This project removed a 1920s-era concrete diversion weir and ineffective fish ladder on Pennington Creek at the Rancho El Chorro Outdoor School in San Luis Obispo County, replacing approximately 160 linear feet of channel with engineered step pools. A new fish screen was installed at the diversion intake with a minimum bypass flow protective of steelhead critical habitat. The project opened 2.3 miles of perennial upstream habitat to federally threatened South-Central California Coast steelhead, with juveniles observed using the restored channel just six days after construction ended.
Location: Pennington Creek, approximately 0.9 miles upstream/northeast of Highway 1, on the grounds of the Rancho El Chorro Outdoor School, unincorporated San Luis Obispo County, CA. Pennington Creek originates in the coastal Santa Lucia Range, flowing southwest to Chorro Creek, which flows northwest to the Pacific Ocean at Morro Bay.
Historical Fish Presence: South-Central California Coast steelhead (Oncorhynchus mykiss), a federally threatened distinct population segment. Pennington Creek provides spawning and rearing habitat. The Chorro watershed is designated a Core 2 watershed in the NMFS South-Central California Steelhead Recovery Plan.
Project Lead: Trout Unlimited
Project Partners: Althouse and Meade, Inc. (biological/environmental services); Waterways Consulting, Inc. (engineering and design); Pat Molnar General Engineering, Inc. (construction contractor); California Conservation Corps; California Department of Fish and Wildlife (CDFW); NOAA National Marine Fisheries Service (NMFS); U.S. Fish and Wildlife Service (USFWS); San Luis Obispo County Office of Education; Morro Bay National Estuary Program
CFPF Funding: $40,000.00
Project Description: A 1920s-era concrete diversion structure and associated fish ladder on Pennington Creek at the Rancho El Chorro Outdoor School were identified by CDFW as a high-priority passage barrier. The ladder was ineffective at both low and high flows and did not meet passage criteria for all salmonid life stages, preventing steelhead access to 2.3 miles of perennial upstream habitat. The project removed the weir and ladder and reconstructed approximately 160 linear feet of stream channel as a series of engineered step pools at a 5% grade. A CDFW/NMFS-compliant fish screen was installed at the diversion intake, and the diversion system was redesigned to passively maintain a minimum bypass flow of 0.24 cfs protective of steelhead critical habitat. Riparian revegetation included 112 arroyo willow live stakes and container-grown native trees and shrubs.
Expected Completion: Fall 2018.
Project Effectiveness: Post-construction hydraulic monitoring conducted January 17, 2019 (Waterways Consulting, Inc.) confirmed that flow velocities met CDFW/NMFS design criteria for both juvenile and adult steelhead passage (measured maximums of 2.3–3.5 ft/sec vs. a 5 ft/sec design limit). Flow depths met juvenile requirements throughout the reach. Adult depth requirements (1 ft minimum) were met at the boulder weirs and at many points across the reach, though slightly below threshold at some monitored cross-sections; the reach was assessed as visually passable by adults. Juvenile steelhead were observed using the restored channel as early as October 16, 2018 — just six days after construction ended — suggesting rapid recolonization of the reach. Annual monitoring for vegetation survival and structural stability is required through 2021.
