SAN LUIS OBISPO CO. - Work is expected to begin along the Cuesta Grade on Tuesday.
Caltrans crews will rebuild a retaining wall along southbound Highway 101.
About two-miles of the far right slow lane will be closed for up to six months.
The construction starts near Santa Margarita.
"Be aware of slower moving vehicles, mainly big rig trucks, that could be moving through that area," says Jim Shivers, Caltrans spokesperson.