"The accident occurred at what we call the US Filter dam, just north of Ames & almost visible from Hwy 69 opposite Ada Hayden Park. I'd say it's a 3-4 ft drop at most levels. It is obvious as you approach from upstream & is routinely run by canoes, kayaks, and tubers, but for those that choose to use it, there's an EASY portage river-right accross the dam structure itself.
"We're told that the concrete structure caps the original rock-and-crib mill dam, and that the four large timbers sometimes visible on the downstream side are part of the original cribbing. The concrete cap has a sloping downstream surface but does create a small hydraulic at it's base.
"I think it's fair to say that as low-head dams go, most of us never considered this one particularly dangerous. I suspect Tom had run it before on numerous other occasions. I don't know if the hydraulic could have been a factor, but it is easy to imagine someone swamping as they scraped across the dam (the water was relatively low on the 17th) or hit a standing wave or timber at it's base. Capsizes here are not uncommon.
"There is no warning sign at this dam, but that situation will soon be remedied as part of the federal Recreational Trails Grant improvements being made by Story County Conservation & the Skunk River Paddlers."