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TABLE 13-3A-4 As-g uilt Storage Capacity Summary Pond 010 Capacity Elevation Staae (AC.-Et.l Descri ptlon 6776.00 0 0 Bottom of Pond Excavation 6784.00 8.00 9.56 Elevat ion of Principal Spillway G 1004 sediment storage 6787.54 11.54 19.33 10-Yr, 24-H r. Peak Stage 6787.60 11.60 19.65 Crest of Emergency Spillway 6789.89 13.84 27.24 25-Yr. , 24-Hr. Peak Stage 6790.36 14.36 29.15 100-Yr ., 2q-Ht. Peak Stage 6794.00 18.00 44.70 Top of Embankment Seneca does not anticipate any other inflow to the pond at this time. The principal spillway will be nonclogging and will automatically d ewater t he Ponding area to maintain the design capacity for the ru noff Volume for a 1 0-year, 24-hour storm even[. Any additional dewatering required wi ll be done by pumping the wat er out of the pond and using Lt for eith er dust sup ression or trans ortin It to anot her ond for treatment or p p g , p discharging the water according [ o the approved Colorado NPDES permit. Spillways This sediment pond has two separate spillways; a principal and an emergency. Please see Exhibit 13-4A for location of spillways. The principal spillway consists of a 6-inch diameter dewatering orifice cut Snto a 3fi-inch CMP riser which drops into the 24-inch CMP barrel. This pipe w311 keep the pond level at the 6784.0 elevation. Maximum estimated elevation (peak stage) above the principal spillway with the passage at the 10-year, 24- hour event will be 6787,54, this leaves 0.06 feet to the emergency spillway (elevation 6787,61. The embankment portion of the emergency spillway consists of a trapezoidal channel as shown on Exhibit 13-4A. Assuming the principal spillway was Plugged, the trapezoidal channel could safely pass the runoff volume from the 25-year, 24-hour storm. The emergency spillway outflow channel consists of a tlprapped trapezoidal channel which was • untlerlayed with Mira fl 600X geot extile Isee Addendum 13-3A-D for specificatlonsl~ 13-3A-8 Revised 08/30/96