251203_42 ERW_Stormwater Report

Project Name 42 ERW Description Proposed Site Improvements Recharge BMP Input Parameters Parameter BMP Area Symbol Unit 5646.0 sq.ft dBMP 3.6 in dBMPu 76.8 in dEXC 85.8 in Post-development Land Segment Location of BMP , SegBMP 0 unitless Depth of lower surface of BMP, must be>=dBMPu Input Zero if Location is distributed or undetermined BMP or LID Type Subsurface Infiltration Basin Root Zone Water capacity Calculated Parameters Value ABMP BMP Effective Depth, this is the design variable Upper level of the BMP surface (negative if above ground) Analysis Date 09/25/25 Parameter Empty Portion of RWC under Post-D Natural Recharge ERWC Modified to consider dEXC Empty Portion of RWC under Infilt. BMP Symbol Value ERWC 0.59 EDRWC RERWC Unit Parameter Symbol Value Unit in Inches of Runoff to capture Qdesign 0.55 in 0.00 in Inches of Rainfall to capture Pdesign 0.69 in 0.00 in Recharge Provided Avg. over Imp. Area 25.7 in Runoff Captured Avg. over imp. Area 25.7 in BMP Calculated Size Parameters ABMP/Aimp BMP Volume Aratio VBMP CALCULATION CHECK MESSAGES 0.15 unitless 1,694 cu.ft Parameters from Annual Recharge Worksheet System Performance Calculated Parameters Post-D Deficit Recharge (or desired recharge volume) Annual BMP Recharge Volume Vdef 28,650 cu.ft Post-D Impervious Area (or target Impervious Area) Aimp 36,895 sq.ft Root Zone Water Capacity RWC 3.59 in RWC Modified to consider dEXC DRWC 0.00 in Climatic Factor C-factor 1.67 no units Average Annual P Pavg 49.0 in Avg BMP Recharge Efficiency %Rainfall became Runoff %Runoff Infiltrated %Runoff Recharged %Rainfall Recharged Recharge Design Parameters Volume Balance-> Solve Problem to satisfy Annual Recharge dBMP Check---> OK dEXC Check---> OK 78,977 cu.ft BMP Location---> Location is selected as distributed or undetermined 100.0% 78.5% 66.8% 66.8% 52.4% Represents % Infiltration Recharged OTHER NOTES % Pdesign is accurate only after BMP dimensions are updated to make rech volume= deficit volume. The portion % of BMP infiltration prior to filling and the area occupied by BMP are ignored in these calculations. Results are % sensetive to dBMP, make sure dBMP selected is small enough for BMP to empty in less than 3 days. For land % Segment Location of BMP if you select "impervious areas" RWC will be minimal but not zero

sensetive to dBMP, make sure dBMP selected is small enough for BMP to empty in less than 3 days. For land % Segment Location of BMP if you select "impervious areas" RWC will be minimal but not zero as determined by Recharge Requirement dr in 9.3 the soil type and a shallow root zone for this Land Cover allowing consideration of lateral flow and other losses. over Imp. Area How to solve for different recharge volumes: By default the spreadsheet assigns the values of total deficit recharge volume "Vdef" and total proposed impervious area "Aimp" from the "Annual Recharge" sheet to "Vdef" and "Aimp" on this page. This allows solution for a single BMP to handle the entire recharge requirement assuming the runoff from entire impervious area is available to the BMP. To solve for a smaller BMP or a LID-IMP to recharge only part of the recharge requirement, set Vdef to your target value and Aimp to impervious area directly connected to your infiltration facility and then solve for ABMP or dBMP. To go back to the default configuration clik the "Default Vdef & Aimp" button.