Field studies were performed on a 15 km long section of the sewage system, which comprised 6 settlements and consisted of pipelines and wells. System contained of pressure and gravity plastics pipelines and concrete wells. Sewage from the furthest located settlement was pumped to a well in subsequent settlements. After connection with local sewage, it was pumped further down to the wastewater treatment plant. COD and BOD5, temp., sewage pH, cond., petroleum ether extractable matter as well as the content of sulfides and dissolved O were detd. In addn. contents of H2S, NH3, MeH in the air inside the well were also measured. Correlations between parameters of air, sewage and corrosion of concrete were also studied. The biggest traces of corrosion were obsd. in expansion wells directly connected with the main pressure pipelines transporting total sewage from each settlement. In the expansion wells, where concrete corrosion was found, the concn. of H2S in the air above the sewage exceeded 200 ppm. A strong correlation between the H2S and NH3 content in the air in the wells was also obsd.