the south american rubber boom ended because of competition from asian producers and synthetic rubber, and the railroad became redundant. initially, the brazilian government was forced to maintain the superfluous facilities because of its obligations under the treaty of petrópolis. however, in 1972 brazil completed the trans-amazonian highway linking bolivia to navigable regions of the amazon and the railroad was abandoned. the (iirsa) south american integration project includes a series of hydroelectric dams that will transform the madeira river rapids into navigable lakes, finally realizing gibbon's vision of fast and efficient access to bolivian markets (two of the four dams already exist, the santo antônio dam and the jirau dam). if the project is completed, "more than 4,000 km of waterways upstream from the dams in brazil, bolivia, and peru would become navigable."