Sewer Cleaning & Inspections: Why are they important

Sewer Cleaning & Inspections: Why are they important
November 19, 2021

Performing routine cleaning and inspections of a sewer collection system optimizes infrastructure performance, planning and spend

As time passes, Ontario’s sewer systems face increasing pressures from the growing population, ageing infrastructure, and the unpredictability of climate change. Together these factors can put great strain on a sewer system’s performance and can lead to capacity issues and asset deterioration and/or damage over time. Many of these sewer systems are also predisposed to experiencing backups, sinkholes, seepage, sewage overflows or flooding that can affect neighbouring roads, homes, businesses and environments (lakes and rivers). Such occurrences can put people’s health, property, and utility owners’ budget spending at risk.

The misfortune of underground sewer infrastructure is that it is out of sight and out of mind when it comes to spending priorities. Operational and structural defects like a blocked or damaged pipe somewhere in the sewer system can remain unknown until a serious problem occurs. By performing routine sewer cleaning and inspections, utility owners take proactive and preventative measures that help ensure system performance levels are always met, budget optimization materializes over the asset’s lifespan, and liability claims are mitigated if not eliminated.

Informative Image showcasing results from a study conducted by the American Society of Civil Engineers in 1998 that identifies top activities in a successful sewer maintenance program. The table highlights each activity and the average frequency of use (% of system/year). The table lists Cleaning at 29.9%, Root removal at 2.9%, Manhole inspection at 19.8%, CCTV Inspection at 6.8% and Smoke testing at 7.9%.

According to a study conducted by the American Society of Civil Engineers (ASCE), the most important activities in a successful maintenance program are sewer cleaning and CCTV (Closed Circuit Television) pipe inspections. Table 2 shows the average frequency of these various activities.

What Is Sewer Cleaning?

Sewer cleaning is the process of removing built-up, unwanted materials like trash, debris, cooking oils, grease, and roots that have made their way into a sewer system. It helps keep the sewer system clean and clear, promoting efficient water flow.

Most sewer cleaning occurs as part of a routine maintenance program. Other times sewer cleaning is performed in response to an emergency callout resulting from an overflow, blockage, or damaged sewer mainline, catch basin, culvert or lateral.

How Are Sewers Cleaned?

While there are several technologies used to clean sewer blockages and act as a preventative maintenance tool, hydraulic cleaning methods remain the most commonly used to date.  They use water and water velocity to clean the internal walls of sewer pipes. The most effective and safe, chemical-free process that prevents damage to pipes is hydro jetting.

Hydro jetting, also referred to as jetting or flushing, uses high-pressure water propelled through a hose and out a specialized nozzle to clean and break down debris and grease build-up.  Water pressure is typically strong enough to clear blockages, cut roots within pipes and push debris towards a chamber for vacuum removal.

Jetting nozzles come in a variety of forms from static to rotational to specialty hydromechanical nozzles. Using the right nozzle has a significant impact on cleaning success. Consideration must be given to the type of pipe being cleaned (pipe material, size, and condition) and the project factors related to the pipe, such as the type and extent of blockage or fouling that needs to be removed, and whether the focus is on cleaning or simply removing a blockage.

How Often Should A Cleaning Be Performed?

Informative image showcasing a jetting nozzle attached to a hose, which is about to enter a storm sewer drain to conduct a sewer cleaning.

Timing for sewer cleaning varies and is dependent on the age of the infrastructure, location, pipe construction material, subsurface conditions (depth to groundwater, depth to bedrock, soil properties, etc.), and other variables. Even the quantity and type of equipment needed, availability of trained technicians, and the amount of the sewer network that needs cleaning will be key consideration factors that help define the frequency of sewer cleaning activities.

There is no one-size-fits-all plan. Each utility owner must determine what constitute an effective cleaning frequency plan for each of their specific systems. However, performing CCTV inspections will certainly help with deciding how often any particular section of the system should be cleaned based on historical issues.

What is a CCTV Sewer Inspection?

