I purchased a house that had undisclosed water problems.
My house is built in 1942 and is mostly (2300 of 4000 sq.ft.) underground and it takes up the entire width of the city lot on which it sits. The construction is approximately 10 inch thick steel reinforced concrete shell then 18 inched of airspace followed by an inner shell construction of cement block and some wood framed walls as well. Air ducts, waterlines and electricity runs in the airspace.
The first year(2006) a second sump was installed to alleviate the flooding that occurs regularly in the basement. The flooding returned the following spring.
I dismantled the inner wall along the flooded side of the house and discovered rusted air ducts, rotted wood and mold everywhere. I tore out the air ducts and replaced them after I tracked the water to its entry point (or so I thought). I proceeded to hand dig (property is too tight for machinery) a trench 11 feet deep and 3 feet wide the entire length of the 72 feet flooding side of the house. I replaced the clogged round asphalt tile drain with modern corrugated and socked drainpipe leading directly into the sump, sealed the entire wall of the home with sealer and 8 mil plastic. I then filled the bottom of the trench with pea gravel for 4 feet and #57 river rock for the next 4 feet and clay based topsoil as a topper. During that digging I also discovered what I assume is a dry-well/spring-drain that was covered over with turf.

The next heavy rains brought the water back into my home through the inner footer joint and the foundation (wasn't the wall after all). I am about to place a 3rd sump at the point of entry , before I do this does anyone have a better idea than busting up a concrete and re-bar floor that may structurally support such a heavy concrete and re-bar shell?

https://sites.google.com/site/myhouseonjeannette/

Sorry forgot to include the link to a few pics and things centered around the house.

My first guess (my experience is in highway and bridge construction drainage issues) would be that the water is coming from a spring or rising water table. In other words the water is coming "up" while your drainage is mostly designed to capture surface water penetrating down to the footing level.
What is the elevation of the bottom of the 11 foot trench compared to the pint where the water first shows up (by the way how did you protect against cave-in of an 11 foot deep by 3 foot wide, hand dug trench)?
Sounds like the drain you installed is not low enough to capture water coming up before it comes through a joint or crack. I am not familiar with the "socked drain" term but assume that is a perforated pipe with a filter cloth covering to prevent silt from entering the pipe?
A sump pump diameter hole cut into the floor with a small jack hammer should not do damage to the structure but since it is a unique design, if you have concerns you should consult a structural engineer. Also, there is no guarantee that one additional sump will have the capacity to handle the total water problem. You are extra deep into the ground so you may be seeing water that your neighbors never encounter.
I did not see any pictures on the link.

Click on the link,
https://sites.google.com/site/myhouseonjeannette/

Then click on "Underground photos" in upper left of screen.

Click on "Underground repairs" to see a person that is very lucky to be alive.

Thanks HK but wish I hadn't seen that. Makes the contractors I worked with look like saints. Joe must like to live dangerously for sure.