For the most part, 2011 has been a tough weather year, especially for growers. During the spring, some areas of the country received record rains, washing out plantings; summer blew in with a vengeance, with searing temperatures and widespread drought. In August, the US Climate Prediction Center warned that the La Niña weather pattern could likely continue into 2012, worrying those who realize 2011 may be the worst drought year since the 1950s. Agricultural losses may reach the billions of dollars.
The erosion control industry has also felt the impact. Many crews likely had to reseed projects after spring’s torrential rains; summer projects were slow to germinate, and airborne dust became a recurring problem. Water, sometimes the line of first defense against dust, became a too-precious commodity-due not only to the costs of rewatering a site time and again, but also because, in some areas, the water was too valuable to merely spread on dirt. Fortunately, there are products on the market that can stretch water use and increase its effectiveness.
Solutions That Hold Up
Segments of the US were parched in 2010, as well. To control dust on soil stockpiles and gravel haul roads, the US Army’s Fort Drum in upstate New York began a pilot program in April 2010 using dust-control products from Cincinnati, OH’s Innovative Turf Solutions.
On Fort Drum’s gravel haul road, 110 gallons of Innovative Turf’s Extreme Dust Control (EDC) was sprayed on 550 square yards. The haul-road site was monitored for dust, only on non-windy days (as surrounding areas were composed of dirt and sand); effectiveness of the application was analyzed as trucks drove over the roadway. EDC was 100% effective for dust control for three months.
Also beginning in April, a 1,350-square-yard soil stockpile site was monitored for both dust control and erosion. Initially sprayed with Innovative Turf’s EC-46 (110 gallons mixed with 550 gallons water), soil was taken from one part of the stockpile and used in other areas of the complex. The stockpile was then refilled to its original capacity, but the new fill dirt was left untreated.
Three months later, after a consistent, heavy rainfall throughout the night and early morning, follow-up photos were taken for comparison purposes. The EC-46-treated portion of the soil stockpile remained intact.
Piles of Dust Into Mighty Hillsides
It’s difficult enough to keep dust down on a flat surface; on a hillside, the task is nearly impossible.
Felicity, OH’s Utter Construction Power Plant & Earthworks Services is currently creating a power-plant landfill in Winfield, WV, and, due to the state’s topography, most of the soil it needs to stabilize is located on hillsides.
“We’re making a landfill for power plants, which will receive coal combustion byproducts and ash. We clear the hillsides out, creating a large bowl, and put down clay and PVC liners,” says safety supervisor Chris McIntyre. “Approximately 25 to 30 acres of hillside slopes have been disturbed, and we not only have to keep dust down, but also keep the hillsides from washing away.” To accomplish this, Utter Construction uses Soil-Sement, a product of Canton, OH’s Midwest Industrial Supply. “We’ve used a similar product in the past, but Soil-Sement was spec’ed here, and we’ve been applying it twice a week. It seems to be working well.”
McIntyre’s firm, which has been working the site since April 2011, has a three-year contract for the work and plans to use Soil-Sement for the duration. “The entire landfill project will take about 20 years,” he says. “Right now we’re building cells two and three of 10.”
He explains the application process: “We mix 8:1 water to Soil-Sement, which is put in a bulk water truck, and we spray it onto the hillsides. One “˜tote’-275 gallons-of Soil-Sement does two acres.” That application ratio can change, depending upon needs. “You can mix 1:1, or as thin as 20:1, depending on what it’s for; 20:1 is likely just dust control. But since we also want to prevent washouts, we’ve found a happy medium with the 8:1 mix. When applied, it looks like wet Elmer’s Glue-milky. When it dries, it’s clear.”
This year’s weather made Soil-Sement mandatory. “It costs about $900 per acre to have this put down,” McIntyre says. “Yes, putting down water to contain dust would be cheaper, but it was so hot this past summer, we would have had to be watering all the time. We use the Soil-Sement to shore hillsides up for weekends, as we can’t be here on Saturday. Soil-Sement makes a crust; it’s a bonding agent, somewhat impervious to rain. If we don’t control erosion, it would wash out into other people’s property, roads, and ponds. Plus we need to combat “˜fugitive dust’-the client wants to avoid EPA sanctions for that.”
