United States
Environmental Protection
Agency
Office of Water Regulations
and Standards (WH-552)
Industrial Technology Division
Washington, DC 20460
EPA 440<1 -88-061
May 1988
Office of Water
Development Final
Document for
Effluent Limitations
Guidelines and
New Source Performance
Standards for the
Ore Mining and Dressing
Point Source Category
Gold Placer Mine Subcategory
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DEVELOPMENT DOCUMENT
FOR FINAL
EFFLUENT LIMITATIONS GUIDELINES AND
NEW SOURCE PERFORMANCE STANDARDS
FOR THE
ORE MINING AND DRESSING POINT SOURCE CATEGORY
GOLD PLACER MINE SUBCATEGORY
Lee M. Thomas
Administrator
Rebecca W. Hanmer
Acting Assistant Administrator for Water
Martha Prothro, Director
Office of Water Regulations and Standards
Thomas O'Farrell, Acting Director
Industrial Technology Division
Ernst P. Hall, P.E., Chief
Metals Industry Branch
Willis E. Umholtz
Project Officer
May 1988
Industrial Technology Division
Office of Water
U.S. Environmental Protection Agency
Washington, D.C. 20460
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This Page Intentionally Left Blank
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5
TABLE OF CONTENTS
Section Page
I Summary 1
Subcategorization for Gold Placer Mines ... 2
Overview of Limitations and Standards .... 3
Best Practicable Technology 3
Best Available Technology 4
Best Conventional Technology 4
New Source Performance Standards 4
Pretreatment 5
Best Management Practices 6
II Final Regulation 7
Subcategory M 7
Applicability 7
Effluent Limitations 7
Best Management Practices 11
Storm Exemption 11
III Introduction 13
Purpose 13
Legal Authority 13
General Criteria for Effluent Limitations . . 15
Prior EPA Regulation 17
General Approach and Methodology 23
Industry Profile 23
IV Industry Subcategorization 71
Technical Considerations for Influencing
Subcategorization 71
Economic Considerations
80
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TABLE OF CONTENTS (Continued)
Section Page
Subcategorization for Gold Placer Mines. ... 80
V Wastewater Use and Wastewater Characterization 85
Data Collection 85
Sampling and Analysis 94
Water Use 96
Raw Wastewater Characterization 97
Characteristics of Treated Wastewater .... 98
VI Selection of Pollutant Parameters 129
Selected Pollutant Parameter 129
Toxic Pollutants 130
Conventional and Nonconventional Pollutants. . 133
VII Control and Treatment Technology 137
End-of-Pipe Treatment Technologies 137
In-process Control Technology 138
VIII Cost, Energy and Other Non-water Quality Issues 161
Development of Cost Data Base 161
Capital Cost 162
Annual Cost 164
Treatment Process Costs 165
Model Mines 168
Estimated Costs for the Treatmer 169
Non-water Quality Aspects of Pollution
Control 170
IX Best Practicable Technology (BPT) 221
Subcategorization of Placer Gold
Mines 221
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TABLE OF CONTENTS (Continued)
Section Page
IX (Continued)
Technical Approach to BPT 222
Options Selection 225
BPT for Gold Placer Mines 225
Specialized Provisions for Gold Placer Mines: 226
Storm Exemption
Guidance for Implementing the Storm Exemption 228
X Best Available Technology Economically
Achievable (BAT) 233
Technical Approach to BAT 233
BAT Options Selection 234
BAT for Gold Placer Mines 236
Storm Exemption 238
XI New Source Performance Standards (NSPS) 241
NSPS For Gold Placer Mines 244
Storm Exemption 246
XII Pretreatment Standards 247
XIII Best Conventional Pollutant Control
Technology (BCT) 249
XIV Best Management Practices (BMP) 251
XV Acknowledgements 255
XVI References 257
XVII Glossary 263
111
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LIST OF TABLES
Table Paqe
III-l
III-2
III-3
III-4
III-5
III-6
III-7
III-8
III-9
IV-1
V-l
V-2
V-3
V-4
V ^
V-5
» *J
V-6
V-7
V-8
V-9
V-10
Mineral Activity in Alaska by Mining Camp
As of 1982
Reported Refined Gold Production, Number of
Operators, and Industry Employment in Alaska
by Region and Mining District, 1985-86 ....
Profile of Alaskan Gold Placer Operations . .
Profile of California Gold Placer Mines . . .
Profile of Colorado Gold Placer Mines ....
Profile of Idaho Gold Placer Mines
Profile of Montana Gold Placer Mines
Profile of Alaskan Gold Placer Operations -
1986
Partial Profile of Small Placer Gold Mines . .
Principal Studies Relied Upon in the Development
of Effluent Limitations for Gold Placer Mining.
Gold Placer Mine Studies - 1976-1986
Facilities Visited in the Sampling Effort . .
EPA Chemical Analysis Methods
Size Distribution of Permitted Mines In Alaska
Evaluation of Water Usage Sluicing Operation -
Alaskan Gold Placer Mines (1984-1986) ....
Recycle of Wastewater at Alaskan Gold Placer
Recycle of Wastewater at Alaskan Gold Placer
Mines Expressed by Production - 1984
Summary of Alaskan Gold Placer Industry by
Production (from Tri-aqpncv Data)
45
46
47
48
51
52
53
56
59
81
104
105
106
109
-L \J J
110
-L. -L \J
110
111
112
-L _L £•
113
114
iv
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LIST OF TABLES (Continued)
Table Paqe
V-ll Amount of Mines Per Mining District Recycling
in Alaska (1984) 114
V-12 Summary of Process Discharge Raw Effluent TSS
Concentrations Data, 1983 - 1986) 115
V-13 Priority Organics Detected in the 1984 EPA
Study 116
V-14 Priority Metals Sampling Results from Gold
Placer Mines Final Effluents - 1984 Sampling . 117
V-15 Settling and Chemical Analysis Data for Five
Mines - 1986 118
V-16 Trace Element Analysis 119
V-17 TSS Concentration Levels After Simple Settling 120
V-18 TSS Concentration Levels After Chemically
Aided Settling 120
V-19 Alaska Sampling Data Gold Placer Mine
Discharges, 1983 - 1986 121
V-20 24-hour Simple Settling Test:
Solids Concentrations at
Various Detention Times 122
V-21 EPA Treatability Study - 1984 123
V-22 Total Suspended and Settleable Solids Tests
1984 and 1986 124
V-23 EPA Treatability Study - 1986 125
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LIST OF TABLES (Continued)
Table
Page
VII-1
VII-2
VII-3
VII-4
VII-5
VII-6
VII-7
VIII-1
VIII-2
VIII-3
VIII-4
VIII-5
VIII-6
X-l
Size Distribution of Gold
Pilot Test Water Quality
Percent Gold Recovery
Size Distribution of Gold
Test Run
Pilot Test Water Quality
Samples
Gold Recovery Data . . .
Percent Gold Recovery
Placer Mining Wastewater
Open Cut
Placer Mining Wastewater
Cut
Placer Mining Wastewater
Cut
Placer Mining Wastewater
Cut
Placer Mining Wastewater
Small Dredge
Placer Mining Wastewater
Large Dredge
Added to Each Run
Data
Added to Each
Data for Composite
Options - Very Small
Options - Small Open
Options - Medium Open
Options - Large Open
Options -
Options -
Pollutant Reduction Benefits
147
148
149
150
151
152
153
173
175
177
179
181
182
251
VI
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LIST OF FIGURES
Figure Page
III-l Principal Placer Gold-Producing Camps 60
in Alaska
III-2 Gold Production and Value of Production
in Alaska, 1880-1986 61
III-3 Side View of 18-Cubic-Foot Yuba Manufacturing
Division 110 Dredge 62
III-4 Basic Design for a Prospector's Rocker .... 63
III-5 Schematic of a Grizzly 64
III-6 Schematic of a Trommel 65
III-7 Schematic of a Vibrating Screen 66
III-8 Schematic of a Sluice Box 67
III-9 Types of Riffles 68
111-10 Schematic of a Shaking Table 69
III-ll A Long Tom 70
IV-1 Distribution of Alaska Gold Placer Mines by
Size 82
IV-2 Distribution of Placer Mines in the Lower 48
States by Size 83
V-l Gold Placer Mine Settleable Solids 126
V-2 Gold Placer Mine Total Suspended Solids. . . . 127
V-3 Gold Placer Mine Typical Toxic Metal
Removal 128
VII-1 Placer Mining Wastewater Treatment - Typical
Settling Pond Plan 154
VII-2 Placer Mining Wastewater Treatment - Settling
Pond - Typical Section 155
VII-3 Schematic of Recirculation of Process Waters
at a Gold Placer Mine 156
VII-4 Pilot Test Recycle Facility - Plan View . . . 157
VII-5 Pilot Test Recycle Facility - Side View . . . 153
vii
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LIST OF FIGURES (Continued)
Figure
7II-6 Recycle Flow Schematic
VIII-1 Placer Mining Wastewater Treatment Options -
Simple Settling
VIII-2 Placer Mining Wastewater Treatment Options -
Recirculation
VIII-3 Placer Mining Wastewater Treatment Options -
Chemically Aided Settling
VIII-4 Placer Mining Industry Generic Water System
Schematic - Open Cut - Option A
VIII-5 Placer Mining Industry Generic Water System
Schematic - Open Cut - Option B .
VIII-6 Placer Mining Industry Generic Water System
Schematic - Open Cut - Option C
VIII-7 Placer Mining Industry Generic Water System
Schematic - Dredge Mining - Option A
VIII-8 Placer Mining Industry Generic Water System
Schematic - Dredge Mining - Option B
VIII-9 Placer Mining Industry Generic Water System
Schematic - Dredge Mining - Option C
VIII-10 Placer Mining Wastewater Treatment Options -
Polyelectrolyte Feed Systems
VIII-11 1987 Placer Mining Study - Polyelectrolyte
Cost
VIII-12 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 1 Pond - Simple
Settling - Very Small
VIII-13 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 1 Pond - Simple
Settling - Small
VIII-14 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 1 Pond - Simple
Settling - Medium
VIII-15 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 1 Pond - Simple
Settling - Large
Page
159
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
Vlll
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Figure
LIST OF FIGURES (Continued)
Paqe
Placer Mining Wastewater Treatment Options •
Option A - Dredge - Simple Settling - Small
Placer Mining Wastewater Treatment Options •
Option A - Dredge - Simple Settling - Large
VIII-16
VIII-17
VIII-18 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 3 Ponds - Simple
Settling - Very Small
VIII-19 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 4 Ponds - Simple
Settling - Small
VIII-20 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 4 Ponds - Simple
Settling - Medium
VIII-21 Placer Mining Wastewater Treatment Options -
Option A - Open Cut - 4 Ponds - Simple
Settling - Large
VIII-22 Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 1 Pond - Recirculation -
Very Small ,
VIII-23 Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 1 Pond - Recirculation -
Small
VIII-24 Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 1 Pond - Recirculation -
Medium ,
VIII-25 Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 1 Pond - Recirculation -
Large
VIII-26 Placer Mining Wastewater Treatment Options -
Option B - Dredge - Recirculation - Small
VIII-27 Placer Mining Wastewater Treatment Options -
Option B - Dredge - Recirculation - Large
VIII-28 Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 3 Ponds - Recirculation •
Very Small
VIII-29 Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 4 Ponds - Recirculation •
Small
198
199
200
201
202
203
204
205
206
207
208
209
210
211
IX
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LIST OF FIGURES (Continued)
Figure
Page
VIII-30
VIII-31
VIII-32
VIII-33
VIII-34
VIII-35
VIII-36
VIII-37
IX-1
X-l
Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 4 Ponds - Recirculation
Medium
Placer Mining Wastewater Treatment Options -
Option B - Open Cut - 4 Ponds - Recirculation
Large
Placer Mining Wastewater Treatment Options -
Option C - Chemical Treatment - Very Small . .
Placer Mining Wastewater Treatment Options -
Option C - Chemical Treatment - Small
Placer Mining Wastewater Treatment Options -
Option C - Chemical Treatment - Medium . . . .
Placer Mining Wastewater Treatment Options -
Option C - Chemical Treatment - Large . . . .
Placer Mining Wastewater Treatment Options -
Option C - Chemical Treatment - Dredge -
Small
Placer Mining Wastewater Treatment Options -
Option C - Chemical Treatment - Dredge -
Large
Open Cut Mine (BPT)
Open Cut Mine (BAT)
212
213
214
215
216
217
218
219
231
252
x
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GOLD PLACER MINE SUBCATEGORY SECT - I
SECTION I
SUMMARY
This development document presents the technical data base
developed by EPA to support effluent limitations guidelines and
standards for the Gold Placer Mining Subcategory of the Ore
Mining and Dressing Point Source Category. The Clean Water Act
(CWA) designates various levels of technology as the basis for
effluent limitations: best practicable technology (BPT), best
available technology economically achievable (BAT), best
conventional pollutant control technology (BCT), and best
available demonstrated technology (BDT). Effluent limitations
guidelines based on the application of BPT, BAT, and BCT are to
be achieved by existing sources. New source performance
standards (NSPS) based on BDT are to be achieved by new
facilities.
The effluent limitations guidelines and standards described in
this document are required by Sections 301, 304, 306, 307, and
501 of the Clean Water Act (the Federal Water Pollution Control
Act Amendments of 1972, 33 USC 1251 et seq., as amended by the
Clean Water Act of 1977, P.L. 95-217 and the Water Quality Act of
1987, P.L. 100-4) ("the Act"). This regulation is being
promulgated in conformance with the Consent Decree in Trustees
for Alaska y^ Thomas, (No. A85-440 (D Alaska, May 7, 1986)), and
augments the regulation promulgated on December 3, 1982 for the
ore mining industrial category. To recognize inherent differ-
ences in ore mining, the 1982 regulation was divided into 11
major subcategories. Twenty-seven subdivisions were created
within the 11 subcategories based largely on whether the
discharge was from a mine or a mill. Further divisions were
based upon the process employed at the mine or mill. Gold placer
mining was included initially in the subcategory under gold ores;
however, it was not included in the 1982 regulations because EPA
did not have sufficient technical or economic data on which to
base an appropriate regulation. Further consideration led to the
establishment of a separate subcategory (outside of gold ores)
specifically for gold placer mining.
To gather the technical and economic information necessary to
promulgate a regulation, an extensive sampling and analysis
effort was undertaken during the 1983, 1984, 1985, and 1986
mining seasons. As part of this effort, 69 placer mines were
visited by EPA. Sampling was conducted at all 69 of these mines,
and treatability testing of wastewater was performed on 63 of
them. A total of 106 treatability tests were performed,
including 47 simple settling and 59 chemically assisted settling
tests. Four of these mines also were included as part of a ten-
site Method Detection Limit Study for Settleable Solids conducted
in 1985. In addition, two studies were conducted in 1984 and
1986 on small particle gold recovery to determine the effect of
high suspended solids concentration in wash water on sluice box
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GOLD PLACER MINE SUBCATEGORY SECT - I
operation. Many mining operations, including those visited in
these investigations, provided economic and technical operating
information. Data collected includes National Pollutant
Discharge Elimination System (NPDES) data and discharge
monitoring reports (DMRs) as well as information submitted by EPA
Regions VI, VIII, IX, and X and the Alaska Departments of
Environmental Conservation, Natural Resources, Fish and Game and
Commerce and Development.
During the 1986 mining season there were over 450 active
commercial gold placer mines in the United States. The number of
operations including recreational and assessment mines could be
in excess of 1,000. Approximately 42 percent of these commercial
mines are located in Alaska. Promulgation of this regulation is
expected to have greatest impact on the industry in Alaska, as
substantial water discharge regulations are in place for the gold
placer mines in the lower 48 states.
SUBCATEGORIZATION FOR GOLD PLACER MINES
EPA has created a separate subcategory in the ore mining and
dressing point source category known as "gold placer mine" to
regulate operations which mine or process gold placer ore by
gravity separation methods, bucket-line dredge mining, and all
mechanical mining practices. EPA separated gold placer mines
from the subcategory regulating other gold ores (i.e., hard rock
ores), and established this new subcategory because the mining
and processing methods employed in gold placer mines are
substantially different from hard rock mining methods. The
Agency considered further subcategorization of gold placer mining
on the basis of size of facilities, mining method, ore processing
method, wastewater treatability (including mineralogy),
topography, location, control technologies, climate (including
rainfall), water use, solids waste generation, number of
employees, reagent use, and age of facilities.
The final regulation does not apply to the following segments:
1. Mines processing less than 1,500 cu yds per year.
2. Dredges processing less than 50,000 cu yds per year.
3. Dredging operations conducted in open waters.
The 1,500 cu yds per year cutoff excludes the small recreational,
hobby or assessment operations which discharge a very low volume
of process water. Dredges, processing less than 50,000 cu yds
per year, are not covered by this regulation because the Agency
does not have adequate data, both technical and economic, to
prepare a model. This regulation also does not apply to mining
in open waters (i.e., marine waters, in the coastal zone (beach),
or in very large rivers) because: (1) the Agency does not, at
present, have a data base adequate to address this group; and (2)
the limitations that might be developed may require different
conditions because of uncertainty about the technology employed,
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GOLD PLACER MINE SUBCATEGORY SECT - I
the reasonableness of various treatment alternatives, and the
potential need to protect certain marine water resources.
After a thorough review of all available data, EPA determined
this level of subcategorization of gold gold placer mining was
appropriate for this regulation.
OVERVIEW OF THE LIMITATIONS AND STANDARDS
The effluent limitations and standards supported by this document
are intended to control the discharge of process wastewater
pollutants from mining and gold placer recovery efforts. In
addition, other excess waters, including mine surface drainage,
melting snow or permafrost, and groundwater infiltration, are
unavoidably commingled with process water as a result of these
activities. Under BAT and NSPS of this regulation, process water
would be recirculated in its entirety with a discharge allowed
for commingled excess process wastewater after treatment.
The presence or absence of the 126 toxic pollutants and one
nonconventional pollutant, e.g., settleable solids, was
determined in EPA's sampling and analysis program. All 126 toxic
pollutants have been excluded from regulation in the gold placer
mine subcategory based upon one of the following criteria: (1)
they were not detected, (2) they were present at levels not
treatable by known technologies, or (3) they were effectively
controlled by technologies upon which other effluent limitations
are based. Two toxic pollutants, arsenic and mercury, were
identified in treatable amounts in the untreated discharges from
gold placer mines. However, EPA is not promulgating limitations
for these pollutants because they will be adequately controlled
by the BPT and BAT limitations on settleable solids.
This regulation also includes a storm exemption when there is
excessive precipitation. Treatment systems are to be designed,
constructed, and operated to contain and treat the volume of flow
that would result from a 5-year, 6-hour rainfall plus the normal
volume or flow from the gold recovery process including any
excess waters. Because of pond design and site differences, the
design condition is based on a 5-year, 6-hour rainfall rather
than the 10-year, 24-hour rainfall required for the rest of the
ore mining category.
BEST PRACTICABLE TECHNOLOGY (BPT)
The factors considered in defining BPT include the total cost of
application of BPT in relation to the effluent reduction
benefits. In general, BPT represents the average of the best
performance of existing operations with common characteristics
and focuses on end-of-pipe treatment rather than in-process
controls. Three effluent control technologies were considered
for BPT: (1) simple settling, (2) simple settling with
recirculation of process water, and (3) chemically assisted
settling. While the 1977 date for compliance with BPT has
passed, BPT is being promulgated for use as a baseline from which
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GOLD PLACER MINE SUBCATEGORY SECT - I
the Agency evaluates other segments of the CWA. BPT for all
mines covered by this regulation is based on simple settling to
achieve 0.2 ml/1 settleable solids.
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE (BAT)
The factors considered in assessing BAT include the age of
equipment and facilities involved, the process employed, process
changes, and non-water quality environmental impacts. The
statutory assessment of BAT includes cost considerations, but the
primary determinant of BAT is effluent reduction capability.
Water recirculation with simple settling has been selected as the
basis for BAT. This technology achieves substantial removal of
the process wastewater pollutant generated during the operation
of a gold placer mine. No more advanced technology has been
demonstrated which can be applied to reduce the discharge of
process wastewater pollutants. The commingled wastewater
provision and storm exemption would be applicable under BAT.
BEST CONVENTIONAL POLLUTANT CONTROL TECHNOLOGY (BCT)
BCT replaces BAT for control of the conventional pollutants:
total suspended solids (TSS), pH, biochemical oxygen demand
(BOD), oil and grease (O&G), and fecal coliform. Fecal coliform,
BOD, and O&G were not found in significant concentrations above
the background of the intake water at gold placer mines. The pH
of the discharges was also very similar to the pH of the intake
water, which was approximately neutral. However, solids in the
wastewater discharges from gold placer mines have long been
identified as the major pollutant in placer mine discharges.
TSS, a conventional pollutant, is the parameter which measures
solids. The same three technologies considered for BPT were
considered for BCT. No BCT limitations are being promulgated for
this subcategory because no more stringent technology for
additional removal of conventional pollutants has been
demonstrated for universal application in gold placer mining.
NEW SOURCE PERFORMANCE STANDARDS (NSPS)
New facilities have an opportunity to implement the best and most
efficient ore mining and milling processes and wastewater
treatment technologies. Accordingly, Congress directed EPA to
consider the best demonstrated process changes and end-of-pipe
treatment technologies capable of reducing pollution to the
maximum extent feasible through a standard of performance which
includes, "where practicable, a standard permitting zero
discharge of pollutants."
The complete elimination of the discharge of process wastewater
pollutants is not possible for gold placer mining since water in
excess of that required for processing is unavoidably commingled
with process water, as described above. Standards for new source
gold placer mines are being promulgated based on the same
technology as promulgated for BAT. The same general
characteristics of wastewater, costs to treat, and percentages of
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GOLD PLACER MINE SUBCATEGORY SEcV'- I
pollutant removals are expected in new sources as found in
existing sources. New source standards equivalent to existing
source limitations would not pose a barrier to entry.
PRETREATMENT STANDARDS FOR EXISTING AND NEW SOURCES
All existing gold placer mines are point sources and direct
dischargers; there are no known existing indirect dischargers and
no new source indirect dischargers are anticipated. (Indirect
dischargers are those facilities which discharge to a publicly
owned treatment works.) Consequently, pretreatment standards,
which control the level of pollutants that may be discharged from
an industrial plant to a publicly owned treatment works, are not
included in this final regulation.
BEST MANAGEMENT PRACTICES (BMP)
The Clean Water Act authorizes EPA to prescribe "best management
practices" to prevent the release of toxic and hazardous
pollutants from plant site runoff, spillage or leaks, sludge or
waste disposal, and drainage from raw materials storage
associated with the manufacturing or treatment process. In gold
placer mines, infiltration, surface drainage and runoff, and mine
drainage are associated with mining and beneficiation operations
and may contribute significant amounts of pollutants to navigable
waters. Accordingly, EPA is including five BMP's in this
regulation which represent good mining practices typical of well-
run mining operations. This rule requires the inclusion of BMP
in gold placer mine permits, to the extent applicable in each
permit.
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GOLD PLACER MINE SUBCATEGORY SECT - I
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GOLD PLACER MINE SUBCATEGORY SECT - II
SECTION II
FINAL REGULATIONS
SUBCATEGORY M
EPA has added a Gold Placer Mine Subcategory, Subpart M to the
Ore Mining and Dressing Point Source Category for the purpose of
establishing effluent limitations and standards for the process
wastewaters from this segment of the mining industry.
APPLICABILITY
The following gold placer mining operations are not regulated
under this rule:
a) Operations processing less than 1,500 cu yds per year
of ore
b) Dredges processing less than 50,000 cu yds per year
of ore
c) Dredging operations working in open waters
EFFLUENT LIMITATIONS
The following effluent limitations are promulgated for all
sources:
BPT
The following effluent limitations represent the degree of
effluent reduction attainable by the application of the best
practicable control technology currently available (BPT).
Except as provided in 40 CFR 125.30-125.32, any existing point
source subject to this subpart must achieve the following
effluent limitations representing the degree of effluent
reduction attainable by the application of the best practicable
control technology currently available (BPT):
(a) The concentration of pollutants discharged in process
wastewater from an open-cut mine plant site shall not exceed:
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GOLD PLACER MINE SUBCATEGORY SECT - II
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(b) The concentration of pollutants discharged in process
wastewater from a dredge plant site shall not exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
BAT
The following effluent limitations representing the degree of
effluent reduction attainable by the application of the best
available technology economically achievable (BAT).
Except as provided in 40 CFR 125.30-125.32, any existing point
source subject to this subpart must achieve the following
effluent limitations representing the degree of effluent
reduction attainable by the application of the best available
technology economically achievable (BAT):
(a) The volume of process wastewater which may be
discharged from an open-cut mine plant site shall not exceed the
volume of infiltration, drainage and mine drainage waters which
is in excess of the make up water required for operation of the
beneficiatibn process. The concentration of pollutants in
process wastewater discharged from an open-cut mine plant site
shall not exceed:
8
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GOLD PLACER MINE SUBCATEGORY SECT - II
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(b) The volume of process wastewater which may be
discharged from a dredge plant site shall not exceed the volume
of infiltration, drainage and mine drainage waters which is in
excess of the make up water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from a dredge plant site shall not
exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
New Source Performance Standards (NSPS)
Any new source subject to this subpart must achieve the following
NSPS representing the degree of effluent reduction attainable by
the application of the best available demonstrated technology:
(a) The volume of process wastewater which may be
discharged from an open-cut mine plant site shall not exceed the
volume of infiltration, drainage, and mine drainage waters which
is in excess of the makeup water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from an open-cut mine plant site
shall not exceed:
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GOLD PL'ACER MINE SUBCATEGORY SECT - II
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(b) The volume of process wastewater which may be
discharged from a dredge plant site shall not exceed the volume
of infiltration, drainage, and mine drainage waters which is in
excess of the makeup water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from a dredge plant site shall not
exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(c) Notwithstanding any other provision of this chaptert
the Regional Administrator or Director of a State agency with
authority to administer the NPDES program shall in designating
new source gold placer mines take into account and base the
decision on whether one or more of the following factors has
occurred after promulgation of these regulations.
1. The mine will operate in a permit area which is not
covered by a currently valid NPDES Permit
2. The mine significantly alters the nature or quantity of
pollutants discharged.
3. The mine discharges into a stream into which it has not
discharged under its currently valid NPDES permit.
4. The mine will operate in an area that has not been
mined during the term of the currently valid NPDES
permit.
5. Such other factors as the Regional Administrator or
State Director deems relevant.
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GOLD PLACER MINE SUBCATEGORY SECfT'- II
Best Management Practices (BMP)
The following best management practices are specific requirements
which shall be included in each NPDES permit for all mining
operations regulated under this subpart to the greatest extent
applicable in each such mining operation.
(a) Surface water diversion; The flow of surface waters
into the plant site shall be interrupted and these waters
diverted around and away from incursion into the plant site.
(b) Berm construction; Berms, including any pond walls,
dikes, low dams, and similar water retention structures shall be
constructed in a manner such that they are reasonably expected to
reject the passage of water.
(c) Pollutant materials storage; Measures shall be taken
to assure that pollutant materials removed from the process water
and wastewater streams will be retained in storage areas and not
discharged or released to the waters of the United States.
(d) New water control; The amount of new water allowed to
enter the plant site for use in ore processing shall be limited
to the minimum amount required as makeup water for processing
operations.
(e) Maintenance of^ water control and solids retention
devices; All water control devices such as diversion structures
and berms and all solids retention structures such as berms,
dikes, pond structures, and dams shall be maintained to continue
their effectiveness and to protect from unexpected and
catastrophic failure.
STORM EXEMPTION
The following specialized provision applies only to Subpart M:
If, as a result of precipitation (rainfall or snowmelt), a
source subject to this subpart (gold placer mine subcategory) has
an overflow or discharge of effluent which does not meet the
limitations or standards of this subpart, the source may qualify
for an exemption from such limitations and standards with respect
to such discharge if the following conditions are met:
(i) The treatment system is designed, constructed, and
maintained to contain the maximum volume of untreated process
water which would be discharged from the beneficiation process
into the treatment system during a 4-hour operating period
without an increase in volume from precipitation or infiltration,
plus the maximum volume of water runoff resulting from a 5-year,
6-hour precipitation event. In computing the maximum volume of
water which would result from a 5-year, 6-hour precipitation
event, the operator must include the volume which should result
from the plant site contributing runoff to the individual
treatment facility.
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GOLD PLACER MINE SUBCATEGORY SECT - II
(ii) The operator takes all reasonable steps to maintain
treatment of the wastewater and minimize the amount of overflow.
(iii) The source is in compliance with the BMP in 140.148
and related provisions of its NPDES permit.
(iv) The operator complies with the notification
requirements of Section 122.41 (m) and (n) of this Title. The
storm exemption is designed to provide an affirmative defense to
an enforcement action. Therefore, the operator has the burden of
demonstrating to the appropriate authority that the above
conditions have been met.
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GOLD PLACER MINE SOBCATEGORY SECT - III
SECTION III
INTRODUCTION
PURPOSE
The 1982 ore mining regulations were divided into eleven
subcategories, one of which was designated for gold ores. At
that time, gold placer mines were included as a subcategory under
gold ores. However, because of insufficient data, EPA did not
promulgate regulations for gold placer mines when the 1982
regulations were promulgated. Further consideration led to the
establishment of a separate subcategory for gold placer mines (no
longer a part of gold ores). The purpose of this document is to
present the technical information used to develop regulations for
this newly created subcategory.
EPA has conducted various studies to determine the presence and
concentrations of toxic {or "priority") pollutants in the waste
water discharged from the gold placer mining segment. This
development document presents the technical data base compiled by
EPA with regard to these pollutants, as well as conventional and
nonconventional pollutants, and evaluates their treatability for
regulation under the provisions of the Clean Water Act.
This document also outlines the technology options considered and
the rationale for the option selected at each technology level.
These technology levels are the basis for the limitations and
standards of the final regulations. No pretreatment standards
are proposed, because there are no known indirect dischargers in
this subcategory, nor are there likely to be, because most
operations are rural and far from any publicly owned treatment
works (POTW).
LEGAL AUTHORITY
These regulations are established under authority of Sections
301, 304, 306, 307, and 501 of the Clean Water Act {the Federal
Water Pollution Control Act Amendments of 1972, 33 USC 1251 e_t
seq., as amended by the Clean Water Act of 1977, P.L. 95-217, and
the Water Quality Act of 1987, P.L. 100-4 {the "Act")).
The Federal Water Pollution Control Act Amendments of 1972
established a comprehensive program to "restore and maintain the
chemical, physical, and biological integrity of the Nation's
waters," Section 101{a). By July 1, 1977, existing industrial
dischargers were required to achieve "effluent limitations
requiring the application of the best practicable control
technology currently available" (BPT), Section 301(b)(1)(A). By
July 1, 1983, these dischargers were required to achieve
"effluent limitations requiring the application of the best
available technology economically achievable . . . which will
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GOLD PLACER MINE SUBCATEGORY SECT - III
result in reasonable further progress toward the national goal of
eliminating the discharge of all pollutants" (BAT), Section
301(b)(2)(A). New industrial direct dischargers were required to
comply with Section 306 new source performance standards (NSPS),
based on best available demonstrated technology. The
requirements for direct dischargers were to be incorporated into
National Pollutant Discharge Elimination System (NPDES) permits
issued under Section 402 of the Act. Although Section 402(a)(l)
of the 1972 Act authorized the setting of requirements for direct
dischargers on a case-by-case basis, Congress intended that, for
the most part, control requirements would be based on regulations
promulgated by the Administrator of EPA. Section 304(b) of the
Act required the Administrator to promulgate regulations
providing guidelines for effluent limitations setting forth the
degree of effluent reduction attainable through the application
of BPT and BAT. Moreover, Sections 304(c) and 306 of the Act
required promulgation of regulations for designated industry
categories, Section 307(a) of the Act required the Administrator
to promulgate effluent standards applicable to all dischargers of
toxic pollutants. Finally, Section 301(a) of the Act authorized
the Administrator to prescribe any additional regulations
"necessary to carry out his functions" under the Act.
EPA was unable to promulgate many of these regulations by the
dates contained in the Act. In 1976, EPA was sued by several
environmental groups, and in settlement of this lawsuit, EPA and
the plaintiffs executed a settlement agreement that was approved
by the Court. This agreement required EPA to develop a program
and adhere to a schedule for promulgating for 21 major industries
BAT effluent limitations guidelines and new source performance
standards covering 65 priority pollutants and classes of
pollutants. See Settlement Agreement in Natural Resources
Defense Council, Inc. y_._ Train, 8 ERC 2120 (D.D.Cl 1976) ,
modified, 12 ERC 1833 (D.D.C. 1979), modified by Orders of
October 26, 1982, August 2, 1983, January 6, 1984, July 5, 1984,
and January 7, 1985.
On December 27, 1977, the President signed into law the Clean
Water Act of 1977 (P.L. 95-217). Although this act made several
important changes in the federal water pollution control program,
its most significant feature was its incorporation of several
basic elements of the NRDC Settlement Agreement program for toxic
pollution control. Sections 301(b)(2)(A) and 301(b)(2)(C) of the
Act required the achievement, by July 1, 1984, of effluent
limitations requiring application of BAT for toxic pollutants,
including the 65 priority pollutants and classes of pollutants
that Congress declared toxic under Section 307(a) of the Act.
Likewise, EPA's programs for new source performance standards are
now aimed principally at toxic pollutant controls. Moreover, to
strengthen the toxics control program, Section 304(e) of the Act
authorizes the Administrator to prescribe best management
practices (BMP) to control the release of toxic and hazardous
pollutants from plant site runoff, spillage or leaks, sludge or
waste, and drainage from raw material storage associated with, or
ancillary to, the manufacturing or treatment process.
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GOLD PLACER MINE SUBCATEGORY SECT -III
Promulgation of the Ore Mining and Dressing Point Source Category
regulation on December 3, 1982 (47 FR 54598) satisfied the
requirements of the Settlement Agreement for the ore mining and
dressing category. The regulation for gold placer mines is not
issued pursuant to the agreement.
The proposed regulation for gold placer mines, 50 FR 47982 and
subsequent notices of information, provide effluent limitations
guidelines for BPT and BAT and establish NSPS on the basis of the
authority granted in Sections 301, 304, 306, 307, and 501 of the
Clean Water Act. As explained earlier, pretreatment standards
(PSES and PSNS) were not proposed for the gold placer mine
subcategory of the ore mining and dressing point source category,
since no known indirect dischargers exist nor are any known to be
in the planning stage. In general, ore mines and mills,
particularly gold placer mines in Alaska and several other
states, are located in rural areas, far from any POTW.
GENERAL CRITERIA FOR EFFLUENT LIMITATIONS
BPT Effluent Limitations
The factors considered in defining BPT include the total cost of
applying such technology in relation to the effluent reductions
derived from such application, the age of equipment and
facilities involved, the process employed, non-water quality
environmental impacts (including energy requirements), and other
factors the Administrator considers appropriate [Section
304(b)(1)(B)]. In general, the BPT technology level represents
the average of the best existing performances of plants of
various ages, sizes, processes, or other common characteristics.
Where existing performance is uniformly inadequate, BPT may be
transferred from a different subcategory or category. BPT
focuses on end-of-pipe treatment rather than process changes or
internal controls, except where the latter are common practice.
The cost-benefit inquiry for BPT is a limited balancing,
committed to EPA's discretion, which does not require the Agency
to quantify benefits in monetary terms. See, e.g., American Iron
and Steel Institute v EPA, 526 F.2d 1027 (3rd Cir. 1975). In
balancing costs in relation to effluent reduction benefits, EPA
considers the volume and nature of discharges expected after
application of BPT, the general environmental effects of the
pollutants, and the cost and economic impacts of the required
pollution control level. The Act does not require or permit
consideration of water quality problems attributable to
particular point sources or industries, or water quality
improvements in particular water bodies. Therefore, EPA has not
considered these factors. See Weyerhaeuser Co. v. Costle, 590
F.2d 1011 (D.C. Cir. 1978). —
BAT Effluent Limitations
The factors considered in assessing BAT include the age of
equipment and facilities involved, the process employed, process
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GOLD PLACER MINE SUBCATEGORY SECT - III
changes, and non-water quality environmental impacts, including
energy requirements [Section 304(b)(2)(B)]. At a minimum, the
BAT technology level represents the best economically achievable
performance of plants of various ages, sizes, processes, or other
shared characteristics. BAT may include process changes or
internal controls, even when these technologies are not common
industry practice. The statutory assessment of BAT "considers"
costs, but does not require a balancing of costs against effluent
reduction benefits (see Weyerhaeuser v. Costie, supra). In
developing the proposed BAT regulations, however, EPA has given
substantial weight to the reasonableness of costs. The Agency
has considered the volume and nature of discharges, the volume
and nature of discharges expected after application of BAT, the
general environmental effects of the pollutants, and the costs
and economic impacts of the required pollution control levels.
Despite this expanded consideration of costs, the primary
determinant of BAT is effluent reduction capability. As a result
of the Clean Water Act of 1977, 33 USC 1251, et seq., the
achievement of BAT has become the principal national means of
controlling water pollution due to toxic pollutants.
BCT Effluent Limitations
The 1977 Amendments added Section 301(b)(2)(E) to the Act
establishing best conventional pollutant control technology (BCT)
for discharges of conventional pollutants from existing
industrial point sources. Conventional pollutants are those
specified in Section 304(a)(4) [biological oxygen demanding
pollutants (BODS), total suspended solids (TSS), fecal coliform,
and pH], and any additional pollutants defined by the
Administrator as "conventional" (to date, the Agency has added
oil and grease, 44 FR 44501, July 30, 1979).
BCT is not an additional limitation but replaces BAT for the
control of conventional pollutants. In addition to other factors
specified in Section 304(b)(4)(B), the Act requires that BCT
limitations be assessed in light of a two-part "cost-
reasonableness" test. American Paper Institute v_^ EPA, 660 F.2d
(4th Cir. 1981). The first test compares the cost~7or private
industry to reduce its conventional pollutants with the costs to
publicly owned treatment works for similar levels of reduction
from their discharge of these pollutants. The second test
examines the cost-effectiveness of additional industrial
treatment beyond BPT. EPA must find that limitations are
"reasonable" under both tests before establishing them as BCT.
In no case may BCT be less stringent than BPT.
New Source Performance Standards
The basis for NSPS under Section 306 of the Act is best available
demonstrated technology (BDT). New operations have the
opportunity to design and utilize the best and most efficient
processes and wastewater treatment technologies. Congress
therefore directed EPA to consider the best demonstrated process
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GOLD PLACER MINE SUBCATEGORY SECT - III
changes, in-plant controls, and end-of-pipe treatment
technologies that reduce pollution to the maximum extent
feasible.
Pretreatment Standards for Existing Sources
Section 307(b) of the Act requires EPA to promulgate pretreatment
standards for existing sources (PSES).
There are no ore mines, including gold placer operations, that
currently discharge to a POTW. By the nature of their locations,
it is unlikely that any indirect dischargers exist. Therefore,
no PSES are being promulgated at this time.
Pretreatment Standards for New Sources
Section 307(c) of the Act requires EPA to promulgate pretreatment
standards for new sources (PSNS) at the same time that it
promulgates NSPS. New indirect dischargers, like new direct
dischargers, have the opportunity to incorporate the BDT,
including process changes, in-plant controls, and end-of-pipe
treatment technologies, and to use plant site selection to ensure
adequate treatment system installation. Due to the location of
placer gold deposits, future operations are expected to be
located in rural areas far from any POTW. Therefore, no PSNS are
being promulgated at this time.
PRIOR EPA REGULATION
Effluent limitations guidelines and standards are not directly
enforceable against dischargers. Instead, they are incorporated
into a National Pollutant Discharge Elimination System (NPDES)
permit, which is required by Section 402(a)(l) of the Clean Water
Act for the discharge of pollutants from a point source into the
waters of the United States. If EPA has not established
industry-wide effluent limitations guidelines and standards to
cover a particular type of discharge, Section 402(a)(l) of the
Act expressly authorizes the issuance of permits upon "such
conditions as the Administrator determines are necessary to carry
out the provisions of this Act." In other words, this section
authorizes a determination of the appropriate effluent
limitations (e.g., BPT, BCT, BAT), on a case-by-case basis, based
on the Agency's "best professional judgment" (BPJ).
The establishment of effluent limitations in NPDES permits on a
case-by-case basis is a two-step process. First, EPA must
identify the appropriate technology basis. The second step in
the permitting process is the setting of precise effluent
limitations which can be met by application of that technology at
that site. The Clean Water Act does not require dischargers to
install the technology which is the basis of the limitations;
dischargers may meet the effluent limitations in any way they
choose.
Regulation p_f the Ore Mining and Dressing Category
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GOLD PLACER MINE SUBCATEGORY SECT - III
On November 6, 1975, EPA published interim final regulations
establishing BPT requirements for existing sources in the ore
mining and dressing category (see 40 FR 41722). These
regulations became effective upon publication. However,
concurrent with their publication, EPA solicited public comments
with a view to possible revisions. On the same date, EPA also
published proposed BAT and NSPS (see 40 FR 51738) for the ore
mining and dressing point source category, which included gold
placer mines.
On May 24, 1976, as a result of the public comments received, EPA
suspended certain portions of the interim final BPT regulations,
including the portion which applied to gold placer mining, and
solicited additional comments (see 41 FR 21191). EPA promulgated
revised, final BPT regulations for the ore mining and dressing
category on July 11, 1978 (see 43 FR 29711, 40 CFR Part 440). On
February 8, 1979, EPA published a clarification of the BPT
regulations as they apply to storm runoff (see 44 FR 7953). On
March 1, 1979, the Agency amended the final regulations by
deleting the requirements for cyanide applicable to froth
flotation mills in the base and precious metals subcategory (see
44 FR 11546).
On December 10, 1979, the U.S. Court of Appeals for the Tenth
Circuit upheld the BPT regulations, rejecting challenges brought
by five industrial petitioners, Kennecott Copper Corp., y_._ EPA,
612 F.2d 1232 (10th Cir. 1979). The Agency withdrew the proposed
BAT, NSPS, and pretreatment standards on March 19, 1981 (see 46
FR 17567).
On June 14, 1982, EPA again proposed BAT, BCT, and NSPS for the
ore mining point source category. On December 3, 1982, final BAT
and NSPS limitations for the ore mining point source category
were promulgated without limitations for gold placer mining.
Regulation of Gold Placer Mines
The 1976-1977 Permits
In 1976 and 1977, EPA issued 170 permits to Alaska placer miners.
Because there were no promulgated effluent limitations and
standards for gold placer mines at that time, these permits were
based on BPJ. In addition, these permits included limitations
designed to satisfy Alaska's water quality standards.
Each of the permits had identical effluent limitations,
monitoring requirements, and reporting requirements. The permits
required treatment of process wastes so that the maximum daily
concentration of settleable solids was 0.2 milliiiters per liter
(ml/1). In addition, the permits required monthly monitoring for
this pollutant or, instead of monitoring to establish compliance
with the settleable solids limitation, each permittee was given
the option of installing a settling pond with the capacity to
hold 24 hours' water use. The technology basis for the
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GOLD PLACER MINE SUBCATEGORY SECT - III
settleable solids limitation was settling ponds. In addition,
the permittee could not cause an increase in turbidity of 25 JTU
(Jackson Turbidity Units) over natural background turbidity in
the receiving stream at a point measured 500 feet downstream from
the final discharge point. EPA added the turbidity limitation at
the request of the State of Alaska, which included the turbidity
requirement in its certification of these permits under Section
401 of the Clean Water Act to ensure compliance with its state
water quality standards.
In June 1976, Gilbert Zemansky requested an adjudication of the
1976 NPDES permits as an interested party. Subsequently, the
Trustees for Alaska (Trustees) and the Alaska Miners Association
(Miners), as well as others, were admitted as additional parties
to the proceeding. The Trustees and Zemansky argued that the
permit terms were not stringent enough and that EPA should have
selected recirculation as the model BPT technology and required
zero discharge of any pollutants, while the Miners argued that
the terms were too stringent and not achievable. After the
initial adjudicatory hearing, the Regional Administrator for
Region X issued his Initial Decision on October 25, 1978,
upholding the terms of the permits.
The Trustees, Zemansky, and the Miners each petitioned the
Administrator of EPA to review the initial decision. On March
10, 1980, the EPA Administrator issued his decision on review.
The Administrator held that the Regional Administrator's findings
regarding settling pond technology "conclusively establish that
any less stringent control technology does not satisfy the
requirements of BPT" (Decision of the Administrator (Ad. Dec.) at
15). The Administrator also found that "the Regional
Administrator was in doubt about the facts respecting the extra
costs of recycling. ..." Therefore, the Administrator remanded
the proceedings to the Regional Administrator "for the limited
purpose of reopening the record to receive additional evidence on
the extra cost of recycling in relationship to the effluent
reduction benefits to be achieved from recycling" (Ad. Dec. at
22). The Administrator directed the Regional Administrator to
determine whether recycling constitutes BPT based on the
additional evidence received.
After the Administrator rendered his decision, the Trustees
requested the Administrator to: (1) determine the effluent
limitations necessary to meet state water quality standards; (2)
determine appropriate effluent monitoring requirements in the
event the Regional Administrator did not determine that zero
discharge was required; and (3) direct the Regional Administrator
on remand to determine effluent limitations for total suspended
solids or turbidity, for arsenic, and for mercury based on BPT in
the event he did not determine that zero discharge is required.
On July 10, 1980, the Administrator issued a Partial Modification
of his decision, directing the Presiding Officer "to allow
additional evidence to be received if he determines on the basis
of the record that such additional evidence is needed to make the
requested determinations" (Partial Modification of Remand at 3).
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GOLD PLACER MINE SUBCATEGORY SECT - III
The hearing on remand was held in March and June 1981, and the
Presiding Officer issued his Initial Decision on Remand (Rem.
Dec.) on March 17, 1982. After reviewing the costs and effluent
reduction benefits associated with both settling ponds and
recirculation, the Presiding Officer held that "the preponderance
of the evidence in this case indicates that zero discharge is not
'practicable' for gold placer miners in Alaska" (Rem. Dec. at
17). He also ordered EPA to modify the permits to include
monitoring requirements for settleable solids and turbidity, and
to require monitoring for arsenic and mercury, for at least one
season, "to determine whether or not [they] constitute a problem
with placer mining" (Rem. Dec. at 19-20).
On September 20, 1983, the Administrator denied review of the
Initial Decision on Remand. Both the Trustees for Alaska and
Zemansky, as well as the Alaska Miners Association, petitioned
the Ninth Circuit Court of Appeals for review (Case No. 83-7764
and Case No. 83-7961). The Ninth Circuit consolidated the cases
and issued its decision in Trustees for Alaska v. EPA and Alaska
Miners Association v. EPA on December 10, 1984 (749 F.2d 549).
In this court proceeding, the Miners raised various legal issues,
including certain constitutional challenges, each of which was
dismissed by the Court. Specifically, the Court held that: (1)
the Clean Water Act's permit requirements applied to placer
mining, i.e., when discharge water is released from a sluice box
it is a point source; (2) EPA's failure to establish effluent
limitations guidelines and standards for the placer mining
industry could only be challenged in district court; and (3) the
Miners' challenge to the assignment of the burden of proof in the
administrative hearings was not timely—it should have been
raised when the permit regulations establishing that standard
were promulgated.
The Court also dismissed the Miners' constitutional claims as too
speculative or premature. The Miners had claimed, e.g., that the
permit conditions constituted a taking of their vested property
rights in violation of the Fifth Amendment; the permits' self-
monitoring, reporting, and record keeping provisions infringed
their constitutional privilege against self-incrimination; and
the permits' inspection provisions infringed their rights under
the Fourth Amendment to be free from unreasonable searches.
The Court dismissed most other challenges to the permits as moot
since the permits expired before this case reached the Ninth
Circuit, and EPA had issued two sets of subsequent permits (in
1983 and 1984) based on newer, more complete records by the time
the Court heard this case. The Court specifically held that
EPA's choice of settling ponds as "best practicable control
technology" (BPT) was moot because a different standard, "best
available technology" (BAT), now applies.
However, the Court held that the form of the limitations included
in the permits to ensure achievement of state water quality
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GOLD PLACER MINE SUBCATEGORY -SECT - III
standards was not moot since both the permits at issue and the
subsequent permits incorporated state water quality standards
directly into the permits. After reviewing the definition of
"effluent limitation," the legislative history of the 1972
amendments to the Clean Water Act, and relevant court cases, the
Court held that EPA should not have incorporated the state water
quality standard for turbidity, which was a receiving water
standard, directly into the permits. Instead, the Court held
that the permits must include end-of-pipe effluent limitations
necessary to achieve the water quality standards. The Court also
held that EPA should have given the Trustees the "opportunity to
present in a public hearing their case for proposed effluent
limitations or monitoring requirements for arsenic and mercury."
The 1983 Permits
During the proceedings on the 1976-1977 permits, EPA issued
additional permits to Alaskan placer miners. In 1983, EPA issued
269 new permits. The 1983 permits were issued for the 1983
mining season and differed from the 1976 permits in several
respects. For example, the 1983 permits contained a daily
maximum discharge limit of 1.0 ml/1 and a monthly average
discharge limit of 0.2 ml/1 on settleable solids. The 1983
permits also included a limit on arsenic based on the Alaska
state water quality standards.
The Trustees for Alaska and Gilbert Zemansky requested an
evidentiary hearing on the 1983 permits which the EPA Region X
Regional Administrator granted. On February 16, 1984, the
proceedings were dismissed for several reasons, including
expiration of the 1983 permits and the Agency's intent to issue
new permits that would take effect in the next mining season
(i.e., the summer of 1984). No one appealed the decision within
the Agency or petitioned for judicial review of the decision.
The 1984 Permits
In 1984, EPA issued BAT permits to 445 placer miners (the first
set was issued on June 8, 1984; additional permits were issued on
June 14, 1984). The technology basis for the BAT permits, like
the BPT permits, was settling ponds. Based on additional data
developed since the BPJ permits were issued, the instantaneous
maximum settleable solids discharge limit was 1.5 ml/1 and the
monthly average limit was 0.7 ml/1. Monitoring was required
twice per day, each day of sluicing. The permits incorporated
Alaska's state water quality standards for turbidity and arsenic
and required visual monitoring for turbidity.
The 1985, and 1987 Permits
On January 31, 1985, in response to the Ninth Circuit opinion,
which held that permits must include end-of-pipe effluent
limitations necessary to achieve state water quality standards
(see above), EPA proposed to modify the 1984 permits to include
effluent limitations for turbidity (5 NTUs above background) and
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GOLD PLACER MINE SUBCATEGORY SECT - III
arsenic (0.05 mg/1). On February 12, 1985, EPA proposed permits
for 93 additional mines. These permits proposed the same
limitations as the 1984 permits except that they included the
effluent limitations for turbidity and arsenic, just mentioned,
rather than simply citing the state water quality standards. The
Alaska Department of Environmental Conservation certified the
permits with the stipulation that the settleable solids effluent
limitation not exceed 0.2 ml/1. This superceded EPA's proposed
limit of 0.7/1.5 ml/1 described above. On May 10, 1985, EPA
issued both the modified permits to miners holding permits in
1984 and the new permits to the 1985 applicants. A total of 539
permits were issued, and approximately 20 evidentiary hearing
requests were received by the Agency. Included in these requests
were challenges to all the permits which were filed by the
Trustees for Alaska and the miner's Advocacy Council. On January
30, 1987, a decision was issued which granted a hearing on some
issues while denying on others. The partial denials were
appealed to the Administrator by both the Trustees for Alaska and
the Miner's Advocacy Council and the Administrator subsequently
denied the petitions for review. The partial hearings were
postponed pending appeal. Permits issued for 1987 were
essentially the same as the 1985 permits. Evidentiary hearing
requests were again received for the 415 permits issued in 1987,
and the Regional Administrator issued a decision denying in part
and granting in part the requests. Petitions for review of the
partial denied are pending before the Administrator. Several
miners have requested that the hearings on the 1985 and 1987
permits be consolidated. Commencement of the hearings on both
permits awaits a ruling by the Administrator on the petitions for
review of the partial denial of a hearing on the 1987 permits.
The 1985 Proposal
On November 20, 1985, EPA proposed BPT, BAT, BCT, and NSPS for
Gold Placer Mining. The Agency proposed three subcategories for
the industry:
1. Large dredges, with a production rate greater than
4,000 cu yds per day, which operate in a self-contained
pond.
2. All mines using all mining methods with production
rates greater than 20 cu yds per day and less than 500
cu yds per day of "bank run" ore.
