PB95-963109
                              EPA/ESD/ROf-90/125
                              February 1995
EPA  Superfund
      Explanation of Significant Difference
      for the Record of Decision:
       Fairchild, Intel, and Raytheon Sites
       (MEW Study Area), Mountain View, CA
       September 1990

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FAIRCHI:LD, I:UEL, AND RAYTHEON SI:TES
KI:DDLEFI:BLD/ELLI:S/WHI:SHAH (HEW) STUDY AREA
KOUN'l'AI:N VI: 0 , CALI:FORNI:A
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EXPLANATI:ON OF SI:GNI:FI:CANT DI:FFERENCES
United states Environmental Protection Aqency
Reqion I:X -- San Francisco, california
September 1990

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Fairchild, Intel, ,and Raytheon Sites
Middlefield/Ellis/Whisman Study Area
Mountain View, California
EXPLANATION OF SIGHZP'ICAN'r DIFFERENCES
I.
INTRODUCTION
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The purpose of this document is to explain the significant.
differences between the Record of Decision (ROD) signed by the
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U.s. Environmental Protection Ag~ncy (EPA) on June 9, 1989 and
the remedy that will be implemented at the Middlefield/Ellisl
Whisman study Ar~a (MEW Site).
Under Section 117 of the
Comprehensive Environmental Response, Compensation, and Liability
Act of 1980" as amended by the Superfund Amendment and
Reauthorization Act of 1986 (CERCLA), 42 U.S.C. S 9617, EPA is
required'to publish an Explanation of Significant Differences
(ESD) whenever a significant change is made to a final remedial
action plan.
This document provides a brief background on the
MEW Site, describes the change to the ROD that EPA ,is now making
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, and explains the ways in which this change affects implementation
of the remedy selected by EPA in June of 1989.
Based on the technical data in the administrative record,
EPA is changing the ROD to provide that the numerical standards.
characterized as "goals" in the original ROD are final cleanup
"standards".
This change is made to clarify and ensure that EPA
is selecting in the ROD a specific remedial action rather than
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deferring to a later date to set these standards.
EPA is issuing
this ESD to effectuate this change in lieu of amending the ROD
because the change does not result in a fund~ental change to the
overall remedy selected in the June 9, 1989 ROD.
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II.
BACKGROUND
site Name and Location.
The MEW Site is located in
A.
Santa Clara County in the City of Mountain View, California.
The
MEW site is divided into a Local study Area (LSA) and a Regional
study Area (RSA).
Figure 1-1 identifies the LSA and RSA, along
with local roads and landmarks.
The LSA consists of (i) two
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National Priority List (NPL) sites:
Intel Corporation (Intel)
and Raytheon Company (RaYtheon); (ii) one proposed NPL site:
Fairchild Semiconductor Corporation (Fairchild); and (iii)
several non-NPL sites.
The LSA encompasses about 1/2 square mile
of the RSA and contains primarily light industrial and commercial
areas, with so~e 'residential areas' west of Whisman Road. The RSA
encompasses approximately 8 square miles and includes Moffett
Naval Air Station (another NPL site) and NASA Ames Research
Center, along with light industrial, commercial, agricultural,
residential, recreational, and municipal land uses.
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Various owners or occupants in the. area around the
intersection of Middlefield Road, Ellis street, Whisman Road, and
the Bayshore Freeway (U.S. Highway 101), are or were involved in
the manufacture of semiconductors, metal finishing operation,
parts cleaning, aircraft maintenance, and other activities
requiring the use of a variety of chemicals.
Local facilities
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with current occupants are presented in Figure 1-2.
Site
investigations at several of these facilities have revealed the
presence of toxic chemicals in the subsurface soils and iri the
groundwater.
B.
Identification of Lead and SUDDort Aaencies.
Since May
1985, EPA~has been the lead agency at the MEW Site.
The
California Regional Water Quality Control Board - San Francisco
. Bay Region (RWQCB) and the California state Department of Health
Services (DHS) are the support agencies for the MEW Site.
C.
Circumstances.
During negotiations with Potentially
. Responsible Parties (PRPs) to implement. the remedy selected by
EPA in the June 9, 1989 ROD, EPA.determined that the language
contained in the ROD and in the administrative record concerning
the selected remedial action was ambiguous.
EPA is issuing this
ESD to clarify that it has selected a remedial action with final
cleanup staQdards for the MEW Site.
