When considering the purchase of manhole covers, it is important to consider he long term durability to get the most value. High-quality composite manhole systems have a life expectancy over 30 years and require little maintenance. Contrary to this, cast iron systems require a significant amount of maintenance and will not last a full 30 years. Replacement of these systems needs to be figured into the total cost when comparing the two options.
While some may be concerned with the safety of using composite over cast iron, fully traffic rated covers can withstand weight 30% higher than the current weight limits set by US DOT. This means they are incredibly safe and can hold more weight than is legally allowed on the road. Providing extra strength ensures that the stability with being there regardless of the age of the cover.
Other benefits of composite covers, when compared to cast iron covers, is that the composite ones are 63% to 85% lighter than cast iron covers, which can easily weigh over 200 pounds. The lighter weight makes them easier to move, install, and open. The lighter weight will also reduce the risk of injury by road and utility workers that are installing or opening them.
Additionally, they have no scrap value, so this will decrease, if not eliminate the risk of covers getting stolen. Theft is a serious problem all over the world. In Calcutta, India, there was a 2-month period when over 10,000 manhole covers were stolen for scrap value. They were replaced with concrete covers, which were also stolen for the scrap value of the rebar inside the concrete. Replacement manhole covers can be pricey, especially if they need to be replaced more than once.
Composite manhole covers also reduce or eliminate the risk of manhole events. A manhole event is an accident that may range from puffs of smoke from a short-circuit to full explosions that result in manhole covers flying through the air. According to the Consolidated Edison Company, in 2014 alone, there were 3,369 events in New York City. Of those, 32 were explosions, which puts everyone in the area of the event at great risk.
Manhole events are more likely to happen in the summer because with air conditioners running, there is a high volume of electricity running through them. Composite covers will not conduct electricity in that way, which is why the concern over dangerous events is reduced dramatically.
These are just some of the many reasons high-quality composite covers are a better value than cost iron covers. While concrete covers were only briefly mentioned, it is worth stating that concrete covers are significantly heavier, the break down over time and they still have scrap value, which makes them a target for theft.