One-pass trencher installs slurry wall through hard soils

The DeWind one-pass trenching machine

The DeWind one-pass trenching machine

EI Paso Energy Company purchased a site for their new facility, which was an old pre-World War II munitions factory. It had a significant groundwater contamination problem which demanded immediate attention before any development could be started.

The environmental engineering company hired to investigate and propose a solution decided to completely contain the pollution before a remediation solution was implemented. The most cost-effective and reputable solution for containment was the installation of a soil/bentonite slurry wall around the entire site. This would extend deep enough to key into a clay confining layer, between 47 and 65 feet below grade, to contain the contaminants.

However, preliminary test borings showed extremely hard soil conditions, including a 20 foot thick layer needing up to 100 blows per inch near the bottom of the proposed wall. This was much too hard for conventional installation equipment alone. Additional methods would have to be used to break up the hard layer, adding to the cost.

A new employee had recently overseen the installation of a DeWind OnePass Trenching Company soil/bentonite wall for another company. A unique technology was brought in that mixed the slurry wall in place using a large chain saw-like trencher. He said the wall was installed quickly, surgically and exceeded post permeability testing requirements.

De Wind personnel flew out to the job site to evaluate the overall project parameters. Some of the formidable construction challenges were wetlands crossings, buried rubble, marl layers soaked with dense non-aqueous phase liquid (DNAPL), with Level C or B site construction conditions, and, of particular interest, a dense soil strata. This extended, on average, from 25 feet below grade to weathered rock, or saprolite 65 feet below grade, with blow counts of 100 per one inch. Installation of the 7,600 linear feet of soil/bentonite wall was completed in two months and it passed all post-permeability testing.

About DeWind One-Pass Trenching

DeWind One-Pass Trenching is the Leader in Deep Trenching Technology. Our technology allows us to install groundwater control/remedial systems underground, under the water table and IN A SINGLE PASS without the need to pump, treat, shore, or dig mass excavations. You will not find these one-of-a-kind machines anywhere else. DeWind designs, builds, and operates these Deep One-Pass Trenchers that can achieve installation rates of hundreds of feet per day. We have been in business 25+ years and work all over North America.


  • In-situ mixed slurry walls up to 75+ feet deep
  • Groundwater/product recovery trenches up to 40+ feet deep
  • PRB walls up to 40+ feet deep

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