Current through Register Vol. XLI, No. 50, December 13, 2024
Section 47-34-3 - Classification of Dams3.1. Types of Dams - For the purpose of this rule, dams are divided into four general types: 3.1.a. Embankment Dams - Embankment dams are usually constructed of materials which exhibit rock-like or soil-like properties.3.1.b. Gravity Dams - Gravity dams are usually constructed of concrete or masonry materials which form a rigid body.3.1.c. Waste Disposal Dams - Waste disposal dams are usually constructed of waste materials such as fly ash or coal refuse. The reservoir is utilized to dispose of waste material, thereby creating a continuously decreasing freeboard condition.3.1.d. Dams of Multiple Type - In cases where a dam exhibits properties of more than one type, such as gabion structures or roller-compacted concrete, the person or his or her agent must apply design techniques which are reasonably applicable to the particular structure involved.3.2. Dam-Related Measurements.3.2.a. Measuring Dam Height - The height of a dam is measured from the crest or uppermost point on the dam to the lowest point in the natural bed of the stream or watercourse at the downstream toe of the dam. Gravity overflow dams must be measured to the highest level which is greater than ten percent (10%) of the total crest length of the dam. The height of dams with sloping crests shall be determined by a weighted-average height above the natural bed of the stream or watercourse, excluding spillways.3.2.b. Measuring Reservoir Volume - For purposes of determining whether a dam meets the criteria set forth in subsection 2.12. as applied to reservoir volume calculations, the volume must be calculated at the crest elevation of the dam that is equivalent to the elevation used in determining the dam height.3.2.c. Incised Reservoirs - The height of the embankment of an incised reservoir must be measured using the method set forth in paragraph 3.2.a. Reservoir volume must be calculated from the crest of the embankment to the elevation of the lowest point in the natural bed of the stream or watercourse at the downstream toe. That portion of the water stored below stream grade shall not be included in determining whether a dam meets the criteria set forth in subsection 2.12.; however, it must be reported in the application as part of the total reservoir volume.3.3. Dams in Series - If the Secretary determines that a series or combination of water-impounding structures within the same watercourse, or within the tributaries of the watercourse, which cumulatively meet the definition of "dam" set forth in subsection 2.12. constitute a hazard to human life, and failure of one or more of the impounding structures may induce failure of any or all of the remaining impounding structures, he or she may require the owner or owners of each impounding structure to comply with the requirements of this rule.3.4. Incidental Dams. 3.4.a. Roadfills. 3.4.a.1. If the Secretary finds that a roadfill has become a hazard to human life or property through the frequent or continuous impoundment of water, he or she may order the owner of that roadfill to take all steps that are necessary to protect life or property in accordance with the emergency powers provided under W. Va. Code § 22-14-10.3.4.a.2. A certificate of approval will not be required for roadfills.3.4.b. Bridges. 3.4.b.1. If the Secretary finds that a bridge has become a hazard to human life or property through the frequent or continuous impoundment of water, he or she may order the owner of that bridge to take all steps that are necessary to protect life or property in accordance with the emergency powers provided under W. Va. Code § 22-14-10.3.4.b.2. A certificate of approval will not be required for bridges.3.4.c. Diversions - A certificate of approval will be required for dikes or other structures used to divert water and otherwise meeting the definition of "dam" set forth in subsection 2.12.3.4.d. Stream Encroachments - If the Secretary finds that a natural drainway has been restricted by filling or other artificial means so that the restriction can or does impound water, and the fill and resulting reservoir meets the height and storage requirements of a "Dam" as defined in this rule, he or she may order the fill removed or require a certificate of approval or both.3.5. Classification of Dams - The applicant for a certificate of approval must propose the hazard classification for his or her dam based upon the classification guidelines listed in paragraph 3.5.b. and the hazard evaluation performed pursuant to paragraph 3.5.c. The classification proposed by an applicant is subject to approval by the Secretary. 3.5.a. Changes in Dam Classification - The Secretary will periodically review the hazard classification of each dam subject to this rule and may reclassify a dam if he or she determines that the hazard potential has changed. The owner shall be notified by the Secretary of any hazard classification change.3.5.b. Hazard Classifications. 