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~_ - 2 - <br />' requires them. Some facilities are, however, required immediately <br />and these have been or are in process of construction. <br />1972 Thorne Report Water Summary <br />The Thorne study identifies the following water and drain- <br />' age related areas of concern: <br />' 1. [4ater yield from Strain Gulch has little significance under <br /> normal consideration. There is a potential, however, for <br /> damaging flash floods from high intensity summer storms. <br />' 2. The quarry operation will have little, if any influence on <br /> the volume of flood flow that may come from the watershed. <br /> 3. Drainage facilities should be provided to allow safe pass- <br />' age of the 100-year flood through the operations area with <br /> due regard to provisions for debris, sediment control, and <br /> erosion protection. <br />' 4. Drainage water should not be allowed to flow uncontrolled <br /> over the end slope of the operating area fill. This area <br />' should also be stabilized to protect against erosion. <br /> 5. The quality of water from Strain Gulch is general:Ly better <br /> than the quality of water in its receiving stream, Bear <br />' Creek. <br /> 6. Consideration must be given to provisions for drainage for <br />' the road to the top of the quarry. <br /> During the mining operation there will be some modification <br />' to historic drainage patterns. Following completion oi` the <br /> mining and rehabilitation of the area, drainage will also have <br />' been modified from the historic condition. The potential for <br /> damaging flash floods from high intensity summer storms exists <br /> under the historic condition as well as future conditions. <br />' This report will define drainage facilities required during the <br /> mining operation so that the damage potential to downstream <br />' areas is not increased over the historic condition, and gener- <br /> ally will describe possible drainage considerations after <br />' mining is completed and the area has been rehabilitated. The <br /> facilities required during mining when erosion and sediment <br />' will be major problems will be different from those required <br />' j~\ Leonard Rice Consulting Water Engineers. h: ~~~`~ <br />