Contaminated sediments in harbors, rivers, and coastal waterways are a persistent environmental challenge. When contaminants are bound up in bottom sediments, one of the most effective remediation strategies is subaqueous capping — placing an engineered cap over the contaminated zone to prevent contaminant migration and restore aquatic function. But it isn’t always the right answer. Here’s how to think about when it is.
What Subaqueous Capping Does
A subaqueous cap is placed directly on contaminated sediment while it remains in place on the bottom of the waterbody. Rather than dredging and removing contaminated material — which carries its own risk of resuspension and spread — a cap isolates the contaminants beneath a layer of clean, engineered material. Flint provides subaqueous capping field services, including furnishing and panelizing reactive core mats for in-place capping.
The Reactive Core Mat Advantage
Flint’s approach uses reactive core mats designed around the specific contaminants present in the sediment. By targeting the particular pollutants at a given site, this methodology reduces the required cap thickness needed to safely contain them — meaning less material, less disturbance to the aquatic environment, and a more efficient path to regulatory compliance.
When Subaqueous Capping Is the Right Call
Subaqueous capping is generally most appropriate when contaminated sediments are relatively stable, when capping can effectively isolate the contaminants of concern, and when dredging and removal would create unacceptable risk of resuspension or spread.
