7 Del. Admin. Code § 5103-5.0

Current through Reigster Vol. 28, No. 6, December 1, 2024

Section 5103-5.0 - Hazard Classification of Dams

5.1 General Requirements

5.1.1 Dams shall be classified in accordance with the federal classification system into three classes that are rated according to the potential damage that could be caused if the dams fail. Those three classes shall be designated as follows:

5.1.1.1 Class I High Hazard Potential

5.1.1.2 Class II Significant Hazard Potential

5.1.1.3 Class III Low Hazard Potential

5.1.2 Per state legislation and these Regulations, Class III Low-Hazard dams are exempt from the requirements of these Regulations.

5.1.3 The Department will use the guidelines in this section to classify dams according to hazard. Probable future development of the area downstream from the dam, which might be affected by its failure, will be considered in determining the hazard classification.

5.1.4 The Department may, at its discretion, change the hazard class of any proposed or existing dam.

5.2 Description of Hazard Class

5.2.1 Class I - High Hazard Potential: This classification includes any dam whose failure or misoperation will cause probable loss of human life. The existence of normally occupied homes in the area that are susceptible to significant damage in the event of a dam failure will be assumed to mean "probable loss of life." Recreational facilities below a dam, such as a campground or recreation area, may be sufficient reason to classify a dam as having a high-hazard potential.

5.2.2 Class II - Significant Hazard Potential: This classification includes any dam whose failure or misoperation will cause possible loss of human life, economic loss, environmental damage, and disruption of lifeline facilities, or can impact other concerns. This classification applies to predominantly rural agricultural areas, where dam failure may damage isolated homes, major highways, or railroads or cause interruption of service of relatively important public utilities.

5.2.3 Class III - Low Hazard Potential: This classification includes any dam whose failure or misoperation is unlikely to cause loss of human life but may cause minor economic and/or environmental losses. This classification applies to rural or agricultural areas where failure may damage farm buildings other than residences, agricultural lands, or non-major roads. Class III dams are exempted from the requirements of these Regulations.

5.3 Determination of the Hazard Class

5.3.1 The hazard classification shall be determined by establishing a danger reach downstream of the dam by conducting a dam breach analysis and routing the dam breach flood wave through the downstream valley. At the discretion of the Department, this analysis may require routing several spillway design floods through the danger reach, with and without the effects of failure of the dam, including at a minimum the following events:

5.3.1.1 100-year frequency flood

5.3.1.2 50 percent probable maximum flood (PMF)

5.3.1.3 Probable maximum flood (PMF)

5.3.1.4 A sunny day failure for dams with permanent pools

5.3.2 The applicant shall use computational methods for analyzing dam failure flooding that are generally acceptable in the engineering community and are verifiable, reliable, and acceptable to the Department.

5.3.3 The Department shall determine and assign the hazard classification according to the criteria above based on:

5.3.3.1 An evaluation of hydrologic calculations assuming ultimate development of the watershed using existing comprehensive plans and zoning; and

5.3.3.2 Review of potential damage within the danger reach.

5.3.4 Failure damage potential shall consider future development and use of the area flooded throughout the danger reach and the damage that would be expected from a complete breaching of the dam. If, in the opinion of the Department, future development is probable in the area flooded throughout the danger reach, the dam shall be categorized as Class I.

5.3.5 The classification of the proposed dam shall be assigned by the Department after the applicant has provided information on the potential damage within the danger reach, as defined herein. After the classification has been assigned, the inflow design flood and spillway design may be established.

7 Del. Admin. Code § 5103-5.0