T here are cases of well water contamination by oil and gas drilling where no one is able to determine the cause. For example:

Ellsworth well, Ft. Lupton, Weld County, Colorado Aug. 7, 2009
Ellsworth Water Well Investigation Conclusion
COGCC Complaint Investigation No. 200196553

The method used by the COGCC staff to investigate and address the impact to your water well has been thorough and appropriate. The COGCC staffs conclusion , supported by all the investigation records , is that your water well contains a mixture of both biogenic and thermogenic gas and that the thermogenic gas appears to be from oil and gas activity; however , the COGCC staff has been unable to identify any current activity or existing well as the source of the impact . As previously discussed , all current oil and gas wells within 1/2 , mile of your water well are operating properly and not leaking gas , but this does not negate the possibility of a prior leak that was subsequently remediated. Based on our experience investigating other groundwater impacts , as well as our review of oil and gas well records and water well samples , we do not believe that the gas in your water well is attributable to an oil and gas well located more than 1/2 mile away.

Because no responsible party for the water well impact can be identified , the staff will no t be issuing a notice of violation (NOAV) or pursuing enforcement against any oil and gas operator as a result of the investigation of Complaint No. 200196553. Because Noble voluntarily has constructed a water treatment system to mitigate the gas in your well water and because all oil and gas wells within 1/2 mile of your water well are operating properly , the COGCC staff considers the situation mitigated and COGCC complaint No. 200 196553 closed.

David Neslin, Director, Colorado Oil & Gas Conservation Commission
Written Answers to Follow-Up Questions from the Senate Committee on the Environment and Public Works

Submitted May 17, 2011

COGCC investigated the Ellsworth drinking water well in Weld County Colorado and found that the Ellsworth well has been contaminated by a mixture of biogenic (natural) and thermogenic (from gas drilling operations) contaminants. Although there were a number of gas wells drilled near the Ellsworth drinking water well, COGCC was unable to determine the particular source because the leaking well may have been fixed and the mixture of biogenic and thermogenic sources made it impossible for COGCC to “fingerprint” the source well. One of the companies responsible for the drilling entered into a voluntary agreement with the Ellsworth s for replacement water.

Question. Do you agree that this is a verified case of gas drilling operations causing groundwater contamination, even though the particular well that caused the contamination was never determined?

Answer. As the COGCC reported in 2008, the methane contamination found in the Ellsworth water well included thermogenic methane that appeared to be from oil and gas activity. The COGCC could not, however, attribute this methane to gas drilling operations as opposed to subsequent well production.

Type: WATER WELL Date: 10/16/2009
Complainant: Fred Webb 15948 WCR 38 Platteville CO 80651
Description of Complaint: Sampling by KMG/Anadarko has identified a possible impacted water well due to O&G activity.
COGCC Response: investigation is completed and operator has arranged for the well owner to obtain a city water tap as a replacement for the impacted water well.


Neslin, COGCC Senate testimony Neslin Testimony EnviroPublicWorksQA.pdf


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