Sentence:  An optional cast-in-place concrete <WSD>waler</WSD> is shown at each anchor row location. The concrete <WSD>walers</WSD> are cast against the earth after installation of the helical anchors and prior to excavation for the next lift. Concrete <WSD>walers</WSD> can reduce the required thickness of shotcrete for the remaining facing. The <WSD>walers</WSD> also improve punching resistance at the helical tie back locations. 
Meaning of the word marked with <WSD> tags:  A plank of wood, block of concrete, etc., used for support or to maintain required separation between components in order to help maintain the form of a construction under stress.