U.S. Route 53 traverses the state of Minnesota, from Duluth at the southwest end of Lake Superior, ending 240 km later at the Canadian border. On its way it crosses the socalled Iron Range, an area rich in iron ore, which has served the raw material needs of the American steel industry since the 19th century.
Today, the ore deposits in the Iron Range are far from depleted. On the contrary, just south of the city of Virginia, a mining company is in the process of expanding an old mine pit. As it happens, Route 53 currently runs right on top of the planned expansion and needs to be relocated. The main element of the relocation project is a new bridge across the neighbouring Rouchleau Mine Pit.
Minnesota’s highest bridge
Abandoned in 1977, the Rouchleau Pit has since served as a tourist attraction. The new bridge will be 335 metres (1,100 ft) long with an elevation of 61 metres (200 ft), making it the highest bridge in elevation in Minnesota.
The construction of the foundations of the bridge started in December 2015 with the installation of 30-inch piles. Drilling deep piles into very hard ground with a high iron content is quite a challenge. Due to strength requirements the holes need to be drilled 12 metres into hard rock – way deeper than at a typical bridge construction site.
Veit USA took the challenge of the drilling work. For the casing advancing system, Veit considered two suppliers.
Tight time schedule
– Veit had heard about Robit through the industry grapevine. They contacted us and presented their two challenges: deep piles in a mine site and a very tight delivery time, says David Delorme, General Manager of Robit Inc.
– We were selected because we were able to supply on a very short notice. We designed a system for the conditions Veit described, and delivered in six weeks – exactly as promised. What about the drilling work itself – how has it been coming along?
– This is the biggest piling job for Robit Inc so far. Despite the technical challenges posed by the rock and the length of the piles, we haven’t faced any major problems, and we are well within schedule, David says.
The installation of the 30-inch piles is set to be completed by mid-March, 2016. Work on the site continues at a swift pace though. The new bridge spanning the Rouchleau Pit should be open to traffic in late 2017 – offering a magnificent new lookout spot for travellers on Route 53.
Bridge construction for Route 53 relocation, Virginia, Minnesota
• 5 x 762 mm (30”) QL200s pilot bit
• 35 x 762/12,7 (30”) mm DTH RoX+ HD (Heavy Duty) ring bit
• Bermingham Reverse Circulation (RC) drill tube system
• Bermingham 50 m lead
• 4 x 25 bar compressor + oiler
• Drill hole depth: 53 m, into hard rock 12 m