INDUSTRIAL STORMWATER
FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and
Dressing) Facilities
U.S. EPA Office of Water
EPA-833-F-06-022
December 2006
What is the NPDES stormwater permitting program for industrial
activity?
Activities, such as material handling and storage, equipment maintenance and cleaning, industrial
processing or other operations that occur at industrial facilities are often exposed to stormwater. The
runoff from these areas may discharge pollutants directly into nearby waterbodies or indirectly via
storm sewer systems, thereby degrading water quality.
In 1990, the U.S. Environmental Protection Agency (EPA) developed permitting regulations under the
National Pollutant Discharge Elimination System (NPDES) to control stormwater discharges associated
with eleven categories of industrial activity. As a result, NPDES permitting authorities, which may be
either EPA or a state environmental agency, issue stormwater permits to control runoff from these
industrial facilities.
What types of industrial facilities are required to obtain permit
coverage?
This fact sheet discusses stormwater discharges from metal mining (ore mining and dressing) facilities
as defined by Standard Industrial Classification (SIC) Major Group 10. Metal mining is defined
here as all ore mining and/or dressing and beneficiating operations performed at mills operated
in conjunction with the mines served or at mills (i.e., custom mills) operated separately. Facilities
and products in this group fall under the following categories, all of which require coverage under
an industrial stormwater permit if discharges of stormwater have come into contact with any
overburden, raw material, intermediate products, finished product, byproduct or waste products
located on the site of such operations:
4 Iron Ores (SIC 1011)
4 Copper Ores (SIC 1021)
4 Lead and Zinc Ores (SIC 1031)
4 Gold Ores (SIC 1041)
4 Silver Ores (SIC 1044)
4- Ferroalloy Ores, Except Vanadium (SIC 1061)
4 Uranium-Radium-Vanadium Ores (SIC 1094)
4- Miscellaneous Metal Ores, Not Elsewhere Classified (SIC 1099)
Permit coverage is required of all phases of mining operations, whether active or inactive, as long
as there is exposure to significant materials. This includes land disturbance activities such as the
expansion of current extraction sites, active and inactive mining stages, and reclamation activities
at those establishments primarily engaged in mining, developing mines, or exploring for metallic
minerals (ores).
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
A stormwater permit generally is not appropriate for the following types of mines:
4 Sites or parts of sites which are determined to cause or contribute to water quality standards
violations
4 Active facilities and those under reclamation, which have discharges subject to effluent
limitation guidelines under NPDES, including other non-stormwater discharges such as from
floor drains in maintenance buildings and preparation plant areas
4 Pollutant seeps or underground drainage from inactive mines and refuse disposal areas that do
not result from precipitation events.
For these types of sites, contact the EPA or state NPDES permitting authority to determine if and what
type of discharge permit may be necessary.
What does an industrial stormwater permit require?
Common requirements for coverage under an industrial stormwater permit include development of a
written stormwater pollution prevention plan (SWPPP), implementation of control measures, and sub-
mittal of a request for permit coverage, usually referred to as the Notice of Intent or NOI. The SWPPP
is a written assessment of potential sources of pollutants in stormwater runoff and control measures
that will be implemented at your facility to minimize the discharge of these pollutants in runoff from
the site. These control measures include site-specific best management practices (BMPs), maintenance
plans, inspections, employee training, and reporting. The procedures detailed in the SWPPP must be
implemented by the facility and updated as necessary, with a copy of the SWPPP kept on-site. The in-
dustrial stormwater permit also requires collection of visual, analytical, and/or compliance monitoring
data to determine the effectiveness of implemented BMPs. For more information on EPA's industrial
stormwater permit and links to State stormwater permits, go to www.epa.gov/npdes/stormwater
and click on "Industrial Activity."
What pollutants are associated with my facility's activities?
Pollutants conveyed in stormwater discharges from metal mining (ore mining and dressing) facilities
will vary. There are a number of factors that influence to what extent industrial activities and
significant materials can affect water quality.
4 Geographic location
4 Topography
4 Hydrogeology
4 Extent of impervious surfaces (e.g.,, concrete or asphalt)
4 Type of ground cover (e.g., vegetation, crushed stone, or dirt)
4 Outdoor activities (e.g., material storage, loading/unloading, vehicle maintenance)
4 Size of the operation
4 Type, duration, and intensity of precipitation events
Because of the land-disturbing nature of the ore mining and dressing industry, contaminants of
concern generated by industrial activities include total suspended solids (TSS), total dissolved solids
(TDS), turbidity, acid drainage, and heavy metals. Although there are many activities that occur at a
facility, this fact sheet only covers those activities that occur outdoors and where activities or materials
may be exposed to precipitation.
