Hollywood, Mount Lee Drive
The City of Los Angeles invited Wirtgen to develop a recycling option to an asphalt overlay for Mount Lee Drive. In situ recycling was seen as a viable alternative to hauling in new materials and asphalt through very narrow winding residential streets. A recycling option was also of interest to investigate possible cost savings for future projects.
The 2300m of steep winding road is the only access road to the famous Hollywood sign and various communication antennas on the peak of the hill. The only access to the road is through the residential area of Hollywoodland, consisting of narrow roadways, not designed to withstand regular heavy vehicle activity.
The conventional method of rehabilitating Mount Lee Drive would have involved hauling in and out some 3,400 tons of material. Due to the restricted access through residential areas the largest truck size could have had a 10 tons capacity resulting in a minimum of 340 trips with heavy loaded vehicles. By using the in-situ recycling method these trips are reduced to 15 trips of 30tons tankers of penetration grade bitumen for foam bitumen.
After test pit investigations and mix designing it was established to recycle the top 150mm of material (consisting of 75mm asphalt and 75mm gravel) with 3% bitumen without the addition of cement. During the mix design process it was noted that the material do not retain its strength well when soaked, the results however still adhere to the requirements for a BSM layer.