Trench warfare

You have just finished laying the pipe and you feel the satisfaction of a job that's coming together. However, if you used a conventional trencher, the hard work isn't over yet. You have to backfill. Worse yet, you see rain approaching and you know you will never get the trenches closed before it arrives.

On jobsites where you can mechanically backfill with a blade or bucket without damaging turf, large, open-cut trenches are easy to cover quickly. However, you still have to dedicate labor and machine resources to backfilling. Are there alternatives that are more labor-efficient and less destructive to landscapes? Fortunately, yes.

Many irrigation contractors have vibratory plows, mini-trenchers and mini-loaders in their equipment arsenal. These machines can be less destructive, more portable or, with the use of different attachments, more versatile than conventional trenchers. They also minimize backbreaking labor which, arguably, may be one of the most important advantages in today's labor-shy work environment.

Shake, rattle and roll

One alternative to trenching is so-called “trenchless” technology, such as vibratory plowing. Jon Kuyers, rubber tire product manager for Vermeer, says that vibratory plows originated in the mid-1960s as an alternative for installing cable. The method was both quicker and more efficient than open-cut trenching. By the late 1960s, irrigation contractors discovered them, and a new era in irrigation began.

Vibratory plows typically have four wheels with articulated steering (a pivot point between the front and rear tires). Most irrigation-type models are pedestrian operated (walk-along), which helps minimize size. Most are less than 36 inches wide. Thus, they can easily fit through gates and other narrow openings. Ride-on models are available, too. However, their larger size restricts their use at sites where accessibility is limited and maneuverability is at a premium.

Smaller walk-behind units also are available. These smaller machines are compact and usually weigh less than 1,000 pounds. They are more maneuverable than larger units and suitable for shallow wiring and smaller lines, such as irrigation laterals and drip lines.

To install pipe with these machines, attach the irrigation pipe behind the plow blade, located on one end of the machine. As you proceed forward with the machine, you can lower the plow blade into the ground as deep as 2 feet. A hydraulic motor spins a set of weights that causes the blade to vibrate in an up-and-down motion. The vibration helps loosen the soil, and the pipe is pulled through the narrow channel that the blade creates.

“The main advantage of vibratory plows is that they produce less soil disturbance by not displacing the soil. Therefore, there is less restoration,” says Richard Greenwell, compact trencher product manager for Ditch Witch. Less restoration means that you do not have to commit costly resources to backfilling. This saves time and relieves your employees of backbreaking handwork.

Because vibratory plows do not excavate the soil, they are less destructive than standard trenchers on established turf. The existing sod heals quickly and, after a few days, there is no evidence that you were even there. You do not need to reseed, nor do you have to return to the site to topdress the trenches after they settle.

Vibratory plows avoid other problems associated with exposed trenches, as well. A few years back, I was installing irrigation lines on a commercial property. I had excavated the trenches and installed the lines when an unexpected thunderstorm arrived before I could backfill the trenches. The rain poured into the trenches, floated the pipe and deposited backfill beneath the piping. Following the storm, the pipe was too shallow for the specifications and we had to re-dig the trench. In this case, a vibratory plow would have saved much time and effort.

A boring topic

You can also purchase a boring attachment for some vibratory plows or buy a stand-alone borer. Boring capabilities dramatically enhance machine utility and allow you to install pipe in “congested areas, under sidewalks and patios and around natural obstacles,” says Kuyers. Because most irrigation layouts involve these obstacles to one degree or another, having this capability can increase your efficiency. Also, these obstacles no longer limit your irrigation designs; therefore, you gain design flexibility as well.

There is a price to pay for the versatility and efficiency that these machines afford. Vermeer and Ditch Witch machines are priced in the $7,000 to $30,000 range, depending on the options. “A contractor must first look at the amount and scope of work to be done. If the machine will not have appropriate utilization, then rental may be an option,” says Kuyers.

If you perform only a few installations a month, buying these machines is a decision that may not pay off. However, if you have so much irrigation work that you can't keep up, these machines can give you the flexibility and efficiency that you dream of. “It depends on how much work a contractor does. Vibratory plowing is very economical if the soil conditions are conducive for plowing,” says Greenwell.

Sometimes smaller is better

Although standard trenchers are ideal for installing larger-diameter pipe and digging deep trenches, they can be overkill for irrigation and cable installations where a smaller trench is all that's needed.

Cable, water- and gas-line installation contractors have used disc trenchers for years to cut through rock and other subsurface debris that chain and boom trenchers and vibratory plows cannot penetrate. The same idea has been scaled-down for use in irrigation and shallow wire installations. These mini-trenchers, or disc trenchers, are the most compact, lightweight trenchers on the market.

