BEFORE and AFTER 



View of Blow-Oui Showing the Slight Sag 



IN December of 1908 occurred 

 one of the most remarkable 

 events in the annals of Hy- 

 draulics. Duringthatyear we had 

 built a reservoir dam with a small 

 spillway, 42 feet high on a clay 

 foundation, the rock being at too 

 great a depth to warrant excava- 

 tion. While the clay was appar- 

 ently sound, it developed that 

 there was a water-bearing stratum 

 some 20 feet below the surface 

 that communicated withthe pond. 

 After a period of soaking fall 

 rains when the reservoir was full 

 and running over the spillway, 

 the attendant noted water boiling 

 up through the soft earth some 

 50 feet below the dam. This 

 rapidly increased and in a few 

 minutes the water broke through 

 in volume and in less than an 



hour the whole reservoir was empty and a "blow-out" formed 53 feet wide, 20 feet deep, and extend- 

 ing 50 feet above and below the dam. With any other type of dam the whole structure would have 



immediately collapsed into the pit and the disaster would have been final. How completely, although 



unwittingly, our dam escaped this catastrophe is bes: shown in the photograph. By close scrutiny a 



sag of about five inches can barely be detected in the down stream view. 



What happened was that the steel used in reinforcing the floor to distribute base pressures chanced 



to be sufficient to convert the floor 



into the bottom chord of a girder 



so that the dam sagged only to an 



amount representing the elasticity 



of the steel. The deck was not 



cracked nor was any damage done 



to the structure itself. The cut-off 



wall was afterward carried down to 



rock and piers built under the ex- 

 posed buttresses which were jacked 



up level. The hole was then filled 



up and the dam is today doing ser- 

 vice as if nothing had happened 



as witness the photograph. The 



location of the "blow-out" on the 



cut is about one-half inch from the 



further end of the dam. 



It is proper to say that by their 



express stipulation written into the 



contract the owners assumed all 



responsibility for the foundations, 



the responsibility of this company 



beginning with the superstructure 



itself. 



Respectfully submitted, 



Dam at Re-levelled and Re-filled Altar tha Blow-out 



t- 



AMBURSEN HYDRAULIC CONSTRUCTION CO., E " 



88 Pearl St., Boston, Mass. 

 NEW YORK OFFICE, City Investing Bldg. 165 Broadway 



AII r* j- L u L jj j x I Ambursert Hydraulic Construction Company of Canada, Ltd. 



All Canadmn .namr.es should be addressed to J 4QS Dorche ? Ur Streeti West> Montreal, P. Q. 



