Keeping closer watch over ESC practices
By Roberta Baxter
In past decades, you could often locate a construction site of any size by the dust cloud overhead, sediment in a nearby stream, or the muddy tracks in the street. That’s all changing as a result of more stringent regulations and a plethora of products to meet the challenges.
Requirements to meet National Pollutant Discharge Elimination System (NPDES) Phase II standards, as well as air-quality regulations restricting small airborne particles known as PM10, have forced contractors to consider what leaves each construction site, whether it is mud from truck tires, sediment washing into a stream, or dust swirling into the air.
Products to meet the challenges of erosion and sedimentation on construction sites range from silt fences to blankets and mats to devices that remove mud from truck tires. Many contractors are employing several methods in concert to ensure that their sites meet requirements.
Minnesota Silt Fences
Dan Neaton and his brother, Chris, own and operate Neaton Brothers Erosion Control based in Mayer, MN. For their area, Dan Neaton says, the most common sediment control measure at construction sites is silt fence. He also says that silt fence is the most cost-effective best management practice (BMP), especially if it is plowed in deeply enough during installation to hold well. “They work well as long as we don’t ask too much of them,” he says. A 2-inch rain in a short time can blow out any silt fence or fill it up with sediment so that it fails. Still, he says, “Silt fence is the best bang for the buck.”
For installation of silt fence, the Neatons use a Silt Fence Installer made by Burchland Manufacturing of Gilman, IA. Dan Neaton has used other brands, but he likes the Burchland model because it places a full foot of fence underground, and the fence is tightly held in the ground even before compacting. The machine also has a tight turning radius with a front-end pivot. He notes that one of the most common ways for a silt fence to fail is through undermining, and he has not had that problem in the couple of years that he has used the Burchland installer.
Another measure that Neaton Brothers Erosion Control uses is temporary seeding or hydromulching. Crews plant a cheaper seed mix than would be used for permanent seeding and apply it to a stockpile or bank that will be sitting for more than a month. One of the company’s large projects involved adding lanes to the interchange of I-35 and Minnesota State Highway 62. Crews installed silt fence around the site and hydroseeded the area.
After the collapse of the I-35W bridge across the Mississippi River in Minneapolis last August, Dan Neaton says, silt fences were installed around the collapsed site, and a floating curtain was placed in the river for sediment control during the investigation and rebuilding. A temporary road had to be built to bring in heavy equipment.
For their jobs, the Neaton brothers use monofilamented fencing for strength. The silt fencing will last up to two years—unless a dozer runs over it, according to Dan Neaton.
Controlling Dust at a Hospital Site
Jim Currie of Kitchell Contractors has a challenging construction project: expansion of a complex that is an active hospital campus. A total of 450,000 square feet is being added to the Banner Desert Medical Center in Phoenix, AZ, and the central utility plant is being increased significantly to handle the load. Parking lots are also being expanded.
A loop road has been constructed to handle construction traffic with minimum disruption to the patients and visitors. Silt fence was placed at low points.
One primary concern with this construction is preventing mud and dirt from entering the neighboring streets. In the dry Arizona climate, any soil on the street quickly turns to dust as cars pass over it, and the area has recently added enforcement officers to ensure that dust control and erosion control requirements are met. To prevent the problem, Grizzly Trackout Control Devices from Trackout Control LLC, headquartered in Tempe, AZ, were installed at egress points in multiple locations. The Grizzlys come in 8-foot by 10-foot or 8-foot by 20-foot sections consisting of alternating-height metal bars. The devices were installed over 3-inch aggregate as a base.
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Photo: Environmental Systems |
| Controlling erosion, sediment, and dust has become a construction-site priority. |
Currie notes that the Grizzly devices are very effective. He appreciates that they are heavy enough to handle 10-yard cement mixers and 10-wheel dump trucks. They can also be moved from site to site with a forklift. “They put up with abuse and shake the dickens out of a truck,” Currie says. He has found that the best technique is for truck drivers to hit the grates at speeds between five and 10 miles an hour to get the best amount of shaking to dislodge the dirt. In situations with clay soil, Currie adds hoses to spray off the trucks and a trough to capture the runoff so it stays onsite.
He also says that the Grizzly Trackout Devices are easy to maintain. If needed, they can be elevated with a forklift and shaken, and the aggregate underneath can be respread if needed. The Arizona Department of Environmental Quality likes the system because it is effective.
Mats Work
Pinkerton & Laws of Marietta, GA, is a 50-year-old company that specializes in hotel construction across the southeastern United States. Lawrence W. Weidmann, CPESC-IT, the environmental compliance specialist for the company, says that many project managers put erosion control measures under the direction of the grading contractor. Many times, the job gets little attention or ignored completely. Weidmann contends that hiring an erosion control contractor provides a better solution for the site, ensuring compliance with regulations, usually at a cheaper cost. He agrees that the most common measure is the silt fence, and he likes to recommend the wire-wrapped Type C silt fence because it has an excellent filtration rate. This type of fence also requires minimum maintenance—and maintenance, he notes, is critical to achieve the best outcome.
