DONALDSONVILLE — The crash of a 600-foot-long tanker ship into the Sunshine Bridge on Sunday is at least the 21st time maritime traffic has hit the Mississippi River span since it was built in St. James Parish in the early 1960s.

On Sunday around 1:30 p.m., the Dank Silver, one of the Sultanate of Oman’s fleet of ocean-going vessels moving petroleum and other industrial products around the world, crashed into the protective fender system surrounding one of the huge concrete piers that support the steel bridge more than 120 feet in the air, state and federal officials said.

The southbound foreign-flagged ship, which was under control of a local river pilot at the time, was carrying gasoline out of Burnside and hit the pier for reasons that remain under investigation by the U.S. Coast Guard.

The Dank Silver crash is only eight months removed from the Oct. 12 crash in which a crane barge was pushed into the bridge’s superstructure. That crash almost brought the bridge down, a state highway official testified last month before a federal investigative panel.

Ship and barge crashes with the support piers at the water level are far more common in the Sunshine Bridge’s history. In fact, 18 of the 21 known bridge crashes since the bridge was opened in 1964 involved one of the bridge’s lower support piers and other structures.

A 1998 analysis for the state highway department that looked at the then 12 known crashes found the Sunshine Bridge is not difficult to navigate but has a relatively narrow main span for maritime traffic to pass through, making the support piers and fenders vulnerable.

“The Sunshine Bridge has three piers in the river and a relatively short main navigation span of 825 feet, which mostly likely contributed to the large number of substructure hits," the report by consultant Modjeski and Masters found. “The relatively large percentage of accidents reported may also be due to the fact that even minor collisions could result in fender damage.”

The report noted the effects of increasing river traffic and called then for steps to mitigate that risk, including a kind of Coast Guard river traffic control system then under consideration.

The agency fully implemented that system from the mouth of the river to Port Hudson in late 2010, with the Sunshine Bridge marking the downstream boundary of a special control area for the Coast Guard system.

The crash on Sunday shut for two hours the two-thirds-of-a-mile-long span that links Convent on the east bank with Donaldsonville on the west bank and is used by commuters and commercial traffic from St. James and surrounding river parishes.

Coast Guard officials said Sunday's crash did not spill any of the gas into the river, but state highway officials already said this week that the fender system will have to be replaced at a cost to be determined.

Officials with the state Department of Transportation and Development plan to close one direction of traffic at a time briefly over four hours Thursday night to make further inspections of the damage. The intermittent closures are expected to last from 8 p.m. Thursday to midnight.

The tally of Sunshine Bridge maritime crashes, while not comprehensive, was calculated by The Advocate from the 1998 state crash analysis, a U.S. Coast Guard report of a 2006 crash that noted prior past crashes and recent testimony before the federal panel investigating the Oct. 12 crash.

The reports and testimony cover much of the bridge’s history, but not completely, and don’t account for crashes that may never have been reported to authorities.

Capt. Steve Hathorn, president of the New Orleans-Baton Rouge Steamship Pilots Association, said one of his organization’s specially licensed pilots designated to handle ocean-going traffic on the river between New Orleans and Baton Rouge was piloting the ship at the time of the crash.

While he said he could not speak to the specifics of the crash itself, he noted it happened during a time of extended high water on the Mississippi that he and other river pilots say can make travel more difficult as currents speed up.

“It pushes equipment and personnel to their limits,” Hathorn said.

But data collected from reports documenting past crashes suggest they may be just as likely in high water and as in low. Of the 21 known crashes, river levels could be documented for 16 of them, and, for those 16 crashes, the river levels ranged across a nearly even distribution, high and low.

Lt. Rachel Ault, spokeswoman for the Coast Guard, said Tuesday that her agency’s maritime casualty investigations focus on four factors: hardware, equipment on the boat, machinery, charts; software, such as safety management programs and other information; the surrounding environmental conditions; and “liveware,” the decision making of the crew.

“Every investigation will look into all of these factors to see if there was an issue with a specific factor or if there was a mismatch between two factors,” such as if someone misreads a map, she said in a statement.

An email to Oman Shipping Co., the manager of the Dank Silver that is based in Muscat, Oman, a Persian Gulf nation, was not returned by deadline Tuesday.

After the Oct. 12 crash, which remains under investigation by the Coast Guard and U.S. National Transportation Safety Board, the Sunshine Bridge was shut for more than a month. Then it reopened partially for several months afterward as a state contractor made more than $6 million in repairs.

Even before Sunday’s crash, the bridge had remained under partial closures for previously scheduled maintenance work delayed by the October crash.

For additional travel information about the latest lane closures on the bridge, call 511 or visit 511la.org.

Out-of-state travelers may call 1-888-ROAD-511 (1-888-762-3511). Motorists may also monitor the LA DOTD website at http://www.dotd.la.gov/, by selecting MYDOTD, or by visiting the DOTD Facebook and Twitter pages.

Follow David J. Mitchell on Twitter, @NewsieDave.