A. For the purpose of this chapter, retaining walls shall be essentially vertical, and shall be constructed of concrete, masonry, or wood treated with an approved preservative under the treating and quality control requirements specified in the uniform building code standards 25-12, or wood of natural resistance to decay, as defined in chapter 25 of the uniform building code.
B. Such retaining walls shall be engineered to resist all imposed loads.
C. All retaining walls exceeding thirty inches (30") in height shall have a fence, wall or guardrail at least three feet (3') above the highest adjacent ground level. In open guardrail type fencing, intermediate members shall be so placed that a sphere nine inches (9") in diameter cannot pass through. (Prior code § 86004)