xvEPA
United States
Environmental Protection
Agency
Office of Research and
Development
Washington DC 20460
EPA/540/AR-92/015
October 1992
Demonstration of a Trial
Excavation at the McColl
Superfund Site
Applications Analysis Report
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
-------
-------
EPA/540/AR-92/Q15
October 1992
Demonstration of a Trial Excavation
at the McColl Super fund Site
Applications Analysis Report
Risk Reduction Engineering Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Printed on Recycled Paper
-------
Notice
The information in this document has been funded by the U.S
(EPA) under Contract No.
Program.
approved for publication as a U.S.
does not constitute endorsement or recommendation for use.
.S. Environmental Protection Agency
vative Technology Evaluation (SITE)
id administrative review and has been
EPA document. Mention of trade names or commercial products
68-02-4284 and the Superfund Innovative Technology Evaluation (SITE)
It has been subjected to the Agency's peer review and administrative review and has been
u
-------
Foreword
The Superfund Innovative Technology Evaluation (SITE) program was authorized in the 1986
Superfund amendments. The program is a joint effort between EPA's Office of Research land
Development and Office of Solid Waste and Emergency Response. The purpose of the program is to
assist the development of hazardous waste treatment technologies necessary to implement new
cleanup standards which require greater reliance on permanent remedies. This is accomplished
through technology demonstrations which are designed to provide engineering and cost data on
selected technologies.
This project describes the trial excavation performed at the McColl Hazardous Waste Site.
Excavation at this site presents unique problems due to the high potential for release of sulfur dioxide
and volatile odorous compounds contained in the waste. The excavation demonstration was used to
obtain information on the utilization of an enclosure and associated air treatment systems around the
excavation to minimize air emissions and the use of foam vapor suppressants to reduce emissions from
the waste during excavation. In addition, information was obtained on processing the tar fraction of
this waste by mixing it with cement and fly ash. The demonstration is documented in two reports: 1)
a Technology Evaluation Report describing the field activities and laboratory results; and 2) this
Applications Analysis Report, which interprets the data and discusses the potential applicability of the
technology.
A limited number of copies of this report will be available at no charge from EPA's Center for
Environmental Research Information, 26 Martin Luther King Drive, Cincinnati, Ohio 45268.
Requests should include the EPA document number found on the report's cover. When the limited
supply is exhausted, additional copies can be purchased from the National Technical Information
Service, Springfield, VA 22161, (703) 487-4650. Reference copies will be available at EPA libraries
in the Hazardous Waste Collection.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
.HI
-------
Abstract
In June 1990, the U.S. Environmental Protection Agency's Region IX Superfund Program, in
cooperation with EPA's Air and Energy Engineering Research Laboratory (AEERL), and EPA's
Superfund Innovative Technology Evaluation (SITE) Program performed a trial excavation of
approximately 137 cubic yards Of waste at the McColl Superfund Site in Fullerton, California. The
purpose of this work was threefold: 1) to determine if the waste could be excavated by use of
conventional equipment, 2) to decide if any treatment was necessary to improve the waste's handling
characteristics, and 3) to determine the magnitude of air emissions that could result from excavation
efforts. This information will be useful in me planning of a full-scale remediation of the highly acidic
petroleum refinery waste buried at the site. The trial excavation was conducted within a temporary
enclosure from which air was exhaustejd through a sodium-hydroxide-based wet scrubber and
activated-carbon-bed adsorber to reduce air emissions of sulfur dioxide and volatile organic com-
pounds. Vapor-suppressing foam was used in an attempt to suppress atmospheric releases from the
raw waste during excavation, storage, and processing. The air exhaust was monitored for total
hydrocarbons and sulfur dioxide before and after the air emission control system. In addition, total
hydrocarbons and sulfur dioxide were monitored along the site perimeter to determine the potential
impact of air emissions on the nearby community.
The McColl waste consists of mud, tar, and char. Excavation was conducted with a trackhoe, and
the waste was separated into stockpiles of mud, tar, and char for subsequent study and experimentation.
Upon completion of the work, the majority of the waste was placed back into the excavation pit and
covered with topsoil. Excess waste materials was stockpiled on-site in a controlled manner.
This Application Analysis Report presents an evaluation of the equipment used to control
emissions and to measure the resulting [emissions before and after the ah- control system. An
assessment of the foam vapor suppressants and information on the full-scale remediation costs of the
technology are also provided. The information contained in this report will assist in planning the full-
scale remediation of the McColl site and other similar waste sites throughout the country.
IV
-------
Contents
Foreword , iii
Abstract iv
Figures ,...„. ;.. vii
Tables . viii
Abbreviations and Symbols :. ix
Acknowledgements .. 1 x
1. Executive Summary 1
Introduction 1
Objectives , 1
Conclusions ; ...1
Design of Air Emission Control Technologies 2
Economic Analysis . 2
2. Introduction > 3
Purpose, History, and Goals of the SITE Program 3
SITE Program Reports 3
Key Contacts 4
3. Technology Applications Analysis 5
Technology Description 5
Conclusions Reached During SITE Demonstration at the McColl Site 5
Applicability of Air Emission Control Technologies 6
Wet Scrubber 6
Carbon Adsorption..... ...8
Vapor-Suppressing Foam , ...„ 9
Enclosure Structure 11
Other Equipment : , .....12
4. Design Analysis ,. 13
Design of Excavation Operations , 13
Air Ventilation System Design 18
Design of Air Pollution Control Devices ;>. 21
.5. Economic Analysis 25
Introduction 25
Basis for Process Design, Sizing, and Costing 26
Results of Economic Analysis 30
Conclusions and Recommendations 32
References.
.33
-------
Appendices |
A. Description of Technologies I 35
Enclosure and Exhaust Air Control System ....35
Foam Vapor Suppressants i 38
Waste Treatment Techniques 38
B. Summary of SITE Demonstration at McColl Superfund Site 43
Introduction J 43
Site Characteristics 43
Objectives 43
Excavation and Waste Processing 1 45
Waste Characteristics .1. 46
Community Impact .; . 47
Health and Safety Issues .; .'. 47
Costs of Excavation and Tar Processing.... , 47
C. Applicability of the McColl Enclosure and Excavation Technologies to Current CERCLA Sites 49
VI
-------
Figures
4-1 Excavation of North Half of Sump R-2
4-2 Excavation of Center Column in Sump R-2
4-3 Positioning of Enclosure on Sump R-2
4-4 Air Ventilation System Schematic for Excavation Enclosure...
A-l Enclosure Plan and Section
A-2 Excavation Site Enclosure
A-3 General Arrangement of Ventilation Air Cleaning Equipment.
A-4 Ventilation Ah- Cleaning Equipment and Ducting Layout
A-5 Scrubber Cross Section
A-6 Pug Mill
A-7 Pug Mill Paddles During Tar Processing
A-8 Char/Mud Crusher Schematic
B-l McColl Site
..14
..14
..15
..23
..35
..36
..37
..38
..39
..40
..41
..41
..44
vu
-------
Tables
4-1 Planning Results for Excavation Under an Enclosure at McColl 16
4-2 Total Excavation Quantities and Material Types :... 16
4-3 Conversion of Bank Measurement Volumes to Loose Measurement Volumes 17
4-4 Bulk Density of Composite Contaminated Material Stream 17
4-5 Excavation Cycle Time L... 18
4-6 Operating Time Requirements for Excavation of Composite Waste Stream 18
5-1 Lease and Purchase Costs for Excavation, Backfill, and Storage Equipment and
Enclosure Movement 27
5-2 Air Ventilation System Specifications and Costs 28
5-3 Estimated Costs for Waste Excavation, Waste Storage, and Fugitive Emission Control... 31
A-l Scrubber and Fan Specifications I 39
A-2 Specifications for Carbon Bed Adsorber ; 39
A-3 Properties of Foam Reagents 1 40
A-4 Fly Ash and Portland Cement Properties 40
B-l Maximum and Average Trial Excavation Rates ; 45
B-2 Waste Characteristics, As-Received Basis , 46
B-3 Summary of Onsite Costs i 47
C-l Current CERCLA Sites Where the McColl Enclosure and
Excavation Technologies May Be Applicable 50
Vlll
-------
Abbreviations and Symbols
AA Atomic Absorption
acfm Actual cubic feet per minute
AEERL Air and Energy Engineering Research Labora-
tory
APCD Air pollution control device
ARAR Applicable or Relevant and Appropriate Re-
quirements
ASTM American Society for Testing and Materials
BOAT Best demonstrated available technology
BNA Base neutral/acid (extractable)
CAM-WET California Wet Extraction Test for Metals
CCR California Code of Regulations .
CEM Continuous Emission Monitor
CERCLA Comprehensive Environmental Response,
Compensation, and Liability Act of 1980
CFR Code of Federal Regulations
cm/s Centimeters per second
cfm Cubic feet per minute
ft3 Cubic feet
yd3 Cubic yards
DAS Data acquisition system
DHS California Department of Health Services
DSA Drum storage area
EPA U.S. Environmental Protection Agency
EP Tox Extraction Procedure Toxicity Test-leach test
FID Flame ionization detector
ft/s Feet per second
g/ml Grams per milliliter
GC/MS Gas chromatograph/mass spectrometer
h Hour
hp Horsepower
HSWA Hazardous and Solid Waste Amendments to
RCRA-1984
ICP Inductively coupled plasma
IDLH Immediately Dangerous to Life and Health
kW Kilowatt(s)
LDRs Land disposal restrictions
Ib/min Pounds per minute -
MACT Maximum achievable control technology
m/s Meters per second
MDL Method detection limit
mg/kg Milligrams per kilogram
mg/m2 - min Milligrams per square meter per minute
mg/1 Milligrams per liter
ml/g
NAAQS
NCP
NIOSH
NPL
ORD
OSHA
OSWER
PAHs
Pb
PCBs
PEL
PID
ppb
PPE
ppm
psi
QAPP
RCRA
RFP
RI/FS
ROD
RPD
RREL
SARA
SITE
SO
SROA
TCLP
TECP
THC
TNMHC
TOC
TSCA
TSP
\ig/m3
VOC
Milliliters per gram
National Ambient Air Quality Standards
National Contingency Plan
National Institute for Occupational Safety and
Health
National Priorities List
Office of Research and Development
Occupational Safety and Health Act
Office of Solid Waste and Emergency Response
Polycyclic aromatic hydrocarbons
Lead
Polychlorinated biphenyls
Permissible Exposure Limit
Photoionization detector
Parts per billion
Personal protection equipment-
Parts per million
Pounds per square inch
Quality Assurance Project Plan
Resource Conservation and Recovery Act of
1976
Request for proposal
Remedial Investigation/Feasibility Study
Record of Decision
Relative Percent Difference
Risk Reduction Engineering Laboratory
Superfund Amendments and Reauthorization
Act of 1986
Superfund Innovative Technology Evaluation
Program
Sulfur dioxide
Supplemental Reevaluation of Alternatives
Toxicity Characteristic Leaching Procedure
Totally encapsulating chemical suit
Total hydrocarbons
Total nonmethane hydrocarbons
Total organic carbon
Toxic Substances Control Act of 1985
Total suspended particles
Micrometer
Micrograms per liter
Micrograms per cubic meter
Volatile organic compound
IX
-------
Acknowledgements
This report was prepared under joint direction and coordination of Jack Hubbard, Superfund
Innovative Technology Evaluation (SITE) Project Manager, U.S. Environmental Protection Agency
(EPA), Office of Research and Development, Risk Reduction Engineering Laboratory, Cincinnati,
Ohio and Pam Wieman, McColl Project ^llanager, United States Environmental Protection Agency,
Region IX, Hazardous Waste Management Division, Superfund Program. Contributors to and
reviewers of this report included John Blevins, EPA-Region IX, Gordon Evans of EPA's SITE
Program and Richard Gerstle of IT Corporation, Cincinnati, Ohio. Authors were Majid Dosani of IT
Corporation in Cincinnati and Edward Aiil of Edward Aul and Associates, Inc., Chapel Hill, North
Carolina. I
-------
Section 1
Executive Summary
Introduction
Region IX of the U.S. Environmental Protection Agency
(EPA), in cooperation with EPA's Air and Energy Engineering
Research Laboratory (AEERL) and EPA's Superfund Innova-
tive Technology Evaluation (SITE) Program, and with assis-
tance from theCaliforniaDepartmentof Health Services (DHS),
conducted a trial waste excavation project at the McColl Su-
perfund site in Fullerton, California.
In the early to mid-1940s, the McColl site was used for
disposal of acidic refinery sludge, and in 1982, it was placed on
the National Priorities List (NPL). The McColl waste is known
to release volatile organic compounds (VOCs) and sulfur
dioxide (SO2) whenever disturbed. Since 1984, the entire site
has been covered with soil in an attempt to minimize atmo-
spheric emissions of VOCs and SO2.
In February 1989, EPA and DHS issued a proposed plan for
the McColl project that named thermal destruction, either on or
off site, as the preferred remedy. Important components of this
remedy are the excavation and waste-handling activities that
must occur as a precursor to thermal destruction or any other
remedy that would involve ex-situ treatment of the waste.
Region IX determined that the trial excavation was necessary to
ascertain if the McColl waste could be excavated with conven-
tional equipment without releasing significant amounts of
VOCs and SO2 into the surrounding community. The trial
excavation was also necessary to define the treatment needed,
if any, to improve the handling characteristics of the waste as a
precursor to thermal destruction. A summary of the SITE
demonstration at the McColl site is presented in Appendix B.
Objectives
The objectives of the trial excavation at the McColl Super-
fund site were as follows:
1. To excavate approximately 100 yards of waste to
assess waste-handling characteristics and to deter-
mine if any treatment is required to improve handling
characteristics as a precursor to thermal destruction.
2. To determine the atmospheric emissions resulting
from the excavation activities.
3. To assess the degree of SO2 and total hydrocarbons
(THC) emissions control achieved through the use of
an enclosure and an enclosure exhaust treatment
system.
4. To determine the emission levels for SO2 and VOCs
at the fenceline of the McColl site as an indicator of
impacts on the local community.
5. To assess the effectiveness of vapor-suppressing
foam.
6. To assess potential problems that might occur during
excavation.
Conclusions
Based on the goal and objectives of the project, EPA believes
that the trial excavation was successful and that significant
information was obtained that will be useful in the design phase
of the full-scale remediation. The conclusions reached were as
follows:
Excavation under an enclosure is technically feasible.
Excavation and waste-handling activities are not
feasible without an enclosure equipped with an ex-
haust treatment system.
Existing technologies can be used to treat SO2 and
THC emissions generated by excavation activities.
Waste material was successfully treated to improve
its handling characteristics so it could be easily
processed into a thermal destruction unit if desired.
Workers were able to perform excavation and treat-
ment of the waste material at McColl while wearing
Level B or Level A personal protective equipment
(PPE) within the enclosure.
-------
The trial excavation had no significant adverse
pacts on the surrounding community.
im-
The vapor-suppressing foam did not perform as well
as expected in controlling SO2 and THC emissions
within the enclosure and therefore cannot be relied
upon exclusively to control emissions during activ-
ity-related disturbances of waste.
Design of Air Emission Control Technologies
System designs prepared for full remediation of the 12
sumps at the McColl Superfund Site call for the use i of the
excavation and fugitive emission control systems evaluated
during the McColl trial excavation. The general workflow for
the scenario evaluated calls for waste to be excavated from one
sump under an enclosure (with dimensions of 120 ft wdde by
300 ft long by 60 ft high) and loaded into rolloff bins for
transport by truck to the storage facility. Backfill operations
take place simultaneously at a second sump under a Second
enclosure. At the same time, a third enclosure is erected on the
next sump to be excavated. In this manner, excavation and
backfill operations proceed continuously to provide feed mate-
rial to the final treatment system. Storage operations takb place
under a fourth enclosure (with dimensions of 120 ft widely 240
ft long by 57 ft high).
The use of an enclosure for excavation and backfill opera-
tions requires that the larger sumps be excavated in two or more
steps, which results in re-excavation of a portion of these
sumps. Overall, approximately 25% more material must be
excavated when the enclosure is used than would be required
without the enclosure. Assuming the final treatment operations
process a nominal 100 tons/day of contaminated material plus
additives, the time required to excavate the entire volume of
material at the McColl site is estimated to be approximately 6.4
yrs, based on 300 operating days/yr. Evaluation of jwaste-
specific excavation rates indicates that excavation operations
arc not the rate-limiting step under this treatment scenario.
Under the requirement that workers inside the enclosures
operate in Level B PPE, calculations indicate that excavation
operations could produce an average of about 160 tons/day of
contaminated material over an 8-hr operating period and about
235 tons/day over a 12-hr period. j
For waste excavation at the McColl site, SO2 will be the
primary contaminant of concern and the basis for the air
ventilation system design. A system has been designed to
maintain SOa exposure for Level B-equipped workers at or
below 50 ppm. This SO2 level was selected as a reasonable
compromise between the Immediately Dangerous to Life and
Health (BDLH) level of 100 ppm and the Permissible Exposure
Limit(PEL) level of 2ppm. This level was selected by EPA for
conceptual design purposes only. It is recognized that the actual
acceptable level of emissions within the enclosure will be
dictated by OSHA regulations and any applicable or relevant
appropriate requirements (ARARs). The 50-ppm concentra-
tion limit, together with projections for "upper reasonable" SO2
emission flux rates and extent of waste surface areas exposed,
result in the specification of a 130,000 acfm ventilation airflow
rate for the excavation enclosure; 27,000 acfm for the backfill
enclosure; and 32,000 acfm for the storage enclosure.
Air pollution control devices (APCDs) have been designed
to remove contaminants from the ventilation air before this air
is released to the atmosphere. Each APCD train consists of a
35,000-acfm wet scrubber for SO2and paniculate matter (PM)
emissions control, three 12,000 acfm modular GAC units
operating in parallel for THC/organics emissions control, and
associated fan, blower, and ducting systems. For full-scale
remediation, the air delivery system will be arranged to provide
a continuous flow of fresh air past workers in high-emission
areas. In addition, the exhaust system will be designed to
capture emissions close to their sources to minimize the amount
of contaminants that escape into the general enclosure volume.
This approach will require that flexible, movable exhaust and
air-supply ducting be extended from the enclosure walls to
areas within the enclosures. In addition, the ducting should be
fitted with hoods to maximize emissions capture. Based on the
air ventilation requirements and the APCD size limitation, four
APCD trains will be required for the excavation enclosure and
one APCD train each will be required for the backfill and
storage enclosures.
Economic Analysis
The cost for full excavation of all contaminated material at
the McColl site with the systems described in the preceding
paragraphs was estimated to be $69.2 million, which translates
to a cost of $593/ton of in-place waste. This cost assumes that
equipment is purchased at the start of remediation; the esti-
mated cost to lease equipment over the 6.4-yr .remediation
period would be approximately 7% higher. The break-even
time period between the purchase equipment option and the
lease equipment option is about 3 yrs. These estimated costs
include waste excavation, waste storage, and fugitive emissions
controls; however, they do not include the final waste treatment
and disposal systems or pretreatment systems;
The largest components of the estimated costs are labor
(22%), supplies/consumables (21%), equipment (12%), and
utilities (11%). Most of the cost items are directly influenced
by the amount of time required for remediation. These cost
estimates reflect a 6.4-yr remediation period, based on a final
treatment processing rate of 100 tons/day. Excavation rate
calculations indicate that excavation operations are not the rate-
limiting step under this scenario and that remediation activities
could be accomplished in less time, which would reduce overall
costs.
Specification of the SO2 limit within the enclosure dictates
the size, and hence the cost, of the air ventilation system and
APCD equipment For the design examined, the marginal costs
for fugitive emission control are slightly more than twice the
costs for excavation without such control.
-------
Section 2
Introduction
This section presents information about the Superfund In-
novative Technology Evaluation (SITE) Program, discusses
the purpose of this Application Analysis Report, and provides
a, list of key personnel who may be contacted for additional
information.
Purpose, History, and Goals of the SITE Pro-
gram
In response to the Superfund Amendments and
Reauthorization Act of 1986 (SARA), the EPA's Office of
Solid Waste and Emergency Response (OSWER) and Office of
Research andDevelopment(ORD)establishedaformalprogram
called the SITE Program to promote the development and use
of innovative technologies to clean up Superfund sites across
the country. The primary purpose of the SITE Program is to
enhance the development and demonstration of innovative
technologies applicable to Superfund sites so as to establish
their commercial availability.
The SITE Program comprises four major elements:
• Demonstration Program
• Emerging Technologies Program
•. Measurement and Monitoring Technologies Pro-
gram
• Technology Transfer Program
The objective of the SITE Demonstration Program is to
develop reliable engineering performance and cost data on
selected technologies so that potential users can evaluate each
technology's applicability to a specific site compared with the
applicability of other alternatives. Demonstration data are used
to assess the performance and reliability of the technology, the
potential operating problems, and approximate capital and
operating costs.
Technologies are selected for the SITE Demonstration
Program through annual requests for proposal (RFPs). Propos-
als are reviewed by EPA to determine the technologies with the
most promise for use at Superfund sites. To qualify for the
program, a new technology must have been developed to pilot
or full scale and must offer some advantage over existing
technologies. Mobile technologies are of particular interest.
Once EPA has accepted a proposal, the Agency and the
developer work with the EPA Regional Offices and State
agencies to identify a site containing wastes suitable for testing
the capabilities of the technology. The developer is responsible
for demonstrating the technology at the selected site, and is
expected to pay the costs to transport, operate, and remove the
equipment. The EPA is responsible for project planning,
sampling and analysis, quality assurance and quality control,
preparing reports, and disseminating information.
