Free Additional Attachments to Main Document - District Court of Arizona - Arizona

SFUND RECORDS CTR 120930 SFUND RECORDS CTR 0217-00962

PHOENIX GOODYEAR AIRPORT SUPERFUND SITE

Goodyear, Arizona EXPLANATION OF SIGNIFICANT DIFFERENCES #5 Explanation of Significant Differences to September 1989 Record of Decision and May 1993 Explanation of Significant Differences #2. September 2002 I. INTRODUCTION In 1989, the United States Environmental Protection Agency ("EPA") issued a Record of Decision ("ROD") selecting the final remedy for contamination at the Phoenix-Goodyear Airport ("PGA") North Superfund Site ("Site") in Goodyear, Arizona. This Explanation of Significant Differences ("ESD") reestablishes that the air emissions control mechanism for the soil gas remedy under the ROD as granular activated carbon ("GAC") for the northern portion of the PGA Site - PGA-North.1 In 1993, EPA issued an ESD which altered the ROD's soil gas remedy for PGA-North from treatment of air emissions from the Soil Vapor Extraction ("SVE") system from GAC to treatment by thermal oxidation ("thermox"). The SVE system with thermox functioned for four years, but was shut off for reevaluation in 1998 and has not been restarted due to community concerns regarding potential dioxin emissions from the thermox treatment unit. Due to current Site conditions, including high levels of residual soil gas contamination and increased spread of Site groundwater contamination, this ESD returns the soil gas remedy to SVE using GAC.

The soil gas remedy at the southern portion of the PGA Site was closed out in 1999. See Polygon 96/92/27A Closure Report: Phoenix Goodyear Airport South (1999X Accordingly, this ESD only applies to the PGA-North soil gas remedy.
1

1

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 1 of 15

Section 117 of the Comprehensive Environmental Response, Compensation, and Liability
Act of 1980 ("CERCLA"), as amended, and 40 C.F.R. Section 300.435(c)(2)(i) (55 Fed Reg.

8666, 8852 (March 8, 1980)), require EPA to publish an ESD when significant, but not fundamental, changes are being considered to a final remedy plan as described in a ROD. If
changes to a ROD would fundamentally alter the scope, performance or cost of the selected
remedy, a ROD amendment is required. 40 C.F.R. Section 300.435(c)(2)(ii). EPA is issuing this ESD to provide notice of modifications to the 1989 ROD and ESDs subsequent thereto

which significantly, but do not fundamentally, affect the selected remedy. Because this ESD

does not propose a fundamental change to the remedy in the 1989 ROD with respect to scope,
performance or cost, no formal public comment period is required. 40 C.F.R. §300.435(c)(2)(i). This ESD and supporting documentation will become part of the PGA Administrative Record. Copies of the Administrative Record for the PGA Site including this ESD have been

placed at the following locations: Avondale Public Library 328 West Western Avenue Avondale, AZ 85323
(602)932-9415

EPA Region 9 Superfund Records Center 95 Hawthorne Street - Suite 403S San Francisco, California 94105 (415)536-2000
If additional information becomes available, EPA will revise the Administrative Record to reflect

such material.
EPA has made this ESD and supporting information available to the public through the

Administrative Record and information repository for the PGA Site. Additionally, EPA is

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 2 of 15

publishing a notice in the Arizona Republic, the West Valley View, and Prensa Hispana that
briefly summarizes the BSD and announces its availability for review. In accordance with 40

C.F.R. Section 300.515(h)(3), EPA has provided a fifteen day comment period for the State of Arizona. The State's comments on this ESD are summarized in Section IV of this document and

are also included in the Administrative Record.
H BACKGROUND The following provides a brief background of the PGA Site, the 1989 ROD and

subsequent relevant ESDs. Because this ESD only pertains to PGA-North, the background will

focus only on PGA-North contamination and cleanup.
A. Site Background and Description

The PGA site is located in Goodyear, Arizona, approximately seventeen miles west of Phoenix in the western part of the Salt River Valley. The PGA site was divided into a northern

and southern portion when Site investigation determined that there were separate contaminant

source areas.
PGA-North consists of the Unidynamics property, located at 102 S. Litchfield Road, and all areas with groundwater contamination in excess of site clean-up standards related to and

emanating from that property. Attachment 1 to this ESD provides a map indicating the
approximate boundaries for the entire PGA Superfund site. Current land uses on and near the Site are agricultural, industrial, and residential.