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D.
statement Reqar?inq the Administrative Record.
This
ESD will become part of the Administrative Record file located
at:
U.s. Environmental Protection Agency, Region IX
Superfund Records Center
75 Hawthorne street -
San Francisco, CA 94105
Hours: M-F 8:00 a.m. - 4:30 p.m., and
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Mountain View Public Library
585 Franklin street
Mountain View, CA 94041.
Hours: M-TH 10:00 a.m. - 9:00 p.m.
F, Sat., and Sun. 10:00 a.m. - 6:00 p.m.
E.
Site Historv.
During 1981 and 1982, preliminary
investigations of facilities within the LSA found significant
concentrations of contaminants in the soil and the groundwater. .
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By 1984, the Fairchild, Intel, and Raytheon Sites 'were proposed
for inclusion on the federal National Priorities List (NPL).
Intel and Raytheon were listed on the NPL in June 1986.
In 1985,
under the direction of the RWQCB, five companies within the LSA'.""
[Fairchild; Intel; Raytheon; NEC Electronics, Inc. (NEC); and
Siltec. Corporation (Siltec)] initiated a joint investigation to
document and charaqterize the distribution of chemicals emanating
from their facilities.
In April 1985, the RWQCB adopted Waste
Discharge Requirements for each of the five companies.
On August 15, 1985, Fairchild, Intel, and Raytheon entered
into an Administrative Consent Order with EPA, the RWQCB, and the
DHS.
Under the terms of the Consent Order, the three companies
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conducted a Remedial Investigation and Feasibility Study (RI/FS)
of the contamination emanating from the LSA.
Prior to and during
site investigations, the companies conducted interim cleanup
activities at the MEW Site.
These interim remedial actions
included tank removals, soil removal and treatment, well sealing,
construction of slurry walls, and treatment of groundwater from
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several extraction wells.
NEC and siltec declined to enter into
the Administrative Consent Order.
The RI was concluded in July 1988.
A draft Feasibility
Study and EPA's Proposed Plan were presented to the community for
a 60-day review and public comment period beginning in November
1988.
In May 1989, Special Notice Letters for the Remedial
Design/Remedial Action. (RD/RA) Consent Decree were "sent out to
Fairchild, Intel, Raytheon, NEC, Siltec, and twelve (12) other
PRPs.
EPA signed the ROD on June 9, 1989.
F.
Nature and Extent of Contamination.
Industrial
activities conducted with~n the MEW Site required the storage,
handling, and use of a large number of chemicals, particularly
solvents and other chemicals used in a variety of manufacturing"
processes.
Significant quantities of volatile organic chemicals
were used for degreasing, process operating, and general
maintenance.
Product and waste solvents and other chemicals were
piped and stored in underground tanks, pipelines, and sumps.
Chemical releases occurred, for the most part, below the ground
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surface and migrated downward into the aquifer system.
presence of these chemicals in the subsurface soils and
The
groundwater is primarily the result of leaks from the subsurface

tanks and lines, sumps, chemical handling and storage areas, and
utility corridors.
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Investigations at the MEW site have re~ealed the presence of
over 70 chemical compounds in the groundwater, surface water,
sediments, and 'subsurface soils. Three major classes of
chemicals were investigated during the RI:
(i) volatile organic
compounds, (ii) semi-volatile acid and base/neutral extractable
organic compounds, and (iii) priority pollutant metals.
Of these
three classes, volatile organics' were found to be the most
pr~valent. 1
Since over 70. chemicals were detected at the MEW Site, a
subset of 15 key chemicals of primary concern was selected in
order to focus on those contaminants that were most "likely to
pose risks to' human health; welfare, and the'environment. The
chemicals of primary concern consist of 11 organics of concern
and 4 inorganics of concern. Of these 15 chemicals of primary
concern, trichloroethene (TCE) is the predominant chemical found
at the MEW Site. EPA's decision to designate only 15 chemicals
as "chemicals of primary concern" was based in part on the
assumption that the sampling provided a complete picture of the
actual contamination in the groundwater (generally, chemicals
detected in less than 5% of the samples extr~cted are not
considered to be "chemicals of primary concern"). Once
implementation of the remedy has begun, the groundwater beneath
the MEW site will be monitored periodically for the chemicals
that have not been designated as chemicals of primary concern to
ensure that no areas of high chemical concentration have gone
undetected, that the calculations of health-based ri~ks remain
valid, and that the remediation is effective.
