The steep slopes of New York City’s aqueducts

If you’re a golf course superintendent or a college campus groundskeeper and you frequently lament the sheer size of the area you must mow, don’t be so quick to complain. In New York City, there’s a group that has you beat. They have to keep up with mowing on 250 miles of aqueducts, along with a collection of reservoir dams. Not only is the job spread out a massive distance—New York City’s drinking water flows in a series of aqueducts from as far away as the Catskills—but almost all of the mowing takes place on severely steep slopes.

AEBI Terratracs can be used to mow manicured turf, as well as dense vegetation.

“There are three major systems that provide water to New York City,” says John Vickers, acting chief for the western operations division of the NYC Bureau of Water Supply. “There’s the Croton System, which is the oldest and it’s on the eastern side of the Hudson River; and then there’s the Catskill System and the Delaware System, which originate on the western side of the Hudson River.”

Vickers and a staff of about 90 “watershed maintainers” are responsible for the latter two systems, including the facilities. “Those two systems provide about 90 percent of the city’s drinking water,” he says. Amazingly, 95 percent of New York City’s drinking water reaches consumers via gravity—just 5 percent needs to be pumped to maintain pressure. Water in the Delaware System is delivered via pressure tunnel. On the Catskill System, which is older, a variety of cut-and-cover—essentially a man-made river that is then covered—as well as pressure tunnel and other means are used.

The watershed maintainers handle a variety of tasks, but one of the most important is mowing. “We mow the dams that impound the reservoirs, and we mow the aqueducts,” Vickers explains. “The mowing is critical, because we don’t want to have tree growth on those structures—the roots could damage the earthen embankments. Mowing also provides us visibility in case there are problems that need to be addressed.”

The Catskill aqueduct alone, for example, includes a 30-mile stretch of cut-and-cover, grassed area to maintain. “We mow that just once a season. The crews essentially start at one end in the spring, and by the time November comes around, they’re at the other end,” Vickers says. In addition to mowing, there are culverts to inspect and unplug, animal burrows to fill in and other maintenance duties to perform.

The Terratrac’s were outfitted with front-mounted Alamo SH88 flail mowers, just one of the many attachments that can be added. Mowing is generally done with teams mowing in the same direction.

“The dams are typically mowed several times each summer,” says Vickers. The goal isn’t perfection. “The grass that we’re mowing has nothing in common with a golf course,” jokes Vickers. “Here, everything is rough.”

Still, there are some similarities between the maintenance done on dams and aqueducts and more highly manicured landscapes. “We seed areas using native grasses when we can,” says Vickers. “We’re always trying to keep things covered.” If a construction project disturbs an area, crews work quickly to reseed the bare area and get the grass growing. “Seeding, mulching and other erosion control measures are very important on the slopes,” he explains.

Given the severe nature of the sites, special equipment is required to handle the mowing and other maintenance. “Probably 70 percent of the area we mow is steep; the embankments and the aqueducts themselves feature a lot of slope,” says Vickers. With those challenges in mind, New York City recently purchased a fleet of six AEBI Terratrac TT270 tractors. Each of these units was equipped with front-mounted Alamo SH88 flail mowers.

“They are the largest tractors we sell at this time,” says Doug Beach, with AEBI New England (, who helped New York City select and outfit the Terratracs. “The safety of the operator was paramount to the city, but the other thing they were buying was productivity,” says Beach. “With a job that size, they needed something that could do the job better, quicker, cheaper and safer.”

AEBI, a century-old company, is based in Burgdorf, Switzerland. The AEBI TT270 tractors (AEBI calls them “implement carriers”) selected by New York City have four-wheel drive, four-wheel steering, hydrostatic transmissions and 95 hp turbo-diesel engines, as well as dust-proof cabs with air conditioning. High-volume, low-pressure tires minimize compaction while adding stability.

The stability and low ground pressure of the Terratracs have proven to be up to the challenge of mowing the dams and aqueducts, says Vickers. “We’re very happy with them,” he states. “We have six units now, and we’re looking to purchase three more. We had other mowers in the past that did a pretty good job, but we noticed we were starting to get some ruts on the dams and aqueducts. The AEBI’s have helped us to smooth those areas out and prevent rutting. You can attach additional wheels to both the front and rear axles that provide greater flotation for the tractor.”

Representatives of AEBI came over from Switzerland to assist in training New York City employees who would be operating the Terratracs on the dams and aqueducts.

The additional wheels also help increase stability, which Vickers says increases productivity. “We find that we’re becoming more efficient—we’re able to go faster and we’re now getting done with aqueduct mowing about three weeks earlier than we were before.”

With miles of dams and aqueducts to mow and maintain, New York City purchased six AEBI Terratrac TT270 tractors. To increase stability and prevent rutting, additional wheels can be attached to the four-wheel drive, four-wheel steer units.

AEBI’s Terratrac are specifically designed to offer a wide stance with a low center of gravity, but they retain the functionality of a more traditional tractor, says Beach. “There are a lot of different attachments available for the TT270,” he says. “You can put on snowblowers, plows, forklifts, brooms, front-end loaders, deep-tine aerifiers, rototillers. They’re pretty much tractors with a Category 1 and 2 on the back, and a Category 1 on the front. So, as long as you have those kinds of attachments, they’ll hook right on, as long as the weight and horsepower requirements are matched to the tractor.”

In fact, New York City is considering doing just that. “We’re looking to purchase a front-loader attachment that we could use to fill in animal burrows, as well as a snowblower attachment to help clear snow around the facilities and roads at the crests of the aqueduct,” says Vickers. “That would let us take advantage of the machines in the winter as well.”

While aqueducts represent a rather unusual application, Terratracs are frequently used to mow dams, ski trails, landfills, golf courses and any other type of property with steep slopes. For those who don’t have a large enough area or frequent enough mowing demand to warrant purchasing a specialized slope mower, AEBI New England offers contract mowing services using its Terratracs, says Beach.

However, if you’ve got a couple hundred miles of slopes to mow, it makes sense to consider buying a whole fleet.

Patrick White is a freelance writer and editor and frequent contributor to Turf.