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Photo: Environmental Systems |
| Paper-fiber mulch and tackifier help stabilize a site. |
He used to specify rock bags for inlet protection but now uses the inlet filters manufactured by Blocksom & Co. of Michigan City, IN. The coir-fiber mats are bonded to a fiberglass backing, providing strength and filtration.
For construction entrances, Weidmann relies on geotextile fabric with rock underlayment. If needed, wash stations are added, with berms to keep the water onsite.
As erosion control specialist for single-family construction for the City of Winston-Salem, NC, Russell Yoder has researched and tried several products. The area had more than 2,000 single-family home permits in 2006, so erosion control measures at these sites is crucial.
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Photo: American Erosion Control |
| Some sediment control measures can stand up to vehicle traffic. |
Yoder saw an ad for Blocksom & Co. in Erosion Control and ordered some samples of the mats. So far, he says, they are working great. He expects contractors in his area to take advantage of any technology available. Most construction sites have silt fences with stone construction entrances, with only one entrance per site. The mats from Blocksom are used around curb inlets.
Many companies, such as Dell Computers, Honda Jet, and FedEx, have recently built plants near Winston-Salem. With more growth predicted for the area, Yoder predicts he will continue to be busy. He prefers to monitor the construction sites himself to avoid penalties for unmet requirements.
Pennsylvania Suburbs
At a construction site in Pennsylvania, Sharon Dotts, P.E., CPESC, of Gilmore & Associates observed the results of installing Flexterra Flexible Growth Medium (FGM). As project manager in the land design department, Dotts says she has seen rilling problems on projects with medium slopes. The current housing project includes homes at the top of a ridge; the top had to be graded down to form building pads. The slope was steep, with a 2.5:1 ratio.
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Photo: American Erosion Control |
| Controlling the perimeter of a site |
Flexterra, from Profile Products of Buffalo Grove, IL, is applied hydraulically and is made up of wood fibers, crimped interlocking fibers, and additives. Dotts says the product was sprayed on a slope 600 feet long and 30 feet wide. Seed was added, and Dotts was pleased to see the slope stabilized in a matter of days rather than weeks. She adds that no rilling has occurred even after rainfall. “I’m remarkably impressed,” she says. Gilmore & Associates has amended its standard notes to include Flexterra in future projects.
California Homebuilders
Kip Scott is project manager for Award Homes, currently working in the Hayward, CA, area. Construction of a 600-condo community began last fall, and Scott says that one of the first steps was putting ESC measures in place. The project began near the start of the rainy season in California, so part of the winterizing process was ensuring that sites were ready for rainfall. Straw is applied to future home sites, and Perimeter Guard, from ERTEC Environmental Systems, is put in place. ERTEC, based in Alameda, CA, supplies the sediment control rolls as well as curb inlet guards. Rock bag check dams are also used onsite to protect areas such as gullies.
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Photo: American Erosion Control |
| Reusable sediment control devices create berms on a large site. |
During last year’s rainy season, Scott says, the ERTEC products were very effective. He uses them in concert with straw mulch and says they filter stormwater better than other techniques and methods he has used in the past. “The ERTEC products are very user friendly,” he notes. Scott appreciates their ease of maintenance and the fact that they are reusable and recyclable.
Environmental Systems of Modesto, CA, also uses ERTEC products, according to the company’s Russ Daveggio. For recent residential construction sites, Daveggio says, crews install what Environmental Systems calls its “winterizing package.” The system includes Perimeter Guard, straw wattles, and custom-made curb inlet filters and rock bags. If the site is not going to be active during the rainy season—lasting from October 15 to April 15—installers hydromulch with a paper-fiber mulch and soil tackifier from EnviroTech. With the soils bound in place, the builder can be sure of meeting the October 15 deadline for having erosion control measures in place. For sites that will be under active development, Environmental Systems places wood excelsior blankets and wattles behind sidewalks, as well as its own drain and wet filters and gravel bags around the site and curb inlets. Crews build a geotextile/rock construction entrance and conduct weekly street sweeping to mitigate airborne particles down to the PM10 level. Sites with slopes will also be hydroseeded.
Daveggio says some contractors are now requesting Perimeter Guard even though the initial cost is higher. The more effective performance gives the contractor the extra assurance that he will not be hit with a fine for noncompliance to NPDES Phase II regulations.
Eels in Tennessee
A new kind of eel is showing up all over Tennessee. Manufactured by American Erosion Control LLC in Knoxville, the Erosion Eel sediment control roll functions as silt fence, check dam, or inlet protection. The device is a geotextile bag filled with filter media consisting of wood chips and recycled shredded tire rubber. The flexible Eel can be placed in a variety of shapes closely matching the perimeter of a site or a curb inlet. It is reusable and recyclable.
