The Vanport Bridge will again be closed to traffic for a period Saturday morning because of deliveries of equipment to the Shell Chemicals construction site.

This is the third time in the last month that PennDOT has announced a closure of the bridge and each time has initially declined to specify exactly why. In a news release issued Friday, the state transportation agency would say only that the bridge was closing because of river traffic “unrelated to PennDOT.”

This time, however, a PennDOT spokesman in Harrisburg confirmed to The Times that the closure is related to barge shipments to the Shell site in Potter Township.

Spokesman Rich Kirkpatrick said the bridge will be closed in “an abundance of caution” because some of the barge shipments will be docked near the bridge. He also admitted that PennDOT officials previously hadn’t given the exact reason for the closure because Shell asked them not to.

“Shell has asked us not to reference them in regard to their river shipments,” Kirkpatrick said.

For this weekend’s closure, the bridge will completely close to traffic from 8:30 to 10 a.m. Saturday.

Drivers traveling eastbound on Interstate 376 will be detoured using Route 68 toward Midland, over the Shippingport Bridge, onto Route 18 and back to the interstate. The westbound detour will follow Route 18 to the Rochester-Monaca Bridge, onto Route 51 and back to I-376.

On Friday, May 4, PennDOT announced late in the afternoon that the Vanport Bridge would close that Sunday for one hour. That closure was postponed at the time, and no reason was given for the postponement.

The following Friday, May 11, PennDOT again announced the bridge would close. This time, the bridge closed to traffic for an hour as large equipment was transported via barge to the Shell cracker plant site along the Ohio River.

For this weekend’s closure, PennDOT confirmed Friday morning that the bridge would close Saturday. Electronic signs had been posted along the interstate since at least Wednesday warning drivers about an impending closure.

“As for the closure, this is river traffic and unrelated to the department,” spokesman Steve Cowan said Friday.

A spokesman for Shell could not be immediately reached for comment.