ABSTRACT
The Jordão River Dispersion is part of the Segredo 1260 MW Hydro Complex Power Plant, and is located five kilometers from Jordão River outfall, between Reserva do Iguaçu and Foz do Iguaçu Brazilian countries, in Paraná State, latitude 52°05’, longitude 25°45’. The elevation quota is approximately 560 m from the Atlantic Ocean level. It is operating since may 1996. The dam presents a 9 m diameter tunnel, 4.7 km long, a Roller Compacted Concrete dam and a 6.5 MW powerhouse. The dam is 95 m high, 550 m long and incorporates a 300 m long spillway defined for a maximum design flow of 7300 m3/s. The upstream face is of conventional concrete (CVC) with thickness varying from 0.8 to 1.4 m base to the top. The downstream face is of RCC, with cement consumption between 75 to 105 kg/m3. This dam was the first large RCC in Brazil and it was designed with conservative assumptions. Defects and cracks in upstream CVC, mainly in the contraction joints, were responsible for the presence of leakages, mainly in lower drainage gallery. It was observed during the first investigation of the reservoir that the seeping water carries solid materials. This was visible at the lower gallery and at the downstream face of the dam. In order to analyse the amount of solid materials in the percolated water, a comprehensive physicochemical program was carried out to determine the chemicals ions leached out of the RCC. From the first results, the total soluble chemical elements transported from the dam body were estimated to be close to 10 tons/year. This material was reduced to less than 4 tons/year in the analyses carried out in the last year investigated. The chemical composition is essentially sodium and potassium ions (97%), followed by Ca2+, Si4+ and Al3+, constituents of cement and crushed stone compositions. The conclusion of statistical physicochemical analyses of ion concentrations is that in 5 to 7 years the quantities will be the same as for the water in the reservoir. The solution process will stop.
