Faster, cheaper fiber microtrenching gains acceptance

by Steve Blum • , , , ,


Verizon’s microduct ready to be installed near Sea Ranch in Sonoma County.

In what could lead to the first large scale urban use of fiber microtrenching in the U.S., Verizon and the City of New York have agreed to test it at 12 sites. Verizon has used microtrenching for other fiber projects, including one last year in a rural part of California.

You can see a video of the process here. It involves sawing a narrow trench – 2 cm wide and up to 30 cm deep – into the roadway, inserting thin, flat microduct, and then sealing it back up. Because it’s relatively shallow, there’s less chance of hitting existing underground utilities. It’s a fast process too, reducing, and sometimes eliminating, street closure times.

The New York project has an open access element to it. Depending on the width used, the skinny microduct can handle several fiber cables. The city has said other network providers can participate in the pilot project.


California State Route 1 ready to be repaved. The Coke can is for scale and was not harmed in the making of this picture.

Verizon already has at least one microtrenching pilot project going in California. In 2010, Caltrans approved microtrenching along ten miles of State Route 1 in Sonoma County and, as U.C. Santa Cruz network engineer Jim Warner discovered while on vacation, construction was underway last summer. He dug out the permit, which details the specs Verizon needed to meet, including cutting to a minimum depth of 10 cm and patching the slice in the road.

If there are no complications, microtrenching can cut the cost of fiber installation by as much as two-thirds. Maintenance costs could be a little higher, because the shallower depth exposes a cable to more damage, for example during street repaving. And cutting into the surface could have more impact on road durability than drilling underneath it. Overall, it’s a lower impact process though, so assuming quality specs can be met it should be easier to get agency approval and start work.