As any Jack or Jill fetching water knows, an unstabilized hill is a dangerous place to climb. Gravity can be a real problem, for rocks as well as water carriers. Whatever it is, if it’s on a slope, it’s just a matter of time before it starts slip-sliding away. From landfills and lake banks to debris flows in canyons, it is someone’s job to keep slopes in place. Fortunately for Jack and his ilk, the market is awash with advancements. Slope stabilization is a thriving industry, and when these people “hit the slopes,” they aren’t just playing around.
Pile It High and Deep, But Don’t Let It Float Away
Jerry Heinz is job foreman for Prairie Restorations Inc. in Tolono, IL, about two hours south of Chicago. A commercial landscape installation company, the firm restores landfills and roadsides for government agencies. “We began as a niche market for landfill restoration, but the governor [the recently indicted and impeached Rod R. Blagojevich] slashed the EPA budget, and the last landfill we restored was two years ago.”
Heinz says that of the 30 Illinois landfills identified as high priority for restoration and abatement, only 18 have been completed. “We worked on 13 of them,” he says. “I have seen gullies big enough to dump a semi, with garbage floating into streams. After restoration, they look like parks.”
In September 2007, Heinz restored the 26-acre Saline County Landfill in Harrisburg, IL. “There was a lot of erosion, and 21 of the 26 acres had in excess of a three-to-one slope,” he recalls. “It had been recapped with a 1-foot layer of topsoil over 3 feet of clay and a liner. We had to establish a cover strong enough to hold over the winter. We were required to use the seed mixture specified by the engineering firm, but they allowed us to decide how we would cover it with mulch. We took this challenge to our Finn supplier, Jeremy Taylor of Applied Turf Products (ATP) in Missouri, and went with his recommendation.”
Taylor recommended Finn Corp.’s HydroBlend 600, which acts as a growth enhancer and soil stabilizer. Prairie Restorations spent 10 days on the project, losing a couple of days to a heavy rain that wiped out the soil preparation and required starting over.
“The work went smoothly because we had the site to ourselves,” Heinz says. “The only problem was getting the water to the work site. We were pumping from a retention pond on the property. It was muddy and sloppy near the pond, but the site itself was dry.”
Heinz says a high germination rate is vital for sloped sites, which require quick emergence for growth and establishing soil stabilization. HydroBlend 600 proved ideal for this project. “We had a warm spell, and with the moisture from the rain, the hydroseed just popped. Seven days after we had applied our last load of Finn product, we had a meeting with the site owner and the engineer, and they couldn’t believe it. There was already a green-grass tint over the landfill. The following spring there were no serious erosion problems, and the growth before freezing was enough to hold the soil over the winter. We were never called back.”
From roadside ditches on interstates and highways to a recent 33-acre project on a park, Heinz is always looking for the quickest emergence to prevent slope erosion. “This product is the best we have ever used to secure a quick stand for slope stabilization,” he says.
Using the Right Program
When it comes to landscape installation, Todd Reinhart says it’s all about having a program in place. His 23-year-old firm, Reinhart’s Ground Maintenance in Bloomington, IN, specializes in generalizing. “We do it all,” says Reinhart. “We are a total commercial landscape service, from dirt and site work to trees and maintenance.”
But successful landscaping requires organization, planning, and most of all training. Reinhart says his company turned an important corner about three years ago when it bought a Finn HydroSeeder from Jeremy Taylor at ATP. “He brought us up to speed in just a few weeks,” Reinhart says. “He told us the product we needed and trained us in rates of application, amounts, and the results we could expect. He even helped us figure bidding costs. It’s not trial and error anymore. We were calling about a seeder, and a relationship developed.”
Reinhart notes, “We used to do “˜seed-straw-crimp.’ It was labor intensive. Now we use the HydroSeeder, and it’s comparable in cost because there’s less labor. People might say hydroseeding doesn’t give a good result, but that’s because they don’t know how to do it. The results depend on knowledge and the product being used. It’s the overall approach that matters.”
Reinhart says he knew he was getting good results, but they were difficult to quantify because there was no comparison factor. In the fall of 2007, he got his evidence.
“There was a 40-acre parcel along a main thoroughfare in Bloomington, and 15 acres needed seeding. When we got near the end, there was a half-acre of slope with runoff down toward the main road. We got the part behind the sidewalk where there was a steep berm. Another firm was hired to do the part between the sidewalk and the curb. We used our best mulch and all Finn products. In just 10 days we had a fantastic stand of grass on the hill. The competition had zero grass and patchy ground. They didn’t use any tackifier, and even though they had less slope, the ground was washing away. We had a side-by-side comparison.”
