It has been nearly a year since the Port of Seattle Commission asked its staff to study how to offload sewage sludge from cruise ships, but the five-member elected board is barely closer to finding out what it needs to know to make that happen.

The port staff estimated last year that the average cruise ship setting sail to Alaska from Seattle produced 28,000 gallons of sewage sludge during its weeklong voyage, meaning that Seattle’s 150 Alaska-bound cruise ships produced 4.2 million gallons of sludge last year — enough to fill six Olympic-size swimming pools.

That’s not exactly the image that the cruise lines want to promote as passengers from all over the U.S. and the world descend on Seattle in airplanes, buses and cars with bags packed for a trip to see some of the most pristine country that the U.S. and Canada have to offer.

Eager to reap the economic benefits of having cruise lines fill their ships with supplies and people in Seattle, the port has been working aggressively to expand its cruise business and expects 211 sailings this year.

A 2007 study commissioned by the King County Council found that pumping the sludge into trucks, which would take it to Renton’s South Treatment Plant, is the best option for disposing of the fecal matter onshore.

In Stockholm and Bermuda, cruise ships hook up to a pipe to offload their sewage; locally, cruise ships collect the sewage and filter out the most solid parts, treating the strained liquid to levels similar to the results from King County’s West Point plant, and then dumping it into Puget Sound. The King County study estimated it would cost $3 million to install the pipes to pump sewage out of the cruise ships but did not recommend that option.

At issue is the rest of the story: Cruise ships wait until transiting the open ocean to dump the leftover sewage sludge, though some use other means for dealing with it.

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