The vegetation Utter Construction cuts down is stockpiled as “top dressing” for the eventual landfill, and also to use for erosion control. “Since we’re disturbing nature and habitat for animals, we want to do as much as we can to keep dust from spreading off the site. Once the vegetation is gone, there’s nothing to hold the dirt to the site-except Soil-Sement. Oh, and of course, after 15 or 20 years, when the landfill is finished and closed, clay and topsoil will be spread over it, someone will plant grass and trees, and the area will again go back to nature.”
Driving Dust Down
Rural areas often do not blacktop roads, opting instead for graveled routes. Cass County, MO, treats its 750 miles of gravel roads with DustGard from North American Salt in Overland Park, KS. In addition to keeping dust levels down (which makes homeowners living on those routes happy), Cass County finds it doesn’t have to smooth out or grade the roads as much, because DustGard stabilizes the gravel.
“Our county contains 750 miles of gravel roads,” says Public Works Director Chuck McCulloh. “Usually, gravel remains dusty until it rains-and this past summer, that wasn’t often. We pick high-traffic roads-usually 280 average daily traffic [ADT]-on which we dust-control and stabilize; we can’t do all of them. In our rural county, those high-traffic areas are usually near residential areas, schools, cemeteries, and so on.
“DustGard comes prepared from the vendor,” he explains. “We prep the road-get it ready, get it watered-then Scotwood Industries of Overland Park, KS, delivers and spray-applies the DustGard for us. This is performed once a year, although on really high-ADT roads we might do it twice.”
Although McCulloh has been using DustGard since he arrived in Cass County in 2009, he had previous experience with the product. “I had used it in a county in Colorado, and also at a coal company where I once worked. DustGard is cost effective; after it’s applied, we don’t have to put a blade on it [smoothing/grading the gravel] again for six months. It stabilizes the road, holds it together. Treated roads even hold up better during heavy rains and snow. We also stabilize roads with magnesium chloride. I would like to get set up where we could spray short stretches of roads ourselves.”
Dust in the Wind Makes the News
Dust made the national news in July 2011, when Phoenix, AZ, experienced not one, but two haboobs in less than two weeks. (The word haboob, from the Arabic meaning “strong wind,” refers to a type of intense dust storm commonly observed in arid regions throughout the world.)
“Haboobs can spring up without warning,” says Mark Shaffer, media relations director for Arizona’s Department of Environmental Quality (ADEQ). “The only early warning we got was Twitter traffic from 40 miles away. Haboobs are common in the desert, they happen here all the time-but the last really big one that came close to the size of the July 5 event happened in the late ’90s. We weren’t even cleaned up from the first one when the second one hit on July 18.”
“Longtime residents said it was the worst dust storm they’d ever seen,” reports Colleen McKaughan, associate director in USEPA Region 9’s Air Division. “Phoenix’s dust storm was a regional wind event. Such storms periodically happen during summer’s monsoon season. High winds during July, August, and September are a seasonal weather pattern. No one knows why the July 5 storm was so big. It was perhaps a ‘hundred-year’ dust storm.”
The dust storm was likely fueled by a storm front that threatened rain, but produced none. According to McKaughan, Phoenix continued to have problems with air quality for some time after the first storm. “As the city didn’t get the rain, dust was re-entrained in the following days. If the rain had come, that would have held down the dust. The second dust storm certainly didn’t help.”
The storm didn’t require any major cleanup; however, Shaffer notes, “Carwashes and pool cleaners were very busy out here. Two or three hours after the storm, the air somewhat cleaned up, at least for the next morning. No health warnings were in effect. Our public health message, which we reinforced after the first storm, was telling people to go inside right away and not to use evaporative coolers, which draw in outdoor air.” (Evaporative coolers are often used in dry climates instead of air conditioning.)
Local residents do get some warning about possible dust conditions, sometimes from state or local health departments, or at least local weathercasters, who note when conditions are “right” for a dust storm. “We watch for six pollutants to warn people about. If people aren’t aware that conditions are bad, they won’t avoid it,” McKaughan says. One piece of luck: “Sand tends to fall out of a wind, as it’s a bigger, heavier particle than clay or loam soil dust. It isn’t something to be particularly worried about someone breathing in. It’s the smaller particles that can harm lungs. Also, if sand’s flying around, people tend to mask their faces.”
“The only health problems that were predicted from the dust storms was that there might be an increased number of cases of valley fever, an infirmity caused by spores in the dust, something that’s always been prevalent in Phoenix’s soil,” Shaffer says. (“Valley fever,” Coccidioidomycosis, is an infection caused by inhaled spores of the fungus Coccidioides immitis, which exists in soil. It is most commonly seen in the desert regions of the southwestern United States, as well as Central and South America.)
