The "whistling well" that hisses out methane not far from Barrow is one of 26 old oil and gas wells in the nation's largest stretch of wild land that the Bureau of Land Management in Alaska hopes to clean up, a federal official said this week.

The $50 million effort in the 23-million-acre National Petroleum Reserve-Alaska follows years of complaints from Alaska officials who mocked the federal government for limiting oil development in the reserve without dealing with its own mess.

The effort won't remove all the clutter and pollution left over from four decades of drilling that began in the 1940s, first by the U.S. Navy and later the U.S. Geological Survey.

But it's making a large dent in the 50 wells that need some form of cleanup, including some that were never properly plugged with cement to prevent leaks, according to the BLM.

Eighteen wells are scheduled to be cleaned up this spring and summer. The BLM is hopeful that after that, enough money will be left over to clean up more soon after, said Nicole Hayes, BLM project coordinator for the legacy cleanup. Hayes spoke in an interview Wednesday.

A top priority is the Iko Bay No. 1 Well that's leaking methane, a potent greenhouse gas, about 15 miles southeast of Barrow. Drilled in 1975, it emits a soft whistling noise, leading to its nickname from locals.

Greenhouse gases contribute to global warming by preventing solar heat from radiating back into space.

The well is covered by a small building and could also pose a danger if a subsistence hunter or anyone else took shelter there and struck a match, Hayes said.

"There are holes in it so it's fairly well ventilated, but if someone used it as a refuge to have shelter, it's probably not the safest place," Hayes said.

She said she didn't know the amount of methane the well has been leaking.

At other wells across the huge region, fuel barrels and other debris were dumped and left to rust, fouling groundwater and tundra in areas that provide important habitat for caribou, waterfowl and fish.

In all, the Navy and the USGS drilled 136 wells in the reserve, an Indiana-size tract created shortly after World War I to provide the Navy with an emergency supply of oil. Many of them did not undergo remediation, the BLM determined.

As part of the effort, three wells were cleaned up last year at Umiat on the eastern side of the reserve, in an area where explorer Linc Energy in recent years has pursued what it says is a large oil deposit.

One contractor involved in the project, Marsh Creek of Anchorage, recently launched efforts to clean up wells at Cape Simpson about 50 miles southeast of Barrow, the nation's northernmost city, Hayes said.

The company had to wait for Arctic coastal waters to freeze solidly enough for trucks to make supply runs on an ice road to Barrow to support a remote camp housing about 20 workers.

The cleanups can be complex. To determine a well's condition -- and whether it needs a new cement plug that can extend down more than 100 feet -- contractors must first melt through permafrost using a saltwater brine.

In a previous round of cleanups that began in 2002, BLM and the U.S. Army Corps of Engineers plugged and addressed 21 of the so-called legacy wells, at a cost of $99 million.

This latest effort is more efficient because the money arrived in a large chunk, instead of in spurts, after Sen. Lisa Murkowski secured $50 million in the Helium Stewardship Act of 2013, officials said.

The money has allowed the agency to deal with clusters of wells rather than one at a time, reducing high mobilization costs in the remote areas, Hayes said.

The agency is working more closely with state agencies this time, she said, including the Alaska Oil and Gas Conservation Commission, which is tasked with protecting health, safety and efficiency in Alaska oil fields.

In the last round of cleanups, some wells were not properly cemented, forcing BLM to fix them again. The concrete plugs are needed because old iron casings and wellheads can corrode over time, causing leaks.

"We're making sure we do it right this time," Hayes said.

Cathy Foerster, AOGCC chair, said she was frustrated after the initial cleanup because the remediation work wasn't done properly. Now, she's pleased that BLM is making rapid progress and working closely with the state.