THE cost of Clydebank's state-of-the-art district heating project has jumped by nearly a third, according to a leaked report.

The project at Queens Quay is designed to draw heat from the River Clyde and provide cheaper heat to public buildings and homes.

It has always been unanimously supported by elected politicians and drawn backing from residents and campaigners who hope it will help tackle fuel poverty and reduce the area's carbon footprint.

But in confidential papers to go before councillors at a special meeting next week, they will discuss costs rising from £15.1million to £19.5m – a rise of £4.4m.

That 30 per cent rise is being blamed on how "unique" the project is, particularly blending it with the rest of the Queens Quay infrastructure development, which was already well underway when the heating work started.

West Dunbartonshire Council (WDC) bosses have called in external construction experts to carry out a review of the "significant increase" in costs.

The review itself will cost taxpayers another £49k.

Councillors at Tuesday’s special meeting voted 10 to seven to take discussions behind closed doors because of commercial sensitivity. The papers will remain secret.

Council leader Jonathan McColl argued they needed to be free to ask questions of council officers and get answers.

But Councillor Jim Bollan said previous discussions of the project had all been public and were only going behind closed doors once costs went up by millions.

Labour wanted the debate moved to another date when missing councillors could attend and hold it in Clydebank, where the project is meant to be.

WDC was previously given £6.1m from the Scottish Government's Low Carbon Infrastructure Transition Programme (LCITP) in 2016. The local authority will apply for more cash from LCITP.

The new Clydebank Care Home, health centre and proposed social housing at Queens Quay are all depending on the district heating plan.

Councillors will also be asked to agree new commercial terms with Clydeside Regeneration Limited (CRL), the owners of the former John Browns yard.

That will see upfront funding rise from £900k to £3.5m.

Read more: First pipes laid at West Dunbartonshire Council's district heating network

Finding successful bidders to operate the centre and network also caused delays.

The report states that once Vital Engeri was appointed, there was a "fuller understanding" of the design needs.

It added: "This resulted in a significant re-design of the existing outline design work done previously for the pipe network as well as re-design of the pump chamber and associated infrastructure."

One of the changes included bringing the pipe network closer to the surface to make repairs easier.

Delays alone are costing £2.2m with another £579,000 on additional design. Materials costs have added another £1.8m to the project.

Two of the biggest cost hikes have come from materials for the energy centre building, with cladding alone shooting up £278k.

A Scottish Power requirement for changes to the sub-station added £73k, while features such as access roads, stairs and fences will cost an extra £180k.

The report insists: "All of the above costs were unexpected and could not have been foreseen at the time the original project budget was established."

Fit-out of the energy centre adds about £1m beyond the original budget, half of that from the project taking longer.

Because the roads for Queens Quay couldn't be finished until the pipes were laid for district heating, the roads contractor claimed for £710k for loss and expense.

There were some savings, such as £184k from the redesign of the pipe network.

But the estimate of £500k for the design and build of the abstraction chamber to get the heat out of the Clyde, "was arrived at before there was detailed knowledge of both the size of the equipment installed, and the condition of the existing structures within which the chamber had to be situated".

That more than quadrupled the cost for that portion alone to £2.3m.

Read more: Future of heating scheme is secured

The council report also describes conflicts between the different parties involved at Queens Quay that led to "threats of, and actual halting of work".

When the district heating project is finished, the council will own an energy supply company to run it.

Heating will also be provided to West College Scotland, Clydebank Leisure Centre, Aurora House, Titan Enterprise Centre, Clydebank Town Hall and Clydebank Library.

WDC hopes it will eventually extend to the Golden Jubilee Hospital, Dalmuir and then other parts of the town.