EPA/ROD/R07-05/040 2005
EPA Superfund
Record of Decision:
RAILROAD AVENUE GROUNDWATER CONTAMINATION SITE EPA ID: IA0001610963 OU 01 WEST DES MOINES, IA 09/19/2005
Ciher
RECORD OF DECISION
for the
Northern Plume
Operable Unit 1
Railroad Avenue Groundwater Contamination SiteWest Des Moines, Iowa
Prepared by:
U.S. Environmental Protection Agency
Region VII
Kansas City, Kansas
September 2005
40221019
Contents
Abbreviations and Acronyms i
I. Declaration D-1
II. Decision Summary 1
1.0 Site Name, Location, and Description 1
2.0 Site History and Enforcement Activities 2
3.0 Community Participation .': 3
4.0 Scope and Role of Interim Response Action 4
5.0 Site Characteristics 45.1 Physical Characteristics 55.2 Nature and Extent of Contamination 75.3 Contaminant Migration and Conceptual Site Model 8
6.0 Current and Potential Future Site and Resource Uses 12
7.0 Summary of Site Risks 137.1 Human Health Risk Assessment 137.2 Ecological Risk Assessment 167.3 Risk Assessment Summary and Conclusion 16
8.0 Remedial Action Objectives 17
9.0 Description of Alternatives 189.1 Alternative 1: No Action ; 199.2 Alternative 2: Monitored Natural Attenuation 20
9.3 Alternatives: Extraction with Recovery Wells/On-site Tray Aeration/Surface
Water Discharge 229.4 Alternative 4: In-Situ Stripping Wells 24
10.0 Comparative Analysis of Alternatives 2610.1 Overall Protection of Human Health and the Environment 26
10.2 Compliance with Applicable or Relevant and AppropriateRequirements (ARARs) 27
10.3 Long-Term Effectiveness and Permanence 2710.4 Reduction of Toxicity, Mobility, and Volume Through Treatment 27
10.5 Short-Term Effectiveness 28
10.6 Implementability 2810.7 Cost 2910.8 State/Support Agency Acceptance 2910.9 Community Acceptance 30
11.0 Principal Threat Wastes 30
12.0 Selected Remedy 3012.1 Summary of the Rationale of Selected Remedy 3012.2 Description of Selected Remedy 31
12.3 Summary of Estimated Costs 3512.4 Expected Outcomes of the Selected Remedy 36
13.0 Statutory Determinations 3613.1 Protection of Human Health and the Environment 37
13.2 Compliance with ARARs 3713.3 Cost Effectiveness 38
13.4 Utilization of Permanent Solutions and Innovative Treatment Technologiesto the Maximum Extent Practicable 38
13.5 Preference for Treatment which Reduces Toxicity, Mobility, orVolume 39
14.0 Documentation of Significant Changes 39
III. Responsiveness Summary RS-1
Tables
Table 1 VOC Data Summary (Monitoring Wells)Table 2 VOC Data Summary (Water Supply Wells)Table 3 Medium-Specific Exposure Point Concentration SummaryTable 4 Selection of Exposure PathwaysTable 5 Non-Cancer Toxicity DataTable 6 Cancer Toxicity DataTable 7 Summary of Cancer Risk for Each Population EvaluatedTable 8 Summary of Hazard Indices for Each Population EvaluatedTable 9 Risk SummaryTable 10 Comparative Analysis of AlternativesTable 11 Metals, Geochemical, and Biochemical Data SummaryTable 12 Monitored Natural Attenuation Screening Step 1Table 13 Present Worth Cost EstimateTable 14 Final Cleanup Levels
Figures
Figure 1 Site Vicinity MapFigure 2Contaminant Contour Map
Figure 3 Conceptual Site ModelFigure 4Plot of TCE, DCE, and VC vs. Distance Downgradient from Source Area
May 2004Figure 5 Plot of TCE, DCE, and VC vs. Distance Downgradient from Source Area
November 2004
Abbreviations and Acronyms
ARARs applicable or relevant and appropriate requirements
BCF bioconcentration factor
bgs below ground surface
BTEX benzene, toluene, ethylbenzene, and xylene
CERCLA Comprehensive Environmental Response, Compensation, and
Liability Act
cis-1,2-DCE cis-1,2-dichloroethene
CFR Code of Federal Regulations
cfs cubic feet per second
COC contaminant of concern
COPC contaminant of potential concern
DNAPL dense non-aqueous phase liquid
DO dissolved oxygen
EPA U.S. Environmental Protection Agency
EPC Exposure Point Concentration
ESD explanation of significant difference
ESI expanded site inspection
FS feasibility study
ft feet
gpm gallons per minute
HI hazard index
HQ hazard quotient
IAC Iowa Administrative Code
IDNR Iowa Department of Natural Resources
MCL maximum contaminant level
mg/kg milligram per kilogram
MNA monitored natural attenuation
msl mean sea level
Railroad Avenue Groundwater Contamination SiteNorthern Plume Record of Decision
MTBE methyl tert-butyl ether
MW monitoring well
NAPL non-aqueous phase liquid
NCP National Contingency Plan
NPDES National Pollutant Discharge Elimination System
NPL National Priorities List
O&M operation and maintenance
ORP oxidation-reduction potential
OSHA Occupational Safety and Health Administration
OU Operable Unit
PA/SI preliminary assessment and site investigation
PCB polychlorinated biphenyl
PCE Tetrachloroethene
PCOPEC preliminary contaminant of potential ecological concern
POTW publicly owned treatment works
PRP potentially responsible party
RAC Response Action Contract
RAO remedial action objective
RBC risk based concentration
RCRA Resource Conservation and Recovery Act
RD remedial design
RfD reference dose
RI/FS remedial investigation/feasibility study
RI Remedial Investigation
ROD record of decision
SARA Superfund Amendments and Reauthorization Act
START Superfund Technical Assistance and Response Team
SVOC semivolatile organic compounds
TBC to-be-considered
Railroad Avenue Groundwater Contamination SiteNorthern Plume Record of Decision
TCE Trichloroethene
TCLP Toxicity Characteristic Leaching Procedure
Aig/L micrograms per liter
VC vinyl chloride
VOC volatile organic compound
WDM West Des Moines
WDMW West Des Moines Well
Railroad Avenue Groundwater Contamination SiteNorthern Plume jjj Record of Decision
I. Declaration for the Record of Decision
Northern Plume
Operable Unit 1
Railroad Avenue Groundwater Contamination Site
West Des Moines, Iowa
Site Name and Location
The Railroad Avenue Groundwater Contamination site, Comprehensive
Environmental Response, Compensation, and Liability Information System (CERCLIS)
identification number IA0001610963, is located in West Des Moines, Iowa, a suburb of
Des Moines, Iowa, in southwest Polk County in south central Iowa. Two separate source
areas and their respective contaminant plumes have been identified at the Railroad
Avenue site. Because there are two separate and distinct plumes, the site has been
separated into two operable units (OUs): OU 1 - Northern Plume, and OU 2-Southern
Plume. This Record of Decision (ROD) addresses the Northern Plume (OU 1) of the
Railroad Avenue Groundwater Contamination site.
Statement of Basis and Purpose
This decision document presents the Selected Remedy for the Northern Plume OU
of the Railroad Avenue Groundwater Contamination site in West Des Moines, Iowa. The
Selected Remedy was chosen in accordance with the Comprehensive Environmental
Response, Compensation, and Liability Act of 1980 (CERCLA), as amended by the
Superfund Amendments and Reauthorization Act of 1986 (SARA), and to the extent
practicable, the National Oil and Hazardous Substances Pollution Contingency Plan
(NCP). This decision is based on the Administrative Record for this site.
The state of Iowa concurs with the selected remedy.
Dl
Assessment of the Site
The remedial action selected in this ROD is necessary to protect the public health or
welfare and the environment from actual or threatened releases of hazardous substances
into the environment.
Description of Selected Remedy
This ROD addresses groundwater contaminants of the Northern Plume. The
Southern Plume and Northern Plume contaminants that are captured by the West Des
Moines well field were addressed in a separate ROD approved September 26, 2003. The
Northern Plume contaminants that are not captured by the West Des Moines well field are
addressed in this ROD.
The principal threat at this site is chlorinated volatile organic compounds (VOCs)
contamination in groundwater. The source materials for the VOCs in the Northern Plume
are currently unknown despite thorough investigative efforts. However, concentrations of
VOC contaminants in suspected Northern Plume source areas appear to be diminishing
through natural attenuation processes. The specific VOCs which have been identified as
contaminants of concern (COCs) are tetrachloroethene (PCE), trichloroethene (TCE), cis-
1,2-dichloroethene (cis-l,2-DCE), and vinyl chloride (VC).
The selected remedy will permanently and significantly reduce the toxiciry, mobility,
and volume of the site COCs through natural attenuation processes as the principalelement of remediation. The major components of the selected remedy for groundwater
include the following:
• Institutional controls including local or state well restrictions and public
education to prevent use of contaminated groundwater
• Restoration of the aquifer by reduction of the COCs through natural attenuation
processes
• Performance of monitoring at the site to confirm the effectiveness of the
attenuation processes
D2
Statutory Determinations
The selected remedy is protective of human health and the environment, complies
with federal and state requirements that are legally applicable or relevant and appropriate
to the remedial action, is cost effective, and utilizes permanent solutions and alternative .
treatment (or resource recovery) technologies to the maximum extent practicable. This
remedy also satisfies the statutory preference for remedies that employ treatment as a
principal element (i.e., this remedy reduces the toxicity, mobility, or volume of
contaminants through treatment). Because hazardous substances above health-based
levels are expected to be onsite in five years, a review will be conducted within five years
after completion of the remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment. . ;
Data Certification Checklist
The following information is included in the Decision Summary Section of the ROD.
Additional information can be found in the Administrative Record for this site.
• COCs and their respective concentrations
• Baseline risk represented by the COCs
• Cleanup levels established for COCs and the basis for the levels
• How source materials constituting principal threats are addressed
• Current and future land use assumptions from the baseline risk assessment
• Groundwater use that will be available at the site as a result of the selected
remedy
• Estimated capital, operation and maintenance (O&M), and total present worth
costs; discount rate; and the number of years over which the remedy cost
estimates are projected
D3
Decisive factors that lead to selecting the remedy
Authorizing Signature
Date
D4
II. Decision Summary
1.0 Site Name, Location, and Description
The Railroad Avenue Groundwater Contamination site is in West Des Moines, Iowa,
which is a suburb of Des Moines, Iowa, in southwest Polk County in south central Iowa,
(Comprehensive Environmental Response, Compensation, and Liability Information
System [CERCLIS] identification number IA0001610963). This Record of Decision
(ROD) was developed by the U.S. Environmental Protection Agency (EPA), as lead
agency, with support from the Iowa Department of Natural Resources (IDNR). Costs for
remedial efforts at the Northern Plume portion of the site are being paid by the Superfund
trust fund.
The Railroad Avenue site consists of the West Des Moines water treatment plant
well field, the areas of groundwater contamination, and the potential source areas of the
contamination (Figure 1). The site is approximately 1,000 acres in size. The West Des
Moines well field contains 22 West Des Moines municipal water supply wells
(WDMWs) that currently supply water to the West Des Moines water treatment plant.
Historically, five municipal wells had been taken offline as a result of the volatile
organic compounds (VOCs) contamination: WDMW-6, -7, -12, -13, and -21. However,
interim response actions completed at the site in November 2004 have allowed these
wells to be returned to service. Wells WDMW-2, -10, and -11 were abandoned because
of well production problems.
Two separate and distinct source areas and respective contaminant plumes have been
identified through the EPA Expanded Site Inspection (ESI) and remedial investigation
(RI) sampling efforts. Because of the two plumes, the site has been separated into two
operable units (OUs): OU 1 - Northern Plume, and OU 2 - Southern Plume.
The EPA is the lead agency for the Northern Plume. The Northern Plume lies along
Railroad Avenue in West Des Moines, Iowa, approximately between First and Thirteenth
Street, east of wells WDMW-5, -6, 12, and -13 (Figure 1). The source area for the
Northern Plume has not been identified. Several suspected source areas for the Northern
Plume were investigated during the ESI. The ESI included collecting and analyzing
sediment, surface water, groundwater, surface soil, and subsurface soil samples from
targeted industrial business properties and surrounding areas.
The Southern Plume is located northwest of wells WDMW-19, -20, and -21 where a
release of trichloroethylene (TCE) has occurred (Figure 1). Further investigation and
remediation of the Southern Plume are being performed by the potentially responsible
party (PRP) with the IDNR as the lead agency.
2.0 Site History and Enforcement Activities
The Railroad Avenue Groundwater Contamination site was first identified in 1993
when a routine water distribution sample collected by the city of West Des Moines was
found to contain cis-l,2-dichloroethene (cis-l,2-DCE) at 1.2 micrograms per liter (ug/L).
The drinking water standard for DCE is 70 ug/1. Subsequent sampling of well WDMW-
13 detected cis-l,2-DCE at significantly higher concentrations than the water distribution
sample, once at a level higher than the drinking water standard in 1996.
The contamination in the West Des Moines municipal wells was formally brought to
the attention of the EPA after a site investigation was conducted by the IDNR at a
potential source area in 1996.
The EPA performed a Preliminary Assessment/Site Investigation (PA/SI) under the
Superfund Technical Assessment and Response Team (START) program for well
WDMW-13 in October 1997. Results of the PA/SI identified two potential groundwater
contaminant plumes at locations along Railroad Avenue between West Des Moines wells
WDMW-12 and WDMW-13 and 10th Street. While contaminants were found in wellsWDMW-6 and -7, a distinct groundwater contaminant plume near these two wells was
not identified. Soil sampling conducted at five potential source areas could not determine
a primary source area. However, due to the variable groundwater flow gradients induced
by the water supply wells adjacent to the site, additional source areas south of the
investigated areas along Railroad Avenue were proposed for investigation.
An ESI was conducted by EPA in November and December 1999. Groundwater,
surface soil, subsurface soil, sediment, sewer, and surface water samples were collected
to confirm the results of the PA/SI and to investigate additional areas. Results from the
ESI confirmed that there were two source areas and separate groundwater contaminant
plumes in the southern and northern portions of the study area. Results also indicated a
need for further investigation east of the Northern Plume and south of the Southern Plume
to further delineate the plume areas and to locate any other potential source 'areas.
The EPA held a community meeting on October 24,2000, in West Des Moines,
Iowa, to present a review of the results of the ESI. Questions from the public concerning
the site were answered.-
In December 2000, IDNR used direct-push sampling techniques to collect
ground water samples at the water table and at equipment refusal (i.e., at bedrock) at three
locations along Railroad Avenue. The samples confirmed results of the ESI.
The EPA performed the RI and Feasibility Study (FS) under the Remedial Action
Contracts (RAC) program in several phases. Characterization efforts were typically
performed on a semi-annual basis beginning in April 2001 and continuing through at least
May 2005.
A previous interim remedial action that addressed those portions of the Northern and
Southern Plumes which is captured by the West Des Moines well field was authorized in
a ROD dated September 26, 2003. The interim remedial action construction was
completed in November 2004. The previous interim remedial action included increasing
the treatment capacity of the West Des Moines water treatment plant by constructing new
aerators.
3.0 Community Participation
The Community Relations Plan, the Administrative Record of Activity, the Baseline
Risk Assessment, the RI Report, the Focused FS Report, and supporting documentation
were made available to the public for a public comment period which began on July 11,
2005, and was continued until August 10, 2005. The documents were available at EPA
Region VII Headquarters in Kansas City, Kansas, and the West Des Moines Public
Library, West Des Moines, Iowa. The notice of the availability of these documents and
the time and location of the public meeting were published in the Des Moines Register on
July 10, 2005. A fact sheet summarizing the Proposed Plan and preferred alternative was
mailed to residents and local administrators on July 12,2005. A public meeting was held
during the public comment period at West Des Moines, Iowa, on July 25, 2005. At this
public meeting the Proposed Plan was presented to a broader community audience than
those that had already been involved at the site. At the public meeting, representatives
from EPA and the IDNR answered questions about the conclusions of the RI/FS, the
remedial alternatives, and the proposed remedial action. The EPA's response to the
comments received at the public meeting, as well as written comments received during
the comment period, are included in the Responsiveness Summary (Section III), which is> •
part of this ROD.
4.0 Scope and Role of the Action
This ROD addresses groundwater contaminants of the Northern Plume that are not
captured by the West Des Moines well field. Contaminants of the Southern Plume and
Northern Plume: that are captured by the West Des Moines well field were addressed in a
separate ROD approved September 26, 2003. The Southern Plume is being addressed by
the PRP with the IDNR as the lead agency. This ROD includes previous remedial action
efforts and presents the final action selected for the Northern Plume.
Several potential source areas for the Northern Plume were investigated; however, a
specific source area for the Northern Plume was not identified. During the RI, it was
determined that the western portion of the Northern Plume has adversely affected nearby
municipal water supply wells. As a result, the EPA conducted a focused FS to address
contaminated groundwater in close proximity to the municipal water supply wells,
specifically wells WDMW-5, -6, -12, and -13 in the northern West Des Moines well field
area. Therefore, EPA pursued an interim action remedy in September 2003 for theSouthern Plume and the northern West Des Moines well field area of the Northern Plume
which included increasing the treatment capacity of the West Des Moines water treatment
plant by constructing new aerators. In this ROD, EPA will address the final remedy for
the Northern Plume OU.
5.0 Site Characteristics
The physical characteristics of the site, the nature and extent of contamination, and
migration of contaminants are discussed in this section. Physical characteristics
discussed include topography and surface hydrology, regional hydrogeology and soils,
and site geology and hydrogeology. The location of contaminant sources and distribution
of the contaminants of concern (COCs) are discussed.
5.1 Physical Characteristics
The Railroad Avenue site lies within the flood plain of the Raccoon River and glacial
terrain of the Central Lowland Plains. The topography of the site area is relatively flat
with a gentle south-southeasterly slope toward the Raccoon River. The local relief of the
site vicinity is about 150 feet. The elevation ranges from approximately 800 feet mean
sea level (msl) along the Raccoon River to about 950 feet msl on the higher bluffs.
Surface drainage in the site vicinity flows south-southeast via storm drains to a retention
pond or a flooded gravel pit (Gravel Pit Lake) and eventually discharges into the Raccoon
River, which is located along the southeast edge of the site area (Figure 2). Jordan Creek,
which flows eastward along the north side of the Raccoon River Park and drains much of
southeast West Des Moines, also discharges into the Raccoon River. The perennial
Raccoon River flows easterly and has an annual mean discharge of about 2,770 cubic feet
per second (cfs) in the West Des Moines area. Approximately 10 miles downstream of
the site, the Raccoon River discharges into the Des Moines River. The Des Moines River
flows to the east and has a mean annual discharge of 6,790 cfs. The site is situated within
the 25-year flood plain of the Raccoon River, which last flooded the site area in July
1993.
The site lies above the alluvial aquifer of the Raccoon River. The site is underlain
with alluvial sediments consisting of unconsolidated clay, silt, sand, and gravel whichoverlay shale and coal of the Cherokee Group of the Pennsylvanian System. Boring logs
for the twelve monitoring wells (MW-1 through MW-12) and six observation wells (OB-
1 through OB-6) installed as part of the Phase 3 RI indicate the thickness of the
unconsolidated material to be thinnest in the western portion of the site, grading thicker
toward the east. The alluvial aquifer is unconfined and consists of permeable, sorted, and
stratified sand and gravel deposits. Depth to bedrock in the western portion of the site is
approximately 37 feet; depth to bedrock at the eastern portion of the site is approximately
52 feet.
The upper portion of the unconsolidated sediments is characterized by 0 to 7 feet of
fill material consisting of clay, silt, sand, and miscellaneous materials. The fill material is
underlain by silty clay to depths ranging from 5 to 19 feet below ground surface (bgs).
Underlying the silty clay are relatively thick units of sand and gravel interbedded with
localized clay and silt lenses containing natural organics. The natural organics
encountered include wood fragments and lignite lenses up to four inches thick. The
thickest silty clay lens encountered was ten feet thick and was encountered in well MW-3.
