Construction-Site Stabilization

March 1, 2007

Few things can disturb a landscape like the onset of construction. Unlike the neat, finite framework of buildings, sediment is often difficult to work with and control. And this is without even considering the impact a of a strong spring rain pushing sediment into neighboring storm drains or waterways.

Even as the buildings and structures are being secured in the ground, contractors work to keep the ground itself secure from washout and their project protected as they must work within local, state, and federal requirements. On construction sites, meeting the National Pollutant Discharge Elimination System (NPDES) Phase II requirements is only as easy as selecting the right sediment control solution for each challenging site, both during and after construction.

When Water Is Threatened
The Tampa Bay Water Authority hired Barnard Construction to protect the C.W. Bill Young Regional Reservoir from stormwater runoff pollution for the 1,100-acre site in Lithia, FL, which included sensitive wetland areas. The aboveground reservoir, Florida’s largest reservoir of drinking water, holds more than 15 billion gallons of water essential to area residents.

“For us to build the reservoir, we had to dewater the ground, had to build the embankment,” explains Mike Fuller, project superintendent at Bozeman, MT-based Barnard Construction, the contractor for the project.

When the vegetation had been removed around the site, it was discovered that the soil was natural clay.       

“Once the water came across the site, we had turbid water,” says Fuller. “We used Ciba [Specialty Chemicals Corp.]’s Magnafloc to coagulate the solids out of the water.”

Photo: Ciba Specialty Chemicals
Floc bags helped coagulate solids out of the water at a Florida aboveground reservoir.
Photo: Ciba Specialty Chemicals
A mixing area during the first phase of a project

Maximum turbidity concentrations were limited to 36 nephelometric turbidity units in the water leaving the site.

“We had the site graded all at once,” notes Fuller. “We used sod for the main erosion protection. We had silt fence-280,000 feet of silt fence-across the entire site, but silt fence isn’t going to stop turbid water. We used the Ciba.”

The stormwater treatment plan implementation took place from about October 2002 until August 2003. Site inspections were performed daily. Workers had not anticipated the multiple rain events that dominated what was supposed to be the area’s dry season. The flow of stormwater was as much as 6,000 gallons per minute, according to Naresh Kanderi of Suffolk, VA-based Ciba Specialty Chemicals.

“We couldn’t have built the site without getting rid of the water. To get rid of the water, we had to chemically treat it,” says Fuller. “Typical BMPs wouldn’t work.”

Sodding, swales, and ponds were some of the post-construction measures the company took to control sediment and erosion in the area.

Protection often extends beyond the construction site itself, as when a site borders sensitive wetlands.

A massive construction project can mean facing an increased risk of losing large amounts of sediment but only if the proper precautions aren’t taken. Silt fence is one way project planners can help stabilize a site’s land while construction continues.

“We recently installed a 10,000-linear-foot project for Alessio Brothers Excavating out of Rockdale, Illinois,” says Al Kuda, president of AAA Silt Fencing based in Lemont, IL. “The project was on Diehl Road and Freedom Drive in Lisle, Illinois. We plowed the entire perimeter as well as a double row in front of the wetlands and other key areas of concern.”

The company installed the fencing with the Burchland Manufacturing Silt Fence Installer. “I feel the ability to install unheard-of footages in a single day that we would never have been able to do with the trench-and-backfill method,” says Kuda. “Once the fabric is plowed in and compacted, it is most durable and resistant against washouts in high-flow, concentrated areas of concern. We typically space our stakes 4 to 5 feet and staple a lath on every stake to ensure the fabric has long-lasting durability and will not be blown down in rain and wind. The only way it falls is by being driven through by various careless people who don’t know what its importance is.”

Photo: Soil-Tek
Steep slopes were a challenge on an Iowa Speedway project.

At the Lisle project, a row of silt fencing was installed around the project’s dirt stockpile to prevent washout into nearby curbs, inlets, and a high-traffic street.

“We also installed inlet protection with silt fencing and inlet fabric, woven monofilament fabric tucked in and around the inlet cover,” explains Kuda. “Alessio Brothers Excavating graded areas of concern in stages while we installed other BMPs, [including] wattles, excelsior logs, blankets, and inlet protectors.”

Inspections were conducted every seven days during construction and within 24 hours of a rain event greater than 0.5 inch.

Compliance issues that arise during the construction process itself require a speedy response, and keeping the construction process moving can be a concern.

In the process of blasting through layers of rock to excavate a detention basin in 2005 at the Boulder Business Park outside of Allentown, PA, workers with Whiting Turner encountered groundwater contaminated with fine coal sediment. They sought a way to isolate this water from a nearby stream.

