Thanks for everyone's good advice. I have looked around the perimeter
of the building and found that someone in the past had attempted to put
in a cheap french drain system on one side of the building, but it is
sitting partially above ground now and obviously is no longer
effective. Looks like it's time for a shovel brigade party, new pipe
and a lot of gravel. The other side of the building was relandscaped
last year, so I didn't go poking about there yet - I need to notify
some ladies in the church before I go digging in the new shrub bed.
Regarding the last suggestion posted - I can't access the middle of the
duct to dig a sump pit, because this underslab concrete duct runs
directly beneath the long central hallway - perhaps a large indoor
fountain/baptismal font would cover it up? I've left the sump pump in
the duct return access for now and will pump out the water as needed.
We've had a wet summer, so that has made matters worse. Thanks again!