What Is the Stormwater Infiltration Trench Sizing Calculator?
The Stormwater Infiltration Trench Sizing Calculator designs stone-filled subsurface infiltration reservoirs for Low Impact Development (LID) stormwater management.
How Does the Stormwater Infiltration Trench Sizing Calculator Work?
It computes aggregate void storage capacity and checks native soil percolation rates to ensure both complete storage and rapid exfiltration.
Stormwater Infiltration Trench Sizing Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Mass balance void volume storage and Darcy bottom percolation exfiltration kinetics.
How to Use the Stormwater Infiltration Trench Sizing Calculator
- Enter required Water Quality Volume (WQv).
- Input gravel void ratio (typically 40%) and proposed depth.
- Specify measured soil infiltration percolation rate and max allowed drain-down time.
Step-by-Step Example Calculation
50 m³ Commercial Site Runoff Trench
Input Values:
Understanding Your Result
Trench Footprint Area: Surface area required for bottom percolation.
Calculated Drain-Down Time: Total hours required to empty the reservoir.
Max Allowable Depth: Deepest permissible excavation to avoid exceeding drain-down limits.
Factors That Affect the Result
- Subsoil permeability is the primary bottleneck: soils with < 10 mm/hr percolation require larger surface areas or underdrains.
When Should You Use This Calculator?
- Parking lot perimeter swales, residential development LID retrofits, highway median runoff capture, and groundwater recharge.
Assumptions & Limitations
- Assumes bottom infiltration only (conservative engineering practice neglecting sidewalls) and pretreating runoff to avoid silt clogging.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard EPA and state stormwater manual BMP sizing procedure.