complete drainage report rev 9

Docusign Envelope ID: E802A2F1-2485-417E-948D-E0A4008C75BD The summary of the existing conditions discharges is as follows. Hydrocad output for the existing conditions is provided in the appendix of this report. 2 YR 10YR 100 YR POA-1 7.08 15.93 35.21 POA-2 17.53 38.43 83.14 POA-3 .13 .32 .75 Proposed Conditions Point of Analysis 1 (POA#1) POA#1 is the area of the site that drains to the Canoe Brook in the western portion of the property. The stormwater management systems designed for this are Large Scale Basin #1, and porous pavement systems 5&6. Large Scale Infiltration Basin #1 This stormwater system collects water from Kusik Drive some new building roof areas and the lawn areas adjacent. The proposed Tc for the area flowing to Detention 1 uses the following input Sheet flow 59 lf @2% over grass Tc= 9 minutes Shallow concentrated flow 425 lf over pavement @ 6.5% Tc = 1.7 minutes Pipe flow 425 lf pipe , 2.5 fps Tc = 3.4 minutes Total Tc = 14.1 minutes Basin 1 is designed as a large scale basin without exfiltration as an outlet. The Basin details do include soil replacement with a permeable sand to allow infiltration to occur. Water quality is achieved with MTD’s at each inlet location to meet the water quality requirement. 5