant migration is retarded.
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However, because aquitard integrity is not fully characterized, continual ground water
monitoring is proposed. In addition, the Navy will conduct additional field work to
further investigate whether contaminant migration is occurring.
Comment 2d: Hydrographs of groundwater levels in monitoring wells along the edges of the Site 1
landfill in the AJ aquifer shown as Figure 8A and the monitoring wells completed in the
landfill refuse shown as Figure SCshow a close tracking of fluctuations indicating that
the two bodies of groundwater to be connected. They both show highest levels in the
spring of the year the lowest in the fall of the year. They also indicate that the
groundwater mound that accumulated in the landfill (as leachate) culminating in
highest levels in the spring leaks out of the landfill reaching their lowest levels in fall.
Response: The Navy agrees that the hydrographs from wells inside the landfill fluctuate similarly
as compared to Al-aquifer zone wells and that this indicates that the leachate zone and
A1-aquifer zone may be hydraulically connected. Other information indicates that the
connection is not significant and that there is little contaminant movement. For
example, Al-aquifer monitoring well Wl-12 was installed through the SWRP basin.
Groundwater elevations from Wl-12 and surface water elevations from the pond staff
gauge indicate the Al-aquifer is at a higher pressure and is confined. In addition,
hydrographs show that leachate elevations are consistently above groundwater
elevations, indicating that the two water bodies are responding similarly to
precipitation, and that there is a sustained gradient. This information, and more
importantly, the lack of chemical data showing contaminant migration, has led the
Navy to believe that the two water bodies are not significantly in communication.
However, because it is not known conclusively, continual groundwater monitoring is
proposed. In addition, the Navy will conduct additional field work to further evaluate
whether contaminant migration is occurring.
Comment 3: Site Characterization of Site 1: We believe that further studies should have been
conducted at Site 1, in particularly to the testing of the clay cap and the AJ aquifer
beneath the landfill, and, if required, oftheA2 aquifer beneath the landfill.
In addition, further exploration should be performed along the south side of the Site 1
landfill between monitoring wells WJ-J4 and Wl-15, a downgradient area lacking
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characterization. This is to check possible southward leachate migration (refer to
Figure 13). A permanent monitoring well in the Al aquifer is required and possibly
another separate well sensing the A2 aquifer may be required.
Although it could be concluded that the Al aquifer is contaminated by saltwater
intrusion at Site 1, certain contamination in the leachate still has the potential to affect
the baylands ecosystem. Furthermore, the condition of the A2-aquifer beneath the site
area is yet unknown.
Response: Although additional information regarding the aquitard beneath the landfill would be
helpful, it is not necessary. The Navy's approach to investigating landfills has been to
focus on evaluating whether contamination is migrating from the landfill. The Navy
will conduct additional field work to investigate whether contamination is leaving the
landfill and migrating in groundwater between monitoring wells Wl-14 and Wl-15. A
phased approach will be used for this investigation. If impacts to the A1-aquifer are
discovered, the A2-aquifer will then be investigated as well. In addition, a subsurface
groundwater collection trench has been proposed to protect potential ecological
receptors in the SWRP.
Comment 4: Site Characterization of Site 2. On page 50 under Site 2 Hydrogeology, the text
indicates that similar conditions as Site 1 exist in that nearly impermeable clay beds
occur beneath the landfill. However, there appear to be no mounding of groundwater
within the landfill as at Site 1. Groundwater levels occur at the bottom of the landfill
as Site 2 is located adjacent to the drainage pumping station at Building 191. Again,
as at Site 1, the integrity of the clay beds to be nearly impermeable has not been
substantiated. As at Site 1, the hydrographs in the Al aquifer (Figure 21) and leachate
levels (Figure 22) appear to fluctuate coincidentaUy, indicating a common groundwater
body. Leachate (and also groundwater) fluctuating from a yearly highest level in the
spring to lowest levels in the fall indicate leachate is migrating from the landfill. Any
plume migration in the Al aquifer would be controlled by drainage pumping at Building
191.
Response: At Site 2, there is no mounding, it does not appear that there is a separate leachate
zone, and most refuse is not saturated. Contaminant migration at Site 2 can be
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controlled by pumping at Building 191. Please see the response to Comment 2
regarding the integrity of underlying soils.
CommeraS: Site Characterization jf Site 2. The report states on page 55 that borehole logs and
associated cross sections also show that there is inert fill soil (sand and gravel) devoid
of refuse located below the water table within landfill boundaries. However, on Figure
18, borehole W2-10 shows refuse below the water table atop a silty sand aquifer bed
(AJ aquifer). Refuse characterized in boring W2-10 indicated metal inclusions, tar,
petroleum odor, and potychlorinated biphenyls at 28,000 parts per billion (ppb).
Arsenic was noted to be l,830ppb in the leachate. Nearby monitoring well V/2-8
indicates a relatively high vinyl chloride content of!20ppb in the leachate (Appendix
B).
Response: Borehole W2-10 does show refuse located below the water table, as indicated on page
50 of the FS report. Monitoring well W2-10 is considered a leachate monitoring well
and detections from this well do not require remediation for groundwater.
Comment 6: Site Characterization of Site 2. The A2-aquifer was not explored beneath the landfill.
Monitoring well W2-7, located on the eastern edge of the landfill, is completed in the
A2 aquifer but we were unable to find any analytical datum for this well in Appendix C.
This well may be located on the upgradient side of the landfill.
Response: Monitoring data show that well W2-7 is upgradient from the landfill. A2-aquifer
monitoring data was not presented in the FS because A1-aquifer impacts have not been
evident. However, the OU5 RI report (IT 1993b) contains A2-aquifer data. Should
future impacts occur, the A2-aquifer will be investigated accordingly.
Comment 7: Site Characterization of Site 2. Lateral plume migration away from the site through the
AJ aquifer generally has not been apparent. The AJ and A2 aquifer beneath the
landfill are yet to be tested.
Response: Investigations have focused on lateral migration in the Al-aquifer. This is the most
likely aquifer to be impacted by the OU1 landfills since it is the closest aquifer to the
landfill refuse. The horizontal gradient at Site 2 is relatively large as a result of
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Building 191 's strong influence. Also, the hydraulic conductivity is typically an order
of magnitude larger in the lateral direction. Therefore, the horizontal groundwater
flow is likely much larger than the vertical flow. The Navy believes that lateral
migration will occur in the A1-aquifer before contamination (1) migrates vertically
down to the A2-aquifer and then (2) migrates laterally to the landfill perimeter through
the A2-aquifer.
Comment 8: Remedial Plan for Sites 1 and 2. We believe capping of the sites along with attendant
gas interceptor trench, groundwater collection trench, and a monitoring program
would serve as an appropriate remedy for Sites 1 and 2. In as much as there appear to
be uncertainties in possible inclusions of hazardous materials in the landfill and
incomplete characterization of the sites, we believe a cap with the greatest optimal
performance be installed. In addition, the monitoring gap at Site 1 between wells Wl-
14 and Wl-14 and W]-15 would have to be remedied.
Response: The Navy has agreed to revise the cap design to include an impermeable layer that may
further limit infiltration into the landfills. The Navy will also investigate the
monitoring gap at Site 1 between wells Wl-14 and Wl-15.
Comment 9: Lone-term Pumping at Building 191. We believe the Navy should provide assurances
that the drainage pumping at Building 191 be sustained in order to provide long-term
effectiveness of the remedy. Long-term pumping would also be required for the
effectiveness of mitigation proposed for other OUs on the base.
Response: Pumping at Building 191 will be continued as necessary to provide for long-term
effectiveness of the remedy. A review of the remedy and lift station operation will be
conducted periodically to ensure that the remedy continues to provide adequate
protection of human health and the environment.
Comment 10: Although it is the District's desire that implementation of the final remedy be initiated
as soon as possible, we believe our concerns should be appropriately addressed or the
FS be appropriately amended first.
Response: Please see the response to Comment 8.
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Comment 11: We are also represented on the RAB and on the THE Committee of the RAB. We
substantially concur with the comments brought forth by the THE Committee for the
OU1 FS.
Response: Please see the response to the RAB and RAB THE committee comments.
3.2.6 Comments from RAB Members
Mr. David C. Click
Comment 1: The FS directly conflicts with historic evidence and with the findings of previous
investigations regarding the base of the Site 1 landfill and, as presented, is misleading
at best regarding the communication of the landfill and the underlying aquifer:
Comment 1A: First paragraph on page 13 states that the excavation for the landfill reportedly
extended in depth from 2- to 21-feet below msl; however, the cross-sections (Figures 5-
7) which appear to be based solely on the monitoring well logs only characterize the
landfill to 11- to 13-feet below msl.
Response: No records were kept regarding the initial depth of any excavations at Site 1. The
information included in the text was obtained from interviewing base personnel during
IAS activities. The physical evidence collected during the OU1 RI/FS does not
confirm that the depth of refuse extends 21 feet below msl at Site 1. The physical
evidence regarding landfill depth is summarized below.
Nine borings have been extended through Site 1 landfill refuse. The maximum
refuse depth has been measured at 12.9 feet below msl at boring Wl-ll(F).
In addition to borings through the landfill, the Navy conducted an electrical
resistivity survey to locate the base of the landfill. The survey did not support
the more reliable borehole logs. Survey results indicated that the landfill base
is approximately 5 to 10 feet shallower than found in borings. The electrical
resistivity information was not mentioned in the FS report since it did not
accurately depict boundaries relative to soil boring information. However, the
RI report discusses the results in detail (IT 1993a).
If refuse extended 21 feet below msl, data indicate that the leachate zone would
be in direct contact and communication with the A1-aquifer zone. If these two
water bodies were in direct communication, sustained leachate mounding would
not be observed. Water elevation data indicate that leachate elevations are
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above groundwater elevations and that leachate is "mounded." If the leachate
zone was in direct contact with the Al-aquifer, mounding would not likely
occur.
• Perimeter groundwater data collected to date do not indicate that contamination
is migrating into the Al-aquifer at the landfill boundary. If the aquitard
between the Al-aquifer zone and leachate zone was significantly breached,
contaminant migration may be more likely. However, the Navy will conduct
additional field work to address data gaps.
The physical evidence indicates that the information obtained from interviews may not
be completely accurate. However, there is no practical or reliable method that can be
used to verify or disprove anecdotal information. Therefore, the Navy will continue to
monitor perimeter groundwater for releases of contamination from the landfills.
Comment IB: The cross-section on Figures 5-7 indicate the base of the landfill to be a 11- to
13-feet below msl with a clay layer underlying the fill material and overlying the
A-l aquifer which is depicted to be at 14- to 20-feet below msl. If the original reported
depth of the landfill is up to 21-feet than based on this data the landfill does in fact
intercept to A-l aquifer and there very likely is direct communication between the
leachate and the ground water. Figure 11, although only a concept model, provides
and exaggerated thickness of clay beneath the landfill.
Response: Please see the response to Comment 1 A. Even if portions of the refuse zone extended
21 feet below msl, groundwater monitoring data collected to date indicate that this
characteristic is not resulting in contaminant migration. Again, the Navy has agreed to
conduct additional field work before this conclusion can be supported. If contaminant
migration is found during the additional investigation, the Navy will address the
contaminated groundwater plume. If additional field investigation results confirm
previous conclusions regarding migration, continual groundwater monitoring is the
appropriate action, regardless of whether anecdotal information is true and refuse
extends 21 feet below msl.
Comment 1C: The third paragraph on page 25 suggests that Monitoring Well Wl-11 characterize the
groundwater conditions with respect to the landfill, leachate, and the firmer surface
water channel; however, the data provided in Figures 6 and 7 suggest that the well is
screened entirely within the landfill material and does not depict the channel at all.
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Response: The text is incorrect. The cross section is based on information from borelog Wl-11.
The borelog indicates that Wl-11 is screened in refuse and that Wl-11 characterizes
leachate.
Comment ID: The second paragraph on page 27 indicates that borings were advanced along the
former drainage channel where the channel intersects the boundaries of the landfill;
however, this is not depicted on Figure 4 which suggests an absence of perimeter
channel borings.
Response: Unfortunately, these two monitoring points were inadvertently omitted from Figure 4.
The perimeter channel borings do, however, exist.
Comment 2: Since actual and/or potential communication of the Site 1 landfill leachate with the
underlying shallow A1-aquifer ground-water is significant to characterization of the
landfill, in the assumptions and results of the health risk analysis, and in the closure
design, it is imperative that the issue of the vertical and lateral extent of the landfill be
resolved prior to proceeding with closure design.
Response: The actual or potential communication of the leachate and A1-aquifer will continue to
be evaluated through additional field investigation and continual groundwater
monitoring. Please see the response to Comment 1 regarding vertical extent of refuse.
Regarding the horizontal extent, the Navy will dig trenches to confirm landfill
boundaries.
Comment 3: There appears to be a significant difference in the hydraulic data presented in the FS
for the Site 1 landfill and the text of the FS and previously presented reports:
(A) Figure 12 clearly illustrates that the hydraulic conditions of the leachate have
not been fully characterized with a significant absence of data along the entire
southern extent of the landfill. In fact, the data suggests direct capture of the
leachate with flow of the leachate/groundwater to the south beneath the
landfill.
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(B) Figure 13 depicts the direction of groundwater flow within the A-l aquifer
beneath the landfill and adjacent areas and supports the argument that the site
hydrology is directly influenced by the existing airfield drainage system. The
flow path for groundwater beneath the landfill is southerly between Monitoring
Well Wl-14 and Monitoring Well Wl-15 where there is a complete absence of
leachate and groundwater monitoring. These conditions contradict the claim of
assurance by PRC that there is no off-site migration of leachate and that
groundwater has not been impacted.
(C) The fourth paragraph on page 35 addresses the direct/potential migration of
leachate from the landfill to the Al-aquifer groundwater supporting the
argument that the landfill and A1-hydraulic characteristics have not been fully
documented with direct attention to the southern boundary.
Response: The Navy will conduct additional field work to investigate the presence of
contamination migrating past the southern landfill boundary.
