You drive over them every day in cities across America.
But do you know just how much a manhole cover weighs?
Weights for manhole covers will vary depending on its diameter and materials used in its construction.
However, the standard manhole cover will weigh 90 to 150 pounds or more.
Larger-diameter covers that are used by many cities can weigh upwards of 250 pounds.
The reason why manhole covers are so heavy is mainly for safety reasons. Their heavier weight helps hold them in place as you drive your car over it. There are a few other reasons, but safety is the most important.
Manhole covers are also a target for thieves who steal them and take them to the scrap yard for cash. This is a bigger issue for larger cities, due to the number of covers overall.
Thieves will drive a van around, and two or more people will pop open the cover with a crowbar and put them in the back of the van.
In Georgia, police busted a ring of these thieves who were found with nine covers in their van.
Manhole covers are typically made from a mixture of cast iron and concrete, which adds to their weight.
~ Fun Fact ~
Why are manhole covers round? There are many different answers to this question, but the most common answer is that they are round so that cover will not fall into the manhole itself. This is unlike a rectangular or square cover that could fall in, if lined up incorrectly.
Resources:
http://www.usfoundry.com/usfoundry/engineering/specifications/
https://www.newsweek.com/manhole-covers-stolen-scrap-metal-89575
https://www.drainagesuperstore.co.uk/blog/manhole-cover-sizes-and-load-classes/