V
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United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R06-90/064
September 1990
Superfund
Record of Decision
Arkwood, AR
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50272-101
1 REPORT DOCUMENTATION i. REPORT NO. 2
1 *" PAGE EPA/ROD/R06-90/064
1 4. Title and Subtitle
SUPERFUND RECORD OF DECISION
Arkwood, AR
First Remedial Action - Final
7. Author(s)
9. Performing Orgainization Name and Address
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
3. Recipient's Accession No.
5. Report Date
09/28/90
6.
8. Performing Organization Rept. No.
10. Pro(ecVTask/Work Unit No.
11. ContracUC) or Grant(G) No.
(C)
(G)
13. Type of Report » Period Covered
800/000
14.
15. Supplementary Notes
16. Abstract (Limit: 200 words)
The 15-acre Arkwood site is a former wood treatment facility in Boone County, Arkansas.
Land use in the vicinity of the site is primarily agricultural and light industrial.
Approximately 200 residences are located within one mile of the site, and 35 domestic
water supply wells are within 1.5 miles of the site. In addition, numerous springs
including New Cricket Spring, are found on, and adjacent to the site. The site is
characterized as karst terrain formed by the solution of limestone and dolomite by
ground water. Ground water on, or near the site is highly susceptible to contamination
as a result of underground cavities, enlarged fractures and conduits which hinder
monitoring and pumping. From 1962 to 1973, Arkwood operated a PCP and creosote wood
treatment facility at the site. Subsequently from 1973 to 1984, Mass Merchandisers,
Inc. (MMI) leased the plant and continued operations until the lease expired, and MMI
removed all remaining inventory and materials offsite. In 1986, the site owner
dismantled the plant. State investigations conducted during the 1980s documented PCP
and creosote contamination in surface water, soil, debris, and buildings throughout the
site. Contaminated surface features at the site include the wood treatment facility, a
sinkhole area contaminated with oily waste, a ditch area, a wood storage area, and an
(See Attached Page)
.
17. Document Analysis a. Descriptors
Record of Decision - Arkwood, AR
First Remedial Action - Final
Contaminated Media: soil, sludge, debris, gw, sw
Key Contaminants: organics (dioxin, oils, *PAHs, PCP)
b. Identifiers/Open-Ended Term*
c. COSAT1 Reid/Group
L 18. Availably Statement
19. Security Class (This Report)
None
20. Security Class (This Page)
None
21. No. of Pages
96
22. Price
(See ANSI-Z39.18)
See Instruction* on Rtvtnt
OPTIONAL FORM 272 (4-77)
(Formerly NTlS-35)
Department of Commerce
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EPA/ROD/R06-90/064
Arkwood, AR
First Remedial Action - Final
Abstract (Continued)
ash pile. In 1987, EPA ordered the site owner to perform an immediate removal action,
which included implementing site access including fencing and sign postings. This Record
of Decision (ROD) addresses remediation of all affected media, and provides the final
remedy for the site. The primary contaminants of concern affecting the soil, sludge,
debris, ground water and surface water are organics including pentachlorophenol (PCP),
PAHs, and dioxin; and oils.
The selected remedial action for this site includes excavating approximately 21,000 cubic
yards of contaminated soil and sludge from the railroad ditch, wood treatment facility,
storage areas and ash pile; pretreating these materials by sieving and washing the soil;
incinerating approximately 7,000 cubic yards of pretreated materials exceeding cleanup
levels onsite; backfilling washed coarse materials pretreated to below cleanup levels as
well as any residual ash; decontaminating onsite structures and debris, followed by
onsite or offsite disposal; covering the site with a soil cap and revegetating the area;
onsite pumping and treatment of 3,000 gallons of oily sinkhole liquids and any waste
water from decontamination activities using filtration and granular activated carbon,
followed by onsite discharge of treated liquids, and incineration of any free phase oil;
disposing of any residuals offsite; implementing site access restrictions including
fencing; monitoring drinking water and ground water; providing municipal water lines to
affected residences; monitoring New Cricket Spring for a two-year period to measure the
success of natural attenuation. If PCP levels still exceed State standards after two
years, a treatment system will be implemented for the spring. The estimated present
worth cost for this remedial action is $10,300,000. O&M costs were not provided.
PERFORMANCE STANDARDS OR GOALS: Action levels for soil excavation and treatment include
PCP 300 mg/kg (based on the leachability of PCP from site soil), carcinogenic PAHs
6.0 mg/kg (10~5 excess cancer risk), and dioxin 20 ug/kg (ATSDR).
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION €
1445 ROSS AVENUE SC'TE 1200
DALLAS TEXAS 75202 2733
ARKWOOD, INC.
OMAHA, ARKANSAS
RECORD OF DECISION
DECLARATION
SITE NAME AND LOCATION
Arkwood, Inc. Site
Omaha, Boone County, Arkansas
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial action for
the Arkwood, Inc. site in Omaha, Arkansas, which was chosen in
accordance with CERCLA, as amended by SARA, and, to the extent
practicable, the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This decision is based on the
administrative record for the site.
The State of Arkansas concurs with the selected remedy.
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 Record of Decision (ROD) , may present an imminent and
substantial endangerment to public health, welfare, or the
environment.
DESCRIPTION OF THE SELECTED REMEDY
The principle threat from this site is direct contact with the site
soils that are contaminated above health based levels, and the long
term threat to the ground water. The low level threat from this
site is from direct contact with soils that are contaminated below
the health based levels, and from New Cricket Spring which contains
pentachlorophenol above the Maximum Contamination Level. The site
soils are contaminated with pentachlorophenol (PCP), polynuclear
aromatic hydrocarbons (PNAs), and dioxin to an approximate depth
of one to two feet on the main site, and four to five feet in the
railroad ditch area. The selected remedy will destroy the site
contaminants that are above health based levels, thereby
eliminating the principle threat from the site. The topsoil cap
and the remedy for New Cricket Spring will adequately reduce the
low level threats.
The selected remedy for the contaminated soils is;
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Construct a temporary incinerator on the site,
Excavate all soils that contain greater than 300 mg/kg PCP,
or greater than 20 Mg/kg dioxin as 2,3,7,8 TCDD equivalents,
or greater than 6.0 mg/kg PNAs as Benzo-a-pyrene equivalents
(affected soils).
Excavate the soils from the on-site sinkhole,
• Sieve and wash the excavated soils,
Backfill the washed coarse materials that no longer meet the
definition of affected soils,
Incinerate on-site all washed materials that still meets the
definition of affected soils,
Backfill ash in the excavated areas,
• Place a top soil cap over the entire site,
Seed the site with native grasses.
Fence the entire site to prevent access
Shallow ground water on the site is contaminated with PCP. Only
one spring in the area, New Cricket Spring, which lies
approximately 1000 feet northwest of the site, has consistently
shown contamination with PCP. No drinking water wells have been
shown the presence of site contaminants. The area is underlain by
karst geology which prevents the use of monitor wells as a method
of predicting contaminant movement, or recovery wells as a method
of remediation. Therefore, ground water remediation focuses on New
Cricket Spring. The source remediation described above is expected
to reduce the degree and amount of ground water contamination. The
selected ground water remedy is;
Monitor area springs during, and two years after the soils
remediation to determine the degree to which natural
attenuation is taking affect,
• If pentachlorophenol levels are above State of Arkansas water
quality standards after a post-remedial monitoring period of
two years, erect a water * treatment system at New Cricket
Spring to treat to State of Arkansas Water Quality Standards,
• Treat New Cricket Spring until levels fall below state
standards.
Monitor selected drinking water wells for 30 years.
Provide selected well water users with city water lines to
remove any uncertainty in their water supply.
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DECLARATION
The selected remedy is protective of human health and the
environment, complies with Federal and State requirements that are
legally applicable or relevant and appropriate to the remedial
action, and is cost effective. This remedy utilizes permanent
solutions and alternative treatment technologies to the maximum
extent practicable, and satisfies the statutory preference for
remedies that employ treatment that reduces toxicity, mobility ,
or volume as a principle element.
Because this remedy will result in hazardous substances remaining
on-site above levels that allow for unlimited use and unrestricted
exposure, the five-year review for site soils will apply to this
action. Five year reviews for New Cricket Spring, and the ground
water monitoring program, will also be required.
Robert E. Laytq/f
Regional Administrator
Region VI
Environmental Protection Agency
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ARKWOOD, INC. 8UPERFDMD SITE
RECORD OF CONCURRENCE
The Arkwood, Inc. Superfund site Record of Decision has been
reviewed by me, and I concur:
Garret ^Bondy,
Hazardous Waste Management Division
Superfund Enforcement Branch
Arkansas/Louisiana Section (6H-EA)
«ark Peycke /
Office of Regional Counsel
ALON Section (6C-WA)
Hazardous Waste Branch
George Alexander
Regional Counsel (6C)
:ker, Chief
Hazardous Waste Management Division
Superfund Enforcement Branch (6H-E)
Allyn M. Davis, Director
Hazardous Waste Management Division (6H)
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TABLE OF CONTENTS
DECISION SUMMARY
I. Site Name, Location and Description 1
A. Name, Location and Address 1
B. Area and Topography of Site 1
C. Adjacent Land Uses 1
D. Natural Resource Uses 1
E. General Surface and Subsurface Conditions 5
F. Location and Distance to Nearby Human Populations . 11
G. Site Surface and Subsurface Features 11
II. Site History and Enforcement Activities 14
A. History of Site Activities 14
B. State and Federal Removal and Remedial Actions ... 15
C. CERCLA Enforcement Activities 15
III Highlights of Community Participation 16
IV. Scope and Role of Response Action Within Site Strategy . 17
V. Summary of Site Characteristics 19
VI. Summary of Site Risks 33
A. Human Health Risks 33
B. Environmental Risks 38
VII. Description of Alternatives 39
A. Common Design Elements 39
B. Description of Alternatives 43
A. No Action 43
B. Site Monitoring and Restricted Access 44
C. Incinerate Sludges 44
Cl. Incinerate Sludges/Topsoil Cap Over Entire
Site 45
D. Incinerate Sludges/Consolidate and Cap-In-Place
Affected Soil 45
E. Incinerate Sludges/Consolidate. Sieve-and-Wash
and Cap-n-Place Affected Soils 47
F. Incinerate Sludges/Sieve-and-Wash. Biologically
Treat Sand/Fines and Cap-In-Place Affected
Soils 49
G. Incinerate Sludges/Landfill Affected Soils On-
Site 50
H. Incinerate Sludges and Affected Soils On-
Site 51
VIII. Summary of Comparative Analysis of Soil Alternatives . 52
A. Threshold Criteria 52
B. Primary Balancing Criteria 55
C. Modifying Criteria 59
IX. Description of Ground water Alternatives 60
A. Natural Attenuation with Monitoring 61
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B. Ground water Recovery/Treatment/Surface Discharge . 61
X. Summary of Comparative Analysis of Ground water
Alternatives 61
A. Threshold Criteria 63
B. Primary Balancing Criteria 63
C. Modifying Criteria 64
XI. The Selected Remedy 64
A. Soil 64
B. Ground water 65
XII. Statutory Determinations 66
A. Protection of Human Health and the Environment ... 66
B. Compliance With Applicable or Relevant and
Appropriate Requirements 67
C. Cost-Effectiveness 68
D. Utilization of Permanent Solutions and Alternative . 68
E. Preference For Treatment As a Principal Element . . 68
XIII. Explanation of Significant Differences 68
XIV. Responsiveness Summary 70
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LIST OF FIGURES
Figure 1-1 State of Arkansas 2
Figure 1-2 Site Location Map 3
Figure 1-3 Site Location Map ,. 4
Figure 1-4 Site Geology 6
Figure 1-5 Area Springs 8
Figure 1-6 Area Wells 10
Figure 1-7 Site Features Map 12
Figure IV-1 Excavation Limits 18
Figure V-l Site Features Map 23
Figure V-2 Railroad ditch PCP Concentration 0-6" 26
Figure V-3 PCP Concentrations 0-6" Main Site 28
Figure V-4 PCP Concentrations 1-2' Main Site 29
Figure V-5 Site Monitoring Wells 31
Figure VII-1 Affected Soils 46
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LIST OF TABLES
Table V-l Migration Pathways 21
Table V-2 Concentrations 25
Table V-3 Well Flow Rates 32
Table VI-1 Contaminant Mass 34
Table VI-2 Carcinogenic Risk Summary 36
Table VI-3 Non-carcinogenic Risk Summary 37
Table VIII-1 Summary of Comparative Analysis . 53
Table X-l Summary of Comparative Alternatives 62
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I. Site Name, Location and Description
A. Name, Location and Address
The Arkwood, Inc. site is located west of U. S. Highway
65 and one-half mile southwest of Omaha, Boone County,
Arkansas (Figure 1-1, 1-2.) It occupies portions of
Section 27, T.21 N., R.21 W. A branch line of the
Missouri Pacific Railroad borders the northeastern
limit of the property. The southern and western limits
are bounded by Cricket Road. Highway 65 forms the
eastern property boundary (Figure 1-3).
B. Area and Topography of Site
The site is relatively flat and gently sloped to the
northwest, having been excavated for fill for the rail-
road. It is roughly triangular shaped and covers
approximately 15 acres. It is surrounded by hilly
terrain dominated by ridges and steep-sided valleys.
C. Adjacent Land Uses
Within the vicinity of the Arkwood site, many of the
ridges and hilltops have been clear-cut to be used as
pasture land for grazing livestock. Many of the
steeper valley sides and "V" shaped valley floors
remain heavily wooded and provide timber to local
sawmills.
Many of the local farmers are involved in the poultry
industry and raise chickens and turkeys for a major
food chain supplier. These local producers raise
chickens and turkeys in numerous large poultry houses.
Other small industrial operations are located within a
short distance of the Arkwood site including a charcoal
plant and a relatively small scale sawmill that also
does minor amounts of wood preserving.
D. Natural Resource Uses
The only known major natural resource use in the
vicinity is timber. Softwood trees (predominantly
pines) are harvested for pulpwood and manufactured
building materials such as chipboard and plywood.
Hardwood trees are harvested for lumber and charcoal.
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Arkwood. Inc. Site
*
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Figure 1-1
State of Arkansas
Arkwood, Inc. Site
U.S. Environmental Protection Agency
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ARKWOOD
H
BOONE COUNTY ARKANSAS. GENERAL
HIGHWAY MAP. ARKANSAS STATE HIGHWAY
_L AND TRANSPORTATION DEPARTMENT. 1S14.
I
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Figure 1-2 Site Location Map
Arkwood, Inc. Site
Omaha, Arkansas
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Figure 1-3 Site Location Map
Arkwood, Inc. Site
Omaha, Arkansas
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The sawmill and the charcoal plant located southeast of
the site utilize local timber.
E. General Surface and Subsurface Conditions
Area Geology
The Arkwood, Inc. site is located in the Springfield
Plateau province of the Ozark Highlands region of
Northwestern Arkansas. Much of this area is underlain
by rocks of Ordovician to Mississippian ages. Much of
the area, including the Arkwood, Inc. site is located
in a karst terrain (see Figure 1-4) formed by the
solution of limestone and dolomite by ground water.
The deepest formation of interest at the Arkwood site
is the Roubidoux. The top of the Roubidoux is
approximately 500 feet below the ground surface in the
site area and is a major water supply in northwestern
Arkansas. The site supply well produces water out of
the Roubidoux between 900 and 1000 feet below the
ground surface. The Cotter and Powell formations that
overlie the Roubidoux, are generally not good water
producers across the region. They are present at the
site (Cotter depth is approximately 120 feet, and the
Powell depth is approximately 65 feet) below the near
surface formations and, where they were encountered in
on-site monitoring wells, they were dry.
The near surface formations at the site are the
Sylamore sandstone, and the St. Joe and Boone
limestones. On the site the uppermost formation, the
Boone, has been deeply weathered and most of the
resulting soils have been excavated. A schematic
diagram of the site geology is shown on Figure 1-4.
Area Ground Water
The Arkwood site is located in a karst terrain formed
by the solution of limestone and dolomite by
groundwater. This results in the enlargement of
underground fractures and joints in the rock,
eventually resulting in caves and sinkholes, and leads
to the replacement of surface runoff by underground
drainage through the enlarged fractures and joints. As
a result, surface drainage can become intermittent and
widely spaced or absent.
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Ground water flow occurs by one of two primary methods
in a karst environment; flow along fine fractures and
bedding planes, and turbulent conduit flow along
solutionally enlarged pathways. If monitoring or
recovery wells are drilled into karst geology, three
general flow scenarios are possible. First, the well
could be dry, having not intercepted either fractures
or conduits. Second, the well may intercept small
fractures bearing low flow rates of groundwater with
the well having a very small area of influence (i.e. on
the order of feet). Third, the well could intercept a
conduit, possibly resulting in high pumping rates.
However, it is not possible to predict where to drill
in order to intercept these conduits. This was
demonstrated during the Arkwood RI, in which two wells
drilled on site were dry, and the rest had very low
production rates. No conduits that transmitted
substantial water were encountered.
Springs
A total of 54 springs have been identified within a
1.5-mile radius of the site (Figure 1-5). These
springs discharge from hillsides or in valley bottoms.