The activities, pollutant sources, and pollutants detailed in Table 1 are commonly found at metal
mining (ore mining and dressing) facilities.
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
Table 1: Common Activities, Pollutant Sources, and Pollutants at Metal Mining (Ore Mining and
Dressing) Facilities
Activity
Site preparation
Mineral extraction
Beneficiation activities
Leaching
Other activities
Equipment/vehicle fueling
and maintenance
Reclamation activities
Pollutant Source
Road construction
Removal of overburden
Removal of waste rock to expose the
metal
Blasting activities
Milling
Flotation
Gravity concentration
Amalgamation
Waste rock storage
Raw material loading
Process materials unloading
Raw waste material transportation
Heap leach piles
Sedimentation pond upsets
Sedimentation pond sludge removal and
disposal
Air emission control device cleaning
Fueling activities
Parts cleaning
Waste disposal of oily rags, oil and gas
filters, batteries, coolants, and degreasers
Fluid replacement including hydraulic
fluid, oil, transmission fluid, radiator
fluids, and grease
Site preparation for stabilization
Pollutant
Dust, TSS, IDS, turbidity
Dust, TSS, nitrate/nitrite
Dust, TSS, TDS, pH, turbidity, fines, heavy metals
Dust, TSS, TDS, pH, turbidity, fines, chemical
reagents, acids, heavy metals
TSS, TDS, pH, turbidity, heavy metals
Dust, TSS, TDS, pH, turbidity, heavy metals,
mercury
Dust, TSS, TDS, pH, turbidity, heavy metals
Dust, TSS, TDS, turbidity, heavy metals
Diesel fuel, oil, gasoline, chemical reagents
Dust, TSS, TDS, turbidity, heavy metals
Dust, TSS, TDS, pH, turbidity, heavy metals,
cyanide
TSS, TDS, turbidity, pH, heavy metals
Dust, TSS, TDS, turbidity, pH, heavy metals
Dust, TSS, TDS, turbidity, metals
Gas/diesel fuel, oil
Solvents, oil, heavy metals, acid/alkaline wastes
Oil, heavy metals, solvents, acids
Oil and grease, arsenic, lead, cadmium,
chromium, chemical oxygen demand (COD),
and benzene
Dust, TSS, TDS, turbidity, heavy metals
What BMPs can be used to minimize contact between stormwater
and potential pollutants at my facility?
A variety of BMP options may be applicable to eliminate or minimize the presence of pollutants in
stormwater discharges from metal mining facilities. You will likely need to implement a combination
or suite of BMPs to address stormwater runoff at your facility. Your first consideration should be for
pollution prevention BMPs, which are designed to prevent or minimize pollutants from entering
stormwater runoff and/or reduce the volume of stormwater requiring management. Prevention
BMPs can include regular cleanup, collection and containment of debris in storage areas, and other
housekeeping practices, spill control, and employee training. It may also be necessary to implement
treatment BMPs, which are engineered structures intended to treat stormwater runoff and/or
mitigate the effects of increased stormwater runoff peak rate, volume, and velocity. Treatment BMPs
are generally more expensive to install and maintain and include oil-water separators, wet ponds, and
proprietary filter devices.
Sediment ponds, discharge diversion techniques, as well as methods of runoff dispersion, are control
strategies often used to minimize impacts of significant materials on stormwater. For mine sites
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Sector G; Metal Mining (Ore Mining and Dressing) Facilities
requiring additional sources of water for processing operations, rainfall events as well as stormwater
run-on will be managed for use in dust suppression, processing, and washing activities. Many mine
sites are already equipped with sedimentation ponds and other established process wastewater
treatment methods in order to meet effluent limitation guidelines. Additional stormwater
management practices used at metal mining facilities are described further in this fact sheet.
BMPs must be selected and implemented to address the following:
Good Housekeeping Practices
Good housekeeping is a practical, cost-effective way to maintain a clean and orderly facility to prevent
potential pollution sources from coming into contact with stormwater. It includes establishing protocols
to reduce the possibility of mishandling materials or equipment and training employees in good
housekeeping techniques. Common areas where good housekeeping practices should be followed
include trash containers and adjacent areas, material storage areas, vehicle and equipment maintenance
areas, and loading docks. Good housekeeping practices must include a schedule for regular pickup
and disposal of garbage and waste materials and routine inspections of drums, tanks, and containers
for leaks and structural conditions. Practices also include containing and covering garbage, waste
materials, and debris. Involving employees in routine monitoring of housekeeping practices has proven
to be an effective means of ensuring the continued implementation of these measures.
