Bay Area Agencies lead the charge on roadway recycling
Over the past two years there has been a sizeable increase in the number of San Francisco Bay Area and Northern California agencies moving towards cold in-place recycling (CIR) as an integral part of their annual road maintenance programs. Cold in-place recycling has been in existence for 25-plus years, but only over the past few years has it become a more widely accepted tool for many agencies to use in their street maintenance, rehabilitation and reconstruction programs.
CIR allows agencies to reconstruct old, tired roads with extensive alligator cracking, shallow potholes and thermally distressed and crumbling asphalt sections into brand new roadways without removing one of their most valuable assets, the aggregates already in place. Traditional roadway rehabilitation and reconstruction involves the grinding (or pulverizing) and off-haul of the top 2” to 6” section exhibiting this distress and the replacement of that section brought in from the closest asphalt plant. Approximately every 4,000 sq.ft. section of recycled roadway takes an 80,000 lb. truckload of materials off local roads, reducing emissions and avoiding the damage that these heavy loads cause roads. The agency pays to remove the aggregates and pays for the replacement materials. Because of the added efficiency in this process, projects can be completed in approximately half the time it would take using more conventional methods. The resulting cost savings can be anywhere from 20 to 40 percent compared to traditional repair methods which in today’s world is one of the primary drivers for the adoption of CIR.
CIR is done utilizing a recycling “train.” This train can come in many different iterations, all with the same basic functionality – it grinds a top layer of the roadway surface into small pieces called reclaimed asphalt pavement (RAP), mixes this RAP with binding agents (typically hot liquid asphalt or emulsions, cement, water) and lays the material back down to provide a new structural section in preparation for a thin wearing course applied over the top to act as a moisture barrier.
The icing on the cake is the environmental benefits which are receiving more and more recognition as the adoption rate of new and more environmentally friendly processes increase. Starting in 2003 a landmark report “Environmental Road of the Future: Life Cycle Analysis, Energy Consumption and Greenhouse Gas Emissions” by M. Chappat and J. Bilal was released and provided an in-depth comparison of 20 different pavement methods and their greenhouse gas emissions by ton. This study put CIR at the top of the list as the least energy intensive paving process. Further supporting the cause of recycling initiatives, many international, federal and state agencies, and even several contractors and suppliers have developed their own version of an environmental or sustainability “calculator.” There are at least a dozen different sustainability calculators in the marketplace and it remains to be seen which of these will be widely accepted throughout the industry. So far several have gained some traction.
The Federal Highway Administrations Infrastructure Evaluation Sustainability Tool is a sustainable pavements rating system that assesses the sustainability of a road or project over its entire lifecycle.
Greenroads and the Greenroads Ratings System has been modeled after the system widely in use for certifying buildings and developments, the Leadership in Environmental Excellence in Design certification system. Greenroads measures the sustainability of projects in roadway and bridge construction projects.
The National Asphalt Pavement Association has a greenhouse gas calculator specifically for measuring the comparable greenhouse gas emissions based on fuel use.
These are but a small sampling of the sustainability or eco calculators available today, all focused on the need to consider the environmental impact of projects in an industry that has traditionally been late to the “green party,” favoring the more conservative, old-school approaches that have been in place for many years. As roads continue to deteriorate and agencies are continually pushed to do more with less, methods such as cold in-place recycling should be one tool in any agencies toolbox.
The San Francisco Bay Area’s Metropolitan Transportation Commission (MTC) doesn’t have an eco calculator but has a “consider recycling first” policy. Their Climate Initiatives Program recently awarded $2.0 million to a CIR project in Sonoma County. Sui Tan of MTC’s Regional Streets and Roads Program perhaps summed it up best when he said “CIR is a win-win for motorists, city and county budgets and the environment. We expect CIR projects to become more and more common around the region as more contractors invest in the needed equipment.”
As more agencies become comfortable with CIR and other environmentally friendly processes to enhance their annual road maintenance programs they will be able to do more (and more good) for less.