3. All mines, all mining methods (except group 2, large
dredges) with a production rate greater than 500 cu yds
per day of "bank run" ore.
Small mines processing less than 20 cu yds per day were proposed
to be not regulated by these regulations. BPT proposed for
regulated subcategories except dredges with capacities of more
than 4,000 cu yds per day was based on simple settling with
limitations on settleable solids of 0.2 ml/1 and total suspended
solids (TSS) of 2,000 mg/1. No discharge of process water was
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GOLD PLACER MINE SOBCATEGORY SECT - III
proposed for dredges that process more than 4,000 cu yds per day.
BAT proposed for mines processing 20 to 500 cu yds per day was
also 0.2 ml/1 of settleable solids, with no discharge of process
water for the two larger subcategories. BCT was proposed at
2,000 mg/1 TSS for mines processing between 20 and 500 cu yds per
day of ore, with no discharge from the two larger categories.
NSPS was proposed equivalent to BAT and BCT for each subcategory.
Notices of_ New Information
In response to comments received on the proposed regulation, the
Agency collected additional economic and technical information on
gold placer mining. The Agency published two notices of
availability of new information in the Federal Register and
requested public comment on each of them.
The first Notice of New Information was published in the Federal
Register on February 14, 1986 (51 FR 5563). The additional
information identified in the Notice included technical and
economic data that had been collected and a method detection
limit study for settleable solids in placer mining effluent. The
Agency extended the comment period on the proposal to provide for
public comment on this information. The second Notice of New
Information was published in the Federal Register on March 24,
1987 (52 FR 9414). In addition to the additional data collected,
the Agency announced changes in its economic methodology and
identified possible alternate regulatory options under
consideration. A new comment period was provided to allow public
comment on this information.
GENERAL APPROACH AND METHODOLOGY
From 1973 through 1976, the EPA Effluent Guidelines Division
obtained data on Alaskan gold placer operations as part of its
general study of the ore mining and dressing point source
category. Because the category itself was so large and diverse,
the Agency determined after promulgating interim final BPT
limitations that the data base for gold placer mines, in general,
and gold placer mines in Alaska, Colorado, Montana, California,
Idaho, Washington, Oregon, and Nevada, in particular, was
inadequate to form the basis of national effluent limitations
guidelines and standards. From 1977 through the present, the
Agency has undertaken several sampling surveys and data
collection efforts aimed at resolving various issues. A
discussion of the major study tasks and their results is
presented in Section V of this report.
INDUSTRY PROFILE
Historical Perspective
Prior to the Alaska purchase in 1867, the existence of gold in
placer form in Alaska was known to the Russians, the English of
the Hudson Bay Company, and members of the Western Union
Telegraph exploration party, but little exploitation of these
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GOLD PLACER MINE SUBCATEGORY SECT - III
deposits took place. Gold placer mining in Alaska was started
primarily by California gold rush prospectors moving up the
coast. Significant events which stimulated this activity were
gold discoveries in the Juneau vicinity (1880), Rampart (1882),
Forty-mile district (1886), and Birch Creek (Circle) district
(1893). The Klondike gold rush of 1897-1898 in Canada also
stimulated Alaskan prospecting. Additional deposits were
discovered in Nome (1898), Fairbanks (1902), and the Tolovana
(Livengood) district (1914). High-grade deposits were mined out
rapidly, but the introduction of large-scale permafrost thawing,
hydraulic stripping, and mechanized excavation methods increased
the productivity of placer mining and allowed working of lower-
grade deposits. Mechanical dredges were introduced in Nome in
1905 and large electric-powered dredges were employed in Nome and
Fairbanks in the 1920s.
In 1940, Alaska was the leading gold-producing state with
production of 750,000 troy ounces, mostly from placer mines.
(One troy ounce is equal to 31.1 grams, 1.097 ounces
avoirdupois.)
Placer mining activity was substantially reduced during World War
II, and operations after the war remained at a low level because
of rising operating costs and a government-fixed gold price of
$35 per troy ounce. Dredging was reduced to only a few
operations in the 1960s. Relaxation of federal restrictions on
prices and private ownership of gold in the 1970s and an increase
in the market price stimulated gold mining activity in the later
1970s; several hundred placer mines came into operation. In
1982, gold production was more than 160,000 troy ounces from
placer mining alone (total Alaskan gold production for 1982 from
lode and placer mines was in excess of 175,000 troy ounces).
Almost all of the gold produced in the United States outside of
Alaska was produced in the following 17 states: Alabama,
Arizona, California, Colorado, Georgia, Idaho, Montana, Nevada,
New Mexico, North Carolina, Oregon, South Carolina, South Dakota,
Utah, Virginia, Washington, and Wyoming. Gold mining in the
United States began in North Carolina, with Georgia joining in
production in 1829, and Alabama in 1830. Production began in
other states as prospectors moved west. The most important gold
discovery, because of its influence on western development, was
at Sutter's Mill in California in 1848. Later discoveries were
made in most other Western states and territories.
Early mining was largely by placer methods with miners working
stream deposits by various hydraulic techniques. The gold was
recovered by gravity separation or by amalgamation with mercury.
During the period 1792 through 1964, 88 percent of the production
came from gold ores (51 percent - lode; 37 percent - placers) and
12 percent as a by-product from other metal mines. The total
U.S. gold production as of 1980 was 319 million ounces with lode
gold mining supplying about 50 percent, placer mining 35 percent,
and base metal mining (by-product) accounting for 15 percent!
Lode mining is defined as "hard rock" mining using either open
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GOLD PLACER MINE SUBCATEGORY SECT - III
pit or underground methods of mining minerals that are in place
as originally deposited in the earth's crust or that have been
reconsolidated into a composite mass with waste rock. The sought
after mineral is not in a "free" or loose state.
Description of the Industry
Nature of_ Deposits
Placer mining is the process involved in the extraction of gold
or other metals and minerals from primarily alluvial deposits
which may be from recent ("young" placers) or ancient deposits
("old " "ancient," or "fossil" placers). Current placer mining
activity generally takes place in young placers originating as
waterborne or glacially-deposited sediments. For many years,
gold has been the most important product obtained, although
considerable platinum, silver, tin (as cassiterite, Sn02),
phosphate, monazite, rutile, ilmenite, zircon, diamond and other
heavy, weather-resistant metals or minerals have been produced
from these deposits at various locations in the world. Since
gold has a high specific gravity (19.3), it settles out of water
rapidly and is found associated with other heavy minerals in the
deposits.
Most placer deposits consist of unconsolidated or
semiconsolidated sand and gravel that actually contain very small
amounts of native gold and other heavy minerals. Most are stream
deposits and occur along present stream valleys or on benches or
terraces of pre-existing streams. Placer gold deposits are also
occasionally found as beach or offshore deposits as at Nome,
Alaska.
Residual placers are defined as deposits found spread over a
local gold bearing lode deposit as a residual of the decay or
erosion of that deposit and are found at a number of localities
such as Flat, Happy, and Chicken Creeks in the Iditarod District
of Alaska, but have not been an important source of gold. Creek
bench deposits are found in virtually all the districts. Modern
creek placers occupy the present creek channels and usually
contain gravels from a few feet to 10 feet or more thick. The
ancient placers are those in benches or terraces along present
streams. The deeply buried channels or "deep gravels" are
deposits of ancient streams which are now buried by alluvium.
The best examples of these deposits are in the interior of
Alaska, particularly in the Fairbanks, Hot Springs, Tolovana, and
the Yukon-Tanana region. The gravels are ordinarily 10 to 40
feet thick but are buried under black humus (sometimes called
muck), fine gray sand, silt, and clay which may be 10 to 30 feet
or more thick.
Bench placers have the characteristics of modern creek placers
but are higher than the present bed of the stream. Present
streams have cut into the deposits forming surface terraces that
resemble benches. High-bench deposits result from the action of
streams of a former drainage system with no direct relation to
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GOLD PLACER MINE SUBCATEGORY SECT - III
existing drainage channels. These high gravels are sometimes
called "bar" deposits. Some of the best examples are in the
Rampart, Hot Springs, and Ruby Districts. Some of the high bench
deposits near Nome between Dexter and Anvil Creeks have been very
productive.
Beach placers are resorted deposits that have been formed by wave
action which erodes adjacent alluvial deposits and concentrates
their gold along the beach. Examples of these deposits are at
Lituya Bay, Yakataga and Kodiak Island. The most important beach
placers are at and near Nome. At Nome, there are both submerged
and elevated beach placers formed at various times particularly
over the last million years when the sea level fluctuated. In
most cases, the beach lines, usually gravels, covered with muck
and overburden, have been very productive. Their thickness
ranges from 30 to 100 feet.
Other types of placers include river bar, gravel plain, those
associated with bedding planes and crevices of the bedrock, and
some placers in which the bedrock has formed or is overlain by a
sticky clay or "gumbo" in which the gold may be distributed.
The presence of beds of clay or "hardpan" in placer deposits may
influence the distribution of the gold. The clay beds form
impervious layers (false bedrock) on which concentration of gold
takes place and prevents the gold from working below them.
Location
Gold placer mining in the United States is located almost
entirely in Alaska and the seven Western states of California,
Colorado, Idaho, Montana, Nevada, Oregon, and Washington. Data
received on the 1986 mining season indicate 457 operating
commercial mines, with 265 (58 percent) operating in the lower 48
states and 192 (42 percent) in Alaska. Small recreational and
assessment mining activities bring the total number of operations
considerably higher, possibly in excess of 1,000; however, there
is no known reliable information on the smaller operations.
Information obtained by the Agency indicates considerable change
in the industry since 1982; while the industry in the Lower 48
has grown by 34 percent, the number of mines in Alaska has
dropped over 36 percent. Activity in Alaska and the major
producing states in the Lower 48 has been reviewed by the Agency
and included in the data base for this regulation.
Alaska
Figure III-l (p. 60) shows locations of major gold producing
camps in Alaska. Table III-l (p. 45) lists cumulative production
information for these camps since their discovery. Historically,
the size of the mining activity has fluctuated with the price of
gold and other factors. Figure III-2 (p. 61) illustrates the
dramatic fluctuation of activity in Alaska over the past century.
Recently, factors other than the price of gold have been
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GOLD PLACER MINE SUBCATEGORY if SECT - III
controlling the size of gold placer mine activity in Alaska.
Despite an average 23 percent increase in the price of gold from
1985 to 1986, gold placer mining activity in the state of Alaska
has dropped off sharply. While the number of permits issued has
declined only slightly (446 in 1984, 437 in 1987), the number of
active placer mines as reported by the Alaska Division of
Geological and Geophysical Surveys shows a more substantial
decline:
Year No. of Mines
1982 304
1985 266
1986 195
A study done by Louis Berger and Associates, identified the areas
around Fairbanks (the Eastern Interior region) as the most
dependent upon placer mining. Alaska's Division of Geological
and Geophysical Surveys reported a 49 percent decline in
employment for placer mining in this area during 1986. Table
III-2 (p. 46) shows the changes in number of operators,
employees, and production by region for 1985 and 1986. The
reasons cited for the decline of placer activity in Alaska are
uncertainty about state water quality regulations and two
lawsuits related to mining on Federal lands in Alaska.
Lower 48_
Gold placer mining in the lower 48 states fluctuates from year to
year, primarily based on the price of gold. The exact number of
mines in each state varies considerably. Information collected
on Idaho, Montana, Colorado, California, Nevada, Oregon, and
Washington is summarized below:
Idaho. Based upon a review of applications for
dredging and gold placer mine permits in Idaho and other
information in the Idaho Department of Land files, there are
approximately 29 active gold placer mines and 42 inactive mines
in the state. Twenty-seven of the 29 active operations are
located in ten counties with the majority of these located in two
counties. The volume of ore sluiced per day ranges from
approximately 36 cu yds to 4,800 cu yds, with the sizes and types
of operations being basically similar to those in Alaska and
Montana.
Montana. There are 50 gold placer mines (employing
mechanical, open-cut methods) in Montana which have discharge
permits or are otherwise known to exist. It is likely that there
may be another 60 mines that do not have discharge permits (some
may not discharge wastewater). The mines are located in the
western portion of the state. There are no known hydraulic
mining operations or mechanical dredges operating in Montana.
However, the Montana Department of Health and Environmental
Sciences has issued water discharge permits to approximately 97
suction dredges, which generally are quite small (2- to 4-inch
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GOLD PLACER MINE SUBCATEGORY SECT - III
diameter). The mining methods, classification methods,
wastewater treatment technologies, and size of the operations all
appear similar to those encountered in Alaska.
Colorado. A review of the Colorado Water Pollution
Control Division's files indicated that only four gold placer
mines in the state had permits to discharge wastewater. Other
sources indicate that there may be as many as 19 more gold placer
mines in the state. This apparent discrepancy may be explained
by several possibilities including: (a) no discharge of
wastewater; (b) inactive status; (c) improper classification as a
gold placer mine; and (d) discharge without a permit. The gold
placer mines for which permits have been issued are relatively
small (less than 150 cu yds per day), seasonal, open-cut mines
employing settling ponds for treatment of wastewater.
California. According to the U.S. Bureau of Mines, one
large dredging operation was expected to recover 20,000 to 25,000
troy ounces of gold annually. There are likely to be other
operations, but no data on these operations are available. It
has been estimated that there may be as many as 25 operating gold
placer mines in California, but all are thought to be zero
discharge operations.
Nevada. According to Reference 6, 157 troy ounces of
gold were obtained from gold placer deposits in Nevada. However,
little is known about any active gold placer mine operations. It
has been estimated that there are six commercial gold placer
mines in Nevada.
Oregon. Several small gold placer mines (small suction
dredges) were reported as operating along gold-bearing drainages
in southwestern Oregon. Production is unknown. It is thought
that there may be 25 to 50 operations in Oregon.
Washington. It has been estimated that there are 30
gold placer mines in Washington, but little is known about them.
No state discharge standards are in effect.
Production
Most gold placer deposits contain a few cents to several dollars
worth of gold per cu yd (1 cu yd weighs about 1.5 tons); a rich
placer deposit would contain only a few grams of gold per ton of
gravel. The largest placer deposits have yielded several million
ounces of gold, but most have been much smaller. The Bureau of
Mines has estimated that gold placer deposits contributed as much
as 3 percent of the U.S. total annual production in 1982. Taking
the State of Alaska's 1982 estimates of gold placer production
and comparing them to the Bureau of Mines 1982 total gold
production indicates that Alaska gold placer deposits contributed
approximately 10 percent of total U.S. gold production, while
1986 data indicates Alaska production was approximately 4 percent
of total U.S. gold production.
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GOLD PLACER MINE SUBCATEGORY SECT - III
Figure III-2 (p. 61) is a plot of historical gold production and
value in Alaska for the period 1880-1986. Based upon recent
estimates performed by the State of Alaska's Division of
Geological and Geophysical Surveys, gold placer production in
Alaska was 160,000 troy ounces in 1986, a decline of 16 percent
from the previous year.
Gold Prices
Gold prices during the last 20 years have been subject to wide
variation as illustrated in Table III-3 (p. 47). Gold placer
mining should be viewed against the backdrop of fluctuating
prices, since the factor of rising prices can stimulate
prospecting, influence the number of active operations, cause
increases in production, and allow the mining of lower grade
ores, while decreasing prices have the opposite effect.
Summary of_ Mining and Processing Methods
The mining and processing methods in use today in Alaska and the
other gold placer mining states are similar in many respects to
those in use elsewhere in the ore mining and dressing category.
Three important differences exist in this category: (a) the
nature of the deposits requires that a great deal of material
must be excavated or moved and then processed to remove an
accessory or trace constituent (gold) and, because gravity
separation methods are used, a great deal of water per unit of
production is needed; (b) the climate and location of many
operations dictate harsh operating conditions and constant
maintenance; (c) some permanently frozen overburden and ore
deposits must be thawed in order to be exploited which, in turn,
produces excess water to be treated prior to release.
The actual mining season varies with location and availability of
water but generally ranges between 40 and 137 days per year, with
the average operation probably in the 100-115 operating day range
for the entire United States; Alaska would be lower. This range
is most typical for operations in the industry as a whole, but
there are a few operations in the conterminous states which
operate with longer seasons (270 days).
Before 1930, open cut gold placer mines operated with steam-
powered shovels, scrapers, draglines, cableway excavators, and
reciprocating and pulseometer pumps. The development of the
lightweight diesel engine, which resulted in the advent of
diesel-powered bulldozers, draglines, and pumps brought about a
revolution in open cut placer mining methods in Alaska, as well
as other states.
The introduction in the mid-1930s of efficient modern excavating
equipment and portable centrifugal pump units made it possible to
work many deposits that could not be mined earlier by the more
cumbersome machines. Improvements in gravel washing and recovery
systems were developed simultaneously.
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GOLD PLACER MINE SUBCATEGORY SECT - III
Readily movable steel sluiceboxes with hoppers and grizzlies,
mounted on steel trestles with skids, replaced awkward and less
desirable wooden structures. The steel sluiceplate, often called
the slick plate, was one of the most influential improvements; it
was responsible for the development of simple and flexible mining
techniques. The use of portable diesel-driven centrifugal pumps
allowed the recycle of wastewater to supplement limited water
supplies. Utilization of draglines, bulldozers and loaders in
combination facilitates the removal of both frozen and thawed
overburden as well as the handling of gravel and bedrock during
sluicing. Improved designs of processing equipment, using
revolving trommels and stacker conveyors mounted on crawler-type
tracks, were developed into successful washing and recovery
plants at several properties.
The choice of excavation equipment, the beneficiation system, and
arrangement of the plant is based essentially upon the size and
physical characteristics of the deposits as well as on the water
supply, the ultimate choice depending on the funds available for
initial capital investment and the personal preference of the
operator.
Mining Methods
Dredging Systems. Dredging systems are classified as hydraulic
or mechanical, depending on the method of digging, and both are
capable of high production. A floating dredge consists of a
supporting hull with a mining control system, excavating and
lifting mechanism, beneficiation circuits, and waste-disposal
systems. These are all designed to work as a unit to dig,
classify, beneficiate ores, and dispose of waste.
a. Hydraulic Dredging Systems. Whether the lifting force is
suction, suction with hydrojet assistance, or entirely hydrojet,
hydraulic dredging systems have been used much less frequently
than mechanical systems in large commercial gold placer mining.
Suction dredges have become quite popular with the small or
recreational gold placer miner.
However, in digging operations where mineral recovery is not the
objective, the hydraulic or suction dredge has greater capacity
per dollar of invested capital than any mechanical system because
the hydraulic system both excavates and transports. The
hydraulic dredge is superior when the dredged material must be
moved some distance to the point of processing.
Hydraulic digging is best suited to relatively small-size loose
material. It has the advantage over mechanical systems in such
ground when the material must be transported from the dredge by
either pipeline or barge. In easy digging, excavation by
hydraulic systems has reached depths of about 225 feet, but
excavation for mineral recovery to date has been much less, only
about one-third of that depth.
Even with efficiently designed units and powerful pumps, the size
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GOLD PLACER MINE SUBCATEGORY ^ECT - III
of the gold that can be captured by hydraulic dredging is
limited. The ability of a hydraulic system to pick up material
in large part depends upon intake and transport velocities that
must be increased relative to specific gravity and size of
particles. If the gold occurs as nuggets, especially large
nuggets, the velocity required for capturing the gold can cause
excessive abrasion in the entire system. In addition, higher
velocities require more horsepower. When the flake size of the
gold is very fine, higher velocities make gold recovery in the
sluice box very difficult. Undercurrent systems solve this
problem.
The digging power of hydraulic systems has been greatly increased
with underwater cutting heads. One disadvantage of a cutterhead
is that it must be designed with either right- or left-hand
cutting rotation, which results in less efficient digging when
the dredge is swung in one direction, especially in tough
formations. As digging becomes more difficult and the cutterhead
is swung across the face in the direction so that its blades are
cutting from the old face to the new, the cutterhead tries to
climb onto and ride the scarp. This produces considerable impact
stress through the power-delivery system and reduces the capacity
of the cutter.
The principal uses of large hydraulic dredges have been for non-
mining jobs such as in digging, deepening, reshaping, and
maintaining harbors, rivers, reservoirs, and canals; in building
dams and levees; and in landfill and reclamation projects.
Hydraulic systems in mining have been used to produce sand and
gravel, mine marine shell deposits for cement and aggregate,
reclaim mill tailings for additional mineral recovery, and to
mine deposits containing diamonds, tin, titanium minerals, and
monazite.
(b) Mechanical Dredging Systems. Digging systems on continuous
mechanical dredges can be a bucket-ladder, rotary-cutter, or
bucket-wheel excavator, each with advantages peculiar to specific
situations. The bucket-ladder or bucket-line dredge has been the
traditional gold placer mining tool, and is still the most
flexible method where dredging conditions vary. Gold placer
dredges, rated according to bucket size, have ranged from 1 1/2
to 20 cubic feet, although the larger equipment has been used in
non-mineral harbor work.
Excavation equipment consists of a chain of buckets, traveling
continuously around a truss or plate-girder ladder, that scoop up
a load as they are forced against the mining face while pivoting
around the lower tumbler and then dump as they pivot around the
upper tumbler. The ladder is raised or lowered as required by a
large hoisting winch through a system of cables and sheaves.
Before the development of the deep digging dredges, the maximum
angle of ladder when in its lowest digging position was usually
45° below the horizontal. During the last few years in Malaysia,
18-cubic-foot dredges digging from 130 to 158 feet below water
level have often been operating at angles of 55° and sometimes
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GOLD PLACER MINE SUBCATEGORY SECT - III
more. At its upper position, the ladder inclines about 15° below
the horizontal. Figure III-3 (p. 62) is a side view of the 18-
cubic-foot Yuba Manufacturing Division, Yuba Industries, Inc.,
No. 110 dredge that was designed to dig 85 feet below water
level.
Compared with any hydraulic system, the bucket-line dredge is
more efficient in capturing values that lie on bedrock or in
scooping up the material which sloughs or falls from the
underwater face. It is more efficient when digging in hard
formations, because its heavy ladder can be made to rest on the
buckets providing them with more ripping force. Bucket size and
speed can be varied with formation changes in the deposit
according to the volume of material that can be processed through
the gold-saving plant. Most bucket-line dredges used in placer
mining have compact gravity-system processing plants mounted on
the same hull as the excavating equipment. The waste stacking
unit, also mounted on the same hull, combines with other dredge
functions to make the dredge a complete and efficient mining
unit. The advantages of an integral waste distributing system
trailing behind the excavator become readily apparent when
considering that up to 10,000 cubic yards of oversize waste must
be disposed of each day on a large dredge. To assure a high
percentage of running time, dredge components must be designed
for long life and relatively easy and quick replacement of parts.
Dredging experience has shown that most parts need to be larger
and heavier than theoretical engineering designs indicate, and
the simpler their design, the lower their replacement and
installation costs.
The advantages of the bucket-line dredge as compared to the
hydraulic dredge are as follows. The bucket-line dredge:
o Lifts only payload material, whereas a hydraulic
system expends considerable energy lifting water
o Loses fewer fines which contain most of the fine
or small fraction gold
o Digs more compact material
o Cleans bedrock more efficiently
o Allows more positive control of the mining pattern
o Has a simpler waste disposal system compared to a
hydraulic system with an onshore treatment plant
o Requires less horsepower
The disadvantages of mechanical systems compared to hydraulic
systems include: (1) they require more initial capital
investment per unit of capacity; and (2) they require a secondary
pumping system if the excavated materials must be transferred to
a beneficiation plant which is distant from the dredge.
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Open Cut Methods. Many perennially frozen and buried gold placer
deposits in Alaska cannot be mined profitably without modern
earthmoving equipment. In general, this equipment is used to
mine deposits where the size, depth, and characteristics of the
deposit and the topography and condition of the underlying
bedrock prohibit dredging. Bulldozers, draglines, loaders and
scrapers are used to mine some deposits by open-cut methods. As
indicated earlier, the choice of excavation equipment, recovery
system and the mining method is based on the size, degree of
consolidation, the physical characteristics of the deposits, and
the water supply.
a. Bulldozers. Whether used exclusively or in combination with
other earthmoving equipment, bulldozers are employed in all
phases of open-cut gold placer mining. They are used for
stripping muck and barren gravel overburden, pushing pay dirt to
sluiceboxes, stacking tailings, and constructing ditches, ponds,
and roads. Rippers attached to bulldozers may be used to
excavate bedrock where gold has penetrated fractures and joints
or frozen ground. According to a Canadian study, bulldozers are
utilized at about 80 percent of Yukon Territory placer mines.
The tractor sizes range from 100 to 460 horsepower. Straight
blades normally are preferred due to their versatility. Scrapers
have limited utility but may be used in special circumstances.
b. Draglines. Although draglines are less mobile than
bulldozers, they can move materials at a lower cost per unit.
Because of their high initial cost when new, most of these units
are used and rebuilt. Draglines are used essentially for the
same purposes as bulldozers, plus a dragline can move material
from underwater conditions. The 1 1/2 cu yd bucket capacity is
preferred although the 3/4-, 1-, and 2 cu yd sizes are not
uncommon.
Draglines are not used extensively in Alaska or in Canada's Yukon
gold placer industry. Experienced operators are very difficult
to find. Draglines have been used effectively for cleaning
settling ponds, feeding hoppers for trommels, and stacking
tailings.
c. Loaders. Front-end loaders are the second most common
equipment type and are used extensively at gold placer mines
(111-21). Although they are usually mounted on rubber tired
wheels, they also can be track-mounted. Front-end loaders have
the following advantages:
o The economic load and carry distance may be as far as
700 feet.
o Classification equipment such as grizzlies can be
more easily utilized than with bulldozers.
o Wheel loaders have a greater flexibility in moving
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GOLD PLACER MINE SUBCATEGORY SECT - III
material (e.g., out of pits, around tailings piles).
o Skilled operators are readily available or can be
easily trained.
Hydraulic Methods. Hydraulic mining, also known as
hydraulicking, utilizes water under pressure which is forced
through nozzles to break up and transport the gold placer ore to
the recovery unit (usually a sluice box). The adjustable nozzles
are also known as monitors or giants. They are also used to
break up or wash away overburden. If done in stages, frozen muck
can be thawed effectively. A pump, or occasionally, gravity is
used to produce the required pressure. Pure hydraulic mining is
not currently being used in this industry.
Monitors or giants can swing in a full circle and through a wide
vertical angle. Modern design utilizes the resultant forces to
counterbalance the units for ease of operation.
Hydraulic mining (sometimes called hydraulicking) was used as an
effective method of mining in water rich geographic areas.
However, with the advent of modern earthmoving equipment and
restrictions on the availability and pollution of water, the use
of hydraulic mining has declined. Today there are no known
wastewater discharges from hydraulic gold placer mines in the
U.S. It appears quite unlikely that hydraulic mining will be
revived as a common mining method because of the efficiency and
low cost of mechanical earthmoving.
There appear to be no situations in which the mechanical
earthmoving systems cannot be used effectively to remove ore from
the mine. Hence, in any field application where hydraulic mining
methods were being considered, the owner would need to evaluate
the economic benefits of the hydraulic mining against the now
standard mechanical mining approach.
Because all mines can use the methods costed by the Agency, this
rule applies to all mine activities, including hydraulicing.
Other Associated Activities. There are many activities which
occur at mine sites which are either directly or indirectly
related to operation of a gold placer mine. The remaining
portions of this subsection address these activities.
a. Prospecting and Evaluation. Sampling methods include various
types of drilling (mainly churn and core drilling) and excavating
(trenches, pits, and shafts). Other than possible erosion of
disturbed soils, sampling methods generally involve only minor
effects on water quality. However, processing of samples can in
some circumstances produce significant quantities of a sediment-
laden effluent.
Processing methods and the resultant amount of sediment produced
depend on the size of sample processed. Small samples, from a
few pounds up to a few tons, can be processed by hand with a
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GOLD PLACER MINE SUBCATEGORY SECT - III
rocker and a pan. A steady flow of water 4 to 5 gallons per
minute is sufficient to operate a small (1x4 foot) rocker.
With reuse, net consumption of water may be as low as 50 to 100
gallons per cubic yard. Figure III-4 illustrates a basic design
for a prospector's rocker.
Bulk samples of up to several cubic yards can be excavated by
hand or with a tractor-mounted backhoe. These samples are
processed in a small sampling sluice 6 inches to 24 inches in
width and 6 to 20 feet in length. When working by hand, two
people can process and evaluate one to three cubic yards per day.
When working with a backhoe and excavating relatively closely
spaced test pits, about 100 cubic yards per day can be processed.
Water requirements vary from a minimum of 50 gallons per minute
for a 6-inch sluice to several hundred gallons per minute for a
24-inch sluice.
b. Stripping Vegetation. Mining areas are stripped for the
following purposes:
o To remove the insulating layer to allow thawing of
permafrost
o To remove organic material which would interfere with
processing
o To expose the overburden and minable ore
Mechanical stripping of vegetation can expose erodible soils and,
therefore, can significantly degrade water quality. Where
stripped soils are on a slope, gully erosion can result.
Hydraulic removal of vegetation is usually a part of hydraulic
thawing and stripping overburden and can significantly degrade
water quality.
c. Thawing Permafrost. There are basically four methods of
thawing frozen ground:
1. Mechanical removal of the insulating layer of surface
vegetation and overburden, and solar thawing
2. Hydraulic removal (using monitors) of the surface
vegetation and combined cold surface water and solar
thawing
3. Hot or cold water thawing of the frozen ground by
driving or jetting closely spaced well points and
injecting water into the frozen ground that surrounds
the well point (steam has also been used in this
manner)
4. Diverting surface water over or against frozen ground
(ground sluicing)
d. Stripping Overburden. In many districts, gold placer gravels
35
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GOLD PLACER MINE SUBCATEGORY SECT - III
are overlain by silty, organic-rich deposits of barren, frozen
organic laden material which must be removed prior to mining.
Geologically, the material is thought to be primarily colluvium
(material transported by unconcentrated surface runoff) but may
also contain loess (wind-blown deposits). Some areas are
particularly noted for high organic and high ice contents. Other
types of overburden are barren alluvial gravels, broken slide
rock, or glacial deposits. There are two primary methods of
stripping used—mechanical and hydraulic. Each will be discussed
below.
Mechanical stripping refers to the use of excavating equipment
for removal of overburden. Miners who mechanically strip
overburden generally utilize the same equipment for mining. Few
have specialized stripping equipment, e.g., shovels, scrapers,
draglines, bucket wheel excavators. Mechanical stripping can be
constrained by permafrost, severe space limitations for
overburden dumps, difficult workability of weak thawed silts, and
thick overburden deposits.
If the hydraulicking is done in stages, frozen muck can be thawed
effectively and stripped. Pumps and occasionally gravity are
used to produce the required water pressure. The major
constraint to the application of hydraulicking, other than
environmental considerations, is probably lack of an adequate
water supply. Construction of storage reservoirs and lengthy
ditches and diversions are frequently necessary. Although the
water quality effects stem primarily from the hydraulicking
itself, unstable diversions, ditches, and reservoir dikes washed
out by floods also contribute to the sediment load. Some
recirculation of thaw water is being done in Alaska.
Processing Methods
There probably is no such thing as a single "typical" mine due to
the wide variation in processing equipment used, overburden
characteristics and methods of removal, type of deposit, size
range of the gold recovered, topography, etc. Therefore, the
actual equipment and mining methods used will probably be some
combination of mining methods and processing technology discussed
here.
A large percentage of the present gold placer mining operations
use some type of sluice box to perform the primary processing
function, beneficiation; but a few jig plants are used.
Many operations make use of feed classification. Some of the
most prominent equipment is discussed under various headings
below.
Classification. Classification (screening) involves the physical
separation of large rocks and boulders from smaller materials
such as gravel, sand, and silt or clay. The object of
classification is to prevent the processing of larger-sized
material which is unlikely to contain gold values. Gold placer
36
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GOLD PLACER MINE SUBCATEGORY ''SECT - III
miners who were interviewed as part of a previous study reported
that this practice improves the efficiency of gold recovery. The
reason was attributed to the fact that a lower flow rate of water
may be required compared to the high flow rate necessary to wash
large rocks through the sluice. The low flow rate enhances the
settling and entrapment of smaller-sized gold particles in the
sluice. Use of increased rates of flow when classification is
not practiced is thought to cause some of the finer gold
particles to be washed through the sluice and be lost. Operating
conditions also are enhanced by preventing the entry of large
rocks and boulders which must be removed manually when lodged in
the box.
a. Grizzlies. A grizzly is a large screen of a fixed opening
size which serves to reject oversize material and prevent it from
entering the sluice. This oversize material is then discarded.
Typically, a grizzly would be inclined to facilitate removal of
the rejected material. Grizzlies operated wet usually produce
the best results. Figure III-5 (p. 64) is a schematic of a
grizzly.
The advantage of a grizzly is that it prevents processing of
coarse material which is unlikely to contain gold, and it allows
a shallower depth of flow over the sluice riffles which enhances
recovery of fine gold. This can result in a water use reduction.
b. Trommels. A trommel is a wet-washed, revolving screen which
offers the following advantages:
o It washes the gravel clean and helps in disintegrating
gold-bearing clayey material by impact with oversize
material and strong jets of water
o It screens and distributes slimes, sand, and fine
gravel (usually less than 1/2 inch) to the processing
section and discards the oversize material
Taggert reported that plants equipped for removal of oversize
material with subsequent treatment in sluices are capable of
processing 60 to 67 percent more ore per unit area of a sluice.
Figure III-6 illustrates a trammel.
c. Fixed Punchplate Screen-High Pressure Wash (Ross Box). The
Ross Box is essentially a punchplate with hole sizes generally
1/2 to 3/4 inch in diameter. A dump box receives the gold placer
ore, while a header with several nozzles delivers wash water into
the dump box in a direction opposite to the flow of the ore.
This turbulent washing action washes undersize material through
the punchplate where it is diverted to outside undercurrents
fitted with riffle sections. These side channel sluices handle
the material smaller than 3/4 inch. Oversize material is washed
down the center channel which is fitted with riffles to collect
coarser gold. Water flow is controlled to each of the sluice
areas.
37
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GOLD PLACER MINE SUBCATEGORY SECT - III
d. Vibrating Screens. A vibrating screen is a screen which uses
vibration to improve the rate at which classification occurs.
Generally, 1/2 to 3/4 inch screens are used with the oversize
material rejected to a chute or tails stacker conveyor belt
(Figure III-7, p. 66). These screens usually are loaded by a
front-end loader, dragline, or a backhoe, but in some cases they
are loaded via conveyer belts. In some configurations, several
size screens are stacked and different size classifications are
sluiced independently. Wet screening normally is used to break
up clay and loosely bound particles.
Sluices. A sluice is a long, sloped trough into which water is
directed to effect separation of gold from ore (Figurre III-8, p.
67). The ore slurry flows down the sluice and the gold, due to
its relatively high density, is trapped in riffles along the
sluice. Other heavy minerals present in the ore are also trapped
in these riffles. These other minerals are generically called
"black sands" and are separated from the gold during final clean-
up, i.e., in small sluices, vibrating tables, gold wheels or
amalgamation.
Sluice boxes are usually constructed of steel. Typically, a
sluice is 6 to 12 meters (20 to 40 feet) long, and 60 to 120 cm
(24 to 48 inches) wide. Longer sluices are used where the ore is
not broken up prior to sluicing. Shorter and narrower sluices
are used in prospecting and during clean-up operations. Water
depths in sluices may vary from 3.8 cm to 15.2 cm (1.5 inches to
6 inches). The slope of the sluice boxes ranges from 8.3 cm to
16.6 cm vertical per meter horizontal (1 to 2 inches per foot).
The grade of sluice boxes can be varied depending upon the ore.
In general, the recovery of fine gold requires shallower and
wider sluices. The majority of the gold is recovered in the
first several feet of riffles. The following discussion describes
various types of riffles used in sluices. Figure -111-9
illustrates some of the riffles described.
a. Hungarian Riffles. The Hungarian riffle design is widely
used in placer mining. Hungarian riffles are essentially angle
irons mounted transversely in the sluice box. The riffles are
spaced 3.8 to 7.6 cm (1.5 to 3 inches) apart. The size and
spacing of the riffles are designed to maximize gold capture and
to minimize packing of the riffles with non-gold bearing
particles. These riffles are sometimes custom-modified with
notches and holes to improve gold recovery. A coarse, fibrous
matting such as a carpet (e.g., AstroTurf) or coconut husks may
be placed under the riffles to capture and retain the gold for
further processing. Sections of riffles can be removed to
withdraw the carpet.
b. Expanded Metal. Expanded metal of various sizes may be used
as the riffle in sluices and is gaining widespread acceptance in
the industry. A number of tests have shown the direction of
placement of the expanded metal does not affect gold recovery.
Expanded metal appears to perform very well in recovery of small
38
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GOLD PLACER MINE SUBCATEGORY ':i' SECT - III
particle sized gold.
c. Horizontal Pole Riffles. Wooden poles placed perpendicular
to the flow have been used to create riffles at placer mines.
This type of riffle has been used in small-scale, remotely
located operations because the riffle can be made with locally
available materials. Wooden poles are not as durable as their
steel counterparts, and their use has largely been discontinued.
d. Longitudinal Pole Riffles. Wooden poles, usually spruce, are
placed parallel to the direction of flow through the sluice. The
spacing between these pole riffles varies from 3.8 cm to 7.6 cm
(1.5 inches to 3 inches). Similar to horizontal pole riffles,
longitudinal pole riffles are not believed to be in widespread
use.
e. Other Riffle Types. Wooden blocks, rocks, rubber and plastic
strips, railroad rails, heavy wire screen, and cocoa mats have
been used at various times as riffles in gold placer mining.
These riffle designs are not in common use today.
Clean-Up Methods. Many accessory heavy minerals found in the
gold placer ore are also concentrated by the methods discussed in
this section. Therefore, it is essential that the concentrate
collected from the sluice is separated into gold values and the
unwanted accessory heavy minerals. The following discussion
presents methods in use today.
a. Jigs. In general, the concentrate is fed as a slurry to a
chamber in which agitation is provided by a pulsating plunger or
other such mechanism. The feed separates into layers by density
within the jig with the lighter gangue being drawn off at the top
with the water overflow, and the denser mineral (in this case
gold) drawn off on a screen on the bottom. Several jigs may be
used in series to achieve acceptable recovery and high
concentrate grade. In addition to clean-up of concentrate from
sluices, large jigs are also used as the primary beneficiation
process to recover gold from ore in lieu of sluices. Large
dredges often use a number of jigs in series to recover gold from
sized or screened ore, and several open cut mines are using jigs
in the primary recovery or beneficiation of sized ore.
b. Tables. Shaking tables of a wide variety of designs have
found widespread use as an effective means of achieving gravity
separation of finer ore particles 0.08 mm (0.003 inch) in
diameter (Figure 111-10, p. 69). Fundamentally, they are tables
over which flow ore particles suspended in water. A series of
ridges or riffles perpendicular to the water flow trap heavy
particles while lighter ones are suspended and flow over the
obstacles with the water stream. The heavy particles move along
the ridges to the edge of the table and are collected as
concentrates (heads) while the light material which follows the
water flow is generally a waste stream (tails). Between these
streams may be some material (middlings) which has been partially
diverted by the riffles. These are often collected separately and
39
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GOLD PLACER MINE SUBCATEGORY SECT - III
returned to the table feed. Reprocessing of heads or middlings,
or both, and multiple-stage tabling are common.
c. Spirals. Spiral separators, i.e., Reichert and Humphrey
concentrators, provide an efficient means of gravity separation
for large volumes of material between 0.1 mm and 2 mm (0.004 to
0.08 in) in diameter. Spirals have been widely applied,
particularly in the processing of heavy sands for titanium
minerals. Spirals consist of a helical conduit about a vertical
axis. The ore, or in this case concentrate, is fed with water to
the conduit at the top and flows down the spiral under gravity.
The heavy minerals concentrate along the inner edge of the spiral
from which they may be withdrawn through a series of ports. Wash-
water may also be added through ports along the inner edge to
improve the separation efficiency. In large plants, several to
hundreds of spirals may be run in parallel, although in gold
placer mining operations, a small number is usually sufficient.
Several open cut mines have been reported as using spirals in the
primary recovery of gold from gold placer deposits.
d. Gold Wheels. A gold wheel is a gravity separation device
used during cleanup to separate the gold from the "black sand."
The wheel may vary between 30 cm to 112 cm (12 inches to 44
inches) in diameter and may rotate at a rate up to 42 rpm. The
rotational speed on most units can be controlled by the operator.
Inside the wheel, there are 0.64 cm (1/4 inch) to 1.27 cm (1/2
inch) channels arranged in a helix in the plane of the table.
The wheel is tilted with only small angles being capable of
separating materials of relatively different specific gravities.
Conversely, steeper angles separate materials with little
difference in specific gravity. Water is sprayed onto the wheel
from several ports at a rate of 10 gpm or less. This water can
be recirculated if needed. Gold concentrate is placed along the
perimeter of the wheel, and the gold works its way to the center
where it is withdrawn. The lighter material flows over the
perimeter lip of the wheel and is captured and reworked to
recover any remaining gold. Surfactants (e.g., liquid soap) are
sometimes added to the water to aid in recovery of the gold by
reducing surface tension of the water.
e. Small Sluices. Small sluices are simply scaled-down versions
of the sluices described above. The advantage of using a small
sluice is that only small amounts of concentrate are processed at
a rate conducive to maximize gold separation from other heavy
minerals in the concentrate. Several passes or several small
sluices may be used in series to ensure that no gold is lost.
Only small amounts of water are required because the size range
of the concentrate is relatively restricted.
f. Magnetic Methods. A large proportion of the heavy mineral
concentrate from which the gold is extracted may contain minerals
(primarily magnetite) which exhibit magnetic properties. The
basic process involves the transport of the concentrate through a
region of high magnetic field gradient. In large-scale
applications of this method, an electromagnet may be used, but at
40
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GOLD PLACER MINE SUBCATEGORY SECT - III
small operations, a hand magnet is often employed. This method
is often applied along with other methods to effect the best
separation of the gold from other heavy minerals in the
concentrate.
g. Chemical Methods. There are two chemical methods in use in
the gold industry today which may be used in association with
gold placer mining: amalgamation and cyanidation. Amalgamation
was used on a wider scale in the past but is not commonly used
today except for cleanup of a concentrate. Cyanidation is not
known to be used for extraction of gold from a concentrate but
could be used to rework tailings from gold placer operations by
heap leaching. Wastewater from such heap leach operations is
regulated under 40 CFR Part 440.100 (Subpart J).
Amalgamation. Amalgamation is the process by which mercury
is alloyed, generally to gold or silver, to produce an amalgam.
The amalgam is placed in a small retort to recover the mercury
for reuse and to reclaim the gold.
Cyanidation. This process is not widely used in Alaska for
primary extraction of placer gold but is being used extensively
in the lower 48 states to recover gold from low grade ores by
heap or vat leaching. It has been economically applied in the
recovery of gold from tailings left by hard rock gold mills and
from low grade deposits. The cyanidation process involves the
extraction of gold or silver from fine-grained or crushed ores,
tailings, low grade mine rock, etc., by the use of dilute
potassium or sodium cyanide in strong alkaline solutions. After
dissolution of the gold, the gold is absorbed onto activated
carbon or precipitated with metallic zinc usually in dust form.
The gold may be recovered by filtering with the filtrate being
returned to the leaching solution. Some interest and use of this
process is currently occurring in Alaska.
Small-Scale Methods. The methods described in this sub-section
are primarily utilized by recreational or assessment operations.
The various small-scale methods are similar to regular methods in
that they employ principles based upon gravity separation. Small-
scale methods are responsible for only a very small percentage of
all gold placer mine production. A few representative methods
are described below.
a. Gold Pan and Batea. Panning currently is mostly used for
prospecting and recovering valuable material from concentrates.
The pan is a circular metal dish that varies in diameter from 6
to 18 inches with 16-inch pans being quite common. The pans
often are 2 to 3 inches deep and have 30- to 40-degree sloping
sides. The pan with the mineral-bearing gravel or sand is
immersed in water, shaken to cause the heavy material to settle
toward the bottom of the pan, and then the light material is
washed away by swirling and overflowing water. This is repeated
until only the heavy concentrates remain. In some countries, a
conical-shaped wood pan, called a batea, is used. This unit has a
12- to 30-inch diameter with a 150-degree apex angle. It is
41
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GOLD PLACER MINE SUBCATEGORY SECT - III
often used to recover valuable metals from river channels and
bars.
b. Long Tom. A long torn is essentially a small sluice box with
various combinations of riffles, matting, expanded metal screens,
and occasionally, in the old days, amalgamating plates. A long
torn usually has a greater capacity than a rocker box and does not
require the labor of rocking. It consists of a short receiving
launder, an open washing box six to twelve feet long with the
lower end a perforated plate or screen set at an angle, and a
short sluice with riffles. The component boxes are usually set
on slopes ranging from 1:12 to 1.5:12. A long torn is illustrated
in Figure III-ll (p. 70).
c. Rocker Box. Rocker boxes are used to sample placer deposits
or to mine high-grade areas when installation of larger equipment
is not justified. The box is constructed of wood and is
essentially a short, sloped box chute over which the pay dirt and
water flow as the box is rocked back and forth. A screen is
mounted at the head of the box to reject oversize material. It
may be fitted with riffles and usually has a canvas or carpeted
bottom.
d. Dip Box. The dip box is useful where water is scarce and
where an ordinary sluice cannot be used because of the terrain.
It is portable and has about the same capacity as the rocker box.
The box is about 2 to 4 meters (6 to 12 feet) long, and 0.3 meter
(12 inches) wide with 0.15-meter (6-in) sides. The bottom of the
box is covered with burlap, canvas, or thin carpet to catch the
gold. Over this is laid a 0.3 by 1.0 meter (1 by 3 ft) strip of
heavy wire screen of about 0.6 mm (1/4-in) mesh. Material is
dumped or shoveled into the upper end and washed by pouring water
over it from a dipper, bucket, hose, or pipe until it passes
through the box. Large rocks are removed by hand and riffles may
be added to the lower section of the box to improve recovery
e. Suction Dredge. Small suction dredges are being used
successfully for prospecting or for recreational or small (part-
time) ventures. The pump sizes most commonly found in use vary
from one to four inches. The pump is usually floated immediately
above the area being worked. There are two basic assemblies that
are commonly used: (1) the gold-saving device is in a box next
to the suction pipe and carried under water, and (2) the other
system uses two hoses in the nozzle—one transporting water to
the head and the other transporting material to the surface of a
gold-saving device, i.e., usually a small sluice box with tails
being deposited back into the stream.
Industry Practice
Until recently, little detailed information was available
concerning gold placer mining operations in Alaska and other
states. However, during the last few years, EPA has embarked upon
efforts described elsewhere in this document to identify specific
operations and obtain information concerning gold placer mining
42
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GOLD PLACER MINE SUBCATEGORY INSECT - III
practices, water use, wastewater treatment technologies employed,
flow, etc. This information has been obtained by site and
sampling visits, review of Tri-agency report forms from Alaska,
visits to various state pollution control agencies, from the gold
placer miners, and from other sources.
Some characteristics of the operations emerge from examination of
the information gathered which serve to place gold placer mining
in perspective. Most operations are located in remote areas far
from supplies and the amenities of civilization or a developed
infrastructure. Electric power is usually generated on-site by
the operators, with fuel delivered periodically to the site over
land routes or by air. Many operations are family-owned and
operated, and over 95 percent probably employ seven or fewer
persons. Most of the operations are seasonal, generally
averaging between 100 to 115 operating days per year. The size
of the operations ranges from processing less than 20 cu yds per
day to as much as 12,000 cu yds per day. Although gold is very
valuable, the amount contained in the gold placer ore is very low
with even the richest deposits containing only a few grams of
gold per cubic yard; the gold gives a value of a few cents to
over eight dollars per cubic yard of ore and more depending upon
the current international price for gold.
Wastewater treatment technology employed in the gold placer mine
subcategory generally ranges from treatment with settling ponds
and discharge to partial recycle or recirculation of the total
process water flow. The majority of gold placer mines provide
simple settling, and a few employ tailings filtration for solids
removal. No advanced treatment technology methods are known to
be employed in Alaskan operations today, although some operators
have tried or continue to try flocculant addition. Recycle or
recirculation of process water is practiced at many mines in
Alaska, primarily to conserve water. The percentage of process
water recycled at a single mine may vary from 0 to 100 percent
during a single seasori, subject to changes in precipitation and
mining location. Data obtained by the Agency through the Alaska
Department of Environmental Conservation shows that nearly 30
percent of the miners indicated, at permit application time, an
intention to recycle 100 percent of their process water. An
additional 30 percent intended to recycle some portion of their
process water. No field confirmation of the information
contained in the permit applications was conducted.
The remainder of this section consists of Tables III-4, III-5,
III-6, III-7, and III-8 (pp. 51-56), which are profiles of the
Alaska, California, Colorado, Idaho, and Montana gold placer
mines surveyed and for which some data were available. Table
III-9 (p. 59) contains profiles of Alaskan gold placer mines
visited in 1986 by EPA collecting data and conducting
treatability testing. The objective of Tables III-4 to III-9 is
to provide information and data gathered at gold placer mining
operations in this subcategory. Discussion of an operation or
presentation of data and information does not imply that the gold
placer mining operation is exemplary, typical, or represents good
43
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GOLD PLACER MINE SUBCATEGORY SECT - III
wastewater treatment. This list does not include all existing
gold placer mines, particularly with respect to the hundreds of
recreational or assessment operations which are believed to
exist. Rather, the tables that follow present a summary of data
and information that EPA has obtained which serve to illustrate
the range of operations in the United States today. Although
limited production has been reported from other states, the
Agency has no precise data on the number of gold placer mines or
production in other states.
44
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GOLD PLACER MINE SUBCATEGORY SECT - III
Table III-1.
Mineral Activity in Alaska by Mining Camp
as of 1982
Map
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
Camp
(b)
Gold
Production Discovery Map
(tr. oz.) Date No.
Nome 4,348,000
Solonon 251,000
Bluff 90,200
Council 588,000
Kdyuk 52,000
Fairhaven (Candle) 179,000
Fairhaven (Inmachuk) 277,000
Kougarok 150,400
Port Clarence 28,000
Noatak 39,000
Kbbuk (Squirrel River) 7,000
Kobuk (Shungnak) 15,000
Kdyukuk (Hughes) ' 211,000
Koyukuk (Nolan) 290,000
Chandalar 35,708
Marshall (Anvik) 120,000
Qoodnews Bay 29,700
Kuskokwim (Aniak) 230,600
Kuskokwim (Georgetown) 14,500
Ruskokwim (McKinley) 173,500
Iditarod 1,364,404
Innoko 400,000
Tolstoi 87,200
111 anna (Lake Clark) 1,500
Skwentna (included in
Yentna production)
Yentna (Cache Creek)
Kantishna
Ruby
Gold Hill
Hot Springs
Rampart
Tblovana
Fairbanks
Chena (included in
Fairbanks production)
115,200
65,000
420,000
1,200
450,000
105,000
387,000
7,940,000
1898
1899
1899
1897
1899
1901
1900
1900
1898
1898
1909
1898
1910
1893
1905
1913
1900
1901
1909
1910
1908
1906
1902
1905
1903
1907
1907
1898
1882
1914
1902
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
Camp
(b)
Gold
Production
(tr. oz.)
Discovery
Date
Bonnifield 50,000 1903
Richardson 103,000 1905
Circle 800,000 1983
Woodchopper-Coal Creek
(included in Circle production)
Seventymile (included in Fortymile
production)
Eagle 45,000 1895
Fortymile 417,000 1886
Valdez Creek 44,000 1904
Delta 2,500
Chistochina-Chisna 177,000 1898
Nabesna 93,500 1899
Chisana 50,000 1910
Nizina 143,500 1901
Nelchina 2,900 1912
Girdwood 125,000 1895
Hope (included in Girdwood)
production)
Kbdiak 4,800
Yakataga 15,709
Yakutat 2,500
Lituya Bay 1,200
Porcupine 61,000
Juneau(GDld Belt) 7,107,000
1895
1898
1867
1867
1898
1880
1898
1869
Ketchikan-Hyder 62,000
Sundum 15,000
Glacier Bay 11,000
Chichagof 770,000 1871
Willow Creek 652,052 1897
Prince William Sd. 137,900 1894
Uhga Island 107,900 1891
(a)-Compiled from U.S. Geological Survey publications, U.S. Bureau of Mines records,
Alaska Division of Geological and Geophysical Survey records and publications,
Mineral Industry Research Laboratory research projects, and other sources.
