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~' • • <br />~II ~I~~I~~I~~~~~ ~I~ <br />sss <br />DATE: November 22, 1993 <br />T0: Bill York-Feirn <br />FROM: Berhan Keffelew <br />RE: Permit No. M-93-043 - Hydrology Review <br />As requested I have reviewed the hydrology portion of the application <br />Exhibit G and the DOW flats project summary. Mining, reclamation, and water <br />storage and the following comments. <br />The mining plan shows the operator plans to mine the headwater of the <br />channel in the southeast portion of the second ridge. <br />a. What is the peak flow for this stream or channel? <br />b. Is the entire stream going to be mined? If so, how is it going to <br />impact the entire water balance of the downstream area? Please <br />provide quantitative data to show the water contribution to overall <br />hydrologic balance both surface and ground water so the Division <br />can make a determination of the impact to downstream water users. <br />c. Are there plans to expand the mining beyond the 4th ridge? If not <br />are there plans to place upland diversions along the maximum <br />extensions of the pit area around the northeast corner of the 3rd <br />ridge to avoid drainage from entering the unnamed drainage channels <br />on the west side. <br />2. Operator provided surface water sub basin areas. No peak flows were <br />calculated for the unnamed stream channels. Please provide the peak <br />flows for these channels and the entire sub water basins. The following <br />criteria must be used to determine peak flows. <br />a. Acreage of watershed. <br />b. Type of soil. <br />c. Type of vegetation. <br />d. Slope of the drainage area or hydrolytic length for the evaluation <br />should also include the impact the mining operation is going to <br />have on the overall drainage water supply contribution to the <br />irrigation ditches and canal due to the creation of a large pit or <br />quarry. <br />