High river levels kept Marschel Wrecking crews off the water for the past 60 days but they wasted no time taking out two remaining concrete piers from the old Highway 47 bridge on Saturday.
After a week of saw cutting the piers into 100,000-pound pieces and moving them to the river bank, two explosive blasts Saturday morning pulverized the remaining concrete, which is now mostly cleared from the river bottom.
Marschel Wrecking project manager Jeremy Frye said the blast came from deep below the water line.
“We drilled 18 holes between 35 and 40 feet deep in the piers,” Frye said. “We used explosives specifically designed to break up concrete. It’s the same used to blast rock on the highway and in quarries.”
Frye explained crews have been back to work for about a week and a half. They had to wait until the river level was back to 20 feet before having access to the piers.
First on the list was to cut down one remaining piece of the old steel bridge structure that had remained in place since the original demolition blast took down 90 percent of the old bridge span in mid-April.
At that time, Frye said one of the explosive charges designed to cut steal hadn’t properly ignited.
That was not a problem Saturday as the blast sent river water and small pieces of pier concrete flying onto the new bridge as the explosives detonated near bedrock in the river bed.
“We had wrapped all of the piers in steel woven fabric to try and contain as much as we could,” Frye said. “We wanted everything to go straight down and keep debris from flying.”
Frye added they worked with the Missouri Department of Transportation to close traffic on the new bridge to allow for the blast and the cleanup of debris that landed on the road deck, which was dropped into the river.
“We had expected it to be 15 minutes of closure, but it ended up being about 25 minutes,” Frye said. “The new bridge was inspected and everything was fine. Then we began scooping the concrete out of the water.”
Frye added they must remove all concrete debris and other material from the river to specific depths.
Although the old concrete piers were not drilled all the way to bedrock, Frye said anything remaining is so deep and will be covered over and never seen again.
As on Tuesday, all of the steel was already out of the water and a final sonar scan was scheduled for Wednesday to find any remaining debris.
“The sonar has a very high definition display and will identify even the smallest pieces of steel even if they are buried in the mud,” Frye said.
The final pier on the Washington side of the river will be cut down as well and Frye said a very small amount of explosives will be used to break down the concrete further.
Any remaining pieces of concrete will be left in place since it is part of the wing dyke on that bank.
“In the next few weeks, we will remove the steel and other demolition debris on the Warren County side of the river,” Frye said. “A couple more weeks and we will be done. It’s been a great project except for the river rising.”
Frye added Marschel Wrecking will move on to other demolition projects of buildings and the company was awarded the contract to remove two Interstate 44 bridges spanning the Meramec River near Interstate 270 in Fenton, but those will be demolished by equipment only and not explosives.
Jason and Joanne Marschel, founders and owners of Marschel Wrecking grew up and live in Warrenton. Frye also is from Warren County.
Marschel Wrecking began in 2007. The company has grown to employ 100 people and has 20 to 25 jobs going on throughout the day, which takes them throughout metro St. Louis and Illinois.