Superfund Record of Decision Des Moines TCE Operable Units 2 and 4 Des Moines IA


                                    EPA/ROD/R07-97/030
                                    1997
EPA Superfund
     Record of Decision:
     DES MOINES TCE
     EPA ID: IAD980687933
     OU 02, 04
     DES MOINES, IA
     12/13/1996

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       I am submitting for your approval the attached Record of Decision (ROD)  for Operable Units (OU)  2
and 4 of the Des Moines TCE Superfund Site in Des Moines, Iowa.  I have reviewed the package and
recommend your approval of the ROD.  Please indicate your approval by signing the ROD Declaration.

       This ROD presents the selected remedy to address contamination in OU2 and OU4 remaining after
three previous removal actions.  The selected remedy calls for continued maintenance of the previous
removal actions and land use restrictions to maintain an industrial land use.

       A public meeting was held on June 11,  1996,  to present the preferred remedy to the public and to
receive feedback regarding public acceptance of the remedy.  During the meeting, members of the public
were generally supportive of the remedy.  Several comments were received during the public comment
period.  The U.S. Environmental Protection Agency's  (EPA) response to the comments is found in the
responsiveness summary in the ROD.  The Iowa Department of Natural Resources (IDNR) has provided a letter
to EPA indicating its general agreement with the selected remedy.

       If you have questions or concerns regarding the selected remedy,  please contact me or Mary
Peterson, the project manager, at extension 7882.

Attachment

cc:  Bob Drustrup, IDNR

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RECORD OF DECISION DECLARATION

SITE NAME AND LOCATION

    Des Moines TCE Site
    Operable Units 2 and 4
    Des Moines, Iowa

STATEMENT OF BASIS AND PURPOSE

This decision document presents the selected remedial actions for operable units 2 and 4  (OU2 and OU4) of
the Des Moines TCE Superfund Site in Des Moines, Iowa.  The remedies have been chosen in accordance with
the Comprehensive Environmental Response, Compensation, and Liability Act of 1980  (CERCLA), as amended by
the Superfund Amendments and Reauthorization Act of 1986  (SARA),  and, to the extent practicable, with the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP).   This decision is based on the
administrative record for the site.

The Iowa Department of Natural Resources  (IDNR) is in agreement with the selected remedy.

ASSESSMENT OF THE SITE

Actual or threatened exposures to hazardous substances in OU2 and OU4, if not addressed by implementing
the remedial actions selected in this record of decision  (ROD) , may present a current or potential threat
to public health, welfare, or the environment.

DESCRIPTION OF THE REMEDY

The selected remedy is the final remedial action for OU2 and OU4, and represents the final remedial
action for the Des Moines TCE Site.  A significant amount of risk reduction was achieved by a series of
three removal actions conducted in OU2 and OU4.  The removal actions accomplished the following
activities:

       •      Building Removal Action:   Contaminated dust was removed from interior surfaces of several
              onsite buildings.   Protective coatings were applied to the walls and floors of the buildings
              to encapsulate any residual contamination.   Contaminated insulation materials were replaced
              or repaired,  and a former aldrin tank and surrounding structure and soils were dismantled
              and removed from the site.

       •      Surface Cap Removal Action:  An asphalt cap was constructed as a protective cover over the
              majority of contaminated soils in OU2 and OU4.

       •      South Pond Area Removal Action:   Contaminated soils were excavated and transported offsite
              for disposal.

The selected remedial action will provide for the continuation of the risk reduction achieved by the
removal actions, and will ensure the overall protectiveness by restricting use of the property to
industrial activities.  The main components of the selected remedy include:

       •      Maintenance activities as called for by the response action Operation and Maintenance (O&M)
              Plans:
       •      Periodic seal  coats applied to the existing asphalt cap:
       •      Sampling of soils at the South Pond discharge area  during  CERCLA reviews:   and
       •      Land use restrictions to maintain industrial use of the property.

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STATUTORY DETERMINATIONS

The selected remedy is protective of human health and the environment, complies with Federal and state
requirements that are applicable or relevant and appropriate, and is cost effective.  The selected remedy
utilizes permanent solutions to the maximum extent practicable.  Cleanup actions already performed as
part of the OU4 removal actions removed the soils most highly contaminated with pesticides and herbicides
for off-site disposal. EPA evaluated alternatives involving excavation and off-site disposal of
additional pesticide and herbicide contaminated soils, but found those alternatives did not provide an
appreciably higher degree of protectiveness than the capping alternative so long as the cap is properly
maintained.  The selected remedy utilizes alternative treatment technologies or resource recovery
technologies to the maximum extent practicable.  EPA evaluated treatment alternatives in the feasibility
study, but found they, did not provide an appreciably higher degree of protectiveness and were not cost
effective.  Because the selected remedy will result in hazardous substances remaining onsite, EPA will
conduct a review of the adequacy of the selected remedial actions no less often than every five years as
required by Section 121 of SARA.

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                                             TABIiE OF CONTENTS
                                   DBS  MOINES TCE OPERABIiE UNITS 2  AND 4
                                        RECORD OF DECISION SUMMARY

1.0    SITE NAME,  LOCATION,  AND DESCRIPTION 	  1

2.0    SITE HISTORY AND ENFORCEMENT ACTIVITIES 	  3
       2 .1   Facility History 	  3
       2 .2   Site  History 	  3
       2.3   Response Actions in OU2 and OU4 	  4
              2.3.1   Building Response Action 	  4
              2.3.2   Surface Capping Response Action 	  4
              2.3.3   South  Pond Area Response Action 	  5
       2.4   Other Enforcement Activities 	  5

3. 0    HIGHLIGHTS  OF COMMUNITY PARTICIPATION 	  7

4.0    SCOPE AND ROLE OF OPERABLE UNITS 	  7

5.0    SUMMARY OF  SITE CHARACTERISTICS  	  7
       5.1   Operable Unit 2 	  7
              5.1.1   Surficial Contamination 	  7
              5.1.2   Subsurface Soils	  8
       5.2   Operable Unit 4 	  8
              5.2.1   OU4 Buildings	  8
              5.2.2   Surface Soils	  9
              5.2.3   South  Pond Area	  9
       5.3   Media and Contaminants of  Concern 	  10

6. 0    SUMMARY OF  SITE RISKS 	  10
       6.1   Contaminant Identification 	  10
              6.1.1   Operable Unit 2 	  10
              6.1.2   Operable Unit 4 	  11
       6.2   Exposure Assessment 	  12
              6.2.1   Operable Unit 2 	  12
              6.2.2   Operable Unit 4 	  12
       6.3   Toxicity Assessment 	  13
       6.4   Risk  Characterization 	  14
       6.5   Environmental Risks 	  14

7. 0    DESCRIPTION OF ALTERNATIVES 	  15
       7.1   Buildings 1-5 and the Maintenance Building 	  16
              7.1.1   Building Alternative 1 - No Further Action 	  16
              7.1.2   Building Alternative 2 - Limited Action 	  16
              7.1.3   Building Alternative 4 - Source Layer Removal/Disposal  	  17
       7.2   Soil  Beneath Asphalt Cap 	  18
              7.2.1   Soil Alternative  1 - No Further Action 	  18
              7.2.2   Soil Alternative  2 - Limited Action 	  18
              7.2.3   Soil Alternative  4 - Source Removal/ Disposal 	  19
       7.3   South Pond Area 	  19
              7.3.1   Sediment Alternative 1 - No Further Action 	  19
              7.3.2   Sediment Alternative 2 - Limited Action 	  20
              7.3.3   Sediment Alternative 4 - Source Removal/ Disposal 	  20

8.0    SUMMARY OF  COMPARATIVE ANALYSIS  OF ALTERNATIVES 	  21
       8.1   Comparative Analysis of Building Alternatives 	  22
              8.1.1   Overall Protection of Human Health and the Environment  	  22
              8.1.2   Compliance with ARARs 	  22
              8.1.3   Long-Term Effectiveness and Permanence 	  22
              8.1.4   Reduction of Toxicity,  Mobility,  or Volume Through Treatment 	  23
              8.1.5   Short-term Effectiveness 	  23
              8.1.6   Implementability  	  23
              8.1.7   Cost 	  23
              8.1.8   State  Acceptance  	  23
              8.1.9   Community Acceptance 	  23
       8.2   Comparative Analysis of the Soil Alternatives 	  24

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8.2.1 Overall Protection of Human Health and the Environment 24
8.2.2 Compliance with ARARs 24
8.2.3 Long-Term Effectiveness and Permanence 24
8.2.4 Reduction of Toxicity, Mobility, or Volume Through Treatment 24
8.2.5 Short-term Effectiveness 24
8.2.6 Implementability 24
8.2.7 Cost 25
8.2.8 State Acceptance 25
8.2.9 Community Acceptance 25
8.3 Comparative Analysis of the Sediment Alternatives 25
8.3.1 Overall Protection of Human Health and the Environment 25
8.3.2 Compliance with ARARs 25
8.3.3 Long-Term Effectiveness and Permanence 25
8.3.4 Reduction of Toxicity, Mobility, or Volume Through Treatment 25
8.3.5 Short-term Effectiveness 26
8.3.6 Implementability 26
8.3.7 Cost 26
8.3.8 State Acceptance 26
8.3.9 Community Acceptance 26

9. 0 THE SELECTED REMEDY 26

10.0
STATUS
10.1
10.2
10.3
10.4
CORY DETERMINATIONS
Protection of Human Health and the Environment
Compliance with ARARs
Cost Effectiveness
Utilization of Permanent Solutions and Alternative Treatment Technologies
or Resource Recovery Technoloaies to the Maximum Extent Practicable
30
. . 30
. . 30
. . 30
. . 30
10.5 Preference for Treatment as a Principal Element 31

RESPONSIVENESS SUMMARY 32

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RECORD OF DECISION SUMMARY
DBS MOINES TCE SITE
OPERABIiE UNITS 2 AND 4
DBS MOINES, IOWA

1.0 SITE NAME, LOCATION, AND DESCRIPTION

The Des Moines TCE site is located in the south central portion of the city of Des Moines. Iowa,
adjacent to the Raccoon River. The site includes a portion of the Des Moines Water Works facility, the
Dico, Inc. (Dico) property, the industrial area north of the Raccoon River, the Tuttle Street landfill
to the east, and the Frank DePuydt woods to the south. In all, the Des Moines TCE site encompasses more
than 200 acres and has been divided into four operable units by the EPA. Operable units 2 and 4 (OU2 and
OU4) are the subject of this record of decision (ROD). A site map is presented on Figure 1 which depicts
the boundaries of OU2 and OU4.

Operable Unit No. 1 (OU1) involves the remedy to address the volatile organic compound (VOC)
contamination in the ground water that has threatened the Des Moines public water supply. A remedy,
including a ground water extraction, treatment, and monitoring system, was designed and is being
implemented by Dico

OU2 consists of the Dico property and a portion of the Frank DePuydt Woods and was originally
referred to as the South Area Source Control. OU2 originated to address the sources related to the
ground water contamination being addressed under OU1. Eventually OU2 was subdivided to separately
address the issues and area related to the VOCs (now the revised OU2) and the area which involved the
formulation of pesticides and herbicides (now OU4). A remedial investigation (RI) was completed for OU2
by Dico in 1993. Late in 1994, efforts to complete the OU2 feasibility study (FS) were combined with
efforts for the OU4 FS

Operable Unit No. 3 (OU3) is located north of the Dico property. EPA conducted the OU3 RI/FS and
signed the OU3 Record of Decision (ROD) in September 1992. Contaminant levels found in the OU3 area were
significantly lower than contaminant levels found in the areas to the south on and around the Dico
property. Results of the OU3 RI did not indicate any of the properties in the OU3 area are a source of
contamination. The OU3 ROD provided for continued ground water monitoring and acknowledged that the OU 1
remedy is capturing this low level contamination. The industrial area north of the Dico property remains
a part of the Des Moines TCE Site in that remedial activities consisting of ground water monitoring
continue. The Iowa Department of Natural Resources (IDNR), through a Superfund State Contract, is
conducting this monitoring.

