Water Storage Dams and Reservoirs
Dam safety statutes are enumerated in Idaho Code §§ 42-1709 through 42-1721. The definition of height to be used for determining compliance with Idaho Code is measured vertically from the natural bed of the stream or watercourse at the downstream toe of the barrier to the maximum water storage elevation.
Hydraulic structures greater than or equal to ten (10) feet height and reservoirs that impound a volume of water greater than or equal to fifty (50) acre-feet are regulated by the IDWR Dam Safety Program for benefit of public safety, unless specifically exempted per Idaho Code § 42-1711.
Note that regardless of size, any water storage embankment may be regulated for public safety if IDWR determines that the potential failure consequences would result in significant damage to downstream life or property. Owners who desire to construct, enlarge, alter, or repair a water storage dam or water diversion structure meeting the definition and dimensions described above must submit an Application for Construction or Enlargement of a New or Existing Dam. In addition to submitting an application with the requisite fees, the owner must also submit a properly prepared design for IDWR’s review and approval. The design generally will be expected to meet or exceed the prescriptive design and construction requirements enumerated in the IDAPA 37.03.06. Persons who propose to construct a dam or hydraulic structure equal to or greater than ten (10) feet high and with a corresponding reservoir volume greater than or equal to fifty (50) acre-feet capacity must engage the services of a qualified professional engineer who is currently licensed in Idaho. The design drawings, reports, specifications, and other design information deemed necessary for construction shall bear the engineer’s professional seal and signature, and shall be submitted to IDWR for review and approval. Inspection during construction shall be performed by IDWR for the purpose of securing conformity with the approved plans and specifications. If, at any time during construction, site inspection reveals that the work is not being accomplished in accordance with the approval of IDWR and the approved design, IDWR may order that no further work be done until compliance has been effected and approved.