STREAMLINED REMEDIATION SYSTEM EVALUATION (RSE-LiTE)
FOR A GROUND WATER PUMP AND TREAT SYSTEM
EATON CORPORATION FACILITY
KEARNEY, NEBRASKA
SUBMITTED:
DECEMBER 9,2005
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Office of Solid Waste EPA 542-R-05-024
and Emergency Response December 2005
(5102G) www.epa.gov/tio
clu-in.org/optimization
Remediation System Evaluation for a
Ground Water Pump and Treat System
Eaton Corporation Facility
Kearney, Nebraska
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NOTICE
This report is an independent third party analysis and represents the views of the authors. This
document is not a U.S. EPA policy, guidance or regulation. It does not create or impose any
legally binding requirements or establish U.S. EPA policy or guidance. The information is not
intended, nor can it be relied upon, to create any rights enforceable by any party in litigation with
the United States or any other party. The information provided maybe revised periodically
without public notice. Use or mention of trade names does not constitute endorsement or
recommendation for use. Standards of Ethical Conduct do not permit EPA to endorse any
private sector product or service.
The U.S. Environmental Protection Agency funded the preparation of this document by
Geotrans, Inc. under EPA Contract No. 68-C-00-181 Task Order #40 to Tetra Tech EM, Inc,
Chicago, Illinois.
For further information about this report, please contact the EPA's Office of Solid Waste, Mike
Fitzpatrick, (703) 308-8411, fitzjgatrickjriikj^ or the EPA's Office of Superfund
Remediation and Technology Innovation, Ellen Rubin, (703) 603-0141, rubin.ellen@epa.gov.
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EXECUTIVE SUMMARY
A Streamlined Remediation System Evaluation (RSE-Lite) involves a team of expert
hydrogeologists and engineers, independent of the site, conducting a third-party evaluation of a
ground water pump and treat system or other remedy of environmental contamination. It is a
broad evaluation that considers the goals of the remedy, site conceptual model, above-ground
and subsurface performance, and site exit strategy. The evaluation includes reviewing site
documents, communicating with the site team, and compiling a report that includes
recommendations to improve the efficiency and effectiveness of the remedy. Recommendations
with cost and cost savings are provided in the following four categories:
Improvements in remedy effectiveness
Reductions in operation and maintenance costs
Technical improvements
Gaining site closeout
The recommendations are intended to help the site team identify opportunities for improvements.
In many cases, further analysis of a recommendation, beyond that provided in this report, may
be needed prior to implementation of the recommendation. Note that the recommendations are
based on an independent evaluation by the RSE-lite team, and represent the opinions of the RSE
team. These recommendations do not constitute requirements for future action, but rather are
provided for the consideration of all site stakeholders.
The Eaton Corporation facility ("Eaton") is located on East Highway 30 in Kearney, Nebraska.
The facility covers an area of 365,000 square feet and began operations in 1969 with engine
valve manufacturing. Onsite remediation began in 1986 after trichloroethene (TCE) was found
in production wells. On April 20, 1993, Eaton Corporation entered into an agreement with the
U.S. Environmental Protection Agency (EPA) Region 7 to delineate and remediate TCE
contamination downgradient of the facility. An interim system began operation in 1996, was
reconfigured in 1998 to improve plume capture, and reconfigured again in 2003 to adapt to a
change in the direction of plume migration.
The current approach to remediation includes an onsite pump and treat (P&T) system to contain
the onsite TCE contamination and an offsite P&T system to intercept the downgradient plume.
This RSE-lite applies primarily to the offsite P&T system.
The RSE-lite team provides the following recommendations for improving remedy effectiveness,
reducing cost, improving technical operations, and gaining site closure:
Due to a change in the direction of plume migration, the site team should consider
removing the point-of-entry treatment (POET) systems at the properties along Pool
Avenue, but should consider routinely (e.g., on an annual basis) sampling the residential
wells at the two properties along 56th Road south EW-4.
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EPA and Nebraska Department of Environmental Quality (NDEQ) have expressed
concern regarding historical changes in the direction that the plume is migrating and have
suggested numerical modeling in the past. The RSE-lite team suggests using water level
measurements (currently collected as part of the monitoring program) to develop
potentiometric surface maps. These maps should improve the site team's understanding
of ground water flow patterns and plume migration. The RSE-Lite team believes that a
numerical model will be difficult to calibrate given the transience of the system in the
past. Accurately determining and representing historical irrigation pumping/infiltration
rates will be difficult, as will be selecting appropriate water level targets for calibration.
Furthermore, since future irrigation conditions will be variable and hard to predict, the
results of scenario-based simulations will likely cover such a large range of possibilities
that such simulations will be of little use from a management perspective. The site team
may learn about the system through development of a numerical model, but the RSE-lite
team believes that this benefit is likely not worth the cost at this time.
Because permanent monitoring wells cannot be installed downgradient of the plume due
to access constraints, the RSE-lite team suggests that the site team use direct-push
sampling to gather samples in specifically recommended locations. The results of these
samples can help the site team confirm that plume capture is adequate.
The RSE-lite team recommends using the information from the potentiometric surface
maps, direct-push samples, and other previous studies to evaluate plume capture. This
effort might involve simple modeling comparable to what the site team has done in the
past, but it would not involve the development of a more complex numerical ground
water flow model.
To reduce annual costs while maintaining effectiveness, the RSE-lite team suggests
reducing the ground water monitoring frequency from quarterly (and in some cases
monthly) to semi-annually. Implementing this recommendation could result in savings of
approximately $20,000 to $25,000 per year.
