Hawaiian Cement making the most of waste material

With its wet processing system from CDE, Hawaiian Cement’s Puunene Quarry has the ability to switch between making a blended concrete sand and jig rock. Photo: P&Q Staff

Parts supply has been a challenge for aggregate producers everywhere over the last year. Just imagine what it’s been like for producers in Hawaii.

“Anytime we’re dealing with a vendor, next-day air is not next-day air,” says Sean Haggerty, general manager of Hawaiian Cement’s Halawa Valley Quarry in Aiea, Hawaii. “Delays are exacerbated with us. We have to plan for that.”

One silver lining for the Oahu-based Halawa Valley Quarry amid the supply hubbub is the performance of its wet processing plant, which it commissioned a few years ago with CDE. The system encompasses a variety of CDE-manufactured solutions, including an M4500 modular wash plant and an AggMax 250 logwasher, as well as an AquaCycle thickener that recycles the majority of water used.

“I think it’s been three years now since we ordered any major components,” says Will Mason, a quarry supervisor at the Halawa Valley Quarry, referring to the wet processing system. “We have a hiccup here and there, but nothing that can’t be fixed right away. The CDE guys react pretty fast when we need something, but we very seldom have issues with the plant. It sustains itself really well as far as productivity.”

The Hawaiian Cement experience with wet processing isn’t limited to the Halawa Valley Quarry, though. The company’s Puunene Quarry on Maui was actually first of the two Hawaiian Cement operations to dive into CDE technology.

The Puunene Quarry is now in its sixth year with a CDE system that includes an M2500 modular wash plant operating alongside an AquaCycle thickener. Keoni DeRego, quarry manager at Hawaiian Cement’s Puunene Quarry, says the plant’s performance was nearly flawless in its first three years. To date, he says the plant is meeting the expectations Hawaiian Cement put forth from the start.

“Other than common wear, the plant works really well,” DeRego says.

While the two Hawaiian Cement operations share Knife River as a parent company, the applications at the Halawa Valley Quarry and Puunene Quarry are vastly different. According to DeRego, the differences have as much to do with the varying geology of the Hawaiian Islands as anything.

“If you go down the chain of islands to Oahu, it is a much older island,” DeRego says. “There’s erosion, and they have quality issues there just because the rock they’re dealing with is much older and degraded.

“Geologically, Maui is really ideal for making rock,” he adds. “It’s probably at its best state right now material wise.”

Still, the two Hawaiian Cement operations called for their own unique wet processing systems, with the company turning to CDE for answers in both cases.

The Puunene Quarry

Hawaiian Cement’s David Gomes says his company was one of the first in North America to partner with CDE. The Puunene Quarry is now six years in with its CDE system. Photo: P&Q Staff

A significant change in the market years ago ultimately dictated the need for a wet processing system at the Puunene Quarry. David Gomes, general manager of the site on Maui, explains.

“Our pit has a single layer with dirt above the rock shelf and below the rock shelf,” Gomes says. “Historically, we’ve always scalped out a 1 1/2-in. minus. In that, there are red clay balls called saprolite. That’s no good for concrete or asphalt.

“We were able to sell that 1 1/2-in. minus as a structural fill for many years,” he adds. “But once portable crushers came out, they started making their own fill, crushing and reusing on-site. So we had an abundance of this 1 1/2-in. minus reject material.”

And that waste material required quite a bit of management.

“We basically had a D9 dozer pushing it all day long just to get it out of the way,” Gomes says. “The material was about 35 to 38 percent of everything. That was the hard thing for us: For every ton we put in, we weren’t getting a ton of saleable or usable product. We had so much reject out there.”

Hawaiian Cement leaders gave Pit & Quarry tours of two aggregate operations this fall, including a site in Kahului on Maui. In this photo, Keoni DeRego, quarry manager of Hawaiian Cement’s Maui Concrete & Aggregate Division, poses atop the CDE-built wet processing plant that’s in its fifth year of operation in Kahului. Photo: P&Q Staff

Hawaiian Cement also faced a mounting challenge at its Waikapu Quarry on Maui, where sand was becoming scarce. A visit from a Knife River mainland colleague, however, led to a discovery with Waikapu’s own waste material.

“He looked at it and said we had a bunch of sand in there,” Gomes says. “When we sent it off to get it tested, sure enough it classified as sand.”

With the addition of a CDE wet processing system at the Puunene Quarry, Hawaiian Cement addressed the waste issues at both Maui sites.

“What we’re dealing with primarily is reject material [at the Puunene Quarry] and turning that reject material into something of value, recapturing as much of the good rock as we can to put back into our ‘A’ grade,” says Gomes, noting that the addition of the wet processing system allowed the Puunene Quarry to cut its reject by 32 percent. “The other thing is to make a concrete sand by blending reject from [the] Waikapu Quarry and the balance of natural sands that we have left.”

According to Gomes, the wet processing system allowed Hawaiian Cement to take what was once estimated as three to four years of remaining sand and extend that to about 10 years.

“We wanted to make sure we had something that was well-integrated, self-contained as much as possible and uses as little water as possible,” Gomes says. “CDE has done that very well.”

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