Waterford — Millstone Power Station is conducting an evacuation drill Wednesday afternoon that may affect traffic on Route 156.

The on-site test is done every six years at the nuclear power complex and is required by the Nuclear Regulatory Commission “to demonstrate our ability to evacuate the site in the unlikely event of a serious incident,” said spokesman Ken Holt.

Most of the power station’s 1,085 employees will be involved, though they haven’t been told precisely when the drill will take place, Holt said.

Waterford police will be on hand to direct traffic, he added.

Any residents with concerns should contact Holt at 860-440-0132.