The Mackenzie Valley gas pipeline project is still only a concept, but the National Energy Board has begun laying out the conditions under which it could be built.

In a letter sent to the pipeline's proponents this week, the board sets out a long list of conditions to be applied to the pre-construction, construction and operational phases of the project — and says more are likely to come before a final decision is made.

For example, the board says members of the joint venture — Imperial Oil, Shell Canada, Exxon Mobil, ConocoPhillips and the Aboriginal Pipeline Group — must prove 90 days before beginning construction that the pipeline's design would be able to withstand the seasonal changes of the permafrost.

It also wants the companies to provide an emergency response plan two months before they start construction.

Other conditions address pipeline design over slopes and water crossings, welding standards and energy efficiency.

The companies will also have to share the information they have gathered on ice thickness and ground temperature.

The board finished its public hearings regarding technical and economic aspects of the project in December.

A second round of public hearings by the joint review panel into the social and environmental impact of the project is still under way.

The latest cost estimate pegged the construction tab at $7.5 billion, but the companies are now updating that projection in light of rising costs.