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Septic Study Evaluates Monitoring

The coastal area in Charlestown requires the use of nitrogen-reducing septic systems for new installations to reduce nitrogen in the ground water (drinking water) and coastal ponds.

At the April 8 Town Council meeting, Town Environmental Scientist Matt Dowling and URI researcher Bianca Ross presented research data on monitoring the effectiveness of these systems.

The only way to determine whether a system is functioning is to collect and analyze the effluent. Dowling explained that in a previous study, URI researchers had collected samples from advanced septic systems throughout Rhode Island and compared the data to samples from Barnstable County, Massacusetts — the Cape and Islands — where regular effluent monitoring is required. Not surprisingly, the study found that regular, mandatory monitoring had a positive impact on reducing nitrogen levels.

A study conducted by URI in 2014 determined that septic systems contribute 80 percent of the nitrogen in the salt ponds. Advanced treatment systems are required only for new construction, major rebuilds, or if an existing conventional system fails, so there are still many conventional septic systems on coastal properties. Many septic systems in Charlestown are older systems that do not remove nitrogen, and at the time of the study, 138 systems were un-permitted or substandard.

In densely populated Quonochontaug, where groundwater is the principal source of drinking water, nitrate pollution of wells has become a problem that becomes more acute during the summer, when the demand for water increases along with septic use and  homeowners apply lawn fertilizers containing nitrogen.

As we get more and more of these systems and as we improve the performance of these systems with my study, with other studies, with monitoring efforts, we’re definitely hoping to reduce the nitrogen overall,” (Ross) said.

This post uses excerpts from an April 20 article in The Westerly Sun by Cynthia Drummond. The entire article, with many more details, may be viewed here.

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