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 .

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STONE DAM البلد TOP OF 290 - FEET_ . CORE WALL MARCH 1ST 1901 EMOVED DISINTEGRATED FLIMESTONE SHATTERED LIME STONE THE NEW CROTON DAM LONGITUDINAL SECTION ON AXIS OF DAM , SHOWING CORE WALL REMOVED AND ITS DEFECTIVE LIME STONE FOUNDATION , WHICH HAS BEEN EXCAVATED FOR THE EXTENSION OF THE DAM . AK GATE HOUSE . CHAMBERS TO BE REMODELED AND REINFORCED in ordinary cases , where the wall below the original sur- face of the ground is in a narrow trench and protected by original soil .