Generations of Charleston, Illinois, residents have grown accustomed to the distant sound of roaring engines and churning machinery from nearby limestone quarries. For a while, they’d also gotten used to long periods of unexpected silence, as operators stopped to tend to an aging diesel rock crusher.

But the familiar sounds have overtaken the quiet once again, thanks to assistance from the local electric cooperative.

Mike Vaughn is superintendent of Charleston Stone, which has been operating quarries along Illinois’ Embarras River since 1958. He says the company’s 20-year-old, 400-horsepower primary rock crusher was down for maintenance or assembly 100 to 120 days a year.

“Diesel obviously has its drawbacks, like a lot of rebuilding,” Vaughan says. “It wears the engines out.”

When Sam Adair heard about Charleston Stone’s difficulties, the key accounts representative at Coles-Moultrie Electric Cooperative paid a visit to the plant. Company officials told him about equipment failures, reduced operations from cold weather, and the other challenges of maintaining aging machinery.

A co-op analysis found that an electric crusher would be quieter and more reliable and would operate at 95% efficiency, Adair says. In addition, assuming diesel costs of $2.50 per gallon, an electric crusher could save Charleston Stone as much as $5,000 a year in energy costs while increasing the co-op’s electricity sales by about $28,000 annually.

“The added load for Coles-Moultrie would mean lowering the cost for Charleston Stone,” says Adair, also the co-op’s manager of marketing and member services.

The company was convinced.

Leveraging REDLG

Coles-Moultrie first looked for a way to take some of the sting out of the $1.2-million capital investment it would take to fund the diesel-to-electricity conversion. With the help of its G&T, Prairie Power Inc., the co-op applied for financing through the U.S. Department of Agriculture’s Rural Economic Development Loan and Grant (REDLG) program.

Under REDLG, electric co-ops support economic development projects with zero-interest pass-through loans, offering development options that otherwise might be too costly to pursue.

Coles-Moutrie received a $400,000 loan for the Charleston Stone project, and in less than a year, the new electric unit was up and running.

“It is important for us to have relationships with our key accounts in order to collaborate and utilize resources together,” says Amy Borntrager, Coles-Moultrie’s interim president and CEO.

The REDLG funding allowed the company to preserve its capital for operating costs, and the overall operation of the electric crusher has been flawless since it started work in 2017.

“What Charleston Stone was trying to accomplish and the fact that we had the opportunity to add this load was well worth Coles-Moultrie’s time and investment,” says Jim Wallace, the co-op’s director of operations and engineering. “We put in some infrastructure that would allow us to be able to, with one switch, open and close [the circuits] in case of an emergency or in case of any work that needed to be done.”

‘Trouble-free’ operation

Working from its original metering point, the co-op was able to combine the service to regulate power at the company’s two processing sites. Engineers recommended upgrades to 7,200-volt lines on quarry sites on both sides of the river.

The modifications have reduced Charleston Stone’s annual diesel consumption and taken a lot of uncertainty out of the company’s projected energy costs. It’s also cut dramatically into downtime for oil changes, equipment repairs, and mechanical failures, saving as much as $360,000 a year in lost production.

The company’s mobile rock crusher includes a mounted transformer that can be quickly wired to pole-mounted terminals, ensuring consistent reliability with negligible fluctuations in power quality. The new equipment can process 400 to 500 tons of material per hour.

While it has not changed the company’s product mix, increased production led Charlestone Stone to add five new employees to its 20-member local workforce.

“The electricity seems to be trouble free. It’s always there,” says Charleston Stone’s Vaughn, adding that the electric crusher operates well even under Illinois’s severely cold winters. “It’s a lot better than a diesel engine with a lot less maintenance. The electric motors are happy at any temperature. It’s been beneficial.”