Section 10.06 - Size and Hazard Potential Classification(1)General. Dams shall be classified for purposes of establishing inspection schedules and adherence to design criteria, in accordance with their potential for damage to life or property in the area downstream from the dam in the event of failure of the dam or appurtenant facilities. This determination shall be made by the Commissioner and noted on the owner's Certificate of Registration. It may be necessary to periodically reclassify dams as additional information becomes available and/or conditions change. The criteria established in 302 CMR 10.06(2) through (4) shall be used by the Commissioner to determine the size and hazard potential classification based upon the extent of development downstream from the dam, taking into consideration factors such as height, type of structure and volume of impoundment, pursuant to M.G.L. c. 253.(2)Size Classification. The classification for size based on the height of the dam and storage capacity shall be in accordance with 302 CMR 10.06(2): Size Classification Table. The height of the dam is established as described in 302 CMR 10.06 with respect to maximum water storage elevation. The storage capacity of the dam is the volume of water contained in the impoundment at maximum water storage elevation measured as defined in 302 CMR 10.06(2). Size class may be determined by either storage or height, whichever gives the larger size classification. SIZE CLASSIFICATION TABLE
Category | Storage (acre-feet) | Height (feet) |
Non-jurisdictional* | Not in excess of 15 regardless of height | Not in excess of six regardless of storage capacity |
Small | >= 15 and <50 | >= 6 and <15 |
Intermediate | >= 50 and <1000 | >= 15 and <40 |
Large | >= 1000 | >= 40 |
*For dams not in excess of 6 feet in height or having maximum impounding capacity not in excess of 15 acre-feet, the Commissioner shall make jurisdictional determination by taking into consideration factors or combination of factors such as height, type of structure, volume of the impoundment, extent of downstream development, and other factors deemed appropriate by the Commissioner. |
(3)Hazard Potential Classification. The classification for hazard potential shall be in accordance with 302 CMR 10.06(3): Hazard Potential Classification Table. The hazards pertain to potential loss of human life or property damage in the event of failure of the dam or appurtenant works. Development of the area downstream from the dam that would be affected by its failure shall be considered in determining the classification. Dams will be subject to reclassification if the Commissioner determines the hazard potential has changed. HAZARD POTENTIAL CLASSIFICATION TABLE
High Hazard Potential (Class I) | Dams located where failure will likely cause loss of life and serious damage to home(s), industrial or commercial facilities, important public utilities, main highway(s) or railroad(s). |
Significant Hazard Potential (Class II) | Dams located where failure may cause loss of life and damage to home(s), industrial or commercial facilities, secondary highway(s) or railroad(s) or cause interruption of use or service of relatively important facilities. |
Low Hazard Potential (Class HI) | Dams located where failure may cause minimal property damage to others. Loss of life is not expected. |
(4)Dams in Series. If an upstream dam failure has the capability to create failure of a downstream dam because of its failure flood wave, it shall have the same or higher hazard potential classification as the downstream dam. If the failure flood wave of the upstream dam will not cause failure of the downstream dam, the upstream dam may have a different hazard potential classification from the downstream dam.(5)Failure Damage. The extent of potential damage resulting from a dam breach may justify designating damage as either major or minor. (a) Such a designation may be made after a detailed analysis has established the relative impact of the probable dam breach and has considered the following factors: 1. the conditions prior to and after a dam breach;2. the extent to which access has been affected, both before and after a dam breach; and(b) Potential damage to habitable structures will be considered minor when habitable structures are not within the direct path of the probable flood wave produced upon failure of a dam or where such structures will experience:1. no more than 2.0 feet incremental rise of flood water above the lowest ground elevation adjacent to the outside foundation walls; or2. no more than 2.0 feet incremental rise of flood water above the lowest habitable floor elevation of the structure; the lower of the two elevations governing.(6)Hazard Potential Reconsideration. An owner may at any time request the Commissioner to reconsider the hazard potential classification of their dam. The owner's request must be filed by a registered professional engineer, in a form provided by the Commissioner which provides the findings of the engineer's technical analysis and investigations which may support a change in classification. The Commissioner will issue a written decision to the owner and the registered professional civil engineer within 30 days of receipt of a request for hazard potential reconsideration, and such decision shall be final and binding upon the parties.(7)Hazard Potential Classification Review. While it is recommended dam safety practice to review the classification of each dam during each subsequent periodic Phase I Formal Inspection, to ensure the accuracy of Hazard Potential Classification of dams, each dam owner shall hire a qualified Registered Professional Engineer to review the classification of their dam(s) at least on a frequency of ten years or as otherwise ordered by the Commissioner.Amended by Mass Register Issue 1332, eff. 2/10/2017.