Many different types and brands of conditioners are used in tunneling based upon soil conditions present along the alignment. Conditioners are generally categorized as foams, polymers and bentonites. On recent projects, DCA consultants have observed the use of Soilax S products (available from the manufacturer Boraid Products), which are surfactants (i.e., detergents) and mixed with clean water as a foaming conditioner. Sometimes, a cellulose product, like Soilax C, is added into the conditioner mix to provide added strength to the soap bubbles, which helps when the conditioner is injected into certain soil formations. Thickening agents, such as polymers and a bentonite (a naturally occurring clay), are also used for different soil conditions. These include such products available from Mapei Products. These are just examples of some products that could be used. The construction specifications would require any conditioners to be inert (chemically inactive).