It took 4,000 tons of rip-rap — large chunks of limestone — and six to eight weeks of careful placement of the rocks to complete the bank stabilization project on the Cottonwood River on Road G south of Road 160.
“That’s quite a pile of rubble out there,” Commission Chairman Marshall Miller said during Thursday’s commission meeting. “It’s just one of the things we get to do in Lyon County to save agriculture and the roads.”
Chip Woods, Lyon County engineer, said the bank stabilization area is 650 feet long. Bank stabilization is done to protect nearby agricultural lands and to prevent erosion of the bank and road wash out. Part of the process involved moving the road because the steep drop-off posed a danger.
The project’s estimated cost is $120,000 with 75 percent of that reimbursed by the Federal Emergency Management Agency and 10 percent reimbursed by the state, leaving the county to pay 15 percent of the project.
“It keeps the bank from eroding out. That’s why FEMA participates, to keep the road open,” Woods said.
A second and much larger project is underway on Road W6 near Neosho Rapids on the Neosho River. The 1,300-foot-long project will take 7,600 tons of rip-rap. This project is partially completed. It is estimated to cost $250,000 and, weather permitting, should be completed by the first of November.
To prepare the banks for stabilization, county crews remove trees and put down a geotextile fabric under the dirt to prevent plants from growing up through the rocks. According to an online article from Ohio State University, geotextile fabric applications are designed to keep soil and gravel (or other earthen materials) separate. By keeping the soil and gravel separated, the fabric improves the stability, load-bearing capacity and drainage of the site.
The material is porous so that water can get through, but nothing else. The county ordered 360 rolls of the material for the two projects, which cost around $20,000.
“It’s really pricey,” Woods said.
Rocks, all from a quarry in Reading, are then strategically placed on top of the dirt. The rocks can’t touch the water because of Corps of Engineers regulations, Woods said.
“You can’t just dump it and push it down the bank,” he said. “You have to lay all of those down. You want to keep the banks in as much as possible.”
The rip-rap has to be a certain size, too, with a certain percentage being more than 80 pounds. And the rocks have to be irregularly shaped, Woods said.
Woods said what takes the most time is getting the permits for the project. It can take 120 days to get one from the Division of Water Resources. This makes planning ahead a necessity, Woods said.
The bank stabilization should last forever, Woods said.
“It all depends on Mother Nature,” he said as he stood near the site on Road W6. “Unless Mother Nature has torrential floods, this stuff will stay here forever.”