1240815StormWaterManagementReportrcd 3 12 2026

Volume volume) BMP Location---> OK Represents Post-D Impervious Area Avg BMP Recharge Aimp 11,238 sq.ft 41.6% % Infiltration (or target Impervious Area) Efficiency Recharged OTHER NOTES %Rainfall Root Zone Water Capacity RWC 3.69 in 78.5% became Runoff % Pdesign is accurate only after BMP dimensions are updated to make rech volume= deficit volume. The portion RWC Modified to %Runoff DRWC 1.12 in 0.7% consider dEXC Infiltrated % of BMP infiltration prior to filling and the area occupied by BMP are ignored in these calculations. Results are %Runoff Climatic Factor C-factor 1.67 no units 0.3% Recharged % sensetive to dBMP, make sure dBMP selected is small enough for BMP to empty in less than 3 days. For land %Rainfall Average Annual P Pavg 49.0

ough for BMP to empty in less than 3 days. For land %Rainfall Average Annual P Pavg 49.0 in 0.2% Recharged % Segment Location of BMP if you select "impervious areas" RWC will be minimal but not zero as determined by Recharge Requirement dr 0.1 in over Imp. Area the soil type and a shallow root zone for this Land Cover allowing consideration of lateral flow and other losses. 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. 144

0.14 0.00 0.00 0.12 0.1 0.00 Cumulative Annual Recharge Depth (in) 0.10 0.00 Event recharge Depth (in) cumulative 0.08 recharge over imper Area required rech 0.00 depth over imp Area 0.06 Pdesign 0.00 0.04 Event Recharge Averaged over imp Area 0.00 0.02 0.00

0.02 0.00 0.00 0.10 0.10 0.00 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 Precipitation Depth (in) 145

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VIII Vill MOUNDING CALCULATIONS MOUNDING CALCULATIONS 147 147

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PIPES SYSTEM MOUNDING CALCULATIONS Input Values 2.90 R Recharge rate (permeability rate) (in/hr) Specific yield, Sy (dimensionless) 0.150 Sy default value is 0.15; max value is 0.2 provided that a lab test data is submitted Horizontal hydraulic conductivity (in/hr) 2.90 Kh Kh = 5xRecharge Rate (R) in the costal plan; Kh=R outside the coastal plan 20.000 x 1/2 length of basin (x direction, in feet) 5.000 y 1/2 width of basin (y direction, in feet) 2.50 t Duration of infiltration period (hours) 10.00 hi(0) Initial thickness of saturated zone (feet) 12.406 h(max) Maximum thickness of saturated zone (beneath center of basin at end of infiltration period) 2.406 Δh(max) Maximum groundwater mounding (beneath center of basin at end of infiltration period) Distance from Ground-water center of basin in x Mounding, in feet direction, in feet 2.406 0 2.296 10 Re-Calculate Now 1.233 20 0.120 30 Groundwater Mounding, in feet 0.007 40 3.000 0.001 50 0.001 60 2.500 0.001 70 0.001 80 2.000 0.001 90 1.500 1.000 0.500 0.000 0 10 20 30 40 50 60 70 80 90 100 -0.500 Disclaimer This spreadsheet solving the Hantush (1967) equation for ground-water mounding beneath an infiltration basin is made available to the general public as a convenience for those wishing to replicate

mer This spreadsheet solving the Hantush (1967) equation for ground-water mounding beneath an infiltration basin is made available to the general public as a convenience for those wishing to replicate values documented in the USGS Scientific Investigations Report 2010-5102 "Groundwater mounding beneath hypothetical stormwater infiltration basins" or to calculate values based on user-specified site conditions. Any changes made to the spreadsheet (other than values identified as user-specified) after transmission from the USGS could have unintended, undesirable consequences. These consequences could include, but may not be limited to: erroneous output, numerical instabilities, and violations of underlying assumptions that are inherent in results presented in the accompanying USGS published report. The USGS assumes no responsibility for the consequences of any changes made to the spreadsheet. If changes are made to the spreadsheet, the user is responsible for documenting the changes and justifying the results and conclusions. 145 149

POROUS PAVERS MOUNDING CALCULATIONS Input Values 2.90 R Recharge rate (permeability rate) (in/hr) Specific yield, Sy (dimensionless) 0.150 Sy default value is 0.15; max value is 0.2 provided that a lab test data is submitted Horizontal hydraulic conductivity (in/hr) 2.90 Kh Kh = 5xRecharge Rate (R) in the costal plan; Kh=R outside the coastal plan 30.000 x 1/2 length of basin (x direction, in feet) 16.000 y 1/2 width of basin (y direction, in feet) 2.25 t Duration of infiltration period (hours) 10.00 hi(0) Initial thickness of saturated zone (feet) 13.680 h(max) Maximum thickness of saturated zone (beneath center of basin at end of infiltration period) 3.680 Δh(max) Maximum groundwater mounding (beneath center of basin at end of infiltration period) Distance from Ground-water center of basin in x Mounding, in feet direction, in feet 3.680 0 3.667 10 Re-Calculate Now 3.447 20 1.850 30 Groundwater Mounding, in feet 0.200 40 4.000 0.010 50 0.001 60 3.500 0.001 70 3.000 0.001 80 2.500 0.001 90 2.000 1.500 1.000 0.500 0.000 0 10 20 30 40 50 60 70 80 90 100 -0.500 Disclaimer This spreadsheet solving the Hantush (1967) equation for ground-water mounding beneath an infiltration basin