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Chapter 4
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Design Criteria
4.15 Introduction to Utilities Design Criteria

One of the important functions of the right-of-way is to provide space for water, sewer, electricity, street lighting, traffic signals and other utilities, both above and beneath the street surface. There are standard locations for each utility in relation to roadway pavement, curbs, planting strips, and sidewalks, and there are requirements for utility clearances.

The following sections define the design criteria for utilities in the right-of-way:

4.16: Street Lighting
4.17: Street Drainage, Storm Drains and Sewers
4.18: Water Mains
4.19: Fire Protection

In addition to these sections, the following design criteria apply for utility easements and relocation.
4.15.1 Design Criteria

Utility Easements

Need for utility easements: When public utilities for sewer, storm, or power facilities are constructed on private property, a utility easement will need to be granted to the City. These easements are needed to establish rights for the City including, but not limited to, construction, operation, and maintenance access as needed to own and operate the facility.

Easement width: The width of the required easements are governed by factors such as the type of utility, its depth, size or diameter, the equipment needed for maintenance, etc. Sewer, drainage, water, and solid waste easements are prepared by SPU Real Property Services. Minimum easement widths for sewers and storm drains are found in SPU Client Assistance Memo (CAM) 1180: Design Guidelines for Public Storm Drain Facilities. For water mains, the minimum easement width is 20 feet. These are minimums, and site constraints may warrant greater easement widths.

Approvals for easements: Note that all easements (acquisition, relinquishment, and readjustments) for City owned facilities require approval by the Seattle City Council. For utilities owned by other entities, the applicant must contact the owner to determine required approvals for easements.  Planning ahead and working with the City early is highly recommended in order to get all the legal documents signed and recorded in a timely manner before any work is permitted. Council action can take up to 18 months in some cases.

Pipe location within an easement: For individual water, sewer or storm mains, the pipe shall be located in the centerline of the easement. The standard pipe material within an easement is Ductile Iron Pipe (DIP). For certain site conditions and buildover scenarios, SPU may require restrained joint ductile iron pipe, inside a steel casing pipe. For such installations, SPU requires a 25 feet “pit easement” on either the up hill or down hill side of the casing for the event that the pipe and/or casing must be removed. No private connections shall be allowed within the limits of the casing pipe. Generally casing pipes should have a 5 feet minimum distance past the edge of the building in the event of a buildover.

The easement needs a legal description prepared by a licensed professional land surveyor in the state of Washington.

Sewer and storm drains within the same easement: The minimum separation between the sewer and storm drain shall be 7 feet. The width of the easement on one side or the other will depend on pipe size and influence lines between the pipe and the building foundations (if any).

Utility Relocation:

Need for relocation: It may be necessary to relocate or adjust existing utilities to accommodate new street grades or to attain standard clearances when constructing street improvements. This may include street lighting, traffic signal facilities, water, sewer, and drainage mains and appurtenances. It also may be necessary to relocate curb ramps and bicycle facilities.

Site assessment: The applicant is responsible for obtaining and reviewing surveys and as-built plans, taking field measurements, and contacting the affected utilities to determine if relocation or adjustment is required and the associated costs. The cost of utility relocation and adjustment is the responsibility of the applicant.
Relocated utilities as well as new utilities to serve the development site shall be shown on street improvement plans when street improvements are required.

Pole consolidation: When installing new utilities or relocating existing utilities, it is the standard practice of the City of Seattle to reduce the number of poles where possible by combining utilities on one pole.
continue to section 4.16»   
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Detailed Table of Contents
Chapter 4
Design Criteria
4.1 Introduction
4.2 Street Classifications and Street Types
4.3 Design Criteria General Notes
4.4 Grading
4.5 Design Cross Section
4.6 Roadway Width

Roadway Pavement

4.8 Intersections
4.9 Driveways
4.10 Curbs
4.11 Sidewalks
4.12 Crosswalks
4.13 Bicycle Facilities
4.14 Street Trees and Landscape Architectural Standards
4.15 Introduction to Utilities Design Criteria
4.16 Street Lighting
4.17 Street Drainage, Storm Drains and Sewers
4.18 Water Mains
4.19 Fire Protection
4.20 Seattle City Light
4.21 Clearances
4.22 Structures in the Right-of-Way
4.23 Culdesacs and Turnarounds
4.24 Traffic Operations
4.25 Transit Zones
4.26 Street Furniture, Public Art and Unique Objects in the Public Right-of-Way
4.27 Access Easements
4.28 Contact Information
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