Cleaning Up Contaminated Wood-Treating

Sites

September 1995

OTA-BP-ENV-164

GPO stock #052-003-0135-1
Recommended Citation: U.S. Congress, Office of Technology Assessment,

Cleaning Up Contaminated Wood-Treating Sites, OTA-BP-ENV-164 (Washington, DC: U.S. Government Printing Office, September 1995).
iii

Foreword

he Texarkana Wood Preserving Company Superfund site

is a former wood-treating site located in Texas that

treated various wood products with chemical preservatives. These activities left behind contaminated soil and

sludge, that led to contaminated groundwater. In 1990 Environmental Protection Agency (EPA) selected incineration as the

means to clean up contaminated soil at this site. In 1994 Congressman Jim Chapman (D-Texas) asked the Office of Technology Assessment (OTA) to review alternative technologies that

might be used instead of incineration at the Texarkana site. A second, separate study to assess the safety of incineration was also

requested by Representative Chapman.

This report reviews technologies available for hazardous waste

cleanup at wood-treating sites throughout the United States. OTA

found that there are many Superfund wood-treatment sites

located in this country that are very similar in terms of the contaminants present and the options selected for cleanup. OTA

identified a range of such technologies that were selected and that

could be applied to other sites in the future. 

While OTA has not recommended specific technologies for

the Texarkana site, it is clear that a number of them may be

appropriate and could prove useful if more detailed site-specific

studies and tests were carried out. While this study focused on the

Texarkana site, decision makers and the public for other sites

could benefit from this analysis during the process of selecting

future cleanup strategies.

OTA appreciates the assistance and support it received for this

effort from many contributors and reviewers. They provided

OTA with valuable information critical to the completion of this

background paper and important insights about its technical evaluations and projections. OTA, however, remains solely responsible for the contents of this report.

ROGER C. HERDMAN

Director

T
iv

Reviewers

Frank Avvisato

U.S. EPA

OSWER

Edward Bates

U.S. EPA

ORD

Jim Cummings

U.S. EPA

Technology Innovation Office

Al Davis

U.S. EPA

Region 6

Mary Dunn

Texas Natural Resources 

Conservation Commission

Patricia Erickson

U.S. EPA

ORD

Frank Freestone

U.S. EPA

ORD

Cathy Gilmore

U.S. EPA

Region 6

Earl Hendrick

U.S. EPA

Region 6

Fred Schauffler

U.S. EPA

Region 9

Mary Stinson

U.S. EPA

ORD
v

Project Staff

Clyde Behney

Assistant Director

Health, Education, and the

Environment

Robert Niblock

Environment Program Director

Mark A. Brown

Project Director

Michael Bowes

Senior Analyst

CONTRIBUTORS

Peter Johnson

German Reyes

ADMINISTRATIVE STAFF

Kathleen Beil

Office Administrator

Kimberly Holmlund

Administrative Secretary

Nellie Hammond

Administrative Secretary
vii

Contents

1 Introduction and Summary 1

EPA’s Experience With Wood-Treating Sites 1

EPA’s Presumptive Remedies for Wood-Treating Sites 5

Focus of OTA’s Analysis 6

Summary of Cleanup Technologies 6

Conclusions 7

2 Wood-Treating Sites and Their Cleanup 9

Wood-Treating Sites 10

EPA and Wood-Treating Sites 18

EPA’s Presumptive Remedy Approach 19

Summary 20

3 Remediation Technologies for Wood-Treating 

Sites 29

Destruction Technologies 29

Incineration 29

Bioremediation 31

Chemical Dechlorination 32

Separation and Concentration Technologies 33

Soil Washing 33

Solvent Extraction 34

Thermal Desorption 35

Soil Flushing 36

Immobilization Technologies and Institutional 

Controls 36

Physical Isolation and Capping 36

Solidification or Stabilization 36

Removal of Contaminated Materials 37

References 37
| 1

1

Introduction

and Summary

n 1994 the Office of Technology Assessment (OTA) was asked to evaluate technical alternatives to incineration for cleaning

up the Texarkana Wood Preserving Company Superfund site, in Texarkana, Texas. The

25-acre site, a former wood-treating facility in

Bowie County, Texas, became an U.S. Environmental Protection Agency (EPA) Superfund site

in 1986 (27). Wood products had been treated

there with preservative chemicals over many

decades. These activities left behind chemical

preservatives as contaminates in soil, sludge,

sediment, and groundwater (see box 1-1). Using

information available in the late 1980s, the EPA

selected incineration in a 1990 record of decision

(ROD) to clean up soil, sludge, and sediments

contaminated with wastes from wood-treating

activities at Texarkana.

However, public opposition has prevented

incineration from being used at this site.

Recently EPA funds that had been allocated to

building and operating an incinerator were

returned, and today the only work at the site is

ongoing environmental monitoring, and interim

analyses (2). OTA was asked to find and evaluate possible alternatives to incineration that

might be more acceptable to residents who live

nearby. 

This report identifies technologies available

for organic hazardous waste cleanup at woodtreating sites throughout the country. OTA has

identified a range of such technologies that have

been selected in the past and could be applied to

other sites in the future. OTA has not recommended specific technologies for the Texarkana

Wood Preserving Company site. The applicability of a technology to a particular Superfund site

has to be based on many site-specific factors.

Nevertheless, it is clear that a number of the

approaches identified by OTA may be appropriate and could prove useful if more detailed sitespecific studies and tests were done. Although

this study focused on the Texarkana site, decisionmakers and the public could benefit from

this analysis in selecting future cleanup strategies

for other sites.

EPA’S EXPERIENCE WITH 

WOOD-TREATING SITES

The Texarkana Wood Preserving Company site

is a member of a class of sites that have similar

histories and contaminants present. Today EPA

I
2 | Cleaning Up Contaminated Wood-Treating Sites

has considerably more experience with this type

of site than it did in the late 1980s, when cleanup

decisions were made about the Texarkana site.

Since 1980, EPA has identified 56 Superfund

wood-preserving sites in the United States, most

of which are very similar to the Texarkana site

(17). EPA has completed the process of selecting

technologies and cleanup strategies for more

than 30 of these sites. Chapter 2 of this report

gives more details about EPA’s history with

wood-treating sites.

Table 1-1 summarizes the wood-preserving

chemicals and the selected cleanup remedies for

these sites. Sites contaminated only by metal-containing wood preservatives such as chromated

copper arsenate (CCA) were not included in this

survey since this class of contaminant is not

important at the Texarkana site. Table 2-1 in chapter 2 gives more information about these sites

including contaminants present, size of the site,

current land use around the site, and selected

cleanup technologies. Current land use was

BOX 1-1: The Texarkana Wood Preserving Company Site

The 25-acre Texarkana site is a former wood-treating facility in Bowie County, Texas. Surrounding land

use is industrial, residential, and agricultural. Since the early 1900s, several lumber-related businesses

have operated at the site. Wood-treating operations using creosote began in 1954. By 1971 pentachlorophenol (PCP) was also in use for wood treatment. 

State investigations from 1968 and 1984 showed the company to be negligent or delinquent in fulfilling

various permit requirements. Removal actions from 1986 to 1988 included site access restrictions, constructing a berm, and pumping down the creosote-contaminated onsite processing ponds to prevent runoff and overflow.

The present record of decision addresses onsite contaminated soil near the processing ponds and

contaminated groundwater in a shallow aquifer. Incineration with onsite disposal of ash was considered a

proven technique by EPA. The future use of this site is expected to be industrial, and not residential.

Remediation of groundwater in a deeper aquifer will be addressed in a future ROD. The primary contaminants of concern affecting the soil, sediment, sludge, and groundwater are organics including dioxin,

polycyclic aromatic hydrocarbons (PAHs), pesticides, and phenols including PCP. The location of the site

in a 100-year floodplain complicates cleanup of this site.

The cleanup levels for soil specified for the Texarkana site are 3 parts per million (ppm) carcinogenic

PAHs, 2,350 ppm total PAHs, 150 ppm PCP, and 20 parts per billion (ppb) combined dioxins and furans

equivalents. Any potential cleanup technology must meet these levels, or these levels must be adjusted. 

The selected remedial action for this site includes

■ excavating approximately 77,000 cubic yards of contaminated soil (includes any affected sediment

and sludges) and onsite treatment using incineration, 

■ onsite backfilling of ash with the installation of a soil cover (capping) and revegetation,

■ pumping and treatment of approximately 16 million gallons of contaminated groundwater from the

shallow aquifer using carbon adsorption and reinjecting the treated water onsite into the shallow

aquifer, and 

■ use of institutional controls, including site deed restrictions to limit land use. 

According to the ROD, the estimated cost for this remedial action is $47,500,000. Depending on the

remedy actually used, and the results of competitive bidding, the actual costs may be quite different.

SOURCE: Environmental Protection Agency, Region 6, “Record of Decision: Texarkana Wood Preserving Company Superfund

Site,” Dallas, TX, September 1990; Hendrick, E., Senior Project Manager, EPA Region 6, Dallas, TX, written comments, August 9,

1995. 
Chapter 1 Introduction and Summary | 3

TABLE 1-1: Remedy Selection at Wood-Treating Sites,a by date of ROD

Site name

ROD Date

Chemical

Present Remedy Selected

American Creosote 

85-09-30

Creosote

PCPb

Landfill disposal

Burlington Northern

86-06-04

Creosote Bioremediation and capping

Westline site

86-07-03

Creosote Incineration

Coleman Evans

86-09-25

PCP Incineration of more contaminated soil

Baxter/Union Pacific

86-09-26

Creosote

PCP

Barrier wall (plan for more permanent remedy) 

United Creosoting

86-09-30

Creosote 

PCP

Temporary cap and apply innovative technology when available

Mid-South

86-11-14

Creosote

PCP

Remove sludges & oils to offsite facility; stabilization of soil hot spots, then 

capping

Bayou Bonfouca

87-03-31

Creosote

PCP

Incineration and offsite disposal

Midland Products

88-03-24

Creosote

PCP

Incineration

L.A. Clarke 

88-03-31

Creosote Soil flushing, bioremediation

Brown Wood Pre.

88-04-08 

Creosote

PCP

Bioremediation; landfill disposal of heavily contaminated material

North Cavalcade

88-06-28

Creosote

PCP

Bioremediation

Southern Md. Wood

88-06-29

Creosote

PCP

Incineration 

Broderick Wood 

88-06-30

Creosote

PCP

Incineration

South Cavalcade

88-09-26

Creosote Incinerate oily wastes; soil washing & capping (or bioremediation if effective)

Libby

88-12-30

Creosote

PCP

Bioremediation and capping

American Creosote

89-01-05

Creosote

PCP

Incineration

Koppers/Galesbrg

89-06-28

Creosote

PCP

Bioremediation and capping

Cape Fear Wood

89-06-30

Creosote Soil flushing or thermal desorption

Koppers (Oroville)

89-09-13

Creosote

PCP

Soil washing, bioremediation, and capping

Newsom Brothers

89-09-18

Creosote

PCP

Incinerate worst material; offsite disposal of other soils

American Creosote

89-09-28

Creosote

PCP

Bioremediation

(continued)
4 | Cleaning Up Contaminated Wood-Treating Sites

included as an indicator of future land use. The

basic features of the Texarkana site are similar to

those of other wood-treating sites. Figure 1-1

shows how often the various technologies and

strategies are chosen for the selected 40 sites. Usually more than one technology was selected to deal

with various contaminated parts of a single site. 

The wood-treatment industry, which treats

wood with chemicals to preserve them from

decay and insect damage, has operated in the

United States for over 100 years (23). Many

common and widely used wood products are produced by this industry, including railway ties,

fencing posts, outdoor decks, telephone and utilSite name

ROD Date

Chemical

Present Remedy Selected

United Creosoting 

89-09-29

Creosote

PCP

Solvent extraction (critical fluid) with offsite incineration of residues

Havertown PCP

89-09-29

Creosote

PCP 

Landfill disposal

Texarkana Wood

90-09-25

Creosote

PCP

Incineration

Coleman-Evans

90-09-26

PCP Soil washing, bioremediation; solidification/stabilization, then capping

Cabot/Koppers

90-09-27

Creosote Soil washing & bioremediation; then solidification/stabilization

J H Baxter Co 

90-09-27

Creosote

PCP

Bioremediation followed by solidification/stabilization if inorganics are found

Moss-American

90-09-27

Creosote Incinerate sludges & oils; soil washing & bioremediation followed by capping

Arkwood, Inc

90-09-28

Creosote

PCP

Soil washing (incineration if this fails)

Broderick Wood 

91-09-24

Creosote

PCP

Recycle oils (with incineration of residues)

Macgillis & Gibbs

91-09-30

Creosote

PCP

Remove sludges & oils to offsite facility

Saunders Supply

91-09-30

PCP Dechlorination of sludges & sediments; thermal desorption of soils

Idaho Pole

92-09-28

Creosote

PCP

Soil wash & bioremediation, then capping

Koppers (Morrisv.)

