A ballot battle over drilling setbacks may be brewing in Colorado as a grassroots coalition is gathering signatures for an initiative requiring rigs to be at least 2,500 feet from homes and high-occupancy buildings.

The measure is facing stiff opposition from the oil and gas industry, which has built a war chest of more than $10 million, and some criticism from state government agencies.

Colorado Rising, a coalition of environmental and community groups, has to get 98,400 valid signatures on petitions by Aug. 6 to get on the ballot.

The initiative would require setbacks for drilling operations from homes and building, such as schools and hospitals, as well as some sensitive natural areas.

“The goal is to keep large-scale, heavy industrial operations away from communities,” said Suzanne Spiegel, a Colorado Rising campaign coordinator.

An analysis done by the Colorado Oil and Gas Commission (COGCC) staff estimated that the setback measure would make about 85 percent of state-owned and private land unavailable for surface development by the oil and gas industry.

The high percentage came from the inclusion of vulnerable buffer areas, such as hydrologically sensitive land, the commission said.

“Clearly this is an attempt to stop energy development in our state,” said Tracee Bentley, executive director of the Colorado Petroleum Council. “This is bad for Colorado all the way around.”

A fiscal note from the Colorado Legislative Council staff said that while the initiative would not have an immediate impact on state oil and gas severance taxes, “the measure is expected to decrease state revenue in the future from severance taxes, royalty payments from development.” An industry-back issues committee, Protecting Colorado’s Environment, Economy and Energy Independence, has already raised about $10 million to work on several ballot measures. Among the biggest contributors are some of the state’s most active drillers: Anadarko Petroleum Corp., Noble Energy, and Extraction Oil and Gas Inc.

In 2013, the COGCC extended the setback rule to 500 feet from 150 feet for homes and 1,000 feet for high-occupancy buildings. But as the multi-well drill sites have grown larger, suburban homeowners and local officials have called for more protections.

“We have been advocating regulation of large-scale oil and gas operations on the state level,” said Kim Sanchez, Boulder County’s senior planner. “We’ve been pretty disappointed with the results so far.”