Wastewater (Sewer) Overflows

View Wastewater Overflows (The volumes reported are estimates and are assumed to be the net volume lost to the environment. Utilities sometimes are able to recover portions of the total overflow and may not report the recovered volume.)

The Facts on Wastewater Overflows

The EPA estimates that there are at least 40,000 sewer system overflows each year. In South Carolina, over the last 10 years, an average of almost 600 overflows are reported each year.
Untreated sewage from these overflows can contaminate our waters, causing serious water quality problems. Sewage can also back up into basements, causing property damage and threatening public health.

Sewer systems are meant to collect and transport all of the sewage that flows into them to a wastewater treatment facility. When a discharge of raw sewage occurs from the sewage collection system, it's called a sewer system overflow or SSO. Wastewater overflows happen for a variety of reasons:

  • A blockage in the system in dry weather
  • Vandalism
  • Construction activities
  • Pipe failures
  • Pumping failures
  • Grease accumulation
  • Root intrusion into sewer lines
  • A lack of proper maintenance
  • Inflow and infiltration into sewer lines during wet weather overwhelms the sewer system.

Reporting Wastewater Overflows 

Utilities that own and operate sewer collection systems must report overflows to DHEC. As a general rule, utilities are only required to formally report overflows of 500 gallons or more. This is intended to accommodate small releases due to maintenance activities or other causes which should not pose a threat to public health or the environment. However, some utilities elect to report all overflows, including those which are below 500 gallons.

Not all collection systems flow directly to a treatment facility. Some are collection systems only and discharge to sewer systems owned by another entity. These are called Satellite Sewer Systems. Owners of satellite sewer systems are required to:

  • Provide DHEC with basic company/owner information
  • Properly operate and maintain their systems
  • Report sewer system releases(overflows).

Wastewater overflows of at least 5,000 gallons of untreated or partially treated domestic sewage that could cause a serious adverse impact on the environment or public health are considered "significant spills". Wastewater utilities must verbally notify the department of any significant spill within twenty-four hours and by written submission within five days. The twenty-four hour notification should be made to the Environmental Affairs office located in the area of the state where the spill occurs. The five-day notification should be made to the Bureau of Water in Columbia. 

All regulated wastewater systems should report sewer system overflows electronically using the ePermitting database.

Public notification is required for overflows of 5,000 gallons or more or any overflow that has the potential to affect public health. The notification should be sufficient to adequately inform the affected public and may include:

  • Social media posts
  • Phone alerts
  • Press release (website and local press)
  • Signs (posting in the area of release and downstream)
  • Door to door notification and door hangers