Common use of Fish Passage Clause in Contracts

Fish Passage. Fish passage to and from the district waterways is restricted by several features within the drainage infrastructure. A dike system protecting the district from flood and tidal flows generally blocks the passage of adult and juvenile fish. In those cases where waterways intersect the levee system, passage is restricted by a culvert fitted with some sort of tide regulating mechanism or is blocked entirely by the dike system. Either of these features strictly limits the access of fish to and from the system except in those instances where floodwaters top or breach the system. In some cases, waterways that intersect the dike system are fitted with pump stations that facilitate the export of water over and through the dike. These pump stations are often used as backup mechanisms to conventional gravity discharge so that heavy storm related flows can be managed more effectively. Adult and juvenile fish can be entrained into the pumps during their downstream migration where they can be injured or killed. The majority of drainage pump facilities are associated with culvert/tide gate complexes through which upstream and downstream passage of adult and juvenile fish is possible, though limited. The primary point of access for fish to and from the system is located at those intersections where the gravity flow drainage is managed by a culvert fitted with some sort of tide regulating feature. Though tide gates do not completely block the upstream passage of adult and juvenile fish, upstream passage is restricted to very narrow windows of the tide cycles during which the tide gate is open and the discharge velocity does not exceed the upstream swimming capabilities of the individual fish. The window for upstream passage is greater for adult fish than for juvenile fish because of their stronger swimming capabilities. Tide gates do not completely block the downstream passage of adult and juvenile fish though downstream passage is limited to the low tide cycles when the water surface elevation upstream of the tide gate is sufficiently greater than the water surface elevation downstream of the tide gate to create the head differential to open the tide gate.