The investment case going before the city council is for a stadium costing $473 million, with a mostly clear roof.

Christchurch's roofed 25,000-seat stadium could be ready within five years but the pressure is now on to get it planned and built right.

The city council's long-awaited investment case for the stadium, released on Monday, sets out how the city can have the stadium it wants within budget.

If city councillors sign off on the plan this week it will go to Cabinet for the final tick.

The report says a 25,000 seat mostly clear-roofed facility is the best fit for the city, and could be built within the budgeted $473 million, including running costs. Temporary seating was not included but could be added later.

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The chosen option would cost $333m to build and $104.9m to run over 30 years, of which $92.7m would be funded by stadium income, with an annual $4.2m council top-up.

The case found the stadium would cost more to build and run than it would return in economic benefits, but notes the city faces problems without a stadium and some benefits cannot be measured.

Colin Mansbridge, chief executive of The Crusaders rugby franchise, said they were excited the investment case was done but the challenge now was to get the design and planning done right.

"It proves to council and government that it is possible. We're encouraged by what is planned," he said.

"Now it's a case of getting on and making sure its gets done. Getting the right governance and project management is incredibly important."

The investment case for the new stadium has been finalised with plans for a 25,000-seat facility with a mostly clear roof.

COSTS SHAVED OFF

Created by council and government staff, the investment case reveals council staff preferred a $505.3m option from eight considered, but shaved off $28m after Crown officials raised affordability issues.

Savings came from removing a planned elevated walkway, reducing the facade area, replacing paving with grass, and partnering with a technology company to provide big screens.

Originally due to be built in 2017, the stadium has a new spring 2024 completion date.

Canterbury Employers Chamber of Commerce chief executive Leeann Watson said that in designing the stadium to meet a budget, the city must "make sure we are not missing out on maximising our opportunities".

She was pleased the investment case did not rule out exploring other ways of finding funding.

"Our city is growing and the world is changing quickly, so we need to be focused on the future, not the present.

"It is really essential to get the right skills and experience and expertise to get the right people to develop the project."

An artist's impression of inside the new Christchurch stadium, which could be used for sports as well as events and concerts.

BENEFITS FOR THE CITY

Joanna Norris, chief executive of the economic and promotional agency ChristchurchNZ, is pleased the stadium could be open within five years.

"We're competitive with other cities and a stadium is a basic requirement for a modern and competitive within NZ and internationally."

Norris said as well as bringing in spending, the project would boost the city in other ways.

"There is also social benefit, events bring vibrancy to a city making it a better place to live and that's beyond the direct economic benefit."

The report forecasts $395.6m of economic benefit from the stadium over 30 years, including $83.9m from tourism, $103.9m of extra consumer spending, and $53.9m in "civic pride". The amounts estimate what the city would gain compared with the current temporary stadium.

Not having a stadium causes the city four key problems, the investment case says. They are reduced tourism and economic activity, reduced vibrancy and viability of the CBD, delayed private investment because of uncertainty, and the effect on Christchurch's identity as a sporting and cultural capital.

Council citizens and community general manager Mary Richardson said people could examine the investment case and say whether they were willing to invest in it.

Finding extra funding would be a "significant bonus", she said.

STACY SQUIRES/Stuff.co.nz Stuff speaks to people on the street in Christchurch in mid-2017 about what kind of stadium they want for the city.

HOW WILL IT WORK

The Christchurch City Council will own the city's new stadium and likely have its events company Vbase run it, according to the investment case.

The council would also run the construction project. An independent board of about six people will be set up to manage construction, chosen for specific skills and experience with large construction projects.

Council major facilities vertical capital delivery manager Alistair Pearson said the board was "key" to the success of the project.

Mary Richardson said it was important the board could make decisions quickly as any delays would escalate costs by $1m to $1.2m a month.

The investment case recommends a design and build contract is used, meaning a company is paid to both design and build the stadium to a detailed brief.

However a public-private partnership, the private sector builds and operates the stadium and shares the costs, could be used if the right partners were found.

A draft project timeline aims for a detailed design brief to be complete in spring of next year. A contractor to design and build it is to be in place by early 2021, with major construction to start in early 2022. Authorities say these dates could change as the project progresses.

City councillors will meet on Thursday to decide whether to put the investment case forward to Cabinet, which will consider granting the project $220m from $300m fund Labour promised pre-election. Council has committed a capped amount of $253m.

NEW STADIUM SNAPSHOT:

​- A 25,000 seat mostly clear-roofed facility has been decided to be the best fit.

- It has a $473m budget, $80m of which could be sliced off the price if all goes perfectly to plan.

- The council came up with a $500m+ plan, but the Government made it shave off an elevated walkway, some of the facade and paving to cut the cost.

- It will bring $395.6m in economic benefits, which includes $53.9m in "civic pride".

- The stadium profits won't cover operating costs, so ratepayers will have to top it up to the tune of $4.2m a year ($4.1m already budgeted).

- Councillors will meet on Thursday to decide whether to put the investment case forward to Cabinet.

- Major construction will start in early 2022 and it could be finished by spring 2024.

- Not having a stadium could harm vitality, investment and tourism.