REMEDIATION SYSTEM EVALUATION
SOUTH TACOMA CHANNEL/WELL 12A
SUPERFUND SITE
TACOMA, WASHINGTON
Report of the Remediation System Evaluation,
Site Visit Conducted at the
Commencement Bay/South Tacoma Channel Well 12A Superfund Site
August 21-22, 2001
Final Report Submitted to Region 10
December 10, 2001
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NOTICE
Work described herein was performed by GeoTrans, Inc. (GeoTrans) and the United States Army Corps
of Engineers (USAGE) for the U.S. Environmental Protection Agency (U.S. EPA). Work conducted by
GeoTrans, including preparation of this report, was performed under Dynamac Contract No. 68-C-99-
256, Subcontract No. 91517. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
This document (EPA 542-R-02-008q) may be downloaded from EPA's Technology Innovation Office
website at www.epa.gov/tio or www.cluin.org/rse.
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EXECUTIVE SUMMARY
The first operable unit (OU1) of the Commencement Bay/South Tacoma Channel Superfund Site addresses
soil and ground-water contamination associated with the Time Oil property that was first discovered in
public supply Well 12A in 1981. Site contamination primarily consists of chlorinated solvents such as
1,1,2,2, tetrachloroethane (PCA), tetrachloroethylene, and trichloroethylene as well as waste oils and lead.
A number of removal actions have been conducted at the site including excavation of contaminated filter
cake, operation of a vapor extraction system (VES), and operation of a groundwater extraction and
treatment system (GETS). After approximately three years of operation, the VES was shut down in 1997
after removing over 50,000 pounds of contaminants. The GETS has operated since 1988. Contaminated
filter cake as well as light and dense non-aqueous phase liquids (LNAPL and DNAPL) remain in the
subsurface as continuing sources of dissolved phase groundwater contamination.
Based on review of the site documents and a site tour, the RSE team suggests the following
recommendations to improve system effectiveness:
Site managers could use assistance in analyzing capture offered by the GETS and determining the
optimal remedial strategy for the site. A reliable groundwater flow model, and potentially a
contaminant transport model, should be developed and used for simulations to provide this
assistance.
To date, capture zone analyses have been unreliable and adequate capture may not be provided by
the current GETS. Aquifer monitoring data and water level measurements should be used to
construct plume maps showing target capture zones and potentiometric surface maps showing
actual capture zones. The two maps should then be compared as a preliminary analysis of capture.
Augmentation of this analysis should be accomplished by analyzing water quality data from
sentinel monitoring wells and comparing measured water level data with groundwater flow model
predictions.
The current monitoring program involves irregularly spaced sampling events in which different
monitoring wells are sampled. As a result, consistent trends in plume area and migration cannot be
easily gleaned from monitoring data. A selected group of monitoring well should be sampled on a
regular basis so that trends, especially in plume migration, can be determined.
Well 9, like Well 12A, is a public supply well that operates during periods of high water demand.
Given the history of contamination at Well 12A and the proximity of Well 9 to Well 12 A, the
influent to Well 9 should be sampled and analyzed for volatile organic compounds.
These recommendations might require approximately $75,000 in capital costs and might increase annual
costs by approximately $16,000 per year, but could be as high as $125,000 in capital costs and $28,000 in
annual costs if development and use of a contaminant transport model is included.
Recommendations to reduce life-cycle costs include the following:
If it is determined through a capture zone analysis that pumping rates do not need to increase by
more than a factor of five, then the pumps in three of the extraction wells should be replaced with
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smaller models to reduce the use of electricity. While pump replacement may cost up to $14,000,
approximately $8,500 per year could be saved in electricity costs.
The costs associated with discharging the treated water to the stormwater sewer amount to
$60,000. Typically, the RSE team has only seen "hook-up" costs associated with discharges to the
stormwater sewer and not annual costs. The site managers should examine the city polices on
stormwater discharge and investigate alternative locations for discharging the treated water.
If the current carbon treatment system reaches its operating lifetime and requires replacement or if
pumping rates increases substantially, the current treatment system should be replaced by an air
stripper. The capital costs could require as much as $350,000, and annual operation and
maintenance costs would be approximately $40,000 to $50,000 less than the annual costs
associated with the current system.
Implementing the recommendations to reduce costs would require initial investments, but savings from
operations and maintenance could offset these initial investments as well as the costs associated with
recommendations for enhanced system effectiveness and technical improvement.
The RSE team agrees with the site managers that the remaining filter cake should be excavated as it is
currently providing a continuing source of groundwater contamination. In addition, the RSE team supports
the site managers' efforts to identify and screen alternative remedial technologies and strategies. Three
strategies are discussed in this report, and the RSE team suggests that pump and treat continue (for plume
containment) until an appropriate technology is selected and implemented for source removal.
Finally, an approach to implementing the recommendations is provided in Section 6.6, and a summary of
recommendations, including estimated costs and/or savings associated with those recommendations, is
presented in Section 7.0 of the report.
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PREFACE
This report was prepared as part of a project conducted by the United States Environmental Protection
Agency (USEPA) Technology Innovation Office (TIO) and Office of Emergency and Remedial Response
(OERR). The objective of this project is to conduct Remediation System Evaluations (RSEs) of pump-
and-treat systems at Superfund sites that are "Fund-lead" (i.e., financed by USEPA). RSEs are to be
conducted for up to two systems in each EPA Region with the exception of Regions 4 and 5, which already
had similar evaluations in a pilot project.
The following organizations are implementing this project.
Organization
Key Contact
Contact Information
USEPA Technology Innovation
Office
(USEPA TIO)
Kathy Yager
11 Technology Drive (ECA/OEME)
North Chelmsford, MA 01863
phone: 617-918-8362
fax: 617-918-8417
yager.kathleen@epa.gov
USEPA Office of Emergency and
Remedial Response
(OERR)
Paul Nadeau
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Mail Code 5201G
phone: 703-603-8794
fax:703-603-9112
nadeau.paul@epa.gov
GeoTrans, Inc.
(Contractor to USEPA TIO)
Rob Greenwald
GeoTrans, Inc.
2 Paragon Way
Freehold, NJ 07728
(732) 409-0344
Fax: (732) 409-3020
rgreenwald@geotransinc.com
Army Corp of Engineers:
Hazardous, Toxic, and Radioactive
Waste Center of Expertise
(USAGE HTRW CX)
Dave Becker
12565 W. Center Road
Omaha, NE 68144-3869
(402) 697-2655
Fax: (402) 691-2673
dave j .becker@nwd02 .usace .army .mil
in
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The project team is grateful for the help provided by the following EPA Project Liaisons.
Regionl Darryl Luce and Larry Brill
Region 2 Diana Curt
Region 3 Kathy Davies
Region 4 Kay Wischkaemper
Region 5 Dion Novak
Region 6 Vincent Malott
Region 7 Mary Peterson
Region 8 Armando Saenz and Richard Muza
Region 9 Herb Levine
Region 10 Bernie Zavala
They were vital in selecting the Fund-lead P&T systems to be evaluated and facilitating communication
between the project team and the Remedial Project Managers (RPM's).
