Occoquan Dam Siren Test at 10 a.m. on Thursday, Dec. 13

Occoqun Dam Siren

Posted at 2:51 p.m.

At 10 a.m. on Thursday, Dec. 13, there will be an audible test of a new warning siren system installed along the banks of the Occoquan River between the Town of Occoquan and Belmont Bay. 

This is only a test and is being conducted as part of an educational campaign to inform residents and business owners about the new siren system. For this test, you do NOT need to seek higher ground. Representatives from Fairfax Water, as well as officials from the town of Occoquan and Prince William and Fairfax counties will be in and around the town should residents have questions.

The Occoquan Dam Siren system exists to alert persons below the Occoquan Dam in the extremely unlikely event of a structural failure of the dam. If the siren sounds, residents, business owners and visitors inside the inundation zone should seek higher ground.

The inundation zone is a small area adjacent to the banks of the Occoquan River between the Town of Occoquan and Belmont Bay that will flood if the Occoquan Dam experiences a structural failure. The siren will only sound during testing of the system or if the Occoquan Dam fails in a non-weather-related event.

Occoquan Dam Inundation Zone MapThe siren has been installed for two reasons:

  • Because of changing regulatory requirements, one of Fairfax Water’s regulatory agencies – the Federal Energy Regulatory Commission – suggested that a sound-related system be installed to inform people downstream of the dam in the extremely unlikely event of a dam structural failure.
  • Communities closest to the dam, namely the Town of Occoquan, worked closely with Fairfax Water and felt that a siren system would be the most effective and desired form of communication to alert people. 

The siren project is a collaboration between Fairfax Water, the Town of Occoquan, Fairfax County and Prince William County.

For more information, visit www.occoquandamsiren.com/.

About the Occoquan Reservoir and Dam

Fairfax Water owns and operates the Occoquan Reservoir as a drinking water source for Northern Virginia. The Occoquan 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. The dam is approximately 72 feet tall and 70 feet wide at its widest point. It is anchored to the bedrock below the bottom of the dam and to the sides of the reservoir. It contains more than 100,000 cubic yards of mass concrete. That is equivalent to:

  • 10,000 truckloads of concrete
  • Approximately 400,000,000 pounds of concrete
  • A concrete path that is 3 feet wide, 1 foot thick, and 6.3 miles long.

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About Fairfax County Emergency Information

Official emergency information about preparedness, response and recovery from Fairfax County Government.

2 responses to “Occoquan Dam Siren Test at 10 a.m. on Thursday, Dec. 13”

  1. Monica says :

    Tomorrow is Wednesday, not Thursday, as it says in attached. Which day? Thanks.

    Sent from my iPhone

    • fairfaxcounty says :

      The siren test is on Thursday, Dec. 13, at 10 a.m. Apologies for the original post, which has been corrected.