The Emerging Technology Program of the SITE Program
fosters further investigation and development of treatment
technologies that are still at the laboratory scale. The third
component of the SITE Program, the Measurement and Moni-
toring Technologies Program, provides assistance in the devel-
opment and demonstration of innovative measurement and
monitoring technologies.
In the Technology Transfer Program, technical information
on technologies is exchanged through various activities that
support the SITE Program. Data from the Demonstration
Program and existing hazardous waste remediation data are
disseminated in an effort to increase awareness of alternative
technologies available for use at Superfund Sites.
SITE Program Reports
The results of each SITE demonstration are incorporated in
two documents: the Technology Evaluation Report and the
Applications Analysis Report. The Technology Evaluation
Reportprovides a comprehensive description of the demonstra-
tion and its results. This report is intended for engineers
performingadetailedevaluationoftiietechnologyforaspecific
site and waste situation. The purpose of these technical
evaluations is to obtain a detailed understanding of the per-
formance of the technology during the demonstration and to
ascertain the advantages, risks, and costs of the technology for
the given application. This information is used to produce
conceptual designs in sufficient detail to enable the preparation
of preliminary costs estimates for the demonstrated technology.
The purpose of the Applications Analysis Report is to
estimate the Superfund applications and costs of a technology
based on all available data. The report compiles and summa-
-------
design and test data, and other laboratory and field applica-
tions of the technology. It discusses the advantages, disadvan-
tages, and limitations of the technology. Estimated costs of the
technology for different applications are based on available
data on pilot- and full-scale applications. The report discusses
the factors, such as site and waste characteristics, that have a
major impact on costs and performance. I
The amount of available data for the evaluation (of an
innovative technology varies widely. Data may be limited to
laboratory tests on synthetic wastes or may include perfor-
mance dataon actual wastes treatedatthepilotor full scale. The
conclusions regarding Superfund applications that can be drawn
from a single field demonstration are also limited. A successful
field demonstration does not necessarily ensure that a tech-
nology will be widely applicable or fully developed to the
commercial scale. The Applications Analysis attempts to
synthesize whatever information is available and draw reason-
able conclusions. This document will be very useful to those
considering the technology for Superfund cleanups, and it
represents a critical step in the development and commercial-
ization of the treatment technology. :
Key Contacts
Additional information on the demonstration of trial exca-
vation at the McColl Site or the SITE Program can be obtained
from the following sources: '
t,
McColl Site Demonstration
Richard Gerstie, P.E.
IT Project Manager
IT Corporation
11499 Chester Road
Cincinnati, OH 45246
(513)782-4700
Edward F.Aul, Jr., P.E.
Vice President
Edward Aul & Associates, Inc.
115 Cedar Hills Drive
Chapel Hill,NC 27514
(919)942-4411
The SITE Program
Jack Hubbard
SITE Project Manager, McColl Site Demonstration
U.S. Environmental Protection Agency
Office of Research and Development
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7507
Region IX
Pam Weiman
McColl Project Manager
U.S. Environmental Protection Agency
Southern California Section
Superfund Remedial Branch
Hazardous Waste Management Division
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-2242
JohnBlevins
Section Chief ..,,..-...
U.S. Environmental Protection Agency
Southern California Section
Superfund Remedial Branch
Hazardous Waste Management Division
75 Hawthorne Street
San Francisco, CA 94105
(415) 744-2241
-------
Section 3
Technology Applications Analysis
This section addresses the applicability of the waste excava-
tion/processing and emission control technologies to remediate
various sites contaminated with wastes similar to those of the
McColl Superfund Site in Fullerton, California. The evaluation
of the technology's effectiveness and its applicability to other
potential cleanup operations is based primarily on the results of
the SITE demonstration, which are presented in the Technology
Evaluation Report (EPA 1990). The data generated during this
SITE demonstration will be used to aid in the design of an
effective air emission control system to potentially be used
during the full-scale remediation of McColl and other similar
Superfund sites.
Technology Description
Excavation at the McColl site presented unique problems
because of the high potential for the release of sulfur dioxide
and volatile odorous compounds contained in the waste. As a
means of avoiding the potential impact of air emissions on the
nearby community, the following measures were implemented
during trial excavation:
• Use of an enclosure operated under negative pressure
• Use of vapor-suppressing foam
• Operation of an SO2 scrubber
• Operation of an activated-carbon-bed adsorber
The trial excavation was conducted within a temporary
enclosure from which air was exhausted through a sodium-
hydroxide-based wet scrubber and an activated-carbon-bed
adsorber to reduce air emissions of sulfur dioxide and organic
compounds. Foam was used in an attempt to suppress atmo-
spheric releases from the raw waste during excavation, storage,
and processing. The air exhaust was monitored for total
hydrocarbons (THC) and sulfur dioxide (SO2) before and after
the air emission control system. The air was also monitored for
THC and SO2 along the site perimeter to determine the potential
impact of air emissions on the nearby community. A detailed
description of the technology is presented in Appendix A.
Conclusions Reached During SITE Demonstra-
tion at the McColl Site
The overall goal of the trial excavation at the McColl site
was to obtain information on excavation and waste-handling
activities to support the selection of thermal destruction or any
other remedy that would involve excavation activities as a
portion of the preferred remedial action and to aid in the design
of this remedy after its selection in a Record of Decision (ROD).
Of particular interest was whether the McColl waste could be
excavated with conventional equipment without having signifi-
cant adverse impacts on the surrounding community.
Based on the goal and objectives of the project, EPA
believes that the trial excavation was successful and that sig-
nificant information was obtained that will be useful in the
design phase of the McColl remediation process. The results of
the trial excavation, which are discussed in the Technology
Evaluation Report (EPA 1990), are summarized in Appendix
B. Conclusions and observations pertaining to the trial exca-
vation are presented below:
• More than 130 solid yd3 of waste material from
Sump L-4 was excavated with conventional excavation
equipment without significant adverse impacts on the
community.
• Excavation under an enclosure is technically feasible.
The enclosure used during the trial excavation was
successfully operated at or near negative pressure,
which allowed for emissions generated during the
excavation activities to be processed through an
enclosure exhaust treatment system consisting of a
sodium-hydroxide wet scrubber and an activated-
carbon-bed adsorber.
Although unexpected problems during the trial exca-
vation impeded the ability to excavate under the
enclosure, EPA believes that these problems can be
resolved by engineering practices during the design
ofthefinalremediation. Themostimportantimpedi-
ment to the trial excavation was the higher-than-
expected THC and SO2 emissions within the enclo-
sure. These higher-than-expected emissions neces-
sitated upgrading the personal protective equipment
-------
for the workers within the enclosure from Level B to
Level A protection (completely enclosed chemical-
resistant suit with supplied air).
The SOj emissions generated during the excavation
activities can be effectively treated (up to 99% [re-
moval efficiency) with existing technologies. The
high SO2 emissions entering the sodium-hydroxide
wet scrubber were efficiently treated to less than 1
ppm throughout the trial excavation. The removal
efficiencies were greater than 95% during mostof tfie
trial excavation and actually reached as high as 99%.
f
The THC emissions generated during the excavation
activities can be effectively treated (up to 90.7%
removal efficiency) with existing technologies. Al-
though the THC emissions were not controlled as
effectively as expected (greater than 90%) with ac-
tivated carbon, the removal efficiency ranged from
40 to 90.7% throughout the trial excavation. The
EPA believes that the less-than-expected removal
efficiencies can be corrected during the design phase
of the final remediation. Based on other experiences
with activated carbon, this is considered an appropriate
technology for removal of organics. !
I
The wastematerialwassuccessfully treated to improve
its handling characteristics so it could be easily pro-
cessed into a thermal destruction unit if desired. |
!
Lower airflow rates through the activated carbon unit
increased the THC removal efficiencies. This result
supports the theory that residence time is a critical
factor in the ability of activated carbon to remove
organic compounds in an airstream. j
The vapor-suppressing foam did not perform j as
anticipated in controlling SO2 and THC emissipns
within the enclosure, and its use cannot be relied
upon exclusively to control emissions during activ-
ity-related waste disturbances. i
Visual observations and dynamic-condition calcula-
tions indicate that the vapor-suppressing foam was hot
as efficient as expected in controlling emissions from
activities related to excavatingandprocessing the waste.
Visual observations indicated that the foam chemi-
cally reacted with the McColl waste, which inhibited
its ability to form a vapor-suppressing seal on the
waste. This reaction caused the foam to change color
(from yellow to red and orange) and to disintegrate
before forming a seal on the waste. ;
Dynamic-condition calculations indicated that the|ef-
fectivenessof the vapor-suppressing foam ranges from
50to80%»dependingontheactivityandthecompound
of concern. >
Excess water introduced into the enclosure through the
foaming activities had a significant impact on operations
within the enclosure. The excess water made the ground
surface slippery for both workers and equipment
The trial excavation had no significant adverse im-
pacts (i.e., exceedance of health-based levels estab-
lished in the McColl Contingency Plan) on the sur-
rounding community.
Based on observations by personnel during the trial
excavation, the noise level related to the excavation
and treatment activities was minimal. At no time
during the trial excavation were the health-based
levels (established in the McColl contingency plan
for SO2 and THC) exceeded at the fence-line moni-
toring stations. Although a small number of odor
complaints were received during the trial excavation
period, they were not excessive. Most of the com-
plaints were received after the trial excavation/treat-
ment activities were completed for the day, and may
not have been related to the excavation/treatment
activities.
Applicability of Air Emission Control Tech-
nologies
Many Superfund sites in the United States have problems
similar to those at the McColl site-i.e., the generation of toxic
air emissions during waste excavation and transportation that
may affect both site workers and residents of adjacent commu-
nities. Appendix C presents a list Of current CERCLA sites
where the emission control technologies used at McColl site
may be applicable. This section discusses the general applica-
bility and performance of air emission control technologies,
which were used during the trial excavation at the McColl site.
Wet Scrubber
A wet scrubber system is based on the principle of mass
transfer (called diffusion) in which the gaseous effluent stream
containing the contaminant to be removed is brought into
contact with a liquid in which the contaminant will dissolve.
The concentration gradient between the two phases is estab-
lished and diffusion occurs. The mass transfer rate at which
absorption occurs depends on the amount of liquid surface
exposed. It is a function of the liquid recirculation rate, the
packing size and shape, and distribution of the liquid over the
packing support plates.
Packed scrubbers are designed with either crossflow or
countercurrent flow. In the crossflow packed scrubber, the
airstream moves horizontally through the packed bed and is
irrigated by scrubbing liquor flowing vertically downward
through the packing. This scrubber is efficient in removing
noxious gases, entrained liquid particles, and dusts. The gas
-------
stream in the countercurrent-flow packed scrubber moves up-
ward in direct opposition to the scrubbing liquid stream, which
moves downward through the packing.
Countercurrent flow is advantageous in that the gas stream
with higher concentrations of contaminants contacts the spent
liquor at the inlet of the packing, and the fresh liquor coming in
at the outlet of the packing contacts with the least contaminated
gas. This process drives the gaseous contaminant into the
scrubbing liquid. When absorption is accompanied by chemical
reaction, this advantage no longer exists because the gas phase
equilibrium becomes zero.
A large interfacial area is required for the liquid to absorb
gas contaminants effectively. Providing a packing medium
over which the liquid is spread allows a greater area of contact
to be achieved. Not only is a large area required, but continued
liquid surface renewal is essential for efficient absorption. These
characteristics are provided by commercially available packings.
An important feature of the scrubber unit is the design of the
recirculation tank. Acting as a basin, this tank catches the
effluent from the scrubber and provides additional time for the
reactions to occur. The rate of recirculation is based on the
chemical kinetics or treatment time required for each of the gas
contaminants to react with the provided reagents in their re-
spective stoichiometric quantities.
Reagent usage and concentrations are based on the contami-
nants in the effluent gas. The gas contaminant treatment time
or residence time must be considered to determine adequate
column capacity and the optimal liquid-to-gas flow ratio.
One of the advantages of an absorption system is a removal
efficiency in excess of 99%. This not only results in low
emission rates, but also allows recovery of the material for reuse
in the process. Wet scrubbers have relatively small space
requirements and are low in capital cost and energy consump-
tion. The reagent-handling system, however, can substantially
increase the maintenance cost of the system. There are also
some disadvantages. For example, paniculate matter in the gas
stream may cause fouling and pluggage of the packing, and the
blowdown stream must be treated and disposed of in an envi-
ronmentally acceptable manner.
Wet Scrubber Performance During Trial
Excavation at McColl Site
During die trial excavation, a countercurrent-flow, packed-
bed, wet scrubber that used a mixture of sodium hydroxide
(NaOH) in water was used to control SO2 emissions. This
scrubber was designed to achieve an outlet SO2 concentration
of 2 ppm on a continuous basis, assuming that the average inlet
SO2 concentration would be about 10 ppm and the maximum
inlet SO2 concentration would be 200 ppm. The data gathered
during excavation show that the 2-ppm outlet SO2 concentra-
tion limit was met with few exceptions. One exception was a
50-min period on June 13 when the scrubbing liquor pH was
inadvertently allowed to drop to 2.9, well below the specified
control range of 10 to 13. During this period, the outlet SO2
concentration rose to a 5-min average maximum of 12 ppm.
The achievement of the outlet SO2 design criterion was espe-
cially impressive in light of the high inlet SO2 concentrations
experienced during a large portion of the operation.
As a result of these high inlet and low outlet concentrations,
the SO2 removal efficiency of the scrubber was higher than
expected. For the operating days on which daily average SO
inlet concentrations were above 10 ppm, the daily average SO2
removal efficiencies were always above 95%. On many of
these days, SO2.removal efficiencies exceeded 99%.
The normal operating range for the scrubber liquor pH was
established at 10 to 13 by the scrubber manufacturer priorto the
trial excavation. It was noted, however, that operation near the
high end of this range often caused excessive foaming of the
scrubber liquor near the bottom of the packed tower, which
subsequently resulted in an overflow of liquor out through the
inlet ductandinto the filter box. In lightof the high SO2 removal
levels demonstrated by the scrubber, the decision was made to
reduce the pH operating range to 7 to 10. This change elimi-
nated the liquor foaming and overflow problem, while consis-
tently low outlet SO2 concentrations were maintained.
The only other operational problem encountered with the
SO2 scrubber was occasional restrictions in the tower that
caused low ventilation airflow. The first episode occurred on
June 15 and was diagnosed as excessive solids passing through
the filter (upstream of the scrubber) and building up in the
scrubber packing. The low airflow conditions were relieved by
blowing down the scrubber liquor, washing down the packing,
and increasing the frequency of filter inspections and changes.
The filter system used during the trial excavation was a low-
efficiency, field-fabricated system that relied on residential
furnace filters as the filter medium.
The second episode of low airflow occurred on July 11. The
solids contentof the scrubber liquoratthis time wasmuch lower
than during the first episode. Inspection of the packing balls
through the lower access port showed that many contained a
buildup of black, soot-like material that appeared to becomposed
of very fine paniculate matter. Experiments revealed that the
airflow could be returned to normal levels by decreasing the
liquor recirculation flow rate from its normal range of 15 to 20
gal/min to near 5 gal/min. The outlet SO2 concentration re-
mained low even at the lower liquor recirculation flow rate;
therefore, this rate was maintained for the duration of the
program.
At the conclusion of operations, the scrubber was shut down
and opened at the top cone and the bottom access port for
inspection. At the top of the scrubber, the mist eliminator pad
was clean and free of any buildup. The packing balls at the top
of the scrubber were in a similar condition. At the bottom of the
scrubber, packing balls near the access port were found to be
partially obstructed with the previously described black buildup
plus a white crystalline material.speculated to be crystallized
-------
sodium hydroxide. Together, the combined solids filkjd ap-
proximately 25% of the volume of these packing balls. After
the first,6 in. of balls were removed from the lower access port,
however, it was clear that the packing balls in the center bf the
towerwere free of significantbuildup. Theair-distributioh grid
at the bottom of the packed tower was also free of solids
buildup. Thus, the cause of the second incident of low venti-
lation airflow could not be identified. All other portions of the
scrubber were in good working order at the completion of
program operations. j
With respect to a final remediation scrubber, one change
recommended as a result of trial excavation operations would
be the installation of a high-efficiency, industrial, partiqulate-
collection device upstream of the scrubber. This device should
be designed to capture both large and fine particles (e.g., Idiesel
engine emissions) to a high degree and thereby prevent the
buildup of solids in the scrubber liquor and packing material. In
addition, an automatic pH control system should be added that
will maintain thedesiredpHrangeby theaddition of caustic soda,
as opposed to the manual system used during the trial excavation.
Carbon Adsorption ,
Adsorption isaphenomenonthatoccurswhenagas or vapor
is brought into contact with a solid substance, which results in
the gas or vapor (called adsorbates) being collected On the
surface of the solid. This is a result of surface forces acting on
solids, gases, vapors, and dispersed material. The magnitude of
these forces depends on the nature of the solid surface a|nd the
type of molecules in the fluid. The adsorbing solid (or adsor-
bent) is generally an extremely porous material with large
internal surfaces. Adsorption may occur on the solid surface
alone. It may also be accompanied by chemical reaction (so-
called chemisorption). In the chemisorption process, gases or
vapors form actual chemical bonds with the adsorbent surface
groups. i
In a typical full-scale adsorption system, before entering the
adsorber, the gas stream from the emission source is passed
through a filter to remove entrained moisture droplets. Multiple
adsorber vessels are generally provided for on-line regener-
ation of the bed material. Gas will flow through one vessel,
where VOCs are removed, while the other vessel is regenerated
or on standby. Regeneration of the bed is achieved by passing
a hot inert gas such as low-pressure steam through the [unit in
reverse direction. The bed is then dried and cooled by passing
air through it. Dissolved VOCs are generally condensed in a
shell and tube heat exchanger. The VOCs can be recovered by
simpledecantation (in thecaseof water-insoluble materials)or by
distillation (in this case of water-soluble VOCs).
Activated carbon is one of the most versatile of the solid
adsorbents. For a physical adsorption, activated carbon is
limited to high-molecular-weight and nonpolar adsorbates.
Activated carbon can be specially treated with compounds of
transitional elements or chemicals to enhance the adsorption
capability for polar and low- molecular-weight gases or Vapors.
The performance of a carbon adsorption system depends on
the following conditions:
• Type of activated carbon
• Concentration of the adsorbates
• Temperature
• Humidity
• Gas flow rate and velocity.
The various sources and manufacturing processes used in
making activated carbon produce different grades of activated
carbons. An activated carbon with many pores big enough for
gas molecules to enter is very important for effective ad-
sorption. A steeper slope in the adsorption isotherm creates a
higher rate of adsorption. A higher rate of adsorption utilizes
the adsorbent more efficiently.
Carbon has an affinity for nonpolar molecules because of
the differences in their ionic structure. Compounds such as
hydrocarbons and most organic sulfur compounds (exceptHjS)
are adsorbed by carbon. This attraction makes carbon beds
excellent adsorbers of VOCs. Carbon's affinity for water vapor
in high-relative-humidity gas streams and sulfur compounds,
however, will reduce the life of the bed, which results in higher
operating costs for regeneration of the carbon.
Although the relative humidity of an emission stream may
be high, there are methods that can reduce these effects and
extend die life of the carbon bed. One such method is to mix the
gas streams with lower-relative-humidity ambient air. This
process will lower the cost of carbon regeneration by extending
the life of the beds, but it will result in an increased expenditure
for capital equipment and higher power consumption due to the
larger gas volume through the system. An alternative method
of reducing the relative humidity in the emission stream involves
cooling and condensing the water. This can be accomplished in
a shell and tube heat exchanger. The gas stream would then be
reheated to a temperature corresponding to the desired relative
humidity.
Carbon adsorbers are available in packaged units containing
all the necessary equipment. They are available in many
different sizes and configurations up to 100,000 scfm and can
be custom-designed for any application.
Fuel and power costs are minimal, and a high VOC removal
efficiency (99%) can be attained with low inlet concentrations.
Wastewater produced from regeneration of the carbon bed may
contain organic compounds that will require treatment prior to
disposal.
Carbon Adsorber Performance During Trial
Excavation At McColl Site
During the trial excavation, a granular activated-carbon bed
was installed after the wet scrubber. Two types of granular
activated carbons were used in the carbon adsorber to remove
hydrocarbon pollutants from the ventilationairstream. The first
-------
was a coal-based carbon that was used during the first 9 days of
excavation operations between June 7 and 15. The coal-based
carbon was replaced with a coconut-based carbon that was used
during the remaining operation period until system shutdown
on July 18, for a total of 32 operating days.
For an assessment of the performance of these carbons, the
hydrocarbon removal efficiencies associated with the maxi-
mum 5-min average inlet THC concentrations were calculated
and compared over time for the two carbon types. These data
show that the average daily hydrocarbon removal efficiency for
the coal-based carbon ranged from 61.8% (fresh carbon) to
49.4% over a 9-day period. For the coconut-based carbon,
average hydrocarbon removal efficiency ranged from 90.7%
(first full day of operation on newcarbon)to58.4%over the first
nine days of operation. By comparison, the performance of the
coconut-based carbon was slightly superior to that of the coal-
based carbon with respect to both initial activity and activity over
a 9-day period.
For the remainder operating period with the coconut-based
carbon, average hydrocarbon removal efficiency declined from
78.1% on June 26 to 24.2% on July 18. The exception to this
trend was an increase in average removal efficiency from
55.9% on July 10 to 71.6% on July 11. During other short-term
periods on those days, hydrocarbon removal efficiencies reached
93% on July 10 and 92% on July 11. The high removal
efficiencies on July 11 corresponded closely to the periods of
low airflow rates measured on this day; after the airflow rate
was returned to normal levels (by adjustment of the scrubber
recirculation rate), the hydrocarbon removal efficiencies de-
creased. Although no airflow rate data are available for July 10,
thehydrocarbonremovalefficiencydatasuggestthattheflowrate
was also low on this day.
Post-operative inspection of the activated carbon unit showed
no visible damage to or buildup on the spent carbon particles.
Water corrosion was evident on the steel rollers at the bottom
of the accumulator cabinet, however. It is unlikely that this
water came in the form of carryover water droplets from the wet
scrubber because the scrubber mist eliminator packing was in
good condition at the end of operations and the knock-out pot
(installed between the scrubber and the carbon unit) showed
very little water accumulation when checked regularly. A more
likely source of water was air moisture condensation on the
inside of the accumulator cabinet during the cool nighttime and
early morning hours. The air entering the cabinet was no doubt
saturated after passing through the packed-bed scrubber. Contact
of this saturated gas with cold cabinet walls would be sufficient to
cause water condensation and accumulation. Such condensation
and accumulation were noted on the top inside panel of the
accumulator cabinetduringperiodicfieldinspections.Thepresence
of water in the carbon unit was also supported by the hard black
powdery deposits found on the fan vanes and housing after
operations werecompleted. These deposits were likely formedby
the combination of moisture and attrited fine pieces of carbon
from the activated carbon unit.
The presence of moisture in the carbon unit helps to explain
the lower-than-expected hydrocarbon removal performance of
this system during the trial excavation. The design specifica-
tions for this system were 95% THC removal. The inlet THC
concentration, however, was much higher than expected be-
i cause of the low vapor-suppression effectiveness of the foam.
Nevertheless, the manufacturer of the carbon unit still expected
performance levels to be above 90% removal. Moisture
condensation onto carbon particles with subsequent reduction
in active surface area still appears to be the most likely expla-
nation for less than design performance. This explanation is
. consistent with the gradual loss of carbon THC removal effi-
ciency observed over time, as well as the increase in removal
efficiency that occurred when the airflow rate was significantly
reduced on July 10 and 11.
Several options would be available to eliminate moisture
condensation problems for a final remediation activated-carbon
unit These include installation of an air dryer upstream of the
carbon unit to lower scrubbed ventilation air moisture content, use
of a dry scrubber in place of the wet scrubber used for the trial
excavation, adding insulation/heaters to the accumulator cabinet,
andoperatingaductheaterupstreamofmecarbonimittomaintain
ventilation air temperature above the stream's dewpoint.
Vapor-Suppressing Foam
Aqueous, nondraining, air foams, i.e., stabilized foams
(developed by 3M Company) are useful for control of undesir-
able vapors and particulates such as those found at some
industrial sites (cement factories, mines, etc.), at waste sites
accepting hazardous materials (e.g., California Class I or n
sites), or National Priority List sites during remediation activi-
ties. The products work by forming a protective barrier over a
sourceof vapor or particulate emissions. They are sprayed onto
an area and form a tough, continuous, foam layer as they "cure"
in place. For time periods of at least several days, these foams
provide nearly total elimination of emissions of organic chemi-
cal vapors such as benzene, trichloroethylene, cyclohexane,
etc., and complete control of particulates and dust.
Vapor-suppressing foams are made by combining a foam-
ing agent (FX-9162) and a "stabilizer" (FX-9161) with water
and air, using an eductor system, and spraying this solution
through an air-aspirating nozzle. Each agent is proportioned
into the water line at a concentration of 6%. The foam "sets up"
(makes the transition from a fluid to a flexible solid foam) in
about 2 minutes.
It is also possible to use the foaming agent without the
stabilizer for temporary vapor suppression. For example,
during the remediation of a volatiles-containing waste site,
temporary foam could be used to cover the hazardous waste as
it is being excavated. Stabilized foam could be used to cover
trucks after they are loaded, excavation surfaces that are tem-
porarily inactive, and the entire workface overnight or through
weekends.
-------
Depending on the nozzle type chosen and the products used,
foams of various expansions can be made. (Expansion =
Volume of foam -t-Volumeof unfoamedliquid). Foamspf low
expansion (4:1 to 8:1) provide the best control of many VOCs.
Incases of extremely toxic emissions, low-expansion foams are
recommended. A fog nozzle, such as those used by many fire
departments, produces foam in this expansion range when FX-
9161 and FX-9162 are used, each at 6% in water.
In some field situations, highly irregular surfaces make a
somewhat higher foam expansion a more practical choice. The
B oots and Coots medium-expansion nozzle or a foam tube such
as that made by Elkhart can be used to produce foams in the 8:1
to 20:1 expansion range when FX-9161/FX-9162 are used.
A new 3M product, FX-9164 Penetrant, was devploped
specifically to control dust and particulate matter. When FX-
9164 is combined in water with FX-9161 Stabilizer, the liquid
sprayedfrom thenozzle thoroughly wets essentially any iype of
dust or particulate and then gels to form a solid, flexibly mass
noteasily disturbed by wind. FX-9164 is proportioned dt a 1%
conccntrationandFX-9161 ata6% concentrationinto the water
line. Theseproductsworkbestwithafognozzleandareapplied
as a liquid (not as a foam). |
The effectiveness of stabilized foam as a vapor-suppressing
medium is influenced by foam variables such as formulation,
foam depth, expansion ratio, and age, as well as the nature of the
particular hazard. Laboratory and field tests were conducted
with aqueous stabilized foam to investigate the effects of foam
variables and the nature of the hazard on vapor suppression
performance (Aim et al., 1987). The following trends were
noted: j
• For a period of days, the percentage suppression of
hydrocarbons did not change significantly. In a 12-
day laboratory experiment with cyclohexane and a 7-
day field trial with JP-5 fuel, the suppression •yyas
greater than 97%,even after the foam haddehydrated
to form a membrane.
• With high-polarity VOCs such as acetone and MEK,
suppression was in the 90 to 100% range for the first
several hours, decreased to the 80 to 90% range after
10 hours for foam application weights of at least 0,62
g/cm2. The higher polarity allows these VOCs to
diffuse faster than other hydrocarbons through .the
aqueous matrix of the foam.
• In general, vapor-suppression properties of stabi-
lized foams were not greatly affected by variation in
concentration of theFX-9162 foamer and FX-9i61
foam stabilizer components. Some improvement in
suppressing acetone vapors was noted when F.X-
9161 stabilizer concentration was doubled from 6%
to 12%, whereas a slight decrease in suppression of
cyclohexane vapor was noted when the FX-9162
foamer concentration was increased.
Theapplicationweightofstabilizedfoam used should
be determined by the nature of the hazard. Lowering
the application weight of 4:1 expanded foam from
0.62 to 0.31 g/cm2 did not significantly hurt perfor-
mance on cyclohexane; however, doubling the appli-
cation weight of stabilized foam from 0.62 to 1.24 g/
cm2 on acetone cut emissions by more than 50%.
Both laboratory and field tests showed that vapor
suppression performance was affected by the foam
expansion ratio, particularly with nonpolar VOCs
such as cyclohexane. Thus, increasing the air content
of foam to improve coverage should be practiced
only after careful consideration.
Foam Efficiency Evaluation During Trial
Excavation At McCott Site
During trial excavation, two types of water-based foam
supplied by 3M Corporation were selected: a temporary foam
that is effective for up to about an hour, and a stabilized foam
that is effective for at least a day. The earlier reported foam
effectiveness values were based on measurements of emissions
from stationary samples of waste (i.e., static conditions) with
and without foam application. No data were available on the
ability of the foam to control emissions during actual excava-
tion operations (i.e., under dynamic conditions).
Field Use of Foam During Excavation
During excavation, temporary foam was sprayed manually
on freshly excavated waste material or initially on stored
material. Stabilized foam was then sprayed on all waste surface
areas at the end of each work day. The overall qualitative
assessmentof the foam vapor suppressants used during this trial
was that they were not as effective as expected. This assessment
was based on visual observation of the foam, which disintegrated
and neither adhered well to the raw wastes nor formed a
cohesive film. The foam appeared to react with the highly
acidic waste and sometimes turned from greenish yellow to
deep red. Moreover, total hydrocarbon and sulfur dioxide
concentrations of the airstream in the enclosure exhaust control
system were higher than expected, primarily because the foam
failed to control them. When stabilized foam was placed on the
waste at the end of a period of activity, air concentrations slowly
decreased. This decrease, however, was partially due to no
fresh waste being excavated and exposed and partially due to a
constant flow of ambient ventilation air sweeping across the
enclosure, which had the effect of reducing concentrations, to
an equilibrium level. In an effort to increase the effectiveness
of the stabilized foam, the concentration of stabilizer was
increased. The intent was to double the stabilizer concentration.
Analytical data from 3M indicated the concentration increased
from 9.6 to 10.5%. Although the increase in the foaming
strength increased the foam's effectiveness, it did not solve the
existing problems.
10
-------
Foam Use During Mud Excavation and Movement
No significant SO2 emissions were observed for either mud
excavation or movement; small increases in THC concentra-
tions were recorded during these operations. The latter were
likely due both to THC emissions from operating equipment
with diesel engines and to emissions from mud waste. Because
of the limited number of comparison periods and the low
emission levels recorded for excavation with and without foam,
no substantial conclusions can be drawn regarding foam-control
effectiveness.
Foam Use During Tar Excavation and Movement
For tar excavation, the use of low-strength (9.6%) foam
resulted in a 73 % reduction in the average SO2 change rate* and
a 65% reduction in the average THC change rate. Other factors
being equal, the concentration change rate is directly propor-
tional to the waste emission rate. During the tar movement
periods, both low- and high-strength (10.5%) foams were
applied. Use of low-strength foam during tar movement opera-
tions resulted in a 50% reduction in the average SO2 change rate
and a 55% reduction in the average THC change rate. Increasing
the foam concentration to higher strength (10.5%) resulted in a
79% reduction in the average SO2 change rate and a 73% re-
duction in the average THC change rate. No data are available
for tar excavation with high-strength foam.
Foam Use During Char Excavation and Movement
Because of the high emissions expected and observed during
char excavation and movement, these operations were always
conducted with foam being applied. As a result, no data are
available for char operations without foam and, hence, no levels
of foam-control effectiveness can be established. The data do
show, however, that foam-controlled average SO2 and THC
concentration changerates were higher forchar excavation than
for tar excavation.
With respect to char movement, average SO2 concentration
change rates were 23% lower with high-strength foam (10.5%)
than with low-strength foam (9.6%). Average THC change
rates were 35% lower with high-strength foam than with low-
strength foam.
Problems Related to Foam Application
The traction difficulties encountered by the wheel-mounted
loader on the muddy floor of the enclosure were due to the
chemical breakdown of temporary and stabilized foam caused
by the char and tar wastes and the accumulation of purge water
from stabilized foam applications. At the completion of stabi-
lized-foam applications, foam and water had to be purged from
the delivery lines to prevent the foam from setting up in the
system; purging was not required after temporary foam appli-
cations. The foam breakdown and purge water accumulation
resulted in a layer of mud and foam 6 to 12 in. deep on the floor.
Besides making traction difficult for the loader, the mud also
prevented the free movement of tar and waste bins about the
enclosure (because of sinking) and made personnel footing
quite uncertain.
For the trial excavation, the problem was addressed by
.substituting a track-mounted Bobcat for the wheel-mounted
loader. Because of the Bobcat's smaller bucket size, this
change reduced the waste-moving productivity of operating
personnel. In addition, personnel took more care in directing
the stabilized-foam purge water into 55-gal drums rather than
onto the enclosure floor.
If foam application is retained for a full-scale remediation,
it may be necessary to devise a drainage system around waste-
handling areas to drain off accumulated water. In addition,
portable blowdown tanks should be located near foaming
operations to catch purge water and to remove it periodically
from the enclosure. Depending on the success of these systems,
track-mounted equipmentmay be requiredfor material-handling
operations.
A more effective vapor-control system would be desirable
to address these concerns in the full-scale remediation. Alter-
native formulations for foam should be investigated, especially
those that contain chemical bases and have the potential for
chemically bonding with the surface of the acidic McColl
waste. Alternatively, other vapor-suppression systems should
be evaluated, including the use of lime or limestone slurry such
as that applied to suppress dust in coal mines.
Even with improvements, however, the vapor-suppression
system cannot be expected to provide complete control of waste
emissions becauseofthedynamicconditionsofwasteexcavation
and movement. Maintaining pollutant concentrations inside
the enclosure between the Immediately Dangerous to Life and
Health (IDLH) and Permissible Exposure Limit (PEL) levels
will require a larger air-ventilation system. This means a larger
fan, air pollution control devices (APCDs), and associated
ducting. By generating a higher airflow rate, the larger venti-
lation system would provide more frequent turnover of the air
inside the enclosure and hence lower pollutant concentrations.
Enclosure Structure
For Superfund sites, where a fugitive air emission problem
exists, an enclosure structure can be very effective during the
excavation and transportation of waste. The enclosure ventila
* Change rate is the rate at which SO2 concentration increases over time.
Change rate = Cone, of SO2 at end of activity (ppm) - Cone, of SO2 at start of activity (ppm)
Time elapsed (min).
11
-------
lion air will be routed through an emission-control system to
prevent the escape of significant air emissions into the area
surrounding the excavation zone.
i
During the trial excavation at the McColl site, a rigid-frame,
PVC-covered enclosure structure was erected over part jof the
L-4Sumpprior to the startof excavation. Theenclosure proved
to be effective in preventing the escape of air emissions during
excavation. !
Problems Related to Enclosure Structure
The enclosure created a confined worik space in which tempera-
tures were approximately 20°F above the outdoor temperature.
During the trial excavation, diesel engines were operated on the
trackhoc,backhoe/loader,Bobcat,andpugmill. Theemissionsinside
the c^osuren^tingfrom these engines direcdyconmTjuted to woik
stoppages due to low visibility, and high THC levels. The exhaust
gases Horn diesel engines add heat, paniculate matter, and hydrocar-
bon species to the enclosure air (SO2 contributions were no doubt
smallbecauseof the low sulfur contentin diesel fuel). I
. I
ThehighemissionlevelsofSO.andTHCmeasuredforthetarand
char waste materials during the trial excavation caused work stop-
pages. Thesewcrediietohealmandsafelyconcerns,andinterference
with equipment steering and braking systems. Since the ventilation
air flow rate was fixed, this system was notable to pro vide enough
fresh air to keep pollutant concentrations below design levels.
Other Equipment
For the full-scale remediation, one approach would be to use
electric engines instead of diesel engines. The pug mill could
have been equipped with an electric engine for the trial excava-
tion had the electrical demand requirements not exceeded the
available supply on site. Further work should be conducted on
the size of the pug mill required for full-scale remediation and
the associated power requirements. It also may be possible to
use an electrically powered gantry crane system inside the
enclosure to move the material and to excavate some or all of the
waste materials.
If diesel engines on some of the operating equipment cannot
feasibly be eliminated for the full-scale remediation, a system
for directly venting the engine exhaust to the APCDs should be
investigated. It may be possible to suspend movable ducting
from the enclosure ceiling and to connect it to engine exhausts.
Such ducting would directly transport exhaust gases to the
APCD system without their entering the enclosure air. This
approach would be easiest to accomplish on equipment that
does not move about much within the enclosure (e.g., a pug mill
or trackhoe). For more mobile equipment, it might be more
feasible to direct exhaust gases through a filter, a carbon
canister, and a water cooler system mounted directly on the
machine. This approach would probably require frequent
changing of the filter media, carbon, and water to maintain its
effectiveness.
12
-------
Section 4
Design Analysis
The excavation and fugitive emission control systems
evaluated during the McGoll trial excavation have been used in
system designs prepared for the excavation operations, air
ventilation system, and air pollution control devices (APCDs)
associated with a commercial-size site remediation effort .
These designs illustrate how these systems could be applied to
a site where the excavation or handling of wastes would result
in the release of significant fugitive emissions that could pose
a potential health risk to nearby communities. In the example
scenario, system designs are developed for full remediation of
the 12 sumps at the McColl Superfund site in Fullerton, Cali-
fornia.
The scope of the remediation activities evaluated in this
analysis includes excavation of waste and associated material
under a rigid-frame enclosure, backfilling of the excavated
sump under a second enclosure, erecting a third enclosure on the
next sump to be excavated, and transport of the waste material
to an onsite storage facility consisting of a fourth stationary
enclosure erected over a concrete pad. The fugitive emission
control systems include vapor-suppressing foam application
units, air ventilation systems for each enclosure, the APCDs
required to reduce emissions of SO2 and THC in the ventilation
air to acceptable levels, an APCD emissions monitoringnetwork,
and a perimeter ambient air monitoring network. The scope
does not include the final waste treatment and disposal systems
or pretreatment systems.
The general workflow calls for waste to be excavated from
one sump under an enclosure and loaded into rolloff bins for
transport by truck to a storage facility consisting of a stationary
enclosure. Backfilling operations will take place simulta-
neously at a second sump under an enclosure. While excavation
and backfilling operations are proceeding under the first two
enclosures, a third enclosure will be erected on a third sump.
After excavation operations are completed on the first sump, the
excavation equipment and crew will be moved to the third sump
to begin its excavation. Backfill equipment and crews will
move to the second sump to complete its backfill. Following
completion of backfill operations, the backfill enclosure will be
disassembled and reassembled on the next sump (or sump
section) to be excavated. This sequence will be repeated until
all sumps on the site are completely excavated and backfilled.
This arrangement has the advantage of allowing continuous
excavation operations to provide feed material to the final
treatment system. It is, however, only one of several feasible
scenarios for the excavation of waste at the McColl site.
Design of Excavation Operations
Overall Excavation Rate
The maximum digging depth required to remove all waste
and potentially contaminated soil at the McColl site is 55 feet.
The sump requiring this depth of digging, identified as R-2, is
approximately 144 ft wide and 144 ft long. The widest enclo-
sure routinely available from Sprung Instant Structures, Inc., is
130 feet. The use of such a structure on large sumps such as R-
2 requires the performance of the excavation in two or more
steps, which necessitates re-excavation of some of the sumps.
The use of a larger, specially engineered enclosure that would
allow excavation of the entire sump under one enclosure was
also examined; however, the high cost of the larger enclosure
and APCD system exceeded the excavation cost savings that
would result
The general excavation procedure for a standard-sized enclo-
sure is illustrated in Figures 4-1 through 4-3. The north hah0 of
Sump R-2 will be excavated in the first step. As shown in Figure
4-1, equipment and personnel will descend to a depth of 24 feet in
the first excavation pass; the remaining material will.be removed
inthesecondpass. Because of the potential for cave-ins, the sides
of the sump above the 24-ft level must be sloped in accordance
withOSHArequirements in 29 CFR, Chapter XVH, SubpartP. It
is assumed that the soil and mud at the site will fall into the Type
C category and require the maximum slope of 1.5 foot horizontal-
to-1.0 foot vertical (1.5H/1 -0V). Because the lower portion of the
waste material will be hard char, which formed stable vertical
walls during the trial excavation, it is assumed that this material
can be excavated during full remediation and that the vertical sides
will remain intact while exposed. A slope of 0.5H/1.0V is
specified for the contaminated soil below the waste to provide a
stable support base for the unexcavated waste above the waste.
Figure 4-1 shows that a 120-ft wide enclosure is required to
perform this excavation, which allows for at least 10 feet of
clearance on both sides of the pit for personnel movement
13
-------
NORTH
LEVEL OF
GREATEST DEPTH
FOR PERSONNEL (24 ft.)
—25 II.
—39 II.
Flgum 4-1. Excavation of North Half of Sump R-2.
NORTH
0 It—i
10 (I.-
25 (I.—
39 II.—
55 It.—I
LEVEL OF
GREATEST DEPTH
FOR PERSONNEL (2« It.)
SUMP
R-2
UNEXCAVATEO
CENTER COLUMN
Flgura4-2. Excavation of Center Column In Sump R-2.
14
-------
After the north half of the sump has been excavated, the pit
will be backfilled and the enclosure moved to allow similar
excavation of the south half during the second step. As shown
in Figure 4-2, however, a column of unexcavated material will
be left in the center of the sump after Step 2 is completed. For
this center column tobeexcavated with the same size enclosure,
it will be necessary to backfill the north and south halves of the
sump with Type A soil (cohesive soils such as clay) as defined
by OSHA. This will allow the center column to be excavated
with sides sloping at 0.75H/1.0V (above the 24-ft level) instead
of 1.5H/1.0V. After excavation of the center column material
in the third step, the sump will be backfilled with clean soil for
the final time. The three placements of the enclosure structure
on Sump R-2 corresponding to the three excavation steps are
diagrammed in Figure 4-3. ^
This excavation approach requires double- or triple-han-
dling of a significant amount of material. Excavation of Sump
R-2 will require the most rehandling of material of any of the
sumps because of its depth. The number of enclosure place-
ments and die amount of material that would have to be re-
excavated for the remaining sumps at McColl being remediated
by this technique have been evaluated; the results are summa-
rized in Table 4-1. As shown, the smaller and shallower sumps
require only one enclosure placement, whereas the larger and
deeper sumps may require as many as seven placements for
complete remediation. The estimated total amount of material
to be handled with this approach is 151,700 yd3, which is 25.3%
greater than the in-place volume of waste, contaminated soil,
and sump cover.
A major assumption in this analysis is that excavation
operations will proceed at a pace consistent with feeding
approximately 100 tons of material per day to a pretreatment or
final treatment system. About 90% of this feed material would
be contaminated, and the balance would consist of additives
such as lime or cement. The final treatment device would
operate 6 days/week. Excavation operations would also take
place 6 days/wk, 50 wk/yr, which allows 2 wk/yr for overhaul/
maintenance/downtime. A second assumption is that the onsite
storage facility will accommodate up to 1 week's supply of
contaminated materials.
The overall time required for complete excavation of all 12
waste'sumps at McColl is based on the assumed final treatment
feed rate of 90 tons of waste per day, the bulk density of
excavated waste, and the total amount of contaminated material
(both in-place material and material that becomes contaminated
during re-excavation operations). As shown in Figure 4-1, the
total excavation volume expected at McColl is 151,700 cubic
yards bank measurement (cybm) versus an in-place volume of
121,200 cybm, which results in a re-excavation volume of 30,500
cybm. Based on materials handling experience at the trial
excavation, it is estimated that as much as one-third of this
NORTH
WEST
SOUTH
R-2: 144 ft. E/W X 142 ft. N/S
(AT WIDEST POINT)
ENCLOSURE: 120 ft. X 300 ft.
Figure 4-3. Positioning of Enclosure on Sump R-2.
15
-------
Tab/a 4-1. Planning Result* for Excavation Under an Enclosure at McColl.
Sump
Los Coyotes Area
L-1
L-2
L-3
L-4
L-5
L-6
Ramparts Area
R-1
R-2
R-3
R-4
R-5
R-6
TOTALS
Number of
Enclosure
Positions
4
2
2
1
1
1
4
3
2
2
2
7
31
|
Depth3, ft
I 31
i 35
37
! 33
; 45
35
28
1 55
31
30
i 35
! 45
! —
Length x
Widthb, ft
272 x 151
163x125
142x118
128x76
97x66
118x65
144x132
144x142
161x142
146x116
170x87
234x148
—
In-Place
Volume0,
yd3
13,800
10,500
12,500
6,200
5,700
8,400
8,800
9,800
6,800
7,300
11,800
19,600
121,200
Re-
Excavation
Volumed,
%
18.4
18.4
13.2
0.7
6.7
2.2
7.2
144.9
5.9
10.0
23.3
39.8
—
Total
Excavation
Volume,
yd3
16,300
12,400
14,100
6,600
6,100
8,600
9,400
21,100
7,200
8,000
14,500
27,400
151,700
a Depth of contaminated material. |
b Length and width of sump at grade level.
« Based on CH2M-HHI (1989) i
d Volume to be excavated in excess of in-place volume (including covers) as a results of material re-handling.
Table 4-2. Total Excavation Quantities and Material Typea (cybm)
Material Type
Waste
Designated
Questionable
Clean
TOTALS
In-Place Volume3
72,600
2,000
22,500
24,100
121,200
Reexcavation Volume
10,200
20,300
30,500
Total Volume
72,600
2,000
32,700
44,400
151,700
n Based on CH2M-HIII (1989)
overexcavated material could become contaminated as a result of
contact with other contaminated waste during backfilling and re-
excavation. Table4-2summarizes the estimated quantities of the
various materials to be excavated on the basis of this assumption
and the SROA estimates of in-place materials. ;
The waste material in Table 4-2 was further segregate^ into
mud, tar, and char based on the relative quantities of these
materials encountered in the trial excavation. These quantities
are shown in Table 4-3, in which bank measurement volumes
(equivalent to in-place volumes) are converted to loose
measurement volumes based on the material bulking factors
measured during the trial excavation. The total estimated loose
measurement excavation volume of 209,690 yd3 consists of
143,690 yd3 of contaminated material and 66,000 yd3 off clean
material. \
As discussed, the overall objective of the waste excavation
operations will be to supply 90 tons/day of contaminated
material to final treatment operations. An overall bulk density
of 89 lb/ft3 was estimated for the composite stream of McColl
contaminated material by using the methodology illustrated in
Table 4-4. Thus, 90 tons/ day of contaminated material porre-
sponds to 75 cubic yards loose measurement (cylm)/day of
excavated material. Based on the ratio of clean-to-contami-
nated material shown in Table 4-3,35 cylm of clean material
must be excavated for every 75 cylm of contaminated material,
on average. Thus the overall excavation rate required to supply
90 tons/day of contaminated material to final treatment will be
(75 cylm + 35 cylm =) 110 cylm/day.
At an average excavation rate of 110 cylm/day, the time
required to excavate the entire volume of material at the McColl
site (i.e., 209,690 cylm) is estimated to be 1906 operating days.
Total site excavation operations would be completed in
approximately 6.4 years for the 300 days/year operating scenar-
io discussed earlier.
Waste-Specific Excavation Rates
The feasibility of operating at an overall excavation rate of
110 cylm/day was evaluated by calculating waste-specific
excavation rates and applying a factor to reflect the use of Level
B personal protective equipment (PPE) for personnel working
16
-------
Table 4-3. Conversion of Bank Measurement Volumes to Loose Measurement Volumes
Material Type
Waste -Mud
Waste - Tar
Waste - Char
Designated
Questionable
Clean
TOTALS
Total
Volume,
cybm
13,070
10,160
49,370
2,000
32,700
44,400
151,700
Bulking
Factor
1.5
1.2
1.2
1.5
1.5
1.5
—
Total
Volume,
cylm
19,610
12,190
59,240
3,000
49,050
ee.eoff1
209,690*
Percent of
Total
Material
9.4
5.8
28.3
1.4
23.4
31.8
100
Percent of
Contaminated
Material
13.7
8.5
41.4
2.1
34.3
NA
100
a Ratio of clean-to-contaminated material is 66,600/143,090 = 0.465.
Table 4-4. Bulk Density of Composite Contaminated Material Stream (Basis: 100 ff of contaminated material, loose measurement)
Material Type
Mud
Tar
Char
Designated
Questionable
TOTALS
Volume3, dim
13.7
8.5
41.4
2.1
34.3
100
Bulk Density", Ib/cflm
84
33
74
120
120
—
Weight, Ib
1,151
281
3,064
252
4,116
8,863°
acflm = cubic feet, loose measurement.
b Based on trial excavation measurements.
C8863 lb/100 ft3 = 89 Ib/ft3 composite stream bulk density.
within the enclosure. For a backhoe of the type expected to be
required for this operation, the following average speeds apply
(Church 1981):
• Drag speed for loading - 91 f(/min
• Hoist speed - 60 ft/min
• Swing-return speed - 3.0 revolutions/min
• Loading and dumping constant - 0.13 min.
., Basedonthedepthsofcontaminatedmaterialreportedinthe
SROA, the average total excavation depth of the McColl sumps
is near 37 feet The average effective excavation depth will be
one-half this value, or 18 feet. An average dumping height of
15 feet was assumed for the excavation spoils pile and bucket
length. An average swing-return angle of 120 degrees was
assumed for the trackhoe during excavation operations. Based
on these estimates, an excavation cycle time of 1.02 minutes
was calculated by the methodology shown in Table 4-5. This
cycle time would apply to the excavation of overburden, mud,
and tar. A cycle time of 1.60 minutes was assumed for char
excavation because more time will be required for milling out
of this harder material by using the bucket (Church 1981).
Based on trial excavation results and recommendations in
Church (1981), the dipper factors* (i.e., cubic yards bank
measurement/cubic yards bucket capacity) assumed were 0.46
for overburden and mud and 0.66 for char and tar. The backhoe
bucket capacity for full-scale remediation operations is ex-
pected to be near 3 yd3.
For typical excavations of rock or soil, operations proceed
for an average of approximately 50 min/hr (Church 1981).
The anticipated use of Level B personal protective equipment
(PPE) for the McColl excavation is expected to result in an
overall production efficiency as low as 25% of typical effi-
ciencies, or an average of 12.5 minutes of excavation per
operating hour. This information, plus the factors cited in the
preceding paragraph, were used to estimate excavation rates
for individual waste types, as follows:
12.S min/oper. h x 0.46 cylm/yd3 bucket capacity x 3.0 yd3 bucket/load
1.02min/load
= 16.9 cybm/oper. h
Applying the trial excavation bulking factor of 1.5 yields an
excavation rate of 25.4 cylm per operating hour. This excava-
tion rate applies to overburden and mud excavation. The same
procedure, but with different values for the dipper factor, cycle
time, and bulking factor, was used to calculate excavation rates
of 29.1 cylm/h and 18.6 cylm/h for tar and char excavation,
respectively.
A typical day will likely involve the excavation of only one
type of waste. Based on the preceding waste-specific excava-
tion rates (which incorporate Level B PPE effects), the follow
ing operating times can be estimated directly for the five major
types of contaminated materials to achieve the target average
daily excavation volume of 110 cylm:
' Dipper factor is inversely proportional to bulking factor (bulking factor for overburden and mud is 1.5 and that for char and tar is 1.2).
17
-------
Table <1-5. Excavation Cycle Time
Operation
Loading and dumping
Hoisting within pit
Swinging
Hoisting above grade
Returning and lowering to grade
Lowerinq within pit
Rate
Constant
60 ft/min
3.0 rprh
60 ttYmin
3.0 rprrj
190 ft/min
Distance
Constant
19ft
120°
15ft
120°
19ft
TOTALS
Cycle Time, min
0.13
0.32
0.11
0.25
0.11
0.1
1.02
• Mud-4.3 operating hours
• Tar - 3.8 operating hours
• Char - 5.9 operating hours
• Designated or questionable - 4.3 operating hours i
For a composite daily waste stream, the calculations in
Table4-6 indicate an average of 4.8 hr of excavation operations
would be required to meet the target volume of 110 cylm/day.
These system design considerations indicate that excava-
tion of contaminated materials at the McColl site can be readily
accomplished at rates sufficient to supply a final treatment
system operating at 100 tons/day. Calculations indicate that
excavation operations could produce an average of nearly 160
tons/day of contaminated material over an 8-hr operating
period and nearly 235 tons/day over a 12-hr operating period
(the maximum period for daylight operations).
Air Ventilation System Design
The design of the air ventilation system for the enclosure is
predicated on the emission rate of contaminants within the
enclosure and the specified limit for contaminant air concentra-
tions. For the waste at the McColl Superfund Site, SO2 will be
thcprimarycontaminantof concern in lightof the high emission
rates noted during the trial excavation and the concentration
levels required to protect worker health. The ventilation air
system has been designed to maintain worker SO2 exposure (on
an 8-hr time-weighted average) at or below 50 ppm. This level
is chosen as a reasonable compromise between the IDLH level
oflOOppmandthe PEL level of 2 ppm because workers inside
the enclosure will be wearing Level B PPE. This levej was
selected by EPA for conceptual design purposes only.' It is
recognized that the actual acceptable level of emissions within
the enclosure will be dictated by OSHA regulations and any
applicable ARARs. This 50-ppm maximum SO2 concentration,
together with the SO2 emission rate, defines the ventilation air
requirements within the enclosure. For this discussion, design
of the ventilation system for the excavation enclosure will be
considered first, followed by the designs for the backfill and
storage enclosures.
Excavation Enclosure Ventilation System
At the McColl site, waste is expected to be excavated via a
backhoe operating within the pit at the working face. Excavated
waste will be loaded onto a spoils pile near the working face to
allow the backhoe to workat maximum efficiency. A front-end
loader will pick up waste from the spoils pile and carry it to the
truck-staging area near one end of the enclosure. The loader
will load the waste directly into a truck's waste container (most
likely a 40-yd3 rolloff bin). After the rolloff bin is full, a layer
of stabilized foam will be applied to the top surface and a tarp
will be placed over the container to control emissions during
transport and storage. The truck will then leave the excavation
enclosure via a vehicle air lock and transport its load to the
storage area.
Emissions of SO2 within the excavation enclosure will come
from two major source types: dynamic waste surface areas and
static waste surface areas. Dynamic surface areas are those
where the waste is being actively moved or disturbed. Static
areas are those where the waste is exposed but is not being
moved or subjected to regular disturbances. The dynamic waste
areas will include the moving/disturbed areas associated with
the working face, spoils pile, rolloff bin, backhoe, and loader
buckets. Based on the trial excavation experience, no foam will
be applied to these areas for vapor suppression because the
effectiveness of foam is limited under dynamic conditions and
Tabto4-G. Operating Time Requirement* for Excavation of Composite Waste Stream (Baala: 110 cylm of excavated material,
avoraga dally volume)
Material Type
Mud
Tar
Char
Designated
Questionable
Clean
TOTALS
l
Volumer %
9.4 :
5.8 i-
28.3 ;
1.4
23.4
31.7
100.0
Volume, cylm
10.3
6.4
31.1
1.5
25.7
34.9
110.0
Excavation Rate,
cylm/opr. hr
25.4
29.1
18.6
25.4
25.4
25.4
—
Required
Operating Hours
0.41
0.22
1.67
0.06
1.01
1.37
4.75
18
-------
because of other problems (such as slippery surfaces) related to
its use. Static areas within the enclosure will consist of all other
areas of exposed contaminated materials that are not actively
involved in the excavation operations. Stabilized foam will be
applied to these areas to suppress emissions. Based on the trial
excavation experience, an average suppression efficiency of
70% is assumed to be achievable for these static areas by
reapplying stabilized foam every 3 days.
Previous investigations at the McColl site indicated that SO2
(and THC) emissions from contaminated materials occur in two
forms: 1) as higher-level "puff emissions generated immedi-
ately following waste disturbances, and 2) as lower-level steady-
state emissions generated after puff emissions have subsided
(Radian 1982). The duration of the puff emissions is on the
order of 30 seconds to 1 minute, whereas measurements indi-
cate that steady-state emissions may continue indefinitely.
Based on data from the previously cited field investigations,
"upper reasonable" SO2 emission flux rates at McColl were
estimated to be 47,000 mg/m2-min for puff emissions and 1000
mg/m2-min for steady-state emissions. These rates are char-
acteristic of the upper range of the rates measured, but they do
not include rates that were significant "outliers."
There will be four sources of puff emissions within the
excavation enclosure, all associated with waste disturbance or
movement operations. The first source will be at the excavation
working face. The greatest source of puff emissions will be the
char waste at the site because it accounts for the greatest volume
of vapor-releasing material and has been associated with very
high SO2emission levels (as measured during the trial excavation
and previous field-study flux chamber measurements). Based
on the preceding excavation operations discussions, the cycle
time for char excavation is expected to be near 1.6 minutes. This
implies an average of nearly 38 buckets per operating hour,
assuming that operations continue uninterrupted for an hour.
Based on bucket dimensions, the exposed surface area of the
working face is estimated to be near 2 m2.
The second source of puff emissions will be the deposit of
excavated material by the backhoe onto the spoils pile near the
working face. The frequency and the exposed area for puff
emissions will be the same for this operation as for excavation
because the same equipment will be involved.
The third puff emission area will be the pickup of waste
material off the spoils pile by the loader. The frequency of
disturbances by the loader is expected to be about 23 buckets/
hour for a 5-yd3 loader working in conjunction with a 3-yd3
backhoe. The surface area of disturbed waste will be approxi-
mately 3.5 rn2, based on typical loader bucket dimensions.
The fourth area of puff emissions will be the deposit of waste
by the loader into a rolloff bin. Because the same equipment will
be used for this operation as for waste pickup from the spoils pile,
the disturbance frequencies and areas will also be the same.
For design purposes, the maximum SO2 emissions likely to
be emitted at any time during planned operations must be
considered. Therefore, puff emissions are assumed to persist
for a full minute and to occur simultaneously within the enclo-
sure. Overall SO2 puff emissions from dynamic waste areas
were estimated by summing the disturbance areas and frequen-
cies just discussed and applying the upper reasonable emission
flux rate:
Edp= 47,000 mg SO2/min-m2 (38 buckets/h x 1 min/bucket x 2 m2 x 2
+ 23 buckets/h x 1 man/bucket x 3.5 m2 x 2) x 1 g/IOOO mg x 1 h/60 min
= 246gSOjAnin
Steady-state SO2 emissions will be generated from both
foam-controlled surfaces and uncontrolled surfaces. The un-
controlled surfaces correspond to the dynamic operations for
which foam will not be used; after puff emissions have sub-
sided, these areas will continue to emit SO2 at the lower steady-
state rate. These dynamic waste areas will include the following:
• Bin Area - The surface area of a 40-yd3 rolloff bin
(with dimensions of 21.8 ft by 7.4 ft) will be approxi-
mately 22 m2 after allowing for a 1.5 bulking factor.
• Excavation Spoils Pile - The spoils pile is assumed to
have a working volume of 40 yd3 arranged in a cone
with a diameter of 20 ft and a height of 10 ft, corre-
sponding to an exposed area of 62 m2 after bulking.
• Loader and Backhoe Buckets-The loader and back-
hoe buckets are estimated to contribute 4 m2 and 2 m2,
respectively, to the uncontrolled steady-state emis-
sion area (in addition to their roles in generating puff
emissions).
The total uncontrolled steady-state emission area is esti-
mated to be 90 m2. Steady-state SO2 emissions from these areas
will be generated at the following rate:
Ed,ss = 1>00° m8 SOj/min-m2 x 90 m2 x 1 g/lOOOmg
= 90 g SO2/min
Controlled steady-state SO2 emissions will be generated
from static waste surfaces to which vapor-suppressing foam has
been applied. The maximum estimated static area corresponds
to the contaminated area that will be exposed at the completion
of the first excavation pass in Sump R-2. For this sump,
material will be excavated to the 24-ft level during the first
excavation pass. The contaminated area exposed at this point
will consist of a 14-ft vertical wall and the floor of the pit, which
will be in the shape of a semicircle with a 40-ft radius. The
vertical wall will have a width of approximately 122 ft at the top
and91 ftatthebottom. The combined area of these two surfaces
will be near 372 m2. The steady-state SO2 emissions from these
surfaces will be reduced by approximately 70% by the applica-
tion of stabilized foam, which yields net static area steady state
emissions of:
19
-------
1,000 mg SO2Anin-m2x 372 m2x (1.0 - 0.7) x 1 g/1000 m&
The overall maximum SO2 emission rate within the enclo-
sure, E,, will be the sum of the individual rates estimated in the
preceding three equations. Thus the overall emission rate is
estimated as 246 + 90 + 1 12 - 448 g SO2/min, or 7.4 g SO2/sec.
This will be a maximum emission rate because it assumes that
all component emissions occur at the same time and at maxi-
mum levels, which is not likely to occur in actual practice. The
air ventilation system design should be based on this maximum
potential SO2 emission rate, however. !
The air ventilation flow rate will be a function of the overall
SO2 emission rate, defined earlier, and the maximum allowable
SQjConcentration within theenclosure. For thepurposes of this
design, a maximum allowable SO2 concentration of SO ppm
within the enclosure has been selected as a reasonable compro-
mise between the IDLH level of 100 ppm and the PEL of 2 ppm.
This level was selected by EPA for conceptual design purposes
only. It is recognized that the actual acceptable level of
emissions within the enclosure will be dictated by OSHA
regulations and any applicable ARARs. j
Under steady-state conditions, the mass of SO2 leaving the
enclosure with the ventilation air will be equal to the mass of
SO2 being emitted within the enclosure:
Et = 50ppmxF
or
F = Et/50ppm I
where F is the ventilation air flow rate. Where the total; SO2
generation rate is 448 g/min, the required ventilation air flow
rate to maintain enclosure air concentration at SO ppm or below
is given by: !
periods of lower SO2 generation rates, the concentrations within
the enclosure will be below 50 ppm if the ventilation system is
maintained at the specified air flow rate.
Backfill Enclosure Ventilation System
During backfill operations, clean soil will be trucked into
the backfill enclosure and moved into position by a front-end
loader. A vibrating roller will be used to pack the backfilled
soil. Backfill operations are expected to cause negligible
disturbanceof waste surfaces; therefore.puff emissions are also
expected to be negligible. A wall of contaminated material,
however, will be fully exposed at the start of backfill operations,
which will emit SO2 at the steady-state rate reduced by the
application of foam.
For design purposes, the largest wall of contaminated ma-
terial will be exposed at the start of backfilling of Sump R-2.
This wall will be approximately 124 ft at the top, 26 ft at the
bottom, and 45 ft high, with a total surface area of 314 m2. The
estimated static area steady-state SO2 emission rate was calcu-
lated in the same manner as used for the excavation enclosure:
EfJSS - 1000 mg SCymin-m2 x 314 m2 x (1.0 - 0.7) x 1 g/1000 mg
= 94 g/min
Since there will be no puff emissions or uncontrolled steady-
state emissions in the backfill enclosure, total SO2 emissions will
be equal to the calculated static area steady-state emissions.
The maximum allowable SO2 concentration within the
backfill enclosure will also be set equal to 50 ppm. The air
ventilation requkement for this enclosure was calculated in the
same manner as for the excavation enclosure:
F =
94 g SQa/min x 1 Ib S
-------
Waste Storage Enclosure Ventilation System
Like backfill operations, waste storage operations will be
characterized by steady-state emissions from controlled static
waste areas (with negligible puff or uncontrolled steady-state
emissions). The requirement to maintain 1 week's supply of
contaminated material for feed to final treatment can be accom-
modated by 17 rolloff bins with approximate 40-yd3 capacities.
The surface area of the contaminated material in these bins will
be covered with foam and a tarp.
The total waste-emitting surface area of the bins in the
storage area at full capacity will be near 374 m2, based on the bin
dimensions and bulking factor cited earlier. Based on the same
estimating procedures shown earlier, the total SO2 emission
generation rate within the storage enclosure was estimated to be
112 g SOj/min. This emission rate translates to air ventilation
requirements of 32,400 acfm to maintain SO2 concentrations
within the enclosure below 50 ppm.
