United States        Office of
          Environmental Protection   Emergency and
          Agency           Remedial Response
EPA/ROD/R07-92/057
September 1992
SERA    Superfund
          Record of Decision
          Des MoinesTCE ,IA

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NOTICE
The appendices listed in the index that are not found in this document have been removed at the request of
the issuing agency. They contain material which supplement, but adds no further applicable information to
the content of the document. All supplemental material is, however, contained in the administrative record
for this site.

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.
50272-101
REPORT DOCUMENTATION 11. REPORT NO.
PAGE EPA/ROD/R07-92/057
I 2.
3. Recipienfs Accession No.
4. Title and Subtitle
5. Report Date
SUPERFUND RECORD OF DECISION
Des Moines TCE, IA
Second Remedial Action - Final
7. Author(s)
09/18/92
6.
8. Performing Organization Rept No.
9. Performing Orgainization Name and Address
10. ProjecVTask/Work Unit No.
11. Contract(C) or Grant(G) No.
(C)
(G)
12. Sponsoring Organization Name and Address
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C- 20460
13. Type 01 Report & Period Covered
Agency
800/000
14.
15. Supplementary Notes
PB93-964302
16. Abstract (Umit: 200 words)
The Des Moines TCE site is located southwest of downtown Des Moines, PolkCounty, Iowa.
Land use in the area is predominantly industrial and commercial, and part of the site
lies within the floodplain of the Raccoon River. An underground infiltration gallery,
used by the Des Moines Water Works, is located directly south of the site and serves
as a source of public drinking water. EPA site investigations began in the mid-1970's
when chlorinated organic contaminants were detected in the Des Moines public water
supply. Water from the Des Moines Water Works north infiltration gallery was found to
be contaminated with trichloroethylene (TCE), dichloroethylene (DCE) , and vinyl
chloride at levels above accepted drinking water standards. Several businesses that
handled the contaminants of concern are or were located within the site boundaries. A
1986 ROD addressed OU1 and provided for extraction of ground water in the floodplain
of the Raccoon River through recovery wells and treating the water using air
stripping, with discharge to the Raccoon River. This ROD addresses OU3, which
encompasses potential sources of ground water contamination in an area north of the
Raccoon River, commonly known as the "North Plume." Future RODs will address the
South Area Source Control unit as OU2 to mitigate the release of contamination
(See Attached Page)
17. Document Analysis a. Descriptors
Record of Decision - Des
Second Remedial Action -
Contaminated Media: None
Key Contaminants: None
Moines TCE, IA
Final
b. Identifiers/Open-Ended Terms
c. COSA TI Field/Group
9. Availability Statement
19. Secu rity Class (This Report)
None
21. No. 01 Pages
14
I
20. Security Class (This Page)
Nnnp
22. Price
(See ANSI-Z39.18)
See Instructions 0" Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department 01 Commerce

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EPA/ROD/R07-92/057
Des Moines TCE, IA
Second Remedial Action - Final
Abstract (Continued)
entering the ground water, the South Pond Drainage Area Source Control unit as OU4 to
address pesticide soil contamination in the southeast portion of the site, as well as
contaminated buildings on the adjacent Dico property. Based on samples taken at
13 ground water monitoring wells installed in OU3 only one of the 13 wells showed
contamination at levels of concern. In general, the contaminant concentrations in that
well have shown a decreasing trend in the last five sampling rounds. No specific source
of contamination in this well was found during EPA'S investigation of OU3.
The selected remedial action for OU3 includes no action with periodic groundwater
monitoring. Ground water from the OU3 area will continue to be captured and treated by
the OUI extraction and treatment system. There are no present worth costs associated
with this no action remedy.
PERFORMANCE STANDARDS OR GOALS:
Not applicable.

