Too Much Fill Dirt

We made a decision to have our pool built. They started digging yesterday and stated that we had some underground water coming through. Nothing major they said. Today they told us that we have too much fill soil and will need to have an engineer perform an analysis. They mentioned that they may have to "spear" the pool now and that are looking possibly $10K more.

A couple of questions that would be great to get some of your feedback on.

This one is somewhat off-topic - This is a new construction home and I am concern that this may be an issue all around our home.

2 - Anyone had this experience before and what does "spearing" encompass? They are very vague in explaining some of the processes.

3 - If it is just the water problem, does that usually use gravel/rock drainage system or is it more complex than that?

Newby so I might have missed including some critical details. I am just concerned that the building may be looking to get more $ for things that are not needed.

Thanks!