2506 MELVIN AVE 2018-01-02 MF Import

� P/illows Apartmrnts ihainage SNdy C09/162009 SITE Hl'DRAULIC ANALYSIS (conw) 1 Pervious Pavement Desi�(contJ : � Pervious Pavement CN Correction: Since the Sidewalk&Patio Surfaces will be"Pervious or Porous Cement Pavements" a cornction in the cuc�off coefficient from these surfaces is wazranted (� to retlect their reduced impact on the stormwater volume from this project. 1 Pervious Pavement CN factor correction: � Sidewalk& Patio Surface Area=2,400 SF (ti.055 Acres) Let CN =90 Impervious CN =(0 188 +0 01341(981 +0.055(90)=96.43 Tc = 7.0 0.256 Pervious CN=86 Tc= 10.00 ' P(6-month)= 0.99 p2 = 1.5 P10 = 2.2 �_ P100 = 3.2 � Sidewalk Pervious Pavement Design Total Sidewalk Area=7,A9fff'SF 3�ti q Proposed Pervious Paving= 1,500 (6�/0) =0.0344 ACRES ' Potential Void Space Volume with underlying porous material with voids=030 1-foot depth • 1,500 SF " 03 45�CF Safety Factor= 1s i 0/496 = L633 IWe will treat the proposed porous sidewalk as a potendal infiltration trench. At issue, is whether the soil fa;�print under the porous concrete surface can absorb the storm runoff collected into the void spaces. The geotechnical repott indicates that the absocption of ' runoff is feasible in the reaz of the site due t the presence of advance outwash soils below a depth of 3 to 5 feet. These soils were considered suitable receptor soils for infiltration dischazge. A long term infiluation rate was pmvided to be 2.0 in/hour or 30 min/in. With ,_ a Safety Factor of 2 we can design with a percolation rate of 1"/hour or 60 min/in. By routing the 2-yeaz, 10-yeaz and 100-yeaz hydrographs across the proposed pervious � pavement surface assuming 1-foot of pervious sub-grade with 30% void space, we find that our pervious pavement can easily dispose of the expected storm water flows. 1 � � � PROIECT:OSdIl �