Comment 4: The groundwater data presented in Figure 13 and in previous reports illustrate that the
existing airfield drainage system is a primary hydraulic control far the A-l aquifer and
has a direct impact on the southerly migration of the landfill leachate. The significance
of this man-made hydraulic control seems to have been discounted by PRC in
consideration for closure and any change (either a decrease or increase in pumping of
groundwater) will have a direct impact on the hydraulic conditions beneath (and
possibly within) the Site 1 landfill. Since hydraulic control of the landfill leachate and
protection of the underlying groundwater are primary functions of the closure,
maintenance of the man-made hydraulic controls must be accounted for in the closure
design and reflected in the cost allocations.
Response: The ROD adequately states the necessary performance standards of the remedy. The
operation of the pump station (as a man-made hydraulic control) will be accounted for
in the closure design. Because the pump station is operated and maintained by NASA
as an essential aspect of their current land use, the O&M cost need not be reflected in
the cost allocations for the Navy's remedy selection.
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Comment 5: The analytical test data indicate that contaminated sediments exist beyond the currently
identified boundaries of the Site 1 landfill. This would suggest that the lateral extent of
the landfill has not been fully determined. It is recommended that some shallow
exploratory trenches be advanced around the perimeter area to assure that the
boundaries of the landfill have been confirmed and that the ensuing closure plan
account for the revised landfill configuration.
Response: The Navy will dig exploratory trenches along the landfill boundaries to confirm the
boundary location.
Comment 6: The last paragraph on page 44 indicates that "It can not be confirmed that TPH
compounds have migrated from the landfill to the SWRP." Understanding the data
presented, it is recommended that additional sampling points be established within and
beyond the landfill boundary to Junker evaluate. In absence of such data it should be
concluded that these compounds have migrated and that there is a mechanism and
pathway for future leachate migration.
Response: The Navy has proposed a groundwater collection trench to be located between the
landfill and the SWRP. This trench will be sampled and, if contamination is migrating
above AWQC, corrective action will ensue.
Comment 7: The closure design includes a leachate interceptor trench along the northern
boundaries of the landfill; however, based on the hydraulic data presented the
groundwater and leachate migrate southerly beneath the landfill toward the airfield
drainage system. Therefore, this interceptor trench is located "up-gradient" of the
landfill and has no practical use for monitoring as designed with the exception of
political/public perception.
Response: The interceptor trench is not located upgradient of leachate and may have a practical
use. The leachate is mounded above the A1-aquifer and the SWRP at Site 1 and there
is a radially outward gradient from the leachate zone to the SWRP. The SWRP is
downgradient from leachate. The A1-aquifer generally flows from north to south,
however, the A1-aquifer is not located between the leachate zone and die pond. The
comment suggests that if contamination migrates past landfill boundaries, it can only
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migrate straight down through predominantly clayey soils into the aquifer and proceed
south in the A1-aquifer. However, contamination may also migrate from the landfill to
the pond through sand stringers that may be located in the clay. The interceptor trench
was proposed because (1) the Navy realizes that the clay may not be completely
continuous between the landfill and the pond, (2) there is a gradient from the landfill to
the pond, and (3) the leachate-SWRP exposure pathway is the only viable exposure
pathway associated with leachate contaminant migration at Site 1. The Navy will
conduct additional field work to investigate contaminant migration to the southwest.
Comment 8: Section 1.3.5 confirms that the northern perimeter drainage system connected to the
pump lift station (Building 191) has direct influence on the groundwater conditions at
Site 2 and as such any change or termination in pumping will result in direct impact to
the groundwater and leachate conditions of the landfill. It is therefore restated that the
groundwater control of Building 191 be a direct line item of the closure plan.
Response: Please see the response to Comment 7 in Section 3.2.3.
Comment 9: There appears to be conflicting arguments in the text regarding sporadic detection of
leachate compounds in the Site 2 perimeter monitoring wells which is interpreted by
PRC that there is direct connection of the leachate with the A-l aquifer groundwater.
The conclusions presented on page 64 indicate that contaminants are not emanating
from the landfill. The documented contribution of barium to the groundwater from the
leachate as presented on page 65 further supports hydraulic connections to the
Al-aquifer. If the monitoring has detected leachate compounds in the perimeter wells
in the past, although not at the frequency for regulatory controls to be enforced, then
these migratory pathways must be considered for the future and not casually avoided in
the closure design assumptions/parameters.
Response: Migration pathways are being considered. Continual groundwater monitoring is
proposed to identify any potential future impacts and to further evaluate inorganic
concentrations in groundwater.
Comment 10: The conclusion that "no contaminant plumes are emanating from either landfill' as
stated at the end of the first paragraph on page 74 is not consistent with the data and
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discussions presented elsewhere in the report or in the following paragraph which
states that leachate chemicals have been detected in surrounding groundwater
monitoring wells. Although there may not be "significant hazardous waste streams" or
"slugs" flowing from either landfill, there is strong evidence that the leachate at both
sites is migrating and is in communication with the A J-aquifer groundwater.
Response: The landfill is probably the source of the infrequent and low detections; however,
corrective action is not necessary. Corrective action would not be considered until
chemicals were consistently detected in groundwater at concentrations exceeding water
quality objectives developed for the protection of aquatic life. Tables 2 and 6 show
that only very low, infrequent detections have occurred.
Comment 11: There is an absence of data for both sites in reference to potential impacts to the
A2-aquifer. Continued consideration that the Al-aquifer has not been impacted, which
has not been definitively proven, does not preclude investigation of the A2-aquifer.
This issue is significant with respect to Site 1 which has demonstrated historic evidence
of downward (vertical) gradients within the Al-aquifer and at Site 2 where leachate
compounds have been detected in the Al-aquifer.
Response: A phased approach has been employed which focuses on investigating lateral migration
into the Al aquifer. This is the most likely aquifer to be impacted by the OU1 landfills
since it is closest to the landfill refuse. The Navy's approach has been to investigate
the Al-aquifer, and if contamination is found, then investigate the A2-aquifer.
Regarding vertical gradients, the comment states that Site 1 has demonstrated historic
evidence of downward (vertical) gradients within the Al-aquifer. This statement has
not been supported. The Navy has compared data from Wl-7 (an A2-aquifer well) to
an extrapolated Al-aquifer potentiometric surface and found that upward gradients may
exist.
Comment 12: In preliminary review, it appears that minor modifications to Alternative 2 (using a
synthetic fabric liner) would provide greater assurance of closure with significant cost
savings to the Navy. The cost estimates as presented appear to overestimate the
construction cost for the closure earthwork activities and underestimates the availability
of competent contractors for this type of construction.
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Response: The Navy has agreed to modify Alternative 2 to include a low-permeability liner. The
Navy anticipates that this modification will increase costs by $1,772,000.
Comment 13: The construction cost data appears to be direct labor, material, or equipment charges
and does not appear to include items as: indirect charges, benefits, overhead, or profit
related to the construction, indirect charges for consulting activities, or projected
inflation. Cost data should be reviewed/prepared with same considerations of other
government cost estimates. If the Navy will be responsible for continued community
involvement during the 30-year postclosure period (for example, public meetings,
newsletters, etc.) than the cost involved for the Navy and the Navy's contractors should
be considered as a line-item.
Response: The purpose of the cost estimate is to compare alternatives. Items common to all
alternatives have little impact on the analysis. The cost estimates were prepared in
accordance with EPA guidance (1988) and is accurate to plus 50 percent-minus
30 percent.
Comment 14: The cost estimates for monitoring reports appears low compared to the actual data
analysis, discussions, modeling updates, communication/conferences, etc. which will
likely be involved during the life of the project (excluding the reproduction charges).
Response: Please see the response to Comment 13.
Comment 15: It is recommended that the site closure designs be reviewed with the consideration that
leachate migration has and will occur at both sites and that a leachate control system
be included in the design.
Response: An interceptor trench and continual groundwater monitoring have been included in the
design to guard against impacts from potential future migration. However, based on
current data, additional leachate control systems are not necessary at this time. To
efficiently allocate limited resources, the Navy should not implement additional
leachate control unless necessary.
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Ms. Cvnthia Sievers
Comment 1: Closing the Moffett Field Landfills, A Suggested Logical Approach
Step 1: Place OUJ FS "on hold"
Rationale:
• Comments indicate additional data needed for remedy
• No pressing use for the land involved
• Current data doesn 't seem to indicate any immediate threat to human health
requiring immediate action related to closures.
Step 2:
a. Expand OUJ to incorporate other two landfills
b. Conduct additional investigation at Sites 1 and 2 including:
i. Add monitoring wells to cover "gap " at Site 1 Landfill
ii. Trench to better define perimeter of Sites 1 and 2
Hi. Revisit analysis of depth and base material as per questions raised by
draft FS
iv. Investigate ramifications of pistol range at Site 1
c. Initiate accelerated contracting process for work on other landfills
d. Define perimeters of other landfills
e. Further investigate materials disposed of in which landfill by:
ii.
in.
iv.
Re-interviewing base personnel to determine which landfill they referred
to calling disposal at "the" landfill
Reviewing manifests of hazardous materials disposed from time Navy
began manifesting used solvents, PCBs, etc. to off-base sites to better
understand exactly what materials and quantities were being generated
at a particular time
Reviewing solid waste disposal contracts for similar data re: solid waste
Reviewing golf course history as it relates to landfill usage
/. Incorporate risk data and ecological study data into designing remedies
Rationale: Remedies can be developed regarding cap design(s), monitoring systems,
need for cutoff walls, leachate management, methane management, and long-term
general management based upon better understanding of:
Size and shape of landfills
Groundwater flow as it relates to base material in landfills
Integrity of landfills regarding leakage
Actual location of landfills and materials to be managed
Risk to human and ecological receptors
Possible reduced costs due to economies of scale
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Response: The overall strategy of capping the landfills, installing a gas interceptor trench,
installing a groundwater collection trench, and continuing groundwater and gas
monitoring (with corrective action contingencies) is an adequate and cost-effective
approach to address the OU1 landfills; placing OU1 activities on hold is not necessary.
The Navy will conduct additional field work to further investigate the potential for
contaminant migration at Site 1. The outcome of this investigation will not influence
the cap selection since the Navy has also agreed to include low-permeability caps
constructed with a hydraulic conductivity less than 1x10* cm/sec. Therefore, OU1
activities can proceed with only minor modifications to the current schedule.
3.2.7 Comments from the League of Women Voters
The LWV of Los Altos, Los Altos Hills and Mountain View and of Sunnyvale-Cupertino know that the
Navy is committed to meeting community standards as you proceed with environmental cleanup
activities at Moffett Field. Community standards are high here. For the following reasons, the Federal
government, the State of California, and local regulatory agencies have held polluters to a high
standard of cleanup and remediation in Santa Clara County:
• Santa Clara County is the onfy urban county in California that relies upon groundwater for
50% of our drinking water. The Santa Clara Valley Water District is internationally known for
its expertise in groundwater recharge, utilizing our vast underground aquifer system as a water
bank.
• The southern end of San Francisco Bay south of Dumbarton Bridge is a unique ecological
resource. Here the Bay is shallow with little flushing action either from tides or from heavy
fresh water runoff, hence pollutants tend to build up in Bay sediments and wetlands. Since the
South Bay is a major stop on the Pacific Ffywayfor migrating birds, the ecological health of
the South Bay has far-ranging importance to not only the birds and the fish but to the food
chain which supports them. While the San Francisco Bay is one of the world's great estuary
systems, the South Bay may well be its most fragile component.
In light of the above circumstances, local government and private industry in Santa Clara County lead
the nation in investigating hazardous material spills, designing remediation and prevention strategies,
studying aquifers, and in expending millions if not billions of dollars to cleanup past mistakes and to
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prevent future ones. Most federal laws and regulations relating to leaking underground storage tanks,
toxic gas management, and groundwater protection began here.
The LWV believes the OUJ FS is inadequate. Data gaps will not allow an appropriate design to be
developed unless adequate answers to the following questions are incorporated.
Comment 1: Site Investigation Questions. What additional steps will be taken in the design phase to
better define the outer perimeter boundaries of Sites 1 and 2? What additional
trenching and/or borings will be conducted in order to determine the lateral extent of
the landfills prior to design of cap, leachate collection systems, and monitoring
systems?
Response: The Navy will dig trenches to confirm the boundaries of the OU1 landfills.
Comment 2: Site Investigation Questions. What criteria will the Navy use to conclude that
boundaries of the sites have been reached (for example, no longer finding PCBs in the
soil)?
Response: The Navy will excavate trenches parallel to the currently estimated boundary at
locations where the boundary is questionable. The Navy will visually examine
excavated soils to determine whether the trench is within the landfill boundary. If
native soils are present, the Navy will conclude that the trench is outside the landfill.
Comment 3: Site Investigation Questions. Does the pistol range on the site present lead
contamination problems or the danger to cap construction personnel from either soil
contaminated lead or from possible live ammunition?
Response: Lead contamination at the landfill surface has not been characterized. This information
is not needed to implement capping at the landfills. During cap construction, heavy
equipment could generate fugitive dust emissions. Construction workers will mitigate
any potential hazards by using PPE such as respirators. In addition, dust suppression
strategies, such as wind speed alarms can be implemented to reduce fugitive dust
emissions. Unexploded ordnance has not been found at Site 1 during site
investigations.
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Comment 4: Site Investigation Questions. The OU1 RI cited specific amounts of various hazardous
materials that were buried in the landfills. This detail is missing from the OU1 FS.
How does the Navy explain what happened to the following hazardous wastes disposed
of in the Site 1 Landfill according to the OW RI:
110,000 gallons of TCE, toluene, MEK, and solvents
368,000 pounds of ash
16,000 pounds of asbestos
24,000 gallons of paint, lacquer, and thinner
51,000 gallons of jet fuels
3,300 gallons of waste oil in 55-gallon drums
12,000 gallons of used lubricant oil
1,260 gallons of transformer oil
580 transformer filters
Sawdust contaminated with transformer oil?
Similarly, what has happened at the Site 2 Landfill to hazardous wastes disposed of
there according to the OU1 RI:
75,000 to 150,000 gallons of TCE, toluene, MEK, and solvents
69,000 pounds of ash
16,000 pounds of asbestos
43,500 gallons of paints, lacquer, and thinners
Unknown amount of waste oil buried in 55 gallon drums
Unknown amounts of used lube oil
1,440 filters with fuel sludge, lead compounds and rust
870 gallons of transformer oil
Unknown amounts of transformer oilfillers
Unknown amount of sawdust contaminated with transformer oils possibly
contaminated with PCBs?
