Lagoon Pond is sick, healing will be costly
Martha's Vineyard Times File Photo
A draft scientific study released this week calculates that Oak Bluffs and Tisbury would have to reduce the amount of nitrogen from septic systems reaching Lagoon Pond by 34.6 percent and prevent any nitrogen sources from new development, in order to meet federal and state water quality standards for the pond.
After scientific analysis that measured plant life, water quality, and the amount of nitrogen flowing from septic systems and other sources, the study's authors labeled the health of Lagoon Pond "impaired" in shallower waters, and "degraded" in the deeper basins.
The study is part of the Massachusetts Estuaries Project, to assess the health of coastal salt ponds, through a collaboration of the University of Massachusetts Dartmouth and the Massachusetts Department of Environmental Protection (DEP).
The most practical solution to reduce nitrogen loads is a new sewer infrastructure to serve the dense development around the popular salt pond, according to the analysis of a local environmental engineering firm, and local officials.
According to that analysis, a general cost estimate for extending sewer infrastructure from existing treatment plants that would adequately reduce the nitrogen load from the current flow into Lagoon Pond could cost $3.4 million or more annually to build, operate, and maintain over 20 years.
Typically, sewer costs are funded through some combination of taxpayer funds and user fees.
The report is in draft form. It is now under review by town officials, and could change based on their comments.
The Massachusetts Estuaries Project is an effort to provide solid scientific analysis to help communities, so they can plan the most effective way to restore the health of coastal embayments.
The new study adds empirical evidence to what boaters, fishermen, and homeowners have observed for some time: the health of the pond is deteriorating. The study documented the loss of plant life including eelgrass, the increase in sunlight-blocking algae, and current levels of oxygen and chlorophyll.
The key measure of the pond's health is the amount of nitrogen getting into the water. The study found that 76 percent of the controllable watershed nitrogen came from septic systems within the Lagoon Pond watershed. The total nitrogen load from septic systems currently amounts to 75.8 pounds per day, or 27,667 pounds per year. According to the study, the towns should reduce that amount by nearly half, in order to restore the health of the pond.
The most prominent effect of the deteriorating health of the pond is the loss of eelgrass, which serves as a support environment for shellfish, fish, and other aquatic species.
"The primary habitat issue within the Lagoon Pond embayment system relates to the general loss of eelgrass beds and impaired infaunal habitat.
"Fringing eelgrass beds within the upper reach of the eastern arm of the estuary have declined significantly from 1995-2006," the study's authors write.
"Within the shallow western arm, infaunal habitat is presently moderately impaired by nitrogen and organic matter enrichment, while infaunal habitat within the deep basins of the eastern arm is virtually absent.
"Restoring these habitats is the focus of the nitrogen management threshold analysis."
Also circulated this week is the first draft of a case study of Lagoon Pond by Wright-Pierce, a New England based engineering firm hired to evaluate solutions to the nitrogen overload. The towns of Oak Bluffs and Tisbury funded the analysis to guide them toward the most practical solution for meeting water quality standards. The draft report could change with comments from local officials.
The report's author presented his findings to about 25 people Wednesday, March 2, at the Oak Bluffs library.
The engineering study says the Lagoon Pond watershed covers 3,900 acres surrounding the pond. There are about 2,100 developed parcels within the watershed, nearly all of them with private septic systems. Currently 367,400 gallons of wastewater flow through groundwater into the pond every day. The Martha's Vineyard Commission (MVC) estimates that future development will increase that flow to 552,000 gallons per day.
Currently, about 60 percent of the wastewater generated through septic systems comes from Oak Bluffs, 33 percent comes from Tisbury, and 7 percent from West Tisbury.
"While it may be a simple mathematical exercise to apportion the responsibility for nitrogen control based on current wastewater flows," the study's author writes, "this may not lead to the least-cost control strategy."
The report suggests four possible options to divide the cost of meeting water quality standards. The four options take into account only nitrogen control of the current wastewater flows.
