Idaho counties running out of space for their garbage may have an inexpensive option, courtesy of the U.S. Bureau of Land Management.

Legislation, yet to be signed by President Reagan, would help counties by providing cheap land, said Jack Sept, Bureau of Land Management spokesman.The new law will end BLM's self-imposed moratorium on selling and leasing land for municipal sanitary landfills. The law would allow the BLM to sell property for as low as $2.50 an acre.

"Because of our moratorium, there was no way a community could acquire lands for a sanitary landfill, short of outright purchase at fair market value," BLM State Director Delmar Vail said. "Many communities simply cannot afford this."

BLM leases about 40 landfill sites on public land in Idaho.

Since the land would be sold rather than leased, responsibility for compliance with state and federal regulations would fall on the city or county operating the landfill, including monitoring of the site for up to 30 years after it is closed.

Under current law, a landfill would revert to the BLM when the site is filled. With the new rules, the land would revert to the BLM only if the purchaser did not develop the landfill within five years, said Sharon LaBrecque, a BLM realty specialist with the Burley District.

The lease on Twin Falls County's Murtaugh dump runs out in 1991, but the 40-acre site has enough capacity to remain open for up to 30 years, said Darrell Heider, county solid-waste management director.

When the lease is up, the county would have the option to purchase the Murtaugh site from the BLM under the new legislation.

The new law would free the BLM from liability for the sites it otherwise would have leased. Though BLM does annual checks on leased sites, it does not have the personnel to deal with hazardous-waste problems such as the pesticide drums found at the Murtaugh dump, LaBrecque said.

If a site contains toxic materials, the BLM cannot sell it unless it has been thoroughly cleaned up.