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RECORD OF DECISION
DECLARATION
REMEDIAL ALTERNATIVE SELECTION
SITE NAME AND LOCATION
Des Moines TCE Site, Operable Unit Three - North Plume
Des Moines, Iowa
STATEMENT OF BASIS AND PURPOSE
This decision document presents the selected remedial
alternative for Operable unit 3 of the Des Moines TCE Site in Des
Moines, Iowa. The Operable Unit remedy was 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) 42 U.S.C.
section 9601 et seq., and, to the extent practicable, the
National Oil and Hazardous Substances Pollution Contingency Plan
(NCP) 40 C.F.R. Part 300. This decision is based on the
documents and information contained in the Administrative Record
for the site. A copy of the Administrative Record is available
for review in the U.S. Environmental Protection Agency (EPA)
Region VII Docket Room in Kansas City, Kansas and at the Des
Moines Public Library in Des Moines, Iowa.
The State of Iowa concurs on the remedy selected for this
Operable Unit.
DESCRIPTION OF THE SELECTED REMEDY
In consultation with the State of Iowa, EPA has determined
that no remedial action, other than continued monitoring, is
required for Operable Unit 3 of the Des Moines TCE Site at this
time. Ground water samples will be collected and analyzed on a
periodic basis from selected monitoring wells in the Operable
Unit 3 area. The monitoring well network and sampling frequency
will be reassessed after two years of operation. In addition,
this monitoring effort will be evaluated in a five year review.
DECLARATION STATEMENT
EPA conducted a remedial investigation in the Operable unit
3 area from 1988 to 1992. As part of the remedial investigation,
EPA completed a risk assessment which concluded that the hazard
presented to the public by contaminants located within the area
are below a level that requires a remedial action. The
co~taminant levels currently present a carcinogenic risk of 3 x
10 and a noncarcinogenic risk of 0.004 and the contaminant
levels have been shown to be steadily declining.
Because the selected remedy results in hazardous substances,
pollutants or contaminants being left at the site above hea1th-

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based levels, EPA will conduct a review of the continued adequacy
of the selected remedy no less than once every five years as
required by Section 121 of SARA. Analytical data collected from
the ground water monitoring wells will be used in the review to
ensure the selected remedy remains protective of human health and
the environment. These reviews will continue until such time
that monitoring is no longer required.
ris Kay
gional Administrator

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RECORD OF DECISION
DECISION SUMMARY
DES MOINES TCE SITE
OPERABLE UNIT 3
DES MOINES IOWA
Prepared by:
U. S. Environmental Protection Agency
.
Reg10n VII
726 Minnesota Avenue
Kansas City, Kansas 66101
August, 1992

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DECISION SUMMARY
RECORD OF DECISION
DES HOINES TCE SITE
OPERABLE UNIT 3
CONTENTS
section
Paqe
L
site Location and Description
1
2 .
Site History and Enforcement Activity
Highlights of Community Participation
1
3.
4
4.
Scope and Role of Selected Remedy for the
Operable Unit
4
5.
Site Characteristics
6
6.
Summary of Risk
7
7.
Explanation of Significant Changes
I
9
Attachments
Responsiveness Summary
Administrative Record Index

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DECISION SUMMARY
RECORD OF DECISION
DES HOINES TCE SITE
OPERABLE UNIT 3
1. SITE LOCATION AND DESCRIPTION
The Des Moines TCE site is located in the south-central part
of the city of Des Moines, Polk County, Iowa, near the downtown
commercial/industrial section of the city. Because of the
complexity of the Des Moines TCE site, the United States
Environmental Protection Agency (EPA) has divided overall site
cleanup into four discrete actions, referred to as operable
units. Operable Unit I, referred to as the "Protection of Ground
Water" operable unit, addresses those actions necessary to
prevent ground water contamination from entering the Des Moines
Water Work's underground gallery system, which serves as a source
of public drinking water for Des Moines and several surrounding
communities. Operable unit 2, referred to as the "South Area
Source Control" operable unit, addresses those actions which may
be possible to mitigate the release of contaminants entering the
ground water. Operable unit 3, referred to as the "North Plume"
operable unit, addresses possible sources of ground water
contamination north of the Des Moines Water Works and Raccoon
River. Operable unit 4, referred to as the "South Pond/Drainage
Area Source Control" operable unit, has recently been proposed to
address pesticide soil contamination in the southeast portion of
the Des Moines TCE site and contaminated buildings on the Dico
property.
This Record of Decision selects the remedial alternative for
Operable unit 3. Operable Unit 3 encompasses an area north of
the Raccoon River, commonly referred to by EPA as the "North
Plume", approximately bounded by 16th and 24th Streets on the
east and west, High Street on the north, and the Des Moines Water
Works on the south. Operable Unit 3 includes uplands above the
Raccoon River and extends onto the flood plain of the Raccoon
River. The area is zoned commercial/industrial and includes
several small businesses and light industrial facilities. The
Des Moines Water Works is located south of the Operable unit 3
area in the flood plain of the Raccoon River. Figure 1 shows the
approximate boundary of Operable Unit 3 and its relationship to
Dico and the Des Moines Water Works.
2. SITE HISTORY AND ENFORCEMENT ACTIVITIES
EPA began investigating the Des Moines TCE site in the mid-
1970s when chlorinated organic contaminants were detected in the
Des Moines public water supply. Water from the Des Moines Water
Works north ground water infiltration gallery was found to be
1

