Read “Enduring the Elements” in the January 2017 issue of Water & Wastes Digest.
This article also appeared in PKG Company Connection.
Owner: The City of Bismarck, North Dakota
Project Summary: More than 6,800 cubic yards of structural concrete are being used in the construction of a new Trickling Filter and Trickling Filter Pump Station in Bismarck, North Dakota. These structures are being built well below the area’s water table, and the more than 6,800 cubic yards of concrete will protect them against the effects of Mother Nature.
One component of the project that is already protected against the elements is V-Bio wrapped and zinc-coated AMERICAN Ductile Iron Pipe. The zinc coating system is a proven, life extending product for iron pipe that recently became available in domestic markets. Zinc has been used overseas to extend the life of iron pipe for many years. V-Bio enhanced polyethylene encasement provides additional protection in aggressive soils.
“Ductile iron pipe was specified for the project due to aggressive soils in the area and the depth of bury,” said Ken Weber PE, senior project manager with AE2S. “Testing was done to confirm the corrosiveness of the soil, and V-Bio wrap was included in the specifications. Once we learned of the zinc coating, we also felt it was the right product for this application.”
“Because of existing soil conditions, the owner decided to add a measure of safety and longevity to the installation by using zinc-coated AMERICAN ductile iron pipe and V-Bio enhanced polyethylene encasement. PKG’s relationship with AMERICAN began the day we opened our doors in 1995, and since then we have completed several projects with AMERICAN at our side.”
The $21.9-million Bismarck Wastewater Treatment Facility Trickling Filter Improvements project includes the construction of a new Trickling Filter Pump Station and a new 150-foot Trickling Filter. The expansion will not only replace an aging pump station but will also provide the city with 50 percent more treatment capacity, allowing it to meet anticipated growth over the next 20 years and improve operational flexibility. The project began in October 2015 and is scheduled for completion in July 2017.
The project requires a substantial amount of subsurface dewatering in order to excavate at depths exceeding 40 feet. The ground water level in the area fluctuates with the elevation of the nearby Missouri River, and under normal conditions, the water level will range from 8 feet to 14 feet below the existing grade at the jobsite.
“Excavating at these depths presents a unique challenge for any installation,” said Darin Pfingsten, president of PKG Contracting, Inc. “With one end of the pump station bearing at a depth of about 44 feet below the existing surface, we elected to sub-cut the entire area to an elevation 15 feet below the surface. It is also at this elevation that a nearly 100-foot diameter cofferdam retention structure was installed, which consists of steel sheet pilings driven to a depth of 65 feet below the existing ground surface. A total of just under 21,000 cubic yards was excavated to complete the cofferdam structure.”
Key Players: The city of Bismarck’s wastewater plant currently treats an average of more than six million gallons of wastewater a day. Wastewater is collected from almost 18,000 customers and delivered to the treatment facility through a 290-mile network of pipelines.
PKG Contracting, Inc. is the general contractor on the improvement project and once complete, will have self-performed more than 70 percent of the work. Major work includes earthwork, site piping, cast-in-place concrete, helical piers, precast work, process equipment and process piping.
AE2S is providing engineering services for the project, including designing, bidding and providing construction management services.
What They Used: AMERICAN is providing approximately 2,000 linear feet of Class 250 Fastite and Flex-Ring® ductile iron pipe in sizes ranging from 24 to 48 inches.
What They Said: “Because of existing soil conditions, the owner decided to add a measure of safety and longevity to the installation by using zinc-coated AMERICAN ductile iron pipe and V-Bio enhanced polyethylene encasement,” said Pfingsten. “PKG’s relationship with AMERICAN began the day we opened our doors in 1995, and since then we have completed several projects with AMERICAN at our side.”
“AMERICAN’s products have been approved and installed on AE2S projects for years,” said Weber. “Jeff Blakely keeps us up-to-date on product changes, and he will ask questions about what we are trying to achieve and provide solutions regarding product applications.”