Two construction projects could combine into a traffic nightmare for Portland-bound commuters who don’t plan ahead for about the next two weeks.The Oregon Department of Transportation has announced the westbound Interstate 84 ramp to northbound Interstate 5 will be closed for the next 12 days. The closure, scheduled to begin at 10 tonight, is expected to last until 5 a.m. Aug. 6. Beginning 5 a.m. on Friday, only the I-84 westbound left lane will be open at the I-5 interchange, with all traffic exiting to southbound I-5.“This could be a tremendously disruptive closure,” said Oregon Department of Transportation spokesman Don Hamilton. “We’re fearing major traffic backups on westbound I-84 Thursday morning … there could be delays on southbound I-205 and northbound I-205 both getting onto I-84 westbound into downtown Portland.”It is the second of three construction-related ramp closures that could cause significant delays, the agency said in a news release.ODOT estimates it could take as long as three hours to travel between I-205 and I-5 along I-84. To make the situation worse, traffic is anticipated to spill off the highway and into surface streets as drivers search for quicker routes.ODOT made similar announcements about the first ramp closure that ran from July 8 through Monday. C-Tran also anticipated and warned its passengers of “major gridlock” when ODOT closed the ramp that connects I-5 southbound to I-84 eastbound.However, C-Tran spokeswoman Christine Selk said conditions were not nearly as bad as anticipated and the agency didn’t have to rely on the extra buses it had lined up to accommodate the delays.