Sanitary Sewer Rehabilitation Program

The sewer rehabilitation process involves placing a liner into the sewer, inflating it to fit the shape of the existing sewer and then hardening it into a new solid pipe inside of the existing one. The process costs about a quarter of the traditional approach of excavating and replacing the old pipes with new ones, and it takes about half a day, instead of multiple days, to complete.

Do not dispose of any water via your indoor plumbing during construction. This includes most indoor plumbing fixtures such as toilets, sinks, bathtubs, showers, dishwashers, washing machines, floor drains, etc.

Do not use any more water. Although your sewer service is blocked during the liner installation, there is typically sufficient storage in the service to accommodate accidental toilet flushing or hand-washing without causing a backup. If you used a lot of water, such as by taking a shower or running the dishwasher, check the floor drains or bathroom on your home’s lowest level for signs of a backup.

If you have concerns regarding tenants using water during the installation process, please contact the Utilities Division at 303-441-3200. Arrangements can be made to shut off the water supply to the building during the installation process.

Homeowners are responsible for their sewer services from the home all the way to and including the connection to the city main in the street. The city’s work only rehabilitates the city’s main sewers and will not impact or address any issues with your home’s sewer service. Local plumbing companies can use the same lining technology the city uses, which can represent a significantly cheaper alternative to replacing sewer service.

The city continuously inspects its sewer system for structural defects using a robotic camera. Approximately 70% of Boulder’s sanitary sewers were constructed in the post-World War II period using clay pipes. Over time, factors such as shifting soils or heavy traffic loads can cause these clay pipes to develop cracks and defects. The last inspection showed that the sewer serving your building had sufficient structural defects to warrant installation of a liner.

The Utility Division’s Sanitary Sewer Rehabilitation Program is funded by wastewater use rates paid by Boulder residents and businesses. In 2014, City Council approved a 30 percent wastewater rate increase to expedite rehabilitating the city’s aging sewer infrastructure. This additional funding will allow the city to rehabilitate or replace its clay sewers over a 20-year period versus the 100-year period allowed by previous funding levels.

The rehabilitation work is completed using a unique trenchless technology that does not require any excavation.

• Step 1: Cleaning - Crews clean the pipe with a high-pressure jet hose and remove any debris that has accumulated in the line. Debris is then vacuumed out of the system and taken to a landfill.
• Step 2: Inspection - Crews use a robotic CCTV camera to inspect the line and identify if it is ready for the liner to be installed. This process also identifies the location of all service connections on the line so they can be reinstated after the liner is in place.
• Step 3: Bypass Pumping - The process requires that the sewer main be dry, so crews use bypass pumps to allow users upstream to remain in service. Bypass pumps are set at manholes upstream and discharge further downstream from the main being rehabilitated.
• Step 4: Liner installation - A spool of PVC pipe is warmed up, making it malleable enough to pull into the old sewer main, or “host pipe”. The pipe is then blown up with compressed air to fit tightly inside the host pipe. Once the new line has cooled, it is a fully structural “pipe in a pipe”. The installed liner is then checked for defects with a camera prior to reinstating service connections.
• Step 5: Service Reinstatement - After the pipe has cooled and inspected, a robotic cutter is placed into the main and driven to the location of each service connection. This cutter opens a hole in the same location of the original tap, allowing the service line to return to operation.
• Step 6. Final Inspection - Following the tap reinstatement, the newly lined pipe is inspected with a CCTV camera and documented to verify the quality of the installation and provide a record of the completed product.