Design of Air Pollution Control Devices
This section considers the design of major components of
the ventilation air pollution control trains. Each train will
consistofawetscrubber for control of SO2and paniculate matter
(PM) emissions, a granular activated carbon (GAC) unit for
control of hydrocarbon/organics emissions, and an associated
fan, blower, and ducting system. The equipment designs for
each train will be identical. For illustration purposes, the
discussions that follow focus on the APCD trains for the
excavation enclosure.
Wet Scrubber System
The wet scrubber system design will be comparable to the
NaOH-based scrubber system used during the trial excava-
tion. An NaOH-based scrubber system is advantageous in this
application because its considerable buffering capacity allows
it to accommodate wide swings in SO2 inlet concentrations
while maintaining high SO2 removal rates and low outlet
concentrations. The largestNaOH-based wet scrubber manu-
factured by Interel Corporation, the supplier of the trial exca-
vation scrubber, is rated at 35,000 acfm.* This unit, Interel
Model GW 300, includes 10 feet of packing, a 950-gal sump,
an automatic pH control, an automatic sump level control, an
automatic blowdown system, a mist eliminator, and 300 gal/
min recirculation pump. The unit is constructed of high-
density polyethelene, as was the trial excavation scrubber.
The Model GW 300 is designed to achieve greater than 95%
SO2 removal and greater than 90% PM removal when operated
according to specifications.
The scrubber tower will be filled with 2-in.-diameter plastic
packing balls, which provide a high mass transfer coefficient
and yet operate at a pressure drop in the range of 2 to 5 inches
of water across the bed. The high-void-space design of the
packing material allows the scrubber to accomplish PM re-
moval at air loadings of up to 2000 mg/m3 without plugging.
The highestPMloadingexpectedamongtheexcavation, backfill,
and storage enclosures will be less than approximately 120 mg/
m3.
For accommodation of the specified total air ventilation
flow rate of 130,000 acfm, four Interel Model GW-300 scrub-
bers will be required for the excavation enclosure, each operat-
ing at an average of 32,500 acfm. One scrubber unit will be
required for each of the backfill and storage enclosures operat-
ing at the average air ventilation flow rates specified. Each
APCD train will have one wet scrubber unit
Granular Activated Carbon System
The THC adsorption performance of the GAC unit used
during the trial excavation was less than the level expected
based on other similar applications. This lower-than-expected
performance was believed to be due primarily to moisture
condensation within the carbon bed, which reduced the effec-
tive activated carbon surface area. For avoidance of such
problems during full-scale remediation, it is recommended that
a small gas burner be installed in the ducting between the wet
scrubber and the GAC units that is capable to raising the
temperature of the air stream by 20° F. This is a common
saturation approach temperature difference used in industrial
applications to avoid condensation while allowing for the
natural variability of industrial operations.
For operation in the South Coast Air Quality Management
District, the burner should be designed to fire natural gas. Heat
balance calculations indicate that a burner firing approximately
700 ft3/h (or 700,000 Btu/h) of natural gas will be sufficient to
raise the temperature of the scrubber effluent air by 20°F.
Downstream of the natural gas burner, the total gas flow rate
will be increased from 32,500 acfm at the inlet to the scrubber
to about 35,200 acfm as a result of natural gas combustion and
saturation of the air stream with water in the scrubber. Assuming
that the wet scrubber operates near 100°F during the summer
months, the temperature of the gas entering the GAC unit will
be 120°F.
The largest GAC modules available from TIGG Corpora-
tion, the supplier of the trial excavation GAC unit, are rated at
12,000 acfin.** Three such units (TIGG ModelN-12000) will
be required to operate in parallel for each scrubber to match the
* Personal communication from P. Briscoe, Interel Corporation, to E. Aul, Edward Aul and Associates, Inc., April 10,1991.
** Personal communication from J. Sherbondy, TIGG Corporation, to E. Aul, Edward Aul and Associates, Inc., March 22,1991.
21
-------
scrubber flow rates. A fourth module will be added to allow
change-out of spent carbon without shutting down the ehtire
train. Each unit will be a radial-flow module similar in design
to the unit used during the trial excavation. Inlet gases jflow
downward through a vertical cylindrical distributor in the
center of the unit and then flow outward through an annular
carbon bed to an accumulator cabinet that collects the gases and
directs them to a downstream fan. The pressure drop across the
three parallel GAC modules is expected to be in the range of 5
to 8 inches of water. Each cannister will hold approximately
5100 Ib of activated carbon, for a total of 15,300 Ib of carbon on-
strcam per train. At 12,000 acfm, the gas residence time in the
carbon beds will be near 0.8 second. This design, in connection
with the previously discussed gas burner, should consistently
provide at least 90% removal of THC in the inlet gas stream.
One of the key parameters affecting the operation of carbon
adsorbers is the amount of adsorbate (THC emissions in this
case) captured on the carbon beds. This factor determines the
makeup rate for fresh carbon and the spent carbon generation
rate, both important economic parameters. For a given set of
operating conditions, the maximum (or equilibrium) amount of
adsorbate captured on the bed is a function of the inlet 'con-
centration and can be calculated from an adsorption isotherm of
the form (Vatavuk 1990): I
me = apb |
where mc = Ib adsorbate/lb adsorbent at equilibrium '
p = partial pressure of adsorbate in gas stream (psia)
a, b 3 isotherm parameters. 1
The isotherm parameters are particular to the adsorbate,
type of carbon, and adsorption temperature and are best deter-
mined in the laboratory under representative conditions. For
design purposes, however, the adsorption isotherm parameters
for the mixture of hydrocarbons expected from excavation
operations can be estimated by using a representative organic
species such as toluene. Toluene was selected because it has
nearly the same molecular weight as the average molecular
weight of the THC mixture. For toluene adsorption on 4x10
mesh carbon at 77 °F,the values of a and bare 0.551 and 0.110,
respectively. The inlet concentration of THC during excava-
tion operations is estimated to be 14.2 ppm, which corresponds
to 2.08 xKr* psia. Substituting this value into the preceding
• equation with the appropriate isotherm parameters yields:
mc= 0.551(2.08 xlO-4)0-110 !
= 0.217 Ib adsorbate/lb carbon !
[
In actual practice, the amount of adsorbed carbon is not
allowed to reach the equilibrium level because the bed'js ad-
sorption capacity would be exhausted at this point and the outlet
concentration would quicklyrise to the inletlevel. Foravoidance
of this type of adsorbate breakthrough, carbon beds are typically
allowed to operate until they reach 50 to 75% of equilibrium
loading. Using the 75% level for design purposes implies that
the maximum loading of carbon for the excavation ventilation
ah- system will be 0.217 x 0.75= 0.163 Ib adsorbate/lb carbon.
During nonoperating hours, the THC concentration of the
ventilation air is projected to fall quickly to less than 1 ppm. At
this low level, only minimal THC adsorption would beexpected
in the carbon-beds even If the enclosure is ventilated continu-
ously. Thus, the useful life of carbon-bed modules will depend
primarily on the duration of excavation operations.
Based on the calculated maximum loading rate, the useful
life of the carbon-bed adsorbers for the four excavation enclo-
sure APCD trains (each with 15,300 Ib of carbon in three
parallel N-12000 adsorbers) is about 435 operating hours. The
previously discussed operating scenario for excavation calls for
approximately 5 hours of excavation per day, or 30 hours per
week. On this basis, a fresh charge of 15,300 Ib of carbon would
provide design-level THC adsorption for approximately 100
days, which implies that one spent GAC module should be
changed out for a fresh carbon module every 33 days. Annual
requirements for fresh carbon and for the disposal of spent
carbon will be slightly more than 53,000 Ib/year.
Ducting System, Blower, and Fan
A ducting system will be provided to exhaust ventilation air
from the enclosure and to supply fresh makeup air. An induced-
draft (ID) fan will be located at the end of the exhaust ducting
to draw ah" from the enclosure and through the wet scrubber and
GAC modules. A forced-draft (FD) blower at the end of the
inlet ducting will push fresh air from outside the enclosure to
points inside. Exhaust ducting must carry ventilation air
containing dust from excavation operations. For medium- to
high-density dust, a gas velocity of about 4,000 ft/min is
recommended (Vatavuk 1990). At this velocity, a duct diam-
eter of approximately 3 ft is required to accommodate 32,500
acfm of airflow. The diameter of the inlet ducting will also be
specified as 3 ft to provide portability within the enclosure.
To increase the effectiveness of the air ventilation system,
the ah" deli very system will be arranged to provide a continuous
flow of fresh ah" past workers hi high emission areas (e.g., the
working face). The exhaust system will also be designed to
capture emissions close to their source to minimize the amount
of contaminants that escape into the general enclosure volume.
This requires that exhaust and air supply ducting be extended
from the enclosure wall to areas within the enclosure, as
illustrated in Figure 4-4. On the supply side, air will be drawn
from the atmosphere by a blower operating outside the enclo-
sure and directed into the enclosure through fixed ducting
(outside the enclosure) and movable ducting (inside the enclo-
sure). The movable ducting inside the enclosure will be
positioned near the high-emission working areas so that fresh
ah" will flow past workers, preferably in the workers' breathing
zone. The ducting inside the enclosure will be made of light-
weight plastic or similar material that will allow the ducting to
be flexible and easily moved for optimum positioning.
22
-------
APCD
Train A
APCD
Train C
Transport Truck
with Roll-Off Bin
Air Supply
Bio war A
Figure 4-4. Air Ventilation System Schematic for Excavation Enclosure.
In a similar manner, exhaust ducting will extend within the
enclosure to allow placement near major emission sources.
This ducting will also be made of flexible and light-weight
material to facilitate movement and placement near sources. A
hood will be required at the end of each duct to maximize
emissions capture. Based on ACGIH recommendations, a
capture velocity of 500 f(/min at the face of the hood is specified
for this operation (McDermott 1985). This corresponds to a
square hood with dimensions of 8 ft by 8 ft for the ventilation
flow rate of 32,500 acfm per train. A similar hood, equipped
with baffles, is recommended for the air-supply ducting so that
air velocities near workers are not high enough to cause sig-
nificant dusting or unstable working conditions. The total
length of exhaust ducting is estimated to be 300 ft for each
train, which includes 150 ft of fixed, stainless steel ducting
outside the enclosure (to connect the scrubber, GAC unit, and
fan) and up to 150 ft of flexible ducting inside the enclosure.
Air-supply ducting would also require up to 150 ft of flexible
ducting inside the enclosure but only about 50 ft of fixed,
carbon-steel ducting outside the enclosure to reach blowers.
The air ventilation system for the excavation enclosure calls
for four trains of 32,500 acfm airflow each. It is recommended
that three of these trains be positioned in the manner described
in the preceding paragraph so that fresh air is supplied and
contaminated air is exhausted locally near the excavation
working face, the spoils pile, and the truck-staging area. The
fourth system would exhaust air from the general enclosure
volume and maintain a slight negative pressure within the
enclosure to minimize/eliminate air leakage from inside the
enclosure to the outside. This general arrangement is illustrated
in Figure 4-4.
In the design of the FD blower, consideration must be given
to the volume of air to be delivered and the pressure drop in the
ductingtobeovercome. The maximum volumetric flowrate for
fresh air is specified as 35,000 acfm for each train. For a 3-ft-
diameter duct, this flow rate corresponds to an air velocity of
about 4950 f(/min. The pressure drop through the ducting can
be estimated as follows (Vatavuk 1990):
23
-------
AP = 1.38x
where AP = static pressure loss (inches water/100-ft duct)
Q = Volumetric flow rate of gas (acfm)
V = Gas velocity (ft/min)
For the air supply system, !
AP = 1.38 x 10-7(35,000-°-5)(4,9502-5) j
= 1.3 in. water/100-ft duct '
t
The pressure drop across 200 ft of air supply ducting would
be about 2.6 in. water. Anadditionalpressuredropofl in. water
is allowed for ducting fittings, elbows, baffles, and [related
obstructions, which brings the total estimated pressure drop in
the air supply ducting to 3.6 in. water. |
A motor specified for the blower must have sufficient
horsepower to turn the blower at required speeds. Horsepower
requirements for motors of this type are determined .by the
following equation: '
BHP = 0.0001575 x Q x AP/n
where BHP = motor brake horsepower (HP) i
n = motor efficiency
A blower developing a static head of 3.6 in. of water and
supplying 35,000 acfm of air will require approximately 40 HP
when operating at a typical efficiency of 50%:
BHP = 0.0001575 x 35,000 x 3.6/0.5
= 40 HP
For the exhaust ducting of each APCD train, a fan must be
able to draw a maximum of 35,000 acfm from inside the
enclosure and through the scrubber, GAC unit, and associated
ducting. The maximum pressure drop in this train is estimated
to be 20 in. of water, based on specifications for individual
equipment pieces and the trial excavation experience. Avail-
able fan curves for an ID radial-blade centrifugal fan indicate
that a fan with a wheel diameter of about 60 in. will be required
(Vatavuk, 1990).
The horsepower requirement for a motor of this type is
calculated in the same manner as discussed for the blower. For
a fan drawing 35,000 acfm of air and overcoming 20 in. of water
pressure drop, a motor of approximately 220 HP will be
required.
24
-------
Section 5
Economic Analysis
Introduction
The objective of this economic analysis is to estimate the
cost of a commercial-size site remediation effort using the
excavation and fugitive emission control systems evaluated
during the McColl trial excavation. This evaluation illustrates
how these systems could be applied to a site where excavation
or handling of wastes would result in the release of significant
fugitive emissions that could pose a potential health risk to
nearby communities. In the example scenario, costs are esti-
mated for full remediation of the 12 sumps at the McColl
Superfund site in Fullerton, California.
Costs have been estimated for the full excavation of all
contaminated material at the McColl site, which consists of an
estimated 72,600 yd3 of waste (consisting of mud, tar, and char,
as discussed in Section 3), 2000 yd3 of designated material, and
22,500 yd3 of questionable material (CH2M-HILL 1989).
Designated materials are soils directly adjacent to the wastes
that fail one or more of the Federal or State hazardous waste
criteria, based on an analysis of soil borings. Questionable
materials are soils exceeding the background chemical concen-
tration levels, but not qualifying as designated. An additional
22,500 yd3 of clean soil forming sump covers also must be
excavated. This makes a total of 121,200 yd3 of in-place ma-
terial to be excavated during full remediation.
The scope of the remediation activities examined in this
analysis includes excavation of waste and associated material
under a rigid-frame enclosure, backfilling of the excavated
sump underasecond enclosure, erectingathirdenclosureon the
next sump to be excavated, and transport of the waste material
to an onsite storage facility consisting of a stationary enclosure
erected over a concrete pad. The fugitive emission control
systems include vapor-suppressing foam application units, air
ventilation systems for each enclosure, the APCD used to
reduce emissions of SO2 and THC in the ventilation air to
acceptable levels, an APCD emissions monitoring network,
and a perimeter ambient air monitoring network.
This scope does not include the final waste treatment and
disposal systems or pretreatment systems. Such systems as
offsite disposal in a RCRA landfill, onsite thermal treatment
(e.g., incineration), or offsite thermal treatment, among others,
have been considered for this site; however, are not included in
the scope of this economic analysis. The costs of such systems,
as well as the costs of integrating such systems with the
excavation and storage approaches considered, would have to
be added to the costs developed in this analysis to arrive at an
estimate for full remediation and disposal.
Depending on the final waste treatment option selected, the
specification of one week of storage capacity may or may not
be appropriate. For onsite treatment options such as incinera-
tion, the one-week storage capacity would be desirable to allow
treatment operations to continue if excavation operations were
temporarily slowed or halted. For offsite treatment options, this
capacity probably would not be needed.
Conceptual designs have been developed for the excava-
tion/backfill/storage operations, ah- ventilation systems, and air
pollution control systems, as discussed in Section 4. Based on
these designs, costs for major equipment items such as the
enclosures, foam delivery trailers, SO2 scrubbers, and GAC units
were provided by their respective manufacturers/suppliers.
Two costing options were evaluated for acquisition of equip-
ment for excavation, backfilling, storage, and enclosure
movement: l)leasingoftheequipment(costsbasedonliterature
data) and 2) purchase of equipment (costs provided by equip-
ment suppliers). Cost estimates for minor equipment were
based on literature cost data. All costs have been adjusted to a
July 1990 basis and to an Orange County, California, location
by using historical cost indices. This design and costing
methodology is consistent with an order-of-magnitude estimate
as defihedby the American Association of CostEngineers, which
has an accuracy of plus 50 to minus 30%.
Results of the economic analysis and apparent trends are as
follows:
• The estimated costs of waste excavation and storage
at the McColl site range from $69.2 million (for the
purchase option) to $74.3 million (for the lease
option), or from $593/ton to $637/ton. The marginal
costs for fugitive emission control are nearly twice
the costs of excavation without such control.
• These costs reflect a remediation duration of 6.4
years, based on a specified final treatmentprocessing
rate of 90 tons/day of contaminated material. Exca-
vation rate calculations indicate that excavation op-
erations are not the rate-limiting step under this
25
-------
scenario but that remediation activities could be
accomplished inless time, which wouldreduceoverall
costs. !
Specification of the SO2 concentration limit within
the enclosure dictates the size and cost of the air
ventilation system and APCD equipment.
Basis for Process Design, Sizing, and Costing
The basis forsystem process designs, equipmentsizing, and
costestimates areprovided in thefollowingsubsections, arranged
according to the 12 cost categories specified by the SITE
program. As discussed earlier, these costs encompass the waste
excavation, backfilling, storage, and fugitive emission control
systems, but they do not include systems for final treatment of
excavated wastes. Detailed discussions of design analysis for
cxcavation/backfill/storage operations, air ventilation systems,
and air pollution control systems are presented in Section 4.
Relevant design information that impacts cost estimates is
summarized in the following subsections. '
Site Preparation Costs
Based on the trial excavation experience, the enclosures will
be placed on approximately level surfaces to ensure a good seal
at tiie bottom; this minimizes outleakage of contaminated air
during excavation/backfill operations. Although the supplier,
Sprung Instant Structures, Inc., has indicated that legs can be
added to accommodate slopes, level surfaces arepreferred from
the standpoint of worker safety and equipment performance.
Because the McColl site terrain is characterized as; gently
rolling, a limited amount of clearing and grading will be
required to provide level surfaces above and around the 12
sumps. In addition, connections must be installed for electric
power, water, and natural gas from a point near the entrance of
the site to the three major sump areas (i.e., Upper Ramparts,
Lower Ramparts, and Los Coyotes) as required for operation of
the APCD systems. Costs of these site preparation activities
have been extrapolated to full scale from the costs incurred
during the trial excavation (EPA 1990). Costs have also been
added for providing anew equipment decontamination station,
a personnel decontamination trailer, an office trailer, and a
security check station. These costs are based on estimates from
equipment suppliers.
Permitting and Regulatory Costs
Because McColl is a Superfund site, it is assumed that no
Federal or State permits will be required. Nevertheless, it is
recommended that project officials coordinate their activities
closely with Federal OSHA, State OSHA, and other State and
local regulatory groups. ' !
Equipment Costs
Equipment required for this project can be divided into five
general areas: excavation, backfill, storage, air ventilation
system, and foam application. For excavation operations, a
Caterpillar 245, or equivalent, track-mounted hydraulic back-
hoe with a 14.5-ft stick and a 3-yd3 bucket is expected to be
used. This backhoe would have a 31-ft maximum depth of cut
for an 8-ft level bottom and a maximum reach of 46 ft at ground
level (Caterpillar Tractor 1985).
In addition to the track-mounted backhoe, other major
equipment pieces required for excavation operations are a 6-yd3
track-mounted, front-end loader and two off-highway trucks
capable of hauling 40-yd3 rolloff bins. Backfilling of clean soil
is accomplished with a 5-yd3 wheel-mounted loader operating
at the borrow area and a 5-yd3 track-mounted loader, a 10-ton
tandem roller, and two off-highway 50-ton capacity dump
trucks operating inside the enclosure. A total of 24 rolloff bins
are included in the storage equipment costs (EPA 1990). Other
supporting equipment required for excavation and backfill
operations include a fuel and lube truck, a mechanics and
welding truck, a water wagon, a crew truck, a pickup Sruck, a
forklift, and compressors to provide air for the Level B sup-
plied-air respirators. Costs for this supporting equipment are
included in the excavation equipment category. Information
regarding estimated lease and purchase costs for these equip-
ment items is summarized in Table 5-1.
The air ventilation system consists of several equipment
components. A blower provides fresh air to selected areas
inside the enclosure to minimize worker exposure to air con-
taminants and to promote air mixing within the enclosure. A
packed-bed scrubber operating on exhaust ventilation air from
the enclosure is designed to remove 95% of the incoming SO2
by reaction with sodium hydroxide. A small gas burner is
specified in the ducting between the scrubber and G AC unit to
raise the temperature of the air stream by 20°F to avoid potential
moisture condensation on the GAC. After the gas burner, three
modular GAC units operating in parallel are used to reduce total
hydrocarbon emissions by 90% before the air is vented to the
atmosphere. Ventilation air is drawn from the enclosure and
through the scrubber and GAC units by an induced-draft fan
capable of overcoming an estimated 20 in. of water pressure
drop. A summary of specifications and costs for the APCD
equipment is provided in Table 5-2.
