Building in Florida ia a bitch. It is hard to find anything solid to put foundations on. Huge sections of US 92 are floating on pontoons because they couldn't find solid ground. When my wife and were in college our apartment was close to I-75. When they were widening it through Gainesville we could hear them driving in the concrete to get to something solid for the bridges. One day it was bam, bam, bam, whoomph! They hit a cave and the pilings just disappeared! Took them a while to come up with a new plan. They ended up pouring a huge concrete base to "float" the bridge on.