Every type of construction project—building, road, bridge—involves erosion control. As soon as removal of an existing structure starts or a shovel turns over grass to expose the soil beneath, the need for erosion control begins.
Reclaiming an Airport Site
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Denver, CO, is the location of one of the largest urban infill projects in the nation, and erosion control is a big part of the project. The construction that has been going on there for several years is on the site of Denver’s former airport, Stapleton International.
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Denver outgrew this airport, which was named for a former mayor. The facility was closed in February 1995 and replaced by Denver’s new International Airport.
Once the concrete from the old airport’s runways had been removed and recycled, some roads and other infrastructure were added. Then the 4,700 acres were ready for site development preparation work for the thousands of homes (and churches, schools, and shopping centers) to be built there over the next few years. The conversion from busy metropolitan airport to suburbia has involved a number of different construction companies. The overall responsibility for development rests with the firm Forest City Stapleton.
With this much construction taking place, there is a lot of soil on residential lots that has to be kept onsite. Jaime Hernandez, project manager for Down to Earth Compliance of Aurora, CO, says that about three-fourths of the development has been done.
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“The demand for housing is skyrocketing here, and the more homes they build, the more work for us,” he notes.
Employees of Down to Earth Compliance are responsible for erosion control on the lots where homes are being constructed by many different builders. To keep sediment on these lots while construction is taking place, they rely on erosion control wattles made by Gator Guard of Boise, ID, and supplied by Bowman Construction Supply of Denver.
Hernandez says that he is convinced of the value of using Gator Guard, even if it costs more than some other products. With Gator Guard, “you can tell the difference when you jump on it or step on it. You can understand how it will last.”
He explains that similar products made by other companies have a sponge-like inner lining that absorbs water. In Denver’s cold winter weather, a product made this way will freeze to the ground. Moving it risks tearing it and having to waste time and money to replace it. Hernandez says that Gator Guard “holds up very well. It could rain or snow or the temperature could drop rapidly, and you could still pull it out. It still does its job, but a wattle with a sponge inside will be frozen and difficult to yank or pull out.”
“The majority of the builders already know the name Gator Guard. It’s like hot pancakes—it’s selling pretty good,” notes Hernandez.
And as for using the cheaper, basic silt fences that will likely need to be replaced, “We tell them, ‘You’re saving money’ by going with Gator Guard,” he adds.
Gator Guard makes two types of black erosion control wattles. Besides the Standard, the company’s basic type, there is a heavier, more durable model called the Extreme. These wattles weigh only 8 pounds and measure 6 inches in diameter. They come in 25-foot lengths.
Down to Earth Compliance once used the Standard model but now prefers to install the Extreme model. It maintains almost the same height, even after vehicles repeatedly driving over it.
“About a year and a half ago we did a demo with the Extreme for a couple of months. [At the end] we decided that it’s a pretty good product,” says Hernandez. He notes that even when a vehicle runs over the Extreme Gator Guard wattle, “there are no marks from your tires.”
After the final grading of the site, he says, “We remove the Gator Guard. The majority of it is reusable, so we sometimes reuse it. We try to help the builders keep their costs down.”
Asked about environmental regulations and inspections on erosion control projects, Hernandez says, “We’ve already dealt with nine state inspectors. They will hire more inspectors, so we try to give our expertise and help the builders.”
He adds, “All of the cities are getting stricter, but we need to protect our waters. Once we explain why we do [erosion control] and why we need it, then people understand.”
Hernandez says that the biggest challenge in doing erosion control work is getting and keeping good employees. “We already get all the parties involved together to explain what we have to do and why and the products we use are effective. But it takes time to install [erosion control measures properly].”
SpreadRite LLC of Birmingham, AL, completed an erosion control project on a 3-acre site that sits alongside Highway 280 in Birmingham. Eventually, a car dealership will be built there.
“The site had been developed in early 2016, but it was left unfinished. A local compliance agency insisted that the developer get it in compliance, so we were called in,” says Hunter Bruce, owner of SpreadRite LLC.
Credit: D2 LAND AND WATER RESOURCE
The SpreadRite crews brought in heavy equipment for regrading and did revegetation to bring the site into compliance.
“We started work on July 27, 2016. Heavy—three inches plus—rain fell three days later,” says Bruce. “It rained and it rained. Every now and then you get a job where you get smacked by the weather.”
That day with more than 3 inches of rain was followed by a day with 2 inches of rain. All of it fell within 30 hours.
Then, after the rains came the drought. It lasted for 74 days, costing the SpreadRite crews extra effort with watering to get the vegetation established. Weather, however, was not the only challenge on the project.
“Mid-July to August is when you start looking for armyworms. Once they’re spotted, we take the last 15 to 20 jobs we’ve done and look at them daily [to see if the worms have infested those sites, too].”
