2012 Projects
Coho Salmon | Steelhead/Rainbow Trout | Trinity County | Trinity River

Conner Creek Fish Passage Improvement Project

In 2012 Conner Creek was selected as one of NFHP’s annual list of 10 Waters to Watch. Read more here

Project Location: Conner Creek is a tributary to the Trinity River below Lewiston Dam. The project is located in T 33N, R 11W, Section 2 MDBM. Take State Highway 299 west out of Weaverville for approximately 8 miles, and turn left at Dutch Creek Road, crossing the Trinity River. Turn right on Red Hill Road and drive west/southwest for approximately 2.2 miles. Turn right on to Conner Creek Road. The Crossing is located approximately 350 feet from the intersection of Conner Creek Road and Red Hill Road. The staging area is located at the intersection.

Project Description: The primary purpose of the Conner Creek Fish Passage Improvement Project was to improve fish passage at two stream crossings that were  barriers to juvenile and adult coho salmon within the federally threatened Southern Oregon Northern California Coast Evolutionarily Significant Unit (SONCC coho salmon ESU), and Forest Service sensitive Klamath Mountains Province steelhead Distinct Population Segment (KMP steelhead DPS). The project intended to restore unimpeded access to upstream spawning and rearing habitat by replacing two Trinity County maintained stream crossings that were complete and partial passage barriers to adults and juveniles during the range of migration flows. The objectives of the Conner Creek Road portion of the project (Crossing #1) were to provide for the full range of fish passage during migration flows and the estimated 100-year flow events, consistent with the NOAA’s National Marine Fisheries Service’s ‘Guidelines or salmonid Passage at Stream Crossings’ (2001). Additional objectives at Crossing #1 included decreasing the potential for upstream headcutting, restoring the natural floodplain function at the crossing, maintaining existing riparian trees that provide stream cover and bank stabilization and having all of the non-construction tasks completed in order to facilitate replacement of the upstream Red Hill Road crossing (Crossing #2; planned for early summer 2012). Replacing the undersized culvert on Red Hill Road with a properly sized structure that permits full migration would also eliminate the potential for approximately 2,190 cubic yards of road fill from delivering to the downstream reaches of Conner Creek and the Trinity River.

Crossing #1 Background, Pre-Project Conditions and Challenges: Prior to removal, the 6-foot tall, 14-foot wide, 18-foot long concrete box culvert set at 2% grade with three offset baffles lining one-half of the culvert bottom blocked access to approximately 2.5 miles of high quality perennial, cold-water refugia for juveniles and good quality spawning habitat for adults, primarily Forest Service sensitive Klamath Mountains Province steelhead. It was a complete barrier to all species and life stages at all migration flows, primarily due to the outlet jump. The offset baffles within the box culvert are also ineffective at improving passage and slowing flows as they are regularly clogged with woody debris, with all of the flow sheeting across the unbaffled section of the culvert.

Replacing the Crossing #1 afforded access to approximately 0.20-mile of this habitat. The planned replacement of the 10-foot diameter, 66-foot long circular steel culvert set at 3% grade with 10 offset, steel ramp baffles at Crossing #2 would complete the project. This crossing is a partial barrier to adult salmonids and resident trout, violating the State Fish and Game Departments’ passage criteria on 55% of migration flows.  It is a complete barrier to all age classes and species of juveniles, primarily due to the outlet leap and flow velocities within the culvert.  The steel ramp baffles most likely improve adult passage, but are ineffective at reducing velocities during migration flows for juvenile passage.

The size, complexity and permitting timelines for the entire project necessitated that it be completed in two consecutive construction seasons; Crossing #1 in 2011 and Crossing #2 in 2012. The successful replacement of both Crossings would improve access to upstream habitat consisting of a dense riparian zone of mixed hardwoods and conifers, numerous pools formed primarily by bedrock and boulders, and cool water temperatures, especially during late summer base flows. It would also allow for improved and safer passage of higher levels of sediment and large woody debris due to the 2008 Eagle Fire that burned within the upper 40 percent of the watershed. Replacing and modifying both crossings would not only improve fish passage conditions and access to habitat, but would also improve flow capacities, thereby reducing the maintenance requirements and emergency response expenditures for the Trinity County Department of Transportation.

Project Actions and Deliverables at Conner Creek Road – Crossing #1:

  • Provide for passage during the full range of migration flows for adult and juvenile salmonids at Conner Creek Road, consistent with the 2001 NOAA’s National Marine Fisheries Service  Stream Crossing Guidelines;

  • Improve the flow capacity at the Crossing to allow for the estimated 100-year flow events (estimated at 1155 cfs) and associated bedload and debris transport;

  • Improve Riparian Reserve function over the long-term by increasing flow capacity, connecting the upstream and downstream floodplains at both Crossings, maintaining existing canopy cover of riparian hardwoods as safely feasible and allowing for improved passage of other aquatic organisms;

  • Improve the Crossing’s capacity to convey expected pulses of LWD and sediment loads from the 2008 Eagle Fire;

  • Eliminate the potential for approximately 250 cubic yards of road prism fill from delivering to Conner Creek;

  • Decrease the potential for upstream headcutting if the crossing should fail;

  • Reconnect the downstream 0.75 mile reach of Conner Creek to the Trinity River, consistent with the Trinity River Total Maximum Daily Load Allocation Plan for Sediment (EPA 2000);

  • Complete the non-construction tasks at Crossing #1 by October 15, 2011 (or the start of the Wet Weather Operations season) in order to facilitate replacement of Crossing #2 at Red Hill Road in early summer 2012.