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contaminated with trichloroethylene (TCE), dichloroethylene
(DCE), and vinyl chloride at levels above accepted drinking water
standards. Extensive investigations were conducted to identify
the source or sources of the contamination entering the public
drinking water supply through the north infiltration gallery.
These investigations culminated in a remedial investigation
and feasibility study (RIjFS) for what is now referred to as
Operable unit 1. In 1986, EPA signed a Record of Decision (ROD)
for Operable Unit 1, selecting an operable unit remedial action
to prevent ground water contamination from entering the Des
Moines Water Works' underground gallery system. The remedial
action included capture and extraction of contaminated ground
water by recovery wells, treatment of the recovered ground water,
and an extensive ground water monitoring program to verify the
effectiveness of the ground water capture system. This remedial
action was placed into operation in December 1987 and continues
in operation at this time.
While Operable Unit 1 has successfully mitigated entry of
contaminated ground water into the Des Moines Water Works
underground gallery system, it did not address the sources of
this contamination. EPA designed Operable Unit 2 to identify and
remedy the sources of the VOC ground water contamination located
on the Dico property. An RI has been performed and the FS is
currently under development for Operable unit 2. Operable Unit 4
will deal with the contaminated buildings and related drainage
areas on the Dico property.
In March 1988, the Operable Unit 1 ground water monitoring
program identified contaminated ground water entering the
recovery system from the north or west of the recovery system, in
addition to from the east towards the Dico property. In
September 1988, EPA initiated the Operable Unit 3 remedial
investigation to determine the nature and extent and identify
potential sources of this ground water contamination. This
investigation consisted of soil gas surveys, subsurface soil
sampling and analysis, installation of ground water monitoring
wells, and collection and analysis of ground water samples.
Results of the investigation are detailed in the "Remedial
Investigation Report, Des Moines TCE Operable unit 3, April
1992". This document and other relevant information obtained
from the RI are contained in the Operable unit 3 Administrative
Record.
In general, the Operable Unit 3 investigation found that
TCE, trichloroethane (TCA), tetrachloroethylene (PCE), and DCE
are present at low concentrations at isolated locations within
the study area. EPA performed a potentially responsible party
search in the Operable Unit 3 area and determined that several
businesses are or were located within the site boundaries that
handled the contaminants of concern. However, specific sources
3

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of these contaminants were not found during the investigation
performed in the area.
3. HIGHLIGHTS OF COMMUNITY PARTICIPATION
EPA opened the public comment period for the Proposed Plan
on July 6, 1992 with a notice published in the Des Moines
Register. Fact sheets which highlighted site activities and the
proposed remedy and indicated the public hearing date were mailed
to 254 individuals and 30 media companies who had expressed
interest in the site in the past. These fact sheets were mailed
by EPA on July 9, 1992.
EPA held a public hearing on July 23, 1992 at the Wallace
State Office Building in Des Moines to discuss the proposed
remedy with the public. Comments were solicited by EPA from the
public at the hearing. Only two comments and/or questions were
received by EPA during the hearing. A summary of these comments
and EPA's response to them are included in the Responsiveness
Summary attached to this Record of Decision.
The public comment period closed on August 4, 1992. No
comments were received by EPA during the comment period other
than those received during the !hearing on July 23.

4. SCOPE AND ROLE OF SELECTED REMEDY FOR THE OPERABLE UNIT
Operable unit 3 was designed to extend the existing
monitoring system, to assure protection of the Des Moines water
supply, and to investigate the extent and potential source(s) of
contamination detected in the Operable unit 1 northern monitoring
wells. The current investigation has been completed. This
Record of Decision was prepared to present the Agency's selected
alternative for Operable Unit 3.
EPA has selected a No Action Alternative for Operable unit 3
of the Des Moines TCE site. The Operable Unit 3 area includes
the contamination that remains in the general vicinity north of
the Raccoon River within boundaries previously described. Ground
water contamination that enters the alluvial setting, in general
in the south and east portion of Operable Unit 3, and originating
from the Operable Unit 3 study area, will continue to be captured
and treated by the Operable Unit 1 active ground water extraction
and treatment system. This system currently includes a network
of six ground water extraction wells' and an air stripper/ground
water treatment system. The extraction wells in operation and
located at the northern edge of the Dico property have provided
the principal withdrawal point for the contamination originating
in the direction to the north, in the vicinity of Operable Unit
3.
4

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since the startup of the Operable unit 1 system, much lower
levels of contamination have been detected in the alluvium and
northern portion of Operable Unit 1. Though these low levels
continue to be evident, the Operable unit 1 system continues to
successfully capture and treat the contamination.
The selected remedy provides for long term operation and
maintenance (O&M) that will consist of periodic monitoring of the
ground water. Selected wells installed as part of the Operable
Unit 3 investigation will be monitored on a periodic basis
(sampled once every six months) to ensure protection of the Des
Moines public water supply. The wells also will be monitored to
confirm that the ground water flow pattern continues in a manner
as described by this investigation and the available technical
literature. The monitoring schedule and the number of wells
monitored will be evaluated after two years to assess the
adequacy of the monitoring program.

