United States Office of EPA/540/R-502a

Environmental Protection Research and Development July 2004

Agency Cincinnati, OH 45268

EPA Stabilization of Mercury in 

Waste Material from the Sulfur 

Bank Mercury Mine 

Innovative Technology Evaluation Report 
EPA/540/R-04/502 

July 2004 

Stabilization of Mercury in Waste 

Material from the Sulfur Bank Mercury 

Mine 

Innovative Technology Evaluation Report 

National Risk Management Research Laboratory 

Office of Research and Development 

U.S. Environmental Protection Agency 

Cincinnati, Ohio 45268 
Notice 

The information in this document has been funded by the U.S. Environmental Protection Agency 

(EPA) under Contract Nos. 68-C5-0036 and 68-COO-179 to Science Applications International 

Corporation (SAIC). It has been subjected to the Agency’s peer and administrative reviews and has 

been approved for publication as an EPA document. Mention of trade names or commercial 

products does not constitute an endorsement or recommendation for use. 

ii 
Foreword 

The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation’s 

land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to 

formulate and implement actions leading to a compatible balance between human activities and the ability 

of natural systems to support and nurture life. To meet this mandate, EPA’s research program is providing 

data and technical support for solving environmental problems today and building a science knowledge 

base necessary to manage our ecological resources wisely, understand how pollutants affect our health, 

and prevent or reduce environmental risks in the future. 

The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for investigation of 

technological and management approaches for preventing and reducing risks from pollution that threaten 

human health and the environment. The focus of the Laboratory’s research program is on methods and their 

cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; 

protection of water quality in public water systems; remediation of contaminated sites, sediments and 

ground water; prevention and control of indoor air pollution; and restoration of ecosystems. NRMRL 

collaborates with both public and private sector partners to foster technologies that reduce the cost of 

compliance and to anticipate emerging problems. NRMRL’s research provides solutions to environmental 

problems by: developing and promoting technologies that protect and improve the environment; advancing 

scientific and engineering information to support regulatory and policy decisions; and providing the technical 

support and information transfer to ensure implementation of environmental regulations and strategies at 

the national, state, and community levels. 

This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is 

published and made available by EPA’s Office of Research and Development to assist the user community 

and to link researchers with their clients. 

Lawrence W. Reiter, Acting Director 

National Risk Management Research Laborator 

iii 
Abstract 

This report summarizes the findings of an extensive treatability study of three stabilization 

technologies for mercury immobilization on materials collected from the Sulfur Bank Mercury Mine 

(SBMM), located north of San Francisco, in Lake County, California. The SBMM site is believed to be 

contaminating the adjacent Clear Lake environment with mercury derived from historic mining 

practices at the site. The study was conducted as a joint effort between EPA’s Superfund Innovative 

Technology Evaluation (SITE) Program and the Mine Waste Technology Program (MWTP). Two 

mercury contaminated materials were selected for treatment by three types of stabilization 

technologies. 

The purpose of the study was to determine the effectiveness of the three stabilization technologies for 

immobilizing mercury in the waste rock materials and therefore reducing leachable mobile mercury in 

the effluent. Several mercury-bearing materials from the site were considered for testing. A material 

with high levels of leachable mercury was selected as the primary target of the study, and is referred 

to as “Mercury Ore”. As a secondary objective, treatment effectiveness was evaluated on material 

that was lower in mercury concentration, but present in large quantities and is referred to as “Waste 

Rock”. 

Three stabilization technologies were evaluated as part of this study: (1) a Silica Micro Encapsulation 

(SME) process developed by Klean Earth Environmental Company (KEECO), (2) an inorganic sulfide 

stabilization technology (ENTHRALL®) developed by E&C Williams, and (3) a generic phosphate 

treatment. 

The primary objective of this study was to determine the effectiveness of the three stabilization 

technologies (silica encapsulation, phosphate, and sulfide) in reducing the quantity of leachable 

mercury from SBMM material. Waste material evaluated in this study consisted of “mercury ore” from 

the south white gate pile and “waste rock” from the north yellow pile. The mercury ore was the 

primary test material due to its demonstrated ability to produce consistent and detectable levels of 

leachable mercury. The waste rock was included because it is a common material at the site, even 

though it yields lower levels of leachable mercury. In order to evaluate the performance of the three 

technologies, the leachable and mobile mercury (defined as the mercury in the <25μ filtered leachate 

fraction) from control columns receiving no treatment was compared to the leachable and mobile 

mercury in the treatment columns. Specifically, the objective was to achieve a 90% reduction in the 

total mass of mercury leached from each treatment relative to the control over a 12-week continuous 

column leaching study. 

Leachability results from the no treatment control columns revealed that the predominant source of 

leachable mercury was found in the particulate fraction, i.e. approximately 96%. The phosphate 

treatment dramatically increased the levels of both the particulate and dissolved fractions (<0.45μm) 

over the course of the 12-week study. The dramatic rise in leachable mercury brought about by the 

phosphate treatment invalidates its utility as a remedial alternative for materials at the SBMM site. 

The E&C William’s ENTHRALL®

 Technology did not appear to be effective in reducing the levels of 

mobile mercury in the mercury ore column tests. The total mass of mercury in both the particulate 

and dissolved fractions are statistically similar to the control. KEECO’s Silica Micro Encapsulation 

Technology applied both in situ and ex situ, was effective in reducing mobile mercury (<25 μm) very 

close to the 90% reduction goal of the study. However, there was a significant increase in the mass 

mercury levels in the dissolved fraction (<0.45μm). The in situ applications exhibited a 198% 

increase relative to the control, and the ex situ exhibited a 238% increase. 

iv 
Contents 

Notice.................................................................................................................................................. ii 

Foreword............................................................................................................................................ iii 

Abstract............................................................................................................................................... v 

Tables ............................................................................................................................................... viii 

Figures ............................................................................................................................................... ix 

Abbreviations and Acronyms .............................................................................................................. x 

Acknowledgement ............................................................................................................................ xii 

Executive Summary.......................................................................................................................... xiii 

1.0 Introduction ......................................................................................................................... 1-1 

1.1 Background............................................................................................................ 1-1 

1.1.1 Description of the SBMM Site................................................................... 1-1 

1.1.2 E&C Williams Enthrall®

 Technology ......................................................... 1-1 

1.1.3 Kleen Earth Environmental Company Silica Micro Encapsulation (SME) 

Process..................................................................................................... 1-2 

1.1.4 Phosphate................................................................................................. 1-3 

1.2 Brief Description of the Superfund Innovative Technology (SITE) and Mine 

Waste Technology (MWTP) Programs.................................................................. 1-4 

1.3 The SITE Demonstration Program and Reports ....................................................1-4 

1.4 Purpose of the Innovative Technology Evaluation Report (ITER)......................... 1-5 

1.5 Sources of Further Information...............................................................................1-5 

2.0 Technology Application Analysis ........................................................................................ 2-1

2.1 Key Features of the Stabilization Process............................................................. 2-1 

2.2 Operability of the Technology................................................................................ 2-2 

2.3 Applicable Wastes ................................................................................................. 2-2 

2.4 Availability and Transportability of Equipment....................................................... 2-2 

2.5 Materials Handling Requirements ......................................................................... 2-2 

2.6 Range of Suitable Site Characteristics .................................................................. 2-3 

2.7 Limitations of the Technology................................................................................ 2-4 

2.8 Applicable or Relevant and Appropriate Requirements (ARARs) for 

Stabilization Processes ......................................................................................... 2-3 

2.8.1 Comprehensive Environmental Response, Compensation, and 

Liability Act (CERCLA) ............................................................................. 2-3 

2.8.2 Resource Conservation and Recovery Act .............................................. 2-5 

2.8.3 Clean Air Act (CAA ................................................................................... 2-5 

2.8.4 Clean Water Act (CWA)............................................................................ 2-6 

2.8.5 Safe Drinking Water Act (SDWA)............................................................. 2-6 

2.8.6 Occupational Safety and Health Administration (OSHA) Requirements.. 2-6

 3.0 Economic Analysis.............................................................................................................. 3-1 

3.1 Introduction ............................................................................................................ 3-1

v 
3.2 Cost Estimate Scope ............................................................................................. 3-1 

3.3 Factors Affecting Estimated Cost ...........................................................................3-1 

3.4 Issues and Assumptions........................................................................................ 3-2 

3.4.1 Site Characteristics................................................................................... 3-2 

3.4.2 Design and Performance Factors............................................................. 3-2 

3.4.3 Financial Assumptions.............................................................................. 3-2 

3.5 Basis for Economic Analysis ................................................................................. 3-2 

3.5.1 Site Preparation ........................................................................................ 3-2 

3.5.2 Permitting and Regulatory Requirements ................................................ 3-2 

3.5.3 Capital Equipment .................................................................................... 3-2 

3.5.4 Startup and Fixed Costs ........................................................................... 3-3 

3.5.6 Labor......................................................................................................... 3-3 

3.5.6 Consumables and Supplies...................................................................... 3-3 

3.5.7 Utilities ...................................................................................................... 3-3 

3.5.8 Effluent Treatment and Disposal .............................................................. 3-3 

3.5.9 Residuals Shipping and Disposa.............................................................. 3-4 

3.5.10 Analytical Services ................................................................................... 3-4 

3.5.11 Maintenance and Modifications ................................................................ 3-4 

3.5.12 Demobilization/Site Restoration ............................................................... 3-4 

3.6 Vendor Cost Estimates .......................................................................................... 3-4 

3.6.1 E&C Williams Enthrall®

 Technology ......................................................... 3-4 

3.6.2 KEECO’s SME Technology ...................................................................... 3-7 

3.7 Cost Summary .................................................................................................... 3-10 

4.0 Treatment Effectiveness ..................................................................................................... 4-1 

4.1 Pre-demonstration Studies .................................................................................... 4-1 

4.1.1 SPLP Characterizations ........................................................................... 4-1 

4.1.2 Leachability Studies.................................................................................. 4-2 

4.1.3 Geochemical and Mineralogical Evaluation of Particulates ..................... 4-3 

4.1.4 Extended Leachability Study .................................................................... 4-4 

4.1.5 Conclusion From Leachability/Characterization Studies .......................... 4-5 

4.1.6 Pre-Demonstration Kinetic Column Studies ............................................. 4-6 

4.2 Project Objectives.................................................................................................. 4-6 

4.2.1 Primary and Secondary Objectives .......................................................... 4-6 

4.2.1.1 Primary Objective ........................................................................ 4-7 

4.2.1.2 Secondary Objectives.................................................................. 4-9 

4.3 Experimental Design.............................................................................................. 4-9 

4.3.1 Column Studies ........................................................................................ 4-9 

4.3.2 Humidity Cell Tests................................................................................ 4-11 

4.3.3 Mineralogical and Geochemical Tests .................................................. 4-11 

4.3.4 Humic/Fulvic Acid Tests ........................................................................ 4-11 

4.4 Results ................................................................................................................ 4-12 

4.4.1 Kinetic Column Study Results ............................................................... 4-12 

4.4.1.1 Column Studies on Mercury Ore Material – Primary Objective. 4-12 

4.4.1.1.1 Control Column ........................................................ 4-15 

4.4.1.1.2 Phosphate Treatment............................................... 4-16 

4.4.1.1.3 E&C Williams Sulfide Treatment .............................. 4-17 

4.4.1.1.4 KEECO In Situ and Ex Situ ...................................... 4-18 

4.4.1.2 Waste Rock Column Studies.................................................... 4-20 

4.4.2 Humidity Cell Tests................................................................................ 4-22 

4.4.3 Synthetic Precipitation Leaching Procedure (SPLP)............................. 4-23 

4.4.4 Humic/Fulvic Acid Leaching Tests......................................................... 4-23 

4.4.5 Geochemical and Mineralogical Analyses............................................. 4-25 

vi 
5.0 

4.5 Developer’s Comments ...................................................................................... 4-25 

4.5.1 E&C William’s Comments...................................................................... 4-25 

4.5.2 KEECO’s Comments ............................................................................. 4-25 

Quality Assurance Summary ...............................................................................................5-1

5.1 Introduction ............................................................................................................ 5-1 

5.2 Conclusions and Data Quality Limitations ............................................................. 5-1 

vii 
Tables 

Table Page 

2-1 Potential Federal and State ARARs for Stabilization Remediation Processes .............. 2-4 

3-1 Labor Unit Costs ............................................................................................................ 3-9 

3-2 Cost Summary .............................................................................................................. 3-10 

4-1 SPLP Leachability Results from Various SBMM Materials ............................................ 4-2 

4-2 Replicate SPLP Analyses on Roasted Tailings .............................................................. 4-2 

4-3 Results of Triplicate SPLP Leaching Experiment ........................................................... 4-3 

4-4 Results from the Modified MWMP Leachate Test with Variable Filtration ..................... 4-3 

4-5 Results from the Extended Leachability Study ............................................................... 4-5 

4-6 Mercury in Untreated Mercury Ore and Waste Rock Materials...................................... 4-6 

4-7 Kinetic Column Leachability Study ................................................................................. 4-7 

4-8 Treatability Study Test Parameters ................................................................................ 4-8 

4-9 Total Mass Mercury Leached from Mercury Ore Columns Over Twelve Weeks ......... 4-13 

4-10 Mercury Ore Leachability Results By Week ................................................................. 4-14 

4-11 Weekly Average Mass Mercury Leached from Waste Rock Columns ......................... 4-21 

4-12 SPLP Results for Mercury Ore and Waste Rock Material............................................ 4-23 

4-13 Results from the Humic/Fulvic Acid Leaching Tests .................................................... 4-24 

5-1 Accuracy Data for Mercury for SBMM Column Leachates............................................. 5-1 

5-2 Accuracy Data for Mercury for SBMM Extended Column Leachates ............................ 5-1 

viii 
Figures 

1-1 Features of the SBMM site ............................................................................................. 1-2 

4-1 Locations of samples from SBMM site ........................................................................... 4-1 

4-2 Turbidity and leachable mercury from SPLP and MWMP tests ..................................... 4-3 

4.3 Mercury adsorbed on clay particles as indicated by the number of x-ray counts 

 adjusted by the sample................................................................................................... 4-4

4-4 Comparison of the total mass mercury leached from the mercury ore columns .......... 4-13 

4-5 Dissolved and particulate leached Hg (mass) from mercury ore control columns ........ 4-16 

4-6 Turbidity vs. Hg for the <0.45μm fraction – mercury ore control columns.................... 4-16 

4.7 Dissolved and particulate leached Hg (mass) from mercury ore phosphate columns .. 4-17 

4-8 Dissolved and particulate leached Hg (mass) from mercury ore sulfide columns........ 4-18 

4-9 Dissolved and particulate leached Hg (mass) from mercury ore KEECO 

in situ columns .............................................................................................................. 4-18 

4-10 Dissolved and particulate leached Hg (mass) from mercury ore KEECO 

ex situ columns ........................................................................................................... 4-18 

4-11 Turbidity vs. Hg for the <0.45μm fraction – mercury ore, KEECO, 

 and control columns...................................................................................................... 4-19 

4-12 pH of KEECO and control column effluents – mercury ore material ............................ 4-19 

4-13 Turbidity vs. Hg for the <0.45Fm fraction waste rock phosphate column ..................... 4-20 

4-14 Turbidity vs. Hg for the <0.45Fm fraction waste rock KEECO columns....................... 4-22 

4-15 Results from Humidity Cell tests on mercury ore material - <25μm fraction ................ 4-22 

4-16 Results from Humidity Cell tests on mercury ore material - <0.45μm fraction ............. 4-22 

4-17 Turbidity vs. Hg for the <0.45μm and <0.1μm fractions –humic/fulvic 

 acid leaching tests ....................................................................................................... 4-25 

ix 
Abbreviations and Acronyms 

AQCR Air Quality Control Regions 

AQMD Air Quality Management District 

ARARs Applicable or Relevant and Appropriate Requirements 

ASTM American Society for Testing and Materials 

CAA Clean Air Act 

CCNY City College of New York 

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act 

CFR Code of Federal Regulations 

CSCT Consortium for site characterization 

CV Coefficient of variation 

CWA Clean Water Act 

DI Deionized 

DOE U.S. Department of Energy 

ECWI E&C Williams Incorporated 

EPA U.S. Environmental Protection Agency 

FS Feasibility study 

G&A General and administrative 

HSWA Hazardous and Solid Waste Amendments 

ICV Internal calibration verification 

ITER Innovative Technology Evaluation Report 

IM Interim measure 

KEECO Kleen Earth Environmental Company 

LCS Laboratory control sample 

L/hr Liters per hour 

mg/Kg Milligrams per kilogram 

mg/L Milligrams per liter 

mL Milliliter 

MS/MSD Matrix spike/matrix spike duplicate 

MWMP Meteoric Water Mobility Procedure 

MWTP Mine Waste Technology Program 

NA Not analyzed 

NAAQS National Ambient Air Quality Standards 

NCP National Oil and Hazardous Substances Pollution Contingency Plan 

NPDES National Pollutant Discharge Elimination System 

NRMRL National Risk Management Research Laboratory (EPA) 

NSCEP National Service Center for Environmental Publications 

ND Non-detectable, or not detected at or above the method detection limit 

NPDWS National primary drinking water standards 

NTU Nephelometric turbidity unit 

OSHA Occupational Safety and Health Administration 

ORD Office of Research and Development (EPA) 

OSWER Office of Solid Waste and Emergency Response (EPA) 

PDI Prosonic Drilling Company 

ppb Parts per billion 

ppm Parts per million 

ppmv Parts per million by volume 

PPE Personal protective equipment 

PQL Practical quantitation limit 

PVC Polyvinyl chloride 

x 
POTW Publicly owned treatment works 

QA/QC Quality assurance/Quality control 

QAPP Quality assurance project plan 

RI/FS Remedial Investigation / Feasibility Study 

RCRA Resource Conservation and Recovery Act 

RPD Relative percent difference 

RSD Relative Standard Deviation 

SARA Superfund Amendments and Reauthorization Act 

SAIC Science Applications International Corporation 

SBMM Sulfur Bank Mercury Mine 

SDWA Safe Drinking Water Act 

SEM/EDS Scanning Electron Microscopy/Energy Dispersive Spectroscopy 

SME Silica Micro Encapsulation 

SVE Soil vapor extraction 

SPLP Synthetic Precipitation Leaching Procedure 

SW-846 Test methods for evaluating solid waste, physical/chemical methods 

SWDA Solid Waste Disposal Act 

SITE Superfund Innovative Technology Evaluation 

S.U. Standard units 

TCLP Toxicity Characteristic Leaching Procedure 

TER Technology Evaluation Report 

μg Micrograms 

μg/L Micrograms per liter 

μm Micron 

UCL Upper confidence level 

USEPA United States Environmental Protection Agency 

USGS United States Geological Survey 

w/w Weight to weight ratio 

XRD X-ray diffraction 

XRF X-ray fluorescence 

xi 
Acknowledgments 

This report was prepared under the direction of Mr. Edward Bates, the EPA Technical Project 

Manager for this SITE demonstration, and Mr. Roger Wilmoth, Director of EPA’s Mine Waste 

Technology Program, both of the National Risk Management Research Laboratory (NRMRL) in 

Cincinnati, Ohio. EPA review of this report was conducted by Diana Bless of USEPA and Dan 

McMindes of USACE. . 

The demonstration required the combined services of several individuals from MSE-Technology 

Applications (MSE-TA), and Science Applications International Corporation (SAIC). Ms. Suzzann 

Nordwick served as the project manager for MSE-TA. Dr. Scott Beckman of SAIC served as the 

SITE work assignment manager for the implementation of treatability study activities and completion 

of all associated reports. The treatability study was performed at MSE-TA’s facility in Butte, Montana. 

The cooperation and efforts of these organizations and individuals are gratefully acknowledged. 

This report was prepared by Dr. Scott Beckman, Ms. Melissa Hammett, and Ms. Rita Stasik of SAIC. 

Ms. Stasik also served as the SAIC Quality Assurance (QA) Coordinator for data review and 

validation. Joseph Evans (the SAIC QA Manager) internally reviewed the report. 

xii 
Executive Summary 

Three innovative technologies for in situ stabilization of 

heavy metals were demonstrated in a large-scale 

treatability study performed on materials from the Sulfur 

Bank Mercury Mine, a superfund site in northern 

California. The treatability study was jointly sponsored by 

two EPA programs; the Mine Waste Technology 

Program (MWTP) and the Superfund Innovative 

Technology Evaluation (SITE) Demonstration Program. 

The purpose of the study was to determine the 

effectiveness of these stabilization technologies for 

immobilizing mercury in sulfide mine waste materials 

such as those found at the Sulphur Bank Mercury Mine 

(SBMM) site and therefore reduce the potential for 

leaching and mobilizing mercury into the environment. 

The SBMM is a non-operating facility located on the 

South shore of Clear Lake in northern California where 

some of the highest mercury concentrations in the world 

have been recorded. Several mercury-bearing materials 

from the site were considered for testing. A waste 

material with high levels of leachable mercury (mercury 

ore) was selected as the primary target of the study. As 

a secondary objective, treatment effectiveness was 

evaluated on a waste material that was lower in mercury 

concentration, but present in large quantities (waste 

rock). 

Stabilization technologies use chemical reagents to 

reduce the mobility of contaminants in a solid matrix. 

The three processes used in the treatability study are: 

(1) the Silica Micro Encapsulation (SME) process, 

developed by Klean Earth Environmental Company 

(KEECO) which encapsulates metals in an impervious 

microscopic silica matrix, thus preventing metals in the 

treated material from leaching into the environment, (2) 

Enthrall®

, developed by E&C Williams, Inc., which uses 

an inorganic sulfide chemical to bind metals within the 

matrix, and (3) a generic phosphate treatment that forms 

insoluble phosphate salts containing the contaminant. 

Since metal contaminants cannot be destroyed, each of 

the selected technologies is targeted to inhibit the 

release of mercury from the mine materials into the 

environment. 

The treatability study took place at the research facility of 

MSE in Butte Montana, from November 15, 2000 to April 

29, 2001. The primary test procedure was an in situ 

kinetic column leach. The vendors each applied their 

reagent to four-kilogram splits of each of the two test 

materials that had been loaded into 3-foot PVC columns. 

The SME technology was applied ex situ as well, and 

then the treated material was loaded into the columns. 

To evaluate each technology’s ability to reduce the 

amount of leachable mercury, single pass, low flow 

leaching was performed for twelve weeks, with weekly 

sampling for mercury and other constituents. The 

primary objective of the study was for each technology to 

achieve a 90% reduction in the mass of mobile mercury 

in the leachate over the twelve week period, as 

compared to untreated control columns receiving a water 

leach. Several secondary studies were performed 

along with the primary column study, including humidity 

cell testing to simulate extreme weathering conditions, 

and humic/fulvic acid leaching to simulate the effect of 

high molecular weight organic constituents from 

vegetative caps. Treated and untreated samples and 

leachates were also analyzed to determine other 

chemical characteristics and mineralogical changes due 

to the treatments. 

Conclusions from the study are summarized below: 

• Pre-demonstration leachability studies revealed that 

the dominant form of leachable mercury was in a 

particulate and mobile form. These studies 

indicated that leaching with a meteoric solution 

released particulates that remained suspended in 

solution and therefore could be mobile in a 

groundwater and/or surface water hydraulic system. 

Levels of dissolved mercury were low in these 

leaching studies. Based on these tests, a 

continuous column leaching test design was used to 

collect effluent samples over a 12-week period to 

evaluate leachable mercury in mobile (<25μm) and 

dissolved (<0.45μm) fractions from treated and 

control columns. 

• The conventional phosphate treatment dramatically 

increased the levels of mobile mercury (<25μm 

fraction) over the course of the12-week study in the 

mercury ore columns. A 947% increase in the total 

xiii 
mass of mercury leached occurred relative to the 

control. 

• E&C Williams’ sulfide treatment did not appear to be 

effective in reducing the levels of mobile mercury in 

the mercury ore column tests. There was no 

significant difference in the cumulative levels of 

mobile mercury in the effluent from the sulfide 

treatment relative to the control. 

• KEECO’s Silica Micro Encapsulation Technology 

was effective in reducing mobile mercury (<25 μm) 

very close to the 90% reduction goal of the study. 

However, the dissolved mercury portion (<0.45μm) 

of the mobile fraction increased by approximately 

200% relative to the control. 

• A leachability test using humic and fulvic acids on 

untreated mercury ore was performed to determine if 

these organic acids would accelerate the release of 

mercury from the waste material. A vegetative cap 

may be used to reduce meteoric water infiltration, 

and plant derived organic acids could impact 

mercury leachability. Leaching with humic/fulvic 

acids did not increase the generation of either 

particulate or dissolved mercury under the 

conditions of the test. 

xiv 
Section 1.0 

Introduction 

This section provides background information about the 

Superfund Innovative Technology Evaluation (SITE) 

Program and the Mine Waste Technology Program 

(MWTP), discusses the purpose of this Innovative 

Technology Evaluation Report (ITER), describes the 

Sulfur Bank Mercury Mine (SBMM) site, and describes 

the technologies that were applied in the treatability 

study on the SBMM materials. Key contacts are listed at 

the end of this section for inquires regarding the SITE 

and MWTP Programs, the technologies, and the site for 

which the treatability study was conducted. 

1.1 Background 

A treatability testing program was conducted to 

determine the effectiveness of in situ stabilization 

technologies on controlling the release of mobile 

mercury from the Sulfur Bank Mercury Mine in Lake 

County, California. Three stabilization technologies 

were evaluated during this study: (1) E&C Williams’ 

Enthrall® sulfide based treatment, (2) Kleen Earth 

Environmental Company’s (KEECO) Silica Micro 

Encapsulation (SME) process, and (3) a generic 

phosphate treatment. Pre-demonstration studies 

identified suitable materials from the site for testing, 

identified a potential mercury release mechanism, and 

evaluated several leachability protocols. Samples of two 

types of material from the site (mercury ore from the 

south white gate pile and waste rock from the north 

yellow pile) were collected and screened in the field, 

then taken to the research facility of MSE in Butte, 

Montana for demonstration testing. Kinetic column 

leaching tests were performed to determine the 

effectiveness of the treatments in reducing the 

generation of mobile mercury. 

1.1.1 Description of the SBMM Site 

The Sulfur Bank Mercury Mine (SBMM) is an EPA 

Superfund site, located on the south shore of the Oaks 

Arm of Clear Lake, in Lake County, California (Figure 1-

1). With a surface area of 68 square miles, Clear Lake 

is the largest lake entirely in California and is a popular 

fishing, resort and watersport destination; thus the 

mercury contamination in the lake has caused great 

concern. Sulfur Bank was mined periodically from 1865 

to 1957 with open pit mining beginning in 1915. In the 

late 1920’s, heavy earthmoving equipment began to be 

used on a large-scale basis, which dramatically 

increased the environmental impacts of mining. Various 

mining activities over the years have deposited amounts 

of mercury in the Clear Lake ecosystem. 

Several pits were excavated at the mine, the larger 

being Herman Pit, which is located a few hundred feet 

from the lake. Surface runoff, subterranean streams, 

surface seeps and groundwater have all played a part in 

filling the pit, which seeps through the waste rock dam 

into Clear Lake. Metal-laden acid mine drainage results 

from the interaction of surface and ground waters with 

sulfide bearing mine wastes, in and around the pit. 

Degradation of water quality in Clear Lake may have 

been caused largely by sulfate and acidity loading from 

the Sulfur Bank Mercury Mine, though the transport 

mechanisms remain unclear. 

1.1.2 E&C Williams Enthrall®

 Technology (as 

provided by E&C Williams) 

Enthrall® is a chemical stabilization process that uses 

inorganic sulfide to target heavy metals and/or cyanide 

in soil, liquid or sludge. The product, available in solid, 

liquid or granular form, has been developed for use in inline treatment systems. The granular, pelletized form 

has also been developed that can be used as a reactive 

filter bed, which captures metals by forming sulfide 

bonds as the contaminated solution flows through the 

pellets. The treatment forms a permanent bond between 

the Enthrall®

 surface and heavy metals. Bonds remain 

resistant to leaching even though subsequent conditions 

may involve harsh pHs, as has been demonstrated by 

the Multiple Extraction Procedure that subjects materials 

repeatedly to an acidic environment. According to E&C 

Williams, a typical conventional treatment increases the 

volume of the treated material by 25 to 200%, whereas 

the ENTHRALL®

 addition often increases volume by only 

5-10%. The smaller volume is advantageous during 

treatment, as less material must be handled. 

Additionally, the reduced quantity of treated material that 

must be transported or stored can significantly lower 

costs. 

1-1 
Figure 1-1. Features of the SBMM site. 

The ENTHRALL® technology is applicable to in-line 

process streams and wastes containing heavy metals 

and/or cyanide and may be applied by either in situ or ex 

situ methods. The reagent may be applied to the 

surface and mixed in, or may be injected under pressure 

to achieve contact with deeper materials. 

Successful application of the ENTHRALL®

 reagent must 

take place in a neutral to alkaline environment. When 

the calcium sulfide reagent is applied under acidic 

conditions, some hydrogen sulfide gas is produced, 

which reduces the effectiveness of metals stabilization. 

No hazardous residuals are produced by the technology. 

In an in-line process the residual would be a 

nonhazardous form of the original potentially hazardous 

material, which could then be stored on site or disposed 

of in a Subtitle D landfill. 

1.1.3 Kleen Earth Environmental Company Silica 

Micro Encapsulation (SME) Process (as 

provided by KEECO) 

Klean Earth Environmental Company (KEECO) has 

developed a Silica Micro Encapsulation (SME) process, 

which encapsulates metals in an impervious microscopic 

silica matrix, thus eliminating the availability of the 

metals to have adverse human health or environmental 

effects. KEECO has developed three products for 

applying the technology to water (KB-1), solid waste 

(KB-SEA) and radioactive wastewater (META-LOCK). 

KB-SEA was used in this treatability study. 

The SME process is a high-performance, low-cost 

technology for preventing and treating metal 

contamination in water and soils, as it uses silica, which 

is one of the most common and inert substances on 

earth. The durability of silica also contributes to the 

value of the treatment, which works by isolating the 

metals in question from contacting the environment. 

Metals cannot be destroyed, nor can they be broken 

down into other forms, so the most effective control 

method is to simply isolate them from contacting 

humans and the natural environment. KEECO’s SME 

process differs from typical stabilization treatments in 

that the chemical formulation causes an electrokinetic 

reaction which facilitates transport of the metals towards 

the SME reactive components, thus enhancing contact 

with the target metals and reducing the amount of 

chemical required to achieve the desired results. The 

1-2 
use of silica itself is another significant departure from 

more typical stabilization treatments. 

The SME reagent is designed to be applied in situ by 

mixing a small amount, in either dry or slurry form, into 

the contaminated soil. Boulder-sized material would be 

coated with a slurry of the reagent. The volume of the 

material should only be increased by 1-2% due to the 

quantity of reagent added. If the reagent is applied dry, 

a small amount of water may be added to initiate the 

chemical reaction. A reaction period of 48 hours is 

recommended before initial testing for results. For areas 

of high metals concentration, a tilling device may be 

used to produce further contact between reagent and 

contaminated soil. This may be indicated in areas of 

high concentration and hydraulic transport rates. 

SME is applicable to wastewater, sediment, sludge, soil, 

mine waste, radioactive wastewater and other complex 

media. Silica bridging between encapsulated particles in 

treated materials increases compressive strength over 

time, which can enhance the usefulness of the treated 

waste as backfill. 

One problem that could be encountered with 

stabilization treatments is that weathering and exposure 

to changes in pH can break down the bonding and allow 

metals to be released. The long-term stability 

associated with SME treated wastes may indicate 

applicability for large in situ applications where treated 

materials will remain on site, exposed to the 

environment. The SME technology has been designed 

to treat metals-contaminated water and soils without 

producing any hazardous by-products. 

Where the technology is applied correctly and in a 

manner that allows for thorough contact with the metal 

contaminants of concern, no hazardous wastes should 

be produced. Water treatments using the SME products 

produce a dense sediment or sludge that can be 

separated from the water and disposed of on-site or in a 

sanitary landfill. Treated soils and other solids can be 

left in place or used as backfill material. 

The effectiveness of the SME process is somewhat 

dependent on the substrate pH. Highly alkaline 

substrates (such as unstable sludge from water 

treatment plants, or soils that have been amended with 

lime) having a pH greater than 8 may produce 

resistance to the reactive process. In such an 

environment, a pretreatment step to lower the pH by 

may be necessary prior to the addition of SME. In this 

case, an evaluation of the effectiveness and economics 

of the multi-step treatment would be required. 

According to KEECO, the single most limiting factor in 

the effectiveness of the SME technology is contact with 

the metal-bearing particles. Where the chemicals 

cannot make contact with all the metal bearing 

substrate, for example in the in situ treatment of large 

waste rock or tailings piles, effectiveness would be 

limited. KEECO is in the process of designing deep 

subsurface injection methods to more effectively 

introduce the reagent, in an effort to overcome this 

inherent limitation of in situ treatment. SME is solely 

applicable as a stabilization technology and cannot be 

used as a reactive barrier. 

1.1.4 Phosphate 

Phosphate-based binders have been used successfully 

to reduce solubility of heavy metal contaminants, 

particularly lead, in soils. The reagents form bonds with 

metal ions to form insoluble metal complexes called 

pyromorphites. The kinetics of the reaction depends on 

the phosphate form in the reagent. Phosphates have 

been used in in situ remediation by land farming 

(plowing and grading), injection, and surface application 

and auguring. 

During the design phases of the treatability study, there 

was an interest in testing phosphate as a binding agent 

for mercury. A generic phosphate reagent was obtained 

for testing. Phosphates stabilize metals by chemically 

binding them into new stable phosphate phases, such as 

apatites, and other relatively insoluble phases in the soil. 

Phosphates have been included in the reagent mixes for 

stabilizing lead during remediation of several Superfund 

sites. 

Metals stabilized in apatite minerals are durable and 

resistant to leaching because the mineral structure is 

stable from pH 2 to 12 and up to 1000 degrees C, in 

liquids or solids and through geologic disruptions. 

Previous studies have indicated that as little as 1% (w/w) 

phosphate addition could remediate metal-contaminated 

soils. 

Earlier studies have found phosphates to be effective at 

stabilizing copper, lead, zinc, cadmium, nickel, 

lanthanides and actinides (Chen et al., 1997). 

Generally, the process is applicable to inorganics, 

including radionuclides, but not to organic contaminants 

or pesticides. 

As with all stabilization remediations, the success of the 

process is dependent on the reagent and the waste. 

Generally, site-specific treatability studies are required. 

1-3 
Additionally, long-term stability has not been identified 

for very many combinations, so durability studies may be 

required. Lead phosphate is toxic by inhalation, so the 

formation of that compound would also have to be 

evaluated. While phosphate-binding has been well 

documented for lead remediation, there is little 

information on mercury stabilization. 

1.2 Brief Description of the Superfund Innovative 

Technology Evaluation (SITE) and Mine 

Waste Technology (MWTP) Programs 

The SITE Program is a formal program established by 

the EPA's Office of Solid Waste and Emergency 

Response (OSWER) and Office of Research and 

Development (ORD) in response to the Superfund 

Amendments and Reauthorization Act of 1986 (SARA). 

The SITE Program promotes the development, 

demonstration, and use of new or innovative 

technologies to clean up Superfund sites across the 

country. 

The SITE Program's primary purpose is to maximize the 

use of alternatives in cleaning hazardous waste sites by 

encouraging the development and demonstration of 

new, innovative treatment and monitoring technologies. 

It consists of three major elements: 

• Demonstration Program, 

• Consortium for Site Characterization 

Technologies (CSCT) 

• Technology Transfer Program. 

The objective of the Demonstration Program is to 

develop reliable performance and cost data on 

innovative technologies so that potential users can 

assess the technology's site-specific applicability. 

Technologies evaluated are either available 

commercially or close to being available for full-scale 

remediation of Superfund sites. SITE demonstrations 

usually are conducted at hazardous waste sites under 

conditions that closely simulate full-scale remediation 

conditions, thus assuring the usefulness and reliability of 

the information collected. Data collected are used to 

assess: (1) the performance of the technology; (2) the 

potential need for pre- and post-treatment of wastes; (3) 

potential operating problems; and (4) the approximate 

costs. The demonstration also provides opportunities to 

evaluate the long-term risks and limitations of a 

technology. 

Existing and new technologies and test procedures that 

improve field monitoring and site characterizations are 

explored in the CSCT Program. New monitoring 

technologies, or analytical methods that provide faster, 

more cost-effective contamination and site assessment 

data are supported by this program. The CSCT 

Program also formulates the protocols and standard 

operating procedures for demonstration methods and 

equipment. 

The Technology Transfer Program disseminates 

technical information on innovative technologies in the 

Demonstration and CSCT Programs through various 

activities. These activities increase awareness and 

promote the use of innovative technologies for 

assessment and remediation at Superfund sites. The 

goal of technology transfer activities is to develop 

interactive communication among individuals requiring 

up-to-date technical information. 

The Mine Waste Technology Program (MWTP) is an 

interagency effort by the EPA and U.S. Department of 

Energy (DOE) focused on developing and proving 

technologies that provide solutions to the remedial 

problems of abandoned mines and the compliance 

issues of active mines throughout the United States. 

Excluding coal production, the mining industry produces 

between 1 and 2 billion tons of mine waste annually. 

The 1985 Report to Congress estimated the total 

noncoal mine waste volume in the United States at 50 

billion tons. MWTP priorities include at-source control 

technologies, improvements of short-term technologies 

for the alleviation of extreme environmental problems 

and implementing resource recovery methods to help 

alleviate the costs of remediation. 

1.3 The SITE Demonstration Program 

and Reports 

Technologies are selected for the SITE Demonstration 

Program through annual requests for proposals. This 

solicitation ended in 1995. EPA Office of Research and 

Development (ORD) staff review the proposals to 

determine which technologies show the most promise 

for use at Superfund sites. Technologies chosen must 

be at the pilot- or full-scale stage, must be innovative, 

and must have some technological and/or cost 

advantage over existing technologies. Mobile 

technologies are of particular interest. 

Once the EPA has accepted a proposal, cooperative 

agreements between the EPA and the developer 

establish responsibilities for conducting the 

demonstration and evaluating the technology. The 

developer is responsible for demonstrating the 

technology at the selected site and is expected to pay 

any costs for transport, operation, and removal of the 

1-4 
equipment. The EPA is responsible for project planning, 

sampling and analysis, quality assurance and quality 

control, preparing reports, disseminating information, 

and provides arrangements for transporting and 

disposing of treated waste materials. Usually, results of 

Demonstration Programs are published in three 

documents: the SITE Demonstration Bulletin, the 

Technology Capsule, and the Innovative Technology 

Evaluation Report (ITER). The Bulletin describes the 

technology and provides preliminary results of the field 

demonstration. The Technology Capsule provides more 

detailed information about the technology, and 

emphasizes key results of the SITE demonstration. The 

ITER provides detailed information on the technology 

investigated, a categorical cost estimate, and all 

pertinent results of the SITE demonstration. An 

additional report, the Technology Evaluation Report 

(TER), is not formally published. The TER contains the 

raw data collected during the demonstration and 

provides a detailed quality assurance review of the data. 

For the treatability study using KEECO’s SME, E&C 

Williams’ Enthrall®, and a generic phosphate technology, 

a SITE Capsule and ITER have been prepared; all for 

use by remedial managers in making detailed 

evaluations of the technologies for applications to 

specific sites and wastes. A TER is also submitted for 

this demonstration to serve as verification 

documentation. 

1.4 Purpose of the Innovative 

Technology Evaluation Report (ITER) 

This ITER provides information on a treatability study 

performed using KEECO’s SME, E&C Williams’ 

Enthrall®

, and a generic phosphate treatment. This 

report includes a comprehensive description of the study 

and its results. The ITER is intended for use by EPA 

remedial project managers (RPMs), EPA on-scene 

coordinators (OSCs), contractors, and other decisionmakers carrying out specific remedial actions. The ITER 

is designed to aid decision-makers in evaluating specific 

technologies for further consideration as applicable 

options in a particular cleanup operation. This report 

represents a critical step in the development and 

commercialization of a treatment technology. 

To encourage the general use of demonstrated 

technologies, the EPA provides information regarding 

the applicability of each technology to specific sites and 

wastes. The ITER includes information on cost and 

desirable site-specific characteristics. It also discusses 

advantages, disadvantages, and limitations of the 

technology. 

Each SITE demonstration evaluates the performance of 

a technology in treating a specific waste matrix. The 

characteristics of other wastes and other sites may differ 

from the characteristics of the treated waste. Therefore, 

a successful demonstration of a technology at one site 

does not necessarily ensure that it will be applicable at 

other sites. Data from the demonstration may require 

extrapolation for estimating the operating ranges in 

which the technology will perform satisfactorily. Only 

limited conclusions can be drawn from a single field 

demonstration. 

1.5 Sources of Further Information 

EPA Work Assignment Manager 

Ed Bates 

U.S. EPA 

National Risk Management Research Laboratory 

(NRMRL) 

26 W. Martin Luther King Dr. 

Cincinnati, OH 45268 

(513) 569-7774 

Mine Waste Technology Program 

Roger Wilmoth 

U.S. EPA 

National Risk Management Research Laboratory 

(NRMRL) 

26 W. Martin Luther King Dr. 

Cincinnati, OH 45268 

(513) 569-7509 

E & C Williams Project Manager 

Charlie Williams 

E & C Williams, Inc. 

120 Varnfield Dr, Ste. A 

Summerville, SC 29483 

(843) 821-4200 

KEECO Project manager 

Amy Anderson 

19023 36th Ave. West, Ste. E 

Lynnwood, WA 98036 

(425) 778-7165 

1-5 
Section 2.0 

Technology Application Analysis 

This section addresses the general applicability of 

stabilization processes to sites containing mercury 

contamination, with specific information regarding the 

technologies evaluated in the SBMM treatability study 

where appropriate. Since the report is based on a 

treatability study rather than a field scale demonstration, 

there is no actual treatment system to describe; however, 

the vendors were asked to conceive and provide cost 

estimates for a full scale application to two piles at the 

SBMM site. Details on the selected piles can be found in 

Section 3.2. 

Stabilization technologies include a broad range of 

treatment options that are designed to immobilize 

contaminants in the existing material, rather than reducing 

or removing them. Stabilization processes depend on a 

chemical reaction between the reagent and the 

contaminant of concern to stabilize the contaminant within 

the matrix. All of the technologies in this treatability study 

are stabilization methods, each comprised of a unique 

chemical system. The technologies in the study are also 

innovative in that a reduced volume of reagent is required 

as compared to traditional stabilization processes. This is 

beneficial in that it reduces the amount of material that 

must be handled and stored during treatment, and 

generally produces treated material with a minimal 

increase in volume. 

Limited information on mercury stabilization is available; 

therefore, the analysis is based on the body of data that is 

available, and on the more widely available information on 

stabilization treatments for other heavy metals, as well as 

information provided by the technology vendors who 

participated in the treatability study. 

2.1 Key Features of the Stabilization 

Process 

The primary components of a stabilization treatment 

system are the reagents and equipment used to mix it into 

the treatment matrix. In addition to the treatment reagent, 

the matrix characteristics and depth of the material and the 

application type (in situ or ex situ) would determine the 

equipment requirements. Unless ground or surface water 

contamination is an immediate concern (e.g. very shallow 

water table beneath treatment zone), monitoring can be as 

simple as auguring samples from the treated pile after the 

treatment has been performed in order to determine the 

success of the treatment. 

The application design for ECWI’s ENTHRALL® process 

would use a proprietary sonic drilling rig subcontracted 

from Prosonic Drilling Company, Inc (PDI) of Phoenix, 

Arizona. The reagent would be injected directly into the 

pile at 15 foot intervals, which should allow the reagent to 

thoroughly permeate the material. 

KEECO’s design calls for a modified ex-situ approach 

wherein a mixing facility would be constructed adjacent to 

each pile. The material would be hauled by dump trucks to 

the facility where it would be dumped onto a mixing pad, 

reagent would be mixed in by a front end loader and the 

material would be hauled back to the pile by dump truck 

and then replaced and compressed in place. Each mixing 

facility would be enclosed to prevent fugitive dust 

emissions. 

2.2 Operability of the Technology 

Stabilization processes are among the simplest of 

remediation technologies, consisting mainly of a chemical 

reagent and the mixing/drilling equipment required to apply 

it. The effectiveness of stabilization technologies is largely 

dependent on the degree of contact between the reagent 

and the contaminated matrix. Thorough mixing is desirable 

to ensure the maximum particle contact, though in in situ 

treatments, mixing may not be practical and application of 

the chemical would have to be accomplished by drilling and 

injection into the material. In such cases, care would have 

to be taken in designing the application to ensure complete 

contact between the reagent and the treated matrix. 

Existing environmental conditions are generally not a 

problem and may be incorporated into the process (e.g. 

natural moisture content of the matrix). In most 

stabilization technologies, the chemical reaction takes 

place quickly, making weather and temperature much less 

significant factors than in other methods with longer 

treatment times. 

2-1 
Ensuring thorough contact with contaminants in the matrix 

is easier in ex situ applications due to the ease of mixing 

when material is moved to the treatment locale, which can 

consist of moving to a lined pad near the area of 

contamination. In situ treatments are inherently more 

complicated, but developing technologies for this form of 

application is desirable because of the reduced cost, 

reduced contact with contaminants, and lowered risk of 

spillage and air contamination during transport of the 

material to a treatment facility. 

The chemical reagents used in stabilization technologies 

are usually applied dry or are available in a concentrated 

form that can be mixed with water on site, thus minimizing 

the amount of chemical that must be transported. For 

smaller applications, where equipment is likely to be used 

for only a few days, portable generators and mixers can be 

rented, reducing capital investments. At large treatment 

sites it may be more cost effective to purchase equipment; 

however, the treatments designed by the technology 

vendors for the Sulfur Bank Mercury Mine site use either 

specialized equipment that would be subcontracted, or 

heavy equipment in such quantity that purchase would not 

be feasible. In addition to environmental remediation 

applications, stabilization treatment is also applicable to 

industrial waste products and to contaminated waters, as 

discussed in detail in Section 2.3. 

2.3 Applicable Wastes 

As discussed in the previous section, stabilization 

technologies are applicable to solid matrices such as 

contaminated soil or mine wastes. Stabilization treatment 

is also applicable to industrial waste products that are still 

in the production system and to contaminated waters, 

though this is more likely to be used in a contained system, 

as opposed to a natural environment, because the resulting 

contaminated sludge would have to be removed. Since the 

process works by binding an environmentally neutral 

element with contaminants in the environment, there are 

minimal hazardous byproducts. The process is also 

applicable in situations where subsurface utilities limit or 

preclude the use of technologies requiring excavation, 

though special care would have to be taken when drilling 

was used in the product application. 

2.4 Availability and Transportability of 

Equipment 

Stabilization technologies can be implemented anywhere 

the chemical can be delivered and a drill rig/mixing 

equipment can be used. Since all-terrain drill rigs are 

available, most locations would be accessible. KEECO’s 

silica technology would be applied by mixing with front end 

loaders in a facility constructed on site for that purpose. 

Standard earth-moving, heavy equipment that is normally 

moved from site to site would be used. Application of the 

ENTHRALL® technology as used in the SBMM treatability 

study would require the use of a sonic drill rig. The rig is 

truck-mounted and easily transportable to the site. 

2.5 Materials Handling Requirements 

Materials handling for stabilization processes are generally 

limited to transporting the reagent to the site, and mixing 

and applying it to the contaminated matrix. There should be 

no residuals or waste products that have to be removed 

from the site, other than a small quantity of personal 

protection equipment (PPE), which could be removed from 

the site in a sealed drum, by a facility qualified to dispose 

of hazardous waste. 

For an application such as the piles at SBMM, where the 

treatment matrix is unconsolidated rock, minimal site 

preparation would be required. The size of the piles can be 

measured, with the depth of the piles being estimated from 

pre-mining topographic maps. Where dumping records are 

not available, core samples may be taken to verify 

consistency of material in the piles, and some sampling 

should be done regardless of records to check for changes 

in the material since it was deposited. 

Drilling services are generally subcontracted to a company 

that has both the required equipment (drill rigs, augers, 

samplers) and personnel trained in drilling operation. If 

work is to be performed on a hazardous waste site, drilling 

personnel must have the OSHA-required 40-hour health 

and safety training. Process monitoring would be required 

initially to ensure that the reagent was making full contact 

with the contaminated matrix, and samples of posttreatment material would be collected at intervals 

throughout the application to determine the success of the 

technology, and any modifications that were required. 

ECWI would subcontract drilling and injection of the 

reagent for the SBMM project. All personnel working on 

site would be required to complete safety training. The 

SBMM treatment designed by ECWI calls for one weekly 

sample of treated material to be collected and analyzed for 

leachable mercury. This would ensure that sufficient 

reagent was being applied and that complete contact 

between reagent and contaminated material was being 

achieved. 

KEECO’s design includes two mixing facilities, each of 

which would be operated two shifts per day. Their 

2-2 
sampling plan calls for one sample of treated material to be 

collected daily by each shift. 

2.6 Range of Suitable Site Characteristics 

Stabilization technologies can be applied at any site that is 

accessible to the drilling and mixing equipment. Electrical 

power and water would be required at most sites, but if 

necessary, a generator could provide electricity and water 

could be hauled in. Application of reagents would need to 

be done when temperatures were above freezing to avoid 

the reagent solidifying before full contact with the targeted 

contaminant was made. 

2.7 Limitations of the Technology 

The main limitation of stabilization technologies is that 

while the process is easily applied to most solid wastes, the 

success of the treatment depends on a very specific 

chemical reaction. To ensure complete stabilization, the 

reagent must be mixed into the soil thoroughly enough to 

ensure complete contact; therefore success is limited by 

mechanical access to materials. Very deep or relatively 

impermeable bodies of material would not be thoroughly 

treated without specialized equipment and application 

techniques, which could make in situ treatment difficult. 

The pH of the material being treated can limit the 

effectiveness of the reagent, but this can often be remedied 

by adding the appropriate buffering material to the reagent 

before it is applied. 