Minimizing Exposure
Where feasible, minimizing exposure of potential pollutant sources to precipitation is an important
control option. Minimizing exposure prevents pollutants, including debris, from coming into contact
with precipitation and can reduce the need for BMPs to treat contaminated stormwater runoff. It can
also prevent debris from being picked up by stormwater and carried into drains and surface waters.
Examples of BMPs for exposure minimization include covering materials or activities with temporary
structures (e.g., tarps) when wet weather is expected or moving materials or activities to existing
or new permanent structures (e.g., buildings, silos, sheds). Even the simple practice of keeping a
dumpster lid closed can be a very effective pollution prevention measure.
Erosion and Sediment Control
BMPs must be selected and implemented to limit erosion on areas of your site that, due to
topography, activities, soils, cover, materials, or other factors are likely to experience erosion. Erosion
control BMPs such as seeding, mulching, and sodding prevent soil from becoming dislodged and
should be considered first. Sediment control BMPs such as silt fences, sediment ponds, and stabilized
entrances trap sediment after it has eroded. Sediment control BMPs should be used to back-up
erosion control BMPs.
Because ore mining and dressing is largely a land disturbance activity, BMPs that minimize erosion
and sedimentation will be most effective if installed at the inception of operations and maintained
throughout active operations and reclamation of the site. From the construction of access and haul
roads, to closure and reclamation activities, implementation of BMPs is often essential to minimizing
long-term environmental impacts to an area.
A number of structural collection devices have been developed to remove sediment from runoff
before it leaves the site. Several methods of removing sediment from site runoff involve diversion
mechanisms previously discussed, supplemented by a trapping or storage device. Structural practices
typically involve filtering diffuse stormwater flows through temporary structures such as straw bale
dikes, silt fences, brush barriers, or vegetated areas.
Structural practices are typically low in cost yet require periodic removal of sediment to remain
functional. As such, they may not be appropriate for permanent use at inactive mines. However, these
practices may be effectively used as temporary measures during active operation and/or prior to the
final implementation of permanent measures.
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
Management of Runoff
Your SWPPP must contain a narrative evaluation of the appropriateness of stormwater management
practices that divert, infiltrate, reuse, or otherwise manage stormwater runoff so as to reduce the
discharge of pollutants. Appropriate measures are highly site-specific, but may include, among others,
vegetative swales, collection and reuse of stormwater, inlet controls, snow management, infiltration
devices, and wet retention measures.
A combination of preventive and treatment BMPs will yield the most effective stormwater
management for minimizing the offsite discharge of pollutants via stormwater runoff. Though not
specifically outlined in this fact sheet, BMPs must also address preventive maintenance records or
logbooks, regular facility inspections, spill prevention and response, and employee training.
All BMPs require regular maintenance to function as intended. Some management measures have
simple maintenance requirements, others are quite involved. You must regularly inspect all BMPs to
ensure they are operating properly, including during runoff events. As soon as a problem is found,
action to resolve it should be initiated immediately.
BMPs for Metal Mining Facilities
EPA has identified a wide variety of best management practices (BMPs) that may be used to mitigate
discharges of contaminants at mines. Many of the practices focus on sediment and erosion control
and are similar to BMPs used in the construction industry. These controls to prevent erosion and
control sedimentation are the most effective if they are installed at the inception of operations and
maintained throughout active operations and reclamation of the site. For more details on the use and
implementation of these practices you are encouraged to obtain a copy of one or more of the many
good sediment and erosion control books available on the market. The following categories describe
best management practice options for reducing pollutants in stormwater discharges at metal mining
facilities.
4 Discharge Diversions. Discharge diversions provide the first line of defense in preventing the
contamination of discharges, and subsequent contamination of receiving waters. Discharge
diversions are temporary or permanent structures installed to divert flow, store flow, or limit
stormwater run-on and runoff.
These diversion practices have several objectives. First, diversion structures can be designed
to prevent otherwise uncontaminated (or less contaminated) water from crossing disturbed
areas or areas containing significant amounts of contaminated materials, where contact may
occur between run-on and site materials. These source reduction measures may be particularly
effective for metal mining facilities because they prevent run-on of uncontaminated discharges
from contacting exposed materials and/or reduce the flow across disturbed areas, thereby
lessening the potential for erosion. Second, diversion structures can be used to collect or divert
waters for later treatment, if necessary. The usefulness of these control measures are limited
by such factors as the size of the area to be controlled and the type and nature of materials
exposed and nature of precipitation events.