OU4 has been defined by EPA to include portions of the Dico property, Buildings 1 through 5 and
the Maintenance Building and surrounding soil, soil and sediment associated with the former aldrin tank
and South Pond Area; and the drainage channel south and east of the Dico property up to the railroad
spurs owned by the Norfolk Southern Corporation.

Land use in the vicinity of the site is commercial/industrial. As of 1990, the Planning
Department of the city of Des Moines has designated the Dico property as "heavy industrial district"
while the southern portion of OU4 is designated as "floodplain". A drainage area on the Dico property
known as the South Pond is a wetland area.

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Some of the activities conducted within the OU2 and OU4 areas involved bulk chemical storage and
distribution. As reported in the OU2 RI DiChem, formerly located in Buildings 1 through 5 of OU4,
purchased bulk guantities of various solvents for repackaging and distribution to commercial clients in
the 1950s and 1960s. These solvents included perchloroethylene, TCE, toluene, xylene, and
1,1,1-trichloroethane. The solvents were stored in large aboveground containers and then packaged in
55-gallon drums for distribution. A drum cleaning area was located to the west of the Dico Production
Building. The drum fill area was located immediately north of Building 1. DiChem also distributed
guantities of hydrochloric, phosphoric, and sulfuric acids from the 1940s through the 1970s.

Other activities conducted almost exclusively within the OU4 area involved pesticide and herbicide
formulation. Buildings 1 through 5 and the Maintenance Building were used by DiChem for the formulation
of technical grade pesticides and herbicides into products for sale. The primary formulation activities
were conducted within Buildings 2 and 3 while Buildings 4 and 5 were primarily used for chemical storage
and delivery and product storage. These activities reportedly occurred from the mid- 1950s through the
early 1970s.

2.2 Site History

The Regional Administrator signed a ROD for OU 1 on July 21, 1986. The OU 1 remedial action
includes the capture and extraction of contaminated ground water by recovery wells, treatment of the
recovered ground water, and monitoring an extensive ground water well network to verify the effectiveness
of the ground water capture system. EPA issued Dico an administrative order pursuant to section 106 of
the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), reguiring it to
implement the selected remedial action.

On August 8, 1989, Dico entered into an administrative consent order pursuant to sections 104 and
122 of CERCLA, which reguired Dico to conduct an RI/FS for OU2 (OU2 RI/FS Order). When Dico began the
OU2 RI, OU2 encompassed all of Dice's property. However, during the OU2 RI, portions of the Site,
including soils and several Dico buildings, were found to be contaminated with pesticides and herbicides,
apparently resulting from pesticide formulation operations conducted in the 1950 to 1970 time period.
This area was separated out of the OU21 investigation geographically as a separate operable unit, OU4.

The OU2 RI/FS Order called for a phased submittal of an RI report, and, after EPA approved the RI
report, submittal of the FS report. Dico completed an OU2 RI Report which EPA approved in February 1993.
In addition to the OU2 RI, Dico and EPA conducted several additional investigations, focusing on specific
areas and contaminants of concern. Dico submitted an OU2 FS Report under the Order, but the report was
not finalized.

In July 1993, flood waters from the Raccoon River inundated the site and deposited several inches
of sediment within the Dico buildings. Dico personnel flushed some of the sediment from the buildings
following subsidence of the flood waters to retrieve inventory contained in Buildings 1 and 2. However,
the majority of the sediments and inventory remained in the buildings until they were cleaned in
accordance with an EPA-approved plan.

In the fall of 1993. Titan Wheel International Inc (Titan) purchased the Dyneer Corporation,
Dice's corporate parent. In the summer of 1995. Titan closed the Dico plant and transferred its wheel
manufacturing operations to another facility in Des Moines. Currently, only limited operations are being
conducted at the site. Titan's future plans for the site are unknown at this time.

2.3 Response Actions in OU2 and OU4

Following Titan's purchase of Dice's corporate parent in 1993, Titan expressed interest in
expediting cleanup of the OU2 and OU4 areas to enable it to resume pre-flood activities. In addition, a
group of chemical companies potentially liable for the pesticide contamination, also indicated its
interest in expedited cleanup actions. In response to these parties, EPA issued three action memoranda
and corresponding administrative orders, each calling for response actions to address threats in specific
areas of OU2 and OU4. Descriptions of the three removal or response actions are provided below.

For purposes of this ROD, EPA assumes that all response action construction has been properly
completed and that the reguired maintenance activities are being properly conducted. However, if the
Respondents to the administrative orders fail to comply with the orders, the EPA may reevaluate remedial
alternatives, and may take whatever actions are necessary to protect public health and the environment
over the long term.
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2.3.1 Building Response Action

In March 1994, EPA signed an action memorandum to address contamination associated with various
interior portions of DICO Buildings 1 through 5 and the Maintenance Building, and the former aldrin
mixing tank, annex, and surrounding soils. The action memorandum called for cleaning of the interior
surfaces of the buildings, demolition and disposal of the aldrin tank and annex structure, excavation and
disposal of the soils surrounding the aldrin tank, encapsulation of building walls and floors, and
securing of building insulation. The action memo also called for development of a response action
maintenance plan to ensure the continued integrity of the cleaning and encapsulations actions. A
Unilateral Administrative Order (UAO) was issued to Dico to conduct the work. To date, the substantive
portions of the work reguired by the action memo have been completed.

2.3.2 Surface Capping Response Action

In June 1994, EPA signed a second action memorandum calling for a removal action to address the
threats associated with pesticide contamination of soils in OU2 and OU4. Specifically, the action memo
reguired either excavation of soils or the capping of soils containing the pesticides aldrin, dieldrin,
and chlordane above specified health-based levels. A UAO was issued to Dico reguiring it to conduct the
work. Dico selected the capping alternative and constructed an asphalt cap over a large portion of both
the OU2 and OU4 areas. The action memo also reguired a response action maintenance plan to ensure the
continued integrity of the cap.

2.3.3 South Pond Area Response Action

In December 1995, EPA signed an action memorandum to remove or reduce the threat presented by
contaminants in soils and sediments found in and around the South Pond Area (SPA) , in stockpiled soil
resulting from excavations in the drainage ditch adjacent to and cast of the DICO facility, and remaining
in the drainage ditch. An Administrative Order on Consent (AOC) was negotiated with a group of chemical
companies known as the DiChem Customer Group to conduct the reguired work. The DiChem Customer Group
retained Burns and McDonnell Waste Consultants, Inc. (B&M) to conduct the work on its behalf. The South
Pond Area Removal Action Work Plan (B&M 1996) describes the characterization and removal activities that
were conducted. The plan calls for characterization of soils around the SPA and excavation of soils
containing aldrin, chlordane above health-based cleanup levels. Excavated soils were transported to an
EPA-approved offsite facility for disposal. Construction activities for this response action were
completed in September 1996. The action memo also calls for post removal monitoring to ensure that
contaminated sediments remain in the bottom of the South Pond, and do not wash out into the east drainage
ditch.

2 . 4 Other Enforcement Activities

Dico continues to operate the groundwater extraction and treatment system for OU1 pursuant to the
a CERCLA Section 106 administrative order issued by EPA on July 21, 1986. On April 21, 1995, the United
States filed a civil complaint against Dico seeking reimbursement of EPA's responsive costs associated
with OU1. That matter is currently in litigation.

3.0 HIGHLIGHTS OF COMMUNITY PARTICIPATION

The RI/FS and Proposed Plan for OU2 and OU4 of the Des Moines TCE Site were made available to the
public on June 3, 1996. These two documents are part of the administrative record for the site which has
been available for review by the public at the Des Moines City Library. The notice of availability of
these documents was published in the Des Moines Register on June 3, 1996. A public comment period was
held from June 3, 1996 through July 5, 996 and a public meeting was held in Des Moines, Iowa on June 11,
1996. At this meeting, representatives from the EPA Region 7 presented the preferred remedial
alternatives for OU2 and OU4, and provided the opportunity for public comments. A response to the
comments received at the public meeting and during the public comment period is included in the
Responsiveness Summary attached to this ROD.

4.0 SCOPE AND ROLE OF OPERABLE UNITS

Remedial action at the Des Moines TCE site is being implemented through a seguence of four
operable units. The phasing of cleanup actions at the Des Moines TCE site has provided the opportunity
to achieve significant risk reduction more guickly than addressing the entire site at one time. As
previously mentioned, remedial actions for OU1 and OU3 consisting of groundwater extraction and treatment
and long term monitoring are ongoing.
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The response actions conducted within OU2 and OU4 served to significantly reduce the risk to human
health and the environment in these areas. However, contamination remaining in OU2 and OU4 continues to
present a threat to human health and the environment. Remaining threats in OU2 and OU4 include
unacceptable risks due to potential exposure of onsite workers and residents to contaminated soils
beneath the surface cap. In addition, contaminated soils beneath the surface cap present a continued
threat to the environment through the potential leaching of contaminants to the groundwater. The
remedial action authorized by this ROD will provide for long term risk reduction in OU2 and OU4, and will
be the final remedial action for the site

5.0 SUMMARY OF SITE CHARACTERISTICS

This section describes the conditions as defined by several separate investigations of the OU2 and
OU4 areas of the site. More detailed information regarding the results of the investigations can be
found in the OU2 RI report and addendum (Eckenfelder 1993) and the OU4 RI report (Black and Veatch 1995).

5.1 Operable Unit 2

5.1.1 Surficial Contamination

Contaminants detected in OU2 soils include VOCs, metals, polychlorinated biphenyls (PCBs), and
pesticides. Areal distribution of the contaminants is widespread across OU2. The contaminants which
contributed most significantly to health risks in OU2 include the pesticides aldrin, dieldrin, and
chlordane. All of the OU2 soils known to be contaminated have been covered by an asphalt cap as a result
of the surface cap response action conducted in 1994, and are no longer accessible for exposure provided
the cap is properly maintained. The maximum concentrations of contaminants found above health-based
cleanup levels in OU2 include 0.036 mg/kg aldrin, 7.9 mg/kg dieldrin (for a combined maximum
aldrin/dieldrin concentration of 7.936 mg/kg),and 4,880 mg/kg lead. (See OU2 RI) While contamination is
widespread across OU2, certain areas contain higher concentrations of contaminants. For example, the
highest concentrations of pesticides are found east, northwest, and south of the Production Building and
north of Building 1. Elevated lead levels up to 4,880 mg/kg are found in surface soils along the west
side of the Production Building. The above levels of contaminants remain beneath the surface cap in OU2.

5.1.2 Subsurface Soils

The original purpose of the OU2 RI was to locate the sources contributing to the groundwater VOC
contamination being addressed by OU1. The OU2 RI report provides detailed information regarding the
concentrations and locations of VOCs in OU2 subsurface soils. In general, the highest concentrations of
VOCs (55,000 ug/kg TCE, 130,000 ug/kg 1,2-dichloroethylene [1.2-DCE]) were found in the vicinity of the
previously existing degreasing vat and nearby former drum cleaning area. The concentrations of VOCs are
of the same order of magnitude in both the surficial fill material and deeper natural soils. The
presence of these compounds at depth suggests that the downward migration of the compounds has occurred.

In 1991, Dico conducted a treatabillty study to evaluate the potential effectiveness of vapor
stripping technologies to treat the subsurface VOC contamination. The treatabitity study concluded that
in-situ vapor stripping was not a viable option due to low vapor flow rates and VOC removal rates
achieved during the study.

