On highways under construction and those being repaired throughout North America, the challenge for contractors is to come up with effective methods for erosion and sediment control.
Common challenges include working around traffic-which sometimes means working during non-peak hours or at night-protecting existing inlets and catch basins along the roadways, and dealing with a lack of centralized sediment basins.
Road Widening in South Carolina
Hinged slope areas presented a challenge on a road-widening project for the South Carolina Department of Transportation on I-20 east of Columbia. The project started in October 2012 with a completion date scheduled for mid-2014.
The project contractor was struggling to establish vegetation on the slopes because of upland flow making its way across the impermeable interstate roadway, explains J.R. Stewart of Filtrexx International.
“The contractor was looking for a BMP that could slow the velocity of the sheet flow while not causing flooding on the interstate,” Stewart says.
That BMP was Filtrexx SiltSoxx, a tubular sediment-trapping and stormwater filtration device. The SiltSoxx are filled with Filtrexx FilterMedia, applied with a pneumatic blower device or its equivalent.
SiltSoxx can be used as a silt fence replacement, filtering out sediment and soluble pollutants such as phosphorus and petroleum hydrocarbons on and around construction sites. The water is filtered as it passes through the media’s organic structure. Water may also temporarily pond behind the BMP, allowing deposition of suspended solids. The SiltSoxx are also used to reduce runoff flow velocities on sloped surfaces.
The product requires no trenching or soil disturbance. It is designed for easy removal and requires less maintenance than silt fence. It can also be recycled.
“In addition to the SiltSoxx being used in a sediment control perimeter application, compost socks also were utilized as weighted check dams in concrete swales throughout the project,” Stewart adds.
The product is accepted by SCDOT as a Type F weighted inlet protection device.
“That acceptance allowed them to utilize the compost socks for the check dam application in the concrete swales,” Stewart points out.
The contractor on the job was Sam Johnson, president of J&S Care of Aynor, SC, a highway construction and erosion control company specializing in DOT erosion control work. Johnson notes that when it rained during the road widening, “all of the water was coming down the interstate like it was supposed to, but once it came off of the concrete on the side, there was so much water coming off so quickly it would wash out the embankment.”
Turf reinforcement mats were the first erosion control method applied. To prevent the washouts, J&S installed the Filtrexx SiltSoxx along the side of the road to mitigate the problem.
“It allowed the water to dissipate, and instead of running off down to one spot, it ran off to multiple areas.” The water was released slowly, Johnson says.
Johnson finds SiltSoxx easy to install.
“They hold up extremely well,” he says. “These have been out there going on a year, and they haven’t had any breakdown whatsoever. If we want to pick them up or clean them up, we can do that easily as well.
“The DOT approved them because, one, if a car hit it, it wasn’t going to cause any major damage; two, it is easy to put down; and, three, it was able to slow the water down and keep it from blowing out the shoulder of the road.”
On road construction projects such as this one, washouts are a common problem, notes Johnson. “One inch over an acre is 27,000 gallons of water. At one time, we got 3 inches of rain in less than two hours. It was like a monsoon. All of it was going to one spot because it was coming down the slope and hinging over into the outfalls.”
The TRMs couldn’t prevent the washouts.
“It blew out the erosion control mat and blew the seeding out,” says Johnson. “But once we put the SiltSoxx in, the water worked down into that sock and slowed it down to a point where it flowed over and around or through.”
Before the installation, Johnson’s company was constantly visiting the site to fix washouts and other problems. “We haven’t had to go back since,” he says. “There haven’t been any issues anymore.”
It took about 30 days before J&S Care got approval to install the Filtrexx product.
“The DOT didn’t want to jump to conclusions due to cost, but there wasn’t anything else to do,” Johnson says. “There was no other way to handle it that we or anybody else could figure out.”
He says that getting project managers to use measures such as sediment basins or sediment control check dams to deal with water coming down slopes is sometimes difficult. “It’s out of sight, out of mind, but they’re not the ones out there digging the mud back out of the creeks with a bucket,” he says. “I would like to see more preventative measures to catch that water before it gets down in the creek or swamp.
“The Filtrexx SiltSoxx did what it was designed to do-keep the water from spilling off into one central location and overloading that area. It did a good job of that.”
Working in a Wetland
Clayton Worley, president of Erosion Control of Central Florida, works on highway projects in Florida where the high water table is a concern.
“The majority of our work is on DOT roadsides-anything having to do with erosion control, including sediment barriers, silt fence, staked turbidity, floating turbidity, and also sod,” Worley says.
In a recent project, Erosion Control of Central Florida was called upon to provide services for an electric company that was reconstructing access roads to its power poles.
“Probably 80% of the job was in a wetland, and we had to use the staked turbidity barriers on both sides where they were putting in this new road,” Worley says. “The engineer recommended it in certain spots, and it was up to me to use what I thought would be the best. We went with the staked turbidity.”
The company installed 10,000 feet of Aer-Flo Tough Guy Turbidity Barriers for the project, which began in April 2013.
