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Point and Non-Point pollution

The following is the second in a series of articles about the Pomme de Terre Watershed and the TMDL studies that are now underway studying the pollution problem in the watershed.

When dealing with water impairments, there are two types of water pollution we are dealing with. These are called point pollution and non-point pollution. What is the difference between the two, which is worse, and which pollutes our waters more?

Let's start with point pollution. When most people think of ways our waters get polluted, they usually think of a factory with belching smokestacks and pipes spewing brown liquids directly into an adjacent body of water. The image also usually includes foam and dead fish floating belly up near the effluent pipe. This is an image of classic point source pollution. The EPA defines point source pollution as "discrete conveyances, such as pipes or man-made ditches that discharges pollutants into the waters of the United States." This includes not only discharges from municipal sewage treatment plants and industrial facilities, but also storm drainage from larger urban areas, certain animal feedlots and runoff from many construction sites.

Since the passage of the Clean Water Act of 1972, wastewater treatment plants, industries, and concentrated animal feedlots must have a National Pollutant Discharge Elimination System (NPDES) permit in order to release wastewaters into receiving waters in accordance with the Clean Water Act. Since its introduction in 1972, the NPDES permit system is responsible for significant improvements in our nation's water quality. Because of the NPDES system, we know where the point sources are and how much "stuff" they are putting into the water. Consequently, point sources are relatively easy to monitor and regulate, and can often be controlled by treatment at the source.

Non-point pollution is pollution that, unlike pollution from industrial and sewage treatment plants, comes from many diverse sources. Non-point pollution is caused by rainfall or snowmelt moving over the ground. As the runoff moves, it picks up and carries with it natural and man-made pollutants, finally depositing then into our surface waters like the Pomme de Terre River. Loading of pollutants from non-point sources enter our water via sheet flow of runoff, rather than through a pipe.

Non-point sources include runoff from agricultural fields and pastures, urban runoff from areas with populations of less than 100,000, runoff and leakage from failed septic systems, and construction site runoff to name a few. Field runoff from agricultural fields may contain sediment, fertilizer, pesticides and animal waste. Due to the variety of sources, non-point pollution is difficult to measure and regulate.

With the clean up of point sources because of the Clean Water Act, non-point sources of pollution are now the dominant inputs of pollution to our nation's waters. According to the EPA, sediment from non-point sources is the number one pollutant of our nation's surface waters. In the early days of the Clean Water Act, efforts focused on regulating discharges from traditional point source facilities, with little attention paid to runoff from fields, streets and other "wet-weather" sources. Starting in the late 80s, efforts to address polluted runoff have increased significantly. For non-point runoff, voluntary programs including cost-sharing with landowners are the key tools to remediate the non-point problem.

The next article will focus on the Fecal Coliform problem in the watershed.

Shaun McNally is the Pomme de Terre Watershed Project Coordinator. He is located in the Stevens SWCD office in Morris. 320-589-4886 ext. 109

The Pomme de Terre River Association maintains a website: