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' ponds and be released to the gulches below. In later mining stages when <br />a pit has been excavated, the water will be captured in the pit; it will <br />then percolate into the groundwater table and emerge in downstream <br />areas. <br />t Under historic conditions, Che peak flow in Unnamed Gulch A resulting <br />from a 6-hour, 100-year storm is approximately 200 cfs; the peak flow in <br />Unnamed Gulch B under the same conditons is approximately 130 cfs. <br />' Under the drainage plan outlined in this report, the peak flow rate in <br />Unnamed Gulch B will never exceed 100 cfs. The peak flow rate in <br />Unnamed Gulch A will depend on the final design of components of the <br />' quarry's internal drainage system, but will not exceed the historic rate <br />of 200 cfs for the 6-hour, 100-year storm. <br /> The effects of the expanded gravel mining operation on water quality <br /> parameters are not expected to be significant. Based on information <br /> contained in the Thorne report, a short-term increase in the sediment <br /> load in Bear Creek and Turkey Creek is probable following high-intensity <br /> storms in the area; these effects should only be noticeable for a <br /> distance of about two miles downstream from the site, where Bear Creek <br /> and Turkey Creek enter Bear Creek Lake. <br />' Ground water levels are generally below the deepest portion of the <br /> quarry pit, as is evidenced by the fact that the existing pit is essen- <br /> tially dry. Similar geologic and hydrologic conditions should be <br />' encountered to the south of the present quarry pit; consequently, the <br /> proposed quarry expansion should have no noticeable impact on ground <br /> water quality or quantity. <br /> <br /> <br />11 <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br />Impacts on downstream water rights are not expected to be significant <br />during the course of the mining operations under Alternatives I and II. <br />Protection of these rights may be a more serious concern, however if the <br />mining or post-mining land use plan for the area calls for diverting <br />water into the pit to form a permanent lake or pond. In this event, it <br />may be necessary to adjudicate a water storage right for the pit and <br />construct an outlet works or other means Eor making controlled releases <br />of water to the natural channel(s) downstream. <br />Prepared by: <br />BISHOP ASSOCIATES, <br />:i~%~ r ~;~i: _ <br />~- <br />Michael J. Boyd <br />Reviewed by: <br />INC. BISH ~~ INC. <br />C~ F. isho <br />Water Resources Engineer <br />President ~~_~ F• 9ts\ <br />pr ~ ~aT_ ~q <br />~r ~ f h <br />~(, tUV11 1 <br />O ~~% <br />~' ,r\`:J <br />sT'9 FnSjOY.IIL ~'~ o ~~ <br />~FOF CD <br />R <br />