United States Office of
Environmental Protection Emergency and
Agency Remedial Response
EPA/ROD/R04-92/117
July 1992
Superfund
Record of Decision:
Ciba-Geigy (Mclntosh Plant),
AL
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NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement. but adds no further applicable information to
the content of the document. All supplemental material is, however. con1ained in the administrative record
for this site.
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REPORT DOCUMENTATION 11. REPORT NO. I ~ 3. Reciplenfs Accession No.
PAGE EPA/ROD/R04-92/117
4. TIlle and Subti1le s. Report Date
SUPERFUND RECORD OF DECISION 07/14/92
Ciba-Geigy (McIntosh Plant), AL
6.
Third Remedial Action - Final
7. Aultlor(s) 8. Performing Organization RepL No.
9. Performing Orgainlzation Name and Address 10. ProjectfT askIWork Unit No.
11. Contract(C) or GranI(G) No.
(C)
(G)
1~ SponsorIng Organization Name and Add...... 13. Type 01 Report & Period Covered
U.S. Environmental Protection Agency 800/000
401 M Street, s.w.
Washington, D.C. 20460 14.
15. Supplementary Noles
PB93-964002
16. Abatract (Umit: 200 worel8)
The 1,SOO-acre Ciba-Geigy site is an active chemical manufacturer in an industrial
area in McIntosh, washington County, AI abarna . A wetlands area borders the site
property, and part of the site lies within the floodplain of the Tornbigbee River. From
1952 to 1965, Ciba-Geigy, formerly Geigy Chemical Corporation, manufactured primarily
DDT and BHC. After 1965, when the production of DDT and BHC were ceased, Ciba-Geigy
began to manufacture laundry products, herbicides, insecticides, agricultural chelating
agents, sequestering agents, plastic resins and additives, anti oxidants, and specialty
chemicals. In 1982, during an investigation of an adjacent chemical company, EPA
identified onsite contamination in a drinking water well on the Ciba-Geigy property.
In 1985, EPA issued a RCRA permit that included a corrective action plan requiring
Ciba-Geigy to remove and treat ground water and surface water contamination at the
site. Further investigations by EPA revealed 11 former waste management areas of
potential contamination onsite. These areas contain a variety of w~ste, debris,
pesticide by-products and residues. In 1987, Ciba-Geigy installed an additional
wastewater treatment system and four ground water monitoring wells. Two previous RODs
in 1989 and 1991 addressed the contaminated shallow alluvial aquifer and contaminated
(See Attached Page)
17. Document Analysis L Descriptors
Record of Decision - Ciba-Geigy (McIntosh Plant), AL
Third Remedial Action - Final
Contaminated Media: soil, sludge, debris
Key Contaminants: VOCs (benzene, toluene, xylenes), other organics (pesticides),
metals (arsenic, chromium, lead), inorganics (cyanides)
b. IdentiliersfOpen-Ended Terms
c. COSA 11 Reid/Group
18. AvailabiDty Statement 19. Security Class (This Report) 21. No. of Pages
None 68
20. SecurIty Class (This Page) tt PrIce
Nnn~
OPTIONAL FORM 272 4-
50272-101
(See ANSI-Z39. t8)
See Instructions on Reverse
( 77)
(Formerly NT1S-35)
Department 01 Commerce
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EPA/ROD/R04-92/117
Ciba-Geigy (McIntosh Plant), AL
Third Remedial Action - Final
Abstract (Continued)
sludge and soil at 10 of the 11 former waste management areas. This ROD addresses a
final remedy for OU4, which includes contaminated soil and sludge in former waste
management Area 8 and the upper dilute ditch. A future ROD will address OU3, the
contamination within the floodplain and lower portions of the dilute ditch. The primary
contaminants of concern affecting the soil, sludge, and debris are VOCs, including
benzene, toluene, and xylenes; other organics, including pesticides; metals, including
arsenic, chromium, and lead; and inorganics, including cyanide.
The selected remedial action for this site includes removing nonchemical construction/
demolition debris from the surface of Area 8, excavating approximately 63,000 cubic yards
of contaminated soil and sludge from the areaas possible until concrete structures, the
water table, or the iron slurry waste are encountered, or to a depth of 20 feet;
solidifying or stabilizing approximately 46,000 cubic yards of soil that contains less
than 2,500 mg/kg total organics and no gamma-BHC; using an innovative thermal technology
to treat approximately 17,000 cubic yards of soil, sludge, and other waste, which is not
amenable to other treatment; fixing/stabilizing approximately 46,000 cubic yards of iron
slurry waste in-situ, monitoring air emissions and ground water; backfilling and
establishing a vegetative cover over excavated areas; disposing all treated soil, sludge,
slurry waste, and debris residuals onsite in a RCRA land vault; and implementing
institutional controls, including deed and ground water use restrictions. In areas where
clean-up levels are not attained, but no further excavation can occur, the technology(s)
to be used will be based on treatability and leachability studies to be conducted during
the RD stage. The estimated present worth cost for this remedial action is $49,723,000,
which includes an unspecified O&M cost for 30 years.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific soil and sludge clean-up goals are
based on health-risk levels to assure that drinking water MCLs would not be exceeded in
the ground water as a result of contaminants leaching through soil or sludge. Actual
clean-up levels to be used will be determined for atrazine, diazinon, prometon, simazine,
4,4-DDD, 4,4-DDT, 4,4-DDE, and bladex using the summers and pest and models, and based on
the proximity of the waste to the ground water table. It is anticipated that site
contaminants that do not have specified clean-up levels in this ROD will be reduced to
acceptable levels when established clean-up levels are met for the most toxic and mobile
contaminants.
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DECLARATION
of the
RECORD OF DECISION
OPERABLE UNIT FOUR
Site HAXE AND LOCATION
Clba-Geigy Site
McIntosh, Washinqton County, Alabama
STATEMENT OF BASIS AND PURPOSE
This decision document (Record of Decision), represents the selected
remedial action for Operable Unit Four for the Ciba-Geigy Site,
McIntosh, Alabama, developed in accordance with the Comprehensive
Environmental Response, Compensation and Liability Act of 1980
(CERCLA), as amended by the Superfund Amendments and Reauthorization
Act of 1986 (SARA) 42 U.S.C. Section 9601 et sea., and to the extent
practicable, the National Contingency Plan (NCP) 40 CFR Part 300.
This decision is based on the administrative record for the Ciba-Geigy
Site.
The State of Alabama has concurred on the selected remedy.
ASSESSMENT OF THE Site
Actual or threatened releases of hazardous substances from the
Ciba-Geigy Site, if not addressed by implementing the response
selected in this ROD, may present an imminent and substantial
endangerment to public health, welfare or the environment.
action
D£SCRIPTION OF SELECTED REMEDY
This operable unit is the third of four proposed operable units. The
first operable unit at this Site addressed contamination of the
shallow (alluvial) aquifer. Operable unit two addressed a principal
threat, the highly contaminated soils and sludges at ten of the eleven
former waste management areas. Operable unit three will address
contamination within the floodplain including the effluent ditch
(previously called the lower portions of the dilute ditch) and areas
in the Tombigbee River within close proximity to the Site. Operable
~U1it four, which is the subject of this Record of Decision, addresses
contamination in former waste management area 8 (the area not
addressed in OU#2).
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The major components of the selected remedy for operable unit four
include:
Excavation of approximately 63,000 cubic yards of contaminated
soils and sludges until established cleanup levels are reached or
until excavation limits are reached.
Solidification/stabilization of up to 46,000 cubic yards of
moderately contaminated soils and sludge containing no gamma-BHC
and less than 2,500 ppm total organics, as an innovative
application of this technology which may be proven effective
during the remedial design;
Utilization of an innovative thermal technology or dechlorination
if proven effective during the remedial design for treatment or
pretreatment to LDR treatability variances of contaminated soils;
On-site thermal treatment of approximately 17,000 cubic yards of
highly contaminated soils and sludge and of waste not amenable to
final treatment using the innovative technology dechlorination or
the innovative application of solidification/stabilization (up to
46,000 cubic yards);
Disposal of treated soil and residual ash from the thermal
treatment process in an on-site RCRA Minimum Technology Subtitle C
landvault(s);
In-situ stabilization/fixation treatment of approximately 46,000
cubic yards of iron slurry waste;
In-situ soil flushing combined with isolation walls and extraction
wells to remediate areas where the risk based cleanup levels are
not achieved before excavation is terminated. Innovative
technologies (in-situ vacuum extraction or in-situ bioremediation)
may also be used in addition to or instead of in-situ soil
flushing, if during the remedial design either technology is found
to be effective in reducing contaminant concentrations in the soil
and is cost effective. If either technology is proven to be more
effective than in-situ soil flushing in reducing the
concentrations of the contaminants in the soil and more cost
effective, it will be used instead of in-situ soil flushing. If
either technology is not as effective as in-situ soil flushing in
reducing the concentration of the contaminants in the soil it will
not be utilized in place of in-situ soil flushing, however, it may
be used in concert with in-situ soil flushing if the combination
enhances the remediation in reaching cleanup levels and is cost
effective.
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Issuing a public notice in a local newspaper and sending a fact
sheet to persons on the mailing list at the completion of the 30%
design report. The purpose of the fact sheet and the public
notice would be to inform the public of the technologies selected
that were proven effective during the treatability studies
conducted during the remedial design;
Backfilling the excavated area with common fill, vegetating the
area and the establishment of a suitable vegetative cover;
Operation and maintenance of landvault(s) for a min~um of thirty
years; and
Institutional controls for land use and groundwater use
restrictions.
STATUTORY DETERMINATIONS
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, and is cost-effective. This
remedy satisfies the preference for treatment that reduces toxicity,
mObility, or volume as a principal element. Finally, it is determined
that this remedy utilizes a permanent solution and alternative
treatment technology to the max~um extent practicable.
Because this remedy will result in hazardous substances remaining
on-site at the areas addressed by operable unit four above
health-based levels, a review will be conducted within five years
after commencement of the remedial action to ensure that the remedy
continues to provide adequate protection of human health and the
environment.
~fY1~
r GREER C. TIDWELL, REGIONAL ADMINISTRATOR
7- /+- 92-
DATE
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RECORD OF DECISION
SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
CIBA-GEIGY Site
OPERABLE UNIT FOUR
McINTOSH, WASHINGTON COUNTY, ALABAMA
PREPARED BY:
U. S. ENVIRONMENTAL PROTECTION AGENCY
REGION IV
ATLANTA, GEORGIA
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1.0
1.1
2.0
3.0
4.0
5.0
6.0
-i-
TABLE OF CONTENTS
Site Location and Description................................1
Site History and Enforcement Activities......................1
Highlights of Community Relations............................7
Scope and Role of Operable Units.............................8
Summary of Site Characteristics..............................9
4.1 Geology-/Soils...........................................9
4 . 2 Hydroqeo1 ogy- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3 Surface Water... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
4.4 Sample Results From Former Waste Management Area 8.....12
Summary of Site Risk................................. .0..... .13
5.1 Contaminants of Concern............................... .16
5.2 Exposure .Assessment.... 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
5.3 Toxicity .Assessment................................... .20
5.4 Risk Characterization...................... . . . . . . . . . . . .23
5.5 Environmental Risk..................................... 24
5 . 6 Cleanup Levels......................................... 25
Description
of Alternatives................................ .29
No Action............. . . . . . . . . . . . . . . . . . . 30
6.1 Alternative No. 1 -
6.2 Alternative No. 2 -
6.3 Alternative No. 3 -
6.4
7.0
7.1
Containment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Removal, Solidification/stabilization,
and On-Site Disposal.................... 31
.
Alternative No.4 - Removal, On-Site Thermal Treatment, and
On-Site Disposal......................... 32
Summary of Comparative Analysis of Alternatives.............35
Overall Protection of HUman Health and the Environment......36
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7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
8.0
9.0
9.1
9.2
9.3
9.4
9.5
10.0
-ii-
TABLE OF CONTENTS
- cont. -
Compliance With
ARARS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Long-Term Effectiveness and Permanence......................38
Reduction of Toxicity, Mobility or Volume Through Treatment.38
Short-Term Effectiveness.................................... 39
Implementabili ty. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Cos t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
State Acceptance...................... . . . . . . . . . . . . . . . . . . . . . .40
Comm.uni ty Acceptance... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Summary of Selected Remedy.................................. 40
Statutory Determination..................................... 53
Protective of Human Health and the Environment..............53
Attainment
of ARARs......................................... 53
Cost Effectiveness.......................................... 55
Utilization of Permanent Solutions to the Max~um
Extent Practicable..................................... 55
Preference for Treatment as a Principal Element.............56
Documentation of Significant Changes.........................56
Appendix A - Responsiveness SUDDIlary
Appendix B - Concurrence Letters
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Table 4-1
Table 4-2
Table 5-2
Table 5-3
Table 5-6
Table 5-7
Table 5-8
Table 5-9
Table 8-1
-iii-
LIST OF TABLES
Chemical of Potential Concern in Study-Wide Soils........14
Chemicals Of Potential Concern in Area 8 Soil............15
Health Effects Criteria For Oral Exposure
To Chemicals Of Concern.................................. 21
Health Effects Criteria For Inhalation Exposure to
Chemicals Of Concern.................................... .22
Groundwater Cleanup Levels Provided in OU #1.............26
Groundwater Cleanup Levels For
Deep Soil Treatment . Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Direct Contact Soil Cleanup Levels.. .....................28
Subsurface Soil Cleanup Levels
For Groundwater Protection...............................29
Treatment Standards For Soils At The Ciba-Geigy Site.....50
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Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
-iv-
LIST OF FIGURES
Ciba-Geigy Corporation, Vicinity Map......................2
Si te Locations............................................ 4
Generalized Geologic Cross-Section.......................11
Projected Location of Where the Summers and Pestan
Models will be Applied..........................."....... .19
Process Flow Chart for Treatment of Contaminated
50 i 1 s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6
Deep Soil Remediation Flow Chart.........................51
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Decision S.~"Y
Record of Decision
Operable unit Pour
Ciba-Geigy Site
xc Intosh, AlabA_a
1.0 Site LOCATION AND DESCRIPTION
The Ciba-Geigy Corporation McIntosh facility is located in southern
Washington County, northeast of McIntosh, Alabama, approximately 50
miles north of Mobile, Alabama (Figure 1). The operating facility is
located at 31° 15'00" north latitude and 87° 58'00" west longitude.
The operating facility, which encompasses approximately 2.4 square
miles, is situated between the Southern Railroad right-of-way on the
west and extends nearly to the escarpment separating the upland
terrace from the floodplain of the Tombigbee River. The property
boundaries extend beyond the railroad westward toward U.S. Highway 43.
The northern edge of the property merges into an undeveloped pine
forest. To the south the property is bounded by an Olin Corporation
facility which has also been identified as a Superfund Site. The
southeastern portion of the property extends to the banks of the
Tombigbee River.
The facility is located in an industrial setting. The Ciba-Geigy
Superfund Site ("Site") is contiguous with the facility boundary. The
Areas of Contamination (AOCs) addressed by CERCLA are located on the
McIntosh facility due east of the current production area. The AOCs
are roughly divided by the river water reservoir (see Figure 2). Area
8, which is addressed by this ROD, is located in the southern half of
the AOC to the east of the reservoir. The nearest population center
is the town of McIntosh, which is located approximately two miles to
the southwest.
