Intake Gates
Giant intake gates allow the river to pass through the dam. They are each 17 feet wide and 39 feet high. Due to the extreme variations in water levels (especially during the spring thaw) 10 flood gates, known as "sluicegates", were added so that excess water could pass through the dam quickly. These sluicegates allow a maximum discharge of 16,100 cubic meters of water per second. The highest flow of the St. John River ever recorded at Mactaquac was 12,200 cubic metres per second.