(b)-Camp names are those that appear in official recording-district records. Many
are also known by other names, some of which are shown in parentheses.
Source: Ref. 31
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GOLD PLACER MINE SUBCATEGORY SECT - III
Table III-2.
Reported Refined Gold Production, Number of
Operators, and Industry Employment in Alaska
By Region and Mining District, 1985-86.
Region and
mining district
Northern
Chandalar
Shungnak
Koyukuk-Nolan
Western
Nome
Kougarok
Koyukuk-Hughes
Port Clarence
Fairhaven
Ruby
Solomon
Koyuk
Council
Eastern Interior
Circle
Livengood-Tolovana
Fairbanks
Fortymile
Manley-Eureka
Richardson
Bonnifield
Kantishna
Rampart
Southcentral
Cache Creek
Nizina
Chistochina
Valdez Creek
Kenai Peninsula
Nelchina
Southwestern
Innoko-Tolstoi
Iditarod-George River
Moore Creek
Nyac
Crooked Creek
Lake Clark-Mulchatna
Southeastern and
Alaska Peninsula
TOTAL
Mechanized
units8
1985
Production
(troy oz)
Number of
employees
Mechanized
units8
1986
Production
(troy oz)
Number of
employees
18
40
14,400
40,000
70
340
42
4,500
53,000
15
363
135
66,000
740
83
45,350
375
38
52,500
263
30
39,000
268
32
17,000
125
33
18,000
128
100
150
266
190,000
1,545
195
160,000
1,155
*Mechanized-placer and small lode operations are Included; small 'recreational-assessment' projects »uch as panning, long-
torn sluicing, «uction-dredging, and pick-and-shovel prospecting are not included. We estimate that 95 operations employed 275 people in
1985 and 80 operations employed 230 people in 1986.
46
-------
GOLD PLACER MINE SUBCATEGORY SECT - III
Table III-3. Variations in Yearly Gold Prices
Year Tr.Oz.
p Preliminary
1935 - 1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987p
$ 35.00
39.26
41.51
36.39
41.25
58.60
97.81
159.74
169.49
125.32
148.31
193.55
307.50
612.56
459.94
375.91
424.00
360.66
317.66
377.00
446.41
Source: U.S. Bureau of Mines, U.S. Geological Survey, and U.S.
Treasury Department
47
-------
Table III-4. Profile of Alaskan Gold Placer Operations
00
MINE
CODE
4109
4110
4126
4127
4132
4133
4134
4138
4169
4170
4171
4172
4173
4174
4175
4176
4178
4180
LOCATION
(DISTRICT)
50
50
31
31
5
5
5
4
50
50
50
47
47
47
47
47
47
47
OPER. DAYS
PER YEAR
100
60
245
245
Unk.
180
210
80
189
132
112
122
138
122
102
120
90
131
CLASSIFICATION
METHOD
USED
Screens
Trommel and
hyd. prewash
Trommel
Trommel
None
Unk.
None
Vibrating Screens
None
Grizzly
Trommel
Trommel
None
Grizzly
None
Grizzly
Grizzly
Vibrating Screens
VOLUME
SLUICED
ICU. YD/DAY)
1,350
750
6,800
Unk.
90
1,000
2,000
90
900
1.000
1.000
2,750
3,500
2,500
1,000
1,250
1,500
1,900
MINING
METHOD
Open Cut
Open Cut
and Hyd.
Mech. Drdg.
Mech. Drdg.
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
WASTEWATER
TREATMENT
TECHNOLOGIES
USED
Settling Ponds (2)
Settling Ponds (5)
Settling Ponds (5)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (3)
Settling PondfftO)
Settling Ponds (5)
Settling Pond (1)
Settling Pond (1)
Settling Ponds (3)
Settling Ponds (3)
Settling Ponds (2)
None
Settling Pond (1)
Settling Ponds (3)
Settling Pond (1)
RECYCLE (%)
0
75
100
>0
0
0
0
30
98
0
0
-17
>0
50
0
0
0
0
DAILY
DISCHARGE
VOLUME
(GPM)
3,000
1,000
0
3,140
1.350
675
23,000
1.050
224
2,400
1,800
6,000
3.500
1,260
8,000
3,500
2.500
2.500
o
o
f
o
o
M
'Z.
M
cn
a
m
o
M
O
8
K
cn
w
n
-------
Table III-4. Profile of Alaskan Gold Placer Operations (Continued)
MINE
CODE
4183
4185
4189
4190
4193
4197
4211
4213
4216
4217
4219
4222
4223
4224
4225
4226
4227
LOCATION
(DISTRICT)
47
47
50
51
51
59
14
50
12
12
53
31
47
51
47
50
51
OPER. DAYS
PER YEAR
Unk.
107
122
104
80
102
152
120
132
154
162
150
120
65
120
162
183
CLASSIFICATION
METHOD
USED
Unk.
Trommel
Trommel
None
Derocker
Screens
Trommel
None
Vibrating Screen
Vibrating Screen
None
Trommel
Grizzly
None
None
Jig
Non6
VOLUME
SLUICED
(CU. YD/DAY)
Unk.
800
950
2,500
900
200
4.000
250
300
350
1,000
700
1,000
300
900
1,500
Unk.
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Drdg.
Open Cut
Open Cut
Open Cut
Open Cut
Mech. Drdg.
Open Cut &
Suet. Drdg.
Open Cut
Open Cut
Open Cut
Hyd.&
Open Cut
WASTE WATER
TREATMENT
TECHNOLOGIES"
USED
UtfkM*
nfOflQ
Settling Pondi (2)
Settling Ponds (4)"
Settling Ponds (2)
Settling Pond (1)
Settling Pond (1)
Settling Pond with
Tailings Filtration
Settling Ponds (2)
Settling Ponds (3)
Settling Ponds (3)
Settling Ponds (4)
Settling Pond (1)
Settling Pond (1)
Settling Ponds (2)
Settling Ponds (4)
Settling Ponds (2)
Settling Pond (1)
RECYCLE (%)
>0
<50
0
50
50
75
>0
97
0
0
93
45
0
0
50
50
0
DAILY
DISCHARGE
VOLUME
(GPM)
1,400
3,200
1,500
1,800
700
450
3,600
60
800
2.000
450
1,800
2,500
2,000
3.000
2.200
4,000
<£>
-------
Table III-4. Profile of Alaskan Gold Placer Operations (Continued)
MINE
CODE
4229
4230
4231
4232
4233
4234
4235
4236
4239
4240
4241
4242
4243
4244
4245
4247
LOCATION
(DISTRICT)*1'
47
58
50
47
5
58
47
58
14
47
47
47
51
51
51
5
OPER. DAYS
PER YEAR
135
120
168
108
162
90
107
213
Unk.
122
117
89
107
122
88
150
CLASSIFICATION
METHOD
USED<2)
Unk.
Unk.
Trommel
FPS*
Grizzly
Grizzly
Norn
Trommel
None
Vibrating Screen
& Grizzly
Grizzly
None
Unk.
None
Unk.
FPS
VOLUME
SLUICED
(CU. YD/DAY)
1.400
300
500
1,020
99
500
1,000
2,000
Unk.
500
850
800
26
615
400
500
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Hyd.
(Booming)
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Hyd. and
Open Cut
Open Cut
Open Cut
Open Cut
WASTEWATER
TREATMENT
TECHNOLOGIES
USED
Settling Ponds (5)
Settling Pond (1)
Settling Pond (1)
Settling Pondi (2)
Settling Ponds (3)
None
Settling Pond (1)
Settling Pond (1)
Settling Ponds (2)
None
Settling Pond (1)
Settling Ponds (4)
Settling Ponds (2)
Settling Pondi (2)
Settling Ponds (2)
Settling Pond (1)
RECYCLE (%)
0
0
90
50
0
0
0
0
>0
0
0
0
0
0
0
0
DAILY
DISCHARGE
VOLUME
(GPM)
5300
6,700
800
2,000
417
1,500
3,000
580
450
2.000
2,300
3,500
1,500
3,000
2,500
2.000
Ul
o
* FPS • Fixed punch-plate screen.
-------
Table III-5. Profile of California Gold Placer Mines
MINE
CODE
4260
COUNTY
Yuba
OPER. DAYS
PER YEAR
364
CLASS.
METHOD
Trommel
Jigs
VOLUME
PROCESSED
(CU. YD/DAY)
12.360
MINING
METHOD
Mccn. DrcoQft
WASTEWATER
TREATMENT
TECHNOLOGY USED
Seepage Ponds
RECYCLE
(%)
Partial
DAILY
DISCHARGE
VOLUME
(gpm)
0
f
o
s-
M
z'.
w
en
G
to
w
o
O
cn
M
o
-------
Table III-6. Profile of Colorado Gold Placer Mines
NJ
MINE
CODE
4267*
4268"«
4269
4270
COUNTY
San Juan
Arapahoe
Gilpin
Montrose
OPER. DAYS
PER YEAR
60
Seasonal
150
Unk.
CLASS.
METHOD
Screens
Screens
Trommel
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
<135
Unk.
100-150
150
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
WASTEWATER
TREATMENT
TECHNOLOGY USED
Sett) ing Pond (1)
Settling Ponds (2)**
Settling Ponds (3)
Settling Ponds (2)
A
RECYCLE
0
>0
>0
Unk.
DAILY
DISCHARGE
VOLUME
(gpm)
300
35
120
13
• Requested inactivation of his discharge permit
•• One pond for each of the discharge points
•••Sand and gravel also recovered at this mina
-------
Table III-7. Profile of Idaho Gold Placer Mines
u>
MINE
CODE
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
COUNTY
Idaho
Idaho
Idaho
Shoihone
Idaho
Cutter
Idaho
Owyhee
Idaho
Ada
Idaho
Boise
Boite
OPER. DAYS
PER YEAR
Seasonal
Seasonal
Seasonal
Seasonal
Seasonal
Seasonal
Seasonal
Unk.
Seasonal
Unk.
Unk.
Seasonal
Seasonal
CLASS.
METHOD
Trommel
Screen,
Trommel
Trommel
Screens
Unk.
Grizzly,
Screens
Grizzly,
Vibrating
Screens,
Crusher
Grizzly,
Trommel
Jigs & Table
Trommel
Unk.
Unk.
Trommel
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
320
100
100
100
100
320-400
320
Unk.
800-1000
Unk.
approx. 1600
Unk.
Unk.
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Unk.
Open Cut
Open Cut
Open Cut
Floating
Wash Plant
Open Cut
Open Cut
Open Cut
Open Cut
WASTEWATER
TREATMENT
TECHNOLOGY USED
Settling Ponds (3)
(possible use of
flocculants)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (3)
Settling Ponds (3)
Settling Ponds (3)
Settling Ponds (4)
Settling Ponds (2)
Unk.
Settling Ponds (?)
Settling Ponds (?)
Settling Ponds (?)
RECYCLE
(%)
100
100
approx. 100
0
Unk.
Partial
100
Unk.
100
Unk.
0
0
0
DAILY
DISCHARGE
VOLUME
(gpml
0
0
approx. 0
approx. 670
Unk.
Unk.
0
Unk.
0
Unk.
Unk.
Unk.
Unk.
-------
Table III-7. Profile of Idaho Gold Placer Mines (Continued)
MINE
CODE
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
COUNTY
Bonneville
Unk.
Power
Idaho
Boise
Idaho
Idaho
Idaho
Idaho
Unk.
Idaho
Clearwater
OPER. DAYS
PER YEAR
Seasonal
Year
Round
Year
Round
Seasonal
Seasonal
Seasonal
Seasonal
Year
Round
240
Seasonal
Unk.
Unk.
CLASS.
METHOD
Trommel
Magnetic
Separators,
Amalgamator
Vibrating
Screen
Unk.
Grizzly,
Trommel
Trommel
Trommel,
Jigs
Trommel,
Vibrating
Screens
Screens
Trommel
None
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
approx. 125
4,800
280
120-160
500
320
800
500
160
125
800
800
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Dredge
WASTE WATER
TREATMENT
TECHNOLOGY USED
Settling Ponds (3)
Settling Pond (3)
(lined with
bentonite)
Settling Ponds (2)
Settling Ponds (3)
Settling Ponds (2)
Settling Ponds (4)
Flocculants maybe
used
Settling Ponds (?)
with use of sen! ing
agents (flocculants?)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (?)
Settling Pond (1)
RECYCLE
(%)
100
approx. 100
100
100
100
100
0
0
Partial
Partial
0
Partial
DAILY
DISCHARGE
VOLUME
(gpm)
0
Slight
0
0
0
0
approx. 900
2,500
20
Unk.
Unk.
Unk.
-------
Table III-7. Profile of Idaho Gold Placer Mines (Continued)
en
ui
MINE
CODE
4296
4297
4298
4299
COUNTY
Boise
Idaho
Elmore
Idaho
OPER. DAYS
PER YEAR
approx. 180
Unk.
Unk.
Unk.
CLASS.
METHOD
Grizzly,
Trommel,
Screens,
Magnetic
Separator,
Jigi & Table
Trommel,
Screeni,
Jigi,
Bowls
Grizzly,
Trommel
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
1.600
1,600
36
800
MINING
METHOD
Open Cut
Open Cut
and
Suction
Dredge
Open Cut
Suction
Dredge
WASTEWATER
TREATMENT
TECHNOLOGY USED
Settling Ponds (4)
Settling Ponds (3)
with discharge to
tailings
Settling Ponds (3)
Settling Pond (1)
RECYCLE
(X)
approx. 100
unk.
Partial
Partial
DAILY
DISCHARGE
VOLUME
(gpm)
approx. 0
approx. 0
Unk.
0
-------
Table III-8. Profile of Montana Gold Placer Mines
MINE
CODE
4261
4264
4262
4263
4341
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
COUNTY
Lewis &
Clark
Broadwater
Missoula
Broadwater
Broadwater
Meagher
Ravalli
Missoula
Powell
Powell
Powell
Broadwater
Powell
Meagher
Meagher
Meagher
Powell
OPE R. DAYS
PER YEAR
270
200
270
100
+90
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
CLASS.
METHOD
Grizzly,
Trommel
Grizzly,
Trommel
Trommel
Trommel
Trommel
Unk.
Unk.
None
Unk.
Trommel
Unk.
Unk.
Unk.
Trommel
Unk.
Unk.
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
320-500
200
300-400
300
100
Unk.
100
15
25
Unk.
40 to 60
2
40 to 60
50 to 100
100
40 to 50
Unk.
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
WASTE WATER
TREATMENT
TECHNOLOGY USED
Settling Ponds (3)
Settling Ponds (2)
Settling Ponds (4)
Settling Ponds (4)
None
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Ponds (?)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
RECYCLE
(%»
100
100
100
Partial
0
Unk.
0
0
0
0
Unk.
0
0
0
Partial
0
0
DAILY
DISCHARGE
VOLUME
(gpm)
0
0
0
Unk.
Unk.
0
800
190
150
Unk.
250
0
380
160
0
0
250
-------
Table III-8. Profile of Montana Gold Placer Mines (Continued)
en
MINE
CODE
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
COUNTY
Mineral
Lewis and
Clark
Lewis and
Clark
Lewis and
Clark
Powell
Meagher
Meagher
Granite
Madison
Jefferson
Lincoln
Powell
Beaverhead
Silver Bow
Madison
OPER. DAYS
PER YEAR
link.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
CLASS.
METHOD
Unk.
Trommel
Unk.
Unk.
Vibrating
Screens
Trommel
Trommel
Trommel
Unk.
Trommel
Unk.
Shaker
Screens
Trommel
Wash Plant
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
2 to 3
37
50
24
50
400
160
150
100
500
200
60
700
300
250
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
WASTE WATER
TREATMENT
TECHNOLOGY USED
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Pond (1)
Settling Ponds (3)
Settling Ponds (3)
Settling Ponds (4)
Settling Pond (1)
Settling Ponds (4)
Settling Ponds (5)
Settling Pond (1)
Settling Ponds (2)
Settling Pond (1)
Settling Pond (1)
Settling Ponds (2)
RECYCLE
(%)
0
Partial
0
approx. 100
0
0
0
0
Partial
0
Partial
0
0
0
>0
DAILY
DISCHARGE
VOLUME
(gpml
0
0
25
approx. 0
250
400
400
300
<900
<100
400
150
Unk.
600 to 700
1.500
-------
Table III-8. Profile of Montana Gold Placer Mines (Continued)
00
MINE
CODE
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
COUNTY
Meagner
Lewis and
Clark
Beaverhead
Powell
Lewis and
Clark
Powell
Powell
Meagher
Silver Bow
Meagner
Mineral
Powell
Madison
Jefferson
OPER. DAYS
PER YEAR
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
CLASS.
METHOD
i roiiwwl
Grizzly
Screens
Unk.
Trommel
Trommel
Trommel
Trommel
Grizzly
Trommel
Jigs
Trommel
Trommel
Unk.
Unk.
Unk.
Unk.
Unk.
VOLUME
PROCESSED
(CU. YD/DAY)
325
300
300
25
Unk.
200
600
50
>100
50 to 100
50
300
250
20
MINING
METHOD
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
Open Cut
WASTEWATER
TREATMENT
TECHNOLOGY USED
Settling Pond (1)
Settling Ponds (3)
Settling Ponds (3)
Settling Ponds (?)
Settling Ponds (2)
Settling Ponds (2)
Settling Ponds (3)
Settling Pond (1)
Settling Ponds (2)
Settling Pond (1)
Settling Ponds (4)
Settling Ponds (3)
Settling Pond (1)
Settling Pond (1)
RECYCLE
- (%)
0
>0
0
>o
0
>0
100
0
if water needec
Unk.
approx. 100
approx. 100
approx. 100
approx. 100
DAILY
DISCHARGE
VOLUME
(gpm)
100
700
300
3.000
600
approx. 0
0
500
150
320
approx. 0
approx. 0
approx. 0
approx. 0
-------
m
Table II1-9. Profile of Alaskan Placer Gold Operations - 1986
Wastewater
Mine
Code
4922
4998
4999
5000
5001
5002
5003
5004
Location
(District)
Nome
Valdez Creek
Innoko
Innoko
Ruby
Ruby
Nome
Nome
Oper. Days
.Per Year
275
240
160
90
140
180
120
80
Classification
Method
Used
Unk.
Grizzly
None
None
None
None
Vibrating
screens
Vibrating
screens and
grizzly
Volume
Sluiced
fCu yd/bay)
5500
2250
450
200
Unk.
75
950
3000
Mining
Method
Mech.
dredge
Open cut
Open cut
Open cut
Open cut
Open cut
Open cut
Open cut
Treatment
Technologies
Used
Settling
ponds (2)
Settling
ponds (5)
Settling
ponds (2)
Settling
pond
Settling
pond
Settling
pond
Settling
ponds (2)
Settling
ponds (2)
Reycle (%)
65
0
0
0
0
99.5
100
Unk.
Discharge
Volume
(GPM)
1460
4100
7200
1220
5830
20
0
Unk.
o
o
f
>
w
50
SB
H
z
M
CO
a
to
o
g
*j
8
50
K)
CO
o
1
M
H
-------
CTl
o
o
o
o
M
w
CO
G
Qd
O
M
O
O
CO
M
O
(-3
Figure III-l. Principal Gold Placer-Producing Camps in Alaska
-------
GOLD PLACER MINE SUBCATEGORY SECT - III
wwi
WW2
IIOO-i
Total gold production
approximately
60.1 million ounces
1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990
Source: Ref. 4
Figure III-2.
Gold Production in Alaska,
1880-1986
61
-------
o\
o
f
o
f
s
3:
M
z
en
G
0
O
W
O
O
cn
w
o
Figure III-3. Side View of 18-Cubic-Foot Yuba Manufacturing Division. 110 Dredge Designed
to Dig 85 Feet Below Water.
-------
GOLD PLACER MINE SUBCATEGORY SECT - III
0
i» T "* *-)f diameter-
- threaded rods
t
13-
r«
21-
ELEVATIONS
(apron removed)
>
r S^L . — -rf
5
(-i 113J" 4
• i«r >•
Hopper bottom, 24-gage
galvanized iron, V holes
on Dj" centers-v
24 gage galvanized iron
Pins holding rocker to frame
!•»*•
SECTION
Source: Ref. 55
Figure III-4. Basic Design for a Prospector's Rocker.
63
-------
WATER BAR
ORE LOADED HERE
WATER
SUPPLY
COARSE MATERIAL
TO CHUTE
TOP VIEW
FRONT VIEW
SIDE VIEW
WET FINES
FALL THROUGH
TO SCREEN BELOW
WATER IN
O
f
a
o
w
W
cn
a
CD
o
W
O
O
*)
K
cn
M
O
f-3
Figure III-5. Schematic of a Grizzly.
-------
FRONT VIEW
cr>
01
ORE ENTERS
FROM FEED
HOPPER OR
OTHER
CLASSIFICATION
DEVICE
SIDE VIEW
SCREENED OR SLOTTED
SECTION
~J
CHAIN DRIVE
INTERNAL BAFFLES
DESIGNED TO
INCREASE TURBULENCE
SPLASH PLATE
WATER SUPPLY TO
WATER BAR
COARSE MATERIAL
TO TAILS SLACKER
WET FINES FALL THROUGH
TO SCREEN OR SLUICE BOXES
o
o
•ti
f
>
o
M
W
CO
a
tn
o
en
w
o
1-3
Figure III-6. Schematic of a Trommel.
-------
ORE LOADED
FROM FRONT END
LOADER, CONVEYOR
BELT, OR OTHER
CLASSIFICATION
DEVICE
WATER BAR
WATER IN
COARSE MATERIAL TO TAILS STACKER
WATER IN
TUNED SCREENS
OF DIFFERENT
SIZES
SPRING
WATER IN
X
SIDE VIEW
COARSE MATERIAL TO TAILS STACKER
FINES FALL THROUGH
TO SLUICE BOXES
SPRIN(
Figure III-7. Schematic of a Vibrating Screen
(Double Screen Deck).
o
F
O
50
&
M
W
a
CD
n
05
w
n
-------
ORE AND WATER ENTER
AT SLICK PLATE
ORE AND WATER
GOLD AND "BLACK SANDS"
RETAINED BETWEEN RIFFLES
ASTRO-TURF
CARPET
STEEL BOTTOM
WATER AND COARSE MATERIAL
TO SETTLING PONDS
SLICK PLATE
SIDE VIEW
o
o
o
M
Z
w
CO
G
CO
CO
M
O
WATER AND COARSE MATERIAL
Figure III-8,
Schematic of a Sluice Box
(With Hungarian Riffles).
-------
4(Mb. rails, 30 iMt long.
*tol
.. lV»UTan*t iron,
•nds bent down to give
a riffled surfac* r»
desirvd
01
00
nch apart at b«M
12 gage straps. IV wide
Roofing nail
ocks may
bereufhfy
shaped or
laid as quarried
V rod or pipe
spaced at 1" cental
"o
a
o
O
JO
S
M
2
CO
a
dd
o
CO
M
O
Typei of riffles: A. Transverse wooden, steel-capped riffles used on
dredges. B. Transverse pole riffles. C. Longitudinal pole riffles. O.. Trans-
verse wooden riffles, square section. E. Transverse wooden riffles, beveled
section. F. Transverse wooden riffle, steel-capped, inclined section. G.
Transverse wooden riffles, steel clad, with overhang. H. Longitudinal
Source: Ref. 7
Figure II1-9
wooden riffles capped with cast-iron plates, f. Wooden-block riffles for
large sluices. J. Wooden-black riffles for undercurrents. K. Stone riffles.
L. Longitudinal rail riffles on wooden sills. M. Transverse angle-iron riffles.
N. Transverse angle-iron riffles with top tilted upward. O. Longitudinal
riffles made of iron pipe. P. Transverse cast-iron riffles used in undercurrents.
-------
GOLD AND HEAVY
PARTICLES (HEADS
WASHED DOWN TO
END TROUGH
en
vo
LIGHTER PARTICLES (TAILS AND MIDDLINGS)
COLLECT IN DIRECTION OF WATER FLOW
TOP VIEW
CONCENTRATE
LOADED HERE
ADJUSTABLE FLOW
JJ D D Jj ff
SHAKING MECHANISM
LOACTED UNDER TABLE
WATER
SOURCE
SIDE VIEW
3
>
ATER SOURCE
z
w
CO
G
to
5
w
CO
w
0
Figure 111-10. Schematic of a Shaking Table,
-------
GOLD PLACER MINE SUBCATEGORY SECT - III
(Gravel and water enter here
i
(l-inch drop per foot
of length
Perforated screen
n
Lined with 1/8-inch =^
• heet iron F T
Lined with
1/8-inch sheet
iron
6* to 12'
]
b
I
-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
SECTION IV
INDUSTRY SUBCATEGORIZATION
During development of effluent limitations and new source
standards of performance for the ore mining and dressing
category, consideration was given to whether uniform and
equitable regulation could be applied to the industry as a whole
or whether different limitations and standards ought to be
established for various subcategories of the category. Ore
mining and dressing was subdivided into ten subcategories, based
primarily on ore type, with one additional subpart used for
category-wide definitions. These subcategories were further
subdivided into discharges from mines (mine drainage) and
discharges from mill or beneficiation processes. Initially, gold
placer mines were included in Subpart J along with other gold
mining. However, EPA decided not to regulate gold placer mines
at that time because available information on gold placer mines
was inadequate. Placer deposits and extraction techniques are
significantly different from those covered under Subpart J.
TECHNICAL CONSIDERATIONS FOR INFLUENCING SUBCATEGORIZATION
In developing regulations for gold placer mines, EPA considered
whether further subcategorization was necessary. Placer
operations are conducted as land surface activities similar to
many other industries covered under the ore mining and dressing
regulation. The resultant water pollution problems associated
with these activities are affected by a variety of factors such
as size of operation, climate, and topography.
During the promulgation of the regulation for ore mining and
dressing, an exhaustive list of possible subcategorization
schemes was developed. Drawing on the experience gained from
this, the following specific factors were used by the Agency to
review the technical aspects of gold placer mining.
1. Size of mine
2. Age of facility
3. Number of employees
4. Processes employed
- Mining methods
Ore processing methods (including
classification)
Reagent use
5. Water use or water balance
6. Treatability of pollutants (including mineralogy of the
71
-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
ore and overburden)
7. Wastewater characteristics
8. Treatment and control technologies
9. Treatment costs
10. Non-water quality environmental impacts
Solid waste generation
Energy requirements
11. Unique plant and site characteristics
Topography and geographic location
Climate and rainfall
A detailed discussion of each of these factors is presented
below.
Size of^ Mine (Capacity to Process Ore)
An industry profile demonstrates a convenient and rational means
to divide the industry on the basis of size (capacity to mine, or
through-put, calculated as cubic yards per day or year of ore
processed). Size is an appropriate criterion for
subcategorization because many of the differences between mines
are directly related to size. Principal among these are the
mining and ore processing methods employed, mass of pollutants
discharged in the wastewater, and economic viability of the mine.
One conceptual division is based on whether a facility is "non-
commercial" or "commercial" (i.e., small capacity versus large
capacity). The non-commercial operations (recreational, hobby,
and assessment types of operations) tend to be very small, while
the commercial operations vary in size from fairly small to very
large. Table IV-1 (p. 81) shows a partial profile of small, non-
commercial mines versus larger, commercial mining ventures. The
non-commercial mines or operators may number over 1,000 and be
the largest number of mines both in Alaska and in the
conterminous 48 states. However, EPA has been unable to obtain
substantial data on these extremely small operations.
For purposes of this regulation, we have defined extremely small
mines as those which process less than 1,500 cubic yards of ore
per year. Because they process a low total volume of ore, they
generally discharge a very low volume of process water. Such
small mines characteristically have little mechanized equipment
and are usually intermittent in operation. They include weekend
panners, small suction dredges, small sluices, and rocker box
operations.
The extremely small designation also applies to small-scale
assessment mines. Assessment mines include those operations that
could develop a commercial or larger type of operation but, for
72
-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
one of several reasons, are doing only a limited amount of work
adequate to maintain legal control of their property. This group
also covers prospecting, testing, and development work.
This regulation does not cover gold placer mines that mine or
process less than 1,500 cubic yards of ore per year. These
unregulated mines are usually non commercial operations, such as
recreational, hobby assessment mines, for which there is little
available data on which to base limitations. Even though these
mines are not covered by this regulation, they are not exempt
from the CWA requirement that they must obtain an NPDES permit
for any wastewater discharge. Regulated gold placer mines vary in
size from 1,500 cu yds per year, to many thousands of cu yds per
day processed by the largest dredges. The proposed regulation
segmented the industry into two subcategories based on the volume
of ore processed. This distinction was made on the basis of
economic modeling at the time of proposal which indicated
marginal profitability for mines processing less than 500 cu yds
per day of ore. Improvements in economic modeling indicate that
this distinction no longer is appropriate.
Modeling for the final regulation separated dredges from open cut
mines. For the purpose of economic analysis, open cut mines were
divided into four size groupings. Using these sizes, the impact
of the potential regulations on the mines was analyzed and no
substantial size oriented difference in the impact was found.
Technically, while the open cut mines use a variety of standard
earth-moving equipment to move overburden and recover ore, they
are essentially similar even though there is a size difference.
The ore is moved and processed in an essentially similar manner
even though different equipment may be employed. The technology
for water control and pollution control appears to be equally
applicable to all open cut mines irrespective of size. The
Agency has, therefore, concluded that subcategorization of open
cut mines by size is not appropriate.
Bucket-line dredges all use the same mechanisms for removal of
the ore and are essentially similar in the ore processing and
tailings disposal processes. The only substantial variant among
dredges is the size of the machine. The technologies for control
of wastewater pollutants appear to be equally applicable to all
sizes of dredges. Economic analysis for dredges indicates that
there is no significant adverse impact on either the large or
small size dredge analyzed.
Very late in the regulatory development process, the Agency
became aware of several very small dredges which were not
specifically examined in the technical or economic analysis. The
technical information available on these dredges indicates that
their individual annual production is less than 50,000 cu yds per
year. Since no economic model was constructed for this size
unit, there is no specific evaluation of the impact on them.
Because data on which to regulate these very small dredges has
not been collected and analyzed, they are not being regulated
under this rule. EPA, therefore, will make a small-size cutoff
73
-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
for bucket-line dredges at 50,000 cu yds per year. The few
existing dredges (three or four) of this size will be regulated
by the use of BPJ permits.
Age of Facility
Many placer mines have been operated in the same general location
in excess of 50 years (usually under different management). A
number of these deposits have been reworked several times to
recover gold which was missed or by-passed by previous operators
for one of several reasons (i.e., gold price differentials that
make lower grades more attractive, inefficiencies in the
operation, oversight by the operator, or extension of the deposit
in depth or area). Mining equipment and processing equipment
(sluices) are repaired or replaced as needed. The same operating
techniques and wastewater treatment systems applicable to this
subcategory may be employed at old or new mines or at new
locations within an existing operation without consideration of
the age of the facility. Therefore age of the operation is not a
basis for subcategorization.
Number p_f Employees
The amount and quality of process wastewater generated is
directly related to the size (through-put capacity), the mining
and recovery processes employed, the amount of water available,
the degree of recycle employed, the effectiveness of wastewater
treatment employed, plus the site-specific factors related to
each individual mine (i.e., treatability, mineralogy, location,
topography, geology, overburden and pay dirt characteristics,
etc.). There may be a loose correlation between the number of
employees and the size of a mine, but the modified economic
analysis used for development of the final regulation showed no
basis for subcategorization based on number of employees.
Processes Employed
Mining Methods
There are two general mining methods being employed in the
industry today—mechanical and hydraulic. The choice of mining
method is determined by the general geology, grade of ore
(assay), size, configuration and depth of the deposit, type and
thickness of overburden, geographic details of the site, and
availability of water. The mechanical approach to mining
utilizes considerably less water than the hydraulic method. With
the advent and adaptation of the small, high powered diesel
engines to tractors, loaders, shovels, draglines, backhoes, and
vehicles, the miner is able to move mechanically larger volumes
of material (ore and waste) economically, thus significantly
expanding the use of mechanical mining. The 150- to 460-
horsepower diesel tractors have the capability to rip, strip,
move, and stockpile a considerable amount of material. The units
can feed 1,500 to 4,000 cubic yards of ore daily. The mines
employ a surface, open-cut method.
74
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GOLD PLACER MINE SUBCATEGORY SECT - IV
Another mining method in current use that is classified as
mechanical mining is the use of mechanical buckets in dredging
operations. The ore is cut, mined, and moved mechanically in
buckets attached to a continuous chain. The dredge has a self
contained method to process the ore and to dispose of the waste
material. These obvious physical differences provide a basis for
subcategorization.
The hydraulic system of mining uses varying amounts of water.
Small suction dredges often use less than 100 GPM and large
hydraulic water cannons can use over 10,000 GPM. The small
suction dredges are often used non-commercially by hobbyists. A
number of larger suction dredge operations have existed in the
past and possibly could operate in the future. The hydraulic
water cannon mining technique virtually has been replaced by
mechanical means. The hydraulic system, if used to clear or move
overburden, utilizes a large amount of water and generates a
large amount of pollutants in the wastewater. The hydraulic
system can also be used to thaw overburden but is very water use-
intensive. Smaller hydraulic cannons are used to load ore into
the sluices, for mixing purposes and for the movement of wastes.
Regardless of the mining method employed, the processing of ore
generally employs similar gravity and physical separation methods
to produce a concentrate.
Ore Processing Methods (Including Classification)
Gold placer mining currently utilizes several gravity and
physical separation methods to process ore and recover the free
gold. The scope of this rule is limited to this particular type
of ore processing. Currently, all areas of the country utilize
straight sluicing, sluices with punch plates and undercurrents,
sluices with varying degrees of classification, jigs, spirals,
cyclones, and tables to separate the gold in the ore. Although
physical classification of the ore by particle size is considered
a part of ore processing, it was also examined as a potential
basis for subcategorization. The various methods of
classification all have the same goal—to reduce the volume of
ore for further processing. By separating a portion of the ore
by particle size into a direct waste component (gangue or
tailings), classification reduces the total amount of water
needed to process the ore. This reduces the volume of wastewater
to the treatment system (see "Placer Mining Wastewater Treatment
Technology Project, Phase 3 Final Report - Draft," January 1985
by Shannon & Williams, Inc.). The total tonnage of particulate
matter in the wastewater effluent is reduced by the amount
classified out of the ore. Based on the wide variations in type
and degree of classification utilized, plus the fact there is no
fundamental difference in the type of pollutants produced with or
without classification, classification is not considered to be
appropriate as a means of subcategorization.
Reagent Use
75
-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
Current operations for which the Agency has information do not
use reagents to recover free gold in gold placer mining. Mercury
coated copper recovery plates located in the flow stream at the
end of the sluices have been employed in the past but have lost
their appeal in the current operating schemes and regulatory
requirements. None was observed during the last several years of
site visits by the Agency. In addition, this subcategory (gold
placer mines) is limited in scope to include only gravity
separation (recovery) methods. Thus the use of reagents would be
covered under the existing regulation for the ore mining and
dressing point source category at 40 CFR Part 440, Subpart J.
Water Use or Water Balance
The rate of water use or water balance is affected by many
different factors, not the least of which is the personal
preference of each individual miner. Water use can be affected
by the mining method employed, the beneficiation process used,
the degree of ore classification used prior to gold recovery, the
type of deposit, the type and amount of overburden, water
availability, gold particle size and shape, climate, rainfall,
and geographic location. All of these factors can vary widely
and, considered in combination, make water use extremely site
specific. As a result of this lack of uniformity, the Agency is
not subcategorizing gold placer mines by water use or water
balance.
Treatability (Mineralogy of_ the Ore and Overburden)
Gold placer mining generates wastewater that is relatively
consistent in the types of pollutant ("muddy water" subject to
variation in composition from different sources), while the
quantity of pollutants found in the wastewater varies
considerably. The amount of pollutants depends on several
factors in addition to the size of operation. The mineralogy of
the waste rock and soil involved, amount of classification used,
and the degree of recycle or treatment employed bear directly
upon the quantity of pollutants produced and discharged to the
environment.
The mineralogy of an ore deposit often determines the recovery
(beneficiation) process to be used. Consideration must be given
to both the valuable portion (free gold in this case) and the
waste (gangue) portion of the gold placer ore. Placer deposits
are usually either alluvial or glacial in origin. The alluvial
deposits generally concentrate the heavier portions of the ore,
while glacial action tends to scatter all segments of the deposit
on a random basis. Both types produce a wide range of particle
shapes and sizes, and particle composition varies by the original
source of the material. All of these factors may affect the
treatability of the effluent. Settling rates for the particles
vary by size, shape, and composition (specific gravity). In
addition, if the particle is colloidal, the electromagnetic
forces involved tend to keep these particles in suspension for a
longer period of time. The nature and composition of soils at
76
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GOLD PLACER MINE SUBCATEGORY SECT - IV
placer deposits may vary widely within small distances because of
the mechanism of placer formation. This wide range of particle
size and composition and erratic distribution possible in these
ores make it impossible to use mineralogy as a basis for
subcategorization.
Wastewater Characteristics
As stated previously, the characteristics of the wastewater
created by gold placer mining vary as the mineralogy varies from
one ore deposit to the next. The extreme diversity in wastewater
characteristics make them unsuitable factors for
subcategorization. Detailed discussions of wastewater
characteristics, the pollutants of concern, and Agency samples at
gold placer mines are included in Section V of this document.
Treatment and Control Technologies
Currently, the end-of-pipe wastewater treatment and control
technology commonly used at gold placer mines is settling pond(s)
(either single or multiple in series) either with or without
recycle. There are a number of variations in site-specific
layouts. The applicable technologies for all types of
configurations of gold placer mines are similar. Therefore,
treatment and control technologies do not provide a basis for
subcategorization.
Treatment Costs
To estimate the costs of treatment, economic models were
developed that characterize the industry-wide range of operating
conditions of mines and dredges. These models were described
earlier in this section under "Size of Mine" and are discussed in
greater detail in Section VIII of this document. Because many
differences among mines are related to size, treatment costs were
not used as primary criteria for subcategorization but were
considered after the size criterion was applied to the industry-
Non-water Quality Environmental Impacts
Solid Waste Generation
Physical and chemical characteristics of solid wastes generated
by treatment of gold placer mining wastewater are determined by
the ore and overburden characteristics. Those are beyond the
control of the operator and are site specific. The miner
recovers a fraction of a percent of the ore mined (less than a
fraction of an ounce per ton mined). The majority of the solids
removed in the beneficiation process simply fall out at the
discharge end of the sluice before wastewater treatment. The
characteristics of the solid wastes generated by wastewater
treatment are unrelated to differences in currently employed
mining and process technology with the exception of recirculation
in both mechanical and dredge operations (i.e., zero discharge).
Current wastewater process technology is virtually identical in
77
-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
this segment (settling ponds) for all types of mining operations.
Therefore, this factor is not a basis for subcategorization.
Energy Requirements
Energy requirements in this segment vary widely. The main use of
energy in wastewater control and treatment is for pumping water
when recycle or recirculation is required. However, this energy
requirement would be only a slight increase over the energy
presently required to supply process water at mines pumping wash
water to the beneficiation process. Energy for pond construction
and maintenance is only a small fraction of the energy required
for mining and processing. It is very difficult to reliably
identify energy requirements specifically related to wastewater
treatment. Therefore energy requirement is not selected as a
basis for subcategorization.
Unique Plant and Site Characteristics
Topography and Geographic Location
There are approximately 195 gold placer mines in Alaska and 265
mines in the 48 conterminous states, with the vast majority
located in seven western states (California, Colorado, Idaho,
Montana, Nevada, Oregon, and Washington). The majority of site-
specific information the Agency has is representative of mines in
Alaska.
Topography differs among mining areas and from site to site
within areas (i.e., seashore marine gravels to broad, gently
sloping valleys to rugged, narrow, steeply sloping valleys).
These differences can affect the operation, particularly in
regard to waste disposal and settling pond location and size.
Rainfall accumulation and runoff from steep slopes can cause
problems as well. Narrow valleys with steep slopes place
constraints upon the location of ponds in terms of area
available, construction costs, and the costs associated with
pumping against a greater head for recirculation. Topography has
an impact on construction and cost of operation. However, based
on the current data available to the Agency, topography does not
significantly affect wastewater characteristics or treatability,
and thus is not a basis for subcategorization.
Information regarding mines which would be unable to build
adequate settling ponds due to topography and lack of space was
requested in the notice of proposed rulemaking. Several
commenters responded that they did not have adequate space but
did not provide specific information regarding the extent of
available space or other information on which the claim of lack
of available space could be evaluated. The lack of space for
settling ponds was not documented and there is basis for EPA to
develop limitations addressing this alledged circumstance.
Therefore topography has not been selected as a basis for
subcategorization.
78
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GOLD PLACER MINE SUBCATEGORY SECT - IV
Figures IV-1 and IV-2 (pp. 82 and 83) are plots of production
versus percentage of mines in each production interval for Alaska
(separately on Figure IV-1) and California, Colorado, Idaho, and
Montana (shown as a group on Figure IV-2). These data show the
same general distribution by size for the two areas. There are
several minor differences between these two general areas of
location; harsher climatic conditions, shorter length of
operating season, the availability of water, and higher costs to
operate prevail in Alaska.
EPA has concluded that the many similarities in the mines of
Alaska and the conterminous 48 states are compelling; none of the
above-mentioned differences is of such significance as to warrant
subcategorization on this geographical basis.
Regardless of the geographic location, the various gold placer
mines have similar problems regarding wastes (both liquid and
solids). Logistics, operation, and communications problems are
exacerbated in the more remote areas but these do not affect the
quantity or quality of the effluent wastewater from a given
operation. There is a wide range of site-specific conditions
present throughout but, as also discussed under size or capacity
to process ore, the similarities in mines regardless of
geographic location is significant. Geographic site specific
factors in Alaska cause production costs to be higher than in the
lower 48; these higher costs have been taken into account in the
compliance costing and economic impact analysis. Because
wastewater characteristics in Alaska and the lower 48 are
similar, location is not being used as a basis for
subcategorization.
Climate and Rainfall
There is a wide diversity of climatic and rainfall conditions in
the locations where gold placer mines are operated. Gold placer
mine operators cannot choose a location with more favorable
climate or rainfall conditions but must accommodate whatever is
present at the discovery site. Some mines in Alaska are located
in regions close to the coast and, as a result, have milder
climate and more abundant rainfall which, in turn, allows for a
longer mining season with fewer problems related to the
availability of process water. Other mines are located in
interior areas, including mountainous terrain, with resultant
colder, harsher climates and possibly reduced rainfall for part
of the operating season. These areas have shorter mining seasons
and may have to contend with permafrost and a shortage of water.
Some of these areas are fed by glacial meltwater, which
compensates for the lack of adequate rainfall.
Climate and rainfall may have a direct bearing on the length of
mining season, occurrence of permafrost, availability of process
water (possibly necessitating recycle), and, to some degree, on
the types of mining and recovery processes used. The increased
costs associated with these conditions have been taken into
account, but these factors do not control the size of mining
79
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GOLD PLACER MINE SUBCATEGORY SECT - IV
operation, the quality or quantity of wastewater (except as it
affects the degree of recycle employed), or the treatment
technology used. Therefore, these factors are not a basis for
subcategorization.
ECONOMIC CONSIDERATIONS
EPA's economic assessment is presented in the report "Economic
Impact Analysis of Effluent Limitations and Standards for the
Placer Gold Mining Industry." This report estimates the
investment and compliance costs for the placer gold mines covered
by this regulation. Compliance costs are based on engineering
estimates of capital requirements and construction expenses as
set forth in Section VIII of this document. The report also
estimates the economic effect of compliance costs in terms of
mine closures, employment losses, profitability impacts, and
regulatory costs as a percentage of sales and as a percentage of
operating costs. Modifications to the economic analysis since
the time of proposal show no basis for subcategorization of small
mines.
SUBCATEGORIZATION FOR GOLD PLACER MINES
As the revised economic model no longer indicates a need for
subcategorization due to impacts on small mines, the overall
subcategorization scheme is identical to the subcategorization
based on technical considerations. This final rule contains two
regulated segments; the rule applies to all open-cut mines
processing more than 1,500 cu yds per year of ore and to all
bucket-line dredges processing more than 50,000 cu yds per year
of ore. The rule does not apply to open-cut mines processing
less than 1,500 cu yds per year of ore, to bucket-line dredges
processing less than 50,000 cu yds per year of ore, or to dredges
operating in open waters (i.e., marine and coastal waters or
large rivers).
80
-------
Table IV-1. Partial Profile of Extremely Small (< 20 cubic yards/day) Gold Placer Mines.
oo
Volume
Wastewater
ually
Discharge
Mine Name/Owner State
1-EW
2-PJ
3-ES
MT
MT
MT
Oper. Days
per Year
Unk.
Unk.
Unk.
Class.
Method
None
Unk.
None
Processed
Mining
(cu. Yd/Day) Method
15
2
2-3
Open-Cut
Open -Cut
Open-Cut
Treatment
Technology Used Recyle (%)
Settling
Settling
Settling
Pond
Pond
Pond
(1)
(1)
(1)
0
0
0
Volume
(gpnQ
180
Unk.
250
and seepage
4-JD
5-HM
6-GH
7 -AH
8-CN
9-EC
10-JD
11 -JA
12-AC
MT
MT
MT
MT
MT
MT
MT
MT
AK
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
Unk.
150
Unk.
None
None
Wash
Plant
None
None
Unk.
Unk.
Unk.
20
2
10
15-20
0.5
Unk.
20
3
2-4
Open-Cut
Suction
Dredge
Open-Cut
Open-Cut
Hand
Shovel
Suction
Dredge
Open-Cut
Suction
Dredge
Suction
Dredge
Settling
Settling
Settling
Settling
None
None
Settling
Settling
None
Pond
Pond
Ponds
Pond
Pond
Pond
(1)
(1)
(1)
(1)
(1)
approx.
100
0
0
0
0
0
100
>0
0
approx.
0
10
200
100
(part time)
80
175
0
170
Unk.
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o
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M
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a
M
M
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Frontier TEchnlcal Associates, Inc. Report of 1984 Field Survey, David Harty.
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ALASKA MINES DISTRIBUTION
BY SIZE
20-99 200-299 400-499 600-699 BOO-B99 1000-1099 1200-1299 1400-1499
100-199 300-399 500-599 700-799 900-999 1100-1199 1300-1399 >1500
Figure IV-1.
PRODUCTION (CUBIC YARDS PER DAY)
Distribution of Alaska Gold Placer Mines by Size
Source: Computer Summary of Tri-Agency Forms - 1983
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o
o
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PO
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LOWER 48 DISTRIBUTION BY SIZE
20-99 200-299 400-499 600-699 800-899 1000-1099 12°°'129^,nn ,,00 «nn
100-199 300-399 500-599 700-799 900-999 1100-1199 1300-1399 >1500
PRODUCTION (CUBIC YARDS PER DAY)
Figure IV-2. Distribution of Gold Placer Mines in the Lower 48 States by Size
Source: Permit Files from Montana, Idaho, Colorado, and California
8
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-------
GOLD PLACER MINE SUBCATEGORY SECT - IV
This Page Intentionally Left Blank
84
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GOLD PLACER MINE SUBCATEGORY SECT-V
SECTION V
WATER USE AND WASTEWATER CHARACTERIZATION
The wastewater characterization program for placer gold mining
was undertaken primarily to provide a data base for development
of effluent limitations and standards for gold placer mining.
The data acquired has also been used to support EPA Regions VIII,
IX, and X in developing NPDES permit conditions and identifying
pollutants of concern. Pollutants of particular concern were
suspended and settleable solids, turbidity, and toxic metals.
This section identifies the sites sampled and parameters analyzed
by studies during 1982 through 1986. It also describes sample
collection, preservation, and transportation techniques and
identifies the analytical methods used. Finally, it describes
the pollutants and their concentrations found in both the raw
wastewater and treated effluents. All data obtained during these
studies are included in the administrative record of this
rulemaking.
DATA COLLECTION
EPA determined during the rulemaking effort that produced the
1982 Ore Mining and Dressing regulation that economic and
financial information about Alaskan gold placer mines was
inadequate to develop and promulgate effluent guidelines. The
information available was incomplete and anecdotal, as it had
been developed primarily in the course of public hearings and
other meetings.
The Agency, with the cooperation of the gold placer miners,
conducted an information-gathering effort during the 1983, 1984,
1985, and 1986 mining seasons. EPA already was conducting an
examination of effluent and receiving water quality
characteristics which was expanded to incorporate an economic and
financial component.
Although EPA has historical data from gold placer mines from as
early as 1976, and many subsequent years, the Agency primarily
relied upon the studies performed in 1984, 1985, and 1986 since
this data on treatment performance was more current and more
fully documented than earlier studies. The majority of the
economic data also were obtained in 1984, 1985, and 1986. Table
V-l (p. 104) lists those studies most influential in developing
the gold placer mining effluent limitations. A tabulation of all
applicable studies of the gold placer mines is shown in Table V-2
(p. 105). The reference numbers assigned to the studies listed in
Table V-2 are used throughout this section to identify each
study. Within the text of this section, studies by EPA and EPA
contractors are not differentiated because the contractors were
performing under the immediate technical direction of an EPA
85
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GOLD PLACER MINE SUBCATEGORY SECT-V
project officer. Table V-2 and Section XV, however, indicate
which contractor was involved.
The majority of the information collected was from Alaska because
the impact of the regulation is expected to be greatest there.
Existing state regulations in the lower 48 will minimize impact
in most of these states. However, data on facilities in the
lower 48 states were collected from state contacts and site
visits. These data were also used in development of the
regulation. All site visits included the collection of data on
existing treatment. Studies performed in Alaska provided data on
pilot-scale treatment technology, the effects of recycle and
recirculation, costs of operations and treatment, and the
economic viability of mines.
EPA Region X - 1982 Study
EPA Region X conducted sampling visits at 51 sites during 1982.
EPA Region X ^ 1983 Study
For the 1983 sampling effort conducted by EPA Region X, a size-
structured random sample was drawn from 409 Tri-agency gold
placer mining permit applications on file at EPA Region X. A
primary sampling group of 34 mines was supplemented by a
similarly structured secondary group of 31 mines to provide an
adequate sample in the event of nonresponse, failure to locate,
intermittent or ceased operations, or other obstacles to
information-gathering and sampling.
The 34-mine sampling proved impossible to achieve. Distance,
accessibility, intermittent nature of the operations, equipment
breakdowns, and location uncertainties combined to reduce the
sample size. Both time and budget constraints made it necessary
to treat the primary and secondary sample components as a single
sample of 65 mines, and to attempt to contact each potential
respondent at least once rather than to make repeated visits to
the primary sample group in order to verify the operational
status of each. Site visits were actually conducted at 60 gold
placer mines.
EPA Region X - 1984 Study
During the 1984 mining season, site visits were conducted by EPA
Region X personnel to seven mines.
EPA 1984 - Treatability Study
EPA gathered data during the 1984 mining season at gold placer
mines in Alaska. Studies included treatability tests of
effluents with and without polyelectrolyte settling aids, flow
determination, sampling and profiling the mine's equipment costs,
physical layout, and wastewater treatment system. Mine sites
were screened using available data from 1983 and through
discussions with EPA, Region X, Alaska DEC, individual miners
86
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GOLD PLACER MINE SUBCATEGORY SECT-V
and miners' associations. Twenty mines were selected for further
screening and on-site visits. These 20 mines were selected to be
representative of mines found over the State of Alaska
considering: geographical location, type of mining, size, depth
and type of overburden, topography, and treatment employed
(including high rate recirculation).
These 20 mine sites were visited in June 1984 by EPA and a
mineral consultant; an engineering work-up and fact sheet was
completed at each mine. The mines represented the seven mining
districts with the largest population of mines; mines had
capacities of 50 cu yds per day to over 3,000 cu yds per day;
water use varied from once-through to over 90 percent recycle;
overburden varied from none to over 60 feet; and mines located in
broad flood plains and narrow valleys were represented. The data
collected were reviewed by EPA, and 10 mines were selected as
representative of the site factors considered. These 10 mines
were than sampled and on-site treatability studies were
performed.
During the month of July and August 1984, a field crew visited
each of the 10 mines selected and conducted on-site treatability
testing as well as sampling and analyses for settleable solids
and turbidity. Samples were prepared for laboratory analyses of
TSS, arsenic, and mercury and flow measurements were made at each
of the 10 mines selected. The crew were on site 2 to 4 days at
each mine.
