Hamilton Kent Blog

Winter woes for aging infrastructure

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Polar vortices, snowstorms and El Ninos—the past few years haven’t been easy on people weather-wise, but how has our infrastructure been keeping up with cyclical changes? We’ve outlined three major problems facing our infrastructure as a direct result of snow, salt, and cold temperatures.

Why are our manholes exploding?

During the week following winter storm Jonas from January 22 to 24, the Fire Department of New York (FDNY) responded to more than 400 manhole fires across the city. This wasn’t a new phenomenon; during January and February 2014, the FDNY responded to 3200 manhole fires.

So why doesn’t this happen in every city after a big snowstorm?

Some cities across the United States run their power lines underground, as a way to avoid power outages due to ice storms, high winds and other natural disasters. The grids for these lines in cities, such as New York City or Los Angeles, run underneath our roadways. These are accessible through manhole covers into underground utility vaults.

Power companies speculate that the most likely cause of the fires is a combination of old, frayed wires, water, and road salt.

The corrosive, salty water gets in through the manhole covers and erodes the rubber, lead, or paper insulation on the wires. The wires are conducting about 13,000 volts of electricity and cause sparks.

The insulation, in turn, catches fire or melts, releases dangerous, noxious gases that cause built up pressure underneath the manhole covers.

What can happen in this type of high-pressure situation is the high-voltage wires can ignite the built-up gasses, causing an explosion. The manhole cover could flip over, or launch up to at least 50 feet in the air—as it did in this video. Although it’s rare for an actual explosion of this caliber to happen, manhole fires are much more common.

This puts everyone on the street at risk of injury. A heavy, cast-iron manhole hit a man in 2015—and he survived.

Power companies do continued maintenance on these wires, to make sure they aren’t fraying. They’re also replacing solid manhole covers with grates as a means of releasing the pressure from built up gasses.

This won’t however, prevent manhole fires from happening. This is where a watertight system would help to prevent conductive and corrosive salty water from entering into the system in the first place.

Freeze and thaw wear and tear

A manhole affected by a freeze-thaw cycle is one that could end up sinking into the ground. This can lead to an uneven dip in the road or infiltration-related concrete failures.

Water gets into the porous concrete, freezes as the temperature drops, and causes the concrete or asphalt—which doesn’t have enough elasticity—to crack. This can also cause existing cracks to widen. More water leaks in, leading to significant pavement damage. This can be happening as often as daily, with temperatures rising and falling with the sun throughout the winter season.

If too many cracks occur, water can eventually get into the ground below and cause erosion of the underlying soil through leaks into the manhole structure. This in turn allows the road surface to sink, creating potholes and further likelihood of damage to the manhole.

A properly sealed manhole structure, connections and frame can at least prevent the infiltration of surface water and soil into the sewer structure, and avoid the additional road surface damage. Additionally, a rubber manhole frame will absorb much of the shock and vibration created by roadway traffic, protecting the surrounding road surface from additional cracking and the underlying manhole structure from structural damage.

Stormwater overflow after a big snowstorm

Winter storm Jonas didn’t just increase the number of manhole explosions across the east coast of the United States this winter. With massive amounts of melting snow—as was the case following this snow storm—the runoff needs somewhere to go. Our stormwater and sanitary systems aren’t always prepared for it.

This type of thaw can cause overcapacity problems on sanitary sewers that are not watertight. As the melting snow and ice runs into leaky manhole covers, the surface water inflow can cause sewer overflows and surcharge of sanitary water into roadways and waterways, and in some cases, major flooding.We’ve spoken before about how properly maintained stormwater sewers should be built to handle the proper climate of an area, and this is no exception.

Stay safe this winter and spring as El Nino continues to hand us surprises in our weather. Ask your local government representatives and sanitary collection system departments to research the right infrastructure solutions for your city, town or region. Hamilton Kent is happy to be a resource to any agency or firm.

Photo: Dan Kitwood/Getty Images