“Dust wasn’t considered a significant health and pollution problem until the mid-1970s,” says Marty Koether, a managing partner of EarthCare Consultants LLC, based in Tucson, AZ. “And each situation has a unique set of circumstances–soil conditions, climate, weather, road use, disturbed or undisturbed soil, environmental concerns, financial considerations, and so on.”
Also known as The Dust Doctor, Koether and his two partners started their consulting company in 1995. Before that he worked in paving and asphalt restoration, along with erosion control, using geotextiles and hard armor.
“It was while I was working on erosion control projects that I discovered a real need for dust control,” Koether says. “To me, soil stabilization is synonymous with dust control and sediment and erosion control. Unless you have a stable surface, you will always have dust during the dry season, and you will have sediment runoff and erosion during rain events. Basically, by stabilizing the soil, we achieve both dust control and erosion control.”
Since his initial involvement in dust control, Koether has participated in a number of dust palliative studies for evaluation of soil stabilization and dust control products. He has worked with Mohave County, AZ; the City of Scottsdale, AZ; and the City of Phoenix Aviation Department, as well as URS Corp., on evaluations of fugitive dust control measures for the Arizona Department of Emergency and Military Affairs. From 2003 to the present he has provided soil stabilization products, services, and consulting to Mohave County Department of Public Works to stabilize native road subgrades prior to chip-sealing.
Koether and his partners recommend Soil-Sement, manufactured by Midwest Industrial Supply Inc. in Canton, OH. “In 1995 I did over six months’ worth of research on the different soil stabilization products that were on the market. What we discovered then was that Midwest Industrial Supply was the grandfather of the dust control industry regarding environmental stewardship.
“Environmental concerns of using dust control products are a significant issue nationwide,” continues Koether. “Effective dust control improves air quality, but we have to remember that we must protect other resources, such as water. Soil-Sement does not carry any chemicals into the stormwater system because it is not water soluble, so in the same way paint doesn’t run off your house when it rains, it doesn’t run off the surface that it has been applied to during wet conditions.” He notes that Midwest Industrial Supply has subjected the product to tests according to EPA guidelines regarding water quality, toxicity, and carcinogenic properties.
“Research and testing proves that stormwater runoff from areas treated with Soil-Sement will not contain concentrations that exceed benchmark values of the parameters designated in the National Pollutant Discharge Elimination System [NPDES] Storm Multi-Sector General Permit for Industrial Activities,” Koether says, adding that the product’s Material Safety Data Sheets (MSDSs) “do not contain any of the disclaimers found in the majority of the other manufacturers’ products’ MSDSs. This industry isn’t really regulated. It is a “˜buyer beware’ market, and people really need to study the products they intend to use in great detail.”
Not only environmental safety but also performance should be tested, he believes. Koether claims there is not enough unbiased testing of dust suppressant products within the industry. “Until industry standards for testing fugitive-dust emissions are implemented and repeated under controlled conditions, an element of doubt will continue to linger over the industry. Contractors are being forced to make decisions without knowledge of which products work best under the conditions at hand.”
One of the places where Soil-Sement is in use today is Mesa, AZ. Larry Tucker is a transportation supervisor for the city, which has a population of 450,000. With an annual rainfall of approximately 7 inches, which tends to fall in about five separate rains, the city of Mesa is dry and dusty. And keeping up with the Air Quality Particulate Standard set by the Arizona Department of Air Quality is a regular, ongoing task.
“We’ve increased our street sweeping in the last five years,” Tucker says. “We sweep regularly on major streets, on streets beside freeways, and on any street beside a dirt lot.”
Tucker says the City of Mesa no longer allows parking or activity of any kind on an untreated lot or surface-for example, an unpaved parking lot. “We have to coat those areas with a soil palliative or with recycled asphalt.”
Unpaved road shoulders pose another challenge for the city. Unless there is a curb or gutter, the area must be treated. “We shoot Soil-Sement over unpaved shoulders, all 32 miles of them,” Tucker says, adding that the entire treatment process costs the City of Mesa approximately $150,000 a year.
The city has been using Soil-Sement for four or five years, according to Tucker. He says it is faster and easier to apply than recycled asphalt or a rock product such as an aggregate-based course. Tucker says Soil-Sement costs less than an aggregate but must be applied frequently, as often as once a year in an area without traffic. “We’re more likely to use it on dirt lots and shoulders.”