92-12-23

PCP Thermal desorption & dechlorination (incineration if this fails)

Popile, Inc.

93-02-01

Creosote

PCP

Bioremediation and capping

American Creosote.

93-04-28

Creosote

PCP

Incinerate sludges; bioremediation of soils

Rentokil Virginia

93-06-22

Creosote

PCP

Incinerate sludges & oils (with dechlorination for dioxins); thermal desorption 

for soils, followed by capping

Montana Pole

93-09-21

Creosote

PCP

Incinerate sludges & oils; soil flushing & bioremediation

NOTES:

a Additional wood-treating sites with primarily metals contamination are not included in this table. 

b Sites with PCP use can be expected to have some dioxin contamination.

TABLE 1-1: Remedy Selection at Wood-Treating Sites,a by date of ROD (Cont’d.)
Chapter 1 Introduction and Summary | 5

ity poles, and other wood products intended for

outdoor use. 

Wood preserving typically involves treating

the wood under pressure with the preservative

chemicals pentachlorophenol (PCP), creosote,

or chromated copper arsenate (CCA), usually

dissolved in some suitable solvent (23). These

activities often left behind widespread soil, sediment, sludge, and water contamination at the site.

The preservative PCP always contains some

dioxin and furan impurities, and creosote contains polycyclic aromatic hydrocarbons (PAHs).

These compounds are considered by EPA and

other health agencies to be likely human carcinogens (see boxes 2-1 and 2-2 in chapter 2 for more

information about creosote, PAHs, PCP, and

dioxins). 

The presence of any one of these contaminants, including dioxins and furans present as

impurities in PCP, has not necessarily dictated

the use of any one technology such as incineration (see tables 1-1 and 2-1). Dioxins and furans,

when they occur at contaminated wood-treating

sites, are always in very much smaller concentrations compared with the primary site contaminants PCP or creosote. Dioxins and furans are

present at a wood-treating site as low-level impurities contained in the PCP used at the site for

wood preservation. This has led to very different

cleanup strategies for this type of site compared

with other sites where the primary contaminate is

dioxins or furans. For an analysis of technologies

for cleanup of dioxin contaminated soils, see the

Office of Technology Assessment (OTA) background paper “Dioxin Treatment Technologies”

(4). Table 1-1 also shows that before 1990, incineration was more commonly selected as the primary cleanup strategy. After 1990, incineration,

if it was selected at all, appears to be only one

part of an overall cleanup strategy. For example,

incineration may be chosen for the cleanup of

small, highly contaminated “hot spots” while

bioremediation is chosen for dealing with the

remainder of the site.

EPA’S PRESUMPTIVE REMEDIES FOR 

WOOD-TREATING SITES

EPA’s experience over the years with cleaning

up wood-treating sites has led to an evolution

and maturation in EPA’s cleanup approach.

Some cleanup technologies that EPA now considers established were not seriously considered

when decisions were made about the Texarkana

site. EPA’s experience with this type of site has

provided new cleanup options. 

Today EPA formally recognizes wood-treating sites as a class of site that has similar problems and similar cleanup options. It recently

summarized the variety of successful technologies and approaches that have proven useful for

cleaning up wood-treating sites such as the Texarkana site. EPA refers to proven technologies

for a class of sites as “presumptive remedies.”

EPA reviewed successful cleanup strategies for

wood-treating sites with similar characteristics,

including the contaminants present, the environmental media affected by those contaminants,

and the cleanup technologies selected (23). The

fact that contaminated wood-treating sites had

many features in common made it practical and

FIGURE 1-1: Frequency of cleanup 

strategies for wood-treating sites

Superfund cleanup strategies selected by EPA for 40 woodtreating sites contaminated with pentachlorophenol (PCP) or

creosote. Many of these treatments are used together at a single site as part of a treatment train.

SOURCE: Office of Technology Assessment
6 | Cleaning Up Contaminated Wood-Treating Sites

useful for EPA to summarize successful cleanup

technologies. 

On the basis of this review of many full-scale

cleanup projects at wood-treating sites, EPA concluded that a variety of demonstrated treatment

technologies are capable of meeting stringent

cleanup requirements (16,21,23). EPA presumptive remedies for contaminated soil, sludge, and

sediments at wood-treating sites are bioremediation, thermal desorption, or incineration for

organic contaminants, and immobilization for

inorganic contaminants. Chapter 3 provides more

information on how these technologies have performed with the various contaminants found at

wood-treating sites. Although EPA focused

mostly on technologies that had proven themselves in full-scale cleanup projects at contaminated wood-treating sites, it also considered

certain other technologies that had less performance data available (21,23). EPA has not yet

developed presumptive remedies for contaminated groundwater at these sites.

FOCUS OF OTA’S ANALYSIS

This report presents OTA’s analysis of the treatment technologies and strategies selected by

EPA for cleaning up contaminated soil at woodtreating sites. OTA’s identification of these technologies is intended to capture the evolution

since the mid-1980s of the approaches EPA has

available to clean up contaminated soil, sludge,

and sediments at these sites. OTA gathered information on various technologies selected for use

to clean up Superfund wood-treating sites from

two main sources. The first source was OTA’s

review of EPA’s decisions and the technology

selected for the cleanup of Superfund woodtreating sites as they are described in the ROD

for each site. The second source was an analysis

of the presumptive remedy strategy recently

developed by EPA for wood-treating sites. Considering both of these sources, OTA concluded

that EPA has selected at least 10 different

approaches for cleaning up contaminants at such

sites. 

OTA did not try to compare the relative safety

or hazards of these alternatives to incineration.

Nevertheless, some concerns should be kept in

mind when comparing the safety and hazards of

incineration to any alternative. Concerns about

possibly toxic emissions from incinerators used

for cleaning up wood-treating sites are likely to

apply equally or possibly even more to some of

the alternative technologies reviewed by OTA. In

most cases the emissions that would come from

these alternative technologies are less well characterized than those for incineration. 

Many alternative technologies are less mature;

they have less of a record by which their relative

safety can be judged. At some sites the technologies selected by EPA have not yet been fully

implemented, and their success cannot be evaluated. Some alternatives may work well with certain types of sites, but poorly or not at all with

others. Soil cleanup standards and relevant

cleanup laws may vary for each site. Nevertheless, some of the alternatives evaluated by OTA

will undoubtedly be useful alternatives to incineration for cleaning up contaminated soil, sludge,

and sediment at wood-treating sites. 

SUMMARY OF CLEANUP TECHNOLOGIES

OTA looked at the treatment strategies that EPA

selected in 47 RODs for 40 different wood-treating sites. Table 1-1 summarizes this review, and

figure 1-1 lists the various technologies and

approaches selected by EPA, as well as how

often they were selected. Chapter 2 gives further

information about the various sites and the technologies selected for them, and chapter 3 provides more detailed information about the

technologies and approaches. 

In virtually every case, several different technologies and other approaches were selected in

combination to make a complete site cleanup

strategy. Sometimes one technology such as

incineration or bioremediation was selected as

the key technology for addressing the main contamination source. However, in general no single

technology can clean up an entire wood-treating

site, and a combination of control and treatment
Chapter 1 Introduction and Summary | 7

strategies is chosen (17). For example, capping a

site and making some restrictions on future use

after incineration or bioremediation was used in

more than half the RODs reviewed by OTA.

Capping involves providing some type of cover,

made of clean soil and other materials, that isolates contamination from the environment and

limits human exposure. 

OTA also reviewed EPA’s recently released

presumptive remedies strategy for cleaning up

contaminated soil, sludge, and sediments at

wood-treating sites. This strategy is a summary

of EPA’s experience with technologies that have

proven successful in full-scale cleanups of such

sites (17). Only full-scale successfully demonstrated technologies and strategies were included

in EPA’s list of presumptive remedies, which

eliminated some of the less mature technologies

listed in figure 1-1. EPA selected as wood-treating site presumptive remedies bioremediation,

thermal desorption, or incineration for organic

contaminants; immobilization is the presumptive remedy for inorganic contaminants. Chapter

3 describes these technologies. 

EPA concluded that bioremediation is the primary presumptive remedy for organic contaminants such as PCP or creosote. If bioremediation

is not feasible, thermal desorption may be appropriate. For some situations, such as the treatment

of sludge “hot spots” with very high concentration of contaminants, EPA concluded that incineration may be the best choice (17). 

CONCLUSIONS

EPA today has a range of technologies and strategies available for addressing contaminated

wood-treating sites. Some of the technologies

were not available when EPA completed the

ROD for the Texarkana wood-treating site in

1990; others were too new to have been evaluated thoroughly. Although every Superfund site

has some unique characteristics and cleanup

requirements, it is likely that some combination

of technologies may be applicable as alternatives

to incineration for cleaning up the Texarkana

site. OTA found that typically several different

technologies and control methods are put

together for an overall cleanup strategy in order

to meet the requirements of a specific woodtreating site. In virtually no wood-treating site

reviewed by OTA was a single technology such

as incineration or bioremediation selected as the

only form of cleanup. 

The availability of new strategies for cleaning

up contaminants from wood-treating sites suggests that EPA could reexamine the cleanup

decisions made in the 1990 ROD for the Texarkana site. This would be responsive to concerns

among some in that community about those earlier decisions. However, there are significant

risks with choosing alternatives to incineration.

EPA cautions that some alternatives are good

only for certain contaminants under specific conditions. They might be much less effective for

other situations. Thus, an alternative technology

should be selected only if it has been tested and

proven under the specific conditions for the site

where it is to be used. It should also be pointed

out that EPA’s chosen technology for a given site

may not have been found in practice to be effective at that site. At some of the sites reviewed by

OTA, according to some EPA officials, cleanup

has not been completed or was not as successful

as had been hoped. 

Although some of these incineration alternatives have significant track records so that their

possible use at a specific site can be evaluated,

none are as mature and developed as incineration. For example, in its presumptive remedies

strategy, EPA warns that the effectiveness of the

primary presumptive remedy, bioremediation, is

site and contaminant specific, requiring careful

site characterization and treatability studies of

appropriate scale. Thus, selection of some of

these alternatives may carry with it a greater risk

that cleanup goals for a specific site will not be

adequately met.

The permanence of the cleanup offered by

these alternative technologies is also a factor.

Incineration was often selected by EPA in the

past in part because it offered a permanent

reduction in the concentrations of contaminants,

including dioxins and furans in soil and sludge.
8 | Cleaning Up Contaminated Wood-Treating Sites

Some alternatives, such as bioremediation and

capping, give less complete destruction of contaminants, even though they can offer adequate

protection of human health and the environment

by eliminating exposure. If the cleanup strategy

selected leaves significant concentrations of contaminants after the cleanup is complete, it will

be necessary to monitor the site for as long as the

contaminants remain, possibly indefinitely.
| 9

2

Wood-Treating

Sites and Their

Cleanup

he wood-preserving industry treats lumber with various chemicals to protect

against insect damage and decay. Chemically preserved wood is used in products for outdoor use such as railway ties, fencing,

telephone poles, exterior plywood panels, and

outdoor decks (23). The industry has operated in

the United States for over 100 years, with sites

often having operated for decades (23). Spills

from the treatment process have left many of

these sites heavily contaminated with the chemicals used to preserve wood.

U.S. Environmental Protection Agency (EPA)

has identified 56 wood-treating sites among the

Superfund sites in the United States (17).

Because the processes that have been used at

these wood-treating sites are generally so similar,

the contamination and cleanup needs are also

similar. Recognizing this, EPA has recently

moved to standardize the process for selecting

cleanup remedies. Following a thorough review

of past experience with remedial activities, the

Superfund program has developed a short list of

preferred cleanup technologies or presumptive

remedies for wood-treating sites. It is intended

that presumptive remedies will be selected for

future remedial actions at all wood-treating sites,

except under unusual site-specific circumstances.

Wood-treating sites are one of three categories of

sites for which EPA has designated presumptive

remedies.

For sites contaminated with preservatives such

as those used at the Texarkana Wood Preserving

site, EPA suggests bioremediation as the preferred cleanup remedy. If bioremediation is

found to be infeasible, thermal desorption methods are to be considered. Incineration may be

selected if bioremediation and thermal desorption are not feasible. In downplaying the role of

incineration among the presumptive remedies,

EPA stresses the difficulty in gaining public support, but recognizes the method’s effectiveness.

In addition to the technologies that EPA now

identifies as presumptive remedies, a number of

other innovative technologies have been selected

for use at wood-treating sites in recent years.

OTA has reviewed 47 records of decision

(RODs) for 40 Superfund wood-treating sites to

investigate the selection of remedies. This chapter provides a description of the contaminants

typically found at wood-treating sites, a list of

the remedies that have been selected at Superfund wood-treating sites, and a summary of

EPA’s recent efforts to standardize the remedy

selection process at wood-treating sites. The

T
10 | Cleaning Up Contaminated Wood-Treating Sites

remedial technologies are described in greater

detail in chapter 3.

