Public Notice: Clean Water Act Certification for the Mammoth Wastewater Collection System Rehabilitation Project in Yellowstone National Park

The proposed project is to rehabilitate and replace existing components of the Mammoth Wastewater Collection System to reduce the amount of naturally occurring arsenic within the collection system. The project includes replacing and rehabilitating gravity sewer mains and manholes through pipe bursting, cured-in-place pipe (CIPP) lining, open cut excavation, gravity sewer main point repairs, and manhole replacement and rehabilitation. Manhole rehabilitation includes, but is not limited to, epoxy coating application, concrete bench repairs, installation of inside drop connection and replacement of manhole steps.

Work completed below the ordinary highwater mark includes:

• Installation of CIPP lining in gravity sewer pipe for the full pipe segment from manhole to manhole, resulting in approximately 91 square feet of temporary disturbance from contractor access to the site. No excavation is required.
• Replacement of one existing manhole with a new precast concrete sewer manhole, resulting in approximately 141 square feet of temporary excavation and approximately 140 square feet of temporary disturbance from contractor access to the site.
• Installation of CIPP lining in one gravity sewer pipe section for the full pipe segment from manhole to manhole and rehabilitation of one manhole, resulting in approximately 770 square feet of temporary disturbance from contractor access to the site. No excavation is required.
• Open cut excavation to repair two 10 linear foot segments of a gravity sewer main and replacement of one manhole, resulting in approximately 589 square feet of temporary excavation and approximately 938 square feet of temporary disturbance from contractor access to the site.

Upland work completed for the project includes replacing gravity sewer piping through pipe bursting (includes excavation for access pits) and open cut excavation, installation of CIPP lining in gravity sewer piping, replacing existing sewer manholes with new precast concrete sewer manholes, and manhole rehabilitation.

Impacts to aquatic resources from the project will be temporary due to excavation to access the collection system and from contractor access to the site to perform repairs.

Public Comments

Submit comments as described in the “How to Comment” box at the righthand side of this webpage. The EPA must receive comments by 11:59 pm MST on January 17, 2025.

All comments received prior to the end of the comment period will be considered in the preparation of the Clean Water Action Section 401 Water Quality Certification and will be part of the administrative record. Contact Estella Moore ([email protected]; 303-312-6329) to request additional information, public notice updates, submit comments or provide additional information relevant to this certification.

Notice of any extension of the comment period will be published on this page and sent to those who have requested updates.

At this time there is no opportunity to review the submitted material and documents in person at an EPA office. These documents are only available electronically and can be provided upon request.

Public Hearings

Any person may request, in writing within the comment period specified in this notice, that a public hearing be held to consider this application. If the Administrator, in his or her discretion, determines that a public hearing is appropriate or necessary, the EPA will schedule a public hearing. You may request a public hearing using the information in the “How to Comment” box on the righthand side of this webpage.