This reservoir replaced a previous version in 2004 and, it turns out, was an award-winning project due to its unique approach to the problem of limited space.
The challenge faced by the design/construction team was that because the reservoir was surrounded by houses, it was impossible to expand beyond the existing footprint. A unique concentric tank system was used, so that one of the two tanks sits inside of the other, and the tanks operate in tandem. However, one can continue operating if the other needs to be taken out of service for cleaning, etc.
Next time you pass through, take a load off. The bench has a pleasant throne-like quality and is surprisingly comfortable, for a concrete seat.