As Ken Barker and his team were carving a new bicycle trail through the woods west of Coralville's Creekside Ballpark, they began digging into a hill toward the top and were faced with sandy, shifting soil.

In cyclocross, sand is used in courses as a common, if challenging, obstacle slowing down cyclists as they work their way through the loose grain. But for someone building a permanent course that will have to stand up to the hard wear of riders and rain, sand presents a challenge.

"So we had to get a little creative," said Barker, who runs Backyard Trails, a Cedar Rapids-based company that consults on biking trail projects.

Working with the City of Coralville's Parks and Recreation Department, they armored the assent with limestone ridges, adding some needed structure to the switchbacks, and some sloping berms to the corners. They finished the area, called Sand Crane, with a wood frame that drops riders over the twisted remains of an old car.

Alex Buhmeyer, the Coralville Parks Superintendent, said he's excited about the new intensities the trail introduces to the park system. The trail, he explained, is a continuation of the singletrack trail network Coralville's already built up through areas like the Woodpecker Singletrack Trail System. He said his favorites were some of the blue or intermediate trails, but he said he hopes to see Barker pull a black diamond section out of the sandy hill.

"It's still a lot of green level (or beginner) trails, but there's more topography, more climbing and downhill. Based on what segment you choose, you can adjust to your comfort level," Buhmeyer said.

In total, the Flow Trail cost the city $70,000 in construction, design and operations costs.

"It ended up being a more technical section, but really opens up the trail to riders looking for a challenge," Barker said. "... They're designed to be fun, but you can get exercise on them. You can escape the grind, and there's a whole bunch in there to build your skills to meet the challenges."