Public Notice for Comment - Sheridan Existing Landfill and Sheridan Old Landfill

Wyoming Department of Environmental Quality

Public Notice: Sheridan Existing Landfill and Sheridan Old Landfill

The purpose of this notice is to inform the public of activity at the Sheridan Existing Landfill and Sheridan Old Landfill, located respectively east and west of East Ridge Road, southeast of the Interstate 90 crossing of the BNSF Railroad, in parts of Sections 25, 26, and 36, T56N, R84W, in Sheridan County, Wyoming.

In accordance with Wyoming Solid Waste Rules and Regulations Chapter 2 Section 9(b)(i)(E)(VIII), Chapter 2 Section 14(a)(iii), and Chapter 17 Section 5(c)(i), notice is hereby given that the City of Sheridan, with oversight and assistance from the State of Wyoming, Department of Environmental Quality (WDEQ) as part of the WDEQ Landfill Remediation Program, has completed a Nature and Extent Investigation and an Assessment of Corrective Measures and intends to implement remedial measures related to groundwater contamination at the Sheridan Existing Landfill and Sheridan Old Landfill.

Remediation actions are required at these landfills to control contaminated groundwater and the contamination source (i.e., the buried waste) and bring the groundwater back into compliance with groundwater protection standards. At both landfills, waste buried prior to approximately 1991 is partially in contact with groundwater and has neither a modern bottom membrane liner system nor modern cap system to control the flow of water through the waste.

The proposed remedial measure for these issues at the Existing Landfill is to excavate the buried waste in these older areas and rebury it in the new lined landfill cell which is currently being built to modern standards onsite. The proposed remedial measure for these issues at the Old Landfill is to install a set of wells into the buried waste and pump contaminated groundwater out of the waste and into new lined evaporation ponds to be constructed onsite. These are the remediation actions selected as most appropriate for these landfills.

With these remediation actions in place, the existing groundwater contamination is expected to naturally attenuate and return to normal background concentrations and meet standards over time. Groundwater will continue to be monitored to make sure these measures are effective. If they are found to not be effective, further remedial actions will be evaluated and implemented as appropriate.

Multiple reports associated with the contamination at this site are available for public review and comment. They are the Nature and Extent Study, dated February 2019; Final Assessment of Corrective Measures Report, dated January 2020; Supplemental Nature and Extent Study, dated September 2022; and Assessment of Corrective Measures Supplemental Report, dated December 2023. These reports are available to review in person at Sheridan City Hall, Utilities Department, 55 Grinnell Plaza, Sheridan, WY 82801; and at WDEQ Casper Field Office, 444 West Collins Drive, Suite 1400, Casper, WY 82601. These reports are also available to review online at (Click on the Project Reports link. Be aware files are quite large and may take time to open or download.)

Any interested person has the right to provide comments on these reports and the selected remediation actions. All comments will be considered by the City and WDEQ. The period for providing comments, shall begin on January 15, 2024, and end on March 15, 2024. Comments must be submitted in writing to the Department of Environmental Quality, Solid and Hazardous Waste Division, Suzanne Engels, Administrator, 200 West 17th Street, Cheyenne, WY 82002, or submitted using the DEQ comment portal provided at All written comments must include the name and full mailing address of the person providing the comment and the interest the individual has in the project. If substantial negative comments are filed, a public meeting or hearing will be held by WDEQ at the discretion of the Administrator.

In accordance with the Americans with Disabilities Act, special assistance or alternative formats will be made available upon request for individuals with disabilities.

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