Debris Management

• Trashracks• Screen Cleaning Systems

Trash racks - Criteria

• “Open channel intakes shall include a trash rack which shall be kept free of debris.”

• “In certain cases, a satisfactory profile bar screen can substitute for a trash rack.”

• Comment - No trashrack would be rare situation - such as an on-river screen.

Trashracks

Trashracks

Trashracks

Trashrack Spacing

• Salmon can reject passage through small bar spacing's (3”).

• Recommend no smaller than 4”, but only go this small if there is a compelling reason to do so.

• Usually 6” – 9” spacing works pretty well.• Need to carefully assess what debris may be

present.

Trashrack Maintenance

• Install at a 1:5 (horizontal:vertical) slope (or flatter) for ease of cleaning.

• Provide easy access for cleaning.• Provide range of freedom for manipulating

debris.• Need to clean trashrack whenever head drop

exceeds a few inches, or whenever debris accumulates

Cleaning Systems

Main Criteria for Cleaning Systems

• Effective, reliable, proven, approved by NMFS• Head differential to initiate cleaning = 0.1 ft• Automated cleaning for most systems

Traveling Brush Cleaning System

Air Burst Cleaning System

Water Jet Cleaning System

Rotation – Vertical

Traveling Screens Cleaning System

Rotation – Drum Screen Cleaning System

Flow Distribution and Balancing

Approach flow – poor conditions

Approach flow - good conditions

Correcting Channel Configuration – Hydraulic Modeling

Channel Configuration – Approach Flow Conditions

Balancing Screen Approach Velocity

Balancing Screen Approach Velocity

Baffles for Adjusting Approach Velocity

Baffles for Adjusting Approach Velocity

Swift FSC – Offset Orifice Baffle Panels

Balancing Rotary Drum Screens

Cylindrical Screen Without Internal Baffles

Cylindrical Screen With Internal Baffles