The onsite remediation system reportedly consists of two air strippers operating in series.
The RSE-lite team did not specifically review this system, but given the relatively low
influent concentrations, it is likely that a single air stripper would be sufficient to meet
discharge standards. The site team should evaluate if operation of one of the air strippers
could be discontinued.
Suggestions are made for improving the remedy progress reports. These suggestions
include providing updated plume maps and potentiometric surface maps along with
current and historical ground water sampling results.
Finally, the RSE-lite team suggests that the site team consider possible exit strategy alternatives
for the current offsite P&T System. TCE concentrations have decreased to less than an order of
magnitude above the cleanup standard of 5 ug/L. The RSE team believes that there is a potential
for conditions to exist where the offsite plume is stable (i.e., will not expand beyond its current
extent) with or without continued pumping at the offsite extraction wells, even though MCLs
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might be exceeded at some locations. The RSE-lite team recommends that site stakeholders
consider that a set of conditions may occur where it may be appropriate to discontinue pumping
at offsite extraction wells even if MCLs are exceeded at some monitoring locations. The
appropriateness of discontinuing pumping would likely require field data and transport modeling
(analytical or numerical) that substantiate the stability of the plume extent due to dispersion,
dilution, and any other factors.
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TABLE OF CONTENTS
EXECUTIVE SUMMARY i
TABLE OF CONTENTS iv
1.0 INTRODUCTION 1
1.1 PURPOSE 1
1.2 RSE-LiTE PROCESS 2
1.3 PARTICIPANTS ON RSE-LiTE CONFERENCE CALL 2
1.4 DOCUMENTS REVIEWED 2
2.0 BACKGROUND 4
2.1 SITE HISTORY 4
2.2 SITE CONCEPTUAL MODEL 4
2.3 GROUND WATER REMEDIAL SYSTEM 6
2.4 REMEDY GOALS 7
2.5 COSTS 7
3.0 RSE-LITE FINDINGS 8
3.1 FINDINGS PERTAINING TO REMEDY PROTECTIVENESS 8
3.2 FINDINGS PERTAINING TO COST-EFFECTIVENESS 10
3.3 FINDINGS PERTAINING TO REMEDY PROGRESS AND SITE CLOSURE 11
4.0 RSE-LITE RECOMMENDATIONS 12
4.1 RECOMMENDATIONS TO IMPROVE SYSTEM PROTECTIVENESS 12
4.1.1 Remove POETS from Residential Wells Along Pool Avenue but Sample
Residential Wells South of EW-4 along 56th Road 12
4.1.2 Develop Potentiometric Surface Maps 12
4.1.3 Conduct Limited Direct-Push Sampling Annually for Three Years 12
4.1.4 Continue to Evaluate Capture 13
4.2 RECOMMENDATIONS TO REDUCE SYSTEM COST 14
4.2.1 Reduce the Ground Water Sampling Frequency 14
4.2.2 Reconsider Need for Two Air Strippers for Onsite Treatment 15
4.3 RECOMMENDATIONS FOR TECHNICAL IMPROVEMENT 15
4.3.1 Revise Progress Reports 15
4.4 RECOMMENDATIONS TO SPEED SITE CLOSEOUT 15
4.4.1 Consider Possible Exit Strategy Alternatives for the Current P&T System 15
FIGURES - PREPARED BY THE SITE CONTRACTOR AND INCLUCDED FOR REFERENCE
iv
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1.0 INTRODUCTION
1.1 PURPOSE
In 2003 and 2004, the EPA Corrective Action program and the EPA Office of Superfund
Remediation and Technology Innovation (OSRTI) sponsored independent optimization
evaluations called Remediation System Evaluations (RSEs) at five RCRA sites with pump and
treat (P&T) systems. These RSEs involved an independent team of experts reviewing site
documents, interviewing site stakeholders, and providing recommendations for improving
remedy effectiveness, reducing costs, and gaining site closure.
An RSE involves a team of expert hydrogeologists and engineers, independent of the site,
conducting a third-party evaluation of site operations. It is a broad evaluation that considers the
goals of the remedy, site conceptual model, above-ground and subsurface performance, and site
exit strategy. The evaluation includes reviewing site documents, visiting the site for 1 to 1.5
days, and compiling a report that includes recommendations to improve the system.
Based on the positive results of these RSEs, EPA Technology Innovation Field Services Division
and the Office of Solid Waste (OSW) have commissioned a new pilot study that involves
developing and piloting a streamlined RSE process that reduces the cost of resources relative to a
full-scale RSE, based on the consideration that many sites do not require a full-scale RSE and a
streamlined RSE will provide same level of beneficial results at a reduced cost. This streamlined
RSE or "RSE-lite" evaluation includes reviewing site documents, conducting conference calls
with the site team, and compiling a report of recommendations.
For this new pilot study, up to five RCRA Corrective Action facilities with operating remedies
have been selected to receive streamlined RSEs or "RSE-lites". The site managers have been
asked to provide site documents for review by the RSE-lite team. After reviewing the
documents, the RSE-lite team has communicated with the site managers to learn more about the
sites and fill in information gaps not covered by the site documents. As part of this streamlined
effort, no site visit has been conducted.