1.1
Site HISTORY AND ENFORCEMENT ACTIVITIES
The Ciba-Geigy McIntosh facility, formerly owned by Geigy Chemical
Corporation, began operations in October 1952, with the manufacture of
one product, dichlorodiphenyl-trichloroethane (DOT). Through 1970,
Geigy expanded its McIntosh facilities by adding the production of
fluorescent brighteners used in laundry products; herbicides;
insecticides; agricultural chelating agents; and sequestering agents
for industry.
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.
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1
WASHINGTON COUNTY,
ALABAMA i
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In 1970, Geigy merged with Ciba (Chemical Industry in Basel,
Switzerland), forming the Ciba-Geigy Corporation. Since then
Ciba-Geigy has continued to expand its operations with the added
production of resins and additives used in the plastics industry,
anti-oxidants, and small-volume specialty chemical products (i.e.
water treatment chemicals and fire fighting foams). The present
facility occupies approx~ately 1,500 acres and employs about 1,200
workers.
The EPA Region IV Environmental Services Division of Athens, Georgia
(ESD) conducted an investigation in August 1982 o~ the Olin Chemical
Company located adjacent to the Ciba-Geigy Site. As a part of the
investigation, ESD sampled a drinking water well on Ciba-Geigy
property. This sampling indicated the presence of hazardous
substances which warranted further evaluation of the contamination
problem at Ciba-Geigy. In June 1983, the Hazardous Ranking System
(RRS) survey was completed and the Site was assigned a ranking of
53.42. The Ciba-Geigy McIntosh Plant was included on the National
Priorities List (NPL) in September 1983.
In October 1985, EPA issued Ciba-Geigy a RCRA Permit, which included a
corrective action plan requiring Ciba-Geigy to remove and treat
contaminated groundwater and surface water at the site. The
corrective action plan stipulated that Ciba-Geigy would prepare a
Remedial Investigation/Feasibility Study (RI/FS) for the disposal
areas being studied by the Superfund program. Figure 2 depicts the
location of CERCLA areas within the Ciba-Geigy Site.
The ten units closed under the RCRA permit include:
Diazinon Wastewater Sewer: Utilized to pipe Diazinon waste to
the Diazinon Destruct Impoundment. Closure under post
closure care in 1976.
Triangular Impoundment: Constructed in the 1970s to decompose
Diazinon residues. Closure during interim status completed.
in 1986.
Rectangular Impoundment: Constructed in 1972-1973 to hold
sludge from the dilute impoundment. Closure during interim
status completed in 1987.
Class C Landfill: Permitted by Alabama in 1973 and permitted
under RCRA Interim Status regulations. Closure during
interim status completed in 1987.
3
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@
FIGURE Z
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I CIBA-GiIGY-S;I;'''-o~nd;''; - - - - - - - - - - - - - - - - - - - - - - - - - - -.
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I TRASH .
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AREA or CONTAMINA.TION I ". '.
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- . . . - . - - . . - - . - - - - - - - - - - - - - - .I
CIBA. GEIGY CORPORATION
PLANT SITE
MciNTOSH, ALABAMA
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Biological Sludge Landfill: Permitted by Alabama in 1978 and
later operated under RCRA Interim Status for disposal of
dewatered sludge. Closure during interim status completed in
1987.
Diazinon Destruct Impoundment: Constructed in 1965.
under post closure care completed in 1989.
GK-44 Impoundment: Put into service in early 1970s.
Constructed for the GK-44 wastes high in nitrogen compounds.
Its use was discontinued in the late 1970s. Closure under
post closure care completed in 1989. .
Closure
Effluent Diffuser Line: Constructed in late 1968 to convey
effluent for discharge into the Tombigbee River. Taken out
of service in 1973 due to a change in the wastewater
treatment system, closure of RCRA impoundments, and a change
in the NPDES permit.
Effluent Disposal Well: Installed in 1971. Used for the
injection of biotreated effluent to reduce the quantity of
NaCl discharged into the river. The use of the well was
unsuccessful and it was plugged in 1983. ADEM required no
post-closure monitoring.
Dilute Ditch: This ditch collected dilute wastewater and
surface water runoff to be conveyed to the Dilute
Impoundment. Use ceased in 1971. Continued monitoring of
this ditch under a RCRA Corrective Action permit.
Pursuant to the Corrective Action portion of the permit, in 1987,
Ciba-Geigy installed a groundwater pumping system to intercept and
remove contaminated groundwater from the shallow alluvial aquifer.
The water removed from these wells was treated in the plant's existing
on-site wastewater treatment system until fall 1988, when the plant's
new biological wastewater treatment system was completed and used to
treat the groundwater. The treated water is discharged into the
Tombigbee River in compliance with appropriate National Pollutant
Discharge Elimination System (NPDES) Regulations.
Ciba-Geigy has installed four (4) corrective action monitoring wells
along the southern boundary of the property to monitor the
effectiveness of the pumping well system. The effectiveness of the
pump and treat system in preventing the migration of contaminated
groundwater off-site and reducing the concentrations of contaminants
in the groundwater is well established.
5
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EPA completed the Superfund decision document (the Record of Decision
or ROD) for operable unit one in September 1989 after public comments
were carefully considered. The ROD identified the EPA selected
remedy, "No Further Action". This selection was based on the
established effectiveness of the groundwater pump and treat system
already installed under the RCRA permit to address groundwater
contamination in the shallow aquifer at the Site.
In accordance with the corrective action plan, Ciba-Geigy retained
BCM, a technical consultant, to perform the RI/FS. Field work, which
began in October 1985, was conducted by BCM on Ciba's behalf, with
EPA's oversight. The"principal finding of the RI study was the
definition of the extent of contamination from eleven additional waste
management areas within the study area that will be addressed under
CERCLA.
The CERCLA Site has been grouped and divided into two Areas of
Contamination (AOC) based on their relative proxLmity to each other.
The AOCs are roughly separated by the reservoir (See Figure 2).
In January 1990, Ciba-Geigy submitted the FS report. This report
identified and screened alternatives for cleanup at the eleven former
waste management areas. In September 1991, EPA issued a ROD
addressing soil contamination at 10 of eleven 11 former waste
management areas, (OU2), at the Site.
The major components of the selected remedy for OU2 include:
Excavation of contaminated soils and sludges until established
cleanup levels are reached or until site specific excavation
limits are reached.
On-site thermal treatment of approxLmately 65,000 cubic yards
of highly contaminated soils and sludge;
Solidification/stabilization or the utilization of an
innovative technology proven effective during the remedial
design, of approximately 62,300 cubic yards of moderately
contaminated soils and sludge;
Disposal of treated soil and residual ash from the thermal
treatment process in an on-site RCRA Minimum Technology
Subtitle C landvault(s);
6
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In-situ soil flushing combined with isolation walls and extraction
wells to remediate areas where the risk based cleanup levels are
not achieved before, excavation depth of 20 feet is reached.
Innovative technologies (in-situ vacuum extraction or in-situ
bioremediation) may also be used in addition to or instead of
in-situ soil flushing, if during the remedial design either
technology is found to be effective in reducing contaminant
concentrations in the soil and is cost effective.
Issuing a public notice in a local newspaper and sending a fact
sheet to persons on the mailing list at the completion of the 30%
design report. The purpose of the fact sheet and the public
notice would be to inform the public of the technologies selected
that were proven effective during the treatability studies
conducted during the remedial design;
Backfilling the excavated areas with common fill and vegetating
the area and the establishment of a suitable vegetative cover,
Operation and maintenance of landvault(s) for a minimum of thirty
years; and
Institutional controls for land use and groundwater use.
EPA will continue its CERCLA enforcement activities and will notify
Ciba-Geigy prior to the initiation of the remedial design for
-participation in the selected remedial action. Should Ciba-Geigy
decline to conduct future remedial activities, EPA will either take
additional CERCLA enforcement actions or provide funding for these
activities while seeking cost recovery for all -EPA-funded response
actions at this Site.
2.0
HIGHLIGHTS OF COMMUNITY RELATIONS
The RI for the Ciba-Geigy Site was released to the public in
August 1988. The FS and the Proposed Plan for the Ciba-Geigy
Site addressing Operable Unit 2, were released to the public on
July 30, 1990. An addendum to the FS addressing the
contamination in Area 8 (OUi4), was released to the public in
April 1992. The Proposed Plan addressing QUi4 was released to
the public on April 30, 1992. These documents were made
available by placement in both the administrative record docket
and the information repository maintained at the EPA docket room
at Region IV Headquarters in Atlanta, Georgia and at the McIntosh
Town Hall, in McIntosh, Alabama. Pursuant to regulations, a
public comment period was held from April 30, 1992 through
May 29, 1992.
7
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I
A notice was placed in the Mobile Press Register on April 30,
1992 announcing the comment period. In addition to the public
comment period and the administrative record files, a public
meeting was held on May 19, 1992 in McIntosh Alabama. At this
meeting representatives from EPA answered questions and addressed
community concerns.
A response to all significant comments received during the public
comment periods is included in the Responsiveness Summary
(Appendix A), which is a part of this Record of Decision.
This decision document presents the selected remedial action for
operable unit four of the Ciba-Geigy Site, chosen in accordance
with CERCLA, as amended by SARA and to the maximum extent
practicable, the NCP. The decision for this Site is based on the
administrative record. The requirements under Section 117 of
CERCLA/SARA for public and state participation have been met for
this operable unit.
3.0
SCOPE AND ROLE OF OPERABLE UNITS
Due to the size of the facility, the number of areas and the variety
of contaminants, the problems at the Ciba-Geigy Site are complex. As
a result EPA has organized the work into four (4) operable units
(OUs). The operable units at this Site as identified in the ROD
issued for Operable Unit Two in September 1991 are:
OU .1
OU .2
Contamination of the shallow (Alluvial) groundwater aquifer.
Contamination of soils at ten of eleven former waste
management areas.
OU .3
Contamination within the floodplain, the effluent ditch
(previously called the lower portion of the dilute ditch) and
areas in the Tombigbee River within close proximity to the
Site.
OU .4.
Contamination of soils in former waste management
Area 8 and the dilute ditch (previously called the upland
portion of the dilute ditch).
This Operable Unit (OU #4), addresses the contamination of soils at
former waste management area 8. The Dilute Ditch was closed in
accordance with an approved RCRA Closure Plan. The ditch, as well as
other closed units, was excavated, capped and is being maintained
through RCRA Post-Closure care. Upon further evaluation, EPA has
8
-------
decided to continue addressing the Dilute Ditch under RCRA authority,
as administered through the HSWA Permit.
The January 1990 Draft Feasibility Study Report and the February 1992
addendum to the Feasibility Study Report submitted by Ciba-Geigy
document the development, screening and detailed evaluation of
potential alternatives for remediation of former waste management area
8 identified and initially characterized during the Remedial
Investigation. EPA has evaluated the alternatives and the risk posed
by the contaminants as they relate to the "CERCLA" Site. Based on
this evaluation, EPA has determined the alternative or combination of
alternatives which will achieve the CERCLA cleanup objective, to
remediate the source of contamination and prevent current or future
exposure to contaminated groundwater at former waste management area
8. This operable unit is consistent with past work conducted at the
Site and future work to be conducted.
4.0
SUMMARY OF Site CHARACTERISTICS
4.1
GEOLOGY/SOILS
The Ciba-Geigy property is located within the Southern Pine
Hills, which are elevated features that regionally slope
southward toward the Gulf of Mexico. These hills are dissected
by various river systems that feed into the Gulf. The plant is
located upon a low terrace adjacent to the Floodplain of the
Tombigbee River. The property lies within the boundaries of the
Mobile Graben, a downthrown fault block paralleling the river.
The surficial and shallow geology can be broken into three
distinct features. The uppermost layer is a relatively
continuous clay layer containing sand and silty sand lenses and
clay layers that range from only a few feet to over 50 feet in
thickness. Underlying the clay layer are Pleistocene-age
alluvium and low terrace deposits of interbedded gravel, silt,
and clay with thicknesses ranging from 60 to 100 feet. These
deposits outcrop throughout the area.
Underlying the low terrace deposits are alternating layers of
Miocene-age gravels, sands, and clays. Regionally, Upper Miocene
clay hydraulically separates the Miocene and Pleistocene deposits
(See Figure 3).
Erosion and redeposition of these sediments reflect dynamic
depositional environments which are common on a regional scale.
This has resulted in a complex subsurface stratigraphy.
9
-------
Variations of physical characteristics (e.g. porosity, grain
size, hydraulic conductivity) both vertically and laterally
within the strata complicate the movement of water in the
subsurface.
Nine different soil series are located within the area of the
plant. These soils are generally loamy clays and sands that
range from well drained to poorly drained. Permeability of the
soil ranges from moderate to low.
4.2
HYDROGEOLOGY
Both the Pleistocene and Miocene strata are water bearing and
represent two distinct aquifers, the Alluvial and Upper Miocene.
They are separated by a number of shale and clay aquitards and
aquicludes.
The Alluvial aquifer is composed of the recent and Pleistocene
terrace and alluvial deposits. The thickness of the aquifer and
the water level depend on the thickness and configuration of the
overlying clay layer. Under natural, semi-confined conditions,
the saturated thickness of the Alluvial aquifer ranges from less
than 30 feet to over 50 feet. Recharge of the Alluvial aquifer
comes locally, from rainfall, streams, and reservoirs. High
floods in the river floodplain also recharge the aquifer.
The groundwater flow of the Alluvial aquifer normally slopes
gently to the south-southeast toward the Tombigbee River.
However, the flow of groundwater is modified by the pumping and
capture of contaminated groundwater by the plant and recharge
from the Site reservoir. This system was designed to reduce the
level of contaminants in the groundwater below the facility and
prevent further migration of the contaminated groundwater. The
concentrations of contaminants present in the groundwater has
decreased and the operation of the intercept wells has reversed
the direction of groundwater flow as a result of the pumping.
The Upper Miocene underlying the plant is a confined aquifer of
sands and gravels capped by a clay layer about 100 to 130 feet in
thickness. Recharge of this aquifer is believed to come from
regional infiltration in outcrop areas up-dip to the north. In
contrast to the Alluvial aquifer, the quality of Upper Miocene
water can be effected by regional influences such as salt domes
or saltwater intrusion from the Gulf of Mexico.
10
-------
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LEGEND
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CLAY
SAND
NOTES:
I. ELEVATIONS RELATIVE TO
MEAN SEA LEVEL
2. BA~ED ON SOIL BORING
DA , A fROM PELA '884.
-------
Paleo-channeling has been found to exist in the surface of the
Miocene clay. However, during the investigation for the
Groundwater Corrective Action Program, and as a part of the
RI/FS, it was determined that the two aquifers are not
hydraulically connected.
4.3
SURFACE WATER
The Ciba-Geigy facility property lies within the Tombigbee River
Basin which has a drainage area of 8,378 square miles. The
Tombigbee River flows past the Site, converging further south
with the Alabama River to form the Mobile River.
Surface water features at the Ciba-Geigy plant include the
diverted Johnson Creek on the northern edge of the property, and
a large, man-made reservoir between the manufacturing area and
the waste management facilities. Surface water runoff on the
northern, undeveloped corner of the property drains off-site
through ditches into the Tombigbee River. The surface water
system south of Johnson Creek has undergone extensive change. In
addition to a new wastewater treatment system, a new stormwater
management system has been constructed to replace the old
combined dilute wastewater/stormwater system, which used
stormwater sewers, open surface ditches, and the dilute ditch to
convey mixed dilute wastewater and stormwater to the dilute
impoundment.
