Monitoring Of Earth And Rock Dams

The Electricity Commission of New South Wales owns and operates eleven dams. The purpose and some salient details of these structures and the instruments installed to monitor performance are given in Table 1A and 1B.

It is standard Commission practice for the dam designers to be responsible for obtaining and interpreting performance data during the construction and contract maintenance periods. At the end of the maintenance periods, responsibility for this work is transferred to the Power Development Division and it is this phase of the work which is covered in this paper.

Each dam is inspected at least once a year and a formal inspection report prepared. Depending upon conditions of the structures and their past performances, additional inspections are made at more frequent intervals of those features of a dam which may be causing concern.

With the exception of Tallawarra No. 1 Ash Dam, Wangi Ash Dam and Ulan Water Supply Dam, each dam has been instrumented to some extent with ground water level observation pipes, piezometers, settlement cross arm installations, as well as survey monuments to observe horizontal and vertical movements and weirs to measure seepage rates. The numbers and types of instruments installed have been determined having regard for the size, importance and condition of the structure, and to some extent the consequences of failure.