ENFORCE20083

• Permit No: C1981048
• IBM Index Class Name: Enforcement
• Doc Date: 3/12/1987
• Doc Name: POND 15-P20 DESIGN CAPACITY
• From: MLRD
• To: TRINIDAD BASIN MINING CO
• Violation No.: CV1986068
• Media Type: D
• Archive: No

1
STATE OF COLORADO
Roy Romer, Govei
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
DAVID C. SHELTON, Director
DATE: March 5, 1987
T0: Trinidad Basin Mine~~~/j11e
FROM: Randall P. Price ~"a
RE: TRINIDAD BASIN MINING, NOTICE OF VIOLATION C-86-068,
SEDIMENT POND DESIGN
In reference to the Trinidad Basin Mines notice of violation NOV C-86-068
issued on September 30, 1986 for failure to maintain sediment pond 15-P20 I
have reviewed the original pond design submitted February 2, 1982 and the
following are my comments and recommendations.
Pond 15-P20 was designed to control runoff from a 6.7 acre area of which 4.2
acres are disturbed. Based on the information given in the permit total
runoff from this area for a 10 year 24 hour precipitation event would be
1.3 inch runoff X6.7 acres = .73 acre feet.
'~'i nc IF~es
The design volume for the pond at the emergency spillway is
204,500 cubic feet or
204,500 cubic feet = 4.7 acre feet.
square ee per acre
The pond design allowed for .42 acre feet of sediment storage or a level in
the pond of 2.7 feet from the bottom. During the inspection on
February 10, 1987 sediment levels could not be determined because the pond did
not have a sediment level marker. The pond as designed has a principle
spillway 10 feet above the bottom of the pond giving a capacity of 2.2 acre
feet - .42 acre feet sediment storage or a 1.8 acre feet runoff retention or
more than double the anticipated 24 hour 10 year runoff. The emergency
spillway is designed to be 5 feet above the principle spillway. From the
inspection the outlet of the principle spillway appeared to be much lower that
than 5 feet below the emergency spillway. It appeared that the riser pipe to
the principle spillway was removed or broken off. If a riser pipe is
installed on to the outlet pipe to the design specifications the maximum
sediment storage volume could be reached with enough room for an additional 1
acre foot of sediment.
423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]