COSTS OF REMEDIATION AT MINE SITES
January 1997
U.S. Environmental Protection Agency
Office of Solid Waste
401 M Street, SW
Washington, DC 20460
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Costs of Remediation
DISCLAIMER
The mention of company or product names is not to be considered a n
endorsement by the U.S. Govern ment or by the Environmental Protection
Agency.
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TABLE OF CONTENTS
1.0 INTRODUCTION 1
1.1 Cost Factors 1
1.2 Organization of Report 3
2.0 ACID ROCK DRAINAGE 4
2.1 Waste Rock Pile 5
2.2 Underground Mine Drainage 10
3.0 SEEPAGE AND OVERFLOW FROM LEACH SYSTEMS AND TAILINGS
IMPOUNDMENTS 13
3.1 Overflow or Breach of an Impoundment Structure 13
3.2 Leakage from the Face or Toe of a Dam 14
4.0 MINE SITE CASE STUDIES 16
4.1 Overview 16
4.2 Case Studies 20
5.0 REFERENCES 58
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1.0 INTRODUCTION
Costs associated with the remediation of modern mine sites are not well documented in the
public record of published literature for several reasons, including the following:
• Remedial measures may be designed and implemented in response to compliance and
enforcement actions, chemical spill events, state permit requirements, etc. However,
while specific remedial actions taken must be reported regulatory agencies, costs
typically are not.
• Some actions may involve limited, short-term actions (i.e., cleaning up minor spills);
however, others may require more complex, long-term solutions that are often
completed in multiple phases. Cumulative cost data are unlikely to be readily available
for such long-term actions.
• Costs are often considered proprietary to the mine operator.
The objective of this project is to develop data on the costs of addressing typical environmental
problems that arise at modern mines. EPA collected information for this report throughout 1995. The
costs presented may be used by permit writers, regulatory agencies, enforcement personnel,and mine
operators for mine planning (including financial assurance), as well as estimating the costs of future
enforcement and/or remedial actions. These costs do not reflect permitting and legal expenses. Total
remedial costs associated are dependent on location, nature and extent of the problem, type and
duration of required remedial actions, and regulatory agencies involved.
1.1 Cost Factors
The costs associated with mine site remediation are highly variable (MEND, 1995) because of
the site-specific nature of many environmental problems encountered at mine sites. Table 1-1 presents
some of the factors that can influence costs associated with mine-site remediation. This list is not
intended to be all-inclusive.
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Table 1-1. Factors That Influence the Cost of Remediation at Mine Sites.
Category
Remediation Goals
Waste Characterization
Sampling
Water Quality
Site Characteristics
Liners
Site Hydrology
Water Treatment
Site Operations
Regulatory Considerations
Factors
Level of clean-up required/desired
Type and volume of material/waste
Number and frequency of sampling events
Methods selected/required
Degree of contamination (water and sediments)
Quantity of metals loadings
Lateral extent of plume/contamination
Acid Rock Drainage (ARD) issues
Size of operation
Site access (remote, etc.)
Climate (temperature, precipitation, etc.)
Geologic materials
Elevation
Topography (steep slopes, etc.)
Soil
Clay
Amended soil
Synthetic
Soil and subsurface properties
Precipitation
Flow rate (groundwater and surface water)
Water control (routing, diversions, etc.)
Type of treatment (passive vs. active, chemical usage, etc.)
Volume to be treated
Management of treatment residuals
Length of time required
Effect on production
Time to achieve remediation goals
Total ore and waste rock tonnage
Extent of site impacts
Earthwork requirements
Labor
Imported materials, if any
National Pollutant Discharge Elimination System (NPDES)
and state surface water and groundwater quality
requirements
Resource Conservation and Recovery Act (RCRA) and state
waste management rules
State/Federal mine design, operating, and reclamation
requirements
Dam safety requirements
Local regulations, including zoning
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Table 1-1. Factors That Influence the Cost of Remediation at Mine Sites (cont.).
Category
Factors
Water Quality Monitoring
Number of analytes and analyses
Laboratory analysis
Size of area to be monitored
Number of sampling stations
Groundwater monitoring
Surface water monitoring
Reclamation Requirements
Area to be revegetated
Type and amount of cover materials
Feasibility and duration
Post-reclamation land use
Any one of these factors can significantly impact the final cost of remediation at a mine site.
Actual incurred costs will vary considerably, and careful consideration of site-specific factors is
necessary to achieve an accurate cost estimate.
1.2 Organization of Report
The remainder of this report presents available information on costs of remedial measures.
Sections 2.0 and 3.0 provide general information from published materials on the ranges of costs
associated with common environmental problems at mine sites. Section 2.0 addresses acid drainage,
while Section 3.0 describes control of discharges from waste impoundments and piles. Ranges of cost
data are provided because costs are highly variable and dependent on site-specific factors (see Table 1-
1). Section 4.0 provides case studies of remedial measures undertaken at modern mining operations.
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2.0 ACID ROCK DRAINAGE
In this report, the term acid rock drainage (ARD) refers to drainage from the natural oxidation
of sulfide minerals contained in rock that is exposed to air and water, resulting in the production of
sulfuric acid (Steffen, Robertson, and Kirsten, 1989). This phenomenon is often referred to as acid
mine drainage (AMD). However, it is not necessarily confined to mining activities but can occur
wherever sulfide-bearing rock is exposed to air and water. Some natural springs are acidic, usually in
the vicinity of outcrops of sulfide-bearing rock. The principle components of the ARD process are
reactive sulfide minerals, oxygen, and water (Steffen, Robertson, and Kirsten, 1989). The oxidation
reactions, which are often accelerated by biological activity, yield low-pH water having the potential to
dissolve and mobilize heavy metals that may be contained in the water, rock, or elsewhere. If water is
available as a transport medium, the resultant drainage can contain products of the acid generation
process, typically elevated levels of metals and sulfate. This drainage can have detrimental impacts on
water quality.
Mining sometimes results in the exposure of mine wastes, tailings, or mine workings that
contain sulfides in sufficient quantities to result in acid generation. However, not all operations that
expose sulfide-bearing rock will result in ARD. Acid drainage will not occur if the sulfide minerals are
sulfur deficient or if the rock contains sufficient alkaline material to buffer and neutralize the acid. In
the latter case, the pH may be raised as a result of neutralizing reactions as the drainage passes through
the waste. The quality and rate of release of ARD is governed by various chemical and biological
reactions at the source of acid generation and along the drainage path.
More acidic waters can carry greater amounts of metals in ionic form than can more neutral
waters. The oxidization of sulfide minerals (and other materials) begins when slightly acidic rain water
comes into contact with sulfide-containing rock. The acidic rain water begins to react with the sulfide
minerals, and the majority of the remaining sulfide minerals are oxidized and carried away by the
sulfuric acid or ferric sulfate solutions that have been generated.
The degree to which sulfide minerals are dissolved is dependent on the amount of sulfur ion
and total metals present. In many sulfide minerals, the amount of sulfur is insufficient for complete
oxidation. In others, the sulfur ion is completely consumed during oxidation of the mineral. Minerals
such as pyrite, chalcopyrite, and pyrrhotite contain excess sulfur and, therefore, generate excess sulfuric
acid (H2SO4). High concentrations of sulfuric acid continue to oxidize other minerals until the acid is
neutralized locally or until the low-pH waters generated travel away from the source. The sulfuric acid
and ferric sulfate are usually derived locally but may, in some cases, come from an external source
such as circulating groundwater. Pyrite is generally considered to produce the majority of free sulfuric
acid.
The initial oxidation of pyrite is generally expressed by the following equation (Drever, 1988):
4FeS2 + 14O2 + 4H2O = 4FeSO4 + 4H2SO4 (2-1)
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As shown in Equation 2-1, each mole of pyrite (FeS 2) generates one mole of free sulfuric acid (H 2SO4).
This reaction becomes self-generating in the presence of water and oxygen.
If ARD is not controlled, it can pose a threat to the environment due to the toxicity of heavy
metals and other pollutants. Figure 2-1
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POTENTIALLY ACID GENERATING
WASTE ROCK RLE
|H20
INFILTRATION OF
PRECIPITATION
02 IN AIR
H,0
SULPHID1C WASTE ROCK
BASIC WASTE ROCK
AMD
GENERALLY
LOW pH
HEAVY METALS
OTHER
CONTAMINANTS
ACID GENERATION /NEUTRALIZATION
DURING MIGRATION
Figure 2-1. Schematic Showing Concept of Acid Generation and ARD Migration.
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(Steffen, Robertson, and Kirsten, 1989) presents a conceptual schematic of acid generation and
migration through a waste rock pile. The process involves the sulfide-containing and basic rock present
in the pile, the potential sources of oxygen and water, and the acid generation/neutralization occurring
where these elements are in contact. This figure illustrates water percolating through the dump, coming
into contact with both acid-generating and -neutralizing materials, and emerging from the ore as ARD.
ARD may occur from natural sources, as well as in locations where sulfide-containing rock has
been exposed during excavation and construction, mining, or other activities. Steffen, Robertson, and
Kirsten (1989) list the following as sources of ARD from mining operations:
Waste rock dumps from metal mines and spoil piles from coal mining,
• Drainage from underground workings,
• Surface runoff from open pit mine faces and pit workings, and
Ore stockpiles and spent ore piles from heap leach operations.
For the purposes of this report, costs have been developed for remediating environmental
problems resulting from waste rock piles and drainage from underground workings. These two
scenarios are considered indicative of estimated remedial costs associated with ARD-caused
environmental problems.
2.1 Waste Rock Piles
2.1.1 Typical Environmental Problems
Waste rock is generated by excavation and construction operations performed to access an ore
body at a mine, especially at open pit mining operations. As sulfide-containing waste rock is exposed
to precipitation and runoff, ARD may develop. Because most modern open pit mines generate
significant quantities of waste rock, the potential for developing ARD is relatively high if the requisite
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geochemical regime is present. The chemical and physical properties of the waste rock pile will
significantly affect the chemical concentration of ARD and the rate of change of that concentration
(Steffen, Robertson, and Kirsten, 1989). Different ARD concentrations and characteristics will result
in variable costs of remedial actions for waste rock piles.
The potentially severe environmental problems resulting from waste rock piles and
underground mines that generate ARD usually produce negative impacts on the quality of both surface
water and groundwater in proximity to the mine. A change in the pH of downgradient surface waters
may have detrimental effects on beneficial uses of those waters, such as domestic supply, agricultural
supply, aquatic habitat, etc., primarily because of the dissolution of material and other impacts to the
water chemistry discussed above.
2.1.2 Engineering S olutions
The goal of remediation at an ARD-producing site is reducing the migration of ARD to the
environment. Water is the transport mechanism for contaminants, and, therefore, the solutions to
ARD-caused problems usually focus on preventing the contact of water with the ARD source (Steffen,
Robertson, and Kirsten, 1989), thus inhibiting the generation of acid and water outflows.
Suppression of acid generation is usually accomplished through one of four methods, including
(1) exclusion of oxygen from the waste; (2) exclusion of water from the waste; (3) addition of
chemicals that react with sulfuric acid generated and neutralize the water; and (4) promotion of the
chemical reaction by adding oxygen and water to consume all available pyrite, leaving only the more
insoluble sulfates behind and, thus, mitigating ARD generation.
Management of water contact with an ARD source is accomplished through four methods: (1)
diversion of all surface water away from the source, (2) prevention of groundwater infiltration into the
source; (3) prevention of precipitation infiltration into the source, and (4) controlled placement of acid-
generating waste (Steffen, Robertson, and Kirsten, 1989).
Diversion of Surface Water : Diversion of surface water can be accomplished by constructing
diversion ditches and berms or by selecting a site that will avoid high-flow runoff areas. Construction
of diversion ditches and berms may be a short-term solution. However, long-term structures can be
designed to minimize debris accumulation and control erosion. Diversion structures do require periodic
inspection and maintenance even if they are designed for long-term use. In addition, flow volumes
used for the design of diversion structures can be reduced by locating waste rock piles away from the
bottoms of drainages and minimizing their surface areas. Costs incurred in constructing diversion
structures to reduce potential surface water flow through the pile, as presented in Table 2-1, should be
compared to the construction and operation costs incurred in selecting an alternative site. The costs
presented in Table 2-1 include only direct costs incurred during remedial action.
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Table 2-1. Summary of Estimated Costs of Engineered Solutions
for Acid Rock Drainage for Waste Rock Piles (U.S. Dollars/Ton of Waste)
(MEND, 1995)a.
Remedial Technology
Diversion Ditches and Berms
Collect and Treat
Collect and Treat with Soil Cover
Composite Soil Cover
Synthetic Liner
(200-year life)
Lowest Observed Value
$1.00/yd3 material moved b
$0.02C
$0.20b
$0.12C
$0.26b
$0.69C
$0.83b
$8.00/yd2b
Highest Observed Value
$50.00/yd3 material movedb
$0.12C
$0.49b
$0.42C
$0.66b
$0.87C
$1.01b
$40.00/yd2 b
a The values shown include only direct costs and not legal or permitting expenses.
b Final unit costs in 1994 dollars.
0 Capital unit costs in 1994 dollars.
Note: Actual costs may be more or less than those shown in the table based on site-specific
circumstances.
Similary to waste rock piles, tailings piles may also be significant ARD sources. Costs
associated with tailing ARD mitigation are presented in Table 2-2.
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Table 2-2. Summary of Estimated Costs of Engineered Solutions
for Acid Rock Drainage for Tailings (U.S. Dollars/Acre of Tailings Footprint).
Remedial Technology
Collect and Treat
Collect and Treat with Soil
Cover
Composite Soil Cover
Synthetic Liner (200 year life)
upper estimates = capital costs
lower estimates = final costs
Lowest Observed Value
$131,000a
$452,000b
$192,000a
$423,000b
$40,000
$48,000
$45,000
$51,000
Highest Observed Value
$205,000a
$503,000b
$385,000a
$558,000b
$649,000a
$877,000b
$628,000a
$854,000b
a Capital unit costs in 1994 dollars (MEND, 1995).
b Final unit costs in 1994 dollars (MEND, 1995).
Note: Actual costs may be more or less than those shown in the table based on site-specific
circumstances.
Prevention of Groundwater Infiltration : Contact of groundwater with an ARD source may be
prevented by intercepting or isolating groundwater before it enters the waste material, or by selecting a
site to avoid areas where groundwater infiltration is limited. Because collection and interception
methods are prone to failure in the long term, site selection is the best method of management. As an
example, a gravity-controlled water system is much more trouble-free than a pumping system. The
performance and cost of different groundwater interception and isolation methods vary over a wide
range, depending on hydrogeologic and other site-specific parameters. The estimated costs of these
engineering solutions are presented in Table 2-1.