Response: The above-listed estimates were originally presented in the IAS and transferred to the
RI. All of the information regarding types and quantities of waste disposed at the
landfills were obtained from personal communications with current or previous staff at
Moffett Field. Confirming the accuracy of this anecdotal information is extremely
difficult at OU1. No documentation or disposal records were kept for the landfills and
it is impossible to verify any information obtained from interviews without actively
excavating the landfills. A fate and transport analysis would have little value since the
waste could have been disposed in drums.
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To address this concern, the Navy has (1) reviewed the IAS (NEESA 1984) and
examined the basis for the assumptions regarding disposal, (2) identified approaches in
EPA guidance (EPA 1991, 1993) regarding similar circumstances since these
circumstances are common to many landfills, and (3) considered additional remediation
strategies that regard anecdotal information as potentially accurate.
One explanation for the differing information in the IAS and collected data is that the
IAS is not accurate. To evaluate this further, the following paragraphs contain a
summary of the IAS and places emphasis on the basis for assumptions made.
The IAS contains an extensive survey of waste generation rates and disposal practices
at Moffett Field from the 1930s to the early 1980s. The information is based on record
searches, on-site surveys, and civilian and military personnel interviews. The IAS
presents waste generation rates from different groups that have resided at Moffett
Field, most notably Public Works, P-3 Orion patrol squadrons and jet squadrons,
aircraft intermediate maintenance departments, and general operations (such as the fire
department, photography lab, and naval exchange gas station). Of these groups, Public
Works and the squadrons reportedly used the landfills for waste disposal. Waste
disposal at the landfills from Public Works and the squadrons are summarized below
from the IAS.
Public Works operated, maintained, and repaired buildings, structures, and other
facilities at Moffett Field. Public Works is comprised of metal and welding shops,
paint shops, utilities shops, electrical shops, pipe shops, the steam plant, the building
trades shop, the transportation division, and the pesticide shop. Of these shops and
divisions, the paint shop, the electrical shop, the pipe shop, and utilities shop disposed
of waste at the landfills.
According to the IAS, the paint shop had an area of Site 2 reserved for paint shop
waste. Paints and thinners were disposed in cans, as it was easier to dispose of wastes
in barrels at the shop rather than on the ground. The paint shop staff never observed
pools of liquid or chemical smells at the landfills.
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The electrical shop reportedly used paper elements to filter oil from transformers. The
crews used about seven to eight filters in a filter press and filtered about two to three
20- to 30-gallon capacity transformers per month in the summer. The shop generated a
few dozen filters per year, as well as small amounts of sawdust used to soak up spilled
transformer oil. The filtering was done on site and the filters were dried in an oven.
The electrical shop reportedly used the landfills only for disposal of paper transformer
oil filters.
Jet squadrons operated at Moffett Field from 1950 until 1962. According to personnel
interviewed, most oily and solvent wastes were collected in 55-gallon barrels and
stored beside hangars. The outside corners of the hangars reportedly were used to
store barrels of waste materials. According to the IAS, the barrels were either hauled
to the runway landfill (Site 1) by station personnel or disposed of down storm sewers
around the hangars, or off the edge of the aprons. The amount of liquid wastes taken
to Site 1 is not known; however, the IAS estimates that a total of 1.5 million gallons
were generated and assumes 5 to 10 percent of the 1.5 million gallons generated were
disposed at the landfills. The basis for this assumption is unknown.
Seven P-3 Orion squadrons have been stationed at Moffett Field since 1962, which was
near the time that Site 1 began operations and Site 2 ceased operations. Disposal
methods reportedly varied. In the early 1960s, much of the solvents were poured
down deck drains, around the hangars, and around the aprons, or placed in barrels and
stored around the hangars. Personnel interviews indicated that some of the waste
containerized in 55-gallon drums was hauled to Site 1 in the early 1960s. The amounts
are not known.
The IAS reports of disposal practices contain several inconsistencies. The IAS
indicates that barrels were disposed of at Site 1 from 1950 to 1962, however, the Site 1
landfill did not exist before 1962. In addition, the IAS states that 1.5 million gallons of
liquid waste were generated by the Orion squadrons from 1962 to 1978 (that is, during
the operating period of Site 1). However, the report tables indicate that 687,000
gallons of liquid waste were generated. The IAS then assumes that 5 *o 10 percent of
the 1.5 million gallons was disposed at Site 1. Both the 5 to 10 percent estimate and
the 1.5-million-gallon estimate are arbitrary. The IAS also states that 1.5 million
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gallons of liquid waste were generated during the jet era at Moffett Field, however,
report tables indicate that 528,000 gallons were generated. The report again arbitrarily
assumes that 5 to 10 percent of the 1.5 million gallons (1,363 to 2,727 55-gallon
drums) were disposed at Site 2. The estimates appear to be arbitrary and speculative,
and are inconsistent with other estimates in the IAS report.
Another explanation for the differing information in the IAS and collected data is that
the collected data do not adequately depict landfill content. There is no question that
the landfill content is not fully characterized and it is not known what was disposed in
the landfills. Notably, this circumstance is not unique to Moffett Field. Many
Superfund landfills have the potential to contain a wide variety of wastes, including
drums of waste. EPA guidance (EPA 1991, 1993) is very clear on how to address
these sites. Landfill characterization is not recommended and containment is die best
remedy unless (1) the location of the drums is known, (2) the location is easily
accessible, and (3) removal will reduce the principal threat. At Moffett Field,
geophysical surveys do not show any drum disposal areas within Site 1. Leachate and
groundwater data show low concentrations. Lastly, information presented in the IAS
regarding waste disposal is questionable. The stated assumptions appear to have no
basis and are difficult to verify.
The Navy's strategy has been to evaluate containing the refuse through capping and,
most importantly, to recognize that if any previously drummed waste begins to migrate
from the landfill, the monitoring program will detect the release and corrective action
will be implemented.
An additional strategy to protect against the possibility of buried, drummed waste
mobilizing and migrating off-site was evaluated. This strategy includes enhancing
containment with a subsurface interceptor trench with a vertical barrier along the
northern boundary of Site 1. This trench has been added as a corrective action
contingency measure and will be in place in the event contamination migrates. The
interceptor trench, in conjunction with capping and monitoring, will protect adjacent
surface water. Only the northern boundary of Site 1 is presently selected for the
possible additional containment because this area is upgradient to the SWRP
ecosystem. Releases along other borders will not affect sensitive ecosystems and
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additional containment is not warranted. Additional field work will be conducted to
investigate contaminant migration along the southwestern border. Any releases along
these borders could be addressed by containment or hydraulic control if needed. Site 2
is not considered for the additional containment since hydraulic control is easily
maintained near the site by the Building 191 lift station.
The reason for omitting the RI (actually IAS) estimates of the quantities of waste were
from the FS is that evidence collected during field investigations does not support the
estimates. The Navy did not intend to misrepresent or suppress information. Chemical
data from leachate wells do not support the estimates that hundreds of thousands of
gallons of liquid waste were dumped in the landfill.
Comment 5: Leachate Investigation and Management Questions. At Site 1 a significant gap (500+
feet) exists in the groundwater monitoring system. How many wells does the Navy
intend to place in that "gap * in order to get a clearer picture of groundwater flow and
possible leachate leakage? On what technical basis was the number of wells deemed
adequate?
Response: The number and location of monitoring wells will be based on cone penetrometer test
(CPT) results and HydroPunch (HP) sampling results. CPTs will locate permeable
sediments. HP groundwater samples will be collected at locations with saturated
permeable sediments and groundwater samples will be sent to a laboratory.
Monitoring wells will be placed based on these results. The field work plan will
discuss these activities in more detail.
Comment 6: Leachate Investigation and Management Questions. How will the /Vavy address
possible vertical migration of leachate into lower level aquifers due to existence of
porous material in the bases of the Site 1 and Site 2 landfills (sand lenses, peat layers.
etc.)?
Response: Current groundwater monitoring data and soil boring data do not indicate that porous
material exists beneath refuse or that contamination is migrating past the landfill
perimeters. The Navy has focused the groundwater investigations on the uppermost
aquifer (the Al-aquifer). The A1-aquifer is closest to the landfill refuse. In addition,
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horizontal gradients in the A1-aquifer are generally equal to or greater than horizontal
gradients in the A2-aquifer. Therefore, groundwater contamination will migrate to
landfill boundaries in the A1-aquifer before they (1) vertically migrate downward to the
A2-aquifer and then (2) migrate horizontally to landfill boundaries. If A1-aquifer
impacts are discovered, additional investigation will focus on the A2-aquifer.
Comment 7: Is it accurate to say that part of the waste in the Site 1 Landfill is sitting in a
combination of groundwater and leachate? If so, what are the environmental
implications of this and what are the implications for design of an adequate leachate
collection system?
Response: Part of the waste in the Site 1 landfill is sitting in a combination of groundwater and
leachate. The concentrations of chemicals in this leachate and groundwater
combination are low. The existence of this contamination is not cause for corrective
action because the point of compliance is the landfill perimeter and contamination is not
migrating. Therefore, the Navy will continue to monitor groundwater at the landfill
perimeter and implement corrective actions if necessary. If corrective actions are
required, leachate and contaminated groundwater can be extracted by pumping wells
and interceptor trenches and treating the contaminated water above ground.
Comment 8: If the waste in the Site 1 Landfill is currently partially immersed in
groundwater/leachate, what type of barrier can be designed to prevent leachate from
migrating into the adjacent slough, the Cargill salt ponds, and the SWRP (for example,
a slurry wall) ?
Response: The SWRP north of the landfill is downgradient from leachate, indicating a potential
for contaminant migration into the pond. Groundwater chemistry data do not show that
contamination is migrating past the northern landfill boundary. Field investigations
have indicated that low-permeability bay mud (barriers to contaminant migration) exists
between the refuse/Ieachate zone and the SWRP. The integrity of this barrier has not
been completely characterized and it is not known whether this layer is completely
continuous. Therefore, the Navy proposed to install a subsurface interceptor trench
between leachate and the SWRP. The trench would contain perforated pipe and gravel
to facilitate groundwater collection. In addition, an impermeable liner would be
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installed on the downgradient side (pond side) of the trench to further contain
contaminants.
Regarding the slough/Cargill Salt Ponds, groundwater chemistry data do not show that
contamination is migrating past the eastern landfill boundary. Also, water elevation
measurements show that the slough/Cargill Salt Ponds are upgradient from the
groundwater surrounding the Site 1 landfill, indicating there is not a potential for flow
from leachate to the slough/Cargill Salt Ponds. In addition, field investigations indicate
that low-permeability barriers also exist between the leachate zone and the
slough/Cargill Salt Ponds. Therefore, the Navy did not propose an interceptor trench
for the eastern boundary. The Navy will continue to monitor water elevations and
groundwater chemistry in surface water, groundwater, and the leachate zone. Further
containment can be added in the future if needed.
Comment 9: Is it feasible to pump out and treat the groundwater/leachate at Site 1 ? What type of
system could be used? How much would construction as well as operation and
maintenance costs be for such a system? How long would it need to operate?
Response: Based on current data, it is not feasible to pump out leachate at this time because
contamination plumes are not known to be migrating. In addition, the FS report
discusses contaminant transport modeling to illustrate future potential for migration
from the Site 1 landfill. Based on the modeling in Section 3.7 of the FS report,
contaminant plumes are not expected to occur in the future. In the unlikely event
contaminant migration occurs, leachate can be pumped from the landfill if necessary.
Comment 10: Financial Assurance Questions. What financial assurance mechanism will the Navy be
using to assure sufficient funds are in place for closure and for 30+ years post-closure
maintenance program for Moffett'sfour landfills?
Response: Postclosure maintenance activities will be funded through annual DoD environmental
restoration budgets. These budgets are proposed by NAVFAC headquarters in
Washington D.C. and are approved as part of a total budget package each year by
Congress and the President. While congressional actions cannot be anticipated, it is
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NAVFAC's responsibility to request the necessary money for the upcoming fiscal
year's environmental restoration work.
Comment 11: Financial Assurance Questions. If, over time, gas and groundwater monitoring
programs reveal a need for corrective actions who will decide:
a. When corrective action is necessary
b. What remedy is needed
c. How will the remedy be funded
Response: The first two questions will be decided by RWQCB, DTSC, EPA, and the Navy, with
input from the community. NAVFAC, DoD, Congress, and the President will decide
how corrective actions will be funded (please see the response to Comment 10).
Comment 12: Financial Assurance Questions. Will the RWQCB have access to these funds for
corrective action if the Navy fails to implement closure, postclosure maintenance or
needed corrective actions (in a timefy fashion) ?
Response: RWQCB does not have access to Navy funds.
Comment 13: Financial Assurance Questions. How will maintenance of the subdrain system at
Moffett be funded and, if necessary, upgraded to prevent inundation of the landfills?
What is the estimated cost for maintaining the subdrain system?
Note: We understand that the Moffett actions are governed by CERCLA but it makes
no sense to us that a CERCLA site should be required to do less than a standard solid
waste landfill since it is presumably a greater threat to public health, welfare, and the
environment. Otherwise why would it be governed by CERCLA ?
Response: Maintenance of the subdrain system will be funded by annual budgets. Costs have not
been estimated at this time. The subdrain's maintenance needs will be incorporated in
the station-wide ROD. OU1 landfill closure and postclosure are governed by the same
regulations as a standard solid waste landfill and are not required to do less.
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Comment 14: The LWVs throughout California support comprehensive measures to provide maximum
protection to human health and the environment from the adverse effects of hazardous
materials, including pesticides. An integrated approach should be taken to prevent
harmful exposures through soil, surface and groundwater contamination,
bioaccumulation, air pollution, and direct contact. We believe all levels of government
share responsibility for preventing exposures.
Frankly, we are disappointed in the OU1FS and in the inadequate data base upon
which it is based. However, we are convinced that the Navy, EPA, and community
have learned a great deal in the course of the Feasibility Study review. As a result.
future Moffett Remedial Investigations will include more complete data upon which to
base the FSs that follow. Finally, we believe that the public interest is best served by
the Navy moving forward if the RODfulty incorporates improvements in the project
suggested by California regulatory agencies, local governments, and the community.