This RSE-lite report for the Eaton Corporation facility ("Eaton") in Kearney, Nebraska is one of
the RSE-lite reports from this new pilot study. The facility was nominated by EPA OSW based
on a nomination from EPA Region 7. The report consists of the following elements:
A brief summary on site history, site conceptual model, ground water remedial
system, remedy goals, and costs
Recommendations to improve remedy effectiveness and efficiency of the operating
pump and treat system
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1.2 RSE-LiTE PROCESS
Once a site is selected, a representative of the RSE-lite team contacts the site project manager to
obtain site documents for review. The documents typically include information pertaining to site
investigations, remedy design, and remedy operations and maintenance (O&M). Upon
reviewing this information, the RSE-lite team conducts a conference call with the remedy project
manager to address questions that may have arisen as part of the document review or other
information gaps. Based on the site documents and the information from communications with
the site project manager, the RSE-lite team prepares a short report documenting
recommendations for improving efficiency and effectiveness. The text of the RSE-lite report
includes a brief background of the site, and a recent site progress report is included as an
attachment for more detailed site information.
1.3 PARTICIPANTS ON RSE-LiTE CONFERENCE CALL
The following individuals participated the conference call as part of RSE-lite:
Dan Saathoff, Eaton Corporation
Jeff Allen, Eaton Corporation
Jeff Williamson, URS
Jeff Johnson, RPM & Hydrogeologist, EPA Region 7
Robert Tobin, Nebraska Environmental State Quality
Mike Fitzpatrick, EPA HQ
Peter Rich, GeoTrans, Inc.
Doug Sutton, GeoTrans, Inc.
Yan Zhang, GeoTrans, Inc.
1.4 DOCUMENTS REVIEWED
The following documents were reviewed as part of this RSE-lite:
Slide presentation describing the history of the site
Cross-sections of the stratigraphy immediately underlying the site
Selected correspondence between the facility and EPA regarding extraction system
A proposal from the USGS to develop a site-specific MODFLOW simulation for the site
Groundwater Quality Survey (Phase 8) Report, July 1998
Groundwater Quality Survey (Phase 9) Report, February 2003
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A figure showing the current projected plume configuration and the location of the four
active off-site extraction wells
Documentation of the monthly extraction rates
Quarterly Progress Report - Removal Action Detailed Site Assessment, Fourth Quarter
2004 October 2004 Through December 2004, January 2005
Table of ground water monitoring well analytical results, January 2005
Table of direct push ground water sample analytical results, February 2005
Figure of direct push sampling locations and TCE plume, March 2005
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2.0 BACKGROUND
2.1 SITE HISTORY
The Eaton Corporation facility ("Eaton") is located on East Highway 30 in Kearney, Nebraska.
The facility covers an area of 365,000 ft2. The facility production began operation in 1969 with
engine valve manufacturing.
The on-site remediation system began operation in 1986 after trichloroethene (TCE) was found
in production wells. TCE underground storage tanks were emptied and removed. NDEQ
Stipulation and Agreement (SAA) dated January 1989 required further investigation including a
soil gas survey and installation of additional monitoring wells. The investigation results
indicated that the on-site contamination was contained and the deep aquifer was not significantly
impacted by the contamination in the shallow aquifer.
On April 20, 1993, Eaton Corporation entered into an agreement with the EPA Region 7. The
Administrative Order on Consent for Removal Activities applied to the presence of TCE and
associated degradation products in ground water monitoring wells located east and downgradient
of Eaton Corporation's engine work production facility. The Order generally required the
delineation of TCE in ground water in the vicinity of monitoring well S-7, located within the
Kearney Municipal Airport property, and the subsequent remediation of ground water which
poses a threat to human health, safety, or the environment.
In 1993, Eaton prepared and implemented a Removal Action Work Plan. In 1995, Eaton
finalized an interim action proposal. Construction of the interim action system began in
November 1995 and was completed in February 1996. The system was reconfigured in 1998
after the Groundwater Quality Survey (Phase 8) Report in July 1998 proposed changes to the
system to provide more effective extraction and treatment. Another system modification was
conducted in 2003 which included relocating the existing ground water extraction system to
better intercept the area of highest TCE concentrations.
2.2 SITE CONCEPTUAL MODEL
Hydrogeology
Subsurface material at the site consists of fine-grained alluvial sand from 16 to 30 feet below
ground surface (bgs) and coarse-grained alluvial sand with gravel from 30 to 70 feet bgs. Site
hydrogeology consists of a single unconfined aquifer unit extending to a depth of approximately
70 ft bgs that overlies alluvial clay with fine-grained sand that acts as an aquitard. Monitoring
wells have been completed in both the shallow and deep portions of this unconfined aquifer.
Concentrations in the unconfined aquifer increase with depth, and concentrations at the base of
the aquifer are typically 2 to 10 times those at the water-table.
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The depth to water table ranges from 24 to 35 feet bgs, and the saturated thickness is
approximately 30 to 40 feet. The hydraulic conductivity averages 1,000 feet/day in the aquifer
and 0.002 to 0.3 feet/day in the aquitard. The horizontal hydraulic gradient is approximately
0.001 directed to the east-northeast. The estimated Darcy velocity is therefore approximately 1
foot per day. The porosity is estimated to be 0.27 based on field measurements. Therefore, the
estimated seepage velocity is approximately 4 feet per day.
Sources, Contaminants of Concern, and Plume Extent
TCE and associated degradation products are the primary contaminants of concern at the site.
The ground water contamination may be related to historical operations of the TCE solvent
degreaser and the associated former underground tanks and piping system. There are other
potential VOC sources in the area that may have also contributed to the observed ground water
contamination. The consent order for the site specifically refers to remediation of ground water
contamination downgradient of the Eaton facility.
