Land survey and geotechnical report before design: what Seattle and Eastside cities ask for

Short answer: a land survey and a geotechnical report are two documents from two kinds of licensed professional, and the city decides which of them your project needs. In Seattle, SDCI’s permit pages list a topographic survey when a site contains a steep slope or known slide area, and a geotechnical report when it contains a steep slope, potential slide, known slide, liquefaction, landfill or peat settlement prone area; for an addition or alteration, that applies to projects with exterior work or foundation changes. Eastside cities print their own triggers, set out below. The order that saves rework is survey first, geotechnical report second, design third.

Piper Cole designs and administers construction; I do not build. I cannot tell you from this page whether your lot needs a report: the city page named in each section decides. The code text was not read, so a line here is what the city publishes, and the code controls if the two differ.

Five documents and who may prepare each

A city can ask for a survey without a soils report, and different professionals prepare them.

Document	What it is	Who may prepare it, from the sources
Boundary survey	A survey that establishes or reestablishes a lot’s lines and corners (WAC 332-130-020).	A professional land surveyor registered under chapter 18.43 RCW, with the “signed seal of the land surveyor who had responsible charge” (WAC 332-130-050).
Topographic survey	A survey of the ground’s relief, usually as contour lines and spot elevations. RCW 18.43.020(7) includes “the survey of land areas for the purpose of determining the topography thereof” in land surveying.	The same licensed land surveyor. Seattle’s Tip 103 says to hire a licensed surveyor to prepare it.
Tree survey or plan	Location, species and trunk size of trees on the plans; see the trees section.	Seattle’s Tip 103 says the locations of structures and other physical features, trees among them, “will be included in a topographic survey prepared by a licensed land surveyor.” Kirkland and Mercer Island add an arborist report in the cases their pages name; see the trees section.
Wetland or stream delineation	A field determination of a wetland boundary, with a report, under the federal manual and regional supplements (WAC 173-22-035).	In Seattle, a wetland professional meeting Director’s Rule 19-2006: a current Professional Wetland Scientist with the rule’s delineation experience, or someone the Director finds meets its degree and experience criteria.
Geotechnical report	A report on surface and subsurface conditions with design recommendations.	In Seattle, a Washington licensed Professional Engineer (Civil) with at least four years of experience under a licensed civil engineer, signed and stamped (DR 5-2016). Mercer Island: a “Washington State Licensed Geo-technical, Geological or Structural Engineer.”

To check a license, the state Board of Registration for Professional Engineers and Land Surveyors links a license lookup from its home page.

Boundary survey and topographic survey

The boundary survey answers where the lot lines are; setbacks are measured from them. The topographic survey answers what is on the lot and how the ground lies. Bellevue publishes one standard titled boundary and topographic survey, and Mercer Island’s chart says site boundary and topographic information are always required. WAC 332-130-145 calls for statements on a map showing topography: its purpose, the source and interval of its contours, the basis of its elevations and a limitation of use, so tell the surveyor the survey is for design and a permit.

Bellevue prints a detailed standard (page undated, footer 2024). The survey must come from a Washington registered Professional Land Surveyor, be under 5 years old at permit submittal, tie to two City survey control monuments, show structures, utilities and recorded easements, give 2 foot contours for areas under 40 percent slope, mark the top of any 40 percent slope and identify critical area boundaries.

Many height limits are measured from an average grade; Mercer Island’s chart, for one, measures 30 feet from average building elevation. Where that is so, a one foot error in the surveyed average moves the height limit one foot. Existing conditions and as built drawings works that arithmetic and lists, city by city, when a remodel needs a survey; this page does not repeat it.

