Revised Stormwater Management Report

DocuSign Envelope ID: DB0533B0-B14B-449D-A0A8-3B9C3C0DF5D9 Point of Analysis 3 Point of analysis 3 discharges to an existing drainage system in Howell Drive. This municipal system flows to the east away from the onsite streams. This drainage area is only for disturbance associated with one half of the emergency access road which will be gated closed and will have little vehicle traffic. The design achieves stormwater management standards of quantity , quality and recharge with the use of a small scale subsurface infiltration basin with soil replacement. Filterra water quality treatment devices will be provided prior to discharge to the system. Existing Conditions are: woods with light underbrush. The existing Tc is calculated with the following factors. 70 LF. Of sheet flow @12% with woods coverage Tc= 7.6 minutes 40 lf of shallow concentrated Flow @ 12% woods cover. Tc= .4 Total Tc=8 minutes The proposed Tc is calculated as follows: 50 lf sheet flow @ 12% grass Tc = 3.8 60 lf @ 12% grass swale Tc= .2 Total Tc = 4 minutes. PA-3 Summary STORM 2 10 100 EXISTING .13 .30 .66 PERMITTED .06 .21 .53 ` 11 BASIN 12 0 0 0 TOTAL 0 0 0