Working Together: Case Study; Replacement of a Combined Force Main Serving Multiple Municipalities

North Cornwall Township (North Cornwall) is a growing municipality in central Pennsylvania. North Cornwall is responsible for the operation and maintenance of the Dairy Road Pumping Station (PS) which conveys wastewater flows originating from four separate municipalities to the City of Lebanon wastewater treatment plant (WWTP). Wastewater flow is conveyed from the Dairy Road PS via a combined force main which serves both the Dairy Road PS and the nearby Cleona Boulevard PS. Although the Cleona Boulevard PS is operated by a neighboring municipality, North Cornwall is responsible for the maintenance of the combined section of the force main as a stipulation of an intermunicipal agreement. The combined section of the force main consists of approximately 2,000 feet of 14-inch diameter ductile iron pipe. Since July 2004, the pipe has sustained five (5) breaks within the combined section. As the result of two breaks in March 2007, North Cornwall initiated design to replace the force main. Testing completed on excavated pieces of the force main indicated that the pipe was deteriorating from both the inside and the outside due to the corrosive composition of the local soils. During the preliminary stages of the design, numerous technical and political issues were encountered. Three significant issues encountered were sizing the force main, choosing the preferred replacement alternative, and cost sharing. Developing flow projections for the new force main involved multiple meetings between the four municipalities and involved legal interpretation of the numerous intermunicipal agreements. Two primary alternatives were established; replacement of the force main with a similar alignment, and separate the stations utilizing two parallel force mains. Two municipalities preferred the separation alternative to; however, this alternative had significantly higher costs. The other two municipalities preferred the less expensive alternative of a new combined force main. Value engineering, to reduce the estimated cost of the parallel force main alternative, included evaluation, of trenchless lining of the existing pipe to serve as one of the parallel lines.