Three environmental groups asked the state Wednesday to increase minimum setbacks for oil and gas drilling to 1,000 feet for homes and 1,500 feet for schools, hospitals and nursing homes.

Boulder-based Western Resource Advocates, along with San Juan Citizen's Alliance, of Durango, and Western Colorado Congress, of Grand Junction, asked the state Oil & Gas Conservation Commission in a letter to begin a rulemaking process on the matter.

"Residential setbacks are perhaps the most urgent piece of unfinished business from the 2007 rulemaking," the letter reads. "Five years later, drilling activity increasingly targets populated areas on both the Front Range and Western Slope."

State regulations call for setbacks of 350 feet of a wellhead from buildings in urban areas and 150 feet in low-density areas. The 2007 rulemaking mentioned in the letter refers to two key laws passed that year called the Colorado Habitat Stewardship Act and the Oil and Gas Commission Reform Act.

Western Resource Advocates recently found that nearly 200 active or proposed drilling sites were within 2,000 feet of at least one school in Weld, Boulder, Broomfield and Adams counties.

The letter comes as controversy