Combined Sewer System

Avoid Contact with Combined Sewer Overflows (CSO's)

Warning sign
CSO Warning sign

DC WASA is committed to improving the quality of the receiving waters within the District. Discharges may be dangerous to the public, due to the high flow of water that may exit these sewer outfalls. Potentially harmful substances may also be present in these discharges. The public is advised to stay away from any sewer pipe discharge. For small rainfalls, the effects of CSOs on the receiving waters typically last less than 24 hours. For larger rainfalls, greater than 1" of rain, the effects of CSO on water quality can last up to three days. The public is also reminded that the District of Columbia Department of Health has imposed a ban on swimming in all rivers and creeks in the District and any contact with rivers and creeks immediately downstream of any sewer pipe discharge should be avoided.

What can you find in this section?

  • CSS Overview
    Review basic information on the Combined Sewer System.
  • CSS Contacts
    Find contact information and additional resources for issues related to the Combined Sewer System (CSS) and Municipal Separate Storm Sewer System (MS4).
  • Preventing Sewer Overflows
    Learn what you can do to help local water quality.
  • CSO Predictions
    CSOs should only occur during wet weather. This page explains more and presents predictions on their occurance.
  • CSS Reports
    Monthly and quarterly reports on program status and consent decree compliance.