At each mine, the treatability tests were performed in three
parts. First, jar tests were used to select the appropriate
polyelectrolytes and to determine dosage at each site. Second,
settling column tests, with and without polyelectrolytes, were
conducted over a period of two hours. Finally, a long-term (up
to 24 hours) unaided settling test was conducted. The results
indicated an optimal dosage of polyelectrolyte of about 2.0 mg/1.
The conclusions of this study are discussed under the treated
wastewater characteristics of this section.
The existing wastewater treatment system was evaluated by
sampling the influent water, effluent from the sluice, effluent
from the ponds or discharge to the receiving water, and other
points to evaluate water quality, i.e., recycled water and run
off. Using dye, flow patterns were observed to determine
detention time or identify short-circuiting in the ponds. Flow
meters, weirs, and free pipe discharges were used to determine
the flow from the sluice and discharge from the ponds. The sizes
of the ponds were measured using a range finder and the depths
were determined using a "sinker" at various locations in the
ponds.
EPA Treatability Studies - 1983
The treatability studies evaluated both unaided and polymer-aided
settling. Unaided and unaided settling column tests were
conducted at each of the eleven mines visited.
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GOLD PLACER MINE SUBCATEGORY SECT-V
EPA Settleable Solids Method Detection Limit Study
During July of 1985 EPA personnel performed a field study, the
major purpose of which was to establish the Method Detection
Limit (MDL) of Settleable Solids in wastewaters discharging from
gold placer mining operations. This study also included the
gathering of background data and sampling of the mines visited.
The data gathering and Method Detection Limit testing were
performed at ten gold placer mine sites in Alaska. These sites
which represent several Alaskan geographical locations were
selected by U.S. EPA personnel. Where possible background data
was obtained by completing fact sheets and several points of the
existing mine water system were sampled and analyzed for
temperature, pH, settleable solids, turbidity and total suspended
solids.
The sampling, analysis, and testing to establish the MDL for
settleable solids in wastewaters discharging gold placer mining
operations were performed in accordance with the following
procedure:
o "Guidelines Establishing Test Procedures for Analysis
of Pollutants under the Clean Water Act" 40 CFR part
136 (49 FR No. 209 Friday October 26, 1985)
o "Definition and Procedure for the determination of the
Method Detection Limit" Appendix A, Revision 1.11,
prepared by EPA's office of Research and Development,
Environmental Monitoring and Support Laboratory (EMSL),
Cincinnati, Ohio.
The sampling and testing was coordinated with EMSL and samples of
the water used for the testing were sent to EMSL for duplicate
testing.
The computed field testing and the EMSL study results for
settleable solids MDL in wastewaters discharging from Gold Placer
Mining Operations were 0.16 ml/1 and 0.19 ml/1 respectively.
Based on these the results of both the field and laboratory
studies it was determined that values of settleable solids in
wastewater discharging from gold placer mining operations can be
read with a reasonable degree of accuracy to below 0.2 ml/1 using
the volumetric method outlined in Standard Methods and 304(h) of
the Agency's "Methods for Analyses of Water and Wastewater".
EPA 1986 - Treatability Study
EPA gathered data during the 1986 mining season at gold placer
mine sites in Alaskan mining areas which had not been previously
visited by EPA. The study included sampling, flow
determinations, and treatability testing of the processing plant
effluent, profiling the mine's equipment costs and the preparing
of a physical layout of the wastewater treatment system at each
88
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GOLD PLACER MINE SUBCATEGORY SECT-V
mine.
During the last half of June and the first half of July 1986, EPA
conducted on-site treatability testing and sampling at each of
eight mine sites. On-site analyses were performed for pH,
temperature, turbidity, and settleable solids. Liquid and solid
samples were prepared for laboratory analyses of TSS, IFB metals,
and acid soluble metals. Sludge samples from settling ponds
(usually first pond) were analyzed for percent solids, IFB
metals, and a trace elements analysis (ICP).
Existing treatment systems were evaluated by sampling the
influent water, effluent from the processing plant, recycled
water, if it existed, and effluent from the final pond. When
possible, flow measurements were made using weirs, free pipe
discharges and or timing of transit time of an object over a
known distance. Where possible, sludge samples were taken in the
first active pond and sketches of the system prepared. Utilizing
the pond sizes and measured depths, pond volumes were determined.
At each mine treatability tests were performed in two phases.
First, jar tests were used to select the appropriate chemical
dosage. Treatability tests were then performed which consisted
of simple settling tests and two chemically assisted settling
tests. The tests were run over a 2- or 6-hour period.
Conclusions and results of this study are presented in the
treated wastewater characteristics of this section.
Of the eight mine sites sampled during the field testing program,
six sites were processing ore using sluice boxes, one site was a
dredge operation, one site was hydraulically stripping overburden
and was not sluicing ore at the time of sampling, and one of the
six sluice box sites was intermittently sluicing ore.
1986 Placer Mining Full-Scale Field Investigations of_ Chemical
Treatment
This investigation was the first attempted by the Agency on a
scale similar to an actual discharge from a gold placer mine
operating under a partial recycle system. The testing simulated a
treatment system using polyelectrolyte on a continuous basis
treating wastewaters discharging from a gold placer mine. These
tests had two major purposes: first, to try to confirm the data
collected in previous field studies using bench scale tests and
seconds, to generate data which would define possible scale-up
problems when using chemicals to treat effluents from gold placer
mining operations.
Two sites in Alaska were selected for the testing program. Only
one polyelectrolyte was available at the site for testing. At
both locations, samples were taken of the untreated wastewater
and the settling pond effluent. These samples were analyzed for
settleable solids and turbidity at both sites and total suspended
solids at one site. The data developed during the testing
provides additional information to support the testing previously
89
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GOLD PLACER MINE SUBCATEGORY SECT-V
done by the Agency on a bench scale in Alaska. The report also
indicates that the processes were operated with limited success
at each site. Limitations associated with these tests included:
1. Achieving proper mixing
2. Maintaining dosage levels
3. Reducing operator time required
"Development and Demonstration of_ Treatment Technology for The
Placer Mining Industry" (1985)
This study was sponsored by the Canadian Government through
Environmental Protection Services. The final report indicated
that the project had the following specific objectives:
1. To develop a coagulation - flocculation methodology
suitable for removal of the colloidal solids associated
with aqueous discharges from placer mining operations.
2. To develop and optimize the low energy hydraulic mixing
systems required for efficient coagulant mixing and
particulate flocculation.
3. To design and install a full-scale effluent treatment
system at a selected placer mining operation in the
Yukon.
4. To demonstrate at full-scale the ability of the
technology to treat adequately the process discharges
from placer mining operations.
5. To develop realistic cost estimates of the treatment
technology and to evaluate the impact of its
implementation on the placer mining industry in the
Yukon.
The study was conducted during the 1984 mining season using the
results of previous studies a short list of candidate polymers
was prepared. This list was reduced using jar tests. The jar
tests were also utilized to design the mixing and settling
structure.
The demonstration testing was performed at two sites using a dry
polymer feed system and weir box system for mixing flocculation.
When the mixing and flocculation systems are properly installed
and operated the polymer produces a good settling solid.
Some of the conclusions from the study are as follows:
1. Coagulation of placer mining wastewater with anionic
polymers was effective in reducing the discharges of
suspended particulate matter.
2. Polymer dosage requirements were related to the
suspended solids content of the process water treated
90
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GOLD PLACER MINE SUBCATEGORY SECT-V
and the treatment objective.
Effluent Quality Polymer Dosage
(TSS mg/1) (kg/kkg TSS)
1000 0.071
500 0.129
250 0.261
100 0.865
3. Primary settling pond design and maintenance is a
critical factor in achieving effective treatment at low
polymer dosages.
4. The full-scale polymeric coagulation system performance
was similar to the performance predicted at laboratory-
scale by jar testing.
5. The cost for application of polymer aided settling is
most sensitive to the chemical requirements.
1984 Wastewater Treatment Technology Project
The Alaska Department of Environmental Conservation (ADEC) funded
a study to address the potential loss of gold recovery during
recirculation. This study was divided into two parts—a pilot-
scale study and a field study.
1986 Fine Gold Recovery Study
The primary purpose of this study was to determine the effect of
varying levels of total suspended solids in the sluice feed water
on riffle packing and gold recovery in a pilot-scale sluice box.
A secondary purpose of this study was to determine the
interrelationships between gold recovery and viscosity.
Canadian Department of Indian and Northern Affairs
Treatability Study
The treatability studies performed for the Canadian Department of
Indian and Northern Affairs were similar to the EPA treatability
studies. Unaided and polymer-aided settling column tests and
coagulation jar tests using organic polymers were performed at
several mines. Unaided settling column tests were performed at
four placer gold mines and polymer-aided settling column tests
were performed at two mines. All mines were located in the Yukon
Territory of Canada.
Settling column tests were performed on simulated sluice
effluents. Soil samples from the mine were mixed with a known
volume of water to produce the simulated wastewater. A six-inch-
diameter, six-foot-long plexiglas column with sampling ports at
If 3, and 5 feet from the bottom was used. Settling column tests
were performed to determine settling rates and settling pond
effluent quality. These settling column tests were conducted for
91
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GOLD PLACER MINE SUBCATEGORY SECT-V
a period of 18 to 19 hours. Turbidity values at the end of
unaided settling tests ranged from 80 NTU to 2,200 NTU.
Two organic polymers were used in performing standard jar tests
on simulated placer mine wastewaters. Non-ionic and anionic
polymers were also used in the 1984 EPA treatability study. In
this study, the anionic polymer produced the best results at each
of the mines tested. Relatively low dosages of this anionic
polymer removed a high percentage of the turbidity and suspended
solids from the wastewater. Polymer dosages between 3 and 20
mg/1 were effective. Jar tests at an additional mine proved
ineffective in that 20 mg/1 of an anionic polymer was required to
produce a supernatant TSS of 500 mg/1.
Lime, alum, and ferric chloride were independently tested on this
wastewater at dosages of 100 mg/1. Using these inorganic
coagulants, TSS concentrations between 100 and 200 mg/1 were
achieved.
Based on the jar tests, two polymer-aided settling column tests
were conducted. The duration of these tests were relatively
short as most of the turbidity and suspended solids were removed
from the wastewater during the first few minutes of the test.
Polymer dosages selected for use in the column tests were 3 mg/1
and 10 mg/1. At these dosages, final TSS concentrations of 30.5
mg/1 and 10.5 mg/1, respectively, were achieved.
In summary, this Canadian treatability study of Yukon gold placer
mine wastewaters supports the basic conclusions of several of the
EPA treatability studies. First, unaided or natural settling of
gold placer mining wastewater over relatively long periods of
time does not produce a high quality effluent. Second, several
organic polymers have been identified which can produce
relatively low turbidity and suspended solids concentrations in
placer gold mining wastewater at dosages of approximately 10
mg/1.
Lower 48 Study
EPA visited six mines in the lower 48 states (five in Montana,
and one in California) to obtain operational, economic, and water
quality information relative to the operation of mines outside of
Alaska.
Water Quality Study - 1976
This study was one of the first studies conducted which attempted
to evaluate water quality from mining operations. Many of the
mines visited did not have settling ponds installed, and
therefore little information on the effectiveness of settling
ponds was obtained.
NEIC Study - 1977
The EPA National Enforcement Investigations Center (NEIC) sampled
92
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GOLD PLACER MINE SUBCATEGORY " SECT-V
eight mines with ponds. The results indicate a wide range of
settleable solids levels achieved ranging from <0.1 to 15 ml/1.
Mercury was not detected in the effluent from any of the settling
ponds. The ponds are characterized as not being designed or
built to obtain effluent goals, but to provide a temporary
holding pond or sump for process water for the beneficiation
process, i.e., sluice.
Wastewater Treatment Study ^ 1979
In 1978, EPA sampled the effluent from eleven operating Alaskan
gold placer operations. Five mines achieved settleable solids
readings of less than 0.1 ml/1. The total suspended solids
(TSS) concentrations ranged from 76 to 5,700 mg/1 in the
effluent. No turbidity readings were obtained. Arsenic
concentrations in the final effluent ranged from <0.002 mg/1 to
1.2 mg/1. It was noted that the highest settleable solids and
TSS readings occurred with the highest arsenic and mercury data
which suggested a concentration of TSS with arsenic and mercury.
Pond retention time and volume were not measured, but the visual
assessment indicated inadequately sized ponds are included in
this data.
Settling Pond Demonstration Project ^ 1982
This study included an evaluation of a demonstration pond and
settling column tests. Seven mines employing settling pond
treatment technology were visited and sampled. Ponds sampled do
not necessarily represent adequate sized ponds. Therefore, the
results do not indicate the best effluent quality that can be
achieved. Settleable solids concentrations- ranged from <0.1 to
19.5 ml/1. At one mine, an increase in settleable solids,
turbidity, and TSS increased during the year indicating that the
pond was filling up. Turbidity readings in the pond effluent
during this study ranged from 160 to 6,900 NTU and averaged 2,676
NTU.
Another of the major objectives of this study was to evaluate the
sedimentation rates of particles from placer mine sluice
discharges. Settling column tests were conducted on the
wastewater from 15 individual mines. Wastewater was obtained
from sluice box effluents. Turbidity values were taken 1.5 feet
and 5.5 feet below the initial height of the settling column.
This study concluded that reductions in turbidity to the Alaska
standard of 25 NTU above natural conditions could probably not be
obtained in a practical manner by sedimentation alone."
Extrapolation of the data indicated that approximately 60 days of
sedimentation would be necessary to achieve the 25 NTU standard
under the laboratory conditions of the test. Based on the
settling column tests, the study concluded that it would not be
practical to design a demonstration settling pond to achieve
state turbidity standards.
A 22-day settling column test was conducted at one mine. After
93
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GOLD PLACER MINE SUBCATEGORY SECT-V
528 hours of quiescent settling, the TSS and turbidity values
were 120 mg/1 and 390 NTU, respectively. Even after 22 days, a
considerable amount of dilution water from the creek would be
needed to meet the State of Alaska water quality standard for
turbidity.
At 15 mines, six-day settling column tests were conducted. The
average TSS concentration from the 15 mines after six days of
quiescent settling was 931.3 mg/1. The average turbidity reading
obtained at the end of the same period was 1,543.7 NTU.
SAMPLING AND ANALYSIS
Pollutants
Detailed data on conventional, nonconventional, and toxic
pollutant concentrations in raw and treated process wastewater
streams were collected in a comprehensive sampling and analysis
program. Information available from the 1982 ore mining
regulations indicated that toxic organic pollutants would not be
expected to be significant in placer mining wastewaters because
the ore consists of natural earth materials. Reagents are not
used in processes covered by these guidelines.
Mine Sites Sampled
Samples were obtained at each mine visited in 1983, 1985, and
1986 (except mines not operating). In 1984 EPA visited 20 mines
but only 10 were sampled. A list of facilities visited (by mine
code) is presented in Table V-3 (p. 106). The parameters that
were analyzed during the program are shown in Table V-4 (p. 109).
Analysis was performed according to the EPA Chemical Analysis
methods as listed in Table V-5 (p. 110).
The use of a pre-selected random sample as an information-
gathering procedure by Region X in the 1983 study was based
largely on the needs of the economic component of the study. The
Agency had sampled effluent and receiving waters during the 1982
mining season, employing the simple selection strategy of taking
samples at any mine whose sluice was in operation at the time it
was visited. It was reasoned that information developed only
from mines with operational sluices might bias the economic study
toward the more efficient and better situated operations.
Stratification of the sample was based on the requirements of the
water sampling portion of the study. This was intended to obtain
information from mines of various sizes and with a broad range of
sluice water treatment or controls (e.g., sedimentation,
recycle). The final composition of the sample was a compromise
that reflected the competing requirements of economic and
effluent control data gathering. Table V-6 (p. 110) presents a
summary comparison of the size distribution of permitted mines in
Alaska and the mines sampled.
Sample Collection, Preservation and Transportation
94
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GOLD PLACER MINE SUBCATEGORY SECT-V
Collection, preservation, and transportation of samples were
accomplished in accordance with procedures outlined in "Methods
for Chemical Analysis of Water and Wastes," EPA Report No. EPA/4-
79-020, March 1979, USEPA Environmental Monitoring and Support
Laboratory, Cincinnati, OH, Appendix III of "Sampling and
Analysis Procedures for Screening of Industrial Effluents for
Priority Pollutants" (published by the EPA Environmental
Monitoring and Support Laboratory, Cincinnati, Ohio, March 1977,
revised April 1977), "Sampling Screening Procedure for the
Measurement of Priority Pollutants" (published by the EPA
Effluent Guidelines Division, Washington, D.C., October 1976)
or other EPA-approyed procedures.
Samples were obtained from some or all of the following
locations:
o Intake water
o Influent to beneficiation process
o Influent to treatment
o Effluent from treatment
o 500 feet downstream of discharge into receiving
stream
All samples obtained were grab samples. In general, the
following types of samples were collected at each site:
1. Total suspended solids—sample filtered in the field
using preweighed glass fiber filters; filter weighed
subsequently in the laboratory;
2. Total metals—sample collected for determination of
total arsenic and mercury; preserved in the field with
1:1 HN03 to a pH less than 2;
3. Total recoverable metals—samples collected for
determination of total recoverable arsenic; preserved
in the field with five ml/1 concentrated nitric acid;
4. Dissolved metals—sample filtered through a 0.45 micron
filter; preserved with 1:1 HNO3 to a pH less than 2;
5. Acid Soluble Metals—Samples collected for
determination of acid soluble metals were acidified
with (1:1) nitric to a pH of 1.75+ 0.1 and allowed to
digest for approximately 16 hours - filtered using
0.45 um membrane filter before shipping to laboratory.
6. Settleable solids—determined immediately in the field
using an Imhoff cone;
7. Turbidity—sample analyzed in the field using a field
nephelometer (dilutions often necessary);
95
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GOLD PLACER MINE SUBCATEGORY SECT-V
8. pH and Temperature—analyzed in the field using a
calibrated pH meter and a thermometer.
Sample numbers, locations, dates, times, etc. were noted and a
sketch of the site and sample locations was prepared. Field
measurements of pH, temperature, turbidity, and settleable solids
were recorded.
All sample containers were labeled to indicate sample number,
sample site, sampling point, individual collecting the sample,
type of sample (influent, effluent, etc.), sampling dates and
times, preservative used (if any), etc.
All samples being sent for outside analysis were packed in
waterproof plastic foam-insulated chests which were used as
shipping containers. Sample shipments were made by air freight to
the laboratories as soon as possible.
WATER USE
Classification
Mines which employ classification (sizing or screening) of ore
prior to sluicing typically use less water than mines which do
not classify. Estimated water use rates for mines that use
classification and for mines using no classification are shown in
Table V-7 (p. Ill) for various levels of production. Average
water usage at mines employing classification methods (grizzlies,
screens, and trammels) is approximately 5.6 cubic meters of water
per cubic meter of ore (1,467 gal per cu yd). At mines using no
classification, the average water usage is 9.0 cubic meters of
water per cubic meter of ore (2,365 gal per cu yd).
Water Recycle and Recirculation Practices at Alaska Placer Gold
Mines
Recycle practices at various production levels were investigated.
It was determined for 1984 that some degree of recycle is
practiced at all mine sizes; however, approximately one-half
(50.7 percent) do not recycle any process wastewater. This
compares with the projected 60 percent that thought they might
use some recycle as stated on their Tri-agency permit
applications for 1985, 1986 and 1987.
Table V-8 (p. 112) lists the number of mines recycling
wastewater, grouped by production level and the amount of recycle
employed. Table V-9 (p. 113) lists the quantity of mines
practicing recycle by percentage. This information was obtained
from a computerized Summary of Tri-agency Forms compiled from
mines which submitted completed Tri-agency forms in 1984. These
forms are submitted by the miner prior to the mining season and
are an estimate of what the miner plans to do, not necessarily
what will actually be done. Table V-10 (p. 114) summarizes the
Alaskan gold placer industry by production level from information
submitted on Tri-agency forms.
96
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GOLD PLACER MINE SUBCATEGORY SECT-V
The larger mines are small in number but sluice approximately
one-third of the total volume of material. Based on production
levels above, 21.3 percent of the industry during 1984 is
achieving 90-100 percent recycle of the process wastewater.
Geographic Distribution of_ Mines Which Recycle
The geographic distribution of mines practicing some degree of
recycle was examined to determine if location played any
significant role in determination of recirculation practices.
Table V-ll (p. 114) summarizes the approximate percentage of
mines in each mining district and the corresponding percentage of
partial and total wastewater recycling operations for the 1984
season only. Based upon the analysis presented above, recycling
or recirculating of wastewater at gold placer mines in Alaska is
practiced in all major Alaskan mining districts. Many facilities
which recirculate do so because of limited water availability.
RAW WASTEWATER CHARACTERIZATION
The sampling programs previously described provided the data EPA
used to determine the presence and concentration of pollutants in
placer mining wastewater. In determining the characteristics of
raw gold placer mining wastewater, EPA relied primarily on the
1983, 1984, and 1986 data.
Below is a discussion, according to pollutant parameter, of the
existence and concentrations of pollutants found in raw gold
placer mine wastewater.
TSS
The parameters used to measure solids include total suspended
solids (TSS) and settleable solids (SS).
Total suspended solids (TSS) data in raw placer wastewater that
was used for development of limitations is listed in Table V-12
(p. 115). TSS data on raw effluent is a measure of all solids
including those solids that would be measured as settleable
solids. The subcategory average was rounded to 20,000 mg/1 TSS.
This average was used in all computations for this regulation,
including calculations of sludge volume accumulating in ponds and
metals removal estimates.
For each mine where more than one solids analysis was conducted
on the raw wastewater, the average of all individual analyses was
used as the value for that mine in computing the industry
average. Three mines, nos. 4922, 4998 and 5002, were not used to
compute the average. Mine 4922 was a dredging operation using
thaw field water in the dredge pond having TSS levels not
representative of the subcategory. Mine 5002 was conducting
hydraulicing operations for overburden removal and was not
sluicing at the time of sampling. Mine 4998 was operating
intermittently during the sampling period.
97
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'TO'-
GOLD PLACER MINE SUBCATEGORY SECT-V
Metals
The metals present in raw placer effluent are a naturally
occurring component of the soil. These metals were shown by the
data collected to be almost entirely in the solid form. The
preservation technique for total metals analysis mentioned
earlier in this section involves acid addition to the sample,
which solubilizes metals. Acid digestion further solubilizes
these metals. Individual mine and average values of total metal
for the 27 metals tested in 1986 in raw placer gold wastewater
are listed in Table V-15 (p. 118). Table 16 (p. 119) shows the
effluent levels measured for 41 trace identity.
The data presented on raw wastewater and wastewater after
chemically aided settling shows that most metals are removed to
near or below the detection limit. This is further confirmation
of the physical state of metals in gold placer mine wastewaters.
Other Measured Parameters
The water used in placer gold operations does not vary
appreciably in pH from source, through processing, to discharge.
The pH of waters measured was close to neutral at all sampling
locations. The temperature is also unaffected to any noticeable
extent. Turbidity is increased considerably due to solids
content; the turbidity of raw placer wastewater is such that
dilution is necessary to allow measurement with this light
scattering technique.
CHARACTERISTICS OF TREATED WASTEWATER
In determining the characteristics of treated gold placer mine
wastewater, EPA relied on data from the 1983, 1984, and 1986
studies. EPA found that earlier data collection efforts did not
always document the operating conditions of the treatment options
at the mine sites. The data used take into account the
maintenance, construction, and operation of treatment systems and
are considered representative of actual current operating
practices.
Below is a discussion, according to pollutant parameters, of the
existence and concentrations of pollutants found in treated gold
placer mine wastewater.
Toxic Organic Compounds
In 1984, samples of treated final effluent from ten mines were
analyzed for the presence of toxic organics. Table V-13 (p. 116)
lists the ten mines by code and shows that only two of the toxic
organics (methylene chloride and bis(2-ethylhexylphthalate) were
detected in the final effluents.
Metal Pollutants
98
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GOLD PLACER MINE SUBCATEGORY SECT-V
Table V-14 (p. 117) presents the results of analysis for the 13
toxic metals in samples taken from the final discharge of ten
Alaskan placer mines during 1984. During the 1986 Alaskan placer
mining season, the final discharge from eight mines were sampled.
Analyses were performed for 27 metals and 41 elements. Data
collected during the summer of 1986 were analyzed for use in
determining the effectiveness of metals concentration reduction
achieved by simple settling and by chemically aided settling.
The data were obtained in sampling efforts conducted at eight
different mines to obtain information on the settling
characteristics of certain pollutants in the wastewater. Data
from three of the mines were not used in the analysis for the
reasons stated previously. The operations of the mines from
which data were used are considered to be typical of gold placer
mining operations.
Influent and effluent concentration measurements were taken for
settleable solids, total suspended solids (TSS), and metals from
both simple settling tests and chemically aided settling tests.
A summary of the data collected and some analysis of these data
are presented in Figures V-l through V-3 (pages 126-128).
The final regulation is based on three hours of quiescent
settling which provides removal for the majority of contaminants.
A pond sized for 4 hours of detention time should provide
equivalent removal; the additional hour of detention time in the
pond is included to allow for non-ideal settling conditions due
to turbulence and end effects in flow patterns into and out of
the pond.
The metals data available for gold placer mining operations
consist of initial (raw waste) concentrations and concentrations
after 6 hours of settling. An estimation technique was developed
to estimate the metals concentration levels after 3 hours of tube
settling (which approximates 4 hours of pond detention time).
Since metals constitute a certain proportion of TSS, it is a
reasonable assumption that metals settle out of the wastewater in
a manner similar to TSS. Metals concentrations in the effluent
after 3 hours of settling were estimated based on the
corresponding TSS settling characteristics. The TSS
concentration data were fitted to a non-linear model containing
an exponential time-rate decay function. Settleable contaminants
would be expected to settle according to such a relationship.
Analysis of variance (ANOVA) procedures were performed to test
the assumption that the TSS data can be characterized by this
non-linear model. The ANOVA results indicate a good fit of the
TSS data to the non-linear model shown below. The methodology
for the estimation procedure is outlined below:
1. Fit the TSS data, mine by mine, to a non-linear equation of the
form:
A
A
TSS concentration - a e"rt + ft
where t - settling time (hours)
99
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GOLD PLACER MINE SUBCATEGORY SECT-V
and a, /9 and F are constant parameters estimated from the
data
A A
2. Using the "shape" parameter from the TSS curve, T , solve for /9
and a for each metal using the metals concentrations observed at
t-0 (initial) and t-6 (final, after six hours). This procedure
assumes that the curve describing the metals settling process has
the same general shape as the curve describing the TSS settling
process.
3. Using these estimated parameters calculate the estimated metal
concentration, on a mine by mine basis, after three hours of
settling by the equation:
/v
metal^ concentration - oc^ e""t + /?^
where t - time (hours) - 3 hours
and &i and 0^ are estimated constant parameters for metal^
A
and T is the "shape" parameter based on TSS data.
At four of the five mines used in the study, two settling tests
were performed at each of the four to determine the effectiveness
of chemically aided settling. In the additional tests, TSS
concentrations were not measured up to the full 6 hours. For
these four mines, the parameters were estimated using the data
pairs (TSS concentration and settling time) from both samples
together. Metals concentrations were also measured in the
additional samples. All the metals samples were analyzed for the
initial concentrations and again after the full 6 hours of
settling time. The parameters for the metals were estimated
using the average initial and 6-hour concentrations where two
samples were taken.
Averages were then taken for TSS across all mines for each of the
time intervals. These averages were then fit to the equation in
the same manner as the individual mines data. Estimates derived
for the parameters were then used to calculate the theoretical
concentrations at the specified time intervals.
Over the 3 years of gold placer mining data, the average influent
TSS concentration is approximately 20,000 mg/1. This 20,000 mg/1
average influent TSS concentration was used in the environmental
assessment and economic impact modeling studies. For the 1986
settling test data, the average influent TSS measurements were
lower - 14,436 mg/1 for the simple settling. The average initial
TSS concentration for the calculated 3-hour simple settling was
adjusted to 20,000 mg/1 to compensate for the lower influent TSS
concentration levels in the samples. This was done in order to
have a more adequate estimate of the overall effect of simple
100
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GOLD PLACER MINE SUBCATEGORY SECT-V
settling on gold placer mine discharges. Correspondingly, the
metals concentrations were adjusted proportionally to reflect the
higher initial TSS concentration. The adjustment to the initial
metals concentrations is given as follows:
20,000 mg/1 TSS
adjusted metals cone. = x actual metals cone.
actual TSS
The estimated TSS concentrations at each time interval based on
an influent TSS concentration of 20,000 mg/1 are displayed in
Tables V-17 and V-18 (pp. 120) as "CALCULATED BASED ON 20,000
mg/1 TSS". Metals concentrations after 3 hours' settling but
adjusted to an initial TSS concentration of 20,000 mg/1 are shown
in Table V-16 (p. 119) as the 3-hour settled column. Additional
data collected during the 1986 study but not in Table V16 are
shown in Table V23.
Solids
The results of data collected from the effluent of gold placer
mines (using existing treatment) during 1983-1986 are presented
in Table V-19 (p. 121).
Settling tests were conducted at several sites in Alaska during
1983, 1984 and 1986. Eight-inch-diameter settling tubes were
filled with raw wastewater and allowed to settle, simulating the
activity of a treatment pond. Under these quiescent settling
conditions, the largest portion of suspended and settleable
solids removal occurred during the first 2 to 3 hours of
settling.
In the 1984 Treatability Study, 24-hour simple settling tests
were performed on ten mines. The wastewater was sampled at 1 1/2
to 1 ft below the surface at 0, 1, 2, 3, 6 and 24 hours. As for
the 2-hour settling test, the solids in the supernatant would be
consistently less than indicated here because the water was
sampled well below the surface of the testing device. A
tabulation of TSS and SS concentrations for these time periods
for the ten mines is presented in Table V-20 (p. 122). The
results show a decrease in all parameters throughout the 24-hour
period; however, the 24-hour settling test results indicate that
the improvement from 3 hours to 24 hours is minimal.
In addition, the 1984 study of in place treatment revealed that
properly designed, operated, and maintained settling ponds will
remove very high percentages of pollutants associated with the
solids encountered in the wastewater from placer mines. An
evaluation of these ten existing treatment facilities tested in
1984 indicated that four of the mines should be deleted from the
data base: two of the mines selected had not maintained the ponds
and the ponds were filled with sludge causing short circuiting
and severely reduced detention, one mine had no point source
discharge because of recirculation and one mine had a unique and
unusual distribution of colloidal clays in the ore. Eliminating
the data from these four mines and averaging the analysis from
101
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GOLD PLACER MINE SUBCATEGORY SECT-V
the remaining six mines resulted in the averages listed in Table
V-21 (p. 123).
Settling tests over 3 hours in duration were conducted at 17
mines during 1984 and 1986. The settleable solids content of the
wastewater from these mines after 3 hours of quiescent settling
is shown in Table V-22 (p. 124). The 1986 data collected for TSS
in settling tests is presented in Table V-17 (p. 120). Additional
settling beyond 3 hours, while ensuring removal of any residual
settleable solids, does not greatly alter the removal of
suspended solids from the wastewater. Based on the data obtained
in pilot settling tests, engineering requirements and experience
for design and construction of actual field installations, an
additional hour of settling time (i.e., 3-hour settling test vs.
4-hour field design) would be required to compensate for flow
velocity changes in the pond.
The average TSS level in raw gold placer gold mine wastewater was
determined to be 20,000 mg/1. To evaluate the effectiveness of
simple settling and chemical aided treatment technologies, the
TSS concentration data from Table V-13 (p. 116) were fitted to a
nonlinear model containing an exponential time rate decay
function. The nonlinear model was used to predict the
concentrations of solids that would be present in average gold
placer mine wastewater following 3 hours of simple settling.
These results are presented in Table V-16 (p. 119). Three hours
of simple settling on wastewater containing 20,000 mg/1 TSS is
predicted to result in an effluent containing 1670 mg/1 TSS.
Coagulation and Flocculation
Settling tests performed in Alaska during the 1983 mining season
demonstrated that polyelectrolytes had a potential as a method to
treat gold placer mining wastewater and the 1984 and 1986 Alaskan
field tests confirmed the chemical viability of treating gold
placer mining wastewaters with polyelectrolyte. The 1984
Treatability Study testing program was designed to determine the
quality of water discharging from ponds at various detention
times and determine the optimum dosage of polyelectrolyte
required for optimum treatment.
A combination of polymers in many instances proved more effective
in reducing the contaminant levels than application of a single
polymer. These tests are not all inclusive but offer a
comparison between simple settling and flocculent-assisted
settling.
The 1986 testing program was utilized to extend the data base
into Alaskan gold placer mining areas where testing was not
performed previously. Table V-16 (p. 119) presents a summary of
the 1986 results after 6 hours of chemically aided settling.
The conclusions of the 1986 Treatability Study showed that, in
general, a dosage of about 3.5 mg/1 of polyelectrolyte was
optimum. At times a combination of polymers was more effective
102
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GOLD PLACER MINE SUBCATEGORY SECT-V
in reducing the contaminant levels. While these tests are
empirical, they do offer a comparison between simple settling and
chemically assisted settling.
At the site operating by hydraulically stripping overburden the
polymers available at the site for testing did not perform
satisfactorily. This site also has very poor simple settling
characteristics. The results of these tests confirm the
conclusions made during the 1983 and 1984 studies that
considerable reduction in solids can be achieved by chemically
aided settling and that metals are in suspension and would be
removed incidentally with the removal of suspended solids. It
further supports EPA's belief that simple settling facilities
designed, constructed, and operated as outlined in this section
can consistently attain less than 0.2 ml/1 settleable solids.
103
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Table V-l. Principal Studies Relied Upon in the Development of Effluent Limitations
for Gold Placer Mining
Study Title (Code Name)
Purpose and Number of Sites Visited
Year
1984 Treatability Study
(1984-A)
Method Detection Limit Study
(1985-A)
1983, 1984, 1986 Treatability
Studies
Fine Gold
Recovery Study (1984-B)
1984 Wastewater Treatability
Project (1984-E)
Fine Gold
Recovery Study (1986-C)
1986 Treatability Study
Study (1986-A)
(20)
Engineering site visits to obtain
obtain economic and operational data,
wastewater sampling, and treatability
studies
(10)
Sample visits to determine settleable
solids detection limits
(24)
Test simple and flocculent-aided
settling
Pilot-scale study to determine fine
gold recovery
(2)
Coagulation-flocculation treatability
study
Pilot-scale study to determine fine
gold recovery
(5)
Process and effluent water sampling
and chemically aided treatability
studies
1984
1985
1983, 1984,
1986
1984
1984
1986
1986
§
f
O
w
S
H
W
W
G
dd
e
CO
w
o
-------
GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-2. Gold Placer Mine Studies - 1976-1986
Study
Code
1986-A
1986-B
1985-A
1985-B
1986-C
1984-A
1984-B
1984-C
1984-D
1984-E
1983-A
1976
1979-A
1977
1979-B
1982-A
1982-B
1983-B
1981-A
Study Title, Author, and Date Reference
EPA/KRE Treatability Study, 1986
EPA/CENTEC Full-scale Flocculant Study, 1986
EPA/KRE Method Detection Limit Study, 1985
Canadian Dept. of Environment - 1985 Placer
Study
EPA/L.A. Peterson and Associates Fine Gold
Recovery, September 1986
EPA/KRE Treatability Study - 1984
EPA/Peterson Pilot Scale Sluice Study - 1984
EPA Region X - 1984 Study
EPA/FTA Study - 1984 (Lower 48)
Shannon and Wilson - 1984 Wastewater Treatment
Technology Project
EPA/FTA and KRE - 1983 Treatability Studies
Dames and Moore - 1976 Study
Calspan Corp. - 1979 Study
EPA/NEIC - 1977 Study
ADEC - 1977, 1978, 1979 Reports
R&M Consultants - 1982 Treatability Study, Site
Visits, and Pond Design Manual (for ADEC)
EPA Region X - 1982 Study
EPA Region X - 1983 Study
Canadian Dept. of Environment - 1981 Yukon
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1983-C
NOTE: See
and
Study 19
Canadian Dept. of Environment - 1983 Yukon
Study 20
Section XV for full designation of contractors
other Contributors to this document.
105
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-3. Facilities Visited in the Sampling Effort
(Continued)
Study Code (See Table V-2)
1983-B 1982-B 1983-A1 1983-A2 1984-D 1984-A 1984-C 1985-A 1986-A
Mine Code
4235
4236
4237
4239
4240
4241
4242
4243
4244
4245
4247
4248
4249
4250
4251
4252
4253
4254
4255
4260
4262
4975
4978
4988
4998
4999
5000
5001
5002
5003
5004
X
X
X X
X
X
X
X
X X
X X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
106
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-3.
Mine Code
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4216
4217
4219
4222
4223
4224
4225
4226
4227
4229
4230
4231
4232
4233
4234
Facilities Visited in the Sampling Effort
(Continued)
Study Code (See Table V-2)
1983-B 1982-B 1983-AJ 1983-A2 1984-D 1984-A 1984-C 1985-A 1986-A
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
107
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-3. Facilities Visited in the Sampling Effort
Study Code (See Table V-2)
Mine Code
4107
4109
4110
4126
4127
4132
4133
4134
4138
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1983-B
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1982-B 1983-A1 1983-A2 1984-D 1984-A 1984-C 1985-A 1986-A
X
X X
X
X
X
X
X
X
X XX
X
X
X X
X XX
X
X
X
X
X
X X
X
X
X
X X
X
X
X
X X
X X
X
X
X
108
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GOLD PLACER MINE SUBCATEGORY SECT-V
Table V-4. Sample Parameters Analyzed
Parameter 1983-B 1983-A1 1983-A2 1984-A 1984-C 1985-A 1986-A
pH
TSS
Set. Solids
Turbidity
Total As
Oiss. As
Acid Sol. Hg
Tot. Rec. As
Tot. Hg
Oiss. Hg
Acid Sol. As
Spec. Gravity
Prior. Organ.
Temperature
IFB Metals
•^^^^^^^
X
X
X
X
X
X
—
X
**
* *
—
X
—
X
__
X XX
X XX
X XX X
X XX
X XX
X X
—
X X
X XX
X
—
—
x
X XX
__ _-. — — — —
X X
X X
X X
X X
X
—
X
—
X
— --
X
— --
— —
X X
X
Trace Elements
Analysis
109
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GOLD PLACER MINE SUBCATEGORY SECT-V
Table V-5. EPA Chemical Analysis Methods
Parameter EPA Method
pH 150.1
TSS 160.2
Sett. Solids 160.5
Temperature 170.1
Turbidity 180.1
Acid Soluable Metals 200.1
Trace Elements Analysis 200
Priority Organics 1618, 1624
1625
Mercury 245
Arsenic 206
Antimony 204
Selenium 270
Silver 272
Thallium 279
Other Metals 200
Table V-6. Size Distribution of Permitted Mines in Alaska
Permitted Sampled
Size* Mines Mines**
100-750 cu.yd./day 87% 48%
750-3500 cu.yd./day 20% 44%
>3500 cu.yd./day 3% 7%
Mean Capacity (yd3/day) 756 1170
Mean Employment (persons) 4.3 6.0
*Sluicing capacity used for this study:
**Applies to EPA 1983 Region X sampling only
110
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-7. Evaluation of Water Usage Sluicing Operation
Alaskan Gold Placer Mines (1984-1986)
Average
All Mines
All mines with classification
All mines without classification
Mines with production >1,500 to
<70,000 cu yd/yr all mines
Mines with production >1,500 to
<70,000 cu yd/yr with classification
Mines with production >1,500 to
<70,000 cu yd/yr without
classification
Mines with production 70,000 to
<230,000 cu yd/yr all mines
Mines with production 70,000 to
<230,000 cu yd/yr with classification
Mines with production 70,000 to
<230,000 cu yd/yr without
classification
Mines with production 230,000 and
greater cu yd/yr all mines
Mines with production 230,000 and
greater cu yd/yr with classification
Mines with production 230,000 and
greater cu yd/yr without
classification
2630
2132
3260
2223
1806
2219
3207
2272
4890
3500
3800
3350
gal/cu yd
1864
1467
2365
2319
1962
2631
1442
993
2250
1487
1280
1590
Source: Ref. 27
111
-------
Table V-8. Recycle of Wastewater at Alaskan Gold Placer Mines
Volume of Ore Sluiced Per day (cu yds/day)
;.«*'"..'"
Recycle
Percent
0
1-24
25-49
50-74
75-89
90-99
100
Total
No. of
Mines
95
4
6
23
8
8
38
182
<1000
Percent of
Mines
42.6
1.8
2.7
10.3
3.6
3.6
17.0
81.6
1000
No. of
Mines
14
1
5
5
0
1
3
29
to 2500
Percent of
Mines
6.3
0.4
2.2
0
0.4
0.7
1.4
12.9
>2500
No. of Percent of
Mines Mines
4 1.8
0 0
2 0.9
3 1.4
0 0
0 0
3 1.4
12 5.5
O
O
D
•u
£
o
3
M
Z
w
CO
a
CO
0
M
a
o
50
K
cn
M
O
Source: Ref. 15
-------
U)
Table V-9. Recycle of Wastewater at Alaskan Gold Placer Mines
Expressed by Production - 1984
Volume of Ore Sluiced Per day (yd3/day)
Total
57,415
34.5
49,900
129.9
59,450
35.6
a
<1000
Recycle
Percent
0
1-24
25-49
50-74
75-89
90-99
100
No. of
yd 3 /day
24,070
690
2,510
11,040
3,240
4,620
11,245
Percent of
Mines
14.4
, 0.4
1.5
6.6
1 2.0
2.8
6.8
1000
No. of
yd3/day
23,800
1,500
9,000
9,700
0
1,200
4,700
to 2500
Percent of
Mines
14.3
0.9
5.4
5.8
0
0.7
2.8 *
>2500
No. of Percent of
yd3/day Mines
13,600 8.1
0 0
11,000 6.6
21,050 12.6
0 0
0 0
13,800 8.3
O
PLACER MINE SU
n
w
O
O
K
w
M
n
Source: Ref. 15
-------
GOLD PLACER MINE SUBCATEGORY SECT-V
Table V-10. Summary of Alaskan Gold Placer Industry by
Production (from Tri-agency Data)
<1000 (gpm) 1000 to 2500 (gpm) >2500 (gpm)
Mines 81.6% 13.0% 5.4%
Production 34.5% 29.9% 35.6%
Table V-ll. Amount of Mines Per Mining District Recycling
in Alaska (1984)
Percentage of Percentage of
Mining District Mines Recycling Mining Operations
Circle 15.4 17.5
Fairbanks 26.4 24.2
Forty Mile 7.3 7.2
Hot Springs 1.8 1.3
Iditarod 0.0 0.9
Innok 0.9 0.0
Koyukuk 6.4 6.3
Kuskikwin 3.6 2.3
Seward 2.7 4.6
Seward Peninsula 6.4 4.0
Other Districts 29.1 30.9
Source: Ref. 15
114
-------
GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-12,
Summary of Process Discharge Raw Effluent
TSS Concentrations (mg/1)
(Data, 1983 - 1986)
Mine
Numbe r
4900
4901
4903
4904
4906
4907
4909
4919
4920
4921
4922
4923
4928
4931
4933
4941
4943
4944
4963
4975
4978
4980
4985
4987
4988
4995
4998
4999
5000
5001
5002
5003
5004
TOTAL
w/o 4922
w/o 5002
w/o 4922 &
5002
Number
of
Analyses Total
15
3
4
5
7
1
1
7
8
4
5
4
4
3
1
9
4
4
7
1
1
12
5
6
1
7
5
5
5
4
3
5
5
N
161
156
158
153
234520
33400
17215
186240
108876
10460
6920
124647
185978
32780
220520
14562
51628
8520
48910
196383
43932
23652
53810
5780
30470
399056
101986
279841
74440
426633
94313
26992
25278
19082
367630
110985
104555
SUM
3669994
3449474
3302364
3081844
Standard
Average Deviation
15635
11133
4304
37248
15554
10460
6920
17807
23247
8195
44104
3641
12907
2840
48910
21820
10983
5913
7687
5780
30470
33255
20397
46640
74440
60948
18863
5398
5056
4771
122543
22197
20911
E ( AVG ) SD ( AVG )
23666 24696
23027 24809
20576 17717
19817 17481
3837
613
4285
5777
7692
0
0
10743
18365
2115
10667
3891
2296
0
0
14425
139
1319
1868
0
0
21649
8982
13560
0
17693
16162
4243
3151
1768
55376
14170
14489
E(VAR)
7857
7769
6372
6233
115
-------
GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-13. Priority Organics Detected in the 1984 EPA
Study
Mines Sampled
(Listed by Code)
4249
4173
4247
4169
4248
4180
4244
4250
4251
4252
Pollutant Detected
Methylene Chloride
Methylene Chloride
Methylene chloride
Bis(2-ethylhexylJphthalate
None
None
None
None
None
None
None
Concentration
(mg/1)
0.022
0.023
0.017
0.068
116
-------
Table V-14. Priority Metals Sampling Results from Gold Placer Mines
Final Effluents - 1984 Sanpling
Mine
Code
4180
4180
4173
4173
4250
4250
4251
4251
4247
4247
4252
4252
4169
4169
4244
4248
4248
4249
4249
Avgs*
TSS
773
773
3,515
3,515
425
425
1,431
1,431
619
619
-
3,360
3,360
1,175
178
178
117
1,158
Ag
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
0.01
As
0.275
0.412
0.066
0.072
0.168
0.167
0.004
0.064
0.075
0.032
0.009
0.004
0.220
0.220
0.085
0.110
0.120
0.078
0.077
0.119
Be
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.02
0.02
<0.01
<0.01
<0.01
<0.01
<0.01
0.007
Cd
0.01
0.02
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.05
0.02
<0.01
<0.01
0.08
0.08
0.03
0.01
<0.01
<0.01
<0.01
0.019
Concentration (mg/1)
Cr Cu Hg Ni
0.09
0.13
0.09
0.08
<0.05
0.09
0.08
0.09
0.35
0.10
<0.05
<0.05
0.56
0.48
0.23
0.22
0.25
0.06
0.06
0.160
0.15
0.30
0.08
0.09
0.04
0.09
0.10
0.11
0.49
0.27
0.05
0.05
0.52
0.45
0.14
0.14
0.14
0.05
0.06
0.175
<0.0005 0.16
0.0007 0.24
<0.0005 <0.10
0.0006 0.12
<0.0005 <0.1
<0.0005 <0.1
<0.0005 <0.10
<0.0005 <0.10
0.0009 0.38
0.0008 0.11
<0.0005 <0.1
0.0050 <0.1
0.0005 1.06
0.0006 0.40
<0.0005 <0.10
0.0011 0.38
0.0009 0.36
<0.0005 0.12
<0.0005 <0.10
0.0008 0.20
Pb
0.075
0.155
0.028
0.032
0.006
0.006
0.007
0.056
0.150
0.080
0.016
0.018
0.230
0.195
0.27
0.019
0.021
0.011
0.013
0.073
Se
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
<0.005
0.0025
Zn
0.12
0.26
0.08
0.09
<0.02
0.07
0.08
0.15
0.89
0.33
0.03
0.04
0.90
0.78
0.29
0.26
0.28
0.02
0.03
0.25
Sb
0.005
0.002
<0.002
<0.002
0.015
0.015
0.011
0.034
0.002
0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.005
Tl
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
<0.002
0.004
0.004
<0.002
<0.002
<0.002
<0.002
<0.002
0.001
o
o
f
D
PLACER
3
M
Z
M
cn
a
CO
0
(-3
O
K
cn
M
0
(-3
1
*Averages for numbers listed as "less than" «) are calculated using 1/2 their
value. (For example <.01 = .005 for averaging purposes.)
-------
TABLE V-15
SETTLING AND CHEMICAL ANALYSIS DATA FOR FIVE MINES - 1986
(mg/1)
00
RAW WASTE
Property] 4999 |
Al
Sb
As
Ba
Be
B
Cd
Ca
Cr
Co
Cu
166.000|
0.304]
0. 247]
5.040]
0.008 |
0.560]
0. 109]
89.000]
0.293]
0.269]
1.210]
Fe |366.000|
Pb
Mg
0.327]
6.000]
Mn | 12.800]
Hg | 0.0036]
Mo
0.050]
Ni | 0.267]
Se | 0.005]
Ag I 0.0018]
Na
5.640]
Tl | 0.005]
Sn
Ti
0.050|
4.980]
V | 0.681 I
Y | 0. 165]
Zn
1.080 I
TSS | 10700 I
5000 |
50.900]
0.050]
0.026]
0.808]
0.0025]
0.050]
0.037]
23.200]
0.114]
0.078 |
0. 147]
106.000]
0. 100]
31 .000]
5. 190]
0.0007]
0.050]
0. 143|
0.005]
0.0005]
3.240]
0.005]
0.050|
0.423]
0. 127]
0.025]
0.352 |
3590 |
Mi ne No
5001 |
50.200]
0.207 I
0.057]
1.010]
0.0025]
0.121 |
0.060]
58.300]
0.088]
0. 130]
0.520]
180.000]
0. 100]
32.800]
3.740]
0.0004]
0.050]
0. 167]
0.005]
0.0005]
4.240|
0.005]
0.050|
0.447 |
0.258]
0.070]
0.565 |
4870 |
DATA
5003 |
84.800]
0.332|
0.037]
4.000]
0.0025]
0.050]
0.080J
1560.00]
1 SIMPLE SETTLING
5004
526.870
0.991
Average
175
0
0.275] 0
4.660] 3
0.033
0.
