Digital Extra

Usually, we're lucky. Sometimes we skate over the edge, but even then we're usually lucky. Over and over, a slight change in circumstances could have multiplied the toll on the environment.

The most dramatic spill in recent years came on the afternoon of June 23, 1989, when, after 36 hours on the bridge, Capt. Iakovos E. Georgudis was preoccupied with a complicated calculation. His tanker, the World Prodigy, piled up on Brenton Reef, off Newport.

The World Prodigy spill led to a frantic, largely successful $4 million cleanup. Like the rest of recent marine accident history, it could easily have been a lot worse.

Although the World Prodigy spilled 290,000 gallons of Bulgarian No. 2 heating oil, that was only a fraction of the 7 million gallons the 560-foot tanker was carrying. Had the tanker broken up, the result could have been disastrous. But the seas were light, keeping much of the oil that did leak from spilling over containment booms, and northerly winds helped push much of the oil that did escape away from Narragansett Bay.

Perhaps the worst spill inside the Bay followed the collision of the U.S. tankers Gulfoil and S.E. Graham in the fog off Fort Adams in Newport on Aug. 7, 1958. The 501-foot Gulfoil had just unloaded a cargo of oil in East Providence, leaving its tanks full of vapor when it hit the 250-foot Graham, inbound with nearly a million gallons of gasoline. The Graham caught fire and the Gulfoil exploded. Fifteen of the 53 crewmen involved died, and about half of the Graham's cargo, 500,000 gallons of gasoline, spilled. News stories at the time, however, focused their attention on the threat to the ferry service that linked Newport and Jamestown then.

Argo Merchant spilled millions: There was another bad spill Sept. 1, 1960, when the tanker P.W. Thirtle ran aground off Jamestown. Submerged rocks punctured its tanks. Initial reports said that more than a million gallons spilled. Those estimates were later dramatically reduced, but enough thick black bunker oil went overboard to appear up and down the Bay, and as far south as Block Island, as far east as Westport, Mass., and as far west as Gardiners Island, off Long Island.

On Dec. 15, 1976, the tanker Argo Merchant broke up spectacularly after running aground on Nantucket Shoals, off Cape Cod, dumping 7.6 million gallons of heavy, residual No. 6 oil and creating a slick 130 miles long and 30 miles wide. The Argo Merchant grounding showed what can happen when the weather is not kind: The North Atlantic pounded the tanker to pieces.

During the post-World Prodigy era, there have been a series of hits and near-misses, several of which could also have easily dwarfed the World Prodigy spill.

Wareham, Mass., July 21, 1989: A tanker carrying nearly 900,000 gallons of unleaded gasoline lost its steering and ran aground as it approached the Cape Cod Canal. Tugboats freed the 245-foot coastal tanker Northern Sun from the mud after two hours.

June 10, 1990, in Buzzards Bay: The cruise ship Bermuda Star ranaground, putting a 90-foot gash in its hull and leaking 7,500 gallons of oil from four ruptured tanks. The ship was carrying 100,000 gallons of oil. Shortly afterward, experts said they could detect no significant environmental damage from the spill.

June 22, 1990, off Weekapaug, R.I.: A barge spilled 960 gallons of gasoline into Block Island Sound after colliding with a fishing boat in dense fog 4 miles offshore. The spill, just a fraction of the 3.5 million gallons the barge carried, evaporated quickly after the sun came out. The barge continued to its destination, Braintree, Mass., after pumping gasoline from a cracked starboard tank to undamaged tanks on its other side.

Sabin Point, Narragansett Bay, Dec. 9, 1990: The barge George Morris, carrying 2.4 million gallons of gasoline, ran aground after the tug towing it missed a turn in the channel. None of the cargo leaked, but the Coast Guard called it a potential major spill.

Dec. 21, 1992, off New London: A barge carrying a million gallons of home heating oil ran aground on Black Ledge, an area of shoals about a mile offshore, before dawn, although the lighthouse marking the ledge was operating. It was unclear how much spilled, with estimates ranging from 3,000 to 20,000 gallons.

Dec. 30, 1993, off Warwick's Conimicut Point: The 554-foot Norwegian tanker Bow Petros ran aground in heavy fog while trying to leave Narragansett Bay. At that point, the channel turns left, to the east, to round the point. The Bow Petros didn't, plowing within 100 yards of the beach. But the ship was empty, it ran into soft sand rather than rocks, and was easily refloated.