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( . _ . <br /> ( Housing Hope Short Plat <br /> Drainage Analysis <br /> � Page 5 . . <br /> ( �or the second phase,expected to begin in late fall,construction on the sites will be limitec!to aroas <br /> up-slope from tlie creek setback line.The wei vaults will be installed prior to any b4ilding/road <br /> Iconstruction. The wet vaults will then be used to manage dra�nage that occurs during the building <br /> construction. <br /> In the Spriag/Summer 1'997,conswction of foot bridges and uails and planung of riparian <br /> vegetadon in the croek corridor wi4l occur. <br /> Brainage Calculations and Methuds <br /> 9JaterWorks (Vr,rsion d.l lg)computer software progra�n has been utilizetl I.o analyze the dtainage <br /> basins for th2 site and design the wet detention vaults. An SCS Type IA storm was used in th� � <br /> unalysis. Surface water runoFf flow rates, storage volumes, time of concentration, and inflow <br /> � rates,etc„ weie estimated by WaterWorks software. Additional calculations and assumpdons <br /> used for dee drainage-analysis such as grit removal volume requirements, peak flows in Pigeon <br /> � Creek, off-site runoff ra�es, etc.,ae provided in the Appendix. <br /> Cunclusion and Recornmendations <br /> L .. . _ . . <br /> Since the d;,tention system is sized to release stoim water within O.a2 efs or below er.isting <br /> ! conditions�vnofF rates, it is ow•opinion that there should be no signiCicant adverse drainage <br /> � impacts associated witli die subject development provided the detailed conswction drawings are <br /> � prepared and u•e f�;llowed with rire. <br /> � Temporary Erosian ConU•ul Measores <br /> Standard BMP's would be empbyed to prevent silt laden waters from being deposited on the <br /> lexisting streets' syszems or from ente�•ing Pigeon Creek. BMP's could include but not be limited <br /> to rock construction enhances, silt fencing ac tces of 511s, slope stabilizntion for cud ill slopes, <br /> ( and/or liay bale check dams in constnicted swales. The need for temporary siltation ponds would I <br /> also be evaluated. The detention vaults and wall (along driveway on Lot 1-3)constructed at the � <br /> Istu�t of phase two,could be used as siltation convol measures during the main buildinp�road <br /> x � <br /> I <br />