Four in 10 new oil and gas wells near national forests and fragile watersheds or otherwise identified as higher pollution risks escape federal inspection, unchecked by an agency struggling to keep pace with the U.S. drilling boom, according to an Associated Press review that shows wide state-to-state disparities in safety checks.

Roughly half or more of the wells on federal and Indian lands were not checked in Colorado, Utah and Wyoming, despite potential harm that has led to efforts in some communities to ban new drilling.

In New Castle, a tiny community in the Colorado River valley, homeowners expressed chagrin at the large number of uninspected wells, many on federal land, that dot the steep hillsides and rocky landscape. Like elsewhere in the West, water is a precious commodity in this Colorado town, and some residents worry about the potential health hazards of any leaks from wells and drilling.

“Nobody wants to live by an oil rig,” Joann Jaramillo, 54, said. “We surely didn’t want to.”

About 250 yards up the hill from Jaramillo’s home, on land that was a dormant gravel pit when she bought the house eight years ago, is a drilling operation that operates every day starting at 7 a.m., sometimes going until 10:30 p.m. Jaramillo said the drilling began about three years ago.

Even if the wells were inspected, she questioned whether that would ensure their safety. She said many view the oil and gas industry as self-policing and non-transparent.

“Who are they going to report to?” she asked.

Government data obtained by the AP points to the Bureau of Land Management (BLM) as so overwhelmed by a boom in the drilling technique known as hydraulic fracturing, or fracking, that it has been unable to keep up with inspections of some of the highest-priority wells.

The agency designates wells as high priority based on a greater need to protect against possible water contamination and other environmental and safety issues. Factors include whether the well is near a high-pressure formation and whether the drill operator has a clear track record of service.

“No one would have predicted the incredible boom of drilling on federal lands and the number of wells we’ve been asked to process,” Linda Lance, the bureau’s deputy director, said. Since fracking reached a height in 2009, about 90 percent of new wells on federal land use the process, which involves pumping huge volumes of water, sand and chemicals underground.

“The current rate of inspections is simply not acceptable to us,” Lance said.

The agency oversees 100,000 oil and gas wells on public lands, 3,486 of which received the high-priority designation.

According to BLM records for fiscal 2009 to 2012, 1,400 of those high-priority wells, spread across 13 states, were not federally inspected. Wyoming had the most, 632, or 45 percent. South Dakota had 1 out of 2 wells uninspected, and Pennsylvania had 1 out of 6.

All the higher-risk wells were inspected in six states — Alabama, Michigan, Mississippi, New York, Ohio and Texas.

Many more wells are located on private lands, where state officials take the lead in ensuring they comply with environmental laws, with mixed results. Nationwide, there were nearly 500,000 producing gas wells in 2012, according to Energy Information Administration data. More than 1,800 new wells were being drilled in March alone.

Dennis Willis, a former BLM field officer in Price, Utah, says he routinely provided input on oil leasing and drilling decisions on federal land before his retirement in 2009. He described a situation of chronic underfunding dating to at least the early 2000s, when BLM management made it clear that issuing new permits would be a priority over other tasks, according to a 2002 memorandum from supervisors in Utah to field officers. At the time, fracking was becoming more widely used.

“There certainly wasn’t a shortage of spills, leaks, pipeline failures and other problems,” said Willis, who now does consulting work for conservation organizations and other groups.

“It’s a disaster waiting to happen,” he said.

In interviews, BLM officials acknowledged persistent problems in keeping up with inspections but said they were not aware of any major safety issues arising from the uninspected wells.

Lance said BLM field managers are making judgment calls to minimize the risk of potential harm to surrounding communities. The agency also is reviewing whether it needs to slow down the pace of the issuance of permits to ensure public safety.

Officials noted that money provided by Congress for oil and gas operations has declined since 2007, while the number of wells drilled on federal and Indian lands has increased by roughly one-third.

“We’re trying to do the best we can with limited resources,” Lance said.

If approved by Congress, the BLM’s 2015 budget request of $150 million for oil and gas operations would allow the agency, with the help of fees collected from oil and gas companies, to conduct the bulk of its required inspections over three years. Unlike in past years, $48 million will be earmarked for inspections. The BLM has made similar budget requests for several years with little success.

Public concern is evident in Colorado, where increased drilling in suburban and rural areas has led community groups to push nearly a dozen oil and gas local-control initiatives for the November ballot. Of the wells drilled from 2009 to 2012, the BLM designated more than 400 on federal and Indian lands in Colorado as high-priority. Even more were placed in the category in Wyoming and North Dakota. More than 160 of Colorado’s un­inspected high-priority wells are near New Castle, on the edge of White River National Forest.

Colorado Gov. John Hickenlooper (D) has been seeking a legislative compromise that could satisfy concerns over the health and safety effects of fracking.

Regulators contend that overall, water and air pollution problems from fracking are rare, but environmental groups and some scientists say there has not been enough research on those issues.

Jaramillo said residents in the canyon have mixed feelings about fracking.

“The people that really like it are the people who are getting money out of it,” she said. “The people who don’t are really worried about, ‘Is it going to ruin the water? Is it going to ruin the land? Is it going to ruin the air?’ ”

Associated Press

Yen reported from Washington. Michelle Price in Salt Lake City and Kevin Begos in Pittsburgh contributed to this report.