[1]
Editor's Note: Former Chapter 17.20, Design and Improvement Standards for the Subdivision of Land, adopted by Ord. 2740, was repealed by Ord. 2764, 6/9/2025.
The standards contained in this chapter are to be used as the basic standards for addressing the approval criteria for subdivisions, boundary line adjustments, lot consolidations, and BSIPs. The decision making entity may require additional standards be met if it is determined necessary to meet the approval criteria for a particular application.
(Ord. 2764, 6/9/2025)
A. 
Required Improvements:
Every applicant may be required to grade and pave streets and alleys, install curbs and gutters, sidewalks, monuments, sanitary and storm sewers, water mains, fire hydrants, street lights and name signs, together with all appurtenances in accordance with specifications and standards of this code, approved by the Public Works Department, and in accordance with other standards of the City.
B. 
Supervision and Inspection:
A licensed engineer or engineering firm, acceptable to the Department of Public Works, shall be responsible for the supervision and inspection of all subdivision improvements. All improvements shall be certified in writing as completed in accordance with plans and specifications as approved by the Department of Public Works.
C. 
Permits:
Prior to proceeding with any improvements, the applicant shall obtain those permits from the City as are necessary. The applicant is also responsible for complying with all applicable permit requirements of other Federal, State and local agencies.
(Ord. 2764, 6/9/2025)
A. 
Environmental Considerations:
1. 
Critical Areas:
a. 
Land that contains a critical area or its buffer as defined in TMC Title 18, or is subject to the flood zone control ordinance as defined in TMC 16.52, shall be subdivided to reflect the standards and requirements of TMC 18.45 (Environmentally Critical Areas), and/or TMC 18.46 (Planned Residential Development (PRD)), and/or TMC 16.52 (Flood Plain Management).
b. 
No lot shall be created that does not contain an adequate building site, given the environmental considerations of the lot and current development standards.
2. 
Trees:
In addition to meeting all applicable requirements of TMC Title 18, every reasonable effort shall be made to preserve existing trees and vegetation and integrate them into the subdivision's design. Unless impractical for reasons not the fault of the applicant, property lines shall be designed such that all existing significant trees are located on a single parcel. Any existing significant trees for which ownership will be shared between more than one property owner shall have a tree maintenance agreement placed on the face of the plat.
B. 
Compatibility with Existing Land Use and Plans:
1. 
Buffer Between Uses:
Where residential or mixed-use subdivisions are proposed adjacent to land use districts which permit exclusively commercial or industrial uses, and where natural separation does not exist, adequate landscape buffer strips and/or solid fences for screening shall be provided.
2. 
Conformity with Existing Plans:
The location of all streets shall conform to any adopted plans for streets in the City. If a subdivision is located in the area of an officially designated trail, provisions shall be made for reservation of the right-of-way or for easements to the City for trail purposes. The proposed subdivision shall respond to and complement City ordinances, resolutions, and comprehensive plans.
3. 
Other City Regulations:
All subdivisions shall comply with all adopted City regulations. In the event of a conflict, the more restrictive regulation shall apply.
4. 
Accessory Structures:
If a subdivision, short subdivision, or boundary line adjustment in a residential zone would result in an accessory structure remaining alone on a lot, the structure must be demolished before preliminary approval, or the owner must provide a bond or other financial guarantee acceptable to the Director in the amount of 150% of the cost of demolition and assurance that the accessory structure will be demolished if a primary use is not established on the lot within 12 months of final approval.
C. 
Utilities:
1. 
Generally:
All utilities designed to serve the subdivision shall be placed underground and, if located within a critical area, shall be designed to meet the standards of the critical areas overlay zone. Those utilities to be located beneath paved surfaces shall be installed, including all service connections, as approved by the Department of Public Works; such installation shall be completed and approved prior to application of any surface materials. Easements may be required for the maintenance and operation of utilities as specified by the Public Works Department.
2. 
Sanitary Sewers:
Sanitary sewers shall be provided to each lot at no cost to the City and designed in accordance with City standards. Septic systems may be installed when approved by the Seattle-King County Department of Public Health and when the existing sewer system will not be available to the lot within the life of the preliminary approval.
3. 
Storm Drainage:
The storm drainage collection system shall meet the requirements of the City's stormwater ordinance standards found at TMC Chapter 14.28 and TMC Chapter 14.30.
4. 
Water System:
Each lot within a proposed subdivision shall be served by a water distribution system designed and installed in accordance with City standards. Locations of fire hydrants and flow rates shall be in accordance with City standards and the Uniform Fire Code.
D. 
Blocks:
1. 
