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The latest phase of upgrading the sanitary sewer lines in Sioux Falls will be an earth-shaking event. That's because crews are using dynamite to remove tons of bedrock in Yankton Trail Park.
Twice a day, the alarm sounds: alerting everyone within earshot of Yankton Trail Park of the big bang to come.
The earth heaves briefly in a muffled explosion; breaking up the Sioux quartzite underneath that's too hard and thick to tackle with a backhoe.
"Essentially, the shock wave from the explosion goes up through the rock and fractures the rock," Trent Lubbers of Sioux Falls Public Works said.
The explosions will unearth enough bedrock to fill a football field eight and a half feet high.
Crews will dig a hole 23-feet deep, put explosives in, put down a blasting cap, cover it with gravel and let the blasting begin. They'll be doing that for the next couple of months.
"We need to break that rock up so we can create the trench to lay that pipe into," Lubbers said.
The dynamite blasts will clear a pipe trench nearly a mile long. It's all part of the effort to boost the capacity of the city's sewer system, one charge at a time.
And explosives experts are at the scene of each blast to ensure that they're done safely. City officials say drivers on Interstate 229 should not feel any impacts from the detonations.
Crews are doing the work over the winter, so the park can be re-opened to traffic this spring.
The bike path will also be closed for a few weeks next month and in April. But, crews will make an alternative route for the path, so you'll still be able to use it in that area.
Click on the video player below for an explanation of the process.