United States
Environmental Protection
Agency
Office of
Emergency and
Remedial Response
EPA/ROD/R07-86/005
July 1986
Superfund
Record of Decision
Des Moines TCE, IA
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~
'"\
TECHNICAL REPORT DATA_-
(PittUt ntld 'nslNctions on the nllme be/on com"letin,J -. -
1. REPOAT NO. 12. 3. RECIPIENT'S ACCESSION"NO.
EPA/ROD/R07-86/005
.. TITL.E AND SU8TITL.E 5. REPORT DATE
SUPERFUND RECORD OF DECIS ION July 21, 1986
Des Moines TCE 6. PERFORMING ORGANIZATION CODE
7. AUTHORCS) 8. PERFORMING ORGANIZATION REPORT NO.
e. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM EL.EMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
U.S. Environmental Protection Agency Final ROD ~<>nnrt
401 M Street, S.W. 1.. SPONSORING AGENCY COOE
Washington, D.C. 20460 800/00
15. SUPPL.EMENTARV NOTES
16. ABSTRACT
The Des Moines TCE site, in the flood plain of the Raccoon River, is located just _.
southwest of downtown Des Moines, Polk County, Iowa, near where Fleur Drive crosses the
Raccoon River. The area has industrial/commercial use and recreational parkland use. A
major feature of the site is the underground infiltration gallery used by the Des Moines
Water Works (DMWW) as a source of the public water supply. The site was discovered in
1984 after trichloroethylene (TeE) was detected in the city's public water supply. The
Dico Company, operating since at least 1961, disposed of an unknown quantity of oily
waste sludge containing TCE onto their parking lot for dust control and into a drainage
ditch on their property. Two other businesses that used TCE have operated on the site
area in the past, one an aircraft parts manufacturer and the other a printing company.
However, the major source of ground water contamination is the soil at the Dico
Prope r ty . Most of the area east of the Raccoon River has been filled to raise the land
above flood Ie ve 1. Contaminants may have been disposed in those areas along with fill
mater ial. Migration has caused contaminated ground water to flow into the underground
infiltration gallery system. The primary contaminants of concern include: TCE, PCE,
1,2-dichloroethane, vinyl chloride.
The selected remedial action for this site includes: extraction wells to collect the
contaminated ground water: isolation of the northern-most section of the north gallery:
(See Attached Sheet)
17. KEY WORDS ANO DOCUMENT ANAl. YSIS
a. DESCRIPTORS b.IOENTIFIERS/OPEN ENDED TERMS C. COSA TI Field/Group
Record of Decision
Des Moines TCE
Contaminated Media: gw, soil
Key contaminants.: VOCs, TCEs, sludges
18. DISTRIBUTION STATEMENT 19. SECURITV CL.ASS ITilis Reportl 21. NO. OF PAGES
None «;?
20. SECURITY CL.ASS IT/lis pagel 22. PRtCE
None I
!PA '0'''' 2220-1 (Rev. .-77)
PIIIEVIOUS EDITION IS OISSOLETE
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EPA/ROD/R07-86/005
Des Moines TCE
16.
ABSTRACT (continued)
treatment of the ground water through air stripping to remove 96 percent of
the TCE; discharge of the treated water to the Raccoon River; operation of
the west extraction wells until established effluent levels are achieved for
four consecutive months. The capital cost for the selected remedial
alternative is estimated to be $1,196,000. The estimated annual cost of O&M
is $63,000. Since this is an operable unit, the duration of operation of
this response action will be dependent on the final response action selected.
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.
Record of Decision
Remedial Alternative Selection
SITE
Des Moines TCE
Des Moines, Polk County, Iowa
DOCUMENTS REVIEWED
I am basing my decision primarily on the following documents describing
the analysis of cost-effectiveness of remedial alternatives for the Des Moines
TCE site:
o Des Moines TCE Remedial Investigation Report, December 1985
o Des Moines TCE Operable Unit Feasibility Study Report, April 1986 (Draft)
o Summary of Remedial Alternative Selection
0- Responsiveness Summary
o Administrative Order
.DESCRIPTION OF SELECTED REMEDY
The Selected Remedy for the operable unit for the protection of the
public water supply includes the following major components:
o Extraction wells to collect the contaminated ground water.
o Isolation of the northern~ost section of the north gallery.
o Treatment of the ground water through air stripping to
remove 96 percent of the trichloroethylene (TCE).
o Discharge of the treated water to the Raccoon River.
~ o. Operation of the west extraction wells until well
effluent contains less than 5 micrograms per liter (ug/l)
of TCE for four consecutive months.
o Duration of operation of east extraction wells will be
determined as part of the source' control operable unit.
DECLARATIONS
Consistent with the Comprehensive Environmental Response, Compensation.
and Liability Act of 1980 (CERCLA), and the National Contingency Plan (40 CFR
Part 300, November 20, 1985', I have determined that the above described
remedy at the Des Moines TCE site is a cost-effective remedy that provides
adequate protection of public health, welfare, and the environment. The
above described remedy will be consistent with the permanent remedy. The
action will require future operation and maintenance activities to ensure the
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2
continued effectiveness of the remedy. These operation and maintenace
activities will be considered part of the approved action. I have also
determined that the action being taken is a cost-effective alternative when
compared to the other remedial options reviewed.
The State of Iowa has been consulted and agrees with the approved
remedy. An unilateral administrative order will be issued to one or
more parties for the implementation of this action.
The State, EPA, or Potential Responsible Party will undertake an
additional operable unit feasibility study to evaluate source control.
If additional remedial actions are determined to be necessary, a Record
o( Decision will be prepared for approval of the future remedial action.
'l-2-I-C{b
Date
- ~ /
-' / t; c"
/7 /Nyr" I ~
4na1 dmjnistrator
Attachments:
Summary of Remedial Alternative Selection
Community Relations Responsiveness Summary
Administrative Order
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SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
DES MOINES TCE
CONTENTS
PAGE
Site location and Description
1
Si te Hi story
1
Current Site Status
1
Enforcement
3
Alternatives Evaluation
6
Recanmended Alternative
29
Operation and Maintenance
34
Community Relations
38
Consistency with other Environmental laws
. 39
Schedule
39
F utu re Act ions
39
-..----
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LIST OF FIGURES
FIGURE
PAGE
2
1
2
Des Moines TCE Site Map
Total VOCs in the Ground Water
4
7
3
4
Screening Summary Qf Remedial Technologies
Conceptual layout of Operable Unit Response Action
30
LIST. OF TABLES
TABLE
1
Standards Comparison of Contaminants
Detected in Ground Water
Descriptions of Remedial Alternatives Evaluated
5
9
2
3
Development of Alternatives
Technical Evaluation of Alternatives
10
16
4
5
Summary of Detai1ed~nalysi~.,of Alternatives
25
33
6
7
Surface Water Criteria
Summary of Analysis of the Recommended Alternative
Monitoring Schedule for the Recommended Alternative
35
37
8
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SUMMARY OF REMEDIAL ALTERNATIVE SELECTION
DES MOINES TCE
DES MOINES, POLK COUNTY, IOWA
SITE LOCATION AND DESCRIPTION
The Des Moines TCE site is a plume of volatile organic compounds
(VOCs) in the floodplain of the Raccoon River. The site is located just.
southwest of downtown Des Moines, Polk County, Iowa, near where Fleur Drive
crosses the Raccoon River. The area has industrial/commercial use and
recreational parkland use. A major feature in the site is the underground
infiltration gallery used by the Des Moines Water Works (DMWW) as a source
of the public water supply. The general site area is shown on Figure 1.
The major source to the contaminated ground water is soil containing
VOCs located at the Dico Company, Inc., property at 200 Southwest Sixteenth
Street. There is an other source of the VOC contamination preliminarily
tdentified north of the Dico property and one potentially east of the property.
Existing information indicates that these other sources have less contribution
.of contaminates to the ground water.
SITE HISTORY
The Des Moines TCE site was discovered after trichloroethylene (TCE) was
detected in the public water supply for the City of Des Moines. Numerous
investigations found that the major source of the contaminants was on the
Dico Company property. The company, a subsidiary of the Dyneer Corporation of
Connecticut, is a manufacturer of metal wheels and brakes. The company used
the solvent Tri-C1ene, of which TCE is a primary component, to degrease metal
parts during the manufacturing. The company disposed of the oily waste
sludge containing TCE from the degreasing process onto their'parking lot for
dust control and into a drainage ditch on their property. The company stopped
these practices in 1979. The quantity of wastes disposed of is not currently'
known.
The Dico Company has operated at the site since at least 1961. The
company has reorganized several times since its beginning. The current
company has been in existence since at least 1979. Two other businesses that
used TCE have operated in the site area in the past. One was an aircraft
parts manufacturer and the other was a printing company. Most of the area
east of the Raccoon River has been filled to raise the land above flood
level. Contaminants may have been disposed in those areas along with the
fill material.
CURRENT SITE STATUS
The Des Moines Water Works, which provides drinking water to the
citizens of Des Moines and surrounding communities, has a three-mi1e long
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SITE MAP
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3
underground infiltration gallery system, similar to a horizontal well, in the
alluvium of the Raccoon River. The northern-most portion of the gallery is
in the site area. When the complete gallery is operating, the ground water
flow direction is from the site toward the gallery. This causes contaminated
ground water to flow into the gallery. In April 1984, the use of 'the north
gallery was discontinued due to the contamination. The south gallery usage
is limited because the ground water gradient created by pumping the south gallery
causes the contaminants to move through the north gallery to the south gallery.
Since the OMWW ceased using the north gallery, ground water flow has
returned to its natural flow patterns toward the southeast. This has caused
further migration of the contaminants in the ground water away. from the-site.
The major source' of the ground water contamination is the soi1 at the
Oico property. Soil contamination has been detected down into the saturated
zone around 30 feet below the land surface. The ground water contamination
has been detected down to the bottom of the alluvium, approximately 45 feet
below the surface. The known aerial extent of VOC ground water contamination
is shown on Figure 2. The maximum and mean levels of VOCs detected in the ground
water are shown on Table 1. Table 1 also shows applicable health standards used
for comparison with the concentrations detected. Further information on the
contamination is given in the Remedial Investigation Report.
Some of the health concerns related to the contaminants at the site
include the potential for the VOCs to cause cancer. Vinyl chloride is a
known human carcinogen. TCE, 1,2-dichloroethane and tetrach10rothy1ene are
suspected human carcinogens. TCE can also cause neurological impairment and
liver and kidney damage.
Remediation at this site has been divided into two operable units in order
to more rapidly implement an action to protect and renew use of the public
water supply and to control .further migration of the contaminants. Source control
will be examined following implementation of this operable unit remedy.
ENFORCEMENT
In late December 1985, EPA contacted those persons who now own or had
in the past owned property on which contamination had been found during the
remedial investigation and preceeding investigations. A meeting was held with
those parties in early January 1986 to ascertain their willingness to conduct a
feasibility study and response action at the site. Although none of these parties
was willing to undertake the feasibility study, there was agreement reached that
the EPA would conduct such a feasibility study on an expedited basis. Several
of these parties regularly participated in conference calls held to review
and discuss this feasibility study and offered technical advice and assistance
during that process. Upon completion of the feasibility study, EPA again met
with these parties and extended the invitation to them to implement the response
action. None of these parties was willing to enter into an administrative order
on consent to implement the response action. EPA now anticipates issuance of a
unilateral order to one or more of these parties requiring implementation of the
selected response action.
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TOTAL VOLATILE ORGANIC
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Table 1
STANDARDS COMPARISON OF CONTAMINANTS,
DETECTED IN GROUND WATER
Groundwater Safe Drinking EPA Drinking Water Health Advisories Life-
:
Concentration Water Act I-Day 10-Day Longer Term time
Maxi- 10 kg 10 kg 10 kg 70 kg 70 kg
Chemical mum Mean MCL RMClc Child Ch1ld Child Adult Adult
Trichloroethylene 8.467 338 5b 0
Tetrachloroethylene 72 1.1 -- Og 34.000 1.940 6.800
Trans 1.2-dichloroethylene 2.000 128 70 2.720 2. 720 1.000 3.500 70
1.1-Dichloroethylene 6 0.3 7b 7 1.000 1.000 1.000 3.500 70
Vinyl chloride 95 5 Ib 0 2.600 2.600 13 46
Chloroform 7.3 0.09 100a
1.I-Dichloroethane 9 0.3
1.2-Dichloroethane 2 0.06 5b 0 740 740 740 2.600
1. 1. I-Trichloroethane 6 0.1 200b 200 140.000 35.000 35.000 125.000 200
1.2-Dichloropropane 5 0.1
All values in ug/l
AWQC
Dri nki ng
Watere
2.7
0.8
0.033
2
0.19
0.94
18.400f
a Safe Drinking Water Act (SOWA) Primary Maximum Contaminant level (MCL) - Enforceable drinking water standard.
Total trihalomethanes. .,
b SDWA Proposed Final MCls - Enforceable drinking water standards proposed for volatile organic compounds (VOCs).
c SDWA Final Recommended Maximum Contaminant levels (RMCL) - Nonenforceable health goals for drinking water set
at a level representing "no known or anticipated adverse effects on the health of persons...allows an
adequate margi n of safety. II .
d Health Advisories - Short-term risk assessments for noncarcinogens end points of toxicity. Considered to
be exposure levels which would not result in adverse health effects over a specified short time period ( 1 day.
10 days. longer term).
e Clean Water Act Ambient Water Qualit~ Criteria (AWQC) - Criteria to protect human health frOm ingestion of
contaminated water. Presents the 10- cancer risk unless noted otherwise.
f AWQC for protection from toxic effects of contaminants.
g 5DWA proposed Final RMCl.
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6
ALTERNATIVES EVALUATION
The remedial action objectives of this response action address an
operable unit for the protection and renewed use of the public water supply.
The objectives are to:
o Cost effectively provide a remedial alternative that
effectively mitigates and minimizes threats and provides
adequate protection to the public health from exposure
to contaminated water provided by the OMWW that would be
obtained through operation of the north gallery.
o Control the ground water contaminant migration, and
therefore reduce the threat to the public health by
reducing the area where potential exposure could occur.
To achieve these objectives, several technologies were evaluated for the
containment, collection, treatment, and discharge of the contaminated ground
water. These technologies were screened as required by 40 CFR 300.68(g) to
eliminate those technologies of greater cost that would not provide substan-
tially greater protection, those that were not feasible or reliable for the
site, and those that do not effectively contribute to the protection of the
public health and welfare and the environTIent. The technologies that were
reviewed are listed on Figure 3. As shown on Figure 3, several technologies
were eliminated for various reasons as specified on the figure. The Operable
Unit Feasibility Study (OUFS) Report should be reviewed for further details
on the screening process which was conducted. ~
For the containment of the contaminated ground water, the use of vertical
barriers, horizontal barriers, and gradient controls was examined. Horizontal
barriers were eliminated from further evaluation due to the industrial land use
in the area, decreasing the reliablity of a cap for the site. Use of the north
gallery and extraction wells was examined for collection of the contaminated
water. .~ ..'''''
For the treatment of the ground water, air stripping, carbon adsorption,
and treatment at the Puhlicly Owned Treatment Works (POTW) were reviewed. Both
carbon adsorption and treatment at the POTW were eliminated prior to the detailed
analysis. Carbon adsorption will achieve a high level of contaminant removal,
however the annual operational costs could range from. two million to ten million
dollars while air stripping operational costs could range from $5,000 to $130,000
per year. Carbon adsorption was eliminated because of higher operational costs.
Treatment at the POTW was eliminated because the current POTW facility does not
have the capacity to treat the contaminated water. Biological treatment and
thenmal treatment were both reviewed and eliminated during the screening.
Biological treatment requires more highly concentrated wastes to be efficient.
Thenmal destruction of the contaminants would be effective and reliable, although
it would exceed the cost of air stripping by at least an order of magnitude. Use
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OINIUL 11181'0"1 ACTION
III...DlAL TICHNOLOGY
NO ACTION
NONI
CONTAINMINT
GIIAOIINT CONTIIOL
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YIIITICAL IAAAIIAI
IIITAACTION
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UTAACTION I
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TAIATMINT! -
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TlCHNOLOGY fOUND NOT TO II TlCMNICALLY YIAIU AT 1"1,
"IMIDIATION 08llCTIYI
CONTIIOL -
'''OTICT - CONTA.
WATlIlIUWLY MIGIIATION
.
.
.
.
.
.
.
.
.
..
IVALUATION -.V
Nef IIIOUIIII'I NO ACTION TO II CAIIIIIID THIIOUOH THI OETAILeO ANAL 'III I Of AL TlIlNATlYII
IIILlAILI AND IfflCTlYllN IlIDUClNO THI OUANTITY ANO YILOCITY Of CONTAMINANT MIOAATION.
INITALLATION Of liE LlAIU CAf IIOT AIIUIIIO OUi TO INOUlTIIIAL NATUIII 0' IITI. YIIITICAL MIOIIA TlON Of GIIOUNOWA TEll
CONTAMINANTI OOW_ARO INTO IHALI AOUICLUDI.I HOT A SIGNIFICANT 'IIOILIM AT liTE.
OllAOllNT CONTIIOL IINOI'INOINT 0' 0- O,.IIATIONI - I"IILOWI YIA IIITIIACTION/lNJICTION WILLI II fOJlNTlALLY YIAIU,
IIITIIACTION ",OCIII fOJlNTlALLY YIAIU INCLUDU IIITIIACTION WILLI INlTAllATION Of WlSUllfACI DIIAINS IIIIOT COlT IffECTIYI
IN HIGHLY flIIMIAILI MATEIIIAlI, -- NOIITH GALLIRY CANNOT IE USEO fOil DIUNKIHO WATER If NO TRIATMINT IS 'ROYIOID,
DISCHAIIGI 0' UNTIIIATIO CONT AMINATIO OllOUNOWA TIll TO THI IIACCOON AIYIII WOULD LIKELY IIElUL T IN UCUOANCI Of IUllfACI WATlII
CRITIAIA fOR TCI. ONIITI OU' WILL INJECTION II NOT COlt IffECTlYI ANa II NOT AllOWIO IN IOWA.
