2020-04-06_PERMIT FILE - M2019054 (2)

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Plateau Hanford Site is a semi-arid shrub-steppe ecosystem with hot, dry summers and cold,wet winters (Easterly et al. 2017).The semi-arid climate presents a number of dust control challenges. Soil moisture at the surface is relatively low throughout much of the late spring,summer,and early fall,and the dry soil conditions increase the susceptibility of disturbed soils to wind erosion. Winds at Hanford typically average between 7 and 8 mph and wind gusts over 25 mph are common (43%of year) (Hoitink et al. 2005).The shrub-steppe landscape is water-limited,with an average of 7 in/yr(177 mm/yr) precipitation and natural recharge rates varying up to 4 in/yr(100 mm/yr)depending on land cover (Hoitink et al. 2005;Truex et al., 2015).These conditions lead to relatively sparse and short vegetation (< 2 m height)compared to wetter environments(Hoitink et al. 2005).The biological soil crust(e.g. mosses, lichens, and algae that typically act to stabilize the soil surface in undisturbed communities and minimize water and wind erosion) is fragile and does not readily reestablish after soil disturbance. Due to limited water and low-density vegetation cover, Hanford soils tend to be particularly susceptible to wind erosion and fugitive dust emission, as are the soils in the Skull Creek area. However, by applying the published low and high application rates of 2 mm/ft2 and 100 mm/ft2 to the square footage of area for which dust suppression is likely to be needed,the range of water volume needed for dust suppression can be estimated: The Strip Mine has indicated that they will be excavating on approximately 140 acres of land at the proposed site. If we assume that they will require dust control on 20%of that excavation land at any given time,approximately 28 acres of land will require daily dust control. The Moffat County Department of Roads and Bridges will require that the ingress/egress from the site to State Highway 40 along the westerly route be maintained for dust control. 3.29 miles of County Road 104= 17,371 linear feet,x 20 ft.wide=347,424 sq.feet. 347,424 ft2 x 1 ac =7.98 ac 43,560 ft2 7.98 ac of County Road+28 ac of mining activity= 35.98 ac requiring dust suppression At the conservative water application rate of 2 mm/day/ft2: 2 mm x 35.98 ac x 43,560 ft2 x 1 inch x 1 ft x 7.48 gal =76,925 gal per day -day 1 ac 25.4 mm 12 in ft3 At the high end of published water application rates of 100 mm/day/ft2: 100 mm x 35.98 ac x 43,560 ft2 x 1 inch x 1 ft x 7.48 gal =3,846,234 gal per day -day 1 ac 25.4 mm 12 in ft3 At a recommended application rate of 4.5 mm/day(Yonkofski et al,Table 4-3, pg 4.7): 4.5 mm x 35.98 ac x 43,560 ft2 x 1 inch x 1 ft x 7.48 gal = 17,284 gal per day day 1 ac 25.4 mm 12 in ft3 At the low end of the published application rate of 2 mm-ft2/day,the mine would consume its annual allotment of 325,851 gal (1 ac-ft/yr) in 4.2 days. At the high end of the published application rate of 100 mm-ft2/day,the mine would consume its annual allotment of 325,851 gal (1 ac-ft/yr) in 0.085 days.At Skull Creek Homeowners pg 2