Today about 30 cubic yards of dirt and rock fell onto Honolulu-bound lanes of Kalaniana'ole Highway near the right turn to Kamehameha Highway at 4 a.m., said Department of Transportation spokesman Scott Ishikawa. It took three hours to clear the debris. The cleanup slowed traffic, which was backed up to Castle Medical Center.

The contractor will be scaling back 2 to 2› feet in area covering 30 to 40 feet along the hillside, said Ishikawa. "It's a temporary measure, enough to stabilize," Ishikawa said. "We want to get this done before any heavy rainfall creates potential landslide."

A larger landslide occurred in the same area on May 20. About 40 cubic yards of dirt fell onto the right lane of Kalani'anaole Highway, forcing the closure of the roadway for nearly 2› hours.

The state recently identified the Honolulu-bound lanes of Kalani'anaole Highway at Castle Junction to be at the fifth-highest risk of rockfall among 66 O'ahu highway sites. The state report noted that high, steep slopes of volcanic rock are highly deteriorated and there is no rockfall catchment in the area, where traffic is heavy.

The top four rockfall hazard sites are Kalaniana'ole Highway at Makapu'u; Kamehameha Highway in the vicinity of Waimea Beach Park; Kamehameha Highway near Kahuku; and Kalaniana'ole Highway Kailua-bound at Castle Junction.