PERMFILE118832

• Permit No: C1981039
• IBM Index Class Name: Permit File
• Doc Name: Rockcastle 5/21/92
• Section_Exhibit Name: Reclamation Project Binder
• Media Type: D
• Archive: No

May 1992 Rockcastle Coa/ Company • Grassy Creek Mine ~ 4
i only 0.0009 acre-feet (1.5 cubic yards) for the Pit 2 area and 0.0012 acre-feet (1.9 cubic
yards) for Pit 3. These differences in calculated annual sediment loss are so small as to
be negligible given the accurary of the calculation method.
)n evaluating whether or not sedimentation pond removal is justified, it is important to
keep the intent of Rule 4.05.2(2) in mind. The focus of this regulatory requirement is to
minimize additional sediment contributions to receiving drainages above baseline levels
and to prevent any significant changes in water quality. The difference in calculated
annual sediment loss noted above would probably not be measurable in the receiving
drainage, especially when distributed over the entire drainage year. Other mitigating
factors include the existence of contour furrows on both of the subject reclaimed areas
and heavily vegetated undisturbed areas between the pit disturbance areas and the
receiving drainages. The contour furrows offer significant sediment trapping and
retention capacity as demonstrated by the following simplified calculations:
Contour Furrow Cross-Sectional Area (1 foot deep w/ 2:1 sideslopes): 2 sq. ft.
Linear Feet of Contour Furrow ~ 50 foot spacing:
Pit 2 - 16,000 ft.
Pit 3 - 31,000 ft.
Sediment Storage Capacity:
• Pit 2 - (16,000 * 2)/43,560 = 0.73 acre-feet
Pit 3 - (31,000 * 2)/43,560 = 1.43 acre-feet
When the sediment storage capacity of the contour furrows is compared with the
calculated differences in annual sediment yield, it becomes apparent that the existing
control structures have adequate capacity to store the incremental sediment amounts for
periods exceeding 500 years.
Rockcastle recognizes that removal and reclamation of Ponds 2 and 3 and the associated
collection ditches will result in short-term increases in sediment loss from the pond and
ditch areas. With respect to the pond areas, Rockcastle proposes to address this concern
by regrading the reclaimed pond areas to ensure positive drainage, reseeding and
mulching these areas as soon as practicable after regrading, and installing either sediment
fences or permeable rock berms downgradient of the reclaimed pond areas.
Existing collection ditches vary in depth and are generally heavily vegetated. Rockcastle's
objectives in reclaiming these ditches will be to eliminate the linear ditch profile in order
to breakup and disperse runoff and prevent channel flow and co minimize, where
possible, disturbance of existing established vegetation. These objectives will be
accomplished by backfilling and grading any ditch segments greater than 0.5 foot in
depth, extending contour furrows across regraded ditch areas, and reseeding and mulching
reclaimed ditch segments. Under this proposed reclamation plan, no continuous ditch
segments greater than 20 feet in length will be retained regardless of depth.
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