Featured Video: Sewer Dye Testing

A municipal sanitary sewer system is designed to collect and transport wastewater from homes, offices, businesses, restaurants and other sources to a municipal wastewater treatment plant for treatment and safe discharge into the environment. If other sources of water are allowed to enter the sewer system, the collection system and wastewater treatment plant can become over loaded allowing untreated water to be discharged. This is defined as sanitary sewer overflows, or SSO’s. One of the biggest sources of excess water is infiltration of storm water and groundwater into the sanitary sewers. A method to detect this infiltration is through dye testing.

Dye testing is a simple procedure where storm drains, yard drains, and the outside of the foundation walls of the house, or other areas are flooded with water to simulate a period of heavy rainfall. The colored water is pumped through the ground and storm water system and appears in the sanitary sewer collection system where leaks occur. This test is simple and complements smoke testing that may have been done previously.

The dye testing procedure can be accomplished in the following steps.

1. Isolating a section of the storm water network to test by plugging pipes at specific locations. 
2. Then, bright-dyed water is pumped into the storm water network until it reaches capacity. 
3. Remote CCTV cameras are deployed into the sanitary sewer system, where any points of storm water ingress are highlighted clearly by the dyed water.

Once the testing is completed, the locations of these sources of infiltration makes the process of repairing these leaks far more straightforward facilitating effective piping and system repairs which keep infiltration to a minimum.

A video showing how dye testing can be carried out is shown below:

Managing Sanitary Sewer Overflows (SSOs)

The U.S. EPA estimates that approximately 23,000 to 75,000 sanitary sewer overflows (SSOs) occur in the United States each year. An SSO is defined by the release of untreated sewage into the environment through an overflow, spill, basement backup, or unpermitted discharge before completed treatment at the sewage plant. These overflows can degrade water quality, cause property damage, and pose serious threats to public and environmental health due to the release of harmful pollutants, disease causing microorganisms, metals, and nutrients into the environment. 

Section 301 of the Clean Water Act prohibits the discharge of pollutants to any Water of the United States from a point source without a National Pollutant Discharge Elimination System (NPDES) permit. To address compliance challenges associated with SSOs, the EPA recently completed a National Compliance Initiative that first began in 2000 to reduce the discharge of raw sewage in national water ways.

SSOs occur through debris or grease blockages, root intrusion, vandalism, inflow and infiltration, improper design, aging infrastructure, operational mistakes, and structural, mechanical, or electrical failures. Typically, the most frequent culprit takes the form of blockages. After an overflow, clean up and response is not only expensive, but traumatic for the impacted communities.

In Queens, NY a sewage backup on the Thanksgiving holiday weekend of 2019 flooded the basements of approximately 100 homeowners creating a putrid odor and exposing the community to harmful pathogens. Liability for residential damages and repairs to the pipe was projected to reach millions of dollars.  The culprit for the backup? While operators initially theorized a grease induced fatberg was to blame, investigation later revealed a collapsed sewer pipe instigated the SSO.

In New England and around the country, many communities maintain collection systems of 100 years old or more. Aging infrastructure exacerbates SSO prevention challenges. As years of wear on system equipment increases, the likelihood of mechanical or electrical failures as well as the opportunity for inflow and infiltration increases. Pipe deterioration due to natural freeze-thaw cycles, environmental conditions, water flow, and water chemistry can also increase the likelihood of structural failures. When this deterioration is not routinely inspected and maintained, resulting failures will only add further hydraulic stress to the system.

The frequency of SSOs can be reduced significantly through preventative maintenance and the implementation of an appropriate asset management program. To upgrade your preventative maintenance program, an article from the March 2017 Kansas Lifeline discusses the basics of lift station maintenance. The Georgia Association of Water Professionals provides a more comprehensive guide of collection system maintenance practices in its 2016 guide Wastewater Collection System Best Management Practices.

Developing an asset management program will allow systems to plan for the replacement or rehabilitation of aging pipes, pumps stations, valves, manholes, and collection system infrastructure. During program development systems can predict and plan for population changes, capacity objectives, equipment deterioration, and more. To encourage proper asset management of collection systems, the EPA developed the CMOM program. CMOM stands for Capacity, Management, Operations, and Maintenance.  The information-based management approach encourages dynamic collection system management through the prioritization of activities and investments. Utilities can access how well their current practices meet the CMOM framework using this Self Assessment Checklist and the EPA Evaluation Guide for CMOM at Sanitary Sewer Collection Systems. Follow up this evaluation by integrating CMOM best practices into a new or updated asset management program using this blog post.

Even with the implementation of these programs, systems should still prepare for the event of an unexpected overflow. As in Queens, NY, preventative maintenance and asset management did not stop the SSO on the Thanksgiving weekend. Systems must be prepared to respond swiftly with a Sanitary Sewer Overflow Response Plan. These emergency response plans will limit potential damages and reduce community distress. By combining preventative maintenance, asset management, and emergency response planning, systems can ensure that their community and its environment have the best protection from SSOs.