The staked barriers are continuous panels of impervious vinyl-polyester fabric that are designed to contain stormwater runoff or redirect it to proper channels or retention areas. Land installation is similar to that of silt fence, with 8 inches below grade and 36 inches above grade attached to stakes. The staked barriers also can be installed in up to 18 inches of water.
The fabric curtain features a heat-sealed hem about 44 inches wide along the top edge. To install, a narrow trench 8 inches deep is dug along the perimeter line. Stakes are driven every 6 feet along the downslope side of the trench. The barrier’s upper portion is attached to the stakes with staples, wires, or nylon ties, keeping the top of the barrier 36 inches above grade. The curtain’s lower edge is placed in the trench and then backfilled. The system is designed to work best in porous soils on moderately sloped sites. The stakes may be wood or metal, including rebar.
“This is one of the best methods as far as controlling sediment from getting into the water, because obviously the quality is better than silt fence, and the specs are different,” notes Worley. “It keeps more of the water from getting into the wetlands.”
The turbidity barriers are manufactured two ways: one with the stakes already attached and the other with no stakes attached. Worley prefers the latter.
“It takes a little longer to put up, but it’s easier for us because the attached rolls are so heavy,” he says. “It’s easier for us to attach it ourselves. We are equipped with the proper tools and air guns.”
The frequency of the maintenance of the turbidity barriers depends on who is working on the road construction project, Worley says.
“Sometimes they treat it as a wall,” he says. “It’s not a wall. It’s like a fence. You can only put so much weight on it. Some of these contractors don’t maintain it, but if they take care of it like they are supposed to, it works great.”
Aer-Flo turbidity barriers can be reused, Worley points out, making them a cost-effective option.
Bridge Work in Altoona
A combination of erosion control methods was recently applied in an Altoona bridge project in Iowa through the Iowa Department of Transportation. Work on the NW 34th Avenue Bridge over Interstate 80 began in March 2013 and was completed in October.
Soil-Tek, which provides erosion and sediment control installation and stormwater pollution prevention plan (SWPPP) services, based its approach to the job on specifications from the Iowa Department of Transportation.
BMPs used included Soil-Tek’s e-tube biodegradable filter sock, Willachoochee Industrial Fabrics’ silt fence, ScourStop, bonded fiber matrix from Profile Products, wood excelsior mat from Western Excelsior, and P300 turf reinforcement mat from North American Green.
Ryan Cheeseman, project manager with Jensen Construction in Des Moines, IA, says the Altoona bridge project involved a four-span bridge over I-80 running north and south with a concrete beam, three piers, and bridge embankments on both ends.
Soil-Tek worked as a subcontractor on the project, which was executed on a closed roadway over the top of the interstate. The company installed eight small silt basins across the project, Cheeseman says.
“We were able to put in wood excelsior mat and TRM in those ditches to get some vegetation going to keep any sediment from leaving the site,” says Brian Denham, general manager and vice president for Soil-Tek. “We did have some challenges with regard to heavy water flow off of the project into the storm sewers.
“There was also regular straw mulching, blowing big round bales on the project,” he adds. “Due to the severity of the slopes, we suggested they use more bonded fiber matrix on the project to hold the slopes better than what typically we see straw mulch do on 3:1 type slopes. That was the only change on the project-we were able to add in more of that product and create a more successful project for the state.”
The e-tube filter sock was used for perimeter control and ditch check applications and wrapping for inlet protection.
Standing Up to Traffic
In Twin Falls, ID, the Syman Co., an erosion control company that assists its clients with environmental compliance for construction, development, and industrial projects, was involved in a 2010 project to install approximately 15,500 linear feet of water main. Work included installation of air/vacuum vaults, blow-off assemblies, hydrants, excavation, and surface restoration of the roadway on Blue Lakes Boulevard.
“The largest part of the earth disturbance was within the existing road rights of way or previously disturbed developed areas,” notes Brad Simpson, project manager and estimator for the Syman Co. “The contractor, Owyhee Construction, used Gator Guard in a few areas where other BMPs kept getting run over or destroyed by local traffic and sediment would migrate onto the roadways.”
Gator Guard sediment control wattles are designed for 20 times less soil loss than straw wattles. They weigh 8 pounds and measure 6 inches by 25 feet. They are made with recycled foam and UV-resistant geotextile, with an apron to minimize underflow washouts. The wattles are reusable.
“We started using straw wattle in the beginning and switched over and used the Gator Guard,” says Simpson. “People were cutting around corners and trashing what we had there, and contractors were parking on it. Once we put the Gator Guard in, people would still continue to run over it, and contractors would still park on it, but it would just pop back up; we didn’t have to keep replacing it. It held up during the rest of the project. It was highly effective and required minimal maintenance after it was installed.”
The sediment was captured behind the Gator Guard and remained on the shoulder of the road, allowing the contractor to keep a cleaner job site because of it, says Simpson.
“Gator Guard continues to be a “˜go-to’ BMP in these types of situations because of its rigidity,” he says.
The Syman Co. installed Gator Guard “mainly for cost and ease of installation and the fact that it was rigid enough to stand up to the environment,” notes Simpson.
