2018: 86% Reduction of Sewage Spills in Mobile Bay!

In 2018 we were excited to see a big drop in the number and amount of reported sanitary sewer overflows (SSOs)! What is an SSO? An SSO, also known as a sewage spill, is when raw sewage spills from a manhole, pump station, or other part of the sewage system. Sewage spills can  reach our waterways and diminish water quality in our creeks, rivers and bays. This significantly hurts our ability to swim, fish, and play.

Fig. 1: Map of SSO locations reported in 2018, with symbol sized based on volume of spill

In 2018, a total of 281 sewage spills released 3.5 million gallons of untreated sewage into our local waterways. While it still sounds bad, this amount was a drastic improvement from the 25.8 million gallons released in 2017. This is exciting as we see our no-holds barred war on sewage spills creating tangible improvements. For comparison, the spill volume for 2017 and 2018 are as follows:


Most Impacted Waterways

  1. Gumtree Branch

  2. Eslava Creek

  3. Rock Creek

  4. Threemile Creek

  5. Tatumville Gully

Most Impacted Watersheds

  1. Three Mile Creek

  2. Upper Dog River

  3. Fly Creek

  4. Upper Blackwater River



In 2018, the utility with the highest amount of sewage overflows was in Prichard, totaling 45% of all reported spills. Some reported spills are given exact gallons or are put within a range. These ranges can be very large and relatively inaccurate. When these values are added to our SSO map, we use the higher value within the range.



There are many causes for overflows, but the most common is heavy rain. Because some utilities have old sewage lines with breaks and holes, rainwater can get into these pipes and cause overflows. Where utilities have not invested enough in repairing and replacing their sewage lines, heavy rains and flooding cause large spills. Occasionally this will also be referred to as Inflow and Infiltration, when groundwater or stormwater enters the sewer system.


Top 5 Reasons for Spills

  1. Rainfall - 75%

  2. System Failure - 14%

  3. Blockages  - 6%

  4. Lightning / Power Loss  - 2%

  5. Broken or Damaged Lines - 2%

System failure is a broader term to describe events such as a pump failure, lifts station failure, mechanical failures, and failure of any other part of the system that keeps everything running smoothly.

Blockages are when grease, rags, flushable wipes, or other things that shouldn't go down drains cause sewage spills. Learn more about how you can help prevent grease blockages here and other ways you can prevent sewage spills here.

Sometimes, during strong storms, critical pump stations in sewage systems lose power. These power failures can cause large sewage spills if the pump station doesn’t have a source of backup power. Mobile Baykeeper advocates that utilities have backup generators at all critical pump stations.


Mobile Baykeeper has an online SSO map that we update on a weekly basis with information provided by the Alabama Department of Environmental Management (ADEM). We recently updated our SSO map so that it is simpler to use.

Check out the map The Map to see if there are sewage spills near you !

For a weekly updated SSO map, go to mobilebaykeeper.org/sewer or ADEM’s SSO Map.

Have any SSO map questions? Email Sarah Asher at sasher@mobilebaykeeper.org