Tempe Town Lake is one of Arizona’s most popular urban outdoor destinations. More than two million people visit the location each year to boat, fish and attend concerts, firework shows and a variety of festivals.
It is also one of the fastest growing urban areas in the U.S. Therefore, the Tempe Town Lakes sewer system needed an upgrade to support the growing population. Since this was an environmentally sensitive and public location, the construction site required careful attention.
When the sewer rehabilitation project contract was awarded to a major trenchless technology contractor, Rain for Rent was chosen to provide equipment and service solutions for the bypass-pumping portion of the project.
Scope of project
The project required a complete high-flow bypass system consisting of pumps, piping and service technicians. Rain for Rent provided 111,000 ft of approximately 21 miles of 20-to-24-in. HDPE pipe to bypass the existing sewer lines that ranged in diameter from 15-to-56-inches.
The six pump stations required 12 DV-300i, 12 in. pumps, eight DV-400, 16 in. pumps, two DV-350, 14 in. pumps and five DV-150i, 6 in. Power Prime pumps. The stations also required two automatic-start Flygt submersible pumps, complete with portable generators. Sound attenuated pumps were used near noise sensitive residential areas.
Rain for Rent’s Engineering Team designed a bypass pumping and piping system to handle the maximum flow rates projected by the city with a built-in safety factor. This system successfully bypassed a peak flow of 85 mgd with a maximum designed capacity of 110 mgd.
The project contractors, vendors and engineers diligently worked individually and as a team with the construction manager during the pipe inspections, which lasted over two weeks.
Project challenges
One of the many pumping challenges involved a deep manhole with a 37 ft suction lift. Vacuum prime pumps cannot function with a suction lift this deep, so Rain for Rent designed a solution with an automated submersible pump system, complete with float controls and powered by two large generators.
Another problem stemmed from unforeseen groundwater fluctuations, which caused an 18 ft deep suction pit’s groundwater level to rise within 10 ft of grade.
However, these various pumping challenges were successfully overcome and the project was completed on time.
