1987-12-01_PERMIT FILE - C1981017 (278)

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PART I Page 4 of 20 Permit No. : CO-0000396 • A. TERMS AND CONDITIONS (Continued) Applicable to outfalls 001, 006, 007, 008, 009, 010, 011, 012, 013, 014, 015, 016, 017, and 018. c. Effective during periods of precipitation greater than the 10-year, 24-hour event for this facility. Any discharge or increase in volume of a discharge caused by precipitation within any 24-hour period greater than the 10 year, 24-hour event (or series of storms or snowmelt of equivalent volume) may comply with the following limitations instead of limitations of Part I.A.1. a and b. 1/ Flow (M®) - monitor only pH - (Standard Units) shall remain between 6. 5 and 9.0 b/. Oil and grease shall not exceed 10 mg/l b/ in any grab sample nor shall there be a visible sheen. Salinity - monitoring only. g/ h/ d. Additional conditions - effective at all times. • There shall be no discharge of floating solids or visible foam in other than trace amounts. The discharge shall not contain any sanitary sewage or other pollutants not associated with active mining operations. 3. Requirements for Effluent Limitation Compliance Determination Within 90 days of the effective date of this permit, the permittee shall submit to the Division, documentation which specifies the 10-year, 24-hour precipitation event (in inches of rain) and the volume of water from active mining areas, preparation plants, and associated areas which would result from a 10-year, 24-hour precipitation event. This documentation shall identify the gauge station being used. Documentation may be in the form of a letter or other indication from the Colorado Mined Land Reclamation Division, the Federal Office of Surface Mining, the Federal Environmental Protection Agency, or other appropriate agency acceptable to the Colorado Water Quality Control Division. It shall be the permittee's responsibility to document both the rainfall amount and the volume of storm runoff produced, should a precipitation event occur (pursuant to 40 CFR 434.63(c)) . 4. Post - Mining Areas Pursuant to 40 CFR 434, commencing at the time active mining ceases and reclamation begins, all applicable discharges shall be subject to • limitations other than those specified above. These post-mining limitations shall remain in effect until bond release. The permittee shall notify the Division upon cessation of active mining so that appropriate permit modifications can be made. See Part I.A.4.c.