Need for Sanitary Sewer Inspections

Authored by Robert Brandom, P.E., Water Resources Project Manager

Cities and agencies are often in need of rehabilitating and upgrading their sanitary sewer collection system. To start the process, they need to know the condition of their system and where major defects are located.  A comprehensive inspection can reveal details about the system’s current condition. The key components of a collection system that should be inspected are:

1. gravity-flow sewer pipes
2. manholes that join connecting sewers and provide entryway into the system
3. lift stations that pump pressurized flows from lower elevations to higher elevations in the system
4. force mains, which are pipes that transport pressurized flow from the lift stations.

Defect Impacts
Sewer and manhole defects can undermine the integrity of the sewer system infrastructure, can allow wastewater to exfiltrate into the soil and groundwater, and can allow excessive rainwater in the form of inflow and infiltration to enter the sewer leading to potential overflow conditions.

Sewer structural defects include cracked pipe, broken pipe, and offset sewer pipe connections that leave large gaps.  Sewer operation and maintenance (O&M) defects including heavy roots and grease deposits can lead to sewer blockages that can then lead to overflows.  Manhole structural defects include corroded and broken manhole lids and frames, and deteriorated manhole walls.  Manholes located in storm water drainage pathways can provide a pathway for rainwater to enter the sewer system. 

Inspection Process
There are different types of inspection processes that provide insight into the condition of a system. 

Companies can videotape the sewers using closed circuit television (CCTV). They log the video footage in a report, rating the defects observed consistent with a nationally-accepted ratings scale for sewer defects.  The cost is approximately $0.65 to $0.80 per foot of pipe and depends on the diameter of the pipe. 

Manholes can be field inspected.  Digital photographs are taken and an inspection form is filled out to report manhole characteristics and defects. Manholes can be inspected for approximately $40 to $50 per manhole.

Lift Stations can also be inspected in the field to report age, condition, and operations defects associated with the pumps, motors, piping, building, mechanical equipment, and electrical and instrumentation controls.  The cost to inspect a lift station is dependent on the size and type of station.

Force mains, like sewers, can be videotaped (and at the same unit cost.)  Older metal force mains were not lined to help prevent corrosion. Corrosion, in the form of tuberculosis, encrusts the inside of the pipe over time, which reduces the pipe diameter and increases the work load on the pump.

Jack & bore operation during construction for the sewer capacity relief project in Yorba Linda.

After the Inspections
After the inspections are conducted, the deficiencies need to be assessed and prioritized for improvement. Improvement projects then need to be developed, cost estimated, and ordered within a capital improvement program.  Hall & Foreman’s Public Works Division is ready to help cities and agencies improve their sewer collection system infrastructure.  Contact us at info@hfinc.com to learn how we can assist you.