Sampling results in 1991 indicated that TCE concentrations increased significantly in some
offsite monitoring wells screened in the deeper portion of the unconfined aquifer, and by 1994
TCE concentrations above 1,000 ug/L were found approximately 5,000 feet downgradient of the
facility. By 1995 TCE was observable 18,000 feet downgradient. The current extraction wells
are located approximately 18,000 to 19,000 feet downgradient of the facility.
Potential Receptors
EPA believes that there are no current drinking water receptors within the current plume
footprint. There are six private drinking water wells nearby, all of which are outside of the
plume boundary, and all of which are screened in the deep aquifer beneath the aquitard. Two of
the wells had previously been screened in the unconfined aquifer but were replaced by deep
wells completed beneath the aquitard. Three of the wells have point-of-entry treatment (POET)
systems that use both Ultraviolet (UV) radiation and granular activated carbon (GAC) for
treatment. These treatment systems are maintained once per year. A temporary POET system is
also maintained for the Kearney raceway drag strip, which is only used a few days during the
summer each year. The RPM indicates that it is unlikely that two shallow wells that were
replaced with deeper wells were the only wells in the area screened in the shallow aquifer but
exact numbers were not reported to the RSE-lite team. All domestic wells in the immediate
vicinity of the plume are now screened in the deeper aquifer, which is believed to be
hydraulically separated from the shallow aquifer containing Eaton's TCE plume. However, two
other wells are located within 1.5 miles NE and downgradient of the current downgradient edge
of the plume. Where these wells are screened is not currently known. While these wells are
located in the historic direction of plume migration, an exact prediction of the future direction of
plume migration is difficult due to complicated patterns of irrigation pumping that have resulted
in historical changes in flow direction. The site team also reports a high likelihood of high nitrate
concentrations throughout the region in the unconfined aquifer due to non-point sources, which
might affect the quality of drinking water.
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Irrigation pumping is the primary use for ground water in the surrounding area, and the operation
of these wells appears to impact ground water flow direction and velocity. Within the plume
there are two irrigation wells that are still in use, but the site team has determined that there is an
acceptably low risk associated with this use.
2.3 GROUND WATER REMEDIAL SYSTEM
System Description
There are two ground water remediation systems installed:
An onsite remediation system to contain and remediate the onsite plume
An offsite interim action system to remediate the off-site plume
The onsite ground water remediation system was installed and began operation in December
1986. The system includes one extraction well referred to as the North Shallow Production
(NSP) well, two air stripping towers in series, and discharge of treated water to two on-site
ponds. In 1995, the system was modified to allow for effluent discharge to the plant process
water system. The system flow rate is currently around 190 gpm with an influent TCE
concentration of 25 to 30 ug/L in 2004.
The offsite interim action system is the focus of this RSE-lite. The history of that offsite interim
action is summarized as follows:
The interim action system began operation in February 1996 with single extraction well
pumping at 1,000 gpm. The design influent TCE concentration was 660 ug/L. The
influent ground water was treated with an air stripper tower to reach the design effluent
TCE concentration of 3 ug/L. The treated ground water was then returned to the aquifer
through two injection wells. The average extraction well pumping rate was reduced to
650 gpm by November 1997 due to frequent shutdowns resulting from decreased
capacity of the injection wells.
Based on recommendations documented in Groundwater Quality Survey (Phase 8)
Report in July 1998, the single extraction well was abandoned and two new extraction
wells (EW-1 and EW-2) were installed in December 1998 further downgradient to
intercept higher TCE concentrations. The two extraction wells were pumped at 600 gpm
each. The air stripping tower was modified to increase its hydraulic capacity and was
also relocated approximately 1 mile north. The injection well was abandoned and a
pipeline was constructed to discharge treated effluent to the Wood River. The modified
system began operation in July 1999.
Due to increased TCE concentrations near monitoring well S-24, more monitoring wells
were installed and a direct push investigation was conducted in 2002. The results of the
investigation indicated that the plume had shifted to the southeast and had migrated
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further downgradient. Extraction from EW-1 and EW-2 has largely been discontinued;
the wells are only sporadically used. A new extraction well was installed (EW-4), and an
existing irrigation well was converted into an extraction well (EW-3). During the
irrigation season, the water extracted from EW-3 and EW-4 is used by a local farmer for
irrigation. During the non-irrigation season, the extracted water is treated by the air
stripper and discharged. The average pumping rates at EW-3 and EW-4, since August
2003, are 745 gpm and 450 gpm, respectively.
System Monitoring
The current monitoring program includes approximately 20 monitoring wells and process
monitoring as follows:
Approximately 20 monitoring wells are sampled on quarterly basis.
The air stripping towers and extraction wells are sampled on monthly basis.
Of the monitoring wells sampled quarterly, four are also sampled on a monthly basis to
monitor plume change. These four wells are S-24, S-30, S-31, and S-32.
Three samples (influent, between UV and GAC, and effluent) are collected from each of
the POET systems once per year.
2.4 REMEDY GOALS
The interim goal of off-site remediation system is to prevent migration while the ultimate goal is
to reduce TCE concentrations to MCLs.
2.5 COSTS
The costs to operate, maintain, and monitor the interim offsite system are approximately $85,690
per year, excluding project management and reporting costs. These costs also do not include
capital costs associated with installation of additional monitoring wells or other non-routine
costs. The remedy operates relatively consistently and automatically, requiring very little labor.
