# Combined sewer outfalls, and the four answers a blank can mean

URL: https://municorn.us/data/sso-combined-sewer-outfalls/
Updated: 2026-09-21
Tags: data, sewer, overflow

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EPA's outfall inventory covers 34 states, so a permit missing from it is in one of several positions and none of them is a zero.

Whether a discharge was a failure or a permitted event in a storm depends on the
sewer it came out of. A combined system carries sewage and stormwater in one
pipe, and has outfalls built for the overflow. A separate sanitary system has
neither. The overflow reports a utility files give the number of events. They do
not record which kind of sewer produced them.

EPA publishes a national inventory of combined sewer overflow outfalls, which
answers that question for the permits it lists. Retrieved on 15 September 2026,
it held 9,664 outfall rows against 894 permits and 873 facilities, across 34
states.

## Four answers, and one of them is a count

The four bullets below are the join's own words, printed as it produces them.

- EPA's national combined sewer overflow outfall inventory lists combined-sewer
  outfalls against this permit.
- EPA's combined sewer overflow outfall inventory covers this state and lists no
  outfall against this permit. That is not a filing that the system is separate
  sanitary, so no kind is asserted here.
- EPA's combined sewer overflow outfall inventory carries no row for this state
  at all, so it says nothing about this permit either way. This is an absence of
  coverage, not an absence of outfalls.
- This permit is not in EPA's combined sewer overflow outfall inventory, and
  nothing available here establishes which state it is in, so its absence cannot
  be read as coverage or as a finding.

Only the first of those four is a count. Printing zero for the other three would
answer a question nobody asked the inventory.

## How a permit is matched

By permit number. A facility name, a place name, or two spellings that look like
the same utility are not enough, and none of them is used.

## What is never published from this

The word sanitary. Sixteen states have no row in the inventory, so an absence
there is a gap in coverage and is not a report by any utility that its system is
separate. Nothing is added up across states and nothing is turned into a share.

_Municorn.us · https://municorn.us/data/sso-combined-sewer-outfalls/ · CC BY 4.0 https://creativecommons.org/licenses/by/4.0/ · updated 2026-09-21_

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