Diversion dikes, curbs, and berms are temporary or permanent diversion structures that prevent
runoff from passing beyond a certain point, and divert runoff away from its intended path.
Dikes, curbs or berms may be used to surround and isolate areas of concern, diverting flow
around piles of overburden, waste rock, and storage areas, to minimize discharge contact with
contaminated materials and to limit discharges of contaminated water from confined areas.
4 Drainage/Stormwater Conveyance Systems. Drainage or stormwater conveyance systems can
provide either a temporary or a permanent management practice which functions to channel
water away from eroded or unstabilized areas, convey runoff without causing erosion, and/or
carry discharges to more stabilized areas. The use of drainage systems as a permanent measure
may be most appropriate in areas with extreme slopes, areas subject to high velocity runoff,
and other areas where the establishment of substantial vegetation is infeasible or impractical.
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INDUSTRIAL STORMWATER FACT SHEET SERIES
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For instance, several BMPs may be useful stormwater and erosion control methods. Some
examples of drainage/stormwater conveyance systems include:
- Channels or gutters
- Open top box culverts and waterbars
- Rolling dips and road sloping
- Roadway surface water deflector
- Culverts
4 Runoff Dispersion. Drainage systems are most effective when used in conjunction with runoff
dispersion devises designed to slow the flow of water discharged from a site. These devices
also aid stormwater infiltration into the soil and flow attenuation. Some examples of velocity
dissipation devices include:
- Check dams
- Rock outlet protection
- Level spreaders
- Serrated slopes and benched slopes
- Contouring
- Drop structures
4 Sediment Control and Collection. Erosion and sediment controls limit movement and retains
sediments, preventing transportation offsite. Several structural collection devices have
been developed to remove sediment from runoff before it leaves the site. Several methods
of removing sediment from site runoff involve diversion mechanisms previously discussed,
supplemented by a trapping or storage device. Structural practices typically involve filtering
diffuse stormwater flows through temporary structures such as straw bale dikes, silt fences,
brush barriers or vegetated areas.
Structural practices are typically low in cost. However, structural practices require periodic
removal of sediment to remain functional. As such, they may not be appropriate for
permanent use at inactive mines. However, these practices may be effectively used as
temporary measures along haul roads and access roads. Several examples of sediment control
and collection BMPs include:
- Gabions, riprap, and native rock retaining walls
- Biotechnical stabilization
- Straw bale barrier
- Vege ta ted b uffer strips
- Silt fence/filter fence
- Siltation berms
- Brush sediment barriers
- Sediment traps or catch basins
- Sediment/settling ponds
4 Vegetation Practices. Vegetation practices involve establishing a sustainable ground cover by
permanent seeding, mulching, sodding, and other such practices. A vegetative cover reduces
the potential for erosion of a site by: absorbing the kinetic energy of raindrops which would
otherwise impact soil; intercepting water so it can infiltrate into the ground instead of running
off and carrying contaminated discharges; and by slowing the velocity of runoff to promote
on-site deposition of sediment. These practices include:
- Topsoiling
- Broadcast seeding and drill seeding
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- Willow cutting establishment
- Plastic matting, plastic netting and erosion control blankets
- Mulch-straw or wood chips
- Compaction
Typically, the costs of vegetative controls are low relative to other discharge mitigation
practices. Given the limited capacity to accept large volumes of runoff, and potential erosion
problems associated with large concentrated flows, vegetative controls should typically be used
in combination with other management practices.
4 Capping. Capping or sealing of waste materials is designed to prevent infiltration, as well
as to limit contact between discharges and potential sources of contamination. Ultimately,
capping should reduce or eliminate the contaminants in discharges. In addition, by reducing
infiltration, the potential for seepage and leachate generation may also be lessened.
In some cases, the elimination of a pollution source through capping contaminant sources
may be the most cost effective control measure for discharges from inactive ore mining
and dressing facilities. Depending on the type of management practices chosen the cost to
eliminate the pollutant source may be very high. Once completed, however, maintenance costs
will range from low to nonexistent.
4 Treatment. In some cases (e.g., low pH and/or high metals concentrations), BMPs, and sediment
and erosion controls may not be adequate to produce an acceptable quality of stormwater
discharge. Under those circumstances additional physical or chemical treatment systems
may be necessary to protect the receiving waters. Treatment practices are those methods of
control which normally are thought of as being applied at the "end of the pipe" to reduce the
concentration of pollutants in stormwater before it is discharged. This is in contrast to many
BMPs, where the emphasis is on keeping the water from becoming contaminated. Treatment
practices may be required where flows are currently being affected by exposed materials
and other BMPs are insufficient to meet discharge goals. These practices are usually the most
resource intensive as they often require significant construction costs and monitoring and
maintenance on a frequent and regular basis.
