The decision is due to be published on 3 October. Welton added that it would then take about a month to finalise finance for the scheme.
Welton spoke as Balfour posted a pre-tax profit of £48m for the six months to 29 June, up 17% on the same period last year. Turnover grew by £249m to £1.68bn.
Balfour’s operating profit fell slightly in its building division, which reported a profit of £21m compared with £22m last year.