Pervious Pavement¶
Source: NJ Stormwater BMP Manual, Chapter 9, Section 9.6 (2026)
Pervious pavement systems — including pervious concrete, porous asphalt, and permeable interlocking concrete pavers (PICP) — allow stormwater to pass through the pavement surface into a stone reservoir base course, from which it infiltrates into native soil below or drains through a perforated underdrain. The stone reservoir provides temporary storage between storm events and distributes infiltrated volume across the base area.
Pervious pavement serves dual functions: it replaces a conventionally impervious surface with a volumetric-reducing GI surface, and it provides on-site stormwater management without consuming additional site area beyond the paved surface itself. This makes it particularly effective on sites with limited open space for surface-based BMP footprints.
GI Classification (2026): Pervious pavement qualifies as Green Infrastructure when the stone reservoir base infiltrates captured runoff into native soil with confirmed Ksat per Chapter 12. Systems with an impermeable liner and underdrain only — no native soil infiltration — are classified as Non-GI in the 2026 edition and do not generate VRC.
Primary stormwater functions:
- Groundwater recharge — native soil infiltration from stone reservoir base
- Volumetric reduction — VRC credit generation toward GI Requirement (when GI-qualifying)
- Water quality treatment — TSS removal through filtration in stone reservoir and native soil
- Eliminates equivalent impervious surface area from the runoff drainage calculation
When engineers choose this BMP:
Pervious pavement is selected for parking lots, access drives, low-traffic roads, and pedestrian plazas on sites where confirmed permeable soils support GI qualification; no heavy vehicle traffic would compromise structural integrity; adequate surface maintenance (vacuuming) is committed to in the O&M Agreement; and the paved surface area itself is the most efficient location for stormwater management without consuming additional open land.
Source: NJ Stormwater BMP Manual, Ch. 9, Section 9.6 (2026)
| Parameter | 2026 Requirement | 2023 Requirement | Notes |
|---|---|---|---|
| Stone reservoir depth | Sized to store WQV from contributing tributary area plus pavement surface | Same | Clean open-graded stone, no fines |
| Stone specification | Clean NJDEP-specified open-graded aggregate; no fines | Same | Fines content eliminates void storage capacity |
| Minimum native soil Ksat (GI config) | ≥ 0.52 in/hr; per Chapter 12 field investigation | General Ksat reference | 2026: explicit Ch. 12 requirement added |
| SHWT separation | ≥ 2 ft below proposed stone reservoir base (non-traffic areas) | 2 ft | 2026 adds higher threshold for vehicle surfaces |
| SHWT separation (vehicle traffic) | ≥ 3 ft below reservoir base | 2 ft | 2026 increases separation; pollutant attenuation distance |
| Ch. 13 mounding analysis | Required when reservoir footprint > 3,000 ft² or SHWT < 4 ft below base | General guidance | 2026: explicit trigger criteria added |
| Pavement types | Pervious concrete, porous asphalt, PICP | Same | Select based on traffic loading and maintenance capacity |
| Surface maintenance | Vacuum sweeping ≥ 2× per year | Same | Critical — lack of maintenance is the leading failure cause |
2026 Key Changes: - Chapter 12 Ksat investigation now explicitly required for all GI-qualifying installations - Increased SHWT separation (3 ft) for vehicle-traffic areas to ensure pollutant attenuation before groundwater contact
Source: NJ Stormwater BMP Manual, Ch. 9, Section 9.6; Ch. 12; Ch. 13; Ch. 14 (2026)
Soil Permeability
- GI qualification requires field-confirmed Ksat ≥ 0.52 in/hr at stone reservoir base elevation
- Not suitable in pure HSG D soils or heavily compacted fill; in-situ conditions must be verified
- Even when Ksat is marginal, pervious pavement may be designed with partial underdrain and native infiltration at reduced VRC credit
- See Soil Permeability Testing
Seasonal High Water Table
- ≥ 2 ft separation from SHWT for non-traffic areas; ≥ 3 ft for vehicle-use surfaces (2026)
- Separation measured from stone reservoir base elevation, not pavement surface
- See Seasonal High Water Table
Groundwater Mounding
- Required when stone reservoir footprint > 3,000 ft² or when SHWT < 4 ft below reservoir base
- Large parking lots can generate significant horizontal groundwater mounding even when individual cell Ksat appears adequate
- See Groundwater Mounding
Traffic Loading
- Not suitable for heavy vehicle traffic (heavy trucks, buses) without structural design review
- PICP is the most structurally flexible pervious pavement type for moderate vehicle loads
- Avoid using pervious pavement in areas with heavy winter sand/salt application — sand fills voids and accelerates clogging
Source: NJ Stormwater BMP Manual, Ch. 9, Section 9.6; Ch. 12; Ch. 13 (2026)
Pervious pavement maintenance is non-negotiable for long-term performance. Surface clogging is the primary failure mechanism and is entirely preventable with regular vacuuming.
