Abstract: Methods of forming layers of material upon or below the earth's surface and above the water table to prevent or effectively inhibit the flow of groundwaters through such laters of initially unconsolidated materials. Chemical components are added to materials such as incinerator ash or other waste materials deposited in a landfill operation to create alkaline conditions which, when contacted by water, induce precipitation of calcite in sufficient quantities to produce a cementing action which retards leachate formation. In another aspect, a site is prepared for use as a landfill with an essentially hydraulically sealed sub-base by choosing a site with alkaline soils or carbonate bedrock and adding appropriate chemical components to cause calcite to precipitate when contacted by water, which may be applied directly or by naturally occurring precipitation.

Abstract: A method of artificially sealing cracks, fissures or other voids in earth strata under alkaline conditions, or in alkaline structural materials. Sealing is effected by induced precipitation of calcium carbonate, usually in the form of calcite, either in alkaline rocks, in other rocks where alkaline groundwaters are present, or in structures of alkaline materials such as cement or marble. A number of examples are discussed for effecting the desired precipitation including application of aqueous solutions which affect either calcium or carbonate ion concentration, increasing pH by degassing of carbonated water and application of slurries of less stable forms of calcium carbonate (aragonite and vaterite) to result in precipitation of the more stable form (calcite).