Grace and Tenacity
Hard-armor systems help battle the elements and balance project budgets.
In any economy, but especially during a recession, it’s no secret
that reliability is the primary concern for contractors across the
United States. Building materials at a construction site must perform
the job they have been designed to complete, and perform it effectively
the first time they are used. Today there is little margin in any budget
for a solution that needs to be reworked.
When a project requires manmade structures because natural solutions
alone don’t have the strength to handle the stabilization of a
site—because of water velocity, steep slopes, or proximity to
residential areas—solutions running the gamut from gabions to retaining
walls can be both practical and cost effective.
Flood Protection in Historic Missouri
An ecologically sensitive recreation area downstream from Mark
Twain Lake, the Clarence Cannon Dam near Hannibal, MO, had to be shut
down following flooding in 2008. Floodwaters had overtopped the levee to
the west side of the dam, and water erosion widened the channel,
explains Greg Tarbutton, a project manager at Randy Kinder Excavating
based in Dexter, MO. The company was contracted to install hard armor at
the project, which totaled more than $6 million as work continued and
moved toward conclusion this fall.
“We were widening the Salt River below the dam as well as armoring
the slopes and the entrance road, which is the levee,” says Tarbutton.
The company used 60,000 square feet of articulated concrete block from
West Lorne, ON–based International Erosion Control Systems. “The owner
of the job, the St. Louis District of the US Army Corps of Engineers,
wanted articulated concrete blocks to armor the slope.”
|Photo: RANDY KINDER EXCAVATING
Early excavation of channel and slope debris after the unloading process
This permanent solution required careful planning prior to the
project’s onset in February 2011. Tarbutton says the blocks were placed
not only along the dam itself, but also along the levee road as an
erosion control measure.
“It’s on a 1:1 slope. We had to place it on a slope and around a
radius to fit right,” he says. “IECS creates the shop drawings for how
they will go together.”
In addition to winter weather challenges—work continued onsite during
a 24-inch snowstorm—water posed the greatest engineering challenge and
“We had to work 24 hours a day, seven days a week during the low-flow
period. It started March 15 through April 11,” says Tarbutton, noting
that 30 people were working on the site at the time below the dam.
“There’s water in the way. We had to keep 50 cubic feet of water per
second moving. We created a siphon system beside the dam to remove the
water from our work area. Basically, we rerouted the river.”
In addition, the company replaced an interim repair at the 2008 flood
site, which had been mainly composed of approximately 2,000 tons of
“We replaced it with a range from 650-pound to 5,000-pound riprap,”
says Tarbutton. “The riprap came from Central Stone Co., which was
really close to the work site.”
A single gate that has remained closed at the entrance road will soon
open the site to visitors again when the area has been reclaimed. The
10-acre area will be reseeded with a native mix of grasses, including
fescue, which will be covered with straw mulch. Located on a bluff on
the east side of the river, with flat land to the left of the project,
the articulated blocks have performed well at the site, which isn’t the
first location at which Tarbutton has used the IECS system.
“We were excited about getting to do these again,” he says. ”They go together well.”
Securing Slopes in California
The suburban hillsides in San Clemente, CA, can have steep
terrain. When a new Target location was being constructed in the city,
retaining walls were one way the site could be expanded to best handle
the parking the retailer needed, according to Darien Osborne, P.E.,
senior project engineer at Soil Retention Products, based in Carlsbad,
“It was more cost effective to go with segmental retaining walls and
more grading to increase the footprint,” he says. “Larger walls were
needed to accommodate that.”
It was these larger walls—with a maximum height of approximately 25
feet—coupled with the strength of the company’s Verdura retaining wall
system and the ability to include plantings that convinced developers
this was the right system for the site, a decision that was reached at
the end of 2009.
“The slopes that we had to cut into to retain were buttressed slopes
because of potential slope instability. We had to redesign the earth
buttress for that large slope,” says Ted Miyake, principal engineer at
NMG Geotechnical Inc., based in Irvine, CA, who was the geotechnical
engineer at that site. “Local planning agencies like the aesthetics of
MSE [mechanically stabilized earth] walls. They’re also plantable.
That’s sometimes a factor. I believe a tieback wall was also looked at.
“It’s often that the site is not necessarily graded for a store,” he
adds. “Often the location is desirable, but the prior grading didn’t
necessarily anticipate the end user.”
Flow from the box culvert into the stilling dam falls onto 48-inch A-Jacks units. ArmorFlex protects the channel’s side slopes.
Although MSE walls are widely used for stability in southern California, the site’s soil presented some initial challenges.
“The soils were highly expansive clays,” says Miyake. “The native
soils were deemed unsuitable. Rather than import backfill, we chose to
lime-treat the site. That was much more cost effective. Otherwise, they
would have had to haul the clay off. Rather than doing that, we
lime-treated the percentage of the soil that would have been exported
and used that behind the wall. When we had to redesign the slope
buttress because of the space constraints, we chose to reinforce the
soil to get higher strengths for the buttress. We also included layers
of geogrid to increase the strength of the buttress. We had some
concerns going in; we did a geologic map, and it turned out to be a
little more favorable.” A 3-foot layer of soil below the building itself
was also treated with lime, he explains.
