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Evaluation of Minimum Well Seal Depth in Idaho


The Idaho Department of Water Resources (IDWR) was asked by the Idaho Ground Water Association (IGWA) to identify and evaluate geographic areas of the State where hydrogeologic conditions might warrant alternatives to the 38-foot minimum well surface seal depth and to eliminate the waiver requirement in those areas. In response to this request, IDWR evaluated three areas where hydrogeologic conditions have a potential to accommodate alternative minimum well surface seals. The objective of the evaluations was to determine if a minimum well surface seal of 38 feet is appropriate for the areas, or if an alternative seal depth is appropriate based on specific hydrogeologic conditions. IDWR used a number of criteria to identify areas where hydrogeologic conditions have potential for alternative sealing depths including input from licensed well drillers, driller reports, published geologic maps and reports, regional IDWR well inspector experience, and areas of known or suspected contamination. Using these criteria, IDWR evaluated hydrogeologic conditions in three specific areas of the state:

  • the northern Long Valley area of Valley County (or the Donnelly Area)
  • the upper Big Wood River Valley of Blaine County
  • the Island Park Area of Fremont County

The resulting report of these evaluations is listed below.


Questions arose in the 2013 Idaho Legislature regarding minimum surface seal depths for wells in Idaho. Director Gary Spackman committed to legislators to evaluate the minimum surface seal depth currently in the Well Construction Standards Rules and review options in the rules to provide for alternative sealing depth requests. The minimum well seal evaluation includes a peer review of the 2008 well log study completed by the Department during the negotiated rule making for revision of the well construction rules, an independent evaluation of well seal depths in Northern Idaho, review of the waiver process concerning waivers of the minimum well construction standards, and identification of areas which may require or provide for alternative sealing depths based on the unique geology of the area.

IDWR contracted with Dr. Dale Ralston, Ph.D., P.E., P.G. to peer review the 2008 IDWR well log study, to conduct an independent evaluation of minimum surface seal depths in Northern Idaho, and to provide an analysis of minimum surface seal depths necessary to protect Idaho’s groundwater.

Dr. Ralston has worked for over 40 years throughout Idaho with groundwater resources and well construction, including 25 years as a professor of hydrogeology at the University of Idaho and approximately 15 years as a private consultant. He has worked with the National Ground Water Association, teaching classes in hydrogeology and proper well construction.

Included on this page are the following documents and presentations:

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