"尾煤沉淀池" can be translated as "tailings coal settling pond" or "tail coal sedimentation tank/basin".
"Tailings coal" refers to the coal residue or waste material that remains after the extraction or processing of coal.
"Settling pond" or "sedimentation tank/basin" describes a structure designed to allow suspended solids to settle out of a liquid through gravity.
Both translations are acceptable, but the choice may depend on the specific context or the preferred terminology in the relevant industry or field.