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

 
NOTICE

Work described herein was performed by GeoTrans, Inc. (GeoTrans) and the United States Army Corps

of Engineers (USACE) 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. 
i

EXECUTIVE SUMMARY

The first operable unit (OU1) of the Commencement Bay/South Tacoma Channel Superfund Site addresses

soil and groundwater 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 12A, 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
ii

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 pumpand-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

(USACE 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
iv

The project team is grateful for the help provided by the following EPA Project Liaisons.

Region1 

Region 2

Region 3

Region 4

Region 5

Darryl Luce and Larry Brill

Diana Cutt

Kathy Davies

Kay Wischkaemper

Dion Novak

Region 6

Region 7

Region 8

Region 9

Region 10

Vincent Malott

Mary Peterson 

Armando Saenz and Richard Muza

Herb Levine

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).
v

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 BAG FILTERS ...................................................... 11

4.3.3 GAC UNITS ....................................................... 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
vi

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 SURFACE 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
1

1.0 INTRODUCTION

1.1 PURPOSE

In the OSWER Directive No. 9200.0-33, Transmittal of Final FY00 - 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 (USACE), using a process called a Remediation System Evaluation (RSE),

which was developed by USACE. 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, USACE, Kansas City District

Rob Greenwald, Hydrogeologist, GeoTrans, Inc.

Peter Rich, Civil and Environmental Engineer, GeoTrans, Inc.

Doug Sutton, Water Resources Engineer, GeoTrans, Inc.
2

1.3 DOCUMENTS REVIEWED

Author Date Title

US EPA 3/18/1983 Record of Decision for an Initial Remedial Measure,

Commencement Bay/South Tacoma Channel Well

12A, Groundwater

US EPA 5/3/1985 Record of Decision, Commencement Bay/South

Tacoma Channel Well 12A, Groundwater and Soil

ICF Technology, Inc. 5/1990 Final Work Plan: Operation and Maintenance of

Groundwater Extraction and Carbon Adsorption

Treatment System (Revision 0)

ICF Technology, Inc. 1/1991 Final Work Plan for Time Oil Investigation

ICF Technology, Inc. 11/1991 Evaluation of GET Effectiveness, Commencement

Bay-South Tacoma Channel (Well 12-A) Site

EPA 7/1998 Five Year Review

ICF Kaiser/ URS Greiner 9/1999 LNAPL and Soil Investigation Report Revision 1

EPA 9/1999 Explanation of Significant Differences (ESD) Soil

and Groundwater 1994 ROD

URS Greiner 10/1999 Preliminary Remedial Process Option Screening and

Data Gaps Memorandum, Commencement Bay,

South Tacoma Channel/Well 12A Superfund Site,

Tacoma, Washington

URS Greiner 12/1999 Groundwater Summary Report

URS Greiner 9/2000 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 SITE LOCATION, HISTORY, AND CHARACTERISTICS

1.5.1 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
3

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 OU3. 

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. 
4

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
5

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). 
6

2.0 SYSTEM DESCRIPTION

2.1 SYSTEM OVERVIEW

The groundwater 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). 
7

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. 
8

3.0 SYSTEM OBJECTIVES, PERFORMANCE AND CLOSURE 

CRITERIA

3.1 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 Concentration (ug/l)

tetrachloroethylene (PCE) 5

trichloroethylene (TCE) 5

trans 1,2 dichloroethylene (trans 1,2 DCE) 100

cis 1,2 dichloroethylene (trans 1,2 DCE) 70

vinyl chloride 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 AprilJune 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

Concentration (ug/l)

5-year review Quarterly report

1,1,2,2 PCA 6.48 10.7*

PCE 4.15 10.7*

trans 1,2 DCE 32,800 1.85

TCE 55.6 80.7

vinyl chloride 2.92 100

pH 6-9 6-9

* Effluent discharge for for PCA and PCE combined is 10.7 ug/L.
9

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.
10

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,
11

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.
12

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 lbs 185

1

 of carbon

4 months

month

30 days

 day

0.9 lbs of contam.

 lbs of carbon

 lb of contam.

× × =

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.
13

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.
14

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.
15

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.
16

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 finitedifference 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. 
17

• 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
18

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
19

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.
20

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. 
21

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. 
22

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 USACE Engineering Pamphlet EP 1110-1-27 at

http://www.usace.army.mil/inet/usace-docs.

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
23

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. USACE 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
24

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. 
25

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.
26

Table 7-1. Cost Summary Table

Recommendation Reason

Estimated Change in

Capital

Costs 

 Annual

Costs

Life-cycle

Costs*

Life-cycle

Costs **

6.1.1 Obtain accurate and

reliable water level

measurements and develop

associated potentiometric

surface maps

Effectivness $5,000 $0 $5,000 $5,000

6.1.2 Develop a groundwater

flow model

Effectiveness $50,000 $12,000 $410,000 $243,000

6.1.2b (optional) Develop a

contaminant transport model

Effectiveness $50,000 $12,000 $410,000 $243,000

6.1.3 Analyze capture zone Effectiveness $20,000 $4,000 $140,000 $84,000

6.1.4 Improve well-sampling

program

Effectiveness $0 $0 $0 $0

6.1.5 Monitor Well 9 for VOCs

(costs incurred by city)

Effectiveness $0 $0 $0 $0

6.2.1 Replace pumps in

extraction wells

Cost

reduction

$14,000 ($8,500) ($241,000) ($123,000)

6.2.2 Examine city stormwater

discharge policies and

investigate alternative discharge

locations

Cost

reduction

$4,000 ($60,000) ($1,796,000) ($963,000)

6.2.3 Consider replacing carbon

treatment system with an air

stripper

Cost

reduction

$350,000 ($50,000) ($1,150,000) ($456,000)

6.4.1 Excavate remaining filter

cake

Gain site

closeout

$500,000 $0 $500,000 $500,000

6.4.2 Maintain contaminant

capture while continuing to

screen alternative remedial

technologies and strategies

Gain site

closeout

not

quantified

not

quantified

not

quantified

not 

quantified

6.4.2.3 Develop a site

description for distribution to

vendors of source removal

technologies

Gain site

closeout

$5,000 $0 $5,000 $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
FIGURES
(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).
re 1-2 of the Preliminary Remedial Process Options Screening and Data Gaps Memorandum, Commencement Bay, South Tacoma 

e, Tacoma Washington, October 1999 and Figure 3-1 of the Groundwater Summary Report, South Tacoma Channel/Well 12A Site,

THE TIME OIL PROPERTY INDICATING THE LOCATIONS OF THE GROUNDWATER EXTRACTION WELLS AS WELL 

NATED SOIL, DNAPL, AND FILTER CAKE

, December 1999).
U.S. EPA National Service Center 

for Environmental PublicationsP.O. Box 42419Cincinnati, OH 45242-2419

Solid Waste and Emergency Response(5102G)

542-Octowwwwww