Direct push has always produced good samples. But at Horizon Construction and Exploration LLC in Wisconsin, they’ve found that larger-diameter samples can make things on the jobsite even more interesting.

On a project in Milwaukee’s historical Third Ward District last spring, using a Geoprobe 3230DT combo rig and its DT60 sampling system, the crew found themselves bringing up full-sized bricks in soil samples through the freshly paved asphalt of a parking lot.

“That was something I’d never seen before out of a sample core,” says Horizon Vice President Adam Sweet, a mostly self-taught driller who worked on the project. “Usually, you’re doing sample cores and they’re like 1½, 2 inches in diameter. You can’t tell what’s down there. All you see is a bunch of ground-up garbage that you pounded into your spoon.”

It was the Geoprobe customer’s first job with the rig.

“With the DT60, you’re taking such a large sample core, I had never seen whole objects come up inside my core. It was incredible to see, just absolutely incredible. From a geology standpoint, I was like, ‘Wow! This is neat!’ ”

The project is in an area, like a lot of urban spots in the Rust Belt, that has found new life.

“The Third Ward in Milwaukee is a very high real estate market right now,” Sweet says. “So what they’re doing is they’re pretty much turning all these old industrial buildings — and it’s going on everywhere down here, every block — into condo units. And they’re selling something fierce. … So this is a really nicely done, landscaped parking lot that was for one of the condo units next door.”

The lot is on the site of a former industrial facility that had seen a range of uses over the years. In fact, Horizon had dug up a petroleum tank from the same site a few years before pavers moved in to repurpose it.

Getting Started

Horizon was hired by Kapur & Associates, an engineering consulting firm that does government, municipal and private work that includes transportation and road design, civil site design, stormwater system design and other projects. Often, that work has Kapur & Associates running into environmental issues that must be monitored or remediated. Travis Peterson, the firm’s environmental manager, has worked with Horizon many times over the years when his firm has needed drilling services.

“I’ve known Adam and worked with Adam at Horizon for many, many years. I couldn’t even count how long,” he says.

He recalls the impetus for the Third Ward job.

“My client had already developed the parking lot and it was basically brand new asphalt,” he says. “I did not want to disturb it, cut it, rip it, anything at all, for them. As parking lots go, it was a pretty nice one. I had to figure out a method to preserve it as much as I could.”

As it turns out, Geoprobe had recently paid Horizon a visit, promoting the 3230DT and its large-core DT60 sampling system. Sweet liked what he heard about the possibility of taking 4-inch core samples via direct push.

“How is that even possible?” he asks. “That’s a lot of pipe to ram into the ground. But these new Geoprobe rigs, these bigger ones, they have a ton of power.”

After some back and forth between Sweet and Peterson, the project’s demands and scope sounded like a promising try-out.

“We had six monitoring wells … to put in in one day. It was a brand-new parking lot that had been paved just a week prior,” Sweet says. “Travis had called looking for a method that was not only quick — because six monitoring wells is a lot to do in a day, whether they’re shallow or not, that’s just a lot of flush mounts to set, everything — but he was also looking for a method that was clean. … I said ‘Travis, there’s this DT60 method. Not a lot of people have used this before. It’s very, very new.’ I had bought some of the equipment as a test. He said, ‘Sure, sure, let’s give it a shot. Does it meet code and everything?’ I said, ‘Yes, it does, and there’s zero cuttings involved in it,’ which was a bonus. So we didn’t have any drums involved in the project. There was no waste stream to get rid of. He was all excited about it.”

And the 3230DT performed as expected, getting the job done quickly. Kapur & Associates liked that the same rig could do both the soil sampling and the installation of 2-inch groundwater monitoring wells.

“The rig that Adam brought out very much met those needs,” Peterson says. “There was next to no visible disturbance and the job went very, very smoothly. I was really impressed by how it (the rig) did, especially because you get a good volume of sample.”

“It was very, very clean. It was like we weren’t even there when we left,” Sweet adds.

Low waste was a preference for Peterson on the job, saving Kapur & Associates’ client money on industrial drilling waste disposal. He says, between hollow-stem augers and direct push, the cost difference is negligible, particularly when you consider disposal.

“In fact, for this one the time savings was better than a normal hollow-stem auger,” Peterson says. “So you have extra time with the hollow-stem auger methodology, and then you have all the soil cuttings. You’ve got to figure it’s about a 55-gallon drum per about 20 foot well. Because of some contaminant types, some of the disposal fees can be rather significant per drum. So, when we looked at this — and also considering … the newly constructed parking lot surface and whatnot — all of those factors into one, I just said, ‘You know what? I need to go in this direction.’ ”

“Basically, I think it was his first job with the rig. It went incredibly well.”

‘Unbelievable’ Features

In the months he’s had the 3230DT, Sweet has grown to really like it.

“There’s some features now on this rig we absolutely love that we’ve talked to the Geoprobe engineering department about putting on their littler rigs, too,” he says. “They have a side clamp assembly that comes out the side of the head. It grabs the drill pipe from the side of the head. I am in love with that feature. The stuff that we do with that — not just on this project, but every project — is unbelievable. It’s literally like having another driller’s helper out there with me.”

Peterson was impressed enough that he recommends Horizon and their 3230DT for other jobs that might benefit from the larger sampling system and a machine that can both sample and install monitoring wells.

“I’ve recommended it to several other people I’ve talked to, other consultants,” he says.

“Drilling contractors may come out and probe first, and then they blind drill down to depth after the probing is done,” Peterson adds. “So, you end up having two rigs out there or they just bring out a hollow-stem auger, but you’re still producing all that waste. This just seems to be an all-in-one methodology that produced a lot less soil cuttings, yet did everything you want it to do by probing and creating the hole with everything in one step.”

The 3230DT joins a growing fleet at Horizon that includes other Geoprobes like a 7822DT and a track-mounted 5400, which Sweet says they use a lot because it can fit through a 36-inch doorway. They also have an AMS PowerProbe and an AMS CRS17-C sonic rig. The company serves Wisconsin, Illinois, Indiana, Michigan and Minnesota.