In 2010, the Transportation and Development Institute (T&DI) of the American Society of Civil Engineers (ASCE) hosted the first national Green Streets and Highways conference. This came from a need for stormwater managers to learn more about the world of road managers and vice versa. Stormwater managers realize that roads cover about 25% of urban areas, generating significant property damage from water pollution, minor flooding and combined sewer overflows in older cities. Not surprisingly, road managers view stormwater as a lower priority compared to road user safety and efficiency. Also, road agencies generally are larger than stormwater agencies at every level of government, and that typically translates into greater financial, technical and political clout.
Most road agencies view permeable pavement as suitable for car parking lots and alleys with occasional applications in low-volume residential streets. Such projects are at the margins of road agency priorities and their budgets, and many of these applications lie in the private sector. Permeable pavements have yet to be embraced by road agencies because they are seen as new and untried under regular truck or bus traffic. This is where more structural testing and evaluation of hybrid pavements may allow for more passes from higher-weight vehicles. This can place permeable pavement more in the mainstream of the road manager’s world.
Along these lines, moving permeable pavements more into mainstream acceptance and use by road managers will require several components. As noted, first and foremost is accelerated, full-scale load testing to validate the ability to withstand truck traffic. Such testing must result in structural design methods and easy-to-use, reliable thickness charts. While there has been some full-scale load testing for pervious concrete and porous asphalt, a recent full-scale load study by UC Davis on PICP resulted in design charts. This magazine issue includes a summary of the UC Davis work, cost savings implications for designers and where the charts will be used.
The second component is specifications. Cities and county road agencies often rely on, adopt and adapt construction specifications developed by state departments of transportation (DOT). Even provisionally issued specifications by a state DOT tells local road agencies that a particular technology such as permeable pavement has been vetted by knowledgeable experts. There are currently two DOTs that have published PICP specifications; Caltrans and Washington, DC. ICPI assisted in developing these. We hope to do more of this.
The third component is training. There are two sides to the training coin: one is for contractors that results in certification of competent, experienced individuals; the other is inspection training for road agency personnel. ICPI has seen fast growth in PICP classes for contractors and in those receiving a PICP Specialist Designation. This credential is becoming a requirement in local and state agency specifications. To help address this need, an inspection presentation is now available for ICPI members to present to stormwater and road agency personnel.
The fourth component is maintenance/management procedures and costs. A critical maintenance aspect for permeable pavements is regular surface cleaning with vacuum equipment. Permeable pavement will be more readily embraced by state DOTs and especially by local road agencies when existing street cleaning equipment can be used for cleaning. Regularly maintained PICP performs for decades. However, many installations don’t see regular cleaning that results in restoration of the surface infiltration with powerful vacuum equipment and perhaps water. ICPI has funded maintenance research in the past. This includes work by North Carolina State University and the Toronto and Region Conservation Authority. ICPI and its sister organization, the ICPI Foundation for Education and Research, are reviewing more research options for the near future.
This issue’s cover story features another realm where the two worlds of stormwater and pavement are usually close together, and that’s on military bases. These mostly self-contained environments are of such a scale that one person or a small group of people down the hall from each other manage pavements and drainage. There are a growing number of them using interlocking and permeable interlocking concrete pavements. The cover story provides an example of integrating the two worlds of pavement and drainage management from a need to solve flooding problems and pavement rehabilitation.
As industry, academia and governments address the four requirements for permeable pavement that lead to it becoming mainstream road infrastructure, the two managerial worlds will work more closely together. One resource that can support this process is ASCE publishing a new book called Permeable Pavements.