Combined Sewer Overflow (CSO)
Definition
A system where stormwater runoff and sewage flow through the same pipes to treatment plants. During heavy rain, these combined systems overflow, releasing untreated sewage and polluted stormwater directly into rivers and streams. Louisville has one of the nation’s largest CSO problems with 55 overflow points that discharge approximately 9 billion gallons of untreated sewage and stormwater into the Ohio River annually.
Louisville Context
Much of Louisville’s sewer system was installed nearly 100 years ago, so in heavy rain rainwater can mix with wastewater and overwhelm the pipes (MSD, July 2018). A federal consent decree requires MSD to reduce sewer overflows, and the cost of that work is passed to ratepayers through sewer bills.
Why It Matters
CSOs contaminate Louisville’s waterways with raw sewage, creating public health risks and environmental damage. The massive infrastructure investments to fix this problem directly impact your monthly sewer bills, which have increased to help pay for it.
My Proposal
I support completing CSO elimination on schedule while maximizing green infrastructure solutions that provide community benefits (parks, rain gardens, tree canopy) rather than only underground tunnels. I’ll advocate for MSD to pursue federal infrastructure grants to reduce ratepayer burden.