Federal authorities are investigating Egan and Egan Marine after a barge explosion that killed a 29-year old worker and released thousands of gallons of oil into a Chicago shipping canal. (Chicago Fire Dept.)

The captain of a boat pushing a barge was sentenced to six months in prison Friday for a negligent explosion that killed a deckhand and caused hundreds of thousands of gallons of a petroleum byproduct to spill into the Chicago Sanitary and Ship Canal in 2005.

The sentencing came a year after Dennis M. Egan, 36, of Topeka in west central Illinois, and the company that owned the barge had been convicted in federal court in Chicago. In a rare criminal conviction for a workplace fatality, U.S. District Judge James Zagel found both defendants guilty of one count of negligent manslaughter of a seaman and one count of negligently discharging oil pollution to a navigable waterway.

On Friday Zagel also sentenced Egan Marine Corp. to three years of supervised release and ordered it to pay restitution of $5.3 million to cover the cost of the spill.

Egan was piloting a tugboat pushing a barge on the canal when the barge exploded, killing Alexander Oliva, 29, sinking the barge and spilling 600,000 gallons of concentrated slurry oil, a petroleum byproduct.

Zagel found that Egan illegally ordered Oliva, of Oak Lawn, to use a small propane torch to heat a frozen discharge pump moments before the barge was to be unloaded. It was traveling to the Ameropan Oil facility in Chicago from the ExxonMobil plant near Joliet.

An orange fireball erupted from the barge just after it cleared the Cicero Avenue bridge around 4:40 p.m. on Jan. 19, 2005, surveillance video showed. Much of the heavy steel plating atop the barge was peeled away by the explosion and debris was thrown hundreds of feet onto the bridge, busy with traffic.

Oliva's body wasn't recovered from the canal until days later.

Zagel said that while the explosion meant it was "difficult to find proof that's fully direct" about what happened, he was swayed by expert witnesses who testified that a standpipe vent allowing petroleum fumes to escape onto the deck was open at the time of the blast.

He also relied on expert testimony that found that the heating system on the barge had been disconnected from the discharge pump, bolstering prosecutors' claims that Oliva used the torch to heat the pump. The judge credited Egan for having "the will ... to tell the truth" when he acknowledged to investigators after the explosion that he had sent Oliva to work on the pump.

Prosecutors charged Egan and Egan Marine in 2010 shortly before the five-year statute of limitations ran out.

Oliva's family has settled lawsuits against Exxon and Egan, their attorney previously told the Tribune. Egan Marine's owner previously told the newspaper he directly paid the family $100,000, half of the company's $200,000 liability under maritime law.

Earlier this week, Egan Marine filed a lawsuit in Cook County Circuit court against ExxonMobil and an employee, alleging they were negligent in loading the barge with oil contaminated with materials that made it more unstable and explosive than the barge workers expected.