Sig Alert, 210 Freeway, Claremont 11:23 a.m.

A big rig overturned and spilled dirt and rocks on the westbound 210 Freeway this morning after colliding with another semi truck, snarling traffic for several miles. The California Highway Patrol issued a Sig Alert in the 11:23 a.m. crash, shutting down the two right lanes and the Base Line Road on-ramp to the westbound 210. The freeway wasn't expected to be completely reopened until about 2 p.m., said Officer Francisco Villalobos. Villalobos said traffic was backed up to about Mountain Avenue in Upland.