Sewer Outfall Inspection Program - South
The Department of Water Management (DWM) has contracted with Hydromax USA to conduct sanitary sewer cleaning and inspection at various locations within the City’s sewer service area beginning in January 2022 and continuing for a period of five years.
Sewer cleaning and inspection are among tasks performed in-house by the City; however, there are sewer mains and large diameter outfalls in locations that are difficult or impossible to access with equipment and vehicles used by City staff. This contract will clean and inspect roughly 225 miles of sewer lines in busy City streets or those located off-road and alongside creeks and wetlands.
During this project, cleaning crews will access the sewers through existing manholes located in streets, right-of-ways, and easements. No disruptions to sewer service are anticipated during cleaning and inspection; however, it is recommended that residents leave their toilet seats down when not being used, in the improbable event that back pressure from the cleaning causes toilets to bubble.
A map showing the anticipated cleaning and inspection schedule for the current contract year is provided. Door hangers in English and Spanish will be distributed seven days prior to any work anticipated in your area. This contract will focus primarily on sewer lines that discharge to the South Durham Water Reclamation Facility. A similar project focusing on sewer lines that discharge to the North Durham Water Reclamation Facility is anticipated to begin in Summer 2022.
WHY IS CLEANING AND INSPECTION NECESSARY ?
The City owns and maintains approximately 1,100 miles of sanitary sewer mains and outfalls. Cleaning and inspection of the sewers are vital tools in maintaining and evaluating the City’s sewer collection system. Condition assessment enhances the ability of the City to make technically sound judgments regarding management of these assets. Sewer cleaning is also a requirement for compliance with the City’s wastewater collection permit issued by the North Carolina Department of Environmental Quality (NCDEQ).
WHAT DOES SEWER CLEANING AND INSPECTION WORK ENTAIL?
Sewer cleaning is primarily conducted through hydro-jetting. Hydro-jetting is a sewer cleaning process that utilizes a low volume of water under high pressure. This is a standard industry approach designed to scour the walls of underground pipes, removing potential obstructions (e.g., grease, roots, sediment) from the interior of the pipe. Mechanical cleaning equipment is used as needed if hydro-jetting is not sufficient to properly clear the sewer line.
Once the sewer pipe segments have been cleaned, a robotic camera is sent underground for video inspection of each pipe segment. Crews observe the inside of the sewer pipes making digital notes via computer attached to the camera to assess and rate each segment's condition. This inspection data is then entered into the City’s asset management system with a "score" based on the condition, which allows the City to schedule pipe maintenance, repairs and replacements as necessary. The assessments are made consistent using the Pipeline Assessment Certification Program (PACP) rating system, which is standard practice in the industry. Sonar equipment is used on large diameter sewers to assess the condition of the pipe below the water surface.
HOW LONG DOES IT TAKE?
Cleaning and video inspection each pipe segment can take from a few hours to a few days. Parking and traffic impacts will be minimal in the area, with appropriate controls and signage in place. A map showing the anticipated cleaning and inspection schedule is provided below. Door hangers in English and Spanish will be distributed seven days prior to any work anticipated in your area.