“As a general rule, we tell people if there are conditions that could make high-pollution days. Construction sites and the like need to water exposed ground, or take other measures to keep the dust down. Usually, dust from residential yards isn’t a problem. In Phoenix, if people don’t have grass, they have a lot of rocks in place,” Shaffer says.
Owens Lake Dust Down
California’s Owens Lake has been a misnomer since 1926, after the city of Los Angeles diverted the Owens River, the lake’s feeder, into its own viaduct. Draining the lake made problems for local residents in more ways than one; in addition to removing a water source, the dry lakebed became the country’s largest single source of PM10 dust. As Theodore Schade, air pollution control officer for the Great Basin Unified Air Pollution Control District (GBUAPCD), noted in 2006, “Owens was a salt lake-mainly sulfate- and carbonate-salt instead of sodium chloride. Whatever water flowed in evaporated and left the salts. When the wind blows like crazy here, as it often does, that salt is blown over a wide area.”
The GBUAPCD stated that Los Angeles had to fix the lake by the end of 2006; it was soon evident that the project would be more costly and take much more time, than initial projections. (For complete details, see “Los Angeles Still Owing on Owens Lake Project,” in Erosion Control’s March/April 2006 issue.)
Five years have passed; what’s the progress report? “We’re well on our way,” Schade reports. “Almost 40 square miles of the lakebed have been controlled. Los Angeles has already spent over a billion dollars on the project and is committed to 5 more square miles. When that’s done, 96% of the control will be finished.”
Before the project began, the GBUAPCD installed test plots to discover which mitigation process would work best-gravel, plants, or water. Because of the costs of its purchase, transportation, and installation, plus the fact that it might also produce dust, gravel seemed like a less-than-optimal choice. Finding the perfect plant species for the job was nearly impossible; there were some drought-tolerant plants that would flourish on the arid site, just as there were some plants that could tolerate Owens Lake’s salt content. But no plants were found to be both salt- and drought-tolerant, and the establishment of any plant materials would take time-and time was of the essence.
It seems somewhat ironic that water was deemed the best choice for Owens Lake’s dust problem; although gravel and plants have been used on 20% of the site, the remaining 80% of the mitigation is accomplished by water. Where does this precious water come from? Los Angeles has “un-diverted” a percentage of its water back to Owens Lake. Fortunately for the city, it is very water-conscious, and because of its conservation efforts, the loss of this water thus far has not been a major strain.
“Water’s the cheapest, but it’s water, which evaporates,” notes Schade. “In this area, the fresh water evaporation rate is about 12 feet per year. Los Angeles has made a “˜forever’ commitment to put precious water on the lakebed. Yes, once you put gravel down, you’re done-but gravel is more expensive. This project has cost $20 million to $30 million per square mile; this fall, we’ll put down 2 square miles of gravel-1,300 acres. That’s over a million tons of gravel.”
The plants that cover 10% of the site were also costly. “Plants are very expensive, plus you need water for them. All plants have been drip irrigated; there are 3 square miles or so out there containing 5,000 miles of drip-irrigation tube.
In essence, when you put plants in this sort of area, you’re running a farm that has no product or crop. Some projects may use flooding water for watering plants-which is easy to operate-but here water evaporates too quickly. Drip irrigation makes the most of the water used. In the project’s next phase, we’ll make water use more efficient, so we’re using the least amount of water.” Water is also bringing wildlife back to the area. “Add water, then you get algae, bugs, and birds-an ecosystem. You can’t dry it all up later and put down gravel.”
Costs are still mounting. “Of course, you take care of the biggest problem areas first, which ends up costing the least, by volume. The last areas to be mitigated are the most expensive parts of it. The last 5 square miles are slated to be finished in 2013. We think there are about 3 more square miles that need controls; Los Angeles is fighting us on those.”
All this money and work are paying off-somewhat. “Dust storms still crop up from time to time, which we post on our website’s “˜dust cam’ link. We’re constantly measuring PM10 levels; levels are down almost 80%, but the levels are still below standard. The USEPA has not fined us yet, because we’re working on it.” What would the EPA do if the problem isn’t totally solved? “If you don’t do the mitigation, your state could lose some of its highway funding. However, because Owens Lake is here, that loss of funding would only have an impact on our area, not the L.A. area,” Schade says.