Without backing complaints that Utahn Danny Wall approved sweetheart deals for buyers of failing thrifts in 1988, federal officials confirmed this week that the deals were expensive.

Resolution Trust Corp. Chairman L. William Seidman told the Senate the deals will cost taxpayers $69 billion over the life of contracts signed - but $2.2 billion may be saved by pumping $18 billion to $20 billion to pay off interest early or to refinance.That was the first phase of an RTC review of the 1988 deals approved by Wall - a phase designed to look merely at their cost. The second phase, due in November, will look at whether sales were fair and competitively bid, or were improper sweetheart deals.

Wall, a longtime aide to Sen. Jake Garn, R-Utah, was the nation's top regulator of thrifts in 1988. He arranged subsidized incentives to encourage investors to take over failing thrifts to avoid their default and keep S&L insurance funds solvent.

Wall said his actions saved the government money despite their expense. He resigned under pressure last December at the height of complaints about the S&L crisis, with Garn saying Wall was being made a scapegoat by the Bush administration.

Seidman presented the RTC's findings about the cost of the 1988 deals to the Senate Banking Committee, where Garn is its ranking Republican and where Wall was the top Republican staffer for years.

Garn said the report - which has seven volumes, is 3 feet high, contains 2,721 pages and cost $3.5 million - "is thorough and balanced, but it is not as helpful in saving the treasury as some had might have hoped or predicted."

He urged the government to save whatever possible by refinancing deals and paying interest early - if money can be raised to do that. "The report said $2.1 billion to $2.2 billion in savings might be attainable. That is a significant amount of money - at least in Utah," Garn said.

He also called on Congress not to dwell only on past problems with S&Ls but to work on legislation to restructure the financial industry - which he complains the House continually blocks.

The RTC already has asked for $100 billion for fiscal 1991, which starts Oct. 1. Seidman said if the additional $18 billion to $20 billion is spent, at least $2 billion could be saved by taking several steps, including the prepayment of $11.3 billion in promissory notes in 1991.