OffllTl OU'WILLINJICTION IIIIOT COlT IffECTIYI OUi TO HIOH TIIAN_TATION AND DIIfOIAL CO"I.
IIITIIACTIOfI ",OCI....I fOTiNTIALLY VlAlLI INCLUDE IIITIIACTION WlLU 011 USI Of THI D_IIOIITH OALLlIIY
IIOLOGIC;AL TIIIATMINT AlOUlIIl1 HIGHIII ITIIINOTIt WAITI TO II IffECTIYI.
'HYlICALlCHIMICAL TAIATMINT ",OCIIIU fOTINTIALLY YIAIU INCLUDI AIIIITIII"IIiO
THIRMAL DUTRUCTIOH ",OCIISIIINCLUDINO AOTAIIY KILN. HIOH TEWIIIATUAI fLUID WALL RIACTOA AND fLUIDIZED liD.
ARI HOT lCONOMICAll Y COMfETITIYI WITH OTHIII 'HYIICAUCHEMICAL TAIATMINT 'IIOCISSEI.
OffllTl TAIATMINT AT THI DEI MOINES fOTW IS NOT VIAILI DUE TO INADlOUAU HYDRAULIC CA'ACITY. OffllTl TAIATMENT AT A
RCAA fACILITY .1 NOT CO" IffECTIYE DUE TO HIOH TRANIfORTATION AND TRIATMINT COSTI,
ONIITI,DISCHAROI Of TIIIATIO OllGUNDWATER VIA liE INJECTION INTO AOUlfEII. OISCHARGI TO IIACCOON IIIYIIL
Offll1l OISCHAAOE 0' TAEAUD GAOUNOWATIII, ALTHOUOH TECHNICALLY YIAIU, II NOT NICIIIARY IINCI LlU COITL Y
" ONIITI DISCHARGE II AYAILAILI. '
IIOLOGICAL TA'ATMENT II.OUIAI. _H.II ITllllIOTN "AlT' TO If .ffICTIY., ALID .UfflCl.NT O.MONITIIA JlD fEllfOIlMANCI
II NOT AVAILAlLI.
INIITUGROUNOWATlII fHYIICALlCHIMlCAl TIIIATMINT ffIOCIISEI HAYIIIOT IUN SUfflClINTlY fIIDYIN TO ALLOW IVALUATION,
Of EffECTIVENEII ANa RELIAILITY,
INDIYIOUAL-I TIIIATMINT II NOT TlCHNICALL Y fAACTICU fOA A DIITIIIIUTION IYSTIM AI LAIIOI AI DU MOINU,
.. FIGURE 3
SCREENING SUMMARY OF
REMEDIAL TECHNOLOGIES
DES MOINES TeE
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8
of individual home treatment units was eliminated from further evaluation
because it would not meet the operable unit objectives and would not be
technically practical for a distribution system as large as the one for the DMWW.
Discharge of both treated and untreated water was examined. Onsite
discharge of untreated ground water into the Raccoon River and into a deep
injection well was eliminated because discharge into the river would likely
exceed surface water criteria and deep injection wells are not permitted in
Iowa. Transport of the contaminated water or treated water to an offsite
facility was eliminated because it would not be cost effective due to the high
transportation and disposal costs. Disposal of treated water via di~charge
to the Raccoon River, to the Water Works for use in the water supply, and
reinjection into the alluvial aquifer were examined.
. The remedial action alternatives for the operable unit that were
evaluated in detail, included combinations of the technologies that
remained after the initial screening. These alternatives are shown on
Table 2. As specified in 40 CFR Part 300.68(f), these alternatives included:
(1) alternatives that attain applicable or relevant and appropriate Federal'
public health and environmental requirements, (2) alternatives that exceed
applicable or relevant and appropriate Federal public health, and environmental
requirements, and (3) the no action alternative. Technologies for treatment
or disposal at an offsite facility were also evaluated, but were eliminated
from further review during the initial screening. An alternative that does
not attain applicable OP relevant and appropriate Federal public health and
environmental requirements was not examined because the response action was
needed for the immediate protection of the public health. Table 3 describes
how the technologies and alternatives evaluated meet the requirements of 40 CFR
300.68(f).
As required by 40 CFR 300.68(h), a detailed evaluation was conducted
on each of the alternatives. Each analysis included: . 1) refinement of the
alternative, 2) detailed cost estimation, including operation and maintenance
costs and distribution of cost overtime, 3) evaluation in terms of engineering
implementation, reliability, and constructability, 4) an assessment of the
extent to which the alternative is expected to effectively prevent, mitigate,
or minimize threats to and provide adequate protection to public health and
welfare and the environment, 5) an evaluation of the extent to which the
alternative attains ~r exceeds applicable or relevant and appropriate Federal
public health and environmental requirements, and 6) an analyses of any adverse
environmental impacts. Analyses of recycle/reuse, waste minimization, waste
biodegradation, or destruction, or other advanced, innovative or alternative
technologies were reviewed in the initial screening where appropriate, although
will be reviewed again in more detail during source control evaluation
where they will be more appropriate.
The detailed analysis of each alternative is summarized in the following
sections. A summary of each alternative and its engineering effectiveness to
protect the public health and welfare and the environment is given. More
detailed information is located in the OUFS Report.
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Alternathe 1
Alternathe 2
Alternative 3
Alternative 4
Alternative 5
Alternative 6
Alternative 7
Table 2
DESCRIPTIONS OF REMEDIAL ALTERNATIVES EVALUATED
Collection via north gallery
Air stripping treatment of combined north
ga 11 ery flow
Discharge to DMWW
Collection via north gallery
Air stripping treatment
Discharge to DMWW
Collection via north gallery
Isolation of the northern-most
Air stripping treatment
Discharge to Raccoon River
Collection via extraction wells
Slurry wall
Ai r stripping treatment
Discharge to Raccoon River
Collection via extraction wells
Air stripping treatment
Discharge to river
Collection via extraction wells
Slurry wall
Air stripping treatment
Reinjection to aquifer
No action
and south
section of the north gallery
-------
Table 3
DEVELOPMENT OF ALTERNATIVES
40 CFR 300.68(f) Requirement
o. Alternatives for treatment or
disposal at an offsite facility
o Alternatives that attain applicable
or relevant and appropriate Federal
public health and environmental
requirements
o Alternatives that exceed applicable
or relevant and appropriate Federal
public health and environmental
requirements
o No action alternative
Technology or Alternative Evaluated
o Offsite deep well
~ Offsite treatment
o Offsite treatment
facility
o Offsite discharge of treated
ground water
inject ion
at POTW .
at RCRA
o Alternative 1
o Alternative 2
o Alternative 3
o Alternative 4
o Alternative 5
o Alternative 6
o Alternatives 1 and 2 evaluated
treatment of the water to .
2.6 ug/l, which exceeds the
Safe Drinking Water Act
requi rements
o Alternative 7
-------
11
Alternative 1:
Collection via North Gallery - Air Stripping Treatment
of Combined North and South Gallery Flow - Discharge
to DMWW
Under this alternative, all ground water collected from both the north
and south galleries would be treated by air stripping for removal of vacs.
The treated ground water would subsequently be reintroduced into the DMWW
treatment process.
This alternative meets the objectives of the operable unit to minimize
the public health threat from use of the north gallery and controls the
migration of the contaminants. Air stripping treatment is a proven technology
fo.r removing vacs. Compared to the other alternatives, this alternative
would would result in the greatest concentration of contaminants in the
DMWW finished water. Extensive monitoring would be necessary to determine'
if adequate drinking water quality was maintained in the stripper effluent.
This alternative presents a potential risk to the public' in the event of
poor treatment system performance or failure. The DMWW wbuld have to rely
wholly on their other water sources during times of periodic cleaning of
the units and during equipment failure. This alternative attains or exceeds
. applicable or relevant and appropriate Federal public health and environment
requirements. No adverse environmental impact would result from operation
of this alternative.
Alternative 2:
Collection via North Gallery - Air Stripping Treatment -
Discharge to DMWW
Under this alternative, the 'northern-most section of the north gallery
would be isolated frOm the remainder of the north gallery, and ground water
would be extracted from the isolated portion of the gallery. The water
drawn through this isolated section would be treated for removal of vacs
using an air stripping tower. Treated water would be discharged to the
DMWW facilities for use in the public water supply.
This alternative meets the objectives of the operable unit. It would
result in lower vac concentrations in the DMWW finished water than Alternative
1. This is the result of treating a smaller portion of the gallery flow
and subsequently diluting the treated flow with the remaining gallery and
other DMWW water sources. A vertical barrier separating the northern-most
gallery section from the remaining portion of the north gallery is an
effective method of preventing contaminated ground water, collected north
of the vertical barrier, from migrating to the remaining portion of the
gallery system. Extensive monitoring would be required to insure that
adequate drinking water quality was maintained. The effects of poor air
stripper perfonmance is reduced from that of Alternative 1 because of a
higher dilution factor. This alternative attains or exceeds applicable or
relevant and appropriate Federal public health and environmental require~ents.
No adverse environmental impact would result from operation of this alternative.
-------
12
Collection via North Gallery - Air Stripping -
Discharge to Raccoon River
Alternative 3 incorporates the same ground water collection system as
Alternative 2. A barrier would separate the northern-most section from the
remainder of the gallery, and the contaminants would be collected from the
northern-most section. The ground water would be treated by air stripping.
The treated water would be discharged to the Raccoon River.
Alternative 3:
The objectives of the operable unit are substantially met by this
alternative, although discharge of the treated water to the river would
cause a loss of about 11 percent of the gallery resource. Discharge of
the treated ground water to the river would provide for a higher degree of
effectiveness concerning protection of the drinking water supply. However,
in the event of treatment system failure or poor performance, contaminated.
water could be discharged to the Raccoon River and could result in exceedance
of the surface water criterion. This criterion is for the protection of
the downstream Des Moines River's use as a drinking water supply. Complete
failure of the treatment system would be expected to cause an estimated
concentration of 7 ug/1 TCE in the Des Moines River. The proposed maximum
contaminant level for TCE in the regulations of Safe Drinking Water Act is
5 ug/l.
In the event of a collection system failure for the northern-most section
of the north gallery, contaminated ground water could be drawn around the
vertical barrier and into the remaining portion of the gallery. This could
result in degradation of the drinking water at the DMWW. However, adequate
safeguards could be provided to ~iscontinue use of the gallery system in the
event of a collection system failure.
This alternative attains applicable or relevant and appropriate Federal
public health and environmental requirements. No adverse environmental impact
would result from operation of this alternative.
Alternative 4:
Collection via Excavation Wells - Slurry Wall -
Air Strfpping Tr~atment - Discharge to River
Under this alternative, seven extraction wells would be installed 1n the
plume area to collect the contaminated ground water to prevent migration of
the main contaminant plume to the gallery system and to control migration of
the plume to the south or east. A slurry wall would be located east of the
Raccoon River to contain the ground water. The ground water would be treated
using air stripping and then discharged to the Raccoon River.
The collection system would be operated in two phases. In the first
phase, all seven wells would be operating. The north gallery would not
be operational during Phase I. Following cleanup of the area west of the
slurry wall, Phase II would begin. During Phase II, the wells east of the
Raccoon River would be operated and the north gallery could be used to supply
water to the DMWW.
-------
13
Because use of the north gallery would not be available until Phase II,
the objectives of the operable unit would not be achieved until Phase II
begins. The use of the slurry wall and the extraction wells to control the
hydraulic gradients would prevent migration of the contaminants to the
gallery system. Trace levels of the contaminants would remain west of the
Raccoon River and would be drawn into the gallery during Phase II, but would
be below drinking water criteria. The use of the slurry wall and the extraction
wells to control the hydraulic gradient would effectively prevent the migration
of the contaminant plume to the gallery system. However, the reliability of
this system may be diminished during periods of high ground water level resulting
from flooding, which may cause ground water flow reversals. In addition, this
system would present more operational complexity than the previously discussed
alternatives. Pumping rates must be monitored and maintained to provide for
eastward hydraulic gradients across the slurry wall as well as maintaining
adequate zones of capture for the extraction wells, preventing contaminants
from migrating through or around the slurry wall and to the gallery.
Monitoring of the treatment system performance would not be as critical as
for Alternatives 1 and 2 since the treated water would be discharged to the
Raccoon River. System failure would result in the discharge of contaminated
water to the Raccoon River in excess of discharged criteria, thus potentially
adversely affecting the Raccoon River or Des Moines River water quality. Complete
.failure of the treatment system would be expected to cause an estimated discharge
of 4,000 ug/l TCE, resulting in a concentration of 70 ug/l in the Raccoon River
and 9 ug/l in the Des Moines River.
In the event of a collection system failure: contaminated ground water could
be drawn around the slurry wall and into the gallery, thus affecting DMWW water
quality. The time for contaminants to migrate around the slur~ wall and affect
the DMWW water quality would be greater for this alternative than for the other
alternatives because of the presence of the slurry wall. Adequate safeguards
could be provided to discontinue use of the gallery system in the event of a
collection system failure. Treatment of surface water from the Des Moines and
Raccoon Rivers could be performed until implementation of appropriate corrective
action.
This alternative attains applicable or relevant and appropriate Federal
public health and environmental requirements. No adverse environmental
impact would result from operation of this alternative.
Alternative 5:
Collection via Extraction Wells - Air Stripping
Treatment - Discharge to River
Alternative 5 consists of a system of extraction wells installed in the
plume area to collect the contaminated ground water to prevent migration of
contaminants to the north gallery and to control migration of the plume to the
east or south. Contaminated ground water would be treated with air stripping
and then discharged to the Raccoon River.
As with Alternative 4, the collection system would be operated in two
phases. In the first phase, all wells would be operated. The north gallery
-------
14
would not be operated until TCE in the effluent from the extraction wells
west of the river is reduced to below 5 ug/l. Phase II consists of operating
the east extraction wells to control the migration.
This alternative is similar to Alternative 4 except a slurry wall would
not be present east of the Raccoon River. The extraction system,;without the
presence of a slurry wall, would have to create sufficient hydraulic gradients
east of the north gallery to prevent contaminants from migrating to the gallery
system. As with Alternative 4, trace levels of contaminants remaining west of
the Raccoon River would be drawn into the gallery but would be below drinking
water criteria. These contaminants would be reduced further by dilution with
the gallery water and with other DMWW water.
The operational complexity would be more than Alternative 4 since
monitoring would be more critical to maintain proper hydraulic gradients so
that contaminants are not collected by the gallery. Reliability of the
collection system is questionable because of the operational difficulty in"
maintaining a ground water divide east of the north gallery by varying pump
rates in the extraction wells and the gallery system.
Failure of the collection system could result in contaminants being
drawn into the gallery system. Effects on the DMWW water quality would occur
-more quickly with this Alternative than with Alternative 4 since the slurry
wall of Alternative 4 acts to impede contaminant migration to the gallery.
However, adequate safeguards can be provided to discontinue use of the gallery
system in the event of a collection system failure. Treatment of surface water
from the Des Moines and&Raccoon Rivers could be performed until the implemen-
tation of corrective action." ..
Treatment system performance and the effects of system failure or poor
performance are similar to Alternative 4. Complete failure of the treatment
system would be expected to cause an estimated discharge of 800 ug/l TCE,
resulting in a TCE concentration of 60 ug/l in the Raccoon River and 9 ug/l in
the Des Moines River during low flow conditions. The risk to public health
and aquatic life during the period between system failure and gallery shutdown
is considered short-term and is not considered great.
The operable unit objectives would be met after Phase II was operational.
This alternative attains applicable or relevant and appropriate Federal public
health and environm~ntal requirement. No adverse environmental impact would
result from operation of this alternative.
Alternative 6:
Collection via Extraction Wells - Air Stripping
Treatment - Reinjection to Aquifer
Alternative 6 consists of a system of extraction wells installed in the
plume area to collect the ground water to prevent migration of contaminants
to the north gallery and to control migration of the plume to the east or
south. A 1,000 foot-long slurry wall would be positioned on the north side
of the river near the end of the north gallery. Ground water would be treated
using air stripping treatment, and the effluent would be discharged to the
-------
15
river during Phase I and reinjected into the aquifer west of the river during
Phase II.
As with Alternatives 4 and 5, Phase I would continue until TCE concen-
trations in the west extraction wells decrease below 5 ug/l. During Phase I,
the north gallery would not be operated, but it would be operational during
Phase II. The objectives of the operable unit would be met during Phase II.
Since the reinjection system would be dependent on the extraction system,
the effects of failure of the extraction system would be similar to Alternative
5. However, failure or poor performance of the treatment system would have
greater impacts on the DMWW water quality than Alternatives 3, 4, and 5, since
these alternatives discharge to the river. Under failure or poor performance
of the treatment system, contaminants could be reinjected into the aquifer of
which some portion would be collected by the gallery. As a result, monitoring
is important to assess proper performance of the treatment system if adequate
water quality for the DMWW is to be maintained. Daily analysis of air stripper
effluen~ would be important to minimize adverse effects on the DMWW water
quality resulting from fluctuations in treatment system performance. If design
conditions are representative of field conditions, air stripper performance
would be adequate to meet reinjection criteria.
. The operational complexity is similar to Alternative 5 although the ground
water divide is more easily maintained using reinjection wells and the short
slurry wall segment. However, monitoring and periodic maintenance may be
important to prevent clogging of the reinjection wells, thus reducing the
effectiveness in maintaining the ground water divide. Maintenance of the
reinjection wells would require discontinuing use of the gallery. Treatment
of surface water from the Des Moines and Raccoon Ri..vers could be performed
until appropriate action could betaken. Proper design, monitoring, and
maintenance would be required to maintain proper hydraulic gradients and
treatment system efficienci~s to protect the DMWW wate~ quality.
Alternative 6 attains applicable or relevant and appropriate Federal public
health and environmental requirements. A waiver of the state ban on injection
wells ~ould be needed. No adverse environmental impact would result from
operation of this alternative.
Alternative 7:
No Action
The no action alternative does not meet the objectives of the operable
unit to protect the public water supply or control the migration of the
contaminants. If the DMWW resumed operating the north gallery, contaminants
would be carried into the water supply and would remain in the finished water
even after regular treatment by the OMWW. Under these conditions, VOCs
above the proposed maximum contaminant levels would be consumed by the users
of the water supply. If the north gallery remained unused, the contaminants
would still periodically migrate to the south gallery.
