AN ORDINANCE amending Section 1.20.010 of the Seattle Municipal Code and Ordinances 383 and 1836 to adopt an updated vertical and horizontal reference datum for all City of Seattle departments and outside entities as a standard reference plane upon which elevations are based in the City of Seattle, or on properties and/or infrastructures owned, funded or maintained by the City of Seattle, or requiring City of Seattle permits or applicants, and amending subsection A of Section 23.22.020 of the Seattle Municipal Code to require that certain measurements for preliminary plats be based on the updated vertical and horizontal datum.

WHEREAS, the local vertical datum was established in 1883 by Ordinance No. 383, and amended in 1891 by Ordinance No. 1836, known as the City of Seattle Datum; and

WHEREAS, the current City of Seattle Datum was established by inconsistent and outdated methods and technologies and does not provide a consistent and reliable single vertical reference datum; and

WHEREAS, it is in the interest of the City of Seattle to have a standard, regional, and consistent vertical and horizontal reference system; and

WHEREAS, it is in the interests of the public safety, health and welfare that elements of the City of Seattle's infrastructure, utilities and transportation share a common vertical and horizontal reference system; and

WHEREAS, the United States National Geodetic Survey has established a national standard vertical reference system known as the North American Vertical Datum of 1988; and a national horizontal reference system known as the North American Datum of 1983, adjusted in 1991; and

WHEREAS, RCW 58.20 establishes the "Washington coordinate system of 1983," based on the North American Datum of 1983, as determined by the National Geodetic Survey of the United States Department of Commerce, as a system for expressing positions or locations of points on the surface of the earth; and

WHEREAS, state, local, and regional entities have adopted the Washington Coordinate System as a standard for expressing positions and locations of utilities, transportation elements, and other infrastructure in Geographic Information Systems, engineering records, mapping and land records; and

WHEREAS, published coordinates for the United States National Geodetic Survey geodetic control monuments, that provide the physical constraints for establishing coordinate values in the Washington Coordinate System, represent the 1991 adjustment of the North American Datum of 1983, and the City of Seattle's primary control network monuments have been constrained to said monuments and adjusted to the North American Datum of 1983 (1991 adjustment) per WAC chapter 332130-060; and

WHEREAS, present surveying, engineering and Geographic Information Systems methods and technologies provide for and make practicable the establishment and adherence to a common horizontal reference system; and

WHEREAS, the Central Geographic Data Base of the City of Seattle Geographic Information System was developed in and maintained in the North American Datum of 1983 (1991 adjustment), and a long standing goal of the City of Seattle Geographic Information Systems is to include elements from engineering design projects and other sources of horizontally reference spatial features; NOW, THEREFORE,

BE IT ORDAINED BY THE CITY OF SEATTLE AS FOLLOWS:

Section 1. Section 1.20.010 of the Seattle Municipal Code and Ordinances 383 and 1836 are amended as follows:

1.20.010 Datum point established.

A. Original datum point. A base or datum point or line is established on the lower step at the entrance to the Pioneer Block in The City of Seattle, at the southwest corner thereof, the point or datum line being 19.79 feet below the top of the step, the point or datum line being in correspondance correspondence with the datum point or line heretofore fixed by Ordinance No. 383.

B. New datum point. The North American Vertical Datum of 1988 (NAVD88) and the North American Datum of 1983 (1991 adjustment) [NAD83 (1991)] are adopted as the new official vertical and horizontal datums of the City of Seattle; said Datums being defined by a series of stable, monumented points and reference stations established and maintained by the United States National Geodetic Survey.

Section 2. To distinguish between the historical and new vertical datum when it is necessary to refer to both, they shall be known respectively as the City of Seattle Datum and NAVD88 respectively.

Section 3. Work which constitutes the "practice of engineering" or the "practice of land surveying", RCW Chapter 18.43 [effective date 1995 c 356], including but not limited to, land survey maps, plans, records of surveys, plats, short plats, descriptions of real property, and boundary line adjustments, which are performed by or for the City of Seattle, or on properties and/or infrastructures owned, funded or maintained by the City of Seattle, shall reference the NAVD88 datum when there is a vertical component of the work or whenever an elevation is noted; and shall reference the NAD83 (1991) datum when there is any reference to a horizontal datum (any reference to bearings, azimuths, or geographical or state plane coordinates).

Section 4. All land survey maps and plans, records of surveys, plats, short plats, boundary line adjustments, and legal descriptions submitted to the City for its approval, and all plans, elevations, maps, drawings and legal descriptions submitted to obtain permits for construction and development of private improvements, shall reference the NAVD88 datum when there is a vertical component of the work or whenever an elevation is noted, and shall reference the NAD83 (1991) datum when there is any reference to a horizontal datum (any reference to bearings, azimuths, or geographical or state plane coordinates).

Section 5. The City of Seattle Standard Specifications for Road, Bridge, and Municipal Construction, Standard Specification 1-05.5, shall be amended to require the NAVD88 datum as the vertical datum and the NAD83 (1991) as the horizontal datum for all work referenced in Section 3.

Section 6. Subsection A of Section 23.22.020 of the Seattle Municipal Code, Content of preliminary plat application, as last amended by Ordinance 119791 is further amended as follows:

A. Every preliminary plat application shall consist of one (1) or more maps together with written data including the following:

1. The name of the proposed subdivision;

2. North point arrow and scale; the location of existing property lines; streets, building, if any; watercourses and all general features;

3. The legal description of the land contained within the subdivision;

4. The names and addresses of all persons, firms and corporations holding interest in the lands, including easement rights and interest;

5. The proposed names, locations, widths, and other dimensions and bearings of proposed streets, alleys, easements, parks, lots, building lines, if any, and all other information necessary to interpret the plat, including the location of existing utility and access easements which are to remain, all horizontal references (any reference to bearings, azimuths, or geographical or state plane coordinates) shall reference the North American Datum of 1983 (1991 adjustment);

6. The location of streets in adjoining plats and the approximate locations of adjoining utilities and proposed extensions into the plat;

7. The names of adjoining plats;

8. The name, address and telephone number and seal of the registered land surveyor who made the survey or under whose supervision it was made;

9. The date of the survey;

10. All existing monuments and markers located by the survey;

11. The zoning classification applicable to the land within the subdivision;

12. The conditions of or the limitations on dedications, if any, including slope rights;

13. Contour intervals as required, based upon City datum the North American Vertical Datum of 1988;

14. Property information including, but not limited to, address, legal description, and Assessor's Parcel number;

15. Evidence of ownership or authorization from the property owner to make the application;

16. A signed statement of financial responsibility by the applicant and owner acknowledging financial responsibility for all applicable permit fees;

17. Drainage plan;

18. Landscape plan;

19. Identification of any adjacent property within three hundred (300) feet of the proposed subdivision that is owned or controlled by the applicant; and

20. Specific location and description of all trees at least six (6) inches in diameter measured four and one-half (4 1/2) feet above the ground, with species indicated.

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Section 7. This ordinance shall take effect and be in force on January 1, 2004 if approved by the Mayor, but if disapproved, it shall take effect as provided by Municipal Code Section 1.04.020D.

Passed by the City Council the ____ day of _________, 2003, and signed by me in open session in authentication of its passage this _____ day of __________, 2003. _________________________________ President __________of the City Council

Approved by me this ____ day of _________, 2003. _________________________________ Gregory J. Nickels, Mayor

Filed by me this ____ day of _________, 2003. ____________________________________ City Clerk June 10, 2003 version #4 t