1010 N BROADWAY EVCC 2018-01-01 MF Import

CONVEYANCE DESIGN SUMMARY The proposed storm drain system is designed to convey surface runoff from the Everett Community College east parking lots,the !TC and surrounding area,. For sizing the lower part'€ the line,a future expansion area was assumed east of Broadway Ave(See Assumed Future Expansion Map). The pprkirg lots are divided int°two basins,designated A and B,which both currently discharge to Broadway rive. (see Current Conditions Map). The proposed storm drain system is designed to convey the.24hr,25yr storm evert which has a rainfall depth of 2.60 inch as defined in the COE Stormwater Management Manual. A peak runoff rate for each basin was, calculated with Waterworks st ttware l: ing the SBU I method. The Waterworks calculations art- included in Appendix A and ars:summarized below_ basin Peak Flow Parking Lot Basin A (3.1 AC) 1.8cfs Parking Lot Basin B (3.3 AC) 1.9cfs ITC Roof and Surrounding Area(1.8 AC) C.).7cfs Future Expansion—East of Broadway Ave. 3.5cfs The piles were sized to convey the 25yr runoff without exceeding 9f%capacity, A 12 inch pipe is adeguae to convey the runoff from the parking lots and ITC are... The line was upsized to an 18 inch along Tower St.to facilitate the possible future expansion f the college east of Broadway Ave(See Pipe Capacity Spreadsheet). Everett Community Colle February . 01 Stormwater Hydraulics Repot -6- Reid Jlsddiefali''