Following several weeks of demolition, work on Essentia Health's Vision Northland has now turned to blasting to remove over 44,000 cubic yards of rock from the construction site — or enough to create a 70-foot-tall pile that could cover the ice at Amsoil Arena.
Crews will blast twice a day — at noon and 4 p.m. — every weekday until April, with an air horns sounding five minutes and one minute before a blast. It won't sound like an explosion, instead it will sound like a "muffled thud," according to a news release from Essentia.
Essentia held a trial run Tuesday, which went according to plan. “The test blast followed all safety measures and protocols and went according to plan,” Phil Johnson, project manager for McGough Construction, said in the release. “It met all compliance specifications according to data from our engineers.”
The blasting will occur along Fourth Avenue East, starting on Superior Street and moving up to Second Street. With some blasts occurring near Interstate 35 tunnels, Essentia says it's closely working with the Minnesota Department of Transportation.
The process will remove 330-350 cubic yards of rock each day, which will prepare the site for the foundation of the 14-story hospital bed tower. The foundation is expected to be done next spring, according to the release.
Construction on the $800 million Vision Northland project started in September. The three-year project will bring a new hospital bed tower, larger surgical suites and clinic space — all to better serve Essentia patients and prepare the health system for future industry changes, the hospital said.
People within a 300-foot radius of the site may feel the blast, which isn't expected to impact patient care at the downtown campus. To minimize vibrations, excavation near buildings will be done with mechanical tools.
To prevent flying rock, mats and tires will cover blast sites. And safety officers and vibration sensors are placed across the excavation area to ensure federal and state protocols are followed.
The excavated rock may be used as breakwater along Duluth's Lakewalk and Bayfield County's Lake Superior shoreline, according to Essentia.
This type of rock excavation is common in Duluth, and information from previous blasting done to construct I-35 and Duluth Clinic's First Street Building will be used to help guide current excavation.