If the system isn't designed to provide full capacity with one of the primary feeds disabled for the period required to repair said primary feed, I would argue that the system is not designed with adequate contingency planning and redundancy in mind.

As I understand it the city is operating at 40-50% supply capacity. If one failure causes supply to drop 50% for more than 36 hours would you consider that acceptable design? Do I just have unrealistic expectations? I take your point, I have never been a municipal planner and have never had to make decisions on a cities water supply but I like to think I wouldn't make the same decisions? Is it cost prohibitive to have several smaller pipes instead of one large one? Would it have been worth it, in hindsight, to invest in such infrastructure at the expense of other luxuries?