Table 4 includes a technical evaluation of the engineering implementability,
reliability and constructability of each alternative. Table 5 is a summary
of the 1) technical evaluation, 2) the assessment for the protection to the
-------
teehn Ica I
traluatlon Crltarla
PDIJ'ORIWICZ
Effecthaoe..
ProtacUon of IIIIIIf IIater SUppl,
o abU It, to c:cmhol untreated
contulnenh4 IIroundvater fr..
reechln9 bI1IIf Unlshed wlter
o bI1IIf flnl.bed water coatulnant
l"ell re..lol09 efter trelt88nt
a toll of bI1IIf wlter re.ourea.
Prn...Uoa of G~dvater Contulnut
"1lIraUoo
Useful Life of C08PODent.
'able 4 IPa98 I of "
ftCIIIIlCAL !:VALUAtiON OF ALT£RtfAtlVm
om "OINES Tel ours
AlternaU.. I
ColleeUoa viI Nortb Gallerr--Alr
Shlpplnll Treataent of Comlned North
and South Gallery Flow--Dlschar\18 to bI1IIf
Altarnatlve 1 la tha 80It effeetlve alterna-
tlye In thl. catevorr .Ince ell gellerr
wlter Is balll9 tnatad. No contulnate4
9rouodveter c:ou14 relch flol.bad DKNII watar
wltbout flr.t balo9 trlltad.
tr..tad wlter .11 I _t 4rlaklll9 .atu
atu4ar41 .
trlee I..el coat_loanta .11 I ftIIIla 10 DIIIIII
Uo1abe4 .atar. Altemathe 1 result. 10
9reltest ..s. of contulnenta In DIIW
Uo18be4 .Iter.
No lOll of ..ter n.ourea. _14 occur.
Known area of hlqhest coat-Inatlon near tbe
Dlco propert, wou14 ba c:ontllne4.
No CIOII()Dnlllta an anUclpated to a.c:aad tllelr
useful life durlnll operltlonel parlod prece4ln9
Unll r-cl1al actloo 13 ,.....1. .
AHemIU.. 2
Collection viI North O8llerr--Alr
Strlppln9 Treat.Hnt--
Dlschar98 to bI1IIf
Verr eUeet he In pre..nUnll IIntreated
contulnent. fr.. reachlnll DMMM flnl.had
.ater.
PotenUa' for cantulnanh to nac:b the
untreated lower portions of the N. Gl11err
.. con8l4ere4 verr .lIlIbt due to the
presenee of the vertical blrrler In4
..JntenlUlCOt of a b,drlullc 9r84J...t. tow81'48
the Fleur Drhe .actlon.
treated wlter will _t 4rlakln9 water
.tlUldar41 .
trIce 18Yel c:cmtulD8Dh will ftIIIln In
IJIIIIII Un1ahe4 wlter. AltemlUve 2 result.
10 about 15' of Altemltlve I'. contaalnant
8&8S In IJIIIIII flolshe4 water.
No lo.a of wlter resource. woul4 occur.
Itnown Irea of hlC)hest contulnlUon aear
the Dlco propert, wou14 be coatllne4. \
No CIOIIpOIIIfth In anUclpated to e.c:ee4
their useful life durlnll operltlonll period
prac:e4lD9 Unll rllle4111 acUon 13 ,earll.
. I
IDrlnklnll water standards ue presented In Table 1. Drlnklnv wlter standards an based on _Ung propose4 88111-
bcont88lnant leyel. tMeL'.1 or concentrltlons resultlnll In en Increased cancer risk of one case In one .111100.
Nol ~pl1c8ble
cGA( . Granullr Ac:llvltad Carboo
AHemaUve ]
Collection vi. North Gellerr--Alr
Slrlpplnll TreaI8lnl--
Discharge to River
Verr e.Heet... In pnnntlll9 untreated
contulnant. fro. relcbl09 DIIW flnlshe4
water.
Potllltill for contulnant. to nach the
untreeted lower portions of tile N. Glllerr
I. oon.ldere4 verr .lll1ht due to presence
of the verticIl barrier Isolltlng lbe nortb-
em porUon of the N. Glllerr an4 ..Inten-
anee of e h,4r.ullc IIra41ent towards tbe
Fleur Drive .ec:tlon.
N/Ab. No treated qroundvater I. 4l8cherqe4
to DfIIIII.
lister re.ource. fr08 Fleur Drive section of
N. Gallerr wou14 be lost lesll..led reduce4
flow . 2 to ] 11941.
Itnown erM of hl9best oontulnatlon near
the Dlco propert, wou14 be contained.
No C08poIMIftt. are Intlclpated to exceed
their useful life durlnll operational period
prece4ln9 Unel r_4lal actloo 13 ,earsl.
-------
f8cbn Ice I
"aluatlon Criteria
pERPOllWlCt!
Effect hen..,
Protection of bIIIf lIater SUppl,
° Abltlt, to control untnated COIIt_l-
nated groundwater fr08 reacblng DKWM
Unllhed water
° DMIIII flnlabed .atal' cont..lo88t
levala re88lnlng aftar treat..nt
° to.. of IIGIII ..tel' naoureea.
rra"oUDD of G..-dwatar Cont_loat
"Igratlon
U..ful La fa of CCI8POII8D18
,
I
Table 4 .- (Pa98 2 of 91
Attematl.. .
Collection .Ia EXtraction Mell.--
Slurry lIa!l--Alr Stripping
'reat.ant--Dlachal'",a to River
Very affectl.. 10 pra..ntlDCJ I8Itreate4
contulnenta fl'08 reaching DIIIIII flnhhed
.atar.
PotenUal for 819!'8t1DD of tr- I_I. of
VOC cont..lnaot. to the N. Gallery e.l.t.
but I. con.ldared .llght. Cont..lnant.
.ould have to 81grate around the edge. of
the .Iarry watt.
'lTace la..l. of COIIt-loM18 _14 ~Io 10
vroundwater followlog Phase I CD8Pletlon 88d
.ould loltlall, raach the gallary .,.t...
!be.. trace I..el. of coot..lo88t. vould b.
reduced further b, dltuUon In the I11III.
II/Ab. 110 tn.ted 9I'ClUll4vater Ja 4lad1ar984 to
DMIIII.
Pot8llUal _tt re4uc:tIDD of floor 10 nwr Dr.
.ecUon of N. Gallery durlog lov groundwater
table condition..
IIIDwD IU'88 of 1I19h8.t COII188loation 08U' the
Oleo propert, would b. contained.
110 COIIpDII8Dt8 8n anticipated to 88C884 tll8l I'
u..ful 11 fa durlD9 operatlon.1 period preceding
final 1'-"1.1 acUon fJ '''1'81. .
Attematl.e 5
Collection "Ia EXtraction 8811.--Alr
StrlpplnQ Treateent--
DI.charge to River
Vary affectl.a In pn.entlDCJ untnated
eont..lnanta (1'08 reaching DI1IIII flnhhed
.ater.
Potential for 8191'ati0n of trace la.el. of
VOC eont..lnenta to the N. Gallery e8l.ta
but la coa.ldered .11",ht. All cont..lnanta
8a, not be captured b, tha ..traction I,.t..
and a" 8lgr,ta to tha N. Gallery. Alao.
h,draullc Qradlant. produced b, pueplng tha
Nortb Gallery .a, occa.lonall, be aufflclent
to ovel'C088 Qradlentl Induced b, the
aatractlon a,atea.
'lTace I..al. of cantuln8llt. _14 .....10
10 Qroundvater follovlnQ Phasa I coaplatlon
aod would Initial I, reach tha Qallery
.,.tell. These trace levell of cont...lnan18
.auld be reduced further b, dilution In the
I111III.
N/Ab. 110 tnated qrouadvater Ja c!lladlal'Q84
to DIGIII.
Potential _II reduction In noor In naur
Dr. 8ecUon of IIortb Gallery durln9 low
Qroundwater table condition.. Potential
(or reduction In water resource. I. 9reater
then In Alternative C.
bowa a.... of blQlle.t COIItaloation O8ar
the Dlco propert, would be cont.lned.
110 C08pOIIen18 an aoUc:Jpated to e.C88c!I
tb.lr u..ful IHe during op..tlonal period
precedlnQ fine I r.-4lel actloa fJ ,ear81.
80rlniling ..tar .tanderde an pn88tlted 10 Tabl. 1. DrlnlrlllQ .atar .t8llc!larda era baaed on _Ung proPOled 88111-
bcontaalnant la.el. IMeL'.1 or concentration. reaultlD9 In an Increa.ed cancer 1'1811 o( one ca.e In one .IIJlon.
IIot AppllcabJe
cGAC . GranuJar Actl.ated Car1xm
Altematl.a 6
Collection "Ia EXtraction NeJI,--Alr
StrlpplnQ Treat.ent--
Reinjection 10 Aquifer
Very affeetl.. In pn"entlnQ untreated
contaalnenl' fro. reachlnQ DIIIIII flnl.ed
valer.
Potential for 8191'atlon of traee le"al. of
VOC contaalnant. to the Nortb Gallery exl.t.
but la eonaldered .1I9ht. All cont..lnants
8" not be capturad b, tha extr,cllon ay.te..
Hydraulic gradient. produced by puapln9 the
North Gallery .a, occaalonally ba 8ufflclent
to o.ercoae 91'adlenta Induced by the
extraction and reinjection 8,at...
'1'1'- J..." of contulnent. voul4 I'888ln In
9roundwater follawln9 Pha,e I coapletlon and
wouJd Inltlall, reach tha 9allery .,.t...
The.e tnce I..els of cont...lnenls would be
reduced further b, dilution In the DMWW.
Since tnated .ater I. reinjected to aqul fer.
traca JeveJ conl..lnant. wlJJ occur In DMWW
flnl.hed water. Cont..lnant 88.S In lhe
(Inlabed vater would be Je.s lhan Altema-
the 2.
to.. of .ater resource. I. .119ht dua to
reinjection of lreated 9roundwaler.
1tnown ana of hl9h8.t contulnatlon near
the Dleo propert, woule! be contained.
No C08pOII8fIt. an anticipated to exceed thai I'
u.e(uJ II(e durln9 operational period
precec!llnQ final reaedlal acUon 13 ,eanl.
-------
Tecbnlcal
e.aluallon Crllarla
RELIABILln
Deeonalraled Perfor88n08
o FOt8lltiai for poor perfo~
or failure of a,at- or ~-
n.nts lassualn9 deal9" crll.rla
are reprea.nlatlva of actual
lIeld condltlon,1
o Operational fledblHt, to addre..
varletlons belween &esl9" criteria
and aclual field condltlona
Operation and Ilalnt8ll811C8 II8GulntMIIll
o Operational ODIIPle.lt,
o aellance on 8OftltorlD9 resultl
o Malnt8lla- requlr_tl and
frequenq
table 4
Altemathe 1
Collection via North Gellery--Alr
Strlppln9 Treetftnt of Collt)lned North
and Soulh Gellery Plov--D1ach8rge to DII1IIf
Plaur Dr. 'ectlon of North OIUery II a wood
tlllt)er conduit built la 1909. Continued func-
tlonln9 of thll lectlon la eapeeted over the
operational period precedlnv final r8ft4lal
actton. However, a potent tal a.lltl for
reduced flova with resultln9 poteatlal for
lDOO8Plete coatalneent of cont88lnallon due
to atructural failure of 9allery lectlona.
l'a91 ] of 91
Altematl..a 2
Collection ..Ia North Gellery--Alr
Slrlppln9 Treal8ent--
D1aeharge to DII1IIf
Flaur Dr. lectlon of North Ganery II a
.004 tlllller conduit built la 1909. Con-
tinued funetlonlnv of thla aecllon II
e.peetad o..ar the operational period pre-
cedln9 flnlt re..dtal actton. "OWIYer, 8
potenltal e.llta for reduced flo., .tth
resullln9 polenllal for Incollplele con-
lal...enl of conlulnatlon due lo alruc:tural
fellure of gellery lectlona.
Air ItrlpplllQ II 8 prov811 t~lOCJJ 8IIC1 lbouleS Air ItrlpplDQ II a prov811 t~lOCJJ 8IIC1
perfonl adequalel, accordtn9 to &eltva crlterle. lhould perfonl adequate I, 8CCOreSlav to
dealID criteria.
,.'
Air atrlpperl pro..lde 8 rage of r_el
efflclenc:lal, tbua aUowlnv for a.-
..arlatlona ID InfluenV,cont..laut COIIOID-
tratlonl. Larve Incr...el of 'Dfluent .
concentratlona relatl..e to eatl..ted concen-
tratlonl 19reater lhu 1.5 tI..1 calcul8led
TCE lafllllat COIIC8IItratlonl .a, result In
the OI8eS for addltlonel air It ripper
capacity to ...t drlnklDQ .ater criteria.
"..Iblllt, to brpe.. to rl.er ID IVeat of
Inlbillt, to lilt drlokla9 .ater crlterle
e.lal. .. .eJJ a. .but cSown of tbe Veller;
.a,at... Loaa of ..jor .atar reaource If
atrlpper effJuent requlrea b,peaaln9 to
rl..er or ahut down, reaultla9 In tbe DII1IIf
ulln9 o.a IIolnea aneS Rac:c:aoa R1..r .ater.
OperaUOII8J Cll8plllllt, II nlaU.el, 1IIIpIe ..eS
la aot e.peeted to IlgnlflcaatJ, effect the
IltemaUve'1 nU8bIUl,.
81- tnateeS .Iler II MID9 all4 .. eSrlaklDV
.ater, 8Oaltorln9 fr8QUlDC1' and accuracy are
..ary 18pOrlut. for reHable operatloa.
No unusual ..lnt8llanee requlnwnt.8 e.llt that.
.., decreaae rell8blllt, of the alt.emall.e.
'erUCll ban-Ier ecroal the Nortb Ganary
I. expected t.o perfone adequat.eJ, over
operatlonel period precedln9 flaal rl8e4lal
acUon.
Air etrlpper. provl41 a rIDge of re8O'fll
efflclenele., thul ellovlag for 8081 ..erl-
atlona In Innuent contulnant. coaceatra-
tlon.. Large lacre.... of Influent.
concentretlnn. relative to eatl..ted CODCeD-
tratlona 19reeter than 1.5 tl..e calculeted
TCE Influent. colIC8Dtretlonl ee, result ID
the need for additional elr atrlpper
capaclt, t.o _t drlnkla9 .eter criteria.
FI..lbUIt, to brpeaa to rl.er ID IY8Dt of
Inlbillt, t.o ...t eSrlnklnv .et.er criteria
..I.ta .. ..JJ .. abut down 01 tbe valJery
a,at... If t... Vinery a,at- requlrea ahut.
40tm or the .trlpper efnueat. requlrea
bypa88lnv ta rher, the IIIIIW _leS u.. OIl
Nolne, and Rac:c:aoa JU.er .ater.
Operational ~llIIlt, la nleU..I, ailiple
8IIC1 la not expect.ed to al9OlflcaatJ, effect
t.be allemathe'l reUabIUt,.
8111e8 tneteeS .ater I. blllIQ all4 .. c1rlnk-
1n9 ...ter, -Uorln9 frequl!DCJ and
accurecy ere "ery Ilportant. for rei IIble
operaUon. Because 8UCb Ie.. 9roundweter
I. bela9 tre.ted reletl"e to Alt.emettve I,
8OD1t.orln9 Ie not. ea crlt.lcal.
No unusual ..Intenanee requlr.....t. ..tat
t.bat. 84' decre..e reliability of the
eltemaUve.
eDrlnkln9 wahr atendarda are preaanted In Table 1. Drlnkln9 .ater atandareS. ere be sed on ...tln9 proposed ...1-
bcont..lnant level. IMeL'.' or concenlratton. reauILln9 In en Inereaaed cencer rtak of one case In one .llllon.
Not Applicable
c(ip.C . Grenu I If AcUnted Carbon
Allemetl..e ,
CollectIon vie Nortb Gellery--Alr
Strlppln9 Treel.ent.--
Diseherqe to RIver
Plaur Or. .ectlon of North GaUery I. e wood
tl8b.r conduit buIlt. In 1909. Continued
funcUontnv of thIs secUon I. ecpeeted over
the operatlon.1 period prece~ln9 fInal reee-
eSlll action. "owe.er, a potent III ...Iat.
for reduceeS flowa .Ith resultln9 potential
for Incollpl..te contaln..nt 01 cont_lnaUon
due to structure I failure of 9allery
aectlone.
Air etrlpplDQ II 8 proven teel8loloqy 8114
shouleS perfora aeSequatel, accordln9 to
4Ial9O criteria.
Vertical barrier acro.. the North OeUery II
e.pecteeS to perfora adequat.el, o"er opere-
tlonal period prec.4ln9 flael re8ldlal
acUon.
Air Itrlppers pfO'fl48 a range af reeoval
efUelenelea, thus eUovln9 for .0-
verlatlons In lafluent cont-Inent
concentration.. Large Increase. 0' 'nllu-
ent. concentrations relellve to estl.ated
concentraUons 19reater than 1.5 UftS
calculeted TCE Influent concentratIon' ..,
result. 10 the need for additional air
atrlpper cepaclt,.
If stripper effluent 'aUe to _t river
discharge crlterle, the 9allery .,at..
would be sbut cSowa antll repe'r. could be
..48. Losa of .ater resource .ould re.ult.
In the DII1IIf usln9 Des IIolnes end Raccoon
Jlher w8ler.
Operetlonal Cllllplealt, I. relatl.el, siliple
and Is not. ..xpected to sIgnificant I, effect.
the aaemathe'. nUabUIt,.
Since treated .at..r I. not vaeeS lor eSrlnkln9
water end aufflel.nt potent lei exist for the
rlYer to eSl1ute contulnenla to below
.eppllcable waler uae criteria, 8Onltorlnv
result.s for rl"er dl.cbarge.ere not a.
critical a. for Altematlvee I and 2.
No unu...al ..lntenanC'S requlr.....ta ulst
that sa, deere..e rellabillt, of the
eltemethe.
