The article mentions their plan is to bury the tanks. That is stupid expensive, and one of the reasons existing water storage tanks are never buried in the US.
Buried water storage tanks are not rare. The San Francisco Water Department has some in their system.[1][2] They're basically roofed concrete reservoirs. Those store clean, processed water.
Those could have been fully buried or hidden, but, being visible only from the air, it wasn't worth it.