The new system segregates all wastewater, dilute and process, to
the wastewater collection and transfer system and then on to the
biological wastewater treatment system. All stormwater sewers
have been renovated and all open ditches have been replaced with
stormwater sewers draining to stormwater retention tanks capable
of holding a one-inch rainfall over the entire developed
manufacturing area of the plant. All initial rainwater retained
is transferred to the biological wastewater treatment plant. All
stormwater overflow (rainfall above one inch) is diverted to
established drainageways discharging to t~e Tombigbee River.
4.4
SAMPLE RESULTS FROM FORMER WASTE MANAGEMENT AREA 8
The primary emphasis for analytical testing during the RI was to
determine the nature and extent of the soil contamination at the
Site. As a result, soil and waste samples were collected and
analyzed to determine the chemical contamination present at the
12
-------
Site. The following is a brief description and a volume estimate
of former wAste management area 8 to be addressed in operable
unit four, under CERCLA authority.
Table 4-1 snmmArizes the maximum, and minimum concentrations and
detection frequency for the contaminants found in the soil
throughout the Site.
During the development of this ROD it was determined, based on
toxicity, mobility, and frequency of detection, that if certain
contaminants were excavated and remediated to acceptable levels,
the remaining contaminants would also be excavated and remediated
to acceptable levels. The selected contaminants of concern for
area 8 are presented in Table 4-2 (also see section 5.1).
AREA 8
(Bluffline Area)
Area 8 is located along a bluffline constructed by the United
States Corps of Engineers and is currently grassed with the
bluffline escarpment stabilized with rip-rap to minimize so~l
erosion. The bluffline contains massive quantities of non-
chemical construction/demolition rubble such as concrete
fragments (some very large), piles of crushed concrete, bricks,
stone fiberglass, asbestos, metal debris and alternate layers of
residues from open burning, all covered with clay fill. The
estimated volume of contamination in Area 8 is 128,000 cubic
yards.
5.0
SUMMARY OF Site RISKS
CERCLA directs the Agency to conduct a baseline risk assessment
to determine whether a Superfund Site poses a current or
potential threat to human health and the environment in the
absence of any remedial action. The baseline risk assessment
provides the basis for' determining whether or not remedial action
is necessary and the justification for performing remedial
action.
13
-------
1-
TABLE 4-1
CIIPICAl.S OJ PaTEl "AI. COIICUIf I. STun'WIDI SOILS
CIIA'GEIGT NeI.T05N FACILITY
"
Concentr.tl~ (mg/kl)
....................... Detect lort
Anel yc.. Nini- NaJli- Fr~y Ca)
Volatile OrtaniCI
.................
Acet~ 0.0145 664 7'9.94 ~
BeNene IIMOL 5650 32 . 94
C.rbon disulfide alGI. 162 6 . 94
OIlorobeNene IIMOL 41' 49 . 94
Chlorofonl 0.0067 16600 11 . 94
Ethylbenzene IIMOL 72300 26 . 94
lII,xylene IIMOL 18/.000 29.94
"ethylene chloride aNDL 373 66-' 94
~p'Xylenes aNDL 67100 27 . 94
Tetrachloroethylene 0.0053 2070 5 . 94
TolYIfW ' IIMOL 6360 38.94
B..e/Meutral EJltr.ct.bl.s
.........................
1,2,4'Trichlorobenlenl IIMOL 81 22 . 89 / '
1,2'Dlchlorobenlene BNDL 107 23 . 89
1,4'Dichlorobenzene BNDL 546 31 . 89
An II I". eNDL 1100 7 . 89
IIi trobenlene IIMOL 746 20'89
Acid EJitrect.bles
................. ~
2,4,6'Trlchloraphenol 0.729 120 5 . 92 ...
2,4'Dichlorophenol 0.111 11.5 6 . 92
Chlorlneud Pesticides ' ,
......................
4,4"000 aNDL 8560 50 . 89
4,4"00E 0.255 8410 40 . 89
4,4"00T aMaL 3780 41 . 89
Alpfl.-aMC BNDL 4370 ]4-89
BeU-BHC aMaL 751 19 . 89
Gan8-B"C IIMOL 753 14.89
"anuflCtured Pesticide.
-.-....................
MIl t tV" BNDL 310 19 . 94
Atrn,,,. BNDL 4310 24 . 94
ClIlorobtnli Iltt SMaL 650 34 - 94
ClIloropropylate 0.2 522 22 - 94
C"_I i". aMaL 960 20 - 94
Oi.li.,., IIMOL 786 36-94
Ga leerort SMaL 750 14-94
. r "etllldithiort ($~8Cide) BMaL 47 1]-94
"etollClllor (DUll) aNDL 150 17 - 94
PrC81tort SMaL 64 35 - 94
PrC81tryn BNDL 410 28 - 94
Pro,.ll.. BNDL 11 7000 11 - 94
$18811.. 0.14 1100 32 - 94
T ertl8ltGft aNDL 8700 22 - 94
T ertlutt1n 0.1 557 19 . 94
T et1lldlyt 81'" BNDL 327 21, - 94
Tol"'-- aNDL 15200 36.94
Metat.
,,'
Ar."'le
Chr.ha
Copper
Lead
.
IICII.
1.3
0.99
IICIL
150 ' 84 - 91
1490 91 - 91
2250 (b) 91 - 91
180 91 - 91
10.5 94-94
A. , ,",\,'
OR QUF-" '.-~ \ '
~O ~~,',~,:,! ;
(;7,1: ,," ',':'""
ey8ft1 dt8
........
Cy8ftldl, Totat
. ..
"
BMDL . Below _tltod detectiort II.it
(.) R..,r..."t. tlte IUIIbef" of ~'es in 'lftich tll. ch_ic8l ... detlCted
~,. tile total ~r of _lyl. slllPles.
(b) The ...i.u. c~r concantr.tion in study-.lde soil. IhGMn in tfte .1 'eport
(108 1988) .. pres"'ted on P8P '-J in a.,..,.aia , i. 131,000 ..,.,- Tlli.
vII,. w.. N'" 11ft "" .".1,.11 of .ast. I" . drta ift Zone I. Tllia ....t.
o '.J......J---' ~-','- - 1-- ~:-_'.~ . 'I '~ J ,_-:.>, rl '-, -':;,',. -;- j'-:'-i;_<~,.. I) :,::~~' ~-.I \' '.;'-"
-------
'~.EJL 4-2
CHEMICALS OF POTENTIAL CONCERN IN SITE 8 SOIL
G~tric "'ean
Concentrclt 1 on
mg/kg
"'aaillUll
Concentrat ion
mg/kg
Oetection
Frequency (a)
Volatile Orqanics
..... ..... .. ... ...... ...... .. .. .. .. .. .. ...
Benzene 0.01.11, 1.01 7 - 17
CI'Ilorotlenzene 0.0618 1.98 11 . 17
Cnlorotorlll 0.0220 0-372 5 . 17
m-xylene 0..21,7 21,10 13- 17
o.p-)(ylenes 0.179 1200 13 - 17
Toluene 0.197 3150 II, - :7
Base/Neutral EJ.tracubles
.e................-.............-.......
1.2.I,-rrichlorobenzene 0.337 1.36 2 - 17
Nitrobenzene 0.130 0.269 1 . 17
Chlorinated Pesticides
.... .......- ................ "'....- -.
1,.1,' -ODD 2.2 1,2 7 . 17
1,.1,' 'ODE 1.72 27.8 5 . 17
I,.I,"ODT 1.06 1,7.8 3 - 17
"'anutactured Pesticides
.................-.....-.-..........-
Ametryn 0.905 310 5 - 17
Atrazine 1.10 17 7 - 17
Cyanezi". 0.531 710.2 10-17
Diazinon 2.i,8 720 7 . 17
Galecron 0.&103 750 7 - 17
"'ethidathion (Supracide) 0."'- 1,1 10 . 17
"'etolachlor (Dual) 1.8lo 150 10 - 17
Prometon 0.84 9.9 7 - 17
Prometryn 1.76 '-10 12 . 17
PropaZ1ne 1.07 1180 3 . 17
Sirna: Ine 28.3 1100 15 - 17
TerbYneton 2.0 1,2 6 . 17
Terbutryn 1.22 75.5 8 . 17
Terbuthylazine 2.76 280 1lo - 17
Tolcan 1.50 3.9 1 - 17
"'etals
Arsenic 13.10 150 15 . 17
Cnromi~ 135 1'-90 17 - 17
Copper 164 22.5 17 - 17
Lead 55 180 17 . 17
Cyanides
.........-...
Cyanide. Tota~ 0.1,21 10.5 17 . 17
.-
.....
rc
(.)~epresents the ~r of samples in .hich the chemical ..s detected
.:per tft. total ~r of analyZed samples.
.
-------
5.1
CONTAMINANTS OF CONCERN
The majority of the wastes and residues generated by production
operations at the facility have been managed, treated, and
disposed of on-site throughout the Site's history. The waste
disposed of in Area 8 are covered with 4-8 feet of fill material
and sod. There is no evidence of contaminated surface material
in this area. Therefore, the media of concern is subsurface
soil. The classes of chemicals measured in the various
environmental media in the Remedial Investigation were evaluated
for inclusion as chemicals of potential concern in the risk
assessment by application of screening criteria.
The criteria which resulted in elimination of chemicals included:
Site contaminant concentrations below background concentrations;
measurements below quanti tat ion limits; a combination of low
toxicity and low concentration or low persistence and low
concentration and low frequency of detection.
The chemicals of concern for the Site include high molecular
weight chlorinated pesticides (BHC isomers), Site-manufactured
pesticides ( atrazine, diazinon, prometrYn, simazine), volatile
solvents ( chloroform, toluene, xylenes) and metals (copper,
lead, arsenic, chromium and an iron slurry waste). The media of
concern for this operable unit is contaminated subsurface soil.
The maximum and minimum concentrations of analytes found in the
subsurface soil throughout the Ciba-Geigy Site are contained in
Table 4-1.
The geometric mean and maximum concentrations for the chemicals
of potential concern in Area 8 are summarized in Table 4-2.
5.2
EXPOSURE ASSESSMENT
Whether a chemical is actually a concern to human health and the
environment depends upon the likelihood of exposure, i.e. whether
the exposure pathway is currently complete or could be complete
in the future. A complete exposure pathway (a sequence of events
leading to contact with a chemical) is defined by the following
four elements:
o
A source and mechanism of release from the source,
A transport medium (e.g., surface water, air) and
mechanisms of migration through the medium,
The presence or potential presence of a receptor at the
exposure point, and
o
o
16
-------
.
A route of exposure (ingestion, inhalation, dermal
absorption) .
If all four elements are present, the pathway is considered
complete.
An evaluation was undertaken of all potential exposure pathways
which could connect chemical sources at the Site with potential
receptors. A11 possible pathways were first hypothesized and
evaluated for completeness using EPA's criteria. Three current
potentially complete exposure pathways and one future exposure
pathways remained after screening. The current pathways
represent exposure pathways which could exist under current Site
conditions while the future pathway represents exposure pathways
which could exist, in the future, if the current exposure
conditions change. The current exposure pathways were developed
for the Ciba-Geigy Areawide Risk Assessment. Since there is no
known surficial contamination in Area 8 it is unlikely that the
pathways are complete for this Area. Exposure by each of these
pathways was mathematically modeled using generally conservative
assumptions.
The current pathways are:
o
inhalation by nearby residents of contaminated dust
particles;
o
inhalation by nearby residents of volatile chemicals
from subsurface sources in the past waste management
area; and
o
ingestion of venison by local hunters from deer feeding
in vegetated areas of the impacted area.
The future pathway is:
o
ingestion of contaminated groundwater.
The exposure point concentrations for each of the chemicals of
concern and the exposure assumptions for each pathway were used
to estimate the chronic daily intakes for the potentially
complete pathways, with the exception of the groundwater pathway.
The chronic daily intakes were then used in conjunction with
cancer potency factors and noncarcinogenic reference doses to
evaluate risk.
17
-------
The groundwater at the Ciba-Geiqy Site currently contains
concentrations of the Site contaminants at levels which would
pose an unacceptable risk to human health if the water was being
used for human consumption. However, the surficial aquifer is no
longer being used as a source of potable water at the Ciba-Geiqy
plant. Also the ongoing groundwater extraction and treatment
system is capturing the contaminated groundwater. As a result,
this is not a current complete exposure pathway. The former
waste management area 8 is a contributor to the contaminated
groundwater.
The future groundwater exposure pathway was evaluated by
comparing soil concentrations with health-based soil cleanup
levels. The health-based soil cleanup lev~ls were calculated
using groundwater models, to assure that drinking water max~um
contaminant levels (HCLs), as established under the Safe Drinking
Water Act or health-based levels would not be exceeded in the
groundwater as a result of contaminants leaching through the
soil. As with all models, certain assumptions apply. At the
Ciba-Geiqy Site, some of the wastes extend to or near the
groundwater surface while other areas have a significant amount
of uncontaminated clay beneath the waste. As a result, two
models have been applied to the areas of contamination. The EPA
health-based subsurface soil cleanup levels are based on either
the Pestan or Summers models, which are used to est~ate
groundwater contaminant concentrations resulting from migration
of contaminants through the soil column. The Pestan and Summers
Models incorporate Site-specific aquifer characteristics and
chemical-specific soil-water partition coefficients.
The Pestan model would be used in portions of area 8 where Ciba-
Geiqy can demonstrate to EPA's satisfaction that an
uncontaminated zone exists between the contaminated soil and the
groundwater surface (See Figure 4 for an est~ate of the portion
of Area 8 where the models will be applied). The Summers model
would be used in areas where contamination has extended to or is
near the groundwater.surface.
The major assumptions about exposure frequency and duration that
were included in the exposure assessment were: .
o
For the ingestion of venison scenario, it was assumed
that a local hunter kills one deer per year and that the
venison yield from the deer is 44 kg. This quantity of
venison was conservatively assumed to be consumed
annually throughout a 70-year lifet~e.
18
-------
B44 0B46
o B22 8310 ~B32.., -.
877 , 88~+ 824+
835,0 878/
.....0 - - 0
- - .
B37+ 872+. 823+
.
\
,
,
\
\
"-
'.....
8 863+
1:s61 0
scale
!
50
l 1 ~O -'
100 200
feet
onu)
o
1329
NORTH
'.JI::: J , L'
1
0846
%74
o
1315
CJ345
B25
o
o 075
0876
- -
- --
8
851 +8 '
B65+
.
8840
811
8
o
B50
D79*
,
.' ~ 10+
I
I
849+
8830 .8B71*
867+
8 Be 1*
8880+
, -
.....
.862+
.....
.
. soil sample location meeting
criterion for Summers model
+ soil contamination near water
table
* deepest soil sample shows
contamination
o soil S~l~ location not meeting
criter . ,I!for Summers model
- boundary of Si te 8
- - a rea cons idered for the Summers
model
006
PlGUT'i:: 4
LEGEND
---
-------
o
For the inhalation of ambient air scenario it was
assumed that an individual lives in the nearest
residence (2.5 km from the Site) and inhales 20 m3 of
air per day over a 70-year lifetime. All particulate
matter at the exposure point was assumed to be
respirable and delivered to the pu1monary region of the
lung. The chemicals of concern were assumed to be 100
percent bioavailable.
o
In all scenarios a standard body weight of 70 kg was
used.