Glenn Gagnon, sales operations foreman for Mesa, oversees crews in charge of grading, rights of way, drainage ditches, and retaining and catch basins. He says the city has used many other products but prefers Soil-Sement. “It’ll last about a year,” he says. “We couldn’t get that life out of the others.” Gagnon says the city has tried lignite sulfide, “a smelly brown product”; calcium chloride; various resinous products; and a variety of polymers.
The product, which Gagnon says “smells and looks like Elmer’s glue,” is shot out of a distribution truck, making it relatively easy to apply.
Dust abatement is a “big deal” in Mesa, according to Tucker. “We’re always on the border of compliance,” he says, referring to air-quality standards that limit dust to 10 parts per million.
There is only 1 mile of dirt road in all of Mesa, so the main areas of concern are those where traffic is not the main issue. “Every temporary parking lot or construction site must have a water truck and a sweeper, and those areas are swept at least once daily,” Tucker says. “In a high-traffic area like a freeway, you’ll see a fleet of sweepers. We don’t have much wind, but there’s a particulate problem if there’s any wind at all.
“We’re out there all the time,” he adds, “at least 165 days a year.”
Mohave County is another area using Soil-Sement, according to Koether. “We have been under contract with Mohave County Department of Public Works since August 2004 to provide product and applications for road-subgrade stabilization. Their contract is the most stringent performance-based contract we have ever encountered. We had to provide ASTM lab test results showing the product application rate that would achieve a certain unconfined compressive strength with the county’s control soil. Based on the rate established, that amount of product must be applied on every road treated with that product.”
Mohave is a relatively large rural county, according to Nicholas Hont, assistant director of public works for the county, which maintains about 1,500 miles of dirt or gravel roads. “The maintenance itself causes potential problems from time to time,” Hont says.
For dust control, county maintenance crews typically use water in areas where it is available. However, in the past three years, the county has treated and improved approximately 30 miles of road as part of a maintenance test program approved in 2004 by the Mohave County Board of Supervisors. “So-called soil stabilizers are being used for the improvement of unpaved dirt and gravel roads throughout the county,” Hont says.
Mohave County’s testing program defines soil stabilization as “improving the geotechnical engineering properties of soils and aggregates through the application of stabilizer additives,” according to Hont. “Chemical additives are mixed into the road subgrade and aggregate base material to achieve increased soil strength. The stabilized aggregate surface is treated with chip seal to reduce water infiltration and provide an improved driving surface.”
Koether adds that tanks are measured daily to ensure that the proper amount of product is applied on each road. He says samples are taken daily while it is being applied and are tested later in the lab on the control soil. “If the established unconfined compressive strength is not then achieved, the county will discount payment for the product that was applied. We have bid the contract twice since it started, and Soil-Sement has been the only polymer and only soil-stabilization product that has met the performance standards required in the specifications.”
Hont says many other soil stabilization additives are available on the market, among them polymers, enzymes, lignosulfites, petroleum emulsions, and tree resins. “The most promising products appear to be polymers, enzymes, lignosulfites, and possibly petroleum emulsions, but to date only a polymer supplier was able to meet the county’s requirements and specifications.”
The results of the county’s soil stabilization have been satisfactory, according to Hont. “The road structural section created this way is capable of carrying relatively low-volume traffic loads, the dust is eliminated, and future maintenance costs are reduced by eliminating the need for regular grading, or blading, of the dirt or gravel road.”
Providing Site Services
A relatively new industry has arisen to meet the needs of busy contractors who have enough to think about without worrying how they will meet government specifications for clean air.
Judy Pipkin is an office manager, inspector, and trainer for a private company, United Site Services in Reno, NV, which assists contractors in maintaining compliance with the EPA’s stormwater regulations under the Urban Drainage and Flood Control Act established in 1999.
“We’re on the contractors’ side,” Pipkin says. “Our job is to keep them in compliance and out of trouble.”
Each state that has responsibility for NPDES permitting is ultimately in control for compliance to the federal regulations, according to Pipkin. “If the states and cities aren’t enforcing the regulations, then contractors won’t bother to hire regulatory help services. There are not always enough state and city inspectors to watch all new job sites. If nobody is watching, the general atmosphere is “˜Why worry?’ And you can’t blame the contractors; they have so many other things to worry about on their job sites.”
Landscaping and site-service companies are in heavy competition these days, according to Pipkin, who says that engineers and individual consultants are getting into the game as well.
As part of her job, Pipkin trains contractors and subcontractors. “I outline rules and regulations, tell them what to expect from the federal and state governments, and teach them how to implement best management practices.”
