Sewage-related policy decisions rely heavily on scientific and technical advice but there are deep disagreements among experts on the most suitable recommendations. One such example is the Capital Regional District (CRD), British Columbia, Canada, where scientists have publicly positioned themselves either against (anti-treatment) or in favour (pro-treatment) of building a wastewater treatment (WWT) facility. The aim of the study is to analyse how scientists from the two sides frame the problem, the relative weight they place on different risks and uncertainties, and how the framing of risks and uncertainties are used to support their policy-recommendations.