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CRWA Baseline Water Quality Monitoring


Volunteer Monthly Water Quality Monitoring Project

How to Interpret CRWA Data

On a monthly basis, CRWA collects water samples from 35 sites along the entire length of the Charles River.  Previously CRWA analyzed all of the samples for fecal coliform bacteria.  However in anticipation of the water quality standards changing from fecal coliform bacteria to Escherichia coli (E. coli) bacteria, CRWA has made the switch and now collects and analyzes samples for E. coliE. coli bacteria is a better indicator of health risks.  In the past, CRWA's laboratory analyzed samples for fecal coliform bacteria, which is one parameter used by the state for surface water quality standards.   

According to the U.S. Environmental Protection Agency and Massachusetts Department of Environmental Protection (DEP), the swimming standard for E. coli is 126 colony forming units per 100 milliliters (cfu/100mL) and the boating standard is 630cfu/100mL.  

The standards for fecal coliform are set by the Massachusetts Department of Environmental Protection to indicate level of health risk. The DEP recommends not swimming or fishing when bacteria counts exceed 200cfu/100mL, and not boating on days when levels rise above 1,000cfu/100mL.

In conjunction with collecting water samples for bacteria, in-situ measurements of temperature, and depth are also conducted on a monthly basis.

On a quarterly basis, in March, June, September, and December, CRWA takes a closer look at the water quality of the Charles River. Besides E. coli, additional testing is conducted for enterococci, nitrate plus nitrite, ammonia, total kjeldahl nitrogen, total nitrogen, phosphorus, orthophosphate, chlorophyll a, and phaeophytin.  From 1995 through 1997, river samples were analyzed for biochemical oxygen demand, however, due to consistently low levels, testing for biochemical oxygen demand was discontinued.

Click here for a list and explanation of parameters CRWA tests for on a regular basis.

For further information about CRWA’s methodology for water testing, or if you are interested in volunteering to collect water samples, please contact CRWA's Volunteer Coordinator at 781-788-0007 x228.

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