The largest sodium-hydroxide-based scrubber module
available from Interel is rated at 35,000 acfm capacity.* Thus,
four such modules will be required for the excavation enclo-
sure, whereas only one module would be required for the
backfillandstorageenclosures. Although the useof four APCD
trains for the excavation enclosure complicates operations from
the standpoint of the operation and movement of the systems,
the smaller size is desirable to maintain portability around the
*Person»l communication from P. Briscoe, Interel Corporation, to E. Aul, Edward Aul and Associates, Inc., July 17,1990.
26
-------
Table 5-1. Lease and Purchase Costs for Excavation, Backfill, and Storage Equipment and Enclosure Movement"
Quantity
1
1
2
1
1
1
1
1
1
1
1
1
1
2
• 24
1
1
2
Equipment
Excavation operations
Track-mounted backhoe, 3-yd3
Track-mounted loader, 3-yd5
Off-highway trucks, 40-yd3
Fuel and lube truck
Mechanics and welding truck
Water wagon
Crew truck
Pickup truck
Forklift, 10-ton
Air compressor
Backfill operations
Track-mounted loader, 5-yd3
Wheel-mounted loader, 5-yd3
Tandem roller, 10-ton
Off-highway trucks, 40-yd3 .
Storage operations
Rolloff bins, 40-yd3
Enclosure movement
Articulated boom lift, 500-lb
Truck-mounted crane, 10-ton
Rolling tower scaffolding, 20-ft
Lease Cost",
$/month
23,600
10,500
26,100
3,900
3,900
3,900
1,700
560
3,600
1,010
10,500
10,500
2,100
26,100
280
11,400
7,500
600
Purchase Cost0, $
571,300
301,400
818,600
170,400
170,400
170,400
19,100
16,900
85,200
•32,300
301,400
230,200
86,500
818,600
210,200
82,200
192,600
2,600
a All costs are adjusted to July 1990 and Orange County, California, site.
b Source: Means (1990).
c Sources: Personal communications from E. Hooks, Caterpillar - Gregory Poll Equipment Co., August 23,1991;
W. Wilkarson, D&J Trucks, Inc. August 23,1991; B. Bergstrom, Hyster Co., June 19,1991; and M. Nelson,
Prime Equipment Co., June 12,1991, to E. Aul, Edward Aul& Associates, Inc.
site as the enclosures are moved. In addition to the six operating
APCD trains, a seventh train will be purchased as an onsite
backup unit.
The largest GAC modules available from TIGG are rated at
12,000 acfm.* Three such units will be required to operate in
parallel for each scrubber to match the scrubber flow rates. A
fourth module will be added to allow change-out of spent
carbon without shutting down the entire train.
A trailer-mounted foam application system supplied by
Boots & Coots will be used to apply vapor-suppressing foam to
exposed static waste surfaces in the three enclosures. This
system includes a water tank, a stabilizer tank, a foam tank, a
proportioning system, and a diesel-powered booster pump
sized to provide up to 500 ft2 of double-strength stabilized foam
per minute. A nitrogen cap system is also incorporated to
prevent deterioration of the stabilizer by air or moisture during
operation and recharging. A separate foam trailer will be
required for each of the enclosures, plus a spare trailer as onsite
backup. As in the trial excavation, the trailers will be operated
outside the enclosure to supply foam via hoses for application
to waste surfaces inside the enclosure. The cost of purchasing
each trailer is approximately $35,000.** Another $5,000 per
unit has been added for hosing and nozzles.
A final category of equipment is the equipment required to
erect and then teardown the rigid-frame enclosures to be posi-
tioned over sumps during excavation and backfilling opera-
tions. Based on the trial excavation experience and discussions
with representatives of Sprung Instant Structures, this equipment
will include two 20-ftrolling scaffolding towers, agas-powered
lift with an articulated boon capable of reaching to 60 ft, and a
10-ton truck-mounted crane.
Startup and Fixed Costs
The major cost items included in this category are the three
excavation and backfill enclosures, the APCD monitoring
network, and the perimeter monitoring network. The excava-
tion and backfill enclosures are each 120 ft wide by 300 ft long
by 60 ft high. These width and length requirements are based
on detailed excavation planning for the 12 sumps at McColl. As
in the trial excavation, the enclosure structures consist of
aluminum support members covered by a PVC skin. Each
enclosure includes two 60-ft-long air lock tunnels that will
allow vehicle entry and exit with a minimum of outieakage of
air from inside the enclosure. Two additional smaller air locks
are provided for personnel entry and exit
*Personal communication from J. Sheibondy, TIGG Corporation, to E. Aul, Edward Aul and Associates, Inc., March 22,1991.
**Personal communication from B. Smith, Boots & Coots, to E. Aul, Edward Aul and Associates, Inc., April 2,1991.
27
-------
Table 5-2. Air Ventilation System Specifications and Costs
Component/Specifications
Air supply blower '
35,000-cfm throughput
4 inches water pressure drop
40-hp motor !
Air supply ducting ;
3-ft diameter
50 ft of carbon steel (exterior) ;
150 ft of FRP with hood (interior) I
SOa scrubber ;
35,000-cfm throughput
2 to 5 inches water pressure drop j
10-ft packed bed ,
300-gpm recirculation pump j
Automatic controls for pH and sump level
Slowdown pump I
Reagent metering pump
Mist eliminator
HOPE construction
Induced-draft fan
35,000-cfm throughput
20 inches water suction pressure
220-hp motor !
Reagent storage tank
550-gallon capacity i
FRP construction
Slowdown wastewater storage tank pump
2000-gallon capacity
FRP construction
220-qpm transfer pump !
Duct burner I
20°F temperature rise
1 million Btu/h heat input !
GAG adsorber modules
3 operating modules, 1 spare
12,000-cfm throughput each
5 to 8 inches water pressure drop
51 00-lb carbon each
0.8-second gas residence time ',
Air exhaust ducting
3-ft diameter
150 ft of 31 6 SS (exterior)
150 ft of FRP with hood (interior)
TOTAL EQUIPMENT COSTS
Estimated Costa
$18,000
$24,700
$120,000
$20,900
$1,800
$6,700
$5,000
$80,000
$136,600
$413,700
Costs are for equipment only and do not include freight and installation costs.
The fourth enclosure for storage is smaller; it measures 120
ft wide by 240 ft long by 57 ft high. Because of the heavy
vehicular traffic and potential requirement to move rollqff bins
inside, the enclosure is erected over a 6-in. pad of 3500-psi
reinforced concrete. Installed costs for the pad are estimated
to be$6.24/ft? (Means 1990). The estimated costs for thp three
excavation and backfill enclosures are $1,242,500 each, as
supplied by Sprung Instant Structures; costs for the storage
enclosure are estimated to be $510,250.* Delivery costs to the
site would be negligible because McColl is only 40 miles from
Sprung's Fontana, California, operations office. Startup costs
also include costs for four closed-circuit television systems to
monitor operations within the enclosures, as was done during
the trial excavation.
A perimeter monitoring network is called for in the McColl
Community Safety/Contingency Response Plan for continu-
ous monitoring of SO2 and THC in the ambient air around the
site during remediation. The network consists of seven sta-
tions on the perimeter of the site and three stations at interior
locations, each equipped with an SO2 analyzer, a THC ana-
lyzer, calibration equipment, and strip chartrecorders. Each of
*Pcnon*l communication from C. Spitzka, Spnmg Instant Structures, Inc., to E. Aul, Edward Aul and Associates, Inc., July 17,1990.
I
. i 28
-------
these stations will be housed in a climate-controlled 8 ft by 24
ft office trailer; A meteorological station is also specified to
measure and record data for windspeed, wind direction, and
temperature. Four data acquisition systems are required for data
storage and manipulation. Total costs for the system, including
installation, are estimated to be $864,500 (Radian 1983).
A similar network will be operated to monitor and record the
emissions reduction performance and outlet emissions for the
six APCD trains operating on the site. For each train, an SO2
analyzer will determine SO2 concentrations in the ventilation
air entering the scrubber and exiting the stack; a THC analyzer
will determine THC concentrations entering the GAC units and
exiting the stack. System support hardware and housing
analogous to that for the perimeter network will be required for
the APCD network. Both networks will be connected to a
central control station via buried communication cables. Total
installed costs for the APCD network are estimated to be
$471,400 (Radian 1983).
Labor Costs
As discussed in Section 4, remediation activities would be
conducted on a schedule of 6 days/wk and 50 wk/yr. Operating
labor would include equipment operators for the backhoe,
track-mounted loader, two wheel-mounted loaders, tandem
roller, four trucks, and a fuel/lube truck. Five other laborers and
a mechanic would be required for excavation, backfill, and
storage operations. Tear-down, movement, and re-erection of
the excavation and backfill enclosures will require a team of 12
laborers, acraneoperator.anda Sprung technical consultant for
approximately 30 days per move. In addition, project man-
agement personnel would include a site manager, two.opera-
tions supervisors, and a safety officer.
One team of two laborers would be required to operate the
excavation foam application trailer; a second team of two
laborers would operate the backfill and storage trailers because
of their more intermittent operation. A part-time supervisor
would also be required to oversee the foam trailer operations
and maintenance.
Combined labor requirements for the perimeter and APCD
monitoring networks consist of three technicians, a data ana-
lyst, a quality assurance technician, a part-time meteorologist,
and a part-time supervisor.
Supplies and Consumables
, A major consumable for excavation, backfill, and storage
operations would beLevel B safety gear. Costs for Level B gear
for 15 persons are estimated to be $180/person per day, based
on the trial excavation experience (EPA 1990). Backfill clay
(i.e., Type A soil) for Sump R-2 is expected to have a delivered
cost of around $4/ton (Means 1990).
A second major consumable for these operations will be
vapor-suppressing foam. Based on experience from the trial
excavation and discussions with the foam trailer supplier, 5 gal
of foamer and 10 gal of stabilizer are expected to be required to
cover 1200 ft2 of static waste surface with a foam layer of 3/4-
to 1-in. thickness.* It is assumed that the foam will have to be
reapplied every 3 days to undisturbed surfaces so as to maintain
an overall average vapor-suppression effectiveness of 70%.
The costs for 3M-brand foamer and stabilizer solutions are
approximately $21/gal and $42/gal, respectively (3MCompany
1990).
The air ventilation system will require makeup sodium
hydroxide, which is available as a 50 weight percent solution in
water at a cost of around $0.20/lb,** andreplacement activated
carbonatacostofaround$1.00/lb.*** As discussed in Section
4, it was assumed that the carbon is allowed to reach 75% of
equilibrium loading before being replaced with new virgin
carbon.
If excavation and backfill equipment pieces are purchased,
it will be necessary to provide fuel and lubricants on a regular
basis for this machinery. Total costs for these items are based
on a diesel fuel price of $ 1.30/gal and typical hourly consump-
tion rates for equipment operated under expected conditions
(Caterpillar 1985). Fuel and lubricant costs are not included
under the lease option because thesecosts are typically included
in the monthly lease rate.
Utilities Costs
The only significant utilities required for waste excavation
and storage are associated with the air ventilation system.
These are electricity for the blower, an induced-draft fan, a
scrubber circulation pump, and natural gas to be burned in the
induct burner located between the scrubber and GAC unit Unit
costs of $0.10 per kilowatt-hour for electricity and $4.00 per
million Btu for natural gas are used in the analysis.
Effluent Treatment and Disposal Costs
A wastewater effluent stream will be generated by the SO2
scrubbers because of the need for periodic purging of collected
sulfur and dust This wastewater will be disposed of as a
hazardous waste, as the ventilation air may contain hazardous
constituents. Calculations indicate that SO2 generation rates
and the desire to maintain outlet SO2 gas concentrations at or
below 2 ppm will be controlling factors in determining the
wastewater purge frequency and amount These factors dictate
that the blowdown rate for each excavation APCD train will be
near 280 gal/operating day; blowdown rates for the backfill and
storage APCD trains will be lower because of lower SO2
generation rates. At these blowdown rates, the solids content of
the wastewater will be near or below 3 weight percent, which is
acceptable from the standpoints of pumpability and disposal.
*Personal communication from B. Smith, Boots & Coots, to E. Aul, Edward Aul and Associates, Inc., April 8,1991.
**Price quotation from Holchem Inc., Orange, CA, June 8,1990.
***Persoiral communication from J. Sherbondy, TIGG Corporation, to E. Aul, Edward Aul & Associates, Inc., March 22,1991.
29
-------
It is assumed that wastewater will be collected from individual
APCD trains and held in a central storage tank on site. )Vaste-
water will be picked up at the site on a weekly basis and
transported to a RCRA-certified disposal facility. In 1990,
costs per shipment for this service were $0.55/gal plus $350 for
transportation and $200 for analytical services, which are
included in the Analytical Costs category.*
Residual and Waste Shipping, Handling, and
Treatment Costs
Disposal costs will also be incurred for spent activated
carbon. Like scrubber wastewater, spent carbon must be
disposed of ataRCRA-permittedfacih'ty. Because of land-ban
restrictions, itisexpected that the spent carbon will be disposed
of by incineration at a cost of about $1.20/lb (Ensco[1991).
Analytical costs are estimated at $500/sample and are included
in the Analytical Costs category.
Results of Economic Analysis
Itemized costs estimated for waste excavation, waste stor-
age, and fugitive emission controls for the McColl Superfund
site are summarized in Table 5-3. The quantity of contaminated
material to be removed at this site totals 97,100 yd3 or 116,700
tons. As shown in the table, total estimated costs for the
purchase equipment option, including project contingency and
management, are $69.2 million, which translates to a cost of
$593/ton removed. The purchase equipment option has lower
overall estimated costs than the lease equipment option -$74.3
million, or $637/ton. The higher costs of fuelsAubricants and
maintenance under the purchase option are more than offset by
the lower costs for equipment over the projected 76-mo reme-
diation period. Based on these factors alone, the break-even
time period for the lease option and purchase option is slightly
over 3 years. The largest components of the estimated purchase
option costs are labor (22%), supplies/ consumabies (21%),
equipment (12%), and utilities (11%). All other categories
account for less than 10% of overall costs.
Analytical Costs
Analytical costs for wastewater and spent carbon were
discussed previously. In addition, wastewater analysis costs of
S200/sample have been allowed for two water- runoff; events
per year. Finally, general analytical costs of $500/day are
allowed for waste, soil, and groundwater samples in the absence
of a site sampling and analysis plan.
Facility Modification, Repair, and Replacement
Costs !
Equipment maintenance costs have been estimated;for the
air ventilation systems and foam-application trailers. In both
cases, annual costs for maintenance labor and materials were
estimated to be 4% of the purchase cost of operating [equip-
ment (spare units excluded). No maintenance costs are included
for excavation, backfill, storage, and enclosure movement
equipment under the lease option, as these costs are reflected
in their lease rates. Under the purchase option, annual main-
tenance costs are estimated as 4% of purchase costs, i
Decontamination/Demobilization Costs ;
Based on the trial excavation experience, decontamination
costs are estimated to be approximately $1700 per, major
equipment piece (EPA 1990). Itisassumedthatequipmentwill
bcdccontaminatedan averageof 12 times duringthereme^liation
effort for maintenance or change-out In addition, costs to
recontour the site (after excavation/backfill) to prevent water
accumulation and erosion are included at a rate of $4L50/yd3
yard (Radian 1983). Itisassumedthatasoil volume equivalent
to 20% of the total contaminated site volume will require
recontouring. Demobilization costs are included in equipment
mobilization costs. i
The impact of fugitive emission controls on overall costs
can be estimated by adding the costs for site preparation
(withoututilityhookups),costs for site decontamination/demo-
bilization, and those costs (i.e., equipment, labor, supplies/
consumables, analytical, and maintenance) specifically associ-
ated with waste excavation, backfill, and storage. For the
purchase option, costs for these items total approximately $23
million, based on the information in Table 5-3. Thus, the
addition of fugitive emission control systems raises overall
costs by nearly $46 million, or a factor of 2.0.
. Most of the cost items in the Table 5-3 are directly influ-
enced by the amount of time allowed for remediation. Setting
the overall excavation rate at 90 tons/day of contaminated
material for feed to final processing results in a projection of 6.4
years for complete remediation of the site. Calculations of
excavation rates based on equipment cycle times and the
assumption of 25% overall work efficiency due to Level B
protective equipment indicate that excavation and backfill
operations are not limiting in this case (see Section 4 for
details). The overall time required for remediation, and hence
costs, would be reduced if the final treatment processing rate
were increased.
The specification of the SO2 limit within the enclosures
dictates the size and cost of air ventilation systems. At the 50-
ppm SO2 limit, equipment costs for the ventilation systems are
estimated to be $3.9 million, or 5.6% of total costs. Costs for
equipment of this type often follow the "0.6 power rule" as
throughput or capacity is increased (i.e., costs increase in
proportion to the ratio of capacities raised to the 0.6 power).
Using this relationship, ventilation system costs are projected to
increase to approximately $10 million for an SO2 limit of 10
ppm and to $27 million for an SO2 limit at the 2 ppm PEL level.
At the latter limit, nearly all the costs for Level B safety
equipment ($5.1 million) could be deleted. The increase in size
and/or number of APCD trains, however, would significantly
*Personal communication from S. Browning, Asbuiy Environmental Services, to E. Aul, Edward Aul and Associates, Inc., July 25,1990.
1 30
-------
Table 5-3. Estimated Costs for Waste Excavation, Waste Storage, and Fugitive Emission Control.'
Item
1 . Site Preparation
Clearing/grading
Electric/water/gas hookups'5
Equipment decon. station
Personnel decon. trailer
Office/security trailers
Subtotal
2. Permitting and Regulatory
3. Equipment
Excavation equipment
Backfill equipment
Storage equipment
Foam trailersb
Air ventilation systemb
Enclosure erection/tear-downb
Subtotal
4. Start-up/Fixed Costs
Three Excavation/backfill enclosures15
One Storage enclosure/pad1*
APCD monitoring network15
Perimeter monitoring network15
Subtotal
5. Labor Costs
Excavation
Backfill
Storage
Enclosures'5
Foam application15
Air ventilation system15
APCD monitoring network15
Perimeter monitoring network15
Subtotal
6. Supplies and Consumables
Safety equipment
Fuel/lubricants
Backfill day
Foam chemicals'5
Sodium hydroxide1"
Activated carbonb
APCD monitoring network15
Perimeter monitoring networkfa
Subtotal
7. Utilities
Air ventilation system15
APCD monitoring network15
Perimeter monitoring network6
Subtotal
8. Effluent Treatment/Disposal
9. Residual/Waste Disposal
10. Analytical Costs
Scrubber wastewater*5
Spent activated carbon*5
Wastewatei*5
Spent carbonb
Runoff water analyses
General site samples
Subtotal
1 1 . Equipment Maintenance
Foam application system b
Air ventilation system15
Excavation equipment
Backfill equipment
Storage equipment
Enclosures'5
Subtotal
Decontaminate field equipment
Re-contour site
Subtotal
13. Contingency 10%
Lease Option, $
58,600
293,900
22,800
70,000
21,100
466,400
0
5,984,000
3,735,200
510,700
160,000
3,851,500
747,500
14,988,900
1,878,100
686,800
508,600
864,500
3,938,000
3,852,400
1,968,600
1,051,600
412,500
2,278,000
1,461,100
2,540,800
1,579,800
15,144,800
5,154,300
0
38,000
2,925,200
751,400
2,699,900
348,000
1,112,400
13,029,200
7,480,800
122,300
147,800
7,750 900
3,801,000
2,626,900
63,700
88,200
5,200
954,500
1,111,600
26,800
841,100
0
0
0
653,500
1,521,400
160,000
85,800
245,800
6,462,500
3,231,200
74,318,600
Purchase Option, $
58,600
293,900
22,800
70,000
21,100
466,400
0
2,356,000
1,436,600
210,200
160,000
3,851,500
277,400
8 291 700
1,878,100
686,800
508,600
864,500
• 3938000
3,852,400
1,968,600
1,051,600
412,500
2,278,000
1,461,100
2,540,800
1,579,800
1 5 1 44 800
5,154,300
1,249,300
38,000
2,925,200
751,400
2,699,900
348,000
1,112,400
14,278,500
7,480,800
122,300
147,800
7 750 900
3 801 000
2,626,900
63,700
88,200
5,200
954,500
1111 600
26,800
841,100 ,
600,300
307,400
53,500
724,200
2,553,300
160,000
85,800
245,800
6,020,900
3,010,400
69,240,200
a Quantity of waste excavated = 116,700 tons; Volume of waste excavated = 97,100 cubic yards.
b A marginal cost item associated with fugitve emission control.
31
-------
complicate the logistics of moving the enclosures and associ-
ated ventilation equipment around the site.
The operating costs associated with the use of activated
carbon for THC control are estimated as $2.7 million for
replacement virgin carbon and $2.6 million for spen't carbon
disposal. Given these significant costs, it may prove less
expensive overall to regenerate the spent carbon therinally on
site. Such a system would have higher initial equipment costs
but lower operating costs. Other emissions associated with the
regeneration process, such as nitrogen oxides and participates,
should alsobeevaluated,however. As an alternative toactivated
carbon systems for THC control, some sites may also consider
thermal or catalytic incineration. ;
Foam chemicals also represent a significant fraction of the
costs of supplies/consumables. In the full remediation plan, foam
usage has been reduced over the trial excavation experience by
specifying that only stabilized foam be used on static waste areas
and that temporary foam not be used on dynamic areas. Officials
of 3M Company have indicated that improved foam performance
might be achieved by further experimentation with application
techniques and foam formulations. For the final remediation plan,
other vapor-suppressing systems may also merit consideration,
such as alimeslurry that dries on contactor the"shotcrete" system
used in mining operations for wall stability and dust control. Any
increase in thedegreeofvaporsuppression will directlyreduce the
size and cost of required ventilation systems.
