from the apron surface or pavement to flow directly through the valve 42 into the storm sewer system should an accident occur whereby a contaminating fluid such as aircraft jet fuel hydraulic fluid lavatory truck spill or other contaminant be accidentally discharged onto the apron surface 16 and flow by gravity to the receptacle the sensor 34 will detect its presence and immediately generate a signal to the control unit which in turn will automatically close the valve 42 and open the valve 40 to the storage tanks or to the central vacuum system the control unit can also serve other functions cause an alarm to sound at a manned facility so that an appropriate agency can be contacted to investigate the spill and arrange a cleanup if necessary and illuminate an indicating light on a display panel to show the location of the catchbasin from which the signal originated in both embodiments a manual or automatic routine may be arranged whereby all the valves valve 28 in the embodiment of fig1 are closed upon the detection of an emergency e g a large spill or a spill combined with a heavy rainfall this will cause as discussed above a flooding of the area adjacent to the catchbasin until mobile trucks or other preventive measures are arranged for to remove the hazardous medium from the receptacle and the vicinity of the catchbasin while the embodiment of fig2 employs two valves the objects of the invention can be met by using a single three way valve having a single inlet and two outlets one to the storm sewer system and one to the storage.