Four former managers of a Big Dig contractor have been convicted on conspiracy and fraud charges for delivering substandard concrete to the massive highway project, prosecutors said Tuesday.
Six former managers of Aggregate Industries NE Inc. were indicted in 2006 on charges they falsified records to hide the inferior quality of more than 5,000 truckloads of concrete. They were accused of recycling concrete that was too old or already rejected by inspectors.
Two of the managers pleaded guilty last month.
Late Monday, four others were convicted after a trial, including Robert Prosperi, of Lynnfield, Mark Blais, of Lynn; Gregory Stevenson, of Furlong, Pa., and John Farrar, of Canterbury, Conn.
"While we regret that these former employees have been found guilty, the jury has spoken and it would be inappropriate for us to second-guess them," Aggregate said in a statement. "It is important to note, however, that the evidence at trial once again showed that the concrete provided by Aggregate Industries Northeast to the Big Dig was both safe and strong."
In 2007, Aggregate pleaded guilty to fraud and agreed to pay a $50 million settlement to end civil and criminal investigations. Under the settlement, the firm was allowed to avoid debarment, a sanction that would have kept the company from bidding on state and federal contracts.
Formally called the Central Artery and Third Harbor Tunnel project, the Big Dig buried Interstate 93 in tunnels beneath downtown and connected the Massachusetts Turnpike to Logan Airport with a third tunnel beneath Boston Harbor.
The $15 billion Big Dig - considered the costliest highway project in U.S. history - was plagued by
construction problems, leaks, falling debris and huge cost overruns.
On July 2006, Milena Del Valle and her husband were driving through an Interstate 90 connector tunnel when 26 tons of concrete ceiling panels crashed onto their 1991 Buick, crushing to death the 39-year-old mother of three.
But the case against Aggregate was never connected to this crash.
The NTSB's July 2007 accident report said the wrong type of adhesive was used to secure the concrete slabs in the tunnel ceiling, and the Massachusetts Turnpike Authority contributed to the accident by failing to implement a timely tunnel inspection program.
This program aired on August 4, 2009. The audio for this program is not available.