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Rimrock Mine Sediment Pond Certification <br />The site inspection was conducted on September 24, 2003. It was a sunny warm day of <br />approximately 70 degree temperature during the visit. The pond contained a fairly <br />significant amount of water in the deepest portion of the pond (approximately 12-18 <br />inch depth). The water in the pond was very cloudy from suspended clay. There were <br />no erosional problems or any other stability problems with the pond and there was no <br />evidence that the recent storm had caused a discharge in the principal spillway. Both <br />spillways were functioning properly. Engleville Gulch was wet at the surface in some <br />areas. Vegetation was strong on both the inside and outside slopes of the embankment. <br />The pond is to be left as a permanent impoundment for use in the grazing operation. <br />The staff gage in the pond showed 3.7 feet and since the bottom of the sediment level <br />is 2.0 feet, the water level was 1.7 feet high. <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 />1) Constructed Elevations: The elevations listed below were checked with a precision <br />level 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 allow more sediment storage. The 10 year - 24 <br />hour runoff storage was still present above the principal spillway. <br />2) Width of Emergency Spillway Design: 12 feet. Measured: 12.2 feet. <br />3) Depth of Emer ency Spillway Design: 1.55 feet. Measured: 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 site <br />visit. <br />