Riverton requires a lot specific soils report for every new single family home and commercial building permit (Riverton Building). That covers new buildings, not every repair or garden wall, but it shows how seriously the city takes site conditions.
The city also warns that public utility easements can limit where you can build, even where zoning setbacks would otherwise allow it. That matters for retaining walls and masonry fences near lot lines.
Reused foundation stones on Park Avenue
Riverton's historic tour includes the Dome Church Foundation Stone marker at 1728 Park Avenue, where granite benches were made from the foundation stones of the church that stood there from 1908 to 1939 (Historic Riverton Tour). Good stone can outlast the building it was cut for.
The city's published soils report requirement covers new single family homes and commercial buildings. A retaining wall may still need engineering depending on height and load; ask the city.