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