February 9, 2022
Wetland restoration

For the last 70 years, US Ecology remains committed to our mission of protecting human health and the environment. Wetlands have a special place in our hearts as they are highly productive and biologically diverse systems that enhance water quality, control erosion, maintain stream flows, sequester carbon and provide a home to at least one third of all threatened and endangered species.

That’s why we were excited to support one of our customers in the aerospace industry on a project to remediate a wetland on their property in Westminster, MA. Previous site investigations indicated that upland and riverbank soils, as well as groundwater, were impacted by cadmium at concentrations exceeding regulatory levels. Erosion of soil and discharge of impacted groundwater into the Whitman River resulted in cadmium concentrations in the wetland hydric soil, river sediments and riverbank soil to greater than site-specific, risk-based clean-up goals.

US Ecology determined that the installation of temporary and intermediate erosion and sediment control were imminent and began operations by developing a plan that incorporated best management practices. Our team of professionals constructed a minimally invasive series of access travel paths through mature upper woodlands that lead to the remote work area.

During the installation of a cofferdam that was meant to divert water flow to provide a safe and efficient work environment for our crew, we discovered that the riverbed profile required a different type of barrier. A thin veneer of sediment underlain by cobble resulted in significant water seepage and bypass. We decided to install an intermediate barrier wall using polyethylene-coated, one cubic yard “super sack” bags filled with certified clean aggregate to retard the cofferdam bypass. The barrier wall also served as a sedimentation barrier and turbidity curtain, retaining excavation materials and discharge from the heavy flow of the embankment seep. Later, the certified clean aggregate within the super sacks was reused as clean backfill after the cofferdam was removed. Within the cofferdam we worked on dewatering, treatment and discharge. Approximately 450 tons of RCRA-characterized soil was then excavated, treated withTerraBond® SC and transported to a third-party facility for disposal. Additionally, our crew excavated and removed 100 tons of non- RCRA contaminated soil that was conditioned with a drying agent to prepare it for disposal.

A primary objective of the project was to restore the wetland in its configuration and elevation. To achieve that, we replaced the contaminated sediments with clean materials and revegetated the area with native plant species consistent with the existing conditions. To replicate the gradation of the riverbed cobble, US Ecology sourced harvested river rocks of multiple sizes creating a custom blend to better imitate the natural composition of the riverbed. Stabilization served a dual purpose to restore the areas that were disturbed during the remediation and to protect the restored wetland area from river erosion during the grow-in phase.

Wetland restoration before and after

In conformance with the Massachusetts Contingency Plan (MCP), Westminster Conservation Commission and U.S. Army Corps of Engineers/Massachusetts General Permit 17, the final remedy implemented by US Ecology resulted in restored resource areas and a wetland that will once again contribute to ecosystem productivity.