Sealing Conduits entering large concrete Manholes

[jjs]

An existing installation of conduits on a site go from manhole to manhole. Some have low voltage cables, others have 480V, others 4160v
The manholes were not installed correctly 10 years ago and allow surface water and ground water into the system. The water fills the conduits and goes to the next manhole. It is hard to figure out which manholes are leaking since the whole system acts as a storm sewer.
The contractor wants to seal the conduits, as well as epoxy the inside of the manholes (some are 7' deep) to try and isolate all the systems and figure out if there are still leaks anywhere.

Should they seal the conduits? Is Trapped condensation giong to be a problem? Is Trapped heat going to be a problem?
Is there any other reason not to seal them?

If it is ok to seal the ends of the conduits, what would be a good product to use?

Thanks

 

[RichB]

We seal ours with a foam product--if you don't need back into the conduits then there is an air bag system the Phone Co uses. I don't have any interest in the following companies other than this is what we use--The foam is called DuoFil-400 and the bags are T-Dux--Don't recall the manufacturers but just google tham

 

[don_resqcapt19]

It is almost impossible to keep the water out. I would look at sump pumps in the manholes.