British Columbia's mammoth Site C hydro-electric project is seriously behind schedule, plagued by quality problems and marked by secrecy, says an assessment by an international dam expert.

E. Harvey Elwin - hired by a First Nation asking for a court injunction to aspects of the dam's construction - expresses concern about work at the job site in his 196-page report citing internal BC Hydro and government documents, many of them previously confidential.

“In my opinion, it is the sign of a large performance problem with the (main) contractor meeting the requirements of the specifications and quality of work,” he wrote in the report filed Wednesday in B.C. Supreme Court.

In a letter accompanying a progress report to the B.C. Utilities Commission dated July 11, BC Hydro president Chris O'Riley said the project remains “on time and within budget.”

Spokespeople for the provincial government and contractor Peace River Hydro Partners did not immediately respond to requests for comment.

Elwin, who has worked on dams around the world including China's Three Gorges project, concludes the dam's construction is likely to take years longer than BC Hydro says.

The 1,100-megawatt dam and generating station on the Peace River in northern B.C. would flood parts of the traditional territory of the West Moberly and Prophet River First Nations.

In January they filed a civil court case, alleging their rights have been violated.

West Moberly also applied for an injunction to halt construction pending the outcome of the rights case. That motion goes to court Monday.

Elwin's report was filed in support of West Moberly's case.

BC Hydro has argued any injunction would create heavy budget overruns. It says a two-year injunction would cost an extra $660 million and a three-year stoppage would cost $1.1 billion.

Based on documents BC Hydro was forced to release as part of the court process, Elwin disagrees.

He found that stopping work in 13 areas the West Moberly are most concerned about would delay completion of major milestones by a few months at most. He concluded the cost of a three-year injunction would be $71 million.

Elwin expresses serious concern at the number of reports detailing construction problems.

“I have observed that there are always a large number of (non-conformance reports) generated and being processed. It is also evident that many are not closed rapidly,” he writes.

“The number, frequency, and lengths of time to close (such reports) are an indicator of the quality of work.”

Projections for placing concrete are “overly optimistic and not realistically achievable,” he says.

Last year, Elwin says contractors placed 35 per cent of the concrete they were supposed to for a major section of the dam. At that rate, Site C will take well over a decade to finish, significantly past its 2024 completion date, Elwin suggests.

O'Riley's letter acknowledges the project has had problems meeting its construction schedule. It has also had safety concerns.

He said an agreement has been reached with the main contractor that will accelerate some activities and provide incentive payments to meet deadlines. That's projected to cost up to $325 million.

“While the agreement will draw on our contingency budget ... we have been able to manage the costs within the existing construction budget,” O'Riley wrote.

Elwin is skeptical.

“I seriously doubt the capability of the (main) contractor to take on and effectively perform to an accelerated schedule,” says his report.

Additional safety staff have been hired and on-site safety conferences are being held, said O'Riley.

“The overall health of the project has significantly improved and is now classified as 'yellow,' or having some concerns,” O'Riley wrote.

In an affidavit filed in court earlier this month, Elwin is highly critical of BC Hydro's public disclosure.

“The extremely high level of confidentiality and the lack of availability of quantitative progress, cost, and schedule status and progress information in the Site C Project ... is extraordinary,” he writes.

“I have never seen in 50 years a major public project or program being put in place for its ratepayers by a public agency providing as little information.”

BC Hydro spokesman Greg Alexis said the company has been open about the project.

“BC Hydro has voluntarily provided the B.C. Utilities Commission with quarterly reports since the start of construction,” he said. “They are all posted to our website.”

The report vindicates West Moberly's concerns, said band lawyer Tim Thielmann.

“It's absolutely clear that there are major, major risks to the project,” he said.

Thielmann suggested that BC Hydro's initial calculations about the delay and cost implications of an injunction may have been an attempt to scapegoat others for problems it knew were coming.

“The appearance, at least, is that there was a shifting of the blame for the delay of the proponent's own challenges at the dam site onto the shoulders of others that wanted to propose changes.”

Site C was approved by the federal government. Environment Minister Catherine McKenna has said the government will defend the project's environmental assessment, consultation processes and federally issued permits.

About $2.4 billion has already been spent on construction.