Louisville rerouted stormwater to idle pipes, saving $200M

Like most older American cities, Louisville's sewer system combines stormwater and wastewater in the same pipe network. During heavy rain, the combined flow regularly exceeded the fixed capacity of pipes and treatment plants, forcing untreated overflow directly into the Ohio River and local streams — a problem every part of the industry treated as a capacity shortfall to be solved by digging bigger pipes and building bigger storage tanks, the default multi-hundred-million-dollar fix.

The Louisville Metropolitan Sewer District partnered with Tetra Tech to question that framing: at any given moment during a storm, some parts of the pipe network were at capacity while other parts, elsewhere in the same system, sat with spare room the fixed-infrastructure view had no way to see or use.

Rerouted stormwater in real time to idle capacity elsewhere in the same pipe network, saving $200M in avoided construction.

Sensors and forecasts revealed spare capacity in parts of the network during storms.

Dynamic rerouting used that idle capacity, increasing effective system capacity.

Avoided building new pipes and tanks, saving over $200 million.

Software and sensors cost far less than physical expansion.

Before expanding capacity, check if idle capacity exists elsewhere in the network at the moment of overflow; dynamic rerouting can capture it.

Real-time control has saved MSD more than $200 million in infrastructure construction costs that would otherwise have gone toward physically expanding pipes and storage, according to MSD chief engineer Angela Akridge, while helping the district move toward eliminating or capturing and treating up to 98% of combined system flow once the related Integrated Overflow Abatement Plan projects are complete.