United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R09-91/064
September 1991
Superfund
Record of Decision:
Mesa Area Ground Water
Contamination, AZ
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50272.101
REPORT DOCUMENTATION 1'. REPORT NO. I~ 3. A8dpIenI'I Acce88ion No.
PAGE EPA/ROD/R09-91/064
4. TIlle and SI.f31Iae 5. Report Date
SUPERFUND RECORD OF DECISION 09/27/91
Mesa Area Ground Water Contamination, AZ
6.
First Remedial Action - Final
7. Author(a) 8. Perfonnlng Organization Rept. No.
g. Perfonnlng Org8lnlza1lon Nama and Add- 10. ProjectlTuklWork Unit No.
11. Contraet(C) or Grant(G) No.
(C)
(0)
12. Sponaorlng Organization Name and AcIchu 13. Type 01 Report & Period Covered
U.S. Environmental Protection Agency 800/000
401 M Street, S.W.
Washington, D.C. 20460 14.
15. SUpplementary Notel
16. Ab81ract (UrnI1: 200 WOrdl)
The 80-acre Mesa Area Ground Water Contamination site is a semiconductor manufacturing
facility in Mesa, Maricopa County, Arizona. Land use in the area is predominantly
industrial and residential. The site overlies two aquifers: a Lower Alluvial Aquifer
(LAA), which is used by the residents of Mesa as a drinking water source, and an Upper
Alluvial Aquifer (UAA). Since 1966, Motorola, Inc., has used the site for the
production of semiconductors and the storage of chemicals in an underground storage
system. Onsite manufacturing processes involve the use of solvents, acids, and bases.
In 1983, Motorola identified VOCs, including TCE, in ground water originating from the
LAA. Subsequent investigations by Motorola revealed high levels of VOC-contaminated
soil in the main chemical handling area, and VOC and chromium contamination in the
UAA. From 1983 to 1987, Motorola performed a partial closure of the underground waste
solvent storage system under RCRA authority. In 1984, Motorola installed ground water
monitoring wells, later converted these into extraction wells, and pumped contaminated
ground water from the UAA. Since 1987, as a result of Motorola's actions,
contamination levels have been consistently below MCLs. However, by 1991, the
contaminated ground water plume had migrated to over 1 mile southeast of the site. In
(See Attached Page)
17. Document Analylil L DelcrfplOlI
Record of Decision - Mesa Area Ground Water Contamination, AZ
First Remedial Action - Final
Contaminated Media: soil, gw
Key Contaminants: VOCs (PCE, TCE)
b. IdentilieralOpen-Ended Tenna
c. COSA TI FleldlGrcq>
18. Availability Statement 111. Secu11y a... (ThI1 Report) 21. No. 01 Pagea
None 42
20. Secu11y CIIII (Tbll Page) 22. PrIce
tJI\no
(See ANSI-Z39.18) s.. ",.1ruCti- on ~- ut' 72 (4-17)
(Fonner1y NTlS-35)
Department 01 Commerce
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EPA/ROD/R09-91/064
Mesa Area Ground Water Contamination, AZ
First Remedial Action - Final
Abstract (Continued)
1991, EPA dropped the Mesa Ground Water Contamination site from the NPL and referred
the site to the RCRA program because the site is a RCRA facility, the ground water
contamination is solely from the Motorola facility, and no public drinking water
supply wells have been contaminated. This action will be implemented by the PRP under
State supervision, and incorporated as a component of the Corrective Action Plan under
RCRA. This Record of Decision (ROD) documents final remediation of contaminated soil
and ground water. The primary contaminants of concern affecting the soil and ground
water are VOCs including PCE and TCE.
The selected remedial action for this site includes treating shallow onsite soil using
soil vapor extraction, controlling VOC emissions using carbon adsorption, followed by
offsite disposal of carbon residuals; onsite and offsite pumping of contaminated
ground water; treating the ground water onsite using vacuum degasification, followed
by carbon adsorption to remove VOCs; discharging the treated water from the degasifier
to the deionized water treatment plant for reuse in manufacturing and other facility
processes; disposing of remaining wastewater at a publicly owned treatment works
(POTW); and rehabilitating two deep industrial ground water supply wells to prevent
them from acting as conduits for contaminant plume migration from the upper to the
lower aquifer. The estimated present worth cost for this remedial action is
$7,144,000, which includes an annual O&M cost of $581,000 for 13 years.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific soil clean-up goals are based on
State st~ndards, and include PCE 14 mg/kg. Chemical-specific ground water clean-up
goals are based on SDWA MCLs, and include PCE 5 ug/l and TCE 5 ug/l.
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MESA AREA
GROUNDWATER CONTAMINATION SITE
RECORD OF DECISION
u.s. EPA
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I.
II.
10.
11.
Mesa Area Groundwater contamination site
Table of contents
Declaration
...........................................1
1.
site Name and Location
...........................1
2.
statement of Basis and
Purpose. . . . . . . . . . . . . . . . . .. 1
3.
Assessment of the site
...........................1
4.
Description of the Selected Remedy............... 1
5.
statutory Determinations......................... 2
Decision Summary...................................... 3
1.
site Name, Location and Description .............. 3
2.
Site History and Enforcement Activities .......... 4
3.
community
Participation .......................... 5
4.
Scope and Role of the Response Action ............ 6
5.
site Characteristics ............................. 6
6.
Summary of Site Risks.......................... .. 7
7.
Description of Alternatives ...................... 13
Summary of Comparative Analysis of Alternatives .. 18
8.
9.
Se 1 ected Remedy.................................. 22
statutory Determinations ......................... 24
Documentation of Significant Changes ............. 28
i
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List of Fiqures
Figure 1 - Location of Motorola, Inc., Mesa Center .... 3A
Figure 2 - Location of Investigation Area ............. 3B
Figure 3 - Waste Solvent Transport and Storage System. 3C
Figure 4 - VOC Concentrations in Water From UAU ....... 6A
List of Tables
Table 1 - Concentrations of Chemicals of Concern ...... 8
Table 2 - Risk Estimates for Potential Groundwater Use. llA
Table 3 - Risk Estimates for Air Emissions From Soil.. l1A
Table 4 - Remedial Action Alternatives ................ 13A
Table 5 - Applicable or Relevant and Appropriate
Requirements for the Motorola Mesa Site .... 13B-1
Table 6 - Cost Estimates for Alternative B............ 24A
ii
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I.
DECLARATION
1.
site Name and Location
Mesa Area Groundwater Contamination
Motorola, Inc.
2200 West Broadway Road
Mesa, Arizona 85202
2.
statement of Basis and Purpose
This Record of Decision (ROD) presents the remedial action the
United states Environmental Protection Agency (EPA) and the state
of Arizona selected for the Mesa Area Groundwater Contamination
site in Mesa, Arizona. This document was developed in accordance
with the Comprehensive Environmental Response, Compensation and
Liability Act of 1980 (CERCLA), as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA), and, to the
extent practicable, the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP).
This decision is based upon the contents of the Administrative
Record for the Mesa Area Groundwater contamination site.
3.
Assessment of the site
Actual or threatened releases of hazardous substances from this
site, if not addressed by implementing the response action
selected in this ROD, may present a current or potential threat
to public health, welfare, or the environment.
4.
Description of the Selected Remedy
The selected remedy is the final remedy for the Mesa Area
Groundwater Contamination site. It is designed to address
and groundwater that are contaminated with volatile organic
pounds (VOCs). The major components of this remedy consist
soil
com-
of:
o
On- and off-facility extraction of groundwater and on-
facility treatment by vacuum degasification with carbon
adsorption to remove VOCs;
o
Soil-vapor extraction of shallow soils on-facility with
. carbon adsorption to remove the VOCs; and,
o
Rehabilitation of two deep industrial water supply
wells to prevent them from acting as conduits for con-
tamination to move from the upper to lower aquifer
units.
1
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These remedial actions address the principal threat and primary
risk at the Mesa Area Groundwater Contamination site by removing
and permanently destroying the contaminants from the groundwater.
While the contamination in the soil is not considered a principal
threat at the site, soil contamination exists at levels above
state Health Based Guidance Levels. The Remedial Action Plan and
Feasibility study demonstrate that soil-vapor extraction is the
most cost-effective method of addressing this contamination at
this site. These actions will significantly reduce the toxicity,
mobility and volume of hazardous substances in the groundwater
and soil at this site.
5.
statutory Determinations
The selected remedy is protective of human health and the en-
vironment, complies with Federal and state requirements that are
legally applicable or relevant and appropriate to the remedial
action, and is cost-effective. This remedy uses permanent solu-
tions and alternative treatment (or resource recovery) tech-
nologies to the maximum extent practicable, and satisfies the
statutory preference for remedies that employ treatment to reduce
toxicity, mobility, or volume as a principal element.
At completion, this remedy will result in no hazardous substances
remaining on-site above health-based levels. During implementa-
tion, there will be a period of time where VOC levels in the
"groundwater will be above health-based levels. However, since
this site is no longer on the National Priorities List and the
State of Arizona will be implementing this remedy, a five-year
review, pursuant to CERCLA section 121, will not be required for
this site.
John ~ W VLL- .
Deputy Regional Administrator
q. %7. q I
Date
2
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II.
DECISION SUMMARY
1.
site Name, Location and Description
The Mesa Area Groundwater contamination site is also known as the
Motorola Mesa site. The Motorola, Inc. Mesa Center is located at
2200 West Broadway Road, in the western portion of Mesa, Arizona,
in Maricopa County. Figure 1 shows the location of the site
within the Phoenix area, and Figure 2 shows the Center in Mesa.
The SO-acre facility is zoned for industrial use and surrounded
by a mixture of light industrial and residential properties. The
nearest residences are 200 feet north of the facility. The
cement-lined Tempe Canal is located one-half mile to the west.
There are no critical habitats, wetlands, endangered species, or
known historic sites in proximity to or affected by the site.
This site is not situated in a flood plain.
The Motorola Mesa Center sits on alluvial units deposited by the
Salt River, located four miles north of the Center. The deposits
are divided into three major units: the Upper Alluvial Unit
(UAU) , the Middle Alluvial Unit (MAU) , and the Lower Alluvial
Unit (LAU). The UAU is comprised of boulders, gravel and sand to
a depth of 300 feet. Groundwater in this unit is found at a 100
foot depth and is not presently used as drinking water in the
area because of high levels of dissolved solids. However, the
aquifer does not exceed secondary drinking water standards and
could be used as a drinking water source. The 350 feet thick MAU
is much finer-grained than the UAU and LAU, and acts as an
aquitard between the two units. The LAU is coarse-grained and is
the primary drinking water aquifer in the region. Several wells,
owned by the City of Mesa and the Salt River Project (SRP), a
water purveyor, tap this aquifer in vicinity of the Motorola
facility, the closest of which are SRP wells one-half mile to the
west.
The Motorola facility is paved and consists of several large
buildings used in the production of semiconductors, for the
storage of product and chemicals, and for administrative pur-
poses. The facility also contains a deionization plant that
produces ultra-clean water for the manufacturing process, several
water storage tanks, cooling towers for the facility, and large
parking areas for employees. Figure 3 shows the major buildings
and the waste solvent transport and storage system. Three of the
lines and all the tanks in the system, shown on this figure, were
removed as a part of a RCRA partial closure (discussed further in
the following section).
3
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FIGURE 2- LOCATION OF INVESTIGATION AREA
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FIGURE 3 - WASTE SOLVENT TRANSPORT AND STORAGE SYSTEM
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2.
site History and Enforcement Activities
Motorola, the only Responsible Party at this site, has manufac-
tured semiconductors at this facility since 1966, and continues
operations today. Motorola uses solvents, acids and bases in
their manufacturing processes. In the spring of 1983, Motorola
detected trichloroethylene (TCE) and other VOCs in water from in-
dustrial water Supply Well Number 2 (SW-2), which taps the LAU
and is located on the facility.
In June 1983, Motorola commenced a hydrogeologic investigation
into the source and degree of contamination.EPA proposed the
site for listing on the National Priorities List (NPL) in 1985,
and named the Arizona Department of Environmental Quality (ADEQ)
as the lead agency. The Remedial Investigation (RI) commenced in
1986, and Motorola completed this investigation in February 1988.
Motorola also completed the final phase of the Feasibility Study
(FS) in December 1988. After further work on the Feasibility
Study, Motorola submitted a Remedial Action Plan in April 1991.
The Arizona Department of Health Services (ADHS), under contract
to ADEQ, also finalized a Risk Assessment in April 1991.
Beginning in 1984, Motorola installed monitoring wells. Motorola
discovered high levels of VOCs, up to 1,000 parts per billion
(ppb) tetrachloroethylene (PCE), 700 ppb TCE, 500 ppb
dichloroethylene (DCE), freon and trichloroethane (TCA) in the
Upper Aquifer unit. Initially, Motorola also detected chromium
up to 60 ppb. Motorola began converting monitoring wells into
extraction wells and pumping contaminated groundwater from the
UAU. Motorola gradually expanded this extraction program off-
facility, while continuing the RIfFS, and by 1990 had extracted
over 1000 acre-feet of groundwater. Since 1987, chromium consis-
tently has been measured at levels below the Maximum Contaminant
Level (MCL) of 50 ppb, and PCE has decreased to 250 ppb, TCE and
DCE to below 100 ppb. However, by 1991, the groundwater con-
tamination had migrated to over one mile southeast of the
facility to Southern Avenue.
The Remedial Investigation discovered that VOC contamination in
the groundwater, at levels above the MCLs, was limited to the
UAU. The source of contamination was located in the main chemi-
cal handling area of the facility (near the two storage tanks and
the chemical mix line depicted on Figure 3). VOCs leaked into
the groundwater from three possible sources: VOCs may have
leaked from the underground storage and transport system used for
waste solvents (see Figure 3); small amounts of solvent could
have spilled onto the surface in the main chemical handling area;
and, solvents could have been carried into the groundwater
through the storm runoff system which used natural depressions to
percolate runoff.
4
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Soil investigations revealed VOCs in the soil were limited to the
main chemical handling area. These VOCs were found only in the
upper ten feet of soil, and probably were prevented from
. vo~tilizing into the air by the pavement covering the facility.
PCE was found in concentrations up to 17 mgfkg, and was the only
VOC detected above the State Health Based Guidance Levels
(HBGLs).
From 1983 to 1987, Motorola performed a partial closure of the
underground waste solvent storage system under the Resource Con-
servation and Recovery Act (RCRA) authority. Motorola tested,
cleaned and removed most of the underground waste solvent system.
After pressure testing the lines, Motorola removed the under-
ground storage tanks and three of the five waste solvent lines.
The two other lines, which passed the pressure test, were left in
place after steam cleaning.
In February 1991, EPA released its final rule for the listing of
the Mesa Area Groundwater site, dropping it from the National
Priorities List (NPL). Instead of listing the site on the NPL,
EPA referred it to the RCRA program because: it is a RCRA
facility; the contamination is solely from Motorola; and, no
public drinking water supply wells have been contaminated.
This Record of Decision documents the selected remedy that
Motorola will implement under ADEQ supervision. The State imple-
mented Remedial Action Plan and EPA's Record of Decision will be
incorporated as a component of the Corrective Action Plan in the
RCRA permit for this facility.
3.
community Participation
Motorola completed a Community Relations Plan in 1986. Three
fact sheets were sent since that date to update the community on
activities at the facility. The RIfFS, Remedial Action Plan and
other documents were available for public review at the library
at ADEQ and at the Dobson Ranch Branch Library near the site. On
June 21, 1991, the Arizona ReDublic newspaper announced the
public comment period, the public meeting and the availability of
the Remedial Action Plan. Public comment period for the proposed
plan was June 19, 1991 to July 22, 1991.
In accordance with CERCLA sections 113(k) (2) (B) (i-v) and 117,
representatives from ADEQ, ADHS, and Motorola held the public
meeting on July 11, 1991. At this meeting and hearing, the rep-
resentatives presented information and answered questions about
the proposed plan. Representatives from the Arizona Department
of Water Resources, EPA, and the City of Mesa also were present
at the meeting. A response to comments received during the
public comment period is included in the Responsiveness Summary
prepared by ADEQ.
5
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4.
scope and Role of the Response Action
The scope of this response action is to address, as a final
remedy, the principal threats and primary risks associated with
the entire site. The groundwater at this site poses the prin-
cipal risk to human health and the environment due to the pos-
sible ingestion, inhalation and contact with water contaminated
by the Motorola Mesa facility.
To date, Motorola has begun clean-up of groundwater to reduce the
risk from and migration of the contamination. This ROD estab-
lishes the final remedy for the site. The groundwater will be
extracted and treated to the Maximum Contaminant Levels. The
soils also pose a potential threat to human health and the en-
vironment. The soils will be treated through soil-vapor extrac-
tion to Arizona Health Based Guidance Levels. Finally, the two
deep industrial water supply wells will be rehabilitated so that
they will not act as a conduit between the contaminated upper
aquifer unit and the lower aquifer units.
5.
site Characteristics
The Motorola Mesa site contamination consists of PCE, TCE, DCE,
Freon-113 and TCA in the Upper Aquifer Unit at levels exceeding
the Federal Maximum Contaminant Levels (MCLs). The Upper Aquifer
unit presently is not used as a source of drinking water in this
area because of high levels of dissolved solids. However, the
levels do not exceed secondary drinking water standards and the
aquifer potentially could be used as a drinking water source.
Additionally, soil in the main chemical handling area on the
facility is contaminated with low levels of VOCs in a shallow
zone beneath the pavement.
The possible sources of the contamination from Motorola were:
leakages from the underground waste solvent storage and transport
system; accidental spills of solvents onto the surface; and,
percolation from the drainage basins for the storm runoff system.
Levels of VOCs in the groundwater have been detected as high as
1,000 ppb for PCE, 700 ppb for TCE, 500 ppb for DCE and below 500
ppb for the other solvents. The presence of Non-Aqueous Phased
Liquids (NAPLs) has not been detected and is not suspected. The
groundwater contamination extends to more than one mile
downgradient (southeast) of the facility, to Southern Avenue, and
approximately 3200 acre-feet of water is affected. Figure 4
shows the extent of groundwater contamination. In the so~l, only
PCE has exceeded Arizona's Health Based Guidance Levels (14 mg/kg
for PCE) , at a level up to 17 mg/kg.
