Sewer System Improvements

Sewer System Evaluation and Improvements

Weston & Sampson was selected by the City of Lebanon to evaluate and recommend improvements to its 14,000-foot sewage pressure pipe, which had experienced sewage overflows. The system was designed and constructed in 1986 to serve Lebanon and the Town of Enfield, and to protect the water quality in the lake. The system, which transports sewage from the Enfield Village to the Lebanon sewer system, includes an elaborate network of sewer collection infrastructure in the village area and along Route 4A, four wastewater pump stations (three in Enfield and one in Lebanon), and a pressure pipe connecting the two sewer systems.

Weston & Sampson’s evaluation included:

  • Hydraulics assessment to ensure flow conditions sufficient to maintain flushing velocities in the pressure sewer, and evaluation of system hydraulics under both 40- and 20-psi set points
  • Inspection/evaluation of the existing air/vacuum release valves, and recommendations for their replacement and the for the location of an additional valve
  • Cleaning of the lower 3,000 feet of pressure main under the Mascoma River

It was suspected that due to the lowering of the control valve pressure to 20 psi, the flushing velocities were insufficient to thoroughly clean the pipe and the pipe was partially blocked at the low point. Montauk Services of Hackensack, NJ, was contracted to pig the pressure pipe. Pig launching and receiving stations were temporarily installed in the system and 10-inch foam pigs were sent through the pipe using an external pump system.


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