SMALL DAMS PETITS BARRAGES

complete construction was in 2001, including an RCC inflow spillway, a holding reservoir, and
three outflow spillways (service, auxiliary and emergency).
The RCC structure consists of an approach apron starstepped chute, stilling basin and
training walls. The spillway is 12,6 m high, and the slope of the chute is 3H:1V. The steps are
0,6 m high. The RCC mixture contained 216 kg/m 3 cement and 44 kg/m 3 fly ash.
The RCC spillway operates during every rain event generally a flow in the wash,
normally a few times a year. Figure 7.10 shows the inflow water during a 2004 storm. The
storm carried heavy sediments loads, evidenced by the presence of a large pile of sediment in
the basin of the RCC structure. In 2005 a strong storm deposited boulders up to 91 kg on the
RCC steps and distributed the sediment pile throughout the detention basin (Figure 7.11).
Although RCC is still a relatively new method of construction for this application
(i.e. spillways constructed on embankments or overtopping protection embankments)
performance data is limited. Structures that have been overtopped show strong evidence that
the RCC has performed satisfactorily when subjected to hydrostatic pressures and flows
containing very abrasive sediments, as reported by Abdo and Adaska in 2007.
In addition to proper structural design, the primary factors that have contributed to the
successful performance of these structures are related to the RCC mix design and sound
construction methods, namely;
Fig. 7.10 – 2004 storm overview at Red Rock Detention Basin spillway
(Abdo and Adaska, 2007)
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