A study done by the Washington State Department of Ecology in 1992 found an average dust emission rate of 1.2 tons per acre per month for active construction sites. Another study by the same agency listed earthmoving, traffic, and general disturbance as the major dust-generating factors in construction work.
Dust-generating work has to be done, of course. But for the public good, the dust and particulates so generated has to be minimized and controlled.
Controlling dust and particulates reduces soil erosion and gives workers and nearby residents cleaner air to breathe. The community water supply is cleaner, too. Improved visibility means safer driving.
There are economic benefits as well. Less dust results in less money spent on cleaning vehicles and equipment or replacing gravel on roads.
With such significant health and environmental benefits, communities usually require that dust and particulate matter be controlled as much as possible. One example is Bernalillo County in New Mexico. The county, which includes Albuquerque, requires that dirt tracked onto paved surfaces be promptly removed. Construction, landscaping, and roadwork operations are required to control dust and particulates at all times. The county requires that managers of projects that will disturb three-quarters of an acre or more of soil obtain surface disturbance permits. These permits are granted by the Environmental Health Department.
Tightening of federal and state air-quality laws probably will cause more communities to require dust abatement permits before work on projects can begin. Some cities or counties already have these permits from their air pollution control authorities in force.
Communities with requirements for fugitive dust control typically suggest they be met by best management practices (BMPs). These practices can include not scheduling work during times of high winds; watering; establishing temporary vegetation; and using matting, mulch, gravel, or windbreak fences.
Sequential site clearing can also reduce dust and particulates significantly. Common-sense measures, such as requiring lower speeds for all vehicles passing through the construction area and having drivers wash the wheels of construction vehicles, help without increasing cost.
Spray-on or till-in chemical soil treatments, or soil stabilizers, not only reduce current dust but also prevent the conditions that would allow more to develop in the future. Weather conditions and amount of traffic determine which type of treatment is best for a site.
Chemical soil treatments include anionic asphalt emulsion, latex emulsion, resin-water emulsions, polymer emulsions, calcium chloride, and magnesium chloride. Products used near people, wildlife, and bodies of water must be nontoxic and environmentally safe over the long term.
El Paso County
DustGard, a liquid magnesium chloride from North American Salt/Compass Minerals, fills that bill. One of its enthusiastic users is Pete Cozzolino, highway superintendent for El Paso County in Colorado.
“It works really well, but you’ve got to have plenty of water,” Cozzolino says. “It lasts 120 days or better before we have to regrade. Then we get another two months of use.”
Cozzolino’s territory is elevated, dry, and windy. For about three years he has depended on DustGard for dust control and soil stabilization on El Paso County’s 99 miles of unpaved roads. It is applied to the roads that get 200 or more cars per day, or where citizens complain about dust. Most of the county’s roads get the surface coat application, which will last three to four months.
“We put in water 3 to 4 inches deep,” Cozzolino says, “then we shoot it the next day. We don’t let it dry out. The water’s the key. Get it deep or the surface coat will break up, like potholes.”
Roads with the heaviest traffic, especially corners, intersections, and hills, receive Cozzolino’s preferred, more thorough stabilization process, which lasts longer.
“We use .7 rate of application for 4, 5, 6 inches. The flop [ratio of water to magnesium in the mixture] has to be perfect. It has to be right. You can’t get it too greased. When it’s just perfect, that’s when the stabilization turns out nice,” he explains.
Since El Paso County began using DustGard, “that’s 99 miles of roads we’re not grading for three to four months,” Cozzolino says. “The phone isn’t ringing off the hook with complaints, and road safety is much better.”
Cozzolino hasn’t noticed any stricter air-quality enforcement, though state officials sometimes call about dust when gravel is being hauled out of the pit for work during the summer months.
A PAW Trail
Sometimes dust control and soil stabilization affect just one person at a time. Imagine being a blind person out on a trail. You are listening with pleasure to the calls of different birds. The breeze brings delightful scents of pine, spruce, and other trees. But not knowing what your next step might encounter would be scary.
Fortunately, there are organizations that work to make nature both accessible and safe for people with disabilities. One such organization is Partners for Access to the Woods (PAW) in Granby, CO.