Five are used as domestic water supplies. Only one
spring, New Cricket Spring, has been demonstrated to be
hydraulically connected to the site in a down gradient
direction. However, during one sampling after very
heavy rains, PCP was detected in the Railroad Tunnel
spring. Pentachlorophenol (PCP) has been detected in
two of the 54 springs, New Cricket Spring and the
railroad tunnel spring.
New Cricket Spring is approximately 1,000 feet
northwest of the site. It issues from a small cave-
like opening in a hillside. There are no known users
of the water from New Cricket Spring. The flow from
the spring is variable with base flow over the last
several years at about 15 gallons per minute. Under
base flow conditions the water from the spring
disappears back into the ground within 200 feet. PCP
has been detected in this spring at levels of 0.3 to
3.9 mg/1.
The Railroad Tunnel Spring is located in the south wall
of the railroad tunnel immediately north of the site.
The flow from this spring is also highly variable. At
times there is barely enough flow to wet the wall of
the tunnel. At others it pours out of the wall with
enough force to hit the other side of the tunnel.
Pentachlorophenol was found in this spring only once
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late in the RI at a level of 0.061 mg/1 after a major
rainfall. There are no known users of the Railroad
Tunnel Spring.
Wells
A total of 35 wells have been identified within 1.5
miles of the site (Figure 1-6). The major use for well
water is as domestic water supply. Most of the wells
on which data was obtainable are producing from more
than 200 feet below the ground surface. None of the
wells are completed in the soil horizon upon which the
site lies, and none have been confirmed as being
contaminated with constituents of concern from the
site1'2.
Shallow Aquifer Classification
The shallow karst aquifer beneath the site may be
classified as a Class lib aquifer. While it is not
currently used as a drinking water source, similar
water-bearing units that discharge to springs in the
area are. The base flow of 15 gpm also classifies the
aquifer as Class lib based on the "sufficient flow"
criteria3. This particular part of the shallow karst
aquifer is closely connected to the surface, has no
apparent connection with deeper, water supply aquifers,
and is not currently being used as a drinking water
supply.
Deep Aquifer
There appears to be no connection between the shallow
karst aquifer and deeper water supply aquifers. The
water chemistry has been demonstrated as being suffi-
ciently different to confirm this lack of connection4.
During the RI one well shoved contamination during a
sampling event. The contamination did not appear to be connected
with the site. In an immediate follow up sampling, the veil shoved
no contamination, thus it is believed that the contamination vas
due to lab contamination.
2 Remedial Investigation, Arkvood, Inc Site, Volume I, March
30, 1990, Section 4.6.3
3 Guidance on Remedial Actions for Contaminated Ground Water
at Superfund Sites, EPA/540/G-88/003, page 2-4 to 2-6
4 Remedial Investigation Report, Arkvood, Inc. Site, Volume
I, March 30, 1990, Section 4-7
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Additionally, a shallow unit (the Sylamore Sandstone)
appears to act as an aquiclude, restricting downward
migration of the shallow ground water in the vicinity
of the site5. Almost all of the 54 springs in the area
discharge above the Sylamore sandstone. No ground
water in the deeper producing zones has been detected
to have contamination. This evidence, along with the
lack of water in the Powell and Cotter formations
indicates that shallow ground water that occurs near
the site does not recharge the deeper water bearing
units used for drinking water.
F. Location and Distance to Nearby Human Populations
The site is located approximately one-half mile
southwest of the small town of Omaha, Arkansas
(population estimated at 200). It is estimated that
fewer than 200 people live within one mile of the site.
There are seven residences that are accessed by Cricket
Road, the road on the southwest side of the site.
There are two residences within 500 feet of the site.
G. Site Surface and Subsurface Features
1. Former Wood Treating Facility
The site has remnants remaining from its former
use as a wood treating site (see Figure 1-7, Site
Features Map). The existing structures and
remnants are as follows.
a. Debarking shed - Parts of the debarking
machinery and shed are still on site. The
shed covers less than 1,000 square feet and
is constructed with what appears to be
treated lumber and timbers covered with a tin
roof. The machinery is mostly disassembled
and all that is left is part of the mecha-
nism that fed the logs into the debarker.
b. Well house - The well house is a small
(approximately 10 foot by 10 foot) building
housing the well pump and an approximately
5000 gallon water storage tank.
c. Old Foundations - There are numerous founda-
tions on the site. They include those for
the pressure vessel, a maintenance building,
5 Remedial Investigation Report, Arkwood, Inc. Site, Volume
I, March 30, 1990, section 4.2.3
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office and the concrete ramp and foundations
for a truck scale.
2. Sinkhole
There is a feature on site that has been commonly
referred to as a sinkhole. This feature does not
meet the geologic criteria of a sinkhole (i.e. a
funnel shaped feature with subterranean drainage
formed by a collapse of soil and rock into a
conduit below the throat of the sinkhole leading
to bedrock conduits and cavities). This
"sinkhole appears to be a depression in the top of
the bedrock that is longer in one horizontal
direction than the other. It appears to have a
limited depth and currently holds water. This is
opposed to most sinkholes that readily drain to
the ground water system.
During part of the facility operating history,
waste water and chemicals were disposed of in this
depression. Apparently during part of this time
the feature drained into the subsurface, but is
has apparently been sealed off with clay and
highly viscous material.
3. Railroad Ditch Area
The railroad ditch area is shown on Figure 1-7,
It is a low area between the main site and the
railroad bed. Whether the low area was excavated
by personnel from the railroad or Arkwood, Inc.
during plant operation is not known. It may have
been left low after excavation of the railroad to
grade.
According to Mass Merchandisers, Inc., the former
operator of the site, spent treatment fluids were
disposed of in this depression until 1973 or 1974
when rising oil prices caused a modification of
site practices to the recycling of most of the
oils from the site. Very localized shallow
contaminated ground water appears to occur in a
"bath tub" formed toy a low area in the top of the
rock that surrounds the ditch area. The evidence
from monitoring wells and borings in the area is
that the top of rock is relatively impervious and
the sludges and highly contaminated soils occur in
an area of about 6,300 square feet to an average
depth of 4.5 feet.
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II. Site History and Enforcement Activities
A. History of Site Activities
1. Operations
The Arkwood plant site was originally excavated by
the railroad to obtain material for the
construction of railroad embankments between 1954
and 1962. In 1962, Arkwood, Inc. opened a single
cylinder PCP and creosote wood treatment facility
and operated the site until 1973. From 1973 to
1984, Mass Merchandisers, Inc. (MMI) operated the
plant under a lease agreement with the owner. MMI
ceased operations in 1984, at which time MMI sold
or removed its remaining inventory and materials
prior to the expiration of its lease in 1985. The
owner subsequently dismantled the plant in 1986.
The Arkansas Department of Pollution Control and
Ecology (ADPCE) initially received a complaint in
1981 by a railroad worker about potentially
affected water in the railroad tunnel. Subse-
quent preliminary investigations found detectable
levels of PCP in the ground water in the immediate
area surrounding the facility. The Environmental
Protection Agency (EPA) proposed that the site be
added to the National Priorities List (NPL) in
1985. On March 31, 1989, the site was added to
the NPL.
2. Investigations
In response to the railroad worker's complaint,
representatives from the ADPCE and the Arkansas
Department of Health conducted an inspection of
the Arkwood facility on June 19, 1981. Samples of
surface water taken during the inspection showed
levels of PCP from 2 to 4 xng/1. On October 6,
1981 the ADPCE conducted a site inspection for the
purpose of conducting an interim status standards
inspection. The inspector made various
recommendations regarding upgrades to the plant to
reduce pollution .problems.
In March 1985, ADPCE filed a Site Inspection
Report for the Arkwood site. The inspection
documented PCP and creosote contamination of the
site.
In January 1986, EPA sent the Field Investigation
Team (FIT) to perform a reconnaissance inspection
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to support the listing of the site on the NPL.
The FIT catalogued the amounts of waste present on
site, and recommended sampling of area wells.
In May of 1985, MMI and EPA entered into an
Administrative Order on Consent (AOC) for MMI to
perform the Remedial Investigation and Feasibil-
ity Study. Due to site access problems, the RI/FS
did not begin until 1987, and was completed in May
1990.
B. State and Federal Removal and Remedial Actions
In February of 1987 EPA sent the Technical Assistance
Team (TAT) to the site in order to assess the need to
perform an immediate removal action. The TAT responded
in April, 1987 that the site access was unrestricted,
and that local children used the site for recreational
activities. The TAT recommended a six foot chain link
fence to restrict access6. EPA prepared an immediate
removal request which was signed by the Regional
Administrator. In August of 1987, EPA issued an
Administrative Order to the Potentially Responsible
Parties to perform the removal which included fencing
the site entrance, and the posting of warning signs
across the site entrance. The site owner responded on
August 12th and 13th by erecting the fence and posting
the signs. An "After Action Report" was filed by Greg
Fife, EPA On Scene Coordinator on September 8, 1987,
closing out the removal action7. This removal action
made site access more difficult for area children,
however it is still relatively easy to get on the site.
C. CERCLA Enforcement Activities
A review of EPA and ADPC&E records revealed PRPs for
the site including the owners and former operators of
the site. In October, 1985 EPA sent § 104(e) letters
to Mr. Bud Grisham and Mr. H.C. Ormond, former owners
of the site, and Mass Merchandisers, Inc. (MMI), a
former operator of the site, notifying them of their
potential liability for the site and requesting
information regarding the site. In November 1985, EPA
sent notice of an impending RI/FS to the same parties.
MMI responded to the notices with a good faith offer to
6 Ecology and Environment/ Inc./ April 22, 1987, Tranamittal
Memorandum to Pat Hanmack, OSC
7 Arkvood/ inc. site/sit* IA3/ After Action Report/ August
12 / 1987 to August 13, 1987, Greg Fife/ 9/8/87
-15-
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perform the RI/FS, the owners did not respond to the (H
notice. On May 15, 1986, EPA and MMI entered into an
Administrative Order on Consent for MMI to perform the
RI/FS. In September 1986, EPA sent an additional §
104(e) letter to Mr. Bud Grisham, agent for Mr. H.C.
Ormond in response to reports that Mr. Ormand was
removing site buildings and contamination. EPA never
received a response to the §104(e) letter. Based on a
later review of the site deed, EPA determined that Ms.
Mary Burke was the current owner of the site. In June,
1987 EPA sent a Notice Letter to Ms. Burke notifying
her of her potential liability for the site.
In about November 1986, Mr. Bud Grisham, acting as
legal representative for the site owner, refused to
grant access to the site for the RI/FS. EPA referred
the case to the Department of Justice (DOJ) in March
1987, for DOJ to file suit to gain access to the site
for the RI/FS. On July 12, 1988, DOJ and the attorney
for Mr. Grisham signed a Consent Decree allowing EPA
and its agents access to the site for the purpose of
conducting the RI/FS and any required response action.
The RI/FS field work began soon thereafter.
Ill Highlights of Community Participation
A Community Relations Plan for the Arkwood, Inc. site was
finalized in February 1987. This document lists contacts
and interested parties throughout government and the local
community. It also establishes communication pathways to
ensure timely dissemination of pertinent information, and
emphasizes the need for community involvement. A Public
Workshop was held in February 1987 to explain the overall
Superfund process and the specifics of the RI. Fact sheets
were released in September 1987, January 1988, June 1989,
and September 1989. Another workshop was conducted in
February 1990 to explain the results of the RI.
The Proposed Plan was released to the public in July 1990.
All of the site related documents are available at the Boone
County courthouse and Library. The Administrative Record is
available locally at the Omaha Public School Library. A
public comment period was held from July 16 to August 15,
1990 and extended to September 14, 1990. In addition, a
public meeting was held on -July 25, 1990 in the Omaha Public
School cafeteria to present the other alternatives as well
as the proposed plan. All comments received by EPA prior to
the end of the comment period, including those expressed
orally at the public meeting, are addressed in the
Responsiveness Summary which is Section XI of this Record of
Decision.
-16-
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IV. Scope and Role of Response Action Within Site Strategy
The selected alternative provides for the removal and
destruction via incineration of the dioxin contamination to
a level of 20 M9/kg as 2,3,7,8 TCDD equivalents, PNA levels
to 6 mg/kg as Benzo-a-pyrene equivalents, and PCP levels to
300 mg/kg. All site materials are to be excavated as shown
in Figure IV-1. These materials are to be treated to
destroy the site contaminants to the criteria specified
above. This will eliminate any direct contact threat from
the soils contaminated above the health based treatment
goals on the site, and reduce the incremental risk from the
overall site to less than 10 .
The selected remedy also reduces significantly the long term
threat to the ground water posed by the geologic uncertainty
at the site. The karst geology under the site poses a
significant threat of failure for any capping type remedy at
the site. In a karst geologic setting, the formation of
sinkholes is a potential problem. If a sinkhole were to
open beneath consolidated contaminated site soils,
contaminated soils would be flushed directly into the upper
aquifer, and thence off-site. For this reason, the
contaminants must be permanently destroyed at the site.
The ground water emerging at New Cricket Spring will be
monitored for a period of time during and following the
remediation to determine if natural attenuation is
occurring. If natural attenuation does not cause the PCP
level in the spring to decrease to State Water Quality
Standards, then a water treatment unit will be erected at
the spring to treat the water to the appropriate standard.
Selected well water users will be provided with a city water
line to eliminate any concerns about the ground water
quality in the area.
The selected remedy will provide for a permanent solution
for the site. No further actions will be required following
the selected remedy. As will be discussed in Section VI,
Summary of Site Risks, the majority of the site health risk
is due to the long term direct contact with site
contaminants. Additionally, there also exists a long-term
risk to the ground water due to the geology in the area.
The Remedial Investigation detected no air-borne
contamination and no drinking water well contamination. The
Remedial Action described in this Record of Decision will
eliminate the threat of direct contact with the site
contamination, will eliminate the long-term threat to the
ground water, and will provide for the treatment of the
affected ground water to the state water quality standards.
The contamination in the railroad ditch, and the site soils
-17-
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contaminated above the action levels for dioxin, PNA and PCP
will be excavated, and incinerated. Thus the only direct
contact threat is to workers on site during the excavation
and incineration of the material. This contact will be
minimized with proper personal protective equipment. The
topsoil cap and fencing will virtually eliminate the threat
of direct contact from the low levels (below health based
numbers) of contaminants remaining on the site.
V. Summary of Site Characteristics
A. Types of Contamination
Three major contaminants are found at the Arkwood, Inc.
site. Two of the contaminants are actually classes of
compounds. One class is chlorinated dibenzo dioxins
and furans, referred to in this document as dioxins,
while the other class is polynuclear aromatic
hydrocarbons (PNAs). The third contaminant is
Pentachlorophenol (PCP). Some of the dioxins and PNAs
are considered to be cancer causing. The third
compound, pentachlorophenol, is not considered
carcinogenic, but is toxic at concentrations found on
site.
Cancer causing Compounds:
Many of the PNAs are known or suspected carcinogens.
The different compounds vary in toxic potency. The
exposure and uptake of these compounds vary with the
circumstances on the site and with the mixture of PNAs
present. In order to relate the complex mixture of
PNAs to a standard, the EPA has drafted an equivalency
rating for each type of PNA compound. This equivalency
system relates each type of the carcinogenic PNAs to
the toxicity of benzo-(a)-pyrene, considered the most
toxic PNA. This system is described in "Comparative
Potency Approach for Estimating the Cancer Risk
Associated With Exposure to Mixtures of Polycyclic
Aromatic Hydrocarbons", Interim Final Report, April 1,
1988, ICF-Clement Associates. The PNAs found at the
Arkwood site include all of the carcinogenic PNAs (PNA-
c) at various levels throughout the site.
Some dioxin and furan isomers are probable human and
known animal carcinogens, and are present in the soils
at the site. The potential threat to human health
posed by chlorinated dioxin and furans is based on the
established criteria for 2,3,7,8-tetrachlorodibenzo-p-
dioxin (TCDD). As with PNAs, the different types of
dioxins and furans have different toxic potencies.
Chlorinated dibenzofurans and other isomers of dioxin
-19-
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,
are expressed in toxic equivalents of 2,3,7,8-TCDD.
Therefore, although 2,3,7,8-TCDD is not present at the
site, the target action level for dioxin and furans is
expressed in equivalencies of 2,3,7,8-TCDD. The system
used to relate the site's dioxin concentration to
2,3,7,8 TCDD is described in "Interim Procedures for
Estimating Risks Associated with Exposures to Mixtures
of Chlorinated Dibenzo-p-Dioxin and -Dibenzofurans
(CDDs and CDFs) and 1989 Update", EPA/625/3-89/016,
March 1989. The majority of dioxin and furans found at
the site are the hepta and octa isomers of dioxin and
furan.
Non Cancer Causing Compounds:
Although some compounds at the site do not cause
cancer, they may cause other health effects. The
chemicals of concern in this group are
pentachlorophenol and the non-carcinogenic PNAs. The
non-cancer causing PNAs are related through potency
factors to naphthalene, a non-carcinogenic PNA. This
system is described in the April 5, 1990 Memorandum
from Pei-Fung Hurst to Jon Rauscher regarding
"Available Toxicity Information for PAHs" (PAH is
another abbreviation for PNA compounds). In the
Endangerment Assessment the risks are expressed as a
Hazard Index. The Hazard Index is a method of
assessing the overall potential for non-carcinogenic
effects. A Hazard Index of one or more indicates that
the safe threshold for exposure to these non-
carcinogenic compounds has been exceeded.