While the surface soils in OU2 contain elevated levels of pesticides and metals, these
contaminants are not found above health-based levels of concern at depth. The analytical results
indicate that the pesticides in shallow soils are relatively immobile and that the metals contamination
is not widespread in OU2.

Overall, the VOCs in OU2 subsurface soils do not pose a significant direct contact human health
risk because they are located below ground which prevents direct contact exposures. With the
construction of the asphalt surface cap, direct contact exposures to VOCs are further prevented and the
effect of leaching VOCs to groundwater via surface infiltration is reduced because surface water will
drain from the cap rather than infiltrate through the soils. In addition, any contaminants which reach
groundwater will ultimately be captured by the OU1 groundwater treatment system. EPA, therefore, does
not believe that additional actions are necessary to address the subsurface VOC contamination in OU2.

5.2 Operable Unit 4

OU4 investigations included characterization of Buildings 1-5 and the Maintenance Building and
surrounding soils, the former aldrin tank and annex area, a drainage ditch east of Buildings 4 and 5,
stockpiled soil piles adjacent to the drainage ditch, and the SPA.
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5.2.1 OU4 Buildings

The primary contaminants detected in Buildings 1-5 and the Maintenance Building were aldrin,
dieldrin, chlordane, PCBs, and dioxin. The highest levels of aldrin, dieldrin, and chlordane were found
in the concrete floor of the Maintenance Building at concentrations of 7,680 mg/kg, 69.6 mg/kg, and 30.5
mg/kg, respectively. Lower levels of aldrin, dieldrin, and chlordane were found in Buildings 2, 3, and 4.
Dioxin was found only in the concrete floor of Building 2 at a concentration 0.00623 mg/kg, PCBs were
found in the insulation of Buildings 2-5 and the Maintenance Building. The highest concentration found
was 29,000 mg/kg in Building 3. The only location where PCBs were not isolated in the building
insulation occurred in Building 4 where PCBs were detected in a wipe sample of the concrete floor. This
incident is believed to be the result of damaged ceiling insulation which accumulated on the floor.
Detailed information regarding the concentrations and locations of contaminants can be found in the OU4
RI report.

The majority of the contamination was removed from the buildings as a result of the cleaning
actions which removed contaminated dust from the buildings. However, residual pesticide contamination
may, remain beneath the surface coatings applied to the walls and floors of the buildings, and PCB
contamination remains in the building insulation. The levels of aldrin, dieldrin, chlordane, and dioxin
which may remain beneath the surface coatings have not been determined. The building insulation was
taped and secured in place to prevent exposure to the PCBs.

The OU4 soil data indicate that pesticides were released from the buildings to the outside soils.
If proper maintenance of the surface coatings applied to the building walls and floors is not effectively
implemented, residual pesticides may again be released to the surrounding environment. Potential
migration pathways include personnel and vehicular traffic and any drainage from the buildings.

5.2.2 Surface Soils

The various OU4 investigations revealed that aldrin, dieldrin, chlordane, and dioxin are present
in the surface and shallow subsurface soils. Aldrin, dieldrin, and chlordane were found above
health-based cleanup levels at numerous locations across OU4. The highest concentration of aldrin was
10.0 mg/kg detected in the surface soil at the northwest corner of Building 4. Dieldrin was found at a
maximum concentration of 26.0 mg/kg in the surface soil located east of the Maintenance Building. The
maximum concentration of chlordane, 18.4 mg/kg, was found in the surface soil at the southwest corner of
the Maintenance Building.

5.2.3 South Pond Area

The South Pond Area (SPA) includes the South Pond and surrounding soils, the drainage ditch east
of the Dico property, and stockpiled soil piles between Buildings 4/5 and the cast drainage ditch.
Through the various OU4 investigations, samples were collected from each of these areas to determine the
extent of contamination.

Surface soils around the South Pond contained various levels of aldrin, dieldrin, and chlordane.
Aldrin and dieldrin were the only contaminants found above health-based cleanup levels. The maximum
concentrations were 3.6 mg/kg aldrin and 59.0 mg/kg dieldrin which were found in the surface soils along
the northwestern edge of the pond. Sediment samples collected from the bottom of the pond also contained
aldrin and dieldrin above health-based cleanup levels. The highest concentration of aldrin found in
sediment was 7.3 mg/kg and the highest concentration of dieldrin found in the sediment was 17.0 mg/kg.

Samples collected from the east drainage ditch contained combined concentrations of aldrin and
dieldrin up to 7 mg/kg. The stockpiled soil piles contained a maximum combined aldrin and dieldrin
concentration of 3.5 mg/kg.

Assuming the SPA removal action is conducted as reguired by the action memorandum, all
contamination above health-based cleanup levels will have been removed from around the South Pond, the
east drainage ditch, and stockpiled soil piles. These soils will be excavated and removed from the site
for offsite disposal. The SPA response action will not address the South Pond sediments, so the levels
of aldrin and dieldrin presented above will remain in the bottom of the pond.

5.3 Media and Contaminants of Concern

Following completion of construction activities associated with the SPA response action, there
will remain only three points sampled during the OU2 and OU4 investigations which have not been addressed
by one of the response actions. None of these points contained contaminants above a level of concern.
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Currently, assuming completion of the SPA response action construction, contamination remaining in
OU2 and OU4 includes:

• Pesticides and metals in surface soils of OU2 which have been covered by an asphalt cap;
• VOCs in surface and subsurface soils of OU2 which have been covered by an asphalt cap;
• Residual pesticides beneath the surface coatings in Buildings 2,3,4, and the Maintenance
Building;
• PCBs in the insulation of Buildings 2-5 and the Maintenance Building;

6.0 SUMMARY OF SITE RISKS

During the RI/FS process for OU2 and OU4, various evaluations were performed to estimate the
health or environmental problems that could result if the soil contamination was not cleaned up. These
evaluations are commonly referred to as baseline risk assessments (BRAs). The baseline risk assessments
evaluated the potential adverse effects to human health and the environment presented by OU2 and OU4
under current and projected future land use conditions. Six baseline risk assessment documents have been
developed for OU2 and OU4 of the Des Moines TCE Site, and are listed below.

• OU2 Baseline Risk Assessment which includes results from the OU2 RI for soil
• OU2 Risk Assessment Memorandum which is presented as an addendum to the OU2 Baseline Risk
Assessment to address a potential future residential population.
• OU2 Assessment Addendum which revises the original BRA based on data collected following
flooding of the site in the summer of 1993.
• OU4 Building Removal Action Risk Assessment Memoranda which address contamination in the
buildings, including surface contamination and air contamination.
• OU4 Focused Risk Assessment Memorandum addresses contamination in the South Pond Area,
stockpiled soils and the East Drainage Ditch.
• OU4 Baseline Risk Assessment which addresses soil and sediment contamination not evaluated
by the previous risk assessments for OU4.

Each of these risk assessment documents was prepared to evaluate potential risks to human health
and the environment for specific exposure scenarios of interest, given the nature and extent of site
contamination in various areas of OU2 and OU4.

6.1 Contaminant Identification

6.1.1 Operable Unit 2

For the OU2 BRA. various site media were evaluated including surface and subsurface soils,
sediments, groundwater, and surface water. The site media were analyzed for 150 constituents including
the categories of VOCs, semi-VOCs, pesticides/PCBs, and inorganics. To reduce the number of constituents
of interest to a manageable number, several constituents were eliminated based on the following
guidelines:

• Any constituent not detected at least once in a given media.
• Laboratory contaminants;
• Naturally-occurring constituents;
• Constituents determined to be due to anthropogenic sources;
• Low freguency and range of detection, and
• EPA's Concentration-toxicity screening procedure.

Upon completion of the elimination process, 25 constituents of interest were retained for
evaluation in the risk assessment (Eckenfelder 1993). Table 2-16 from the OU2 BRA lists these 25
constituents and the affected media, and is included as Appendix A. The upper 95th confidence limit
(UCL) concentrations of the constituents of interest were used to evaluate the associated risks.

6.1.2 Operable Unit 4

To evaluate the risks associated with OU4, three separate risk assessments were conducted in
association with the three areas which were the subject of response actions. Risks were evaluated
separately for Buildings 1-5 and the Maintenance Building. the South Pond Area, and the remaining area
of OU4 including the capped area and all other areas not evaluated by the first two risk assessment
efforts.

Building 1-5 and the Maintenance Building
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The constituents for which health risks were evaluated include nine pesticides and herbicides and
PCBs as listed in Appendix B. The affected media for which exposure pathways were identified includes
dust inside the buildings and soil outside the buildings. The 95th UCL concentrations were used to
evaluate the associated risks. (OU4 Building Removal Action Risk Assessment Memorandum, 1992)

South Pond Area

A Focused Risk Assessment memorandum was prepared to evaluate current recreational exposures and
potential future occupational and residential exposures in the South Pond Area. This risk assessment
evaluated risks due to 31 constituents in soil and sediments. A list of the 31 constituents is included
as Appendix C. Risk calculations were based upon the 95th UCL concentrations. (OU4 Focused Risk
Assessment Memorandum, 1995)

OU4 Capped and Exposed Soils

The OU4 BRA was prepared to evaluate the risks posed by contaminated soils remaining beneath the
asphalt cap as well as areas in OU4 which were not addressed by the earlier risk assessments (Buildings,
and South Pond Area). The media of interest in the OU4 BRA include surface soils (0-2') for current
exposure scenarios, and deep soils (0-12') for future exposure scenarios. Using data collected from
several different investigations, the OU4 BRA considered 68 constituents of interest including VOCs,
semi-VOCs, pesticides, dioxins, and inorganics. The 95th percent UCL concentrations were used in the
risk characterization calculations, except where the data set was comprised of fewer than 10 data points.
For the latter case, the highest detected concentration was used. (Black and Veatch 1995) Two tables
from the OU4 BRA showing the exposure point concentrations for the constituents of interest for both
capped and exposed soils are included as Appendices D and E.

6.2 Exposure Assessment

6.2.1 Operable Unit 2

The OU2 risk assessments evaluate numerous potential exposure pathways for the various media under
then current and potential future land use scenarios. Risks associated with groundwater exposures were
not quantified because the existing groundwater extraction and treatment system was assumed to prevent
current and future groundwater exposures. (Eckenfelder 1993)

Under the current land use scenario, exposure pathways for occupational and recreational
populations were evaluated in the OU2 BRA. The exposure pathways for which risks were quantified include
site workers and persons recreating at the site (both adults and children) exposed to surficial and
shallow soils through incidental ingestion and dermal contact. In addition, risks were quantified for a
recreational child exposed to surface water and sediment through incidental ingestion.

The OU2 BRA assumed future land uses to be limited to industrial and recreational activities. The
exposure pathways for which risks were quantified include site workers and persons recreating at the site
exposed to surficial and shallow soils through incidental ingestion and dermal contact. Exposure of
children to surface water and sediment through incidental ingestion was also quantified.

Ecological exposure pathways were identified under both current and future land use scenarios for
terrestrial, avian, and aquatic biota. Ecological risks associated with these pathways were not
quantified, but were evaluated qualitatively in the OU2 BRA.

Other risk assessments prepared for OU2 evaluated a future residential land use scenario. The
exposure pathways quantified include potential future workers and residents exposed to surface and
subsurface soils. Surface soils included soils from the ground surface to two feet below ground.
Subsurface soils included soils from a depth of six inches below ground surface to all depths from which
soil samples were collected.

6.2.2 Operable Unit 4

Buildings 1-5 and the Maintenance Building

Risks were quantified for occupational workers exposed via inhalation of contaminated dust inside
the buildings, and incidental ingestion and dermal contact with contaminated soil outside the buildings.