Treatment options may involve a range of maintenance controls. High maintenance treatment
techniques require manpower to operate and maintain the BMP. Low maintenance cost
techniques have initial capital costs but operate with low long-term maintenance after being
implemented. At a few sites, treatment measures other than high maintenance measures may
be appropriate to address specific pollutants. Several examples of treatment BMPs include
chemical or physical treatment, oil/water separators, and artificial wetlands.
An example of a high maintenance technology that is found at many active metal mining
facilities is chemical/physical treatment. The most common type of chemical/physical treatment
involves the addition of lime or other such caustics to remove metals. Metals may be removed
from stormwater by raising the pH of the stormwater to precipitate them out as hydroxides.
After metals precipitation, the addition of some form of acid or carbon dioxide may be
required to reduce the pH to acceptable levels. Polymer addition may be required to enhance
the settling characteristics of the metal hydroxide precipitate. In general, this practice requires
significant operator participation to ensure proper neutralization and/or precipitation and thus
may not be cost effective for most stormwater discharges.
Another example of a high maintenance treatment technology is an oil/water separator. An
American Petroleum Institute (API) oil/water separator or similar type of treatment device
skims oil and settles sludge to remove oil from water. This type of BMP system can be effective
for improving water quality either alone or in conjunction with other treatment practices.
The use of artificial wetlands is another method of treating process wastewater from inactive
mines. There has been extensive research on the use of artificial wetlands as a means of
mitigating acid mine drainage. They can be an effective system for improving water quality
either alone or in conjunction with other treatment practices. The complex hydrologic,
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
biological, physical, and chemical interactions that take place within a wetland result in a
natural reduction and cleansing of influent pollutants. Wetland processes are able to filter
sediments and absorb and retain chemical and heavy metal pollutant through biological
degradation, transformation, and plant uptake.
Artificial wetlands are designed to maintain a permanent pool of water. Properly installed
and maintained retention structures (also known as wet ponds) and artificial wetlands will be
most cost-effective when used to control runoff from larger, intensively developed sites. These
artificial wetlands are created to provide treatment but also provide a wildlife habitat, and
may enhance recreation and landscape amenities.
BMPs for Site Activities
A number of sites and activities found at metal mining facilities require the implementation of
BMPs to prevent the contamination of stormwater. Implementation of BMPs are required not only
for mineral extraction sites and material piles, but for discharges from roads accessing these sites.
Additionally, restabilization must occur with any disturbed areas. An overview of additional BMPs that
may be applicable at haul or access roads; pits or quarries; overburden, waste rock, and raw material
piles; and reclamation activities are discussed below.
4 Haul Roads and/or Access Roads. Placement of haul roads or access roads should occur as far
as possible from natural drainage areas, lakes, ponds, wetlands, or floodplains where soil will
naturally be less stable for heavy vehicle traffic. If a haul road must be constructed near water,
as little vegetation as possible should be removed from between the road and the waterway,
as vegetation is a useful buffer against erosion and is an efficient sediment collection
mechanism. The width and grade of haul or access roads should be minimal and designed to
match natural contours of the area. Construction of haul roads should be supplemented by
BMPs that divert runoff from road surfaces, minimize erosion, and direct flow to appropriate
channels for discharge to treatment areas or other well-stabilized areas.
4 Equipment/Vehicle Fueling and Maintenance. Fueling and maintenance activities should be
conducted indoors or under cover on an impermeable surface. Berms, curbs, or similar means
should be used to ensure that stormwater runoff from other parts of the facility does not flow
over maintenance and fueling areas. Runoff from fueling and maintenance areas should be
collected and treated or recycled. Proper waste management and spill prevention and response
procedures should be implemented. Select good housekeeping procedures to minimize the
amount of contaminated runoff generated (e.g. use dry cleanup methods, use drip pans, and
drain parts of fluids before disposal). Conduct inspections of fueling areas to prevent problems
before they occur.
4 Pits or Quarries. Excavation of a pit or quarry must be accompanied by BMPs to minimize
impacts to area surface waters. As little vegetation as possible should be removed from these
areas during excavation activities to minimize exposed soils. In addition, stream channels and
other sources of water that may discharge into a pit or quarry should be diverted around that
area to prevent contamination.
BMPs can be used to control total suspended solids levels in runoff from unvegetated areas.
These can include sediment/settling ponds, check dams, silt fences, and straw bale barriers.
