2023-01-05_REVISION - C1981019 (13)

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requirements. The Division also finds that planned demolition and reclamation of facility areas are sufficient to: • Prevent damage to fish, wildlife, and related environmental damages and prevent additional contributions of suspended solids to streamflow or runoff outside the permit area (Rule 4.04(1)). • Control and minimize diminution or degradation of water quality and quantity (Rule 4.04(2)). • Control and minimize erosion and siltation (Rule 4.04(3)). • Control and minimize air pollution (Rule 4.04(4)). • Prevent damage to public or private property (Rule 4.04(5)). • Minimize damage, destruction, or disruption of services provided by wells, pipelines, railroads, electric lines, and telephone lines (Rule 4.04(6)). HI. Hydrologic Balance Rule 4.05 The Permit is found to be in compliance with the requirements of Rule 4.05. A. Water Quality Standards and Effluent Limitations - Rule 4.05.2 There are 10 outfalls currently approved at the Colowyo Mine. These outfalls correspond to sediment ponds listed below in Section D and sumps adjacent to Taylor Creek. The outfalls are monitored for water quality as part of Colowyo's Colorado Discharge Permit System (CDPS) permit no. CO-00458161. The Division's review of Discharge Monitoring Reports associated with CO-00458161 indicated an exceedance of limitations for Total Suspended Solids (TSS) at East Taylor Pond (outfall number OlOA). Based on a memorandum of understanding with the Colorado Water Quality Control Division (WQCD) and the Division, the WQCD is responsible for enforcing CDPS permit conditions. No violations were issued by WQCD in association with CO-00458161 during the 2017-2022 permit term. Colowyo's current CDPS permit and plan associated with the Collom Pit area is under review by the WQCD. Surface drainage from all disturbed areas passes through sediment ponds with some exceptions. The Division has granted Small Area Exemptions (SAES) for some areas on the mine site. SAES include the area along the East Side Collection Ditch, the topsoil stockpiles along Haul Road A, and the East Taylor Holding Pond and pump station (shown on Map 11 and Map 12 of the PAP). Additionally, a total of three areas are permitted as SAES in the Collom Area. The SAES include a 1.4 acre zone along the east side of the pit in Section 1, a 7.66 acre area along the east side of the pit in Section 2, and a 2.6 acre area on the west side of the pit in Section 34. These sites are relatively small and analysis indicates that standard treatment facilities (i.e., large sediment ponds) are not necessary for the drainage to meet the effluent limitations of Rule 4.05.2 and the applicable State and Federal water quality standards for receiving streams. More information on Proposed Decision and Findings of Compliance January 5,2023 Permit Renewal No. 8 Page 135