The Lower Aquifer Unit is the source for all drinking water in
the region. No wells that tap this unit exist downgradient of
the facility within two miles, and no drinking water wells have
been affected by the contamination from this Motorola facility.
Motorola has detected only low levels of VOCs in the LAU, at 1 to
6
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32
FIGURE II - VOLATILE ORGANIC CHEMICAL CONCENTRATIONS IN WATER FROM
THE UPPER ALLUVIAL UNIT IN SEPTEMBER-NOVEMBER 1990
6A
-------
2 ppb, in the two deep supply wells on the facility. Motorola
suspects that these wells may act as conduits from the UAU to the
LAU and will rehabilitate these wells, as a part of the selected
remedy, to eliminate this possibility.
The contaminants of concern at this site are those hazardous sub-
stances that demonstrate toxic affects to human health and the
environment, persist at levels above the cleanup levels and are
consistent~y detected. The contaminants of concern for the
groundwater are PCE, TCE and DCE. The contaminant of concern for
the soil is PCE. The contaminants are all VOCs and most are pos-
sible carcinogens.
Current risks posed at the site, calculated to be 5 x 10-5, and
potential routes of exposure are more fully discussed in the fol-
lowing "Summary of Site Risks" section.
6.
summary of site Risks
The Arizona Department of Health Services (ADHS) prepared a Risk
Assessment for the Motorola, Inc. Mesa Center in April, 1991.
This Risk Assessment characterized the current and potential
threats to human health if no action to remediate the contamina-
tion were taken. The Risk Assessment analyzed potential threats
from contaminants migrating in the groundwater, contaminants in
the soil and contaminants released from the soil. For the
groundwater risk calculations, ADHS used two sets of data points:
1983/84 and 1989/90. The earlier set of data represents the
worst case of contamination when VOC levels were at their
highest. The calculations using this data gives the baseline
risk. Motorola began extracting groundwater in 1984, and since
that time VOC levels have substantially decreased. ADHS used the
1989/90 data to calculate the risks currently at the site. The
Risk Assessment also analyzed potential risks during implementa-
tion of the proposed alternatives.
Identification of contaminants of Concern
The Remedial Investigation/Feasibility Study (RI/FS), and subse-
quent Remedial Action Plan, identified groundwater and soil as
the exposure media of concern at this site. Chemicals are con-
sidered a concern to public health if detected levels are above
background levels, appear in multiple samplings, and are deter-
mined to pose a health risk. The RI/FS explained that
trichloroethylene (TCE), trichloroethane (TCA), .
tetrachloroethylene (PCE), dichloroethylene (DCE), Freon-113 and
chromium have been found in the groundwater beneath the facility.
Since 1983, chromium concentrations have steadily declined, and
since January, 1988, chromium has been detected above the Maximum
Contaminant Level (MCL) only three times. These three samples
are not considered valid data points because analyses before and
after the detections are well below MCLs. The Risk Assessment
7
-------
identified TCE, PCE, and DCE as the only chemicals exceeding the
MCLs and as the contaminants of concern for groundwater. In the
soil, PCE is the contaminant of concern, and was detected in con-
centrations greater than the Arizona Health Based Guidance Levels
(HBGL). (ADHS developed HBGLs, through a risk assessment ap-
proach, as a means to evaluate what levels of contaminants may
cause adverse human health affects. The levels have not been ad-
justed to account for non-health factors such as economics or
treatment technology feasibilty, and are not site-specific.)
Concentrations of the chemicals of concern that have been re-
corded are found in Table 1.
Table 1:
Concentrations of Chemicals of Concern
Media ComDound Ranoe Mean MCL/HBGL*
Soil PCE <0.1 - 17 mg/kg 4.3 mg/kg *
14 mg/kg
Groundwater PCE <0.5 - 1100 ppb 247.1 ppb 5 ppb
1983 - 1984 TCE <0.5 - 650 ppb 162.9 ppb 5 ppb
DCE <0.5 - 380 ppb 79.9 ppb 7 ppb
Groundwater PCE <0.5 - 240 ppb 17.4 ppb 5 ppb
1989 - 1990 TCE <0.5 - 80 ppb 37.3 ppb 5 ppb
DCE <0.5 - 17 ppb. 3.5 ppb 7 ppb
*
Arizona HBGL are starred, all others are MCLs
EXDosure Assessment
The second step of the Risk Assessment identified possible ex-
posure pathways. An exposure pathway is considered complete when
a chemical of concern contacts an organism. ADHS determined that
the possible exposure pathways for the contaminants of concern
are: inhalation of VOC vapors volatilizing from the soils; in-
halation of VOCs released from the contaminated water treatment
and storage system at the facility; and, ingestion, inhalation,
and dermal contact with contaminated water from a public or
private well that could be drilled into the VOC-contaminated
groundwater plume. Under current land use, there are no private
or public drinking water wells providing water that exceeds MCLs
for VOCs that originated from the Motorola Mesa facility. .
Potentially exposed populations are adults and children living
near the facility, workers at the facility and people living in
residences that could be built over the facility, if Motorola
were to close. ADHS calculate~ potential exposure concentrations
from soil-gas to be 0.134 ug/m , if the soil-vapors were to col-
lect inside a room in a building. The calculated potential ex-
posure concentrations for inhalation from the water treatment and
8
-------
storage system were modeled for the closest residences to
tanks. Using a wind model and a wind dilution9facto5 the
centration~ were calculated to be: 4.31 ~ 10- 3mg/m for
4.28 x 10- mg/m3 for PCE, and 2.53 x 10- mg/m for TCE.
the
con-
DCE,
Two sets of data were used to calculate potential exposure con-
centrations from groundwater. Using 1983/84 data, average con-
centrations for water from the most contaminated area were calcu-
lated to be: DCE at 129 parts per billion (ppb), PCE at 402 ppb
and TCE at 249 ppb. Using 1989/90 data, average concentrations
for water in the most contaminated area were: DCE at 4.6 ppb,
PCE at 60.8 ppb and TCE at 25.6 ppb.
The Risk Assessment calculated the average and the reasonable
maximum exposures to the contaminants for children and adults.
For the average exposure, the calculations used the assumptions
that an individual (a 70 kg adult or 18 kg child) could be ex-
posed 365 days/year for nine years. For the reasonable maximum
exposure an individual (a 70 kg adult or 34 kg child) could be
exposed 365 days/year for 30 years.
Toxicitv Assessment
The next step of the Risk Assessment was to determine the car-
cinogenic and non-carcinogenic toxicity of the contaminants of
concern. Risk was calculated differently for carcinogenic and
non-carcinogenic risks.
Carcinogenic Effects
EPA's Carcinogenic Assessment Group developed cancer potency fac-
tors (CPFs), also called Slope Factors, to estimate excess
lifetime cancer risks associated with exposure to potentially
carcinogenic chemicals. CPFs, which are expressed in units of
(mg/kg-day)-l, are multiplied by the estimated intake of a poten-
tial carcinogen, in mg/kg-day, to provide an upper-bound estimate
of the excess lifetime cancer risk associated with exposure at
that intake level. The term "upper bound" reflects the conserva-
tive estimate of the risks calculated from the CPF. Use of this
approach makes under-estimation of the actual cancer risk highly
unlikely. Cancer potency factors are derived from the results of
human epidemiological studies or chronic animal bioassays to
which animal-to-human extrapolation and uncertainty factors have
been applied.
EPA uses a weight-of-evidence system to convey how likely a
chemical is to be a human carcinogen, based on epidemiological
studies, animal studies, and other supportive evidence. The sys-
tem uses groupings to classify probability of carcinogenicity:
Group A are chemicals that are demonstrated human carcinogens;
Group B are probable human carcinogens; Group C are possible
human carcinogens; Group D are not classifiable as to human car-
cinogenicity; and, Group E show evidence of non-carcinogenicity
9
-------
to humans. Group B is subdivided into two groups. Group B1
shows limited human evidence for carcinogenicity, and Group B2
shows sufficient animal study evidence but inadequate human
evidence of human carcinogenicity.
For the chemicals of concern at the Motorola Mesa facility DCE is
classified as Group C, a possible human carcinogen. DCE can be
absorbed orally, by inhalation and through dermal routes. There
have been 16 animal carcinogenicity studies, but most have been
judged to be inadequate. There are also several negative
studies, resylting in the classification of Group C. DCE's CPF
is 6.0 x 10- for ingestion, and 1.2 for inhalation.
PCE is readily absorbed through the lungs, less so by ingestion
and dermal contact. It has been found to be carcinogenic in
animal studies, but not carcinogenic in the limited number of
human studies, there~ore it is a Group B2. The inges~ion CPF
for PCE is 5.1 x 10- , and inhalation CPF is 3.3 x 10- .
TCE is easily absorbed through inhalation and ingestion, and less
through dermal contact. It demonstrates carcinogenicity in
animal studies and is classified as Group B2, a probable human
c~rci~ogen. The_~PF for ingestion is 1.1 x 10-2, and for inhala-
t~on ~s 1.7 x 10 .
