At location 2 near Desha, Arkansas the existing concrete gate and entrance sills had to be removed in order to let sufficient water into the powerhouse.  These were left in place during the powerhouse construction in order to keep the lock stable until construction was complete.  The sills were drilled and blasted after the powerhouse was complete.  The newly constructed powerhouse was only about 50 feet from the front of the concrete gate sill. 

The concrete was poured with the existing walls of the lock during construction and had to be blasted without damaging any of the concrete to remain.  At lock #1 this was all done underwater.