0.080] 0
0.266] 0
1730.00|692
0.131] 0 .584] 0
0.321 |
0.329]
140.000|
0. 100]
108.000]
28.700]
0.0012]
0.050]
0.664]
0.005]
0.0028 |
17.000]
0.005]
0. 148|
0. 100]
0.056]
0.289]
0.519 I
15100 |
1 .840] 0
1 .330
0
683. 000] 295
2.110
0
258.000] 87
88.700
0.0090
0.256
27
0
0
3.540| 0
0.005] 0
0.0116
7.820
0
7
0.005] 0
0.356| 0
0.281
0. 100
1
0
1 . 100] 0
2.820
37928
.580
.377
. 128
. 104
0097
.316
. 1 10
. 100
.242
.528
.707
.000
.547
. 160
.826
.003
.091
.952
.005
.003
.588
.005
. 131
.252
. 244
.330
1 .067
14436
6 Hour
Average
26.870
0.078
0.082
0.550
0.0025
0.217
0.022
40.000
0.061
0.043
0. 176
126.494
0. 123
19.510
1 .441
0.0008
0.050
0.057
0.005
0.0009
6.332
0.005
0.050
1 .004
0. 127
0.032
0. 164
914
Initial
Calc'td
316.536
0.679
0.231
5.595
0.017
0.570
0. 199
1247.719
0.436
0.951
1 .275
531 .826
0.987
157. 132
50. 165
3 Hour
Calc'td
33. 193
0.089
0.085
0.663
0.0029
0.224
0.025
56.752
0.069
0.063
0. 198
133.955
0. 145
21.913
2.414
0.0054] 0.0009
0. 164
1.717
0.009
0.006
13.680
0.009
0.236
2.257
0 .441
0.595
1 .924
20000
0.052
0.081
0.005
0.001
6.413
0.005
0.053
CHEM AID
6 Hour
Average
0.581
0.050
0.010
0.050
0.025
0.050
0.005
33.850
0.025
0.025
0.013
0.909
0. 100
6.113
0. 199
0.0004
0.050
0.020
0.005
0.005
6.685
0.005
0.050
1 .027 0.041
0.132 0.025
0.044 0.025
0.201 0.014
1670 9
NOTES: Raw waste data is directly from simple settling tests. Average data is linear
average of values recorded in tests. Initial and three hour calculated data is
calculated as described in the text of this Section and has been normalized to 20,000
mg/1 TSS in the raw waste.
o
o
f
o
f
o
V
3
M
ra
w
a
ro
o
o
o
V
K
to
ra
o
-------
o
o
_Table_ V-16
50
METALS SAMPLING RESULTS FROM PLACER GOLD MINES FINAL EFFLUENT
1986 ALASKAN PLACER MINING STUDY £
M
Z
W
3
5
TRACE ELEMENTS ANALYSIS
50
MINE
NUMBER
4922
4998
4999
5000
5001
5002
5004
NOTES
Au Bi
ND ND
ND DET
ND ND
ND ND
ND ND
ND ND
ND ND
Ce
DET
ND
DET
DET
DET
DET
DET
Dy
ND
<10(
ND
ND
ND
ND
ND
Er
ND
) ND
<100
ND
<100
ND
ND
Eu
ND
ND
ND
ND
ND
ND
ND
Ga
ND
ND
ND
ND
ND
ND
ND
Gd
ND
ND
ND
ND
ND
ND
ND
Ge
<500
ND
ND
ND
ND
ND
ND
Hf Ho
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
ND ND
I
ND
ND
<1000
ND
ND
ND
ND
In Ir La Li Lu Nb Nd Os P Pd Pr Pt Re Rh Ru S Sc Si Sm Sr Ta Tb Te Th Tm U W Yb Zr
ND ND ND ND ND ND ND <200 DET ND ND ND ND ND <500 DET ND DET ND ND ND ND ND ND ND ND ND ND ND
ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND DET ND ND ND ND ND ND ND ND ND ND ND ND ND
ND ND ND ND ND ND ND <200 DET ND ND ND ND ND <500 DET ND DET ND ND ND ND ND ND ND ND ND ND ND
ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND DET ND DET ND ND ND ND ND ND ND ND ND ND ND
ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND DET ND DET ND ND ND ND ND ND ND ND ND ND ND
ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND DET ND DET ND ND ND ND ND ND ND ND ND ND ND
ND ND ND ND ND ND ND ND ND BD ND ND ND ND ND DET ND DET ND ND ND ND ND ND ND ND ND ND ND
All Values in ug/1 H
ND - Not Detected O
DET - Element Metal possible present but of a value not definable H
T - Total Metals L
A - Acid Soluable Metals • ^
-------
Table V-17. TSS Concentration Levels After Simple Settling
Mine Test
Number Number
4999
5000
5001
5003
5004
Average
5
9
13
22
26
14436
4671
Total Suspended Solids (mg/1)
Time (hrs)
0
10700
3590
4870
15100
37920
1
5400
1670
1905
150
14230
2
4500
1260
1176
63
102
3
4210
1050
1084
59
92
4
3690
868
936
32
88
5
3420
848
852
34
53
6
2920
828
757
28
39
1420
1299
1123
1041
914
o
O
o
M
NJ
O
Calculated Based
on 20,000 mg/1 TSS
20000
4472
1868
1167
1008
962
950
Table V-18. TSS Concentration Levels After Chemically Aided Settling
z
M
CO
a
03
o
5
M
O
O
Mine Test
Number Number
4999
4999
5000
5001
5003
5004
6
7
10
14
23
28
Totally Suspended Solids (mg/1)
Time (hrs)
0
3840
869
3060
5930
43100
12000
0.5
40
36
41
30
113
62
1
27
23
24
26
22
20
2
27
23
22
17
20
14
3
26
21
12
8
10
4
23
18
12
9
5
5
23
11
8
6
6
24
8
2
3
en
M
O
Average
15840
49
23.8 20
18.4 18
12
9.3
-------
GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-19
Mine No,
4903
4941
4943
4928
4921
4904
4923
4931
4901
4920
4944
4987
4906
4941
4919
4995
4985
4920
4963
4900
4904
4907
4980
4989
4909
4988
4922
4998
4999
5000
5001
5002
5003
5004
Alaska Sampling Data Gold Placer Mine
Discharges, 1983-1986
TSS (Average)
(mg/1)
12
3480
16
1251
953
6505
28
175
650
2800
1304
315
3288
3137
819
173
1111
8440
678
4025
124
3850
896
100
266
252
1433
600
2213
22
193
71
50
4
121
-------
GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-20. 1984 24-hour Simple Settling
Test: Solids Concentrations at Various Detention
Times
Settling
Time-Hours
Settleable
Solids ml/1
Suspended Solids
mg/1
0
1
2
3
6
Range
Average
Range
Average
Range
Average
Range
Average
Range
Average
3.2 to 125
47.
0.2
1.
0 to
0.
0 to
0.
0 to
0.
3
to
75
1.
47
0.
16
0.
05
6
0
4
1
5,580 to
27,
400 to
6,
183 to
5,
116 to
4,
29 to
3,
51
000
11
600
12
200
12
900
12
900
,413
,825
,320
,700
,000
24 Range
Average
0 to <0.1
19 to 9,120
2,800
Turbidity
NTU
2,016 to 34,560
20,000
603 to 21,600
10,000
281 to 32,000
11,300
128 to 30,240
9,950
38 to 35,280
9,650
27 to 25,200
7,700
122
-------
OJ
Table V-21. EPA Treatability Study
Values for 6 Mines
Water Supply
Settleable
Solids (ml/1)
TSS (mg/1)
Turbidity
(ntu)
Arsenic
(mg/1)
Mercury
(mg/1)
Min.
0
26.5
4.7
0.0080
<0.0005
Max.
0.28
743
805.5
0.2220
0.0017
Avg.
<0.2
303
330
0.0915
0.0006
- 1984
Sluice Discharge
Min.
5.9
8,699
6,975
0.3065
<0.0005
Max.
148.8
66,639
43,440
2.4
0.0030
Avg.
48.2
28,589
22,258
0.8058
0.0012
Final Effluent
Min.
0
173
129
0.0045
<0.0005
Max.
<0.2
4,025
11,610
0.3760
<0.0015
Avg.
<0.2
1,550
2,968
0.2290
0.0006
§
IT1
o
IT1
s
M
V
3
Z
M
CO
a
£
w
0
?<
Note: For all raw data listed at less than the detection limit a 1/2 value of the detection
limit was used for the averages including values for zero and trace.
CO
M
O
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Table V-22
Mine No.
4900
4906
4919
4920
4941
4963
4985
4987
4995
4904
4980
4922
4998
4999
5000
5001
5002
5003
5004
Total Suspended and Settleable Solids Tests
1984 and 1986 (3 hours of Quiescent Settling)
TSS (mg/1)
1984
10,110
4,270
4,791
8,520
7,441
1,715
131
3,970
15,380
2,040
4,207
1,050
1,084
41,700
59
92
SS (ml/1)
0.2
0.3
0.4
<0.2
0.4
0.1
TR
<0.1
TR
0.51
0.2
TR
•TR
TR
l.O2
TR
TR
TR = Trace
•"•Sample was taken from dredge pond
At the time of sampling, mine was hydraulicking overburden, not
sluicing ore
124
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Table V-23. EPA Treatability Study - 1986
O
O
tr1
D
Average (6 mines using sluice boxes)
Water
Supply
NJ
Ul
Settleable Solids (ml/1)
T.S.S. (mg/1)
Turbidity (NTU)
Total Arsenic (mg/1)
Acid Soluble Arsenic (mg/1)
Total Mercury (mg/1)
Acid Soluble Mercury (mg/1)
Processor
Recirc. Water
Trace
28
43
<20
<20
<0.2
<0.2
<0.1
35
50
27
<20
<0.2
<0.2
Process
Effluent
58
9790
10,630
76
24
1.1
<0.2
Final Pond
Effluent
610
1290
42
24
0.9
<0.2
td
2
fd
en
a
tc
o
O
§
K
CO
M
O
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Figure V-l
GOLD PLACER MINING
Settleable Solids
SS
ml/1
60
50
4Q
30
20
10
Simple Settling
Chemically Assisted Settling
234
Settling Time - Hours
i
6
Settling Time
(Hours)
0
1.0
2.0
3.0
4.0
5.0
6.0
Average of 1984 and 1986 Data
SS - (ml/1)
Simple Settling
60.6
2.2
0.5
0.15
0.10
Trace
Trace
Chemically Asstd. Settling
60.6
Trace
0
0
0
0
0
126
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GOLD PLACER MINE SUBCATEGORY
SECT-V
TSS
mg/1
24,000_
20,000_
16,000_
12,000_
8,000_
4,000_
Figure V-2
GOLD PLACER MINING
Total Suspended Solids
-Simple Settling
Chemically Assisted Settling
1
0
1
1
1
1
2
i
3
i
i
4
i
5
i
i
6
Settling Time - Hours
1986 DATA
Settling Time
(Hours)
0
0.25
0.50
1.0
2.0
3.0
4.0
5.0
6.0
TSS - (mg/1)
Simple Settling
20,000
7,512
3,176
1,670
1,147
966
903
Chemically Asstd. Settling
20,000
96
21
21
21
21
21
21
21
127
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GOLD PLACER MINE SUBCATEGORY
SECT-V
Figure V-3
GOLD PLACER MINING
Typical Toxic Metal Removal
1200_
Concentration
rag/1
1000
800
600
400
200
Total Metal Remaining After Simple Settling
0
234
Settling Time - Hours
I
6
1986 DATA
SettlingTime
(Hours)
0
3.0
6.0
Arsenic
128
94
82
Copper
707
247
176
Zinc
1067
293
164
128
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GOLD PLACER MINE SUBCATEGORY SECT - VI
SECTION VI
SELECTION OF POLLUTANT PARAMETERS
The Agency has studied placer mining wastewaters as well as other
ore mining and dressing wastewaters to determine the presence or
absence of toxic, conventional, and nonconventional pollutants.
According to the requirements of the Clean Water Act of 1977
(CWA), 129 toxic pollutants are to be studied in the formulation
of these limitations and standards (see Section 307 (a)(l), Table
1 of the Act).
EPA conducted sampling and analysis at facilities which
represented a wide range of locations, operating conditions,
processes, water use rates, topography, production rates, and
treatment technologies (settling ponds—single or multiple;
recycle and recirculation). The quantities and treatability of
pollutants in these treated wastewaters form the basis for
selection of pollutant parameter for regulation.
The Administrator is required by the CWA to consider the
regulation of all toxic pollutants and categories of pollutants
listed under Section 307 but is not specifically required to
regulate any of them.
The criteria used for exclusion of pollutants from regulation in
this subcategory are summarized below:
1. The pollutant is not detectable in effluents within the
subcategory by approved analytical methods representing
state-of-the-art capabilities.
2. The pollutant is detected in only a small number of
sources within the category and is uniquely related to
only those sources.
3. The pollutant is present in only trace amounts and is
neither causing nor likely to cause toxic effects.
4. The pollutant is present in amounts too small to be
effectively reduced by technologies applicable to this
subcategory.
5. The pollutant is effectively controlled by the
technologies upon which are based other effluent
limitations and standards.
SELECTED POLLUTANT PARAMETER
EPA has selected settleable solids (SS) as the only directly
regulated parameter for effluent discharge from gold placer
129
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GOLD PLACER MINE SUBCATEGORY SECT - VI
»•
mines. The reelrculation of process water and the removal of
settleable solids in any waters discharged from the mines will
adequately control all pollutants found in effluents from this
subcategory. These pollutants include metals which are removed
with the solids and turbidity which is reduced when solids are
reduced. Settleable solids has been selected as the regulated
parameter to best control solids because the most stringent
demonstrated technology for this subcategory, simple settling,
provides reliable removal of SS. The removal of TSS and
incidental removal of metals and turbidity by this technology^! is
highly variable and does not produce a consistent enough database
on which to base an effluent limitations and standards. ; ;
-_' «;..'- „, ' '•• , ,1
TOXIC POLLUTANTS
Organic Pollutants
The toxic organic compounds generally are not naturally
associated with metal ores. On the basis of the study of the
entire ore mining and dressing category in the United States, EPA
excluded 114 of the toxic organic pollutants during the 1982 BAT
rulemaking for, the category. No information has been developed
during the course of these studies or provided to EPA by the
public which indicates that any of the organic priority
pollutants are present in amounts that are treatable. In
addition, organic reagents are not used in this subcategory
because it relies on gravity separation methods to extract cfbld
from the ore. Therefore, organic pollutants were not expected to-
be present in the wastewater from gold placer mining operations.
Screening analysis was performed to confirm this assumption.
In 1984, samples for the toxic organics were collected and
analyzed. Treated final effluent samples from ten mines were
analyzed for the presence of toxic organics (see Table V-15, p.
118). Two of the toxic organics (methylene chloride and
bis(ethylhexyl)phthalate) were detected in the final effluent of
placer mining operations.
In the sampling for the toxic organics, 117 toxic organics were
not detected and therefore were excluded from further
consideration based on Criterion 1 above. The particular
organics detected are not known to exist in natural ore
formations and their presence is questioned. Additionally, these
organics occur in organics analysis laboratories (methylene
chloride) and in some sampling equipment. This leads to the
belief that they may be artifacts of the laboratory and sampling
procedures rather than pollutants existing in the subcategory.
Moreover, the two toxic organics detected also could have been
excluded based on Criteria 3 and 4.
The gold placer mining subcategory does not , use reagents or
chemicals for the processing of gold from ore. All processing
relies on physical or gravity separation, so any contaminants or
pollutants present generally would originate from the ore. Oil
and grease could be present, in some instances, from hydraulic
130
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GOLD PLACER MINE SUBCATEGORY SECT - VI
fluids or fuels; however, in most cases good housekeeping
practices will control this parameter. Therefore, based on data
available for the ore mining category as a whole and knowledge of
the processes and ores used in gold placer mining, the Agency
will not further consider the regulation of toxic organic
pollutants for this subcategory.
Metal Pollutants
Data on the presence of metals in treated effluent are shown in
Table V-15 (p. 118). The toxic metals are excluded from
regulation based on Criteria 3, 4 and 5, 6, and 7. However,
because of the frequent occurrence of arsenic and the cumulative
effects of mercury, these two metals are discussed further below.
Arsenic
Arsenic is a normal constituent of most soils, with
concentrations ranging up to 500 mg/kg. It occurs mostly in the
form of arsenites of metals or as arsenopyrite (FeS2.FeAs2).
Arsenic is known to be present in many complex metal ores—
particularly, the sulfide ores of cobalt, nickel and other
ferroalloy ores, antimony, lead, gold and silver. It may also be
solubilized in mining and milling by oxidation of the ore and
appear in the effluent stream.
The chemistry of arsenic in water is complex and the form present
in solution is dependent upon such environmental conditions as
pH, organic content, suspended solids, and sediment. The
relative toxicities of the various forms of arsenic apparently
vary from species to species. For inorganic arsenic(III), acute
values for 16 freshwater animal species ranged from 812 ug/1 for
a cladoceran to 97,000 ug/1 for a midge, but the three acute-
chronic ratios only ranged from 4.660 to 4.862. The five acute
values for inorganic arsenic(V) covered about the same range, but
the single acute-chronic ratio was 28.71. The six acute values
for MSMA ranged from 3,243 to 1,403,000 ug/1. The freshwater
residue data indicated that arsenic is not bioconcentrated to a
high degree but lower forms of aquatic life may accumulate higher
arsenic residues than fish. The low bioconcentration factor and
short half-life of arsenic in fish tissue suggest that residues
should not be a problem to predators of aquatic life.
The available data indicate that freshwater plants differ a great
deal as to their sensitivity to arsenic(III) and arsenic(V). In
comparable tests, the algae Selenastrum capricornutum was 45
times more sensitive to arsenic(V) than to arsenic(III), although
other data present conflicting information on the sensitivity of
this alga to arsenic(V). Many plant values for inorganic
arsenic(III) were in the same range as the available chronic
values for freshwater animals; several plant values for
arsenic(V) were lower than the one available chronic value.
The other toxicological data revealed a wide range of toxicity
based on tests with a variety of freshwater species and
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GOLD PLACER'" MINE SOBCATEGORY SECT - VI
endpoints. Tests with early life stages appeared to be the most
sensitive indicators of arsenic toxicity. For example, an effect
concentration- of 40 ug/1 was obtained in a test on inqirgajiic
arsenic(III) with embryos and larvae of a toad. " -
The procedures described in "Guidelines for Deriving Numerical
National Water Quality Criteria for the Protection of Aquatic,
Organisms and Their Uses" indicate that, except possibly where a
locally important species is very sensitive, freshwater aquatic
organisms and their uses should not be affected unacceptably *.if
the 4-day average concentration of arsenic(III) does not exceed
190 ug/1 more than once every 3 years on the average and if the
1-hour average concentration does not exceed 360 ug/1 more (.than
once every 3 years on the average.
The procedures described in the Guidelines indicate that, except
possibly where a locally important species is very sensitive,
saltwater aquatic organisms and their uses should not be affected
unacceptably if the 4-day average concentration of arsenic(III)
does not exceed 36 ug/1 more than once every 3 years on the
average and if the 1-hour average concentration does not exceed
69 ug/1 more than once every 3 years on the average. This
criterion might? be too high wherever Skeletonema cosrarum or
Thalassiosira aestivalis are ecologically important.
Mercury
Mercury's cumulative nature makes it extremely dangerous J-to
aquatic organisms since these organisms have -the ability" to
absorb significant quantities of mercury directly from the water
as well as through the food chain.. Methyl mercury is the major
toxic form; however, the ability of certain ^microbes to
synthesize methyl mercury from the inorganic forms renders all
mercury in waterways potentially dangerous.
The best available data concerning long-term exposure of fish to
mercury(II) indicate that concentrations above 0.23 mg/1 caused
statistically significant effects on the fathead minnow and
caused the concentration of total mercury in the whole body to
exceed 1.0 mg/kg. Although it is not known what percent oE the
mercury in the fish was methylmercury, it is also not known
whether uptake from food would increase the concentration in the
fish in natural situations. Species such as rainbow trout, cohc-
salmon, and, especially, the bluegill, might'suffer: chronic
effects and accumulate high residues of mercury about the ^ame^s
the fathead minnow. s i!
With regard to long-term exposure to methylmercury, Mctfim et al
(1976) found that brook trout can exceed the FDA action lev
-------
GOLD PLACER MINE SUBCATEGORY SECT - VI
locally important species is very sensitive, freshwater aquatic
organisms and their uses should not be affected unacceptably if
the 4-day average concentration of mercury does not exceed 1.2 x
10-5 mg/1 more than once every 3 years on the average and if the
1-hour average concentration does not exceed 2.4 x 10-3 mg/1 more
than once every 3 years on the average. If the 4-day average
concentration exceeds 9.12 x 10-5 mg/1 more than once in a 3-year
period, the edible portion of consumed species should be analyzed
to determine whether the concentration of methylmercury exceeds
the FDA action level.
One of the reasons that limits for arsenic and mercury are not
being established is that limiting the discharge of solids (the
principal pollutant in the wastewater from placer mines) controls
other pollutants which are also found in the solid form.
Arsenic, mercury, and other metals found in discharges from
placer mines are substantially reduced by the incidental removal
associated with the control and removal of settleable solids. By
controlling settleable solids at the BPT and BAT levels discussed
in Sections IX and X, any arsenic and mercury in the discharge
would be reduced to levels that are below the level at which they
can be effectively treated by other technologies available for
this subcategory. Furthermore, as shown in Table V-15 (p. 118),
metals concentrations for current discharges are frequently below
the analytical detection limit.
The Agency finds that it may not always be feasible to directly
limit each toxic that is present in a waste stream. Surrogate or
indicator relationships provide an alternative or direct
limitation of toxic pollutants according to Criterion 5. Section
V discusses the data analysis which has been performed to
determine the presence of total arsenic and mercury in gold
placer mining treated effluent. Based upon the relationships
developed, these metals have been shown to be associated with the
solids portion (either settleable or suspended) of the wastewater
stream rather than the dissolved portion. Furthermore, the data
available indicate that after removal of the solids the levels of
toxic metals are too low to further reduce by the application of
any other treatment technology being considered. The data
available on the removal of metals from gold placer mining
wastewaters indicate clearly that the level of metals in the
wastewaters is reduced as the amount of settleable and suspended
solids in the wastewater is reduced. The available data do not
provide the basis for the mathematical correlation required to
provide a surrogate relationship; however, the correlation is
adequate to support the use of settleable solids as an indicator
for toxic metals removals.
CONVENTIONAL AND NONCONVENTIONAL POLLUTANTS
High or low pH values in process waters can result in
solubilization of certain ore components and can adversely affect
receiving water pH. Acid conditions can result in the oxidation
133
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GOLD PLACER MINE SUBCATEGORY SECT - VI
of sulfide minerals in certain ores. -No pH problems have been
encountered in placer mining discharges. The water u^ecl in
placer gold operations does not vary appreciably in pH *from
source, through processing, to discharge. The pH of waters
measured was close to neutral at all sampling locations.
Solids
Fish and other aquatic life requirements concerning su£|ieriidjgd
solids can be divided into those whose effect occurs in the water
column and those whose effect occurs following sedimentation to
the bottom of the water body. Noted effects are similar for 'both
fresh and marine waters. :•..,-.',.
The effects of suspended solids on fish have been reviewed by the
European Inland Fisheries Advisory Commission (1965). This
review identified four means by which suspended solids adversely
affect fish and fish food populations:
1. By acting directly on the fish swimming in water where
solids are suspended, and either killing them or
reducing their growth rate, resistance to disease,
2. By preventing the successful development of fish eggs
and larvae
3. By modifying natural movements and migrations of fish
4. By reducing the abundance of food available to the* fish
Settleable materials which blanket the bottom of water bodies
damage the invertebrate populations, block gravel spawning beds,
and, if organic, remove dissolved oxygen from overlying waters.
In a study downstream from the discharge of a rock quarry where
inert suspended solids were increased to 80 mg/1, the density of
macroinvertebrates decreased by 60 percent while in areas of
sediment accumulation benthic invertebrate populations v also
decreased by 60 percent regardless of the suspended solid
concentrations. Similar effects have been reported downstream
from an area which was intensively logged. Major increases in
stream suspended solids (25 mg/1 suspended solids upstream vs.
390 mg/1 downstream) caused smothering of bottom invertebrates,
reducing organism density to only 7.3 per square foot versus 25.5
per square foot. Solids in suspension that will settle in one
hour under quiescent conditions because of gravity are settleable
solids. '
When settleable solids block gravel spawning beds which contain
eggs, high mortalities result, although there is evidence, that
some species of salmonids will not spawn in such areas.
It has been postulated that silt attached to the eggs prevents
sufficient exchange of oxygen and carbon dioxide between the egg
and the overlying water. The important variables are particle
/"
'i •
134
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GOLD PLACER MINE SUBCATEGORY SECT - VI
size, stream velocity, and degree of turbulence.
Deposition of organic materials to the bottom sediments can cause
imbalances in stream biota by increasing bottom animal density,
principally worm populations, and diversity is reduced as
pollution-sensitive forms disappear. Algae likewise flourish in
such nutrient-rich areas, although forms may become less
desirable.
Plankton and inorganic suspended materials reduce light
penetration into the water body, reducing the depth of the photic
zone. This reduces primary production and decreases fish food.
The NAS committee recommended that the depth of light penetration
not be reduced by more than 10 percent. Additionally, the near
surface waters are heated because of the greater heat absorbency
of the particulate material which tends to stabilize the water
column and prevent vertical mixing. Such mixing reductions
decrease the dispersion of dissolved oxygen and nutrients to
lower portions of the water body.
The presence of solids in placer gold mining discharges has been
documented in the sampling programs described in Section V. The
results of sampling conducted by EPA between 1983 and 1986 are
presented in Table V-20 (p. 122).
Asbestos
The 1982 final effluent limitations and standards for ore mining
and dressing excluded the toxic pollutant asbestos from direct
regulation because effluent limitations on solids (TSS)
effectively controlled the discharge of asbestos (chrysotile).
Asbestos was found in all raw waste discharges and all effluent
from all ore mines and mills where an analysis was made for
asbestos (88 samples representing 23 facilities). EPA found a
high degree of correlation between solids and chrysotile asbestos
in the raw wastewater and treated wastewater and concluded that
settling technology was so successful at removing solids, a
specific limitation on asbestos was not appropriate in light of
the correlation with solids and the expense of monitoring
specifically for asbestos.
Turbidity
Turbidity is the property of a material to scatter light as the
light passes through a water columm in which the material is
suspended. The treatments considered for this subcategory do not
directly control turbidity but control settleable solids or
suspended solids. While removing these solids from water will
tend to reduce the level of turbidity, there is no good
correlation between SS or TSS and turbidity. Since turbidity is
a water quality parameter it is highly site specific and the
control and regulatory levels necessary to meet the water quality
requirements must be equally site specific. For these reasons,
turbidity is not further considered for regulation.
135
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GOLD PLACER MINE SUBCATEGORY SECT - VI
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136
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GOLD PLACER MINE SUBCATEGORY SECT - VII
SECTION VII
CONTROL AND TREATMENT TECHNOLOGY
This section discusses the techniques for pollution abatement
available to gold placer mining. General categories of
techniques are: in-process controls, end-of-pipe treatment, and
best management practices. The current or potential use of each
technology in gold placer mining and the pollutant reduction
effectiveness of each are discussed.
Selection of the optimal control and treatment technology for
wastewater generated by this subcategory has been influenced by
several factors:
1. There are some differences in wastewater composition
and treatability caused by ore mineralogy, ore particle
size and distribution, and processing techniques.
2. Geographic location, topography, and climatic
conditions often influence the amount of water to be
handled, treatment and control strategies, and costs.
3. A mine operator must frequently rebuild the treatment
facilities because of the progressively moving nature
of these operations.
END-OF-PIPE TREATMENT TECHNOLOGIES
This subsection presents a discussion of technologies which may
be employed for the treatment of wastewater discharged from gold
placer mining operations. Most mines are in remote locations, so
that the type of equipment and the availability of outside
construction services must be considered. For a given site, the
terrain is most important to define design, construction and
maintenance requirements for treatment facilities. The following
factors were also considered in reviewing the available and
appropriate treatment and control facilities for gold placer
mines:
1. Engineering considerations for construction of
treatment facilities in most mining locations,
including settling pond size, number of ponds,
drainage diversion and water use reduction
2. The length of the gold placer mining season which
ranges from about 2 to 4 months in Alaska and from 5
to 10 months in the lower 48
3. Design considerations due to climate, especially
rainfall and temperature
137
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GOLD PLACER MINE SUBCATEGORY SECT - VII
4. Construction equipment available to, and practices
employed by, the mining crew to install treatment or
control facilities
The ore mining category currently uses some form of sedimentation
technology which usually involves settling basins, clarifiers, or
ponds. Large concrete settling basins and clarifiers normally
found at typical "hard rock" ore mines generally are not found
because they are not adaptable to conditions related to frequent
moves, seasonal operation, and the remote location of gold pLacer
mines. Other technologies impractical for gold placer mining
include granular media filtration, adsorption, chemical
treatment, and ion exchange.
IN-PROCESS CONTROL TECHNOLOGY
Process changes are available to existing mines that will improve
the quality or reduce the quantity of wastewater discharged from
mines. Use of in-process changes will reduce end-of-pipe
treatment costs and improve treatment effectiveness.
Classification *
Mines which employ classification (sizing or screening) of the
ore prior to sluicing typically use less water than mines which
do not classify. Several different classification devices are
commonly employed at, gold placer mines—such as grizzlies,
trommels and screens (fixed and vibrating). Each of these
devices removes oversized material prior to sluicing. Removal of
oversized material reduces water usage because less material is
sluiced and a lower water velocity is required to move the
smaller rocks down the sluices. 'Descriptions of grizzlies,
trommels and screens are found in Section III. Estimated watfr
use rates for each of the classification devices and for mines
using no classification are shown in Table V-8 (p. 112). Average
water use at mines employing classification methods (grizzlies,
screens and trommels) is approximately 5.57 cu m water per cu m
are (1467 gal per cu yd of ore processed). At mines using no
classification, the average water use is 8.97 cubic meters df
water per cubic meter of ore (2365 gal per cu yd).
Classification is common practice in the industry. A significaiti
number of mines, especially those mines in water short areas,
consider it good mining practice to reduce water usage by
classifying. In Section III, Tables III-4 to III-8 (pp. 48-56)
indicate *that over 50 percent of the mines use some form of
classificatiqn.
High Pressure ~ Low Volume Spray Nozzles
One of the factors that affects the amount of water required at
gold placer mines is the cohesiveness of the ore particles.
Mines washing ores which contain a significant percentage of clay
particles generally use greater volumes of water to break up the
ore = during beneficiation than mines processing ores with larger
138
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GOLD PLACER MINE SUBCATEGORY SECT - VII
particle sizes and less clay. Screening in conjunction with the
use of high pressure, low volume spray nozzles prior to sluicing
can assist in breaking up the agglomerated ore, freeing the gold
particles. This type of operation will use less water per unit
of ore processed than if large volume low pressure nozzles were
employed.
Sluice Design
The amount of water required for sluicing is a function of slope,
width, water depth, riffle type, riffle spacing, ore particle
size, composition and size distribution of the ore as discussed
above. However, sluice design and the efficiency of a given
sluice in recovering gold is most often the result of trial and
error by the miner to obtain the best recovery of gold from a
particular ore. Numerous mining text books and journals have
published design parameters for sluice boxes plus describing
"normal" operation requirements. A 1986 study performed upon ore
from a mine in Yukon, Canada is a clear presentation of the many
variables involved in the proper design and operation of a sluice
box.
Control
Water use can also be reduced by stopping the influent flow to
the beneficiation process during extended periods when ore is not
being loaded into the process. This will decrease the total flow
into the settling ponds and increase the settling time.
Continued water flow in the absence of ore is sometimes called
"running clear" and is to be avoided.
Simple Settling
Simple settling is the process by which wastewater is given a
period of time to sit undisturbed in a pond or vessel. This
quiescent settling time allows gravity to act on the settleable
solids in the wastewater.
The use of ponds for both primary and secondary settling is very
common in gold placer mining. The wastewater entering these
ponds from the mining and ore processing operations contain a
high solids loading. Primary settling ponds are often used to
remove the heavy particles and then secondary settling ponds are
used to remove the finer particles.
Design Construction and Operation qf^ Settling Ponds
To achieve the desired results or effluent from a settling
pond(s), the pond must be properly designed, installed, and
maintained. It was apparent from the visits to many mine sites
that the ponds were of insufficient size to treat the wastewater.
The ponds may have had sufficient volume to adequately treat the
mines' flow when constructed, but gradually, the solids settling
from the wastewater reduced the volume of the ponds, reducing
their effectiveness. Also, the ponds at some mines visited were
139
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GOLD PLACER MINE SUBCATEGORY SECT - VII
"short-circuiting" (i.e., wastewater flowed straight through the
pond without much, if any settling) due to improper placement of
the influent and effluent points.
A properly designed pond should have the influent in the middle
of one end and the effluent at the middle of the other end or as
far from the influent as is possible. Ideal ponds have the
length two to three times the width and adjustable weirs at the
influent and effluent points. These weirs are utilized to
determine and direct the flow into and out of the ponds and to
control water height in the ponds.
The disposal of sludge deposited in the ponds can be handled by
two methods: (1) Sludge can be removed from the ponds
periodically, using mechanical means such as dredges, slurry
pumps, front end loaders, backhoes or drag lines, and disposed in
the area used for tailings disposal; or (2) sludge can be left in
the pond until the pond fills and is closed by proper
reclamation. Both approaches require the pond volumes to be
increased above that required for detention of the wastewater
being treated so that the volume of sludge does not intrude on
the volume required for proper wastewater detention and
treatment. The increased volume of the ponds will depend upon
the method of sludge disposal being utilized, and the amount of
solids present in the wastewater that will settle. The ponds
will be smaller in volume if the sludge is removed periodically.
Therefore, in sizing the settling pond for a mine site, the
following must be determined:
1. Volume of wastewater to be treated (process water,
excess water, and storm runoff)
2. Amount of sludge to be stored in the pond
3. Method of sludge handling
4. Drainage from a 6-hour 5-year storm event
Using these data, ponds of proper size to treat the wastewater
generated can be designed and installed. A typical pond plan and
cross section is presented on Figures VII-1 and VII-2 (pp. 154-
155).
1. Determination of Wastewater Volume To Be Treated
The volume of wastewater to be treated in placer mining
operations is determined from the actual amount of water used in
the beneficiation process (sluicing) (process water), the excess
water consisting of surface water and infiltration which enters
the pond, and the storm water runoff from the mine site (the
beneficiation area and the mine area) for a 5 year, 6 hour storm
intensity which the pond should be designed to handle.
140
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GOLD PLACER MINE SUBCATEGORY SECT - VII
The size of the ponds and cost of construction discussed in
Section VIII are based on the volume of water to be treated. At
most mine sites the major flow to be treated is the process
water used for the beneficiation process, i.e., sluicing.
Minimizing process water use by high pressure, low volume nozzles
for pre-wash, and ore classification will result in smaller ponds
and lower costs for treatment of process water.
2. Determination p_f S_ludgj; Volume To Be Handled
The volume of sludge is computed by determining the amount of
suspended solids present in the wastewater entering the pond and
the amount of suspended solids present in the wastewater
discharging the pond after the required settling time. Using the
difference between the influent and effluent suspended solids and
the volume of wastewater being treated, and knowing the solids
content of the sludge, the volume of sludge to be handled can be
computed. Using this data and the methods of sludge handling,
the volume of the pond required for sludge storage can be
determined.
3. Method of Sludge Handling
Each mine is site specific in the design manner in which sludge
will be handled throughout the mining season. Some mines plan to
clean out the ponds on a regular basis to maintain the desired
wastewater detention time, while others will plan to build new
ponds as needed to maintain permit requirements throughout the
mining season. Proper sludge disposal is critical for the
desired performance of the pond.
4. Storm Water Exemption
The storm exemption allows the discharge of untreated or
inadequately treated wastewater when the treatment ponds are
designed to contain (and treat) the rainfall runoff from the mine
site caused by a 5-year, 6-hour storm. Failure to design
adequate retention volume into the ponds denies the mines
eligibility for the storm water exemption
Pond Design Example
For example, an operation (small model mine) sluices 35,000 cu
yds per year (70 cu yds per hour - 8 hr/day, 50 min/hr, 75
days/yr) and produces 1,350 gpm process wastewater plus 20
percent excess water or 1620 gpm (43,300 cu ft per 4 hours) water
to the treatment pond. Sludge deposited from this water into
each of 4 ponds constructed during the season (or ponds cleaned)
(20,000 mg/1 solids in process wastewater, 57 percent solids in
the sludge) would require 53,000 cu ft of pond volume. The
minimum pond volume-assuming 4 ponds constructed per year - is
96,300 cu ft. To be eligible for the storm exemption an
additional volume would be required. Assuming that the mine area
is 175 ft x 720 ft ard the 5 year 6-hour storm event is 1.5 in.
141
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GOLD PLACER MINE SUBCATEGORY SECT - VII
of rain, the added volume is 15,750 cu ft. A pond approximately
70 x 108' filled to a height of 10 ft would be required to
contain the volumes of water, sludge and excess stormwater. This
size pond would be predicted to achieve a settleable solids level
of less than 0.2 ml/1 as determined from treatability tests of
simple settling. Attention to detail will be required to address
such factors as: surface area of the pond, rate of flow through
the pond, eliminating short circuiting of flow across the pond,
and entrance and exit effects of the wastewater. A number of
handbooks are available to assist the mine operator in the
design, construction, and maintenance of ponds, including "Placer
Mining Settling Pond Design Handbook," January 1983, State of
Alaska Department of Environmental Conservation and "Placer
Mining Demonstration Grant Project Design Handbook," March 1987,
ADEC and ADNR. The use of the concepts depicted in such
handbooks will greatly aid and facilitate the mine operator in
designing wastewater treatment ponds.
Coagulation and Flocculatiori
The majority of the suspended solids present in placer mine
effluent after simple settling are very fine (presumably
colloidal) in size and do not readily settle without the aid of
chemicals. Chemicals can be introduced to the wastewater which
will coagulate small particles into particles large enough to
settle by gravity or be removed by other physical methods. The
major chemicals used for coagulation are called polymers (or
polyelectrolytes). Polymers operate by forming a physical bridge
between particles, thereby causing them to agglomerate forming a
floe. The floe, an agglomeration of small particles, is
generally settleable. When the polymer alone does not form
particles that will settle due to lack of particle weight,
coagulant aids such as lime or ferric sulfate are used to add the
required weight.
Coagulant aids are normally added ahead of the settling facility.
The coagulant must be added and mixed with the wastewater by a
turbulent action such as an in-line mixer to ensure complete
mixing and dispersion of the coagulant into the wastewater.
After complete mixing, the treated wastewater must pass through a
flocculation stage which allows the particles to come in contact
with each other so that the agglomeration can occur to form a
floe.
A complete demonstration of the technical and economic
feasibility of a flocculant system for gold placer mines has yet
to be made. The Agency and others including several miners have
made a number of studies but as yet an adequate data base to
support this technology has not been developed.
NaturaJL Filtration
Removal of solids by filtration is achieved by passing the
wastewater through a medium where the pore sizes are smaller than<:
the particles being removed, thereby trapping the particles. At
142
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GOLD PLACER MINE SUBCATEGORY SECT - VII
many placer mines, filtration is performed naturally as the
wastewater is discharged through the tailings from the mining
operations. Those particles larger than the pore size in the
tailings are trapped and removed. Tailings filtration may be
beneficial in that the fines are recombined with the coarse
tailings. No specific data are available to determine the
removal efficiencies or the effluent quality from existing
treatment at gold placer mines because the discharge is not
generally discrete, but is most often diffuse in the form of
seepage.
Recirculation of_ Process Waters
Recirculation is the continued reuse of water internally within a
process. Water in gold placer mines is used as the transport
medium for mined solids and is used to move these solids from the
slick plate feed to a screen or trommel, through a sluice or
other separation device, and on into a solids retention device or
pond. After the water has released its solids burden, it may be
withdrawn from the pond and returned to the slick plate to repeat
the process. As applied to gold placer mining, recirculation is
the continued reuse of the same water as the transport medium
for solids (ore) to or through the classification process, the
beneficiation process, and into the solids removal process.
Figure VII-3 (p. 156) illustrates schematically the recirculation
of process water at a gold placer mine. Under this definition,
any water used to remove ore from the mine; transport, classify,
beneficiate, or treat that ore; and remove any solids from these
processes would be returned for reuse to the system. A major
reduction of the pollution load on the receiving waters can be
achieved through recirculation of process water. This also
conserves water and is in practice at some gold placer mines.
Approximately 60 percent of the mines have indicated that they
plan to recycle all or a portion of their process water. Those
that recycle or recirculate process water at a gold placer mine
require the installation of a pump at the pond and piping to the
head of the mining operation. The size of the pumps and piping
would be based on the required process flow.
Recirculation of process water at gold placer mines has several
advantages and disadvantages as summarized below:
Advantages
1. Allows mining especially in water short areas and
minimizes water use elsewhere.
2. Reduces mass of pollutant to the receiving stream.
3. May require smaller or fewer settling ponds to meet
effluent limitations.
143
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GOLD PLACER MINE SUBCATEGORY SECT - VII
Disadvantages
*' • ' '
1. Higher pumping costs because of additional energy
requirements. :
2. Higher piping costs because more pipe may be required.
A concern of the industry was that fine gold recovery decreases
when recirculated water containing suspended solids is reused in
the sluice. However, only limited scientific data were available
to address this issue. Therefore, the Alaska Department of
Environmental Conservation (ADEC) funded a study (VII-3) s to
address the potential loss of gold recovery during recirculation.
This study was divided into two parts, a pilot-scale study and a
field study. EPA expanded on this study and funded a1
supplemental study (in 1984) on the effects of recirculation on
gold recovery. The EPA study (VII-4) used essentially the same
set-up as the ADEC study. In both of these studies, a 15-
centimeter-wide (6-in), 2.4-meter-long (8-ft) sluice with a feed
hopper and slick plate were used (see Figures VII-4 and VI!--5/
pp. 157-158). The slope of the sluice during both studies was set
at 1.75:12.
In the EPA study, ore from an operating mine in the Fairbanks
District was used. The ore was screened and only material finer
than 20 mm (0.75 in) was used in the pilot-scale tests. A new
batch of ore with an unknown quantity of gold was used during
each run. The material was resluiced after each run to determine
the gold loss. The gold used in the study was -30 to +60 mesh.
A known quantity of gold was added'to the ore prior to each run
in order to have a statistically significant amount Of gold in
the sluice box. The size distribution of gold added during each
test run is shown in Table VII-1 (p. 147). The major results of
this study are summarized on Tables VII-2 and VII-3 (pp. 148-
149). Gold loss at all suspended solids levels due to
recirculation is minimal.
After reviewing the results of the previously discussed studies
EPA decided to perform an additional study during the 1986 mining
season (VII-15). The primary purpose of this additional study
was to determine the effect of varying levels of total suspended
solids in the sluice feed water on riffle packing and gold
recovery in a pilot scale sluice box. A secondary purpose to the
new study was to determine the interrelationships between gold
recovery and viscosity. This study utilized a system consisting
of the 15-centimeter-wide by 2.5-meter-long (6 in by 8 ft) sluice
box used in the previous studies, a 10-hp centrifugal water pump,
and a recirculation tank. The sluice box was preceded by a
vibrating screen mounted over a feed hopper with a hydraulic lift
feeding the sluice and followed by a secondary receiving system
consisting of a wedge wire screen, slurry pump, hydrocyclone,
reichert spiral and Gemini shaking table. The total pilot plant
system is presented schematically in Figure, VII-6 (p. 159).
144
-------
if T t
GOLD PLACER MINE SUBCATEGORY SECT - VII
Ore from an operating mine in the Fairbanks District was used for
this study. This dirt was dry screened though a 20 mm (0.75 in)
wire screen and only that passing the screen was utilized in the
testing. Each test run was made using a separate portion of the
screened ore. To insure that a statistically significant
quantity of gold was present in the sluice box fine gold was
added to the ore during each test run. The size distribution of
gold added to each test run is shown in Table VII-4 (p. 150). The
major results of this study are summarized in Tables VII-5, VII-
6, and VII-7 (pp. 151-153). Based on the results of this test
program, it appears that both run duration .and influent water
suspended concentration influence the rate of riffle packing and
gold migration. Gold starts to migrate after the riffles become
packed, see Table VII-7. This confirms the best professional
practice in gold placer mining to clean up when the riffles
become packed.
Treatment Effectiveness
This section compares the raw and treated effluent
characteristics. Data for this comparison were collected from
treatability tests and from an examination of operating mines.
Table V-18 (p. 120) indicates the average treatment effectiveness
after 6 hours of simple quiescent settling, after 6 hours of
chemically aided settling, and calculated treatment effectiveness
after 3 hours of simple settling based on 20,000 mg/1 initial TSS
for various pollutants.
The long-term, daily, and monthly achievable levels are
determined statistically using the effluent data obtained in 1984
at existing facilities sampled by EPA headquarters and EPA Region
X sampling teams, and data from treatability studies conducted by
EPA. As previously discussed in Section V, some of the effluent
data from existing facilities does not represent good treatment
which can be obtained by properly designed, constructed, and
operated settling ponds. Also, by referring to the data, i.e.,
total suspended solids analysis for the same day, large
differences in reported values are observed which, if considered
as individual values, cause a large standard deviation from the
mean and push up the long term average. The effect of using data
from under sized or poorly constructed and operated treatment
facilities is two fold: (1) it increases the simple average or
mean and (2) the peak values, e.g., outliers, increase the
statistically determined attainable long term average
limitations.
During reconnaissance sampling in 1983 through 1986 EPA measured
the SS in the effluent from sampled mines. This data is
summarized in Tables V-19 and V-22 (pp. 121 and 124) and shows
that about 60 percent of the existing mines were meeting the SS
limit of 0.2 ml/1. Footnotes on Table V-22 indicate the logical
reasons for failure of some mines to achieve the 0.2 ml/1 level
when such reasons were known.
During the 1983, 1984 and 1986 mining seasons EPA made
145
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GOLD PLACER MINE SUBCATEGORY SECT - VII
treatability tests at mines in Alaska. The data for the 1983
season is not reproduced here because the tests were only two
hour settling tests and are not relevant to the present
regulation. The 1984 and 1986 data are displayed in Table V-22
(p. 124). These settling tests show that six of the eight mines
sampled in 1986 were achieving the SS MDL of 0.2 ml/1 after three
hours of quiescent simple settling: one mine that did not
achieve the MDL was hydraulicing overburden and not sluicing at
the time of sampling and the other mine, a dredge, achieved the
MDL after four hours of quiescent settling.
The 1984 data show that seven of the ten mines sampled achieved
the MDL of 0.2 ml/1 with three hours of quiescent settling: the
reasons for failure to achieve the MDL in three hours are noted
on the data table. All of the mines samples achieved the MDL
within six hours.
From this data we conclude that the treatment effectiveness of
simple quiescent settling is applicable to the requirement that
mines achieve the MDL of 0.2 ml/1 before discharging wastewater.
DEMONSTRATION STATUS
EPA personnel have observed six mines and one dredge in Alaska in
1986 and 1987 operating in a recirculation mode. Additionally
one dredge in the lower 48 has been observed to operate in that
mode. This data is considered to be the primary basis for
considering recirculation of process water to be a demonstrated
technology. In addition, EPA has information from a contractor
(See Reference No. xx) that in 1984, over 20 percent of the
production by the subcategory was processed with wash water that
was 90 to 100 percent recycled. Data obtained by the Agency for
the 1985, 1986, and 1987 mining seasons indicate that 30 percent
of the subcategory in Alaska was planning to be able to operate
on total recycle of process water, with another 30 percent of the
gold placer mines performing partial recycle. Many states in the
Lower 48 have existing regulations requiring recirculation of
total flow. Recycle or recirculation is employed in most mining
districts for which the Agency has information (generally because
of existing regulations or a shortage of water), indicating that
pumping and powering of the pumps is a viable process change even
in remote locations.
146
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GOLD PLACER MINE SUBCATEGORY SECT - VII
Table VII-1. Size Distribution of Gold Added to Each Run
Run No.
1
2
3
4
5
6
Total
-30 + 50
Mesh
9.9612
10.0079
10.2561
10.3743
9.8473
10.2897
-50 + 60
Mesh
2.5279
2.6490
2.4956
2.5238
2.6621
2.5169
Total
12.4891
12.6569
12.7517
12.8981
12.5094
12.8066
60.7365
15.3753
76.1118
Note: Amounts of gold are presented in grams,
Source: Ref. 33
147
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GOLD PLACER MINE SUBCATEGORY SECT - VII
Table VII-2. Pilot Test Water Quality Data (Sluice Influent)
Parameter
TSS
Turbidity
Settleable Solids
Specific Gravity
Viscosity @ 20 C
Vise. @ Run Temp.
Run Duration
Water Duty
SLUICE INFLUENT
Run
2 3
217
95
-0.1
0.998
1.0
2.0
34
0.22
39,100
24^00
180
1.022
1.8
3.2
39
0.19
58,800
30,000
270
1.034
2.0
2.9
37
0.21
90,100
46,000
400
1.052
3.0
4.9
38
0.20
194,000
134,000
680
1.122
4.2
7.7
38
0.20
187,000
108,000
650
1.118
4.1
6.2
14
0.56
TSS 10,000
Turbidity 2,200
Settleable Solids 25
Specific Gravity 1.004
Viscosity @ 20 C 1.5
Vise. @ Run Temp. 3.0
Units: TSS
Turbidity
Settleable Solids
Specific Gravity
Viscosity
Run Duration
Water Duty
SLUICE EFFLUENT
48,000 65,100 98,300 199,000 204,000
24,000
200
1.029
1.7
3.1
33,000
290
1.039
2.2
3.1
39,000
420
1.060
2.8
4.6
128,000
680
1.122
4.4
8.1
100,000
660
1.133
4.9
7.3
mg/1
NTU
ml/1
gm/cc at 20 C
cp(centipoise) - gm mass/cm sec
min
yd3/1000 gal (cubic yards of pay dirt
sluiced using 1000 gallons of water)
Note: "-0.1" denotes less than 0.1
Source: Ref. 33
148
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GOLD PLACER MINE SUBCATEGORY
SECT - VII
Table VII-3. Percent Gold Recovery
TOTAL GOLD
Riffle
Run
1
2
3
4
5
6
1
99.63
99.59
99.54
99.40
99.08
97.84
2_
0.32
0.38
0.39
0.52
0.71
1.83
3_
-0.01
0.02
-0.01
0.04
0.04
0.08
4
0.01
0.01
-0.01
0.03
0.03
0.08
Gold Loss*
0.04
-0.01
0.05
0.02
0.13
0.18
-50 + 80 MESH GOLD
Riffle
Run !_
99.00
98.97
98.96
98.41
97.96
1
2
3
4
5
6
95.42
2
0.81
0.94
0.86
1.41
1.79
4.03
3
0.02
0.05
0.03
0.06
0.10
0.25
4
0.05
0.02
0.04
0.08
0.04
0.09
Gold Loss*
0.12
0.03
0.11
0.04
0.11
0.21
Note: "-0.01" denotes less than 0.01 percent
*Recovered after sluicing by suction dredge
Source: Ref. 33
149
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GOLD PLACER MINE SUBCATEGORY SECT - VII
Table VII-4. Size Distribution of Gold Added to Each Test Run
(EPA Funded Second Study, 1986)
Run No.
1
2
3
4
5
-50 + 70
Mesh
16.9192
19.0723
4.7762
18.4704
18.9047
-70 + 100
Mesh
16.2044
18.7591
3.0793
19.0145
19.0682
Total
33.1236
37.8314
7.8555
37.4849
37.9729
Note: Amounts of gold are presented in grams.
Source: Ref. 32
150
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GOLD PLACER.MINE SUBCATEGORY SECT - VII
Table VII-5. Pilot Test Water Quality Data For Composite Samples
Parameter
Suspended Solids
Turbidity
Settleable Solids
Specific Gravity
Vise. @ Run Temp.
Run Duration
Screened Water Duty
Bank Yard W.D.
Suspended Solids
Turbidity
Settleable Solids
Specific Gravity
Vise'."'@ Run Temp.
Run
ill
SLUICE INFLUENT
249,000 285,000 421,000
59,000 74,000 76,000
280 400 420
1.155 1.178 1.282
2.8 3.5 4.1
315 315 60
0.5 0.5 0.5
0.6 0.6 0.6
SLUICE EFFLUENT
292,000 313,000 469,000
67,000 80,000 88,000
350 440 440
1.182 1.200 1.296
3.2 3.5 6.1
62,300 348
19,000 17
120 <0.1
1.040 1.000
1.8 1.0
315 315
0.5 0.5
0.6 0.6
95,400 29,700
21,000 4,000
130 36
1.062 1.020
2.0 1.5
Units: Suspended Solids
Turbidity
Settleable Solids
Specific Gravity
Viscosity
Run Duration
Water Duty
mg/1
NTU
ml/1
gm/cc at 20 C
cp(centipoise) - gm mass/cm sec
minutes
yd3/1000 gal (cubic yards of pay dirt
sluiced using 1000 gallons of water)
151
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GOLD PLACER MINI SUBCATEGORY SECT - VII
Table VII-6. Gold Recovery Data
Riffle Section Genemi Table
Run 1
+50
-50+70
-70+100
-100
Total
Run 2
+50
-50+70
-70+100
-100
Total
Ru« 3
+50
-50+70
-70+100
-100
Total
Run 4
+50
-50+70
-70+100
-100
Total
Run 5
+50
-50+70
-70+100
-100
Total
Notes :
1
0.8816
10.2954
9.3542
0.6031
21.1325
0.3340
12.9604
11.3537
0.6011
25.2492
0.2337
2.9018
2.6023
0.1407
5.8785
0.8800
14.0653
11.2215
0.5912
26.7580
1.2494
15.7981
15.9866
0.9314
33.9655
2
0.1596
4.0721
5.4994
0.4949
10.2260
0.1062
4.2468
6.2027
0.3781
10.9338
0.0429
0.4666
0.9973
0.0917
1.5985
0.2340
2.9334
4.9325
0.3753
8.4752
0.0188
0.9817
2.3041
0.1968
3.5014
3
0.0074
0.1871
0.6804
0.1147
0.9896
0.0034
0.1957
0.6885
0.0817
0.9693
0.0021
0.0263
0.1298
0.0204
0.1786
0.0025
O.O'lll
0.0453
0.0066
0.0655
0.0019
0.0071
0.0222
0.0035
0.0347
(1) Gold weights are in grains.
(2) Gemeni table designations A,
A
0.0230
0.0398
0.0375
0.0084
0.1087
0.0068
0.0401
0.0655
0.0134
0.1258
0.0002
0.0004
0.0004
0.0000
0.0010
0.0035
0.0051
0.0069
0.0004
0.0159
0.0022
0.0051
0.0054
0.0005
0.0132
B and C are:
B
0.0054
0.0174
0.0354
0.0051
0.0633
0.0083
0.0748
0.1593
0.0273
0.2697
0.0014
0.0015
0.0015
0.0001
0.0045
0.0000
0.0004
0.0003
0.0001
0.0008
0.0004
0.0033
0.0025
0.0004
0.0066
C,
0.0011
0.0041
0.0062
0.0023
0.0117
for Runs 1, 2, 4 and 5, A is the first 4 hours, 15 minutes of
operation and B is the last 25 minutes of operation.
