DISCOVERY BAY -- Boaters who navigate the Delta waters in far east Contra Costa County may need to find alternate routes next week.

The Old River drawbridge will be closed to boaters next week from 8 a.m. Monday and not open again until 4 p.m. Thursday while Burlington North Santa Fe railroad conducts mechanical repairs to the drive system that raises and lowers the bridge and performs other maintenance on the bridge, spokeswoman Lena Kent said.

The bridge work could also cause some delays to Amtrak service on the rail line, officials said.

"BNSF understands that the bridge outage may be an inconvenience; however, we hope that the boating community understands that these measures are necessary for (their) safety for the hundreds of passengers and train crews that operate over this bridge on a daily basis," Kent said.

Mariners are advised to schedule openings at the nearby Middle River drawbridge, though 12-hour advance notice must be given, according to the Coast Guard.

Both drawbridges are owned by BNSF.

The railroad is asking that boaters who use the drawbridge to consider refraining this week and find alternative routes; but if they must use the bridge, that they do it between the hours of 10 p.m. and 4 a.m. so as not to delay Amtrak trains, Kent said.

There are about 12 Amtrak trains that run through the area between 5 a.m. and 8 p.m. on weekdays.

It takes at least three hours to raise the older Middle River bridge because it must be unbolted to be raised up, she said.

Vessels with vertical clearance under 11 feet that can safely pass through the may continue to do so during the work, according to the Coast Guard.

Contact Paul Burgarino at 925-779-7164. Follow him at Twitter.com/paulburgarino.