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NEW YORK STATE MUSEUM 



Bridge site. It is therefore advisable to locate any such structure 

 as a dam at a point as far down stream on this site as other engi- 

 neering factors permit. 



b " Tongore " site. At Tongore, be'd rock is at least a hun- 

 dred feet deeper than at Olive Bridge. In the deeper parts, below 

 the 400 foot line the deposits as indicated by the wash borings [see 

 sections] are interpreted as a fairly continuous succession of till, 

 stratified sands and gravels, and laminated sands and clays belong- 

 ing to two or three different stages of accumulation. Upon this 

 the heavy upper till was laid down. It is believed that the records 

 fully support this view and that the stratified or laminated materials 

 were accumulated at a time when a temporary dam existed at some 

 point still farther down the Esopus valley. It is apparent further- 

 more that the most porous zone is at the junction of the upper 

 till and the lower stratified deposits and in part is represented by 

 the assorted pebbles of stream wash — in general not far from the 

 400 foot line. These middle zone deposits are believed to extend 

 continuously through the drift ridge that forms the northern half 

 of this site. As before noted, though rather impervious vertically, 



Fig. 17 Plan and geologic section at the Tongore site. The dots on the map indicate 

 exploratory borings and the course of the buried channel of the preglacial Esopus creek 

 is shown making a right angle bend to the north. The section shows the buried chan- 

 nel, the new postglacial channel and the great accumulation of porous modified drift 

 which is regarded as one important objection to this site for the dam. 



some of these deposits allow ready lateral movement of water. This 

 is held to account for the rather ipersistent occurrence of springs 

 or seepage along the creek bank at about this level both above and 