3.5.b.1. Class 1 (High Hazard) Dams - Class 1 dams are those dams located where failure may cause loss of human life or major damage to dwellings, commercial or industrial buildings, main railroads, important public utilities, or where a high risk highway may be affected or damaged. This classification must be used if failure may result in the loss of human life.3.5.b.2. Class 2 (Significant Hazard) Dams - Class 2 dams are those dams located where failure may cause minor damage to dwellings, commercial or industrial buildings, important public utilities, main railroads, or cause major damage to unoccupied buildings, or where a low risk highway may be affected or damaged. The potential for loss of human life resulting from failure of a Class 2 dam must be unlikely.3.5.b.3. Class 3 (Low Hazard) Dams - Class 3 dams are those dams located in rural or agricultural areas where failure may cause minor damage to nonresidential and normally unoccupied buildings, or rural or agricultural land. Failure of a Class 3 dam would cause only a loss of the dam itself and a loss of property use, such as use of related roads, with little additional damage to adjacent property. The potential for loss of human life resulting from failure of a Class 3 dam must be unlikely.3.5.b.3.A. An impoundment exceeding forty (40) feet in height or four hundred (400) acre-feet storage volume shall not be classified as a Class 3 dam.3.5.b.3.B. A waste disposal dam, the failure of which may cause significant harm to the environment, shall not be classified as a Class 3 dam.3.5.b.4. Class 4 (Negligible Hazard) Dams - Class 4 dams are dams where failure is expected to have no potential for loss of human life, no potential for property damage and no potential for significant harm to the environment. Examples of Class 4 dams include: dams across rivers, failure of which under any conditions will not flood areas above normal stream bank elevations; dams located in the reservoir of another dam which, under any conditions, can contain water released by failure of the Class 4 dam; and dams in series where the toe of the Class 4 dam(s) is in close proximity to the reservoir of a dam which can contain failure of the Class 4 dam(s) under any condition. In considering a request for a Class 4 designation, the Secretary may require written concurrence from the owner(s) of downstream dams that may be affected by failure of the Class 4 dam. Approval for use of this classification is vested in the Secretary, and will be based on engineering evaluation of the dam(s) and downstream areas in question.3.5.c. Hazard Evaluation.3.5.c.1. Downstream Hazards - In evaluating the hazard potential of a dam in order to determine its hazard classification, a complete evaluation of the downstream area which will be affected in the event of dam failure must be performed. A sudden flooding of inhabited land accompanied by a water flow with damaging velocity, a wall of water, or the flooding of inhabited structures will all be deemed to have the potential to result in a loss of human life. The planned or potential future development of downstream areas must also be considered when evaluating hazard classification.3.5.c.2. Dam Break Analysis - An applicant must perform a downstream breach analysis to evaluate and map the downstream inundation area under assumed normal conditions and overtopping failure conditions.3.5.c.2.A. The Secretary may waive the downstream breach analysis required under subparagraph 3.5.c.2. for a Class 2 or Class 3 or Class 4 dam where downstream conditions prevent any future introduction of new facilities or residences that thereby change the hazard classification of the dam.3.5.c.3. Upstream Hazards - No dam shall be constructed which, during maximum pool conditions, will flood upstream dwellings, public utilities, primary highways, or main railroads unless otherwise approved by the Secretary based upon site-specific conditions.3.5.d. Risk Assessment - The applicant may propose a risk assessment according to the following provisions to determine the effect upon dwellings or other buildings downstream (paragraph 3.5.d.1.), to reduce the hazard classification (subdivision 3.5.b.) or to reduce the design storm requirements (paragraph 7.1.a.2.) based upon failure of the dam by overtopping. The applicant must include appropriate calculations to support the request for hazard classification or design storm requirement reduction. The Secretary will not consider risk assessment based upon planned evacuation, probability of inhabitation, or monetary recovery of property damage. If both paragraph 3.5.d.1. (Dwellings or other Buildings Affected Downstream) and paragraph 3.5.d.2. (Highways Affected Downstream) pertain to the downstream area, then the hazard classification representing the greatest risk category and the largest of the design storm requirements resulting from the above calculations shall apply. Approval of hazard classification reduction or reduction of design storm requirements based upon risk assessment is vested in the Secretary, and will be based on engineering evaluation of the dam(s) and downstream areas in question.3.5.d.1. Dwellings or Other Buildings Affected Downstream - The Secretary may consider reduced design storm requirements (subparagraph 7.1.1.b.) within the approved hazard classification, if the applicant can demonstrate that all affected dwellings, commercial and industrial buildings or important public utilities will be inundated and evacuated prior to the dam failure. The applicant must also demonstrate that the potential for loss of human life resulting from the dam failure is not significantly increased from that which occurs immediately prior to the dam failure.3.5.d.2. Highways Affected Downstream - The Secretary may consider reduced hazard classification (paragraph 3.5.b.) and reduced design storm requirements (subparagraph 7.1.a.2.), if the applicant can demonstrate that affected highway(s) will be impassable and traffic will be stopped in the dam failure inundation area due to the highway(s) being flooded by high water prior to the dam failure. The applicant must also demonstrate that the potential for loss of human life resulting from the dam failure is not significantly increased from that which occurs immediately prior to the dam failure.