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Mike Boulay -30- April 11, 2011 <br />CAM : Sediment pond 4 no longer exists. Design for ponds 1 and 2 are shown <br />on Map-13. Ponds 1 and 2 are entirely in cut, no embankment will be <br />constructed for either pond. <br />54. The Division has a general concern regarding the sediment pond designs and <br />their location. The long ponds immediately adjacent to the railroad track <br />embankment could cause stability problems over time due to saturation of the <br />embankment fill. Does the design and location of these ponds meet the Union <br />Pacific railroad's requirements governing the construction of embankments? <br />CAM : No longer applicable. The railspur could be considered as a haul road <br />not in the disturbed area as defined in Rule 4.05.2(4) and, therefore, falls under <br />Rule 4.03.1(4)(iv), best management practices will apply. Please see revised <br />sediment pond configuration as shown on Map-16. <br />55. Under Rule 2.05.3(4), in the Sedcad designs, CAM is using 1.4 inches, 1.8 <br />inches and 2.2 inches as the design precipitation events for the 10 yr 24 hour <br />event, 25 year 24 hour event and 100 year 24 hour event respectively. However, <br />referring to the NOAA Atlas 2 "Precipitation-Frequency Atlas of the Western <br />United States", the Division obtained values of 1.6 inches, 2.0 inches and 2.6 <br />inches respectively. It appears that CAM may have used the NOAA May to <br />October precipitation event figures rather than the NOAA annual precipitation <br />event figures. Please justify the precipitation event values used in the <br />Sedcad designs or revise the Sedcad designs accordingly. <br />CAM: Precipitation values have been revised. Please see revised Exhibit 9. <br />56. Under Rule 2.05.3(4), in the Sedcad designs for the west culverts, a curve <br />number of zero is used for the irrigated wetlands area, citing a ground cover of <br />100% as justification for that curve number. If the wetlands are saturated or are <br />comprised of standing water, a precipitation event could produce runoff, in spite <br />of the vegetative cover. Please describe the nature of the wetlands as it <br />relates to the determination of the curve number. <br />CAM: Revised the Curve Number to 74, based on cover of 97.33%, which equates to <br />"Good", for a soil type of 'C'. Please see revised page Exh 9-49. <br />57. Please add a more detailed description in Section 2.05.3(4)(a)(ii)(C) on permit <br />text 2.05-18 and in the Probable Hydrologic Consequences Section <br />2.05.6(3)(b)(iii) starting on permit text page 2.05-49 for the process of dewatering <br />the sediment ponds, including how Reed Wash will be protected from erosion <br />and siltation from disposal of the pond water.