TECHNOLOGY EVALUATION REPORT:
SILICATE TECHNOLOGY CORPORATION, SOLIDIFICATION/STABILIZATION OF
PCP AND INORGANIC CONTAMINANTS IN SOILS; SELMA, CA
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
-------
NOTICE
The information in this document has been funded by the U.S. Environmental Protection
Agency under Contract Nos. 68-03-3484 and 68-CO-0047, and the Superfund Innovative Technology
Evaluation (SITE) program. This document has been subjected to the Agency's peer review and
administrative review and it has been approved for publication as a U.S. EPA document. Mention of
trade names or commercial products does not constitute an endorsement or recommendation for use.
n
-------
FOREWORD
The Superfund Innovative Technology Evaluation (SITE) program was authorized by the 1986
Superfund Amendments and Reauthorization Act (SARA). The program is a joint effort between
EPA's Office of Research and Development (ORD) and Office of Solid Waste and Emergency
Response (OSWER). The purpose of the program is to assist the development of hazardous waste
treatment technologies necessary to implement new cleanup standards that require greater reliance on
permanent remedies. This assistance is accomplished through technology demonstrations that are
designed to provide engineering and cost data on selected technologies.
This project was a field demonstration under the SITE program and was designed to analyze
the Silicate Technology Corporation solidification/stabilization technology. The technology
demonstration took place at a lumber treating facility in Selma, California. The demonstration effort
was directed to obtain information on the performance and cost of the technology and to assess its use
at this and other Superfund or uncontrolled hazardous waste sites. Documentation related to this
technology consists of two reports: (1) an Applications Analysis Report that evaluates and discusses
the potential applicability of the STC treatment process; and (2) this Technology Evaluation Report
that describes field activities and laboratory results.
Copies of this report can be purchased from the National Technical Information Service,
Ravensworth Building, Springfield, Virginia 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
in
-------
ABSTRACT
T i, ,This Jechnol°gy Evaluation Report evaluates the solidification/stabilization process of Silicate
Technology Corporation (STC) for the on-site treatment of contaminated soil The STC
immobilization technology uses a proprietary product (FMS Silicate) to chemically stabilize and
microencapsulate organic and inorganic wastes, and to physically solidify contaminated soils.
, The/0SIS demonstrati°n was conducted under EPA's Superfund Innovative Technology
Evaluation (SITE) Program in November, 1990, at the Selma Pressure Treating (SPT) wTod
preserving site in Selma, California. The SPT site was contaminated with both organics
predominantly pentachlorophenol (PCP), and inorganics, mainly arsenic, chromium, and'copper
Extensive sampling and analyses were performed on the waste both before and after treatment to
compare physical, chemical, and leaching characteristics of raw and treated wastes STC's
contaminated soil treatment process was evaluated based on contaminant mobility measured bv
numerous leaching tests; and structural integrity of the solidified material, measured by physical
t?f^T ^ m0rphol°fcal tions. This report provides a comprehensive description of
the SITE demonstration and its results including a description of data collection activities, testing
procedures, and quality assurance and quality control (QA/QC) results.
Conclusions resulting from this SITE demonstration evaluation are that: (1) the STC process
chemically stabilized contaminated soils containing both inorganic and semivolatile organic
SvT^W 846 ^LT^nf °AS ^ redUCed by 91 t0 91 Percent as d*ermined%y total waste
Sf«IS, ^f6: MetJl°d 8270); (3).arse^ and copper were immobilized based on various leach-
est cr tena (4) chromium concentrations were very low prior to and after treatment, but showed
shght to moderate increase in leachability after treatment; (5) PCP concentrations remained above
California state regulatory threshold levels after treatment; and metal concentrations in the treated
S ^We?r7°nT ^ bdOW Calif°mia StatC regUlat°ry thresholds; «*> the «hort-term physical
stability of the treated waste was good, with unconfined compressive strengths well above landfill
solidification standards; (7) due to the addition of reagents, treatment resuL in a volume ncrea e of
59 to 75 percent (68 percent average) and a slight bulk density increase; (8) six-month monitoring
showed increased concentrations of the contaminants released from the treated waste- (9) eighteen-
month monitoring showed improved percent reductions for arsenic and PCP relative'to 6-month cured
sample test results; (10) thirty-two-month monitoring showed comparable percent r^fcTfe PCP
relative to 18-month results, but arsenic leachability more closely resembled 6-month re Ss (11)
chromium and copper showed slight to moderate increases in leachate concentrations over toe
although copper concentrations at 32 months more closely resembled 28-day results than either'e
month or 18-month results; and (12) unconfined compressive strengths increased an average S 145
and 245 percent for 32-month and 18-month samples, respectively, relative to 28-day values.
IV
-------
TABLE OF CONTENTS
Section
NOTICE -. ii
FOREWORD ...' iii
ABSTRACT iv
LIST OF TABLES ix
LIST OF FIGURES x
ABBREVIATIONS - - - - xi
CONVERSION OF U.S. CUSTOMARY UNITS TO SI UNITS xiv
ACKNOWLEDGMENTS xv
1.0 EXECUTIVE SUMMARY 1-1
1.1 INTRODUCTION . 1-1
1.2 OVERVIEW OF THE SITE DEMONSTRATION 1-2
1.3 SUMMARY OF SITE DEMONSTRATION RESULTS 1-3
2.0 INTRODUCTION 2-1
2.1 SITE PROGRAM . 2-1
2.2 PURPOSE OF THE TECHNOLOGY EVALUATION REPORT 2-3
2.3 SITE DEMONSTRATION OBJECTIVES . . . 2-3
3.0 TECHNOLOGY DESCRIPTION .3-1
3.1 PROCESS CHEMISTRY 3-1
3.2 TREATMENT PROCESS . . 3-2
3.3 FACTORS AFFECTING THE PERFORMANCE OF THE TECHNOLOGY . . . 3-5
3.3.1 Waste Characteristics 3-5
3.3.2 Volume/Density Increase . . . 3-6
3.3.3 Operating Conditions 3-7
3.3.4 Climate and Curing Conditions . .3-8
4.0 DESCRIPTION OF THE DEMONSTRATION SITE - 4-1
4.1 SITE BACKGROUND 4-1
4.2 SITE DESCRIPTION . . . 4-2
4.3 SITE CONTAMINATION CHARACTERISTICS 4-2
-------
'see
TABLE OF CONTENTS (continued)
Section
5.1.1 Preliminary Treatability Study ........................... 5_2
5.1.2 Arsenic-Spiked Treatability Study ......................... 5.7
5.1.3 Reagent Mixture and Ratio Selection ...................... 5_10
5.2 PILOT-SCALE DEMONSTRATION FIELD ACTIVITIES .. 5-1 1
5.3 LABORATORY ANALYSES ..................... ..... 5_16
5.4 QUALITY ASSURANCE/QUALITY CONTROL PLAN . . . . . . . . . . . . . . 5.47
6.0 ANALYTICAL PROCEDURES AND RESULTS ......................... 6_1
6.1 PURPOSE ................................. 6.J
6.2 MATERIALS BALANCE ............... ................. 6-1
6.2.1 Materials Balance ................................... g_l
6.2.2 Additives Ratio .................................... g_4
6.2.3 Volume Expansion Ratio ............................... 6-5
6.3 LEACHING TESTS ...................................... 6.6
6.3.1 Toxicity Characteristic Leaching Procedure (TCLP) ...... 6-7
6.2.2 TCLP-Distilled Water (Modified TCLP) ............. ..... 6-18
6.3.3 TCLP-Cage Test (Modified TCLP) ...... ......... 6-26
6.3.4 CALWET ............................... ....... 6_26
6.3.5 ANS 16.1 (Modified) ................. '.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 6-30
6.3.6 Summary of Leach Tests ............................. 6-40
6.4 CHEMICAL ANALYSES
6.4.1 Organics ........................................
"6.4.2 Inorganics ............... g 53
6-4.3 pH ......................... '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 6-53
6-4.4 Eh ........................................... 6.62
6.4.5 Acid Neutralization Capacity ........................... 6-62
6.4.6 Neutralization Potential .............................. 6-62
6.4.7 Loss On Ignition ................................... 6_63
6.4.8 Oil and Grease Analysis ....................... 6-63
6.5 PHYSICAL TESTS ...................................... 6.63
6.5.1 Particle-Size Analysis ................................ 6-67
6.5.2 Moisture Content .................................. g_67
6.5.3 Bulk Density ..................................... g_gg
6.5.4 Permeability .................................... g_gg
6.5.5 Unconfined Compressive Strength (UCS) ....... ' ............ 6-69
vi
-------
TABLE OF CONTENTS (continued)
Section
6.5.6 Wet/Dry Weathering Test 6.69
6.5.7 Freeze/Thaw Weathering Test \'_ 6-70
6.6 PETROGRAPHIC ANALYSES 6.71
6.6.1 Optical Microscopy 6-72
6.6.2 X-Ray Diffractometry (XRD) ' ] ' 5.79
6.6.3 Scanning Electron Microscopy (SEM) 6-81
6.6.4 Fourier Transform Infrared Spectroscopy (FTIR) 6-90
6.7 LONG-TERM MONITORING 6 92
6.8 QUALITY ASSURANCE RESULTS '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. 6-109
6.8.1 Quality Assurance Review of Critical Parameters 6-111
6.8.1.1 Detection Limits 6-111
6.8.1.2 Holding Times 6-111
6.8.1.3 Accuracy and Precision 6-114
6.8.1.4 Sample Contamination 6-118
6.8.2 Quality Assurance Review For Non-Critical Parameters 6-119
6.8.2.1 Detection Limits 6-119
6.8.2.2 Holding Times 6-120
6.8.2.3 Accuracy and Precision 6-120
6.8.2.4 Sample Contamination 6-123
6.8.3 Overall Completeness of the Analytical Data 6-124
6.8.4 Quality Assurance Review For Long-Term Data 6-124
6.8.4.1 Holding Times 6-125
6.8.4.2 Accuracy and Precision 6-125
6.8.4.3 Sample Contamination 6-127
6.8.4.4 Completeness of Long-Term Data 6-127
6.8.5 Quality Assurance Review for Additional Studies 6-128
6.8.5.1 Holding Times 6-128
6.8.5.2 Accuracy and Precision 6-128
6.8.5.3 Sample Contamination 6-129
6.8.5.4 Completeness 6-130
6.9 SUMMARY OF RESULTS 6_130
vn
-------
TABLE OF CONTENTS (continued)
Section Page
7.0 DEMONSTRATION COSTS 7-1
7.1 U.S. EPA SITE CONTRACTOR COSTS 7-1
7.1.1 Phase I: Planning Stage 7-1
7.1.2 Phase II: Demonstration Stage 7-2
7.2 DEVELOPER (STC) COSTS 7-2
8.0 REFERENCES 8-1
via
-------
LIST OF TABLES
Table
Page
3-1 Operating Parameters for the STC SITE Demonstration 3.7
5-1 Area Characterization Sample Data for SPT Site 5 3
5-2 TCLP Analyses of Treatability Samples of STC-Treated Wastes 5"4
5-3 Analytical Results of TWA, CALWET-Distilled Water, and TCLP-Cage for
Treatability Samples
5-4 Analytical Results for Arsenic-Spiked Raw and Treated Waste 5"g
5-5 STC-Treatability Study Batch Contents 5 ,"0
5-6 Analytical Results for PCP and Arsenic Treatability Study 5^1
6-1 Analytical and Measurement Methods \ ~
6-2 Summary of Materials Balance Data ' ' /,
6-3 Regulatory Thresholds for Critical Analytes of the SPT Waste 68
6-4 Analytical Results for TCLP Leachates go
6-5 Arsenic lon-Speciation for STC-Treated Wastes '.'.'.'. 6 17
6-6 Analytical Results for TCLP-Distilled Water Leachates . . ' '.'. ' '. 6"l9
6-7 Analytical Results for TCLP-Cage Leachates r"97
6-8 Analytical Results for CALWET
6-9 ANS 16.1 Leachate Analyses for STC-Treated Waste (Batch 3)
6-10 Total Waste Analyses (TWA) for PCP
6-11 TWA for PCP Using Modified Acid Extraction '.'.'.'.'.
6-12 Analytical Results for TCLP-pH 12 Leachates '.'.'.'.'.'.'.'.'. 6^48
6-13 PCP Concentrations for SPT Site Waste Upon Heating .... 6"50
6-14 Analytical Results for Dioxins in STC-Treated Wastes 6-51
6-15 Analytical Results for Dibenzofurans in STC-Treated Wastes 6~52
6-16 Metal Analyses of Water and Sand Additives 6"54
6-17 Metal Analyses of Reagent Mixture (Sand Plus Reagents) '.'.'.'.'. 6~54
6-18 Total Waste Analyses (TWA) for Inorganic Target Analytes . 6~55
6-19 Analytical Results for pH, Eh, Loss on Ignition, and Neutralization Potential for Raw' '
and Treated Wastes
6-20 pH, Eh, Loss on Ignition and Neutralization Potential for Sand, Water, and STC
Reagent Mixture
6-21 Oil and Grease Analyses of STC-Treated Waste 6"64
6-22 Physical Characteristics of the STC Raw Waste 6~65
6-23 Physical Characteristics of STC-Treated Wastes and Reagent Mixture 6~66
6-24 Wet/Dry Weathering Data of STC-Treated Wastes .... 6"70
6-25 Freeze/Thaw Weathering Data of STC-Treated Wastes . . 6~71
6-26 Petrographic Analysis of STC-Treated Wastes 6"74
6-27 Abundance of Mineralogic Phases in X-ray Diffraction Analysis of Raw and Treated
Wastes
* f^ 52O
u-^,o ryujiyaLs Percentage Weight Loss Data for Raw Wastes 691
6-29 Pyrolysis Percentage Weight Loss Data for Treated Wastes 6 91
6-31 Analytical Results for TCLP-Distilled Water Leachates '.'. 6-104
6-32 18-Month Weathered Monolith Test Results 6~108
6-33 Long-Term Chromium Analysis - TCLP-Distilled Water (Batch 5) . 6-110
6-34 Long-Term Unconfmed Compressive Strength 6 110
6-35 Long-Term Permeability Testing 6-110
ix
-------
LIST OF FIGURES
Page
3-1 Schematic Diagram for STC Treatment Process 3.3
4-1 Regional Location Map - SPT Site, Selma, California '.'.''.'.'.'.'. 4-3
4-2 Areas of Contamination at the SPT Site 4.4
5-1 SPT SITE Demonstration Layout 5..13
6-1 TCLP - PCP 6..14
6-2 TCLP - Arsenic '.'.'.'.'.'.'.'.'.'.'. 6-14
6-3 TCLP - Chromium '.'.'.'.'.'.'. 6-15
6-4 TCLP - Copper ['/_] 6_.15
6-5 TCLP-Distilled Water - PCP '.'.'.'.'.'.'.'.'.'.'.'. 6-24
6-6 TCLP-Distilled Water - Arsenic '.'.'.'.'.'.'.'. 6-24
6-7 TCLP-Distilled Water - Chromium '.'.'.'.'.'.'. 6-25
6-8 TCLP-Distilled Water - Copper 6_25
6-9 TCLP-Cage - PCP 6-28
6-10 TCLP-Cage - Arsenic '.'.'.'.'.'.'.'.'.'.'.'.'. 6-28
6-11 TCLP-Cage - Chromium '.'.'.'.'.'.'.'.'. 6-29
6-12 TCLP-Cage - Copper 6 29
6-13 CALWET - PCP '.'.'.'.'.'.'.'. 6-36
6-14 CALWET - Arsenic ' \ \ 6.36
6-15 CALWET - Chromium . . \ 6.37
6-16 CALWET - Copper 6 37
6-17 TWA - PCP .' ." 6_44
6-21 STC Solidified Waste Core (Batch 4) '. " " 6.75
6-22 Longitudinal Cut of Solidified Reagent Mixture and Sand 6-75
6-23 Poorly Consolidated Solidified Waste Core (Batch 1-QC) 6-76
6-24 Photomicrograph Showing Less Uniform Binder Distribution 6-76
6-25 Photomicrograph Showing Soil Particles Surrounded By Densely Pigmented Binder
(Batch 5) 6_77
6-26 Longitudinal Cut of Solidified Waste Core (Batch 4) 6-77
6-27 Longitudinal Cut of Solidified Waste Core (Batch 5) 6-78
6-28 Scanning Electron Image of Poor and Well Bonded Aggregate (Batch 1) 6-82
6-29 Backscattered Emissions Image 6_g4
6-30 Elemental Spectrum of Area in Figure 6-29 (Batch 3) 6-84
6-31 Backscattered Emissions Image (Batch 5) 6-85
6-32 Titanium Map of Figure 6-31 (Batch 5) g_85
6-33 Backscattered Emissions Image (Batch 5) 6-86
6-34 Chromium Map of Figure 6-33 (Batch 5) 6-86
6-35 Copper Map of Figure 6-33 (Batch 5) 6-87
6-36 Arsenic Map of Figure 6-33 (Batch 5) 6-87
6-37 Backscattered Emissions Image of Typical Distribution (Batch 1) 6-88
6-38 Air Void in Paste (Batch 1) 6-88
6-39 Scanning Electron Image of Paste and Aggregate (Batch 3) 6-89
6-40 Aggregate Paste Bond (Batch 3) g_89
-------
ABBREVIATIONS
ACI
AEA
amp
ANS
ARAR
ASA
ASTM
BSE
CAA
CEPA
CALWET
CERCLA
CFR
CLP
cm
CRWQCB
CWA
°C
DOE
DOT
EDX
Eh
EP
EPA
ESBL
FIT
ft
FRTL
FTIR
g
gal
HCP
HDPE
hr
HRS
HSL
HSWA
kg
kV
L
Ib
LDR
LI
mA
American Concrete Institute
Atomic Energy Act
ampere
American Nuclear Society
applicable or relevant and appropriate requirement
American Society of Agronomy
American Society for Testing and Materials
backscattered emissions
Clean Air Act
California Environmental Protection Agency
California Waste Extraction Test
Comprehensive Environmental Response, Compensation, and Liability Act
Code of Federal Regulations
Contract Laboratory Program
centimeter
California Regional Water Quality Control Board
Clean Water Act
degree Celsius
Department of Energy
Department of Transportation
energy dispersive X-ray
oxidation/reduction potential
Extraction Procedure
Environmental Protection Agency
Engineering-Science, Inc. Berkeley Laboratory
Field Investigation Team
foot
Federal Regulatory Threshold Limit
Fourier transform infrared spectroscopy
gram
gallon
gallons per hour
Hazard Communication Program
high-density polyethylene
hour
Hazard Ranking System
Hazardous Substance List
Hazardous and Solid Waste Amendments
kilogram
kilovolt
liter
pound
Land Disposal Restriction
leachability index
milliampere
XI
-------
ABBREVIATIONS (continued)
MDL
meq
mg
mo
mm
MSDS
mV
NC
ND
NIOSH
NPDES
NPL
NRC
ORD
OSHA
OSWER
PAH
PCB
PCDD
PCDF
PCP
POTW
PPE
ppb
ppm
psi
QA/QC
QAPjP
RCRA
RFP
RI/FS
RM
ROD
RPD
SARA
SDWA
sec
SEM
SI
SITE
SPT
STC
STLC
TCLP
TCP
TER
method detection limit
milliequivalent
milligram
month
millimeter
Material Safety Data Sheet
millivolt
not calculable
not detected
National Institute of Occupational Safety and Health
National Pollutant Discharge Elimination System
National Priorities List
Nuclear Regulatory Commission
Office of Research and Development
Occupational Safety and Health Administration
Office of Solid Waste and Emergency Response
Polycyclic aromatic hydrocarbon
Polychlorinated biphenyl
Polychlorinated dibenzo-p-dioxin
Polychlorinated dibenzofuran
Pentachlorophenol
Publicly Owned Treatment Works
personal protective equipment
parts per billion
parts per million
pounds per square inch
Quality Assurance/Quality Control
Quality Assurance Project Plan
Resource Conservation and Recovery Act
Request For Proposal
Remedial Investigation/Feasibility Study
reagent mixture
Record of Decision
relative percent difference
Superfund Amendments and Reauthorization Act
Safe Drinking Water Act
second
Scanning Electron Microscopy
International System of Units
Superfund Innovative Technology Evaluation
Selma Pressure Treating
Silicate Technology Corporation
Solubility Threshold Limit Concentration
Toxicity Characteristic Leaching Procedure
Tetrachlorophenol
Technology Evaluation Report
xn
-------
ABBREVIATIONS (continued)
TMSWC Test Methods for Solidified Waste Characterization
TPH Total Petroleum Hydrocarbons
TSCA Toxic Substances Control Act
TSDF treatment, storage, and disposal facility
TTLC Total Threshold Limit Concentration
TWA Total Waste Analysis
UCS unconfmed compressive strength
UIC Underground Injection Control
VER volume expansion ratio
VOC volatile organic compound
wk week
yr year
XRD X-ray diffractometry
xni
-------
Length
Volume
Weight
CONVERSION OF U.S. CUSTOMARY UNITS TO SI UNITS
inches x
inches x
inches x
feet x
gallons x
cubic yards x
pounds x
short tons x
25.4
2.54
0.0254
0.3048
3.785
0.7646
0.4536
0.9072
= millimeters
= centimeters
= meters
= meters
= liters
= cubic meters
= kilograms
= metric tons
Temperature
5/9
x (° Fahrenheit - 32) = ° Celsius
Note:
1000 liters
1000 kilograms
= 1 cubic meter
= 1 metric ton
xiv
-------
ACKNOWLEDGMENTS
This document was prepared under the direction of Mr. Edward R. Bates, U.S. EPA
Superfund Innovative Technology Evaluation (SITE) project manager, Risk Reduction Engineering
Laboratory, Cincinnati, OH. Contributors to and reviewers of this report include Mr. Bates, Terry
Lyons, and Patricia Erickson, U.S. EPA, Cincinnati, OH; Greg Maupin, Silicate Technology
Corporation, Scottsdale, AZ; Amy Tarleton, David Badio, and Susan Fullerton, Engineering-
Science, Fairfax, VA; Presbury West, Construction Technology Laboratories, Inc., Skokie, IL; Jim
Bob Owens, Radian Corporation, Austin, TX; Paul Dean, David Liu, Robert Foster, Patricia Sinski,
and Jim Styers of PRC Environmental Management, Inc.
This report was prepared for the EPA's SITE program by Ingrid Klich, edited by Lori
Brasche, and word processed by Debra Johnston, Kamlah McKay, and Gay Phillips, all of PRC
Environmental Management, Inc., under Contract Nos. 68-03-3484 and 68-CO-0047. Paul Dean
served as project manager for PRC Environmental Management, Inc.
xv
-------
1.0 EXECUTIVE SUMMARY
1.1 INTRODUCTION
The Silicate Technology Corporation (STC) immobilization technology is a
solidification/stabilization treatment process that was evaluated under the U.S. Environmental
Protection Agency's (EPA) Superfund Innovative Technology Evaluation (SITE) Program. This
immobilization technology is designed to treat organic and inorganic contaminants, thereby reducing
the leaching potential of these constituents in contaminated soils and sludges. For purposes of this
report, "solidification" refers to the physical consolidation of contaminated soil into a hard, rock-like
material. "Stabilization" refers to the chemical immobilization of hazardous contaminants.
Proprietary silicate mineral reagents bind the contaminants within a layered alumino-silicate mineral
structure prior to encapsulating the waste in a cement-like material, thus producing a high-strength,
leach-resistant monolith.
The STC technology demonstration was performed at the Selma Pressure Treating (SPT) site
in Selma, California during November, 1990. In general, the STC SITE demonstration had the
following four objectives:
« Assess the technology's ability to chemically stabilize both organic and inorganic
contaminants.
0 Assess the structural characteristics of the treated waste and the effectiveness of
, solidification/stabilization over a 3-year period.
« Determine the volume and density increases resulting from the treatment process.
« Develop information required to estimate the capital and operating costs for the
treatment system.
The purpose of this report is to present technical information from the SITE demonstration
that is useful for implementing the STC immobilization technology at Superfund, Resource
Conservation and Recovery Act (RCRA), and uncontrolled hazardous waste sites. Section 2 presents
an introduction and overview of the SITE program and describes the purpose of the Technology
Evaluation Report (TER). Section 3 describes the STC technology, equipment necessary for
1-1
-------
implementation of the technology, and relevant factors affecting the STC technology. Section 4
describes the SPT site contamination characteristics and gives a background discussion of the previous
studies at the site. Section 5 gives a detailed account of the demonstration procedures, including an
overview of the quality assurance/quality control plan. Section 6 discusses the analytical results for
the various leaching, chemical, and physical tests used to evaluate the STC technology and includes a
report on the QA results. Section 7 presents the demonstration costs for both the SITE contractors
and the developer.
1.2 OVERVIEW OF THE SITE DEMONSTRATION
The SPT site was selected to evaluate the effectiveness of STC's immobilization technology
for soils contaminated with both organic and inorganic constituents. The waste material was reported
to contain pentachlorophenol (PCP; 1,900 to 8,400 mg/kg), arsenic (375 to 1,900 mg/kg), chromium
(1,900 mg/kg), and copper (1,500 mg/kg). In addition, oil and grease levels ranged from 10,000 to
20,000 mg/kg. Prior to treatment, soil pH was slightly acid to neutral and moisture content ranged
from 4 to 6 percent (COM, 1989 and U.S. EPA, 1990a).
During the SITE demonstration, approximately 16 tons of contaminated soil material were
treated. STC's proprietary alumino-silicate compounds were added to the waste to chemically fix,
and thereby immobilize, heavy metals and semivolatile organic constituents. Addition of a silicate
solidifying agent microencapsulated the adsorbed contaminants, thereby producing an additional
physical barrier to leaching.
The STC SITE demonstration required 6 days to complete once all of the treatment equipment
was mobilized. Initial processing consisted of treating clean sand with the proprietary reagent mixture
used by STC. On each of the following 5 days, one 2.5-cubic-yard batch of contaminated soil was
treated. Surface hardpan and sand from an unlined, dry waste-disposal pond was collected to a depth
of 2 to 3 feet and thoroughly mixed prior to the addition of STC reagents and water. Significant
inhomogeneity in the treated waste from Batch 2 resulted in pretreatment screening of the remaining
batches (3 through 5), and led to the exclusion of Batch 2 from additional analytical evaluations.
Detailed descriptions of waste samples collected from each of the batches are included in section 6.5.
In general, Batch 1 consisted of contaminated waste from a soil horizon approximately 1 foot deep,
1-2
-------
while Batch 2 consisted of a shallower hardpan surface horizon (down to 8 inches). Batches 3, 4 and
5 were composite blends of the first two soil horizons.
Samples of raw and treated waste were submitted for chemical and physical characterization
after a 28-day cure period. Analytical testing was targeted towards selected inorganic constituents
(arsenic, chromium, and copper) and organic contaminants (primarily PCP), using various leach tests
plus total waste analysis (TWA) extraction procedures. EPA SW-846 Methods 8240 and 8270 were
used for the chemical analyses of volatile and semivolatile organic compounds, respectively. Metals
were analyzed using EPA SW-846 Methods 3010, 3020, 3050, 7060, 7421, 7740, 7841, 7471, and
7470 (U.S. EPA, 1986b). Leach tests included the EPA SW-846 Method 1311 Toxicity
Characteristic Leaching Procedure (TCLP); a modified TCLP Distilled Water test; a TCLP-Cage test;
the California Waste Extraction Test (CALWET) as described by the California Health and Safety
Code, Section 66700; and a modified version of the American Nuclear Society (ANS) 16.1 leaching
procedure (ANS, 1986). Additional chemical and physical characterization of the raw and/or treated
waste included pH, Eh, loss on ignition, neutralization potential, particle size analysis, bulk density,
permeability, unconfmed compressive strength, wet/dry and freeze/thaw analyses, petrographic
analysis, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared
spectroscopy (U.S. EPA, 1992).
1.3 SUMMARY OF SITE DEMONSTRATION RESULTS
The sampling and analysis conducted on the raw and treated wastes for the STC SITE
demonstration can be grouped into four general classes: leaching tests, chemical tests, physical tests,
and petrographic examinations. To constitute treatment under Superfund, immobilization (i.e.,
solidification/stabilization) technologies must chemically limit the solubility or mobility of the
contaminants. Specifically, before a technology can be selected as a treatment alternative, EPA
guidance suggests that an immobilization technology demonstrate a significant reduction (i.e., a 90 to
99 percent reduction) in the mobility of chemical constituents of concern (OSWER Directive No.
9200.5-220). The reduction in mobility is evaluated using the TCLP for inorganics and TWA for
volatile and semivolatile organics. In addition, federal and state regulatory thresholds must be met to
allow for legal disposal as nonhazardous wastes either on site or off site. The following conclusions
about the effectiveness of STC's solidification/stabilization treatment process are based on results of
1-3
-------
analytical data and general observations from the SITE demonstration as discussed in Section 6 of this
report.
PCP (Targeted for treatment):
TWA extract concentrations of PCP were reduced 91 to 97 percent.
TWA extract concentrations of PCP were well above the California state regulatory
total threshold limit concentration of 17 mg/kg prior to and after treatment.
Percent reductions of TCLP leachate concentrations of PCP varied from negative
percentages to greater than 81 percent.
TCLP-Distilled Water leachate concentrations of PCP were reduced 80 to 97 percent.
PCP concentrations were well below the federal regulatory threshold TCLP
concentration of 100 mg/L prior to and after treatment.
CALWET leachate concentrations of PCP were above California's solubility threshold
limit concentration of 1.7 mg/L prior to and after treatment.
Stabilization of semivolatile organic compounds (exclusive of PCP) and volatile
organic compounds could not be evaluated due to the low concentrations of these
analytes in the waste.
Arsenic (Targeted for treatment):
« TCLP leachate concentrations of arsenic were reduced 35 to 92 percent.
« TCLP-Distilled Water leachate concentrations of arsenic were reduced 98 percent or
more.
« 'Arsenic concentrations were below the federal regulatory threshold TCLP
concentration of 5.0 mg/L prior to and after treatment.
« CALWET leachate concentrations of arsenic were both over and under the California
state regulatory solubility threshold limit concentration of 5.0 mg/L after treatment.
0 TWA extract concentrations of arsenic were both above and below the California state
regulatory total threshold limit concentration of 500 mg/kg prior to and after
treatment.
Chromium (Not targeted for treatment):
TCLP leachate concentrations of chromium were increased as a result of treatment.
1-4
-------
Percent reductions of TCLP-Distilled Water leachate concentrations of chromium
varied from 42 to 54 percent.
Chromium concentrations were below the federal regulatory threshold TCLP
concentration of 5.0 mg/L prior to and after treatment.
CALWET leachate concentrations of chromium were well below the California state
regulatory solubility threshold limit concentration of 560 mg/L prior to and after
treatment.
TWA extract concentrations of chromium were below the California state regulatory
total threshold limit concentration of 2,500 mg/kg prior to and after treatment.
Copper (Not targeted for treatment):
TCLP leachate concentrations of copper were reduced 90 to 99 percent.
TCLP-Distilled Water leachate concentrations of copper were reduced 86 to 90
percent.
CALWET leachate concentrations of copper were both over and under California's
solubility threshold limit concentration of 25 mg/L prior to and after treatment.
TWA extract concentrations of copper were below the California state regulatory total
threshold limit concentration of 2,500 mg/kg prior to and after treatment.
Long-Term Results:
TCLP extracts for metals and TWA extracts for PCP of the 6-month cured samples
showed increased concentrations of contaminants released from the treated waste.
Analyses for the 18-month cured samples showed improved percent reductions relative
to the 6-month cured sample test results, averaging 88 percent reduction for arsenic,
"and 96 percent reduction for PCP.
Analyses for the 32-month cured samples showed TWA extract concentrations of PCP
to be comparable to 18-month results. TCLP extract concentrations of arsenic at 32
months were comparable to 6-month results.
Chromium and copper concentrations showed slight to moderate increases in the
TCLP extracts over time, although copper concentrations at 32 months more closely
resembled 28-day results than extracts at either 6 months or 18 months.
Physical Properties:
Unconfined compressive strength (UCS) of the treated wastes was moderately high
after 28 days, averaging 260 to 350 pounds per square inch (psi). Eighteen-month
UCS tests showed an average 245 percent increase in physical strength with time.
1-5
-------
UCS results from 32 months showed an average 27 percent decrease in strength from
the 18-month results, but were still greater on average than the 28-day results by a
factor of 2.5.
« Permeability of the treated waste was low (< 1.7 x 10"7 cm/sec).
0 Relative cumulative weight losses from 12 wet/dry and 12 freeze/thaw cycles were
less than 1 percent.
« Due to addition of reagents, treatment of the wastes resulted in volume increases
ranging from 59 to 75 percent (68 percent average), with slight increase in bulk
density.
« Petrographic and scanning electron microscopy examinations indicated good binder-to-
aggregate bonding. Constituents comprising the reagent mix binder included calcium
hydroxide, glass, portland cement, and black pigment. Soil constituents were
predominantly quartz and feldspar with minor hornblende and trace mica.
Treatment Technology:
» No equipment-related problems occurred during the 6-day technology demonstration.
» The process equipment used during the demonstration was capable of mixing all
components, including the waste material, into a homogeneous, solidified product,
provided that pretreatment screening or size reduction of surface hardpan material was
conducted.
1-6
-------
2.0 INTRODUCTION
This section provides background information on the Superfund Innovative Technology
Evaluation (SITE) program and the purpose of this report. In addition, this section also presents the
objectives of the STC SITE demonstration program.
2.1 SITE PROGRAM
The Superfund Amendments and Reauthorization Act (SARA) of 1986 (Section 209(b))
amends Title III of the Comprehensive Environmental Response, Compensation, and Liability Act of
1980 (CERCLA) by adding Section 311. Section 311 directs the U.S. Environmental Protection
Agency (EPA) to establish an "Alternative or Innovative Treatment Technology Research and
Demonstration Program." In response to the SARA directive, EPA has established a formal program
to accelerate the development, demonstration, and use of new or innovative treatment technologies.
This program is called the SITE program, and is administered by the Office of Research and
Development (ORD).
The primary purpose of the SITE program is to enhance the development and demonstration
of innovative technologies applicable to Superfund sites, thereby establishing the commercial
availability of these technologies.
The SITE program has four objectives:
Identify and remove impediments to the development and commercial use of
alternative technologies.
Conduct a demonstration program of the more promising innovative technologies to
establish reliable performance and cost information for site characterization and
cleanup decision making.
Develop procedures and policies that encourage selection of available alternative
treatment remedies at Superfund sites.
Structure a development program that nurtures emerging technologies.
2-1
-------
One of the most important components of the SITE Program is the Demonstration Program,
through which EPA evaluates field- or pilot-scale tested technologies that can be scaled up for
commercial use. The Demonstration Program is the primary focus of the SITE Program because the
innovative alternative technologies evaluated are close to being available for remediation of Superfund
sites. The main objective of the Demonstration Program is to develop performance, engineering, and
cost information for innovative technologies. With this information, potential users can make
informed decisions on whether to use these technologies to remediate hazardous waste sites.
Specifically, potential users can use this information to compare the technology's effectiveness and
cost to other alternatives and make sound judgments regarding applicability of the technology for a
specific use.
Each year the EPA solicits proposals to demonstrate innovative technologies for permanent,
long-term site cleanups. The most promising technologies are chosen for participation in the SITE
demonstration program. ORD, and EPA regional personnel match these technologies with a list of
potentially appropriate sites.
The results of the demonstration identify possible limitations of the technology, the potential
need for pre- and post-processing of wastes, the types of wastes and media to which the process can
be applied, the potential operating problems, and the approximate capital and operating costs. The
demonstrations also permit evaluation of long-term risks. Demonstrations usually occur at Superfund
sites or under conditions that duplicate or closely simulate actual conditions found at Superfund sites
to ensure the reliability of the information collected and acceptability of the data to users.
Developers are responsible for demonstrating their innovative systems at selected sites and are
expected to pay the costs to transport equipment to the site, operate the equipment on site during the
demonstration, and remove the equipment from the site. EPA is responsible for project planning,
sampling and analysis, data quality assurance and quality control, report preparation, and information
dissemination.
2-2
-------
2.2 PURPOSE OF THE TECHNOLOGY EVALUATION REPORT
The Technology Evaluation Report (TER) is one of two reports resulting from the SITE
demonstration. The TER provides a comprehensive description of the demonstration and its results,
including a description of data collection activities, testing procedures, and QA/QC results. This
report is intended for technical professionals making detailed evaluations of the technology for a
specific situation. The information contained in the TER is used to produce conceptual designs in
sufficient detail to prepare preliminary cost estimates for the demonstrated technology.
The second report resulting from the SITE demonstration is the Applications Analysis Report
(AAR). The AAR presents estimates of the costs of implementing a technology and describes its
Superfund applications based on available data. The AAR is intended to be used by decisionmakers
responsible for implementing remedial actions and to help them determine whether a technology has
merit as an option for a particular cleanup situation.
2.3 SITE DEMONSTRATION OBJECTIVES
The overall goal of the Silicate Technology Corporation (STC) demonstration at the Selma
Pressure Treating (SPT) site was to evaluate the effectiveness of the STC immobilization technology
as a long-term remedial measure at Superfund, Resource Conservation and Recovery Act (RCRA),
and uncontrolled hazardous waste sites. The SPT site was selected for the demonstration based on its
waste characteristics, the results of treatability testing, and site logistical considerations. STC's
technology is designed for sites with moderate-to-high concentrations of both organic and inorganic
contaminants, including poly cyclic aromatic hydrocarbons (PAHs) and heavy metals as were reported
by CDM at the SPT site (CDM, 1988a and b). The primary objective of this demonstration was to
determine if the STC technology could reduce the potential teachability and mobility of contaminants
as measured by total waste analysis (TWA) for organics and the Toxicity Characteristic Leaching
Procedure (TCLP) for inorganics. In particular, the principal contaminants for assessing the STC
technology were pentachlorophenol (PCP) and arsenic. Other objectives of this demonstration were
to:
2-3
-------
Determine if the STC technology could reduce the teachability of contaminants as
measured by other leaching methods.
Determine if the STC technology could reduce leachate concentrations of PCP and
metals below applicable regulatory limits to allow for legal disposal as a nonhazardous
waste.
Determine the homogeneity of mixing and structural characteristics of the waste
treated by the STC technology.
Determine the volume and density increase of the waste treated by the STC
technology due to added reagents.
Determine if the STC technology could treat contaminated soils to produce a
monolithic block that would resist the effects of weathering.
Determine whether the treated, solidified waste could maintain its structural properties
and stabilization effectiveness over a 3-year period.
Develop capital and operating cost models for the technology that can be used reliably
in the Superfund and RCRA decision-making process.
2-4
-------
3.0 TECHNOLOGY DESCRIPTION
STC's treatment process uses silicate compounds that chemically stabilize organic and
inorganic constituents in contaminated soils and sludges. Proprietary silicate reagents adsorb organic
and inorganic contaminants prior to solidifying the waste with a cementitious material, resulting in a
high-strength, leach-resistant monolith. Treatability tests and site investigations were conducted to
determine the necessary types and dosage of reagents according to the waste characteristics. The
following section discusses the general STC treatment process chemistry, major process equipment
needed for the STC technology, and major factors that can affect the technology. All information
presented is provided by STC. Specific procedures used in the SITE demonstration are detailed in
Section 5.
3.1 PROCESS CHEMISTRY
STC has developed two groups of reagents: SOILSORB HM for treating wastes with
inorganic constituents and SOILSORB HC for treating wastes with organic constituents. These two
groups of reagents can be combined to treat wastes containing both organic and inorganic
contaminants. The specific proprietary reagents P-4 and P-27 were combined to treat contaminated
soils from the SPT site.
Stabilization by the STC process of wastes with inorganic constituents involves silicate-
forming reactions resulting in the incorporation of heavy metal ions into the crystal lattice structure of
a highly insoluble calcium-alumino-silicate compound. The reactions effectively immobilize the
contaminants, thereby reducing the potential for leaching. A silicate solidifying agent
microencapsulates the alumino-silicate compound to form another physical barrier to leaching. The
result is a very stable compound analogous to common rock-forming silicate minerals.
STC's technology for treating organic wastes uses a three-step process in which organic
compounds in the waste are sequestered by a modified alumino-silicate mineral. The silicate is
surface-modified with organic compounds, creating a layered structure that consists of organic layers
sandwiched between the alumino-silicate layers. Upon mixing with the organic wastes, this modified
silicate adsorbs organic contaminants into the layers of the organically surface-modified alumino-
3-1
-------
silicate compound through a partitioning reaction. STC claims that the organic layers of the modified
silicate can adsorb as much as 20 times their own weight of organic constituents. In addition, STC
also claims that the organics adsorbed cannot be physically squeezed out of the layered silicate
structure.
The first step of the contaminant immobilization process involves partitioning similar to a
liquid/liquid extraction. If a waste containing a polynuclear aromatic compound such as anthracene is
mixed or combined with a water-immiscible oil, the anthracene will migrate into the oil phase and
remain there. STC's technology is based on this concept, except that it uses a solid organic phase
instead of oil. This partitioning follows basic laws of physical chemistry and can in general terms be
predicted for any organic compound based on its water solubility.
The second step of the stabilization process involves the morphology of the alumino-silicate
structure. As the organic waste constituents partition to the organic layers of the surface-modified
silicate, the layered alumino-silicate plates tend to bond with the surface of the waste, thereby creating
a physical barrier and thus reducing leachability.
Finally, the third step of the stabilization process is the addition of STC's proprietary silicate
solidifying agent, which microencapsulates the layered alumino-silicate structure and bonds the
solidifying agent to the exposed layered-silicate surfaces. This microencapsulation of the adsorbed
organics further reduces leachability by forming another physical barrier to leaching. STC claims that
the alumino-silicates used for the organic partitioning reaction and the silicates used for the
microencapsulation reaction can be shown to be thermodynamically stable compounds, analogous to
common, rock-forming silicate minerals.
3.2 TREATMENT PROCESS
Treatment of contaminated soil typically begins with the separation of coarse material from
fine material in a mechanical separator (Figure 3-1). This separation is accomplished by using a
shaker screen to isolate the coarse material greater than 3/8 inch in diameter. This coarse material is
sent through a shredder or crusher, which reduces it to the size required for the STC technology.
3-2
-------
Figure 3-1. Schematic Diagram for STC Treatment Process
Contaminated Soil Process
BACKHOE
COARSE
SCREEN 1
SHREDDER
-------
The screened waste is loaded into a batch plant where it is weighed and the appropriate amount of the
STC proprietary reagents - SOILSORB: P-4 and P-27 - as determined during treatability testing are
added. This mixture is conveyed to a pug mill mixer (or equivalent, such as a ready-mix cement
truck) where water is added and the mixture is thoroughly blended. When this technology is used to
treat sludges, the waste is placed directly into the pug mill for addition of reagents and mixing.
Reagents are then added in amounts that can be adjusted according to variations in organic and
inorganic contaminant concentrations determined during treatability testing. The mixing process
continues until the operator determines that the materials are thoroughly homogenized, up to
approximately 60 minutes per batch. The treated material is then placed in confining pits for on-site
curing, or cast into molds for curing and subsequent transport and disposal off site.
Hardware for the treatment process includes processing and materials-handling equipment.
With the exception of STC's liquid reagent metering equipment, conventional construction equipment
readily available for purchase or rental in most areas can be used. Such equipment typically would
have the capacity to treat up to 40 cubic yards of contaminated soil per day; however, only 2.5 cubic
yards per day were processed during the demonstration.
Process equipment for soil treatment using STC's technology includes the following:
Pretreatment screen Pretreatment screening is normally accomplished with a shaker
screen to separate fine material (< 3/8-inch diameter) from coarse material (> 3/8-
inch diameter). Pretreatment screening down to 0.04 - 0.08 inch (1-2 mm) diameter
was required for the STC demonstration since a crusher was not used, and it was
necessary to ensure that individual aggregates of untreated waste did not bias the
chemical analyses.
Crusher or shredder A crusher or shredder is used to further reduce waste
aggregate size prior to mixing, if necessary.
Weight conveyor - The weight conveyor is used to weigh and transfer screened
material to the pug mill.
Pug mill A pug mill, cement-mixer, or other conventional construction equipment
can be used as a mixing vessel.
Liquid reagent metering equipment Liquid reagent metering is accomplished with
STC's mobile liquid meter, which is mounted on a 20-foot bed trailer. This
equipment includes two 500-gallon tanks.
3-4
-------
Materials handling equipment for soil treatment includes the following:
Front-end loader/backhoe for excavation and transport of waste material on site.
All-terrain forklift for moving 3-ton forms filled with treated waste.
3.3 FACTORS AFFECTING THE PERFORMANCE OF THE TECHNOLOGY
Several factors can influence the performance and cost effectiveness of the STC solidification/
stabilization technology, including (1) waste characteristics, (2) volume/density increase, (3) operating
conditions, and (4) climate and curing conditions. The following subsections discuss these factors in
detail.
3.3.1 Waste Characteristics
The ability of the STC solidification/stabilization technology to solidify and chemically
stabilize organic and inorganic contaminants in a waste depends on the characteristics of the waste.
The characteristics that may affect the performance of the STC technology include clay content, coal
and lignite content, moisture content, oil and grease content, pH of the waste, volatile organic
concentrations, and aggregate size of the waste. Wastes with high clay content (> 50 percent) may
release clay into the mixing water, which may result in a large concentration of these clay particles
near the surface of the solidified matrix, producing an inferior quality matrix. Coal and lignite in
excess of 1 percent may also impair the quality of the solidified waste mixture. Wastes with very
high moisture content should be treated as sludges, and may therefore require larger amounts of
reagents for solidification.
Oils and grease (and other nonpolar organics) may have deleterious effects on the ability of
the matrix to set and thus may reduce the unconfined compressive strength of the treated waste. STC
reports that levels of up to 60 percent oil and grease have been successfully treated. Low pH wastes
(e.g., acid sludges) may react with the relatively higher pH materials used in the reagent mixture,
resulting in incomplete solidification. Such wastes must be neutralized prior to treatment.
3-5
-------
For wastes with large aggregate sizes, incomplete mixing can occur, which may result in
pockets of untreated waste within an otherwise homogeneous waste/reagent mixture. Well-graded raw
wastes (i.e., wastes with several different particle sizes) will form more stable monolithic blocks than
poorly-graded (one-sized) raw wastes. Additional screening and size reduction of the SPT
contaminated soil aggregates down to 0.04-0.08 inch (1-2 mm) diameter was necessary to ensure that
individual aggregates did not bias the chemical analyses.
Wastes containing volatile organics may release these organics during the mixing process,
resulting in artificially high percent reductions for these constituents. In addition, the concentrations
of metals or semivolatile organics in the waste may impair the ability to meet desired levels of these
constituents in the treated waste. For example, if the objective of the treatment is to render a waste
nonhazardous, the higher the contaminant concentration in the raw waste, the higher the concentration
in the treated waste, and even after 90 percent reduction in TWA or leachate concentrations, the
technology may not be appropriate for some wastes because the wastes may still be considered
hazardous after treatment.
3.3.2 Volume/Density Increase
The STC technology, like any immobilization technology, may be less desirable for use in
treating wastes as the ratio of the volume and/or density of the treated waste to the volume and/or
density of the raw waste increases. Off-site disposal of treated wastes becomes more difficult and
costly with increasing volume, since disposal costs are usually on a unit volume or total weight basis.
Based on the results of this demonstration, volume increases of 59 to 75 percent can be expected after
treatment. The volume increase depends on the characteristics of the waste being treated and the
desired performance specifications. The bulk densities of the wastes showed only minor increases of
0.6 to 11 percent, with an average increase of 5.5 percent resulting from the addition of reagents
during treatment. For on-site disposal, the above increases may be desirable in situations where
additional soil material is needed for backfilling and leveling depressions. The increased volume
would reduce the costs of purchasing, transporting, and placing fill material at the site.
3-6
-------
3.3.3
Operating Conditions
Several operating conditions for the STC stabilization/solidification technology can be varied
to account for differences in the characteristics of the waste to be treated. Such operating parameters
for the STC process include mixer power, mixing time, and the additives ratio for the reagents used
to treat the raw waste, as shown in Table 3-1. Any of these operating conditions can be modified to
accommodate differences in waste characteristics. Operating conditions can also be modified to yield
treated waste better suited for a particular disposal option or use.
The power delivered to the mixer can have a significant effect on the degree of mixing of the
waste. Wastes that are exceptionally viscous or that have larger particle or aggregate sizes may
require a larger power output by the mixer.
Variations in mixing time can result in differences in the chemical properties of the treated
waste through processes such as oxidation/reduction reactions. Arsenic in Batch 4 is thought to have
been reduced from arsenate (V) to the more mobile species arsenite (III) during the inordinately long
pretreatment mixing time (4.5 hours). Supplemental analyses for selected samples from Batches 3, 4,
and 5 indicate that the raw waste from Batch 4 contained higher quantities of the arsenic ion-species
arsenite (205 mg/kg) and lower amounts of arsenate (20 mg/kg) relative to Batches 3 and 5, which
had high arsenate (61 mg/kg and 260 mg/kg, respectively) and low arsenite values (<2 mg/kg in
both batches). The net result in this case was that the arsenic in Batch 4 was more easily leached
under the acid TCLP conditions, thus the anomalously low percent reduction for the TCLP extract in
Batch 4.
Table 3-1. Operating Parameters for the STC SITE Demonstration
Parameters
Waste soil weight (Ibs)
Silica sand weight (Ibs)
Dry reagent weight (Ibs)
Water added (Ibs)
Batch
RM
0
1,972
695
422
1
5,000
0
1,732
2,172
2
5,000
0
1,723
3,850
3
4,000
0
1,382
1,71*3
4
4,000
0
1,413
1,760
5"
4,464
0
1,638
1,759
3-7
-------
Table 3-1. Operating Parameters for the STC SITE Demonstration (continued)
Parameters
Water lost during curing (Ibs)
Mixer power (hp)
Current to mixer (amp-hr)
Pretreatment mixing time (min)
Treatment mixing time (min)
Additives ratio"
Batch
RM
NA
29
17
0
22
NC
1
97
29
83
50
60
0.761
2
NA
29
77
60
40
NC
3
41
29
77
60
40
0.764
4
71
29
248
270
60
0.776
5
67
29
79
60
45
0.746
RM
NA
NC
a
b =
Reagent mixture
Not analyzed
Not calculated
The additives ratio is the sum of the weight of additives, including water ofhydration, divided by
the weight of wastes.
Batch 2 was not analyzed due to inhomogeneity of the treated waste.
The additives ratio for the process can be varied to account for differences in the composition
of certain wastes. For example, the volume of water added in the process should be adjusted to
account for the moisture content of the waste. Certain waste streams with high moisture content may
not be easily treated using solidification/stabilization procedures. The amount of water used in the
process should be decreased with increasing moisture content of the waste to be treated.
3.3.4
Climate and Curing Conditions
The curing temperature and the curing time will have an effect on the physical characteristics
of the treated waste. Solidified wastes should be allowed to cure for several weeks; The American
Concrete Institute (ACI) and the American Society for Testing Materials (ASTM) guidelines for
construction materials recommend a cure time of 28 days (ACI Standard 318) at 16° to 27°C
(ASTM, Method C31-90). In general, treated wastes cured at higher temperatures will cure faster,
but may have lower structural integrity compared to that of wastes cured at lower temperatures. (An
exception to this correlation is waste that is cured at temperatures at or below freezing.) In general,
treated wastes cured at constant room temperature will become increasingly stable with increasing
3-8
-------
time, although blocks of treated waste that are exposed to the effects of weather for an extended
period of time may begin to break down as a result of weather conditions, including precipitation and
freeze/thaw cycles.
Below-freezing temperatures and heavy rain could have an adverse impact on the operation of
the STC immobilization technology. If sub-freezing temperatures are expected, the mixer and water
source should be insulated or heated to avoid freezing of the water used in the process. The mixer
should also be covered during periods of heavy rain, because such precipitation could interfere with
the solidification of the treated waste. Raw materials, including the reagents, should also be protected
from precipitation.
3-9
-------
4.0 DESCRIPTION OF THE DEMONSTRATION SITE
The Selma Pressure Treating (SPT) site in Selma, California was selected for demonstrating
the STC technology based on its waste characteristics, the results of treatability testing, and site
logistical considerations. The following section provides background information about the SPT site
and information regarding contamination at this site.
4.1 SITE BACKGROUND
The SPT site has been used for chemical treatment of lumber since 1942. The original wood-
preserving process consisted of dipping the lumber into a mixture of pentachlorophenol (PCP) and oil,
and allowing the excess fluid to drip off as the wood dried on open storage racks. In 1965, the site
operators converted their process to a pressure-treating process that consisted of two steps:
(1) conditioning the lumber to reduce moisture content and increase permeability, and
(2) impregnating the wood with chemical preservatives.
Federal and state agencies have been jointly involved in regulatory and enforcement actions at
the site since the 1970s. The California Regional Water Quality Control Board (CRWQCB) was first
to impose discharge standards, monitor water quality, and require the owners to submit operational
reports. On January 13, 1981, the following agencies conducted an Uncontrolled Hazardous Waste
Site Investigation: EPA's Field Investigation Team (FIT), California Environmental Protection
Agency (CEPA), and CRWQCB. SPT site owners filed for bankruptcy on April 13, 1981, and the
plant closed its operations in June 1981. On September 4, 1981, CRWQCB issued a Cleanup and
Abatement Order for the SPT site. The landowner, Selma Leasing Company, indicated that it could
not comply with the Cleanup and Abatement Order; however, an attorney for the company indicated
to CRWQCB that Selma Leasing Company would accept responsibility for the geotechnical
investigation. In February 1982, Sawmill Properties, Inc. acquired the facility, but stipulated that
Selma Leasing Company continue to accept responsibility for the investigations of contamination
caused by past operations. Sawmill Properties, Inc., reopened the plant in Summer 1982, as the
Selma Treating Company. In August 1983, EPA scored the SPT site at 48.83 using the Hazard
Ranking System (HRS). Based on this information, the site was placed on the Superfund National
Priorities List (NPL) in September 1983. Following a remedial investigation/feasibility study
4-1
-------
(RI/FS), a Record of Decision (ROD) was signed on September 24, 1988, and a Pre-Remedial Design
Soil Boring Report was completed in June 1989 (COM, 1989).
4.2 SITE DESCRIPTION
The SPT site is located approximately 15 miles southeast of Fresno, California, adjacent to
the southern city limits of Selma, California (Figure 4-1). The site is situated in the center of the San
Joaquin River Valley, an area that contains numerous vineyards. The entire SPT site covers 18 acres;
however, the actual wood-treatment area of this site covers only 3 to 4 acres. While zoned for heavy
industrial use, the site is located in a transition zone between agricultural, residential, and industrial
areas with approximately 12 residences and businesses located within 1/4 of a mile. The CRWQCB
has classified the ground-water resources in the vicinity of the SPT site as a beneficial use, sole-
source aquifer. This resource provides the necessary domestic water supply for the surrounding
communities and scattered county residences. Surface-water irrigation systems are also supplemented
by this ground-water resource.
4.3 SITE CONTAMINATION CHARACTERISTICS
From 1942 to 1971, wastes from the lumber treatment plant were disposed of in various
ways: (1) runoff into drainage ditches and a percolation ditch; (2) drainage into dry wells;
(3) spillage on open ground; (4) placement into an unlined pond and a sludge pit; and (5) disposal in
an adjacent vineyard through pipelines (Figure 4-2). Known chemical preservatives used at the site
include:
Fluor-chromium-arsenate-phenol (1966 to 1973)
Woodtox 140 RTU (1974 only)
« Heavy oil penta solution (1977 only)
LST concentrate (1970 to 1979)
« Copper-8-quinolinoate (1977 to 1980)
» PCP (1970 to present)
« Chromated-copper-arsenate (CCA) (1953 to present).
4-2
-------
Figure 4-1. Regional Location Map - SPT Site, Selma, California
CALIFORNIA
18 HiBh SchJS W.II j
i- CL - t^gt i»*"**" *4~ttMj * J// 1
' CD' ~
: TTtoral
,"V -Memorial .'
- M . 4.
Selma Treating
Company
^ .f \ "j
.J..,., _J ' 'I
4-3
-------
Figure 4-2. Areas of Contamination at the SPT Site
t
VINEYARD
Waste Sludge Pit
C
Wood
Treatment
Area
Unlined Waste Disposal Pond
A SITE DRAINAGE DISCHARGE
AREAS
B DRAINAGE DITCH
C PERCOLATION DITCH
D DRY WELLS
E AREAS WHERE SPILLS, LEAKS
& DRIPPINGS HAVE OCCURRED
F WASTE DISPOSAL SITES
G PIPELINE FOR OFF-SITE
DISCHARGE OF WASTE
4-4
-------
A contaminated ground-water plume emanating from the site has been identified in addition to
pervasive soil contamination beneath the SPT site. The Pre-Remedial Design Soil Boring Report
(CDM, 1989) for the site indicates that the primary metal contaminants are arsenic (375 to 1,900
mg/kg), chromium (1,900 mg/kg), and copper (1,500 mg/kg). PCP was also reported (1,900 to
8,400 mg/kg), along with associated degradation and impurity products including polychlorinated
dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and chlorinated phenols.
Hydrocarbon-related constituents were reported at the site and are thought to have resulted from the
use of diesel fuel as a carrier for the PCP. The hydrocarbon-related constituents include volatile
organic compounds such as benzene, toluene, and xylene, plus polycyclic aromatic hydrocarbons
(PAHs) such as naphthalene and pyrene. Results from the Final Remedial Investigation Report and
the Pre-Remedial Design Soil Boring Report (CDM, 1988a and 1989) confirm that the highest levels
of contamination occur in the first 5 feet of the soil material.
4-5
-------
5.0 DEMONSTRATION PROCEDURES
The procedures that were used during the STC immobilization technology demonstration were
developed to test the technology using contaminated soils from the Selma Pressure Treating (SPT) site
near Fresno, California. Based on the SPT site characteristics and the results of treatability testing, a
demonstration plan was prepared that detailed the proposed sampling, analytical, quality assurance,
and health and safety procedures (U.S. EPA, 1990a and b). This section summarizes the actual
demonstration procedures, including waste characterization and treatability testing, field activities,
laboratory analyses, and the quality assurance/quality control plan.
5.1 WASTE CHARACTERIZATION AND TREATABILITY TESTING
The SPT site was considered for demonstration of the STC technology because its waste
contained elevated mixtures of organic and inorganic contaminants. Preliminary waste samples from
the SPT site were collected in September, 1989 to characterize the waste, to confirm contaminants of
concern for the SITE demonstration, and to conduct treatability studies to optimize the STC process.
Four primary objectives for the preliminary sampling for waste characterization were to
1) obtain data to determine if STC's processes could stabilize organic and inorganic contaminants; 2)
obtain data to determine if STC's processes could effectively treat wastes found at the SPT site; 3)
identify potential waste feed areas for STC's demonstration; and 4) obtain data to determine if the
testing and analytical methods used in the preliminary sampling were effective so that appropriate
methods could be selected for the full-scale demonstration. The objectives of the preliminary
sampling were accomplished through the collection and analysis of area characterization and
treatability samples. Area characterization samples were site samples that were analyzed to determine
the concentration of contaminants in the raw samples and were not subjected to treatment.
Treatability samples were site samples that were subjected to the STC's treatment process and
subsequently analyzed to determine the effectiveness of the technology. All samples were collected
from an unlined waste disposal pond known to contain the major contaminants desired to test the
ability of the STC treatment process to stabilize organic and inorganic contaminants.
5-1
-------
5.1.1 Preliminary Treatability Study
Table 5-1 presents chemical and leaching data for the area characterization samples as
determined by TWA and TCLP (using standard EPA SW-846 methods), and CALWET (as described
in the California Health and Safety Code, Section 66700). Detectable concentrations of volatile
organic contaminants by TWA included methylene chloride and toluene. Base neutral contaminants
included naphthalene and phenanthrene. Acid extractable compounds detected by TWA included
2,3,4,6-tetrachlorophenol (400 mg/kg) and PCP (8,400 mg/kg). No pesticides or PCBs were
detected. Arsenic (1,900 mg/kg), chromium (1,900 mg/kg), and copper (1,500 mg/kg) were also
detected by TWA. TCLP leachates were analyzed for volatile and semivolatile organics and metals,
but no significant amounts of leachable organics (above TCLP guidelines) were detected in the sample
extract. Low concentrations of metals were detected in the TCLP extract sample; however, the levels
did not exceed the TCLP Waste Characteristic Test guidelines. The area characterization sample was
further subjected to the CALWET method and was determined, based on California regulations, to its
concentrations of PCP (3.2 mg/L), arsenic (20 mg/L), and copper (60 mg/L).
The treatability samples were processed by STC in November, 1989. Treatment entailed
mixing the waste with a proprietary solidification reagent in three different reagent-to-soil ratios:
minimum (50 percent of presumed optimum); presumed optimum; and maximum (150 percent of
presumed optimum). These reagent-to-soil ratios correspond to additives ratios of 0.22, 0.42, and
0.62 respectively. The treated material was poured into molds and allowed to cure for 28 days.
Four samples of the treated waste were submitted for analysis, one for each reagent
concentration plus a duplicate of the optimum reagent concentration. Extracts of the treated wastes
were generated using the TCLP and the extracts were analyzed for volatile organics, semivolatile
organics, and metals. Table 5-2 presents the TCLP analytical results for the treatability samples.
Analysis of the TCLP extracts from the treatability samples for organics indicated that no
sample contained significant amounts (above TCLP guidelines) of leachable organics. Several
compounds were detected at higher concentrations in the treatability samples compared to the TCLP
extracts of the area characterization samples. Methylene chloride was detected in several samples at
greater concentrations than those detected in the area characterization samples: Acetone was detected
5-2
-------
Table 5-1. Area Characterization Sample Data for SPT Site
Analyte
Methylene Chloride
Toluene
Total Xylenes
Naphthalene
Phenanthrene
2-Methylnaphthalene
Pentachlorophenol (PCP)
2,3,4, 6-Tetrachlorophenol
Arsenic
Cadmium
Chromium
Copper
Nickel
Lead
Zinc
Concentrations (ppm)
TWA
0.067
0.058
< 0.025
34a
86
<50
8,400
400
1,900
8b
1,900
1,500
8
21
48
TCLP
< 0.005"
<0.005d
0.01 ld
0.057d
0.006a-d
0.008a'd
4.3C
0.440d
1.7
<0.01
0.06
7.5d
0.04d
<0.1
0.24d
CALWET
NA
< 0.005
< 0.005
0.016"
NA
< 0.020
3.2
NA
20
0.1
4.0
60
<0.4
<1
0.7
NA
a
b
c
d
Not analyzed.
Estimated concentration (below reporting limit).
Spiked sample recovery not within control limits.
Calculated from a diluted analysis.
Analyte not applicable to the toxicity characteristic.
5-3
-------
Table 5-2. TCLP Analyses of Treatability Samples of STC-Treated Wastes
Analyte
Methylene Chloride6
Acetone6
Toluene6
Total Xylenes6
Phenol6
Benzole Acid6
Naphthalene6
2,4 , 6-Trichlorophenol
Pentachlorophenol (PCP)
Phenanthrene6
Bis(2-ethylhexyl)phthalate6
Arsenic
Cadmium
Chromium
Copper6
Nickel6
Lead
Zinc6
Concentrations (mg/L) ;
Minimum
Reagent Mixture
0.034
0.130
< 0.005
< 0.005
0.027
< 0.050
0.008"
0.005"
26C
<0.010
<0.010
0.1 ld
<0.01
<0.05
0.18
<0.04
<0.1
0.027
Optimum
Reagent Mixture*
<0.005/< 0.005
0.140/0.130
<0.005/< 0.005
<0.005/< 0.005
0.021/0.023
0.007"/< 0.050
<0.010/<0.010
<0.010/<0.010
0.033"/2.3C
<0.010/< 0.003"
0.044/< 0.010
0.035/0.049
<0.01/<0.01
0.63/0.64
4.2/4.3
0.089/0.085
<0.1/<0.1
0.27/0.28
Maximum
Reagent Mixture;
< 0.005
0.170
< 0.005
< 0.005
0.038
< 0.050
0.009"
<0.010
13C
<0.010
<0.010
0.077d
<0.01
<0.05
0.17
<0.04
<0.1
0.095
a = Duplicate analysis of treatability sample.
b = Estimated concentration (below reporting limit).
c = Calculated from a diluted analysis.
d = Post digestion spike for Furnace AA analysis is out of control limits (85-115 percent),
while sample spike absorbance is less than 50 percent of spike absorbance.
e = Analyte not applicable to the toxicity characteristic.
5-4
-------
in several samples when it was not detected in the area characterization samples. Phenol was detected
in all treatability samples at higher concentrations than in the area characterization samples.
Pentachlorophenol was detected at greater concentrations than the area characterization samples for
the minimum- and maximum-reagent-mixture treatability samples. PCP was present in the sample
duplicate at a level approximately two orders of magnitude higher than in the original optimum-
reagent-mixture treatability sample. 2,4,6-Trichlorophenol was detected in the minimum-reagent-
mixture treatability sample, but was not detected by either the TWA or the TCLP extract analysis of
the area characterization samples. Bis(2-ethylhexyl) phthalate was detected in one of the optimum-
reagent-mixture treatability sample when it was not detected in the area characterization samples. In
general, the sample duplicate of the optimum-reagent-mixture treated sample showed good
corroboration with its sample counterpart.
Analysis of the TCLP extracts for metals indicated that several metals (chromium, nickel, and
zinc) were elevated in concentration in the optimum-reagent-mixture treatability sample waste and the
corresponding duplicate sample as compared with the area characterization samples.
Based on the analytical results of STC's waste treatment at three different reagent-to-soil
ratios, treatability samples with the least leaching ability (optimum treatment dose) were chosen for
further analyses, and additional characterization and treatability studies. In March 1990, the
treatability samples were analyzed by TWA, CALWET-Distilled Water, and TCLP-Cage tests for
volatile organics, semivolatile organics, and 32 Hazardous Substance List (HSL) metals. The results
for these analyses are presented in Table 5-3. Acetone, PCP, and phenanthrene were the only
organics detected in the treatability samples. Acetone, however, was also detected in the associated
laboratory blank. Results of the TWA for metals indicated that levels of arsenic, chromium, copper,
and cadmium were above typical background levels. Cobalt was not detected in the TWA of the
characterization samples.
PCP was detected in the CALWET-Distilled Water leachate of the treatability sample. Small
amounts of arsenic, chromium, copper, and zinc were also detected. Methylene chloride and acetone
were detected in the CALWET-Distilled Water leachate of the treatability sample, but also in the
associated laboratory blanks.
5-5
-------
Table 5-3. Analytical Results of TWA, CALWET-Distffled Water, and
TCLP-Cage for Treatability Samples
Analyte
Methylene Chloride
Acetone
Phenol
2,4,6-Trichlorophenol
Pentachlorophenol (PCP)
Phenanthrene
Arsenic
Cadmium
Chromium
Cobalt
Copper
Lead
Nickel
Zinc
Concentrations (ppm)
TWA
<1.3
2.8a'b
NA
NA
840
54a
l,300e-f-g
6
860
5.7h
810e-g
21«
6.9
45*
CALWET-
Distffled Water
0.010"
0.190"
0.037a
0.010a
40d
NA
0.0441e's
NA
0.067
NA
0.37
<0.1
NA
0.038
TCLP-Cage
o.ooe"'''1
O.ISO"-0-1
0.0501
NA
31c,d
NA
0.01e'S
0.073C
<0.05
NA
<0.03f
41C
0.15c-j
6.6'-'
NA = Not analyzed
a Estimated concentration (below reporting limit).
b = Compound -was detected in blank.
c = Detected at a higher concentration than in original area characterization analysis.
d Calculated using a greater dilution than the primary analysis.
e = Spiked sample recovery not within control limits.
f = Post digestion spike for Furnace AA analysis out of control limits (85-115 percent),
while sample absorbance is less than 50 percent of spike absorbance.
g = Duplicate analysis not within control limits.
h Not detected in original area characterization analysis.
i = Analyte not applicable to the toxicity characteristic.
5-6
-------
The only volatile organic compounds detected in the TCLP-Cage leachate of the treatability
sample were methylene chloride and acetone; both also were detected in the associated laboratory
blank. PCP was the only semivolatile compound detected. Lead concentrations exceeded the
regulatory threshold for the TCLP, thereby classifying the sample as a hazardous waste. Small
amounts of cadmium, nickel, and zinc were also detected in the TCLP-Cage leachate of the
treatability sample.
5.1.2 Arsenic-Spiked Treatability Study
An additional characterization and treatability study was conducted in February, 1990 to
determine the ability of STC's treatment process to chemically stabilize organic and inorganic
contaminants in the presence of high concentrations of arsenic. Samples of raw waste collected in
September, 1989 (area characterization samples) were homogenized and spiked with arsenic. Spiked
samples were then characterized by TWA, TCLP, and TCLP-Distilled Water analyses. The spiked
samples were also sent to STC. STC treated the spiked waste samples with a predetermined optimum
amount of solidification reagents, poured the mixture into 250-mL Teflon molds and allowed the
molds to cure for 28 days. The treated samples were analyzed in the same manner as the raw waste
spiked with arsenic.
Table 5-4 presents the analytical results for the arsenic-spiked raw and treated waste. Arsenic
was detected in the raw waste sample at 5,100 mg/kg, considerably higher than the addition of
approximately 500 mg/kg during the spiking procedure. (The concentration of arsenic in the raw
waste collected at the SPT site in September, 1989 had previously been determined to be 1,900 mg/kg
by TWA.) Several factors may have contributed, solely or in combination, to the unexpectedly high
concentration of arsenic in the spiked raw waste. For example, the arsenic solution may not have
mixed evenly with all soil particles, or may not have chemically bonded evenly throughout the soil.
Uneven mixing or chemical binding could result in areas of higher or lower arsenic concentration
within the waste sample. Treated samples had somewhat less elevated concentrations of arsenic.
PCP was present in the raw waste but was not detected by TWA in the duplicate treated waste
samples.
5-7
-------
Table 5-4. Analytical Results for Arsenic-Spiked Raw and Treated Waste
Analyte
Pentachlorophenol (PCP)
Phenanthrene
Benzoic Acid
Arsenic
Cadmium
Chromium
Copper
Lead
Nickel
Zinc
1
Concentrations (ppm)
TWA
Raw Waste
1,140"
<100
NA
5,100"
31
3,500
2,400d'e
37°
9.7
53e
=======
Treated
Waste"
<580/<580
100C/99C
NA
4,400c/3,300e
31/18
2,900/3,500
1,600/2,100
54/40
9.1/8.4
47/46
TCLP
Raw Waste
4.8b
NA
<250f
22d'c
0.051
0.076
10f
NA
NA
0.3f
=
Treated
Waste"
41b/120b
NA
<2,500f/240c'f
3.1/3.0
0.014/0.014
1.0/1.1
< 0.03V < 0.03'
NA
NA
0.094f/0.079f
__. ...._.._| i ..:.... i ....i i
TCLP-Distilled Water
Raw Waste
14b
NA
NA
22d'e
0.065
0.13
2.7
NA
NA
0.17
=
Treated
Wastes
48b/53b '
NA
NA
0.72/0.58
<0.01/<0.01
0.051/<0.05
<0.03/<0.03
NA
NA
<0.02/<0.02
oo
NA = Not analyzed.
a = Duplicate analysis of treated waste sample.
b = Calculated using a greater dilution than the primary analysis.
c' = Estimated concentration (below reporting limit).
d = Spiked sample recovery not within control limits.
e = Duplicate analysis not within control limit.
f = Analyte not applicable to the toxitity characteristic.
-------
Besides the expected increased concentration of arsenic, other metals were also detected in the
spiked raw and treated waste at concentrations higher than those detected in the original area
characterization and treatability samples. These metals include: cadmium, chromium, copper, lead,
and zinc. Lead increased in concentration for the treated waste.
Raw and treated waste samples were analyzed for semivolatile organic compounds and metals
following TCLP extraction. Elevated concentrations of PCP were detected in all samples.
Concentrations of PCP in the treated waste samples were greater than levels detected in the raw waste
TCLP analysis. In fact, the concentration of the duplicate exceeds the TCLP regulatory threshold,
classifying that sample as hazardous waste even though the raw waste was not classified as a
hazardous waste. TCLP extracts of raw and treated waste in the previous study (not spiked with
arsenic) contained consistently lower concentrations of PCP than treated samples in this treatability
study (spiked with arsenic). PCP concentrations for TCLP extracts in the previous study were not in
excess of the TCLP guidelines.
In general, detected concentrations of metals in the TCLP leachates were lower in the treated
waste samples than in the raw waste sample. However, concentrations of chromium were higher in
the treated waste TCLP leachate than in the raw waste TCLP leachate. Neither of the treated waste
samples exceeded the TCLP regulatory threshold for arsenic even though the spiked concentration of
arsenic as measured by TWA in the raw waste (5,100 mg/kg) was unexpectedly high compared to the
experimental protocol (500 mg/kg added). All other concentrations of metals in the raw and treated
leachate were below TCLP regulatory thresholds.
As compared with the previous study, elevated concentrations of PCP were detected in all
samples of the raw and treated waste TCLP-Distilled Water leachates. Additionally, concentrations of
PCP in the treated waste TCLP-Distilled Water leachate were higher than the concentration in the raw
waste sample. In general, concentrations of metals were lower in the treated waste TCLP-Distilled
Water leachates than in the raw waste TCLP-Distilled Water leachate.
5-9
-------
5.1.3
Reagent Mixture and Ratio Selection
Finally, a small-scale treatability study was conducted just prior to the pilot-scale
demonstration to fine-tune the reagent-to-waste ratio for the technology demonstration at the SPT site.
In September, 1990, treatability samples were collected from the unlined waste pit area. Waste
samples were shipped separately for analysis and to STC for treatment. The raw waste sample was
subjected to TWA for PCP and extraction by TCLP followed by analysis for arsenic.
STC treated the waste sample by mixing the waste with proprietary solidification reagents
(identified as P3, P4, P5, P27, and S6) in five different batch mixes. The contents of each of the five
batches are listed in Table 5-5. The treated material was poured into 125-mL PVC bottles (molds)
and allowed to cure for 28 days. Following curing, the five treated samples were analyzed in
duplicate for the same parameters as the raw waste sample.
Table 5-5. STC-Treatability Study Batch Contents
Treated Waste
Constituents
(grains)
Waste
Water
P27
P3
P4
P5
S6
Batch
1
800
120
200
80
0
0
0
2
400
120
100
0
40
0
0
3
400
80
80
0
0
0
40
4
400
80
100
0
40
0
0
5
400
80
80
10
10
10
10
Results of the TWA for PCP and TCLP extraction followed by analysis for arsenic are
presented in Table 5-6. PCP was detected in the raw waste sample at a concentration of 17,000 ppm,
considerably higher than concentrations of PCP detected in the samples of the previous
characterization and treatability studies using waste from the same unlined pit area. Concentrations of
PCP in all samples and duplicates from the five separate treated waste batches were all less than the
5-10
-------
concentration detected in the raw waste sample. Treated waste from Batch 2 contained the least
amount of PCP.
Table 5-6. Analytical Results for PCP and Arsenic Treatability Study
Analyte
PCPa
Arsenicb
Raw
Waste
17,000d
2.1
Concentrations (ppm)
1
1,500/640
0.13e/0.095e
Treated Wastes (Batch)0
2
640/770
0.073e/0.090e
3
980/960
0.38V0.038e
4
4,100d/2,500d
0.028e/0.038e
5
2,200d/3,600d
0.33e/0.31e
a = TWA
b = TCLP
c = Duplicate analysis of treated waste sample.
d = Calculated from a greater dilution than the primary dilution.
e Spiked sample recovery not -within control limits.
Arsenic was detected in the TCLP extract of the raw waste sample at a concentration of 2.1
mg/L. This result is consistent with results of the previous studies where the concentrations of
arsenic in the TCLP extract of a raw waste sample and duplicate from the same site were 1.6 and 1.8
mg/L. Results of the arsenic analyses for the five treated waste samples and duplicates show that
Batch 4 had the lowest concentration of arsenic, followed by Batch 2, 1, 3, 5 in order of increasing
concentrations of leachable arsenic. Neither the raw nor any of the treated waste samples exceeded
the TCLP regulatory threshold for arsenic. Based on the results of this treatability study, the reagents
used in Batch 2 were selected for the pilot-scale demonstration.
5.2
PILOT-SCALE DEMONSTRATION FIELD ACTIVITIES
Following EPA's approval of the demonstration plan, site preparation and equipment
mobilization for the demonstration began in mid-November, 1990. The demonstration was divided
into three stages, including site preparation, technology demonstration, and site demobilization. Site
preparation began 1 week prior to the treatment technology demonstration. EPA and its contractors
established a waste treatment area, staging and storage areas, a decontamination zone, and a public
5-11
-------
viewing area, as depicted in Figure 5-1. To implement thetechnology at the SPT site and to meet the
demonstration objectives, the EPA SITE team and STC personnel used the following on-site
provisions:
A 50- by 100-foot mixer pad area for the STC process equipment and temporary
accumulation of waste and treatment reagents. The mixer pad area was constructed
with a plastic liner and berm.
A 45- by 6-foot gravel and compacted soil area for an office and sampling trailer. An
area appropriate for parking and equipment staging was also provided.
A 15- by 50-foot area lined with 20-mil high-density polyethylene (HOPE) liner to
place and store the solidified waste. The treated waste was discharged into cardboard
forms mounted on pallets and placed in the storage area. The storage area was graded
in such a way that a low point in the liner existed for collection of any rainwater
runoff from the solidified waste.
A dumpster for containment and disposal of all nonhazardous waste.
A diesel electric generator to supply 480-volt, 3-phase, 500-amp service for the STC
process equipment. In addition, standard electric power was provided by a portable
generator for the support trailer, equipment, and miscellaneous needs.
Process and wash water for the treatment unit and decontamination. This water was
obtained from the facility's potable water. Approximately 220 gallons of water were
needed per treated batch.
A scale for weighing reagents and raw wastes.
A heavy equipment decontamination area bermed and lined with 20-mil plastic for
cleaning large equipment. This area was also provided with a pump for the collection
" of wash water.
A personnel decontamination station adjacent to the equipment decontamination area.
The station was supplied with appropriate basins, brushes, water, and soap. This area
also included several tables to function as an equipment drop, a first-aid station, and
emergency eye-wash facilities.
A 3,000-gallon Baker wastewater tank used to contain decontamination water.
A gasoline-powered, high-pressure cleaner to clean the STC process equipment and
other heavy equipment.
Three 55-gallon drums to contain contaminated clothing, supplies, and other materials
that could not be disposed of in the dumpster. These drums were disposed of at
appropriate off-site facilities.
5-12
-------
Figure 5-1. SPT SITE Demonstration Layout
I
Vineyards
Process Equipment
Storage Area
Trailer
Paved Area
Public Viewing Area
Solidified
Block
Storage
Area
7
Personnel
Decontamination
Area
3,000 Gallon
Baker Tank
Waste Excavation Area
~ Temporary
[ V. Raw
V_/ Waste
Storage
Vineyards
Mixer
Pad
Chain
Link
\ Fence
Scale: 1/2 inch = 10 feet
-------
A 45-foot office and sampling trailer for EPA personnel, contractors, and STC
personnel.
A portable telephone for ordering supplies, scheduling deliveries, and emergency
communications.
Sanitary facilities for personnel involved with the demonstration.
A public viewing area for the demonstration.
A locked chain-linked fence constructed around the work area upon completion of the
demonstration. Entry to the SPT property was restricted during the demonstration
between 5:00 p.m. and 8:00 a.m.
A backhoe/front-end loader was used to excavate contaminated waste from the unlined waste
disposal pond. To ensure that the soil with the highest concentrations of contaminants was tested, the
first 2 to 3 feet of soil from the disposal pond were used for the demonstration. Therefore, it was
necessary to excavate an approximately 300-square-foot area to provide the total amount of
contaminated soil needed for the demonstration. The excavation was lined with a layer of 20-mil
HDPE and backfilled with 1 foot of sand overlain by 1 foot of crushed stone (1-inch diameter) and
clean soil at the conclusion of the demonstration.
Contaminated soils from the unlined waste disposal pond were transported to the processing
area, where temporary storage piles covered by 10-mil HDPE were set up as necessary prior to batch
processing.
Upon completion of the equipment setup, STC conducted a startup and test run to ensure that
the equipment was operating properly and that all SITE team members understood the sampling
procedures. During this procedure, a small batch of clean silica sand (1,972 Ibs) was treated with
STC's reagents (695 Ibs). This initial "reagent mixture" run constituted a treatment process blank.
Waste treatment began with the transport of approximately 5,000 Ibs of raw waste material to
the 5-cubic-yard high-intensity batch mixer. The contaminated soil was blended in the mixer until
STC personnel determined that the waste was adequately homogenized. Pretreatment grab samples
were taken directly from the discharge from the mixer at three separate time intervals and placed into
sample containers prior to the addition of treatment reagents. Mixing continued for up to 1 hour
5-14
-------
following the addition of the reagents. The treated material was then discharged into three 1-cubic-
yard cardboard forms. Samples were collected from the forms immediately after the treated waste
was discharged from the mixer. For each batch run, complete records were maintained of pertinent
operating parameters including weight of the contaminated soils, STC reagents, and water added;
mixer power; and mixing time (see Table 3-1).
Certain contaminated soils (PCP-encrusted "hardpan") treated during the demonstration were
not well mixed after treatment; the treated waste contained numerous large (0.5 inch) inclusions of
untreated waste aggregates. These pockets of untreated waste resulted in the exclusion of Batch 2
from analytical evaluation. The problem was solved in subsequent batches by passing the raw waste
through a series of screens prior to treatment, reducing the raw waste aggregate size to approximately
0.04 to 0.08 inch (1-2 mm) diameter. This pretreatment allowed for adequate mixing to occur; the
subsequent batches (i.e., Batches 3 through 5) appeared to be homogeneous mixtures.
The generation of large amounts of contaminated dust from the movement of equipment,
supplies, and site personnel caused fouling of the intake to the photoionization device that was used
for air monitoring. This dust problem was remedied through the application of a light spray of water
to the site from a water truck. An additional problem was a dust cloud of reagents created upon
initially mixing the dry reagents with the waste in the mixer. Consequently, a tarp was secured over
the top of the mixer after adding (but before mixing) the dry reagents. Although no downwind
residents or receptors appeared to be affected by the small dust cloud "puff" of finely divided dry
reagents during the demonstration, slurrying the reagents prior to addition is desirable for future uses
of the technology.
Prior to waste excavation for subsequent treatment, all STC equipment that would come in
contact with raw waste materials was decontaminated. In addition, all process equipment was
decontaminated between batch runs and at the conclusion of the demonstration. A portable high-
pressure cleaner was used to decontaminate the equipment. Water and wastes generated from the
cleaning of equipment were pumped to a 3,000-gallon Baker wastewater tank and stored on site for
subsequent disposal. Personnel decontamination wash water and wastes were collected from wash
basins and also placed in this tank for off-site disposal. All sampling equipment was cleaned with a
5-15
-------
nonphosphate detergent and triple rinsed with distilled water before reuse. The resulting wash water
was stored on site for disposal.
Once all test runs were completed and equipment decontaminated, all test equipment was
demobilized and removed from the SPT site. Decontamination and demobilization took
approximately 2 weeks. Residual wastes from the demonstration included 1,000 gallons of water and
wastes from decontamination, three 55-gallon drums of contaminated clothing and disposable
sampling supplies, and a 30-cubic-yard dumpster containing miscellaneous nonhazardous trash. The
decontamination wastes, drums, and dumpster wastes were disposed of by EPA personnel and
contractors at appropriate facilities.
The 1-cubic-yard cardboard form containing treated clean sand and 15 similar forms filled
with treated wastes were placed on wooden pallets in the western section of the demonstration site.
After 28 days, the cardboard forms were removed and disposed. The exposed monoliths of treated
waste were be inspected periodically for 32 months. After the 32 months monitoring period, EPA
disposed of these wastes according to the cleanup criteria selected for the SPT site.
5.3 LABORATORY ANALYSES
The contaminants of regulatory concern at the SPT site were arsenic and PCP; however, other
target analytes of secondary importance to the pilot-scale demonstration were chromium, copper,
nickel, and lead, as well as other semivolatile organic compounds such as phenanthrene,
tetrachlorophenol, phenol, and naphthalene. The corresponding critical measurements for the
demonstration were TCLP for arsenic (and other inorganic analytes) and TWA for PCP (and other
organic analytes). Noncritical measurements included TCLP for organic analytes, and TCLP-Distilled
Water and CALWET leach procedures for both organic and inorganic analytes. Additional noncritical
measurements for the demonstration included the TCLP-Cage and the modified American Nuclear
Society (ANS) 16.1 leach tests, analysis for PCDDs and PCDFs, engineering and geotechnical tests,
and petrographic examinations. In addition, chemical characterization of the raw and treated waste
included pH, Eh, loss on ignition, and neutralization potential. Acid neutralization capacity tests
originally planned for the untreated wastes could not be completed due to the acidic nature of the raw
5-16
-------
waste samples. Instead, neutralization potential measurements were conducted on both the raw waste
and treated waste samples.
For critical measurements, six or more field replicate samples were collected, depending on
data variability as determined in the initial treatability tests on waste samples from the SPT site.
Field replicate samples for metal contamination were analyzed for arsenic, chromium, copper, nickel,
and lead only. Replicate samples were also analyzed for semivolatile organic compounds including
PCP. In addition, field replicate geotechnical/engineering samples were collected to determine
unconfmed compressive strength, permeability, and petrographic examination, but not for particle
size, water content, bulk density, wet/dry, or freeze/thaw testing.
5.4 QUALITY ASSURANCE/QUALITY CONTROL PLAN
EPA-approved sampling, analytical testing, and quality assurance and quality control
(QA/QC) procedures were followed to obtain data of known quality. Details on QA/QC procedures
are presented in the demonstration plan (U.S. EPA, 1992). Quality assurance results are presented in
Section 6.8 of this report.
5-17
-------
6.0 ANALYTICAL PROCEDURES AND RESULTS
6.1 PURPOSE
Performance data were collected from the STC solidification/stabilization treatment
process demonstration at the SPT site to evaluate the overall performance of the STC
immobilization technology as it was applied to wastes from the SPT site. The following sections
describe these results in detail and include results from the leaching tests, chemical tests, physical
tests, and petrographic examinations. Table 6-1 summarizes the analytical and measurement
methods used for each of the various analyses. This section also presents a discussion of the maiss
balance between raw and treated waste, long-term test results, and quality assurance (QA) results.
6.2 MATERIALS BALANCE
This section describes materials balances, the additives ratio, and volume expansion. The
purpose of performing these analyses is to provide information on the extent of dilution of wastes
and the increase in volume that occurred as a result of treatment. When comparing the
concentrations of contaminants in the TCLP extracts or total contaminant concentrations in the
wastes before and after treatment, it is important to consider the dilution that occurred as a result
of the addition of reagents as part of the treatment process. In addition, this analysis provides
information on the quantity of material that will require land disposal capacity if this process is
used. The volume expansion ratio can be used to estimate final disposal capacity needed for a
known quantity of raw waste.
6.2.1 Materials Balance
Table 6-2 presents materials balance information for each of the four batches that were
sampled and analyzed as part of demonstration. The data in this table are based upon information
collected during the demonstration and information obtained from laboratory analyses.
Approximately 4,000 to 5,000 pounds of contaminated soil were treated for each test
batch. Dry reagents were added for each batch in amounts that varied from 34 to 37 percent of
the raw waste by weight, with an average value of 35 percent. The amount of water added ranged
from 39 to 44 percent, with an average value of 42 percent, of the contaminated soil weight. Each
test batch produced approximately 3 to 4 cubic yards of treated material.
6-1
-------
Table 6-1. Analytical and Measurement Methods
title
TCLP
TCLP-Distilled
Water
TCLP-Cage
CALWET
Modified
ANS 16.1
Metals:
Sb, Be, Cd, Cr,
Cu, Ni, Ag, Zn,
Pb, Na, Al, Ba,
Ca, Co, Fe, Mg,
Mn, Mo, K, V
Pb.TI.As.Se
Pb
Tl
As
Se
Hg
Volatile
Organic
Compounds
Semivolatile
Organic
Compounds
PCDDs and
PCDFs
Method
TCLP
TCLP
TCLP-Cage
CALWET
Modified
ANS 16.1
3050
3010
6010
3050
3020
7421
7841
7060
7740
7471
7470
TWA
8240
TWA
8270
TWA
8280
Raw
Waste
Treated
Waste
Reagent
: Clean
Sand
Process
Water
Leachate
Digestates
6-Month
Long-Term
6-Month
Long-Term
Leachate
18- and 32-
Month
Lorig-Term
i
18- and 32-
Month
Long-Term
Leachate -
0\
to
-------
Table 6-1. Analytical and Measurement Methods (Continued)
Title
oH
Eh
Neutralization
Potential
Loss On
' Ignition
Oil and
Grease
Particle
Size
Moisture
Content
Bulk Density
Permeability
Unconfined
Compressive
Strength
Wet/Dry
Weathering
Freeze/Thaw
Weathering
Petrographic
Method
EPA 9045
EPA 9040
Modified
EPA 9045
ASTM
D-1498
Sobeck,
1978
ASTM
C-114
Modified
EPA 413.2
ASTM
D-422
ASTM
D-2216
TMSWC-4
ASA-13.2
TMSWC-2
TMSWC-13
ASTM
D-1633
TMSWC-12
TMSWC-11
Modified
ASTM
C457/C856
Raw
Waste
*
Treated
Waste
-
»
'
Reagent
Mixture ;
.
'
Clean
Sand
»
Process
:Water
i Leachate
: Digestates
6-Month
Long-Term
6-Month
Long-Term
18- and 32-
Month
1
.
18- and 32-
Month
Long-Term
Leachate
ON
-------
Table 6-2. Summary of Materials Balance Data
Parameters
Raw waste weight (Ibs)
Dry reagent weight (Ibs)
Water added (Ibs)
Water lost during curing (Ibs)
Additives ratio
Bulk density of raw waste (Ib/ft3)
Bulk density of treated waste (Ib/ft3)
Volume expansion ratio
Volume increase (%)
Batch
1
5,000
1,732
2,172
97
0.761
88.6
98.0
1.59
59
3
4,000
1,382
1,713
41
0.764
96.1
96.8
1.75
75
4
4,000
1,413
1,760
71
0.776
96.1
98.6
1.73
73
5
4,464
1,638
1,759
67
0.746
96.1
101.1
1.66
66
6.2.2
Additives Ratio
Reductions in leachable and total PCP, arsenic, chromium, and copper concentrations in
the treated wastes may result from diluting the raw wastes with binders used in the treatment
process. Therefore, the additives ratio was calculated for each treatment batch, to correct for the
dilution of the raw waste by the addition of the process reagents. The additives ratio was
determined using the following equation:
AR-Z-
w
where:
AR = Additives Ratio
Wr = Weight of dry reagents
Ww = Weight of water added
Wc = Weight of water lost during curing
W, = Weight of raw waste
6-4
-------
For example, the weight of raw waste for Batch 1 was 5,000 pounds. The weight of the STC dry
reagents for Batch 1 was 1,732 pounds. The weight of water added was 2,172 pounds and the
weight of the water lost during curing was 97 pounds. Therefore, the calculation of the additives
ratio for Batch 1 is as follows:
Additives Ratio = *'732 + (2,172 - 97) =
5,000
The additives ratios determined for each treatment batch are shown in Table 6-2.
6.2.3 Volume Expansion Ratio
The volume expansion ratio (VER) between treated waste and raw waste was calculated
for each treatment batch using the following equation:
(W + W) B
VER = ^ 2i_i
where:
VER = Volume expansion ratio
Ws = Weight of raw waste
Wa = Weight of dry reagents and water, minus water lost during curing
Bs = Bulk density of raw waste (88.6 to 96.1 lb/ft3)
Bt =. Bulk density of treated waste (96.8 to 101.1 lb/ft3)
For example, the variables for Batch 1 are as follows:
Ws = 5,000 pounds
Wa = 3,807 pounds
Bs = 88.6 lb/ft3
Bt = 98.0 lb/ft3
Therefore, the VER for Batch 1 is 1.59. The VER for each treatment batch is shown in Table 6-
2.
6-5
-------
These ratios indicate that the contaminated soils from the SPT site increased in volume
from 59 to 75 percent. The VER may allow prospective users of the STC technology to estimate
the volume of treated waste that will need to be disposed of, transported, or stored if it is known
how much raw waste is present at a site. It should be noted, however, that the VER is a site-
specific value, requiring an estimate of the in-situ bulk density of the raw waste.
6.3 LEACHING TESTS
For purposes of comparison and to assess the ability to meet state and federal regulations,
several leach tests were chosen to evaluate the STC immobilization technology. These tests include
the Toxicity Characteristic Leaching Procedure (TCLP) and two modified versions of the TCLP:
(1) TCLP-Distilled Water and (2) TCLP-Cage. In addition, the California Waste Extraction Test
(CALWET) and the modified American Nuclear Society (ANS) 16.1 leach test were utilized. An
additional modified TCLP test, TCLP-pH 12, which used a 0.1 M borate buffer solution as the
leaching medium, was conducted as well (see Section 6.4). These methods and the results are
described in the following subsections.
Leaching tests were performed on both raw and treated wastes cured for 28 days, as well
as the reagent mixture. Analytical results presented in this report are limited to contaminants of
regulatory concern, including PCP and arsenic, which were targeted for treatment during the
demonstration. Analytical results for chromium and copper, although not target analytes for
treatment, are also reported. For each of the analytes the results are reported as average values for
six or more samples of raw and treated waste, and include sample standard deviation values (that
is, an estimate (s) of the universe standard deviation (a), if an infinite number of measurements
could be made). In addition, the results include calculated percent reductions accounting for
dilution effects of added reagents by incorporating the additives ratio for each batch tested (see
Section 6.2.2). The additives ratio is the weight of additives, including water of hydration,
divided by the weight of wastes. Thus, percent reduction was calculated using the following
formula:
Percent Reduction = [l - (1 + Additives Ratio) x ^"^nfrarion of Treated Waste]
[ Concentration of Raw Waste \
6-6
-------
In general, when a constituent was not detected in the treated waste, the reporting limit
for the treated waste was used to calculate a minimum value for the percent reduction (indicated
by ">"). Reporting limits are calculated by multiplying the method detection limit by a dilution
factor specific for each analysis. If a constituent was not detected in the raw waste, the percent
reduction was not calculable. It should be mentioned that as a result of the dilution associated
with the STC treatment, negative percent reduction values may be expected even if the
concentrations show a decrease in values from the raw to the treated waste. Table 6-3 summarizes
federal and California regulatory thresholds for the critical analytes. These thresholds classify
wastes as hazardous or nonhazardous, depending on whether the concentration of a contaminant
exceeds the given threshold value.
6-3.1 Toxicity Characteristic Leaching Procedure (TCLP)
The TCLP determines the concentrations of extractable organic and inorganic constituents
using an acidic extraction solution and is designed to evaluate a waste's potential for leaching
contaminants when the waste is codisposed with municipal waste in a landfill. This test is the
basis for EPA's regulation of solid waste containing arsenic and other heavy metals as hazardous
wastes. Because the TCLP is a regulatory test for RCRA hazardous wastes, it is likely to be
considered in determining the success of future applications of the STC technology to other
wastes.
The sample material was prepared by crushing, cutting, or grinding the waste if the
surface area of the solid sample was less than 3.1 cm2 or the aggregate size was larger than 9.5 mm
diameter. This step, however, was not necessary with the contaminated soils from the SPT site.
The leaching procedure involved a liquid-to-solid ratio of 20 to 1, maintained at a specified pH
using an acetate buffer. The waste-leaching medium mixture was agitated in a rotary extractor
for 18 ± 2 hours and was filtered through a 0.6 to 0.8 mm glass-fiber filter. The pH and type of
leaching medium used depended on the alkalinity of the solid phase of the waste.
Table 6-4 presents a summary of PCP, arsenic, chromium, and copper concentrations in
TCLP extracts for the raw and treated wastes. In addition, Figures 6-1 through 6-4 graphically
show concentrations of target analytes in the raw and treated wastes for PCP, arsenic, chromium,
and copper, respectively. Average concentrations are depicted by solid symbols for the raw waste
and open symbols for the treated wastes. Error bars associated with each symbol represent the
standard deviation for each average of six analytical results.
6-7
-------
Table 6-3. Regulatory Thresholds for Critical Analytes of the SPT Waste
Constituents
Pentachlorophenol (PCP)
Arsenic
Chromium (hexavalent)
Chromium (total)
Copper
Federal
FRTL (mg/L)*
100
5.0
5.0
State of California
TTLC (mg/kg)b
17
500
500
2,500
2,500
STLC (mg/L)c
1.7
5.0
5.0
560
25
a = Federal Regulatory Tlireshold Limit, based on TCLP.
b - Total Threshold Limit Concentration, based on TWA,
c = Solubility Threshold Limit Concentration, based on CALWET.
6-8
-------
Table 6-4. Analytical Results for TCLP Leachates
Constituent: PCP
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (mg/L)
Haw Waste
1.4
1.6
1.4
1.5
1.7
1.4
1.5 ± 0,13
2.8C
2.1
2.0
2.4
2.4
1.9
2.3 ± 0.33
1.5
2.5
2.1
1.5
0.89
2.0
1.75 ±0.57
1.1
0.085"
3.8C
3.0
2.6
3.1
2.3 ± 1.4
Treated Waste
3.9C
5.2C
0.73
3.0
3.7
4.0
3.4 ± 1.5
0.25'*
0.25'-8
0.25f*
0.25f-g
NA
NA
81
-460
31
6-9
-------
Table 6-4. Analytical Results for TCLP Leachates (continued)
f f -.J.
Constituent: Arsenic
Batch.
1
Average
3
Average
4
Average
5
Average
Concentrations (mg/L)
Raw Waste
1.3
2.2
1.3
2.2
2.3
1.6
1.8 ± 0.47
1.1
0.99
0.97
0.88
0.93
1.5"
U ±0.23
2.0
2.3
2.3
2.2
3.6s
2.0
2.4 ± 0.60
3.1
3.6
3.3
3.3
3.8
2.9
3,3 ± 033
- Treated Waste
0.048d
0.096d
0.05 ld
0.044d
0.19d>q
0.084"
0.086 ± 0.055
0.09 ld
0.08 ld
0.10d
0.1 6d*
0.097d
0.078
0,10 ± 0.030
0.9 ld
0.76d
0.67d
l.ld
0.84d
0.97
0.88 ± 0.15
0.56
0.47
0.61
0.65
0.60
0.40
0.55 ± 0.095
Average Percent
Reduction"*
92
83
35
71
6-10
-------
Table 6-4. Analytical Results for TCLP Leachates (continued)
Constituent: Chromium - :
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (mg/L)
Raw Waste
0.051
0.21
0.053
0.20
0.22
0.052
0.13 + 0.087
0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
0.071
0.073
0.077
0.083
0.23s
0.084
0.10 + 0,062
0.24
0.25
0.24
0.28
0.37"
0.23
0.27 ± 0.053
Treated Waste
0.24
0.25
0.24
0.25
0.24
0.25
0.245 ± 0.0055
0.19
0.20
0.18
0.17
0.18
0.20
0.19 ± 0.012
0.29
0.28
0.29
0.27
0.27
0.27
0.28 ± 0.0098
0.32
0.31
0.33
0.29
0.29
0.38
0.32 ± 0.033
Average Percent
Reduction"-1"
-230
NC
-390
-110
6-11
-------
Table 6-4. Analytical Results for TCLP Leachates (continued)
Constituent: Copper
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (mg/L)
Saw Waste
2.2
4.5
2.4
4.4
4.5
2.5
3.4 i 1.2
1.5
1.5
1.4
1.2
1.2
1.5
1.4 ±0.15
6.2
6.1
6.2
6.5
8.7q
5.5
6.5 ± IA
9.2
9.3
8.8
9.5
12.0q
7.8
9.4 ± 1.4
Treated Waste
0.087
0.085
0.090
0.089
0.089
0.099"
0.090 ± 0.0048
0.074
0.077
0.070
0.067
0.071
0.088
0.0745 ± 0.0074
0.10
0.10
0.11
0.10
0.10
0.11
-------
Table 6-4. Analytical Results for TCLP Leachates (continued)
NA = Not analyzed
NC = Not calculable
a = Percent Reduction = [l - (1 + Additives Ratio) x Ct>ncen*"^on of Treated Waste] x 1M
L Concentration of Raw Waste j
b = The additives ratio is the weight of additives, including water of hydration, divided by the weight of
raw wastes. Values are 0.761, 0.764, 0.776, and 0.746 for Batches 1, 3, 4, and 5, respectively
c = Reported value was calculated using a greater dilution than the primary analysis.
d = Spiked sample recovery not within control limits.
e = Estimated concentration; compound was detected but at a concentration amount less than the
reporting limit.
f = Laboratory reporting limit; compound was not detected.
g = Sample failed surrogate recovery criteria.
q = Falls Q test (Shoemaker, 1974); value may be disregarded with 90% confidence (although it has
been used to calculate the average value).
S = ue) m0y ^ dlSregarded With 95% confldence (Chough it has been used to calculated the average
6-13
-------
Concentration (ppm)
JO
-t=j J
a
TO
I
H
O
5.
n'
W
I
D
g»
Ui
o
a
VQ
e
o\
i
0
^ w
i
i
^
n
Concentration (ppm)
H 1-
>
ON
o e
H »
" M
o
i-o-i
-^
-------
Batch
Figure 6-3. TCLP Chromium
§
+-*
I
§
12'
10-
1
Raw
Treated
0-
3
Batch
Figure 6-4. TCLP -- Copper
6-15
}
-------
The TCLP test showed mixed results for PCP, with percent reductions ranging from -460
to greater than 81 percent. Batches 1 and 4 showed increases in extractable PCP after treatment.
However, extractable concentrations of PCP in both the raw and treated wastes were well within
the Federal Regulatory Threshold Limit (FRTL) of 100 mg/L for PCP.
Results for arsenic were variable among the four batches evaluated using the TCLP, with
percent reductions ranging from 35 to 92 percent. Batch 4 depicts an anomalously low percent
reduction of only 35 percent. This poorer-than-expected performance may be attributed to the
inordinately long raw-waste mixing time for this batch (4.5 hours). Arsenic concentrations in the
TCLP extracts were below the FRTL for both the raw and treated wastes.
Table 6-5 presents supplemental ion-chromatography analyses from TWA-extracts of
arsenic for selected samples from Batches 3, 4, and 5. These results indicate that the raw waste
from Batch 4 contained higher quantities of the arsenic ion-species arsenite (205 mg/kg) and
lower values of arsenate (20 mg/kg), relative to Batches 3 and 5, that had higher arsenate (61
mg/kg and 260 mg/kg, respectively) and lower arsenite values (<2 mg/kg in both batches). It is
likely that most of the Batch 4 arsenic was reduced from arsenate (V) to arsenite (III) during the
long raw-waste-mixing process, thereby rendering the arsenic contaminant more mobile and easily
leached under acid TCLP conditions. Alternatively, the STC process was not effective in
converting arsenite to arsenate or a species which could be chemically stabilized; small amounts of
both arsenite and arsenate were detected in the Batch 4 treated waste.
Chromium was not a target analyte for treatment because of very low leachable
concentrations in the raw waste. Treated waste samples consistently leached greater quantities
than the raw waste. TCLP tests for chromium in the treated waste showed large negative values
for percent reduction ranging from -110 to -394 percent. However, both raw and treated waste
concentrations of chromium were well below the FRTL of 5 mg/L for total chromium. Leachate
concentrations of chromium from the raw waste of Batch 3 were below detection limits and
therefore percent reductions were not calculable.
Copper concentrations in the TCLP extracts showed the greatest percent reduction
following the STC treatment, even though copper was not a target analyte for treatment Percent
reductions ranged from 90 to 99 percent. Initial concentrations in the raw waste extracts were also
low
6-16
-------
Table 6-5. Arsenic lon-Speciation for STC-Treated Wastes
slii: Constituent
Arsenate (V)
Arsenite (III)
-
=^======
Batch
3
''X-. ..-.- . ' ',,.
-.;:>:;:/ 'Average
4
^ Average '";':
5
Average
3
^:- .'; A ver'age . "''
4
: / Average
5
.;'... Average
^-
=====*======
Concentrations (mg/kg)
Raw Waste
43
78
603 ' .
21
18
19.5
240
280
260
<2.0
<2.0
<2.0
140
270
205
<2.0
<2.0
;<2.o
Treated Waste
<2.0
<2.0
<2.0
40
<2.0
<2.0
<2.0
<2.0
<2.0
<2.0
<2.0
<2.0
13
7
<2.0
<2.0
^.-: :*$$£ :J&
y=^=^=^=^=i
Average Percent
Reduction"*
>94
-91
>99
NC
94
NC
NC
a
b =
Not calculable
Percent Reduction = [l - (1 * Additives Ratio) x Concetttr
-------
6.2.2 TCLP-Distilled Water (Modified TCLP)
The TCLP-Distilled Water test is a modification of the standard TCLP designed to
determine the mobility of contaminants present in the waste under neutral pH conditions. The
test determines extractable constituents using water in place of an acid extraction solution, and is
used to detect amphoteric metals and other constituents mobilized by matrix pH. All other steps
of the TCLP (including liquid-to-solid ratio and duration of extraction time) remain the same
Table 6-6 depicts the analytical results for the various analytes in the TCLP-Distilled Water
extracts. Figures 6-5 through 6-8 graphically show the concentrations of target analytes in the
raw and treated wastes for PCP, arsenic, chromium, and copper, respectively. Average
concentrations are depicted by solid symbols for the raw wastes and open symbols for the treated
wastes. Error bars associated with each symbol represent the standard deviation for each average
of six analytical results. In each case, concentrations of contaminants in the leachates from the
treated wastes were less than concentrations in the leachates from the raw wastes. In the case of
chromium, however, for Batches 4 and 5 there was considerable overlap between raw and treated
waste concentrations.
PCP showed better stabilization characteristics under the neutral leaching conditions of
this procedure than under the standard acid TCLP. Percent reductions following the STC
treatment ranged from 80 to 97 percent based on this modified TCLP. Raw waste leachate
concentrations from the TCLP-Distilled Water test, however, are an order of magnitude greater
than those generated under the acid leaching conditions of the TCLP.
Arsenic depicted a high percent reduction level of 98 percent or greater for all four
treatment batches. In addition, arsenic concentrations in the leachates of the raw waste were low
(<1.5 mg/L), below the FRTL.
Chromium, although not a target analyte for treatment because of very low concentrations
in the initial treatability TCLP raw waste leachates, showed mixed results following the STC
treatment based on the TCLP-Distilled Water test. Percent reductions ranged from -42 percent to
greater than 54 percent. Chromium was not detected in the treated waste leachates of Batches 1
and 3, although the raw waste leachates for these batches contained more chromium than the
leachates for either the raw or treated wastes from Batches 4 and 5.
6-18
-------
Table 6-6. Analytical Results for TCLP-Distilled Water Leachates
Constituent: PCP
Batch
1
Average
3
Average
4
; Average
<
Average
Concentrations (mg/L)
Raw Waste
13
34e
23
61
36
41
35 i 16
69
48
28
15
43
37
40 ±18
49e
49e
50e
32
36
26
40 ±10
68
65
71
110
93
71
80 ±18
Treated Waste
2.5
5.5
3.6"
2.5
3.0
6.8
4.0 ± 1.8
0.69
0.64
0.59
0.47
0.60
0.50
0.58 ± 0.083
3.9
3.5
3.2
4.1
4.0
4.5
3.9 ± 0,46
2.5
2.3
2.2
4.3
3.4
3.6
3.05 ± 0.85
Average Percent
Reduction**
80
97
83
93
6-19
-------
Table 6-6. Analytical Results for TCLP-Distilled Water Leachates (continued)
Constituent:.. Arsenic
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (mg/L)
Haw Waste
0.95°
1.0C
0.71°
0.82°
0.91C
0.42
0.80 ± 0.21
0.66C
0.72C
0.75C
0.80C
Q.7Tf
0.65
0.725 ± 0.060
1.3
1.3
1.3
1.1
1.4
1.1
1,25 1 0.12
1.2
1.1
0.97
1.1
0.96
1.1
14 ± 0.091
Treated Waste
<0.01f
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.010
0.010'
0.013
<0.010f
<0.010f
<0.010
0.0115 ±0.0021
0.013
0.013
0.011
0.011
0.013
<0.010
0.012 ± 0.001 1
Average Percent
Reduction"*
>98
>98
98
98
6-20
-------
Table 6-6. Analytical Results for TCLP-Distilled Water Leachates (continued)
Constituent: Chromium
Batch
1
Average^
3
Average
4
Average
5
Average
Concentrations (mg/L)
Raw Waste
0.21
0.31
0.091
0.16
0.20
0.17
0.19 ± 0.072
0.20
0.18
0.18
0.066s
0.22
0.19
0.17 ± 0.054
0.079
0.060
0.10
0.067
0.066
0.067
0.073 ± 0.0145
0.15
0.11
0.063
0.057
0.10
0.15
QJOS ± 0.040
Treated Waste
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
0.066
0.055
0.055
0.052
0.050
0.060
0.056 + 0.0058
0.078
0.077
0.079
0.076
0.084q
0.079
0.079 ± 0.0028
Average Percent
Reduction*'1'
>54
>48
-42
-25
6-21
-------
Table 6-6. Analytical Results for TCLP-Distilled Water Leachates (continued)
Constituent: Copper '
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (rag/L)
Raw Waste
0.49
0.73
0.25
0.37
0.45
0.43
0.45 ±0.16
0.41
0.37
0.36
0.21i
0.45
0.41
0.37 i 0.084
0.98
1.1
0.97
0.97
1.0
0.92
0.99 ± 0.060
0.71
0.54
0.45
0.50
0.50
0.63
0.555 ± 0.097
Treated Waste
0.030
0.030
0.031
<0.030
<0.030
0.032
0.031 ±0.00096
0.030
0.030
<0.030
<0.030
<0.030
<0.030
<0.030
0.056
0.053
0.055
0.055
0.055
0.051
0.054 ± 0.00 J 8
0.032
0.031
0.032
0.031
0.034
<0.030
0.032 ±0.0012
Average Percent
Reduction1^
88
>86
90
90
6-22
-------
Table 6-6. Analytical Results for TCLP-Distilled Water Leachates (continued)
a = Percent Reduction = fl - (1 + Additives Ratio) x Concentrati°* of Treated Waste}
[ Concentration of Raw Waste \
b = The additives ratio is the weight of additives, including water ofhydration, divided by the weight of
raw wastes. Values are 0.761, 0.764, 0.776, and 0.746 for Batches 1, 3, 4, and 5, respectively
c = Duplicate analysis not within control limits.
d = Estimated concentration; compound was detected but at a concentration less than the reporting
limit. 6
e = Reported value was calculated using a greater dilution than the primary analysis.
f = Post digestion spike for Furnace AA analysis of control limits (85-115%), while sample absorbance
was less than 50% of spike absorbance.
q = Fails Q test (Shoemaker, 1974); value may be disregarded with 90% confidence (although it has
been used to calculate the average value).
s = Value may be disregarded with 95% of confidence (although it has been used to calculate the
average value).
6-23
-------
Concentration (ppm)
p
to
-I
p
b\
p
bo
to
H
~ p
ore
o\
H
O
IT1
B
S"
w
p
B
o\
I
H
n
d
3!°
(D
a.
i
Q
Concentration (ppm)
W
B9
R
o 8
LO
O
4
o
I-
Ul
o
-J OO
o o
-H »-
O
-
-------
Concentration (ppm)
Concentration (ppm)
tt
TO*
n
o\
i
00
H
n
IT* oj
2
5T
rt-
S w
s. g
* *
P
*4-
n
1 4*.
n
o
T3
a
t
p p p p 1 >
ONJ-t^bsOOi >ts> *
*fl
MM*
c
rtl
ON
I
^- 1 0 I *tl w <
0
o ^ 1
5f w
H W p
^1 63 -^^ O
8 1 1 ^
r* **
n *+
h. 5
O t-^Hf ' ^
0
o
1.
i
o o o _
b P :- P K> P
3 Lft l-» Wl tO L/l IP
J Y- 1 h H 1 1
. K« i fe 1
' J?l 1 r *
r .p- -I
t> ^
H W
§ |
'
-------
Copper, also not a target analyte for treatment, showed slightly lower percent reductions
under the neutral TCLP-Distilled Water leach than under the acetic acid TCLP, with values
ranging from 86 to 90 percent. Copper concentrations for the raw waste leachates were, however,
much lower than for the standard acid TCLP.
6.3.3 TCLP-Cage Test (Modified TCLP)
The TCLP-Cage test is a modification of the standard TCLP designed to determine the
mobility of contaminants in treated wastes. Its distinguishing characteristic is that the treated
sample is not crushed or ground before leaching. Rather, a monolith or bulk sample of solidified/
stabilized waste is used for the leaching procedure. All other steps of the TCLP (including
selection of extraction fluid) remain the same. Results for the TCLP-Cage test are presented in
Table 6-7. Figures 6-9 through 6-12 graphically show the analytical results with open symbols
representing average concentrations of the treated wastes. Error bars associated with each symbol
represent the standard deviation for each average of three analytical results.
One would expect greater leaching under standard TCLP test conditions than under the
conditions of the TCLP-Cage test, due to the increased exposed surface area resulting from
crushing the solidified waste; however, this result was not typically the case for the metals. For
the metals that were calculated, all but three cases showed higher concentrations in the TCLP-
Cage leachates when compared to the TCLP.leachates; however, the results were highly variable,
especially for chromium and copper in Batches 4 and 5 where standard deviation values exceeded
mean values. For PCP, on the other hand, lower leachate concentrations from the treated wastes
were obtained for the TCLP-Cage test than the TCLP in all batches, except Batch 3 for which
PCP was not detected using either the TCLP or the TCLP-Cage test. All TCLP, TCLP-Cage, and
TCLP-Distilled Water leachate concentrations for PCP, arsenic, and chromium from the treated
waste samples were below the regulatory levels for the TCLP test. However, leachates from raw
waste samples were also below these levels.
6.3.4 CALWET
The CALWET method consists of an extraction similar to the TCLP extraction, except that
the CALWET uses a citric (triprotic) acid solution for leaching solid material over a 48-hour
period, at a liquid-to-solid ratio of 10 to 1. Following the leaching perio'd, separation of the
6-26
-------
Table 6-7. Analytical Results for TCLP-Cage Leachates
Constituent
PCP
Average
Arsenic
Average
Chromium
Average
Copper
Average : : = /
: : A f Concentrations (mg/L)
Batch
1
0.077" '
5.5a
0.28
2.0 ±3.1
0.30
0.35
0.33
0.33 ± 0.025
0.73
0.33
0.76
0.61 ±0.24
1.9
0.82
2.1
1.6 ±0.69
=====================
3
< 0.250"
<0.250b
<0.250b
<0.250
0.11°
0.11
0.13
0.12 ± 0.0115
0.15
0.14
0.13
0.14 ±0.010
0.096
- 0.10
0.092
i 0.096 ±0.0040
=====================
4
0.053*
0.033a
0.25"
. 0.11 ± 0.12
0.95
0.55C
0.72
0.74 ± 0.20
0.10
0.28
1.60
0.66 ± 0.82
0.13
0.16
4.00
1.4 ± 2.2
5
0.075*
0.073"
NA
0.074 ±0.001
0.23
0.30
0.23
0.25 ± 0.040
0.31
0.11
1.30
0.57 ±0.64
0.91
0.08
4.40
1.8 ±2.3
to
NA = Not Analyzed
a = Value reported is an estimated concentration; compound was detected, but at a concentration less than the reporting limit.
b = Laboratory reporting limit; compound was not detected.
c = Post digestion spike for Furnace AA analysis out of control limits (85-115%), while sample absorbance was less than 50% of spike absorbance.
-------
7s
£
o
8
o
»
no
ffi
Concentration (ppm)
PppppppppOi-*
Iff++++-°°
P
CtQ
<
n
o\
?
n
65
orq
n>
t
1
Concentration (ppm)
K-,
g
0
3
I
-------
Concentration (ppm)
Concentration (ppm)
23
TO*
P
b
P
Lx
JO U)
l/< b
TO
N>
o\
I
H
n
P
ere
O
o
ri
C8
CO
3
*a
TO
>
n
o
a
a
o
o
S
-------
extracts is achieved by filtration through a 0.45-^m membrane filter, centrifuging prior to
filtration, if necessary. As a result of its greater acid concentration, longer leaching time, and
greater buffering capacity, the CALWET is a more aggressive leach procedure than the TCLP
Analytical results for the CALWET are presented in Table 6-8. Figures 6-13 through 6-16 depict
the data graphically with solid symbols representing raw waste average concentrations of three
analytical results and open symbols representing treated waste average concentrations of three
samples for PCP and six samples for each of the metals. Error bars associated with the average
concentrations of arsenic in the raw and treated wastes overlap for Batch 5.
Raw waste leachate concentrations of PCP and arsenic were above the Solubility Threshold
Limit Concentrations (STLC) of 1.7 and 5 mg/L respectively for the CALWET, a regulatory
criteria used by the state of California (see Table 6-3). Leachable chromium concentrations in the
raw waste were well below the total chromium STLC of 560 mg/L. Copper in the raw waste
leachate from Batch 3 was below the STLC of 25 mg/L and leachate from soil used in Batches 1,
4, and 5 were above this limit.
STC treated wastes were not effectively stabilized based on results from the CALWET
procedure. PCP concentrations in the treated waste leachates increase with respect to the raw
waste leachate concentration, thus resulting in negative percent reductions ranging from -135 to
-1,829 percent. Arsenic values showed mixed results, with percent reductions ranging from -44
to 37 percent. All batches showed reductions in arsenic leachate concentrations after treatment
however, Batches 4 and 5 resulted in average leachate concentrations above the STLC of 5 mg/L
Chromium concentrations in the CALWET leachates, like PCP, increased following the STC
treatment, resulting in negative percent reductions ranging from -205 to -375 percent. Chromium
leachate concentrations, however, remained below the STLC limit of 560 mg/L. Copper
concentrations were slightly reduced upon treatment; Batch 1 was brought below the STLC of
25 mg/L for the treated CALWET leachates. Batch 3 was below this threshold prior to treatment.
Overall, percent reductions for copper ranged from 2 to 22 percent.
6.3.5 ANS 16.1 (Modified)
The ANS 16.1 leach test is used by the nuclear industry to identify the mechanisms that
control leaching and to indicate the amount of possible leaching from a monolithic solid This
leach test is used to simulate contact with rapidly flowing groundwater by. using a static sequential
leaching method. A 10-week modification of ANS 16.1 for solidified wastes was used to
approximate leaching from treated waste by demineralized water that flowed around the sample
6-30
-------
Table 6-8. Analytical Results for CALWET
Constituent: VC?
Batch
1
Average
3
Average
4
Average
5
Average
" , s
Concentrations (mg/L)
Raw Waste
1.7
2.4
2.8
2,3 ± 0.56
2.3
2.4
3.1
2.6 ± 0.44
3.1
3.2
3.3
3.2 ± 0,10
2.7
3.0
2.9
2.9 ± 0.15
Treated Waste
13
10
14
12 ±2.1
2.8
4.8q
2.8
3.5+1.15
34"*
26
26
29 ± 4.6
30
30
35*
32 ± 2.9
Average Percent
Reduction"'*
-842
-135
-1,493
-1,829
6-31
-------
Table 6-8. Analytical Results for CALWET (continued)
1 Constituent: Arsenic
Batch
Average
3
Average
4
:- Average
<
Average
,f
Concentrations (mg/L)
Raw Waste
11
13
14
NA
NA
NA
13 ± 1.5
9.4
8.3
8.6
NA
NA
NA
8,8 ± 0.56
28
29
29
NA
NA
NA
29 ± 0.58
29
29
26"
NA
NA
NA
n± 1.7
Treated Waste
3.6
5.2
5.2
5.9
4.4
3.1
4.6 ± 1.1
6.8
5.2
4.2
4.4
2.6
4.1
4.55 ± I A
23
26
21
23
23
24
23 ± 1.6
18
16
19
21
20
26
20 ± 3,4
Average Percent
Reduction^
37
9
-44
-25
6-32
-------
Table 6-8. Analytical Results for CALWET (continued)
Constituent: Chromium
Batch
1
Average
3
Average
4
Average
5
. Average
Concentrations (mg/L)
Raw Waste
2.9
3.1q
2.9
NA
NA
NA
3,0 + 0.115
2.1
2.2
1.9
NA
NA
NA
2,1 ± 0.15
7.2
6.5
7.6
NA
NA
NA
7J ± 0,56
6.9
7.2
6.6
NA
NA
NA
63 ± 0.30
Treated Waste
3.9
5.1
6.0
5.7
6.1
4.1
5.15±0.96
4.4
3.9
3.6
3.8
3.3
3.8
3.8 ± 0.36
19
19
19
18
18
21q
19 ± I.I
18
18
18
17
17
20"
18 ± 1,1
Average Percent
Reduction"'1'
-205
-224
-375
-355
6-33
-------
Table 6-8. Analytical Results for CALWET (continued)
Constituent: Copper
Batch
1
Average
3
lii:SS:§lA' verage , ' .. 'v
4
ilf J:;:l;:;;;Average; ;':' ' .' ' ,v,;
5
lilP^Avefage ,:#;, -:
" ' '
1
Concentrations (mg/L)
Raw Waste
27
28
28
NA
NA
NA
28 + 0.58 :i
18
18
17
NA
NA
NA
18 ± 0.58
58
54
61
NA
NA
NA
58 ± 3.5
63
65
56
NA
NA
NA
: 61 ±; 4.7
Treated Waste
11
12
13
14
14
10
12 ±1.6
8.1
9.4
8.8
9.0
8.6
9.1
8.8 ± 0.45
32
33
31
31
31
33
32 ± 0.98
33
33
32
32
33
35q
33 ± 1.1
Average Percent
Reduction*-*
22
12
2
6
6-34
-------
Table 6-8. Analytical Results for CALWET (continued)
NA = Not analyzed
a = Percent Reduction = [l - (1 * Additives Bate) x Concentration of Treated Waste} x 1(x)
[ Concentration of Raw Waste \
b = The additives ratio is the weight of additives, including water ofhydration, divided by the weight of
raw wastes. Values are 0.761, 0.764, 0.776, and 0.746 for Batches 1, 3, 4, and 5, respectively.
q = Fails Q test (Shoemaker, 1974); value may be disregarded with 90% confidence (although it has
been used to calculate the average value).
6-35
-------
Concentration (ppm)
Concentration (ppm)
o
-4-
to
-«
o
-t-
N>
O
I-
on
B
t
-------
Concentration (ppm)
Concentration (ppm)
c
H-t
3
ore'
i
o\
3 4
Batch
;. CALWET Copper
u,
h- tO Ui -t^ ^-ft Qi *-l O
ooo-oooo . "
1 1 1 1 1 1 1
a
ore
E
t
ffi
O\
1
H- »
(J>
O
o » *; "
o* ? s
H 50 ' S.
H » O ^
fT) 3 » *
te ^ BT
g 1
O H** g *
OB__^^_J| W>
^^^Ti
,_! l_> tO tO
tj! O W> O *^i
1 1 1 ! i
1 i
»»
> >
I
NI-JS-J
W^^rm
-------
(The initial leach periods were lengthened because previous experience indicated that solidified
matrices were barely wetted during the standard ANS 16.1 leach periods.) Samples were leached
without agitation using demineralized water with an electrical conductivity of less than
5 //mhos/cm at 25°C and a total organic carbon concentration of less than 3 milligrams per liter.
The samples were submerged in the water for specified time intervals, after which the leachate
was collected and set aside for analysis. The sample was then re-extracted in another aliquot of
demineralized water. The cycle was repeated to obtain five leachates for each sample over the
10-week period. Because the material was not ground as part of the test, the ANS 16.1 leach test
provides information on the ability of the treated solid waste material to contain contaminants.
Several factors should be considered in reviewing the results of this test. First, the test is
normally conducted on monolith-like solids generated by solidification/stabilization processes in
the nuclear industry. Such solids may differ in both chemical and physical characteristics from
those generated by the STC contaminated soil process. In addition, the test was not performed on
the raw wastes because of the friable nature of the contaminated soil.
PCP results were only slightly higher than minimum reporting limits, and only negligible
amounts of each of the three selected metals - arsenic, chromium, and copper - were detected
in the leachate extractions after each test period (Table 6-9). Except for chromium after the
second test period, all metal values were at or near the minimum reporting limits.
As part of the ANS 16.1 leachability test, the leachability index (LI) is recommended as a
standard method for evaluating solidified waste forms:
u = log (A
\D.
where De is the effective diffusion coefficient (cm2/sec), and B is constant (1 cm2/sec). The
diffusive strength for a given analyte within the solidified matrix is regulated by its chemical
activity (that is, effective concentration) as well as the permeability of the waste form. The
determination of a diffusion coefficient based on Pick's Law has been documented in the ANS
16.1 leachability test for solidified low-level, radioactive wastes. The equation for a semi-infinite
medium diffusion model with uniform initial concentration and zero surface concentration is:
6-38
-------
Table 6-9. ANS 16.1 Leachate Analyses for STC-Treated Waste (Batch 3)
Constituent
PCP
Average
Arsenic
Average
Chromium
Average
Copper
Average
PH
Concentrations (mg/L)
Day 14
0.37
0.21
0.15
0.21
0.235 ± 0,094
<0.004
<0.004
<0.004
<0.004
<0.004
<0.01
<0.01
<0.01
<0.01
<0.0l
0.027
0.022
<0.02
<0.02
0.022 ± 0,0033
11.6
Day 28
0.078
0.15
0.16
0.11
0,125 ± 0.038
0.0052^
<0.004
<0.004
<0.004
0.004 ± 0.0006
0.16"
0.040
0.010
<0.01
0,055 ± 0.071
<0.02
<0.02
0.02
<0.02
<0.02
11.6
Day 42
0.13
0.17
0.090
0.11
0,125 ± 0.034
<0.004
<0.004
<0.004
<0.004
<0.004
0.036"
0.013
<0.01
<0.01
0.017 ± 0.0125
0.035"
<0.02
<0.02
<0.02
0.024 ± 0.0075
11.0
Day 56
0.18
0.088
0.13
0.13
0.13 ± 0.038
<0.004
<0.004
<0.004
<0.004
<0.004
0.011
<0.01
<0.01
<0.01
0.010 ± 0.0005
<0.02
<0.02
<0.02
<0.02
<0.02
11.2
Day 70
0.080
0.094
0.12
0.12
0.10 ± 0,020
<0.004
<0.004
<0.004
<0.004
<0.004
<0.01
<0.()1
<0.01
<0.01
<0.01
0.02
<0.02
<0.02
<0.02
-------
Ao
°. - i|JL
where:
An = Contaminant loss during leaching period, n (mg)
A0 = Initial amount of contaminant in specimen (mg)
V = Volume of specimen (cm3)
S = Surface area of specimen (cm2)
tn = Time (sec)
De = Effective diffusion coefficient (cm2/sec)
(EA }
The linearity of a plot of -S- versus t for a given analyte indicates that the
\ AO J
release of an analyte from the solid to the aqueous solution is limited by diffusion. The
leachability index is thus used to compare the relative mobility of contaminants on a uniform
scale. This scale varies from very mobile, for a leachability index of 5 (De = 10'5 cm2/sec) or leiss,
to immobile, for values of 15 (De = 10'15 cm2/sec) or greater. The leachability index was calculated
from the results for PCP, arsenic, chromium, and copper. The values of the leachability indices
for the STC-treated wastes are as follows:
PCP
Arsenic
Chromium
Copper
- LI
- LI
- LI
- LI
=
=
=
=
10.8
12.2
11.0
10.9
These values are well above the Nuclear Regulatory Commission's minimum leachability index
standard of 6. However, the standard for this index has no specific basis in terms of human or
environmental risk or toxicity.
6.3.6 Summary of Leach Tests
PCP showed considerably greater mobility under neutral leaching conditions in the raw
waste than under acid TCLP or CALWET conditions. The treated wastes, however, showed very
similar leachability of PCP under both acid and neutral TCLP conditions. Arsenic appeared to be
well stabilized by the STC treatment under neutral leach conditions. Acid leaching, however, as
6-40
-------
under TCLP and CALWET conditions, resulted in increased arsenic mobility in the treated waste
relative to neutral leaching conditions. Chromium was generally rendered immobile by STC's
treatment process under neutral leaching conditions. In all acid leachates, chromium
concentrations for the treated wastes were significantly higher than for the raw wastes. The raw
waste, however, showed no difference in leachability of chromium between acid and neutral
TCLP conditions. Copper in the raw waste was slightly less mobile under neutral conditions than
under acid leaching conditions. Treated waste leachate concentrations showed copper to be
essentially immobile under both acid and neutral TCLP conditions.
6.4 CHEMICAL ANALYSES
The raw and treated wastes were analyzed for organic and inorganic constituents using
TWA. In addition, chemical characterization of the raw and treated waste included pH, Eh, loss
on ignition, and neutralization potential. Results are also presented for a STC solidified reagent
mixture blank, as well as the sand used for the blank, and the process water used to mix each
treatment batch. Oil and grease extracts were also analyzed for both the raw and treated wastes.
6.4.1 Organics
Pentachlorophenol (PCP) was the main organic contaminant of concern at the SPT site
Based on information from the site treatability study, replicate samples were analyzed for other
constituents, including semivolatile organics such as tetrachlorophenol (TCP), phenanthrene,
naphthalene, and phenol. Concentrations of these constituents were found to be negligible and
therefore are not included in this report. TCP was, however, detected in an auxiliary study where
a modified TCLP method (using a borate buffer solution at PH 12) was performed followed by
analysis for PCP and TCP.
Table 6-10 presents TWA (SW 846 Method 8270) data for PCP in the raw and treated
wastes. Multiple test results are shown for both the raw and treated wastes, since multiple samples
were obtained of raw and treated waste for each batch. The variance in concentrations for each
batch represents differences existing between discrete samples within that batch. For comparison
purposes, average values have been used for each batch of raw and treated waste because averages
may provide a more reliable indicator of overall treatment effectiveness, as there is no
justification for matching any single raw waste value to any single treated waste value. Figure 6-
17 graphically shows the average concentrations of PCP for each batch, including standard
deviation values shown as error bars.
6-41
-------
Table 6-10. Total Waste Analyses (TWA) for PCP
Batch
1
Average
% Reduction**
3
Average
% Reduction1'*
4
Average
% Reduction**
Concentrations (rag/kg)
Raw Waste
2,600
1,500
2,000
2,600
3,400
2,000
2,350*660
v
l,700f
2,200C
2,200'
2,000
2,200
1,600
2,000 * 270
«
6,400'
6,800
8,900
7,300
9,000
7,800
7,700 * If100
...
Treated Waste Data Options
1
200"
82°
140°
480"
480"
480"
310 i 190
77
34C
480d'g
480"'g
480d'g
54c'g
480d|g
330*225
64
480d|g
480d>g
480dlg
480d'g
480d'g
200C
430 * 110
90
2
200°
82C
1406
NA
NA
NA
140*59
89
34C
NA
NA
NA
54C
NA
44*10
96
NA
NA
NA
NA
NA
200°
200*0
95
$
200°
82C
140°
106°
106'
106°
120*42
91
34C
106e
106e
106e
54C
106e
' 85 * 33
92
106e
106e
106e
106°
106e
200C
120*38
97
4
200C
82°
14
-------
Table 6-10. Total Waste Analyses (TWA) for PCP (continued)
Batch
5
Average
% Reduction"*
Concentrations (rag/kg)
Raw Waste
6,300
10,000
9,600
8,300
7,000
8,700
8f300 1 1,400
Treated Waste Data Options
1
480"*
480"*
400°
370°
480"*
NA
440*53
91
2
NA
NA
400°
370°
NA
NA
385*15
92
3
106e
106e
400°
370C
106'
NA
220*150
95
4
0
0
400°
370°
0
NA
150*210
97
5
47
49°
230*
NA
NA
NA
110 * 105
98
6
47
49c
203'
400°
370°
NA
210 * 170
96
ON
-k
NA = Not Analyzed
a - Percent Reduction =
1 - (1 * Additives Koto) * Concerto** of Trtatod Etote
Concentration of Raw Waste
b '= The additives ratio is the weight of additives, including water ofhydration, divided by the weight of raw wastes. Values are 0.761, 0.764, 0.776, and
0.746 for Batches 1, 3, 4, and 5, respectively.
c = Value reported is an estimated concentration; compound was detected but at a concentration less than the reporting limit.
d = Laboratory reporting limit; compound was not detected.
e = Estimated concentration using twice the method detection limit.
f = Reported concentration was calculated using a greater dilution than the primary analysis.
g = Sample failed surrogate recovery criteria.
Option 1 = Percent reduction calculation based on using laboratory reporting limits for samples for which PCP was not detected.
Option 2 = Percent reduction calculation based on using actual measured or laboratory estimated concentrations onfy; samples for which PCP was not
detected were not included in calculation.
Option 3 = Percent reduction calculation based on using twice the method detection limit for samples for which PCP was not detected.
Option 4 - Percent reduction calculation based on using values of 'zero for samples for which PCP was not detected.
Option 5 = Percent reduction calculation based on using PCP concentrations from modified EPA method 8270.
Option 6 = Percent reduction calculation based on using PCP concentrations from modified EPA method 8270 and laboratory estimated concentrations
from original analysis.
-------
o\
Concentration (ppm)
00
TO
o\
H-l
^4
H
Q
-------
As is evident from the treated waste data, PCP was not detected in many samples, although
observable (estimated) concentrations were detected at levels significantly below the reporting
limit. Reporting limits were determined by multiplying the method detection limit by a dilution
factor specific for each analyte. Establishing reporting limits for PCP by TWA of treated samples
presented problems because of the high concentrations of PCP and the correspondingly large
dilution factors necessary to reach the analytical method quantitation range for PCP
(approximately 100 to 200 i/g/kg).
Several options for calculating percent reductions of PCP for TWA are presented in Table
6-10. Percent reductions for Option 1 are calculated using the laboratory reporting limits for all
samples for which PCP was not detected. Option 2 uses actual measured concentrations or
laboratory estimated concentrations only for calculating percent reductions. Percent reductions
for Option 3 were calculated using "assigned" concentrations of twice the method detection limit
(that is, 2 x 53 = 106 mg/kg) for the samples for which PCP was not detected. Option 4 uses
"assigned" values of zero for such samples in calculating percent reductions.
To obtain PCP data with lower reporting limits, additional samples were analyzed by
TWA, using different dilution steps than had been used when analyzing the initial raw waste and
treated samples for PCP quantitation. The results of these analyses are presented in Option 5.
Finally, Option 6 presents calculated percent reductions using the concentrations from the
additional analysis, plus estimated concentrations from the original analysis. Assigning nondetects
a value of twice the detection limit is conservative in light of the precision of the method for PCP
(± 50 percent), and the observable concentrations detected near or below the method detection
limit. (Note: Because the method detection limit is defined on an aggregate basis, it is not
unusual for individual laboratories to achieve significantly lower instrument noise than is assumed
in the method). In addition, the results of the additional analysis by TWA, presented in Option 5,
show PCP concentrations in treated waste that are consistently well below twice the method
detection limit.
6-45
-------
The extractable concentrations of PCP, as measured by TWA, were reduced by 89 to 99
percent (Options 2 and 5), indicating that the STC treatment was effective in stabilizing the
organic component of the SPT waste. The STC process, however, was not capable of reducing the
PCP concentrations below the required total threshold limit concentration (TTLC) for the State of
California, but the concentrations of PCP were below the federal regulatory threshold limit for
PCP as measured by the TCLP.
Additional Studies: pH and Temperature
Additional studies were performed to evaluate PCP containment under various pH
extremes. The first study involved PCP extraction and analysis after partially dissolving the
treatment matrix. This alternate TWA procedure used a combination of SW 846 Methods 3510 and
3550 to prepare the sample for analysis. In order to dissolve some of the cementitious portion of
the treatment matrix and disrupt the structure of the silicate or organophilic silicate portion of the
matrix, the material was crushed to pass 1 mm, then acidified with HC1 to PH<2. The acidified
aqueous phase was then subjected to solvent extraction according to Method 3510. After removal
of the aqueous phase, the residual solids were subject to solvent extraction according to Method
3550. The organic phases from each procedure were analyzed according to Method 8270.
Table 6-11 shows PCP analysis results obtained from this low-PH study for both raw and
treated wastes. Raw waste concentrations are totals from both the acid and solid phases of the
extraction procedure. The results were consistent with average raw waste concentrations obtained
during the pilot-scale demonstration. Batches 1, 3, and 5 resulted in slightly lower concentrations,
but still within 1 standard deviation of the mean obtained in original raw waste TWA. Batch 4
results of this low-PH study showed greater concentrations of PCP than the original Method 8270
analysis. Treated wastes show reductions in PCP concentrations from those in the raw wastes;
however, PCP concentrations in the treated waste are much higher than PCP concentrations '
obtained from the conventional TWA method. Acid treatment disrupted the treatment matrix as
evidenced by color changes and turbidity in the extraction liquids. The conventional analysis '
indicated treatment-associated percent reductions of 91 to 99 percent. The modified analysis used
in this study indicated substantially lower percent reductions. Acid disruption of the matrix
allowed recovery of 42 to 67 percent of the extractable PCP from the raw waste. The
environmental relevance of these results is not known, because the treated waste is unlikely to
contact either organic solvents or strong acids in the disposal setting. The missing fraction of the
PCP (33 to 58 percent) may still be bound to the treatment matrix, or may have decomposed.
6-46
-------
Table 6-11. TWA for PCP Using Modified Acid Extraction
Batch
1
3
4
5
Concentrations (rag/kg)
Raw Waste
2,240
1,310
8,730
6,290
Treated Waste*
830
500
2,060
1,990
.
Percent Reduction1*
35
33
58
45
a = Results reported as the mean of duplicate samples.
b = Percent Reduction = [l - (1 + Additives Katio) x Concetara^on of Treated Waste}
I Concentration of Raw Waste j'
c -
Table 6-12 shows analytical results for an additional study performed to determine whether
organics might be leached from the raw and treated waste under alkaline leaching conditions. The
analyses were conducted using a modified TCLP at pH 12 using a 0.1 M borate buffer solution.
The waste amount, leachate volume, and leaching time remained the same as for the standard
TCLP. PCP was considerably more mobile under alkaline leaching conditions than under neutral
or standard TCLP conditions, and showed percent reductions that ranged from 90 to 96 percent.
TCP was not detected in the majority of the raw and treated waste samples from the SPT site.
The small amounts of TCP detected in this study appear to be stabilized with percent reductions
ranging from 86 to 91 percent reduction.
An additional study was performed to investigate the possibility of PCP volatilizing or being
steam stripped as a result of the heat of hydration caused by the stabilization/solidification
treatment processes. The heat of hydration generated during solidification using Portland cement
may be expected to reach as much as 60° to 70°C. (The STC treatment reagents contain neither
Portland cement nor any other exothermic reagents.)
6-47
-------
Table 6-12. Analytical Results for TCLP-pH 12 Leachates
Constituent
PCP
TCP
Batch
1
3
4
5
1
3
4
5
Concentrations (mg/L)c
Raw Waste
110d
88d
320"
320d
1.8e
1.4e
5.4°
6.1e
Treated Waste
6.2
1.9d
13d
17d
ND
O.lle
0.29e
0.43e
Percent Reduction *
90
96
93
91
NC
86
91
88
ND = Not detected
NC = Not calculable
a
b
c
d
e
= Percent Reduction = [l - (1 + Additives Ratio) x Concentra^>^ of Treated Waste] x 10Q
[ Concentration of Saw Waste j
= The additives ratio is the weight of additives, including water ofhydration, divided by the weight of
wastes. Values are 0.761, 0.764, 0.776, and 0.746 for Batches 1, 3, 4, and 5, respectively.
= 0.1 M borate buffer solution used in leaching.
Reported value was calculated using a greater dilution than the primary analysis.
Value reported is an estimated concentration; compound was detected but at a concentration less
than the reporting limit.
Raw waste from each of the four batches was combined, homogenized into a single
sample, and heated to increasingly higher temperatures within airtight glovebags for one hour
intervals. Five temperature ranges, each of one hour duration, were investigated for the study:
70° to 110°C, 110° to 200°C, 200° to 230°C, 230° to 300°C, and 300° to 330°C. PCP was analyzed in
the waste before and after the heating process. Air monitoring for PCP and volatile organics, via
three specific air sampling media (carbon adsorption tubes, impinger tubes, and cellulose ester
particulate filters) was conducted during each temperature interval to identify any particulate or
volatile release of these contaminants. A duplicate sample of the homogenized waste was analyzed
6-48
-------
at each of the five temperature intervals to monitor reproducibility of the results. A detailed
description of the treatment procedure is presented in the "PCP Thermal Study Final Report"
(Kiber Associates, Inc., 1992).
Results of PCP analysis of the waste before and after heating are presented in Table 6-13
and show an average percent reduction greater than 99 percent. Air sampling results of the
glovebags showed no detectable PCP in the air sampling media during the temperature ranges
which most closely represent heat of hydration temperatures (60° to 70°C). Negligible amounts of
methylene chloride, chloroform, and tetrachloroethane were detected during the temperature
range of 70° to 110°C. PCP was detected along with other volatile compounds in greater
concentrations at higher temperature levels. The highest concentration of PCP detected in either
of the glovebags was during the fourth interval (230° to 300°C). Although the duplicate samples
showed different behavior upon heating, the results do show that nearly all the PCP was lost by
heating the contaminated waste to 330°C. However, only an insignificant fraction of the total PCP
was recovered in air sampling. The theoretical boiling point of PCP is 310°C with decomposition,
suggesting that decomposition could account for most of the loss of PCP.
Dioxins and Furans
Analytical results for polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated
dibenzofurans (PCDFs) are reported in Tables 6-14 and 6-15, respectively. In more than half of
the raw waste samples, dioxin concentrations were less than the reporting limits, and percent
reductions were not calculable. For the remaining dioxin analyses, percent reductions ranged
from -1,011 to 10 percent. Almost one-third of the PCDF analyses did not show concentrations
above the reporting limits. The remaining calculated percent reductions for PCDF ranged from
-169 to 18 percent. Extremely low initial concentrations for both the PCDDs and the PCDFs in
the raw wastes from the SPT site make evaluating the effectiveness of the STC treatment process
for these compounds very difficult.
6-49
-------
Table 6-13. PCP Concentrations for SPT Site Waste Upon Heating
Concentrations (mg/kg)
Raw Waste
5,100
Glovebag 1*
"
Heated Raw Waste
2.7
11.0
Glovefaag 2*
ND
ND = Not detected
Average Percent Reduction
"
99
»
Temperature Interval (°C)
70-110
110-200
200 - 230
6-50
-------
Table 6-14. Analytical Results for Dioxins in STC-Treated Wastes
Constituent
ii
2,3,7,8-TCDD
TCDD
PeCDD
HxCDD
HpCDD
OCDD
t
3
_:
Batch
1
~~~~^^
3
4
5
1
3
4
5
1
3
4
5
1
3
^B^.
4
5
1
3
4
5
1
3
4
5
=========5
Concentrations (mg/kg)
Raw Waste"
<0.0001
<0.0001
<0.0020
<0.0020
<0.0001
<0.0001
<0.0020
<0.0020
<0.0002
<0.0001
<0.0020
0.0022
0.099
<0.0001
0.110
0.405
1.80
<0.0002
4.80
6.75
10.0
<0.0005
30.0
37.5
Treated Waste"
<0.0025
-
<0.0002
<0.0020
<0.0020
_
<0.0025
0.0048
<0.0020
<0.0020
0.013
0.057
0.027
0.014
0.092
0.190
0.200
0.210
1.85
4.20
4.30
5.10
18.5
26.0
51.0
69.0 T
i
Percent Reduction1"
__
NC
NC
NC
NC
NC
NC
NC
1 NC
NC
NC
NC
-1,011
,
-63
.
NC
-223
10
_
-81
NC
-59
-32
-226
NC
-202
-221
NC = Not calculable
a = Results reported as the mean of duplicate samples.
b = Percent Reduction = fl - (1 + Additives Ratio) x Concen^otu>n of Treated Waste\
I Concentration of Saw Waste \ *
c - '
6-51
-------
Table 6-15. Analytical Results for Dibenzofurans in STC-Treated Wastes
Concentrations (rag/kg)
Percent Reduction^
ATC
a
c =
= Not calculable
= Results reported as the mean of duplicate samples.
- Percent Reduction = [l - (1 * Additives Ratio) x Concentration of Treated Waste]
L Contratration of Raw Waste \ *
6-52
-------
6-4.2
Inorganics
9PT , . 'K'chromi''°''a'>d Copper were contaminants of regulatory concern a,, he
PT sue, routme tota, waste analyses (TWA, were performed for the 23 standard Hazardous
Substance Us, (HSL) metals, p,us molybdenum. These anaiyses .ypicaUy did no, iden,ify
addmonal anomalousiy high Quan,i,ies of meta,s other than element commonly found in soi,s
such as ,ron and aluminum. Tables «.,« and 6-,7 show analytic* result for inorganic
constituentsanaiyzed for in ,he sand, wa,=r, and reagen, mixture additives. Leachate anaiyses are
also mcluded for the sand and reagent mixture additives.
fa, *,. evaluation despite ,he expec,a,ion that concemratio!! ^^^."^
by the STC process except by di.ution due to the addition of treatment reagen,s (Table 6-18,
Ftgures 6-18 through 6-20 graphical.y show average concentrations of TWA for arsenic
chromium, and coPPer, respective.y, inc,udi»g standard deviation values shown as error'bars
Treated waste TWA results show tha, concentrations of arsenic, chromium, and copper we
reduced m absolute terms after treatment; however, after the dUution from added reagents is
accounted for, mostly negative percent reductions are obtained.
The sKewness of TWA percent reduction data most UWy indicates tha, the treatment reagents
m,M 8 °"' a"°°"reduc"on potlmtial of <"<= n«' A'7atiVely' 'he treMm8nt " -y O^ade or otherwise !Z,,
uiaifix. s>o mat tne acid digestion/extraction of thp a i t- i
of the theoretical available contamination. ° ' *""" PrOPOrtiO"
6.4.3
PH
rangmg from 6.3 to 7., After treatment the pH was much higher with values of ,« 6
The sand and water additives had slight basic characteristics with a PH of M and 8.0 resPec,i e,y
and the STC reagen, blank mixture was very basic with a pH of ,2.5 (Tabje 6-20).
6-53
-------
Table 6-16. Metal Analyses of Water and Sand Additives
==================
; : .Constituent-
Aluminum
Arsenic
Calcium
Chromium
Copper
Iron
Magnesium
Manganese
Potassium
Sodium
Zinc
=====
==========
Water - TWA" (mg/L)
<0.2
<0.01
20
<0.05
<0.03
0.05
4.1
<0.02
2.15
17
0.037
========
Sand- TWA(mg/kg)
780
<2
310
<10
<6
1200
<200
9.3
<200
<200
<4
=^== .
Sand - TCLP (mg/L)
0.30
<0.01
11
<0.05
<0.03
<0.1
<1
0.072
1.1
1,300
0.053
a = Results reported as mean of duplicate samples.
Table 6-17. Metal Analyses of Reagent Mixture (Sand Plus Reagents)
f Constituent
Aluminum
Arsenic
Barium
Calcium
Chromium
Copper
Iron
Magnesium
Manganese
Potassium
Selenium
Sodium
Zinc
' ' =
TWA
(rag/kg)
4,300
2.5
27
61,000
12
<6
3,100
930
27
1,400
<1
1,100
8.1
====================
=====
TCLP
(mg/L)
<0.2
<0.01
0.21
1,900
0.07
<0.03
<0.05
5.5
<0.02
19
16
<0.02
==============
======
TCLP
Distilled Water
(mg/L)
0.56
<0.01
0.40
660
<0.05
<0.03
<0.05
<1
<0.02
19
<0.005
14
<0.02
===== L
======
TCLP-Cage
(mg/L)
<0.2
<0.07
0.21
2,000
0.053
<0.03
<0.05
11
<0.02
15
0.006
23
<0.02
=========
CALWET
(mg/L)
15
<0.1
<1
1,200
<0.5
<0.3
24
<10
0.32
51
<0.05
8,600
0.39
6-54
-------
Table 6-18.
=====
Constituent: Arsenic
Total Waste Analyses (TWA) for Inorganic Target Analytes
...
Batch
1
Average
3
Average
4
Average
5
__ Average :
Concentrations (mg/kg}
Saw Waste
380C
450C
360C
390C
300C
910s
465 ± 220
260C
220C
240C
260C
380^
260
270 ± 56
1,700C
1,600C
1,400C
1,700C
2,000C
1,800
1,700 ± 200
2,200C
2,200C
2,300C
1,900C
1,800C
2,700
2400 ± 320
=== '
Treated Waste
290
340
290
380
280
270
310 ±43
160C
320^
160C
150C
190C
210
200 ±64
850C
1,000C
1,000C
1,200°*
1,000C
920C
995 ±120
1,200C
1,100C
1,800C
1,200C
2,600C
1,400
1,550 ± 570
«^ _
Average Percent
Reduction3'1'
-17
-29
-4
-24
6-55
-------
Table 6-18. Total Waste Analyses (TWA) for Inorganic Target Analytes (continued)
Constituent; Chromium
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (rag/kg)
Saw Waste
340
450
340
320
480
510
410 ±83
420
280
290
290
480
300
340 ±85
1,900
1,700
1,700
1,700
1,700
1,800
1,750 ± 84
2,100
2,000
2,200
1,900
2,000
2,500
2,100 ± 210
=======^=
Treated Waste
330
360
340
330
340
350
340 ± 12
260C
260C
210C
280C
350C
230
265 ± 48
860C
1,000C
1,000C
990C
960C
890C
$50 ± 61
1,500C
1,400C
1,300C
1,100C
1,200C
1,100
1,300 ± 160
==±
Average Percent
Reduction*-1'
-48
-36
4
-5
^==^=
6-56
-------
Table 6-18. Total Waste Analyses (TWA) for Inorganic Target Analytes (continued)
=======
Constituent: Copper
Batch
1
Average
3
Average
4
Average
II
5
.
f Average
" '
Concentrations (rag/kg)
Raw Waste
340
390
330
330
380
450
370 ± 47
360
310
290
290
410
310
330 ± 48
1,200
1,200
1,100
1,200
1,200
1,100
1,200 ± 52
1,200
1,300
1,300
1,200
1,300
1,300
1,300 ± 52
Treated Waste
260
290
280
280
280
270
280 ± 10
220
220
200
200
240
200
210+16
570
670
650
640
640
620
630 ± 34
930C
870C
760C
680C
720C
730
7SO ± 97 |
Average Percent
Reduction**
-32
-15
4
-8
6-57
-------
Table 6-18. Total Waste Analyses (TWA) for Inorganic Target AnaJytes (continued)
a = Percent Reduction = fl - (1 + Additives Ratio) x Concentration of Treated Waste] lflfl
I Concentration of Raw Waste ] *
b = ^^ff^^^^^f^^ves, including water of hydration, divided by the mass of raw
wastes. Values are 0.761, 0.764, 0.776, and 0.746 for Batches 1, 3, 4, and 5, respectively.
c = Duplicated analysis not within control limits.
q = Fails Q test (Shoemaker, 1974); value may be disregarded with 90% confidence (although it has been
used to calculate the average value). ««««» oeen
0* ^ (USTe8arded "** 95% co"fidence (Chough it has been used to calculate the average
5 =
6-58
-------
Table 6-19. Analytical Results for pH, Eh, Loss on Ignition, and Neutralization Potential
for Raw and Treated Wastes
Analysis
pH (pH units)
Eh (mV)
Batch
1
m^0ye&g$
3
Average
4
Average
5
Average
1
;;:y;;::;;;;::|iyerage
3
Average
4
Average
5
Average
Raw Waste
7.2
7.2
6.9q
7,1 ± 0.2
6.9
7.0
6.9
6,9 ± 0.1
6.2
6.3
6.3
6,3 ± 0.1
6.9
6.9
6.8
6.9 ± 0.1
385
387
394
389 ±5
393
392
395
393 ±2
421
420
422
421 ± 1
399
400
399
399 ± 1
Treated Waste
12.4
12.5
12.5
12.5 ± 0.1
12.6
12.6
12.6
12.6 ± 0-0
12.5
12.5
12.5
12.5 ± 0,0
12.5
12.6
12.5
12.5 ± 0.1
166
157
165
163 ±5
164
165
165
165 ±1
156
167
174
166 ±9
173
172
178
174 ±3
6-59
-------
Table 6-19. Analytical Results for pH, Eh, Loss on Ignition, and Neutralization Fotentifa/
for Raw and Treated Wastes (continued)
Neutralization Potential
(meq/gram)
Loss on Ignition (%)
tial
=^==
Batch
1
!li|s$Wage
3
4
|;.l;;v:;:.;A^erage . ':;
5
" Average
1
Average
3
Average
4
Average
5
Average
====:=
I " '*=====:
Raw Waste
0.11"
0.14
0.13
0.13
0.14
0.13 ± 0,01
0.13
0.15
0.11
0.12
043 ± 0.02
0.11
0.12
0.14
NA
:>. ':';:Q02mm
-------
Table 6-20. pH, Eh, Loss on Ignition and Neutralization Potential for Sand, Water,
and STC Reagent Mixture
Analysis
pH (pH units)
|^Verage;;--;';;:-"^::;.:Ci:'":, S'v" .
Eh (mV)
Average :
Neutralization Potential
(meq/gram)
^Average ' ." '' v ..'..
Loss on Ignition (%)
Average
Sand
8.6
366
NA
:: ''-'- .-'---' .. . -:"H
12.2
Water
8.0
7.9
7.95
365
371
368
NA
-".; ':',".-' . . ' : . ,'
.- ..-,'-..-' , ' , - ' '.
' ':';: '-, ., " *- ,;-.; .;
NA
Reagent
Mixture
12.5
_ __
144
' ]:. \ --''.«'-^'v.i';-j;v:v x^\-:-i '
3.5
3.7
3.9
3.7±0.2:::;:
17.6
NA = Not analyzed
6-61
-------
6.4.4 Eh
The Eh is a measure of the oxidation-reduction potential of the material. Modified EPA
Method 9045 was used to determine Eh for both the raw and treated wastes, as well as for the
sand, water, and reagent mixture (Tables 6-19 and 6-20). Measurements were made with an Eh
electrode and the waste (or sand/reagent blank) and water slurries prepared for the pH test.
Oxidation-reduction potential ranged from 389 to 421 mV for the raw waste, with slightly lower
values of 366 and 368 mV for the sand and water additives, respectively. The STC reagent blank
mixture and treated wastes reveal much lower Eh values of 144 and 163 to 174, respectively. The
decrease in the oxidation-reduction potential as a result of treatment indicates a reduction of
metal valence/oxidation states and a less oxidizing environment.
6.4.5 Acid Neutralization Capacity
The acid neutralization capacity determines the buffering capacity of the material being
tested. This test was not completed because of the acidic nature of the raw waste samples.
Instead, neutralization potential measurements were conducted on both the raw and treated waste
samples.
6.4.6 Neutralization Potential
The neutralization potential of cementitious reagents and treated wastes, reported in terms
of milliequivalents (meq) per gram as shown in Tables 6-19 and 6-20, measures the amount of
neutralizers present in the material. Samples of the cured treated waste and the STC reagent
mixture weighing 100 grams each were dried to a constant weight at 60°C. The samples were
ground to pass a 60-mesh sieve. Two-gram aliquots of each of the samples were placed into flasks
and standardized hydrochloric acid (HC1) added. The mixtures were heated to near boiling until
no gas evolution was visible. The samples were then brought to volume with deionized water,
boiled for 1 minute, and allowed to cool. The sample mixtures were titrated with standardized
sodium hydroxide (NaOH), and the neutralization potential calculated from the milliliters of acid
consumed by the sample.
The result is expressed in calcium carbonate equivalents and represents tons of calcium
carbonate available to neutralize 1,000 tons of material, based on the assumption that an acre
plow-layer contains 2 million pounds of soil. Average neutralization potential values ranged from
6-62
-------
0.12 to 0.15 meq/gram for the raw waste material. The treated waste and reagent mixture both
had higher average values of 3.6 to 3.7 meq/gram.
6.4.7 Loss On Ignition
The American Society for Testing and Materials (ASTM) Method Cl 14 for loss on ignition
is a technique for determining the total moisture (including water of hydration) and carbon
content of a cementitious solid. Samples were ignited at a temperature of 950°C for 15 minutes.
The percent of weight loss was calculated based on the weight of the original sample. Percent loss
on ignition values range from 6.3 to 8.3 for the raw waste, with the sand value at 12.2 percent loss.
The STC reagent mixture lost 17.6 percent upon ignition, while the treated wastes had values
ranging from 24.3 to 26.2 percent loss (see Tables 6-19 and 6-20).
6.4.8 Oil and Grease Analysis
Oil and grease in samples of the raw and treated wastes were extracted by sonication
according to a modified EPA SW-846 Method 3550. Five grams of the solid were added to 25
milliliters (mL) of freon and sonicated. The leachates were acidified with HC1 to a pH of less
than 2 and extracted with multiple aliquots of freon in a separatory funnel. Freon was then added
to the extract to bring it to 100 mL in volume. The oil and grease in the extracts were determined
by infrared spectroscopy and are shown in Table 6-21. Calculated percent reductions in the
treated waste range from 32 to 52 percent. Although the STC treatment process was not entirely
effective in reducing the amount of extractable oil and grease in the SPT site waste, the presence
of small quantities (< 2 percent) of oil and grease did not appear to adversely affect solidification
of the waste as determined by petrographic observations (discussed in Section 6.6).
6.5 PHYSICAL TESTS
Physical tests performed on the raw and/or treated wastes include particle-size analysis,
moisture content, bulk density, permeability, unconfined compressive strength, wet/dry
weathering, and freeze/thaw weathering. These waste characteristics are summarized in Tables 6-
22 through 6-23 and are discussed in the following sections.
6-63
-------
Table 6-21. Oil and Grease Analyses of STC-Treated Waste
Constituent: Oil and Grease
Batch
1
Average
3
Average
4
Average
5
Average
Concentrations (mg/kg)
Raw Waste
11,000
10,000
11,000
10,670 ± 580
12,000
12,000
11,000
11, 670 ±560
18,000
20,000
19,000
19,000 ± 1,000
19,000
20,000
20,000
19,670 ± 580
Treated Waste
4,000
3,700
3,500
3,730 ± 250
3,200
3,000
3,400
3£00y:20bf :
7,000
8,000
6,900
7,300 ± 600
7,300
7,800
7,100
7,400 ± 360
Average Percent
Reduction"*
38
52
32
34
a = Percent Reduction = fl - (1 + Additives Ratio) x Concentr<»*°* of Treated Waste] x 1QQ
I Concentration of Raw Waste \
b = The additives ratio is the weight of additives, including water of hydration, divided by the weight of wastes
Values are 0.761, 0.764, 0.776, and 0.746 for Batches 1, 3, 4, and 5, respectively.
6-64
-------
Table 6-22. Physical Characteristics of the STC Raw Waste
Analysis
Mean
Particle
Size
(mm)
Average
Moisture
Content
(%)
Average
Bulk
Density
(g/cm3)
Average
1
0.065
0.070
0.060
0.060
0.064 1 0.005
4.3
5.9
4.4
4.9
NA
4#±Q.7
1.57
1.34
1.36
' NA
NA
NA
1.42 ±0.13
Batch
2
0.085"
0.0851*1
0.080"
NA
0,083 ± 0.003
3.4
3.2
3.6
NA
NA
3A ± 0.2
1.73
1.72
1.53q
NA
NA
NA
1.66 ±0.11
3
0.060
0.065
0.065
0.060
0.063 ± 0.003
4.9
4.7"
4.9
NA
NA
4.8 ± 0.1
1.57
1.34
1.36
1.73
1.72
1.53
" 1.54 ± 0.17
4
0.060
0.075
0.085
0.075
0.074 ± 0.40
3.0
2.8
3.4
NA
NA
3.1 ± 03
1.57
1.34
1.36
1.73
1.72
1.53
1,54 ± OJ7
5
0.075
0.070q
0.075
NA
0.073 ± 0.003
5.5"
3.1
2.6
3.1
3.1
3.5 ± U
1.57
1.34
1.36
1.73
1.72
1.53
1*54 ±0.1 7
NA = Not analyzed
a = Calculated from weight loss at W5°Q moisture content = (*** ^ight - dry weight)
dry weight
b = Numerous Batch 2 soil aggregates (PCP-encrusted "hardpan") of up to 10 mm in diameter
remained through the waste homogenization and treatment processes. Batch 2 treated waste was
therefore excluded from analytical evaluation.
q = Fails Q test (Shoemaker, 1974); value may be disregarded with 90% confidence (although it has
been used to calculate the average value).
6-65
-------
Table 6-23. Physical Characteristics of STC-Treated Wastes and Reagent Mixture
Analysis
Moisture
Content
(%)
Average
Bulk Density
(g/cm3)
Average
Permeability
(cm/sec x 10'7)
Average (x 10"7)
Unconfined
Compressive
Strength
(psi)
Average
Batch
1
2.4
3.0
2.3
NA
2.6 ± 0.38
1.57
1.60
1.55
1. 57 ±0,03
1.3
1.6
2.1
1.7 ± 0.40
190
300
210
260
250
720'
320
240
220
300 ± 160
3
2.2
1.7
1.9
NA
1.910.25
1.57
1.53
1.56
1.55 ± 0.02
2.1
0.4 1'
2.1
1.5 ±0.98
290
250
320s
260
270
270
280
280
280
280 ± 20
4
16.1
16.4
2.3
3.8
9.7 ± 7.65
1.59
1.57
1.58
1. 58 ±0.01
0.48
1.3
0.96
0.9 ± 0.41
310
240
230
190
300
280
170
380
230
260 ± 65
5
6.2
4.8
11.6
12.4
8.8 ±3,81
1.60
1.66
1.59
1.62 ± 0.04
2.9"
1.1
1.1
0.8 ± 0.47
400
420
370
350
310
340
430
260
250
350 ± 65
RM
1.5
3.7
7.1
NA
4.J ± 2.82
1.94q
1.91
1.91
1.92 ± 0.02
1.7
1.6
1.2
1.5 ±0.27
710
860
420q
480
710
680
790
780
710
680 ± 140
RM = Solidified reagent mixture
NA = Not analyzed
a = Calculated from weight loss at 60>C; moisture content = (wet weight ~ *? ^M x 100.
dry weight
q = Fails Q test (Shoemaker, 1974); value may be disregarded with 90% confidence (although it has been used to
calculate the average value).
s = Value may be disregarded with 95% confidence (although it has been used to calculate the average value).
6-66
-------
6.5.1 Particle-Size Analysis
The particle-size distribution of the raw waste was determined by ASTM Method
D422-63, a combined sieve and hydrometer analysis. The sieve analyses were performed on that
fraction of each sample larger than 0.074 mm (retained on the No. 200 sieve). This analysis
consisted of passing a sample through a set of sieves and weighing the portion of material retained
on each sieve. Hydrometer analyses were performed on the finer fractions (less than 0.074 mm).
The hydrometer method is based on Stoke's Law and involved preparing a dilute suspension of
fine particles in water, measuring the specific gravity of the suspension at specified time intervals,
and correlating settling velocity, particle diameter, and time to determine the particle-size
distribution. Particle size was not determined for the treated wastes because they were monolithic
solids.
The mean particle size for the raw waste ranged from approximately 0.06 to 0.08 mm.
This particle-size range is representative of very-fine sand material. Uniformity coefficients of
10 to 20 determined from the particle-size distribution curves indicate that the contaminated soil
wastes were well-graded, consisting of several different particle sizes. The sand used in the
reagent blank mix had a mean particle size of 0.65 mm.
6.5.2 Moisture Content
Moisture content is defined as the ratio of the weight of water retained by a solid to the
dry weight of solids, expressed as a percent. The moisture content of the raw waste and untreated
reagent mixture was determined by ASTM Method D2216-80. Moisture was determined on a
dry-weight basis by measuring the mass of water removed when the sample was dried to a
constant mass at 105° ± 5°C. The moisture content of the treated waste and reagent mixture was
determined by TMSWC-4 (Test Methods for Solidified Waste Characterization; Stegeman and
Cote, 1991). This method required that the sample be ground and pass through an ASTM No. 10
sieve. The sample weight was measured before and after it was dried in an oven maintained at 60°
± 3°C. The dry weight must be constant (weight change of less than 0.03 gram in 4 hours).
The moisture content for the raw waste ranged from 3.1 to 4.9 percent. Moisture content
of the treated waste was more variable, ranging from 1.9 to 9.7 percent, with up to 7.7 percent
standard deviation. The solidified reagent blank mixture had an average nioisture content of 4.1
percent. Batches 1 and 3 showed a decrease in moisture content, whereas Batches 4 and 5
6-67
-------
increased in moisture content following treatment. (There was considerable sample-to-sample
variability for treated Batches 4 and 5 and for the solidified reagent blank mixture.)
6.5.3 Bulk Density
Bulk densities of the raw and treated wastes are important in the materials balance analysis
to determine the expansion in volume of the material that may be attributed to the treatment
process. Bulk density of raw waste samples was determined using the American Society of
Agronomy (ASA) 13-2 Core Method. With this method, a cylindrical metal sampler was driven
into the soil to the desired depth and removed to preserve a known volume of sample as it existed
in-situ. Bulk density was calculated based on a soil sample of known volume and its mass. Bulk
densities of the treated waste were determined using TMSWC-2, which was performed after the
sample had sufficiently cured for 28 days. The bulk density was determined by weighing a
cylinder of the treated waste and measuring the dimensions of the core, then dividing the volume
into the mass.
Batch 1 represents the soil horizon at depths of 12-24 inches, directly below the surface
hardpan, consisting predominantly of sandy material with an average bulk density of 1.42 g/cm3.
Batch 2 represents the surface hardpan material (0-12 inches) with a higher average bulk density
of 1.66 g/cm3. (Because of the mixing problems with Batch 2, treated samples were not further
analyzed.) Bulk densities for raw wastes from Batches 3, 4, and 5 represent a calculated average
bulk density (1.54 g/cm3) because these batches were composites of soils from the two differing
soil horizons. Bulk densities of the treated, mixed batches (3, 4, and 5) were slightly higher (1.55
to 1.62 g/cm3) than the raw waste average bulk density for those batches. Batch 1 showed the
greatest increase in bulk density upon treatment (1.57 g/cm3). The solidified STC reagent blank
mixture had a bulk density of 1.92 g/cm3.
6.5.4 Permeability
Falling-head permeability was determined for the treated wastes using TMSWC-13. This
method required solidified core samples of the treated waste and the solidified reagent mixture
measuring 3 inches in diameter and 3 inches high. Permeability was determined with a triaxial
cell by measuring changes of water volume over time under controlled temperature and pressure.
6-68
-------
Average permeabilities of the treated wastes ranged from 0.8 x 10'7 cm/sec to 1.7 x 1(V7
cm/sec. The solidified reagent mixture showed a permeability of 1.5 x 10"7 cm/sec. These values
are of the same order of magnitude as the permeability requirements for hazardous waste landifill
soil barrier liners of 10'7 cm/sec (40 CFR Part 264 Subpart N).
6.5.5 Unconfined Compressive Strength (UCS)
UCS is defined as the load per unit area, pounds per square inch (psi), at which an
unconfined cylindrical sample fails a compression test. UCS determinations were performed on
molded samples of solidified waste according to ASTM Method D1633-84, which uses strain-
controlled application of an axial load to measure the UCS.
Average values for the treated waste samples after 28 days of curing ranged from 259 psi
to 349 psi, with the solidified reagent blank mixture having the greatest measured strength of 682
psi. The results of this test indicate that the UCS of the products of the STC solidification/
stabilization process meet the EPA guidance of 50 psi for placement in a landfill (U.S. EPA,
1986a). These values are, however, significantly below the American Concrete Institute (ACI)
minimum recommended unconfined compressive strength of 3,000 psi for the construction of
sidewalks (ACI, 1992).
6.S.6 Wet/Dry Weathering Test
Wet/dry weathering tests were performed on molded samples of the treated wastes and the
solidified reagent blank mixture according to TMSWC-12. This test was performed using two
specimens of treated waste 4.5 cm in diameter and 7.4 cm high. One of the specimens was the test
sample; the other was the control. Each sample was removed from its mold, weighed, and placed
in a beaker. The control was placed in a humidity chamber maintained at 22° ± 3°C, while the test
specimen was dried in a vacuum oven at 60° ± 3°C for 24 hours. The test specimen was cooled to
room temperature in a desiccator. Upon cooling, 230 mL of distilled water at room temperature
were added to each of the sample beakers. Both samples were placed in the humidity chamber for
24 hours, then sprayed with distilled water to remove loosely attached particles from the
specimens. The specimens were transferred to two newly tared beakers. The original beakers
were placed into an oven at 60° ± 3°C to evaporate the water and dry them to a constant weight.
This cycle was repeated 11 more times, with the weight loss recorded each time. The corrected
relative weight loss of the test specimen was obtained by subtracting the relative weight loss of the
6-69
-------
control from the relative weight loss of the sample. Thus, the results are expressed as the
cumulative corrected relative weight loss percentage incurred through 12 wet/dry cycles,
normalized to a control that was not subjected to the wet/dry cycles. These results are shown in
Table 6-24.
Table 6-24. Wet/Dry Weathering Data of STC-Treated Wastes
Batch
1
3
4
5
RM
Cumulative Corrected Relative Weight Loss (%)
Cycle
1
0.03
0.00
0.02
0.03
0.02
Cycle
^
0.04
-0.01
0.01
0.02
0.02
Cycle
3
0.02
-0.04
-0.01
0.02
0.04
Cycle
4
0.01
-0.05
-0.01
0.01
0.04
Cycle
5
0.01
-0.06
-0.05
-0.02
0.02
Cycle
fi
0.00
-0.08
-0.06
-0.03
0.02
Cycle
7
-0.01
-0.08
-0.09
-0.07
0.00
Cycle
8
-0.02
-0.10
-0.13
-0.08
0.001
Cycle
9
-0.01
-0.14
-0.14
-0.11
-0.01
Cycle
1ft
-0.03
-0.16
-0.17
-0.13
-0.01
Cycle
11
-0.04
-0.18
-0.19
-0.16
-0.02
Cycle
li
-0.04
-0.21
-0.20
-0.17
-0.02
RM = Solidified reagent mixture
The results of the test for all of the batches and the solidified reagent blank mixture show
that less than 1 percent of the core weight was lost from the 12 wet/dry cycles. Negative values
show that the weight loss of the control specimens was greater than the weight loss of the test
specimens. These results suggest that the treated material and the reagent blank mixture withstood
the stresses of the wet/dry weathering test with little weight loss, indicating durability in an
exposed environment.
6.5.7
Freeze/Thaw Weathering Test
Freeze/thaw weathering tests were performed on molded samples of the treated wastes and
the solidified reagent blank mixture according to method TMSWC-11. The test is similar to the
wet/dry weathering test except that the test specimens are placed in a freezer at -20° ± 3°C for 24
hours. The test was performed using two specimens of treated waste 4.5 cm in diameter and 7.4
cm high. One of the specimens was the test sample; the other was the control. Each sample was
removed from its mold, weighed, and placed in a beaker. The control was placed in a humidity
chamber maintained at 22° ± 3°C, while the test specimen was placed in a freezer at -20° ± 3°C for
24 hours. Both beakers were removed from their respective chambers. 230 mL of distilled water
at 4° ± 3°C were added to the beaker containing the frozen specimen, and"230 mL of distilled
6-70
-------
water at room temperature were added to the beaker containing the control specimen. Both
samples were placed in the humidity chamber for 24 hours, then sprayed with distilled water to
remove loosely attached particles from the specimens. The specimens were transferred to two
newly tared beakers. The original beakers were placed into an oven at 60° ± 3°C to evaporate the
water and dry them to constant weight. This cycle was repeated 11 more times, with the weight
loss recorded each time. The corrected relative weight loss of the test specimen was obtained by
subtracting the relative weight loss of the control from the relative weight loss of the sample.
Results of this test shown in Table 6-25 were expressed as the cumulative corrected relative
weight loss percentage incurred through 12 freeze/thaw cycles, normalized to a control that was
not subjected to the freeze/thaw cycles. Results for all wastes and the solidified reagent blank
mixture indicate that 1 percent or less of the molded cylinder weights were lost over the 12
freeze/ thaw cycles. The results suggest that the treated wastes and the solidified reagent blank
mixture successfully withstood the stresses of freeze/thaw weathering and will be durable in an
exposed environment.
Table 6-25. Freeze/Thaw Weathering Data of STC-Treated Wastes
Batch
1
3
4
5
RM
Cycle
1
0.00
-0.02
-0.02
0.00
-0.03
Cycle
2
0.01
-0.05
-0.03
-0.02
.-0.05
Cumulative Corrected Relative Weight Loss (%)
RM = Solidified reagent mixture
6.6
PETROGRAPHIC ANALYSES
Solidified samples from the STC SITE demonstration were examined using optical
microscopy, scanning electron microscopy (SEM), X-ray diffractometry (XRD), and Fourier
transform infrared spectroscopy (FTIR) techniques. The samples consisted of small cylindrical
cores that had been taken from waste from Batches 1, 3, 4, and 5. In addition, a solidified blank
6-71
-------
sample made from clean sand mixed with the STC proprietary reagent mixture was also analyzed.
The cores were cut into appropriate sample sizes for the microscopic examination, and an adjacent
piece was cut for the SEM examination. A portion of the remainder of the cores was broken off
and about 50 grams reduced to small pieces. A fraction passing a 3/8-inch sieve but retained on a
No. 8 sieve was submitted for FTIR examination. The rest of the sample was ground in a ring and
puck mill until the whole sample was finer than a No. 150 sieve. These fine powder samples were
submitted for additional FTIR and XRD analyses. Further preparation of samples is described in
the following subsections.
Five samples of the raw waste were also submitted for optical microscopy, FTIR, and
XRD analyses. Samples from Batch 1 were obtained from the deeper soil horizon (approximately
1 to 2 feet) while those from Batch 2 were from the shallower hardpan horizon (down to 1 foot).
The remaining samples consisting of Batches 3, 4, and 5 were composite blends of the first two
soil horizons. Batch 1 was the only batch analyzed that was not sieved as part of the pretreatment
process. These samples are described in greater detail in the following subsection.
6.6.1 Optical Microscopy
Qualitative petrographic examination of twelve cylindrical cores was performed in
accordance with ASTM Method C856-83, "Standard Practice for Petrographic Examination of
Hardened Concrete." The cores were cut longitudinally and examined using a stereomicroscope at
magnifications up to 45 X. Freshly broken surfaces were also studied using the stereomicroscope.
Preparation of petrographic thin sections consisted of cutting a rectangular block 1 inch wide and
0.5 inch thick from the top portion of each core to a depth of approximately 1.8 inches. These
rectangular blocks of solidified material were placed on glass microscope slides with epoxy resin,
and reduced to a thickness of approximately 20 micrometers (0.00079 inch). A polarized-light
microscope at magnifications up to 400 X was used to determine aggregate and binder mineralogy
and microstructure. In addition, five raw waste samples were also examined using a
stereomicroscope.
The unconsolidated, raw waste samples consisted mainly of very-fine grained (<0.2 mm)
quartz, feldspars (potassium feldspars and plagioclase), hornblende, clay, and mica. Granitic lithic
fragments up to 10 mm diameter were also observed. The soils were grayish-brown to dark brown
and had a strong odor of oil. Wood fragments and other organic debris were present in small
6-72
-------
amounts in all of the samples. Many of the larger particles had shiny coatings, presumably oil.
Clumps of clay-size material appeared to be held together by an oily substance.
Results of the thin-section analyses of the solidified waste cores are detailed in
Table 6-26. In addition, Figures 6-21 through 6-27 show examples of photographs of the cores
and photomicrographs of the thin sections. Two cores for each of Batches 1, 3, 4, 5, and the STC
reagent mixture were qualitatively analyzed. Evaluation criteria for this examination consisted of
consolidation, hardness, microcracking, estimated air content, binder distribution, bonding, phases
present in the binder material, and soil constituents.
In general, the cores of the solidified waste and reagent material were well consolidated
(Figures 6-21 and 6-22). The outer portion of one of the QC samples was very poorly
consolidated (Figure 6-23). This sample was somewhat soft, but cohesive, and resistant to
fracturing from moderate impacts. Some of the cores displayed faint layering, and hardness
ranged from soft to moderately hard with only minor microcracking observed. The estimated air
content was three to five percent for Batches 3, 4, and 5, and five to seven percent for Batch 1
and the solidified reagent mixture. The air-void system was nonuniform and the voids contained
no secondary deposits (Figure 6-24). The binder was moderately soft, generally evenly
distributed, and the binder-aggregate bond was moderately tight. The binder microstructure was
difficult to interpret because of the presence of large amounts of black opaque material that acted
as a pigment (Figure 6-25). In areas where this material was not abundant, the binder contained
patches of calcium hydroxide (portlandite), small amounts of green-brown stained glassy phase,
and traces of residue portland cement clinker. Carbonation of the binder material around small
air voids was observed and is the result of a reaction between calcium hydroxide and air. The
soil-binder system appears to be well mixed based on distribution and size of the soil clumps
(Figure 6-26). The average size of soil fragments is 1.5 mm. Clumps with diameters up to 1 cm
occur and are typically surrounded by a black, tar-like rim (Figure 6-27).
6-73
-------
Table 6-26. Petrographic Analysis of STC-Treated Wastes
Os
-Li
4^
Treated Wastes (Batches)
Characteristics
Binder Distribution
Consolidation
Hardness
Bond
Air Content
(estimated)
Microcracking
Phases present in
binder
Soil constituents
RM
Uniform
Well consolidated
Moderately hard
Moderately tight
5% to 7%
None
Calcium hydroxide
Black pigment
Isotropic glass
Portland cement
Quartz, microcline;
No oily clumps
1
Nonuniform
Under consolidated
Moderately soft
Moderately tight
No estimate made
Minor
Calcium hydroxide
Black pigment
Isotropic glass
Portland cement
Quartz, plagioclase
feldspar, potassium
feldspar, horn-
blende, clay,
biotite, wood
fragments, misc.
organic debris,
paper
1--QC
Nonuniform
Well consolidated
Soft
Moderately tight
5% to 7%
None
Calcium hydroxide
Black pigment
Isotropic glass
Portland cement
Quartz, plagioclase
feldspar, potassium
feldspar, horn-
blende, clay,
biotite, wood
fragments, misc.
organic debris,
paper
3
Uniform
Well consolidated
Moderately soft
Moderately tight
3% to 5%
Minor
Calcium hydroxide
Black pigment
Isotropic glass
Portland cement
Quartz, plagioclase
feldspar, potassium
feldspar, horn-
blende, clay,
biotite, wood
fragments, misc.
organic debris,
paper
4
Uniform
Well consolidated
Moderately soft
Moderately tight
3% to 5%
None
Calcium hydroxide
Black pigment
Isotropic glass
Portland cement
Quartz, plagioclase
feldspar, potassium
feldspar, horn-
blende, clay,
biotite, wood
fragments, misc.
organic debris,
paper
-'' S'
5 Uniform
Well consolidated
Moderately soft
Moderately tight
3% to 5%
None
Calcium hydroxide
Black pigment
Isotropic glass
Portland cement
Quartz, plagioclase
feldspar, potassium
feldspar, horn-
blende, clay,
biotite, wood
fragments, misc.
organic debris,
paper
RM = Solidified reagent mixture
-------
Figure 6-21. STC solidified waste core (Batch 4).
Figure 6-22. Longitudinal cut of solidified reagent mixture and sand.
6-75
-------
Figure 6-23. Poorly consolidated solidified waste core (Batch 1-QC).
Figure 6-24. Photomicrograph showing less uniform binder distribution. Green arrows show
clay lumps. Red arrows show spherical air voids. Binder contains wood fragments
(brown). 200x magnification (Batch 1).
6-76
-------
Figure 6-25. Photomicrograph showing soil particles (white) surrounded by densely pigmented
binder. Binder contains wood fragment ' (arrows). 200x magnification
(Batch 5).
Figure 6-26. Longitudinal cut of solidified waste core (Batch 4). Note abundance of soil
particles. Arrow shows coated clumps of soil.
6-77
-------
Figure 6-27. Longitudinal cut of solidified waste core (Batch 5). Arrows show coated clumps
of soil particles.
6-78
-------
6.6.2 X-Ray Diffractometry (XRD)
Two untreated and six solidified waste samples were examined using XRD techniques.
The contaminated soil samples represented both the deep (Batch 1) and shallow (Batch 2) soil
horizons. Four of the solidified samples were treated waste (Batches 1, 3, 4, and 5), one was the
solidified waste QC sample, and one was the solidified STC reagent mixture. All samples were
ground and passed through an ASTM No. 15 mesh sieve, then ground to a fine powder. The
powders were then packed from the backside into an aluminum XRD sample holder. A Phillips
X-ray diffractometer equipped with a theta-compensating slit, a graphite monochrometer, and a
scintillation detector was used. Copper K-alpha radiation was generated at 40 kV and 35 mA.
The signal was processed through a ratemeter set at a scale of 1,000 with a time constant of 2
seconds and a background suppression setting of 1.2.
The patterns for each of the cores were examined, and phases that could be identified
were roughly classified as major, minor, or trace to indicate their relative abundance. Results of
this qualitative XRD analysis are summarized in Table 6-27. Batches 1 and 2 of the raw waste
consisted of similar mineralogic phases and are listed together. Similarly Batch 1 and 1-QC are
listed together.
Components of the untreated waste were also present in the solidified waste samples, as
expected. In addition to quartz, the raw waste samples contained a considerable amount of clay -
weathered from the two mineral groups, plagioclase feldspar and potassium alkali feldspar and
minor amounts of hornblende and trace mica. The micas consist of biotite and/or illite; peak
weakness prevented more positive identification.
The solidified STC reagent mixture contained predominantly quartz with minor amounts
of potassium feldspars. Minor portlandite (calcium hydroxide) and traces of gypsum and
ettringite were also detected.
The treated waste samples were all characterized as containing major amounts of quartz
and oligoclase with slightly lesser amounts of the potassium feldspars microcline and orthoclase.
Minor amounts of portlandite were detected in all solidified samples as well as traces of ettringite
and either illite and/or biotite. Some samples had traces of hornblende. An elevated background
from roughly 25 to 30 degrees 2-theta indicated that the binder material was primarily
amorphous. One or two very small additional peaks were observed in the solidified materials, but
6-79
-------
-------
they were not sufficiently distinct for identification. These peaks may be the result of alumino-
silicate hydrates formed by the binder. No peaks were observed for unhydrated portlandite
cement materials, indicating the cement content was fairly low. These analyses indicate that the
STC process used predominantly silica and potassium-aluminum silicates in addition to calcium
hydroxide and sulfates to form the binding agent.
6.6.3 Scanning Electron Microscopy (SEM)
Only solidified samples were submitted for SEM analysis. These included one from each
of Batches 1, 3, 4, and 5; a QC sample from Batch 1; and a sample from the solidified STC reagent
blank mixture. Sections of cores that had been cut to approximately 2.5 cm by 4.5 cm by 1 cm
were used. An attempt was made to impregnate these sections with epoxy prior to grinding and
polishing, but not all samples were receptive to the epoxy. Polished samples were mounted on
aluminum stubs and coated with carbon. After elemental analysis was complete, samples were
coated with gold to provide better imaging at high magnifications. Secondary electron (SE)
emissions provided the normal mode of imaging in the SEM. Backscattered emissions (BSE)
allowed imaging with elemental contrast -- light elements (e.g., silicon and calcium) result in dark
areas and heavy elements (e.g., copper and iron) show up as light areas. The SEM was also
equipped with energy dispersive X-ray (EDX) fluorescence analysis, providing an elemental
analysis. Once EDX identified the elements present, elemental mapping capabilities were used to
determine the location of elements by dot mapped photographs. SEM photomicrographs include
the following information as read from left to right: beam energy in keV; magnification factor
divided by 1,000; a scale bar and the number of microns the bar represents; and an identification
number.
The SEM analyses indicated relatively good binder-to-aggregate bonding except in rare
cases where oily particle coatings prevented good bonding. The oil has a dual negative effect of
preventing wet cement paste from penetrating and binding to the aggregate and also may partially
inhibit hydration of the cement. An example of paste absence resulting from an oily coated
aggregate is shown in Figure 6-28. The oily coated aggregate with a very poor bond to the paste
is in the lower right, while other aggregates in the same view demonstrate good bonding. Lack of
paste surrounding the aggregates may also be the result of paste removal during sample
preparation. In general, however, the quality of the surrounding binder sufficiently
microencapsulated such particles.
6-81
-------
Figure 6-28. SE image of poor and well bonded aggregate (Batch 1).
6-82
-------
The following elements were commonly detected using the EDX probe: calcium, silicon,
iron, aluminum, potassium, and chlorine, with-minor amounts of sulfur, arsenic, chromium,
titanium, and copper. An EDX probe of the bright area in Figure 6-29 detected the presence of
chromium, copper, and arsenic. An elemental spectrum of the entire area of Figure 6-29 is shown
in Figure 6-30. Elemental maps of the heavy metal contamination suggest good containment of
the metals. Figure 6-31 shows an embedded particle in which a substantial amount of titanium
was detected. The elemental dot map for titanium (Figure 6-32) reveals that although small
amounts of this element are detected in the surrounding area, titanium from the particle is
primarily contained in the particle itself. Another example shows a BSE image of the bright area
in Figure 6-33 where copper, chromium, and arsenic were detected. Maps depicting the location
of these elements are provided in Figures 6-34, 6-35, and 6-36, respectively. There appear to be
boundaries on the maps that correlate well with the boundary of the bright image. Mixing of
binder and waste followed by consolidation did not appear to cause migration of metals from
contaminated particles into the surrounding material.
Air voids are generally rounded in shape, vary in size, and appear relatively open in all of
the treated samples. A typical area of distribution for air voids is shown in Figure 6-37. Voids,
paste, aggregate, and areas of contamination are evident by their shades of gray as related to their
elemental content. The dark areas in this image show rounded voids indicating good
consolidation; irregular shaped voids would indicate poor consolidation. Figure 6-38 shows an
open air void in paste.
SEM analyses are also useful for observing paste morphology of the solidified samples. An
area showing typical aggregate/paste bond is Figure 6-39. There is some removal and/or absence
of paste around aggregate edges and also signs of aggregate pull-out indicating less-than-optimum
bonding. A higher magnification of such an aggregate/paste bond is shown in Figure 6-40.
6-83
-------
Figure 6-29. BSE image. Cu, Cr, and As were detected in the bright area (Batch 3).
Ca
Si
Al
FS
132
oooo
-.02 - 21.45 KEU.
i OO
SEC
Figure 6-30. Elemental spectrum of area in Figure 6-29 (Batch 3).
6-84
-------
Figure 6-31. BSE image. Ti was detected in the particle (Batch 5).
Figure 6-32. Ti map of Figure 6-31 (Batch 5)
6-85
-------
Figure 6-33. BSE image. Cu, Cr, and As were detected in the bright area (Batch 5).
Figure 6-34. Cr Map of Figure 6-33 (Batch 5).
6-86
-------
Figure 6-35. Cu map of Figure 6-33 (Batch 5).
Figure 6-36. As map of Figure 6-33 (Batch 5).
6-87
-------
Figure 6-37. BSE image of typical distribution (Batch 1).
Figure 6-38. Air void in paste (Batch 1).
6-88
-------
Figure 6-39. SE image of paste and aggregate (Batch 3).
Figure 6-40. Aggregate paste bond (Batch 3).
6-89
-------
6.6.4 Fourier Transform Infrared Spectroscopy (FTIR)
Four raw waste samples and six solidified waste samples were analyzed ~ using FTIR
techniques to evaluate the thermal stability of the treated waste samples relative to raw waste
samples. Each of the solidified waste samples were crushed to a diameter of 3/8 inch or less, but
were large enough to be retained on a No. 8 sieve. Solidified waste processed to pass a No. 150
sieve was also evaluated for each batch.
Approximately 50-250 milligrams (mg) were taken from each sample and heated
sequentially at 100°, 200°, 300°, 400°, and 500°C in a Wilks Pyro-chem pyrolysis unit. Infrared
spectra of the condensed organics volatilized from the sample and weight loss data were recorded
after each pyrolysis run. A few of the solidified waste samples were pyrolyzed at 600°C after all
of the data gathered at lower temperatures showed no evidence of organic materials released on
heating. The infrared data were collected using a Bio-Rad FTS-7 Fourier Transform infrared
spectrophotometer. To assure an adequate signal-to-noise ratio for the infrared data, 250 scans
were coded at four wavenumber resolution. All spectra were obtained using attenuated total
reflectance (ATR) techniques. It was determined from the analyses of the raw waste samples that
less than 1 percent (by weight) of organic volatiles could be detected by this technique.
These analyses were directed toward the condensed volatile species because it was believed
that higher-boiling species make up the bulk of the organic contaminants in the soils. It should be
noted that water and lower-boiling aromatic species (such as toluene and xylenes), which might be
present in the soils, were not detected by the method of analysis used in this investigation.
Tables 6-28 and 6-29 depict the pyrolysis weight loss data for both the raw and treated
waste samples. Based on this data, the total amount of organic materials volatilized from the raw
soil samples was approximately 1 to 2 percent (by weight) of the samples. Since some weight loss
was recorded after each pyrolysis run, it is believed that a substantial amount of adsorbed water
was also released from the waste samples upon heating. The weight loss after each pyrolysis run
of the solidified waste material is believed to be due to the presence of water both as an adsorbed
species and as water of hydration of the silicate matrix.
Pyrolysis of the raw waste samples showed that the organic compounds were volatilized
between 200°C and 300°C. There is no evidence of the presence of condensed organic compounds
below 200°C or above 300°C. The organic materials volatilized from the four raw waste samples
6-90
-------
were all similar in composition. Infrared analysis identified these materials as a mixture of
aliphatic and aliphatic-substituted aromatic hydrocarbon compounds. The spectra also showed
evidence for the presence of carboxylic acid groups (possibly from the oxidation of unsaturated
hydrocarbon species), and nitrogen-hydrogen bonds present as amine or amide groups. This
composition is consistent with the residue from a heavy oil, such as diesel oil. PCP was not
specifically detected in the infrared spectra of the organic pyrolyzates.
Table 6-28. Pyrolysis Percentage Weight Loss Data for Raw Wastes
Temperature
(C)
100
200
300
400
500
1
2.49
0.78
0.93
0.62
0.62
Batch
3
1.92
0.70
1.05
0.35
0.00
4
0.99
1.16
1.65
0.83
0.99
5
0.18
2.18
1.45
0.91
Table 6-29. Pyrolysis Percentage Weight Loss Data for Treated Wastes
Temperature
(°C)
100
200
300
400
. 500
600
Batch
RM
2.87
3.06
1.72
0.13
1.02
0.00
I
2.88
9.05
1.59
1.69
1.59
-
1 -QC
2.74
4.25
7.40
1.77
0.53
3
3.23
7.32
7.04
0.72
0.50
4
5.87
7.45
2.42
0.09
0.84
1.30
5
12.07
3.37
0.90
0.41
0.49
0.66
Pyrolysis of the solidified waste sample showed almost no evidence for the release of
organic contaminants. No organic compounds were detected after pyrolysis of the solidified
waste, either in the form of large chunks (3/8-inch diameter), or as a processed powder (<150
mesh). One exception yielded a small amount of primarily aliphatic hydrocarbon species, after
pyrolysis of the sample in chunk form, at 400°C. Although these results are only qualitative, they
indicate that any volatilization of organic components in the STC-treated waste available for
volatilization were substantially retarded by the STC silicate matrix.
6-91
-------
6.7 LONG-TERM MONITORING
Samples of both the treated wastes and the reagent blank mixture remained on site for 32
months following the demonstration to evaluate the long-term stability of the treated waste.
Samples in uncovered containers were stored in ventilated lockers at ambient temperatures. Bulk
treated waste was cast by batch into cardboard cylindrical forms (which were removed after a 28-
day curing period). The resulting monoliths were stored in a lined, uncovered, open-air pad.
Long-term samples were analyzed at 6, 18, and 32 months after the STC demonstration
using TWA for PCP and TCLP for arsenic, chromium, and copper. The 32-month cured samples
were also analyzed using TCLP-Distilled Water for arsenic, chromium, and copper. Physical
testing included unconfined compressive strength tests at 6, 18, and 32 months and permeability
testing at 32 months. Results for the long-term TWA and TCLP tests are presented in Table 6-30.
Averages of six samples for the analyses of 6-month and 32-month cured samples and four
samples for the analyses of 18-month cured samples are compared to both the raw waste samples
analyses and the treated 28-day cured sample analyses. Calculated percent reductions are also
presented.
In general, the chemical stability of PCP treated by the STC process as measured by TWA
was maintained over the 32-month period. TWA of PCP after the 6-month period showed
somewhat greater extractable concentrations for Batches 4 and 5 than after the initial 28-day
period. Extractable concentrations of PCP generally remained consistent for Batches 1 and 3 over
this time period. The 18-month analyses showed decreased concentrations of PCP in the treated
waste; however, Batch 5 continued to show considerable analytical variability. Percent reductions
following the 18-month period averaged 96 percent reduction. For Batches 3, 4, and 5, the 32-
month analyses were consistent with the 18-month analyses and did not indicate any significant
changes in concentrations of PCP in the treated waste. However, Batch 1 did show an apparent
increase in the concentration of PCP in the treated waste (mainly due to an outlier concentration
more than 4 times greater than the average of the other 5 samples). As a result, the percent
reduction for Batch 1 decreased from 98 percent at 18 months to 86 percent at 32 months.
(Discarding the outlier concentration results in a Batch 1 percent reduction of 91 percent at 32
months.) Percent reductions following the 32-month period averaged 93 percent reduction.
6-92
-------
Table 6-30. Long-Term Test Results
PCP-TWA
Batch
1
Average
% Reduction'*
3
Average
% Reduction *
Concentrations (nag/kg)
Raw Waste
2,600
1,500
2,000
2,600
3,400
2,000
2,350 * 660
1,700'
2,200°
2,200'
2,000
2,200
1,600
2,000 t 270
Treated Waste
28-day
200C
82C
140C
106'
106'
106'
120*42
91
34C
106'
106'
106'
54'
106e
85*33
92
6-month
54C
106'
106'
140
100
120
100*29
92
120
97
69
110
100
100
99*17
91
18-month
44^
24C
Iff
19c
NA
NA
27*12
98
26C
9°
42C
43C
NA
NA
30*16
97
32-month
170
74
110
180
88
530s
190 * 170
86
110°
44
28
30
13
71
49*36
%
o\
i>
UJ
-------
Table 6-30. Long-Term Test Results (continued)
PCP-TWA
Batch
4
Average
% Reduction ".b
5
Average
% Reduction *
Concentrations (mg/kg)
Raw Waste
6,400*
6,800
8,900
7,300
9,000
7,800
7,700 * 1,100
6,300
10,000
9,600
8,300
7,000
8,700
8,300 * 1,400
Treated Waste
28-day
106°
106e
106°
. 106e
106°
IMF*
120*38
97
106"
106°
400C
370C
106'
NA
220 t 150
95
6-month
520
340
320
420
280
360
370 * 85
91
900
640
550
560
l,660q
510
800*440
83
18-month
100*
100"
100°
94q
NA
NA
99*3
98
1,200"
58C
220°
160°
NA
NA
410 * 530
91
32-month
110
160
160
70
46
85
. 105 1 47
98
500
480
280
280
510 -
440
415 1 110
91
ON
-------
Table 6-30. Long-Term Test Results (continued)
Arsenic-TCLP
Batch
1
Average
% Reduction"*
3
Average
% Reduction **
Concentrations (mg/L)
Raw Waste
1.3
2.2
1.3
2.2
2.3
1.6
1.8 * 0,47
«»*
1.1
0.99
0.97
0.88
0.93
1.5q
1,1 * 0.23
*+*
Treated Waste
28-day
0.048*
0.096s
O.Q51g
0.044*
0.19s*
0.084*
0,086 ± 0,055
92
0.091*
0.081*
0.10*
0.16**
0.097*
0.078
0,10 ± 0,030
83
6-month
0.19
0.32
0.18
0.17
0.24
0.33
0.24 ± 0,071
77
0.30
0.29
0.28
0.25
0.22
0.23
0.26 * 0,033
56
18-month
0.062d
0.071d
0.063d
0.087"
NA
NA
0.071 * 0,011
93
0.073
0.060
0.056
0.24q
NA
NA
0.11 1 0.089
82
32-month
0.56
0.57
0.57
0.16
0.19
0.36
0,40 ±0,19
61
0.12
0.17
0.16
0.16
0.19
0.22
, 0,17 * 0.033 ,
72
-------
Table 6-30. Long-Term Test Results (continued)
ON
<0
ON
Arsenic-TCLP
Batch
4
>
Average
% Reduction*"
5
Average
% Reduction ""
Concentrations (mg/L)
Raw Waste
2.0
2.3
2.3
2.2
3.6s
2.0
Z4 * 0.60
+"«*
3.1
3.6
3.3
3.3
3.8
2.9
33 1 0.33
fe*
-------
Table 6-30. Long-Term Test Results (continued)
Chromtum-TCLP
Batch
1 .
Average
% Reduction1*
3
Average
% Reduction '*
Concentrations (mg/i)
Raw Waste
0.051
0.21
0.053
0.20
0.22
0.052
0.13 1 0,087
-***
0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05.
-H4-+
Treated Waste
28-day
0.24
0.25
0.24
0.25
0.24
0.25
0.245 * 0.005
^230
0.19
0.20
0.18
0.17
0.18
0.20
0.19 * 0.012
NG
6-month
0.27
0.29
0.29
0.28
0.28
0.28
0.28 i 0.008
-280
0.27
0.24
0.25
0.24
0.25
0.24
0.25 * 0,012
NC
18-month
0.34
0.405
0.42
0.255
NA
NA
0.355 ± 0.075
-380
0.27
0.26
0.30
0.35
NA
NA
0.295 * 0.040
. NC
32-month '
0.65
1.1
0.70
0.50
1.2
0.46
0.77 * 0.31
-940
0.48
0.50
0.53
0.51
0.40
0.42
0.47 1 0,052
- NC
-------
Table 6-30. Long-Term Test Results (continued)
Chromium-TCLP
Batch
4
Average
% Reductioa '*
5
Average
% Reduction "*
Concentrations (mg/L)
RawWaste
0.071
0.073
0.077
0.083
0.23s
0.084
0.10 t 0.062
,.,.
0.24
0.25
0.24
0.28
03T
0.23
0.27 * 0.053
,..
Treated Waste
28-day
0.29
0.28
0.29
0.27
0.27
0.27
0.28 * 0.010
-390
0.32
0.31
0.33
0.29
0.29
0.38
0.32 * 0.033
-110
6-month
0.52
0.55
0.36q
0.55
0.58
0.52
0.51 1 0.078
-810
0.67
0.58
0.68
0.61
0.65
0.60
0.63 * 0.04
-310
18-month
1.09
1.23
1.29
1.13
NA
NA
1.2 * 0.091
-2,000
0.82
1.1
1.2
1.1
NA
NA
1.1 * 0.16
-610
32-raontb !
1.7
1.6
1.3
1.5
1.3
1.3
1.45 * 0.18
-2,500
1.2
1.3
1.2
1.1
1.1
1.1
1.2 ± 0.082
-680
OS
vb
00
-------
Table 6-30. Long-Term Test Results (continued)
Copper-TCLP
Batch
1
Average
% Reduction"*
3
Average
% Reduction *
Concentrations (mg/L)
Raw Waste
2.2
4.5
2.2
4.4
4.5
2.5
3.4 * 1,2
1.5
1.5
1.4
1.2
1.2
1.5
1.4 ± 0.15
Treated Waste
28-day
0.087
0.085
0.090
0.089
0.089
0.099"
0.090 * 0.005
95
0.074
0.077
0.070
0.067
0.071
0.088
0.075 ± 0.007
91
6-month
0.12
0.11
0.11
0.11
0.13
0.12
0.12 1 0,008
94
0.16
0.13
0.13
0.12
0.16
0.14
0.14 * 0,017
82
19-month
0.29
0.39
0.59
0.18
NA
NA
0.36 * 0,17
81
0.13
0.17
0.175
0.099
NA
NA
- 0,14 « 0,036
82
32-menih t
0.10
0.41s
0.11
0.07
0.11
0.08
0,15 * 0,13 .
92
0.08
0.08
0.09
0.07
0.14
0.13
0,098 * 0,029
88
ON
vo
vo
-------
Table 6-30. Long-Term Test Results (continued)
Copper-TCLP
Batch
4
Average
% Reduction "*
5
Average
% Reduction *"
Concentrations (mg/L)
Raw Waste
6.2
6.1
6.2
6.5
8.7"
5.5
6,5 * 1,1
9.2
9.3
8.8
9.5
12"
7.8
9.4 * 1,4
Treated Waste
28-day
0.10
0.10
0.11
0.10
0.10
0.11
0,10*0.005
97
0.055
0.058
0.085q
0.054
0.057
0.064
0.062 t 0.012
99
6-month
0.25
0.25
0.25
0.27"
0.25
0.25
0.25 * 0,008
93
0.17
0.27q
0.16
0.13
0.14
0.14
0.17 1 0.052
97
18-month
0.56
0.87
1.26
0.92
NA
NA
0.90*029
75
0.96
1.4
1.8
1.6
NA
NA
144 1 036
74 .
32-month *
0.14
0.17
0.22
0.17
0.10
0.10
. 0,15*0,046
96 '
0.10
0.11
0.11
0.10
0.10
0.09
0.10 * 0,QOS
98
o
o
-------
Table 6-30. Long-Term Test Results (continued)
NA = Not analyzed
a =
c
a
e
f
g
Percent Reduction = fl - (1 + AdtUOva Ratio) x Cone*atraa°n iltcludi"S waler ofhydration, divided by the weight of raw wastes. Values are 0.761, 0.76*, 0.776,
0.746 for Batches 1, 3, 4, and 5, respectively.
Value reported is an estimated concentration; compound was detected at an amount less than the reporting limit
Ttte anafyte was found in the associated blank as well as in the sample.
Estimated concentration using twice the method detection limit.
Reported concentration is calculated using a greater dilution than the primary analysis.
Spiked sample recovery not within control limits.
vJLQn teSt^emake?lml'«e "7 be disre&arded with 90% Confidence (although it has been used to calculate the average value).
Value may be disregarded with 95% confidence (although it has been used to calculate the average value).
o\
i
t»
o
-------
No consistent trends emerged from TCLP testing for arsenic in the long-term treated
wastes. Average 6-month TCLP leachate concentrations of arsenic for Batches 1 and 3 increased
from the 28-day concentrations. Average arsenic concentrations in Batches 4 and 5 were slightly
lower in the 6-month tests; however, high analytical variability for these two batches indicates
that the arsenic content in the leachate of the 6-month cured samples was similar to that of the
28-day cured sample leachate. Percent reduction for the 6-month period ranged from 77 to 55
percent. The TCLP leachate concentrations of the 18-month cured samples for arsenic showed
significant decreases from the 28-day and 6-month leachate concentrations. Percent reductions
improved over the 18-month period, initially ranging from 35 to 92 percent reduction after 28
days to 82 to 93 percent after 18 months. The TCLP leachate of the 32-month cured samples
showed increases in concentration of arsenic from the concentrations observed at the 18-monith
period. The average percent reduction for arsenic across all batches decreased from 88 percent at
18-months to 68 percent at 32 months. Comparing the 32-month cure data to the 28-day cure
data for arsenic presents mixed results. For Batches 1 and 3 the leachate concentration of arsenic
increased over the long term. Consequently, the percent reductions for Batches 1 and 3 decreased
from the 28-day cure to the 32-month period. However, for Batches 4 and 5 the leachate
concentration of arsenic decreased over the long term. Percent reductions for Batches 4 and 5
increased from the 28-day cure to the 32-month period.
Although chromium was not a critical contaminant for treatment based on its low
leachable concentrations in the raw waste, leachable concentrations in the treated waste steadily
increased over time to approximately three times the concentrations obtained following the 28-day
cure. Average percent reductions for chromium dropped from -243 percent reduction after the
initial 28-day curing period to -467 percent reduction after 6 months. Chromium concentrations
in the leachate of the 18-month cured samples showed increases of between 20 to 135 percent
with time, resulting in greater negative percent reductions. The chromium concentration in the
leachate of the 32-month cured samples continued to show increases with time, resulting in even
greater negative percent reductions. The average increase in chromium concentration in the
leachate from the 18-month cure to the 32-month cure was 52 percent. The average increase in
chromium concentration in the leachate from the 28-day cure to the 32-month cure was 271
percent. Average percent reduction for chromium across all batches decreased from -243 percent
at 28 days to -987 percent at 18 months to -1,358 percent at 32 months.
With the exception of the 18-month cured samples, leachable concentrations of copper
remained consistent over the long-term study. Copper showed no significant change in TCLP-
6-102
-------
extract concentrations for Batches 1, 4, and 5 between the 28-day cure and 6 months. Batch 3
showed a slight increase in TCLP-extract concentration after 6 months. This resulted in a
decrease in the percent reduction for copper from 90 to 82 percent for Batch 3. Average percent
reduction for copper after 6 months was 92 percent. After 18 months, average percent reductions
for copper dropped to 78 percent reduction. The copper concentrations in the leachate at 32
months showed slight to moderate decreases from the leachate concentrations for the 18-month
cure samples. Average percent reduction for copper across all batches increased to 93 percent for
the 32-month cure. With the exception of Batch 5, the copper concentration in the leachate for
the 32-month samples statistically did not increase from the concentrations in the leachate for the
28-day samples.
Table 6-31 presents the TCLP-Distilled Water results for arsenic, chromium, and copper.
The TCLP-Distilled Water leachate concentrations of arsenic were essentially unchanged from the
28-day to the 32-month samples. Percent reductions were 98 percent for all batches except Batch
4 which decreased from 98 percent at 28 days to 93 percent at 32 months. The chromium
concentration in the TCLP-Distilled Water leachate increased from the 28-day to the 32-month
samples. Percent reductions for chromium decreased significantly from the 28-day to the 32-
month samples. The percent reductions for copper after 32 months decreased moderately from
the 28-day samples. Average percent reduction for copper decreased from 89 percent at 28 days
to 82 percent at 32 months.
Table 6-32 presents additional long-term (18-month) results for samples collected from
the weathered monoliths that remained exposed on the demonstration site. TWA for PCP and
TCLP for arsenic, chromium, and copper were used to evaluate the level of leaching from both
the surface and interior cores of the monoliths. These results are compared to average raw waste
concentrations for each of the batches. Chromium is the only contaminant that showed increased
concentrations in the weathered monolith cores, as well as slight increased concentrations in the
weathered surface over the 18-month time period. In general, the weathered monolith surfaces
had higher concentrations of contaminants than the weathered monolith cores. One exception is
chromium in Batch 3 for which the weathered core contained greater leachable quantities than the
weathered surface. Table 6-33 shows additional long-term ion-speciation analyses for chromium
(VI) relative to total chromium in both raw and treated waste TCLP-Distilled Water extracts for
Batch 5. The wastes were analyzed 8 months after the demonstration, revealing greater leachable
quantities for both chromium (VI) and total chromium in the treated waste. The 8-month leachate
6-103
-------
Table 6-31. Analytical Results for TCLP-Distilled Water Leachates
Constituent: Arsenic , ,
Batch
'
Average
Percent Reduction
3
Average
Percent Reduction
4
Average
Percent Reduction
- Average
Percent Reduction
Concentrations (ing/l.)
Raw Waste
0.95C
1.0C
0.71C
0.82C
0.91C
0.42
0.80 ± 0.21
0.66C
0.72C
0.75C
0.80C
0.77*
0.65
0.725 ± 0.060
1.3
1.3
1.3
1.1
1.4
1.1
1,25 ± 0.12
1.2
1.1
0.97
1.1
0.96
1.1
1.1 ± 0.09
Treated Waste
28-day
<0.01f
<0.01
<0.01
<0.01
<0.01
<0.01
98
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
>98
<0.010
0.010'
0.0 13q
<0.010f
<0.010f
<0.010
<0.011 ±0.001
>98
0.013
0.013
0.011
0.011
0.013
<0.010
$?$
32-month
0.02q
<0.003g
<0.003g
NA
NA
NA
<0.009
>9a
<0.003g
<0.003g
0.06q
NA
NA
NA
<0.02
>95
0.06
0.03
0.07
NA
NA
NA
0.05 ± 0.02
93
0.04q
<0.003g
<0.003g
NA
NA
NA
<0.015
>98
:
6-104
-------
Table 6-31. Analytical Results for TCLP-Distilled Water Leachates (continued)
Constituent: Chromium
Batch
1
Average
Percent Redaction
3
Average
Percent Reduction
4
Average
Percent Reduction
Average
Percent Reduction-
- - Concentrations (mg/L)
Raw Waste
0.21
0.31
0.091
0.16
0.20
0.17
0,19 ± 0.072
0.20
0.18
0.18
0.066"
0.22
0.19
0.17 + 0.054
44 »<
0.079
0.060
0.10
0.067
0.066
0.067
0.073*0,015
--
0.15
0.11
0.063
0.057
0.10
0.15
OJ05 ± 0.040
~,
Treated Waste
28-Day
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
>54
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
>4S
0.066"
0.055
0.055
0.052
0.050
0.060
0.056 ± 0.006
-36
0.078
0.077
0.079
0.076
0.084'
0.079
0.079 ± 0.003
-31
32-month
0.29
0.28
0.34
NA
NA
NA
0.30 ± 0.032
-178
0.36
0.28
0.22
NA
NA
NA
0.29 + 0.07
*201
0.84
0.90
0.74
NA
NA
NA
0.83 ± 0,081
-1900
0.73
0.66
0.67
NA
NA
NA
0.69 ± 0.037
6-105
-------
Table 6-31. Analytical Results for TCLP-Distilled Water Leacfaates Ccontinued)
Constituent: Copper
Batch
1
Average
Percent Redaction
3
Average
Percent Reduction ,
4
Average
Percent Redaction
Average
Percent Redaction
Concentrations (n»E/L>
Haw Waste
0.49
0.73
0.25
0.37
0.45
0.43
0.45 ± 0.16
****
0.41
0.37
0.36
0.2 lq
0.45
0.41
0.37 ± 0.084
+****
0.98
1.10
0.97
0.97
1.00
0.92
0,99 ± 0.060
+***
0.71
0.54
0.45
0.50
0.50
0.63
0,555 ± 0.097
.4*M :
Treated Waste
28-day
0.030
0.030
0.031
<0.030
<0.030
0.032
<0.0305 ± 0.001
>88
0.030
0.030
<0.030
<0.030
<0.030
<0.030
<0,030
>86
0.056
0.053
0.055
0.055
0.055
0.051
0.054 ± 0.002
90
0.032
0.031
0.032
0.031
0.034
<0.030
<0,032 * 0.001
>90
32-month
0.04
0.04
0.06q
NA
NA
NA
0.05 + 0.01
80
0.05
0.04
0.03
NA
NA
NA
0.04 ± 0.01
81
0.08
0.1 Oq
0.08
NA
NA
NA
0.09 ± 0.01
84
0.06
0.05
0.06
NA
NA
NA
0.06 ± 0.006
6-106
-------
Table 6-31. Analytical Results for TCLP- Distilled Water Leachates (continued)
a = Percent Reduction = [l - (1 + Additives Ratio) x Concentration of Seated Waste]
! Concentration of Raw Waste \ *
b = °^^'^^^^
c - Duplicate analysis not within control limits.
d - ^^concentration because compound was deleaea a an amcuntkss than
e - Reported value was calculated from a greater dilution than the pHmay analysis.
1 '
6-107
-------
Table 6-32. 18-Month Weathered Monolith Test Results
NA = Not analyzed
a = Results reported as the mean of six samples.
b ~ Results reported as the mean of two samples.
=====
Constituent
PCP-TWA
Arsenic-TCLP
Chromium-TCLP
Copper-TCLP
=====
Batch
1
3
4
5
1
3
4
5
1
3
4
5
1
3
4
5
'
Raw Waste
(ppm)*
2,350
1,980
7,700
8,320
1.82
1.06
2.40
3.33
0.13
<0.05
0.10
0.27
3.42
1.38
6.53
9.43
==========
Treated Waste (ppm)
Weathered Monoliths
Cores^
20
17
41
97
0.088
0.053
0.247
0.502
0.326
0.207
1.160
1.325
0.239
0.141
1.122
0.767
Surface
50
NA
NA
260
.
NA
0.170
NA
0.650
_ _
NA
0.076
NA
0.391
NA
0.243
NA
1.000
6-108
-------
contained approximately four times the quantity of total chromium compared to the 28-day
TCLP-Distilled Water leachate, and almost three times as much total chromium as the initial raw
waste sample, again indicating that STC's stabilization treatment process does not reduce the
leaching of total chromium over the long term. Increased quantities of the ion-species chromium
(VI) in the 8-month leachate compared to the raw waste values indicate that STC's treatment
process results in the oxidation of chromium, thereby rendering it more mobile.
The physical strength on the STC-treated waste was evaluated after 6, 18, and 32 months
using the unconfined compressive strength (UCS) test. Results reported in Table 6-34 show an
average increase in strength of 43 percent over the 6-month period and 347 percent over the 18-
month period. The average strength decreased over the 32-month period, resulting in an average
increase of only 243 percent from the 28-day results, compared to the 347 percent increase in
strength observed after 18 months. Permeability for all batches decreased over time. Permeability
results are reported in Table 6-35. For the 28-day samples the permeability ranged from 0.9 x 10'7
cm/sec to 1.7 x 10'7 cm/sec. For the 32-month samples the permeability ranged from 1.2 x 10'7
cm/sec to 4.2 x 10'7 cm/sec.
6.8 QUALITY ASSURANCE RESULTS
This section of the report presents a summary of quality assurance (QA) validation results
for data obtained during the STC demonstration. Of primary interest are the analyses of raw and
treated wastes, water, and various leachates for pentachlorophenol (PCP) and arsenic as the critical
parameters. Selected non-critical parameters were also included to provide both a characterization
of the contaminated soil and a comprehensive evaluation of the proposed technology. Non-critical
parameters included volatile organic compounds (VOCs), semivolatile organic compounds other
than PCP, metals other than arsenic, oil and grease, Eh, pH, and loss on ignition. All analyses
discussed in this section were performed by the Engineering-Science, Inc. Berkeley Laboratory
(ESBL). A more detailed discussion of the validation process and its results and findings is
presented in the "Quality Assurance Report for the STC Site Demonstration" (Engineering-Science
Inc., 1992). In general, the usability of the data generated by ESBL to meet the objectives of the
demonstration is not affected by the QA outliers found during validation of the data.
6-109
-------
Table 6-33. Long-Term Chromium Analysis TCLP-Distilled Water (Batch S)
Constituent
Chromium (VI)
Total Chromium
=====
Raw Waste
(ppm)
<0.01
<0.01
0.13
0.12
11 ii.i.
28-day
Treated Waste
(ppm)
NA
0.08
============
8-month
Treated Waste
(ppm)
0.15
0.18
0.31
0.32
NA = Not analyzed
Table 6-34. Long-Term Unconfined Compressive Strength
Batch
1
3
4
5
Unconfined Compressive Strength (psi)
28-day*
301 ± 162
278 ± 20
259 ± 65
347 ± 65
6-month"
480 ± 41
450 ± 85
350 ± 230
420 ± 190
18-month*
958 + 63
763 + 19
1,017 + 73
1,375 ± 26
32-month
688 ± 114"
720 ± 48°
679 + 109d
795 ± 136"
a
b
c
d
Results reported as mean and standard deviation of three samples.
Results reported as mean and standard deviation of eight samples.
Results reported as mean and standard deviation of two samples.
Results reported as mean and standard deviation of nine samples.
Table 6-35. Long-Term Permeability Testing
Batch
1
3
4
5
======
a = Results reported as mean and s
b = Results reported are from single
1
Permeability (10'7 cm/sec)
28-day*
1.7 ± 0.40
1.5 ±0.98
0.9 ± 0.41
1.5 ± 0.27
=========!
tandard deviation of three samples.
samples.
32-month1'
4.2
2.8
1.2
2.0
6-110
-------
6-8-! Quality Assurance Review of Critical Parameters
Critical parameters that were identified to evaluate the immobilization technology include
PCP and arsenic, both formerly common wood-treating agents. Since QA criteria that apply to
the PCP analyses also apply to all other semivolatile analytes, semivolatile analyses in general are
discussed here. Similarly, QA issues concerning all metals are discussed here, even though arsenic
is the only critical parameter within this fraction.
6.8.1.1 Detection Limits
The detection limits for semivolatile organic compounds, determined by gas
chromatography/mass spectroscopy (GC/MS) in accordance with the procedures of a specific
method, are the method detection limits (MDL). The MDL is the smallest concentration of an
analyte that is distinguishable from background by the instrument used for the analysis. The
MDL values presented in the quality assurance project plan (QAPJP) are based upon the values
listed in EPA Method 8270. The actual values obtained are dependent upon several test-specific
factors: the specific instrument used, the matrix type, dilution factor, and other conditions under
which the analysis was performed. Due to excessive concentrations of PCP in some samples,
occasionally in the percent range, dilution factors can be in the range of 1,000 to 2,500.
Therefore, it was possible that contaminants present at low concentrations relative to PCP may not
have been detected. This was not considered a critical issue, however, as PCP contamination was
the primary organic contaminant of concern. Detection limits for metals, determined by various
methods, are specific to their analysis methods.
6.8.1.2 Holding Times
Different holding times criteria exist for the quantitation of semivolatile organic
compounds, depending on whether or not the sample is a leachate. Non-leachate samples were
prepared within 14 days of sample collection. A maximum holding time of 40 days was specified
between preparative extraction and determinative analysis, so that a maximum 5-day holding time
was allowed between field collection and determinative analysis for non-leachate samples.
Leachate samples included TCLP, TCLP-Distilled Water, and CALWET samples. A maximum
holding time of 14 days was specified between field collection and the beginning of leachate
extraction, and a 7-day holding time was specified between the end of leachate extraction and
preparative extraction. During this evaluation, the leaching period was considered to end at
6-111
-------
leachate filtration. Forty days were specified between preparative extraction and determinative
analysis; therefore, a maximum 61-day holding time was considered acceptable from field
collection to determinative analysis.
Some semivolatile samples violated holding time criteria. Three specific problems were
identified. First, the holding time criteria of 40 days between preparative extraction and
determinative analysis was violated in pretreatment and reagent mix total waste analysis. Second,
CALWET samples from pretreatment soils often exceeded the maximum allowable holding time
from sample collection to leachate extraction. Third, some TCLP-Distilled Water and CALWET
samples from pretreatment soils were not filtered immediately after leachate extraction.
In the first holding time issue mentioned above, several samples violated the 40-day
maximum holding time between preparative extraction and determinative analysis. Violations
ranged between 1 to 12 days over the allowable 40-day holding time. The method blanks
associated with these samples met all holding time criteria.
A study was performed by ESBL to determine if the accuracy of the PCP analyses was
significantly compromised by violating the 40-day holding time between preparative extraction
and determinative analysis. The results of this study were inconclusive due to imprecision, as
indicated by high relative percent differences (RPD) between analyses, and a lack of QC
information. The study consisted of two experiments. In the first experiment, four samples that
violated the 40-day holding time were reanalyzed 34 days beyond the allowable holding time. The
RPDs between the original analyses and the re-analyses were 17, 18, 16, and 100 percent. The
low RPDs in three of the four samples are evidence that PCP concentrations in the samples remain
constant beyond the 40-day holding time. In the fourth sample, the PCP concentration in the re-
analysis was three times higher than that of the original analysis, possibly indicating operational
error.
The purpose of the second experiment was to determine if PCP concentrations in samples
that met all holding time requirements change significantly after holding times have expired. If
the PCP concentrations in these samples could be shown to be independent of holding time, then
the relevance of the 40-day holding time would be lessened and results from samples analyzed
beyond holding time could be allowed to stand unflagged. Four treated waste samples analyzed
within the allowable 40-day holding time were reanalyzed 2, 5, 15, and 49 days beyond holding
time. PCP concentrations remained relatively constant with time, but precision was poor. RPDs
6-112
-------
between the original analyses and their re-analyses varied from 9 to 149 percent. Only three of
sixteen RPDs met the usual RPD acceptance limit of 50 percent for PCP. Since the results were
too imprecise to be conclusive, samples that violated the holding time received qualifying flags.
All positive detections were flagged as estimated values, and all non-detects were flagged with the
sample reporting limit as estimated. Since exceeding the allowable holding time could cause a loss
of target analytes from the sample, the results of these samples may be biased low.
The second holding time problem involved some CALWET analyses from raw waste
samples held in excess of the maximum allowable 14-day holding time between field collection
and leachate extraction. Several environmental samples exceeded the maximum allowable holding
time by 8 to 10 days. Again, positive results were flagged as estimated, and non-detects were
flagged with the reporting limit as estimated.
Third, several samples were shelved for an excessive length of time between the end of
leachate extraction and leachate filtration. The leachates were left in light and at room
temperature, possibly causing the concentrations of analytes in the samples to drop significantly
due to processes such as photo-oxidation. All CALWET samples in one sample group were
filtered 6 days after the end of leachate extraction. Also, several TCLP-Distilled Water samples
sat for 5 to 6 days between extraction and filtration.
A study was performed by ESBL to determine if the accuracy of the PCP analyses was
compromised by the holding times and the storage conditions of the leachate samples between
leachate extraction and filtration. Three TCLP leachate samples were analyzed from each of three
composite raw waste samples for a total of 9 samples. For each composite, the first leachate
sample was filtered immediately after extraction, the second leachate sample was left at room
temperature for five days and then filtered, and the third leachate was left at 4°C for 5 days and
then filtered. In two composite samples, the PCP concentration was higher in the immediately
filtered extract than in the extracts filtered after a 5-day waiting period. The other composite
yielded a lower PCP concentration in the immediately filtered extract than in the extracts filtered
after a 5-day waiting period. More importantly, results were precise and reproducible. RPDs
between PCP concentrations in the immediately filtered samples and the samples left at room
temperature for 5 days were found to be 16, 8, and 56 percent. RPDs between PCP
concentrations in the immediately filtered leachates and the samples left in refrigeration for 5
days were 41, 6, and 48 percent. By comparison, the maximum allowable. RPD for PCP in matrix
spike/matrix spike duplicate (MS/MSD) samples is 50 percent. Therefore, any effects that the
6-113
-------
holding time and storage conditions had on the PCP concentrations in the leachate were
considered minimal in comparison to the precision limitations of the method. Hence, PCP results
in leachate samples filtered several days after extraction were considered to be valid, and these
data remained unflagged.
Finally, the re-analysis of one TCLP-Cage blank violated the 40-day holding time criteria
between preparative extraction and determinative analysis. Positive results were flagged as
estimated, and non-detects were flagged with the sample reporting limit as estimated.
Concentrations estimated in this sample may be biased low.
Several different holding time criteria exist for the evaluation of metals analyses. For
leachate samples, 180 days is allowed between sample collection and the start of the leachate
extraction procedure, except for mercury, for which 28 days was allowed. Between preparative
extraction and determinative analysis, 28 days was allowed for mercury and 180 days was allowed
for the analysis of all other metals. Since preparative extraction dates were not provided, the data
could not be validated for this holding time. For waste and water samples, 180 days was allowed
between sample collection and determinative analysis for all metals except mercury. A maximum
holding time between sample collection and analysis of 28 days was allowed for mercury.
The above holding time criteria for metals were met for all but the CALWET samples
from one sample group. For these environmental samples and their associated extraction blank,
leachate filtration followed leachate extraction by 13 days. No standard holding time was
specified, since metals are not susceptible to photo-oxidation, volatilization, or other degradation
processes as organic compounds. Therefore, the quality of the data was not expected to be
adversely affected due to the lengthy holding time. Thus, no corrective action was taken for these
data.
6.8.1.3 Accuracy and Precision
The accuracy of the analytical results was evaluated using the percent recoveries of
surrogate compounds added to each individual sample prior to analysis and the percent recoveries
of matrix spike compounds in MS/MSD samples. The precision of the analytical results was
evaluated using the relative percent difference (RPD) for percent recoveries of matrix spike
compounds in the MS/MSD samples. The recovery of spiking compounds, is an indication of the
6-114
-------
effect of the sample matrix upon the accuracy of the analysis results. Also, unusually high or low
recoveries may indicate operational error.
Both surrogate and spike percent recovery samples were used to determine the precision
and accuracy of semivolatile analyses. Based on results of these QA measures, the overall degree
of accuracy and precision for semivolatile analyses was considered to be acceptable. Nevertheless,
several different sources of matrix interference were identified. The most severe matrix
interference problems were attributed to the reagent mixture. It appeared that the spiked
compounds reacted with or remained tightly bound to the reagent matrix during sample
preparation. Therefore, sample spiking was not considered to be a meaningful assessment of
analytical accuracy and precision for samples containing the reagent mixture.
Six surrogate compounds were added to each individual semivolatile sample prior to
analysis to obtain information about the accuracy of the analysis. The evaluation of surrogate
recoveries served two basic purposes: 1) to evaluate the severity of matrix interference and 2) to
determine if any fundamental problems exist with the analytical process. The percent recovery
(PR) of surrogate compounds was calculated using the following equation:
%R = (MS or MSP) - SR
where:
MS = Matrix spike concentration
MSD = Matrix spike duplicate concentration
SR = Sample result concentration
SA = Concentration of spike added
Matrix interference may reduce the accuracy of an analysis. For example, lower recovery
might be expected from a waste sample than from a water sample since a portion of the surrogate
compounds may remain adsorbed to the waste. During the STC demonstration, the high
concentration of PCP in some of the environmental samples may have presented matrix
interference.
6-115
-------
Surrogate recoveries were also used to determine if any functional problems existed with
the analytical process. Unusually high or low recoveries are often caused by errors in sample
extraction, improperly calibrated equipment, or other instrument or operator errors. In such
cases, the samples were re-extracted and re-analyzed in order to provide a more accurate result.
Acceptable surrogate recovery intervals were established for each of the six semivolatile
surrogate compounds and for each physical state of the samples. Fundamental problems with the
analytical procedure or excessive matrix interferences were suspected if the surrogate compounds
were not recovered within the acceptable ranges. For samples with surrogate recoveries out of
specification, samples were flagged and corrective action was taken. Surrogate recovery
percentages were reported for every environmental sample and method blank sample that
underwent analysis. If any two surrogates within a base/neutral or acid fraction were out of
specification, or if any one surrogate compound was recovered at less than 10 percent, a re-
analysis of that sample was performed. In cases where matrix spike/spike duplicate pairs were
analyzed and the associated environmental sample was out of specification, the MS/MSD results
were considered to be the re-analysis.
Although the majority of the analyses met acceptance criteria, some samples failed to meet
surrogate recovery criteria, even after re-analysis. Two sources of possible matrix interference
were identified: 1) the reagent mixture used in the demonstration and 2) the compounds spiked
into samples as part of the MS/MSD analysis. In addition, surrogate compounds were not
recovered from some pretreatment samples that required large dilutions. Finally, operational
errors were encountered, requiring re-analysis for the samples involved.
The analysis of MS/MSD samples gives an indication of the accuracy and the precision of
analytical results. For semivolatile analyses, eleven compounds were spiked into and recovered
from MS/MSD samples. The recovery of spiked compounds is an indication of the effect of the
sample matrix upon the accuracy of the analysis results. Also, fundamental problems with the
analytical process may be suspected if unusually high or low recoveries were achieved. The
recovery of spiked compounds is calculated using the same equation as for percent recovery of
surrogate compounds discussed above.
The precision of analytical results is indicated by the RPD between the MS and MSD
samples. The RPD gives an indication of the reproducibility of the analytical results. Low RPDs
indicate a precise, reproducible analysis, while high RPDs may indicate a matrix effect or
6-116
-------
operational error, causing precision problems between duplicate samples. The RPD is calculated
using" the following equation:
RPD m (MS - MSP)
(MS + MSD)I2
where:
MS = Matrix spike concentration
MSD = Matrix spike duplicate concentration
Semivolatile MS/MSD samples were analyzed in conformance with the STC SITE
demonstration QAPJP. At least one MS/MSD pair was analyzed for every twenty environmental
samples of the same matrix. Percent recoveries were not calculated for the matrix spike
compound PCP in samples originally containing high concentrations of PCP. In these samples,
spiked amounts of PCP were insignificant relative to the amount of PCP already in the sample!,
and recoveries were approximately an order of magnitude greater than spiked amounts. Several
MS/MSD analyses yielded recoveries and RPDs that did not conform to acceptable limits. Matrix
effects were suspected in samples from which spiking compounds were recovered at unacceptable
percentages, but met RPD criteria. In these cases, reproducibility of results was demonstrated.
More severe matrix effects or operational problems must be suspected if RPD values are also out
of the specified control criteria. In all cases where QC criteria were not met, both a calibration
check standard and a blank spike sample were analyzed to demonstrate that the laboratory
analytical system was in control.
The accuracy of metals analyses was evaluated using spike recoveries for MS samples.
Precision of metals analyses was evaluated using RPDs calculated for laboratory duplicate samples.
Spike recovery limits range from 75 to 125 percent and do not apply when the sample
concentration exceeds the spike concentration by a factor of four or more. Corrective action was
taken in cases where percent recovery criteria were violated. In cases where the recovery of a
metal spike exceeded 125 percent but the metal was not detected in relevant environmental
samples, the data was considered acceptable for use. If the spike recovery of a metal was less than
75 percent or greater than 125 percent, the metal detected in associated environmental samples
was qualified as estimated. If a percent recovery of a spiking metal was less than 30 percent and
the metal was not detected in associated environmental samples, then the data was qualified as
unusable.
6-117
-------
Arsenic samples were both precise and accurate. Percent recoveries for arsenic were well
within the QC range, except a few minor violations. The worst violation, in MS/MSD results for
one sample, was a 131 percent recovery, 6 percent above the upper limit. Results for arsenic were
also reproducible. Only two samples had an RPD that exceeded 20 percent. Both of these were
waste samples, indicating that a matrix effect may potentially be attributed to the waste medium.
Also, percent recovery criteria for metals in general were violated much more often in waste
samples than in leachate samples, further indicating a matrix effect caused by the waste. Finally,
selenium was often recovered below the minimum acceptable level in TCLP and CALWET
leachates. Since selenium results were reproducible, another matrix effect was suspected rather
than operational error.
6.8.1.4 Sample Contamination
The existence and magnitude of contamination problems were assessed by evaluating the
results of blank analyses. Ideally, blank samples should contain no contaminants. In reality,
however, sample contamination is a frequent occurrence, and it is important to determine if trace
compounds detected in the environmental samples originate on the site or are introduced in transit
or in the laboratory during analytical preparation. The extent of contamination in the method
blanks associated with each environmental sample batch was assessed to determine the certainty of
the reported contaminant quantities in the environmental samples for both metals and semivolatile
organics.
In the semivolatile organic fraction, compounds detected in the method blanks included
PCP, phthalate esters, and one detection of N-nitroso-dimethylamine. The detection of N-
nitroso-dimethylamine appeared in the one TCLP extraction blank; however, no N-nitroso-
dimethylamine was detected in any of the environmental samples. Therefore, it appears that the
detection was due to laboratory contamination. The phthalate esters detected in blank samples
included diethylphthalate, di-n-butylphthalate, bis(2-ethylhexyl)phthalate, and di-n-octyl-
phthalate. Of these compounds, bis(2-ethylhexyl)phthalate was detected most frequently. All
environmental samples associated with phthalate contaminated blanks either were free of phthalate
detections or had detections on the same order of magnitude as those in the blanks, indicating that
their presence was due to laboratory contamination. Phthalate esters are components of plastic,
and are considered to be common laboratory contaminants.
6-118
-------
PCP was detected in several method blanks, and is not considered to be a common
laboratory contaminant. Since PCP was detected frequently at relatively high concentrations in
the enwronmental samples, some degree of cross contamination was suspected Standard
evaluation procedures were used in each case to determine if the detected PCP was from the
sample or resulted from contamination. Three CALWET environmental samples contained PPP
c0ncentrations ranging from ^ tQ ^ ^ ^ ^ ^ ^ ^ ^
CALWET extraction blank which contained 190 ^g/L of PCP. A portion of the PCP detected in
each environmental sample likely appears as the result of sample contamination, therefore the PCP
concentrations may be biased high.
Metals occurring in preparation b,anks included sodium, potassium, zinc, aluminum
ca c,um, and iron. There were no detections of arsenic in any preparatory blanks throughout the
analyses. The most frequen,,y occurring Wan* contaminant for the me,a,s fraction was sodium
Sodmm was detected a, concentrations ranging from 1 to 9,500 milligrams per ,i,er (mg/L) in '
aqueous samples. Sodium was detected ataos, exclusively in TCLP and CALWET extraction
blanks. Th,s result was expected, since sodium is a component of the extraction sototions
Detect, of these metals in associated environment* samples were pualified indicating tha, the
detected analytes originated in the laboratory or during transit rather than on the job site
Instrument calibration blanks were no, reported, and thus the meals data is unqua,ified with
regard to these blanks.
6-8.2 Quality Assurance Review For Non-Critical Parameters
Non-critical parameters were identified in the test plan to provide further information for
the charactenzauon of the contaminated soil and for the evaluation of the solidification/
stabilization treatment process. Volatile organic compounds (VOC), Eh, pH, loss on ignition, and
oil and grease analyses were performed.
6.8.2.1 Detection Limits
The de^on ,,m,,s for volatile organic compounds, determined by OC/MS in accordant
w«h the procedures of EPA Method 8240, are the MDL, The MDL values presented in the
QAPjP are based upon values listed in EPA Method 8240. However, the actual values obtained
are dependent upon several sample-specific factors- n th* *~-e-
' apeciric instrument used' 2) the matriv
ypa; 3) d,u,ion factors; and 4) other conditions under which the analyses' were perfumed. The
6-119
-------
only dilutions used in volatile analyses during the course of this project were 1 and 5 Therefore
detections are as low as possible and the analyses were sensitive enough to detect trace levels of '
contamination.
The detection limits for oil and grease analyses in the QAPJP are based on those listed in
EPA Method 413.2. Detection limits for oil and grease were 1 mg/L for aqueous samples and 10
mg/kg for waste matrices. The detection limit in the QAPJP for the loss on ignition analyses was
based on that found in ASTM Cl 14. The detection limit for these analyses was 0.2 percent Since
non-detects are not possible in Eh and PH analyses, detection limits are not applicable.
6.8.2.2 Holding Times
Two holding times criteria were specified for volatile analysis of leachate samples A
maxamum of 14 days was allowed from sample collection to the start of leachate extraction Also
a maximum holding time of 28 days was allowed between sample collection and determinative '
analysis. The holding time for volatile analysis for TWA samples was 14 days from sample
collection. All volatile analyses performed in the course of this project were completed within
allowable holding times. Holding times were considered to start at the end of the 28-day curing
period for treated waste and reagent mixture samples.
A maximum holding time of 28 days between sample collection and determinative analysis
was specified for oil and grease. All oil and grease analyses performed during the course of the
project met this holding time criteria. Again, the holding time for the reagent mixture and post-
treatment samples was considered to begin at the end of the 28-day curing period.
6.8.2.3 Accuracy and Precision
For volatile organic compounds, the accuracy of the analytical results was evaluated using
the percent recovery of surrogate compounds spiked into each sample and the percent of matrix
spike compounds in MS/MSD samples. Precision of the analytical results was evaluated using the
RPD for percent recoveries of spike compounds in the MS/MSD samples. Three volatile surrogate
compounds were added to every environmental sample and blank sample prior to volatile organic
analysis to obtain information about the accuracy of the analytical system. The recovery of
surrogate compounds served two basic purposes: 1) to evaluate the severity of matrix interference
and 2) to determine if any operational problems exist with the analytical process. Since some
6-120
-------
degree of error is expected, acceptable recovery were established for each of the three surrogate
compounds and for each physical state of the samples.
Surrogate compounds were recovered from every environmental sample and method blank
sample that underwent analysis. If one or more volatile surrogate compounds were out of
specification for a single sample, a re-analysis was performed. In cases where MS/MSD pairs
were analyzed and the associated environmental sample was out of specification, the MS/MSD
results were considered to be the re-analysis. Ideally, the surrogate recoveries in the re-analysis
should closely match those of the original analysis, demonstrating that the analysis is being
performed properly and that matrix interference is the source of the problem. However, if the
results of the re-analysis were within acceptance criteria, these results were reported and the "
problem with the original analysis was considered due to instrumentation or operator error.
Corrective action was taken in cases where volatile surrogate recoveries were out of
specification. If one or more of the surrogate compounds were out of specification but had
recoveries greater than 10 percent, positive results for the sample were flagged as estimates and
non-detects were estimated using sample reporting limits. If any surrogate compound in the
volatile fraction was recovered at less than 10 percent, then positive results were flagged as
estimates and non-detects were flagged as unusable.
The volatile analyses that did not conform to surrogate recovery specifications were
considered out of compliance due to matrix effects and not operational error in the analytical
system. Three major sources of matrix interference were identified: 1) the spiking procedure in
the MS/MSD analysis, 2) the soil matrix, and 3) the reagent mixture that was being tested in the
field demonstration.
MS/MSD sample analyses tended to result in excessive recovery of 1,2-dichloroethane-d4-
however, in each case, the accompanying non-spiked sample met surrogate recovery criteria
Also, surrogate compounds in relevant extraction and method blanks were recovered at acceptable
percentages, discounting operational error. A similar trend was observed in semivolatile analyses
These results strongly suggest that the compounds spiked into the samples for MS/MSD analysis
were a source of matrix interference. Since the environmental samples did not undergo a spiking
process, the accuracy of these results is not believed to have been adversely affected
6-121
-------
Another trend observed in the volatile surrogate recovery data was that in some samples,
toluene-d8 was recovered slightly in excess of its maximum acceptable recovery limit. The high
toluene-dS was attributed to matrix effects in all cases. Surrogate recovery results were shown to
be reproducible; relative percent differences between the waste samples and their re-analyses
varied from 1 to 6 percent. Also, all extraction and method blanks for volatile analyses met
surrogate recovery criteria, discounting operational error.
Two of the samples with high toluene-d8 recovery also failed surrogate recovery criteria
for bromofluorobenzene (BFB). One sample had a BFB recovery of 206 percent, suggesting an
operational error, while another yielded a BFB recovery of 73 percent, one percentage point below
the minimum allowable percentage. Results from both of these samples were flagged unusable.
By far, the environmental sample in most serious violation of surrogate recovery criteria was a
volatile analysis of the reagent mixture, resulting in a 448 percent recovery of toluene-d8 and no
recovery at all for the surrogate compound BFB. The analysis yielded only non-detects and the
results were flagged as unusable. Matrix interference from the reagent mixture was suspected to
be the cause of these unusual recoveries. The associated MS and MSD samples displayed similar
results. All method blanks analyzed in association with the sample had surrogates which met the
recovery criteria, ruling out operational error. Semivolatile analyses of samples containing the
reagent mixture displayed similar problems with surrogate recoveries. It is postulated that the
BFB remained sorbed to the reagent mixture during analysis.
The precision and accuracy of volatile analyses were further evaluated using MS/MSD
samples. Five compounds were spiked into and recovered from MS/MSD samples and analyzed
for volatile constituents. Percent recoveries and RPDs were calculated using the same equations as
were used for the critical parameters. At least one MS/MSD sample pair was analyzed for each
twenty samples of the same matrix and dilution factor. All MS/MSD sample pairs except for
volatile analysis of the reagent mixture met the recovery criteria. Volatile MS/MSD analyses were
further evidence of significant matrix interference caused by the reagent mixture. Percent
recoveries were excessive for three of the five spiking compounds in both the MS and MSD
samples associated with the reagent mixture. Also, RPDs for three volatile spiking compounds
exceeded maximum allowable values. A method blank that underwent MS/MSD analysis on the
same date as the reagent mixture samples, met recovery criteria, discounting operational error.
The accuracy and precision of oil and grease analyses was quantitated using MS/MSD
analyses. All MS/MSD samples analyzed for oil and grease met acceptance criteria. Percent
6-122
-------
recoveries ranged from 85 to 121 percent, which is within the acceptable range of 75 to 125
percent stated in the QAPjP. Although no maximum acceptable RPD has been set, the largest
RPD obtained was only 3 percent, indicating that analyses were precise and reproducible.
MS/MSD samples were analyzed at acceptable frequencies. For aqueous matrices, one
MS/MSD pair was analyzed from an environmental sample and one was analyzed from a method
blank sample. A total of two aqueous samples were analyzed for oil and grease. For the waste,
four MS/MSD pairs were analyzed from environmental samples and three were analyzed from
method blank samples. A total of 29 waste samples were analyzed for oil and grease.
6.8.2.4 Sample Contamination
The existence and magnitude of contamination problems were assessed by evaluating the
results of method blank analyses. Hence, method blanks were examined for contamination and
the related environmental samples were evaluated with respect to the identified contamination to
determine the certainty of reported values. For both the volatile organic fraction and the oil and
grease fraction, method blanks were reported appropriately for each matrix and for each leachate
extraction procedure. Method blanks were not analyzed for the other non-critical analyses.
Methylene chloride was detected frequently in volatile method blanks. Concentrations of
methylene chloride in the blanks ranged from 8 to 28 vg/L in blank aqueous samples and
11 to 21 fjg/kg in blank waste samples. Methylene chloride detections in the environmental
samples were roughly of the same order of magnitude as the detections in the method blanks. In
the environmental samples, concentrations of methylene chloride ranged from no detection to 21
Ag/L in aqueous samples and from no detection to 140 j^g/kg in waste samples. Methylene
chloride is a common laboratory contaminant, and thus all methylene chloride detections in
environmental samples were qualified as non-detects.
Oil and grease were also examined for contamination problems as determined by method
blank association. At least one method blank was reported for each matrix. Oil and grease were
not detected in any of the method blanks associated with this project.
6-123
-------
6.8.3 Overall Completeness of the Analytical Data
The QAPjP defines completeness as an assessment of the amount of valid data obtained
from a measurement system, compared to the amount of data that was planned to be obtained so
that a particular statistical level of confidence in the data results from the measurement system.
This measurement system is comprised of the various analytical methods used throughout the
course of the project including GC/MS analysis for volatiles and semivolatiles, atomic absorption
for metals, and EPA Method 413.2 for quantitation of oil and grease. The degree of completeness
is the number of analyses with acceptable data divided by the total number of samples collected
and tested, multiplied by 100.
There were very few data collected in this project that were determined unacceptable.
Three volatile analyses, one semivolatile CALWET extraction blank, and four semivolatile
environmental samples were flagged unusable due to surrogate recovery violations. The selenium
analysis in one sample was flagged unusable due to inadequate recovery of the metal in the
MS/MSD analysis. Results for all other metals in the same sample were acceptable. In another
sample, silver was flagged unusable due to inconsistent recoveries in the MS/MSD analysis.
The QA objective for the degree of completeness for the STC SITE demonstration was 90
percent. Based on the data collected, the degree of completeness exceeds 99 percent. Therefore,
the objective for degree of completeness was met.
6.8.4 Quality Assurance Review For Long-Term Data
This summary presents quality assurance (QA) validation for data obtained during analysis
of six month long-term treated samples, including both semivolatile and metal analyses with PCP
and arsenic identified as the critical parameters. Six environmental samples underwent total waste
analysis by EPA Method 8270; three samples were analyzed for PCP only, and three samples were
analyzed for semivolatiles plus tetrachlorophenol (TCP). Metals data was obtained from six
environmental analyses of TCLP leachates from treated samples. For each batch, one leachate
sample was analyzed for 24 project-specified metals and five leachate samples were analyzed for 5
project-specified metals.
6-124
-------
6.8.4.1 Holding Times
Holding times criteria were examined using criteria set forth in the QAPJP. The holding
times criteria related to field collection did not apply to the long-term samples. Evidence was
provided that exceeding holding times did not severely affect the quality of semivolatile or metals
analyses. The holding times between preparative extraction and determinative analysis were met
in all cases.
6.8.4.2 Accuracy and Precision
The accuracy and precision of the semivolatile analyses were evaluated using surrogate
recoveries and MS/MSD results. Percent recoveries of surrogate compounds were used to evaluate
the accuracy of individual analyses; a set of surrogate recovery results was required for every
environmental sample. MS/MSD results were used in evaluating both the accuracy and precision
of the analyses. Percent recoveries indicated the accuracy, while RPDs between recoveries in the
spike and spike duplicate were used as a measure of precision. One MS/MSD pair was required
for every 20 samples of the same matrix and concentration level. Results of the MS/MSD analysis
affect samples of the same matrix and concentration level.
Surrogate recoveries were reported as required for every environmental and blank sample
analyzed for semivolatiles. Twenty-eight environmental samples were analyzed for semivolatiles.
Twelve of those did not meet the surrogate recovery criteria. Normally, when surrogate recovery
results are unacceptable (two surrogate compounds in the same fraction are outside the recovery
range or any one surrogate compound is recovered at less than 10 percent) a re-extraction and re-
analysis is performed. However, no re-extractions were performed, since surrogate recoveries
were not considered to be a valid test for accuracy due to the sorptive nature of the media.
Surrogate compounds were suspected to primarily adsorb to the reagent matrix rather than pass
onto the GC column for analysis. Thus, low surrogate recoveries were considered to reflect
adsorptive capacity of the reagent mixture rather than the accuracy of the analytical procedure.,
The analytical procedure was considered to be acceptable based on surrogate recoveries
from blank samples. Surrogate compounds were recovered from six blank samples. Every blank
sample yielded recoveries within acceptable intervals, with one exception. One method blank
showed a high recovery of 2-fluorobiphenyl. However, no corrective action was required, since
2-fluorobiphenyl is a base/neutral surrogate, and its recovery affects base/neutral analytes only.
6-125
-------
PCP, the target analyte, is an acid fraction compound, and all acid fraction surrogates met
recovery criteria.
Both accuracy and precision of semivolatile analyses were evaluated using MS/MSD
results. MS/MSD analyses were performed for the twelve PCP analyses, and the twelve analyses
for semivolatiles plus tetrachlorophenols. All environmental and MS/MSD analyses were of soil
samples, evaluated at medium level. Acceptance criteria were met for one pair of MS/MSD
samples with the following exceptions: 1) the percent recovery for pyrene was low at 8 percent in
both the MS and MSD samples, although the RPD for pyrene was acceptable, and 2)
4-Nitrophenol was not recovered in either MS or MSD sample. These results reflect the sorptive
nature of treated waste samples containing the reagent mixture. PCP was recovered high at 132
percent in the MSD sample, causing the RPD to be high. High recovery of PCP was an expected
occurrence due to high concentrations of PCP in the environmental sample.
The accuracy and precision of metals analyses was evaluated on the basis of MS/MSD
samples. Accuracy was evaluated by examining the percent recoveries, and precision was judged
on the basis of relative percent differences in recoveries between the MS and MSD samples. One
MS/MSD was required for every twenty similar environmental samples.
One MS/MSD analysis was used to evaluate the 24-metal analyses. Percent recoveries
were not calculated for arsenic and calcium because the sample concentrations were greater than
four times the matrix spike concentration. Selenium was recovered low at 28 percent in the MS
analysis and 25 percent in the MSD analysis; however, the RPD between these figures was
acceptable. Selenium was recovered low in previous spiked samples of TCLP and CALWET
leachates and thus may be lost in the leaching process. Selenium results in four samples were
flagged as unusable.
One MS/MSD analysis was adequate to evaluate the accuracy and precision of the 5-metal
analyses, since there were twenty analyses for 5 metals. The results complied with QC criteria.
Percent recoveries were not calculated for arsenic, because the sample concentration was greater
than four times the matrix spike concentration. Two laboratory control samples were also
analyzed to monitor overall performance. In both samples, the laboratory control sample
recoveries were within the specified control limits, indicating acceptable results.
6-126
-------
In general, the percent recovery for semivolatile surrogates, and acid surrogates in
particular, were consistently extremely low. In many of the samples containing the reagent mix,
no acid surrogates were recovered. These results suggest that a significant portion of the spiked
compounds remained absorbed to the reagent mixture during the analysis. These results also
indicate that the reagent mixture would have the same effect on target compounds similar to the
surrogates. This trend supports the effectiveness of the reagent mixture on phenolic compounds
since all three acid surrogate compounds were phenols.
6.8.4.3 Sample Contamination
Two method blanks were analyzed to determine if contamination problems existed for the
semivolatile analyses. No detections occurred in analyses of either of the two method blanks.
Thus the environmental analyses were considered to be free of contamination. For the metals
analyses, contamination problems were assessed using six blank analyses. Four TCLP extraction
blanks were analyzed for 24 metals, one preparation blank was analyzed for 24 metals, and one
preparation blank was analyzed for 5 metals. Zinc was the only detected contaminant, appearing
in the TCLP extraction blanks at 0.022 to 0.032 mg/L, slightly above the reporting limit of 0.02
mg/L. Two zinc detections in environmental samples were considered to have originated from
contamination during laboratory preparation or analysis of the samples, and were thus qualified as
non-detects. In the first case, zinc was detected at 0.028 mg/L, with the associated TCLP
extraction blank at 0.030 mg/L zinc. The second environmental sample yielded a zinc detection of
0.022 mg/L, while the associated TCLP extraction blank detected zinc at 0.020 mg/L. Both
detections of zinc in the two samples were qualified as non-detects.
6.8.4.4 Completeness of Long-Term Data
All semivolatile samples were analyzed with acceptable QC results. Completeness for the
semivolatile fraction of the six month long-term samples is therefore 100 percent. In the metals
fraction, results for selenium were determined unusable in four samples due to MS/MSD
violations. Since there were 196 specific results, the degree of completeness for metals analyses is
98 percent. The degree of completeness for the entire set of data is estimated to be over 99
percent. Thus, the goal of 90 percent stated in the QAPJP has been met.
6-127
-------
6.8.5 Quality Assurance Review for Additional Studies
In addition to the analyses described in the STC QAPjP, three studies were conducted to
1) obtain lower reporting limits for the target compound PCP, and TCP (see Section 6.4.1);
2) determine if PCP would be more easily leached from soils at high pH levels (pH = 12) (see
Section 6.4.1); and 3) analyze total and hexavalent chromium from TCLP-Distilled Water leachates
for one raw waste and two treated waste samples of Batch 5 (see Section 6.7).
6.8.5.1 Holding Times
Holding times were examined using the criteria set forth in the STC QAPjP. The holding
times between leachate extraction and preparative extraction and between preparative extraction
and analysis were acceptable for all samples of the first two studies involving PCP and TCP. A
study conducted as part of this project provided evidence that holding time violations did not
severely affect the quality of semivolatile analyses. For the chromium leachate samples, a 180-day
holding time was allowed between sample collection and leachate extraction. This holding time
was exceeded for all leachate samples, since the work was requested by the EPA Project Manager
after the holding time had expired. It was agreed that holding time criteria related to sample
collection would not be applied toward specially requested work orders. Additionally, the
180-day holding time requirement between preparative extraction and analysis was met for all
samples in this study. Thus, no flags were issued on the basis of holding time requirements for
any of the additional studies.
6.8.5.2 Accuracy and Precision
Surrogate recoveries were reported as required for every environmental sample. Violations
of surrogate recovery QC criteria were noted for the first study involving PCP and TCP analysis.
The surrogate compound, 2-fluorophenol (2-FP), was recovered below the minimum acceptable
percentage (25 percent) in all fourteen environmental analyses in the study. 2-FP was recovered
at less than 10 percent in ten analyses performed on environmental samples. The only samples
with acceptable recovery of 2-FP were the method blanks. The recovery of the base-neutral
compound 2-fluorobiphenyl (2-FBP) exceeded the upper recovery limit in three environmental
samples. However, since 2-FBP is the only base-neutral compound out of compliance, the
acceptance criteria were met and no corrective action was necessary. The acid fraction surrogate
phenol-d5 was not recovered in four environmental samples. Also, 2,4,6*-tribromophenol, another
6-128
-------
acid fraction surrogate, was not recovered in one sample. Finally, in two diluted samples
surrogate compounds were not recovered due to dilution.
The low surrogate recoveries from the first study involving PCP and TCP analyses may
indicate sorption of the surrogate compounds to the matrix, since these samples contain the
reagent mixture, which readily adsorbs some organic compounds. The blank analyses conformed
to surrogate recovery criteria, indicating that the analytical system was in control. The above
samples were flagged, indicating that they did not meet surrogate recovery criteria; however,
surrogate recovery is not a highly valid test for accuracy due to the sorptive nature of the sample.
No re-analyses were performed.
In the second study involving PCP leachability at pH 12, surrogate compounds were
recovered within acceptable intervals for all environmental and blank samples. Some spike/spike
duplicate samples were analyzed as a test for accuracy and precision. A matrix spike sample was
analyzed as part of this study. Although this study was not anticipated in the approved QAPJP, all
QAPJP and EPA Contract Laboratory Program (CLP) criteria were met, with the exception of one
compound, 4-chloro-m-cresol, which was recovered just above its acceptance limit. Since a
duplicate was not analyzed, no relative percent differences (RPD) were obtained. The critical
matrix spike/spike duplicate (MS/MSD) compound, PCP, met both percent recovery and RPD
criteria. For this reason, no flags were issued on the basis of MS/MSD criteria. All internal
standard areas were within acceptable CLP acceptance criteria.
The accuracy and precision of the chromium analytical results were evaluated on the basis
of MS/MSD samples. Accuracy was evaluated by examining the percent recoveries of spiked
analytes, and precision was judged by the RPDs in recoveries between the MS and MSD samples.
Percent recoveries and RPDs were in acceptable ranges for both total and hexavalent chromium.
One MS/MSD pair was adequate, since only four samples were evaluated in this study. Since all
MS/MSD requirements were met, no flags were issued.
6.8.5.3 Sample Contamination
Contamination problems were examined for all three studies. Blank samples were free of
detectable contamination in the first study; however in the second study, PCP was detected at
43 ng/L in the extraction blank. PCP concentrations in associated environmental samples ranged
from 88,000 ng/L to 320,000 ng/L. Based on the evaluation criteria set forth in CLP "Functional
6-129
-------
Guidelines", the data from the environmental samples were valid and required no flagging. The
method blank in the second study yielded no detections. An extraction blank and a preparation
blank were analyzed in the third study involving chromium analysis in order to determine if any
sample contamination had occurred. Neither blank yielded any detections. Therefore, the
samples were considered to be free of contamination and no flags were issued.
6.8.5.4 Completeness
All of the data required for the three additional studies were analyzed in an acceptable
fashion. No flags were issued for unusable data, indicating that all of the data was usable. Thus,
the degree of completeness for the three additional studies is 100%.
6.9 SUMMARY OF RESULTS
The STC immobilization technology reduced the short-term mobility and leachability of
arsenic and copper as measured by the TCLP and TCLP-Distilled Water methods. The
solidification/stabilization treatment process was also successful in reducing the mobility and
potential leachability of PCP as measured by the TCLP-Distilled Water test and TWA. However,
leachability was not effectively reduced for chromium as measured by any of the leaching
procedures, except possibly the ANS 16.1 test. However, chromium was not targeted for
treatment in this demonstration and no specific additives were included to treat chromium. In
addition, the CALWET leach test showed very inconsistent trends for all of the analytes.
Based on California state regulatory levels for legal disposal as nonhazardous waste in
landfills, the STC treatment process did not consistently meet total (TTLC) or solubility (STLC)
threshold limit concentration requirements for SPT waste. CALWET leach results were both
below and above California's STLC levels for arsenic, copper, and PCP. TWA for chromium and
copper were well below California's TTLC; however, TWA for arsenic and PCP were above
California TTLC requirements for both the raw and treated wastes. Federal leach criteria could
not be adequately evaluated since TCLP concentrations of arsenic, chromium, and PCP were
below federal TCLP regulatory levels in both the raw and treated wastes.
Preliminary evidence based on freeze/thaw and wet/dry durability tests suggests that the
physical and structural characteristics of the STC-treated wastes would resist the normal effects of
weathering. Low unconfined compressive strengths of the treated waste, although above
6-130
-------
minimum levels for disposal in landfills, were not sufficient for construction purposes. Additional
tests would be needed to determine the appropriate reagent mixture necessary to meet construction
requirements, if desired. Initial six-month TCLP-extract and TWA showed increased
concentrations of contaminants released from the treated waste. Eighteen-month analyses showed
improved percent reductions for arsenic, averaging 88 percent reduction, and PCP averaging 96
percent reduction. Chromium and copper concentrations showed slight to moderate increases in
the TCLP-extracts over time. Unconfined compressive strengths increased an average of 71
percent.
6-131
-------
7.0 DEMONSTRATION COSTS
The cost of demonstrating STC's solidification/stabilization treatment process at the Selma
Pressure Treating site was approximately $1.5 million. This cost includes site characterization and
preparation, demonstration planning and field work, laboratory analyses, and report preparation.
The developer's portion of this cost was approximately $100,000. The balance of approximately
$1.4 million was allocated to the U.S. EPA SITE Program.
7.1 U.S. EPA SITE CONTRACTOR COSTS
Technical support to the U.S. EPA SITE program for the evaluation of the STC technology
was provided by a contractor and subcontractors. Each SITE project is divided into two phases:
planning (Phase I) and demonstration (Phase II). Phase I costs are actual costs; Phase II costs
include actual costs plus labor estimates through the completion of report preparation. Specific
activities under each phase and a cost breakdown for each phase are presented below.
7.1.1 Phase I: Planning Stage
Phase I activities included:
Solidification/stabilization technology review
Protocol evaluation
Site characterization, sampling, and analysis
Treatability testing
Development of the demonstration plan
Site subcontractor procurement
Costs for Phase I activities are summarized below:
* Labor $ 117,240
Equipment and supplies $ 8,500
Travel $ 16,980
Laboratory analyses $ 62,860
7-1
-------
7.1.2 Phase II: Demonstration Stage
Phase II activities included:
Mobilization and site preparation
Sample collection and field oversight
Sample processing after the 28-day curing period
Laboratory analyses
Report preparation
Long-term testing
Costs for Phase II activities are summarized below:
Labor $494,940
Equipment and supplies $ 85,000
« Travel/transportation $ 18,000
Analytical $630,167
Labor costs include estimates through report preparation. Transportation costs include
equipment mobilization and demobilization. Analytical costs include long-term testing.
7.2 DEVELOPER (STC) COSTS
The costs presented in this section were provided by STC. These costs were based upon all
expenses incurred by STC in preparing for and conducting the SITE demonstration.
Labor $ 25,500
Travel $ 21,710
Equipment $ 34,400
Transportation $ 4,060
Raw Materials $ 3,595
Miscellaneous $ 12,600
Equipment and miscellaneous costs include such one-time costs as. health and safety
equipment and training. Raw materials costs include the STC proprietary reagents.
Transportation costs include equipment mobilization and demobilization.
7-2
-------
8.0 REFERENCES
American Concrete Institute, 1992. The Building Code Requirements for Reinforced Concrete
with Commentary, ACI 318-92.
American Nuclear Society, 1986. Measurement of the Leachability of Solidified Low-Level
Radioactive Wastes by a Short-Term Test Procedure, ANS 16.1.
American Society for Testing and Materials, 1991. Annual Book of ASTM Standards. ASTM
Philadelphia, PA.
American Society of Agronomy, 1965, Methods of Soil Analysis, Part 1, Madison, WI.
CDM Federal Programs Corporation, 1988a. Final Remedial Investigation Report for the Selma
Pressure Treating Site, Selma, California, March.
CDM Federal Programs Corporation, 1988b. Feasibility Study Report for the Selma Pressure
Treating Site, Selma, California, June.
CDM Federal Programs Corporation, 1989. Pre-Remedial Design Soil Boring Report for the
Selma Pressure Treating Site, Selma, California, June.
Engineering-Science, Inc., 1992. Quality Assurance Report for the STC SITE Demonstration,
October.
Kiber Associates, Inc., 1992. PCP Thermal Study Final Report, May.
Shoemaker, D.P., C.W. Garland, and J.I. Steinfeld, Experiments in Physical Chemistry, 3rd ed.,
1974. McGraw-Hill, New York.
Stegemann, J.A. and P.L. Cote, 1991, Investigation of Test Methods for Solidified Waste
Evaluation - A Cooperative Program, Environmental Protection Series, Environment
Canada Report No. EPS 3/HA/8, January.
U.S. EPA, 1986a. Prohibition on the Placement of Bulk Liquid Hazardous Waste in Landfills,
Statutory Interpretative Guidance. EPA/530/SW86/016.
U.S. EPA, 1986b. Test Methods for Evaluating Solid Waste, SW-846, Volumes IA and II, Third
Edition, EPA Document Control Number 955-001-00000-1.
U.S. EPA, 1990a. STC SITE Program Demonstration Plan, Volume I: Draft Test Plan, October..
U.S. EPA, 1992. STC SITE Program Demonstration Plan, Volume III: Quality Assurance Project
Plan, October.
8-1
------- |