Concrete removal around Green Lake
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Some of the ground around Green Lake was lake bed a little over a century ago. HistoryLink's history of the park records that the lake was lowered six feet when work began in earnest in 1910, its outlet creek bed was filled in, and the shoreline was built out with fill in several campaigns after that.
That history shows up on the City's maps. By our overlay of the City's critical-area layers on the Green Lake neighborhood boundary, about 15% of it is mapped liquefaction-prone and about 4% falls inside polygons the City labels as the Green Lake non-methane landfill. This page explains what those labels change for a driveway or patio removal, and what they do not. If you want the job quoted, we can pass your details to one local concrete removal company, free of charge.
Local facts for Green Lake
- Lake lowered six feet
- When work began in earnest in 1910, Green Lake was lowered by six feet to accommodate the North Trunk Sewer, and the dried outlet creek bed was filled in. Source: HistoryLink, Green Lake Park (Seattle)
- 288,000 cubic yards of fill
- The playfield was raised above the lake with 288,000 cubic yards of fill carried in on tram cars behind a 6,500-foot dike. Source: HistoryLink, Green Lake Park (Seattle)
- Mapped liquefaction and old fill
- Our overlay of the City's ECA layers on the Green Lake boundary (measured 13 October 2026): about 15% liquefaction-prone and about 4% inside the City's Green Lake non-methane landfill polygons. Source: City of Seattle GIS, ECA Liquefaction Prone Area layer (with ECA Landfills (Historical) layer)
- Standard grading thresholds apply
- In liquefaction-prone areas and abandoned landfills, a grading permit is needed when the standard thresholds are met, such as replacing 750 square feet or more of hard surface. Source: SDCI, Grading Permit
How the shoreline was made
Olmsted's 1908 plan recommended lowering the lake four feet. HistoryLink says the city went to six, to accommodate the new North Trunk Sewer along the eastern shore, which also ended the outlet creek. To build the playfield, crews ran a 6,500-foot dike and brought in 288,000 cubic yards of fill on tram cars. In the 1930s the Parks Department filled more shoreline and, in HistoryLink's words, laid new pipe through the garbage fill so spring water reached the lake clean.
That history is about the park, and it does not tell you whether a given house sits on fill. The City's mapped polygons are what tell you about a particular lot.
What 'liquefaction-prone' means on a permit
SDCI describes liquefaction-prone areas as sites with loose, saturated soil that lose the strength needed to support a building during earthquakes. It is an earthquake label, so it matters most for new foundations.
For grading, SDCI's permit page treats liquefaction-prone areas and abandoned landfills differently from slopes. A grading permit is needed there if the work meets the standard citywide thresholds, rather than the lower 25-cubic-yard line used on steep slopes. In practice that means the 750-square-foot hard-surface rule and the 5,000-square-foot land-disturbance rule, which SDCI says covers removing pavement and walkways.
SDCI also notes that the code's limits on disturbing critical areas apply whether or not a permit is needed, and it offers 20 minutes of free coaching for questions like this.
Where Green Lake ends and Wallingford begins
Even the neighborhood line is soft. HistoryLink notes that John Wallingford's first big addition sat north of 50th Street, and that many people living there today call it Green Lake rather than Wallingford. If you are not sure which page describes your street, the City's mapped critical-area status is what counts, not the name. The neighborhood is a mix of houses and apartments: 42.5% of housing units in the City's Green Lake community reporting area are single detached homes.
- Check your parcel on the City's GIS map for steep slope, liquefaction and landfill layers.
- A slab removal that is then replaced with new concrete over 750 square feet needs a closer look.
- Any sidewalk or curb work in front needs an SDOT Street Use permit.
Questions about concrete removal in Green Lake
What is a liquefaction zone?
SDCI describes liquefaction-prone areas as sites with loose, saturated soil that lose the strength needed to support a building during earthquakes. Seattle maps them as one of its environmentally critical areas.
Does a liquefaction-prone lot need a permit to remove a patio?
Not just for being mapped. SDCI's grading page says a permit is needed in liquefaction-prone areas when the work meets the standard thresholds, such as disturbing 5,000 square feet or adding or replacing 750 square feet or more of hard surface. Most patios are smaller than that.
How do I find out if my Green Lake lot is mapped?
SDCI points owners to the City's GIS map, which shows zoning and environmentally critical areas, including liquefaction and historical landfill layers, for each parcel.
Near Green Lake
Sources
- HistoryLink, Green Lake Park (Seattle)
- HistoryLink, Wallingford - Thumbnail History
- SDCI, Grading Permit
- SDCI, Environmentally Critical Areas Exemptions
- City of Seattle GIS, ECA Liquefaction Prone Area
- City of Seattle GIS, ECA Landfills (Historical)
- City of Seattle GIS, Neighborhood Map Atlas Neighborhoods
- City of Seattle, Neighborhood ACS data
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