B. Clean Up Levels
Table V-l summarizes the migration pathways and
potential exposure points for the various media on the
site.
The clean up levels for the site are as follows;
PCP 300 rag/kg,
Dioxin/Furan 20 ng/kg as 2,3,7,8 TCDD equivalents.
PNA-c 6 mg/kg. as B(a)P equivalents
The clean up level for PCP was set at 300 ppm based on
the leachability of PCP from site soils. During the
FS, leachability tests were performed on the site soils
to provide a correlation between PCP concentrations in
the soils to PCP concentrations in the leachate from
the soils. According to the correlation, a soil PCP
concentration of 300 mg/kg resulted in a leachate
-20-
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containing approximately l mg/1 PCP. Since 1 mg/1 is ^^
the MCL for PCP, 300 mg/kg PCP was selected as the soil
clean up level based on protection of the ground water.
The clean up goal for PNA-c and dioxin were set
assuming an industrial scenario. While the
Endangerment Assessment assumed that the most probable
future land use would be occasional visits by hunters
and other recreational users, an industrial use
scenario was assessed because it is possible, and not
entirely unlikely that the site may be used for some
industry in the future. Since an industrial use would
require more stringent clean up goals than the
occasional use scenario, industrial based goals were
selected. Using the industrial scenario, a clean up
goal for PNA-c was calculated. THe scenario assumed a
working life of 30 years, at 260 days per year and an
adult soil ingestion rate of 100 mg per exposure.
These calculations resulted in 10"6, 10"5, and 10"4 goals
corresponding to 0.6, 6.0, and 60 mg/kg of PNA-c as
B(a)P equivalents. Based on these calculations, a PNA-
c remediation goal of 6.0 mg/kg corresponding to a 10"5
risk was selected. A goal of O.g mg/kg, corresponding
to a 10"6 was not selected because, such a goal would
require far more excavation than is necessary to meet
the 300 mg/kg PCP level, and would result in much
higher remediation cost, and would require crushing and
grinding of large volumes of rocks and increasing
material handling problems.
The dioxin/furan clean up level was selected based upon
the Agency for Toxic Substances and Disease Registry
(ATSDR) recommendation of 20 Mg/kg for industrial use
sites.
C. Sources/Extent of Surface Contamination
1. Sinkhole - The sinkhole location is shown on Figure
V-l (Site Features). It is in the northwestern quarter
of the site near the debarking shed and the
foundation/catch basin for the pressure vessels. It
has been covered by boards and a lOxlO-foot concrete
slab about two inches thick.
During site operations, spent treatment liquids and
other contaminated surface water were disposed of in
the sink-hole. The practice was stopped based on
ADPC&E recommendations due to contaminated ground water
in the area. The estimated volume of liquid in the
sinkhole is 3,000 gallons. Of this volume, most is
water with a surface layer of black oily material. The
-22-
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-------
bottom appears to be covered with a hydrated layer of
bentonite or bentonite-like clay. The liquid level in
the sinkhole appears to be persistently higher than the
water levels in the nearby monitoring wells. Thus the
sinkhole does not appear to be in communication with
the epikarst water bearing zone on the site8.
Examination of material from the sinkhole found non-
aqueous phase liquids (NAPL) on the water. These NAPL
interfered with the analysis for PNAs, PCP, and dioxin
in the water and soils in the sinkhole. Thus, the
levels of these contaminants remain unknown for these
materials in the sinkhole. Since the levels of
contamination in the soils and water is unknown, the
volumes of contaminated soil and water are unknown, and
will have to be further delineated during the design
phase. However, it is expected that the volumes in the
sinkhole are not significant compared to the volume
requiring treatment over the entire site.
2. Railroad Ditch Area - The railroad ditch area is
also shown on Figure V-l. It is a low area between the
main site and the railroad bed. Spent treatment fluids
were disposed of in this depression until 1973 or 19749
when rising oil prices caused a modification of site
practices to the recycling of most of the oils from the
wood treatment process. Very localized contaminated
ground water appears to occur in a low area in the top
of the this rock formation that surrounds the ditch
area. The evidence from monitoring wells and borings
in the area is that the top of rock is relatively
impervious and the sludges and highly contaminated
soils occur in an area of about 6,300 square feet to an
average depth of 1.8 feet10.
Figure V-2 shows PCP concentration contours at 0-6"
depth. Table V-2 shows maximum and average
concentrations of PCP as 6200 mg/kg and 2712.5 mg/kg,
PNAs-c at 371.2 mg/kg and 117.9 mg/kg as B(a)P
equivalents, and dioxin at 120.55 M9/kg and 36.5
as 2,3,7,8 TCDD equivalents. It is estimated that
approximately 1,350 yds3 are above the clean up
8 Remedial Investigation Report/ Arkwood, Inc. Site, March
30, 1990, Section 4.2.3
9 Mass Merchandisers, Inc., response to §104(e) letter,
January 14, 1986
10 Feasibility Study Report, ArXvood, Inc. Site, March 30,
1990, Figure 6-2, and associated text.
-24-
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TABLE V-2
CONCENTRATIONS OF CONTAMINANTS
Area
Railroad Ditch
Contaminant
PCP mg/kg
PNA-c mg/kg
Dioxin
Concentration
Maximum Average
6200.0 2712.5
371.2 117.9
120.5 36.5
Treatment/Trolley PCP mg/kg
PNA-c mg/kg
Dioxin
6800.0 702.0
49.3 183.0
20.3 6.2
Wood Storage
PCP mg/kg
PNA-C
Dioxin Mg/kg
1700.0 296.0
89.0 2.05
27.8 11.8
Ash Pile
PCP mg/kg
PNA-c mg/kg
Dioxin Mg/kg
3700.0 357.6
182.0 42.7
37.7 9.18
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criteria in the railroad ditch, and will require
treatment.
3. Trolley/Treatment area - The trolley/treatment area
is shown in Figure V-l. It is an area about 60x200
feet at the southeast end of the pressure vessel. The
wood was treated in this area and then was placed onto
a trolley that ran on rails across this area to a point
where it was hauled to other parts of the site for
storage. Soils in this area are stained from drippings
from the freshly treated materials.
Figure V-3 shows PCP concentration contours at 0-6"
depth while Figure V-4 shows the same at l'-2' depth.
Table V-2 shows maximum and average concentrations of
PCP as 6800 mg/kg and 702 mg/kg, PNAs as B(a)P
equivalents as 49.3 mg/kg and 49.43 mg/kg11. Dioxin,
as 2,3,7,8 TCDD equivalents, as 20.27 Mg/kg and 6.2
jig/kg were found in this area. It is estimated that
1,850 yds3 are above the clean up criteria in this area
and will require treatment.
4 . Wood Storage Area - The wood storage area comprises
roost of the Southeastern two-thirds of the site. This
area is where treated wood was stored prior to
shipment. The contamination in this area is a result
of treatment chemicals dripping off the freshly treated
wood during storage.
Figure V-4 shows PCP concentration contours at 0-6"
depth while Figure V-5 shows the same at l'-2' depth.
Table V-2 shows maximum and average concentrations of
PCP as 1700 mg/kg and 296 mg/kg, PNAs as B(a)P
equivalents, as 89 mg/kg and 2.05 mg/kg, and dioxin as
2,3,7,8 equivalents, as 27.8 Mg/kg and 11.8 Mg/kg. It
is estimated that 17,325 yds are above the clean up
criteria and will require treatment.
5. Ash Pile - The Ash Pile as shown on Figure V-l. It
is a small area of material on the slope to the
railroad on the northwest end of the site. This area
is where ash from burning spent chemicals and wood
chips was disposed of.
The average concentration of PNAs in this area is higher
than the maximum detected value. This is due to high detection
limits in many samples. The average concentration was calculated
using one-half of the detection limit resulting in a higher average
concentration.
-27-
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Table V-2 shows maximum and average concentrations of
PCP as 3700 ing/kg and 357.6 mg/kg^ PNAs as 182 rag/kg
and 42.7 mg/kg, and dioxin as 37.74 Mg/kg and 9.18
Mg/kg as 2,3,7,8 TCDD equivalents. It is estimated
that 300 yds are above the clean up criteria and will
require treatment.
C. Extent of Ground Water Contamination
A total of 12 wells were installed at the site. Six
were installed in the main site area, and six were
installed in the railroad ditch area. The locations of
these wells are shown on Figure V-5. None of the site
wells intercepted conduits with high flow rates. Table
V-3 shows the depths, flow rates and PCP concentrations
in each well. PCP was the only site contaminant found
in the wells. Since the solubility of PCP in water is
25 mg/1, samples which contained higher levels
contained waste in an oil phase on the top of the
water. As shown on Table V-3, the only wells that
contained an oily layer were those around the railroad
ditch. It is believed that the ditch is the source of
this oily layer and that the remediation of the ditch
would eliminate this localized oily contamination.
A total of 54 springs have been identified within a 1.5
mile radius of the site. Of these, 13 were sampled
during the RI. As stated earlier, only New Cricket
Spring was confirmed to show site related contamination
(PCP). The railroad tunnel spring has shown PCP only
once during the RI. The other springs have not shown
contamination. New Cricket Spring showed PCP levels
from 0.3 to 3.9 mg/1 with concentrations decreasing as
flow increased. Out of the six sampling events, the
railroad tunnel spring showed PCP once at 0.061 mg/1
after a major rainfall. The MCL for PCP is 1.0 mg/1.
Thirty-five drinking water wells were identified within
a 1.5 mile radius of the site. Of these, 15 were
sampled during the RI. No site related contamination
was found in any well. It is believed that the
contaminated upper aquifer and the deeper water supply
aquifer are not connected.
-31-
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TABLE V-3
WELL FLOW RATES AND PCP CONCENTRATION
Well
PW-1
MW-1
MW-2
MW-3
MW-4
MW-5
MW-6
MW-7
MW-8
MW-9
MW-10
MW-11
Area
Main Site
Main Site
Main Site
*
Main Site
Railroad Ditch
Railroad Ditch
Main Site
Main Site
Railroad Ditch
Railroad Ditch
Railroad Ditch
Railroad Ditch
Depth
Feet
105
45
54
50
19
23
112
58
21
15
19
23.
Flow Rate
Dry
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VI. Summary of Site Risks
A. Human Health Risks
1. Contaminants
The average concentrations and total mass of
contaminants in the various areas are shown on Table
VI-1.
2. Endangerment Assessment
An "Endangerment Assessment" was performed by MMI as
part of the Remedial Investigation. To assess the risk
posed by the site, representative concentrations of the
various contaminants were calculated. The
representative concentrations (mg/kg) used by MMI in
the exposure assessment were:
Trolley Wood
Parameter Treatment Area Storage Area Railroad Ditch
PCP mg/kg 102 74.8 126
cPNAs mg/kg (total) 46.6 25.4 38
ncPNAs mg/kg 76.8 37.1 59.8
Dibenzodioxins/
Dibenzofurans Mg/kg 1.0 2.0 8.0
(as 2,3,7,8 TCDD equivalents)
However, since the Endangerment Assessment was
completed, EPA policy has changed regarding the
toxicity of the various isomers of dioxin in relation
to 2,3,7,8 TCDD. This change resulted in an increase
in the calculated representative dioxin concentration,
as 2,3,7,8 equivalents. Therefore, EPA recalculated
risk using the revised representative dioxin
concentrations which resulted in dioxin contamination
at 6.2 Mg/kg in the trolley treatment area, 12.4 Mg/kg
in the wood treatment area and 36.5 Mg/kg in the
railroad ditch area (all levels are 2,3,7,8 TCDD
equivalents).
The pathways of potential exposure to site constituents
were determined to be: • exposure to PCP through both
ground and surface water at New Cricket Spring and
exposure to PCP, PNAs, and dioxin on the site. Routes
of exposures were determined to be through ingestion
and dermal contact.
Three exposure scenarios were developed to assess risk
from the site in the Endangerment Assessment: Exposure
Scenario I, which reflects current site conditions;
-33-
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Exposure Scenario II, which represents the most
probable future land use of occasional visitations by
hunters and other recreational use; and Exposure
Scenario III, which represents a worst-case residential
scenario of maximum exposure.
The visitation patterns for each scenario are:
Exposure Scenario I: This scenario represents the
current site conditions. The exposure is assumed to be
six times a year for railroad personnel and 12 times a
year for adults of the general public to the railroad
ditch with no access to the main site and no exposure
to the site soils;
Exposure Scenario II; This scenario represents the
roost probable future land use. in this scenario
exposure is assumed to be twelve exposures per year for
adults and six times a year by 6-12 year-old children
to the railroad ditch and the main site, and twelve
exposures per year by adults to New Cricket Spring.
Exposure Scenario III: This scenario represents the
worst case of people living on the site. Exposure is
expected to be daily by adults and children to affected
soil on the main site, and drinking water from a well
drilled on the main site pumping water from the upper
aquifer containing 5.7 mg/1 of PCP. Exposure to other
contaminated areas of the site are assumed to be twelve
exposures per year by adults and 6-12 year-old children
to the railroad ditch, and daily exposure by adults to
New Cricket Spring.
Table VI-2 presents the results of risk calculations as
revised by EPA to reflect the revised dioxin potency
factors.
In the Endangerment Assessment the Hazard Index for the
site was also calculated. The Hazard Index is
calculated to determine what levels of exposure to a
non-carcinogenic chemical will result in adverse health
effects. A Hazard Index of one or greater represents
an unacceptable risk to human health. Results of these
calculations are shown in Table VI-3.
Conclusions drawn from these calculations are:
1. There is no significant environmental impact
evident at this time due to the off-site migration
of contaminants.
-35-
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TABLE VI-2
Summary of Carcinogenic Risk Estimates
Exposure Scenario Scenerio I - Current Site Conditions
Cancer
Location Risk
Railroad Ditch 1E-04
Exposure Scenario II - Most Probable Future Land Use
Cancer
Location Risk
Railroad 1E-04
Ditch
Main Site 8E-05
Exposure Scenario III - Worst-Case Residential Exposure
Cancer
Location Risk
Railroad 2E-04
Ditch
Main Site 4E-03
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TABLE VI-3
Summary of Non-Carcinogenic Risk Estimates
(Assuming No Remedial Action)
Age Hazard
Location Group Index [a]
Exposure Scenario I - Current Site Conditions
Railroad Adult 0.044
Ditch Railroad
Personnel 0.044
Exposure Scenario II - Most Probable Future Land Use
Railroad 6-12 0.18
Ditch Adult 0.044
Total 0.22
Main Site 6-12 0.097
Adult 0.025
Total 0.12
New Cricket 6-12 NA
Spring Adult 0.076
Total 0.076
Exposure Scenario III - Worst-Case Residential Exposure
Railroad 0-6 NA
Ditch 6-12 0.18
Adult 0.044
Total 0.22
Main Site 0-6 10
6-12 5.8
Adult 1.5
Total 17
On-Site 0-6 12
Ground Water 6-12 6.7
Adult 5.3
Total 24
New Cricket 0-6 NA
Spring 6-12 NA
Adult 0.25
Total 0.25
-------
2. The total carcinogenic risk for the site under
current site conditions (Scenario I) is associated
with the railroad ditch, and is 1 x 10"4 for
adults of the general public and 3 x 10"5 for
railroad personnel. Risk is higher for the
general public than for railroad personnel since
the public is assumed to visit the site more
frequently and for a longer period of time.
3. Under the most probable future land use conditions
(Exposure Scenario II), the total cancer risk for
the main site is estimated at 8 x 10'5. The risks
associated with the railroad ditch increase, from
those in Scenario I, to 1 x 10"4 due to visitation
by children.
4. Carcinogenic risks are highest in the worst-case
residential scenario exposure (Scenario III). The
carcinogenic risk of the Main Site is 4 x 10"3,
and for the railroad ditch area the carcinogenic
risk becomes 2 x 10"4, because of the increased
exposure of adults and children to the
contaminants.
5. Noncarcinogenic risks are highest in Exposure
Scenario III. In Exposure Scenarios I and II
(current conditions and most probable future land
use pattern) no hazard index for any of the
constituents exceeds unity (1.0) at any exposure
point, indicating no expected adverse
noncarcinogenic effects. Hazard indices do exceed
unity in Exposure Scenario III for the main site
(HI=17), and from drinking the water from a well
on the main site (HI=24).
6. The risk assessment for New Cricket Spring
indicates that no adverse noncarcinogenic effects
are expected from PCP exposure to water from New
Cricket Spring, under any of the three exposure
scenarios (HI less than .25).
B. Environmental Risks
There have been no environmental impacts identified for
off-site areas. No endangered species are known to
inhabit the area on or near the site .
