What This Solves
Designs a permeable pavement system by calculating the required base course depth to store and infiltrate stormwater runoff from the pavement surface and any contributing drainage area.
Best Used When
- You are designing a parking lot, driveway, or walkway with permeable pavers, porous concrete, or porous asphalt
- You need to size the aggregate base layer to provide adequate storage for a design storm
- You want to verify infiltration capacity and check whether an underdrain or overflow is needed
Do NOT Use When
- You are designing a vegetated rain garden or bioretention basin instead of pavement — Use Rain Garden Calculator
- You need a subsurface infiltration trench rather than a pavement system — Use Infiltration Trench Calculator
Key Assumptions
- Aggregate base has uniform porosity throughout the depth
- Subgrade soil infiltration rate is constant and does not vary with depth or saturation
- The pavement surface is 100% permeable (no surface ponding or runoff)
- Contributing drainage area runoff is directed to the permeable pavement and not bypassed
- No clogging of the surface or aggregate over time (assumes proper maintenance)
Input Quality Notes
Subgrade infiltration rate is the most important input. Field infiltration testing is essential. For conservative design, use the low end of measured rates and consider a long-term reduction factor (e.g., 50% of initial rate) to account for clogging.
Calculate Permeable Pavement Design
For educational purposes only. Not a substitute for professional engineering judgment.
Permeable Pavement Design Overview
Permeable pavement systems allow stormwater to infiltrate through the surface into an aggregate base for temporary storage and infiltration to subgrade. They combine stormwater management with functional paved surfaces.
- Surface Infiltration - Water passes through paver joints or porous material
- Base Storage - Aggregate voids store water temporarily
- Subgrade Infiltration - Water slowly percolates to native soil
- Drain Time - Should drain within 24-72 hours for water quality
Paver Surface Infiltration Rates
| Paver Type | Min (in/hr) | Typical (in/hr) | Max (in/hr) |
|---|---|---|---|
| Interlocking Concrete Pavers | 10 | 100 | 400 |
| Concrete Grid Pavers | 50 | 200 | 600 |
| Plastic Grid Pavers | 100 | 500 | 1000 |
| Porous Concrete | 50 | 300 | 700 |
| Porous Asphalt | 30 | 200 | 500 |
| Gravel-Filled Pavers | 200 | 500 | 1200 |
Source: ASCE MOP 77 (2006), Manufacturer Specifications
Aggregate Porosity Values
| Aggregate Type | Min | Typical | Max |
|---|---|---|---|
| ASTM #57 Stone | 0.35 | 0.40 | 0.45 |
| ASTM #2 Stone | 0.38 | 0.42 | 0.48 |
| ASTM #3 Stone | 0.38 | 0.42 | 0.46 |
| Crushed Stone | 0.30 | 0.35 | 0.40 |
| Open-Graded Base | 0.32 | 0.38 | 0.42 |
Source: ASCE MOP 77 (2006), ASTM Specifications
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Last verified: February 2026