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• Blue Ribbon Mine - AHR Page 4 <br />The flow through the 10 foot diameter culvert is calculated by measuring the depth of <br />flow at each end of the culvert. The depth of flow is converted to flow area. The <br />upstream and downstream flow area are averaged and multiplied by the flow velocity. <br />The flow velocity is calculated by determining the time it takes an object to float through <br />the culvert. The calculated flow in Hubbard Creek for the third quarter 1997 was 13.1 <br />cfs. It was calculated as follows: <br />Upstream Flow Area (26" Deep) <br />Downstream Flow Area (22" Deep) <br />Average Flow Area <br />Hubbard Creek Velocity (55'= 47 Sec) <br />12.5 SF (SF=Square Feet) <br />9.9 SF <br />11.2 SF <br />1.17 FPS (FPS =Feet per Second) <br />Hubbard Creek Flow (I 1.2 X 1.17) <br />HYDROLOGIC IMPACTS <br />13.1 CFS (CFS =Cubic Feet per Second) <br />The probable hydrologic consequences section of the permit, which begins on page 120, discusses <br />the impact the mine might have on the quality of water in Hubbard Creek. The quality of water in <br />Hubbard Creek is influenced by run-off it receives from the mine property. The mine could <br />• contribute both dissolved and suspended solids to the run-off from the property. The primary <br />potential sources of detrimental effects on water quality caused by the mining operation are or <br />were: <br />1) Increased erosion from land disturbance; <br />2) Increased oil and grease from use of machinery; and <br />3) Increased salt load due to water seeping through the mine bench which was <br />reconstructed with underground coal mine waste. <br />The erosion from land disturbance should be minimal to nonexistent because the mine was <br />reclaimed and vegetated in 1986 and sedimentation control features are in place and functional. <br />Oil and grease should not be a factor because there is little use of machinery on the property. An <br />increase in the conductivity measurements in downstream Hubbard Creek would indicate an <br />increased salt load. Enclosed is a graph which presents quarterly conductivity measurements in <br />Hubbard Creek from 1982 through 1998. The conductivity measurements vary between 87 and <br />420 umhos/cm but there is no indication the conductivity in downstream Hubbard Creek has <br />increased since 1982. <br />The 1998 hydrologic monitoring data indicates the hydrologic impact from the reclaimed mine site <br />is minimal to nonexistent. <br />• <br />