Sewage Spill Trends & Data
Every reported sanitary sewer overflow in our database, seen from above — how many spills are reported each year, what causes them, how often they reach a waterway, and how much rain is to blame.
Overflows reported by year
Reported sanitary sewer overflow events per year across all tracked states and data sources.
Note: the steep pre-2023 ramp largely reflects the rollout of the EPA's electronic reporting rule — more states coming online, not necessarily more spills happening. Earlier years are under-reported rather than quieter.
What causes overflows
Reported events by primary cause category.
- Root Intrusion32,869 · 26%
- Rainfall / Flooding28,543 · 23%
- Equipment Failure25,097 · 20%
- Other / Unknown22,007 · 18%
- Grease / FOG15,638 · 12%
- Capacity Issue1,309 · 1%
Reaching a waterway, by year
Share of each year's reported overflows that reached a river, stream, lake, or other surface water.
Values are the percentage of that year's reported events flagged as reaching surface water. Reporting completeness for this field varies by state and year.
Data sourced from EPA ECHO and state reporting systems. Figures reflect reported overflows and carry the reporting limitations described on our data & methodology page.