A three-year project began this week to shore up Snake River levees.

Crews from Westwood Curtis Construction are tearing out vegetation and replacing rocks on the 4-mile John Dodge Levee, starting near the Gros Ventre River confluence and working toward the Highway 22 bridge over the Snake.

“Because of the freezing and thawing, rocks that were 400 pounds are reduced to the size of gravel,” said Kenny Koebberling, U.S. Army Corps of Engineers project manager for the Jackson levee system.

The work is capped at $250,000 a year. Work this year should wrap up before Thanksgiving.

Work will resume in the spring to repair high-priority levees, primarily ones that block water from reaching residential areas, Koebberling said.

Koebberling believes some of the rock placed on the levee 50 years ago wasn’t up to demands. The “armor” rocks, which are supposed to protect the levee, haven’t held up over the decades.

The Army wants to repair the levee during the autumn to avoid high water in the spring. It’s easier to replace rocks when the river isn’t near its peak, Koebberling said. It’s also more expensive to patch a levee during flood season.

“We’re trying to take a proactive approach to the problem instead of the reactive one like it has been,” he said. “You get mediocre repairs at best when you’re doing it in high water.”

Crews also are clearing vegetation from the levees. That part of the project has bothered residents who don’t like seeing trees being ripped from the riverside.

Koebberling said the Corps has to clear the vegetation to work on the levees. Trees and brush make it difficult for monitors to observe the levees in the spring, during flood season, and their roots erode the levee.

Also, “If you have a tree that falls halfway into the water, it slows the water down and directs it into the levee,” Koebberling said.

Meanwhile, Yellow Iron Excavation is hauling rocks to build up the Corps’ stockpile, which was depleted last summer when crews were trying to ward off floodwaters. Flood managers used 22,000 tons of rock during the 2011 flood season to repair levees. Yellow Iron is hauling in 12,500 tons of rock, some of which is being used for the levee repairs, Koebberling said.

The Corps partners with Teton County for levee maintenance and repairs. Koebberling said he relies on staff from the county engineer’s office and the road and levee department to monitor the levees, talk to landowners and handle routine tasks.

“They run the posse,” he said.