Is this an existing sewer manhole or are you designing for new construction?
How long do you want the manhole to last? Is there a lot of H2S created at this location or upstream (turbulence, length of time the sewage has been in the sewer at that location, etc.)?
If this is an existing structure and there are steel fittings (e.g. ladder rungs), are they corroding rapidly? Is there a lot of sacrificial thickness in the design? Is it reasonably easy to apply an epoxy lining to this particular structure?
There are lots of questions that can guide you towards an appropriate answer.
Big mahalos - This is new construction and should be designed to last 50 years. I'm struggling with what is the threshold value for H2S, and how to model H2S migration in the pipe network.
PS - NASSCO is a pay wall, but I appreciate the reference.
Coatings have received bad publicity because the older synthetics, such as coal tar epoxy, did not protect the concrete for more than a few years. Tnemec Series 434 among others, do afford long-term protection, presumably for 50 years or more.
The need for protection depends on the climate conditions and the amount of flow. Low flow and hot weather leads to corroding sewers.