IV
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TABLE OF CONTENTS
EXECUTIVE SUMMARY i
PREFACE iii
TABLE OF CONTENTS v
1.0 INTRODUCTION 1
1.1 PURPOSE 1
1.2 TEAM COMPOSITION 1
1.3 DOCUMENTS REVIEWED 2
1.4 PERSONS CONTACTED 2
1.5 SITE LOCATION, HISTORY, AND CHARACTERISTICS 2
1.5.1 LOCATION AND HISTORY 2
1.5.2 POTENTIAL SOURCES 3
1.5.3 HYDROGEOLOGIC SETTING 4
1.5.4 DESCRIPTION OF GROUND WATER PLUME 4
2.0 SYSTEM DESCRIPTION 6
2.1 SYSTEM OVERVIEW 6
2.2 EXTRACTION SYSTEM 6
2.3 TREATMENT SYSTEM 6
2.4 MONITORING SYSTEM 6
3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE CRITERIA 8
3.1 CURRENT SYSTEM OBJECTIVES AND CLOSURE CRITERIA 8
3.2 TREATMENT PLANT OPERATION GOALS 8
3.3 ACTION LEVELS 9
4.0 FINDINGS AND OBSERVATIONS FROM THE RSE SITE VISIT 10
4.1 FINDINGS 10
4.2 SUBSURFACE PERFORMANCE AND RESPONSE 10
4.2.1 WATER LEVELS 10
4.2.2 CAPTURE ZONES 10
4.2.3 CONTAMINANT LEVELS 11
4.3 COMPONENT PERFORMANCE 11
4.3.1 EXTRACTION WELLS AND PUMPS 11
4.3.2 BAGFILTERS 11
4.3.3 GACUNITS 12
4.3.4 CONTROLS 12
4.4 COMPONENTS OR PROCESSES THAT ACCOUNT FOR MAJORITY OF MONTHLY COSTS 12
4.4.1 UTILITIES 13
4.4.2 NON-UTILITY CONSUMABLES AND DISPOSAL COSTS 13
4.4.3 LABOR 13
4.4.4 CHEMICAL ANALYSIS 13
4.5 RECURRING PROBLEMS OR ISSUES 13
4.6 REGULATORY COMPLIANCE 13
4.7 TREATMENT PROCESS EXCURSIONS AND UPSETS, ACCIDENTAL CONTAMINANT/REAGENT
RELEASES 13
4.8 SAFETY RECORD 13
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5.0 EFFECTIVENESS OF THE SYSTEM TO PROTECT HUMAN HEALTH AND THE ENVIRONMENT . 14
5.1 GROUND WATER 14
5.2 SURFACE WATER 14
5.3 AIR 14
5.4 SOILS 14
5.5 WETLANDS AND SEDIMENTS 14
6.0 RECOMMENDATIONS 15
6.1 RECOMMENDED STUDIES TO ENSURE EFFECTIVENESS 15
6.1.1 OBTAIN ACCURATE AND RELIABLE WATER LEVEL MEASUREMENTS AND DEVELOP
ASSOCIATED POTENTIOMETRIC SURF ACE MAPS 15
6.1.2 DEVELOP GROUNDWATER FLOW MODEL OF THE WELL 12A OPERABLE UNIT 15
6.1.3 ANALYZE CAPTURE ZONE OF EXTRACTION WELLS 17
6.1.4 MAKE AQUIFER MONITORING PROGRAM CONSISTENT 18
6.1.5 ENSURE ANNUAL SAMPLING AND ANALYSIS OF VOCs IN WATER FROM WELL 9 ... 19
6.2 RECOMMENDED CHANGES TO REDUCE COSTS 19
6.2.1 REPLACE EXTRACTION WELL PUMPS 19
6.2.2 EXAMINE CITY OF TACOMA POLICIES ON STORMWATER DISCHARGE AND/OR CONSIDER
ALTERNATIVE DISCHARGE LOCATIONS 20
6.2.3 CONSIDER REPLACING GAC TREATMENT WITH AIR STRIPPING 20
6.3 MODIFICATIONS INTENDED FOR TECHNICAL IMPROVEMENT 21
6.4 MODIFICATIONS INTENDED TO GAIN SITE CLOSE-OUT 21
6.4.1 EXCAVATE REMAINING FILTER CAKE 21
6.4.2 EVALUATE REMEDIAL PROCESS OPTIONS BASED ON ANALYSIS OF GROUNDWATER
MODELING 21
6.4.2.1 PASSIVE APPROACH: SWITCH TO MONITORED NATURAL ATTENUATION ... 21
6.4.2.2 MODERATE APPROACH: CONTINUE PUMP AND TREAT AS A CONTAINMENT
REMEDY 22
6.4.2.3 AGGRESSIVE APPROACH: SOURCE REDUCTION OR REMOVAL 22
6.5 UNUSED EQUIPMENT 23
6.6 SUGGESTED APPROACH TO IMPLEMENTATION OF RECOMMENDATIONS 23
7.0 SUMMARY 25
List of Tables
Table 7-1. Cost summary table
List of Figures
Figure 1-1 Site layout of the Well 12a operable unit indicating monitoring wells sampled during the March
1993 and/or April 1998 monitoring events that had concentrations above MCLs
Figure 1-2 Layout of the Time Oil property indicating the locations of the groundwater extraction wells as
well as areas of contaminated soil, DNAPL, and filter cake
VI
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1.0 INTRODUCTION
1.1 PURPOSE
In the OSWER Directive No. 9200.0-33, Transmittal of Final FYOO - FY01 Superfund Reforms Strategy,
dated July 7,2000, the Office of Solid Waste and Emergency Response outlined a commitment to optimize
Fund-lead pump-and-treat systems. To fulfill this commitment, the US Environmental Protection Agency
(USEPA) Technology Innovation Office (TIO) and Office of Emergency and Remedial Response (OERR),
through a nationwide project, is assisting the ten EPA Regions in evaluating their Fund-lead operating
pump-and-treat systems. This nationwide project is a continuation of a demonstration project in which the
Fund-lead pump-and-treat systems in Regions 4 and 5 were screened and two sites from each of the two
Regions were evaluated. It is also part of a larger effort by TIO to provide USEPA Regions with various
means for optimization, including screening tools for identifying sites likely to benefit from optimization
and computer modeling optimization tools for pump and treat systems.
This nationwide project identifies all Fund-lead pump-and-treat systems in EPA Regions 1 through 3 and 6
through 10, collects and reports baseline cost and performance data, and evaluates up to two sites per
Region. The site evaluations are conducted by EPA-TIO contractors, GeoTrans, Inc. and the United States
Army Corps of Engineers (USAGE), using a process called a Remediation System Evaluation (RSE),
which was developed by USAGE. The RSE process is meant to evaluate performance and effectiveness (as
required under the NCP, i.e., and "five-year" review), identify cost savings through changes in operation
and technology, assure clear and realistic remediation goals and an exit strategy, and verify adequate
maintenance of Government owned equipment.
The South Tacoma Channel/ Well 12A Superfund Site was chosen to receive an RSE based on an initial
screening of the pump-and-treat systems managed by USEPA Region 10 as well as discussions with the
Superfund Reform Initiative Project Liaison for that Region. This site has high operation costs relative to
the cost of an RSE and a long projected operating life. This report provides a brief background on the site
and current operations, a summary of the observations made during a site visit, and recommendations for
changes and additional studies. The cost impacts of the recommendations are also discussed.
A report on the overall results from the RSEs conducted for this system and other Fund-lead P&T systems
throughout the nation will also be prepared and will identify lessons learned and typical costs savings.
1.2 TEAM COMPOSITION
The team conducting the RSE consisted of the following individuals:
Frank Bales, Chemical Engineer, USAGE, Kansas City District
Rob Greenwald, Hydrogeologist, GeoTrans, Inc.
Peter Rich, Civil and Environmental Engineer, GeoTrans, Inc.
Doug Sutton, Water Resources Engineer, GeoTrans, Inc.
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1.3
DOCUMENTS REVIEWED
Author
US EPA
US EPA
ICF Technology, Inc.
ICF Technology, Inc.
ICF Technology, Inc.
EPA
ICF Kaiser/ URS Greiner
EPA
URS Greiner
URS Greiner
URS Greiner
Date
3/18/1983
5/3/1985
5/1990
1/1991
11/1991
7/1998
9/1999
9/1999
10/1999
12/1999
9/2000
Title
Record of Decision for an Initial Remedial Measure,
Commencement Bay/South Tacoma Channel Well
12A, Groundwater
Record of Decision, Commencement Bay/South
Tacoma Channel Well 12 A, Groundwater and Soil
Final Work Plan: Operation and Maintenance of
Groundwater Extraction and Carbon Adsorption
Treatment System (Revision 0)
Final Work Plan for Time Oil Investigation
Evaluation of GET Effectiveness, Commencement
Bay-South Tacoma Channel (Well 12-A) Site
Five Year Review
LNAPL and Soil Investigation Report Revision 1
Explanation of Significant Differences (ESD) Soil
and Groundwater 1994 ROD
Preliminary Remedial Process Option Screening and
Data Gaps Memorandum, Commencement Bay,
South Tacoma Channel/Well 12A Superfund Site,
Tacoma, Washington
Groundwater Summary Report
Quarterly Status Report
1.4
PERSONS CONTACTED
The following individuals were present for the site visit:
Kevin Rochlin, RPM, USEPA Region 10
Bernard Zavala, Hydrologist, USEPA Region 10
Neil Thompson, RPM, USEPA Region 10
1.5
1.5.1
SITE LOCATION, HISTORY, AND CHARACTERISTICS
LOCATION AND HISTORY
The Commencement Bay, South Tacoma Channel Superfund Site located in Tacoma, Washington consists
of three geographically isolated operable units (OUs): the City of Tacoma Well 12A (OU1), the Tacoma
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Landfill (OU2), and the South Tacoma Field (OU3). The remedies at the individual OUs are not expected
to affect the remedies at the other OUs. This report documents the findings and recommendations
associated with a Remediation System Evaluation (RSE) conducted at OU1 (Well 12A) and therefore does
not address the remedies at OU2 or OUS.
OU1 encompasses City of Tacoma Production Well 12A, located on Pine Street between 38th Avenue and
South Tacoma Way, and the primary source of contamination for the OU, which is the property of the
former Time Oil Company located at 3811 South Tacoma Way, 0.5 miles to the northeast of Well 12A.
The area near the Time Oil property is industrial and commercial, and the area near Well 12A is residential
and commercial. A map of the area is included in Figure 1-1. Commencement Bay is located
approximately 6 miles directly to the north or 3 miles to the northeast. Interstate 5 is adjacent to the
operable unit to the east.
Various removal and remedial actions have been conducted at the site:
In 1983 an initial remedial measure involved installing and operating air stripping towers on Well
12A. That well and the stripping towers continue to operate for public water supply during periods
of peak demand.
