Microtrenching Offers Economical Installation Option

By Jeff Griffin, Senior Editor | December 2012, Vol. 67 No. 12

“A project in an area that would have been priced at $20 -- 25 per foot, now is approximately $15 per foot,” Trawick continued. “Daily productivity -- the number of feet trenched per day -- also has increased.”
As 2012 nears an end, more than 500,000 feet of Q-Trench construction has been completed, Trawick emphasized.

The MT55 trencher used in the Q-Trench system is a 60-horsepower, four-wheel drive model with a trench cutting component developed by the Charles Machine Works specifically for use in the Quanta system. The microtrencher component resembles a large circular saw. The MT55’s saw can be offset to enable trenching near curbs and other obstacles. It is equipped with industrial diamond carbide bits to cleanly cut the trench to the project’s exact width and depth specifications.

A vacuum hose from a vacuum excavator is connected to the trenching attachment and removes spoil as the excavation is made, transferring it to a holding tank where it is contained for later disposal.

When conduits have been placed in the trench, Micro Trench Backfill is mixed with water and fills the trench. After curing, an asphalt sealer is mixed with water and fills the trench. After curing, an asphalt sealer is applied. Both the asphalt sealer and backfill were developed for Quanta Services by SuperGrout Products.

When mixed with water, the grout becomes the consistency of milk and is installed by a two-person crew using a simple mixer and application wand. Trawick said the fluidity of the grout allows it to surround the cable track without jeopardizing the integrity of conduit holding the fiber cable. In less than 12 hours, the grout becomes structurally sound, and sealer can be applied. This eliminates the possibility that fiber networks will become exposed in shallow trenches due to erosion and weathering. The grout will not erode, but it is relatively easy to remove should it become necessary to access the conduits.

After the excavation is filled, a cap is applied to the surface.

Trawick said the core process of Quanta’s exclusive microtrenching process has not changed since its introduction, but improvements have been made.

“The most significant enhancement,” he said, “is the asphalt sealer. Quanta has worked with SuperGrout to create a sealer that has more elasticity, yet is denser than its predecessor, and it stands up to more variant temperature swings.”

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Microtrenching seldom is the only method used to install underground conduit on a project. Directional drilling and conventional trenching still are used in appropriate circumstances.