Worked example: a Kirkland addition and the survey policy

Kirkland’s Planning Department Survey Policy (code DevSvcs-PMC-1.2-20150810), which the city’s permit checklist cites, requires a topographic survey with two foot contours for all new structures and additions. It excuses a single-family addition if one of three conditions is met:

1. The lot is essentially level: no grade change greater than two feet between property corners.
2. The footprint, excluding uncovered decks, changes less than 25 percent, the height of the addition does not exceed the height of the existing roof line, and the addition is not on a part of the property that is topographically lower than the existing building.
3. The building is designed two or more feet below the maximum height.

Take a hypothetical lot with an 1,800 square foot footprint, a 3 foot grade change between corners and an addition no taller than the existing roof line, on ground no lower than the house. Condition 1 fails, since 3 exceeds 2. A 405 square foot addition passes condition 2: 405 / 1,800 = 22.5 percent. A 495 square foot addition fails it: 495 / 1,800 = 27.5 percent, so a survey is required unless condition 3 applies. The policy does not say what the 25 percent is measured against; the example uses the existing footprint, and a Kirkland planner should confirm that. The policy sets a separate rule, with its own exceptions, for the property line survey; this example does not work that one.

What a geotechnical report is and what it contains

SDCI’s page, titled Geotechnical (Soils) Reports, says these reports may include “Information about the surface and subsurface character of your site” and design recommendations for foundations, retaining walls, drainage, slope stability, seismic design and shoring. If SDCI asks for one, it usually requires a report specific to your site and project, and a report for a nearby site can help you gauge the likely scope.

Director’s Rule 5-2016 (effective May 2, 2016, listed Active) outlines the contents: a site plan with existing and proposed structures, property lines and existing contours if available; geology and landslide history; field explorations and laboratory tests; subsurface conditions and groundwater; analyses; and recommendations on siting, earthquake design, slope stability, foundations, excavation, grading, drainage and erosion control. Bellevue’s outline (February 27, 2019) also calls for the results of field soil infiltration tests for on-site stormwater management, which feed the stormwater design.

For the architect, the useful part is the recommendations. In a Seattle landslide-prone area the engineer must recommend the most naturally stable portion of the site and the preferred location of the structure, and review the plan set against the report. DR 5-2016 builds the report on a site plan showing existing and proposed structures and site improvements, with existing contours if available, which is why the survey comes first and a rough massing goes to the engineer.

When each city asks for a geotechnical report

City	What its document says	Document and date
Seattle	For an addition or alteration, a report is required for projects with exterior work (other than window, siding or roofing replacement) or foundation alterations when the site contains steep slope, potential slide, known slide, liquefaction, landfill or peat settlement prone areas. DR 5-2016 requires one in a landslide-prone area or when the Director wants more soils analysis. A waiver is requested by a modification to submittal requirements, approved before intake.	SDCI addition or alteration and new building pages (undated); DR 5-2016
Bellevue	Required for all Clearing and Grading Permit applications. It may be waived for single-family permits if the applicant shows little or no soil or groundwater risk and that no on-site stormwater practices are required. It must be under five years old, or updated by addendum or letter. Which projects need that permit was not read.	Geotechnical Report Requirements, February 27, 2019
Kirkland	Required if construction occurs in an area with soft compressible soils, landslide or seismic hazards, or unique or deep foundations; and for construction on or within 25 feet of a regulated slope.	Single Family/Duplex Permit Checklist (undated)
Mercer Island	Required when the structure goes in a sensitive or critical area (landslide, steep slope, seismic or erosion hazards, among others), with the engineer’s original signature and stamp and a statement of risk.	Geological hazards page; substantial residential projects page (both undated)
Redmond	Listed “if applicable”; it “may be required due to difficult soils, steep slopes or other lot requirements.” The table lists it for a new home and an addition, and none for a remodel with no added square footage.	Residential Application Packet, published 09/2026
Sammamish	May be required within a landslide hazard area, steep slopes, erosion hazard areas or critical aquifer recharge areas, or with a soil bearing above 1500 psf. Reports go to third party peer review at the applicant’s cost.	Residential Addition Submittal Checklist, form 2025-02-ADDN

Seattle’s pages disagree on one trigger. The SDCI permit pages list a topographic survey for steep slope and known slide sites; Tip 101, updated June 30, 2026, adds potential slide. Tip 101 also says neither a survey nor a report is needed if all work is interior with no foundation alteration and exterior work is only window, siding and roofing replacement. Ask SDCI which applies. SDCI says most of its ECA maps are advisory and that it uses detailed property information, such as a topographic survey or wetland report, to confirm a critical area. Hillside and view lots covers the Seattle steep slope rules in depth.