Response: The Navy revised the cap design and will conduct additional field work as a result of
comments received during the June 1995 public comment period.
3.2.8 Comments from the Silicon VaUey Toxics Coalition
Note: SVTC submitted a written statement of which portions were presented at the June public
meeting. In addition, SVTC submitted a set of written comments. The public meeting written
statement and associated responses are listed first, followed by the full set of written comments
and associated responses.
Written Statement:
My name is Peter Strauss. I am the Director of Environmental Management with MHB Technical
Associates in San Jose. I am the Technical Advisor to SVTC, which has a Technical Assistance Grant
from the EPA to help it participate in the decision making process regarding the Superfund sites at
Moffett and the so-called MEW companies south of the Bay shore Freeway.
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I first commented on a draft FS in 1993. Since then, two other drafts were completed. 1 wish to
commend the Navy for being responsive to the concerns that I raised about the capping of the landfills.
Briefly, the Navy has agreed to alter its proposed plan in several ways:
1) Added minimization of infiltration as a remedial action objective (RAO), thereby adding
an extra foot of material to the cap;
2) Integrated OU1, as originally defined as constituting soils only, with groundwater
3) Waiting to design and implement a remedy until information was developed on the
ecological effects of alternatives;
4) Sampled in additional areas that our hydrologist identified;
5) Describing some details about the monitoring and sampling plan;
6) Adding a leachate collection trench to the northern boundary between the Site 1 landfill
and the SWRP. Leachate will be transferred to one of the treatment facilities;
7) Developing a rudimentary contingency plan should leachate migrate outside the
boundaries of the landfills.
I think that these are major improvements to the original proposed remedy.
However, I believe that the plan has to be improved. Four general areas that will need improvement
are: 1) the contingency plan involving detections of leachate outside of the landfills needs to be
strengthened; 2) a contingency plan should be developed that deals with the event that the use of the
facility changes, or the federal government no longer wants to operate and maintain the drainage
system at Moffett; 3) to the degree possible, the remediation strategy should try to enhance the quality
of surrounding wetlands; and, 4) that all measures should be taken to have the remedy conform to
community standards.
1. While I realize that little leachate has been detected in this area previously, it is
important to establish guidelines or criteria for when the leachate system will be
mechanically activated. The FS proposes that this be done when leachate exceeds the
ambient water quality criteria. The FS states that hydraulic control or a packaged
leachate system can be implemented ifAWQC are exceeded. I propose that activation
levels be set at percentage of the AWQC, in combination with an increase in the level
detected at existing wells for two consecutive quarters. This seems quite reasonable to
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me, as it would allow time to plan the remediation and gain approvals from regulatory
agencies.
Regarding Site 2. while I recognize that hydraulic control could be maintained by lift
station 191, 1 am concerned that there is no contingency plan if monitoring wells detect
leachate migration. The aeration nozzle at Building 191 can only effectively treat some
VOCs, and will not treat PCBs and semivolatile organic compounds (SVOCs), and
inorganics. Therefore, I recommend that the Navy develop a contingency plan to treat
leachate from Site 2, if monitoring points outside the landfill detect contaminants at
levels similar to Site 1.
Additionally, I am concerned that relatively few AWQC are established for organic
compounds. It is important that action levels be established for all possible
constituents.
Response: The collection trench will be activated when AWQC for the protection of aquatic life
are exceeded in groundwater in the trench. This strategy is conservative and protective
because contaminant levels in the trench will not be representative of surface water
contaminant levels. Surface water is downgradient from the trench and contaminant
levels will be reduced by processes such as adsorption and dilution between the trench
and surface water. Therefore, if AWQCs are exceeded in the trench, corrective
actions can be initiated before AWQCs are exceeded in surface water.
Using AWQC is conservative. The National Oceanic and Atmospheric Administration
(NOAA), Coastal Resources Coordination (CRC) branch, provides guidelines to
identify potential impacts to coastal resources and habitats that are likely to be affected
by waste sites. For groundwater, NOAA recommends using a screening level of 10
times the AWQC. According to NOAA, this conservative screening provides a high
degree of confidence that any sources eliminated from future consideration pose no
potential threat to resources of concern (NOAA 1994).
At Site 2, a corrective action would consist of a groundwater extraction and treatment
that addresses specific contaminants that are migrating. Groundwater can be extracted
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prior to reaching the Building 191 lift station and treated for metals, SVOCs, PCBs, or
VOCs, if necessary.
AWQC have been identified for over 100 organic compounds, including chlorinated
solvents, benzene, toluene, ethylbenzene, polynuclear aromatic hydrocarbons (PAHs),
SVOCs, PCBs, and pesticides. The Navy will continue to update triggering levels as
information becomes available.
2. The FS is incomplete in that the RAs evaluated assume that the facility will continue to
be used at levels similar to current use. After thinking this through, I think that this
issue poses the largest potential problem to the Navy and the Community.
As you know, some community members are opposed to having Moffett Field continue
to operate. With budget slashers going to work in Washington, I don't think we can
assume that the Department of Defense or NASA is going to want to operate the
airfield.
So the question arises of what would happen if the drain system and the pumps are
turned off. Would elimination of pumping inundate some of the areas, and defeat the
purpose of the remedy? Who would have responsibility for maintaining the drainage
system, in the event that Moffett is not operated as an airfield? These are all questions
that should be thought about, before a remedy is implemented. At the very least, there
should be some institutional mechanism to pass along knowledge of the remedy and
consequences of not maintaining the drainage and pumping system.
Response: While Moffett Federal Airfield remains federally-owned land, the necessity of
continued O&M of the pump station shall be noted in the Master Plan for the
government's land uses and, in the event of any future conveyance of the property,
shall be addressed by appropriate notices and land use covenants binding on subsequent
property owners. While the CERCLA deed covenant and notice requirements would
be applicable to any property transfer, any change in land use (either before or in
connection with a transfer) would also be subject to an evaluation pursuant to the
National Environmental Policy Act (NEPA), which would require the Government to
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solicit public comment and evaluate the environmental impacts, including any possible
effect on the remedial activities at OUL
3. / believe that efforts should be made to protect, and wherever possible, enhance
existing wetlands, including the SWRP to the north of Site L I think it is important to
recognize that this is somewhat degraded wetland that is potentially habitat for
endangered species (salt harvest mouse). By enhancing the wetland, possibly by
removing or creasing the levees to allow for more tidal flushing, pickleweed
communities which are essential for the salt harvest mouse may become established.
Response: Efforts will be made to re-establish pickleweed destroyed during cap construction. A
replacement plan will be submitted during the RD to outline re-establishment efforts.
4. The Navy should be held to the same standards as private parties, including the Cities
of Mountain View and Sunnyvale. In this context, an early comment on a draft FS
requested that the Navy investigate and consider other remedies for old landfills that
abut the San Francisco Bay. I provided a list of landfills that I knew about. It would
seem prudent, if the Navy has not investigated these landfills, with the addition of
Mountain View and Sunnyvale, that it does so before the remedy is implemented.
Response: Information was received about Oyster Point, Third Avenue Landfill, and the old
Stinson Beach Landfill. The following paragraphs summarize information obtained
and discuss applicability to OU1.
CIWMB was contacted for information regarding Oyster Point. The remedy was
selected to prevent leachate migration and included a single-layer, low-permeability cap
and a slurry wall. The cap was constructed solely with bay muds. The landfill was
closed in the early 1970s and the area is now a marina. It is not known whether
leachate migration was occurring, however, a slurry wall was constructed. Since it is
not known whether leachate migration was occurring, it is difficult to compare these
circumstances and associated remedy to OU1.
CIWMB was also contacted for information regarding the Third Avenue Landfill.
The remedy was a multilayer clay cap and shoreline reconstruction. Waste is located
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below the water table, however, leachate migration was not occurring. No remedy was
implemented to restrict potential leachate migration. This circumstance is similar to
Site 1; however, at Site 1 a groundwater interceptor trench is proposed to protect
surface water from potential future leachate migration.
Caltrans was contacted for information regarding the Stinson Beach Landfill. The
remedy was excavation, dewatering, segregation of hazardous and nonhazardous
wastes, disposal, and restoration. Leachate migration was a concern at the Stinson
site, but it was not occurring. This remedy was completed as a mitigation project to
restore intertidal mudflat habitat destroyed during reconstruction of Route 1. The
remedy was apparently not pursued to control leachate migration.
CIWMB stated that apparently several old landfills around the bay have waste below
the water table. However, leachate migration is generally not a problem.
The Navy must comply with the same landfill closure regulations as local landfills.
CIWMB has identified 14 CCR solid waste landfill closure regulations as applicable for
OU1. During the public comment period, CIWMB stated that the Navy's proposed
alternative would not meet specified performance standards in 14 CCR. As a result,
the Navy has agreed to revise the proposed plan based on a prescribed, state pre-
approved configuration for the two landfill caps at OU1. Additional public comments
will be solicited from December 20, 1995 to January 31, 1996 on this revised proposal.
In addition, a public meeting will be held January 16, 1996 regarding the revised
proposal.
Written Comments from Peter Strauss of SVTC:
As a result of concerns raised by the THE Committee of the RAB and regulatory agencies, I have
reviewed previous SVTC comments, the Navy's response, and the Navy's commitments. Below I have
elaborated on some of our earlier concerns, my understanding of the Navy's commitments, and issues
that still need to be addressed. Additionally, following discussions with DTSC and the RAB on
August 9 and JO, 1995 respectively, I have included a framework for developing a contingency plan
should the Navy find that leachate is migrating from Site 1.
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The written comments contain some passages which are underlined, in bold, or both. Underlined
passages are meant to highlight previous SVTC concerns. Bold passages are what we believe to be
Navy commitments. Bold and underlined passages are SVTCs recommendations and action items.
Comment 1: "It is inappropriate to develop a remediation strategy which does not take full account
of existing and potential communication between the leachate in landfill material and
the eroundwater under and around the landfills. * (December 1993}.
The original remediation strategy articulated in the OU1 Draft FS did not take account
of groundwater at all. After regulatory pressure, the Navy agreed to consider both
soils and groundwater at the landfills, which makes common sense. In 1993, we
requested that the Navy provide information on the "the radius [and! or depth of
groundwater that is soine to be considered."
Based on recent discussions at RAB meetings and meetings with regulators, it is
unclear that the radius and depth of eroundwater that was considered was adequate.
Refer to comments about potential groundwater flow on the southern boundary of the
Runway Landfill, and anecdotal information that the waste was buried 21 feet below
ground surface. If the depth of waste is in fact 21 feet, then existing monitoring wells
within the landfill, and those surrounding the landfill would be sufficient to detect the
migration of potentially contaminated groundwater.
Response: The Navy has focused groundwater investigations on the uppermost aquifer at the
landfill perimeter. If any groundwater impacts become evident, the radius and depth of
subsequent groundwater investigations will be increased to encompass the plume of
leachate that has migrated.
Comment 2: Minimizing infiltration should be a remedial action objective. (December 1993}. There
is no reason to believe that leachate from the landfills will not eventually migrate. One
may hypothesize that it may be minimal and retarded by surrounding clays, but there is
little doubt that it will eventually migrate. Therefore, we have argued that a strategic
objective of the remediation at the site should be to minimize infiltration, to slow
migration of leachate.
On July 25, 1994, after a technical meeting with Dr. Oberdorfer and me, the Navy
committed to add minimizing infiltration as an RAO presentations. First, in a response
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to DTSC Comment 105, dated April 10, 1995, the Navy stated that "minimizing
infiltration is not a primary cap function." Second, this was re-iterated at the August
10 RAB meeting. Third, during the public hearing, the Navy's consultant failed to
include minimizing infiltration as a RAO.
There is nothing in the Remedial Action Plan that would limit infiltration, but for the
cap. Although minimizing infiltration is included in the final FS as an RAO, it is
important that it be futtv considered in the design of the remedy. It is not clear from
the response to DTSC's comments cited above whether this has been done, or whether
the Navy intends to do this.
Response: The Navy has agreed to revise the OU1 landfill cap configurations to include a
low-permeability layer to minimize infiltration.
Comment 3: There is a disconnect between the amounts of hazardous materials detected in the OU1
Rl/draft FS and the tons of liquid and solid hazardous materials that were reported in
the IAS. (December 1993).
Although we recognize that the IAS was based on anecdotal information, we
recommended that the Navy reconcile this disparate information in the FS. It is
difficult to dismiss these anecdotal reports merely because a few borings and wells have
not shown heavy contamination. Other explanations could exist, including that these
contaminants are now in the Bay or groundwater, that they have degraded, that they
weren 't located by the borings, or that they were disposed of at another landfill on the
base. In fact, there is a third landfill heated within the Golf Course that was identified
by IT in 1988. (December 1993). (Subsequently, it was discovered that there is
actually a fourth landfill).
With respect to the Navy's first response to this comment, (i.e. "The Navy does not
agree that reconciliation of the past fate of landfill refuse is needed. These
data...would be based on speculation."), we responded that it is incumbent upon the
Naw to prove that the IAS was incorrect. (April 14. 1994).
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On July 20, 1994, the Navy described the reasons why it believes that IAS may be
incorrect, and committed to a strategy of enhancing containment by evaluating a
vertical barrier at the northern boundary of Site 1, and corrective action should
drummed waste begin to be detected migrating from the site. It is not clear that the
Navy has followed through with this commitment. For example, although the Navy
proposed that a vertical leachate collection trench be installed at the north side of
Site 1, the plan does not offer any concrete remedy should drummed waste begin to
migrate to the south. In liaht of the Al-aquifer gradients traveling north to south, the
location of additional vertical barriers needs to be re-evaluated. (See Comment 6,
below).
Additionally, although many reasons were given by the Navy for not adopting the
information from the IAS, it seems that enough questions have been raised by the KAB,
that the issue of what is in the landfills requires some revaluation and explanation,
with public review before the RAB. We recommend that the Navy befin with the July
20. 1994 response to SVTC comments as a starting point, as we believe that this was
a food first effort to attempt to address this issue.