Non-Carcinogenic Effects
EPA developed reference doses (RfDs) for indicating the potential
for adverse health effects from exposure to chemicals exhibiting
noncarcinogenic effects. RfDs, which are expressed in units of
mg/kg-day, are estimates of lifetime daily exposure levels for
humans, including sensitive individuals. Estimated intakes of
chemicals from environmental media (e.g., the amount of a chemi-
cal ingested from contaminated drinking water) can be compared to
the RfD. RfDs are derived. from human epidemiological studies or
animal studies to which uncertainty factors have been applied
(e.g., to account for the use of animal data to predict effects
on humans).
The chronic and subchronic (short term) RfD for DCE is 9 x 10-3
mg/kg-day. For PCE, the Ihronic RfD is 1 x 10-2 mg/kg-day, and
subchronic RfD is 1 x 10- mg/kg-day. There are no RfDs for TCE.
Risk Characterization
The last step of the Risk Assessment is to characterize the ac-
tual and potential risks. When data are available, quantitative
risk characterizations are performed that are evaluated qualita-
tively. When data are not available, a risk assessment discusses
possible risks qualitatively. The Risk Assessment for this site
calculated the risk from TCE and PCE quantitatively. The CPF
10
-------
for DCE is relatively high (1.2 for inhalation) but the weight of
evidence classifies it as a Group C carcinogen. Therefore, ADHS
used a modified RfD approach to calculate risks from DCE.
Excess lifetime cancer risk is calculated as the incremental
probability of an individual developing cancer over a lifetime
due to exposure to a carcinogenic compound. Excess lifetime can-
cer risks are determined by multiplying the intake level with the
cancer potency factor.
Potential concern for noncarcinogenic effects of a single con-
taminant in a single medium is expressed as the hazard quotient
(HQ) , or the ratio of the estimated intake derived from the con-
taminant concentration in a given medium to the contaminant's
reference dose. By adding the HQs for all contaminants within a
medium, or across all media to which a given population
reasonably may be exposed, the Hazard Index (HI) can be genera-
ted.
To establish a baseline, ADHS calculated the risk from the con-
taminants at this site historically, using groundwater data from
1983 and 1984. Motorola collected this data prior to initiating
the groundwater reclamation that began decreasing the levels of
VOCs detected in the groundwater. ADHS looked at a number of
possible exposure scenarios in the Risk Assessment. Table 2 sum-
marizes the calculated risk levels for groundwater for all ex-
posure pathways added together (inhalation, ingestion and dermal
contact) from potential uses of the groundwater, for historical
VOC levels and if no action were taken to remediate the site.
The potential exposures modeled were: showering and drinking the
groundwater from a private well that could be drilled into the
contaminated portion of the groundwater, both immediately beneath
the facility ("onsite" in the table), and just downgradient of
the facility boundary ("offsite"); and, drinking and showering
with water from the Salt River Project (SRP) wells, which are
west of the plume.
Table .2 shows that the risk representing reasonable maximum ex-
posure (RME) from groundwater (through ingestion, inhalation and
dermal conttct) at 1983-1984 levels was 4 x 10-4 for an adult,
and 1 x 10- for a child. Using morS current 1989-1990 data, tge
total risk was calculated as 5 x 10- for an adult, and 1 x 10-
for a child. The reasonable maximum exposure risk from
groundwater at the Maximum Contaminant Leve~s, for all routes of
possible exposure, is calculated as 4 x 10- . .
Under current conditions there is no exposure to the soil, be-
cause the entire facility is paved or has buildings covering the
soil. Soil-vapor could leak through cracks in the pavement.
Table 3 summarizes the risks from air emissions from the soil.
The risk representing the reasonable maximum exposure, for a
residence that possibly could be built where the facility now
11
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Table 2: Summary of carcinoqenic Risk Estimates
for Potential Groundwater Use Under No Action Alternative
Well Location
and Date of Data
Onsite (1983/84)
Onsite (1989/90)
Offsite (1989/90)
SRP (1989/90)
*
*
Table 3:
Adult Child
Averaqe RME Average RME
1 x 10-4 4 x 10-4 7 x 10-5 1 x 10-4
1 x 10-5 5 x 10-5 8 x 10-6 1 x 10-5
7 x 10-6 2 x 10-5 3 x 10-6 7 x 10-6
7 x 10-7 3 x 10-6 4 x 10-7 9 x 10-7
*
*
*
*
*
*
*
*
*
*
summary of carcinoqenic Risk Estimates
for Air Emissions from soil
Adult Child
Average RME Average RME
Potential On-facility
Residence
Indoors 3 x 10-8 9 x 10-8 3 x 10=: 6 x 10-8
Outdoors 1 x 10-6 4 x 10-6 1 x 10 3 x 10-6
On-site Workers
Indoors 2 x 10=: 7 x 10-9 N/A N/A
Outdoors 9 x 10 3 x 10-7 N/A N/A
Off-facility
Residence
Outdoors 5 x 10-12 2 x 10-11 6 x 10-12 2 x 10-11
11A
-------
stands, is calculated as 4 x 10-6 £or an adult, and 3 x 10-6 for
a child. However, currently the site is zoned for industrial
purposes only and no houses could be built on the property.
Therefore, the Risk Assessment for this site demonstrated the
hisiorical risk prior to any groundwater response action was 4 x
10- for an adult, triggering the need for clean-up at this site.
The potential risk representing the reasonable maximum exposures
fr~m t~is ~it7' assuming curE!nt contami~int.levels, is 5 x 10- ,
wh~ch ~s w~th~n EPA's 1 x 10 to 1 x 10 r~sk range.
Environmental Risk
In vicinity of the Motorola Mesa facility there are no critical
habitats and no endangered species affected by contamination from
this site. The ecological effects due to releases from the
Motorola Mesa facility are not expected to be significant for the
following reasons: 1) the entire facility is paved and the sur-
rounding area is developed into residential and industrial uses,
thus there are few habitat resources for wildlife; and, 2) the
only surface water in the area that is affected is the cement-
lined Tempe Canal. The VOC levels in the water from the SRP
wells that enter the canal are very low, and the water in the
canal averages 0.5 and 0.6 ppb for PCE and TCE, respectively.
These amounts are expected to volatilize quickly upon movement
down the canal.
Summary
All risk estimates in the Risk Assessment were based on a number
of assumptions regarding contaminant concentrations and fate, ex-
posures, doses, and toxicity information. There was uncertainty
associated with the process at all stages. Although ADHS made
point estimates of risk, it should be recognized that each one
represents a range of possibilities and is only an indicator.
ADHS took care at each step to ensure that assumptions and es-
timates were representative of upper bounds. When possible, ADHS
used 95% upper bound estimates for data and assumptions used in
the calculations in the Risk Assessment. True risk may be much
less than calculated. This was done purposely to be protective
of public health.
In conclusion, based on the Risk Assessment and the Remedial
Investigation/Feasibility study, before any remedial action,
releases of hazardous substances from this site presented .an im-
minent and substantial endangerment to public health, welfare,
and the environment. Response action to date has reduced site
risk, but the site still exceeds Maximum contaminant Levels and
warrants additional remedial action.
12
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7.
Description of Alternatives
The goal of the remedial action is to ensure no human or environ-
mental exposure to the groundwater and soil contamination caused
by this Motorola facility, and to clean the groundwater to the
Maximum contaminant Levels (MCLs) and the soils to the Health
Based Guidance Levels (HBGLs).
The Feasibility study for this site identifed several remedial
action alternatives of which five were refined and explained in
the May 1991 "Remedial Action Plan for the Motorola, Inc. Mesa
Center". The five remedial action alternatives are described
below, and in Table 4.
Alternative A - No Action
The Superfund program requires that the "No Action" alternative
be considered at every site. Under this alternative, Motorola
would discontinue all existing groundwater pumping and treatment,
and would use only the existing wells to monitor the extent of
contamination.
ARARS
This alternative would not meet the threshold criterion of com-
pliance with Applicable or Relevant and Appropriate Requirements.
specifically, this alternative would allow PCE, TCE and DCE to
remain in the groundwater at concentrations above MCLs. The
ARARs for this site are listed on Table 5.
Risk
The risk posed by this site, as a reasonable maximum exposure, to
an adult drinking the groundwater benegth the facility under the
No Action Alternative would be 5 x 10-. The risk from soil-~as
to an adult at a potential on-site residence would be 4 x 10-
Cost
Annual monitoring costs for the No Action alternative are calcu-
lated to be $30,000 per year.
Alternative B. C. D and B
The remaining alternatives consist of groundwater and soil com-
ponents. The description of the alternatives is broken into a
description of the groundwater action, soil action, ARARs, risks
posed by the alternative, cleanup time and cost.
13
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Table 4: Remedial Action Alternatives
Alter- Cost Meet
native Description ($1000) Time ARARs?