A groundwater extraction and treatment system (GETS) was constructed and began operation in
1988 and continues to operate. According to the 5-year review, as of March 31, 1998 more than
13,364 pounds of volatile organic compounds had been removed from groundwater.
A vapor extraction system (VES) was constructed on and adjacent to the Time Oil property
between September 1992 and August 1993, and 5,000 cubic yards of contaminated filter cake were
concurrently excavated during construction. Operation of the VES began in 1994 and ended in
February 1997 resulting in the removal of 53,545 pounds of hydrocarbons and chlorinated
solvents.
1.5.2 POTENTIAL SOURCES
Chlorinated organic solvents were first discovered in Well 12A in 1981 leading to listing of the site on the
National Priority List (NPL) on September 8, 1983. A 1982 Remedial Investigation identified the Time Oil
property, located approximately 0.5 miles to the northeast of the well, as the primary source of
contamination.
The Time Oil property had historically been used for various practices including oil recycling as well as
paint and lacquer manufacturing. Oil recycling and solvent processing began as early as 1927 and
continued to 1991 with occasional interruptions due to changes in ownership and a large fire in 1976. The
Time Oil Company vacated the premises in 1991, and the space has since been used as a warehouse for
heating, ventilation, and air conditioning equipment.
In addition to a number of possible leaks and spills over the years, some of the filter cake generated during
oil recycling was used as fill material in 1982 for constructing the Burlington North Railroad spur to the
north of the Time Oil Property. Subsequent investigations have identified this filter cake as a primary
source of dissolved phase contamination of 1,1,2,2 tetrachloroethane (PCA), tetrachloroethylene (PCE),
and other organic solvents discovered in Well 12A.
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Despite previous efforts of source removal, a number of sources of dissolved phase contamination still
remain on or near the Time Oil property. Both light and dense non-aqueous phase liquids (LNAPL and
DNAPL) have been identified beneath the property and an additional area of filter cake has been identified
to the east of the Time Oil building. Figure 1-2 outlines approximate known or suspected locations of the
filter cake, LNAPL, and DNAPL. The LNAPL exists primarily within a smear zone near the water table
where it coats soil particles and partially fills voids in the soil. The presence of DNAPL is evidenced by
high soil concentrations of chlorinated solvents (in excess of 29,500,000 ug/kg of combined PCA and PCE,
as stated in Table 3-1 of the 1999 Groundwater Summary Report) at depths exceeding the historical low
groundwater level of 40 feet below ground surface.
1.5.3 HYDROGEOLOGIC SETTING
The site is located in the Puget Lowland, which is underlain by thick accumulations of unconsolidated to
semi-consolidated late Tertiary to Holocene age deposits. These sediments partly fill the Puget Trough, a
large north-south structural basin. Within the immediate area comprising Well 12A and the Time Oil
building, the following geologic depositional sequence exists from the surface downward: Holocene
alluvium, Pleistocene till of the Vashon glaciation, Pleistocene pro-glacial and recessional outwash deposits
of the Vashon glaciation, Pleistocene Pre-Vashon unconsolidated deposits, and older semi-consolidated
sediments. The principal aquifers of interest reside in the Vashon and Pre-Vashon glacial deposits which
are primarily sand and gravel and extend 200 to 300 feet below ground surface.
The surface topography ranges between approximately 245 to 325 feet above National Geodetic Veritcal
Datum (NGVD) from the South Tacoma Channel northeast of the Time Oil property to the southwest
uplands. The Time Oil property is approximately 255 feet above NGVD, and the water table at that
location is 30 to 35 feet below ground surface. The high porosity and high permeability deposits of the
aquifer often form discontinuous lenses with occasional deposits of silts and clays. As a result, the quantity
of water available at different locations varies greatly.
According to the December 1999 Groundwater Summary Report, groundwater beneath the site primarily
flows through a 50-foot thick sand and gravel layer that extends from the water table at 225 feet above
NGVD to 175 feet NGVD. Reportedly, in the area of the Time Oil property and beneath this layer there is
a fine-grained till aquitard with an approximate thickness of 40 feet, but this aquitard does not appear to
exist near Well 12A. In fact, Well 12A is screened between 155 and 180 feet above NGVD and had a
sustained pumping rate during the period of high demand in 1998 of approximately 670 gpm.
The regional groundwater flow is from west to east with a relatively flat gradient of 0.0006 feet/foot.
Previous calculations of groundwater velocity indicated flow to the northeast at 120 feet per year between
Well 12A and the Time Oil property and 690 feet per year to the northeast of the Time Oil Property. The
operation of Well 12A, however, depresses the potentiometric surface and reverses the normal groundwater
direction up to and including the Time Oil building and surrounding properties. Operation of the well only
occurs around August of each year during the periods of high demand for water.
1.5.4 DESCRIPTION OF GROUND WATER PLUME
Chlorinated solvents including PCA and PCE were originally discovered in Well 12A suggesting migration
of the contaminants nearly 2,000 feet to the southwest of the Time Oil property. Aquifer monitoring from
1993 confirms this southwesterly extent of contamination with concentrations of PCA as high as 100 ug/L
(CBW-9) over 500 feet to the southwest of Well 12A. Sampling records in the 1999 Groundwater
Summary Report indicate that no samples have been collected in monitoring wells in the vicinity of Well
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12A since 1993. The City of Tacoma has sampled Well 12A for volatile organic compounds, however,
and, according to Figure 5-1 in the 1999 Groundwater Summary Report, has found a decreasing trend from
approximately 550 ppb in May 1988 to less than 10 ppb in October 1997.
The 1998 aquifer monitoring event indicates trichloroethylene (TCE) contamination in monitoring wells
500 to 1000 feet downgradient (to the northeast) of the Time Oil property (5.2 ppb in CH2M-4 and 20.3
ppb in CH2M-3); however, the other site-related contaminants including PCA, PCE, and DCE were
undetectable in these wells during that monitoring event.
Concentrations in the immediate vicinity of the Time Oil property in 1998 were as high as 17,100 ug/L
PCA and 3,400 ug/L TCE. Thus, while concentrations near Well 12A have decreased significantly since
discovery in 1982 and concentrations to the northeast of the Time Oil property remain relatively low or
even undetectable, the concentrations in the source area remain high enough to suggest that LNAPL,
DNAPL, and remaining filter cake are likely providing a continuing source of contamination.
Figure 1-2 highlights wells sampled during the 1993 and 1998 aquifer monitoring events that had
contaminant concentrations exceeding the maximum contaminant levels (MCLs).
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2.0 SYSTEM DESCRIPTION
2.1 SYSTEM OVERVIEW
The ground-water extraction and treatment system (GETS) was installed and began operation in 1988. The
system, which uses granular activated carbon (GAC) to remove the contaminants from the extracted
groundwater, has a design capacity of 500 gpm but operates at approximately 50 gpm due to unexpectedly
low yielding extraction wells.
2.2 EXTRACTION SYSTEM
The extraction system originally consisted of a single extraction well (EW-1) designed to extract water at
500 gpm. While a maximum sustained pumping rate of approximately 300 gpm was achieved in this well
during 1988, the maximum sustained pumping rate decreased to approximately 150 gpm by November
1988. By January 1991 the pumping rate had decreased to below 100 gpm, and it continued to decrease to
approximately 50 gpm in 1999. Evidence of iron fouling was found in the treatment system and wells;
however, despite treatment in 1996 with hydroacetic acid, redevelopment, and downhole camera work that
confirmed the well screen was free from fouling, the well continues to operate at approximately 50 gpm.
To augment EW-1, four additional extraction wells were installed in 1995. While the design yield of each
of these wells is 50 gpm, each well is only capable of operating at approximately 10 gpm. In June 2000 the
extraction system (excluding EW-5, which was not operational due to thermal overloading) collectively
pumped approximately 74 gpm.
The locations of all extraction wells are indicated on Figure 1-2.
2.3 TREATMENT SYSTEM
The treatment system is located outside on a concrete pad surrounded by a chain-link fence. The system
consists of two bag filters arranged in parallel that precede two 20,000-pound GAC units arranged in
series. Effluent from the second carbon unit is discharged to the Thea Foss Waterway via storm drains.
During carbon replacement, extracted water is stored in a 7,050-gallon effluent tank that is filtered to
capture GAC fines after carbon replacement.
2.4 MONITORING SYSTEM
Approximately 8 aquifer monitoring events have occurred at the site since operation of the GETS began in
1988. Samples have been collected from over 60 sampling locations, but a maximum of 20 wells has been
sampled during any one event. Approximately 30 active monitoring wells in addition to the 5 extraction
wells remain. Although samples have been analyzed for semi-volatile organic compounds and pesticides,
samples are generally analyzed only for VOCs and total petroleum hydrocarbons (TPH).
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Process monitoring includes sampling from three locations in the treatment plant on a monthly basis. The
samples are collected from the influent, intermediate, and effluent water and are analyzed for VOCs.
Intermediate samples represent process water after passing through the first carbon vessel but before
passing through the second vessel.