In a diverse waste body, such as the piles found at SBMM, 

the majority of the material being treated is not necessarily 

the same as the relatively small amount of material that 

was sampled prior to treatment application. Heterogeneous 

matrices may require extensive testing to insure that the 

mode of treatment is applicable to the entire volume. If 

heterogeneity affects performance, than separate 

treatment scenarios may need to be developed for each 

component. This may impact cost and schedule. 

As with any technology, results in the field often differ from 

lab scale results, so modifications to the process may be 

required during application. Stabilization treatments are 

generally designed to be one-time applications, but due to 

the variability of the reaction and potential interferences, 

additional applications may be indicated. 

2.8 Applicable or Relevant and 

Appropriate Requirements (ARARS) 

for Stabilization Processes 

The National Contingency Plan (NCP) of 1985, codified in 

Title 40 Code of Federal Regulations (CFR) Part 300, 

delineates the methods and criteria used to determine the 

appropriate extent of removal and cleanup for hazardous 

waste contamination. The NCP required compliance with 

Federal applicable or relevant and appropriate 

requirements (ARARs) in order to make use of other 

programs’ or agencies’ standards. The Comprehensive 

Environmental Responsibility, Compensation and Liability 

Act (CERCLA), as amended by the Superfund 

Amendments and Reauthorization Act (SARA) of 1986 

codified and expanded the provisions. 

This subsection discusses specific federal ARARs that are 

pertinent to the application of stabilization technologies, 

including the transport, treatment, storage, and disposal of 

wastes and treatment residuals. State and local regulatory 

requirements, which may be more stringent than those set 

by the federal agencies, must also be addressed by 

remedial managers. ARARs that apply to stabiliation 

remedial technologies have been promulgated in various 

regulatory acts, including: (1) the Comprehensive 

Environmental Response, Compensation, and Liability Act; 

(2) the Resource Conservation and Recovery Act; (3) the 

Clean Air Act; (4) the Clean Water Act; (5) the Safe 

Drinking Water Act, and (6) the Occupational Safety and 

Health Administration regulations. These six regulatory 

acts are discussed below; with specific ARARs that may be 

applicable to the stabilization process being identified in 

Table 2-1. 

2.8.1 Comprehensive Environmental Response, 

Compensation, and Liability Act (CERCLA) 

The CERCLA of 1980, as amended by SARA of 1986, 

provides for federal funding to respond to releases or 

potential releases of any hazardous substance into the 

environment, as well as to releases of pollutants or 

contaminants that may present an imminent or significant 

danger to public health and welfare or to the environment. 

SARA states a strong statutory preference for remedies 

that are highly reliable and provide long-term protection. It 

directs EPA to do the following: 

• use remedial alternatives that permanently and 

significantly reduce the volume, toxicity, or the 

mobility of hazardous substances, pollutants, or 

contaminants; 

2-3 
Table 2-1. Potential Federal and State ARARs for Stabilization Remediation Processes. 

Process Activity ARAR Description Basis Response 

Waste RCRA: 40 Standards that apply to Chemical and physical Chemical and physical 

Characterization of 

Untreated Waste 

CFR Part 261 

(or State 

equivalent) 

identification and 

characterization of 

wastes. 

properties of waste 

determine the suitability 

of treatment by a 

stabilization/solidification 

analyses must be 

performed to determine if 

waste is a hazardous 

waste. 

process. 

RCRA: 40 

CFR Part 264 

(or State 

equivalent) 

Standards apply to 

treatment of wastes in a 

treatment facility. 

Applicable to stabilization 

processes only when 

applied in a waste 

treatment facility. 

Compliance with 

requirements for 

operations, record keeping, 

and contingency planning. 

Waste 

Processing CAA: 40 CFR 

Part 50 

(or State 

equivalent) 

Regulations govern toxic 

pollutants, visible 

emissions and 

particulates. 

Mixing reagent into soil 

could create particulate 

dust in the air. 

Where materials being 

treated cause dust 

particulate, surface should 

be wetted, or dust 

containment facilities 

installed. 

SARA: Standards that apply to Applicable to stabilization Application must be 

Determination of 

Cleanup 

Standards 

Section 

121(d)(2)(ii); 

SDWA: 40 

CFR Part 141 

surface & groundwater 

sources that may be used 

as drinking water. 

processes only when 

runoff or seepage of 

solutions from treatment 

may contact surface and 

designed to ensure no 

significant amounts of 

runoff or seepage into 

groundwater. 

groundwaters. 

Waste Disposal 

RCRA: 40 

CFR Part 262 

Standards that pertain to 

generators of hazardous 

waste. 

Generated hazardous 

wastes would, in most 

cases, be limited to PPE, 

other contaminated 

Generators must dispose of 

wastes at facilities that are 

permitted to handle the 

waste. Generators must 

supplies and possibly 

washwater. 

obtain an EPA ID number 

prior to waste disposal. 

OSHA: 29 

CFR Parts 

Worker health and safety 

standards 

CERCLA remedial 

actions and RCRA 

Workers must have up to 

date training and medical 

Worker Safety 1900-1926; 

or State 

corrective actions must 

follow requirements for 

monitoring; use of 

appropriate protective 

equivalent the health and safety of 

on-site workers. 

equipment is required. 

2-4 
• select remedial actions that protect human health 

and the environment, are cost-effective, and 

involve permanent solutions and alternative 

treatment or resource recovery technologies to the 

maximum extent possible; and 

• avoid off-site transport and disposal of untreated 

hazardous substances or contaminated materials 

when practicable treatment technologies exist 

[Section 121(b)]. 

In general, two types of responses are possible under 

CERCLA: removal and remedial actions. Superfund 

removal actions are conducted in response to an 

immediate threat caused by a release of a hazardous 

substance. Remedial actions are governed by the SARA 

amendments to CERCLA. As stated above, these 

amendments promote remedies that permanently reduce 

the volume, toxicity, and mobility of hazardous substances 

or pollutants. 

Stabilization technologies qualify for use in CERCLA 

remedial actions as the process may permanently reduce 

the mobility of the contaminants of concern. Most 

stabilization processes also reduce toxicity in the treated 

matrix by binding contaminants in a neutral compound. 

On-site remedial actions must comply with federal and 

state ARARs, which are determined on a site-by-site basis. 

These regulations may be waived under six conditions: (1) 

the action is an interim measure, and the ARAR will be met 

at completion; (2) compliance with the ARAR would pose a 

greater risk to health and the environment than 

noncompliance; (3) it is technically impracticable to meet 

the ARAR; (4) the standard of performance of an ARAR 

can be met by an equivalent method; (5) a state ARAR has 

not been consistently applied elsewhere; and (6) meeting 

the standard for that particular ARAR, with respect to the 

degree of protection or reduction of risk afforded by it, 

would incur such costs that standard and remedial actions 

at other sites would be jeopardized. These waiver options 

apply only to on-site actions, and justification for the waiver 

must be clearly demonstrated. 

2.8.2 Resource Conservation and Recovery Act 

(RCRA) 

RCRA, an amendment to the Solid Waste Disposal Act 

(SWDA), was passed in 1976 to provide a framework for 

achieving environmentally sound management of both 

hazardous and nonhazardous wastes. Subtitle C of RCRA 

regulates the generation and handling of hazardous waste, 

with most of the regulations also being applicable to 

CERCLA activities. The Hazardous and Solid Waste 

Amendments (HSWA) of 1984 greatly expanded the scope 

and requirements of RCRA. 

RCRA defines two types of hazardous wastes: 

characteristic and listed. Criteria for identifying 

characteristic hazardous wastes, given in 40 CFR Part 261 

Subpart C, are: ignitability, corrosivity, reactivity, and 

toxicity. 40 CFR Part 261 Subpart D provides a list of 

wastes from specific and nonspecific industrial sources, 

which comprise the “listed” wastes. RCRA regulations do 

not apply to sites where RCRA-defined wastes are not 

present. 

RCRA regulations define hazardous wastes and regulate 

their transport, treatment, storage, and disposal. These 

regulations are only applicable to stabilization processes if 

RCRA defined hazardous wastes are present. 

In a typical stabilization application, hazardous wastes 

would be limited to the material being treated, and a small 

amount of personal protective equipment (PPE) that may 

have become contaminated during treatment. If wastes 

were determined to be hazardous according to RCRA, 

essentially all RCRA requirements regarding the 

management and disposal of this hazardous waste would 

have to be addressed by the remedial managers. 

In order to legally generate any hazardous waste, the 

responsible party must obtain an EPA identification 

number. Other applicable RCRA requirements may 

include a Uniform Hazardous Waste Manifest (if the waste 

is transported off-site), restrictions on placing the waste in 

land disposal units, time limits on accumulating waste, and 

permits for storing the waste. 

Requirements for corrective action at RCRA-regulated 

facilities are provided in 40 CFR Part 264, Subpart F and 

Subpart S. These subparts also generally apply to 

remediation at Superfund sites. Subparts F and S include 

requirements for initiating and conducting RCRA corrective 

action, remediating groundwater, and ensuring that 

corrective actions comply with other environmental 

regulations. Subpart S also details conditions under which 

particular RCRA requirements may be waived for 

temporary treatment units operating at corrective action 

sites and provides information regarding requirements for 

modifying permits to adequately describe the subject 

treatment unit. 

2.8.3 Clean Air Act (CAA) 

The CAA establishes national primary and secondary 

ambient air quality standards for sulfur oxides, particulate 

matter, carbon monoxide, ozone, nitrogen dioxide, and 

2-5 
lead. It also limits the emission of 189 listed hazardous 

pollutants such as vinyl chloride, arsenic, asbestos and 

benzene. States are responsible for enforcing the CAA. 

To assist in this, Air Quality Control Regions (AQCR) were 

established. Allowable emission limits are determined by 

the AQCR, or its sub-unit, the Air Quality Management 

District (AQMD). These emission limits are based on 

whether or not the region is currently within attainment for 

National Ambient Air Quality Standards (NAAQS). 

The CAA requires that treatment, storage, and disposal 

facilities comply with primary and secondary ambient air 

quality standards. Provided that the stabilization reagents 

are mixed into the soil matrix without generating excessive 

dust, there should be no clean air issues associated with 

the process. 

2.8.4 Clean Water Act (CWA) 

The objective of the Clean Water Act is to restore and 

maintain the chemical, physical and biological integrity of 

the nation's waters by establishing federal, state, and local 

discharge standards. If treated water is discharged to 

surface water bodies or Publicly Owned Treatment Works 

(POTWs), CWA regulations will apply. A facility desiring to 

discharge water to a navigable waterway must apply for a 

permit under the National Pollutant Discharge Elimination 

System (NPDES). When a NPDES permit is issued, it 

includes waste discharge requirements. Discharges to 

POTWs also must comply with general pretreatment 

regulations outlined in 40 CFR Part 403, as well as other 

applicable state and local administrative and substantive 

requirements. Stabilization technology applications involve 

minimal amounts of water, and should produce no excess 

solution; therefore, CWA criteria would not generally apply. 

2.8.5 Safe Drinking Water Act (SDWA) 

The SDWA of 1974, as most recently amended by the Safe 

Drinking Water Amendments of 1986, requires the EPA to 

establish regulations to protect human health from 

contaminants in drinking water. The legislation authorized 

national drinking water standards and a joint federal-state 

system for ensuring compliance with these standards. The 

National Primary Drinking Water Standards (NPDWS) are 

found in 40 CFR Parts 141 through 149. There should be 

minimal effluent from the treated material during a 

stabilization process, so safe drinking water regulations 

would only apply where any effluent, if produced, could 

impact surface or groundwater drinking water sources. 

2.8.6 Occupational Safety and Health Administration 

(OSHA) Requirements 

CERCLA remedial actions and RCRA corrective actions 

must be performed in accordance with the OSHA 

requirements detailed in 20 CFR Parts 1900 through 1926, 

especially Part 1910.120, which provides for the health and 

safety of workers at hazardous waste sites. On-site 

construction activities at Superfund or RCRA corrective 

action sites must be performed in accordance with Part 

1926 of OSHA, which describes safety and health 

regulations for construction sites. State OSHA 

requirements, which may be significantly stricter than 

federal standards, must also be met. 

All personnel who are working at a hazardous waste site 

are required to have completed an OSHA training course 

and must be familiar with all OSHA requirements relevant 

to hazardous waste sites. Workers at hazardous waste 

sites must also be enrolled in a medical monitoring 

program. An acceptable program must include: (1) a 

health history, (2) an initial exam before hazardous waste 

work starts to establish fitness for duty and as a medical 

baseline, (3) periodic examinations (usually performed 

annually) to determine whether changes due to exposure 

may have occurred and to ensure continued fitness for the 

job, (4) appropriate medical examinations after a suspected 

or known overexposure, and (5) an examination at 

termination. 

For most sites, minimum PPE for workers will include 

gloves, hard hats, steel-toed boots, and Tyvek7 coveralls. 

Depending on contaminant types and concentrations, 

additional PPE may be required, including the use of air 

purifying respirators or supplied air. At the sites where 

stabilization treatments will be applied, the minimal list of 

PPE will usually be sufficient. Noise levels are not 

expected to be high, except during the operation of mixing 

and drilling equipment. During these activities, noise levels 

should be monitored to ensure that workers are not 

exposed to noise levels above a time-weighted average of 

85 decibels over an eight-hour day. If noise levels were to 

exceed this limit, then workers would be required to wear 

hearing protection, however, hearing protection should be 

available for any level of discomfort from noise. The levels 

of noise anticipated are not expected to adversely affect 

the community, but this will depend on proximity to the 

treatment site. 

2-6 
Section 3 

Economic Analysis 

3.1 Introduction 

The purpose of this economic analysis is to estimate 

costs (not including profits) for commercial treatment of 

mercury-contaminated material at the Sulfur Bank 

Mercury Mine in Northern California using the Enthrall® 

and SME technologies that were demonstrated in the 

treatability study. Since a field-scale demonstration has 

not been performed, best efforts to reasonably estimate 

costs have been based on past experience of the 

vendors and reasonable engineering assumptions. The 

cost figures provided in this economic analysis are 

considered “order-of-magnitude” estimates, and may 

significantly change if field testing is performed. 

The technology vendors were asked to provide cost 

estimates based on twelve categories of costs that are 

associated with typical cleanup activities at Superfund 

sites. Where the vendor did not supply costs, an 

estimate has been included based on past SITE 

program experience, or generic treatment costs. The 

phosphate treatment was applied in the treatability study 

as a generic treatment, and based on the results, further 

experimentation and product modification would have to 

be performed before the reagent would be considered 

for use at the SBMM site; therefore, vendor costs for a 

full scale treatment using phosphate were not included 

in the estimates. 

3.2 Cost Estimate Scope 

The technology vendors were asked to provide cost 

estimates for treatment of two piles at the site, the North 

Waste Pile and the Waste Rock Dam. For purposes of 

the cost estimate, the mercury content in the piles was 

assumed to be the same as that in the mercury ore used 

in the treatability study. 

The vendors were asked to estimate costs based on the 

following dimensions: 

North Waste Pile: 

Surface area = 894,000 square feet 

Volume = 877,000 cubic yards 

Estimated maximum depth = 75 feet 

Calculated average depth = 26.5 feet 

Waste Rock Dam: 

Surface area = 1,034,000 square feet 

Volume = 556,000 cubic yards 

Estimated maximum depth = 70 feet 

Calculated average depth = 14.5 feet 

The costs associated with typical cleanup activities at 

Superfund sites have been broken down into 12 

categories: 

(1) Site Preparation 

(2) Permitting and Regulatory Activities 

(3) Capital Equipment 

(4) Start-up and Fixed 

(5) Labor 

(6) Consumables and Supplies

 (7) Utilities 

(8) Effluent Treatment and Disposal 

(9) Residuals Shipping & Disposal 

(10) Analytical Services 

(11) Maintenance and Modifications 

(12) Demobilization/Site Restoration 

The technology vendors were asked to estimate costs 

for treating the specified piles based on the above 

categories. 

3.3 Factors Affecting Estimated Cost 

Since the technologies have only been applied to SBMM 

materials in the small scale of the treatability study, 

rather than a field scale demonstration, it is understood 

that the costs presented here are estimates only, based 

on past experience of the vendors and engineering 

assumptions as specified in the following descriptions. 

There are a number of factors that could affect the 

actual cost of treatment of mercury-contaminated 

material using stabilization technologies. Cost estimates 

in this report have been provided by the vendors based 

on the assumption that the mercury and other metals 

content is the same as that in the material that was 

3-1 
treated in the treatability study. A larger sampling of the 

material in the piles would be required prior to an actual 

application and the results could indicate significantly 

different concentrations. Analytical evaluation of the 

actual materials to be treated may also indicate that 

modifications to the reagents are necessary, which could 

impact costs. The characteristics of the material may 

also be a factor. Estimates are based on “typical 

material” characteristics; however, the actual material 

may require special handling depending on particle size, 

stability and compaction. Should the initial sampling 

results vary widely, additional sampling points would be 

required in order to ensure that the proper reagents and 

ratios were applied. 

3.4 Issues and Assumptions 

This section summarizes the major issues and 

assumptions used in estimating the cost of implementing 

the Enthrall®

 and SME technologies at full-scale. The 

vendors were given the dimensions of the piles and told 

that the material would be assumed to match the 

mercury ore material. Additional assumptions were 

specified by ECWI and KEECO in presenting their costs. 

3.4.1 Site Characteristics 

The Sulfur Bank Mercury Mine is comprised of two pits 

and extensive piles composed of various materials. 

Cost estimates have been prepared for two existing piles 

at the site, but characteristics of the material in the piles 

were assumed to be the same as that in the mercury ore 

from the treatability study. The maximum depth at any 

point in the pile has been estimated based on pre-mining 

maps. Since the volume of both piles was estimated 

from maps, the actual volume could differ due to map 

scaling or errors, and changes in the heap topography 

over time. 

For purposes of cost estimation, characteristics for a 

typical site material were assumed. These included the 

assumptions that the material is unconsolidated, with 

sizes ranging from fines to large gravels and that the 

rock can be completely treated by the methods 

described in the following vendor sections. 

3.4.2 Design and Performance Factors 

ECWI and KEECO each designed the application 

technique for their respective reagents. These 

processes are described in later sections with details of 

each vendor’s cost estimates. Both processes include 

monitoring or pilot testing to verify complete contact 

between the reagent and the contaminated material in 

order to optimize treatment performance. The products 

used in the treatability study are all designed to be a 

one-time application. 

3.4.3 Financial Assumptions 

All costs are presented in 2001 U.S. dollars without 

accounting for interest rates, inflation or the time value of 

money. Insurance and taxes are assumed to be fixed 

costs lumped into the Startup and Fixed Costs category 

(see subsection 3.5.4). 

3.5 Basis for Economic Analysis 

In this section, each of the 12 cost categories that reflect 

typical clean-up activities encountered at Superfund 

sites, will be defined and discussed. These 12 cost 

categories form the basis for the estimated costs 

submitted by the vendors and presented in sections 

3.6.1 and 3.6.2. 

3.5.1 Site Preparation 

Since the material being treated is already in piles and 

will be treated on site, the site preparation for 

implementing the stabilization technologies would be 

limited to bringing the necessary equipment for 

application and monitoring to the site, and constructing 

usage and storage facilities. Storage facilities for 

chemicals and fuels would have to comply with 

environmental regulations governing the site. The 

SBMM site is already fenced so no additional security 

costs should be incurred. 

3.5.2 Permitting and Regulatory Requirements 

Several types of permits may be required for 

implementing a full-scale remediation. The types of 

permits required will be dependent on the type and 

concentration of the contamination, the regulations 

covering the specific location, and the site’s proximity to 

residential neighborhoods. Extensive studies have 

previously been conducted on contamination in Clear 

Lake, so pretreatment site characterization should also 

be minimal for permitting purposes. 

If site characterization were required for permitting, the 

non-analytical costs incurred for receiving approval from 

the regulatory agency to install the treatment system 

would be included under the Permitting and Regulatory 

Activities category. These costs would include the 

preparation of site characterization reports that establish 

a baseline for the site contamination, the design 

3-2 
feasibility study for the pilot system, and meetings with 

regulators for discussing comments and supplying 

related documentation for acquiring approval for 

installing and implementing the treatment. 

Depending upon the classification of a site, certain 

RCRA requirements may have to be satisfied as 

discussed in section two of this report. Since the SBMM 

site is an active Superfund site, it is possible that the 

technology could be implemented under the umbrella of 

existing permits and plans. Certain regions or states 

have more rigorous environmental policies that may 

result in higher costs for permits and verification of 

cleanup. Added costs may result from investigating all 

of the regulations and policies relating to the location of 

the site, and for conducting a historical background 

check for fully understanding the scope of the 

contamination. 

3.5.3 Capital Equipment 

Capital equipment includes all equipment for the 

treatment process, whether it is purchased or rented. 

Different specialized equipment is required for each of 

the technologies as specified in the following vendor’s 

cost estimates. For this particular project, all equipment 

costs were based on rental or subcontracting rates 

rather than purchases. 

3.5.4 Startup and Fixed Costs 

Startup and Fixed costs can include such variables as 

insurance, taxes, initiation of monitoring programs, 

contingency funds, and the cost of physically starting the 

treatment such as building facilities, transporting 

equipment, etc. In requesting cost estimates from the 

vendors for the SBMM piles, the list of cost categories 

was provided, but developing and categorizing costs 

was left up to the vendors. Physical startup costs have 

been included in the site preparation category, leaving 

insurance, taxes, etc. in the startup costs, where they 

were included in the vendor’s estimate. 

Often, insurance and taxes are estimated to be 10% of 

the total annual purchased equipment costs. 

Contingency costs that allow for unforeseen 

circumstances such as strikes, floods and price 

variations, are often estimated at the same cost as 

insurance and taxes. 

3.5.5 Labor 

Included in this subsection are the labor costs of 

implementing the technologies and the associated 

monitoring that would be required to verify the results of 

the process. Where labor is performed but accounted 

for in other categories, an explanation has been included 

in those categories. The hourly labor rates presented in 

this subsection are loaded, which means they include 

base salary, benefits, overhead, and general and 

administrative (G&A) expenses. Travel and per diem 

expenses are additional costs included in this section. 

Monitoring requirements for this project are based on the 

assumption that the material characterization has 

already been done, and costs are required only for the 

tests that would be necessary to determine the degree 

to which the process is working, and to satisfy 

environmental monitoring requirements. Sampling labor 

would include collecting and appropriately packing 

samples for shipping to the analytical lab and then 

delivering the samples to the nearest shipping office. 

3.5.6 Consumables & Supplies 

The category of consumables and supplies consists of 

materials used in the treatment process and supplies 

bought to support the treatment effort. In the SBMM 

treatments, the reagent and diesel fuel account for the 

consumables and supplies would consist primarily of 

personal protective equipment (PPE) and miscellaneous 

supplies. 

PPE is routinely used by individuals who are active in 

treatment application, sample collection, and during any 

activity in which there is a potential for being exposed to 

contaminated soil or groundwater. Expendable items 

would primarily include nitrile gloves and tyvek coveralls; 

and possibly spent respirator cartridges if the work is 

conducted in Level C or higher. 

3.5.7 Utilities 

Utilities are generally comprised of electricity and water. 

At the SBMM site, the equipment in both treatment 

scenarios is diesel fueled, so only a small electrical cost 

to supply lighting and possibly for a phone and facsimile 

hookup would be needed. A water source would be 

needed for decontamination and incidental activities; 

however those costs are considered negligible. 

3.5.8 Effluent Treatment and Disposal 

For these technologies there is no effluent produced; 

therefore, it is assumed that there will be no effluent 

treatment and disposal expense. 

3-3 
3.5.9 Residuals Shipping and Disposal 

No residuals would be anticipated from an in situ 

stabilization process conducted according to the method 

used in the treatability study. For the modified ex situ 

process designed by KEECO, material is removed from 

the pile to an adjacent mixing facility where it is mixed 

with reagent. At this point in the treatment process, 

KEECO considers the treated material to be residuals 

and included the cost of returning the material to the 

original location in the residual handling costs. Disposal 

of small amounts of decontamination wastewater that 

may be generated from cleaning sampling equipment is 

considered negligible. 

3.5.10 Analytical Services 

All samples of treated material would be sent to an offsite analytical laboratory. The level of testing required to 

substantiate site cleanup was specified by each of the 

vendors in their respective treatment scenarios. Both 

vendors based costs on analysis of leachable mercury 

only. Unlike the treatability study, which determined 

success by percent reduction in comparison with a 

water-leach control, actual remediation projects focus on 

attaining a specific cleanup concentration target level. 

3.5.11 Maintenance and Modifications 

Remediation efforts often include installation of a 

treatment system that would require ongoing 

maintenance. Using heavy equipment to apply the 

reagent directly to portions of the material would perform 

both treatment scenarios designed for the SBMM site. 

Maintenance on the equipment would be performed as 

required and no significant amounts of maintenance 

should be required elsewhere on the project. 

Modifications would be determined by analytical results, 

and should only be necessary in the volume or 

technique of reagent application. 

3.5.12 Demobilization/Site Restoration 

Demobilization and site restoration are performed at the 

conclusion of the treatment project, and would therefore 

be a one time cost. Restoration of a mine site often 

includes capping and revegetation; however, this is 

beyond the scope of the treatment designs for the 

SBMM site. For these cost estimates, it was assumed 

that demobilization/site restoration would consist of 

returning the equipment to the appropriate locations, and 

dismantling the mixing facilities in KEECO’s design. It 

should be noted that boreholes in ECWI’s design are not 

cased wells and it was assumed that no abandonment 

procedures would be required. 

3.6 Vendor Cost Estimates 

This section presents the cost estimates provided by the 

technology vendors. The estimates were to be based on 

the twelve cost categories specified above. In sections 

where a cost was not estimated by the vendor, an 

estimate has been included based on available 

information. 

3.6.1 E&C Williams Enthrall®

 Technology 

ECWI designed an in situ treatment that was based on 

an application strategy related to the techniques used in 

the treatability study. In this method, a truck-mounted 

sonic drill rig would be used to drill into the pile and 

inject the ENTHRALL®

 reagent at depth intervals that 

were calculated to allow for complete permeation of the 

material. ECWI would provide the chemical reagent and 

serve as technical consultants, but would subcontract 

the actual drilling and injection to Prosonic Drilling 

Company, Inc (PDI) of Phoenix, Arizona. Drilling costs 

in this estimate are based on information supplied by 

PDI. 

Based on previous experience, ECWI has estimated 

costs on the assumptions that application at each 

borehole will treat a radius of 15 feet, and that injection 

to the average depth of the pile will provide sufficient 

treatment. Two rigs would operate concurrently on the 

heap, with one tanker truck supplying reagent to both. 

The rig would drill to the specified depth, inject the 

reagent and pull out the shaft, leaving a dispensable 

drive point in each hole. The treatment design calls for 

two eight-hour shifts on each rig per day. It was 

assumed that boreholes could be left in the pile and 

would not require abandonment procedures. Prior to 

beginning full-scale application, on-site pilot injection 

holes would be required to test the design assumptions. 

Costs were estimated by ECWI for each of the specified 

piles, based on the assumption that treatment of the 

piles would take place sequentially, requiring only one 

mobilization and demobilization cycle. The following 

cost estimate is based on the 12 cost categories 

described above, and was provided by ECWI, except 

where otherwise indicated. 

(1) Site Preparation: There is minimal site preparation 

required for the working site since the drill rigs are 

mobile and designed for field work. Prior to beginning 

treatment at the site, ECWI personnel would obtain 

3-4 
training in spill containment and remediation procedures 

at ECWI’s expense, and would visit the site to determine 

requirements and costs to construct storage areas with 

secondary containment for diesel fuel and the chemical 

reagent. ECWI would provide poly storage tanks with 

secondary containment as working storage for the 

drilling/injecting teams at no charge to the project. 

ECWI did not include a cost for the fuel and chemical 

storage and secondary containments in their estimate. 

Based on general information available from 

miscellaneous vendor publications a rough estimate for 

the fuel and reagent containers and secondary 

containments has been made at $40,000. 

(2) Permitting and Regulatory Activities: PDI is 

licensed to work in California. Any additional required 

business licenses or permits would be the responsibility 

of ECWI, and they would have to be informed of such 

requirements in advance of a site application with 

sufficient lead time to procure the appropriate permits. 

As discussed in Section 3.5.2, permit requirements are 

very site specific, and may be modified by the existing 

status of the project as a superfund site. ECWI has not 

been to the site, or been informed of permitting 

requirements so a cost for this budget item was not 

included in their estimate. 

RCRA and State regulations may have to be satisfied in 

addition to Superfund requirements. Since the site is an 

active Superfund site, it is possible that the technology 

could be implemented under the umbrella of existing 

permits and plans held by the site owner or other 

responsible party. Added costs may result from 

investigating the regulations and policies relating to the 

location of the site. Based on past experience with 

similar projects, the cost associated with permitting 

activities was estimated at $20,000. 

(3) Capital Equipment: Major equipment for the 

treatment at SBMM would consist of two rotosonic drill 

rigs and a fluid tanker with pumping equipment, both to 

be supplied by PDI. Costs for use and operation of this 

equipment was provided on a per-diem basis. The cost 

per day for the rigs, including operators, is $5,300. The 

cost for the fluid tanker, including an operator who would 

transport and assist in injecting fluid is $750.00 per day. 

The combined total costs for capital equipment would be 

$1,633,500 according to the individual pile costs as 

follows: 

North Waste Pile 

The estimated time for set up, drilling, injection of 

reagent, moving between holes and tearing down is 160 

man-days for the North Waste Pile, based on 12-hour 

day maximums. This equates to $848,000 for drilling 

equipment and $120,000 for the fluid tanker, totaling 

$968,000 in capital equipment costs. 

Waste Rock Dam 

For treatment of the Waste Rock Dam, the estimated 

time for set up, drilling, injection of reagent, moving 

between holes and tearing down is 110 man-days, 

based on 12-hour day maximums, which would amount 

to $583,000 for drilling equipment and $82,500 for the 

fluid tanker, totaling $665,500 in capital equipment 

costs. 

(4) Start-up and Fixed Costs: This category typically 

includes mobilization costs and initial supplies to begin 

operations. Mobilization costs to transport the drill rigs 

and support equipment from PDI’s office in Arizona to 

the site would be $25,000. Mobilizing ECWI’s tanks and 

other equipment to the site would cost another $20,000, 

bringing the total to $45,000. 

(5) Labor: The treatment design calls for two shifts per 

day. The term “days” in the labor costs refers to mandays consisting of 8 hours. Labor costs for the crews 

who run the rigs have been included in the 

subcontractor’s costs for the rigs under capital 

equipment. ECWI would also provide labor, which 

would include ten full-time workers with regular 

supervisory visits from ECWI management. ECWI 

would also contract professional assistance, including 

geologists and project managers. A safety officer would 

be appointed for on-site processing periods, and ECWI 

would be responsible for ensuring that site personnel 

were current in the 40 Hour HAZWOPER training. 

ECWI considers the cost of safety training to be an 

overhead expense and not a cost the project would pay. 

Workers would be employed to work 8-hour days at an 

hourly rate of $15 plus $80 per diem. [Note: An hourly 

rate of $15 hour (loaded) is considered low. Anticipate 

higher labor rates. Also, a supervisor will be required at 

a higher rate.] Three professionals would be hired at the 

rate of $150 per hour, but would only be needed for 2 

hours a day, and would not be required for the entire 

duration of the project. The per diem rate for the 

professionals would be $100 per day. The combined 

labor total is $903,300, which breaks down as follows: 

North Waste Pile 

The required ten workers for 160 days would cost 

$320,000. Three additional professionals for two hours 

per day, plus per diem, for 100 days would add another 

$120,000 in consultation fees. The wages for the PDI 

3-5 
drilling crew were included in the cost of the rig, which 

was listed under capital costs, but an additional per diem 

of $85.00 for each member of the four-man crew over 

the period of 160 days would add $54,400. Providing for 

shift travel for off-work days at $2,500 every ten days 

equals $40,000. The total labor costs would equal 

$534,400. 

Waste Rock Dam 

Ten workers for 110 days would cost $220,000. Three 

additional professionals would be needed for an 

estimated 70 days for two hours per day with per diem, 

which would add another $84,000 in consultation fees. 

The wages for the PDI drilling crew were included with 

the rig under capital costs, but an additional per diem of 

$85.00 for each member of the four-man crew over the 

110 days period would add $37,400. Providing for shift 

travel for off-work days at $2,500 every ten days equals 

$27,500. The total labor costs would equal $368,900. 

(6) Consumables and Supplies: Costs predominately 

consist of the chemical reagent. Additional costs also 

include diesel fuel, an expendable drive point for each 

borehole and a small quantity of other supplies 

necessary for administrative and safety concerns. The 

unspecified supplies would constitute a very minor cost 

and are not detailed here. 

The required quantity of reagent has been determined 

by 1:10 w/w ratio of reagent to material. The weight of 

the material was calculated by multiplying the volume of 

each pile by a typical density for a mixed soil type, 1.5 

tons/cubic yard. If the density of the material in the pile 

were determined to be higher, then more reagent would 

have to be applied to maintain the same ratio. The 

ENTHRALL® addition rate was determined from its 

weight of 9.2 pounds/gallon, which converts to 217.39 

gallons per ton of reagent. 

Diesel fuel usage was estimated at 100 gallons/day for a 

total of 110 days. Fuel costs are highly variable, but 

based on an anticipated maximum of $2.00/gallon, this 

brings the total diesel cost to $22,000. 

The expendable drive points, which would be required 

for drilling and would be left in the borehole, cost $14 

each. Based on the assumption that each borehole will 

treat an area with a radius of 15 feet, the number of 

boreholes that would be required to inject the reagent 

into each pile was calculated from the specified surface 

areas. The category total costs would be $57,008,477 

for the reagent and $50,840 for other supplies and 

consumables. 

North Waste Pile 

Applying the ENTHRALL®

 reagent at a 1:10 w/w ratio to 

the 1,315,500 tons of material in the North Waste Pile 

would require 28,597,826 gallons which would cost 

$34,889,348. This equates to a reagent cost of $26.52 

per ton of material. If the density of the material in the 

pile was determined to be higher than 1.5, more reagent 

would have to be applied to maintain the same ratio. 

Based on a density of 1.7 tons per cubic yard, the cost 

would be $39,541,261. 

The surface of the North Waste Pile was specified as 

approximately 894,000 square feet. This would require 

960 boreholes, each of which would be 25 feet deep 

based on the average depth of the pile being 26.5 ft. 

The cost of 960 expendable drive points, at $14 each, 

would be $13,440. 

Waste Rock Dam 

Applying the ENTHRALL®

 reagent at a 1:10 w/w ratio to 

the 834,000 tons of material in the Waste Rock Dam 

would require 18,130,435 gallons which would cost 

$22,119,130. This equates to a reagent cost of $26.52 

per ton of material. 

The surface of the Waste Rock Dam was specified as 

being approximately 1,034,000 square feet. This would 

require 1,100 boreholes, each of which would be 15 feet 

deep based on the average depth of the pile being 14.5 

ft. The cost of 1,100 expendable drive points, at $14 

each, would be $15,400. 

(7) Utilities: Electricity and water are usually the 

primary utilities required for a remediation project. An 

overall electrical requirement was estimated at 

$500/month for four months, or $2,000. Incidental 

amounts of water would be required for cleaning and 

human usage, but the cost should be small and was not 

included in the estimate. 

In order to have a night shift running, a light plant would 

need to be provided, and could be rented for $175 per 

day. A reduced cost for lighting may be achieved if the 

commercial power grid is accessible from the treatment 

site. Portable generators may provide electricity for 

incidental usage also, but access to the commercial 

power grid is preferred. Portable toilets should be 

provided for field workers, and can be rented for $65 a 

month, which would total $520 for the life of the project, 

treating both piles. 

North Waste Pile 

Utilities for the project were not separated by piles with 

the exception of light plant rental, which would cost 

3-6 
$14,000 for the 80 calendar days that would be required 

for the North Waste Pile. 

Waste Rock Dam 

Running the light plant on the Waste Rock Dam for the 

duration of treatment application, 55 days, would run 

approximately $9,652. 

(8) Effluent, Treatment and Disposal: In this in situ 

application of the technology, no effluent requiring 

treatment or disposal would be generated. 

(9) Residuals, Shipping and Disposal: As this is an in 

situ technology, no residuals requiring treatment or 

disposal would be anticipated. 

(10) Analytical Costs: Further investigation of the site 

would be required in order to define required monitoring 

parameters. Assuming that mercury is the only 

constituent requiring analysis, and that TCLP or SPLP 

followed by cold-vapor analysis is to be performed, the 

cost for each sample including the fees for a one-week 

turnaround time should be approximately $200 for each 

sample. A flow model would be used to estimate the 

time for the reagent to permeate the material and for the 

treatment reaction to occur. Sampling of treated material 

would begin on a weekly basis when the model indicated 

that the treatment was complete. ECWI would be 

responsible for sample collection and for getting the 

analysis performed Copies of the analytical report would 

be sent from the laboratory to a designated third party 

for review and storage, while the originals would be 

maintained by ECWI until the treatment phase of the 

project was closed. Based on the $200 per sample, 

ECWI estimated the analytical costs to be approximately 

$10,400. This was based on approximately one year of 

weekly sampling, with one target metal of mercury and a 

one-week turnaround on results. 

(11) Maintenance and modifications: Maintaining 

equipment owned by ECWI and PDI would be the 

responsibility of the respective owners. No modification 

of equipment is anticipated; however, modifications to 

the process may be found necessary in technique or 

reagent application, but these should not significantly 

impact costs. ECWI allocates approximately 

$25,000/year for maintenance. 

(12) Demobilization/Site Restoration: ECWI 

estimated the cost of demobilizing their own equipment 

from Clear Lake back to Summerville, SC to be $20,000. 

Demobilizing PDI’s rigs would cost approximately 

$25,000. No site restoration costs were estimated. 

3.6.2 KEECO’s SME Technology 

KEECO refers to the approach that was designed for 

use at the SBMM site as a modified ex situ process, in 

that the material is removed from its location for 

treatment, but only to an adjacent on-site facility for the 

addition and mixing of the reagent. The costing is based 

on a design that includes building a mixing facility 

adjacent to each of the piles. Each facility would consist 

of a concrete mixing corral with raised side berms inside 

an enclosed portable building. Each facility was 

designed for an hourly throughput of 300+ tons per hour 

per facility and would be equipped with an air handling 

unit, reagent delivery silos and a water storage tank to 

wet the soils in order to prevent fugitive dusts during the 

mixing process. 

Excavators and dump trucks would be employed to 

move the material from the pile to the mixing facility. The 

material would be dumped in the mixing facility where a 

measured amount of reagent would be applied from the 

silo. Water would be applied to control fugitive dusts as 

a front end loader mixed the reagent into the material. 

In KEECO’s design, the treated material is considered 

“residual” and costs for returning it to the heap and 

compacting it after treatment has been performed are 

covered under the residuals category. 

KEECO used a typical density for mixed soil types, 1.5 

tons per cubic yard, to calculate the weights that were 

used in the cost estimate. The calculated weights are 

1,315,500 tons, in the North Waste Pile and 834,000 

tons in the Waste Rock Dam. The cost estimate 

provided by KEECO was based on the combined mass 

of the two piles; therefore figures are presented for 

treatment of 2,149,500 tons without differentiating time 

and effort between the two piles. The treatment time 

required to treat the entire mass is 247 working days, 

based on an average daily throughput of 8,700 tons per 

day. 

The cost estimates for KEECO’s application were based 

on the assumption that mixing operations would be 

scheduled to operate on a 16 hours (consisting of two 8­

hour shifts) per day, five days per week basis. A daily 

use factor of 90 percent of the design capacity was used 

based on the simplicity of the operation and reliability of 

the standard equipment selected. Based on an 

expected daily throughput of 8,700 tons per day, it is 

estimated that the mixing operations will be completed in 

247 working days (one year). An additional training 

period of five days prior to treatment beginning and ten 

days at the end for demobilization should also be 

included in the schedule. 

3-7 
The cost estimate provided by KEECO is based on a 

preliminary design, which was produced without the 

benefit of data from a pilot project; therefore, cost ranges 

presented in this estimate may be wider than would 

normally be expected in a fully developed cost estimate. 

It should also be noted that SME reagent use rates in 

this cost estimate were taken from the lab scale 

treatability study, whereas historically, field use rates are 

considerably lower than lab use rates resulting in 

reduced reagent costs. 

The cost estimate has been developed according to the 

twelve categories specified in Section 3.2 above. 

(1) Site Preparation: The primary preparation cost 

would be the construction of the mixing facilities, which 

was estimated at $420,000 each. The total site 

preparation costs for facilities at both piles would be 

$840,000. 

(2) Permitting and Regulatory Activities: The cost for 

State and Federal air treatment permits for the mixing 

facilities is estimated to be $20,000 including labor for 

data review, estimating emissions and permitting fees. 

Construction permits were estimated to be $2,500 and 

permitting costs for onsite disposition of the treated 

material were estimated at $40,000. Costs for 

permitting, regulatory activities, monitoring and waste 

transportation and disposal are highly dependent on the 

site, and as such could be significantly higher than the 

estimated total of $62,500. 

(3) Capital Equipment: Heavy equipment would be 

rented or leased for the project. The following 

equipment list includes monthly rental rates for each 

piece of equipment: 2 excavator/backhoes at $15,000, 2 

10-KW generators at $1,000, 4 dump trucks at $4,000, 4 

front end loaders at $14,000 and 1 water truck at 

$3,000. The total monthly equipment rental would be 

$107,000, bringing the total for the estimated 12-month 

project duration to $1,284,000. 

(4) Start-up and Fixed Costs: This category includes 

transportation of personnel and equipment, safety 

training, working capital, insurance, monitoring, and a 

contingency fund. Transportation costs for 14 pieces of 

rental equipment were assumed to be $7,000. The 

transportation of personnel cost was based on the 

purchase of six $1,200 round trip airline tickets for a total 

of $7,200. The remaining project staff would be hired 

locally. Safety training would consist of a 40 hour 

HAZWOPER course, which each member of the site 

team would be required to complete. Based on a crew 

size of 32 persons, the estimated cost of the training 

would be $57,000. Total transportation and training 

costs are estimated at $71,200. 

Working capital consists of the costs of borrowing capital 

for operating supplies, utilities, and labor necessary to 

keep the project running without financial constraints. 

Working capital for this project is estimated at 

$1,000,000, based on maintaining 2 months of payroll, 

and sufficient inventory for all other items. The cost of 

capital is assumed to be 9% of the working capital, 

making the estimated working capital cost $90,000 per 

annum. Insurance was estimated at $50,000 per year 

and a contingency factor should be included in the 

budget to cover unforeseen events, for which KEECO 

estimated $150,000 as an appropriate figure. 

Environmental monitoring is assumed to be required for 

fugitive dust emissions from the mixing facility only, and 

was estimated to cost $6,000. The combined total of 

costs in this category is $367,200. 

(5) Labor: It is assumed that treatment operations 

would be conducted over 247 days, working in two 

shifts, for a total of 16 hours per day, 5 days per week. 

Total labor cost for treatment is estimated to be 

$2,986,800. Table 3-1 gives a breakdown of the 

number and types of employees, expected pay rates 

and the number of hours that would be required for each 

type of labor. 

3-8 
Table 3-1. Labor Unit Costs. 

Description Number of 

Persons 

Cost Per 

Hour 

Total Hours Total Cost 

Site Manager 1 $90 2096 $188,640 

Foreman 2 $55 4192 $230,560 

Truck Driver 8 $40 16768 $670,720 

Excavator Operator 4 $45 8384 $377,280 

Front End Loader Operator 8 $45 16768 $754,560 

Water Truck Driver 2 $40 4192 $167,680 

Laborer 4 $35 8384 $293,440 

SSHO 1 $65 2096 $136,240 

Facility Operator 2 $40 4192 $167,680 

TOTAL $2,986,800 

(6) Consumables and Supplies: The most significant 

cost in the treatment estimate is the chemical reagent. 

The material requires a 5% by weight add ratio. The 

estimated cost of $23,107,000 assumes that a 

temporary batch mixing plant would be established on 

site to defray excessive transportation costs. This also 

assumes that utilities are available to support the 

operation of a temporary batch mixing plant. 

Diesel fuel is required to operate the earth moving 

equipment and generators. It was estimated that fuel 

consumption would be 50 gallons of fuel per piece of 

equipment per day. This amounts to 650 gallons of fuel 

per day. Using a rate of $1.40 per gallon, daily fuel cost 

was estimated to be $910. Assuming 247 operating 

days, total fuel costs were estimated to be $224,770. 

Supplies consist of operating supplies and SME reagent. 

Operating supplies consist of items such as safety 

equipment, PPE, office supplies, custodial supplies, 

potable water and the like. Operating supplies were 

estimated at 1 percent of annual labor, or $29,600. 

Combining the three costs for consumables and supplies 

brings the category total to $23,361,370 for 

consumables and supplies. 

(7) Utilities: Water is used to minimize fugitive dust 

emissions during operations. Assuming a water use rate 

of 2 percent of the volume being treated, and a cost of 

$2 per 1000 gallons, the total cost of water for the 

project would be estimated at $20,600. Electricity would 

be required, but incidental usage should not add 

significant costs. 

(8) Effluent, Treatment and Disposal: The treatment 

process produces no effluent, however, cleaning PPE 

and equipment may produce wash water that requires 

decontamination. It was assumed in the cost estimate 

that this would be a small enough quantity that any 

associated costs could be absorbed into the overall 

project costs. 

(9) Residuals, Shipping, & Disposal: Residuals from 

the SME process can include treated waste, waters and 

sludge and waste from decontamination activities. It 

was estimated that treated material could be moved 

from the treatment facility, replaced and compacted 

onsite for $3 per ton or $6,448,500 for the entire project. 

This figure includes the equipment and labor used to 

return the treated material to the pile (not included in the 

previous cost sections) as KEECO differentiated 

treatment from residuals handling in these costs. It is 

expected that the project would generate one drum of 

contaminated PPE each week. Assuming a disposal 

cost of $500 per drum, the disposal cost for PPE was 

estimated at $26,000. The total cost of residuals, waste 

shipping, handling and transport was estimated to be 

$6,474,500. 

(10) Analytical Services: It was assumed that 4 

composite samples would be taken each day: one per 

shift per facility. It was also assumed that the sample 

number would be increased by 10% to provide QA/QC 

samples. With an assumed cost of $90 per sample to 

analyze for leachable mercury, the estimated cost for 

analytical services is $97,800. 

(11) Maintenance and Modifications: Maintenance 

costs vary with the nature of the wastes, and the time 

between failures of the equipment. For the purposes of 

this cost estimate, these costs were assumed to be 2% 

of the cost of facilities and equipment and were 

estimated at $38,480. 

(12) Demobilization/Site Restoration: It was assumed 

that a total of 10 days would be required for 

3-9 
demobilization activities. It was further assumed that the 

entire project staff would be involved in the 

demobilization effort. Demobilization efforts will include 

facility dismantlement, equipment decontamination, and 

transportation. It is assumed that demolition of the 

mixing pads would not be required. Costs for the 

demobilization effort were estimated at $157,000. 

3.7 Cost Summary 

Table 3-2 presents the summarized costs by category 

for treating the SBMM piles. The volume of material at 

the SBMM site is extremely high compared to most 

waste sites, resulting in very large figures in the cost 

estimates; however the cost per cubic yard of treated 

material by either technology is in the low end of the cost 

range for comparable stabilization technologies. A study 

Table 3-2. Cost Summary. 

conducted for EPA in 1997 entitled “Recent 

Developments for In Situ Treatment of Metal 

Contaminated Soils” reported that, according to vendors 

of stabilization technologies, in situ applications range 

from $20 to $40 per cubic yard for treatment under 

optimum conditions, ranging upwards to $200 to treat 

high concentrations at great depths. 

The cost estimates were developed independently by 

the vendors (with additions as noted) and because of 

differences in exclusions and assumptions, cannot be 

used for direct cost comparisons, but do provide an 

overview of cost magnitudes and a breakdown into cost 

categories and percentages of total costs. KEECO 

included working capital and contingency financing in 

their startup costs, and ECWI did not include these in 

their estimate, but they would be relevant costs to any 

ECWI KEECO 

ITEM Category 

Cost* 

Percent of Total 

Cost 

Category 

Cost* 

Percent of Total 

Cost 

Site Preparation $40,000** 0.1% $840,000 2.4% 

Permitting and Regulatory $20,000** 0.0% $62,500 0.2% 

Equipment $1,633,500 2.7% $1,284,000 3.6% 

Startup and Fixed $45,000 0.1% $367,200 1.0% 

Labor $903,300 1.5% $2,986,800 8.4% 

Chemical Reagent $57,008,000 95.3% $23,107,000 64.7% 

Other Supplies & Consumables $50,840 0.1% $254,370 0.7% 

Utilities $26,145 0.0% $20,600 0.1% 

Effluent Treatment & Disposal $0 0.0% $0 0.0% 

Residuals and Waste Handling $0 0.0% $6,474,500 18.1% 

Analytical $10,400 0.0% $97,800 0.3% 

Maintenance & Modifications $25,000 0.0% $38,480 0.1% 

Site Demobilization $45,000 0.1% $157,000 0.4% 

Total Operating Costs $59,807,000 100.0% $35,690,000 100.0% 

Cost per Ton $27.82 $16.60 

*Costs rounded to a maximum of five significant digits. 

**Costs for this category not provided by vendor; assumed value as described in Section 3.6.1.

3-10 
project. The largest area of discrepancy, residuals 

handling, is a legitimate difference between the two 

processes, however, as the ENTHRALL®

 process would 

not generate residuals whereas handling treated 

material is a major element of KEECO’s SME process. 

It is clear for both treatments that the chemical reagent 

is the largest cost factor, at $26,700,000 (68% of total 

costs) for SME and $57,008,000 (93.5% of total costs) 

for ENTHRALL®

. The vendors based their application 

ratios on the amounts used in the treatability study, and 

if it was determined that the quantity required for a field 

application was reduced, then associated reagent costs 

would also be lower. Neither vendor indicated any cost 

reduction for high volume usage. 

The equipment cost of $1,633,500 for the Enthrall® 

treatment constitutes only 2.7% of the total, but is the 

second highest cost category. KEECO’s process is 

unusual in that it requires residual handling to the extent 

that it is the second highest cost factor, lowering the 

equipment costs to the fourth highest category despite 

the $1,283,000 estimated cost. 

3-11 
Section 4.0 

Treatment Effectiveness 

4.1 Pre-demonstration Studies 

Pre-demonstration studies were undertaken to: (1) attain 

a suitable test material with sufficient mercury 

leachability for treatability testing; (2) elucidate the 

mechanism(s) of mercury leaching to develop 

appropriate testing procedures; and (3) provide samples 

of material to vendors, along with the testing criteria, to 

optimize their processes prior to the large-scale 

treatability studies. 

Leachability methods for solid waste were developed to 

simulate the leaching behavior of the material when 

subjected to specific solutions and conditions. For 

example, the Toxicity Characteristics Leachability 

Procedure (TCLP) and the Synthetic Precipitation 

Leachability Procedure (SPLP) were developed for 

simulating the leaching conditions for landfilled wastes. 

The Meteoric Water Mobility Procedure (MWMP) and 

the Humidity Cell Procedure were developed specifically 

to simulate the conditions encountered by mining waste. 

Each leachability procedure may provide different 

results, based on the leaching fluids used, duration, 

leachate preparation, and nature of the waste material. 

In order to quantitatively evaluate the effectiveness of 

the stabilization technologies tested for the mercury 

contaminated SBMM material, it was necessary to 

identify both a suitable material and leaching protocol. 

The objectives for the study required a material with 

leachable levels of mercury so that a reduction of 90% 

from a control could be observed. Furthermore, the 

leaching protocol would need to simulate the generation 

of mercury from the SBMM material so that the 

stabilization technologies could appropriately control the 

types and levels of mercury being generated from the 

site. 

4.1.1 SPLP Characterizations 

Leachability characterizations of materials from several 

locations at the SBMM site using the SPLP method 

demonstrated generally low overall mercury leachability. 

Figure 4-1 is an aerial photograph of the SBMM 

depicting the locations of samples collected for SPLP 

characterization. Table 4-1 presents the SPLP results 

as well as the whole rock mercury values. The levels of 

leachable mercury generated by the SPLP method for 

the tested materials were too low to be used in this 

technology evaluation. SPLP leachability was low even 

for materials exhibiting high whole rock mercury values 

of 1,000 mg/Kg. 

Figure 4-1. Locations of samples from SBMM site. 

The lack of appreciable leachable mercury from SBMM 

materials despite high levels of whole rock mercury 

prompted additional studies to determine a suitable 

material and leaching protocol for the technology 

evaluation. Furthermore, the additional studies 

investigated possible mechanisms of mercury 

leachability from SBMM materials. 

4-1 
Table 4-1. SPLP Leachability Results from Various SBMM Materials. 

LOCATION Total SPLP Mercury 

Mercury 

#1 Waste Rock - Shoreline Material #1 (Middle Shoreline Pile) 762 mg/Kg ND (0.2) μg/L 

#2 Waste Rock - Shoreline Material #2 (Northwest Pit Shore) 37.5 mg/Kg ND (0.2) μg/L 

#3 Waste Rock - Shoreline Material #3 (West Shoreline Pile) 175 mg/Kg ND (0.2) μg/L 

#4 Drill Cuttings MW11D 0 to 25 feet 41.9 mg/Kg ND (0.2) μg/L 

#5 Drill Cuttings MW11D 25 to 45 feet 58.5 mg/Kg ND (0.2) μg/L 

#6 Drill Cuttings MW15D 0 to 20 feet 76.1 mg/Kg 1.39 μg/L 

#7 Mercury Ore (South Hill White Pile) 1000 mg/Kg 19.9 μg/L 

#8 Waste Rock (South Hill Waste rock Pile) 905 mg/Kg 10.5 μg/L 

#9 Waste Rock (North Side Gray Pile) 35 mg/Kg 0.47 μg/L 

#10 Waste Rock (North Side Waste rock Pile) 484 mg/Kg 9.84 μg/L 

4.1.2 Leachability Studies 

Roasted tailings from the site were used in a series of 

studies to determine mechanisms of mercury 

leachability. The roasted tailings are material derived 

from the retorting of the ore. This material was used 

because it exhibits consistent levels of whole rock 

mercury and constant particle size. 

Replicate analyses using the SPLP method on the 

roasted material revealed consistent whole rock mercury 

values, but highly variable SPLP leachates (Table 4-2). 

Visual observations of the leachate from the SPLP 

extraction revealed a correlation between the visual 

turbidity of the sample and the concentration of mercury. 

This association prompted a more thorough evaluation 

of the relationship between leached particulates and 

extractable mercury. 

Table 4-2. Replicate SPLP Analyses on Roasted 

Tailings 

Replicate 

Total Hg 

(mg/Kg) 

SPLP Hg 

(μg/L) 

SBMM-RF#1 25.7 60 

SBMM-RF#2 26.6 195 

SBMM-RF#3 37.8 487 

The original roasted tailings material tested in triplicate 

was further studied. Triplicate samples of the roasted 

tailings were analyzed for total mercury (whole rock) and 

SPLP extractions. The extracts were filtered through a 

0.7μm filter (standard for the method) and analyzed for 

SPLP Hg, pH, total solids, and turbidity. The remaining 

extract was filtered through a 0.45μm filter and analyzed 

for the same analytes, as well as a 0.2μm filter. The 

experiment resulted in the generation of nine leachate 

samples (triplicate analyses at three levels of filtration). 

Results form the experiment (Table 4-3) indicates that 

total mercury was consistent between the three 

replicates (as observed in the original analysis). SPLP 

mercury at the standard filtration (0.7μm) was lower but 

exhibited much lower variability as compared to the 

original triplicate analyses. SPLP mercury at the 0.45μm 

and 0.2μm levels produced ND at the 1.0 μg/L level. 

The results from the study suggested that leachable 

mercury is associated with particulates. Furthermore, 

there is a strong association between the turbidity in the 

sample and the level of filtration. Although the finer 

filters produced non-detect values, there is a correlation 

between the SPLP mercury and turbidity. The results 

from this experiment prompted an additional experiment 

to determine the relationship between particle size, 

turbidity, and leachable mercury. 

Results from the test are presented in Table 4-4. There 

is a strong relationship between level of filtration, 

turbidity, and mercury content. Furthermore, the 

relationship between turbidity and mercury content is 

illustrated by plotting the mercury values for the filtered 

samples from both the SPLP and modified MWMP test 

(Figure 4-2). There is a high correlation between the 

turbidity of the sample and the mercury content of the 

leachate. This suggests that mercury in leachate 

samples is associated with particulates of various sizes, 

and is not predominately found in a dissolved state. 

4-2 
Table 4-3. Results of Triplicate SPLP Leaching Experiment 

Total Hg 

(mg/Kg) 

Reporting 

Limit 

SPLP 

(μg/L) 

Reporting 

Limit 

pH 

(SU) 

Total 

Solids 

Turbidity 

(NTU) 

(mg/Kg) (μg/L) (mg/L) 

Replicate 1 24 0.049 

0.7μm 3.0 1.00 6.15 64 29.2 

0.45μm ND 1.00 3.26 48 7.24 

0.2μm ND 1.00 2.85 58 0.35 

Replicate 2 23 0.052 

0.7μm 5.2 1.00 7.09 24 40.2 

0.45μm ND 1.00 3.63 24 0.58 

0.2μm ND 1.00 3.19 10 0.43 

Replicate 3 22 0.049 

0.7μm 3.6 1.00 6.89 34 36.1 

0.45μm ND 1.00 3.85 26 0.59 

0.2μm ND 1.00 6.13 ND 0.49 

Table 4-4. Results from the Modified MWMP Leachate 

Test with Variable Filtration 

160 

R2

 = 0.9863 140 

120 

100 

80 

60 

40 All filter blanks, Hg = ND 

0.7 μm filter blank had turbidity = 0.28 20

0

Filtration 

Level 

Hg 

μg/L 

pH Turbidity 

(NTU) 

Unfiltered 402 4.07 362 

25 μm 18.2 4.31 140 

8 μm 7.4 4.25 64 

2.5 μm 1.2 4.25 3.5 

1 μm 0.7 4.25 0.76 

0.7 μm 0.6 4.65 1.17

Turbidity (NTU) 

0 5 10 15 20 

Leachable Hg (ug/L) 

Figure 4-2. Turbidity and leachable mercury 

from SPLP and MWMP tests. 

4.1.3 Geochemical and Mineralogical Evaluation of 

Particulates 

A mineralogical and geochemical study was performed 

at the City College of New York to characterize the 

particulate fractions generated during leaching and to 

identify potential mechanisms for release and transport. 

Roasted tailings were placed in distilled water for three 

weeks without agitation. The water immediately became 

4-3 
cloudy, and the degree of turbidity appeared to per sist 

unchanged throughout the three week period.

rea Figure 4-3. Mercury

0.01 0.1 1 10 100 

) 

0.1

1

10

100

1000 

Suspended

adsorbed on clay particles

indicated by the number of x-ray counts

Sieve Size (microns

Stirred 

Mercury-Adsorbed Clay Weight-Adjusted Counts 

Characterizations were performed both on fines that 

were suspended in the water and on particles

suspended by stirring the mixture. Both the suspended 

particles and the particles re-suspended (stirred) are 

termed auto-released solids due to their ability to easily 

dissociate from the solid matrix. 

The structure of auto-released solids was determined by 

using standard techniques for the x-ray analysis of claysized particles. Preliminary study of a randomly oriented 

sample demonstrated that the auto-released particles 

belong primarily to the clay mineral family. Glycolation 

treatment revealed that the auto-released particles 

contain chlorite-smectite interlayer clays. The clay thus 

possesses both a filled metal-hydroxide layer and

partially filled expandable interlayer. as

Sieving and mounting procedures were used to estimate 

the quantity of mercury on particles of various sizes. 

The procedure involves entrapping mercury on sieves of 

varying sizes using a Mylar filter to fix the particles to the 

sieve material. The mylar-shielded samples were then 

analyzed using a Philips 1410 series x-ray fluorescence 

spectrometer and counting times of 400 seconds on 

both peak and background. The results are plotted as 

counts-above-background adjusted by weight using the 

relationship: 

Cadjusted 

Cpeak −Cbackground = W 

Where: Cpeak is the number of counts on the mercury

peak using a LIF200 crystal, 

Cbackground is the number of counts at ± 1 degree

of the peak maximum, and 

W is the microgram weight of the clay. 

The adjusted counts indicate the distribution of mercury 

within the sample irrespective of the amount captured on 

a given sieve. Since the actual weight of sample is 

greater toward the larger sieve sizes, the relative error 

increases as the sieve-size decreases. The plot of this 

distribution (Figure 4-3) indicates that the bulk of the 

mercury is carried by the 10 to 20 micron clay fraction, 

but that a given amount of mercury is present in all sieve 

fractions, including the <0.45μm set. The results 

establish that clay is auto-released from roasted tailings. 

adjusted by the sample.

4.1.4 Extended Leachability Study 

Three SBMM solid matrices were evaluated by a 

modified MWMP (Meteoric Water Mobility Procedure) 

over various time intervals to assess the change in 

leachability of mercury over time. The study was 

conducted to determine if dissolved mercury is 

generated when leaching times and exposure to 

aqueous solutions is extended. Conventional leaching 

procedures require only a 24-hour exposure to the 

leaching agent. The samples chosen for this exercise 

consisted of: (1) a roasted tailings composite, (2) waste 

rock (shoreline #1) form the middle shoreline pile, and 

(3) waste rock (# 10) from the north side waste rock pile. 

Whole rock mercury concentration of each matrix are 25 

ppm for the roasted tailings, 762 ppm for the shoreline 

#1, and 484 ppm for the mine tailings #10. 

The modified MWMP utilized a 1:1 ratio of solid material 

to leaching medium (deionized water) placed in a 

column-type apparatus and exposed to the leachate in a 

single pass manner over a 24-hour period. After each 

24-hour period the leachate volume was collected and 

reapplied to the top of the column. The solution was 

passed back over the solids in the column until the end 

of the test period (for 72 hour tests) or for five days 

(Monday-Friday). For the 1, 2 and 4 week test periods, 

the solution was allowed to remain in contact with the 

solids over the weekend (with the column top covered), 

and then drained over 24 hours starting again on 

Monday. 

4-4 
The following tests were performed: 

Matrix # of Tests Test Duration 

Roasted tailings 5 24 hrs 

 72 hrs 

 1 week

 2 weeks

 4 weeks 

Waste Rock (spl#1) 2 24 hrs 

 2 weeks 

Waste Rock (spl#10) 2 24 hrs 

 2 weeks 

The leachate from each test was split, with one-half of 

the sample set-aside for unfiltered analyses, while the 

second-half of the leachate sample was filtered through 

a 0.45μm filter. The leachate samples (unfiltered and 

filtered) were analyzed for the following analytes: 

mercury, sulfate, pH, turbidity, and total solids. 

Analytical results from the study are presented in Table 

4-5. For the roasted tailings, and as in previous studies, 

mercury appears to be associated with the particulate 

fraction (>0.45μm). For the unfiltered samples, mercury 

leachability is lower for the two week and 4 week 

samples. Mercury leachability, therefore, does not 

increase with longer leaching cycles, and actually 

decreases. For the filtered samples, mercury 

concentration is low and variable. There is no indication 

that extended leaching results in the generation of 

significant dissolved mercury. 

Waste Rock spl#1 exhibited the highest leachable 

mercury concentration of the unfiltered samples. 

Table 4-5. Results from the Extended Leachability Study 

Although high particulate mercury concentrations were 

encountered, filtered mercury was low. The sample 

completely dissociated after five days into a hydrous 

clay, necessitating cessation of the leaching tests. The 

hydrous clay was submitted to CCNY for 

characterization. The sample was characterized as a 

mixture of two clays with properties similar to the autoreleased clays from the first roaster fine study. 

Furthermore, the sample contained very high mercury 

content as measured by X-ray fluorescence. The 

complete dissociation of the sample and the presence of 

high mercury content in the clay fraction provide further 

evidence for a particulate transport mechanism. 

Extended leaching of the waste rock spl #10 failed to 

provide significant concentrations of mercury in either 

the unfiltered and filtered fractions. There is some limited 

evidence that mercury content decreases over time in 

both fractions. 

4.1.5 Conclusions from Leachability and 

Characterization Studies 

The following conclusions are based on the results from 

the previously discussed studies: 

• Mercury is found associated with particulates that 

auto-release from SBMM material and can remain 

suspended, and therefore mobile, in solution. There 

is no strong evidence from any of the leaching 

studies that a dissolved mercury fraction exists in 

the leachate. 

• There may be clays in the material that are easily 

dissociable, contain mercury, and can be suspended 

and transported in an aqueous medium. Since the 

clays are expanded layer smectites, the mercury 

Unfiltered Filtered (0.45um) 

Total Total 

Hg pH Sulfate Turbidity Solids Hg pH Sulfate Turbidity Solids 

Sample (ug/L) (m g/L) N TU (m g/L) (ug/L) (m g/L) NT U (m g/L) 

Roasted T ailings 24 hrs 20.0 6.86 9.7 434 333 3.30 7.26 10.2 19.4 NA 

RoastedT ailings 72 hrs 14.0 7.52 10 154 250 2.30 7.4 10.1 5.77 NA 

Roasted T ailings 1 week 16.0 7.25 10.4 188 190 1.50 7.71 7.8 4.42 NA 

Roasted T ailings 2 weeks 8.3 7.38 10.2 90.1 220 ND (1.2) 7.12 10.3 25.1 NA 

Roasted T ailings 4 weeks 2.5 7.18 15.1 99.6 200 8.3 7.32 13.9 36.2 NA 

W aste Rock (spl #10) 24 hrs ** 96.1 3.11 7010 155 9110 2.20 3.13 5270 0.42 NA 

W aste Rock (spl #10) 24 hrs 9.0 3.04 2630 4.9 3440 6.00 3.09 2350 0.52 NA 

W aste Rock (spl#10) 2 W eeks 7.5 3.15 2360 8.15 3300 ND (2.5) 3.24 2210 0.1 NA 

** spl #1 was observed to com pletely dissociate to a clay-m ud after approx. 5 days 

NA = Not Applicable 

ND = N on detectable at level in parentheses 

NR = Not Reported 

4-5 
may be bonded within the interlayers. These clays 

may be associated with the ore and rock, or may 

exist as discrete deposits that were segregated 

during the mining process. 

• Mercury associated with the particulates may 

undergo further chemical and biological diagenetic 

changes in the groundwater and/or lake environment 

that release dissolved mercury during transport. 

• The remedial solution may require technologies that 

can control the release of particulates from SBMM 

materials. 

• The leaching protocol for the stabilization evaluation 

should simulate the generation of mercury-laden 

particulates from a solid matrix. 

4.1.6 Pre-demonstration Kinetic Column Studies 

A kinetic column configuration was investigated as a 

leaching protocol for evaluating the effectiveness of the 

stabilization technologies. In the kinetic column, 

leaching solutions are continuously passed over the 

material. For this evaluiation material from the south 

white gate pile (“mercury ore”) and “waste rock” were 

tested. For the mercury ore material, whole rock 

mercury concentrations ranged from 300-1360 mg/Kg 

and SPLP mercury concentrations as high as 113 μg/L 

were encountered (Table 4-6). For the waste rock 

material, whole rock mercury concentrations ranged 

from 130 to 450 mg/Kg with leachable mercury below 10 

μg/L in all three samples. Two kinetic column studies 

were initiated for each of the materials. For one set of 

experiments, leachant (15 L de-ionized water adjusted to 

a pH of 5) was applied to the column in flow-through 

Table 4-6. Mercury in Untreated Mercury Ore and 

 Waste Rock

unfiltered sample and filtered through a 0.45μm filter. 

The results, presented in Table 4-7, indicated that: (1) 

the flow-through method generated higher and more 

consistent leachable mercury, (2) the unfiltered samples 

contained significantly higher levels of mercury, and (3) 

the mercury ore material generated significantly higher 

levels of leachable mercury. Based on these results a 

kinetic column leaching protocol using mercury ore 

material from the site and focusing on control of the 

particulate fraction would be relevant for evaluating the 

performance of the stabilization technologies. 

4.2 Project Objectives 

For all MWTP and SITE projects, specific objectives are 

defined in a Quality Assurance Project Plan (QAPP) 

prior to the initiation of treatability studies or fieldwork. 

The QAPP specifies the objectives to be achieved and 

provides experimental design. This section states the 

project objectives and summarizes each of the 

experiments performed as part of the treatability study. 

4.2.1 Primary and Secondary Objectives 

Objectives are subdivided into two categories: primary 

and secondary. Primary objectives are those goals of 

the project that must be achieved in order to adequately 

compare demonstration results with the claims made by 

the developer(s). The analytical results and field 

measurements required for achieving primary objectives 

are referred to as critical measurements. Secondary 

objectives are specified to obtain additional information 

of interest about the technology, but are not imperative 

for validating developer claims. The data and field 

measurements required for achieving secondary 

Matrix Total Hg 

(mg/Kg) 

SPLP Hg 

(μg/L) 

Mercury 

Ore 

751 37 

312 0.5 

1360 113 

Waste 

Rock 

447 1.5 

441 0.9 

130 5.6 

mode 

as a single-pass leach. The second set of experiments 

used approximately 15 liters of the solution in a recycle 

mode. Leachate was analyzed for mercury both as in an 

objectives are referred to as noncritical measurements. 

Immobilization of mercury in material from the Sulfur 

Bank Mercury Mine (SBMM) was the goal of the 

treatments used in this treatability study. The objectives 

of the study are to evaluate the technologies’ ability to 

achieve this end. Primary objective satisfaction was 

evaluated by treating “mercury ore” material from the 

site. The same testing process was applied to “waste 

rock” material to achieve secondary objectives. The 

actual testing procedures are described in their 

respective sections below. The success of the various 

treatments was evaluated by measuring the parameters 

as specified in Table 4-8. 

4-6 
Table 4-7: Kinetic Column Leachability Study 

Leach Time 

(days) 

Hg in Mercury Ore Leachate (μg/L) Hg in Waste Rock Leachate (μg/L) 

Recirculating Flow-through Recirculating Flow-through 

Unfiltered 

2 210 410 0.6 1.2 

9 210 530 0.3 2.1 

15 180 420 0.4 ND 

23 90 410 0.8 1.0 

29 93 270 0.1 ND 

38 140 390 0.2 0.2 

2 11 28 ND ND 

<0.45μm 

Filtered 

9 11 9.0 ND ND 

23 5.0 7.0 ND ND 

29 2.0 9.0 ND ND 

38 2.0 7.0 ND ND 

4.2.1.1 Primary Objective 

The primary objective of the treatability study was to 

evaluate each technology’s ability to immobilize, and 

therefore reduce the leachability, of mobile mercury in 

the SBMM mercury ore material. Mobile mercury is 

defined in this project as the mercury associated with the 

<25μm filtered fraction. Previously discussed studies 

revealed that particulates containing mercury are 

released from SBMM materials and can become 

suspended and therefore mobile in aqueous systems. 

The <25μm fraction was chosen based on the results 

from the previous studies. Success at immobilizing 

mercury was to be determined by comparison of the 

amount of mobile mercury (<25μm fraction) in each 

treatment columns leachate to the amount of mercury in 

leachate from untreated control columns. Each 

technology and control was tested in triplicate. After 

being loaded into columns and treated, the material was 

leached daily with fresh deionized water, adjusted to a 

pH of 5.0. The leachate was collected, measured, 

filtered and analyzed weekly for the critical parameters 

of dissolved and total mercury. The original design 

called for a minimum of eight weeks of leaching. This 

was extended an additional four-weeks for one of each 

type of column during the study. 

Each technology was evaluated to determine the 

reduction in the cumulative mass of mercury in the 

<25Fm filtered leachate, relative to the control column 

<25Fm filtered leachates. The target reduction for the 

treatments was 90%. Mercury mass was calculated 

from leachate concentrations by multiplying the 

concentration in micrograms per liter by the volume of 

total sample collected each week (in liters), resulting tin 

the total micrograms leached from each column. 

Percent Mercury Reduction was determined from the 

difference between the amounts of mercury leached 

from treated columns and control columns as follows: 

Mercury Mass(control) – MercuryMass(treated) x 100

 Mercury Mass(control) 

Where Mercury Mass is the summation of the average 

weekly mercury mass for each treatment or control over 

the 12-week test. 

Mercury mass was determined for each column each 

week and then averaged for that week and summed to 

derive the total mass of mercury leached for each 

treatment or control. Leachate characteristics were also 

collected for turbidity, pH, redox potential, sulfate, 

sulfide, conductivity, alkalinity/acidity and the metals 

arsenic, iron and antimony. Primary and secondary 

objectives of the treatability study are summarized in 

Table 4-8. The table gives a description of the objective 

and the method by which each was evaluated. 

4-7 
Table 4-8. Treatability Study Test Parameters 

Matrix Parameter Classification Type Purpose 

Kinetic Test Column Mercury-dissolved Non-critical Analytical Primary objective: evaluating 

Leachates - (<0.45μm) leachable Hg reduction 

mercury ore material, 

treated and untreated 

controls 

Mercury-mobile 

(<25μm) 

Critical Analytical 

Leachate volume Critical Field 

Metals (As, Fe, Sb) Non-critical Analytical 

Secondary objective: Evaluate 

leachate quality after treatment of 

primary test matrix 

Sulfate Non-critical Analytical 

Sulfide Non-critical Analytical 

Alkalinity Non-critical Analytical 

Acidity Non-critical Analytical 

Turbidity Non-critical Field 

pH Non-critical Field 

Conductivity Non-critical Field 

Redox potential Non-critical Field 

Mercury ore material 

prior to leaching, SPLP (Hg/As/Sb/Fe) Non-critical Analytical 

Secondary objective: evaluate 

impact of treatment on 

treated and untreated conventional leachability 

X-ray diffraction Non-critical Mineralogical Secondary objective: evaluate 

mineralogical changes of solids 

after treatment 

X-ray fluorescence Non-critical Mineralogical 

SEM/EDS Non-critical Mineralogical 

Secondary Objective: assess 

Humidity Cell Test Non-critical Analytical weathering effects on treated 

material 

Mercury ore material 

after leaching, treated 

and untreated control 

X-ray diffraction Non-critical Mineralogical Secondary objective: evaluate 

mineralogical changes of solids 

after leaching X-ray fluorescence Non-critical Mineralogical 

SEM/EDS Non-critical Mineralogical 

Kinetic Test Column 

Leachates 

Waste rock material, 

treated and untreated 

controls 

Mercury-dissolved Non-critical Analytical Secondary objective: evaluate Hg Mercury-mobile reduction in second matrix Non-critical Analytical 

Leachate Volume Non-critical Field 

Metals (As, Fe, Sb) Non-critical Analytical 

Secondary objective: Evaluate 

Sulfate Non-critical Analytical 

Sulfide Non-critical Analytical 

Alkalinity Non-critical Analytical 

Acidity Non-critical Analytical leachate quality after treatment of 

Turbidity Non-critical Field secondary test matrix 

pH Non-critical Field 

Conductivity Non-critical Field 

Redox potential Non-critical Field 

Waste rock material, X-ray diffraction Non-critical Mineralogical Secondary objective: evaluate 

mineralogical changes of solids 

after treatment 

prior to leaching, 

treated and untreated 

X-ray fluorescence Non-critical Mineralogical 

SEM/EDS Non-critical Mineralogical 

Secondary objective: evaluate 

SPLP Non-critical Analytical impact of treatment on 

conventional leachability 

Waste rock material X-ray diffraction Non-critical Mineralogical Secondary objective: evaluate 

mineralogical changes of solids 

after leaching 

after leaching, treated X-ray fluorescence Non-critical Mineralogical 

and untreated control SEM/EDS Non-critical Mineralogical 

4-8 
4.2.1.2 Secondary Objectives 

Secondary objectives are designed to provide 

information, in addition to the critical parameters, for 

evaluating the effectiveness of technology applications. 

The secondary objectives are: 

Assess Mercury Contaminant Reduction in Treated 

Waste Rock Test Material: The same kinetic column 

leach test that was described for the primary mercury 

ore material was also run on the waste rock material, 

with results being evaluated in the manner described 

above. The waste rock material columns were not run in 

triplicate, but were run in duplicate for the control and 

single for the treatments. 

Evaluate Leachate Quality After Treatment and 

During Column Testing: During and at the end of the 

column leach tests, filtered samples were analyzed for 

parameters in addition to mercury, in order to assess 

changes in the leachate chemistry. Samples were 

analyzed for the additional metals: arsenic, iron, and 

antimony, as well as pH, redox potential, sulfate, sulfide, 

conductivity, alkalinity/acidity, and turbidity. This 

analysis was done on both mercury ore and waste rock 

column effluents. 

Evaluate Mineralogical Changes in the Treated 

Material: Samples of the mercury ore material were 

collected after reagents had been applied, but before 

leaching was begun for the evaluation of the 

mineralogical changes that may have occurred during 

treatment. Mineralogical analyses included x-ray 

diffraction, x-ray fluorescence and optical mineralogy. 

Humidity Cell Test Protocol Using the Mercury Ore 

Material: Mercury ore material that had been treated 

but not leached was subjected to the Humidity Cell Test 

procedure. Leachate from the test was evaluated for 

both dissolved (<0.45μm) and mobile mercury (<25μm), 

and again reductions were evaluated by comparison to 

leachate from controls cells. Two control cells and one 

cell for each technology were run. 

Evaluate Treated Materials for Conventional (Static 

Test) Leachability: After the reagents had been 

applied, but prior to the start of kinetic leach testing, 

samples of the treated and untreated (control) material 

were evaluated to determine the leachability of mercury 

and other metals in a static test protocol. Routine 

leachability testing is most commonly performed using 

the Synthetic Precipitation Leaching Procedure (SPLP) 

method 1312 as described in SW846, which is a onetime contact over a 24 hour duration. Both of the 

material types were subjected to SPLP leaching, which 

was performed on each of the treated materials and an 

untreated control sample. Resulting leachates were 

analyzed for mercury, antimony, arsenic, and iron. 

4.3 Experimental Design 

Several tests were designed to achieve the project 

objectives. In order to assure that the critical mercury 

ore material was homogenous so that each test unit 

(column or humidity cell) received equitable material, 

splits were carefully prepared. As it was collected in the 

field, the mercury ore material was screened to pass a 

0.5-inch mesh. The material was transported to MSE’s 

research facility where it was thoroughly mixed and split 

into batches of 5-6 kilograms. Each batch was split to 

obtain a 300 to 500 gram sample for mercury analysis. 

The requirement for successful homogenization of 

samples was a Relative Standard Deviation (RSD) of 

<25% for whole-rock mercury content. The analysis of 

the 32 split batches yielded a mean of 1,969 mg/Kg Hg, 

with a standard deviation of 313, resulting in an RSD of 

16%, indicating successful homogenization. 

4.3.1 Column Studies 

The primary objective was achieved by performing 

column leach studies on the mercury ore material. Each 

column consisted of a 3-foot 4-inch section of clear 

schedule 40, 3-inch diameter PVC pipe, fitted with a cap 

on the bottom. A drain in the cap connected to 0.25-inch 

tubing. Columns were prepared by filling the first two 

inches with 1/8-inch stone to provide a drain layer. After 

the treatment on material in the columns was completed, 

two more inches of the 1/8-inch stone was added to the 

top surface to disperse the liquid being dripped onto the 

column. 

For the ex situ application, four batches of mercury ore 

material were treated with KEECO’s KB Sea dry 

reagent. Half of a batch (~2000 grams) was spread out 

in a bin and half of the dry reagent was sprinkled on top 

of it. The other half of the material and reagent were 

added in the same manner and the entire amount was 

thoroughly mixed together by hand turning. A total of 

195.46 grams of KEECO’s KB Sea dry reagent was 

added to each batch. Four kilograms from each of three 

batches was loaded into columns. The fourth batch was 

reserved for physical and chemical investigations, SPLP 

and humidity cell testing on treated material. 

The three in situ treatments on mercury ore material 

were each applied to four columns, again to provide 

4-9 
triplicate samples and an additional quantity of treated 

material for physical and chemical investigations, SPLP 

and humidity cell testing. In situ application was 

accomplished by loading the material into the columns in 

“lifts” of approximately 5 to 7 inches, with first and last 

lifts having somewhat more variability in depth. As each 

lift was placed, a liquid form of the reagent was added 

by the use of a garden sprayer, which allowed the 

solution to be injected into the material. This procedure 

was repeated until four kilograms had been treated in 

each column. 

E&C Williams provided the ENTHRALL®

 reagent in a 

concentrated form, which was diluted with three parts 

deionized water to one part product. The four treatment 

columns with mercury ore material were each loaded in 

seven lifts. A total of 300 ml treatment solution was 

applied to each column as described above. 

Phosphate treatment was provided in liquid form and 

was diluted with one part deionized water to three parts 

phosphate. Four columns were loaded with mercury ore 

material and treated in six lifts, as described above and 

300 ml of the diluted phosphate was applied to each 

column. 

KEECO’s KB-1 product was applied to the mercury ore 

material for the in situ treatments. The reagent was 

applied as-supplied, with 1,184 ml being applied to each 

4,000 gram column load. The first and last lifts were 3 

inches deep, with intermediate lifts being 6 to 6.5 inches 

thick. Again, four columns were treated in this manner 

to allow for leachability testing in triplicate and enough 

treated material for further testing. 

Since testing on the waste rock material was secondary 

to testing on the mercury ore, a less intensive regimen 

was prescribed. Columns were loaded and treated as 

above for leachability testing, but instead of treating an 

entire column to provide SPLP and laboratory analysis, 

a small amount of material was treated. A 500-gram 

sample of material was placed in a 500-ml sample jar 

and treated with the same ratio of reagent to material as 

was used in the columns with mercury ore material. 

Two columns were loaded with waste rock material and 

treated with E&C Williams’ ENTHRALL®

 process as 

described above. As with the mercury ore material, 

each column was loaded with 4,000 grams of material 

and treated with a total of 300 ml ENTHRALL®

 solution. 

A 500-gram portion of the material was treated with 37.5 

ml ENTHRALL®

 for SPLP and laboratory analysis. The 

phosphate product was demonstrated on the waste rock 

material in the same manner, with the same quantities 

being applied. Products were diluted as described for 

mercury ore material above. 

The KEECO treatments on the waste rock material were 

only tested in one column each. For the ex situ 

application, 217.84 grams of KB-Sea was mixed into 

4,000 grams of waste rock material, and loaded into a 

column. A 500 gram portion was treated with 27.23 

grams of reagent for lab analysis. In situ treatment of 

the waste rock material was performed by loading the 

column in lifts, as previously described, and applying 

KB-1 reagent to each lift. The initial and final lifts were 

three inches deep, with intermediate lifts being 6-6.5 

inches thick. A total of 1,305 ml of KB-1 was applied to 

the column. 

Three columns were each loaded with 4,000 grams of 

mercury ore material and two columns were loaded with 

the same amount of waste rock material. These were 

the experimental controls for the testing that was to 

follow. 

Kinetic leach testing was then used to determine the 

success of the treatments. Deionized-distilled water, pH 

adjusted to 5.0, was applied at a constant rate of 0.09 

L/hr, with leachate being collected weekly. The original 

design called for leaching to continue for a minimum of 8 

weeks. The entire volume of effluent was collected and 

mixed weekly. After recording the volume, the effluent 

was taken to the lab where measurements of turbidity, 

pH, conductivity and redox potential were taken. 

Approximately 3 to 4 liters of leachate was then filtered 

through a 25μm filter for analysis of mobile mercury and 

through a 0.45μm filter for dissolved mercury analysis. 

Unfiltered samples from weeks 1, 4 and 8 were analyzed 

for total mercury to provide data on the relationship 

between total, dissolved and mobile mercury. Where 

necessary to satisfy secondary parameters, additional 

analysis was also performed, as detailed below. 

After the initial eight week leach period, the columns 

were allowed to rest for four weeks. This was intended 

to simulate a drying period during which oxidation 

reactions would naturally occur in a dump or pile. If the 

mercury leachability was due to chemical reactions, 

there should have been a peak in mercury when 

leaching was restarted. Following the rest period, one 

column of each treatment type and one control was 

leached for another four weeks. 

The column studies on the waste rock material were 

similar to the mercury ore column studies with the 

exception that the KEECO treatments were tested on 

only one column each and E&C Williams’ columns and 

4-10
the phosphate columns were run in duplicate. The 

waste rock material control columns were also run in 

duplicate. Application rates and sampling were identical 

to the study on the mercury ore material. 

In addition to mercury analysis, weekly samples were 

analyzed for sulfate, sulfide, alkalinity and acidity to 

satisfy secondary objectives. Sample splits for weeks 1, 

4 and 8 were also analyzed for the metals antimony, 

arsenic and iron. 

4.3.2 Humidity Cell Tests 

“Humidity cell” testing, detailed in ASTM D 5744-96, is a 

protocol designed to meet kinetic testing regulatory 

requirements for mining wastes and ores. In this test 

method, the sample is subjected to alternate periods of 

dry air, moist air and water leaching in an effort to 

simulate the weathering process that the ore would 

undergo in a natural environment. The rigorous 

conditions applied in the test design subject the material 

to potential worst-case scenarios in that the extreme 

changes from moist to dry air and complete wetting of 

the ore. 

For the treatability study, humidity cell testing was 

performed on the mercury ore material only. A 1,000 

gram aliquot of each of the treated materials and the 

untreated material was placed in each cell. To perform 

the initial leach, one liter of deionized water was slowly 

added to each in a manner that would avoid hydraulic 

agitation. The flooded sample was allowed to sit for one 

hour, and then the cell was drained overnight into a 

sample collection vessel. Dry air was then introduced 

into the cell at a rate of two to three liters per minute for 

three days. This was followed by a wet air purge for the 

following three days. Wet air was created by using a 

humidifier with DI water at a temperature of 30+ 2°C. 

The wet air was supplied for three days at approximately 

the same rate. The first week’s testing was completed 

by a Deionized water leach, as described above. The 

cycle of dry-air purge, wet-air purge and water leach was 

repeated weekly for a total of seven weeks after the 

initial water leach. Leachate was collected and analyzed 

for dissolved and mobile mercury, pH and turbidity, 

sulfate, sulfide and acidity/alkalinity. 

4.3.3 Mineralogical and Geochemical Tests 

Mercury ore and waste rock samples were analyzed for 

mineralogical parameters by optical microscopy, x-ray 

diffraction (XRD) and x-ray fluorescence (XRF) in the 

Department of Earth and Atmospheric Sciences at the 

City College of New York (CCNY). 

X-ray diffraction is a technique for gathering information 

about the structural state, including the degree of 

crystallinity of the materials in a sample. At the CCNY 

lab, the samples were pulverized in an agate mortar and 

pestle and mixed with a lanthanum boride standard. 

The samples were then mounted on a quartz nonreflecting holder and step-scanned at 0.02 degrees two 

theta over the appropriate range at 40kv/20 milliamps 

with a counting time of 1-4 seconds per step. For unit 

cell refinements, peak locations were obtained using a 

Philips APD package for single peak fits, or by a 

modified Pearson-VII peak fitting or related algorithm. 

Upon correction for peak position error, reflections were 

analyzed for unit cell parameters using either a Philips 

unit cell program or an in-house program that provides 

estimations of cell axes and angles and standard errors. 

For mineral identification, peak positions were obtained 

using the Philips APD package for fitting all spectral 

positions. 

Samples were prepared for analysis by x-ray 

fluorescence by pulverizing under methanol in an agate 

mortar and pestle to a grain size of less than 50 microns. 

The pulverized material was then mixed in a 40:60 

(rock:flux) ratio with lithium tetraborate and fused at 

1000 degrees centigrade for 20 minutes. The material 

was then poured onto a hot aluminum plate and pressed 

into a pellet, approximately 0.6 inches in diameter. The 

pellets were epoxyed into one inch cylindrical holders 

leaving a glass face exposed. The glass is polished to a 

smooth face using silicon carbide polish, then corundum, 

and finally diamond micro-polish. For quantitative 

analysis, an automated Philips 1400 series x-ray 

fluorescence spectrometer was used under standard 

conditions, typically 50kv 50 ma for 50-100 seconds. 

Oxide values were determined using linear least squares 

corrections of data. Semi-quantitative XRD was also 

performed on samples that had been pulverized as 

above, then dispersed in distilled water and collected on 

0.2 or 0.4 μm polycarbonate filters. The dried filters 

were then pressed into borax holders at about 20 tons 

pressure. The samples were analyzed using the 

spectrometer and compared to linear least squares 

corrections based on USGS pellets and standard 

analyzed minerals. 

4.3.4 Humic/Fulvic Acid Tests 

All natural environmental systems contain some amount 

of decomposed plant and animal matter called humus. 

The soluble portion of humus is called humic acids, and 

is further broken down into three fractions: humic acid, 

ulmic acid and fulvic acid. Humic acid is a long chain 

molecule, high in molecular weight, dark brown and 

4-11
soluble in alkaline solutions and is insoluble in water, 

acids, ethanol and acetone. Fulvic acid is a short chain, 

low molecular weight molecule. It is soluble in acid, alkali 

and water and is waste rock in color. 

Mercury and methyl mercury bind strongly to soil and 

sediments by forming strong complexes with organic 

substances, including humic acids. Previous studies 

have indicated that humic and fulvic acids dissolve 

mercury from cinnabar in the environment, and 

subsequently release it into aqueous systems. 

Vegetative caps can be used on tailings and piles to 

inhibit the downward migration of meteoric waters 

through evapo-transpiration, and help stabilize the pile 

from erosion and collapse. A vegetative cap may 

produce these organic acids, which could then seep 

down and mobilize mercury in the underlying material. 

In order to determine whether this would be a concern at 

SBMM if a vegetative cap would be considered, a 

supplemental test was added to the original 

experimental design. The additional test for humic/fulvic 

acid leachability was a modification of the MWMP 

described earlier. The design used glass columns 50 

cm tall and 2.5 cm in diameter. Five identical columns 

were loaded with untreated mercury ore material. Three 

of these columns were leached with a synthetic 

dissolved organic carbon mixture consisting of 20 mg/L 

of humic acid and 10 mg/L of fulvic acid in deionized 

water. To ensure complete dissolution of the acids, the 

pH of the solution was brought to 9.0 with a sodium 

hydroxide addition, and then adjusted to a pH of 6.0 by 

adding acetic acid. The remaining two columns were 

leached with deionized water adjusted to a pH of 6.0 as 

a duplicate control. The 1:1 ratio from the MWMP was 

maintained, so the design called for the columns to be 

slowly leached with one solution volume equaling one 

material volume over each 24-hour period. The columns 

were loaded with 150 grams of material. 

Leachate was collected on days 3 and 7 and then 

weekly for weeks 2, 3 and 4. The entire volume of 

leachate was collected, mixed and filtered. Each sample 

was analyzed after filtration through 25μm and 0.1μm 

with additional filtration at 0.45μm performed on day 

seven and week four. Turbidity and pH were measured 

immediately after each sample was filtered. 

4.4 Results 

Results are presented in this section for each set of 

tests. 

4.4.1 Kinetic Column Study Results 

The column studies were the primary leaching method to 

evaluate the effectiveness of the stabilization 

technologies on SBMM material. In particular, column 

tests using the mercury ore material were used to 

evaluate the primary objective, i.e. 90% reduction in the 

cumulative mass of mercury leached from the <25μm 

fraction relative to the control columns. Column study 

results will be presented individually for the mercury ore 

and waste rock material. 

4.4.1.1 Column Studies on Mercury Ore Material – 

Primary Objective 

Overall, the column studies using the mercury ore 

material enabled a quantitative evaluation of treatment 

effectiveness. Variability between the triplicate columns 

was low and detectable levels of mercury were 

encountered in all effluents from the control and 

treatments. 

Evaluation of the primary objective for each technology 

consisted of summing the total mass of mercury leached 

from the <25μm fraction (volume x concentration) from 

an average of the triplicate columns over the 12-week 

test and comparing to the mass of mercury leached from 

the control column. For definitional purposes, this 

fraction is considered the “mobile” fraction based on 

previous studies that demonstrated the potential for 

particulate (colloidal) transport. In addition to calculating 

the mobile fraction, the “dissolved” fraction was 

determined by using data from the <0.45μm analyses, 

as well as calculating the “particulate” fraction as the 

difference between the <25μm and <0.45μm fractions. 

Table 4-9 presents a summary of the total mass (in 

micrograms) of mercury leached for each treatment and 

the control over the 12-week testing period on the 

mercury ore material. The table shows the mercury 

mass of the <25μm filtered (mobile), the <0.45μm 

(dissolved), and calculates the particulate fraction (as 

the difference between the <25μm and <0.45μm 

fractions). The last column shows the calculation for the 

% difference in mass of mercury of the mobile fraction 

for each treatment relative to the control column. Figure 

4-4 is a graphical presentation of the data presented in 

Table 4-9. The graph shows the mobile fraction leached 

and illustrates the contribution of the particulate and 

dissolved fractions. 

4-12
Table 4-9. Total Mass Mercury Leached from Mercury Ore Columns Over Twelve Weeks 

Treatment 

Mass Hg (μg) 

Leached 

<25μm 

(Mobile) 

Mass Hg (μg) 

Leached 

<0.45μm 

(Dissolved) 

Mass Hg (μg) 

Leached 

0.45μm to 25μm 

(Particulate) 

% Difference Relative 

to Control 

<25μm Fraction 

(Mobile) 

Control 12,509 488 12,021 

Phosphate 131,018 74,211 56,808 947% 

E&C Sulfide 13,836 731 13,105 11% 

KEECO In Situ 1,532 1,452 80 -88% 

KEECO Ex Situ 1,723 1,650 72 -86% 

-

l lfi

ion ( i ) 

ion (Di

20,000 

40,000 

60,000 

80,000 

100,000 

120,000 

140,000 

Total Mass Hg (ug) 

Contro Phosphate E&C Su de KEECO In Situ KEECO Ex 

Situ 

25um to 0.45um fract Part culate

<0.45 um fract ssolved) 

Figure 4-4. Comparison of the total mass mercury leached from the mercury ore columns. 

Table 4-10 presents the leachability data for each week A discussion of the results from the control columns and

of the 12-week test period. The table shows the mass of each set of treatment columns are presented and

mercury (in micrograms) leached from the control and discussed relative to the primary objectives.

treatment columns during each week of leaching for both Observations of the technology’s performance and

the particulate fraction (25μm–0.45μm) and the applicability to SBMM material are made when

dissolved fraction (<0.45μm). appropriate.

4-13
Table 4-10. Mercury Ore Leachability Results By Week 

Week Treatment 

Average Whole

 Rock Hg 

Concentration 

Mercury 

Mass Removed 

(μg) 

(mg/Kg) Particulate Dissolved 

25μm -0.45μm <0.45μm 

Week 1 Control 1888 1276.3 14.6 

Phosphate 1830 48623.0 66318.0 

 E&C Williams ENTHRALL® 1867 506.6 12.4 

KEECO SME In Situ 2101 19.8 92.1 

 KEECO SME Ex Situ 2066 6.1 16.0 

Week 2 Control 1888 671.7 15.1 

Phosphate 1830 2933.1 3078.3 

 E&C Williams ENTHRALL®

 1867 495.7 19.2 

KEECO SME In Situ 2101 14.6 149.5 

 KEECO SME Ex Situ 2066 1.5 193.7 

Week 3 Control 1888 891.4 37.7 

Phosphate 1830 584.3 1563.1 

 E&C Williams ENTHRALL®

 1867 1054.3 38.2 

KEECO SME In Situ 2101 0.00 194.8 

 KEECO SME Ex Situ 2066 0.00 266.4 

Week 4 Control 1888 1477.5 52.9 

 Phosphate 1830 738.8 954.5 

 E&C Williams ENTHRALL®

 1867 1668.0 85.1 

KEECO SME In Situ 2101 23.3 177.2 

 KEECO SME Ex Situ 2066 33.5 222.0 

Week 5 Control 1888 1559.3 67.3 

Phosphate 1830 592.4 509.4 

 E&C Williams ENTHRALL®

 1867 1392.5 106.1 

KEECO SME In Situ 2101 3.5 140.6 

 KEECO SME Ex Situ 2066 0 170.5 

Week 6 Control 1888 11196.0 40.7 

Phosphate 1830 657.5 359.0 

 E&C Williams ENTHRALL®

 1867 1688.8 99.7 

KEECO SME In Situ 2101 5.0 137.2 

 KEECO SME Ex Situ 2066 5.8 155.1 

Week 7 Control 1888 1050.3 56.9 

Phosphate 1830 NA NA 

 E&C Williams ENTHRALL®

 1867 1761.0 86.7 

KEECO SME In Situ 2101 6.4 110.5 

 KEECO SME Ex Situ 2066 1.9 129.0 

NA = Not Analyzed 

4-14
Table 4-10 continued. Mercury Ore Leachability Results By Week 

Week Treatment 

Average Whole

 Rock Hg 

Concentration 

Mercury 

Mass Removed 

(μg) 

(mg/Kg) Particulate 

25μm -0.45μm 

Dissolved 

<0.45μm 

Week 8 Control 1888 935.3 27.8 

Phosphate 1830 425.8 220.4 

 E&C Williams ENTHRALL®

 1867 1375.5 64.9 

KEECO SME In Situ 2101 8.8 101.5 

 KEECO SME Ex Situ 2066 16.4 111.2 

Week 9 Control 1888 915.0 55.5 

Phosphate 1830 912.6 452.4 

 E&C Williams ENTHRALL®

 1867 1248.5 60.5 

KEECO SME In Situ 2101 0.00 119.9 

 KEECO SME Ex Situ 2066 4.4 128.5 

Week 10 Control 1888 823.0 22.7 

Phosphate 1830 489.4 188.9 

 E&C Williams ENTHRALL®

 1867 707.2 31.2 

KEECO SME In Situ 2101 1.3 80.4 

 KEECO SME Ex Situ 2066 0.0 93.9 

Week 11 Control 1888 705.3 43.4 

Phosphate 1830 422.1 261.3 

 E&C Williams ENTHRALL®

 1867 620.6 56.2 

KEECO SME In Situ 2101 0.0 77.0 

 KEECO SME Ex Situ 2066 0.0 84.7 

Week 12 Control 1888 519.8 53.2 

Phosphate 1830 428.8 305.5 

 E&C Williams ENTHRALL®

 1867 586.1 70.6 

KEECO SME In Situ 2101 6.8 71.6 

 KEECO SME Ex Situ 2066 6.0 79.5 

NA = Not Analyzed 

4.4.1.1.1 Control Column 

Mercury leachability from the control columns was 

calculated as a comparative benchmark for the 

treatment columns as well as to elucidate potential 

leaching properties of the mercury ore material. The 

total mass of mercury leached from the control in the 

<25μm fraction was 12,509 μg over the course of the 12­

week period. This was derived from the average of the 

three replicate columns. Overall, variability between the 

three columns was low with an average coefficient of 

variation (CV) of 30%. The CV is calculated as the 

standard deviation over the mean (as a percent), and is 

a normalized measure of the parameter’s variability. 

The <0.45μm fraction exhibited a total mass mercury of 

488 μg, and also exhibited a relatively low coefficient of 

variation of 36%. The calculated total mass mercury in 

the particulate fraction (25μm to 0.45μm) was 12,021 μg. 

4-15
Control Coulmn - White

Detectable levels of mercury were encountered in all 

weekly effluent fractions with mass means (of the three 

columns) ranging from 573 μg to 1,627 μg for the <25μm 

fraction, and 14.59 μg to 67.31 μg for the <25μm 

fraction. 

Figure 4-5 depicts the mass of mercury leached 

(particulate and dissolved) from the control columns 

(average of the three columns) over the 12-week test 

period. Overall, there are much greater levels of 

particulate-associated mercury in the leachate over the 

entire test period as compared to the dissolved mercury. 

After the fifth week of leaching, particulate mercury 

concentration (Figure 4-6) of samples filtered through 

the 0.45μm filter reveals a general linear relationship. 