Bruce and his son first spotted that year’s infestation of armyworms while they were playing golf. The golf course’s mature Bermuda grass drew the worms.
“We saw them on Friday, but then it rained, so we were forced to wait until Monday before we could do anything,” he recalls. At the project site, “the hillside had been pretty green. Over that one weekend, it was completely cleared by the worms.”
He adds, “With ProGanics”—a Biotic Soil Media from Profile Products—“we had gotten the grass growing within seven to 10 days. In mid-August, it looked like Augusta National. Then [after the worms arrived] it looked like a pig pen.”
Mature armyworms are “the diameter of a number two pencil, and about two inches long,” Bruce explains. “Moths fly in and lay their eggs on grass. Some years are worse than others; 2016 was the worst year for armyworms that I have seen.”
The reason the damaging armyworms were so bad that year was the extensive flooding that occurred in Louisiana. The moths were forced to fly north to find grass that wasn’t flooded so they could lay their eggs.
Bruce says that the infestation of armyworms was so bad that news media across the state ran stories to educate homeowners about the damage to their lawns. When the temperature drops to 55°, the worms will die. Stopping them in warmer weather requires two applications of pesticide, 10 days apart.
To counter the damage, “we did chemicals to kill the worms and then overseeded. The worms ate the millet, the temporary crop, but [not] the fescue or Bahia, because those didn’t grow until winter,” he says.
Bruce says that in the blend of grasses used for reseeding, the crimson clover came up in a week. “We kept checking for runoff, but there wasn’t any.”
To keep sediment in place on the site, the crew relied on eTubes from Soil-Tek, filled with compost and placed at frequent intervals.
“We used eTubes [that were] 12 inches in diameter for running ditch checks. We fill them ourselves. We put about 50 ditch checks on that site,” he says.
He describes eTubes as “the Cadillac of tubular devices.” He prefers them because they’re “heavier, filter better, and last longer.” Other erosion control products used by the SpreadRite crew include ProGanics and ProMatrix, an Engineered Fiber Matrix, on the slopes. Both are made by Profile Products.
“We blew straw, and used Tornado Tack [also from Profile Products] on the flats,” says Bruce.
This project was “a tricky steep site. Managing the water was the biggest hurdle. We diverted water, taking it from the east side to the west in three distinct swales,” explains Bruce, describing his team’s work as “a permanent band-aid [until final construction on the land].”
Bruce says that the main challenge of doing erosion control projects is “putting in the best product that’s made. We want something that will last not just for one month or two months.”
He notes, “Central Alabama is a real test for erosion control. We have heavy clay soil, steep terrain, and heavy rainfall, averaging 60 inches in a year.”
Ospreys in Hawaii
The MV-22 Osprey, made by Bell Boeing, is a multimission tiltrotor military aircraft. It can do both vertical and short-space takeoffs and landings. With a wingspan of 46 feet, the Osprey is the primary assault support aircraft for the US Marine Corps. The aircraft’s versatility accounts for its popularity with the Marines.
The MV-22 Osprey combines the speed and range of a turboprop plane with the maneuverability of a helicopter. It can carry as many as 24 Marine combat troops and is flown by a crew of four (pilot, co-pilot, and two flight engineers).
The Osprey is flown from Marine Corps bases in various locations, including the Marine Corps Base Hawaii. This base is on the windward side of the island of Oahu, about 12 miles from Honolulu.
The demand for more MV-22 Ospreys there required the construction of a new hangar designed for the aircraft. Charged with site preparation and erosion control for that construction is Koga Engineering & Construction.
Marine Corps Base Hawaii is only about 300 yards from beautiful—and environmentally sensitive—Kaneohe Bay. The state of Hawaii includes the bay in its list of waters needing the highest level of protection and monitoring.
“The job site is big compared to the size of the hangar, and we want to make sure nothing gets into the bay,” says Garett Ichimura, project manager for Koga Engineering and Construction of Honolulu.
The size of the new hangar is 57,000 square feet. To protect Kaneohe Bay and the Pacific Ocean into which it flows, the project area is about 14 acres.
An essential part of providing that protection comes from the installation of 20,000 SiltSoxx made by Filtrexx of Akron, OH. The tubular SiltSoxx consist of FiberMedia encased in FiltrexxMesh.
Russell Inouye, projects supervisor and vice president of Koga, says the Siltsoxx used in this project are 8 inches in diameter and 20 feet long.
“We’ve used Filtrexx Siltsoxx on various projects,” he notes. “An erosion control plan typically is included with projects, documents which we follow. Sometimes the engineers specify SiltSoxx. Generally, on most of our jobs, we choose to use them over a silt fence. They provide better effectiveness.”
Work on the project began in July 2016 and is expected to be completed by the end of this year.
“The area involved with the whole project is quite large, so we used a lot of BMP measures, including egress and ingress pads and inlet protection,” says Inouye.
