2024 Earthquake Bulletin
05/20/2024 07:00 update
At 10:23AM on April 5, 2024, a magnitude 4.8 earthquake occurred with the epicenter located within 5 miles of the Spruce Run and Round Valley Reservoirs. Due to the magnitude and proximity of this event, a Dam Advisory Condition (Advisory) was declared for all high hazard dams within the Authority’s Raritan System, as required by the dams’ Emergency Action Plans (EAPs) and NJDEP Bureau of Dam Safety (Dam Safety) standards.
Over the following hours, days, and weeks the dam embankments, instrumentation, and appurtenant structures were intensively inspected and monitored by teams of Authority engineers, technicians, and consulting engineers with no dam safety concerns being identified. The Authority has been in regular, collaborative discussions with Dam Safety since the original April 5 earthquake regarding ongoing inspection and monitoring protocols and the continuation of Advisory status during subsequent seismic activity. Authority staff have reviewed the activity history of 173 seismic events from April 5 through today and identified a clear trend of reduced frequency and magnitude. After consultation with Dam Safety, a mutual decision was made to cancel the Advisory, effective immediately.
The Authority intends to return to normal inspection frequency, which includes at least daily observations by our security staff and/or technicians who are trained to identify dam safety concerns. Inspection frequency may be increased again based on future seismic activity.
04/05/2024 16:00 update
Following consultation with the NJDEP Bureau of Dam Safety, as a precautionary measure, the NJWSA Dam Advisory condition will remain in effect until further notice.
NJWSA will continue to monitor the dams as we continue to experience aftershocks. No further updates will be provided unless there is a change in conditions at any of the dams. Notification about any change to the Dam Advisory condition will be issued.
04/05/2024 15:00 update
Conditions are unchanged from the previous update at noon.
04/05/2024 12:00
Following the occurrence of a magnitude 4.8 earthquake located 6km ESE of Califon, NJ, at 10:23am EST on April 5, 2024, the NJWSA declared a Dam Advisory Condition, as required by its Emergency Action Plans, for the dam at Spruce Run Reservoir and the three dams at Round Valley Reservoir. No such condition was issued for the dam at Manasquan Reservoir.
In the following hour, all downstream communities identified in the NJWSA’s Emergency Action Plans for each dam were notified and the four dams were inspected in person by a team of NJWSA engineers. NJWSA reviewed all dam instrumentation and found no anomalies. NJWSA also consulted with the NJDEP Bureau of Dam Safety and its consulting engineer for rehabilitation projects occurring at Spruce Run and Round Valley reservoirs, Schnabel Engineering, LLC.
As of 12:00pm EST, no dam safety concerns have been identified. A small sinkhole was identified near the Spruce Run dam, but it is not considered to be a dam safety issue at this time. The dams will continue to be monitored appropriately and further updates will be issued.