5.3
TOXICITY ASSESSMENT
Toxicity values are used in conjunction with the results of the
exposure assessment to characterize Site risk. EPA has developed
critical toxicity values for carcinogens and noncarcinogens.
Cancer potency factors (CPFS) have been developed by EPA's
Carcinogenic Assessment Group for estimating excess lifetime
cancer risks associated with exposure to potentially carcinogenic
chemicals. CPFs, which are expressed in units of (mg/kg/day) -1,
are multiplied by the estimated intake of a potential carcinogen,
in mg/kg/day, to provide an upper-bound estimate of the excess
lifetime cancer risk associated with exposure at that intake
level. The term "upper bound" reflects the conservative estimate
of the risks calculated from the CPF. Use of this conservative
approach makes underestimation of the actual cancer risk highly
unlikely. Cancer potency factors are derived from the results of
human epidemiological studies or chronic animal bioassays to
which animal-to-human extrapolation and uncertainty factors have
been applied. The CPFs for oral ingestion and inhalation
exposure to the contaminants of concern for the areawide study
are contained in Tables 5-2, and 5-3 respectively.
Reference doses (RfDs) have been developed by EPA for indicating
the potential for adverse health effects from exposure to
chemicals exhibiting noncarcinogenic effects. RfDs, which are
expressed in units of mg/kg/day, are estimates of lifetime daily
exposure levels for humans, including sensitive individuals.
Estimated intakes of chemicals from environmental media can be
compared to the RfD. RfDs are derived from human epidemiological
studies or animal studies to which uncertainty factors have been
applied (e.g., to account for the use of animal data to predict
effects on humans). These uncertainty factors help ensure that
20
-------
~ 5-2
HEALTH EFFECTS CRITERIA FOR ORAL EXPOSURE TO CHEMICALS OF CONCERN
Reference Dose EPAICAC
Cancer
Ch_ic:al ( R fO) Uncertainty Potency Fac:tor I/eignt of
(mg/kg/~y) Fac:tor (a) Sourc:e (b) (l1Ig/kg/day)-1 EVIdence (C)
Acetone IE-I 1,000 tRIS
Ametryn ge-3 1 ,000 IRI5
Ani line
Arsenl c 1.0E.3 5. 7E'3 8Z
Atrazine EPA 1. 7S A
8enzene 5E-1o 1,000 tRIS" C
......8 IRIS 2.9E-Z
"lplla-8HC A
beta.8HC 6.3 ~2
ganrna-BHC 3e-1o 1.8 ::
1,000 IRIS 1.3- 82.C
Carbon disulfide IE-1 100 IRIS
Chlorooenzene 3E-Z. 1,000 HEA
Chlorooenzilate EPA... 5.5E-2 32
Chi oroform 1.0£-2 1,000 IRIS 6.1E-3 52
Chloropropylate Cd) 1E-2 1,000 CI8A-CiEICiY
ChrOllli "" III 1 100 IRIS
Chroml"" VI 5E.3 500 IRIS
Copper 3.7E-2 HEA
Cyanazine Z.OE.3 300 IRIS
Cyanide (as Hydrogen Cyanide) 2.0E-2 100 IRIS
Olazinon 9.0E-1o 10 EPA
000
DOE - -....
!JOT 5E-1o 100 IRIS 3 .l.E -I. ~~ 82
1,2-0iC:hlorobenzene 9£'2 100 HEA 4.......
1 ,10-0 1 c:nI orooenzene 1.0£.1 1,000 HA 2.l.E.2 ~ - 82
2,4.0lchloropnenol 3E-3 100 IRIS
2,l.-Olnltrotoluene EPA 0.68 92
2,6-0lnitrotoluene ORIIL l..83
., E thyloenzene 1E-1 1,000 IRIS
Galecron HAS 9.l.E-1 32
Lead 6E-4 "'ClG
",etnidathion 1E-3 100 IRIS ::
"'etnylene cnloride 0.06 100 CRIS 7.5E-3 52
"'etolachlor 1.5E- 1 100 (RIS
NItrObenzene 5E-4 10,000 IRIS
Promecon 1. 5E - 2 1,000 tRIS
Prometryn 4E-3 1,000 IRtS
PropelZ i ne ZE.2 300 IRIS
S 1111.11 I ne 5E.3 1,000 IRIS
S imetryn
TerbUneton (d) 7.5E-2 100 CIBA-CiEICiY
Terbutryn 1.0£-3 100 IRIS
Teroutnylazine (d) 3.5E-3 100 CI8A.CiEICiY
Tetrachloroethylene 1.0E-2 1,000 IRIS 5. 1 E . 2. 82
TOlban (d) 2.5E-3 100 CI8A-CiEIGY
Tolut!ne 3.0E-1 100 IRIS
I,Z,4-Tric:nlorobenzene 2.0E-2 1,000 ! RIS
2,l.,6.Yricnlorophenol 2.0E-2 8Z
Xylenes (mi lied) 2 100 IRIS
(a) uncertainty factors used to develop r.ferenc. dOses consist of ~ltiples of 10, each factor representIng a
specific: ar~ yncertainty inherent in the data available. The standard uncertainty factors include:
. A 10-foltCf8ctor to account for the variation in sensitivity among the members of the human populatIon;
. A 10-fold lector to account for the uncertainty in elltrapolating animal data to the ca~e of hunans;
. A 10-fold factor to account for uncertainty in eAtrapolating from lesS tftan cftronlC NOAELS to cftronlc
HOAELs and;
. A 10-fold factor to ac:count for the uncertainty in elltrapolating fr~ LOAELS to llOA£Ls.
(b) Sourc:e of Reference Dos.s: IRIS a ch..ic:al files of tn. Integrated Risk Information Syst..; MClCi = Maximum
Contaninant Level GOal; HEA a He.lth Effects Assessment; HA . Healtn Advisory; liAS: National Academy ot
Science; ORNL a Oak Ridg. National 8IbOrator;es.
(c) weigllt of evidence C:lassificatian sen... for carc:inogens: A.-HUIan Carcinogen, sufficient evidence from hunan
epidellii olQ9ical studies: "--protlabl. "\811\ Carcinogen, l illi teel evidence fr08 epi4881i olOtlcal studi es and
adequate evidenc. frCIII aniNl stYCIies; 82"Pr~le H\88I\ Carcinogen. inacl8Qult. eVldenc. frCIII epidemloloeJical
studies ancI 8dequ8te evidence fr08 ani..t UYC!ift; C, 'Possibl. H- Carcinogen, l illn tecl ,vldenCe In .,,1111815
in the absence of n~ data; O-.Noe Classified IS to nUl8n carcinogenic:ity; and E..EvidenCe of
lIoncarc:inogenic:ity.
(d) AcceptaOle ~11y intake derived by Cibl-G.igy frOll tn. resultS of unpublished studies perfonned by Clba-Gelgy.
. = Rev I P.v pendi ncJ.
.. : elltra safety tactor of 10 vas applied to
Ted Faroer 1988)
... = Health "'..., r/l..1r~tal Effects Profile
acc:ount for possible carC:inogenicity (verbal c:omaunication -
(HEEP) 1984 and ".rbll comaunlcation - Boo Mc:GaU9/1y 1988.
-------
TABLE 5-3
MEALTH EFFECTS CRITERIA fOR INHALATION EXPOSUIE TO CHEMICALS OF CONCERN
Reference 0058 EPAJCAG
Cancer
(RfO) uncertainty Potency Factor lIelgllt of
Cllemical (mgJkgJday) Factor (a) Source (b) (mg/ltg/day).1 Ev'Qence (c j
Acetone
Ailletryn
Ani l ine
Arsenic '50
Atrazine A
9~nzene 2.9E.2
alptla-9HC A
beU-SHC 6.> 82
gal1'lM-9HC 1.8 C
Cyanazine ....8
CarDOn disulfide
CIIlorobenzene 5E-3 10,000 HEA
ChlorOl)enzilate
Chloroform 8.1E-2 52
Chloropropylate
Chromi\A1\ III 5.1E-3 HEA
Chroml\A1\ VI 1.1 A
Copper 1.0E-2 HEA
Cyanide (as Hydrogen Cyanide)
Diazlnc1n
ODD
DOE
OOT 3.I.E-1- 92
1.2-0ichlorobenZene I.E-2 1.000 HEA - ..
1.I.-OichlorobenZene '-
2.4-0IChloropllenol ~ ...
2.400initrotoluene
2.600inltrotOluene ..-
Ethylbenzene
Galecron
Lead 4.3E04 NMQS NO 62
Methidathion
Methylene chloride I.I.E -2 32
Metolaclllor
Piltrobenzene 6.0E-4 10.000 HEA ....8
Prometon
prometryn
PropaZlne
Simazlne
Slmetryn
TerbUneton
TerOutryn
TerOuthyl az i ne
Tetrachloroethylene 3.3E-3- 82
Tolban
Toluene ' 100 HEA
1.2,4-Trichlorobenzene 3e-3 1.000 HEA
2.4.6.Trlchloropnenol 2E-2 82
Xylene~ (mi xed) 4E-' 1.000 HEA
(a) uncertainty f..-.rs-used to develop reference doses c~sist of multiples of 10. elch factor representing a specific
area of uncert~ty inherent in the dati IVlilable. The standard uncertainty factors include:
. A 10-fold ~tor to account for the vlriation in sensitivity among the members of the human population;
. A 10-fold ~tor to ICCount for tne uncertainty in e.trapolatint animal data to the case of humans;
. A 10-fold '-actor to account for uncertainty in e.trapolat1nt froa les~ than chronic NOAELs to cnronic NOAELS;
and;
- A 10-fold factor to account for the uncertlinty in e.trapolatint frOll LOAELS to NOAELS.
(b) Source of ~eference Doses:
HeA. Hellth Effects Assessment; ~ . .Itionel A8bient Air Quality Standard-
(c) weight of evidence classificltion sc".,. for carcinogens: A.-HU88n Carcinogen. sufficient evidenCe from IIuman
epideftliol09ical studies; B,-.prob8Dll HYMn Carcinogen. lillitlG evidence frOll epidllftiOl09ical st...:ties and aaequate
evidence frOll anilll8l Studies; BZ--prob8Dll HYMn Carcinoeen. i~te eviaence trOll! epicl8llliol09icll u..csle,. ancl
a~te evidence frO/ll anl18l studies; C- .possible MUllIn C.rcinogen. limited evidence in aniNls In the aD~ence 0;
human data; Do-Not Classified a5 to hu..n Clrcinogenicity; and E.oEvldence of Nonc.rcinogen1clty.
- z ~eview pendi"9.
NO : Not d~t~rmin~
-------
the RfDs will not underestimate the potential for adverse
noncarcinogenic effects to occur. The RfDs for oral ingestion
and inhalation exposure to the contaminants of concern for the
areawide study are contained in Table 5-2, and 5-3 respectively.
5.4
RISK CHARACTERIZATION
Human health risks are characterized for potential carcinogenic
and noncarcinogenic effects by combining exposure and toxicity
information. Excessive lifetLme cancer risks are determined by
multiplying the estLmated daily intake level with the cancer
potency factor. These risks are probabilities that are generally
expressed in scientific notation (e.g., 1xlO-6). An excess
lifetLme cancer risk of lxlO-6 indicates that, as a plausible
upper bound, an individual has a one in one million additional
(above their normal risk) chance of developing cancer as a result
of site-related exposure to a carcinogen over a 70-year lifetLme
under the assumed specific exposure conditions at a Site.
The Agency considers individual excess cancer risks in the .range
of lxlO-4 to 1xlO-6 as protective; however the 1xlO-6 risk level is
generally used as the point of departure for setting cleanup
levels at Superfund sites. The point of departure risk level of
1xlO-6 expresses EPA's preference for remedial actions that
result in risks at the more protective end of the risk range.
Potential concern for noncarcinogenic effects of a single
contaminant in a single medium is expressed as the hazard
quotient (HO) (or the ratio of the estLmated intake derived from
the contaminant concentration in a given medium to the
contaminants's reference dose). A HO which exceeds one (1)
indicates that the daily intake from a scenario exceeds the
chemical's reference dose. By adding the HOs for all
contaminants within a medium or across all media to which a given
population may reasonably be exposed, the Hazard Index (HI) can
be generated. The HI provides a useful reference point for
gauging the potential significance of multiple contaminant
exposures within a single medium or across,media. An HI which
exceeds unity indicates that there may be 'a concern for potential
health effects resulting from the cumulative exposure to multiple
contaminants within a single medium or across media.
The health risks resulting from exposure to the current pathways
are as follows: the upper bound excess lifetime cancer risk
associated with inhalation of airborne particulate matter was
lxlO-8; the cancer risk associated with inhalation of
23
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volatilized chemicals from the combined source areas was 3x10-10;
and the cancer risk associated with ingestion of venison was
2x10-10. None of the non-carcinogenic chemicals of potential
concern exceeded a hazard quotient of one (1).
The future pathway based on groundwater contamination resulting
from leaching of contaminants from the soil was evaluated by
comparing the health-based soil cleanup levels and the soil
concentration of the contaminants of concern in the former waste
management area 8. Table 5-9 contains this comparison. The soil
cleanup levels represent the residual soil concentrations that
would not cause Federally regulated drinking water standards to
be exceeded as a result of contaminants leaching through the
soils to the groundwater.
The soil excavation levels for the carcinogenic contaminant of
concern (gamma-BHC) is based on the Federal maximum contaminant
level (MCL). The model-calculated soil remediation levels for
noncarcinogenic contaminants of concern reflect the proposed MCL
for simazine and a hazard quotient (HQ) of one (a concentration
that will not exceed the chemical-specific acceptable daily
intake or reference dose) for the other noncarcinogenic
chemicals. In addition this number is reduced to allow for the
groundwater to provide only 20% of the acceptable daily intake.
The comparison of the health-based cleanup level concentrations
for 'the protection of groundwater with the actual soil
concentrations indicate that the soils in the former waste
management area 8, contain concentrations of Site-related
contaminants which exceed the health-protective soil levels.
The potential current exposure pathways are not producing an
unacceptable level of risk and consequently will not drive the
remediation of the former waste management areas. However, since
the subsurface soils are either currently contributing or could
potentially contribute in the future to unacceptable levels of
groundwater contamination, this pathway will dictate the
remediation of the contaminated subsurface soils. Although the
surface soil is not currently well characterized, the direct
contact pathway could potentially require the remediation of
some surface soils.
5.5
ENVIRONMENTAL RISK
The source area is presently covered with fill and therefore is
not easily accessible to certain terrestrial species. For this
reason the source areas are not expected to have toxic effects on
24
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those terrestrial animals at this time. However, the ecological
assessment indicates that the Site may have toxic effects on
certain plant species, as well as robins and shrews in the areas
of concern in the future. The selected remedy based on
protection of human health will eliminate the potential for such
toxic effects since the environmental exposure pathways will not
exist. The environmental impact for the bottom dwelling aquatic
communities in Johnson Creek, the floodplain, and the Tombigbee
River will be further evaluated in Operable Unit '3.
