The project to four-lane US 30 between Tama and US 218 has four components. The upgrade to four lanes in each county are separate pieces, on slightly different timetables. The interchange with US 218 should start any time. The middle piece (literally) is the IA 21 interchange at the Tama/Benton county line. This will change a landscape that hasn’t been altered since the Bohemian Alps cutoff opened in 1937.
There’s a meeting June 5 in Belle Plaine about the interchange. The diagram, however, is already online. Note that the right-of-way acquisition needs are less than typically necessary for a new interchange. That’s because there used to be short connectors in each quadrant.
The center of the interchange, where a bridge for 21 will cross over four-lane 30, is nearly the same point as the current intersection, because the four-lane will shift slightly and obscure the hiccup in the straight line that exists today because a bridge was built parallel to existing 30. This hiccup is, incidentally, the only place you can get a good look at oncoming traffic so as to pass the semi that you have been stuck behind for 15 miles and will otherwise keep following for another 15 why yes I have experience(s) with this why do you ask?