Retaining walls, rockeries, modular block walls, rock walls, or any other structures which retain soil, retain earth surcharge, protect an exposed soil face, or serve as a gravity retaining wall, shall, for the purposes of this chapter, be known as retaining structures. Retaining structures shall be consistent with the following:
A. Height Measurement. The height of a retaining structure shall be measured from the point at which the ground elevation of the city-approved finish grade intersects with the retaining structure to the highest point of the retaining structure as illustrated in Figure 12.14.152-1.
B. Retaining Structure Location, Maximum Heights and Minimum Separation within Setbacks.
1. All retaining structures, including footings or foundations, shall be set back at least one foot from any property or right-of-way line, unless the applicant provides a recorded easement from the adjacent property owner or owners to allow either all or a portion of the retaining structure to be on or closer to an adjacent property.
2. Within rear and front yard setback areas, retaining structures shall not be higher than four feet. Two or more up to four-foot high retaining structures may be permitted within rear or front yard setbacks, provided the retaining structures are separated by a distance that is equal to two times the height of the structure as illustrated in Figure 12.14.152-2 and 12.14.152-3.
3. The maximum slope gradient allowed between retaining structures shall be a four-foot horizontal to a one-foot vertical (4H:1V) slope.
4. Within side yard setback areas, retaining structures shall not be higher than six feet as illustrated in Figure 12.14.152-2.
C. Retaining structures located outside the setback or yard area shall be consistent with the following:
1. Retaining structures shall have a maximum height of 12 feet;
2. All retaining structures shall be separated by a distance that is equal to the height of the downslope retaining structure; and
3. A maximum slope gradient of four feet horizontal to one-foot vertical (4H:1V) shall be placed between retaining structures;
These provisions are illustrated in Figure 12.14.152-5 below.
4. The community development director, in consultation with the public works director, may waive or reduce the wall separation distance, may increase the maximum allowed slope gradient between retaining structures up to a three-to-one slope (3H:1V), and may increase the allowed maximum height of a retaining structure if the applicant demonstrates the reduced separation distance and/or increased gradient and/or wall height is necessary to:
a. Reduce potential adverse impacts to a critical area(s) or buffer(s) as defined by Chapter 14.04 BMC; or
b. Retain a greater number or diameter inches of significant trees; or
c. Permit the installation of transportation improvements; or
d. The alternative separation, slope gradient, or height is in the public interest.
D. All retaining structures, building or structure foundation walls or the walls of surface water vaults or facilities that are visible from adjacent public rights-of-way or residential properties shall apply the following:
1. All retaining structures four or more feet in height shall be constructed of or faced with brick, stone, split-face or fluted concrete block, textured poured-in-place concrete, or other materials with texture to reduce the apparent mass of the wall, as illustrated in Figure 12.14.152-6;
2. All retaining structures greater than six feet in height shall be installed with hanging and/or climbing vegetation above or below the wall, and/or shall be installed with a bas-relief sculpture or other art forms as approved by the community development director, which sculpture or art shall be incorporated on or into the face of the wall, as illustrated in Figure 12.14.152-7.
(Ord. 2269 § 7, 2018).