Both sides of Highway 243 south of Idyllwild will be shut down Wednesday while crews blast away overhanging boulders that pose a danger to motorists using the two-lane mountain corridor.
According to Caltrans, the boulders were identified during culvert repairs following heavy flooding that damaged large sections of the highway last year.
The unstable rocks are adjacent to a bend in the highway in the area of Saunders Meadow, Caltrans District 8 spokeswoman Terri Kasinga said.
She said crews will dislodge the boulders using limited blasting techniques, requiring a full highway closure from noon to 2 p.m. Wednesday, between Mountain Center and Idyllwild.
Partial closures will begin about 6 a.m. and continue until 6 p.m., during which time crews will keep a lane available and use flagging to move north- and southbound traffic through the area where the removals will take place, Kasinga said.
The work should conclude Wednesday, but may continue into Thursday if necessary, officials said.
Caltrans recommended that motorists use state Route 74 as an alternate passage to avoid travel delays.