I'm planning to build a 10x8 shed that will house the pipework and electrical equipment for a new well I recently had drilled. I would like the shed to sit on a concrete slab just for the quality of life it provides. My well contractor suggested that I pour the slab first, leaving 1x1 holes roughly 1' in from the corners where I can run pipework through afterwards. 

* Once the slab is finished with the holes, does it compromise the integrity of slab if I were to dig out the dirt between the hole and the edge of the slab to run the pipes?
* How best to fill/pack dirt back in after the pipes are put in place? Should I fill the holes with concrete, or just pack in gravel to be flush with the surface of the slab?

Rough drawing of what it'll be like:
[![enter image description here](https://i.stack.imgur.com/TlBwH.png)](https://i.stack.imgur.com/TlBwH.png)