How does bucket-ladder dredging mine placer deposits?

A bucket-ladder dredge is a mechanical system used for the underwater excavation of placer deposits. It operates as a floating plant consisting of a hull that supports an excavating mechanism, beneficiation circuits, and waste-disposal systems.1

The excavation process functions as follows:

• Mechanism: An endless chain of open buckets travels around a rigid, adjustable frame known as a ladder.12
• Digging: The lower end of the ladder is lowered to the mine face—the bottom of the pond—where the buckets dig into the material.12
• Lifting: As the chain rotates, the filled buckets are pulled up the ladder, supported by rollers, toward the center of the dredge.12
• Processing: The buckets dump their load into a feed hopper at the top of the ladder, where the material enters a treatment plant to recover valuable minerals.12
• Disposal: Once the valuable material is removed, the remaining waste is discharged off the back of the dredge.1

This method is highly flexible and remains a traditional, widely used tool for mining under varying conditions.13