-------
bdlalCIII
!raluatlon Crlterle
RELIABILITY
De8on.trated Perlor88D08
o Potential lor poor perfonanCII
or fallura of a,.te. or C08pO-
nent. I.s.ualnv deal9" criteria
.re repr.sentatlv. of actual
field condltlon.1
o Operational Ile.lblllt, to .arla-
tlon. betw..n de.IVO criteria 8041
actual field coodltloo.
,
.
. Tabla 4
(pava 4 01 91
Altematl.. 5
Colleetlon .Ia EXtraction Mell.--Alr
Strlpplnv Tr..t8eOt--
Discharge to Rlv.r
Collection 01 coat..lneted 9f'OUDdwater
using extraction w.ll. I. a proven tech-
nolo91 and .hould perlon adequate I,.
EItractlon well equlpeent located In 11004
plain ahould not b. .dver.el, effected If
Inundated. However, contulnant capture
could be affected b, change. In b,draullc
vredlent8 resulting frae river flooding and
blgh vroundwater I.vela.
Air .trlpplll9 I. . proven tecboolO9J and
.hould perfon adequate I, according to
d.al9O criteria.
Hrdrau1lc gndleat. p~ b, pu8l)lag the
N. Gallery .., be eufflclent to overC'188
gradlenta 1ndu0e4 b, tbe ntnctloo .,at_.
Air atrlppers provide a t'8llva 01 n81Vel
efllcl.ncle., thu. allowing lor .088 v.rla-
tlon. 01 Inlluent cont..lnant concentra-
tion.. Larga Increa.e. 01 Influ.nt
concentr.tlons rel.tlve to e.tl-ted canoan-
tratlon. Ivr..ter than 1.5 tI... calcul.ted
.Tel Influent coocentntlonl .., reault In
~be need for 84dltlooal air .trlpper
c.peclt, to ...t dl.cb8rva requlre88at..
II .trlpper elllU8Dt lalla to ...t rlyer
dl8Cb.rge criteria, the 98llery ".t.. would
be .hut down until repair. could be 1184e.
Lo.. 01 water ra.ource would re.ult 81141 the
IIIW would use De. Moln.. 8114 Raccoon River
weter.
CollectlOll "at- n1lablllt, 01 AUema-
U.. 5 I. the ....t depen4eat 00 accurate
pradlctiOll 01 equlfer propertl.. le.g.,
peneabllll" river recbarva ratel. If
actual propertlee vary .ub.tantl.ll, fra8
predlct.d, addltlOD.1 extraction nlJe
.nd/or verl.tlon. In pu8plng r.te. .., be
required.
AorlnUng water .tanard. .re pre_ted I. Table 1 . o,ln'llI9 water .tandards en b..ed OD _tllI9 propo..d ...1-
bcootulnant level. IItCL'.1 or colIC8ntr.tlon. r..ultlll9 In an Increased cancer ria' of one c..e In on. Dillion.
Not Applicable
Caac . Graoular Activated CerboD
AUematl.. .
Collection via EXtraction "lla--
Slurry Nall--Alr Stripping
Tr..t8ent--DI.ch.rge to River
CollectlOll 01 coat..lnated groundwater u.11I9
e.tr.ctlon w.ll. I. a proven tecbnolo9f .nd
.bould perfon adequ.t.I,. Istractlon w.11
equlpMnt located In flood phln .hould not be
adver..I, affected II Inundated. Howev.r,
OOtIt,,'nant capture could be .ffected b, c:lwtge.
In b,draullc gr.dlent. re.ultlng frae rlv.r
floodlnv and blVh vroundwater 1...Je.
Ilurry wel1 I. ..peeled to perlon according to
de.lgn criteria ov.r operatlon.1 period
preceding fln.1 re.edl.1 action.
Air .trlpplD9 la a proven tectmolO9J and .houl41
perlon adequ.tel, according to de.lgn criteria.
Air .trlpper. provide e range 01 rD809al elll-
clnc:l.a, tbu. allowlnv for - variation.
.. 01 InfhlDOt cont..lnant coac:entratlOll'.
Large Incre..e. of Influent concentration.
reletlve to ..tl_ted concentretlon.
Igra.tar than 1.5 tI... calcul.ted TC!
Influent concentratlonl aa, reault In the
...4 for addltlon.1 elr .trlpper capaclt, to
...t dl.db8rge requlr8880t..
II atrlpper ellluent lalla to ...t rl..r
418Cb8rge criteria, the vallery .,st.. would
be .but dowo until repair. could be ..de.
Loa. of wster re.ource would re.ult ud the
I»IIIr would u.e De. Moine. and Raccoon IIlvet
w.ter.
CollectlOll "It- nUllbtUt, t. "17
depetldeat 011 accurate predlcUC8I of aquifer
properties le.g., peraeablllt" river re-
dlarva r.tel. If actu.1 propertle. var,
sub.teatlall, Irae predicted. ad4ltlon.1
e.tr.ctlon 8ell. and/or ..rlatloo. In puap-
Ing rst.. .., be required.
AllemlU.. 6
COllection via E8tractlon Nell.--Alr
Stripping Tr.ataent--
RO!lnj.ctJon to aquifer
Collection and conhl_t 01 cont..lnated
groundwater ualnv ..tractlon and rO!lnjectlon
.ell. la e proven tecbnolO9f an4 should
perfoe. .dequatel,. E8tractlon/relnjectlon
wO!I1 O!qulpaent loc.ted In flood plain should
not be .dvers.l, affected If Inundated.
1I08ever, cont..lnant capture could be .ffecte
b, ch.nges In h,dreullc gradients resulting
fro. rlv.r flooding .nd blgh groundvatO!r
levela.
RelnjeeUon well8 .e, uperlence decreased
effectlv.ness wltb tl.. due to clogging
prOOI....
Slurry wall .. ..peeled to perron according
to design criteria over operational period
preceding fln.1 r.ndlel acUon.
Air stripping Is e pro
should perloe. adequ.tel, according to design
crlt.rle.
Hrdrau1lc gradients produced b, pu8l)1 ng the
N. Gallery -, be sufficient to ovucoae
gr.dlent. Induced b, the extraction s,stea.
Air .trlpper. provide a ranve 01 re.....1
efflclencl.a, thus allowing for 'ODe
varl.tlon. of I.flu.nt contaalnent concen-
tr.tlon.. Large Incr.ss.a of Influent
concentr.tlon. relative to estl.ated COIIcen-
traUons Igreater than 1.5 UDeS calculatO!d
Tel Influent concentration crlterlal .a,
re.ult In the 0884 for additional .Ir
.trlpper caP8Clt, to aeet reinjection
criteria.
II .trlpper .'fluent Ian. to -t
reinjection crlterls, the gal leer ".t..
would be .hul down unUI repeln could be
..de. Lo.. of 8ater re.ource would result
8114 tbe DIIIIII would u.e De. Moines and
Raccooa River wat.r.
Collection 11114 nllljection .,.t..
re1lablllt, .. .ery dependent on accurate
predlctloo Of equller propertle. 'e.g.,
peroeablllt" river nebsrge ratel. If
actue) propertlea vary SUb.tantla)), fr08
predlcte4, addltlon.1 ..tracllon w.ll.
and/or varletlon. In puaplng rate. .a, be
required. A4dltlon.1 relnjecllon w.ll.
.a, .1.0 be required.
-------
'eclmlc:el
ttllultlon Crlt.rl1
RELIAIIILln IConUnuRGI
Operltlon end "1Int.nance JeQulr888nt.
o Operatlonll coapl..lt,
o R.llanct on aonltorlog r.sult.
o Kalntenence requlrneota and
f requenCJ
'8111. 4
AIt.mltl.. .
Collection wll EXtraction NeIll--
SlurI" Wall--Alr Strlpplnq
'reat.ent--Ollcharqe to Alw.r
fh8 need to ..Iot.ln h,dr.ullc qradlent. to the
"It acroll the Ilurr, vIII Introducel 108'
operational C08plexlt,. Thla la not expected to
Ilqnlflclntl, errect tba .ltemltlw.'1
r.U8II1l1t,.
Since trelted vat.r II oot 0184 for drlokln,
vlter and lufflclent potent III ..llt for the
rlwer to dilute cont..lnentl to below .ppllcabl.
vlt.r UI. crlterll, IOnltorlnq relulta for rlw.r
dllcharq. ar. not &8 critical &8 for .
AIt.meth.a I, ), and 6. Under 0 low flllir
conditions, lOoltorln, 18 18portenl,l9 ..,ur.
rlw.r dllcharve criteria ar. oot .xceeded. .
110 unusual ..Intanlnct r89U1~ta ,"at th.t
aa, decreaa. rellabillt, of the altematl...
IP..,. 5 of "
AltemaUn 5
Collection wll Extraction NeIII--Alr
Strlpplnq 'reet8ent--
Dischsrqe to Rlwer
11811ablllt, of collection 1,lt.. II
qu.ltlonabl. b.CIUII of operatlon.1
difficult, In "Intelnlnq I qroundvlt.r
dlwld. b, warrlnq puap rlt.. In e.tr.ctlon
valli and tb. qaller, 1,lt... 6I&8onll
qroundwlt.r warletlonl fr.. loflltratlon,
rhar lewel and q.ller, puaplqe aa, ..ke
tbll difficult. Kalntenence of the
vroundvlt.r dlwlde ne.r rIeur Or. and north
of the rher vlll ba especlall, dIfficult.
Rellablllt, prohl... could b. 81tlqated If
rIeur Orlw. lectlon of North Galler, .aa
DOt Ufed clurtn, e.tr.ctlon and treat8ent.
Since treated vater II not n.ed for
drlnkloq .It.r and lufflclent potential
e.I.t for the rlwer to dIlute cont..lnant.
to below appllcabl. ..t.r use crlterl.,
8Onltorlnq relult. for rlwer dlacharqe II"
not aa crltlcil I' for Altematlwe. I,
2 Ind 6. Under 0 low flow condltlona,
8OOltorlnv Is lap!tlVnt to assure rlw.r
dl8cbarva crlterll are not .xceeded.
110 unusual ..Iotananct r89U1~tI ....t
tbat .., deerea88 r.llabillt, of tb.
all.math..
'Drlnunq vater Itandards are pr..ented In Tabl. 1.. Drlntlnq vater .t8Jld8rd8 .re b.aed on _Unq proposed aul-
bCOftt..lnant lew.11 (MeL'11 or concentr.tlonl r'SUJ~lnq In an Incre...d cancer rllt or on. caee In one 81111on.
cNot Applicable
GAt . Grlnular Actlwate~ Carbon
Altemlthe 6
Collection .11 EXtraction Wenl--Alr
Strlpplnq Tr~at..nt--
ReInjection to Aquifer
Operatlonll eoaple.lt, I. 1181181' to Alter-
natlw. 5 Ilthouvh qround..ter dlwlde II 801"
elall, ..Intalned .Itb reinjection ..lls and
the lhort Ilurr, v.U leqHnt. Aellablllt,
prohl.. could be 81t1qated If rieur Drive
lactlon of North Galler, vas not uled durlnq
e.trlctlon Ind treat8l0t.
Since reinjected treated 9roundvltar vlll be
used b, the DMWW for drlnklnq VItiI',
8Onltorlnv frequenCJ and Iccurlcy requlreaent
Ire wer, llportant to reliable operltlon
(8111181' to Altemlthe 21.
Rel01ecUon veil. 81' require periodic 811n-
tenance to prewent cl09qlnq of the veils and
thus tbelr reliability as a wertlcal blrrler
control. Thla perIodic ..Intenlnee ..y
requlr. .hut down of qlller, s,stea.
-------
T8ctm I cal
Ir.lu,tlon Crlt.rl.
. '
t,bl. 4
AU.matlY. 1
Collection ~Ia North GlII.ry--Alr
8trlpplno Tr..t_nt of Collblned North
and South GlII.r, 'Iow--Dlacharg. to DKNW
S,at.. '1..lblllt, to ACC088048t.
Potential 'Inal Reaedlal Actlona
COIPA!l81L1'I'Y 111ft I'OrDrrIAL FIlIAL IIDlFJlIAL ACTIONS
O.fol LI f. of c~u for PotenUal
Final Relledlal cons
Air .trappen _I" eantlnua to tre.t 9I'0UIId-
.at.r, how.~.r, aouree control ..,aurea auch ..
anhaneed I.achlno of cont..lnant. to oroundw,ter
.., require additional treat..nt c.p.clt, or
coltectlon and treateent a,at.., to ..et
drloklno .at.r criteria for the oall.ry ..t.r.
Additional tr..talnt capaclt, could be pro~lde"
on a .hort- o~ long-tena ba.la potential I,
I..olvlng GAC .ddltlon or additional air
atrlpplog uolta.
0811.ry .,at- coul4 coatlnIJ8 to operate II
part of ftoal oroundwater cleanup reaedlal
action. Addltlon.1 collection, and trntMnt
a,at- .., be required to .ddre.. the a.t.nt
of o~erall alt. cont..tnatad groundwat.r aa
.al1 a. e.tract the 8O,t bea~II, cont..lnate4
grOUDdWater to a.pedlte groundwater cleanup.
" !
IP8C)8 6 of 9!
A1t.maU~. 2
Collection ~Ia North Gellery--Alr
Stripping Treataent--
DI,charqe to DKNW
Air .trlppera would continue to treat
groundwat.r , howev.r, aouree control
..a,ure. auell a, enhanced leachlno of
cont..lnant. to groundwat.r aa, require
additional treataent capaclt, or collection
.nd treat..nt .,.tea. to ..et drinking
watar criteria for the vallery .ater.
Additional treat..nt capaclt, could ba
provided on a ,hort- or I@ng-tera basla
potenU.Il, In~ohtng GAC addition or
additional air .trlpplng unlta.
IIorth Gelt.ry could continue to oper.t. u
part of final groundwater cleanup r18edlal
action. Additional collection and
traat..nt .,.te.. a., be required to
addre,. tha e.tent of ..erall alt.
cont..lnate4 groundwater a' wall as ..tract
the 8O,t heavll, contaalnated groundwater
to expedlt. groundwater cleanup.
Air .trlpper _14 not ..cee4 III u..ful IIfa If Air .trlpper woul11 not ..cee4 Ita u..ful
u,ell for up to 30 ,eer, a, part of a flnel 11ft If used for up to 30 ,ear. a' part of
,,884lal action. a final ".edlal acUon.
LoOQ t.... nM4lal action cl.anup .., require
use of North Gallery for 30 ,ear,. Thl, aa,
.xceed useful life of North Gallery.
."
Long ta... ntle4lal action cl.anup .., re-
qulra use of North Gallery for 30 ,ear,.
this .., exceed u.eful Ilfa of North
GaJJery.
aDrlnlr.lng .ater atan4ar.s. ere preH1lted 10 Tabl. 1 . Drlnklno w.ter 8tan4ar.s. are bued on _Ung propo,ea ...1-
bCORt..lnant le.al. IMeL'a! or concentration. r'lUltlng In an Incr.a.ed cancer risk of one case In one alllioo.
Not Applicable
cGAC . Granular Actlv.ted Carboo
A1tematl~. 3
Collection via North Gallery--Alr
Stripping Treataent--
Discharge to River
Air .trlpper. WOUIII eantlnua to treat
groundwater , lIowa~er, source control
aeasure. .uch es enhanced leaching of
contaelnants to groundwater aa, require
additional treateent capaclt, or collection
and treat..nt .,.te.. to aeet drinking
..t.r criteria for the gallery .ater.
Additional treataent capaclt, could be
pro~lded on e .hort- or l@Dg-tena basi.
potentlall, Involvlno GAC addition or
additional air ,tripping untts.
North Gallery eoul4 contlnu. to operate a.
part of final groundwat.r cleanup re..dlal
action. Mdttlond coJJecUon and
treat..nt s,ste.. aa, be required to
address the extent of ..erall site
contaalnated groundwater a. well 85 e.tract
the 80st heavll, contaalnated qroundvater
to expellite groundwater cleanup.
Air .trlpper waulll not exeeell it. useful
11ft If used for up to 30 years as part of a
final r...dlal action.
Lon" te,. re..dl.1 action cteanup .., re-
quire use of North Gallery for 30 ,ears.
TIlls .., exceed useful life of North Gallery.
-------
I'
. '1b1e 4
'hdIn1c:e 1
twlluallon Crlterll
aUlmlthe .
Collection viI Ellrletloa ..".--
Slurry IIln--Alr SlrlppllMJ
Traalaenl--Dlleherqe lo River
CtllPAtJlIlLJn 111'"' FOTDITIAL PINAL RDmIIAL ACtUHI
Srsl- "e.lblllt, to :~~le
Potential FInal he a con.
air .trlppen would continue to tnlt qround-
.allr, bowever, .ouree conlrol .eaaurea .uch ..
eob8nc8d leachlnq of contulnantl lo qrounctvaler
.., require Iddilional lr.al.enl caplellr or
collectloa and lreatAenl a,al.. lo prolecl
glilery .aler qualll,. Addlllon.1 treal.ent
capacll, could be provided 00 a shorl- orc
long-tera bllie polentlell, Involvlnq GAC
Iddltlon or Iddltlonel Ilr Ilrlpplnq unlle.
I,
2Irtractlao ..n .,.t- _Ia conUnue to
operate II part of lbe qrounctvlter cleanup
IInal rlMdlel action. Mdltlonal collection
and tna188nl .,.t- .., be required to
Iddnll lhe e.t.nt of oy.ren alte coolalnated
groundwaler II ..n .. e.lract the ..at heavll,
coolulOllea groundwatar to ..pedlte 9roundwaler
cleaoup.
Useful Life of C08pODIDta for 'IDal
R.,..,dlal actions
air Itrlppen and eatnc:tloa ..n. would not
e.08Id thalr useful live. for up to 30 rears
aa part of a flDal reaedlel eetlon.
Slurry .111 .111 II'el, contlDDl to be
effecllve for at leaat 30 ,eara.
"
r
t 7 of 91
altematlve 5
Collection via Eslraellon ..II.--Alr
Slrlppln9 Trealaenl--
Dlscharqe lo River
air .trlpper. .oula continue to trelt
qroundwaler, however, .ouree control
aeuures IUch as enhanced le.chlng of
c:onlulnanls to qroundvater '1' require
addilionel trell.ent clpaclt, or cnllectlOD
and trellllnt .,sle.. to prolect gillery
'Iter qual It,. Addilionel treat.ent
capaclt, could be provided 00 a short- or
10ng-lera blsl. potential I, Involving GA(c
Iddltlon or additional air .trlpplng unit..
