In the wake of the Flint water crisis, a huge spotlight has been turned on infrastructure in American, and specifically, the country’s miles-long network of aging underground water pipes. While there are new short-term efforts to bring fresh water into Flint, plans have been in the works for several years that should provide a long-term solution.
In 2013, ground was broken on the Karegnondi Water Authority (KWA) pipeline, a multi-year water intake pipeline project that will bring raw water 75 miles from Lake Huron west along the I-69 corridor through Michigan’s Sanilac, Lapeer, St. Clair and Genessee Counties. This will include servicing the City of Flint.
Years in the making, the $285 million project has many parts: a new state-of-the-art water intake facility that bores 6,000 ft. into Lake Huron, two water treatment plants, plus three new pump stations. But even with all the peripheries, the KWA pipeline project is just that - a pipeline.
Headquartered in Grand Blanc, Zito Construction is a family owned and operated firm specializing in excavating, road building, water mains and sewer mains on private developments and public works projects throughout Michigan. In 2013, the company was contracted by the KWA to install 36-in.-diameter steel Class 150 pipe along an approximately 14-mile stretch of the mainline from Genessee to Lapeer County. With that completed in 2014, the KWA again awarded Zito an approximately $18 million contract to install 68,500 linear ft. of much larger 60-in.-diameter spiral steel transmission pipe across parts of Lapeer County.
Zito Construction began the second portion of the pipeline in April 2015. With such a distance to cover, the contractor is installing extremely long 50-ft. joints of pipe. The more than 1,600 jumbo pieces of pipe are being placed in an open cut trench ranging from 5 to 25 ft. deep. Because the trench is deeper than 5 ft., a trench protection system is required. And therein lies the biggest challenge for the veteran underground utility contractor.
Customized Trench Shoring Solution
There are only so many ways to shore a trench and still be able to install pipe 50 ft. long, with soil conditions typically being the primary factor driving the choice of trench protection system.
“Ground conditions along the pipeline can best be described as ‘sandy to swampy,’” says Jeremy Drielick, senior engineering technician, Rowe Professional Services Company, the engineering firm responsible for Zito’s second portion of the KWA pipeline.
“Because of the ground conditions, we knew we couldn’t slope the trench and not take out the whole road in some places,” says John Zito, president of Zito Construction. “If we could have sloped it, we might have moved along faster, but sloping or some kind of shoring just wasn’t economical. We knew we were going to need a (trench) box. A very big trench box.”
Even with the trench protection system decided, Zito Construction still faced many challenges. The question remained how to you install 50-ft. sticks of pipe in a trench box. For help, the company turned to Efficiency Production, a leading manufacturer of trench shielding and shoring.
“We’ve built several custom trench shields in the past exactly for the same purpose, installing joints of pipe 50 ft. or longer,” says Mike West, Efficiency Production’s vice president of engineering. “The key is designing a box with enough pipe clearance so the contractor can angle the pipe into the box and under spreader arches.”
The solution was to use two trench shields with custom high-clearance arches instead of spreader pipe on the abutted ends of the boxes. “The shields we built for Zito, however, are different in that the lead box is so much longer than the trailing box,” says West. “What you end up with is a lot of space to get the pipe into the front box and under the arches, and then just enough space in the second box to shield the connection work.”
The custom trench shields are a combination of an HDHT12-842 steel trench shield with 12-in.-thick sidewalls, 8 ft. high and 42 ft. long, adjoined with an XLD-816 steel trench shield with 4-in.-thick sidewalls, 8 ft. high and 16 ft. long. The hi-clearance arches on one end of each box are abutted to each other, and the boxes are secured together with shackles for easy pulling through the trench. The opposite end of each trench shield has 9-ft. spreaders to match the overall width of the arches.
The result is a trench shield almost 60 ft. long with more than 11 ft. of pipe clearance – plenty of room for Zito Construction’s excavator operator and crew to angle the spigot end of the pipe into the connected boxes and up to the bell end of the installed pipe. The pipe is then tack-welded and heat shrink wrapped on the outside before a welding crew from Utah-based subcontractor National Welding traverses the inside of the pipeline to permanently weld all the joints from the inside.
“The box is working well,” says Zito. “Our record is 11 sticks of pipe in one day.”
Zito Construction is anticipating being finished installing this section of pipeline by June 2016. Once completed, the new KWA pipeline will supply treated and untreated water to the municipalities of the region, industrial customers, agribusinesses, rural agriculture developments and residential commercial light and heavy manufacturers. The boundaries of the water supply will encompass over 2,400 sq. miles and over a half million people.
Equipment On Site
To wrangle both the big pipe and the big combined trench box into and through the trench, Zito has a fleet of equipment on site, including:
- Cat 345D, Cat 349EL, Cat 375L, and 390F excavators
- Cat 966G and Cat 950G wheel loaders
- Volvo A35G dump truck
- John Deere 450J and Cat D3 dozer
- Two smaller trench boxes
- Dewatering equipment from Mersino Equipment Rental
- Two Efficiency Production Stone Mizer bedding boxes