This suggests that the mercury from the control column 

leachates is associated with sub-micron particles, such 

as clays, which can transport the mercury as a colloidal 

suspension. This may have important implications in the 

transport and fate of mercury in the SBMM-Clear Lake 

system. 

8

6

4

Hg (ppb) 

0 

0 2 4 6 8 10 

Turbidity (NTU) 

Figure 4-6. Turbidity vs. Hg for the <0.45μm fraction – 

mercury ore control columns. 

2

steadily decreased to week 12. The four-week rest 

period between weeks eight and nine did not 

significantly increase the mass of leachable mercury in 

either the particulate or dissolved fractions, suggesting 

that chemical oxidative processes are not enhancing 

mercury leachability with a water rinse. 

The pH of the effluent over the course of the 12 weeks 

was relatively constant with a mean of 4.16 (CV=6.25%) 

and ranged from 3.54 to 4.52. The Eh of the solutions 

indicated oxic conditions throughout the test with a mean 

of 455 and a range from 384 to 500. There are no 

correlations between either the pH and leachable 

mercury or Eh and leachable mercury under the 

leaching conditions of this test. 

2000 

1000 

1250 

1500

Mass Hg Leached (ug)

Particulate 

Dissolved 

Mercury Ore Control 

The total mass mercury leached from the phosphate 1750 

4.4.1.1.2 Phosphate Treatment 

columns was compared to the control columns to 

evaluate the primary objective. The total mass of 

mercury leached from the phosphate treatment in the 

<25μm fraction was 31,018 μg over the course of the 12- 

week period. This represents a significant increase in 

leachability of 947% relative to the control. The overall 750 variability between the three columns was low with a CV 

500 of 22%. The <0.45μm fraction exhibited a total mass 

mercury content of 74,211 μg over the 12-week test 250 

period. The overall variability between the three columns 

was low with a CV of 24%. The weekly average mass of 

mercury ranged from 646 μg to 114,941 μg for the 

<25μm fraction, and 189 μg to 66,318 μg for the <0.45 

μm fraction. The calculated total mass of mercury in the 

particulate fraction (25μm to 0.45μm) was 56,808 μg. 

The phosphate treatment dramatically increased the 

levels of both the particulate and dissolved fractions 

over the course of the12-week study. Figure 4-7

depicts the leachability profile over time for both the 

particulate and dissolved fractions. The mass of 

mercury leached was extremely high during the first two 

0 

1 2 3 4 5 6 7 8 9 10 11 12 

Week 

Figure 4-5. Dissolved and particulate leached Hg 

(mass) from mercury ore control columns. 

As observed in the pre-demonstration studies, it does 

not appear that the <0.45μm fraction contains truly 

dissolved mercury. A plot of the turbidity vs. mercury 

4-16
Phosphate Column - White

Mass Hg Leached (ug) 

5000 

4000 

3000 

2000 

1000 

0 

x Particulate 

G Dissolved 

Mercury Ore Phosphate 

1 2 3 4 5 6 7 8 9 10 11 12 

Week 

Figure 4-7. Dissolved and particulate leached Hg 

(mass) from mercury ore phosphate 

columns. 

weeks, so these values are not shown on this graph in 

order to maintain scale for subsequent weeks. 

Although approximately 88% of the total leached 

mercury in both the dissolved and particulate fractions 

was leached out in the first week, significantly higher 

levels of mercury were still leached from the phosphate 

treatment during subsequent weeks as compared to the 

control. For example, from weeks 2 through 12 the 

total mass mercury leached from the phosphate 

treatment’s dissolved fraction was 7,893 μg as 

compared to 473 μg from the control over the same 

period. 

The pH of the solutions averaged 6.7 (6.38 to 6.87) and 

exhibited very low variability (CV=2%). The pH of the 

phosphate effluents was higher than the control. The 

average Eh of the solutions was slightly lower (338) than 

the control but still exhibited oxic leaching conditions. 

The Eh ranged from 166 to 420. 

As with the control column, there is evidence that the 

mercury in the <0.45μm fraction is associated with submicron particles. This suggests that the phosphate 

treatment accelerated the breakdown of the mercury ore 

material matrix and facilitated the release of particulates. 

Therefore, it does not appear that the increase in 

mercury brought about by the phosphate treatment is 

due to true dissolution. The phosphate treatment greatly 

exaggerated the processes releasing mercury from the 

solid matrix. 

The dramatic rise in leachable mercury brought about by 

the phosphate treatment invalidates its utility as a 

remedial alternative for materials at the SBMM site. 

Additional investigations could be carried out to 

determine the cause of the increased leachability for the 

purpose of identifying potential mechanisms that may be 

responsible for mercury leachability from SBMM (if 

occurring) and other mercury-bearing materials. 

4.4.1.1.3 E&C Williams Sulfide Treatment 

The total mass mercury leached from the sulfide 

treatment columns was compared to the control columns 

to evaluate the primary objective. Total mass mercury 

leached from the sulfide treatments averaged 13,835 μg 

in the <25μm fraction over the course of the 12-week 

study. This represents a slight, and statistically 

insignificant, increase in the leachable mercury. The 

overall variability between the three replicate columns 

was low, exhibiting a CV of 14%. The total mass of 

mercury in the <0.45μm fraction was 731 μg over the 12­

week testing period, and exhibited low variability 

between the three replicate columns (CV=30%). The 

range of weekly mass mercury values was 515 μg to 

1,847 μg for the <25μm fraction, and 12.41 μg to 106 μg 

for the < 0.45μm fraction. The calculated particulate 

fraction (25μm to 0.45μm) was 13,105 μg. 

The mass of mercury leached over the 12-week period 

is depicted in Figure 4-8. As illustrated in the figure, the 

overall pattern and magnitude of mercury leachability is 

similar to the control. Furthermore, as in the control 

columns, it appears that the leachable mercury in the 

<0.45μm fraction is associated with sub-micron particles. 

The average pH in the effluent over the course of the 12­

week test was 4.01 (3.26 to 4.41) and exhibited a low 

CV of 8%. The Eh of the solutions indicated oxic 

conditions with an average value of 469 and a range of 

469 to 507. 

The E&C William’s ENTHRALL®

 technology did not 

appear to be effective in reducing the levels of mobile 

mercury in the mercury ore material column tests. The 

total mass of mercury in both the particulate and 

dissolved fractions are statistically similar to the control. 

Furthermore, the temporal pattern and magnitude of 

mercury leaching between the control and sulfide 

treatment are similar. In addition, the association of 

mercury with particulates is very similar to the control. 

E&C Williams provides an explanation for their 

technology’s performance in Section 4.51. 

4-17
E&C Williams Sulfide - White

Keeco In Situ Column - White

Mercury Ore KEECO Ex Situ 

2000 

treatment. Overall variability was very low with a CV of 

16% for the in situ and 15% for the ex situ. The 

1000 

1250 

1500 

1750 

Particulate 

Dissolved 

Mercury Ore Sulfide 

750 250

calculated total mass mercury in the particulate fraction 

columns. 0 

Mass Hg Leached (ug) 

Disso ved l

Particulate 

Mercury Ore KEECO In Situ 

4.4.1.1.4 KEECO In Situ and Ex Situ 1 2 3 4 5 6 7 8 9 10 11 12 

Week 

Both of the KEECO treatments (in situ and ex situ) will 

be discussed in this section, since performance results Figure 4-9. Dissolved and particulate leached Hg 

for both modes of treatment were similar. The total (mass) from mercury ore KEECO in 

mass mercury leached from each of the KECCO situ columns. 

treatment columns was compared to the control columns 

to evaluate the primary objective. Figures 4-9 and 4-10

(25μm to 0.45μm) was extremely low, i.e. 80 μg for the 

in situ treatment and 72 μg for the ex situ treatment. 

225 500 Mass Hg Leashed (ug) 200 250 

175 

0 150 

125 

1 2 3 4 5 6 7 8 9 10 11 12 100 

Week 75 

50 Figure 4-8. Dissolved and particulate leached Hg

(mass) from mercury ore sulfide 25

present the temporal mass mercury leachability results 

for the in situ and ex situ columns, respectively. Note 

that the overall level of mercury leached was much lower 

than the control and other treatments, but unlike the 

other tests, the mass of mercury was much higher in the 

<0.45μm fraction (dissolved) than in the 25μm – 0.45μm 

fraction (particulate). 

In general, both modes of application performed similarly 

in terms of levels and timing of mercury leaching. The 

total mass mercury leached in the <25μm fraction from 

the in situ and ex situ columns was 1,532 μg and 1,723 

μg, respectively. This represents a reduction in 

leachability of 88% (in situ) and 86% (ex situ) as 

compared to the control. The overall variability between 

the three replicate columns for both applications was 

very low, 17% for the in situ and 12% for the ex situ. 

Weekly total mercury mass ranged from 76 μg to 201 μg 

for the in situ columns, and 22 μg to 265 μg for the ex 

situ columns. The <0.45μm fraction exhibited total mass 

mercury of 1,452 μg for the in situ, and 1,650 μg for the 

ex situ. This represents an overall increase in mercury 

for that fraction as compared to the control. Weekly 

mass mercury ranged from 71.55 μg to 195 μg for the in 

situ treatment and 16 μg to 266 μg for the ex situ

0 

l

Keeco Ex Situ Column White 

Disso ved 

Particulate 

1 2 3 4 5 6 7 8 9 10 11 12 

Week 

Figure 4-10. Dissolved and particulate leached Hg 

(mass) from mercury ore KEECO ex 

situ columns. 

KEECO’s Silica Micro Encapsulation Technology applied 

both in situ and ex situ, was effective in reducing mobile 

300 

Mass Hg Leached (ug) 250 

200 

150 

100 

50 

4-18 
mercury (<25μm) very close to the 90% reduction goal 

of the study. Furthermore, the process was very 

effective in reducing the generation of mercury 

associated with the particulate fraction (25μm to 

0.45μm). Both the in situ and ex situ treatments 

achieved a 99% reduction in particulate-associated 

mercury relative to the control. However, there was a 

significant increase in the mass mercury levels in the 

dissolved fraction (<0.45μm). The in situ applications 

exhibited a 198% increase relative to the control, and 

the ex situ exhibited a 238% increase. The form of 

mercury in this fraction for the KEECO treatment 

appears to be in a truly dissolved state as compared to 

the nano-particulate nature of the <0.45μm fraction from 

the control columns. This is based on the relationship 

between mercury concentration and turbidity in the 

<0.45μm fraction for the KEECO treatments and control 

as depicted in Figure 4-11. For the control (and for the 

other treatments), there is a general linear relationship in 

which the samples with higher mercury concentrations 

exhibit higher turbidity (presence of particles). It is 

postulated that the mercury in these effluents are 

associated with sub-micron particles (such as clays) that 

carry the mercury in the interstitial layers. The KEECO 

effluents from the <0.45μm fraction exhibit higher 

mercury with little or no turbidity, indicating that the 

mercury is not associated with sub-micron particles and 

is in a truly dissolved state. Hg (ppb) 

25 

20 

15 

10 

5 

0 

0 1 2 3 4 5 6 7 8 9 10 11 

Turbidity NTU 

Figure 4-11. Turbidity vs. Hg for the <0.45μm fraction – 

mercury ore, KEECO and control columns.

The increase in the dissolved mercury concentration 

(relative to the control and other treatments) may be due

l 

itu 

Contro

KEECO In Situ 

KEECO Ex S

to the elevated pH in the KEECO effluents. Figure 4-12

depicts the pH results from the KEECO effluents and the 

control effluents over the 12-week test period. As 

illustrated in the graph, the pH of the control effluents 

maintained a near constant pH of around 4 over the 

course of the study. Both of the KEECO treatments 

effluents’ pH was elevated relative to the control, starting 

out at approximately 12 and stabilizing to around 9. 

Furthermore, after an initial drop after the first two 

weeks, the pH did not decrease over the duration of the 

study. This indicates that the KEECO treatments 

permanently modified the geochemical properties of the 

mercury ore material. The increase in dissolved 

mercury due to the elevated pH is supported by an 

Eh/pH leaching study on SBMM material1

. The study 

demonstrated that alkaline conditions favored the 

dissolution of mercury. The maximum solubility 

occurred between a pH of 10 to 10.5. Furthermore, the 

addition of iron (in the form of ferric nitrate) inhibited the 

solubility of mercury at all pHs. 

14 

12 

10 Control 

8 

pH KEECO 6 In Situ 

4 

KEECO 2 Ex Situ 

0 

123 4 5 6 7 8 9 10 11 12 

Week 

Figure 4-12. pH of KEECO and control column 

effluents – mercury ore material. 

The data from the column studies suggests that two 

mercury mobilization/immobilization processes are 

occurring due to the KEECO treatments. The treatment 

was effective in inhibiting the generation of particulate 

associated mercury, which under the leaching conditions 

in the control test, is the dominant mercury mobility 

mechanism. The control of the generation of particulate 

associated mercury is probably due to the physical 

stabilization and binding of the matrix. However, due to 

the elevated pH brought about by the treatment, a 

chemical reaction dissolved a portion of the mercury. It 

1

 Characterization and Eh/pH Based Leaching Tests of 

Mercury-Containing Mining Wastes from the Sulfur Bank 

Mercury Mine, Lake County, California. EPA/600/R02/032, September 2001. 

4-19
is important to note that the amount of mercury 

dissolved by the KEECO treatment is still significantly 

less than the mass of particulate mercury leached from 

the control. The KEECO treatment may have bound the 

matrix, thereby reducing the overall reactive surface 

area available for mercury dissolution. It is suggested 

that in order to inhibit the dissolution of mercury due to 

elevated pH, the vendor should consider iron 

amendments as part of their process for this material. 

4.4.1.2 Waste Rock Column Studies 

Results from the columns studies on the waste rock 

material are presented in Table 4-11. The whole rock 

mercury concentration in the waste rock was 

approximately one-half the levels in the mercury ore 

material, yielding lower levels of leachable mercury as 

compared to the mercury ore material. However, the 

levels of leachable mercury in the particulate fraction 

from the mercury ore material control columns were two 

orders of magnitude greater than from the waste rock 

control columns. This indicates that the waste rock may 

be less prone to releasing particulates when exposed to 

a leaching solution. The average pH from the waste 

rock control column leachates was 3.36 (3.06 to 3.61) 

and was lower than the pH from the mercury ore column 

controls (4.16). The Eh of the leachate solutions 

indicated oxic conditions throughout the 8-week period 

(mean=522, range 485-573). 

than the average from the mercury ore columns (6.7). 

The average Eh (383) indicated oxic conditions 

throughout the test and was similar to the average Eh of 

the mercury ore column leachates (338). 

There appears to be minimal differences between the 

leaching characteristics of the E&C Williams Sulfide 

treatment and the Control for the waste rock material. 

However, the E&C Williams treatment may have slightly 

reduced leachable levels of mercury in both the 

particulate and dissolved fractions. This is indicated by 

the greater numbers of non-detect levels of mercury 

encountered in the E&C Williams treated waste rock 

material relative to the control. The pH from the weekly 

effluents averaged 3.25 (3.15 to 3.39), which was similar 

to the pH of the control effluents, and lower than the 

average weekly effluent of the treated mercury ore 

material (4.01). Eh conditions indicated oxic conditions 

throughout the testing period (mean of 534). 

45

40

35

Hg (ppb)30

25

20

Although there was significantly less mercury in the 

leachate from the waste rock column studies, the tests 

revealed similar technology performance results. The 

large number of non-detect values in the tests makes 

quantitative assessments and numerical comparisons 

difficult. However, a semi-quantitative discussion of 

each technology application follows. 

A demonstrated in the mercury ore material columns, 

the phosphate treatment greatly increased the levels of 

mercury from the waste rock material (as compared to 

the control) in both the particulate (25μm to 0.45μm) and 

dissolved (<0.45μm) fractions. Since the phosphate 

treatment increased the level of mercury in the <0.45μm 

fraction (relative to the control), it was possible to 

evaluate the relationship between mercury concentration 

and turbidity. As depicted in Figure 4-13, there is a 

relationship between the mercury concentration and 

turbidity, indicating that leachable mercury in the waste 

rock material may also be associated with sub-micron 

particles. Therefore, it is concluded that the mercury 

generated from the waste rock material is associated 

with particulates. The pH of the weekly leachate 

samples averaged 4.99 (3.71 to 5.61), which was lower 

15 

10 

5 

0 

0 5 10 15 20 25 30 35 40 45 50 55 

Turbidity (NTU) 

Figure 4-13. Turbidity vs. Hg for the <0.45Fm fraction

waste rock phosphate column. 

The leachability characteristics of the KEECO 

treatments on the waste rock material performed 

similarly to the mercury ore material. As in the mercury 

ore material tests, the KEECO treatments reduced the 

levels of particulate-associated mercury in the leachate. 

However, due to low levels of overall particulate 

generation in the control columns, the magnitude of this 

reduction cannot be quantitatively assessed. As 

observed with the mercury ore material, the KEECO 

treatment increased the levels of dissolved mercury 

demonstrated by an increase in the mass of mercury 

4-20
Table 4-11. Weekly Average Mass Mercury Leached from Waste Rock Columns 

Week Treatment Average Whole 

Mercury 

Mass Removed 

 Rock Hg Conc. (μg) 

Particulate Dissolved 

(mg/Kg) 25μm -0.45μm <0.45 μm 

Week 1 Control 864 43.6 11.2 

Phosphate 889 411.7 35.8 

 E&C Williams ENTHRALL®

 976 55.9 19.5 

 KEECO In Situ 776 16.3 60.2 

KEECO Ex Situ 900 1.3 23.8 

Week 2 Control 864 3.3 2.4 

Phosphate 889 2772.2 172.1 

 E&C Williams ENTHRALL®

 976 ND ND 

 KEECO In Situ 776 18.3 75.0 

 KEECO Ex Situ 900 0.0 58.6 

Week 3 Control 864 1.9 ND 

Phosphate 889 4533.7 320.7 

 E&C Williams ENTHRALL®

 976 ND ND 

 KEECO In Situ 776 7.7 57.4 

 KEECO Ex Situ 900 0.0 65.3 

Week 4 Control 864 0.0 2.0 

Phosphate 889 2990.2 383.4 

 E&C Williams ENTHRALL®

 976 ND ND 

 KEECO In Situ 776 14.2 50.6 

 KEECO Ex Situ 900 0.0 57.7 

Week 5 Control 864 2.2 2.9 

Phosphate 889 1888.8 311.4 

 E&C Williams ENTHRALL®

 976 7.8 ND 

 KEECO In Situ 776 6.3 42.4 

 KEEC) Ex Situ 900 2.8 45.8 

Week 6 Control 864 ND ND 

Phosphate 889 514.9 128.2 

 E&C Williams ENTHRALL®

 976 ND ND 

 KEECO In Situ 776 1.5 42.7 

 KEECO Ex Situ 900 1.4 43.2 

Week 7 Control 864 ND ND 

Phosphate 889 NA NA 

 E&C Williams ENTHRALL®

 976 ND ND 

 KEECO In Situ 776 3.1 33.2 

 KEECO Ex Situ 900 0.0 35.8 

Week 8 Control 864 ND ND 

Phosphate 889 1623.2 229.1 

 E&C Williams ENTHRALL®

 976 ND ND 

 KEECO In Situ 776 6.1 33.9 

 KEECO Ex Situ 900 5.8 28.8 

ND = Not Detected 

NA = Not Analyzed 

4-21 
generated in the <0.45μm fraction. Due to the low 100000 turbidity in the leachate from the <0.45μm fraction 

(Figure 4-14), it appears that the mercury is truly 

dissolved and not associated with sub-micron particles. 10000 

100 

5 10 

1 2 3 4 5 6 7 8 

4 Week 

Y Control ECWI Sulfide 

KEECO Ex Situ 

3 

KEECO In Situ 

Phosphate 2 

Figure 4-15. Results from Humidity Cell tests on 1 mercury ore material - <25μm fraction. 

0 

0 1 2 3 4 10000

Turbidity (NTU)

1000 

As seen in the mercury ore column tests, the KEECO 

treatment significantly increased the pH of the leachates 

from the waste rock material relative to the control. This 

Hg (ppb)

1000

pH increase may be responsible for the increase in 

dissolved mercury relative to the control. Hg (ppb) 

Figure 4-14. Turbidity vs. Hg for the <0.45μm fraction 

waste rock, KEECO columns. 

4.4.2 Humidity Cell Tests 

Hg (ppb) 

100

10

Results from the humidity cells on the mercury ore 

material generally agree with the column studies from 

both the mercury ore and waste rock materials. Figures

4-15 and 4-16 present the weekly results for the controls 

and each treatment for the <25μm and <0.45μm 

fractions, respectively. Note that due to the wide range 

in mercury concentrations, the Y-axis is presented on a 

logarithmic scale. As demonstrated in the previous 

tests, the phosphate treatment significantly increased 

the levels of mercury in the leachate relative to the 

control. Based on the humidity cell results, the E&C 

Williams sulfide treatment reduced the concentration of 

mercury in both the <25μm and <0.45μm fractions 

relative to the control. For the KEECO treatments, there 

is a reduction in the concentration of the <25μm fraction 

relative to the controls, and an increase in the <0.45μm 

fraction relative to the controls. This is consistent with 

previous findings in which the KEECO treatments 

(relative to the controls) reduced the levels of particulate 

associated mercury, but increased the amount of 

1 

0.1 

1 2 3 4 5 6 7 8 

Week 

Y Control ECWI Sulfide 

KEECO Ex Situ KEECO In Situ 

Phosphate 

Figure 4-16. Results from Humidity Cell tests on 

mercury ore material - <0.45μm fraction 

dissolved mercury in the leachate. As in the column 

tests, the KEECO process increased the pH of the 

effluents relative to the control columns. This increase 

4-22
in pH may be responsible for the increased levels of 

dissolved mercury (<0.45μm fraction). However, the 

KEECO process greatly reduced the generation of 

particulate-associated mercury, thus causing an overall 

reduction in the levels of mobile mercury (<25μm). 

4.4.3 Synthetic Precipitation Leaching Procedure 

(SPLP) 

SPLP tests were performed on un-treated and treated 

mercury ore material to evaluate the performance of the 

technology and to compare this widely used leaching 

procedure to the results of the column and humidity cell 

tests. Results from the SPLP tests are presented in 

Table 4-12. 

Table 4-12. SPLP Results for Mercury Ore and Waste 

Rock Material 

Mercury Ore Waste Rock 

Sample (μg/L) (μg/L) 

Control 1 (untreated) 479 5.5 

Control 2 (untreated) 6260 0.4 

Control 3 (untreated) 224 

Control 4 (untreated) 2090 

Control Mean 2263 2.95 

Phosphate 1 11900 3200 

Phosphate 2 13100 

Phosphate Mean 12500 3200 

Sulfide 1 2650 9.7 

Sulfide 2 404 

Sulfide Mean 1527 9.7 

KEECO In Situ 1 5 

KEECO In Situ 2 10 

KEECO In Situ Mean 7 Not Analyzed 

KEECO Ex Situ 1 5 2.2 

KEECO Ex Situ 2 10 

KEECO Ex Situ Mean 7 2.2 

The SPLP results on the untreated mercury ore material 

(control) exhibit a wide range of values and are much 

higher than previously performed SPLP tests on material 

from the site. The SPLP results on the untreated waste 

rock material are low. The average SPLP value for the 

untreated mercury ore material is almost 1,000 times 

greater than the waste rock untreated material even 

though the whole rock mercury concentration of the 

mercury ore material is only two times higher than the 

waste rock material. Column and humidity cell 

leachability was also higher for the mercury ore material 

relative to the whole rock mercury as compared to the 

waste rock, but not as great as encountered in the SPLP 

tests. The high SPLP values in the mercury ore material 

may be due to the agitation during leaching which may 

be dislodging more mercury-bearing particles in the 

mercury ore material relative to the waste rock. This 

may be the case if the mercury in the mercury ore 

material is associated with fractures, which would be 

more prone to contact with leaching solutions under 

agitation. 

As demonstrated in both the column and humidity cells, 

the SPLP results indicate a significant increase in 

mercury leachability after phosphate treatment for both 

the mercury ore and waste rock materials. For the 

sulfide treatment, the SPLP results do not indicate a 

statistically significant reduction in mercury leachability 

relative to the control for either the mercury ore or waste 

rock material. For the KEECO treatments, there is a 

significant decrease in mercury leachability relative to 

the control for the mercury ore material. Due to low and 

variable leachable mercury in the waste rock control, 

there is no demonstratable leachability reduction for this 

material. 

Due to the high variability associated with leachability 

results from the SPLP test on the materials studied in 

this investigation, SPLP testing may not be a reliable 

measure of mercury leachability or technology 

performance. This may be due to the heterogeneous 

association of mercury in the materials, the agitation of 

the matrix during testing, and the relatively small sample 

size used for testing. If SPLP testing is used, several 

replicates may need to be analyzed and/or larger 

sample sizes may be used in order to minimize the 

variability. 

4.4.4 Humic/Fulvic Acid Leaching Tests 

A modified meteoric water mobility procedure (MWMP) 

continuous leaching test using a humic/fulvic acid 

solution (treatment) and a deionized (DI) water control 

was performed to determine the effects of plant derived 

high molecular weight organic acids on mercury 

leachability in mercury ore material from the SBMM site. 

