_GENERAL DOCUMENTS - C1981017 ‎(301)‎

• Permit No: C1981017
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Name: Bid Documents ‎(IMP)‎
• Permit Index Doc Type: General Correspondence
• Media Type: D
• Archive: No

Metal Mining SWMP Guidance Document
Page 5
The description of the BMPs shall include:
I) Stormwater diversion: Describe how and where stormwater will be diverted away from
material handling and storage areas to prevent stormwater contamination.
2) Materials handling and spill prevention: Where materials can impact stormwater runoff,
practices that reduce the potential for contamination shall be described and implemented.
For example, materials should be stored and handled in covered areas to prevent contact
with stormwater; chemicals should be stored within berms or secondary containment devices
to prevent leaks and spills from entering stormwater runoff.
3) Sediment and erosion prevention: Describe practices that will be used to reduce erosion and
prevent sediment delivery to State waters. These could include structural (such as silt
fences, sediment ponds, drop structures, check dams) and non-structural (such as mulching
and revegetation) methods.
In each case where stormwater pollution potential exists, appropriate preventive measures must
be identified and implemented.
"Nonstructural" BMPs are mainly definitions of operational or managerial techniques. In addition, there are a
multitude of "structural" BMPs which should be considered, depending upon the industrial activity. Structural
BMPs include physical processes ranging from runoff diversion structures to oil/water separators to retention
ponds.
When selecting BMPs, the most important ones to evaluate first are those which limit the source of the
pollutant. It is much more efficient, from both a cost and environmental standpoint, to prevent the pollution in
the first place than to clean up contaminated stormwater. For example, a BMP requiring that any vehicle
maintenance that involves fluid exchange must take place indoors, results in the removal of a pollutant source
(i.e., oil/hydraulic fluids) from possible contact with stormwater. (Of course, the handling of the pollutant
inside must still be addressed, though not necessarily in the SWMP.)
Once source reduction BMPs have been evaluated, then more costly options, such as mitigation of impacts, or
stormwater treatment through detention storage, should be considered if necessary. The BMPs selected are up
to the judgment of the individual permittee. However, it is important to keep in mind that a fully implemented
SWMP will constitute compliance with Best Available Technology (BAT) and Best Conventional Technology
(BCT), as mandated under the Federal Clean Water Act. Basically, this means that, in order to comply with
your permit, the appropriate measures must be taken in keeping with the pollutant(s) involved and the risk
potential at the facility.
BMPs applicable to the mining areas have long been standard under mining permits. Contact the Dept. of
Natural Resources, Division of Minerals and Geology at [phone] for more information.
There are many other BMPs available as well. For more specific information, see the List of Available
Documents, available from the Division. This includes ordering information for local and national BMP
manuals.
c. Preventive Maintenance - The SWMP shall identify a preventive maintenance program. This
program shall involve maintenance of stormwater management devices (maintenance of dikes
separating mine drainage from stormwater, cleaning oil/water separators, catch basins, etc.) as