A CCTV sewer inspection refers to the process of using a camera to see inside buried pipelines and assess the conditions of a sewer network. This can include blocked, broken, clogged, collapsed, corroded, cracked, and disjointed pipes. These conditions are recorded, scored and documented by highly qualified technicians to help utility owners prioritize repairs, rehabilitation, and operation and maintenance (O&M) activities to keep their sewer systems functioning properly.

CCTV sewer inspections have come a long way with the National Association of Sewer Service Companies (NASSCO) standards and the vast improvements in technology, leading to standardized data collection and high-quality reporting on conditions.

How Are CCTV Sewer Inspections Performed?

CCTV sewer inspections can require several different tools depending on the field conditions and the size of the pipe being inspected. They include tractor-mounted CCTV cameras and push cameras.

Informative Image showcasing a robotic crawler with pan and tilt camera about to enter a manhole to conduct a sewer inspection..

Tractor Mounted CCTV Cameras: This technology consists of CCTV cameras and accompanying lights mounted on robotic crawlers that are connected to a remote control and a video monitor. The crawler is inserted into the sewer mains, and as it progresses through the network of pipes, the CCTV takes footage (video and/or photos) and relays it to the monitoring computer systems. These CCTV crawlers come in a wide variety of configurations (lateral launch, pan and tilt, etc.) They are capable of navigating bends and curves in the pipeline, and can accurately capture the internal conditions of pipes (big or small).

Push Cameras & Electromagnetic Sonding: To navigate smaller diameter pipes, the push camera can be inserted into a pipeline manually and pushed, using the sturdy cable, into the line. Because the camera is equipped with an electromagnetic sonde, the horizontal alignment of the sewer pipe can be verified and marked on the ground surface to identify the location of any areas of concern.

Before an inspection can be performed, a sewer cleaning is completed to ensure a clean, unobstructed view of interior walls, joints, cracks and other features can be captured properly by the high-quality CCTV video. It’s also necessary to remove debris that may block the travel pathway for robotic and push cameras during the investigation process.

It is important to note that cleaning a sewer system is a prerequisite of a CCTV sewer inspection, according to NASSCO standards and the Ontario Provincial Standard Specifications (OPSS) 409.

When Are Sewer Inspections Required?

CCTV sewer inspections programs are important and required for the evaluation of…

  • effectiveness of pipeline cleaning activity (post-clean inspection),
  • cause and extent of a blockage before remediation,
  • infiltrations and inflows into pipe systems,
  • pipe conditions in preparation for rehabilitation work,
  • construction of new or renewed pipes to ensure they meet specifications and to document as-built conditions,
  • conditions before a utility accepts ownership and responsibility of a new pipe
  • pre and post-construction activities above the pipe to ensure no damage occurs
  • changes in pipeline conditions (structural or O&M) over time, and
  • determine which pipes require repair, replacement or rehabilitation.

 As Benjamin Franklin once said, “An investment in knowledge pays the best interest.

Similarly, implementing a regular sewer inspection program will help utility owners keep a pulse on the current conditions of their assets. The information from each inspection can be used to adjust cleaning and inspection frequency for critical and ageing assets, and aid in planning a maintenance strategy or capital improvement program.

Proactive Sewer Cleaning and Inspection is Smart Business

As Ontario sewer systems age, deterioration, blockages, overflows and collapses become a major concern. With population growth and more frequent and severe storms (climate change) gnawing at its heels, these issues will exacerbate, making sewer planning and resilience increasingly important. Performing routine sewer cleanings and inspections enables utility owners to stay ahead of the curve, optimizing the performance level of their sewer systems and budget spending over the long term.

Every dollar spent on a sewer cleaning and inspection builds value and provides a healthy return on investment. It helps utility owners effectively identify and prioritize maintenance needs and improve long-term infrastructure plans, reduce emergency repairs, mitigate risks of environmental damage, and avoid exposure to liabilities such as claims related to health, safety, property damage, and water quality.  It also supports compliance with local regulations including the Ontario Water Resources Act and the Environmental Protection Act, and potentially lower insurance costs. That is what we call money well spent.

 

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