A total of 5 columns were tested, three with the organic 

solution (containing humic and fulvic acids) as triplicate 

test columns and the other two columns as the DI water 

control columns. The MWMP utilized a 1:1 ratio of solid 

material to leaching medium (humic/fulvic acid or 

deionized water) placed in a column-type apparatus and 

continuously leached over a 4-week period. Samples 

were collected for mercury and other characteristics 

twice during the first week and on a weekly basis over 

the next three weeks. Leachate volumes were 

measured for each sample so that the mass of mercury 

leached could be calculated. The treatment solution 

4-23
contained 10 mg/L humic acid and 5 mg/L fulvic acid, 

adjusted to a pH of 6. The control solution consisted of 

DI water adjusted to a pH of 6. All samples were filtered 

through either a 25μm or 0.1μm filter to determine the 

relative amounts of mobile (<25μm) and dissolved 

(<0.1μm) associated mercury. Table 4-13 presents the 

results from the humic/fulvic acid leaching tests for the 

<25μm and <0.1μm fractions. A 0.1μm filter was 

selected for these studies (as compared to the 0.45μm 

in previous studies) to characterize more of the truly 

dissolved fraction. For each leaching interval the total 

mass in μg was calculated, as well as the average 

μg/day. The total mass of mercury (μg) was calculated 

between the mercury leached from the treatment versus 

the control for this fraction (Prob>t 0.2907). For the 

<0.1μm fraction, the average mass mercury was 5 μg for 

the humic/fulvic treated columns and 18 μg for the 

control columns. A t-test demonstrated a significant 

difference between the mercury leached in the treatment 

versus the control (Prob>t 0.0315). Therefore, for the 

SBMM mercury ore material tested under the conditions 

of the experiment, there was no increase in the 

particulate or dissolved mercury due to leaching with 

humic and fulvic acids. Furthermore, it appears that the 

humic/fulvic acids may have reduced the levels of 

dissolved mercury relative to the control. However, the 

for each treatment and control. overall levels of dissolved mercury leached from the

Table 4-13. Results From the Hum

Days 

1 to 3 

4 to 7 

8 to 14 

15 to 21 

22 to 28 

Total 

Days 

1 to 3 

4 to 7 

8 to 14 

15 to 21 

22 to 28 

ic/Fulvic Acid Leaching Tests

<25 Micron Fraction 

HA/FA 1 HA/FA 2 HA/FA 3 Control 1 Control 2 

ug ug/day ug ug/day ug ug/day ug ug/day ug ug/day 

114.89 38.30 16.06 5.35 150.55 50.18 83.26 27.75 114.74 38.25 

75.33 18.83 67.94 16.99 151.28 37.82 97.09 24.27 109.95 27.49 

42.44 6.06 120.29 17.18 249.73 35.68 509.86 72.84 212.55 30.36 

50.55 7.22 100.87 14.41 129.50 18.50 86.35 12.34 134.53 19.22 

77.91 11.13 33.64 4.81 197.93 28.28 120.46 17.21 88.14 12.59 

361.12 338.80 878.98 897.02 659.91 

<0.1 Micron Fraction 

HA/FA 1 HA/FA 2 HA/FA 3 Control 1 Control 2 

ug ug/day ug ug/day ug ug/day ug ug/day ug ug/day 

0.58 0.19 0.89 0.30 1.28 0.43 5.41 1.80 4.29 1.43 

0.75 0.19 1.38 0.34 12.37 3.09 11.69 2.92 13.72 3.43 

2.88 0.41 2.94 0.42 13.93 1.99 43.32 6.19 67.67 9.67 

4.43 0.63 19.65 2.81 9.91 1.42 11.70 1.67 10.52 1.50 

3.64 0.52 0.70 0.10 2.70 0.39 7.03 1.00 5.59 0.80 

No significant pattern of mercury release over time was 

observed for either the treated or control columns for 

both the fractions tested. Therefore, the results were 

grouped for the treatment and control for both fractions. 

Statistical analyses were performed to determine 

differences between the treatment and control for each 

fraction. 

As with all previous leaching tests, the leachable 

mercury was predominately associated with the 

particulate fraction for both the humic/fulvic acid treated 

columns and the control. For the <25μm fraction, the 

average mass mercury was 105 μg for the humic/fulvic 

treated columns and 156 μg for the control columns. A 

Students t-test demonstrated no statistical difference 

mercury ore material were low as compared to the 

particulate-associated mercury. The higher levels of 

dissolved mercury in the control samples relative to the 

humic/fulvic acid treated samples may be attributable to 

differences in the pH of the effluent samples. The 

average pH of the control effluents was 6.31 as 

compared to a pH of 4.58 for the humic/fulvic acid 

treated material. As previously noted, an EPA study 

observed higher dissolved mercury with increasing pH. 

The humic/fulvic acid tests also corroborated previous 

leaching experiments regarding the form of mercury 

leached from the mercury ore material. A plot of 

mercury vs. turbidity in Figure 4-17 reveals a linear 

relationship between turbidity (particulates) and mercury 

concentration. This relationship also extends to some of 

4-24
Hg (ppb) 700 

600 

500 

400 

300 

200 

100 

0 

<

<0.1um 

25 um 

0 100 200 300 400 500 600

Turbidity (NTU)

Figure 4-17. Turbidity vs. Hg from the <25μm and 

<0.1μm fractions from the humic/fulvic 

acid leaching tests. 

the <0.1μm fraction samples. This is significant since 

several samples of the <0.1μm filtered leachates 

exhibited relatively high turbidities indicating the 

presence of sub-micron colloidal material. The 

correlation between mercury and turbidity further 

supports a release of mercury associated particulates as 

a leaching mechanism. 

4.4.5 Geochemical and Mineralogical Analyses 

Geochemical and mineralogical analyses were 

performed on untreated and treated mercury ore 

material by optical petrography and x-ray diffraction. 

The purpose of the analyses was to document any 

mineralogical or geochemical changes in the bulk 

properties of the mercury ore matrix attributable to the 

treatment technologies. Optical petrography and x-ray 

diffraction did not reveal any significant differences in the 

bulk mineralogy or geochemistry between the untreated 

and treated mercury ore materials examined. One 

noteworthy exception is higher phosphorus content in 

the phosphorous treated sample. 

The examination did reveal some information relating to 

the mineralogical properties of the mercury ore material. 

Samples were sieved using a sequential stack of brass 

sieves in the order 500, 250, 150, 125, 63 microns. 

Petrographic examination reveals that the rock 

fragments are typical of an altered volcanic rock, 

comprising variably devitrified glass, secondary silica 

deposits, and siliceous aggregates with probable 

secondary sulfides. 

The samples were further wet-filtered (10-44 micron 

fraction) with distilled water retaining more than 95% as 

sediment. The retained sediment was analyzed by x-ray 

diffraction to assess mineralogical characteristics. The xray diffraction revealed that only minor amounts of 

mineral are present in the bulk sample. Two phases of 

particular interest, quartz (peak at 26.64) and cinnabar 

(peak at 26.52) are not matched by the presence of a 

pronounced diffraction maxima. A minor broad peak 

may indicate the presence of one or both phases, but is 

not definitive. The presence of amorphous phases 

(glass, secondary silica, possible biogenic silica, and 

silica-bearing aggregates) is supported by the presence 

of a broad radial distribution. 

4.5 Developers’ Comments 

The technology developers (E&C Williams and KEECO) 

were asked to comment on the performance of their 

processes based on the results from this treatability 

study. Their responses to this request are presented in 

this section. These responses do not reflect the views 

and assessments of either the Mine Waste Technology 

or SITE programs and are presented here as a courtesy 

to the technology developers. 

4.5.1 E&C Williams’ Comments 

As we understand it, the KEECO system is one that 

microencapsulates the soil/rock particles, sequestering 

the leachable metals. Our calcium sulfide system is 

different because we effect a chemical change, forming 

metal sulfides which are insoluble and immobile. So, 

our chemistry is more dependent on the number and 

amount of metals in the soils. We had requested an 

assay or characterization of the soils in order to confirm 

our suspicions that the mercury ore soil contained more 

metals, and more of them, than the waste rock. We 

already knew from your work that the mercury content is 

greater in the mercury ore soils. Our chemistry reacts 

more on a "one-to-one" basis, making the dosage more 

critical than a gross encapsulation. Plus, all metals 

capable of forming sulfide compounds compete equally 

for the sulfide molecules. So, if a lot of iron is present, 

for example, that will "eat" the sulfides as readily as a 

regulated metal. This isn't unusual for remediation or 

treatment work where the chemistry is less dependent 

on encapsulation. 

Our conclusion on the performance of the calcium 

sulfide system is that the dosage simply undershot the 

level of metals, and a larger dose is all that is necessary 

4-25
to achieve the desired results. We are comfortable with 

the application by injection, although we will recommend 

that the points of injection be slightly increased so as to 

slightly overlap the treated areas. 

4.5.2 KEECO’s Comments 

Project Methods and Observations 

In an effort to provide a comparison of in-situ treatment 

versus ex-situ treatment of the mining waste rock from 

the Sulfur Bank Mercury Mine Superfund site, KEECO 

performed two distinctly different process application 

techniques for the SITE project test program. The 

overall goals established by EPA were to demonstrate 

non-aggressive, realistic methods of chemical 

amendment into the mine waste while producing 

significantly decreased mercury mobility. Effectiveness 

would be verified throughout the series of tests outlined 

in the project Test Plan. Therefore, in truth, the 

challenge was not only one of demonstrating that the 

technology was able to achieve the goals of mercury 

stability under a variety of leaching conditions, but that it 

was able to do so using less-than-ideal techniques for 

chemical incorporation. 

Project Approach 

The SME product KB-SEA was utilized for these tests. 

For the ex-situ column samples, the dry chemical was 

evenly broadcast over the test material followed by 

gentle blending using a spoon to represent the type of 

mixing that may be expected through the use of an 

excavator to blend the material on site. 

For the in-situ treatment, a slurry form of the product 

was prepared by mixing the dry chemical with deionized 

water. The untreated materials were loaded into the 

columns prior to chemical amendment. A predetermined volume of chemical slurry was then applied 

to each column and allowed to infiltrate through the pore 

spaces. Although this technique is limited in its ability to 

make effective contact between the metal contaminants 

of concern and the reactive components of the SME 

chemical, the results proved better than anticipated, as 

outlined in Sections 2 and 3. Despite favorable results 

from these laboratory tests, KEECO believes that it is 

unlikely that the conditions present in the column would 

accurately represent the conditions encountered on-site 

using in-situ treatment techniques. Geochemical 

conditions and transport mechanisms in the waste piles 

are complex and not properly replicated in these 

laboratory test cells. As such, a pilot test on-site would 

be highly encouraged prior to full-scale treatment. 

KEECO Objectives 

In addition to the objectives of the study as outlined in 

the project Test Plan, KEECO established further 

objectives for the technology performance. They 

included: 

 A comparison of in-situ versus ex-situ treatment for 

comparable trends, ability to control total metal 

contaminant release, stability under each of the 

project test methods and consistency of test results 

from column to column; 

 Verification of previously established theories that 

materials treated with the SME Technology will 

exhibit greater stability over time. 

While this project proved useful in assessing in-situ 

versus ex-situ chemical amendment and the ability of 

the process to withstand various leach test conditions, 

the tests will not however, demonstrate the optimum 

performance of the SME Technology when incorporated 

into materials using more aggressive mixing techniques. 

Therefore, the differences between optimum technology 

performance and performance as achieved with limited 

mixing cannot be assessed from this study. 

Effectiveness of SME Technology Application -

Mercury ore (Primary) Test Material 

Despite the fact that the average whole rock mercury 

concentration of the KEECO sample materials were 

slightly higher (about 200 mg/kg) than the control, the 

sulfide and the phosphate samples, effectiveness of the 

SME application is evident as compared to results from 

all other tests. 

When applied to the mercury ore samples, the SME 

chemical produced higher initial pH values than the 

established target end points identified by KEECO Lab 

for optimum performance. This suggests that the 

samples were slightly over-treated. This could be due to 

the mild mixing technique employed for the test, thus 

releasing unreacted chemical into the leachate rather 

than expending it in the reactive process typically 

accomplished through vigorous mixing. However, both 

the selected application techniques and the higher initial 

pH appear to have only minor impacts on sample 

stability. 

Column Testing Observations 

There are a number of observations that can be made 

from the column tests. Comparisons between in-situ 

4-26
versus ex-situ performance are discussed in Section 2.5. 

Overall, the SME treated columns achieved a significant 

reduction in leachable mercury as compared to the 

control columns. The objectives of the Test Plan were to 

achieve a 90% reduction in the cumulative mass of 

mercury in the test leachates relative to the control 

column leachates. For the in-situ columns, as observed 

in weeks 4, 8, 9 and 12, the total mass of mercury 

released was reduced by an average of 90.8% relative 

to the control, thus meeting the primary project objective. 

For the ex-situ columns, an average of 88.2% reduction 

of the mercury released into the leachate was observed 

relative to the control.2

 These figures were derived 

using the formula for %Hg reduction as outlined in the 

project Test Plan. 

Another observation that can be made from the column 

testing is that the majority of the mercury released from 

the SME treated material was in a dissolved state. 

Therefore, while the unfiltered and 25μm fraction results 

are more favorable with SME, results collected solely 

from the 0.45μm fraction indicate that the SME columns 

leached a greater mass of dissolved mercury than both 

the control and sulfide treated columns. This is likely 

due to the method utilized to amend the samples, 

leaving some of the material untreated. Dissolved 

mercury will readily percolate under the influence of 

filtration due to precipitation from untreated material 

when the irrigation water is applied. Whereas, 

suspended particulates that may be liberated from the 

untreated material upon the outset of irrigation readily 

adsorb to neighboring silica-encapsulated materials 

before percolating completely through the column; 

thereby minimizing the release of mercury from the 

material that may not have received a thorough 

application of SME product. Typically, the goals of 

treatment for any project are to reduce the metal release 

to background levels. By week 12, after gradual 

improvement over time, the average mean concentration 

of dissolved mercury in the SME leachate was within 1.8 

μg/L of the control columns. 

As previously mentioned, one of the objectives that 

KEECO established for this study was to verify the 

theory that SME treated materials will exhibit increased 

stability over time. Results gathered from both the 

unfiltered and dissolved fraction data support this theory. 

In addition, the coefficient of variation improved over 

2

 Week 1 results were not included due to the high variability 

of the results, suggesting that the reactive process was not yet 

complete. However, in week 1, the in-situ columns produced 

a 96.3% reduction in the mass of mercury release relative to 

the control; the ex-situ columns exhibited a 75.5% reduction. 

time, demonstrating the ability of the chemical to control 

the mercury release to consistent levels despite 

variations of total mercury present in the untreated 

material. This supports the prediction that material 

containing widely variable mercury concentrations or 

“hot spots” can be effectively treated with a single 

application of SME chemical to the entire material 

volume without having to separately treat the highly 

concentrated portions. 

The drying phase that was undertaken between test 

weeks 8 and 9 did not show any significant impact on 

mercury stability in the SME-treated columns. A 1.5 

μg/L increase in mean Hg concentration in the ex-situ 

columns was observed after the rest period, with a 4.6 

μg/L increase evident from the in-situ columns. This 

suggests that the onset of irrigation after the drying 

period may have released a small amount of mercury 

into the leachate from the untreated material that may 

have been near the lower portion of the columns. As 

compared to the other test columns, the SME column 

increases were minimal, with a 19.1 μg/L increase from 

the control column, a 75.3 μg/L from the phosphate 

column and a 35.1 μg/L from the sulfide column. The 

minimal amount of total release evident from the SME 

treated columns suggests that a large contaminant 

plume is unlikely from SME stabilized materials after 

exposure to atmospheric oxygen. 

SPLP Test Observations 

The stability of mercury under static test conditions 

following treatment with SME was evident as compared 

to the control sample material. The control sample 

released a mean mercury concentration of 2143.6 μg/L, 

while the SME samples released 7.2 μg/L and 10.1 μg/L 

Hg, a 99.6% average decrease in leachable mercury 

relative to the untreated sample. The samples also 

exhibited greater than a 99% improvement in mercury 

stability relative to the sulfide and phosphate treated 

material. 

Humidity Cell Test Observations 

The released mercury in the humidity cell tests is 

primarily in a dissolved state. This is likely due to the 

limited mixing technique not allowing for effective 

contact and encapsulation of portions of the mercurybearing material. Particulate or suspended mercury, if 

not encapsulated, will tend to adsorb to neighboring 

encapsulated material; therefore, the release of larger 

fraction particulate mercury is minimized. Even in this 

adsorbed state the mercury is quite resistant to leaching. 

This is evident when comparing the total mercury 

4-27
released from the control, sulfide and phosphate cells to 

that released from the SME-treated cells. Although the 

dissolved mercury concentrations were slightly higher 

from the SME cells, the total mercury released in the 25 

μm and 0.45 μm samples combined was much lower 

overall. 

In-situ versus Ex-situ 

Overall the SME Technology appears to be a viable 

option for stabilization of mercury in the mercury ore pile 

material, regardless of whether the technology is applied 

“in-situ” or “ex-situ.” Both techniques exhibited 

comparable stability that remained consistent throughout 

the testing period. The greatest variations were 

observed within the data gathered during week 1 of the 

column tests. The in-situ columns appeared to release a 

much lower mean concentration of mercury immediately 

after treatment than the ex-situ columns (19.8 versus 

125 μg/L respectively). However, from week 2 

throughout the conclusion of the testing, the mean 

concentrations of mercury in the in-situ versus ex-situ 

samples were typically within 1 to 3 μg/L of each other. 

The robust nature of the technology reaction despite 

substantially different treatment methods is evident in 

these test results. 

After the drying period between test weeks 8 and 9, the 

ex-situ columns produced slightly better results, with an 

increase in the mean mercury concentration of only 1.5 

μg/L from week 8 to week 9. In-situ columns produced a 

mean mercury concentration increase of 4.6 μg/L over 

the same period. By the end of the 12-week testing 

period, when comparing mean concentrations of 

mercury evident in the leachate of the in-situ versus exsitu columns, a difference of only 0.2 μg/L was evident. 

With the exception of week 1 data, similar trends were 

also observed in regards to dissolved versus mobile, 

suspended mercury in the leachate. Of the total mercury 

released into the leachate, the majority of the mercury 

was present in the 0.45 μm fraction for both the in-situ 

and ex-situ columns. 

Because contact between the metal contaminants of 

concern and the SME product is essential in order to 

achieve proper stability, effective mixing techniques are 

critical for the overall long-term stability of the treated 

substrate. 

Effectiveness of SME Technology Application -

Waste rock (Secondary) Test Material 

Treatment of the waste rock pile test material with the 

SME chemical KB-SEA was conducted to replicate an 

ex-situ treatment method as well as an in-situ treatment 

method as outlined in Section 1. Initial results, based 

upon the pH of the leachate immediately after treatment, 

showed that the in-situ material successfully achieved 

the targeted pH end point of approximately 9.0. The exsitu material appeared to be slightly overtreated with a 

pH of approximately 11.5 evident in week 1. 

Since each test method involved treatment of only one 

column of waste rock pile material, statistical averaging 

and the ability to identify data spikes and anomalies 

cannot be accomplished. 

Column Testing Observations 

The SME treated waste rock pile samples all released a 

higher concentration of mercury into the leachate as 

compared to the control column results for all samples 

evaluated, with the exception of some of the week 1­

leachate samples. 

The liberated mercury evident in the SME column 

leachate appears to be predominantly in the 0.45 μm or 

dissolved fraction. This was also evident in the mercury 

ore pile testing. 

Over the 8-week column test, a reduction in the 

concentration of the mercury in the leachate was 

achieved in the SME-treated columns, suggesting 

enhanced stability over time. However, the control 

sample leachate remained at or below the detection limit 

of 0.2 μg/L for the majority of the 8-week test period. 

While the SME treated materials never exceeded a 

mercury concentration of 6.1 μg/L in the leachate, the 

sulfide sample performed better with most of the 

samples at or below the detection limit. Unfortunately, 

since the control column also remained within detection 

limits for the majority of the sample testing, no 

technology could clearly be identified as successful for 

these tests. 

The ex-situ and in-situ columns appeared to generate 

similar results after week 3, and by the conclusion of the 

8-week test period, the concentrations of mercury were 

with 2-4 μg/L of each other. 

4-28
SPLP Test Observations 

The SME in-situ column material did not undergo SPLP 

testing. The ex-situ column test material performed 

better under SPLP test conditions than the control 

samples, the phosphate samples and the sulfide 

samples. However, the mercury leached from the 

control sample material (only 3 μg/L) was again quite 

low; therefore, no single technology could be identified 

as having achieved a significant reduction in the 

leachable mercury as compared to the untreated 

materials. 

The results of the waste rock pile tests were fairly 

inconclusive, but suggest that further characterization of 

the waste rock pile material should be undertaken to 

determine whether chemical stabilization or any other 

treatment is warranted. 

4-29
Section 5.0 

Quality Assurance Summary 

5.1 Introduction 

Quality Assurance (QA) may be defined as a system of 

activities the purpose of which is to provide assurance 

that defined standards of quality are met with a stated 

level of confidence. A QA program is a means of 

integrating the quality planning, quality assessment, 

quality control (QC), and quality improvement efforts to 

meet user requirements. This includes all actions taken 

by project personnel, and the documentation of 

laboratory and field performance as specified in the 

QAPP. The objective of the quality assurance program 

is to reduce measurement errors to agreed upon limits 

and to produce results of acceptable and known quality. 

The QAPP specified the necessary guidelines to ensure 

that the measurement system was in control and 

provided detailed information on the analytical approach 

to ensure that data of high quality could be obtained to 

achieve project objectives. The results of the QA 

processes applied to the Suulfur Bank project are 

summarized below. 

5.2 Conclusions and Data Quality 

Limitations 

A review of the critical sample data and associated QC 

analyses was performed to determine whether the data 

collected were of adequate quality to provide proper 

evaluation of the project's technical objectives. The 

critical parameters included mercury in the leachates 

from the kinetic column studies. The results of the 

measurements designed to assess the data quality 

objectives are summarized below, along with a 

discussion of the impact of the data quality on achieving 

the project’s technical objectives. 

Accuracy: Samples were collected and analyzed from 

each of the test columns over an initial 8-week period. 

Spiked duplicate samples were analyzed and recovery 

data were compared to the control limits established in 

the QAPP (80-120% recovery). All spikes (36 MS/MSD 

pairs) met QA objectives, as summarized below in Table 

5-1. In addition, spiked blanks, or laboratory control 

samples (LCSs), also met recovery limits of 85-115%. 

A select number of test columns were allowed to sit 

undisturbed for several weeks and the leaching process 

was then continued for an additional 4 weeks. These 

extended column leachate samples were also spiked, 

LCSs were analyzed and accuracy assessed. These 

data indicated as well that accuracy objectives were 

achieved, as noted in Table 5-2. 

Table 5-1. Accuracy Data for Mercury for SBMM 

Column Leachates 

Leachate Fraction 

MS/MSD 

Average % 

Recovery 

LCS 

Average % 

Recovery 

Total 102 100 

25μm filter 102 102 

0.45μm filter 104 100 

Table 5-2. Accuracy Data for Mercury for SBMM 

Extended Column Leachates 

Leachate Fraction 

MS/MSD 

Average % 

Recovery 

LCS 

Average % 

Recovery 

Total 107 106 

25μm filter 100 102 

0.45μm filter 100 104 

Accuracy was further assessed through the analysis of 

second-source standards, or Initial Calibration 

Verification (ICV) standards. These standards were 

analyzed after each initial multi-point calibration curve 

and all ICV concentrations were within 10% of the “true” 

concentration, as required in the QAPP. 

Precision of the mercury analyses was assessed by the 

Relative Percent Difference (RPD) between the spiked 

5-1 
duplicate sample concentrations. Data quality objectives 

were established in the QAPP as RPD of less than 20%. 

All spiked duplicates, in both the original 8-week study 

and the extended study, had RPD values less than 10%, 

therefore data met the objectives for precision. 

Sensitivity objectives in terms of detection limits and 

practical quantitiation limits were met for all samples. 

Completeness objectives for the project were met. A 

few non-critical parameters were not analyzed for some 

leachates due to sample volume; this did not affect 

overall data collection efforts. 

Comparability was addressed in the QAPP through the 

use of EPA approved methodology. Mercury was 

determined in accordance with SW846 Method 7470 for 

all critical column study leachates. 

Representativeness refers to the degree with which a 

sample exhibits average properties of the site at the 

particular time being evaluated. This is assessed in part 

by the analysis of field duplicates, which also provide 

insight into the homogeneity, or heterogeneity, of the 

matrix. Field duplicate samples have inherent in the 

result combined field and analytical variability. 

Periodically throughout the 8-week column study, 

leachate samples were collected in duplicate. Mercury 

analysis of these samples indicated that reproducibility 

between the samples was within guidelines (RPD < 

20%), with the exception of three duplicate leachate 

samples (see Table 2-3) filtered through 0.45 um filters 

that had RPD values >50%. 

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