Prevention of Precipitation Infiltration : The most practical method of controlling precipitation
infiltration is by installing a low-permeability cover or liner, which is commonly constructed from soil
and/or synthetic materials. These covers can be applied to near horizontal rock faces in open pits,
underground mines, and waste rock piles. An important consideration in selecting the most appropriate
cover material or combination of materials is the length of time during which control is required. The
estimated costs of these engineering solutions are presented in Table 2-1.
Controlled Placement of Waste : Controlling ARD migration in waste rock piles can be aided
by engineered placement methods such as cellular pile construction, compacting, mixing with low
permeability material, etc. (Steffen, Robertson, and Kirsten, 1989). These methods of placing waste
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rock to minimize infiltration should be considered in conjunction with other control methods, such as
impermeable covers to further reduce infiltration.
2.2 Underground Mine Drainage
The environmental problems resulting from acid drainage from underground mines are similar
to those from waste rock piles. However, the costs associated with remediation are different. The
ARD from underground workings generally occurs as a point surface discharge, typically containing
low-pH water. This point will usually be the lowest elevation entry into the mine.
Environmental problems from underground mines producing ARD cause negative impacts to
the quality of both surface water and groundwater in proximity to the mine. The engineered solutions
to these environmental problems are intended to manage contaminated waters and keep those waters
from affecting rivers, streams, and groundwater uses.
Surface water may flow into underground mines through portals and ventilation shafts, as well
as through fractures and fissures. Groundwater contamination is common at underground mines, and
its interception, treatment, and control can be achieved by various methods that depend on the site's
geology and hydrologic characteristics.
The cost for designing, installing, and maintaining water treatment systems is approximately
proportional to the volume of water requiring treatment times the amount of material per unit volume
of water. Moreover, the location of the site, the annual average precipitation amount, and the retention
characteristics of the mine or ore pile can cause variations in flow rates. The design of the water
treatment system must account for high- and low-flow fluctuations based on seasonal variations in
precipitation. The operating cost of most water facilities is dependent on power consumption, reagent
consumption, and personnel requirements. These costs must be calculated for each site. Daily direct
costs can range from $100 to $1,500, depending on the complexity of the process and the flow volume
treated. Once a water treatment facility is built, the volume of water treated does not significantly
affect the cost.
2.2.1 Treatment Methods
Several methods of water treatment are currently being used or tested at mine sites, including
lime precipitation, evaporation, biologic treatment using aerobic and anaerobic bacteria, wetland
treatment systems, electrolyticwinning, and ion encapsulation in zeolites. The costs of these treatment
methods are presented in Table 2-3.
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Table 2-3. Cost To Treat Acid Rock Drainage
(Dollars/Gallon/Minute Flow).
Remedial Technology
Lime Precipitation
Evaporation
Passive Wetland
Range of
Average Capital Cost
$2,900 to $6,400/gal/min a
$2,000 to
$6,000/gal/min
$2,900 to
$18,500/gal/mina
Range of Average Annual
Operating Costs
$700 to
$3,600/gal/mina
$200 to
$2,200/gal/min
$120 to
$420/gal/mina
a From Gusek (1995).
Note: Actual costs may be more or less than those shown in the table based on site-specific
circumstances.
The volume of water discharged from mines and waste piles located in dry climates is generally
low, whereas discharge volumes tend to be higher in wetter climates. Low flows can typically be
processed by evaporation methods or the use of wetlands. The costs associated with these processes are
small, including the cost of an impoundment, miscellaneous plumbing, and importing peat for the beds
and monitoring. A treatment system for a mine site demonstrating an average flow of less than 5
gallons per minute could be constructed for less than $10,000. Annual operating costs may average
10 percent of the initial construction cost. Large-scale process plants can have capital costs exceeding
$20 million with annual operating costs exceeding $500,000 (Gusek, 1995).
For higher flow rates, the preferable system is lime precipitation. The standard lime process
plant includes a receiving pond, lime storage bins, and mixing tanks where the lime is added and mixed
with the influent. The influent then passes through a thickening tank where the precipitate is settled and
dewatered. The pH of the overflow water is adjusted, if necessary, and the overflow water is
discharged. Engineering for this type of plant includes the grading of a site, construction of ponds,
purchase of tanks and process machinery, and fabrication. Fabrication of a weather-tight building to
house the apparatus in colder climates is also necessary. The cost of this type of a facility may range
from $50,000 to tens of millions of dollars (Gusek, 1995). Maintenance and operation of the facility
may cost from several hundred to several thousand dollars per day, depending on the water flow
volume and the amount of metals dissolved. Each plant must be specifically designed for the volume
and characteristics of the waste water and the level of treatment required.
2.2.2 Collection of Acid Water
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Acidic waters generated from mines can usually be diverted and collected at a single point
where they are either gravity fed or pumped to a treatment plant. Waters generated from waste piles
can be more difficult to direct to a single point. Associated costs include rehabilitation of the mine
openings, surface grading and plumbing. Pump installation and operating costs are an additional cost, if
they prove necessary. Operational costs must account for variable water flow rates and the pumping
distance and elevation from the source(s) to the treatment plant.
Drainage from waste piles can be more difficult to collect. The factors affecting water
collection depend on the location and size of the waste piles, the topography underlying the piles, and
the permeability of the underlying strata. If the waters can be diverted to a single collection location by
gravity, then the costs are similar to those for mine openings. If the installation of a collection system
involves excavations, dikes and impoundments the cost is greatly increased. The cost of moving rock
and dirt generally ranges between $5 to $50 per cubic yard. When the location, types, and quantities of
borrow materials are known, a cost estimate can be developed.
If the waste is not overlying an impermeable membrane or if it does not have the proper
characteristics to seal itself from the underlying strata, it is possible that acid water (or other waste
water) will infiltrate through porous underlying strata. In this scenario, it may be necessary to drill a
series of dewatering and collection wells into the strata to remove acid drainage. The configuration of
the dewatering wells may be designed to encircle the area, to create a capture zone (cone of depression
in the water table) associated with a single well, or in a line to form a curtain. Drilling costs, including
materials, generally range from $10 to $50 per linear foot of borehole. These costs are dependent on
the location of the site, the depth of the borehole and the amount of rig downtime beyond the control of
the contractor.
Upon completion of drilling and testing of the dewatering wells, a pump collection system can
be designed and installed along with the required plumbing. The cost of this system is dependent on the
number of dewatering wells, the depth of the boreholes, the amount of water, and the elevation and
distance the water has to be pumped. Pumps operating in acidic waters are usually designed to resist
the affects of corrosion. If no electric power lines exist at the site, additional expenses are incurred to
bring in power lines, install generators to maintain engine powered pumps.
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3.0 SEEPAGE AND OVERFLOW FROM LEACH SYSTEMS
AND TAILINGS IMPOUNDMENTS
Typical environmental problems occurring at the site of a tailings or leach system
impoundment are a result of pollutant-laden process water overflowing or escaping through the dam;
percolating downward into the groundwater; or moving through a breach in the retaining dam.
3.1 Overflow or Breach of an Impoundment Structure
The effects of a downstream release normally are a result of a higher than anticipated
precipitation event or failure of an impoundment structure. The structural failure of an impoundment
may be instantaneous. In this case, nothing can be done to stop the damage as it occurs. The solution
to this situation normally requires rebuilding the dam and initiating a cleanup of the materials deposited
downstream (or downgradient) from the site. If the breach or outflow is certain, but not immediate,
measures can be taken to prevent the event. Such measures include increasing dam and liner height,
directing flows to secondary structures, or implementing procedures to provide for a controlled release.
3.1.1 Dam Breach
The cost of the repair of an impoundment dam normally includes engineering design, location
and procurement of materials, haulage of materials and installation. The haulage costs for the fill
material are highly dependent on the distance that the material must be transported. The costs of
material placement typically range from $5 to $50 per cubic yard with the engineering costs averaging
10 percent of the total cost of the project.
The cost of clean up of the tailings and miscellaneous debris that flow out of the impoundment,
is based on the type and amount of tailings spilled, the standards set for clean up and the water flow
volume in the stream (if a stream exists). For example, if a small spill occurred next to a large river,
the river may disseminate all or most of the tailings, making tailings removal impossible. Another
scenario might involve a small spill occurring in a drainage which contains no active stream. In this
case, it may be possible to return the solids from this spill back to their original location, using
earthmoving equipment. The cost of moving the material back in place can be as little as a few dollars
per cubic yard. If the spill consists of only natural materials without any toxic constituents, it might be
feasible to leave the material in place and reclaim it.
Another scenario might involve a large toxic spill occurring along a small active stream. This
type of spill could generate the highest cleanup cost. It may be necessary to use earthmoving
equipment, dredges and hand laborers to remove material from the stream and adjacent riparian areas.
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The cost of this type of cleanup is so site specific that it can only be estimated following determinations
made by the site engineers and regulatory agencies involved.
3.1.2 Overflow of an Impoundment
Releases of water from an impoundment can be anticipated if the overflow is expected to occur
as a normal result of the mining operation. In the case of a sudden high flow precipitation event, the
overflow could occur unexpectedly as in the dam breach described above. The remedial actions
described above in Section 3.1.1 can be similarly applied to an overflow.
In a scenario where there is a gradual rise in the water level of the impoundment caused by
greater than annual average precipitation or increase in discharge from the processing plant, a solution
can be designed and implemented prior to the overflow. Some solutions might include increasing the
height of the impoundment, building an additional impoundment, and installing/increasing the size of
water treatment plant/controlled discharge (see Section 2.2.1).
3.2 Leakage from the Face or Toe of a Dam
Leakage from a dam can be stopped either by modifying the dam or by collecting, treating, and
discharging the leakage. Modern tailings ponds generally contain enough fine grained material that
they tend to plug themselves with the "slimes" generated from the milling process. If water leakage
occurs, the most common solution in a wet climate is to construct a water treatment plant and then
collect, treat, and discharge the water. In a dry climate, where a mine typically has water shortages,
collected solution is often reclaimed and returned to the mill for re-use.
The waters contained in impoundments commonly found at modern cyanide and acid leach
plants contain a lower percentage of suspended solids and as a result can be more susceptible to leakage
than conventional process mills. In this case, it is very important to stop all leaks both for
environmental and economic reasons. Repair of a leak may be as simple as replacing or repairing an
impermeable liner. This could involve engineering of the repair, procurement of materials and
installation by laborers. The cost of repairing a small leak may be as little as a few hundreds of dollars.
The costs of repairing a leak that occurs below a large leach pad/pond can be much higher. As
an example, if a leak develops near the center of a hypothetical pad having horizontal dimensions of
200 by 200 feet and a height of 50 feet, the leak must first be isolated. The expense and time spent
locating the leak are dependent upon the experience of the mine operator and the amount of monitoring
and detection instrumentation already located near the pad. It may be necessary to drill a series of
angle boreholes to ascertain the location of the leak. After locating the leak, the overlying material
must be excavated to expose the leak. The excavation must be engineered to insure stable slopes for
safety reasons. In this hypothetical scenario, approximately 15,000 cubic yards of material would have
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to be removed to reach and expose the leak. The calculated cost for removing the material from the
pad would be $75,000, if the cost for hauling material is $5 per cubic yard. The cost of repairing the
leak would additionally involve engineering time, materials and labor. The total cost to repair this type
of leak is estimated to be approximately $100,000.
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4.0 MINE SITE CASE STUDIES
4.1 Overview
The initial objective of this project was to develop comprehensive data on remedial measures
undertaken at selected modern mining operations throughout the United States, specifically focussing
on cost data. Such detailed cost data, if available, would allow for site-by-site comparisons of the unit
costs associated with addressing specific problems, and the factors that influence those costs.
Unfortunately, there is generally no centralized source of information on modern mine site remedial
costs, at the national level or in most States.
To collect site-specific cost information, EPA had it's contractor (SAIC) contact State offices
responsible for regulating mining activities as well as reviewing published literature. State office visits
were then conducted to obtain publicly available file materials documenting remedial activities. Such
visits were undertaken in South Dakota, South Carolina, Nevada, Colorado, and Montana. Information
on remedial activities in Arizona was obtained from the EPA Region IX Office in San Francisco.
Overall, information was reviewed for many non-coal mining sites (more than 100 modern/post-1980
operations) where remedial actions have been taken to address actual or perceived threats to the
environment. Cost data were not readily available, except for Arizona and South Dakota. This is
largely because most States do not require submittal of these data. Where cost information was found
in other States, it was primarily submitted on a voluntary basis. Similarly, while the literature provides
extensive information on many significant environmental incidents, it also does not typically include
cost information (presumably, at least in part, because such data are considered proprietary). As a
result, the only comprehensive approach to cost data collection would be to contact the mining
companies themselves. Such an effort was beyond the scope of this report.
Despite the above limitations, cost data were obtained for 24 modern (post-1980) mining
operations throughout the western United States. These data are summarized in Table 4-1 and the
accompanying case studies. The problems encountered at case study sites are representative both of
environmental effects common to many mines (ARD issues, water management difficulties, etc.) as
well as unique site-specific issues. One site, Noranda's Montanore Project represents a proposed
mining operation where cost data were available for water collection and treatment options. This
information was included because it is also applicable to water treatment costs associated with remedial
activities at other sites. The varying level of detail in the case studies reflects the inconsistency of
available data and ranges from a single dollar value for total remedial costs at a site, to breakdowns of
each individual cost element (including site characterization, and design, construction, and maintenance
of remedial alternatives). In most of the case studies, the level of detail regarding the site is not
sufficient to estimate unit costs (per acre, gallon etc.). For example, many of the case studies do not
present water flow data, the acreage affected or remediated, or the dimensions of tailings dams, heaps,
waste rock piles, etc.
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Costs of Remediation
Table 4-1. Examples of Costs for Remedial Measures at Specific Sites.
Name and Location
of Mine
Type of Problem
Remedial Action Taken
Cost Data (Dollars)
Microgold II Mine
Florance, Idaho
Releases of mercury from
plant contaminated soils and
tailings pond. Did not
significantly impact
groundwater, although source
of elevated levels in two wells
is unknown (might have been
background).
Excavation and encapsulation of soil using
synthetic liner and cover.
$120,000 was put into
escrow for clean-up.