12 Endangerment Assessment, ArXvood, Inc. Site, August 30,
1989, Section 1.5
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VII. Description of Alternatives
Nine alternatives for soil and sludge remediation were considered
in the Feasibility Study. They are:
Alternative A - No Action
Alternative B - Site Monitoring and Restricted
Access
Alternative C - Incinerate Sludges
Alternative Cl - Incinerate Sludges/Topsoil Cap Over
Entire Site
Alternative D - Incinerate Sludges/Consolidate, and
Cap-In-Place Affected Soil
Alternative E - Incinerate Sludges/Consolidate,
Sieve-and-Wash and Cap-In-Place
Affected Soils
Alternative F - Incinerate Sludges/Consolidate,
Sieve-and-Wash, Biologically Treat
Sand/Fines and Cap-In-Place
Affected Soils
Alternative G - Incinerate Sludges/Landfill
Affected Soils On-Site
Alternative H - Incinerate Sludges Affected Soils
On-Site
A. Common Design Elements
Several of the alternatives include common major elements.
These descriptions and design bases are incorporated by
reference in sections developing the alternatives.
Fencing
Fencing the site perimeter to control access is included in
all alternatives except the No Action Alternative.
Design Basis:
Length 5,000 feet
Height 6 feet
Type Cyclone with 3 strands barbed
wire
Decontaminate and Remove Existing Structures
Several existing structures and other miscellaneous
materials will be removed and decontaminated for disposal
either on-site or at an off-site municipal landfill. This
action will be undertaken under all alternatives except A
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(No Action) and B (Site Monitoring and Restricted Access.)
These structures and materials include:
- the concrete slab covering the sinkhole
- other visible foundations
- a storage tank
- debarking shed
- miscellaneous trash and debris
Visible concrete slabs and foundations will be removed,
decontaminated by steam cleaning until no visible oil or
chemicals remain, broken into pieces of manageable size and
transported to a municipal landfill. The water collected
from steam cleaning will be analyzed for PCP and treated
through the waste water treatment unit (described later) if
the PCP concentration exceeds State of Arkansas Water
Quality Criteria. The storage tank and building will be
dismantled, decontaminated and disposed of in the same
manner.
Miscellaneous trash and debris will be either disposed of at
a municipal landfill or removed and handled with the
affected soils. They will be placed under the cap,
landfilled or incinerated with the affected soils.
Incinerate Sludges
Sludges have been identified in the railroad ditch area and
possibly in the sinkhole. The sludges are defined as highly
contaminated soils in which visible contamination is
present, and are estimated at 425 yds3. While the sludges
represent the most highly contaminated materials on site,
soils surrounding these sludges are also highly contaminated
(see section V. Summary of Site Characteristics, for a
description of concentrations). In Alternatives C through
G, these sludges are excavated, shipped in bulk, and
incinerated off-site at a permitted commercial incinerator
approved to accept CERCLA site wastes. Under Alternative H,
the sludges would be excavated and incinerated on-site along
with affected soils.
At the railroad ditch area, the cover soil is removed and
handled with other affected soils as indicated under
descriptions of the individual alternatives. The limits of
sludge excavation are determined by visual observation, as
there is a clear demarcation between sludges and underlying
soils . The excavation is backfilled as work proceeds to
minimize the chances of excavation collapse.
13 Remedial Investigation Report, Arkvood, Inc. Site Volume
It Table 4-6, Pages 10 through 13
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At the sinkhole, the concrete pad will first be removed and
handled as stated under the previous section. All pumpable
liquids would be removed, treated on-site, and discharged.
If free phase oil is present in the sinkhole liquids, it
would be separated and packed in drums for incineration with
the sludges. The manner of treatment for the sinkhole
fluids water phase would depend on the alternative. In
alternatives C, Cl, D, G, and H, a waste water treatment
unit would be installed and treated water would be
discharged on-site. In alternatives E and F, the water
would be combined with the wash water for treatment. The
sinkhole sludge is then excavated and loaded in trucks for
transport to the off-site incinerator (or carried to the on-
site incinerator in Alternatives H.)
Excavate Affected Soils
Affected soils are defined as those soils containing levels
of contaminants greater than 300 mg/kg PCP, 6 mg/kg PNA-c
and 20 Mg/kg dioxin as discussed in Section V., Summary of
Site Characteristics. The volume of affected soils,
excluding the sludges is approximately 20,400 yds .
Excavation would be performed using common earth-moving
equipment. In alternative D, the affected soils would be
partially excavated for consolidation in a smaller area for
capping (i.e., affected soil beneath the consolidation area
would be left in place.) In alternatives E through H, all
of the affected soils would be excavated. Some excavation
and stockpiling of affected soils will be necessary prior to
construction of site facilities, such as a treatment unit,
since these units would be located on affected areas. The
location of these facilities varies with the alternatives.
Stockpile sizes of affected soils will be determined during
the design process depending of the flow rates of the
incinerator. The stockpiles will be required to meet all
RCRA requirements for stockpiles, including berms and
storage times.
The actual extent of excavation for alternatives E through H
will be based on verification sampling and analyses
performed during the excavation.
Composite Cap
In Alternatives D, E, and F/ a composite cap is placed over
the consolidated soils to minimize the generation of
affected leachate by percolation of rain water.
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The cap is a composite design of (from top to bottom):
- native grasses
- topsoil
- fill
- geofabric
- drainage layer
- flexible membrane liner
- recompacted clay
It would be constructed by placing and compacting the
underlying affected materials, then placing and compacting
three feet of clay in lifts. A flexible membrane liner is
placed over the clay and covered by six inches of a porous
media (sand or gravel) to drain infiltrating rain water from
the cap. A geofabric is placed over the porous media to
prevent the finer fill from clogging the drainage layer.
One foot of fill and six inches topsoil is then placed to
provide moisture and nutrient support for a vegetative
cover. Finally, native grasses are established to control
erosion and to maximize evapotranspiration of percolating
rainfall.
In alternatives Cl through H, a topsoil cap will be placed
over all site soils (except, in the case of Alternatives D
through G, those soils already under a composite cap.) This
cap will be seeded with native grasses for protection from
wind and erosion. The topsoil cap will prevent direct
access with any residual affected soils, thereby reducing
the incremental risk from the site to less than 10"6. By
minimizing storm water contact with affected soil and
enhancing evapotranspiration of percolating water, the
potential for generation of affected leachate will be
decreased. Maintenance of the topsoil cap will consist of
periodic mowing and replacement of any lost topsoil.
Waste Water Treatment
A small waste water treatment unit is included in
Alternatives C, Cl, D, G, and H. This unit will be used
during construction to treat miscellaneous affected liquid
streams, such as storm water, decontamination water, and
sinkhole fluids. It will be reused during the post-closure
care and monitoring period to treat affected ground water or
leachate.
Storm water falling on open excavations, stockpiles and
process equipment during the construction and operation
period will be considered potentially affected by
constituents of concern. Storm water falling on unaffected
portions of the site will be allowed to run off and will not
be collected. After a rainfall, any storm water collected
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in open excavations will be sampled and analyzed for the
water quality parameters necessary to meet the National
Pollutant Discharge Elimination System (NPDES), including
PCP. If the NPDES requirements are met without treatment,
then the storm water will be considered unaffected and will
be discharged. If the NPDES requirements are not met, then
the water will be treated in the waste water treatment unit
and discharged.
Sinkhole fluids and decontamination water will be pumped
from drums into a cone-bottom tank where any free phase
organic and solids can be separated from the water. A
portable pump will be used to transfer affected storm water
from the excavation to the cone-bottom tank. Any settled
solids or floating organic will be removed from the cone-
bottom tank and placed in drums for disposal. The water
from the cone-bottom tank will be pumped through a cartridge
filter to remove solids, followed by two disposable granular
activated carbon (GAC) canisters piped in series, and then
discharged. The spent carbon canisters will be sent off-
site for regeneration and reused.
To determine when the GAC units will be regenerated, a flow
totalizer installed downstream of the filter will measure
the total volume of water treated through the unit. After a
preset volume (to be determined during start-up) has been
treated, the primary GAC unit effluent will be analyzed for
breakthrough of indicator constituents (e.g. PCP,
fluoranthene, phenanthrene, and pyrene.) Breakthrough will
be considered to have occurred when either the PCP
concentration or the indicator PNAs concentrations reach the
NPDES requirements. When breakthrough occurs, the primary
unit will be shipped off-site for regeneration, the
secondary unit will be placed in the primary position, and a
new GAC unit will be placed in the secondary position.
B. Description of Alternatives
A. No Action
This alternative would leave the site in its current
condition and provide ground water monitoring to detect
any impact on ground water for 30 years. This
alternative does not change the levels of contaminants
left exposed, does not decrease the risk from the site,
and does nothing to reduce risk of further ground water
contamination.
Implementation Time: 0 year
Capital and Operation Cost: $0
Maintenance Cost: $291,000
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B. Site Monitoring and Restricted Access
In this alternative, site access is controlled by
fencing the site perimeter and by institutional
controls as necessary to limit exposure through direct
contact with affected soils. Monitoring to detect any
impact on ground water would be performed for 30 years.
This alternative does not change the levels of
contaminants left exposed on site. This alternative
decreases the risk only by further restricting site
access, and does nothing to reduce the risk of further
ground water contamination.
Implementation Time: 0.3 Year
Capital and Operation Cost: $67,000
Maintenance Cost: $340,000
Net Present Value: $410,000
C. Incinerate Sludges
In this alternative, the railroad ditch and sinkhole
sludges are excavated, shipped in bulk, and incinerated
off-site. The contaminants would be required to be
shipped according to all applicable Department of
Transportation (DOT) regulations for hazardous
substances. The selected off-site incinerator will be
in compliance with the CERCLA off-site policy, and will
be permitted to accept these types of wastes.Cover
soils from the railroad ditch (i.e., clean soils above
the sludge) are backfilled into the excavation.
Sinkhole fluids are treated on-site along with
equipment decontamination water and any affected storm
water in a waste water treatment unit to NPDES
requirements. The site is then fenced to control
access, and existing structures are removed. This
alternative would destroy approximately 425 yds of
contaminated materials, leaving approximately 20,400
yds3 of affected soils and the rest of the site in an
unchanged condition.
The risk reduction achieved would be the result of the
elimination of the risk due to the railroad ditch area,
and the further restriction of site access. The risk
of further ground water contamination would be reduced
by excavating the railroad ditch, but the remaining
20,400 yds of affected soils would still pose a very
significant threat to the ground water.
Implementation Time: 0.5 year
Capital and Operation Cost: $1.8 million
Maintenance Cost: $.34 million
Net Present Value: $2.1 million
-44-
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Cl. Incinerate Sludoes/Topsoil Cap Over Entire Site
In this alternative, the railroad ditch and sinkhole
sludges are excavated (approximately 425 yds3) , shipped
in bulk according to DOT regulations for hazardous
waste shipments, and incinerated off-site at an
incinerator permitted to receive these wastes and in
compliance with the CERCLA off-site policy. Cover
soils from the railroad ditch are backfilled into the
excavation. Sinkhole fluids are treated on-site along
with equipment decontamination water and any affected
storm water in a waste water treatment unit to meet
NPDES requirements. The entire site is covered with a
topsoil cap. The site is fenced to control access, and
existing structures are removed.
The removal of the sludges eliminates the risk due to
the sludges. The topsoil cap reduces the incremental
risk from the site due to the direct contact with the
soils, and the fence further reduces the risk by
further restricting site access. However,
approximately 20,400 yds of affected soils would
remain on site. The risk of further ground water
contamination would be reduced by excavating the
railroad ditch sludges, but the remaining 20,400 yds3
of affected soils would still pose a very significant
threat to the ground water.
Implementation Time: 0.5 year
Capitol and Operation Cost: $2.68 million
Maintenance Cost: $.39 million
Net Present Value: $3.1 million
D. Incinerate Sludges/Consolidate and Cao-In-Place
Affected Soil
As with Alternative C, existing structures are removed
and the railroad ditch and sinkhole sludges are
transported according to DOT regulations and
incinerated off-site at a permitted facility in
compliance with the CERCLA off-site policy. The
affected soils shown in Figure VII-1 (approximately
20,400 yds ) are excavated and consolidated over the
remaining affected soils and capped with a composite
cap in compliance with RCRA construction requirements.
The remainder of the site is then covered with a
topsoil cap. The effectiveness of the composite cap at
controlling the migration of constituents will be
tracked by the monitoring program. Sinkhole fluids,
decontamination water and any affected storm water are
-45-
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treated to meet NPDES requirements in an on-site waste
water treatment unit and discharged.
This alternative treats the same amount of waste as
Alternative C (approximately 425 yds3) . The composite
cap, combined with the topsoil cap, effectively reduces
the direct contact threat from the main site, and the
fence further reduces the risk by further restricting
site access. The composite cap will also reduce the
amount of leachate produced from precipitation.
However, under this alternative highly contaminated
materials would be left on-site and would still pose a
significant long-term threat to the ground water. The
uncertainty of the area geology makes this remedy a
less than permanent remedy, with a significant threat
to the ground water remaining.
Implementation Time: 2.0 years
Capital and Operations Cost: $3.7 million
Maintenance Cost: $.39 million
Net Present Value: $ 4.1 million
E. Incinerate Sludges/Consolidate. Sieve-and-Wash and
Cap-n-Place Affected Soils
As with Alternative D, the site is fenced, existing
structures are removed and the railroad ditch and
sinkhole sludges are transported according to DOT
regulations to a permitted incinerator off-site in
compliance with the CERCLA off-site policy. Sinkhole
fluids, decontamination water and affected storm water
are treated along with the spent sieve-and-wash water
to meet NPDES requirements and discharged. All of the
affected soils (approximately 20,400 yds3) are
excavated as shown on Figure VII-1. The affected soils
which are excavated and required to be stockpiled, will
be stored in accordance with RCRA requirements for
surface storage units. The affected soils are then
sieve and washed. The washed soils that are tested and
meet the clean up criteria will be backfilled on site.
Those washed soils that do not meet the clean up
criteria will be consolidated and placed on site under
a composite cap that meets RCRA requirements. The site
is then covered with a topsoil cap.
The sieve-and-wash process is designed to remove
constituents of concern from the affected soils before
capping or additional treatment. Constituent removal
via soil washing is accomplished by two mechanisms:
-47-
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by washing the soil particle surface, dissolving
constituents into the water, which can be more
easily treated by biological or other means, and
by abrasion of some of the surface material,
leaving a slightly smaller particle with
significantly decreased constituent concentration.
The material that was abraded from the surface is
much higher in constituent concentration than the
original coarse soil and becomes affected
sand/fines. Affected sand/fines which are
generated from the coarser fractions by this
mechanism would be handled along with the original
affected sand/fines.
The wash water slurry containing affected sand and
fines is pumped to a sludge thickener. The thickened
sludge is de-watered using a precoated plate-and-frame
filter. The filter cake is transported to the
consolidation area for capping. The filtrate stream is
combined with the thickener supernatant and treated to
remove organics. The treated water is recycled to the
sieve-and-wash process and then discharged upon project
completion.
A wash water treatment unit is provided in this
alternative to de-water the sand/fines slurry and treat
the wash water for recycle. Treated wash water will
ultimately be discharged/upon completion of the
project.
According to the Treatability Study, there are three
streams resulting from the sieve and wash treatment.
There is a coarse fraction defined as the +12 mesh
material, a sands/fines fraction or -12 mesh material
and a water fraction with PCP carried off from the wash
process which will be treated in the washwater
treatment unit for recycle and re-use.
Some or all of the coarse fraction (+12 mesh,
approximately 66% of the site soils) can be washed to
residual constituent concentrations of 200 to 300 mg/kg
PCP and 10 to 100 ing/kg total indicator PNAs. Data is
not available to assess if the course soils would meet
the dioxin clean up criteria, however, the dioxin is
expected to be similarly distributed as the other
contaminants, and therefore it is expected that the
coarse fraction will meet the dioxin clean up criteria.
Testing also indicated that by washing an even more
course fraction, than the +12 mesh fraction, lower
residual concentration in the course fraction can be
achieved.
-48-
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The sieve-and-wash process leaves approximately 34% of
the site soils in the sand and fines fraction (-12
mesh) with contamination levels likely remaining above
the treatment goals. Washing the sand/fines fraction
results in residual concentrations in the sand fraction
of 250 to 550 mg/kg PCP and approximately 130 mg/kg
total indicator PNAs. In the fines fraction, the
process results in levels of 1,300 to 1,900 mg/kg PCP
and approximately 320 mg/kg total indicator PNAs. As a
result of the levels remaining in the soils, these
washed soils would be consolidated under a composite
cap constructed to RCRA requirements.
This alternative will eliminate the risk from the
railroad ditch by incinerating the sludge found there.
The sieve-and-wash will effectively reduce the volume
of material that remains above the treatment goals.
Risk from direct contact is greatly reduced by the
composite and topsoil caps. The composite cap will
also reduce the amount of leachate from precipitation.
However, under this alternative, highly contaminated
materials would remain on site and would still pose a
significant long term threat to the ground water. The
uncertainty of the area geology makes this remedy a
less than permanent remedy, with a significant threat
to ground water remaining.
Implementation Time: 2 years
Capital S Operating Cost: $6.4 million
Maintenance Cost: $.4 million
Net Present Value: $6.6 million
F. Incinerate Sludaes/Sieve-and-Wash. Biologically Treat
Sand/Fines and Cap-In-Place Affected Soils
In Alternative F, the site is fenced, existing
structures are removed and the railroad ditch and
sinkhole sludges, approximately 425 yds3, are
transported according to DOT regulations to a permitted
incinerator in compliance with the CERCLA off-site
policy and incinerated. The affected soils are
excavated and treated by sieving-and-washing, followed
by biological treatment of the sand/fines fraction.
