Solidification and stabilization are treatment technologies that achieve remediation goals by mixing contaminated materials with reagents that reduce leaching, and thus mobility, of the contaminants. Rain, stormwater runoff, and groundwater flow can leach contaminants from soil, sludge, and other wastes in the environment and transport them to groundwater or nearby surface water bodies, increasing potential exposure pathways for human and ecological receptors. The CLU-IN Solidification/Stabilization (S/S) Focus Area has been updated to reflect the current state of the science, including new screening questions for considering S/S as a remedy.