UPDATE: The siren test is complete. We apologize for any inconvenience.
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An audible test of the Occoquan Dam siren system installed along the banks of the Occoquan River between the Town of Occoquan and Belmont Bay will be held on Tuesday, November 18, 2025 at 10am. People living and commuting in the area will hear a loud siren at that time. Please note that during the test, there is no need to seek higher ground when the siren sounds.
Fairfax Water is responsible for the test which is expected to be an annual exercise to test functionality. “The test is diagnostic and ensures the functionality of the connections and control system which were recently upgraded,” said Susan Miller, Fairfax Water’s public affairs officer.
An additional purpose for the event is to help residents and tourists become accustomed to the presence of the siren and how to react in the event of an emergency at the dam.
“We’re going to be communicating in every way we can to let people know what is happening and what to do ahead of time,” said Miller.
In the unlikely event of a structural failure at the dam, a loud siren will sound, and residents and visitors will be expected to vacate to higher elevations to avoid rapidly approaching water. A map on the related website marks “impact zones” which primarily impact the historic district of Occoquan. Those on the water at the time of the siren are encouraged to get on land as quickly as possible. The map and instructions can be found at www.occoquandamsiren.com.
The Occoquan Dam, known as “the High Dam” was built in the early 1950s to create the Occoquan Reservoir that now holds approximately 8.3 billion gallons of water. The dam is inspected and maintained on a routine basis. The structural integrity of the Occoquan Dam is very sound.
“Rigorous maintenance and improvements to the dam have made it even stronger today than when it was constructed,” said Miller. “It is extremely unlikely that the dam would become structurally compromised but we still want everyone to be prepared and safe.”
The siren project is a collaboration between Fairfax Water, the Town of Occoquan, Fairfax County, and Prince William County and was first installed during fall 2012.
In the event of cancellation, the test will be held on Tuesday, November 25, at 10 am
For more information, visit www.occoquandamsiren.com.