Length:
Residential blocks shall not be less than 300 feet nor more than 1,000 feet in length (600 - 2,000 feet for commercial and industrial areas). Where circumstances warrant for the purpose of implementing the Comprehensive Plan, the Director may require one or more public pathways of not less than six feet nor more than 15 feet in width, either by dedication or easement, to extend entirely across the width of the block to connect public rights-of-way.
2. 
Width:
Blocks shall be wide enough to allow two tiers of lots, except where abutting a major street or prevented by topographical conditions or size of the property, in which case the Director may approve a single tier.
3. 
Pedestrian Considerations:
Blocks, roads, and pedestrian improvements, shall be designed to provide a safe and convenient pedestrian network.
E. 
Lots:
1. 
Arrangement:
Insofar as practical, side lot lines shall be at right angles to street lines or radial to curved street lines. Each proposed lot shall have access to a public street. New flag lots shall not be permitted. Access requirements may be met by establishing common drive easements.
2. 
Lot Design:
The lot area, width, shape, and orientation, shall be appropriate for the location of the subdivision, for the type of development and land use contemplated, and shall conform with the requirements of the zoning ordinance.
3. 
Corner Lots:
Corner lots may be required to be designed with additional width to allow for the additional side yard requirements.
F. 
Landscaping:
1. 
Landscaping shall conform with Public Works standards and the requirements of TMC Title 18.
G. 
Street Signs:
The applicant shall be responsible for the initial cost of any street name or number signs, or street markings, including installation thereof, that Public Works finds necessary for the subdivision.
H. 
Lighting:
Street lighting shall conform to the Department of Public Works standards unless the Director of Public Works requires alternative fixtures, poles, and/or spacing to contribute to an overall design concept of the subdivision.
I. 
Monumentation:
1. 
Imprinted Monument:
All monuments set in subdivisions shall be at least 1/2 inch x 24-inch steel bar or rod, or equivalent, with durable cap imprinted with the license number of the land surveyor setting the monument.
2. 
Centerline Monument:
After paving, except as provided in TMC Section 17.20.030.I.4, monuments shall be driven flush with the finished road surface at the following intersections:
a. 
Centerline intersections.
b. 
Points of intersection of curves if placement falls within the paved area; otherwise, at the beginnings and endings of curves.
c. 
Intersections of the plat boundaries and street center lines.
3. 
Property Line Monumentation:
All front corners, rear corners, and beginnings and endings of curbs shall be set with monuments, except as provided in TMC Section 17.20.030.I.4. In cases where street curbs are concentric and/or parallel with front right-of-way lines, front property line monumentation may be provided by brass screws or concrete nails at the intersections of curb lines and the projections of side property lines. If curb monumentation is used, it shall be noted on the plat, and also that such monumentation is good for projection of line only and not for distance.
4. 
Post-Monumentation:
All monuments for exterior boundaries of the subdivision shall be set and referenced on the plat prior to plat recording. Interior monuments need not be set prior to recording if the developer certifies that the interior monuments shall be set within 90 days of final subdivision construction inspection by the Department of Public Works, and if the developer guarantees such interior monumentation.
5. 
Post-Monumentation Bonds:
In lieu of setting interior monuments prior to final plat recording as provided in TMC Section 17.20.030.I.2 the Director of Public Works may accept a bond in an amount and with surety and conditions satisfactory to the Director, or other secure method as the Director of Public Works may require, providing for and securing the actual setting of the interior monuments.
(Ord. 2764, 6/9/2025)
A. 
Extension:
Proposed street systems shall extend existing streets at the same or greater width, unless otherwise approved by the Department of Public Works and authorized by the Director in approval of the subdivision. Where appropriate, streets shall be extended to the boundaries of the subdivision to ensure access to neighboring properties. The City's goal is to have an integrated system of local streets whenever practical. Grading of steep topography may be necessary to achieve this objective. However, in critical areas, the layout and construction of streets shall follow the standards and procedures of TMC Chapter 18.45.
B. 
Frontage Dedication:
Dedication of property as right-of-way along frontages may be required when it is necessary to meet the minimum street width standards or when lack of such dedication would cause or contribute to an unsafe road or intersection.
C. 
Names:
All proposed street names or numbers shall be subject to approval by the Department of Community Development.
D. 
Intersections:
Any intersection of streets, whatever the classification, shall be at right angles as nearly as possible and not be offset insofar as practical.
E. 
Street Layout:
Street layout shall provide for the most advantageous development of the subdivision, adjoining areas, and the entire neighborhood. Evaluation of street layout shall take into consideration potential circulation solutions. While it is important to minimize the impact to the topography from creating an integrated road system, improved site development and circulation solutions shall not be sacrificed to minimize the amount of cut and fill requirements of the proposal. Where critical areas are impacted, the standards and procedures for rights-of-way in TMC Chapter 18.45 shall be followed.