5.6
CLEANUP LEVELS
The September 1989 ROD for Operable Unit 11, Groundwater
Remediation, addresses the contaminated groundwater exposure
pathway. The cleanup levels of the currently operating
groundwater pump and treat system which are applied at the Site
boundary ensures that concentrations of contaminants in the
groundwater do not exceed Maximum Contaminant Levels (HCLs) or
Minimum Detection Levels (HeLs) for any future consumers of this
water are contained in Table 5-6. The cleanup levels for
groundwater in deep soil treatment areas are contained in Table
5-1. The groundwater cleanup levels in the deep soil treatment
areas have been generated to ensure localized isolation and
treatment of contaminated groundwater near Area 8. These levels
are either the Federal MCLs or 1 x10-4 health based
concentrations which were used to determine the soil excavation
levels. All cleanup levels applied at this Site are within EPA's
acceptable 1 x 10-4 to 1 x 10- risk range . The 1x10-6 risk level,
MCL or MDL was used to calculate acceptable concentrations of
contaminants at the Site boundary and for ingestion and
inhalation. Subsurface soil and its surrounding groundwater
cleanup levels are applied at the 1 x 10-4 risk level since this
is an industrial site and in this case it would be more cost
effective to let any residual contamination be captured by the
currently operating groundwater pump and treatment system. This
is consistent with areas in Operable Unit #2 requiring no
localized deep soil treatment. Groundwater extracted in the soil
flushing portion of the remediation will be treated by the
existing pump and treat system.
The ROD for Operable Unit .1 did not address the sources of
contamination. Addressing the contamination source will decrease
the time required to pump and treat. Cleanup levels for the
contamination source (the subsurface soils) for groundwater
protection are based on the Federal HCL for the carcinogen
25
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(qamma-BHC) and a hazard quotient of 1 for noncarcinoqens. This
cleanup level provides an acceptable exposure level that is
protective of human health. Althouqh there is no evidence that
surface soils are contaminated in this area, cleanup levels are
provided which should be achieved in the top 12 inches of soil.
Cleanup levels for contaminated surface soil are based on a
worker exposure scenario and assume a commercial/industrial land
use. These levels are based on the ingestion and inhalation
exposure routes and represent a 1x10-6 risk level for carcinogens
and a hazard quotient of 1 for noncarcinogens. The cleanup
levels for direct contact of surface soils are listed in Table
5-8.
The following groundwater cleanup levels are being applied at the
property boundary for qroundwater leaving the Site to ensure that
any future groundwater consumers will not be exposed to
unacceptable concentrations of Site-related chemicals in the
qroundwater. The concentrations presented represent either the
regulated Maximum Contaminant Level (MCL) or the Minimum
Detection Level for the constituents listed.
TABLB 5-6
GROUNDWATER CLBANUP LIVBLS
AS PROVIDED IN ROD ADDRESSING OU'l
Contaminants
Cleanup
Goal (ug/1)
Aniline
Arsenic
Benzene
Alpha-BHC
Ganuna-BHC
Carbon Tetrachloride
Chlorobenzene
Chloroform
Cresols (m-p-)
Methyl Ethyl Ketone
Naphthalene
Toluene
26
10
50
5
.05
0.2
5
5
5
10
10
10
2000
-------
For the in-situ remediation processes, the following groundwater
cleanup levels would be applied to any groundwater withdrawal wells
installed within the RCRA defined point of compliance or within the
areas identified during the Remedial Action. The withdrawal wells
would be installed in areas where subsurface soil cleanup levels were.
not achieved before excavation limits were reached.
TABLE 5-7
(lx10-4 Risk Corresponds)
GROUHDWATBR CLEARtJP LEVELS FOR DBBP SOIL TRBATXBIr.r AREAS
Compound
Cleanup
Level (ug/l)
0.6
2.0
0.2
0.2
10.0
10.0
10.0
6.0
140.0
630.0
14.0
1.0
3.0
28.0
alpha-BHC
beta-BHC
Lindane
delta-BHC
DOT
DDD
DDE
Diazinon
Chlorobenzilate
AmetrYn
Bladex
Simazine
Atrazine
PrometrYn
27
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DBLB 5-8
SOIL CLIWnJP IaEVBLS lOR OU'.
AT TIll CIBA-GBIGY Site
The following table provides the direct contact cleanup levels.
These levels will be applied to the top 12 inches of soil
throughout the area of contamination. The cleanup level for
gamma-BHC represents a 10-6 risk level. The cleanup levels for
the remaining chemicals represent an HQ of one (1).
Contaainant
18-6 ltJ.8k
Direct Contact Pathway
(IICJ/kg)
Gamma-BHC
*Diazinon
*Atrazine
*Bladex
*Simazine
*Prometryn
4
1,800
10,000
4,100
4,100
8200
* These chemicals are not considered to be carcinogens.
Therefore, the cleanup levels do not represent a carcinogenic
risk level.
The cleanup levels for gamma-BHC and simazine in the following
table are soil levels derived to achieve based on the MCL and
proposed MCL, respectively in the groundwater. The cleanup
levels for the remaining chemicals represent a concentration
which, when combined with the Site specific exposure assumptions,
will yield a daily intake which does not e,xceed the chemical's
reference dose (RfD). The RfD is an estimate of the lifetime
daily exposure level for humans, including sensitive individuals,
which will not produce adverse health effects. In addition the
risk based concentration has been reduced to allow groundwater to
provide only 20% of the acceptable daily intake.
28
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DBLB 5-'
SU8S1JRPACB SOIL CLBARUP LBV8LS POR OU..
DUB m GROUMDWAftR IRGBS'IIOR PAIfBWAY
Va~illlUlll
S~r's Pestan Concentration Pound
Con'taminant (aq/kg) (J8Cj/kg) (.g/kg)
Gamma-BHC 1.0 37 422
*Diazinon 10 10 720
*Bladex 2.0 37 23
*Simazine 3.7 1000 321
*Atrazine 3.6 19 1809
*Prometryn 38.5 1557 4029
* These chemicals are not considered to be a carcinogens.
cleanup levels do not represent a carcinogenic risk level.
Therefore, the
Although the contaminants of concern are not the only contaminants at
the Site, they were chosen based on toxicity, mobility and frequency
of detection throughout the Site. It is anticipated that contaminants
at the Site which do not have cleanup levels presented in this ROD
will be reduced to acceptable levels when cleanup levels are met for
the most toxic and most mobile contaminants for which cleanup levels
have been established.
The groundwater at the Ciba-Geigy Site currently contains
concentrations of Site-related contaminants at levels which would pose
an unacceptable risk (cumulative risk in excess of 1x10-6) to human
health if the water was being used for human consumption. Actual or
threatened releases of hazardous substances from this Site, if not
addressed by implementing the response action selected in this ROD,
may present an ~inent and substantial endangerment to public health,
welfare, or the environment.
6.0
DESCRIPTION OF ALTERNATIVES
Eleven alternatives for remediation of contaminated soils at Area 8 of
the Ciba-Geigy Site were evaluated in the Feasibility Study Report.
After reviewing comments received during the initial comment period
for OU#2, the concepts of the eleven alternatives were reduced to four
alternatives based on the similarities in their technologies.
29
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6.1
ALTERNATIVE NO.1 - No Action
The no action alternative is carried through the screening process as
required by the National Oil and Hazardous Substances Pollution
Contingency Plan (NCP). This alternative is used as a baseline for
comparison with other alternatives that are developed. Under this
alternative, EPA would take no further action to min~ize the impact
soil contamination would have on the groundwater. Contaminants in the"
soil would continue to leach into the groundwater at levels which
would exceed groundwater protection standards. The overall remedial
action levels would not be achieved within 100 years by utilizing this
alternative. There is no cost associated with this alternative since
no additional activities would be conducted.
6.2
ALTERNATIVE NO.2 - Containment
This alternative consists of placing a soil bentonite slurry wall
around the perimeter of the area to prevent lateral migration of
contaminants in the groundwater. A multilayered RCRA cap would be
placed over the area to minimize the vertical migration of soil con-
tamination. Solidification/stabilization may be required in one
portion of the Site containing soft waste to increase the strength of
the waste to sufficient levels to support a cap system. The area
would be revegetated following construction activities. Soil
contamination would not be reduced, but isolated from the environment
by the cap and slurry wall. Institutional controls (land and
groundwater use restrictions) would be necessary to ensure the
integrity of the alternative. Following the construction of the cap
and slurry wall, the Site would be monitored to verify the
effectiveness of the remedy. The overall remedial cleanup levels as
defined in operable unit one, would not be achieved within 100 years
by utilizing this alternative. The alternative could be constructed
in 10 months. The present worth cost of this alternative, including
operation and maintenance, is estimated to be $10,909,000.
Elements Common to Alternatives 3 and 4
The remaining two alternatives involve the excavation of soil which
exceeds health-based cleanup levels. Although the actual excavation
levels are not Applicable or Relevant and Appropriate Requirements
(ARARS), they were established, in part, to ensure that the Federally
regulated drinking water standards (ie., Maximum Contaminant Levels),
which are ARARS, are not exceeded by contaminants leaching from the
soils into the groundwater. Excavation would be conducted using
conventional methods. Excavations may be terminated before cleanup
30
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levels are reached for any of the following situations (excavation
limits for this Site).
1. When large concrete structures are encountered such as building
foundations, reinforced concrete slabs and concrete roadway sections
connected with reinforcing steel, which require different types of
materials handling and excavation methods;
2. When the water table is encountered. This means that soil
removal methodologies would change and further pretreatment would be
required for the thermal treatment process of those soils. Depending
on the volume of soils removed from below the water table, there could
be an adverse effect on the existing pump and treatment system.
3. When a depth of 20 feet is reached. Below this depth, excavation
poses additional hazards to workers requiring different OSHA standards
and increasing the cost of excavations.
4. When the iron slurry waste is encountered. This material will be
treated by in-situ stabilization/fixation. Cost effectiveness and
implementability were considerations in the decision(s) to halt
excavation.
The four situations above have been defined as excavation limits.
ALTERNATIVE NO.3 - Removal. Solidification/stabilization,
and On-Site Disposal
This alternative consists of the excava~ion of contaminated soil and
sludge within the Site until the established cleanup levels or
excavation limits are reached (see section 6.2, Elements Common to
Alternatives 3 and 4). The excavated material would be
solidified/stabilized.
6.3
After solidification/stabilization, the material would be disposed of
in an on-site landvault after RCRA LDR treatment standards, pursuant
to a treatability variance, are met. In accordance with Superfund
Land Disposal Restriction (LDR) Guidance t~A, for herbicides, which
are similar and are applicable to Site contaminants, a treatability
variance requires that the selected technology must demonstrate a
90-99.9 percent reduction in the contaminants of concern.
Uncertainty exists regarding the effectiveness of
solidification/stabilization of material contaminated with elevated
concentrations of organic contaminants. Therefore, treatability
studies would be conducted to determine the effectiveness of this
31
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alternative in meeting the legislated treatment standards.
Solidification/stabilization would be utilized for soils where it is
proven effective in reducing the contaminated soil concentrations to
Land Disposal Restrictions (LDRs) treatability variance levels. This
area also contains an iron slurry waste that is completely unsuitable
for pugmill stabilization. This waste would be treated by the
utilization of an in-situ fixation process which would achieve the
leachate requirements of LOR. The NCP establishes a presumption that
treatment to the legislated standards based on the Best Demonstrated
Available Technology is generally inappropriate for CERCLA
contaminated soil and debris (55 FR 8758-62, (March 8, 1990».
Therefore, compliance with the land disposal treatment standards would
be achieved pursuant to a treatability variance for CERCLA
contaminated soil and debris. This treatability variance would be
granted upon ROD signature. The landvault would be designed in
accordance with applicable RCRA regulations. The areas would be
backfilled following excavation activities. Following Site
remediation, the excavated areas would be vegetated. If the
subsurface excavation levels are not achieved before excavation limits
are reached, institutional controls (i.e., land and groundwater use
restrictions) would be necessary to restrict exposure to the
contaminated subsurface soil and to prevent exposure to contaminated
groundwater. The overall remedial action levels would not be achieved
within 100 years by utilizing this alternative. ~ternative 3 could
be constructed in 12 months. The present worth cost of this
alternative is estimated at $30,359,000.
6.4
ALTERNATIVE NO.4 - Removal. On-Site Thermal Treatment,
Solidification/stabilization and On-Site Disposal
This alternative consists of:
1.
The Excavation Process
The excavation of contaminated sludge and soil within the Site until
the established cleanup levels or excavation limits are reached.
2.
Application of Innovative Technologies to Excavated Materials
Treatability studies would be conducted during the Remedial Design to
determine the effectiveness of selected technologies on soils at the
Site. Three potential pre-treatment options include:(l) solvent
extraction, followed by liquid injection incineration: (2) low
temperature thermal desorbtion, followed by treatment of desorbed
volatile organics/air mixture and (3) critical fluid injection
followed by liquid injection incineration. These options for pre-
treatment would be evaluated during the design to determine if the
32
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main thermal treatment process and/or cost effectiveness can be
enhanced while still meeting levels as adjusted by the treatability
variance. Treatability studies would be conducted to determine if the
contaminated soils are amenable to treatment or pretreatment by
dechlorination to treat the waste to LDR treatability variance levels
or to ~prove the performance of the Pr~ary Treatment. These studies
may also be used to determine if such treatment or pretreatment will
improve the performance of the solidification/stabilization of wastes'
containing no gamma-BHC or organic content less than 2500 ppm.
Finally, treatability studies would be conducted to determine whether
solidification/stabilization might be an effective treatment
technology for soils containing no gamma-BHC and containing less than
2,500 ppm total organics. This is an innovative application of the
solidification/stabilization process. If this technology is proven
effective, it will be used for these soils rather than the Pr~ary
treatment.
3.
Innovative Application of Solidification/Stabilization Technology
According to results from subsurface soil borings collected by Ciba-
Geigy during RI/FS field activities, portions of Area 8 may contain
manufactured pesticides that exceed the health-based cleanup levels
requiring them to be excavated, but are not mixed with a RCRA waste.
The manufactured pesticides of concern are toxicity characteristic
analytes and therefore have no toxicity characteristic regulatory
levels. ~though no regulatory levels are exceeded for any toxicity
characteristic analytes and it has been determined that the soil is
not a RCRA hazardous waste, these manufactured pesticides exceeded the
health-based cleanup levels, requiring that they be excavated and
treated.
All soils which are mixed with a RCRA waste that exceed the cleanup
levels will undergo thermal treatment or dechlorination and be treated
to legislated (LDR) treatment standards, as adjusted by a CERCLA
treatability variance upon signing of the ROD. Additionally, it is
anticipated that it will be necessary to thermally treat some of the.
soil contaminated with manufactured pesticides that exceed the health-
based levels which contain a total organic concentrations above 2,500
ppm.
Soils containing less than 2,500 ppm total organics may be amenable to
treatment using a solidification/stabilization process. This
application would represent an innovative application of this
technology since EPA has min~al information on stabilization of
manufactured pesticides. The NCP encourages the use of innovative
technologies at Superfund sites. For this reason, and because this
33
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application may be effective at the Site, solidification/stabilization
treatment will be evaluated during the treatability studies for these
waste. If the stabilization process is unsuccessful, thermal
treatment will be used to treat these waste.
4.
Pr~ Treatment: On-site Thermal Destruction
The primary treatment technology for the contaminated excavated
material not amenable to final treatment by the innovative
technologies would be on-site thermal destruction. The contaminated
soil may require pretreatment to remove debris present before the
thermal treatment process. The excavated soil would be blended in a
tank which meets the definition of a tank in Section 260.10 of the
Code of Federal Regulations (40 CFR). The purpose of the blending is
to achieve a homogeneous mixture prior to thermal treatment to ensure
proper incinerator operations and to comply with operating conditions
determined in the trial burn.
