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I live in an older neighborhood. The streets are lined with utility poles and wires strung everywhere. Back several years ago, a major ice storm hit our area and lines started falling all through the neighborhood. Mary and I were standing outside, watching the snow and ice cover our yard. All of a sudden, we heard a boom, a crash, and a whole lot of cussin' going on. It was the neighbor down the street, hollering each time a tree limb smashed down on his pickup truck.

Utility Boxes: What Lies Below

Steve Maurer, IME
I live in an older neighborhood. The streets are lined with utility poles and wires strung everywhere. Back several years ago, a major ice storm hit our area and lines started falling all through the neighborhood.

Mary and I were standing outside, watching the snow and ice cover our yard. All of a sudden, we heard a boom, a crash, and a whole lot of cussin' going on. It was the neighbor down the street, hollering each time a tree limb smashed down on his pickup truck.

We were out of power for a week and a half before the utility company finally had time to repair the damage in our neighborhood.

That was back in 2009 … eleven years ago. A lot has changed since then, not just in our neighborhood, but all across our town.

Most of our wired utilities—electricity, cable, and phone—are moving underground. Even our newly installed fiber optic internet is buried beneath the street level, not strung high overhead.
Utility box covers dot the landscape these days. During my daily morning run … well, jog … I pass by countless covers on my route.

Ah, what lies below. Sounds like a good title for a horror story.

And it can be a horror story if the wrong underground utility box is installed.

They're "baked" with various ingredients, each designed for a specific application.
Three of the "recipes" are:

  • Monolithic polymer concrete (aggregates combined with a polymer resin)
  • Fiberglass-reinforced polymer or FRP
  • High density polyethylene or HDPE
Each type is manufactured for strength and durability, and must meet specific test ratings to ensure compatibility with the applications they're used for.

The ANSI Tier rating system is often used, but the "K" rating system is also applied for application conformity.

The Tier system defines designated use for intended traffic conditions, either non-deliberate or deliberate vehicular traffic.

Where only pedestrian traffic is anticipated (people, bikes … dogs), a Tier 5 rating suffices. You'll find these boxes used in sidewalks and grassy areas like yards.

Tier 8 boxes are designed for sidewalk applications and built with a safety factor for non-deliberate vehicular traffic. Think … student drivers.

Tiers 15 and 22 are designed for driveways, parking lots, and off-road applications where the box may be subjected to occasional non-deliberate heavy vehicle traffic. Think trash truck here.

If you have a utility box set up near a commercial trash bin, you'd better make sure that it will hold up should the newbie driver miss his marks, so to speak.

For deliberate vehicular traffic, there's a whole other set of standards. You'll use the AASHTO H-20 standard that specifies a certified precast concrete, cast iron, or other standard recognized materials to be used in the construction.

If your enclosure placement will definitely have heavy vehicle traffic, this is the only way to go.

Finally, all underground utility boxes are required to pass rigid, three-position testing. Using the ANSI/SCTE 77 2017 standard, the enclosure must stand up to test loading from the sides (a lateral load), from the top edge or vertical wall (downward load) and at the cover, also a downward load.
Yep, what lies below … it's a lot more than what you may realize.
Photo courtesy of Hubbell
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