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An extensive area of. groundwater contamination has been
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defined in the RI and is'presented in Figure 2.
CUrrent MEW Site
data indicate that chemicals are present primarily in the A, B1,
and B2aquifer zones.
Chemicals have also been detected in
localized areas of the B3, C, and deeper aquifer zones.
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Subsurface soil contamination has been found at the
Fairchild, Intel, and RaYtheon facilities, along with the
facilities of other PRPs within the RSA.
G.
DescriDtion of the June 9. 1989 ROD.
Soil Remediation.
In the June 9, 1989 ROD, EPA's
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selected so~l remedy is in-situ vapor extraction with treatment
.py.vapor phase granular activated. carbon, andexc;:avation .with
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treatment by aeration.
In the ROD, EPA established a cleanup
goal for soils of 1 part per million (ppm) trichloroethene (TCE)
for soils inside of existing slurry walls and 0.5 ppm TCE for
soils outside of the slurry walls. . Chemicals found in the
subsurface soils were generally similar to those found in
adjacent groundwater samples.
As part of the RD/RA, some
additional soil investigation may be necessary in certain areas
to ensure the effectiveness of the remedy.2
2 Since TCE was the predominant chemical at the MEW Site,.
. it was selected as the indicator chemical to monitor the extent
of soil contamination and the progress of soil remediation for
all chemicals at the MEW Site. Because other chemicals present
in the subsurface soils may not be commingled with TCE and may
act as a continuing source of contamination to the groundwater,
it will be necessary to closely monitor the remediation of the
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2.
Groundwater Remediation.
In the June 9, 1989 ROD,
EPA's selected groundwater remedy is extraction and treatment.
Extracted groundwater will be treated usin~ air stripping towers.
Airborne emissions will meet all Bay Area Air Quality Management
District emissions standards.
It~is anticipated that emission
controls utilizing granular activated carbon will be required
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once the full remedy is implemented.
The extracted groundwater
will be reused to t~e maximum extent feasible, with a goal of
100% reuse.
Extracted water which cannot be reused will 'be
discharged to local streams.
Allowable discharges to local
streams will be regulated by the National Pollutant Discharge
Elimination System (NPDES) of the Clean Water Act.
,In the June. 9, 1989 ROD, 'EPA set groundwater cleanup goa~s
of 5 parts per billion (ppb) TCE for the shallow aquifers (which
are not currently used for drinking water) and 0.8 ppb TCE for
the deep aquifers (which are used for drinking water).
The
shallow aquifer cleanup goals also applied to the aquifers inside
the slurry walls..
Although over seventy chemicals have been detected in the
soil and groundwater at the MEW Site, TCE is the predominant
chemical.
Therefore, TCE is ~sed as a broad indicator of the
soils to ensure that all chemicals are remediated so that their
respective concentration levels are at or below applicable or
relevant and appropriate requirements (ARARs) and do not exceed
maximum cumulative risk levels.
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size and extent of contamination.
The ratio of TCE to other
chemicals found at the MEW Site is high, enough such that when TCE
is reduced to the cleanup level of 5 ppb in the shallow aquifers
and 0.8 ppb in the deep aquifers, it is assumed that the other
chemicals found at the MEW site will be reduced to concentrations
that meet applicable or relevant and appropriate requirements
(ARARs) and do not exceed maximum cumulative risk levels.]
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] With respect to the organic chemicals found in the
groundwater, EPA selected a health-based cleanup strategy that
provided (i) for carcinogens, a cumulative excess lifetime cancer
risk no greater than 10-5 for the shallow aquifers and 10-6 for
the deep aquifers, and (ii) for n9n-carcinogens, levels
protective of human health, welfare, and the environment based on
ARARs and reference doses. Selecting 5 ppb and 0.8 ppb as, the
cleanup levels for TCE in the shallow and deep aquifers,
respectively, was based on the assumption that by reducing the
concentrations of TCE to these levels the concentrations of the
other chemicals at the 'MEW Site would be proportionately and
,correspondingly reduced to: (i) levels with risks low enough to
meet a cumulative excess lifetime cancer risk no greater than 10-
5 for the shallow aquifers and 10-6 for the deep aquifers, and
(ii) levels at or below ARARs or levels based on reference doses
for non-carcinogens in the shallow and deep aquifers. If the
levels of the various chemicals are not reduced at the same rate
as TCE or if some of the existing chemical compounds begin to
transform into more toxic compounds at a rate faster than'
anticipated, then EPAls assumption that TCE accurately acts as an
indicator chemical may need to be re-assessed. Thus, chemical
concentrations will be monitored throughout' the RD/RA process to
assess the validity of EPA's underlying assumptions and to
determine whether TCE remains an appropriate indicator chemical
for reducing concentrations of the other chemicals.
