About 25 gallons of sewage from private system overflows into tributary PORTLAND, Oregon (KPTV) — Sewage from a privately-owned system overflowed into a tributary of Fanno Creek on Monday, according to the Portland Bureau of Environmental Services. At about 4:30 p.m., city crews responded to a sewage release in the 7900 block of Southwest 40th Avenue. BES said the release was stopped within the hour. According to BES, about 25 gallons of sewage overflowed from a maintenance access hole on the property’s parking lot, through a private storm system, and to a small creek that flows through a steep, forested edge of Gabriel Park and to Fanno Creek.