Depth to groundwater across the site area ranged from approximately 9 to 14 feet
bgs. Groundwater table contour maps were developed from the groundwater elevations.
The groundwater flow direction on November 4, 2004, is illustrated on Figure 2. As
illustrated, the flow direction for groundwater is to the east-southeast. Water levels
measured on other dates confirmed this groundwater flow direction. On the basis of the
groundwater contours, it appears that groundwater is recharged from upgradient flow and
infiltration of precipitation. Groundwater flows toward, and discharges into; the Gravel
Pit Lake and Raccoon River south and southeast of the site. The average horizontal
hydraulic gradient at the site varies seasonally from approximately 0.0006 foot per foot
(ft/ft) to 0.0015 ft/ft.
A pump test was performed at West Des Moines Water Supply well WDMW-13 as
part of the RI efforts. Results of the pump test indicate the hydraulic conductivity of the
alluvial aquifer to be approximately 193 feet per day. Assuming an effective porosity of
25 percent for the aquifer, the groundwater seepage velocity across the site is estimated to
be approximately 222 feet per year (ft/yr) to the east-southeast in the summer and
approximately 139 ft/yr to the east-southeast in the fall.
The alluvial aquifer is underlain by the Cherokee Group of the Pennsylvanian
system, which is approximately 400 feet thick and consists primarily of shale with thin
layers of clay, siltstone, sandstone, limestone, and coal. Bedrock encountered in
monitoring wells drilled during the Phase 3 RI was shale and coal. Although the shaleunits of the Cherokee Group will most likely act as an aquitard, preventing further
downward vertical migration of contaminants, sandstone layers within the Cherokee
Group provide groundwater to some wells in the southern half of Polk County with yields
from 5 to 25 gallons per minute (gpm). The thicknesses of these sandstone units are quite
variable and the depth of wells drilled into them varies between 75 and 100 feet.
The bedrock aquifer used as a water supply at the Railroad Avenue site consists of
the Jordan Aquifer (wells WDMW-1, -3, and -4). The Jordan Aquifer consists of
fractured and porous sandstone and dolostone of the Cambrian-Ordovician System which
can yield significant amounts of water. The Jordan Aquifer is approximately 2,500 feet
bgs. Because of the considerable depth of the Jordan Aquifer, it is extremely unlikely to
be affected by contaminants in the alluvial aquifer. . . . .
The site lies within the northeast part of the Forest City Basin bedrock structure. No
major faults have been mapped at the surface in the site vicinity, and none are known to
be active within the Holocene Epoch.
5.2 Nature and Extent of Contamination
The nature and extent of contamination in the groundwater at the Railroad Avenue
site was evaluated from the ESI and RI sampling events. The monitoring wells and the
water supply wells were sampled and analyzed for the presence of VOCs, semi-volatile
organic compounds (SVOCs), pesticides, and polychlorinated biphenyls (PCBs). The
majority of the analytical results for all wells were non-detect. Data validation efforts
qualified results where necessary and screened out contaminants identified as potential
laboratory contaminants. Because of the frequency of detection and elevated
concentrations, the contaminants tetrachloroethene (PCE), TCE, cis-l,2-DCE, and vinyl
chloride (VC) were determined to be the COCs for the Railroad Avenue Groundwater
Contamination site. The analytical results are summarized in Table 1 for the monitoring
wells and Table 2 for the West Des Moines water supply wells. Also presented in Table1 and Table 2 are the maximum contaminant levels (MCLs) for the analytes.
The concentrations of TCE, cis-l,2-DCE, and VC in groundwater have been
contoured in Figure 2 to illustrate the horizontal extent of contaminants in the aquifer.
PCE was not included in the figure because PCE was consistently detected in only one
well (MW-6) during the RI sampling events.
The surface water samples were only analyzed for VOCs. The analytical results for
the surface water samples were all non-detect for VOCs.
Diffusion bag samplers were used to evaluate the vertical stratification of VOCs at
the site. Diffusion samplers were located at depths correlating to the five most granular
zones of wells MW-3, MW-7, and MW-10. The diffusion bag results indicate a slight
trend for higher concentrations of contaminants in the lower part of the aquifer.
However, significant vertical stratification of contaminants is not indicated so that
targeting vertical zones for remedial efforts will not be beneficial.
5.3 Contaminant Migration and Conceptual Site Model
Several years of site data have been collected to evaluate site conditions. Results of
the ESI and RI indicate the primary migration pathway of contaminants at the Railroad
Avenue site is through groundwater. The conceptual model of the site is illustrated in
FigureS.
The source area or source areas for the Northern.Plume contaminants at the Railroad-
Avenue site have not been specifically identified despite thorough investigation efforts.
However, the source areas for the site contaminants are most likely a single, or several,
local businesses which improperly managed production and/or waste solvents. Several
historical and active local businesses in the site area were evaluated during the ESI.
The COCs for the site are PCE, TCE, cis-l,2-DCE, and VC which are halogenated
aliphatic compounds. PCE is widely used in the dry cleaning industry and as a solvent
for degreasing. TCE is a common solvent used for degreasing of metals, textile
processing, gas purification, and in the manufacturing of Pharmaceuticals. Cis-l,2-DCEis occasionally used in the production of solvents; however, its presence in the
environment is usually as a result of the degradation of PCE and TCE. VC is also used to
a limited extent in manufacturing processes, but as with cis-l,2-DCE, VC in the
environment is usually a result of the degradation of PCE or TCE to cis-l,2-DCE which
degrades to VC.
The migration of the COCs in groundwater is complex and subject to several
physical and chemical processes including biochemical processes and groundwater
transport. Initially, the COCs leach vertically downward into groundwater from
contaminated subsurface soils in the source area where the contaminants were originally
released. As the COCs enter the groundwater, diffusion and advection processes control
8
the migration of the contaminants. Diffusion causes the contaminants to spread in all
directions within groundwater; adsorption processes cause the COCs to remain sorbed to
the aquifer matrix. At this site, advective flow is a dominant migration process and
causes contaminants to migrate along with groundwater in the direction of groundwater
flow. Once in the groundwater, biodegradation processes reduce the persistence of the
site contaminants. The COCs typically degrade into daughter compounds through the -
loss of chlorine atoms. For example, PCE typically degrades to TCE, TCE typically
degrades to cis-l,2-DCE, cis-l,2-DCE typically degrades to VC, and VC can degrade to
ethene. Finally, ethene (which is not chlorinated) can degrade to carbon dioxide and
water.
While advective flow processes cause contaminants to migrate along with
groundwater in the direction of groundwater flow, biodegradation processes, including
reductive dechlorination, will simultaneously degrade the site contaminants.
Biodegradation is a preferred natural attenuation process because hydrocarbons are
eventually reduced to more stable, less toxic compounds. Studies have determined that
chlorinated aliphatic hydrocarbons including PCE, TCE, and cis-l,2-DCE readily degrade
in anaerobic environments.
Biodegradation of PCE and TCE is occurring at the Northern Plume area as
evidenced by the low concentrations of PCE and TCE and the relatively elevated
concentrations of cis-l,2-DCE and VC which are degradation products of PCE and TCE.
The extent of TCE, cis-l,2-DCE, and VC are illustrated in Figure 2. Figure 2 shows that
the highest concentrations of the suspected source contaminant TCE are located near thesuspected release area, whereas down gradient of the source area, the concentrations of
TCE are lower and the daughter contaminants (cis-l,2-DCE and VC) are higher.
Other indicators of biodegradation may be identified by the evaluation of site
geochemical data. Analytical results show the absence of electron acceptors such as
dissolved oxygen (DO) and nitrate within the plumes. However, sulfate, another less
easily consumed electron acceptor, is present indicating the aquifer is not at the optimal
reducing condition for reduction of the cis-l,2-DCE plume. The presence of VC
indicates that the cis-l,2-DCE plume is reducing, although at a slower rate than PCE and
TCE. The presence of electron donors, such as carbon sources, also supports the
occurrence of reductive dechlorination processes. Natural organic carbon was
encountered in borings drilled in the area which indicates the availability of a carbon
source to support reductive dechlorination. The presence of reductive dechlorination by-
products such as ferrous iron and methane also indicates the occurrence of reductive
dechlorination processes.
-Site data indicate PCE, TCE, and cis-lj2-DCE may be biodegrading at-an optimal
rate and that expansion of these plumes may not occur. However, site data indicate that
biodegradation of the VC plume may not be occurring. The aquifer is anaerobic which
does not easily allow biodegradation of VC. The VC plume continues to expand toward
the Gravel Pit Lake and Raccoon River; however, the VOC contaminants that eventually
reach these surface water bodies appear to be attenuating through natural processes as
indicated by the absence of VOCs above detection limits in the surface water samples.
The COCs are also adsorbing to the aquifer matrix which will impede contaminant
: extraction. Studies at other sites contaminated with chlorinated hydrocarbons indicate
that two to four times the dissolved concentrations can be expected to be sorbed to the
aquifer matrix. Significant amounts of chlorinated solvents can result in accumulations
of non-dissolved phase contaminants (i.e., dense nonaqueous phase liquids [DNAPL]).
However, to date DNAPL has not been identified at the site.
The groundwater flow direction at the Railroad Avenue site is primarily to the east-
southeast toward the Gravel Pit Lake and the Raccoon River. The distribution of the
plumes also shows evidence of an east-southeasterly groundwater flow trend. The
migration rates and paths for the Northern Plume contaminants have been evaluated usinggroundwater flow and contaminant transport computer models and are discussed in the
Technical Memorandum: Groundwater Model Northern West Des Moines Well Field,
July 8, 2003. A MODFLOW groundwater flow model was developed and calibrated to
site water level measurements and pump test data. A contaminant transport model was
developed to simulate contaminant migration in groundwater in the Northern West Des
Moines well field. Assumptions used in development of the model included establishing
no-flow boundaries where the bedrock forms boundaries of the alluvial aquifer and that
the WDMWs south of well WDMW-9 would not significantly affect migration of the
Northern Plume.
10
The model shows that the contaminant plumes will continue to be captured by wells
in the West Des Moines well field and will also eventually reach Gravel Pit Lake and the
Raccoon River. The VOC contaminants that eventually reach the surface water bodies
will most likely attenuate through natural processes.
Initial concentrations of the TCE, cis-1 j2-DCE, and VC contaminant plumes in the
model were the levels reported in the RI Report for the November 2002 sampling event in
combination with the ESI data. Together, these data were used as the starting point for
predictive modeling of contaminant transport.
The scenarios that were evaluated in the model include: Scenario 1 - No Action (all
wells pumping); Scenario 2 - Current Response Action (wells WDMW-5, WDMW-8, and
WDMW-9 pumping); and Scenario 3 - Potential Response Action (all wells pumping,
except well WDMW-7).
Model results for Scenario 1 (before shutting down any of the north pumping wells)
estimate that the MCL for cis-l,2-DCE is exceeded at well WDMW-13 within
approximately one year. Although, as with any transport contaminant modeling effort,
estimating the actual time of plume arrival is uncertain, it does appear that the MCL for
cis-l,2-DCE will be exceeded fairly quickly if well WDMW-13 was returned to
operation. The TCE plume is reduced to below the MCL in nearly one year, the VC
plume is reduced to below the MCL in less than ten years, and the cis-l,2-DCE plume is
nearly gone at forty years with only a small fraction (within the error of the model)
remaining.
Model results for Scenario 2 indicate that MCLs will not be exceeded in the
extraction wells that are operating under this scenario (i.e., pumping wells WDMW-5,
WDMW-8, and WDMW-9 without pumping wells WDMW-6, WDMW-7, WDMW-12,
and WDMW-13). The TCE plume is estimated to be reduced to below the MCL in less
than one year, the VC plume is reduced to below the MCL in less than ten years, and the
cis-1,2-DCE plume is reduced to below the MCL in nearly thirty years. However, the
capture zone is reduced, which would allow migration of the plumes toward Gravel Pit
Lake and the Raccoon River.
11
Scenario 3 evaluates contaminant capture with aggressive pumping at recovery wells
WDMW-5, WDMW-6, WDMW-8, WDMW-9, WDMW-12, and WDMW-13. The
modeled maximum pumping rates under Scenario 3 were 20 percent of the historical
daily average. Aggressive pumping would accelerate removal of contaminants from the
capture zone of the extraction wells. The TCE plume is estimated to be reduced to below
the MCLin less than one. year, the VC plume is reduced to below the MCL in nearly ten
years, and the cis-l,2-DCE plume is reduced to below the MCL in less than thirty years.
Bioaccumulation of halogenated aliphatic compounds is not expected to be
significant, based on the low octanol-water partition coefficients and low
bioconcentration factor values of the COCs.
6.0 Current and Potential Future Site and Resource Uses
The Railroad Avenue Groundwater Contamination site is in West Des Moines, Iowa,
which is a suburb of Des Moines, Iowa. The Northern Plume site lies along Railroad
Avenue between First Street and Thirteenth Street. The western portion of the Northern
Plume site contains a softball field complex, light industrial and commercial areas, and
single-family dwellings. Further to the east, the site is mostly commercial and residential.
The Valley Junction shopping district is located in the 100- to 300-block area along Fifth
Street. The Valley Junction shopping area has been renovated with brick sidewalks and
ornamental street fixtures. The eastern portion of the site is a residential area consisting
primarily of single-family dwellings. The southern part of the North Plume site consists
of light industrial businesses and a surface water detention basin. Future use of the site isanticipated to be similar to current uses.
Groundwater in the Railroad Avenue site and vicinity is currently used as the
primary water source for the city of West Des Moines and local industries. It is
anticipated to continue to be used as the city's water source indefinitely. Water supply
wells used by the city of West Des Moines have been impacted by the North Plume
contaminants. Surface water in the Railroad Avenue site is used recreationally.
12
7.0 Summary of Site Risks
The baseline risk assessment estimates what risks the site poses if no action was
taken. It provides the basis for taking action and identifies the contaminants and
exposure pathways that need to be addressed by the remedial action. This section of the
ROD summarizes the results of the baseline risk assessment for this site.
7.1 Human Health Risk Assessment
A human health baseline risk assessment was prepared for the Railroad Avenue
Groundwater Contamination site for drinking water. This summary presents an overview
of the risk assessment prepared for the site. The complete risk assessment may be
consulted in the Administrative Record file for a more detailed evaluation of the site
risks. The human health risk assessment qualitatively evaluated soils at the site and
quantitatively evaluated groundwater at the site. Contaminants identified in the soil were
found to be at acceptable health risk levels and will require no further action.
Contaminants identified in the groundwater, however, were found to be at unacceptable
health risk concentrations.
7.1.1 Identification of Contaminants of Concern
Risk assessment is an analysis of the potential adverse health effects that may result
from human exposure to chemical contaminants present at the site. The risk assessmentidentified several contaminants of potential concern (COPCs) in groundwater. Risk
management evaluation of the COPCs relative to natural occurrence, prevalence, and site
history determined the COCs for the Railroad Avenue site. The COCs at the Railroad
Avenue site are PCE, TCE, cis-l,2-DCE, and VC in groundwater. These VOCs may pose
adverse health effects at relatively high concentrations or exposures. Tables 3.1 through
3.8 summarize the COPCs and the Exposure Point Concentrations used in the human
health risk assessment.
13
7.1.2 Exposure Assessment
The exposure pathways evaluated in the risk assessment are presented in Figure 3
which shows the conceptual site model for the site. Table 4 summarizes all of the
scenarios and pathways considered in the risk assessment. As shown, health risks to both
current and future residents and workers from exposure (ingestion, dermal contact, and
inhalation) to groundwater were evaluated. The exposure pathways are also included in
Tables 3.1 through 3.8.
7.1.3 Toxicity Assessment
The human health risk assessment evaluated exposures to carcinogenic and non-
carcinogenic contaminants at the site. Tables 5.1 and 5.2 summarize the non-cancer
toxicity data and Tables 6.1 and 6.2 summarize the cancer toxicity data.
7.1.4 Risk Characterization
For carcinogens, risks are generally expressed as the incremental probability of an
individual's developing cancer over a lifetime as a result of exposure to the carcinogen.
Excess lifetime cancer risk is calculated from the following equation:
Risk = GDI x SF
where: risk = a unitless probability (e.g., 2 x 10"5) of an individual's developing
cancer
GDI = chronic daily intake averaged over 70 years, milligrams per
kilogram-day (mg/kg-day)
SF = slope factor, expressed as (mg/kg-day)"1
These risks are probabilities that usually are expressed in scientific notation (e.g., 1 x
10~6). An excess lifetime cancer risk of 1 x 10~6 indicates that an individual experiencing
the reasonable maximum exposure estimate has a 1 in 1,000,000 chance of developing
cancer as a result of site-related exposure. This is referred to as an "excess lifetime
cancer risk" because it would be in addition to the risks of cancer individuals face from
14
other causes such as smoking or exposure to too much sun. The chance of an individual's
developing cancer from all other causes has been estimated to be as high as one in three.
The EPA's generally acceptable risk range for site-related exposures is 10"4 to 10"6.
The potential for noncarcinogenic effects is evaluated by comparing an exposure
level over a specified time period (e.g., lifetime) with a reference dose (RfD) derived for a
similar exposure period. A RfD represents a level that an individual may be exposed to
that is not expected to cause any deleterious effect. The ratio of exposure to toxicity is
called a hazard quotient (HQ). A HQ less than 1 indicates that a receptor's dose of a
single contaminant is less than the RfD and that toxic noncarcinogenic effects from that
chemical are unlikely. The Hazard Index (HI) is generated by adding the HQs for all
COCs that affect the same target organ (e.g., liver) or that act through the same/
mechanism of action within a medium or across all media to which a given individual
may reasonably be exposed. A HI less than 1 indicates that, based on the sum of all HQs
from different contaminants and exposure routes, toxic noncarcinogenic effects from all
contaminants are unlikely. A HI greater than 1 indicates that site-related exposures may
present a risk to human health.
The HQ is calculated as follows:
Non-cancer HQ = CDI/RfD
where:
GDI = Chronic daily intake
RfD = reference dose.
The GDI and RfD are expressed in the same units and represent the same exposure
period (i.e., chronic, subchronic, or short term).
A summary of carcinogenic risks for each population is presented hi Table 7; a
summary of non-carcinogenic risks for each population is presented in Table 8.
15
As indicated in Table 7, unacceptable cancer risks resulted for the hypothetical future
resident at locations MW-6, MW-8, and well WDMW-13. There were also unacceptable
cancer risks for the hypothetical future industrial worker at MW-8. The carcinogenic
risks are associated with the COCs - TCE and VC, and the COPCs - bis(2-ethylhexyl)
phthalate and arsenic.
As indicated in Table 8, six exposure scenarios had total HI values that were above
1: the hypothetical future child and adult residents at well locations MW-6, MW-8, and
well WDMW-13. The non-carcinogenic risks are associated with the COCs - TCE and
VC, and the COPCs - manganese, arsenic, and l,2-dibromo-3-chloropropane.
Tables 9.1 through 9.11 present risk information for COPCs and media/exposure
points that could hypothetically trigger the need for remedial action. Risk management
evaluation of the COPCs relative to natural occurrence, prevalence, and site history
determined the COCs for the Railroad Avenue site. The COCs at the Railroad Avenue
site are PCE, TCE, cis-l,2-DCE, and VC in groundwater.
7.2 Ecological Risk Assessment
The Screening-Level Ecological risk assessment evaluated analytical data as they
relate to ecological risks at the Railroad Avenue Groundwater Contamination site. The
risk assessment identified several preliminary contaminants of potential ecological
concern (PCOPECs). Risk management evaluation of the PCOPECs relative to natural
occurrence, prevalence, current and future site use, and site history determined thatcurrent and future ecological risks posed by site contaminants are at acceptable levels.
