Sewage infrastructure conveys sewage or runoff, including melt water, rain and stormwater. It ends at the point of entry into a sewage plant or when the sewage is discharged into the environment. The components of sewage infrastructure primarily consist of pipes, but they also include manholes, pumping stations, storm overflows, receiving drains and screening chambers. Sewage systems may be classified into gravity and sanitary sewers. Gravity sewers include simple sewers, combined sewers and storm drains, where sanitary sewers consist of effluent sewers and vacuum sewers.
An effective maintenance program is essential to the operation of a sewage system. The potential deficiencies of a poorly maintained system include infiltration/inflow (I/I), sanitary sewer overflows (SSOs) and stoppages. Successful sewer infrastructure maintenance consists of the following phases:
Sewer Infrastructure Cleaning
Cleaning sewer infrastructure requires forcing pressurized water through sewer lines, commonly known as hydro-jetting. This process removes remove any accumulated solid debris, typically grease, roots and scale. Roots often require additional measures such as mechanical removal via root saws and chemical treatment to inhibit future growth. The combination of these methods is highly effective in reducing stoppages caused by roots when performed on a regular basis.
Each infrastructure component should be cleaned about once every five years, although areas with a history of problems may require more frequent cleaning. Maintenance crews should note the cleaning dates for each component for later entry into an asset management system. They should also note any deficiencies in sewer systems at this time.
Sewer Infrastructure Inspection
Maintenance crews often use video cameras to perform the routine inspection of sewer systems. They typically look for pipe defects such as obstructions, excessive deposits and obstructions. They also note the location of the defect and its appropriate service address. An inspection may be necessary to identify the cause of a stoppage, which should also include a second inspection after removing the stoppage to assess the condition of the pipe. Some systems may require specialized contractors to inspect them, depending on the size and nature of the component.
Municipalities should require video inspection of new sewer lines prior to final acceptance, usually after they’ve been installed for at least 30 days. This inspection should occur after completing specific tests such as those for air, pipe deflection, joints and general visual inspections. The primary purpose of the final inspection is to ensure the lines have been installed according to specifications and are free of construction defects. It also establishes the baseline of the sewer system, which future inspectors can use as a basis of comparison.
Sewer Infrastructure Assessment
An asset management system should store the data that crew members collect during the cleaning and inspection phase of sewer maintenance. Analysts can then use this data to assess the overall condition of a sewer system’s infrastructure, especially pipes and manholes. They can also use these results to optimize the cleaning and inspection schedules in addition to identifying needed repairs and rehabilitation. Visual inspections typically provide the basis of assessment for surface facilities and manholes, but they can also indicate where video inspection of these components may be warranted.
Most of the assessment data for sewer lines comes from video inspections, since technicians can’t visually inspect these components. Analysts can use the information on pipe conditions to direct maintenance strategies for both the long and short term. These strategies may include cleaning, replacement and rehabilitation.
Sewer Infrastructure Repair
Sewer infrastructure tends to deteriorate more rapidly than other types of construction due to their severe operating conditions. Physical damage due to cracks, joint displacement and root intrusion can all lead to significant leakage of a sewage system, resulting in greater risk to public health. Hydrogen sulfide (H2S) is a major component of sewer gas, which can corrode sewer components.
The application of a cementitous material is one of the most common types of sewer repairs, although this option requires particularly good best practices due to the presence of water. The methods of applying cement material onto a substrate can be classified into low-pressure wet spray and high-pressure dry spray techniques. Low-pressure wet spray is the most common due to the small amount of material that it loses. However, high-pressure dry sprays can rehabilitate concrete structures quicker and apply thicker layers of material with each pass.
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SoftDig provides a complete range of Subsurface Utility Engineering (SUE) services, including sewer infrastructure maintenance. Contact us today to learn more about how we can help you with your underground utilities.