Response: The northern location selected for the groundwater interceptor trench is the most
appropriate. A potential for flow (gradient) has been measured from the leachate zone
to the SWRP. Therefore, the trench was positioned between the Site 1 landfill and the
SWRP to protect ecological receptors at the SWRP. It is not necessary at this time to
develop contingencies in the event leachate is migrating southward. Any releases along
the southern border could be addressed by additional containment or hydraulic control
systems, if needed. There are no receptors close to the southern boundary. There
would not be any immediate threat to human health and the environment, and
therefore, it is not cost-effective to construct contingencies at this time.
The issue regarding the content of the landfills will be revisited when the Navy
conducts a radiation survey. This is the only remaining information that is needed to
implement the remediation strategy. Any additional information regarding the content
of the landfills will not change the proposed remedial strategy.
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Comment 4: The Solid Waste Assessment Test (SWAT) concluded that leachate contained elevated
levels of organic compounds and metals, and that seepage could enter surface waters.
It also concluded that the A-l aquifer was contaminated at this location, (i.e. Site 1).
but suggested that contamination mav be from another source. (December 1993).
The Navy responded that corrective action strategies appropriate for OW landfills
include hydrauUcatty controlling gradients through leachate extraction and treatment,
or combining extraction with vertical barriers. Additionally, disparities between
leachate contaminants and the A-aquifer contaminants suggest a source other than
landfills. The Navy responded that the SWAT stated that "upgradient sources have not
beenfulfy evaluated, [and] the concentrations of metals found in the A-aquifer are not
considered definitive of landfill leakage."
First, the final plan and the ROD should describe in detail the additional
enhancements to the containment strategy that mav include vertical barriers and
hydraulic control through leachate extraction (See comment 9 below). Also, has
further analysis of uveradient sources led to anv chance of opinion or shed new lieht
on this subject? Please identify possible uperadient sources of heavy metals and
organics.
Response: The only subsurface barriers needed at this time have been described in the FS report
and proposed plan.
At Site 1, no upgradient sources have been identified. At Site 2, some of the plumes
identified in the OU5 FS are upgradient. However, comparisons of upgradient and
downgradient concentrations enable the Navy to determine whether Site 2 is
contributing to groundwater contamination.
Comment 5: The desien fe.g. base materials of the old landfills] needs to be better understood
before a remedy is proposed. (December 1993)
Based on the data presented, it appears that the Navy does not know much about the
initial design of these landfills. There is not an adequate description of the base
material or the sides of the landfill to make a reasonable judgement pertaining to how
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these may contain the fill materials for long durations. In order to contain the landfill
contents, it is essential that design characteristics of the existing landfill be well
understood. (December 1993)
The Navy responded to this comment by stating that the conductivity of "surrounding"
soils has been tested and evaluated. Since the remediation strategy is one of
containment, it is crucial that the Navy be as certain as possible that base materials
won't leak, and that waste is not deposited below a clay layer, as suggested at the July
13, 1995 RAB meeting. Based on the present knowledge of the titholofn of the
landfills, we recommend that this issue be re-evaluated.
Additionally, it appears that groundwater flowing into the landfill, with a downward
gradient from North to South. This exacerbates our concerns about the need to
understand the containment (or lack thereof) of the fill before developing a remedial
plan, and importantly, and raises the question of whether the remediation strategy of
containment can be successful with only a cap. There may have to be several other
elements to the remedial action plan before it can be designed to successfully contain
leachate and groundwater. Therefore, the final plan should state that additional
remedies may be needed if contamination outside the landfill is found. This
statement should be as specific as possible.
Response: The permeability of underlying soils has not been fully characterized. Extensive
sampling or excavation would be required if it was necessary to completely
characterize the soil beneath the landfill. However, this information is not necessary
and the Navy does not assume that clay layers beneath the landfills are continuous.
The information from the limited soil investigations offered a possible explanation for
the lack of evidence of contaminant migration. However, it would be difficult to prove
conclusively that naturally occurring barriers to groundwater movement exist.
Therefore, because it is not known conclusively, continual groundwater monitoring and
contingency plans to protect nearby vulnerable receptors are proposed. In addition, the
Navy will conduct more field work to further investigate potential contaminant
migration.
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The corrective action requirements under 23 CCR discuss the necessity for additional
remedies to address leachate migration.
Comment 6: We noted (December 1993} that groundwater at Site 1 flows in the south-southeast
direction, towards Building 191. It appeared, however, based on Figures 3, 4 and 5,
that most soil sample points and groundwater wells located outside of Site 1 were found
on the north side of the landfill. Plate 1 and page 18 (of Draft FS) indicated that no
samples were collected or analyzed from the borings and wells to the south-southeast of
Site 1. We also asked whether the Navy believed that there are enough monitoring
points on the south-southeast side of Site 1 ? (December 1993}
The Navy's response (dated February 4,1994) to these two comments stated that the
OUJ Technical Memorandum and the additional field work plan describe groundwater
flow patterns in detail and the adequacy of the monitoring network. At that point in
time, there were four monitoring wells south and southeast of Site 1. The OU1
Additional Field Investigation, Technical Memorandum of December 29, 1993, shows
the locations of four new monitoring wells at Site 1: one at the west-southwest
perimeter; one a the southeastern perimeter; and another on the southern perimeter
(the fourth is located at the northern perimeter). The location of the new well on the
southern perimeter was screened to monitor "shallow concentrations of contaminants"
migrating towards the Building 191 pump house. At this point in time, it was not
apparent to Navy consultants (although it was suspected) that mounding of
groundwater was occurring in Site 1. There are a number of problems with this
response which have been brought to our attention through the excellent work of the
RAB.
First, there are very different potentiometric surfaces described in the Technical
Memorandum (Figures JO and 11) from those described in the Final FS (Figures 12
and 13). There is not an explanation of why the potentiometric surfaces changed from
the Technical Memorandum, based on fourth quarter 1993 data, and the FS, based on
February 1994 data. Assuming that there are perched water zones within the landfill.
Figure 11 of the Technical Memorandum depicts yet another elevation and gradient.
As a result, we believe that the Now must explain and reconcile these differences. In
it mtft n.^0 cieaar anv assumptions that went into the models used to map
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the elevations. With relatively few data points inside the perimeter of the landfill, it is
difficult to realistically depict leachate or groundwater contour levels.
A second problem is that it has never been clear how the Navy has differentiated
between leachate and the shallow groundwater in the A-l aquifer. Since the wells
inside the landfill are drilled to the base of the landfill, one cannot differentiate between
leachate and groundwater within the aquifer. The Technical Memorandum treats
leachate and groundwater as one in the same, and it would appear that this would be a
rational explanation if the bathtub model of the landfill is correct, as implied in the
Technical Memorandum. In contrast, the FS conceptual model, however, depicts a
semi-confined A1-aquifer that is below the base of the landfill (see Figure 11 of the FS).
However, the measured depth of this A1-aquifer is 0.7 to 1.0 feet below the leachate
levels (at approximately Wl-11, see Figures 12 and 13 of the FS). Since the elevation
of leachate level at this monitoring point is approximately 8 feet above the base of the
landfill (see Figure 7, then it must be concluded that Al-aquifer is flowing through the
landfill. We do not believe that this fact is in dispute: however, we are concerned that
there may have been conclusions drawn based on a reliance on models of groundwater
movement as depicted by the FS conceptual model. I draw two conclusions from this.
a) There appears to be an imaginary line between leachate and groundwater, for
they both will mix in the landfill. Therefore, this conceptual model is incorrect.
Because of the apparent contradiction (conceptual model versus actual
results}, we ask whether the hvdroeeoloev of the site is understood enough to
develop a remediation strategy, and that the conceptual model be modified.
Potentiometric surfaces are developed by relatively few number of data points
for the size of the area, and we feel strongly that the Now must father more
information before it develops a remedial design.
b) Because of the concern that the Now men have relied on an incorrect
conceptual model, we recommend that oast assumptions and conclusions
related to the framework that a semi-confined Al-aauifer beneath the landfill
(Site 1) be revisited, and adjusted if need be.
c) The remedial investigations and strategies cannot and should not be locked in
jime as new techniques or new information is developed* OU1 appears to be
a case-in-point where the results of an investigation were frozen in time,
without regard to changing information. Apparently there have been changes
of assumptions between the Technical Memorandum and the OU1 draft-final
FS, in which the potentiometric surfaces based on February 1994 data were
first presented. Because of this apparent change, the monitoring well data gap
to the south, as brought to your attention by the RAB, is very evident. Despite
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SVTC's early concerns raised in December 1993 about the sufficiency of the
monitoring well system on the south side of Site 1, the Navy does not appear to
have adjusted the monitoring well system to account for new information. We
stronrlv believe that the remediation plan needs to be flexible as new
information is developed.
Response: The Navy's conceptual model of the hydrogeology has changed since the Technical
Memorandum as new information has been received and evaluated. The current
conceptual model is described in the May 15, 1995 submittal of the FS report.
Additional data will be collected and incorporated into the conceptual model, as
appropriate.
The Navy believes that the hydrogeology of the site is adequately understood such that
a remedial strategy can be developed. The current hydrogeologic conceptual model
may be updated as additional information becomes available; however, changes to the
conceptual model do not significantly affect the remediation strategy.
Groundwater elevation data indicate that the water pressure in the A1-aquifer is above
atmospheric pressure at some OU1 locations, indicating that the Al-aquifer is semi-
confined. This conclusion does not affect the remedial strategy, as the remedial
strategy is adequate regardless of whether the Al-aquifer is semi-confined.
The groundwater monitoring and corrective action requirements found under 23 CCR
allow for flexibility as new information becomes available.
Comment 7: The FS is incomplete in that the RAs evaluated assume that the facility will continue to
be used at levels similar to current use. Some community members are opposed to
having Mofiett Field continue Ions-term operations under NASA, almost as if there had
not been a chanee in stewardship. (April 14. 1994}
'The remedial action (RA) should not foreclose future options, such as reducing or
eliminating flights, and significantly scaling back industrial activity. The RA should
account for, wherever possible, a reduced use scenario where pumping from
Building 191 no lonner occurs. Elimination of Dumping would create 3 stronger
horizontal force on landfill contents and may affect eroundwater levels, and will likely
160
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change groundwater flow patterns and direction in some areas." Consequently.
migration of constituents via eroundwater/leachate transport is more likely to occur.
(April 14. 1994)
As federal commitments to the facility seem to be influx, we think that there is a strong
need to look ahead at the possibility of the drain system being turned off. We were
pleased to hear that the Navy, based on the meeting at DTSC and the RAB in August
1995, also thinks that this is enough of a possibility that it will discuss potential
remedies and contingencies as part of the response to the public hearing and
comments. We believe that more investigation should take place, including: 1) an
evaluation of expected environmental effects on the landfitts should the drain system
be turned off: and. 2) an investigation and description of low cost techniques that
could be installed now which would mitifate some or all of the negative
environmental effects identified in 1) above. We also ask that a yen specific
contingency plan be described which would alienate the effects of turning off the
drain, which cannot be avoided b\ low cost techniques described in 2} above.
Response: Please see the response to Comment 7 in Section 3.2.3.
Comment 8: "7 believe that efforts should be made to protect, and wherever possible, enhance
existing wetlands, including the storm water retention pond to the north of Site 1. In
the context of the Ecological Assessment. I think it is important to recognize that this is
a somewhat degraded wetland that is potentially habitat for endangered species (salt
harvest mouse). Bv enhancing the wetland, possibly bv removing or creasing the
levees to allow for more tidal flushing, pickleweed communities which are essential for
the salt harvest mouse nun become established. * (April 14. 1994)
We are pleased that the Navy has agreed to install a leachate collection trench on the
nonh side of Site 1 to protect this potentially fragile ecosystem. We also believe that
prior to remedial design, it is important that the Navy take an independent look at
possibilities for enhancing the existing wetlands. We therefore recommend that an
independent evaluation ofwavs to enhance the wetlands be made a formal
commitment.
161
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Response: Comment noted.
Comment 9: The remedial proposal is based on the assumption that should leachate migrate from
the landfills, it will be detected and appropriate remedies can be installed, as required.
This concept is insufficient unless the FS contains a contingency plan that establishes
action levels that will require action, and what those actions are Uketv to be. I propose
that action levels be set at a fairly low percentage of the maximum contaminant level
(MCL). in combination with an increase in the level detected at existing -wells. For
example, if the TCE MCL is Sppb. I would propose that remedial action fin this
instance, likely to be leachate collection and treatment] be triggered when TCE is
detected at 25 percent of the MCL. and concentrations have increased over two
quarters. (The above is an example of how a tripi>erinf> mechanism could work, not a
proposed standard.) (April 14. 1994}
We have since revised the proposed action levels. Our current proposal is that action
levels be set at 25 percent of the Water Quality Criteria, triggered when concentrations
of contaminants increase over two consecutive quarters. This would at the very least
give the Navy time to plan a remedy and a treatment for contaminated leachate. We
stronelv recommend that the Now adopt this criteria for the leachate collection
trench north of Site 1.
With regards to potential leachate migration south of Site 1, a detailed contingency
plan should be developed and included as pan of the ROD. Below, we have suggested
the following framework on how to develop this plan.
a) The plan should be detailed enough to provide the public and the regulators
with sufficient information and criteria for action so that it will act as a
verifiable commitment in the ROD:
b) Because we don't know what will be found bv additional wells on the
southern ed?e of Site 1. several scenarios should be included in developing
the plan. For example, the followinf presents a ran?e of findings: 1) no
detectable finding of leachate migration: 2) mifration of heavy metals. VOCs
and SVOCs. above the MCL but below the AWOC: and. 3) migration of
heavy metals. VOCs and SVOCs. above the AWOC.
c) For each scenario, a plan should be articulated. For example, if scenario I
is found, the contingency mav commit to further monitoring: if scenario 3 is
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found* the plan mav commit to a leachate extraction and treatment system
either within, or on the edee of the landfill*
Response: The collection trench will be activated when AWQC for the protection of aquatic life
are exceeded in groundwater in the trench. This strategy is conservative and protective
because contaminant levels in the trench will not be representative of surface water
contaminant levels. Surface water is downgradient from the trench and contaminant
levels will be reduced by processes such as adsorption and dilution. Therefore, if
AWQCs are exceeded in the trench, corrective actions can be initiated before AWQCs
are exceeded in surface water.
