The Mashpee Board of Selectmen learned Monday that Popponesset Bay may be the most polluted bays in southeastern Massachusetts.
Brian L. Howes, a researcher at the University of Massachusetts Dartmouth School of Marine Science and Technology, reported water quality data that was collected from the town’s two main estuaries during the summer of 2018. He made the presentation to the selectmen on Monday.
Dr. Howes said that other towns across the region are also struggling with poor water quality, but Popponesset is especially bad, and it is not getting better.
“I can think of no estuary in Southeastern Massachusetts that has no area within it that is impaired by nitrogen,” Dr. Howes said. “But, this is extreme.”
The other estuary within Mashpee, Waquoit Bay, is not much better off: it is also significantly impaired by nitrogen.
Dr. Howes presented data collected as part of the Mashpee Water Quality Test Program, a volunteer-run program organized by the Mashpee Waterways Committee and Mashpee Wampanoag Tribe. The program provides water samples from more than 30 sites in Popponesset Bay and Waquoit Bay in the summer months.
For one slide in the presentation, Mr. Howes showed that every sampling station in Popponesset Bay had a reading of total nitrogen over .5 milligrams per liter, well over a water-quality threshold of 0.3 milligrams per liter. Some parts of the estuary, including the Mashpee River, had a reading close to 1.5 milligrams per liter. It was similar for Waquoit as well.
Of the some 30 sampling stations in both bays, every one was found to be impaired.
Dr. Howes noted that the only reason for optimism is that the shellfish grown in the local estuaries have made a minor improvement. Dr. Howes saw about a 25 percent improvement where the Mashpee Department of Natural Resources planted oysters in the Mashpee River. Also, Hamblin Pond and Great and Little Rivers had minor improvements as well, where the department planted some 11 million quahogs.
“After spending a lot of time going over this data, I wanted to find something positive to say,” Dr. Howes said. “That’s all I got.”
Last year’s samples represents the tenth year the data has been collected through the program, which Dr. Howes said represents a critical amount of data. While in the past, a particularly rainy season could explain the high levels of nitrogen concentration, or a particularly hot year. But 10 years allows them to draw real conclusions.
Dr. Howes said that to improve the bays’ water quality and to meet standards, it is clear that the pollution needs to be captured at its source before it runs into the bays.
To stop pollution of estuaries, the options are a) to increase the flow of an estuary by maybe dredging; b) to capture nitrogen in transit to an embayment; or c) to capture the nitrogen at its source.
In Mashpee, Dr. Howes said, the bays are already at maximum flow. Even if the channel into Popponesset Bay is opened further, the UMass researcher said that the tidal exchange would not change the water quality.
“No dredging option will get more bad water out and good water in,” Dr. Howes said.
Some 80 percent of the source of nitrogen, Dr. Howes said, originates at residential septic systems. Nitrogen from the wastewater collected in the systems seep into the groundwater which then flow with gravity toward the bays. The best option for Mashpee is collect nitrogen before it reaches the bays.
When pushed by selectmen, Dr. Howes said that building sewers and collecting wastewater before it gets to the groundwater would improve the water quality.
The presentation had a bit of a somber feel. Or, as Dr. Howes said, it was “depressing.”
It ended, however, with board chairman Andrew R. Gottlieb saying that the board could continue as is, watching the highly degraded resources become more and more degraded, or “we can do something about it.”
He said that the town did not waste money with shellfish, as was seen with the results. Hamblin’s Pond and Great River had some improvements to water quality. With a bigger investment, the results would be bigger. Ending on a happy note, Mr. Gottlieb said, the town should expect more relief if it invests in sewer infrastructure.
Then, a few minutes later after the presentation, the board decided to pull funding articles proposed for the October Town Meeting that would have paid for the design of a sewer collection system along the Mashpee River and for a treatment plant near Asher’s Path.