Cost Category
Project management and reporting
Labor - recovery system O&M
Labor - ground water sample collection
Laboratory analysis
Electrical costs
Chemicals and materials*
Total
Approximate Annual Cost
Note Reported
$1,000
$5,000
$35,690
$10,000
$34,000
$85,690
* Assumed to be "other direct costs" associated with the sampling program, such as equipment and materials
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3.0 RSE-LITE FINDINGS
In general, the RSE-lite team observed a conscientious site team that has adapted well to
changing site conditions. The findings indicated below are not intended to suggest a deficiency
in the remedy design, operation, or other actions of the site team. These findings are also not
intended to suggest requirements for the site. Rather, they are the opinions of a third-party
evaluation team and are only provided for consideration by the site team.
3.1 FINDINGS PERTAINING TO REMEDY PROTECTIVENESS
The Phase 9 ground water quality survey, conducted in 2003, consisted of 18 direct-push
ground water samples collected in a grid pattern, eight ground water samples from
monitoring wells, and three soil gas samples. No TCE was detected in the soil gas
samples. Subsequent to the RSE-lite call, the RPM indicated that EPA had informed the
facility (in a letter dated January 9, 2003) that soil gas data would not be accepted as a
demonstration that vapor intrusion poses no risk because even well designed soil gas
studies have reportedly had limited success in accurately documenting such risks. The
RPM also indicated that vapor intrusion is not an issue that needs additional evaluation as
long as the existing P&T system is in place and no residences are built within the existing
footprint of the plume but that additional evaluation of this potential receptor pathway
might be required in the future if circumstances change. Under such circumstances, the
RPM suggested that the facility might be able to invalidate vapor intrusion as a threat if
the facility can show that samples collected from the top of the water table in the
downgradient portion of the plume are contaminant-free (based upon the knowledge that
contaminant concentrations generally increase with depth, likely in part due to
precipitation recharge/dilution in the downgradient part of the plume).
There are six private drinking wells located in the vicinity. All six private wells are
located outside of the plume area. Four of them are screened in the deep aquifer where
there is no impact from contamination, and two of them that were originally screened in
the shallow aquifer have been replaced with wells in the deep aquifer. None of these
residential wells have detectable TCE concentrations.
EPA and NDEQ have noted that the extraction system has been modified twice to
address changes in plume migration. In addition, the recent direct-push investigation
conducted in February 2005 indicates the presence of contamination beyond the
extraction system and further downgradient than where previous impacts had been
detected. There is concern on behalf of EPA and NDEQ that the ground water flow in
the region is not sufficiently understood and that additional changes might need to be
made to control plume migration. EPA has suggested the use of numerical ground water
modeling to assist with the migration control effort.
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The site team reports that access for additional monitoring wells downgradient of the
extraction system is limited due to the use of the land for farming. Sampling in this area
has therefore been accomplished through direct-push investigations and the use of
temporary well points.
The ground water monitoring event in January 2005 and the direct-push investigation
conducted in February 2005 indicated that there is a significant decrease in
concentrations since October/December 2002 and April 1998. The maximum TCE
concentration during in April 1998 was 600 ug/L. By the October/December 2002
sampling the highest concentration was 110 ug/L, and by early 2005, the maximum
concentration was 35.3 ug/L. The attached figure, prepared by the site contractor,
compares the TCE plume interpreted based on 2002 and 2005 sampling results.
Analytical results of selected monitoring wells and direct-push locations from the 1998,
2002, and 2005 sampling events are listed in the following table for comparison. A
general decrease is observed, with order of magnitude decreases observed in multiple
locations. In some locations, increases are observed, but this is attributable to plume
migration upgradient of the current extraction network.
Sample ID
S-9D
S-11D
S-12D
S-17D
S-21D
S-24D
S-26D
S-27D
S-28D
S-30D
S-31D
S-32D
GS-102 (2002) / GS-216 (2005) 1
GS-101 (2002) / GS-215 (2005) 1
GS-104 (2002) / GS-214 (2005) 1
GS-105 (2002) / GS-213 (2005) 1
GS-108 (2002) / GS-202 (2005) 1
GS-107 (2002) / GS-203 (2005) 1
GS-109 (2002) / GS-204 (2005) 1
TCE in 1998
(ug/L)
120
1.4
430
3.2
19
1.9
600
420
1.3
N/A
N/A
N/A
TCE in 2002
(ug/L)
33
22
25
20
1.5
52
18
30
95
10
ND
110
18
20
18
8
7
11
8
TCE in 2005
(ug/L)
13.0
9.2
19.7
6.0
<0.5
26.4
14.0
7.0
29.8
7.8
<0.5
23.9
0.5
35.3
11.4
8.1
3.6
8.2
0.7
Note:
1. The 2005 direct-push sample was collected near the 2002 direct-push sample.
The direct-push investigation conducted in February 2005 indicated that TCE
contamination is present downgradient of extraction wells EW-3 and EW-4 and
downgradient of areas where TCE was previously observed in 2002. However, it is
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possible that this contamination was present before 2002 and before the installation of
EW-3 and EW-4. For example, in December 2002, the furthest downgradient samples
were collected from GS-107, GS-108, and GS-109 where TCE concentrations were 11
ug/L, 7 ug/L, and 8 ug/L, respectively. Therefore, the TCE concentrations that were
observed downgradient of these locations in 2005 at GS-208 (5.1 ug/L) and GS-209 (7.6
ug/L) could have already been present. For this reason, the RSE-lite team does not
believe that this downgradient contamination recently observed in 2005 is an indication
of insufficient capture provided by EW-3 and EW-4. Furthermore, the concentrations are
so close to the standard of 5 ug/L that additional remedial effort (e.g., additional
pumping) in this area would likely provide a negligible improvement in remedy
effectiveness.