2IrtractloD .en .,at. _Ia continue to
operate.. part of the qroundvater cleanup
IInal r8edlal ecUon. Mdltlonal
collectloo and treataent .,steu "' be
required to Iddress the e.tent of overall
alte contulnalad qroundwatar al .ell as
..tract the "It heavll, conluln.ted
groundwater to expedite groundvater
cleanup.
Air Itrlppel'l lad ..trectlon VIlli .oula not
e.oeed their usaful lIves for up to 30 ,ears
as part of a final reaedlal action.
'orloltlnq .ater atandards are p..._ted In 'lble 1. Drlnltlnq .ater .tandlrds Ire based on _tlng proposed ...1-
bconlulnanl Ilvlla IIICL'a) or conceDlraU...a rasullllMJ In an Incrused cancer ria' of one case In one .11110n.
Nol Applicable .
cGA( . Granular ActIvated Cartloa
AUemaUve 6
Collectlon via EllracllDn "ell.--Alr
Slrlpplnq Treallenl--
Relnjecllon to Aquifer
Air .trlpper. would coDtlnua to treat
qroundvltar, howevar, .ource control aeuure.
such a. enhanced leachlnq of cantulnanls to
qroundvater .a, require addilional lreal.ent
capacll, or collection and trealaenl s,slees
to protect qallery water quallt,. Addillonil
treltaenl capaclt, could be provided on a
ahorl- or lon2-tere blsls polenllall,
Involvlnq GAt addltloo or addilional air
Itrlpplnq units.
2Irtractlon .e11 1,lt.. could continue to
operate u part of lhe qrounctvller cleanup
IInll reaedlal action. Addltlonll collection
and trelt..nt .,Sleas 81' be required lo
address lhe e.lent of overall slle conl..l-
oaled qroundvlter as ..II as exlrlcl lhe lOst
heavll, cont..lnlted qroundvater to expedlle
qroundvater cleanup.
Air .trlppers .ad a.tractlon .ell. .ould not
e.ceed their useful lives for up to 30 years
u part of a final re..d181 action.
Slurry ..n .1 n II tel, continue to be
.ffecllve for It lelst 30 years.
Reinjection ",ne II' not have a lonq tere
useful life of 30 ,een. Hay require
replace.ent or rehabl1 HaUon al periodic
Inlenlls.
-------
Tec:tln I ce 1
Evalu.tlon Cr.terl.
IKPLDmnABILln
Easa of In.tallatloD and TI.. to
Impl"."nt
TI- to AcIIla.. ours OIjecth..
~
RI.t to Public Haaltb and tbe ED.lroo-
..,nt In Ev"nt of S,st.,. rallure
Safety DurlDG CODatructlon
'able '4
AnemaU.. 1
COllection .Ia North Gallery--Alr
StrlpplnQ Treat.ent of CClllblned North
and South Galler, Flov--DJ,charqe to I»I1/II
.18C888nt or tbe elr atrl~r UDlta Ie
within the flood plein and will require
el..atlon abo.e the lOO-,ear flood le.el to
protect treat_ot .,at.. froe floodlnv.
".Ia ..y require eddl Uonal COII.trucUon
U.. U CQ8p8red 10 AHunathes ., 5, 8DIJ
..
lnaUtuUonel hqIIl..-te (pentte, ete.1 u,
dela, .tartup.
ours abjecUy.. _t upon e,.t- startup.
IeU..ted U.. for aedVO 8IId CODstrucUon" to
10 _lb8.
A allQbt rlak to public bealtb 10 ..eot of air
atrlpper failure could be OIDlelaed br dall,
_Uorlnv to redutI the U.. between 81at.
failure and correctl.e ectloo (altber atopplnv
vallery pu8P8ve or brP88.IDV atrlpper effluent
to rher).
No elvolflC8llt _tracUon eefet, buard8.
(Pe.,. 8 of 91
AnemeU.e 2
COllection .Ie North Gallery--Alr
Strlpplnq Treat....t--
Dlachar,e to I»I1/II
Pl8C888nt of the elr etrlpper unite Ie
within the flood plain end will requIre
elenUon abon the 100-,e... flood le..1
protect treatNnt a,at.,. froe floodln".
".Ia .., require additional conatructlon
U- u c:oep...ed to AltemaU.e. ., 5, 8114
..
In.tltutlonal requl..-te (penlte, eta.1
.., dela, etartup.
ours abjecthee ..t upon 81.t- etutup.
leu..ted U.. for dealVO IIId COII.trucUon
7 to 11 _lb..
A eUvbt rlek to _lie "e1tb 10 eYeot of
air etrlpper failure could be 81DI81aed b,
dal1, 8Onltorlnv to redue tbe U.. bet-
a,at88 failure and correctl.e action
(eUher etapplnq vallery PUIlp898 or
brpu.alov atrlpper efflueDt to rl.er.
A rlet to public bealtb would ..let If
cootulnanta 81.,..ate to lonr I1IItreated
porUooa of tbe Nortb Gallery.
110 elvolUcaot conetrucUon e"et, ha..rda.
Sc8a poteDUal nlate for wortara to be
exposed. to 108 l..al cont_loded vround-
water durlo" conetrucUon of the PUIlp
atatlon. Sufficient heelth end safet,
protection cen be used to protect oneUe
construction workera.
&orlnklnq .ater .taodards are preaented In Tabla 1 . Drlntlo" wlter atandards are based on aeetlnq proposed ...1808
bconl..lnanl 1...la (KeL'a) or concentrations reaultln" In an Increa..d cancer rlak of on. cas. In on. 811110n.
Nol Appllcabl.
cGAC . Granular Actl.at.d Carbon
AaemaU.e J
Collection .Ia Nortb Gallery--"Ir
Strlpplnv Treataent--
DJscharqe to IIher
PI_t of the air etrlpper unlta Ie
wIthin the flood plain and wl1l requIre
el'.ltlon abo.e the lOO-,ear of 10ld le..l
to protect heataent a,al88 froe floodlnv.
Thla e., requlr. addlUonal construction
U- u c:oepared to Alt.mathes ., 5, and
S.
Inatltutlonal requl..-ts (peralte, etc. I
as, dele, atartup.
ours abjectl.ea ..t upon a,.t.. atartup.
tsUeeted U.. for deslVO 8IId construcUon 1
to 11 aontba..
II rlak to public healtb would a.let If
contulnanl8 elvrete to lower UDtreated
porUons of tb. Nortb Gallery.
Coeplete tnet8ent 81at- faUure would
result In e.ceedanC8 of dlachlrve crlterle
durin" U- required to detect failure.
No alvolflcent public health or en. I ron-
88fttal l8p8Cta are e.peeted durlnq period
of e.ceed811C8 prior to vallery ahutdovn.
110 elvolUcent conetructlon s"et, haauds.
So8e potenUal a.late for workers to he
espo8ed to 108 lewal contulnlted qround-
w.t.r durin" construction of the pu8p etatlon
Sufficient health and safet, protection Cln b
uaed to protect onelta conatructlon .orkere.
-------
Tectmlcal
EYaluallon Criteria
I "PLDlDrrAilILln
Ease of Inltallallon 11\4 TI.. to
'apleaent
TI- to Ac:hle... ours CII:!aethaa
SAFm
Risk to Public Health an4 EbwlrOD8lnt
In Event of Syst"" failure
Safet, Durlnq Conltructlon
Table 4
Altamatha .
ColleeUon wla ElIlracUon 11811.--
Slurry lIaUnAlr Strlpplnq
Trealaent--Dlacharqe to Rlwar
('age 9 of 91
Altemathe 5
Collaetlon wla EXtraction 11811.--Alr
Strlpplnq Treataent--
DI.charqe to Rlwer
Ph..e 1 tnporary .Ir .trlw-r operaUon -, be Pha.e 1 tnporary air .hlpper operaUon
Intarrupted If operation la requlre4 4urloq hlvb .a, be Interrupted If operation la required
rl..r flow perlodl. 4urlnq hlvh rl..r flow periods.
IIIIUtuUon.1 requlr_lIl8 (pezwlt., etc. I II'
dela, .tutup.
!aU..ted U.. for dellqn and eoa.trucUon 8 to
11 8OIIthl. OUTS objecth.. ..t upon eoepleUoo
of Pbaae 1 eltracUon. PIta.. 1 ...trecUon la
..U..t.4 to lake 1 to 6 .....th., hcnrewer, 4ue to
ra4ueed flow In the ylclnltr of the Ilurry wall
r.lultlnq In leI. fl08hlnq of oont..lnant. .
froe tbe aqulf.r, the Pba.e I .atrectlon period
.., be lonqar than for Altematlwe. 5 an4 6.
The Pbale 1 .atracllon proea.. can be Inilialed
prior to coapletlon of conltructlon. 'I.. lo
achlewe ours objectlwel .a, require 11 80nlha or
loo\llr.
:i
A rl.k to public healtb wou14 e.l.t If cont..l-
nant. .I\lrate to Nortb Gall.ry.
The rl.k to public healtb all4 .quatlc life In
e.ent of air Ilrlw-r failure II nol conlldere4
qreat. TI- between .,.IN failure an4
correct he ecUon (.topplnq \lallery puepaqel
. will be .lnl.l&e4 b, ""nltorlnq on e /!allr bull
1111 Uall, followed b, 1088 I... frequent
8OnJtorlnq.
ID ..ent of ..trac:Uon .,at.. f.Uan the .larry
wall woul4 prowlde .088 deal, before
cont..lnanll c:oul4 reaeb nortb qallery nlath..
to Altemallwe. 3, 5, an4 6.
I'IItenU.l ellpORn of con.tnactlon worken to
ha.arcSou. w..te 4urlnv .Iurry waU or ..11
Inltallalloa. A4equal. bealtb and ..fel,
prolecUon can be Uled to proteet workln
Oarlnv conatrucUOD.
CoDatrucUOD CDIItrol. to pmeat 81..,raUon of
cont..lnat.4 80111 and potential reI..... of
wolatlle orqanlCl relultlnv fr08 .Iurry wall
eacawatlon, a. well as aeeel. to work areal,
will be required to protect workarl an4 r.ll-
dentl In the area. Sufficient conltructlon
control. .allt to prowlde a48quate protection.
IlIltltutlonal requlreaeatl (pereltl, etc. I
.., 4.la, .tutup.
!atl.ated tl.. for dealqn and oonltructloll
5 to 9 8ODth..
About 2 to 6 80ftthl required for co8pletlon
of Plta.e 1 followlllV conltructlon, after
wblch qallery 1,lte. can b. operated.
A rllk to public healtb woul4 .allt If con-
t..lnantl 81vrata to Nortb Gllllry.
The rllk to public healtb aquaUc life In
"ent of air Ihlpper faUure II not
consl4ere4 great. TI.. betWIlft .,.tN
failure an4 correct he ecUon (.topplnv
vallery pUlpaqal will be .lnl.l.ed br
801IJtorlnq on . /!allr bull Inltlall,
followe4 b, 1088 lell frequent 8ODltorlnv.
In ewent of ..traction 1,lt.. failure
c:ontulnanla wool4 .Iqrate to Nortb GaU.ry
Ilower than Altematlwal 1 and 3.
I'IItenUal "poRn of c:on.tructlOD workarl
to ha..r4oua "It. durlnq ..11 InltllleUon.
A4equate bealtb an4 laf.t, protection can
be 01.4 to protect work.n 4urln9
oonltructloa.
ConitrucUOII oontroll to prennt .1..,raUon
of oont..lnate4 _terlall an4 potentlll
relea.el of wolatlle orqanlca resultlnv
froe..11 InltellaUon, al w.ll al
reatrlctlnq aeeeal to work ara.., will b.
required to protect workera and re.ldents
In the ar.a. Sufficient conatructlon
c:ontroll eallt to prowlde a4equate
protec:Uon.
- -,
aDrlnklnq water Itan4sr4. are prelented In Tabl. 1. Drlnkln9 wet.r Itan/!ardl ar. bued on _tln9 propoled IUUII-
bcoot..lnant lewell (IItL'11 or concentratlonl relultlnq In an Increaled cancer rllk of one eale In one .111100.
Not Applicable .
cGAC . Granular Ac:tlwated Carbon
Allamathe 6
Colleetlon .Ia £Itractlon Ilelll--Alr
Strlppln9 Treat..nt--
Reinjection to Aquifer
Pbase 1 tnporary air Itrlpper operation
.8' be Interrupted If operation II required
durlnv bl\lh rlwer flow periods.
InaUtuUonal requlr_ta (perella, etc. I
18' dela, Itutup.
!atl.ated tI- for dealqn and oonstrucUon II
7 to 11 8Ofttbl.
About 2 to 6 IODths requl red for co8pletlon
of PIt..e I Hovlnq construction, aftar whlc
9allary a,at. A can ba operated.
'Ipe cros.ln9a un4er rl..r will requlra
ad4ed construction tl... RI.er crossln9
woul4 ba 40ne durln9 aaalonal low 9round-
water perl04s.
A rllk to public health .ou14 ealst In ewent
of air .trlpper failure or If contulnanta
.Ivrate to North Gallery.
TI.. between I,stea failure 8n4 correctlwe
action 'Itoppln9 'latter, pu8p8981 will be
8lnl.hed br 8OnJlorln9 at /!all, Intenall.
I'IItenUal IIIpORre of construction workers
to ha.ardOUl waste Gurlnv ..11 In.tallatlon.
Adequate bealth an4 IIfat, protection can be
Uled to protect workara durlnq conltructlon.
Conatructlon eoatrols to pr8Yent .19ratlon of
contulnated aolll an4 potential relea.es of
.olatlle orvenlcs relultln9 frOl Ilurr, wall
.' alcuatlon, as ..11 al ac:call to work areas,
will be required to protect workerl an4
resident. In the .rea. Sufficient
con.tructlon control I ..18t to prowlde
adequate protection.
-------
Tmle 5 "ege 1 of 41
SUIIIARY 0' DETA1LtD ANALYSIS or ALTEalATIVES
DES MOINES TeE ours
Eveluatlon Criteria
AltemaU.e I
Collection .Ie North Gellery--Alr
Stripping TreetHnt of C08blned North anel
South Geller, Flow--Dllchlrqe to DHNW
No contulnlted groundweter coulel reech
flnllheel DHWW weter without flrlt being
treeted.
Tfx:IIIIlCAL EVALUATION
Trace l."el contulnut. ,,11 1 reaaln In
DIM! fln1lhec1 water. Low el11utlon
following treet.-nt, relultl In greate.t
"II of contulnentl In DHNW flnllheel
.ater C08pered to other alternative..
IIonl torlng fl'8qU8llCf 1c1811,1 enc1 eceuracy
are .ery laportant to 1,lt.. rellmillt,
.Inee .atar II Ulec1 for elrlnklng.
AddIUonel conltrvcUon U.. .., be
required c:oapered to Alternatlv.1 4, ~,
anel 6 alDCe treatHnt a,at- M' require
conatruc:tlon In floodplain.
In ennt of treelMnt .,at- failure,
c:ontulnenta In gallery "ater wOuld
preaent blgher r1ek to public beal tb tbaD
Alternatlvea J, 4, and 5.
PotenUal edlta for rec1ucec1 flowa enel
reduced c:ontaln88Ot of contulnatlon In
long-tere elue to atruc:tural failure of
Fleur Drhe lectlon of North Gellery '"ood
conatructlon 19091.
bU..ted U.. for c1ealgn enc1 c:onatrvctlon
rangee froe 6 to 10 8ODtll8. ours
Objectlvea ..t upon a,at.. atartup.
Alternethe J
Collection .Ia North Gellery--Alr
Stripping Treat..nt--
Dllcharge to DHNW
Trace la.ela of contulnuta will re..ln In
DHNW flnhhec1 veter. Due to higher
dilution of treeted "ater, ..ee of contu-
Inenta In DIOIII 11 mout 15' of ...a fme
Alternethe 1.
nexlbillt, to bypeaa to llac:c:oon IIher III
1.lnt of Inabillt, to ...t drinking "ater
criteria "hila continuing uae of reaalnlng
portion of vellery.
Monitoring frequenc:y Cc18II,1 enc1 ec:c:urecy
ere .ery laportent to 1,lt.. rellabillt,
alnce weter II uled for elrlnklng. Monitor-
InV ec:c:urecy lell c:rltlc:el than
Allernethe I due to hlgber dllutloa froa
otber DHNW .eter.
Additional conltrvctlon U.. .., be
required c:oeperec1 to Alternathel 4, 5, enc1
6 Iince treat.-nt I,st.. ae, require
cooatrucUon In floodplain.
In e.ent of treet880t S,lt.. fellure, con-
t..lnants In gallery "ater "ould present
higher rhk to public healtb then
Alternative. J, 4, and 5.
PotenUel e"lt. for reduc:ec1 flowl enel
reduc:ec1 conteln88Dt of contulnatloD In
long-tere due to 8lructural failure of
Fleur Drhe section of Nortb Gellery lwood
conatructlon 19091.
EaU..ted tI.. for c1ellgn end conltrvctlon
ranges froe 1 to 11 IOnthl. ours
Objectlvel ..t upon a,lt.. atertup.
AltemaU.e J
Cnllectlon via North Gellery--Alr
Stripping Treateent--
Discharge to River
No treeted groundwater II dlecharged to
the DHNW. D1echarge II to the llaccoon
IIher. .
So.. lOll of vater rllourcel 12 to J IIODI
to DHNW alnce Fleur Drive section of North
Gellery "III ellacherge to Raccoon III.er.
Monitoring frequlncy enel ac:c:urac:y II lei'
critical thin Alternatlvel I, J, anel 6
. .Ince treetec1 groundwetlr II dllchargeel to
llacc:oon Rlvlr. TreatHnt s,ltea failure
or poor perforaance would not effect down-
Itreu publiC coneuaptlon If leYIII
r..alned below J60 ug/I. The nearest
down.tre.. drinking water ueer Is Ottuava,
100 allea down.tre.. on Del Molnea IIlyer.
hrlods of treataent s,at.. failure Dr
poor perforeance would be considered
short-tire "ould not be expected to
present a rlak.
