New Force Main Ensures Wastewater Treatment Reliability

Existing force mains in service for 37 years

January 31, 2003

HDPE pipe being inserted into abandoned 60-inch sewerline.
A new $2.2 million raw sewage force main is currently under construction at the Salt Lake City Water Reclamation Plant.  The project was designed by Boyle Engineering, and the construction contract awarded to Gerber Construction Company.  The work is scheduled for completion in October 2003.

The new main parallels two existing mains that run from the main sewage pump station to the 56 million gallon per day capacity advanced secondary wastewater treatment plant. The two existing force mains have been in continuous service since 1965 and have never been inspected to determine their condition.  There have been several repairs made to the existing concrete force mains, according to wastewater manager Jon Adams. “We have no idea of the physical condition of the two existing mains after conveying an estimated 500 billion gallons of raw sewage,” said Adams.  Taking the existing force mains out of service has been impossible until the new force main is in place.

The length of the force main is approximately 3600-feet.  Fourteen hundred feet of pipe is to be buried directly.  The remaining 2200-feet is to be slip-lined into an existing 60-inch concrete sewer pipe that runs adjacent to a canal. Originally built in 1915 to convey raw sewage to the city’s treatment ponds, it was abandoned in 1965 when the new reclamation plant was built. The slip-lined portion is to be completed with HDPE pipe with an outer diameter of 54-inches.  “The existing concrete pipe was used to cut down costs by not having to trench for this reach of the new force main,” notes Adams.

According to reclamation plant engineer Ronielle Peltier, slip-lining large diameter pipe is challenging because many things can go wrong during the process.  Fortunately the slip-lining portion of this project was completed in a short period of time and conditions were very favorable.

Besides enhancing the reliability of the plant, the new force main will also allow peak flows up to 140 million gallons per day to be conveyed to the treatment facility during extreme wet weather events.

Once the new force main is in service, the old ones will be taken out of service and manholes cut into the concrete pipe. The old force mains will be inspected and repairs made to bring them up to standard. The completion of this work will greatly improve the reliability of the existing sewage pumping and conveyance system.