A permeable pavement BMP for pedestrian routes
Permeable pavement engineered as a stormwater BMP — supporting LID design, MS4 programs, and runoff reduction. Tested per ASTM F1551 for permeability and EPA 1311/1312 for leaching.
Engineered as a stormwater BMP
Same hydrologic function as other permeable pavement BMPs — captures rainfall, detains in open-graded aggregate, discharges via infiltration or underdrain. Different surface: bound stone and recycled rubber instead of porous concrete or PICP.
Stormwater design properties
Reference data for infiltration calculations, BMP sizing, and treatment train design.
| Parameter | Flexus value | Reference / notes |
|---|---|---|
| BMP category | Permeable pavement (source control) | Equivalent functional category to PICP, porous concrete, and porous asphalt in most state BMP manuals (e.g. VA DEQ Spec No. 7, MN Stormwater Manual) |
| Surface permeability | > 200 in/hr | ASTM F1551. Engineered well above typical design storm intensities for pedestrian drainage areas |
| Reservoir layer | Open-graded aggregate (No. 57 / No. 2) | Sized per project — combines structural support and stormwater storage. Voids ratio typically 0.35–0.40 |
| Underdrain | Optional, raised-elbow recommended | Specified when subgrade infiltration is insufficient (< 0.5 in/hr) or where 24–48 hr drawdown is required |
| Setbacks | Per local code | Typical: 50–100 ft from water supply wells; ≥ 3 ft above seasonal high groundwater (reference local stormwater manual) |
| Runoff reduction credit | Per jurisdiction | Determined by local BMP manual. Flexus functions as a permeable pavement BMP — credits typically follow that category |
| Pretreatment | Not required from sheet flow | Run-on from impervious areas should be minimized or treated upstream to limit sediment loading |
| Maintenance | Periodic debris clearing; low-pressure rinsing as needed | Surface infiltration can be restored if sediment accumulates. Protocol in installation guidelines |
Compared to other permeable pavement BMPs
Same BMP category as PICP and porous concrete — different surface technology suited specifically to pedestrian routes.
| Property | Flexus | PICP | Porous concrete | Porous asphalt |
|---|---|---|---|---|
| Application | Pedestrian routes | Pedestrian + vehicular | Pedestrian + vehicular | Vehicular (light) |
| Surface permeability | > 200 in/hr | Variable, depends on joints | Typically 100–700 in/hr new | Typically 100–600 in/hr new |
| ADA surface | Firm, stable, slip-tested | Joint width affects ADA performance | Firm, stable | Firm, stable |
| Recycled content | SBR rubber component | Varies by manufacturer | Minimal | RAP possible |
| Maintenance | Surface rinsing | Joint vacuuming | Vacuum sweeping | Vacuum sweeping |
| Submittal package | Single spec pack, Division 32 | ASCE 68-18 reference standard | ACI 522 reference standard | NAPA reference |
Flexus is positioned for pedestrian-route applications where PICP joints, exposed aggregate concrete, or sealed asphalt are not the design intent. For vehicular applications, refer to PICP, porous concrete, or porous asphalt per ASCE 68-18 and applicable BMP guidance.
Stormwater engineer FAQ
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Yes. Flexus captures rainfall at the surface, infiltrates through the bound aggregate matrix into an open-graded reservoir, and discharges via infiltration or underdrain. Permeability target >200 in/hr, tested per ASTM F1551. Acceptance is project-by-project — not pre-approved by any regulatory body.
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Yes. Credit values are determined by the local jurisdiction. Reference the applicable state BMP manual and consult the local stormwater authority. Flexus does not pre-assign credit values.
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>200 in/hr, tested per ASTM F1551. Long-term performance depends on base prep, drainage area, sediment loading, and maintenance. Full test report in the spec pack.
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Yes. Flexus reduces effective impervious area and integrates with bioswales, rain gardens, and infiltration trenches as part of an LID treatment train. Counts as pervious for impervious-cover calculations where local code recognizes permeable pavement.
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Yes — TCLP (EPA 1311), SPLP (EPA 1312), and RCRA metals including mercury. Results within applicable regulatory thresholds. Reports in the spec pack.
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Source-control BMP. Stands alone for small pedestrian drainage areas; combines with downstream BMPs for larger sites. Where subgrade infiltration is limited, specify an underdrain with raised elbow for 24–48 hour detention.
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Typical: 50–100 ft from water supply wells, 3 ft minimum vertical separation from seasonal high groundwater, 0.3–0.5 in/hr minimum subgrade infiltration for infiltration-based discharge. Underdrain where conditions can't be met.
Spec it. Verify it. Build it.
Download the spec pack for ASTM and EPA test reports, CSI Division 32 specification language, and cross-section details. Request a physical sample to verify surface character before specifying.