Virginia Administrative Code › Title 4 - CONSERVATION AND NATURAL RESOURCES › Agency 50 - VIRGINIA SOIL AND WATER CONSERVATION BOARD › Chapter 20 - IMPOUNDING STRUCTURE REGULATIONS › Part I - General › Section 4VAC50-20-30 - Definitions

Current through Register Vol. 40, No. 24, July 15, 2024
The following words and terms when used in this chapter
					 shall have the following meanings unless the context clearly indicates
					 otherwise:
"Acre-foot" means a unit of volume equal to 43,560 cubic
					 feet or 325,853 gallons (equivalent to one foot of depth over one acre of
					 area).
"Agricultural purpose" means the production of an
					 agricultural commodity as defined in § 3.2-3900 of the Code of Virginia
					 that requires the use of impounded waters.
"Agricultural purpose dams" means impounding structures
					 which are less than 25 feet in height or which create a maximum impoundment
					 smaller than 100 acre-feet, and operated primarily for agricultural
					 purposes.
"Alteration" means changes to an impounding structure that
					 could alter or affect its structural integrity. Alterations include, but are
					 not limited to, changing the height or otherwise enlarging the dam, increasing
					 normal pool or principal spillway elevation or physical dimensions, changing
					 the elevation or physical dimensions of the emergency spillway, conducting
					 necessary structural repairs or structural maintenance, or removing the
					 impounding structure. Structural maintenance does not include routine
					 maintenance.
"Alteration permit" means a permit required for any
					 alteration to an impounding structure.
"Annual average daily traffic" or "AADT" means the total
					 volume of vehicle traffic of a highway or road for a year divided by 365 days
					 and is a measure used in transportation planning and transportation engineering
					 of how busy a road is.
"Board" means the Virginia Soil and Water Conservation
					 Board.
"Conditional Operation and Maintenance Certificate" means a
					 certificate required for impounding structures with deficiencies.
"Construction" means the construction of a new impounding
					 structure.
"Construction permit" means a permit required for the
					 construction of a new impounding structure.
"Dam break inundation zone" means the area downstream of a
					 dam that would be inundated or otherwise directly affected by the failure of a
					 dam.
"Department" means the Virginia Department of Conservation
					 and Recreation.
"Design flood" means the calculated volume of runoff and
					 the resulting peak discharge utilized in the evaluation, design, construction,
					 operation and maintenance of the impounding structure.
"Director" means the Director of the Department of
					 Conservation and Recreation or his designee.
"Drill" means a type of emergency action plan exercise that
					 tests, develops, or maintains skills in an emergency response procedure. During
					 a drill, participants perform an in-house exercise to verify telephone numbers
					 and other means of communication along with the owner's response. A drill is
					 considered a necessary part of ongoing training.
"Emergency Action Plan or EAP" means a formal document that
					 recognizes potential impounding structure emergency conditions and specifies
					 preplanned actions to be followed to minimize loss of life and property damage.
					 The EAP specifies actions the owner must take to minimize or alleviate
					 emergency conditions at the impounding structure. It contains procedures and
					 information to assist the owner in issuing early warning and notification
					 messages to responsible emergency management authorities. It shall also contain
					 dam break inundation zone maps as required to show emergency management
					 authorities the critical areas for action in case of emergency.
"Emergency Action Plan Exercise" means an activity designed
					 to promote emergency preparedness; test or evaluate EAPs, procedures, or
					 facilities; train personnel in emergency management duties; and demonstrate
					 operational capability. In response to a simulated event, exercises should
					 consist of the performance of duties, tasks, or operations very similar to the
					 way they would be performed in a real emergency. An exercise may include but
					 not be limited to drills and tabletop exercises.
"Emergency Preparedness Plan" means a formal document
					 prepared for Low Hazard impounding structures that provides maps and procedures
					 for notifying owners of downstream property that may be impacted by an
					 emergency situation at an impounding structure.
"Existing impounding structure" means any impounding
					 structure in existence or under a construction permit prior to July 1,
					 2010.
"Freeboard" means the vertical distance between the maximum
					 water surface elevation associated with the spillway design flood and the top
					 of the impounding structure.