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3.1
3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE
CRITERIA
CURRENT SYSTEM OBJECTIVES AND CLOSURE CRITERIA
The GETS is operating based on the 1985 ROD. This ROD does not establish cleanup goals for soils or
groundwater; rather, it proposes to establish cleanup goals at some later date. These goals have not been
established for the site. The default limits are the MCLs:
Contaminant
tetrachloroethylene (PCE)
trichloroethylene (TCE)
trans 1,2 dichloroethylene (trans 1,2 DCE)
cis 1,2 dichloroethylene (trans 1,2 DCE)
vinyl chloride
Concentration (ug/1)
5
5
100
70
2
An MCL has not been set for 1,1,2,2 tetrachlorethane (PCA). The Washington Sate Model Toxics Control
Act specifies 0.219 ug/L; however, this concentration limit does not apply as a cleanup level for the site.
3.2
TREATMENT PLANT OPERATION GOALS
The GETS effluent is discharged via storm sewer to the Thea Foss Waterway. The discharge requirements
differ in the 5-year review (based on surface water discharge to the Thea Foss Waterway) and the April-
June 2000 Quarterly Status Report (based on 1988 water quality criteria for organisms). The limits as
stated in both documents are provided in the following table.
Contaminant
1,1,2,2 PCA
PCE
trans 1,2 DCE
TCE
vinyl chloride
pH
Concentration (ug/1)
5-year review
6.48
4.15
32,800
55.6
2.92
6-9
Quarterly report
10.7*
10.7*
1.85
80.7
100
6-9
* Effluent discharge for for PCA and PCE combined is 10.7 ug/L.
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3.3 ACTION LEVELS
The action levels for the removal of the air stripping towers for wellhead treatment at Well 12A have not
been established, nor have the action levels for soils and groundwater been established. The influent VOC
concentrations to Well 12A have remained significantly below the design criteria for the air stripper. The
decision to discontinue the vapor extraction system at the source area was made based on a substantial
decrease in the amount of contamination recovered and by the correspondingly reduced concentrations in
extracted vapor concentrations. It was not based on predetermined levels.
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4.0 FINDINGS AND OBSERVATIONS FROM THE RSE SITE VISIT
4.1 FINDINGS
The RSE team found a maintained and functional facility. The GETS is now 13 years old and is reaching
the end of its designed life. The observations and recommendations given below are not intended to imply a
deficiency in the work of the designers, operators or site managers but are offered as constructive
suggestions in the best interest of the EPA and the public. These recommendations have the benefit of
several years of operating data unavailable to designers or site managers.
Acknowledgment of LNAPL and DNAPL as continuing sources of dissolved phase contamination has
caused site managers to reconsider the approach to addressing contamination associated with the Well 12A
operable unit. Recent efforts have focused on screening remedial options and identifying data gaps
necessary for evaluating these options. A Preliminary Remedial Process Options Screening and Data Gaps
Memorandum dated October 1999 identifies a number of remedial options and suggests the compilation of
a remedy evaluation and optimization (REO) report to further evaluate these options. In addition, this
memorandum identifies data gaps such as the extent of DNAPL. The Groundwater Summary Report
dated December 1999 also provides a site conceptual model, outlines data deficiencies, and discusses
various remedial options.
4.2 SUBSURFACE PERFORMANCE AND RESPONSE
With respect to groundwater extraction, the GETS has underperformed the design criteria for the extraction
rate by half an order of magnitude (i.e., a factor of 5), possibly resulting in lower than expected
contaminant recovery and capture.
4.2.1 WATER LEVELS
Although water levels have historically been measured in monitoring wells within the operable unit, the
1999 Groundwater Summary Report suggests that water levels measured prior to October 1999 may have
been biased due to improperly surveyed wells. Thus, water level measurements made on October 21, 1999
and October 27, 1999 (after the wells were re-surveyed) may provide the most reliable information
pertaining to water levels. However, the potentiometric surface maps that have been generated from the
October 1999 measurements contain questionable interpretations. For both October 1999 data sets, water
level contours are found intersecting each other, suggesting that at a given point and time the water table is
at two elevations. In addition, it appears that these potentiometric surfaces incorporate water levels
measured in the extraction wells during pumping, thereby biasing the drawdown in favor of contaminant
capture.
4.2.2 CAPTURE ZONES
The GETS was originally designed to pump 500 gpm and to prevent contaminant migration toward Well
12A. However, the system operates at less than 100 gpm and in the absence of pumping from Well 12A
(which does not pump a majority of the time), contamination is more likely to migrate to the northeast,
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which is away from Well 12A and toward Commencement Bay. With this discrepancy between the
original design parameters and the current operating conditions, it is possible the system is not adequately
capturing targeted contamination.
While a capture zone analysis was attempted in the 1999 Groundwater Summary Report, it is based on
potentiometric surfaces that are unreliable due to intersecting water level contours and the incorporation of
water levels measured from extraction wells.
4.2.3 CONTAMINANT LEVELS
Contaminant levels in source area wells have fluctuated, but EW-1, EW-2, and EW-3 show significant
decreases in VOC concentrations since 1995. EW-4 and EW-5, however, have not shown such decreases.
In spite of the progress made in EW-1, EW-2, and EW-3, however, concentrations are still well above
cleanup levels and the presence of LNAPL and DNAPL provides continuing sources of contamination.
As for the extended portions of the plume, data have not been consistently collected in monitoring wells
near Well 12A. Yearly samples from Well 12A taken and analyzed by the City of Tacoma indicate that
VOC concentrations in the public well have declined. Despite this sampling effort it is difficult to determine
progress made in reducing plume extent to the southwest (toward Well 12A). Wells over 100 feet to the
east and northeast of the Time Oil property that were sampled in April 1998 have undetectable
concentrations of VOCs with the exception of TCE, which was detected at concentrations above MCLs at
locations over 1,000 feet to the east and northeast of the property. The greatest extent of PCA, TCE, DCE,
and PCE contamination, as determined by the same sampling event, is to the south and southeast of the
Time Oil property.
4.3 COMPONENT PERFORMANCE
The system was operational approximately 90% of the time in 2000 and was operational 95% of the time in
November 2001.
4.3.1 EXTRACTION WELLS AND PUMPS
All five extraction wells have failed to meet design criteria since installation. EW-1 was designed to extract
500 gpm but extracted a maximum of 300 gpm and now only extracts 50 gpm. EW-2 through EW-5 were
designed to each extract 50 gpm, but collectively, they extract less than 50 gpm. Iron fouling is suspected as
the primary reason for the consistent decrease in performance of EW-1; however, previous rehabilitation
attempts of that well have not increased performance. The reduced capacity of EW-2 through EW-5 compared
to EW-1 is likely due to the smaller well diameters and because they reach less permeable glacial till at
shallower depths. Thus, EW-1 may screen a larger interval of sand and gravel and is also deeper allowing for
more drawdown within the well before the pump is shut off by level controls.
4.3.2 BAG FILTERS
Two bag filters are arranged in parallel to filter the influent to the treatment system and reduce fouling of the
carbon units due to suspended solids.
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4.3.3 GAC UNITS
Two GAC units are arranged in series and each contain 20,000 pounds of GAC. Pressure gauges are present
before and after each vessel to indicate the pressure drop across each vessel and the potential need for
replacement. Between November 1991 and December 1998 ten replacements of the lead vessel occurred, with
an average of 293 days between each one. As few as 181 days and as many as 710 days have passed between
a carbon replacement. Based on carbon usage statistics provided in the 1999 Groundwater Summary Report,
on average 640 pounds of contaminants are removed with 20,000 pounds of GAC suggesting a ratio of
approximately 30 pounds of carbon to one pound of contaminants.
In 2000 and the first half of 2001 replacement of carbon occurred approximately every four months. At an
influent concentration of approximately 1 mg/L and a total extraction rate of 75 gpm, chemical loading is
approximately 0.9 pounds per day of VOCs, which translates to approximately 185 pounds of carbon to 1
pound of contaminant.
20,000 Ibs of carbon month day 185 Ibs of carbon
x x =
4 months 30 days 0.9 Ibs of contam. llbofcontam.
Thus, the recent use of carbon per pound of contaminant is higher than has previously been achieved.
4.3.4 CONTROLS
The system has an autodialer and emergency stop switches for plant safety.
4.4 COMPONENTS OR PROCESSES THAT ACCOUNT FOR MAJORITY OF
MONTHLY COSTS
The following monthly costs were approximated by the RSE team based on information provided by the
RPM.
labor: plant operation (3 man days per month) $2,500
labor: project management $2,500
labor: sampling events $2,500
GAC (replacement and disposal) $5,000
Stormwater discharge $5,000
Electricity $1,200
$18,700 per month
This monthly cost of $18,700 translates to an approximate annual cost of $225,000 per year.
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4.4.1 UTILITIES
Natural gas is not used at the site, but electric motors with a combined rating of over 35 horsepower are
used to power the 5 extraction well pumps. The costs for discharge to the storm sewer were obtained from
the site manager and suggest an average monthly cost of approximately $5,000.
