(This technical specification is to be used to guide the writer in the contract requirements for Deep Soil Mixing (DSM) construction for a specific site. Included are ___________________ to be filled in with project specific data. Also included are [ ] which denote options to be considered for specific design requirements. Optional subsections are denoted by *. Parenthetic remarks ( ) are included when appropriate to provide the writer with additional, nonessential information. Most [ ] and * are used to include DSM designs which go beyond the standard design and may include addition of proprietary additives, injection of air for vapor phase extraction of organics. All [ ], ( ), and * should be filled in or omitted from the writer’s specification.) DEFINITIONS DEEP SOIL MIXING is a soil improvement technique used to construct cutoff or retaining walls and treat soils in-situ. This is accomplished with a series of overlapping stabilized soil columns (typically 36-inch diameter). The stabilized soil columns are formed by a series of mixing shafts (2 to 4) guided by a crane supported set of leads. As the mixing shafts are advanced into the soil, (grout/slurry) is pumped through the hollow stem of the shaft and injected into the soil at the tip. The auger flights and mixing blades on the shafts blend the soil with grout or slurry in pugmill fashion. The mixing shafts are positioned to overlap one another and form a continuously mixed overlapping column. When the design depth is reached, the augers are withdrawn and the mixing process is repeated on the way to the surface. Left behind are stabilized DSM columns having the following (property/properties): (low permeability, improved bearing capacity, or shear strength, immobilized contaminants, and when reinforced, able to withstand differential soil and hydrostatic loading). SLURRY is a stable colloidal mixture of water and bentonite clay and/or attapulgite clay. Other additives may be used as approved by the Engineer to enhance the behavior of the slurry. GROUT is a stable colloidal mixture of water and Portland cement. Additional materials such as bentonite clay, attapulgite clay or fly ash may be added.