A coalition of environmental groups has asked the state of Colorado to stop oil and natural-gas companies from re-drilling wells close to homes.

The Sierra Club Rocky Mountain Chapter and a dozen other groups have asked the state Oil and Gas Conservation Commission to close what it called the "setback loophole." The provision allows a well to be re-drilled regardless of proximity to a structure.

About 4,000 active oil and gas wells are closer to homes than the 350-foot minimum distance required by the state, according to the Sierra Club.

There also are about 82,000 abandoned wells, and early trends show that about 55 percent of those kinds of wells are being re-drilled.

"The setback loophole denies the (Colorado Oil and Gas Conservation Commission) the power to prevent and mitigate adverse environmental and human health impacts," the Sierra Club said.

The Sierra Club also urged the state to adopt a minimum setback from wells to homes of 2,000 feet.