"Height" means the hydraulic height of an impounding
					 structure. If the impounding structure spans a stream or watercourse, height
					 means the vertical distance from the natural bed of the stream or watercourse
					 measured at the downstream toe of the impounding structure to the top of the
					 impounding structure. If the impounding structure does not span a stream or
					 watercourse, height means the vertical distance from the lowest elevation of
					 the downstream limit of the barrier to the top of the impounding
					 structure.
"Impounding structure" or "dam" means a man-made structure,
					 whether a dam across a watercourse or structure outside a watercourse, used or
					 to be used to retain or store waters or other materials. The term includes:
(i) all dams that are 25 feet or
				  greater in height and that create an impoundment capacity of 15 acre-feet or
				  greater, and
(ii) all dams that
				  are six feet or greater in height and that create an impoundment capacity of 50
				  acre-feet or greater. The term "impounding structure" shall not include:
(a) dams licensed by the State Corporation
				  Commission that are subject to a safety inspection program;
(b) dams owned or licensed by the United
				  States government;
(c) dams
				  operated primarily for agricultural purposes which are less than 25 feet in
				  height or which create a maximum impoundment capacity smaller than 100
				  acre-feet;
(d) water or silt
				  retaining dams approved pursuant to § 45.1-222 or 45.1-225.1 of the Code
				  of Virginia; or
(e) obstructions
				  in a canal used to raise or lower water.
"Impoundment" means a body of water or other materials the
					 storage of which is caused by any impounding structure.
"Life of the impounding structure" and "life of the
					 project" mean that period of time for which the impounding structure is
					 designed and planned to perform effectively, including the time required to
					 remove the structure when it is no longer capable of functioning as planned and
					 designed.
"Maximum impounding capacity" means the volume of water or
					 other materials in acre-feet that is capable of being impounded at the top of
					 the impounding structure.
"New construction" means any impounding structure issued a
					 construction permit or otherwise constructed on or after July 1, 2010.
"Normal or typical water surface elevation" means the water
					 surface elevation at the crest of the lowest ungated outlet from the
					 impoundment or the elevation of the normal pool of the impoundment if different
					 than the water surface elevation at the crest of the lowest ungated outlet. For
					 calculating sunny day failures for flood control impounding structures,
					 stormwater detention impounding structures, and related facilities designed to
					 hold back volumes of water for slow release, the normal or typical water
					 surface elevation shall be measured at the crest of the auxiliary or emergency
					 spillway.
"Operation and Maintenance Certificate" means a certificate
					 required for the operation and maintenance of all impounding structures.
"Owner" means the owner of the land on which an impounding
					 structure is situated, the holder of an easement permitting the construction of
					 an impounding structure and any person or entity agreeing to maintain an
					 impounding structure. The term "owner" may include the Commonwealth or any of
					 its political subdivisions, including but not limited to sanitation district
					 commissions and authorities, any public or private institutions, corporations,
					 associations, firms or companies organized or existing under the laws of this
					 Commonwealth or any other state or country, as well as any person or group of
					 persons acting individually or as a group.
"Planned land use" means land use that has been approved by
					 a locality or included in a master land use plan by a locality, such as in a
					 locality's comprehensive land use plan.
"Spillway" means a structure to provide for the controlled
					 release of flows from the impounding structure into a downstream area.
"Stage I Condition" means a flood watch or heavy continuous
					 rain or excessive flow of water from ice or snow melt.
"Stage II Condition" means a flood watch or emergency
					 spillway activation or impounding structure overtopping where a failure may be
					 possible.
"Stage III Condition" means an emergency spillway
					 activation or impounding structure overtopping where imminent failure is
					 probable.
"Sunny day dam failure" means the failure of an impounding
					 structure with the initial water level at the normal reservoir level, usually
					 at the lowest ungated principal spillway elevation or the typical operating
					 water level.
"Tabletop Exercise" means a type of emergency action plan
					 exercise that involves a meeting of the impounding structure owner and the
					 state and local emergency management officials in a conference room
					 environment. The format is usually informal with minimum stress involved. The
					 exercise begins with the description of a simulated event and proceeds with
					 discussions by the participants to evaluate the EAP and response procedures and
					 to resolve concerns regarding coordination and responsibilities.
"Top of the impounding structure" means the lowest point of
					 the nonoverflow section of the impounding structure.
"Watercourse" means a natural channel having a well-defined
					 bed and banks and in which water normally flows.