AG 2003: Survey and Basemap

Overview

Base maps and surveys are required to protect the City, private property, easements, rights- of-way (ROW), and are essential for planning, designing, and constructing improvements in the right-of-way. The City of Seattle requires a complete base map and survey as part of any Street Improvement Permitting (SIP) application work within the right-of-way (ROW) so that our SIP team can review and issue your permit.

All base maps and surveys are required to meet certain standards, identified in this Applicant Guide and in the Survey and Basemap Checklist. For example, the Survey and Basemap must be prepared and stamped by a licensed land surveyor registered in Washington State and are required to protect the City, private property, easements, rights- of-way (ROW), and are essential for planning, designing, and constructing improvements in the ROW. 

Base maps and surveys are made up of three components: Control, Topographic Survey, and the Base Map. Depiction of these components must meet specific drafting requirements. 

Control is required so that right-of-way limits, property lines and other legal lines to properly construct ROW improvements. A topographic survey shows all topographic elements that identifiable with visual group survey methods. A base map provides detailed information on the location, type, and size of infrastructure elements both above ground and buried. 

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Drafting Requirements

Standard Abbreviations, Shading, and Symbols: 

Features on the base map and survey should be shown and noted in accordance with standard abbreviations. Shading and symbols found in the Standard Plans for Municipal Construction Standard Plans No 002 and 003 are available at Seattle Public Utilities' Standard Specifications and Plans webpage

If there is no standard abbreviation, shading and/or symbol for specific elements on the base map or survey the abbreviation, shading and/or symbol used must be shown in a legend. Symbols should be scaled to match existing conditions. 

  1. Sheet Size 
    • Sheet size must be 22" x 34"
  2. Washington State Licensed Land Surveyor's stamp 
    • All base maps and surveys require a Washington State Licensed Land Surveyor's stamp, signature with date, and contact information. 
  3. Readability 
    • All information provided on base maps and surveys must be readable. 
  4. North Arrow 
    • Compass Orientation: the north arrow should be oriented with plan north to the left or top of the sheet. 
  5. Graphical Scale 
    • The minimum scale allowed for surveys is 1" = 40'. 
  6. Bar Scale
    • All base map and survey documents must include a bar scale.   
  7. Lettering 
    • All lettering for base maps or surveys should be L80 (0.08"). 
  8. Street Names
    • Street names for all frontages are required to be shown on all base maps and surveys. 

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Control Requirements

Control

Control refers to lines - often called centerlines, monument lines, and/or survey. These lines are not topographic features; they are legally defined by survey control markers such as monuments, brass plugs, tacks, and other types of markers. Control lines are connected from survey marker to survey marker. Survey markers can be found on almost every street and intersection within the public ROW. In fact, it is the placement of survey markers that defines the legal boundaries of the City's property lines. City property defined by these boundaries is known as the "Public Right of Way." The primary purpose of the public ROW is to allow for the movement of people, goods, and services. Public ROW is property within which the City of Seattle owns and maintains public infrastructure. Public ROW contains roadways, walkways, and various public infrastructure and is generally adjacent to private property. A base map and survey must contain ROW lines depicting boundaries of the portion of land the City regulates. Like control lines, ROW lines are not topographical features; they are legally defined and recorded at a specified offset distance from the control lines.

Boundaries of the Topographic Survey and Base Map

The topographic survey information must be shown for the full width of the rights of way adjacent to the project site, for at least 10' beyond the rights of way onto the private parcel(s) being improved, and for at least 50 linear feet along the ROW beyond all of the boundaries of the project site and/or proposed work. The entire intersection including all four corners up to 20' beyond  the far point of tangency of each curb return or roadway edge must be included in the survey for projects located adjacent to an intersection. If the rights of way adjacent to the project site are not improved with curb and sidewalk the survey boundaries may at the request of the SIP Project Manager need to be extended to include the entire block. If improvements will be made to an unopened or unimproved alley the survey boundaries must extend to the intersecting street(s).

The limits of the base map may be less than the limits of the topographic survey. Base map information must be shown in the area where ROW improvement construction will impact existing infrastructure elements.

Vertical Datum

The Vertical datum for all survey work for Street Improvement Permitting (SIP) plans shall be the Current NGS Vertical Datum. A minimum of two vertical benchmarks are required (one must be the nearest City of Settle published benchmark. The rest may be site benchmarks)  and the data sheets for the benchmarks are required to be submitted. All elevation information shall be in U.S. survey feet. The benchmarks used to establish ties to the datum must be shown in the surveyor's notes per the Survey and Basemap Checklist requirements.

