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Land Subsidence, Salt Dissolution

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This bulletin, number 214 of the Kansas Geological Survey, is unusual in that it makes public in permanent form a report by a consulting geologist prepared for an industrial client based on prior original research work by the author for a federal agency. The industrial client, the Solution Mining Research Institute (SMRI), is described more fully [. . .] in the original "Foreword" by its editor, Thomas B. Piper. The federal agency involved is the former Atomic Energy Commission (AEC), now succeeded by the Department of Energy (DOE). These organizations have generously cooperated by releasing this material for publication.

The author, Dr. Robert F. Walters, has actively engaged in prospecting for oil and gas within the State of Kansas, through his own company, Walters Drilling Co., Wichita, Kansas for more than 25 years. He is a graduate of the University of Rochester, New York, B.Sc. cum laude and M.Sc. in Geology, and of The Johns Hopkins University, Baltimore, Maryland, Ph.D. His long and distinguished career in the geology of Kansas began with his Ph.D. dissertation, "Buried Pre-Cambrian Hills in Northeastern Barton County, Central Kansas," which appeared as an award-winning article in the Bulletin of the American Association of Petroleum Geologists in 1946. Dr. Walters is also past president and an honorary member of the Kansas Geological Society, a Fellow of the Geological Society of America, and holds membership in the American Geophysical Union (AGU) and the Society of Economic Geologists (SEG). He gave greatly of his time and energy while serving on the Advisory Council of the Kansas Geological Survey for 10 years from 1963 to 1973, including five years as chairman. The quality and thoroughness of his work are evident in this report.

On behalf of the Kansas Geological Survey, thanks are extended to SMRI and DOE for permission to publish the material in this bulletin in essentially its original form, as it was submitted to SMRI in June 1976. In addition, SMRI has kindly released data from its 1977 drilling program at the Cargill sinkhole which is included as Appendix D of this bulletin. Readers interested in the subsurface conditions beneath the sinkhole pictured on the cover will find that Figure 39, incorporates information from early brine wells with information from two later research drilling programs to give a comprehensive interpretation of the subsurface anatomy of a spectacular surface sinkhole.

William J. Ebanks, Jr.
Subsurface Geology Section
Kansas Geological Survey
University of Kansas
Lawrence, Kansas 66044

Foreword, 1976

(Solution Mining Research Institute)

Pictured on the cover of this report is a surface crater which formed near the Hutchinson, Kansas plant of the Cargill Salt Company in November 1974. Craters of this type are recognized to be the end result of a long-term sequence of activities related to production of salt under methods largely replaced by modern techniques--the crater, or sinkhole as these occurrences are known, is the last of a chain of events starting with salt extraction and requiring a special set of conditions to culminate in a surface collapse. Because these happenings present risk to safety and security of surface installations, interrupt operations of the plant involved, and in that their occurrence is not planned, they are evidence that salt well operators arc not in full control of their extractive technology. This report is directed to an investigation into the causes which contributed to the Hutchinson 1974 crater with the long-term Objective of developing salt production technology which will preclude their occurrence. Included also are descriptions of other examples of subsidence in Kansas having similar origin related to oil well operations--since they are also the result of salt dissolution, their occurrence and a proposed explanation for their cause will also be discussed.

This investigation was sponsored by the Solution Mining Research Institute, Inc. The Solution Mining Research Institute is a technical association of companies engaged in production of salt by the solution mining method. Sinkholes and subsidence related to extraction of salt by dissolution are a topic of considerable concern to the Institute because of the adverse reactions these events create at the time they happen--a response common to all geological events of this magnitude. The Institute has as one of its objectives the study of various aspects of salt extraction--this report is part of the Institute's continuing effort directed to further expanding our knowledge in this sensitive area.

The Hutchinson 1974 portion of this report was originally prepared by Ralph E. O'Connor for the State of Kansas Department of Health and Environment; in its present form the subject has been expanded upon by Dr. Walters to include material based on his experience with salt in Kansas. Cooperation of the Cargill Salt Company in releasing information in this report and in permitting subsequent investigation into the sinkhole mechanism at the Hutchinson site is noted with appreciation as is the cooperation of Mr. O'Connor and the State of Kansas Department of Health and Environment in allowing use of much of the material in their publication.

The Institute is fortunate in having the services of Dr. Walters, who is an authority on oil and gas operations in Kansas, and also has extensive experience with Kansas salt probably because of its close association with petroleum but also because of his personal interest.

Thomas B. Piper
Chairman (1976) Technical Committees
Solution Mining Research Institute


The surface crater, or sinkhole, pictured on the front cover formed in a few hours, during which the surface slowly subsided, leaving the railroad tracks suspended in midair. Subsidences of this type are not without warning, and investigation indicates that they are only the end result of a special sequence related to removal of subsurface support--in this case, rock salt, by dissolving methods employing brine wells. Other evidence of subsidence resulting from dissolution of rock salt caused by man's activities are available for study. In all, thirteen examples known to the author are discussed, five of which are related to solution mining of salt, and eight of which are related to oil and gas operations.

This report begins with a summary of the regional geology of salt deposits in Kansas. Such information is not concisely available elsewhere. headers interested only in subsidence features due to salt dissolution may wish to proceed directly to Part II.

It is the author's conclusion that these rare and unusual instances of surface settlement related to salt extraction have a common history of slow surface downwarping involving an area of several acres and a time frame of many months or years, but in cases where surface materials are water-saturated sands and gravels, and the underlying bedrock layers are breached, a surface sinkhole forms in a few hours or days.

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Kansas Geological Survey, Geology
Placed on web July 24, 2009; originally published February 1978.
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