Every few months since late last year, a Panamax cargo ship filled to the brim with sand has sailed from Canada to Hawai'i to deliver a natural resource that seemingly is in abundance throughout these islands surrounded by sandy shores.

The granules, grayish-tan in color, aren't for Isle beaches or golf courses. They're for another important use: construction.

Precious Hawai'i sand is disappearing at an alarming rate — not only from beaches, but also from inland ground deposits that for decades have supplied one of the main ingredients in concrete.

Recently, restrictions to removing inland dune sand from Maui has forced one of Hawai'i's biggest concrete suppliers, Hawaiian Cement, to regularly import sand from British Columbia. And the state's other main supplier, Ameron Hawaii, may have to do something similar in the near future.

"I think we're looking at the sunset of local sand sources," said Chip Fletcher, a geology and geophysics professor at the University of Hawai'i-Manoa. "These are islands, and sand is limited. Much of it is under buildings and roads, so it was only a matter of time before we ran out of easily available supplies."

The Canadian sand imports have increased concrete prices and construction costs, and have made the state more dependent on foreign supplies of a commodity affected by global supply and demand, shipping availability and fuel prices.

ONCE TAKEN FROM BEACH

Historically, sand for construction in Hawai'i before the 1970s was often taken from beaches statewide, as well as from accessible inland supplies deposited thousands of years ago when sea levels were higher.

As beach sand was placed off limits and more inland sand was covered by development, concrete companies on O'ahu turned to crushed volcanic rock for many years.

But the angular nature of the so-called "mansand" made concrete more difficult to work with and expensive compared with smooth, round sand. Crushed limestone has similar properties that led to Maui dune sand becoming the predominant use for O'ahu concrete since the 1980s.

Then about three years ago, concerns over large numbers of ancient human burial sites within sand strata led the Maui/Lana'i Burial Council to question if a county special use permit was required to process sand. The county later determined such a permit was necessary, and ordered an assessment of its inland sand resources.

According to a 2006 study commissioned by Maui County, sand exported to O'ahu between 1986 and 2005 totaled an estimated 4 million tons — the rough equivalent of 130,000 semi-truck loads and 73 percent of all Maui sand used for concrete.

The study by Howard Hanzawa of SSFM International Inc. estimated that a roughly five-year supply of readily available dune sand remains on Maui.

Hanzawa's study raised concerns that Maui may exhaust inland supplies of clean sand ideal to replenish eroding beaches.

In response, then-Mayor Alan Arakawa urged the County Council to impose a moratorium on sand exports to preserve the resource for Maui use.

No moratorium was adopted, but in April, the Maui Planning Commission conditionally allowed Hawaiian Cement to continue mining sand from an agricultural site owned by Alexander & Baldwin Inc. provided it didn't export any to O'ahu. By then, however, Hawaiian Cement had already explored and begun sand shipments from Canada.

PRICIER CONCRETE

Tim Folks, Hawaiian Cement technical services manager, said the company partnered with aggregate supplier Grace Pacific for an initial shipment late last year, and since has imported another three loads from various Canadian suppliers to amass a stockpile.

"You don't want to be sitting around and run out," he said, adding that there have been no construction project delays because of importing sand from Canada.

Concrete prices, however, are a little higher because of the Canadian sand. Because of competitive reasons, Folks would not say exactly how much more.

Most of the Panamax ships, supersized vessels designed to narrowly fit through the Panama Canal, each have brought around 40,000 tons of sand mined by different companies in various parts of British Columbia.

Folks said Hawaiian Cement is still exploring a long-term contract with a regular supplier for quarterly shipments, but that all the sand is silica sand from granite rock reduced by glaciers as opposed to Hawai'i's calcium carbonate sand from marine organisms.

"These are very long-term sources," he said. "British Columbia seems to be a very good resource."

Unlike Hawaiian Cement, Ameron has been allowed to continue exporting Maui sand to O'ahu. Ameron said it has a five- to six-year stockpile of sand already mined from the area being developed into the Maui Lani residential community.

Still, Ameron last month faced a challenge to halt exports during a Maui Planning Commission hearing that considered renewing the company's sand business permit.

Ameron, which supplies more than half of all concrete used on O'ahu, argued that it had projects that need to be supplied, and was able to obtain a one-year permit extension.

Eric Yoshizawa, Ameron's vice president of Maui operations, said concerns over losing sand for beach replenishment are misplaced because the company is willing to supply sand for beach projects.

Yoshizawa also said that once projects like Maui Lani are built, the sand won't be available, so it makes sense to extract the sand for current needs wherever those needs might be. Storing sand for long periods, he added, can be expensive and difficult since dune sand tends to blow away.

Looking ahead, Ameron and Hawaiian Cement expect to have to import sand to Maui for concrete in about five years as permitted sand supplies on the island are exhausted.

2 YEARS OF SAND LEFT?

Some estimates predict an end to the supply could be in as little as two years unless new local sources are tapped.

Wayne Kawano, president of the Cement and Concrete Products Industry of Hawai'i, said the issue needs to be addressed. "We need to do something," he said. "I think we're all just sitting on our hands."

There may be large viable inland sand supplies that haven't been discovered, but finding and mining them may not be very likely given environmental concerns, permitting requirements and cost.

Rob Parsons, conservation chairman of the Sierra Club's Maui affiliate, said remaining inland sand should be preserved for beach needs, especially since pumping clean sand from offshore hasn't been proven on Maui.

"We need to learn from the mistakes of the past," he said.

Fletcher, the UH geology professor, said he's disappointed that local sand supplies haven't been better managed, but he isn't surprised that another previously abundant resource needs to be imported.

"Forty years ago we could feed ourselves," he said. "Sustainability in the Hawaiian Islands has been going into the basement for a long time, and this is another example."

Reach Andrew Gomes at agomes@honoluluadvertiser.com.