For a Seattle site with a potential steep-slope environmentally critical area (ECA), define the survey around the proposed work and the questions the architect, civil engineer, geotechnical specialist, and reviewing agency need answered. The topographic survey measures agreed site conditions; it does not by itself establish geotechnical safety or guarantee an ECA determination.
Treat the map as a screening input
Seattle’s steep-slope map is advisory. The City says actual ground topography informs whether the site is treated as a steep-slope ECA. Check the current SDCI ECA code guidance and project-specific permit path with the design team. Do not translate a map color directly into a buildability conclusion.
Mark the decisions on a plan
Send the surveyor the current concept, parcel and title material, known grading or retaining work, access route, utility corridor, and any SDCI comments. Ask the architect and engineer which slope breaks, walls, structures, drainage features, trees, and adjacent conditions their design needs. Specify contours, spot elevations, work limits, vertical datum, benchmark, and digital files before fieldwork.
Some information may come from specialists rather than the survey crew. A geotechnical professional evaluates soil and slope stability; an arborist or environmental specialist identifies features within their discipline. The survey can locate their marked points or delineations when that is part of the agreed scope. Keep each source and responsibility visible on the base map.
Review the base before committing the design
Have the design and geotechnical teams examine the delivered survey against the proposed disturbance area and current agency requirements. If the concept changes, check whether the measured area and detail still cover the new work. A missing grade break or off-site condition is cheaper to identify while the layout can still move.
Terrane’s boundary and topographic guide for architects explains the broader base-map handoff. For a steep-slope site, send the concept, available specialist findings, relevant SDCI correspondence, marked survey limits, and the next design decision.
The first deliverable should make constraints and unknowns legible to the whole team, without claiming that a survey settles the permit or geotechnical question.
