sentences:  The phosphorus load of the Illinois has been subject of controversy in the area, even reaching the United States Supreme Court in 1992.The Environmental Protection Agency (EPA) has classified the Illinois as Section 303(d) of the Clean Water Act, listing it as an "impaired and threatened water" due to the high phosphorus loads.As a result of the applicable strict phosphorus effluent regulations, SSWWTP upgraded its system in 2011.