4 Overburden, Waste Rock, and Raw Material Piles. Overburden, topsoil, and waste rock, as
well as raw material and intermediate and final product stockpiles, should be located away
from surface waters, other sources of water and from geologically unstable areas. In addition
surface waters and stormwater should be diverted around the piles. As many piles as possible
should be revegetated, (even if only on a temporary basis). At closure, remaining piles should
be reclaimed.
4 Reclamation Activities. When a mineral deposit is depleted and operations cease, a mine
site must be reclaimed according to appropriate state or federal standards. Closure activities
typically include restabilization of disturbed areas such as access or haul roads, pits or
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quarries, sedimentation ponds or work-out pits, and remaining waste piles. Overburden and
topsoil stockpiles may be used to fill in a pit or quarry (where practical). Recontouring and
revegetation should be performed to stabilize soils and prevent erosion.
Major reclamation activities such as recontouring roads and filling in a pit or quarry can
only be performed after operations have ceased. However, reclamation activities such as
stabilization of banks, reseeding, and revegetation should be implemented in mined out
portions, or inactive areas of a site as active mining moves to new areas.
EPA recognizes that quarries are frequently converted into reservoirs, or recreational areas, after the
mineral deposit is depleted. However, this does not preclude the reclamation of disturbed areas above
the quarry rim.
Typically, the costs of stabilization controls are low relative to other discharge mitigation
practices. Given the limited capacity to accept large volumes of runoff, and potential erosion
problems associated with large concentrated flows, stabilization controls should typically be used
in combination with other management practices. These measures have been documented as
particularly appropriate for mining sites.
BMPs for Various Extraction Techniques
Metals are recovered by three basic extraction techniques: surface mining; underground mining; and
placer mining. Each type of extraction method may be followed by varying methods of beneficiation
and processing. Due to similarities in mining operations for many of the minerals within this industry,
activities, significant materials, and materials management practices are fairly uniform.
4 Surface mines. Materials management practices at surface mines are typically designed to
control dust emissions and soil erosion from extraction activities, and offsite transport of
significant materials. Settling ponds and impoundments are commonly used to reduce TSS
and other contaminants in process generated wastewaters. These controls may also be used
to manage stormwater runoff and run-on with potentially few alterations to on-site drainage
systems.
Impoundments are used to manage tailings generated at facilities engaged in flotation or
heavy media separation operations. These impoundments are used to manage beneficiation/
processing wastewaters generated at the facility and may also be used to manage stormwater
runoff.
4 Underground mines. Materials management practices for significant materials at the surface
of underground mining facilities are similar to those materials management practices used
at surface mining operations. However, waste rock or mill tailings are in some cases being
returned to the mine as fill for the mined-out areas or may be directed to a disposal basin.
4 Placer mines. Settling ponds are used to manage process wastewaters and are, in some cases,
being used to manage contaminated stormwater runoff.
4 Inactive mines. Inactive mine sites also require implementation of BMPs. Inactive ore mining
and dressing operations are those where industrial activities are no longer occurring. When
active, mineral extraction could have occurred from surface mines, solution mines, placer
operations, or underground mines. These sites require permit coverage until reclaimed because
significant materials may remain on-site, and, if exposed, are potential sources of stormwater
contamination. Due to the seasonal nature of this industry, mine sites can become temporarily
inactive for extended periods of time. Temporarily inactive sites are not viewed the same as
permanently inactive sites.
Implement BMPs, such as those listed below in Table 2 for the control of pollutants at metal mining
facilities, to minimize and prevent the discharge of pollutants in stormwater. Identifying weaknesses
in current facility practices will aid the permittee in determining appropriate BMPs that will achieve
a reduction in pollutant loadings. BMPs listed in Table 2 are broadly applicable to metal mining
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facilities; however, this is not a complete list and you are recommended to consult with regulatory
agencies or a stormwater engineer/consultant to identify appropriate BMPs for your facility.
Table 2. BMPs for Potential Pollutant Sources at Metal Mining (Ore Mining and Dressing) Facilities
Pollutant Source
BMPs
Haul Roads and/or
Access Roads
Construction of haul roads should be supplemented by BMPs that divert runoff from road
surfaces, minimize erosion, and direct flow to appropriate channels for discharge to treatment
areas. Examples of BMPs include:
- Install dikes, curbs, and berms for discharge diversions.
- Install conveyance systems such as channels, gutters, culverts, rolling dips and road sloping,
and/or roadway water deflectors.
- Use check dams, rock outlet protection, level spreaders, stream alternation and drop
structures for runoff dispersion.