Lucky Friday Mine
Mullan, Idaho
100 gallons of copper sulfate
solution overflowed a tank,
drained into a sump and
eventually into the Coeur
d'Alene River.
Installed concrete curbing around tanks,
installed paving in tank area and planted
willows and other vegetation along river.
$47,700
Copper Cities
Magma Copper
Arizona
Unauthorized
discharges/seepages from
waste management and
process solution units; NPDES
non-compliance.
Construction of 100-year, 24-hour
collection facilities and pumpbacks.
NPDES compliance
costs/remedial measures:
1991-$180,000 to
$300,000
early 1993 - $544,173
O&M costs (an
unspecified portion
allocated to
repairs/remedial
activities):
1991 - $696,620
1992-$155, 188
Pinto Valley
Magma Copper
Arizona
Unauthorized
discharges/seepage from
tailings and leach dumps,
ponds, and solution ditches,
including storm overflows and
tailings and solution dam
breeches.
Repair of tailings and solution dams; new
and increased seepage collection activities.
Costs to respond to non-
compliance 1992/93 order
for problems:
$636,537
Miami Operations
Cyprus Miami
Miami, Arizona
NPDES non-compliance,
unauthorized discharge of
wastewater to surface and
groundwater.
Broad improvements in site-wide water
management practices over a 10 year
period. Discontinuation of unauthorized
discharges including elimination of an
unlined acid sump, groundwater pumping;
construction of runon and runoff controls
and additional enhanced containment
systems, and waste rock excavation and
capping.
Total capital costs for
improved water
management and NPDES
compliance were slightly
greater than $1 million.
Cyprus Sierrita Mine
Sierrita, Arizona
Unauthorized discharge to
surface water from process
pond (ARD issues) and tailing
water reclaim line.
To address pond seepage, constructed
hydraulic barriers; replace PVC pipe with
steel-encased pipe.
$101,030 for pond,
$70,000 for pipe
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Costs of Remediation
Table 4-1. Examples of Costs for Remedial Measures at Specific Sites (cont.).
Name and Location
of Mine
Type of Problem
Remedial Action Taken
Cost Data (Dollars)
Ray Complex
ASARCO
Arizona
Subsurface leakage of
solutions from leach dumps,
ponds, and processing
facility - low pH and elevated
copper; also water quality
impacts from contaminated
runoff.
Repair leaks in facilities and
impoundments, dig drainage trenches to
intercept leaks, drive a 13,000-foot long
water diversion tunnel, build diversion
dams and construct wetlands, provide long-
term water treatment.
Net capital cost for
NPDES compliances have
exceeded $40 million with
annual O&M cost for the
treatment plant, ongoing
surface water monitoring,
and maintenance of
containment structures
exceeding $1.5 million in
1993.
Magma Copper
Company
Superior Division
Arizona
Unauthorized discharges.
Seepage of tailings and acidic
mine water to surface water.
Elevated metals levels -
copper, cadmium, lead, and
zinc.
Construction of seepage collection and
pumpback systems, improved water
reclaim in the mill (especially acidic
water), and remediation of contaminated
soils.
Capital costs of NPDES
compliance activities to
manage/control discharges
reported in 1991 as about
$280,000.
Thompson Creek
Tonopah Mineral
Resources
Challis, Idaho
Acid generation from tailings
and waste rock; unanticipated
discharge from tailings pond.
No decision on approach to long-term
remediation of tailings made to date.
Short-term installation of tailings seepage
pumpback. Options for long-term include
pyrite removal in mill; buffering; water
treatment, etc.
$7.5 million bond for
water quality protection
added for ARD
remediation. Other total
remediation cost
estimates: $6 to $25
million.
Grey Eagle Mine
Noranda
Happy Camp,
California
Tailings impoundment was
source of water quality
impacts (active 1982-86).
Water treatment plant used during active
operations; tailings pond closed with
geotextile cover and revegetated surface.
Treatment costs not
available; but liner cost
$131,000 per acre
(unknown how many
acres).
Franklin Consolidated
Mine
Idaho Springs,
Colorado
Pyritic upper tailings pile
eroding into Gilson Gulch,
fine grained tailings in lower
pile moved 100 feet by wind
For upper tailings pile, graded and
compacted tailings; earthen berm and
runon controls installed. For lower pile,
cover source of blowing tailings with
burlap and clean-up of windblown tailings;
also berms installed in mill to contain
spills.
State bond was increased
by $16,000 to cover clean-
up costs.
Gilt Edge Mine
Lead, South Dakota
Acid water drainage and
releases of cyanide into
surface and groundwater;
long-term from spent ore/pits
and short-term from pad leaks.
For spent ore and pit seepage, installed
collection and treatment ponds in
drainages; treatment using reverse osmosis;
spent ore eventually to be capped. For
short-term pad leak, installed plug, repaired
pad, and installed treatment for excess
water.
Estimated at $3.7 million
for long-term impacts;
$350,000 for pad leak.
Paradise Peak Mine
FMC Gold
Nevada
Oil spill in the vicinity of the
maintenance shop. Spill
caused by failure of oil
skimmer in shop clean-up
water sump. Little potential
for hydrocarbons to impact
ground or surface water.
Sealing the point of discharge, installing
berms around the contaminated area,
performing soils removal, and ceasing
water washdowns (use of dry reagent).
$103,801
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Costs of Remediation
Table 4-1. Examples of Costs for Remedial Measures at Specific Sites (cont.).
Name and Location
of Mine
Type of Problem
Remedial Action Taken
Cost Data (Dollars)
Buckskin Operation
Douglas Co., Nevada
Seepage containing cyanide in
groundwater downstream from
tailings impoundment.
Pump impoundment and install new lined
pond; install tailings water reclaim system.
Approximately $200,000
Dee Gold Mining
Newmont Gold
Elko, Nevada
Water containing cyanide
seepage from tailings dam;
detected in nearby alluvial
aquifer.
Installed groundwater recovery wells and
vertical interceptor ditch; pumped
recovered water to tailings impoundment.
Approximately $2 million
Jerritt Canyon
Independence Mining
Elko, Nevada
Seepage from tailings
impoundment
Delineate seepage, install ground water
recovery system and modify mill process to
allow for recovered groundwater and
tailings water re-use.
Approximately S2.1
million
Goldstrike Mines
American Barrick
Elko, Nevada
Break in waterline caused
pond overflow resulting in
release of 25,000 to 30,000
gallons seepage/runoff.
Decommissioned waterline and pump out
of ponds.
$160,000 (Includes study
of impacts)
Buckhorn Operation
Cominco Resources
Carlin, Nevada
Leaks from fuel lines and
pipes; and diesel spill.
Elevated total petroleum
hydrocarbons in groundwater.
Collection of surface water runoff with oil-
water separation, groundwater treatment by
bioremedial solution and recovery/oil-
water separation; soils excavation.
Over $290,000
Richmond Hill
LAC Minerals
Lead, South Dakota
Unanticipated acid drainage
from spent ore (2.7 million
tons).
Short-term: installation of runon/controls;
construction of seepage collection and
treatment system; and liming of rock.
Long-term: return spent ore to pit and
install impervious cap.
$8.5 million
(additional bonding
requirement)
Wharf Resources
Lead, South Dakota
Nitrate in ground water
downgradient of spent ore
pile; may also be contribution
from blasting residues.
Installation ion exchange system to treat
spent ore removal for nitrate.
Approximately $2 million
Golden Sunlight Mine
Whitehall, Montana
Cyanide leakage from tailings
impoundment; environmental
threats associated with ground
movement in mill caused by
massive weight of a waste
rock pile.
Redesigned tailings impoundment,
installed pumpback wells, provided
alternative water wells and treatment of
local domestic wells. For ground
movement impacts, pumpback wells
installed, waste rock moved to more stable
area, and improved process solution
containment systems installed.
$12 million has been spent
as of March 1995 to
address ground movement
effects; an additional $1.8
million in costs expected
in 1995. (No cost data for
tailings seepage.)
Zortman-Landusky
Mine
Pegasus Mining
Montana
Extensive ARD/AMD
drainage to surface and
groundwater from pits, cut ore,
and waste rock; also cyanide
releases from heaps and spent
Installed pumpback systems and built a
treatment plant; considering other, long-
term/improved containment and treatment
options.
$720,000 for current
treatment plant; in 1993-
94, $2.8 million spent on
reclamation (unclear how
much for environmental
impacts); drafts of
proposed compliance
plans suggest significant
additional costs to be
incurred.
Montanaore Mine
Noranda
Kootenai National
Forest, Montana
Proposed mine will have
tailings pond with anticipated
seepage of 450 gallons per
minute
Proposing a seepage collection system with
wetlands, evaporation or electrocoagulation
treatment.
Projected cost of water
management/treatment
ranges from $2.5 million
to $20.4 million.
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Costs of Remediation
Table 4-1. Examples of Costs for Remedial Measures at Specific Sites (cont.).
The cases studies describe a wide range of different levels of environmental concern as well as
mine sizes. Overall, they generally support the previous chapters by showing that remedial costs are
highly site-specific. Of additional note, the cost data for some sites only provides the expenditures to
date. Future costs may be significant, especially where the long-term performance of a remedial
alternative cannot be accurately predicted and/or perpetual care is likely to be required.
4.2 Case Studies
4.2.1 Case Study No. 1 - Elevated Nitrate in Groundwater at Leached Ore Piles
Site Name: Wharf Resources, Lead, South Dakota
Type of Mining: Cyanide Heap Leaching, on/off pad with spent ore neutralization
Nature of Environmental Effects : During the late 1980s, elevated levels of nitrate were
observed in groundwater monitoring wells downgradient of Wharf s spent ore pile. Some nitrate
loadings may also been the result of residuals from blasting operations.
Remedial Actions: Installation of the countercurrent ion exchange technology (CCIX) to
reduce nitrate and nitrite levels in the spent ore/process solution. Ion exchange is a commonly used
methodology for reduction, because the nitrate shows affinity for several types of resins. The CCIX
system uses countercurrent flow through a packed bed resin with nitrogen removal and regeneration
occurring simultaneously.
Costs of Remedial Activities : According to the South Dakota Department of the Environment
and Natural Resources, the company's cost for installing the CCIX at the Wharf site was approximately
$2 million. This does not include long-term operating costs, such as the costs associated with managing
rinse solution.
References: SD DENR, 1995. SD DENR, 1991c.
4.2.2 Case Study No. 2 - ARD from Spent Ore Disposal/Waste Rock Pile
Site Name: Richmond Hill, LAC Minerals, Lead South Dakota
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Costs of Remediation
Type of Mining: The Richmond Hill mine is located in the Black Hills regions of South
Dakota. Cyanide heap leaching operation with an on/off pad and spent ore neutralization. The facility
is located at between 5,500 and 6,000 feet with approximately 28 inches of precipitation annually.
Nature of Environmental Effects : In 1992, the State of South Dakota observed acid mine
drainage associated with spent ore disposal at the Richmond Hill mine in the Black Hills. An initial
sample taken from the toe of the waste rock dump had a pH of 3.1 and subsequent additional sampling
showed pH levels of 2.6 and 3.6 with elevated levels of sulfate, TDS, aluminum, copper, iron, and
manganese acidic conditions and high concentrations of metals and sulfates. The original mine plan
included processing a small quantity of sulfide rock and the State incorporated limited measures to
address acid drainage in the mining permit. However, the actual generation of acid drainage was
significantly greater than originally anticipated; necessitating more extensive short- and long-term
mitigation measures. After additional testing, LAC Minerals determined that all of the waste rock
generated during operations, 2.7 million tons, was acidic.
Remedial Actions: Remedial activities for acid drainage involved both short- and long-term
actions. In the short term, the facility constructed treatment ponds at the toe of the dump and added
caustic (some water is also diluted with uncontaminated storm water). Treated water can either be land
applied or discharged via an NPDES permit. Other short-term measures included: removal of sulfide
ore and placement on the pad, construction of runon controls, and addition of some neutralizing
materials to the pile.
The long-term remedy for the site involves removal of acid generating waste rock and
placement in the pit (presumed to also be acid generating). An impervious cap will then be installed.
Costs of Remedial Activities : According to the State, the cost of remedial measures at the site
(primarily for long-term actions) is shown by the increase in the reclamation bonding requirements for
Richmond Hill. After acid drainage was discovered, the surety bond for the site was increased by
approximately $8.5 million. This includes the following subcosts.
Moving Waste Rock to the Pit $2,521,000
Reclaiming Remaining Waste Dump $150,000
Cover for Waste Rock in Pit $653,000
Haul Sulfide ore from Pad $65,000
Regrade and Revegetate Pad 3 $780,000
Regrade and Revegetate Pads 1 $126,000
3:1 Pad Base Addition $4,221,000
APPROXIMATE TOTAL $8,500,000
These amounts do not include the initial costs of delineating the extent of the problem and designing
alternatives.
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Costs of Remediation
References: SD DENR, Undateda. Durkin, 1994.
4.2.3 Case Study No. 3 - Impoundment Overflow
Site Name: American Barrick Goldstrike Mines, Elko, Nevada
Type of Mining: American Barrick operates a cyanide heap leaching operation near Elko,
Nevada. Waste rock/spent ore is managed in an on-site dump.
Nature of Environmental Effects : During summer 1993, American Barrick began to observe a
sustained flow in the sedimentation pond that was not caused by surface runoff (instead it was likely
seepage from the dump). The sedimentation pond is used to manage runoff from the waste rock pile.
Runoff from the dump collects in the sedimentation pond. The gully in which the pond is located
drains to Rodeo Creek, an ephemeral drainage. In late July 1994, between 25,000 and 30,000 gallons of
water overflowed the pond (i.e., were discharged without a permit). The water flowed approximately
1,900 feet down Rodeo Creek from the point of intersection of the gully and the creek.
Regulatory Action: The State issued a Finding of Alleged Violation and Order (FOAV) for the
release. (All of the information in this summary was included in the facility's written presentation for a
Show Cause hearing related to the Order). In the Order, the State required that the operator delineate
the extent of any impacts on soils and shallow groundwater. According to American Barrick's
contractor, sulfate was the only parameter observed at elevated concentrations in ground water and soils
(high sulfate levels were also found in the seepage).
Remedial Actions: American Barrick determined that a water line located above the pile was
likely source of the discharge. This pipe was subsequently decommissioned. Further, Barrick pumped
millions of gallons of water from the sedimentation pond to the tailings pond, to ensure no other
discharges.
