A study on the long-term economic impact of building a $20 million hotel and spa and of closing the Harris County Callaway Airport was approved by a 5-0 vote Tuesday night by the Harris County Commission.

The study was requested by Callaway Gardens and Resort, which has agreed to pay the full cost for the Georgia Tech Economic Development Institute to conduct the study and issue a report to the county. The institute had agreed to do the study for about $15,850, but county officials said Callaway has asked that it be expedited, which could mean higher cost.

The study, which was started Feb. 28, is to be completed by May 9, and the county could terminate it for any reason on 30-day notice, said county attorney John Taylor.

Commissioner Danny Bridges asked whether the county, on similar projects, hasn't asked for money up front.

County Manager Carol Silva said she would not mind asking for the money when the county signs the contract and returns it.

Chairman Harry Lange said county officials have talked with institute officials about the study and are looking for:

_ Whether there will be any financial impact while the hotel and spa are under construction.

_ The long-time economic impact of the hotel and spa.

_ Impact of closing the airport or the county taking it over and operating it.

Edward Callaway, chairman of the Ida Cason Callaway Foundation Inc., had asked commissioners to consider closing the county's only public airport, which is operated by Callaway, because potential investors in the hotel/spa project have said they wouldn't put up the money unless the airport is closed.