Moving mountains

Moving mountains, or rather, glacial erratics, was one of the primary obstacles in Big Sky Land Management’s scope of work when it was tasked with clearing land in May 2019 as part of a subdivision construction project in the mountains of Big Sky, Montana.

Glacial erratics are rocks that were transported by glacier, sometimes for hundreds of miles, and then left behind when the glacier melted. These rocks can come in a variety of sizes, from as small as a pebble to as large as a boulder. Unfortunately for the company, they received the full gamut, with the largest of the rocks being 20-feet-tall, 20-ton boulders.

Big Sky Land Management, based in Big Sky, has been providing excavation, landscaping and forestry services throughout the Big Sky area for more than 10 years. The company’s excavation services include site work, road and trail construction, residential and commercial foundations, utility line digging, clearing and more.

While the company is used to having to deal with obstructions on its projects, the size and quantity of the glacial erratics presented some significant financial and logistical challenges during the site work for the subdivision. Namely, Big Sky Land Management says the erratics presented complications for its crew of 12 related to time, accessibility and transportation at the site.

The task at hand

At first, the company’s system consisted of hammering the boulders down to a manageable size with an Atlas Copco hammer attachment on their Case CX350D excavator before sending the resulting material to a dump. Simultaneously, they were waiting for trucks to bring aggregate fill material in from a quarry pit in Bozeman, Montana, and spending $40 a yard to do so.

“We [were] working on a very remote job site up here, and trucking [in aggregates] is a big issue. Bringing material could take up to two hours at times,” Justin Miller, CEO and founder of Big Sky Land Management, says. Even after waiting for the material to arrive, they only received 10 yards at a time.

“The biggest challenge,” Miller says, “was trying to find a way to take a useless product and turn it into something we could use on the job site.”

With a remote job site, the cost of having trucks bring material to them and paying to dispose of the erratics was more expensive than if they were in a more accessible location. When the expenses started to accumulate, Big Sky had to reconsider their processes, the cost and whether their system would keep them on schedule and within budget.

When it was determined that their current system was a detriment to their efficiency, they decided to look at other options. Their priority was finding a solution to manage the glacial erratics and solve the additional transportation challenges the project presented.

Unearthing a solution

After doing some research, the owners of Big Sky Land Management discovered MB Crusher’s BF120.4 crusher bucket and grew interested when the unit seemed to check off all the boxes. The BF120.4 is a portable machine, which would make it easy to transport to the job site. Additionally, due to its versatility, it would allow the operators to crush the glacial erratics down to a ¾-inch-minus size. Most importantly, by allowing the contractors to process the material on-site, it would eliminate the need to ship the erratics to the dump since the material could be used for fill for roads and foundations in the subdivision.

The production rate also intrigued them. To process 5-inch-minus materials, they could reach a production rate of 62 cubic yards per hour and could even crush as a small as half an inch if needed.

However, before investing in the unit, Big Sky reached out to MB Crusher to learn more about the equipment, its compatibility with their Case CX350D excavator, and to explore other options in the range if it wasn’t the right fit. After speaking to MB Crusher’s team, Miller ultimately moved forward and purchased the unit.

“The BF120.4 crusher bucket was a good fit for Big Sky Land Management because of the challenges on their job site,” according to a spokesperson for MB Crusher. “With their site in a remote location, it took trucks up to two hours to bring their equipment and they were throwing away material that they could be using. Also, the crusher was good fit for their excavator because of their machine’s operating weight and the required production rate for the job.”

Once the BF120.4 arrived and was installed on their excavator, Miller says they saw the benefits immediately. After pulling the boulders out of the ground, the Big Sky team hammered the ones that needed it and assembled the resulting pieces in a pile before using the crusher to scoop them up and crush them into smaller fractions.

Hitting pay dirt

Miller says that after investing in the BF120.4, the team saw significant increases in project efficiency.

“The BF120.4 is making, maybe, 60 yards an hour out of the 5-inch-minus, so we’re moving right along. It’s changed our dump truck laps from two hours to more like 15 minutes.”

With the volumes of material that required processing and the size the team needed to reduce the material to, Miller says that the bucket crusher was pivotal in helping the team meet its goals.

Without the BF120.4, Miller says that Big Sky Land Management would have had to keep using their previous process, which would have left them spending money and incurring unnecessary downtime waiting for material.

Miller says being able to convert the erratics into useful material that didn’t need to be shipped off-site helped the company significantly recoup costs on the project.

“Taking useless rocks that we pretty much would have to throw away and turning it into fill … has given us a lot of savings,” Miller says. “We’re doing a lot more crushing now. We’re using [the crusher] on other job sites. Currently, we’re doing a similar project in another location. We’re able to now keep all of our rock inhouse, and this saves the client a lot of money. Both on the [Big Sky] project and the one we’re on now, we’ve probably saved the contractor in the ballpark of around $250,000 on each because we’re doing all the crushing on-site with material that’s already part of the project. There is a little bit of a cost that goes along with us crushing it, but all in all, it’s been a success.”

This article originally ran in the Nov. Dec. issue of Construction & Demolition Recycling magazine. Therese Arenas is a marketing assistant at MB Crusher and can be reached at marketing@mbamerica.com.