Maggie and Susie Creeks are tributaries to the Humboldt River and are designated recovery sites of the federally threatened Lahontan cutthroat trout (LCT - Oncorhynchus clarkii henshawi
). LCT are present in the upper reaches of Maggie Creek and its tributaries and were historically present in Susie Creek. Non-native fish in the Humboldt River threaten LCT through predation, competition, and hybridization. In order to protect the remaining LCT population on Maggie Creek and its tributaries and create an area for LCT reintroduction on Susie Creek, Otis Bay assisted the Bureau of Land Management (BLM) with fish barrier designs to prevent upstream passage of non-native fish into LCT recovery areas.
To develop an appropriate fish barrier design, Otis Bay completed hydrologic and hydraulic assessments, excavated soil test pits, and reviewed fish leaping abilities. Using historical data of annual peak flows from USGS gage stations located at Susie and Maggie Creek, Otis Bay modeled flow volumes using the U.S. Army Corps of Engineers’ HEC-RAS computer program to determine depth of water before and after installation of the fish barrier, flow velocities, and extent of backwater effects. Otis Bay analyses included a Log Pearson III distribution of historical peak flows to determine reoccurrence intervals for floods from 2-100 years. On site, soil test pits were sampled to determine if soil conditions were suitable to drive sheet piles, and to determine depth of groundwater, depth to bed rock and soil profile. To assess effectiveness of the fish barrier design, Otis Bay discussed and calculated fish jumping capabilities and presented findings in the final report. Investigations executed in this report resulted in the development of recommendations for construction materials, barrier design plan drawings, construction specifications, and a construction sequence.
A final report and construction specifications were submitted to BLM in August, 2011. An environmental assessment, Finding of No Significant Impact (FONSI), and decision record to authorize construction based on Otis Bay’s designs were passed on November 1, 2011.