In New Castle, a tiny Colorado River valley community, homeowners expressed chagrin at the large number of uninspected wells, many on federal land, that dot the steep hillsides and rocky landscape.

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

NEW CASTLE, Colo. — 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 America’s drilling boom, according to an Associated Press review that shows wide state-by-state disparities in safety checks.


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. We surely didn’t want to,’’ said Joann Jaramillo, 54.

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 an active drilling operation that operates every day from 7 a.m. until sometimes 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 nontransparent.

‘‘Who are they going to report to?’’ she asked.

Government data obtained by the Associated Press point to the Bureau of Land Management as so overwhelmed by a boom in a new 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. That’s an agency designation based on a greater need to protect against possible water contamination and other environmental and safety issues.


Factors also include whether the well is near a high-pressure formation or whether the drill operator lacks a clear track record of service.

Senator Edward Markey, Democrat of Massachusetts, a member of the Senate Environment and Public Works Committee, said Monday that he will press Interior Secretary Sally Jewell to explain what the department will do to increase well inspections in light of the report.

‘‘The fines Interior Department inspectors can levy on oil and gas companies who violate drilling safety requirements amount to a slap on the wrist — they are nowhere near a sufficient financial deterrent to ensure that companies put safety ahead of speed.

Now there is increasing evidence that potentially dangerous wells go uninspected altogether,’’ he said. ‘‘We need to ensure that the oil industry is paying its fair share to drill on public lands.’’

BLM’s deputy director, Linda Lance, said the current rate of inspections ‘‘is simply not acceptable to us.’’

‘‘No one would have predicted the incredible boom of drilling on federal lands, and the number of wells we’ve been asked to process,’’ she said. Since fracking reached a height in 2009, about 90 percent of new wells on federal land are drilled by the process, which involves pumping huge volumes of water, sand, and chemicals underground.

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 years 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.

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

Lance said BLM field managers are making judgment calls to minimize the risk of potential harm to surrounding communities.