Know What’s Below: Buried fiber optic cable safety

Jim Hayes
Jim Hayes
Published On
May 14, 2021

When someone mentions safety, of course the first thing you think about is protecting your workers and yourself from harm on the job. While obviously important, I want to address another safety issue: installed fiber optic cable plant safety.

On Jan. 26, 2021, a fiber in Brooklyn, N.Y., was accidentally cut, causing internet outages along the East Coast. Technicians rushed to make repairs and the outage only lasted a few hours, but the damage caused chaos in the area.

Internet, telephone service and CATV network (the most popular broadband connection in the United States) outages can affect a large number of people and are especially serious in these times when people are working or attending school at home.

The “DIRT Report” (damage information reporting tool) is published each year by the Alexandria, Va.-based Common Ground Alliance, also known as the Call Before You Dig people. The latest report for 2019 says that there were more than 500,000 incidents of damage to utilities in 2019, which was an increase of 4.5% from the prior year, with damages costing around $30 billion. Fortunately, only about 8% of those damage incidents involved telecom, data or CATV cable plants. That’s still a lot of incidents.

About half of the reported incidents of damage to underground cables were caused by digging and the other half by directional boring. The DIRT Report only looks at underground cables.

The Fiber Optic Association has been asking them to add aerial cables to their surveys since so many telecom cables are still run on poles, which can be affected by traffic accidents, weather and target practice. Additionally, many cable cuts occur when cables are exposed in manholes, pedestals, buildings, entrance facilities or telecom rooms, or when a tech just makes a dumb move—er, mistake.

What can the designer or installer of cable plants do to reduce the chances of such incidents? The most important thing is to label the cables as fiber optics and mark the location of cables that are underground, aerial or anywhere exposed. Marking can help to ensure people are aware not to disturb these important fiber optic cables. That also holds for premises cables since installers are often asked to remove unused cables to reduce the fire hazards, as required by the National Electrical Code.

When installing underground outside plant cables, guidelines exist for how to bury cables that will help reduce the chance of damage, starting with burying cables at the proper depth. Underground OSP cable ducts or cables are generally buried in trenches about 3 feet (1 meter) deep. About halfway down, a marker tape should be buried that can serve as a warning to those digging on top of the cable and be used for cable location in the future.

Shallower burials are sometimes needed to clear other utilities and in hard rock conditions. Here, one should cover the duct with a concrete slab or poured concrete followed by a marker tape above it. Wherever possible, install above-ground signs indicating the location of an underground fiber optic cable, just like the buried pipelines.

Microtrenching has become popular in cities and rural installations for its fast installation and lower costs. Grooves in the pavement should be 8–12 inches deep and backfilled with the proper materials to ensure cable protection while providing a rugged surface for the road. Markers are difficult with microtrenching, but a conductive marker should be installed above the ducts. Some microtrenching jobs also use colored backfill to indicate the location of the ducts on the roadway.

Whenever you are installing underground duct or cables, it’s critical to know what’s already there to ensure you can avoid them. Start with Call Before You Dig, but remember that not everything is included in their databases. That means your cables may be at risk in the future unless good location data is part of your cable plant documentation and is shared with the proper authorities.

To protect yourself during installation, use magnetic or radar locators to find utilities before digging, even if you think you have good data on the utilities buried there. If trenching, it’s advisable to dig a pilot hole first, in case there is something unknown or hard to locate buried in your path.

Just like personal safety, cable plant safety requires constant attention to details and following the proper procedures.

The DIRT Report can be downloaded at www.cga-dirt.com/annual.

About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor

Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.JimHayes.com.

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