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1 1 1 - 5 ' center was determined to be appropriate. These holes wo ld extend vertically 4 feet requiring a total of six (6) rings o 42 total holes. c/ ' The Qaa storm was designed to outfall into the standpipe by using ll:e sharp-crested weir performance equation..Water will pond to a maximum depth of approximately one foot above the standpipe. This is based on a t~~tal /~ clogging of all perforations -an unlikely event unless a major storm occ~irs. ' The outlet Prom the upper pond will discharge to the lower pond and the lower pond will discharge into the natural drainage. The entire pipe system is designed to be 24" corrugated steel pipe (CSP). The pipe would be 16 gage with 2'/a- x '/s" corrugations. The emergency spillway has been designed to safely pass a Qioo storm event considering both the standpipe perforations and the standpipe are ' plugged. Size has been based on abroad-crested weir performance and a Manning's channel. This results Ina 23 Poot.wide spillway that operate:. at approximately of 6" in depth. The upper pond has been designed with rock ' riprap on the embankment portion of the outfall of the spillway. The lower pond has been designed with a spillway but no protection because a ~a:oo storm flow will likely never reach the pond. The outlet could, however, be plugged necessitating a spill capability. Outfall is onto a natural limestone roc' k. `~' 4~( Maintenance oP the sediment basin system is planned to be by visual ' inspection by the Operator after storm events. The depth of silt will be ~` ~+-'''`~ measured by painted depth marks at 1 Poot intervals on the vertical riser:o in ,(~ both ponds. Silt will be removed by the Operator's equipment onsite in the "l ~p~^' ' quarry. Silt will be transported to the quarry's waste stockpile. An 8 Poot wide maintenance road has been designed for front end loader access into both ponds. The Operator has "dragllne" equipment available to perform silt removal from the roadway !n the event access !s not possible.. ' The sediment pond system Is designed adjacent to the realigned access road. A 1:1 embankment will be cut resulting In the need for safety barrier. ' A standard Colorado Department of Highways (CDOH) Type 3 guard rail (W Beam with wooden posts) is proposed along the access road adjacent £o the ponds where the total depth exceeds Pour feet. ' Details of the sediment basin system design have been included on Exhibit C while grading is shown on Exhibit B. DESIGN CALCULATIONS ' The detailed design calculations are included In this portion of the TR•-20 model for hydrology of the area for the design storms followed by the hydraulic calculations for the sediment basin. 1