Martha’s Vineyard salt ponds face environmental dilemma

Shoreline development, as in this house in a development on Major's Cove on Sengekontacket Pond, has contributed to the problem. — Photo by Ralph Stewart

Updated 9:15 am, October 12.

Town officials in Edgartown, Oak Bluffs, and Tisbury face a daunting environmental task if they are to restore the health of three popular salt ponds. The task is outlined in three reports presented last week that describe goals to improve water quality in Farm Pond, Sengekontacket Pond, and Lagoon Pond.

State scientists say that if they fail, the ponds may deteriorate to the point where very little aquatic life can survive, boaters will have to navigate through an unsightly algae scum, and shoreline homeowners will have to endure awful smells.

“Coastal communities,” the scientists wrote in a series of report to the towns, “rely on clean, productive and aesthetically pleasing marine and estuarine waters for tourism, recreational swimming, fishing and boating, as well as for commercial fin fishing and shellfishing.”

The Massachusetts Department of Environmental Protection (DEP) suggested what action the three towns must take, and offered guidance on how to do it, based on years of scientific study of the three ponds.

The recommendations include a combination of sewering, stormwater management, natural wetlands filtering, and new town bylaws to limit fertilizer use.

Up to now, DEP has relied on firm suggestions and taken the view that solutions will take time. On Cape Cod, and in other states, activists have sued local, state, and federal governments for failure to comply with the federal Clean Water Act and speed up the process. Courts could impose sanctions or clean-up plans.

Any solution, by necessity, will have to take a regional approach. The Farm Pond watershed is located entirely in Oak Bluffs, but Sengekontacket Pond straddles the border of Edgartown and Oak Bluffs, and Lagoon Pond straddles the border of Tisbury and Oak Bluffs.

According to DEP, aquatic plant and animal life is already affected by the amount of nitrogen getting into all three ponds from natural sources, as well as controllable sources such as septic systems, storm runoff, and fertilizer.

The effects are measured in the loss of eelgrass beds, periodic algae blooms, and lower numbers of aquatic animals.

Reversing the decline will mean more than simply reducing the amount of nitrogen loading now. It will mean controlling nitrogen from future development within the pond watersheds.

Oak Bluffs town administrator Bob Whritenour said the target limits set by DEP will be the regulatory framework for restoring the ponds.

“These limits will drive all of our future efforts to reduce nitrogen in our coastal ponds,” Mr. Whritenour said. “We are at a critical phase in our water quality improvement efforts.”

Total nitrogen

After measuring and analyzing the ponds for a period of five years or more, state scientists determined that nitrogen loading is already signficantly higher than levels in a healthy pond, and set specific targets that will restore the health of the salt ponds.

According to the Marine Estuary Program studies, an average of 58.8 kilograms (about 130 pounds) of nitrogen enter Sengekontacket Pond every day.

Last month, DEP issued reports setting the target levels for Total Maximum Daily Loads (TDML) that would restore the ponds to healthy levels. The reports are in draft form, and they could change, based on comment from local officials. The towns have 30 days to respond to the new limits, but Oak Bluffs has already asked for an extension of the comment period.

For Sengekontacket Pond, state regulators set a target of 50 kilograms of nitrogen per day.

According to the report, septic systems in private homes surrounding the ponds account for nearly half the nitrogen that enters Sengekontacket Pond, and it accounts for 80 percent of the controllable nitrogen sources. The next highest controllable source is commercial fertilizers like lawn and garden products. That accounts for 12 percent of the controllable sources of nitrogen. Storm-water runoff from paved or hard surfaces accounts for 7.5 percent.

For Lagoon Pond, the current level is 101.7 kg per day, and the target level is 74 kg per day. In Lagoon Pond, 76 percent of the controllable sources of nitrogen come from septic systems, 11 percent from storm runoff, 8 percent from agriculture, and 5 percent from commercial fertilizer.

In Farm Pond, much small by comparison, current nitrogen loading amounts to 6.46 kg per day, and the target level is set at 4.88 kg per day. The report attributes 69 percent of the nitrogen to septic systems, 12 percent from runoff, and 10 percent from commercial fertilizer.

Value judgement

The deteriorating ponds threaten the value of shoreline property. At the Oak Bluffs selectmen’s meeting September 25, Terry Appenzellar and Duncan Ross represented Friends of Sengekontacket, an advocacy group working to improve the health of that pond. Ms. Appenzellar brought a dramatic example of the problem to the meeting. She set a large jar filled with unsightly algae collected from Sengekontacket Pond on the selectmen’s meeting table. She told them she would spare them a demonstration of the smell, by keeping the jar closed.

“You smelled it all summer,” Ms. Appenzellar said. “You couldn’t help but smell it.” She said algae growth, which is fed by nitrogen loading, threatens the value of shoreline property owners.

“In Oak Bluffs, there are 32 riparian owners, with $50 million in assessed property value that could be negatively impacted by continued bad smells. In Edgartown, there are 56 houses, worth $80 million in assessed value.”

Friends of Sengekontacket has tried to engage homeowners in the effort to clean up the ponds, with limited success. She said only one of the many homeowners associations that surround the pond agreed to meet with Friends of Sengekontacket to discuss the issues. She said the group has mailed a letter with a number of steps homeowners could take to reduce nitrogen loading, but follow-up conversations were met with little interest.

The group urged selectmen to consider a number of actions. Designating the watersheds as districts of critical planning concern (DCPC) would give the towns considerable authority to control new development. A town bylaw regulating lawn fertilizer would help, Ms. Appenzellar said.

The Friends of Sengekontacket also urged selectmen to consider requiring periodic inspection and testing of septic systems, to insure they are working properly.

Sewer issues

The studies show that the largest source of controllable nitrogen getting into the ponds, by a wide margin, comes from septic systems. One solution is expanding the town sewer systems to those homes within the watershed. But town officials say that introduces a new set of problems. First among the issues is how to pay for any new sewering projects. Both Oak Bluffs and Tisbury would need costly expansion of their sewer plants to handle a signficant increase in wastewater treatment.

Town officials are also concerned that expanding sewage infrastructure could trigger more growth, increasing the burden on schools, roads, and water systems.

Ms. Appenzellar said the town will play a critical role on this issue. “Coordinate the use of sewering resources and alternatives,” she urged Oak Bluffs selectmen. “Sewering is not the only answer.”

Alternatives to sewering could include composting toilets, small scale sewage treatment systems, and nitrogen removal technology for each individual property.

This article was updated to reflect a clarification in the role of the Martha’s Vineyard Commission. The commission can hold hearings, debate the issues, and create guidelines for regulation of a district of critical planning concern, but it is the town which holds the authority to control growth, by adopting the guidelines as a change to its zoning bylaws.