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 portions 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 .

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dam . It is rubble masonry , faced on the water side with cut stone in regular courses and the lower side is in steps of large blocks of stone . A channel for the overflow is excavated in the rock back of the wall leading down to the river below the dam . The main stone dam , according to the original plan , was to be 600 feet long , extending from the spillway to the foot of the slope at the south side of the valley , thence an embankment and core wall 568 feet long was to continue to the end , making a structure 2,168 feet long . The main stone dam is rubble masonry , faced on both sides , above the surface of the ground , with cut stone in regular courses . It is 297 feet high from the deepest point of the foundation , which is 131 feet below the bed of the river . Its greatest width at the base is 206 feet and the width at the top is 20 feet . At the junction with the core wall according to the original plan it had a height of 230 feet .