Why are manhole covers in the road, where tires go over them?

It’s expensive to relocate an entire sewer or stormwater system when the world above them shifts.

Anyone else enjoy the feel of driving on smooth roads?

No bumps, no jostling, no vibration; just cruising along what might as well be ice.

Sometimes you’re driving and a manhole cover is in the lane, ruining that otherwise small moment of tranquility.

Reader Dave Hetteen of Kenmore (yeah, it’s King County and technically outside our coverage area, but I’ll allow it) wondered why those bumpy cast iron discs end up in the path of tires.

“It seems to me that designers of streets, sewers, water lines, power lines, fiber optics, etc., make very little effort to place manhole covers in the center of lanes, or on lane divider lines, where nobody has to drive over them,” he wrote in an email. “I realize there are a handful of utilities that are buried below the streets, but it just seems like little effort is made to place manholes where they don’t have to be driven over. Couldn’t they do a better job of that?”

Cities could, but it would cost millions to redo existing utility systems and roads, just to avoid that bump.

Generally, most manhole covers are out of the travel path. But when you drive over one, blame development, growth and time.

Kenmore city engineer John Vicente said often the reason one of those cast iron plates is in the lane is because the road was expanded or moved.

Imagine a road that was built 50 years ago, and at that time, the sewer or stormwater system was installed. Let’s say it was one lane, each direction.

Jump to today, and there are almost certainly more homes that the road serves. More homes means more traffic. Plus, now we want to include space for biking, pedestrians and parking, and probably more lanes for vehicle traffic.

Instead of digging up and relocating all of the pipes and catch basins, they stay put while the road configuration above it morphs.

“It’s a lot cheaper than building a whole new storm system,” Vicente said. “The only time you really see a catch basin in the middle of a lane is because the road didn’t used to be there.”

Another less common reason is if the water flow shifts. That happens over time or because of a sudden shift, like an earthquake.

In Kenmore, the city manages the stormwater system, including about 4,700 manhole covers it owns and another 2,600 it regulates. The sewer system is operated by a separate district.

Generally, cities try to put catch basin access (most people probably call them manhole covers) near the side of the road and along the curb. If that can’t be done because other utility lines are already there, the middle of a lane and out of wheel paths is preferred.

That’s the case for Everett, which has 7,204 sewer manholes and 16,851 catch basins, including drainage manholes.

“As a general rule, we attempt to not locate structure lids in wheel travel paths,” principal engineer Tom Hood said in an email. “However, typically, the only scenario in which this is possible is in construction of an entirely new road. If the entire road section is new, then lane widths can be determined, and all utilities can (usually) be laid out to avoid this situation, as there are no existing conflicts to work around.”

Doing so is complicated for Everett, which has steadily tried to update its aging infrastructure. Most streets and underground utilities have existed for decades and are not easily relocated.

“Any new utility lines installed, whether part of a street improvement project or for some other reason, typically have to be tied in to an existing mainline, which requires a manhole or catch basin to provide the ability to clean the lines. Sometimes existing manholes were originally placed in or behind the sidewalk and end up in a wheel path when the street is widened. Relocating sewer lines for this scenario is often prohibitively expensive.”

Lynnwood has 5,558 storm manholes, catch basins, and inlets, plus another 2,532 sanitary sewer manholes, city engineer David Mach said in an email. For a new road, crews generally would put sewer lines, as the deepest, along the center of the road. Typically the storm system goes along the curb. Waterlines must be 10 feet away from the sewer, and are generally located between the storm and the sewer.

“It is the city’s practice to place structures in the middle of a lane or along a lane stripe, but this isn’t always possible,” he said. “There are many things going on underground which leads to structures being placed in all different places.”

Then there also can be buried gas, telecommunication and power lines.

“With all this subsurface infrastructure, things can get very crowded,” Mach said.

Have a question? Email streetsmarts@heraldnet.com. Please include your first and last name and city of residence.

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