Under the cover of early-morning darkness in South Texas last March, a tanker truck ferrying fluids from an oil and gas drilling site rumbled down a country road spewing its toxic load all over the place.

The concoction of drilling fluid, which typically includes undisclosed and dangerous chemicals, oil, metals shavings and naturally occurring radioactive materials, coated eight miles of roadway, according to a Karnes County Sheriff's Department report obtained by InsideClimate News.

The spill has prompted an investigation by the sheriff's department, the Texas Commission on Environmental Quality (TCEQ) and the state Railroad Commission.

If not for surveillance video given to the sheriff's department, the trucker responsible for the dumping may have disappeared into the night. But the video caught the distinctive flash from the reflective stripes on the tanker. It was the telltale clue detectives needed.

Although sheriff's investigators couldn't determine whether the illegal dumping was intentional, it highlights the growing problem of how to dispose of billions of gallons of contaminated fluids left over from both the drilling and production phases of oil and gas development using hydraulic fracturing, or fracking.

Karnes County is at the epicenter of a drilling boom in the 26-county Eagle Ford Shale region of South Texas. It's one of the most active drilling areas in the country, where nearly 9,000 wells have been sunk and another 5,500 approved since 2008. Drilling and fracking a single well in the Eagle Ford can take 4.9 million gallons of water, according to a report to the U.S. Environmental Protection Agency.

All of that contaminated liquid waste has to be disposed of in some way. Among the approved disposal methods in Texas are injecting the unwanted fluid into deep underground wells, recycling, pumping it into huge open pits to evaporate or spraying it on top of sprawling waste fields. The pits and waste fields are being cited as a major source of noxious fumes and harmful airborne chemicals.

States are solely responsible for regulating the disposal of the toxic drilling waste, in part because of exemptions from federal environmental laws, and the rules vary widely across the country. Texas laws remain comparatively lax.

The waste fluid is disposed of wherever it is convenient and out of sight, said Sharon Wilson, an organizer with the Earthworks' Oil and Gas Accountability Project in Texas.

"There is so much of this that they don't know what to do with it," she said. "So it's not surprising that there are cases where it's just dumped anywhere."

Whodunnit?

The "anywhere" that sparked the investigation in Karnes County was along Farm-to-Market Road 81, a rural, two-lane stretch of blacktop just west of Hobson. A driver reported the mess after the side of his pickup became smeared with an oily substance; a landowner later provided the critical video to law enforcement.

Texas Department of Transportation officials closed the road so it could be cleaned up by a hazardous-waste disposal company, according to the sheriff's department report. Karnes City firefighters worried there may be flammable substances and potentially deadly hydrogen sulfide in the mix.

Sheriff's investigators soon narrowed the possible offenders to two trucking companies that had been hauling fluid from three oil and gas wells being drilled by Marathon Oil Corp, one of the largest Eagle Ford development companies with 211,000 acres under its control.

One trucking company provided GPS data to investigators proving its tankers did not drive the contaminated route, according to the sheriff's report. That left the second company—On Point Services—as the focus of the investigation.

When the On Point Services tanker left the Marathon drilling site, it contained 20 to 30 barrels (840-1,260 gallons) of contaminated drilling fluid, according to the report. Records show the tank was empty when it arrived at facility where tankers are cleaned out.

The driver told sheriff's investigators the valve of the back of his tanker sometimes leaked, though he said he couldn't remember whether he checked on that particular load to see if the valve was closed, according to the report.

When contacted by detectives, On Point Services owner Winfred Stanfield denied his company was responsible.

In a brief interview with InsideClimate News, Stanfield suggested that his company may not have been at fault, saying five other companies had been "implicated." He did not elaborate.

"I don't want to touch this story at all," Stanfield said before hanging up.

Yet when confronted by sheriff's investigators with evidence—the video, the driver's admission and documents showing the On Point Services truck drove the route at the time it was contaminated—Stanfield blamed the driver, according to the report. He said the driver was not competent.

Although the detective said he thought the drive was competent, he told Stanfield he could not prove that his driver intentionally spilled the liquid on the highway.

"If I could I would file criminal charges on him," according to the 10-page report prepared by Robert Ebrom Jr., the Karnes County chief deputy and one of the detectives in the case. Karnes County Sheriff Dwayne Villanueva declined to comment though a spokeswoman who said the department couldn't discuss the case until after the two state agencies wrapped up their investigations.

TCEQ spokeswoman Andrea Morrow said the agency had not yet completed its investigation.

The Railroad Commission is reviewing the incident to determine whether enforcement action is warranted, according to spokeswoman Michelle Banks.

'Pooh-Poohed Away'

The Karnes County incident comes on the heels of a similar episode in neighboring Wilson County. In that incident, Amber Lyssy, who runs an organic farm with her husband, came upon a tanker truck stopped in the middle of the dirt road near her home outside of Poth, Texas, last January.

Lyssy described seeing a brownish colored fluid with a strong diesel odor.

"It was gushing out and pooling on the road," she said in an interview.

Lyssy hurried home to drop off her children and alert her husband and dinner guests to what was happening. She returned with a friend but the tanker was gone. She scooped up a sample of the fluid in a canning jar and alerted law enforcement authorities and county officials.

"It was just pooh-poohed away," Lyssy said.

Caption: On the evening of Jan. 14, 2014, Amber Lyssy encountered a tanker spilling fluid onto a rural road in Wilson County, Texas. She hurried home to drop her children off and return with a camera and jars to collect samples of the foul smelling fluid.



Read more: Fracking the Eagle Ford Shale: Big Oil & Bad Air on the Texas Prairie