F. 
Privately Owned Streets:
1. 
Privately owned streets shall only be authorized when they meet the following criteria:
a. 
Allowing privately owned streets in the area being subdivided will not adversely affect future circulation or access to neighboring properties; and
b. 
Adequate and reasonable provisions are made for the future maintenance and repair of the proposed privately owned streets; and
c. 
The proposed privately owned streets can accommodate potential full (future) development on the lots created; and
d. 
The City of Tukwila determines that dedication of the proposed street as right-of-way is unnecessary due to potential traffic volume, street patterns, land use, lot patterns, or any other metric.
2. 
Privately owned streets shall meet the minimum requirements of the appropriate street type for the proposed project. See TMC Section 17.20.050 for street types. An applicant may choose a smaller width for a privately owned street, provided the width meets all life safety requirements. The Department of Community Development shall establish alternative widths when necessary to meet the minimum requirements of life safety standards, or if the City determines additional street components are needed due to site circumstances, including, but not limited to: topography, traffic volume, street patterns, on-street parking, lot patterns, land use, or the need for additional pedestrian, bicycle, or transit facilities.
3. 
Public Access:
Privately owned streets shall provide permanent public access for non-motorized travel via easements. Access to privately owned streets by pedestrians or bicyclists shall not be blocked by any physical obstructions. Sidewalks installed on privately owned streets shall connect to any existing sidewalk network on adjacent streets. Terms of the public access may be established; however, terms may not include restrictions on bicycle usage of vehicle lanes or prohibitions of usage by the public after 6:00 AM or before 10:00 PM.
a. 
Exceptions:
Requirements for providing public access may be waived by the Department if the applicant can demonstrate one or of the following:
(1) 
Allowing public access would expose the public to unavoidable health or safety hazards, such as active railroad tracks or hazardous chemicals related to the primary use, that cannot be prevented by any practical means; or
(2) 
The area is limited to authorized personnel and inherent security requirements of the use cannot be satisfied through the application of alternative design features or other solutions; or
(3) 
Allowing public access would cause unavoidable environmental harm, that cannot be adequately mitigated; or
(4) 
Public access is not feasible due to the configuration of existing parcels, structures, or streets, such that potential access areas are blocked in a way that cannot be remedied reasonably by the proposed development; or
(5) 
Significant undue and unavoidable conflict between the proposed access and adjacent uses would occur and cannot be mitigated.
G. 
Public Streets:
1. 
Streets that do not meet the criteria found at TMC Section 17.20.040.F.1 shall be designated as public streets.
2. 
The minimum total width of the right-of-way and the minimum width of the street components for public streets shall be as shown in TMC Section 17.20.050. The City shall establish the appropriate street type for all existing and proposed new streets. The Department of Community Development shall require alternative widths when necessary to meet the minimum requirements of life safety standards, or if the City determines additional street components are needed due to site circumstances, including but not limited to: topography, traffic volume, street patterns, on-street parking, lot patterns, land use, or the need for additional pedestrian, bicycle, or transit facilities.
H. 
Street Components and Improvement Requirements:
All new streets, all streets interior to a subdivision, and the half of all streets that abut the perimeter of a subdivision, shall use the following general component standards. These standards shall also be used for improvements to the frontages of parcels undergoing development, when required by TMC Title 18. Standards specific to each of the street types may be found at TMC Section 17.20.050.B, or in the Tukwila Infrastructure Design and Construction Standards. Alternative designs may be considered provided they meet the goals of the comprehensive plan and this chapter and comply with all life-safety requirements. In areas of conflict between this section and any other adopted standard, including the Tukwila Infrastructure Design and Construction Standards, the standards of this section shall be used.
1. 
Sidewalks:
a. 
All new sidewalks shall be a minimum of 6 feet in width.
b. 
No obstacle, including utilities or street furniture, shall be placed within the required sidewalk space.
2. 
On-Street Parking:
Streets may provide parallel on-street parking.
a. 
On-street parking lanes may not exceed 9 feet in width.
b. 
On-street parking spaces may be counted toward minimum parking requirements for proposed uses within the associated project.
c. 
All streets with on-street parking lanes shall feature, at a minimum, a 6-foot wide buffer zone adjacent to the curb. The buffer zone shall be installed between the sidewalk and the parking lane.
3. 
Intersections and Crossings:
a. 
Pedestrian crossings at intersections and driveway entrances shall be raised to curb height.
b. 
On-street parking lanes shall end at least 20 feet from each intersection.
c. 
New streets with on-street parking shall feature curb bulbs at intersections to shorten pedestrian crossing distances.
d. 
