The Charles River
The Charles River flows 80 miles from Hopkinton, Mass. to Boston Harbor. The Charles River is the most prominent urban river in New England. It is a major source of recreation and a readily-available connection to the natural world for residents of the Boston metropolitan area. The entire Charles River drains rain and melted snow from a watershed area of 310 square miles. Two hundred and sixty-eight square miles of that watershed area drain over the Watertown Dam into the Lower Charles River. The remaining 42 square miles drain directly into the Lower Charles River.
Throughout most of the 20th century, the Charles River in Boston was known for its contaminated water. The reputation of the Charles River was popularized out of state by the song Dirty Water by the Standells, which peaked at #11 on the Billboard singles chart on June 11, 1965. (The song has a chorus containing the lines "Well I love that dirty water / Boston you're my home.") The Charles River Watershed Association (CRWA) was also founded in 1965.
Starting in the late 80s, efforts were made to start cleaning up the Charles River. In 1988, as the result of a lawsuit from the Conservation Law Foundation (CLF), the Massachusetts Water Resources Authority (MWRA) created a combined sewer overflow system to address sewage in the Charles River. (See the image below to see the impact of the results of the lawsuit.) In 1995, the CRWA, EPA, municipalities, and Massachusetts state agencies launched the Clean Charles Initiative, which included a report card for the Charles River that is issued by EPA scientists annually. The first grade the Charles River received was a D for the year 1995. The Charles River's grade peaked at A- in 2013 and 2018. The EPA relies on sample data collected by the CRWA to construct its report card.
On the federal level, laws and regulations related to the cleanliness of water bodies are administered by the EPA. The first act that gave this authority to the EPA was the Clean Water Act (CWA), which was passed into law in 1972 (this is not to be confused with the Safe Drinking Water Act, which was enacted in 1974). The CWA did various things, including making it illegal to discharge pollutants into navigable waters without a permit, allowing the EPA to set wastewater standards for industry, and allowing the EPA to set national water quality criteria recommendations for polluntants in surface waters.