Fish Passage Effectiveness at Road Crossing Culverts in the Puget Sound Region, Washington

Fish passage barriers at road–stream crossings are widely recognized as salmon (Oncorhynchus spp.) habitat restoration priorities in Washington State and throughout the Pacific Northwest of the USA. More than 3,500 fish passage barriers (mostly culverts) have been repaired in Washington streams since 1999, costing more than US$139 million. We evaluated fish passage at 77 randomly selected culverts (new and repaired) that were issued permits during three time periods (1998, 2003, and 2007). This sample represents approximately 85% of the fish passage culverts permitted in the Puget Sound region of Washington State during the last 10 years. All study culverts were permitted for fish passage under the Washington Department of Fish and Wildlife’s (WDFW) hydraulic project approval (HPA) permitting process and evaluated using physical criteria in the WDFW’s fish passage barrier standard. Our results indicate that 30% of culverts (23 of 77) permitted under the HPA process for fish passage were, in fact, barriers. Culverts permitted as no-slope (one of the most common design types) or as an unknown design type were barriers in 45% of cases. Most culvert failures were due to noncompliance with permit provisions, particularly culvert slope, and a lack of critical evaluation of proposed plans in the context of site conditions by permitting biologists. We found no relationship between barrier status and permit date, experience of permitting biologists, quality of permit, or project sponsor type (private, public, or restoration entity). These results indicate the need for mechanisms to ensure better compliance from project sponsors and an improved process to critically evaluate the adequacy of proposed plans in the context of project site conditions.