The RSE-lite team has reviewed the previous modeling efforts conducted by the site team
and agree with the interpreted capture zones for EW-3 and EW-4. The actual capture
zones may even be more extensive than those interpreted by the site team. The capture
zones also appear to be sufficient to capture the core of the plume (S-28 northeast to GS-
215), even if the ground water flow shifts directly to the east. The RSE-lite team also
acknowledges that the ground water flow pattern has a history of shifting. However,
predicting this shifting would be extremely difficult. Although numerical modeling
could be used to simulate ground water flow, the RSE-Lite team believes that a numerical
model would be difficult to calibrate given the transience of the system in the past.
Accurately determining and representing historical irrigation pumping/infiltration rates
will be difficult, as will be selecting appropriate water level targets for calibration.
Furthermore, since future irrigation conditions will be variable and hard to predict, the
results of scenario-based simulations will likely cover such a large range of possibilities
that such simulations will be of little use from a management perspective. The site team
may learn about the system through development of a numerical model, but the RSE-lite
team believes that this benefit is likely not worth the cost at this time.
The decreasing TCE concentrations downgradient of the facility suggests that
containment and/or mass removal provided by the onsite remediation system has been
effective. Continued decreases in the concentrations at S-9 and other wells downgradient
of the facility will confirm that onsite pumping is providing sufficient capture/removal of
onsite contamination.
3.2 FINDINGS PERTAINING TO COST-EFFECTIVENESS
The remedy appears to be operated cost-effectively. Based on the reported costs, the site team is
running the treatment plant efficiently with little operator labor. The highest costs are in two
categories: laboratory analysis and chemicals/materials.
The laboratory analytical costs appear to be relatively high compared to the monitoring
scope of work described in Section 2.3 of this report. The RSE-lite team estimates that
analytical costs for the above-described monitoring scope of work should cost
approximately $25,000 to $30,000. In addition, the monitoring program could likely be
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modified to reduce the number of samples collected without sacrificing protectiveness as
discussed in Section 4.2 of this report.
3.3 FINDINGS PERTAINING TO REMEDY PROGRESS AND SITE CLOSURE
No institutional control exists for the site. The facility has been tracking if new water
supply wells are installed in the area.
TCE concentrations have decreased by more than an order of magnitude over the past
seven years, and the highest TCE concentration is less than one order of magnitude over
the cleanup standard of 5 ug/L. The current site exit strategy is to attain MCLs in the
downgradient part of the plume. There is no current strategy for potentially terminating
ground water extraction at the downgradient extraction wells prior to attaining MCLs at
all wells.
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4.0 RSE-LITE RECOMMENDATIONS
4.1 RECOMMENDATIONS TO IMPROVE SYSTEM PROTECTIVENESS
4.1.1 Remove POETS from Residential Wells Along Pool Avenue but Sample Residential
Wells South of EW-4 along 56th Road
Due to the migration of the plume to the east or southeast, the residential wells to the north no
longer appear to be threatened by the plume. These residential wells are also likely deep enough
to avoid being affected even if the plume were present in the unconfined aquifer immediately
above these residential wells. As with the other residential wells in the area, these two private
wells are sufficiently deep that they likely would not be receptors even if the plume were present
in the unconfined aquifer immediately above them. The site team should, however, routinely
(e.g., on an annual basis) sample the residential wells at the two properties south of EW-4 along
56th Road. This should not have a significant impact on annual costs associated with the remedy.
4.1.2 Develop Potentiometric Surface Maps
Water levels from site monitoring wells are routinely collected and presented in quarterly
reports, but potentiometric surface maps are not routinely developed for inclusion in the report to
illustrate the data. Given the concern of EPA and NDEQ regarding ground water flow patterns,
it is recommended that the potentiometric surface maps be developed for each round of future
water level measurements. To gain perspective on past ground water flow patterns, the site team
should also consider developing potentiometric surface maps for previous rounds of water level
measurements. The maps using historical data should provide the site team with an improved
understanding of the potential seasonal changes in the water levels and the potential ground
water flow patterns that changed the direction of plume migration. The future maps should help
the site team better anticipate future plume movement. When developing these maps, the water
levels from operating extraction wells should not be included as they may bias the interpretation.
Developing historic potentiometric surface maps (assuming quarterly data over 7 years),
evaluating them for trends in the ground water flow pattern, and potentially discerning a reason
for the change in plume direction would cost on the order of $10,000. Developing future
potentiometric surface maps should add less than $500 per year to the current reporting costs.
The resulting interpretation, however, may help the site team better anticipate and control plume
migration for a reasonable cost. As mentioned above, the RSE-lite team does not believe that
information gained from developing and using a numerical modeling for the site would be worth
the cost at this time.
4.1.3 Conduct Limited Direct-Push Sampling Annually for Three Years
To evaluate plume capture, the site team should consider conducting limited direct-push
sampling events on an annual basis for three years. The events should be limited to five
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locations (i.e., a one-day event) with sampling locations in the vicinity of GS-208, GS-209, and
GS-210 plus GS-206 and GS-212. The data from the various events can be compared to
determine if there is a consistent trend. A consistent increase in concentrations near GS-208
through GS-210 would suggest that capture is inadequate, and a consistent decrease would
suggest that capture is adequate. Similarly, a consistent increase near GS-206 and GS-212 might
suggest that the plume is migrating to the southeast. The potentiometric surface maps proposed
in Section 4.1.2 of this report would help confirm this potential change in the migration
direction.