7.3 Risk Assessment Summary and Conclusion
The excess carcinogenic risks to current lifetime residents (adult and child) were
calculated to be 6 x 10~6 to 2 x 10~5 and excess carcinogenic risk to current industrial
workers was calculated to range from 1 x 10"6 to 3 x 10"6. The excess carcinogenic risk to
future lifetime residents (adult and child) was calculated to range from 1 x 10^ to 7 x 10~3
and excess carcinogenic risks to future industrial workers were calculated to range from
8 xlO'5 to 3x10" (Table 7).
16
The non-carcinogenic risk (expressed as HQs) to current lifetime resident adults,
current lifetime resident children, and industrial workers was calculated to be 0.5, 1, and
0.2, respectively. The maximum noncarcinogenic risks to future lifetime resident adults,
future lifetime resident children, and industrial workers were calculated to be 4, 11, and 1,
respectively (Table 8).
The remedial action selected in this ROD is necessary to protect the public health or
welfare or the environment from actual or threatened releases of hazardous substances
from this site. However, no current unacceptable risk exists since no one is drinking
contaminated water.
8.0 Remedial Action Objectives
The Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA), as amended by Section 121(b) of the Superfund Amendments and
Reauthorization Act of 1986 (SARA), requires selection of remedial actions which ensure
protection of human health and the environment, attain applicable or relevant and
appropriate requirements (ARARs), are cost effective, use permanent solutions and
alternative treatment technologies or resource recovery technologies to the maximum
extent practicable, and satisfy the preference for treatment that reduces the toxicity,
mobility, or volume of contaminants or provide an explanation as to why they do not. To
satisfy CERCLA requirements, remedial action objectives (RAOs) were developed for
the Railroad Avenue site. General response actions were then developed to attain the
RAOs.
The RAOs developed for the contaminated groundwater at the Railroad Avenue site
within the West Des Moines well field area are identified below.
• Prevent ingestion of groundwater having concentrations of the site COCs in
excess of current regulatory drinking water standards. The current regulatory
drinking water standards for the COCs are the MCLs. The MCLs are the
maximum permissible levels established by the Safe Drinking Water Act
[40 Code of Federal Regulations (CFR) 141] for a contaminant in water that is
17
delivered to any user of a public water system. The MCLs are discussed in further
detail in the following section.
• Comply with Iowa Surface Water Criteria for COCs.
The primary focus,of the remedial action is to address remediation of the
contaminated groundwater which is the primary risk posed from the site.
9.0 Description of Alternatives
CERCLA requires that the selected site alternative be protective of human health and
the environment, be cost effective, comply with other environmental laws, and use
permanent solutions, alternative treatment technologies, and resource recovery
alternatives to the maximum extent practicable. In addition, the statute includes a
preference for the use of treatment as a principal element for the reduction of toxicity,
mobility, or volume of the hazardous substances.
The Focused FS Report prepared for the Northern Plume dated February 25, 2005,
evaluated in detail four remedial alternatives (including the no action alternative, which
EPA is required to consider by law) for addressing the contamination associated with the
Northern Plume at the Railroad Avenue Groundwater Contamination site. As part of the
process of choosing a remedy, the remedial alternatives from the FS are compared and
evaluated using nine criteria that appear in the National Oil and Hazardous Substances
Pollution Contingency Plan (NCP). (These criteria and evaluations are discussed in
Section 10 below.)
For the purpose of analyzing and comparing the remedial alternatives, EPA
estimated costs of the alternatives by making certain assumptions, such as estimating the
remediation time for pumping and treating groundwater. The EPA Superfund policy is to
try to estimate costs with "+50/-30 percent" accuracy.
The present worth of each alternative was calculated for all alternatives assuming a 7
percent discount rate for up to 30 years. The present worth is a summary measure of cost
that, for comparison purposes, turns a stream of payments or costs over a future period of
18
years into the equivalent of a single lump sum in the present. The cost estimates, as
discussed above, are conceptual, with an estimated +50 percent to -30 percent level of
accuracy. The alternatives from the Focused FS Report are described in the remainder of
Section 9. Section 10 compares the alternatives. Section 12 discusses the selected
alternative; Section 12 also discusses several additional measures that will be taken as
part of the selected remedy, including-remedial design activities.
All of the alternatives, except the no further action alternative, include institutional
controls as a common element. The institutional controls include the following:
• Implementation of well permitting requirements to limit use of groundwater at the
site. The permitting requirements would consist of an ordinance passed by the
city of West Des Moines, Iowa, prohibiting the installation of new wells if city
water is available. If a local ordinance could not be passed, a protected water
source designation at the state level would be sought. In a protected water source
area, new well installation would be restricted.
• Public education would inform local officials on well drilling restrictions and be
used to inform citizens of the potential health hazards associated with exposure to
contaminated groundwater. Public education would be implemented through
informational meetings and flyers.
9.1 Alternative 1: No Action
Estimated Capital Cost: $0
Estimated Annual Operation & Maintenance (O&M) Cost Range: $0 to $50,500Estimated Present Worth Cost: $111,300
Estimated Construction Timeframe: 0 months
Estimated Time to Achieve RAOs: Indeterminate
The NCP requires that the EPA considers a no further action alternative as a baseline
against which other remedial alternatives can be compared. Under this alternative, no
further action would be taken to monitor, control, or remediate groundwater
contamination. Alternative 1 would not meet the RAOs because it does not minimize any
future potential exposure at the site. The costs for this alternative are for the required
five-year review.
19
9.2 Alternative 2: Monitored Natural Attenuation
Estimated Capital Cost: $24,000
Estimated Annual O&M Costs Range: $15,300 to $90,300
Estimated Present Worth Costs: $430,000
Estimated Construction Timeframe: 1 month - - - •
Estimate Time to Achieve RAOs: Greater than 30 years
Alternative 2 would rely on the aquifer's ability to lower contaminant concentrations
through monitored natural attenuation (MNA) processes. This alternative includes
groundwater and surface water monitoring to confirm continued efficiency of the natural
attenuation of contaminants and institutional controls to minimize potential health risks
associated with groundwater contaminants still undergoing attenuation.
As discussed in Section 5.3, several years of site data have been collected to evaluate
site conditions. Advective flow processes cause contaminants to migrate along with
groundwater in the direction of groundwater flow while biodegradation processes
simultaneously degrade the site contaminants. Biochemical processes at sites include
biodegradation where chlorinated hydrocarbons are eventually reduced to more stable,
less toxic compounds.
Biodegradation of PCE and TCE is occurring at the Northern Plume site as
evidenced by the low concentrations of PCE and TCE and the relatively elevated
concentrations of cis-l,2-DCE and VC which are degradation products of PCE and TCE.Figure 2 illustrates that the highest concentrations of a potential source contaminant,
TCE, are located near the suspected release area, whereas downgradient of the suspected
source area, the concentrations of TCE are lower and the concentrations of daughter
contaminants (cis-l,2-DCE and VC) are higher.
The EPA has developed site screening criteria for identifying sites where efficient
biodegradation is occurring. The site data were evaluated using the screening criteria and
indicate evidence of an adequate biodegradation rate for PCE, TCE, and cis-1,2-DCE.
20
Site data indicate PCE, TCE, and cis-l,2-DCE may be biodegrading at an optimal
rate and that expansion of these plumes may not occur. However, site data indicate that
biodegradation of the VC plume may not be occurring. The aquifer is anaerobic which
does not easily allow biodegradation of VC. The VC plume continues to expand toward
the Gravel Pit Lake and Raccoon River; however, the VOC contaminants that eventually
reach these surface water bodies appear to be attenuating through natural processes as
indicated by the absence of VOCs, including VC, above detection limits in the surface
water samples.
This alternative would include implementation of local or state well permit
restrictions and public education. In addition, groundwater monitoring would be included
to evaluate the effectiveness of the natural attenuation processes. A detailed sampling
and quality assurance plan would be written before the groundwater monitoring activities
began. The sampling and quality assurance plan would include sample locations,
sampling frequency, sampling procedures, sample analysis methods, and sample
documentation procedures.
For the purpose of developing this alternative, it was assumed that one new
monitoring well would be installed downgradient of the VC plume along First Street.
The final location of the well would be determined during remedial design and would be
contingent upon access agreements with the property owners.
It was assumed that the groundwater monitoring would consist of sampling the newmonitoring well, the twelve existing monitoring wells, three surface water sample
locations, and four WDM water supply wells (WDMW-5, WDMW-6, WDMW-12, and
WDMW-13) quarterly for years one and two; semiannually for years three, four, and five;
and annually after year five until RAOs are attained. The frequency of the monitoring
may be re-evaluated and modified after the five-year reviews or after review of the
monitoring data by the EPA and IDNR. The groundwater samples would be analyzed for
VOCs.
It was assumed that the surface water monitoring would consist of collecting two
samples from the Gravel Pit Lake and one sample from the Raccoon River at the same
21
frequency of the groundwater samples. The surface water samples would also be
analyzed for VOCs.
The results of the sample analysis would be used to confirm the rate and direction of
groundwater contaminant migration. If the monitoring results indicate that the plume is
•migrating towards new receptors, further.remedial actions would be initiated.
9.3 Alternative 3: Extraction with Recovery Wells/Onsite Tray Aeration/Surface Water
Discharge
Estimated Capital Cost: $532,000
Estimated Annual O&M Costs Range: $44,500 to $145,000
Estimated Present Worth Costs: $1,343,000
Estimated Construction Timeframe: 17 to 18 months
Estimated Time to Achieve RAOs: Greater than 30 years
Alternative 3 would include extraction of contaminated groundwater using recovery
wells followed by onsite tray aeration treatment and discharge of the treated groundwaterto Gravel Pit Lake. The recovery wells would be pumped at a rate to hydraulically
control the groundwater flow which would provide containment of the groundwater
contaminant plume.
Groundwater would be extracted using three new recovery wells. Groundwater flow
equations were used to estimate the location and extraction rate of the recovery wells that
would prevent migration of contaminants to surface water bodies. It is estimated that
each recovery well would be pumped at 70 gpm to achieve a 1,380-foot-wide capturezone for each well. Strategically placing three recovery wells would achieve plume
containment and prevent migration of contaminants to the Gravel Pit Lake and Raccoon
River.
The water would be piped to an onsite treatment plant and treated by air stripping
with tray aerators. The groundwater would be pumped through a tray aeration system to
remove the contaminants. In a tray aeration system, the contaminated groundwater enters
the top of the treatment system and flows across a series of aeration trays. Air passes
upward through openings in the trays and bubbles up through the water. The bubbles and
22
water form a very turbulent mixture that is excellent for stripping the COCs from the
water and volatilizing them into the air. The vapor/contaminant mixture is removed from
the system and released to the atmosphere or treated. The system can be readily expanded
to accommodate an increase in influent flow or contaminant concentration by addition of
additional trays.
Based on available information from air stripping tray aeration vendors and the Iowa
Air Quality Standards, it is anticipated that the air stripper off-gas would not have to be
treated. Further evaluation of emission rates would be evaluated during the engineering
design.
Once collected and treated, the extracted groundwater from the recovery wells would
be discharged directly to Gravel Pit Lake through a newly constructed discharge line.
Treatment plant operation efficiency would be evaluated by collecting and analyzing
influent, effluent, and emission samples.
The final location of the recovery wells, onsite treatment system, and discharge
piping would be determined during the remedial design.
This alternative would include implementation of local or state well permit
restrictions and public education. In addition, groundwater monitoring would be included
to evaluate the effectiveness of plume containment by the recovery well. A detailed
sampling and quality assurance plan would be written before the groundwater monitoring
activities began. The sampling and quality assurance plan would include samplelocations, sampling frequency, sampling procedures, sample analysis methods, and
sample documentation procedures.
It was assumed that monitoring would consist of sampling the twelve existing
monitoring wells, three surface water sample locations, the three new recovery wells, and
four WDM water supply wells (WDMW-5, WDMW-6, WDMW-12, and WDMW-13)
quarterly for years one and two; semiannually for years three, four, and five; and annually
after year five until RAOs are attained. The frequency of the monitoring could be re-
evaluated and modified after the five-year reviews or after review of the monitoring data
23
by the EPA and IDNR. The groundwater and surface water samples would be analyzed
for VOCs.
It was assumed that the surface water monitoring would consist of collecting two
samples from the Gravel Pit Lake and one sample from the Raccoon River at the same
frequency of the groundwater samples. The surface water samples would also be
analyzed for VOCs.
The results of the sample analysis would be used to evaluate the rate and direction of
groundwater contaminant migration and determine if adjustments in recovery well flow
ratios are needed. If the monitoring results indicate that the plume is migrating towards
new receptors, further remedial actions would be initiated.
9.4 Alternative 4: In-situ Stripping Wells
Estimated Capital Cost: $670,000
Estimated Annual O&M Costs Range: $66,900 to $171,900
Estimated Present Worth Costs: $1,844,000
Estimated Construction Timeframe: 17 to 18 months
Estimated Time to Achieve RAOs: Greater than 30 years
Under Alternative 4, two lines of in-situ stripping wells would be placed along theeastern and southern edges of the plume to treat the contaminated groundwater as it
migrates towards the Gravel Pit Lake and Raccoon River. Based on information from
vendors, it is estimated that the in-situ stripping wells would have a radius of influence ofapproximately 150 feet. Therefore, it is estimated that ten in-situ stripping wells would
be required to act as a barrier between the plume and the surface water bodies.
In-situ stripping wells are double-screened wells that re-circulate groundwater in the
aquifer by pulling groundwater in through the lower well screen and recharging the
aquifer through the upper screen using air lift pumping. The air lift pumping would
simultaneously strip the VOCs from the contaminated groundwater that is pulled in
through the lower well screen.
24
The stripped VOCs are then discharged from the in-situ stripping well to the air.
Based on available information, it is not anticipated that treatment of the VOC-laden air
would be required. Further evaluation of emission rates would be conducted during the
engineering design.
This alternative would include implementation of local or state well permit
restrictions and public education. In addition, groundwater monitoring would be included
to evaluate the effectiveness of the in-situ stripping wells protection of the Gravel Pit
Lake and Raccoon River. A detailed sampling and quality assurance plan would be
written before the groundwater monitoring activities began. The sampling and quality
assurance plans would include sample locations, sampling frequency, sampling
procedures, sample analysis methods, and sample documentation procedures. Wells from
the existing monitoring well network would be used as much as possible to avoid
duplication of effort and to minimize the number of new monitoring wells installed. One
new monitoring well would be added to the existing monitoring well network to allow
evaluation of the effectiveness of the in-situ stripping wells..
It was assumed that the groundwater monitoring would consist of sampling the new
monitoring well, the twelve existing monitoring wells, the shallow and deep piezometer
at each in-situ treatment well, three surface water sample locations, and four WDM water
supply wells (WDMW-5, WDMW-6, WDMW-12, and WDMW-13) quarterly for yearsone and two; semiannually for years three, four, and five; and annually after year five
until RAOs are attained. The frequency of the monitoring could be reevaluated and
modified after the five-year reviews or after review of the monitoring data by the EPAand IDNR. The groundwater and surface water samples would be analyzed for VOCs.
It was assumed that the surface water monitoring would consist of collecting two
samples from the Gravel Pit Lake and one sample from the Raccoon River at the same
frequency of the groundwater samples. The surface water samples would also be
analyzed for VOCs.
The results of the sample analysis would be used to evaluate the rate and direction of
groundwater contaminant migration. If the monitoring results indicate that the plume is
migrating towards new receptors, further remedial actions would be initiated.
25
10.0 Comparative Analysis of Alternatives
Nine criteria are used to evaluate the different alternatives individually and against
each other in order to select a remedy. The nine evaluation criteria are: (1) overall
protection of human health and the environment; (2) compliance with ARARs; (3) long-
term effectiveness and permanence; (4) reduction of toxicity, mobility, or volume of
contaminants through treatment; (5) short-term effectiveness; (6) implementability; (7)
cost; (8) state/support agency acceptance; and (9) community acceptance. This section of
the ROD profiles the relative performance of each alternative against the nine criteria,
noting how it compares to the other options under consideration. The nine evaluation
criteria are discussed below and are summarized in Table 10.
10.1 Overall Protection of Human Health and the Environment
Overall protection of human health and the environment determines whether an
alternative eliminates, reduces, or controls threats to public health and the environmentthrough institutional controls, engineering controls, or treatment.
Human health and the environment would be adequately protected by Alternatives 2,
3, and 4. Alternatives 3 and 4 would provide the highest overall protection of human
health and the environment since groundwater contaminants are contained. Alternative 3
collects and treats the extracted groundwater before contaminants migrate to
downgradient surface water bodies. Similarly, Alternative 4 would provide treatment ofthe groundwater that passes through the line of in-situ treatment wells before
contaminants migrate to downgradient surface water bodies. Alternative 2 would provide
the next best overall protection of human health and the environment through observed
and documented natural attenuation processes. Alternative 1 would provide the least
overall protection of human health and the environment since Alternative 1 provides no
means of control to prevent public exposure to contamination and no monitoring of
plume changes.
26
10.2 Compliance with Applicable or Relevant and Appropriate Requirements (ARARs)
All the alternatives except Alternative 1 would comply with chemical-specific and
action-specific ARARs. No location-specific ARARs were identified for any alternative.
Alternatives 2, 3, and 4 would meet chemical-specific ARARs in the long term through
•MNA processes. Alternatives 3 and 4 contain the groundwater plume above cleanup
levels (i.e., MCLs) in addition to MNA processes reducing onsite contaminant levels.
10.3 Long-Term Effectiveness and Permanence
Long-term effectiveness and permanence consider the ability of an alternative to
maintain protection of human health and the environment over time.
Biodegradation of COCs at the site would be effective and permanent under
Alternatives 2, 3, and 4. Alternatives 3 and 4 would provide best long-term effectiveness
and permanence because the groundwater plume containing COCs above cleanup levels
(i.e., MCLs) would be contained. Because no remedial actions would occur,
Alternative 1 would provide the lowest long-term effectiveness and permanence.
10.4 Reduction of Toxicity, Mobility, or Volume of Contaminants Through Treatment
Reduction of toxicity, mobility, or volume of contaminants through treatment
evaluates an alternative's use of treatment to reduce the harmful effects of principal
contaminants, their ability to move in the environment, and the amount of contaminationpresent.
Alternatives 2, 3, and 4 would be effective in reducing the toxicity and volume of
contaminants at the completion of the remedial actions. However, under Alternative 2
the reduction of the toxicity of contaminants would occur through natural processes rather
than treatment efforts in the last phases of the chemical reduction process as the COCs
eventually degrade to non-toxic compounds. Alternatives 3 and 4 meet the statutory
preference for treatment as a principal element of the alternative and also reduce mobility
of contaminants. Because groundwater monitoring would not be conducted under
Alternative 1, there would be no mechanism to evaluate or demonstrate the reduction in
27
the toxicity, mobility, or volume of contaminants through natural attenuation processes.
Therefore, reduction in the toxicity, mobility, and volume of contaminants under
Alternative 1 cannot be presumed.
10.5 Short-Term Effectiveness
Short-term effectiveness considers the length of time needed to implement an
alternative and the risks the alternative poses to workers, residents, and the environment
during implementation.
Alternatives 2, 3, and 4 would reach cleanup goals in a similar timeframe which is
estimated to be in excess of thirty years. However, Alternative 3 may reach cleanup goals
slightly sooner because the recovery wells would increase the hydraulic gradient at the
site, resulting in an increased migration rate of the plume. Short-term risk would exist to
the community from onsite groundwater contaminants which are relatively slower to
attenuate. However, the short-term risks would be mitigated through institutional
controls. Alternatives 3 and 4 would contain the plume. The containment efforts may
need to operate in excess of thirty years. Alternative 1 would not include any action and
may not meet RAOs.
There would be no increase in short-term risks to workers under Alternative 1;
however, there would be a continued risk to the community because contaminants above
cleanup levels (i.e., MCLs)s would remain onsite unmanaged and unmonitored.
Alternative 2 would have minor, controllable increased risk to the community duringconstruction, and worker protection would be required during monitoring well
installation. Alternatives 3 and 4 would have the greatest short-term risks, although still
moderately low, from construction of the new onsite treatment plant, associated pipelines,
and in-situ stripping wells.
