The sale of Cal Expo and the swapping of that fairground site for one in Natomas — proposed in a plan to build a new Sacramento arena downtown — are far from a done deal.

While the Sacramento City Council agreed at its meeting Tuesday to enter an exclusive negotiating agreement with the developer, a detailed look at the feasibility and economics of such a move has just started for Cal Expo.

On Friday, consultants will present the California Exposition and State Fair board with the first report in an analysis encompassing the arena proposal from developer Gerry Kamilos and the Sacramento Convergence LLC. The consultants will also come up with alternatives for upgrading and expanding the current state fair site.

But Cal Expo officials and their consultants — Andy Plescia of A. Plescia and Co., Gruen Gruen & Associates, and RCH Group — don't necessarily agree with some of the projections provided by the developers.

For starters, there's the value of the land that Cal Expo sits on. The arena developers indicate they believe the value of Cal Expo to be nearly $200 million, or $570,260 per acre, if all 350 acres are sold and privately developed, according to the consultants' report.

Land values will be vital for negotiations in such a complex proposal, which calls for the Kamilos group to buy and develop the Cal Expo site and for the fairgrounds to move to the Arco Arena site after that North Natomas property is donated to the state. Agreeing on what these sizable properties are worth, or on the costs of relocation or renovation, may be especially difficult with the current state of the real estate market.

The land value estimates included in the Convergence proposal rely on comparable real estate sales data, which Cal Expo officials and consultants say is not enough to forecast the value of the land.

That data doesn't take into account the unique features at Cal Expo or the value of the land after it has been redeveloped. Whether parcels are sold for a hotel, office buildings, retail or housing helps determine its value, said Cal Expo Deputy General Manager Brian May.

"You can't appraise property without a plan," he said. For that reason, Cal Expo officials have never had the state fair site appraised.

However, the arena proposal also offers to give Cal Expo 25 percent of the difference between what Cal Expo sells the land for and what it sells for after the fairgrounds property goes through the entitlement process and is resold in parcels.

The consultants working for the state fair board are now evaluating the arena proposal, the practicality of moving the fairgrounds, the viability of using the Arco Arena site, and the possibility of staying put but selling or leasing some land for private development to finance state fair improvements.

The Convergence group also estimates that expanding and improving the existing fairgrounds site would cost $207 million. Cal Expo officials have not previously studied such a cost, May said. That is now part of the consultants' work.

Over the next month, the consultants plan to identify two or three alternatives for expanding the fairgrounds at the present site. The full analysis is expected to be finished this summer. The Cal Expo board will then consider what would be in the state fair's — and taxpayers' — best interest, May said.

The Convergence group has set August as the target date for state legislation related to the proposal for the $400 million, 19,000-seat arena.

California State Fair photos by Kati Garner.