In the first option, each town would implement nitrogen controls based on the amount of wastewater that flows into the pond from their town. In that solution, Oak Bluffs would shoulder most of the burden, because 60 percent of the wastewater comes from Oak Bluffs.
In the second option suggested, Oak Bluffs would collect, treat, and dispose of all the wastewater, about 173,000 gallons per day. The town could work out an agreement to share the cost with other towns within the watershed. That scenario might be feasible if Tisbury cannot expand its sewer infrastructure, or the cost of expanding it is prohibitive, according to the case study.
The third option would have Tisbury expand its wastewater plant and collect all wastewater from its side of Lagoon Pond. That would still leave about 60,000 gallons per day that Oak Bluffs would have to treat.
The fourth option would be to sewer only the most densely developed neighborhoods. On the Tisbury side, those would include the area roughly bounded by State Road, Edgartown-Vineyard Haven Road, Oklahoma Avenue, and the Lagoon Pond western shoreline. On the Oak Bluffs side, neighborhoods bounded roughly by Eastville Avenue, County Road up to Meadow View Road, and the eastern shoreline of the pond are included. Sewering those neighborhoods would remove enough nitrogen to meet the water quality standards.
"Regardless of the cost of the option selected, the responsibility for those costs should be the subject of separate discussions," the case study author wrote. "Simply stated, the town building the infrastructure need not be the sole source of the capital expenditures."
Both Oak Bluffs and Tisbury are already working toward the goals set out in the estuaries study.
"I'm encouraged the two towns are working together," Oak Bluffs wastewater plant manager Joe Alosso said.
At the Oak Bluffs annual town meeting in April, voters will be asked to take the first step toward sewering some of the neighborhoods along the Oak Bluffs side of Lagoon Pond. A warrant article will ask that they approve money for permitting and design of a sewer line from the Martha's Vineyard Hospital, to the Oak Bluffs fire station. "That's the most densely populated area, the smallest lots with the most year round homes," Mr. Alosso said. The project would provide sewer service to 454 lots. Of those, 119 are undeveloped.
Mr. Alosso expected the wastewater commission to award a contract this week to a firm that will install new leaching beds on a parcel near the wastewater plant known as the Leonardo property. The contractor should begin work in 30 to 45 days, according to Mr. Alosso. The new leaching beds, along with some new technology for the plant, will expand capacity enough to handle the additional flow from the Lagoon Pond neighborhoods. However, according to the study, Oak Bluffs would need two to three times its present capacity to handle projected future growth.
Tisbury has different issues. Currently, according to the study, the Tisbury wastewater treatment plant has about 30,000 gallons of unused capacity. Factoring in growth projections, the town would need new capacity at least double, and as much as 4.5 times the existing capacity to achieve water quality goals.
Another limiting factor for Tisbury is disposal sites. The town is currently working to acquire rights for sub-surface disposal of treated wastewater, outside of nitrogen-sensitive watersheds.
Sticking to standards
How the state and federal governments can enforce the water quality standards is a murky area. The Clean Water Act of 1972 established the standards. The federal government set targets for nitrogen levels, and handed to each state the responsibility for implementing measures to reach the targets. It is unclear whether the Massachusetts DEP can force an individual town to clean up its waters. But the state could apply other kinds of pressure.
"The only clear angle that the state has with the local towns, the leverage to get them to move forward, is through their grant programs, their revolving funds programs, and any kind of loans," MVC water resource planner Bill Wilcox said. "At this stage it's not at all clear there are any legal avenues."
A bigger incentive could come from the possibility that private groups could sue.
The Conservation Law Foundation and the Coalition for Buzzards Bay joined to sue the federal Environmental Protection Agency (EPA) last fall. The groups say they are concerned about a lack of action by Barnstable County and the Cape Cod Commission, but have not yet taken legal action against the local agencies.
The environmental groups accuse the federal government of violating the clean water act, by failing to follow through with plans to clean up Cape Cod bays and ponds. The lawsuit contends that if EPA had required state and local governments to implement plans already drawn up in response to the Clean Water Act, taxpayers would not now be facing clean up costs that could reach several billion dollars.