Novel shoreline cap for controlling sheen and dissolved‐phase constituent discharge

Abstract

A novel, multilayered shoreline cap was designed and installed to mitigate the release of petroleum light nonaqueous phase liquid (LNAPL) and dissolved‐phase groundwater constituents to the Willamette River in Portland, OR. Releases of LNAPL related to upland impacts caused occasional sheens on a portion of the river within the Portland Harbor Superfund Site. The frequency and volume of sheens decreased following the installation of an upland sheet pile barrier wall, but occasional sheens related to LNAPL impacts stranded downgradient of the wall continued–prompting the design of a shoreline remedy. Because the site is located within the Portland Harbor Superfund Site, the cap was designed to mitigate sheen and to meet the objectives specified in the Portland Harbor Record of Decision including limiting the discharge of certain dissolved‐phase constituents of interest. The cap design was the first instance of combining an oleophilic bio‐barrier to mitigate sheen and an activated carbon layer to capture dissolved‐phase constituents. No sheens have been visually observed since cap installation.

Editor's perspective—Highlights of recent remediation technology innovations published in Remediation

“…Reactive caps are often implemented at contaminated sediment sites to prevent mobile contaminants in sediments from being released into the overlying water body. Researchers at Colorado State University in Fort Collins, Colorado developed an innovative oleophilic biobarrier (OBB) for intercepting and absorbing, and then treating petroleum‐based light nonaqueous phase liquids (LNAPLs) in groundwater discharging into surface water bodies (Gentry et al, 2020). Oleophilic materials have a stronger affinity for oil than water and will tend to retain LNAPLs.…”