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<br />~i <br />Also, specify how stockpiled plant growth medium will be stabilized until used <br />in reclamation, and indicate the location of stockpiles on Exhibit E-map. <br />You have indicated that a crusher, screening plant, batch plant, and possibly a <br />wash plant and asphalt plant, scales and an office may be located on the site. <br />If any of these facilities are going to be on a concrete foundation, the cost <br />of removing the structure must be included in Exhibit D under reclamation <br />COSt9. <br />You have indicated that ground water <br />The Soil Conservation Service descri <br />indicates that the water table is 12 <br />location. Be aware that you will be <br />if ground water is exposed, you will <br />the Office of the State Engineer. <br />will not be encountered during excavation. <br />~tion included in this application <br />to 18 inches below the surface at this <br />limited to very shallow excavations, and <br />be required to obtain a well permit from <br />You have stated that no disturbance to the hydrologic balance or off-site <br />damage will occur as a result of this operation. The proposed mine plan <br />indicates that excavation will take place in an intermittently active river <br />channel. The undisturbed river channel is currently in a state of dynamic <br />equilibrium, any excavation within the river channel will disrupt the <br />equilibrium, and lead to disturbance of the hydrologic balance and off-site <br />impacts which may include: <br />1. Headward erosion or down-cutting upstream from the excavation. The stream <br />will establish a new gradient to compensate for the lowered base elevation <br />created by the excavation. <br />2. Scour downstream from the site will result. Removal of the stream bed <br />gravel will create an area of net deposition, in other words, the stream <br />will dump its sediment load in the area of excavation. The flow exiting <br />the site will be stripped of its sediment load, and will scour the river <br />channel and beaches to re-establish its equilibrium sediment load. <br />3. Lowering of the water table. Excavation of channel gravels will lower the <br />water table in the area of excavation, as well as up and downstream due to <br />headward erosion and downstream scour. This may have a deleterious impact <br />on riparian vegetation which relies on groundwater as a source of <br />moisture, and may impact nearby water wells. <br />PLease assess the affects of these impacts, both up and downstream, on <br />structures (bridges, irrigation diversions, roads, residences, etc.j, water <br />wells and riparian vegetation, stream bank stability, and aquatic life forms. <br />Describe how you will minimize possible adverse impacts of in stream <br />excavation, including a description of river geomorphology for 1 mile up and <br />downstream of the site. This description should include a profile of the <br />stream gradient, selected cross-sections of Che channel, as well as data on <br />seasonal flow volumes and stream and bed sediment load. <br />-2- <br />