Every day, 60 feet under the lanes of Marginal Tietê Highway, construction workers excavate the earth to build a tunnel. The project progresses one yard for each 12-hour shift.

By early 2020, the site will give the city of São Paulo a super tunnel 4.5 miles long, through which the sewage produced by two million residents will flow.

This is one of the most important stages of the Tietê Project, a set of infrastructure works led by Sabesp, the state's water, and sewage company, to turn Tietê River - one of the main bodies of water that cross the city - clean again.

The super tunnel should receive the sewage from a portion of São Paulo that starts in the Zoo, in the south, to downtown.

The construction is part of the state government's main environmental goal, the Tietê Project, which spent US$ 2.8 billion since 1992, not adjusting for inflation. In the project's first years, Sabesp and the government said that by 1998 fishes would be living in Tietê, and that in 2005 it would be completely clean.

All that optimism didn't pan out. According to nonprofit SOS Mata Atlântica, the river is still considered dead for 76 miles (from 330 miles in the 1990s) out of 683.5 miles of the river's length.

^{Translated by NATASHA MADOV}

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