Three city pages, one 40 percent figure

City	Wording	Arithmetic
Seattle	Slopes that rise at least 10 feet over a horizontal distance of 25 feet or less (SDCI relief page)	10 / 25 = 0.40, or 40 percent
Mercer Island	Critical slopes: a 12-foot rise in any 30 foot run (Do I Need a Survey chart, 1/2021)	12 / 30 = 0.40, or 40 percent
Bellevue	Steep slopes greater than 40 percent (residential site plan page)	Greater than 0.40

On a 2 foot contour survey, suppose, for a hypothetical slope, that the 100 and 112 foot contours are 28 feet apart: 12 / 28 = 42.9 percent, over the figure in all three wordings. At 32 feet apart, 12 / 32 = 37.5 percent, under it. A site can still be a critical area without being steep, because SDCI also lists landslide-prone, liquefaction-prone and peat-settlement-prone areas, and each city’s code sets how a slope is measured; the codes were not read for this page. Kirkland’s checklist says “regulated slope” and gives no figure on the page read. See sloped lot house design.

Wetlands, streams and trees

Wetlands. Seattle’s Director’s Rule 19-2006 (effective August 16, 2006, listed Active) requires a delineation report when a map review or site visit finds wetland indicators. The professional flags the boundary, SDCI staff visit to verify it, an approved delineation is generally accepted for three years, and the boundary is surveyed and monumented. The rule cites the State Manual “or subsequent editions,” while WAC 173-22-035 points to the federal manual with regional supplements, so ask SDCI which it applies.

Trees. Each city asks for tree information on a different sheet:

• Seattle. The site plan shows location, species and diameter at 4.5 feet of Tier 1 to 4 trees, including off-site trees whose canopies or roots reach the lot (Tip 103, August 20, 2025). See the tree ordinance guide.
• Bellevue. All trees on the site plan, with Latin name and diameter at breast height.
• Kirkland. A Tree Retention Plan, and an arborist report if the plan requires one.
• Mercer Island. A Tree Plan, and an arborist report when removing or working within the dripline of a tree.
• Redmond. A Tree Removal Plan as needed; removing a significant tree, at least 6 inches at 4.5 feet, needs a permit.

The order that saves rework

1. Gather what exists: any prior survey, prior geotechnical reports, the title report. Kirkland accepts a legible, stamped and signed existing survey if the original markers are in place.
2. Read your city’s checklist for your project type and mark each “if applicable” line.
3. Order the survey with the contour interval, datum, trees and critical area boundaries your city names. Tip 103 asks for 2 foot intervals on sloping sites.
4. Order a wetland or stream delineation if the site shows indicators, so the boundary goes on the survey.
5. Give the geotechnical engineer the survey and a rough massing.
6. Design to the report, then have the engineer review the plan set. A structural engineer works from the foundation recommendations; see structural engineers for remodels.
7. Fit construction to the printed seasons. Seattle: in general no excavation in landslide-prone areas, and proposed excavation, including open temporary slopes, between November 1 and March 31 needs technical analysis approved by the Director. Mercer Island: no clearing, grading, filling or foundation work October 1 to April 1 on erosion, potential slide or steep slope hazard lots, unless waived with a geotechnical evaluation. Under DR 5-2016 the geotechnical engineer monitors construction as the Director requires, and occupancy is not approved until the Director accepts the final report.

Ask each professional for a written scope and schedule.