Solvent contamination was first discovered in certain areas of the Site by the Arizona

Department of Health Services ("ADHS") in 1981. During the following two years, EPA and
ADHS sampled area wells, revealing trichloroethylene ("TCE") contamination in 18 agricultural,

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 3 of 15

private and City supply wells in the Goodyear area. Other hazardous substances found at PGANorth during initial investigation include acetone, methyl ethyl ketone ("MEK"), 1,1,1-

trichloroethane ("TCA"), tetrachloroethylene (PCE), and other VOCs. EPA added the PGA site
to the National Priorities List ("NPL") on September 8, 1983. (Federal Register. Vol. 48, No.

175, p. 40671 (originally listed as "Litchfield Airport Area Superfund Site")).
A single ROD was produced for both the northern and southern portions of the PGA site

and was signed by the EPA Regional Administrator on September 26, 1989.2 The selected
remedy for PGA-North is a pump and treat system for groundwater contamination in the A and C

Subunits and an SVE system with emissions controls for the vadose zone.3 Remedial action at
PGA-North is being carried out by Unidynamics-Phoenix, Inc., through its parent company Crane Corporation ("Crane Co."), under a 1990 Unilateral Administrative Order. EPA, with the

assistance of Arizona Department of Environmental Quality ("ADEQ"), authorizes and oversees
all cleanup activities at the Site. B. Soil Gas Remedy at PGA-North a. Soil Gas Remedy Selection

The remedy selected in the ROD for contaminated soil gas at PGA-North was

implementation of an SVE system with vapor-phase GAC air emission controls in the contamination target areas. "Target areas" are those areas where VOCs were detected in soil
Groundwater and soil contamination at the southern portion of the site was originally addressed through a ROD of the Section 16 Operable Unit, which was signed on September 29, 1987. The remedy selected in the Section 16 ROD was determined to be consistent with that designated for the entire site in the 1989 ROD.
2

The ROD's designated remedy for PGA-South is treatment of Subunit B/C groundwater and operation of an SVE system with emissions control for the vadose zone. Remediation at PGA-South has been conducted by the Goodyear Tire and Rubber Company.

3

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 4 of 15

samples at levels higher than 1 microgram per liter (see Attachment 2). The ROD provides that
the identified target areas may be expanded or reduced, as necessary, in order to remove 99 percent of the contaminants from the soil. Additionally, the ROD provides that, where SVE is

not wholly effective, excavation and treatment of the soils may be required. The cleanup standard for VOC contamination in Site soils, as identified in the ROD and BSD #2, is the removal of contaminants from Site soils "until EPA is convinced the levels
remaining will not cause or contribute to groundwater contamination in excess of the cleanup

standard for groundwater." The cleanup level for TCE at the Site is 5 micrograms per liter. To determine the impact of soil contamination on groundwater, EPA utilizes modeling to
determine the quantity of leachate from soil contamination impacting the groundwater. The

modeling is based upon VOC vapor samples taken from soil vapor monitoring wells and
conversion of those soil vapor concentrations to total soil concentrations. To determine leachate

generation potential, EPA uses a VLEACH model, and the resultant groundwater impact from

the leachate is modeled using Mixcell.
EPA has issued four prior ESDs altering the remedy selected in the ROD. Two of those
ESDs are relevant to this BSD. In January 1991, BSD #1 identified the PGA-North soil

contamination target areas and clarified that soil excavation was one of a number of potential
remedial options, rather than the sole option, should the SVE remedy ultimately be unsuccessful. In May 1993, EPA modified the ROD again through an BSD #2, which changed the air emissions

control from GAC to thermox with wet scrubbing.
b. Soil Gas Remedial Design

In 1991 and 1992, under EPA oversight, Unidynamics designed the soil gas remedy as

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 5 of 15

described in the ROD. In late 1991, Unidynamics installed two SVE extraction wells within the

ROD-designated target areas. During testing for contaminant concentrations and pressure data,

soil gas samples were collected that showed levels of TCE at an average level of 475 parts per
million ("ppm"), acetone at an average level of 299 ppm, and MEK at an average level of 1477

ppm. Based on the high level of contaminants found in these initial tests, estimates revealed that

4,000 pounds per day of GAC would be required to treat the air emissions from the SVE system.
The high quantities caused Unidynamics concern regarding the overall cost of the remedy and the

safety of transport of the potentially combustible GAC from the system for disposal. Additional
concerns were raised regarding potential spontaneous combustion of the GAC canisters when

used for treatment of the MEK and acetone that were detected in the soils. Accordingly,
Unidynamics evaluated several SVE emissions control technologies, the results of which were contained in Evaluation of Alternatives for Treatment of Extracted Soil Vapor During SVE Pilot Testing (March 13, 1992).

