One other small point - did your builders mention weep holes? These might be needed in order to drain any water from behind the retaining wall, so that pressure doesn't build up there. If you see something like *perps* mentioned on the drawings, then these are the perpendicular gaps left between the bricks (instead of mortar) to allow for water seepages. However, if the height of the retaining wall is only 1.5 ft, you might not need these weep holes, but it would be better if the water could escape !