The week before Memorial Day, the city of Seattle will install in Lake Union a straight line of five buoys equipped with flashing warning lights that will alert boaters, kayakers and other watercraft of seaplanes’ impending takeoffs and landings, the Seattle Office of Planning & Community Development (OPCD) told Crosscut.

It’ll be a de facto airstrip in the lake — but not in the traditional sense with a cordoned-off physical lane exclusive only to aircraft. Boaters and other lake users will still be able to access the waters around the buoys; the idea is now they’ll have forewarning not to be in the area at the wrong time. (Aviators who will make use of the warning buoys are referring to it as a “seaplane advisory area,” while a government permit application formally called it a “takeoff/landing area.”)

Such a water runway has been several years in the making with the goal of improving safety on Lake Union for the increasingly congested mix of sailboats, powerboats, yachts, planes, kayakers and paddle-boarders, among others.

“This warning system is intended to support public safety on the water but does not change any current regulations about right of way for boaters or airplanes,” OPCD spokesman Jason Kelly said in a statement.

The new warning buoys conveniently and coincidentally arrive this spring as more seaplane activity descends on the lake. Kenmore Air this week debuted a highly lauded flight that will shuttle passengers — mostly tech workers to start, so it’s being dubbed the “nerd bird” — between South Lake Union and downtown Vancouver, B.C.’s Coal Harbour twice daily on weekdays.

Officials at Kenmore Air — which operates the new route in a “joint venture” with Vancouver’s Harbour Air — have been working with city, state and federal officials to get approval for a Lake Union airstrip for the past five years. Public plans for it were revealed about three years ago, as the city sought permit approval from various stakeholders: the U.S. Coast Guard, the U.S. Army Corps of Engineers, the Washington state departments of Natural Resources and Fish & Wildlife and the Muckleshoot Tribe.

“It’ll be a line of buoys that when they flash, there’s a sign that says ‘move away,’ ” Kenmore Air’s chief pilot Chuck Perry told Crosscut this week. “The theory is, that should give us an increased margin of safety for getting in and out of the lake when the lake is really congested.”

The buoys will be present only in the summer season, roughly between Memorial Day and Labor Day. “That’s the only time we need it,” Perry said.

But some other business owners that rely on Lake Union aren’t enthused by the new water runway, although they acknowledge it has the potential to make travel safer on the water.

“It’s going to take up a lot of space on the lake,” said John Meyer, an owner of the Northwest Outdoor Center off Westlake Avenue, which rents kayaks and stand-up paddle boards on Lake Union and offers classes for beginners. “It’ll be more difficult for everybody to get around — whether sailboats, power boats, kayakers, paddleboarders. … They’re turning Lake Union into an airport, and it’s not one.”

Seaplanes have a decades-long history in Lake Union beginning with the famous Boeing name. One hundred and two years ago this June, Bill Boeing took to the skies in his first flight using a seaplane that taxied into takeoff from Seattle’s Lake Union.