For Run 3, A is the first 30 minutes of operation, B is for
31 to 45 minutes, and C is for 46 to 60 minutes.
152
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GOLD PLACER MINE SUBCATEGORY SECT:,- VII
Table VII-7. Percent Gold Recovery
Riffle Section Genemi Table
Run 1
+50
-50+70
-70+100
-100
Total
Run 2
+50
-50+70
-70+100
-100
Total
Run 3
+50
-50+70
-70+100
-100
Total
Run 4
-50+70
-70+100
-100
Total
Run 5
+50~
-50+70
-70+100
-100
Total
1
2.71
31.66
28.76
1.85
64.98
0.89
34.52
30.24
1.60
67.25
3.05
37.81
33.91
1.83
76.60
2.49
39.83
31.78
1.67
75.77
3.33
42.10
42.61
2.48
90.52
2
0.49
12.52
16.91
1.52
32.44
0.28
11.31
16.52
1.01
29.12
0.56
6.08
12.99
1.19
21.82
0.66
8.31
13.97
1.06
24.00
0.02
2.62
6.14
0.52
9.33
3
0.02
0.58
2.09
0.35
3.04
0.01
0.52
1.83
0.22
2.58
0.03
0.34
1.69
0.27
2.33
0.01
0.03
0.13
0.02
0.19
<0.01
0.02
0.06
<0.01
0.09
A
0.07
0.12
0.12
0.03
0.34
0.02
0.11
0.17
0.04
0.32
0.00
<0.01
<0.01
0.00
0.01
0.01
0.01
0.02
<0.01
0.05
<0.01
0.01
0.01
<0.01
0.04
B
0.02
0.05
0.11
0.02
0.20
0.02
0.20
0.42
0.07
0.72
0.02
0.02
0.02
<0.01
0.06
0.00
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.02
C
0.01
0.05
0.08
0.03
0.17
Notes: Gemeni table designations A, B and C are:
for Runs 1, 2, 4 and 5, A is the first 4 hours, 15 minutes of
operation and B is the last 25 minutes of operation.
For Run 3, A is the first 30 minutes of operation, B is for
31 to 45 minutes, and C is for 46 to 60 minutes.
153
-------
FIGURE VI I-1 PLACER MINING WASTEWATER TREATMENT
TYPICAL SETTLING POND PLAN
Ul
^
. '
\
N- ;
-0
WEIR*
H-
h/
Vi
TTTTTTTTT
Pond Volune Sufficient To
D §• A vf 1 HA DA «iii 1 §• A H ^ A4An4 fj\n T 1 m A
p*rov i ae r\Bquirea ueient ion i tne
For Water Being Treated Plus
vo i uno rtoqu iroo ror OIUQQO otoroyo
%i: 1 1 ill JL i i
Y/
— <
0 "
WE!
\
1=^ i
EFFLUENT
^
Length-2 to 3 x Width
-------
FIGURE VI I-2 PLACER MINING WASTEWATER TREATMENT
SETTLING POND - TYPICAL SECTION
B ft.
AREA 2
X
Ui
Ul
FREEBOARD
STORM WATER CONTAINMENT
WATER
(Volume To Provide Required Detention Tine)
SLUDGE
(Volune Required for Sludge Storage)
wmm
NOTES:
AREA 1: Core of bern (nixed coarse and fine tailings)
AREA 2: Fines (Silt.clay or other fine material) If
fines not available, appropriate material
should be used as replacement.
-------
Recirculation
Classification
Beneficiation
Makeup
Water
Solids Separation
Simple Settling
Pond
O
O
f
a
w
3
en
G
tD
O
w
O
cn
w
O
I
-------
GOLD PLACER MINE SUBCATEGORY SECT - VII
Figure VII-4
PILOT TEST
RECYCLE FACILITY
(PLAN VIEW)
SCOle' I/*'- I'
Hand-Held
Wcsh Hose
Wash Water
Control Volve
Spray Bar Water
Control Volve
Sluice-/
Effluent
Recycle
Pump
Recycle Water
Pump Intake
Three-Compartment
Woter Tank
157
-------
Figure VII-5
PILOT TEST RECYCLE FACILITY
(SIDE VIEW)
scale: i/i". r
Hand Held
Wash Mote-
Feed
Tank-
Ul
00
Sluice Box
Pump
Intake
O
tr1
a
s
z
M
0)
a
a
o
§
I
-------
Figure VII-6
SHAKENSCREEN
PEED MOP*!*
ui
SPMAYE
(HYDRAULIC
ILIFT
CYCLONE OVERFLOW
MYDROCYCLONB
RSICNBRT SPINAL
CONCENTRATOR
TAILINOS
BNTNATE
4EMENI TABLE
WATEN
NECVCLI
NCCYCLE NETUNN FLOW
NECVCLB
TANKS (!)
O
s
O
8
s
H
Z
cn
G
to
O
s
td
O
8
cn
td
O
I
<
N«t«: Not
«• •••!•.
RECYCLE FLOW SCHEMATIC
-------
GOLD PLACER MINE SUBCATEGORY SECT - VII
This Page Intentionally Left Blank
160
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
SECTION VIII
COST, ENERGY AND OTHER NON-WATER QUALITY ISSUES
DEVELOPMENT OF COST DATA BASE
Costs of different treatment options for various sizes and types
of gold placer mines are presented here. These costs are
presented in detail in Reference VIII-1.
Estimate Assumptions
Generalized capital and annual costs for wastewater treatment
processes at gold placer mining facilities are based on gallons
per minute of process water flow. All costs are expressed in 1986
dollars (Engineering News Record, Construction Cost Index (CCI) =
4332: third quarter of 1986).
The cost estimates were based on assumptions regarding system
loading and hydraulics, treatment process design criteria,
material, equipment, personnel and energy costs. These
assumptions are documented in detail in this section. The
estimates prepared have an accuracy of plus or minus 30 percent.
The wastewater treatment unit processes studied are as follows:
A - Simple settling (primary settling)
B - Recirculation
C - Chemically aided settling
These unit processes were then used in the following treatment
options:
OPTION
A - OPEN CUTS
- 1 Pond
A - DREDGES
A - OPEN CUTS
- 3 or 4 Ponds
DESCRIPTION
Simple settling of total flow (process
and excess water) in a pond having 4-hour
detention time. Pond built once per mining
season. Discharge of total flow.
Pumping of total flow (process and excess
water) from the dredge pond to a simple
settling pond having a 4-hour detention time.
Pond built once per mining season. Discharge
of any or all flows.
Simple settling of total flow (process and
excess water) in a pond having 4-hour
detention time. Pond built three or four
times per mining season depending on mine
model. Discharge of total flow.
161
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GOLD PLACER MINE SUBCATEGORY SECT - VIII
B -
OPEN CUTS
1 Pond
B - DREDGES
B -
OPEN CUT
3 or 4 Ponds
C - OPEN CUT
Simple settling of total flow (process and
excess water) in a pond having 4-hour
detention time followed by recirculation of
process water. Pond built once per mining
season. Discharge of excess flow.
Recirculation of the process water within the
dredge pond recirculation system and pump the
excess water to a simple settling pond having
a 4-hour detention time. Pond built once per
mining season. Discharge of excess flow.
Simple settling of total flow (process and
excess water) in a pond having 4-hour
detention time followed by recirculation of
process water. Pond built three or four
times per mining season depending on mine
model. Discharge of excess flow.
Chemical treatment of total flow (process and
excess water) discharging Open Cut Options 1
or 2. Chemical addition (polyelectrolyte,)
followed by secondary settling having 3thp,ur
detention time. Pond built once per mining
season. Discharge of total flow.
Pumping of total flow (process and excess
water to a settling pond having 3-hour
detention time. Chemical (polyelectrolyte)
added ahead of pond. Pond built once per
mining season. Discharge of any or all
flows.
The above options are shown schematically in Figures VIII-1
through VIII-3 (pp. 183-185).
CAPITAL COST
Capital Cost of Facilities ''"-',
Figures VIII-4 through VIII-6 (pp. 186-188) present schematic
representations of generic gold placer mine treatment systems for
all open cut mining treatment options. Schematic representations
of generic gold placer mine treatment systems for all dredge
mining treatment options are presented on Figures VIII-7 through
VIII-9 (pp. 189-191). These diagrams show the distances assumed
between the various facilities. These distances were used to
determine the material required for the systems and the
subsequent costs.
Settling Ponds
Construction costs for settling ponds were based upon assumptions
(specifically documented later in this section) regarding the
C - DREDGES
162
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GOLD PLACER MINE SUBCATEGORY SECT - VIII
detention time and geometry of the ponds. Costs for earthmoving
were based on a cost per cubic yard of material moved. The cost
of earthmoving was determined by contacting the largest retailer
of earth-moving equipment and a leasing agency in Alaska. Using
this data the earthmoving capacity and costs of both new and old
equipment are as follows:
MINE
MODEL
EQUIPMENT NEW
Very Small
Open Cut
Small
Open Cut
Medium
Open Cut
Large
Open Cut
Small
Dredge
Large
Dredge
D6D Dozer
930 Loader
D7G Dozer
966C Loader
D8K Dozer
988B Loader
D9L Dozer
988B Loader
D8K Dozer
966C Loader
D8K Dozer
966C Loader
OPERATING CAPACITY
OLD NEW
150yd3/hr 120yd3/hr
125yd3/hr 100yd3/hr
300yd3/hr 240yd3/hr
250yd3/hr 200yd3/hr
450yd3/hr 360yd3/hr
420yd3/hr 340yd3/hr
640yd3/hr 520yd3/hr
420yd3/hr 340yd3/hr
LEASE COST*
OLD
450yd3/hr 360dy3/hr
250yd3/hr 200yd3/hr
450yd3/hr 360yd3/hr
250yd3/hr 200yd3/hr
$80.87/hr $ 64.72/hr
$71.19/hr $ 49.65/hr
$91.86/hr $ 71.16/hr
$79.27/hr $ 64.15/hr
$124.75/hr $ 89.53/hr
$141.80/hr $102.54/hr
$201.16/hr $134.47/hr
$141.80/hr $102.54/hr
$124.75/hr $ 89.53/hr
$ 79.27/hr $ 64.15/hr
$124.75/hr $ 89.53/hr
$ 79.27/hr $ 64.15/hr
*Includes equipment, insurance, fuel, operator and nominal
maintenance. Fuel cost used was $1.75 gallon (these estimates
also reflect maneuvering time).
The estimated costs and hours to construct the
were determined using both new and old machines.
Sludge Handling
settling ponds
All sludge which enters settling ponds is handled in the pond
system. This is accomplished by constructing the ponds with
sufficient capacity, in addition to that required for wastewater
settling, to contain the estimated volume of sludge produced per
year. A solids concentration in the sludge (settled solids) of
57 percent was used to calculate the pond volumes needed.
Costing for the earthmoving required for the sludge volume is
based on the cost of equipment presented under settling ponds.
The estimated costs and hours for sludge handling were determined
using both new and old machines.
Piping
Capital costs for piping, using aluminum pipe, were obtained from
various suppliers and from References 1 and 2. The costs include
the cost of the pipe, delivery to the site, and installation.
163
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GOLD PLACER MINE SUBCATEGORY SECT - VIII
Piping was sized based on normal velocities and pressure drop
used in engineering design. A minimum design velocity of 2-1/2
feet per second was used.
Capital costs for horizontal centrifugal pumps with diesel engine
drives, were obtained from vendor quotations and from References
1 and 2. Installation and delivery costs were added. The costs
include piping and valves at the pump location.
Polyelectrolyte Feed Systems
The capital costs for the polyelectrolyte feed systems were
obtained from vendor telephone quotations and installation and
delivery costs were added.
The polyelectrolyte feed system consists of a mixing and storage
tank, mixer, solution metering pump and small generator. The
polyelectrolyte feed solution would be prepared daily and
delivered to the wastewater by the metering pump set at the
proper dosage rate. The wastewater and polyelectrolyte solution
will be blended using a static mixer. This feed system is shown
schematically on Figure VIII-10 (p. 192).
Capital Cost of_ Land
Land costs were not included in the estimates since the
facilities would be constructed on land which is part of the
mining claims. Therefore, no additional costs would be incurred
for the land needed for the treatment facilities.
Delivery and Installation Costs
All equipment costs were increased by appropriate percentages to
account for delivery and installation at remote regions in
Alaska.
ANNUAL COST
Annual Equipment Depreciation Costs
Initial capital costs were depreciated on the basis of a 14
percent annual interest rate with assumed life expectancy of 7
years for general, civil, structural, mechanical, and electrical
equipment. However, since the settling ponds will be constructed
yearly, their cost is written off every year.
n
(r) (1+r)
CRF=
n
(1+r) -1
164
-------
GOLD PLACER MINE SUBCATEGORY * SECT - VIII
where CRF = capital recovery factor
r = annual interest rate
n = useful life in years
Therefore, CRF = 0.23319
Annual cost of depreciation was computed as:
Ca = B (CRF)
where Ca = annual depreciation cost, and
B = initial capital cost
Annual Cost of Operation and Maintenance
Maintenance
Annual maintenance costs were assumed to be 3 percent of the
total mechanical and electrical equipment capital costs (unless
otherwise noted) which excludes the annual costs of the ponds.
Reagents
A polyelectrolyte cost of $2.25/lb, delivered, was used to
estimate the annual chemical costs.
A dosage of 8 mg/1 (0.066 pounds per 1,000 gallons) was assumed
in calculating the annual cost for polyelectrolyte. This
assumption is based on the tests performed during the 1983, 1984,
and 1986 treatability studies.
Annual Cost of_ Energy
The energy cost required for wastewater treatment is the cost of
fuel to drive the required engines. Fuel cost at $1.75 per
gallon, including delivery, was used.
Facilities were assumed to operate 8 hours per day and 60 days
per year for very small open cut mines, 8 hours per day and 75
days per year for small open cut mines, 10 hours per day and 83
days per year for medium open cut mines, 20 hours per day and 85
days per year for large open cut mines, 24 hours per day and 100
days per year for small dredges, and 24 hours per day and 148
days per year for large dredges.
TREATMENT PROCESS COSTS
Simple Settling
Capital Costs
The required sizes of simple settling ponds was determined by
hydraulic loading and design data obtained during field settling
tests. Simple settling ponds were sized for each option based on
the appropriate detention times. All pond volumes include the
165
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GOLD PLACER MINE SUBCATEGORY SECT - VIII
required volume to treat the process flow plus an additional 20
percent for excess water. This volume was increased by 20
percent for freeboard and the volume for sludge storage was added
to arrive at the total pond volume required. It was assumed that
new ponds would be built when the detention time dropped below
the design figure due to sediment buildup. A sludge sediment
solids concentration of 57 percent was used for design purposes.
The wastewater was assumed to flow to and from the pond by
gravity. In all options having more than one simple settling
pond, it was assumed that three or four such ponds would be
constructed each mining season at different locations and that
the spent ponds would not be refilled.
The cost of pond construction for all options is based on the
construction cost of the pond walls. The cost presented is for
the construction of one longitudinal wall and one transverse
wall, which is the dam on the down stream end. This approach was
used since normal mining operations would stack tailings in such
a manner to basically form the longitudinal walls required for
the pond.
Secondary Settling
Capital Costs
The required sizes of secondary settling ponds were determined by
hydraulic loadings. Secondary settling ponds were sized for the
required detention times, previously indicated based on either
total flow of process and excess flow or excess flow alone. All
pond volumes have provisions for freeboard and sediment storage.
The wastewater was assumed to flow to and from the ponds by
gravity. One secondary pond would be constructed during the
mining season. The same method described under simple settling
was utilized when determining the cost of the secondary ponds.
Annual Costs
Since the ponds will only be constructed for one mining season,
the annual cost was assumed to be the total construction cost for
each pond.
Piping
Capital Costs
If recirculation is practiced, piping will be required from the
recirculation pumps to the processing plant. This length of pipe
is dependent on the conditions at each site (site specific).
Figures VIII-4 and VIII-5 (pp. 186-187) show typical layouts of
placer mine treatment systems with assumed distances. The length
of pipe from one end of the settling pond to the other will
depend upon the flow rate which dictates the pond size and
configuration.
166
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GOLD PLACER MINE SUBCATEGORY SECT - VIII
Prices for aluminum piping were obtained from manufacturers and
costs for transportation to the site and installation was added.
The pipe costs per thousand feet of pipe for various diameters
are as follows:
Size (dia.) $/1000 ft.
6" 4,075
8" 6,375
10" 7,830
12" 9,260
14" 10,850
Pipes were sized based on normal values of pressure drop and
velocity.
Annual Costs
Annual costs for piping systems were assumed to include the
following: (1) depreciation calculated at 14 percent annual
interest over 7 years for equipment (CRF = 0.23319), and (2)
annual maintenance at 3 percent of capital equipment costs.
Chemical Addition
Capital Costs
The capital costs were estimated for the polyelectrolyte feed
system as presented schematically on Figure VIII-10 (p. 192).
This feed system would feed the polyelectrolyte solution directly
into the wastewater flow utilizing a static mixer to mix the
wastewater and the polyelectrolyte.
Annual Costs
Depreciation of capital cost for the polyelectrolyte systems
assumed a 14 percent annual interest rate with life expectancies
of 7 years for equipment (CRF = 0.23319). Additional costs were
estimated as follows: annual maintenance was assumed to be 3
percent of capital equipment cost: chemicals were costed at $2.25
per pound for polymer. The cost of polyelectrolyte per 100 hours
operation versus flow rate is plotted on Figure VIII-11 (p. 193).
This figure indicates the cost for several chemical dosages.
Capital Costs
The recirculation pumps were assumed to be horizontal,
centrifugal types complete with diesel engines. The pumps are
normally supplied as a package which includes the pump engine,
and fuel tank and are either skid or wheel mounted.
Pumping equipment costs were based on vendor quotations. Local
167
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
piping, valves, and fittings were costed based on standard pump
piping configurations and the costing methodology in Reference 1.
Pumping equipment selection was based on hydraulic flow
requirements assuming a total dynamic head of 150 TDH# in feet.
Total capital costs estimates include pumps, diesel engine
drivers, piping valves, fittings, installation, and shipping.
Annual Costs
Annual cost for water pump systems were assumed to include the
following: (1) depreciation calculated at 14 percent annual
interest over 7 year for equipment (CRF = 0.23319). (2) annual
maintenance at 3 percent of capital equipment costs, and (3) fuel
computed at $1.75 per gallon, and (4) the cost of labor required
for the operation and installation.
Construction Time
Due to the relatively short operating period per year available
at many sites, the time required to construct and operate the
wastewater treatment facilities can reduce the total available
time for mining. Therefore, estimates were also prepared on the
time required to construct, install and operate the various
facilities. This includes pond construction, equipment
installation and chemical solution preparation, If ponds or
equipment installation was required more than once per year the
additional time was included in the estimate.
MODEL MINES
Development of Models
To estimate the costs of treatment, economic models were
developed that characterize the industry-wide range of operating
conditions of mines and dredges. Six baseline models were
developed to reflect small to large processing capacities,
including four model open cut mines and two model dredges. The
operating conditions assumed for each model are described below.
Very Small Open Cut
The very small open cut mine model is baseline mine processing
18,000 cubic yards of pay gravel annually, operating 8 hours per
day and 60 days per year. The baseline model has a process water
flow of 875 gpm based on a water application rate of 1,167
gallons per cubic yard.
Small Open Cut
The small open cut mine model is a baseline mine processing
35,000 cubic yards of pay gravel annually, operating 8 hours per
day and 75 days per year. The baseline model has a process water
168
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
flow of 1,350 gpm based on a water application rate of 1,157
gallons per cubic yard.
Medium Open Cut
The medium open cut mine model is a baseline mine processing
150,000 cubic yards of pay gravel annually, operating 10 hours
per day and 83 days per year. The baseline model has a process
water flow of 2,250 gpm based on a water application rate of 623
gallons per cubic yard.
Large Open Cut
The large open cut mine model is a baseline mine processing
340,000 cubic yards of pay gravel annually, operating 20 hours
per day and 85 days per year. The baseline model has a process
water flow rate of 2,500 gpm based on a water application rate of
625 gallons per cubic yard.
Small Dredge
The small dredge mine model is a baseline dredge which processes
216,000 cubic yards annually, operating 24 hours per day and 100
days per year. The baseline model has a process water flow rate
of 1,660 gpm based on a water application rate of 1,000 gallons
per cubic yard.
Large Dredge
The large dredge mine model is a baseline dredge which processes
an average of approximately 810., 000 cubic yards annually,
operating 24 hours per day and 148 days per year. The baseline
model has a process water flow rate of 3,800 gpm based on a water
application rate of 1,000 gallons per cubic yard.
Excess Water
All mines will be required to handle and treat water in excess of
that used for processing. This excess water is due to drainage,
ground water infiltration, natural thawing and other
miscellaneous waters entering the active mining area. The actual
volume of water will vary and must be determined on a site
specific basis.
The cost of treating this excess water, which can be determined
from the appropriate curve will have little impact on total cost
if the mine is treating the total wastewater discharging from the
active mining area. To determine a cost for the treatment of the
excess water an excess water volume of 20 percent of the process
flow was assumed.
ESTIMATED COSTS FOR THE TREATMENT
The estimated costs for each option previously discussed are
presented in tabular and graphic form on the following tables and
169
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
figures. Estimates of total fixed annual cost, total annual pond
costs, total annual operating cost, total annual cost and total
annual hours required are presented on the summary tables for
each mine model category for each appropriate treatment option.
A plot of the estimated total annual cost versus flow is
presented in Figures VIII-12 through VIII-37 (pp. 194-219).
The estimated total fixed annual cost is the depreciation cost
for mechanical equipment such as pumps, piping, chemical feed
systems, etc., using estimated costs of the equipment delivered
to site. The depreciation cost is based on a 14 percent annual
interest rate with assumed life expectancy of 7 years (0.23319
factor).
The estimated items total annual operating cost include some or
all of the following depending on the treatment option used:
o Equipment installation cost based on estimated
installation hours, any miscellaneous supplies to
install and any equipment required in the installation.
o Equipment maintenance cost based on 3 percent of
mechanical and electrical equipment capital cost
(purchase price).
o Energy cost for equipment based on the fuel
requirements per hour for equipment such as pumps,
number of hours operating per day and number of days
operating per year.
o Service cost based on the estimated hours per season to
service equipment such as recirculation pumps.
o Operator costs based on the estimated hours per season
to prepare the chemical solution required in the
treatment of the wastewater.
o Cost of chemicals based on dosage determined during
field testing, flow to be treated in gpm, number of
operating hours per day and number of operating days
per year.
Tables VIII-1 through VIII-6 (pp. 173-183) are summary tables for
each mine model presenting the summary cost for each applicable
option and treatment combination.
NON-WATER QUALITY ASPECTS OF POLLUTION CONTROL
The elimination or reduction of one form of pollution may cause
other environmental problems. Therefore, Sections 304(b) and 306
of the Act require EPA to consider the non-water quality
environmental impacts (including energy requirements) of certain
regulations. In compliance with these provisions, EPA has
considered the effect of this regulation on air pollution, solid
waste generation, water scarcity, and energy consumption. While
170
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
it is difficult to balance pollution problems against each other
and against energy utilization, EPA is promulgating regulations
which best serve often competing national goals.
The following non-water quality environmental impacts (including
energy requirements) are associated with the final regulation.
The impacts identified below are justified by the benefits
associated with compliance with the limitations and standards.
A. Air Pollution - Imposition of BPT may cause a minor
increase in the emissions of dust from the movement of earth to
build settling ponds recommended for the gold placer mining
subcategory. These emissions are not expected to create a
substantial air pollution problem. BAT and NSPS will not result
in any increase in air pollution above BPT. The Agency does not
consider this to be a significant impact.
B. Solid Waste - EPA estimates that the promulgated BPT
limitation for gold placer mines nationwide will generate
1,838,000 kkg (2,021,300 tons) per year of solid wastes (sludge)
(wet basis - 1986 production levels) as a result of wastewater
treatment; BAT will generate 1,977,000 kkg (2,174,800 tons) per
year solid waste from raw waste. These sludges will be comprised
of soil solids containing very small concentrations of toxic
metals, including arsenic, antimony, beryllium, cadmium,
chromium, copper, lead, mercury, nickel, selenium, silver,
thallium, and zinc. Because these sludges are characteristic of
the soils indigenous to the particular mine and contain no
additives, it is the Agency's view that solid wastes generated as
a result of these guidelines will not be considered as hazardous
under RCRA. Furthermore, an analysis was made of the toxic
metals data collected for raw and treated wastewaters at five
mines in 1986. This analysis showed that even if all of the
toxic metals taken out of the water in the sludge were extracted
by the RCRA EP test, the sludge would not be classified as a
hazardous (toxic) waste under RCRA.
C. Energy Requirements^ - EPA estimates that the achievement
of BPT effluent limitations will result in the consumption of
approximately 155,800 gallons of additional diesel fuel per year.
The BAT technology should increase the energy requirements above
BPT by 485,200 gallons per year. NSPS will not add any
additional energy requirements. To achieve the BAT effluent
limitations, a typical direct discharger will increase total
energy consumption by 14.2 percent of the energy consumed for
production purposes. This increase in energy consumption is not
considered to be of national significance.
D. Consumptive Water Loss - Treatment and control
technologies that require extensive recirculation and reuse of
water often result in the substantial consumption of water
because the water is used as a cooling mechanism. Because the
gold recovery processes do not generate heat or require cooling
of water, loss through evaporation is negligible. the Agency
concludes that the consumptive water loss is negligible and that
171
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
the pollution reduction benefits of recirculation outweigh the
impact on consumptive water loss.
172
-------
TABLE NO. VIII-1
PLACER MINING WASTEWATER OPTIONS
1987. COSTING STUDY
VERY SMALL OPEN CUT
SUMMARY
U)
I) OPTION A -
PROCESS FLOW IN GPM
SIMPLE (PLAIN) SETTLING - NEW
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
II) OPTION A - SIMPLE (PLAIN) SETTLING - OLD
III) OPTION A
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
MODEL
875
1000
EARTHMOVING EQUIPMENT
0
2630
0
2630
33
EARTHMOVING
0
2630
0
2630
40
0
2790
0
2790
35
2000 3000
- ONE POND
0 0
3830 4730
0 0
3830 4730
48 58
4000
0
5410
0
5410
66
5000
0
6100
0
6100
73
6000
0
6640
0
6640
80
7000
0
7230
0
7230
86
8000
0
7690
0
7690
92
9000
0
8220
0
8220
97
1000C
0
8630
0
8630
102
EQUIPMENT - ONE POND
0
2790
0
2790
43
0 0
3840 4740
0 0
3840 4740
59 71
0
5410
0
5410
82
0
6100
0
6100
91
0
6640
0
6640
99
0
7230
0
7230
107
0
7690
0
7690
114
0
8220
0
8220
121
0
8630
0
8630
127
- SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - THREE PONDS
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
IV) OPTION A - SIMPLE (PLAIN) SETTLING - OLD
V) OPTION B -
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
5670
0
5670
72
EARTHMOVING
0
5670
0
5670
87
RECIRCULATION - NEW EARTHMOVING EQUIPMENT -
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
3430
2630
4880
10940
46
0
6010
0
6010
75
0 0
8150 10090
0 0
8150 10090
102 123
0
11470
0
11470
141
0
12990
0
12990
156
0
14090
0
14090
169
0
15410
0
15410
180
0
16350
0
16350
192
0
17540
0
17540
204
0
18380
0
18380
213
EQUIPMENT - THREE PONDS
0
6010
0
6010
93
ONE POND
3440
2790
0 0
8150 10090
0 0
8150 10090
126 150
4960 6220
3830 4730
7410 10110 11090
13640 18900 22040
48
63 73
0
11470
0
11470
171
9630
5410
11450
26490
82
0
12990
0
12990
192
11930
6100
12540
30560
90
0
14090
0
14090
207
19150
6640
19160
44950
97
0
15410
0
15410
222
19240
7230
19180
45650
104
0
16350
0
16350
237
19620
7690
19230
46540
111
0
17540
0
17540
252
21000
8220
32820
62030
116
0
18380
0
18380
264
22560
8630
33830
65020
121
VI) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT - ONE POND
TOTAL FIXED ANNUAL COST: 3430 3440 4960 6220 9630 11930 19150 19240 19620 21000 22560
TOTAL ANNUAL POND COST: 2630 2790 3840 4740 5410 6100 6640 7230 7690 8220 8630
TOTAL ANNUAL OPERATING COST: 4860 7390 10080 11070 11430 12520 19140 19160 19210 32800 33810
TOTAL ANNUAL COST: 10920 13620 18880 22020 26470 30540 44930 45630 46520 62010 65000
TOTAL ANNUAL HOURS REQUIRED: 53 56 74 86 98 108 116 125 133 140 146
8
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TABLE VIII-1 (CONT.)
VERY SMALL OPEN CUT
SUMMARY
VII) OPTION
VIII) OPTION
IX) OPTION C
PROCESS FLOW IN GPM
B - RECIRCULATION - NEW EARTHMOVING
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
B - RECIRCULATION - OLD EARTHMOVING
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
- CHEMICAL TREATMENT OF TOTAL FLOW
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
MODEL
875
EQUIPMENT
3360
5670
5010
14040
127
EQUIPMENT
3360
5670
4950
13980
142
1000 2000
- THREE PONDS
3370 4800
6000 8150
5860 11090
15230 24030
130 160
- THREE PONDS
3370 4800
6090 8150
5800 11030
15170 23970
148 184
3000
5980
10090
12080
28150
182
5980
10090
12020
28080
209
4000
9360
11470
12460
33280
202
9360
11470
12390
33220
232
5000
11620
12990
13550
38160
218
11620 ,
12990
13490
38100
254
6000
18750
14100
20180
53020
231
18750
14100
20110
52960
270
7000
18800
15410
20200
54420
244
18800
15410
20140
54350
286
8000
19160
16350
20260
55760
257
19160
16350
20200
55710
302
9000
20420
17540
33850
71800
270
20420
17540
33780
71740
318
10000
21960
18380
34860
75190
280
21960
18380
34790
75130
331
- NEW EARTHMOVING EQUIPMENT
1140
990
6430
8560
60
1140 1300
1040 1360
7140 12850
9320 15510
63 92
1300
1700
18530
21530
120
1470
1900
24230
27600
148
1470
2180
29920
33570
176
1630
2350
35620
39600
203
1630
2600
41310
45540
230
1790
2740
47010
51540
257
1790
2970
52700
57460
283
1960
3090
58400
63450
310
X) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
1140 1140 1300 1300 1470 1470 1630 1630 1790 1790 1960
990 1040 1360 1700 1900 2180 2350 2600 2740 2970 3090
6430 7140 12850 18530 24230 29920 35620 41310 47010 52700 58400
8560 9320 15510 21530 27600 33570 39600 45540 51540 57460 63450
62 66 96 124 153 181 209 236 263 290 317
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TABLE NO. VIII-2
PLACER MINING WASTEWATER OPTIONS
1987 COSTING STUDY
SMALL OPEN CUT
SUMMARY
ui
PROCESS FLOW IN GPM
1000
MODEL
1350
2000 3000 4000
5000
6000
7000
8000
9000
10000
I) OPTION A - SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - ONE POND
II)
III)
IV)
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
OPTION A - SIMPLE (PLAIN) SETTLING - OLD
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
1840
0
1840
21
EARTHMOVING
0
1790
0
1790
25
0
2090
0
2090
24
0 0
2480 3070
0 0
2480 3070
28 33
0
3490
0
3490
38
0
3960
0
3960
42
0
4290
0
4290
45
0
4690
0
4690
49
0
4980
0
4980
52
0
5350
0
5350
55
0
5600
0
5600
58
EQUIPMENT - ONE POND
0
2030
0
2030
29
0 0
2410 2990
0 0
2410 2990
34 41
0
3390
0
3390
46
0
3850
0
3850
51
0
4170
0
.4170
56
0
4560
0
4560
60
0
4840
0
4840
64
0
5200
0
5200
67
0
5400
0
5400
71
OPTION A - SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
OPTION A - SIMPLE (PLAIN) SETTLING - OLD
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
4970
0
4970
56
EARTHMOVING
0
4850
0
4850
68
0
5600
0
5600
64
0 0
6560 8190
0 0
6560 8190
76 88
0
9220
0
9220
100
0
10530
0
10530
108
0
11350
0
11350
120
0
12510
0
12510
128
0
13210
0
13210
136
0
14270
0
14270
140
0
14900
0
14900
148
EQUIPMENT - FOUR PONDS
0
5450
0
5450
76
0 0
6390 7980
0 0
6390 7980
92 108
0
8980
0
8980
120
0
10260
0
10260
132
0
11050
0
11050
144
0
12180
0
12180
156
0
12870
0
12870
164
0
13910
0
13910
172
0
14510
0
14510
180
V) OPTION B - RECIRCULATION - NEW EARTHMOVING EQUIPMENT - ONE POND
TOTAL FIXED ANNUAL COST: 3460 4910 5000 6280 97000 12000 19250 19350 19740 21140 22720
TOTAL ANNUAL POND COST: 1840 2090 2480 3070 3490 3960 4290 4690 4980 5350 5600
TOTAL ANNUAL OPERATING COST: 6620 9930 13100 14300 14670 15960 24060 24080 24130 41090 42310
TOTAL ANNUAL COST: 11910 16930 20580 23650 27860 31920 47600 48130 48850 67570 70620
TOTAL ANNUAL HOURS REQUIRED: 68 72 76 82 88 93 97 101 105 108 112
VI) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT - ONE POND
TOTAL FIXED ANNUAL COST: 3460 4910 5000 6280 9700 12000 19250 1935Q 19740 21140 22720
TOTAL ANNUAL POND COST: 1790 2030 2410 2990 3390 3850 4170 4560 4840 5200 5440
TOTAL ANNUAL OPERATING COST: 6610 9920 13090 14290 14650 15950 24050 24070 24120 41070 42290
TOTAL ANNUAL COST: 11850 16850 20490 23550 27740 31800 47460 47980 48690 67410 70450
TOTAL ANNUAL HOURS REQUIRED: 72 77 82 90 96 102 108 112 117 120 125
8
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TABLE VIII-2 (CONT.)
SMALL OPEN CUT
SUMMARY
PROCESS FLOW IN GPM
MODEL
1000 1350 2000
3000 4000 5000 6000 7000 8000 9000 10000
VII) OPTION B - RECIRCULATION - NEW EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST: 3370 4740 4800
TOTAL ANNUAL POND COST: 4970 5600 6560
TOTAL ANNUAL OPERATING COST: 7330 10640 13830
TOTAL ANNUAL COST: 15670 20980 25190
TOTAL ANNUAL HOURS REQUIRED: 127 136 150
5970
8190
15050
29210
164
9350
9220
15430
34000
178
11610
10530
16740
38880
188
18740
11350
24840
54930
201
18790
12510
24880
56180
211
19140
13210
24940
57290
220
20400 21940
14270 14900
41890 43120
76570 79950
225 235
VIII) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
3370 4740 4800 5970 9350 11610 18740 18790 19140 20400 21940
4850 5450 6390 7980 8980 10260 ' 11050 12180 12870 13910 14510
7270 10580 13770 14990 15370 16680 24780 24820 24880 41830 43060
15480 20780 24960 28940 33690 38540 54570 55790 56890 76140 79510
139 148 166 184 198 212 225 239 248 257 267
IX) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - NEW EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
1140 1140 1300 1300 1470 1470 1630 1630 1790 1790 1960
740 810 920 1170 1290 1500 1590 1783 1870 2050 2120
8850 11340 15970 23080 30210 37310 44440 51550 58670 65780 72900
10720 13290 18200 25550 32960 40280 47660 54960 62330 69610 76970
69 81 103 136 168 201 233 266 298 330 363
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X) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
1140 1140 1300 1300 1470 1470 1630 1630 1790 1790 1960
720 790 900 1140 1260 1470 1560 1750 1830 2000 2070
8850 113-40 15970 23080 30210 37310 44440 51550 58670 65780 72900
10710 13270 18180 25530 32940 40240 47630 54920 62290 69570 76930
70 82 105 138 170 204 236 269 302 334 367
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TABLE NO, VIII-3
PLACER MINING WASTEWATER OPTIONS
1987 COSTING STUDY
MEDIUM OPEN CUT
SUMMARY
I) OPTION A -
II) OPTION A
III) OPTION A
PROCESS FLOW IN GPM
1000
2000
MODEL
2250 3000
4000
5000
6000
7000
8000
9000
10000
SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - ONE POND
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
- SIMPLE (PLAIN) SETTLING - OLD
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
1890
0
1890
17
EARTHMOVING
0
1720
0
1720
20
0
2550
0
2550
22
0 0
2690 3160
0 0
2690 3160
23 26
0
3590
0
3590
30
0
4070
0
4070
33
0
4410
0
4410
36
0
4830
0
4830
38
0
5120
0
5120
40
0
5500
0
5500
43
0
5760
0
5760
45
EQUIPMENT - ONE POND
0
2320
0
2320
22
0 0
2440 2880
0 0
2440 2880
23 26
0
3260
0
3260
30
0
3700
0
3700
33
0
4010
0
4010
36
0
4390
0
4390
38
0
4660
0
4660
40
0
5000
0
5000
43
0
5240
0
5240
45
- SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
IV) OPTION A - SIMPLE (PLAIN) SETTLING - OLD
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
5040
0
5040
48
EARTHMOVING
0
4640
0
4640
56
0
6670
0
6670
60
0 0
7010 8320
0 0
7010 8320
64 72
0
9370
0
9370
80
0
10700
0
10700
88
0
11530
0
11530
92
0
12700
0
12700
100
0
13420
0
13420
104
0
14490
0
14490
112
0
15130
0
15130
116
EQUIPMENT - FOUR PONDS
0
6100
0
6100
72
0 0
6400 7620
0 0
6400 7620
76 84
0
8560
0
8560
96
0
9790
0
9790
104
0
10540
0
10540
112
0
11640
0
11640
120
0
12280
0
12280
128
0
13280
0
13280
132
0
13850
0
13850
140
V) OPTION B - RECIRCULATION - NEW EARTHMOVING EQUIPMENT - ONE POND
TOTAL FIXED ANNUAL COST: 3490 5070 6030 6380 9820 12140 19340 19540 19940 21390 22980
TOTAL ANNUAL POND COST: 1890 2550 2690 3160 3590 4070 4410 .4830 5120 5500 5760
TOTAL ANNUAL OPERATING COST: 8790 17690 19250 19300 19670 21372 32280 32320 32370 55770 57400
TOTAL ANNUAL COST: 14160 25310 27970 28840 33080 37580 56030 56680 57430 82660 86140
TOTAL ANNUAL HOURS REQUIRED: 69 75 76 80 85 89 93 95 98 102 104
VI) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT - ONE POND
TOTAL FIXED ANNUAL COST: 3490 5070 6030 6380 9820 12140 19340 19540 19940 21390 22980
TOTAL ANNUAL POND COST: 1720 2320 2440 2880 3260 3700 4010 4390 4660 5000 5240
TOTAL ANNUAL OPERATING COST: 8750 17650 19210 19260 19630 21330 32240 32280 32330 55730 57360
TOTAL ANNUAL COST: 13960 25040 27680 28520 32710 37170 55590 56210 56930 82130 85580
TOTAL ANNUAL HOURS REQUIRED: 69 75 76 80 85 89 93 95 98 102 104
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TABLE VIII-3 (CONT.)
MEDIUM OPEN CUT
SUMMARY
VII) OPTION
PROCESS FLOW IN GPM
B - RECIRCULATION - NEW EARTHMOVING
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
1000
EQUIPMENT
3390
5040
9700
18130
124
MODEL
2000 2250
- FOUR PONDS
4850 5800
6670 7010
18640 20200
30150 33010
140 145
3000
6050
8320
20260
34630
155
4000
9440
9370
20650
39460
165
5000
11710
10700
22380
44790
175
6000
18790
11530
33300
63610
181
7000
18940
12700
33350
64990
190
8000
19300
13420
33410
66140
196
9000
20600
14490
56810
91910
205
10000
22150
15130
58450
95730
211
VIII) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST: 3390 4850 5800 6050 9440 11710 18790 18940 19300 20600 22150
TOTAL ANNUAL POND COST: 4640 6100 6400 7620 8560 9790 , 10540 11640 12280 13280 13850
TOTAL ANNUAL OPERATING COST: 9540 18480 20040 20110 20500 22220 33140 33190 33260 56660 58290
TOTAL ANNUAL COST: 17570 29430 32240 33770 38500 43720 62470 63770 64840 90540 94290
TOTAL ANNUAL HOURS REQUIRED: 132 152 157 167 181 191 201 210 220 225 235
IX) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - NEW EARTHMOVING EQUIPMENT
00
X) OPTION C -
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
CHEMICAL TREATMENT OF TOTAL FLOW
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
1140
730
12020
13880
82
1300
910
21870
24080
127
- OLD EARTHMOVING
1140
680
12020
13840
82
1300
850
21870
24020
128
1300
950
24320
26580
137
1300
1160
31700
34160
171
1470
1280
41550
44290
215
1470
1480
51380
54330
260
1630
1580
61230
64430
304
1630
1760
71060
74450
348
1790
1850
80910
84550
392
1790
2020
90740
94560
436
1960
2100
100590
104640
480
EQUIPMENT
1300
880
24320
26510
139
1300
1080
31700
34080
173
1470
1180
41550
44200
217
1470
1380
51380
54220
262
1630
1460
61230
64320
306
1630
1640
71060
74330
351
1790
1720
80910
84420
395
1790
1890
90740
94420
439
1960
1950
100590
104500
483
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TABLE NO. VIII-4
PLACER MINING WASTEWATER OPTIONS
1987 COSTING STUDY
LARGE OPEN CUT
SUMMARY
PROCESS FLOW IN GPM
1000
I) OPTION A - SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING
II) OPTION A
III) OPTION A
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
- SIMPLE (PLAIN) SETTLING - OLD
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
2770
0
2770
16
EARTHMOVING
0
2330
0
2330
19
MODEL
2000 2500
EQUIPMENT - ONE
0 0
3810 4320
0 0
3810 4320
22 24
3000
POND
0
4700
0
4700
25
4000
0
5370
0
5370
29
5000
0
6060
0
6060
32
6000
0
6590
0
6590
34
7000
0
7180
0
7180
37
8000
0
7630
0
7630
39
9000
0
8160
0
8160
41
10000
0
8570
0
8570
43
EQUIPMENT - ONE POND
0 0
3190 3630
0 0
3190 3630
26 28
0
3930
0
3930
30
0
4480
0
4480
35
0
5070
0
5070
38
0
5510
0
5510
41
0
6010
0
6010
44
0
6380
0
6380
47
0
6840
0
6840
50
0
7170
0
7170
52
- SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
IV) OPTION A - SIMPLE (PLAIN) SETTLING - OLD
V) OPTION B -
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
RECIRCULATION - NEW EARTHMOVING
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
0
6720
0
6720
44
EARTHMOVING
0
5730
0
5730
52
0 0
9050 10380
0 0
9050 10380
56 60
0
11230
0
11230
64
0
12730
0
12730
72
0
14450
0
14450
80
0
15650
0
15650
84
0
17150
0
17150
88
0
18170
0
18170
96
0
19530
0
19530
100
0
20440
0
20440
104
EQUIPMENT - FOUR PONDS
0 0
7640 8810
0 0
7640 8810
64 72
0
9510
0
9510
76
0
10740
0
10740
84
0
12230
0
12230
92
0
13220
0
13220
100
0
14520
0
14520
108
0
15360
0
15360
113
0
16560
0
16560
120
0
17300
0
17300
124
EQUIPMENT - ONE POND
3580
2770
16460
22810
70
VI) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
3580
2330
16420
22330
73
5270 6590
3810 4320
34520 37640
43600 48560
78 81
- ONE POND
5270 6590
3190 3630
34480 37600
42930 47820
82 85
6690
4700
27670
49060
82
6690
3930
37630
48250
87
10180
5370
38050
53590
88
10180
4480
38010
52670
94
12540
6060
41280
59880
92
12540
5070
41240
58850
98
19950
6590
62880
89410
95
19950
5510
62840
88290
102
20100
7180
62910
90190
99
20100
6030
62870
89010
106
20540
7630
62980
91150
102
20540
6380
62940
89860
110
22150
8160
110750
141060
104
22150
6840
110710
139700
113
23780
8570
113910
146260
107
23780
7170
113870
144820
116
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TABLE VIII-4 (CONT.)
LARGE OPEN CUT
SUMMARY
VII)
PROCESS FLOW IN GPM
OPTION B - RECIRCULATION - NEW EARTHMOVING
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
1000
EQUIPMENT
3430
6720
17380
27540
124
2000
- FOUR
4940
9050
35470
49460
140
MODEL
2500
PONDS
6130
10380
38610
55120
146
3000
6190
11230
38640
56060
151
4000
9600
12730
39050
61370
162
5000
11890
14450
42300
68640
173
6000
19100
15650
63910
98650
179
7000
19190
17150
63960
100291
185
8000
19560
18170
64030
101770
195
9000 10000
20930 22490
19530 20440
111810 114980
152300 157910
201 207
VIII) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT - FOUR PONDS
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
3430 4940 6130 6190 9600 11890 -19100 19190 19560 20930 22490
5730 7640 8810 9510 10740 12230 13220 14520 15360 16560 17300
17230 35320 38450 38490 38890 42150 63750 63800 63880 111650 114820
26390 47890 53390 54180 59230 66270 96060 97510 98800 149130 154610
132 148 158 163 174 185 195 205 211 221 227
00
o
IX) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - NEW EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST: 1140 1300 1300 1300
TOTAL ANNUAL POND COST: 920 1180 1290 1490
TOTAL ANNUAL OPERATING COST: 23850 44010 54080 64150
TOTAL ANNUAL COST: 25910 46500 56670 66940
TOTAL ANNUAL HOURS REQUIRED: 127 217 263 307
1470 1470 1630 1630 1790 1790 1960
1660 1910 2040 2270 2390 2600 2700
84300 104440 124600 144740 164890 185030 205190
87430 107820 128270 148640 169070 189420 209840
397 487 577 666 756 846 935
X) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST: 1140 1300 1300 1300 1470 1470 1630 1630 1790 1790 1960
TOTAL ANNUAL POND COST: 810 1020 1110 1290 1430 1650 1770 1970 2070 2260 2340
TOTAL ANNUAL OPERATING COST: 23850 44010 54080 64150 84300 104440 124600 144740 164890 185030 205190
TOTAL ANNUAL COST: 25800 46340 56490 66740 87200 107560 127990 148340 168750 189080 209480
TOTAL ANNUAL HOURS REQUIRED: 128 219 264 309 399 489 579 668 758 848 937
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TABLE NO, VIII-5
PLACER MINING WASTEWATER OPTIONS
1987 COSTING STUDY
SMALL DREDGE
SUMMARY
PROCESS FLOW IN GPM
MODEL
1000 1660
2000 3000 4000 5000 6000 7000 8000 9000 10000
I) OPTION A - SIMPLE (PLAIN) SETTLING - MEW EARTHMOVING EQUIPMENT-
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
4000 4460 71BO 8250 10610 11480 13020 15400 25010 32930 40770
2860 3600 3930 4850 5540 6250 6800 7310 7880 8320 8740
22730 27010 35700 48440 52910 57230 57410 87070 96460 105680 114900
29580 35080 46800 61530 69060 7-1960 77230 109780 129350 146930 164400
87 95 98 106 113 119 125 130 135 139 143
II) OPTION A - SIMPLE (PLAIN) SETTLING - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST;
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
4000 4460 7180 8250 10610 11480 13020 15400 25010 32930 40770
2600 3260 3550 4390 510 5660 6150 6600 7130 7520 7900
22710 26990 35690 48430 52900 57210 57390 87050 96450 105670 114880
29300 34720 46410 61060 68520 74350 76560 109060 128590 146120 163550
131 137 143 149 155 160
92
101
106
115
124
III) OPTION B - RECIRCULATIQN - NEW EARTHMOVING EQUIPMENT
00
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST;
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED;
2460 2610 2640 3080 3120 3530 4000 4050 4360 4420 4470
1230 1540 1670 2000 2390 2640 2860 3070 3260 3440 3610
9910 9940 14140 14200 18420 18470 13530 22740 22780 27000 27010
13600 14090 18450 19290 23930 24630 25380 29850 30400 34850 35090
71 75 76 SO £2 85 87 89 91 92 95
IV) OPTION B - RECIRCULATION - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
2460 2610 2640 3080 3120 3530 4000 4050 4360 4420 4470
1130 1400 1520 1320 2170 2390 2600 2780 2950 3120 3270
9890 9920 14130 14190 18400 18460 18510 22730 22770 26980 26Q90
13470 1.3930 18280 19080 23700 24380 Z5100 29550 30080 34510 34730
74 73 79 83 86 90 92 95 97 99 101
V) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - NEW EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
5180 5840 8560 9670 12220 13130 14850 27150 35080 43100 1630
3010 3850 4200 5190 5930 6680 7280 7820 8430 8900 9350
35450 42070 54330 70700 80250 88000 92430 127000 148840 168510 188280
43690 51770 67100 85550 98400 107820 114560 152070 184410 212500 240730
249 341 386 522 654 787 918 1050 1180 1311 1440
VI) OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
5180 5840 8560 9670 12220 13130 14850 17Z50 27150 35080 43100
2770 3490 3800 4690 5360 6050 6580 7070 7620 8050 8450
35440 42060 54320 70690 80240 87990 92520 126990 148830 168500 188260
43390 51390 66680 85040 97810 107160 113850 151300 183590 211620 239810
255 349 394 531 666 799 932 1065 1196 1327 1458
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-------
TABLE NO. VIII-6
PLACER MINING WASTEWATER OPTIONS
1987 COSTING STUDY
LARGE DREDGE
SUMMARY
PROCESS FLOW ID GPM
1000
MODEL
2000 3000 3800 4000 5000 6000 7000 8000 9000 10000
I) OPTION A - SIMPLE (PLAIN) SETTLING - NEW EARTHMOVING EQUIPMENT - ONE PRIMARY POND
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
4120 7400 8570 10940 10990 11980 13570 15990 25940 33890 41800
3390 4670 5760 6440 6590 7430 8090 8700 9370 9900 10400
33320 56360 71170 77650 77670 84020 84200 127990 141450 154710 167970
40830 64430 85500 95020 95250 103420 105860 152680 176750 198500 220170
148 156 162 168 174 180 185
116
129
139
II) OPTION A - SIMPLE (PLAIN) SETTLING - OLD EARTHMOVING EQUIPMENT
TOTAL FIXED ANNUAL COST: 4120 7400 8570
TOTAL ANNUAL POND COST; 3070 4220 5210
TOTAL ANNUAL OPERATING COST; 33310 52350 71150
TOTAL ANNUAL COST: 40500 63970 84930
TOTAL ANNUAL HOURS REQUIRED: 122 138 150
til) OPTION B - RECIRCULATION - NEW EARTHMOVING EQUIPMENT
10940 10990 11980 13570 15990 25940 33890 41800
5810 5950 6710 7310 7850 8460 8940 9390
77640 77650 84000 84190 127970 141440 154700 167950
94390 94590 102690 105070 151810 175830 197530 219140
159 160 170 177 184 192 198 204
CD
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST;
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
2490 2680 3140 3180 3190 3650 4120 4180 4550 4610 4670
1550 2070 2580 2850 2920 3320 3590 3840 4170 4390 4590
14430- 20690 20750 26990 26990 27050 27110 33340 33390 39620 39640
18470 25440 26470 33020 33090 34010 34820 41360 42100 48610 48900
97 102 107 110 110 114 116 119 121 123 125
IV)
V)
VI)
OPTION B - RECIRCULATION - OLD EARTHMOVING
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST:
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST;
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
OPTION C - CHEMICAL TREATMENT OF TOTAL FLOW
TOTAL FIXED ANNUAL COST:
TOTAL ANNUAL POND COST;
TOTAL ANNUAL OPERATING COST:
TOTAL ANNUAL COST:
TOTAL ANNUAL HOURS REQUIRED:
EQUIPMENT
2490
1420
14430
18340
100
2680
1890
20690
25260
106
- NEW EARTHMOVING
5320
3630
49650
58610
352
8810
5020
75920
89750
552
3140 3180
2350 2600
20750 26990
26240 32760
111 115
EQUIPMENT
9600 12570
6190 6920
99200 111690
114990 131180
749 904
3190
2660
26990
32830
115
12630
7090
112510
132230
944
3650
3020
27050
33720
119
13680
7980
123630
145280
1137
4120
3270
27110
34500
122
15450
8690
129330
153480
1331
4180
3490
33340
41020
126
17890
9350
179280
206520
1523
4550
3800
33390
41730
128
28150
10060
206750
244970
1715
4610
3990
39620
48220
131
36150
10640
231740
278530
1907
4670
4180
39640
48490
133
44230
11180
256810
312220
2098
- OLD EARTHMOVING EQUIPMENT
5320
3290
49640
58250
359
881.0
4530
75900
89240
562
9600 12570
5590 6240
99190 111680
114380 130490
760 917
12630
6400
112500
131520
957
13680
7210
123610
144500
1152
15450
7850
129320
152620
U47
17890
8440
179260
205590
1541
28150
9090
206740
243980
1734
36150
9600
231720
277480
1927
44230
10090
256790
311110
2119
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GOLD PLACER MINE SUBCATEGORY SECT - VIII
FIGURE VI I 1-1 PLACER MINING
WASTEWATER TREATMENT OPTIONS
SIMPLE (PLAIN) SETTLING
INFLUENT
IProeiK and Evceti Uaiarl
SlhPLE SETTLINO
4 Hour OBI. Tine
plui sludge ttoragt
(Built onoe par tgoion)
•»• EFFLUENT
(Prooati and Excess Voter)
OPTION -A- OPEN CUT - 1 POND
INFLUENT
and Exo*«« Water)
SlhPLE SETTLINO
4 Hour Get. Tina
plu« tludga storage
[Bui 11 three or four
11nei par year)
•*• EFFLUENT
(Process and Exae»s Wat«r(
OPTION -A- OPEN CUT - 3 OR 4 PONDS
DREDGE
POM)
Process and
Watir
SII*ff>LE SETTLINO
4 Hour Get. Tine
plus sludge storage
(Bui11 an OB par
Pracan and
Exeati Wottr
Discharged
or Returned
To
Dredge Pond
OPTION -A- DREDGE
183
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
FIGURE V I I I - 2 PLACER MINING
WASTEWATER TREATMENT OPTIONS
RECIRCULATION
INFLUENT
(Prodaii and Exoeii
REUSE ^_
SlfcPLE SETTLING
4 Hour Oat. Tina
piut tludqa itoraqe
iBuilt once par taoson)
EFFLUENT
(Exoan Voter )
RECYCLE OF
PROCESS WATER
OPTION -B- OPEN CUT - 1 POND
INFLUEt/T
(Proc»«s and
d Evoefft Voter)
SlfcPLE SETTLING
4 Hour Oat . Tin*
plui tludgt storogs
IBul i 1 thr«8 or four
1 tnas per ^ tor 1
c1
REUSE ^_
EFFLUENT
Water)
PUtPtND-lDOX
RECYCLE OF
PROCESS WATER
OPTION -B- OPEN CUT - 3 OR 4 PONDS
REUSE
PROCESS
EXCESS
WATER
SlbPLE SETTLING
4 Hour D«t. Tine
plus sludqa norag«
{Quill ono< per ssasonl
OPTION -B- DREDGES
EFFLUEhTT
(Excel) VatwI
184
-------
GOLD PLACER MINE SOBCATEGORY SECT - VIII
FIGURE VI I I-3 PLACER MINING
WASTEWATER TREATMENT OPTIONS
CHEMICALLY AIDED SETTLING
INFLUENT <
(Proceai and Exoai* Vatert
(Effluent fron Treainant
Option Al
SECONDARY SETTLING
3 Hour Dat. Tina
plui iludga ttorage
(Built onoe par
EFFLUENT
(Prooaii and Exoa*« Water)
OPTION -C- OPEN CUT
DREDGE
POND
CHEMICAL
ADDITION
Process and
Exoan Voter
SECONDARY SETTLING
3 Hour D«t. Tin*
plua sludge •toroga
(Built onoe per •ea*on)
and
Voter
Ditohargad
». or Raturnad
To
OPTION -C- DREDGE
185
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
v
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186
-------
FIGURE VII I-5 PLACER MINING INDUSTRY
GENERIC WATER SYSTEM SCHEMATIC
OPEN CUT - OPTION B
STREAM
oo
-j
I
RECYCLE PROCESS WATER
EXCESS
WATER
PROCESS
PLANT
TTT
111
SIW>LE
SETTLING
POND
300'* X
o
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FIGURE VI I I-6 PLACER MINING INDUSTRY
GENERIC WATER SYSTEM SCHEMATIC
OPEN CUT - OPTION C
STREAM
00
00
|5
EXCESS
WATER.
