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Just One Word: Plastics!
Bob Boole, owner and president of Kettles Construction in the St. Petersburg, FL, area, installs seawalls around channels and canals. According to his experience, determining what type of lining is necessary often depends on the land use or the property owner’s needs. “Usually the person who wants the most use of his property wants a vertical wall, so he can use his yard up to the water line,” Boole says.

Boole has used materials from Atlanta, GA–based CMI Waterfront Solutions, whose ShoreGuard seawall and bulkhead systems have various material, strength, and color options and 15 different designs covering applications from light residential to heavy-duty industrial use.

Consulting engineers draw up the plans for most Kettles jobs, and they take into account historical rainfall data such as five- and 10-year storms. “Walls are built higher than the highest tide,” Boole explains. “Engineers look at soil types, too; they must determine rainwater penetration so we can properly anchor the wall, so we don’t get movement. This area has sandy soil. For stability, we have to drive walls into the ground 4 or 5 feet.” Although Boole can purchase a variety of shades from CMI, he finds gray is the most popular seawall color.

Due to the variety of natural waters in the state, some jobs involve the US Army Corps of Engineers. “Some projects they do have to approve, but most are residential or commercial properties on the water’s edge. A common example of our typical job: boat canals, usually up to 100 feet wide, where houses abut the canals. We build the seawalls along the canals. We strictly do existing waterways. Our task is retaining land from falling into the waters,” Boole says.

The average seawall erected is 5 feet high. “A minimum of 40% of the sheet length is set into the ground,” Boole says. Each wall section is made from sheets as long as 20 feet. “The higher the bank, the higher the sheet has to be to hold back the land and to keep the water from lapping up into the land.”

He notes that the canals are also used to receive stormwater runoff. “Stormwater goes through drains into these canals; we put a hole through the seawall to allow the pipes to drain in.” 

Depending on the project, Boole’s company also uses other erosion control methods, such as 18-inch-diameter riprap, but, as a rule, he doesn’t use vegetation in these types of projects. On a recent project, he notes, “We did a replacement wall that was sinking in Snell Isle. The existing seawall was 40 years old; we put a new wall in front of it. CMI’s vinyl walls should last 50 years.”

Containing Indiana Lake
During its recent Cedar Lake enhancement project, LakeMaster of Muncie, IN, used a vinyl seawall.

Photo: Presto Products

Traditional concrete walls are no longer a contractor’s only choice.

“We were stopping erosion on this manmade, self-contained lake,” explains LakeMaster President Bud Willitzer. “In the past, we’d done a couple of other projects at this lake, because sediment builds up. This time, some of the banks were eroding because of new homes built around the lake. We put in beige CMI sheet vinyl retaining walls, which blended into the area’s ground-clay color. Depending on the slope, we installed walls 3 to 4 feet in height.”

There are various ways to determine which panels to use. “That depends on the needed height of the wall and the soil consistency,” Willitzer says. “In spring, the lake’s management put vegetation in, which keeps further sediment from coming through into the lake, and the greenery also looks nice.”

Cedar is a self-contained lake—runoff water is its source and it’s not attached to a stream. “Of course, if we’re putting in a seawall, we look at storm data to determine what the highest water level is going to be. We don’t have to put the wall to the top of the lake—we usually install walls 28 to 30 inches over the normal pool height,” Willitzer says.

As it’s designed for recreation, serving powerboats, the approximately 700-acre lake does sometimes experience wakes that can lap the shore and pull in sediment; however, “putting in the vinyl walls is really cleaning it up,” Willitzer adds. “A 4-foot concrete tile [channeling stormwater runoff] in the area opens up into the lake. We’ve also enhanced the tile opening, so there’s no wash or erosion from that.”

Stormwater runoff entering the lake comes from other areas of the city, although there is no plan to replace the existing 4-foot tile with a larger one. “There’s no expansion in this particular area,” he notes. “Now, most everything’s built up. Our project was to stop any more erosion.”

