Prioritize Needs for Sanitary Sewer System

A well-performed sanitary sewer evaluation study (SSES) provides owners with valuable information to enhance their asset management databases. Multiple tasks are accomplished when an SSES is performed.

These include:

• Establishing an inventory of the system. By collecting information such as diameters, elevations, materials and conditions, a baseline to begin assessing the entirety of the system is created.
• Using smoke and dyed-water testing or CCTV review to identify structural defects that could allow for rainfall-induced inflow and infiltration (I/I) to enter the sanitary sewer system.
• Identifying high I/I areas of the system based on flow monitoring results. Flow monitoring is used to determine average daily dry weather flow (ADDF), which establishes the amount of I/I entering the system with accurate accompanying rainfall data.
• Using flow monitoring data to determine pipe capacities, identify system restrictions and run predictive system-wide models.

Compiled together, this information can be fed into a GIS database for future referencing, planning and rehabilitation. Any asset—from manholes and inlets to sewer line segments and siphon structures—found during an SSES can be a part of an asset management program.

“An asset management program draws its strength from the completeness of its inventory, so it is imperative that an owner has as much knowledge of their system as possible,” said Daria Sakharova, a civil engineer in GBA’s Omaha office. “Nothing is ever too small or too trivial to note, and missing information can actually have detrimental effects.”

Over the last ten years, GBA has performed SSES services with the City of Omaha, Nebraska. This partnership began with a complex manhole inspection project. Because these manholes have high concentrations of hydrogen sulfide gas, which is a product of sanitary sewer waste and deadly to humans, it was crucial for the city to pick a partner that could accomplish these inspections safely. GBA’s experience using self-contained breathing apparatus (SCBA) equipment to perform inspections, along with years of experience in the sanitary sewer industry, positioned the team well to help the city.

Since partnering with Omaha, GBA has completed 23 projects in various portions of the city’s system. These projects focused on discovering the current state of assets and which assets were critical to system performance.

GBA used a wide variety of technology when working on the city’s SSES.

This includes:

• Remote inspection equipment, like Panoramo and 360-degree video cameras, was used for manhole inspections.
• SL-Rat, an acoustic inspection system and laser profiling were used to determine pipe degradation and scour in sewer line assessments.
• Tablets that collected smoke-testing results, which feed directly into GIS databases and remove the need for pen-and-paper forms.
• Remote-controlled cars and boats with cameras that inspected pipes with standing water or other obstructions.

“It has been fun to come up with new ways to use technology to get the job done,” said Sakharova.

By working on these projects, the GBA team has gained extensive experience that will inform decisions on future projects. For example, Sakharova explained that every city’s sewer system is unique, which means what works in one area may not be applicable in another. Because of this, a project team should do trial runs on everything before moving too quickly.

Another important takeaway that the project team learned was the importance of establishing clear communication pathways. Asset management involves many different departments and divisions of a municipality. When working with the City of Omaha’s staff, GBA worked to understand each group’s goals and communicated progress so everyone could be on the same page.

When municipalities hold budgeting sessions, sanitary sewer improvements are often overlooked because there is a lack of reliable data to drive these discussions. GBA and the City of Omaha have identified how important this data is to build a case for these projects. Ultimately, these improvements promote the health and safety of our populations. Without establishing holistic solutions to a system-wide asset management program for sanitary sewers, directives cannot be made for future improvements or developments.

Partnering with a city to establish these programs has long been a passion and primary business for GBA.