One of the busiest and most criticized interchanges in central Iowa is getting its first major redesign in more than 60 years. Crews have started building a $164 million flyover bridge at the Southwest Mixmaster in West Des Moines, KCCI 8 reported.
What's being built
The new bridge will replace the original cloverleaf loop ramp that carries southbound Interstate 35/80 traffic to eastbound I-235, according to KCCI. The two-lane flyover will take that traffic up and over the existing lanes and send it toward downtown Des Moines on eastbound I-235.
Two cranes are now in place and earth is already moving, KCCI reported. The project is expected to be finished by 2029.
Why the ramp is being replaced
"Traffic outgrew that loop ramp many years ago. And so, by replacing that with a two-lane flyover, we can handle a lot more traffic," Allison Smyth, a traffic engineer with the Iowa Department of Transportation, told KCCI.
Smyth said more than 15,000 vehicles use the cloverleaf ramp every day, far more than it was designed to carry. Drivers have long found getting onto the ramp to be a tricky move, KCCI reported.
West Des Moines Mayor Russ Trimble, who attended a DOT open house on the project, said safety is the main benefit. "This is one of the most dangerous intersections in the metro. So, I'm really looking forward to having better traffic flow and, more importantly, better safety in this area," he said.
Smyth said once it opens, drivers will "be able to make it there a lot more safely and have a lot more reliable commute times."
What drivers and crews should expect
The DOT has told drivers to expect slowdowns, detours and lane changes throughout construction, according to KCCI. With the Mixmaster tying together I-35, I-80 and I-235 on the west side of the metro, those changes will affect a lot of traffic, including work trucks and equipment headed to job sites across the region.
Why it matters for contractors
A $164 million interchange project is a major job for Iowa's heavy civil industry. Bridge work at this scale draws on earthmoving, piling, concrete, rebar, structural steel or precast girders, paving, drainage, lighting and traffic control, and it often supports suppliers of aggregate, ready-mix and steel for years. KCCI's report did not name the prime contractor, so subs and suppliers looking for work should check Iowa DOT's contract records for the project's lettings and awards.
There's also a practical side for every contractor in the Des Moines metro, not just road builders. Three years of lane shifts and detours at the junction of I-35/80 and I-235 will affect crew travel times, material deliveries and equipment moves. Builders with projects in West Des Moines, Waukee, Clive, Urbandale and downtown should factor Mixmaster delays into schedules and delivery windows, and check Iowa DOT traffic updates before big pours or crane moves.
In the long run, the payoff is a safer, faster connection. Once the flyover opens, contractors who move people and materials between the west suburbs and downtown should see more reliable trips through one of the metro's most difficult interchanges.