The existing Highway 61 Bridge in Hastings spanning the Mississippi River is a two-lane bridge averaging 30,000 vehicles daily. Built in 1950, the bridge had become functionally obsolete, with a narrow roadway and not enough clearance to accommodate today’s traffic. In 2008, the state legislature passed transportation funding that allowed the Minnesota Department of Transportation to accelerate the bridge project five years ahead of schedule.
The new Hastings Bridge includes four lanes of traffic, a pedestrian/bike path, a modern anti-icing system, a public art display, and a scenic overlook. It features the longest free-standing arch main span in North America, and has a 100-year lifespan. The overall project costs were estimated at $120 million.
Braun Intertec was retained to provide geotechnical drilling services. We started drilling from a barge that included cores as deep as 200 feet below the water surface. We also drilled in six feet of water on a log jam over which the contractor spread a woodchip mat. We then drove out onto a pile-supported platform 25 feet above the water surface, which was designed specifically for our drill rig. To access a steep riverbank slope, the contractor moored a barge as close to shore as possible and extended crane ramps from the barge out to the steep slope. The drillers carefully maneuvered the rig onto the crane ramps and performed the boring from the ramps.
In addition to drilling, we were also asked to perform ultrasonic testing on half of the 42-inch spiral welded pipe piles, equaling more than 2.3 miles of weld inspection. The piles support the piers for the new bridge and extend approximately 150 feet into the ground. We inspected the welds to verify the quality and note any deficiencies. To meet schedule demands, Braun Intertec NDE inspectors performed the testing over the weekend to move ahead of the contractor’s schedule. Our other project involvement includes Storm Water Pollution Prevention Planning (SWPPP), pre-condition surveys, and vibration monitoring and testing during construction.
