Ledgestone Concrete Retaining Wall System for Highway Road Construction

County chooses 16.5 ft. tall Redi-Rock gravity wall to widen roadway—without closing lanes

Project Name: Old Milton Highway Walls - Case #131

Customer Name: Walla Walla County

Design / Specifying Engineer: Walla Walla County Dept. of Public Works Chief of Engineering & Construction, David Eids, P.E.

Block Manufacturer: Wilbert Precast

Wall Installer: Premier Excavation

Project Location: Walla Walla, WA

Year Built: 2011


Minimizing traffic disruptions was a major priority when Walla Walla County in Washington launched a highway widening project in 2011.

Widening Old Milton Highway required a tall retaining wall to be built in a tight space. Plus, the wall needed to be built without disturbing traffic on a vineyard/winery access road parallel to the highway but some 30 ft. above.

The challenge? The retaining wall needed to be 500-ft. long and stand 16.5 ft. tall at its highest point.

Walla Walla Installation


Searching for a retaining wall solution that would allow the County to construct a tall gravity wall, Walla Walla engineers turned to Redi-Rock. Both engineering and aesthetics were major benefits of the Redi-Rock system in this application.

"Redi Rock's ability to provide a 60 inch block allowed the wall to meet bearing and stability requirements without using reinforcement," explained David Eids, who is Chief of Engineering & Construction for the Walla Walla County Dept. of Public Works. "This also minimized the excavation required which allowed the access road to remain open during the project."

It's no secret that Redi-Rock is known for building tall gravity walls using massive, one-ton blocks to get the job done. But this 16.5 ft. tall wall gave engineers the chance to show just what Redi-Rock blocks are really capable of.

The existing site consisted of a loess soil (sandy silt in this case). To achieve 16.5 ft. in the highest portion of the wall, Eids designed it using five courses of 3420-lb. Redi-Rock 60 in. base blocks at the base of the wall, five courses of 41 in. blocks, and one course or 28 in. blocks.

"Other alternatives considered would have required additional excavation and impacted the access road to the residence and winery," Eids said.

An additional benefit was the superior aesthetics the system offered. Redi-Rock is available in three natural stone textures, but the County felt the newest, most natural texture—Ledgestone—would be the best fit for the project.

"Although rural, this area borders an urban area with numerous wineries," Eids explained. "It was felt that the Ledgestone finish could decrease the possibility of graffiti and the colored natural rock type finish would blend in with the surrounding terrain."


In total, the project required 989 Redi-Rock blocks, equaling roughly 6,000 sq. ft. The installation phase of the project took only 3.5 weeks.

The County was so pleased with the outcome of this project that they've since specified Redi-Rock for another project where Redi-Rock gravity walls were designed as bridge abutments.

Walla Walla Finished Wall

Design Manual

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