Heave due to expansive clay soils is a common problem in some areas of the US. Injection systems treat expansive clays beneath buildings, and landfills with the pressure injection of an aqueous solution of water, lime or lime/flyash slurry, or potassium chloride. Water injection preswells expansive clays prior to construction. Lime injection fills the desiccation pattern of expansive clay with slurry and stabilizes the surface of the pad for workability, for building pads, streets, parking lots, and runways. Lime/flyash injection improves low-strength soils to improve bearing capacity and/or trafficability of runways, landfills, and bridge approaches. Potassium chloride injection arrests heave occurring beneath existing structures by limiting the amount of water underlying clays can absorb. Hayward Baker has experience with the full range of heave control techniques to provide effective heave control for most projects.