Li the full remediation plan, it has been assumed that the excava-
tion and backfill enclosures will have to be torn down andreerected
each time theenctosuresaremoved. For smaller enclosures, Sprung
InSantStructure officials have indicated that structures can jbemoved
viawheelsoracranewithouttearingthemdown. The feasibility of
movinglaigerstructures in this nianr^ \AiUbsdetermirKxl during the
fall of 1991 atasite in the Southwest, where a similar large structure
will be used for remediation of a hazardous waste site.* I
I"
Several site-specific factors that have influenced the esti-
mation of costs for excavation and fugitive emission controls
for the McColl site should be considered when extrapolating
designs and costs to other sites. First, the depth, width, and
length of contaminated sumps largely determine 1) the size of
the enclosure required for excavation, 2) the number of enclo-
sure movements, and 3) the amount of material that rriustbe re-
excavated. For other sites, a detailed excavation plan should be
developed that takes these factors into consideration. |
i
Second, SO2 emissions from the McColl waste are higher
than those for hydrocarbon or other species and, combined with
the toxicity characteristics of SO2, determine the ventilation
rate required for the enclosure to protect worker health. If SO2
emissions are not significant, emissions of specific hydrocar-
bon species (e.g., benzene) would dictate the size of the venti-
lation equipment and the associated capital and operating costs.
Finally, because this site is located in Southern California,
no provisions have been added for freeze protection of equip-
ment such as the scrubber and foam application systems. In
colder climates, such provisions will add to the cost of equip-
ment and to operational complexity.
Conclusions and Recommendations
Conclusions
The design and economic analyses performed for the Mc-
Coll Superfund site indicate that excavation of waste under an
enclosure for control of fugitive emissions is technically fea-
sible and is expected to cost around $69 million (1990), or$593/
ton. The addition of the enclosures and other fugitive emission
control systems increases the cost of excavation, backfill, and
storage by an estimated factor of 2.0.
Total remediation costs are most sensitive to the overall
processing rate of the final treatment system. This rate effec-
tively determines the time required in the field for remediation
and, hence, the costs of remediation. Excavation and backfill
costs are also sensitive to the geology of the contamination,
especially thedepth, length, and width of areas toberemediated.
Ventilation/APCD system costs are sensitive to the emission
limits set for hazardous species within the enclosure.
Recommendations
It is recommended that EPA use the excavation rate as the
limiting factor for remediation time instead of the final process-
ing rate when investigating the costs for waste excavation and
storage. Also, the feasibility and costs of using thermal regen-
eration of activated carbon instead of replacement/disposal
should be investigated as a means of reducing operating cost!!
for THC control. In the same vein, the use of thermal or
catalytic incineration should be evaluated for THC control as an
alternative to activated carbon adsorption. Finally, research
should be conducted on alternative foam formulations and on
the use of lime slurry and shotcrete systems for the suppression
of vapors from acidic refinery sludge wastes such as those
present at the McColl site.
* Personal commtlnication from I. Fisher, Sprung Instant Structures, Inc., to E. Aul, Edward Aul and Associates, Inc., April 25,1991.
I 32
-------
References
Caterpillar-Gregory Pool Equipment Co. 1991. Personal
communication. Hooks, Caterpillar-Gregory Pool Equipment
Co., toE. Aul, Edward Aul & Associates, Inc., August23,1991.
Caterpillar Tractor Co., 1985. Caterpillar Performance
Handbook. Peoria, IL, 1985.
Church, H.K. Excavation Handbook. McGraw-Hill Book
Company, New York, NY.
CH2M-HILL. 1989. Supplemental Reevaluation of Alter-
natives: McColl Site.Fullerton, California (FinalReport),U.S.
Environmental Protection Agency, Region IX, San Francisco,
California, under Contract No. 68-01-7251. February 1989.
D&J Trucks. 1991. Personal communication from W.
Wilkerson, D&J Trucks, Inc., to E. Aul, Edward Aul & Asso-
ciates, Inc., August 23,1991.
Hyster. 1991. Personal communication from B.Bergstrom,
Hyster Co., to E. Aul, Edward Aul & Associates, Inc., August
23,1991.
McDermott,H.J. 1985. Handbook of Ventilation for Con-
taminant Control. 2nd Ed. Butterworth-Heinemann Publish-
ers, Boston, MA.
Prime Equipment Co. 1990. Personal communication from
M. Nelson, Prime Equipment Co., to E. Aul, Edward Aul &
Associates, Inc., June 12,1991.
QMC Cranes. 1991. Personal communication from R.
Robery, QMC Cranes, Inc., to E. Aul, Edward Aul & Associ-
ates, Inc., June 17,1991.
9
Radian Corporation. 1982. McColl Site Investigation: Phase
1 (Final Report).
Radian Corporation, 1983. Cost-Effectiveness Evaluation
of Remedial Action Alternatives for the McColl Site, Fullerton,
California. Prepared for State of California, Department of
Health Services, Sacramento, CA.
R.S. Means Company, Inc. 1990. Means Site Work Cost
Data 1991. R.S. Means Company, Inc., Kingston, MA, 1990.
U.S. Environmental Protection Agency (EPA). 1990.
Technology Evaluation Report: SITE ProgramDemonstration
of a Trial Excavation at the McColl Superfund Site. Risk Re-
duction Engineering Laboratory, Cincinnati, Ohio. December
1990.
Vatavuk, W. M. 1990. Estimating Costs of Air Pollution
Control. Lewis Publishers, Chelsea, MI.
33
-------
-------
Appendix A
Description of Technologies
Several measures were implemented during excavation
operations to ensure that these operations did not create a public
health impact. These measures were aimed at controlling air
emission releases from the operations, which represented the
only potential source of impact expected. The measures
implemented for this purpose were as follows:
• Use of enclosure structure
• SO2 scrubber
• Activated carbon unit
• Use of vapor-suppressing foam
Waste processing technologies planned during this program
consisted of size reduction by crushing the char and mud wastes
and tar solidification by using cement and fly ash mixtures.
Enclosure and Exhaust Air Control System
Excavation Enclosure
Arigid-frame.PVC-covered enclosure structure was erected
over part of the L-4 sump and adjoining land prior to the start
of excavation. Before its erection, the site was graded to
provide a smooth, level area. The enclosure, supplied by
Sprung Instant Structures and shown in Figures A-l and A-2,
was nominally 60 ft wide by 157 ft long and 26 ft high at the
center. The white opaque PVC cover was 26 mils thick and
impervious to gaseous emissions. The lower edge was covered
by 12 to 18 in. of soil along the ground level to prevent air
leakage. Translucent panels located along the roof peak allowed
light to enter. Personnel entry was through an airlock door,
which minimized fugitive emissions during entry. Equipment
was moved inside the enclosure through a sliding door that was
14 ft high and 9 ft 5 in. wide.
60ft
,Door
156ft. 11-1/4 in.
zza
4 in. X 6 in.
Aluminum
I Beam
5 ft x 9 ft, 6 in. Std. Vestibule Entrance
PLAN
-60ft-
SECTION
Figure A-1. Enclosure Plan and Section.
35
-------
View from east side.
Wew from west s/rfe showing air emission control system and monitoring trailer.
Figure A-2. Excavation Site Enclosure.
36
-------
The volume of the enclosure was approximately 192,000 ft3, and
akwasdrawnthiough the building atarateof approximately 1000ft3/
min. This air entia^ the buOdbg through five small, adjustable, slot-
type air vaits and was exhausted through three dampered openings
alongthewestsideofmebuilding. This exhaust system provided an
airtumoverrateofaboutTairchangesperdayandmaintainedaslight
negative pressuns of about 0.005 inch of water inside the enclosure.
This ventilation air rate was based on maintaining the SO2 level in the
enclosurebelow lOOpptn. ThiswasinturnbasedonanestimatedSO2
release from the exposed waste anda95%reduction in thesereleases
by use of foam suppressants.
The enclosure proved to be very effective in preventing the
escape of any air emissions and was quite satisfactory even
though it created a confined work space in which temperatures
were approximately 20°F above the outdoor temperature.
Air Emission Control System
The enclosure ventilation air was routed through an emission
control system consisting of a wet scrubber and an activated carbon
bed in series,followedbyafan and ventstack, as shown in Figures A-
3 and A-4. The basis for the design of the air control system is
discussed in detail in the Technology Evaluation Report.
Wet Scrubber
A counterflow, packed-bed, wet scrubber that used a mix-
ture of sodium hydroxide (NaOH) in water was used to control
sulfur dioxide emissions. The system was designed for a
nominal gas flow rate of 1000 ft3/min at 100°F and a maximum
outlet SO2 concentration of 2 ppm. The maximum inlet SO2
concentration was estimated to be 200 ppm; therefore, the
required control efficiency was 99%. A maximum pressure
drop of 10 inches of water was specified. The scrubber selected,
based on Figure A-3 these specifications, was supplied by
Interel Corp. in Englewood, Colorado. The specifications for
the actual scrubber and fan are shown in Table A-l, and the
scrubber cross-section is shown in Figure A-5.
In operation, scrubber liquid was initially maintained at a
pH of 10 to 13. When considerable scrubber liquor foaming
was encountered at this pH level, the pH was reduced to the 7
to 10 range after operation showed that the high SO2 removal
could be maintained in this range without foaming. The
nominal liquor i ecirculation rate of 20 gpm provided a liquor-
to-gas ratio (L/G) of 20 gal/1000 ft3/min.
Activated-Carbon Bed
For the reduction of VOC emissions, a granular activated
carbon bed was installed after the wet scrubber. A knockout
chamber was inserted between the scrubber and carbon bed to
trap any liquid carryover from the scrubber. Specifications for
this adsorber called for a 95% minimum removal of total
organics at a flow rate of 1000 ft3/min at 100°F and a pressure
drop not to exceed 5 in. of water.
Dampered
, Openings
Door
Inlet
Vent A
Door
-fsj-
Fan (w/Stack)
Activated Carbon
Cabinet
Knock Out Pot
Wet Scrubber
Filter Holder
Inlet
VentE
Air
Lock
Door
Inlet .
Vent C
Door
Inlet
VentD
Figure A-3. General Arrangement of Ventilation Air Cleaning Equipment
37
-------
HTN
i
Wet
Scrubber
Enclosure
^x"
Sample
Ports
Ducting Dust
From Filter
Openings and
IBIBHwJ j»S?Sa 1
iHhJ
\
\
Ground Level [__
'i
1
1
i
i •
!
Plywood
Base
K
O
I
Ducting
Stack
Connections Sample
A Ports >v.
f
[nock
utPot
55 gal
)rum)
Ductina
•
H
\\
~~ Ductina
Activated
Carbon
Cabinet
Plywc
\
\
)0(
3 *
p.
*
Base • ~_
i^^
Fan
_Mgtor
FJgun A-4. Ventilation Air Cleaning Equipment and Ducting Layout
The radial-flow, packed-bed, carbon adsorber selected was
NIXTOX Model 1500 from TIGG Corp. in Pittsburgh,
Specifications for this unit are shown in Table A:2. I
Foam Vapor Suppressants |
Two types of water-based, commercially available foam
supplied by 3-M Corporation were selected for this study: a
temporary foam that is effective for up to about 1 hr, and a
stabilized, more permanent foam that is effective for at least 1
day. These foam reagents are mixed with water and sprayed
onto the waste through a hand-held nozzle. The temporary
foam is a mixture of 6% concentrate and 94% water.'and the
morepermanentfoamisproducedbyaddinga6%concentration
of stabilizer to the temporary foam mixture. The foam was
generated in a self-contained, trailer-mounted system (Boots &
CootsModel 100) outsideof the enclosureandpumpedjthrough
a hose that passed under the enclosure's edge to an air-aspi-
rating nozzle. The temporary foam was sprayed on freshly
excavated waste surfaces in the excavation pit and on waste in
storage areas. Stabilized foam was sprayed on all exposed
waste after each day's work was completed. According to 3M,
200 gal of foam concentrate (FX 9162) and 200 gal of foam
stabilizer (FX9161)are required to formal-in.-thicklayerover
1 acre of surface, or about 0.9 gal/100 ft2. The properties of the
two types of foam used in this work are shown in Table A-3.
Waste Treatment Techniques
Tar Treatment
Because of its viscous nature and size (as excavated), the tar
was expected to require some type of solidification and size
reduction before it could be fed to a thermal destruction system.
The two solidification agents most widely used with hazardous
waste are porfland cement and lime-based pozzolana (Arniella
1990). In addition to providing stabilization, these agents were
expected to reduce the acidity of the low-pH tar to mitigate SO2
emissions during processing. Both of these agents were eval-
uated during the McColl tar treatment operations.
Pozzolana is a material that contains aluminum and silica and
that hardens at ambient temperatures in the presence of lime and
water (by itself, however.itdisplaysnocementingreactions). The
two most common pozzolanic materials are fly ash and cement
kiln dust Fly ash from a nearby powerplant was used for the
McColl tests because it was readily available (cement kiln dust is
itself considered a hazardous material in California and therefore
more difficult to transport and use). The chemical and physical
properties of the fly ash and porfland cement delivered to the
McColl Site are summarized in Table A-4.
Excavated tar was combined with porfland cement, fly ash,
and water inapugmill.both to mix these materials and to reduce
38
-------
Gas
Outlet
Mist -
Eliminator
Spray
Nozzle
Packed
Bed
Electrical
Panel
Recirculation
Pump
Liquid
Reservoir
Not to Scale
Table A-1. Scrubber and Fan Specifications*
Scrubber
Scrubber size
Design flow rate
Diameter
Sump capacity
Circulation rate
Pump motor
Type of packing
Packing height
Scrubber overall height
Type of mist eliminator
Empty weight
Operating weight
Purchase price
GWX1200
1200ft3/min
24 inches ,
190 gallons
25 gal/min
1.5hp
2-inch hollow spheres
11 feet
17 feet .
Chevron
650 Ib
2350 Ib
$22,600
Fan
Material of construction
Corrosion-resistant coating
Gas flow rate (standard air
density)
Static pressure (Neg./Pos.)
Motor rating
Purchase price
Steel
Polyurethane
1200ft/min
20 inches WG
7.5 hp
$2,200
aSupplied by Interel Corp. 5/14/90.
Table A-2. Specifications for Carbon Bed Adsorbed
Flow rate, max.
Temperature, max.
Connections
Diameter/height
Adsorbent fill
Minimum contact
Shipping weight
Materials of construction
Purchase price
Lease payment per month
Virgin TIGG5C 0410. per fill
1500ft3/min
350°F
7-in. duct
32-in./44-in.
300-lb virgin TIGG
5C 0410 (coal-based)
0.4 second
475 Ib
Coated mild steel with
316 stainless steel
screen
$2450 FOB plant
(including initial carbon
fill)
$700
$600
Figure A-5. Scrubber Cross Section.
aFrom TIGG Corporation, 3/3/90.
the size of the tar lumps. The pug mill used for this project
(Figure A-6) was a Barber Green Mixer (Model 848) that
reportedly was built during the 1950s. At one end of the mill,
tar, cement, and fly ash were charged into a small feed hopper
with a capacity of approximately 1.2 yd3. The material moved
down through the hopper and flowed onto a moving belt The
clearance between the bottom of the hopper and the belt was
almost 8 in. The belt transported the material to the head of the
pug mill, where water was added manually. The mill consisted
of two shafts fitted with short heavy paddles that rotated in the
opposite inward direction (from the bottom to the top) in an
open half cylinder. Themixing/conveyingactionofthepaddles
pushed the material from the head of the mill to its tail, where
the mixed material fell into a small product hopper (approxi-
mately 2-yd3 capacity). The hopper, in turn, emptied directly
onto the ground. The feed belt and paddle shafts were powered
by a 175-horsepower diesel engine.
The pug mill cylinder was approximately 10 ft long, 45 in.
wide, and 27 in. deep, which corresponds to an overall volume
of 5.1 yd3. The paddles were 7 in. long and 4 in. wide at the tip.
Two paddles (set at 180 degrees from each other) were set every
6 in. along the two tapered shafts; mis resulted in a clearance of
2 in. between paddle sets. As shown in Figure A-7, each set was
offset 90 degrees from adjoining sets. The throughput capacity
of the mill was reported to be almost 100 tons/hr.
Char and Mud Treatment
The objective of the char and mud processing operations
planned for this project was to reduce the size of these materials
to less than 2 in. so they would be suitable for feed to a thermal
destruction system. Thecrusherbroughton site for this purpose
was a Masterskreen Explorer, manufactured by M&KK Quarry
39
-------
Table A-3. Properties of Foam Reagents*
Properties i
Appearance
Density, Ib/gal i
Viscosity at 77°F (25° C), cp
Specific gravity at 77°F (25°C)
pH at 77°F (25°C) :
Flash point, °F
Freeze point, °F 1
Minimum-use temperature, |°F
Storage temperature, °F i
Noncorrosive
Moisture-sensitive
Price, $/lb
FX-9161foam
stabilizer
Yellow, clear
liquid solution
8.99
1500
1.08
—
200
—
—
40 to 100
Yes
Yes
4.65
FX-9162foam
concentrate
Amber liquid
solution
8.51
2300
1.02
7.8
—
28
32
35 to 120
Yes
No
2.55
aFrom 3M Corp., St. Paul, MN.
Table A-4. Fly Ash and Portland Cement Properties*
!
Silicon dioxide, %
Aluminum oxide, %
Iron oxide, % >
Sulfurtrioxide, % i
Calcium oxide, %
Loss on ignition, % :
Bulk density b, Ib/ft3
Classification !
Fly ash
61.04
18.59
5.16
1.07
5.97
0.29
86
Class F
Portland
cement
22.61
3.78
3.25
1.84
65.15
0.88
78
TypeV
aFrom Amcal Minerals Corporation, 1990.
''From field measurements
Figure A-6. Pug Mill (with Product Hopper In Foreground).
40
-------
Plant Ltd. in 1989. With this system, material is dumped into
a 4-yd3 tray feed hopper fitted with 6-in. stationary bars. From
the hopper, material is transported by a feed belt into the jaws
of the crusher. After passing through the crusher, material is
picked up by a product conveyor and transported to a vibrating
screen with 2-in.-square openings. Undersize material passes
through the screen to the ground, whereas oversize material
rolls of f the screen to another pile on the ground. The conveyor
belts, crusher, and hydraulic control system were powered by
a diesel engine.
The crusher was expected to operate on both char alone and
on a mixture of char and mud. A schematic of the crusher is
shown in Figure A-8. The overall dimensions of the unit were
51 ft long, 7 ft wide, and 17 ft deep. .
Figure A-7. Pug Mill Paddles During Tar Processing.
2-in.
Vibrating
. Screen
Bar Screen
Feed Hopper
Over
Size
Product
Figure A-8. Char/Mud Crusher Schematic.
41
-------
-------
Appendix B
Summary of SITE Demonstration at McColl Superfund Site
Introduction
The McColl hazardous waste site is ae inactive waste
disposal facility located at 2650 Rosecrans Avenue in the city
of Fullerton, Orange County, C A. The site was used in the early
and mid-1940s for the disposal of acidic refinery sludge, a by-
product of the production of aviation fuel. A series of pits or
sumps were excavated on the site to receive the refinery sludge
at that time. Onsite disposal of refinery sludge ceased in 1946.
From 1951 through 1962, fill material (soil) and drilling mud
from oil exploration activities near the Coyote Hills were
deposited in some of the pits in an attempt to make the site
suitable for future development
By 1962, the Upper Ramparts area had been covered with
soil and has existed since that time as unoccupied open space.
In the early 1980s, aclay cap was placed on the Lower Ramparts
area to reduce odors. The Los Coyotes area was covered with
4 to 5 ft of soil and developed as part of the Los Coyotes Country
Club golf course.
Areas east of the McColl site were subdivided and devel-
oped for residential housing in the late 1970s and the early
1980s. Recreational facilities were constructed west of the site
attheRalphB. Clark (formerly Los Coyotes) RegionalPark. As
the population increased and development continued, residents
began complaining of odors emanating from the site. Odor
complaints were first received by the Orange County Health
Departmentin 1978. Subsequent environmental investigations
at the site identified extensive contamination. In 1982, the
McColl site was placed on the National Priorities List (NPL).
In February 1989, EPA and DHS issued a proposed plan for
the McColl project that named thermal destruction, either on or
off site, as the preferred remedy. Important components of this
remedy are the excavation and waste-handling activities that
must occur as a precursor to thermal destruction. The overall
goal of the trial excavation was to obtain information pertaining
to these activities to support the selection of thermal destruction
as the preferred remedy and to aid in the design of a thermal
destruction remedy or any other remedy involving excavation
of the waste material after its selection in a Record of Decision
(ROD).
Region IX of the EPA determined that the trial excavation
was necessary to ascertain if McColl waste could be excavated
with conventional equipment without releasing significant
amounts of VOCs and SO2 into the surrounding community.
The trial excavation was also necessary to define the treatment
needed, if any, to improve the handling characteristics of the
waste as a precursor to thermal destruction, or any other remedy
which would involve treatment of the waste.
