The Key Elements of Maintaining Sewer Infrastructure – Clean, Inspect, Assess and Repair
February 8, 2017
Let’s face it, sewers are susceptible to wear and tear just like any other infrastructure. Although not visible from the surface, pipelines are prone to deterioration from both the inside and out. To minimize costly emergency repairs, it’s important to maintain sewer systems. There are four key factors to keeping your infrastructure operating at optimum efficiency.
Debris, sediment, roots, calcite, concrete, foreign objects – all can cause havoc in a sewer pipeline. System owners need a crew of skilled operators who have the expertise to get those pipes cleaned properly and quickly, regardless of the conditions. Keeping sewer infrastructure free of obstructions is the first step to preventing downtime and emergency call outs. Proper cleaning is also required to permit a full view of the pipe interior when it comes time to make rehabilitation recommendations or perform repairs.
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Cleaning is misunderstood. The level of effort and equipment needed to clean sewers can vary significantly. One sewer might require a quick flush from a combination sewer cleaning machine and can be completed in minutes — while another sewer can take additional equipment and days of work. But they are often considered to be the same thing by owners and engineers.
Given the very large difference in effort needed to clean sewers, depending on what one means by that — it make sense for owners and engineers to recognize the nature of the work being requested of its contractors or field staff. The bottom line — what is the purpose of the cleaning?
- Flush — a prescribed number of passes with a standard sewer cleaning nozzle to reduce the likelihood of sewer backups and help identify potential sewers that require cleaning
- Clean to Inspect — water flushing, the mainstay of the municipal contract, typically performed on mass throughout sewer systems, mostly in small diameter, regularly maintained sewers that are easy to access and where CCTV work is likely to follow
- Clean to Assess — this includes robotic cutting, sump dewatering, flow control and video assisted reaming tools — often requires high pressure powered special tools working in tandem with a robotic cutting robot to permit a full view of the pipe to be obtained so that appropriate assessment can be made.
- Clean to Repair — this is the highest level of pipe preparation. It includes all of the steps from clean to assess plus removal of excessive calcite, sharp edges and verification of pipe diameter to permit rehabilitation to take place
- Inspect to Clean — often the preferred method in trunk sewers or difficult to access sewers where the cost to clean the sewers is orders of magnitude higher than the inspection cost. In these cases, it makes sense to triage of the lines through inspection so the extent of cleaning can be determined.
Detecting faults is not an easy task, so regular inspections are wise. Inspecting sewers requires advanced technologies that can navigate through and withstand hostile environments, as well as a contractor with an exceptionally high skill level in complicated, confined space entries.
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This is not an area where system owners should choose lower cost over experience. Specifications help, but the real goal is to ensure that you get an inspection performed by operators not just with PACP Certification — but with years of experience and a host of sensors appropriate to the job being requested (see image 2)
It’s important to ensure the integrity of sewer infrastructure, as damaged pipes are a hazard to public health and the environment. Beyond CCTV technologies, there are a wealth of multi-sensor tools that an experienced contractor can bring to bear to determine the extent of the problem. Electroscan, pipe penetrating radar, 3D lidar and sonar are just some the of tools available from a good contractor.
Owners will also want an experienced contractor that knows what repair methods are constructible and appropriate for the specific needs of the pipe, conditions of the work and the goals of the client. Context is very important in making the assessment. Does a localized repair make sense or is a complete line repair more appropriate? What type of repair is appropriate cured-in-place pipe (CIPP), grout, sliplining? Finally, what type of repair is constructible under the existing conditions? An experienced contractor can help.
Once a decision is made to perform repairs, the next choice is to determine the type of repair. The two basic choices are spot repairs or holistic repairs. No-dig spot repairs are a typical choice when the line is in good condition but has isolated areas in need of repair. Holistic no-dig repairs, like grouting of all joints in an otherwise structurally sound pipe or complete manhole to manhole where defects are present throughout the pipe are common remedies.
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In the case of engineered repairs, system owners will want to make sure they get an engineered design stamped by an experienced professional. In the case of non-engineered repairs, like grouting, owners will want to make sure the ASTM standards are followed.
Selecting the right repair for the right part(s) of the pipe is dependent upon a proper assessment. A proper assessment is dependent on getting a good inspection. A good inspection is dependent on cleaning the pipe appropriately.
Understanding that not all cleaning is the same is your first step, selecting a good contractor is the second step of the clean, inspect, assess and repair process.
Randy Kowal is the COO and Gord Henrich is the technology specialist at Robichad NODIG Sewer Solutions, a contractor specializing in trenchless no-dig sewer rehabilitation.