Pipkin also does weekly inspections to make sure a site remains in compliance. “For example, we watch storm drain inlets to make sure they are protected with filter bags or other products that will keep the drains clean.”
Like other states in this arid zone of the country, Nevada has more than its share of dust. “Everybody has runoff problems,” Pipkin says. “But rainfall keeps the dust compacted. Since we don’t have much rain, we must use dust palliatives.”
While water is used 90% of the time as a temporary suppressant, Pipkin likes to see vegetation as the ultimate goal for any site. “At a mall, for instance, we ask the contractor to provide specs outlining the proportion of paving versus landscape versus buildings. It is important to offset paving with berm areas in order to treat the runoff before it reaches the street. Landscaping is no longer just an aesthetic concern; it is also used to act as filters.”
For vacant lots during construction, Pipkin prefers hydraulically applied solutions with a green-colored adhesive for maximum visibility. “That way you can see that the area is already mulched and tackified, and people tend to stay off it.”
While, practically speaking, regulatory measures often are viewed as just one more headache for those in the construction business, Pipkin fully supports the EPA’s initiatives. “Dust palliatives, regulations to maintain dust particles on each site-it all affects the environment.”
Port of Houston
The City of Houston, TX, has made a name for itself in environmental circles. If Houston Mayor Bill White had had his way, Houston would have been the first place in Texas with health standards for hazardous air pollutants in the local nuisance ordinance, thresholds that don’t exist on the state or federal level, according to a report in the March 9 Houston Chronicle. As of March 21, the issue was still being debated after lawmakers filed bills barring a municipality from using a nuisance ordinance to crack down on pollution from outside its boundaries.
As president and founder of AAA Asphalt Paving Inc. in Houston, Mike Hoffman has expanded the company’s role as civil contractor and taken on a project in dust control at the Port of Houston.
“Our name doesn’t really apply to all we do,” Hoffman says. “We do all phases of civil construction, including roads, bridges, and installing stormwater, water, and sewer pipes.”
The Port of Houston is a 25-mile-long complex of public and private facilities with a port that ranks 10th in the world in total tonnage. More than 200 million tons of cargo moved through the port in 2006, and it had to be offloaded and parked somewhere, at least temporarily. This is where Hoffman’s company entered the picture.
AAA Asphalt, which started in 1991 and incorporated in 1995, bid for and received a job to apply the dust suppressant Soiltac to 100 acres of roads and storage lots at the port beginning in March 2007.
“The area gets massive amounts of traffic, with trucks loading and unloading,” Hoffman says. And while Houston gets “more than its share of winter rains,” the summer droughts lead to dust. And dust, wherever it comes from, gets the attention of the regulatory agencies.
The project to reduce dust and comply with particulate regulations involved spraying Soiltac, a co-polymer supplied by Soilworks LLC of Gilbert, AZ. According to Hoffman, Soiltac is mixed with water, which not only dilutes the chemical but also acts as a conveyance to deposit it into the soil. “As the water dries, the Soiltac bonds.”
Chad Falkenberg, whose company manufactures Soiltac, says that 80,000 gallons of concentrate, or 560,000 gallons of diluted solution, were used on the project. He says the product was specified by the Port of Houston Authority after recommendations from Fugro Consultants LP, a geotechnical engineering company headquartered in Houston.
Previous to this application, the “laydown yards” at the port were unpaved and unstabilized. In addition to truck traffic, they were subject to heavy loads: forklifts weighing over 50,000 pounds as well as rolls of steel and pipe, Hoffman says. “All this leads to potholes, which lead to dust. It’s a remedy to reduce particulate matter.”
Falkenberg notes that work on the project had to be done between 4:00 p.m. and 7:00 p.m. because of the volume of traffic passing through the site. “Some single-acre sites, or laydown yards, receive over 200 tractor-trailers a day,” he says, adding that these vehicles typically weigh 80,000 pounds.
Hoffman says this work is not typical of what he generally does; he is still primarily a civil contractor. “But the calls [about dust control] are increasing. And when the calls increase, the jobs increase.”
Dust Control at Airports
On March 15, 2007, the EPA issued a press release saying that the Phoenix area had failed to meet the federal clean-air standard for coarse particulate matter (PM10), or dust, by the December 31, 2006, deadline: “The primary causes of dust pollution in the Phoenix area are from windblown dust from construction sites, road building activities, agricultural fields, unpaved parking lots and roads, disturbed vacant lots and paved road dust.”