WOOD-TREATING SITES

The wood-preserving industry pressure treats

wood with chemicals that protect against insects

and fungus. Just a few preserving chemicals have

been widely used by the industry. The oldest preservative process treats wood with creosote, a

tarry liquid derived from coal (see box 2-1) (17).

Pentachlorophenol (PCP) became widely used as

a preservative after 1950, although its purchase

and use is now restricted (see box 2-2) (17).

Metal salts made from chromium, copper,

arsenic, or zinc (e.g., chromated copper arsenate

[CCA]) are now the most frequently used preservatives. The metal salts present special cleanup

problems that we do not consider in this paper.

Almost 60 wood-preserving sites are on the

National Priorities List, which lists facilities eligible for cleanup under the Superfund program.

Hundreds more may have been abandoned and

are in need of cleanup. Most of these sites

present similar cleanup problems (see the

descriptions of five Superfund wood-treating

sites presented in boxes 2-3 through 2-7). The

older sites in need of cleanup typically used creosote and PCP. The treatment process produced

significant spillage, waste sludges, and contaminated wastewater. The Texarkana Wood Preserving site is typical of the many wood-treating sites

that have used creosote and PCP over a number

of decades. 

At these sites, wood was generally treated

under pressure with creosote or PCP in a heated

oil-based solution (21,23). After treatment, the

wood was removed from the pressure chamber

and allowed to drip dry outside, resulting in large

volumes of contaminated soil. Other treatment

wastes include wastewater and sludges. Wastewater was generated as a condensate in the treatment process and also by rinsing tanks and

equipment. After separation of recoverable

chemicals, wastewater was often spread onsite or

stored in evaporation ponds. An oily sludge gradually accumulates in wastewater evaporation

areas and also in treatment cylinders and storage

tanks. This sludge was historically dumped into

unlined pits onsite. Sludge pits found at woodtreating sites can contain very high concentrations of the preservative chemicals, which may

limit treatment options for these areas (17).

The preservatives PCP and creosote are found

as contaminants, alone or in combination, at

nearly all abandoned wood-treating sites in the

United States (21,23). Both of these materials

can be hazardous to human health. Creosote contains polycyclic aromatic hydrocarbons (PAHs).

Commercial grades of PCP always contain small

amounts of dioxins and furans as impurities. It is

thought that additional dioxins might be generated by heating PCP solutions (17). The dioxins,

furans, and PAHs are considered by EPA and

other health agencies to be likely human carcinogens (see boxes 2-1 and 2-2).
Chapter 2 Wood-Treating Sites and Their Cleanup | 11

BOX 2-1: Creosote and Polycyclic Aromatic Hydrocarbons

Creosote has been widely used as a preservative in the wood treatment industry for more than a century. It is an oily, translucent, brown-to-black liquid with a sharp smoky or tarry odor. Creosote is produced from high-temperature carbonization of bituminous coal. It is not a single chemical, but rather a

complex mixture, containing several thousand compounds. It is about 85 percent polycyclic aromatic

hydrocarbons (PAHs), along with phenolic compounds (about 10 percent) and a variety of other related

chemicals. 

The PAHs contained in creosote are a group of more than 100 related chemicals that are both manmade and naturally occurring. They are found in crude oil, coal, coal tar pitch, and road and roofing tar.

Although in pure form a single PAH is usually a white or pale green solid, they almost always occur as a

mixture of PAHs. Typically, human exposure involves exposure to a mixture of PAHs. 

The human health effects of the individual PAHs found in creosote vary. About 17 PAHs have been

studied extensively. These 17 are considered the most harmful, the most likely to be involved in human

exposure, and the most frequently identified at Superfund sites. People living near waste sites contaminated with PAHs may be exposed to them by contact with contaminated air, water, or soil. Most PAHs that

enter the body are excreted in feces and urine within a few days.

PAHs are considered by EPA and other public health organizations to be human carcinogens. The

Department of Health and Human Services (DHHS) has determined that certain PAHs “may reasonably

be anticipated to be carcinogens.” The International Agency for Research on Cancer (IARC) has determined that certain PAHs “are possibly carcinogenic to humans.” EPA has determined that certain PAHs

“are probable human carcinogens.”

Reports with humans show that individuals exposed to PAHs by breathing or skin contact for long

periods can develop cancer. Some PAHs cause tumors in laboratory animals when breathed, eaten, or

after long periods of skin contact. Mice fed high levels of certain PAHs during pregnancy had difficulty

reproducing and so did their offspring. Offspring from pregnant mice fed PAHs showed other harmful

effects, including birth defects, although there is no information about similar effects in humans.

PAHs have low water solubility, but they can contaminate underground water that comes into contact

with soil contaminated by them. They have been found in some U.S. drinking water supplies. PAHs can

evaporate, but most will stick to solid particles in soil. In soil, most PAHs can break down in weeks to

months, mostly because of microorganisms, although very large PAH molecules are more stable. Some

wood-treatment sites have cleanup standards only for those PAHs considered to be carcinogenic while

other sites may focus on all the PAHs present. 

SOURCE: U.S. Environmental Protection Agency, Office of Research and Development, Contaminants and Remedial Options at

Wood Preserving Sites, prepared by Foster Wheeler Enviresponse, Inc., EPA/600/R-92/182 (Washington, DC: October 1992); U.S.

Environmental Protection Agency, Office of Solid Waste and Emergency Response, “Presumptive Remedies for Soils, Sediments,

and Sludges at Wood Treater Sites,” EPA/540/F-95/006 (Draft), Washington, DC, May 1995; and U.S. Department of Health &

Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry, “Toxicological Profile for Polycyclic

Aromatic Hydrocarbons (PAHs),” draft, Atlanta, GA, October 1993. 
12 | Cleaning Up Contaminated Wood-Treating Sites

BOX 2-2: Pentachlorophenol

Pentachlorophenol (PCP) has been used for many years as a preservative in the wood treatment

industry. It is a manufactured substance not occurring naturally in the environment. PCP was formerly one

of the most heavily used pesticides in the United States. Today its purchase and use is restricted to certified applicators, and it is used industrially as a wood preservative for power line poles, fence posts, etc.

Before restriction, PCP was widely used as a wood preservative. It is made by only one company in the

United States. Pure PCP is a white crystalline material, but the commercial grade form usually found at

waste sites is dark gray to brown. 

Commercial grade PCP used for treating wood is a mixture of many related compounds. It contains

PCP (85 to 90 percent); 2,3,4,6-tetra chlorophenol (4 to 8 percent), more highly chlorinated chlorophenols

(2 to 6 percent), and dioxins and furans (about 0.1 percent). Dioxins and furans are also mixtures of various related compounds. The principal dioxins and furans found in commercial grade PCP have six to

eight chlorine atoms present in their structures. The most toxic dioxin and the one of greatest regulatory

concern is 2,3,7,8-tetrachloro-p-dioxin (TCDD), which contains four chlorine atoms in its structure. 

Analysis of commercial PCP produced in the U.S. has not found TCDD. But some wood-preservation

methods use PCP at higher temperatures, which might produce traces of TCDD from the PCP itself.

Octachloro-dibenzo-p-dioxin (the dioxin containing 8 chlorine atoms) is by far the largest dioxin contaminant, while the most toxic dioxin, TCDD, occurs only at trace or below detection levels. According to EPA,

octachloro-dibenzo-p-dioxin is about 1000-fold less toxic than TCDD. In any event, EPA recommends

that site managers should ensure that sampling for dioxins and furans is conducted at all wood-treating

sites known to have used PCP. 

Public health agencies consider that PCP, at most, might be a human carcinogen. The International

Agency for Research on Cancer (IARC) determined PCP is not classifiable as to its carcinogenicity to

humans, while EPA classified PCP as a “probable human carcinogen”. Large doses of PCP can cause

death, and long-term exposure to lower levels can cause damage to liver, kidneys, blood, and nervous

system. 

However, there is no convincing evidence from epidemiological studies that PCP causes cancer in

humans, although it does cause cancer in some laboratory animals fed large doses for long periods.

Many, but not all, of the harmful effects of PCP may be due to the impurities in the commercial grade,

including dioxins and furans. Although pure PCP might not be a human carcinogen, the small amounts of

dioxins and furans found in the commercial grade of PCP might account for its apparent animal carcinogenicity. 

The physical properties of PCP are such that it will not evaporate very quickly from contaminated soil

or sludge. The most significant human exposure comes through breathing and skin contact, and it does

not seem to accumulate in the human body, but is excreted in urine. After environmental release onto soil

or sludge, most PCP will tend to slowly move with any water that contacts that contaminated soil or

sludge. PCP will tend to stick to soil particles. It is broken down in soils and surface waters by microorganisms and in surface waters and air by sunlight. 

SOURCE: U.S. Environmental Protection Agency, Office of Research and Development, Contaminants and Remedial Options at

Wood Preserving Sites, prepared by Foster Wheeler Enviresponse, Inc., EPA/600/R-92/182 (Washington, DC: October 1992); U.S.

Department of Health & Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry. “Toxicological Profile for Pentachlorophenol,” draft, Atlanta, GA, October 1992; U.S. Environmental Protection Agency, Office of Solid Waste

and Emergency Response, “Presumptive Remedies for Soils, Sediments, and Sludges at Wood Treater Sites,” EPA/540/F-95/006,

PB 95-963410 (Draft), Washington, DC: May 1995.
Chapter 2 Wood-Treating Sites and Their Cleanup | 13

BOX 2-3: The American Creosote Works Site, Pensacola, Florida 

The 18-acre American Creosote Works (Pensacola plant) site is in a dense, moderately commercial

and residential area of Pensacola, Florida. A wood-preserving facility operated at this site from 1902 to

1981. During this time, process wastewater containing pentachlorophenol (PCP) was discharged into

unlined, onsite surface impoundment ponds. Before 1970, these impoundment ponds were allowed to

overflow through a spillway into neighboring bays. After 1970, wastewater was discharged to designated

onsite spillage areas. Additional discharges occurred during periods of heavy rainfall when the ponds

overflowed.

In March 1980, the city found considerable quantities of oily, asphaltic, creosote material in the

groundwater near the site. Because of the threat posed to human health and the environment, EPA and

the state performed an emergency cleanup in 1983. This included dewatering the ponds, treating the

water, and discharging treated water into the city sewer system. The sludge in the ponds was then solidified and capped.

EPA signed a record of decision (ROD) in 1985 requiring all onsite and offsite contaminated solids,

sludge, and sediment to be placed in an onsite RCRA-permitted landfill. A second ROD, signed in 1989,

addresses remediation of contaminated surface soil. A future ROD will address treatment of contaminated subsurface soil, sludge, and groundwater. The primary contaminants of concern affecting the surface soil are organics, including dioxins, carcinogenic polycyclic aromatic hydrocarbons (PAHs), and

PCP. 

The selected remedial action for this site includes

■ excavating and treating 23,000 cubic yards of PAH-contaminated soil using solid-phase bioremediation at an onsite land treatment area. Dissolved oxygen, pH, nutrients, and soil moisture content

will be monitored, 

■ disposal of treated soil onsite in the excavated areas or by spreading the soil over the entire site,

■ spraying collected drain water over the treatment area to moisten soil, 

■ repairing fences around the site, monitoring the site cap, and

■ implementing groundwater use restrictions. 

The estimated cost for this approach is $2,275,000.

SOURCE: Environmental Protection Agency, Region 4, “Record of Decision: American Creosote Works Inc. Site,” Atlanta, GA,

January 5, 1989.
14 | Cleaning Up Contaminated Wood-Treating Sites

BOX 2-4: The Koppers Site, Oroville, California

The Koppers site is a 200-acre operating wood-treating plant in Butte County, California. Nearby land

use is mixed agricultural, residential, commercial, and industrial. Although there is a history of wood-treating operations at the site, they were greatly expanded in 1955 when Koppers Company, Inc., became the

owner and operator. Pentachlorophenol (PCP), creosote, and chromated copper arsenate (CCA) solution

are among the chemicals that have been used at this site. 

Wastewater discharge and other site activities have resulted in contamination of unlined ponds, soil,

and debris. PCP was detected in onsite groundwater in 1971 and in residential wells in 1972. Pursuant to

a state order, Koppers conducted cleanup activities from 1973-74, including groundwater pumping and

discharge to spray fields and offsite disposal of contaminated debris, and process changes, including

construction of a wastewater treatment plant. In 1986, Koppers provided nearby residents an alternate

water supply for domestic uses. 

Following a 1987 explosion and fire at a PCP wood-treatment process facility, EPA issued a removal

order requiring cleanup of fire debris and removal and stabilization of surface soil. 

The present record of decision (ROD) addresses the remaining contamination in onsite soil and

groundwater affected. The primary contaminants of concern are polycyclic aromatic hydrocarbons

(PAHs), PCP, dioxins and furans, and metals including arsenic and chromium. 

