Vertical moisture barriers are typically used to prevent moisture migration under an adjacent structure. Typically a narrow vertical trench is dug and some type of impermeable material is installed. This material could be a heavy polyethylene sheeting, ridged root barrier or lean concrete. Moisture barriers can be used in lieu of excavation and recompaction to protect existing structures.
Vertical moisture barriers are also utilized to prevent moisture wicking from the treated subgrade. They are most often used where routine perimeter moisture maintenance is difficult. City streets, storage tanks and remote structures are all candidates for vertical moisture barrier protection.
Surface Moisture Seal
Surface moisture seals or horizontal moisture barriers are placed to prevent desiccation of moisture conditioned soils. The most common application is on residential lots which have been moisture conditioned but may not be built on for an extended period of time.
Excavation and Recompaction
Moisture conditioning by excavation and recompaction is another means to pre-swelling expansive soils. According to geotechnical engineers excavation and recompaction is defined as: “…excavation of the upper soil, mechanically mixing the soil with water, then recompaction of the excavated soil in controlled lifts. This method of pre-swelling the soils is only effective if the water is uniformly blended with the soil. Simply wetting the surface soil will not achieve the required result.” Unfortunately, uniformly blending takes time and most are not willing to put in the effort needed to properly blend the water into the clay soil, leaving the possibility for swell potential in the soil mass.
Jowell Injection Company only performs excavation and recompaction in certain situations. Typically when excavation and recompaction is only a small portion of a larger water injection project or when the proposed water injection area abuts an existing structure and vertical moisture barriers are not an option.