David Gorman served as the design engineer for streambank stabilization on a project team for the City of Portland to provide protection for critical infrastructure associated with the Tryon Creek Wastewater Treatment Plant. Just upstream of the treatment plant headworks is an above ground 30-inch diameter concrete sewer pipe situated at the top of a 30-foot high bank of Tryon Creek with a slope of 1.5H:1.0V. Recent high flow events on Tryon Creek had scoured the toe of the slope and threatened to undermine the sewer. Mr. Gorman conducted hydraulic and geomorphic analysis of the stream reach and designed a slope toe reinforcement using natural materials and native vegetation for approximately 80 linear feet of bank. He successfully negotiated the Oregon Removal-Fill permit conditions with Oregon Department of State Lands, US Army Corps of Engineers, Oregon Department of Fish and Wildlife, and NOAA Fisheries for the use of rock below the ordinary high water line and designed instream mitigation for the rock. He designed habitat mitigation that included the addition of large wood to Tryon Creek to provide aquatic habitat diversity and cover for native fish and a low flow channel to provide fish passage in late summer within this urbanized stream. Mr. Gorman provided construction oversight in 2014 for the client to assure that the project was installed according to the plans and specifications and to provide field adjustments to the design to accommodate unanticipated site conditions and to optimize the use of imported natural materials.
Tryon Creek Sanitary Sewer Trunk Upgrade Stream Bank Stabilization – Lake Oswego, Oregon
