Construction is about to begin on a $19.9 million project to build an emergency power facility at Honolulu Airport.

Officials held a blessing ceremony Tuesday as the builder, Watts Constructors, prepared to start work.

Four biodiesel-powered generators will be installed that will automatically kick in and provide up to 10 megawatts of electricity to the airport during an emergency. State transportation spokesman Dan Meisenzahl said that is enough to keep the airport operating at full capacity.

He said the state could recoup about $14 million of the cost over 20 years because Hawaiian Electric Co. will pay to use the power when there is no emergency. The utility will also cover the maintenance costs.

Work could be completed as early as late next year.