PERMFILE137350

• Permit No: M1997014
• IBM Index Class Name: Permit File
• Doc Date: 1/29/1997
• Doc Name: STORM WATER AND SEDIMENT CONTROL PLAN ROCKY MTN ROCK PRODUCTS DEER CREEK QUARRY PN M-78-214
• From: DMG
• To: GARY CURTISS
• Media Type: D
• Archive: No

DIVISION OF ,V1IN ERALS AND GEOLOGY
Depanmem ni ~~amral Resources

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DATE: January 29, 1997
T0: Gary Curtiss
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DEP.4RTMEM Of
NATURAL
RESOURCES
Ror Romer
Governor
lames 5. Lochhead
Executive Duector
,xsichael B. Long
FROM: A11en Sorenson G D~v~sion Dlrecmr
RE: Storm Water and'Sediment Control Plan, Rocky Mountain
Rock Products, Deer Creek Quarry, Permit No. M-79-214-AR
A required corrective action listed in the Division's 11/12/96
inspection report for the Deer Creek Quarry was for the operator to
evaluate storm water flows in Wildcat Gulch and through the
disturbed area of the quarry. The operator has provided the
Division with an evaluation of runoff that may be anticipated from
the to year-24 hour storm event in the quarry location, and has
estimated peak runoff from Wildcat Gulch to be 207 cfs. I have
verified the operator's estimate of peak runoff, and have found it
to be appropriate for design purposes.
Another component of the corrective action required in the
Division's inspection report was to desigr. a storm water management
plan that would non-destructively convey the 10 year-24 hour storm
event through the quarry. The operator has provided a design for
an "access asphalt road channel" that will convey peak runoff from
the 10 year-24 hour storm along the quarry access road. I have
verified that the proposed cross-sectional area of the ditch is
adequate to convey the peak flows, however, the Dso of the riprap
needs to be increased from 12" to 21", with a D,,,ax of 27" (see
attached graph). The riprap layer thickness in the ditch needs to
be 27" minimum, and the ditch needs to be lined with a fabric or
appropriately sized granular filter prior to riprap placement. The
1' freeboard in the ditch that has been proposed by the operator
may also have to be increased in the areas of channel bends. As I
recall, there are some very sharp bends in the quarry access road
that would cause superelevation (see attached diagram) and possible
overtopping in the ditch. The required freeboard in the channel
bends should be reevaluated using the following criteria:
1.0 foot plus one-half superelevation.
The Division is alsc concerned with construction feasibility of the
proposed access road-side ditch. The operator has proposed a total
ditch width of 17', and once the ditch is over excavated for