Costs of Remedial Activities : The total costs of remedial measures reported by American
Barrick in 1994 were $160,000. This included $110,612 for pumping water from the sedimentation
pond and $49,108 for preparing the delineation sampling plan. It should be noted that seepage from the
waste rock pile was also observed in 1993. However, there was no discharge from the pond (and no
violation). In 1993, American Barrick also had to pump nearly 2 million gallons of water from the
pond, relocate an equipment washdown area, and modify stormwater management at the waste rock
pile (the State files do not include any cost data from this incident).
Reference: Barrick, 1995.
4.2.4 Case Study No. 4 - Tailings Impoundment Seepage
Site Name: Jerritt Canyon Joint Venture, Independence Mining Company, Elko, Nevada
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Costs of Remediation
Type of Mining: Independence Mining Company operates the Jerritt Canyon Joint Venture in
Elko, Nevada. Detoxified tailings from the vat leaching operation at the site are disposed in a tailings
impoundment. Chlorination is used in the neutralization process. As of October 1991, more than
15,000,000 tons of ore had been processed in the vat leach operations. The tailings impoundment was
initially constructed to provide for full containment (i.e., zero discharge).
Nature of Environmental Effects : The operator, Freeport McMoRan Gold (FMG) at the time,
first suspected seepage from the impoundment in 1983. Nevada Division of Environmental Protection
staff observed seepage from the tailings impoundment during an inspection in 1990. The seepage
appears to flow from the eastern and southern sides of the tailings impoundment. The seepage caused
elevated major ion concentrations, including chloride and TDS levels in the surficial aquifer. Cyanide
has not been detected above the State's action level.
Remedial Actions: Since 1984, the operators of the mine have been investigating/delineating
the seepage and undertaking remedial measures. Remedial measures have included installing a ground
water recovery system. In addition, modifications were made to the milling process and associated
piping to allow for direct reuse of tailings water from the impoundment, as well as re-use of recovered
groundwater.
Costs of Remedial Activities : The most recent cost data available was presented in an October
18, 1991 letter from Independence to the State Bureau of Mining and Reclamation. Independence and
the previous owners had spent nearly $2.1 million on delineating the seepage/contamination, installing a
ground water recovery system, and making modifications to the milling process. Between 1984 and
1990, FMG spent $570,000 and Independence spent $1,500,000 during 1990-1991. Although the
seepage remediation system was operational in October 1991, some additional future investments were
expected by Independence to optimize system performance and maintain the collection system.
References: NDEP, 1990. Independence, 1991.
4.2.5 Case Study No. 5 - Cyanide Leakage from Tailings Impoundment
Site Name: Dee Gold Mining Company, Elko County, Nevada
Type of Mining: Newmont Gold Company now operates a cyanide heap leach operation near
Elko that was formerly operated by Dee Gold. Some of the tailings from the leaching process are
disposed of in tailings disposal facility No. 2. This unit is located in an ephemeral tributary of Boulder
Creek. Boulder Creek, a perennial stream, flows approximately 1,000 feet downstream of the dam.
The tailings dam was initially constructed to provide for full containment (i.e., zero discharge), with
the clay core keyed into the underlying bedrock.
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Costs of Remediation
Nature of Environmental Effects : Monitoring data collected during the 1980s showed cyanide-
laden seepage flowing from the tailings impoundment into the Boulder Creek alluvium. The highest
measured cyanide concentration in the cyanide plume was 6 ppm. According to the operator's
contractor, in November 1990, seepage was detected in the Boulder Creek alluvial aquifer. Seepage
may have been enhanced originally by the initial location of a reclaim pond near the north abutment.
The pond was moved shortly after seepage was detected.
Remedial Actions: To provide short-term seepage control, the facility installed three
downgradient groundwater recovery wells. Collected water was pumped back to the impoundment. In
1991, the operators decided to design and install a vertical interceptor trench drain (VITD) to contain
the seepage from the tailings impoundment. The VITD was planned to be operational in early 1992.
The flows collected in the VITD system would presumably be returned to the impoundment.
Costs of Remedial Activities : As of late 1990 (the most recent cost data), the cost of designing
and installing the VITD system as estimated to be approximately $1.25 million. This does not include
the costs of delineating the seepage, installation and operation of the recovery wells, or ongoing VITD
system operation and maintenance.
References: Dames & Moore, 1990. Rayrock, 1990. Hydro-Engineering, 1991.
4.2.6 Case Study No. 6 - Cyanide Leakage to Groundwater from Tailings Impoundment
Site Name: Buckskin Operation, Douglas County Nevada
Type of Mining: The Buckskin Operation is located 10 miles west of Yerington in Douglas
County, Nevada. The facility was originally operated as a mine and mill by Pacific Silver
Corporation. In 1987, Sonora Mining Corporation purchased the operation and began using the mill to
vat leach ore from Sonera's Jamestown Mine in California (the mine became inactive). Carbon-in-pulp
processing is used for gold recovery. Wet tailings from both Pacific Silver and Sonera's leaching
operations were managed in an impoundment located on the edge of a large alluvial plain. Sonora
modified Pacific Silver tailings disposal methods by greatly reducing the area of ponding/active
disposal. Although the impoundment was generally constructed by Pacific Silver in accordance with
State-approved designs, the operator apparently did not install a liner.
Nature of Environmental Effects : Groundwater contamination was initially observed at the site
during 1987 when cyanide was detected in a water supply well downstream of the tailings
impoundment. These findings influenced Sonera's proposed tailings management proposal. A zero
discharge permit was issued for Sonera's operations in August 1990. Under the permit, the facility was
required to install three groundwater monitoring wells downgradient from the tailings impoundment.
Subsequent monitoring data collected during the 1980s showed cyanide-laden seepage flowing from the
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Costs of Remediation
impoundment into the underlying ground water. The elevated cyanide concentrations appeared to have
been localized; a Geraghty & Miller report from 1991 showed no contamination in off-site wells.
Remedial Actions: During 1987, in response to the initial detection of cyanide contamination,
Sonora conducted a site investigation to delineate the contamination caused by Pacific Silver, altering
Sonera's plans for tailings management. In late 1990, after cyanide was detected in the permit
compliance monitoring wells, the State issued an order to Sonora requiring them to stop the leaks from
the Buckskin tailings impoundment. As a result, Sonora indicated that the company would "pump the
existing impoundment dry" and install a new lined unit. The order specifically required that Sonora
design and install a tailings water reclaim line. Remedial actions were undertaken in 1990-1991.
Costs of Remedial Activities : The 1987 investigation of groundwater contamination by
Sonera's contractor cost approximately $52,000 with modifications to the tailings impoundment design
expected to cost $50,000 - $100,000 (no final cost data available from 1987). No specific cost data
were found on the remedial measures undertaken in 1990-1991. However, in a late 1991 newspaper
article, a company official indicated that the costs of the remedial measures would be approximately
$200,000.
References: Botts, 1990. Bateman, 1990. Wahler, 1987. Bergsohn, 1991.
4.2.7 Case Study No. 7 - Fuel Spill from Ancillary Facilities
Site Name: Buckhorn Operations, Cominco American Resources, Carlin, Nevada
Type of Mining: Cominco American Resources' Buckhorn Operation is a cyanide heap leach
facility near Carlin, Nevada.
Nature of Environmental Effects : In late 1991 and 1992, Cominco observed several releases of
hydrocarbons from ancillary operations. These included: (1) a gasoline release from underground
piping, (2) a diesel fuel leak from underground piping, and (3) a surface spill of diesel oil. The
contamination area associated with the gasoline leak was approximately 1 acre with groundwater
concentrations of Total Petroleum Hydrocarbons of up to 37.9 ppm. The diesel leak from the pipe
contaminated approximately .33 acre with ground water TPH concentrations of up to 1.32 ppm. The
spill contaminated about .8 acre with trace amounts of TPH detected in groundwater. Finally, there are
other localized areas of oil and diesel contamination at the plant site. Surface water contamination was
limited to a confined marsh area with TPH concentrations of up to 1,360 mg/1. In November, 1992 the
State issued a Finding of Alleged Violation and Order (FOVA) for sitewide hydrocarbon
contamination. All of the information in this description is included in the facility's written response to
the FOVA.
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Costs of Remediation
Remedial Actions: The selected remedial measures included collection and oil/water
separation of surface flows, installation of groundwater recovery wells with oil/water separation and
fuel recovery, injection of bioremediation solution through a new injection well and constructed
trenches, and bioremediation of previously excavated soils.
Costs of Remedial Activities : A December 8, 1992 presentation by Cominco American
Resources to the State of Nevada indicated that the cost of delineating the contamination and
implementing selected remedial measures would exceed $290,000. This included site investigation and
remediation activities, however, a complete breakdown of individual cost elements was not available.
References: Cominco, 1992.
4.2.8 Case Study No. 8 - Cyanide Leakage from a Heap/ARD Discharge from Spent Ore
Site Name: Brohm Mining Corporation, Gilt Edge Mine, Lead, South Dakota
Type of Mining: Brohm mining corporation operates a cyanide heap leach facility near Lead,
South Dakota. Over 3,000,000 tons of neutralized spent ore has been disposed of Ruby Creek, which
flows during wet periods. Ruby Creek flows into a perennial stream, Bear Creek.
Nature of Environmental Effects : Beginning in 1993, ARD has been observed in both Ruby
Creek and Strawberry Creek with observed pH levels as low as 1.5-2.0. Historic tailings are the only
wastes found in Strawberry Creek, however, studies completed by the operator have shown a hydraulic
connection between Brohm's pit and Strawberry Creek.
In addition, from June 17 through 19, leakage occurred from one of Brohm's leach pads causing
cyanide releases to ground and surface water. This violated Brohm's zero discharge permit.
Remedial Actions: U.S. EPA issued NPDES permits requiring Brohm to control the discharges
in Ruby and Strawberry Creeks. As a result, Brohm installed a series of treatment ponds and a
temporary holding pond in Ruby Creek. Water treatment is currently done by reverse osmosis. A lined
collection pond for surface water and pumped ground water was also installed in Strawberry Creek.
Further, over 165,000 tons of historic tailings in Strawberry Creek were cleaned-up. As of June 1995,
Brohm was planning to install a second treatment system for all of the water in Ruby and Strawberry
Creeks plus pit water (to be operated until the waste rock is reclaimed and capped). According to the
operator, water quality has now been restored.
To address the 1991 pad leakage, Brohm was required by the State to submit reports
documenting the extent of the contamination, and develop a remediation plan. The settlement between
the State and Brohm included lowering solution levels in the surge pond, installing a bentonite plug in
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Costs of Remediation
the area of the leakage, permanently repairing the pad, and constructing a treatment system for excess
water.
Costs of Remedial Activities : The short-term costs of acid drainage remedial measures are
provided by the facility and long-term reclamation costs are provided by the State's bonding
calculations. The facility's estimates for short-term measures (spent between 1993 and 1995) include:
Interim mitigation and treatment $1,960,000
Historic tailings remediation $451,000
Water treatment system $741,000
ARD plan $208,000
TOTAL $3,360,000
This does not include the January 1994 reported cost ($400,000) for a reverse osmosis unit for water
treatment (presumably their second, the first was purchased in 1993 for $350,000).
As described in the State's bond calculations, approximate long-term costs of remediation for
ARD can be observed in several line items, including:
Ruby waste dump cap $2,162,000
Limestone on Pit Benches $78,000
Pit Cap $650,000
Crusher area cap $48,000
Leach pad cap $472,000
QA of Cap Construction $ 110,000
Pit water treatment $195,000
Ruby dump capital items $661,000*
TOTAL $4,376,000
Capital items include construction of ponds and water diversion ditches, sludge disposal, and
water treatment during a planned four-year reclamation period.
The total reclamation bond for the site is now $8,517,000.
The costs of the remedial measures associated with leakage from the heap are available through
the State's requirement of a performance bond for remediation. The total bond amount was $350,000.
References: SD DENR, 1991a. SD DENR, 1992b. SD DENR, 1993. Brohm, 1995.
SD DENR, Undatedb.
4.2.9 - Case Study No. 9 - Tailings Erosion (Small Operation)
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Costs of Remediation
Site Name: Franklin Consolidated Mining Company, Inc., Clear Creek County, CO
Type of Mining: A small underground mine and cyanide vat leaching operation for gold
production. The operator recently changed the gold recovery process from a Merrill-Crowe circuit to
Carbon-in-Leach. Spent ore/tailings have been disposed of in two units, the upper and lower tailings
impoundments. The upper tailings impoundment contained approximately 7,000 tons of tailings as of
October 1993; the amount in the lower tailings unit was not specified. An additional 2,500 tons of
pyrite concentrate were found in the mill area.
Nature of Environmental Effects : During a mine site inspection by the Colorado Division of
Minerals and Geology on October 15, 1993, State inspectors found that pyritic tailings in the upper
impoundment were continuing to erode into Gilson Gulch. The inspection report notes that Franklin
was required to have submitted a corrective action plan for the eroding tailings by September 30, 1993;
however, no plan had been received as of the date of the inspection. In addition, a drainage pipe was
found at the base of the tailings to direct runoff/seepage into a lined pond. However, the pipe was
apparently not functioning and ponding was observed. At the lower tailings impoundment, pyritic
tailings had been dispersed by wind 100 feet outside of the unit. As a result of the observed impacts,
the State of Colorado Mine Land Reclamation Board issued a Notice of Violation on March 1, 1994.
Remedial Actions: The corrective action plan for the impacts involved grading and erosion
control for the upper pile. The upper pile tailings were to be compacted in a single pile and an earthen
berm constructed to confine these materials. The diversion ditch above the pile was to be "improved"
and deepened. For the lower pile, the plan including wind erosion control by covering with burlap
netting and clean-up of the windblown tailings. In addition to tailings related-activities, the facility was
required to install curbing in the mill building to contain cyanide spills.
Cost of Remedial Activities : The costs of remediation are reflected in post-inspection revisions
to the operator's bond. No specific line item costs for remedial measures are available. However, as
noted in Franklin consultant's February 23, 1994 letter describing the proposed actions, a bond increase
of $16,000 was generally necessary to cover the remedial actions.
References: York-Feirn, 1993. Poulter, 1994.
4.2.10 Case Study No. 10 - ARD and Cyanide Discharges; Metals Loading; Liner Failure
Site Name: Summitville Mine, Summitville, CO
Type of Mining: This Superfund site was a gold mine in the San Juan Mountains of southern
Colorado. Ore was mined from an open pit and beneficiated on a single cyanide heap leach pile. The
facility operated during the mid-1980s. Waste rock from the pit was disposed of in on-site piles. The
site is located in an area of historic underground mining operations.
