Is that a single hull?
No, the hull of a submarine is two parts, the outer hull, which is made of HY-80 steel in the case of the LA class subs, and the inner hull, which is much thicker and stronger. The ballast tanks are between the hulls.
All US subs are constructed with a single pressure hull. However, the ballast tanks are located outside the pressure hull forward and aft of the pressure hull. The area in the photo shows that the forward ballast tank has been crushed all the way back to the forward elliptical bulkhead (i.e. forward most pressure hull).