South Pond Area
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The OU4 Focused Risk Assessment evaluated current recreational exposures and future occupational
and residential exposures. Under the current industrial land use scenario, risks were quantified for
persons recreating in the area exposed to contaminated soils and sediments through incidental ingestion
and dermal contact

OU4 Capped and Exposed Soils

In the OU4 BRA, no human populations were determined to be exposed to soils beneath the asphalt
cap under a current site use scenario. The only current exposure involved recreational populations
exposed to soils not covered by the asphalt cap.

Future land use scenarios evaluated in the OU4 BRA included a future industrial use and a future
residential use. Future worker and resident exposure pathways including incidental ingestion and dermal
contact with soils beneath the asphalt cap were evaluated. In the same way, future workers and residents
exposed to soils not covered by the asphalt cap were evaluated.

6.3 Toxicity Assessment

While numerous constituents of interest were evaluated in the various risk assessments, three
pesticides, aldrin, dieldrin, and chlordane, contributed most substantially to the overall risks.
Toxicity information regarding these primary contaminants is presented in this section. Toxicity
information regarding the other contaminants can be found in the risk assessment documents listed above
in Section 6.0.

Health hazards for chemicals exhibiting non-carcinogenic (non-cancer) effects are evaluated using
established reference doses (RfDs). The RfD is an estimate of the daily exposure to the human population
that is not likely to be harmful over a lifetime. RfDs are expressed in units of mg/kg/day and are
usually derived from animal studies or in some cases from human studies involving workplace exposures.

Health risks for chemicals exhibiting carcinogenic (cancer) effects are evaluated using
established slope factors (SFs) . SFs are used to estimate the upper-bound excess lifetime cancer risk
associated with lifetime exposure to potential human carcinogens. Excess cancer risk is calculated based
on the average daily intake over a lifetime and the cancer SF.

Aldrin, dieldrin, and chlordane are classified by EPA as probable human carcinogens, which means
that there is sufficient evidence of carcinogenicity from animal studies, but insufficient evidence from
human studies. The RfDs and SFs for aldrin, dieldrin, and chlordane for both ingestion and dermal
exposures are shown in Table 6-1. Because toxicity values are routinely updated, Table 6-1 reflects the
values from the OU4 BRA, which contains the most recent toxicity information.

Table 6-1
Toxicity Values

Oral SF
Oral RfD
(kg-day/mg) (mg/kg-day)
Aldrin
Dieldrin
Chlordane
17
16
1.3
3.
5.
6.
,0x10
,0x10
,0x10
-5
-5
-5
Dermal SF
(kg-day/mg)
340
320
26
Dermal RfD
Target Organ
(mg/kg-day)
1,
2,
3,
.5x10
.5x10
.0x10
-6
-6
-6
liver
liver
liver
6.4 Risk Characterization

Excess lifetime cancer risks are determined by multiplying the intake level with the SF.
probabilities that are generally expressed in scientific notation. An excess lifetime cancer risk of
1x10 -6 indicates that, as a plausible upper bound, an individual has a one in one million chance of
developing cancer as a result of site-related exposure to a carcinogen over a 70-year lifetime under the
specific exposure conditions at a site EPA considers carcinogenic risk greater than 1x10 -4 to be
unacceptable, generally triggering a response action to reduce to the risk.

Potential concern for noncarcinogenic effects of a single contaminant in a single medium is
expressed as the hazard quotient (HQ). The HQ is the ratio of the estimated intake derived from the
contaminant concentration in a given medium to the contaminant's RfD By adding the HQs for all
contaminants within a medium or across all media of interest, the hazard index (HI) can be generated.
The HI provides a reference point for gauging the potential significance of multiple contaminant
-------
exposures within a single medium or across media. EPA generally considers an HI greater than 1.0 to be
unacceptable.

For OU2, the current exposure scenarios evaluated in the three risk assessments prepared for OU2
are no longer applicable because the exposure pathways have been eliminated through capping during the
response actions. Assuming the response actions are properly maintained, the only remaining risk in OU2
involves a future residential exposure scenario which poses unacceptable non-carcinogenic risks up to
HI=22 and carcinogenic risks up to 2x10 -3. The contaminants contributing the most significant risk are
aldrin, dieldrin, and chlordane.

For OU4, most of the current exposure scenarios evaluated are no longer applicable because the
exposure pathways have been eliminated through capping or encapsulation conducted during the response
actions. Until the SPA response action is conducted, a current exposure scenario remains valid for
people recreating near the South Pond. Following the response action planned for the South Pond area,
this exposure pathway will also be eliminated. Assuming the response actions are properly maintained,
the only remaining risks in OU4 will involve future residents and workers exposed to soils beneath the
asphalt cap.

The risks to future site workers evaluated in the OU4 BRA are associated with surface and shallow
soils which have been covered by an asphalt cap. Risks to these site workers include both a carcinogenic
risk of 1.7x10 -3 and a noncarcinogenic hazard index of 9.7. These risks would be realized if the cap is
not properly maintained and workers become exposed to the underlying soils.

For the future residential scenario, unacceptable risks are present for both adult and child
residents exposed to soils beneath the asphalt cap. The excess carcinogenic risk associated with this
exposure pathway is 3x10 -2 and the hazard index for noncarcinogenic effects is 144.

The OU4 BRA concludes that the protective cover must be maintained to ensure that risks to site
workers are eliminated and that future use of the site must be restricted to prevent residential
development unless further remedial action is implemented.

6.5 Environmental Risks

Environmental risks were evaluated in the OU2 BRA. Exposures to biota from contaminated media in
OU2 include terrestrial (land) animals and avian (bird) species. Soil exposures may be associated with
such activities as feeding, nesting, or burrowing, and surface water exposures may also exist in the
vicinity of the South Pond.

Detailed ecological assessment was not conducted during the OU2 BRA. Field personnel during site
visits noted that the southern portion of OU2 (in particular the South Pond and Frank Depuydt Woods) is
heavily vegetated and appears to provide habitat for several species of birds and mammals. The OU2 BRA
reports no visible adverse impacts on animal species, and concludes that the potential for such adverse
impacts is not expected to be significant. (Eckenfelder 1993)

Exposure to aguatic biota are potentially present in the South Pond according to the OU2 BRA.
However, no aguatic biota surveys were completed, and the species existing in the South Pond were not
determined. The IDNR indicated during the OU2 BRA that there are no endangered species, threatened
species, critical habitats, or significant natural communities within a three mile radius of the site.
As for terrestrial and avian biota, the OU2 BRA concludes that the possibility of adverse impacts to
aguatic biota exists in the vicinity of the South Pond, but the degree of impact is not expected to be
significant.

Concurrent with the OU4 BRA, a Wildlife Toxicity Assessment was conducted. This assessment
concluded that there may be significant ecological risks associated with portions of OU4, particularly
the South Pond. However, remedial actions in the South Pond and surrounding wetland area would physically
alter or eliminate the habitat the action is intended to remediate. The assessment concluded that
remedial actions in the wetland area should reduce or eliminate the exposure threat to contaminated
media, while preserving the natural habitat to the extent possible. (Black and Veatch 1995)

7.0 DESCRIPTION OF ALTERNATIVES

Remedial alternatives were developed in the feasibility study (FS) for each area which was the
subject of a response action: Buildings 1-5 and the Maintenance Building, the soils beneath the asphalt
cap, and the South Pond Area. The only areas remaining in OU2 and OU4 which were not impacted by the
response actions were shown in the OU4 BRA to have no significant associated risks, so remedial
alternatives were not developed for these few areas.
-------
Remediation goals are established to determine the contaminant concentrations in site media that
pose a risk to human health and the environment, thereby necessitating implementation of a site remedy.
The response actions have reduced risks creating an acceptable risk for industrial use of OU2 and OU4
provided the maintenance activities reguired by the response actions are conducted. However, health
risks are still present for a future site use scenario.

The general remedial action objective for OU2 and OU4 is as follows:

"Maintain the Buildings, asphalt cap, and SPA so that exposure pathways continue to be controlled
or minimized. This will minimize risk for both the current and anticipated future industrial use of the
site, and will protect human health and the environment."

Specific remedial action objectives corresponding with the nature and extent of contamination at
the site and the associated findings of the OU2 and OU4 BRAs, are as follows:

Building-Specific Remedial Action Objective
"To maintain the control of potential exposure pathways related to contaminated materials in
Buildings 1 through 5 and the Maintenance Building, and to protect human health and the environment
during continued and future industrial uses".

Soil-Specific Remedial Action Objective
"To maintain the control of potential exposure pathways related to contaminated soils and to
protect human health and the environment during continued and future industrial uses similar to the
current industrial operations and activities."

South Pond Sediment-Specific Remedial Action Objective
"To minimize the risks from potential exposure pathways related to contaminated sediments and to
protect human health and the environment during continued and future industrial uses.

The remedial alternatives evaluated in detail in the OU2 and OU4 FS are summarized in this
section. Alternatives were developed separately in the FS for the buildings of OU4, the soils beneath the
asphalt cap, and the SPA, hereafter referred to as the "focus areas". The descriptions provided here
identify engineering and treatment components, institutional controls, implementation reguirements,
estimated costs, and major applicable or relevant and appropriate reguirements (ARARs) associated with
each option.

7.1 Buildings 1-5 and the Maintenance Building

At the conclusion of the initial development and evaluation of alternatives in the FS, three
alternatives were retained for detailed evaluation: Building Alternative 1 - No Further Action, Building
Alternative 2 - Limited Action, and Building Alternative 4 - Source Layer Removal/Disposal.

7.1.1 Building Alternative 1 - No Further Action

Building Alternative 1 would involve no further remedial actions beyond the efforts performed
under the building response action. The building response action included cleaning and vacuuming
interior surfaces, placing an epoxy coating on the walls and a urethane coating of the floors, repair or
replacement of ceiling and wall insulation, and inventory parts washing. The response action also
included provisions for maintenance including routine inspections, periodic sampling, and guidelines for
damage repair. The No Further Action alternative, reguired by the National Oil and Hazardous Substances
Contingency Plan (NCP) and CERCLA, is a baseline alternative against which the effectiveness of the other
alternatives can be compared.

No restrictions on future uses of the site would be implemented under this alternative; therefore,
the remedial action objective of maintaining the exclusion of the exposure pathways may not be met by
this alternative. No ARARs were identified for this alternative. No reduction of the toxicity or volume
of contaminated material would be achieved with this alternative; although, the mobility of the
contaminants would be eliminated through the installation and maintenance of the encapsulation materials.

Capital Costs: $0
Annual O&M Costs: $31,900 to $53.900
Present Worth: $597,000
Time to Implement 0 months
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7.1.2 Building Alternative 2 - Limited Action

This alternative would include the same items as Building Alternative I with the addition of land
use restrictions which would ensure that the epoxy/urethane encapsulation and insulation is not
intentionally damaged or removed. The land use restrictions would also prohibit residential development,
restricting the site to industrial uses only.

This alternative would meet the remedial action objectives for the buildings. No ARARs were
identified for this alternative. No reduction of the toxicity or volume of contaminated material would
be achieved with this alternative, although, the mobility of the contaminants would be minimized through
the previous installation and continued maintenance of the encapsulation materials. The long-term
effectiveness of this alternative would be dependent upon the proper conduct of the reguired maintenance
activities.

Capital Costs: $5,000
Annual O&M Costs: $31,900 to $53,900
Present Worth: $602,000
Time to Implement: 2 months

7.1.3 Building Alternative 4 - Source Layer Removal/Disposal

This alternative would involve decontamination of the buildings by removal of a layer of the
concrete floors and removal of the insulation. The decontamination debris would then be disposed of at
an offsite Resource Conservation and Recovery Act (RCRA) hazardous waste landfill or a RCRA solid waste
landfill based on results of sampling during the implementation of the remedial action.

