2008-08-04_HYDROLOGY - C1994082 ‎(2)‎

• Permit No: C1994082
• IBM Index Class Name: HYDROLOGY
• Doc Date: 8/4/2008
• Doc Name: 2nd Quarter 2008 DMRS
• From: Seneca Coal Company
• To: WQCD
• Permit Index Doc Type: DMR’s
• Email Name: DTM
• Media Type: D
• Archive: No

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July 24, 2008 aecoje®
Colorado Department of Health ?uG 4 Vo a
WQCD-PE-B2
4300 Cherry Creek Drive South gigwon01R Sege
Denver, CO 80246-1530 0609 and
RE: Quarterly Discharge Monitoring Report for Permit CO-0000221
Dear Sir or Madam:
Pursuant to the quarterly reporting requirements contained in Colorado
Discharge Permit CO-0000221 for the Seneca Mine Complex, enclosed find
the second quarter 2008 discharge monitoring reports for Points 002 to
006 and 008 to 017. Intermittent discharges were observed at Points
009, 011, 013 and 014.
Due to winter snow, vehicle access to Points 004, 008, 009, 015,; 016
and 017 was closed until May. Monthly visits in April were performed
by snowmobile, all-terrain vehicle or on foot.
Three excursions of effluent limits occurred this quarter at Point 012.
1. A sample collected on April 22 (by Dan Mathews of the Colorado
Division of Mining, Reclamation and Safety) had a settleable solids
(STS) value of 0.9 ml/l. A STS sample collected by Seneca on April 23
had a value of <0.4 ml/1. The effluent limit is 0.5 ml/l (daily max.)
during periods of no precipitation or snowmelt. However, this sample
was collected during a snowmelt runoff event that was greater than; the
10-year, 24-hour (10Yr24Hr) event, and therefore, an alternate of, the
STS limit ("report") is allowed for in Seneca's discharge permit (Part
I.A.1.g., pg. 9). Attached is the SEDCAD Structure Summary for Pond
012, 10Yr24Hr event. This report indicates that the peak discharge
from Pond 012 for that event is 0.96 cfs. Also attached is a flow
recorder chart for Pond 012 (the first page is of the whole chart,
reduced in size, while the second page is an enlargement of the period
of interest). It indicates that the peak stage on April 21 (prior to
the sampling event) was 0.665 feet and the peak stage on April 22
(after the sampling event) was 1.30 feet. Using the observed rating
formula for this flume (CFS = 5.011 x FEET ^1.544), these stages
indicate flow values of 2.67 and 7.51 cfs, respectively, which are both
above the 10Yr24Hr design discharge, 0.96 cfs. Also attached are, the
snowpack report for the nearest NRCS Snotel site, Crosho, and monthly
reports for December through April at the NOAA weather station in
Hayden, Colorado. Both reports indicate that snowmelt was occurring at
the time of the excursion. The NOAA reports also indicate that total
snowfall was 289% of average in December, 172% of average in January,
159% of average in February, and 128% of average in March. The melting
Seneca Coal Company • P.O. Box 670 • Hayden, Colorado 81639
Telephone [phone] • FAX [phone]