As part of the Quiota Creek Fish Passage Enhancement Plan, we performed site reconnaissance and field data collection to evaluate and classify nine fish passage impediments along South Refugio Road. Fish passability was evaluated at each crossing using HEC-RAS and FishXing.

Based on the resulting data, we prepared a watershed-based fish passage enhancement plan entailing alternative formulation and evaluation using a multivariable weighted selection factor approach; conceptual design of culverts, single span bridges, and fishways; flood frequency analysis; and hydraulic analysis.

We also performed topographic surveys, prepared permit drawings, developed final bid documents, and conducted engineering oversight for Quiota Creek Crossing 6. The existing crossing included a concrete low-flow crossing and temporary bridge spanning the road, which created a 6-foot-high fish passage barrier on the downstream edge of South Refugio Road. Using stream simulation techniques, we designed a new crossing incorporating a 48-foot prefabricated concrete arch, wingwalls, strip footings, and a rock weir roughened channel. During design, HDR designers coordinated with National Oceanic and Atmospheric Administration and California Department of Fish and Wildlife engineers and biologists. The new crossing met County requirements for flood and traffic conveyance while significantly improving fish passage for Southern California Endangered Steelhead.