How do you remedy the presence of peat soil in your foundation?

It depends on the depth of the peat. One method is to dig out the peat to reach solid ground. Should this be impractical, another method is to drive pillars down to reach firm ground, in several areas of the foundation's footprint. A concrete raft is laid, incorporating the top foot or more of the pillars, and the building is built on top of the raft.