National Grid prioritizes gas leak repairs through a classification of three grades:
Grade 1 - typically located in densely populated or high traffic areas - these are fixed immediately
Grade 2 - considered not to be of immediate risk to life or property, but potentially may become hazardous - these are prioritized for repair
Grade 3 - deemed non-hazardous to life or property - not prioritized for repair
All of Weston's 141 unrepaired leaks that were reported by National Grid by December 2018, and classified according to gas company standards, are Grade 3 leaks. However, the grading system does not take into account the size of the leak or the amount of methane being emitted. Further, Weston has higher pressure pipes at 60 psi, compared to other communities such as Lawrence or Boston at 0.5 psi, and many of the pipes are made out of corroding cast iron or bare steel.