2018-07-02_PERMIT FILE - C2010089A (19)

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Channel Characteristics The perennial nature of flow occurrence in Tuttle Draw in the vicinity of the NHN permit area is largely due to irrigation. Tuttle Draw is developed on resistant bedrock. The deeply incised yet stable characteristics of the main channel in Tuttle Draw can be attributed to the increased influence by man's activities. In a typical semi -arid environment, (12 to 15 inches annual precipitation), channel geometry and course generally reflect the infrequent and highly variable discharges and sediment loads resulting from intense summer thunderstorms. Semi -arid ephemeral channels often feature shallow and wide bottoms with unstable bank -sides. Ephemeral channels will adjust geometries and courses to accommodate the varying discharges and high sediment loads, often radically changing local reach geometries and courses during large, flash flood events. However, as more upland areas are transformed from natural, semi -arid vegetation to pasture, hay -land and cropland by irrigation, stream -flow variability (discharge and sediment loads) becomes dampened and is controlled by the increased vegetation and manipulation of the drainage system. This results in channels becoming more stable and often more incised, due to lower, less variable flows with lesser sediment loads. This occurrence is reflected in the main channel of Tuttle Draw. Predicted Peak Flows The annual mean and peak discharges were predicted for Tuttle Draw using techniques outlined in the USGS Water Resources Investigations Report 85-4086 titled Estimation of Natural Stream -Flow Characteristics in Western Colorado (Kircher et al. 1985). Using the regression model for the southwestern region, the mean annual discharge and peak discharges from the 2-, 5-, 20-, 25-, 50-, 100- and 500 -year recurrence intervals were predicted at two locations for Tuttle Draw, (see Table 7-38, Volume B of New Horizon 1 Reclamation Plan included in Appendix 2.04.7-2 of this application). Relationships Among Flow, TSS and TDS The interrelationships among certain physical and chemical parameters in surface water often control the chemical quality. Generally, as the discharge (flow) of a stream increases, so does the concentration of total suspended solids (TSS). For streams that commonly experience elevated levels of TSS (104 to 105 in semi -arid environments), total dissolved solids (TDS) is commonly inversely related to TSS, that is, as TSS levels increase, TDS concentrations will decrease. This inverse relationship between TSS and TDS will result in lower proportions of dissolved constituents while conserving the total chemical load of the water. Stock Water Ponds There are a few stock ponds within the permit as shown on Map 2.04.3-1. All surface water bodies shown on Map 2.04.3-1 are owned by the surface landowners. Historically, the ponds were filled with water during irrigation season but dried up during winter months. Now these ponds have dried up since the 2nd Park Lateral water has been diverted through the HDPE pipeline prior to the ponds being mined through. Replacement of the ponds during reclamation will be at the discretion and direction of the surface landowner. The ponds are typically used for livestock watering at the discretion of the surface landowner. WFC owns a surface water body adjacent to the NHN permit area and uses water from that pond for dust suppression at the NHN Mine. Section 2.04.7 Page 25 April 2016 (PR -01)