Using AWQC is conservative. The NOAA CRC branch provides guidelines to identify
potential impacts to coastal resources and habitats that are likely to be affected by waste
sites. For groundwater, NOAA recommends using a screening level of 10 times the
AWQC. According to NOAA, this conservative screening provides a high degree of
confidence that any sources eliminated from future consideration pose no potential
threat to resources of concern (NOAA 1994).
It is not necessary at this time to develop contingencies in the event leachate is
migrating southward. As discussed above, any releases along the southern border
could be addressed by additional containment or hydraulic control if needed. There are
no receptors close to the southern boundary. There would not be any immediate threat
to human health and the environment, and therefore, it is not cost-effective to construct
contingencies at this time.
Comment 10: Because wells inside of the landfill are screened to the bottom of the landfill, leachate
is not truly characterized. Rather, the leachate wells reveal a mixture of leachate and
groundwater. While we are not sufgestinp that you remedy this, this fact should be
taken into consideration in future testing and modeline. For example, we are
concerned that low detects found in areas outside the landfills are not discounted.
and do not become a rationale for saving that no leachate is mifratine. When low
detects are found, we believe that it is the Navy's burden of prop ftp demonstrate that
it is not due to a leak in the landfill.
04MX236inilff\s:\wpdocs\usnavy\niofto\ctt^a236\resp697.doc\jeni
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Response: The monitoring program will be conducted in accordance with 23 CCR. Title 23 CCR
identifies statistical procedures to be used for evaluating monitoring data.
3.2.9 Comments from Santa Clara County Environmental Resources Agency
Comment 1: 14 CCR 17773 - Final Cover: An engineered alternative for final cover is submitted in
lieu of the prescriptive standard for final cover. Engineered alternatives shall onfy be
approved when the operator can demonstrate to the satisfaction of the California
Integrated Waste Management Board (Board) and the local enforcement agency (LEA)
that requirements for proposing an engineered alternative {California Code of
Regulations, Title 14, Section 17773(c)J can be satisfied. The need for an engineered
alternative to the prescriptive cover standard has not been demonstrated.
Response: During the June 1995 public comment period, CIWMB stated that the Navy's proposed
alternative would not meet specified performance standards in 14 CCR. As a result,
the Navy has agreed to revise the proposed plan based on a prescribed, state pre-
approved configuration for the two landfill caps at OU1.
Comment 2: 14 CCR 17781 - Leachate Control During Closure and Post Closure: Leachate must
be monitored, collected, treated and disposed of in an appropriate manner. The OU1
FS does not address the requirement.
Response: Regarding this matter, 14 CCR 17781 also states:
"Leachate control and monitoring shall cease only after the operator
demonstrates, to the satisfaction of the local enforcement agency,
regional board and the Board, that leachate is no longer being
produced, or the discharges of leachate will have no effect on water
quality. This demonstration shall take the form of a written report
submitted to the local enforcement agency, and the Board and the
regional board. Factors the local enforcement agency and the Board
shall consider when ending leachate control shall include monitoring
results, nature of refuse, the presence and design of landfill
164
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containment structures, local hydrology and geology, and local land
and water use."
To address this requirement, the OU1 FS stated that refuse is below the water table
and, as a result, leachate will always be produced. However, Section 1.3 and
Section 2.1 of the FS demonstrate that the leachate produced has no effect on water
quality and that leachate plumes have not migrated and are not expected to migrate in
the future. Therefore, it has been the Navy's position that leachate collection and
treatment is not necessary at this time. DTSC, EPA, and RWQCB concur with this
approach, as it is fundamental to the development of the OU1 FS and subsequent
recommendations.
CommentS: 14 CCR 17783 - Gas Monitoring and Control During Closure and Post Closure:
Landfill gases must be controlled and monitored during closure and post closure for a
period of 30 years or until written authorization to discontinue is given by the Board or
LEA. The OU1 FS does not adequately address the requirements of 14 CCR 17783
through 17783.15.
Response: To provide for the protection of public health, safety, and the environment,
14 CCR 17783 states that the operator shall ensure that landfill gases generated at the
facility are controlled during the periods of closure and postclosure maintenance, in
accordance with the following requirements:
(1) The concentration of methane gas must not exceed 1.25 percent by volume in
air within on-site structures.
(2) The concentration of methane gas migrating from the landfill must not exceed 5
percent by volume in air at the facility property boundary or an alternative
boundary in accordance with Section 17783.5.
(3) Trace gases shall be controlled to prevent adverse acute and chronic exposure
to toxic and/or carcinogenic compounds.
The revised cap configuration for the Site 1 landfill will include gas venting beneath the
low-permeability layer. This combination of layers will facilitate controlled venting of
gas to meet the requirements of 14 CCR 17783. In addition, a gas venting trench will
be constructed around the western perimeter of Site 1 to further meet the requirements
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of 14 CCR 17783. Landfill gases are not being generated at Site 2 and, as a result, gas
venting is not included at Site 2.
Comment 4: 14 CCR 17796 - Post Closure Land Use: Post Closure land use must be compatible
with protection of the final cover and post closure environmental systems. Changes in
proposed land use must be approved by the appropriate agencies. The OU1FS does
not adequately address post closure land use.
Response: Article 7.8 of 14 CCR has been identified as applicable for the OU1 remedial action.
Therefore, the provisions of 14 CCR 17796 will be specified for compliance in the
OU1ROD.
3.2.10 Comments from the National Aeronautics and Space Administration
Comment 1: Alternative 2 is acceptable to NASA only if the Bay Conservation and Development
Commission (BCDC) concurs that it is consistent with the San Francisco Bay Plan.
NASA would like assurance that the remedy selected is acceptable to the state and any
tideUmd trust concerns they may have. Therefore, NASA requests that the Navy submit
a Consistency Determination to BCDC for concurrence.
Response: The Navy has discussed the selected remedy with the BCDC. The BCDC preliminarily
indicated that the remedy will be acceptable; but also identified several concerns. The
Navy will continue to consult with the BCDC throughout the RD to address concerns.
In addition, the Navy is currently investigating the need to prepare a determination of
consistency.
Comment 2: Any wetland mitigation plans to increase or maintain wetlands should be closely
coordinated with NASA.
Response: The Navy will coordinate wetland replacement plans with NASA.
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3.2.11 Comments from California Integrated Waste Management Board
Note: CIWMB comments were provided in letter format. Therefore, the letter received by the Navy is
presented with responses interjected throughout the letter.
CIWMB staff has concerns thai the vegetative soil cap that was presented as the selected remedy in the
Proposed Plan did not meet the final cover standards of 14 CCR 17773. Since this standard was
identified as an applicable requirement in theFS, the NCP threshold criteria for meeting ARARs was
not met.
The FS proposed the soil cap as an engineered alternative to the prescriptive standards of 14 CCR
17773, then compared its feasibility and performance against a multilayered cap and concluded that
the soil cap was more feasible and performed similarly to the multilayered cap, therefore it met the
criteria for an engineered alternative pursuant to 14 CCR 1 7773. CIWMB staff can not concur with
these findings because the multilayered cap exceeds the prescriptive standards, therefore a comparison
of the vegetative cap to the prescriptive standards was not performed. To assist the Navy in making an
appropriate determination regarding the type of soil cap to use on the landfills CIWMB staff is
providing the following guidance.
Pursuant to an interpretation by CIWMB legal counsel, two criteria need to be met before an
engineered alternative can be used in lieu of the prescriptive standards, (1) the prescriptive standard is
not feasible, and (2) the specified engineered alternative performance is consistent with the
performance of the prescriptive standards in limiting infiltration to the greatest extent possible,
controlling landfill gas emissions and compatibility with future reuse of the site.
During the August 9, 1995 meeting, CIWMB provided a unit cost comparison (Table 1 [attached]) of
the multilayered cap and prescriptive standard caps for landfills in the vicinity ofMpffett Field. This
comparison shows that the final cover cost per acre for the prescriptive standard cap ranged between
$82,981 and $20,185 while the multilayer cap cost $200,051. The multilayer cap costs were much
higher because the cap design included many layers that were not required by the prescriptive standard
as shown on Table 2 (attached). Table 2 also provides a comparison of cost estimates for the soil and
multilayered caps with the prescriptive standard cap. Unit costs provided in the FS were used to
develop the costs. Table 2 shows that closure of Site I pursuant to the prescriptive standards would
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save the Navy $1.000. Therefore, based on the information provided in FS, the prescriptive standards
are more feasible than the proposed vegetative cover.
Response: Implementing the prescriptive standard will not save money or resources. CIWMB
costs do not include a drainage layer, biotic barrier, or provisions for gas venting.
These layers may be necessary for OU1 if a cap with a low permeability layer is
implemented. If these three layers are added to the prescriptive standard, the resulting
cap is similar to Alternative 3. The rationale for die additional layers to the
prescriptive standard is described below.
Drainage Layer
The prescriptive landfill cap standard in 23 CCR calls for a 12-inch vegetation layer
overlying a low-permeability layer. This design essentially places an aquitard
12-inches bgs. Without adequate drainage, water may build up on the
low-permeability layer. This water build up could saturate the root zone of vegetation
and weaken vegetation. In addition, this water build up may increase the water
pressure on the low-permeability layer and increase percolation. Therefore, a drainage
layer may be needed to carry this water off the low-permeability layer. Inclusion of
the drainage layer will be further evaluated during the RD.
Biotic Barrier
A biotic barrier is needed to prevent burrowing animals and plant roots from
penetrating through the barrier layer and into refuse. This penetration can significantly
affect the integrity of the barrier layer. A biotic barrier was also included to prevent
burrowing animals from being exposed to landfill refuse. Therefore, a biotic barrier
was also included in Alternatives 2 and 3.
Gas Vents
The Site 1 landfill is generating gases. Placing a low-permeability cover over the
landfill can cause gas pressure to build up under the cap. Increased gas pressure can
cause an increase in horizontal subsurface migration. Horizontal migration off site is
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undesirable because methane can accumulate in enclosures and create an explosive
atmosphere. Therefore, gas venting is needed to alleviate pressure beneath a barrier
layer. Gas venting was not included in Alternative 2 because the cap soil would be
more permeable than surrounding soils, and gases would flow upward not horizontally.
Using the unit costs provided in the FS with a 1-foot thick vegetation layer and
synthetic materials for the drainage layer, biotic barrier, and the low-permeability
layer, the total cost is $4,929,700. This results in an increase of $1,772,100 above
Alternative 2.
According to CIWMB legal counsel's interpretation the feasibility issue alone is enough to require the
prescriptive standards, however, CIWMB staff is providing additional comments on the performance of
the caps to assist the Navy in their decision making process. The HELP Model was used in the FS to
evaluate the performance of the soil cap versus the multilayered cap. The FS concluded that the two
caps were similar in their ability to limit infiltration. After evaluating the input parameters used in the
HELP Model comparison, CIWMB staff cannot concur with these findings for the following reasons.
The HELP model is a useful tool in determining the amount ofleachate that a landfill is likely to
produce because it assumes that any head that builds up on a barrier layer will infiltrate. In addition if
infiltration occurs in one location it is applied evenly over the entire site. This is a conservative
estimate for determining the amounts of leachate produced at a site but not for a comparison of
infiltration rates for landfill caps. State landfill design standards prohibit the buildup of hydraulic head
on a liner system. Therefore, when using the HELP model for cap performance evaluation purposes a
barrier layer cap should have an adequate drainage system.
The drainage design for the multilayer cap used a drainage path length of 450 feet at a 5 percent slope.
Since the HELP model incorporates infiltration while the precipitation is flowing along the drainage
path it is doubtful that any of the precipitation will run off. The model shows that only 0.02 percent of
the precipitation runs off. Generally landfill slopes are constructed at a 3:1 ratio or 33 percent slope
with benches that include collector drains every 50 feet. Therefore, the maximum drainage path that
should be used is 50 feet with a slope of approximately 33 percent. The multilayer cap design could
also be improved by lowering the permeability of the drainage layer to the 1x10' cm/sec range which
would be appropriate for a gravel drainage layer and choosing a barrier layer soil. The model
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considers barrier layer soils highly compacted, the soil that was used was considered moderately
compacted.
Response: The design of a drainage layer could be optimized and the resulting performance could
be increased as noted. However, the important conclusion from the HELP model was
that the difference in infiltration rates is insignificant. For Sites 1 and 2, a 3-foot soil
cap reduces infiltration into refuse to 1.13 inches per year. A multilayer cap only
reduces infiltration to 1.06 inches per year. No significant difference in the amount of
infiltration results, considering that the multilayer cap reduces infiltration an additional
0.07 inches per year as compared to a soil cap. The results show that most
precipitation will be lost through evapotranspiration (91 percent). Therefore, even if
an alternate (and more costly) drainage design was used and all of the remaining
precipitation was removed, the reduction<1 inch annually) would not be warranted.
Most of the already low annual precipitation does not percolate through to the barrier
layer. The Navy conducted a sensitivity analysis using the HELP model to evaluate the
impact of drainage layer slope on infiltration rates. The Navy plotted infiltration as a
function of drainage layer slope. The resulting additional decrease in infiltration from
a 5 percent slope to a 30 percent slope was 0.16 inch. The amount of infiltration is
insensitive to lateral drain slope at these low percolation levels.
For the vegetative cap, a 32-inch evaporative zone depth was used for the grass on the vegetative
cover. Table 3 (see attached) shows several types of grasses used for landfill covers in California.
Their root zones ranged between 6 and 12 inches. An appropriate grass for the vegetative cover model
might be the native Costal Range melic with a root zone of JO inches. If capillary action of the grass
roots is considered the total evaporative zone should be approximately 12 inches.
Response: The 36-inch vegetation layer thickness was selected to accommodate deeper root
systems of nonwoody plants, allow for long-term erosional losses, and provide water
holding capacity to sustain vegetation through dry periods. According to research
documented in the HELP model, 32 inches is an achievable evapotranspiration zone for
the region and the 36-inch soil thickness was selected to take full advantage of this
zone.