Again in Bloomington, Reinhart was hired to landscape the new Welcome Center at Illinois Wesleyan University. It was to be a Leadership in Energy and Environmental Design (LEED)-certified building, and the administration wanted it open by homecoming. “They didn’t want sod,” Reinhart says, “because they would have to water it. But they wanted lawn in two weeks. We assured them we could get it done. We said, “˜Just trust us.’ Sure enough, in two weeks we had a fantastic stand of grass. It’s the blend of seed: that’s what it comes down to.”
It’s a Matter of Management
“If you give Mother Nature back what you’ve taken from her, she’ll replenish it; she’s great at that,” says Lewis Bumpus, solid waste director for Williamson County in Franklin, TN.
After 30 years in the business of solid waste, Bumpus has become an expert in stormwater management. “There’s constant mining on a landfill,” he says. And the 408-acre landfill he has operated since 1998 is beset with extraordinary circumstances.
“We have unique challenges in stormwater management because we’re situated on a divide,” Bumpus says. “It’s a unique geological situation; there are few places where you’ll find a major watershed divide located on an active construction site.”
In addition to its lack of topsoil, the landfill is extremely hilly, rising in many areas to almost 100 feet, according to Bumpus. Because of its location on the divide separating the Tennessee River and the Cumberland River watersheds, any water that escapes enters several streams traversing the property. “One inch of rain falling on an acre of land equals 27,152 gallons of water,” says Bumpus. He adds, “Keeping up with rain is like keeping up with a checkbook. It’s better to manage it along the way.”
When Bumpus came to the landfill in 1998, it was on the Tennessee Division of Environment and Conservation’s 303(d) list for impaired streams. “The Arkansas Creek starts in the property 1,000 feet above sea level, and there are streams everywhere atop the ridge,” he says.
He says there was no aquatic life when he arrived, yet by 2001 the site had received the Stewardship Award for Excellence in Aquatic Resource Preservation from the Tennessee Department of Environment and Conservation. “Now we have 57 species of invertebrates,” says Bumpus, “and 26 species of fish.”
But while the creeks are coming to life and welcoming back species of insects and fish, the challenges continue. “Four of the invertebrates have zero tolerance to silt,” Bumpus says. One of these is the caddis fly, a small mothlike insect with aquatic larvae that make protective cases of silk studded with gravel, sand, twigs, or other debris. The others are the water penny, which Bumpus says looks like a contact lens, and the stonefly and mayfly.
But changing wasteland into parkland isn’t just matter of liking animals and knowing what to plant. As a scientist, Bumpus is always experimenting. “You have to keep the water level in balance,” he says. Using various onsite instrumentation, including an onsite weather station, in-ground lysimeters, and time domain reflectometry sensors, he measures the amount of water lost to evapotranspiration and is able to calculate how much actually enters the groundwater. “The only water we get is from Mother Nature’s sky; no water runs down onto the site.”
But water does run off the site, and for this problem Bumpus has turned to Typar Matrix 3D Geotextile from Fiberweb. “The Typar Matrix is a cellular confinement system composed of a series of geotextile fabric cells in a honeycomb formation that resembles gabion baskets,” Bumpus says. “The open cells are filled with a specified porous material, or ballast, such as sand, earth, rocks, or a similar substance, to produce a stable, self-supporting structure. It makes it nice for erosion control, because the fabric is flexible and you can put it on uneven ground instead of trenching it on a level surface.”
He explains the installation process: “First you dig a trench; there is no leveling. Then you set in the fabric. It fits into the soil and levels itself out. It is extremely light; one person can carry 100 feet of it with no problem. I carry it down in a satchel and no one can believe it. Instead of using a rock check dam, you can run the material across and fill the pockets with rock or close-by materials such as mulch. With traditional gabions, if you fill one before the next one, they swell out, like a potbelly stove. This fabric allows you to fill each one as you go across.”
Bumpus is always experimenting with different fill and ballast materials for use inside of the open cells of the Typar Matrix. “For flood-control applications, you can place sand within the cells to restrict water flow through the material. For sediment-control applications in a ditch, you can use riprap or crushed stone as the fill material to increase flow-through capacity. For perimeter sediment-control applications, you can fill it with mulch for additional filtering,” he says.
“We have a culvert on the side of the landfill where we installed the Typar Matrix in less than an hour using a skid-steer and a backhoe,” Bumpus says. “We took one load of rock and filled the cells. Runoff did overtop the cells during last week’s storms but did not dislodge the system significantly, even in a “˜frog-choker’ rain, the kind that only comes once in 25 years. The matrix allows us to install sediment-control and flood-control devices during a storm event in wet conditions. During a storm, if we see an area where the runoff turbidity is increasing, we can respond rapidly during the storm by adding new matrix cells.”