They use a high-speed, motor-driven, carbide-toothed disc to dig trenches from 0.5 to 4.0 inches wide. An operator can quickly adjust the digging depth to cut as deep as 13 inches. Machine weight varies from 85 pounds for the smallest units up to 430 pounds for the largest saws. Thus, you can easily load, unload and transport them in the back of a pickup.

Many models are available. Some can lay cable, wire or irrigation tubing as you trench, and some also backfill. By changing attachments, you even can use some models to edge landscape plantings and sidewalks.

What makes these units ideal is that they are lightweight, portable and prohibit you from over-excavating the trench. Scott Porter, with E-Z Trench, states that these units are ideal for residential irrigation because they dig a shallow, narrow trench that minimizes backfilling and scarring. They fit easily into tight areas, through gates, next to houses and are easy for one person to operate. “We like to call them portable, walk-behind trenchers or mini-trenchers,” says Porter.

Mike Hale, sales and marketing manager for Little Beaver, producer of Kwik-Trench trenchers, says, “They operate on the same principle as a Skil-Saw. They are great for first-time users because the units have no hydraulics and few levers and switches to operate, and the depth can be easily adjusted while you trench.” Hale adds that you can cut 1-inch-wide trenches and, therefore, nearly eliminate backfilling. Because the trench is so narrow, you do not notice the dip in the soil that is caused by settling.

While these units are not intended for deep trenching, their price, weight and mobility make them ideal for most residential irrigation jobs. “Most of the contractors who use our units also own conventional trenchers for installing the deeper main lines. They use our units to install the smaller laterals where depth and width are not critical,” says Hale.

These units will not cut through rock, but they will trench in rocky soils. They are belt-driven, not chain-driven, so if you hit a large rock or other objects, the belt will slip and the machine will not be damaged.

You can also use mini-trenchers and vibratory plows to install electronic dog fencing, other shallow wiring and propane lines. As contractors know, these revenue streams can be significant and useful, especially during the off-season when irrigation demand declines.

Don't forget loaders

Compact utility loaders have taken the landscaping market by storm in recent years. (See “Equipment for small spaces,” in the November 2000 issue of Grounds Maintenance.) Their size, combined with the versatility of different attachments, makes them a great choice for irrigation contractors who also perform landscape installations, and vice versa.

A big advantage of these machines is that they can be fitted with multiple attachments. They are ideal for contractors who do a variety of tasks from trenching to planting. While most loader units use the conventional chain-and-boom trenching system, some have vibratory plow, boring and earth-sawing capabilities. These machines come in a wide variety of sizes and options including stand-ons, walk-behinds or ride-ons.

Another advantage of these machines is their size. Several of the units available on the market have widths as narrow as 36 to 40 inches. Therefore, they are maneuverable in small areas, and you can make sharp turns with less turf damage. They can fit through most gates and into tight spots, thus making them ideal in residential landscapes that are crowded with obstacles. This eliminates trenching that might otherwise require hand labor.

Although weight varies with the size of the machine, you can control their impact on turf through several options. Rubber or Kevlar tracks exert the least amount of pressure, as low as 2.5 psi. However, some wheeled units can be fitted with large flotation tires that exert pressures as low as 7 psi. For reference, your feet exert 6 to 8 psi when you're standing on turf.

The type of steering also affects the impact that equipment has on turf. Articulated steering causes less tearing and ripping. The tradeoff, however, is that articulated units cannot be fitted with tracks. Thus, you increase the pressure exerted on the turf surface.

Standard skid-steer loaders accept multiple attachments as well. Though not always designed for a light “footprint,” skid steers obviously pose no problem for unbuilt sites with open ground. Plus, several models accept tracks that reduce the impact on the landscape. Don't forget to explore the variety of attachments that may be available for a skid steer you already own.

Know your needs

As with all equipment, the right trenching unit for you is one that you can economically justify and that gets the job done quickly. The performance of all trenching units depends on soil type and the amount of debris encountered. Heavy, clay soils or soils littered with rock or construction debris will require more horsepower and larger machines to quickly lay pipe.

Before making an equipment-purchasing decision, evaluate these limitations. Also, look at the terrain, common obstacles, local ordinances and the “typical” jobsite that you encounter. Call dealers and ask for an equipment demonstration on a jobsite where you are working. It will give you an opportunity to test equipment under real-world circumstances.

Irrigation contractors will always have a use for conventional chain-and-boom trenchers. However, other types of equipment may be more efficient and better-suited for irrigation installations in many circumstances. This is especially true in established turf where less-invasive methods deliver a speedy installation with less backfilling and fewer callbacks to repair damaged turf.

James Houx is a freelance writer and former landscape contractor based in centerview, Mo.

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