A layer of the contaminated concrete floor surfaces would be removed by either shallow grit
blasting or scarification and the resulting debris would be collected and temporarily stored in roll-off
containers. The building insulation and material used to secure the insulation would be removed and also
temporarily stored in roll-off containers. The insulation material would then be disposed of at a TSCA
landfill. The epoxy coatings that were placed on the walls would be left in place and repaired as
necessary.

This alternative would meet the remedial action objectives for the buildings. Minimal residual
risks would remain beneath the epoxy coating on the walls of the buildings after the removal of the
contaminated concrete and insulation. The ARARs identified for this alternative include several
reguirements of the Resource Conservation and Recovery Act (RCRA) pertaining to the generation and
disposal of hazardous and solid wastes. Specifically, provisions in 40 CFR Parts 261 and 268 are relevant
and appropriate for waste analysis and identification of hazardous wastes for materials which are removed
from the buildings. In addition, RCRA reguirements of 40 CFR Part 262 are relevant and appropriate for
the offsite shipment of wastes. The regulations found at 40 CFR Part 761 of the Toxic Substance Control
Act (TSCA) are applicable to actions involving the disposal of material containing PCBs. The IDNR has
identified the Solid Waste Management and Disposal Rule 567-100.3(2)(455B) and Rule contaminated
materials containing up to 10 mg/kg total pesticides in a sanitary landfill. All identified ARARs would
be met by this alternative. Reguirements of the Occupational Safety and Health Act (OSHA), the CERCLA
Offsite Rule, and Department of Transportation (DOT) regulations are not ARARs, but would be followed
during remedial activities.

This alternative would provide long-term effectiveness and permanence by removing contaminated
material from the buildings. This alternative would not directly reduce the toxicity or volume of
contaminated material; however, the contaminated material would be permanently removed from the buildings
and placed in a landfill where the mobility would be reduced.

Capital Costs: $2,824,600
Annual O&M Costs $1,000 to 13,900
Present Worth: $2,876,000
Time to Implement: 8 months

7 .2 Soil Beneath Asphalt Cap

At the conclusion of the initial development and evaluation of alternatives in the FS, three
alternatives were selected to be carried forward to detailed evaluation Soil Alternative 1 - No Further
Action. Soil Alternative 2 - Limited Action, and Soil Alternative 4 - Source Removal/ Disposal.

7.2.1 Soil Alternative 1 - No Further Action
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Soil Alternative 1 would involve no further remedial actions beyond the efforts performed under
the surface cap response action which included placement of an asphalt cap over the majority of the OU2
soils and a large portion of OU4 soils. The response action also included provisions for maintenance
including preventive actions, routine inspections, and guidelines for damage repair. The No Further
Action alternative, reguired by the NCP and CERCLA, is a baseline alternative against which the
effectiveness of the other alternatives can be compared.

No restrictions on future uses of the site would be implemented under this alternative; therefore,
the remedial action objective of maintaining the exclusion of the exposure pathways may not be met. The
only ARARs for this alternative are the Executive Order for Wetlands Protection and the Floodplain
Management Executive Order. These ARARs would be met because no actions would be taken that would damage
the floodplain or wetland area. No reduction of the toxicity or volume of contaminated material would be
achieved with this alternative; although, the mobility of the contaminants would be eliminated with the
installation of the capping materials.

Capital Costs: $0
Annual O&M Costs: $52,600 to $65,500
Present Worth: $844,000
Time to Implement: 0 months

7.2.2 Soil Alternative 2 - Limited Action

This alternative would provide for enhanced maintenance of the asphalt cap and land use
restrictions. An addition to the current maintenance program would include the application of periodic
seal coats over the entire surface of the asphalt cap. The land use restrictions would prohibit the
removal of the asphalt cap and any activities that might damage the integrity of the cap. It would also
prohibit residential development and restrict industries such as human health care and food processing
industries from using the site.

This alternative would meet the remedial action objectives for soils provided that the maintenance
program is executed as reguired. The only ARARs for this alternative are the Executive Order for
Wetlands Protection and the Floodplain Management Executive Order. These ARARs would be met because no
actions would be taken that would damage the floodplain or wetland area. No reduction of the toxicity or
volume of contaminated material would be achieved with this alternative; although, the asphalt cap would
reduce the mobility of the contaminants both through reduction of infiltration and surface erosion. The
long-term effectiveness of this alternative would be dependent upon the willingness of the property owner
to conduct the reguired maintenance activities and the effective enforcement of land-use restrictions.

Capital Costs: $5.000
Annual O&M Costs: $86,600 to $99.500
Present Worth: $1,372,000
Time to Implement: 2 months

7.2.3 Soil Alternative 4 - Source Removal/ Disposal

This alternative would involve the excavation and disposal of contaminated soil and sediments
containing concentrations of contaminants that are responsible for cancer risk egual to or greater than
1x10 -4 It is estimated that 5,300 cubic yards of soil would reguire excavation. The asphalt cap
installed during the response action would be removed and soils would be excavated using standard earth
moving eguipment. Dust suppressants would be used to control dust during excavation and loading
activities. The excavated areas would be backfilled with clean soil and the asphalt cap would be
restored. Characterization sampling of the excavated materials would be performed to determine whether
the material would be disposed of at a RCRA hazardous waste landfill or as a special waste at a RCRA
solid waste landfill.

This alternative would meet the remedial action objectives for soils by removing contaminated
materials from the site. The ARARs identified for this alternative include the same RCRA reguirements
and the IDNR ARARs identified for Building Alternative 4. In addition, the reguirements of the Executive
Order for Wetlands Protection and the Floodplain Management Executive Order would be applicable. This
alternative would comply with all ARARs. OSHA reguirements, the CERCLA Offsite Rule, and DOT regulations
would not be ARARs, but would be followed during remedial activities.

This alternative would provide long-tern effectiveness and permanence by removing the contaminated
soils from the site. This alternative would not directly reduce the toxicity or volume of contaminated
material; however, the contaminated material would be permanently removed from the site and placed in a
landfill where the mobility would be reduced.
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Capital Costs: $2,171,800
Annual O&M Costs: $12,900
Present Worth: $2,209.000
Time to Implement: 6 months

7 . 3 South Pond Area

At the conclusion of the initial development and evaluation of alternatives in the FS, three
alternatives for remediation of the SPA were selected to be carried for detailed evaluation in the FS:
Sediment Alternative 1 - No Further Action, Sediment Alternative 2 - Limited Action, and Sediment
Alternative 4 - Source Removal/Disposal.

7.3.1 Sediment Alternative 1 - No Further Action

Sediment Alternative 1 would involve no further remedial actions beyond the efforts performed
under the SPA response action which includes excavation and offsite disposal of soils around the SPA,
cast drainage ditch, and stockpiled soil piles. The response action also includes provisions for
monitoring the outfall of the SPA to ensure that any contaminated sediments remaining at the bottom of
the pond do not wash out of the pond and recontaminate the east drainage ditch. Monitoring would be
conducted annually for three years following completion of excavation activities. The No Further Action
alternative, reguired by the NCP and CERCLA, is a baseline alternative against which the effectiveness of
the other alternatives can be compared.

No restrictions on future uses of the site would be implemented under this alternative, therefore,
the remedy may not be protective of human health or the environment since the health-based cleanup levels
established in the action memorandum are based upon an industrial use of the area. More protective
cleanup levels would be necessary for a residential setting. The only ARARs for this alternative are the
Executive Order for Wetlands Protection and the Floodplain Management Executive Order. These ARARs would
be met because no actions would be taken that would damage the floodplain or wetland area. No reduction
of the toxicity or volume of contaminated material would be achieved with this alternative.

Capital Costs: $0
Annual O&M Costs: $14,800 to $27,700
Present Worth: $263,000
Time to Implement: 0 months

7.3.2 Sediment Alternative 2 - Limited Action

This alternative consists of land use restrictions and continued soil monitoring of the South Pond
outfall during the reguired CERCLA periodic reviews. The land use restrictions would prohibit
residential development to prevent disturbance of any contaminated sediments remaining in the pond, and
would ensure the protectiveness of the SPA response action cleanup levels. Periodic soil sampling at the
outfall of the pond would confirm whether contaminated sediments in the bottom of the pond remain in the
pond. If sampling shows that contaminated sediments are being washed out of the pond, further action may
be reguired.

This alternative would meet the remedial action objectives for soils. The only ARARs for this
alternative are the Executive Order for Wetlands Protection and the Floodplain Management Executive
Order. These ARARs would be met because no actions would be taken that would damage the floodplain or
wetland area. No reduction of the toxicity, volume, or mobility would be achieved beyond the reduction
of contaminant mobility achieved by the SPA response action. The long-term effectiveness of this
alternative would be dependent upon the effective enforcement of land-use restrictions.

Capital Costs: $5,000
Annual O&M Costs: $14,800 to $28,900
Present Worth: $268,000
Time to Implement: 2 months

7.3.3 Sediment Alternative 4 - Source Removal/ Disposal

This alternative would involve the excavation and offsite disposal of contaminated sediments
remaining in the SPA following the SPA response action. Sediments containing concentrations of
contaminants that are responsible for cancer risk egual to or greater than 1x10 -4 would be excavated and
transported offsite for disposal at an EPA-approved facility. It is estimated that 1,000 cubic yards of
sediment would reguire excavation. Dust suppressants would be used to control dust during excavation and
loading activities. The excavated areas would be backfilled with clean soil and revegetated as necessary
-------
to restore natural conditions around the pond. Characterization sampling of the excavated materials would
be performed to determine whether the material would be disposed of at a RCRA hazardous waste landfill or
as a special waste at a RCRA solid waste landfill. Land-use restrictions would also be included in this
alternative.

This alternative would meet the remedial action objectives for sediments by removing contaminated
materials from the site. ARARs identified for this alternative include the same RCRA reguirements and
IDNR

ARARs identified for Building Alternative 4 and Soil Alternative 4 for waste analysis,
identification of hazardous wastes, and offsite shipping and disposal of waste. In addition, the
reguirements of the Executive Order for Wetlands Protection and the Floodplain Management Executive Order
would be applicable. This alternative would comply with all ARARs. OSHA reguirements, the CERCLA
Offsite Rule, and DOT regulations would not be ARARs, but would be followed during remedial activities.

This alternative would provide long-term effectiveness and permanence by removing the contaminated
sediments from the site. This alternative would not directive reduce the toxicity or volume of
contaminated material; however, the contaminated material would be permanently removed from the site and
placed in a landfill where the mobility would be reduced.

Capital Costs: $270,300
Annual O&M Costs: $12,900
Present Worth: $273,000
Time to Implement 4 months

8.0 SUMMARY OF COMPARATIVE ANALYSIS OF ALTERNATIVES

The remedial alternatives presented above were evaluated in the FS with respect to the nine
criteria reguired by the NCP for the evaluation of remedial alternatives. This section discusses the
performance of the preferred alternatives against the following nine evaluation criteria:

• Overall Protection of Human Health and the Environment - This criterion addresses whether a
remedy provides adeguate protection and describes how risks posed through each exposure
pathway are eliminated, reduced, or controlled through treatment, engineering controls, or
institutional controls.

• Compliance with ARARs - Applicable reguirements are those cleanup standards, standards of
control, and other substantive reguirements, criteria, or limitations promulgated under
Federal or State environmental or facility siting laws that specifically addresses a
hazardous substance, pollutant, contaminant, remedial action, location, or other
circumstance at a CERCLA site. Relevant and appropriate reguirements are those cleanup
standards, standards of control, and other substantive reguirements, criteria, or
limitations promulgated under Federal or State environmental siting laws that, while not
"applicable" to a hazardous substance, pollutant, contaminant, remedial action, location, or
other circumstance at a CERCLA site, address problems or situations sufficiently similar to
those encountered at the CERCLA site that their use is well suited to the particular site.
Compliance with ARARs addresses whether a remedy will meet all Federal and State
environmental laws and/or provide basis for a waiver from any of these laws.

