Environmental Management

There are several dams in Prince William County that are subject to the Virginia Dam Safety regulations. The Virginia Dam Safety Regulations are found here: http://www.dcr.virginia.gov/dam_safety_and_floodplains/index.shtml

Any proposed development that will occur within mapped dam break inundation zones of state regulated dams must be identified on all Preliminary Plats, Subdivision Plan, Site Plan and Minor Site Plan submissions. A dam break inundation zone refers to the area downstream of a dam that would be inundated by the failure of the dam. Learn more about development in dam break inundation zones.

Prince William County Department of Public Works is responsible for the operation and maintenance of the following state-regulated dams. We have also designated the hazard level for each dam as high, significant or low. The dam breach inundation zones have been mapped for these dams:

• Lake Jackson Dam (153006) Significant Hazard
  • A technical memorandum on Lake Jackson Dam and possible modifications has been prepared by the County. You can view it here.
• Silver Lake Dam (153012) High Hazard
• Prince William Parkway Regional SWM Dam (153022) High Hazard
• Innovation at Prince William-Pond 3 Dam (153032) High Hazard
• Locust Shade Park Dam (153053) High Hazard

There are other dams located in Prince William County which are owned, operated and maintained by private entities. Dam breach inundation zones have also been mapped for these dams:

• Lake Montclair Dam (153003) High Hazard
• Upper Occoquan Dam (153004) High Hazard
• Lake Manassas Dam (153002) High Hazard
• Virginia Gateway Regional SWM Dam (153025) High Hazard
• New Bristow Village Dam (153026) Significant Hazard
• Market Center Pond 1 Dam (153030) Significant Hazard
• North Fork Wetlands Bank Dam (153029) High Hazard

All dams, including private dams, in Virginia are subject to the Dam Safety Act and Dam Safety Regulations unless specifically excluded. A dam is excluded if it:

• is less than six feet high;
• has a maximum capacity less than 50 acre-feet and is less than 25 feet in height;
• has a maximum capacity of less than 15 acre-feet and is more than 25 feet in height;
• is used primarily for agricultural purposes and has a maximum capacity of less than 100 acre-feet or is less than 25 feet in height ( if the use or ownership changes, the dam may be subject to regulation);
• is owned or licensed by the federal government;
• is operated for mining purposes under 45.1-222 or 45.1-225.1 of the Code of Virginia;
• is an obstruction in a canal used to raise or lower water levels;

Please note: the height of a dam is defined as the vertical distance from the streambed at the downstream toe to the top of the dam. The maximum capacity of a dam is defined as the maximum volume capable of being impounded at the top of the dam.

For more information about dam safety or development in dam break inundation zones, please contact our office at 703-792-7070 (TTY: 711).