PERMFILE139734

• Permit No: M1997054
• IBM Index Class Name: Permit File
• Doc Name: STORMWATER MANAGEMENT PLAN
• Media Type: D
• Archive: No

Slormwaler Mana¢ement Plan 1728/97
3.2 Plant and Stockpile Sites
• The gravel bar plant and stockpile area will disturb approximately 18 acres for operations
and stockpiles. Initial operations will haul granite from the granite mine to the plant on
the gravel bar. When the 10.2 acres noted for the granite plant area are developed, the
granite plant operations and some stockpiles will be moved to the granite plant area.
•
•
Plant operations associated with the production of rock products include the use of
portable equipment for crushing, screening, and stockpiling. The plant will include
primary, secondary and tertiary crushers. Water will be used to control dust during
operations which will either evaporate or immediately infiltrate into the gravel bar due to
the limited quantities of water involved and the porosity/permeability of the gravel. While
the gravel's ability to absorb water exceeds all water use and known storm water events,
the area will be graded into both the pit areas labeled IB and IA as a precaution. No
reason has been found to expect any of the gravel pits to discharge water during periods
of heavy precipitation. The Mine Base Map shows the locations of the plant equipment,
stockpiles, and other features of the operation are shown on the mine base map.
In addition to the plant grading into the adjacent gavel pit areas, the plant area will be at
least 7' below the buffer area to the north. Gravel will be mined to above the water table
which has been shown to vary from current estimates of 20 to 40' deep demonstrating that
the pits and reduced plant elevation without the known percolation rates could hold and
retain any known storm event.
Process Water Disposal
The operation will involve suppressing dust with water. Water used to suppress dust on
roads, crushers, belts and screens is assumed to evaporate as directed by the State
Engineers Office. Any water used on stockpiles will be lost 4% to evaporation and 96%
into the gravel bar again as directed by the State Engineer's Office. Previous estimates
have been reduced from IS million gallons per year to 1.4 to 9 million gallons per year.
The range results from starting with lower production and expectations to expand sales
with the requisite supporting production. Any water not evaporated will infiltrate into the
gravel bar based on the field percolation test results. Field percolation tests and
surface/ground water hydrology studies done by contractors confirm these conclusions.
Inconceivable discharges from the 2 gravel pit areas are permitted as discharge outflows 1
and 2.
Temporary stabilization practices are listed. Temporary seeding would occur around
roans, ourter slopes ana the temporary topson stocxpile
XX Temporary Seeding _ Mulching
_ Silt Fences _ Erosion Control Blankets
_ Straw Bale Dikes Temporary Drain Diversion
_ Temporary Sediment Basins _ Brush Barriers
_ Sediment Traps/Ponds XX Preserve Existing Vegetative Buffers
XX Stabilize Access Road _ Earth Dikes
XX Draina e Swales/Ditches Check Dam
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