Drainage (generally a sand or gravel layer) can be provided between the EPS geofoam fill and the natural soils to reduce potential uplift forces. Providing for adequate drainage of groundwater and/or surficial waters below the EPS geofoam prevents water from infiltration and reduces the development of uplift forces.
Because of its closed-cell structure and light weight, EPS geofoam is buoyant. Care must be taken during design, construction and post-construction to ensure that the potential flotation forces are accounted for within the hydrological conditions of the site. Adequate surcharge, i.e., soil or pavement cover, or an alternate means of passive restraint must be provided against uplift. Alternately, the material can be installed above the water table or the water table can be lowered using suitable drains or other dewatering systems.