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/porous pavements. Traditional asphalt and concrete parking lot surfaces create significant stormwater runoff, and many municipalities do not allow them in expansion or new build situations. When the entire parking area is constructed using a porous pavement system, stormwater concerns are greatly reduced. Depending on the type chosen, pavements that return rainwater to the aquifer nearly eliminate stormwater runoff and reduce sheet flow and point load erosion problems at the pavement edges. They also reduce the need for additional stormwater infrastructure to convey the water away from the area. Integrating porous pavement systems with asphalt and concrete surfaces can 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 water, which requires less maintenance and less capital expenditure for upsizing stormwater pipes…. 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 »