A No Action 0 & M1: $30 NjA No
B Groundwater: capital1: 1686 13 Yes
- Extract 600 gpm 0 & M: 581
- Vacuum degasification PW: 7144
- In plant use of water
- Rehabilitate deep supply wells
Soil:
- soil-vapor extraction
C Groundwater: capital: 1436 13 Yes
- Extract 600 gpm 0 & M: 506
- Air-stripping PW: 6189
- In plant use of water
- Rehabilitate deep supply wells
Soil:
- soil-vapor extraction
D
Groundwater:
- Extract 1200 gpm
- Vacuum degasification
- In plant use of 600 gpm,
reinjection of 600 gpm
- Rehabilitate deep supply
Capital: 4191
o & M: 1294
PW: 11768
7
Yes
wells
soil:
- Soil-vapor extraction
E
Groundwater:
- Extract 1200 gpm
- Air-stripping
- In plant use of 600 gpm,
reinjection of 600 gpm
- Rehabilitate deep supply
Soil:
- Soil-vapor extraction
Capital: 3561
o & M: 1104
PW: 9947
7
Yes
wells
1 "0 & M"
calculated
and C, for
is operation and Maintenance, "PW"
at a 5% discount rate for 13 years
6 years for Alternatives D and E
- 13A -
is Present Worth
for Alternatives B
-------
Table 5:" Applicable or
Relevant and Appropriate Requirements
Motorola Mesa site
A.
Chemical Specific
Safe Drinking
Water Act (SDWA)
(40 CFR Part 141)
The Maximum Contaminant Levels
(MCLs) of the SDWA are considered
relevant and appropriate since the
groundwater is a potential source
of drinking water. Pursuant to 40
C.F.R. S300.430(e) (2) (i) (B), MCLs
are relevant and appropriate as
in-situ aquifer standards for
groundwater that is or may be used
for drinking water. Specifically,
the MCLs for PCE, TCE, and DCE are
the clean-up levels for the
remedial action.
B.
Action specific
Clean Air Act
(42 U.S.C. S7401-
7642) (40 C.F.R
S50-99)
(C.A.A. S101)
The Clean Air Act (CAA) has been
implemented through a series of
regulations (40 C.F.R.S50-99) that
define the air quality management
programs used to achieve the CAA
goals. The State of Arizona is
responsible for preparation of a
State Implementation Plan (SIP),
which describes how the air quality
programs will be implemented to
achieve compliance with primary
standards. Upon meeting the
primary standards, an area is clas-
sified as "in attainment". The SIP
must" also identify how the programs
will maintain attainment status for
each of the primary pollutants.
Motorola Mesa remedial actions must
comply with the substantive re-
quirements of the CAA and its re-
lated programs, including the EPA-
approved Arizona SIP. Specifi-
cally, both the degasifier/PEDCO
system and the soil-vapor extrac-
tion system must comply with the
substantive provisions of the CAA
and the Arizona SIP.
1.
13B-l
-------
2.
Resource Conserva-
tion and Recovery
Act (40 C.F.R. Part
265, Subpart AA and
BB)
3.
Resource Conserva-
tion and Recovery
Act (40 C.F.R. S261-
264; 42 U.S.C. S6901
et. seq.)
4.
Resource Conserva-
tion and Recovery
Act (40 C.F.R. Sub-
part X)
5.
Clean Water Act
(40 C.F.R. 40~.5)
These RCRA requirements apply to
air emission standards for process
vents and equipment leaks
associated with distillation,
solvent extraction or air stripping
operations. The requirements impact
those operations that manage haz-
ardous waste with organic con-
centrations of at least 10 parts
per million, and are subject to 40
C.F.R. Part 270. Historically, the
hazardous waste concentrations have
exceeded 10ppm at this site, but
under current conditions concentra-
tions are below that level. These
requirements are applicable.
These RCRA requirements are applic-
able to the handling, storage and
removal of wastes off-site, if
these wastes are designated as RCRA
hazardous wastes. These regula-
tions govern identification, gener-
ation, transportation, storage and
disposal of hazardous wastes, and
are applicable at this site.
Air stripping towers and soil-
vapor extraction units are con-
sidered miscellaneous treatment
units under Subpart X of RCRA since
they are not regulated elsewhere
under RCRA. Therefore, the sub-
stantive requirements, including
those governing construction,
operation, maintenance, closure and
postclosure care will be ap-
plicable.
Under these provisions, discharge
of treated groundwater to the local
sanitary sewer must comply with lo-
cal POTW pretreatment programs.
Discharges of treated groundwater
to the sanitary sewer at Motorola
Mesa must meet the substantive
pretreatment sewer discharge stan-
dards of the City of Mesa. The
Clean Water Act is applicable.
13B-2
-------
c.
6.
Arizona Air
Pollution Control
Regulations
(A. R. S. 49-480)
7.
Arizona Revised
statute S49-282,
et seq.; S49-224
8.
Arizona Groundwater
Management Act;
Arizona Revised
statute SS45-454.01
Location-specific
The substantive requirements of the
Arizona Air POllution Control Rules
and Regulations for groundwater and
soil treatment facilities are
applicable.
Portions of the Arizona statutory
code for cleanup of hazardous sub-
stances related to contaminated
groundwater ("Arizona Superfund",
Arizona Revised Statute S49-282, et
seq.) and implementing regulations
(Arizona Administrative Code R18-
7-109, et seq.) are applicable to
the Motorola Mesa site. The im-
plementing regulations incorporate
by reference state law provisions
that (1) establish that all
definable aquifers are drinking
water aquifers unless they qualify
for an aquifer exemption, and (2)
establish water quality standards
for these aquifers. Finally, the
Arizona Superfund statute and
regulations require that, to the
extent practicable, Motorola Mesa
remedial actions provide for the
control, management, or cleanup of
hazardous substances so as to allow
the maximum beneficial use of the
waters of the state.
Section 45-454.01 of the Arizona
Groundwater Management Act (GMA)
is relevant and approprite to
the Motorola Mesa site. For ac-
tivities conducted onsite, the sub-
stantive portions of the provisions
referenced within 545.454.01 of the
GMA shall be applicable.
There are no location-specific ARARs.
13B-3
-------
1.
other Criteria To Be Considered
D.
Arizona Health
Based Guidance
Levels (HBGLs)
(AAC 18-4-R-18-
4-221)
2.
Maricopa County
Bureau of Air
Pollution Control
Rules and Regulations
(Regulation III and
Rule Numbers 200, 210,
220, 320, and 330)
These health based clean-up levels
have not been promulgated and are
therefore not ARARs. HBGLs for
VOCs in the soil are TBCs and
have been selected as the cleanup
levels for the soil remediation.
Maricopa County Rules 200, 210,
220, 320 and 330 are criteria
to be considered for air emissions
at the Motorola Mesa site.
Maricopa County's January 1991
guidelines for implementing Rule
210 require VOC air emission con-
trols for remediation sites where
total uncontrolled VOC air emis-
sions would exceed 3 pounds per
day. The air emission con~ols must
have an overall efficiencY~f at
least 90 percent.
13B-4
-------
Alternative B
Groundwater
Under this proposed alternative, all groundwater with VOC con-
centrations that exceed groundwater cleanup levels would be ex-
tracted from the Upper Aquifer Unit at an approximate rate of 600
gallons per minute (gpm). Motorola would use eight existing ex-
traction wells, four on- and four off-facility, and would install
one additional extraction well off-facility at the downgradient
edge of the plume. Motorola would use these existing and addi-
tional monitoring wells to determine when the contaminated
groundwater has been removed to cleanup levels.
Water that is extracted would be pumped to an existing vacuum
degasifier on the facility for treatment. The degasifier strips
approximately 90% of the VOCs from the water. Water exiting the
degasifier would be used in Motorola's deionized water treatment
plant, replacing water currently supplied by the City of Mesa.
Waste water from the plant and manufacturing processes is dis-
charged to the sewer under a National Pollution Discharge
Elimination System (NPDES) permit. Vapors exiting the vacuum
degasifier would be sent to Motorola's existing permitted carbon
adsorption system that treats solvent emissions from the plant
processes. This system, called the PEDCO system, uses carbon to
~trip the VOCs from the vapor. The carbon is steam-regenerated
and the VOCs distilled out on the facility. The VOCs ultimately
are sent off-site to a permitted hazardous waste incineration
facility.
Note: The following remedial action elements, the deep supply
well modification and soil-gas extraction, are components common
to Alternatives B, C, D and E. These elements will be described
in Alternative B, then referenced in the remaining alternative
descriptions.
The Motorola facility has two supply wells, SW-l and SW-2, on the
facility that tap the Middle and Lower Aquifer units. Both
supply wells would be modified to eliminate the potential for
them to act as conduits for contaminated water to flow from the
Upper Aquifer Unit into the lower aquifer units.
Soil
To clean soil at this site, Motorola would install a soil-vapor
extraction well in the main chemical handling area on the
facility. The extracted soil-vapor would be treated by activated
carbon. The spent carbon would be shipped off-site to a per-
mitted hazardous waste facility for incineration. The soil
clean-up level is the Arizona Health Based Guidance Level (HBGLs)
for PCE in 50i1.
14
-------
After operating the soil-vapor extraction and treatment system,
Motorola would take additional soil samples to determine if the
soil has been cleaned to the HBGLs. Motorola would continue to
extract and treat the soil-vapor until the HBGLs are achieved and
maintained.
ARARs
This alternative will comply with all applicable or relevant and
appropriate chemical-, action- and location-specific require-
ments. The Land Ban requirements of RCRA do not apply to this
remedial action. The ARARs for this, and the remaining, alterna-
tive are identified in Table 5. .