Because data gathered to date on the inorqanics found at the
MEW site are somewhat limited, EPA decided that it would be
premature to exclude the inorganics from the list of chemicals of
primary concern. Four inorganics were selected as chemicals of
primary conQern, but were analyzed as a group rather than
individually. The four inorganics of concern will be monitored
throughout the RD/RA process to ensure that no isolated
concentrations of these chemicals remain undetected and that
adequate data are available for. any future evaluation of the
risks posed by the presence of these chemicals.
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Should this assumption be proven to be false, the other chemicals
of primary concern found in the soil or groundwater at the MEW
Site are to be remediated so that their respective concentration
levels are at or below ARARs and do not exceed maximum cumulative
risk levels".
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. 3.
Sealinq of Potential Conduit Wells.
The remedy
includes the identification and sealing of any potential conduit
wells.
Several abandoned aqriculture wells that acted as
conduits for contamination to migrate from the shallow aquifers
to the deep aquifers have already been sealed.
Additional wells
have been identified for sealing and others may be identified
which will also require sealing.
4.
Maintenance of Slurry Walls.
The remedy also
includes maintaining inward and upward hydraulic gradients inside
of the slurry walls and monitoring the integrity of each slurry
wall system.
Maintaining inward and upward hydraulic gradients
by" pumping inside of the slurry walls will prevent contaminants
from escaping in the event the slurry walls fail~
Selected wells
will be monitored for chemical concentrations and water levels.
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III. EXPLANATION OF SIGNIFICANT DIFFERENCES
This ESD supersedes and clarifies certain points set forth
in EPA's ROD dated June 9, 1989.
Briefly, 'and as explained in
qreater detail below, this ESD ad6resses the followinq issues:
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1.
The cleanup -qoals" established for both qroundwater
and soil contamination at the MEW Site are hereby set
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as final cleanup standards. .
2.
In determining whether future changes should be made to
the ROD, EPA will consider all legally applicable and
appropriate criteria.
3.
If EPA determines that an amendment to the ROD is
necessary, EPA will follow all required procedures,
including the public notice and comment procedures
required by Section 117 of CERCLA, 42 U.S.C. S 9617.
A.
CleanuD Standards.
As discussed in detail in the ROD,
EPA selected remedial actions for both soil and qroundwater
contamination.
The remedy selected for soil contamination is in-
situ vapor extraction with treatment by vapor phase granular
activated carbon, and excavation with treatment by aeration.
EPA
specified two cleanup qoals for soils: 1 ppm TCE for soil inside
of slurry walls located on the Raytheon and Fairchild facilities,
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and 0.5 ppm TCE for all other soils located on the MEW site.
In addition, EPA selected groundwater extraction and
treatment to address the groundwater contamination.
EPA
specified two cleanup goals for groundwater:
5 ppb TCE for the
shallow aquifers and 0.8 ppb TCE for the deep aquifers.
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EPA expressed these cleanup levels as goals because it
recognized that there is an uncertainty as to what actual cleanup
levels will be achieved during the implementation of the remedial
action.
However, this uncertainty inherently exists at many
Superfund sites that are implementing groundwater extraction
treatment remedies or innovative tre~tment technologies.
Accordingly, uponre-evaluation of the administrative record, EPA
has now determined that there is a sufficient basis for changing
the "cleanup goals" established in the ROD to "final cleanup
standards."
A basis for making this change is EPA's
determination that there is insufficient information at this time
to invoke a.waiver of statutorily required. cleanup standards,
pursuant to Section 121(d) (4) of CERCLA, 42 U.S.C. S 9621(d) (4).
Under Section 121 of CERCLA, 42 U.S.C. S 9621, and the
National oil and Hazardous Substances Pollution Contingency Plan
. CNCP), 40 C.F.R Part 300, EPA is required to select a remedy that
is protective of human health and the environment and that meets
all ARARs.
EPA can only select a remedy that does not meet an
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ARAR if it formally invokes a waiver based on at least one of the
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six factors set forth in Section 121(d) (4) of CERCLA, 42 U.S.C. S
9621(d) (4).
