This project completed a preliminary design for a 140-foot long, 3-foot diameter culvert under Boston Harbor Road near Olympia in Thurston County. Located on an unnamed tributary to Gull Harbor, this culvert is currently impassable due to the combination of being undersized, slope, tailwater submergence and inlet drop. The South Puget Sound Salmon Enhancement Group managed all aspects of this project in cooperation with the Thurston County Roads Department and the Capitol Land Trust. Boston Harbor Road is the primary access road for all residents and visitors to Boston Harbor in Thurston County, WA. The tributary flowing under the road at this location is connected to a vast complex of upland freshwater wetlands upstream of this site. This culvert and Boston Harbor Road are located in the transition zone between freshwater riparian forest and the tidally influenced northern slough of Gull Harbor Estuary. This project offers passage opportunities not only to migrating South Sound Salmonids but also has the capacity to create a safe corridor for a variety of aquatic and terrestrial species including large mammals. This project is a small, albeit critical component to the Budd to Henderson Conservation Initiative which will create a wildlife corridor connecting Gull Harbor and Woodard Bay by preserving the upland wetland complex and associated watersheds in perpetuity. Once constructed, this project will benefit chum and coho salmon and steelhead trout.