WSSC Told Emergency Managers All Customers Could Lose Water by 5 p.m. Sept. 29, County Memo Says

At 1:45 p.m. on Sept. 29, WSSC Water told emergency managers it expected some customers to start losing water pressure by 3 p.m., most by 4 p.m., and all of its customers to lose water service by 5 p.m., according to a Nov. 6 memo from Montgomery County’s Office of Emergency Management and Homeland Security (OEMHS) to the County Council.

That did not happen. At about 4 p.m., WSSC set up a temporary workaround that restored full power to its Potomac Water Filtration Plant, and the plant began producing water again, the memo says. OEMHS “is not aware of any customers losing water pressure or service,” it says.

The memo is the county’s first formal account of the outage, which led WSSC to ask all 1.9 million customers in Montgomery and Prince George’s counties to use water only for essential purposes. County Code Section 2-17 requires the Executive to report the facts, costs and long-term implications to the Council within 30 days after an incident that activates the county’s Emergency Management Group. Moderately MOCO obtained the memo from the Council’s Legislative Information Services.

What failed

The Potomac plant runs on two redundant Pepco power feeds and can operate fully on either one, according to the memo. Beginning in mid-September, WSSC and Pepco took one feeder offline for routine maintenance, and the plant kept running on the other.

At about 4:30 a.m. Sept. 29, that remaining feeder failed and water production stopped. Pepco restored the feeder that had been down for maintenance by about 10:30 a.m., but “electrical equipment failures within the WSSC, likely caused by the initial power outage, prevented electricity from supplying the plant,” WSSC told the 1:45 p.m. call with Montgomery, Prince George’s and Maryland emergency managers, according to the memo. As of 10:30 a.m., crews had not identified what caused the primary feeder to fail; the memo does not give a cause.

WSSC repaired an internal transformer at about 12:20 p.m. Oct. 1, which permanently restored power, and on Oct. 6 it repaired and configured “a key electrical component” for the second feeder, restoring both feeds, the memo says. WSSC lifted its essential-use request at 5 p.m. Sept. 30.

How the county responded

WSSC notified OEMHS at 6:30 a.m. and asked at 8:30 a.m. that the county push its essential-use request through Alert Montgomery, which went out at 9:30 a.m., according to the memo’s timeline. After the 1:45 p.m. call, the county stood up its Emergency Operations Center at 2:43 p.m. and moved to full activation at 4 p.m., the same time WSSC’s workaround brought the plant back.

By 6 p.m. the center was fully staffed, and staff worked on contingency plans for public water distribution, firefighting, hospitals and public messaging, the memo says. The county received its first pallet delivery of water by 8 p.m. Montgomery County Fire and Rescue Service reported no interruption to hydrant reliability, and no impacts were reported to local hospitals, county facilities or transportation.

The county’s costs so far are about $21,000, for overtime and extra staffing, bottled water and food for essential staff, a figure the memo calls preliminary. WSSC’s own costs are not included.

What comes next

OEMHS is conducting an after-action review with partner agencies and will give the Council an update with a list of lessons learned within 60 days of the event, the memo says. The incident “highlighted numerous opportunities to improve water emergency preparedness and resilience,” it says, across government operations, emergency services, healthcare, mass care and public information.

WSSC has estimated it needs $155 million in electrical upgrades at the Potomac plant, Moderately MOCO reported Oct. 22. Our Sept. 29 story covered the essential-use request as it happened.

Still unanswered

• What caused the primary Pepco feeder to fail on Sept. 29?
• Which WSSC electrical equipment failed after the outage, and why did it keep power from reaching the plant once Pepco restored service?
• With one of the plant’s two feeds offline for maintenance since mid-September, what backup power was in place if the other failed?

We have not yet put these questions to WSSC Water or Pepco; this story will be updated with any response.

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