Spillway
A unique feature of the Dam is its spillway. The spillway is located on the embankment, rather than on one of the rock abutments. This had never been successfully attempted before in the design of dams of any significant height, due to problems in making allowance for embankment settlements.
In the case of Crotty Dam, the embankment was partly composed of well graded gravels, and thus a very high modulus of embankment deformation was achieved. The high modulus limits embankment settlements. Additionally, the spillway was designed to articulate in order to accommodate any settlement that did occur.
The spillway has a capacity of 240 m³/s and is designed to allow sufficient time for a large jet flow valve located in the diversion tunnel to be opened so that larger floods can be safely handled.
The spillway designers, Sergio Giudici (the chief engineer on the Gordon Dam), Frank Kinstler, Steven Li, Tony Morse and Graeme Maher were acknowledged within the engineering community because the spillway was the first known to provide for articulation of the spillway structure so that movements in its foundations could occur without damage to the overlying structure.
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