HAPPY VALLEY GOOSE BAY, N.L. -- A public inquiry began today into the Muskrat Falls hydro megaproject in Labrador, with an expert witness providing context for common mistakes and root causes of cost overruns that affect megaprojects around the world.

The massive dam and powerhouse harnessing the lower Churchill River near Happy Valley-Goose Bay still isn't complete, but its price tag has climbed to $12.7 billion -- with the bill going to a province of just 530,000 people.

The independent inquiry, led by provincial Supreme Court Justice Richard LeBlanc, will examine how the project was approved and executed, and why it was exempt from oversight from the Public Utilities Board.

The first expert witness on the stand is Oxford University economics professor Bent Flyvbjerg, whose faculty profile refers to him as "the most cited scholar in the world in megaproject planning and management."

Flyvbjerg presented data showing that hydroelectric dams are particularly vulnerable to cost and schedule overruns and are "riskier than all other projects, except nuclear."

Flyvbjerg says many projects are affected by underestimated costs, lack of independent oversight and political optimism about a plan's success -- something he called "optimism bias."