Most reasonable people think of clean water as water that you can touch and splash in without any risk to your health. But under the Clean Water Act of 1972, clean water is defined based on the water's use classification. The Gowanus water is classified at the lowest level, one suited for a body of water that receives excessive sewage flow.
Under the current canal Water Quality Classification (class-SD) the New York City is granted permits--approved under the Clean Water Act, that allow untreated sewage to flow into the canal during rain events. The release of city sewage is allowed as long as a minimum level of dissolved oxygen in maintained the water. There are no limits to the level of pathogens that can be dispersed into the canal from sewage flow.
This explains why, when the city first reopened the old Flushing Tunnel pump in 1998, they declared the canal 'clean" to the dismay of many local residents who continued to watch globs of sewage and Coney Island white fish float down the canal. But under the SD water classification, as long as the city sees to it that the required level of dissolved oxygen exists in the canal water, the city can, and has, made the claim that the canal water is "clean". (Yes, clean water is a relative term.)
The city has embarked on an infrastructure rehabilitation plan that will modernize the Flushing Tunnel located at the head of the canal on Butler street. The Flushing Tunnel opened for operation in 1911 and just celebrated it's 100th birthday. It was designed to connect the stagnate headwaters of the canal to the East River to improve water circulation. After a partial rehab in 1998, the Tunnel was shut down in 2010 and will be getting a new modern pump that is designed to move water from the East River into the head of the canal and flush out the canal contents towards the Gowanus Bay.
With the introduction of more water from the East River, once completed, the rehabilitated Flushing Tunnel is expected to maintain the dissolved oxygen levels in the canal at the required level. This is important, sufficient dissolved oxygen in the canal water is the primary control for reducing the odor of decomposing organic matter (primary sewage).
But without a water quality classification that imposes limits on the levels of pathogens in the canal water, can we really ever claim the water in the canal is clean? The community uses these waters for fishing. The community has been using this canal for light boat recreation for more than ten years. The water standard needs to be brought into line with the actual community use. The State of New York and the EPA need to reclassify the Gowanus to standards that impose institutional controls on pathogen levels. The water needs to be set to a standard that is protective of community health and the environment for all the uses that actually take place here.