Sump pump runs in freezing temperatures?

I have a 60 year old house with clay weeping tile that is hooked into a storm or combined sewer. Never had water problems in the basement.
This summer I built a small addition (300sq') and installed a sump pit, modern weeping tile with the sock and where it met the clay tile I just tied the sock in a knot and butted it up against the clay tile.
It has been well below freezing for a couple of weeks now and I notice that my pump is cycling on for 15 seconds every 10 minutes.
Since it is freezing out, where the hell is all the water coming from? Any thoughts?

It's ground water from below the frost line.

Redwood said:

It's ground water from below the frost line.

Click to expand...

So you think it is normal, nothing to worry about?

When we excavated and the hole was open for a few weeks in August to do footings, foundation there was next to no ground water even after a big rain...

Nothing to worry about as long as the pump handles the flow and doesn't quit or have a power outage...

During the summer the trees drink up much of the ground water. During the winter....not so much. My water table is always higher in winter and the spring. So don't worry, it sounds normal to me.

-rick