  • Provide full fish and flood/debris passage at Conner Creek Road consistent with NOAA/NFMS Fish Passage Criteria;

  • Improve stream conveyance in response to the upslope wildfires of 2008;

  • Eliminate the potential for 250 cubic yards of road prism fill from delivering to Conner Creek;

  • Reconnect downstream watersheds areas consistent with the Trinity River Total Maximum Daily Load Allocation Plan for Sediment (EPA, 2000);

  • Decrease the potential for upstream headcutting if the road should fail;

  • Improve the flow capacity at Conner Creek Road at road crossings

  • Reintroduce large wood routing in the stream;

  • Complete non-construction tasks to facilitate Red Hill Road construction in early summer 2012.

Fish benefits/ecological value: The replacement of Crossing #1 at Conner Creek Road site makes available approximately 0.20-mile of quality spawning and rearing habitat to adult and juvenile salmonids, primarily within the KMP steelhead Distinct Population Segment.  The replacement of Crossing #2 would afford access to the total 2.5 miles of similar habitat consisting of a dense riparian zone of mixed hardwood and conifer trees, many undercut banks, numerous pools formed primarily by bedrock and boulders, quality spawning gravels, and cold water temperatures, especially during late summer base flows.
 
Other benefits: Eliminating the potential for approximately 250 cubic yards of road prism fill at Crossing #1 to deliver to the downstream reaches of Conner Creek and the Trinity River in the event of culvert plugging and failure, decreasing the potential for upstream headcutting, improving the crossing’s capacity for safe LWD transport, 100-year flows and bedload, and decreasing overall maintenance and emergency response work for the Trinity County Department of Transportation.

Amount of habitat made available as a result of project implementation: 0.20-mile at Crossing #1, with a total of 2.5 miles considering Crossing #2
 
Habitat quality and type characterization: Habitat in the treated area provides for all life stages of Forest Service sensitive KMP steelhead and potentially for threatened SONCC coho salmon. Coho salmon have not been documented to date at Crossing #1, or the upstream reaches, primarily due to flow and passage conditions at the confluence with the Trinity River and the stream’s natural downstream gradient and step-pools created by large boulders.
 
Project partners: Trinity County Department of Transportation, Five Counties Salmonid Conservation Program, California Coastal Conservancy, National Association of Counties, USDA Forest Service, National Fish and Wildlife Foundation, USDI Fish and Wildlife Service, NOAA’s National Marine Fisheries Service, the California Department of Fish and Wildlife (CDFG’s Fisheries Restoration Grant Program), and USDI Bureau of Reclamation-Trinity River Restoration Program-Watershed Restoration Program
 
Project cost:  $348,600
 
Project start date:  2007 – design, funding, beginning the permitting process
 
Project end date:  2011 – was the completion of Crossing #1
 
Monitoring and Evaluation:

•    Photo Monitoring: A photo-monitoring program to determine the project’s effectiveness was developed and is being continually implemented. Photo documentation of pre-project conditions was performed. Photo monitoring during construction and post-project monitoring activities has also occurred. Refer to the Five Counties Salmonid Conservation Program site for more project-specific information at www.5counties.org
•    Longitudinal Profile/Thalweg Monitoring: The pre-project longitudinal profile and thalweg surveys collected for designing the crossing was completed in 2006 by SHN Consulting and entered into AutoCAD. Four cross-sections were also measured. An immediate post-project longitudinal profile was collected in December 2011 (Record Survey). The first post-winter longitudinal profile will be taken in April or May 2012 with a second and post-third winter survey planned for spring 2013 and 2014. This information will provide insights into the channel adjustment and will be provided as a case study (as requested) for full stream simulation.
•    Biological Monitoring: Spawning and presence/absence surveys will be conducted at the project site. Initial survey data consists of US Forest Service Stream Condition Inventory (SCI) and spawner surveys, a Five Counties Salmonid Conservation Program fisheries habitat assessment  conducted by Ross Taylor and Associates that includes incidental fish observations, and the Trinity County Migration Barrier Inventory data that was collected prior to development of the project. Crossing #1 was assessed as a complete barrier to juvenile and adult salmonids during the Trinity County barrier inventory, and now provides unimpeded passage through the crossing for all age classes.

Did the project make a difference, and if so, how?

  • Stream length treated/assessed/made more accessible: ~0.20-mile of adult spawning and juvenile rearing habitat, primarily for Forest Service sensitive KMP steelhead.

  • Stream crossings treated (number):  1

  • Sediment prevented from entering the stream (volume in cubic yards): 250 cubic yards

  •  Trees planted (number): 10

  • Area planted/preserved/assessed (area in acres): 0.25-acrearea was re-seeded with native grasses and forbs along the  riparian zone and in the staging area

For a copy of the final report, click here.

​