The Smelter of Quebec Iron and Titanium Corporation at St. Joseph de Sorel, Quebec, is located in an area which is underlain by about 80 feet of compact stratified sand, silt, and clay, followed by at least 150 feet of Leda clay. Five furnaces were constructed during 1950–52, and four more furnaces have been added subsequently. Settlement records spanning some fifteen years are available for the original furnaces.Recently, it was decided to replace No. 1 Furnace with a new unit, the weight of which will be slightly more than twice that of the existing furnace. The present furnace is founded on 32 Franki piles of 75 tons capacity; the piles are 22 feet long and are cut off about 5 feet below ground level. As it was desired to incorporate the existing piles in the foundation for the new furnace it was necessary to know whether new piles could be driven and loaded together with the existing piles without causing overstressing of the latter, which had been preloaded by the weight of the existing furnace.A settlement analysis of the existing furnace foundation was undertaken, in which sensible agreement was obtained with the observed settlements. Predictions of the rebound of the existing furnace foundation during demolition were made and these were in approximate agreement with field observations. Finally, an estimate of the settlement which the new furnace will experience was made.A significant feature of the problem is that a large portion of the total settlement experienced to date is due to consolidation of the underlying Leda clay stratum, despite the fact that the furnace foundation areas are small in size compared to the thickness of the overlying granular deposits, thereby inducing only small increases in pressure in relation to the existing overburden pressure.