In December 1992, EPA approved a pilot test of thermox of the SVE by-products with
wet scrubbing. At that time, thermox was considered a demonstrated technology for treatment of soil contaminated with VOCs with a 99% destruction efficiency. Thermox eliminated the need

to dispose of and regenerate large volumes GAC canisters, thereby reducing the cost of disposal
and eliminating potential hazards inherent in transporting hazardous waste. After pilot testing in
May 1993, EPA approved the use of thermox with a wet scrubber unit as vapor treatment for the
SVE system, and documented that decision in ESD #2.4

PGA-South established an SVE system with air sparging at three different locations between March 1996 and April 1998. hi April 1998, it was determined that soil remediation goals had been reached. This determination was confirmed with soil vapor rebound monitoring

4

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 6 of 15

c.

Implementation of Soil Gas Remedy at PGA-North

Pursuant to BSD #2, Unidynamics constructed an SVE system utilizing thermox with wet scrubbing for emissions control. The SVE system was completed in 1994 and operated for approximately four years. During that time, the SVE system removed approximately 10,000 pounds of VOCs from the soils. However, from 1995 to 1998, the thermox treatment unit experienced numerous technical difficulties, including overheating, which required a number of system shut-downs. The entire SVE system was shut down for overall reevaluation in November 1998. Following the shutdown of the thermox system, community concerns were raised regarding potential dioxin emissions from using a thermox unit to treat SVE emissions. The community expressed concern regarding the dioxin emissions and what was perceived as a lack of community notification regarding the treatment technology. Due to these concerns, in March 2000, EPA briefed the City of Goodyear ("City") regarding the option of restarting the SVE system utilizing GAC instead of thermox. The City reiterated community opposition to the use of thermox, and requested, should EPA restart the SVE system, that all test results be provided to the public prior to full-scale system startup. In September 2001, EPA notified the City explaining that EPA would direct the restart of the SVE system with GAC in order to protect the groundwater from further contamination. On September

from April through July 1998, and by final closure sampling in September of that year. During its operation, PGA-South's SVE system removed 1,768 pounds of chlorinated solvents, including TCE, from the area. (For details, see Polygon 96/92/27'A Closure Report: Phoenix Goodyear Airport South (1999)). Closure was granted at PGA-South for the SVE remedy after monitoring values were inserted into the VLEACH and Mixcell models to determine that groundwater impact from soil contamination was less than five micrograms per liter.

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 7 of 15

25, 2001, the City of Goodyear indicated its support for the SVE system provided that adequate
background evaluations were conducted.

During June 2002, EPA collected soil gas samples from the six multi-tier soil vapor
monitoring probes adjacent to the SVE wells on the Unidynamics property. The testing detected

high concentrations of TCE in all six probes, PCE in one probe, and no MEK or acetone in any

probes (above the detection limit of 1 ug/1 (microgram per liter). The maximum concentrations in parts per million by volume (ppmv) detected for TCE and PCE are shown in the table below.
Maximum Concentrations in Soil Vapor Monitor Wells - PGA North - June 2002

Monitor well
SVM-1 SVM-2 SVM-3 SVM-4 SVM-5 SVM-6

TCE (ppmv) 1,200 580 200 350 110 540

PCE (ppmv) 19 ND ND ND ND ND

MEK (ppmv) ND
ND ND ND ND ND

Acetone (ppmv)
ND ND ND ND
ND ND

Further analysis has confirmed that VOC contaminant concentrations in the soils are high enough
to continue to pose a considerable threat to groundwater requiring continued remedial action at

the Unidynamics property. A more detailed chart comparing the TCE concentrations detected
during 1996, 1997, and 2002 at various depths in each of the six soil vapor monitoring probes is

depicted on Attachment 3.
m. DESCRIPTION OF ESD #5

This ESD returns the soil gas remedy for PGA-North to an SVE system utilizing GAC for

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 8 of 15

emissions control as originally chosen in the 1989 ROD. Although in June 2002 no ketones were

detected above the detection limits, as a conservative measure, the GAC treatment unit will be
designed with a fire protection system which will be activated based on carbon dioxide and/or

carbon monoxide monitoring in case ketones are captured by the SVE system. The cost to
restructure the SVE system for GAC emissions control will likely be less than to revitalize the
current thermox system.

