Laserfiche WebLink
NUCLA PR NO. 2 <br /> Response: <br /> Exhibit "13-5" has been revised to outline the entire Nucla East <br /> watershed area and the hydraulic length of the watershed has been added <br /> to the map. <br /> Comment: <br /> 12. Postmining land use consists of irrigated pasture (page 22-16, Tab <br /> 22) . Has pond 007 sizing taken into account the irrigation return <br /> flow from this proposed activity? If not, this needs to be <br /> incorporated in your plans. <br /> Response: <br /> On pages 7-119 to 7-122 is a discussion of the historical irrigation <br /> flow within the Calamity Draw watershed. Surface water monitoring site <br /> SW-N102 is established on a small tributary of Calamity Draw that <br /> returns irrigation return waters from irrigated fields to the main <br /> channel of Calamity Draw (see Exhibit 7-1) . Measured flows ranged from <br /> 0.1 to 2.2 cfs. This low order of magnitude-type flow will have an <br /> insignificant impact on Pond 007. Pond 007 is designed for the 10-year, <br /> 24-hour storm with a peak inflow rate of 81.5 cubic feet per second (see <br /> Attachment 13-G, Addendum A) . Irrigation flows of this low order of <br /> magnitude will have an insignificant impact. The pond could be assumed <br /> full to the principal spillway when the irrigation water is "turned on" <br /> and Pond 007 will still provide adequate detention time and the <br /> principal spillway is adequately sized to handle a much larger flow than <br /> occurs during the irrigation season. <br /> In addition, the primary irrigation method proposed on page 22-22 is <br /> sprinkler irrigation. Sprinkler irrigation will have very limited <br /> return flow because typically sprinkler irrigation water application can <br /> be controlled to saturate an area without creating excess runoff. Using <br /> this method, the runoff into Pond 007 will be negligible. <br /> Comment: <br /> 13. On page 9 of Attachment 13-G the density of 87 lbs./cu.ft. seems <br /> high. Please justify the use of this density number. Also, it is <br /> stated that 2,667.4 tons of sediment will be deposited in pond 007 <br /> as a result of the 10 yr. , 24 hour storm. How was this value for <br /> tons derived? <br /> Response: <br /> (a. ) Sediment density in a pond that has not been constructed can be a <br /> very subjective matter. In addition, sediment density is a time <br /> dependent value with the density increasing with the increase in years <br /> after deposition. From Peabody's experience in the Western, U.S.A. , <br /> 19 <br />