Virginia Department of Virginia Department of Conservation & RecreationConservation & Recreation

Virginia Dam Safety & Floodplain Programs

William G. Browning, DirectorDam Safety & Floodplain Management

Dam Safety & Floodplain Dam Safety & Floodplain OrganizationOrganization

• Department reorganization effective November 1, 2003

• Merged Dam Safety and Floodplain Management Programs

• Purpose is to reduce risks and hazards to the Commonwealth from dam failure and floods.

Dam Safety & Floodplain Dam Safety & Floodplain OrganizationOrganization

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Dam Safety Program Dam Safety Program

Virginia Dam Safety Act of Virginia Dam Safety Act of 1982; Amended July 1, 20021982; Amended July 1, 2002

• Provides for the proper and safe design, construction, operation and maintenance of impounding structures to protect public safety.

• No impounding structure can ever be completely fail-safe, because of incomplete understanding of/or uncertainties

associated with natural and man-made destructive forces

material behavior and responses to those forces quality control during construction

Code of Virginia Requirements:Code of Virginia Requirements: The law regulates impounding structures

including dams used to retain or store waters or other materials. With a few exceptions, the following structures are regulated:

> Impounding structures 25 feet or higher with a maximum impoundment capacity of 15 acre-feet or more

> Impounding structures 6 feet or higher with a maximum impoundment capacity of 50 acre-feet or more

Definitions:Definitions:

Dam height is the vertical distance from the streambed at the downstream toe to the top of the dam.

Maximum Impounding Capacity of a dam is the volume capable of being impounded at the top of the dam.

Acre-foot is a volume of one foot of depth over one acre of area

50 acre-feet

6’-25’ high

15 acre-feet

25’ or higher

Classifying Regulated DamsClassifying Regulated Dams

• Impounding structures are classified by hazard potential and size

• Hazard potential relates to downstream losses that may occur if the dam fails

Classes of Hazard Potential If Classes of Hazard Potential If Structure FailsStructure Fails

Class I Probable loss of life

Excessive economic loss II Possible loss of life

Appreciable economic loss III No loss of life expected

Minimal economic loss IV No loss of life expected

No economic loss to others

Performance Standards Required Performance Standards Required

for Impoundments*for Impoundments* The required spillway

design flood is based on the combination of :

• hazard classification • size classification

* 4 VAC 50-20-50

Spillway FunctionsSpillway Functions

Prevents dam overtopping

Prevents erosion at base of dam

Classifications of DamsClassifications of DamsClass Dam Size Spillway Design Flood

I LargeMediumSmall

Probable Maximum Flood (PMF)

PMF

½ PMF to PMF

II Large

Medium

Small

PMF½ PMF to PMF100 Year to ½ PMF

III Large

Medium

Small

PMF100 Year to ½ PMF50 Year to 100 Year

IV Small 50 Year to 100 Year

What are the Responsibilities of What are the Responsibilities of Dam Owners?Dam Owners?

Documents Required For Documents Required For Certification:Certification:

Operation and Maintenance Application – I, II & III

Emergency Action Plan - I, II & IIIRe-inspection Report – I & IIInventory Report – III & IV

Note: Class IV inventory report can be completed by owner

Frequency of SubmittalFrequency of Submittal

Class Plan and Report Schedule

I Operation and Maintenance Plan – 6 year intervalRe-inspection report - 2 year interval

II Operation and Maintenance Plan – 6 year intervalRe-inspection Report – 3 year interval

III Operation and Maintenance Plan – 6 year intervalInventory report – 6 year interval

IV Inventory report - 6 year interval.

In addition…In addition…

Owners of Class I, II, III and IV structures shall perform an annual owner’s inspection and submit the report in years when a professional re-inspection is not required.

Upon Submission of Forms…Upon Submission of Forms…

Dam Safety RegionalEngineers: Review submitted

materials May inspect structure Make recommendations

to the Soil and Water Conservation Board

The Soil and Water Conservation The Soil and Water Conservation Board Issues:Board Issues:

• Regular Operation And Maintenance Certificates

• Conditional Operation And Maintenance Certificates

• Construction Permits for new dams• Alteration Permits to repair and/or

upgrade dams• Transfer of Ownership

Regional Engineers Also …Regional Engineers Also …

• Review new construction and alteration applications

• Advocate dam safety to local governments

• Respond to emergencies• Provide training

Number Of Impoundments Number Of Impoundments In DatabaseIn Database

Conditional Regular Being Built

Total Regulated

Non-Regulated*

Total

I 29 79 4 112 43 155

II 13 111 10 134 159 293

III 10 227 12 249 906 1155

IV 0 24 2 26 0 26

*May need permitting based on regulation criteria change July 1, 2002

Types of Non-Regulated DamsTypes of Non-Regulated Dams

Certification Type

I II III IV Total

Agricultural Exemption

1 8 86 0 95

Federal License 29 18 67 0 114

Mining Exemption

5 5 10 0 20

Size Exemption 8 128 741 2 879

Why Does Dam Safety & Floodplain Why Does Dam Safety & Floodplain Management Matter?Management Matter?

• At least 18 declared flood or hurricane disasters since Hurricane Camille in 1969

• Timberlake dam failure killed 2 people

• Flooding is the most costly and frequent Virginia natural hazard

Hurricane Floyd – September 1999Hurricane Floyd – September 1999

• 13 dam failures in eastern Virginia

• Devastated Southampton County and Franklin

• Floodwaters did not receed for 11 days

How Do We Prevent Damage From How Do We Prevent Damage From Floods and Hurricanes?Floods and Hurricanes?

• Through Proper Dam Maintenance

• Build At or Above The Base Flood Elevation

• Elevate, Relocate or Demolish Flood-prone Structures

• Conserve Floodplains for Habitat, Open Space, Flood Capacity and Storage

Dam Safety & Floodplain Dam Safety & Floodplain Management Programs Management Programs

Need Your Help…Need Your Help…

Please Contact Us RegardingPlease Contact Us Regarding

• Use of Downstream Inundation Zones • Training In Floodplain Management &

Dam Safety • Floodplain Ordinance Review• Technical Assistance For Dams &

Floodplain Construction• Floodplain Management Community

Assistance Visit• Dams 6 Feet or Higher That Are Not

Properly Maintained

Contact InformationContact Information

Department of Conservation & Recreation

Dam Safety and Floodplain Management Programs

203 Governor Street, Suite 206Richmond, VA 23219

804-371-6095www.dcr.state.va.us