Where the rubber seal meets the road

Monday

Aug 26, 2013 at 12:01 AMAug 26, 2013 at 2:20 AM

I've noticed the city seems to be replacing a lot of manhole covers recently around the city. The weird thing is they seem to be made of some kind of rubber material. Is that going to hold up? What was wrong with the manhole covers we had before?

I've noticed the city seems to be replacing a lot of manhole covers recently around the city. The weird thing is they seem to be made of some kind of rubber material. Is that going to hold up? What was wrong with the manhole covers we had before?

— Bob P., Medford

As with most road projects, Bob, there's usually a reasonable explanation behind the work that's going on out there.

In this case, we checked in with Medford Public Works just for you.

Typically, when Public Works puts a full layer of asphalt over a road, it is 1.5 inches to 2 inches thick. To bring the manhole covers up to the same height, workers install metal adjustment rings.

However, Public Works has been busy in recent years putting down thin layers of blacktop, often referred to as "microsurfacing."

These thin layers are supposed to be about three-eighths of an inch thick, so there's only a slight dip in the road around manhole covers.

But construction crews contracted by the city laid down the microsurfacing a little thick at a half to five-eighths of an inch. As a result, motorists complained to the city that it affected ride quality.

"They were a little rough," said city engineer Larry Beskow.

The city decided to install rubberized covers over the top of the manholes to make up the height difference.

"We're hoping they last seven or eight years," Beskow said.

Thin metal rings are not advisable to bring the manhole covers up to the right height because they wouldn't withstand the wear and tear, he noted.

The city has installed the rubber covers on East Main Street and Crater Lake Avenue north of McAndrews Road.

When the city needs to repave the roads with a full layer of asphalt, it will then adjust the manhole covers to the right height.

By the way, Bob, other manhole covers owned by local utility companies have not received the same treatment as the covers owned by the city.

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