As promised when they declared the Gowanus Canal a Superfund site, the Environmental Protection Agency is keeping the community informed every step of the way about the agency's work on the heavily polluted waterway.
Earlier this year, and after many months of testing and field work, Christos Tsiamis, Chief Engineer of the EPA's Gowanus Canal Superfund, came in front of the Community Advisory Committee (CAG) to present the Risk Assessment study he had prepared . Last night, at the CAG's general meeting, he presented the Feasibility Study, that is currently in progress and will be issued at the end of the year. Previous to last night's presentation, Tsiamis had engaged and shared the information with some of the other players involved in the clean-up: The NYS Department of Environmental Conservancy, The NYC Department Of Environmental Protection, The Army Corps of Engineers, National Grid, as well as architects from DLandStudio, a firm that was awarded a grant to design a sponge park on the banks of the Gowanus.
Based on the findings of the Risk Assessment, the EPA evaluated different approaches that will enable the agency to eliminate or reduce health risks to humans and wildlife. Tsiamis re-iterated once again that any action taken by the EPA is determined by the CERCLA Superfund Laws and that there are certain criteria that need to be followed. "When we find contaminants, the Superfund Law tells us we need to clean and threat them. That's what we do."
Last night's presentation focused on the best and safest methods that can be employed in this very complex case.
If treatment of the toxic material is not possible at the site itself, the agency can creates conditions that keep contaminants in place and removes the risk of contact with the pathogens. If containment of contaminants is nor feasible, they are removed and disposed of in licensed facilities.
The simplest clean-up available would be to treat the material biologically in place by introducing bacteria. However, in regards to the Gowanus, that hardly will be enough. "Experience tells me that it will not be possible to use bio-remediation in this case because more complex chemicals and metals can not be broken down with bacteria" Tsiamis explained.
The second solution could be to remove the matter and to treat it thermally by heating up the soil contaminants and thereby rendering them non-toxic. Another solution is a physical treatment that would encapsule the toxic material in a solid or rendering it into a non-toxic block.
Capping the material in place is also being considered. A layer of sand could provide a barrier between the material and the water above it. However, in the case of the Gowanus, sand could be displaced by the turbulence caused by the flushing tunnel.
The material could also be capped using a layer of cement to immobilize contaminants, especially metals. New "augmented" caps are now available that are made of less than six inches of clay material that not only creates a barrier, but can also absorb chemicals.
One problem in relation to the Gowanus is that the soft Non-Aqueous Phase Liquids (NAPL) contaminated sludge at the bottom of the Gowanus is too soft and lacks the structural integrity to support such a cap.
According to Tsiamis, "the wisest thing to do is to remove the toxic material and to cap the remaining native sediment with a different buffer." He spoke of adding an' armored cap' with an additional layer of pebbles on top of the native sediment.
It is clear that there will be various approaches and treatments used in different portions of the canal according to their characteristics. It is Tsiamis' intention to take advantage of the newest technology as it becomes available.
Whatever method is used, the EPA is going to make sure that what the canal doesn't get re-contaminated from New York City's Combined Sewer Overflow (CSO's), storm water run-off, and most importantly, free moving toxic product from about 10 to 12 sites along the canal, including Public Place and the Lowe's site.
Christos Tsiamis is committed to continue to engage the other agencies. "This is a golden opportunity to get this right" he told the CAG. "We need the expertise of everyone' and that he 'wants to make sure we are looking at everything." He added: "If we succeed, this will be a crown on everyone's head."
No doubt, this is a historic opportunity to get it right.