methods for increasing hydrophobicity of native water - bearing zones or aquifers comprising the step of permanently embedding non - degradable , solid colloidal materials formed to have a particulate size of less than 10 microns . exemplary materials include activated carbon , zeolites and hydrophobically treated clays . the particulate colloidal materials are coated with an agent to facilitate their distribution , including anionic polymers , chelating agents or combinations thereof . the materials are applied preferably by low pressure injection and are particularly effective at containing the migration of hydrocarbon contaminants , typically present as a plume , for at least several decades .