The selected soil remedy includes

■ onsite biodegradation of 110,000 cubic yards of PCP-contaminated soil, 

■ excavation and soil washing of 200,000 cubic yards of soil contaminated with wood-treating wastes

with disposal of treated soil onsite and treatment of residual contamination in the washing fluid in an

onsite treatment facility, 

■ installation of a low-permeability cap over the wood-treating process area (an interim remedy) and

down gradient extraction wells, and 

■ excavation and chemical fixation of 4,000 cubic yards of soil contaminated with metals, followed by

onsite disposal. 

The groundwater remedy includes pumping and treatment of approximately 22,000,000 cubic yards

of groundwater using activated carbon, reinjection of treated waste to the groundwater, and formalization

of the provision of an existing alternate water supply and extension, if needed, of the water supply during

implementation of the remedy. 

According to the ROD the estimated cost for this cleanup strategy was $77,700,000.

EPA has had some difficulties implementing bioremediation at the Koppers site. It found that the soil

excavated for a bioremediation treatability study was contaminated with more dioxin than anticipated.

This caused the cancellation of the treatability study and a switch to a removal action, placing soil in a

RCRA-approved landfill. The soil washing pilot test showed that soil washing was not capable of meeting

cleanup standards. Bioremediation effectively destroyed PCP but was not effective in reducing dioxins.

The owner is reevaluating soil remedies for the remainder of this site.

SOURCE: U.S. Environmental Protection Agency, Region 9, “Record of Decision: Koppers Co. Inc. (Oroville Plant) Site,” San Francisco, CA, September 1989; Fred Schauffler, Project Manager, EPA Region 9, Oroville, CA, personal communication, July 13,

1995 and written comments, August 8, 1995.
Chapter 2 Wood-Treating Sites and Their Cleanup | 15

BOX 2-5: The Koppers Site, Morrisville, North Carolina

The 52-acre Koppers Morrisville site is a wood-laminating facility in Morrisville, Wake County, North

Carolina. Surrounding land use is a mixture of commercial, light industrial, and rural residential. The site

has been used by lumber companies since 1896. In 1962, Koppers began treating wood at the site using

pentachlorophenol (PCP) and isopropyl ether injected into wood. Process wastes were put into unlined

lagoons. Koppers discontinued wood treatment in 1975, but past wood-treatment processes and associated disposal activities have left the site contaminated with PCP, dioxins, and isopropyl ether affecting

the soil, groundwater, and surface water. 

In 1989, in response to state studies of water contamination from the site, nearby residents began

using public water lines instead of wells to obtain drinking water. In 1990, EPA required extensive studies

of the soil, groundwater, drainage pathways, and ponds, and also determined that additional studies

were needed to further assess contamination of the surface soil in the lagoon and wood-treatment process areas. In 1992, EPA completed a record of decision (ROD) for the site that specified incineration as

the primary remedy and base-catalyzed decomposition (BCD) as the “contingency remedy” whose use

would be dependent upon the results of a treatability study. One driving force for providing for an alternative to incineration was the strong interest of the community. 

The primary strategy was offsite incineration of soil involving

■ excavation of contaminated soils from lagoon and process areas and transportation to an offsite

permitted incineration facility, 

■ extraction of contaminated groundwater from within the plume via extraction well(s) and piping it to

an onsite carbon adsorption treatment unit,

■ use of institutional controls including fencing of the pond, lagoon, and wood-treatment process

areas. 

Base-catalyzed dehalogenation was selected as a contingency cleanup strategy. According to the

1992 ROD, BCD could substitute for offsite incineration if it proved itself in treatability studies. BCD would

involve the excavation of contaminated soils from the lagoon and process areas, and transportation to an

onsite BCD treatment system, 

According to the ROD, the estimated cost for the selected cleanup strategy was $11,500,000.

The treatability study with BCD was completed in August 1993. The results showed that BCD was

effective in treating soil contaminated with both PCP and dioxins. However, it may be premature to consider BCD a general technology for wood-treatment site cleanup. The size of this demonstration was very

small compared to other wood-treatment sites. According to the site engineer at Koppers, the BCD demonstration involved only 700 cubic yards of soil; the amounts of soil requiring treatment at some of the

largest contaminated wood-treatment sites are as much as 100 times larger (see table 2-1). Another concern raised by one EPA wood treatment site manager is that the results from this BCD trial seem to show

significant stack emissions, presumably from the thermal desorption stage, that are equal to or greater

than those that would be seen if incineration had been used instead of BCD. 

For BCD to be considered successful at this site, it had to achieve 7 parts-per-billion (ppb) or lower

dioxin levels in the treated soil. However, the soil levels were fairly low to begin with and dioxin soil concentrations were probably not very important for the choice of BCD as a soil cleanup technology. 

(continued)
16 | Cleaning Up Contaminated Wood-Treating Sites

The neighboring community was brought into the treatability study process. More than 100 citizens

were invited to observe the results of the BCD treatability study. According to one EPA official involved

with the study, the citizen involvement was very helpful in the overall process of developing the alternative. A new ROD has been approved that specifies BCD as the primary means of treating contaminated

soil. Koppers as the principal responsible site owner, is in the process of awarding a contract to build a

full-scale onsite BCD treatment facility. 

SOURCE: U.S. Environmental Protection Agency, Region 4, “Record of Decision: Koppers Site (Morrisville Plant),” Atlanta, GA,

December 1992; B. Hudson, Site Engineer, Koppers Superfund site, Morrisville, NC, personal communication, April 12, 1995; E.

Hendrick, Site Manager, EPA Region 6, Dallas, TX, personal communication, April 12, 1995.

BOX 2-6: The Arkwood, Inc., Site, Omaha, Arkansas 

The 15-acre Arkwood site is a former wood-treatment facility in Boone County, Arkansas. Land use in

the vicinity of the site is primarily agricultural and light industrial. Approximately 200 residences are

located within 1 mile of the site, and 35 domestic water supply wells are within 1.5 miles of the site.

Groundwater on or near the site is highly susceptible to contamination as a result of underground cavities, enlarged fractures, and conduits that hinder monitoring and pumping.

From 1962 to 1973, Arkwood operated a pentachlorophenol (PCP) and creosote wood treatment facility at the site. In 1986, the site owner dismantled the plant. State investigations conducted during the

1980s documented PCP and creosote contamination in surface water, soil, debris, and buildings

throughout the site. Contaminated surface features at the site include the wood-treatment facility, a sinkhole area contaminated with oily waste, a ditch area, a wood storage area, and an ash pile.

In 1987, EPA ordered the site owner to perform an immediate removal action that included implementing site access restrictions, such as fencing and sign postings.

The present record of decision (ROD) addresses remediation of all affected media and provides the

final remedy for the site. The primary contaminants affecting the soil, sludge, debris, and groundwater are

organics including PCP, polycyclic aromatic hydrocarbons (PAHs) and dioxins. 

The selected remedial action for this site includes

■ excavating approximately 21,000 cubic yards of contaminated soil and sludge followed by soil

washing,

■ onsite incineration of approximately 7,000 cubic yards of materials that exceed cleanup levels,

■ incineration of any free oil wood-treating material, 

■ using washed and decontaminated materials and any residual ash for backfilling,

■ covering the site with a soil cap and planting revegetation,

■ site access restrictions including fencing, and

■ monitoring of drinking and groundwater and connecting affected residences to municipal water

lines. 

According to the ROD, the cost of this approach would be $10,300,000.

SOURCE: U.S. Environmental Protection Agency, Region 6, “Record of Decision: Arkwood, Inc. Site,” Dallas, TX, September

1990.

BOX 2-5: The Koppers Site, Morrisville, North Carolina (Cont’d.)
Chapter 2 Wood-Treating Sites and Their Cleanup | 17

BOX 2-7: The United Creosoting Site, Conroe, Texas 

The 100-acre United Creosoting site in Conroe, Montgomery County, Texas, is occupied by a residential subdivision, a distributing company, and a construction company. From 1946 to 1972, the United Creosoting Company operated a wood preserving facility at the site. Pentachlorophenol (PCP) and creosote

were used in the wood-preservation process, and process wastes were stored in waste ponds.

During 1980, the county used soil and waste pond backfill from the site on local roads. After residents

living near the improved roadways experienced health problems, the county sampled and compared

leachate composition from the affected roadways and the site. They determined that leachate from both

the site and the roadways was contaminated with PCP. Roadway soil was subsequently removed and

disposed of using land farm treatment.

In 1983, in response to contaminated stormwater runoff from the former waste pond areas, the property owner was directed under terms of an EPA Administrative Order to regrade contaminated soil, divert

surface water drainage away from the residential portion of the site, and cap the contaminated soil.

The present record of decision (ROD) specifies a final remedy for contaminated soil at the site and

complements a 1986 ROD that determined that no action was necessary to remediate shallow groundwater. The primary contaminants of concern affecting the soil are organics including polycyclic aromatic

hydrocarbons (PAHs), PCP, and dioxins.

The selected remedial action for this site includes

■ excavation and onsite treatment of 94,000 cubic yards of soil containing contaminants that exceed

target action levels using critical fluid extraction with liquid propane,

■ offsite incineration of residues containing the concentrated contaminants produced by this technology,

■ recycling or discharge of wastewater generated during the treatment process, and

■ spreading treated soil on the commercial portion of the site, and backfilling residential areas with

clean fill. 

According to the ROD, the estimated cost for this remedial action is $22,000,000. However, based on

a signed contract for a major portion of the remedial activities and estimates for the remainder of the

work, the expected cost of this cleanup is now expected to exceed $34,000,000.

SOURCE: U.S. Environmental Protection Agency, Region 6, “Record of Decision: United Creosoting Co. Site,” Dallas, TX, September 1989; Hendrick, E., Senior Project Manager, EPA Region 6, Dallas, TX, written comments, August 9, 1995.
18 | Cleaning Up Contaminated Wood-Treating Sites

Sometimes residues of the preserving chemicals can be found at a site in a nearly pure form

(21,23). Typically though, the highest concentrations of waste contaminants are found near treatment areas and waste pits (23). At many woodtreating sites, the primary contamination has

moved through the soils into nearby ground and

surface waters (23). Because PCP and most

PAHs have very low water solubility and were

often used after being dissolved in oil, the contaminants can form non-aqueous phase liquids

(NAPLs) when they come in contact with ground

or surface water (23). This means that the contaminant is in a liquid form that either floats on

or sinks below water it contacts. Contaminants in

the form of NAPLs are particularly difficult to

locate and treat.

EPA AND WOOD-TREATING SITES

Since 1980, EPA has classified 56 wood preserving sites as Superfund sites (17). At about 40 of

these sites, EPA has completed the process of

selecting a cleanup strategy for the soil, sludge,

sediments, and water contaminated by woodtreatment wastes. EPA’s process for selecting a

cleanup strategy at a Superfund site is described

in the ROD, which summarizes the basis for the

decision and describes the remedial strategy.

EPA’s work with wood-treating sites has produced about 47 RODs for 40 such sites. The

details of these sites, the cleanup strategies

selected by EPA, and the current land use of the

area surrounding the site are summarized in table

2-1. Current land use was included as an indicator of future use of a contaminated site.

Not surprisingly, the similarity in the contamination across wood-treating sites has resulted in

the selection of similar treatment and remediation strategies. At least 10 approaches have been

selected by EPA for cleaning such sites. For the

treatment of contaminated soil, sludge, and sediments at wood-treating sites, table 2-1 shows that

EPA has generally selected from among the following strategies: bioremediation, incineration,

thermal desorption, soil washing or flushing,

chemical dechlorination, solvent extraction, site

capping, solidification and stabilization techniques, construction of barrier walls, and disposal in RCRA authorized landfills. Figure 1-1 in

chapter 1 shows how often EPA selected various

strategies for dealing with soil, sludge, and sediments at 40 wood-treating sites as revealed in 47

RODs.

Incineration was a frequently selected remedy

during the period from 1986 to 1990. Since 1990,

the selected remedy is much more likely to have

been bioremediation (perhaps in combination

with soil washing or with limited incineration of

the most contaminated wastes), thermal desorption, or chemical dehalogenation. Groundwater

at wood-treating sites is typically dealt with by

pump-and-treat methods in conjunction with

ongoing monitoring. According to EPA, a general approach now used at wood-treating sites is

bioremediation to remove creosotes and PCPs

from soil, followed by capping and immobilization to deal with residual dioxins or metals (i.e.,

to ensure they do not leach from the soil). The

Libby Groundwater site (see table 2-1) is one

place where such an approach is being tried (1).

Generally no single technology can be used to

clean up an entire wood-treating site (8). Rather,

as in most of the RODs reviewed by OTA, a

combination of treatment technologies and control methods will be required. Boxes 2-3 through

2-7 illustrate the variety of technologies selected,

although many of these have not yet been fully

implemented. Often some contamination will

remain even after cleanup, and various institutional or engineering control strategies must be

used to prevent exposure to the remaining contamination. For example, the combination of

bioremediation or incineration followed by sitecapping (covering the site with a liner and clean

soil) and restrictions on future site use was used

in more than half the cases. 

