Riverbank Source Control Measure, Portland Harbor

OUR CHALLENGE

Historical riverbank fill composed of erodible soil containing PCBs sloughed into the river during flood events at an upland industrial facility, affecting the stability of the facility and presenting a pathway for potential recontamination of a future sediment remedy.  The remedial design has to account for habitat improvement, upland property operations, and the structural integrity of a large dock—all along a hard–to–access and steep riverbank profile.   

OUR APPROACH

Integral designed and oversaw construction of a riverbank remedy that included excavation, backfilling, regrading, and habitat restoration.  Work elements included protecting structures, using unique disposal solutions to lower project carbon emissions and costs, identifying acceptable backfill material, and improving the habitat to meet permitting requirements. We minimized greenhouse gas emissions by identifying onsite beneficial reuse options for 8,400 cubic yards of excavated soil within an obsolete industrial building basement and on an existing landfill.  Integral implemented several engineering solutions including floating heavy equipment to the beach in locations where upland-based equipment could not be used, and placing material partially by hand where large equipment use was restricted.  

Habitat improvements included constructing a habitat corridor between beach and upland riparian areas, enhancing an alcove north of the excavation area, and making extensive native plantings. The upper beach was vegetated with more than 3,000 native shrubs and trees over 0.73 acres. Approximately 1.74 acres of riverbank and berm riparian areas were planted with more than 6,000 native trees and shrubs. 

OUR IMPACT

Our riverbank source control measure was completed in 2016—one of the few successfully implemented early action projects on this riverine Superfund site. Since that time, it has prevented bank erosion of historical fill from impacting adjacent sediment.  This measure provides valuable riparian habitat and will protect the future sediment remedy from recontamination.