Keeping traffic on the move and invasive weeds out of roadside areas is a full-time job in a bustling city like Atlanta. The region’s long growing season, high humidity and subtropical climate create perfect conditions for weeds to pop up wherever they want, threaten pavement integrity and change the look of the landscape.
Maintaining both form and function for the road systems in this city of nearly 5 million is no easy task, but the Georgia Department of Transportation (GDOT) is up to the challenge.
Ray Dorsey is the northern agronomist manager for GDOT and is responsible for managing vegetation on hillsides and ditch banks, along rights-of-way and everything in between. GDOT even monitors cracks and crevices in the pavement to protect it from weed invasions that could cause major problems. To meet the department’s complex vegetation goals, Dorsey and his team developed a plan that integrates mechanical and chemical vegetation management to reduce labor costs and get long-term control. The result is roadsides that are clean and green, created on a budget.
A complex backdrop
Over the past few years, GDOT has watched funding for road maintenance and right-of-way beautification dwindle to half its predownturn level, so the crew has had to get creative to do more with less. Dorsey and the team at GDOT have developed a program to fight weeds and protect the landscape, all while staying within the confines of its shrinking budget.
Along with budget limitations, federal Clean Air Act mandates for reducing air pollution have put increased pressure on GDOT to maintain existing roads, rather than expand lanes and potentially exacerbate air-quality problems. The existing infrastructure has to be maintained without making travelers feel as though they are crammed into a dingy, outdated system that is only marginally functional.
While good right-of-way maintenance may not reduce the number of vehicle-miles traveled in the Atlanta area, it can prevent additional construction delays for traffic, reducing the time motorists spend to get across town and the impression they have of road quality. It also can be a big budget saver for the agency.
Let the good ones grow
Like other Southern cities, Atlanta has a variety of tough-to-control weeds that invade roadside right-of-way areas. Kudzu creeps over walls and barriers, absorbing vegetation and structures like guardrails, walls and barriers. In guardrail areas, foxtail juts out around stakes and metal structures, completely obscuring these important safety devices. Tall grasses like johnsongrass can grow out of control, requiring multiple mowings each season to keep them manageable. Weeds even creep through cracks in the pavement, pushing their way through and creating major maintenance headaches.
Even beneficial vegetation can go astray. Bermudagrass is a perennial, warm-season grass that blankets more than 18,000 miles of primary and secondary highway roadsides throughout the state. It permits drainage to keep roadways clear of puddles and stays green throughout most of the spring and summer.
But with the moisture-rich, long growing season of Atlanta, bermudagrass can overgrow and clog roadside areas, preventing water runoff and inhibiting driver sight lines if left uncontrolled. To manage the plant’s potential negative aspects, Dorsey implemented a bermudagrass seedhead suppression program.
While mowing has traditionally been the quick and easy answer to limiting the plant’s growth, it requires a great deal of labor and creates safety and environmental hazards from flying debris, mower air emissions and the spreading of seeds of invasive plants as mowers move down the roadsides. Unmowed rights-of-way look more like a wilderness than well-groomed shoulders, so keeping the grasses low for the longest period possible between mowings greatly improves aesthetics. And with fuel costs soaring as budgets shrink, Dorsey realized it was time for a change.
“Mowing alone doesn’t cut it anymore. We now mow only one time each year and have expanded our herbicide program to help with seedhead suppression to control the growth of the plants we want to keep,” Dorsey said. “In some cases, we’re battling an overgrowth of desirables or unwanted vegetation in high-traffic areas and in other instances we’re knocking back the invasives so that native grasses can survive.”
In springtime, around the time of a normal first mowing cycle, GDOT treats the roadsides with 4 oz./acre of Plateau herbicide. The crew broadcast applies the herbicide from 1,000-gal tank spray trucks, which cover a lot of ground and protect the workers from highway accidents and flying debris. Todd Horton, market development specialist for BASF, helped Dorsey develop the integrated management plan.
“[The herbicide] allows GDOT to suppress bahiagrass seedheads without totally eliminating the plant, so the right-of-ways still look green and neat,” Horton said. “Using this herbicide can provide growth suppression for up to 120 days and can eliminate a second mowing cycle.”
By adding herbicide treatments to the mowing program, GDOT has been able to reduce costs and reduce the impact on the environment. After the spring herbicide application, mowing is not required on roadsides until August, which will provide adequate control through the rest of the growing season. By implementing the integrated program, GDOT was able to reduce the cost of mowing from $15 million to $6.7 million for FY 2010 and is well on its way to maintaining a 50% mowing budget reduction.
One of the major changes Atlanta has made to its roadway system is the addition of concrete barriers along major highways. Because of ever-increasing traffic due to explosive population growth, GDOT has converted former ditch space into new lanes on high-traffic roads. Atlanta is concentrated with shoulders, barrier walls, landscaped areas, general populations and traffic, and GDOT is doing everything it can to combat weeds that creep into these concrete structures.
Dorsey and his crew know that even one blade of grass growing in a barrier or road area can point to problems underneath the surface. These seemingly minor invaders have the strength to pry open crevices and expand cracks, opening the way for other erosive forces, degrading pavement integrity and increasing maintenance costs.
“If grasses and weeds get a foothold in the cracks and crevices along the pavement, we can count on a major expense and a major inconvenience for drivers,” Dorsey said. “Weeds can crack the pavement and then we have to spend money on repairs—either resurfacing with asphalt or fixing with concrete, which is both a hassle and an eyesore.”
Not only do weeds like to sprout through pavement and create unwanted cracks, tall grasses like foxtail creep up the guardrails, creating a wild tangle of vegetation that can obscure both their form and function.
“We’ve successfully knocked back the foxtail using [the herbicide], spraying anywhere from pavement edge out 30 ft,” Dorsey said. “Keeping that plant down keeps the sight lines clear and the guardrails looking great.”
Some weeds are tough to control with herbicides. Kudzu tends to resist any herbicide program out there.
“Getting our arms around kudzu control is really a challenge,” Dorsey said. “You can’t control the whole vine, and most vines come right off the right-of-way and the patches grow really big. In some cases, the vine can grow 18 in. a day.”
To combat the weed before it swallows up more terrain each day, Dorsey uses Transline herbicide. While the program can’t provide eradication, GDOT continues to fight back against kudzu, commonly called “the weed that ate the South.”
Investment pays off
2010 promises to bring new challenges for GDOT, with a zero-growth budget and new weed threats on the horizon. Georgia has faced an unprecedented drought in the past few years, and with the recent wet weather, Dorsey expects to see an unprecedented resprout of weeds that may have been dormant for several seasons.
“Timing our applications will be critical,” Dorsey said. “We need to get out there early to knock down the problem weeds and keep the program on track.”
But, the team is prepared—they are providing more training for application crews and collaborating with vegetation experts at area universities and companies like BASF to improve the program. Because of the work so far, the GDOT vegetation management program is a finalist for a 2010 Quality Vegetation Management (QVM) Project Habitat Award, a program that recognizes dedication to environmental stewardship and responsible and efficient use of herbicides.
“I continue to be impressed with all the work GDOT has done to build a great integrated program,” Horton said. “The GDOT team’s dedication to quality vegetation management is evident every time I drive the state roads in Georgia, and I know we can expect great things for the future.”