In some cases a sequence of cleanup remedies

in a “treatment train” may be needed to address

the various contaminants. For example, when

metallic wastes are mixed with organic (PCP and

creosote) contaminants, bioremediation or thermal desorption to remove the organics may be

followed by immobilization to control the metal-
Chapter 2 Wood-Treating Sites and Their Cleanup | 19

lic waste (10). A variety of treatments may also

be used to clean up different areas of a contaminated site. Hot spots can be particularly difficult

to clean. A site manager may prefer to excavate

sludges, perhaps incinerating this material, while

applying bioremediation to the less contaminated

soils (1). These combined approaches have been

specified in the remedial actions for wood-treating sites reviewed by OTA.

The selection of a technology as documented

in a ROD does not necessarily mean that the

technology proved effective. In many cases,

cleanup has not been completed at the sites

reviewed by OTA; in other cases, an unsuccessful trial of the selected technology has led to a

change in plans.

EPA’S PRESUMPTIVE REMEDY 

APPROACH

EPA has found that most wood-treating sites

have very similar characteristics (21,23). EPA

has determined that it is useful to group woodtreating sites together based upon their common

characteristics, such as the contaminants present,

the environmental media affected by those contaminants, and the cleanup technologies selected

(23). Past experience with such sites can be summarized to streamline future site investigations

and remedy selection (21,23). 

As part of an effort to accelerate cleanup at

Superfund sites, the EPA Superfund program is

putting together a group of cleanup strategies

that have been used successfully at similar sites

in the past (21,22,23). EPA has also reviewed

other technologies that have less available performance data but nevertheless may be appropriate or useful for wood-treating sites (21, 23).

EPA calls these proven cleanup technologies

for common site types presumptive remedies.

Presumptive remedies are technologies for common types of sites selected on the basis of historical patterns of remedy selection and EPA’s

scientific and engineering expertise (23). EPA’s

presumptive remedies program uses Superfund

program experience in an effort to streamline

cleanup (23). The presumptive remedy approach

focuses only on proven technologies. In general

the approach would not consider a small-scale

demonstration such as pilot plant demonstrations

as sufficient proof for a recommended presumptive remedy (1). However, some other technologies with more limited performance data are also

considered by EPA (21,23). 

EPA’s presumptive remedies for treating soil,

sludge, and sediments at wood-treating sites with

organic contamination from creosote and PCP

are bioremediation, thermal desorption, and

incineration. Immobilization is the presumptive

remedy for treating inorganic contaminants at

sites where metallic salts have been used (23).

The presumptive remedy process is a decisionmaking strategy for selecting among these remedies. EPA expects to use this process at all woodtreating sites and expects to select one of the

remedies unless there are unusual site-specific

circumstances. Bioremediation should be chosen

unless it is shown to be infeasible. Incineration

should be selected only if bioremediation and

thermal desorption have both been shown to be

infeasible. So far, EPA’s presumptive remedy

approach for wood-treating site cleanup covers

only the contaminated soils, sludges, and sediments at wood-treating sites. EPA is currently

working on presumptive remedies for groundwater cleanup at wood-treating sites (23).

According to EPA’s presumptive remedy

analysis for wood-treating sites, incineration is

the most technically developed and proven technology (see table 2-2); however, it was not designated by EPA as the primary presumptive

remedy because of the difficulty in getting public

support for incineration. The other technologies,

including bioremediation, have track records

indicating they may be appropriate for this type

of site; however, the selection of technologies

that are less proven or less capable than incineration will always bring a greater risk of failure to

achieve cleanup goals.

EPA divided the presumptive remedy project

for wood-treating sites into two parts. One

project was directed toward summarizing

cleanup of PCP and creosote contamination. A

second effort was to evaluate dioxin cleanup
20 | Cleaning Up Contaminated Wood-Treating Sites

issues separately, but EPA has not yet completed

this aspect of the problem (1). Thus, the woodtreating site presumptive remedies documentation from EPA does not specifically address the

dioxin issue (1). For example, bioremediation

might have some limitations as a remedy for sites

like Texarkana, where PCP has been used. It

might give excellent results for cleaning up the

PCP and creosote, but it is not likely to adequately clean up the associated dioxins. Other

approaches may be needed to supplement bioremediation in such cases, such as soil capping and

site use restrictions (1).

EPA warns that the remediation technologies

considered in its presumptive remedy strategy

are at different stages of technical maturity—

from proven to innovative to emerging. Application of a specific technology to clean up a woodtreating site requires careful matching with specific site conditions. Estimates of treatment costs

for more mature technologies such as incineration and bioremediation can be quite reliable, but

estimates for innovative and emerging technologies can be less reliable. Incineration and biological treatment are proven at the commercial scale

(17). Nevertheless, most alternatives, including

biological treatment and thermal desorption,

require site-specific treatability tests to ensure

they will work (17). 

As a practical example of the risks of using

less mature technologies, the wood-treating site

project was the first presumptive remedy

approach attempted by EPA, but because of

delays it will be the third one actually published

(1). The main delay was caused by questions

about the efficacy of bioremediation, the primary

presumptive remedy indicated for wood-treating

sites (1). Although bioremediation has been

selected for a number of wood-treating sites, it

has only been completed at very few sites (1).

Moreover, there have been some failures with

bioremediation, sometimes caused by simple

oversights by the site managers and facility operators, such as overlooking the proper monitoring

of soil pH (1). Bioremediation also may have difficulty achieving very stringent cleanup levels

sometimes required for carcinogenic PAHs.

SUMMARY

In summary, contaminated wood-treating Superfund sites are a common type of site in the

United States. The wood-treating processes and

the types of chemicals used as wood preservatives were very similar at all wood-treating sites,

thus the contamination problems and the technologies and strategies that appear to work at these

sites are also similar. EPA’s decisions about how

to clean up contaminated wood-treating sites

show that, in general, about 10 technologies or

strategies are used at these sites, almost always in

combination. EPA has analyzed wood-treating

site cleanups and, based on success stories, recommends about a half dozen different technologies as presumptive remedies for cleaning up

such sites. EPA warns that most of these alternative technologies will not work in all situations

and that a site-specific analysis almost always

will be required. Nevertheless, it appears that

decisionmakers have a range of options for

addressing cleanup problems at wood-treating

sites.
Chapter 2 Wood-Treating Sites and Their Cleanup | 21

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

American Creosote 

Pensacola, FL

FLD008161994

85-09-30

Creosote,

PCP

PAHs Commercial & 

residential

12 ? RCRA landfill of soil 

and sludges

American Creosote 

Pensacola, FL

FLD008161994

89-09-28

Creosote, 

PCP

PAHs, 

PCPs, 

Dioxins

Commercial & 

residential

18 23,000 yd3 soil Bioremediation of soil

American Creosote 

Jackson, TN

TND007018799

89-01-05

Creosote, 

PCP

PAHs Partially 

developed

60 ? Incineration of 

sludges offsite at a 

fixed facility or onsite 

in a mobile incinerator

American Creosote 

Winnfield, LA

LAD000239814

93-4-28

Creosote, 

PCP

PAHs, PCP Mixed 

agricultural, 

residential, & 

recreational

34 25,000 yd3

highly 

contaminated 

sludge, 

250,000 yd3

soil

Incineration of 

sludge; 

bioremediation of soil

American Crossarm 

& Conduit

Chehalis, WA 

WAD057311094

93-06-30

Creosote, 

PCP

PAHs, 

PCP, 

dioxins

Commercial, 

light 

industrial, 

residential, & 

recreational

? ? Remove most highly 

contaminated soil; 

capping; institutional 

controls

Arkwood, Inc. 

Omaha, AR

ARD084930148

90-09-28

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Agricultural & 

light industrial

15 21,000 yd3

soil & sludge, 

3,000 gal 

sinkhole liquids

Soil washing or 

incineration onsite if 

washed soil exceeds 

PCP, dioxin, or PAHs 

cleanup levels; pump 

and treat oily 

sinkhole liquids; 

monitor groundwater

Baxter/Union 

Pacific Tie Treating 

Laramie, WY

WYD061112470

86-09-26

Creosote, 

PCP

PAHs, PCP ? 140 ? Slurry barrier wall to 

delay offsite 

movement of 

contaminated 

groundwater and 

surface soils while 

planning and 

implementing more 

permanent remedies

Bayou Bonfouca

Slidell, LA

LAD980745632

87-03-31

Creosote PAHs ? 55 150,000 yd3

sediment

Incineration, capping

(continued)
22 | Cleaning Up Contaminated Wood-Treating Sites

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

Broderick Wood 

Products Co. 

Denver, CO

COD000110254

91-09-24

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Predominately 

industrial

64 2,170 yd3

sludge, 500 gal 

oil

Transport sludge and 

oil to a RCRA 

recycling facility; 

offsite incineration of 

recycler residues 

(amended remedial 

action)

Broderick Wood 

Products Co. 

Denver, CO

COD000110254

88-06-30

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Primarily 

industrial

64 4,000 yd3

sludge, 31,000 

yd3 soil

Incineration onsite of 

sludge; groundwater 

monitoring

Brown Wood 

Preserving 

Live Oak, FL

FLD980728935

88-04-08 

Creosote, 

PCP

PAHs Rural & light 

agriculture

55 11,500 tons soil Biodegradation and 

transport of most 

severely 

contaminated soil and 

sludge to a RCRA 

hazardous waste 

facility; and groundwater monitoring

Burlington Northern 

Brainerd/Baxter, MN

MND000686196

86-06-04

Creosote PAHs Industrial & 

residential

? 9,500 yd3 soil Bioremediation of soil 

and sludge; capping 

with a RCRAapproved cover

Cabot/Koppers, 

Gainesville, FL

FLD980709356

90-09-27

Creosote PAHs Commercial 

& residential

99 6,400 yd3 soil Soil washing and 

bioremediation 

followed by 

solidification and 

stabilization; 

pumping and 

treatment of 

groundwater; 

monitoring groundwater and surface 

water

Cape Fear Wood 

Preserving 

Fayetteville, NC

NCD003188828

89-06-30

Creosote PAHs Industrial, 

agricultural, 

and residential

9 ? Soil flushing or a low 

thermal desorption 

process

Coleman Evans, 

Jacksonville, FL

FLD991279894

86-09-25

PCP PCP Residential & 

light 

commercial & 

industrial

11 9,000 yd3 soils 

and sediments

Incineration of more 

contaminated soil; 

groundwater pump 

and treat

(continued)

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)
Chapter 2 Wood-Treating Sites and Their Cleanup | 23

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

Coleman Evans

Jacksonville, FL

FLD991279894 

90-09-26

PCP PCP Residential, 

light 

commercial & 

industrial

11 27,000 yd3 soil 

& sediment

Soil and sediment 

washing; 

bioremediation, 

solidification, and 

stabilization of fines or 

sludges; covering the 

solidified mass; 

pumping and 

recovering 

groundwater

Havertown PCP Site 

Haverford Twp, PA

PAD002338010

91-09-30

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Mixed 

residential & 

commercial

12-15 ? Interim remedies 

include free product 

recovery wells, an 

onsite groundwater 

treatment plant, and 

monitoring 

groundwater

Havertown PCP Site 

Havertown, PA

PAD002338010

89-09-29

Creosote, 

PCP 

PAHs, 

PCP, 

Dioxins 

Commercial & 

residential 

12-15 200 barrels 

soil, 6,000 gal 

wastewater

Offsite land disposal 

of soil; oily debris and 

wastewater stored; 

multimedia monitoring

Idaho Pole Co. 

Bozeman, MT

MTD006232276 

92-09-28

Creosote, 

PCP

PAHs, PCP Light industrial 50 42,000 yd3 soil Bioremediation, soil 

flushing, capping

J H Baxter Co. 

Weed, CA

CAD000625731

90-09-27

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Operating 

wood site, 

pasture, 

woodland, & 

residential

33 >41,000 yd3

soil

Biological treatment 

and chemical fixation 

of contaminated soil; 

groundwater 

pumping with 

biological treatment; 

multimedia monitoring

Koppers 

(Morrisville)

Morrisville, NC

NCD003200383

92-12-23

PCP PCP, 

Dioxins

Commercial, 

light industry, 

& rural 

residential

52 2,930 yd3 soil Offsite incineration; 

treatability studies for 

dechlorination as a 

contingency remedy

Koppers Co., Inc., 

(Oroville Plant) 

Oroville, CA

CAD009112087

89-09-13

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Operating 

wood site, 

agricultural, 

residential, 

commercial, 

& industrial

200 334,000 yd3

soil, 

22,000,000 

yd3

groundwater

Biodegradation in 

situ or washing of soil; 

capping; pump and 

treat groundwater

Koppers Co., Inc. 

Galesburg, IL

ILD990817991

89-06-28

Creosote, 

PCP

PAHs, PCP Sparsely 

populated

105 15,200 yd3 soil Bioremediation

(continued)

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)
24 | Cleaning Up Contaminated Wood-Treating Sites

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

Koppers Co., Inc. 

