The National Capital Commission has signed an agreement in principle with RendezVous LeBreton to redevelop LeBreton Flats, a coveted 21-hectare patch of mostly vacant land beside Ottawa's core.

There's still a long way to go — it could take at least 18 months of further talks to reach a master agreement, negotiations NCC CEO Mark Kristmanson characterized Thursday as potentially "challenging."

The Ottawa Senators-led winning bid to develop the land centred around a new NHL arena, and also included an accessible community centre, 4,000 units of housing, a French-language public school and public space. The investment for the entire proposed development is thought to be $4 billion.

Kristmanson said Thursday the agreement lays out the conditions for an eventual sale of public land to RendezVous LeBreton.

A major condition of the agreement is that RendezVous LeBreton will pay full market value for the land. The NCC will subtract the amount it costs to clean up the contaminated soil — expected to be in the tens of millions of dollars — from the final purchase price, though no figures have been agreed to.

Kristmanson says the master plan will take to 2019. Federal approvals will also be expected in 2019, with the municipal processes also taking place in 2019. Shows that construction COULD start in 2019-2020. —@jchianello

"I am thrilled to be one step closer to bringing Ottawa Senators fans a more enjoyable fan experience," said Senators owner Eugene Melnyk in a news release issued Thursday.

"Though there are still many hurdles to overcome, today we have moved closer to realizing a vision for LeBreton Flats — creating a place of pride for Ottawa residents, the Ottawa Senators hockey team and visitors."

Ottawa Senators owner Eugene Melnyk (centre) listens during the NCC board of directors meeting on Thurs., Jan. 25, 2018. Melnyk said in a statement he's thrilled to be a step closer to building a downtown arena for his team. (CBC)

"This was an important step," said Ottawa Mayor Jim Watson after the meeting. "If we couldn't agree on the land, the whole project would be stuck in the mud."

Watson said today's news allows the city to start its own talks with RendezVous LeBreton.

No price tag yet

Negotiating a land deal has been slow-going, with RendezVous LeBreton chosen as the preferred bid in spring 2016.

Senators owner Eugene Melnyk once mused about the team playing in a new downtown rink in 2020-21.

That timeline is all but impossible, with a land deal not expected to be finalized until the summer of 2019 at the earliest.​

NCC CEO Mark Kristmanson said 'a strong majority' of the NCC's board of directors approved the agreement during a private meeting Wednesday. (CBC)

Marco Zanetti, the NCC's director of real estate, said the cost of the land will be determined only after the final cost of cleaning up the soil is known. The site became contaminated over decades of industrial use.

Kristmanson said the plan is to decontaminate the site bit-by-bit over the next 15 to 20 years of development.

When asked by reporters about how much the federal government would contribute, Kristmanson would only say the plans for LeBreton Flats would benefit federal taxpayers.

Development to happen in 2 phases

Zanetti said the redevelopment will take place in two phases, not three as originally planned. The first phase of the development, which could begin as early as 2019 or 2020, will include the arena, an accessible sports centre and all public spaces such as the new Sensplex.

Kristmanson said the NCC maintains final say over land use and design.

Today's meeting is also the first for five new board members.

At the start of the meeting, new board member Norm Odjick — the first Indigenous member ever — declared an unspecified conflict of interest on the LeBreton Flats file, meaning he could not speak to the issue or ask questions.

Odjick has been director general of the Algonquin Anishinabeg National Tribal Council since 2004, and the Algonquins have been consulting on LeBreton since 2016.

CBC's city affairs analyst Joanne Chianello reported details of Thursday's meeting on Twitter @jchianello and on our liveblog.