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CIWMB staff have conducted several runs of the HELP Model Version 3.03 using drought weather
conditions from a San Francisco weatherstation with an average annual precipitation of 1 2.99 inches
which is similar to the synthetically produced 12.5 inches used in the FS comparison. After making the
adjustments stated above to the HELP Model input parameters, staff found that the performance of the
barrier layer cap significantly exceeded the performance of the soil cap in limiting infiltration. The
HELP evaluation in the FS should be adjusted to reflect the above comments.
Response: The Navy agrees that making the suggested adjustment of reducing the evaporative
zone to 10 inches will result in increased flow through the lateral drainage layer. The
Navy believes making the suggested adjustments ignores the benefits of the dry climate
at Moffett Field and enhances the detriments of the dry climate at Moffett Field.
During the August 9, 1995 meeting PRC staff stated that it was not necessary to reduce infiltration
because the waste is in.groundwater and was not migrating from the site. Title 14 CCR 17709
prohibits the disposal of waste in groundwater, except as approved by the RWQCB. Pursuant to
discussions with the Regional Board it is not a matter of the leachate migrating from the site but if
groundwater impairment has occurred, see 23 CCR 2510. Since groundwater monitoring wells located
in the waste show groundwater impairment and there is a significant amount of waste above the
groundwater table, at a minimum a corrective action of source control (that is, capping) must be taken.
Staff can not concur with the statement that leachate is not migrating from the site, because adequate
down gradient groundwater monitoring has not been provided.
Response: The Navy has agreed to further investigate contaminant migration at identified
downgradient locations.
The second performance goal considers the need to limit landfill gas emissions. Landfill gas
characterization test results in the Air Quality Solid Waste Assessment Test (Air SWAT) (IT 1992) show
that the landfill decomposition gasses consists of 52 percent menthane and carcinogenic trance gasses
such as vinyl chloride at 210 ppb. The FS states that the landfill gas is not a potential health threat
and calculations for nonmethane organic compounds (NMOQ show that landfill gas emissions do not
need to be controlled. CIWMB staff can not concur with these findings because the Air SWAT was
never approved by the Bay Area Air Quality Management District, and the potential health risk of the
210 ppb of vinyl chloride, a Class A carcinogen, were never evaluated.
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The FS states that the Air SWAT data was used to determine a potential carcinogenic risks of less than
lxW7from landfill gas emissions. Staff found that the Air SWAT proposed integrated surface sampling
to determine if methane or carcinogenic trace gasses were emitting from the site but onfy a surface
emissions screening with aflame ionization detector was conducted at 39 degrees Fahrenheit and 3 to 4
mile per hour wind speed. It is not likely than much methane gas was being produced at 39 degrees
and aflame ionization detector is not designed to detect trace gases such as vinyl chloride. The landfill
gas characterization data that shows 210 ppb of vinyl chloride should be used to determine the
potential health risks posed by the landfill gas.
Response: It is likely that 210 ppb of vinyl chloride in the subsurface would attenuate through the
3-foot soil cap and disperse once it reached the surface to undetectable levels.
However, the Navy has agreed to revise the cap configuration to include a
low-permeability layer and an associated gas collection and venting system to mitigate
any potential threats.
The FS states that calculations for NMOC emissions show that landfill gas does not need to be
controlled. CIWMB staff can not concur that landfill gas does not need to be controlled. CIWMB staff
can not concur that landfill gas does not need to be controlled. Calculations for NMOC emissions are
used to determine if the landfill is producing enough NMOCs to impact the ozone layer. These
calculations do not consider the need to control landfill gas emissions to prevent a potential health or
explosive threat as required by 14 CCR 17783.
Since the intended postclosure land use of the site is a firing range which provides potential receptors
and ignition sources it is unlikely that landfill gas emissions will not require control. The landfill cap
design should be evaluated with consideration of the performance goals of 14 CCR 17783, Landfill Gas
Monitoring and Control and the prescriptive standards in 14 CCR 17796, Postclosure Land Use.
Response: The Navy has agreed to revise the cap configuration to include a low-permeability
layer and an associated gas collection and venting system to mitigate any potential
threats.
The above discussion has shown that adequate proof has not been provided to show that the vegetative
cap is more feasible than the prescriptive standard. In addition, it does not show that the vegetative
cap provides infiltration protection to the greatest extent possible, controls landfill gas surface
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emissions, or is compatible with the intended postclosure land use. Additional monitoring, modeling
and risk assessment will be necessary to justify the vegetative cover. Staff is concerned that additional
time and money may be spent by the Navy and will not provide results that will justify the soil cap.
Therefore, staff recommends Alternative 2, the vegetative cover, be modified by replacing the lower two
feet of vegetative soil with a less expensive foundation and barrier layer material, and if necessary have
a drainage layer installed.
Response: The Navy has agreed to include landfill caps that will more clearly meet the
specifications in 23 CCR 2581 because regulatory agencies do not believe that
Alternative 2 is in compliance with applicable landfill closure regulations. As a result,
the proposed plan was revised based on the prescribed, state pre-approved
configuration for the two landfill caps at OU1. Instead of 3-foot soil caps, the landfill
caps will at a minimum contain 1 foot of topsoil overlying a low-permeability layer.
These layers will be built on a 2-foot foundation layer. In addition to this minimum
requirement, the Navy will include a biotic barrier and possibly a drainage layer
between the impermeable layer and topsoil to protect the integrity of the impermeable
layer and drain percolated water off the cap. The biotic barrier will prevent burrowing
animals and deep plant roots from puncturing this layer. The drainage layer provides a
pathway for percolation to flow off the cap. Inclusion of the drainage layer will be
evaluated further during the RD. The Navy will also include gas venting beneath the
impermeable layer to prevent gas pressure build-up and horizontal subsurface gas
migration.
3.2.12 Other Written Comments
Mr. Walter E. Wallis. P.E.
There are some folks who speak of man's activities on earth as having raped that virgin earth. I have
news for them - in terms of "contamination," the earth was a confirmed harlot long before man came
on the scene. The La Brea Tarpits are hardly the result of any national defense program, yet their
presence has not deterred the development of Los Angeles. Water is an excellent solvent and the
prehistoric recipient of all the earth's debris, which included the whole gamut of organic and inorganic
possibilities, specifically including radioactivities. If the standards being applied to military base
cleanup were generally applied, then all asphalt paving and the underlying soil would have to be
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excavated and removed to a hazardous waste dump, and all graveyards receptive of embalmed corpses
would have to be encapsulated.
It is in this reality context, rather than in the Bambi Biology, Pinocchio Physiology and other Aquarian
'Sciences" that drives the latter day Mother Earth religion, that contamination cleanup must be
evaluated.
I would oppose a groundwater collection trench unless it can be demonstrated that the plume from any
dump constitutes either a threat to an aquifer that is currently being pumped or that the affected aquifer
is discharging contaminants into the bay waters in quantities and concentrations constituting a clear
and present danger to the biosphere. Geology suggests that any drinking water source contamination
is unlikely.
I oppose a soil cap, both because of the expense of establishing and maintaining such a cap, and
because a cap would halt whatever natural remediation processes that vegetation and efflorescence
might now be proceeding. If a cap is necessary for methane recovery, it should be paid for out of the
profits, if any, from sale of that methane.
If water can be pumped from the contaminated plume and used to irrigate the golf course and other
landscape features ofMqffett without causing harmful concentrations of materials, while at the same
time air scrubbing volatiles, this should be considered. This could perhaps be combined with use of
treated effluent from the adjacent Palo Alto treatment facility.
Monitoring should continue, both to determine whether some as yet unknown phenomena might
constitute a threat and to evaluate the progress of both natural bioremediation and to try any newly
developed assisted bioremediation.
The process of base cleanup being demanded, the unreal standards of what shall constitute clean and
the restriction on land reuse until remediation has been completed all have been structured not to solve
any threat to public health and safety, but to serve as the stinking albatross around this nation's neck
as punishment for policies that countered the demands of the aesthetically advantaged. I would far
rather spend scarce defense dollars on active measures of defense than for the expiation of imagined
sins.
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Response: The groundwater collection trench is proposed as a contingency and will be activated
only if contamination is found to be migrating towards surface water. This
contingency plan was developed considering the uses of the aquifer. The landfill caps
are necessary to contain and isolate the refuse, control hazards associated with landfill
gas and leachate, and comply with state regulations. These benefits outweigh any
potential benefits of leaving the landfills exposed to the surroundings.
Mr. Peter B. Newman
Thank you for inviting public comment on the proposed plans for OU1. First, my credentials:
although I live in Mill Valley, my parent's home is in Los Altos Hills. I have relatives in Palo Alto and
San Jose, and friends all over the South Bay. My father (deceased) was a naval engineer in the Pacific
in World War II. / have enjoyed the annual summer air show from Moffett ever since I was a kid. I
have nothing but positive feelings for the Navy and for Moffett Airfield, and by virtue of the above I
consider myself a neighbor of Moffett, albeit a very concerned one.
Having said all that, I will tell you that I am not a raving environmentalist either, but I am less than
impressed with the Navy's plan for the "cleanup". I have enclosed the ad from today's Chronicle
inviting this comment because, by serendipitous accident, on its backside is a news item about the
pollutions at McClellan Air Force Base. Also, I lived adjacent to the Presidio from 1984 to 1992, and
I saw repeated disregard for the environment, including the storage of leaking transformers [dioxin]
less than 500 feet from San Francisco Bay. My father's stories from his days in the Navy do not help
my confidence.
I hope my grandchildren will someday live in the South Bay, drink its waters, maybe even recreate in a
cleaned-up Bay. What you proposed is not a cleanup, but a burial. It's not even a decent internment
— those solvents will be in the groundwater (if they aren 't already) before my kids even have kids, and
they'll have to dig up the soil cap to remove and disable the carcinogens and heavy metals if we are
ever to have a healthy environment.
Although I support myself as a businessman, I have a strong streak of scientist in me; my favorite
magazine is Science News, and I often consider returning to UC Berkeley for an advanced degree in a
hard science. It may sound like science fiction to you, but there are emergent technologies (for
example, ultrahighsound, plasma ovens, etc.) that offer the real possibility of reducing dangerous
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molecules to their atomic components, and of reclaiming poisonous metals so they do not harm the
ecological life web. I wish that the Navy would consider spending some research dollars on figuring
out how to clean up the messes they (and the other armed forces) have left at bases all over America.
perhaps instead of just one missile on another unnecessary nuclear sub.
Response: The remedy was developed based on criteria such as implementability and cost-
effectiveness. Research has shown that the most cost-effective solution to landfill
contamination are based on containing wastes and monitoring at the landfill perimeter
for any migration from the landfill. If contaminant migration is detected, it can be
addressed through corrective actions such as subsurface collection trenches. Because
landfills are heterogeneous, excavation followed by treatment or in-place treatment are
not cost-effective solutions and can create hazardous working conditions. In addition,
landfill refuse treatment is difficult to implement because landfills are so
heterogeneous.
Comments from Harding Lawson Associates
Comment 1: We have concluded that the interpretations and conclusions presented in the OV1 FS
and repeated in the Proposed Plan are inadequately supported and that these
documents contain errors, omissions, and misrepresentations that must be corrected
before the documents can fairly represent either the nature and extent of contamination
at the two landfills, or appropriate and cost-effective site cleanup alternatives.
On the basis of our review, we recommend that the May 15, 1995, OV1 FS and the
May/June 1995 Proposed Plan be rejected or withdrawn, and that deficiencies in site
characterization and remedial planning be remediated before those two documents are
revised and reissued. In our opinion, this is the simplest and most straightforward way
of addressing the many problems that have been identified and of creating an easily
understood administrative record that fairly represents both the remedial RI/FS and the
final remedial selection. There does not appear to be any technical reason why this
approach would significantly delay the actual field implementation of remedial actions.
Contrary to this recommendation, we understand that EPA and California DISC staff
would prefer to accept the OU1 FS in its present form and attempt to remedy
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deficiencies through an additional specially established review, comment, and revision
process inserted between the end of the current formal PS/Proposed Plan public
comment period and creation of the draft ROD. It is our understanding that this
preference is motivated by a desire to maintain the current Moffett Field RJ/FS schedule
and allow listing of the OU1FS as "complete." Unless this represents preferential
treatment for the Navy, it appears that this approach will establish a new precedent for
approval of significantly flawed Superfimd deliverables that will be applicable to many
similar public and private Superfimd sites.
Successfully implementing such a deviation from established Superfimd protocols will
require establishing an enforceable framework for ongoing public review and comment
and an enforceable mechanism for continued revision of the Proposed Plan as
fundamental data gaps are filled and will result in some key data gaps, such as gaps in
required groundwater characterization, not being filled until after the ROD is
completed. This will require an enforceable and meaningful mechanism for community
input even after the ROD is completed. At this time, we do not understand how this
can be accomplished consistent with the basic Superfund principle that community input
is cut off after completion of the ROD.
Response: The overall strategy of capping the landfills, installing a gas interceptor trench,
installing a groundwater collection trench, and continuing groundwater and gas
monitoring (with corrective action contingencies) is an adequate approach to address
the OU1 landfills. None of the comments and questions received during the public
comment period have indicated that this remedial strategy is "significantly flawed."
The Navy will conduct additional field work to further investigate leachate migration at
Site 1. The outcome of this investigation will not influence the cap selection since the
Navy has also agreed to include low-permeability caps. Therefore, OU1 activities can
proceed with only minor modifications to the current schedule.
Comment 2: Concurrence with Comments of Others. HLA has reviewed comments, concerns, and
issues submitted by other individuals and groups, including:
August 28, 1995, comments of the THE RAB Committee for Moffett Field, a
community input forum established for Moffett Field cleanups,
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• June 14, 1995, comments from the City of Sunnyvale Department of Public
Works,
• June 4, June 12, and August 7, 1995, comments of the Cost Committee of the
RAB,
• August 10, 1995, outline of recommendations for closing Moffett Field
Landfills, submitted by community member Cynthia Sievers at the August 10,
1995, RAB meeting.
On the basis of our review of the listed documents, we have concluded that our
comments and concerns are all raised in one or more of these documents. Copies of
each of these documents are attached for reference. Rather than restate all of these
previously submitted comments, we simply confirm here that we concur with the factual
issues and questions raised by the earlier comment ors. We believe that all of these
issues and questions need to be adequately addressed before the OU1 FS and the
Proposed Plan will be adequate, and we note that adequately addressing some of these
issues and questions will require additional data collection, technical analyses, and/or
document revision.
