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Underground Protection Products and Safety
By Taylor Clark, Underground Safety Specialist - 3/11/2008
I'll never forget digging a hole with my best buddy, Cory, when I was about five years old. For little boys, digging in the dirt carries with it just about the same excitement as climbing a tree. Exploring something directly above us, or in this case, directly below us, was an exciting and memorable experience. Cory and I still giggle about how ridiculously deep the hole was by the end of the summer and how mad Cory's mom was when she found us up to our ears in mulch and topsoil, right up against the foundation of her Carmel home. I guess you could call it ironic that I now make a living advising contractors on the safest ways to work underground.
Well, even for a couple of chubby, freckled trouble makers like Cory and I, it didn't take long to remove at least one cubic yard of dirt from the ground with garden shovels. One cubic yard of dirt weighs up to 3,500 lbs. The curb weight of a Volkswagon Beetle is roughly 2,700 lbs. Can you see where I'm going? Digging in a hole that you're standing inside is dangerous, and right around 100% of my customers don't have kindergartners using mom's flower bed shovel to dig sewer pipe trenches.
Pro-Tec shoring, before assembly
Shoring and shielding are an absolute necessity for the underground contractor. Actual numbers of trench related fatalities are not maintained by OSHA, but each year nationwide, there are approximately 1,000 workers compensation claims per year regarding trench collapses. Of those claims, roughly 140 resulted in permanent disability and about 75 of those resulted in death. Math will tell us that in our state of Indiana, we should average about 1.5 trench related fatalities per year. To put it in very blunt terms, when cave-ins occur, children lose their fathers and business owners lose their companies.
Underground construction is, indeed a risky business, but my father-in-law is a doctor, so I find it important to note here that I am not an "ambulance chaser." Experienced pipe contractors will use shoring and shielding products as efficiency tools as well. Josh Vancel, a pipe foreman with Poindexter Excavating says:
"If you're not using a box, you're required to bank back the walls of your trench so that it can't cave in on your laborers. Banking back takes up time and fuel, and you end up moving more material than if you'd have just used a trench box that whole time and kept your dirt walls straight vertical."
Contractors today are completely determined to run their expensive construction equipment in the most efficient manner possible. It's not hard to see why trench boxes can serve as an important production tool.
Pro-Tec shoring, installed
At MacAllister Machinery, where dirt contractors are the life blood of our operation, it comes as no surprise that underground protection products are an obvious "bolt on" to the business that we already do. Our Rental Services Department currently owns about 100 trench safety items, all of which are rent-ready out of any of our Cat Rental Stores. Until we entered the trench protection scene, there was not a building in our state from which a contractor could rent an excavator, a trench box, a pump, and another 'auxiliary' machine. Now, contractors can rent or buy every necessary piece for an underground project and expect the same MacAllister service and expertise from no fewer than nine rental branches.
The recent 'buzz' around the MacAllister campfire, when it comes to shoring business, was our project with Bowen Engineering 
in Terre Haute. Bowen Project Designer Doug Stout was responsible for creating a 25 foot deep excavation that measured 30 by 70 feet. The hole had to be 'clear spanned,' meaning no horizontal cross bracing could be used with whatever shoring structure would be installed. Together with Pro-Tec Equipment, out of Charlotte, Michigan, we were able to install a Slide Rail Shoring System that proved to be both safe and economical. Dave Cowan, head of safety equipment at Bowen, stated, "That slide rail system came at just about the same cost to us as driving our own sheeting. When we realized that the slide rail would save us over a month in time, it became a no-brainer."
Seven truckloads of shoring panels and posts arrived in Terre Haute in late April, and the residents of the small neighborhood on Oakland Avenue had a show on their hands. In a matter of just four days, Bowen's crew was able to maneuver a Caterpillar 365 Excavator around a multitude of power lines and other obstacles, and install the system to their desired depth. Bowen had the job completed and the system removed from the ground in just over one month.
Pro-Tec shoring used by Bowen Engineering
at Broad Ripple Canal Project
The physical structures that had to be installed underground consisted of a concrete slab with a screening station and a lift station on the slab. This project was part of an update to Terre Haute's waste water infrastructure. Pipes underground carry the wastewater out of the city by gravity. They are installed at a grade so that anything inside the pipes will run downhill until the pipe cannot be installed any deeper. It is at that point that a lift station pumps the material straight up vertically to a new pipe. That new pipe will run at a downhill grade to the next lift station. The screening station serves to eliminate any solid matter in the waste water so that the lift station does not have to deal with solids. These two structures had to be set in place in very close proximity to each other. Additionally, the site was in the middle of a neighborhood, so there was a road and two houses that were very close to the jobsite. These circumstances meant that the excavation had to be very large, yet it also had to be cut vertically. There was absolutely no room for the hole to be "sloped back" at the top.
The Slide Rail system allowed Bowen to dig this large excavation straight down to their target depth while being completely shored the entire time. A cave in would have not only been dangerous for the workers, it would have also disrupted the foundations of the nearby houses and possible destroyed the road. Due to the "dig and push" method of installing slide rail, the excavation was able to be vibration-less and with minimal soil disturbance. Unlike sheet piling, where crews must pound steel sheets into the ground, Slide Rail can be installed without impact or vibration. The components of slide rail are set in a pilot cut and then an excavator is used to undermine the soil beneath the system. Removing this soil creates a void and allows the slide rail posts and panels to drop down deeper and deeper by gravity and pushing with an excavator bucket.
We are finishing up the paperwork on another large slide rail install in Broad Ripple, directly across from the American Legion. I would invite anyone to come out and catch a glimpse of this project in mid-July.
Pro-Tec shoring from MacAllister
MacAllister is currently Indiana's sole provider of the Pro-Tec Slide Rail Shoring System. Combined with the other shoring solutions at our disposal, slide rail has helped us grow our Underground Safety division to new heights and make working underneath Indiana just a little bit safer. Our shoring inventory is growing each day, along with our customer base and the future is so bright, we're going to need sunglasses. 'Er... maybe safety glasses!