Workers also experienced some weather concerns earlier in the year.
“It was a fairly wet spring for us,” says Miyake, but nothing took the
project off course.
“There were stabilized landslides that were being cut into,” says
Osborne, describing the existing hillside. “There were no failures, but
it was another challenge, at least from the planning standpoint.”
A rough grading of the site was completed in 2011, and approximately
20,000 Verdura units, buff-tan blocks, were installed across 30,000
square feet of property. The wall was prepped for vegetation.
“Untreated and enhanced soils were put into the block cells,” says Osborne. A landscape architect will do the planting.
Miyake is happy with the way the walls have protected against erosion
and with the Soil Retention team who worked on the project. “They’re
extremely efficient and competent and work very well together,” he says
as the store prepared for its opening day.
River Dike Protection in Mexico
Protecting slopes during flooding was a concern in another
corner of the world: the state of Chiapas, located in southwestern
Mexico on the Guatemalan border. In December 2009, Jorge A. Nava G, an
engineer with Tensar International’s Chiapas distributor, Ecomex, met
with Mexico’s National Water Commission and proposed that the commission
use Atlanta-based Tensar International’s Triton Gabion Mattress System
as a way to stabilize dikes and prevent dike failure along the
Zanatenco, Coatan, and Xelaju rivers, which wind through Motozintla,
Papachula, and Tonala, Mexico. Because the tropical area has been
subject to past flooding due to rain events that range from annual
monsoons to cyclone activity, the intent was to save the government
money with this long-term solution.
“This region has to allocate a small budget to protect the riverbanks
from the storms in the rainy season every year. The Triton solution was
40% lower cost than the traditional solution used in the region. They
were able to protect more riverbanks with the same amount of money than
in previous years,” says Rodrigo Valencia, Tensar International manager
for Mexico and Central America.
The commission approved the plans that had been customized for the
needs of each area through which each river passes at high flow volume
and high velocity.
“There were a couple things that made it the system of preference
there,” says Jeff Fiske, the product manager for this Tensar system, who
says he typically provides recommendations for the appropriate use of
variety of marine systems. “One was the flexibility of the system. It
also allowed them to use a lot of materials from the site. For two of
the projects, they were able to use local stone for construction.”
Large quantities of smaller stones could be found locally, while
larger rock would incur higher materials transportation costs. Pakal
Dredging constructed the system onsite, using 4- to 6-inch stones used
to fill each compartment. With the exception of the Zanatenco River
project, which required importing stone from a quarry 15 miles away,
crews were able to use local stone for the construction” Using a
stack-bond pattern, Pakal Dredging placed 4,000 units at the site.
Project labor was another consideration at the site, where a total of
5 million square feet of geogrid was placed during construction.
“It’s also important to note that the system was easy to install,”
says Valencia. “That’s an important benefit in a region where
technically skilled labor is at a premium and very expensive to hire.”
Maryland Landfill Chooses Gabions Solution
Rain, though not at the monsoon level, also posed a challenge
for a waste landfill project near Bel Air, MD. The project to build the
new Harford Waste Disposal Center began in the late fall of 2010, and
workers sliced through the variety of soils in wet conditions at the
site, which had clay in some areas, and could be considered rocky and
sandy in others.
“When you’re cutting out your swale, where you place the baskets, you
have to deal with the rain that’s running down on you and everything
else,” says Jeff Rhodes, project manager at Dixie Construction, based in
Gabions from Fort Smith, AR–based Terra Aqua were selected for use at the 20-acre site.
“They seem to be working out fine,” says Rhodes, who says the site had 3:1 slopes with some 2:1 side slopes as well.
Long labor hours were another challenge for the project, which
extended until June 2011. Native grasses provide some vegetation at the
site, according to Rhodes, including additional swales at the site that
Montana Fishery Gains Long-Term Outlet Protection
In March 2011, workers began an erosion control project in
Deadman’s Basin, a recreational fishery located on a rocky rolling
prairie in Russell County, MT.
“This project was part of an erosion protection for the outlet of the
service spillway of the dam,” explains Clayton Fawcett, P.E., an
Armortec product specialist with West Chester, OH–based Contech
Construction Products Inc. “There is a box culvert running through the
dam, entering a stilling basin and exiting the basin onto 48-inch
A-Jacks units provided by Contech. Additionally, the channel is
protected with ArmorFlex class 50S on the side slopes and downstream
The new system replaces an old one.
“Riprap had been in place on the old outlet,” explains Shawn Higley,
P.E., branch manager for Western Water Consultants, the Helena, MT,
company in charge of designing the $800,000 project. “When the outlet
was lengthened to address high uplift pressures within the dam, a new
energy dissipation system was needed.
