Land Surveyors in Mercer Island, WA

An Island That Got Bigger in 1916

Beginning on August 25, 1916, Lake Washington was drawn down about nine feet so the new ship canal and the Ballard Locks could open. Mercer Island's shoreline moved outward all the way around, and the island now measures about five miles long and two across. Land that had been lake bottom became waterfront, and an owner today may hold a lot described in a pre-1916 deed plus a strip of former shoreland acquired separately or never clearly conveyed at all. When a waterfront title raises that question, the survey shows where the lines fall on the ground; how ownership is resolved is a matter for a title officer or an attorney.

Steep Ground and a Short Building Season

Much of the island is steep, and the city tracks potential landslide, erosion, seismic and steep slope hazards across it. On lots classed as erosion, potential slide or steep slope hazard, the city's Community Planning and Development department does not allow clearing, grading, filling or foundation work between October 1 and April 1. Projects on those lots need a geotechnical report and a pre-application meeting, and missing the dry season can push excavation back half a year, which puts pressure on getting site drawings done early.

Almost Entirely Residential

Outside the small Town Center just south of I-90, the island is single-family homes on large, often wooded lots, many with private docks and bulkheads along East and West Mercer Way. The city's tree regulations mean the location and size of significant trees on a lot can influence where a new house may go, and a lot line revision - the island's term for moving a shared line - goes through the same pre-application step as a subdivision.

What Island Projects Require

A rebuild here almost always starts with a topographic survey showing slopes and trees, combined with a boundary survey that resolves the waterfront line. Neighbours shifting a shared line apply for a lot line revision, and the few larger parcels are divided by short plat. Low lakefront lots may need an elevation certificate. Excavation on the slopes depends on construction staking, and completed homes are recorded with an as-built survey. Town Center commercial transactions call for an ALTA/NSPS survey. The bridges connect to Seattle and Bellevue.

Mercer Island Survey FAQs