Stuyvesant Environmental Contracting has extensive experience in solidification and stabilization of hazardous and non-hazardous product streams. For the purposes of this discussion, "solidification" refers to the amendment of the specific product steam to attain the target compressive strength, shear strength, and finally the practical achievable density of the soils as place in the selected in use. The end use - the beneficial reuse - varies, but can include the use of the product as construction grade fill for site stabilization, roadway sub base, and brownfields restoration. Placement measurements are normally performed using the Modified Proctor Compaction Test, ASTM D1557. This is normally measured in the field with nuclear densometer testing.

"Stabilization" refers to the immobilization of target contaminants of concern in the product/soil matrix such that the contaminants cannot be mobilized, solubilized, and enter into the ground or surface waters. This characteristic is normally measured by the Toxic Characteristic Leaching Procedure (TCLP) using protocol established in SW-846 , or now, more frequently the Synthetic Precipitation Leaching Procedure (SPLP) using Method 1312 in SW-846.

For our projects, the separated sand fraction can meet the regulatory quality requirements and does not require solidification or stabilization. The fines (silt) fraction, produced as a filter cake or "sludge cake", contains the concentrated contaminants from the as-excavated or as-dredged feed stream. In practice today, heavy metals as most amenable to stabilization within the filter cake product. While some organics can also be stabilized, it is encountered less frequently than the treatment of metals.

Stuyvesant Environmental Contracting determines the chemical and process arrangement by first performing treatability studies in the laboratory to select the chemical reagents that will most cost effectively meet the solidification and stabilization requirements. The reagents may include, but are not limited to Portland Cement, fly ash, cement kiln dust (CKD), blast furnace slag, and a wide range of synthetic chemical products. The selected reagents are stored in feed silos and carefully controlled/dosed to a mixing unit, usually a pug mill. The filter cake, fully or partially dewatered, is fed to the pug mill, mixed with the reagent blend, and staged for required curing. Combining our dewatering- and stabilization techniques our company reduces the need for reagents extensively. In the light of reduction of CO2 this new approach brings our company at the top of the processing industry

This approach has been proven to be effective for sediment processing resulting in an end product that can be beneficially reused.