PAW’s director, Carol Hunter, is a strong advocate for finding ways that allow disabled persons to interact as independently as possible with nature. For years, Hunter and other PAW members dreamed of creating a special trail that would truly permit people with disabilities to engage with natural surroundings.
Construction on their dream trail began in June 2012 and will be finished later this year. Called PAW’s Educational Research Trail (PERT), the trail, located near Empire, CO, recreates an old wagon road built from 1860 to 1875 through Berthoud Pass. Students from the Colorado School of Mines used GPS readings to replicate the old road in their design of the trail.
The 500-foot trail “is very different,” Hunter explains. “Most accessible trails are built like they were in Kansas-flat! This is in Colorado, and it’s interpreting a mountainous transportation system built in the 1860s.”
Hunter wanted the trail to be both interesting to traverse and geographically accurate. To depict the mountainous terrain of Colorado, the trail is steeper than the usual 2% grade found on accessible trails.
“That’s why the soil stabilizer is so important,” Hunter says. “There’s nothing for a person with visual impairment to trip on.”
Hunter was concerned about the trail’s surface for three reasons. One was to ensure its stability, essential for use by disabled persons. Written into the Americans With Disabilities Act is the requirement that trails for use by disabled people be “firm and stable,” she notes.
Another concern was the final appearance the trail would present. She wanted the trail to be more than safe; it should also be aesthetically pleasing.
“It is so important to match the trail to the expectations of the recreational user,” Hunter says. “In downtown Denver, it’s okay if the trail is asphalt or concrete, but in a rural area if you use asphalt or concrete it destroys the expectation [of being in a completely natural setting].”
Hunter’s third reason was one of health-avoiding both dust and strong chemicals. “It is important that this project be environmentally safe. For people with disabilities, you have to be careful,” she says.
In planning the new trail, Hunter contacted Bob Vitale, chief executive officer of Midwest Industrial Supply. She had worked with Vitale on other trails and hoped he would donate material for a section or two of the trail. Instead, Vitale offered to donate the material and expertise to build the entire trail. He sent Midwest managers Frank Elswick and Ed Morse to direct the construction.
“I had talked to Bob over the years, but I had not met any other Midwest staff people,” Hunter says. “I was amazed at how dedicated they were in getting a good project. They gave their expertise. They didn’t just donate the product. Midwest really, really
helped us.”
Members of Volunteers for Outdoor Colorado, students from the University of Colorado’s School of Landscape Architecture, and others pitched in to help build the trail.
To stabilize the soil and keep down dust, they used GreenPave.
GreenPave is Midwest Industrial Supply’s proprietary polymer-enhanced, resin-based, organic emulsion that stabilizes soil and thus controls dust. Safe for wildlife and vegetation, it increases loading capacity, prevents moisture penetration, and stands up to severe weather.
GreenPave Base is part of the two-part ResinPave system. GreenPave Chip, a custom-formulated chip binder, can be installed over the Base or directly over asphalt. If it tops asphalt, that saves the cost of removing the pavement.
“I am a huge fan of that product,” says Hunter. “I’ve used this material in two other wheelchair-accessible trails. Once you have it down, it takes very little work to maintain.”
GreenPave “blends with the environment,” she adds. “You don’t know there is a product there. It looks natural. That’s what excites me most about the product.”
The PAW trail will also be used by blind adults and patients from some Denver rehabilitation hospitals. Military veterans recovering from physical and emotional injuries of war can share it with their families. Older adults who need extra-secure footing can use it. Able-bodied adults and children can also enjoy the trail. School children will walk it to understand the history of transportation in Colorado.
Hunter, who will retire in June 2013, says she “wanted to leave something there so people could see what accessibility trails can be. This trail is the beginning of a discussion.”
Keeping a Composting Facility Clean
Founded in 1992, St. Louis Composting is the region’s largest compost producer, serving an area of about 50 miles around St. Louis, MO. The company produces STA (Seal of Testing Assurance)-certified compost, mulches, topsoil, and soil blends, selling by single bags to home gardeners and by truckloads to commercial landscapers.
Applying DustGard on an El Paso County road
Its five composting facilities process roughly 500,000 cubic yards of green material annually-more than one-third of all yard waste generated in St. Louis County. The company recycles yard trimmings gathered by the area’s major waste haulers. It also takes in material collected form curbside greenwaste recycling programs. Landscapers, tree trimming companies, and home- and farm owners can pay a fee to dump branches and other green debris.