Additional construction tl.. aa, be
required coapared to Alternatives 4, 5,
and 6 since treatment syetea aa, requlrl
c:onltrucllon In floodplain.
PotenUal exl.ts for reduc:ec1 flowe and
reduced contalnHnt of conta81natlon In
long-tere due to structural failure of
Fleur Drl.er section of North Gellery
Iwood conatructlon 19091.
!etlaeted tl.. for dl.19O anel construction
renqel froe 1 to 11 IOnths. ours
objectives Ht upon sy.t.. atartup.
-------
!valuation Criteria
TD:IINICAL EVAWAtlOIf
Altematl". 4
Collection via EMtractloft Walia--
Slurry Wall--Alr Stripping Treat.ent--
Dlacharge to River
No tnated groundweter la dl8Cbarged to
the DKWW. Discharge la to the Raccoon
River.
traoe 1e".la of cont_lnanta IIn1 ....aln
In the erea of the Phase 1 extrectlon
and will be collected b, the geJJery
a,atea. Theaa cont..lnant lavela 11111
be reduced further b, dlluUon with
otber DKWW IIater.
T1Ie a1uny 11811 prowldea added effect-
(Ivenesa for contaln.ent of cont..lnanta,
reducing the potential for their
.Igratlon to and collection b, the
gallar, a,at...
Monltorlll9 frequencr and 8CCUracp la
Ie.. critical tban AltemaUves I, J,
and 6 since treated groundwater la
discharged to Raccoon River. Treat88ftt
a,at.. fallur. or poor perfor88ftC8 vould
not effect pub11c consU8ptlon If levela
r...alned below 6JO ug/I (Phaae I opere-
tlonl or J,4oo ug/l (Phue J ope~atlonl.
Periods of tnatMftt .,st- fanute or
poor perfor88nce would be conaldered
sbort-tera vould not be expected to
present a risk.
91008 the ganery .,at- la not aaad,
the uaeful life of al1 a,at.. COIIponeota
ahould be about 3D ,eara, c08patlble
.vlth cleanup perloda for potentlel
groundwater re..dlal actlona.
Adverae .ffecta on DNYM vat.r qual It,
froe extraction a,at.. failure la
dela,ed C08p8red to Alt.roetlvea 3, 5,
end 6 due to preaanee of alurry IIall.',
II8e4 to ..Iotalo IIylkau1lc 91'adlent. to
the ...t acro.. the .Iurry 118)) preaant.
.088 opeetlon coapl..ltle. O"er
Alternative. 1, J, and 6.
I8Uutad tI- for de.11JII ud
conatrucUon ranva. fro. . to 12 -tlla.
Howe"er, Pheae I extraction could be
aterted In J to 5 eontha. Phaaa 1
extraction la eatl..ted to take 2 to
6 eanth. to COtIplete.
'!be abjectIYe of DItIIII a.. of the North
Gallery la not ..t for 5 to 11 8Ontha,
or poulbl, longer. "'.. could be
.Itlgated b, Isolating rlaur Drive
section of Nortb Gallery with a valvad
cutoff vall ao that r....lndar of North
Gallery can be operated during Phase I.
Table 5 ('age J of 4)
Alternative 5
Collection "Ia Eltractlon Nelia--
Air Stripping Treateent--
Discharge to RI"er
No treated groundwater dlsctlarged to
DKWW. Discharge IS to the Raccoon
River.
Trace I.".'a of cont..lnantl 11111
reealn In the area of the Phasa 1
e.tractlon and vIII be collected b,
the gallary ayatee. Thea.
contaelnant levela viii be reduced
further by dilution vlth other DMWM
vater.
R81IabI1It, 01 co11ectlon a,atee la
queatlonabl. due to operational dif-
ficulty In .alntelnlng a groundwater
divide by varying pUJIP rates In
extraction vella and the gallery
a,ate.. Seuonal and periodic
groundwater le"el fluctuation viii
coJIPllcate thla. Reliability
probl.. could be .IUgaled If rlear
Drive aeetlon of North Gallery la
not uaed In Phase J operation In
eddlUon to the planned nonopereUon
In Pha.. I.
Ad"erae .ffecta on DHNW veter
quellty fro. extraction a,at...
fallur. IIould be al.ller to
Alternatives J, 4, and 6.
IIonltorlng frequencr and aceuracr Is
lesa critical than Alternatl"es 1,
J, and 6 aln08 treated groundwater
fa dlacharged to Raccoon River.
Treateent ayst.. fallun or poor
perforaance vould oat effect public
conauapllon If levela r..alned below
410 ug/l.
!8U..ted U- for dellvn 81111 eon-
atructlon rangea froe 5 to 9 8Ontha.
Ph..e 1 e.trecUon la eaUeated to
teke J to 6 80ntba to coapJeta.
'!be abjec:U "e of DIIIIV aa. of the
Nortb GaUery Ie not .-t for 1 to
U eontha, or poulbly longer. Thle
could be .1 Ugated b, bolaUog
rieur Dr"'e aectlon of North Gallery
vlth a "al"ed cutoff vall ao that
r....lndar of North GaUery can be
operated during Phaae 1.
AlternaU"e 6
Collection via Extraction Wella--
Air Strlpplnq Treeleent--
Reinjection to Aquifer
trace la"e18 of contulnated
groundwater vll1 be collected b,
tbe gallery ayste. aa a result of
reln1ectlon of treated groundvater
ea.t of the North Geller,. These
contaelnant le"el8 viII be reduced
further by dilution vlth ather
DKWW vater.
MonltorlnCJ frequencr (4all,1 and
accuracy are very laportant to
a,.te. reliability since treated
groundwater la relnjecled and a08e
portion of the relnjecte4 vater la
collected by the gallery.
Monitoring accuracy la le.a
critical than for Altematl"ea 1
and J.
I18Uablllt, 01 collection .,atee
18 questionable due to operational
caaplexlty of ..Intalnlng ground-
vater 4h14e, howe"er, It Is .ore
eully ..Intalned than Alterna-
Uve 5 beceuse of reinjection
vell8 and slurry IIall .ev-nt.
MItigation of thla proble. could
be ecca.pllshed by not operating
rIeur Drive aectlon of Nortb
Gallery during Phase J.
Reinjection wella eay require
periOdic .alntenance to prevent
cloqqlng, thus reduclnq their
rellablJlty aa e vertical barrier.
Estl.ated tl.. for dealgn and
conatructlon rangea froe 5 to
11 eontha. Ph..e 1 e.tracUon la
eatl.ated to take J to 6 .onth. to
caaplete.
TIle abject! ". of DtMI uae of tll.
, North Gal Jer)' 18 not eet tor 7 to
, 17 eontha, or poaalbl, longer.
"'.. could be .1 tlgale4 by
laolatlng 'leur Drl"e aectlon of
North Geller, with a velved cutoff
.all ao thet r...lnder of North
Gallery can be operated during
Phase 1.
AI ternaUve 7
110 Action
Not Applicable
-------
Evaluation Criteria
pUBLIC HEAL'", Wt1.rARI, AlII
ENVIRONMENTAL EVALUATION
INSTITUTIONAL EVALUATION
"
~
C8Pltal OI.t
Annual OperatlOD , Malntananc8
) Yaar Pre.ent Wortb
10 Year Present Wortb
30 Year Pre.ent Wortb
.'
Table 5 IPaC)e) 0' .1
Alternatl.. I
CoUeetion via North Gallery--Alr
StrlpplnC) Treateent of Coablned North and
South Gallery "....--Dlschargo to DHWW
InC)e.tlon, Inh.latlon, and de..al IdiOrp-
tlon 01 trace le..ts 0' TeE (belov ItCL'sl
by DHWW vater IIse.. vould OCCllr. The RIICL
of 0 uC)/1 0' TeE vould be ewceeded.
Health rl.lI. 'ra Inbllatlon 0' TeE air
.trlpper e81.slons vould be bel.... levela
considered to be representative 0'
ecceptable rlsll.
110 .19111 fleet ad..r.. li111act. e.pectad OD
equatlc orC)aull" In event of bypass to
river.
Se'e DrlnkSn., Water Act require. that
pollutants In public drlnklnC) vater
.uppUes be In concentrations leas tbUI
MCL's. MonllorlnC) and anelysls viII be
required for volaU Ie orC)anlc coapounda at
I»MI 'acUIt,.
PI_t 0' the air .trlppl"" 'acUlt1..
.a, be vlthln tbe flood plain. Ar., Corp.
of EnC)ln..ra Pe..lt PrOCJr.. ReCJUlatlons
and Stateaent of Procedures on rlood plain
Manaveaent and WeUand Protection aay
require construction 98..lt8, eV81uations
of lapscls, and precautions durlnv
construction to alnlahe lapacta.
"location u.l.t- Ind propert,
acquisition policies "1' requtre propertr
owners be coepensated for property
ecqul red for treat..nt fecll I ties.
Co8pUance vllh the Intat 0' RCRA UId
I....a Envlronaental Qualltr Act.
"
Ca8p1la- vltb OSHA requl~t. durin.,
construction and operation.
12,201,000
231,900
J,792,000
3,615,000
.,35),000
aCo.t ..tleates Ire Order-o'-Mavnltude lev.1 estlut.s, tbat la, the cost estlaate bay.
an e.peeted accuracy of .50 and -30 percent.
Altemstlve 2
Collection via North Gallery--Alr
StrlpplnC) Tre.teent--
Discharge to DMWW
InC)eltlon, Inbalallon, Ind de...l adsorp-
tion 0' trace level. 0' TeE Ie I ug/ll by
DIIIIII vater usen vou14 occur. The RltCL 0'
o uC)1I of TeE vould be ewcoeded.
Health rl.lI. 'r08 Inhalation 0' TeE air
stripper e.lsslon. vou14 ba belov level.
considered to be representative of
acceptable risk.
110 .19111 ftcant Idve... lepacts ..pected on
equatlc orC)anll" In event of bypasl to
rJyer.
Sef. Drlnkln., Water Act require. that
pollutaula In pubUc drlnktnC) vater
supplies be In concentrations lese tban
MCL's. MonllorlnC) an4 analrsls v111 be
required for volatile organic coepounda at
DIIIW facllHy.
Placeeent of the air .trlpplnC) '&CIUUe.
ear be vi thin the flood plain. Aray Corps
of Engineer. Perell PrOCJraa ReCJUlaUons
and Stateeent of Procedures on Flood plain
Manaveeant an4 ...tlan4 Protection aay
require construction perelts, evaluation.
of lapact., Ind precautions 4urlnC)
con.tructlon to alnlalle lapacts.
IIIIlocation ...latance an4 propertr
acqulsluon poUc1es ..y require propertr
. owner. be coepensated for property
acquired for treal8ent 'acilities.
Coep1lance wltb the Intent of RCRA 8Jld
lova Envlronaental Qualltr Act.
Coepll811C8 vltb OSHA requlreeent8 durin.,
construction an4 operation.
$1,05,000
116,000
1,75. ,000
2,179,000
2,560,000 "
AHernaUve )
Collection via North Gallery--Alr
Stripping Treateent-.
Discharge to River
"..Hh risks fro. Inhalation of teE al r
Itrlpper e.llslonl vould be belov levels
considered to be representative of
acceptable risk.
Loss 0' C)roundvater nsources of 1 to
3 HGO fro. Fleur Drive section of North
Gallery. Replaceaent vlth lover quality
river vater would Increase vater use
costs.
No IlqnlflCU1t adverae public health or
envlron.ental lapacts ewpected froe .
discharge to river.
Coapllance vlth requlreeants for discharge
of vater Into public surface vaters.
National Pollution Discharge Ellalnatlon
Systea (NPDESI PereH, Cleanllater Act)
lova Water Ouallty Standard.; lova
Effluent and Pretr..at.ent Standards, '-a
Monitoring, Analytical, and ReportlnC)
Requlreeants, lova Wastevater Construction
an4 Operations Peralt..
Plaoeaent of the air strlpplnC) facilities
aay be vlthln the flood plain. Arey Corps
of EnC)lneers Paralt progru ReCJUlation.
and Stateaent of Procedures on Flood plain
Manageaant an4 lIetland Protection aay
require construction peralts, evaluations
of lapacts, and precautions durlnC)
construction to alnlalle lapacls.
RelocatJon assistance and propertr
acquisition policies aay require property
owners be coepensated ror property
ecqulred for tre.t.ent facllHles.
Coapllence vlth the Intent of RCRA an4
love Envlroneental Ouallty Act.
Coepllance vlth OSHA requlreaents 4urlnC)
construction an4 operation.
$1,16.,000
89,400
1,620,000
1,947 ,000
2,241,000
-------
!valuaUoo Criteria
I'\IBLIC HEALTH, IIELFARE, AND
DNIIOIIIDnAL EVAWATIOII
INSTITUrIONAL EVALUATION
CQ!IT
Capital Co.t
Annuel OpereUOII ,
Melntenence
1 Year Preeent Wort.
10 Year Pre.ent Morth
)0 Year Pre..nt Worth
AltemeU.. 4
Col1aetlon viI !:otrlcUon 1le111--
Slurry 1I111--Alr Stripping Treat88Dt--
Discherge to River
Hlllth rhkl fr08 InhallUon of TCE air
Itrlpper ..llllonl would be below levell
conlldered to be representetlve of
ec:c:ephble rle-.
I
Conltruc:tlon of Ilurry val1 '1' npo.e
wor_erl to he.lrdous cont..lnlntl.
Proper heelth Ind 88fet, procedurel
could .IUglte thl1 llpeet.
No 119IIIflcut adverM pd)lIc heelth or
envlr0D88ntel lepecte .xpected froe
discharge to river.
Co8pllance vlth requlr888Dte for dll-
cherge of vater Into public lurfaee
veten. Natlonel Pol1utlon DIsc:h8rge
Ellllnetlon S,lt.. INPDES) Peralt, Cleln
IIlter Act, love IIlter Ouellt, Stendards,
lova Effluent and Pretreeteent
Standarda, lowe Monitoring, Anel,tlcal,
and Reporting Requlrelent., love lIe.te-
wlter Con.truc:tlon and Opeetlon.
Peralt..
Reloc:aUOII e..letence end propert,
ecqulsltlon pollcle. '1' require
propert, ovnere be colpen'lted for
prnpert, eequlred for trel"'nt
feclllUel.
Coepllence vlth the Int.nt of .IICRA end
lowl Envlroneetnel Quallt, Act.
Coepllence vlth OStIA requlnMfltl during
con.tructlon end operltlon.
$2,152,000
41 ,lOG
2,177,000
2,550,000
2,706,000
Table 5 IPlge. of 4'
Alternative 5
Collection .11 !:otrlctlon llelll--
Air Stripping 1relt..nt--
DI.chlrge to River
nealth rll-. frol Inhelallon of teE
elr elrlpper ell..lon. would be
belov levels con. Ide red to be
repre.enlatlve of ecceplable rle_,
No 1190Ificant Idver.e public: heelth
or envlroneenlel llpecl. expected
froe dlscharge lo river.
Caepllanc:e with requlreeentl for
dllcharge of weter Into public
.urfece water.. Nltlonel Pollution
DI.charge EllllneUon S,.tel INPOESI
Peralt, Cleln lIeter Act, low. IIlter
Quellt, Standards, love Effluent and
Pretreeteent Stlndards, lo.e
Monitoring, Anal,tlcal, end
Reporting Requlre..nts, Iowa lIe.te-
veter Construction end OpeeUon,
Peralt,.
RelocaUon e..I.tUlce and propert,
acquisition pollete, ea, require
propert, ovners be COIpen,.ted for
propert, ecqulred for tr.I"ent
fecillties.
Caeplllnc:e vlth the Intent of ACRA
Ind lowl Envlroneetnll Qulllt, Act.
Coepllance vlth OStIA requlreooent.
during con.tructlon end operltlon.
8 941,000
61,700
1,2",000
1,462,000
1,684,000
OLT552/51
'cost .sU..t.. ere Order-of-llaqaltude 1...1 .sU..t.e, thet I., the co.t e.U..te heve
en expected ec:cureey of .50 end -]0 percent.
AHemeUve 6
Collection viI !:otrlctlon lIe11.--
~Ir Stripping Trelt..nt--
Reinjection to Aqul fer
Hlllth rlskl fr08 InhlllUon of
teE elr ,tripper ..198lon, would
be below level. con,ldered to be
represenhtlve of ecc..ptable rl._.
Conltl'1lCUon of .lurry wal1 ..,
..xpo,e worker. to ha.ardous
conteelnlnh. Proper h...11h Uld
8afet, proc..dure. could litigate
lhls Ilpact.
NG .19Olflcant edv..r.e I.pect.
expected on lquatlc orgenl81' 10
event of b,pa..... to river.
U.S. EPA Groundwater ProtecUon
Strltegy require. reinjection of
treated groundwater to ...t
drinking water crlterle .Ince
lqulfer 18 current 1, u,ed for
drlnklnq water ,ource ICla,. III.
Underqround Injection Control
IUIC) Progr.. require'
con.tructlon and operation of
well. colpl, with Class Y wel1..
ReI0C8tlon essl.tance Uld propert,
ec:qul.ltlon pollcle. la, require
propert, owners be coIP..n.at..d for
propert, acqulr..d for tr..atlent
flcl11IUes.
CoepllUlce with the Intent of IICRA
end lowl Envlronlentll QUlllt, Act.
,
CoepllenC18 vlth OStIA requlreeents
during con.tructlon end opeltlon.
81,705,000
81,600
2,0",000
2,)U,OOO
2,580,000
AHemltlve 7
No AcUon
Inge,tlon, Inhllltlon, Ind der-
III Id,oprtlon of teE Ind other
YOC', II level, exceeds stln-
dlrds, crlterll, or heallh
.dvI50r, b, OHWW vlter users.
Reduction In use of qlllery
.,stel for drlnkln9 waler.
Addltlonll cosls for use b,
river water vould be paid b,
users.
