DENNIS ODA / DODA@STARBULLETIN.COM
Workers yesterday installed "soldier" beams -- steel pilings that are sunk 45 to 50 feet into the hillside -- that will provide structural support for the road at Round Top Drive.
Work puts Round Top on track to open by May
New foundations are being installed after rain eroded the hillside in March
The "very challenging" job of anchoring unstable segments of Round Top Drive to Tantalus Mountain is progressing well, a project foreman said two weeks into the four-month job.
Round Top Drive -- closed since March -- could open again by May if there are no significant delays.
New foundations for dangerously eroded portions of the road will be attached by steel and cement pilings to bedrock 30 to 50 feet below the surface, said Birl Yarbrough, a foreman for Schnabel Foundation Co., the contractor in charge of foundation work for the $4.3 million city road project.
Triggered by heavy March rain last year, tons of cinders slid onto Round Top Drive in four separate landslide incidents. The road has been closed since then.
Work to make Round Top Drive useable again has been divided between the city, which is responsible for the road, and the state Department of Land and Natural Resources, which is responsible for the mountainside land.
Three-quarters of the cost of the road repairs will be paid with federal emergency funds, and one-fourth will be paid by the city, said Eugene Lee, director of the city Department of Design and Construction.
The city roadway repair that is under way now was preceded by $1 million in work to stabilize the mountainside in the late summer. A DLNR contractor removed 27 trees and 14,000 cubic yards of cinders. The state will pay for an additional $3 million in slope stabilization work after the city roadwork is complete.
It appears that the state will be able to do its second phase of work while the road is open, DLNR engineering administrator Eric Hirano said yesterday. One lane might need to be closed for some phases of the work, he said.
Schnabel and subcontractors began work Jan. 8 on four segments of Round Top Drive that were eroded so badly that they need major foundation work before repaving can begin.
When the foundation work is complete, local contractor T. Iida Contracting Ltd. will handle grading, paving, drainage and guardrail work to complete the job. Both portions of the job are expected to be complete by the end of April.
The four segments that need foundation work are all on the "hairpin turn" near Maunalaha Valley, where 30 families lease land from the DLNR.
The new road surface will be supported on the outer side of the road by soldier piles. These steel-reinforced pillars are made by digging a 55-foot-deep hole inside a 32-inch-diameter steel casing, inserting a 14-inch side steel I-beam and then pouring concrete into the space between them, Yarbrough said.
On the uphill side of the road, the support will be steel-reinforced concrete extending about 30 feet underground before hitting bedrock, Yarbrough said.
Underneath the roadway surface, the soldier piles on the downhill side of the road will be anchored to the cement support on the uphill side by high-strength steel cable.
The road will be 22 to 24 feet wide, with a curb, guardrail and shoulder. Each of the four segments of work will be finished with a cement wall that shows between five and nine feet above the slope of the hillside, Yarbrough said.
All of the underground work will done by drilling, Yarbrough said, because the fragile hillside cannot handle pile-driving.
The 55-foot-long I-beams had to be welded on the mountainside because nothing longer than 40 feet long could make it up around the hairpin turn, Yarbrough said. And a smaller-than-normal crane is being used for the job because a heavier one could not make it safely up the road.
DENNIS ODA / DODA@STARBULLETIN.COM
Birl Yarbrough, superintendent for Schnabel Foundation Co. of Walnut Creek, Calif., worked yesterday on cutting the tops off support beams that were sunk 45 to 50 feet into the ground at Round Top Drive.