Any affected soils which are required to be stockpiled,
will be stored in compliance with RCRA surface storage
requirements. The sand/fines slurry is pumped to a
double-lined impoundment with surface aerators for
biological treatment in a RCRA compliant impoundment.
-49-
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Alternative F provides destruction of. constituents of
concern in the sand/fines fraction by biological
treatment. The treated soils which achieve the
treatment goal are backfilled on-site; the soils not
achieving the treatment goal are placed on-site under a
composite cap constructed to RCRA requirements. The
biologically treated slurry is discharged to a de-
watering system from which the solids are tested for
indicator compounds and either backfilled as clean or
contaminated soils depending upon the remaining
contaminant levels. The sinkhole fluids, equipment
decontamination water and affected storm water are also
treated in the biological treatment system. The
remainder of the site is covered with a topsoil cap.
Any water discharge must meet NPDES requirements.
The Treatability Study showed that biological treatment
could reduce the PCP in the soils by 85%, or from 2400
mg/kg to 170 mg/kg, and PNA concentrations by 80%, or
from 420 mg/kg to 18 rag/kg total indicator PNAs. The
treatment did not reduce the concentrations of the
dioxin in the soils.
This alternative eliminates the threat from the
railroad ditch via incineration of the sludges found
there. The sieve and wash and biological treatment
further reduce the threats due to the PCP and PNAs.
The threat of direct contact to the site soils is
minimized due to the topsoil and composite caps, and
the risk is further reduced by further restricting site
access by fencing the site. However, these treatments
will not destroy the dioxin at the site, which is
responsible for much of the risk at the site.
Implementation Time: 6 years
Capital & Operation Cost: $13.2 million
Maintenance Cost: $.4 million
Net Present Value: $13.6 million
G. Incinerate Sludges/Landfill Affected Soils On-Site
In this alternative, the railroad ditch and sinkhole
sludges are excavated (approximately 425 yds ), shipped
in bulk according to DOT regulations for hazardous
waste shipments, and incinerated offsite at an
incinerator permitted to receive these wastes and in
compliance with the CERCLA off site policy. The
affected soils are excavated and consolidated in an on-
site landfill constructed to the RCRA minimum
technology requirements for a landfill. Closure would
require post closure monitoring and care.
-50-
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Sinkhole fluids are treated on-site along with
equipment decontamination water and affected storm
water in a wastewater treatment unit to the State of
Arkansas Water Treatment Standards. The remainder of
the site is covered with a topsoil cap, and the site is
fenced.
Monitoring of the leachate collection system is
provided in addition to the ground water monitoring
program to detect any leaks from the landfill during
the post-closure care period. This will be
accomplished by measuring liquid levels in the leachate
collection system sumps on a quarterly basis.
This alternative treats approximately 425 yds3 of the
most highly contaminated materials but leaves
consolidated in a landfill 20,400 yds3 of affected
soils. The direct contact threat is removed in this
alternative and the landfill will minimize the amount
of leachate produced. However, under this alternative,
highly contaminated materials would remain on site and
would still pose a significant long term threat to the
ground water. The uncertainty of the area geology
makes this remedy less than permanent, with a
significant threat to the ground water remaining.
Implementation Time: 2 years
Capital & Operation Cost: $5.1 million
Monitoring cost: $.4 million
Net Present Value: $ 5.5 million
H. Incinerate Sludges and Affected Soils On-Site
For Alternative H, an on-site incinerator with
afterburner and appropriate air pollution control
devices is constructed. While a permit for the
incinerator would not be required, the incinerator
would be designed the meet the RCRA performance
standards for incinerators. All site materials, both
sludges and soils, above 300 mg/kg PCP, 6 mg/kg PNA-c
and dioxin above 20 Mg/kg 2,3,7,8 TCDD equivalents are
excavated (20,825 yds), and incinerated on site. The
incinerator effectively destroys the constituents of
concern in both the site sludges from the railroad
ditch and sinkhole, and the affected soils. Incinera-
tor ash and neutralization sludge will be backfilled
on-site.
Stockpiling of affected soils may be required, and this
will be addressed in the design of the incineration
system. Any stockpiling of soils will be designed to
-51-
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meet all RCRA storage requirements. All of the
contaminated water from the sinkhole will be treated
along with the collected stormwater and incinerator
water in an on site water treatment plant to NPDES
standards and discharged. The excavated areas will be
backfilled with clean soils and a topsoil cap will be
placed over the entire site. The site will be fenced
to restrict access.
This alternative eliminates the direct contact threat
from the railroad ditch and site soils. The long-term
threat to the ground water is eliminated since no
contamination above health-based levels are left on-
site. The topsoil cap will eliminate the threat from
contact with any soils remaining with contaminants
below the clean-up goals. The fence further reduces
the risk by restricting site access.
Implementation Time: 3 years
Capital and Operations Cost: $18 million
Maintenance Cost: $0.39 million
Net Present Value: $18.4 million
VIII. Summary of Comparative Analysis of Soil Alternatives
This section of the Record of Decision subjects the soil
alternatives to an evaluation based on the nine criteria. A
narrative evaluation of the alternatives is presented for each
criterion in the following sections, along with a comparative
evaluation of the alternatives. See Table VIII-1, Summary of
Comparative Analysis for a comparison of the Threshold and
Primary Balancing Criteria.
A. Threshold Criteria
1. Overall Protection of Human Health and the
Environment
Alternatives A (No Action) and B (Site Monitoring and
Restricted Access) are not protective of human health
and the environment relative to the other alternatives,
because they do nothing to remove or destroy the site
contaminants, or eliminate the direct contact threat to
the soils. These alternatives also do not eliminate
the long-term threat to the ground water posed by the
site geology.
Alternatives C (Incinerate Sludges) and Cl (Incinerate
Sludges/Topsoil Cap over Entire Site) are both more
protective of human health and the environment than
alternatives A and B, based on the destruction of the
sludges. Alternative Cl provides additional protection
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by providing a topsoil cap that eliminates the excess
risk due to direct exposure. However, these
alternatives do not afford adequate long term
protection of ground water.
Alternatives D (Incinerate Sludges/Consolidate and Cap-
in-Place Affected Soils) and G (Incinerate
Sludges/Landfill Affected Soils Onsite) each include
containment of affected soils as well as incineration
of the sludges. The containment of the soils reduces
the possibility of contact, which reduces the risk from
the site. The reduced risk allows these alternatives
to provide better protection of human health and the
environment than the preceding alternatives.
However,because high levels of contaminants would
remain in place, a large degree of uncertainty
regarding the protectiveness to the area ground water
remains.
Alternatives E (Incinerate Sludges/Consolidate, Sieve-
and-Wash and Cap-In-Place Affected Soils), F
(Incinerate Sludges/Consolidate, Sieve-and-Wash,
Biologically Treat Sand/Fines and Cap-In-Place Affected
Soils) and H (Incinerate Sludges and Affected Soils
Onsite) provide increased reduction in the excess risk
by reducing the levels of PNAs and PCP in the soil.
However, neither Alternative E nor F destroy dioxin and
thus would leave high levels (up to 45 M9/kg as 2,3,7,8
TCDD) of dioxin on site. Only alternative H destroys
the PCP, PNAs and dioxin and thus is the most
protective alternative. Alternative E permanently
destroys more contaminants than alternative D and is
therefore more protective. Alternative F provides even
more treatment and is more protective than Alternative
E. Alternative H is more protective than Alternative
F.
2. Compliance with Applicable or Relevant and
Appropriate Requirements
All of the alternatives will comply with ARARs.
However, Alternatives A through G do not comply with
the dioxin action level for industrial uses, set by the
Agency for Toxic Substances and Disease Registry. This
action level is a "to be considered" (TBC) requirement,
rather than an ARAR, and sets a treatment level for
dioxin in an industrial use area as 20 ny/Kg.
Alternative H will comply with this TBC.
Any on site water discharge resulting from any of these
alternatives would not be required to obtain a
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discharge permit, but would be required to meet any
NPDES discharge requirements.
Any alternative that requires stockpiling of the
affected soils would be required to comply with the
RCRA requirements for such activities.
An onsite incinerator would not require a permit but
would be required to operate within the RCRA
requirements found in 40 CFR Section 264 Subpart 0.
B. Primary Balancing Criteria
3. Long-term Effectiveness and Permanence
Alternatives A (No Action) and B (Site Monitoring and
Restricted Access) are rated low, since neither
alternative provides any certainty of long-term
protectiveness. The magnitude of the excess risk from
the site is unchanged from existing conditions in
either alternative.
Alternatives C (Incinerate Sludges) and Cl (Incinerate
Sludges/Topsoil Cap Over Entire Site) are more
effective due to the incineration of the sludges. Both
alternatives effectively remediate the worst
contamination at the site, and reduce the risk due to
the railroad ditch. These alternatives, however, leave
high concentrations of contaminants onsite and thus, do
not afford a high degree of permanence, and because of
the uncertainty of the geology, do not provide long
term protection of the ground water
Alternatives D (Incinerate Sludges/Consolidate and Cap-
in-Place Affected Soils) and G (Incinerate
Sludges/Landfill Affected Soils Onsite), provide a
decrease in excess risk and afford a greater certainty
of long-term success than the preceding alternatives,
due to the containment of the affected soils. However,
the remaining high concentrations of contaminants do
not afford a large degree of permanence and still
represent a significant long term threat to ground
water, due to the uncertainty of the karst geology.
Alternatives E (Incinerate Sludges/Consolidate, Sieve-
and-Wash and Cap-in-Place Affected Soils), F
(Incinerate Sludges/Consolidate, Sieve-and-Wash,
Biologically Treat Sand/Fines and Cap-In-Place Affected
Soils) and H (Incinerate Sludges and Affected Soils
Onsite) provide increasing treatment of the site
contaminants. The magnitude of the remaining risk and
the potential for exposure of humans and the
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environment to the remaining contaminants is reduced in
these alternatives. Alternatives E and F, however,
still leave contaminants above health based
concentrations consolidated and capped at the site.
These alternatives do not destroy the dioxin from the
main site which is responsible for much of the risk at
the site. Because of the uncertainty of the karst
geology, these alternatives do not afford an adequate
level of long term protection and permanence. Only
Alternative H provides long-term protection by
destroying to below the action levels, all the
contaminants of concern found in the soils.
4. Reduction of Toxicity, Mobility, or Volume Through
Treatment
Alternatives A (No Action) and B (Site Monitoring and
Restricted Access) are rated low since neither
decreases the toxicity, mobility or volume of
contaminants at the site.
Alternatives C (Incinerate Sludges), Cl (Incinerate
Sludges/Topsoil Cap Over Entire Site), D (Incinerate
Sludges/Consolidate and Cap-in-Place Affected Soils),
and G (Incinerate Sludges/Landfill Affected Soils
Onsite) all provide increased reduction of toxicity,
mobility and volume of contaminants via sludge
incineration.
Alternatives E, (Incinerate Sludges/Consolidate, Sieve-
and-Wash and Cap-In-Place Affected Soils), F
(Incinerate Sludges/Consolidate, Sieve-and-Wash,
Biologically Treat Sand/Fines and Cap-In-Place Affected
Soils) and H (Incinerate Sludges and Affected Soils
Onsite) achieve additional reduction of toxicity,
mobility and volume of site contaminants over the
previous alternatives. In Alternatives E, the sieve-
and-wash process removes a portion of the PCP, but not
the PNAs or dioxin. In Alternative F, the additional
biological treatment further destroys the PCP and
destroys much of the PNAs, but not the dioxin. In
Alternative H, all the contaminants of concern are
destroyed permanently. Alternative H is, therefore,
the most effective at reducing the toxicity, mobility
and volume.
5. Short-term Effectiveness
Alternatives A (No Action) and B (Site Monitoring and
Restricted Access) are rated low since neither
alternative reduces the short-term risk.
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Alternatives C (Incinerate Sludges), F (Incinerate
Sludges/Consolidate, Sieve-and-Wash, Biologically Treat
Sand/Fines and Cap-In-Place Affected Soils) and H
(Incinerate Sludges and Affected Soils Onsite) provide
treatment of site contaminants via removal and
incineration of the sludges. Alternatives F and H
include additional treatment, but pose a small
potential risk to workers and the environment during
construction and operation periods of up to six years.
During construction and operations of Alternatives F
and H, workers will be exposed to affected soils
because increased handling of the soil is required.
For this reason, Alternatives F and H are less
effective in the short-term than Alternative C.
Alternative E (Incinerate Sludges/Consolidate, Sieve-
and-Wash, and Cap-In-Place Affected Soils) effectively
remediates affected materials in a shorter time than
Alternatives F and H (approximately one to one-and-
one-half years). The construction and operation of
less complex facilities pose less risk to workers and
the environment. Less soil handling is required for
Alternative E than for Alternative F. The treatment of
affected soils in a relatively short time frame
provides an improvement over Alternative C, which does
not address the soils. Alternative E is, therefore
rated above Alternatives C, F and H.
Alternatives Cl (Incinerate Sludges/Topsoil Cap Over
Entire Site), D (Incinerate Sludges/Consolidate and
Cap-In-Place Affected Soils) and G (Incinerate
Sludges/Landfill Affected Soils Onsite) are roost
effective in the short-term and are rated the highest.
These alternatives effectively remediate the site to
remove potential short-term threats to human health and
the environment via sludge incineration. However, as
stated earlier, these alternatives leave high levels of
contaminants in place that pose a long term threat to
ground water. Construction activities for these
alternatives are expected to be completed within two
years, minimizing the short-term risk to workers, the
community or the environment due to the handling of
affected soil.
6. Implementability
Alternative H (Incinerate Sludges and Affected Soils
Onsite) is a complex alternative to implement. Since
the system operates at high temperatures, specialists
in maintenance and operation are required. A trial
burn (demonstration of performance) with associated
analytical and reporting requirements is mandatory
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prior to operation; analytical and reporting
requirements during operation are also more demanding
than for other alternatives.
Alternative F (Incinerate Sludges/Consolidate, Sieve-
and-Wash, Biologically Treat Sand/Fines and Cap-In-
Place Affected Soils) is also more difficult to
implement than the remaining alternatives. Although
the biological treatment system is not overly difficult
to design and construct, it requires more
sophistication relative to the remaining alternatives,
is difficult to operate and requires a long time period
for operation.
Alternative E (Incinerate Sludges/Consolidate, Sieve-
and-Wash, and Cap-In-Place Affected Soils) is less
complex and requires less effort to implement than
Alternatives F and H. The sieve-and-wash system is not
well-established and would require pilot testing.
However, it consists of only a few pieces of equipment
which are all well accepted in other, similar
applications and are readily available from several
manufacturers. The sieve-and-wash system is designed
conceptually to have enough flexibility to be reliable
in this application. It is more easily implemented
than alternatives F and H
Alternative G (Incinerate Sludges/Landfill Affected
Soils Onsite) is less complex and requires less effort
to implement than Alternative E. Design, construction
and maintenance of landfills is a well-established
technology, and experienced construction contractors
are readily available.
Alternative D (Incinerate Sludges/Cap-in-Place Affected
Soils) is easily implemented. This alternative
requires minimal construction, operation and
maintenance of facilities. Design and construction of
a cap is a well-established technology, and experienced
contractors are readily available.
Alternatives A (No Action) and B (Site Monitoring and
Restricted Access) do not require much effort. These
alternatives are therefore most easily implemented and
are rated the highest.
Alternatives C (Incinerate Sludges) and Cl (Incinerate
Sludges/Topsoil Cap Over Entire Site) are the most
easily implemented of the treatment alternatives, since
they require only excavation and transportation of a
modest volume of sludges and capping. Minimal
construction, operation and maintenance of facilities
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is required under Alternatives C and ci. The necessary
equipment, specialists, transportation and disposal
capacity are readily available.
7. Cost
The net present value costs (construction costs plus
operations and maintenance costs) of the alternatives
are:
Alternative A $290,000
Alternative B $400,000
Alternative C $2,100,000
Alternative Cl $3,100,000
Alternative D $4,100,000
Alternative E $6,600,000
Alternative F $14,000,000
Alternative G $5,500,000
Alternative H $18,000,000
C. Modifying Criteria
8. State Acceptance
The State of Arkansas concurred with the remedy as
proposed, but believes that a sieve and wash pre-
treatment process should be included before
incineration. Since the selected remedy includes the
sieve and wash process, this state comment os
satisfied. The State also expressed a desire that in-
situ vitrification be evaluated as a possible
alternative. EPA has evaluated this alternative and
this issue is discussed in the responsiveness summary.
The State also agreed that they shared EPA's concern
that the site's karst geology represents a long term
uncertainty, but that the formation of a large sinkhole
was unlikely. This issue is also discussed in the
Responsiveness Summary.
9. Community Acceptance
The community of Omaha, Arkansas does not want
incineration to be done at the Arkwood site. They
believe that having an 'incinerator so close (less than
one-half of a mile) to the local public school will
create greater health risks to the community than the
site now does. EPA has received significant opposition
to the incineration from the city, and residents of
Omaha. The local school district has expressed a
preference for the sieve and wash alternative.
