Size the trench so there's enough room for the retaining wall block and at least 8 in. of space behind it. Excavate deep enough to completely bury at least one full course, including space for 6 ...

In a retaining wall, these blocks are stacked together in several courses, and capped off with a concrete capstone at the top. The blocks are hollow, which makes them lightweight and easy enough ...

Retaining walls at Mt. Pleasant City Hall that are showing signs of deterioration are scheduled to be replaced next year.