• Long-term Effectiveness and Permanence - This criterion evaluates the ability of a remedy to
maintain reliable protection of human health and the environment over time. The criterion
includes the consideration of residual risk and the adeguacy and reliability of controls.

• Reduction of Toxicity, Mobility, or Volume Through Treatment - This criterion evaluates the
preference for a remedy that employs treatment technologies that reduce health hazards,
contaminant migration, or the guantity of contaminants at a site.

• Short-term Effectiveness - Short-term effectiveness refers to the period of time needed to
complete the remedy and any adverse impacts on human health and the environment that may be
posed during the construction and implementation of the remedy.

• Implementability - This criterion evaluates the technical and administrative feasibility, of
a remedy, including the availability of materials and services needed to implement the
remedy. It also includes coordination of Federal, State, and local governments which may be
necessary to implement a remedy.
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• Cost - This criterion examines the estimated costs for each remedial alternative. For
comparison, capital and annual O&M costs are used to calculate a present worth cost for each
alternative.

• State Acceptance - This criterion assesses the position of the state regulatory agency
regarding the remedial alternatives preferred by EPA.

• Community Acceptance - This criterion considers the level of community support for EPA's
preferred alternatives by reviewing public comments received during the public comment
period or at the public meeting.

These nine evaluation criteria have been developed by EPA to address the CERCLA statutory
reguirements and technical, cost, and institutional considerations which the EPA has determined
appropriate. The evaluation criteria serve as the basis for conducting the detailed analysis during the
FS and for subseguently selecting an appropriate remedy.

The first two criteria are threshold criteria. These criteria must be met for an alternative to
be considered a remedy for a site. The next five criteria are balancing criteria. Tradeoffs are made
among the alternatives with respect to these criteria. The last two criteria are modifying criteria and
are used to modify the preferred alternative as appropriate following the public comment period.

8.1 Comparative Analysis of Building Alternatives

8.1.1 Overall Protection of Human Health and the Environment

All of the building alternatives would provide protection of human health and the environment for
continued industrial uses of the property. The limited action alternative, Building Alternative 2, would
meet the remedial action objective for the buildings by maintaining the control of the exposure pathways
through implementation of land use restrictions and continued maintenance of the building encapsulation
materials. Building Alternative 4 would also provide protection of human health and the environment
because the contaminated materials would be permanently removed from the buildings. Building Alternative
1 would not meet the remedial action objective because it would not provide for future use restrictions.

8.1.2 Compliance with ARARs

There are no ARARs associated with Building Alternatives 1 and 2. Building Alternative 4 would
comply with the ARARs identified in Section 7.1.3 pertaining to waste analysis, identification of
hazardous wastes, and offsite shipping and disposal of waste. While OSHA is not an ARAR, OSHA
reguirements for worker health and safety would be followed for all of the remedial alternatives.

8.1.3 Long-Term Effectiveness and Permanence

Building Alternative 2 would provide long-term effectiveness by ensuring the integrity of the
building encapsulation materials through the implementation of land use restrictions and continued
maintenance Building Alternative 1 would not provide long-term effectiveness because no provisions for
restricting the uses of the buildings or removal of the encapsulation materials would be provided
Building Alternative 4 would eliminate the long-term residual risks by removing the contaminated concrete
surfaces and insulation materials. None of the alternatives would provide a truly permanent solution
because residual risks would remain. Of the alternatives, alternative 4 would provide more permanence
because it would remove at least some of the contaminated material from the site.

8.1.4 Reduction of Toxicitv, Mobility, or Volume Through Treatment

None of the developed alternatives would involve methods to treat the contaminants that would
reduce the toxicity or volume of the wastes. Building Alternative 2, through site use restrictions,
would prevent removal of the encapsulation material which would eliminate the mobility of the
contaminants. Building Alternative 1 would eliminate the mobility of the contaminants, but would not
provide for long-term measures to ensure the immobility is maintained. Building Alternative 4 would
remove contaminated materials from the buildings and place them in a RCRA landfill or TSCA landfill as
appropriate, which would ultimately reduce the mobility of the contaminants.

8.1.5 Short-term Effectiveness

Building Alternatives 1 and 2 would reguire practically no time to implement, with no adverse
impact to site workers or area residents. Building Alternative 4 would reguire approximately, 8 months
to implement. Building Alternative 4 would also present higher short-term risks of exposure to the
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community and workers during the concrete surface and insulation removal efforts and transportation.

8.1.6 Implementabilitv

Building Alternatives 1 and 2 would be easily implemented. The land use restrictions under
Building Alternative 2 could be easily added to the property deed with coordination between EPA and the
city. Building Alternative 4 would involve the use of readily available eguipment and resources.

8.1.7 Cost

The present worth cost of Building Alternative 1 is estimated at $597,000. The present worth cost
of Building Alternative 2 is estimated to be $602,000, and the present worth cost of Building Alternative
4 is $2,876,000.

8.1.8 State Acceptance

The Iowa Department of Natural Resources (IDNR) has provided oversight assistance to EPA
throughout the history of the Des Moines TCE site. The IDNR participated in the public meeting in
support of EPA's preferred alternative.

8.1.9 Community Acceptance

To a large extent, the community is supportive of the limited action alternative. However, the
Iowa Environmental Council reguested EPA to consider the source removal alternative. EPA's response to
their reguest is included in the Responsiveness Summary.

8.2 Comparative Analysis of the Soil Alternatives

8.2.1 Overall Protection of Human Health and the Environment

All of the soil alternatives would provide protection of human health and the environment for
continued industrial site uses, but not for residential use. Soil Alternative 2 would meet the remedial
action objective for the soils by maintaining control of the exposure pathways through implementation of
land use restrictions and enhanced maintenance of the asphalt cap. Soil Alternative 4 would also provide
a high degree of protectiveness by removing contaminated soils from the site. Soil Alternative 1 would
not meet the remedial action objective because it would not provide for future land use restrictions to
prevent residential development.

8.2.2 Compliance with ARARs

ARARs identified for the soil alternatives were presented in Section 7.2.3 above. Soil
Alternatives 1 and 2 would comply with ARARs regarding the protection of floodplains and wetlands because
no actions would be taken that would damage the floodplain or wetland area. Soil Alternative 4 would
comply with ARARs pertaining to waste analysis, identification of hazardous wastes, and offsite shipping
and disposal of waste. While OSHA is not an ARAR, OSHA reguirements for worker health and safety would be
followed for all of the remedial alternatives.

8.2.3 Long-Term Effectiveness and Permanence

Soil Alternative 2 would provide long-term effectiveness by ensuring maintenance of the cap and
restricting future site uses, but would not provide permanence as residual risks would remain beneath the
cap. Soil Alternative 1 would not provide long-term effectiveness or permanence because no provisions for
restricting future uses of the site or removal of the cap would be provided and residual risks would
remain beneath the cap. Soil Alternative 4 would provide both long-term effectiveness and permanence
through the elimination of the long-term residual risks at the site by removing the contaminated soils
posing risks greater than 1x10 -4.

8.2.4 Reduction of Toxicitv, Mobility, or Volume Through Treatment

None of the developed alternatives would involve methods to treat the contaminants that would
reduce the toxicity or volume of the wastes. Soil Alternative 2 would reduce the mobility of the
contaminants by reducing wind and surface erosion. Soil Alternative 1 would reduce the mobility of the
contaminants, but would not provide for long-term measures to ensure the immobility is maintained. Soil
Alternative 4 would remove the contaminated soils from the site and place them in a RCRA landfill, which
would ultimately reduce the mobility of the contaminants.
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8.2.5 Short-term Effectiveness

Soil Alternatives 1 and 2 would require practically no time to implement. Soil Alternative 4
would require approximately 6 months to implement. In addition, Soil Alternative 4 would present hiqher
short-term risks of exposure to the community and workers durinq the soil excavation efforts and
transportation.

8.2.6 Implementabilitv

Soil Alternatives 1 and 2 would be easily implemented. The land use restrictions under Soil
Alternative 2 could be easily added to the property deed, but would require coordination between EPA and
the city Soil Alternative 4 would involve the use of readily available equipment and resources.

Cost
The present worth cost of Soil Alternative 1 is estimated at $844,000. The present worth cost of
Soil Alternative 2 is estimated to be $1,372,000, and the present worth cost of Soil Alternative 4 is
$2,209,000.

8.2.9 State Acceptance

The Iowa Department of Natural Resources (IDNR) has provided oversiqht assistance to EPA
throuqhout the history of the Des Moines TCE site. The IDNR participated in the public meetinq in
support of EPA' s preferred alternative.

8.2.9 Community Acceptance

To a larqe extent, the community is supportive of the limited action alternative. However, the
Iowa Environmental Council requested EPA to consider the source removal alternative. EPA' s response to
their request is included in the Responsiveness Summary.

8 . 3 Comparative Analysis of the Sediment Alternatives

8.3.1 Overall Protection of Human Health and the Environment
Sediment Alternative 2 meets this criterion and would meet the remedial action objective for the
sediments throuqh the implementation of land use restrictions to prevent residential development.
Sediment Alternative 4 would also provide a hiqh deqree of protectiveness by removinq contaminated
sediments from the site. Sediment Alternative 1 would not meet the remedial action objective because it
would not provide for future land use restrictions.

8.3.2 Compliance with ARARs

Sediment Alternatives 1 and 2 would comply with ARARs as identified in Section 7.3.3 reqardinq the
protection of floodplains and wetlands because no actions would be taken that would damaqe the floodplain
or wetland area. Sediment Alternative 4 would comply with ARARs pertaininq to waste analysis,
identification of hazardous wastes, and offsite shippinq and disposal of waste. While OSHA is not an
ARAR, OSHA requirements for worker health and safety would be met for all remedial alternatives.

8.3.3 Long-Term Effectiveness and Permanence

Sediment Alternative 2 would provide lonq-term effectiveness by conductinq soil monitorinq of the
outfall of the South Pond and restrictinq future site uses, but would not provide permanence as residual
risks would remain in the bottom of the pond. Sediment Alternative 1 would not provide lonq-term
effectiveness or permanence because no provisions for restrictinq future uses of the site would be
provided and residual risks would remain in the pond. Sediment Alternative 4 would provide both
lonq-term effectiveness and permanence throuqh the elimination of the lonq-term residual risks at the
site by removinq the contaminated sediments posinq risks qreater than 1x10 -4.

8.3.4 Reduction of Toxicitv, Mobility, or Volume Through Treatment

None of the developed alternatives would involve methods to treat the contaminants that would
reduce the toxicity, volume, or mobility of the wastes. However, Sediment Alternative 2 would reduce the
mobility of the contaminants by ensurinq the contaminated sediments remain in the pond and do not wash
out into the east drainaqe ditch. Sediment Alternative 1 would reduce the mobility of the contaminants
in the short term (three years) , but would not provide for lonq-term measures to ensure the immobility is
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maintained. Sediment Alternative 4 would remove the contaminated sediments from the site and place them
in a RCRA landfill, which would ultimately reduce the mobility of the contaminants.

8.3.5 Short-term Effectiveness

Sediment Alternatives 1 and 2 would require practically no time to implement. Sediment
Alternative 4 would require approximately 6 months to implement. In addition, Sediment Alternative 4
would present hiqher short-term risks of exposure to the community and workers durinq the sediment
excavation efforts and transportation.

