APPCOR11214

• Permit No: C1981039
• IBM Index Class Name: Application Correspondence
• Doc Date: 11/17/1981
• Doc Name: ADEQUACY REVIEW-Hydrology
• From: MLRD
• To: BRIAN MUNSON
• Media Type: D
• Archive: No

. ~ = ~ III IIIIIIIIIIIII III
sss
STATE OF COLORADO RIG H4RD D. LA MM. Gov moor
DEPARTMENT OF NATURAL RESOURCES
D. Monte Pascoe, Executive Director
MINED LAND RECLAMATION
423 Centennial Building, 1313 Sherman Street
Denver, Colorado 80203 Tel. [phone]
David C. Shelton
November I7, 1981 Director
T0: Brian Munson D
FROM: R.A. Domin gue~ ~fv
RE: The Rockcastle Company's Grassy Creek Mine - Adequacy Review
File No. C-039-81
Dear Brian,
I have read the entire permit application for the Rockcastle Company's Grassy
Creek mine and have carefully reviewed the information given on hydrology and
sediment control. I have identified a few concerns associated with the
mining and reclamation plans.
Possibly the major item of concern is the wholesale disregard of vegetation
and wildlife mitigation requirements. There may be a mechanism by which we
can allow the conversion of the land use on the post-mining surface and
thereby allow a seed mix greatly at variance with the species composition of
the pre-mining surface, but some measures must be taken to reduce the impact
of this change on wildlife. The inclusion of shrubs in the seed mix and/or
the utilization of tree islands are possible techniques for wildlife mitigation.
Also of concern is the fact that haul roads at the site will be left after
mining. The proposed haul road to Pit 4 will have fill slopes over one hundred
feet long in many places. Since haul roads are exempted from sediment pond
control requirements, measures taken to control erosion on these Large fill
slopes are of great concern. Topsoil removed from the surface beneath the
proposed road should be replaced on the fill slope, the entire area mulched
or matted and fast growing bunch and sod-forming grasses planted. The sediment
yield from the fill slope has the potential to exceed the sediment yield from
the Pit 4 reclaimed surface. The Rockcastle Company must describe in detail
measures taken to prevent off-site damage due to road fill slope erosion.
Drainage Culverting:
Of concern is the fact that the specific methods used and parameter inputs
for estimation of the peak flows at culvert installations are not given.
That is, Rockcastle says they have used one of two references listed to
determine peak flows, but no specific information is given on how the values
shown on page III-16 were obtained.