§ 9.4.3. Retaining Walls

A.

Design  

1.

Applicants are encouraged to use building foundations as retaining walls to retain slopes. There is no limit on the height of building foundation walls serving as retaining walls, provided the resulting building does not exceed the district height standards.

2.

Where retaining walls are necessary, they are limited as follows:

a.

Retaining walls must be separated horizontally by at least 4 feet from other retaining walls. This horizontal separation area must be graded to capture stormwater and not sloped such that stormwater will run off.

b.

Each tier between retaining walls must be vegetated and maintained with a mix of native, evergreen and deciduous shrubs, to be approved by the City Arborist, as follows:

i.

One shrub every 4 linear feet; and

ii.

The Director may waive this landscaping standard for retaining walls that slope back and contain natural planting.

B.

Measurement  

1.

Total retaining wall height is considered to be the vertical distance between finished grade level at the front of the wall and the grade level at the back of the wall at the same section.

2.

Any portion of a retaining wall extending above the finished grade is considered to be a fence or wall, subject to the requirements of Sec. 8.2.10.

C.

Maintenance and Replacement Existing legally permitted and constructed retaining walls may be maintained and repaired, provided the maintenance and repair do not result in an increase in the height of the wall.

D.

In RE-, RD- and RU- Districts In order to protect trees and vegetation on sites and to protect the character of the neighborhood, the following standards apply to all lots in RE-, RD- and RU- Districts.

1.

In the side building setbacks:

a.

In all RE- districts, retaining walls may encroach up to 10 feet into required side building setbacks.

b.

In all RD- districts, retaining walls may encroach up to half the depth of the required side building setbacks.

c.

In all RU- districts, no encroachment for retaining walls is allowed into the required side building setbacks.

2.

In the rear building setbacks:

a.

In all RE- Districts, no retaining walls are allowed within 20 feet of the rear lot line.

b.

In the RD-27, RD-18, and RD-15 districts, no retaining walls are allowed within 15 feet of the rear lot line.

c.

In the RD-12, RD-9, RD-7.5, and RU- districts, no retaining walls are allowed within 10 feet of the rear lot line.

3.

Newly constructed retaining walls are subject to the following requirements:

a.

Up to 6 feet in height as a single wall or tiered walls.

b.

Over 6 feet in height requires tiered retaining walls (each not to exceed 6 feet in height).

c.

Wing walls (retaining walls that allow daylighting of a basement) are permitted to be up to 12 feet in height if they are inward facing and finished with durable materials (stucco, brick, or stone). If they are to encroach into the building setbacks, the wing walls have to be a maximum of 6 feet in height and meet the retaining wall setback requirements above.

E.

In All Other Districts The following standards apply to all districts other than those addressed in Sec. 9.4.3.D.

1.

Newly constructed retaining walls are subject to the following requirements:

a.

Up to 8 feet in height as a single wall or tiered walls.

b.

Over 8 feet in height requires tiered retaining walls (each not to exceed 8 feet in height), which require a building permit.

F.

Materials All retaining walls must be finished with stucco, brick or stone. With approval of the Director, architectural segmented or modular block walls may be approved. No unfinished concrete masonry units or other similar materials are allowed.

G.

Permits and Indemnification  

1.

Retaining walls over 4 feet in height require a retaining wall permit and an indemnification.

2.

Retaining walls over 6 feet in height require a professional engineer's certification regarding the design of the wall.

3.

A retaining wall permit is required where an assemblage of tiered retaining walls and slopes results in an excess of a 2:1 slope.

4.

Where a retaining wall of any height supports a surcharge, a retaining wall permit may be required by the Director. Surcharge is any vertical load imposed on the retained soil that may impose a lateral force in addition to the lateral earth pressure of the retained soil. Examples of surcharges include:

a.

Sloping retaining soil;

b.

Structure footings supported by the retained soil;

c.

Adjacent vehicle loads supported by the retained soil.

5.

During the permit review process, the global stability of any series of tiered retaining walls will be reviewed. A safety factor of at least 1.5 is required.

6.

Where a retaining wall might impact (either visually or structurally) an existing structure, adjacent property, a street, a buffer, a utility, or other similar significant interest, the Director may require plans, details, cross-sections, and professional engineer calculations beyond those cited in this Section.

( Ord. of 4-17-2018(7) , §§ 9-41—9-46.1)