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Flatirons, Inc. — Surveying & Engineering <br />Sediment Area Summary <br />Description <br />Area <br />(ac) <br />10 -year, 24 -hour <br />Volume <br />(cf) <br />Available <br />Volume <br />(cf) <br />Location <br />Basin A <br />3.96 <br />11,944 <br />11,944 <br />TSF <br />Berm Contact* <br />0.29 <br />674 <br />11,944 <br />TSF <br />West TSF Contact <br />0.24 <br />258 <br />1900 <br />West Side of TSF <br />South TSF Contact <br />0.48 <br />517 <br />750 <br />South Side of TSF <br />Table 2 <br />*Berm Contact volume is included in Basin A <br />TSF Emergency Spillway <br />The emergency spillway for the TSF is located on the east embankment at the northeast <br />corner. Flow from the spillway travels approximately 10 feet in the TSF Spillway Chute <br />channel down the outside face of the TSF and into a 2 -feet deep channel with 3 to 1 side <br />slopes. The TSF Spillway Chute channel will direct flows to the TSF Spillway channel at <br />the toe of the TSF embankment which will in turn direct flows southeasterly away from the <br />toe of the TSF and convey the flows to the East Diversion channel. The TSF Spillway <br />channel is separate from the South TSF Contact channel. The top and outside face of the <br />spillway, the TSF Spillway channel, and the Spillway Chute channel will be protected by <br />riprap and underlain by a non -woven geotextile fabric. <br />The spillway is designed to pass twice the peak 100 -year runoff directed to the TSF <br />without raising the water surface elevation more than half the height (0.5') at the top of the <br />spillway. The 100 -year peak flow from Basin A to the TSF is 11.4 cfs. The spillway is <br />designed to pass 22.8 cfs, and not exceed a depth of 0.5 feet. The emergency spillway is <br />30 -feet wide, and lined with 10 -inch riprap (d50) from the top of the spillway to the toe of <br />the TSF embankment. <br />Calculations for the emergency spillway, the TSF Spillway Chute channel, and the TSF <br />Spillway channel can be found in Appendix B. Detail drawings of the spillway and <br />- channel cross sections are found on Drawing D -2 in the map pocket in the back of this <br />- report. <br />Open Channels <br />Ditches and swales are used to convey surface flows around and through the property. The <br />channels prevent mixing offsite flows with flows from impacted areas. The channels are <br />Union Mill 11 March 5, 2014 <br />