Mannion Sinkhole Mitigation Project


SCH Number
Public Agency
Regional Water Quality Control Board, Region 1 (North Coast), Santa Rosa
Document Title
Mannion Sinkhole Mitigation Project
Document Type
NOE - Notice of Exemption

Document Description
The primary purpose of the Project is to mitigate property damage due to the failing culvert installed under the foundation of the residence and is creating a sinkhole endangering the structure. The Project would include rerouting the existing culverted seasonal stream around the residence to discharge to the bank of the Russian River approximately 70 linear feet north east of the existing outfall. The proposed Project includes installing rock rip rap to divert existing seasonal flow into an open channel constructed to be approximately 3 feet wide and 60 linear feet long, then into a 90-foot long 24-inch diameter smooth, double walled HDPE (High Density Polyethylene) culert, then to an outfall constructed of rock riprap and willow planted bioengineered structuure. The final stage of the project will be to permanently decommission the existing culvert that leads to the sinkhole.

Contact Information
Gil Falcone
Regional Water Quality Control Board, Region 1 (North Coast), Sa
Lead/Public Agency
5550 Skylane Boulevard, Suite A
Santa Rosa, CA 95403

Phone : (707) 576-2830


Other Location Info
Duncan Mills

Notice of Exemption

Exempt Status
Categorical Exemption
Type, Section or Code
Reasons for Exemption
The project involves replacement of the existing drainage facility that will have the same purpose and capacity at the same site.

Disclaimer: The document was originally posted before CEQAnet had the capability to host attachments for the public. To obtain the original attachments for this document, please contact the lead agency at the contact information listed above. You may also contact the OPR via email at or via phone at (916) 445-0613.

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