Decade of research shows major improvement in Blackstone River

Ray Wright at work on the Blackstone River

Decade of research shows major improvement in Blackstone River

After more than 10 years of data collection and analysis of the water quality in the Blackstone River, Raymond Wright feels confident saying, “The river water quality has improved greatly. You can clearly see this by comparing the water quality from my current study to that 10 years ago.”

The URI civil engineering professor, along with Assistant Research Professor Oran Viator and others, authored a comprehensive assessment of the river’s water quality for the U.S. Environmental Protection Agency in 2001.

“If we hope to say in another 10 years that the water quality is much better than what it is today, we have to continue to improve the level of wastewater treatment at the point sources and provide special

attention to identifying and eliminating the major non-point sources of pollution in the watershed,” Wright said.

As the birthplace of the American Industrial Revolution, the Blackstone River has a long history of poor water quality due to the many industries that dumped contaminants into the river. Some of those pollutants remain in the sediments that have accumulated behind the 19 dams along the 46-mile long river extending from Worcester to Pawtucket, and those sediments continue to affect the river’s water quality.

During the summer months when the water level is usually quite low, Wright said rainstorms increase the velocity of the river flow and churn up the contaminants in the sediment. Those contaminants become suspended in the water, sometimes for several days, flowing downstream and settling to the bottom behind the next dam.

During dry weather when the water level is low, pollutants become concentrated because little water is available to dilute them. The dry season is also the time when water temperatures rise, speeding up biological and chemical oxygen-demanding reactions and sparking algae blooms.

According to Wright, one of the major problems in the river remains the high algae productivity of the ecosystem, primarily in the river reaches just above and below the Massachusetts and Rhode Island border, caused by the upstream additions of nutrients, especially phosphorous. The major source of phosphorous continues to be from municipal wastewater facilities that discharge into the river.

While the two largest wastewater plants -

Upper Blackstone and Woonsocket - have made great advances in cleaning up their effluent, they remain the largest sources of several pollutants in the river. During the late summer and early fall, the Upper Blackstone facility is the largest source of nitrate and phosphorous to the river. The Woonsocket facility is the river’s largest source of ammonia, though the river is much larger in Woonsocket so the dilution rate is higher.

Another major water quality issue still facing the river is non-point sources of pollution - those sources that cannot be traced to a particular place, especially roadway run-off and failing septic systems. “Every vehicle on the roadway is a potential source of oils, metals, rust, exhaust fumes and more,” said Wright. “When it rains, those pollutants move off the road and find their way into the river.”

The focus of Wright’s current studies is to identify some of the “hot spots of non-point sources” along the Massachusetts section of the river. With funding from the U.S. Army Corps of Engineers and the Massachusetts Department of Environmental Protection, he regularly toured the Massachusetts stretch of the river by kayak to collect water samples, especially at Fisherville and Rice City Ponds in Northbridge, the two sites of greatest concern.

Wright’s studies will lead to the development of the river’s total maximum daily load. “That’s the measurement of how much pollution the river can receive and assimilate and still meet water quality standards. In most situations, the river is meeting the standards today,” Wright said.