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Waterfront homeowners on Mercer Island planning to build homes, patios, docks — or major additions to them — should be prepared to do landscaping as well.

The City Council, tightening proposed shoreline rules, has decided to require homeowners to create a 20-foot-wide buffer extending the width of the property,
at least half of it covered with native plants, when redeveloping their property.

That’s a significant change from an earlier version of the city’s shoreline master program update, which would have required landscaping on only 25 percent of the lakeside buffer.

The earlier approach was rejected by the state Department of Ecology as failing to adequately protect Lake Washington and habitat along the water’s edge.

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The change brings Mercer Island’s shoreline plan more in line with other plans already approved by Ecology.

The state agency’s insistence that the island city change its plan also suggests the shoreline plan being considered by the Bellevue City Council — which wouldn’t require any native vegetation for most projects — likely would not satisfy Ecology.

Under state law, a new generation of updated shoreline plans for 262 cities, towns and counties must gain Ecology’s approval before they can take effect.

Ecology has approved 74 plans of jurisdictions including King County, Kirkland and Redmond. It is reviewing Seattle’s plan, which deals with Lake Union industries and houseboats, along with other commercial and residential properties.

Those plans must result in no net loss of ecological function — meaning any development harming rivers, lakes or saltwater shorelines must be offset by actions that help restore water quality or habitat.

Mercer Island Mayor Bruce Bassett said some owners of the city’s 713 waterfront lots will be disappointed by Monday’s council action, “but I think we have a council that recognizes there’s got to be a balance between what the homeowner would like to have for their pleasure” and what makes sense for the health of the lake and ecosystem.

The council’s action amends the shoreline plan written by the Mercer Island Planning Commission, which blasted the state’s shoreline requirements as complex, confusing and contentious.

The council adopted the plan in 2011, subject to Ecology’s review. Under the plan, a property owner adding more than 500 square feet to a home would have to put vegetation on 25 percent of a 20-foot-wide area along the shore, with native plants on 25 percent of the five feet closest to the water.

Ecology objected to that standard, noting that the amount of vegetation was inadequate.

In order for Mercer Island’s plan to pass state muster, Ecology said in a preliminary ruling, it would have to require owners to plant native vegetation on an area at least as large as the area of new construction.

Ecology recommended going even further, requiring native plants on 50 percent of the 20-foot vegetation strip for smaller projects, on 75 percent for projects over 1,000 square feet, and on 90 percent for projects over 1,500 square feet.

The City Council agreed, by consensus, to require the 50 percent and 75 percent native vegetation — but not the 90 percent.

When it came to private docks, the council bucked Ecology advice and U.S. Army Corps of Engineers rules. Instead of limiting docks to a width of 4 feet within 30 feet of shore, the council decided to allow them to be 5 feet wide.

“If you have a 2-year-old and a 6-year-old walking down the dock, you can’t do it on a 4-foot dock,” Councilmember Jane Meyer Brahm said, noting that the Americans with Disabilities Act standard for public docks is a minimum width of 5 feet.

Councilmember Mike Cero objected to what he called the state’s “continuing ratchet, ratchet of regulations” that erode homeowners’ rights to enjoy their land.

“The council-approved language is ratcheted up enough. We don’t need to go to the recommended language,” Cero said of Ecology’s guidance on vegetation.

But Councilmember Mike Grady called for stricter rules on docks and revegetation.

Lake Washington is an important public resource, he said, and “we have a huge responsibility to protect it as best we can.”

Keith Ervin: 206-464-2105 or

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