Gillette-Madison Well Field Project

Investigation Documents

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The DEQ received notification of water quantity and quality issues on August 11, 2017 for two existing and two deeper, replacement private domestic wells located 18 miles northeast of the Town of Moorcroft, Wyoming.  The two existing domestic wells which had previously produced a good quantity of water had gone dry and the two deeper replacement wells had identified low pH (< 4 s.u.) in them. 

A public meeting was held on October 12, 2017 in the Town of Moorcroft to answer questions on the recent water quality/quantity issues.  In addition, a survey was distributed to identify well owners that may have noted potential water quality issues and to solicit access to sample those wells.

The study area is shown on the “Study Area” figure at the link below.  The study area encompasses the majority of private domestic and stock wells and several springs that DEQ identified for sampling. 


DEQ mobilized water sampling crews to the study area on October 25, 2017. A total of 55 locations were sampled and analyzed for the analytes identified in the Gillette Madison Well Field Private Water Well Sampling List (Click here to view).  Of the 55 locations, 32 were domestic wells, 12 were identified as domestic/stock wells, 10 were stock wells and one location was a spring.  All private well owners were provided with their water quality results.

Based on Workgroup #3 meetings in April 2018 and after review of the data from the 2017 private water well sampling, a number of potential data gaps were identified by workgroup members and the consultant. To address these data gaps the DEQ collected additional samples from 13 previously sampled water wells and one spring, collected initial samples from 5 additional water wells in accordance with the October 2017 sampling list, collected 3 surface water samples (2 stream samples and one spring), and measured water levels in conjunction with the State Engineer’s Office on sampled water wells (if accessible). 

The DEQ has released its final report into low pH and low water conditions reported in the vicinity of the City of Gillette's Madison wellfield in Crook County.


The Main Report and Appendices are available below in the Resource Tab.


Questions regarding this report can be directed to Nicole Twing at or 307-777-8275. 


For a list of Fact Sheets regarding Common Contaminants found in groundwater, please click here.

Based on Workgroup #1 meetings, and a review of available well integrity information provided by the City of Gillette, a recommendation was made to have the five new Gillette-Madison water wells, be re-logged for well integrity concerns. The City of Gillette had contracted for Schlumberger to conduct integrity logging of the five water wells, based on suggestions provided by the well-integrity expert hired by Workgroup #1. Reports prepared by the logging expert have been finalized and are available for M11, M12, M13, M14 and M15. 
Questions regarding the well integrity reports can be directed to Lily Barkau at or 307-777-7072.

An advisory group consisting of an Executive Committee and three (3) working groups was established to facilitate and oversee the development of plans and schedules, to implement preferred options that address the overall objective, and to investigate the cause of impacts to private wells in the study area.  The Executive Committee consists of one (1) representative each from DEQ, Water Development Office, State Engineers Office, Oil and Gas Conservation Commission, and the City of Gillette.  The DEQ representative was the chairperson of the executive committee.  In addition, the working group hired an independent consultant to assist with the data review and investigation of the cause of impacts.

The structure of the working groups, members of the Executive Committee and Working Groups and the task for the specified working group can be downloaded here.


Questions regarding the working groups can be directed to Lily Barkau at or 307-777-7072.