Texarkana, TX 

TXD980623904

88-09-23

Creosote, 

PCP

PAHs, PCP Residential 62 3,300-19,400 

yd3 soil

Soil washing, offsite 

disposal 

Koppers Co., Inc. 

Texarkana, TX

TXD980623904

92-03-04

Creosote, 

PCP

PAHs, PCP Residential 62 ? Soil washing; 

relocating residents; 

deed restrictions

L.A. Clarke and Son

Fredericksburg, VA

VAD007972482

88-03-31

Creosote PAHs na 40 118,000 yd3

soil

Soil flushing and 

in-situ 

biodegradation; 

sediments 

biodegradation; 

landfarming 

excavated surface 

soil, sediments, and 

subsurface wetland 

soil; and 

groundwater 

monitoring

Libby Groundwater 

Contamination Site 

Libby, MT

MTD980502736

86-09-26

Creosote, 

PCP

PAHs, PCP Active lumber 

& plywood mill

? ? Reduce human 

exposure to 

contaminated 

groundwater by 

continuing and 

expanding a “buy 

water” plan 

sponsored by the 

onsite company; 

monitoring

Libby Groundwater 

Contamination Site 

Libby, MT

MTD980502736 

88-12-30

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Residential 

areas & 

businesses

? >30,000 yd3

soil & debris

Biodegradation of 

soil and debris; 

recycling and 

incinerating 

recovered NAPLs; 

capping; 

groundwater 

bioremediation; 

groundwater 

monitoring

Macgillis & Gibbs 

Co / Bell Lumber 

Pole 

New Brighton, MN

MND006192694

91-09-30

Creosote, 

PCP

PCP, 

PAHs, 

Dioxins

Residential & 

commercial

24 100,000 gal. 

PCP waste oil 

& sludges

Removing and 

separating PCP waste 

oil and sludges; 

wastewater 

bioremediation; 

groundwater pump 

and treat

(continued)

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)
Chapter 2 Wood-Treating Sites and Their Cleanup | 25

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

Mid-South

Mena, AR

ARD092916188

86-11-14

Creosote, 

PCP

PAHs, PCP ? 57 80,000 yd3 soil Hot spot stabilization; 

RCRA cap; oil and 

sludges transported 

to a RCRA facility; 

groundwater pump 

and treat; and 

groundwater 

monitoring

Midland Products 

Ola, AR

ARD980745665

88-03-24

Creosote, 

PCP

PAHs, PCP ? 37 <24,600 yd3

soil, sediments 

& sludges, 

450,000 gal 

groundwater, 

620,000 gal. 

lagoon fluids

Thermal destruction 

of contaminated 

soils, sludges, and 

sediments; wasteand groundwater 

pump and treat

Montana Pole and 

Treating

Butte, MT

MTD006230635

93-09-21

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Primarily 

industrial

? 262,000 yd3

soil, 9,100 yd3

debris, 26,500 

gal sludge 

LNAPs, and oil

Bioremediation of soil 

hot spots; soil flushing 

and in-situ 

bioremediation; 

incinerate offsite 

sludge, NAPLs, and 

oil; bioremediation or 

UV oxidation of 

groundwater

Moss-American 

Kerr-Mcgee Oil Co.

Milwaukee, WI

WID039052626

90-09-27

Creosote PAHs Railroad 

loading & 

undeveloped 

parkland

88 210,000 yd3

soil & sediment

Soil washing and 

bioremediation; 

covering remaining 

soil; removing 

pure-phase liquid 

wastes for offsite 

incineration; and 

groundwater 

monitoring

Newsom Brothers 

Old Reichold 

Columbia, MS

MSD980840045

89-09-18

Creosote, 

PCP

PAHs, PCP Primarily 

residential

81 30,300 yd3 soil, 

7,300 yd3

sediment, 650 

yd3 tar-like 

waste

Offsite disposal of soil 

and sediment; offsite 

incineration of tar 

and soil and sediment 

containing RCRA 

hazardous wastes. 

No remedial action 

planned for 

groundwater

(continued)

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)
26 | Cleaning Up Contaminated Wood-Treating Sites

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

North Cavalcade 

Street Site 

North Cavalcade, 

TX

TXD980873343 

88-06-28

Creosote, 

PCP

PAHs Residential, 

commercial, 

& industrial

21 22,300 yd3 soil, 

5,600,000 gal 

groundwater

Biodegradation in 

situ of soil (after pilot 

testing); groundwater 

pump and treat; 

offsite incineration of 

groundwater NAPLS 

Popile, Inc.

El Dorado, AR

ARD008052508

93-02-01

Creosote, 

PCP

PAHs, 

PCP, other 

organics

Mixed rural, 

residential, 

and 

commercial

41 165,000 yd3

soil and sludge

Bioremediation and 

capping; slurry walls 

to contain 

groundwater

Reilly Tar & Chem. 

St. Louis Park, MN

MND980609804

90-09-28

Creosote PAHs Residential 80 ? Pump and treat; 

groundwater 

monitoring

Rentokil Virginia 

Wood Preserving 

Richmond, VA

VAD071040752

93-6-22

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Light 

industrial, 

commercial, 

& residential

? 70 yd3

sediment & 

sludge, 12,400 

yd3 soil

Incinerate sediment 

and sludge offsite 

(with dechlorination 

for dioxins); pump 

and treat surface and 

groundwater; lowtemperature thermal 

desorption for soil; 

capping treated soil; 

monitoring 

groundwater

Saunders Supply 

Co.

Chuckatuck, VA

VAD003117389

91-09-30

PCP PCP, 

Dioxins

Mixed 

residential & 

commercial

7.3 25,000 tons soil Dechlorination of 

sediment; 

low-temperature 

thermal desorption of 

soil and sediment; 

monitoring 

groundwater

Selma Pressure 

Treating Co.

Selma, CA

CAD029452141

88-09-24

 PCP PCP, 

dioxins

Agricultural, 

residential, 

and industrial

<4 16,100 yd3 soil Solidification/

stabilization, capping

(continued)

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)
Chapter 2 Wood-Treating Sites and Their Cleanup | 27

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

South Cavalcade 

Street,

Houston, TX

TXD980810386

88-09-26

Creosote PAHs Residential, 

commercial, 

& industrial

66 30,000 yd3 soil, 

50,000,000 gal 

groundwater

Soil washing and 

capping; 

groundwater and soil 

washings pump and 

treat; offsite 

incineration or 

recycling of NAPLs; 

groundwater 

monitoring. 

Bioremediation of soil 

and groundwater if 

PRP demonstrates 

equivalent 

performance and 

costs

Southern Maryland 

Wood Treating 

Hollywood, MD

MDD980704852

88-06-29

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Agricultural & 

residential

25 102,000 yd3

soil & sediment

Incineration onsite of 

soil, sediments, and 

tank liquids; ground 

and surface water 

pump and treat; 

multimedia monitoring

Texarkana Wood 

Preserving Co. 

Texarkana, TX

TXD008056152

90-09-25

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Industrial, 

residential, 

agricultural

25 77,000 yd3

soil, sediments 

& sludges, 

16,000,000 gal 

groundwater

Incineration onsite of 

soil, sediment, and 

sludges; pump and 

treat groundwater

United Creosoting 

Conroe, TX

TXD980745574

89-09-29

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins

Currently 

occupied by a 

company & 

residential 

subdivision

100 94,000 yd3 soil Critical fluid 

extraction onsite of 

soil; offsite 

incineration and 

disposal of the liquid 

organic concentrate 

residues from critical 

fluid extraction; air 

monitoring

United Creosoting 

Conroe, TX

TXD980745574

86-09-30

Creosote, 

PCP

PAHs, 

PCP, 

Dioxins (no 

tetra)

Business & 

residential

100 ? Dispose of the soils 

contaminated when 

an appropriate 

facility or innovative 

technology becomes 

available; temporary 

cap over 

consolidated soils

(continued)

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)
28 | Cleaning Up Contaminated Wood-Treating Sites

Site Name

Location

ROD No.

ROD Date

Chemical 

useda

Primary contaminantsCurrent

land use

Site

area/

acres

Vol. material

to be treated Remediation strategyb

Westline Site 

Westline, PA 

PAD980692537

86-07-03

Creosote PAHs na 40 710 yd3 soil Incineration of 

deposits with a high 

heating value and 

low ash content; 

transport wastes to 

offsite RCRA facility

Wyckoff Co./

Eagle Harbor, 

Bainbridge Island, 

WA,

WAD009248295

92-09-29

Creosote, 

PCP

PAHs, PCP Primarily 

residential

40 <7,000 yd3 

sediment

Solidification/

stabilization; offsite 

disposal if 

necessary; capping

TABLE 2-1: Cleanup Strategies Selected by EPA for Superfund Wood-Treating Sites (Cont’d.)

TABLE 2-2: Evaluation of Presumptive Remedies for Wood-Treating Sites

Contaminants at Site

Presumptive Remedy 

Selected Efficiency of Contaminant Removal

PCP Incineration 90-99% (B,P,F)a

Creosote Thermal desorption 82-99% (B,P,F)

Creosote and PCP,

PCP and CCA,

Creosote and CCA, or

Bioremediation Average of 87% for PAHs and 

74% for halogenated phenols and creosols (P)

Creosote, PCP, and CCA Immobilization 80-90% TCLPb (B,P,F)

CCA Immobilization 80-90% TCLP (B,P,F)

SOURCE: U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, “Presumptive Remedies for Soils, Sediments, and Sludges at Wood Treater Sites,” EPA/540/F-95/006 (Draft), Washington, DC, May 1995.

NOTES: 

a Performance efficiencies have been demonstrated in benchmark (B), pilot scale (P), or (F) final remedies.

b The toxicity characteristic leaching procedure is a test of the effectiveness of immobilization methods.
| 29

3

Remediation

Technologies for

Wood-Treating Sites

he following are short descriptions of

some of the major cleanup technologies

and strategies used by EPA for cleaning

wood-treating sites. Remedies are

divided into three groups: destruction technologies; separation and concentration technologies;

and immobilization, engineering, and institutional controls.

The remediation technologies described here

are at different stages of technical maturity. Evaluations of the effectiveness and potential problems in applying mature technologies such as

incineration and bioremediation can be quite reliable. Evaluations of innovative and emerging

technologies are much less reliable. For that reason, the selection of a less mature technology as

a cleanup remedy will always require a trial demonstration to show that it works at the specific

site. Such demonstrations are crucial, because

unique local characteristics of soils and contamination can have unanticipated effects on performance. It should also be realized that some

combination of treatment and control strategies

is likely to be required for site cleanup, rather

than any single technology.

DESTRUCTION TECHNOLOGIES

Destruction technologies use thermal, chemical,

or biological means to chemically alter contaminants to non toxic or less toxic forms. Table 3-1

summarizes the effectiveness of some destruction technologies for contaminants found at

wood-treatment sites. 

❚ Incineration

Incineration, perhaps the oldest waste treatment

technology, uses very high temperatures to burn

waste materials. Incineration exposes organic

contaminants in soils, sludges, sediments or

other materials to very hot temperatures, greater

than 1,000°F, in the presence of air (7,17). These

conditions result in the combustion (burning) and

destruction of organic wastes. A secondary combustion chamber (afterburner) may be used to

help ensure that unburned organics do not enter

the flue gases. Flue gases are then quickly cooled

to below 350°F to minimize the possibility of

organics (like dioxin) reforming in stack emissions. Gases are then treated in air pollution control equipment to remove particulates and acids

T
30 | Cleaning Up Contaminated Wood-Treating Sites

before release through the stack. Incineration,

either onsite or offsite, was selected as part of the

cleanup strategy in 18 of 47 records of decision

(RODs) for wood-treatment sites reviewed by

OTA. However, in some instances, public concerns about the use of incineration have delayed

its application.

Incineration has effectively treated soil,

sludge, sediment, and liquids containing all of

the organic contaminants found at wood-treating

sites, and is considered by EPA to be proven at

the commercial scale. If a site cleanup requires

destruction of dioxins or furans, incineration is

among a limited group of effective technologies

(17). According to EPA, a “substantial body of

trial burn results and other quality assured data

verify that incineration can remove and destroy

organic contaminants (including dioxins and

furans) to the parts per billion or parts per trillion

level” (17,23). It has been shown in practice to

achieve more stringent cleanup levels than can

be consistently attained by any other wood-treatment site remedy (23). Incineration may be

particularly effective for treating highly contaminated hot spots such as the sludge pits that are

often present at wood-treatment sites. For these

reasons, EPA has recently designated incineration as one of the presumptive remedies to be

considered in treating organic contaminants in

soils, sludges, and sediments at wood-treating

sites.

