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3. Begin mining Phase 1 C. <br />4. Upon completion of mining in Phase 1 C construct permanent wetlands per the proposed <br />layout. <br />5. Continue to mine in Phases 1B, 3, or 4, while concurrently reclaiming the mined areas to <br />permanent wetlands using the wetlands in Phase 1 C as a buffer to prevent <br />non-compliance with COE regulations. <br />6. Once all of Phases 1B, 1C, 3, and 4 have been reclaimed to permanent wetlands, Phase 2 <br />can be mined without the need for any temporary wetlands. <br />5.4 Operation of SWSP <br />Kehn has continued irrigated agriculture on the northeast and southwest fields on the <br />Timnath Pit property. The SWSP documentation previously issued de;alt only with the <br />consumptive use of water in the gravel mining operation. Further analyses were performed to <br />include the current agricultural use in our consideration of the operation of the SWSP. <br />The average total irrigation water requirement for current crops over the 1960-1989 study <br />period is 205.1 AF. No consideration has to be given to return flows for this water because it is <br />being diverted and consumed as it had been historically. Tables G:l and (J.2 in Appendix G <br />address the consumptive use and irrigation water requirement of the crops currently cultivated on <br />the property. The mining operations in the Timnath Pit consume an average of 67.6 AF per year <br />based on the study period. Any water diverted as a substitute supply for the pit consumption will <br />require releases to maintain historic return flows. Based upon 40 percent total return flow that is <br />50 percent surface and 50 percent subsurface, the required yearly return flow for 67.6 AF of <br />' ~ diversions is 27.0 AF. The total yearly depletions are 299.7 AF. The average yearly historical <br />actual consumptive use of Boxelder water on the property was 323.8 AF. Subtracting the current <br />use from the historic consumptive use results in a surplus of 24.1 AF per year. A summary of <br />historic and current water use on the Timnath Pit property is provided as Table G.3 in <br />Appendix G. <br />Two avenues for the operation of the SWSP exist and may be found agreeable by the <br />State Engineers Office (SEO). Some bypass credit may be given for the 118.7 AF of <br />consumptive use water that can be shown as not being diverted for crop consumption, or a means <br />to divert, store and return the 94.6 AF substitute supply may be required. In the latter case, it is <br />our recommendation that the existing farm diversion and ditches be utilized, with any necessary <br />modifications, to divert the substitute supply into the pond created by the excavation of the pit in <br />Phase lA and pumped back to the river by means of permanent or portable pump with the <br />volume and timing indicated in Table G.3. In the case that this avenue of operation for the <br />T.IOPEMCodkcOllcodkc0! firm! ~•eporl.doc 22 ANdER50N CONSULTING ENC{INEERS~ ANC. <br />