4.4.2 NON-UTILITY CONSUMABLES AND DISPOSAL COSTS
Carbon replacement costs required approximately $1.50 per pound and equaled approximately $60,000 in
2000.
4.4.3 LABOR
Approximately three man days per month are used to operate and maintain the system. This includes any
oversight for carbon replacement, cleaning the paddle wheels on flow sensors, inspecting the pump and
looking for leaks, and general cleanup.
4.4.4 CHEMICAL ANALYSIS
Costs for chemical analysis are not billed to the site as chemical analysis is accomplished in the EPA
Regional laboratory through the Contract Laboratory Program (CLP).
4.5 RECURRING PROBLEMS OR ISSUES
The most significant problem affecting the site is the reduced yield from all of the extraction wells.
4.6 REGULATORY COMPLIANCE
The plant regularly meets all discharge requirements.
4.7 TREATMENT PROCESS EXCURSIONS AND UPSETS, ACCIDENTAL
CONTAMINANT/REAGENT RELEASES
In one documented instance, the flow meter for an extraction well ruptured allowing extracted water to fill
the extraction well vault and discharge onto the street and into the storm sewer.
4.8 SAFETY RECORD
The GETS has an excellent safety record with no documented injuries.
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5.0 EFFECTIVENESS OF THE SYSTEM TO PROTECT HUMAN
HEALTH AND THE ENVIRONMENT
5.1 GROUND WATER
Well 12A and the rest of the public wells in that well field, including Well 9 (located 1,000 feet to the west
of Well 12A), represent the most significant known receptors of groundwater contamination. However,
Well 12A is protected by an air stripping system that has regularly met its design criteria and influent
concentrations to Well 12A are consistently far below the designed influent concentration. Thus, water
provided by Well 12A is not threatened by VOC contamination from the Time Oil property. It is believed
that Well 12A captures contaminants that are pulled to the southwest of the Time Oil property and therefore
provides protection to the other public wells when they operate. Institutional controls prohibit extraction
and use of water that exceeds the 10"6 hazard level.
5.2 SURFACE WATER
Commencement Bay is the closest surface water body to the site. It is located approximately 3 miles
downgradient of the site. The April 1998 aquifer sampling event suggests that site related contamination
has not extended more than 1,000 feet from the Time Oil property. Given the relatively flat hydraulic
gradients and previous estimates of groundwater velocity to the northeast of the source provided in the 1999
Groundwater Summary Report, the travel time for contamination to reach the bay (approximately 3 miles
away) in the absence of adequate capture may be approximately 20 years. With adequate capture, surface
water is not and will not be impacted by site-related contamination.
5.3 AIR
Asphalt and concrete around the site limit passage of any vapor contamination from the subsurface to the
ambient air. Air from the stripping towers on Well 12A is not treated with vapor phase carbon and is
discharged to the atmosphere. However, at influent concentrations less than 100 ug/L and a pumping rate of
670 gpm (which was sustained during the high-demand period for water in 1998) the discharge to air is less
than 1 pound per day during periods of operation.
5.4 SOILS
Contaminated soils including the filter cake remaining to the east of the Time Oil building are covered with
asphalt or concrete and therefore do not represent exposure pathways to the public.
5.5 WETLANDS AND SEDIMENTS
Wetlands and sediments are not impacted by site-related contamination.
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6.0 RECOMMENDATIONS
6.1 RECOMMENDED STUDIES TO ENSURE EFFECTIVENESS
6.1.1 OBTAIN ACCURATE AND RELIABLE WATER LEVEL MEASUREMENTS AND DEVELOP
ASSOCIATED POTENTIOMETRIC SURFACE MAPS
The 1999 Groundwater Summary Report states, "The capture zone analysis, completed in October 1999,
consisted of a survey of wells (northings, eastings, and elevations) because existing survey information was
questionable and some wells had no survey data." This statement puts into question all water level
measurements made prior to October 1999. The RSE team recommends that the site managers review the
site survey information, including the 1999 surveying data, and use previous depth-to-water measurements
to "correct" historical water level measurements at the site. Accurate water level measurements at different
points in the Site's history are important for calibration of the recommended groundwater flow model as
well as providing insight into capture provided by the GETS during different pumping and hydrologic
conditions.
Site records indicate the following survey events at the site:
In 1989 Woodward and Clyde Consultants surveyed a number of wells labeled WCC.
In 1989 HCE, Inc. resurveyed all existing wells near the Time Oil property.
In 1995 White Shield, Inc. surveyed mostly extraction wells and some monitoring wells.
In 1999 White Shield, Inc. resurveyed the monitoring wells.
Once accurate and reliable water level measurements have been obtained, potentiometic surface maps should
be generated. Development of these maps should not include the water levels from operating extraction
wells because water levels from these operating wells may be substantially lower than in the surrounding
aquifer. Use of water levels from extraction wells could therefore potentially bias the potentiometric surface
maps in favor of capture.
Assuming reliable and complete survey information is available, approximately $5,000 may be required to
convert the historical depth-to-water measurements to water level measurements and to develop the
associated potentiometric surfaces.
6.1.2 DEVELOP GROUNDWATER FLOW MODEL OF THE WELL 12A OPERABLE UNIT
A reliable groundwater flow model of the Well 12A operable unit would provide two significant benefits to
site management:
It would allow a more accurate analysis of the capture zone of the current GETS and optimization of
well locations and pumping rates for a modified GETS.
It would provide site managers with a tool to better evaluate remedial process options and choose among
passive, moderate, and aggressive remedial strategies.
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The history of groundwater extraction in the Well 12A operable unit provides an abundance of hydraulic
data to develop a well-calibrated model. The complexity of the site and the associated model would likely
require a moderate to high level of expertise with groundwater modeling.
The model should be developed with a sufficiently large three-dimensional domain to adequately address
future site management decisions. Such a domain would include Well 12A, Well 9, and possibly other
supply wells in the southwest portion of the operable unit and possibly Commencement Bay to the north and
northeast. In the vertical extent, the model should include the conductive aquifer and aquitard beneath the
Time Oil property but should also extend to a depth beyond the bottom of Well 12A.
Once the domain and proper boundary conditions are established, the model should be calibrated using the
abundance of pumping and water level data. The calibrated model should be able to reproduce with
reasonable accuracy the measured water levels resulting from three pumping scenarios: 1) Well 12A
pumping with the GETS shutdown, 2) both Well 12A and the GETS pumping, and 3) the GETS pumping
with Well 12A shutdown. Such a model will require specifying heterogeneity of aquifer recharge and
hydraulic conductivity (i.e., those parameters varying with location) and therefore must be numerical rather
than analytical.
Once these steps have been achieved, the model can be used for capture zone analysis and as a tool in the
decision-making process. A contaminant transport model (that uses either particle tracking or finite-
difference approximations) may also help in the decision-making process as it would help estimate time
frames for contaminant transport and degradation as well as the potential benefit of aggressive source
removal. Such a transport model would incorporate both advection and dispersion and would require
contaminant sources to be specified, including the remaining filter cake as well as LNAPL and DNAPL. A
well-delineated contaminant plume would be required for calibration, and estimated parameters for
contaminant sorption and degradation would also have to be specified. In the opinion of the RSE team,
incorporation of multiphase transport into the transport model would not be cost or time effective.
Development and initialization of the groundwater flow model, however, may require additional field efforts
to characterize the extent of the DNAPL.
A well-calibrated groundwater flow model (as briefly described in this report) could be developed by
modeling experts for approximately $50,000. An accompanying transport model, if constructed, would cost
another $50,000. In addition, between $12,000 and $24,000 per year would be required for updating the
model calibrations based on new data. The RSE team would defer development of the proposed transport
model until the groundwater flow model is developed, calibrated, and proven reliable as a site management
tool.
By comparison, modeling efforts proposed by the current contractors for "reverse modeling" (memorandum
dated August 13, 2001) to estimate distances of contaminants from various receptors would require
significantly less effort than the modeling efforts recommended in this RSE report and could not be used in
analyzing the capture zone. Two potential shortcomings of the proposed reverse modeling effort should be
noted.
First, the reverse modeling effort will utilize a quasi three-dimensional analytical model. While
relatively easy to implement, such models are incapable of incorporating heterogeneity in recharge
and hydraulic conductivity and therefore could not be adequately calibrated using site pumping and
water level data. Without adequate calibration, the model cannot reliably represent the subsurface
conditions around Well 12A and beneath the Time Oil property.
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Second, the list of principal assumptions in the "reverse modeling" memorandum will assume
groundwater flow in the direction of Well 12A and no pumping from the GETS. However, previous
hydrogeologic data suggest, in the absence of pumping from the GETS, that groundwater near the
source flows away from Well 12A and groundwater flow directions vary depending on the extent of
pumping from Well 12A.
In the opinion of the RSE team, the above shortcomings of the proposed reverse modeling effort could
render the results unreliable and therefore adversely impact site management decisions.
6.1.3 ANALYZE CAPTURE ZONE OF EXTRACTION WELLS
To date, capture zone analyses at the Well 12A operable unit have included questionable interpretations
(intersecting groundwater contours on the interpreted potentiometric surfaces and the use of water level data
from operating extraction wells). These previous capture zone analyses also do not include a clear
presentation of the capture zone superimposed on the extent of the contaminant plume targeted for capture.
Thus, analysis of the capture zone for the site should be revisited and updated regularly given newly
obtained data.
Due to the complexity of subsurface environments, adequate capture is difficult to determine with any one
process; rather, converging lines of evidence are often needed to demonstrate capture.
Preliminary analysis using measured water levels:
For this preliminary analysis, the first step is to accurately delineate the contaminant plume through aquifer
monitoring events and construct a plume map. Once this map is complete, the target capture zone should be
determined based on the remedial objectives. This target zone may encompass the entire plume, or it may
only encompass the source areas and/or highly contaminated areas of the plume.
The second step is to develop a reliable potentiometric surface map using water level data collected from
piezometers and monitoring wells. This map should not include water levels taken from operating extraction
wells because the reduced water levels in these wells inaccurately represent the water levels in the
surrounding aquifer thereby biasing the analysis in favor of capture. Arrows indicating groundwater flow
directions and the associated capture zone should be provided on this map. It should be noted that capture is
indicated by groundwater flow directions toward the extraction wells and not simply by evidence of
drawdown.
The third step is to overlay the plume map (including the target capture zone) with the potentiometric
surface map including the interpreted capture zone. If the actual capture zone encompasses the target
capture zone, then this preliminary analysis suggests capture.
It should be noted that while this approach provides the best preliminary analysis for capture, an insufficient
number of monitoring wells and piezometers may be available for clearly resolving the potentiometric
surface in heterogeneous formations.
Secondary analysis using sentinel monitoring wells:
Monitoring wells downgradient of the contaminant plume can be regularly sampled and analyzed for the
contaminants of concern. If the concentrations in these monitoring wells remain undetectable then this adds
evidence supporting capture at least between the source and the monitored well. However, because
groundwater flow and contaminant transport is relatively slow, a long period of time, perhaps years, may be
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required before sentinel monitoring wells would show a potential increase in concentration. Thus, the use of
sentinel monitoring wells may require years of sampling and analysis to confirm capture.
Similarly wells within the extended portions of a plume can be monitored to determine if contaminant
concentrations are decreasing, remaining the same, or increasing. If concentrations are decreasing this may
(but does not necessarily) suggest capture of the source or upgradient portions of the plume. If
concentrations remain the same or increase, however, capture is not adequate. Once again, a substantial
amount of time, perhaps years, may be required before a definitive conclusion about capture can be drawn
from concentration trends in such wells.
Secondary analysis using gradient pairs or triplets:
The hydraulic gradient indicating the direction of groundwater flow can be measured by placing two or three
piezometers in a cluster and measuring water levels from each of the piezometers. By comparing the
measured water levels in each of the piezometers, the groundwater flow direction can be determined in the
proximity of the cluster. A flow direction in the vicinity of a cluster directed toward an extraction well
provides additional evidence for capture, at least at the location of the cluster.
It should be noted that this approach only indicates flow directions in specific areas where clusters are
located, and placing a sufficient number of clusters to adequately evaluate capture can be costly.
Secondary analysis using a groundwater flow model:
By constructing a well-calibrated groundwater flow model, site managers can compare measured water
levels with modeled water levels. If the two sets compare and the model indicates capture, then actual
capture in the aquifer is likely occurring. This often provides the most thorough analysis of capture as the
model has the capability of incorporating site-specific recharge, hydraulic conductivity zones, and pumping
configurations. In instances where a three-dimensional model is available, this approach also allows for
evaluation of capture in both the vertical and horizontal directions, an evaluation that is extremely difficult
with the aforementioned preliminary and secondary analyses. The complexity of the model would depend on
the complexity of the site. In the case of the Well 12A operable unit the complexity of the subsurface and
the various pumping configurations that occur (including Well 12A and the other supply wells), a numerical
model with at least moderate complexity is recommended.
The RSE team recommends that converging lines of evidence be drawn from a number of these types of
analyses. A preliminary analysis should be accomplished with plume maps and potentiometric surfaces, and
the results from this preliminary analysis should be augmented with those from monitoring already installed
sentinel wells and groundwater flow modeling. This comprehensive approach should be conducted on a
regular basis, perhaps semi-annually or annually. The preliminary analysis will likely require
approximately $15,000 upfront to collect and organize previously obtained data and to develop appropriate
CADD drawings for the site. Compilation of previous plume and potentiometric surface maps and
comparison of the associated target and measured capture zones would likely cost an additional $5,000.
Regular analysis incorporating new data on a annual or semi-annual basis would likely cost an additional
$4,000 per year. Augmenting this analysis by viewing trends in monitoring wells should result in a
negligible cost increase, and augmenting it with modeling simulations as described in Section 6.1.1 are
included in the $12,000 to $24,000 estimate provided in that section.
6.1.4 MAKE AQUIFER MONITORING PROGRAM CONSISTENT
The aquifer monitoring program has not resulted in regularly scheduled monitoring events since 1993.
Between 1989 and 1993 one event was conducted per year. Two events were conducted in 1995 and one in
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1998. In addition, each monitoring event involves sampling different wells, making it difficult to analyze
remediation progress or to validate plume capture. For example, monitoring in 1993 involved sampling of
wells to the southwest of the Time Oil property near Well 12A; however monitoring in 1998 did not involve
sampling of these wells. Thus, it is difficult to evaluate the progress toward remediation in that portion of
the aquifer.
Up to 20 monitoring wells (the same number sampled in 1998) should be sampled on a semi annual basis
with the purpose of delineating the plume. The results will be helpful in constructing plume maps for
capture zone analyses and for initializing a transport model if one is developed. If plume containment is
chosen as the final remedy for the site, the sampling of wells in the source area will not be as significant as
sampling near the border of the target capture zone and the extended plume. Thus, in the case of a
containment strategy, only a few of the selected 20 monitoring wells should be located in the extraction area.
In addition, sampling the concentrations from the individual extraction wells could be eliminated, especially
given that the treatment plant influent is sampled monthly.
Sampling up to 20 wells twice per year would cost approximately $30,000 for labor such that no increase in
costs is expected. As analytical costs are not billed to the site, they are not included in the cost estimates.
However, as a note, approximately 25 samples (including field and trip blanks) would need analysis for
VOCs per event, at a cost of approximately $125 per sample (approximately $6,500 per year).
6.1.5 ENSURE ANNUAL SAMPLING AND ANALYSIS OF VOCs IN WATER FROM WELL 9
Water from Well 12A is sampled and analyzed annually for VOCs, and these samples have indicated a
reduction in VOC contamination in the influent to that well. It is unclear if the other supply wells in the
same well field, including Well 9, are sampled for VOCs. Given that Well 9 is the closest supply well to
Well 12A, it would be prudent to sample and analyze for VOCs the influent to it. If contamination is
present beyond suitable risks, consideration should be given to treating the extracted water from the well or
shutting down the well.
6.2 RECOMMENDED CHANGES TO REDUCE COSTS
6.2.1 REPLACE EXTRACTION WELL PUMPS
The pumps in EW-2, EW-3, and EW-4 are oversized for the yields of these wells. EW-2 and EW-4 have
7.5 horsepower pumps and EW-3 has a 10 horsepower pump. These pumps each push approximately 10
gpm of water against approximately 115 feet of head 35 feet from the water table to the ground surface,
approximately 20 feet to the top of the GETS, and across 60 feet of pressure drop (over 25 psi) through the
GETS. Movement of water with a pump efficiency of 50% would require approximately 0.6 horsepower.
Using a 1.5 horsepower pump would easily accommodate this current load and could provide additional
flow if necessary. Thus, converting from the current pumps to 1.5 horsepower pumps as currently used in
EW-5 would save over 20 horsepower. Assuming approximately $0.05 per kilowatt hour, a savings of
approximately $700 would be realized each month (approximately $8,500 per year). Installing the three
new pumps would likely cost approximately $14,000. Thus, if the current GETS is selected as the final
remedy or as an interim remedy for three or more years, it would be cost-effective to replace the pumps as
suggested.
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6.2.2 EXAMINE CITY OF TACOMA POLICIES ON STORMWATER DISCHARGE AND/OR
CONSIDER ALTERNATIVE DISCHARGE LOCATIONS
The costs associated with discharging plant effluent to the stormwater system are the highest seen by the
RSE team during a nationwide evaluation of pump and treat systems. Although the RSE team has found
equivalent costs for discharging to a sanitary sewer, in the course of evaluating 17 Fund-lead P&T systems
and other professional experience, the RSE team has only found costs associated with "hook up" to a
stormwater system and not a continuing cost for discharge. The site managers should examine the policies
of the City of Tacoma related to stormwater discharge and investigate alternative discharge locations. In
this rare case, it may actually be cost effective to discharge to a sanitary sewer instead. Also, through
negotiations, it may be possible to reduce the costs of stormwater discharge by further reducing effluent
concentrations. If this is the case, it may be cost effective to enhance the GETS.
