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Rimrock Mine Sediment Pond Certification <br />The site inspection was conducted on April 2, 2004. It was a cloudy mild day of <br />approximately 53 degree temperature during the visit. Weather reports stated that rain <br />was due for that day and clouds present at 1:30 PM confirmed that it would rain, the <br />site was extremely dry, as in bone dry. There was no water in the pond or in Engleville <br />Gulch. There were no erosional problems or any other stability problems with the pond <br />and there was no evidence that the recent storm had caused a discharge in the principal <br />spillway. Both spillways were functioning properly. Engleville Gulch was wet at the <br />surface in some areas. Vegetation was adequate on both the inside and outside slopes <br />of the embankment. The pond is to be left as a permanent impoundment for use in the <br />grazing operation. The staff gage in the pond showed 2.0 feet of sediment level and no <br />water above that point. <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 Spillwav Design: 12 feet. Measured: 12.2 feet. <br />3) Depth of Emergency 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: ] 0 ft. Measured: 10.2 ft - 10.6 feet. <br />5) Princinal S illway 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 />