Nearly six metres below a South Delta residential area, workers are making upgrades to a water storage reservoir that holds millions of litres of drinking water.

Work at the Pebble Hill reservoir began in the fall of 2021 to prepare for natural disasters years from now.

Metro Vancouver has been steadily upgrading its reservoirs since the '90s to ensure it can provide water to the region following the "Big One" — a megathrust earthquake expected to hit the B.C. coast someday.

They were built at di…