The discharge policies should also be evaluated to estimate costs if increased pumping is required for
improved capture or more aggressive source removal through pumping. The RSE team is unable to quantify
costs associated with EPA personnel examining the City of Tacoma policies or negotiating with the City. If
a contractor is hired for this purpose, one could estimate approximately $4,000 (16 hours for examining the
policies and 24 hours for possible negotiations with a billing rate of $100 per hour). Costs of alternate
discharge locations or improvements to the GETS should be weighed against the potential savings in
eliminating or reducing the current discharge costs of $60,000 per year.
6.2.3 CONSIDER REPLACING GAC TREATMENT WITH AIR STRIPPING
Depending on the future of the remedy, consideration should be given to replacing the current GAC
treatment system with an air stripping system. Plant maintenance for an air stripper would be similar to the
current maintenance associated with the carbon system. While a cost increase of $13,000 per year would
result from operation of an air stripper with a 15 horsepower blower, the estimated cost of $63,000 per year
for carbon replacement could be eliminated. Thus, a net potential savings of $50,000 per year could result.
At current flow rates and influent concentrations chemical loading from the air stripper to the atmosphere
would be less than 1 pound per day (similar to the loading from operation of Well 12A). However, if
pumping rates were to increase due to the need for increased capture, that chemical loading could increase if
influent concentrations remain the same. If vapor phase carbon is required to polish the air stripper offgas,
additional costs would be approximately $10,000 per year (replacement of 3,000 pounds of carbon once per
year at approximately $3 per pound). In this case, approximate savings of $40,000 per year would result.
The decision to implement this change should be weighed against the capital costs for scoping the work,
contracting, design, implementation, and maintenance associated with operation start up. The expected costs
for design and construction of an air stripping system with a design flow rate of 500 gpm with offgas
treatment would likely cost $350,000 if it is installed in the current location of the GETS. Such a change
would not likely be cost effective unless the current GETS required replacement or pumping rates and
chemical loading increase by a factor of two or more resulting in a substantial increase in carbon
replacement costs.
It should be noted that an air stripping system could also be installed in the VES building and plumbed into
the already installed vapor phase carbon units with the capability of onsite steam regeneration. Installing
such a system would likely cost approximately $500,000 and would require an additional $60,000 per year
to operate due to the steam regeneration system. Thus, installation of such a system should only be
considered if chemical loading rates are expected to reach 5 to 10 pounds per day for a number of years.
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6.3 MODIFICATIONS INTENDED FOR TECHNICAL IMPROVEMENT
The RSE team did not note any recommendations for technical improvement beyond those cited as
recommendations to improve effectiveness, reduce costs, or gain site close-out. In the opinion of the RSE
team, the issue of underproducing extraction wells remains the most consistent problem meriting technical
improvement at the site. As addressing this issue depends on the remedial options considered by the site
managers, this topic of improving groundwater extraction is discussed in Section 6.4.2.2
6.4 MODIFICATIONS INTENDED TO GAIN SITE CLOSE-OUT
6.4.1 EXCAVATE REMAINING FILTER CAKE
Despite removal filter cake on the Time Oil and Burlington North Railroad properties, approximately 300 to
500 cubic yards of filter cake still remains on the east side of the Time Oil building. This filter cake
provides a continuing source for the contaminants of concern, and the RSE team agrees with the site
managers that it should be excavated. Estimates from the site managers indicate that excavation and
disposal of the filter cake will cost approximately $500,000.
6.4.2 EVALUATE REMEDIAL PROCESS OPTIONS BASED ON ANALYSIS OF GROUNDWATER
MODELING
As mentioned in Section 6.1.1, the RSE team recommends a groundwater flow model, and potentially a
contaminant transport model, to evaluate both capture of the contaminant plume and to assist in deciding on
future remedial approaches. The RSE team notes three categories of approaches to future remedial strategy
ranging from passive to aggressive depending on future monitoring and modeling results.
6.4.2.1 PASSIVE APPROACH: SWITCH TO MONITORED NATURAL ATTENUATION
This passive approach becomes valid if further monitoring and modeling efforts suggest that site-related
contamination will not adversely impact any receptors. Transport modeling, for example, would have to
demonstrate that although a continuing source remains, migration of contaminants is sufficiently slow to
allow natural degradation of the contamination before it reaches any receptors.
Such modeling efforts would require a well-calibrated transport model and reliable evidence regarding in
situ degradation of site-related contaminants. The 1999 Groundwater Summary Report suggests that
elevated chloride concentrations indicate the possibility for degradation of chlorinated solvents. Also,
hydrocarbons from waste oil exist in the subsurface and provide nutrients for reductive dechlorination
through cometabolism in anaerobic conditions. Additional data should be collected on parameters that affect
the potential for reductive dechlorination, including but not limited to oxidation-reduction potential (ORP),
dissolved oxygen, iron, nitrate, and sulfate. However, it should be noted that reductive dechlorination may
successfully transform PCE to TCE, TCE to DCE, and DCE to vinyl chloride as well as transform PCA to
trichloroethane or other daughter products. These daughter products are as significant or possibly more
significant hazards for human and environmental health and more effectively degraded in aerobic conditions.
Thus, complete degradation of chlorinated aliphatic compounds such as PCE and TCE to harmless
constituents would ideally involve anaerobic conditions to transform these compounds to vinyl chloride and
aerobic conditions to transform vinyl chloride to harmless end products.
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With two contrasting environments required for full degradation of contamination, the potential of a
successful remedy with natural attenuation is unlikely unless aquifer conditions are artificially adjusted
through nutrient and/or oxygen addition.
6.4.2.2 MODERATE APPROACH: CONTINUE PUMP AND TREAT AS A CONTAINMENT REMEDY
Given the presence of LNAPL and DNAPL as continuing sources of dissolved phase contamination, pump
and treat likely will not succeed as a restoration remedy. Pump and treat, however, can potentially succeed
as a containment remedy. The current GETS or modifications to the current GETS may provide adequate
containment of site-related contaminants. A capture zone analysis conducted as specified in
Recommendation 6.1.2 will indicate if the GETS provides adequate capture. If it does, then the current
system can be used as a containment remedy until new approaches are developed to address the source
areas.
If adequate capture is not provided by the current GETS, then increased pumping and new extraction wells
may be required. The groundwater flow model, especially in conjunction with optimization packages such
as MODMAN, could be used to determine the optimal locations and pumping rates for new wells.
If new wells are installed, steps should be taken during design and installation to ensure the maximum
amount of flow is available. EW-1 was originally capable of extracting 300 gpm compared to the
approximate extraction rates of 10 gpm for each of the other extraction wells. Thus, the design features
responsible for the relatively high initial yield of EW-1 should be emulated. These features include 1) using
a large diameter casing and 2) drilling the well deeper to allow for more drawdown within the well before the
pump is shut off by level controls.
To avoid reductions in flow over time as were apparent with EW-1, a well maintenance program should be
initiated to prevent new wells from fouling. In the case of EW-1, iron fouling likely decreased the yield of
the well. The flow rate continued to decrease from installation in 1988 to the present, but the only
documented well rehabilitation effort occurred in 1996, eight years after fouling became evident. Regular
monitoring of the specific capacity of the wells and a yearly well-maintenance program would warn of
significant fouling and address the problem before irreversible reductions in the well yields occurred. More
information about well maintenance can be found in USAGE Engineering Pamphlet EP 1110-1-27 at
6.4.2.3 AGGRESSIVE APPROACH: SOURCE REDUCTION OR REMOVAL
A number of proven and experimental technologies exist that can aid in reducing subsurface sources of
contamination. These technologies include but are not limited to excavation, in situ heating, air sparging,
and injection of chemicals for in situ oxidation or enhancement of biodegradation. Despite the abilities of
these technologies to remove mass, each of these technologies have limitations that should be considered.
One limitation common to each of these technologies (with the exception of extensive excavation) is that
inevitably some LNAPL or DNAPL will remain in pore spaces providing continuous sources of
contamination and possibly making it impracticable to return groundwater to its "beneficial use". However,
aggressive source removal may sufficiently reduce the extent of the source such that monitored natural
attenuation is subsequent a viable option.
Another limitation is the potential for short or long term impact of above-ground business operations.
Excavation would result in a long term impact and destruction of some local buildings. The other
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technologies would likely result in relatively short term impacts but also possible destruction of local
buildings. Many of these technologies generate heat and vapor that could impact business activity at the
surface. Heating the subsurface facilitates contaminant recovery by mobilizing or vaporing the
contaminants, and in situ chemical oxidation destroys contaminants producing heat and vapors as a
byproduct. If restarted, the VES could serve to help control and extract vapors generated from such
technologies.
Simulations with a groundwater flow and contaminant transport model could assist site managers in
determining the amount of source reduction necessary to proceed with monitored natural attenuation. The
RSE team recommends that site managers compile a brief description of the site and to distribute this to
vendors of various technologies to determine if site conditions merit bench and/or pilot testing of the
vendors' respective technologies. Developing and distributing the site description should require
approximately $5,000. Vendors typically provide an initial assessment of the applicability of their
technology free of charge.
6.5 UNUSED EQUIPMENT
The VES system, which includes an onsite carbon regeneration system and phase separator, has not
operated since February 1997. Elements of this system, if not used in conjunction with aggressive source
removal technologies, may be useful at other EPA sites. USAGE has a program designed to help the
transfer of unused government equipment from Fund-lead sites to other Fund-lead sites where the equipment
can be used. The contact for this program is
Lindsey K. Lien, PE
U.S. Army Corps of Engineers
12565 West Center Road
Omaha, NE 68144-3869
(402) 697-2580
Lindsey.K.Lien@nwd02.usace.army.mil
6.6 SUGGESTED APPROACH TO IMPLEMENTATION OF
RECOMMENDATIONS
As evidenced by site documents such as the Preliminary Remedial Process Options Screening and Data
Gaps Memorandum dated October 1999, the site managers for the Well 12A operable unit are considering
alternate remedial strategies for the site because site data indicate the current GETS likely will not restore
the aquifer to its "beneficial use". The RSE team applauds this proactive site management and encourages
further consideration of remedial options.
The RSE team recommends continuing to screen alternative remedial technologies and strategies, but
suggests that the current GETS or a modified version continue operation to provide capture of the
contamination until an alternate strategy is selected and implemented. As the current GETS may not offer
sufficient capture, the RSE team recommends immediate implementation of the recommendations in Section
6.1. A thorough analysis of the capture zones (6.1.2) will likely require the recommended groundwater flow
model (6.1.1) and changes in the monitoring program (6.1.3). A preliminary capture zone analysis as
suggested in 6.1.2, however, can and should be conducted based on existing water level and water quality
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data. In addition to assisting in the capture zone analysis, the recommended model can also be used for
evaluating and planning the site remedial strategy.
In terms of cost reduction, the RSE team suggests immediate examination of the City of Tacoma discharge
policies and consideration of alternate discharge locations (6.2.2). A cost savings of up to $60,000 per year
could result if discharge fees can be eliminated. Such costs savings may even be more significant if the
extraction rate of the GETS is increased. Replacement of the extraction well pumps (6.2.1) should wait
until the preliminary capture zone analysis is completed. If this preliminary analysis suggests that adequate
capture would require pumping on the order of 300 to 500 gpm or larger, new extraction wells with a larger
capacity may be required and the current pumps could be used. Otherwise, the current pumps should be
replaced as soon as possible with smaller models. Replacement of the GETS with an air stripper (6.2.3)
should only be considered if additional pumping for capture would more than double the chemical loading
rates to the GAC units or if the GETS requires replacement due to substantial maintenance.
For recommendations regarding site closeout, removal of the filter cake (6.4.1) can be conducted
immediately while evaluation of the remedial strategies should be largely based on rigorous modeling and
data analysis. The RSE team advises that pump and treat continue as an interim remedy to provide capture
of the contamination until a source removal process can be identified that will remove the LNAPL and
DNAPL or sufficiently reduce their extent such that monitored natural attenuation is viable based on
modeling efforts and risk assessments.
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7.0 SUMMARY
The observations and recommendations given below are not intended to imply a deficiency in the work of
either the designers or operators, but are offered as constructive suggestions in the best interest of the EPA
and the public. These recommendations obviously have the benefit of the operational data unavailable to the
original designers.
The RSE process is designed to help site operators and managers improve effectiveness, reduce operation
costs, improve technical operation, and gain site closeout. Recommendations to improve effectiveness
include generating a groundwater flow model (and potentially a contaminant transport model) to assist in
evaluating capture and screening remedial technologies, conducting a thorough capture zone analysis,
improving the current monitoring program, and sampling influent to a local supply well for VOCs.
Recommendations to reduce costs include examining the discharge policies of the City of Tacoma and
investigating alternative discharge locations, replacing extraction well pumps with smaller models, and
possibly replacing the carbon treatment system with an air stripper. Recommendations regarding site
closeout include excavating the remaining filter cake that provides a continuing source of contamination and
proceeding with screening of remedial strategies based on data analysis and modeling efforts. For this
report, independent recommendations for technical improvement were not made; rather, they were included
in the other recommendation categories.
Table 7-1 summarizes the costs and cost savings associated with each recommendation. Both capital and
annual costs are presented. Also presented is the expected change in life-cycle costs over a 30-year period
for each recommendation both with discounting (i.e., net present value) and without it.
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Table 7-1. Cost Summary Table
Recommendation
6. 1. 1 Obtain accurate and
reliable water level
measurements and develop
associated potentiometric
surface maps
6.1.2 Develop a groundwater
flow model
6.1.2b (optional) Develop a
contaminant transport model
6.1.3 Analyze capture zone
6.1.4 Improve well-sampling
program
6.1.5 Monitor Well 9 for VOCs
(costs incurred by city)
6.2.1 Replace pumps in
extraction wells
6.2.2 Examine city stormwater
discharge policies and
investigate alternative discharge
locations
6.2.3 Consider replacing carbon
treatment system with an air
stripper
6.4.1 Excavate remaining filter
cake
6.4.2 Maintain contaminant
capture while continuing to
screen alternative remedial
technologies and strategies
6.4.2.3 Develop a site
description for distribution to
vendors of source removal
technologies
Reason
Effectivness
Effectiveness
Effectiveness
Effectiveness
Effectiveness
Effectiveness
Cost
reduction
Cost
reduction
Cost
reduction
Gain site
closeout
Gain site
closeout
Gain site
closeout
Estimated Change in
Capital
Costs
$5,000
$50,000
$50,000
$20,000
$0
$0
$14,000
$4,000
$350,000
$500,000
not
quantified
$5,000
Annual
Costs
$0
$12,000
$12,000
$4,000
$0
$0
($8,500)
($60,000)
($50,000)
$0
not
quantified
$0
Life-cycle
Costs*
$5,000
$410,000
$410,000
$140,000
$0
$0
($241,000)
($1,796,000)
($1,150,000)
$500,000
not
quantified
$5,000
Life-cycle
Costs **
$5,000
$243,000
$243,000
$84,000
$0
$0
($123,000)
($963,000)
($456,000)
$500,000
not
quantified
$5,000
Costs in parentheses imply cost reductions.
* assumes 30 years of operation with a discount rate of 0% (i.e., no discounting)
** assumes 30 years of operation with a discount rate of 5% and no discounting in the first year
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FIGURES
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FIGURE 1-1. SITE LAYOUT OF THE WELL 12A OPERABLE UNIT INDICATING MONITORING WELLS SAMPLED DURING
THE MARCH 1993 AND/OR APRIL 1998 MONITORING EVENTS THAT HAD CONCENTRATIONS ABOVE MCLs
SOUTH 38TH STREET
600
SCALE IN FEET
1200
LEGEND
PUBLIC SUPPLY WELL
MONITORING WELLS SAMPLED IN MARCH 1993 AND/OR
APRIL 1998 WITH CONCENTRATIONS EXCEEDING MCLs
(Figure compiled from Figures 1-1 and 4-7 of the Groundwater Summary Report, South Tacoma Channel/Well 12A Site,
Tacoma, Washington, ICF Kaiser, December 1999).
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FIGURE 1-2. LAYOUT OF THE TIME OIL PROPERTY INDICATING THE LOCATIONS OF THE GROUNDWATER EXTRACTION WELLS AS WELL
AS AREAS OF CONTAMINATED SOIL, DNAPL, AND FILTER CAKE
APPROXIMATE AREA
OF FILTER CAKE/SOIL
EXCAVATION 1991-1992
APPROXIMATE
LOCATION OF
UST
EXTRACTION
SYSTEM (VES)
TREATMENT
BUILDING
EXCAVATION AND BACKFILL BURLINGTON
NORTHERN RAILROAD SPUR, 1986
-N-
FORMER EAST TANK FARM
FILTER CAKE CURRENTLY
LOCATED BENEATH
CONCRETE PAD
LEGEND
PUBLIC SUPPLY WELL
MONITORING WELLS SAMPLED IN
MARCH AND/OR APRIL 1998 WITH
CONCENTRATIONS EXCEEDING MCLs
EXTRACTION WELL
ESTIMATED AREA OF SOIL CONTAMINATION
THAT MAY OCCUR ABOVE OR BELOW THE
WATER TABLE
PREVIOUS DNAPL DETECTION
CH2M-1
SCALE IN FEET
(Note: Figure compiled from Figure 1-2 of the Preliminary Remedial Process Options Screening and Data Gaps Memorandum, Commencement Bay, South Tacoma
Channel/Well 12A Superfund Site, Tacoma Washington, October 1999 and Figure 3-1 of the Groundwater Summary Report, South Tacoma Channel/Well 12A Site,
Tacoma, Washington, ICF Kaiser, December 1999).
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Solid Waste and
Emergency Response
(5102G)
542-R-02-008q
October 2002
vwwv.clu-in.org/rse
www.epa.gov/tio
U.S. EPA National Service Center
for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242-2419
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