Because consistent locations will be sampled, there is no need for using a mobile laboratory for
field screening. For cost-effectiveness, the samples should just be sent to the laboratory for
analysis.
Due to expected variability in sampling data, particularly data obtained from temporary wells,
the site team should not make a decision on just one round of results. The RSE-lite team
believes this is a cost-effective approach to monitoring plume migration. The estimated cost for
each of these events is approximately $10,000, including oversight, drilling, sampling, and
analysis; however, the RSE-lite team acknowledges that the site team has conducted direct-push
sampling events at the site and would have a better understanding of the associated costs.
4.1.4 Continue to Evaluate Capture
The RSE-lite team believes it is likely that the plume is currently adequately captured, but the
site team should continue to evaluate capture. The evaluation should be relatively straight
forward and should likely include reviewing the potentiometric surface maps to determine the
direction of ground water flow, reviewing concentration data from ground water monitoring and
the recommended direct-push events, and use of a simple calculation to estimate width of
capture. The site team could use Quickflow as they have in the past to evaluate capture, but it
would likely be easier and more cost-effective to use the following simple calculation to estimate
the approximate width of aquifer that will be captured upgradient of each extraction well.
K x b x /' x factor
Where
Q = pumping rate (ft3 per day)
K = hydraulic conductivity (ft per day)
b = saturated aquifer thickness (feet)
w = plume width (feet)
/' = horizontal hydraulic gradient (feet per foot)
factor = assumed to be 1.5 for this site (accounts for other potential sources of water to
the extraction well)
The approximate width of aquifer that will be captured at the line of the wells (in a direction
perpendicular to ground water flow) will be one-half the capture zone width calculated
upgradient of the extraction wells.
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For example, using the following site-specific input parameters, the width of capture upgradient
of EW-3 is approximately 2,400 feet (1,200 feet on each side of the well) and the width of
capture upgradient of EW-4 is approximately 1,500 feet (750 feet on each side of the well). The
width of capture immediately adjacent to EW-3 is approximately 1,200 feet (600 feet on each
side of the well) and the width of capture immediately adjacent to EW-4 is approximately 750
feet (375 feet on each side of the well).
Q = 143,400 ft3 per day (745 gpm) for EW-3 and 88,630 ft3 per day (450 gpm) for EW-4
K= 1,000 feet per day
B = 40 feet
/' = 0.001 feet per foot
Note that these types of calculations are simple, and aquifer heterogeneity and uncertainty with
respect to input parameter values creates uncertainty in the results. For instance, the use of a
"factor" of 1.5 to account for other potential sources of water to the extraction well is subject to
significant uncertainty.
Given that the two extraction wells are 1,200 feet apart, this calculation suggests that the capture
zones of the two wells likely overlap upgradient of the wells to create effective capture for the
majority of the plume. However, the capture zones of the two wells may not overlap
immediately adjacent to the wells. These results will also vary as extraction rates and ground
water flow patterns change. Again, these calculations are simplistic in nature, are subject to
significant uncertainty, and only provide one line of evidence that should be used with other
lines of evidence in evaluating capture.
Many of the steps in conducting an improved capture zone analysis are already covered in
preparing the potentiometric surface maps and conducting the direct push sampling (both
recommended above) and preparing typical reports. Therefore, the cost associated with
implementing this recommendation should be on the order of $500 per year in addition to current
costs and the estimated costs for implementing the other recommendations.
4.2 RECOMMENDATIONS TO REDUCE SYSTEM COST
4.2.1 Reduce the Ground Water Sampling Frequency
The site team should discontinue monthly ground water sampling. The data likely provide little
benefit beyond quarterly or even semi-annual sampling. The RSE-lite team suggests that the site
team maintain the same monitoring wells in its ground water sampling program but reduce the
sampling frequency from quarterly (monthly in some locations) to semi-annually at all locations.
Sampling from the extraction wells could continue on quarterly basis. Making this adjustment
should reduce both the sampling costs (labor, equipment, and materials) and the analytical costs.
Assuming the sampling costs are $39,000 per year ($5,000 for labor and $34,000 for other
costs), this recommended reduction should save approximately $10,000 to $15,000 per year in
sampling costs. Assuming a cost of $100 for laboratory analysis of each sample, this
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recommended reduction should save approximately $10,000 in analytical costs. Therefore, by
implementing this recommendation, the site team should save approximately $20,000 to $25,000
per year without sacrificing the effectiveness of the remedy or its monitoring program.
4.2.2 Reconsider Need for Two Air Strippers for Onsite Treatment
The onsite treatment system was not a focus of this RSE-lite; however, the RSE-lite team noticed
that site documents suggest two air strippers are used in series to treat the water that is extracted
onsite. Given the relatively low concentrations in that extracted water, the site team may want to
determine if both air strippers are required. The site team might be able to save some electrical
costs if the use of one of the onsite air strippers can be discontinued. An estimate of the potential
savings associated with this recommendation is not provided because the RSE-lite team does not
have the operating parameters for the onsite system.
