The New Aesthetic of Retaining Walls

It’s little surprise that engineers, developers, and landscape architects have long appreciated retaining walls. The walls, after all, are adept at limiting erosion and stabilizing steep slopes. But industry pros aren’t these walls’ only fans: Add the owners of 12 turn-of-the-century Victorian homes in Mississippi to the list.

In the late 1990s, eroding soil from a 160-foot-tall cliff threatened to swallow the dozen Victorian homes that had sat proudly since the 1800s in the town of Natchez, MS. Fortunately for homeowners, city officials took action, turning to retaining walls to save these historic structures.

The situation was so dire, in fact, that David Gardner, city engineer for Natchez, says the homes might no longer be standing if not for the two retaining walls construction crews from Atlanta, GA-based Hayward Baker installed in 1996.

“That erosion there was like a cancer,” Gardner says. “It eats away at you until you die. The bluffs kept encroaching into the city, slowly, slowly, taking property and streets. We had to do something.”

Gardner is far from the only city engineer-or landscape architect, developer, or department of transportation engineer-to turn to retaining walls to solve an erosion problem. The walls have been popular for decades thanks to their durability and their ability to stabilize dangerous slopes. What’s changing now is that the manufacturers of such walls are providing engineers and developers more options, ones that focus not only on function but also on, of all things, beauty. It may sound odd to refer to beauty when talking about retaining walls. But architects, homeowners, and property owners are more than ever requiring that the retaining walls used in their projects not only work well but also look good. And this desire is changing the ways in which manufacturers of retaining walls do business.

“Aesthetics are becoming so important in this business,” says Scott Hughey, manager of licensee business for Tensar Earth Technologies, a retaining wall manufacturer based in Atlanta. “We are moving into a phase where architects are demanding that retaining walls look aesthetically pleasing. They want to get away from the 43-foot-high gray wall, and want instead something that looks more natural.”

Contractors, of course, can still choose from the standard types of retaining walls: segmental walls made of interlocking blocks, poured-in-place or cast-in-place walls usually made of concrete, soldier pile, mechanically stabilized earth walls, and soil nail walls. But they can also select walls that are made from differing earth tones that look more like something found in nature, not manufactured in a lab. They can choose larger blocks that look like natural limestone to form their walls. They can even select walls designed specifically to allow for easy vegetation, again turning something plain into something that looks far more natural.

This trend is good news not only for engineers, developers, and landscape architects-who can now find the right wall for any project-but also for property owners and homeowners, who can choose walls that are as visually pleasing as they are functional. And as every builder, developer, contractor, and architect knows, happy property owners mean referrals, and referrals mean more business.

“We would much rather have our licensees sell walls that are varied in color,” Hughey notes. “We are really trying to promote the more natural look. This is one of the more important changes in our business, and it’s pretty obvious why: The natural look is much more aesthetically pleasing. Natural-looking walls are an attractive solution to a problem. They make everyone happy, and that is our goal.”

An Attractive Choice in Historic Natchez
Appearance certainly played a role in Natchez. Gardner wanted to stop the city’s bluffs from eroding, of course, but he also wanted whatever solution he used to be as aesthetically pleasing as possible.

“Natchez is a very historic town,” Gardner says. “We have preservation guidelines stating that we can’t go in and adversely impact properties. I knew that what we were going to do would give this entrance to the city a new look. These bluffs have stood here for centuries. They may be first thing you see, depending on where you enter the town.”

That’s why Gardner chose to go with natural-looking retaining walls. Construction crews first installed a soil nail wall to stabilize the bluffs. They then built two additional retaining walls, mechanically stabilized earth walls from Minneapolis, MN-based Keystone Retaining Wall Systems. The stabilized earth wall that crews installed at the lowest level was especially impressive, running 280 feet in length and standing up to 32 feet high.

Both walls were also examples of the new look for retaining walls. The soil nail wall had a brown die, and Gardner made sure that its texture was left rough, making it look like natural dirt. The mechanically stabilized earth walls were also colored to match the local soil.