In addition, the remedial action for operable Unit 1 will be
evaluated on an annual basis (as required in the ROD for Operable
Unit 1) to assess the performance of the ongoing ground water
extraction and treatment system and its effectiveness in
capturing the contaminated ground water.
A five year review of the {proposed action will be conducted
to ensure that the selected alternative is effective and
accomplishes the goals as stated. The five year review will
include an assessment of the ground water monitoring information
and a review of the institutional controls restricting ground
water use in the Operable Unit 3 area. The county's ordinance
prohibiting usage of ground water for drinking water purposes in
the area supplied by the city public water supply and the city's
enforcement of the ordnance will be assessed. This review will
be conducted in accordance with CERCLA, as amended, and
applicable guidance and in a manner to assure the continued
protection of the public health and environment. A five year
review is required at sites where contamination remains above
health based criteria.
5. SITE CHARACTERISTICS
The Operable Unit 3 area is located in a commercial and
industrial area of Des Moines, which does not include any
residential dwellings.
Topographically the Operable Unit 3 area consists of gently
rolling hills that generally slope to the south and southeast
toward the Raccoon River. Ground surface elevations range from a
high of approximately 950 feet (above mean sea level) in the
northwest portion of the Operable Unit 3 area to a low of
approximately 800 feet along the Raccoon River. On the western
5

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half of the site, the uplands are separated from the Raccoon
River by relatively steep bluffs. The southeastern portion of
the area consists of relatively flat topography 10 to 20 feet
above the elevation of the Raccoon River.
The geologic setting for the site combines lowland flood
plain, glacio-fluvial (alluvial) deposits, and upland glacial
till deposits. These surficial deposits overlay shale,
siltstone, and sandstone bedrock. The alluvial flood plain
deposits beneath the Raccoon River consist of approximately 30
feet of highly permeable sand and gravel, and represent a major
source of water to the Des Moines metropolitan area.
The upland till deposits consist of approximately 60 feet of
unsorted and nonstratified clays, silts, sands, and gravels.
Sand and gravel deposits in the till generally consist of
discontinuous and isolated lenses. The silts and clays in the
till generally have low permeability and tend to inhibit ground
water movement. The majority of Operable Unit 3 lies on the
upland till deposits.

Ground water flow in the upland glacial till deposits is
erratic due to the discontinuity of the sand and gravel layers.
These layers form localized preferential flow zones due to their
highly permeable nature. However they are generally isolated by
relatively impermeable silts and clays which inhibit the ground
water flow. Ground water flow in the upland is difficult to
characterize due to the highly heterogeneous nature of the
glacial till, but is generally to the east and southeast toward
the Raccoon River flood plain. The flow direction is primarily a
result of the elevational difference between the uplands and the
flood plain. The ground water flow velocity in the uplands is
also observed to be relatively slow through the glacial deposits
as a whole. Ground water flow through the alluvium in the flood
plain is relatively rapid and to the east along the flow path of
the river.
In addition, the Ingersol stream channel, which in the past
ran through the area, potentially controls the direction of
ground water flow. The low lying area near this channel was
filled in over the years, and in the early 1900's provided the
general location for the city-constructed Ingersol Run storm
sewer. Upon completion, this combined sanitary/storm sewer
directed drainage and flow toward the Raccoon River in the
vicinity of the Dico, Inc. property. Flow from this sewer
historically was directed to the surface after passing under the
railroad tracks located and running under Fleur Drive Bridge.
This drainage then passed through the Dico property running due
south, on its way to the Raccoon River.
The hydraulic connection between ground water in the upland
till deposits and the flood plain deposits appears to be limited.
6

