Definition - What does Dam Board mean?
A dam board is used to block or divert the flow of a sewer or drain line. Dam boards are either made from natural materials, such as a wooden plank -- hence the name dam board -- or can be made of synthetic materials. In trenchless construction, dam boards are utilized during pipeline repair or rehabilitation projects.
Trenchlesspedia explains Dam Board
The dam board serves the same function as a sewer plug as it blocks a line to prevent the flow of water or other product within the line. Used during trenchless construction, it prevents water from an existing line to flow into a section undergoing rehabilitation or installation. Dam boards can be placed across a sewer or drain downstream from new construction areas to direct flow. Dam boards are removed once the work is completed.