EPA Region 2’s Joel Singerman sent the following note to the Gowanus Canal Community Advisory Group today regarding efforts to address low dissolved oxygen levels in the canal while the flushing tunnel is not operating.
“In an effort to alleviate the low dissolved oxygen (DO) levels in the upper portion of the canal during CSO events while the flushing tunnel is offline, on August 16, 2023, the PRP Group reactivated an air curtain at the 3rd Street bridge. The air curtain is a bubbler that is located on the sediment bed and releases air to serve as a turbidity curtain that vessels can pass over. The sparged air will likely boost DO levels. The air curtain may also discourage the menhaden from swimming into the low DO level areas of the upper canal, and, thus, reduce the likelihood of another fish kill. The air curtain had been switched off for several months, as it was not needed during the capping operations. The PRP Group will operate the air curtain during working hours and monitor the effect on the DO levels. If the air curtain has a positive effect on DO levels, they will operate it during periods of suppressed DO levels in the canal. Because it has not been determined if operating the air curtain at the 3rd Street bridge will have sufficient impact, the DO levels will need to be monitored to decide whether to maintain the air curtain at the 3rd Street bridge, move it, or obtain an additional air sparge setup, which could be as simple as using perforated pipes connected to air compressors.”