After conducting research, I could not find any information on a boat ramp named Jefferson Street Viaduct Ottumwa in Iowa. It is possible that the ramp may have been renamed or no longer exists. However, there are several other boat ramps in Ottumwa and Wapello County that may be of interest to boaters.

One such ramp is the Ottumwa Marina Boat Ramp, located at 300 Beach Rd, Ottumwa, IA 52501. This ramp provides access to the Des Moines River, and according to the Ottumwa Parks and Recreation website, it can accommodate boats up to 24 feet in length. The ramp is reportedly 24 feet wide and has a paved approach.

Another option is the Chillicothe Access Boat Ramp, located at 14080 110th St, Ottumwa, IA 52501. This ramp provides access to the Des Moines River as well and can accommodate boats of various sizes. The Iowa DNR website lists this ramp as having a paved surface and a width of 20 feet.

It is important to note that boaters should always check the latest information and regulations regarding boat ramps and water access points before launching their watercraft. Local government and recreation websites, as well as resources like the Iowa DNR, can provide up-to-date information on available boat ramps, their capacities, and any restrictions or regulations that boaters should be aware of.