Buttressing the Cliffs

While this home near Cleveland has great views of Lake Erie, the homeowners watched with dread as the cliffs retreated closer to the foundation. The home was originally 20 feet from the cliff. The top 10 feet of the 40-ft. cliff, comprised just of topsoil, were particularly unstable.

The good news: A million-dollar home sits atop a 40-foot bluff overlooking Lake Erie, just outside Cleveland, Ohio.

The bad news: The back of the house, originally about 20 feet from the bluff and the cliff face, is now on the precipice. The top 8 to 10 feet of the cliff is topsoil. Below that is about five feet of solid clay, which turns to shale further down.

The objective: Keep the cliff and home from sliding into Lake Erie.

“The softer shale flakes off but it gets harder as you go deeper,” Greg Norton, owner of NCS Construction Services, whose father owns the precarious property. “The lake eats away at the base of the cliff, but it’s the groundwater at the top that does most of the destruction. First the soil, then the clay washes away and then large pieces of rock.”

Plan A
Norton and Chris Andrassy, a civil engineer with Andrassy Engineering in nearby Bay Village whose specialty is designing erosion-control structures on the big lake, first attempted to control the erosion in 2001. After securing the necessary permits from the Ohio Department of Natural Resources and U.S. Army Corps of Engineers several years ago, they placed large boulders (“armor stones”) in the lake 20 feet from the shore to break the wave action.

When that didn’t work…

Plan B

A couple of years later, a concrete seawall was poured that rose 13 feet out of the water from the base of the cliff.
“We didn’t cover the rest of the cliff. We tried to get vegetation to grow but we couldn’t get anything to sustain,” Norton recalls.

When that didn’t work…

Erosion control Plan A placed armor stones 20 feet from the shore to break the wave action of Lake Erie. Plan B, several years later, was erecting a 13-foot tall seawall at the base of the cliff, requiring about 600 cubic yards of concrete. The seawall, with an 18-inch cap on top and resting on a ledge chiseled out of the cliff face, became the footing for the retaining wall.

Plan C

The homeowner wanted a segmental retaining wall to cover the rest of the bluff face. Norton got in touch with Andrassy again.

“I’d done different kinds of retaining walls—SRWs, sheetpile, seawall blocks—but on these kinds of walls, when you’re looking at using a geogrid, you’ve got to have adequate space in your backfill to lock into,” explains Andrassy. In this case, there was little room for geogrid, so a different type of anchoring system had to be used.”
Andrassy started researching alternatives and determined anchor bolts could secure the geogrid to the bluff.

“I’d been interested in that technology for awhile working on these bluffs, so I went through different literature, got some data on the bond strength and ways to distribute anchorage capacity across the wall,” explains Andrassy.

“There are probably different types of anchorages we could have used. We did hydraulic ram tests on a couple of the anchors we selected to make sure they’d hold.”

Using a 2.5-inch drill bit, 75 holes were drilled 6 to 7 feet into the cliff face and anchor bolts cemented into the borings. A steel bar was then attached to the anchor bolts and the geogrid attached to the steel bar to secure the wall to the cliff face.

“Greg was careful about the drilling,” says Andrassy. “He made sure he had plenty of depth, and in a lot of cases he probably over-drilled. Since you’re dealing with some unknowns and with the nature of the rock—hard, competent rock to more crumbling rock—you’ve got to err on the side of caution.”

The existing seawall was used as the footing. The concrete wall extends upward for 17 feet and an 18-inch cap on top rests on a ledge chiseled out of the cliff face. The Versa-Lok wall rests on top of the cap. The seawall required about 600 cubic yards of concrete.

Once the footing was completed, a series of three decks was built that jutted out from the cliff and was connected to a pier on the water by zig-zagging stairways. The retaining wall was built behind the deck/stairway structure.

The Versa-Lok wall begins at about 13 feet above the water level. It’s 65 feet wide and 27 feet tall and was built in three tiers with a slight curve.

“That allowed us to follow the bluff face,” Andrassy explains. “The lower two-thirds of the bluff was very steep, nearly vertical. The rock transitions to soil at the top, so it starts to fall back. That allowed us to bench into the existing face, so each segment has its own footing.”

About 3,000 Versa-Lok standard units in a blended pattern of 80 percent brown and 20 percent gray were used. A special conveyer belt system lowered the blocks down the cliff face one by one; a chute alongside the conveyer was used to transport the backfill aggregate.

“The higher we went with the wall, we had to adjust our system of transport,” says Andrassy. “We had a little innovation going on. Everyone got a good workout. No matter how good you are at moving it, that’s a lot of block.”

“With its flexible slot-and-hole pinning system, Versa-Lok was perfect for the application,” says Norton. “It looks awesome.”

“One of the biggest challenges of the job,” Norton concludes, “was explaining to people what it was going to look like when it was done. The other big challenge was getting the material down there. But I like the challenge. I don’t like cookie-cutter designs.

“There are all these million-dollar houses up here and none of them can get down to the water.” That may change once the neighbors see this wall.

Project Team

• Contractor: NCS Construction, Brunswick, Ohio
  
• Engineer: Andrassy Engineering, Bay Village, Ohio
  
• Versa-Lok manufacturer: 4D/Schuster’s, Sheffield Village, Ohio
  
• Source: Karl Bremer, Editor, VERSA-LOK Retaining Wall Systems.