are they clay units? they almost look like flue tiles but not quite. they would be stacked verticlly on end if so. no way can they be meant for a retaining wall
you can place drainage holes in the bottom of the wall at every 4 foot and paint the wall with a hydocide on the side where the back fill is you will eliminate most of any water problems. besides you can also paint the face side of the cmu wall to cover any kind of staining
I dont know much about the iron you plan to use, but the block should hold with no problem, especially since it is a non load bearing wall. i suggest that you fill the block pier at both ends of the opening fully with grout, also embed a steel plate in the concrete at both ends of the iron so...
a 4 inch block is never to be used as a structural unit, the cells are too small to hold rebar and concret. a 6 inch block is still a bit small to hold back any backfill. i strongly suggest an 8 inch block wall as a minimum for retaining walls. i also reccomend grouting the vertical cells every...