My Dad’s All Set to Work At Microsoft

Tue, Apr 22, 2003

My Dad, a long-time draftsman in a civil engineering firm in Fargo, ND, had this to say about manhole covers:

“It’s like this. Sanitary manhole covers are usually round (and solid, i.e. VERY heavy) but Storm sewer manhole and Inlet covers are usually square or rectangular grates which let water in. The deciding factor is where they are placed relative to the curb line. All covers are actually installed on a concrete generic ‘Mexican Hat’ structure which can be centered or offset to one side. The structure fits on the round concrete casting (5′ - 8″ diameter) and can be made to accept any solid or grated casting. If this part of the world, where river flooding is fairly common, Sanitary manholes and lift stations are either raised above potential flood limits if possible or sealed and bolted shut, making them much more difficult to open. It’s also a very good idea to vent Sanitary manholes and lift station with a portable fan to avoid being overcome by methane and other gasses trapped in them.”

Anyone wonder where I got it? : )