Site Characteristics
The McColl site covers approximately 20 acres, and approxi-
mately 8 acres of the site contain waste in pits or sumps. As shown
in Figure B-l, the site is divided into two distinct areas, the
Ramparts area and the Los Coyotes area. The Ramparts area
comprises the eastern portion of the site and contains six buried
waste pits or sumps (R-l through R-6). The Los Coyotes area,
located immediately southwest of the Ramparts area, also con-
tains six pits (L-l through L-6). The six pits in this area were
covered with soil during the construction of the golf course. The
site is bordered by the West Coyote Hills Oil Field to the north,
housing developments to the east and south of the Ramparts area,
Los Coyotes Country Club golf course to the south, and the Ralph
B. Clark Regional Park to the west All pits are covered with soil,
and the site is secured with a chain-link fence and 12-hr guard.
Objectives
The trial excavation was conducted on a portion of Los
Coyotes Sump L-4 (see Figure B-l). The objectives of the trial
excavation are as follows.
1. To excavate approximately 100 yd of waste to assess
waste-handling characteristics and to determine if any
treatment is required to improve handling characteris-
tics as a precursor to thermal destruction.
More than 130 solid yd3 of waste material (mud, tar,
and char) was excavated under the enclosure by
conventional excavation methods.
During the trial excavation, it was determined that
the mud and char material did not need further
treatment. Forthemud,itwasapparentthatthewaste
could be easily sized to the nominal 2-in.-diameter
thermal destruction requirement For the char, it was
determined that more than 50% of the excavated char
was under 2 in. in diameter and that the remaining
material could easily be sized by conventional meth-
ods (i.e., pug mill, shredder).
43
-------
Rosecrans Avenue
J'L
Ralph B. Clark
Regional Park
Ramparts Area
McColi Site
Los Coyotes
Golf Course
FlQunB-1. McColfSIto. ;
:The tar material was determined to require Addi-
tional treatment to allow for future processing into a
thermal destruction unit. This was accomplished by
mixing the tar with cement or fly ash and water in a
pug mill. The result of this treatment process was
pellets that were less than 2 in. in diameter.
I. To determine the atmospheric emissions resulting
from the excavation activities. i
This objective was only partially achieved during
the trial excavation. Data for SO2 and total hjfdro-
carbons (THC) are reported; however, no data for
organic species or reduced sulfur species are reported.
High-quality data were obtained for SO2 and THC
emissions exiting the enclosure exhaust treatment
system. Five-minute averages for SO2 emissions
were maintained at less than 1 ppm throughout the
project. The highest 5-min average for THC emis-
sions was 98.1 ppm. Samples for organic and re-
duced sulfur compounds were collected from the
stack and analyzed, but the data were determined to
be invalid by an EPA audit
Benzene (a known carcinogen), toluene, ethyl benzene,
and xylenes are known to be the major constituents of
the THC concentrations reported, but no quantifiable
concentrations of these compounds can be reported for
the reason given in the preceding paragraph.
3. ToassessthedegreeofSO2andTHCemissioncontrol
achieved through the use of an enclosure and an
enclosure exhaust treatment system.
44
-------
This objective was achieved by erecting an enclosure
around the excavation area and exhausting the ventila-
tion air through an enclosure exhaust treatment system
consisting of a sodium-hydroxide scrubber and an
activated carbon unit.
The daily average removal efficiency for SO2 ranged
from 71.8 to 99.9%, with greater than 90% removal
being achieved on most days.
The daily average removal efficiency for THC ranged
from 15.8 to 90.7%, with greater than 50% removal
being achieved on most days.
4. To determine the emission levels for SO2 and VOCs at
the fenceline of the McColl site as an indicator of
impacts on the local community.
This objective was partially achieved for the reasons
outlined in Objective 2. Reliable data for SO2 and THC
emissions were collected at four perimeter monitoring
stations, with no levels being detected that would ad-
versely affect the surrounding community.
5. To assess the effectiveness of vapor-suppressing foam.
This objective was partially achieved. Reduction
efficiency rates have been calculated for dynamic
conditions. Reduction efficiency rates could not be
calculated for static conditions because analytical data
were determined to be invalid by an EPA audit
Under dynamic conditions, it has been estimated that
the vapor-suppression foam can be up to 80% effective
for SO2 control and 60% effective for THC control.
6. To assess potential problems that might occur during
excavation.
Assessments were made regarding problems that oc-
curredbecauseof the following: higher-than-expected
emissions of SO2 and THC from the tar and char; high
paniculate diesel emissions; heat gain; working in
Level B and Level A personal protection equipment;
excess water in a confined space; and seepage of tar
material.
Excavation and Waste Processing
Removal of overburden and excavation of the underlying
waste were readily performed with a trackhoe equipped with an
extended boom and a 1-yd3 bucket. The waste, which was
found to be fairly well segregated into layers, was placed in
rolloff bins or piles for subsequent use. Removal of the
overburden proceeded routinely and was followed by excava-
tion of a 3-ft-thick mud layer. A 4-ft-thick tar layer was
excavated next. After the tar was removed, a trench shield was
placed in the excavated area to reduce seepage of additional tar
into the opening. After the tar layer was excavated, a hard, coal-
like, char layer was encountered. This material was broken up
and excavated.
During the tar excavation, SO2andtotalhydrocarbons (THC)
levels within the enclosure increased dramatically and reached
5-min average values of 1000 and 492 ppm, respectively. The
enclosure exhaust treatment system removed up to 99.9% of the
SO2 and 60% of the THC during this excavation period. The use
of the enclosure and enclosure exhaust treatment system pre-
vented any significant amounts of thesepollutants from reaching
the site perimeter, as evidenced by the low concentrations
measured there. The higher-than-expected concentrations within
the enclosure required an upgrading of personal protection
equipment from Level B (coated tyvek overalls with supplied
air) to Level A (completely encapsulating suit with supplied
air).
Char excavation was also accompanied by high concentra-
tions of SO2 and THC, which reached 5-min average values of
755 and 350 ppm, respectively. The enclosure exhaust treat-
ment system operated efficiently during the entire study with up
to 99% removal of the, SO2 and up to 90.7% removal of the THC.
Higher-than-expected levels of SO2 and THC within the
enclosure were caused by the failure of vapor-suppressing foams
to form an impermeable membrane over the exposed wastes. The
foams reacted with the extremely acidic waste, which severely
impacted the foam's ability to suppress emissions.
This ability was improved somewhat, however, when the
concentration of foam reagents in water was increased. Though
difficult to estimate, the overall reduction achieved by applying
foam was estimated at up to 80% for SO2 and 60% for THC,
based on concentrations measured at the enclosure exhaust
treatment system inlet during excavation activities with and
without foam.
In all, 137 yd3 of waste and 101 yd3 of overburden were
excavated. Maximum and average trial excavation rates are
summarized in Table B-1.
The average excavation rates achieved during this trial
excavation will be increased considerably during full-scale
excavation, as fewer observations and measurements would be
needed. Average excavation rates that could be expected to be
achieved during full-scale excavation are estimated at 49,32, and
25 yd3/h for overburden and mud, tar, and char, respectively.
The tar waste was further processed to reduce its size and to
form a solid and easier-to-handle pellet. This was accom-
plished by mixing the tar with cement, fly ash, and water in a
pug mill. Ten test runs were made within the enclosure at
various ratios of tar, cement, fly ash, and water. A ratio of 1 part
tar to between 2.3 and 7 parts cement and fly ash and from 0.26
to 1 part water formed a solid, easy-to-handle pellet Tar
processing rates of approximately 3 tons/h were achieved
during the trial excavation, and it is estimated that this rate could
Table B-1. Maximum and Average Trial Excavation Rates (ydP/h)
Component
Overburden
Mud
Tar
Char
Maximum
51
66
58
9
Average
7.6
: 4.1
-4.3
2.6
45
-------
be increased by up to a factor of 2 with a more continuous
operation. Indications were that tar processing with alkaline
materials such as cement and fly ash reduced the amount of SO2
released by the tar. The mud and char waste fractions did not
require further processing, but could have been fed through the
pug mill if necessary. •
Previous investigations at the McColl site indicated that the
waste has the potential to emit significant amounts of: VOCs,
organic sulfur compounds, and SO2. For the trial excavation,
this potential air emission impact was mitigated by the erection
of a temporary enclosure 60 ft wide, 160 ft long, and 26 ft high
in the center of the excavation area. Airfrom the enclosure was
vented through an enclosure exhaust treatment system consist-
ing of a sodium-hydroxide-based wet scrabber and an acti-
vated-carbon adsorber in series before being released to the
ambient air.
For the trial excavation, this potential air emission impact
resulted in having workers wear Level B or Level A protection
at all times while inside the enclosure. Concentrations of SO2
and THC were continuously monitored before and after the
enclosure exhaust treatment system. !
Waste Characteristics
Three major waste types are present at the McColl ;site: 1)
hard, black, char-like asphaltic wastes; 2) viscous, black, tar-
like wastes; and 3) mud. The predominant waste type found at
the site is a black asphaltic waste that is apparently the result of
chemical and physical changes in acidic refinery sludge that
have occurred over the last 40 years. This asphaltic waste has
a low pH (acidic) and contains elevated levels of organic
compounds. When disturbed, the waste emits sulfur dioxide
(SO.) and hydrocarbon vapors. Because of its acidic nature, the
McColl waste is characterized as RCRA corrosive waste ac-
cording to CFR 261.22.
Borings previously made in theL-4 Sump showed that both
tar and char were present in fairly segregated layers under a
layer of moist soil or mud, which was in turn under Approxi-
mately 8 ft of overburden soil. During previous studies at this
site, two types of air emissions were observed when the waste
was disturbed. The initial disturbance generally caused a high
level or "puff* release of contaminants, followed by a rapid
decline to lower levels (Radian 1983). These steady-state
emission levels were then observed for longer periods of time
and gradually decreased over several hours. The emission
potential in the Ramparts area ranged from 130 to 130,000 mg/
m2 per min for SO2 and 10 to 3600 mg/m2 per min for THC for
all disturbed waste types. Average steady-state emissions from
asphaltic waste were 5200 mg/m2 per min for SO2 and J190 mg/
m2 per min for THC. Hydrocarbon analysis of air isamples
showed an average composition of 60% aliphatic and pxygen-
ated species, 30% aromatic species, and 10% organic sulfur
species. The waste composition did vary from sump to sump,
however, and even with depth within a sump (Schmidt 1989).
Samples of excavated waste were analyzed to determine heat
value and the concentrations of selected constituents. The infor-
mation obtained by these analyses is summarized in Table B-2.
The mud fraction of this waste consisted largely of inor-
ganic, noncombustible material with an ash content of 82.9%
and a heating value of less than 500 Btu/lb. The raw tar sample
contained a high percentage of combustible material and had a
heating value of more than 9000 Btu/lb, an ash content of less
than 2%, and a high sulfur content (10.6%). The treated tar
sample contained cement dust and fly ash (low-sulfur, high-ash
components), and the addition of this material decreased all of
the combustible parameters and increased the ash value. Raw
char has a fairly high ash level (about 55%), a sulfur content of
4.5%, and a heating value of 5200 Btu/lb.
Common indicators for petroleum waste are the concentra-
tions of benzene, toluene, ethylbenzene, and xylene (BTEX).
The McColl samples data show that the tar fraction of this waste
contains the highestlevels of thesecompounds and that the mud
layer contains only a relatively small portion of these com-
pounds.
Toxicity characteristics of the raw tar and char were deter-
mined by the Toxicity Characteristics Leaching Procedure
(TCLP) andCalifbrnia WetTesL No metalconstituents exceeded
the regulatory limit in either case. Benzene in the tar and char
waste extract exceeded the EPA TCLP limit of 500 ng/Iiter by
greater than a factor of 2.
Community Impact
Perimeter air monitoring for SO2 and THC was conducted
continually during this study. Windspeed and wind direction
were also recorded continually at the site. This information was
obtained to comply with the Community Contingency Plan,
which mandates that all site work be stopped if SO2 levels at the
perimeter exceed 0.5 ppm for 5 min or if THC levels exceed 70
ppm for 30 sec. These levels were never reached during this
study. The maximum 1-hr readings obtained at any perimeter
station in June, which was the period of highest emissions from
thewaste, wereO.08 ppm for SO2and21.9ppm for THC. Specific
compounds in the air at the perimeter of the site and in the
neighborhood were sampled and analyzed.
Health and Safety Issues
Both health and safety and commun ity exposure issues
were assessed prior to the trial excavation demonstration. These
issues are discussed in the following subsections:
Table B-2. Waate Characteristics, As-Received Basis
Moisture, %
Sulfur, %
Fixed carbon, %
Ash, %
Benzene, ppm
Toluene, ppm
Xylene, ppm
Ethylbenzene, ppm
Heat value, Btu/lb
Mud
13.2
0.8
0.2
82.9
<0.7
1.5
8.6
0.9
<500
Tar
11.6
10.6
16.9
1.6
240
580
910
140
9160
Treated
tar
8.1
3.6
2.0
75.9
NAa
NA
NA
NA
2200
Char
21.2
4.5
4.0
54.7
97
150
220
35
5200
aNA = Not analyzed. Use of cement additive would
reduce concentrations found in raw tar sample.
46
-------
Worker Safety
Excavation work inside the enclosure was conducted either
in Level B or Level A personal protective equipment Level B
equipment consisted of supplied-air respirators, coated Tyvek
overalls, steel-toed boots, inner and outer gloves, and a hard hat.
Air bottles were mounted on the trackhoe, loader/backhoe, and
Bobcat for operator air supply; other members of the crew used
air lines supplied from air cylinders located outside the enclo-
sure. Level A requirements included the addition of a totally
encapsulating chemical protective (TECP) suit to the preceding
equipment list. Air supplies to these suits were either from air
lines (as previously discussed) or from a self-contained breath-
ing apparatus inside the suits.
The observation camera used was an invaluable tool for
observing/recording activities that occurred within the enclo-
sure. The camera also allowed all workers to be observed from
a health and safety standpoint The camera also assisted in a
reduction of the number of employees necessary within the
enclosure, which allowed for more efficient operations and
reduced the risk of employee accidents.
Community Exposure
Because of the nature of the contamination at the McColl
site, community exposure was determined to be a significant
concern. Perimeter air monitoring for SO2 and THC was con-
ducted continually during this study. Windspeed and wind
direction were also recorded continually. This information was
obtained to comply with the Community Contingency Plan,
which mandates that all site work be stopped if SO2 levels at the
perimeter exceed 0.5 ppm for 5 min or if THC levels exceed 70
ppm for 30 sec. These levels were never reached during this
study.
Based on observations by personnel during the trial excava-
tion, the noise level related to the excavation and treatment
activities was minimal. At no time during the trial excavation
were the health-based levels established in the McColl Contin-
gency Plan for SO2 and THC exceeded at the fenceline moni-
toring stations. Although odor complaints were received dur-
ing the trial excavation period, they were not excessive. Most
of the complaints were received after the trial excavation/
treatment activities were completed for the day, and may not
have been related to the excavation/treatment activities.
Costs of Excavation and Tar Processing
The costs for the field aspects of this trial excavation work
consisted of those involved with the enclosure and the enclo-
sure exhaust treatment system, actual excavation labor and
equipment, foam application, tar processing, and air monitor-
ing. Much of the equipment for this project (e.g., enclosure
framework, scrubber, and excavation machinery) was rented on
a monthly basis; therefore, total costs consisted of the monthly
machinery charges, labor, and fixed costs required to mobilize
and demobilize. These costs are summarized in Table B-3 for
the 2-month duration of the field work.
Table B-3. Summary of Onslte Costs
Item
Enclosure
Air exhaust control system
Foam vapor suppressants
Excavation3
Tar processing
Air monitoring
Total
Total cost, $
70,976
40,415
89,591
82,512
17,367
100.160
401,021
aBased on 18 days of excavation.
47
-------
-------
Appendix C
: Applicability of the McColl Enclosure and Excavation
Technologies to Current CERCLA Sites
Many GERCLA sites share the problem of soil contaminated with volatile organics, volatile metals, and
metal-laden dust that can result in toxic air emissions during waste excavation, processing, and treatment. Table
C-1 presents a list of current CERCLA sites where the McColl enclosure and excavation techniques may be
applicable. These sites were selected based on the existence of airborne contaminants and the site's proximity
to areas threatened by the release of these contaminants. Other site-specific conditions may preclude the use
of some or all of the McColl techniques at certain sites.
49
-------
Table C-1. Current CERCLA Site* Where the McColl Enclosure and Excavation Technologies May Be Applicable
Site name/location
Air contaminants
Threatened areas
Region I - ',
Silresim Chemical Corp.
Lowell, MA
Pesticides, VOCs
Business district
Residential
Region II
Combe Fill North Landfill,-
Mount Olive Township, NJ
Fried Industries, East Brunswick Township,
NJ
Glen Ridge Radium Site. Glen Ridqe, NJ
Montclair/West Orange Radium,
Montclair/West Orange, NJ
Woodland Township, Route 532 and
Route 72 Sites. Woodland Township, NJ
Richardson Hill Road Landfill, Sidney
Center. NY
Port Washington Landfill, Port
Washington. NY
Region III
Abex Corp., Portsmouth, VA
Greenwood Chemical Co., Newton, VA
Rhinehart Tire Fire Dump, Frederick
County, VA
Kane & Lonbard Street Drums, Baltimore,
MD
Ambler Asbestos Piles, Ambler, PA
Brown's Battery Breaking,
Shoemakersville, PA
McAdoo Associates, McAdoo, PA
Taylor Borough Dump, Taylor, PA
Bis (2-ethylhexyl) phthalate,
chlorobenzenes, phenol, VOCs
VOCs
Radon
Radon
Organic solvents
VOCs
Methane
Benzene
Toluene
Xylene
Vinyl chloride
Residential
Residential
Residential
Residential
Residential
Aaricultural
Residential
Residential
Golf Course
School
•Heavy metals
VOCs
VOCs
Acrolein
Benzene
Ethyl benzene
Xylene
Chromium
Asbestos
Lead
Heavy metals
PAHs
Phthalate esters
;VOCs
1 Heavy metals, VOCs
Residential
Residential
Agricultural
Agricultural
Residential
Residential
Plavaround
Residential
Residential
Residential
Community Park
Region IV
Interstate Lead Co., Leeds, AL
Brantley Landfill, Island, KY
Fort Hartford Coal Co., Inc., Olaton, KY
Maxey Flats Nuclear Disposal, Hillboro, KY
Carolawn, Fort Lawn, SC
Lead
Ammonia
Dust
Heaw metals
Ammonia
iTritium
Heavy metals
Phenols
;VOCs
Residential
Residential
Residential
Recreational
Residential
Residential
(continued)
50
-------
Table C-1. (continued)
Site name/location
Air contaminants
Threatened areas
Region V
Taracorp Lead Smelter, Granite City, IL
Berlin & Farro, Swartz Creek, Ml
Feed Materials Production Center,
Fernaid, OH
Lead
Pesticide byproducts
Radon
Residential
Residential
Residential
Agricultural
Region VI
Bayou Sorrel Site, Bayou Sorrel, LA
Combustion Inc., Denham Springs, LA
Dutchtown nontreatment Plant, Ascension
Parish, LA
Lee Acre Landfill, Farmington, NM
Cal West Metals, Lemitar, NM
Volatile organic and inorganic
pollutants
VOCs
VOCs
VOCs
Lead
Industrial
Residential
Agricultural
Residential
Residential
Recreational
Residential
Recreational
Region VII
A.Y. McDonald Industries, Inc., Dubuque,
IA
Peoples Natural Gas Co., Dubuque, IA
White Farm Equipment Co., Charles City,
IA
Missouri Electrical Works, Cape Girardeau,
MO
Weldon Spring Quarry, St. Charles County,
MO
Lead
Cyanide
PAHs
Phenols
Heavy metals, dust
Aroclor 1260, Aroclor 1260, dust
Radioactive dust
Residential
Business district,
Residential
Residential,
Wetlands
Residential,
Wetlands
Industrial
Region VIII
Uravan Uranium Project, Uravan, CO
Richardson Flat Tailings, Summit County,
UT
Silver Creek Tailings, Park City, UT
Uranium
Heavy metals
Heavy metals
Wildlife habitat
Residential,
Recreational
Residential
Region IX
Montrose Chemical Corp.
Torrance, CA
South Bay Asbestos Area, Alviso, CA
United Heckathorn Co., Richmond, CA
DDT
Asbestos-laden dust
DDT
Industrial,
Residential
Residential,
Wildlife Refuge
Residential
Region X
Teledyne Wan Ghana Albany, Albany, OR
Seattle Municipal Landfill, Kent, WA
Metals, VOCs, radioactive dust
1,2-Dichloroethane,
tetrachloroethylene
Residential
Residential
51
-------
-------
1. REPORT NO.
540/AR-92/015
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
2.
4. TITLE AND SUBTITLE
Demonstration of a Trial Excavation at the McColl
Superfund Site
Applications Analysis Report.
3. RECIPIENT'S ACCESSION NO.
PB 93-100121
5. REPORT DATE
October 199?
6. PERFORMING ORGANIZATION CODE*
7. AUTHOR(S)
IT Corporation
9. PERFORMING ORGANIZATION NAME AND ADDRESS
IT Corporation
11499 Chester Road
Cincinnati, OH 45246
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-4284
12. SPONSORING AGENCY NAME AND ADDRESS
Risk Reduction Engineering Laboratory--Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, OH 45268
13. TYPE OF REPORT AND PERIOD COVERED
CY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Manager: S. Jackson Hubbard (513) 569-7507
16. ABSTRACT
fho M r ii txcav.tTc.
-------
-------
-------
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
Please make ail necessary changes on the beiow label,
detach or copy, and return to the address in the upper
left-hand comer.
If you do not wish to receive these reports CHECK HERE D;
detach, or copy this cover, and return to the address in the
upper left-hand comer.
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/540/AR-92/Q15
------- |