THE ST. LAWRENCE SEWER? The Milwaukee Journal-Sentinel launches a three-part report on the state of the St. Lawrence Seaway.

Now, nearly 50 years after the manmade shipping link between the Great Lakes and Atlantic Ocean opened for business, it turns out Seaway boosters were right: Foreign cargo did flood the lakes, but it wasn't what we had hoped for. And the Seaway did change our lives, but not necessarily for the better.

Alas, no spices from the Indies or exotic Teutonic brews in the holds.

Fouled beaches, beleaguered fish populations and ominous wildlife die-offs - all linked to the Seaway and to biologically contaminated ballast spills from overseas freighters - are often written off as a grim but necessary cost of the Great Lakes doing global business.

But with each passing year, that global business is looking more and more like a bust.

Most bulk and container freighters can't even fit into the Seaway, which was undersized from the day it opened. The result is that Great Lakes overseas traffic is limited to a small fleet of pre-World War II-sized ships that typically bring in slabs of foreign steel to feed the region's dwindling manufacturers, and depart with shrinking loads of Midwest grain.

And with the railroads able to price grain shipments by the trainload, and thin-slab casters able to recycle scrap into decent sheet, neither the importers' nor the exporters' price advantage is what it used to be.

One estimate of the total annual economic benefit associated with floating that material in and out of the Great Lakes basin on overseas ships instead of bringing it into the region by some other means, such as trucks or trains or Mississippi River barges, is less than $55 million.

Not much benefit given the possible recreational losses.

Yet the total cost of the two-decade-old zebra mussel invasion just to utilities and municipal drinking systems - which must keep water intake pipes clear of the clustering mollusks - has been estimated at $1.5 billion. That figure likely tops $2 billion when similar expenses to other industries are factored in. Then there are the costs that don't appear in a ledger - the immeasurable price tag of a shredded Lake Michigan food chain, or a family's ability to enjoy a day at the beach.

And the traffic benefits of the Great Lakes are overwhelmingly movements of bulk-cargo through the Upper Lakes in boats so large that they're landlocked. (Leave aside for the moment the possible valuation of recreational opportunities. We can do such things with the proper tools.)

U.S. Seaway boss Albert Jacquez says Great Lakes and Seaway shipping generates $3.4 billion in business revenue annually on just this side of the border. Ships plying these waters move 222 million tons of cargo per year, according to a 2002 Army Corps of Engineers study.

But here is a critical point that gets lost in the Seaway's annual reports and press releases: The overseas portion of that traffic is a skimpy 15.4 million tons - 6.9% of the total cargo moved. And that overseas trade - mostly inbound steel and outbound grain - registers barely a blip on the U.S. import-export charts.

Last year, for example, Seaway grain exports accounted for about 3.6% of the nation's overseas grain shipments, according to the U.S. Grains Council. In a typical year, Seaway steel imports account for around 6% of the U.S. annual total.

Regular readers are aware of these points. Is it time to pull the plug on the St. Lawrence Seaway?