Risk and Response Time
This alternative can be implemented within a few months. Most of
this alternative is in place. Motorola would need only to drill
the extra extraction well and monitoring wells before full im-
plementation. The time to achieve MCLs throughout the con-
taminant plume is calculated to be 13 years. The risks posed by
clean-up under this alternative are based on this estimated time.
The risk, ~or an adult drinking the groundwater, is calculated to
be 9 x 10- during clean-up, and upon achieving the MCLs risk is
calculated to be 4 x 10-6.
Cost
The capital cost for this alternative is $1,686,000, and the
operation and maintenance costs are $581,000. The present worth,
at 5% discount rate for 13 years, is calculated to be $7,144,000.
Alternative C
Groundwater
This alternative also involves on- and off-facility extraction of
contaminated groundwater from the Upper Aquifer Unit at a rate of
600 gpm. The same wells as proposed in alternative B would be
used, including the additional extraction well. The difference
between this alternative and Alternative B is that the water
would be pumped to an on-site air-stripper for treatment. The
VOCs stripped off would then be treated by granulated active car-
bon. The carbon would be disposed of offsite as a hazardous
waste. The treated water would be used in plant processes, as
proposed in Alternative B.
The two deep supply wells on the facility would be rehabilitated
as explained in Alternative B.
15
,;
-------
soil
soil clean-up for Alternative C is the same as is proposed in Al-
ternative B.
ARARs
The chemical-, action- and location-specific ARARs are the same
as for Alternative B. This alternative would meet all the ARARs
discussed in Table 5.
Risk and ReSDonse Time
This alternative would take approximately one year to implement.
The estimated time to complete the remedial action is 13 years.
The risks posed by this alternative are the same as in Alterna-
tive B, since the clean-up time and levels are the same.
Cost
Capital costs for this alternative are calculated to be
$1,436,000 and the operation and maintenance costs are calculated
to be $506,000. The present worth, at a 5% discount rate for 13
years, is $6,189,000.
Alternative D
Groundwater
The existing groundwater extraction program would be expanded for
this alternative. Three on-facility monitoring wells would be
converted to extraction wells, and four additional off-facility
extraction wells would be installed for a total of 16 extraction
wells. The extraction rate would total 1200 gpm from the Upper
Aquifer Unit. Water would be treated in two on-facility vacuum
degasifiers. Vapors from the degasifiers would be sent to the
existing PEDCO VOC emission control system with carbon adsorption
treatment, as described in Alternative B. Six hundred gallons of
the water would be used in the deionized water treatment plant
processes, replacing City of Mesa water, and 600 gallons would be
reinjected up- and side-gradient of the contaminant plume.
Motorola would install eight injection wells, and the necessary
piping to connect them to the facility.
The two deep supply wells on the facility would be rehabilitated
as in Alternative B.
Soil
The soil would be cleaned in the same manner as described in Al-
ternative B.
16
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ARARs
ARARs are the same as for Alternative B, except ADEQ would re-
quire that Motorola obtain an Aquifer Protection Permit for the
offsite reinjection portion of the remedy.
Risk and Response Time
This alternative would take approximately three to four years to
implement. The estimated time to clean the contaminated
groundwater to the cleanup levels is 7 years. The risk posed by
thi~ alternative, during remedial action, is calculated to be 6 x
10- for an adult drinking the groundwater.
Cost
capital costs for this alternative would be $4,191,000 and opera-
tion and maintenance costs would be $1,294,000. The present
worth, at a 5% discount rate for six years, would be $11,678,000.
Alternative E
Groundwater
Contaminated groundwater would be extracted at 1200 qpm under the
same system as proposed in Alternative D. Water would be treated
on-facility using two air-strippers and activated carbon adsorp-
tion for emissions control. As in Alternative D, 600 gpm of
water would be used in plant processes, and 600 gpm would be
reinjected in eight injection wells up-gradient and lateral of
the plume.
The two deep supply wells would be rehabilitated as described in
Alternative B.
Soil
Soil action under this alternative is the same as proposed under
Alternative B.
ARARs
The ARARs for this alternative are the same as described under
Alternative D.
Risk and Response Time
This alternative would take three to four years to implement.
The clean-up time for this alternative is calculated to be seven
years. The risks posed by this alternative during remediation
would be the same as Alternative D.
17
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Cost
The capital costs calculated for this alternative are $3,561,000
and operation and maintenance costs are $1,104,000. The present
worth, at a 5% discount rate for six years, is calculated to be
$9,947,000.
8.
summary of comparative Analysis of Alternatives
Motorola, ADEQ and EPA analyzed the remedial alternatives
developed in the Feasibility study and Remedial Action Plan using
the nine evaluation criteria in the NCP to select a site remedy.
The following is a summary of this comparison. The nine criteria
are: 1) overall protection of human health and the environment;
2) compliance with applicable or relevant and appropriate re-
quirements; 3) long-term effectiveness and permanence; 4) reduc-
tion of toxicity, mobility, or volume through treatment; 5)
short-term effectiveness; 6) implementabilitYi 7) costi 8) State
acceptance; and, 9) communit~ acceptance.
Overall Protection of Human Health and the Environment
Overall protection of~human health and the environment addresses
whether a remedy provides adequate protection and describes how
risks posed through each pathway are eliminated, reduced or con-
trolled through treatment, engineering controls or institutional
controls. Overall protection of human health and the environment
and compliance with ARARs, which is addressed below, are the two
"threshold criteria" that must be met for an alternative to be
deemed acceptable.
All of the alternatives, except the No Action alternative, are
protective of ~uman health and the environment. Risk is reduced
to the 4 x 10- level through the treatment of contaminated
groundwater to the MCLs, and soil-vapor extraction to remove VOCs
from the soil.
The Arizona state Constitution prohibits the placement of in-
stitutional controls. Therefore, prior to and during implementa-
tion of the alternatives there will be no institutional controls
to eliminate the possibility of a private well being drilled into
contaminated groundwater in the Motorola plume; although, Arizona
Department of Water Resources would have to permit such a well
prior to drilling. However, upon completion of the remedial ac-
tion, the contamination from Motorola will not impact future
private and public wells.
The ecological effects due to releases from the Motorola Mesa
facility are not expected to be significant for the reasons
stated in section 6.
18
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ComDliance with ARARs
Applicable requirements are those cleanup standards or other sub-
stantive Federal or state requirements that specifically address
a hazardous substance, remedial action or other circumstance at a
CERCLA site. Relevant and appropriate requirements are those
cleanup standards or other substantive requirements that, while
not "applicable" to a hazardous substance or remedial action, ad-
dress problems or situations sufficiently similar to those en-
countered at the site that their use is well suited. To Be Con-
sidereds (TBCs) are procedures, criteria and/or resolutions that
are not considered ARARs, local regulations for example, but are
relevant to the cleanup of the site.
compliance with ARARs addresses whether a remedy will meet all
Federal and state environmental laws and/or provide for a waiver
from any of these laws. As discussed above, this is the second
threshold criterion that must be met for the selection of a
remedy. These ARARs are divided into chemical-specific, action-
specific and location-specific groups.
With the exception of No Action alternative, all of the alterna-
tives will comply with ARARs.
Lona-term Effectiveness and Permanence
Long-term effectiveness and permanence refers to the ability of a
remedy to maintain reliable protection of human health and the
environment over time. This criterion includes the consideration
of residual risk and the adequacy and reliabilty of any controls.
The remedial alternatives, except the No Action alternative, all
result in minimal residual risk. with the exception of the No
Action alternative, all the alternatives are expected to attain
MCLs, thereby resulting in minimal risk from residual con-
taminants in the groundwater. Numerous Superfund sites have
demonstrated that both groundwater treatment options, vacuum
degasification and air-stripping, are effective in removing VOCs
from water. The existing emission control system at Motorola ef-
fectively removes VOCs from the air by carbon adsorption and the
residual VOCs are sent off-facility for permanent thermal
destruction.
Soil-vapor extraction will remove VOCs from the soil to health-
based levels and remove any source of VOC contamination to the
groundwater. Since this site has dropped from the National
Priorities List and the State of Arizona will be implementing
this Record of Decision and the Remedial Action Plan, a five-year
review will not be required under CERCLA. Additionally, the
rehabilitation of the deep supply wells will eliminate the pos-
sibility that these wells will act as conduits for contamination
to move to the lower aquifer units.
19
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Reduction of Toxicitv. Mobilitv or Volume
Reduction of toxicity, mobility or volume refers to the
preference for a remedy that uses treatment to reduce health
hazards, contaminant migration or the quantity of contaminants at
the site.
All the alternatives, except the No Action alternative, use per-
manent destruction as the primary element to address the prin-
cipal threat of contamination. Groundwater treatment alterna-
tives include either vacuum degasification, or air-stripping with
carbon adsorption. Both of these treatment methods would involve
off-site incineration of the captured VOCs. soil-vapor extrac-
tion with carbon adsorption also will result in the off-site in-
cineration of the VOCs from the soil.
Groundwater pumping is expected to remove contaminated
groundwater that is above MCLs, calculated in 1989 to be 3,200
acre-feet (this was prior to off-facility pumping and treatment
that commenced in the fall of 1989; the current amount would be
less).
