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encounter ground water. Water samples have been obtained <br />from the Webb well to determine baseline values for water <br />quality. Samples will be analyzed on a routine basis tq <br />assure that water quality is not diminished by the <br />proposed operation. <br />Any proposed diversions from one channel to another <br />will be done at non-irrigation times so that downstream <br />users are not adversely affected. <br />SILTATIDN: The streambed material in this area i5 <br />naturally quite coarse since the source of the alluvium <br />is within several miles of this location. A screen test <br />of typical material is summarized below: <br />Screen Size Weight Percent <br />1" 57.9% <br />1/16"- 5/8" 22.9% <br />1/16" 4.5% <br />With less than 10% of the material passing a No. 10 <br />sieve, a very small amount of material would be <br />classified as silt. As discussed in the buckhorn Geatech <br />information, the decreased velocity of the water as it <br />passes through the mined areas allows far the deposition <br />of the bed load. Mast of the material being transported <br />by the river from disturbances in the er.cavated areas <br />will be redeposited before leaving the property. <br />In additign, two 48" culverts will be installed in the <br />Phase I er.cavated area to provide a crossing to the Phase <br />I1 area while it is being mined. The location of these <br />culverts is shown on the Plan View and the Cross <br />Sections. <br />OFFSITE IMPACTS: Headcutting, bank erosion and <br />scouring are all addressed in the buckhorn Geotech <br />information. A wire/rail erosion control structure will <br />be installed at the south end of the permit area to <br />prevent potential headcutting upstream. Potential bank <br />erasion will be controlled on the southwest with riprap <br />and on the southeast with the wire/rail structure added <br />along the er.cavated area, extending northward to the <br />riprap near the Cottonwood tree boundary. Potential bank <br />erasion near the northwest corner of the property will be <br />controlled with riprap which will also provide channel <br />control where the diverted flow re-enters the er.isting <br />channel. Scouring downstream appears unlikely since the <br />calculated flaw velocity, where the streambed gradient <br />returns to the pre-mining slope, is very close to the <br />pre-mining bank-full velocity. <br />The temporary diversion dike, which is to be <br />constructed after Phase I mining, is not intended to <br />withstand a 100-year flood event. The dike will fail if <br />Page ~ (Application) <br />