Article of Interest

Sewage Force Mains — A Forgotton Asset

With growing interest in managing infrastructure assets in a sustainable manner, wastewater utilities are investing in asset inventory and assessments. One component of wastewater systems that is frequently overlooked is pump station force mains.

Unlike gravity sewers, force mains are difficult to access and visually inspect. As a result, force mains are often operated until failure with devastating results. Force mains are among the more critical assets, in that there is often no redundancy, and failure can translate to overflows, environmental impacts, major disruptions of service and costly repairs.

There are many types of force main problems that can compromise level of service, or worse, cause failure. Some of the more common problems include:

• Internal erosion of cement coatings and cement based pipe
• Internal pipe corrosion from sulfides
• External corrosion from aggressive soils
• Reduced capacity due to corrosion and/or tuberculation of iron pipe
• Air binding problems
• Water hammer / surge pressure problems
• Disruption of pipe bedding support from adjacent construction activities or erosion
• Accumulation of grit and/or grease
• Variety of issues related to installation
• Variety of issues  related to design
• Variety of O & M related issues

Given the criticality of force mains, utilities should have a strategy for assessing this important class of assets and for maintaining long-term reliability.

Wright-Pierce has been involved with numerous force main investigations and rehabilitation projects throughout New England. We utilize many of the unique tools to efficiently assess these difficult to access assets. We also have extensive experience with emergency repair of failed pipe lines.