DC Water will be assessing the sanitary sewer lines, manholes, and other features that may be related to flow in sewers in Nicholson Street and Riggs Park NE. This initiative will help us understand the root causes for storm related backups in the separate sewer system in this neighborhood.  Unlike a third of the city that combines storm and sewage in the same pipe, storm pipes and sewage pipes were constructed in this area to separate them.   The flooding that the residents experienced during the September 10th storm, is an indication that there are unintended pathways for storm water to enter the sewer resulting in the backups that the residents experienced.   The study is the first step in the process to identify pathways for rain water to enter the sewer, so that solutions can be engineered to address them.   The project area is defined in the map on back. Work that is currently scheduled to be completed in the field is described below.



  • Manhole Inspections – The condition of each manhole will be assessed for needed repair to eliminate routes for large volume of rain water entry.
  • Flow Monitoring – Flow in specific key manholes will be measured 24 hours per day to pin point location of high flows during rain events.
  • Closed Circuit Television (CCTV) Inspection – CCTV inspection of select sewer pipes will be performed by a robotic camera to evaluate whether there is a cross connection with storm sewer or another entry point that is allowing water to enter the sewers.
  • Smoke Testing – NON-TOXIC, non-staining, white smoke will be blown into the sanitary sewer system during dry weather conditions to verify if there are cross connections with the storm sewers or any other pathways for allowing rain water to enter the sewers that are not easily detectable above ground. 
  • Dye Water Testing – Following smoke testing, if the stormwater entry locations cannot be pin pointed, a non-toxic, water-soluble green dye will be used to help track and/or confirm the connections.



  • Estimated Manhole Inspections start: January 2021 
  • Lateral Inspections in Public Space (weather dependent) start: January 2021
  • Estimated Flow Monitoring start: January 2021
  • Estimated CCTV Inspection start: January 2021
  • Estimated Smoke Testing start: April 2021 (Public Notice will be given prior to start of testing)
  • Estimated Dye Testing start: January 2021
  • Normal work hours:  Monday – Saturday: 7:00am – 5:00pm
  • The schedule for field work is highly dependent on weather.  For example, smoke testing will not be performed within 24 hours after a rain event.
  • Estimated completion of all field work: May 2021



  • CCTV inspections of the sewer will access the sewer through manholes. These, as well as manhole inspections and stormwater inspections, may necessitate the partial or complete closure of local roads, and may affect access or parking in the area. Notice will be given in advance of any needed closures or other prohibited access. Ideally, street closures will occur during the day and most likely will be for a block or two at a time, for a few hours.
  • CCTV inspections will be mostly done during the day. If significant flow is observed during the day, CCTV inspections may be done at night when flows are lower.
  • Door hanger notifications will be distributed 2 to 5 business days in advance of smoke testing in your area. More information and instructions will be included on the door hangers.