St. Francis Church Revetment Environmental Support

In fall 2023, Caltrans identified the potential failure of State Route 1 (SR-1) at postmile (PM) 47.8 when a large-scale log jam accumulated on the Big Sur River as a result of atmospheric rivers. The increased volumes and flow rates in the river dislodged trees, created a log jam, remodeled gravel bars, realigned the thalweg, and scoured the southbound shoulder of SR-1 at PM 47.8. The log jam ultimately redirected flows toward a block retaining wall and timber crib wall supporting the SR-1 embankment, causing further erosion and scour. In late December 2023 and early January 2024, heavy storms undermined the block and timber crib walls, causing portions of the block wall to fall into the Big Sur River. The project involved construction of a new bioengineered revetment along SR-1 and the Big Sur River.

As a subconsultant to Graniterock, SWCA prepared technical reports, including a Natural Environment Study (Minimal Impacts) (NES-MI), an Aquatic Resources Delineation, and USFWS and NOAA Fisheries Biological Assessments. SWCA also supported Caltrans by providing agency coordination and permit acquisition including USACE Section 404; RWQCB Section 401 Water Quality Certification; and CDFW Section 1600 LSAA. During construction, SWCA conducted preconstruction surveys and full-time biological monitoring for steelhead, WPT, FYLF, and CRLF; rescued and relocated fish; installed and managed block nets to maintain a fish-free work area; and prepared postconstruction compliance reports for regulatory agencies. Lastly, SWCA prepared a Compensatory Mitigation Plan, designed the restoration planting plan, and provided monitoring during restoration planting following the completion of construction.