The major advantages of the system? “Ease of installation. It is lightweight and shaped like Lego blocks that interlace. There is less equipment required and less fill material required to build these, as opposed to a typical berm of rock or mulch material. Also, they are easy to demobilize and remove. They can be installed in wet-weather conditions. We can keep extra product in storage onsite, and, if we see in the forecast that we only have three or four hours before a major rainfall, we can prepare the site for the coming storm in one or two hours.”
Teens’ Summer Challenge Turns Erosion Into Enthusiasm
Mike Zimmer, a technician for the Rusk County Land and Water Conservation Department in northwest Wisconsin, is working for the third summer at the Dairyland Reservoir near Ladysmith. Dairyland is a 1,900-acre reservoir suffering from erosion primarily due to wave action at the toe of its banks. “We have steep hillsides, one-to-one in some places,” Zimmer says. “We are cleaning up the area, shaping the banks, taking off some overhangs and laying erosion blankets. It is all hand labor.”
Zimmer is not working alone, however. As part of a summer program called The Environmental Challenge, he has the assistance of some high-school students and their teachers.
Jerry Carow, president of the Wildlife Restoration Association, says he started this program when he was conservation warden for the Department of Natural Resources. “The program involves four high schools,” Carow says, explaining that the largest high school in the area has 300 students and the smallest has only 70. “Each year we choose eight students from each school; there is a big demand, and up to 30 or 40 of them try out.”
The students chosen to participate are accompanied by a teacher from each school and spend five hours a day doing outside service and learning instead of spending that time in a classroom. For their efforts, they earn one-half science credit and a stipend of up to $600. Among their activities over a typical summer are a forage base habitat project that involves placing some 1,400 trees in a flowage to encourage growth from the bottom of the food chain, securing hillsides from erosion, building a community park and a boat landing, fencing streams, and creating stream cattle crossings. “They love the physical work,” Zimmer says. “They get to hang off a hillside over a lake. Who wouldn’t like that? And they can see their progress.”
For the Dairyand Reservoir project, Zimmer had crews using American Excelsior’s biodegradable erosion blankets made with netting technology from Conwed. Curlex blankets consist of barbed, interlocking, curled Great Lakes Aspen excelsior wood fibers. “The system works very well,” Zimmer says. “The blankets hold the moisture and speed up germination. That helps on a site where the sun beats down. We tried hydroseeding and mulch in the past, but it wasn’t enough on the slope, and the layer just sloughed off when it rained. Now, after having installed the erosion blankets, the native grasses are coming in and growing.”
Zimmer says the process of reclaiming the lake banks involves more than just laying down blankets, however. “We put oak logs and rock at the toe of the slope. The oak logs are cut and drilled offsite, then taken by boat and installed by the students. Other students work up above with shovels, grub hoes, and axes to remove any overhangs. Others spread the blankets and seed them with native mixes. We put logs across the slope in terraces, then cut sod and layer it in for steps, placing a row of blanket between. We have planted some trees, too.”
Before the project began three years ago, the banks were eroding into the lake, and sediment was entering the flowage, Zimmer says. “In one place, a road was endangered.”
Carow says the students have spent about eight days on the project each summer. He says the more difficult a job, the better the students like it. “They want to sweat and be tired, to laugh and have fun. There’s no stopping them.”
Zimmer says the dam’s owner, Dairyland Power Cooperative, likes the work the students have done and has donated thousands of dollars toward the project.
Tourists Like Their Hillsides Green
Cambria, CA, a coastal town situated between San Luis Obispo and Big Sur, just south of the late Randolph Hearst’s “castle,” is environmentally conscious and concerned with aesthetics, according to William Kane, president and chief executive officer of Kane GeoTech. “It’s a tourist area,” he says.
Kane’s firm is an independent civil engineering consulting operation dealing with rockfall, debris flow, landslides, and soil stabilization issues. In Cambria, soil, trees, and boulders were tumbling down one of the slopes near the town and falling into the roadway. “It was a maintenance problem for the county and a safety issue,” Kane says. “We were contacted to come up with a plan to stabilize the slope and improve the looks of the site.”
In the past, the solution was often to apply concrete or shotcrete to the slope. “It is unsightly and expensive,” Kane says. “Environmental concerns have pretty well stopped these kinds of projects from being built unless expensive measures are taken to sculpt the shotcrete to look similar to rock.”
Instead, Kane’s firm used Geobrugg’s TECCO Slope Stabilization System. “After cleaning, trimming, and leveling, the surface is covered by a very-high-strength steel-wire mesh tensioned by drilled soil nails or rock nails and spike plates. The mesh fits to the slope face, and in this way prevents slope failure and rocks from breaking out. TECCO steel wire is four times stronger than chain link and therefore doesn’t stretch with the load,” Kane says.