10.6 Implementability
Implementabiliry considers the technical and administrative feasibility of
implementing the alternative such as the relative availability of goods and services.
28
Alternative 1 would be the easiest alternative to implement because no construction
or operation would be required. Alternative 2 would be the next easiest alternative to
implement because the only construction required would be installation of one
monitoring well, and only periodic monitoring would be required. Alternative 4 would be
more difficult to implement because it would require installation and O&M often in-situ
stripping wells. Alternative 3 would be the most difficult to implement, requiring
construction of a new onsite treatment plant, installation of collection and discharge
piping, installation of recovery wells, as well as more extensive O&M.
10.7 Cost
Cost includes estimated capital and O&M costs as well as present worth costs. The
present worth cost is the total cost of an alternative over time in terms of today's dollar
value. Cost estimates are expected to be accurate within a range of+50 percent to -30
percent.
Cost estimates were prepared for each alternative. These estimates are approximate
and made without detailed engineering data. The actual cost of the project would depend
on the final scope of the remedial action and other unknowns. The total present worth of
Alternative 1 would be the lowest at a cost of $111,300. The total present worth cost of
Alternative 4 would be the greatest at a cost of $1,844,000. The total present worth costs
of Alternatives 2 and 3 are estimated to be $430,000 and $1,343,000, respectively.
10.8 State/Support Agency Acceptance
State agency acceptance considers whether the state agrees with the EPA's analyses
and recommendations of the RI/FS and the Proposed Plan.
The IDNR supports the preferred alternative, Alternative 2: Monitored Natural
Attenuation, as proposed by the EPA.
29
10.9 Community Acceptance
Community acceptance considers whether the local community agrees with the
EPA's analyses and preferred alternative. Comments received on the Proposed Plan are
important indicators of community acceptance.
During the public comment period, the community expressed its support for
Alternative 2: Monitored Natural Attenuation, as proposed by the EPA.
11.0 Principal Threat Wastes
The "principal threat" concept is applied to the characterization of "source materials"
at a Superfund site. A source material is material that includes or contains hazardous
substances, pollutants, or contaminants that act as a reservoir for migration of
contamination to groundwater, surface water, or air, or acts as a source for direct
exposure. Contaminated groundwater generally is not considered to be a source material;
however, non-aqueous phase liquids (NAPLs) in groundwater may be viewed as source
material.
The source materials for the VOCs in the Northern Plume are currently unknown
despite reasonable investigation efforts. However, the source materials for the Northern
Plume appear to be diminishing.
12.0 Selected Remedy
This section expands upon the details of the selected remedy from that which is
presented in the Description of Alternatives Section (Section 9) of this ROD.
12.1 Summary of the Rationale for the Selected Remedy
The selected remedy for the Northern Plume of the Railroad Avenue Groundwater
Contamination site will consist of Alternative 2: Monitored Natural Attenuation to be
performed simultaneously with the previous interim action that included expansion of the
stripping capacity at the West Des Moines drinking water plant as documented in the
30
September 26, 2003, ROD. This previously implemented interim remedial action is
intended to protect the West Des Moines water supply from contamination, leaving the
selected remedy to address only the remaining contaminants that do not impact the water
supply system. This alternative will provide the best balance of trade-offs among
alternatives with respect to the evaluating criteria. The EPA believes Alternative 2 in
conjunction with the previous interim action will be protective of human health-and the ,
environment, will comply with ARARs, will be cost effective, and will utilize permanent
solutions and alternative treatment technologies or resource recovery technologies to the
maximum extent practicable.
The main factors influencing EPA in its selection of Alternative 2 as the remedy
include:
• Institutional controls will eliminate or minimize the chance of a receptor being
exposed to the contaminated groundwater at OU 1.
• Site data indicate that significant amounts of source material or NAPLs no longer
remain at OU 1; hence, there is no evidence of principal threat wastes at OU 1.
• Monitoring of OU 1 is warranted because of the levels of COCs detected in the
groundwater at OU 1.
• Current monitoring data at the site indicate that natural attenuation is actively
occurring at the site.
12.2 Description of Selected Remedy
Alternative 2 will rely on the aquifer's ability to lower contaminant concentrations
through MNA processes. The alternative will include groundwater and surface water
monitoring to confirm continued efficiency of the natural attenuation of contaminants and
institutional controls to minimize potential health risks associated with groundwater
contaminants still undergoing attenuation. The estimated timeframe required to attain
cleanup levels is greater than thirty years, which is similar to the other proposed
alternative timeframes. The long timeframe is appropriate for the site since the
31
previously implemented interim action remedy addresses contaminated groundwater that
is collected by the West Des Moines drinking water plant.
Several years of site data have been collected to evaluate site conditions and are
summarized in Tables 1, 2, and 11. Results of the evaluation indicate that migration of
contaminants in groundwater is complex and subject to several physical and chemical
processes. However, contaminant migration at the Railroad Avenue site is strongly
affected by two primary site conditions: groundwater transport, and biochemical
processes.
The groundwater flow direction and current extent of the COCs at the Northern
Plume are illustrated in Figure 2. The groundwater flow direction at the Northern Plume
is primarily to the east-southeast toward Gravel Pit Lake and the Raccoon River. The
distribution of the contaminant plumes also shows evidence of an east-southeasterly
groundwater flow trend. However, distribution of the contaminants indicates that the
groundwater capture zone created from historical periodic pumping of WDM water wells
WDMW-5, WDMW-6, WDMW-12, and WDMW-13 has caused contaminants to migratewest toward these water supply wells.
While advective flow processes cause contaminants to migrate along with
groundwater in the direction of groundwater flow, biodegradation processes
simultaneously degrade the site contaminants. Biochemical processes at sites include
biodegradation which is where hydrocarbons are eventually reduced to more stable, less
toxic compounds. Studies show that chlorinated hydrocarbons such as PCE and TCEand, to a lesser degree, cis-l,2-DCE, can degrade naturally via reductive dechlorination
under anaerobic conditions. Biodegradation of PCE and TCE is occurring at the Northern
Plume site as evidenced by the low concentrations of PCE and TCE and the relatively
elevated concentrations of cis-l,2-DCE and VC, which are degradation products of PCE
and TCE. The extent of TCE, cis-l,2-DCE, and VC are illustrated in Figure 2. Figures 4
and 5 illustrate that the highest concentrations of the source contaminant TCE are located
near the suspected release area, whereas downgradient of the source area, the
concentrations of TCE are lower and the daughter contaminants (cis-l,2-DCE and VC)
are higher.
32
Other indicators of biodegradation include evaluation of materials within the plumes
which act as electron acceptors and electron donors in the reductive dechlorination
process and the presence or absence of by-products of the process within the plumes.
The absence of electron acceptors indicates the occurrence of reductive
dechlorination.processes. -The site geochemical data show the absence of electron
acceptors such as dissolved oxygen and nitrate within the plumes. However, sulfate,
another less easily consumed electron acceptor, is also present indicating the aquifer is
not at the optimal reducing condition for reduction of the cis-l,2-DCE plume. The
presence of VC indicates that the cis-l,2-DCE plume is reducing, albeit at a slower rate
than PCE and TCE.
The presence of electron donors, such as carbon sources, also supports the
occurrence of reductive dechlorination processes. Natural organic carbon was
encountered in borings drilled in the area which indicates the availability of a carbon
source to support reductive dechlorination.
The presence of reductive dechlorination by-products also indicates the occurrence
of reductive dechlorination processes. Site geochemical data show the presence of
reductive dechlorination by-products within the plumes including ferrous iron and
methane.
The EPA has developed site screening criteria for identifying sites where reductive
dechJorination is occurring (Technical Protocol for Evaluating Natural Attenuation ofChlorinated Solvents in Ground Water, EPA /600/R-98/128, USEPA, September 1998).
The site data from May and November 2004 were evaluated using the screening criteria.
Results of the screening evaluation are presented in Table 12 and indicate adequate
evidence for reductive dechlorination of PCE, TCE, and cis-l,2-DCE.
Site data indicate PCE, TCE, and cis-l,2-DCE may be biodegrading at an optimal
rate and that expansion of these plumes may not occur. However, site data indicate that
biodegradation of the VC plume may not be occurring. The aquifer is anaerobic which
does not easily allow biodegradation of VC. The VC plume continues to expand toward
the Gravel Pit Lake and Raccoon River; however, the VOC contaminants that eventually
33
reach these surface water bodies appear to be attenuating through natural processes as
indicated by the absence of VOCs above detection limits in the surface water samples.
The migration rates and paths for site contaminants were further evaluated by
groundwater flow and contaminant transport computer models and are discussed in the
Groundwater Model Technical Memorandum prepared for the site. Results of the
computer groundwater modeling show that the contaminant plumes will continue to be
captured by wells in the West Des Moines well field and will also eventually reach the
Gravel Pit Lake and Raccoon River.
This alternative will include implementation of local or state well permit restrictions
and public education. The alternative will include implementation of well permitting
requirements to limit use of groundwater at the site. The permitting requirements will
consist of an ordinance passed by the city of West Des Moines, Iowa, prohibiting the
installation of new wells if city water is available. If a local ordinance could not be
passed, a protected water source designation at the state level will be sought. In a
protected water source area new well installation will be restricted.
Public education efforts will be performed which will include informing local
officials on well drilling restrictions and informing citizens of the potential health hazards
associated with exposure to contaminated groundwater. Public education will be
implemented through informational meetings and flyers.
Groundwater monitoring will be included to evaluate the effectiveness of the naturalattenuation processes. A detailed sampling and quality assurance plan will be written
before the groundwater monitoring activities begin. The sampling and quality assurance
plan will include sample locations, sampling frequency, sampling procedures, sample
analysis methods, and sample documentation procedures.
One new monitoring well will be installed down gradient of the VC plume along
First Street. The final location of the well will be determined during remedial design and
will be contingent upon access agreements with the property owners.
34
Groundwater monitoring will consist of sampling the new monitoring well, the
twelve existing monitoring wells, the three surface water sample locations, and four
WDM water supply wells (WDMW-5, WDMW-6, WDMW-12, and WDMW-13)
quarterly for years one and two; semiannually for years three, four, and five; and annually
after year five until RAOs are attained. The frequency of the monitoring could be re-
evaluated and modified after the five-year reviews or-after review of monitoring data-by
the EPA and IDNR. The groundwater samples will be analyzed for VOCs.
Surface water monitoring will consist of collecting two samples from the Gravel Pit
Lake and one sample from the Raccoon River at the same frequency of the groundwater
samples. The surface water samples will be analyzed for VOCs.
The results of the sample analysis will be used to confirm the rate and direction of
groundwater contaminant migration. If the monitoring results indicate that the plume is
migrating towards new receptors, further remedial actions will be initiated. •
12.3 Summary of Estimated Costs
The detailed cost summary of the capital and O&M costs associated with the
implementation of Alternative 2 is presented in Table 13. The information in the cost
estimate is based on the best available information regarding the anticipated scope of the
remedial alternative. Changes in the cost elements are likely to occur as a result of new
information and data collected during the engineering design of the remedial alternative.
Major changes may be documented in the form of a memorandum in the AdministrativeRecord file, an Explanation of Significant Difference, or a ROD amendment. This is an
order of magnitude engineering cost estimate that is expected to be within +50 percent to
-30 percent of the actual project cost.
The capital costs include both direct and indirect capital costs. The direct capital
costs include efforts to install one additional monitoring well and legal fees to provide
assistance to the city of West Des Moines or the state of Iowa to implement permitting
requirements. With the addition of indirect costs, the total capital cost is estimated to be
$24,000. The capital costs for this alternative may be assumed by others.
35
The O&M costs associated with implementing this alternative include groundwater
monitoring and five-year reviews. The O&M costs are divided into two types, yearly and
intermittent costs. Yearly costs are those items that do not change over the life of the
alternative. Examples of yearly costs are the annual newsletters for public education.
Intermittent costs are those periodic costs that differ over the life of the alternative.
Examples of intermittent costs are the costs for groundwater monitoring and five-year
reviews.
Annual O&M costs for the first year are estimated to be $56,700 and are estimated to
be between $15,300 and $90,300 for every year thereafter. The total O&M cost for the
life of the project for Alternative 2 is $921,000. The total present worth of the O&M
costs for Alternative 2 is $406,000. The total present worth of Alternative 2 is estimated
to be $430,000.
12.4 Expected Outcomes of the Selected Remedy
The site aquifer is expected to be available as a drinking water resource as a result of
successful completion of the remedy. The selected remedy will require an extensive
period of time (greater than thirty years) to attain final cleanup levels.
Final cleanup levels were established for groundwater at the site based on the MCLs
established under the Safe Drinking Water Act. The final cleanup levels for groundwater
are presented in Table 14. The cleanup level for groundwater will restore the
groundwater to drinking water quality, with respect to VOC contamination.
13.0 Statutory Determinations
Under CERCLA Section 121, EPA must select remedies that are protective of
human health and the environment, comply with ARARs (unless a statutory waiver is
justified), are cost effective, and utilize permanent solutions and alternative treatment
technologies or resource recovery technologies to the maximum extent practicable. In
36
addition, CERCLA includes a preference for remedies that employ treatment that
permanently and significantly reduces the volume, toxicity, or mobility of hazardous
wastes as a principal element. The following sections discuss how the selected remedy
meets these statutory requirements.
• 13.1 Protection of Human Health and the Environment - - -
The selected remedial action will protect human health and the environment. Active
biodegradation processes identified at the site will eliminate the groundwater pathways
through which contaminants pose risks. Restricting future use of groundwater at the site
through institutional controls will prevent inadvertent use of groundwater contaminated
above cleanup levels.
13.2 Compliance with ARARs
Section 121(d)(2) of CERCLA, 42 USC §9621(d)(2), requires that cleanup actions
conducted under CERCLA achieve a degree or level of cleanup which, at a minimum,attains "any standard, requirement, criteria or limitation under any Federal environmental
law...or any promulgated standard, requirement, criteria, or limitation under a State
environmental or facility siting law that is more stringent than any Federal
standard...[which] is legally applicable to the hazardous substance or pollutant or
contaminant concerned or is relevant and appropriate under the circumstances of the
release or threatened release of such hazardous substance or pollutant of contaminant...."
The identified standards, requirements, criteria, or limitations thus adopted from otherenvironmental laws, which govern onsite cleanup activities at this site, are referred to as
ARARs.
For onsite cleanup activities, under Section 121(e)(l) of CERCLA, EPA is not
required to obtain any federal, state, or local permits for actions conducted onsite,
complying only with the substantive (non-administrative) requirements of the identified
federal and state laws. On the other hand, for cleanup activities that will occur offsite,
both the substantive as well as the administrative requirements of such laws will apply to
cleanup activities.
37
This section identifies the ARARs which will apply to the remedy selected for this
site. (The many laws and regulations which apply to offsite cleanup or disposal activities
are not called "ARARs" and are not enumerated here.)
• National Primary Drinking Water Standards-Safe Drinking Water Act (40 CFR
Part 141) and Iowa Water Sources (Iowa Administrative Code (IAC) 567 Chapter
41, 133, & 137): Establishes MCLs for a number of common organic and
inorganic contaminants including the site COCs. These levels regulate the
concentrations of contaminants in public drinking water supplies and are
considered relevant and appropriate for groundwater aquifers potentially used for
drinking water.
• Iowa Protected Water Sources-Purposes-Designation Procedures-Information in
Withdrawal Applications-Limitations-List of Protected Sources (IAC 567
Chapter 53): Provides for designating a protected water source.
• Iowa Water Quality Standards (IAC 567 Chapter 61): Provides for the
maintenance and protection of surface water for aquatic life, agricultural,
domestic, industrial water supply, and recreation.
In addition, all remedial activities for the site would need to comply with
Occupational Safely and Health Administration requirements.
13.3 Cost Effectiveness
The selected remedial action is cost effective, providing overall effectiveness
proportional to its costs. The selected remedy will be effective in the long term,
providing a significant and permanent reduction of the toxicity, mobility, and volume ofcontaminated groundwater contaminants.
13.4 Utilization of Permanent Solutions and Innovative Treatment Technologies to the
Maximum Extent Practicable
38
The EPA has determined, and the state of Iowa has concurred with EPA's
determination, that the selected remedy represents the maximum extent to which
permanent solutions and treatment technologies can be utilized in a practicable manner
for the Northern Plume at the Railroad Avenue Groundwater Contamination site even
though the selected remedy does not satisfy the statutory preference for treatment as a
principal element of-the remedy. Of.those alternatives that are protective of human health
and the environment and comply with ARARs, EPA and the state have determined that
this selected remedy provides the best balance of trade-offs in terms of the five balancing
criteria, while also considering the statutory preference for treatment as a principal
element and considering state and community acceptance. The selected remedy treats the
primary threats posed by VOC-contaminated groundwater, achieving VOC reduction,
although the source material for the contaminants appears to be reduced through
attenuation processes.
The selected remedy will permanently and significantly reduce the toxicity, mobility,
and volume of the site COCs through natural attenuation processes rather than through
treatment as a principal element. The most significant difference among the proposed
groundwater alternatives that met overall protection and ARARs was with regard to the
cost and implementability.
13.5 Preference for Treatment which Reduces Toxicity, Mobility, or Volume
The selected remedy does not satisfy the statutory preference for treatment as a
principal element of the remedy; however, the toxicity, mobility, and volume of the siteCOCs will be permanently and significantly reduced through natural attenuation
processes. Observed active bioremediation processes of the selected remedial action
addresses the primary threat posed by VOC-contaminated groundwater, achieving VOC
reductions, although the source material for the contaminants appears to be reduced
through attenuation processes.
14.0 Documentation of Significant Changes
The selected remedy has not been significantly changed from the preferred
alternative presented in the Proposed Plan.
39
RAILROAD AVENUE SUPERFUND SITEWEST DES MOINES, IOWA
RESPONSIVENESS SUMMARYTO
COMMENTS FROM PUBLIC MEETING
Comment 1: One commenter raised no objection to the proposal, but noted that if humanskeletal remains are uncovered during construction, work should stop immediatelyand proper authorities notified.
Response 1: The EPA will follow the noted steps if excavation uncovers such remains, but wenote that very little excavation will occur on this project.
Comment 2: Two commenters expressed concern about an existing monitoring station on thecorner of 11th and Railroad Avenue and whether it could be removed.
Response 2: As was noted at the meeting, this monitoring station is not for the EPA RailroadAvenue project. An IDNR representative at the meeting agreed to check with thestate's leaking underground storage tank program to ascertain if this station wasfor one of their projects and whether it could be removed.
Comment 3: Another commenter asked about any impacts from the project on futuredevelopment in the area.
Response 3: As we explained at the meeting, we foresee no impact on future developmentfrom our project. There is no surface impact from the contaminated groundwaterin the area, and only one additional monitoring well will be installed during theproject. No impacts to any future development should arise from this project.
Comment 4: A commenter asked if the new aerators at the water works had significantlyreduced contamination in the water supply.
Response 4: Based on data from the operation of the new aerators, they are successfullytreating any volatile organic compounds (VOCs) drawn into the municipal wellsystem. All data following aerator treatment have shown no detections for thesecontaminants.
Comment 5: The same commenter asked if any of this contamination was caused by the floodof 1993.
Response 5: We do not believe the contamination came as a result of the flood of 1993. Thecontamination in the water supply was first discovered in that year, but likely tookseveral years to travel to the well where it was first detected.
Comment 6: A commenter asked if the plume could get into the Des Moines water supplysystem.
Response 6: The remedy specifies monitoring of the plume to make sure it is annuating, andtherefore, we will be watching for this possibility during the remediation period.Based on current data, however, we believe the plume will never reach the Des
.Moines well field area and will be attenuated before it reaches the Raccoon Riverand Gravel Pit Lake.
Comment 7: The same commenter asked if there was anything citizens and businesses need todo now to protect themselves.
Response 7: Since there is no surface impact from the contamination, there is very little thatcitizens and businesses need to do. The only thing they should not do would be todrink groundwater from a private well in the area of the contamination plume.We do not know of any drinking water wells in the area, but if there are, theyshould not be used for drinking. Watering yards or gardens would not be aproblem with such wells, just do not drink it regularly.