Short-term Effectiveness
Short-term effectiveness refers to the period of time needed to
complete the remedy and any adverse impacts on human health 'and
the environment that may be posed during the construction and im-
plementation of the remedy. The following were used to evaluate
the short-term effectiveness of each alternative: protection of
the community and workers during remedial actions; environmental
impacts from implementation of alternatives; and, time until
remedial objectives are met.
Alternative B is most easily implemented since the vacuum
degasifier is in place and currently treating groundwater. This
alternative requires that Motorola only drill one additional well
to extract and treat the groundwater. Additionally, under this
treatment option the risks to air emissions of VOCs from the
remediation is lower than Alternatives D and E because a lower
volume of water is treated and less air emmisions result from the
storage tanks. Therefore, this alternative provides the greatest
short-term effectiveness.
Alternatives D and E would be the second most effective in the
short-term. These alternatives would require three to four years
to implement, plus seven years to clean the contaminated
groundwater to MCLs; thus, the total time would be 11 years.
Risk from air emissions of VOCs from these alternatives, would be
slightly higher than that of alternative B or C, however, th~
level is well below the one-in-one-million level (at 7 x 10- ).
Alternative C is the least effective in the short-term, requiring
15 years to achieve MCLs.
20
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None of the alternatives are expected to pose any appreciable
risk to the community, workers or environment during construction
and implementation. The Risk Assessment calculated risk during
implementation of the ~emedY, and the highest risk from air emis-
sions would be 7 x 10- from alternatives D and E. The greatest
risk from groundwater would be if a private well were installed
in the contaminated portion of the plume, resulting in a
reasonable maximum risk for nine years of exposure of 9 x 10-6.
ImDlementabilitv
Implementability refers to the technical and administrative
feasibility of a remedy, including the availability of materials
and services needed to implement the selected remedy. It also
includes coordination of Federal, state and local governments to
clean-up the site.
Alternative B is the most readily implementable alternative. The
vacuum degasifier currently is in operation on the Motorola
facility. All but one of the extraction wells are in place, and
pumping the extracted groundwater to the degasifier. As the ex-
traction rate is within Motorola's Type II water rights, Motorola
does not need to obtain an additional Poor Quality Groundwater
Withdrawal Permit (PQGWP). This alternative could be implemented
within a few months.
Alternative C would be the second most implementable alternative.
Motorola would need to procure and install the air-stripping
equipment and the additional extraction and monitoring wells.
This alternative also proposes extraction of water that is within
Motorola's Type II water rights and would not require a modifica-
tion of Motorola's PQGWP. This alternative would require ap-
proximately one year to implement.
Alternatives D and E would be the most difficult to implement.
Motorola would need to procure additional Type II water rights to
pump the required 1200 gpm. Additionally, Motorola would need to
find access for the eight additional injection wells and install
the piping for those wells. These alternatives would take three
to four years to implement.
Cost
This criterion examines the estimated costs for each remedial al-
ternative. For comparison, capital costs, operation and main-
tenance costs and present worth are used to compare each alterna-
tive.
Because air-stripping equipment is less expensive than vacuum-
extraction equipment, alternative C costs the least. The capital
costs are $1,436,000 and operation and maintenance costs are
$506,000, for a total present worth of $6,189,000.
21
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Alternative B would be the second lowest cost remedial alterna-
tive with capital costs of $1,686,000, operation and maintenance
costs of $581,000 and a present worth of $7,144,000.
Alternative E, involving air-stripping of twice the volume of
water as alternative C, would be the third lowest cost alterna-
tive. The capital costs would be $3,561,000, operation and main-
tenance of $1,104,000 and a present worth of $9,947,000.
Alternative D is the highest cost alternative. The capital cost
would be $4,191,000, operation and maintenance costs would be
$1,294,000 and the present worth would be $11,678,000.
state Acceptance
state acceptance indicates whether, based on its review of the
RI, FS, and Remedial Action Plan, the state in which the site
resides agrees with the preferred alternative.
The Arizona Department of Environmental Quality (ADEQ) is the
lead agency for this site. ADEQ has worked closely with EPA,
Motorola and the Arizona Department of Water Resources (ADWR) on
this site, and concurs that Alternative B is the preferred alter-
native.
Community Acceptance
Community acceptance refers to the public support of a given al-
ternative.
Community response to the alternatives is presented in the
Responsiveness Summary which addresses comments received during
the public comment period.
9.
Selected Remedy
After balancing the factors discussed in the comparative analysis
of alternatives, EPA and ADEQ selected Alternative B as the final
remedy for the Mesa Area Groundwater Contamination site. The
elements of the alternative Motorola shall implement include:
o Four on-facility and five off-facility extraction wells
which will pump groundwater from the Upper Aquifer U~it at a
rate of 600 gpm. The wells will extend one mile beyond the
facility boundary capturing the full extent of the con-
taminant plume which exceeds the MCLs for PCE, TCE and DCE.
o Groundwater from the extraction wells will be pumped to
the Motorola operating plant and will be treated by vacuum
degasification to remove the VQCs. Water from the
degasifier will be sent to the deionized water treatment
22
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plant and used in manufacturing an~ other facility
processes. Wastewater discharges from the processes will
comply with Mesa's sewer discharge permit requirements.
Vapor from the degasifier will be treated in Motorola's ex-
isting carbon adsorption VOC emisson control system.
o Supply well SW-2 will be rehabilitated to eliminate the
possibility that it would act as a conduit for contamination
to move from the Upper Aquifer Unit to the lower aquifer
units. Supply well SW-1 also will be rehabilitated when it
is no longer used as the primary water source for the
Motorola plant and no longer pumped continually.
o One soil-vapor extraction well will be installed in the
Courtyard area. Soil-vapor will be extracted and treated
with activated carbon to strip off VOCs before discharging
to the air. The spent carbon will be shipped off-site to a
permitted hazardous waste incineration facility. Clean-up
levels for soil will be Arizona HBGLs.
The remedial action objectives are: to remove VOCs that are
above MCLs and HBGLs to eliminate the possible routes of human or
environmental exposure to these contaminants above these levels;
and, to eliminate the vertical and lateral migration of the VOCs
from the Motorola facility.
Motorola shall install several additional wells to monitor the
extent of contamination and cleanup. These wells will be placed
both downgradient and sidegradient of the plume and will tap all
three aquifer units. In the event any of these monitoring wells
detect VOCs or chromium from the Motorola facility in excess of
the MCLs, Motorola shall augment their extraction well pumping
system so as to capture the full extent of the plume that exceeds
cleanup levels. This shall include converting monitoring wells
to extraction wells and installing additional extraction and
monitoring wells if deemed necessary by EPA or ADEQ. Motorola
shall monitor and report monitoring results to ADEQ quarterly.
Motorola also shall continue to monitor water quality from the
Salt River Project wells and Tempe Canal. Motorola shall sample
the SRP wells annually during non-pumping periods and monthly
during pumping periods. The Tempe canal shall be sampled if any
of the SRP wells exceed MCLs and the contamination is from the
Motorola Mesa facility. In the event the SRP wells are heavily
pumped and the groundwater gradient reverses, Motorola sha.ll con-
vert existing monitoring wells to extraction wells or install ad-
ditional extraction wells to prevent the contamination of the SRP
wells, as deemed necessary by ADEQ or EPA .
The length of time to cleanup the plume is estimated to be 13
years. Upon completion of the remediation, achievement of MCLs
in the groundwater and HBGLs in the soil, incremental risks will
23
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be reduced to the four-in-one~million (4 x 10-6) range. Present
worth of this alternative is calculated to be $7,144,000.
Details of the costs are in Table 6.
10.
statutory Determinations
Section 121 of CERCLA establishes several statutory requirements
and preferences with which a selected remedial action for site
must comply. When complete, a remedial action must comply with
applicable or relevant and appropriate environmental standards
established under Federal and State environmental laws unless a
statutory waiver is justified. The selected remedy must also be
cost-effective and utilize permanent solutions and alternative
treatment technologies or resource recovery technologies to the
maximum extent practicable. Finally, the statute includes a
preference for remedies that employ treatment that permanently
and significantly reduce the volume, toxicity, or mobility of
hazardous wastes as their principal element. The following sub-
sections discuss how the selected remedy meets these statutory
requirements.
Protection of Human Health and the Environment
The Risk Assessment performed by ADHS identified potential ex-
posure pathways at this site. These pathways include drinking
contaminated water from a well tapping into the contaminated
aquifer, and volatilization of VOCs from soil into closed struc-
tures. To eliminate the first exposure pathway, the selected
remedy protects human health and the environment through the fol-
lowing treatment process: pumping contaminated groundwater that
exceeds cleanup levels, and extracting VOCs by vacuum degasifica-
tion and off-site incineration to permanently destroy the VOCs.
Additionally, soil-vapor extraction with carbon adsorption on the
facility will remove VOCs from the soil and eliminate the second
possible route of exposure. The spent carbon will be shipped
off-site to an approved RCRA facility for incineration and per-
manent destruction of the VQCs. This will avoid any cross-media
transfer of VQCs.
Most of the elements of this proposed remedy are in place. Im-
plementation of this remedy will proceed quickly and will not
pose any unacceptable short-term risks to the workers and sur-
rounding commgnity. Upon completion, risks from this site will
be in the 10- range.
ComDliance with ARARs
The selected remedy, extraction and treatment of groundwater,
soil-vapor extraction of soils and rehabilitation of the deep
supply wells, will comply with all applicable or relevant and ap-
propriate chemical-, action- and location-specific requirements.
