The Concord School Board is gathering the tools it needs to make a final decision on the district's much-debated proposal to merge the city's eight elementary schools into five larger, more modern buildings.

Last week, rough costs for combining four downtown schools into two expanded buildings were released. The district is still working on an estimate of how much it would cost to make all four schools comply with modern codes and keep them open. These numbers, along with years of other research, will help the board reach a decision, probably before the end of the year.

According to the rough estimates, it would cost $14.7 million to $15.1 million to merge Rumford and Conant. Merging Kimball and Walker would be about $25 million. Assuming that state grants would cover nearly half the cost, the district would need to raise $19.1 million through taxes for the downtown phase of the project.

"You have to have numbers, but these are very rough numbers," said Matt Cashman, the district's director of facilities and planning. "It's a very complicated, complex design. We have a workable tool right now where we can actually show each scenario and break out the cost."

Cashman and school board members stressed that these building plans remain hypothetical. There's no timeline, and plenty of decisions must still be made. The district is also still working out the best way to compare construction costs with the cost of keeping the schools as they are. Next year, the district expects to spend $6.1 million to maintain the four buildings. That number is expected to rise as energy costs grow.

The subject of consolidation has ignited plenty of debates in recent years. Opponents of the project have been particularly vocal, but Vice President Kass Ardinger says the board is hearing from all corners of the community.

"As many people who have doubts about the consolidation, we're getting people who write to us saying they're in support," she said. "There are people on both sides."

But that doesn't mean the district doesn't want more residents to get involved.

"We want public involvement," Cashman said. "Nothing is predetermined. We want to hear everybody's opinion."

The school board has already endorsed a reconfiguration plan that calls for closing Walker and Rumford schools. Kimball would be expanded or replaced to make room for Walker students on that site. Conant would also be overhauled so children from Rumford could attend classes there.

On the east side of the city, Dame and Eastman schools would close. Those students would attend a new school near Broken Ground. Beaver Meadow Elementary School would remain the same.

To help flesh out these plans - and give critics of consolidation a voice - the school board created three task forces. The first imagined what an elementary school of the future would look like. The second, which held its final meeting last week, tallied rough costs for merging the downtown schools. Should the board choose to proceed with the consolidation, a third task force would find new uses for decommissioned schools.

The district decided to look at the four downtown schools first because Walker and Rumford are two of the smallest, least efficient buildings.

Any decision on the plan, school district leaders say, must come soon. Communities that want to receive state school construction grants, which typically cover 43 percent of a project's cost, must submit an application before the end of the year. If Concord doesn't have a rough plan in place, it will be 2011 before the district can apply again.

The board finance and facilities committees will review the consolidation plan Wednesday afternoon. The full board could vote on the project as early as its December meeting.