Willowbrook Community Road Improvements (Overall Winner 2015)

Los Angeles County Department of Public Works has been implementing sustainable pavement treatments in the past few years with positive results. Statewide legislation to reduce greenhouse gas (GHG) emissions was a key element in the development of our sustainable approach that emphasizes the following principles: (1) taking care of roads that are in good condition, first; (2) using recycled materials in the treatment selections; and (3) reutilizing the existing materials in-place. The Willowbrook project, completed in November 2014, is a leading example of the County’s road reconstruction program that incorporates two of the three above-mentioned green approaches. The project is located in the Los Angeles County unincorporated community of Willowbrook near the City of Compton. Due to widespread distresses, base failure, and yielding subgrade, reconstruction of the roads was considered as the best solution for the neighborhood. Consistent with our sustainable approach the scope of work for this project included reconstructing approximately 6 miles of residential roadways (983,000 square feet) by paving 1½ inches of Asphalt Rubber Hot Mix (ARHM) on 3 inches of Cold Central Plant Recycled Asphalt Concrete Pavement (CCPRACP) over 8 to 10 inches of Cement Stabilized Pulverized Base (CSPB). The existing deteriorated Asphalt Concrete (AC) pavement was cold milled. The milled AC was transported to a nearby vacant lot where the material was stockpiled and when ready for placement processed with engineered emulsion to form CCPRACP. The base and native soil were then pulverized, blended with cement and then graded to account for the pavement section. Once the new homogenous subgrade material was reshaped and compacted to form CSPB, the CCPRACP was brought back to the project site, and paved as an asphalt base course over the CSPB. After CCPRACP was constructed a 1½-inch of ARHM was placed over the CCPRACP to return the roads to the original grade. The contract cost for the project was $4,567,000. Compared to traditional reconstruction methods, using CCPR and CSPB treatments saved approximately $2,200,000. In addition to being cost effective, the Willowbrook Project had several environmental benefits. By recycling the existing AC and stabilizing the base/subgrade in place, we eliminated the hauling of existing AC and base from the project site to a landfill and importing of new hot mix and base to the project site. As result of this, we reduced the construction duration and the road closure time which consequently lessened the impacts to the community. Also, the County was able to reduce the energy consumption and GHG emissions by 68% and 57% respectively, as well as reducing landfill deposition by 60,000 tons. In addition, the 1½ inches of ARHM placed as the wearing surface resulted in 18,300 scrap tires being diverted from a landfill.