JOB REPORT

Cold recycling in the midst of ravines and canyons.

“In-situ” cold recycling on a scenic route in Zion National Park

Zion National Park is located in southwestern Utah, close to the border of Arizona. The park’s landscape is characterized by many ravines with numerous canyons. Breathtaking sights of nature attract 2.5 million visitors to Zion National Park each year, and the number has nearly doubled over the last 20 years. The park was closed to car traffic in 1991, and since that time, tourists are driven around the park in tandem buses.

Increasing tourism had left its marks also on “Zion Canyon Scenic Drive”, a panorama road running right through Zion Canyon. The pavement structure showed signs of fatigue and cracking down to a depth of around 1.3 cm. The Federal Lands Highway Division (FHWA) was looking for a method that would enable the panorama road, as well as the approach road leading from the park’s southern entry right up to the Scenic Drive, to be rehabilitated without adversely affecting the landscape.

Dust, noise and damaging vibrations were to be avoided as much as possible during the rehabilitation operation. Tourist traffic was also not to be disturbed. If possible, the tandem buses were to be able to travel on the stretch of road even during the rehabilitation operation. The cost-effective and environmentally friendly “in-situ” cold recycling method was eminently suitable in terms of meeting all these requirements, so that the FHWA decided to use a WR 2500 S cold recycler from Wirtgen for carrying out the recycling operation.

The Wirtgen WR 2500 S cold recycler granulated the pavement both on the 8 km panorama road and the 1.6 km approach road, while simultaneously mixing in Portland cement, water and foamed bitumen. The resulting mix was then compacted as a 6 cm layer by one Hamm 3412 P single-drum compactor with padfoot drum and one tandem roller with vibration, both of which followed right behind the cold recycler. The specified final density of 97% on both the Scenic Drive and the approach road was thus achieved without difficulty.