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IX. Description of Ground water Alternatives
Common Design Elements
Ground water monitoring will be performed during the
remediation and for thirty years following the remediation
in all alternatives. Ground water monitoring will be
conducted according to the following schedule:
Year Frequency
During Remediation Quarterly
1-5 Semi-Annually
6-30 Annually
Monitoring will consist of sampling and analyzing for PCP.
The Remedial Investigation demonstrated that PCP is the only
constituent of concern detected in the ground water. The
following locations will be monitored;
- New Cricket Spring,
- Cricket Spring,
- Railroad tunnel springs,
- Well W-9,
- Well W-llA,
- Well W-11B.
The monitoring data will be evaluated after each sampling
event. If the evaluation indicates that statistically
significant increases in constituents of concern have
occurred, the sampling event will be immediately repeated to
confirm the data. If the data are not confirmed, then
scheduled monitoring will continue. If the data are
confirmed, then quarterly monitoring will occur for one year
(four events.) At the end of that time, data will be re-
evaluated. If the evaluation establishes that significant
increases in constituents of concern have occurred, then a
decision will be made to continue quarterly monitoring,
increase the monitoring frequency, or to re-evaluate the
remedial alternative for ground water. Otherwise, scheduled
monitoring will resume.
Monitoring these locations is expected to detect any off-
site migration of constituents of concern after remediation
of the Arkwood, Inc. site. • In addition, a dye trace study
has been initiated for the Arkwood site. The results of the
dye study will be used to evaluate the effectiveness of the
monitoring system in this remedy. If necessary, the
monitoring network will be expanded to include additional
monitoring locations identified by the dye trace.
The following alternatives were considered for the ground
water at the Arkwood site.
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A. Natural Attenuation with Monitoring
Alternative A relies on lowering the levels of constituents
of concern through naturally occurring physical, chemical
and biological processes. For the karst geologies, such as
at the Arkwood site, Natural Attenuation is a suitable
alternative according to EPA guidance on remedial actions
for ground water . In order to eliminate public concerns
regarding offsite ground water, ground water users im-
mediately down Cricket Creek valley from the site will be
provided with City water.
B. Ground water Recovery/Treatment/Surface Discharge
Water would be recovered from New Cricket Spring, which is
the only source of ground water determined to be affected by
site constituents. While on-site wells were determined to
contain contamination, pumping of these wells would provide
very limited treatment of the ground water because the well
pumping rates are very low, and the wells have a small area
of influence. Thus, only the small amount of contamination
that lies very close to each well would actually be removed.
A water treatment plant designed to accommodate the high
variability of the spring flow rates would be erected at the
spring. The water emerging from the spring would be treated
to the State of Arkansas Water Quality Standards, and
discharged. In order to eliminate the potential for public
concerns regarding offsite ground water, ground water users
immediately down Cricket Creek valley from the site will be
provided with City water.
X. Summary of Comparative Analysis of Ground water Alternatives
This section of the Record of Decision subjects the ground
water alternatives to an evaluation based on the nine
criteria. A narrative evaluation of the alternatives is
presented for each criterion in the following sections,
along with a comparative evaluation of the alternatives.
See Table X-l, Summary of Comparative Analysis, for a
comparison of the Threshold and Primary Balancing Criteria.
u Guidance on Remedial Actions for Contaminated Ground Water
at Superfund Sites, EPA/540/G-88/003, December 1988, Page 5-7.
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A. Threshold Criteria
1. Overall Protection of Human Health and the Environment
Both alternatives, when employed in cooperation with
extensive remediation of the source of contaminants, will in
the long term, result in equivalent levels of protection of
human health and the environment. Drinking water is not
currently affected and ground water concentrations
protective of human health and the environment will result
in the long term with either alternative. As stated
earlier, no damage has been observed off site, under current
conditions.
2. Compliance with ARARs
Alternative A does not comply with ARARs (i.e. the State of
Arkansas Water Quality Standards for PCP) in the short term,
but will in the long term. Alternative B does comply with
ARARs.
B. Primary Balancing Criteria
3. Long-term Effectiveness and Permanence
Both alternatives will result in concentrations protective
of human health and the environment in the long term.
4. Reduction of Toxicity, Mobility or Volume Through
Treatment
Alternative A does not decrease the toxicity, mobility or
volume of constituents at the site through treatment.
Treatment is provided in Alternative B, and toxicity,
mobility or volume of the organic constituents in the ground
water are actively decreased.
5. Short-term Effectiveness
Alternative A is not effective in the short term, since it
may potentially require a number of years of attenuation to
achieve state Water Quality Standards. Water treatment in
Alternative B will lower PCP concentrations in the spring
water in the short term.
6. Implementability
Alternative A does not include capital improvements or
require much effort. This alternative is therefore more
easily implemented. Alternative B includes construction,
operation and maintenance of a fairly complex treatment
facility, therefore, B is less implementable.
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7 . Cost
The net present value costs (construction costs plus
operations and maintenance costs) of the alternatives
are:
Alternative A $0.15 million
Alternative B $4.15 million
C. Modifying Criteria
8. State Acceptance
The State of Arkansas concurs with the ground water
remedy, as presented in the Proposed Plan of Action.
9. Community Acceptance
The community of Omaha has expressed concerns regarding
their drinking water supplies, and are uncomfortable
with the uncertainties in the karst geology and the
difficulties in locating contaminant migration pathways
through the ground water. Overall, the community
appears to support the proposed remedy.
XI. The Selected Remedy
A. Soil
The selected remedy for soils and sludges is Alterative
H described in Section VII. 2.1 above, with one
significant modification from that in the Proposed Plan
of Action. All excavated sludges and soils will be
sieve and washed prior to incineration. This "pre-
treatment" of the excavated materials will concentrate
the contaminants onto a smaller volume, thus reducing
the volume requiring incineration. This reduction in
volume will likely reduce the time and costs from those
originally estimated for alternative H.
Incineration was selected because it was the only
technology identified during the FS that would
permanently destroy the contaminants of concern.
Permanent destruction "of the contaminants was deemed
especially important at this site because of the long
term uncertainty of the area geology.
All sludges and soils containing more than 20
dioxin (as 2,3,7,8 equivalents), 6 mg/kg PNA-c as B(a)P
equivalents, and 300 mg/kg PCP, will be excavated sieve
and washed. The washed materials that are tested and
meet the clean up criteria will be backfilled onsite.
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Those materials that do not meet the clean up criteria
will be incinerated on site
All liquids will be pumped from the sinkhole and
treated in an on-site water treatment unit. The
sludges will be removed from the sinkhole and handled
along with the contaminated site soils. The sinkhole
will be backfilled to existing grade.
The incinerator ash will be backfilled into the
excavated areas along with the excavated materials that
were washed and met the clean up criteria. The
remainder of the excavation will be backfilled with
clean soil. The backfill will be compacted to preclude
settlement and graded to provide drainage and minimize
erosion. The entire site will then be covered with 6
to 12 inches of clean topsoil. The site will then be
seeded with natural grasses and maintained. Institu-
tional controls such as routine inspection and
maintenance of the site, will be continued for at least
30 years following the completion of the remediation.
A notice will be negotiated into the deed to the
property allowing industrial uses but warning against
future excavation on the site.
The revised estimated cost and implementation time for
this remedy are:
Net Present Value: $10,300,000
Time: 2 to 3 years
B. Ground water
The selected remedy for ground water is a combination
of Alternative A and Alternative B described in Section
VII.3 and in the Proposed Plan.
Ground water users immediately down Cricket Valley will
be provided with City water. The ground water
monitoring program described in Section IX.A will be
implemented. Water from New Cricket Spring will be
monitored for two years following the remediation to
allow natural attenuation to remediate the aquifer.
If, after this two year period, the water at New
Cricket Spring does not meet the Arkansas Water Quality
Standards, it will be treated to meet them. Depending
on the quality of water observed through the monitoring
at the other locations, other ground water may require
treatment to the same standards. The Dye Tracing Study
currently being performed could modify monitoring
locations and justify other possible actions such as
treatment at additional locations and supplying city
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water to additional users or require additional
studies.
This remedy was selected because New Cricket Spring is
not highly contaminated, ecological damage from the
site is not apparent, and natural attenuation may occur
quickly following the removal of the source of
contamination at the site. Should natural attenuation
not occur within two years after site remediation, then
the spring will be treated to ensure protection of
public health and the environment. Active remediation
of the shallow contaminated ground water found on site
was not selected because the wells in the area have
very low pumping rates and very small areas of
influence. Because of this, pumping and treating the
ground water would only remove a small amount of
contamination within a very small proximity to these
wells. In addition, since the majority of shallow
ground water contamination was found near the railroad
ditch, it is expected that the remediation will help to
remediate the ground water contamination.
XII. Statutory Determinations
Under its legal authorities, EPA's primary responsibility at
Superfund sites is to undertake remedial actions that achieve
adequate protection of human health and the environment. In
addition, section 121 of CERCLA establishes several other
statutory requirements and preferences. These specify that the
selected remedial actions 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 also must 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
sections discuss how the selected remedy meets these statutory
requirements.
A. Protection of Human Health and the Environment
The selected remedy protects human health and the
environment through the permanent destruction of dioxin,
PNA, and PCP contaminated soil which presents the principal
threat through direct contact, and presents a long-term
threat to the ground water due to the site geology.
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B. Compliance With Applicable or Relevant and Appropriate
Requirements
The selected remedy of excavation, sieve and washing,
incineration, and capping will comply with all applicable or
relevant and appropriate chemical-, action-, and location-
specific requirements (ARARs). Key ARARs are presented
below.
1. Action-specific ARARs:
40 CFR 264 Subpart 0 provides operational standards and
monitoring requirements for hazardous waste
incinerators. Key components of this regulation
include a requirement for a destruction and removal
efficiency, and limitations on HC1 and particulate
emissions. The remedy will be designed such that it
will meet these requirements. A test burn will be
conducted prior to the full scale operation of the
incinerator to determine the operating parameters which
will meet these requirements.
40 CFR 264.251 provides requirements for waste piles of
non-containerized accumulation of solid hazardous waste
that are used for treatment or storage. All stockpiles
of waste awaiting treatment will be required to meet
these construction requirements.
While a water discharge permit is not required for any
on site discharge, the NPDES requirements must be
maintained for any discharge from site work.
2. Chemical-specific ARARs:
There are no chemical specific ARARS for the Arkwood
site. However, there is a "to be considered" action
level for dioxin. The Agency for Toxic Substances and
Disease Registry has established an industrial use
action level of 20 M9/kg 2,3,7,8 TCDD. This remedy
will meet this action level.
3. Location-specific ARARs:
Arkansas State Water Quality Standard Regulation number
2 regarding PCP applies to New Cricket Spring and must
be met with natural attenuation after two years or be
treated thereafter to meet the standards.
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C. Cost-Effectiveness
The selected remedy is cost-effective because it has been
determined to provide overall effectiveness proportional to
its costs. The net present worth value is approximately
$10.3 million, with a $4.15 million contingency two years
after the completion of the remediation if the New Cricket
Spring needs to be treated. While the estimated cost of the
selected remedy is significantly greater than the cost
associated with onsite capping of highly contaminated soils,
the selected remedy destroys the contaminants of concern and
this provides significantly more protection to the public
health and the environment.
D. Utilization of Permanent Solutions and Alternative
Treatment Technologies (or Resource Recovery Technologies)
to the Maximum Extent Practicable
The selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be
utilized in a cost-effective manner for the Arkwood, Inc.
site. Of those alternatives that are protective of human
health and the environment and comply with ARARs, EPA and
the State have determined that this selected remedy provides
the best balance of considerations. These considerations
being; long-term effectiveness and permanence, reduction in
toxicity, mobility, or volume achieved through treatment,
short-term effectiveness, implementability, cost, the
consideration of the statutory preference for treatment as a
principal element, and the consideration of the state and
community acceptance.
Thermal treatment offers long-term effectiveness and
permanence and will significantly reduce the principal
threat and inherent hazards posed by the contaminated soils.
E. Preference For Treatment As a Principal Element
By destroying the dioxin, PNA and PCP contamination in the
soils in an incinerator, the selected remedy addresses the
principal threats posed by the site through the use of
treatment technologies. Therefore, the statutory preference
for remedies that employ treatment as a principal element is
satisfied.
XIII. Explanation of Significant Differences
The Proposed Plan which was released for public comment on
July 16, 1990, proposed on site incineration of all
contaminated site soils, approximately 20,400 yds . During
the public comment period, information was submitted by Mass
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Merchandisers, Inc. (MMI a potentially responsible party),
suggesting a change to a component of the remedy for the
site. EPA has incorporated this into the selected remedy.
The change involves providing a sieve and wash pre-
treatment step prior to the incineration of all affected
soils on site. The advantage of this pre-treatment step
will be to significantly reduce the volume of contaminated
materials to be incinerated, thereby reducing the treatment
time and cost of the remedy.
According to the comments submitted by MMI and the FS,
screening the site soils at the +12" mesh size, results in a
reduced volume of contaminated soils of approximately 70%.
Sampling of these materials resulted in coarse fraction
(greater than 12 mesh) contaminant levels well within the
clean up goal for the site soils. While there is no data on
the resultant dioxin concentrations for the coarse fraction,
the dioxin is expected to be distributed similar to the
PNAs. Testing of the coarse materials will be done prior to
backfilling to ensure that the clean up goal is achieved.
Those coarse soils not meeting the clean up goals will be
incinerated along with the sands and fines (less than 12
mesh) from the sieve and wash.
By reducing the amount of soils requiring incineration, the
treatment cost and time is significantly reduced. According
to MMI's comments, the cost of the remedy is expected to be
approximately $10.3 million (capital and operating cost),
compared to $18 million for the proposed remedy. By
reducing the volume of the material to be treated by 70%, or
to approximately 7000 yds3, the time required for
incineration is reduced to approximately 140 days for the
selected remedy, from 400 days (assuming 50 yds /day
incinerator capacity) in the proposed remedy.
This change to the proposed remedy enhances the selected
remedies balance in regard to the nine evaluation criteria
discussed in Section VII, Summary of Comparative Analysis of
Soil Alternatives. The selected remedy provides for a
reduction of the volume of soils requiring incineration
compared with the proposed remedy. The selected remedy is
also more effective in the short term, is less costly, and
therefore more cost effective than the proposed remedy. In
addition, the State of Arkansas agrees with this
modification to the remedy and community acceptance is
expected to increase since less material will be incinerated
in a shorter period of time. The selected remedy may be
considered a logical outgrowth of the FS, therefore no
additional public comment will be solicited.
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XIV. Responsiveness Summary
The written comments received from Mass Merchandisers, Inc.
(MMI), a potentially responsible party at this site were
extensive and are presented separately from the comments received
from all others. The following are questions and comments
received during the public comment period and at the Public
Meeting held on July 25, 1990, at the Omaha Public School:
1. Comment: The city of Omaha does not feel it is safe, from
an emissions standpoint, to incinerate in the valley, and
close to the Omaha Public School.
Response: EPA believes that a well designed and properly
operated incinerator will not cause health or environmental
problems. Based on the best available information
concerning the risks of incineration, EPA has developed
strict standards that limit the emissions from hazardous
waste incinerators. The incinerator will be required to
demonstrate that it can meet these standards during a test
burn and must meet these standards at all times during the
actual incineration. Air monitors will be placed around the
site and at the school to ensure that air quality is
maintained safely.
2. Question: How long could the incineration and the
possibility of emissions exist?
Response: The time required to incinerate the soils is
dependent on the capacity of the incineration unit and the
amount of materials requiring incineration following the
sieve and wash process. Incinerators with a wide range of
capacities are available. The Feasibility Study estimated
an incinerator feed capacity of 50 cubic yards per day.
Based on this feed rate, incineration of all of the
contaminated materials (approximately 20,400 cubic yards)
would take 400 days. However, adding the sieve and wash
process prior to incineration has been estimated to reduce
the volume to be incinerated to 7,000 yds3 and reduced the
time of incineration (used to estimate costs) to
approximately 140 days.
3. Question: The residents of Omaha would rather leave the
contamination in place than, have it burned and expose the
school children and area residents to the emissions, if the
problem is in the soil now, why put it into the air?
Response: The risk from a well designed and operated
incinerator is much less than the current risk from the
site. The threats posed by the contaminants that now exist
in the site's soils will not be transferred into the air
because all (at least 99.99%) of the contamination will be
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destroyed or removed from emissions during the incineration
process.
4. Comment: The Feasibility Study states that a remedy
involving consolidation and capping of soils from the main
site is an "acceptable" alternative and thus should be the
selected remedy.
Response: The purpose of the Feasibility Study is to present
alternatives for site remediation and to compare them to the
nine evaluation criteria. This comparison to the evaluation
criteria allows EPA to select a remedy that is properly
balanced against the criteria. The Feasibility study does
not provide an assessment of the "acceptability" of any
alternative. EPA has reviewed the consolidation and capping
alternative and has deemed it inappropriate for this site
because it does not provide treatment of site contaminants
to the maximum extent practicable as required by the
Superfund law, is not as permanent a remedy as the
alternative selected, and it does not provide for, long terra
protection of ground water.
5. Comment: The Feasibility Study states that the
consolidation and capping alternative is fully protective of
human health and the environment. Therefore it should be
the selected remedy.
