The difference $ 490,467 being due to this modification , yet there will be a further increase because of the condition of the natural foundation of the core wall , as hereinafter described . In considering this esti- mate one should not loose sight of the fact that there has been a loss sustained of about $ 80,000 , the cost of that part of the core wall that had to be thus abandoned . In March , 1903 , the core wall having been removed , it became apparent that the embankment and core wall would have been undermined and destroyed if completed under the original plan . The core wall was found to be resting upon lime stone that in places was completely disintegrated , to the form of loose sand and other por- tions in the process of disintegrating , were more or less hard , the softer part being in such a condition that it could be easily crushed by the hand to the form of sand and would absorb water as freely as would a sponge . The hardest of this stone was full of eroded , open and mud - filled seams , the existence of mud being evidence that these seams had acted as passageways for water . Under date of April 1 , 1903 , Prof. Burr , who had con- curred in the condemnation of the wall , reported to Mayor Low as to the foundation as follows : " It is most fortunate that the core wall has been removed so as to dis- close the actual situation and thus remove what would have been a source of gravest danger to the completed embankment structure as originally planned . " Prof. J. E. Kemp , of Columbia University and Prof.