Portions of Kuhio Beach will become off-limits starting next week so workers can start pumping 10,000 cubic yards of underwater sand back onto the beach.

"We're trying to bring the beach back to an area that has been eroding," said Peter Young, chairman of the state Department of Land and Natural Resources. "Not only will there be more sand on the beach, they'll still have the great (surf) break at Waikiki."

The $475,000 project is scheduled to last 20 to 30 days, Young said.

It has suffered from two years of stops and starts, including permitting and equipment delays and, most recently, the March sewage spill in the Ala Wai Canal that unleashed unhealthy levels of bacteria in the sand.

Now the project is scheduled to get under way if this weekend's predicted south swell dies down by Monday.

From Monday through Wednesday, workers will first install an underwater pipe that will connect to an 82-foot barge that will sit 2,000 feet offshore. The barge, belonging to American Marine Corp., will use high-pressure pumps to suck sand from the ocean floor and send it streaming into mounds on the beach, where it will be dried and spread to patchy areas.

The width and length of Kuhio Beach won't change. Instead, the imported sand will be used to cover "isolated hot spots" that are "more heavily eroded than others," said Dolan Eversole, a coastal geologist with the University of Hawai'i Sea Grant College Program who is helping state officials with the project.

The new sand will be used to cover spots where there is "literally no beach," Eversole said.

Some surfers have expressed concerns that pulling sand from the ocean bottom will change the contour of Waikiki's shore break. But Young said, "We want to show them this will not affect the break."

"Mother Nature will always figure out what she wants to do," Eversole said. "But we're pretty confident that the sand is not going to impact the surf breaks in any way."

Some swimmers who use the area between the beach and the surf break also worry that the addition of 10,000 cubic yards of sand could dramatically flow back into the ocean and ruin their swimming area.

But 10,000 cubic yards isn't enough sand to fill in the basin where swimmers work out, Eversole said.

Kuhio Beach has been getting so-called "replenished sand" since 1939, Young said, when the north section of the Kuhio Beach breakwater was built. But not much work has been done since 1975, he said.

He hopes next week's scheduled project leads others around the state to commission similar projects and state officials have created an expedited permitting program to help them.

Even though a 1928 agreement allows some Waikiki hotels to prohibit replenishing projects on the beaches that front their hotels, Young said he hopes the Kuhio Beach project shows them the idea works.

"We want to use it for everybody," he said, "whether they be hotels or others across the state."

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.