Halting erosion saves Ky. road and cemetery

When a bad storm caused a cemetery’s steep slope to erode into the nearby road, the Kentucky Transportation Cabinet needed a solution to prevent further erosion of this sensitive area.

“In May of 2010, we had a flood that caused the land to slide a bit. We had debris in the roadway and it looked like there was high potential for it to happen again,” explained David Filliatreau, staff engineer with the Kentucky Transportation Cabinet.

Initially, the Transportation Cabinet considered poured-in-place concrete retaining walls to repair the slopes. But the aesthetics of a concrete wall just wasn’t right for the cemetery setting. In addition, because the retaining walls needed to be built so close to gravesites, minimizing the excavation and reinforcement required was a major priority for the project.

“If we dug too far into the hillside, we would have had issues,” Filliatreau explained.

The Kentucky Transportation Cabinet decided to go with a gravity solution from Redi-Rock for this retaining wall challenge. Four major factors influenced this decision:

• Aesthetics—The look of the project was a major concern for designers. Since it’s in such a high-visibility area, a natural Cobblestone texture proved to be the best choice for the project. “A plain concrete wall just wouldn’t have worked here,” Filliatreau said;  
• Minimized Excavation —“The advantage of using a gravity system is that we only had to excavate 7 to 8 ft back into the slope so we didn’t disturb this sensitive site,” Filliatreau said. Building close to existing infrastructure or property lines is a major benefit of the Redi-Rock system. The massive block size of each block (1 ton+) allows tall gravity walls to be built without geogrid reinforcement in many applications;
• Cost—A gravity wall design translates into minimized excavation and installation time—and also a cost savings as compared to other more labor-intensive systems; and
• Simplicity of installation—“This is the first retaining wall project we’ve installed using state forces and the district has been very impressed,” Filliatreau explained. “It’s pretty intuitive. The simplicity of installing it is one of the biggest draws.”

To create a gravity solution for this project, engineers specified three unique types of blocks:

• 41-in. blocks (measured from face to rear) make up the majority of the walls. These blocks weigh 2,351 lb, as much as a Budweiser Clydesdale. Each block has a knob and groove design, which means the blocks stack up like giant, 1-ton Legos;
• 9-in. Setback blocks are used to increase the batter angle of a wall and allow taller gravity walls to be built; and
• Corner blocks were used as step-downs as the wall transitioned down the slope. “When you’re stepping down a slope, using corner blocks is a good way of capturing that slope. The corner blocks kind of act as speed bumps for water runoff,” explained the local Redi-Rock manufacturer.