Response: To avoid redundancy, please see the response to comments from the above-mentioned
commentors.
3.3 JANUARY 1996 PUBLIC MEETING COMMENTS AND RESPONSES
Comment 1: Mr. Tom Iwamurafrom the SCVWD asked about the material of construction for the
low-permeability layer.
Response: The low-permeability layer will likely be prefabricated and partially constructed from
synthetic materials. For example, the low-permeability layer may be a composite layer
of bentonite and polyethylene membrane. These types of synthetic layers are typically
more cost-effective than clay and are easier to construct. The specific construction
materials will be identified during the remedial design.
Comment 2: Mr. Stewart McGeefrom the City of Sunnyvale raised five concerns regarding the
revised proposal for OU1. Each concern is followed by a response, below. First, Mr.
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McGee was concerned that the revised proposed plan lacked detail regarding the data
gaps associated with groundwater surrounding Site 1.
Response: Concerns about the adequacy of the current groundwater monitoring network were
raised during the June 1995 public comment period. The groundwater monitoring
network is believed to be inadequate because, at a downgradient location along the
southwestern boundary of Site 1, no groundwater monitoring wells are present. RAB
members are concerned that leachate could be migrating from the landfill through this
unmonitored, downgradient area.
To address this concern, the Navy will conduct an additional groundwater investigation
in this southwestern area to evaluate leachate migration. The additional investigation
will be conducted in two phases. The first phase will include techniques to identify
underground sand layers that may serve as preferential migration pathways. This first
phase will also include collecting groundwater screening samples. Data from these two
activities (CPT and HydroPunch) will be used to locate permanent groundwater
monitoring wells. Phase II of the groundwater investigation will include installing and
sampling new groundwater monitoring wells. Data resulting from this field
investigation could trigger corrective action and the groundwater monitoring wells will
be incorporated into the long-term groundwater monitoring plan.
There is also concern that the station-wide ROD and remedial actions should be
postponed until the results of the field investigation are obtained. The overall strategy
of capping the landfills, installing a gas interceptor trench, installing a groundwater
collection trench, and continuing groundwater and gas monitoring (with corrective
action contingencies) is an adequate approach to address the OU1 landfills. This
activities can proceed as planned. The outcome of the investigation will not influence
the remediation strategy because the results can be incorporated into the groundwater
monitoring plan, which includes procedures to implement corrective action plans.
Therefore, any corrective actions identified as a result of the additional field
investigation can be integrated into the groundwater monitoring plan. Cap construction
is also independent of the results of the groundwater investigation because the Navy
has agreed to include low-permeability caps. For these reasons, the groundwater
investigation received little discussion in the revised proposed plan.
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Comment 3: Mr. McGee asked whether the Navy's financial responsibilities will be maintained even
if control ofMoffett Field is transferred to a municipal government or redevelopment
agency.
Response: Postclosure landfill maintenance and monitoring activities will be funded through
annual DoD environmental restoration budgets. These budgets are proposed by
NAVFAC headquarters in Washington D.C. and are approved as part of a total budget
package each year by Congress and the President. While congressional actions cannot
be anticipated, it is NAVFAC's responsibility to request the necessary money for the
upcoming fiscal year's environmental restoration work.
Comment 4: Mr. McGee raised concerns about the current and future O&M of the Moffett Field
subdrain system and the associated Building 191 pump station.
Response: Flooding of the northern portion of the base, which includes the northern end of the
airfield runways and landfills, could occur during the rainy season without continued
pump station operation. Therefore, appropriate institutional controls will be
implemented by the federal government to assure continued O&M of the pump station
and drain system. While Moffett Federal Airfield remains federally-owned land, the
necessity of continued O&M of the pump station shall be noted in the Master Plan for
the government's land uses and, if still necessary in the event of any conveyance of the
property, the required pump station O&M will be addressed by appropriate notices and
land use covenants binding on subsequent property owners.
Comment 5: Mr. McGee stated that the City of Sunnyvale agrees that radiological information
should be collected for the OU1 landfills.
Response: The Navy has included a radiological survey in plans for future field work.
Comment 6: Mr. McGee stated that community participation should be continued during cleanup
activities at Moffett Field.
Response: The Navy supports and encourages continued public participation during the RD/RA
through the Moffett Field RAB, by individual citizens, or by interested groups. The
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Navy will continue to inform the RAB of progress throughout the RD/RA in
accordance with EPA guidance.
Comment 7: Ms. Leslie Byster ofSVTC stated that SVTC members were concerned about continued
public participation. In addition, Ms. Byster indicated that SVTC believes that the
Navy should be held to a cleanup standard that allows complete flexibility in the future
land use. She pointed out that this concern was also shared by a former naval officer
and the Sisters of Notre Dame.
Response: To allow maximum flexibility regarding future land use, the refuse in the OU1 landfills
would have to be excavated, transported, possibly treated, and redisposed into another
landfill. This strategy is rarely pursued for landfill remediation because extreme costs
and hazardous working conditions make landfill excavation and redisposal impractical.
For landfills, research has shown that the most cost-effective solutions to landfill
contamination are based on containing wastes and monitoring at the landfill perimeter
for any migration from the landfill.
Comment 8: Ms. Cynthia Sievers of the LWV expressed concerns regarding groundwater data gaps,
Building 191 O&M, continued public participation, and adequacy of data.
Response: Please see the responses to comments 2 through 7 in this section.
Comment 9: Mr. Lenny Siegelfrom the Pacific Studies Center spoke about several issues. He first
stated that he believed that Moffett Field serves as a model for public participation. He
also indicated that OU1 raises important issues surrounding the relationship of cleanup
and future use of property. He stated that the community should have Jull flexibility
regarding reuse, even if the Building 191 pump station is turned off.
Response: Please see the responses to comments 4 and 7 above.
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3.4 JANUARY 1996 WRITTEN COMMENTS AND RESPONSES
3.4.1 Comments from the City of Mountain View
Comment 1: The City of Mountain View continues to be vitalfy interested in the cleanup efforts
currently underway at Moffett Federal Airfield. It is the City's position that OUJ and
all contaminated sites at Moffett Federal Airfield be cleaned up to a level that will allow
for the maximum flexibility for future land use and meet all health and safety standards.
Response: The Navy's selected remedy meets all applicable regulations and standards. However,
to allow maximum flexibility regarding future land use, the refuse in the OU1 landfills
would have to be excavated, transported, possibly treated, and redisposed into another
landfill. This strategy is rarely pursued for landfill remediation because extreme costs
and hazardous working conditions make landfill excavation and redisposal impractical.
For landfills, research has shown that the most cost-effective solutions to landfill
contamination are based on containing wastes and monitoring at the landfill perimeter
for any migration from the landfill.
Comment 2: The City of Mountain View has concerns regarding the Navy's long-term commitment
for the cleanup of OUI and other contaminated sites at Moffett Federal Airfield. The
City is interested in knowing the mechanism the Navy will use to provide adequate
financial resources for the long-term cleanup of OUJ and other contaminated sites at
Moffett Federal Airfield.
Response: The cleanup of OUI and other contaminated sites at Moffett Field will be funded
through annual DoD environmental restoration budgets. These budgets are proposed
by NAVFAC headquarters in Washington D.C. and are approved as part of a total
budget package each year by Congress and the President. While congressional actions
cannot be anticipated, it is NAVFAC's responsibility to request the necessary money
for the upcoming fiscal year's environmental restoration work.
Comment 3: The City also has concerns regarding the methodology for groundwater sampling
contained in the draft field work plan for OUJ. Groundwater samples should be taken
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at every HydroPunch. Groundwater sampling should not be limited to areas where
only permeable layers exist.
Response: . Groundwater sample collection is not proposed for impermeable layers because
groundwater flow and contaminant migration are typically not significant through such
layers. Groundwater sampling will be focused on permeable layers where
contaminants are more likely to migrate significant distances. In addition, it is often
difficult and time-consuming to collect enough groundwater for analysis from a
subsurface location with low permeability.
3.4.2 Comments from California Integrated Waste Management Board
Comment 1: The proposed capping configuration shown on Figure 4 contains multiple layers with
no dimensions. Staff is concerned about the excessive loading of the landfill slopes
with all this material. The vegetative, biotic. and drainage layer can be combined into
one 12 inch layer that would meet state standards. Please justify the need for the
additional layers that are in excess of the state standards and show that the additional
load on the landfill slopes will not cause a stability or settlement problem.
Response: The justification for the additional layers was provided in the first response to CIWMB
earlier comments in Section 3.2.11. The Navy would be interested in any information
regarding the combined 12-inch vegetative, biotic, and drainage layer and requested
further information from CIWMB. Slope stability and settlement will be evaluated and
a geotechnical report will be prepared. The cap will then be designed to mitigate any
slope stability and settlement concerns identified in the report.
Comment 2: No basis for the Cost Comparison, shown on Table 1 was provided. Please provide a
cost estimate to justify the cost comparison on Table 1.
Response: The cost estimate details will be sent to CIWMB.
Comment 3: It has not been shown that the proposed control measure of landfill gas venting will not
pose a potential health threat. Please provide modeling and risk assessment data to
show that the vents will not pose a potential threat.
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Response: At Site 1, landfill gases will be collected in the gas venting layer and vented to the
atmosphere by riser pipes extending from the gas venting layer, through the cap, and to
the surface. Each riser pipe outlet can be positioned several feet above the breathing
zone to mitigate any possible inhalation hazards.
3.5 MARCH 1997 PUBLIC MEETING COMMENTS AND RESPONSES
Mr. Kevin Woodhouse, Environmental Management Coordinator for the City of Mountain View,
stated that the City of Mountain View would provide comments before the end of the comment period.
3.6 MARCH 1997 WRITTEN COMMENTS AND RESPONSES
3.6.1 Comments from the City of Mountain View
Comment 1: The Draft OU1 Alternatives Analysis Technical Memorandum states that landfill Site 2
"reportedly received wastes from maintenance operations such as scrap equipment,
paint and paint thinners, solvents, lacquer, ash, asbestos, jet fuels, waste oil, fuel
filters, transformer oils and filters, and sawdust contaminated with pofychlorinated
biphenyls (PCBs)" (Page 6). Handling and treatment procedures of such hazardous
wastes should be thoroughly addressed in a health and safety plan prior to excavation
and should comply with all applicable state and federal regulations.
Response: Appropriate health and safety precautions will be observed during construction.
Pertinent regulations concerning procedures for handling hazardous wastes discovered
at Sites 1 and 2 are incorporated in the ROD.
Comment 2: Although PG&Es easement agreement with the Navy requires PG&E to be responsible
for relocating, if necessary, the high-pressure gas main running through OU1, this
possible turn of events could significantly impact the project. Has an evaluation of
project scheduling and (indirect) cost impacts been done in the event the pipeline must
be relocated?
Response: This contingency, while possible, is not considered likely. Consequently, resources
have not been expended to evaluate potential changes to the project schedule and
budget to account for PG&E relocating the pipeline.
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Comment 3: Ifdewatering during excavation reveals contamination levels exceeding regulatory
criteria, how will this contaminated water be handled and treated?
Response: Handling and treatment of groundwater containing contaminant levels that exceed
regulatory criteria will depend on the contaminant concentrations. Discharge to the
Sunnyvale POTW may be possible if concentrations meet POTW discharge
requirements. Other treatment methods such as treatment using granular activated
carbon may be employed depending on the observed groundwater characteristics.
Comment 4: The proposal indicates that the Navy will monitor groundwater for a minimum of 3
years to confirm that groundwater quality is not affected (Page 13). This monitoring
period should be for as long as required by state and federal oversight regulatory
agencies beyond the 3-year minimum.
Response: The Navy will consult with EPA and the state before groundwater monitoring ceases at
Site 2.
Comment 5: The cost estimate for consolidation versus capping includes a margin of error from 50
percent above to 30 percent below. A more accurate cost comparison should be
developed prior to making a final decision on the remedial action alternative to be used
at the site. Does the existing estimate factor in increased capping cost at Site 1 to
handle the additional volume from Site 2 wastes? Increased costs for operating a
CAMU? Increased benefit from having more flexibility with the land use on Site 2?
Response: The cost estimates for the alternatives were prepared to the accuracy specified by EPA
guidance and are suitable for remedy selection. The small amount of waste expected to
be added from Site 2 to Site 1 is not anticipated to have any effect on the Site 1 cap
cost within the accuracy of the estimate. The CAMU does not result in additional
costs. The monitoring, closure, and postclosure activities proposed for Site 1 will
incur the same costs, regardless of the CAMU. No additional costs for CAMU
operation are expected. The potential increased land value at Site 2 was not considered
in the cost analysis for the consolidation alternative.
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Comment 6: Operation of a CAMUfor remediation wastes at Site 1 should be done in compliance
with all applicable state and federal regulations, as should closure and postclosure
maintenance of the Site 1 landfill.
Response: The Navy will follow pertinent regulations concerning procedures for creating a
CAMU as well as for closure and postclosure activities as incorporated in the ROD.
3.6.2 Comments from Mr. Thomas Iwamura, SCVWD
We have reviewed the revised plan on the remedy for OU1 and we are in concurrence with your plan of
consolidating the two landfills at the Site 1 landfill.
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4.0 REFERENCES
California Base Closure Environmental Committee (CBCEC). 1994. Long-term Ground Water
Monitoring Program Guidance. March.
California Integrated Waste Management Board (CIWMB). 1995. Letter from Diane Nordstrom to
Joseph Chou (DTSC) regarding applicable or relevant and appropriate requirements (ARARs)
forOUl. February 18.
California Regional Water Quality Control Board (RWQCB). 1996. Letter from Michael Rochette of
RWQCB to Stephen Chao of Engineering Field Activity West regarding reuse of City of Palo
Alto dredge material. August 15.
International Technology Corporation (IT). 1989. Solid Waste Assessment Test. Naval Air Station,
Moffett Field,' California. March.
IT. 1992. Air Solid Waste Assessment Report, Naval Air Station, Moffett Field, California. August.
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