HYDRO27179 - Laserfiche WebLink

Home Browse Search

Rimrock Mine Sediment Pond Certification The site inspection was conducted on June 27, 1999. It was a sunny day of 87 degree temperature and it appeared that no precipitation had occurred in the previous week. The pond was dry and showed no sign of discharge in the past three months. 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 [he 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 yeaz - 24 hour runoff storage was still present above the principal spillway. 2) Width of Emergenc~Spillwav Design: 12 feet. Measured: 12.2 feet. 3) Denth of Emergenc~Snillwav 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: ]0 ft. Measured: 1U.2 ft - 10.6 feet. 5) Principal Saillwav 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.