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Photo: Environmental Systems |
| Crews unroll and install erosion control blankets. |
Bob Mohney, president and owner of Saddlebrook Homes, builds approximately 225 homes a year in Knoxville and Nashville. Most of the projects are large communities built to handle the growth of the area. In the past he has used silt fence, but he notes that fences often don’t stay up. “Compromise it in one place, and it’s gone,” he says. He also would mulch the trees cleared from a site and spread the mulch across the area or use the woodwaste to form berms. In place of these measures, he now uses the Erosion Eel. There is an added investment upfront for the cost of the devices, he says, but adds that by the time he has to put up silt fence two times because of a failure, he would have paid for the new device. Also, the fact that the Eels can be picked up and reused provides a significant cost savings in the long run. They can be placed with construction equipment, meaning a contractor does not have to wait for someone to arrive with a trencher to install silt fence. Mohney has been using the Eels for perimeter erosion control as well as placing them around catch basins and says he has not had an erosion control failure since he started using them. Another use is to guide stormwater so that it stays on the construction site rather than running out into a neighborhood street.
Mohney also praised the easy maintenance for the Erosion Eel. “I’m a big, big fan,” he says. “And you only have to buy them once.”
Steve Forbes, project manager for infrastructure for Arcadis Engineering in Knoxville, has also been using the Erosion Eel. His initial project was at the Norris Elementary School, where a project involved building a wetlands laboratory for the students. An 18-inch-deep wetlands pond lined with a synthetic liner and geotextile fabric was constructed on the site and then backfilled with soil to create wildlife habitat. With strong community involvement and volunteer labor, the site was completed in fall 2006. No wildlife was added, but by spring 2007, turtles, frogs, and salamanders had moved in.
orbes saw a demonstration of the Erosion Eel at a seminar and asked American Erosion Control if it would like to be involved in the Norris wetlands project. The company agreed, providing the devices at no cost and installing them for the project. The Eels were placed to provide runoff protection and to allow vegetation to become established. The area will be reseeded, and the vegetation will continue to take hold. The Eels will probably be removed and reused at another project next spring.
After seeing the effectiveness at the wetlands project, Forbes says he is using the Eels at other projects, including water and sewer line installations. He says they are easy to place and maintain, and, because they can be placed by one person, labor costs are reduced. Installation doesn’t require heavy equipment, so the Eels can be used in places that would be impossible for a silt fence installation.
Avoiding Fines for Mud
Contractor’s-Services LLC of Lakewood, CA, manufactures and distributes supplies to the contracting industry. Dave Mazzuca, owner and partner of the company, says it also rents and sells equipment. The company was started by people coming out of the construction field, so they know what contractors need.
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Photo: American Erosion Control |
| Different types of sediment control devices can be used in conjunction. |
One of their bestsellers tackles the challenge of tracking sediment offsite. The Rumble Track is an 8- by 10-foot steel plate with angle iron bars designed to open tire treads so that mud and dirt is removed before the truck leaves the construction site. The grates, along with other erosion and sediment control devices, have provided dust control for sites all over southern California. Many sites have signs stating, “If you see dust coming from this project, call …” The effectiveness of the Rumble Track allows contractors to comply with regulations in the Los Angeles and southern California area, which has some of the toughest requirements in the country.
David Marin, stormwater pollution prevention plan enforcer for Oltmans Construction, notes that in California inspections are more stringent, especially from October 15 to April 15. One project he worked on was put on hold because of problems with the erosion and sediment control measures. The site is to be developed for commercial use, and 18 water wells had to be capped first. Marin functions as the erosion control inspector for his company. He recommended the contractor switch from sandbags to straw wattles, especially along the area where employees park. He said that the people were stepping onto the sandbags, breaking them and increasing the sediment problem. Rumble Track sections were added over 3-inch rock to prevent trackout of mud. “The Rumble Track works great if it is maintained,” Marin says. He recommends cleaning the plate every week or so, depending on the traffic it receives. Another recommendation is to replace silt fence with straw wattles, because the strong Santa Ana winds tend to overwhelm silt fences. In addition, many silt fence fabrics have a rating of 1,600 UV hours, and the high incidence of sunshine in California uses up those hours very quickly.
A New Machine
Many sites that receive heavy rainfall require water filtration before the water can be released offsite. Most equipment is large and not easily moved. Two companies, Halo Source of Bothell, WA, and Water Tectonics of Everett, WA, teamed up to provide a solution. The Roadside Assist Box fits on a small 20-foot by 6-foot trailer that can be pulled by a one-ton truck. The equipment can handle 200 gallons per minute and has continuous monitoring of turbidity and pH levels. Inside the trailer, water is pH adjusted (as necessary), treated with StormKlear, and passed through a media filter. It can then can be released without fear of exceeding requirements. The equipment also records turbidity and pH levels to provide assurance of proper operation.
As Trevor Mitchell of Halo Source notes, “Even the sites with perfect erosion control measures can face water turbidity problems.”
One type of development that is especially suited for the Roadside Assist Box is road and bridge construction. The trailer can be placed, allowed to work for a few days, hitched up, and moved to the next location down the road.
Most contractors are using a conglomeration of erosion control measures to ensure compliance for erosion, sediment, and dust control requirements. As regulations tighten, more products and equipment re developed to meet the challenges.
Roberta Baxter specializes in science and technology topics.
EC - March/April 2008
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