Pollution

There are many sources of pollution in the river. The most infamous may be the discharge of PCBs that was legally permitted for decades. The discharge was stopped in 1977 and today - 32 years down the road - the concentration in fish is still high enough to make it unsafe to eat fish from the river north of Troy. Other industrial pollution includes organic wastes from tanneries and paper mills and mercury deposition from precipitation contaminated by smokestack discharges from coal fired electric generators and cement plants. Industry is not the only contributor - fertilizers, pesticides, and animal waste often are washed into the river from farm fields and lawns. Storms also create runoff, containing automotive fluids (oil, gas, antifreeze etc.) and trash from paved surfaces that get into the river through multiple paths. In some cases they run directly into the river. In other cases, where combined storm and sanitary sewers discharge into common treatment plants, storm surges can overwhelm the capacity of the plant causing untreated waste to be washed into the river through overflow discharge pipes. A graph in The State of the Hudson 2009, a report published by the New York State Department of Environmental Conservation, shows four occasions in September and October of 2007 where, following a rain, Fecal Coliform bacteria levels rose in the river from 2 to six times the level considered safe for swimming. Another graph shows that from 1985 to 2005 the average concentration of Fecal Coliform dropped from around 2500 to a few hundred per 100mL of water. This improvement is due in large part to the billions spent building sewage treatment plants in the late 1960s and 1970s. However the sharp rise after a rain is evidence of the overflow problem described above. The DEC report also says that:

In undisturbed watersheds, rain soaks into soil and is stored as groundwater that seeps slowly and steadily into streams. In the Hudson’s watershed, new buildings, highways and parking lots cover land surfaces that prevent water from entering the ground. Instead, it runs into streams as stormwater from downspouts, ditches and catch basins, carrying trash, oil, pet wastes, road salt and other pollutants with it.

Stormwater’s sheer volume can erode banks and sweep away aquatic animals or smother them with mud. These creatures are further stressed as stream flows diminish from flood to trickle. And when rain runs off instead of soaking into soil, there is less groundwater to recharge streams in dry weather. These impacts become apparent when impervious surfaces cover about 10 percent of a watershed.