Sep. 28—ETHAN — Travelers on South Dakota Highway 42 near Ethan will have to wait a little longer for the new bridge over the James River to be completed.
Officials with the South Dakota Department of Transportation said the bridge was originally slated to be completed by August, but work will now likely be ongoing through June of 2022. The most recent delay stems from unexpected subsoil conditions at the construction site which caused a safety structure to collapse. That will prevent contractors from completing the deck — or surface — of the bridge itself on time.
"It's just tough," said Travis Holthaus, engineering supervisor with the SDDOT Mitchell office. "We ran into some delays due to the subsurface soil conditions. They were different from what we had originally found in our borings, and that caused some issues in construction."
Holthaus said the soil turned out to not be able to support the weight of the construction required to complete the bridge as scheduled after an incident of a cofferdam collapsing at the worksite. A cofferdam is a watertight enclosure pumped dry to allow construction work below the waterline and is often used when repairing ships or bridges.
"Soil cohesion is basically the ability for the soil to support a load, and that was lower than what our initial soil borings had shown," Holthaus said. "That caused the cofferdam, the structure used to hold back the soil as they go down into the ground to place concrete, to fail and the sides collapsed, making it unsafe to work."
There were no injuries in the incident, which occurred over a weekend when workers were not on site, but Holthaus said it was concerning enough to reevaluate the project timetable. With the reality of the soil conditions becoming apparent, Holthaus said contractors will not be able to pour the deck of the bridge until at least spring of 2022.
That is the hope at this point, anyway.
"The deck pour will be in early spring and once we get some good days for that work to happen, we'll finish up the asphalt surfacing after that. As of right now we don't have a real good estimate of when that will be, but we hope that we'll be able to get people through there sometime in June," Holthaus said.
The bridge project has turned out to be a lot more difficult to complete than originally anticipated. The construction work was originally slated to begin in 2019, but heavy rains forced a delay to the start of the work until 2020, when the waters of the James River began to recede. Engineers at the time said the two straight years of heavy precipitation made it impossible to start the project.
Now the area is experiencing drought-like conditions, and South Dakota Department of Transportation officials are feeling the frustration at the curveballs Mother Nature and the Earth itself have thrown at the project.
"It's unfortunate, but there's not a whole lot we can do. It's just the nature of the material down there," Holthaus said. "There is a lot of variability. It's unfortunate, but it's part of the deal."
The bridge has been due for an upgrade for some time. The original bridge was constructed in 1958 and spanned about 562 feet. Officials with the SDDOT told the Republic at that time that the bridge had deteriorated to the point where it needed to be replaced. And with the James River a constant threat to flood, officials wanted a new bridge that would resist seasonal flooding.
Normal traffic on Highway 42 has been detoured to Highway 44 between Highway 37 and Highway 81. Highway 42 typically sees around 385 vehicles a day, according to a previous traffic survey. By comparison, Interstate 90 usually sees about 4,100 vehicles a day.
The work was originally expected to cost around $7.25 million, but the new setback will likely drive up that price.
"There will be some additional cost associated with this, but we haven't figured out what that is at this time, " Holthaus said.
Some other construction work has experienced delays and cost increases, as well. One factor contributing to that is the ongoing supply chain issues that have caused delays in a number of industries, such as agriculture equipment manufacturing.
Some contractors with the SDDOT have not been immune to those conditions, though for the most part construction work remains mostly on schedule.
"That has been an issue on some projects. There have been materials shortages that we don't normally see," Holthaus said. "It has caused the cost for the contractors to go up dramatically."
Though the bridge project on Highway 42 has been delayed, most other area construction is proceeding generally as normal. Another major area of construction is taking place on Interstate 90 from two miles west of the junction with U.S. Highway 81 to a little over two miles west of the junction with South Dakota Highway 19 near Humboldt.
That stretch of interstate is undergoing paving with a width limit of 12 feet and traffic routed to opposing lanes, a 65 miles per hour speed limit, no passing and lanes reduced to a single lane until at least November, according to the South Dakota 511 website. There is an over-width detour on South Dakota Highway 42 at exit 350 and ending at South Dakota Highway 19 near exit 379.
"That's doing pretty well. Right now we're looking at probably December for that being completed. That's a full reconstruction of Interstate 90 for those 15 or so miles. There are two bridges that are being reconstructed. One is done and the other one we're looking to pour the deck in the next two to three weeks," Holthaus said.
Contractors are making every effort to expedite the work to finish as soon as possible, and hopefully crews will have better luck on their side in the upcoming months, Holthaus said.
"It's a challenge. With the northern climate we have, we don't have the luxury of an eight to 10 month construction season," Holthaus said.