“The whole project had a good aesthetic look. It all blended in well together,” Gardner says.

Of course, the appearance wouldn’t have meant much if the retaining walls didn’t do their jobs. The bluffs, located along the Mississippi River on the north side of Natchez in what is known as the Clifton Heights Historic District, are composed of loess soil. This is basically wind-blown silt that, when examined under a microscope, looks like tiny flat plates. When dry, this soil has the unusual ability to stand on a vertical face. But when wet, it loses that characteristic and becomes highly susceptible to erosion.

The City of Natchez performed studies on the bluffs and discovered that more than 200 feet of cliff had eroded since Civil War times. It had reached the point where erosion was threatening the city’s streets and historic properties.

The city in 1993 finally qualified for emergency funding from the Natural Resources Conservation Service, an agency run by the US Department of Agriculture. It then spent more than $28 million to shore up the bluffs with retaining walls, a project that wrapped up in late 1996.

But stopping the erosion was just one challenge. Project engineers also needed to restore yard space to the owners of the 12 homes, space that had been steadily eaten away over the years. To do this, crews ran a shelf 25 feet from the mechanically stabilized earth wall toward the Mississippi River. The wall section rising above this shelf was cut back 10 feet, while crews stabilized the remaining area with geogrid soil reinforcements. They then filled this area with 6,000 pounds of lightweight aggregate topped with sod and plants. The original bluff serves as one sidewall of this section, and one of the retaining walls serves as its back wall.

“This was a solution that worked extremely well for us,” Gardner says. “Those walls are still holding up great. They’ve allowed us to save some history in our town. And they look so natural.”

The Aesthetic Factor
The manufacturers of retaining walls have been quick to provide solutions to people like Gardner, engineers searching for walls that look as good as they work. For example, ICD Corporation, a manufacturer of retaining walls based in Milwaukee, WI, manufactures StoneWall Select segmental retaining walls. The components can be stacked without mortar. Because aesthetics have become so important in the business, the company also offers “green walls.” Creative landscape architects and designers can vary the blocks of the company’s green segmental walls to leave space to install as much greenery-plants, shrubs, whatever-that they and their clients would like. This transforms an ordinary retaining wall into a visually pleasing landscape feature.

Bob Dean, ICD Corporation’s president, notes that this type of wall gives landscape architects the ability to be as creative as possible when drawing up plans for their clients. For instance, designers can curve by 4 to 5 feet the retaining walls they install, put in green wall features such as plants and small shrubs, and then move right back to a straight wall. They can even create a basket-weave design of plantings.

“To be honest, all the segmental walls are basically the same; every segmental wall works the same. They all connect with geogrids these days. I think what the developer has to look at is what you can do with the product,” Dean says. “How versatile is it? What features can I take advantage of? Ours look different than anything else on the market.”

Ron Wormus, who is in charge of technical support for Vancouver-based Lock+Load retaining walls, agrees that aesthetics have become crucial in this industry. His company, for instance, has added color concrete blocks to its line of segmental wall products. The company also sets itself apart by manufacturing blocks that are four times larger than are the basic masonry blocks churned out by block machines.

These larger blocks have an appearance similar to limestone. Because they are so large, construction crews can run a 1,000-pound compactor up to the very edge of Lock+Load’s retaining walls without damaging them. Because ground can be compacted to the very edge of these walls-as opposed to other types of retaining walls where compacted earth has to stand about 3 feet from a wall’s face-property owners gain more space for their projects.

“People always want more space,” Wormus notes. “If you are dealing with a limited right of way for a roadway, you want to put a guardrail out as far as you can to get as big a shoulder as possible. Our product allows people to do that.”

Hughey, from Tensar, says the biggest push for eye-pleasing retaining walls is coming from property owners, both commercial and residential. That’s why it’s so important for manufacturers to continually try to develop newer, better-looking products. Manufacturers that ignore owners’ demands risk losing business.

