Wirtgen cold milling machines solve big challenge: A W 210i and W 2100 milled the spillway chute of the Oroville Dam, the highest dam in the US.
North of Sacramento, a W 210i and W 2100 precisely milled the spillway chute of the Oroville Dam, the highest dam in the US. In this process, the milling contractor also benefited from cold milling specialist Wirtgen’s application experience in steep gradient milling.
The damage was initially minimised provisionally by filling the erosion in the surface with rolled concrete, “so that the owner could open the overflow system during the winter months, if necessary,” explains Chris Anderson, project manager at the subcontractor, milling service provider Anrak. This temporary material had to be removed prior to final concrete paving with Portland cement, however, in order to achieve the desired surface quality. To complete this task, the contractor decided to use two cold milling machines from Wirtgen.
This milling drum is fitted with up to 50 per cent fewer picks at larger tool spacings (LA) than a standard milling drum. Fewer picks means a lower cutting resistance, making it possible to mill hard surfaces such as concrete. This process was followed by the W 210i with a standard LA15 milling drum to give the milled surface the finer texture required to pave the new concrete layer. During the job, both machines used the Level Pro leveling system developed by Wirtgen. According to Anrak’s CEO Tom Schmidt, this is a perfect symbiosis: “We have used almost every machine under the sun, but none can compete with the Wirtgen milling machine together with the Level Pro system. It is both reliable and extremely precise. The evenness of the surface is perfectly uniform and the machine always has excellent traction.The latter is important when milling rolled or portland cement concrete. And the vibrations that are unavoidable when milling such a hard surface do not affect the Level Pro system one bit.”
This challenge was solved by attaching steel cables with a total length of more than 450 m to the blades of a large wheel loader and to the rear of the large milling machines, thus securing the machines while work was being carried out. In the process, the heavy steel cables were attached to several hundred trolleys that are normally used for transporting heavy furniture in order to prevent them from rubbing against the ground. “We used the trolleys to prevent the texture of the freshly milled concrete surface from being damaged,” explains Tom Chastain, applications specialist at Wirtgen America.
After the “milling the spillway” sub project had been reliably completed within the scheduled timeframe, the entire rehabilitation project costing US$ 1.1 billion was completed on schedule after around two years.
(Communication by the management of the company)