The utility model discloses an emergency pond suitable for be used for collecting bridge floor runoff in water source ground protection zone, this emergency pond's the outside be masonry barricade (1), and the inboard of masonry barricade (1) is filled layer (9), gravel bed course (8), is prevented osmosis membrane (7) and cast in situ concrete layer (6) for gravel class soil in proper order to interior by outer, wherein, cast in situ concrete layer (6) upper berth is equipped with pollutant absorption and purifies layer (5). To water source ground protection zone special environmental protection requirement and topography restriction, the utility model discloses can play with the bridge floor runoff collect and with water source ground protection zone in the effect of surface runoff isolation, and the utility model discloses can adsorb the pollutant reaches the convenient effect of handling of later stage.