It took about a month to stabilize the 15,000-square-foot slope, which Kane says is 100 feet high. “The contractor first drilled holes in the slope, then installed threaded steel rods about 10 feet on center and grouted them in. TECCO mesh was then laid on the slope with the rods up through it. Then anchor plates were laid over the rods, nuts threaded on and torqued. This pulled the chain link against the slope and made it taut. It actively pushed on the loose rock and soil to contain it.”
Environmentally, the main advantages of TECCO are that it blends with the slope and is difficult to see. In addition, vegetation can grow up through it, further hiding it. “You just spray on hydroseed or put vegetation mats under the mesh. Eventually, you can’t even see the TECCO mesh,” Kane says.
Brian McNeal, general manager for AIS Construction in Carpinteria, CA, did much of the site work at Cambria and says he has seen an upsurge in the use of the TECCO system over the past five years. He says AIS Construction has installed around a half a million square feet of TECCO mesh in North America, including Alaska, California, and Colorado. “All have been successful; there is little to no maintenance for the owners. In contrast, where only a draped twisted-wire mesh is applied, more maintenance is required. Draped wire mesh is a passive system. It is only a mesh curtain with anchors along the top, so that the rocks work their way down and must be handled by maintenance crews. TECCO is an active system: It is pinned and holds the mesh to the hillside, not allowing the rocks to come loose. You can work around trees and existing vegetation, and after a couple of years you don’t see the TECCO mesh at all.”
Installing TECCO at Cambria was a step-by-step process, according to McNeal. “First, we scaled off the precariously perched rocks for worker safety, and then we laid out the anchor pattern in 10- by 10-foot diamond pattern. If the area had a deep ridge or peak, we installed an anchor in the valleys to keep the mesh close. We drilled the anchors from the top down, installing them with cement grout, and tested them for pullout strength. Then we dug 18-inch-by-1-foot-deep pockets around each anchor, working from the top down vertically across the slope. We installed the TECCO mesh using our crane. Sometimes we can use a helicopter if there are no power lines above us. Next, we secured the top of the mesh to the anchors and rolled it down the hill using a crane with a bar going through the center, much like a paper towel roll. As it rolls down, we have two men on ropes rappelling beside it so we can keep it lined up with the anchors.”
McNeal says once the preparation work is done, crews can apply a lot of mesh per day. “Usually we can install 13 10- by 100-foot-long panels or 13,000 square feet per day.”
Although the TECCO panels may be installed, the job isn’t finished, McNeal says. “After we install the TECCO mesh, we go to each seam and connect the panels with hog rings or lacing cable. Then we put on the spike plates. Using hex nuts, we push each plate into a pre-dug hole and tension it to the correct torque, and then hydroseed the slope as necessary.”
McNeal is a big fan of the TECCO system. “It is more cost-effective. Shotcrete costs $30 to $50 a square foot, depending on the slope; TECCO is $15 to $25 a square foot. Aesthetically, TECCO promotes vegetation growth and blends in with the hillside. It is “˜greener,’ and there’s less work to install it, with more vegetation.”
In another application, at a coalmine in Arizona, Kane and AIS Construction used Geobrugg’s SPIDER system. The system uses high-strength steel wire in a spiral rope net that stabilizes rock spurs, overhangs, or single large, weathered, unstable rock formations.
“Rocks were falling onto a conveyer belt at the mine,” Kane says of the Arizona project. “It is a 22-mile belt that extends from the pit to the railroad terminus, and at one point goes through a cut in a mountain. AIS Construction and KANE GeoTech took on this project when several other contractors said it couldn’t be done. We consulted Erik Rorem from Geobrugg North America in Santa Fe, and he suggested the SPIDER to contain the boulders. At the time, it was available only in Europe and was shipped over for this project. With the combination of the new product’s innovative ability to work in difficult conditions, this project was a huge success. We saved the mine a lot of money by not having to move the conveyor away from the rockfall source.
Debris flows or mudslides are not uncommon in the western US, Kane says, because a lack of rainfall between April and November sets the stage for fires, which remove vegetation and leave hillsides vulnerable. He cites the town of Avalon, on Catalina Island off the coast of Los Angeles, situated at the base of a canyon and essentially built on debris flow material once headed for the Pacific Ocean. When the town was threatened by fires in the spring of 2007, Kane was called in to design mitigation measures to stop the mudslides before the winter rainy season. “We again teamed with Geobrugg and AIS Construction to move rapidly and design and install a combination of debris flow barriers and TECCO to prevent part of the town from being inundated with mudslides,” he says.
