Los Angeles County Department of Public Works recognizes the State's GHG emission reduction objectives presented with the passage of AB 32. In addition, the lack of funding for the County's road system has been an ongoing challenge for many years for DPW. DPW has embraced both of these challenges and developed a sustainable approach to address them. As an agency that manages the largest and most diverse County network in the State, DPW is taking the lead to provide greener, cost effective roads by applying a 3-pronged sustainable approach in the rehabilitation, construction, and maintenance of its road network. This approach incorporates principles that (1) focus on taking care of our roads that are in good condition first; (2) use recycled materials from recycled tires or aggregates from existing pavement in the treatment selections; and (3) reutilize the existing materials in-place by recycling the pavement or adding cement to the subgrade beneath the pavement to improve its strength. This 3-pronged approach results in not only meeting the objectives of AB 32 of reducing GHG emissions, but also reduces the impacts to our landfills and community in a cost effective and sustainable way.
(a) Pavement preservation - One of the green practices is to take care of our roads that are in good condition, first. To some this approach might sound misguided. Why would you use scarce resources to fix good roads while the bad roads are the ones that need the repair the most? Many people understand the long term benefits of performing preventative maintenance activities on their homes and automobiles. Painting your house every 10 years or changing the oil in your car every 3,000 miles are activities that preserve the value and improve the performance of these assets. These regularly scheduled preventative maintenance costs are generally far less than the ultimate repair cost and go a long way to keeping the assets in tip-top shape.
(b) Use recycled materials - DPW has been a long time recycler of automobile tires by incorporating them into our pavements. For each lane mile of roadway that incorporates tire particles into the asphalt hot mix 2000 tires are eliminated from going into the landfills. Not only does this approach help reduce the amount of tires going into landfills the addition of tire particles into our pavement mix has resulted in significantly improving the performance of our roads. DPW performed a study that evaluated the performance of “rubber roads” and learned that adding tire particles to our pavement mix resulted in (a) significant reduction in pavement cracking (b) roads lasted 40 to 60 percent longer than conventional asphalt (c) less pavement noise than other pavements treatments and (d) less fading of the roadway surface. DPW is now using recycling asphalt millings called Reclaimed Asphalt Pavement (RAP) into our pavement treatments.
(c) Reutilize existing materials in place - Of all the pavement treatments, reconstruction are pavement treatments that impact the environment the most. Typically, reconstruction projects include removing the existing asphalt and the layers of material below the pavement. Trucks then haul the material away from the project site generally to a landfill. Virgin pavement material with aggregate is then imported to replace what was removed. Significant energy is needed to transport the material in both directions from the project location and raw materials are needed to construct the road. Processes such as "Cold-In-place Recycling (CIR)" and "Cold Central Plant Recycling (CCPR)" refurbish the existing asphalt in-place. Treating the soil beneath the pavement by adding cement, lime or emulsion to the soil provides another in-place treatment opportunity resulting in significant environmental benefits.
Benefits to Environmental Resources
Why is taking care of our good roads first sustainable? Pavement preservation treatments are treatments that are applied directly to the pavement surface and use materials (emulsions - temperature 100-150 degrees) that use far less energy than repairs for the distressed roads. For roads that are in poor condition, generally, the top layer(s) of the road are removed and hauled to a landfill and require hot paving material (temperature 275-300 degrees Fahrenheit) to repair the road. The energy utilized in the operations of removing and hauling the distressed pavement to a landfill, importing new pavement and heating the pavement to a higher temperature all add up to a much larger energy use and greenhouse gas impact than pavement preservation treatments.
Contribution to wellbeing of DPW and the County
Maintaining roads in good condition not only benefit automobile users but other modes of transportation as well including bicyclists, public transportation, and vehicles that support commerce and our states economic engine. Providing a well maintained transportation system is imperative to the vitality and success for all the people who work and live within the community. The ability to effectively move from one place to another is a key element in the economic stability and quality of life of the residents.
Contribution to Economic Health
The treatment cost to preserve the good roads is substantially less; it enables the County to preserve between 4 to 10 times more streets than if we focused on the bad roads. By reutilizing the existing materials in-place is an approach that not only reduces the environmental and public inconvenience impacts on a project it also has the added benefit of saving approximately 40 percent to the project costs. Approximately $12.8 million was saved for DPW's sustainable projects.