CLEVELAND, Ohio -- A federal grand jury returned an indictment against the owner of an oil and gas drilling company on Thursday, charging him with violating the Clean Water Act by dumping more than 20,000 gallons of fracking waste into a river in Youngstown.

In addition to the charges against Benedict Lupo, 62, of Poland, Ohio, the grand jury also returned Clean Water Act indictments against Lupo’s company, Hardrock Excavating, and an employee of the company, Michael Guesman, 34, of Cortland.

Guesman previously told federal agents that on Jan. 31 he dumped a toxic stew of drilling mud containing salt-water, crude oil and several hazardous pollutants, including benzene and toluene, into a storm drain that emptied into a tributary of the Mahoning River, according to a court document. The employee said he was acting on Lupo’s orders.

Fracking, a slang term for hydraulic fracturing, involves injecting millions of gallons of chemical-laced water to crack open rock formations holding gas deposits deep under the Earth’s surface. Ohio allows for disposing of fracking waste in state-permitted injection wells.

In the Lupo case, court documents state, an anonymous tipster alerted authorities from the Ohio Department of Natural Resources that the improper dumping of fracking waste was occurring, and state agents observed the crime as it was being committed, court documents said.

Guesman also said Lupo ordered him to lie if questioned about the dumping, and to tell law enforcement officers he had only emptied the 20,000-gallon waste tanks six times, when in fact he said he had done it more than 20 times, documents state.

Lupo specified that the dumping should only occur at night and after all of the other employees had left the facility, according to court documents.

About 58 mobile storage tanks are kept at the Hardrock facility, and each tank holds 20,000 gallons. Lupo owns about 20 companies, all contained under the umbrella company D&L Energy, located in Youngstown.

Lupo admitted giving the orders, but denied telling his employees to lie or that he had dumped fracking waste on more than six occasions between Nov. 1, 2012 and Jan. 31, 2013, according to a sworn statement by an agent with the U.S. Environmental Protection Agency.

Lupo and Guesman face a maximum sentence of three years in prison and a fine of $50,000 per day of violation, or $250,000, whichever is larger. The company could be fined $50,000 per day of violation, or $500,000, whichever is larger.

"Clean, fresh water is our greatest resource in Northern Ohio," said U.S. Attorney Steven Dettelbach. "We will aggressively investigate and prosecute cases in which people pollute Ohio’s streams, rivers and lakes."

Ohio Attorney General Mike DeWine said the state may also become involved in the dumping case. A preliminary investigation found evidence of illegal storage and transportation of fracking waste, which could result in civil fines of $2,500 to $25,000 per day, he said. Also, steps have been taken to revoke all operating permits granted to Lupo’s companies currently drilling at six fracking sites, he said.

"We will continue to assist in the federal prosecution of this case but we will also pursue with the Ohio Department of Natural Resources any other violations of Ohio’s environmental protection laws," DeWine said. "This case is a reminder that we should look at making state law equal to federal law when it comes to protecting the waters of Ohio."