Response: The Feasibility Study does provide that
consolidation and capping meets this criteria. However,
when EPA selects a remedy, it evaluates the various
alternatives against all nine criteria and selects a remedy
that has the proper balance between all the criteria. The
capping and consolidation remedy was not selected because it
does not provide an acceptable level of long term permanence
and protection of the ground water compared to the selected
remedy.
6. Comment: At the February Open House, EPA representatives
stated that there was "very little chance" of onsite
incineration.
Response: The purpose of the February Open House was to
discuss the findings of the Remedial Investigation, not to
discuss the results of the Feasibility Study, which had yet
to be completed. At that tine, preliminary review of
treatability test results indicated that the sieve and wash
and biological treatment technologies might meet EPA
remedial requirements. However, further review of the
alternative technologies indicated that these treatment
technologies, alone, would not be sufficient to destroy site
contaminants to acceptable levels. Since the incineration
alternative is the only alternative identified in the
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Feasibility Study capable of destroying the site's
contamination to acceptable levels, it was selected as the
appropriate remedy.
7. Question: Did EPA consider bioremediation using
Flavobacterium and would it be possible to bioremediate
during the construction of the incinerator?
Response: Yes, Flavobacteriuro was added to the indigenous
organisms during treatability testing during the Feasibility
Study (Feasibility Study Report, Volume II, page 7-1). As
mentioned above, the biological treatment alternative did
not meet EPA remedial requirements. It would be impractical
to design, construct and implement a bioremedial system
while constructing the incinerator. The incinerator itself
will effectively destroy the contaminants present in the
soil and the effort involved with bioremediating the
contaminated material first would be counterproductive and
unnecessary.
8. Comment: Mass Merchandisers, Inc.(MMI) stated that EPA
had, at an earlier meeting between MMI and EPA, agreed that
the affected soils should be consolidated and capped.
Response: EPA never made this agreement at an earlier
meeting or at any other time. In fact, EPA conveyed to MMI
at an earlier meeting that consolidation and capping did
not appear to be appropriate and that it would be very
unlikely that this alternative would be selected as the
site's remedy.
9. Comment: MMI disagrees with EPA's concern that a sinkhole
could develop under the capped, contaminated soil, allowing
the untreated hazardous materials to migrate into the ground
water. They feel that this should not be a reason to reject
the consolidation and capping alternative they proposed.
Response: Capping some of the most highly contaminated
materials at the site, as preferred by MMI was rejected by
EPA because it does not meet the preference for permanent
treatment to the maximum extent practicable, as specified by
CERCLA. Capping such materials does not provide adequate
long term protection. The site investigation indicated that
the geology is complex, not.well understood, and that
sinkholes while not common, could occur below capped
materials. This degree of uncertainty stressed the need to
comply with the CERCLA preference for permanent treatment.
10. Comment: MMI stated that the levels and types of dioxin
at the site do not pose a risk to human health.
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Response: EPA disagrees with this assessment. EPA
toxicologists have adopted an internationally recognized
policy that relates the less toxic forms of dioxin to the
most toxic form, using toxicity factors. The dioxin types
present on-site are indeed less toxic than the most toxic
form, but are present in sufficiently high concentrations to
pose a risk to human health.
11. Comment: There is a clear trend in scientific opinion
that the risk to human health due to dioxin is overstated.
Response: At present, there is a large amount of discussion
in the scientific community, including EPA scientists,
regarding the potency of dioxin as a human carcinogen.
However, EPA's approach in estimating risks to human health
posed by dioxins, and other hazardous substances at the
site, is well established and scientifically sound.
12. Comment: MMI believes that every possible alternative
should be explored before an incinerator is constructed.
Response: MMI, with EPA oversight, conducted a Feasibility
Study to explore a wide range of possible remedial
alternatives for this site. MMI also submitted, in writing,
a number of additional alternatives they requested EPA
evaluate. EPA has evaluated all of the alternatives in both
the FS and those submitted by MMI and has selected a remedy
it believes will safely and in a cost effective manner,
destroy the threats at the site.
13. Question: Since the ground water from New Cricket Spring
is showing a decrease in contamination, why is excavation
and incineration necessary?
Response: While it is true that New Cricket Spring appears
to be showing a slight decrease in contamination, this
factor is not a true indication of the threats posed by the
site. On-site levels of contamination are sufficiently high
to warrant the degree of remedial action selected. The
selected remedy will permanently rid the site of
contamination above health based levels, and will provide
long-term protection to the ground water and surrounding
environment.
14. Question: Wouldn't rainfall cause the contamination to
spread during the excavation of the soils before
incineration?
Response: Runoff from the site during the excavation
activities will be collected and treated if necessary to
meet NPDES requirements to minimize the possibility of
contamination spreading offsite during the remedial action.
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15. Question: What are the contaminant levels coming out of
New Cricket Spring compared to drinking water standards?
Response: The only contaminant found in New Cricket Spring
is pentachlorophenol (PCP). The drinking water standard
(expressed as a Maximum Concentration Limit, or MCL) for PCP
is 1.01 mg/1. The levels found at New Cricket Spring during
the Remedial Investigation were from 1.0 - 2.3 mg/1.
16. Question: After the remediation, what will the site be
able to be used for?
Response: The remediation goals were set assuming an
industrial use. The site will be able to be used for
businesses but not for residential purposes.
17. Question: Because the contamination has been there so
long, is it likely that much of the contamination has
already degraded or run off the site?
Response: While it is possible that some contamination has
run offsite, very little contamination was found offsite
during the investigation. Some of the site contamination
may have degraded. Regardless, enough contamination remains
onsite to warrant the remedial action selected.
18. Question: What type of emission controls are included on
the incinerators?
Response: The gasses from combustion in the incinerator are
typically treated to remove inorganic acid gasses and
particulate matter. Particulate matter can be removed with
several devices. One of the oldest methods is baghouse
filtration which involves passing the gas through a material
that collects the particulate matter. Another method
involves electrostatic precipitators. The particulate
matter in the gas is electrically charged and collects on
plates that are oppositely charged. The particulate matter
is then cleaned from the plates. Still another approach is
the venturi scrubber. Venturi scrubbers use high pressure
water to remove the particulate matter. Hydrogen chloride
gasses that result from the incineration of chlorinated
compounds (such as PCP and dioxins) are typically removed
using other types of scrubber devices, such as packed bed,
spray tower, and plate tower scrubbers. These scrubbers
bring alkaline water and the combustion gasses together,
providing the greatest possible contact between the water
and the gasses. This allows the hydrogen chloride gas to
dissolve in and be neutralized by the alkaline water.
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19. Question: Will the incinerator have an afterburner?
Response: In order to ensure complete combustion of all
waste constituents, an afterburner, or any other equivalent
devise, is included in all incinerators of hazardous waste.
20. Question: Will my home (the Rose Birmingham residence)
be placed on the city water line and who will pay the water
bill?
Response: The Birmingham well is included as one of the
private wells to be placed on the city water line.
Individual homeowners will be responsible for paying the
water bills.
21. Question: When will the site be cleaned up?
Response: It will likely be a couple of years before
construction of the remedy begins. This time will be used
to attempt to negotiate a settlement with the Potentially
Responsible Parties (PRPs), and to design the actual remedy.
Once the design is complete, remedial construction can
begin. Actual site remediation will likely take between two
and three years.
22. Question: Will local residents get priority jobs
relating to the site's remediation?
Response: If the site work is conducted by the Federal
government, then the services required for the work will be
procured according to the Federal Acquisition Regulations
(FAR). Under the regulation, local businesses are not given
a priority over other businesses. Under the regulations,
only minority businesses and businesses owned by women are
given a priority. However, in the competitive bidding
process under FAR, local businesses often have an advantage
over others since they are located near the site.
23. Question: Can and/or will hazardous waste from outside
the Arkwood site be brought to the site and incinerated? Why
not take the contaminated material to the incinerator that
has been constructed in Jacksonville, Arkansas?
Response: Because the Jacksonville site is not a permitted
commercial disposal facility', waste from the Arkwood site
can not be accepted for incineration. In addition federal
regulations only allow wastes from one Superfund site to be
brought to another if the sites are near one another and the
wastes from the sites are similar. Since no other Superfund
sites are near the Arkwood site, it is unlikely that wastes
from outside the Arkwood site will be incinerated at the
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site. Because of the same regulations, the Arkwood wastes
can not be taken to the incinerator in Jacksonville.
24. Question: Portions of the school playground were
backfilled with soils taken from the site. Has, or will,
the playground be tested?
Response: At this time EPA does not plan any soil testing at
the playground. Further investigation regarding this issue
revealed that all soils that were excavated from the site
and used as backfill at the playground were taken from an
area on the site that was still in its natural, undisturbed
state, located approximately 30 feet above the plant site
and treated wood storage areas. Consequently, the fill
removed from this area would never have been affected by
plant operations or rainwater runoff from the plant site.
25. Question: Were there downstream core samples taken from
Cricket Creek?
Response: Sediment samples were collected from Cricket Creek
155 feet above and 165 feet below the confluence of Cricket
Creek and Cricket Spring Channel. Sediment samples were
also collected in Cricket Spring Channel at approximately
600-foot intervals between New Cricket Spring and the
confluence of Cricket Spring channel with Cricket Creek. No
contamination was detected during this part of the
investigation.
26. Question: Were there any offsite samples taken from the
railroad tracks?
Response: No samples were taken on the railroad tracks.
However, offsite samples taken near the railroad track did
not reveal any site-related contamination.
27. Question: Does contamination in New Cricket Spring
increase with flow, such as after a rainfall event?
Response: Sampling of the Spring following rainfall showed
the contamination to increase slightly at first and then to
quickly decrease as the Spring flow increased.
28. Question: Is there an estimate of how much contamination
is in the ground below the surface soils and will there be
any future studies to determine this?
Response: Results of the remedial investigation show that
approximately 20,800 cubic yards of soils exceed the health
based cleanup levels. However, the materials are, for the
most part, within a couple feet of the ground surface. Some
additional contamination may have migrated to greater depths
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but due to the karst geology, it is not possible to define
where and if this has occurred. It should be stressed that
the selected remedy will destroy the majority of site
contaminants and eliminate the source of contamination,
thereby providing long term protection.
29. Question: Is the original well for the site
contaminated?
Response: No. This well was tested six times, and no site
related contaminants were found.
30. Comment: Incineration is an unacceptable solution
because if the incinerator allows 1 Ib. of hazardous
material to release into the atmosphere per 10,000 Ibs. of
material treated then a total of 3,468 Ibs. of hazardous
materials will be released.
Response: This assumption is factually incorrect. The
incinerator will be required to destroy or remove, before
emitting any gasses, at least 99.99% of the hazardous
substances fed into the incinerator. The commentor is
basing his calculation on the incorrect idea that the
material to be incinerated is 100% contaminated. Since the
feed to the incinerator will contain contamination in the
parts per million range, the emissions will be extremely
small.
The following are questions and comments received in writing
during the public comment period from Mass Merchandisers, Inc.:
1. Comment: Conditions at the Arkwood Site pose no
significant risk to human health and the environment.
Response: Both the Endangerment Assessment (EA) and the
remedial investigation (RI) demonstrated that the site does
pose a risk to the public health and the environment. The
EA indicated that the excess lifetime cancer risk from the
Main Site for the worst-case residential scenario is
approximately one excess cancer case in a thousand
individuals (10 ) , using outdated Toxicity Equivalency
Factors (TEFs) and four excess cancer cases in a thousand
individuals (4 x 10"3) , using the new TEFs. These risk
levels exceed the EPA acceptable risk range established in
the National Contingency Plan of one excess cancer case in
ten thousand individuals (10"*) to one excess cancer case in
a million individuals (10 ). The revised calculations
using the new TEFs for the most probable future land use
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resulted in a calculated risk of approximately one excess
cancer case in ten thousand individuals (10"4) . This risk
level is at the upper end of the EPA acceptable risk range.
The calculations, using the new TEFs, for the Railroad Ditch
for the most probable land use conditions are the maximum
future land use conditions (an increased frequency of
exposure to the ditch by children), result in a calculated
risk of one excess cancer case in ten thousand individuals
(10' ) and two excess cancer cases in ten thousand
individuals (2 x 10"4) , respectively. These risk levels are
at the upper end, and above the EPA acceptable risk range.
Furthermore, the HI demonstrated that the site contained
2,3,7,8 TCDD equivalents above the accepted levels for
industrial uses, and far beyond that for any residential
use. The RI also demonstrated that the site had
contaminated area groundwater above the maximum contaminant
levels (MCL).
2. Comment: The new TEF's have not undergone formal
adoption through Agency rulemaking or any comparable legal
process.
Response: EPA is under no obligation to establish policies
through a formal rulemaking process. The concept of using
TEFs for chlorinated dibenzo-p-dioxins and -dibenzofurans
was peer reviewed and recommended by two Agency wide groups,
the Risk Assessment Forum and the Science Advisory Board.
The new TEFs (1989 Update) were peer reviewed by the Risk
Assessment Forum and were specified for use by a memorandum
from F. Henry Habicht II (Deputy Administrator, EPA), Chair,
Risk Assessment Council, to the EPA Assistant and Regional
Administrators (March 21, 1990).
3. Comment: MMI indicated that the EPA recalculations of
the Toxicity Equivalency Factors (TEFs) for dioxins and
dibenzofurans were not consistent with the Endangerment
Assessment (EA).
Response: The EPA calculations using the new TEFs were done
in a manner consistent with both the EA and EPA policy.
Both the EA and the EPA "calculations" used the geometric
mean of the dioxin and dibenzofuran concentrations.
4. Comment: The EPA made the unilateral decision to
recalculate the risk estimate using new TEF values without
notifying MMI.
Response: EPA is under no obligation (legally or otherwise)
to inform or consult with MMI or any other PRP before making
any risk calculations. A memorandum from F. Henry Habicht
II to the Assistant and Regional Administrators (March 21,
1990) specified the use of the new TEFs.
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5. Comment: The EPA disregarded site specific conditions
when proposing the dioxin cleanup levels of 20 ppb.
Response: EPA evaluated the possible future uses of the
site in selecting its cleanup goals. This evaluation
concluded that while the site is currently unused, it could
be used for industrial purposes. Based upon this possible
use, EPA selected the 20 ppb cleanup goal, which is the
accepted cleanup goal for industrial uses as established by
the Agency for Toxic Substances and Disease Registry.
6. Comment: The proposed plan is incorrect in its statement
that the majority of the site risk is from dioxins and
dibenzofurans.
Response: The Endangerment Assessment indicated that the
majority of the excess cancer risk from the railroad ditch
and main site is attributed to dioxins and dibenzofurans.
EPA calculations using the new TEFs further increased the
risk due to the dioxins and dibenzofurans.
7. Comment: MMI contends that c'Vassification of dioxin as a
probable cancer causing agent is unsubstantiated.
Response: The EPA wide Carcinogenic Risk Assessment
Verification Endeavor (CRAVE) Workgroup classifies dioxin as
a group B2, probable human carcinogen. Classifications
verified by CRAVE Workgroup have undergone extensive peer
review and represent an Agency consensus.
8. Comment: In the submission of Appendix A (Evaluation of
the 1989 Endangerment Assessment for Arkwood), MMI contends
that the dioxin-related risks at the main site and railroad
ditch are on the order of 10"8 or lower.
Response: MMI contracted with a firm to critique the 1989
Endangerment Assessment which was performed by MMI, with EPA
oversight. The critique attacks the Endangerment Assessment
for having used calculations and assumptions that are
consistent with EPA policies and guidance, and advocates the
use of calculations and assumptions that are contrary to EPA
policies and guidance. These result in calculated risks
many orders of magnitude below those calculated by MMI in
the Endangerment Assessment.'
EPA Endangerment Assessment policies and guidance that were
developed to implement the National Contingency Plan, were
subjected to cross-program peer review. The paragraphs
below discuss the most important assumptions and
calculations advocated in the critique, but that are
contrary to EPA policies and guidance.
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In Appendix A, Section 3 of the critique (Selection of
Indicator Chemicals), octachlorinated dibenzo-p-dioxin
(OCDD) and other compounds of concern, such as carcinogenic
PNAs are not included as part of the carcinogenic risk at
the site. The omission of these compounds in the risk
calculations results in a significant understatement site
risks. According to EPA policy and guidance, and the
Arkwood EA, the compounds should be included in the risk
calculations.
A cancer potency factor for 2,3,7,8-tetrachlorinated
dibenzo-p-dioxin (2,3,7,8-TCDD) of 9,700 (mg/kg-day) "1 is
presented in Appendix A, Section 5 of the critique (Dose
Response Assessment). This cancer potency factor or slope
factor has not been verified by the CRAVE workgroup and is
not in accordance with EPA policy. The EPA slope factor for
2,3,7,8-TCDD is 1.56 x 105 (mg/kg-day)"1.
Several exposure parameters used in Appendix A, Section 6
(Exposure Assessment) are not in accordance with EPA
guidance. The MMI submission used soil ingestion rates of 5
mg/day for older children and adults; whereas, EPA guidance
(OSWER Directive 9850.4) recommends soil ingestion rates of
100 mg/day for older children and adults. The MMI
submission used a soil adherence factor of 0.5 ing/cm2, which
underestimates by a factor of 3 to 6 the quantity of soil
adhering to the skin.
