On Sept. 4 the Tisbury planning board will continue a public hearing on Island Housing Trust’s proposed plans for 299 Daggett avenue. IHT seeks a special permit to repurpose a single family homestead into a four-family development. The property sits within the Lake Tashmoo watershed. In the 2017 MassDEP Lake Tashmoo Estuarine Study, the water quality impairment of Lake Tashmoo is described as “significant” and the “major stakeholder for management and restoration of Lake Tashmoo is the Town of Tisbury.”

The study states that daily nitrogen loading to Lake Tashmoo should be reduced by 42.5 per cent in order to “restore conditions and to avoid further nutrient-related adverse environmental impacts” while mentioning that Tisbury should take any reasonable actions to reduce controllable nitrogen sources. Data shows that 80 per cent of the controllable nitrogen load to Lake Tashmoo originates from septic systems. Reductions in onsite subsurface wastewater disposal systems is urged in order to attain lower nitrogen loading.

The year round population of Tisbury has increased 75 per cent over the past four decades. According to the Martha’s Vineyard Commission, Tisbury has a population density of 662.6 year-round residents per square mile. This number does not take into consideration the summer population explosion each year. The Lake Tashmoo watershed has seen extensive seasonal and year round single-family home development. MassDEP estimates that the remaining build-out potential in the watershed can increase the nitrogen load by 38 per cent.

In 1973 Tisbury adopted strong R50 zoning near Lake Tashmoo in an effort to limit the density of population and protect the water quality of Lake Tashmoo. In 1987 they added the R-3A district on the western side of the lake as another means of trying to keep Tashmoo safe. MassDEP states: “Importance is the density of homes. Larger home density means more nitrogen being discharged thus the density determines where to sewer and to maximize reductions.”

The good news is that by reducing the daily nitrogen load by 42.5 per cent, water quality goals can be met throughout Lake Tashmoo. Lake Tashmoo sits within a populous region and is classified as an enclosed embayment with restricted ability to flush pollutants readily. The only fresh water to Lake Tashmoo enters through direct discharge of groundwater. If this groundwater continues to overload the lake with nitrogen, Tisbury will not meet the nitrogen reduction goals and MassDEP can take regulatory action.

I urge everyone with concerns for Lake Tashmoo to write to the Tisbury planning board immediately to ask them to deny IHT’s special permit request. Even with enhanced nitrogen reduction septic systems, this property will produce more nitrogen year round. Tisbury’s housing production plan states that we should “ensure new housing options are sensitive to environmental and infrastructure constraints”. There are already at least five multi-family developments located in the Tashmoo watershed. The watershed should not be asked to absorb another one.

Recently this month the Massachusetts Division of Marine Fisheries closed a portion of Lake Tashmoo due to high fecal contamination. The shellfishing area has been reclassified to “conditionally approved” and will remain closed until Oct. 31, when testing will determine the quality of the water.

If Tisbury continues to turn a blind eye on Tashmoo we will lose it completely.

The meeting on Sept. 4 is an opportunity to let your voice be heard. Write a letter, pick up the phone and call the Tisbury planning board or better yet come to the meeting and let them hear your voice loud and clear.

Connie Alexander

Vineyard Haven