All intersections shall feature crosswalks, and, if determined necessary by the Department, pedestrian crossing signage.
I. 
Street Design:
The design and alignment of all new streets shall conform to the following standards unless otherwise approved by the Department:
1. 
Cul-de-Sacs:
New cul-de-sacs shall not be permitted.
2. 
Curbs and Gutters:
All new streets shall have permanent concrete curbs and gutters according to Department of Public Works standards.
3. 
Storm Drains:
All new streets shall have storm drains consisting of the proper size pipe and catch basins.
4. 
Street Grades:
Street grades shall not exceed 15%. However, provided there are no vehicular access points, grades may be allowed up to 18%, for not more than 200 feet when:
a. 
Exceeding the grades would facilitate a through street and connection with the larger neighborhood; and
b. 
The greater grade would minimize disturbance of critical slopes; and
c. 
The Fire Marshal grants approval of the grade transition; and
d. 
Tangents, horizontal curves, vertical curves, and right-of-way improvements conform to Department of Public Works standards.
J. 
Street Improvements:
The half of all streets that abut the perimeter of a subdivision or development project identified in TMC Title 18 shall be improved to comply with all requirements of this chapter and the Tukwila Infrastructure Design and Construction Standards for new streets. Additional paving may be required to ensure safe and efficient roads exist to serve the subdivision.
(Ord. 2764, 6/9/2025)
A. 
The following table shows minimum standards for street types. Alternative standards may be considered provided they meet the goals of the comprehensive plan and this chapter and comply with all life-safety requirements. In areas of conflict between this section and any other adopted standard, including the Tukwila Infrastructure Design and Construction Standards, these standards shall be used unless otherwise approved by the Director of Community Development and the Director of Public Works.
Type of Street
Total Width
Roadway Pavement Width
Component Requirements
Principal Arterial
80'-100'
48'-84'
The width of components of these street types shall be determined by TMC § 17.20.040.H, as well as the requirements of the Department of Public Works, including the Tukwila Infrastructure Design and Construction Standards.
Minor Arterial
60'-80'
36'-64'
Collector Arterial
60'-80'
24'-48'
Access Road
50'-60'
28'-36'
Alley
20'
15'
Vehicle Lane Width
Sidewalks
Landscaping / Buffer Zone Width
Parking / Flex Zone Width
Neighborhood Yield Street - Single Side Parking (See TMC § 17.20.050.B.1)
40'
11'
6'+6' = 12' Total
5'+5' = 10' Total
7'
Neighborhood Yield Street - Parking on Both Sides (See TMC § 17.20.050.B.1)
50'
12'
6'+6' = 12' Total
6'+6' = 12' Total
7'+7' = 14' Total
Vehicle Clear Zone
Landscaping / Furniture Islands / Clear Zones
Parking Area Widths (optional)
Living Street - Through (See TMC § 17.20.050.B.2)
20' Minimum
10'
10'
7'
Living Street - Dead End (See TMC § 17.20.050.B.2)
20' Minimum
16'
4'
Private Access Lane
Less than 20'
For private access lanes of less than 20 feet of width, see TMC § 17.20.040.F.2.
B. 
Street Specific Standards:
1. 
Neighborhood Yield Streets:
Neighborhood Yield Streets are designed as low speed and low volume streets. These streets allow for single-direction vehicle travel at a time and require vehicles to pass each other by pulling over into loading areas, empty street parking spaces, curb cuts, or other gaps. Neighborhood Yield Streets always feature sidewalks, landscaping strips, and at least one on-street parking lane.
(a) 
Applicability:
Neighborhood Yield Streets are appropriate in areas where the majority of the street's uses are residential or are community amenities such as parks, schools, and gathering spaces. They are not appropriate where the street would serve as a major transportation corridor for regional travel.
2. 
Living Streets:
Living Streets are shared streets where the design enforces that the street is shared by all users, including pedestrians, bicyclists, and vehicle drivers. These streets do not feature curbs and instead utilize other design features and traffic calming devices to compel drivers to drive slowly.
(a) 
Sidewalks:
On Living Streets (TMC § 17.20.050.A), no sidewalk is required, as the street design shall reinforce pedestrian right-of-way within the entire street.
(b) 
Materials:
Living Streets shall be paved with textured or pervious pavement, pavers, or other similar materials that reinforce the pedestrian-priority nature of the street.
(c) 
Improvements:
Streets on the perimeter of a subdivision that are designated as Living Streets but that are subject only to partial improvement shall establish a portion of the 20-foot-wide street pavement as a pedestrian walkway with a minimum width of 5 feet. The street shall meet all other requirements established by this chapter and the requirements of the Department of Public Works and the Fire Department.
(Ord. 2764, 6/9/2025)