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River elevation and ground water elevation data were collected
during the remedial investigation. This data indicates similar
trends in elevation changes of the river and ground water due to
precipitation, but they are not identical. This indicates that
the ground water in the upland area and river are not in direct
communication. Ground water in the upland till occurs under
perched conditions and discharges slowly to the alluvium.
Historic maps obtained from the City during the remedial
investigation shows the Ingersol Run, which has been filled, and
the Ingersol Run storm sewer are situated such that they may
create a preferential flow path which would discharge ground
water from the uplands to the alluvium in the vicinity of Fleur
Drive. In general, ground water flowing from the Operable Unit 3
study area uplands will discharge to the alluvium in the vicinity
of Fleur Drive, via the filled Ingersol Run and the Ingersol Run
storm sewer, and be captured and treated by the extraction system
on the Dico property.
Soil gas surveys and subsurface soil sampling conducted by
EPA in 1988 and 1991, indicate that isolated locations of
contaminants exist in the Operable unit 3 area. These locations
contain low levels of TCE, TCA, and DCE. As a result of these
studies, EPA installed 13 ground water monitoring wells in the
Operable unit 3 area and has conducted 12 rounds of ground water
sampling. Only one of these 13 wells, MW-35, has consistently
shown TCE, DCE, and PCE at levels of potential concern. MW-35 is
a shallow well, approximately 26 feet deep, installed in a sand
lense in the upland glacial till. Since september, 1989,
contaminant concentrations in MW-35 have been sporadic and range
from 22 to 100 micrograms per liter (ug/l) TCE, 11 to 59 ug/l
DCE, and 21 to 350 ug/l PCE. In general, the contaminant
concentrations in MW-35 have shown a decreasing trend for the
last five sampling rounds (since September 1990). Analytical
result for MW-35 samples collected in April 1992 indicate the
well contained 6.7 ug/l TCE, 3.5 ug/l DCE, and 25 ug/l PCE at
that time. The data indicates that the level of TCE is
decreasing in this area.
6. SUMMARY OF SITE RISKS
In conjunction with the Operable Unit 3 remedial
investigation, EPA conducted a risk assessment to evaluate the
risks to human health and the environment that could result from
exposure to contamination in the Operable Unit 3 area. The risk
assessment was prepared using actual Operable unit 3 data and
assumptions made regarding maximum exposures that could be
reasonably expected to occur for an individual at or near the
site. This exposure is defined as the Reasonable Maximum
Exposure (RME), and the person most likely to be exposed to
contaminants at Operable Unit 3 is defined as the RME individual.
The RME individual is used as a reference point in the risk
assessment process to help determine what health related risks
7

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are presented by the site. The risk assessment conducted for
Operable Unit 3 is presented in the Remedial Investigation
Report.
For purposes of the Operable unit 3 risk assessment, EPA
cortsidered the RME individual to be a construction or maintenance
worker who periodically performs activities involving soil
excavation in the Operable Unit 3 area. The RME individual would
be exposed on a periodic and limited basis to contaminated soils
and soil vapors. The additive carcinogenic risk for the RME
individual based upon accidental ingestion of contaminated soil,
dermal contact with contaminated soil, and inhalation of soil
vapors is less than 3 additional cancer cases per 1,000,000
exposed individuals. The additive noncarcinogenic hazard index
for the RME individual was calculated to be .004. When
evaluating the risk resulting from exposure to hazardous
substances for people at or near a Superfund site, EPA considers
the exposure to be unacceptable if it results in a carcinogenic
risk greater than one additional case of cancer for every 10,000
people exposed or a noncarcinogenic hazard index greater than 1.
Thus, the risk posed to the RME individual of 3 cases per
1,000,000 exposed people and the hazard index of .004 falls
within an acceptable risk range.

EPA considered the possib1lity of exposure to hazardous
substances via consumption of contaminated drinking water. EPA
found that the ground water within the Operable Unit 3 area is
not used for public consumption. Also, construction of private
water supply wells within the area of Operable unit 3 is
prohibited by a county ordinance which prohibits construction of
private water supply wells in an area which has access to a
public water supply. Thus, EPA concluded that no risk is
currently presented through consumption of contaminated ground
water.
Exposure to contaminants at Operable Unit 3 for people
living in the area (a residential exposure scenario) was
considered but dismissed because no residences are currently
located within the Operable Unit 3 area. Future residential
development of the area is considered unlikely because of the
commercial and industrial nature of current land use. Therefore,
a future residential exposure scenario was not included in the
risk calculations.
Thus, EPA found that no unacceptable risks are presented by
contaminants in the Operable Unit 3 area.
An ecological risk assessment was not considered necessary
by EPA. The likelihood of exposure to the contaminants by fauna
or endangered species at the site was considered negligible,
given that the entire site is located within an urban
environment. In addition, given that the risk to human health is
8

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within an acceptable range, risk to fauna that may be present at
the site is also believed to be acceptable.
7. EXPLANATION OF SIGNIFICANT CHANGES
The remedy selected and detailed in this Record of Decision
is the same as the remedy described in the Proposed Plan released
for public review and comment on July 6, 1992. No changes have
been made to the alternative.
9

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