FINAL UPDATE — Wednesday, Sept. 30, 5 p.m.: WSSC Water has lifted its Essential Water Use Only request for all customers in Prince George’s and Montgomery counties, ending the conservation measures imposed after an electrical failure disrupted operations at the Potomac Water Filtration Plant Tuesday.

The request was lifted effective at 5 p.m. Wednesday. WSSC said the Potomac plant is producing enough water to meet customer demand, the distribution system has been replenished to normal levels and power delivery to the plant is stable and adequate.

Customers may resume normal water use. No boil-water advisory was issued during the incident.

WSSC said customers’ conservation efforts helped preserve water in the system, maintain adequate supplies for fire protection and avoid the need for a boil-water advisory.

Although system conditions have stabilized, the Potomac plant remains on a temporary internal electrical configuration while crews work toward a permanent power solution. WSSC’s Emergency Operations Center remains activated as the utility continues monitoring operations.

How the emergency unfolded

UPDATE — Tuesday, Sept. 29, 8 p.m.: WSSC Water’s Potomac Water Filtration Plant has returned to full production following an electrical failure that disrupted operations Tuesday, but customers in Prince George’s and Montgomery counties are being asked to continue limiting water use overnight while the utility replenishes system storage.

WSSC says its drinking water remains safe. No boil-water advisory is in effect.

David McDonough, WSSC Water’s deputy general manager for mission support, said during a Tuesday evening briefing that all indications point to an infrastructure failure. He said there was no indication the incident was caused by a cyberattack or other bad actors.

McDonough said the Potomac plant produces about 70 to 75 percent of the water distributed across WSSC’s approximately 6,000-mile system. The plant is normally supplied by two electrical feeds.

One of those feeds had been taken out of service for scheduled Pepco maintenance when the second feed — which was providing all power to the plant — failed at approximately 4:30 a.m. Tuesday and could not be restored, McDonough said.

Pepco restored power to the feed that had been undergoing maintenance at approximately noon. WSSC expected normal plant operations to resume rapidly, but internal electrical failures prevented that from happening.

After additional work, the plant returned to normal operations at approximately 3:45 p.m. and reached full production around 5 p.m. McDonough said a temporary electrical workaround is currently in place and power has been restored to both feeds.

Tuesday evening: system storage recovering

Ben Thompson, WSSC Water’s director of production, said the utility had approximately 89 million gallons of water stored during the evening briefing, while current system demand was approximately 211 million gallons.

Thompson said the Potomac plant was producing at a rate of approximately 160 million gallons, while the Patuxent Water Filtration Plant was producing at approximately 105 million gallons.

With production restored, WSSC is refilling tanks and rebuilding storage throughout the system. Officials said they are looking for a full recovery overnight and will continue monitoring conditions around the clock before making further determinations Wednesday morning.

Officials said they hope conditions will allow the Essential Water Use Only request to be lifted by around lunchtime Wednesday. That is an expectation, not a scheduled end to the conservation request.

Until WSSC formally lifts the request, customers should continue limiting water use.

Residents should continue avoiding outdoor water use and limit showers, toilet flushing, washing machines and dishwashers while the system recovers.

Morning emergency request

WSSC issued the Essential Water Use Only request at 8:45 a.m. Tuesday for all 1.9 million customers in Prince George’s and Montgomery counties after the power problem disrupted operations at the Potomac plant.

The utility said conservation was necessary to preserve water in system storage and for fire protection while crews worked to restore plant operations.

WSSC asked customers to use water only when necessary, take shorter showers, avoid outdoor water use, limit toilet flushing and limit use of washing machines and dishwashers.

WSSC’s original Tuesday morning emergency notice is available on the utility’s website. The Westphalia Gazette updated this story throughout the incident as WSSC restored production and replenished the distribution system.