The 10,000-ft. (3,048 m) ditch was 36 in. (91.4 cm) wide and 54 in. (137 cm) deep in spots and went from the main switch gear installation to each of the six wind turbines.
All construction projects have unexpected surprises and last-minute changes. But a last-minute change helped The Morse Group discover new processes and uncover a new opportunity to save time and reduce cost on this and future jobs.
The Illinois-based electrical contracting giant was just about to start a Wisconsin installation of direct-burial high-voltage underground cables for six 262-ft. (80 m) wind turbines, each with three 135-ft. (41 m) blades, when it was informed that the engineers wanted to switch from hauling in fill material to using the native material.
Bruce Binger, a 20-year industry veteran and the project superintendent for The Morse Group, said, “The engineers learned from test results back just two days prior to the scheduled start of excavating that the native soil would adequately dissipate heat away from the electrical lines to allow them to carry the capacity needed for the installation. So, they wanted to use the native material to backfill as much as possible.”
This was good news for The Morse Group because it reduced the need to purchase and haul in outside fill material. However, the native soil contained a lot of rocks because this area had glacier remains, so the material couldn’t go back into the ditch without separating the rocks out.
No Time to Waste
The development of the wind farm in Dane County for a private software company is located just northwest of Madison, the Wisconsin state capital, and is the county’s first commercial wind farm. The company has already installed a geothermal system and solar panels in its facilities. The addition of these wind turbines to the company’s current sustainable efforts will help them provide around 85 percent of its own energy by 2014.
The project started in October, and the company wanted to complete the installation of the wind turbines by the end of the year. This tight timeframe meant that Binger needed to find a way to separate the good soil from the rock quickly to keep the project on schedule.
It was after lunch on a Wednesday when Binger learned his crew would have to change its backfilling plan, yet still had to start digging by the weekend. To identify possible screening options and solutions, he did an internet search and discovered the hydraulically-powered Allu line of Screener Crusher Processor Attachments.
After doing some further research and watching some product videos on the internet, he contacted Dennis Cade, Allu’s Midwest territory sales manager, to learn more about the product. The screener crusher processor is designed to separate the soil from rock and other debris, and fit on The Morse Group’s 26.5 ton (24 t) Volvo excavator. At the same time, Binger reached out to a trusted veteran equipment colleague who was familiar with the Allu product but completely independent of the company. He was able to vouch for the product’s performance and reliability, ultimately confirming their decision to buy it.
Although the attachment was at Allu’s warehouse in New Jersey, Cade was able to have the attachment delivered to Binger by Friday and get it on site backfilling by Saturday at noon. The arrival in the Midwest of The Morse Group’s screener crusher bucket happened to coincide with Hurricane Sandy wreaking havoc back on the Eastern seaboard. If Binger and Cade had not connected until just a few days later, the in-demand screener crusher attachment would not have left the New Jersey area and arrived in time to complete the project on time.
Fast Solution Delivers
The crew, working on a tight two-week schedule, needed to dig a 10,000-ft. (3,048 m)-long ditch that was 36 in. (91.4 cm) wide and had a 54-in.- (137 cm) deep floor. It went from a main switch gear installation that the electrical lines originate at, to each of the towers.
With the addition of the Allu processor, The Morse Group found a solution that was mobile, quick and easy to use, and could be used with its existing excavator. The three operators of the unit required only minimal training from Cade on how to make material fall succinctly into the bucket’s drums for best production. It was then able to place 18 to 20 in. (45.7 to 50.8 cm) of cover, which exceeded the project material minimal size requirements, immediately over the electrical cables. The first lift of processed fine soil did not require direct compaction. The crew was able to use the rocky spoils it placed off to the side for later upper-lift placement.
The project screening requirements were for ¾-in. (1.9 cm) diameter and below and the Allu screener crusher processor met that requirement. It provided “top quality” material that immediately earned a thumbs-up from the onsite inspector.
“You can really tell the difference when you walk on it,” said Binger. “If you were to just take a regular backhoe bucket and fill the ditch, and then take an Allu processor and fill the ditch, there would be a lot less settling involved after with the area using the screener bucket. The fines just automatically pack in and lock together better.”
The wind farm in Dane County originally posed a new challenge for Binger and The Morse Group. By having to find an acceptable way to separate rocks and debris from native material to refill the ditches, the company was able to realize additional cost savings and discover a new process it can use on future projects.
Other possible solutions required The Morse Group to haul in and install pre-engineered backfill material and haul away any extra native material that wasn’t needed, or to haul in clean soil. The company thus avoided having to haul in soil by the truckload and rent the additional carriers such as wheel loaders that would have been required to move the material, or alternatively placing flowable fill that would be delivered by ready-mix trucks.
In addition, the project was located in the middle of a farm field that was wet some days and would have made it more difficult to get this hauling equipment in and out.
Since the company could use its existing excavator, it required only the screener crusher processor be purchased. The excavator worked well in wet conditions and the bucket was still able to separate native material from the rock and debris, even when it received an inch of rain overnight. This all added up to a significant savings for the company.
“The Allu processor worked excellent. It’s built heavy, and all of our operators have been very happy with its performance.” said Binger. “We needed something quick. The job that we were on was a very fast-paced project — things were evolving very rapidly — but the machine worked exactly like Allu had described and exactly what it looked like in videos on the internet.”
The Morse Group has been so impressed with the screener crusher attachment that it had plans to rent another one, plus use the current one, for an upcoming project, according to the company.
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