Package Plant Would Treat Growing Wastewater Flows from Existing, Proposed Facilities Along Corridor
Island officials for years have discussed creating some type of a common sewage treatment plant near the Martha's Vineyard Regional High School that would serve the growing number of Islandwide institutions locating along the Edgartown-Vineyard Haven road.
Now - with the high school already having gone past its maximum sewage flow while plans move forward for several other major projects along the busy corridor, including a 48,000-square-foot YMCA building - Oak Bluffs officials are putting the issue before the public.
Voters at the April 10 annual town meeting will decide whether the town should spend $350,000 on design and engineering costs for a new plant.
Meanwhile, a feasibility report released last week by the Martha's Vineyard Commission concludes that a $2.7 million underground package sewage treatment plant would have less impact on the environment and be more cost-efficient than building individual systems for the several Islandwide institutions on the Edgartown-Vineyard Haven road.
The Martha's Vineyard Commission crafted the 17-page report to inform Oak Bluffs voters and other Island residents about options for building either a single sewage treatment plant or several plants to serve the central corridor along the road, which falls within the town limits of Oak Bluffs.
The report was prepared by William Wilcox, the commission's water resources planner, and Mark London, its executive director.
The proposed package treatment plant would serve the Martha's Vineyard Regional High School, Woodside Village and Martha's Vineyard Community Services. It would also serve the proposed YMCA building and as many as 50 resident home site properties planned for a 32-acre parcel in the Southern Woodlands.
The report outlines three options: building four separate treatment systems; building a larger combined package treatment plant housed in a 4,275-square-foot structure; or building a smaller "innovative approach" treatment plant largely underground.
The innovative approach plant would use an amphidrome system with added nitrogen removal capacity. Wastewater would be pumped through a filter where oxygen would be added, before being pumped through a sand filter that would reduce the nitrogen level to less than 10 milligrams per liter.
The report recommends the innovative approach plant because it would be more aesthetically pleasing - only a 560-foot structure would be above ground - and would cost less than building four separate plants or a larger above-ground plant.
Building four separate plants, according to the report, would cost approximately $5.9 million, and building an above-ground package plant would cost $4.2 million.
The report says the innovative approach plant would lower inspection and operation costs, and would provide greater wastewater flow for higher efficiency.
The disadvantages of such a plant, the report states, are that the technology is currently operating under only provisional approval by the state Department of Environmental Protection, and also would require additional operator attention.
Joseph Alosso, the wastewater superintendent for both Oak Bluffs and Edgartown, said officials have planned on building a package treatment plant for several years, largely because the regional high school is already beyond its maximum flow. A package plant is designed to handle the flow of relatively few users, unlike a municipal plant.
The state environmental agency likely will require the construction of a wastewater treatment facility near the school sometime in the near future, he said.
"There is no question that some type of treatment facilities will need to be built," Mr. Alosso said.
Another driving force for building a package treatment plant, he said, is the Massachusetts Estuaries Project - a collaborative effort by two state agencies, the Executive Office of Environmental Affairs (through the Department of Environmental Protection) and the University of Massachusetts School of Marine Science and Technology.
The estuaries project will provide water quality, nutrient loading, and hydrodynamic information for coastal waterways across the state, including Sengekontacket Pond and Edgartown Great Pond.
Mr. Wilcox said a package treatment plant would reduce excessively high concentrations of nitrogen - which is linked to the growth of microscopic phytoplankton and algae - that now threaten the Sengekontacket and Lagoon Pond watersheds on which the buildings are located.
The nitrogen sources include residential and non-residential sewage discharges, fertilizer application in landscaping, and storm water discharges. Of the manageable sources, wastewater from septic systems is the largest source of nitrogen, Mr. Wilcox said.
Building the package treatment plant would reduce the discharge of nitrogen at the high school from 30 parts per million to less than 10 parts per million, which under state guidelines is the maximum allowed for facilities which generate 10,000 gallons of wastewater per day.
"Although there are also regulatory issues with the [Department of Environmental Protection], the commission views this primarily as a nitrogen issue," Mr. Wilcox said. "And there is no question that one common treatment facility is better for the watersheds than four or more separate facilities."
The proposed funding model for the construction and engineering costs of the plan is also considered innovative because all the users who benefit from the plant are expected to share both the engineering and construction costs.
The article on the warrant of the Oak Bluffs special town meeting next month stipulates that the $350,000 for engineering costs be shared by the prospective users. The town would essentially front the engineering costs and be reimbursed by the users at a future date.
That same cost-sharing model will be used for the construction cost of the new plant, Mr. Alosso said.
The Oak Bluffs annual town meeting is scheduled for 7 p.m. Tuesday, April 10 at the performing arts center in the high school.