11/13/2017 BOARD OF SELECTMEN Minutes

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MONITORING CONCLUSIONS AND RECOMMENDATIONS Overall,both the Waquoit Bay and Popponesset Bay Estuarine Systems were highly nitrogen enriched and showed impaired nutrient related water quality in 2010-2016, similar to the long- term pattern. The tidal rivers (Mashpee River, Childs River, Quashnet River) and major tributary basins (Eel Pond/River, Shoestring Bay and Ocicway Bay) are all showing poor water quality as evidenced by the Bay Health Index. Only the main basins of Waquoit Bay and Popponesset Bay continue to show moderate -high water quality,but with lower Eel Pond and lower Waqouit Bay showing a decline in 2016. The major water quality event of 2016 was the large prolonged bloom of Cochlodinium(Rust Tide),which was found in many southeastern Massachusetts estuaries, including adjacent Three Bays, and had negative effects on water clarity and bottom water dissolved oxygen as the bloom declined. Although Cochlodiniunz has sometimes been thought to impact shellfish, fortunately there was no evidence of shellfish loss in the recent blooms in Mashpee estuaries. 2016 was also a different weather year,with little rainfall and diminished surfacewater inflows. The extent to which this phytoplankton bloom was a response to relatively rare environmental conditions versus a response to continuing high levels of nitrogen enrichment will be a focus of the Mashpee Water Quality Monitoring Partnership over the next several years, as it directly relates to management and restoration of these estuaries. With watershed development continuing, estuarine conditions have been projected to decline further until nitrogen management is implemented. Nitrogen management within Popponesset Bay has already begun with the maintenance of the flow through the tidal inlet,propagation of oysters within the system and capping of the Town of Mashpee landfill. In addition,watershed nitrogen management planning is underway to reduce the major sources of nitrogen(primarily septic system discharges) and possibly enhancing nitrogen removed during transport from the sources to the estuary by pond and stream restoration. Specific findings: (1) Both Waquoit Bay and Popponesset Bay appear to be showing few additional impairments,although 2016 was a poor water quality year due to the large phytoplankton bloom, and overall the systems continue to support impaired habitat quality. There appears to have been a general gradual improvement in regions of Waquoit Bay and Popponesset Bay which have historically shown significantly impaired water quality(Health Index<30) and small recent improvements or no changes in the moderately impaired areas from 2013-2016 and either stable or variable conditions in the high quality areas (Health Index>60) in the lower main basins. It should be noted that the declines associated with summer 2016 data are driven significantly by the large phytoplarilcton bloom. The importance to this event will depend on if it was a rare event spawned by low flows due to the drought or if it is part of a trend toward increasing bloom frequency and duration due to continued nitrogen enrichment. Overall, in both bays there is a trend of improving water quality in the poorest quality(most nitrogen enriched) areas, which is a positive sign for both estuaries. Unfortunately, both estuaries still support impaired habitats and remain below the water quality levels set by the MassDEP/EPA TMDL. (2) Quashnet River above the bridge was relatively fresh in 2011-2016, continuing the trend of prior years. A separate study(with the Towns of Mashpee and Falmouth) of tidal flows associated with the Quashnet Estuary did not find any major restrictions related to the inlet, bridge or open channel. However, dredging a channel through the flood tidal delta may yield 21