South Durham Phase III Hydraulic Model

Project Facts

The Department of Water Management is beginning a project to develop a hydraulic model of the sewer collection system which drains to the South Durham Water Reclamation Facility (SDWRF). As part of the model development process, survey crews will access large-diameter sanitary sewer outfall easements in order to perform survey and assessment activities. This survey activity began in November 2018 and will be complete in May 2019. Crews will also install hydraulic flow meters in 26 locations throughout the sewer collection system which drains to the SDWRF. These meters were installed in November 2018 and will be removed in May 2019. Crews will return to these sites frequently to perform required maintenance and calibration activities.

Analysis of the hydraulic flow meter data indicated the presence of large amounts of infiltration and inflow into the sanitary sewer system in a small sub-basin. In response, the Department of Water Management will begin smoke testing within the sub-basin shown in the project map. Please note – this smoke is non-toxic and does not leave stains or residue. It is comparable to substances more commonly used in fog machines for entertainment purposes. It appears white to gray in color and has a slight fragrance. It is NOT a fire hazard.

The smoke testing process involves directing smoke into a gravity sewer line via the manhole using an air blower. The intent is for smoke to seep through and assist to visually identify the locations of any holes, cracks, or other defects in the sewer line. Smoke could appear at any point in the system where there is an open break in the line, such as storm drains, sewer cleanouts, manholes, and roof vents. Smoke may also escape through homes, offices, yards, or anywhere poor plumbing exists. Smoke entering a home or building during this testing may indicate a problem with the plumbing. The City is not responsible for plumbing located on private property.

Water Management has partnered with Freese and Nichols and Hydrostructures to perform the testing. Hydrostructures recommends pouring a gallon of water into sinks, tubs, and floor drains not subject to everyday use. This will fill p-traps and help prevent smoke from entering the building. Occupants do not have to be present during testing.

This work is expected to begin mid-July. Door hangers will be distributed by the City’s contractor, Hydrostructures, seven days in advance of any smoke testing.