moisture in basement floor

Hi

We have a cork floor in our basement. House was built in the 30s and the foundation is poured concrete. the house is in eastern ontario. I noticed an area where the cork was raised up considerably...I pulled the floor up and found a moist mound of sludge about 9 inches in diameter. As I dug out the loose sludge i found a rotted piece of wood (could be tree root???). Once I dug out the sludge i had a sizable hole that had concrete on the bottom, concrete on the back end (i assume the footing of the house), and concrete floor on the edges. What was interesting is the shape of the hole was clearly rectangular in nature (like something had been in that spot). This can clearly be seen in the attachments entitled: "floor1" and "floor2".

No biggie i thought. I did a concrete patch on the floor, filling the hole completely. I hadn't gotten around to fixing the floor for 2-3 weeks and i just noticed that around the edges of the patch is a lot of moisture..even a bit of standing water. this can be seen in the attachment entitled: "floor3". Whats more curious is it has been quite dry here over the last little while. Our water main attaches at the front of the house and the 'issue' is at the side of the house.

My questions are:
1. what could have been in the 'hole' originally to cause the perfectly rectangular shape?

2. What are my next steps for diagnosing the problem?

Any guidance or assistance would be greatly appreciated.

thanks

That is interesting. Did you find any material left from rotting or is it very clean. It could be many things. Wood placed a form to pour concrete that was never poured or maybe they were trying to pour some additional ribs for the foundation.
I actually, to answer a bit your second question too, had a similar problem with water and dug a trench under part of the basement slab to drain the water out. It could have been that too.
Either way, don't do like me, get some professional to come out and give you a expert opinion on how to insulate the foundation.

Boy, you could come up with lots of guesses on what it was for but the bottom line is the perimiter drain is not doing it's job.