"Michael Baugh" wrote in message
. ..
The only thing that should go into the sewer line is sewage.
The sewage has been verified as only going in one of the pipes.
Yes, they are likely stubbed off downspout connections. Need
to be gone.
Do you see it some other way?

Before anything is "gone", you must make provision for what feeds into
them. Before you can do that, they must be traced to the source. It would
not make sense to plug them and have the spring rains flood the basement
because you just found out what goes into them. Could they be lines from the
house in the back neighbors sewage? Bet they'd love to have you plug them.

It would be totally irresponsible to plug an underground line now knowing
where it comes from.