Urban Sediment Remediation: Six Insights for Superfund Success

Technology boosts productivity, but only with the right strategy

The tools available today for sediment removal are remarkable. CAT Command is an automated, GPS-linked excavator that can be remotely piloted to handle extremely hazardous materials, work in hard-to-access areas and minimize worker risks. We've also used video calling to connect with an engineer 700 miles away to fix a leaking clamshell bucket in real time. Fixes are faster, remote help is always at hand and visual run-throughs with clients are easier.

Technology also strengthens stakeholder engagement. Social platforms help share tailored messages quickly and widely with specific audiences, but the flip side is heightened scrutiny: everything can be recorded and shared instantly.

Teams can now design and sequence work faster in 3D, 4D and even 5D (including time and schedule). Still, boots on the ground are needed to detect hidden objects in mud or salt marshes, such as old retaining walls or crossings, and to judge whether trees must be removed for access. Artificial intelligence (AI) has not solved that yet, but the potential is growing.

Relying on 'rightsizing' tactics and innovative treatments for constrained urban sites

Urban sediment remediation sites often lack space and access. On a river site in New York City, the working area for equipment and storage was limited, and roads were narrow and filled with traffic. Teams found new ways to store equipment and process sediment on floating barges and tailored plans so only what was needed was on site in the short term.

Another effective approach is working with contractors who have previously worked on the site or in similarly tight spaces. They know how to work safely and efficiently in small, complex environments and can spot blind spots based on prior experience.

Our teams also rely on innovative techniques in these small spaces with limited access. Two examples: in situ bioremediation (ISB) and subaqueous, in situ stabilization (ISS). Both can be applied in sediment in a more 'surgical' and precise way as they require less equipment, access and material than traditional sediment removal.

ISB helps by using additives or bacteria to treat contaminants where they are with minimal disturbance and ISS solidifies sediment by encapsulating the containments instead of removing it. We've recently proven how effective ISB and ISS can be on a Superfund site in New York City, as it heavily reduced time, cost and carbon footprint.

While it does depend on the contaminant and its concentration, ISB and ISS offer major benefits for Superfund sites, especially in tight urban spaces with limited access. At many sites, the last 10% of contaminants are the hardest to remediate because of their chemistry or location, and both tactics can help overcome these challenges.

One of the tools in providing this value is finding way ways to re-use sediment, depending on the contamination levels and properties. Most Superfund sediment material is too contaminated to reuse, however, there is a range of reuse opportunities we've found for less contaminated material. It can be mixed with reagents, such as concrete, to create low-strength construction materials or cosmetic fixtures. Stabilized sediment has been used for landfill daily cover and to work as subgrade material for recreational areas. Clean spoils can be used for filling in community parks and recreation projects. Teams have also cleaned and tested river stones and rocks to create armor stone for erosion control or to rebuild riverbanks. All of these can be used to create new public spaces or community assets.