Not Applicable
Not Applicable
-------
29
public health and welfare and environment, 3) an assessment of public health
and environment require~ents of each alternative, and 4) a cost estimate. All
the alternatives reviewed were within the same relative order of magnitude cost
range.
RECOMMENDED ALTERNATIVE
Description of Alternative
The recommended alternative is a combination of components from Alterna-
tives 3 and 5. The objectives of the operable unit will be accomplished by
isolating the northern-most portion of the north gallery from the gallery
system by the use of a physical barrier placed across the north gallery as,
in Alternative 3 and the use of ground water extraction wells to remove and
control the migration of the contaminated ground water as 1n Alternative 5..
The recommended alternative uses air stripping treatment and discharge of
the treated water to the Raccoon River. The barrier wall, collection
system, treatment system, and disposal method are intended to work
together to cause the ground water gradient to be away from the barrier
wall, thereby preventing contaminant movement to the portions of the gallery
system used to provide water to the DMWW.
Figure 4 shows the conceptual layout of the major components. The actual
locations and number of extraction wells will be developed as part of the
design of the system. The actual size(s) and location(s) of the air stripper(s)
also will be developed as part of the design. Figure 4 shows a temporary
air stripper on the west side of the Raccoon River. The system could be
designed using a temporary stripper with a river cr~ssing to pipe the ground
water to the east air stripper. The following sections present a more detailed
discussion of each component of the recommended alternative.
North Gallery Barrier Wall
A vertical barrier wall will be constructed across the gallery to isolate
the northern-most section of the north gallery from the remainder of the
gallery system and to prevent movement of contaminated ground water to
other sections of the gallery. This barrier will be constructed at or 1n
close proximity to manhole 11. The barrier wall will consist of a soil-bentonite
slurry. It will have steel sheet piling across the gallery section. The
wall will contain a valve so that the northern section of the gallery can
be reopened once remediation is complete. The shale-slurry wall interface
will be constructed 1n such a manner to prevent the flow of ground water
and contaminants beneath the slurry wall. The slurry wall will extend a
sufficient distance on either side of the gallery system to prevent ground
water and contaminant movement from the northern-most section around the
barrier wall into the remainder of the gallery system. This distance is
estimated to be a minimum of 100 feet on either side of the gallery system.
The wall will be constructed to the shale layer, a depth estimated to be
approximately 40-45 feet.
-------
~
o
~}
150
SCALE IN FEET
RIVER
..
..
BARRIER
WALL
0- EXTRACTION WELLS
300
I
l
(
[
,
c:
-------
31
Ground Water Collection System
Ground water collection systens will be installed on both the east and
west sides of the Raccoon River. The purpose of the collection systems is to
remove contaminated ground water from the aquifer and to control contaminated
ground water movement. The collection system on the east side of the Raccoon
River will consist of extraction weTls located at such points so ~s to intercept
the majority of the contaminant plume and control its migration. The collection
system on the west side of the river will consist of extraction wells located at
such points to provide for removal of contaminated ground water in the area
between the Raccoon River, Fleur Drive, and the barrier wall described above.
The approximate locations of these extraction wells are shown on Figure 4;
however, the actual locations and number of extraction wells shall be determined
as part of the design phase of this operable unit response action.
It is anticipated that the objectives of this operable unit response
action can be met by operating these collection systems in two phases. During
Phase I, both collection systems will be operated. The west extraction wells
will be pumped at such a rate so as to maintain a hydraulic gradient in the
ground water away from the barrier wall toward the river. The east extraction
wells will be pumped at a rate to maintain a hydraulic gradient in the
ground water from the west side of the Raccoon River.to the east side of that
river and to prevent migration of contaminants to the east and south of the
.site. A control system to monitor water levels on either side of the barrier
wall will be installed to ensure the gradient is maintained. The ground
water levels throughout the site will be monitored to ensure the gradient is
maintained throughout the site to meet the objectives of the system.
. r
Phase I will continue until such time as the maximum observed TeE
concentration in the ground water in the existing monitoring wells on the west
side of the river is 5 ug/l or less for four consecutive months. The proposed
maximum contaminant level for TeE in the regulations for the Safe Drinking
Water Act is 5 ug/l. When this condition has been met, Phase II operation may
begin. During Phase II operation, only the east extraction wells will be
pumped. The valve in the barrier wall will remain closed during both Phases
I and II. The collection systems will be designed such that the ground water
divide will be maintained between the operational portion of the north gallery
and the contaminant plume during both Phase I and Phase II operations.
All extraction wells will be placed in the sand and gravel aquifer to a
depth of approximately 40 feet. The wells shall be constructed with a galvanized
steel casing with a ten-foot screen placed in the lower portion of the aquifer.
A submersible pump will be placed in the solid casing above this screened
interval. A sampling port and discharge flow meter will be included on each well
for monitoring purposes. The discharge pipes from each of the east extraction
wells will be connected to a single main transfer line running to the appropriate
treatment/disposal systen. The discharge pipes froo each of the west extraction
wells will be connected to a single transfer line running to the appropriate
treatment/disposal system. Sufficient controls, instruments, and alarms will be
provided to insure both proper operation and maintenance of the collection systems
and maintenance of records verifying such proper operation. Sufficient security
will be provided for these controls, instruments, and alarms so as to minimize
the possibility of tampering with these devices.
-------
32
Treatment/Disposal Systems
Treatment/disposal systems will be provided for both the east and west
collection systems to insure safe treatment of the extracted ground water
before discharge to the Raccoon River. Treatment will be provided by air
stripping both to remove a minimum of 96 percent of the TCE preseht in the
ground water prior to discharge and to insure compliance with the surface
water criteria as shown in Table 6. This alternative could be designed with
one stripper tower on either side of the river or one tower on the east side
with a river crossing to pipe the water from the west side to the east stripping
tower. The effluent from each air stripper will be discharged downstream of
the dam to the Raccoon River.
Selection of Remedy Process
CERCLA 101(24} states that a remedial action "...means those actions.
consistent with permanent remedy taken..." It states the a remedial action
includes, but is not limited to, "...such actions at the location of the
release as... on site treatment... and any monitoring reasonably required to
assure that such actions protect the public health and welfare and the
environment..."
. The National Oil and Hazardous Substances Pollution Contingency Plan in
40 CFR Part 300.68(c} specifies: "Response actions may be separated into
operable units consistent with achieving a permanent remedy... Implementation
of operable units may begin before selection of an appropriate final remedial
action if such measure~ are cost effective and consistent with a permanent
remedy..."
It further specifies in 40 CfR Part 300.68(i){1) that: liThe appropriate
extent of remedy shall be determifled by the lead agency's selection of a
cost-effective remedial alternative that effectively mitigates and minimizes
threats to and provides adequate protection of public health and welfare and
the environment.... This will require selection of a remedy that attains or
exceeds applicable or relevant and appropriate Federal public health and
environmental requirements that have been identified for a specific site."
The recommended alternative is consistent with CERCLA 101(24) in that
the contaminated groundwater will be collected and treated onsite through
air stripped. The treated water will be discharged onsite.
.The recommended response action is for the operable unit which addresses
the protection of the drinking water supply and control of the contaminant
migration. The collection, treatment, and disposal of the ground water will
be consistent with the permanent remedy for the site. The permanent remedy
will include measures for source control through treatment or containment of
the soil contaminants.
All the alternatives evaluated were within the same relative order of
magnitude cost range, although the cost estimates show that the recommended
alternative would be less costly than all of the alternatives evaluated
except Alternative 5 and the no-action alternative. That is because less
-------
Table 6
SURFACE WATER CRITERIA
Des Moines River
Raccoon
Ri ver
Criteria Goal Criteria
Trichloroethylene 80.7 0 5
Tetrachloroethylene 8.85 0.68
Trans-l,2-Dichloroethylene 135,000 70 70
l,l-Dichloroethylene 1.85 7 7
Vinyl Chloride 43.5 - 0 1
Ch 1 orofonn 15.7. 100
1,1-Dichloroethan2
1,2-Dichloroethane 243 0 5
1,1,1-Trichloroethane 52,800 200 200
* All values 1n ug/l
-------
34
capital costs are required for this alternative, and this alternative requires
less operation and maintenance costs than most of the other alternatives
evaluated.
The recommended alternative provides for a greater' protection of public
health than Alternatives 1,2, and 6. Through the recommended alternative, the
majority of the north gallery is useable although no treated water is to be
used by the water supply. In Alternative 1, 2, and 6 trace levels of VOCs will
remain in the water after treatment and would be used by the pUblic water supply.
Use of extraction wells, as in the recommended alternative and Alternatives
4, 5, and 6, are more efficient than using the gallery as a collection system.
Wells can be placed in areas to obtain the most efficient removal of the
contaminants and the pumping rates can be regulated in order to control the
hydraulic gradient of the ground water.
Alternative 5 would require greater monitoring as the north gallery would
be protected entirely by the control of the hydraulic gradient.
Table 7 gives a summary of the detailed evaluation of the recommended
alternative. Based on cost, technology, reliability, and operational
~onsiderations, the recommended alternative is the best alternative to meet the
objectives of the operable unit.
OPERATION AND MAINTENANCE (O&M)
The operation and maintenance for the recommended alternative will include
routine maintenance and inspection of the equipment_and sampling both onsite and
offsite. The estimated annual cost of O&M is $63,000. Since this 1s an operable
unit, the duration of operation of the response action will be dependent on the
final response action selected. The duration will, therefore, be determined as
part of the selection of the final response action. The operable unit response
action will be operated by the Respondents to the Administrative Order.
Operation and maintenance activities will include the following:
o Routine operation of the response action equipment so as to
insure proper operation of all equipment at all times.
o Routine inspection and readings from treatment equipment,
control panels, and instrumentation to ver1fy and record
proper operation.
o Routine inspection and readings from the extraction wells
to verify and record proper operation.
o Regular sampling and analysis of the operational north gallery,
monitoring wells, extraction wells, stripper influent and
effluent, Raccoon River and Des Moines River. The monitoring
schedule 1s outlined 1n Table 8. At least nine monitoring wells
-------
Evaluation Criteria
Technical Evaluation
Public Health,
Welfare, and
Environmental
Evaluation
Table 7
SUMMARY OF ANALYSIS OF
THE RECOMMENDED ALTERNATIVE
Alternative
No treated ground water is discharged to the DMWW.
Discharge is to the Raccoon River.
Some loss of water resources (2 to 3 MGD) to OMWW
since the northern-most section of the north gallery
will be discharged to the Raccoon River.
Monitoring frequency and accuracy is less critical
than Alternatives 1,2, and 6 since treated ground
water is discharged to Raccoon River. Treatment
system failure or poor performance would not effect
downstream public consumption if levels remained
below 470 ug/l. The nearest downstream drinking
water user is Ottumwa, 100 miles downstream on
Des Moines River. .
Periods of treatment system failure or poor
performance would be considered short-term would
not be expected to present a risk.
OUFS objectives met upon system startup.
Health risks from inhalation of TCE air stripper
emissions would be below levels considered to be
representative of acceptable risk.
loss of ground water resources of 2 to 3 MGD from
northern-most section of north gallery. Replacement
with lower quality river water would increase water
use costs.
No significant adverse public health or environmental
impacts expected from discharge to river.
-------
Institutional
Evaluation
Costa
Capital Cost
Annual Operation &
Maintenance
3-Year Present Worth
lO-Year Present Worth
30-Year Present Worth
Table 7
Cont'd
Compliance with requirements for discharge of water into
public surface waters. National Pollutlon Discharge
Elimination System (NPDES); Clean Water Act;
Iowa Water Quality Standards; Iowa Effluent and Pre-
treatment Standards; Iowa Monitoring, Analytical, and
Reporting Requirements; Iowa Waste Water Construction
and Operations Permits.
Placement of the air stripping facilities may be within
the floodplain. Army Corps of Engineers Permit Program
Regulations and Statement of Procedures on Floodplain
Management and Wetland Protection may require construction
permits, evaluations of impacts, and precautions during
construction to minimize impacts.
Relocation assistance and property acquisition
policies may require property owners be compensated
for property acquired for treatment facilities.
C~~pliance with the intent of RCRA and .Iowa
Environmental Quality Act.
Compliance with OSHA requirements during construction'
and operation.
$1,196,000
63,000
1,388,000
1,619,000
1,82~000
aCost estimates are Order-of Magnitude level estimates, that 1s, the cost estimate
have an expected accuracy of +50 and -30 percent.
-------
Peri od
Pre-Operation
Startup -- Six months
Six months -- Project
Completion
Table 8
MONITORING SCHEDULE FOR THE
RECOMMENDED ALTERNATIVE
Location
North Gall ery
Monitoring Wells
Extraction Wells
Rive rs
North Gallery
Monitoring Wells
Extraction Wells
Stripper Influent/Effluent
Rivers
North Gall ery
Monitoring Wells
Extraction Wells
Stripper Influent/Effluent
Rive rs
Frequency
Once
Once
Once
Once
Week ly .
Monthly
Monthly
Weekly
Weekly
Monthly
Quarterly
Quarterly
Weekly
. Quarterly
-------
.
38
and all the extraction wells will be sampled according to the
schedule. The surface water will be sampled at three locations,
one upstream of the discharge point in the Raccoon River, one
in the discharge plume in the Raccoon River about 1/4 mile
downstream of the discharge, and one in the Des Moines Rtver
downstream of its confluence with the Raccoon River.
o Analysis will be performed uSing a gas chromatograph. For
quality control purposes, one out of every ten samples will
be sent to an independent laboratory for analysis of VOCs.
o An air quality and monitoring survey will be conducted during
facility startup to evaluate the remote possibility of
exceedance of ambient TCE concentration criteria. The maximum
annual ambient cr!teria for TCE at this site is 0.769 microgram!
cubic meter (ug!m ).
o Preventative maintenance and repair of pumps and other equipment,
will include scheduled maintenance of stripper booster pumps
for bearing or packing replacement, and checks and replacement
of electrical equipment. Cleaning of the system will be
conducted at least once per quarter.
o The location of the ground water divide will be monitored with
automatic water level recording devices placed at strategically
located wells. aReadouts, together with alarms in the air
stripper control room, will alert operators to take corrective
action.
COMMUNITY RELATIONS
Overall, the community supports the alternative recommended by the
EPA. The alternative was developed with much input from the property
owners in the site area, including the Des Moines Water Works and the City of
Des Moines. Prior to the public comment period, those parties including
the Dico Company, the Des Moines Water Works, the City of Des Moines and the
Iowa Department of Natural Resources expressed their support of the alternative.
The EPA has provided information to the community on a continuous basis and
conducted two public meetings to exchange information.
Both the Water Works and the Iowa Department of Natural Resources expressed
their concern of using treated water as a portion of the drinking water source as
shown in alternatives 1, 2, and 6. The City of Ottumwa expressed their
disapproval of discharging treated water to the Raccoon River, as shown in
Alternatives 3, 4, 5 and the EPA-recommended alternative.
Concern was expressed by several entities over a possible air pollution
problem resulting from treatment of the water via air stripping. The
concern appeared to subside after the Agency explained the precautions to be
taken.
-------
.
39
CONSISTENCY WITH OTHER ENVIRONMENTAL LAWS
All the alternatives evaluated would comply with the technical requirements
of the Federal environmental laws. The recommended alternative must comply with
. the technical requirements of NPDES, RCRA,. Fish & Wildlife Coordination Act,
Clean Air Act, Section 401 of Clean Water Act, and Floodplain Management
(Executive Orders 11988 and 11990). Tahle 7 defines the requirements further.
SCHEDULE
Project Milestone
Approve Remedial Action
I~sue Administrative Order
Initiate Design
Complete Design
Initiate Construction
Complete Construction
Date
July 1986
July 1986
July 1986
November 1986
December 1986
December 1986
FUTURE ACTIONS
The operable unit response action will be monitored to determine its
efficiency prior to initiating further action. It is expected that a
feasibility study to evaluate source control alternatives will be conducted
and a second response action evaluated and potentia~ly constructed.
-------
.
COMMUNITY RELATIONS RESPONSIVENESS SUM~ARY
DES MOINES TCE
DES MOINES, POLK COUNTY, IOWA
The U.S. Environmental Protection Agency (EPA) completed the remedial
investigation on the Des Moines TCE site in December 1985. At a public
meeting on December 19, 1985, public officials and residents expressed a
need and desire for an expedited cleanup of the site. The Des Moines
Water Works (DMWW) informed the Agency that the south gallery was only
useable a portion of the time. Pumping of the gallery caused contamination
from the site to migrate to the south gallery in concentrations exceeding
safe levels. The use of the north gallery was discontinued in April 1984
because of contamination in it.
Responding to the need for remediation of the ground water, EPA elected
to divide the site work into operable units; protection of the pUblic water
supply and source control. Since the most immediate need is to restore the water
supply and protect it from the contaminants, an operable unit feasibility study
(OUFS) was initiated on that unit.
Several of the people who own or had in the past owned property on
which contamination had been detected, along with the Iowa Department of
Natural Resources (formerly the Iowa Department of Water, Air and Waste
Management) and the Iowa Attorney General's Office, participated throughout
the development of the OUFS. The Des Moines Water Works and the City of
Des Moines were involved as public entities and as'~roperty owners. Two
meetings were held with these parties. Several of these parties regularly
participated in conference calls held to review and discuss this feasibility
study and offered technical advice and assistance during that development
process. At the conclusion of the OUFS, the EPA-recommended alternative
was discussed with these parties. All of them concurred on the selection.
A fact sheet, which described the OUFS and the EPA-recommended alternative,
was sent out at the beginning of the public comment period on May 21 1986, to
about 400 people. The public comment period continued until June 20, 1986. A
public meeting on the OUFS and recommended alternative was held in Des Moines
on June 12, 1986, during the comment period. It was attended by approximately
35 people, including eight reporters.
During the development of the OUFS, the Des Moines Register, carried
several articles on the alternatives being evaluated. The newspaper
carried a lengthy article, during the comment period, on the EPA-recommended
alternative which included a graphi~al representation of the alternative.
Two major issues were identified during the development of the OUFS
and during the public comment period. Those issues were: 1) potential air
contamination caused by the air stripper, and 2) potential contamination
alternative which fnc1uded a graphical representation of the alternative.
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of the Ottumwa water supply due to air stripper effluent discharge to the
river. .
