Experience Counts To Avoiding Mistakes In Porous Asphalt

Porous asphalt has gained in popularity due to the great environmental benefits it offers, but proceed with caution! Without the proper planning and installation experience, you can do more harm than good.

Potential Stumbling Blocks for Porous Asphalt Installations

Lack of experience is currently a major drawback with this technology. Construction companies or paving companies that do not have sufficient expertise installing porous asphalt surfaces may cause future failings in the surface due to incorrect installation, or could negatively impact the natural environment. 

Some of these risks include:

• Rutting: A tendency to under-compact the subbase can cause infiltration to lead to surface rutting. 

• Reduced Durability: Studies have yet to substantially prove the long-term porosity of porous asphalt, particularly in cold climates where snow removal is common. In addition, a tendency to under-compact due to a weak sub-base can lead to low pavement durability over time.

• Unclear Guidelines and Budgeting: Due to the relative newness of porous asphalt, many building codes may not yet allow it or may not yet have established clear protocol for its use. In addition, the anticipated costs of porous asphalt are difficult to establish up front, as initial estimates for installation (which are typically two-to-three times that of conventional asphalt) do not take into account typically lower maintenance costs over time nor do they account for reduced need for additional storm water management.

• Siting: Porous asphalt may not be able to handle high drainage loads resulting from high surrounding slopes. Siting should be carefully considered when deciding whether to use porous asphalt.
• Proper Maintenance Needs: Some porous asphalt require frequent maintenance because grit or gravel can block the open pores. Maintenance is typically done using industrial vacuums that suck up the sediment. If maintenance is not carried out on a regular basis, the porous asphalt can begin to function more like impervious surfaces

The Environmental Risks of Porous Asphalt

While porous asphalt is generally considered to be beneficial to the natural environment, providing storm water management and filtration for surface impurities, it can also create risk if installed improperly.

Porous asphalt is not designed to manage stormwater from other impervious surfaces on site. A comprehensive stormwater management plan should be part of the project, of which the porous asphalt pavement may only be one piece. In the case of significant storm events, the water table below the porous asphalt can rise to a level that prevents the precipitation from being absorbed into the ground. The additional water will be stored in the open-graded crushed drain rock base, where it will remain until the subgrade can absorb the water. Because of this, it is important is to understand the area’s soil infiltration rate, and design the pavement and base depths to meet the volume of water. Make sure you select an asphalt installation company that has the proper experience working with porous asphalt and can make the right recommendations regarding your specific site needs.

Highly contaminated runoff can be generated by some land uses where pollutant concentrations exceed those typically found in stormwater. Since porous asphalt is an infiltration practice, it should not be applied at stormwater hot spots due to the potential for groundwater contamination. These "hot spots" include:

• commercial nurseries
• recycling facilities
• fueling stations
• industrial storage
• marinas
• outdoor loading facilities
• public works yards
• hazardous materials generators
• vehicle service and maintenance areas
• vehicle and equipment washing and steam cleaning facilities

Basic Construction Company has extensive experience manufacturing and placing open-graded porous asphalt, and understands the local soil conditions in Eastern Virginia. For resources to help select a paving material for your project, and to estimate your project right the first time, download Basic Construction’s free ebooks:

• Tips for Estimating Your Project Right the First Time
• Choosing the Best Material for Your Commercial Asphalt Job
• Project Profitability in Heavy Construction

If your next project is located in Eastern Virginia, contact us at (757) 249-3789 to schedule a paving consultation or to request a bid.