“They ran into some coal that wasn’t anticipated,” says Warren Cohn, the Certified Professional in Erosion and Sediment Control (CPESC) state representative for Pennsylvania and also a BMP product specialist at Norristown, PA-based ACF Environmental. “The basin ultimately was to be lined. The idea was that they were going to dig the basin and line it with the liner. The coal, if they let it sit there, would have settled out.”

The fine coal particles proved a difficult material to filter at the site. The filter bags initially installed at the site didn’t work, and the dark water began to flow into a clean stream serving as a wildlife habitat. Regulators shut the site down while the coal was removed from the pond, explains Cohn, and adequate protection was put into place.

“The particles were too small to be mechanically trapped by the filter,” he says. Profile Products’ Terra-Tubes, knitted tubes containing engineered composites of manmade and wood fibers, as well as performance-enhancing polymers, were eventually selected to remove the coal. “The Terra-Tubes allow the particles to cluster together and facilitated the flocculation and capture of the clustered particles.”

The channel connecting the detention basin was lined with a geotextile fabric, and stones ranging from 1.5 to 4 inches in diameter were set into place to help with water filtration at the site.

Two tiers of 6.5-foot Terra-Tubes were staked by contractors at several intervals along the channel, and within days the tubes were filtering coal.

“It was phenomenal,” says Cohn.

Residential Construction-Site Stability
In August 2006, the type of soil present onsite posed a sediment control challenge at a future housing development in Twinsburg, OH.

“This basically was a reclamation project. We did all this work in order to bring this site into compliance with the EPA,” says Nick Strazar, general manager of Certified Erosion Control of Northeast Ohio, noting that of the site’s 70 acres, about 50 were disturbed and the topsoil was completely stripped. “The soil didn’t have a lot of nutrients. It was in a sensitive area. It bordered a creek called Tinkers Creek.”

Photo: Oregon DOT
Site stabilization tools used on Oregon’s Columbia River Highway-widening project included matting, straw wattles, and compost.

The treatment approach involved a combination of practices to filter sediment from the stormwater as well as prevent erosion, including the use of SiltSoxx from Filtrexx International at the shoulder of slopes. Treatment also included rock checks, turf reinforcement mats, proper grading practices, temporary and permanent seeding, and Filtrexx FilterSoxx. The site was graded in stages. The company worked with Tri-Mor Construction during the installation of the rock checks and riser pipes and during the final grading.

“We worked with the developer to sequence all activity on the project. They had all the heavy equipment,” says Strazar. “We coordinated with them what was going to be done at what point.”

Filtrexx compost blankets were used to protect the perennial grass mix planted for erosion protection. The blankets were placed close to outlet structures on the site and its detention pond.

“They’re hard areas to get to vegetate sometimes,” says Strazar. “We installed what we call a Filtrexx FilterCell for sediment pond overflow. We perform weekly site inspections or after every half-inch rain event.”

Compost 2 inches thick was placed in some of the areas as a Filtrexx compost blanketwas used in an attempt to grow grass quickly for soil stabilization at a difficult time of year.

“August was a very hard time of year to get this done,” notes Strazar. “The seed germinated very quickly; I think it was within five days to a week.”

Certified Erosion Control (CEC) uses an electronic stormwater pollution prevention plan (SWPPP)inspection system, allowing access to all parties with permission.

“As a service, CEC provided weekly inspections during the process and kept local inspectors informed by sending electronic copies of the inspections to the county inspectors for their review,” explains Rod Tyler, chief executive officer of Filtrexx. “In addition, CEC attended meetings with Tri-Mor during biweekly meetings with the county inspectors to make sure questions about products were answered.

Photo: River Valley Organics
Installation of a compost blanket with seed along Pennsylvania’s storm-eroded Route 222

“The CEC inspection program allows permission to be granted to people like local inspectors, so they can check on progress at the sites without actually being there weekly or after each rain event. Inspections are kept in a virtual “˜notebook’ online and can be reviewed as historical documents, or to see what efforts have been taken since the last inspection, if work orders are generated. The system helps alleviate problems associated with having only one master copy of the SWPPPat the job site trailer, and provides great insurance if and when that document mysteriously disappears.”

A combination of materials, including bonded fiber matrix and hydrostraw, helped prevent erosion and control sediment during the construction of 3,000 acres of a partially developed golf resort community called Diablo Grande near Patterson, CA.

“I worked with TRM [turf reinforcement mats] to stabilize the swales,” explains Lucinda Dustin, a senior stormwater management consultant with Stevens, Ferrone & Bailey based in Concord, CA. She also used an Ertech Perimeter Guard in place of straw wattles, utilizing its plastic construction with a plastic filter. “They are lightweight; they are reusable. I used them in the areas where they were constructing homes. There is a lot of traffic. Straw wattles tend to get destroyed really easily in that situation.” The site will be home to a hotel and two 18-hole golf courses. “Everything we do there has to be very specific. We don’t take chances with discharge. It’s highly visible and a very high-profile project,” says Dustin. “They are going to spend $2 million or $3 million just on stabilization.”

Photo: Oregon DOT
Spraying compost material to prevent sediment loss in Oregon

Dustin has worked on the project for five years, and she has seen it graded in stages. “During Phase I, they had to build a 3.2-mile parkway to get to it. It’s in a canyon,” she says. “They also put in a 10-mile sewer line. Literally, we’re building a town.

“The site is crisscrossed with all kinds of waterways. We can’t discharge anything into the waterways.”

ACF Environmental Siltsacks and Earth Saver straw wattles were also installed at the site. Primarily self-contained and set apart from urban areas, Diablo Grande doesn’t have the same post-construction requirements as many other projects.

Another project Dustin worked on that required massive erosion and sediment controls during its construction was the 20-acre Calistoga Ranch in California’s wine country. The ranch is located in a 160-acre watershed, and more than $4 million were spent on the project’s stormwater management program.

“It’s in the bottom of a canyon. In winter, you can see waterfalls created when the rain comes,” says Dustin, adding that the site’s Biter Creek empties into the Napa River.

“When it rains and the creek fills, there are places where that creek is probably 8 to 10 feet deep. By May, it will be bone dry.”

Regulations governing the protection of the Napa River limited the amount of time construction could take place on the site. Working mostly during the winter months, site workers used special inlet bags in the site’s storm drains.

“I created special devices that would retain sediment and hydrocarbons from entering the storm system,” says Dustin. “Storm drains go directly into the creek. We can’t allow anything that’s going to be a disturbance.”

Dustin also used ACF Siltsacks in the storm drains and Earth Saver straw wattles on the site’s slopes.

“You can leave [the wattles] there after the vegetation ends. I used them particularly on the longer slopes because they are easier to work with and they are very effective,” says Dustin. “They really just blend into the whole slope area.”

The entire creek length was vegetated with a native mix and protected with a bonded fiber matrix, stabilizing the banks for years to come.

Stabilizing Roads Under Construction
Roadway construction can introduce various sediment control concerns amid pressing deadlines.          

Just outside of Reading, PA, a roadway severely eroded by storms was the focus of a project approached by Doug Caldwell, president of River Valley Organics based in Wrightsville, PA. Begun in May 2004, the project along Route 222 was completed in about two weeks. Along with a short time frame, workers encountered poor soil and steep slopes.

“We netted the slope first, and then we applied compost to the slope. We used Filtrexx LockDown Netting as well as FilterSoxx,” says Caldwell. “We had applied a compost blanket with seed.”

It was essential to protect the annual rye and crown vetch that was planted to prevent erosion and sediment loss. “Part of the challenge was to get grass to grow on it, because it was a cut-and-fill slope. It was a very large slope and very steep,” he notes. “It wasn’t possible to do any grading prior to the vegetation just because of the steepness of the slope or the relation to the highway.”

The company selected a Filtrexx compost blanket for an erosion control solution. “They couldn’t add topsoil to the slope because they would have to shut down a highway to do it. They needed to get grass growing on this slope,” explains Caldwell. “It had been seeded previously at least once and it had washed out severely.”

The work has held up well during a very severe rainfall after the installation with no washout, according to Caldwell.

During a project to widen the lower Columbia River Highway at Carlson Road in Columbia County, OR, the Oregon Department of Transportation (ODOT) needed to take steps to prevent sediment loss and implement erosion control measures. The road had steep slopes, at least 2:1 in parts, and a combination of materials was needed for the job, including silt fence, straw wattles, and erosion control blankets.

“We also sprayed on compost material, and then later it was temporarily seeded and the slopes were seeded in,” explains Mark Beeson, an ODOT project manager working in the Portland area.

Photo: Ciba Specialty Chemicals
Dredging in the settling area during the
second phase of Florida’s reservoir project

Rob Wattman, the ODOT project coordinator, explains that the temporary seeding was done initially. “We had to kind of over-winter the job,” he says. “That seed didn’t establish itself. The grass didn’t grow back fast enough and thick enough.”

ODOT workers returned in the early spring, implementing permanent seeding with perennial grasses. The site itself was graded in stages, and measures were taken to cope with the heavy rains the area experiences.