PLANT
TIT
1JLJL
SIMPLE
SETTLING
POND
X
300' * X
POND FOR
CHEAICALLY
AIDED SETTLING
OF WASTE WATER
8
5
EXCESS WATER
ESS
a
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FIGURE VI I I-7 PLACER MINING INDUSTRY
GENERIC WATER SYSTEM SCHEMATIC
DREDGE MIN NG - OPTION A
STREAM
GO
VO
TO
DISCHARGE
OR
RETURNED TO
DREDGE POND
BY GRAVITY
EXCESS
WATER
DREDGE
POND
PROCESS AND
EXCESS WATER
SlhFLE
SETTLING POND
-------
FI CURE VI I I - 8 PLACER MINING INDUSTRY
GENERIC WATER SYSTEM SCHEMATIC
DREDGE MINING - OPTION B
STREAM
EXCESS
WATER
RECYCLE OF
PROCESS WATER USING
EXISTING DREDGE
RECYCLE PUtPS
DREDGE
POND
TO DISCHARGE
OR
RETURNED TO
DREDGE POND
BY GRAVITY
EXCEM VATBt
SIWLE
SETTLING POND
-------
FIGURE VIM- 9 PLACER MINING INDUSTRY
GENERIC WATER SYSTEM SCHEMATIC
DREDGE MINING - OPTION C
STREAM
VD
CHEMICAL
FEED
SYSTEM
WATER
DREDGE
POND
rnxxw MB
BCCBM VATVt
TO DISCHARGE
OR
RETURNED TO
DREDGE POND
BY GRAVITY
POTO FOR
CHEMICALLY AIDED
SETTLING
a
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n
2
M
a
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n
a
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-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
FIGURE VI I I-10 PLACER MINING
WASTEWATER TREATMENT OPTIONS
POLYELECTROLYTE FEED SYSTEMS
MIXER
-MIXING AND
STORAGE TAM<
METERING
PUMP-
i-i
STATIC
MIXER
192
-------
FIGURE VI I I-11 1987 PLACER MINING COSTING STUDY
POLYELECTROLYTE COST PER 100 HOURS OPERATION
BASED ON POLY COST $2.2-5 PER POUND
30
FORMULA TO COMPUTE COST
gpn X ng/l X 0.013 X
a:
LU
Li.
O
to
u>
o
LU
O
O
O
w
15
10
V3
O
O
JO ng/L
18 ng/L
IB ng/l
M nq/l
13 ng/l
10 ng/l
a ng/l
0 ng/l
4 ng/t
3 ng/l
I ng/l
(0
FLOW RATE IN THOUSAND O.P.M.
-------
FIGURE No. VI II -12 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION A - OPEN CUT - ONE POND - SIMPLE SETTLING
VERY SMALL OPEN CUT
S
DOL
o
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NEW EARTHftQVING EDUIPnENT
OLD EARTHftOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
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FIGURE No. VI I I - 13 PLACER MININQ - WASTEWATER TREATMENT OPT IONS
OPTION A - OPEN CUT - ONE POND - SIMPLE SETTLING
SMALL OPEN CUT
NEV EARTHrtOVlNG EOUIPnENT
OLD EARTHftOVING EOUJPnOfT
10
FLOW RATE IN THOUSAND O.P.M.
(PROCESS WATER)
-------
FI PURE No. VI II - 14 PLACER MINING - WASTEWATER TREATMENT OPT IONS
OPTION A - OPEN CUT - ONE POND - SIMPLE SETTLING
MEDIUM OPEN CUT
o\
i •
NEV EARTHftOVING EQUIPMENT
OLD EARTHnnVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
-------
VD
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FI PURE No. VI I I - 15 PLACER MININ6 - WASTEWATER TREATMENT OPT IONS
OPTION A - OPEN CUT - ONE POND - SIMPLE SETTLING
LARGE OPEN CUT
10
8
NEV EARTHftOVING EQUIPMENT
OLD EARTHftOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
-------
FIOURE No. VI I I - 18 PLACER MINI NO - WASTEWATER TREATMENT OPT IONS
OPTION A - DREDGE - SIMPLE SETTLING
SMALL DREDGE
ID
00
CO
50
40
30
20
10
NEV EARTHflOVING EQUIPflENT
OLD EARTHflOVING EQUIPflEMT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
8
FIGURE No. VIII- 17 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION A - DREDGE - SIMPLE SETTLING
LARGE DREDGE
240
200
too
120
ao
40
NEV EARfmnOVING EQUIPMENT
OLD EARTHflOVING EQUIPnENT
9
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
P
a
s
w
-------
FIGURE No. VI11-18 PLACER MINING - VASTEVATER TREATMENT OPTIONS
tsj
O
o
OPTION A - OPEN CUT - THREE PONDS - SIMPLE SETTLING
VERY SMALL OPEN CUT
30
23
20
10
NEV EARTHflDVING EQUIPMENT
OLD EARTHflDVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No.VI I I- 19 PLACER MINING - WASTEWATER TREATMENT OPTIONS
CJ
Q
8
(J
OPTION A - OPEN CUT - FOUR PONDS
SMALL OPEN CUT
- SIMPLE SETTLING
18
12
NEV EARTWOVING EQUIPAENT
OLD EARTWOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
0
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FIGURE No, VI I I-20 PLACER MINING - WASTEWATER TREATMENT OPTIONS
en
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OPTION A - OPEN CUT - FOUR PONDS - SIMPLE SETTLING
MEDIUM OPEN CUT
16
is
NEV EARTHflOVING EOUIFnETfT
OLD EARTHnOVING EOUIPnENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
-------
FIGURE No. VI I 1-21 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION A - OPEN CUT - FOUR PONDS - SIMPLE SETTLING
LARGE OPEN CUT
M
O
19
NEW EAffTHnOVING EOUIPAENT
OLD EAffTHnOVINC EOUIPAENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
to
o
f*
FIGURE No. VI II -22 PLACER MINING - WASTEWATER TREATMENT OPTIONS
ANNUAL COST IN THOUSAND DOLLARS
— w * « -^ •
U O U O U O
OPTION B - OPEN CUT - ONE POND - REC 1 RCULAT 1 ON
VERY SMALL OPEN CUT
r«V EARTHrtDVlNG EO
OLD EARTHnOVING EO
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10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
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FIGURE No. VI I I -23 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION B - OPEN CUT - ONE POND - REC I RCULAT I ON
SMALL OPEN CUT
45
30
15
NEV EARTHAOVING EQUIPflENT
OLD EARTHAOVING EQUIPAENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
a
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FIGURE No. VI I I-24 PLACER MINING - VASTEVATER TREATMENT OPTIONS
OPTION B - OPEN CUT - ONE POND - RECIRCULATI ON
MEDIUM OPEN CUT
•0
73
00
45
30
IS
NEV EARTHflOVING EOUlFflENT
OLD EARTHflOVING EDUIPflENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
o
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ba
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FIGURE No. VI I 1-23 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION B - OPEN CUT - ONE POND - RECIRCULATI ON
LARGE OPEN CUT
190
129
too
79
8 ,„
(J
29
NEV EARTHflOVING EQUIPMENT
OLD EARTHrtOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-26 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION B - DREDGE - REC1RCULATI ON
SMALL DREDGE
10
o
00
340
200
160
120
U
40
EAFTTHAOVING EQUIPMENT
OLD EAFTTHAOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M .
(PROCESS WATER)
-------
FIGURE No. VI I I-27 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION B - DREDGE - RECIRCULATI ON
LARGE DREDGE
BO
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30
20
10
NEV EARTWOVING EQUIPflENT
OLD EARTHftOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-29 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION B - OPEN CUT - FOUR PONDS - RECIRCULATI ON
SMALL OPEN CUT
to
I-1
o
80
73
BO
49
O 30
(J
19
NEW EARTHADVING EQUIPMENT
OLD EARTHADVING EQLUPrtENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI II -28 PLACER MINING - VASTEVATER TREATMENT OPTIONS
ao
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5 BO
49
O 30
2 IS
OPTION B - OPEN CUT - THREE PONDS - REC 1 RCULAT ! ON
VERY SMALL OPEN CUT
NEV EARTHAOVING EQ
OLD EARTHAOVING EO
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FIGURE No. VI I I -30 PLACER MINING - VASTEVATER TREATMENT OPTIONS
OPTION B - OPEN CUT - FOUR PONDS - REG I RCULAT I ON
MEDIUM OPEN CUT
170
too
80
BO
40
20
NEV EARTHAOVING EQUIPMENT
CUD EARTHAOVING EDUIPftENT
to
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-31 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION B - OPEN CUT - FOUR PONDS - RECIRCULATI ON
LARGE OPEN CUT
180
190
120
90
80
30
NEV EARTHAOVING EQUIPAENT
OLD EARTHAOVING EQUIPAENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-32 PLACER MINING - WASTEVATER TREATMENT OPTIONS
OPTION C - OPEN CUT - CHEMICAL TREATMENT OF TOTAL FLOW
VERY SMALL OPEN CUT
90
73
eo
45
30
15
NEV EARTHAOVING EdUIPAENT
OLD EARTHAOVING EQUIPAENT
8
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I 1-33 PLACER MINING - WASTEWATER TREATMENT OPTIONS
u
OPTION C - OPEN CUT - CHEMICAL TREATMENT OF TOTAL FLOW
SMALL OPEN CUT
90
73
30
19
NEW EARTHAOVING EQUIP/VENT
OLD EARTHAOVING EQUIP/VENT
a
to
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-34 PLACER MINING - UASTEWATER TREATMENT OPTIONS
8
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OPTION C - OPEN CUT - CHEMICAL TREATMENT OF TOTAL FLOW
MEDIUM OPEN CUT
120
100
80
00
20
NEV EARTHAOVING EQUIPAENT
OLD EARTHAOVING EQUIPAENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-35 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION C - OPEN CUT - CHEMICAL TREATMENT OF TOTAL FLOW
LARGE OPEN CUT
210
179
140
109
70
39
NEV EARTHAOVING EOUIPAENT
OLD EARTHAOVING EOUIPAENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I -36 PLACER MINING - WASTEWATER TREATMENT OPTIONS
en
4
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OPTION C - DREDGE - CHEMICAL TREATMENT OF TOTAL FLOW
SMALL DREDGE
180
Ul
0
M
0
tO
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0
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NEV EARTHAOVING EQUIPMENT
OLD EARTHftOVING EQUIPMENT
10
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
FIGURE No. VI I I-37 PLACER MINING - WASTEWATER TREATMENT OPTIONS
OPTION C - DREDGE - CHEMICAL TREATMENT OF TOTAL FLOW
LARGE DREDGE
210
175
140
105
70
39
NEV EARTHAOVING EQUIPAENT
OLD EARTHAOVING EQUIPAENT
to
FLOW RATE IN THOUSAND G.P.M.
(PROCESS WATER)
-------
GOLD PLACER MINE SUBCATEGORY SECT - VIII
This Page Intentionally Left Blank
220
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GOLD PLACER MINE SUBCATEGORY SECT - IX
SECTION IX
BEST PRACTICABLE TECHNOLOGY (BPT)
This section defines the effluent characteristics attainable
through the application of the best practicable control
technology currently available (BPT) as required by Section
301(b)(l)(A) of the Clean Water Act. BPT reflects the
performance by plants of various sizes, ages, and processes
within the gold placer mine subcategory. Particular
consideration is given to the treatment already in place.
BPT limitations for eleven subcategories of the ore mining
category were promulgated in 1978 and were upheld in the courts
(see Kennecott Copper Corp. y_._ EPA, 612 F.2d 1232 (10th Cir.
1979)). Effluent limitations for gold placer mines were not
promulgated at that time and have been delayed until additional
information could be developed. While the initial date for
compliance with BPT (1977) has passed, EPA is promulgating BPT
because BPT is a necessary baseline for BCT, BAT, and other
requirements of the CWA.
The effluent limitations and standards for all ore mining and
dressing facilities regulated by Subpart M (Gold Placer Mines)
are applicable to point source discharges from active mines,
active mills, and beneficiation plants and are not applicable to
closed or abandoned mines or mills, or to discharges from mine
areas being reclaimed, or to point or non-point sources from
areas outside of the mine area. These effluent limitations apply
to facilities discharging wastewater from mines that produce gold
or gold bearing ores from gold placer deposits and the
beneficiation processes to recover gold or gold bearing ore which
use gravity separation methods. This regulation does not apply
to gold mines extracting ores (hard rock ores and mines) other
than gold placer deposits nor to the gold ore mills associated
with hard rock mines regardless of the extraction process used in
those mills. This regulation does not apply to the. wastewaters
from gold or gold ore extraction processes from gold placer
deposits that use cyanide or other chemicals for leaching gold or
to extraction processes that use froth flotation methods. These
effluents are regulated in the 1982 rulemaking for ore mining.
The data and information contained in this document apply
primarily to the process wastewater discharges from the
beneficiation process. The promulgated effluent limitations and
standards apply to this process wastewater and to mine drainage.
However, any other waters such as surface water, and infiltration
(groundwater) which becomes commingled with the beneficiation
process water or wastewater is also subject to these limitations
and standards.
221
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GOLD PLACER MINE SUBCATEGORY SECT - IX
SUBCATEGORIZATION OF GOLD PLACER MINES
As discussed in Section IV, for the purposes of developing
effluent limitations guidelines and standards, gold placer mining
is defined as a separate subcategory in the Ore Mining and
Dressing point source category. The gold placer mine subcategory
establishes a small size cutoff for both open-cut mines and
dredges. While these small operations are not regulated by those
limitations and standards, they are required by the provisions of
the CWA to obtain an NPDES permit for any discharges to waters of
the United States. Mines that process less than 1,500 cu yds of
ore per year, or dredges processing less than 50,000 cu yds per
year, and operations in open water (e.g., open marine waters,
bays, or major rivers) are not regulated by this gold placer mine
subpart. Mines that process less than 1,500 cu yds of ore per
year generally are intermittent, recreational, prospecting,
development, or assessment operations. Because of the diversity
among these operations, the preferable approach is to develop
effluent limits for them based on the permit writer's best
professional judgment. Dredges processing less than 50,000 cu yd
per year are not included because their existence was brought to
the attention of the Agency very late in the regulatory process
and the Agency was unable to develop, in a timely manner, the
technical data and economic models that are basic to regulation.
This small number of dredges can be regulated using the permit
writer's best professional judgment. Operations conducted in
open waters are not covered because the Agency has little
information as to number, location, or applicable technologies
for these facilities. Permits for these operations will be based
on the permit writer's best professional judgment.
The final economic impact analysis of gold placer mines did not
indicate any need for subcategorization based on economic factors
related to any of the technical options considered or to the
sizes of the facilities regulated. The obvious physical
differences in open-cut mines and dredges make it appropriate to
separately identify these entities in the regulation. No further
subcategorization of the industry was found to be necessary.
TECHNICAL APPROACH TO BPT
The factors considered in identifying BPT include: 1) the total
cost of applying the technology in relation to the effluent
reduction benefits to be achieved from such application; 2) the
size and age of equipment and facilities involved; 3) the
processes employed; (4) non-water quality environmental impacts,
(including energy requirements), and (5) other factors the
Administrator considers appropriate. These factors are
considered below. The Act does not require or permit
consideration of water quality problems attributable to
particular point sources or subcategories, or water quality
requirements in particular water bodies in setting technology-
based effluent limitations and standards. Accordingly, water
quality considerations are not the basis for selecting the BPT
222
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GOLD PLACER MINE SUBCATEGORY SECT - IX
(see Weyerhaeuser Company y_^ Costle, 590 F.2d 1011 (D.C. Cir.
1976)).
The cost-benefit inquiry for BPT is a limited balancing,
committed to EPA's discretion, which does not require the Agency
to quantify benefits in monetary terms (see, e.g., American Iron
and Steel Institute v^ EPA, 526 F.2d 1027 (3rd Cir. 1975)). To
balance costs in relation to effluent reduction benefits, EPA
considers the volume and nature of existing discharges, the
volume and nature of discharges expected after application of
BPT, the general environmental effects of the pollutants, and the
cost and economic impacts of the required pollution control
level.
In general, the BPT level represents the average of the best
existing performances of plants of various ages, sizes, processes
or other common characteristics. Where existing performance is
uniformly inadequate, BPT technology may be transferred from a
different subcategory or category. Limitations based on transfer
technology must be supported by a conclusion that the technology
is, indeed, transferable and a reasonable prediction that it will
be capable of achieving the prescribed effluent limitations (see
Tanners' Council of America v^ Train, 540 F. 2d 1188 (4th Cir.
1976)). BPT focuses on end-of-pipe treatment rather than process
changes or internal controls, except where such are common
industry practice.
The Agency studied gold placer mines to identify the processes
used and the wastewaters generated by mining and beneficiation.
Raw wastewater from the beneficiation process at gold placer
mines, sampled by the Agency over four years, averaged 20,000
mg/1 TSS. The beneficiation processes at these mines produce
over two million tons per year of water born solids (TSS) in the
extraction process.
As discussed in Section VII, the control and treatment
technologies available to gold placer mines include both in-
process and end-of-pipe technologies. Based on the pollutants
found in the wastewater discharge (described in Section V) and
the pollutants selected for consideration for control (see
Section VI), the following four technologies were considered as
possible bases for BPT.
1. Simple Settling - Settling ponds can be installed as
single large ponds, but they often are installed in an
arrangement of two or more ponds in series. Simple settling
removes water-borne solids found in wastewater, and the ponds in
series further reduce settleable solids and total suspended
solids (TSS) loadings in each of the sequential ponds. The
principal involved is the retention of the wastewater long enough
to allow the solids (particulates) to settle while keeping the
velocity of the flow to a minimum approaching quiescent settling
conditions. Sludge storage is critical and must be considered in
the design and construction of a pond.
223
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GOLD PLACER MINE SUBCATEGORY SECT - IX
Virtually all commercial gold placer mines operating since 1984
have settling ponds of varying numbers, sizes, and efficiencies.
The effluent limitations contained in NPDES permits for gold
placer mines were based on the use of settling ponds; as a
result, the technology is available and in use by the industry.
However, sampling data and other information on existing ponds
indicate that many ponds are inadequately designed, constructed,
or maintained to consistently produce an acceptable effluent
quality or concentration of solids (settleable solids and TSS).
Treatment facilities to control solids with simple settling
technology are designed to provide 4 hours of settling in well-
constructed and well-operated ponds. These ponds reduce the flow
velocity to a minimum and have sufficient volume available to
accommodate sludge accumulation and to preclude remixing or
cutting of solids from the sludge back into the effluent. As
discussed in Section VII, the long-term achievable level for
solids, based on 1986 data from existing treatment at placer
mines, is less than 0.2 ml/1 settleable solids. Field tests
indicate settleable solids are reduced to less than 0.2 ml/1 with
about 3 hours quiescent settling as determined by the 1984 and
1986 Alaskan placer mining study and testing program. Adding an
hour to the quiescent settling time derived from settling tests
will provide a retention time in an actual pond with an adequate
margin of reliability considering the pond "end effects" on the
wastewater. Finally, Discharge Monitoring Reports (DMR) from 107
mines which reported to Region X in 1984 revealed over 2,600
individual grab samples with settleable solids at 0.2 ml/1 or
less. This represented approximately 25 percent of the total
number of mines reported on the DMR.
2. Recycle of Process Wastewater - Recycle of process water
from simple settling ponds is discussed in detail in Section VII
and is an in-process treatment technology. Recycle of any
portion of the process water requires the addition of a suitable
pump and piping back to the gold recovery process facility.
3. Recirculation of Process Wastewater - As applied to gold
placer mining, recirculation is the continued reuse of water as
the transport medium for solids (ore) to or through the
classification process, the beneficiation process, and the
wastewater treatment process. This technology is discussed in
greater detail in Section VII.
4. Coagulation and Flocculation - The use of flocculants
is also discussed in detail in Section VII. The Agency has very
limited information on the use of coagulation and flocculation by
gold placer mines in the United States, but this technology is
used by wastewater treatment facilities in many industrial
categories, by many mines and mills in other ore mining
subcategories, and by coal mines and coal preparation plants.
Flocculant addition and coagulation increase the size of
particles for settling by forming floes (large particles) which
settle faster because of the increased weight and size. Pilot
testing of the use of flocculants was conducted at placer mines
which indicates that attainable effluent limitations for
224
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GOLD PLACER MINE SUBCATEGORY SECT - IX
coagulation and flocculation are zero settleable solids and less
than 100 mg/1 TSS.
OPTION SELECTION
Three options for control of wastewater pollutants were
considered for BPT. These are simple settling, simple settling
plus recycle or recirculation, or simple settling plus coagulant
aids. The reasons for selection or rejection of these options
follows. Each technology option may apply equally to mines or
dredges.
Simple settling is a mature technology which is commonly
practiced throughout the subcategory. It therefore conforms to
the minimum considerations for BPT of demonstrated availability.
Hence, simple settling could become the basis for BPT providing
no other more stringent and appropriate technologies are
available.
Simple settling with recycle or recirculation red- ces the
quantities of pollutants discharged. However, it requires in-
process changes and is not commonly practiced throughout the
subcategory. The in-process nature of recirculation and the lack
of common practice throughout the subcategory make this
technology unacceptable as the basis for BPT.
Chemically aided settling or flocculation is also discussed in
detail in Section VII. As indicated in that discussion, the
application of flocculation is neither demonstrated nor commonly
practiced within the subcategory. Therefore, it is unacceptable
as the technology basis for BPT.
Because technology options including recirculation and
flocculation are not acceptable as the basis for BPT, simple
settling has been selected as the basis for BPT. Figure IX-1 (p.
231) illustrates an example of simple settling at an open cut
mine. This technology requires the removal of settleable solids
from all process wastewater to less than 0.2 ml/1 before
discharge.
Implementation of the BPT limi .ations nationwide for open-cut
mines and dredges combined will remove annually from estimated
raw waste 387,499 kg (852,379 pounds) toxic metals and 1,838,592
metric tons (kkg) (2,021,351 tons) TSS. In Alaska alone, 177,004
kg (389,407 pounds) toxic metals and 889,373 kkg (978,319 tons)
TSS will be removed by implementation of BPT. The total annual
cost of achieving BPT at gold placer mines is $1.25 million for
the Alaska gold placer mines and $2.42 millon for all gold placer
mines. There is no projected capital cost for achieving BPT.
The economic impact on the subcategory is discussed in detail in
the "Economic Impact Analysis of Effluent Limitations and
Standards for the Placet" Gold Mining Industry." EPA feels that
the benefit of the BPT effluent limitations justifies the cost of
implementation.
225
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GOLD PLACER MINE SUBCATEGORY SECT - IX
BPT FOR GOLD PLACER MINES
The following effluent limitations represent the degree of
effluent reduction attainable by the application of the best
practicable control technology currently available (BPT).
Except as provided in 40 CFR 125.30-125.32, any existing point
source subject to this subpart must achieve the following
effluent limitations representing the degree of effluent
reduction attainable by the application of the best practicable
control technology currently available (BPT):
(a) The concentration of pollutants discharged in process
wastewater from an open-cut mine plant site shall not exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
b) The concentration of pollutants discharged in process
wastewater from a dredge plant site shall not exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
SPECIALIZED PROVISIONS FOR GOLD PLACER MINES: STORM EXEMPTION
Although permittees in the gold placer mine subcategory will be
entitled to upset and bypass provisions specified in NPDES
permits, this regulation establishes the specific conditions
which must be met in order to be eligible for the storm exemption
established as part of the technology-based requirements of this
regulation. The Agency recognizes that mines, in particular
surface mines, should not be required to construct treatment for
the maximum precipitation event, or series of precipitation
events, that could occur with the resulting effects on wastewater
and mine drainage discharge flows. The Agency, therefore,
226
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GOLD PLACER MINE SUBCATEGORY SECT - IX
established for gold placer mines the criteria to be used by gold
placer miners in designing, constructing, and maintaining the
wastewater treatment facilities, i.e., that the facilities must
be able to contain and treat the maximum volume of wastewater
resulting from processing ore during a 4-hour period plus the
volume that would be discharged from a 5-year, 6-hour
precipitation event. The storm exemption requires that ponds be
designed to retain the volume of wastewater generated during a 6-
hour processing period. The final rule is based on the retention
of process water that would be generated during a 4-hour period,
since, as discussed in Section VII, the Agency bases the
limitations in this regulation on a 4-hour retention period. If
the operator complies with this provision, the operator has an
affirmative defense against an enforcement action for any
violation if he complies with the notification requirements of
122.41(m) and (n) of the general permit regulation. The storm
exemption supersedes the general upset and bypass provisions of
the general NPDES permit regulations only with respect to
precipitation events. The upset and bypass provisions in the
general permit regulations are available in all other applicable
situations. The storm exemption as it applies to gold placer
mining is included below:
If, as a result of precipitation (rainfall or snowmelt), a source
has an overflow or discharge of effluent which does not meet the
applicable limitations or standards, ~the source may qualify for
an exemption from such limitations and standards with respect to
such discharge if the following conditions are met:
The 5-year, 6-hour storm event was chosen as the level at which
the storm exemption would apply because the mine life of most
gold placer mines is projected to be about five to 7 years and
the pond size envisioned at proposal had a six hour retention
time. On the basis of subsequent data, the projected pond size
has been reduced to four hours, but the storm exemption remains
unchanged.
(i) The treatment system is designed, constructed, and
maintained to contain or treat the maximum volume of untreated
process wastewater which would be discharged, stored, contained,
and used or recycled by the beneficiation process into the
treatment system during a 4-hour operating period without an
increase in volume from precipitation or infiltration, plus the
maximum volume of water runoff resulting from a 5-year, 6-hour
precipitation event. In computing the maximum volume of water
which would result from a 5-year, 6-hour precipitation event, the
operator must include the volume which would result from the
plant site contributing runoff to the individual treatment
facility.
(ii) The operator takes all reasonable steps to maintain
treatment of the wastewater and minimize the amount of overflow.
(iii) The source is in compliance with the BMP in 140.148
and related provisions of its NPDES permit.
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GOLD PLACER MINE SUBCATEGORY SECT - IX
(iv) The operator complies with the notification
requirements of the NPDES regulations contained in 40 CFR 122
8122.41 (m) and (n). The storm exemption is designed to provide
an affirmative defense to an enforcement action. Therefore, the
operator has the burden of demonstrating to the appropriate
authority that the above conditions have been met.
GUIDANCE FOR IMPLEMENTING THE STORM EXEMPTION
Following is guidance for implementation of the storm exemption
provision presented above to assist permit writers to include the
provision in NPDES permits and for mine operators who wish to
design, construct, and maintain their treatment facilities to
qualify for the provision.
1. The exemption is available only if it is included in the
operator's permit. Many existing permits have exemptions or
relief clauses stating requirements other than those set forth
above. Such relief clauses remain binding until the storm
exemption is incorporated into the operator's permit.
2. The storm provision is an affirmative defense to an
enforcement action. Therefore, there is no need for the
permitting authority to evaluate each settling pond or treatment
facility permitted.
3. The relief only applies to the increase in flow caused
by precipitation on the facility and surface runoff.
4. Relief is granted as an exemption to the requirements
for normal operating conditions when there is an overflow,
increase in volume of discharge, or discharge from a by-pass
system caused by precipitation.
5. The provision does not grant, nor is it intended to
imply, the option of ceasing or reducing efforts to contain or
treat the runoff resulting from a precipitation event or snowmelt
regardless of the intensity of the precipitation. The operator
must continue to operate the treatment facility to the best of
the operator's ability during and after any precipitation.
6. Relief can be granted from all effluent limitations and
standards, i.e., in BPT, BAT- and NSPS.
7. In general, the relief is intended for discharges from
tailings ponds, settling ponds, holding basins, lagoons, etc.,
that are associated with and are a part of treatment facilities.
The relief most often will be based on the construction and
maintenance of these settling facilities to "contain" a volume of
water.
8. The term "contain" for facilities which are allowed to
discharge must be considered in conjunction with the term "treat"
discussed in paragraph 10 below. The containment requirement is
228
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GOLD PLACER MINE SUBCATEGORY SECT - IX
intended to ensure that the facility has sufficient capacity to
provide 4 hours of settling time for the volume resulting from a
5-year, 6-hour precipitation event. This is the settling time
required to "treat" influent so that it meets the daily effluent
limitations and standards. The theory is that a settling
facility with sufficient volume to contain the runoff from a 5-
year, 6-hour rainfall plus 4 hours' discharge of normal process
wastewater and normal combined waste streams (e.g., without an
increase in volume from precipitation) can provide a minimum 4-
hour retention time for settling of the wastewaters even if the
pond is full at the time the storm occurs. The water entering
the pond as a result of the storm is assumed to follow a last-in,
last-out principle. Because of this, the "contain" and
"maintain" requirement for facilities which are allowed to
discharge does not require providing for draw down of the pool
level during dry periods. The volume can be determined from the
top of the stage of the highest dewatering device to the bottom
of the pond at the time of the precipitation event. There is no
requirement for relief to be based on the facility being emptied
of wastewater prior to the rainfall or snowmelt upon which the
exemption is provided. The term "contain" for facilities which
are allowed to discharge means the wastewater facility's holding
pond or settling pond was designed to include the volume of water
that would result from a 5-year, 6-hour rainfall.
9. The term "treat" applies to facilities which are
allowed to discharge, and means the wastewater facility was
designed, constructed, and maintained to meet the daily maximum
effluent limitations for the maximum flow volume in a 4-hour
period. The operator has the option to "treat" the flow volume
of water that would result from a 5-year, 6-hour rainfall in
order to qualify for the storm water exemption. To compute the
maximum flow volume, the operator includes the maximum flow of
wastewater including mine drainage and groundwater infiltration
during normal operating conditions without an increase in volume
from precipitation plus the maximum flow that would result from a
5-year, 6-hour rainfall. The maximum flow from a 5-year, 6-hour
rainfall can be determined from the Water Shed Storm Hydrograph,
Penn State Urban Runoff Model, or similar models.
10. The term "maintain" is intended to be synonymous with
"operate." The facility must be operated at the time of the
precipitation event to contain or treat the specified volume of
wastewater. Specifically, in making a determination of the
ability of a facility to contain a volume of wastewater or to
provide 4 hours of retention of wastewater to treat a volume or
flow, sediment and sludge must not be permitted to accumulate to
such an extent that the facility cannot hold the volume of
wastewater resulting from 4 hours of normal process wastewater
discharge and normal combined waste streams plus the volume
resulting from a 5-year, 6-hour rainfall. That is, sediment and
sludge must be removed as required to maintain the specific
volume of wastewater required for the exemption, or the
embankment must be build up or graded to maintain a specific
229
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GOLD PLACER MINE SUBCATEGORY SECT - IX
volume of wastewater required, or a new settling pond must be
built and used.
11. The term "contain" for facilities treating only process
wastewater subject to no discharge means the wastewater facility
is designed, constructed, and maintained to hold, without a point
source discharge, the volume of water that would result from a 5-
year, 6-hour rainfall, in addition to the normal amount of water
which would be in the wastewater facility for recirculation and
reuse to the beneficiation process, e.g., without an increase in
volume from precipitation. The operator treating only process
wastewater must provide for freeboard under normal operating
conditions equivalent to the volume that would result from a 5-
year, 6-hour rainfall on the beneficiation process area
(including the ponds).
This storm exemption is applicable to all effluent limitations
and standards, i.e., BPT, BAT, and NSPS.
230
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to
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SETTL NG POND
OPEN CUT AIM
BPT
D
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Figure IX - 1
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GOLD PLACER MINE SUBCATEGORY SECT - IX
This Page Intentionally Left Blank
232
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GOLD PLACER MINE SUBCATEGORY SECT - X
SECTION X
BEST AVAILABLE TECHNOLOGY ECONOMICALLY ACHIEVABLE (BAT)
The effluent limitations in this section apply to existing direct
dischargers. A direct discharger is a facility which discharges
or may discharge pollutants into waters of the United States.
This section presents information on direct dischargers and, in
addition, presents total subcategory data.
The factors considered in assessing the best available technology
economically achievable (BAT) include the age of equipment and
facilities involved, the processes employed, process changes,
non-water quality environmental impacts (including energy
requirements), and the costs of application of such technology
(CWA Section 304(b)(2)(B)). BAT technology represents the best
available economically achievable performance of plants of
various ages, sizes, processes, or other shared characteristics.
BAT may include process changes or internal controls, even when
these are not common industry practice.
TECHNICAL APPROACH TO BAT
Input to BAT selection includes all materials discussed and
referenced in this document. As discussed in Section V,
sampling and analysis programs were conducted to evaluate the
presence or absence of toxic pollutants. A series of pilot-scale
treatability studies was performed at several locations to
evaluate BAT alternatives.
Consideration was also given to:
1. Age and size of facilities and equipment involved
2. Process(es) employed
3. In-process control and process changes
4. Economic achievability of the potential BAT alternative
control or treatment technologies
5. Non-water quality environmental impacts (including
energy requirements)
In general, the BAT technology level represents the best
economically achievable performance of plants of various ages,
sizes, processes, or other shared characteristics. BAT may
include feasible process changes or internal controls, even when
not in common industry practice. This level of technology also
considers those plant processes and control and treatment
technologies which at pilot-plant and other levels have
233
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GOLD PLACER MINE SUBCATEGORY SECT - X
demonstrated both technological performance and economic
viability at a level sufficient to justify investigation.
The Agency has reviewed a variety of technology options and
evaluated the available possibilities to ensure that the most
effective and beneficial technologies were used as the basis for
BAT. EPA examined technology alternatives which could be applied
as the gold placer mine BAT options and which would represent
substantial progress toward prevention of environmental pollution
beyond progress achievable by BPT.
The Clean Water Act requires consideration of costs in BAT
selection but does not require a balancing of costs against
effluent reduction benefits (see Weyerhaeuser v. Costle, 11 ERC
2129 (DC Cir. 1978)). In developing the proposed BAT, however,
EPA has given substantial weight to the reasonableness of costs
and the reduction of pollutants discharged. The Agency has
considered the volume and nature of discharge before and after
application of BAT alternatives, the general environmental
effects of the pollutants, and the costs and economic impacts of
the required pollution control levels. The options presented
represent a range of costs so as to assure that affordable
alternatives remain after the economic analysis. The rationale
for the Agency's selection of BAT effluent limitations is
summarized below.
BAT OPTION SELECTION
EPA considered the same treatment and control options discussed
in Section VII which were considered for BPT as the technology
options for BAT: simple settling, total recirculation of process
wastewater, and coagulation or flocculation of wastewater. EPA
also reviewed the various BAT factors listed above to determine
whether different BAT effluent limitations for certain groups of
gold placer mines might be appropriate. (
Wastewater pollutant levels and pollutant concentrations
achievable by each option were determined using the same
information and data discussed in Section IX for achievable BPT
limitations.
For all gold placer mines subject to this regulation, the end-of-
pipe technology basis for the promulgated BAT .limitation is the
model BPT technology (simple settling) plus recirculation of all
of the process water from the settling pond. Figure X-l (p. 239)
illustrates an example of simple settling with recirculation for
an open cut mine. Discharge of any excess water, which has
commingled with the process water, is allowed after treatment to
achieve 0.2 ml/1 settleable solids. The pollutant specifically
limited under BAT is settleable solids (SS) on the excess water
at 0.2 ml/1. EPA is not requiring any more stringent limitations
because the Agency has not identified any more stringent
technologies demonstrated to control process wastewater
pollutants from these groups of gold placer mines.
234
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GOLD PLACER MINE SUBCATEGORY SECT - X
Dredges which mine placer gold appear to be physically different
from open cut mines because of there physical configuration.
This physical difference also applies to the siting and use of
settling ponds to achieve the BPT and BAT limitations and NSPS.
As shown in Figure VIII-8 (p. 190) the BAT treatment system for a
dredge is essentially similar to the BAT treatment system for an
open cut mine. Because of the different configuration of a
dredge caused by the dredge pond and the pattern of spoil
disposal behind the dredge, the settling pond is located on top
of the spoil immediately behind the dredge. This allows the
process water to be pumped up to the settling pond for
clarification when it is necessary to remove additional solids
not removed in the dredge pond and recirculated to the dredge
pond by gravity. It also allows any excess water which may be
generated in the dredge mining operation to be discharged by
gravity when discharge is permitted. This configuration for
dredge gold placer mines was observed by EPA during the 1987
mining year.
Implementation of the BAT limitations for open cut mines and
dredges will remove annually from estimated raw waste 453,998 kg
(998,656 pounds) toxic metals and 1,977,140 kkg (2,174,854 tons)
TSS from all gold placer mines in the U.S. In Alaska alone,
207,379 kg (456,234 pounds) toxic metals and 956,912 kkg
(1,052,604 tons) TSS will be removed by implementation of BAT.
The total annual cost of achieving BAT at gold placer mines is
$1.94 million for the Alaska gold placer mines and $3.87 million
for all gold placer mines; the projected capital costs for
achieving BAT are $2.77 million for Alaska and $5.32 million for
all gold placer mines, respectively.
A repeated concern of industry commenters is that recirculation
of wash water reduces gold recovery in a sluice because of the
higher concentrations of TSS found in recirculated wastewater
compared to once-through wash water. However, no conclusive data
have been offered by the industry to quantify any loss or; if
there is a loss, what TSS concentration starts to effect a loss.
Lacking any hard and verifiable data from industry, EPA decided
to conduct its own tests to obtain data on the effect of
recirculation on gold recovery. As discussed in Section VII of
this document, EPA funded studies to ascertain if a loss of
recoverable gold occurred in a pilot-scale sluice when the TSS
concentration in the wash water was varied from almost zero to
about 200,000 mg/1. The results of the tests provide EPA the only
hard and verifiable data on the effect of TSS concentration on
gold recovery.
These tests indicate that over 99 percent of the gold is
effectively recovered regardless of the TSS concentration in the
wash water, e.g., recirculation does not affect the recovery of
gold in the size range of +100 mesh. The tests also indicate
there may be some migration of the recovered gold down the sluice
to lower ^riffles as the TSS concentration increases, but settling
of the recirculation water for 3 hours would reduce the TSS
235
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GOLD PLACER MINE SUBCATEGORY SECT - X
concentration to approximately 1,670 mg/1 and, in turn, reduce
any migration. Therefore recirculation of all of the process
water will not materially affect gold recovery in a sluice.
BAT FOR GOLD PLACER MINES
The following effluent limitations represent the degree of
effluent reduction attainable by the application of the best
available technology economically achievable (BAT).
Except as provided in 40 CFR 125.30-125.32, any existing point
source subject to this subpart must achieve the following
effluent limitations representing the degree of effluent
reduction attainable by the application of the best available
technology economically achievable (BAT).
(a) The volume of process wastewater which may be
discharged from an open-cut mine plant site shall not exceed the
volume of infiltration, drainage, and mine drainage waters which
is in excess of the make-up water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from an open-cut mine plant site
shall not exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(b) The volume of process wastewater which may be
discharged from a dredge plant site shall not exceed the volume
of infiltration, drainage, and mine drainage waters which is in
excess of the make-up water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from a dredge plant site shall not
exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
236
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GOLD PLACER MINE SUBCATEGORY SECT - X
The implementation of technology to attain BAT effluent
limitations will not create any additional air pollution
emissions. The amount of solid waste generated by the technology
for BAT limitations is negligible compared to the amount
generated by mining and processing. Land requirements for
settling ponds at open cut mines and at dredges are no more than
the requirements for BPT. There is a small increase in
anticipated land requirements for recycling hardware. However,
land already mined will generally be available.
Recirculation of process wastewater at open cut mines will create
an increase in energy consumption for power to drive
recirculation pumps. At many mines, gravity flow is used to
bring water to the beneficiation process and these mines will
require the addition of a pump, piping and a means to drive the
pump. Most mines do not have electricity available for such
pumps, and EPA believes the mining operations probably will
purchase a form of skid-mounted diesel or gasoline direct drive
engine-pump. In determining the cost to implement the no
discharge of process water requirement by recirculation, EPA
included the cost to purchase a skid-mounted unit and the fuel to
run the unit for those mines that were determined not to have
these facilities. However, in actual practice, EPA has observed
that many mines are already using pumps to supply wash water
either one time through or with recirculation of process water.
Those mines .with pumps to supply wash water will have little if
any increase in energy consumption to recirculate 100 percent of
the process water.
There also will be an increase in energy consumption to provide
power for the equipment to build and maintain the wastewater
treatment facilities (settling and holding ponds). However, in
determining the cost to implement the technology for simple
settling, recycle, or recirculation, EPA used the value of the
equipment and operating time-cost for the equipment and the
equipment operator's time already at the mine. The equipment
time for building and maintaining ponds is a small part of the
total equipment hours available in a mining season; the energy
consumption to build and maintain ponds is a small part of the
total energy requirement for mining in a season.
The Clean Water Act does not require a balancing of costs against
effluent reduction benefits for BAT. However, included in the
record supporting the rulemaking is the Agency's report "Cost
Effectiveness Analysis of Effluent Limitations for the Placer
Gold Mining Industry" which calculates the effectiveness of the
proposed regulation by estimating pounds of pollutants removed
weighted by an estimate of their toxicity, e.g., pound-
equivalents removed. Non-regulated pollutants are included when
they are removed incidently as a result of a particular treatment
technology. The cost-effectiveness of BAT is estimated to be $3
per pound equivalent removed. The cost per pound of solids
removed by BPT is less than $ 1.
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GOLD PLACER MINE SUBCATEGORY SECT - X
STORM EXEMPTION
The storm exemption which applies to BPT also applies to BAT and
NSPS. This exemption is discussed in Section IX.
238
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GOLD PLACER MINE SUBCATEGORY SECT - X
TABLE X-l
Pollutant Reduction Benefits
NATIONWIDE
RAW WASTE
BPT
BAT
Pollutant
TSS (kkg)
(ton)
Toxic ( kg )
Metals (Ib)
2005010
2205511
467317
1028097
Removed
1837592
2021351
387499
852379
Discharged
167418
184160
79818
175718
Removed
1977140
2174854
453998
998656
Discharged
27870
30657
13319
29441
ALASKA ONLY
RAW WASTE
BPT
BAT
Pollutant
TSS (kkg)
(ton)
Toxic ( kg )
Metals (Ib)
970401
1067441
213463
468618
Removed
889373
978319
177004
389407
Discharged
81028
89131
36459
79211
Removed
956912
1052604
207379
456234
Discharged
13489
14837
6084
12384
239
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RECIRCULATION WATER
SETTLING POND
OPEN CUT
Figure X - 1
-BAT
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(BAP
EFFLUENT
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8
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GOLD PLACER MINE SUBCATEGORY SECT - XI
SECTION XI
NEW SOURCE PERFORMANCE STANDARDS (NSPS)
Under Section 306 of the Clean Water Act, new source performance
standards are to be based upon best available demonstrated
technology (BDT). New facilities have the opportunity to
implement the best and most efficient ore mining and milling
processes and wastewater technologies. Congress, therefore,
directed EPA to consider the best demonstrated process changes
and end-of-pipe treatment technologies capable of reducing
pollution to the maximum extent feasible.
BAT for gold placer mines is based on the most stringent
demonstrated technology for treating gold placer mine
wastewaters. New source performance standards therefore can not
be more stringent, but must be equivalent to the BAT limitations.
It is expected that the new source wastewaters will be similar to
process wastewaters of existing sources. Therefore, the costs to
treat and pollutant removal efficiencies from new sources 'are
expected to be similar to existing sources.
The new source criteria contained in the NPDES regulation does
not adequately address several unique features of gold placer
mining (as discussed below). EPA therefore feels that these
criteria could not reasonably be applied to determine new source
placer mines, and that it would be more appropriate to adopt a
list of factors for the Regional Administrator (RA) to use in
determining, on a case-by-case basis, whether a gold placer mine
is a new source under the Act. The adoption of industry-specific
criteria for designation of new sources is consistent with the
new source criteria contained in the NPDES regulations, since 40
CFR section 122.29(b)(l) states that the NPDES provisions apply
"except as otherwise provided in an applicable new source
performance standard." Furthermore, EPA has adopted a similar
approach to determining the existence of new source mining
operations where the characteristics of the subcategory warranted
specialized treatment (see new source criteria for coal mining,
40 CFR Section 434.11(j)).
Applying the new source determination language of Section 306 of
the Act to gold placer mining is problematic due to two unique
standard operating conditions of these operations. Under the
statute, the date on which construction of a facility begins
determines whether it is considered a new source. "Construction"
is defined in Section 306(a)(5) as "any placement, assembly,
installation of facilities or equipment (including contractual
obligations to purchase such facilities or equipment) at the
premises where such equipment will be used, including site
preparation work at such premises."
However, gold placer mines, by their nature, are mobile
241
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GOLD PLACER MINE SUBCATEGORY SECT - XI
operations. First, they continually move up or down a stream as
they mine a pay streak, and they often relocate their mining
activities within a claim or among different claims in search of
ore containing recoverable gold. Second, due to climatic
conditions, Alaskan gold placer mines can only operate during the
summer months.
Under the literal application of the term "construction", a gold
placer mine could be viewed as a "new" new source, every time it
moves to a new location since the mine, in a sense, installs
facilities and equipment at different "premises." Therefore,
over time, virtually all gold placer mines would have to be re-
permitted as new sources.
Also, Alaskan gold placer mines would be defined as new sources
every spring, when they restarted their operations after being
shut down for the winter season. It is characteristic of all
such mines that some or all of their equipment is removed from
the mining site each fall, and replaced in the spring. This
activity, characteristic of all continuous, ongoing gold placer
mine operations in the state, does not necessarily indicate the
commencement of new mining activities. However, a literal
statutory application in this case would result in a large number
of facilities needing to be re-permitted as new sources on an
annual basis.
Designating all gold placer mines to be new sources by virtue of
their continual movement would ignore that this is standard
practice among existing gold placer mine operations. The Agency
believes that such a literal interpretation of the statutory
language would appear to run counter to the intent of the CWA,
which clearly envisions a distinction between new and existing
sources.
Similarly, interpreting seasonal reconstruction of facilities to
require permitting as a new source might be consistent with a
literal reading of Section 306, but EPA believes that such an
approach would ignore a unique aspect of gold placer mines
operating in cold climates. It would be inappropriate to
consider the entire Alaskan gold placer mining industry to be new
sources every spring, as the EPA does not believe that Congress
intended in Section 306 to designate large numbers of facilities
in an entire subcategory as new sources solely because climatic
conditions dictate the routine, yearly dismantling and rebuilding
of their operations.
Given these two special conditions within the industry, rejection
of the literal application of the term "construction" can also be
based on the realization that defining all gold placer mines as
new sources due to seasonal or standard operational changes would
not advance the purposes of: Section 306. Congress adopted that
provision in order to ensure that new facilities, which could
institute production process changes, met the most, stringent
pollution control requirements (see Conf. Rep. 1236, 92nd Cong.,
2d Sess., 127-129). However, these facilities will already be
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GOLD PLACER MINE SUBCATEGORY SECT - XI
controlled by BAT limitations based on the most stringent
pollution control technology that is available to gold placer
mining. As NSPS is being set equal to BAT, designating every
gold placer mine as a new source each season would not result in
any more stringent levels of control than those already
established for existing sources.
The mobile nature of gold placer mines also demonstrates why the
new source criteria contained in Section 122.29(b) of the NPDES
regulations are not appropriate for the determination of new
source gold placer mines. Section 122.29(b)(1), interpreted
literally, would also cause any movement by a mine to classify it
as a new source since, arguably, a mine that moves upstream or to
a new location is being "constructed at a site at which no other
source is located." However, EPA noted in adopting the new
source criteria that they were not designed to address mobile
operations.
Section 511(c) of the CWA provides that the issuance by EPA of
NPDES permits to new sources is subject to the provisions of the
National Environmental Policy Act (NEPA). Therefore, to the
extent issuance of such permits might constitute major federal
actions significantly affecting the environment, NEPA requires
the preparation of an environmental assessment and, if
appropriate, an environmental impact statement prior to permit
issuance (see 40 CFR Section 122.29(c)).
Instead of categorically classifying all gold placer mines as new
sources because of the mobile and seasonal nature of their
operations, the new source criteria in this regulation are to be
considered by the Regional Administrator (RA) or Director of a
state agency administering an NPDES program (Director) as the
basis for determining when a mine has sufficiently altered
location or discharges sue i that the mine is a new source. The
main effect of this determination, as discussed above, is that
the designation may result in the conducting of an environmental
review being required in accordance with NEPA.
The factors listed below must be taken into account in
determining whether a gold placer mine is a new source, and are
intended to guide the permit writer in assessing all of the
circumstances of a particular mine. It is possible that
characteristics of gold placer mining operations may vary widely
and EPA, therefore, may not have anticipated all the
circumstances relevant to a new source determination. A number
of other factors might be considered by the RA or Director during
a new source determination. For example, the retaining berms and
ponds of a previous mine have been destroyed by storms or snow
melt, making complete reconstruction necessary.
The RA or Director shall designate new source gold placer mines
Based on consideration of whether one or more of the following
factors applies after the date of promulgation:
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GOLD PLACER MINE SUBCATEGORY SECT - XI
a) The mine will operate outside of the permit area which
is covered by a currently valid NPDES permit.
b) The mine significantly alters the nature or quantity of
pollutants discharged.
c) The mine discharges into a stream into which it has not
discharged under its currently valid NPDES permit.
d) The mine will operate in a permit area that has not
been mined during the term of the currently valid NPDES
permit.
e) Such other factors as the Regional Administrator or
state Director deems relevant.
EPA is unable to identify any more stringent limitations based
upon a demonstrated technology for gold placer mines covered by
this regulation other than simple settling plus recirculation of
all process wastewater. As discussed elsewhere, chemically aided
settling is not.at this time a demonstrated technology at gold
placer mines. The other technologies examined by the Agency,
including filter dams and tundra filters, are available only on a
site specific basis and therefore are not appropriate as the
basis of nationally applicable, uniform effluent limitations
guidelines and standards.
The Agency does not foresee that these NSPS should pose a barrier
to entry for new source placer mines, as the new source standards
are equivalent to the existing source standards. In fact, the
new sources can design for more efficient process water use and
maximize wastewater reduction, thereby reducing the size and cost
of pollution control facilities. Given this design advantage,
there are no reasons why newly designed systems should at most
equal the cost of retrofitted systems.
NSPS FOR GOLD PLACER MINES
Any new source subject to this subpart must achieve the following
NSPS representing the degree of effluent reduction attainable by
the application of the best available demonstrated technology:
(a) The volume of process wastewater which may be
discharged from an open-cut mine plant site shall not exceed the
volume of infiltration, drainage, and mine drainage waters which
is in excess of the make-up water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from an open-cut mine plant site
shall not exceed:
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GOLD PLACER MINE SUBCATEGORY SECT - XI
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(b) The volume of process wastewater which may be
discharged from a dredge plant site shall not exceed the volume
of infiltration, drainage, and mine drainage waters which is in
excess of the make-up water required for operation of the
beneficiation process. The concentration of pollutants in
process wastewater discharged from a dredge plant site shall not
exceed:
Effluent Limitations
Effluent Instantaneous
Characteristics Maximum
Settleable Solids 0.2 ml/1
(c) Notwithstanding any other provision of this chapter,
the Regional Administrator or Director of a State agency with
authority to administer the NPDES program shall in designating
new source gold placer mines take into account and base the
decision on whether one or more of the following factors has
occurred after promulgation of this regulation.
1. The mine will operate outside of the permit area which
is covered by a currently valid NPDES permit.
2. The mine significantly alters the nature or quantity of
pollutants discharged.
3. The mine discharges into a stream into which is has not
discharged under its currently valid NPDES permit.
4. The mine will operate in an area that has not been
mined during the term of the currently valid NPDES
permit.
5. Such other factors as the Regional Administrator or
state Director deems relevant.
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GOLD PLACER MINE SUBCATEGORY SECT - XI
STORM EXEMPTION
The storm exemption which applies to BPT and BAT also applies to
NSPS. This exemptions is discussed in greater detail in Section
IX.
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SECTION XII
PRETREATMENT STANDARDS
Section 307(b) of the Act requires EPA to promulgate pretreatment
standards for both existing sources (PSES) and new sources (PSNS)
of pollution which discharge their wastes into publicly owned
treatment works (POTW). These pretreatment standards are
designed to prevent the discharge of pollutants which pass
through, interfere with, or are otherwise incompatible with the
operation of POTW. In addition, these standards must require
pretreatment of pollutants, such as certain metals, that limit
POTW sludge management alternatives. The legislative history of
the Act indicates that PSES are to be technology-based and, with
respect to toxic pollutants, analogous to BAT.
EPA did not promulgate PSES or PSNS in the ore mining and
dressing point source category in the 1982 rulemaking nor is it
promulgating such standards for the gold placer mining sub-
category- since there are no known or anticipated discharges to
POTW.
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GOLD PLACER MINE SUBCATEGORY SECT - XIII
SECTION XIII
BEST CONVENTIONAL POLLUTANT CONTROL TECHNOLOGY (BCT)
Section 301(b)(2)(E) of the Act requires categories and classes
of point sources, other than publicly-owned treatment works, to
achieve effluent limitations that require the application of the
best conventional pollutant control technology (BCT) for control
of conventional pollutants as identified in Section 304(a)(4).
BCT is not an additional limitation; rather, it replaces BAT for
the control of conventional pollutants. The pollutants that have
been defined as conventional by the Agency, at this time, are
biochemical oxygen demand, suspended solids, fecal coliform, oil
and grease, and pH.
Section 304(b)(4)(B) of the Act requires that, in setting BCT,
EPA must consider: the age of equipment and facilities involved,
the process employed, the engineering aspects of the application
of various types of control techniques, process changes, non-
water quality environmental impacts (including energy
requirements), and other factors the Administrator deems
important. Candidate technologies must also pass a two-part test
of "cost reasonableness."
The only conventional pollutant of concern in gold placer mining
wastewater is total suspended solids (TSS). The Agency has not
identified any demonstrated technology that provides reliable
removal of TSS; therefore, no ' BCT regulations are being
promulgated at this time.
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GOLD PLACER MINE SUBCATEGORY SECT - XIII
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GOLD PLACER MINE SUBCATEGORY SECT - XIV
SECTION XIV
BEST MANAGEMENT PRACTICES
Section 304(e) of the Clean Water Act authorizes the
Administrator to prescribe "best management practices" (BMP) to
prevent the release of toxic and hazardous pollutants from plant
site runoff, spillage or leaks, sludge or waste disposal, and
drainage from raw materials storage associated with or ancillary
to the manufacturing or treatment process. In gold placer mines,
surface water flows (drainage), infiltration, and mine drainage
may contribute significant amounts of pollutants to navigable
waters.
The gold placer mine subcategory has limitations on the storm
water runoff, mine drainage, and groundwater infiltration and
seepage which enters the treatment system and is commingled with
process wastewater. Similarly, the runoff from the plant site
area is included in the wastewater controlled by effluent
limitations guidelines and standards.
Minimizing the volume of water allowed to enter the plant site
and commingle with the process water is environmentally
desirable, because reducing the volume of incidental water
allowed to enter the plant site reduces the volume of water which
must be discharged and thereby reduces the mass of pollutants
which are discharged to waters of the United States. Diversion
of water around a plant site to prevent its contact with the
active mine and the pollution-releasing materials is an effective
and widely applied control technique at many ore mines.
The BMP explained below and included in the regulation are
necessary for control of the drainage and infiltration water at
gold placer mines, as well as to prevent release of pollutants
removed by treatment processes to the receiving streams under
various types of climatic and seasonal conditions. These BMP
represent good mining practices which are commonly practiced in
all well-operated mining operations.
(a) Surface Water Diversion: The free flow of surface
waters into the plant site area shall be interrupted and these
waters diverted around and away from incursion into the plant
site area.
Such diversion may be accomplished by appropriate means such as
the construction of dikes, berms, or ditches to convey the water
away from or around the plant site. For the purpose of this
requirement, the plant site area is defined as the area occupied
by the mine, necessary haulage ways from the mine to the ore
processing equipment, the area occupied by the ore processing
equipment, the areas occupied by the wastewater treatment
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GOLD PLACER MINE SUBCATEGORY SECT - XIV
facilities, and the storage areas for waste materials and solids
removed from the wastewaters during treatment.
This BMP requirement applies both during the active mining season
and at all other times. It applies for the plant site in active
use and to plant site areas no longer in active use after active
operations have ceased.
(b) Berm Construction; Berms, including any pond walls,
dikes, low dams, and similar water retention structures shall be
constructed in a manner such that they are reasonably expected to
reject the passage of water.
This may be achieved by utilizing on-site materials in a manner
that the fine sealing materials such as clays are mixed in the
berms with coarser materials. Berms should be toed into the
underlying earth, constructed in layers or lifts, and each layer
thoroughly compacted to ensure mechanical and watertight
integrity of the berms. Other impermeable materials such as
plastic sheets or membranes may be used inside the berms when
sealing fines are unavailable or in short supply. The side slope
of berms should be not greater than the natural angle of repose
of the materials used in the berms or a slope of 2:1, whichever
is lower.
(c) Pollutant Materials Storage; Measures shall be taken
to assure that pollutant materials removed from the process water
and wastewater streams will be retained in storage areas and not
discharged or released to the waters of the United States.
These measures may include location of the storage ponds and
storage areas to assure that they will not be w shed out by
reasonably predictable flooding or by the return of a relocated
stream to its original stream bed. The overflows from ponds and
storage areas should be protected from erosion by riprap or rock
plating. Submerged discharges or constant level discharge pipes
through retention dikes should be used where practicable.
This requirement applies both during the active mining season and
at all other times as well as after active mining operations have
moved to new locations.
(d) New Water Control; The amount of new water allowed to
enter the plant site for use in ore processing shall be limited
to the minimum amount required as make-up water for processing
operations.
New water is defined as water from any discrete source such as a
river, creek, lake, or well which is deliberately allowed or
brought into the plant site. Control mechanisms should limit the
flow of new water to the amount needed to supplement other waters
for gold ore processing make-up requirements and shutting off
the flow or exclude new water when the ore processing segment of
the facility is not being operated.
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GOLD PLACER MINE SUBCATEGORY SECT - XIV
(e) Maintenance q£ Water Control and Solids Retention
Devices; All water control devices such as diversion structures
and berms and all solids retention structures such as berms,
dikes, pond structures, and dams shall be maintained to continue
their effectiveness and to protect from unexpected and
catastrophic failure.
The structures should be inspected on a regular basis for any
signs of structural weakness or incipient failure. Whenever such
weakness or incipient failure becomes evident, repair or
augmentation of the structure to reasonably ensure against
catastrophic failure shall be made immediately.
This BMP shall apply both during the active mining season and at
all other times as well as after active mining operations have
moved to new locations.
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GOLD PLACER MINE SUBCATEGORY SECT - XV
SECTION XV
ACKNOWLEDGEMENTS
This document has been prepared by the staff of the Industrial
Technology Division (ITD) with assistance from technical
contractors, other EPA offices and other persons outside of EPA.
This section is intended to acknowledge the contribution of the
persons who have contributed to the development of this report.
The initial effort on this project was carried out by Frontier
Technical Associates (FTA) under the direction of Dr. P. Michael
Terlecky. Specific efforts by FTA included a treatability study
of mines in Alaska, performed in 1983 in cooperation with
Kohlmann Ruggiero Engineers, Inc. (KRE), sampling at mines in
the lower 48 states in 1984, and the report "Reconnaissance
Sampling and Settling Column Test Results at Alaskan Placer Gold
Mines," November 15, 1984. FTA sampling efforts were lead by Mr.
David M. Harty. In addition, FTA produced the Proposal version
of this development document. Much of the information developed
by FTA was incorporated or updated in this draft.
Field sampling efforts were also conducted by Kohlmann Ruggiero
Engineers, P.C. under the direction of Mr. Dominick Ruggiero.
KRE sampling studies were conducted from 1983 through 1986, and
resulted in the following reports: "Treatability Testing of
Placar Gold Mine Sluice Water in Alaska, U.S.," May 11, 1984;
"1984 Alaskan Placer Mining Study and Testing Report," January
31, 1985; "1985 Alaskan Placer Mining Study Report on Gathering
Background Data and Estimating the Method Detection Limit of
Settlable Solids in Wastewaters Discharged from Gold Placer
Mining Operations," January 22, 1986; and "1986 Alaskan Placer
Mining Study Field Testing Program Report.," March 5, 1987. In
1984, Mr. Charles F. Herbert, a minerals consultant, accompanied
KRE on their site visits, and contributed the "Report on Nineteen
Gold Placer Mines, Alaska," July 20, 1984. Mr. Ruggiero provided
considerable technical support in preparing both the previous and
current versions of this document. KRE worked under subcontract
to WESTEC Services, Inc. for the majority of these efforts.
Two field studies were performed by L.A. Peterson and Associates
under the direction of Mr. Laurence A. Peterson. The reports
resulting from these studies are "Investigation of the Effect of
Total Suspended Solids Levels on Gold Recovery in a Pilot Scale
Sluice," September 1984, and "Evaluation of the Effect of
Suspended Solids on Riffle Packing and Fine Gold Recovery in a
Pilot Scale Sluice," September 1986. The first of these efforts
was performed under subcontract to KRE, and the second was
performed under WESTEC.
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GOLD PLACER MINE SUBCATEGORY SECT - XV
WESTEC assisted in two field sampling efforts. In 1986, Mr.
Scott Davis of WESTEC assisted Mr. Willis Umholtz and Mr.
Dominick Ruggiero of KRE in a full-scale flocculent study, and
co-authored the associated report "1986 Placer Mining Full-Scale
Field Investigations Chemical Treatment," November 7, 1986. Also
in 1986, Mr. Peter Crampton of WESTEC (and later Mr. Scott Davis)
participated in a pilot-scale study conducted by the U.S. Bureau
of Mines, investigating the effect of polyethylene oxide
flocculation on gold placer mining wastewater. Ms. Jamie
Mclntyre served as WESTEC Project Manager in the last months of
preparation of this document.
Analytical work for the 1983 treatability study was performed by
Nothern Testing Laboratories, Inc. in Fairbanks, Alaska. All
subsequent analytical work was performed by Centec Analytical
Services in Salem, Virginia and by S-Cubed in San Diego,
California.
Mr. Stephen Neugeboren and Ms. Margaret Silver of the Office of
General Counsel provided legal advice and assistance during the
progress of this project and in the preparation of this document.
Technical supervision of the preparation of this document and the
completion of the gold placer mine project was provided by Mr.
Ernst P. Hall, Chief, Metals Industry Branch with technical
supervision of earlier segments provided by Mr. William A.
Telliard, Chief, Energy and Mining Branch, Mr. Devereaux Barnes,
feting Director, Industrial Technology Division, and Mr. Jeffery
D. Denit, Director, Industrial Technology Division.
The technical project officer for the completion of the project
was Mr. Willis E. Umholtz, Metals Industry Branch with Mr.
Matthew B. Jarrett, also of the Metals Industry Branch, technical
project officer for the early segment of the project and also
providing assistance in the final phases.
Specific appreciation is expressed for the assistance of Ms.
Pearl Smith in word processing arid the preparation of this
document for printing and publication.
Appreciation is also expressed to the federal agencies outside of
EPA that made contributions to this project; to the several
departments of the State of Alaska; and to the University of
Alaska, all of whom have contributed substantially to the
projects conclusion.
Finally, our appreciation must be expressed to the environmental
groups, the miners associations, the mining companies and the
individual citizens who have given of their time and resources to
provide information and their views on this effort.
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GOLD PLACER MINE SUBCATEGORY SECT - XVI
}
SECTION XVI
REFERENCES
1. Alaska Department of Environmental Conservation, "Placer
Mining/Water Quality - Problem Description," Alaska Water
Quality Management Planning Program Section 208 Study
(P.L. 92-500), November 1977.
2. Alaska Department of Environmental Conservation, "Placer
Mining and Water Quality" (Summary Report), November, 1979;
Supplements: Problem Description-Nov. 1977; Technical
Alternatives^June 1978; Management Alternatives-Sept. 1978.
3. Alaska Office of Mineral Development, "Alaska's Mineral
Industry - 1982," Special Report 31, 1983.
4. Alaska Office of Mineral Development, "Alaska's Mineral
Industry - 1986," Special Report 40.
5. Bainbridge, K.L., "Evaluation of Wastewater Treatment
Practices Employed at Alaskan Gold Placer Mining
Operations", Report No. 6332-M-2, Calspan Corporation,
Buffalo, N.Y. July 17, 1979.
6. Berger, Louis and Associates, "The Role of Placer Mining in
the Alaska Economy," prepared for the State of Alaska
Department of Commerce and • Economic Development, March
1983.
7. California Div. of Mines and Geology, "Basic Placer Mining,"
Special publication 41.
8. Calspan Corporation, "Evaluation of Wastewater Treatment
Practices Employed at Alaskan Gold Placer Mining
Operations", Report No. 6332-M-2, July 17, 1979.
9. Canadian Department of Indian and Northern Affairs, "Water
use Technology for Placer Mining Effluent Control", Report
No. QS-Y006-000-EE-A, 1981.
10. Dames and Moore, "Water Quality Data at Selected Active
Placer Mines in Alaska", Report No. 9149-001-22, September
17, 1976, Prepared for Calspan Corporation.
11. Environment Canada, "The Use of Flocculants in Placer
Mining" (a supplement to the paper 'The Attainment and Cost
of Placer Mining Effluent Guidelines'), Canadian
Environmental Protection Service, Yukon Branch, June 13,
1983.
12, Harty, D. M., Frontier Technical Asso., Inc., Letter to
257
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GOLD PLACER MINE SUBCATEGORY SECT - XVI
B. M. Jarrett, U.S. EPA - ITD, November 5, 1984.
13. Harty, D. M. , Frontier Technical Asso., Inc., Letter to
B. M. Jarrett, U.S. EPA - ITD, November 16, 1984.
14. Harty, D. M., Frontier Technical Asso., Inc., Letter to
B. M. Jarrett, U.S. EPA - ITD, November 30, 1984.
15. Harty, D.M. and Terlecky, P.M., "Existing Wastewater Recycle
Practices at Alaskan Placer Gold Mines", Frontier Technical
Associates Memorandum to B.M. Jarrett, U.S. EPA-EGD,
February 29, 1984.
16. Harty, D. M. and Terlecky, P. M. , Frontier Technical Asso.,
Inc., Letter to B. M. Jarrett, U.S. EPA - ITD, March 5,
1984.
17. Harty, D.M. and Terlecky, P.M., "Geographic Distribution of
Mines Employing Partial or Total Recycle", Frontier
Technical Associates Memorandum to B.M. Jarrett, U.S. EPA-
EGD, March 2, 1984.
18. Harty, D. M. Terlecky, P.M., "Reconnaissance Sampling and
Settling Column Test Results at Alaskan Placer Gold Mines",
Frontier Technical Associates Report No. FTA-84-14-211 .
November 15, 1983, Prepared for U.S. EPA Effluent Guidelines
Division.
19. Harty, D.M. and Terlecky, P.M., "Reconnaissance Sampling and
Settling Column Test Results at Alaskan and Lower 48 Placer
Gold Mines," Frontier Technical Associates Report No.
FTA-84-1402-1.
20. Harty, D. M. and Terlecky.- P. M. , "Titanium Sand Dredging
Wastewater Treatment Practices," Frontier Technical
Associates, Inc., Report No. 1804-1, October 20, 1980.
21. Harty, D.M. and Terlecky, P.M., "Water use Rates at Alaskan
Placer Gold Mines using Classification Methods", Memorandum
to B.M. Jarrett, U.S. EPA-EGD, February 29, 1984.
22. Jackson, C. F., "Small-Scale Placer Mining Methods," U.S.
Department of Interior, Bureau of Mines Information
Circular 1C 6611R, February 1983, p. 15-18.
23. Kohlmann Ruggiero Engineers, "1984 Alaskan Placer Mining
Study and Testing," Draft, Prepared for EPA Effluent Guide-
lines Division, Washington, D.C.
258
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GOLD PLACER MINE SUBCATEGORY SECT - XVI
24. Kohlmann Ruggiero Engineers, P.C., "1985 Alaskan Placer
Mining Study Report on Gathering Background Data and
Establishing the Method Detection Limit of Settleable Solids
in Wastewaters Discharging from Gold Placer Mining
Operations" (Preliminary Draft)
25. Kohlmann Ruggiero Engineers, P.C. "1986 Alaskan Placer
Mining Study Field Testing Program Report" (Final Draft)
March 1987.
26. Kohlmann Ruggiero Engineers, P.C., "1987 Costing Study on
Systems to Treat Wastewater Discharges in the Placer Mining
Industry," (Final Draft), November 20, 1987.
27. Kohlmann Ruggiero Engineers, P.C., "Placer Mining Wastewater
Treatment Process Water Usage Report," May 1987 (Draft).
28. Kohlmann and Ruggiero Engineers, "Treatability Testing of
Placer Gold Mine Sluice Waters in Alaska, U.S.", Prepared
for U.S. EPA Effluent Guidelines Division, January, 1984.
29. Lapedes, D. N. (ed), McGraw-Hill Encyclopedia of_
Environmental Science, 1974, p. 342-346.
30. Mineral Facts and Problems, 1980 Edition, U.S. Bureau of
Mines Bulletin 671.
31. Minerals Yearbook - 1982, Volume 1, "Metals and
Minerals," U.S. Bureau of Mines, 1983.
32. Peterson, L.S.; Tsigonis, R.C.; and Nichols, G.E.,
"Evaluation of the Effect of Suspended Solids on Riffle
Packing and Fine Gold Recovery in a Pilot Scale Sluice",
September 1986.
33. Peterson, L.A.; Tsigonis, R.C.; Crionin, J.E.; and
Hanneman,K.L., "Investigation of the Effect of Total
Suspended Solids Levels on Gold Recovery in a pilot Scale
Sluice", September 1984.
34. Poling, G. W. and Hamilton, J. F., "Fine Gold Recovery of
Selected Sluicebox Configurations," University of British
Columbia, undated (1986?).
35. R&M Consultants, Inc., "Placer Mining Wastewater Settling
Pond Demonstration Project", Prepared for the Alaskan
Department of Environmental Conservation, June 1982.
36. Romanowitz, C. M., Bennett, and Dare, W. L., "Gold Placer
Mining - Placer Evaluation and Dredge Selection," U.S.
Bureau of Mines Information Circular 8462, 1970.
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GOLD PLACER MINE SUBCATEGORY SECT - XVI
37.
38.
39.
40.
41.
42.
43.
44.
45.
Shannon and Wilson, Inc. "Placer Mining Wastewater Treatment
Technology Project Phase 1, 2 and 3 Report," Prepared for
State of Alaska Department of Environmental
Conservation, November 1984.
Sigma Resources Consultants, Limited, "Water Use Technology
for Placer Mining Effluent Control," Department of Indian
and Northern Affairs, Canada, Report No. QS-Y006-000-EE-A1,
Whitehorse, Yukon Terr., 1981.
Stanley Associates Engineering, Ltd., and Canviro
Consultants, Ltd., "Development and Demonstration of
Treatment Technology for the Placer Mining Industry," for
Environment Canada, March 1985.
Stanley Associates Engineering Ltd., "Development and
Demonstration of Treatment Technology for the placer Mining
Industry" (Final Report), March 1985.
Taggert, A. F.,
John Wiley, 1945.
Handbook o_f Mineral Dressing, New York:
Thomas, B: I., Cook, D. J., Wolff, E., and Kerns, W. H.,
"Placer Mining in Alaska - Methods and Costs at Operations
Using Hydraulic and Mechanical Excavation Equipment with
Nonfloating Washing Plants," U.S. Bureau of Mines
Information Circular 7926, 1959.
Umholtz, W.E. - USEPA/ITD; Davis, J.S. - Centec Corp., "1986
Placer Mining Full-Scale Field Investigations Chemical
Treatment", November 7, 1986.
U.S. Department of
Preprint "Gold" 1982,
the Interior, Minerals
U.S. Bureau of Mines (Author
Yearbook
J. M.
Lucas) Report No. 1804-1, October 20, 1980.
U.S. EPA, "Final Development Document of Effluent
Limitations and Standards for the Ore Mining and Dressing
Point Source Category," EPA Report 440/1-82/061, November
1982.
46.
47.
48.
U.S. EPA, "Development Document for Interim Final and
Proposed Effluent Limitations Guidelines for the Ore Mining
and Industry," EPA Report No. EPA 440/l-75/061c, October,
1975.
U.S. EPA
"Evaluation
Mines", EPA
National Enforcement Investigations Center,
of Settleable Solids Removal Alaskan Gold Placer
Report No. 33012-77-021,-September, 1977.
U.S. EPA, Region X, "1984 Trend Study," Confidential
(included as entry 5-3.43 in the EPA "Certified Index to
Documents Supporting Proposed Guidelines and Standards for
the Gold Placer Mining Subcategory of the Ore Mining and
Dressing Point Source Category," Nov. 20, 1985).
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GOLD PLACER MINE SUBCATEGORY SECT - XVI
49. U.S. EPA, Region X, Analytical data from Region X field
investigations, 1983.
50. U.S. EPA - Region X, "Draft of General NPDES Permit for
Placer Mining in the State of Alaska," February 1984.
51. U.S. EPA - Response report as a result of public hearings
held in Fairbanks, Alaska, on April 3 and 5, 1984.
52. U.S. EPA, Region X, Trip reports from Region X field
investigations, 1982.
53. U.S. Geological Survey, United States Mineral Resources
(Gold), U.S.G.S. Professional Paper 820, 1973, p. 263-275.
54. Wells, J. H., "Placer Examination, Principles and Practice,"
U.S. Bureau of Land Management, U.S. Department of Interior,
1969.
55. West, J. M., "How to Mine and Prospect for Placer Gold,"
U.S. Department of the Interior, Bureau of Mines Information
Circular No. 8517, 1971.
56. Wimmler, N. L., "Placer Mining. Methods and Costs in
Alaska," U.S. Department of Commerce, Bureau of Mines,
Bulletin No. 259, 1927, p. 10-15.
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SECTION XVII
GLOSSARY
Act, the - The Federal Water Pollution Control Act as amended (33
U.S.C. 1251, 1311, and 1314(b) and (c), P.L. 92-500); also
called the Clean Water Act (CWA) and amendments through
1986.
Active mining area - An area where work or other activity
relating to the extraction, removal, or recovery of any ore
is being conducted. This includes areas where secondary
recovery of ore is being conducted but, for surface mines,
specifically does not include any area of land on or in
which grading to return the land to the desired contour has
been completed and reclamation work has begun.
Administrator - Administrator of the U.S. Environmental
Protection Agency, whose duties are to administer the Act.
Amalgam - An alloy of mercury with gold or another metal. In the
case of placer gold, a "dry" amalgam, that is, one from
which all excess mercury has been removed by squeezing
through chamois leather, will contain nearly equal
proportions of gold and mercury.
Amalgamation - The extraction of precious metals from their ores
by treatment with mercury.
Assay - To determine the amount of metal contained in an ore: 1)
the act of making such a determination; 2) the result of
such a determination.
Assessment work - The annual work upon an unpatented mining claim
in the public domain necessary under U.S. law for the
maintenance of the possessory title thereto.
Auriferous - Containing gold.
Bank run - The measurement of material in place, such as gravel
in the deposit before excavation. In gold placer work,
values normally are reported as cents per cubic yard and,
unless specified otherwise, this means a cubic yard in
place, or bank run.
Bedrock - The solid rock underlying auriferous gravel, sand,
clay, etc., and upon which the alluvial gold rests. In
placer use, the term "bedrock" may generally be applied to
any consolidated formation underlying the gold-bearing
gravel. Bedrock may be composed of igneous, metamorphic, or
sedimentary rock (see False bedrock).
Bench - The surface of an excavated area at some point between
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
the material being mined and the original surface of the
ground on which equipment can be set, moved, or operated. A
working road or base below a highwall as in contour
stripping.
Bench placer - Gravel deposits in ancient stream channels and
flood plains which stand above the present streams.
Berm - A horizontal barrier built for the purpose of
strengthening and increasing the stability of a slope or to
catch or arrest slope slough material; "berm" is sometimes
used as a low dam to impound or deflect water.
Beneficiatioi area - The area of land used to stockpile ore
immediately before the beneficiation process, the area of
land used for the beneficiation process, the area of land
used to stockpile the tailings immediately after the
beneficiation process, and the area of land from the
stockpiled tailings to the treatment system, e.g., holding
pond or settling pond, and the area of the treatment system.
Beneficiation process - The dressing or processing of gold
bearing ores for the purpose of (a) regulating the size of,
or recovering, the ore or product; (b) removing unwanted
constituents from the ore; and (c) improving the quality,
purity, or assay grade of a desired product.
Best Available Demonstrated Technology (BDT) - Treatment required
for new sources as defined by Section 306 of the Act.
Best Available Technology Economically Achievable (BAT) -
The level of technology applicable to effluent limitations
for industrial discharges to surface waters as defined
by Section 301(b)(2)(A) of the Act.
Best Practicable Control Technology Currently Available BPT)
- Treatment required by July 1, 1977, for industrial
discharge to surface waters as defined by Section
301(b)(1)(A) of the Act.
Biochemical Oxygen Demand (BOD) - The amount of dissolved oxygen
required to meet the metabolic needs of anaerobic
microorganisms in water rich in organic matter.
Slowdown - A portion of water in a closed system which is removed
or discharged in order to prevent a buildup of deleterous
material such as dissolved solids.
Bucket-line dredge - A dredge in which the material
excavated is lifted by an endless chain of buckets.
Also known as Connected-bucket dredge. The type of
bucket-line dredge generally employed in gold placer
mining is a self-contained digging, washing, and
disposal unit operating in a pond and capable of
digging, in some cases, more than 100 feet below water.
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Its machinery is mounted on a shallow-draft hull and
the dredge backfills its working pit (pond) as it
advances. The capacity of individual buckets is used
as a measure of dredge size. For example, an "18-foot
dredge" is equipped with buckets each having a struck
capacity of 18 cubic feet.
Bullion - Unrefined gold that has been melted and cast into a
bar. In gold placer mining, the gold sponge obtained by
retorting amalgam is commonly melted with borax or other
fluxes, then poured into a bullion bar.
Cation - The positively charged particles in solution of an
electrolyte.
Cationic flocculants - In flocculation, surface active substances
which have the active constituent in the positive ion. Used
to flocculate and neutralize the negative charge residing on
colloidal particles.
Chemical analysis - The use of a standard chemical analytical
procedure to determine the concentration of a specific
pollutant in a wastewater sample.
Chemical Oxygen Demand (COD) - A specific test to measure the
amount of oxygen required for the complete oxidation of all
organic and inorganic matter in a water sample which is
susceptible to oxidation by a strong chemical oxidant.
Clarification - A physical-chemical wastewater treatment process
involving the various steps necessary to form a stable,
rapid settling floe and to separate it by sedimentation.
Clarification may involve pH adjustment, precipitation,
coagulation, flocculation, and sedimentation.
Clarifier - A basin, usually made of steel or concrete, the
primary purpose of which is to allow settling of
suspended matter in a liquid.
Clean-up - 1) The operation of harvesting gold or other valuable
material from the recovery system of a dredge, hydraulic
mine, or other placer operation.
Coagulation - The treatment process by which a chemical added to
wastewater acts to neutralize the repulsive forces that hold
waste particles in suspension.
Coagulants - Materials that induce coagulation and are used to
precipitate solids or semisolids. They are usually
compounds which dissociate into strongly charged ions.
Coarse gold - The word "coarse," when applied to gold, is
relative and is not uniformly applied. Some operators
consider course gold to be that which remains on a 10-mesh
screen. Others consider individual particles weighing 10
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milligrams or more to be coarse gold. Some apply the term
to any particle that is relatively thick as compared to
its diameter and can easily be picked up with the
fingers.
Composite wastewater sample - A combination of individual
samples of water or wastewater taken at selected
intervals to minimize the effect of the
variability of the individual sample. Individual
samples may have equal volume or may be proportioned to
the flow at time of sampling.
Concentrate - 1) To separate a metal or mineral from its ore or
from less valuable material; 2) the product of
concentration.
Conventional pollutants - pH, BOD, fecal coliform, oil and
grease, and TSS.
Cyclone - The cone-shaped apparatus used as a classifying
(or concentrating) separator into which pulp is fed so as to
take a circular path—coarser and heavier fractions of
solids report at the apex of the long cone (bottom) while
finer particles overflow from the central vortex (top).
Denver jig - Pulsation-suction diaphragm jig for fine material,
in which makeup (hutch) water is admitted through a rotary
valve adjustable as to the portion of the jigging cycle over
which a controlled addition of water is made.
Deposit - Term used to designate a natural occurrence of a useful
mineral, coal, or ore in sufficient extent and degree of
concentration to permit exploitation.
Detention time - The time allowed for solids to collect in a
settling device. Theoretically, detention time is equal
to the volume of the device divided by the flow rate. The
actual detention time is determined by the operating
parameters of the tank.
Discharge - Outflow from a pump, drill hole, piping system,
channel, weir, or other discernable, confined, or discrete
conveyance (see also "point source").
Discharge head - The vertical distance from the center of a pump
to the center of the discharge outlet where the water is
delivered, to which must be added the loss due to friction
of the water in the discharge pipe.
Discovery claim (Alaska) - A claim covering the initial
discovery. Subsequent claims are commonly designated as
one above, two above, three above; one below, two below,
etc., depending on their position in relation to the
discovery claim.
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Drag line - A power excavator equipped with a long boom and a
heavy digging bucket that is suspended from a hoisting line
and is pulled toward the machine by means of a "drag" line.
By manipulating the two lines (wire ropes), the bucket can
be caused to dig, carry, or dump the excavated material.
Such a machine is more properly called a "dragline
excavator."
Drainage water - Incidental surface waters from diverse sources
such as rainfall, snow melt, or permafrost melt.
Dred ge - A self-contained combination of an elevating excavator
(e.g., bucket-line dredge), the beneficiation or gold-
concentrating plant, and a tailings disposal plant, all
mounted on a floating barge.
Drift - A mine passageway driven horizontally within the mine.
Drift (geol.) - Any rock material, such as boulders, till,
gravel, sand, or clay, transported by a glacier and
deposited by or from the ice or by or in water derived from
the melting of the ice.
Drift mining - A method of mining gold-bearing gravel by means of
constructing drifts from shafts, or other underground
openings, as distinguished from surface methods for placer
mining.
Effluent - The liquid, such as treated or untreated wastewater,
that flows out of a unit operation, reservoir, or treatment
plant. The influent is the incoming stream.
Engineering site visit - The purpose of an engineering site visit
(sometimes referred to simply as a "site visit") is to
acquire on-site and operational and mechanical (and
sometimes economic) information about .• particular
industrial site. Usually, water sampling is not a part of
an engineering site visit.
EPA - Environmental Protection Agency.
Expanded metal riffles (expanded metal lath) - A type of pun.ched-
metal screen. The style commonly used in gold placer
mining, for saving fine gold, consists of a latticework of
diamond-shaped openings (about 3/4" x 1-1/2") separated by
raised metal strands that have a decided slope in one
direction. When installed as riffles, with the slope
leaning upstream or downstream, eddies form beneath the
overhangs, thus creating conditions well-suited for the
saving of fine gold. When used as riffles, expanded metal
is generally placed over cocoa matting or carpeting
ma t e r i a1.
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Fine gold 1) Pure gold, i.e., gold of 1000 fineness.
Fineness - The proportion of p>ure gold relative to other
substances, in bullion or in a natural alloy, expressed in
parts per thousand.
Fines - 1) A term that refers to the smaller particle sizes
(approximately 100 mesh); 2) the sand or other small-sized
components of a placer deposit.
Five-year, 6-hour precipitation event - The maximum 6-hour
precipitation with a probable recurrence interval of
once in 5 years as established by the U.S. Department of
Commerce, National Oceanic and Atmospheric Administration,
National Weather Service, or equivalent regional or rainfall
probability information.
Flocculants - Any substances which will cause fine particles to
adhear to form larger particles. Lime, alum, and ferric
chloride are examples of inorganic flocculants and
polyelectrolytes are organic flocculants.
Free gold - Gold uncombined with other substances. Placer gold.
Giant - See Hydraulic giant.
Glacial - Pertaining to, characteristic of, produced or deposited
by, or derived from a glacier.
Gold dust - A term once commonly applied to placer gold,
particularly gold in the form of small particle size.
Grab sample - A single sample taken instantaneously.
Grain - A unit of weight equal to 0.0648 gram, 0.04167
pennyweight, or 0.002083 troy ounce. There are 480 grains
in a troy ounce.
Gram - A unit of weight in the metric system equal to 15.432
grains, 0.643 pennyweight, or 0.03215 troy ounce. There are
31.104 grams in a troy ounce.
Gravel - A comprehensive term applied to the water-worn mass of
detrital material making up a placer deposit. Placer
gravels are sometimes arbitrarily described as "fine"
gravel, "heavy" (large) gravel, "boulder" gravel, etc.
Gravity separation methods - The treatment of mineral particles
which exploits differences between their specific gravities.
The separation is usually performed by means of sluices,
jigs, classifiers, spirals, hydrocyclones, or shaking
tables.
Grizzly - A device for the coarse screening or scalping oE bulk
materials to remove the large waste component. Usually an
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
iron or wood grating, it serves as a heavy-duty screen to
prevent large rocks or boulders from entering a sluice or
other recovery equipment.
Ground sluicing - A mining method in which the gravel is
excavated by water not under pressure. A natural or
artificial water channel is used to start the operation, and
while a stream of water is directed through the channel or
cut, the adjacent gravel banks are brought down by picking
at the base of the bank and by directing the water flow as
to undercut the bank and aid in its caving. Sluice boxes
may or may not be used. Where not used, the gold is allowed
to accumulate or. the bedrock awaiting subsequent clean-up.
A substantial water flow and adequate bedrock grade are
necessary.
Head - Pressure exerted by a column of fluid.
Highwall - The unexcavated face of exposed overburden in a
surface mine, or the face or bank on the uphill side of a
contour strip mine excavation.
Hillside placer - A gravel deposits intermediate between the
creek and bench placers; their bedrock is slightly
above the creek bed, and the surface topography shows
no indication of benching.
Hydraulic dredge - A dredge in which the material to be processed
is excavated and elevated from the bottom of a stream or
pond by means of a pump or a water-powered ejector. Large
hydraulic dredges may be equipped with a digging ladder,
which carries the suction pipe, and a motor-driven cutter
head arranged to chop up or otherwise loosen material
directly in front of the intake pipe. Dredges having this
configuration employ a deck-mounted suction pump, and they
may carry the mineral recover equipment on board the dredge
or, more commonly, they may transport the excavated material
by means of a pipe line to a recovery plant mounted on
independent barges or on the shore. (See Bucket-line
dredge).
Hydraulic giant - The nozzle assembly used in hydraulic mining.
The giant is provided with a swivel, enabling it to be swung
in a horizontal plane, and it may be elevated or depressed
in a vertical plane. Nozzle sizes range from 1 to 10 inches
in diameter, and the larger sizes are provided with a
deflector or a specific configuration, enabling them to be
moved with little effort. In California, giants discharging
as much as 15,000 gallons per minute in a single stream, at
a nozzle pressure of over 200 pounds per square inch, have
been used. The giant is also known as a "monitor." Both
terms stem from manufacturer's trade names.
Hydraulic lift - A suction lift (a piping arrangement) which
utilizes water pressure to pick up and transport material
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(ore) to the sluice. The hydraulic lift provides prewash to
the ore prior to sluicing.
Hydraulic washing - Mining by washing lighter sand and dirt away
with water, leaving the desired heavier mineral.
Hydraulic mining - A method of mining in which a bank of gold-
bearing earth or gravel is washed away by a powerful jet of
water and carried into sluices where the gold separates from
the earth by its specific gravity.
Hydraulic monitor - See Hydraulic giant.
Hydraulicking - Mining by the hydraulic method.
ICP - Inductively coupled plasma. An atomic emission
spectrometric method for trace element analysis of water and
waste method 200-7.
IFB metals - Twenty-seven metallic analytes determined by ICP or
atomic absorption (furnace) procured by EPA-ITD's routine
Invitation-for-BID (IFB)-type contracts.
Infiltration water - That water which permeates through the earth
into the plant site.
Influent - The liquid, such as untreated or partially treated
wastewater, that flows into a reservoir, process unit, or
treatment plant. The effluent is the outgoing stream.
Jig - A machine in which heavy minerals are separated from sand
or gangue minerals on a screen in water by imparting a
reciprocating motion to the screen or by the pulsation of
water through the screen. Where the heavy mineral is larger
than the screen openings, a concentrate bed will form on top
of the screen; where the heavy mineral particles are smaller
than the screen openings, a fine-size concentrate will be
collected in a hutch beneath the screen.
Jigging - Process used to separate coarse materials in the ore by
means of differences in specific gravity in a water medium.
JTCJ - Jackson Turbidity Unit. Unit of turbidity measured using a
candle turbidimeter. (See NTU.)
Lagoon - Man-made pond or lake which is used for storage,
treatment, or disposal of wastes. Lagoons can be used to
hold wastewater for removal of suspended solids, to store
sludge, to cool water, or for stabilization of organic
matter by biological oxidation. They also can be used as
holding ponds, after chemical clarification and to polish
the effluent.
Marine placer - A deposit of placer-type minerals on the ocean or
sea bottom beyond the low-tide line as distinguished from
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
beach placers. Some marine placers may contain material
related to beach deposits formed during periods of low sea
level; others may contain stream-type placers or mineral
concentrations formed on land and later drowned by a
lowering of the coastal region.
Mine - A place where work or other activity related to the
extraction or recovery of ore is performed.
Mine area - The land area from which overburden is stripped and
ore is removed prior to moving the ore to the beneficiation
area.
Mine drainage - Any water drained, pumped, or siphoned from a
mine.
Mining claim - That portion of the public mineral lands which a
miner, for mining purposes, takes and holds in accordance
with the mining laws. A mining claim may be validly located
and held only after the discovery of a valuable mineral
deposit (see Discovery).
Mining patent - A document by which the Federal Government
conveys title to a mining claim.
Monitor - See Hydraulic giant.
Muck (Alaska) - A permanently frozen overburden that can overlie
placer gravels in the interior of Alaska. It is composed of
fine mud, organic matter, and small amounts of volcanic ash.
It varies in depth (thickness) from less than 10 feet to 100
feet or more.
National Pollution Discharge Elimination System (NPDES) permits -
NPDES permits are issued by the EPA or an approved state
program in order to regulate point source discharge to
public waters.
Native gold - 1) Metallic gold found naturally in that state
e.g., placer gold.
New water - Water from any discrete source such as a river,
creek, lake, or well which is deliberately allowed or
brought into the plant site.
Nonconventional pollutants - Any one pollutant not defined as
conventional or toxic pollutants under the Clean Water Act.
NTU - Nephelometric Turbidity Unit. A unit of turbidity measured
with a nephelometer, usually measured against a
formazin polymer standard. Nephelometric turbidity
units will approximafe units derived from a candle
turbidimeter but will not be identical to them (see
JTU) .
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
Nugget - 1) A water-worn piece of native gold. The term is
restricted to pieces of some size, not mere "colors" or
minute particles. Fragments and lumps of vein gold are not
called "nuggets," for the idea of alluvial origin is
implicit. 2) Anything larger than, say, one pennyweight or
one gram may be considered a nugget.
Open cut mine - Any form of recovery of ore from the earth's
surface except by a dredge.
Ore - Gold placer deposit consisting of metallic gold-bearing
gravels, which may be: residual, from weathering of rocks
in-situ; river gravels in active streams; river gravels in
abandoned and often buried channels; alluvial fans; sea
beaches; and sea beaches now elevated and inland. Ore is
the raw "bank run" material measured in place before being
moved by mechanical or hydraulic means to a beneficiation
process.
Overburden - Worthless or low-grade surface material covering a
body of useful mineral. The frozen muck covering dredge
gravels in Central Alaska is an example of placer
overburden.
Pan - 1) A shallow, sheet-iron vessel with sloping sides and a
flat bottom used for washing auriferous gravel or other
materials containing heavy minerals. It is usually referred
to as a "gold pan " but is more properly called a "miners'
pan." Pans are made in a variety of sizes, but the size
generally referred to as "standard" has a diameter of 16
inches at the top, 10 inches at the bottom, and a depth of
2-1/2 inches. Pans made of copper, or provided with a
copper bottom, are sometimes used for amalgamating gold.
2) To wash earth, gravel, or other material in a pan to
recover gold or other heavy minerals.
Panning - Washing gravel or other material in a miners' pan to
recover gold or other heavy materials.
Pay dirt - Auriferous gravel rich enough to pay for mining or
working it.
Pennyweight - A unit of weight equal to 24 grains, 0.05 troy
ounce, or 1.5552 grams.
Permafrost - Permanently frozen ground (see Muck).
Permit area - The area of land in which active mining and related
activities are allowed under the terms of an NPDES permit.
Usually, this is specifically delineated in an NPDES permit
or permit application, Alaska Tri-agency permit application,
or similar document specifying the mine location, mining
plan, and similar data.
Placer deposit - A mass of gravel, sand, or similar material
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
resulting from the crumbling and erosion of solid rocks and
containing particles or nuggets of gold, platinum, tin, or
other valuable minerals that have been derived from the
rocks or veins.
Plant site - the area occupied by the mine, necessary haulage
ways from the mine to the beneficiation process, the
beneficiation area, the area occupied by the wastewater
treatment facilities, and the storage areas for waste
materials and solids removed from the wastewaters during
treatment.
Process wastewater - All water used in and resulting from the
beneficiation process (e.g., the water used to move the ore
to and through the beneficiation process, the water used to
aid in classification, and the water used in gravity
separation), mine drainage, and infiltration and drainage
waters which commingle with mine drainage or waters
resulting from the btneficiation process.
Point source - Any discernible, confined, and discrete conveyance
including but not limited to any pipe, ditch, channel,
tunnel, conduit, well, discrete fissure, container, rolling
stock, or vessel or other floating craft from which
pollutants are or may be discharged.
Priority pollutants - Those pollutants included in Table 1 of
Committee Print No. 95-30 of the "Committee on Public Works
and Transportation of the House of Representatives," subject
to the Clean Water Act of 1977.
Recirculation - The continued use1 of water internally within a
process. As used in gold placer mining, recirculation is
the continual use of the same water used as the transport
medium for solids (ore) to or through the classification,
beneficiation, and solids separation (wastewater treatment)
processes. Recirculation and 100 percent or total recycle
may be similar or even identical.
Reconnaissance - A site visit to gather data with or without
taking samples.
Recycle - The return and reuse of wastewater to a process after
treatment.
Residual placer - Essentially, an in situ enrichment of gold or
other heavy mineral caused by weathering and subsequent
removal of the lode, or other parent material, leaving the
heavier, valuable mineral in a somewhat concentrated state.
In some cases, a residual placer may be essentially an area
of bedrock containing numerous gold-bearing veinlets that
have disintegrated by weathering to produce a detrital
mantle rich enough to mine. In some parts of California,
such areas are known as "seam diggings."
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
Riffle - 1) A designed trap across the bottom of a sluice made
of expanded metal, angle iron, railroad ties, blocks or
slats of wood or stones and arranged in such a manner that
openings are left between them down the sluice to create
eddies to trap the gold; the whole arrangement at the bottom
of the sluice is usually called "the riffles." 2) A
shallow extending across the bed of a stream; a rapid of
comparatively little fall in a stream.
Riprap - Stone of various sizes placed on a surface to prevent
erosion.
River mining - The mining of part or all of a river bed after
diverting the river by means of a flume or tunnel, or by use
of wing dams to divert the river from the working area.
Rocker - A short, sluice-like trough fitted with riffles and
transverse curved supports, permitting it to be rocked from
side to side, used to recover placer gold or other heavy
minerals.
Runoff - That part of precipitation that flows over the land
surface from the area upon which it falls.
Sediment - Solid material settled from suspension in a liquid
medium.
Sedimentation - The gravity separation of settleable, suspended
solids in a treatment facility.
Settleable solids - The particulate material (both organic or
inorganic) which will settle in 1 hour, expressed in
milliliters per liter (ml/1), as determined using an Imhoff
cone and the method described for "Residue-Settleable" in 40
CFR Part 136.
Settlement Agreement of June 7, 1976 - Agreement between the U.S.
Environmental Protection Agency (EPA) and various
environmental groups, as instituted by the U.S. District
Court for the District of Columbia, directing the EPA to
study and promulgate regulations for a list of chemical
substances referred to as Appendix A Pollutants.
Settling pond - A pond, natural or artificial/ for removal of
solids from water.
SIC - Standard Industrial Classification (code).
Slime - Extremely fine particles derived from ore, associated
rock, clay, or altered rock.
Sludge - Accumulated solids separated from a liquid during
processing.
Sluice - To cause water to flow at high velocities for Wastage,
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
excavation, ejecting debris, etc.
Sluice box - An elongated wooden or metal trough, equipped with
riffles and usually a bottom matting, through which alluvial
material is washed to recover its gold or other heavy
minerals.
Sluiceplate - A shallow, flat-bottomed steel hopper arrangement
at the head end of a sluice box. A bulldozer generally is
used to push gold-bearing gravel onto the sluiceplate, from
where it is washed into the sluice by water issuing from a
large pipe or by means of a small hydraulic giant.
Slurry - Solid material conveyed in a liquid medium.
Specific gravity - The weight of a substance as compared with the
weight of an equal bulk of pure water, e.g., placer gold,
with a specific gravity of about 19, is 19 times heavier
than water.
Spiral concentrator - A wet-type gravity concentrator in which a
sandwater mixture, flowing down a long, spiral-shaped
launderer, separates via gravity differentials into
concentrate and tailings fractions. The concentrates are
taken off through ports while the tailings flow to waste at
the bottom.
SS - Settleable solids
Strip - To remove the overlying earth or low-grade or barren
material from a mineral deposit.
Suction dredge - See Hydraulic dredge.
Suction lift - The vertical distance from the level of the water
supply to the center of a pump, to which must be added the
loss due to friction of the water in the suction pipe.
Sump - Any excavation in a mine for the collection of water for
pumping.
Suspended solids - (1) Solids which either float on the surface
of or are in suspension in water, wastewater, or other
liquids and which are removable by a 0.45 micron filter.
(2) The quantity of material removed from wastewater in a
laboratory test, as prescribed in "Standard Methods for the
Examination of Water and Wastewater" and referred to as
nonfilterable residue measured in mass per unit volume
(e.g., mg/1 TSS).
Swell - The expansion or increase in volume of earth or gravel
upon loosening or removal from the ground. The average
swell of gravel is around 25 percent and sometimes is as
high as 50 percent.
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GOLD PLACER MINE SUBCATEGORY SECT - XVII
Table - A concentration process whereby a separation of
minerals is effected by flowing a pulp across a riffled
plane surface inclined slightly from the horizontal,
differentially shaking in the direction of the long axis,
and washing with an even flow of water at right angles to
the direction of the motion.
Tailings - The washed material which issues from the end of a
sluice or other recovery device in a placer operation.
Thaw points - Pipes driven into frozen gravel through which water
or steam is circulated, for weeks or months, to thaw the
ground ahead of mining. Once thawed, the ground does not
freeze again; thawing is usually carried out one to two
seasons ahead of the mining operation.
Total Suspended Solids (TSS) ^lare the residue retained on a
standard glass-fiber filter after filtration of a well-mixed
water sample expressed in milligrams per liter (mg/1)
using the method described for Total Suspended Solids Dried
at 103X-105X in 209C Standard Methods for Examination p_f
Water and Wastewater, 16th Edition.
Treatability study - A study to determine the pollutant removal
effectiveness of a wastewater treatment technology.
Trommel - A heavy-duty revolving screen used for washing and
removing the rocks or cobbles from placer material prior to
treatment in the sluices or other gold recovery equipment.
Troy ounce - One-twelfth part of a pound of 5,760 grains, i.e.,
480 grains. It equals 20 pennyweights, 1.09714 avoirdupois
ounces, 31.1035 grams, or 31,103 milligrams. This is the
ounce designated in all assay returns for gold, silver, or
other precious metals.
TSS - Total Suspended Solids.
Turbidity - An expression of the optical property that causes
light to be scattered and absorbed rather than transmitted
in straight lines through the sample. Turbidity in water is
caused by the presence of suspended particles.
Water Duty - A measure of the effectiveness of water use employed
in mining. The definition of water duty varies widely in
different parts of the world.
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