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Costs of Remediation
Nature of Environmental Effects : From the beginning of operations in the mid-1980s, it
became clear that the initial plan of operations included an inadequate determination of water
management requirements. Subsequent treatment technologies for unanticipated discharges proved
inadequate. Further, acid drainage and associated metals loadings from waste rock piles as well as
historic drainage tunnels were discovered. Finally, the potential for acid generation was underestimated
during mine planning. When operator declared bankruptcy in December 1992, the fluid levels in the
heap were within 5 feet of the emergency spillway (and would have overflowed without treatment). In
addition, avalanches damaged the liner during initial construction necessitating the construction of a
seepage collection and pumpback system.
Remedial Measures: Long-term remedial/site reclamation measures remain to be determined
for the site. EPA/State of Colorado have been operating the wastewater treatment system since the
operator went bankrupt. The current focus is on opportunities for bioremediation to address both
cyanide detoxification and acid generation.
Costs of Remedial Activities : This site presents extraordinary clean-up requirements in a
highly sensitive environment. Because no final remedy has been selected or schedule for site clean-up
completion established, it is impossible to provide detailed cost estimates. However, the long-term
costs of clean-up measures are now projected to approach $100 million.
References: Pendleton, 1995. Plumlee, 1995. Jones, 1993.
4.2.10 Case Study No. 10 - Pre-mine Planning, Proposed Water Treatment Options
Site Name: Noranda, Montanore Mine, Kootenai National Forest, Montana
Type of Mining: Proposed copper and gold underground mining operations with a conventional
flotation mill. Tailings will be managed in an impoundment.
Nature of Environmental Effects : The tailings impoundment is anticipated to have seepage of
up to 1,798 liters per minute; requiring discharge to the Kootenai River Basin. In addition, excess mine
water will be land applied and managed in percolation ponds. Seepage from the percolation ponds can
also impact surface water. To meet applicable State water quality standards, Noranda must provide for
water collection and discharge treatment.
Mitigation Measures : The plan of operations includes plans for a drainage system and options
for water treatment. Constructed wetlands are the least costly suggested treatment technology,
however, their effectiveness are not certain. Active treatment technologies proposed include
evaporation and electrocoagulation.
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Costs of Remediation
Costs of Remedial Activities : The estimated cost of constructing the drainage collection
system is $1.5 million. Wetlands treatment would cost between $1 and 2 million, while evaporation
and electrocoagulation would cost $18.9 and $6.9 million, respectively.
Reference: Marshall, 1990.
4.2.11 Case Study No. 11 - Water Quality Impacts from Tailings Impoundment
Site Name: Noranda, Grey Eagle Mine, Happy Camp, California
Type of Mining: 500-ton-per-day open pit gold mine with vat leach operation. Spent ore
disposed in tailings impoundment. Operations began in 1982 with closure in 1986.
Nature of Environmental Effects : The tailings impoundment was a source of water quality
impacts necessitating construction and operation of a water treatment plant.
Remedial Measures: The water treatment plant was used during active operations. For closure,
an impermeable cover consisting of a geotextile cover with a clay liner and surface revegetation was
required. To date, the cover has proven effective in preventing infiltration through the tailings.
Costs of Remedial Activities : The construction costs of the cover averaged $131,000 per acre
of tailings (the specific area to be covered was unavailable).
4.2.12 Case Study No. 12 - ARD and Cyanide Discharges from Large Heap Leach Operation
Site Name: Zortman-Landusky Mine, Pegasus Mining, Montana
Type of Mining: Extensive surface mining operations with heap leaches and processing
circuits. Active operations began in the late 1970s - early 1980s. Pegasus is currently planning an
expansion of leaching operations. The facility is located in an historic mining district with several
drainages impacted by old adit discharges and/or historic mining.
Nature of Environmental Effects : Acid drainage as well as cyanide releases have impacted
surface and ground water in two separate watersheds. While some impacts have been increased by
releases from historic adit and wastes, Zortman's impacts are evidence by extensive water quality data.
Remedial Measures: Zortman initially installed containment and pumpback systems in each
drainage and have developed a wastewater treatment facility. However, the existing facilities have
proven inadequate to capture all surface and subsurface drainage; they specifically cannot contain
maximum flows. Through an ongoing enforcement action, a broad water quality compliance plan is
being developed.
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Costs of Remediation
Costs of Remedial Activities : No specific cost data are available from the files and the long-
term cost will ultimately depend on the selected remedy. However, a 1994 newspaper article in the
Helena Independence Record cited the mine manager as indicating that the company spent $720,000
constructing the current water treatment facility. Further, he indicated that over $2.8 million was spent
on "reclamation" in 1993-1994 (uncertain how much of this was directed to remediation). Finally, the
size of the site, complexity of the impacts, and types of remedies under consideration suggest that
millions of additional dollars will likely be required for continued monitoring, design, construction, and
maintenance of remedial measures/treatment systems.
References: Independence Record, 1994. Hydrometrics, 1994. Hydrometrics, 1995.
4.2.13 Case Study No. 13 - Cyanide Seepage from Milling Operations
Site Name: Golden Sunlight Mine, Placer Dome, Inc., Whitehall, Montana
Type of Mining: An open pit gold mine with cyanide heap leaching that has been active since
1983. The facility is currently in the process of permitting an expansion. Operations at the site began
in December 1992. However, the facility was shut down between June 1994 and February 1995 due
ground movement and resulting mill damage.
Nature of Environmental Effects : Environmental impacts, from "minor" spills to long-term
effects on the surrounding environment, have been prevalent at Golden Sunlight since the beginning of
operations. The most significant impacts have been associated with ongoing cyanide-contaminated
seepage from the tailings impoundment, sloughing/cracking of waste rock dumps, and the threats of
acid drainage. The most recent environmental/safety incident involved "ground movement" in the plant
area (and related ground water impacts) caused by the massive weight of waste rock in piles at the site
(this is the only incident with available cost data).
Remedial Measures: To address cyanide-contaminated seepage, Golden Sunlight redesigned
the presumably lined tailings impoundment, installed pump-back wells, and provided alternative water
supply wells and water treatment for downgradient domestic water supplies. Pumpback/dewatering
wells have been installed in the plant area to address the ground movement-related impacts (as well as
changing waste rock management practices). Further, the operator moved 15 million tons of waste
rock to a more stable on-site location. Finally, Placer Dome installed a containment system for 12
tanks that hold weak cyanide solution, a concrete corridor to protect water lines, and a stronger tank for
tailings water reclaim storage.
Costs of Remedial Measures : As noted above, there are no remedial cost data for any of the
environmental impacts other than those related to ground movement. To address ground movement,
the operator had spent about $12 million as of March 1995 with an additional $1.8 million expected to
be spent by end of the summer.
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Costs of Remediation
References: Pay Dirt, 1995a. Pay Dirt, 1995b.
4.2.14 - Case Study 14 ARD from Tailings Impoundment
Site Name: Thompson Creek Mine, Tonopah Mineral Resources, Inc., Chain's, Idaho
Type of Mining: The Thompson Creek mine is located in Custer County, approximately 35
miles southwest of Challis. The site consists of an open pit molybdenum mine. Mine ore is
beneficiated by crushing, grinding, and conventional flotation. Tailings are managed in an
impoundment, while waste rock is disposed in two angle of repose piles. Mining began in the mid-
1980s. The mine is located near the Salmon River and its tributaries.
Nature of Environmental Effects : Beginning in the late 1980s, the operator began to observe
acid generation from a tailings impoundment. The impoundment was initially intended to be a zero
discharge unit. However, seepage was encountered from the beginning of operations necessitating the
construction and operation of a pumpback system. In addition, some types of waste rock were found to
have acid generation potential, although no impacts were observed in downstream drainages.
Remedial Measures: Cyprus initially estimated that water quality standards could be met by
diluting impoundment seepage with natural runoff. No water treatment beyond sediment control was
expected to be required. To address the acid drainage, the operator has investigated a wide range of
different potential remedial measures for the tailings impoundment. Such measures have included
conventional treatment systems, application of buffering solution to the tailings, and installation of
pyrite recovery/flotation system in the mill. To address waste rock, the facility uses selective
placement of potentially acid generating materials (including capping/buffering with other non-reactive
rock types). No final selection of a long-term alternative has been made to date.
Costs of Remedial Measures : The long-term costs of remedial measures are difficult to
determine because the final remedy has not been selected. Some evidence of the magnitude of such
costs is provided by the bond required by the State Department of Water Resources for the tailings
impoundment (to address potential water quality impacts that were not expected during mine planning).
As of 1991, the value of this bond was over $7.5 million (no more recent data are available).
Reference: Steffen Robertson & Kirsten, 1982. Steffen Robertson & Kirsten, 199la.
4.2.15 Case Study No. 15 - ARD and Metals Contaminated Seepage of Process Solutions
Site Name: Magma Copper Company, Pinto Valley Division, Copper Cities Unit, Arizona
Type of Mining: Reprocessing of Miami tailings for copper recovery.
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Costs of Remediation
Nature of Environmental Effects : NPDES permit no. AZ0020419 (1986) authorized discharge
of seepage and runoff from the inactive dumps and shop area to Final Creek from discharge point 002,
from inactive dumps to Final Creek via discharge point 003, and from inactive dumps and undisturbed
landscape to Final Creek from discharge point 004, in accordance with effluent limitations, monitoring
requirements, and other conditions. In April 1991, an EPA inspector observed unauthorized discharges
of effluent below the No. 5 A seepage control dam, and at the base of the No. 004 collection dam.
Magma's sampling data from the 5A area indicated that the water was low pH, with elevated
concentrations of copper, zinc, and manganese. A water sample collected above the No. 004 collection
dam contained arsenic, barium, copper, manganese, nickel, lead, and zinc.
Magma noted in response to a June 21, 1991 Findings of Violation and Order (FOV) that the
"outfall location" near the No. 004 collection dam was actually the downstream end of the open channel
spillway of the dam, and attributed it to a nearby spring. Magma also reported in the 1991 response
that the stain below the 5A dam was about 2,000 feet long and six to eight inches wide, with a lower
limit approximately two-thirds of a mile above the confluence of the unnamed wash where it was
located with Final Creek. Magma felt that there was insufficient information that could be used to
estimate the amount of solution that had entered the drainage. Magma found no evidence of
environmental damage as a result of the staining.
In September 1991, a pipe separated at a pump by the No. 002 containment area and acid
(pH=3.5) effluent containing copper, lead, and zinc was discharged to Final Creek for about 30
minutes. (FOV)
Further seepage from the No. 5A seepage control dam was reported in January 1992, and EPA
issued a FOV on January 24, 1992.
Remedial Measures: In order to receive its NPDES permit, Cities Service Company (owner
until 1986) constructed 100-year, 24-hour storm collection facilities in 1981-1982, to capture leaching
solutions from old mine dumps and contaminated stormwater, and prevent them from being discharged.
In 1991, Magma proposed to cease discharges of copper solution from the No. 5 A seepage control dam,
by one of three measures: attempting to redrill and pressure grout the 5A dam; installing caisson and
pumps above the 5A dam; or constructing a new dam. Magma also proposed to move the 004
discharge point to a location upstream of the entrance of the rerouted spring, remove No. 11 tailings
starter dam, and upgrade upstream collection facilities.
Remedial measures taken were reported in a 1/22/93 letter to EPA:
Tinhorn Wash/Outfall 002: Corrective actions taken at Tinhorn Wash included rerouting the
discharge pipeline from the pumping system to prevent a discharge in the event of a future failure of the
pipeline, and relocating the pumping system.
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Costs of Remediation
No. 1 Basin/Outfall 004: To best address EPA's concerns, Magma elected to relocate the
discharge point outfall location approximately 10 feet downgradient of its existing position, and
submitted an NPDES permit renewal application accordingly, in June 1992.
No. 5/5A Basin/Outfall 003: Based on hydrogeologic information, Magma chose to construct a
large containment facility (Zook Dam) to collect the seepage identified by EPA from this area. Other
potentially less costly alternatives, including treating and releasing, may have been acceptable.
However, time constraints precluded Magma from completely investigating, or permitting and
constructing, a treatment system.
Costs of Remedial Activities : In 1991, Magma stated that its expected NPDES compliance
costs were as follows:
No. 5A Seepage Collection Dam: $30,000, $100,000, or $150,000
Move 004 discharge point, remove No. 11 dam, and upgrade facilities: $150,000
In early 1993, Magma reported the following costs of NPDES compliance (Table 4, 2/5/93
letter):
Item Cost Date
Tinhorn Wash/Outfall 002 $ 3,579 1/92
No. 1 Basin/Outfall 004 $ 1,500 estimated 2/5/93
No. 5/5A Basin/Outfall 003 $539,093 1-12/92 (final cost slightly higher)
TOTAL $544,173
O&M costs were described in 2/5/93 letter and provided for November 1986 to 1991, then
updated in a 2/23/93 letter. Costs are estimated because Miami Unit maintenance personnel repair
Copper Cities water control facilities during inspections and in conjunction with work done on non-
NPDES facilities located at the Copper Cities. Magma's estimates for O&M, capital, and other costs of
NPDES related facilities were as follows:
1986 1987 1988 1989 1990 1991 1992
$15,505* $103,618 $80,661 $52,714 $65,874 $155,188 $696,620
* November 5-December 31, 1986
References: Magma, 1991a. USEPA, 1992.
4.2.16 Case Study No. 16 - Tailing Impoundment and Leach Operation
Site Name: Magma Copper Company, Pinto Valley Division, Pinto Valley Operations, Arizona
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Costs of Remediation
Type of Mining: Open pit, concentrator, and dumpleaching/SX-EW.
Nature of Environmental Effects : NPDES permit no. AZ0020401 (1984) authorized discharge
of stormwater overflow from discharge points 002, 003, and 004, and tailings seepage from discharge
point 005 to Pinto Creek. On January 16, 1991, an EPA inspector observed an unauthorized discharge
of effluent surfacing about 50 yards below Gold Gulch 2 reservoir, which contained water and copper
dump leach solution that overflowed from Gold Gulch 1 dam.
On June 22, 1990, and January 16, 1991, an EPA inspector observed effluent surfacing below
the toe of tailings dam no. 3 and flowing toward Pinto Creek. On January 16, the seepage was flowing
at about one gallon per minute. A sample of the seepage contained 0.42 mg/L of total copper.
On August 18, 1989 and January 4, 1991, the face of tailings dam no. 3 failed, and tailings
entered Pinto Creek. An estimated 96,000 gallons of a mixture of tailings and water was discharged in
1989, and an estimated 150 to 250 tons of tailings were discharged to Pinto Creek and its tributaries in
January 1991.
On January 16, 1991, an EPA inspector observed an unauthorized discharge of a mixture of
storm runoff water and industrial water, which consisted of shop runoff water, pump gland water, and
other industrial wastewater, surfacing below the Miller Springs catchments dam and flowing at about
six gallons per minute towards Pinto Creek. A sample collected during the inspection contained 0.0023
mg/L of total copper.
On August 11, 1991, September 5, 1991, and September 23, 1991, the Miller Springs ditch
became plugged, causing the ditch to overflow to a tributary of Pinto Creek and Pinto Creek. An
estimated 3000 gallons of effluent containing suspended solids and copper were discharged on
August 11, an estimated 24,000 gallons were discharged on September 5, and an estimated 39,000
gallons were discharged on September 23.
EPA issued a Finding of Violation on November 27, 1991 (IX-FY92-02), and Magma
submitted a response and preliminary engineering plan on January 29, 1992. Magma notified EPA on
July 15, 1992 that all upgrade projects outlined in the plan and the follow-up quarterly reports had been
completed.
Exceptionally heavy rainfall in January 1993, added to unusually high precipitation in
December 1992, caused area wide flooding and subsequent damage to water control facilities at Pinto
Valley Operation (PVO). Massive rainfall exceeded design capabilities of water management facilities
and resulted in extensive damage. Gila County was declared a state and federal flood disaster area in
January 1993. Pinto Valley Operation facilities were upgraded in 1992 to handle stormwater runoff
from a 100-year, 24-hour storm event, but continuing heavy storm event conditions caused an upset
condition starting on January 8, 1993. The PVO area received 86% of its average annual rainfall in
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Costs of Remediation
seven weeks in December 1992 and January 1993. The PVO mill was shut down for eight days in
January in order to commit all pumping resources to overflow prevention. Millions of gallons of water
were deliberately pumped into the PVO open pit.
In August 1992 and early January 1993, overflow process leachate solution containing sulfuric
acid, beryllium, cadmium, copper, nickel, and zinc was diverted from Gold Gulch I to prevent a breach
in the dam, with overflow contained in Gold Gulch II. In January, approximately 30% of the 20.9
million gallons released was being recovered, compared to 98% in August. On January 19-20, 1993,
Gold Gulch II overflowed into Pinto Creek, releasing approximately 27.7 million gallons of stormwater
and PLS. In February, heavy precipitation again required a bypass of Gold Gulch I to prevent a breach
in the dam, with overflow contained in Gold Gulch II and approximately 658,000 gallons released and
30% recovered.
In January and February 1993, heavy precipitation contributed to an overtopping of the No. 1
Tailings Dam berm, resulting in an erosional event on the face of the dam. Approximately 54.1 million
gallons of storm water and process water, and 90,000 cubic yards of tailings were released.
In July 1994, EPA and Arizona Department of Environmental Quality (ADEQ) announced that
Magma Copper Company would pay $625,000 for Clean Water Act violations at Pinto Valley,
Superior, and Copper Cities. Under the agreement, Magma also undertook a supplemental
environmental project that required the cleanup of pollution in the Pinal Creek drainage area from the
abandoned Old Dominion Mine near Globe, Arizona, and paid $50,000 to initially fund three additional
projects to benefit affected watersheds.
Remedial Actions: Magma planned to upgrade the seepage collection facilities in place prior to
the March 1991 sloughing of the face of tailings dam no. 3, and reconstruct or construct new ancillary
facilities, including access roads, powerlines, and transformers and pipelines.
In early 1993, Magma reported the following NPDES compliance activities:
Upper Catchment/Miller Springs: A hydrologic assessment was performed to establish site
specific conditions. A toe drain collection system was then designed and installed at Upper Catchment
to eliminate seepage to the Miller Springs area. An internal berm was raised and sediment that had
accumulated in the catchment was removed.
No. 1 Seepage Collection System/Outfall 002: To address the moist area below the outfall
culvert, Magma installed an elbow riser on the intake side of the outfall culvert, so as to ensure that an
acceptable amount of stormwater storage capacity was in place to comply with the existing NPDES
permit. A permanent pump and cassion collection structure were also installed to recycle stormwater to
process operation.
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Costs of Remediation
Gold Gulch: A review of hydrogeologic data collected from the area led Magma to decide that
the establishment of a new outfall location would address the issues raised by EPA, and submitted a
revised NPDES permit application. Costs incurred related to Gold Gulch were described as
miscellaneous upgrades to facilities.
Cottonwood Canyon: Magma could not identify the source of the intermittent seeps identified
by EPA. Magma therefore decided to relocate the existing permitted outfall downgradient of the seeps,
and submitted a revised NPDES permit application.
Miscellaneous: Magma incurred costs to lease equipment and for miscellaneous parts and labor.
No. 3 Tailings Dam Expenditures: Magma hired contractors to perform repairs on the face of
the No. 3 Tailings Dam at the time of the slough. These costs were considered costs of NPDES
compliance. Costs were incurred for earthwork, surveying, miscellaneous equipment rental, a pump
study, and pump purchase.
Prior to and after the March 1991 sloughing, Magma incurred additional costs to constantly
maintain and, where necessary, repair the tailings dam face, which Magma considered a cost to operate
and maintain the tailings dam itself, rather than a cost for NPDES compliance. Contractors retained to
perform other tailings dam work are charged to O&M of the tailings dam. Filling in erosional areas on
the benches and assuring proper drainage were also considered O&M activities.
Costs to repair the seepage collection facilities that were in place prior to the sloughing were
considered compliance costs. Following the sloughing, Magma designed and constructed new facilities
engineered to a more rigorous design standard than required for compliance with the existing NPDES
permit. Estimated costs for upgrades from the facilities in place prior to the sloughing, to these more
rigorous design standards, were subtracted from the actual costs for the new facilities.
Extensive remedial activities were performed by Magma following the heavy rainfall period in
December 1992 and early 1993.
Costs of Remedial Activities : Magma submitted a Summary of Expenditures to Comply with
Administrative Orders IX-FY91-27 (Superior), IX-FY92-02 (Pinto Valley), and IX-FY92-08 (Copper
Cities) on January 22, 1993 (not located), and supplemental information on February 5, 1993. Magma's
stated costs for the Pinto Valley Operations were as follows:
Item Cost Date
Upper Catchment/Miller Springs: $ 57,868 10-11/91, 3/92, 6/92
No. 1 Seepage Collection System: $ 5,451 2-3/92
Gold Gulch: $ 4,733 5/92
Cottonwood Canyon: $ 1,000 estimated
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Costs of Remediation
Misc. equipment, materials, parts, labor: $ 61,1511-6/91
Subtotal $130,204 (2/5/93 response)
No 3 Tailings Dam Expenditures: $406,333 (2-7/91)
$100,000 estimated prior in-place seepage collection
facilities to meetNPDES compliance.
Subtotal $506,333
TOTAL $636,537
Magma reported that O&M costs at PVO are generally charged against an operating unit such
as the concentrator, and that NPDES costs are not captured separately. O&M costs for the tailings dam
and industrial water supply facilities are not included. In 1993, Magma's estimates for O&M, capital,
and other costs were as follows (2/23/93 response):
1987 1988 1989 1990 1991 1992
$298,548 $352,366 $359,557 $310,685 $2,076,505 $741,663
A Magma representative stated on October 1, 1993 that the cost of the cleanup of "the spill" at
Pinto Creek was about $250,000 at that point, but that the total cost would not be known for about one
month. Total cost information was not located in EPA's files.
References: USEPA, 1991c. Magma, 1992b. Magma, 1993b. Magma, 1993d. USEPA,
1993. USEPA, 1994b.
4.2.17 Case Study No. 17 - Discharge from Tailings Dam and Process Pond
Site Name: Magma Copper Company, Superior Division, Arizona
Type of Mining: Underground copper mine and milling facilities.
Nature of Environmental Effects : On March 8, 1989, an EPA inspector observed a discharge
from the toe of Tailings Dam No. 6 into an unnamed dry wash tributary to Queen Creek. Magma
ceased this discharge after April 10, 1989. A sample of the discharge contained copper and zinc.
On August 15, 1990, during a storm event, the berms on the east and west sides of Smelter
Pond No. 1 were breached, resulting in an unauthorized discharge of over one million gallons of mine
drainage water to an unnamed tributary of Queen Creek. The discharge contained cadmium, lead,
copper, and zinc, and had a low pH (3.4).
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Costs of Remediation
From April 18 through April 26, 1991, Magma discharged mine drainage or tailings water
containing copper and zinc from an unauthorized discharge point known as Clear Water Ditch.
In a letter dated May 28, 1991, EPA required that Magma, Superior Division, provide
information related to the recent discharges described above, including planned remedial activities and
costs of actions to cease these discharges. EPA issued a Finding of Violation and Order requiring
compliance with NPDES permit requirements on August 28, 1991 (IX-FY91-27).
Remedial Actions: Early in 1993, Magma listed the following activities performed by
contractors:
Install secondary sump below seep pump.
Construction for seepage control.
Install two 450 ft. siphon lines.
Equipment rental.
Install 3 culverts.
Install lime lines sp # 1.
Install culvert NW corner.
Culverts, build-up berm, dig out ends.
Install culverts at depot.
Install alternate power sources for seep pumps.
In June 1991, Magma described the following proposed activities:
• Construct diversion dike at northeast side of Smelter Pond No. 1, to divert runoff from
Clear Water Ditch into Smelter Pond No. 1 for subsequent treatment.
• Increase storage capacity of Smelter Pond No. 1 by installing a pumpback system,
raising Smelter Pond No. 1 crest, dredging contained solid materials, and/or dredging
contained solid materials.
• Sample, analyze, and possibly excavate contaminated soils from Clear Water Ditch and
open drainage channel.
• Enlarge and improve the secondary sump collecting initial seepage from the Smelter
Pond area.
Investigate alternate methods of handling pyrite operations drainage (cyclone overflow
water), such as installation of a pump and associated piping to pump cyclone overflow
water directly to the Mill #2 Settling Pond or Tailings Dam #5 for water reuse within
the mill operations.
• Investigate alternate methods of handling sandfill cyclone overflow water, such as
installation of a pump and associated piping to pump the cyclone overflow water to the
Mill Pond for reuse as process water within the mill.
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Costs of Remediation
Costs of Remedial Activities : In June 1991, Magma estimated that its NPDES compliance
costs would be as follows:
• Dike design, soils drilling/investigation, runoff investigatory work: $61,900 (dike
construction costs currently unknown).
Pumpback system: $120,000; design and runoff characterization work for dam raise:
$12,100; actual dam raise construction costs unknown.
• Contaminated soils, preliminary estimate: $58,300
• Construction of second sump: $3,000; enlargement of this sump: $5,000.
• Anticipated pump/piping costs for pyrite operations drainage: $15,000.
Anticipated pump/piping costs for sandfill cyclone overflow: $5,000.
TOTAL estimated costs: $280,300.
Early in 1993, Magma reported the following NPDES compliance costs:
Contractors: $ 10,615
Magma equipment: $ 55,127
Pumps: $ 2,954
Pipes: $ 10,739
Misc. equipment: $ 3,375
TOTAL: $87,811
O&M/capital/other costs (2/23/93):
1989 1990 1991 1992
$63,226 $113,995 $120,041 $154,476
References: USEPA, 1988. Cyprus, 1989. Cyprus, 1991a. Cyprus, 1991b. Cyprus, 1992.
4.2.18 Case Study No. 18 - Contaminated Groundwater Uncontrolled Process/Mine Water
Discharges
Site Name: Cyprus Miami Mining Corporation, Cyprus Miami Operations, Arizona
Type of Mining: Open pit copper mining with flotation mill and SX/EW.
Regulatory Actions : EPA first issued Finding of Violation and Order No. IX-FY86-78 to
Inspiration Consolidated Copper Company (ICCCo.) on July 28, 1986. EPA then issued modified
orders in October 1986 and February 1987. In July 1988, Cyprus Miami Mining Corp. (Cyprus)
purchased the assets of the Inspiration operations from ICCCo. EPA drafted a revised FOV dated
December 1, 1988 based on a meeting in October 1988 with Cyprus. In August 1989, EPA and Cyprus
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Costs of Remediation
again met, and Cyprus redrafted FOV IX-FY86-78. Cyprus submitted the revised FOV to EPA on
December 18, 1989, including language that Cyprus was not responsible for the CWA violations of
ICCCo., despite remedial actions taken. Cyprus stated that it did not concede the accuracy of any
statement or finding of fact in the FOV. The following violations come from the December 1989
version submitted by Cyprus.
Nature of Environmental Effects : Based on a 1980-1983 groundwater study for the
Globe/Miami area and EPA's inspections, EPA found that subsurface flows of mine wastewater from
Webster Lake, Ellison Pond, and the acid sump (unlined) "created a severe contamination plume in the
alluvial system formed by the former Webster Gulch channel," and subsurface flows from these
sources had advanced and continued to advance downgradient through the Holocene alluvium
underlying Bloody Tanks Wash and Miami Wash. A "significant portion" of the mine wastewater
present in this aquifer, which is "hydrologically linked" with overlying tributaries of Pinal Creek
including Miami Wash and Bloody Tanks Wash, used to surface along portions of Miami Wash and in
the Bixbe Road Seepage Cut just west of Miami Wash, which discharges into Miami Wash. Aerial
photographs of Inspiration Consolidated Copper Company's operations in September 1980, and an EPA
inspection in June 1985, showed that mine wastewater was discharged from the Bixbe Road Seepage
Cut into Miami Wash, and surfaced at various points along portions of Miami Wash, where it continued
downstream to Pinal Creek. In inspections in 1986, EPA observed that mine wastewater continued to
discharge into Miami Wash, which was flowing at flood stage into Pinal Creek, from two sources: the
Bixbe Road Seepage Cut and a culvert in New Webster Gulch near the No. 5 Decant Structure.
In February 1991, EPA issued a new FOV to Cyprus (IX-FY91-06), and then issued an
amended FOV on July 10, 1991. On July 18, 1991, Cyprus submitted costs of past steps taken to
achieve NPDES compliance, and a report by a contractor describing additional NPDES compliance
activities pursuant to the 1991 order and estimating costs for these activities. Cyprus estimated that it
might be able to reduce these estimated contractor costs by performing some of the planned work itself.
