Why would you want the subgrade of your bunker to be so firm that you could bounce a golf ball on it?
You might be interested in considering a PERMA BUNKER when you see the quality of the sand four years after construction.
This picture shows the sand around the Perma Basin that is installed in the PERMA BUNKER. The sand is in the same pristine condition as the day it was installed, because the stabilized subgrade has stopped the contamination that occurs in other bunker construction methods.
Mike Archer with Greenscapes Six has built 1,000 bunkers with this method over the years. This method has many advantages, not the least of which is cost. This bunker method can be less than half of the cost of some other methods being used today, and the longevity is unparalleled. No course has had to replace a PERMA BUNKER to date.