2018-07-09_GENERAL DOCUMENTS - C1981019

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Proposed Decision and Findings of Compliance July 2018 Permit Renewal No. 7 P a g e | 36 The Collom Haul Road will cross within 100 feet of the Wilson Creek and Jubb Creek shown on Map 25E of the PAP. Proper Best Management Practices (BMPs) have been employed prior to any disturbance for the haul road to ensure all surface water runoff is directed through the BMPs before being released. Much of the Little Collom Gulch will be directly impacted by the Collom Pit, the temporary spoil pile, and the Section 25 Pond as show on Map 23C of the PAP. The Section 25 Pond will protect the lower reaches of Little Collom Gulch that will not be disturbed during mining and reclamation activities within the Collom area. It is not anticipated that any of the areas that are to be disturbed within the stream buffer zones will have any long term impact to Wilson Creek, Jubb Creek, or Little Collom Gulch with the proper use of BMPs, sediment control structures, and clean water diversions. No other areas within the Collom disturbance footprint will impact any stream buffer zones. L. Probable Hydrologic Consequences A discussion of the probable hydrologic consequences of mining and reclamation operati ons is contained in Section 2.04.7 of the PAP. The original findings document (1982), an Amended Findings Document for Permit Renewal (1987), and TR-14 (1989) also include discussions of probable hydrologic consequences. Probable Hydrologic Consequences for the South Taylor area are included in Section 2.05.6 in Volume 12 and Section 2.05.6 in Volume 15 for the Collom Area. Potential Effects on Surface Water Quantity The Mine will have very limited regional impacts on surface water. This assessment is based on hydrologic reports from the 1970s and the 1980s, the approved PHC section of the PAP, and past Division findings. Monitoring data in Colowyo’s Annual Hydrology Reports (AHRs) indicate that there have been no significant impacts on water quantit y of these streams due to mining operations at the Mine. The data for flow in Taylor Creek below the mine (monitoring point LTC on Map 10 of the PAP) and data for flow in Good Spring Creek below the mine (monitoring point LGSC on Map 10 of the PAP) indicate small decreases in flow since 1982; however, these decreases are not statistically significant (very low R2 values). On a smaller than regional scale, some impacts are expected. The sizes of drainage areas for some ephemeral and intermittent creeks within the mined area will be changed, thus altering runoff quantities. Other expected changes include:  Hydraulic transmissivities within backfilled pits will be altered, thus changing the hydrologic balance.  Base flow in creeks may be reduced during mining and for several years after mining.  Peak flows in creeks will be reduced due to pits.