Bob wrote:
Greetings,

[SNIP]

Bob, listen to what these other folk are saying. Listen VERY
CAREFULLY.

My mother just settled a year-and-a-half long nightmare involving a
"contractor" who built an addition 2' below grade behind her 30
year-old brick ranch, also on a "gently sloping" lot. It flooded from
Day 1 and got so bad even the roof caved in. I don't know what the
legal term is for an injunction to get a contractor to stop performing
substandard work, and I am by no means a professional (only someone who
bailed on average 25 Shop Vacs full of water each weekend of June 2003
from this nightmare).

The black tubes you refer to are called drain tile or French drains.
Not only should they be connected to "something," there should be a
trench on the property where you can actually see the connection
leading to the lowest, or to one of the lowest, places on the land.
This connection should, as the contractors say, "lead to daylight."
The reason drain tile needs to lead to daylight is because even under
the best circumstances, the cloth-wrapping around the drains will over
time become muddy and clogged. Drain tile, or French drains, are like
underground gutters. They have to have a clear and open place to
discharge their contents, or they will back up and you will have what
God love you, you already seem to have.

I could go on and on, Bob, but let me finish by saying, REAL loud,
R-U-N, D-O-N'-T W-A-L-K to your local Code Enforcement Officer (I'm
assuming you do have a building permit) and ask for his/her help or at
least a visit to the site. If your municipality does not have a
provision in its code for any kind of action to be taken by the
Officer, call another contractor IMMEDIATELY and offer to pay for
his/her appraisal of the source of the flooding. I guarantee you
without even seeing the property that you're right when you say the
land has not been sufficiently graded.

I don't often say this on this newsgroup, but I'll be keeping you in my
prayers.