Effective Alternative to Open-cut
- Shorter time
- Fewer resources
- Less mobilization
- Minimum surface impacts
- no asphalt patching
- no flowable backfill
- no mill & overlay
- less traffic control than open-cut
Benefit-Cost Analysis
- Many variables to consider
- Excavation equipment, shoring, labor
- Pavement restoration & striping
- Traffic control
A Better Way To Fix Sewer Sag
In many cases, a pipe that is suffering from sewer sag, can be fixed without excavation. The ideal situation for using trenchless technology:
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- squeegee or granular bedding
- flexible pipe: pvc & hdpe
- 8” – 12” diameter
- where groundwater is present
- away from upstream manholes
- areas with clear cost-benefit
- paved areas
- utility conflicts
- high traffic areas
- deep excavations
Main Causes Of Sewer Sag & Bellies
- Over-Compaction / Localized Loading
- Insufficient / Improper Haunching
- Pipe Manufacturing Abnormalities
- Disturbance at Service Connections
- Settlement of Underlying Utilities
- Changing Ground Conditions
- Deterioration due to Age
Sewer Sag & Bellies In Gravity Sewers
- Relatively common problem in most municipalities and sewer districts
- Solids drop out when velocity drops below 2.0 feet/second
- Decreased profitability to contractors
- Increased maintenance costs to owners
- Property damage to users
Correct Flow
Pipe With Sewer Sag – Disrupted Flow
How It Works
After a sag or “belly” has been identified, a pre-fix survey of the pipe is conducted to identify the depth and length of the sag(s). With someone safely inside of the manhole, the three pieces that make up the sag removal machine are lowered and installed inside of the pipe. Once assembled, the device is winched into position and then operated pneumatically by an air compressor and hose. Pressure is applied to the legs, pushing the machine into the crown of the pipe over the belly. Vibration is then applied to cause the surrounding bedding to migrate around and underneath the pipe to pick up the belly. The machine is worked thought the pipe and the process is repeated until the bell has been removed.