Honolulu officials have a strong interest in managing stormwater and controlling erosion. With a population of 800,000, seven million tourists annually, strong demand for new buildings (23 high-rise permits and counting granted so far this year), and routine rainfalls of 2 inches within an hour, there are plenty of reasons for concern and stricter regulation.
Matt Lyum, Filtrexx’s manufacturer in Hawaii, says that the stricter regulations (which went into effect in August 2017) are necessary. “We’re surrounded by the ocean with a fragile reef system.”
PHOTOS: SPREADRITE LLC
ProGanics and ProMatrix were applied to the slopes at this Alabama site.
Lyum says that the City of Honolulu’s plans include hiring three full-time enforcement officials. “Every site has to have a water plan prepared. The plan has to be prepared by a certified [water management] planner.”
To be certain that developers comply with their proposed plans for managing stormwater on their sites, Lyum says, each site “will be inspected at least twice by different certified site planners. That’s a huge jump in effective stormwater management.”
Workshops have been held and a 78-page manual developed to explain the new regulations to developers. Lyum says that “even the military sites, which are regulated by the federal government, not the state, have sent representatives to the stormwater workshops.”
He says that most civil engineers working in Hawaii are in Honolulu, but they also work on projects on the other islands. The new stormwater standards will soon take effect around the state.
eTube check dams
Expansion and improvements to Interstate 69 are ongoing in Indiana. The road runs from Indianapolis down to the southwest corner of the state near Evansville. Sections 1 to 4 of the project start at Evansville and end south of Bloomington, on new terrain. Section 5 near Bloomington covers about 21 miles to Martinsville.
The work includes four new interchanges and four grade-separated crossings. The upgrading of State Road 37 to interstate standards adds travel lanes in the north and southbound lanes.
“Section 5 is under a lot of scrutiny because of its proximity to Bloomington. There are high-quality wetlands there and a lot of grade changes, so erosion control [on that section] is important,” explains Jim Blazek, CPESC, vice president of D2 Land and Water Resource in Indianapolis and consultant to the project.
To handle the areas of section 5 that would accumulate more water during storms because of grade changes, Blazek and various engineers involved recommended installing Silt Saver’s Stage Release silt fencing.
Made by Silt-Saver of Conyers, GA, this fence is more expensive than typical silt fences used to contain sediment within the perimeters of a construction site, but Blazek says the extra cost is worth it. “Its strength and durability are far beyond the standard DOT-approved silt fence. It doesn’t rip or tear from the weight of water [accumulating behind it].”
The Stage Release fence can release water faster near the top because it has larger holes there than the holes at the bottom. Water is therefore released at different rates, compared to a standard silt fence that could eventually be overwhelmed in a large storm, thus sending sediment-carrying water over its top.
“With the higher flow rate at the top, we used it in critical areas,” explains Blazek.
These areas that received the higher-performance product didn’t become overrun with water, he notes. Workers did not “have to wrestle water-logged, sediment-filled wattles.”
Extra labor and maintenance costs were avoided. Thus, the more expensive product ended up saving money.
Blazek also likes Silt-Saver fences because of “their strength and the bright green bands on the top. That helps contractors see it and not run over it. The [highly visible] green is also a reminder to check around the site after each rain event.”
The Silt-Saver Stage Release Fence was installed by Earth Images of Greenwood, IN. “The subcontractors mentioned that removal and maintenance of the fence was significantly easier than dealing with mulch-filled tubes or straw bales,” says Blazek.
Other BMPs used on the project include straw wattles, mulch-filled filters, standard silt fence, and rock-filled berms. Drones were used for inspecting BMPs at various stages of the work.
Blazek says that a big effort on this road project was “meeting the people running the project and spending time with them to see where there would be challenges. We did lots of visual checks, both driving and walking the road lanes.”
Another challenge was “getting enough support information to everyone who needed it. This project has a significant traffic control component,” he says. The weather has had an impact as well. “We get a lot of rain—39 inches—in the central part of the state, and we’ve had some massive rain events.”
The project was a joint public-private effort. Principal clients were Indiana Department of Transportation and Indiana Funding Authority. Work began in the fall of 2015. Completion is scheduled for August 2018. The general contractor for the project is The Walsh Group of Chicago, IL, and Crown Point, IN.
Blazek says that because this was a public-private project, “we had a little more leeway to use creative solutions. The contractor knew he had this ongoing challenge [with sensitive areas]. They invited us to come down and wanted to know everything we might use, being proactive.”
Reflecting on planning meetings, Blazek says, “We had the storm sewer system people, design engineers, pavement people, erosion control engineers, specifying engineers, and inspectors all in the room with the contractor and subs. That doesn’t always happen.”
As these projects show, doing erosion control well enough to protect the environment and meet federal and state regulations is challenging work. Fortunately, there are many well-done projects from which to learn and proven BMPs and guidelines to follow.