Background This project stems from a Type II Environmental Review by the City of Portland in 1999 for removal of the E-zone designation from 2.04 acres of drainageways located within the Columbia South Shore Plan District. These drainages were filled as a result of activities associated with the Cascade Station development. The mitigation sites are located adjacent to a completed Army Corps of Engineers wetland mitigation site and adjacent to the 40-mile Loop Trail by the cul-de-sac of N.E. Alderwood Road at Portland International Center.
This Environmental Review was linked to a second Type II Environmental Review in 1999 for impacts to the Environmental Zone from the construction of a bridge over the Columbia Slough. Mitigation consisted of re-vegetation of the environmental zone transition area along the Columbia Slough where the slough crossed the project site.
Mitigation Plan The areas chosen for mitigation for impacts to the E-zone designation consisted of emergent and scrub-shrub wetland adjacent to small, artificial channels. Riparian and upland scrub shrub vegetation was already established in low densities, but there was extensive invasion of weedy species. The mitigation measures increased the density of plantings and implemented a weed management program to control invasive species.
Mitigation for impacts from the construction of a bridge over the Columbia Slough called for enhancement of the 50' transition zone on the north shore of the slough. This enhancement project was included as part of the Intergovernmental Agreement (IGA) with the Bureau of Environmental Services for Columbia Slough re-vegetation.
Status Planting of the E-zone site was completed in April 2000, and a total of 5,927 plants were installed. The Port met its 5 year permit obligation to monitor the E-zone site by the end of 2005. The final monitoring which occurred during the summer of 2005 resulted in at least 80% plant survival with 100% aerial cover in some areas. The Port continues to manage and maintain the site by controlling invasive species and encouraging native plant establishment.