Night work — and traffic delays — are back along Highway 121 between Sonoma and Napa counties.

Caltrans’ $6.5 million construction project to smooth out a bit the curves east of the Sonoma County line has moved on to a paving stage. Weather permitting, the work is being done 7 p.m. to 5 a.m. Monday to Friday and is expected to last through the second or third week of November, Caltrans spokesman Marcus Wagner said.

With one-way traffic controls on the two-lane highway, traffic backups are inevitable. Wagner said delays are less than 30 minutes.

Earlier this month, Wagner had said night work would take a break during the last half of October, but he said last week that a scheduling change caused crews to halt night work in early October instead.

The 1.7-mile construction project, from the county line east to Duhig Road, started in June 2009 and is scheduled to be completed next March.