St. Louis Composting’s 4-acre facility in Maryland Heights, MO, is a transfer station. Trucks ranging in size from large commercial waste haulers to homeowners’ pickup trucks unload yardwaste, including trees, brush, and grass clippings, at the site.
The company’s trucks are loaded onsite to take this greenwaste to the various composting locations. Positioned atop a closed landfill, the facility is close enough to neighbors that the dust and particulates generated would be an air-quality problem.
Local laws concerning air quality have not changed, “but they keep a tight rein on us,” says Dave Gavlick, operations manager for St. Louis Composting.
Unloading raw green materials is done close to the ground, so particulates and dust don’t have the opportunity to be caught by the wind and spread. But loading the company’s transfer trucks with greenwaste is another situation. The trucks are so large and high that front-end loaders with tippers must be used to fill them. With the green material high above ground on an elevated site, the wind can easily blow particulates for some distance. Instead, they are controlled by the use of a DustBoss, manufactured by Dust Control Technology. St. Louis Composting uses the largest DustBoss model.
“It takes about 10 minutes to load a truck” Gavlick explains. “All the time the truck is being loaded, the DustBoss is blowing a fine mist on the material. When the truck is filled, we put a tarp on top of the load.”
The DustBoss works by shooting a fine mist of plain water. There is no expense for chemicals or concern about environmental damage. Because the mist is so fine, it does not wash any material away or cause water to pool or run off.
St. Louis Composting uses one DustBoss at its transfer station, but Gavlick notes, “If I needed more, I would buy them.”
DustBoss is also at the center of a new process for dealing with landfill leachate, by either irrigation or evaporation. A patent for the process was awarded to American Evaporation and Irrigation LLC, a North Carolina company, in January 2012.
“We’re using a mist to catch the particulates,” says the company’s Kelly Houston. “We’re putting in dust supression right at the beginning, suppressing at the source. It’s also useful in odor control, catching the esters coming out of the trash.”
At a landfill, “the working phase would be [done] that day and covered up that night,” he adds. “It’s done from a distance-we can shoot the DustBoss from 100 yards away, making a cloud. The particulate never has a chance to materialize. We use only 30 to 40 gallons to cover an acre of land; we’re trying not to use much water.”
Using the process, landfill leachate can be evaporated instead of being piped into tanks and then into a lagoon. The particulates separate from the water vapor, and the landfill uses it for irrigation of grass. The process uses the fine mist to irrigate even steep slopes; there’s no danger in overwatering newly seeded areas, causing seeds to wash away.
Trail Maintenance
In northwest Stark County, OH, which includes the cities of Canton and Massillon, the Parks Department began using another Midwest Industrial Supply product in June 2012. Soil-Sement is a polymer emulsion for dust control, erosion control, and soil stabilization that dries clear and is nontoxic to the environment.
Independent tests by regulatory agencies prove that Soil-Sement controls PM10 and PM2.5 fugitive dust emissions. The product can be sprayed with hydroseeding equipment or tilled into the soil and compacted.
“We’re doing a test project on 300 feet of the Hoover Trail, near the high school,” says Rob Hoover, construction supervisor for the county’s Parks Department. “It’s a fairly steep grade.”
Starks County has 13 parks, including 25 miles along the old Ohio and Erie Canal. The parks within Stark County have about 90 miles of hiking and biking trails, constructed of 703/10 fine limestone.
“We mixed Soil-Sement with this fine limestone and put it down with a paver,” Hoover explains. “It looks really good, and it’s not going to wash away anytime soon. You could drive a vehicle on it.”
For the performance test, the Parks Department chose two grades of the trail that are close together. One has the Soil-Sement surface and one does not.
“You can clearly see where the fine limestone [alone] does erode and where the Soil-Sement is definitely working,” Hoover says. And with all those trails to maintain, “I’m sure we’ll use more of it,” he adds. “Compared to asphalt, it’s a lot more reasonable in cost and it’s a little flexible.”
Pueblo County
In Colorado, Jim Cruz has been using DustGard on the roads in Pueblo County for “well over 20 years.