Remedial Actions:
1986 FOV issued.
ICCCo. complied with a number of EPA's requirements in the original and first two modified
orders. Among other measures taken, ICCCo. permanently drained and ceased discharging mine
wastewater to Webster Lake and Ellison Pond, and eliminated the unlined acid sump.
Between July 1988 and December 1989, Cyprus attempted to remediate the contamination
plume by removing and disposing of mine wastewater in the aquifer that could contribute to a discharge
at the Bixbe Cut, maintaining tailing interceptor wells, installing two new monitor wells below Hicks
Crossing, increasing the pumping capacity at Kiser Basin to 1200 gpm, increasing burch pumping to
1000 gpm, and performing aquifer modeling work to develop remedial plan.
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Costs of Remediation
1991 FOV
Past steps taken by Cyprus as of July 1991:
• NPDES 001: Sediment was removed from the NPDES 001 containment structure to
reestablish stormwater runoff storage capacity.
• NPDES 003: Improvement included raising the containment structure berm for
increased storage capacity and new culvert installation.
• NPDES 004: Completed construction of earthen containments and dikes for control of
stormwater runoff, with a July 1991 storage capacity of 3.5 million gallons.
• NPDES 005: Improvements included construction of a large (2.3 million gallons)
stormwater containment structure, leach dump terracing, ditching, and berming along
the 005 drainage area. Pre-existing water tanks and mine water truck quick fill were
installed so that mine dewatering water could be used for dust control.
• NPDES 007: Three earthen containment structures (12 million gallon stormwater
storage capacity) were reconstructed along the 007 drainage area using existing sand,
silt, and fill material.
NPDES 005/006 Compliance Plan (July 1991):
The compliance plan intended to eliminate flow at the NPDES 006 compliance point and
contain a 10-year return period storm at the 005 compliance point. The 006 compliance point was
located on a shallow channel incised into the bedrock about 500 feet downstream from a haul road
constructed with wasterock placed in the drainage. Exceedences of the copper standard tend to be
associated with higher discharges (greater than 30 gpm), which were happening approximately 30% of
the time. Discharge at 006 was thought to be sustained by a shallow reservoir of subterranean water
that was recharged during storm events and gradually drained through the fractured granite bedrock
underlying the basin between storm events. Surface drainage above 006 suggested that stormwater
runoff from a considerable portion of the drainage basin discharges from "Feehan's Flume" into a
closed basin created by waste rock placement. The stormwater impounded in the basin below Feehan's
Flume (runoff from 92 acres) was thought to rapidly seep into and through the fractured bedrock that is
present below a relatively thin layer of sediment, leaching copper from the fractured bedrock when the
groundwater table rises after a storm event.
The existing detention basin at the 005 compliance point contained a 1.4-year storm event. The
compliance plan for this drainage proposed enlarging the existing detention basin, constructing another
detention basin downstream, and pumping the captured stormwater to the North Barney Pit. The near-
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Costs of Remediation
term expansion of the Bluebird Pit was expected to reduce the drainage area to the 005 compliance
point, but this was not factored into the modeling effort.
NPDES 005 would receive spillway flow from the proposed detention basin north of the haul
road during storm evens greater than a 11.6 year frequency. The proposed basin would receive storm
runoff pumped from the detention basin in the 005 watershed. The compliance plan was designed to
eliminate discharge at NPDES 005 in 50 out of 58 years, based on SCS rainfall-runoff relationships and
historical precipitation records. The average amount of water delivered to North Barney Pit would be
about 16.9 million gallons per year.
Phase one would prepare the system upstream to accept the pumped storm runoff, with the
water ultimately going to the North Barney Pit. Approximately 6400 linear feet of eight-inch diameter
plastic pipe would be installed to connect the proposed Live Oak Containment structure #2 to North
Barney Pit. The Live Oak Containment structure #2 would be constructed with a clay core, filter
material, and riprap or mine waste. An estimated 21,700 cubic yards of clay and filter material would
be required. A pump station would be installed at Live Oak Containment Structure#2 capable of
pumping at least 1000 gpm into the North Barney pipeline. A 300-foot, 670 cubic yard trench would
then be constructed to divert the Upper Feehan's Flume drainage to Live Oak Containment structure #2.
Phase two would complete three containments (Basins #1, #2, and #3) in the northern section of
the Feehan's Flume watershed. The earthen dike material would come from waste rock. Clay cores
would not be installed because these basins would be pumping stations not intended to store water over
the long term, and because leakage should be captured in basins #4 and #6, downstream. Based on
rainfall-runoff modeling, the proposed earthen dikes were designed to be high enough to contain flows
from 100-year storm events regardless of pumping rate to North Barney Pit. A pipeline from the
proposed basin #4, north of the haul road, would be constructed (pump and pipeline - 700 gpm) (to
where?). A 5550-foot pipeline from #4 to #1 and a 2500-foot pipeline from #1 to North Barney
Pipeline near Live Oak Containment Structure #2 would be constructed, with pump and pipeline in
basin #1 capable of transporting 900 gpm. Phase two earthwork would eradicate the diversion ditch
built in Phase 1.
Phase three activities would include excavation of 40,000 cubic yards from the north half of the
haul road, and 30,000 cubic yards from the eastern toe of the waste dump in order to place 4000 cubic
yards of clay and 10,000 cubic yards of filter material against the south half of the haul road (six feet of
clay between 14 feet of filler). The haul road would serve as a gravity containment structure with an
impermeable upstream face. The containment structure (basin #4) would serve as a pumping station
and stormwater runoff retention basin. The proposed 29 acre feet (AF) detention basin would have a
pumping system of 700 gpm and would receive water from Feehan's Flume, a small concrete
containment structure at the NPDES 006 compliance point (pumped across haul road), and NPDES 005
facilities. In case of overflow, a cut of approximately 70 cubic yards into the native hill east of the
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Costs of Remediation
containment structure would serve as a spillway to the haul road and the two detention basins discussed
in phase six.
Phase four entailed construction of a 350-foot earthen ditch to divert flow in Feehan's Flume to
basin #4.
Phase five entailed construction of a 100-cubic-yard concrete containment structure (basin #7)
to collect excess flow from basin #4, with 350 gpm pumped through 650 feet of eight-inch pipe over the
haul road, and prevent discharge at the NPDES 006 compliance point.
Phase six included enlarging detention basin #5 by a factor of 2.5, to contain 17.7 AF, by
excavating 17,200 cubic yards of earth, and installation of pump and 2000 feet of pipeline to transport
200 gpm to basin #4 (phase three). A smaller detention basin #6 (6.7 AF) would be constructed with a
clay core at the road crossing downstream and would serve as the last containment before flow
discharges to Bloody Tanks Wash, pumping at 200 gpm to detention basin #5 via 1800 feet of eight
inch pipeline. Basins #5 and #6 would have double barrel 36-inch corrugated metal pipe emergency
outlets.
Cost estimates were included in the compliance plan for the following items:
Phase 1 Pipeline from Live Oak Containment #2 to North Barney Pit
Pump and Control Panel
Live Oak Containment #2: place clay and filter
Excavate diversion trench to divert upper Feehan's flume drainage area to Live Oak #2
Phase 2 Basin #1, #2, #3 earthwork/waste haulage
Pump and control panel
Pipeline from basin #4 to basin # 1
Pipeline from basin # 1 to connect to North Barney Pipeline
Phase 3 (basin #4)
Haul road excavation
Waste dump excavation
Excavate key
Excavate spillway
Place clay and filter
Pump and control panel
Phase 4 Excavate trench to divert Feehan's Flume to basin #4
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Costs of Remediation
Phase 5 (basin #7)
Clearing and grubbing
Excavate key
Reinforced concrete, rock fill, 6" stainless steel pipe
Pump and control panel
Phase 6 (basins #5 and #6)
Enlarge existing basin #5
Improve outlet - #5
Pipeline from basin #5 to basin #4
Excavate - #6
Clay fill - #6
Outlet - #6
Pipeline from #6 to #5
Pump and control panel
Costs of Remedial Activities : Past steps taken by Cyprus as of July 1991:
NPDES point no.
001
003
004
005
007
Cost
$ 365
$ 781
$10,755
$26,267 (internal earthwork)
$32,067 (quick fill installation-contractor)
$10,221
TOTAL
$80,456
NPDES 005/006 compliance plan (July 1991):
Phase 1
Phase 2
Phase 3
Phase 4
Phase 5
Phase 6
Subtotal
Mobilization (2.5%)
Subtotal
Engineering/Administration (15%)
Contingencies (15%)
TOTAL
$ 122,770
$ 150,159
$ 229,800
$ 2,400
$ 104,468
$ 144,470
$ 755,000
$ 19,000
$ 774,000
$ 116,000
$ 116,000
$1,006,000
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Costs of Remediation
Detailed containment structure and facility designs, electrical power, pump and piping design
specifications, and equipment selection were not included in the above cost estimate for points 005 and
006.
References: ASARCO, 1994a. USEPA, 1994a. ASARCO, 1994b. Fennemore, 1994.
ASARCO, 1994c.
4.2.19 Case Study No. 19 - ARD from Tailings Dam and Leaching Operations
Site Name: ASARCO, Inc., Ray Complex, Arizona
Type of Mining: Copper mine - open pit, leach dumps, milling and SX-EW
Nature of Environmental Effects : On July 1, 1991, EPA issues an administrative order against
ASARCO. The case was referred to DOJ in September 1991, and DOJ issued a demand letter in
October 1992. Settlement negotiations were initiated in November 1992. As of September 1991,
ASARCO was charged with 16 unauthorized discharges of process water, improper operation and
maintenance, water quality standards exceedences, failure to monitor, and failure to report. Between
September 1991 and June 1994, ASARCO had 18 unauthorized discharges and 154 days of water
quality standards violations stemming from subsurface flows from ASARCO's leach dumps to Mineral
Creek, in addition to NPDES permit violations. ASARCO was asked to address effects including
discharges containing pollutants to Mineral Creek, seepage from pregnant leach solution collection
dams and the electrowinning facility, and runoff from a proposed leach dump and waste rock dump.
In its June 1994 compliance plan, ASARCO described areas at the Ray Mine that ASARCO
had identified as having the potential for adversely impacting water quality; steps that ASARCO had
taken or was planning to take to investigate or address these potential impacts; where possible, an
estimation of the time frame for completion; and where possible, an estimate of costs. ASARCO
updated this information in a sixty-day progress letter dated August 29, 1994.
Subsurface concerns.
Subarea A - North of pit and tunnel inlet. Subsurface conduit of acidic (pH=4) solution to a
point downgradient of the 4D RDA (sulfide leach dump).
Subarea C - South of pit and tunnel outlet. Leaks in the liner of the Big Dome Pond were
detected by an electromagnetic induction survey. Pumpback wells located between the Big Dome Pond
and Mineral Creek encountered "relatively low pH" water, possibly the result of liner leaks.
ASARCO's electromagnetic induction survey also showed an anomaly in the area downgradient
of the Stacker Dam, indicating that the dam might not have been keyed into the bedrock. Seepage was
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Costs of Remediation
detected at one gallon per minute beneath the Lower Slimes Dam, and "low pH" water has been
detected in monitoring wells downgradient of the dam. Electrolyte was seeping from the
electrowinning building as a result of leaks in the electrowinning cells and the floor of the tank house.
Monitor wells encountered "low" pH, high copper water.
ASARCO also reported possible seepage under the dam at the electrowinning impoundment,
which might be captured by the pumpback wells west of the building; possible seepage into Mineral
Creek through an unconformity in the Mineral Creek channel, possibly resulting in a ring of turquoise
stained rock observed in the creek; and approximately 4000 feet of recently exposed cemented
mineralized gravels in the bed of Mineral Creek, which might leach metals back into the creek.
Stormwater runoff.
ASARCO reported that in Subarea A, above the tunnel inlet between Big Box Canyon Dam and
the area where runoff flows into the pit, runoff from overburden dumps enters Mineral Creek. EPA
commented that ASARCO should also address runoff from the new planned 4G dump leach area,
which was exceeding water quality standards.
In Subarea B, the major portion of the mine area, all runoff is or can be directed to the pit.
In Subarea C, the area below the tunnel outlet and below the pit, which drains toward Mineral
Creek, ASARCO also describes stormwater runoff measures, and measures to prevent water from
Dalton's Pond from reaching Mineral Creek or groundwater.
Remedial Actions:
Subarea A.
Subsurface. ASARCO installed an exploratory trench to further delineate the subsurface
conduit, planned to install a drain and sump in this trench with pumpback capacity, and planned to
conduct groundwater monitoring to confirm that the installed control is operating correctly. In the
process of installing the trench, two turn of the century, man-made adits were uncovered, with low pH
(3.9) water containing 65.3 mg/L dissolved copper flowing out of one adit at a rate of 0.73 gpm.A
suspected third adit had not been located. ASARCO filled the trench below the adit with coarse rock
surrounding 25 feet of 32" slotted HOPE vertical collection pipe, and planned to install a pump by
November 1, 1994. ASARCO planned to use the collection pipe to monitor groundwater quality, and
had not yet determined how many additional pumpback wells, if any, would be required, nor what the
associated costs would be.
Stormwater. ASARCO planned to construct two diversion ditches, one on the east side and one
on the west side of the rock deposition areas (RDAs), to divert an estimated 50% of stormwater from
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Costs of Remediation
reaching the 4 and 5 series RDAs. These ditches would be lengthy and would pass through rough
terrain.
ASARCO found that construction of maximum saturation event (exceeding 100-year flood)
containment was not feasible in this area due to topographic and space constraints. Portions of existing
RDAs would have to be removed. ASARCO therefore argued that the only means of insulating
Mineral Creek from runoff from overburden dumps that was technically feasible, and potentially
economically feasible, would be to extend the existing tunnel to a point above the overburden dumps.
Runoff would either be pumped back for reuse or treatment, or drain to the pit area. The tunnel would
have to extend through 13,000 feet of bedrock, underneath the far eastern end of Subarea A, and a small
diversion dam would be constructed to divert Mineral Creek into the tunnel extension. To help offset
the cost of the tunnel, ASARCO proposed to cover more than 60 acres of manmade wetlands below the
tunnel with expanded RDAs. The wetlands were created in the construction of the Little Box Dam and
the Big Box Dam. These measures were required under EPA's recently established stormwater control
program for industrial stormwater discharges, and ASARCO argued that they exceeded the conditions
of its existing permit.