One of these six factors allows a waiver when the
remedy selected is "technically impracticable from an engineering
perspective" [See Section 121(d) (4) (C) of CERCLA, 42 U.S.C. S
9621(d) (4) (c)].
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The authority of EPA to invoke an ARAR waiver based on
"technical impracticability" is limited under'CERCLA. . The use of
the term "impracticable" implies that remedies that are not
demonstrated but that are thought to be feasible cannot be
eliminated because of this waiver.
This waiver should be used in
cases where:
(i) neither existing nor innovative technologies
can reliably' attain the.ARAR in' question, 'or ("ii) attainment of
the ARAR in question would be illogical or infeasible from an
engineering perspective [53 Federal Register 51439 (December 21,
1988)].
Accordingly, based on its re-evaluation of the
administrative record, EPA has determined that there is
insufficient information to. invoke a waiver to ARARs at the MEW
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Site at this time.
Although EPA's original ROD did not formally invoke a
waiver, the Feasibility Study, which is included as part of the
.administrative record, provides that final cleanup standards will.
depend upon the "technical practicability" of achieving those
goals.
EPA, through this ESD, is clarifying that it will
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consider technical practicability or impracticability as a factor
in evaluating whether in the future it should formally invoke a
waiver of an ARAR.
EPA will make such an evaluation, if
appropriate, on the basis of information qenerated during the
Remedial Action phase of the remedy.
:In summary, this ESD supersedes the June 9, 1989 ~OD by
setting final cleanup standards that represent the technical
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parameters of its chosen remedy and therefore are present
enforceable obligations for the MEW Site.
B.
Future Chanaes to the Selected Remedv.
When EPA
selects a remedy for a Superfund site, at a minimum, it must
ensure that the remedy is protective of human health and the
environment, complies with all ARARs (or the record supports a
waiver), utilizes permanent solutions and alternative technology
to the 'maximum extent practicable, and satisfies the statutory
preference for treatment as a principal element (See Section 121
of CERCLA,42U.S.C. S 9621).
EPA selects this remedy based on,
the information in the administrative record.
The administrative record for the MEW ROD and for many
Superfund sites contains data that indicate that there is some
degree of uncertainty as to whether the chosen technologies will
be able to achieve the cleanup standards specified.
EPA
acknowledged in the Proposed Plan for the June 9, 1989 ROD that
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"[c]leanup goals do not necessarily represent the actual 'cleanup
levels' that are eventually achieved, because the effectiveness
of the remedy can only be determined during implementation
[Remedial Action Phase] of the remedy."
(See, Proposed Plan page
7).
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As discussed above, EPA is now changing the June 9, 1989 ROD
by now specifying final cleanup standards rather than just goals.
EPA is making this change because it has determined that there is
insufficient information at this time to invoke a waiver to
ARARs .
However, EPA continues to recognize that it is always
possible that the chosen remedy will be demonstrated to.be
unattainable.
Therefore, EPArecognizes that if data are
.generated that demonstrate t:-hat the selected 'remedy cannot be
achieved, EPA may need to reconsider its decision embodied in the
ROD.
In addition, there are other reasons that could lead EPA to
determine that.the ROD should be changed. . Under Section 121(c)
of CERCLA, 42 U.S.C. S 9621(c), EPA is required to review every
five years all Superfund sites where hazardous substances remain
on the site to ensure that human health and the
environment are
protected.
Therefore, it is possible that EPA may determine that
a 'remedy 'selected in the ROD'should be changed to provide for'
even greater protection to human health and the environment.
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EPA recognizes that new information may be generated during
the RD/RA process that could affect the remedy selected in the
ROD.
This information, which may be developed by the PRPs,
support agencies, public, or EPA, may form the basis for a
proposed amendment to the ROD or an ESD.
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In determining whether
a change to the ROD is appropriate, EPA will consider all legally
applicable requirements.
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C.
Process for Future Amendments to the ROD.
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If new
information is submitted by the public, PRPs, the support
agencies, or developed by EPA during the implementation of the
remedial action, EPA may reconsider the hazardous waste
management approach selected in the ROD.
If EPA determines that
the ROD should be changed it will follow all applicable
requirements, including'those of Section 1.1.7 of CERCLA, 42 U.S.C.
S 961.7.
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Daniel W. McGovern
~egional Administrator
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