According to the AJ's sister publication Construction News, contractors bidding to build the £150 million pool have now been presented with two potential designs by the Olympic Delivery Authority (ODA) - one featuring a steel roof, the other with a never-before-seen wooden structure.
Last year the project, which has already been redesigned to include a simplified and much smaller roof ( Zaha reveals radical changes to Olympic Aquatic Centre), was criticised in a sustainability audit for its lack of environmental features.
Speaking to Construction News, one anonymous bidder for the prize Olympic scheme said: 'One of [the designs] is in steel, the other timber.
'I think [the ODA] wants to show this is an environmental building and find out whether it will be cheaper using timber.
The source added: 'The drawings we've seen are very preliminary and the roof doesn't look massively complex. What they will do is get price and programme on both options and go from there.
'The feeling is they will go for steel in the end, but at the moment the ODA hasn't made its mind up.'
It is understood a steel roof would use around 3,000 tonnes of the material but if a timber roof was chosen only 'a very small amount' would be needed.
More drawings of the project, which is being co-designed with S&P Architects, are due to be shown to bidders in the next few weeks, with the tendering process due to begin in September.