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Centennial Creek-CalTrans Mitigation

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Project Description

Construction of the State Route 46 Corridor Improvement Project has impacted wetlands and other waters in the Union, Whitley 2A, Whitley 2B, and future Cholame section. Onsite mitigation is maximized within the Caltrans right-of-way; however, additional acreage is required by jurisdictional agencies but cannot be accommodated onsite. The remaining acreage of offsite mitigation requirements for the Union segment consists of approximately 0.474 acre of wetlands creation and enhancement, while the Whitley 2A and Whitley 2B segments and Cholame section require approximately 3.292 acres of other waters creation, enhancement, and re-establishment.

The Centennial Creek Mitigation Project intends to improve hydrology and function of the creek by removing and/or replacing undersized culverts, removing hardscaping and debris, and engineering roughened riffles (shallow portions of the creek with large rocks placed to form natural habitat) at intervals along the system to encourage aggradation and reestablishment of a riffle/pool system.  The total area proposed for mitigation is approximately 4.14 acres, which includes 0.53 acres of wetlands creation and enhancement, as well as 3.61 acres of other waters creation, enhancement, and reestablishment.  The improvements to the infrastructure will be followed by over two acres of planting a variety of native species to create vegetation structure and increase plant diversity and habitat quality.  A plant establishment period will be for 3 years, followed by a monitoring period of 7 years, for a total of 10 years after planting to successfully meet agency success criteria. 

Caltrans established a partnership with the City of Paso Robles and the Upper Salinas-Las Tablas Resource Conservation District in 2017 to identify potential project sites to meet its mitigation requirements.  Project design, implementation, maintenance, and monitoring will be the responsibility of the Upper Salinas-Las Tablas Resource Conservation District through funding provided from Caltrans. The property will remain under the ownership of the City of Paso Robles as designated Open Space, with the mitigation site protected by a conservation easement.

Environmental Review 

Caltrans has prepared an Initial Study with Proposed Negative Declaration to determine the potential environmental impacts of implementing the mitigation at Centennial Creek. 

  • The Initial Study with Proposed Negative Declaration has a public circulation period of 30 days.
  • Please submit comments by the public circulation end date of September 17, 2021.
  • Submit comments by voicemail, postal mail, or email to:

                 Jason Wilkinson, Senior Environmental Planner

                 50 Higuera Street
                 San Luis Obispo, CA 93401
                 Phone: (805) 540-9165
                 Email: jason.wilkinson@dot.ca.gov

Find out more information here:

https://dot.ca.gov/caltrans-near-me/district-5/district-5-current-projects/centennial-creek

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