Incinerators have been designed to handle a

wide variety of materials (e.g., soil, rubble,

sludges) and large volumes of material. Still,

practical difficulties with incineration may occur

in treating materials that have high moisture content, high levels of corrosive material, or elevated levels of toxic metals (21,23). Onsite

incineration is also unlikely to be economical for

treating small volumes (less than 5,000 cubic

yards) because of the high costs of setting up and

testing the incinerator (21,23).

Effective incineration requires control and

monitoring of operating conditions, emissions,

and residues. Emissions and residues that may be

of concern include the treated soils, wastewater

from air pollution control equipment, materials

captured from flue gases, and stack emissions.

Metals in soils cannot be destroyed by incineration; they remain in treated soils and ash. If solid

residues contain excessive amounts of toxic metals, they must be treated with a stabilization or

solidification process or disposed of in a suitable

landfill. Wastewater from the air pollution control equipment will contain captured particulates,

trace organics, and caustics that will require

treatment (e.g., carbon adsorption, filtration)

before discharge. Flue gases may contain metals,

other particulates, and acids. These can be

largely removed with the air pollution control

systems that often include wet scrubbers, electrostatic precipitators, and filter bag houses. One

primary public concern has been the possibility

of emission of dioxins and other toxic organics

from the stack. Careful attention to proper operating temperatures and residence times in the

incinerator can greatly limit the amount of these

unburned organics entering the flue gas. While

TABLE 3-1: Effectiveness of Destruction Options for Contaminants at Wood-Treating Sites

Destruction options

Contaminant Incineration Dechlorination Bioremediation

Dioxins/furans ✓✓✗

PCP and related materials ✓✧✧

PAHs ✓✗✓

Metallic compounds ✗✗✗

✓ = Demonstrated effectiveness ✧ = Potential effectiveness ✗ = No expected effectiveness

SOURCE: U.S. Environmental Protection Agency, Office of Research and Development, Contaminants and Remedial Options at Wood Preserving Sites, EPA/600/R-92/182, (Washington, DC: October 1992).
Chapter 3 Remediation Technologies for Wood-Treating Sites | 31

the public has been skeptical about incinerators

and questioned whether design standards will be

maintained in actual operations, safe operation

does appear attainable with carefully designed

and operated technology.

❚ Bioremediation

Bioremediation refers to the use of microorganisms (bacteria and fungi) to break down organic

chemical contaminants (15,17,18). It is a process

analogous to decomposing plant material in a

compost heap. Organic chemicals are ultimately

broken down to carbon dioxide, water, or methane, or converted to microbial cell material. Most

practical methods rely on existing soil microorganisms, rather than introduced cultures of

microorganisms. Bioremediation is considered a

relatively mature technology. As a result of past

experience, EPA has designated bioremediation

as the primary presumptive remedy for the treatment of organic contaminants in soils, sludges,

and sediments at wood-treating sites (17,21,23).

It has been selected for use at 17 of the 47 woodtreating sites reviewed by OTA.

In-situ bioremediation treats soils in place,

with no excavation required. The in-situ methods

generally rely on existing soil microorganisms,

adding nutrient- (e.g., nitrogen) enriched water to

stimulate microbial growth. It is often used in

conjunction with a groundwater pumping and

soil-flushing system. In this system, water is

injected into the soil to circulate nutrients and

oxygen. The groundwater is then recovered,

cleaned, and reintroduced. In appropriate circumstances, in-situ methods have shown promise

for treating soils containing the polycyclic aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP) contaminants typically found at woodpreserving sites. In-situ bioremediation alone is

not effective with very concentrated masses of

contaminants. However, even in those circumstances it may be effective when used in combination with other technologies.

Ex-situ technologies treat excavated soils in

controlled conditions where moisture, temperature, pH, oxygen, and nutrients can be adjusted to

encourage rapid microbial action. Ex-situ methods include the slurry-phase and solid-phase processes. Slurry phase bioremediation mixes

excavated soil or sludge with water in tanks or

lagoons, adding nutrients while controlling oxygen, pH, temperature, etc. Solid-phase bioremediation (sometimes called land treatment or land

farming) places contaminated soil in a lined bed,

with nutrients added. Composting is a variation

of solid-phase bioremediation that allows for

treatment of highly contaminated wastes by

diluting contaminated soil with a bulking agent

such as manure or straw. The increased volume

of treated material is a disadvantage. The solidphase methods have been widely used for hazardous waste treatment and have been demonstrated successful on petroleum refinery wastes

and at wood-treating sites with creosote-contaminated soil and sludge. These methods do require

attention to the potential for secondary groundwater and air pollution. A drainage treatment

system may be required to control leaching

chemicals, and a cover may be needed if volatile

organics could be released to the air while soils

are being mixed or spread. Although in-situ

bioremediation is cheaper, ex-situ bioremediation results in faster and usually better performance.

In pilot scale studies, bioremediation has

achieved cleanup efficiencies averaging 87 percent for PAHs and 74 percent for halogenated

phenols (23). However, the effectiveness of

bioremediation is site and contaminant specific

and the method should be selected only after

careful site characterization. Bioremediation will

not necessarily work for hot spots (such as

sludge ponds) with very high concentrations of

creosote, PCP, and related contaminants. Material from these hot spots might have to be

removed for treatment by other methods.

Although in theory it is feasible to dilute such hot

spots with uncontaminated soil and then treat

with bioremediation, most site managers prefer

to excavate the hot spots and ship the material off

site for incineration or RCRA-approved disposal.

Bioremediation may be appropriate for the

remainder of the site. Bioremediation is not suit-
32 | Cleaning Up Contaminated Wood-Treating Sites

able for treatment of sites with high levels of

inorganic contamination, such as the chromated

copper arsenate (CCA) used at some wood-treatment plants. There are no solid data on the effectiveness of bioremediation for dioxins or furans.

When these contaminants are present, a general

approach is to use bioremediation to reduce PCP

and PAH levels to below action levels in soil,

and then rely on capping and immobilization to

deal with metals or any remaining dioxins.

Bioremediation also works less well for the largest PAH molecules, those with more than 4-rings

in their structure.

❚ Chemical Dechlorination

Chemical dechlorination (also called dehalogenation) uses special chemical mixtures to treat

contaminated soil, sediment, sludges, and oils

(10,13,17,20). A chemical reaction caused by the

additives removes chlorine atoms from pollutants such as pentachlorophenol, dioxins, or

furans. In general, removing chlorine from such

chemicals converts them to less toxic products.

At wood-treating sites, dechlorination must

generally be used in combination with other

technologies such as thermal desorption or bioremediation since the methods do not work with

nonchlorinated materials such as the PAHs.

Dechlorination has been selected as a cleanup

technology in 2 of the 47 wood-treatment site

RODs reviewed by OTA.

Although not yet considered a fully proven

technology by EPA, dechlorination does have

some track record of success for the treatment of

the dioxin, furan, and PCP contaminants often

found at wood-treatment sites. Dechlorination

will not be useful for treating PAHs, which do

not contain chlorine. If site cleanup requires

destruction of dioxins, then dechlorination is one

of very few techniques that are capable of remediation (17). EPA data show that wood-treatment

site wastes containing dioxins and furans treated

with alkali polyethylene glycolate (APEG) for 45

minutes at 160°F showed greater than 99 percent

destruction of the dioxins and furans (10). However, there is some concern that incomplete

dechlorination of the heavily chlorinated dioxins

typically found at wood-treating sites (containing

up 8 chlorine atoms) could result in the production of much more toxic forms of dioxins including the most toxic 2,3,7,8-tetrachloro-p-dioxin

(TCDD, see box 2-2 in chapter 2).

Dechlorination can be used with a variety of

soil types, although some soils may be more

expensive to treat than others (10). The presence

of heavy metals and high soil moisture (greater

than 20 percent) may require special treatment,

and high organic and clay content may require

extended reaction times (21,23). EPA considers

that for each site the special chemical mixture

formulation and optimum process conditions

must be determined using treatability studies

(10). Chemical dehalogenation of soil can be

expensive because excavation is required and

large quantities of reagents are used (10).

The dechlorination technology is dominated

by a number of patented, proprietary processes.

One category of methods uses chemical reagents

referred to as alkali polyethylene glycolate

(APEG) (17). A related approach is the base-catalyzed decomposition (BCD) process, which

uses sodium bicarbonate or similar base mixed in

a heated reactor to treat chlorine-containing pollutants (17).

In the typical APEG process, soil or sludge is

mixed with the reagent to form a slurry. The

slurry is heated in a closed reactor to promote a

chemical reaction. During the reaction, chlorine

atoms in the contaminants are replaced, making a

water-soluble substance that can be washed from

the treated soil. After treatment, residual APEG

chemicals are recovered from the soil and reused.

The treated soil is washed and the washwater filtered through activated carbon to remove the

dechlorinated pollutants. The carbon filter and

spent reagent can be incinerated or sent for landfill disposal. To work properly, APEG dechlorination depends on very good mixing of the

chemical reagent and the contaminated materials,

requiring that soils be excavated and perhaps

crushed. High moisture content in the soil can

reduce the effectiveness of the method. High clay

content will increase the amount of chemical
Chapter 3 Remediation Technologies for Wood-Treating Sites | 33

reagent required. Because of the high cost of

polyethylene glycol, increased reagent use adds

significantly to cleanup expenses.

The BCD process was developed in an

attempt to address some of the practical problems experienced with APEG methods. It uses

cheaper treatment chemicals; its efficiency is less

affected by soil moisture and particle size; and

there are reduced volumes of waste for disposal.

Contaminated materials are heated in the presence of a base (sodium bicarbonate or sodium

hydroxide) and a hydrogen donor compound

such as oil. Hydrogen replaces chlorine atoms in

the pollutant molecule. One proprietary BCD

process in use at a wood-treating site is a combination of dechlorination technologies with thermal decomposition, in a two-stage treatment (3).

The first stage is thermal desorption of soil, in

which organic contaminants are evaporated and

partially decomposed. At this stage, BCD chemicals (e.g., sodium bicarbonate) are added to

enhance evaporation and to provide partial

dechlorination. The contaminants are driven

from the soil as vapors and particulates and then

captured in an oil solution. The remaining gases

are vented to the atmosphere (3). Contaminants

trapped in the scrubbing oil are periodically

treated in a chemical reactor for further dechlorination, again using BCD chemicals. The addition

of BCD chemicals to the soils in the initial thermal desorption stage is claimed to be better than

basic thermal desorption, but more results are

needed to confirm the advantage (3).

There are four main residuals from dehalogenation that can be of concern: the treated soil,

residual reagents, air emissions, and washwater.

Treated soils will contain some amount of the

treatment chemicals along with reaction byproducts from the original pollutants. Although the

treatment compounds do not appear to be toxic,

they may require further treatment, such as

chemical neutralization or incineration, before

disposal. The reaction byproducts in treated soil

have not been well characterized (10). Air emissions released during the heating and mixing of

the contaminated soils must be captured through

condensation or filtration. The efficiency in

removing contaminants from the off gases is not

well known. Washwater used to clean the soils

after treatment will contain traces of contaminants and process chemicals, and may also

require treatment.

SEPARATION AND CONCENTRATION 

TECHNOLOGIES 

Separation and concentration technologies are

designed to remove contaminants from the bulk

of the soils, allowing these cleaned soils to be

returned to the site, and concentrating the contaminants in a smaller volume of soil or solvent.

The contaminants are not destroyed, but concentration allows them to be treated efficiently by

other destructive means such as incineration or

bioremediation. Various distinct technologies fit

into this broad category, some of treating excavated soils and others allowing treatment of soils

in situ. Options for treating excavated soils

include soil washing, solvent extraction, and

thermal desorption. Soil flushing is used to treat

contaminated soils in place, often in combination

with bioremediation. Table 3-2 summarizes the

effectiveness of some separation and concentration options with contaminants found at woodtreatment sites.

❚ Soil Washing 

Soil washing is a water-based process for removing contaminants from excavated soil (17,19).

Contaminants are removed both by dissolving

them in the wash solution and by concentrating

them in a smaller volume of soil fines (the very

smallest, silt-like, soil particles). Contaminants

tend to bind to clay and silt particles, which can

be separated from larger particles and sand. The

particle size separation techniques are similar to

those used in sand and gravel operations. Various

additives (e.g., detergents and acids) can be used

in the water to increase the efficiency of separation. The large fraction of clean soil can often be

returned to the site. In other cases, a combination

of treatment technologies may be required. The

concentrated contaminants in the separated silts

and clays will require treatment by another tech-
34 | Cleaning Up Contaminated Wood-Treating Sites

nology, such as incineration or bioremediation.

The washwater is cleaned by conventional

wastewater treatment methods and then reused in

the process.

The success of soil washing treatment is

closely tied to the characteristics of the soils.

Separation works best for soils with relatively

large percentages of coarse sand and gravel.

Soils with high levels of clay and silt are poor

candidates for soil washing because little reduction in volume of contaminated material can be

accomplished. 