8.3.6 Implementabilitv

Sediment Alternatives 1 and 2 would be easily implemented. The land use restrictions under
Sediment Alternative 2 could be easily added to the property deed with coordination between EPA and the
city. Sediment Alternative 4 would involve the use of readily available equipment and resources.

8.3.7 Cost

The present worth cost of Sediment Alternative 1 is estimated at $263,000. The present worth cost
of Sediment Alternative 2 is estimated to be $268,000, and the present worth cost of Sediment Alternative
4 is $273,000.

8.3.8 State Acceptance

8.3.9 Community Acceptance

To a larqe extent, the community is supportive of the limited action alternative. Environmental
Council requested EPA to consider the source removal alternative. EPA's response to their request is
included in the Responsiveness Summary.

9.0 THE SEIiECTED REMEDY

Based on the evaluation of the relative performance of each alternative with respect to the nine
evaluation criteria, EPA has determined that the limited action alternatives, Buildinq Alternative 2,
Soil Alternative 2, and Sediment Alternative 2 present the best balance of tradeoffs amonq the
alternatives considered for cleanup of OU2 and OU4 at the Des Moines TCE site. The selected remedies
include placement of land use restrictions on the property and maintenance proqrams desiqned to maintain
the risk reduction achieved durinq the three response actions. Because waste remains at the site, EPA
will conduct a review of the remedies at least once every five years as required by CERCLA.

EPA believes the limited action alternatives satisfy the statutory requirements in CERCLA Section
121 for the protection of human health and the environment; compliance with federal and state
requirements that are legally applicable or relevant and appropriate, and cost-effectiveness.

The main components of the selected remedies include:

• Continued maintenance as called for by the response actions;
• Land use restrictions to prevent residential development;
• Periodic seal coats applied to the asphalt cap; and
• Sampling of soils at the South Pond discharqe area durinq CERCLA periodic reviews.

Each of the three response actions served to reduce the risks to human health and the environment
throuqh either the removal of contaminants from the site or by controllinq the exposure pathways. In the
case of Buildinqs 1-5 and the Maintenance Buildinq, cleanup levels were developed for inhalation (air)
exposures and incidental inqestion and dermal contact soil exposures. These risk-based cleanup levels
are presented on Table 9-1 below.

Followinq the buildinq response action, air monitorinq was conducted to determine compliance with
the cleanup levels. At that time, cleanup levels were not achieved in all of the buildinqs. EPA
requested the Aqency for Toxic Substances and Disease Reqistry (ATSDR) to provide a consultation
reqardinq the protectiveness of the contaminant levels remaininq in the buildinqs. ATSDR concluded that
the contaminant levels remaininq in the buildinqs were within EPA's acceptable carcinoqenic risk ranqe of
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1x10 -4 to 1x10 -6 for occupational workers. ATSDR also recommended that the buildings be routinely
ventilated and that air monitoring be periodically conducted. EPA notified Dico of ATSDR's
recommendations and reguested Dico to revise the Building O&M Plan to include routine house cleaning
measures and ventilation, and the air monitoring. To date, Dico has not made the reguested revisions to
the O&M plan. EPA agrees that the contaminant levels achieved by the removal actions in the buildings do
not present a significant health threat for site workers. Further, EPA believes that reasonable measures
have been taken to clean the building surfaces, and would approve the use of these buildings for
industrial uses. However, the minor additions to the O&M Plan mentioned above would serve to further
reduce the potential risks to site workers.

For the soils beneath the asphalt cap, risk-based cleanup levels were developed for aldrin,
dieldrin, and lead, as these were the main contaminants found above levels of concern. The risk
assessments revealed that a combined aldrin/dieldrin concentration of 1.5 mg/kg yielded a residual cancer
risk of 1x10 -4. EPA generally considers a lead concentration of 1.000 mg/kg to be protective for an
industrial setting. ATSDR was consulted and agreed that these levels would be protective for an
industrial setting. For the soils response action, EPA provided for either the excavation and disposal
of soils in OU2 and OU4 containing aldrin, dieldrin, and lead above these risk-based cleanup levels or
capping of the soils in place. Dico chose the capping alternative. Therefore, residual risks greater
than 1x10 -4 remain at the site, but the exposure pathway has been controlled by the placement of the
asphalt cap. EPA believes the capping action to be protective of human health and the environment
provided the cap is properly maintained, and the site remains an industrial setting.

Table 9-1
Building Removal Action Cleanup Levels

Soil Air

aldrin 1x10 -6 mg/m -3
dieldrin 1.5 mg/kg 1x10 -6 mg/m -3
heptachlor Note 1 3x10 -6 mg/m -3
chlordane 18 mg/kg 1x10 -5 mg/m -3
2,4-D Note 1 5x10 -3 mg/m -3
2,4,5-T Note 1 5x10 -3 mg/m -3
2,3,7,8-TCDD Note 1 1x10 -10 mg/m -3

Notes:
1. Cleanup levels for these constituents were not developed because these constituents were not found
in soils around the subject buildings above a level that presented an unacceptable risk for an
industrial use setting.

For the soils and sediments in the South Pond Area, risk-based cleanup levels were developed for
the primary contaminants of concern, aldrin, dieldrin, and chlordane. Levels which represent a 1x10 -4
risk include a combined aldrin/dieldrin concentration of 1.5 mg/kg and a chlordane concentration of 18.0
mg/kg. The South Pond Area response action calls for excavation and offsite disposal of soils and
sediments containing aldrin, dieldrin, and chlordane above these risk-based levels. As mentioned above,
these risk-based levels are based upon an industrial setting, and would not be protective for a
residential setting. For this reason, the land use restrictions called for by the selected remedies are
essential to ensure protection of human health and the environment.

Detailed cost estimates were prepared during the FS and are summarized here in Table 9-2. A
significant portion of the cost of the selected remedies is the cost of O&M. These costs reflect the
level of effort involved in conducting the monthly and annual inspections and preparing the inspection
reports. The present worth costs reflect a thirty year life of the remedy.
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TABIiE 9-2
Cost Summary for the Selected Remedies

Estimated Cost
Building Alternative 2:

Capital costs $5,000
Average annual O&M costs $41.240
Present Worth $602,000

Soil Alternative 2:

Capital costs $5,000
Average annual O&M costs $93,050
Present Worth $1,372,000

Sediment Alternative 2 :

Capital costs $5,000
Average annual O&M costs $21,850
Present Worth $272,000

Total OU2/OU4 Remedy:

Capital costs $15,000
Average annual O&M costs $156,140
Present Worth $2,246,000

10.0 STATUTORY DETERMINATIONS

EPA's selected remedial actions for CERCLA sites must meet several reguirements set forth in
Section 121 of CERCLA. These reguirements include the following:

• Be protective of human health and the environment;
• Comply with ARARs or justify an ARAR waiver;
• Be cost-effective;
• Utilize permanent solutions and alternate treatment technologies or resource recovery
technologies to the maximum extent practicable; and
• Satisfy the preference for treatment that reduces the toxicity, mobility, or volume as a
principal element. OR provide an explanation as to why this preference is not satisfied.

The sections below discuss how the selected remedies meet the statutory reguirements.

10.1 Protection of Human Health and the Environment

The three response actions conducted in OU2 and OU4 provided a high degree of protectiveness by
removing contaminated material from the site or by controlling the exposure pathways. The selected
remedial actions will enhance the protection of human health and the environment achieved during the
response actions by maintaining control of the exposure pathways and restricting land use to industrial
activities. EPA recognizes that the selected remedy would not provide for the protection of human health
and the environment if the site were to be developed as residential property. In the event that the site
is developed for a residential setting, further remedial action will be considered by EPA.

10.2 Compliance with ARARs

The actions included in the selected remedy will comply with all identified ARARs. For the
Building Alternative 2. no ARARs were identified. For the Soil Alternative 2 and Sediment Alternative 2,
applicable reguirements include the Executive Order on Protection of Wetlands and the Floodplain
Management Executive Order. In addition, the OSWER guidance on Considering Wetlands at Superfund Sites
is a TBC. The selected remedial alternatives would comply with these reguirements because no action
would be taken that would damage the wetland or floodplain.
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10. 3 Cost Effectiveness

EPA believes that the selected remedy provides the highest degree of protectiveness in proportion
with its estimated cost. The no action alternatives, including continued maintenance of the response
actions, are almost as costly as the selected alternatives, but do not provide adeguate protection of
human health and the environment.

10.4 Utilization of Permanent Solutions and Alternative Treatment Technologies or Resource Recovery
Technologies to the Maximum Extent Practicable.

The selected remedy utilizes permanent solutions to the maximum extent practicable. Cleanup
actions already performed as part of the OU4 removal actions removed the soils most highly contaminated
with pesticides and herbicides for off-site disposal. EPA evaluated alternatives involving excavation
and offsite disposal of additional pesticide and herbicide contaminated soils, but found those
alternatives did not provide an appreciably higher degree of protectiveness than the capping alternative
so long as the cap is properly maintained. Given the risk reduction achieved by the response actions,
the extent of response considered to be practicable is limited to maintenance of the response actions and
land use restrictions to prevent residential development. An alternative treatment technology, in-situ
vapor stripping, was evaluated in a treatability study for potential application to the VOC contamination
in OU2. The study was conducted prior to the placement of the asphalt cap and concluded that vapor
stripping is not an effective treatment option for the OU2 soils.

10.5 Preference for Treatment as a Principal Element

The selected remedy does not meet this preference. As discussed above, the response actions have
reduced risks posed by OU2 and OU4, and provide for the protection of human health and the environment
for an industrial setting, provided the response actions are properly maintained. The selected remedy
provides for the necessary maintenance activities as well as land use restrictions to maintain industrial
use of the property. Remedial actions involving treatment as a principal element were evaluated in the
early stages of the FS, but were not carried forward for detailed evaluation because such alternatives
did not provide an appreciably of protectiveness, and were not cost effective.
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RESPONSIVENESS SUMMARY

Des Moines TCE Site
Operable Units 2 and 4

The purpose of the responsiveness summary is to provide EPA's response to comments received on the
proposed plan during the public comment period. The public comment period on the preferred remedial
alternatives began June 3, 1996 and ended July 5, 1996. A public meeting was held in Des Moines, Iowa on
June 11, 1996 at the Des Moines City Library. All guestions and comments received during the public
meeting were addressed at the meeting.

Written comments were received during the public comment period from the Iowa Environmental
Council and the Dichem Customer Group. Copies of the comment letters are included in the administrative
record. The discussion below provides a summary of each comment received followed by EPA's response.

Iowa Environmental Council

Comment: What is the rationale for the thirty year maintenance period of the proposed remedy
considering the concentrations of the contaminants at the site and their persistence in the environment?

Response: The thirty year maintenance period is used for calculating the present worth cost of the
remedial alternatives, and does not necessarily represent the actual duration of the remedy. EPA
guidance suggests that when calculating the present worth cost of alternatives, the period of performance
should not exceed thirty years. Maintenance activities to ensure the integrity of the previous response
actions at the site could continue beyond thirty years to ensure continued protection of the public
health and the environment.

Comment: How are the recommended maintenance actions justified considering the persistence of the
contaminants, the location of the site in the center of Des Moines, and the close proximity of the site
to the water treatment plant serving the metropolitan area?

Response: In the consideration of remedial alternatives, EPA must consider several factors including,
but not limited to, protectiveness of human health and the environment, implementability, and cost. EPA
agrees that the contaminants present at the site are persistent in the environment, but the previous
response actions served to eliminate the exposure pathways. EPA believes that the control of exposure
pathways will be an effective way to protect human health and the environment provided that certain
maintenance activities are conducted. EPA has considered alternatives calling for removal of
contaminated soils and building materials. While these alternatives provide an advantage in terms of a
more permanent solution, they were not selected due to high cost and implementability concerns.

