Cochato River Study
Holbrook Junior-Senior High School, Holbrook, Massachusetts
The Cochato River is a small river that starts at Lake Holbrook and flows through Holbrook, Randolph and Braintree. The total length of the River is three miles.In the past, the Cochato was directed into a reservoir for the Tri-Town area. Our study revolves around a particular site on the banks of the Cochato River.
In 1983 the Environmental Protection Agency shut down a chemical company due to its contamination of soils and water surrounding the manufacturing site. The name of this company is Baird and McGuire. Starting in 1912 and ending in 1983, Baird and McGuire site polluted the lands around the Cochato River with heavy metals, floor waxes, dioxins, herbicides, pesticides and solvents. We took samples from points above and below Baird McGuire to determine whether there was still an impact in the surrounding areas.
We selected two different sites, site A, at Lake Holbrook and site B at Union Street, downstream from Baird and McGuire. Data was collected on Dissolved Oxygen, pH, Nitrates, Phosphates and macro-invertebrates. We were surprised by the lower dissolved oxygen levels at site B and the higher Nitrate levels at site B. The pH was much lower on November 10-11, meaning the water was more acidic. The pH was much higher on April 9-10 which means the water was more basic for both sites.
Each macro-invertebrate has its tolerance index, which allows us to analyze the quality of the water. The tolerance value at site A was, much higher than site B, which means the water at Lake Holbrook has more stress impacts than site B. This result surprised us because of what Baird and McGuire did to the river in the past.
Further investigation revealed that the EPA had dredged the river four years earlier in an effort to clean up the contamination. Comparing data, we have come to the conclusion that the Environmental Protection Agency did a very good job. Further study is needed for sites closer to Baird and McGuire as well as more Phosphate and Nitrate sampling. We would like to continue this project next year to see if there are many variances in season and time. A broader macro-invertebrate study will also be done to determine the health of the river in smaller segments, including Lake Holbrook. Bacteriological samples should also be taken due to the thickly settled residential areas.
Holbrook Junior-Senior High School, Holbrook, Massachusetts (2002). Cochato River Study. In Watershed Access Lab Projects. Project 127.
Available at: http://vc.bridgew.edu/wal_projects/127
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