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<br />1 <br />1 <br />1 <br /> <br />1 <br /> <br /> <br /> <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />1 <br />the outlet of the riser pipe. The 8"PVC WQCV riser pipe will connect to the 36" CMP riser <br />pipe. <br />The 16' wide emergency spillway will be placed at 9187.50 so as not to be used during normal <br />operations. Assuming failure of the riser pipe, the emergency spillway is designed to release the <br />proposed 100-year flow of 98.79 cfs at a depth of 1.5'. The top of the pond will be placed at <br />9190.00 to give a 1' freeboard above the emergency spillway. Please see Appendix ] :Rational <br />Calculations. <br />EROSION CONTROL <br />Genera! Concept <br />All ditches will be designed to meet PPACG criteria for slope and velocity. During construction, best <br />management practices for erosion control will be employed based on PPACG. <br />Detention Ponds <br />The detention pond will act as the primary erosion control facilities for this site. The pond will <br />serve dual purposes in facilitating the settling of sediment in runoff during and after construction, <br />and in maintaining runoffto existing levels. With the additional WQCV, sedimentation during <br />small (2-year) storms will be controlled. <br />Sih Fencing <br />Silt fencing will be placed as necessary to prevent suspended sediment from leaving the site during <br />construction. Silt fencing is to remain in place until vegetation is reestablished after completion of <br />construction. <br />Erosion Bales <br />Erosion bales will be placed within the site as necessary in drainage swales. Erosion bales will <br />remain in place until vegetation is reestablished in drainage swales. <br />miscellaneous <br />Best erosion control practices will be utilized as deemed necessary by the Contractor or Engineer <br />and aze not limited to the measures described above. <br />\\Urw16T6742321 U1u1e Creek Gravel PuUteporlv\Dravuge Report 032100.doc <br />