Forget the sharks. The most dangerous specimens currently on view at Baltimore's National Aquarium are dozens of ugly, splotchy, whitish gobs collecting on the outside surfaces of the central tanks.
The substance is called leachate, a chemical discharge indicating that the two huge concrete tanks, not quite 11 years old, are falling apart. What the leachate means is that the aquarium may soon face the most trying times in its storied history.
In September 1993, the aquarium will close and empty the central tanks. During the shutdown, expected to last for at least nine months and perhaps much longer, the aquarium plans to complete a $10.3 million renovation. Taxpayers are being asked to foot $8.75 million of the bill.
The shutdown comes at an inauspicious time. With February's open ing of a critically acclaimed aquarium in Camden, N.J., Baltimore now faces nearby competition.
It comes just when the National Aquarium can least afford comparisons. Already the beluga whales, proven star attractions, are gone after one died last year in a collision with a dolphin.
Now, because of the coming repair work, the aquarium will also be without its popular shark exhibit and the Atlantic Coral Reef. With fully one-quarter of their visitors coming from Pennsylvania, aquarium officials are acutely aware of the competitive threat during a period of renovation.
"Right now we feel we are the best," said Frank A. Gunther Jr., chairman of the aquarium foundation's board of trustees. "If you lose that reputation as the best, it's very difficult to get it back."
Still, Mr. Gunther said, the shutdown is unavoidable.
"The nature of the beast is a short life span," Mr. Gunther said.
"Sure, nobody is happy to have a ring tank last only 12 years [actually less than 11]. But we were cutting edge when we were built. Naturally, the technology has improved since then."
At least one report suggests, though, that the deterioration was premature, raising the possibility of inadequate work during the original $21.3 million construction project.
Aquarium officials stress that the tanks are not in danger of imminent collapse. Not yet anyway.
"You can walk away and do nothing," said Emer C. Flounders Jr., an engineer hired by the aquarium for the project, "but eventually you'll have to shut it down."
The city of Baltimore, which owns the aquarium building, already has anted up $250,000 for the project.
In November, Baltimore voters will be asked to approve $3.5 million for the aquarium from a city bond issue.
Then, next year, the General Assembly will receive a request for another $5 million from state bonds.
Aquarium officials say the public money is crucial. They are likely to often remind voters that the National Aquarium is the state's biggest tourist attraction, one that is, in the words of director Nicholas Brown, "vitally important to Baltimore."
They will also make clear that if they have to raise all the money privately, the repairs will take much longer, giving the new Camden aquarium greater opportunity to slice into the National Aquarium's attendance.
"If we stumble," Mr. Gunther warned, "it will be very difficult to regain the niche that we have now." During the shutdown, Mr. Gunther said, the aquarium plans to have alternative exhibits, including a laser show.
He said the aquarium is also considering cutting its ticket prices during the shutdown.
As it is, the aquarium says it has delayed the repairs until the last moment.
Although the deterioration of the tanks was discovered in 1988, the aquarium was then busily erecting the $35 million Marine Mammal Pavilion and couldn't consider shutting down the central tanks without another attraction ready.
It also had to virtually rebuild the so-called "deep dive" -- once the home of the dolphins and then the beluga whales and now rays -- which was beginning to leak badly.
Although the aquarium has emphasized the necessity for the structural repairs to the concrete tanks, that work actually represents a small part of the project, only about $1.5 million worth.
The aquarium is taking advantage of the emptied tanks to attend many other matters as well.
About $270,000 will go to repair the floor one story below. That fTC floor, above a reservoir tank, supports the life-support apparatus of the central tanks. It was never treated with protective coating and, supported now by makeshift wooden beams, is near collapse.
The aquarium will police the huge observation windows of the central tanks. It will restore the frayed mural above them. And it will replace, at a cost of $1 million, the coral reef, which is disintegrating in the salt water.
Hidden from view of visitors, the aquarium will also fully upgrade the life-support system for the central tanks, creating three separate systems, one for each tank and a third to support the adjoining deep dive. Aquarium officials say the fish in each exhibit can be treated more effectively if they have independent water systems.
In addition, the aquarium plans to vastly improve the lighting and sound systems, including the installation of a sound system that will enable visitors to talk to divers in the tanks.
When done, aquarium officials say the central tanks should last for another 20 years.
Just what went wrong in the last 11 years is not altogether clear, although the aquarium attributes the deterioration of the concrete and underlying steel bars to the failure of the coatings.
Those coatings, applied at the end of construction, are intended protect the concrete from the highly corrosive effects of the salt water in the tanks.
What happened to the coating is a mystery, although Mr. Flanders acknowledged that it would have been reasonable to expect the coatings to have lasted three to five more years.
"I don't know [what went wrong]," he said. "That's really the best answer."
It's not the only answer, though. A report commissioned by the aquarium suggests that the early damage to the tanks was avoidable, raising the possibility that inadequate attention to some details during construction is now catching up with the aquarium.
The report suggests that the damage to the central tanks, the 335,000-gallon Atlantic Coral Reef and the 220,000-gallon shark tank, resulted from the improper cleaning of the concrete surface during construction.
The report says there was "a strong possibility" that a contaminant -- possibly a cleaning or degreasing agent -- remained on the tanks' concrete surfaces when the protective coating was applied.
The presence of a foreign chemical, the report concludes, would have prevented the coating from properly bonding to the walls of the tanks. The chemical also would have attracted salt water through the coating, thereby exposing the concrete surface to the corrosive effects of the salt water.
The $64,000 report was written in December 1990 by Underwater Engineering Services Inc., a Florida firm specializing the evaluation of coatings.
Without offering its own version of what happened, the aquarium dismisses the report's findings, and aquarium officials insist that they got their money's worth from the original coatings.
Ken Tator, a nationally recognized expert in coatings, analyzed the report for The Sun and determined that its finding was "speculative" and unpersuasive.
Still, he said, the presence of a number of "dinner plate-sized blisters" on the coatings, as described in various reports, indicated that something went wrong.
"There are big problems if there are dinner plate-sized blisters," he said.
"Something is grossly wrong. Something has happened that shouldn't have."
In any case, the aquarium did not pursue the matter after receiving the report from Underwater Engineering, dismissing the possibility of trying to recover damages from either the general contractor, Whiting-Turner Contracting Co., or the coating applicator, the Peter Gordon Co.
There would have been "astronomic legal fees," Mr. Brown explained. "We do that and where are we? We might not be able to prove anything."
Whiting-Turner officials declined to comment about the aquarium construction. Paul Gordon, president of Peter Gordon, said he had no idea what might have gone wrong.
If something did go awry during construction, the daily work logs, compiled by the city, which oversaw the project, might provide some insight.
But Dave Montgomery, head of the city's Bureau of Construction Management, said all city records pertaining to construction of the project, arguably the most celebrated of all, have been lost.
"We've searched every nook and cranny and can't find them," he said.