APPCOR11437

• Permit No: C1981048
• IBM Index Class Name: Application Correspondence
• Doc Date: 1/22/1981
• Doc Name: TRINIDAD BASIN MINING-FN 79-53
• From: MLR
• To: MINERAL RESOURCES AND ENGINEERING INC
• Media Type: D
• Archive: No

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DEPARTMENT OF NA'i URAL flESOURC ESU ~ r v '11 nr III IIIIII 111IIII III
D. Monte Pastue, Executive Director
MINED LAND RECLAMA'T'ION
423 Centennial Building, 1313 Sherman Street
Denver, Colorado 80203 Tel. [phone]
January 22, 1981
David C. Shelton
Director
Mr. Darry Fergusson
Mineral Resources and Engineering, Inc.
P.0. Box 758
Golden, Colorado 80401
Re: Trinidad Basin Mining - Our File No. 79-53
Dear Darry:
After reading your letter of January 5, 1981, to Jim Kent of this office, I
find that I cannot agree with your conclusion that this Division's review of
the Trinidad Basin amendment application exceeds the requirements of the
Federal Interim Regulations. Nor can I agree with your statement that "the
criteria used for sediment pond design... has changed with each new staff
hydrologist". Let me briefly respond to those items which you have specifically
questioned in Division review letters dated December 8, 1980, and December 18,
1980:
1. Culvert designs (No. 6, December 8 memo; December 18 memo)
The Interim regulations specifically require that culverts on access and haul
roads be designed to pass the 10 year 24 hour event (715.1~1~2)(iii)). Com-
pliance with this requirement cannot be checked without the requested infor-
mation on type of pipe, culvert slope, etc. With respect to comments on
design headwater and headwall protection, you are referred again to 715.1~1~(2)
(iii), which requires that culverts be "constructed to avoid... erosion at
inlets and outlets". Also, designing a culvert with a headwater depth which
would overtop the road embankment is clearly poor design and contrary to
common sense.
Peak discharge calculations (No. 7, No. 8 December 8 memo; December
18 memo).
This Division has required the use of a basin shape correction factor in peak
flow calculations for well over a year. The use of a weighted curve number is
also nothing new and simply a matter of proper design. This Division reviews
any design which is submitted for correctness and the proper application of
whatever estimating technique the operator may select. This is irrespective
of the design storm event set by the regulations.
3. Ditch des, igns (December 18 memo)
The Federal Interim regulations clearly require a 10 year 24 hour design for
all temporary diversions (715.17(c)(1)). Channel lining requirements can be
found in 715.17(c)(3).
4. Spillway designs (No. 6, No. 10 December 8 memo; December 18 memo)
Under an interim review, the operator has the option of proposing an alternative