To assess if the air emissions from the air stripper would cause a
problem, the EPA Region VII Air Branch and the Iowa Department of Natural
Resources air program reviewed the types and concentrations of contaminants
detected in the ground water. They consulted with other air programs across
the country and developed a recommended maximum annual ambient concentration
level of trichloroethylene (TCE) for the air stripper. They chose to develop
the recommended concentration for TCE instead of one of the other contaminants
because 1t was the contaminant 1n the highest concentration and is a potential
carc1nogen. The number they recommended was based on the potential risk of
one person 1n 1,000,000 of developing cancer due to emission exposure.
Two computer models were used to assess if the recommended maximum
concentration level would be exceeded during operation of the air stripper.at
the Des Moines TCE site. The EPA-approved Industrial Source Complex Long
Tenn (ISCLT) dispersion model was used to predict the ambient concentrations
1n the relatively flat terrain for the proposed air stripper location. To
predict the concentrations in the elevated terrain areas north of the site,
the EPA-approved computer model VALLEY was used. The models predicted that
the ambient levels of TCE will be well below the recommended criteria. The
. computer modeling 1s described in more detail in Appendix D of the OUFS
Report. To insure that the models are correct, the air will be monitored
during the startup of the air stripper. If the average annual ambient level
is higher than the recommended criteria, corrective action will be taken to
reduce the concentrations to safe levels.
. .
The other major concern was the effects of the air stripper discharge on
Ottumwa's water supply. The City of Ottumwa is located about 100 miles down-
stream of Des Moines and obtains its drinking water from the Des Moines River.
Ottumwa 1s concerned that treated water from the air stripper discharged to
the Raccoon River, will affect the quality of their water. The Raccoon River
discharges into the Des Moines River about one mile downstream of the Des Moines
TCE site. Ottumwa has been monitoring their water for TCE and has never detected
the chemical.
To insure that the TCE levels in the treated water discharged from the air
stripper unit would not cause degradation of the Ottumwa water supply, worst
case assumptions were applied in calculating the maximum allowable TCE discharge.
It was assumed that no release of TCE from the river would occur in the 100-mile
stretch between the discharge point and the Ottumwa water intake. Also, the
assumed flow rate in the Des Moines River was the lowest measured 7-day flow in
the last 10 years. The combination of these two assumptions has the same effect
as assuming the Ottumwa water intake is just downstream from the confluence of
the Des Moines and Raccoon Rivers instead of 100 miles downstream.
The proposed maximum contaminant level (MCL) under the Safe Drinking
Water Act for TCE is 5 micrograms per liter (ug/l). The maximum discharge
concentration, therefore, was calculated so that the maximum concentration of
TCE 1n the Des Moines River just downstream of the confluence would be less
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than 5 ug/l. Assuming an effluent discharge rate from the air stripper
of one cubic foot per second (CFS) and low flow rate in the Des Moines
River of 270 CFS, the following calculation was made.
Effluent Concentration = Des Moines Surface Water Criteria x
(River Flow Rate/Effluent Flow Rate)
Effluent Concentration = 5 ug/1 x (270 CFS/l CFS)
Effluent Concentration = 1350 ug/1
The air stripper will be designed to remove 96 percent of the TCE. The
highest level of TCE detected in the ground water was about 8,000 ug/1. The
highest concentration the EPA expects to be treating will be around 3,000
ug/1 because there will be a mixture of water throughout the site with
different levels of concentrations. Removal of 96 percent of the TCE
from water containing 8,000 ug/l TCE will remove 7,680 ug/l, leaving only
320 ug/l to be discharged to the river. If the concentration is 3,000 ug/l
in the influent as expected, the concentration discharged to the river would
be 120 ug/l. Both these levels are well below the maximum level of 1,350 ug/l
which was designed to provide maximum protection of the Ottumwa water supply.
In actuality, the TCE discharged from the site is not expected to be detected
at Ottumwa because of the levels to be discharged, the high dilution in the
Des Moines River, and the additional,potential for volatilization.
The EPA wanted to determine if there could be other sources of TCE
adding to the concentration of TCE in the Des Moines River. It reviewed
historical data of water samples collected from the Des Moines River and
discharges to the river. Other sources of TCE and volatile organic contam-
inants (VaCs) were found. Discharges from two industries and one waste
water treatment plant contained concentrations of TCE and other vacs.
The maximum level of TCEin those 'samples was 34 ug!1 and was 60 ug!1 for
other VOCs. This level combined with the discharge from the air stripper
will not approach the maximum level of 1,350 ug/l. The EPA will collect
samples from the Ottumwa water supply and the Des Moines River prior to
construction.
The following is a summary of comments received by the Agency before
and during the comment p'eriod an'(t EPAls response to those comments.
Comments Received Prior to the Comment Period
Comment: A different combination of technologies other than the six
alternatives under consideration in the OUFS could be the optimal solution.
Response: The EPA agreed with the commentor and recommended a different
combination of technologies other than the alternatives evaluated in the
OUFS.
Comment: The Iowa Department of Natural Resources commented that
"Unless complete removal of contaminants can be achieved, we believe the
option of treatment and discharge into the Des Moines Water Works is the
least desirable from a public health point of view. Discharge of treated
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water into surface waters is probably the most acceptable, as long as the
levels in the Des Moines River do not exceed 5 ppb [parts per billion]
(or similar concentrations for other contaminants) at low flow conditions. II
Response: As shown by the selection of the recommended alternative, the
EPA agrees with the commentor.
Comments: The Iowa Department of Natural Resources expressed their position
that the cleanup level goal for the protection of human health or the
environment should be zero. They recognized the problem that due to
technical and financial constraints that the goal may not be feasible.
Response: The EPA agrees with the State Agency that zero contaminants
entering the environment should be the goal. The 96 percent removal
efficiency for the design of the air stripper is in compliance with Federal
standards, but still results in some discharge of contaminants. The
96 percent removal 1s considered the "best available technology" which 1s
economically feasible. To achieve 100 percent removal, treatment would be.
inhibitively costly and technically infeasible. Therefore, the level of
treatment and resulting discharges to the environment have been selected based
on compliance with Federal and State standards that are not expected to
result in an adverse impact to the public or the environment. Sufficient
monitoring will be provided to ensure that the releases to the environment
.are in compliance with applicable standards and do not result in adverse
impacts to the public and the environment.
Comment: There was a recommendation not to use the north gallery as a
drinking water source, only as an extraction sy~tem. . The extracted water
would be discharged to the river. .
Response: The alternative recommended by EPA is a~variation of the idea in
this comment. In the EPA-recommended alternative, the northern-most section
of the gallery is blocked off and not used until the site is cleaned up. The
recommended alternative differs in that an extraction well system is used
instead of the gallery for collection and the water is treated before being
discharged to the river. The extraction well system will provide for a more
efficient means for the collection of the contaminated ground water than the
use of the gallery system as a collection system. This is expected to allow
for better control for capturing the contaminants, to remove the potential
for contaminants to enter the DMWW water supply, and to decrease the length
of the time and cost of remediation.
Comment: It was recommended that a valve be put into the barrier wall
across the north gallery so that the northern part of the gallery could
be used in the future. .
Response: The barrier wall will be designed with a valve in it 50 that after
the aquifer is cleaned up, the valve could be opened and the water used.
Comment: Throughout the development of the QUFS, comments were made by
property owners and others on the reliability and applicability of the
individual technologies and alternatives being reviewed.
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Response: . Since these comments were made during the development of the
OUFS, they have been incorporated into and addressed in the OUFS report.
Comment: Construction of another water source for the water supply was
recommended instead of correcting the current contaminated area.
Response: An alternative water supply could be provided, but that would
not address the contaminant problem at the site. The Agency's goals at
the site are to provide a safe drinking water supply and address con-
tamination resulting from the site that poses a hazard to the public or
the environment. The approach EPA has taken was to provide renewed use
of the gallery system and contain and treat the majority of the known
ground water contamination at the site. This approach restores an
existing valuable resource to the DMWW and cost-effectively addresses
ground water contamination at the site. The approach of providing an
alternative ground water supply to the DMWW would only increase site
remediation costs because the ground water contamination would still
have to be addressed.
Comment: Commentor stated that "it appears that the major emphasis of
the OUFS is to restore a viable ground water supply system to the DMWW".
It was further stated, the gallery system could not supply the entire water
needs for the DMWW, therefore the use of the water north of valve number 1 .
may do little to address the long-term water quality problem in the DMWW
system.
Response: Due to the increasing need of the DMWW to use the ground water
for part of the water supply source, the Agency accelerated the feasibility
study and remediation process by dividing the site into operable units and
concentrating on the ground water operable unit. The Agency agrees that the
gallery system will not provide the entire DMWW water supply needs. Currently,
the DMWW can only use the gallery a portion of the.~ime because of the
contaminant migration to the ga11~ry. Remediation will allow more reliable
use of the gallery. .
Comment: The increasing levels of nitrates are likely to appear in the
ground water, and therefore the remediation will not provide for a long-term
solution of the nitrate problem faced by the DM~~.
Response: The remediation will restore the use of the aquifer to meet the
immediate needs of the DMWW. The nitrate contamination is not part of
the Des Moines TCE Superfund site. If non-point source releases of
nitrates cause the further degradation of the aquifer, the DMWW will need
to address that problem separately. The EPA is addressing the volatile
organic contamination of the ground water.
Comment: The Iowa Department of Natural Resources submitted a comment
that the OUFS was incorrect with regard to its discussion on mixing zone
criteria. The state regulation requires that the water quality standard
be met based on a mixing zone consisting of 25 percent of the stream flow.
Response: The mixing zone criteria was being used to determine maximum
levels of contaminants that could be discharged to the river. Since NPDES,
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the regulatory program for discharges to surface waters, requires that
Best Available Technology (BAT) must be maintained, the mixing zone criteria
was not used to establish allowable discharge levels for the recommended
alternative. The concentration of contaminants in the discharge when BAT
is required are lower than the level discharged if mixing zone criteria
were used. '
Comment: Commentor recommended air monitoring both during pre-construction
and post-construction.
Response: Since the purpose of the air monitoring is to determine whether
there is health hazard, only post-construction monitoring will be required.
Pre-construction monitoring could provide background information on the
air quality, although it will be the option of the parties constructing the
air stripper, whether to conduct pre-construction monitoring.
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Comment: Commentor had concerns about the location of the air stripper
causing icing problems on the road and being sited in a floodplain.
Response: These types of comments will be addressed during the design of
the air stripper. The stripper can be located and constructed so that
icing is not a problem. If the stripper is located on the floodplain,
the design will comply with Federal requirements for construction on a
floodplain.
Comment: The commentor requested the deletion of the reference to Tuttle
Street Landfill as a possible source of contamination.
Response: Although the remedial investigation did~ot show that the
landfill is a source, it did not rule out the possibility. The Agency,
therefore, will continue to list Tuttle Street Landfill as a potential
source.
Comment: On page 221 of the OUFS report, it states that VOCs were detected
in the ground water in four areas. The commentor thought it was misleading
to specify the four areas without defining the levels of contaminants
detected.
Response: The levels of contaminants detected in the ground water in the
four areas have been well defined in other parts of the report and,
therefore, it is not necessary to revise this one reference to the areas.
Comment: The commentor requested the EPA rename the Tuttle Street Landfill
since it was not operated as a landfill. The commentor said it was being
developed as a commercial or industrial park and accepted fill to raise
the grade or level of the property.
Response: EPA has referred to the area as the Tuttle Street Landfill 'for at
least five years. Earlier reports, such as the 1984 field investigation report
and the 1985 remedial investigation report, refer to the area as the
Tuttle Street Landfill. Those reports cannot be recalled and changed,
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therefore the Agency believes it would be too confusing to change the name
in the OUFS report.
Comment: Commentor suggested that the OUFS report should not refer to
the ground water model used in the OUFS as a "calibrated" model. The
model was used as a conceptual model, but was not a calibrated and predictive
model.
Response: The EPA agrees with the commentor that the model was a
conceptual model. Since the comment will not modify the description or
evaluation of the alternatives, the Agency does not believe it is necessary
to revise and reprint the report in order to make the change in the
report. .
Comment: Early in the feasibility study process, the EPA was evaluating
the feasibility of discharging the contaminated ground water to the Publicly
Owned Treatment Works (paTW), the waste water treatment plant. The City of
Des Moines disagreed with that alternative be~ause their current capacity.
could not handle the amount of water the remedial action would add to the
system.
Response: Through other discussions with the City, the EPA learned
that the sewer system is at and above capacity at times currently. During
times when the system cannot handle the additional influent, the storm
sewers are discharged to the river. Due to the capacity problem, the
Age"cy did not continue reviewing this disposal option.
Comments During the Comment Period
Comment: The proposed alternative only addresses the vacs, not the polynuclear
aromatic hydrocarbons and herbicides.
Response: The vacs are the contaminants in the highest concentrations.
Semi-volatile organics were detected infrequently, but not at concentrations
and frequencies that warrant a remedial action. Herbic1des were only tentatively
identified 1n the ground water. The EPA feels the presence of these compounds
;s questionable and should not be addressed by the OUFS at this time. As .
part of the source control remediation, monitoring will be provided to confirm
the presence or absence of these compounds.
Comment: The City of Des Moines submitted a comment that their proposed
arterial roadway system will be constructed in the general area of the response
action.
Response: This will not alter the selection of the response action. The
designers will work with the City in order to site and build the barrier wall
and extraction wells 1n a manner that will be compatible with the roadways.
The barrier wall could be moved south and still function as required or it
could be built at manhole #1 as envisioned and be designed so that the roadway
will not 1nterfer with 1t. The extraction wells and piping could be sited so
they will not interfer with the proposed ramp. Piping could be enclosed in an
o
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underground concrete structure and not be disturbed by the construction of the
. roadway.
Comment: The commentor recommended instead of using air stripping treatment
where the contaminants would be discharged to the air. to collect the TCE.
separate the chlorine and ethylene. and reuse the product.
Response: The amount of TCE that would be obtained daily from the ground
water in order to recycle it for future use will be very small. less than
5 kilograms per day. The cost of building and maintaining a unit to separate
the impurities and the components of the TCE would be high. Recycling of the
TCE. therefore. would not be considered cost effective.
Comment: A property owner made a comment that they did not believe an
extraction well was needed north of the Dico property. They had modified
the ground water model used in the OUFS in making their determination.
The party states that an extraction well north of the Dico property would,
cause the contamination to move to that property.
Response: Currently. the EPA believes that an extraction well will be
needed north of Dico's property. There is a source of contaminants north of
Dico which must be controlled to keep the contaminant away from the west side of
the Raccoon River. The actual locations of extraction wells will be determined
during design of the system. At that time. it could be decided that a
north well (or wells) is not needed.
Comment: The commentor recommended a third objective to the feasibility study.
That is Uthe Ottumwa Water Works must also be protected from VOC and other
ground water contamination at least as well as th~DMWW.u With this additional
objective. the commentor stated that none of the alternatives reviewed met
the objectives.
Response: The alternative the EPA recommended will protect the Ottumwa Water
Works. The maximum allowable discharge concentrations were based on protecting
downstream water supply users. The maximum concentration of TCE in the
Des Moines River after dilution was set to be less than 5 ug/l. The proposed
maximum contaminant level (MCL) in the Safe Drinking Water Act is 5 ug/l. As
Ottumwa is about 100 miles downstream of Des Moines. the TCE will be further
degraded as it travels to Ottumwa. The Agency expects the concentration at
Ottumwa to be undetectable. The commentor's objective was incorporated into
the OUFS as a part of determining allowable discharge levels.
Comment: The commentor recommended other possible alternatives 50 that
treated or untreated water would not be discharged to the river. He
recommended either Alternatives 1 or 2 as described in the OUFS; but instead
of having an emergency bypass into the river. to have a holding basin as an
alternative. He recommended that the treated water be further treated by
uv-ozone treatment or ozone-hydrogen peroxide treatment and then recharged
into the ground. Another alternative the commentor recommended would be after
air stripping. to follow the treatment with granular activated carbon polishing
before discharging it to a holding tank for use by the Des Moines Water Works.
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The commentor stated that all these of this alternatives would meet the
objectives of the project and provide a safer water supply for Ottumwa and
Des Moines.
Response: The EPA agrees that all three of the alternatives recommended
by the commentor would provide safe water to Des Moines and Ottumwa, but the
Agency also has shown that the EPA-recommended alternative will provide safe
water to both Des Moines and Ottumwa. The commentor's recommended alternatives
would require a greater construction cost and greater operation and maintenance
costs. Since a directive to the Agency is to select cost-effective response
actions and the EPA-recommended alternative provides for safe drinking
water, the Agency must select the least cost alternative.
Comment: The commentor objected to discharge of air stripping effluent to
the river because he stated there was insufficient data for two assumptions
made: 1) TCE is always the VOC in the highest concentration and 2) air stripping
treatment will remove all VOC with the same efficiency.
Response: The EPA has data from five years of work at the site and is
confident that TCE qq the VOC in the highest concentration. The EPA is also
aware that air stripping will not remove VOCs at the same efficiency. There
are other VOCs in the water that will be harder to remove than the TCE, but they
are at much lower concentrations. The EPA is confident that when the water is
treated to remove 96 percent of the TCE, the levels of the other less abundant
VOCs will be removed sufficiently.
Comment: The City of Ottumwa stated that the discharge of ground water to the
river would transfer a health risk and a financial burden to Ottumwa.
Response: Throughout the evaluation and selection of the recommended
alternative, the effects on Ottumwa were explored. There is no indication
that there would be an increased health risk to the citizens of Ottumwa.
As Ottumwa is currently testing for TCE, there would not be any increase
financial burden to Ottumwa.
Comment:
Will the TCE toncent~ate in the fish in the river?
Response: TCE does not bioaccumulate in the muscle or edible portions of
the fish, although it could remain in the liver of the fish.
Comment: There was a concern of an equipment malfunction causing untreated
water to discharge to the river.
Response: The air stripper will be designed with alarms to alert the operator
of an equipment malfunction. Many of the systems currently operating have them
designed so that the extraction wells shut down at any time there is a
malfunction. The corrective action to be taken in case of a malfunction will be
developed during design of the air stripper. .
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