State regulators say at least 84,000 gallons of water contaminated with oil and chemicals used in hydraulic fracturing spilled from a broken well-head in a field about 4 miles north of Windsor.

A mechanical failure at about 9:30 a.m. Monday sent a smelly stream of steaming, greenish fluid onto soil and required fire trucks testing air every 30 minutes to ensure leaking natural gas was not about to explode and the use of a vacuum truck to try to suck up the liquid, state natural resources spokesman Todd Hartman said.

The flow from the well bore was stopped more than 30 hours later.

PDC crews dug trenches around the spill and hired Wild Well Control to plug the well, but not before natural gas leaked, Windsor-Severance Fire Rescue operations chief Mike Blackwill said. “We weren’t going to go right up next to it. There was very limited information.”

The closest homes are about 1,500 feet away.

A Colorado Oil and Gas Conservation Commission inspector and engineer responded to the scene. They don’t yet know whether the spill contaminated groundwater or streams, or whether enforcement action will be taken, Hartman said Wednesday.

“We are still reviewing what happened,” Hartman said.

He said PDC Energy has removed soil from the well pad and is testing other areas for contamination. “Cold weather assisted the cleanup by freezing and immobilizing the material.”

PDC has reported two other spills near Greeley in the past few weeks. Both contaminated groundwater, according to a state database of spills.

A Jan. 22 spill by PDC released 2,880 gallons of oil and covered 3,900 square feet, leaving groundwater contaminated with benzene at a concentration 128 times higher than the state limit along with toluene and xylene chemicals.

About 17 percent of 2,078 oil and gas spills that companies reported since January 2008 have contaminated groundwater. Fracking wastewater is one of the most common substances spilled.

Bruce Finley: 303-954-1700, twitter.com/finleybruce or bfinley@denverpost.com

The Greeley Tribune contributed to this report.