“For a lot of people, these attractive retaining walls are part of their exit strategy,” Hughey says. “A lot of these property owners are looking at staying at a site for a short period of time, say five years or so. They want a cost-effective solution to whatever problems they are having at that site, but they also want something that a potential buyer will look at and think is attractive. That can impact a future sale. So there has to be a balance between function and looks. And that’s what we are trying to provide.”

Strengthening Banks in Tupelo
H-pile and wood lagging walls don’t last forever. Just ask municipal officials in Tupelo, MS. They saw the wood lagging retaining walls that had supported the banks of the Lawndale drainage channel in their city gradually rot during the nearly two decades of its service. They feared that the wall, which sat upstream from a bridge on Lawndale Drive and had suffered from more than 20 years of erosion, would wash away during the next major storm to hit the city.

Engineers faced the challenge of planning and building a replacement retaining wall quickly. They considered several options, including a gabion wall, a sheet pile wall, and a new H-pile and timber lagging wall. Eventually, contractors and engineers chose to install a segmental retaining wall system.

James Glasgow, owner of Con-Terra, a contractor based in Fulton, MS, explains that the segmental walls made sense: They were powerful enough to do the job and easy enough to install quickly-and quick installation was key for this project.

“We had to really time the project right,” he notes. “We had to get everything done between storms. If we had a significant rainstorm, we would have had a real problem getting that wall in there. The advantage of the segmental wall was that once the foundation was in we could do the whole length of the channel quickly.”

In February 2003, Con-Terra crews installed StoneWall Select along the channel. The system of high-strength stackable blocks are made to look like natural stone.

Con-Terra installed a retaining wall that stretched 112 feet long and stood 10 feet tall. It included more than 1,700 square feet of surface area and incorporated six layers of geogrids to help stabilize the bank. It took the company about three weeks to finish the wall.

Though the project went smoothly and the retaining wall is still doing its job today, Con-Terra engineers and workers faced some unusual challenges. The channel drains a large area of the city of Tupelo. During the course of the project, nuisance waters-flowing at about 2 or 3 gallons a minute-continually trickled through the channel. Before installing the segmental wall, Con-Terra crew members had to divert this nuisance water to the other side of the channel. Otherwise, they would not have been about to install the wall’s foundation.

Workers built a small culvert dam that stretched the length of the channel, sending the water out of the construction zone. “It wasn’t a great deal of water,” Glasgow says. “It was just enough so that we couldn’t get compaction. We had to compact our crushed limestone base free of water. We had to be a bit creative, but it did work.

“This wall will last a long time. It’s as close to forever as anything you can imagine,” he says. “That timber wall had been there 20 years. Treated timber doesn’t last forever. Segmented walls do.”

Affordable Beauty
Sometimes achieving just the right look proves too costly. In such cases, developers must be creative.
In Hoover, AL, for example, officials with Cypress Equities, a division of Staubach Development, wanted a unique look for the segmental retaining walls they’d need for their new shopping center development, Inverness Heights Market. Thanks to a local distributor, they were able to meet this challenge.

Initially, Cypress officials considered a segmental retaining wall system that was too costly, and would have pushed the project over budget. Fortunately, Shelby Block, a Pelham, AL-based manufacturer of retaining wall units, came up with a different plan: The company offered Cypress blocks of two different colors. Crews with wall installer J.A. Manning Construction then placed the two colors in a random pattern during construction, achieving the distinctive look Cypress wanted for this new shopping center.

“People have complimented the development,” says Ken Fox, owner of Shelby Block. “It has a nice look to it that these developments sometimes don’t have.”

The project itself-which brought to the area such retail centers as PETsMART, TJ Maxx, and Party City-drew to a close in the spring of 2004. It was not without challenges, though, and the site itself was the source of most of them. The area required the construction of a reinforced slope, installed by site contractor Saiia Construction of Birmingham, AL, before crews could even install the first of three retaining walls.

Each of these retaining walls has its own specific function. The first supports the retail center’s parking area. The second supports an access ramp into the parking area. And the third supports an additional parking area and adjacent soil.

The walls are made up of dry-cast concrete units that are 8 inches high by 18 inches long and 12 inches deep. Shelby Block provided 14,000 square feet of retaining wall units for the project, in two colors: country stone, a tan-grey combination, and cinnamon, which, as the name suggests, is a combination of red and brown.

“This was a pretty big project, and we were involved in it from the start,” Fox notes. “We dealt with the architect, with the owner of the project, with everybody. We were involved from the planning stage through the color coordination into the actual production of the units.”

As Many Uses as There Are Projects
Sometimes the beauty of retaining walls comes not from their color, texture, or ability to hold vegetation. Sometimes it comes from their versatility.

Marvin Wyatt, president of Key West Retaining Walls in Wilsonville, OR, says his company installs about 7 million square feet of modular blocks and panel-and-wire walls annually in eight western states. “There are all kinds of retaining walls out there, for just about any project you can think of,” he says. And different walls work best with different projects.

For instance, for the recent Golden Valley Roadway project, which involves the creation of a highway overpass in Santa Clarita, CA, Key West began installing 12,000 square feet of mechanically stabilized earth retaining walls last November. The walls will hold up the highway for the new overpass. Wyatt and his company had to get creative for this project. Instead of selecting a poured-in-place wall system, Key West instead chose a segmental system manufactured by Lock+Load. The blocks in the system are reinforced by steel, which means that instead of having to work with wider blocks-those 24 inches thick or more-Key West is able to install blocks that are 4 inches thick, meaning that the entire project will eat up far less space than it would have if developers had instead chosen a standard poured-in-place wall.

“There have been so many advancements in the last 20 years in retaining walls. It’s incredible,” Wyatt says. “Years ago, everything was always cast-in-place walls. Today, though, the mechanically stabilized earth wall systems have made it possible to build retaining walls quicker and with less money involved.”

The ways in which developers have stabilized these retaining walls has changed, too. Key West, for instance, uses geogrids as often as possible for this. Geogrids bring their own benefits to a project.

“Thanks to the geogrid material we can use onsite soils for reinforcement,” Wyatt says. “We don’t have to haul in additional outside soil. That, too, saves time and money on these projects. By using geogrids and mechanically stabilized retaining walls, it’s made it possible for a lot of shopping centers, housing developments, and roadways to use onsite soil for reinforcement. That has saved a lot of people a lot of money.”

Of course, shopping centers and highway projects aren’t the only ones on which Wyatt has turned to retaining walls. His company recently built a 16-foot-high mechanically stabilized earth retaining wall outside a new elementary school in Salem, OR. The school, Jesse W. Harritt Elementary, butted against a wetland. Key West was called on to help retain more than 400 linear feet of land against this wetland. The company again used geogrids to help stabilize the retaining wall. “There truly is a retaining wall solution for any project,” Wyatt believes.
He won’t get any argument from Dean Sandri, an engineer with Carlsbad, CA-based Soil Retention Systems. The company stands out from other manufacturers of retaining walls because all of its segmental retaining walls can be vegetated. This aesthetic touch has made a big difference to property owners, Sandri notes.

“Contractors can’t care less about the vegetation,” he says. “They want to build the walls fast and make money. The owners are more interested in aesthetics. For them, aesthetics are like an 8 or 9 on a scale of 1 to 10.”
Contractors, though, should take note, he believes. After all, Sandri’s company has installed walls stretching as high as 45 feet in the city of Calabasas, CA. This is significant because the city regulations state that retaining walls can only stand 6 feet high. How, then, did the project get around these regulations? The city’s officials routinely grant variances because the vegetated walls Soil Retention creates are so visually pleasing.

“A lot of cities here are saying “˜no’ to non-vegetated structures,” Sandri says. “And I expect this trend to continue. What starts here generally ends up traveling across the country.”