Routine Maintenance — Minimum Twice Per Year (Spring and Fall)
- Vacuum sweep entire surface using a regenerative air sweeper or vacuum truck capable of removing fines from pavement voids
- Do not use conventional street sweepers with rotating brushes — they compact fines into the surface and accelerate clogging
- Remove debris (leaves, soil tracked from adjacent unpaved areas) promptly
Annual Inspection
- Observe pavement surface for ponding during or after a significant storm — ponding that persists > 30 minutes indicates surface clogging has reduced infiltration capacity
- Inspect stone reservoir cleanout ports or observation wells (if installed) to confirm reservoir is not fully saturated between storm events
- Inspect underdrain outlet (if present) for blockage
Restricted Activities
- Do not apply sand for winter traction on pervious pavement — sand fills voids and is the leading accelerated clogging agent; use salt-based deicers only if needed
- Do not seal coat pervious concrete or porous asphalt surfaces — sealer permanently eliminates surface permeability
Source: NJ Stormwater BMP Manual, Ch. 8; Ch. 9, Section 9.6 (2026)
Design Errors
- GI qualification assumed without Chapter 12 investigation — VRC credit claimed without confirming native soil Ksat; regulatory reclassification as Non-GI opens a GI Requirement gap
- Adjacent unpaved areas not excluded from drainage — fine sediment from landscaping and bare soil enters pervious surface; surface clogging accelerates far beyond design life
- Stone reservoir specification not enforced — contractor substitutes aggregate with fines content; void storage and infiltration capacity significantly reduced
Construction Issues
- Heavy equipment drives on pervious pavement subbase — stone reservoir compacted; void storage volume lost before pavement is placed
- Fine backfill washed into reservoir from adjacent excavation — construction-phase sediment clogs stone voids before first storm season
Long-Term Performance Risks
- Surface clogging from insufficient maintenance — the most common failure mode; without semi-annual vacuuming, fine particles progressively fill surface voids; system converts to effectively impervious surface within 3–5 years
- Sand deicing application — a single winter season with sand applied can eliminate
50% of surface permeability; nearly impossible to fully recover
Source: NJ Stormwater BMP Manual, Ch. 9, Section 9.6 (2026)
Governing Regulations
| Rule Section | Topic | Engineering Relevance |
|---|---|---|
| N.J.A.C. 7:8-5.3 | Green Infrastructure Requirement | Pervious pavement (GI config) qualifies as GI; VRC credit available |
| N.J.A.C. 7:8-5.4(a) | Groundwater Recharge | Native infiltration from stone reservoir base generates recharge credit |
| N.J.A.C. 7:8-5.3(d) | Water Quality Treatment | TSS removal credit for GI and Non-GI configurations |
BMP Manual Sources
- NJ Stormwater BMP Manual, Chapter 9, Section 9.6 (2026) — Pervious Paving Systems
- NJ Stormwater BMP Manual, Chapter 12 (2026) — Soil Testing and Ksat Investigation
- NJ Stormwater BMP Manual, Chapter 13 (2026) — Groundwater Mounding Analysis
- NJ Stormwater BMP Manual, Chapter 14 (2026) — Volumetric Reduction Standards
- NJ Stormwater BMP Manual, Chapter 8 (2026) — Operation and Maintenance
Related OPAL Pages