The Proliferation of Microtrenching

There is an interesting new trend in fiber construction. Some relatively large cities are getting fiber networks using microtrenching. Just in the last week, I’ve seen announcements of plans to use microtrenching in cities like Mesa, Arizona, and Sarasota Springs, New York. In the past the technology was used for new fiber networks in Austin, Texas, San Antonia, Texas, and Charlotte, North Carolina.  I’ve seen recent proposals made to numerous cities to use microtrenching to build new fiber networks.

Microtrenching works by cutting a narrow cut an inch or two wide and up to a foot deep for the placement of fiber cables. The trench is then sealed with a special epoxy that is supposed to bind the hole to be as strong as before the cut.

Microtrenching got a bad name a few years back when Google Fiber walked away from a botched microtrenched network in Louisville, Kentucky. The microtrenching method used allowed water to seep into the narrow trenches, and the freezing and thawing during the winter caused the plugs and the fibers to heave from the small trenches. The vendors supporting the technology say they have solved the problems that surfaced in the Louisville debacle.

There is no doubt that microtrenching is faster than the more traditional method of boring and placing underground conduit. A recent article cited Ting as saying that a crew can microtrench 3,000 feet of fiber per day compared to 500 feet with traditional boring. Since a big part of the cost of building a network is labor, that can save a lot of money for fiber construction.

I’ve worked with cities that have major concerns about microtrenching. A microtrench cut is generally made in the street just a few inches from the curb. Cities worry since they have to routinely cut the streets in this same area to repair water leaks or to react to gas main leaks. In many cases, such repair cuts are made hurriedly, but even if they aren’t, it’s nearly impossible to dig down a few feet with a backhoe and not cut shallow fiber. This means a fiber outage every time a city or a utility makes such a cut in the street, with the outage likely lasting from a few days to a few weeks.

The bigger concern for cities is the durability of the microtrenched cuts. Even if the technology has improved, will the epoxy plug stay strong and intact for decades to come? Every city engineer gets nervous seeing anybody with plans to make cuts in fairly pristine city streets.

City engineers also get nervous when new infrastructure is placed at a depth they don’t consider as ideal. Most cities require that a fiber network be placed three feet or deeper below other utilities like water and gas. They understand how many cuts are made in streets every year, and they can foresee a lot of problems coming with a fiber network that gets regularly cut. City engineers do not want to be the ones constantly blamed for fiber outages.

There are new techniques that might make microtrenching less worrisome. In Sarasota Springs, New York, SiFi is microtrenching in the greenways – the space between the curb and the sidewalks. The company says it has a new technique to be able to feed fiber under and around tree roots without harming them, thus minimizing damage to tree while avoiding using the city streets. This construction method doesn’t sound as fast as microtrenching at full speed down a street, but it seems like a technique that would eliminate most of the worries of the civil engineers – assuming it really doesn’t kill all the trees.

It probably will take some years to find out in a given city if microtrenching was a good solution. The willingness to take a chance demonstrates how badly cities want fiber everywhere – after all, civil engineers are not known as risk takers. I have to imagine that in many cases that the decision to allow microtrenching is being approved by somebody other than the engineers.

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