What this page did not read

Seattle’s critical areas code (SMC chapter 25.09) and the Eastside cities’ critical area codes were not read for this page. Seattle’s ECA update is scheduled for Council adoption in May to June 2027, with an anticipated July 2027 effective date. Cities not named in the table were not read. The SDCI rule viewer banner on DR 5-2016 and DR 19-2006 says the guidance “may not reflect the most current regulations or requirements,” so confirm both with SDCI. Bellevue’s geotechnical handout is dated 2019 and Kirkland’s survey policy 2015, so ask each city whether a newer version applies.

Where I would start

1. Read your city’s checklist lines on survey and geotechnical report.
2. Pull any survey and report you already have and check their ages.
3. Verify each professional’s license through the state lookup before you sign.

Questions

Do I need a geotechnical report to build or remodel in Seattle?

SDCI decides, from the site and the project. Its addition or alteration page requires a geotechnical report for projects with exterior work (other than window, siding or roofing replacement) or foundation alterations when the site contains steep slope, potential slide, known slide, liquefaction, landfill or peat settlement prone areas. Director’s Rule 5-2016 also requires one in a landslide-prone area or when the Director wants more soils analysis. You may request a waiver by a modification to submittal requirements, approved before your intake appointment.

What is the difference between a boundary survey and a topographic survey?

A boundary survey establishes or reestablishes the lot’s lines and corners. A topographic survey determines the topography of the land, usually shown as contour lines and spot elevations, along with structures, utilities and trees. Washington law includes both within the practice of land surveying (RCW 18.43.020(7)), and Bellevue publishes its survey standard as one page titled boundary and topographic survey.

Who can prepare a survey in Washington?

A professional land surveyor registered under chapter 18.43 RCW. Kirkland’s Survey Policy says property line and topographic survey documents must be stamped and signed by a Washington State licensed surveyor, and Bellevue says its survey must come from a Professional Land Surveyor registered in Washington. The state board says the name on a stamp must match its records on who holds the license, and links a license lookup from its home page.

Who can prepare a geotechnical report?

In Seattle, a Washington licensed Professional Engineer (Civil) with at least four years of professional experience under the direction of a licensed Professional Engineer (Civil) with demonstrated expertise in geotechnical engineering; the report must be signed and stamped (Director’s Rule 5-2016). Mercer Island says a Washington State Licensed Geo-technical, Geological or Structural Engineer, with an original signature and stamp. Bellevue says the report must be signed and sealed by the geotechnical engineer.

How long is a geotechnical report or survey valid?

It depends on the city. Bellevue says a geotechnical report must have been completed less than five years before the application, and a report that is older, or written for a different project on the same site, may be accepted with an addendum or a letter from the engineer. Bellevue also wants a survey under 5 years old at permit submittal. SDCI’s pages read for this guide gave no validity period for a geotechnical report, so ask SDCI.

Is a soils report the same as a geotechnical report?

SDCI uses one page for both: its page is titled Geotechnical (Soils) Reports, and it describes reports prepared by licensed civil engineers with geotechnical expertise. Whether a city accepts a document under some other title is for the city to say.

Can a city waive the survey or the geotechnical report?

Some can. Seattle allows a request to waive the topographic survey or geotechnical report by a modification to submittal requirements, approved before intake. Bellevue says the geotechnical requirement may be waived for single-family permits if the applicant shows little or no soil or groundwater risk and that no on-site stormwater practices are required. Mercer Island’s page describes a waiver of its October 1 to April 1 seasonal limit when supported by a geotechnical evaluation; the page read describes no waiver of the report.

What does the geotechnical report tell the architect about the design?

According to the rules, it reports soil and groundwater conditions and makes recommendations on foundation support, excavation and shoring, grading, drainage and erosion control. In a Seattle landslide-prone area it must also recommend the most naturally stable part of the site and the preferred structure location, so the report can set where the house goes before the floor plan is drawn.