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<br /> <br />Rimrock Mine Sediment Pond Certification <br />s , <br />The site inspection was conducted on December 20, 1998. It was partly clear, partly <br />.cloudy day of 28 degree temperature and no appreciable precipitation had occurred in <br />the previous fe~v days. A slight amount of fresh snow flurries (<%: inch) was present <br />on the ground. The pond contained no water or ice and had only a light dusting of <br />snow in the bottom and on the banks. Engleville Gulch was also dry. The pond is to be <br />left as a permanent impoundment for use in the grazing operation. <br />The following items were checked to see if they coincided with the design shown in <br />the mine permit application. I, Greg Lewicki, did the pond design in March of 1990. <br />I) Constructed Elevations: The elevations listed below were checked with a precision <br />tevel and stadia rod: <br />-Dewatering pipe inlet <br />-Dewatering pipe outlet <br />-Top of Dam <br />-Bottom of Emergency Spillway <br />-Toe of Dam (outside and inside) <br />-Bottom of Pond <br />-A number of points within the pond. <br />All elevations were found to be acceptable. The inlet to the principal spillway was <br />placed at a slightly higher elevation to al}ow more sediment storage. The 10 year - 24 <br />hour runoff storage was still present above the principal spillway. <br />2) Width of Emergencv Spillway Design: 12 feet. Measured: 12.2 feet. <br />3) Depth of Emergency Spillway Design: 1.55 feet. Measwed: 1.60 feet. The spillway <br />showed no evidence of flow or any signs of erosion or other instability. <br />4) Width of top of Dam Design: 10 ft. Measured: 10.2 ft - 10.6 feet. <br />5) Principal Spillway Design: 4.0" pipe placed in compacted embankment. Measured: <br />4" steel pipe placed in compacted embankment. Extensions on this pipe were added to <br />both sides so that the embankment could be widened. Some black plastic hose was also <br />present near the spillway at the time of the inspection but was not functional. The <br />principal spillway pipe was completely free of debris and was functional during the <br />site visit. <br />.. .. ~.. .•c c.,s.~ ~.nyv .. .. .. !. <y ~- .• S f ~ .'i .~~ ~~~y~• ',`y,q~v.'e`cl ~ ~ 4J. n ... .. .~ r ~?~S.iN..:>_..du <br />