“There is also a guardrail that has a drainage curb. They made a rock channel. It was transverse to roadway,” says Wattman. “We built a channel for the water to go down. It was just rock, 3-inch to 5-inch size: a riprap-lined ditch.”

Some roadways handle traffic of a different kind, while facing the same challenges of nature.

Steep slopes provided the biggest challenge for Soil-Tek workers at the Iowa Speedway in Newton, IA. Begun in June 2005, the approximately 225-acre project continues to be inspected, and the speedway will eventually be used for Busch and NASCAR racing.

“We were contracted to manage the stormwater pollution prevention plan,” says Brian Denham, general manager at Des Moines, IA-based Soil-Tek, who was directly involved with the project. “While onsite, the different erosion control methods used were Filtrexx FilterSoxx, Burchland Manufacturing silt fence, erosion control blankets, and single-net straw blankets for slopes.”

Another challenge was to ensure Soil-Tek had resources ready, both staff and equipment, according to Denham, to provide next-day service to its client at the site. Like the racecar drivers, they understood the need for speed.

“That site, for the most part, was graded all at once,” he says, adding there were some 2:1 slopes. “We worked exactly with the grading contractor. If they were grading, we’d be there the next day to put in the erosion control practices.”

Although it was inspected weekly, when a half-inch or greater rain event occurred, the site was inspected within 24 hours.

Photo: River Valley Organics
Crews faced poor soil and steep slopes on Route 222 in Pennsylvania.

“We did seeding and fertilizing with that as well. There were different seeding methods used. There was a little bit of annual with the permanent seed mix. We put a grass that would come up right away,” says Denham. “We used seed fertilizer and straw mulch and hydroseeding using wood fiber. Using hydroseeding, we used a bonded fiber matrix. There are detention basins that we had to go back and seed and mat all the way around.”

The vegetation successfully stabilized the soil. “All the measures that we used on that project worked very, very well,” says Denham. “We felt comfortable with the outcome.”

Keeping Storm Drains Clear
Filtration blocks played a role in sediment control at an ongoing construction site in Loveland, CO, about 7 miles south of Fort Collins. Begun in 1998, the approximately 450-acre residential development will endure construction work for the next four to five years.

Milk crates full of rock, straw wattles, and pulling the sediment from the storm drain itself were methods all tried before the construction company found Newbury Park, CA-based Eco-Blok’s filtration blocks and barriers. John Giuliano, president of Giuliano and Father Construction Co. based in Fort Collins, CO, devised the stormwater management program for the site, which included placing the filtration blocks around the storm drainage boxes.  

“We’re using them to trap and keep sediment under control,” he says. “The filtration blocks stop it at the street level and let the water go on through. Sometimes we’ll use them in landscape areas, mainly inlet protections. The area where they are being used [at this site] is inside the residential development. What we’re finding with the Eco- Bloks is that they stay in place really well and you can remove them for servicing.”

The blocks are removed when they become clogged with sediment, he explains, and cleaned using a pressure washer. They can be set up onsite within approximately 10 minutes, and Giuliano says the blocks can be serviced in about the same amount of time.

Photo: Soil-Tek
The Iowa Speedway project called for such erosion control methods as silt fence, wattles, and blankets.

“A month ago we experienced what our local storm drainage department called a five-year storm. We got 2 inches of rain in a 45-minute period. They were an absolute success,” says Giuliano. “In talking to our local storm drainage department, everything else would have failed, they said. Failure rate was 25% or less, and after talking with our stormwater department, we fared better than they had done. The methods that we used fared better. We stopped a lot of the sediment, almost all of the sediment in the street. It never entered the storm sewer system. We didn’t have to clean out any of our inlet boxes. We found them to be much easier to rehabilitate afterwards. Those same blocks are being used again today.”

Construction at the site was completed in phases.

“We try to disturb in as small pieces as we can,” says Giuliano. “Obviously, we disturb more if there is a demand for lots. We’ll try to do it 20 to 25 acres at a time. At any one time we have 25 to 40 acres at a time. We try to minimize it.”

In addition to water-quality control structures, the company uses other methods of erosion control on the site as well, including hydromulching that includes ground-up paper and tackifier that protects materials on the site from dust and sediment loss.

 “We had some 45-degree slopes and drainageways that had been seeded days before the storm without us reseeding them,” says Giuliano, crediting the tackifier.

Whatever the alteration to the landscape, whether for homes, entertainment venues, or water resources, keeping sediment in place by making provisions in advance of the project is essential to its success. Neglecting erosion control measures during a project’s outset puts the timeline at risk and jeopardizes the project’s budget. The best damage control when it comes to soil retention on construction sites remains proper planning.