Although airports were not mentioned specifically, as the superintendent of building Services at Phoenix Sky Harbor International Airport, Joseph Husband has been doing his part to comply with regulations. He has been involved in maintenance activities at Phoenix Sky Harbor, Deer Valley, and Goodyear airports for more than 16 years. He previously managed the airfield maintenance function for the Phoenix Airport System and is first vice president of the Arizona Airports Association.
“We typically deal with dust maintenance applications as opposed to construction dust control,” Husband says. “During maintenance activities, we do practice dust control measures such as gravel pads, watering, and palliative application.”
Husband says airports have always been at the forefront of dust control due to their unique problem of maintaining visibility ranges that can be compromised by windblown dust or dust rising from jet blast and propeller wash from aircraft. “This is particularly important in the approach and departure areas at the runway ends and also in the unpaved areas immediately adjacent to the runways and taxiways that can be affected by turning aircraft and outboard engine placement.”
To reduce dust, the City of Phoenix Aviation Department Airport System uses all of the common procedures, such as vegetation, soil stabilization, ground cover, and topical treatments. The latter has become the preferred treatment, according to Husband, due to “effectiveness, relative low cost, long service life, and fast application rates.
“We currently use a polymer product,” Husband says. “Our current contract provider isEarthCare Consultants, and the specified product under our contract is Soil-Sement. The product is typically sprayed topically by a distributor truck at one of two specified solution strengths and application rates. An additional option under our contract is that the Soil-Sement is blended with soil and compacted for more permanent stabilization of soil, which provides long-lasting durable surface. Both application techniques result in a soil surface free of dust emissions for 12 to 36 months or more, depending on environmental conditions and frequency of travel over the treated area.”
The City of Phoenix, like any other municipality governing airports, has the goal of achieving acceptably low levels of particulate matter and staying out of the non-attainment category under the federal Clean Air Act. Among the methods used to determine effectiveness in reducing fugitive-dust emissions, Husband listed visual observation of dust activity near aircraft movement areas or on unpaved areas subject to service vehicle traffic; visual observation of air opacity in and around airport areas; lab analysis of treated soil areas; and ball-bearing drop testing. “This is a procedure in which a ball bearing is dropped from approximately 12 inches onto bare soil areas and then an observation is made as to whether a puff of dust occurs at the point and time of impact,” he explains. “This is an unscientific test to determine if soil areas have a “˜crust’ that reduces or eliminates dust emissions.”
Ultimately, the City of Phoenix Airport System is looking for long-term solutions to its dust problem. “We are turning to paving of infields with asphalt as a permanent method to control dust and vegetation,” Husband says. “This method is expensive initially and does require some level of pavement maintenance, but the long-term costs and reduced maintenance activity pay dividends to the airport.”
Military Applications
The military is a major consumer of dust palliatives. As a Marine Corps instructor for arming and refueling operations in Yuma, AZ, Jay Peralta trains teams of soldiers from all of the US military branches and even some foreign nationals in such areas as control of improvised explosive devices, security and convoy operations, and even dust control.
Peralta’s concern, however, is not compliance with the EPA but rather the direct saving of lives as aircraft land on dusty soil. The obvious site for application is a desert in the Middle East, but Peralta’s trainees learn how to keep dust down on similar sites in eastern California and western Arizona. “Those places are not a little dusty,” says Peralta. “Those places are nightmares.”
In training, Peralta teaches dust suppression as part of his course. “We teach them to use the product [in this case, Envirotac] and to conduct operations as if they were part of a team dropped into an undisclosed location and forced to prepare a site for incoming aircraft.”
Envirotac, manufactured by Environmental Products & Applications Inc., is an acrylic co-polymer, which, when it hardens, provides long-lasting dust suppressant, according to Peralta. “We’ve gone in some places close to eight months or a year, and in most longer than a year.”
Peralta says the end user, in this case the military, finds the product easy to apply. “It is mixed with water, and when the water evaporates, it takes the soil particles and forms a thick crust, up to a half-inch, that will keep sand from rising under the rotor-wash of an aircraft.”
Peralta stressed the importance of a dust palliative where aircraft are involved. “We are dealing with multi-million-dollar aircraft and the lives of Marines.”
Why Envirotac? “We trust the product; we’ve been using it about eight years. It is the most cost-efficient and the cheapest we could find; the others [cost more] and perform just the same.”
To anyone investigating this highly competitive market, it is obvious that enterprise is alive and well in the dust control industry. As long as the dust rises, companies will rise and fight for the right to suppress it.