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Sediment Measurement Techniques at the Sediment Ponds <br />1n order to evaluate the erosion at the three sites, it is <br />planned to compare the sediment volume that has been delivered to <br />the ponds for an approximate 9 year period to the standard for <br />the pre-mining sites. <br />The sediment in all ponds except for the Northern #1 Pond will be <br />determined by laying out a tape in each pond and recording a <br />measurement at 10 feet intervals in both directions along the <br />entire bottom of the pond with a Wild theodolite. Measurements <br />will also be made of the principal spillway, emergency spillway <br />and top of dam for known points of comparison to previous data. <br />Once the data is gathered for each pond, a contour map will be <br />generated for each pond and will be subtracted from the original <br />bottom of pond to determine volumes. <br />Knowing the time period elapsed since the original measurements, <br />an annual sediment load can be determined by dividing the total <br />sediment measured by the years that have elapsed. <br />In the case of the Northern #1 pond, the measurement technique is <br />complicated by the fact that the pond is always full of water due <br />to ground water inflow. It will be measured by anchoring the tape <br />• at 10 feet intervals across the pond and using a raft with a <br />stadia rod to measure the sediment level at each 10' x 10' grid <br />point. Once this is done, the volume of sediment is calculated in <br />the same manner as that described above and is compared to the <br />baseline standard. <br />• <br />R~S~ e~~6~ M-izu~ <br />g jq'43 <br />