Posts Tagged: Pervious Pavement

The Integration of Pervious & Impervious Pavements to Address Green Infrastructure Needs

Written by: Samantha Justice, P.E. Green infrastructure incentive programs have become commonplace for new construction and redevelopment regulations. Five of the most common incentives include: Development incentives such as expedited permitting, decreased fees, zoning upgrades and stormwater requirement reductions. Grants Rebates and installation financing Awards and recognition programs Stormwater fee discounts A subset of green infrastructure, stormwater management usually includes the consideration of pervious and porous pavements. Traditional asphalt and concrete parking lot surfaces create significant stormwater runoff, and in many municipalities, cannot be used in expansion or new build situations. When the paved area is constructed completely with a porous pavement, stormwater concerns are greatly reduced. Depending upon the choice, pavements that return rainwater to the aquifer not only nearly eliminate stormwater runoff – they also reduce sheet flow and point load erosion problems at the pavement edges, and reduce need for additional stormwater infrastructure to convey the water away from the area. Porous pavement systems can be directly integrated with asphalt and concrete surfaces to reduce such failures and reduce or eliminate the need for stormwater conveyance channels, pipes, and swales. As a result, downstream stormwater pipe systems see less silt and less water which requires less maintenance… Read more »

Impervious Gravel vs. Porous Aggregate Paving Systems

Written by William G. Handlos, P.E. For two decades, I held the position of City Engineer and frequently had to explain to disbelieving homeowners, developers and elected officials – that gravel driveways and parking lots were not porous. I would explain that for purposes of stormwater runoff, such gravel pavements must be treated exactly as we would concrete and asphaltic pavements. They often bristled at the idea that gravel did not percolate water and were upset to find that their gravel driveway, lots and roadways were assumed to shed 100% of rainwater. So it is with more than a dose of irony that I now have found myself in the position of regularly explaining to local and state officials that aggregate pavements are not necessarily impervious. Stakeholders are so accustomed to repeating the impervious gravel mantra…that they forget to notice that porous aggregate is not the same thing as gravel. I think it is best to start with a primer on the vernacular. A “good” gravel (Image 1) should have 40 to 70% stone, well-graded from 1/4” to 2-1/2” diameter; 20 to 50% sand; and 10% +/- fines. It should resist abrasion, shed water and be capable of being compacted. A… Read more »