5.
Management of Treatment Residuals and pugmill Wastes
Ash from the thermal treatment process and any material from any
technology selected during the Remedial Design would be disposed of in
a landvault after RCRA legislated treatment standards, as adjusted by
a CERCLA treatability variance, are met. Following excavation, the
area would be backfilled and revegetated.
6.
In-situ Remediation Processes
If the excavation is terminated before cleanup levels are achieved,
in-situ soil flushing would be used. In-situ soil flushing may
involve monitoring wells, withdrawal wells, re-injection wells and
isolation walls extending from the land surface to the top of the
Miocene clay, which would be used to flush contaminants from deep
unsaturated sands and decrease the time required to pump and treat
contaminated groundwater.
In addition to the in-situ soil flushing, innovative technologies
(in-situ vacuum extraction or in-situ bioremediation) may also be used
in addition to or instead of in-situ soil flushing, if during the
remedial design either technology is found to be effective in reducing
the concentrations of the contaminants in the soil and is cost
effective. This area also contains an iron slurry waste that is
completely unsuitable for thermal treatment or pugmill stabilization.
This waste would be treated by using an in-situ fixation process which
would achieve the leachate requirements of LDR.
This alternative could be implemented in 14 months.
The present worth
34
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cost of this alternative, including operation and maintenance, is
estimated to be $49,723,000. This estimated cost assumes that
excavations will continue until cleanup levels are achieved or 20 feet
is reached. If excavations are terminated because the groundwater,
iron slurry waste or large concrete boulders are encountered, the
actual cost to ~plement the remedy would be reduced.
7.0
SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES
This section of the ROD provides the basis for determining which
alternative provides the best balance with respect to the statutory
balancing criteria in Section 121 of CERCLA and in Section 300.430 of
the NCP. The major objective of the FS was to develop, screen, and
evaluate alternatives for the remediation of the contaminated soils at
the Ciba-Geigy Site. A wide variety of technologies were identified
as candidates for remediating the contaminated soils at the Site.
These technologies were screened based on their feasibility with
respect to the contaminants present and the Site characteristics. The
technologies that remained after the initial screening were combined
into potential remedial alternatives and evaluated in detail. The
remedial alternatives selected from the screening process were
evaluated using the following nine evaluation criteria:
o
Overall protection of human health and the environment.
Compliance with applicable and/or relevant Federal or State
public health or environmental standards.
o
o
Long-term effectiveness and permanence.
o
Reduction of toxicity, mobility, or volume of hazardous
substances or contaminants.
o
Short-term effectiveness, or the impacts a remedy might have
on the community, workers, or the environment during the
course of implementing it.
Implementability, that is, the administrative or technical
capacity to carry out the alternative.
o
o
Cost-effectiveness considering costs for construction,
operation, and maintenance of the alternative over the life
of the project, including additional costs should it fail.
Acceptance by the State.
o
35
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o
Acceptance by the Community.
The NCP categorizes the nine criteria into three qroups:
(1)
Threshold Criteria - overall protection of human health and the
environment and compliance with ARARs (or invoking a waiver)
are threshold criteria that must be satisfied in order for an
alternative to be eligible for selection;
Primary Balancing Criteria - long-term effectiveness and
permanence; reduction of toxicity, mobility, or volume;
. short-term effectiveness; implementability, and cost are
primary balancing factors used to weigh major trade-offs
alternative hazardous waste management strategies; and
among
(2)
Modifvina Criteria - state and community acceptance are
modifying criteria that are formally taken into account
public comment is received on the proposed plan and
incorporated in the ROD.
The selected alternative must meet the threshold criteria and comply
with all ARARs or be granted a waiver for compliance with ARARs. Any
alternative that does not satisfy both of these requirements is not
eligible for selection. The Primary Balancing Criteria are the
technical criteria upon which the detailed analysis is primarily
based. The final two criteria, known as Modifying Criteria, assess
the public's and the state aqency's acceptance of the alternative.
Based on these final two criteria, EPA may modify aspects of a
specific alternative.
(3)
after
The following analysis is a summary of the evaluation of alternatives
for remediating Operable Unit #4 of the Ciba-Geigy Superfund Site
under each of the criteria. A comparison is made between each of the
alternatives for achievement of a specific criterion.
Threshold Criteria
7.1
OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
All of the alternatives would provide protection of human health and
the environment by minimizinq or controlling the risk associated with
the contaminated soils through treatment or containment and
institutional controls. In Alternative 1, the currently operating
groundwater pump and treat system would continue operating. However,
contaminants in the soil would continue to leach into the groundwater
36
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at unacceptable levels. Cleanup levels for groundwater would not be
achieved within 100 years with Alternative 1. Alternative 2 would
isolate the contamination from the surrounding uncontaminated area.
The alternatives involving excavation, (Alternatives 3 and 4), would
minimize the majority of the risk by removing and treating the
principal source of the soil and groundwater contamination and use of
institutional controls where necessary. However, cleanup levels for
the groundwater may not be achieved within 100 years for alternatives
that do not include deep s011 treatment (Alternatives 1, 2 and 3).
Alternative 4 would provide the best overall protection because it
removes and treats the principal threats between the land surface and
the excavation lLmits and it provides deep in-situ soil treatment for
contaminated soils below the excavation limits.
7.2
COMPLIANCE WITH ARARs
All of the alternatives would comply with all Federal or State ARARs
or justify a waiver. Chemical specific ARARs would be met through
compliance with the groundwater protection standards (ie., MCLs) at
the Point of Compliance as defined in Ciba-Geigy's RCRA permit and
through compliance with the NPDES permit conditions for water removed
and treated in the waste management areas. The landvault utilized in
Alternatives 3 and 4 would be designed in accordance with RCRA
regulations. Soils excavated in Alternatives 3 and 4 would be
analyzed to determine if they are RCRA hazardous waste. If required,
RCRA hazardous waste would be treated to legislated treatment
standards pursuant to a treatability variance prior to land disposal.
Highly concentrated soils would be treated by a thermal treatment
process designed to comply with RCRA regulations for hazardous waste
thermal treatment. It is not anticipated Alternative 3 would achieve
these standards for many of the contaminants of concern due to the
elevated levels present in the contaminated soil. Alternative 4
would be designed to attain these standards as adjusted by the
treatability variance.
Air emissions from the Site would be monitored to ensure compliance
with the Clean Air Act. Fenceline air monitoring will be conducted to
ensure that contaminant concentrations do not exceed levels considered
to be safe for human health. If levels are exceeded, mitigative
procedures such as dust suppression or vapor capture will be employed
to prevent harmful levels of air emissions from leaving the Site.
RCRA design standards will be incorporated into the remedial design of
all remedial activities. Of the four alternatives, alternatives
alternative .4 provides the best compliance with ARARs.
Primary Balancing Criteria
37
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7.3
LONG-TERM EFFECTIVENESS AND PERMANENCE
Alternative 1 would not provide long-term effectiveness and permanence
with respect to the contaminated soils at the Site. Each of the
remaining alternatives would provide long-term effectiveness through
limiting the migration of contamination or treatment of the
contaminated soils at the Site. Over time the effectiveness of
Alternative 2 may decrease as a result of cap/slurry wall failure
caused by improper construction (i.e., keying of the wall into an
unfractured impermeable clay layer) or inadequate operation and
maintenance procedures. However, as long as the cap and slurry wall
are properly maintained, the alternative would be effective. In
Alternative 3, the contaminants are bound to the soil by the treatment
process and the solidified material is contained on-site in a RCRA
landfill. The long-term effectiveness of Alternative 3 is uncertain
since solidifying high level organic contamination has not been
demonstrated to be effective in preventing leaching of the waste into
the groundwater. Alternatives 4 provides a greater level of long-term
effectiveness than Alternatives 2 and 3 because thermal treatment has
been demonstrated to effectively destroy contaminants to the levels
allowed by the treatability variance. Alternative 4 provides the
greatest long-term effectiveness and permanence by the additional
treatment of contaminated soils below the excavation limits.
7.4
REDUCTION OF TOXICITY, MOBILITY OR VOLUME THROUGH TREATMENT
Alternative 1 would not reduce mobility, toxicity or volume at the
source of the contamination. Alternative 2 would isolate the
contamination from the environment, thus minimizing the forces which
drive contaminant mobility. However, toxicity and volume would not be
affected by Alternative 2. Each of the remaining alternatives would
reduce the mobility of the contaminants through treatment.
Treatability Studies would be conducted to demonstrate the level of
mobility reduction resulting in the solidification/stabilization
process proposed in Alternative 3. However, the volume of
contaminated material in Alternative 3 would increase due to the
stabilization process. Alternative 3 would provide minimal reductio~
in toxicity. The toxicity of chemical contaminants at the Site would
be reduced by the thermal destruction process in Alternative 4.
Thermal treatment and destruction of the organic chemical contaminants
at the Site through Alternative 4 would virtually eliminate all toxic
effects of the excavated soils along with a substantial reduction in
volume. Alternative 4 provides the best reduction of toxicity and
mobility through treatment by utilizing innovative in-situ treatments
for contaminated soils currently below the excavation limits.
38
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7.5
SHORT-TERM EFFECTIVENESS
Alternative 1 would not require construction or excavation that would
cause a health risk to workers. However, Alternative 1 would be the
least effective in achieving the overall groundwater cleanup levels in
the shortest time period. All of the remaining alternatives will
require varying amounts of time to implement. None will be
~ediately effective. No threshold toxicity criteria would be
exceeded by implementing Alternatives 2, 3, and 4 and the health risks
to remedial workers is unlikely, particularly when appropriate
monitoring and engineering controls are applied. Of the alternatives
evaluated, Alternatives 3 and 4 are more effective than Alternative 2
because contaminated soil would be removed and treated. Although
Alternative 3 requires removal of contaminated soils down to the
excavation limits. Alternative 4 would be most effective in the
short-term by isolating and treating the contaminated soils below the
excavation limits. These soils are causing the most ~ediate threat
because of their proximity to the groundwater.
7 . 6 IMPLEMENTABILITY
Alternative 1 is currently operating. Technological expertise,
services, equipment and materials are adequately available for the
implementation of Alternative 2. Due to the uncertainty regarding the
effectiveness of solidification/stabilization of material contaminated
with elevated concentrations of organic contaminants a treatability
study would be conducted. A determination would be made at the
completion of the treatability studies, to be conducted during the
remedial design, regarding the effectiveness of
solidification/stabilization of material contaminated with elevated
concentrations of organic contaminants.
Thermal treatment capacity may be limited at the time of
implementation of Alternative 4. New equipment may have to be
designed and constructed as a part of the overall schedule. However,
the technology base does exist for the completion of this requirement.
Ash from the thermal treatment process, any solidified/stabilized
material or any material from the dechlorination process would be
disposed of in a landvault after RCRA legislated treatment standards,
as adjusted by a treatability variance granted upon ROD signature, are
met. In accordance with Superfund LDR Guidance #6A, for herbicides,
which are similar and applicable to Site contaminants, the selected
technology must demonstrate a 90-99.9 percent reduction for the
contaminants of concern to be granted the variance. All of the
alternatives are technically and administratively feasible. However,
the results of the treatability studies would determine the
effectiveness of Alternative 3 on elevated levels of organics.
39
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7.7
COST
Alternative 1 would not require any additional cost since no treatment
of the source is provided. The present worth cost of installing a
slurry wall and cap (Alternative 2) is estimated to be $10,909,000.
Alternatives 3 and 4 are substantially higher in cost due to increased
efforts to permanently treat the contaminated soil. The present worth'
cost associated with solidification/stabilization of the contaminated
soil (Alternative 3) is $30,359,000. Thermal treatment and/or
solidification/stabilization of the contaminants in the soil
(Alternative 4) would cost approximately $49,723,000. This cost could
vary depending on the results of a treatability study to verify the
levels of contamination which could be solidified and still achieve
RCRA land disposal standards as adjusted by a treatability variance
and by the volume of soils which can be excavated before excavation
limits are reached. The treatability study would be conducted during
the remedial design to verify the level of contamination which could
be solidified/stabilized and still achieve RCRA land disposal
standards pursuant to a treatability variance. These costs include
operation and maintenance during the implementation of the alternative
as well as post remediation monitoring.
Ifodifying Criteria
7.8
STATE ACCEPTANCE
, ~'"
The State of Alabama has concurred with the selection of Alternative 4
to remediate the contaminated soil at the Ciba-Geigy Site.
7.9
COMMUNITY ACCEPTANCE
Based on the favorable comments expressed at the May 19, 1992 public
meeting and the lack '.,ff negative written comments received during the
comment periods, it appears that the McIntosh community generally
agrees with the selected remedy.
8.0
SUMMARY OF SELECTED REMEDY
In summary, Alternative 4 will achieve substantial risk reduction
through treatment of a principal threat at the Ciba-Geigy Superfund
Site. LDR treatment standards will be achieved, as adjusted pursuant
to a treatability variance, granted upon ROD signature, prior to
40
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placing the treated excavated material in the on-site landvault. As
shown in Figure 4, the treatment technology which has been
demonstrated to achieve these standards for the RCRA wastes present at
the Site is thermal treatment. Thermal treatment in this alternative
may also include a pre-treatment phase prior to the main thermal
treatment process. Three potential pre-treatment options include:
(1) solvent extraction, followed by liquid injection incineration; (2)
low temperature thermal, followed by treatment of the desorbed .
volatile organics/air mixture; and (3) critical fluid injection,
followed by liquid injection incineration. These options for
pre-treatment will be evaluated during treatability studies to be
conducted during the remedial design to determine if the main thermal
treatment process and/or cost effectiveness can be enhanced while
still meeting levels as adjusted by the treatability variance. If any
of the technologies are proven to enhance cost effectiveness or the
main thermal process, it will be used.
Under certain circumstances, the pre-treatment option could totally
replace the main thermal treatment process. If any of the
pre-treatment technologies are proven to be more effective in reducing
the contaminant concentrations in the soil and more cost effective, it
will be used instead of the main thermal treatment process.
Pre-treatment technologies that are not found to be effective in
reducing contaminated soil concentrations to levels required pursuant
to the treatability variance or that do not enhance cost effectiveness
will not be utilized.
Treatability studies will be conducted to determine the effectiveness
of solidification/stabilization of soils with low levels of
contamination.
According to results from subsurface soil borings collected by Ciba-
Geigy during RI/FS field activities, portions of Area 8 may contain
manufactured pesticides that exceed the health-based cleanup levels
requiring them to be excavated, but are not mixed with a RCRA waste.
The manufactured pesticides of concern are toxicity characteristic
analytes and therefore have no toxicity characteristic regulatory
levels. Although no regulatory levels are exceeded for any toxicity
characteristic analytes and it has been determined that the soil is
not a RCRA hazardous waste, these manufactured Pesticides exceeded the
health-based cleanup levels, requiring that they be excavated and
treated.
All soils which are mixed with a RCRA waste that exceed the cleanup
levels will undergo thermal treatment or dechlorination and be treated
to legislated (LDR) treatment standards, as adjusted by a CERCLA
treatability variance upon signing of the ROD. Additionally, it is
41
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anticipated that it will be necessary to thermally treat some of the
soil contaminated with manufactured pesticides that exceed the health-
based levels which contain a total organic concentrations above 2,500
ppm. .
