Land Development Services

Fairfax County, Virginia

CONTACT INFORMATION: Regular hours for calls and emails are 8 a.m. – 4 p.m., Monday through Thursday, and 9:15 a.m. - 4 p.m. on Friday.

703-324-1780
TTY 711

12055 Government Center Pkwy
Fairfax, VA 22035

Bill Hicks,
Director

Development in Dam Break Inundation Zones

Any proposed development that will occur in the dam break inundation zone of a state-regulated impoundment that has been mapped and is on file with the County must be identified on all Preliminary Plats, Subdivision Plans, Site Plans and Minor Site Plans. A dam break inundation zone is the area downstream of an impoundment that would be flooded by failure of the impoundment’s dam.

As part of the plan review process, the county will notify dam owners and the Virginia Department of Conservation and Recreation (DCR) of any proposed development in the dam break inundation zone of a state-regulated impoundment. DCR is required to determine the potential impacts of the proposed development on the spillway design of the dam and notify the dam owner and the county of its determination. If the proposed development will require changes to the dam’s spillway, the development cannot be approved unless it is modified to avoid changes to the spillway or the developer pays half the cost of the necessary upgrades. In addition, when any part of a proposed subdivision is in a mapped dam break inundation zone, this fact must be noted on the Final Subdivision Plat for the development.

The requirements only apply to proposed developments downstream of a state-regulated impoundment for which a dam break inundation zone map is on file with the county at the time of the official submission of a plan to the county. The requirements for proposed developments located in dam break inundation zones and construction of state-regulated impoundments are contained in the Subdivision Ordinance, the Site Plan Provisions of the Zoning Ordinance and Chapter 6 of the Public Facilities Manual.

State-Regulated Impoundments in Fairfax County

To determine if a proposed development will occur within the mapped dam break inundation zone of a state-regulated impoundment, locate the development site using the Dam Break Inundation Zone Viewer. All available mapped inundation zones have been incorporated in the application. The following is a list of all the dams with mapped inundation zones.

DAM NAME

Tax Map

OWNER/OPERATOR

HAZARD CLASS

Burke Centre 11B Dam

77-4

DPWES

High

Burke Lake Dam

87-4

VA Dept. of Game & Inland Fisheries

High

Carrington Regional Pond Section 1A

28-2

DPWES

High

Dulles Station Regional Pond

15-4

DPWES

High

Fairfax Centre Regional Pond D77

56-2

DPWES

High

Fairview Lake Dam (Holmes Run 2A)

49-4

DPWES

High

Fox Lair Regional Pond Embankment

78-2

Norfolk Southern Railroad

Unknown

Fox Lake Dam

37-3

Fox Lake POA

Low

Hampton Forest Section 4 Regional Pond

55-4

DPWES

High

Hunter Mill Estates Regional Pond

27-2

DPWES

Low

Huntsman Lake (Pohick Creek Dam #8)

88-4

DPWES

High

Kings Park West Section 18 Dam

68-4

DPWES

Significant

Kingstowne Pond 4

91-3

DPWES

High

Lake Accotink Dam

79-2

FCPA

High

Lake Anne Dam

17-2

Reston Association

High

Lake Audubon Dam (Lower South Lake)

27-1

Reston Association

High

Lake Barcroft Dam

61-4

Lake Barcroft WID

High

Lake Barton (Pohick Creek Dam #2)

77-2

DPWES

High

Lake Braddock (Pohick Creek Dam #7)

78-1

DPWES

High

Lake Fairfax

18-1

FCPA

High

Lake Mercer (Pohick Creek Dam #1)

97-2

DPWES

High

Lake Newport Dam

11-4

Reston Association

High

Lake Thoreau Dam (Upper South Lake)

27-1

Reston Association

High

North Twin Lake

66-1

FCPA

Significant

NVCC Annandale Campus Lake Dam

59-3

NVCC

Significant

Pulte McLean Pond D67

29-1

DPWES

High

Reston Northern Sector Pond 1

11-2

DPWES

High

Reston Town Center Western BMP Dam

17-1

Reston Town Center Association

High

Royal Lake (Pohick Creek Dam #4)

78-1

DPWES

High

South Twin Lake

66-3

FCPA

Significant

Upper & Lower Occoquan Dams*

106-3 & 112-2

Fairfax Water

High

Upper Occoquan Sewage Authority Dam

74-1

UOSA

High

West Ox Road Regional BMP Dam

25-3

DPWES

High

Woodglen Lake (Pohick Creek Dam #3)

77-1

DPWES

High

*Currently regulated by the Federal Energy Regulatory Commission

Key:  

BMP – Best Management Practice
DPWES – Department of Public Works and Environmental Services
FCPA – Fairfax County Park Authority
NVCC – Northern Virginia Community College
POA – Property Owners Association
UOSA – Upper Occoquan Sewage Authority
WID Watershed Improvement District

Please note that where impoundments are located in proximity to one another, their inundation zones may overlap. Information provided in the application is compiled from an inventory of dams owned by the Fairfax County Department of Public Works and Environmental Services (DPWES), information on file with the Fairfax County Office of Emergency Management and a list of state-regulated dams provided by the DCR Division of Dam Safety. Dam break inundation zones for many state regulated dams are not currently available.

For more information about dam break inundation zone maps for facilities owned by DPWES, email the Stormwater Planning Division, 703-324-5500, TTY 711. For information about development in dam break inundation zones, contact the Stormwater and Geotechnical Section of the Site Development and Inspection Division at 703-324-1720, TTY 711.

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