4.3 RECOMMENDATIONS FOR TECHNICAL IMPROVEMENT
4.3.1 Revise Progress Reports
The site team should consider revising the frequency and format of the progress reports. First, it
is recommended that reports be prepared on a semi-annual basis in conjunction with the
suggested monitoring frequency. Second, the reports should present recent water level and water
quality data in tables and figures. The figures should include potentiometric surface maps (see
the above recommendation) and updated plume maps. The tables should include both current
and historic water level and water quality data for each sampling location. This would make it
easier for the site team and others reviewing the documents to notice trends in concentrations
and water levels. Finally, because the data would be presented in tables and figures, the text
could be used for interpreting the data rather than simply restating the data. Interpretation
should be relatively limited but should focus on plume capture and progress toward restoration.
Implementing this recommendation might require an additional $1,000 in capital costs to
develop a template for the tables, but it is possible that these changes could be made within the
existing project management and reporting budget, which was not reported as part of this
process.
4.4 RECOMMENDATIONS TO SPEED SITE CLOSEOUT
4.4.1 Consider Possible Exit Strategy Alternatives for the Current P&T System
The TCE concentrations have decreased by an order of magnitude over the past 7 years and are
now within one order of magnitude of the cleanup standard of 5 ug/L. As a result, pumping and
treating ground water is having a diminishing effect on mass removal. The current site exit
strategy is to attain MCLs in the downgradient part of the plume. There is no current strategy for
potentially terminating ground water extraction at the downgradient extraction wells prior to
attaining MCLs at all wells.
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At this site, mitigating plume migration is a primary remediation objective. However, the RSE
team believes that there is a potential for conditions to exist where the offsite plume is stable
(i.e., will not expand beyond its current extent) with or without continued pumping at the offsite
extraction wells, even though MCLs might be exceeded at some locations. For example, it is
possible that, in the future, groundwater concentrations may exceed MCLs at some distance
upgradient of the off-site extraction wells, but may be below MCLs at the extraction wells. In
that case, some concentrations would remain above MCLs within the current plume footprint,
but the extraction wells would not provide any benefit. The plume extent would be stable with
or without continued extraction at those extraction wells.
The RSE-lite team recommends that site stakeholders consider that a set of conditions, such as
the example presented above, may occur where it may be appropriate to discontinue pumping at
offsite extraction wells even if MCLs are exceeded at some monitoring locations. The
appropriateness of discontinuing pumping would likely require field data and transport modeling
(analytical or numerical) that substantiate the stability of the plume extent due to dispersion,
dilution, and any other factors.
The cost for the modeling effort, analysis, and documentation should be approximately $10,000.
The appropriate field data might depend on the particular set of conditions and should be
determined through discussions between EPA, NDEQ, and the facility. These discussions may
require an additional $10,000 in consultant costs. If these efforts ultimately result in
discontinuing pump and treat, it would save electrical costs, operator labor, and process sampling
costs perhaps totaling $15,000 per year. The costs for ground water monitoring would likely
remain for several years. Given the relatively low annual cost savings relative to the evaluation
costs, the facility may wait for a set of site conditions where it is relatively easy and low cost to
demonstrate plume stability.
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Cost Summary Table
Recommendation
4.1.1 Remove POETS from
Residential Wells Along Pool
Avenue but Sample Residential
Wells South of EW-4 along 56th
Road
4.1.2Develop Potentiometric
Surface Maps
4.1.3 Conduct Limited Direct-Push
Sampling Annually for Three Years
4. 1.4 Continue to Evaluate Capture
4.2.1 Reduce the Ground Water
Sampling Frequency
4.2.2 Reconsider Need for Two Air
Strippers for Onsite Treatment
4. 3.1 Revise Progress Reports
4.4.1 Consider Possible Exit
Strategy Alternatives for the
Current P&T System
Reason
Effectiveness
Effectiveness
Effectiveness
Effectiveness
Cost Reduction
Cost Reduction
Technical
Improvement
Site Closure
Estimated
Additional
Capital Costs
($)
<$ 1,000
$10,000
$30,000
$0
$0
Not quantified
$1,000
> $20,000
Estimated Change in Annual
Costs
($/yr)
(<$ 1,000)
$500
$0
$500
($20,000 to $25,000)
Not quantified
$0
(Potentially $15,000 if P&T is
Terminated in the future)
Costs in parentheses imply cost reductions.
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FIGURES*
* Prepared by the site contractor and included for reference
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<0.5
GS-201
GS-202
3.6
21S-GS-218 GS-203
98.2
GS-204
0.7
S-17
2.5
GS-207
6.0ฎ
LEGEND
COUNTY ROAD
INTERMITTENT STREAM
ABOVE GROUND DRAIN
IRRIGATION WELL LOCATION
PRIVATE DRINKING WATER
SUPPLY WELL LOCATION
EXTRACTION WELL LOCATION
MONITORING WELL LOCATION WITH
JANUARY 2005 TCE CONCENTRATION
DIRECT PUSH LOCATION FROM FEBRUARY
GS-204 2005 GROUNDWATER INVESTIGATION WITH
TCE CONCENTRATIONS
GS-209
7.6 ปGS-211
3.2
1.5
GS-210
ESTIMATED ISOCONCENTRATION OF
TCE (M9/L) IN DEEP GROUNDWATER
(DECEMBER 2002)
ESTIMATED ISOCONCENTRATION OF
TCE (jtig/L) IN DEEP GROUNDWATER
(FEBRUARY 2005)
1000 500
1000
SCALE IN FEET
Direct Push Groundwater Investigation
Eaton Corporation
Kearney, Nebraska
DIRECT PUSH SAMPLING LOCATIONS AND TCE PLUME
Figure
2-1
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