(above) Dennis Samsel, Geo Logic, Inc. works with his 7720DT. According to Dennis, the "cool" geology on the other side of the river shows the bedrock at a much higher elevation than where they were working.

Another new direct push machine has been added to the Geoprobe® lineup. It’s another example of how important customer feedback is since this machine was a direct result of listening to customers and designing a work package tailored to their needs.

The Model 7720DT is a great option for customers using the DT325 Dual Tube Sampling System and for augering. The 77-in. stroke of the original 7730DT machine adds eleven inches of work space under the hammer which has been an appreciated convenience to customers. Dennis Samsel, owner of Geo Logic, Inc. in New Albany, IN, was the first owner of a 7720DT. “A 7730DT was too large. And we wanted more than the 6620DT,” Dennis said. “Our 7720DT is just right! It gives us more work space under the hammer with the same small 6620DT footprint!”

The Geo Logic field team has used the machine on a variety of projects. They paired the 7720DT with the MC5 Soil Sampling System in 60-in. lengths and 1.5 in. probe rods at a Superfund site near St. Clairsville, OH.

Versatility Part of 7720DT’s Appeal

“The extra foot of mast stroke gives us a little ‘wiggle room’ when working with 5-ft. rods and augers,” Dennis explained. “The 7720DT has been the single most useable upgrade we’ve made since we bought our first 66 machine.”

Just a few weeks after Precision Sampling, Inc., in Richmond, CA, purchased their first 7720DT, they were asked to salvage a project in a warehouse area. The other custom-built track rig hit shallow refusal, Chris Tatum, General Manager for PSI recalled. “We completed the job with 3-ft. dual tube tooling the same day we arrived. It was just another limited access, shallow, dual tube soil sampling job for us, but to our client it meant the difference between finishing and not finishing the project on time. His observation: ‘Your crew was outstanding and that track rig was just amazing!’.”

“We enjoy the longer stroke,” says J.D. Barker, Owner of Quantex, Inc., in Raleigh, NC. “Our clients ask for 2-in. monitoring wells, so the 7720DT shines. The common scope of work calls for soil sampling and monitoring wells; it’s nice to take one machine to the project site. Overall, the performance is good and we really like its versatility.”

Brendan Brodie, PG, President of EarthCon, Inc. in Greenville, SC, purchased a 7720DT because they wanted a machine for auger drilling work. “The longer stroke makes auger and tooling removal a breeze,” he said. The size and mobility of the machine has allowed them to drill in thickly wooded areas and confined spaces, and to travel in swampy land surfaces, large diameter underground storage tanks pits, uneven terrain, and former settlement lagoon areas. EarthCon recently installed several nested air sparge and vapor extraction wells under a gas station canopy. “We turned 4.25-in. ID hollow stem augers to 60 ft.!” Brendan added. “I was a little skeptical of drilling to that depth with the 4.25 in. augers, but the machine pulled it off. On another job, a two-man EarthCon field team collected 350 ft. of continuous Macro-Core® samples in a single day. “That kind of production is unbelieveable!”, Brendan said.

The weight difference between the 7730DT and the 7720DT is significant (9,600 lb. compared to 6,850 lb.) which makes the 7720DT attractive to international customers. Because of the weight difference,

several of the 7720DT machines have made their way to Australia and New Zealand. Aqua Drilling & Grouting, in Melbourne, Australia, used the 7720DT to re-set monitoring wells in the Docklands development. Lee Strutton, owner of the company, said 120 wells had previously been set 12 months earlier, but 30 of them had been either paved over or had a road put over them. “We’re really happy with it [7720DT]. The extra stroke length makes a difference when using augers and setting wells,” Lee said.

The 7720DT is also less expensive to transport which helps customers avoid CDL issues, and is less likely to require new or different truck/trailer carrier options.

The Model 7720DT is also a good match with the Geoprobe® Automatic Drop Hammer. Dennis Samsel, with Geo Logic, found that they were routinely asked to take their 6610DT with drop hammer to sites that were better suited for the wider-tracked 6620DT undercarriage. They used the Drop Hammer/7720DT combo at the Indianapolis Zoo to investigate the installation of a dry well in the Rhino Exhibit. The 60-in. width of this machine (compared to the 78-in. width of the 7730DT) allowed Geo Logic to easily maneuver in and around the zoo exhibits.

As with other Geoprobe® machine designs, the 7720DT displays qualities that the Geoprobe® brand is noted for: wireless remote control, two-speed probe cylinder that cycles from bottom to top in less than 8 seconds, a hydraulic winch for handling augers and tripping dual tube sampling tools, and hydraulic movement in all three axes for easy probe alignment during sampling or logging. This machine, as with other Geoprobe® track-mounted machines, is powered by a four-cylinder, 54 Hp, liquid-cooled Kubota turbo diesel engine. Geoprobe® engineers like its dependability and small size. It’s quiet and smooth-running, requires minimal maintenance, and has replacement/service parts available all over the world.

Because there are so many equipment options for the machine, it’s versatile for a wide range of environmental and geotechnical projects: sampling, logging, augering, concrete coring, monitoring well installation, and SPT tests. According to Dennis, “It’s a very user-friendly piece of equipment. I can’t wait until we catch up with the farm machine industry so I can add AC and a CD/MP3 player!”