RS2
TABLES
Table 1VOC Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
AnalytePCEPCEPCEPCEPCEPCEPCEPCEPCEPCEPCEPCETCETCETCETCETCETCETCETCETCETCETCETCE
MCL*
W
5
5
Concentration
July 2002
0.5 U0.5 U0.5 U0.5 U0.5 U
'-• 5 . ' •0.5(0.5) U
0.5 U0.5 U0.5 U0.5 U0.5 U
0.960.5 U0.5 U0.5 U6.7 :2.5
0.5(0.5) U2.80.5 U0.5 U0.5 U0.5 U
Nov. 2002
0.5 U0.5(0.5) U
0.5 U0.5 U0.5 U120.5 U0.5 U0.5 U0.5 U0.5 U0.5 U1.5
1.3(1.2)0.510.5 U6.6 :•4.70.5 U2.70.5 U1.10.5 U0.5 U
May 2003
0.5 U0.5 U0.5 U0.5 U0.5 U4.30.5 U
0.5(0.5) U0.5 U0.5 U0.5 U0.5 U1.4
0.830.5 U0.5 U2.12.60.5 U
0.5 (0.5) U0.5 U1.10.5 U0.5 U
Nov. 20031 U1 U
1.0(1.0) U1 U1 U
1.61 U1 U1 U1 U1 U1 U1 U
1.11 .0(1 .0) U
1 U' .7.3 ' ; • ; •
1 U1 U
1.71 U1 U1 U1 U
May 20040.5 U0.5 U0.5 U0.5 U0.5 U6.7 :.:•'".
0.5(0.5) U10 U0.5 U0.5 U0.5 U0.5 U
0.900.930.500.50 U
' : 5.6 • ' , ' . ' , -. 5.5 '• • .0.5(0.5) U
10 U0.50 U0.890.50 U0.50 U
Nov. 2004
NA0.5 UNA
0.5(0.5) U0.5 U
.; 5.2 -•' •0.5 U0.5 U
• 6.5. ••..-.NA0.5 U0.5 UNA0.5 UNA
0.5(0.5) U-6:12.50.5 U
0.983.3NA0.5 U0.5 U
Units
ug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume I of 4 Record of Decision
Table 1 (Continued)VOC Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
MonitoringWell
MW-01MW-02MW-Q3MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analytecis-1 ,2-DCEcis-1 ,2-DCEcis-1, 2-DCEcis-1 ,2-DCEcis-1,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1, 2-DCEcis-1, 2-DCEcis-1 ,2-DCEcis-1 ,2-DCE
VCVCVCVCVCVCVCVCVCVCVCVC
MCL*
(ufi/L)
70
2
Concentration
July 200215
:%>iio '••'200.0.5 U147.3
490(500), 3 7 0
0.5 U4.B5.20.5 U0.5 U0.5 U
0.510.5 U0.5 U0.5 U12(11)290.5 U172.72.3
Nov. 2002
10270(240)2200.5 U1112
4104200.57
46
0.5 U0.5 U
0.5(0.5) U0.5 U0.5 U0.5 U0.5 U171100.5 U8.1116.7 ...
May 200319
' ..• :. 140' •:>;1800.5 U1318
.830220(250)
0.5 U3.64.40.5 U0.5 U
0.830.550.5 U0.5 U0.5 U34
110(120)0.5 U4.321
.12 .
Nov. 200312
'•!•-',• .-V-liBO!'1. '210(220)
1 U1611
820^ 280
1 U4.45.71 U2 U2 U
2.0(2.0) U2 U2 U2 U15 J92 J2 U
' 12 J12 J.12 :J
May 200424
-'2201900.5 U199.1
-;110(130)370;0.5 U4.66.60.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U
2.4(2.0)670.5 U7.6131.2
Nov. 2004NA0.5 UNA
0.5(0.5) U144.8
v 170290 :6.6NA3.60.5 UNA1.7NA
0.5(0.5) U0.5 U0.5 U2.8370.5 UNA5.80.66
Unitsug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 2 of 4 Record of Decision
Table 1 (Continued)VOC Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
MonitoringWell
MW-01
MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09
MW-10MW-11
MW-12MW-01
MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11
MW-12
Analyte
1,1 -DCE1,1 -DCE1,1 -DCE1,1 -DCE
1,1 -DCE1,1 -DCE
1,1 -DCE
1,1 -DCE1,1 -DCE
1,1-DCE1,1 -DCE
1,1-DCE
MTBEMTBEMTBEMTBEMTBEMTBEMTBEMTBEMTBEMTBEMTBEMTBE
MCL*
<PSM
7
None
Concentration
July 2002
0.5 U0.5 U0.60.5 U
0.5 U0.5 U
1.6(1.6)1.20.5 U
0.5 U
0.5 U0.5 U1
0.5 U0.99
0.5 U12
0.5 U
1.5(1.5)1.92.23.2
0.5 U3.2
Nov. 2002
0.5 U0.5(0.5) U
0.5 U
0.5 U0.5 U
0.5 U
0.5 U
1.0
0.5 U
0.5 U
0.5 U0.5 U1.1
1.1(0.9)1.2
0.5 U11
0.5 U1.5
2.37.6
6.3
0.5 U4.1
May 2003
0.5 U0.60.70.5 U0.5 U0.5 U2.5
0.9(0.9)
0.5 U
0.5 U
0.5 U0.5 U0.5 U
0.5 U0.5 U
0.5 U1.1
0.5 U
0.5 U0.5(0.5) U
0.5 U
0.5 U
0.5 U0.5 U
Nov. 2003
1 U1 U
1.0(1.0) U1 U
1 U
1 U
1.31 U
1 U
1 U1 U
1 U--
-
--
-
-
--
-
-
-
May 2004 | Nov. 2004
0.5 U0.690.690.5 U0.5 U0.5 U
0.5(0.5) U10 U0.5 U0.5 U0.5 U0.5 U0.670.750.88
0.5 U13
0.5 U
0.5(0.5) U10 U1.9
3.0
0.5 U4.1
MA
0.5 UNA
0.5(0.5) U0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
NA
0.5 U0.5 U.NA
2.6NA
0.5(0.5) U8.90.5 U
0.5 U1.1
0.5 UNA
0.5 U1.7 J
Units
ug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 3 of 4 Record of Decision
Table 1 (Continued)VOC Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analytetrans-1,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCEtrans-1 ,2-DCE
MCL*
<w/u
100
Concentration
July 2002
0.5 U0.5 U1.30.5 U0.5 U0.5 U
4.7(4.5)3.10.5 U0.5 U0.5 U0.5 U
Nov. 20020.5 U
2.1(1.7)1.30.5 U0.5 U0.5 U3.2
3.90.5 U0.5 U0.5 U0.5 U
May 20031.11.31.30.5 U0.5 U0.5 U4.2
1.9(1.9)0.5 U0.5 U0.5 U0.5 U
Nov. 2003
1 U1.3
1.1(1.1)1 U1 U1 U321 U1 U1 U1 U
May 20040.632.11.30.5 U0.5 U0.5 U
1.2(1.1)10 U0.5 U0.5 U0.5 U0.5 U
Nov. 2004NA0.5 UNA
0.5(0.5) U0.5 U0.5 U1
1.60.5 UNA0.5 U0.5 U
Units
ug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
* Maximum contaminant levels established under 40 CFR 141
ug/L = micrograms per liter
U = Not detected at or above the reportable level shown.
J = The associated numerical value is an estimated quantity.
Duplicate result in parentheses.
NA = not available
Shaded results indicate where contaminant was detected above respective MCL.
Other VOCs detected infrequently at low concentrations include 2-butanone at 0.76 ug/L in well MW-7 in July 2002, toluene at 0.76 ug/Lin well MW-1 in July 2002, and 1,2-dibromo-3-chloropropane at 1.4 ug/L in well MW-8 in July 2002.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 4 of 4 Record of Decision
Table 2VOC Data Summary (Water Supply Wells)
Railroad Avenue Groundwater Site
WellWDMW-01WDMW-03WDMW-04WDMW-05WDMW-06WDMW-07WDMW-08WDMW-09WDMW-12WDMW-13WDMW-14WDMW-15WDMW-16WMDW-17WDMW-18WDMW-19WDMW-20WDMW-21WDMW-22WDMW-23WDMW-24WDMW-25WDMW-01WDMW-03WDMW-04WDMW-05WDMW-06WDMW-07WDMW-08WDMW-09WDMW-12WDMW-13WDMW-14WDMW-15WDMW-16WMDW-17WDMW-18WDMW-19WDMW-20WDMW-21
WDMW-22
WDMW-23
WDMW-24
WDMW-25
AnalyteTCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCETCE
cis-1,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCECis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCEcis-1 ,2-DCECis-1 ,2-DCE
cis-1 ,2-DCE
cis-1 ,2-DCE
cis-1 ,2-DCE
cis-1, 2-DCE
MCL*
(ug/L)
5
5
Concentration
July 2002
0.5 U0.5 UNA0.5 U0.5 U
0.5(0.5) U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U1
0.5 U1.40.5 U0.5 U0.5 U
0.5(0.5) U0.5 U0.5 UNA3
4.50.5(0.5) U
0.5 U0.5 U2.20.540.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.960.5 U
0.5 U0.5 U
0.5(0.5) U
Nov. 2002NANA0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U1.40.5 U1.90.5 U
0.5(0.5) U0.5 U0.5 UNANA0.5 U2.86
0.5 U0.5 U0.5 U2.31.50.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.660.5 U
0.5(0.5) U
0.5 U0.5 U
May 20030.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U1.50.5 U
1.8(1.8)0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U1.35.80.5 U0.5 U0.5 U3.10.540.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U
1.7(1.7)
0.5 U
0.5 U0.5 U
0.5 U
Nov. 20031.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 ul1.0 U1.0 U
1.0(1.0) ul1.41.0 U2.41.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U2.03.81.0 U1.0 U1.0 U1.81.0 U1.0 U1.0 U1.0 U1.0 U
1.0(1.0) U1.0 U1.0 U3.1
1.0 U
1.0 U1.0 U
1.0 U
Nov. 20040.5 U0.5 U0.5 UlNA ~l
0.5(0.5) U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 UNA0.5 U0.5 U
0.950.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 U0.5 UNA I
1.9(2.4)0.5 U0.5 U0.5 U2.10.5 U0.5 U0.5 UNA0.5 U0.5 U0.5 U0.5 U2.6
0.5 U
0.5 U0.5 U0.5 U
Feb. 20051.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U
2.1 (2.0)1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.11.41.0 U1.0 U1.0 U1.5
1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U1.0 U
1.8(1.8) U
1.0 U
1.0 U1.0 U1.0 U
Unitsug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
ug/Lug/Lug/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume I o f 2 Record of Decision
Table 2 (Continued)VOC Data Summary (Water Supply Wells)
Railroad Avenue Groundwater Site
Well
WDMW-01
WDMW-03
WDMW-04
WDMW-05
WDMW-06
WDMW-07
WDMW-08
WDMW-09
WDMW-12
WDMW-13
WDMW-14
WDMW-15
WDMW-16
WMDW-17
WDMW-18
WDMW-19
WDMW-20
WDMW-21
WDMW-22
WDMW-23
WDMW-24
WDMW-25
Analyte
VCVCVCVCVCVCVC
VC
VC
VC
VC
VC
VC
VC
VC
VC
VC
VC
VC
VC
VC
VC
MCL*
(ug/L)
2
Concentration
July 2002
0.5 U0.5 U
NA
0.5 U
0.5 U
0.5(0.5) U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5(0.5) U
Nov. 2002
NA
NA
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5(0.5) U
0.5 U
0.5 U
May 2003
0.5 U0.5 U
NA
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5(0.5) U
0.5 U
0.5 U
0.5 U
0.5 U
Nov. 2003
2.0 U2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
NA
2.0 U
2.0(2.0) U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
2.0 U
Nov. 2004
0.5 U
0.5 U
0.5 U
NA
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
0.5 U
NA
0.5 U
0.5 U
0.5 U
0.5 U
5.1
0.5 U
0.5 U
0.5 U
0.5 U
Feb. 2005
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
1.0 U
Units
ug/Lug/Lug/L
ug/L
ug/L
ug/L
ug/Lug/L
ug/Lug/Lug/Lug/L
ug/L
ug/Lug/Lug/Lug/L
ug/Lug/Lug/Lug/Lug/L
* MCLs established under 40 CFR 141
ug/L = micrograms per liter
U = Not detected at or above the reportable level shown.
J = The associated numerical value is an estimated quantity.
Bolded results indicate contaminant detected above MCL
NA = not availableDuplicate result in parentheses.
Other VOCs detected infrequently at low concentrations include xylene (total) at 3.7 ug/L and 1.5 ug/L in well WDMW-21 in November 2002and November 2003, respectively; chloromethane at 0.51 ug/L in well WDMW-7 in May 2003; chloroethane at 2.9 ug/L in well WDMW-19 inNovember 2003; chloroform at 19 ug/L and xylene (total) at 9 ug/L in well WDMW-9 in November 2004; and chloroform at 1.0 ug/L, ethylbenzene at 2.9 ug/L, m and/or p-xlyene at 4.9 ug/L, and o-xylene at 14 ug/L in well WDMW-7 in February 2005.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 2 of 2 Record of Decision
Table 3.1Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: CurrentMedium: GroundwaterExposure Medium: Groundwater
Exposure Point
Aquifier 1
Tap Water
WDMW*
Chemicalof
Potential
Concern
Trichloroethene
bis(2-Ethylhexyl)phthalate
Manganese
Units
ug/L
ug/L
ug/L
ArithmeticMean
(D
N/A
N/A
266
95% UCL(Distribution)
N/A
N/A
N/A
MaximumConcentration
1.4
27
664
Exposure Point Concentration (2)
Value
1.4
27
266
Units
ug/L
ug/L
ug/L
Statistic
Max
Max
Arith Mean
Rationale
1 Arithmetic mean was not calculated due to only one detection for each chemical.2 The wells used in determining the EPCs were WDMW18, WDMW05, WDMW15, WDMW16, WDMW17, WDMW14, WDMW19, WDMW20.* WDMW - West Oes Moines Municipal Supply WellsN/A - Not ApplicableArith Mean - Arithmetic MeanMax - Maximum Detected Concentrationug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Table 3.2Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe:Medium:Exposure Medium:
CurrentGroundwaterAir
Exposure Point
Water Vapors
from Showerhead
WDMW
Chemicalof
Potential
Concern
Trichloroethene
bis(2-Ethylhexyl)phthalate
Units
ug/L
ug/L
ArithmeticMean
(1)
N/A
N/A
95% UCL(Distribution)
N/A
N/A
MaximumConcentration
1.4
27
Exposure Point Concentration (2)
Value
1.4
27
Units
ug/L
ug/L
Statistic
Max
Max
Rationale
1 Arithmetic mean was not calculated due to only one detection for each chemical.2 The wells used in determining the EPCs were WDMW18, WDMW05, WDMW15, WDMW16, WOMW17, WDMW14, WDMW19, WDMW20.' WDMW - West Des Moines Municipal Supply WellsN/A - Not ApplicableMax - Maximum Detected Concentrationug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Scenario Timeframe: FutureMedium: GroundwaterExposure Medium: Groundwater
Table 3.3Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Exposure Point
Aquifer 1Tap Water
MW-06
Chemicalof
Potential
Concern
cis-1 ,2 DichloroetheneTetrachloroethene
Trichloroethene
Arsenic
Manganese
Units
ug/Lug/L
ug/Lug/L
ug/L
ArithmeticMean
(D
1212
4.7
5.23
1,290
95% UCL
(Distribution)
N/AN/A
N/A
N/A
N/A
MaximumConcentration
1212
4.7
5.23
1,290
Exposure Point Concentration (2)
Value
1212
4.7
5.23
1,290
Units
ug/Lug/L
ug/L
ug/L
ug/L
Statistic
MaxMax
MaxMax
Max
Rationale
1 This column contains the arithmetic average of detected concentrations.2 The groundwater exposure point concentration is the maximum detected concentration at well location MW-06.N/A - Not ApplicableMax - Maximum Detected Concentrationug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Scenario Timeframe:Medium:Exposure Medium:
FutureGroundwaterAir
Table 3.4Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Exposure Point
Water Vapors fromShowerhead
MW-06
Chemical
ofPotential
Concern
cis-1,2 DichloroetheneTetrachloroethene
Trichloroethene
Units
ug/Lug/L
ug/L
Arithmetic
Mean
(D
1212
4.7
95% UCL
(Distribution)
N/AN/A
N/A
Maximum
Concentration
1212
4.7
Exposure Point Concentration (2)
Value
1212
4.7
Units
ug/Lug/L
ug/L
Statistic
MaxMax
Max
Rationale
1 This column contains the arithmetic average of detected concentrations.
2 The groundwater exposure point concentration is the maximum detected concentration at well location MW-06.
N/A - Not Applicable
Max - Maximum Detected Concentration
ug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Table 3.5Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe:Medium:Exposure Medium:
FutureGroundwaterGroundwater
Exposure Point
Aquifer 1Tap Water
MW-08
Chemicalof
Potential
Concern
1 ,2-Dibromo-3-Chloropropanolcis-1,2 Dichloroethene
Trichloroethene
Vinyl Chloride
Manganese
Units
ug/Lug/L
ug/L
ug/L
ug/L
ArithmeticMean
(1)
1.4420
2.7
110
872
95% UCL(Distribution)
N/AN/A
N/A
N/A
N/A
MaximumConcentration
1.4420
2.7
110
872
Exposure Point Concentration (2)
Value
1.4420
2.7
110
872
Units
ug/Lug/L
ug/L
ug/L
ug/L
Statistic
MaxMaxMaxMaxMax
Rationale
1 This column contains the arithmetic average of detected concentrations.
2 The groundwater exposure point concentration is the maximum detected concentration at well location MW-08.
N/A - Not Applicable
Max - Maximum Detected Concentration
ug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Table 3.6Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe:Medium:Exposure Medium:
FutureGroundwaterAir
Exposure Point
Water Vapors fromShowerhead
MW-08
Chemicalof
Potential
Concern
1 ,2-Dibromo-3-Chloropropanolcis-1 ,2 Oichloroethene
Trichloroethene
Vinyl Chloride
Units
ug/Lug/L
ug/L
ug/L
ArithmeticMean
(D
1.4.
