Soil treatment in this context refers to the processing of hazardous and non-hazardous, contaminated upland soils typically originating from Superfund, RCRA, brownfields, and industrial sites. The range of contaminants is as extensive and consists of PCBs, dioxins, heavy metals, organics, and hydrocarbons

To understand the Stuyvesant Environmental Contracting treatment system, it is important to understand the standard methods of classifying soil. A representative soil is sampled and screened on a series of successively smaller standard sieves. The mass of soil retained on each sieve is plotted on a particle size distribution curve.

The curve quantifies the amount of material in each of three key fractions:

1. The "Oversize" material: generally all of the mass greater than 2mm. This fraction includes everything from pea gravel to gross oversize material like concrete rubble, tree limbs, tree trunks, old reinforcing steel, and so on.

2. The "Sand" fraction, sometimes called the "coarse" fraction: material <2mm and >63µm. The sand fraction consists of coarse and fine-grained sand. The interface between the sand and fines of 63µm is standard, but is not fixed for processing purposes, as smaller particles may be usefully included in this fraction.

3. The "Fines" fraction: all material <63µm. This fraction includes clays, silts, and decomposed organics.

The Stuyvesant Environmental Contracting treatment principle is based upon the fact that "most" contaminants "normally" are concentrated in the fine particle size fraction of the soil due to the exponentially high particle surface area coupled with associated particle charges. The "fines" fraction is generally taken to identify those particles smaller than 63 µm in diameter (or approximately 200 mesh). We say that '"most" contaminants "normally" are concentrated in the fines' because there are cases where the sand fraction can also be contaminated.

Therefore, our approach to soil treatment is to remove the oversize material with various forms of screen such as fixed bar screens, rotating trommel screens, log washers, and wet vibrating screens. The selection of the screen will be tailored and selected for the specific site. The sand is separated from the fines using hydrocyclones and up-flow classifiers and then is dewatered using high frequency dewatering screens. The fines - suspended in a large water volume - are coagulated, flocculated, and settled in pre-thickeners and clarifiers, water is removed for reuse or discharge, and thickened solids are dewatered using belt or plate and frame filter presses.