The site is located in an industrial area south of downtown Des Moines, and is bordered to the
west and south by the Raccoon River. Given that the city plans to maintain an industrial zoning for the
Dico property, and the remedy includes land-use restrictions, the maintenance alternative with periodic
reviews by EPA is considered an appropriate remedial approach.

Regarding the close proximity of the site to the Des Moines Water Works, a groundwater extraction
and treatment system has been operating successfully for several years and prevents contaminated
groundwater from entering the city's water supply source. In addition, the pesticides remaining in the
site soils, while being persistent in the environment, have a tendency to adhere to soil and do not
readily migrate into the groundwater. Further, the placement of the asphalt cap prevents groundwater
infiltration from occurring. The presence of aldrin, dieldrin, and chlordane in the soils of OU2 and OU4
do not present a threat to the groundwater in the area.

Comment: Are the seals on the walls and floors of the buildings going to be maintained forever? Does
the maintenance option adeguately protect the public from exposure to PCBS in case of a fire in the
buildings?

Response: The limited action alternative calls for maintenance of the coatings applied to the walls and
floors of the Dico buildings for as long as the contaminants remain above health-based levels. The
maintenance plan calls for periodic inspection and repairs as necessary under normal operating
conditions. Any time the integrity of the encapsulation actions is compromised, repairs will be reguired
to prevent exposure.

Comment: The asphalt cap must remain in place to prevent exposure and must be maintained for more than
thirty years to protect public health. The maintenance of the cap will prevent development of the site
for public use and will preclude any development activity reguiring excavation of site soils.
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Response: EPA agrees that the cap must remain in place and be properly maintained to provide the
necessary protection of public health and the environment. Maintenance activities will continue as
appropriate to assure protection of public health and the environment, and could continue beyond thirty
years. The presence of contaminants remaining at the site necessitates land-use restrictions to prevent
development of the site for public uses. EPA anticipates that the site will continue to be used for
industrial purposes. Activities reguiring excavation could be allowed with careful coordination regarding
the area of excavation and any applicable disposal reguirements.

Comment: The recommended alternative calls for monitoring of the South Pond outfall, but does not
assure that contaminated sediments in the pond will not wash out of the pond during a high rain fall
event.

Response: The purpose of sampling at the outfall of the pond is to determine whether contaminated
sediments have washed out of the pond and recontaminated the east drainage ditch. EPA does not expect
recontamination to occur under ordinary conditions, but recognizes that recontamination could occur as a
result of an exceptionally high rainfall. If the ditch becomes recontaminated, additional response
actions will be considered as appropriate.

Comment: Land use restrictions could have a significant economic impact on the future growth and
development of the city of Des Moines. Given the impact on the city, the cost differential between the
cap maintenance and soil removal alternatives is not that great.

Response: Over the past few years, EPA has closely coordinated its efforts and response actions at the
site with the city. In addition, EPA has discussed the future use of the Dico property with the city to
assure that future uses of the property do not adversely impact the city. In 1989, as part of the city's
Riverpoint Urban Renewal Plan, a portion of the site was designated as high density residential.
However, the city council approved an amendment in January, 1995 which revised the classification to
industrial. The city did not indicate to EPA concern about economic impact due to this revision.

A comparison of the cost differential between the cap maintenance and soil removal alternatives
and the economic impact on the city cannot be made because the economic impact on the city is unknown.
One could claim that restricting the property to industrial use carries a higher potential for jobs which
would have a positive economic impact on the city. The higher cost of the soil removal alternative can
not currently be justified given that the most reasonably anticipated land use for this site is
industrial.

Comment: The acute toxicity of chlordane is increased in the presence of aldrin and dieldrin.

Response: EPA's current risk assessment methodology does not account for synergistic effects or
antagonistic effects (the decreased toxicity in the presence of other compounds). Rather, EPA considers
the effects of multiple contaminants to be additive, which is a conservative approach.

Comment: Reconsider the cost effectiveness of the source removal alternatives in light of the
persistence of the contaminants and the risk of exposure to the public associated with the maintenance
alternatives.

Response: EPA does not believe the additional cost of the source removal alternatives is justified
given the most reasonably anticipated future land use is industrial. For an industrial exposure
scenario, the previous response actions have either reduced the health risks to within EPA's acceptable
range or have effectively eliminated the exposure pathway. For a site which is most likely to remain
industrial, EPA can not justify additional remedial measures beyond the maintenance of the existing
actions. EPA agrees that the effectiveness of the remedy in protecting public health is dependent upon
the success of the maintenance program. If proper maintenance is not conducted, EPA will reconsider
remedial alternatives. In addition, EPA is reguired to conduct reviews at least every five years
whenever contaminants remain at a site. During these reviews, EPA will assess the effectiveness of the
maintenance programs and the protectiveness of the remedy. If EPA finds that the remedy is not
adeguately protecting public health and the environment, additional response actions will be considered.
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Dichem Customer Group

Comment: What is the basis of the thirty year period of operation of the proposed remedy?

Response: The thirty year period is used for calculating the present worth cost of the remedial
alternatives, and does not necessarily represent the actual duration of the remedy. Maintenance
activities to ensure the integrity of the previous response actions at the site could continue beyond
thirty years.
Comment: Long term monitoring of the sediments at the South Pond outfall is not necessary.

Response: Some degree of long term monitoring is reguired by CERCLA for actions which involve
contaminants remaining at the site. For such actions, the NCP reguires EPA to conduct a review of the
adeguacy of the remedy in protecting public health and the environment. These reviews are conducted at
least every, five years. EPA has revised the selected remedy to include sampling at the South Pond
outfall during the periodic reviews instead of annual sampling included in the proposed plan.
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Appendix A

TABLE 2-16

FINAL CONSTITUENTS OF INTEREST IN SITE MEDIA
SOUTH AREA SOURCE CONTROL SITE
MOINES, IOWA
Constituent
Surficial
Soils
Deep
Auger
Borings
Surface
Water
Acetone
Aldrin
Arsenic
Barium
Beryllium
Cadmium
Chlordane (alpha and gamma)
* Chromium (III) c
Chromium (VI) c
^Copper
M,4 '-DDD
1,2-Dichloroethene (cis) d
1,2-Dichloroethene (trans) <
Dieldrin
Heptachlor
*Lead (inorganic)
Manganese
Nickel
*Tetrachloroethene
^Toluene
Trichloroethene
Vanadium
Vi nyl Chiori de
*Xylenes (total)
Zinc
a An "X1 indicates that the parameter has been retained as a constituent of interest in the specified media.
b Toxicity values for alpha and gamma chlordans, were not available in IRIS or HEAST; therefore the generic
constituent of interest 15 chlordane.
c Parameter measured only as chromium. A range of risks will be determined to include both isomers.
d parameter measured as 1,2-dichloroethene (total). A range of risks will be determined to include both
isomers.
* Indicates constituents added after concentration-toxicity screen based upon previous use at site and
prevalence in site media.
-------
Appendix B

Constituents of Interest
Buildings 1-5 and the Maintenance Building

Aldrin

Dieldrin

Endrin ketone

4,4-DDD

4,4-DDT

2,4-D

2,4,5-T

Heptachlor

Chlordane

2,3,7,8-TCDD

PCBs
-------
Appendix C
South Pond Area Data
With Exposure Point Concentrations
For Current and Future Exposures
Focused OU4 Risk Assessment
Location
Depth
Surface
Soil
3S101-110
Mean
95% UCL
Exposure
Maximum Point
Concent- Concert-
ration ration
Analyte (all in PPM)
Pesticides
celta-BHC
4.4'-DDD
4.4'-DDE
4.4'-DDT
Aldrin
alpha-Chiordane
gamma-Chiordane
Dieldrin
Endosulfan sulfate
Endosultan II
Endrin
Endrin ketone
Heptachlor
Heptachlor epoxide

0
0
0

0
0
0
0
0

0
.00125
.0048
. 0073
. 0029
.0087
0.11
0.1
0.64
00245
00245
02245
.0021
00059
. 0027
40
40
40
40
40
40
40
40
40
20
20
40
40
40
1.
2.
2.
2.
3.
2.
3 .
9.
2.
1.
1.
2 ,
1.
1.
.26E+00
.43E+00
.33E+00
.43E+00
.81E+01
.47E+00
.72E+00
.89E+00
.32E+00
.84E-01
.80E-01
.29E+00
.23E+00
.24E+00
2.
5 .
5 .
5 .
8 .
4 .
7 .
1.
5.
3.
3.
5.
2 ,
2.
. 94E+00
.59E+00
.48E+00
.59E+00
.21E+01
.21E+00
.08E+00
. 62E+01
.48E+00
.78E+01
.74E-01
.45E+00
.91E+00
. 92E+00
4 .OOE+01
7.50E+01
7.50E+O1
7.50E+01
8.20E+02
4. OOE+01
8. OOE+01
1.10E+02
7.50E+01
2.25E+00
2.25E+00
7.50E+01
4.10E+01
4 .OOE+01
2
5
5
5
8
4
7
1
5
3
3
5
2
2
.94E+00
.59E+00
.48E+00
.59E+00
.21E+01
.21E+00
.08E+00
.62E+01
.48E+00
.78E-01
.74E-01
.45E+00
.91E+00
.92E+00
Inorganics
Arsenic
Barium
Berryllium
Cadmium
Chromium
Cobalt
Copper
Cyanide
Lead
Magnesium
Manganese
Mercury
Nickel
Selenium
Vanadium
Zinc
7 .
1.
1.
2 ,
7 i
1.
5.
4 .
6 .
6 .
6.
2.
3 .
1.
4 .
4 .
.18E+00
.97E+02
.01E+00
.04E+00
.84E+01
.07E+01
. 67E+01
.16E-01
.28E+02
.48E+03
.52E+02
.36E-01
.02E+01
.33E+00
.03E+01
.30E+02
9.
3.
1.
3.
1.
1.
7
9 .
1.
8 .
8.
5 .
4 .
2.
7
7 .
.40E+00
.32E+02
.70E+00
.30E+00
.57E+02
.48E+01
.84E+01
. 90E-01
.58E+03
.12E+03
.82E+02
.OOE-01
.30E+01
.OOE+00
.21E+01
.28E+02
9
3
1
3
1
1
7
9
1
8
8
5
4
2
7
7
.40E+00
.32E+02
.70E+00
.30E+00
.57E+02
.48E+01
.84E+01
.90E-01
.58E+03
.12E+03
.82E+02
.OOE-01
.30E+01
.OOE+00
.21E+01
.28E+02
-------
Appendix E
Exposed Soils OU4 Data
With Exposure Point Concentrations
For Current and Future Exposures
OU4 Risk Assessment
Location
Depth

Analyte (all in PPM)
Pesticides
delta-BHC
4.4'-DDD
4.4'-DDE
4.4'-DDT
Aldrin
alpha-Chlordane
gamma-Chlordane
Dieldrin
Endrin ketone
Heptachlor ecoxide

Sediment

SP-B
05-1 0'

Sediment

SP-D
05-1 0'

Surface
Soil
SS111-120

Exposure
Point
Concent-
ration
(Maximum)

0
0

0
0
0

0
.001
0014
0038
0.01
0058
.001
.001
.011
0036
.001
0
0
0
0
0

.
.
.
.
.
0
.
0
.
0
0012
0019
0019
0019
0012
.001
0016
.015
0029
.001
0

0
0
.
0
0
.
0
0

0
.
.
00115
.0011
.0045
00099
.0115
.0047
0.005
.0038
00225
00066
1.
1.
4,
1.
1.
4,
5,
1.
3,
1.
.20E-03
. 85E-03
.50E-03
. OOE-02
. 15E-02
.70E-03
. OOE-03
.50E-02
.50E-03
.OOE-03
-------