PERMFILE135522

• Permit No: C1981019A
• IBM Index Class Name: Permit File
• Doc Date: 12/11/2001
• Section_Exhibit Name: EXHIBIT 7 Archived Section 2 Part 2
• Media Type: D
• Archive: Yes

III IIIIIIIIIIIII III Doc Date:12/11/2001
Cxr,~ib:r ~-
TIPTON AND KALMBACH, INC.

CIINTONW MEH RIN G. PRESID ENY
E. R MIGHELL, E%EC~ VICE PR ESIOENT
H P BIS HOp. VICE PRESIDENT
A. J. OEUTSG H. TREASU RER
J. H. TURNf R.SECRETART
Mr. Richard Atkinson
Colowyo Cool Company
5731 State Highway 13
Meeker, Colorado 81641
ONE PAPn CENtRa~.SUrtE mGl
1515 ARq pqw OE SiPEET
DENV ER,COLORADO 80202
pw ONE 130315>2 ~BOB~
Moy 14, 1981
Subject: Colowyo Permit Application
Colorado Mined Land
Reclamation File No. C-019-81
Dear Mr. Atkinson:
GABLE:
4RTIP - DENVER
TW%'
910~931'25a0
In accordance with your request we have reviewed those portions of the Colorado Mined
Land Reclamation's Adequacy Review, Colowyo Coal Company -Colowyo Strip, April 10,
1981, that relate to our engineering work for Colowyo's Permit Application. Our responses to
specific points in the Adequacy Review are os follows:
•
2.05.3 (4) Ponds, Impoundments and Diversions
1 . Culvert Designs: The Adequacy Review stated that in using the McMath
formu- a f~ak flow estimates that incorrect rainfall intensities were used,
We have reviewed the peak flow calculations for the 23 culverts, and in
consultation with Mr. Richard A. Domingue, Reclamation Specialist, Colorado
Mined Land Reclamation Division have concluded that the method outlined
in Colorado Water Conservation Board Technical Manual No. 1 "Manual for
Estimating Flood Characteristic of Natural-Flow Streams in Colorado" is a
more applicable method for determining culvert discharges for drainage areas
of the size and location of these adverts. The discharges were then computed
for each of the culverts, and all of the 18" to 48"diameter culverts were found to
be of adequate size to pass the design 10-year frequency discharges, and the
120" diameter Taylor Creek culvert was found to be adequote to pass its 20-year
design frequency discharge. Table 1 presents data on the culverts including
drainage area, discharge for 10-year or 20-year design frequency, culvert
diameter, inlet head required for the design discharge, and recommendation
for outlet riprap. Toble 2 presents constructed culvert layout details.
~-
2. USLE Calculations: The Adequacy Review asked for justification for use of the
method out fined in "Hydrology and Sedimentology of Surface Mined Lands" by
Haan and Barfield in determining the sediment delivery ratios. In the calculations
submitted with the mine permit applimtion we had computed the delivery ratio