- Install gabions, riprap, native rock retaining walls, straw bale barriers, sediment traps/catch
basins, and vegetated buffer strips for sediment control and collection.
- Keep as much vegetation as possible when building roads and seed as necessary. Stabilize
soil via willow cutting establishment.
Place as far as possible from natural drainage areas, lakes, ponds, wetlands, or floodplains
Width and grade of roads should be as small as possible to meet regulatory requirements and
designed to match the natural contours of the area.
Frequently inspect all stabilization and structural erosion control measures and perform all
necessary maintenance and repairs.
Pits/Quarries or
Underground Mines
FJ Install dikes, curbs, and berms for discharge diversions.
FJ Install conveyance systems such as channels and gutters to control runoff and run-on.
FJ Use serrated slopes, benched slopes, contouring, and stream alteration to direct
uncontaminated discharges away from a pit or quarry.
Q Install sediment settling ponds, straw bale barrier, and siltation berms.
Q Keep as much vegetation as possible when excavating and seed as necessary to minimize the
amount of exposed soils.
Overburden, Waste
Rock, and Raw
Material Piles
Q Overburden, topsoil, waste rock, raw material, or intermediate and final product stockpiles
should be located away from surface waters and other sources of run-on, as well as
geologically unstable areas.
Q Install dikes, curbs, and berms for discharge diversions to control runoff and run-on.
FJ Install conveyance systems such as channels and gutters to control runoff and run-on.
FJ Use serrated slopes, benched slopes, contouring, and stream alteration around piles for
sediment control and runoff dispersion.
FJ Install plastic matting, plastic netting, erosion control blankets, mulch straw, sediment/settling
ponds, silt fences, siltation berms, and/or compaction for sediment control and collection.
FJ Stabilize and recontour piles as necessary.
FJ Vegetate as many piles as possible (involves topsoiling, seedbed preparation, and/or seeding).
Reclamation
FJ Install dikes, curbs, and berms for discharge diversions.
FJ Install conveyance systems such as channels and gutters.
FJ Use check dams, rock outlet protection, level spreaders, stream alternation, drop structures,
serrated slopes, drain fields, benched slopes, contouring, and stream alteration for runoff
dispersion.
EPA-833-F-06-022
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
Table 2. BMPs for Potential Pollutant Sources at Metal Mining (Ore Mining and Dressing) Facilities
(continued)
Pollutant Source
BMPs
Reclamation
(continued)
Q Install gabions, riprap, native rock retaining walls, straw bale barriers, sediment traps/catch
basins, biotechnical stabilization, silt fences, siltation berms, brush sediment barriers, and
vegetated buffer strips for sediment control and collection.
FJ Recontouring and vegetation should be performed to stabilize soils and prevent erosion in
mined out portions or inactive areas of the site as active mining moves to new areas (includes
topsoiling, seedbed preparation, seeding, and willow cutting establishment).
Q If a quarry is being converted into a reservoir or recreational area, disturbed areas above the
quarry rim must still be reclaimed.
Q Use overburden and topsoil stockpiles to fill in a pit or quarry (when practical).
Equipment/vehicle
maintenance
Minimizing Exposure
FJ Perform all cleaning operations indoors or under covering when possible. Conduct the cleaning
operations in an area with a concrete floor with no floor drainage other than to sanitary sewers
or treatment facilities.
FJ If operations are uncovered, perform them on a concrete pad that is impervious and contained.
FJ Park vehicles and equipment indoors or under a roof whenever possible and maintain proper
control of oil leaks/spills.
Q Check vehicles closely for leaks and use pans to collect fluid when leaks occur.
Management of Runoff
Q Use berms, curbs, or other diversion measures to ensure that stormwater runoff from other
parts of the facility do not flow over the maintenance area.
Q Collect the stormwater runoff from the cleaning area and provide treatment or recycling.
Discharge vehicle wash or rinse water to the sanitary sewer (if available and allowed by sewer
authority), wastewater treatment, a land application site, or recycle on-site. DO NOT discharge
washwater to a storm drain or to surface water.
Inspections and Training
FJ Inspect the maintenance area regularly for proper implementation of control measures.
Q Train employees on proper waste control and disposal procedures.
Good Housekeeping
Q Eliminate floor drains that are connected to the storm or sanitary sewer; if necessary, install a
sump that is pumped regularly. Collected wastes should be properly treated or disposed of by a
licensed waste hauler.
Q Use drip pans, drain boards, and drying racks to direct drips back into a fluid holding tank for
reuse.
FJ Drain all parts of fluids prior to disposal. Oil filters can be crushed and recycled.