Soils containing less than 2,500 ppm total organics may be amenable to
treatment using a solidification/stabilization process. This
application would represent an innovative application of this
technology since EPA has min~al information on stabilization of
manufactured pesticides. The NCP encourages the use of innovative
technologies at Superfund sites. For this reason, and because this
application may be effective at the Site, solidirication/stabilization
treatment will be evaluated during the treatability studies for these
waste. If the stabilization process is unsuccessful, thermal
treatment will be used to treat these waste.
In order to conduct the solidification/stabilization treatability
studies, it will be necessary to identify treatment standards with
which to evaluate the effectiveness of the technology.
Solidification/stabilization may involve physical/chemical processes
that do more than s~ply entrap the contaminants. Solidification
performed in conjunction with stabilization would satisfy the
preference for treatment under Superfund and falls within the
program's definition of immobilization.
Concerns have been raised regarding the types of Lmmobilization that
provide for adequate protection. The principal reason for these
concerns rests on the fact that immobilization is not generally
considered a destructive technique but rather prohibits or impedes the
mobility of contaminants.
Although experts are in general agreement regarding the effectiveness
of immobilization for most inorganics and metals, the effectiveness of
immobilization for organics cannot be predicted without testing.
Furthermore, the testing methods available (i.e. leachability tests)
provide different types of information on the mobility of contaminants
depending on the test. For these reasons, Superfund has developed
general guidelines for evaluation and selecting Lmmobilization taking
into consideration the testing methods currently available, scientific
understanding to date, and the NCP expectations regarding treatment.
The preamble to the NCP (SSFR page 8701, 03/08/90) provides the
following guidance regarding treatment effectiveness:
"... The Superfund program also uses as a guideline for
effective treatment the range 90 to 99 percent reduction in the
concentration or mobility of contaminants of concern....EPA
believes that, in general, treatment technologies or treatment
42
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trains that cannot achieve this level of performance on a
consistent basis are not sufficiently effective and generally
will not be appropriate."
The use of any treatment technology, including immobilization, needs
to be weighed against this policy and current knowledge regarding the
technology application.
SUPERFUND POLICY ON USE OF IMMOBILIZATION
Agency policy on the use of Lmmobilization for treatment in view of
concerns that have been raised regarding technology performance
pr~rily for organics is as follows:
Immobilization is generally appropriate as a treatment
alternative only for material containing inorganics, semi-
volatile and/or non-volatile organics. Based on present
information, the Agency does not believe that Lmmobilization is
an appropriate treatment alternative for volatile organics.
Selection of Lmmobilization of semi-volatile and non-volatile
organics generally requires the performance of a site specific
treatability study data generated on waste which is very
similar (in terms of type of contaminant, concentration and
waste matrix) to that to be treated and that demonstrated
through Total Waste Analysis (TWA), a significant reduction
(i.e., a 90 - 99 percent reduction) in the concentration of
chemical constituents of concern.
The need for treatability study data and the importance of conducting
appropriate leachability tests as part of the study are important
parts of this policy statement. Treatability studies to demonstrate
the effectiveness of treatment of organics is needed since we do not
believe that we can predict the degree of performance which may be
provided without such testing.
EPA believes that given the uncertainty associated with ~obilization
of organics, the most stringent leachability test available (i.e.
Total Waste Analysis (TWA» should be used to demonstrate the
effectiveness of the technology. A succes~ful demonstration using TWA
provides a measure of assurance regarding the leachability of the
organics. TWA does not mirror environmental conditions, however, and
does not provide information on the protectiveness under specific
management scenarios for the Lmmobilized product. One or more
leachability tests will be used to evaluate the
solidification/stabilization technology.
43
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The 90 - 99 percent reduction in contaminant concentration is a
general guidance and may be varied within a reasonable range
considering the effectiveness of the technology and the clean-up goals
for the Site. Although this policy represents EPA's strong belief
that TWA should be used to demonstrate effectiveness of
immobilization, other leachability tests may also be appropriate in
addition to TWA to evaluate the protectiveness for a specific
management scenario.
Since the Solidification/stabilization technology is not a proven
treatment technology for organics, treatment effectiveness will be
assessed using the TCLP, Multiple Extraction Procedure and Total Waste
Analysis methods for the manufactured pesticides at the Site. The
stabilized soils from this Site must achieve the following
requirements for the technology to be considered effective.
1.
2.
3.
4.
must be
be stabilized
During the
made to ensure
temperature of
The boiling point of the contaminants to
higher than the boiling point of water.
stabilization process provisions must be
none of the contaminants volatilize. The
process should not exceed 130 degrees P.
The TCLP leachate from stabilized/solidified soils would be
required to at a minimum, yield a leachate that would not
exceed groundwater protection standard multiplied by the most
conservative of the dilution factors used (45) to generate
cleanup levels for the contaminants of concern at the Site.
that
the
TWA will be run and compared to the original analysis of waste
using the same extraction procedures. A 90% reduction in
concentration or mobility of the contaminated soil after
treatment is the treatment goal.
In addition, the solidification/stabilization mixture would be
required to achieve a minimum of 250 psi compressive strength
and must demonstrate a permeability of 1x10-6 or less.
Excavated soil requiring treatment which could not comply with these
standards would be thermally treated or treated by dechlorination.
During the Remedial Design, the treatment standards would be used to
determine the efficiency of the solidification/stabilization
technology.
This decision is consistent with Superfund's guidelines for effective
treatment which recommends a treatment range of 90 to 99 percent
reduction in the concentration or mobility of the contaminants of
concern.
44
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REASORS Solidificat'ion/Stabilization TRBA.TJIBH'r STARDARDS XDST BE
BSTABLISBBD PaR OUt4 A'l TIIB CIBA-GBIGY Site:
1. A volume of the waste to be excavated may contain waste
(manufactured pesticides) that exceed health-based levels. No
leqislated treatment standards exist for these manufactured
pesticides.
2. The proposed treatment must meet Superfund's effective
treatment requirements of 90 - 99 percent reduction in concentration
or mobility.
3. The Dilution Attenuation Factor (DAF) of 45 is the more
conservative of the dilution factors used in qeneratinq the health-
based cleanup levels at the Site. The DAF of 45 x the qroundwater
protection standard is the concentration of leachate EPA has
determined to be safe for the qroundwater usinq the pestan Model. The
Pestan Model assumes that an uncontaminated zone a minimum of four (4)
feet exist between the contaminated waste and the qroundwater surface.
This decision is more conservative than the 1986 TCLP Rule of RCRA,
which added 25 new orqanic constituents to the list of toxic
constituents of concern. The 1986 TCLP rule establishes requlatory
levels for the orqanic constituents based on health-based
concentrations and a DAF developed usinq the subsurface fate and
transport model. In the 1986 TCLP Rule BPA determined, based on the
results of its subsurface fate and transport model, that use of a DAF
of 100 is appropriate for settinq requlatory levels. (This DAF is
sufficient to capture on those waste that are clearly hazardous).
4. In addition, the dilution factor of 45 is more conservative
than the DAF of 100 used in the 1986 TCLP Rule.
5. After the material is stabilized/solidified, it will be placed
in a RCRA class C landvault which will have a leachate collection
system and liner. The landvault will prevent water or any other
liqUids from contactinq the treated material and the treated materials
or any potential leachate will not contact the underlyinq clean soil.
45
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-------
1-
Solidification/stabilization will be utilized for soils mixed with a
RCRA waste where it is proven effective by these treatability studies
in reducing the contaminated soil concentrations to LDR treatability
variance levels or for soils containing manufactured pesticides that
exceed the health-based levels where the performance standards for
effective solidification/stabilization are met.
A new innovative chemical treatment technology, dechlorination, may be"
tested during design and, if found effective, may be used instead of
solidification/stabilization for some low level soils. Dechlorination
uses a base (i.e., sodium hydroxide) and an organic source of hydrogen
and a catalyst to accomplish reductive dehalogenation of halogenated
materials. If dechlorination is proven to be more effective in
reducing the contaminant concentrations in the soil and is more cost
effective, it will be used instead of the solidification/stabilization
process. If dechlorination is proven ineffective in reducing
contaminated soil concentrations to levels pursuant to the
treatability variance and/or does not enhance cost effectiveness it
will not be utilized.
The contaminated soil may require pre-treatment to remove qebris
(i.e., drums, scrap metal, construction rubble etc.) present before
the thermal treatment process. At the time of excavation during the
remedial activities, the debris may be removed from material that is
required to be treated. If drums are encountered, the contents will
be removed from the drums and it will be tested to determine if it is
hazardous waste. A determination will be made based on a method to be
detailed in the remedial design phase of the project as to the
hazardous or non-hazardous nature of the debris. If the debris is
determined to be of a non-hazardous nature, it may be decontaminated
and separated into a category of materials that can be disposed of
off-site and/or recycled. Debris that is determined to be of a
hazardous nature will be treated in an appropriate manner to be
determined at the time of excavation.
The soils to be thermally treated would be blended in a tank which
meets the definition of a tank in Section 260.10 of the Code of
Federal Regulations (40 CFR). The purpose of the blending is to
achieve a homogeneous mixture prior to thermal treatment to ensure
proper thermal treatment operations and to comply with operating
conditions determined in the trial burn. Ash from the thermal
treatment process, any solidified/stabilized material or any material
from the dechlorination process will be disposed of in a landvault
after RCRA LDR treatment standar~s, pursuant to a treatability
variance granted upon ROD signature, are met. In accordance with
Superfund LDR Guidance #6A, for herbicides, which are similar and
applicable to Site contaminants, a treatability variance requires that
47
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the selected technology must demonstrate a 90-99.9 percent reduction
in the contaminants of concern.
In order to provide a constant treatment criterion throughout the
remediation process which will ensure compliance with the treatability
variance, the concentration of each contaminant of concern. in the soil
after treatment must be no greater than 10% of the corresponding
cleanup level. Adherence to this criterion will ensure a minimum of
90% reduction as required by the treatability variance. The
requirement that treated soils contain a concentration less than or
equal to a 90% reduction of the cleanup levels is based on the
assumption that the cleanup levels are the lowest concentrations of
soils that will be excavated. Ensuring that the cleanup levels are
reduced by 90% (leaving a maximum of 10%) complies with the lower
limit of the percentage reduction allowed by Superfund LDR Guidance
6A. In addition to providing a constant treatment level, the soil
before treatment will not have to be analyzed other than for process
control.
In some cases treatability variance standards may be more stringent
than the upper limit of 99.9% in Superfund LDR Guide #6A. For
example, if Gamma-SHC were found at 1000 mg/kg in a Summer's Model
area before treatment, requiring that it be reduced to 0.1 mg/kg, as
in Table 8-1, would amount to a 99.99% reduction. This percent
reduction would still be less stringent than the LDR treatment
standards of 0.066 mg/kg and 0.087 mg/kg for SHCs and DDTs
respectively. Therefore, the treatability variance will still be
applicable.
Table 8-1 provides the treatability variance treatment levels for the
contaminants of concern for this operable unit and some additional
RCRA waste which are present in other areas at the Site and may be
found in low concentrations in this area (no confirmatory data at this
time). These treatment levels must be achieved prior to placement of
treated soils into the RCRA landvault.
Confirmatory samples will be conducted during the remedial design to
ensure that contamination is not present aQove cleanup levels
established in the ROD for surface and subsurface soils.
If confirmatory samples indicate that concentrations of subsurface
soils are above cleanup levels, institutional controls, including deed
restrictions and/or other measures necessary will be utilized to
ensure that any future excavations of the contaminated soil will
include the same handling and treatment as set out in the selected
remedy.
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Pollowing excavation activities, the area will be backfilled and
revegetated. As presented in Pigure 5 (flow chart), if cleanup levels
are not achieved before excavation levels are reached, extraction
wells combined with isolation walls extending from the land surface to
the top of the Miocene clay and in-situ soil flushing will be utilized
to flush contaminants from deep unsaturated soils, thus decreasing the
time required to operate the pump and treat system implemented in
operable unit one. The contaminated groundwater extracted by these
wells will be treated by the currently operating waste water treatment
system. Innovative technologies (in-situ vacuum extraction or in-situ
bioremediation) may also be used in concert with the soil flushing
approach, if during design they are found to be effective in reducing
soil concentrations to cleanup levels. Institutional controls, such
as deed restrictions, will be .established to preclude usage of
groundwater and minimize land use until cleanup levels are achieved.
The results of the treatability studies for all technologies tested
during the remedial design will be evaluated and the technologies to
be used for remediation of the contaminated soils would be determined
and noted in the 30% Remedial Design Report. EPA will then issue a
public notice in a local newspaper and send a fact sheet to persons on
the mailing list to inform the public of the technologies proven
effective and which are to be implemented.
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TABLB 8-1
~ S'lAHDARD !'OR SOILS M' fiIB CIBA-GBIGY Site
The following table provides the max~um concentration
allowed in the residuals after treatment for the contaminants of
concern.
Maximum Concentration Allowed After Treatment
1E-4 Risk
(mq/kg)
1E-4 Risk
Swmners
(mq/kg)
Pestan
Contaminant
DCT
DDD
DDE
Alpha-BHC
Beta-BHC
Delta-BHC
Gamma-BHC
Chlorobenzilate
Diazinon
Bladex
Simazine
Atrazine
prometryn
503
675
1,653
0.4
1.7
0.3
0.1
20.9
1.0
2.0
3.7
3.6
38.5
750
750
1725
15.6
15.2
15.4
3.7
34.0
1.0
37
1000
19
1557
50
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NO DEE~ SOIL
REMUIIATIOM REQUIRED
Figure 6
IN-SITU SOIL REMEDIATION
ARE .U..URfACE CLEANU~ LEYEL.
ACH I EYED .E f OAE E XC""'T I ON
LIMIT. AAE AEACHED'
YES
NO
IAON
.LURRY
IN-.,TU fiXATION
AE.ULT. fAON TAEATASILITY I'
.TUDIE. ON
I
. IN-.ITU "CUUM EXTAACTION I
. IN-.ITU .IOAENEDIATION I
ISOLATION _LLS WITH
WITHDAMAL WELLS INSTALLED I
AAOUND THE CONTAMINATED.
AAEA AND TAEATMENT. i
T H I. M AY S E 8 U P P L E .. E N TED ;
THI. MAY SE
.U~'LEMENTED .Y ONE OA .
MORE TECHNOLOClIES PROVEN i
EffECTIYE IN TAEATASILITY
STUDIE..
CONTINUE DEEP lOlL
RIMEDIATION UNTIL AIIK
.A.ID ClAOUND_TIA CLEANUP
LIYEL. AAI ACHEIVED AT THE
WITHDR.wL WELL..
CONTINUE GROUND-TEA
NONITOIUNG UNTIL
OYERALL GROUND-TEA
CLEANU~ LEYEL. AAE
ACHIIYED.
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Air emissions from the Site will be monitored to ensure compliance
with the Clean Air Act. Fenceline air monitoring will be conducted to
ensure that contaminant concentrations do not exceed levels considered
to be safe for human health. If levels are exceeded, mitigative
procedures such as dust suppression or vapor capture will be employed
to prevent harmful levels of air emissions from leaving the Site.
All treated wastes will be land disposed in accordance with the
substantive requirements of the Land Ban Regulations, pursuant to
Section 3004 of the Resource Conservation and Recovery Act of 1976
(RCRA), as amended by the Hazardous and Solid Waste Amendments of 1984
(HSWA). .