Horizontal Datum

All Street Improvement Permitting (SIP) plans shall be in the Washington State Lambert Grid Coordinate System, North Zone, using the Current NGS Horizontal datum as established in accordance with chapter 58.20 of the Revised Code of Washington (RCW). A minimum of two horizontal control points connected to monumented control stations are required (per RCW 58.20.180) and the units to report how the horizontal control points tie to the datum should be in U.S. survey feet. In all instances where land surveys or deeds reference the control points, scale, elevation and combined grid factors shall be stated for any survey lines used in computing ground distances and areas (per RCW 58.20.180) The horizontal control points used to establish ties to the datum must be shown on the plans and/or be included in the surveyor's notes must be shown per the Survey and Basemap Checklist.

Monuments

At least two monuments shall be shown for each street frontage in plan view. The plans must show and describe all monuments, geometry and references used to establish the right of way, lines referencing the right of way, property lines, easements and any rights in real property shown. The plans must show bearing and distance on property lines and monument lines, or radius, delta angle, and curve length on curving monument lines. For non-tangent curves, a radial bearing will be required. If construction baselines other than the monument line are used, show the relation of each baseline to the monument line Coordinates (northing, easting) and descriptions for all monuments shown including bearing and distance between monuments for each street frontage are required. Dimensions from monument lines to right of way lines are required. A list of source references used to determine the right of way lines should be included with the base map and survey. If the right-of-way is of variable width, show the width at each end of the block and project site boundaries.

Survey Monument Protection

The Permittee must be responsible for referencing and replacing all survey monuments that may be disturbed, destroyed or removed by the project. Prior to beginning work in the ROW, check the GIS map on the 20th floor of the Seattle Municipal Tower or the Quarter Section map in the Engineering Vault on the 47th floor, and the physical location for any monuments that may be impacted by your work. Some monuments may be buried and require further investigation for information in Survey field books.

Complete the first part (Permit Application) of the Application to Remove or Destroy a Survey Monument with the help of a licensed surveyor, and return it to the address provided on the application. Also, send a copy of your application to SPU's Survey Section.

After the work in the ROW is completed, any damaged monuments must be replaced by a licensed surveyor.

With the help of a licensed surveyor, complete and the second part (Completion Report) of the Application to Remove or Destroy a Survey Monument, and return that to the address provided on the application. Also, send a copy of your application to SPU's Survey Section.

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Topographic Survey Requirements

Topographical Feature

Aboveground features known as topographical features are derived from topographic survey data. Topographical features can include, but are not limited to, castings, pavement surfaces, fences, trees, landscaping, creeks, power poles, signal equipment, and drainage features.

All existing underground and surface improvements that can be interpreted from a visual survey must be shown on the topographic survey. This includes but is not limited to ground surface contours, edges of pavements, concrete surfaces, asphalt surfaces, gravel surfaces, channelization, curbs, curb cuts, wheelchair ramps, gutter and flow lines, sidewalks, landscape areas, pedestrian and bike paths, structures, rockeries, retaining walls, fences, bridges, swales, culverts, utilities, vaults and covers.

Contours

Show existing contours at 1-foot intervals for portions of the site with less than 5% slope, at 2-foot intervals for portions of the site with slopes greater than 5% and less than 40%, and for those areas exceeding 40% that will be graded. Show 5-foot intervals for portions of the site with slopes that exceed 40% but will not be disturbed.

Street Trees

Show all existing trees within the right of way and all trees 6" or more in diameter on private property where the drip line abuts or overhangs the right of way. The trunk diameter at 4 ½ feet above grade and drip line shall be shown on the topographic to scale.

Water Features

Show lakes, rivers, streams, ditches, ponds and other surface water features. Show the line of ordinary high water and the top of any well- defined banks. Show the 100-year floodplain, as shown on FEMA maps. Show protected areas including top of bank of Type A, B, and C streams, centerline of Type D streams, and wetlands.

Building Outlets

Show building outlines for buildings located on parcel(s) being improved that are located within 10 feet of the right of way. Provide spot elevations at all vehicle and pedestrian access points.

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Base Map Requirements 

  • Existing Underground Utilities

Detailed information on all existing utilities that will be impacted by construction must be shown on the base map. All visible infrastructure including utilities, structures and appurtenances are shown on the topographic survey. The type, size, horizontal location and elevation of buried utilities and above ground infrastructure and utilities must be included within the area that will be impacted by construction. In addition to providing detailed information on the base map, a list of the sources of the information must be provided. The list shall include the specific source of information such as side sewer cards, franchise and utility maps, vault plans, etc, and plan number for all under and/or aboveground utility information. Utility information obtained from an underground locator, via potholing etc. should be noted as such.

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Accuracy

Base map drawings shall have accuracy to within the following limits: control line and R/W line distance shall at no point have an error in excess of 0.01 feet. All surface features shall be located to within 0.2 feet. Underground features shall be located within +/- 0.5' using as-built plan location and visual indicators.

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Sources for Basemap and Survey Information