420
2.7
110
95% UCL
(Distribution)
N/A
N/A
N/A
N/A
MaximumConcentration
1.4
420
2.7
110
Exposure Point Concentration (2)
Value
1.4
420
2.7
110
Units
ug/Lug/L
ug/L
ug/L
Statistic
MaxMax
Max
Max
Rationale
1 This column contains the arithmetic average of detected concentrations.2 The groundwater exposure point concentration is the maximum detected concentration at well location MW-08.N/A - Not ApplicableMax - Maximum Detected Concentration
ug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Scenario Timeframe:Medium:Exposure Medium:
FutureGroundwaterGroundwater
Table 3.7Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Exposure Point
Aquifer 1
Tap Water
WDMW13
Chemicalof
Potential
Concern
cis-1 ,2 Dichloroethene
Arsenic
Barium
Manganese
Units
ug/L
ug/L
ug/L
ug/L
ArithmeticMean
d)
1.5
14.3
124
1,300
95% UCL(Distribution)
N/A
N/A
N/A
N/A
MaximumConcentration
1.5
14.3
124
1,300
Exposure Point Concentration (2)
Value
1.5
14.3
124
1,300
Units
ug/L
ug/L
ug/L
ug/L
Statistic
Max
Max
Max
Max
Rationale
1 This column contains the arithmetic average of detected concentrations.2 The groundwater exposure point concentration is the maximum detected concentration at well location WDMW13.N/A - Not ApplicableMax - Maximum Detected Concentration
ug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Scenario Timeframe: FutureMedium: GroundwaterExposure Medium: Air
Table 3.8Medium-Specific Exposure Point Concentration Summary
Railroad Avenue Groundwater Contamination Site
Exposure Point
Water Vapors from
Showerhead
WDMW13
Chemical
ofPotential
Concern
cis-1 ,2 Dichloroethene
— -- - —
Units
ug/L
Arithmetic
Mean
(D
1.5
95% UCL(Distribution)
N/A
Maximum
Concentration
1.5
Exposure Point Concentration (2)
Value
1.5
Units
ug/L
Statistic
Max
Rationale
1 This column contains the arithmetic average of detected concentrations.
2 The groundwater exposure point concentration is the maximum detected concentration at well location WDMW13.
N/A - Not Applicable
Max - Maximum Detected Concentration
ug/L - Micrograms per liter
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Table 4Selection of Exposure Pathways
Railroad Avenue Groundwater Contamination Site
1Scenario
Ttmeframe
Current/Future
Medium
Soil
Groundwater
Exposure
Medium
Surface toll
Subsurface soil
Air
Groundwster
Mr
Exposure
Point
Onslte
Onslte
Onstta
Tap Water
Water Vapors at Showertiaad
Receptor
Population
Industrial Worker
Resident
Resident
Industrial Worker
Resident
Resident
Industrial Worker
Resident
Receptor
Age
Adult
Adult
Child
Adult
Child
Adult
Adult
Child
Adult
Child
Adult
Adult
Exposure
Route
Ingestton
Dermal
Ingestion
Dermal
Ingestion
Dermal
Ingestion
Dermal
Ingestion
Dermal
Inhalation
Inhalation
Inhalation
Ingestion
Dermal
Ingestion
Dermal
Ingestion
Dermal
Inhalation
Onslte/
Offslte
Onslte
Onslte
Onslte
Onslte
Onstta
Onslte
Onslte
Onslte
Onslte
Onslte
Onslte
Onslte
. . _
Type of
Analysis
Qua!
Qual
dual
Qual
Qual
Qual
Qual
Qual
Qual
Qual
Qual
Qual
Qual
Quant
Quant
Quant
Quant
Quant
None
Quant
Rationale for Selection or Exclusion
of Exposure Pathway
Workers may be exposed to soil across the site.
Current and future adult residents may be exposed to contaminants In on-slte soil.
Current and future child residents may be exposed to contaminants In on-slte soil.
Current and future adult resident may be exposed to contaminants In subsurface soilbrought to the surface during construction activities.
Current and future child resident may be exposed to contaminants In subsurface soilbrought to the surface during construction activities.
Workers possibly exposed to airborne contaminants via Inhalation of VOCs or fugitivedust emissions.
Adults possibly exposed to airborne contaminants via Inhalation of VOCs or fugitive dustemissions.
Children possibly exposed to airborne contaminants via Inhalation of VOCs or fugitivedust emissions.
Residents currently obtain water from the West Des Molnes Municipal Supply Wells andmay obtain water from offline wells and other monitoring wells In the future.
Residents currently obtain water from the West Des Molnes Municipal Supply Wells andmay obtain water from offline wells and other monitoring wells In the future.
Workers currently obtain water from the West Des Molnes Municipal Supply Wells andmay obtain water from offline wells and other monitoring wells In the future.
Residents currently obtain water from the West Des Molnes Municipal Supply Wells andmay obtain water from offline wells and other monitoring wells In the future.
Railroad Avenue Groundwater Contamination Site
Northern PlumeRecord of Decision
Table 5.1
Non-Cancer Toxicity Data ~ Oral/Dermal
Railroad Avenue Groundwater Contamination Site
Chemical
of Potential
Concern
1 ,2-Dibromo-3-Chloropropane
cis-1,2 Dichloroethene
Tetrachloroethene
Trichloroethene
Vinyl ChlorideArsenic
bis(2-Etnylhexyl)phthalate
bis(2-Ethylhexyl)phthalate
Manganese (water)
Chronic/
Subchronic
NA
Chronic
Chronic
Chronic
Chronic
Chronic
Chronic
Subchronic
Chronic
Oral RfD
Value
NA1E-002
1E-002
3E-004
3E-003
3E-04
2E-002
2E-002
2E-02
Units
NAmg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day_
Oral Absorbtion
Efficiency for
Dermal (1)
NA
100%
100%
100%
100%
95%
55%
55%
20%
Absorbed RFD for Dermal (2)
L Value
NA
1E-002
1E-002
3E-004
3E-003
2.9E-004
1E-002
1E-002
4E-003
Units
NA
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
mg/kg-day
Primary
Target
Organ(s)
NA
Blood
Liver
Liver/Kidney/Fetus
Liver Cell Polymorphum
Skin
Liver
Liver
Central Nervous system
Combined
Uncertainty/
Modifying
Factors
NA
3000
1000
3000
30
31000
1000
1
RfD:1
Source(s
NA
HEAST
IRIS
NCEA
IRIS
IRIS
IRIS
HEAST
IRIS
N/A = Not Applicable
IRIS = Integrated Risk Information System
HEAST = Health Effects Assessment Summary Tables
NCEA = National Center for Environmental Assessment
(1) Source: Risk Assessment Guidance for Superfund. Volume 1: Human Health Evaluation Manual (Part E, Supplemental Guidance for dermal risk Assessment) Interim. Section 4.2 and Exhibit 4-1.
(2) See Risk Assesment text for the derivation of the "Absorbed RfD for Dermal."
Railroad Avenue Groundwater Contamination Site
Northern Plume
Date(s)
NA
07/01/1997
03/11/2003
03/11/2003
03/11/2003
03/11/2003
03/11/2003
07/01/1997
03/11/2003
Record of Decision
Table 5.2
Non-Cancer Toxicity Data ~ Inhalation
Railroad Avenue Groundwater Contamination Site
Chemical
of Potential
Concern
1 ,2-Dibromo-3-Chloropropane
cis-1,2 Dichloroethene
Tetrachloroethene
Trichloroethene
Vinyl ChlorideArsenic
bis(2-Ethylhexyl)phthalateManganese (water)
Chronic/
Subchronic
Chronic
N/A
Chronic
Chronic
Chronic
N/A
N/A
Chronic
Value
Inhalation
RfC
2.4E-004
N/A
4.0E-001
4.0E-002
1.0E-001
N/A
N/A
5.0E-005
Units
mg/m3
N/A
mg/m3
mg/m3
mg/m3
N/A
N/A
mg/m3
Adjusted
Inhalation
RfD(1)
5.7E-005
N/A
1.7E-001
1.1E-002
2.8E-002
N/A
N/A
1.4E-05
Units
mg/kg/day
N/A
mg/kg/day
mg/kg/day
mg/kg/day
N/A
N/A
mg/kg-day
Primary
Target
Organ
Testicular
N/A
Liver/Kidney
CNS/Liver/Endocrine
Liver Cell Polymorphism
N/A
N/A
Central Nervous System
Combined
Uncertainty/
Modifying
Factors
1E+003
N/A
3E+002
1E+003
3E+001
N/A
N/A
1,000
Source of
RfC:RfD
Target Organ
IRIS
N/A
NCEA
NCEA
IRIS
N/A
N/A
IRIS
Dates (2)
(MM/DD/YY)
03/11/2003
N/A06/20/1977
08/01/2001
03/11/2003
N/A
N/A03/11/2003
N/A = Not Applicable
IRIS = Integrated Risk Information System
HEAST = Health Effects Assessment Summary Tables
NCEA = National Center for Environmental Assessment
(1) See Risk Assessment text for the derivation of the "Extrapolated RfD."
Railroad Avenue Groundwater Contamination SiteNorthern Plume
Record of Decision
Table 6.1Cancer Toxicity Data -- Oral/Dermal
Railroad Avenue Groundwater Contamination Site
Chemicalof Potential
Concern1 ,2-Dibromo-3-Chloropropane
cis-1 ,2 Dichloroethene
Tetrachloroethene
Trichloroethene
Trichloroethene
Vinyl Chloride
Arsenic
bis(2-Ethylhexyl)phthalate
Manganese (water)
Oral Cancer Slope Factor
N/A
N/A
5.2E-002
2.0E-02 to 4.0E-01
6.0E-03
1.4E+OOV7.2E-Q1"
1.5E+000
1.4E-002
N/A
Oral to DermalAdjustment
FactorN/A
N/A
100%
100%
100%
100%
85%
55%
4%
Adjusted DermalCancer Slope Factor (1)
N/A
N/A
5.2E-002
2.0E-02 to 4.0E-01
6.0E-03
1.4E+00'/7.2E-01"
1.6E+000
2.5E-002
N/A
Units
N/A
N/A
(mg/kg-day)-1
(mg/kg-<iay)-1
(mg/kg-day)-1
(mg/kg-dayH
(mg/kg-day)-1
(mg/kg-day)-1
N/A
Weight of Evidence/Cancer Guideline
DescriptionN/A
N/A
B2
B2
B2
A
A
B2
N/A
I
Source
N/A
N/A
NCEA
NCEA
NCEA
IRIS
IRIS
IRIS
N/A
Date (2)(MM/DD/YY)
N/A = Not Available.
IRIS = Integrated Risk Information System.
NCEA - National Center for Environmental Assessment.
(1) RAGs Subpart A (1989); RAGs Subpart E (2001); see explanation in text.
(2) For IRIS, last revision date as provided in IRIS.
• Lifetime exposure from birth (child).
~ Lifetime exposure during edullhood (adult).
EPA Group:
A - Human carcinogen
B2 - Probable human carcinogen - indicates sufficient evidence in animals and
Inadequate or no evidence in humans.
N/A
N/A
12/01/2001
08/01/2001
1987
03/11/2003
03/11/2003
03/11/2003
N/A
Railroad Avenue Groundwater Contamination Site
Northern Plume
Record of Decision
Table 6.2
Cancer Toxicity Data - Inhalation
Railroad Avenue Groundwater Contamination Site
Chemicalof Potential
Concern1 ,2-Dibromo-3-Chloropropane
cis-1,2 Dichloroethene
Tetrachloroethene
Trichloroethene
Tricnloroethene
Vinyl Chloride
Arsenic
bis(2-EUiylhexyl)phthalate
Manganese (water)
Unit Risk
N/A
N/A
3.1E-006
1.1E-004
1.1E-004
8.8E-06V4.4E-06"
4.3E-003
4.2E-006
N/A
Units Adjustment
(1)
Inhalation CancerSlope Factor
Units
r N/A | N/A T A T IRIS
N/A
(ug/m3)-1
(ug/m3)-1
(ug/m3)-1
(ug/m3M
(ug/m3)-1
(ug/m3)-1
N/A
N/A
3,500
3.500
3,500
3,500
3,500
3,500
N/A
N/A
1.0E-002
2.0E-02 to 4.0E-01
6.0E-03
3.1E-02V1.5E-02"
1.5E+001
1.4E-002
N/A
N/A
(mg/kg-day}-1
(mg/kg-day)-1
(mg/kg-day)-1
(mg/kg-day)-1
(mg/kg-day)-1
(mg/kg-day)-1
N/A
Weight of Evidence/Cancer Guideline
Description
Source
N/A | N/A
N/A
B2
B2
B2
C
A
B2
N/A
N/A
NCEA
NCEA
NCEA
NCEA
IRIS
NCEA
N/A
Date (2)(MM/DD/YY)
N/A
N/A
12/21/2001
08/01/2001
1987
08/01/2001
03/11/2003
09/20/1995
N/A
N/A= Not Available.
IRIS = Integrated Risk Information System.
NCEA = National Center for Environmental Assessment.
~(1) ExptanatTon^of derivation provided In text.
(2) For IRIS, last revision date as provided in IRIS.
• Lifetime exposure from birth (child).
~ Lifetime exposure during adulthood (adult).
Railroad Avenue Groundwater Contamination Site
Northern Plume
EPA Group:
A - Human carcinogen.
B2 - Probable human carcinogen - indicates sufficient evidence In animals and
inadequate or no evidence in humans.
C - Possible human carcinogen.
Record of Decision
Table 7
Summary of Cancer Risk for Each Population Evaluated
Railroad Avenue Groundwater Contamination Site
Timeframe
Current
Future (MW-6)
Future (MW-8)
Future (WDM W- 13)
Receptor Population*
Resident
Industrial Worker
Hypothetical Resident
Hypothetical IndustrialWorker
Hypothetical Resident
Hypothetical Industrial
Worker
Hypothetical Resident
Hypothetical Industrial
Worker
Carcinogenic
Risks**
6E-06 to 2E-05
!E-06to3E-06
i
1E-04to.2E-04
3E-05to4E-05i1
7E-03 i
3E-04 !1i
3E-04 1t
8E-05 |
1
Chemicals of PotentialConcern
B is(2-ethylhexyl)phthalate
and TCE
Bis(2-ethylhexyl)phthalate,
and TCE
PCE, TCE, and arsenic
PCE, TCE, and arsenic
Vinyl chloride, TCE
Vinyl chloride, TCE
Arsenic
Arsenic
* The cancer risk results for the child and adult were combined to obtain an excess cancer risk for aresident (30-year exposure) (EPA, 1989a).
** A range of cancer risks is provided for the current scenario and future (MW-6). The EPArecommended calculating cancer risks for TCE using a range of draft values, dated August 2001, andthe original provisional value dated 1987. Although TCE was detected in well MW-8, a range wasnot presented since the cancer risks were the same for all cancer slope factors used.
Railroad Avenue Groundwater Contamination SiteNorthern Plume Record of Decision
Table 8Summary of Hazard Indices for Each Population Evaluated
Railroad Avenue Groundwater Contamination Site
Timeframe
Current
Future (MW-6)
Future (MW-6)
Future (WDMW-1 3)
ReceptorPopulation
Adult Resident
Child Resident
Industrial Worker
Hypothetical AdultResident
Hypothetical ChildResident
HypotheticalIndustrial Worker
Hypothetical AdultResident
Hypothetical ChildResident
HypotheticalIndustrial Worker
Hypothetical AdultResident
Hypothetical ChildResident
HypotheticalIndustrial Worker
HazardIndex
0.5
1
0.2
3
7
1
4
11
1
3
7
1
Chemicals of PotentialConcern
Manganese, TCE
Manganese, TCE
Manganese
Manganese, arsenic, TCE
Manganese, arsenic, TCE
Manganese, arsenic, TCE
Manganese, vinyl chloride,TCE,1 ,2-dibromo-3-chloropropane
Manganese, vinyl chloride,TCE,1 ,2-dibromo-3-chloropropane
Manganese, vinyl chloride,TCE,1 ,2-dibromo-3-chloropropane
Manganese, arsenic
Manganese, arsenic
Manganese, arsenic
Railroad Avenue Groundwater Contamination SiteNorthern Plume Record of Decision
Table 9.1
Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timetrame: Future
Receptor Population: Resident
Receptor Age: Adult
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
MW-06
Chemical of
Potential Concern
TrlcMoroetfrane
Arsenic
Manganese
Chemical Total
Radionudide Total
Carcinogenic Risk || Non-Carcinogenic Hazard Risk
Ingestion Inhalation Dermal External
Radiation
Exposure || Primary
Routes Total || Target Organ(s)
Liver/Kidney/Fetus
Skin
Central Nervous System
Ingestion
0.4
0.5
2
3
Inhalation Dermal
0.0005
0.00002
0.04
0.04
Exposure
Routes Total
0.4
0.5
2
3 I~l
Exposure Point Total II II II 3
Exposure Medium Total Jl jl II 3
I
I
Exposure Point Total || ||
Exposure Medium Total II It II
Groundwater Total || || IL 3 1
Receptor Total || || || 3 |
Total Risk Across All Media Total Hazard Across All Media =
Total Liver/Kidney/Fetus HI Across All Media =
Total Skin HI Across All Media =
Total Central Nervous System HI Across All Media =
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.2Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Child
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
MW-06
Chemical of
Potential Concern
Trichloroethene
Arsenic
Manganese
Chemical Total
Radionudide Total
Carcinogenic Risk ]) Non-Carcinogenic Hazard Risk
Ingestlon Inhalation Dermal External
Radiation
Exposure 1 1 Primary
Routes Total j| Target Organ(s)
Liver/Kidney/Fetus
Skin
Central Nervous System
Ingestlon
1.0
1.1
4
6
Inhalation Dermal
0.0010
0.00006
0.12
0.12
Exposure
Routes Total
1.0
1.1
4
6
Exposure Point Total || I || 6
Exposure Medium Total || || || 6 |
Exposure Point Total || ||
Exposure Medium Total
Groundwater Total
"1
[ .
II II I
I II II 6 |Receptor Total [| || || 6
Total Risk Across All Media = Total Hazard Across All Media =
Total Liver/Kidney/Fetus HI Across All Media =
Total Skin HI Across All Media =
Total Central Nervous System HI Across All Media =
1 1-0
I 1.1I 4
I
I
I
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.3Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Adult
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
MW-08
Chemical of
Potential Concern
cis-1,2 Dichloroethene
Trlchloroothene
Vinyl Chloride
Manganese
Chemical Total
Radionudide Total
Carcinogenic Risk || Non-Carcinogenic Hazard Risk
Ingestion
7E-004
7E-004
Inhalation Dermal
3E-006
3E-006
External
Radiation
Exposure || Primary
Routas Total || Target Organ(s)
7E-004
7E-004
Blood
Liver/Kidney/Fetus
Liver Cell Polymorphum
Central Nervous System
Ingestion
1.13
0.2
1.0
1
4
Inhalation Dermal
0.01
0.0003
0.004
0.03
0.04
Exposure
Routes Total
1.1
0.2
0.99
1.2
« I
._ I" 1
Exposure Point Total || 7E-004 ]|~ II 4 |
Exposure Medium Total _J| 7E-004 || _JL 4 I
Air Water Vaporsfrom Showerhead
MW-08Vinyl Chloride
Chemical Total
Radionudide Total
2E-006
2E-006
2E-006
2E-006
I
Exposure Point Total || 2E-006 |P II
Exposure Medium Total || 2E-006 || ||
| Groundwater Total || 7E-004 || [_"" 4 1
| Receptor Total || 7E-004 || || 4
Total Risk Across All Media = Total Hazard Across All Media
Total Blood HI Across All Media =
Total Liver/Kidney/Fetus HI Across All Media =
Total Liver Cell Polymorphum HI Across All Media =
Total Central Nervous System HI Across All Media =
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.4
Risk SummaryRailroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Adult
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
MW-08
Chemical of
Potential Concern
Trichlorotthem
Chemical Total
Radionudide Total
Carcinogenic Risk || Non-Carcinogenic Hazard Risk
Ingestion
1E-005
1E-005
Inhalation Dermal
1E-008
1E-008
External
Radiation
Exposure || Primary
Routes Total || Target Organ)*)
1E-005
|_ 1E-005
Ingestlon Inhalation Dermal Exposure
Routes Total
Exposure Point Total 1 1 1E-005 || 1 1
Exposure Medium Total || 1E-005 ||
Air Water Vaporsfrom Showerhead
MW-08
Tr/c/i/oTDet/iene
Chemical Total
Radionudide Total
1E-006
1E-006
1E-006
1E-006
Exposure Point Total || 1E-006
1
1
CL";_iExposure Medium Total || 1E-006 || I
Groundwater Total || 1E-005 || ||
Receptor Total || 1E-005 || ||
Total Risk Across All Media = Total Hazard Across All Media
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.5
Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Child
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
MW-08
Chemical of
Potential Concern
cis-1.2Dichloroethene
Trichloroethene
Vinyl Chloride (1 ) *
Vinyl Chloride (1) "
Manganese
Chemical Total
Radionudide Total
Carcinogenic Risk || Non-Carcinogenic Hazard Rlak
Ingestion
4E-004
5E-003
6E-003
Inhalation Dermal
2E-006
2E-CM
2E-004
External
Radiation
Exposure I Primary
Routes Total || Target Organ(a)•' '
4E-004
5E-003
6E-003
Blood
Liver/Kidney/Fetus
Liver Cell Polymorphum
Liver Cell Polymorphum
Central Nervous System
Ingestion
2.69
0.6
2.3
2.3
3
11
Inhalation Dermal
0.02
0.0006
0.009
0.009
0.08
0.1
Exposure
Routes Total
2.7
0.6
2.4
2.4
2.9; "ii ~l
. ^"~ I
Exposure Point Total \\~ 6E-003 |[ ]| 11
Exposure Medium Total |[ 6E-003 || || 11 |
Air Water Vaporsfrom Showertiead
MW-08
Vinyl Chloride (1 ) '
Vinyl Chloride (1) "
Chemical Total
Radionudide Total
2E-006
8E-006
1E-005
2E-006
8E-006
1E-005 H
Exposure Point Total || 1E-OOS || ||
Exposure Medium Total 1 1 1E-OOS | 1 1
Groundwater Total || 6E-003 || || 11
Receptor Total || 6E-003 || ||_ 11
Total Risk Across All Media =
(1) The child risk calculation for vinyl chloride has a two-part equation (one is pio-raied and the other is not).