The erosion was stopped for aesthetic reasons, as well as for state regulations. “The owners wanted to fix it, to make it look nice—also the Indiana government wanted Cedar Lake to be cleaned. It didn’t have to be sparkling clean—this is not a tap water source. The stormwater that goes into the lake is not treated,” Willitzer says.

As for choosing materials by cost, LakeMaster projects mix soft and hard armor most of the time. “We want the results to be pleasing to the eye,” Willitzer concludes. “Of course, it doesn’t hurt that there’s also a 50-year guarantee on CMI’s materials.” 

Vinyl Works
Terry Amodio, owner of Amodio’s Shoreline Marine Construction in Youngstown, OH, chooses his materials by what the site dictates.

“The choice depends on the soils and the erosion issue—there can be many variables there. Basically, you have to determine how much load bearing is on top of the wall and what’s the nature of the water flow. Is there boat traffic or not? Data from five- or 10-year storms come into play, but you really want to look at 100-year storm data for the most complete protection. Of course, what you choose depends on what you want to protect. Are you combating erosion around a home? What’s the long-term effect if you don’t fix the problem?” Amodio asks.

How does he account for potential increases in water flow caused by increased development? “All rivers and streams in this area flow into lakes. When we’re working on a stream or river, we ‘read the balance,’ which is done by noting the height and width of the streambed. On navigable waterways, like the Ohio River, there are actual height marks painted on bridge pylons. But if you’re talking about an interstate highway overpass over a creek, you’d have to check the overpass bridge supports for water marks to see how high the creek has run over the years. In some cases, the state monitors these waterways, and you can ask them for readings. 

“If the waterway is on private property, the person maintaining the stream usually has information on its average height,” Amodio continues. “A lot of stormwater is added to streams, creeks, and rivers; this stormwater then flows into lakes, and the majority of the streams/rivers here that leave those lakes empty downstate, into the Ohio River.

“Of course, if our project involves a lake, we check its overflow, where it’s going over the spillway. Lake levels can flux by a couple feet. As some lakes are floodplains too, they can flux 20 feet per year in height—so all that has to be taken into consideration when installing walls to combat erosion. The majority of the projects we work on are manmade flooded valleys, which have created lakes or streams.”

Amodio has been using CMI products for just under a decade. “I use a majority of their products and systems—TimberGuard and sheet piling. We especially like their darker brown color walls although we use many of their colors. However, in certain applications, we’ve also used steel walls coated with epoxy.”

In addition to building walls up to 10 or 12 feet high, Amodio’s company also uses soft armor. “That depends on circumstances, upon the US Army Corps of Engineers or state engineers. On occasion, we will use willow stakes—cuttings off trees that can turn into trees themselves. The willows tend to grow low and take over slopes. They can be somewhat invasive, but not too bad. If the site calls for vegetation, we’ve also used red twig dogwood. In some locations, we’ve installed riprap.”

Photo: Matterhorn California

Even banks along creeks that do not run year-round are subject to gradual erosion.

Photo: Matterhorn California

Recent projects have included shoring up a pier at Conneaut Lake. “It’s a boardwalk-type pier, 15 feet wide and 80 feet long. Its old steel pilings from the early 1940s had rotted out, and the owner was looking for a product to last his, and his kids’, lifetime. We used vinyl piling and walls, and it did protect the shoreline a bit.

“We also recently repaired a dam in an area of Cleveland [Ohio] called Gates Mills, which overlooks the Shenango River. The earth dam’s backside was washing out and could have caused problems for nearby residential homes. We drove in 30-foot sheets to lock the soils in.”

For Berlin Lake in Portage County, OH, Amodio was called in to stop erosion that was threatening homes. “This US Army Corps of Engineers–controlled lake has a lot of homes around it; two families were losing their houses, because the lake fluxes 20 feet per year,” he says.

