The British Engineers, Builders of the Nineteenth Century Halifax Citadel deviated from the time proven Vauban's design for fortifications, by decreasing the retaining wall thickness and providing insufficient drainage. No consideration was given to the specific Canadian climate. Part of the fortification was founded on uncompacted backfill. Sever structural distress was the result. Installation of a drainage network, replacement of frost susceptible soils with granular fill or styrofoam and installation of wall monitoring program increased the structural stability of the walls and provided and in situ intervention with long term benefits.