In the ten years since the business was started, Corbett, Inc., has established a reputation as one of the best residential and commercial irrigation contractors in Massachusetts.

Based in Concord, Massachusetts, Corbett's team of irrigation contracting and engineering specialists has installed more than 1,000 underground irrigation systems and services for more than 750 clients throughout the eastern part of the state.

With a background in commercial and residential construction, excavation, and landscaping, Corbett President Brian Perwak, CIC, CGIA, recognized a need for quality irrigation services in an area where soil conditions are not conducive to placing pipe in the ground, and he made the decision to establish a new irrigation company from the ground up, so to speak.

Perwak perceives lack of experience as a plus that has contributed to Corbett's success.

"Many who start new businesses bring experience that isn't necessarily positive," said Perwak. "By starting fresh, we built our own policies and developed procedures without incorporating 'wrong' ways of doing things learned in other organizations."

Corbett limits its services strictly to designing, constructing, and maintaining irrigation systems, and does not accept general landscaping work. About 60 percent of its business is for commercial projects for which the company usually is a subcontractor. Residential work usually is directly for property owners.

Commercial projects include office parks and building grounds, athletic fields, and equestrian grounds. Notable projects include rainwater-collection systems and installation of drip systems with soil moisture-sensing capabilities that irrigate based on soil moisture levels. Such systems assist colleges and institutions in qualifying for "green" designations.

"Some are design/build projects, but we also implement the designs of others," Perwak said. "Clients include major construction companies as general contractors, as well as landscape architects. We have found that one of the major challenges for a commercial project is the integration and coordination of the subcontracted specialties. It is our goal to understand the scope of the project and how the irrigation activities fit in, in terms of both schedule and function."

Residential jobs usually begin with meetings with homeowners to understand their expectations of a new irrigation system and an evaluation of the site—including locations of underground utilities already in place, and rocks, tree stumps, and any other underground obstacles that could interfere with installing the system.

A system that meets the customer's specification is then designed and a written proposal presented. Once approved, a Corbett field crew installs the system, which typically includes installing pipe and control wiring, sprinkler heads, and the control computer, and often incorporates wireless rain sensors and multiple zone controllers. One-inch-diameter HDPE pipe is used for residential systems, and PVC pipe in diameters up to six inches for commercial projects.

Once the system is complete and tested, Corbett provides documentation, instructs the owner in its operation and provides operational manuals. For both commercial and residential projects, Corbett usually is called on to maintain systems after they are in place.
Corbett makes every effort to limit excavation and surface damage during installation of underground pipe and wiring. Perwak said that, whenever possible, vibratory plowing equipment is used.

"This method can install pipe and cable without digging a trench and filling it in after pipe is in the ground," he said. "Pipe is attached to the machine's plow blade, and the vibrating action of the machine's shaker box allows the blade to be pulled through the ground, pulling in pipe behind it."

Depending on soil conditions, the narrow slit in the ground left by the plow blade often can be quickly restored by driving the tires of the machine over it.

However, some soils are not conducive to plowing and must be trenched.

The most common type of trenchers used for irrigation work are compact models with digging chains equipped with teeth that excavate a narrow trench that can quickly be filled in and compacted.

Perwak believes it is important to use the right specialized equipment that meets the specific needs of installing underground irrigation systems.

For the past several years, Corbett's basic equipment for installing irrigation pipe includes compact, four-wheel drive machines with a vibratory plow on one end and a chain trencher on the other. These machines are small enough to work in small areas, and rubber tires can move over both lawns and uneven terrain, as well as paving.

"Our preference always is to plow," said Perwak. "The vibrating action of the plow blade can move some rocks, but in our area we often do encounter difficult conditions which must be excavated. Having a plow on one end and trencher on the other gives us the capability of having the machine we need, no matter what the conditions."

Corbett uses Ditch Witch® 255sx and 350sx compact vibratory plow/trenchers. The operator walks beside both models during plowing or trenching. The smaller 255sx is powered by a 25-horsepower engine; the larger 350sx model has a 35-horsepower engine. Both have rigid, one-piece frames. The 350sx is equipped with front and rear steer that increases maneuverability.

Recently there has been a trend in the compact industry market for multipurpose equipment that can accommodate scores of specialized attachments, allowing one machine—skid-steer or excavator—to perform many tasks. Perwak said he has never believed such multitasking machines fit his company's needs.

"Because the irrigation trade requires specialized pipe pullers and equipment, I have never been optimistic about multitask machines," he said.

When approached about the new Ditch Witch line of Zahn® equipment, Perwak was not expecting much.

"We need a pipe puller that pulls pipe well, not a machine that performs a multitude of tasks marginally," he said. Perwak agreed to try the R300, the largest model in the Zahn line, but did not expect to find it appropriate to Corbett's needs.

However, he was pleasantly surprised.

"When we tested the Zahn R300, we were all impressed with its superior ability to pull pipe," said Perwak. "This machine pulls pipe better than any machine we have ever used. Not only that, but its trenching capability far surpassed our expectations."

The four-wheel-drive Zahn R300 is powered by a 30-horsepower engine. The operator stands on a platform at the rear of the machine. An articulation joint enables the front-end attachment to perform like a dedicated unit with an InterChange connection that accepts seven front-end components: two types of trenchers, a vibratory plow, bucket, tiller, backhoe, stump grinder, and a tool carrier that can drive a variety of attachments. Perwak said the machine's articulated frame adds to its maneuverability, and during plowing this feature can assist the operator in displacing small rocks from the path of the plow blade.

"We primarily bought the machine for a plow," said Perwak. "But we find the trencher is more productive than our other equipment, and the grading bucket has been a big surprise; we are using it more than expected for backfilling and restoration.

"The Zahn R300 has enabled us to reduce our equipment dependency from three specialized pieces to one amazingly effective and versatile piece."

Weather in New England makes year-round irrigation system construction impossible when the ground is frozen.

To make the most efficient use of good weather, new construction is performed from mid-March through mid-December, with maintenance of customers' systems in April/May and October/November.

In addition to Perwak, the company's key personnel include Mike Greenfield, CIC, CLIA, manager of operations; Frank Degan, project supervisor; and Dina Gentile, manager of office and administrative operations. The number of employees varies with the season and workloads. Corbett is a Certified Irrigation Contractor of the Irrigation Association and a Certified Golf Irrigation Auditor.