• Pro-rated equation was used to do the risk calculation. Adult Cancer Slope Factor has been used.
" Non-prorated equation was used to do the risk calculation. Adult Cancer Slope Factor has been used.
Railroad Avenue Groundwater Contamination Site
Northern Plume
Total Hazard Across All Media =
Total Blood HI Across All Media =
Total Liver/Kidney/Fetus HI Across All Media =
Total Liver Cell Polymorphum HI Across All Media =
Total Central Nervous System HI Across All Media =
11
2.7
0.6
__47.| 2.9
Record of Decision
Table 9.6
Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age. Child
Medium
Groundwater
ExposureMedium
Groundwater
Exposure
Point
Aquiferl -Tap Water
MW-08
Chemical of
Potential Concern
Trtchloroethene
Chemical Total
Radionudide Total
Carcinogenic Risk ]| Non-Carcinogenic Hazard Risk
Ingestion
IE-DOS
6E-006
Inhalation Dermal
IE-009
6E-009
External
Radiation
Exposure || Primary
Routes Total ||_ Target Organ(s)
6E-006
6E-006
Ingestion Inhalation
"
Dermal Exposure
[ Routes Total
J
Exposure Point Total || 6E-006 || II
Exposure Medium Total |[ 6E-006 | |
~ 1..... _ ̂
Exposure Point Total II II II
Exposure Medium Total || || ||
Groundwater Total |j 6E-006 || [|
Receptor Total || 6E-006 || ||
Total Risk Across All Media = 6E-006 Total Hazard Across All Media =
(1) The child risk calculation for vinyl chloride has a two-part equation (one is pro-rated and the other is not).
* Pro-rated equation was used to do the risk calculation. Adult Cancer Slope Factor has been used.
" Non-prorated equation was used to do the risk calculation. Adutt Cancer Slope Factor has been used.
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.7
Risk SummaryRailroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Child
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
MW-08
Chemical of
Potential Concern
Trfc/i/oroefliene
Chemical Total
Radionudide Total
Carcinogenic Risk
Ingestlon
BE-ooe
6E-006
Inhalation Dermal
6C-009
6E-009
External
Radiation
Exposure
Routes Total
6E-OOB
6E-006
Non-Carcinogenic Hazard Risk
Primary
Target Organ(s)
Ingestlon Inhalation Dermal Exposure
Routes Total
_ I
I
Exposure Point Total || 6E-006 || || |
Exposure Medium Total IP 6E-006 )f J ]|
... ]
I
Exposure Point Total || || || |
Exposure Medium Total II 11 II
Groundwater Total || 6E-006 || ||
Receptor Total || 6E-006 || ||
Total Risk Across All Media = Total Hazard Across All Media
(1) The child risk calculation for vinyl chloride has a two-part equation (one is pro-rated and the other is not).
• Pro-rated equation was used to do the risk calculation. Adult Cancer Slope Factor has been used.
" Non-prorated equation was used to do the risk calculation. Adult Cancer Slope Factor has been used.
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.8Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: FutureReceptor Population: Industrial WorkerReceptor Age: Adult
Medium
Groundwater
ExposureMedium
'
Groundwater
ExposurePoint
Aquifer 1- Tap Water
MW-08
Chemical ofPotential Concern
Vinyl Chloride
Chemical Total
Radionudide Total
Carcinogenic Risk || Non-Carcinogenic Hazard Risk
Ingestion
3E-004
3E-004
Inhalation Dermal ExternalRadiation
Exposure || PrimaryRoutes Total || Target Organ(s)
3E-004
3E-004
Ingestion Inhalation Dermal ExposureRoutes Total
""""I
r " ~iExposure Point Total If 3E-004 ||~~ If"
Exposure Medium Total || 3E-004 || iGroundwater Total _|| 3E-OM J|_ ||
[Receptor Total || 3E-OM |[ |1~~ 1
Total Risk Across All Media Total Hazard Across All Media =
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.9
Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Industrial Worker
Receptor Age: Adult
Medium
Groundwater
ExposureMedium
Groundwater
ExposurePoint
Aquifer 1- Tap Water
MW-08
Chemical of
Potential Concern
Trichloroethene
Chemical Total
Radionudide Total
Carcinogenic Risk || Non-Carcinogenic Hazard Risk
Ingeation
4E-000
4E-006
Inhalation Dermal Extemil
Radiation
Exposure 1 1 PrimaryRoutes Total || Target Organ(s)
4E-006
4E-006 J
I
Ingestlon Inhalation Dermal ExposureRoutes Total
_.n_ . .j
Exposure Point Total || 4E-006 ~~|l II I
Exposure Medium Total 1 1 4E-006 || II
Groundwater Total || 4E-006 || || |
| Receptor Total || 4E-006 ||_ 1 1
Total Hazard Across All Media =
Railroad Avenue Groundwuer Contamination Site
Northern Plume Record of Decision
Table 9.10
Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Adult
Medium
Groundwater
Exposure
Medium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
WDMW13
Chemical of
Potential Concern
Arsenic
Manganese
Chemical Total
Radiomidide Total
Carcinogenic Risk ||_ Non-Carcinogenic Hazard Risk
Ingestion
2E-004
2E-004
Inhalation Dermal
9E-009
9E-009
External
Radiation
Exposure || Primary
Routes Total H Target Organ(s)
2E-004
2E-004
Skin
Central Nervous System
Ingestion
1.3
2
3
Inhalation Dermal
0.00006
0.04
0.04
Exposure
Routes Total. .
1.3
2
3
I
Exposure Point Total || 2E-004 HP II 3
Exposure Medium Total ||_ 2E-004 ||_ Jl 3
Exposure Point Total If If"
I
:_]L_ .. . .....
c '"":::Exposure Medium Total || || II
Groundwater Total ]| 2E-004 || || 3
Receptor Total || 2E-004 |] || 3
Total Risk Across All Media = Total Hazard Across All Media =
Total Skin HI Across All Media =
Total Central Nervous System HI Across All Media =
Railroad Avenue Groundwater Contamination Site
Northern Plume Record of Decision
Table 9.11Risk Summary
Railroad Avenue Groundwater Contamination Site
Scenario Timeframe: Future
Receptor Population: Resident
Receptor Age: Child
Medium
Groundwater
ExposureMedium
Groundwater
Exposure
Point
Aquifer 1- Tap Water
WDMW13
Chemical of
Potential Concern
Arsenic
Manganese
Chemical Total
Radionudide Total
Carcinogenic Risk
Ingestlon Inhalation Dermal External
Radiation
Exposure
Routes Total
Non-Carcinogenic Hazard Risk
Primary
Target Organ(s)
Skin
Central Nervous System
Ingestlon
3.1
4
7
Inhalation Dermal
0.00017
0.12
0.12
Exposure
Routes Total
3.1
4
...7... .
rExposure Point Total || || || 7
Exposure Medium Total ]| || || 7 ]
Exposure Point Total II II IP 1
Exposure Medium Total || || ||
Groundwater Total II II II 7
Receptor Total II II II 7
Total Risk Across All Media Total Hazard Across All Media =
Total Skin HI Across All Media =
Total Central Nervous System HI Across All Media =3
Railroad Avenue Groundwater Contamination Site
Nonhem Fiume Record of Decision
Table 10Comparative Analysis of Alternatives
Railroad Avenue Groundwater Contamination Site/Northern Plume
Evaluation CriteriaAlternative 1
No Action
Alternative 2
Monitored Natural Attenuation(MNA)
Alternative 3Extraction with Recovery
Wells/Treatment by On-site TrayAeration/Surface Water Discharge
(Containment)
Alternative 4
In-situ Stripping Wells(Containment)
OVERALL PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
HumanHealthProtection
GroundwaterIngestion forCurrent Users
No current groundwaterusers within OU1 area.
No current groundwater userswithin OU1 area.
No current groundwater userswithin OU1 area.
No current groundwater userswithin OU1 area.
GroundwaterIngestion forPotentialFuture Users
Current risks posed fromcontaminants at the sitewould remainunmitigated, uncontrolled,and unmanaged.
Institutional controls wouldcontrol exposure to potentialfuture users.
Institutional controls wouldcontrol exposure to potentialfuture users.
Institutional controls wouldcontrol exposure to potentialfuture users.
Environmental ProtectionCurrent risks posed fromcontaminants at the sitewould remainunmitigated, uncontrolled,and unmanaged.
Protects environmental receptorsthrough attenuation processes.Monitoring would allowidentification of non-attenuatedCOCs.
Migration of the contaminatedgroundwater would be controlledby pumping. Monitoring wouldallow detection of non-capturedCOCs.
Migration of the contaminatedgroundwater would be controlledby treatment as it passed throughthe in-situ stripping wells placedas a barrier. Monitoring wouldallow detection of non-treatedCOCs.
COMPLIANCE WITH ARARS
Chemical-Specific ARARs Groundwater exceedsPRGs. Time necessary toreduce groundwatercontamination to belowPRGs is unknown.
Groundwater would meetchemical-specific ARARs in thelong term through naturalattenuation processes and wouldbe confirmed throughmonitoring.
Groundwater would meetchemical-specific ARARs in thelong term through naturalattenuation processes and wouldbe confirmed through monitoring.
Groundwater would meetchemical-specific ARARs in thelong term through naturalattenuation processes and wouldbe confirmed through monitoring.
Location-Specific ARARs No location-specificARARs.
No location-specific ARARs. No location-specific ARARs. No location-specific ARARs.
Railroad Avenue Groundwater Contamination SiteNorthern Plume I o f 6
Record of Decision
Table 10 (Continued)Comparative Analysis of Alternatives
Railroad Avenue Groundwater Contamination Site/Northern Plume
Evaluation CriteriaAlternative 1
No Action
Alternative 2
Monitored Natural Attenuation(MNA)
Alternative 3Extraction with Recovery
Wells/Treatment by On-site TrayAeration/Surface Water Discharge
(Containment)
Alternative 4
In-situ Stripping Wells(Containment)
COMPLIANCE WITH ARARS (Continued)
Action-Specific ARARs No action-specificARARs.
Would meet Iowa water qualitystandards and Iowa wellpermitting requirements.
Would meetNPDES dischargerequirements, air release standards,Iowa water quality standards, andIowa well permitting requirements.
Would meet air release standardsfor the in-situ stripping wells,noise control requirements, Iowawater quality standards, and Iowawell permitting requirements.
Other Criteria and Guidance Would allow ingestion ofgroundwater exceedingPRGs.
Institutional controls wouldprotect against ingestion ofgroundwater with contaminationexceeding PRGs.
Institutional controls wouldprotect against ingestion ofgroundwater with contaminationexceeding PRGs.
Institutional controls wouldprotect against ingestion ofgroundwater with contaminationexceeding PRGs.
LONG-TERM EFFECTIVENESS AND PERMANENCE
Magnitude of Residual Risk
Groundwater Ingestion forCurrent Users
No current groundwaterusers within OU1 area.
No current groundwater userswithin OU1 area.
No current groundwater userswithin OU1 area.
No current groundwater userswithin OU1 area.
Groundwater Ingestion forPotential Future Users
Risk from exposure isincreased becausemanagement andmonitoring of plume is notperformed.
Risk would be reduced byimplementing institutionalcontrols.
Risk would be reduced bycontrolling plume migration,accelerated VOC removal, andimplementing institutionalcontrols.
Risk would be reduced bycontrolling plume migration andimplementing institutionalcontrols.
Adequacy and Reliability ofControls
No monitoring of thegroundwater would beimplemented.Groundwatercontaminants wouldremain above PRGs.
Institutional controls at the Cityor State level would be reliable.
Groundwater extraction wouldcontrol contaminant plumemigration and accelerated VOCremoval. Institutional controls atthe City or State level would bereliable.
Barrier of in-situ stripping wellswould control contaminant plumemigration. Institutional controls atthe City or State level would bereliable.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 2 of 6
Record of Decision
Table 10 (Continued)Comparative Analysis of Alternatives
Railroad Avenue Groundwater Contamination Site/Northern Plume
Evaluation CriteriaAlternative 1
No Action
Alternative 2
Monitored Natural Attenuation(MNA)
Alternative 3Extraction with Recovery
Wells/Treatment by On-site TrayAeration/Surface Water Discharge
(Containment)
Alternative 4
In-situ Stripping Wells(Containment)
REDUCTION OF TOXICITY. MOBILITY OR VOLUME THROUGH TREATMENT
Treatment Process Used Would not providetreatment.
Would not provide treatment. Groundwater would be treated at anew on-site plant with airstripping/tray aeration.
Groundwater would be treated byin-situ stripping wells.
Amount Destroyed orTreated
None. None. 90 percent of the volatiles wouldbe removed from the groundwatertreated at the on-site treatmentplant.
Approximately 50 percent ofvolatile mass in the groundwaterthat passes through the line of in-situ stripping wells would beremoved.
Reduction of Toxicity,Mobility, or Volume
None. None. Would reduce mobility ofcontaminated groundwater bypumping.
Would reduce mobility ofgroundwater contamination byproviding a treatment barrier.
Irreversible Treatment None. None. Air stripping would be irreversible. In-situ stripping would beirreversible.
Type and Quantity ofResiduals Remaining AfterTreatment
None. None. None. None.
SHORT-TERM EFFECTIVENESS
Community Protection Continued risk tocommunity through noaction.
Controllable, minor increase inrisk to community duringinstallation of monitoring wells.
Controllable, minor increase inrisk to community duringtreatment plant construction,installation of recovery wells, andinstallation of pipelines.
Controllable, minor increase inrisk to community duringinstallation of in-situ strippingwells and monitoring well.
Worker Protection No risk to workers. Protection required during wellinstallation.
Protection required duringtreatment plant construction,installation of recovery wells, andinstallation of pipelines.
Protection required during in-situtreatment well installation andmonitoring well installation.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 3 of 6
Record of Decision
Table 10 (Continued)Comparative Analysis of Alternatives
Railroad Avenue Groundwater Contamination Site/Northern Plume
Evaluation CriteriaAlternative 1
No Action
Alternative 2
Monitored Natural Attenuation(MNA)
Alternative 3Extraction with Recovery
Wells/Treatment by On-site TrayAeration/Surface Water Discharge
(Containment)
Alternative 4
In-situ Stripping Wells(Containment)
SHORT-TERM EFFECTIVENESS (Continued)
Environmental Impacts Continued impacts fromexisting conditions.
Plume exposure controlledthrough institutional controls.
Migration of the plume would becontrolled by pumping.
Migration of the plume would becontrolled by treatment barrier.Vapors from in-situ stripping wellsmight produce slight odors butwould meet emission standards.
Time Until Action isComplete
Not applicable. In excess of 30 years. The recovery wells, treatmentplant, and pipeline could beinstalled and startup completedwithin 17 to 18 months. Estimatedrun time is in excess of 30 years.
In-situ treatment wells could beinstalled and startup completewithin 17 to 18 months. Estimatedrun time is in excess of 30 years.
IMPLEMENT ABILITY
Ability to Construct andOperate
No construction oroperation would berequired.
Easy to construct onemonitoring well.
Would require significantequipment and controls and wouldbe complex to operate.
Would require equipment andcontrols and would be equallycomplex to operate as Alternative3.
Ease of Doing AdditionalRemedial Action, if Needed
May require RODamendment if futureproblems arise.
May require ROD amendment iffuture problems arise. Wouldnot interfere with additionalremedial actions implemented inthe remaining portion of theNorth Area Plume, if required.
Would be moderately easy toexpand tray aeration groundwatertreatment plant. Would notinterfere with additional remedialactions implemented in theremaining portion of the NorthArea Plume, if required.
Would be easy to extend thebarrier of in-situ treatment wells.Would not interfere withadditional remedial actionsimplemented in the remainingportion of the North Area Plume, ifrequired.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 4 of 6
Record of Decision
Table 10 (Continued)Comparative Analysis of Alternatives
Railroad Avenue Groundwater Contamination Site/Northern Plume
Evaluation CriteriaAlternative 1
No Action
Alternative 2
Monitored Natural Attenuation(MNA)
Alternative 3Extraction with Recovery
Wells/Treatment by On-site TrayAeration/Surface Water Discharge
(Containment)
Alternative 4
In-situ Stripping Wells(Containment)
IMPLEMENTABILITY (Continued)
Ability to MonitorEffectiveness
No monitoring. Failure tomonitor the plume wouldnot allow effectiveevaluation and necessaryresponse to potentialfuture risks.
Monitoring would alloweffective evaluation andnecessary response to potentialfuture risks.
Monitoring and maintenanceinspections would give notice offailure before significant exposurewould occur.
Monitoring and maintenanceinspections would give notice offailure before significant exposurewould occur.
Ability to Obtain Approvalsand Coordinate with OtherAgencies
No approvals necessary. Would need to demonstratecompliance with Iowa surfacewater standards.
Would need to demonstratecompliance with air standards,NPDES permit requirements, andIowa surface water standards.
Would need to demonstratecompliance with air standards andIowa surface water standards.
Availability of Equipment,Specialists, and Materials
None required. No special equipment, materials,or specialist required. Iowalicensed well drillers are readilyavailable.
No special equipment, materials,or specialist required. Iowalicensed well drillers andconstruction contractors arereadily available. Personnel toprovide operation andmaintenance of treatment plantand recovery wells are readilyavailable.
Contractors that specialize in in-situ stripping wells are available.Personnel to provide operationand maintenance of systems arereadily available.
Availability of Technologies None required. MNA evaluation technologyreadily available.
Extraction well technology readilyavailable. Air strippingtechnology developed andcommercially available.
In-situ stripping well technologydeveloped and commerciallyavailable.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 5 of 6
Record of Decision
Table 10 (Continued)Comparative Analysis of Alternatives
Railroad Avenue Groundwater Contamination Site/Northern Plume
Evaluation CriteriaAlternative 1
No Action
Alternative 2
Monitored Natural Attenuation(MNA)
Alternative 3Extraction with Recovery
Wells/Treatment by On-site TrayAeration/Surface Water Discharge
(Containment)
Alternative 4
In-situ Stripping Wells(Containment)
COSTS
Capital Costs
Present Worth of O&MCosts
Total Costs of O&M Costs
Total PresentWorth*
$0
$111,300
$321,000
$111,300
$24,000
$406,000
$921,000
$430,000
$532,000
$811,000
$1,899,000
$1,343,000
$670,000
$1,174,000
$2,702,000
$1,844,000
Notes:State and community acceptance will be evaluated during preparation of the ROD.* Present worth calculated at a discount rate of 7 percent.
