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Mr. Mark Klune WRC File: 1664/2 Page 3 This ditch (see Alt. A on Exhibit 2) bisects the pit area and would place limitations on the portions of the pit that could be mined. At a meeting on May 4, 1988, Mark Klune directed WRC to investigate the possibility of an alternative ditch paralleling the Booth-Orchard Canal along the northeast boundary of the pit. The idea of tying back into the Booth-Orchard Canal was discussed, but dismissed as a possibility because of a negative difference in elevation. On May 6, 1988, WRC along with Mark Klune conducted an additional field survey to determine the feasibility of diverting the flow from the Alt. A ditch to a diversion ditch paralleling but at a lower elevation than the Booth-Orchard Canal and avoiding the property not owned by Valco. We concluded that this ditch could be constructed at a slope of 0.6% + with a minor amount of excavation and using the over-burden to construct a dike parallel to the Booth-Orchard Canal for most of its length. See Alt. B on Exhibit 2. Proposed ditch cross sections are shown on Exhibits 3-A and 3-B. Conclusions and Recommendations 1. The Booth-Orchard Canal is not a feasible alternative for diverting the flaw from the arroyo for the following reasons: a) existing condition b) flat slope limiting capacity c) portion not owned by Val co 2. The straightened portion of the arroyo (Alt. A) can be used with a minimum of rehabilitation to carry the 10-year peak flow through the site. However this will limit the area of the pit that can be mined. 3. When the mining approaches the arroyo (Alt. A) a diversion ditch (Alt. B) can be constructed to divert the flows from Alt. A ditch along the northeastern part of the pit to the Arkansas River. WRC recommends that: 1. The existing straightened arroyo (Alt. A) be upgraded to carry the peak flow from the 10-year storm (600 cfs.) and be used while mining the west portion of the pit. 2. When mining approaches the arroyo, the diversion ditch (Alt. B) be constructed to divert the 10-year flow to the east and into the rive r. 3. Upon completion of the mining in the area of the arroyo, the drainage be allowed to flow into the lake created by the mining operations, and the diversion ditch area within the pit area be mined if desired.