“The problem we had was that large-diameter riprap was located a long
distance away, and the cost to transport it would be astronomical,” he
says. “The riprap design would have required excavation of bedrock to
achieve the required depth. The large-diameter riprap was evaluated
prior to the decision to select A-Jacks, and the A-Jacks came out on
top. We didn’t have to excavate much bedrock to dissipate energy, and
that is what put this product ahead of everything else. The depth of
large-diameter riprap would have been significant in comparison.”
Approximately 1,000 square feet of ArmorFlex engineered block system
and 180 A-Jacks units were used at the site. A-Jacks are concrete units
that interlock to form a flexible matrix. The A-Jacks system is used to
dissipate energy and prevent scour and erosion.
“What we’re trying to do is utilize the roughness of the A-Jacks to
create a very short hydraulic jump, discharging into the irrigation
canal,” says Fawcett. “The primary use of the water is irrigation. They
needed to have the system in place to deal with a high-velocity
The erosion control system needed to be in place before the main irrigation season, which would begin in the area in early May.
“This is an off-channel reservoir system,” explains Higley. “They
divert water from the Musselshell River into Deadman’s Basin. We were
able to push a lot of water through the outlet at very consistent flows.
They could not store any more water and had to let it go. It was tested
under normal circumstances and also under high-flow circumstances and
tested very well.”
Fawcett says the river in the basin hit “record flood stages” last year, and the discharge test was a success at 345 cfs.
“High velocities came out of the outlet structure,” says Higley.
“The A-Jacks performed as well or better than we expected them to. We
were talking velocities coming out of the outlet basin into the A-Jacks
that were around 20 feet per second or so. We used the A-Jacks product
at the end of the hydraulic jump in the higher-velocity zone. The
ArmorFlex was used to provide a good transition into the downstream
channel without significant erosion, to ease the transition to avoid
The project was completed in April 2011 and a full test of the site was conducted in August.
Creeks Rise in the Midwest
The heavy rains that plagued the Midwest in 2011 also tested a
creek bank stabilization project in Palatine, IL. Buffalo Creek
Tributary A winds through a residential suburban neighborhood, where
excess water could affect residents’ property. “Some of the creek
banks were really close to people’s homes,” says Desiree Doland, project
manager of this site and owner of Palatine-based Doland Engineering.
“It took about three years from design to implementation, which took
place in the summer of 2010 until early 2011. The project required Army
Corps of Engineers approval and also required Illinois Department of
Natural resources approval.”
The company installed SheerScape, a retaining wall system by
Atlanta-based Crane Materials International. Five hundred feet of the
material was installed in one section alone, though a total of 940 feet
was used throughout the project. Construction work during the
stabilization also took place within close proximity of peoples’ homes.
“We were limited in easement access. We were able to work within the
creek. It was a lightweight project. We weren’t able to get the cranes
for steel sheet piling; we were also so close to peoples’ homes, and it
posed too much of a risk,” explains Doland, describing the other
material that had been considered for the project.
“They used a geogrid system, an earthen grid system,” she notes. “One
area has a parking lot. The parking lot is adjacent to three-story
apartment building. They had to remove the parking lot, install this
system, and then the parking lot was put back down. The wall was in the
ground for erosion protection at the base. Since we are in a creek, it
had to be buried to an additional depth.
While a façade with the look of stone can be added to the outside of
the SheerScape wall system, the flat panel was all that was used for the
Buffalo Creek project.
Few conditions can test a retaining wall like the historic levels of rain Palatine endured in midsummer 2011.
“The storm that Illinois had during the third weekend of July—it was
off the charts. O’Hare had 5 inches of rain. It was off any chart you
could design for,” says Doland, adding that the retaining wall protected
the area from creek flooding. “It held up perfectly. The wall in our
creek did wonderfully. We had no problems whatsoever. This is literally
15 feet from people’s houses, and there were no complaints.”
Small wetlands were planted in one section of the project site.
“We installed the wall in a two-tiered system to give it a more
aesthetic appearance. It was also a safety issue. It’s two- to
two-and-a-half-foot walls. On the ledge between the two, there were
certain plant types that were used that could tolerate the creek flow
and are still considered attractive,” says Doland. “There were grasses
there were some wildflower vegetation that was suitable.
“We also put in a vine to grow and flower. It will skip the wall and grow along the fences that border people’s yards.”
The wall’s connection with its surroundings has yielded additional
benefits. “It is pretty self-sufficient,” explains Doland. “It’s
supposed to last for decades with no maintenance.”
Little to no maintenance is a benefit that lies at the heart of
hard-armor solutions. Because the materials are designed to stand the
test of time at sites that need strong, permanent erosion protection,
contractors can build a budget knowing there will be no additional
treatment necessary for the future.
Author's Bio: Based in Morgantown, PA, Tara Beecham writes frequently for Forester publications.