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…