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~ ~ III IIIIIIIIIIIIIIII Rimrock Mine Sediment Pond Certification The site inspection was conducted on March 31, 2000 1[ was a partly sunny day of 36 degree temperature and it appeared that no precipitation had occurred in the previous week. The pond was mostly dry except for 3 inches of water in the low area near the principal spillway inlet. There were signs of snowmelt in the past two weeks although the pond showed no sign of discharge. The surface was wet from the snowmelt in the shade and was dry in the sunshine. The pond itself was free of any type of problem with stability or erosion. Engleville Gulch was also dry. The pond is to be left as a permanent impoundment for use in the grazing operation. The following items were checked to see if they coincided with the design shown in the mine permit application. I, Greg Lewicki, did the pond design in March of 1990. 1) Constructed Elevations: The elevations listed below were checked with a precision level and stadia rod: -Dewatering pipe inlet -Dewatering pipe outlet -Top of Dam -Bottom of Emergency Spillway -Toe of Dam (outside and inside) -Bottom of Pond -A number of points within the pond All elevations were found to be acceptable. The inlet to the principal spillway was placed at a slightly higher elevation to allow more sediment storage. The 10 year - 24 hour runoff storage was still present above the principal spillway. 2) Width of Emergency Spillway Design: 12 feet. Measured: 12.2 feet. 3) Depth of Emergency S~Ilway Design: 1.55 feet. Measured: 1.60 feet. The spillway showed no evidence of flow or any signs of erosion or other instability. 4) Width of to~of Dam Design: 10 ft. Measured: 10.2 ft - 10.6 feet. 5) Principal Spillway Design: 4.0" pipe placed in compacted embankment. Measured: 4" steel pipe placed in compacted embankment. Extensions on this pipe were added to both sides so that the embankment could be widened. Some black plastic hose was also present near the spillway at the time of the inspection but was not functional. The principal spillway pipe was completely free of debris and was functional during the site visit.