As project manager, Cruz sticks with DustGard, which contains magnesium chloride, because “it keeps the roads together. It helps with dust control. It helps with melting of snow. It creates a better driving surface, and it helps our [level of needed] maintenance.”
He notes, “Sometimes, if it rains or snows, it can get a little slick in spots.” That occasional situation is more than offset by DustGard’s reliability. In fact, he says that because so many Pueblo County residents feel safe driving on snowy roads, “some people would rather we not use it, because that means that more people are on the road!”
County road crews “scarify the road a bit, spray on DustGard, and roll it,” Cruz explains. The treatment generally lasts eight to 12 months.
Frequency of treatment varies depending on traffic load and inclement weather, but most roads are treated annually. “By the next fiscal year, it needs to be done again,” Cruz says.
“Dryness gets us all the time here, but we add water and rejuvenate it,” he adds. With Colorado’s windy, dry weather, dust is quickly noticeable. As for tightening of air-quality laws, Cruz says he has not seen any mandate so far, but “we try to be proactive in this.”
He adds, “Air quality is a serious concern for people and animals. People are concerned about their cattle breathing in dust, so it’s been a necessity.”
Field Trials
SCI Supply has been running field trials of NaEx’s 605 soil stabilizer and dust control, distributed by Innovative Turf Solutions, mostly in North Dakota and Minnesota.
A larger field trial will be conducted this summer. Soil stabilization and dust control are important on the gravel sections of paved roads near oil fields in Ward County, ND, the site of one of the field trials. These roads carry mainly commercial traffic with a lot of heavy trucks.
Travis Schmit, assistant county engineer for Ward County, says his crews sprayed NaEx’s SD605DS soil stabilizer on the gravel parts of grade rises about 1,100 feet high. Paved on both sides, the gravel sections are 100 feet long and 28 feet wide.
“Pretty much all of the areas are in a basin,” he says. “We haven’t used the product before, but we’re hoping we can reduce maintenance costs.”
Federal funds from a 2011 flood event recovery helped pay for the work. The work was done in September 2012. Schmit has been pleased with the result.
“We’re thinking of applying it twice a year, once at the start of the season-June 1-and once at the end-October 15. We’ll wait until it freezes before using a snow [plow] blade on it,”
he says.
Schmit thinks the SD605DS will do especially well because there is some ambient moisture in the area.
Paul Seidenkranz, erosion control manager for Standard Contracting in St. Paul, MN, is another new user of NaEx’s SD605 and SD605D. He has used SD605 on “a couple of bridge jobs in laydown yards and transportation staging areas.”
His crew sprayed SD605 through a hydroseeding machine, one application to cover 2 acres. “It works really well. This is our first application, so we’re still learning the product,”
Seidenkranz says.
“We were asking a lot of the product, putting it in an area with 20 to 50 trips with trucks an hour,” he adds. “We went to their SD605D product, just a test sample in a small area. It’s better,” Seidenkranz says.
“A moist surface with the straight SD605D is better. A little moisture helped it absorb into the ground. We had good success with penetration when the soil had moisture.”
Seidenkranz stresses that matching a dust-control and soil-stabilizing product to the conditions of a site is important to get the best result. He expects to be doing more testing with the SD605 line.
“We are enthusiastic about the product,” Seidenkranz says. “We can’t wait to get more practical field applications in place. I think that where they’re phasing out calcium chloride for environmental reasons, this will be a good substitute.”
Rod Vaage, branch manager for Brock White in Minot, ND, says his company has also done testing with SD605D. “We did some test strips here in western North Dakota. They were for Ward County and one construction company working for a large oil company.”
He adds, “So far it has set up and held up remarkably well. Our tests were done late in the fall, so we shall see how it holds up through a tough North Dakota winter.”
Vaage notes that oil companies are required to use dust-control products on the gravel roads immediately in front of farmsteads affected by the truck traffic.
If a farmer requests the use of dust control, the oil companies must put it down properly along the farmer’s property.
“This will be a true test of the capabilities of SD605D, as there are few places with the heavy truck traffic and windy dry weather of western North Dakota,” he says.
Dust control will continue to play a significant role in protecting air and water quality everywhere.
As the companies involved create and test new products, they will handle the environmental challenges in even better ways.
