Mamalahoa bypass 60 percent complete

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KEALAKEKUA — Torrential summer rains knocked out construction work for several weeks, and the discovery of shabby fill material on Highway 11 sent a 500-foot retaining wall back to the drawing board to the tune of $900,000.

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KEALAKEKUA — Torrential summer rains knocked out construction work for several weeks, and the discovery of shabby fill material on Highway 11 sent a 500-foot retaining wall back to the drawing board to the tune of $900,000.

But otherwise, construction on the $28 million Mamalahoa Highway bypass and a new intersection at Napoopoo Road is moving ahead fairly smoothly.

“We should be finished by September of this year,” said Warren Lee, director of the Hawaii County Department of Public Works, during a media tour of the project on Friday.

The bypass makai of the Belt Road is designed to move traffic quickly past such congested areas as Honalo, Kainaliu and Konawaena schools. In all, some 50 workers are busy at the site on any one day.

The northern end of the 2-mile extension is set for pouring of the concrete road surface. General contractor Isemoto Contracting Co. has been testing a unique plan for laying the 7.5 inches of concrete. The material will be batched onsite by West Hawaii Concrete rather than trucked in, Lee said. That’ll create a better quality surface with no worries of traffic delays holding up trucks and ruining batches, Lee said.

“Kailua-Kona is too far for the kind of cement we want to use,” project superintendent Jason Kiaha said. “It’ll be about a month to start the concrete. Once we start, there is no stopping. We have to make sure everything is ready.”

Farther south on the line, excavators are still working to fill and grade a 1,000-foot section, and farther along toward the intersection, mounds of gravel must still be leveled to create the subgrade before the surface is poured. Several 10-foot-wide concrete box culverts are in place to handle heavy runoff from the terrain and drywells have been dug to collect runoff from the road surface.

The roadway will have 12-foot lanes and 8-foot shoulders. Lee estimated the project, launched at the end of 2014, is 60 percent complete. Initially, county officials had been hopeful the bypass would be completed in early 2016, but delays getting state approval for an archaeological study pushed back the completion date.

There is significant engineering going on at the intersection of Napoopoo and Highway 11 — a poorly-executed junction that is infamous for crashes. The entire intersection is being moved 100 feet south, and a series of turning lanes and traffic lights are intended to make the area safer.

A 16-foot-high retaining wall has been built on the makai side of the junction, and traffic on Napoopoo will be routed slightly to the west in the next month or two so the existing roadway can be brought up to grade. Relocated water lines and utility poles are among the work still ahead.

To the south of intersection from the Napa store on up to Captain Cook Road, excavators digging to create a long retaining wall had to go down 8 feet farther than planned to find solid earth. The $900,000 added to the project’s bill will pay for a more massive foundation and a wall that will reach 24 feet high.

“Our challenge has been securing the hillside so we can work in there,” Kiaha said.

On another major project — the widening of Queen Kaahumanu Highway to four lanes — work is progressing on schedule, said project manager Ed Brown of Goodfellow Bros. Much of the mass grubbing and earthmoving begun last September is completed, especially on the north end of the 5.2-mile stretch between Kealakehe Parkway and Kona International Airport.

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The stretch between the airport and Kohanaiki is ready for subgrade, Brown said. Crews are working to finish mass grading on the south end of the project and are installing water lines and extending existing culverts. Projects ahead include a retaining wall at Kalako-Honokohau National Historical Park, continued installation of water and sewer lines and intersection work.

“We’re trying to hit it hard,” Brown said. “We want to get this done for the public. We’re very happy with our progress, and we’re definitely on schedule.”

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