Railroad Avenue Groundwater Contamination SiteNorthern Plume 6 of 6
Record of Decision
Table 11Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
MonitoringWell
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analyte
Alkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonateAlkalinity, bicarbonate
Chemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen DemandChemical Oxygen Demand
ChlorideChlorideChlorideChlorideChlorideChlorideChlorideChlorideChlorideChlorideChlorideChloride
Concentration
July 2002
398352387340379298
428(427)460300342329343MANANANANANANANANANANANA12696.954.213484.8109
32(32)58.794.714244.172
Nov. 2002424
370(376)390346397327383525324320425346NANANANANANANANANANANANA125
94(93)53.113182.599.355.460.610315453.188.5
May 2003NANANANANANANANANANANANANA10 UNANANANANA10 UNA10.785.1NANANANANANANANANANANANANA
Nov. 2003
NANANANANANANANANANANANA10.4 U10.4 U
10.4(10.4) U10.4 U10.4 U10.4 U10.4 U261116
10.4 U10.4 UNANANANANANANANANANANANA
May 2004NANANANANANANANANANANANA20 U20 U20 U20 U20 U20 U
20(20) U20 U20 U20 U20 U20 UNANANANANANANANANANANANA
Nov. 2004
NANANANANANANANANANANANANANANANANANANANANANANANANA96.6NA
99.5(103)39.795.990.644.9104NA75.794.0
Unitsmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmgrt.mg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/L
Railroad Avenue Groundwaler Contamination SiteNorthern Plume l o f ? Record Of Decision
Table 11 (Continued)Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analyte
ConductivityConductivityConductivityConductivityConductivityConductivityConductivityConductivityConductivityConductivityConductivityConductivity
Dissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic CarbonDissolved Organic Carbon
Dissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved OxygenDissolved Oxygen
Concentration
July 2002
1390930105711301043NA
104511001220118364011581.51.11.61 U
1.42.31(1) U2.11 U
1.51.91 U
5.450.40.1NA0.1NA0.40.1NA0.20.12.2
Nov. 2002
11821009125711241148142512691189126514729961477
1 U1(1) U1.41 U1 U2
1.52.31 U
1.52.81.10.20.10.10.10.10.10.10.10.10.10.10.1
[ May 2003
NA1155NANANANANA
1404NA
1395961NANANANANANANANANANANANANANA1.7NANANANANA3.4NA0.31.2NA
Nov. 2003
160213001174127615151447149716081335139510541461NANANANANANANANANANANANA0.60.40.40.50.40.50.40.40.50.40.50.5
May 2004
168113131292139813811436167314661392153111101318NANANANANANANANANANANANA0.10.10.10.10.10.10.10.10.10.10.30.1
Nov. 2004NA
1134NA
103011691284115612701075NA9971250NANANANANANANANANANANANANA0.5NA0.50.30.80.40.10.5NA0.50.6
Units
umhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmumhos/cmmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 2 of 7 Record Of Decision
Table 11 (Continued)Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analyte
EhEhEhEhEhEhEhEhEhEhEhEh
EthaneEthaneEthaneEthaneEthaneEthaneEthaneEthaneEthaneEthaneEthaneEthaneEthaneEtheneEtheneEtheneEtheneEtheneEtheneEtheneEtheneEtheneEtheneEthene
Concentration
July 2002
-16-18-108NA-54NA-38-60NA-97
-135-61NA
NA
NA
NANA
NANANANA
NANA
NANA
NANANA
NANA
NA
NA
NA
NA
NA
NA
Nov. 2002
180 R121 R28 R255 R157 R160 R122 R157 R161 R180 R63 R128 RNA
NA
NA
NANA
NA
NANA
NANANA
NANANANA
NA
NANA
NA
NA
NA
NA
NA
NA
May 2003
NA-30NA
NANA
NANA
-60NA
-33-117NANA
NA
NA
NANA
NA
NANA
NA
NANANANANANA
NA
NANA
NA
NA
NA
NA
NA
NA
Nov. 2003
122-33-6431-64
-5-54
-71
-3527
-€0
-19
2 U2 U
2(2) U2 U2 U2 U2 U2
2 U2 U2 U2 U3 U3 U
3(3) U3 U3 U3 U3 U3 U3 U3 U3 U3 U
May 2004
54-0.6-76
21-35
60153
-1875
23
-85-35
2 U2 U2 U2 U2 U2 U
2(2) U2 U2 U2 U2 U2 U3 U3 U3 U3 U3 U3 U
3(3) U3 U3 U3 U3 U3 U
Nov. 2004
NA
-74NA
-135-9
736
-51NA
-98-63NA
2 UNA
2(2) U2 U2 U2 U4
2 UNA2 U2 U
NA3 U
NA
3(3) U3 U3 U3 U3 U3 U
NA
3 U3 U
Units
mvmvmvmvmvmvmvmvmvmvmvmvug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 3 of 7 Record Of Decision
Table 11 (Continued)Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
AnalyteIron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (total)Iron (+2)Iron (+2)Iron (+2)Iron (-1-2)Iron (+2)Iron (+2)Iron (+2)Iron (+2)Iron (+2)Iron (+2)Iron (+2)Iron (+2)MethaneMethaneMethaneMethaneMethaneMethaneMethaneMethaneMethaneMethaneMethaneMethane
Concentration
July 2002
14601370829054914002240
5840(6070)2030674317028904220NANANANANANANANANANANANANANANANANANANANANANANANA
Nov. 2002
9662280(2130)
8510376
32301330161066503900816393054701.62.42.70.83.31.41.71.97.51.32.45.0NANANANANANANANANANANANA
May 2003NA
1680NANANANANA
4010NA
17904140NANA
2200NANANANANA
2600NA
16004400NANANANANANANANANANANANANA
Nov. 2003
8581080
8900(9050)1780405044604320563063701180445062300.51.13.82.13.43.13.63.43.21.63.33.51 U4
3(4)1 U2215190 J1 U
39638
May 2004
9723230901023304240666
453(892)34704242130466047301.02.84.52.23.20.40.03.20.81.23.22.81441
141 U
KD110 J1 U71 U10
Nov. 2004
NA3700NA
1920(1960)337098463743702130NA
47204620NA3.2NA2.43.71.10.83.82.5NA4.43.4NA5
NA
1(1) U71 U3
2101 U
NA1 U2
Units
ug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/Lug/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 4 of 7 Record Of Decision
Table 11 (Continued)Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analyte
Nitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as NitrogenNitrate as Nitrogen
PHPHPHpHpH
PHPHPHpHPHPHPH
SulfateSulfateSulfateSulfateSulfateSulfateSulfateSulfateSulfateSulfateSulfateSulfate
Concentration
July 2002
1.160.310.03 U0.03 U0.10.03 U
0.03(0.03) U0.1
0.050.03 U0.03 U0.03 U7.236.86.9NA6.8NA6.96.8NA7
7.17
229164300200224308
332(335)26021224746.5358
Nov. 2002
1.860.18(0.14)
0.03 U0.03 U0.03 U0.340.390.210.03 U0.03 U0.03 U0.03 U6.97
7.16.86.96.96.96.977
7.26.9210
213(206)29620528033531224827326042.5358
May 2003
NANANANANANANANANANANANANA7
NANANANANA6.9NA7.07.2NANANANANANANANANANANANANA
Nov. 2003
0.03 U0.28
0.03(0.3) U0.03 U0.03 U0.03 U0.03 U0.03 U0.050.03 U0.03 U0.03 U6.77.16.96.57
6.76.97
6.76.86.86.7236163
221(221)20327934233923923623072.5322
May 2004
1.100.030.03 U0.03 U0.03 U0.07
0.63(0.64)0.03 U0.590.03 U0.03 U0.03 U7.07.07.16.96.97.06.97.07.07.07.27.0202178211205244253
224(233)28025623263.4288
Nov. 2004
NA0.25NA
0.03(0.03) U0.03 U0.260.520.03 U0.03 UNA0.03 U0.03 UNA6.9NA6.86.96.86.86.96.9NA7.16.9NA291NA
243(236)206387245389230NA54.5311
Units
mg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/LSUSUSUSUSUSUSUSUSUSUSUSUmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 5 of 7 Record Of Decision
Table 11 (Continued)Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
MonitoringWell
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
AnalyteSulfideSulfideSulfideSulfideSulfideSulfideSulfideSulfideSulfideSulfideSulfideSulfide
TemperatureTemperatureTemperatureTemperatureTemperatureTemperatureTemperatureTemperatureTemperatureTemperatureTemperatureTemperature
Total Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic CarbonTotal Organic Carbon
Concentration
July 2002
MANANANANA
NANANA
NA
NANA
NANA
1314.414.813.5NA
15
13.815.515.112.814.5
1 U7.41.2
1.3
1.2
1.5
7.1(7.2)1.8
1 U1.9
2.7
1 U
Nov. 2002NANANANANANANANANANANANA15
14.314.315.414
15.815.813.714.214.312.213.4
1 U1(1) U1.31 U1 U1 U1 U
1.91.85.131 U
May 2003NANANANANA
NANANA
NA
NANA
NANA
13.5NA
NANANA
NA
13.9NA
14.612.6NANA
NANA
NA
NA
NA
NA
NANA
NANA
NA
Nov. 2003NANA
NANA
NA
NANA
NANA
NANA
NA
14.813.614
14.713.515.215
13.514.114.212.113.5NANANA
NA
NA
NA
NA
NA
NA
NANA
NA
May 2004NANANANA
NA
NANA
NANA
NANA
NA13.413.014.211.713.614.814.813.814.114.312.713.7NA
NANA
NA
NA
NANA
NANA
NANA
NA
Nov. 2004NA
0.033NA
0.075(0.079)0.010 U0.010 U0.010 U0.1051.64NA
0.0350.010 U
NA14.3NA
14.713.415.716.313.414.0NA12.413.4NA1 U
NA1. 1(1.0 U)
1.71 U1 U
1.71 U
NA2.71 U
Units
mg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/LDegCDegCDegCDegCDegCDegCDegCDegCDegCDegCDegCDegCmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/Lmg/L
Railroad Avenue Groundwater Contamination SiteNorthern Plume 6 of 7 Record Of Decision
Table 11 (Continued)Metals, Geochemical, and Biochemical Data Summary (Monitoring Wells)
Railroad Avenue Groundwater Contamination Site
Monitoring
Well
MW-01MW-02MW-03MW-04MW-05MW-06MW-07MW-08MW-09MW-10MW-11MW-12
Analyte
TurbidityTurbidityTurbidityTurbidityTurbidityTurbidityTurbidityTurbidityTurbidityTurbidityTurbidityTurbidity
Concentration
July 2002
5.92.49.1MA2
NA5.12.8NA3.71.81.5
Nov. 2002
0000
0.1000
5.2000
May^2003
NA0
NANANANANA0
NA2.40.8NA
Nov. 2003
00
1.30
0.10.40.81.45000
May 2004
2.14.18.53.54.75.02.65.033
14.33.94.5
Nov. 2004
NA0.2NA-1.75.5-0.83.77.03.5NA4.2-0.6
Units
NTUNTUNTUNTUNTUNTUNTUNTUNTUNTUNTUNTU
NA = Not Available
mg/L = milligrams per liter
ug/L = micrograms per liter
U = Not detected at or above the reportable level shown.
J = The associated numerical value is an estimated quantity.
umhos/cm = micromhos per centimeter
mv = millivolt
SU = standard units (pH)
deg C = degrees Celsius
NTU = Nephelometric turbidity units
R = rejected
Railroad Avenue Groundwater Contamination SiteNorthern Plume 7 of 7 Record Of Decision
Analvte
Table 12
Monitored Natural Attenuation Screening Step 1
Railroad Avenue Groundwater Contamination Site
Northern Plume
Average Concentration in
Most Contaminated Zone
(May and November 2004^) Points Awarded1
Dissolved Oxygen
Nitrate
Iron (II)
Sulfate
Sulfide
Methane
ORP (Eh)
pH
Total Organic Carbon
Temperature
Chloride
PCE (source product)
TCE (source/daughter product)
cis-1,2-DCE (daughter product)
Vinyl Chloride (daughter product)
Ethene/Ethane (daughter product VQ
0.1 mg/L
<0.03 mg/L
3.5 mg/L
335 mg/L
0.11 mg/L
0.16 mg/L
-6mv
7.0 SU
1.7 mg/L
13.6 degrees C
45 mg/L
< 0.5 ug/L
lug/L
330 ug/L
47 ug/L
4 ug/L (maximum')
Total Screening Points
3
2
3
0
0
I2
1
0
0
0
0
0
I2
2
2
1!
163
Total screening points of 16 indicate adequate evidence3 for anaerobic biodegradation of chlorinated
organics.
Note 1 = Table 2.3 (Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground
Water, EPA/600/R-98/128, USEPA, September 1998)
Note 2 = Partial points Table 2.3 (Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents
in Ground Water, EPA /600/R-98/128, USEPA, September 1998)
Note 3 = Table 2.4 (Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground
Water, EPA/600/R-98/128, USEPA, September 1998)
Table 13Present Worth Cost Estimate
Alternative 2 - Monitored Natural Attenuation
Cost Estimate ComponentCAPITAL COSTSMonitoring Well (1 well installed to depth of 50 with 25-foot screen, locking well cap)Assist City Drafting of Well Permitting Requirements
Quantity
50
1
Units Unit Cost Capital Cost | Annual Cost
VLF
LS
$200
$5,000DIRECT CAPITAL COST SUBTOTAL
Bid Contingency (15%)Scope Contingency (15%)
TOTAL DIRECT CAPITAL COSTPermitting and Legal (5%)Construction Services (10%)
CONSTRUCTION COSTS TOTALEngineering Design (8%)
TOTAL CAPITAL COST
$10,000
$5,000$15,000$2,300$2,300
$19,600$1,000$2,000
$22,600$1,800
$24,000
Cost Estimate Component Quantity Units Unit Cost Capital Cost Annual CostANNUAL O&M COSTSGROUNDWATER and SURFACE WATER MONITORING (Analysis Only) +
Years 1 and 2Quarterly sampling of 13 monitoring wells, 4WDM wells, and 3 surface water locations forVOCs (standard turnaround)Years 3 through 5Semi-annual sampling of 13 monitoring wells, 4WDM wells, and 3 surface water locations forVOCs (standard turnaround)Years 6 through 30Yearly sampling of 13 monitoring wells, 4WDM wells, and 3 surface water locations forVOCs (standard turnaround)
88
44
22
EA
EA
EA
$159
$159
$159
$14,000
$7,000
$3,500
GROUNDWATER MONITORING (Labor only)Years I and 22 Level PI persons for 2 - 8 hour days persampling event and 4 - 8 hour days per dataevaluation reportExpenses (including per diem)Years 3 through 52 Level PI persons for 2 - 8 hour days persampling event and 4-8 hour days per dataevaluation reportExpenses (including per diem)Years 6 through 302 Level PI persons for 2 - 8 hour days persampling event and 4-8 hour days per dataevaluation reportExpenses (including per diem)
384
16192
896
4
EA
DAYHR
DAYHR
DAY
$75
$150$75
$150$75
$150
$28,800
$2,400$14,400
$1,200$7,200
$600PLAN PREPARATION / INSTITUTIONAL CONTROLS
Preparation of Health and Safety Plan (Year 1only)Preparation of QA/Sampling Plan (Year 1 only)
40
60
HR
HR
$75
$75
$3,000
$4,500
Railroad Avenue Groundwater Contamination Siie
Northern Plume 1 of 3 Record of Decision
Table 13 (Continued)Present Worth Cost Estimate
Alternative 2 - Monitored Natural Attenuation
Cost Estimate ComponentPrepare Annual NewsletterAnnual Newsletter Publication in Local Newspaper andDirect MailingPublic Informational Meeting @ 5, 10, 15, 20, 25, and30yrsFive- Year Review @ 5, 10, 15, 20, 25, and 30 yrsAbandon Monitoring Wells (13 wells) Year 30 only
Quantity40
1
1
113
UnitsHR
LS
LS
LSEA
Unit Cost$75
$1,000
$5,000
$50,500$1,500
TOTAL PRESENT WORTH O&M COSTTOTAL PRESENT WORTH
Capital Cost
$406,000$430,000
Annual Cost$3,000
$1,000
$5,000
$50,500$19,500
7 percent discount rate used to calculate present worth.+ For each sampling event, includes one duplicate per 20 primary samples and one trip blank.
Railroad Avenue Groundwaler Contamination Site
Northern Plume 2 of 3 Record of Decision
Table 13 (Continued)Present Worth Cost Estimate
Alternative 2 - Monitored Natural Attenuation
Year
123456789101112131415161718 j192021222324252627282930
Yearly O&MCost*
$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000$4,000
IntermittentO&M Costs
$52,700$45,200$22,600$22,600$78,100$11,300$11,300$11,300$11,300$66,800$11,300$11,300$11,300$11,300$66,800$11,300$11,300$11,300$11,300$66,800$11,300$11,300$11,300$11,300$66,800$11,300$11,300$11,300$11,300$86,300
Total Costs of Annual O&MPresent Worth of Annual O&M
Total AnnualO&M Costs
$56,700$49,200$26,600$26,600$82,100$15,300$15,300$15,300$15,300$70,800$15,300$15,300$15,300$15,300$70,800$15,300$15,300$15,300$15,300$70,800$15,300$15,300$15,300$15,300$70,800$15,300$15,300$15,300$15,300$90,300
$921,000$406,000
Intermittent O&M Costs Include:
Year 1 (plans, monitoring)
Year 2 monitoring
Years 3-5 monitoring
Years 3-5 monitoring
Years 3-5, 5-yr review, informational meeting
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6 - 30, 5-yr review, informational meeting
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6 - 30, 5-yr review, informational meeting
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6 - 30, 5-yr review, informational meeting
Years 6 - 30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6 - 30, 5-yr review, informational meeting
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6-30 monitoring
Years 6 - 30, 5-yr review, informational meeting
* Yearly O&M costs include: annual newsletter.
Railroad Avenue Groundwater Contamination Site
Northern Plume 3 of 3 Record of Decision
Table 14Final Cleanup Levels
Railroad Avenue Groundwater Contamination Site
Contaminant
PCE
TCE
cis-1,2-DCE
VC
Final GroundwaterCleanup Levels1
5^g/L
5/^g/L
70/ug/L
2//g/L
Basis for CleanupLevel2
Federal MCL
Federal MCL
Federal MCL
Federal MCL
Notes1 /^g/L - micrograms per liter2 40 CFR Part 141
Railroad Avenue Groundwater Contamination SiteNorthern Plume Record of Decision
FIGURES
!
i!
Milfit
IOWA
2000
LEGEND
^ ALLUVUL AQUIFER WELLS
* JORDAN AQUIFER WELLS
MAP LOCATION WDMW#2, 10. AND 11 HAVE BEEN ABANDONEDBECAUSE OF WELL PRODUCTION PROBLEMSWDMW#2, 10. AND 11 HAVE BEEN ABANDON*BECAUSE OF WELL PRODUCTION PROBLEMSAND ARE NOT SHOWN.
BLACK &VEATCH
FIGURE 1SITE VICINITY MAP
RAILROAD AVENUE GROUNDWATER CONTAMINATION SITE
REV0
o
JO »•O ra
If!iZO ra
PRIMARYSOURCES
PRIMARYRELEASE
MECHANISM
SECONDARYSOURCES
SECONDARYRELEASE
MECHANISMS
PATHWAY RECEPTOR
EXPOSUREROUTE
Current/Future
Industrial
Current/FutureAdult
Resident
Current/FutureChild
Resident
Onsite IndustrialOperations
ImproperSolvent
Management
-> Soil Infiltration/Percolation
Groundwater
Ingestion
Inhalation
Dermal
• •
•
•
•
•
•
This pathway is quantitatively evaluated.
Figure 3Conceptual Site Model
Railroad Avenue Groundwater Contamination Site
Plot of TCE, DCE, and VC vs. Distance Downgradient fromSuspected Source Area May 2004
1000
S«O >.O 5S2
m
'5o
TCEcis-1,2-DCE
0.1500 1000 1500 2000 2500 3000
Approximate Distance Downgradient (feet)
3500 4000
Railroad Avenue Groundwater Contamination SiteNorthern Plume
Figure 4Plot of TCE, DCE, and VC vs.
Distance Downgradient from Source AreaMay 2004
Plot of TCE, DCE, and VC vs. Distance Downgradient fromSuspected Source Area November 2004
1000
O)32. 100o*= *•re ot oC CM0) »-o o>C £1O PO £
x2Q.a
•TCE-cis-1,2-DCEVC
500 1000 1500 2000 2500 3000
Approximate Distance Downgradient (feet)
3500 4000
Railroad Avenue Groundwater Contamination SiteNorthern Plume
Figure 5Plot of TCE, DCE, and VC vs.
Distance Downgradient from Source AreaNovember 2004