“The Corps of Engineers blamed the bad sandy, loamy soil that also has blue clay mixed in with it. To correct this problem, we used riprap, geogrid, and vegetation, as well as vinyl walls. The result—everyone’s foundations stopped moving, and slopes to the lake stopped sliding. During the installation, we ran into stiff shale, just below the heavy clay; we were able to attach the wall to the shale.”

Why use vinyl most of the time? “Because it does work—it retains soils and slows erosion. You need the equipment to install it, but it will last a long time if installed properly. For other jobs, everything has its place too—like riprap and sheet piling—but I like vinyl.”

Just Another Brick in the Wall
Long a standard erosion control solution, retaining walls are highly effective in shoring up streambeds or creek beds. Santa Rosa, CA’s Matterhorn began in 1985 by erecting precast concrete block retaining walls on roadsides, in new developments, and on other such soil-containing projects. When, in 1986, the City of Vacaville, CA, employed the firm to shore up its waterways, Matterhorn soon found it had all the work it could handle, merely by specializing in fortifying streambanks.

The rainfall in the region in January 2006 was nearly record-breaking; the saturated soil was causing many large trees to uproot themselves. Matterhorn was called in to repair an embankment where a large oak tree had collapsed into Napa, CA’s Browns Valley Creek. The tree’s root system opened an area 60 feet long, 30 feet wide, and 18 feet high. After sandbagging off the water flow, Matterhorn erected a wall of its Secura Slope modules on a Helix Anchor foundation, restoring the basic channel alignment with a larger cross section, to provide for easier water flow and better bank stability.

Civil Engineer Brian Ballerini explains details of such a project. “Before installing a wall, volume calculation is done to design the height of the wall. It is also used so we can anticipate the velocity of the water and the resulting force on the wall. Sometimes—not always—this is calculated by the engineer. Many times we calculate the two- and 100-year storms (the extremes between normal flow and high flows). The height of the wall will be dictated by a specific storm, which is generally mandated by the governing agency. A two-year storm—what the creek normally receives—would require a lower wall; designing a wall for the 100-year storm is very expensive. As a compromise solution, a 10-year calculation could be performed and the wall height designed accordingly. For these types of projects, we usually just restore the area to what it was before the bank-breaking event.”

According to Ballerini, the geotextile lining placed behind the wall is generally specified by the manufacturer. The lining’s purpose is to prevent soil from infiltrating the gravel layer directly behind the wall. Not only must the soil be contained, but also its type is very important in terms of the design; soil conditions determine what footings and anchors will be utilized.

Accounting for potential flow and volume increases is not a large concern in small waterways. “Most clients are private property owners who want an economical solution,” Ballerini says. “We examine upstream and downstream effects, but generally more qualitative than quantitative. We ask the question and may apply a factor of safety if applicable.”

Photo: CMI

Vertical walls are appealing because they allow for yard use to the shore.

Photo: CMI

There are cost differences between soft armor (vegetation in combination with various geosynthetic linings) and hard armor (such as retaining walls), but in some instances, soft armor is not a viable option. “Soft solutions can be considerably cheaper, but in urban settings they can be ineffective in areas of the creek that will experience high flows. Plantings are cost-effective in the short run, but if we plant them in spring or summer they don’t have enough time to develop good root systems before the storms come. You may have to replace plants, so the costs increase. On the other hand, with hard armor, even if you have to start late in the season, it goes up fast, and the problem is solved.”

Matterhorn’s experience gives it an edge over many contractors. “Civil engineers are shying away from creek bank repair,” Ballerini explains. “The work is very labor intensive, it has a large number of variables, and it does not fit into our risk-versus-reward equation. The advantage of using a Matterhorn product is that it is design-built, and the contractor is better positioned to deal with the risk associated with these types of projects. Matterhorn projects have stood the test of time. We have used them on many projects without a single failure and no evidence of adverse upstream or downstream effects.”

Scaling Mountains of Paperwork for Clients
Matterhorn’s Phil Zeidman further explains his company’s position. “We end up handling all the details for the client. If they’re contacted by, or contact, the local flood control district, they turn it over to us—we do all the permitting and drawings. Civil Engineer Brian Ballerini also sometimes does drawings for us.

“We will hire civil, soils, and structural engineers and then go to the US Army Corps of Engineers, building departments, and flood departments and juggle all the paperwork and forms—because, if you don’t do such tasks every day of the week, you don’t get it done. So if you’re the homeowner, you can’t do it all.

“After they take on a job, some civil engineers will come to me and ask me to take the ball. For example, there’s a new paperwork hassle: California’s Department of Fish and Game once used the same form every other agency used. Now they have a different form, so you have to fill that out—we’re back to square one; we have to fill out forms for each regulatory player. Thankfully, after 20 years, we have the expertise and rapport with agencies—but such tasks are difficult for the average person. Of course, once you get permits, then comes the easy part of the job—fixing it! To be fair, though, years back, there were a lot of bad repairs done, so that’s why California has all the regulations.”

Reinforce the Alamo!
Vacaville’s January 2006 storm laid siege to Alamo Creek, which winds around the Hidden Acres mobile home park. The park’s new owner, Jim Wagar, knew he had to act.

“What happened with this creek was a progression over the many years; the prior owners didn’t maintain it,” Wagar says. “There was a gradual and consistent erosion of the soil and the bank. It was getting to a point, after we bought it, we knew this would become a problem. At certain points along the bank, where nine homes were located, the banks were steadily eroding, and we were concerned. The unusual storm, which brought torrents of water to the creek bed, did considerable damage. Rather than wait, we decided to be proactive—make it right from the get-go.”

Hidden Acres contains 52 homes on approximately 6.5 acres. An attractive subdivision of single-family homes leads to the park, which ends at a somewhat rural area. Alamo is a natural creek, not one designed for stormwater. “In fact, the creek doesn’t run year round, but during the rainy season it can get quite high. It was near the bank during that storm.”

Wagar consulted with between six and 10 soil engineers about his problem. “One particular engineer told us about Phil Zeidman and Matterhorn; after talking to quite a few different people, what he said just rang right—what he had to say about the retaining wall, how it works, exactly what it would solve. It sounded great to us.”

It turns out that Zeidman had a lot of experience with Alamo Creek. “From that wall, going south to San Pablo Bay, we’ve had a dozen jobs on that creek—behind houses, trailer parks, and city property. The January 2006 storm was perhaps a 50- to 100-year storm—way out of line from the usual. The major problem for the creek is development. Builders paved everything in sight. Therefore, 95% of the water from the sky goes down the creek. No one thought about creeks when making developments.”

Zeidman illustrates how much space a creek needs to handle a large volume of rainwater: “In one section of the creek, builders did take into account the force of rainwater and dug a larger space. Where the creek used to be 3 to 6 feet wide and 5 feet deep, it’s now 8 feet deep and 20 feet wide—and during the big storm that creek was filled to the limit.”

Matterhorn’s Secura Slope blocks were used to construct the retaining wall for Wagar’s project. “We lined the bed from Hidden Acres’ side of the creek and then backfilled the wall with soil so vegetation will grow back, which enables the creek to run effectively while it provides cover and shade for animals. Humans think it looks nice, too,” Zeidman says.

“The slope has retaining walls only on our side of the creek,” Wagar says. “It’s a very impressive wall—we’re very happy with it. Zeidman’s going to put in one more for us farther down the creek. We’re going to have a landscaping company come out and put in some ivy to make the wall more ‘green friendly’ and to aid in erosion control of the very top. The ivy will be planted at the top and trail down the wall.”

How long will Wagar’s retaining wall remain standing? “Forever. Look at the walls the Romans built—they’re still up,” Zeidman chuckles. “Seriously, since we’ve been in business, we’ve never had a failure of our system.”