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COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale - .Page 5. Permit No. COG500000 V. Tl3RMS AND CONDITIONS OF PERMIT rvpectivety, in order ro determine compGantt with the limiu. Since the TSS monitoring frequency is momhly, a 7sS limit of t50 mgR was added so that compliance could 6e determined based on one sample. The Division has amended the definitions fora 30 day as+erage or 7 day aNerage, to be determined by the arithmetic mean of all sampler rnlkcted during a 30 day or 7 day period. 7herefarc, the need for a daily maximum 7SS limit hat been eliminated, and so is not included in this renewal permit. The other 7SS limns shall remain the same, for the applicable categories. c. Phosphorus: The previous permit included Phosphorus (P) monitoring for the Dillon Reservoir drairwge area only. This has been changed to also include Cherry Creek basin, Bear Creek basin and those stare waters tributary to Chatfield Reservoir downstream of the USGS gage at Waterton and on Plum Crnk These .segmcros al! have or will have P limits on distfiarges. In getural, the types offacilities coverad under this permit are not expected to hoer problems with P; however, monitoring will be required on a quarterly basis for all process warn discharges to these basins. If tlu data indicate any potential problems with P kvris at a speck faciliry, then an individual permit with P limits may be required for that facility. d. Gmphrte: In the care of graphite mining, the federal efJTuem guidelines (40 CFR 436.382) colt for a limit for Total Iron. Since the Division has Water Quality Standards in many areas of the state which may be striate than the federal limits, coverage of process water discharges from this type of faciliry must be under an individual permit. B. S~mwater Ditcharees 1. Srormwater vs. Process water When stormwarer mtxcs with process water, the process water limitations (Part bB ojthe ptrnrit) apply to the discharge of that mixed water. The stoemwater section (Part I,C of the permit) is intended to cover those portions of a nonmetallic minerals production operation (except fuel) that art nos already subject to effluent limitations under 40 CFR 436, and to cover srormwarer runoff from asphak and concrete batdt plains. 2. Stormwater Managemem Plan !SWMP) The stormwater regulations primarily apply to areas not covered by 40 CFR Part 436. They require pmnittees ro develop and implement a Stormwater Management Plan (SWMP) to protect the quality ojstormwarer leaving the sire. The plan sha/1 idemify potential sources of pollution (including sediment) whidt may reasonably be expected to affect the quality of stormwater discharge associated with mining activity. In addition, the plan steal! describe the best managemem practices (BMPs) which will be used to reduce the pollutants in stormwater discharges from the mining site. Some aaivdNes required order the SWMP may already be in plan. However, the SWMP will require the permiaee to coordinate these activities with any necessary tow activitiu in an orderly matuur, so that the ruruU is the reduction or elimination of pollutants reaching state wafers from areas not limited by ejfluem limitations. Facilities must implement the provisions of the SWMP rcqutnd under thin part as a condition ojthis pemdt. !t is the permittee's responsibility to notes the Colorado Division ojMining and Geology (formerly the Colorado Mined Land Reclamation Division) of any sign~cam changes at their siu resulting from the implementation of the SWMP. This is so that the Division of Mining and Geology may review the SWMP and incorporate any poremial revisions into the fariliry's reclamation pmnit which might be needed. The SWMP shat! include the following items, at a minimum: