Chapter 12.50
RETAINING WALLS
Sections:
12.50.020 Retaining wall construction and design.
12.50.010 Purpose and intent.
The purpose and intent of this chapter is to:
A. Recognize that, while at the basic level, a retaining wall is a structure that holds or retains soil behind it, retaining walls can also result in visual and physical blight, tree and vegetation removal, impairment of gateway areas, and other impacts that require visual design, planting, topographic, and aesthetic mitigation;
B. Recognize that retaining walls can be built from different materials to achieve the strength required and achieve mitigation and aesthetic goals;
C. Require aesthetic and other design features that mitigate these wall impacts and reflect the community environment, as adopted in retaining wall design standards and this chapter;
D. Recognize that retaining walls are frequently adjacent to noise-sensitive areas such as residential dwelling units and other land uses that are noise sensitive and subject to inequitable noise impacts, which can be intensified by removal of vegetation and trees and/or by the reflected noise from retaining wall surfaces;
E. Require proof of compliance with state regulations for noise attenuation, absorption, and transmission; recognize that compliance may be achieved through a variety of techniques and materials such as the use of tilted retaining walls to direct noise upward, large and small variations of facade to break up low to high frequencies, and sound reflection mitigation;
F. Require landscaping to avoid visual dominance of the retaining wall, potentially discourage graffiti, and add visual quality;
G. Encourage building material choices that ensure aesthetics, durability, maintenance, and cost;
H. Promote cooperation between the State of Washington Department of Transportation (“WSDOT”), the city, and the project proponent; and
I. The intent in this chapter is that the term “shall” (or “shall not” in the negative) represents a requirement to satisfy the regulation. The intent in this chapter is the term “should” (or “should not” in the negative) indicates a provision that is strongly encouraged, but that is not an absolute requirement. Compliance with a “should” provision is voluntary, but highly desirable to the community. (Ord. 1273 § 1, 2023)
12.50.020 Retaining wall construction and design.
A. Public Benefit. Retaining walls located within the right-of-way shall be installed to benefit the general public by supporting or protecting public transportation infrastructure and shall not be for private development gain.
B. Application Type.
1. An application for retaining wall construction and design approval shall be processed pursuant to the requirements in Chapter 16.26 LFPMC for a Type III permit, administrative decision made by the code administrator. The public works director shall be the “code administrator” for the Type III permit decision.
2. For proposed retaining walls 25 feet or more in length and that propose removal of 10 or more trees that are either exceptional, landmark, or significant trees as defined in Chapter 16.14 LFPMC, a neighborhood meeting shall be held pursuant to the requirements in LFPMC 16.26.050; provided, however, that the neighborhood meeting is not required to be held prior to submittal of the application for the retaining wall.
3. For purposes of sending notice of the neighborhood meeting under LFPMC 16.26.050(B), notice shall be mailed to owners of real property within 500 feet of either side of the right-of-way for the entire length of the retaining wall project. For projects involving more than one lot, notice of the neighborhood meeting shall also be sent to the planning commission and tree board. For purposes of sending the notice of application under LFPMC 16.26.040(D)(1)(b), notice shall be mailed to owners of real property within 500 feet of either side of the right-of-way for the entire length of the retaining wall project.
C. Transportation Design Manuals and Regulations. Retaining walls located on private property or right-of-way that support or protect public transportation infrastructure shall, at a minimum, meet the requirements set forth in the latest edition of the Washington State Department of Transportation (WSDOT) Design Manual, Bridge Design Manual, and the International Building Code. These manuals and codes provide policies, procedures, and methods for developing and documenting design improvements to the transportation network.
1. The retaining wall construction type shall be the same from the highest to the lowest portion of each independent wall segment. Where walls are terraced or tiered, all tiers/terraces shall consist of the same wall construction type for the length of each independent segment.
2. Concrete retaining walls shall be coated with a moisture barrier and antigraffiti paint.
3. Total structural isolation is required for public and private retaining walls adjacent to each other.
4. The public works director shall take into account long term maintenance requirements, constructability, and recommendations on same from the applicant’s engineers, and independent third-party engineers.
5. Easements may be required for the maintenance, operation, and replacement of the wall.
6. The applicant shall provide documentation of how the retaining wall design satisfies, or exceeds, applicable WSDOT traffic noise policy and procedures. The documentation should include an assessment of noise impacts from the proposed design, including consideration of tree and vegetation removal, reflected noise, and proximity to residences, as well as proposed reflection and absorption techniques such as the use of tilted retaining walls to direct noise upward and variations in the facade to break up low to high frequencies.
7. Prior to issuing a decision on the retaining wall, the public works director shall obtain, at the applicant’s expense, a written structural review and recommendation from an independent third party with professional expertise and no affiliation with the applicant.
D. Retaining Wall Design.
1. An architectural finish or engineered block shall be used that integrates with and supports the community identity of the city showing a strong relationship to the surrounding natural environment including native trees, flora, and fauna of the region. The architectural finishes included in provision 1 of the retaining wall design standards dated July 27, 2023, are examples that satisfy this requirement. The public works director will review and issue a decision on the architectural finish and engineered block consistent with this section after obtaining, at the applicant’s expense, a written review and recommendation from an independent third party with professional expertise and no affiliation with the applicant.
2. Landscaping treatments shall be used on retaining walls that reduce the harshness of these walls. The landscaping standards included in provision 2 of the retaining wall design standards dated July 27, 2023, are examples that satisfy this requirement. The public works director will review and issue a decision on landscaping treatments consistent with this section after obtaining, at the applicant’s expense, a written review and recommendation from an independent third party with professional expertise and no affiliation with the applicant.
3. As a condition of permit approval, the public works director shall require as needed, based on the impacts and circumstances related to a particular retaining wall, installation of a temporary irrigation system, and the funding for or implementation of a three-year tree and plant monitoring and maintenance plan, including the replacement of failed trees and plants. (Ord. 1273 § 1, 2023)