Utility Line Trenching for the Electric Power Research Institute.

The Soft Trencher was completed for the Underground Transmission Department of the Electric Power Research Institute in 1994 as a prototype machine to dig large utility trenches. The unit employs a telescoping boom with multiple supersonic air jets to loosen and remove the soil by vacuum without physical contact. The unit can dig a trench nominally 3 feet wide by 5 feet deep while continuously discharging the excavated material via an on-board conveyor into an adjacent truck or onto the ground next to the machine. Rocks smaller than 7 inches in size pass through the boom, while larger rocks can be lifted by suction with the boom out of the trench.

Soft Trencher Digging Boom Specifications

Soft Trencher Vehicle Specifications

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Projects

• Hanford Washington
• SRS Drum Project
• Unexploded Ordinance Advanced Technology Demonstration Program
• Boston "Big Dig"

Hanford Washington

Over a four-week period, 14 trenches and 14 light-post holes were cut at the Hanford Nuclear Site. Trench depths ranged from 2 to 8 feet, while widths ranged from 1 1/2 to 3 1/2 feet. The light pole holes were approximately 8 foot deep by 3 foot square. In addition, the Soft Trencher safely uncovered a fiber optic line and a clay sewer line that had not been known to be there. Although the overall excavation rate depended on the percent of time doing non-digging activities including shoring, moving the unit, and trench clean-up, in this predominately sandy soil, an average rate of about 5 to 6 cubic feet per minute was achieved.

Savannah River Drum Project

In the late 90’s, CEG was asked by Savannah River DOE Site to perform a test to see if the CEG’s soft trencher technology could excavate buried drums. A box was constructed that contained a number of 55 gallon drums that were covered with compacted dirt. The CEG soft trencher using AIR-SPADE‚ supersonic nozzles was successful in uncovering the drum tops without damaging them and was much faster than digging by hand. To view a video of the demonstration see the video section of our Reference Library page.

Unexploded Ordnance Advanced Technology Demonstration Program

In late 1995, CEG used the Soft Trencher to demonstrate the capabilities of Safe Excavation technology for remediation of unexploded ordnance for the US Army. Under Phase II of the Unexploded Ordnance Advanced Technology Demonstration Program conducted at the Jefferson Proving Ground, CEG successfully uncovered 13 targets ranging from a 81mm howitzer shell to a 250-pound bomb in an 18-hour period. Excavation rates averaged 3 cubic feet per minute in undisturbed, field type conditions. This was the highest number of targets successfully uncovered by any remediation technology demonstrated during the two-year program. In addition, glass vials were successfully uncovered for a representative of the Corps of Engineers during the demonstration.

Boston "Big Dig"

In 1996 / 1997, the Soft Trencher was taken to Boston for evaluation under the central Artery Tunnel Project. Project engineering felt that vacuum excavation was needed to penetrate the "utility barrier," the maze of intertwined underground utilities roughly up to 10 feet deep under the streets of Boston. The photo shows a test pit being dug near the Federal Bank Reserve Bank in Downtown Boston. The Soft Trencher offered several unique benefits for the "Big Dig." Unlike conventional vacuum trucks that had to stop work to make time consuming round trips miles off-site to dump, the flow-through material design of the Soft Trencher would allow it to remain working on-site and loading standard dump trucks for spoil removal. The electro-hydraulic boom of the Soft Trencher also allowed for one operator to dig continuously without the fatigue associated with manually moving the heavy, rubber suction hoses of conventional vacuum tanks.

To see video of the Soft Trencher in action see our reference library.