Section 0400-45-07-.05 - CLASSIFICATION OF DAMSDams will be classified in accordance to size, hazard potential, and design characteristics in order to formulate a priority basis for selecting dams to be scheduled in the inspection program and also to provide compatibility between guideline requirements and involved risks. When conditions at the dam or the hazard potential changes, the dam may be reclassified, and, if necessary, the dam must be upgraded to meet the standards of the new classification. The downstream conditions will be evaluated for hazard potential reclassification at least every 5 years.
(1) Size. The classification for size is based on the height of the dam and storage capacity in accordance with the table below. The height of the dam is established with respect to the maximum water storage elevation measured from the natural bed of the stream or watercourse at the downstream toe of the barrier, or if it is not across a stream or watercourse, the height from the lowest elevation of the outside limit of the barrier, to the maximum water storage elevation. For the purpose of determining project size, the maximum storage elevation will be considered equal to the top of dam elevation as defined in paragraph (26) of Rule 0400-45-07-.02. Size classification will be determined by either storage or height, whichever gives the larger size category. For size classification purposes, fractions of heights and storages shall be rounded down to the nearest whole number, e.g., 49.9 feet would be classified in the 20 to 49 feet category. Size Classification
| Category | Storage (Ac-Ft) | Height (Ft) |
| Small | 30 to 999 | 20 to 49 |
| Intermediate | 1,000 to 49,999 | 50 to 99 |
| Large | 50,000 or greater | 100 or greater |
(2) Hazard Potential Category.(a) Every dam will be assigned a hazard potential category to reflect the damage which might occur in the event of a dam failure, either structurally or operationally. The hazard potential will take into account a number of factors which will include, but not be limited to: the physical characteristics and degree of development of the site and valley downstream; the relationship of the site to industrial and residential areas; use of downstream properties throughout the danger reach; geological considerations; public and private uses of the impoundment or reservoir; and probable future downstream development.(b) The hazard potential category of a dam may impose different standards at different sites for design and conditions for issuance of a Certificate and will have a bearing upon the frequency of inspections by the Commissioner. The following categories are established to permit the association of criteria with the damage that might result from such a failure.1. Category 1 dams are located where failure would probably result in any of the following: loss of human life; excessive economic loss due to damage of downstream properties; excessive economic loss, public hazard, or public inconvenience due to loss of impoundment and/or damage to roads or any public or private utilities.2. Category 2 dams are located where failure may damage downstream private or public property, but such damage would be relatively minor and within the general financial capabilities of the dam owner. Public hazard or inconvenience due to loss of roads or any public or private utilities would be minor and of short duration. Chances of loss of human life would be possible but remote.3. Category 3 dams are located where failure may damage uninhabitable structures or land but such damage would probably be confined to the dam owner's property. No loss of human life would be expected.(3) Removal of Dams. A dam shall be considered removed if it meets one of the following criteria.(a) A portion of the dam is removed such that at the invert of the removed portion the dam is less than six feet high or has less than 15 acre-feet of storage capacity.(b) A portion of the dam is removed or an open-channel spillway is built such that the invert of the removed portion is at the approximate elevation of the top of the tailings or sediment in the impoundment and the dam can no longer permanently impound water. In the case of embankment dams that receive surface runoff from areas adjacent to the impoundment, the open channel must be sufficiently large to preclude overtopping during the Freeboard Design Storm specified in subparagraph (3)(b) of Rule 0400-45-07-.06 or subparagraph (4)(d) of Rule 0400-45-07-.07, respectively.Tenn. Comp. R. & Regs. 0400-45-07-.05
Original rule filed October 16, 2012; effective January 14, 2013. Rule renumbered from 1200-05-07.Authority: T.C.A. §§ 69-11-101 et seq., and 4-5-201 et seq.