24
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TABLE 6
- COST ESTIMATES FOR ALTERNATIVE B
CAPITAL
Pipeline along Southern Portion of Plant
and adjacent to DI Water Storage Tanks
Pipeline along Dobson Road to Southern Avenue
Connection of Existing Wells to Pipeline
Acid Treatment Syst~m
Vacuum Degasification Equipment
Vapor Treatment Equipment
Permit Studies
New MW-24 and Pipeline
Modify SW-1 and SW-2
TOTAL:
OPERATION AND MAINTENANCE
-
.---- ...--
Labor
Pumping and Carbon Costs for Air Extraction
Pumping Costs for Groundwater
310 Samples for 601 (@ $100 each)
Other Chemical Analyses
Extra Cooling Tower Water Treatment Costs
Maintenance costs (Pre-Treatment)
Acid Costs
TOTAL:
PRESENT WORTH
Expenses (at 5~ for 13 years)
Capital Cost
TOTAL:
24A
COST ($1,000)
$
263
450
100
35
500
150
20
48
120
$1,686
$
75
70
30
31
5
20
270
80
581
$
$5,458
1,686
$7,144
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The Land Ban requirements of RCRA do not apply to this remedial
action. The ARARs are described in .greater detail in Table 5,
and are the following:
Chemical-Specific ARARs:
o The Maximum contaminant Levels (MCLs) of the Safe
Drinking Water Act (SDWA) (40 C.F.R. Part 141) are con-
sidered relevant and appropriate since the groundwater is a
potential source of drinking water. Specifically, the MCLs
for PCE, DCE and TCE are the clean-up levels for the
remedial action.
Action-Specific ARARs
o The Clean Air Act (CAA) (40 CFR Part 50-99) is con-
sidered applicable. The CAA has been implemented through a
series of regulations that define air quality management
programs designed to achieve the CAA goals. The State of
Arizona is responsible for preparation of a State Implemen-
tation Plan (SIP) that describes how these programs will be
implemented to acheive compliance with primary standards.
Motorola Mesa remedial actions must comply with the substan-
tive requirements of the CAA and the EPA-approved Arizona
SIP.
o The Resource Conservation and Recovery Act (RCRA) (40
C.F.R. Part 265, Subpart AA and BB) for air emission stan-
dards for process vents and leaks associated with air strip-
ping are considered applicable.
o RCRA Part 261-264 for the handling, storage and removal
of wastes off-site, if the wastes are considered RCRA
wastes, are considered applicable.
o RCRA Subpart X is considered applicable. Specifically,
air stripping towers and soil-vapor extraction units are
considered miscellaneous treatment units under Subpart X.
Therefore, the substantive requirements for construction,
operation, maintenance, closure and postclosure must be met.
o The Clean Water Act (40 C.F.R. 403.5) is considered ap-
plicable. Under these provisions, discharge of treated
groundwater to the local sanitary sewer must comply with lo-
cal PUblicly Operated Treatment Works (POTW) pretrea~ment
programs.
o The Arizona Air Pollution Control Regulations (A.R.S.
49-480) for groundwater and soil treatment facilities are
considered applicable.
25
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o The Arizona statutory code for cleanup of hazardous
substances related to contaminated groundwater (Arizona
Revised statute S49-282, et seg.) and implementing regula-
tions (Arizona Administrative Code R18-7-109, et seg.) are
applicable to the Motorola Mesa site. The implementing
regulations establish that all definable aquifers are drink-
ing water aquifers, and define water quality standards for
these aquifers. Additionally, the regulations require that
Motorola Mesa remedial actions provide, to the extent prac-
ticable, for the control, management or cleanup of hazardous
substances so as to allow the maximum beneficial use of the
waters of the state
o Section 45-454.01 of the Arizona Groundwater Management
Act is considered applicable.
Location-Specific ARARs
There are no location-specific ARARs.
To Be Considered
o The Arizona Health Based Guidance Levels (A.A.C. 18-4-
R-18-4-221) are to be considered. These levels have not
been promulagated and therefore are not considered ARAR.
However, the HBGL for PCE in soil is the cleanup level for
the soil.
o Maricopa County Rules 200, 210, 220, 320 and 330 are
criteria to be considered for air emissions at the Motorola
Mesa site. Maricopa County's guidelines for implementing
Rule 210 require VOC emission controls for remdiation sites
where total uncontrolled emissions would exceed three pounds
per day.
Cost Effectiveness
EPA believes that the selected remedy is cost-effective in
mitigating the principal risk posed by the contaminated
groundwater and soil in a reasonable period of time. Section
300.430 of the NCP requires EPA to evaluate cost-effectiveness by
comparing all the alternatives which meet the following criteria:
protection of human health and the environment; long-term effec-
tiveness and permanence; reduction of toxicity, mobility or
volume through treatment; and short-term effectiveness. The
selected remedy meets these criteria and provides for overall ef-
fectiveness in proportion to its cost. The estimated present
worth for the selected remedy is $7,144,000.
26
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Utilization of Permanent Solutions and Alternative Treatment
Technoloqies or Resource Recoverv Technoloqies to the Maximum Ex-
tent Practicable
EPA and the State of Arizona determined that the selected remedy
represents the maximum extent to which permanent solutions and
treatment technologies can be utilized in a cost-effective manner
for the remedial action at this site. Except the No Action Al-
ternative, all the proposed alternatives are: protective of
human health and the environment; comply with ARARs; are effec-
tive and permanent in the long-term; and, reduce the toxicity,
mObility, or volume through treatment. The proposed alternatives
differ in their short-term effectiveness, implementability and
cost. EPA and the state determined that the selected remedy
provides the best balance of tradeoffs between these differences.
The selected remedy also satifies the statutory preference for
treatment as a principal element and considers state and com-
munity acceptance. -
To take early action on the contaminant plume, Motorola installed
a vacuum degasifier and connected it to on- and off-facility ex-
traction wells. This system is in place and currently running.
Because of this early action, the .selected remedy, which includes
using this vacuum degasifier and the extraction wells, can be
implemented the fastest of all the remedies proposed. Although
this alternative is more costly than Alternative C, the implemen-
tability and short-term effectiveness were the primary criteria
used to select this remedy. Alternatives D and E take sig-
nificantly more time to implement and are considerably more ex-
pensive.
This remedy offers the same degree of protectiveness and per-
manence as the other proposed alternatives. The selected remedy
permanently removes and destroys the VOC contamination in the
groundwater and soil, thereby utilizing permanent solutions and
treatment technologies to the maximum extent practicable. Addi-
tionally, the rehabilitation of the deep supply wells eliminates
the possiblity that the wells can -act as conduits to the lower
aquifer units before the plume is fully remediated.
Preference for Treatment as a PrinciDal Element
VOC contaminated groundwater will be extracted, and the VOCs
"stripped" off by vacuum degasification. The VOCs then will be
piped to Motorola's existing emission control system that util-
izes carbon adsorption to remove and concentrate the VOCs for
off-site incineration. Additionally, the soil-vapor will be
treated by carbon adsorption and the carbon will be incinerated.
Therefore, this remedy satisfies the statutory preference for
remedies that employ treatment of the principal threat which per-
manently and significantly reduces toxicity, mobility, or volume
of hazardous substances as a principal element.
27
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. '.
11.
Documentation of Significant Changes
The Remedial Action Plan for the Motorola Mesa Site was released
for public comment from June 19, 1991 through July 22, 1991. The
RAP identified Alternative B as the preferred alternative. ADEQ
and EPA reviewed all written and verbal comments submitted during
the public comment period and determined that no significant
changes to the remedy were necessary, based on these comments.
However, upon further review of the Applicable or Relevant and
Appropriate Requirements that Motorola identified in the RAP, EPA
revised the ARARs section in the Motorola RAP to address
deficiencies. specifically, EPA changed the following:
Chemical Specific
1. The Safe Drinking Water Act (40 C.F.R. Part 141) is the
only Chemical Specific ARAR.
2. Motorola identified the Arizona Health Based Guidance
Levels as Chemical Specific ARARs. EPA determined these are To
Be Considered.
3. Motorola also identified the following regulations as
Chemical Specific: Clean Water Act (40 C.F.R. 403.5)i Occupa-
tional Safety and Health Act (29 C.F.R. 1910.120)i
Drinking Water Standards (A.A.C. 18-4-R-18-4-221)i and, the
Arizona Revised Statutes (A.R.S. 49-224). EPA determined that
these are not Chemical Specific ARARs.
Action Specific
EPA added the following Action Specific ARARs: the Resource
Conservation and Recovery Act (RCRA) sections 261-264 (40 C.F.R.
SS261-264)i RCRA Subpart X (40 C.F.R. Subpart X)i the Clean Water
Act (40 C.F.R. 403.5)i and, the Arizona Groundwater Management
Act (A.R.S. SS45-454.01).
To Be Considered
EPA considers the following To Be Considered: the Arizona
Health Based Guidance Levels (A.A.C. 18-4-R-18-4-221)i and, the
Maricopa County Bureau of Air Control Rules and Regulations
(Regulation III and Rule Numbers 200, 210, 220, 320 and 330).
28
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