Envirocon has grown its Geotechnical Services team with the addition of several senior geotechnical professionals. These additions have expanded our capabilities throughout the United States and now include the installation of some of the longest and deepest slurry and reactive barrier walls to control and treat groundwater, the installation of sheetpile containment and excavation support systems, soil mix walls, and innovative in-situ stabilization/treatment systems. Our specialty geotechnical services are comprised of the following:

Slurry Trenching Techniques
These techniques involve the excavation of a trench under a stabilizing slurry without the need of shoring or other excavation support systems. After the trench is excavated to its full depth (up to 95-feet deep with a special long-stick excavator or even deeper when using a clam shell bucket), the trench is then backfilled with various materials, depending on the application.

Slurry Walls - Slurry walls are non-structural vertical barrier walls used to prevent the lateral flow of contaminated or uncontaminated water, or non-aqueous phase liquids (NAPLs). Slurry walls have a long demonstrated history in environmental applications and are often part of a cost-effective containment solution for many sites. After the slurry trench is excavated under a bentonite slurry, the trench is typically backfilled with a mixture soil-bentonite backfill, or depending on site constraints, the trench is excavated under a self-hardening slurry which not only stabilizes the trench during excavation, but acts as the final backfill material. Civil applications include levee strengthening, dam cutoffs, and in the construction of reservoirs.

Bio-Polymer Collection Trenches - Bio-Polymer collection trenches are essentially deep French drains constructed using the slurry trench technique. Instead of using bentonite slurry to maintain the trench stability during trenching operations, a natural biodegradable carbohydrate slurry is utilized. After trenching is complete, horizontal collection pipes, manholes, and aggregate backfill are placed within the trench and a breaker solution is introduced to biodegrade the slurry into a mixture of water and small amounts of natural polymers, which are quickly consumed by naturally occurring organisms in the surrounding soil. Applications include: stabilization of earthen slopes; interception of groundwater plumes; collection of contaminated groundwater; and site dewatering, at a fraction the cost of using conventionally constructed shored or braced excavation techniques. Depths in excess of 60-feet are possible.

Permeable Reactive Barriers Walls (PRB) - Utilizing bio-polymer slurry methods and other more conventional methods for shallower applications (less than 25-feet), a vertical trench is excavated and subsequently backfilled with a reactive material which passively treats the contaminated groundwater as it passes through the wall. Zero-valent iron is the most common reactive material, but any granular material could be emplaced. Envirocon's experience includes the installation of the largest PRB to date.

Soil Mixing Techniques
Soil mixing was first developed in the United States in 1956 by Intrusion Prepakt of Cleveland, Ohio. During the 60's and 70's, the technique was refined by the Japanese and in Europe, and was later re-introduced to the United States in the mid-1980's. The technique uses a mixing head mounted on a hollow drill shaft. As the mixing head is rotated and advanced into the soil, a reagent or stabilizing fluid (typically a cement grout) is injected through the hollow shaft to act as a drilling fluid and is subsequently mechanically mixed in-place with the surrounding soil, forming a column of stabilized soil and grout. Although initially developed for the construction of cut-off walls and soil improvement in civil applications, the technique has an excellent track record for the in-situ stabilization of contaminated soils.

In-Situ Stabilization - By overlapping a series of soil-mixed columns to provide block treatment, soil mixing is a proven cost-effective means of treating a variety of contaminated soils to depths up to 100-feet deep. The stabilization can be augmented by a number of additional reagents that are used to reduce or alter chemical properties to further remediate the contamination.

Soil Mixed Cut-Off Walls - In certain applications where conventional slurry walls may not be possible, soil-mixed cut-off walls are an alternative installation technique. Specific applications include situations where there is limited access adjacent to an existing building, where stability of a slurry trench may be an issue, deep cut-off walls (greater than 80-feet deep), and as a cost-effective alternative to reinforced concrete diaphragm slurry walls.

Jet Grouting - Jet grouting can be considered a type of soil mixing which utilizes high velocity jets (4,000 to 6,000 psi backpressure) to hydraulically shear the soil and blend a cement based grout (or many other self-hardening slurries) to form a cylindrical soil-grout column. Three basic jet grouting systems are available. These systems are: single phase (grout injection only), dual phase (grout + air injection), and triple phase (water + air injection, followed by grout injection). Its environmental applications include the in-situ stabilization of contaminated soil in areas of confined access (i.e., beneath an existing building) and creation of a seepage barrier walls around and beneath active utilities and other obstructions such as boulders, foundations, and buried debris.

Sheetpile Walls
With our experience, Envirocon is able to provide a wide range of options for both earth retention systems and cut-off wall applications. Installation of a sheetpile wall is one option for groundwater cut-off on environmental projects, especially in situations where a slurry wall is not a viable option. Sheetpiling can also be used as part of a shoring system to allow excavation of soils (whether contaminated or not).

Other Geotechnical Techniques
Envirocon can apply other specialty geotechnical techniques to a variety of civil and environmental applications. These techniques include: Grouting and Grout Curtains, Ground Improvement, Specialty Earth Retention Systems, and Design/Build Foundations.