In response to a request from EPA that ASARCO consider interim stormwater containment
measures during construction of the tunnel, ASARCO provided cost information for construction of
containment ponds in Subarea A, but argued that the high cost ($4.4 million) of these ponds made it
overly burdensome for EPA to require interim containment measures in this case.
Subarea B.
Stormwater. As a short term solution, ASARCO constructed dikes and rollovers in all
disturbed areas where runoff can be directed into the pit, to ensure that runoff would reach the pit.
However, due to the increased volume of water in the pit, and the need to reduce water levels to prevent
interference with present operations, ASARCO planned to build a water treatment plant, and was
considering a location above the Elder Gulch tailing pond. Effluent from a new treatment plant would
be discharged in accordance with a revised NPDES permit, or pumped to Elder Gulch Tailings Pond,
where it would mix with other water and be recycled back into operations, depending on the current
water balance. ASARCO constructed a pilot water treatment plant to assess the feasibility of this
project. ASARCO emphasized the need to identify an alternative to pit storage of stormwater, so that
the Pearl Handle Pit could be deepened and new benches opened, in order for mining to continue
beyond 1996.
Subarea C.
Subsurface. ASARCO repaired leaks in the liner of Big Dome Pond. A pumpback well
downgradient from the pond was pumping back low pH water until mid-July, when the pump probes
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Costs of Remediation
had to be lowered because the water level in the well had fallen; as of August 1994, the well was
pumping 3.6 hours per day.
Downgradient of Stacker Dam, ASARCO installed monitoring wells, which would serve as
pumpback wells, one screened in bedrock and one screened in alluvium. If the pumpback system
proved to be insufficient to control flow, ASARCO planned to install a 150-foot cutoff wall in the
drainage. ASARCO also installed monitoring wells, which would serve as pumpback wells,
downgradient of the Lower Slimes Dam, and planned to install a cutoff wall in that drainage, if
necessary.
At the electrowinning building, ASARCO installed two surface collection sumps with
pumpback capacity, at the north and south ends of the building. These sumps were initially concrete,
but were subsequently lined with HOPE due to degradation in the concrete. ASARCO also installed six
pumpback wells, three shallow and three deep, around the tank house, to pump any recovered fluids to
Big Dome Pond; and three shallow wells in the basement of the electrowinning building to dewater the
subgrade. In June 1994, ASARCO was in the process of replacing the electrowinning cells, originally
concrete with PVC liners, with new cells constructed of polymer concrete (vinyl ester resin). Cells
were being lined with HOPE liner until they were replaced. ASARCO initiated a maintenance program
to eliminate piping drips and leaks below the cells; grouted and caulked cracks in the floor; and rebuilt
parts of the floor, including installation of fully welded HOPE liners in select areas of the floor.
Depending on the success of the HOPE floor liner, ASARCO was considering rebuilding the floor and
coating it with polymer concrete. However, the HOPE liner proved effective in preventing solution
from migrating through the floor, and by August 1994 ASARCO planned to install liner wherever
necessary.
Stormwater. To control runoff in this area, ASARCO was constructing a combination of dikes,
dams, ditches, holding ponds, and pumpback systems. ASARCO planned to install new controls in
areas providing less than 10-year, 24-hour containment: the area immediately south of the diversion
tunnel outlet (north of Susie D Dam), the western slope of the Sag Dump, the an area north of the
electrowinning building. ASARCO planned to increase monitoring to include discharges and accept
discharge limitations for four outfalls receiving stormwater that has contacted disturbed ares.
In addition, water collecting in Dalton's Pond (runoff from the mill and mine offices area) was
pumped to Big Dome Pond, where it was treated, put in a process water circuit, or returned to the pit.
ASARCO installed a 2000 gpm pump in the pond to increase dedicated pumping capacity, and
modifications were made to reduce the drainage area to the pond. ASARCO planned to fully line the
pond to prevent subsurface discharge to groundwater. The pollution control dam below the pond was
being raised seven feet.
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Costs of Remediation
Costs of Remedial Activities : As of August 1994, ASARCO's contractor costs for work
required for the Aquifer Protection Permit (APP) for the State of Arizona totaled $2.8 million.
Additional APP studies were expected to cost $577,000.
NPDES compliance costs reported by ASARCO in June and August 1994 were as follows:
Subarea A.
Install trench
Pump, sump, pipeline and electrical equipment
Additional pumpback wells, if needed
Diversion ditches
Stormwater ponds
Extend tunnel
$ 6,000
$10,000
not estimated
$2 million
$4,368,000
$20 to $25 million
Subarea B.
Dikes/rollovers
Build new water treatment plant
Develop alternative to pit storage of sw
Subarea C.
Repair liner leaks, Big Dome Pond
Four pumpback wells
Pumpback system equipment, Stacker Dam
150-foot cutoff wall, Stacker Dam
Pumpback system equipment, Lower Slimes Dam
130-foot cutoff wall, Lower Slimes Dam
Pumpback well installation, Lower Slimes Dam
Electrowinning building
Sumps
Six pumpback wells
Three shallow wells
Install sumps, pumpback pumps, wells
Replacement of all cells
Drip/leak elimination program
Grout/caulk floor
HOPE liner experimental project
HOPE liner in all appropriate areas
Complete floor rebuild/polymer concrete
not estimated
$10 million
not estimated
$16,500
$28,840
$ 8,000
$87,000
$ 8,000
$76,000
$ 5,472
$ 50,000
$ 90,000
$ 20,000
$165,460
$1.1 million
$ 40,000
$ 2,000
$ 65,000
$300,000 to $400,000
$1.8 million
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Costs of Remediation
Dalton's Pond work to date (August 1994) $ 38,194
Line Dalton's Pond $225,000
2,000 gpm pump $ 14,138 (incremental cost of
increasing pump capacity was $9,000)
Water treatment plan $3 million to $10 million
Improvements related to past violations in Subarea C (August 1994): $1,289,441.
O&M costs related to the operation of the water treatment plant, personnel costs to monitor
Mineral Creek and maintain dams and diversion ditches were $527,725 in 1992 and $1,594,418 in
1993. O&M costs for the Big Dome Pond pumpback wells are estimated to be $14,144.
References: ASARCO, 1994a. USEPA, 1994a. ASARCO, 1994b. Fennemore, 1994.
ASARCO, 1994c.
4.2.20 Case Study No. 20 - Fuel Spill at Maintenance Facility
Site Name: Paradise Peak Mine, FMC Gold Corporation, Nevada
Type of Mining: Open pit gold mine with cyanide heap leaching and milling operations
Environmental Effects : In August 1992, an inspection was performed by the Nevada
Department of Environmental Protection. The inspection team found an area of oil spill discharge in
the vicinity of the mine maintenance shop. The facility subsequently found that the source of the spill
was a leak from an underground shop clean-up vault. The vault included a oil skimmer that provided
for separation and recovery of oil from shop drain water. Water was then released to a drainage ditch.
The leak was caused when a mechanical control failure allowed the oil in the vault to flow into the
drainage ditch. FMG admitted being aware of the problem since Summer 1992 and intended to develop
a remedial action plan, however, due to apparent inadvertent oversight little work had been done to
address the problem prior to the inspection. The facility indicated that site investigations showed that
there was little potential for hydrocarbons to reach underlying ground water (prior to undertaking the
remedial actions described below). The operator was issued a Notice of Violation for the release. All
of the information described below was obtained from the facility's written presentation at a State Show
Cause Hearing.
Remedial Measures: Immediately after the inspection, in cooperation with the State, the
facility developed a plan to address the spill. This included: (1) sealing the discharge point from the
vault, (2) restricting access to contaminated area, (3) sampling to determine the nature of the release,
(4) installing berms around the contaminated area to prevent oil migration, and (5) ceasing water
washdowns and using a dry reagent for spill clean-up. Subsequently, after soil sampling, the operator
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Costs of Remediation
conducted a soils removal actions. Approximately 831 tons of contaminated soil was sent off-site for
disposal. Further, the facility proposed to dispose of washwater in the tailings impoundment (it is
unknown if this was approved by the State).
Costs of Remedial Activities : The facility's Show Cause submittal provides cost data for
remedial measures they include (in 1991-1992 dollars):
Site investigation contractor 9,053
Internal FMG labor and equipment 12,894
Analyses 15,926
Waste disposal contractor 41,563
Trucking contractor 14,971
Other 9,441
TOTAL 103,801
In addition, FMC Gold budgeted approximately $10,500 for modifications to allow discharge of
washwater to the tailings impoundment (unclear if this was spent).
References: FMC Gold Company, 1992.
4.2.21 Case Study No. 21 - Copper Sulfate Spill
Site Name: Lucky Friday Mine, Hecla Mining Company, Mullan, Idaho
Type of Mining: The Lucky Friday Mine began operation in 1987 producing gold, silver, lead,
and zinc. The facility consists of an underground mine and 1,000 ton per day flotation mill. Flotation
tailings are managed in an on-site impoundment. The mine is located along the South Fork of the
Coeur dAlene River, one mile east of Mullan, Idaho.
Nature of Environmental Effects : On September 6, 1988, 100 gallons of copper sulfate were
accidentally dumped into the Coeur dAlene River. An employee was mixing copper sulfate solution in
a vat, which overflowed into a sump. The sump drained to the tailings impoundment where the
solution was eventually discharged to the river. The incident was not reported to the State until
September 12, 1988, when State inspectors observed dozens of dead fish and variety of dead aquatic
insects. According to the available references, the impacts of the release (i.e., harm to aquatic
organisms) extended 1.3 miles downstream from the facility. The State determined that it would be at
least seven years before the fishery was restored.
Remedial Measures: Hecla undertook several remedial measures in response to the copper
sulfate spill. Concrete curbing was placed around the copper sulfate mixing tanks. The curbing was
designed to retain the volume of the largest vat. In addition, the east side of the mixing area was paved
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Costs of Remediation
to minimize potential pollutant migration. Further, Hecla planted numerous willow trees and other
vegetation along the river bank where aquatic life was impacted. Finally, the operator initiated a semi-
annual environment auditing program.
Costs of Remedial Activities : No detailed cost information is available related to remediating
the copper sulfate spill. However, in responding to draft Consent Order, the facility noted that over
$47,700 had been spent on remedial measures
References: IDER, 1988. IDER, 1990. Hecla, 1990.
4.2.22 Case Study No. 22 - Mercury Soil Contamination Remediation
Site Name: Microgold II Mine, Powell and Micro Gold II Partnership, Florance, Idaho.
Type of Mining: In 1983, the Microgold II partnership began operation of an open pit mine
with ore being crushed and passed over shake tables where mercury was added. The site only operated
during summer 1983 with 120 tons of ore being beneficiated. The resulting amalgam was then heated,
allowing the mercury to vaporize and gold to be collected. Mercury was captured for reuse. Tailings
from the shaker tables were managed in an unlined tailings pond. The facility was located
approximately 1,400 feet from the west fork of Meadow Creek, which flows into the Wind River, a
tributary of the Salmon River.
Nature of Environmental Effects : Releases of mercury contaminated the soils around the
shaker table mixing area and the sediments in tailings pond. When the State issued a Notice of
Violation and Order in November 1983, mercury levels in the soils were as high as 1,163 ppm.
Subsequent sampling in 1985 found mercury levels of 100-250 ppm in the tailings sediments and 50-
380 ppm in the mixing area soils. Tailings water had mercury only slightly above background. The
State required the operator to sample groundwater. Groundwater data generally showed levels
consistent with background, although the source of elevated levels in two wells could not be
distinguished between mining and a naturally contaminated spring.
Remedial Measures: Under an Administrative Order issued by the Idaho Department of Health
and Welfare (IDHW) in February 1985, the operator was required to conduct a site investigation and
develop a clean-up plan. Three options clean-up options were identified. The option selected by
IDHW involved excavation of contaminated soil and on-site encapsulation (using a synthetic liner and
cover). The clean-up began in Spring 1986 and was completed in October 1986.
Costs of Remedial Activities : No line-item remedial cost information was found in the State
files. However, on August 29, 1986, the State and the facility agreed to a Consent Decree that required
Microgold to place $120,000 in escrow to pay for the clean-up.
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Costs of Remediation
References: IDHW, 1983. IDHW, 1984. CH2M Hill, 1985. U.S. District Court, 1986.
4.2.23 Case Study No. 23 - Unauthorized Discharge of Leach Solution to Surface Water
Site Name: Cyprus Sierrita Mine, Sierrita, Arizona
Type of Mining: Large open pit copper mine with flotation mill and dump leaching/SX-EW
operations.
Nature of Environmental Effects : In 1992-1993, Cyprus Sierrita had unauthorized discharges
of process solution to Demetrie Wash - an ephemeral stream that flows through the site. Long-term
discharges were caused by subsurface migration/seepage from an unlined process pond to the wash.
The bond contains barren solution, other process waters, and storm water runoff. The pond water has
generally low pH and elevated concentrations of copper and zinc. Additional short-term impacts on
Demetrie Wash occurred when a 2.7 million gallons was released after a tailings pipeline broke. The
water was approximately 67% dilute tailings water reclaim and 33% ground water recovered from
wells located downgradient of the tailings impoundment. The water had less than .01 ppm copper.
Remedial Measures: To address the long-term seepage issues, the operator performed a
conductivity study to delineate the source of the seepage. The operator subsequently constructed
hydraulic barriers. For the tailings line break, the operator replace the existing PVC pipe with steel-
encased piping.
Costs of Remedial Measures : As reported to EPA Region IX, the total cost of addressing
subsurface seepage (as of 1994) was $101,030. The cost of replacing the pipeline (also as of 1994) was
$70,000. Of specific note, similar to the other Arizona sites discussed above, Sierrita has also
undertaken facility-wide remedial measures to address unauthorized discharges of process water to
surface and ground water (no cost data were readily available for facility-wide actions but known to be
in the millions). This case study was included as an example of costs associated with a single, unit-
specific remedial action.
Reference: EPA 1994.
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Costs of Remediation
5.0 REFERENCES
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ASARCO 1994c. ASARCO, Inc., T.E. Scartaccini (General Manager, Ray Complex).
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Cyprus 1991a. Cyprus Miami Mining Corporation, O.K. Mortensen (VP General Manager),
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Cyprus 1991b. Cyprus Miami Mining Corporation, O.K. Mortensen (V.P., General Manager),
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Costs of Remediation
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Idaho District Court 1986. Stipulation, Agreement and Consent Decree, August 19, 1986.
IDEP 1990. Idaho Department of Environmental Protection. May 1990. Notice of Violation for Hecla
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Costs of Remediation
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Costs of Remediation
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