Fargo, ND – Sanitary Force Main

Challenge

The City of Fargo had been experiencing rapid growth in the southern part of the city and this growth was expected to continue. The waste water from the southern part of the city had been flowing northward to the city’s waste water treatment plant, via a pipe known as the west side interceptor, which had reached its capacity. The city needed a 36-inch PVC force main with a design capacity of 33 million gallons per day. To avoid having to construct a second waste water treatment facility, the city decided to have this force main flow to the existing treatment plant. The project required considerable coordination with utility companies and property owners.

Solution

This project entailed installing approximately 15,000 feet of 36-inch force main, through a developed part of the city. The force main had to be routed three times across storm sewer Drain 40, which is approximately 13 feet deep and over 100 feet wide. The force main also had to cross two railroad crossings, various city streets, including U.S Highway 10, which is a six lane road with heavy traffic. Boring of 54-inch steel casing pipe was done at three separate locations. The force main crossed eleven streets. Detour plans were created for each street crossing.

Ductile iron fittings, 36-inches in diameter, were used at bends. Restrained joint pipe was used to handle thrust forces at bends, wherever possible, to avoid the use of massive thrust blocks.

Moore Engineering performed a force main evaluation and transient analysis to determine pipe design and vacuum – air release structure locations. Provided all the easement and permanent right-of-way documents for the project. 14,800 lineal feet of 36-inch diameter PVC pipe with restraints was installed.

Project Outcome

All of the sanitary force main was installed by November 30, 2009. All pressure testing was completed in the spring of 2010, along with lift station testing. The system was placed in operation in the spring of 2010. Some of the city’s sewage flows were diverted to the Anderson Lift Station to remove some of the flows to the West Side Interceptor.

The final construction costs were 19 percent lower than the projected construction costs.

The timeline goal of having the force main installed and successfully pressure tested prior to the completion of the Anderson Lift Station was met. The city wanted the force main installed prior to 2010 so that the Anderson Lift Station could be tested in the spring of 2010. All goals were met.

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