In Appendix A, Section 7 (Calculation of Exposure Point
Concentrations), the arithmetic mean is used as
representative contaminant concentrations. The Risk
Assessment Guidance for Superfund Volume I Human Health
Evaluation Manual states that actions at Superfund site
should be based on the reasonable maximum exposure (RME).
Because of the uncertainty associated with sampling, the 95
percent upper confident limit on the arithmetic average is
now being used by EPA as a conservative estimate of the
exposure concentration contacted over time. Use of the 95
percent upper confidence limit was not used by MMI at the
time the EA was completed, and thus was not used in the EA.
However, if the EA were to be conducted today, the 95
percent upper limit would likely be used and the calculated
risks at the site would increase.
As a result of the assumptions used in the critique, the MMI
submission calculates the potential dioxin risks at the site
on the order of one excess cancer case in 100 million
individuals (10"8) . In contrast, the Endangennent
Assessment and the subsequent EPA calculations, which were
conducted in accordance with EPA guidance, indicate that MMI
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submission underestimates site risks by a factor of
approximately 10,000.
9. Comment: MMI contends that there is no scientific basis
of the Toxicity Equivalency Factors (TEFs) for
octachlorinated dibenzo-p-dioxins (OCDD).
Response: In the new TEF approach, OCDD was assigned TEF
value of 0.001. This value was based on a recent study by
Couture et al. (1988) in which male rats were exposed to low
levels of OCDD for 13 weeks. At the end of the study, the
animals exhibited signs of toxicity reminiscent of "dioxin
toxicity." Based on these results, a TEF value of 0.001 has
been assigned to OCDD in the new TEF approach. The new TEFs
were peer reviewed by the Risk Assessment Forum and were
specified for use by a memorandum from F. Henry Habicht II
to the Assistant and Regional Administrators (March 21,
1990).
10. Comment: In the submission of Appendix E, MMI suggests
that 50 ppm of carcinogenic polycyclic aromatic hydrocarbons
(PAHs) would be associated with a 10'6 excess cancer risk
under the most probable future land use conditions at the
Arkwood site.
Response: Several exposure parameters used in Appendix E,
Section 2 (Exposure Assessment) are not in accordance with
EPA guidance. The MMI submission used soil ingestion rates
of 25 mg/day for children aged 0 to 6 years, and 5 mg/day
for older children and adults; whereas, EPA guidance (OSWER
Directive 9850.4) recommends soil ingestion rates of 200
mg/day for children aged 1 to 6 years, and 100 mg/day for
older children and adults. The MMI submission used a soil
adherence factor of 0.5 mg/cm2, which underestimates by a
factor of 3 to 6 the quantity of soil adhering to the skin.
These inconsistencies and others suggest that 50 ppm of
carcinogenic PAH is not an acceptable remediation goal. In
addition, MMI used the draft document "Guidance for
Establishing Target Cleanup Levels for Soils at Hazardous
Waste Sites" (1988) in calculating their remediation goal.
This guidance has not been formally released by EPA and does
not represent Agency policy.
11. Comment: The results of the Treatability Study
clearly indicate that sieve and wash is a cost-effective
means of reducing the volume of contaminants to be dealt
with. Sieve and wash should be included as a pre-
treatment step before any treatment remedy that might be
selected at the Arkwood site.
Response: Sieve and wash has been added to the selected
remedy.
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12. Comment: MMI opposes the incineration of all
affected material at the Arkwood, Inc. site as
presented in the Proposed Plan of Action MMI proposed
that any selected alternative include "sieve and wash"
as part of the remedy.
Response: The remedy in the ROD includes sieve and
wash as part of the remedial action. Therefore, the
selected remedy does not include incineration of the
entire mass of contaminated material.
13. Comment: The water line that is being installed
eliminates any risk due to possible future
contamination of nearby domestic wells.
Response: The Superfund law (the Comprehensive
Environmental Response, Compensation and Liability Act,
CERCLA), and the National Contingency Plan (NCP)
specify a strong preference for the permanent treatment
of hazardous substances that pose a threat to human
health and the environment. Installing water lines, in
lieu of treatment, does not satisfy this preference.
In addition, Section 300.430 of the NCP states that
institutional controls shall not be used as a
substitute for treatment. Therefore, MMI's argument is
contrary to the goals of the Superfund law and
regulations.
14. Comment: MMI submits that further study is
warranted in this case due to the unexpected concern
about dioxin and catastrophic sinkhole development
expressed after completion and approval of the Remedial
Investigation and Feasibility Study Reports.
Response: Further study is not warranted. The RI
characterized site contamination and the Feasibility
Study evaluated a wide range of alternatives that
enabled EPA to select a cost-effective, imp lenient able
alternative that will meet the CERCLA preference for
permanence through treatment. Both the RI and FS
reports discuss the uncertainty and complexity of the
site geology. Throughout the RI and FS reports,
concerns regarding the sinkhole and karst geology are
repeated. In addition, the Endangerment Assessment
identified dioxin as being responsible for the majority
of the site's risk.
15. Comment: MMI contends that EPA has suggested that
incineration is the only acceptable remedial
alternative for soils containing greater than 20 ppb.
However, EPA has selected containment of such soils at
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three sites: the Diamond-Alkali, Selma Pressure
Treating Co., and Broderick Wood Products sites.
Response*. While the RODs for these sites did include
containment as part of the selected remedy, at two of
these sites, Diamond-Alkali and Broderick Wood
Products, containment is considered only an interim
measure. At the Diamond-Alkali site the soils are
being capped onsite, and the ROD requires that a
feasibility study be performed every two years until a
final remedy is selected. At the Broderick Wood
Products site, the majority of the site contamination
is K001 waste (wood-treating waste) and is being
incinerated onsite. The remainder of the site
contamination is being placed into a temporary storage
facility for further evaluation prior to the selection
of the final remedy if the volume is more than 2,500
yds3; if it is less, it will be incinerated onsite
along with the other site waste.
The Selma Pressure Treating remedy required
solidification and capping of wastes that were
contaminated by heavy metals and dioxin. However this
remedy is not considered to be appropriate for
comparison with the Arkwood site since the Selma
remediation was driven by heavy metals contamination
which would have required solidification even in the
absence of dioxin contamination.
16. Comment: EPA's concerns relative to catastrophic
sinkhole failure are not consistent with the
accumulated knowledge regarding the geology of the
Arkwood site and vicinity.
Response: The potential for sinkhole formation is not
the predominant reason why EPA rejected the capping of
high concentrations of hazardous substances, as
preferred by MMI. Sinkhole formation is, however, a
consideration. The CERCLA preference for remedies that
permanently treat wastes to the maximum extent
practicable is the main reason why EPA rejects capping
the majority of the site waste. The knowledge gained
during the RI indicates that the area geology is too
complex to define, that ground water migration pathways
are unknown, and will remain*so, and that the
possibility of sinkhole formation does exist. This
possibility, although low, underscores the need to
comply with the CERCLA preference for permanent
treatment.
17. Comment: MMI contends that Alternative D
(Incinerate Sludges/Cap in Place Affected Soils) is an
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appropriate remedy for the Arkwood, Inc. site. Based
upon the investigations of the area's geology, the
potential for sinkhole development is so low as to not
be considered reasonable. Furthermore, consolidate and
cap-in-place has been selected as the remedy at a
similar site within Region 6, at the Mid-South Wood
site.
Response: See response to comment number 16 regarding
sinkholes. In addition, the remedy selected in 1986 at
the Mid-South site was done so under the requirements
of CERCLA, prior to the reauthorization of CERCLA.
When CERCLA was reauthorized, it was amended to include
a strong preference for permanently treating wastes to
the maximum extent practicable. Alternative D does not
satisfy this preference. While the Mid-South ROD was
signed after the reauthorization of CERCLA, a provision
was made to allow those remedies developed just prior
to the reauthorization of CERCLA, to be selected
according to the requirements of CERCLA.
18. Comment: Alternative D, Incinerate
Sludges/Consolidate and Cap Affected Soils, fully
satisfies all significant remedial concerns.
Response: Alternative D does not adequately satisfy
all of the nine criteria for evaluating remedies. It
does not adequately satisfy the criteria of permanence
and long-term effectiveness because high concentrations
of hazardous substances would remain untreated and pose
a long-term threat. In addition, Alternative-D does
not include treatment to the maximum extent
practicable, as preferred by CERCLA.
19. Comment: MMI contends that a refinement of
Alternative D, "D+2" (Incinerate Sludges/Consolidate
and Stabilize Soils/Cap-In-Place Affected Soil and
Provide Stormwater Controls) will address the concerns
that exist for Alternative D. This will be done
through soil stabilization/solidification to immobilize
the dioxins and render the soils into a non-flowable
mass and through surface water drainage controls to
preclude the formation of sinkholes under the
consolidated mass of affected soils.
Response: Alternative "D+2" is unacceptable because it
does not meet the CERCLA preference for permanent
treatment of hazardous substances to the maximum extent
practicable. This alternative would leave high
concentrations of waste in place, and thus, would not
provide for long-term protection of public health and
the environment. In addition, treatability tests
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conducted during the feasibility study indicated that
stabilizing the Arkwood soils actually increased the
mobility of the PCP. Since the site has already
contaminated ground water with PCP, this remedy is
unacceptable.
20. Comment: EPA rejected a more cost effective
remedy for the Arkwood site, i.e., biological treatment
followed by- solidification, that was recently proposed
at another -wood treatment site in Region 6. Effective
treatment of the dioxin could be achieved by
stabilization after biological treatment.
Response: First, the selected remedy for the Arkwood
site is sieve and wash followed by incineration. Cost
estimates by MMI indicate that this remedy has a cost
of approximately $10.3 million. MMI estimated the cost
of the biological treatment remedy, without
solidification, in the FS at approximately $14 million.
However, during a meeting between MMI and EPA, MMI
stated that the FS probably overstated the biological
reaction time required in this alternative and instead
of the 56 days assumed as necessary in the FS, 14 days
may be enough reaction time. MMI did not provide EPA
with a revised cost estimate for the shorter reaction
time, but estimates by EPA and it's oversight
contractor indicate the sieve and wash, biological
treatment, and solidification remedy would still cost
over $9 million. The selected remedy for a relatively
modest cost increase provides for more permanent and
complete destruction of the site contaminants.
Second, the other Region 6 site referred to is the
Texarkana Wood site. At the Texarkana Wood site, EPA
proposed two possible remedies: An incineration
remedy; and »*.biological treatment remedy. 5"he remedy
selected was the incineration remedy because it
provided for more complete destruction of the site
hazardous substances.
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21. Comment: MMI requests that the agency defer final
remedy selection and allow MMI to conduct a focused
Feasibility Study of a remedy based upon sieve and wash
plus in situ vitrification (ISV).
Response: MMI conducted the RI/FS and could have
considered ISV as an alternative. MMI has noted ,
however, that when it was conducting the RI/FS, ISV was
found to not be commercially practicable alternative.
Even today, ISV is, compared to incineration, in its
infancy as a remedial alternative. EPA has weighed the
benefits of delaying remedy selection to conduct a
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focused feasibility study, versus the benefrts of
selecting a remedy now, and has determined 'that little
benefit would be gained by conducting a focused
feasibility study. Therefore, EPA hasf •selected a sieve
and wash, followed by incineration, remedy." The only
benefit to be gained by conducting a fbcused1"
feasibility study is that the study might show that in-
situ vitrification could work and that it could be
selected as a remedy. However, this would result in a
significant delay in site remediation 'with nothing
gained in the protection of human health and the
environment. ISV has yet to be implemented on a large
scale for the destruction of organics. Enough
treatability testing has not been conducted to
eliminate the unknowns and uncertainties that exist
regarding its ability to effectively and safely destroy
dioxins and other organics similar to the contaminants
found at the Arkwood site. Major concerns -regarding
ISV that would, apply at the Arkwood site "include the
possible lateral migration of vaporized organics into
adjacent soils .a[nd the effectiveness of of-f-gas
collection and treatment. Because of the unknowns and
uncertainties, a focused FS would require extensive
treatability testing for:,this site. Recent EPA
experience at the Northwest Transformer site, in
Everson, Washington, has shown that^such extensive
treatability testing..could take more than a year and
cost hundreds of thousands of dollars. In addition,
the results from ,a/similar FS at the Arkwood site may
not yield "sufficient information on which to base a
decision to implement ISV,- but instead, only indicate a
need to increase the scale of testing.
„,,.», ... - ' j.f
If ISV wars successfully tested and selected as the
remedy", ^nothing would be gained in protecting the
public health £nd» the envi-igDnment by Electing ISV
because; incineration ha& been .demonstrated numerous
times Jto"l£&fejty' and effectively destroy organics such
as those fpurid at "t&e. A^rkwoodsrsite. Past incineration
projects haVe, shawn^thatc^emis^sions'^an be safely
controlled^ ^Effective iSV emissions control, that
would be;'rieqessaryl",at the Arkwood site, have not been
proven to_$qr,k on:,a ^arge scale.'^Furthermore, cost
estimate? from MMI. indicate that the cost of
incineration (approximately $10.3 million) will be
comparable,,Qr lower than ,that^for ISV (approximately
$£l.^million).. ,Since ISV has»'never been used on a
large scale, Icost overruns are very likely. In
contrajst, past experience with incineration enables far
more resliable cost estimates tocbe made. Therefore,
incirtera^ion may..also be mor.ei-cost-effective than ISV.
•• •. "* " ''-* „ » - «•**••> '
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22. .CoTOjneryt: MMI contends that Alternative H
(Incinerate Sludges and Affected Soils On-site) is
critically defective in two of the "primary balancing
criterla'V;Aised to weigh major trade-offs among feasible
al|.ernativejs>— iaiplementability, because incineration
is complex.to implement, and cost-effectiveness. MMI
also .contends;-that this alternative lacks community
acceptance. 3
f " •' . i.' "v
Response: The selected remedy (sieve and wash,
followed.by incineration) is both implementable and
cost effective. ,It does, however, appear to lack
community ^acceptance.. Incineration of contaminated
soils, is, a proven-remedial alternative. While it is a
technically complex procedure, it has been successfully
and .safely implemented at numerous other locations.
Past experience has shown that materials handling of
the feed to incinerators is the most difficult
implementation problem. However, the sieve and wash
process will greatly reduce material's handling problems
by reduci-ng the volume to be incinerated and by
creating a very uniform media to be incinerated.
L
Sieve and was-h with incineration was estimated by MMI
to cost $10,30,0,,000. Sieve and wash with biological
treatment was.,,(estimated by MMI, in the FS, to cost
approximately-$14,000,000 (without including the cost
for solidification). However, as discussed earlier in
the Responsiveness summary, MMI has indicated .that the
reaction time .required for-biological treatment may be
shorter than assessed iin the FS and therefore, costs
may be lower. EPA and it's contractor have estimated
that a sieve and wash, biological treatment., (with
shorter reaction times), and solidification" remedy will
still cost ove£u$10 million. Since there is_ a
substantial bjgnefit gained wi-th th,e dfegree bf^,."
destruction achieved "Joy. inci«eratibny ^comp.ared to the
partial destruction (and* no destructibn. of dlpxins)
achieved with biological treatment, incineration is
cost effective compared.; to biological., treatment.
Regarding the inadequacies of capping^remedies, see
responses to comments #17, 18; and^197"?Given the
previously discussed inadequacies of capping, remedies,
the selected remedy is obviously-cost effective.
- • <• " , , a .
Regarding community acceptance, EPA believes that by
adding the sieve and wash process and thereby reducing
the volume to be incinerated and the time required for
incineration, the selected remedy will gain public
acceptance. EPA also believes that as the community
learns more about the~saT3€y a'nd capabilities of modern
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incinerators that it will further accept the
incineration remedy.
23. Comment: MMI commented that the Administrative
Record was incomplete and should include -a number of
documents.
Response: The listing of the documents to be included
were broken into three separate categories. The
response is therefore also broken into these three
categories.
Miscellaneous Matters
Documents numbered 1, 3, 6, 8, 9, 12-16, 19-23, 26, 27,
29, and 32-34, have been reviewed and placed 'into the
Administrative Record for the site.
Documents numbered 2, 4, 5, 7, 10, 11, 17, 18, 24, 25,
28, 30, and 31 are not included because they consist of
either comments to draft-documents, or responses to
comments regarding draft documents. EPA policy is not
to include draft documents in the Administrative
Record, because they do not reflect final agency
position with regard to the selection of remedy.
Documents Dealing Specifically with :Proiect Schedule
The documents regarding the schedule are not relevant
to EPA's selection of remedy, 'and are, therefore, not
included in the Administrative Record.
Draft or Fi:nal Reports and Plans
Draft documents and any redline versions submitted by a
PRP or their contractor do not reflect" final Agency
position with regard to the selection of remedy and,
therefore, aTe not included in the Administrative
Record. Documents numbered 1,2,4-8,10-15, and 18 are
draft or redline and are not included. Document number
9 is final "and will be included in the final
Administrative Record. Documents number 3, and 16 are
included in the Administrative Record, but were not
included in the index. Document ritiiaber 17 is included
on in the Record as index document number 7997-8201,
dated 5/23/90.
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