4.9 
Before
The concrete has sank about 2.5 inches from its original level.
PolyLEVEL
We drill penny size holes and pump it full of an environmentally friendly polymer which fills the void.
PolyLEVEL
We do this according to how much we need to to fill the voids.
After
The result is a stabilized concrete slab that isn't sinking anymore!