A wide variety of chemical contaminants can

be removed from soils by soil washing techniques. According to EPA documents, treatability studies at seven wood treatment sites show

that soil washing is effective for removing PCP,

PAHs, and metals from contaminated soil. As of

1992, soil washing or soil flushing had been

selected as a remedy in 11 out of 47 RODs at

wood-treating sites. Greater than 95 percent

removal efficiencies have been achieved in

recent pilot scale tests (17). However, the effectiveness of the technology at a particular site

does not guarantee its effectiveness elsewhere.

Site-specific bench or pilot scale treatability tests

are always required to determine the best operating conditions and wash fluid compositions.

❚ Solvent Extraction 

Solvent extraction uses organic solvents to

remove contaminants from excavated soils and

sludges, much like in a dry cleaning process

(11,17). The solvents are organic fluids, compared to soil washing which uses water as a solvent. Solvent extraction is most appropriate for

the removal of organic contaminants. Contaminants are extracted in the solvent, then concentrated for disposal by other means. There are

three general types of processes, distinguished by

the types of solvent used: conventional solvents,

near-critical or liquefied gases, and critical solution temperature (CST) solvents. 

In conventional solvent extraction methods,

alcohols, alkanes, ketones, and similar liquids are

used to remove contaminants. The solvent is

mixed with the contaminated material. After

mixing, the liquid is removed and any residual

solvent is driven from the soil by steam or heat.

The collected solvent, now containing contaminants, is sent to an extractor. The solvent is then

evaporated and collected for reuse, leaving a

concentrated residue of contaminants. Near-critical fluid or liquefied gas processes use butane,

propane, carbon dioxide, or other gases that have

been liquefied under high pressure. These materials seem to diffuse into soil better than standard

solvents, helping remove contaminants. The solvent extracts the contaminants and rises to the

top of the chamber, where it is collected. As

pressure is lowered, the contaminants separate

from the solvent, allowing the solvent to be

reused. CST systems rely on the unique ability of

some materials to mix with water and extract

contaminants at one temperature and to separate

from water at another temperature.

Table 3-2: Effectiveness of Separation Options for Contaminants at Wood-Treating Sites

Separation options

Contaminant Soil washing Solvent extraction Thermal desorption Soil flushing

Dioxins/furans ✧ ✧✓✧

PCP & related materials ✧ ✧✓✧

PAHs ✧ ✓✓✧

Metallic compounds ✓ ✗✧✧

✓ = Demonstrated effectiveness ✧ = Potential effectiveness ✗ = No expected effectiveness

SOURCE: U.S. Environmental Protection Agency, Office of Research and Development, Contaminants and Remedial Options at Wood Preserving Sites, EPA/600/R-92/182, (Washington, DC: October 1992).
Chapter 3 Remediation Technologies for Wood-Treating Sites | 35

Solvent extraction is not a destructive technology. The extracted contaminants may require

further treatment before disposal. Further, there

are a number of waste streams to be considered.

Any water separated from the soils will need

treatment. Solvent systems are designed to work

without air releases, but there must be concern

with the possibility of releases of the volatile solvents. The treated soils may also have significant

traces of solvent, depending on the care taken in

driving out the residual solvent during processing.

According to EPA, treatability studies at five

different sites show that solvent extraction is

very effective for removing PCP, PAHs, and, in

one case, dioxin and furans from contaminated

soil (17). The technology is generally not effective at removing metals contamination. Solvent

extraction, using liquefied propane, has been

selected as the remedy at only one Superfund

wood-treatment site reviewed by OTA.

❚ Thermal Desorption

Thermal desorption uses heat and agitation to

evaporate and separate but not destroy organic

contaminants from soil, sludge, or sediments

(12). Some additional technology is needed for

contaminant destruction. Thermal desorption

systems include rotary dryers, thermal screws,

vapor extractors, and distillation chambers. All

these systems heat the contaminated material to

between 200 and 1,000°F to evaporate, physically separate, and concentrate the organic

contaminants (12, 17). Thermal desorption was

selected as part of the cleanup strategy in 3 of 47

RODs for wood-treatment sites reviewed by

OTA. It has recently been designated by EPA as

one of the presumptive remedies appropriate for

wood-treating sites.

Unlike other processes, such as incineration,

that destroy contaminants, thermal desorption is

a contaminant separation process only (12). The

advantage of thermal desorption is that the volume of the separated contaminants that will

require eventual destruction or storage is substantially reduced by the process. Separated contaminants, contained in the off-gas from thermal

desorption systems (containing vaporized contaminants, particulates, and water vapor) require

subsequent treatment by some other technology,

such as incineration, dehalogenation, or chemical

neutralization. The contaminants are usually captured by condensation or on activated carbon.

Also, specific key organic contaminant classes

can be selectively evaporated and removed with

thermal desorption by carefully controlling the

treatment temperature (12).

Thermal desorption has a proven record for

treating contaminated soils, sludges, and sediments. According to EPA, thermal desorption

has been shown in treatability studies at two sites

to be effective for removing PAHs and PCP from

contaminated soil (17). It can successfully treat

PCP and creosote materials, but not inorganics

such as CCA (23). EPA considers thermal desorption an appropriate alternative technology

for cleaning up PCP and creosote at wood-treatment sites in cases where bioremediation is not

feasible (23). Difficulties may occur in treating

materials that have elevated levels of halogenated organic contaminants or contain mercury

or corrosive materials (21,23). Vendor data indicate thermal desorption technology can process

up to 70 tons per hour (12). However, EPA considers thermal desorption a less mature technology that requires site-specific treatability tests to

ensure it will work at a particular site (12).

Some thermal desorption systems are suitable

for removing dioxins and furans from soils.

Thermal desorption is one of several technologies EPA considers useful in cases of dioxin or

furan contamination (17). However, thermal desorption of some PCP and related compounds

may actually form dioxins and furans at certain

temperatures (23), much as they can form in

incinerator flue gases. Treatment systems must

be designed to minimize dioxin formation and to

remove these compounds from the off gases. A

full-scale proof of performance test with analysis

for dioxins should be done.

All thermal desorption systems require that

the contaminated soil, sediment, or sludge first

be dug up and transported to the system, pro-
36 | Cleaning Up Contaminated Wood-Treating Sites

cesses that may require physical enclosure for

dust control (12). At sites that are heavily contaminated with organics or with high moisture

content soil, thermal desorption may not be cost

effective (7). Very wet soil may require dewatering before treatment. Thermal desorption has not

performed well in soils that are tightly aggregated, largely clay (clay or silt soil may generate

excessive dust), or that contain large amounts of

rock fragments (12). 

❚ Soil Flushing

Soil flushing is an in-situ treatment using water

(perhaps with additives) to extract contaminants

from soils (9,17). Water is injected or soaked into

the soil. An underground collection system

allows removal of the flush water and prevents

contaminated water from spreading offsite. It is

often used together with in situ bioremediation.

The contaminated flushing water will also

require treatment.

Soil flushing is considered an innovative technology with limited experience as to its effectiveness. It can be used for the treatment of

wood-preserving sites, but treatability studies

must precede its selection as a cleanup remedy.

Two treatability studies have shown it to be moderately to highly effective at removing creosote

and other organics from wood-treating sites. In

combination with in-situ bioremediation, soil

flushing may prove to be a very cost-effective

remedy for sites contaminated with PCP and

PAHs. The soil flushing may remove high levels

of contamination that might otherwise interfere

with successful bioremediation.

IMMOBILIZATION TECHNOLOGIES AND 

INSTITUTIONAL CONTROLS

❚ Physical Isolation and Capping 

Even after the best cleanup of a wood-treatment

site some contaminants will remain. Because of

this, various long-term control strategies such as

fencing, restricting future use, and site capping

are used to prevent future human exposure to

remaining contamination. Institutional and engineering controls, such as soil caps and liners,

fences and warning signs, and deed restrictions

are used to reduce potential human exposure.

Ongoing monitoring of remaining contaminants

at a site is required to ensure that the controls

continue to work. Various site-restriction strategies were specified in 14 of 47 RODs for woodtreatment sites reviewed by OTA. Site capping

was specified in 24 of 47 RODs.

Physically capping a site is particularly useful

to complete the overall protection of a complete

wood-treatment cleanup strategy (23). A simple

cap may involve covering the treated area with

uncontaminated soil and putting in suitable

plants. More sophisticated capping may involve

a bedding layer, a gas-collecting layer, a clay

composite barrier, a geomembrane (plastic) composite barrier, a drainage layer, a protective

layer, a vegetative layer, an asphalt-hardened

cap, or a concrete-hardened cap (17, 23). 

These capping techniques can limit direct

human exposure, allow for better water runoff

and drainage, and limit surface water infiltration

and groundwater contamination. A general

approach, used for example at the Libby Groundwater site, is to use bioremediation for soil to

reduce PCP and PAH levels to below action levels, then rely on capping and immobilization for

dioxins. Control of dioxins and furans may be

considered adequate if the contaminated soil

meets leaching characteristic criteria (1).

❚ Solidification or Stabilization 

Solidification and stabilization techniques can be

used to reduce the mobility of residual contaminants in soils (14, 17). Solidification refers to

techniques that embed the waste into a solid

material. Stabilization refers to techniques that

chemically alter or bind the material to reduce its

mobility. Portland cement, fly ash and lime, and

other cement-like materials are commonly used.

The material can be injected into the soil and

mixed in to depths of up to 100 feet. The result

can be a solid mass or a granular material resembling soil.
Chapter 3 Remediation Technologies for Wood-Treating Sites | 37

These immobilization techniques are most

frequently used for the control of inorganic contaminants such as the metal compounds used at

some wood-treating sites. Immobilization has

also been successfully used for cleanups of PAH

and PCP wastes, although this solution always

leaves the concern for future risk since the contaminants are left on the site. It is not a conventional treatment for sites with high levels of

organic contamination. However, solidification

or stabilization can be used as part of a successful treatment train, following soil washing or

bioremediation.

One of the difficulties with these techniques is

in evaluating their long-term performance. Periodic monitoring may be necessary to make sure

that the technology is continuing to prevent the

leaching and spread of contamination. The effectiveness of the technique is measured primarily

in its ability to reduce the leaching of toxic

chemicals from the soils.

❚ Removal of Contaminated Materials

An obvious remedy for contaminated material,

including waste oils, debris, sludge, or soil, is to

transport it to a new site. For some situations—

for example highly contaminated sludge hot

spots or contaminated oil—excavation, transportation, and incineration offsite may be appropriate. However, according to EPA, it is usually too

expensive to ship quantities greater than 5,000

cubic yards of contaminated soil offsite for disposal, and pretreatment may be required before

shipment to another treatment facility (21, 23).

Removal and offsite disposal or treatment,

including incineration, was specified in 12 of 47

RODs for wood-treatment sites reviewed by

OTA.

REFERENCES

1. Avvisato, F., Office of Solid Waste and

Emergency Response, U.S. EPA, Washington, DC, personal communication, June 7,

1995.

2. Hendrick, E., Senior Project Manager, U.S.

EPA Region 6, Dallas, TX, personal communication, April 12, 1995.

3. International Technology Corporation,

“Technical Assessment of Base Catalyzed

Decomposition Technology for Application

to the Times Beach Remediation,” report

prepared for Agribusiness Technologies

Inc., July 19, 1994. 

4. U.S. Congress, Office of Technology

Assessment, Dioxin Treatment Technologies—Background Paper, OTA-BP-O-93

(Washington, DC: U.S. Government Printing Office, November 1991).

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38 | Cleaning Up Contaminated Wood-Treating Sites

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13. U.S. Environmental Protection Agency,

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EPA/540/R-93/519a, Washington, DC,

August 1993.

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Office of Research and Development, Center for Environmental Research Information,

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182, Washington, DC, October 1992.

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013B, Washington, DC, July 1991.

19. U.S. Environmental Protection Agency,

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EPA/540/2-91/020B, Washington, DC, September 1991.

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DC, May 1992.

21. U.S. Environmental Protection Agency,

Office of Solid Waste and Emergency

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Wood Treater Sites,” EPA 540/F-93/020,

Washington, DC, May 1993.

22. U.S. Environmental Protection Agency,

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23. U.S. Environmental Protection Agency,

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24. U.S. Environmental Protection Agency,

Region 4, “Record of Decision: American

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25. U.S. Environmental Protection Agency,

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Site (Morrisville Plant),” Atlanta, GA,

December 1992.

26. U.S. Environmental Protection Agency,

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Inc. Site,” Dallas, TX, September 1990.
Chapter 3 Remediation Technologies for Wood-Treating Sites | 39

27. U.S. Environmental Protection Agency,

Region 6, “Record of Decision: Texarkana

Wood Preserving Company Superfund

Site,” Dallas, TX, September 1990.

28. U.S. Environmental Protection Agency,

Region 6, “Record of Decision: United Creosoting Co. Site,” Dallas, TX, September

1989.

29. U.S. Environmental Protection Agency,

Region 9, “Record of Decision: Koppers Co.

Inc. (Oroville Plant) Site,” San Francisco,

CA, September 1989.