GAC is a proven technology for capturing air emissions from SVE systems, with an

efficiency rate of near 100%, it is capable of removing TCE to below air emission limits. It is
also approved as BACT (Best Available Control Technology) by the Maricopa County Air

Pollution Board (APB). Additionally, utilization of a GAC system allays community concerns
regarding dioxin emissions from the thermox system.

EPA anticipates that, based on the use of GAC, the remedy will cost approximately
$40,000 for system reconfiguration (with a leased vendor-supplied GAC unit) and, at a minimum, $170,000 (including cost of carbon) annually for system operation and maintenance (O&M). To rehabilitate the thermox system would cost, at a minimum, $75,000 and annual O&M costs would run, at a minimum, $50,000 (assuming the thermox system were operated similarly to its operation during the 1990s). The annual O&M costs for the GAC unit are estimated to be higher to operate than the

O&M costs for thermox due to the collection of VOCs in spent carbon canisters which must be
disposed 5 or regenerated at an EPA-approved treatment, storage and disposal facility.

Due to the inability to predict the approximate mass of contaminant in the vadose zone beneath the Unidynamics facility, GAC consumption was calculated using historical influent TCE concentrations collected during operation of the thermox system. As a result, and based on

5

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 9 of 15

However, the annual O&M costs for thermox treatment could be underestimated for the

following reasons: (1) the price has increased for propane or natural gas, which is needed to bum
the contaminated gas vapors; (2) the projected flow rate of 150 cubic feet per minute (cfin) is

higher than the actual flow rate when the thermox treatment unit was operating; and (3) the sampling and monitoring costs could be higher because of the public scrutiny and concern about potential formation of dioxin in the gas emissions from incomplete combustion of the gases.
Issues raised in the 1993 ESD #2 regarding disposal of large quantities of carbon are no longer relevant because the prior carbon usage estimates of 4,000 pounds per day of carbon were based on worst-case soil gas concentrations, prior to initiating the 1992 SVE pilot study. Current
2002 estimates for carbon usage are in the range of 100 pounds per day, and worst-case estimates are not more than 250 pounds per day, even were the SVE extraction system to be significantly
expanded or the flow to be greatly increased.

The SVE system with GAC emissions will be operated until the VLEACH test indicates
the soil gas is no longer impacting the groundwater above cleanup standards. With the present quantity of contaminants detected in the soil gas, it is expected that the system will operate at a

minimum for one year. However, because there was insufficient collection of soil vapor monitor probe data and operational data during the period the thermox treatment unit was operating, the actual time needed to remove sufficient VOCs to meet the VLEACH test requirements is
unknown.

Because the remedy merely returns to the original soil gas remedy in the 1989 ROD in

recent soil gas sampling data, costs associated with annual O&M of a GAC unit may be significantly higher than what is presented. 10

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 10 of 15

order to meet the original cleanup standards, this ESD does not present a fundamental change in
the performance or scope of the remedy.
IV. SUPPORT AGENCY COMMENTS

As required by 40 C.F.R. §300.515(h)(3), EPA has provided ADEQ an opportunity to
review and comment on these changes to the 1989 ROD and 1993 ESD. ADEQ supports EPA

issuing this ESD. Furthermore, due to public concern regarding dioxin emissions from the
thermox system, EPA has provided the City of Goodyear with an opportunity to review and

comment on the changes, and the City supports the changes as well.
V. STATUTORY DETERMINATIONS
Where a remedial action is being taken that differs significantly from that determined in a

ROD, but does not fundamentally alter the chosen remedy in scope, performance or cost, the lead agency must consult with support agencies and produce and publicize an ESD explaining the

changes. This ESD does affect the form and cost of the current soil gas remedy for PGA-North,
but it does not fundamentally alter the scope, performance or cost of the remedy.

This ESD returns the soil gas remedy to that selected in the ROD from the alterations made by ESD #2, but the remedy remains otherwise unchanged. This remedy is protective of

human health and the environment. The change does affect the scope and performance of the
remedy as last articulated, and thus it is significant. This ESD does not, however, fundamentally

alter the remedy selected in the ROD with respect to scope, performance or cost.

VI.

PUBLIC PARTICIPATION ACTIVITIES
Pursuant to 40 C.F.R. §300.435(c)(2)(i), a formal public comment period is not required

for an ESD to a ROD when the difference does not fundamentally alter the remedy selected in the 11

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 11 of 15

ROD with respect to scope, performance or cost. This ESD does not propose a fundamental

change to the remedy in the ROD with respect to scope, performance or cost, and therefore, no

formal public comment period is required. EPA has made this ESD and supporting information
available to the public through the Administrative Record and information repository for the PGA Site. Additionally, due to public interest, EPA has participated in Community Advisory

Group (C AG) meetings and published several fact sheets intended for the public to learn about the changes set forth in this ESD. EPA is publishing a notice in the Arizona Republic, the West
Valley View, and the Prensa Hispana that briefly summarizes the ESD, including the reasons for

such differences, and that announces its availability for review.

Deborah Jordan Branch Chief, Superfund Division EPA Region 9

Date

Attachments: 1. Map Showing Location of PGA North Superfund Site 2. Map Showing VOC Target Areas Identified in ROD 3. Summary of TCE Soil Vapor Well Monitor Results for 1996, 1997 and 2002

12

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 12 of 15

Attachment 3 Summary of TCE Soil Vapor Monitor Well Results Phoenix, Goodyear Airport, Unidynamics Facility TCE (ug/L) VMW Location TCE (ug/L) TCE (ug/L) Nov 1996 Dec 1997 Depth June 2002
SVM-1-10 SVM-1-20 SVM-1-30 SVM-1-40 SVM-1-50 SVM-2-10 SVM-2-20 SVM-2-30 SVM-2-40 SVM-2-50 SVM-3-10 SVM-3-20 SVM-3-30 SVM-3-40 SVM-3-50 SVM-4-27.5 SVM-4-43 SVM-4-53 SVM-4-60 SVM-4-74 SVM-5-27.5 SVM-5-43 SVM-5-53 SVM-5-60 SVM-5-74 SVM-6-27.5 SVM-6-43 SVM-6-53 SVM-6-60 SVM-6-74
19 5.2 23 1200 1600 5 1.7 480 1500 1800 450 250 160 1300 3600 410 660 800 880 1100 75 720 780 710 560 5.2 110 240 260 250

0.8 1.1 110 4300 4100 1.1 0.6 24 4500 3900 5 2.6 22 3200 3600 280 2000 1900 2800 3100 2.6 190 230 250 24 71 2100 2700 2300 2600

32 140 690 2400 6400 .41 160 980 3100 370 67 170 370 1100 1400 210 590 820 920 1900 140 300 590 570 440 10 21 29 32 23

13

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 13 of 15

LEGEND

Area of known soil contamination Estimated extent of groundwater contamination.exceeding the maximum contaminant level for TCE (5ug/M dashed where inferred (approx 70-130 feet underground)

Scale in Miles

the Superfund site.

^

w

FIGURE 1 NORTHERN AREA OF PGA SUPERFUND SITE
remediation activities as part of

Case 2:03-cv-02226-ROS

Document 82-3

Filed 06/27/2006

Page 14 of 15

fl II

i n o · ii

S^SK &£·>»-·
p*»TM4^»--·>-·*·'.

KT

1

iJ<- i'ik*' -·
,

?*W''J^Kf-.4 '-

·'

y^'-V

' V

"·
' · V · ·£,
M Ml l ' ll I

j.*

| i p:
lc^ii^-^^:4
:, 0 6 D W f---,- ^rf..',v^'/-''- · . - / · < -

^iS&tt^X '+*·--s*- ^'.N^p
' 111 I

r.,""·;»^'.^^.. .· _ ·

r»:f^^:
200
LJOENP

i i
Case 2:03-cv-02226-ROS
BDD63605.HA AUGUST 1963

22 · « o

BUILDING N U M B E R SOIL BORING SOIL V A P O R E X T R A C T I O N W E L L AIR INLET WELL

Document 82-3

Filed 06/27/2006

Page 15 of 15

FIGURE 2 T A R G E T A R E A S A, B, AND C FOR SOILS REMEDIAL A C T I O N AT U N I D Y N A M I C S
PHOENIX OOOOYEAR AIRPORT ROD