FJ Promptly transfer used fluids to the proper container; do not leave full drip pans or other open
containers around the shop. Empty and clean drip pans and containers.
FJ Dispose of greasy rags, oil filters, air filters, batteries, spent coolant, and degreasers properly.
FJ Store batteries and other significant materials inside.
FJ Label and track the recycling of waste material (e.g., used oil, spent solvents, batteries).
FJ Maintain an organized inventory of materials.
Eliminate or reduce the number and amount of hazardous materials and waste by substituting
nonhazardous or less hazardous materials.
EPA-833-F-06-022
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
Table 2. BMPs for Potential Pollutant Sources at Metal Mining (Ore Mining and Dressing) Facilities
(continued)
Pollutant Source
BMPs
Equipment/vehicle
maintenance
(continued)
Good Houskeeping (continued)
Q Clean up leaks, drips, and other spills without using large amounts of water. Use absorbents
for dry cleanup whenever possible.
FJ Prohibit the practice of hosing down an area where the practice would result in the discharge
of pollutants to a stormwater system.
FJ Clean without using liquid cleaners whenever possible.
FJ Do all cleaning at a centralized station so the solvents stay in one area.
FJ If parts are dipped in liquid, remove them slowly to avoid spills.
FJ Do not pour liquid waste into floor drains, sinks, outdoor storm drain inlets, or other storm
drains or sewer connections.
Fueling activities
FJ Conduct fueling operations (including the transfer of fuel from tank trucks) on an impervious
or contained pad or under a roof or canopy where possible. Covering should extend beyond
spill containment pad to prevent rain from entering.
Q When fueling in uncovered area, use a concrete pad (asphalt is not chemically resistant to the
fuels being handled).
Q Use drip pans where leaks or spills of fuel can occur and where making and breaking hose
connections.
FJ Use fueling hoses with check valves to prevent hose drainage after filling.
FJ Use spill and overflow protection devices.
FJ Keep spill cleanup material readily available. Clean up spills and leaks immediately.
FJ Minimize/eliminate run-on into fueling areas with diversion dikes, berms, curbing, surface
grading or other equivalent measures.
FJ Collect stormwater runoff and provide treatment or recycling.
FJ Use dry cleanup methods for fuel area rather than hosing down the fuel area. Follow
procedures for sweeping up absorbents as soon as spilled substances have been absorbed.
Q Perform inspection and preventive maintenance on fuel storage tanks to detect potential leaks
before they occur.
Q Inspect the fueling area to detect problems before they occur.
Q Train personnel on fueling procedures in the SWPPP.
Q Provide curbing or posts around fuel pumps to prevent collisions from vehicles.
Q Discourage "topping off" of fuel tanks.
What if activities and materials at my facility are not exposed to
precipitation ?
The industrial stormwater program requires permit coverage for a number of specified types of
industrial activities. However, when a facility is able to prevent the exposure of ALL relevant activities
and materials to precipitation, it may be eligible to claim no exposure and qualify for a waiver from
permit coverage.
If you are regulated under the industrial permitting program, you must either obtain permit coverage
or submit a no exposure certification form, if available. Check with your permitting authority for
additional information as not every permitting authority program provides no exposure exemptions.
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INDUSTRIAL STORMWATER FACT SHEET SERIES
Sector G; Metal Mining (Ore Mining and Dressing) Facilities
Where do I get more information?
For additional information on the industrial stormwater program see
www.epa.gov/npdes/stormwater/msgp.
A list of names and telephone numbers for each EPA Region or state NPDES permitting authority can
be found at www.epa.gov/npdes/stormwatercontacts.
References
Information contained in this Fact Sheet was compiled from EPA's past and current Multi-Sector
General Permits and from the following sources:
4 Idaho Department of Lands.1992. Best Management Practices for Mining in Idaho.
4 Maine Department of Environmental Protection. 2003. "Maine Erosion and Sedimentation
Control BMPs."
www.state.me.us/dep/blwq/docstand/escbmps/
4 U.S. EPA. September 1992. Stormwater Management for Industrial Activities: Developing
Pollution Prevention Plans and Best Management Practices. EPA832-R-92-006.
www.epa.gov/npdes/stormwater
4 U.S. EPA, Office of Science and Technology. 1999. Preliminary Data Summary of Urban
Stormwater Best Management Practices. EPA-821-R-99-012.
www.epa.gov/OST/stormwater/
4 U.S. EPA, Office of Wastewater Management. NPDES Stormwater Multi-Sector General Permit
for Industrial Activities (MSGP).
www.epa.gov/npdes/stormwater/msgp
EPA-833-F-06-022 13
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