174. Every excavation in which a tank has been installed since 11 July 1991 must have an observation well, unless the petroleum equipment installation was erected between 30 April 1999 and 1 April 2007 and meets the requirements of sections 8.29 and 8.78 of Chapter VIII of the Construction Code (chapter B-1.1, r. 2). If two underground tanks are less than 1.5 m apart, at least one observation well must be installed.
The well must consist of a perforated pipe at least 150 mm in diameter installed vertically, extending down at least below the bottom of the tanks, and be accessible from the ground. The pipe must also be enclosed inside a permeable lining if it is buried in sand.