6th Street Bridge Project Blasting Forward

This article was originally published by Keloland News.

There’s not many bridge projects in Sioux Falls that involve blasting.

But the new 6th Street bridge, which spans over the Big Sioux River in downtown Sioux Falls, is much more than just a bridge project. Along with the construction of a new bridge, which will be called the Unity Bridge, there’s a plethora of underground utility work.

That utility work includes blasting through rock, boring under railroad tracks and installing rail crossing elements for a future whistle reduction zone.

“The bridge got a lot of attention, but there really are several big elements to this project,” Wes Philips, city of Sioux Falls principal engineer, told KELOLAND News. “Rock is about a foot below the street surface. So we’re having to do a lot of blasting and excavation to remove that rock to get the utilities installed.”

Some of that blasting happened last week and more blasting of rock is expected with the project. Journey Group is the contractor for the project and hires blast experts within their SFC Civil Constructors crew. Philips described the blasting as “a very niche area of construction.”

“They come in and drill down small holes and put charges in,” Philips said. “Then they cover it up with blast mats to make sure it’s safe. When you hear ‘blast’ you think of a large explosion, but that’s not what we’re going for. We want a blast that fractures that rock enough that an excavator can pull it out.”

On Wednesday, crews were filling in a 15-foot deep trench that was blasted the week before and a sewer main and other utilities were installed. Once the rock is blasted and hauled out, a sand material is installed as the foundation for the new road.

As the construction continues to go east towards where the railroad crosses 6th Street, there’ll be a large bore under the railroad tracks.

“It’s a large conduit that will be bringing the watermain and all the public and private utilities through in one spot,” Philips said. “We can’t take the railroad offline, we can’t remove the tracks, so we’ve got to get the utilities across the railroad and this is the way to do it. That’ll be a very unique procedure for Sioux Falls.”

The boring process is expected to start in four to six weeks. Philips said there’s 19 different utility conduits being installed underneath 6th Street from the Big Sioux River to Weber Avenue.

“The coordination has been challenging, just with all of the construction trucks coming in and out,” Philips said. “Raven and LSS (Lutheran Social Services) are both very close to our project sites. We’ve been working closely with them to minimize the impacts, but being so close they’re in the middle of the project, essentially.”

The various utilities include Verizon, Midco, Xcel Energy, city lights, power, traffic and other fiber optics. In addition to creating a new utility trench, temporary utility lines are also moving throughout the project.

“Every utility has their own processes, rules and regulations,” Philips said.

Bridge over Big Sioux River expected by September

Shortly after the $21.8 million project received city council approval despite the lone bid on the project coming in nearly $10 million than originally estimated, crews built a causeway platform. Demolition of the bridge deck quickly followed as crews wanted to beat higher river flows in the spring when there’s more water in the river from snowmelt and rain.

Work on the bridge for most of the summer now includes installing falsework and formwork for when concrete will be poured for a new bridge deck.

“The bridge will likely be constructed by the end of fall,” Philips said. “But the entire project will be likely about a year from now until complete.”

Along with the blasting, the project is unique because of ongoing construction at Cherpa 2, 3, 4 and a parking ramp which is a more than $160 million project. In April, officials working on Cherpa 2 expected the building to open in September.

The Unity Bridge will also provide a unique view of the Arc of Dreams and downtown Sioux Falls.

“It’ll be really nice when it’s done,” Philips said. “A nice feature that adds to the Arc of Dreams, Sherpa, the Steel District, the 8th Street bridge and then Falls Park to the north.”

Railroad whistle reduction

In addition to the new bridge, road and utility work, the project includes construction of rail crossing elements. Philips said the railroad crossing arms and elements will first be installed where the railroad crosses 6th Street.

The plan is to install other railroad crossing enhancements on 8th Street and other areas the railroad crosses a road downtown. With more railroad enhancements, Philips said trains won’t need to sound the loud whistles when passing through downtown.

“There’ll be crossing arms that stop traffic. That helps the train engineers to feel safer in not blowing their whistles,” Philips said. “They won’t have to blow their whistle nearly as much, which makes it a little quieter downtown.”

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