HYDRO21002

• Permit No: C1981020
• IBM Index Class Name: Hydrology
• Doc Date: 10/28/1997
• Doc Name: STORM EXEMPTION REQUEST CO-0040827
• From: GRAND VALLEY COAL CO
• To: CDOH
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

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GRAND VALLEY COAL COMPANY 999
P.o. Box 70
Loma, Colorado 81524-0070
[phone] Fax (970) 858 - 7690
October 28, 1997
Colorado Department of Public Health and Environment
4300 Cherry Creek Drive South
Denver, Colorado 80222-1530
Re: Storm Exemption Request CO-0040827
To Whom it May Concern;
Grand Valley Coal Company requests relief from the e$]uent limitations for Total Suspended
Solids, Total Iron and Settleable Solids for a discharge that occurred on September 21, 1997.
The discharge was the result of a series of storms that occurred in the mine area from August 18,
1997 through August 22 , 1997. The series of storms were from the remnants of hurricane Linda
which moved through western Colorado. The precipitation that occurred on those days is
tabulated below.
Date 24HR Precip.
9-18 0.4"
9-19 0.4"
9-20 0.75"
9-21 2.50"
9-22 1.2"
Cumulative Precip.
0.4"
0.8»
1.55"
4.05"
5.25"
The 10 yeaz 24 hour precipitation event for the area is 1.7 inches. The storm on September
21, 1997 approximates the 100 yeaz 24 hour event (2.6 inches). It should also be noted that over
3.3 inches of precipitation occurred in 27 hours from the storm on September 21, 1997. The
discharge on September 21, 1997 was necessary to regain storage capacity in the sedimentation
facilities. The capacity regained was adequate to allow total retention of the runoff from the
storm on September 22, 1997. The pond at Munger Canyon is designed to totally retain the
volume of a 10 year 24 hour event but was not adequate to retain the volume from the series of
storms that occurred.
On September 22, 1997, Mr. John Kubic of CDOH was informed of the need to discharge
and that a storm exemption would probably be necessary. Enclosed aze the discharge monitoring
reports for the third quarter of 1997. The quality of the e$luent is noted on the form. The storm
discharge was the only discharge for the quarter and is the fu•st since the pond was constructed in
]981.
Please contact me if there aze questions or if additional information is required.
Sincerely,
ohn M. Walters
Manager of Mine Services