The great increase in the cost of the work is due principally to the four above de- scribed additions and modifications namely : the extra depth excavated under the main stone dam , the first ex- tension of 110 feet of the main stone dam , the extension of the main stone dam necessitating the removal of the embankment and core wall and lastly the additional ex- cavation necessary for the foundation of the last exten- sion . Some idea of what these changes have necessitated may be gained from the consideration of but two items , that of the amount of earth excavation which will be trebled and that of the amount of masonry which will be increased from 550,000 to about 800,000 cubic yards . The value of the work done to March 1 , 1904 is $ 5,363,000 . This most important of all structures to this great city , upon which its welfare would be almost wholly depend- ent , had to be mantled with all possible safeguards against its destruction . Thus the writer being brought face to face with the one paramount necessity that of the safety of this structure , was left no alternative but to modify the plan .

=== seq 12 ===

To take up the first , the embankment : It was to be 150 feet high , and only 650 feet thick at the base . This section , would be not only about 40 per cent . higher than any heretofore built , but in comparison with other high embankments its base was narrow for its height . As an example , the Amawalk dam , which forms one of the upper Croton reservoirs , while only about half the height , 85 feet , yet has a base even wider than that of this embankment of unprecedented height .