After excavation and treatment, treated wastes will be land disposed
when LOR treatment standards for any characteristic waste, listed
waste, or regulated hazardous constituent as adjusted by the
treatability variance granted upon ROD signature are met. The
treatment standards are based on the performance of treatment
technologies determined by the Agency to represent Best Demonstrated
Available Technology (BOAT) as promulgated on June 1, 1990. Wastes
that, as treated, contain RCRA hazardous wastes or hazardous waste
constituents, at concentrations which do not exceed the treatment
standards, are not restricted from land disposal units.
The selected alternative for the Ciba-Geigy Site is consistent with
the requirements of Section 121 of CERCLA and the National Contingency
Plan. The selected alternative will reduce the mobility, toxicity,
and volume of contaminated soil at the Site. In addition, the
selected alternative is protective of human health and the
environment, will attain all Federal and State applicable or relevant
and appropriate public health and environmental requirements through a
LOR treatability variance, is cost-effective and utilizes permanent
solutions to the maximum extent practicable. The selected alternative
for Operable Unit No.4 is consistent with previous remedial actions
conducted at the Site.
Based on the information available at this time, the selected
alternative represents the best balance among the criteria used to
evaluate remedies. Alternative 4 is believed to be protective of
human health and the environment, will attain ARARs (through
application of the treatability variance), would be cost effective,
and would utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum extent
practicable.
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9.0
STATUTORY DETERMINATION
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, when complete, the.
selected remedial action for this Site 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.
9.1
PROTECTIVE OF HUMAN HEALTH AND THE ENVIRONMENT
The selected remedy protects human health and the environment through
treating a principal threat remaining at the Site, the contaminated
soils at former waste management area 8 addressed in this ROD. The
selected remedy provides protection of human health and the
environment by eliminating, reducing, or controlling risk through
treatment, engineering controls and/or institutional controls.
9.2
ATTAINMENT OF THE APPLICABLE OR RELEVANT AND APPROPRIATE
REOUIREMENTS (ARARs)
Remedial actions performed under CERCLA must comply with all
applicable or relevant and appropriate requirements (ARARs). All
alternatives considered for the Ciba-Geigy Site were evaluated on the
basis of the degree to which they complied with these requirements.
The selected remedy was found to meet or exceed the following ARARs,
as discussed below.
Clean Water Act
Perched water at certain areas and stormwater which contacts Site
materials during remediation activities will be routed through the
existing on-site wastewater treatment plant. In addition,
contaminated groundwater extracted by the deep soil treatment
53
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technologies and the current pump and treat system, leachate from the
landvault and incinerator scrubber water will be treated before
discharge into the Tombigbee River through the current NPDES permit.
All current discharge limitations will remain in effect for the total
facility discharge. This includes chemical-specific effluent
limitations based in the Organic Chemicals, Plastics, and Synthetic
Fibers (OCPSF) Guidelines, as well as the biomonitoring requirements
to evaluate compliance with toxicity requirements.
Resource Conservation and Recoverv Act
Many RCRA requirements are considered relevant and appropriate for
remedial activities proposed at the McIntosh plant. The excavated
soils and sludges will be representatively analyzed to determine if
they are RCRA hazardous wastes. If RCRA hazardous waste is found it
will be disposed of in a landvault after RCRA legislated treatment
standards pursuant to a treatability variance, granted upon ROD
signature, are met. EP Toxicity and TCLP analyses will be performed
to ensure that treatment standards, through a treatability variance,
are met. A pilot study and a trial burn will be required to ensure
that the incinerator will meet the Destruction Removal Efficiencies
for the contaminants at the Site. The primary activities include
construction of isolation walls, construction of one or more new
landvaults, solidification/stabilization, incineration, groundwater
pump and treat, and possibly other innovative technologies. RCRA
design standards will be incorporated into the remedial desiqn of all
construction activities so that the substantive requirements of all
applicable RCRA regulations are met.
Other Guidance To Be Considered
Other Guidance To Be Considered (TBCs) include health based advisories
and guidance. TBCs have been utilized in estimating incremental
cancer risk numbers for remedial activities at the sites. The risk
numbers are evaluated relative to the normally accepted point of
departure risk range of lxlO-4 to lxlO-6.
Clean Air Act
Air emissions from the remedial activities at the Site, including
thermal treatment, would be monitored to ensure compliance with the
substantive requirements of the Clean Air Act. Fenceline air
monitoring will be conducted to ensure that contaminant concentrations
do not exceed levels considered to be safe for human health. If
levels are exceeded, mitigative procedures such as dust suppression or
54
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vapor capture will be employed to prevent harmful levels of air
emissions from leaving the Site.
Chemical-Soecific ARARs
Maximum Contaminant Levels (HeLs) and non-zero HCLGs are the
Groundwater Protection Standards set out in the Corrective Action
Program required by the 1985 RCRA Part B Permit. Those Standards have
been incorPOrated into the CERCLA ROD (September, 1989) for the First
Operable Unit, addressing the alluvial aquifer, and are indicated in
Table 5-6.
Waivers
No ARAR waivers are being granted however, the selected alternative
will comply with the LDRs through a treatability variance for the
contaminated soil and debris.
9.3
COST EFFECTIVENESS
The estimated cost of EPA's selected remedy is approximately
$49,723,000. This cost would be reduced if excavation limits are
reached before cleanup levels are achieved. Cost effectiveness is
determined by comparing the cost of all alternatives being considered
with their overall effectiveness to determine whether the costs are
proportional to the effectiveness achieved. EPA evaluates the
incremental cost of each alternative as compared to the increased
effectiveness of the remedy. The selected remedy, Alternative 4,
although most costly, was chosen for its high degree of effectiveness
at reducing the mobility, toxicity, and volume of the contaminants and
its long-term protectiveness. EPA has determined that the cost of the
selected remedy is proportional to the overall effectiveness;
therefore, the remedy is considered cost effective.
9.4
UTILIZATION OF PERMANENT SOLUTIONS TO THE MAXIMUM
EXTENT PRACTICABLE
EPA believes the selected remedy is the most appropriate cleanup
solution for Operable Unit 4 of the Ciba-Geigy Site and provides the
best balance among the evaluation criteria for the remedial
alternatives evaluated. This remedy provides effective protection in
both the short-term and long-term to potential human and environmental
receptors, is implementable, and is cost-effective.
55
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Thermal treatment of the highly contaminated soils, with pre-treatment
options proven effective during the design, and
solidification/stabilization or dechlorination of low level
contaminated soil, if proven effective during the design, with
landvault disposal of the residuals, will effectively reduce and/or
eliminate the mobility of hazardous waste and hazardous substances to
the environment. Isolation from the groundwater combined with in-situ
treatment of any contaminated soils below the depth where excavations.
are terminated will effectively reduce and/or eliminate the mobility
of hazardous waste and hazardous substances to the environment.
9.5
PREFERENCE FOR TREATMENT AS A PRINCIPAL ELEMENT
The statutory preference for treatment will be met because the
selected remedy treats the highly contaminated and most mobile
contaminated soils, a principal threat posed by the Site, and isolates
and treats the lower contaminated soils.
10.0
DOCUMENTATION OF SIGNIFICANT CHANGES
A change has been made to the Selected Remedy since the Proposed Plan
was issued. This change was prompted by comments received during the
comment period. Solidification/stabilization was considered in the
alternatives for some wastes and will be tested for application to
another waste type aside from those discussed previously.
According to results from subsurface soil borings collected by Ciba-
Geigy during RI/FS field activities, portions of Area 8 may contain
manufactured pesticides that exceed the health-based cleanup levels
requiring them to be excavated, but are not mixed with a RCRA waste.
The manufactured pesticides of concern are toxicity characteristic
analytes and therefore have no toxicity characteristic regulatory
levels. Although no regulatory levels are exceeded for any toxicity
characteristic analytes and it has been determined that the soil is
not a RCRA hazardous waste, these manufactured pesticides exceeded the
health-based cleanup levels, requiring that they be excavated and
treated.
All soils which are mixed with a RCRA waste that exceed the cleanup
levels will undergo thermal treatment or dechlorination and be treated
to legislated (LOR) treatment standards, as adjusted by a CERCLA
treatability variance upon signing of the ROD. Additionally, it is
anticipated that it will be necessary to thermally treat some of the
soil contaminated with manufactured pesticides that exceed the health-
based levels which contain a total organic concentrations above 2,500
ppm.
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1-
Soils containing less than 2,500 ppm total organics may be amenable to
treatment using a solidification/stabilization process. This
application would represent an innovative application of this
technology since EPA has minimal information on stabilization of
manufactured pesticides. The NCP encourages the use of innovative
technologies at Superfund Sites. For this reason, and because this
application may be effective at the Site, solidification/stabilization
treatment will be evaluated during the treatability studies for these.
waste. If the stabilization process is unsuccessful, thermal
treatment will be used to treat these waste.
In order to conduct the solidification/stabilization treatability
studies, it will be necessary to identify treatment standards with
which to evaluate the effectiveness of the technology.
Solidification/stabilization may involve physical/chemical processes
that do more than simply entrap the contaminants. Solidification
performed in conjunction with stabilization would satisfy the
preference for treatment under Superfund and falls within the
program's definition of immobilization.
Concerns have been raised regarding the types of immobilization that
provide for adequate protection. The principal reason for these
concerns rests on the fact that immobilization is not generally
considered a destructive technique but rather prohibits or impedes the
mobility of contaminants.
~though experts are in general agreement regarding the effectiveness
of immobilization for most inorganics and metals, the effectiveness of
immobilization for organics cannot be predicted without testing.
Furthermore, the testing methods available (i.e. leachability tests)
provide different types of information on the mobility of contaminants
depending on the test. For these reasons, Superfund has developed
general guidelines for evaluation and selecting immobilization taking
into consideration the testing methods currently available, scientific
understanding to date, and the NCP expectations regarding treatment.
The preamble to the NCP (SSFR page 8701, 03/08/90) provides the
following guidance regarding treatment effectiveness:
"... The Superfund program also uses as a guideline for effective
treatment the range 90 to 99 percent reduction in the
concentration or mobility of contaminants of concern....EPA
believes that, in general, treatment technologies or treatment
trains that cannot achieve this level of performance on a
consistent basis are not sufficiently effective and generally will
not be appropriate."
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The use of any treatment technology, including immobilization, needs
to be weighed against this policy and current knowledge regarding the
technology application.
SUPERFUND POLICY ON USE OF IMMOBILIZATION
Agency policy on the use of immobilization for treatment in view of
concerns that have been raised regarding technology performance
pr~arily for organics is as follows:
Immobilization is generally appropriate as a treatment alternative
only for material containing inorganics, semi-volatile and/or non-
volatile organics. Based on present information, the Agency does
not believe that immobilization is an appropriate treatment
alternative for volatile organics. Selection of immobilization of
semi-volatile and non-volatile organics generally requires the
performance of a site specific treatability study data generated
on waste which is very similar (in terms of type of contaminant,
concentration and waste matrix) to that to be treated and that
demonstrated through Total Waste Analysis (TWA), a significant
reduction (i.e., a 90 - 99 percent reduction) in the concentration
of chemical constituents of concern.
The need for treatability study data and the importance of conducting
appropriate leachability tests as part of the study are important
parts of this policy statement. Treatability studies to demonstrate
the effectiveness of treatment of organics is needed since we do not
believe that we can predict the degree of performance which may be
provided without such testing.
EPA believes that given the uncertainty associated with ~obilization
of organics, the most stringent leachability test available (i.e.
Total Waste Analysis (TWA» should be used to demonstrate the
effectiveness of the technology. A successful demonstration using TWA
provides a measure of assurance regarding the leachability of the
organics. TWA does not mirror environmental conditions, however, and
does not provide information on the protectiveness under specific
management scenarios for the immobilized product. One or more
leachability tests will be used to evaluate the
solidification/stabilization technology.
The 90 - 99 percent reduction in contaminant concentration is a
general guidance and may be varied within a reasonable range
considering the effectiveness of the technology and the clean-up goals
for the Site. Although this policy represents EPA's strong belief
that TWA should be used to demonstrate effectiveness of
immobilization, other leachability tests may also be appropriate in
58
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addition to TWA to evaluate the protectiveness for a specific
management scenario.
Since the Solidification/stabilization technology is not a proven
treatment technology for organics, treatment effectiveness will be
assessed using the TCLP, Multiple Extraction Procedure and Total Waste
Analysis methods for the manufactured pesticides at the Site. The
stabilized soils from this Site must achieve the following
requirements for the technology to be considered effective.
1.
The boiling point of the contaminants to be stabilized must be
higher than the boiling point of water. During the stabilization
. process provisions must be made to ensure that none of the
contaminants volatilize. The temperature of the process should not
exceed 130 degrees F.
2.
The TCLP leachate from stabilized/solidified soils would be
required to at a minimum yield a leachate that would not exceed
groundwater protection standard multiplied by the most
conservative of the dilution factors used (45) to generate cleanup
levels for the contaminants of concern at the Site.
3.
TWA will be run and compared to the original analysis of waste
using the same extraction procedures. A 90% reduction in
concentration or mobility of the contaminated soil after treatment
is the treatment goal.
In addition, the :solidification/stabilization mixture would be
required to achieve a minimum of 250 psi compressive strength and
must demonstrate a permeability of lxlO-6 or less.
4.
Excavated soil requiring treatment which could not comply with these
standards would be thermally treated or treated by dechlorination.
During the Remedial Design, the treatment standards would be used to
determine the efficiency of the solidification/stabilization
technology.
This decision is consistent with Superfund's guidelines for effective
treatment which recommends a treatment range of 90 to 99 percent
reduction in tpe concentration or mobility of the contaminants of
concern.
REASONS Solidification/stabilization ~ STAHDARDS HOST BE
BSTABLISHED FOR OU'4 H TIIB CIBA-GBIGY Site:
1.
A volume of the waste to be excavated may contain waste
,
59
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(manufactured pesticides) that exceed health-based levels.
legislated treatment standards exist for these manufactured
pesticides.
2. The proposed treatment must meet Superfund's effective treatment
requirements of 90 - 99 percent reduction in concentration or
mobility.
No
3. The dilution factor of 45 is the more conservative of the dilution
factors used in generating the health-based cleanup levels at the
Site. The DAF of 45 x the groundwater protection standard is the
concentration of leachate EPA has determined to be safe for the
groundwater using the Pestan Model. The pestan Model assumes that an
uncontaminated zone a minimum of four (4) feet exist between the
contaminated waste and the groundwater surface.
This decision is more conservative than the 1986 TCLP Rule of RCRA,
which added 25 new organic constituents to the list of toxic
constituents of concern. The 1986 TCLP rule establishes regulatory
levels for the organic constituents based on health-based
concentrations and a Dilution Attenuation Factor (DAF) deve~oped using
the subsurface fate and transport model. In the 1986 TCLP Rule EPA
determined, based on the results of its subsurface fate and transport
model, that use of a DAF of 100 is appropriate for setting regulatory
levels. (This DAF is sufficient to capture on those waste that are
clearly hazardous).
4. In addition, the dilution factor of 45 is more conservative than
the DAF of 100 used in the 1986 TCLP Rule.
5. After the material is stabilized/solidified, it will be placed in
a RCRA class C landvault which will have a leachate collection system
and liner. The landvault will prevent water or any other liquids from
contacting the treated material and the treated materials or any
potential leachate will not contact the underlying clean soil.
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