A library advocacy group argued before the D.C. Court of Appeals on Thursday that the city wasted public land in downtown Washington, officially valued at $30 million, by giving it to a private developer in exchange for the reconstruction of a fire station and a library.

As part of the deal, the District gave real estate firm Eastbanc plots of government-owned land that contain the West End Neighborhood Library and a fire station.

In its deal with the city, Eastbanc agreed to cover the cost of rebuilding the neighborhood library and fire station -- worth about $20 million altogether. In exchange, the real estate firm can develop two plots of land on the north side of L Street between 23rd and 24th streets Northwest and another on the northeast corner of M and 23rd streets.

The D.C. Library Renaissance Project is suing the city, saying that its Zoning Commission did not properly scrutinize the agreement in order to make sure taxpayers got a fair deal.

"It was a questionable deal about which the details had never been made completely clear," said Robin Diener, the group's executive director. "The zoning question is do you have to consider the value of the land in a deal like this where the land is being traded for facilities? It's a land-for-construction swap."

The city valued the land at about $30 million, but the advocacy group argues that it could have been worth much more had it been sold on the open market. The Zoning Commission gave Eastbanc flexible land-use designations, although the development will contain housing.

Deborah Baum, attorney for Eastbanc, argued before a three-judge panel that the Renaissance Project Board of Trustees did not have standing to challenge the commission's decision. Furthermore, she said the board does not represent the community's position, which she characterized as supportive of the deal.

"What the District bought was a developer," she said, about what the city got from the deal.

The D.C. Council and then-Mayor Adrian Fenty agreed to the deal in July 2010, and the Zoning Commission approved the development project last year.

"The council and the mayor's office have not served the public well," said Oliver Hall, attorney for the advocacy group. But, he said, it fell on zoning authorities to scrutinize the agreement. "The Zoning Commission is not intended to be a rubber stamp."

The court did not issue a ruling Thursday. A ruling might not be handed down for months even though the case is on an expedited schedule.