Microtrenching: The Low Impact Buried Plant Method

When Yates Engineering Services offers consultation on planning and designing Fiber to the Home (FTTH) deployments, one thing we always recommend is that providers explore least-cost construction techniques. Aerial construction is becoming an increasingly time-consuming process, as poles become more and more congested, and the costs of deploying buried plant can quickly add up. Investigating new innovations in buried plant construction can be one of the first steps toward savings, and once such innovation is the use of microtrenching in placing buried fiber optic—a method that can be low impact on both the environment and the pocketbook.

So what is microtrenching? It’s all in the name. Microtrenching involves cutting a small trench (no more than 3/4” wide and 12” deep) into roadsides, sidewalks, and grassy areas. Fiber is then laid into this trench, and then covered up again—if the trench was in a grassy area, the soil is replaced and reseeded if need be, and if it was in asphalt or pavement, the trench cut can be repaired with a cold patch. Microtrenching methods aren’t just limited to direct burial—conduit can be placed in microtrenches, with the fiber blown through; and the vertical inlaid fiber (VIF) method can be employed, in which cables are stacked inside of a vertical conduit that can withstand up to 2000 lbs of pressure per linear inch. [1] The latter two methods also allow slack to be stored, which facilitates easy repairs and the addition of future paths.

There are several reasons to consider using microtrenching. Because it requires such little excavation, it is ideal for congested areas that are largely paved, where ripping up large chunks of the ground would be expensive, time consuming, and logistically difficult. Small crews with light equipment can cover a lot of ground quickly microtrenching, and can do so with minimal impact. The shallow depth means avoiding surprises like tree roots and existing underground utilities. As time, especially in buried plant construction, is money, all of these advantages add up to some serious savings—in some cases microtrenching is half the cost of traditional burial methods [1] and can mitigate some of the high, prohibitive costs associated with last mile fiber deployments.

However, no method is perfect. There are some practical issues to consider when a provider weighs the pros and cons of microtrenching. The shallow depth of the fiber can make it more vulnerable to damage from contractors installing other utilities. If a road or sidewalk is resurfaced, the fiber will have to be removed and then replaced. Finally, the vulnerability to fiber placed in the road to compression from traffic means that high quality conduit is necessary. Balancing these disadvantages against the positives can help you decide if microtrenching is the right method for you, as there is no such thing as one-size-fits-all solutions.

Yates Engineering Services is committed to helping our clients through every step of Fiber to the Home (FTTH) deployment, and FTTH Consultation is just one of the many services we offer. Contact us today to see how we can help you make your goals a reality!

[1] Stahlbrand, Gary. “Leaving No Trace: Time for an overhaul in FTTH Construction.” ISE Magazine (October 17, 2009).