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Cutline 1 (Caption01_Dow-Johnston ClearSpan.jpg): The working pit dimensions to accommodate the massive lift station needed to be over 60 feet long, and 35 feet wide; and to stay open and properly shored for more than 3 months.
With a custom designed Slide Rail System from Efficiency in his proposal, Johnston’s project bid was much lower than any other bidding contractor.
 Efficiency’s ClearSpan design is unique in that it shores a large excavation without any need for cross-braces. The system stays entirely open by utilizing innovative waler i-beams on the outside of the system at the top, and inside the system to prevent deflection.
“The open workspace is what I liked,” said Brian Barber, Project Superintendent for subcontractor Three Rivers Corporation. “We’ll be able to form-up the structure without having to deal with anything crossing the workspace.”
Johnston installed the entire Slide Rail System in 13 days, rather than the 30 days it would have taken to install an alternate shoring system like tight sheeting.
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Safety, Safety, Safety. For the Dow Chemical Company—the nation’s largest chemical company--safety is the first, last, and all-between consideration. Everything that goes on at their many world-wide facilities is looked at through the prism of safety. Even the rain water…
The Dow Chemical Company is in the process of installing a new 25 x 55 x30 foot lift station at their Midland facility which will hold surface run-off water collected through an existing 54 inch storm sewer line and will pump the water through a new 36 inch line to a recently built 10 million gallon above-ground water storage tank for future treatment.
To tap into the existing storm sewer line, the new concrete structure is to be poured-in-place 35 feet deep in the ground. The working pit dimensions to accommodate the lift station needed to be over 60 feet long and 35 feet wide, and to stay open and properly shored for more than 3 months.
The low bidder for the project was Johnston Contracting, also located in Midland. Owner and operator Lee Johnston has many years of experience working with Dow, inside and outside their main facility. The biggest safety challenge to the project was properly shoring the large and deep working pit that would be open for a long period of time.
Dispelling the sheet-piling myth
“There were two other contractors looking at this job, and they believed it would be a sheet piling job,” said Johnston. “The folks on the project from Dow believed it would be sheet piling, and that was my initial thought. Or it was until I got a visit from Mike Ross at Efficiency (Production, Inc.), who suggested a much more cost-effective alternative to sheeting.”
“I told Lee, ‘We can do this with Slide Rail,’” confirmed Ross, Efficiency’s Custom Engineering and Slide Rail Specialist. “We have a ClearSpan™ Slide Rail System that’s able to shore pits that big and do it better, faster, and cheaper than sheeting.” Indeed, with a custom designed ClearSpan™ Slide Rail System from Efficiency in his proposal, Johnston’s bid was much lower than any other bidding contractor.
“Dig and Push” system reduces over-excavation
Efficiency’s Universal Slide Rail is a component shoring system comprised of steel panels (similar to trench shield sidewalls) and vertical steel posts. The highly versatile system can be used in a variety of configurations. In addition to the obstruction-free ClearSpan™ configuration, Efficiency’s Universal Slide Rail can be configured into small four-sided pits; or in a Multi-Bay™ configuration to install large tanks and structures; or lengths of pipe over 40 ft.
Slide Rail is installed simultaneously as the trench or pit is excavated by sliding the panels into integrated rails on the posts–either double or triple rails depending on needed depth–then pushing the panels and posts incrementally down to grade as the pit is dug; a process commonly referred to as a “dig and push” system. This allows the Slide Rail System to be installed simultaneously as the pit or trench is excavated to grade.
Slide Rail: A cost effective alternative to sheeting
Sheeting is by nature a loud, long, and cumbersome way to secure a large excavation, and requires extra specialized equipment in addition to just an excavator. Johnston installed the entire Slide Rail System in 13 days, rather than the 30 days it would have taken to install an alternate shoring system like tight sheeting. “If we’d used sheeting, we’d have to have double walers and cross braces,” said Johnston. “That would leave us with 12 penetrations to pour the concrete through, and would take an extra month to finish.”
As it was, Johnston had on-site installation assistance from Efficiency’s Slide Rail Systems Manager, Greg Ross. Said Johnston, “We really had no problems installing the system. A big advantage of using an Efficiency system is that not having used slide rail before, Greg Ross was here a couple days to help us get started. That was a big help,” Johnston concluded.
Efficiency ClearSpan™ eliminates all cross-members, obstructions
Three Rivers Corporation, also located in Midland and boasting Dow credentials, is the subcontractor installing the poured-in-place concrete tank. Three Rivers’ Project Superintendent, Brian Barber, also had high praise for Efficiency’s ClearSpan™ System. “The open workspace is what I liked,” he said. “We’ll be able to form-up the structure without having to deal with anything crossing the workspace.”
Adds Ross: “Other manufacturer’s slide rail configurations need to be installed with cumbersome cross-members. Only Efficiency’s ClearSpan system is never encumbered by cross-members at any time.”
The new tank will sit on a 3 foot poured concrete footing. The 2 foot thick walls will be formed 3 feet in from the edge of the footing on all sides. When completed, the new structure will be 30 feet tall and have a capacity to hold more than 100,000 gallons of storm water.
To excavate the pit and install the slide rail components, Johnston used the following equipment:
- 866E Koering excavator with a 3 yard bucket
- 330 Terex crane
- 108 Linkbelt crane with Lead and Drop Hammer to install opposite side posts and panels
- 7.8 Komatsu mini-excavator
Johnston Contracting was founded by Lee’s father, Dean Johnston, in 1965. Specializing in underground utility and chemical plant construction, Johnston Contracting is a member of the Michigan Infrastructure and Transportation Association (MITA).
The Dow Corporation is a diversified chemical company that combines the power of science and technology with the “Human Element” to constantly improve what is essential to human progress. The Company delivers a broad range of products and services to customers in approximately 160 countries, connecting chemistry and innovation with the principles of sustainability to help provide everything from fresh water, food and pharmaceuticals to paints, packaging and personal care products.
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