The expanded vent 18 of the present invention includes a weir 20 located such that {HEAD ~ the normal operating water level} 21 in expanded vent 18 is above {TAIL ~ weir} 20 
The expanded vent 18 of the present invention includes a weir 20 located such that { HEAD ~ the normal operating water level } 21 in expanded vent 18 is above { TAIL ~ weir } 20
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL OTH