Martha's Vineyard is ringed by saltwater ponds that are vital to the Island’s environment, character and economy. The13 tidal and brackish pond systems – including 21individual ponds – comprise a total of over 13 square miles of waters. Their watersheds (the area of land that drains into the pond, either through runoff or groundwater flow) include 64% of the Island. The ponds are productive sources of shellfish and fin fish, important to our commercial fishing industry. They offer a wide range of recreational opportunities, including boating and sport fishing, so important to the Vineyard’s visitor-based economy. They have over 290 miles of shoreline, important environmental resources, favorite spots for beach activities, and prime locations for real estate and viewsheds for many to enjoy. The future health of our ponds is dependent on maintaining water quality.
Our saltwater ponds are in trouble. All of our saltwater ponds are fragile, nitrogen-sensitive waters. Their quality has declined noticeably in the last twenty years as watershed development has occurred – in particular from wastewater disposal from housing and commercial development. Growth has led to deterioration in the water quality in the Vineyard’s coastal ponds, starting the process whose ultimate result can be an odorous, unattractive pond devoid of eelgrass, valuable fish or shellfish, thereby threatening the Vineyard economy.
In limited amounts, nitrogen is important to supporting life in a pond. But when excessive amounts are released in a coastal pond’s watershed – from acid rain, septic systems, and fertilizer – it ends up in the pond where it can destroy important aquatic habitat. With excess nitrogen in a coastal pond, microscopic plants in the water, called phytoplankton, increase dramatically, causing the water to become cloudy and, in extreme cases, green or brown; slime algae increase on the surfaces of pilings, rocks, and eelgrass blades; and drift algae grow to excess, break loose, and wash in to shore, or into eelgrass beds where they collect in unhealthy and unsightly piles. The growth of all these aquatic plants reduces light penetration to plants like eelgrass, which can no longer photosynthesize and therefore decline beginning in the deeper water. In addition to reducing light, the excess plant material takes oxygen out of the water, both at night during respiration and as they die and decay; this lack of oxygen leads to stress and even death of immobile organisms like quahogs, loss of habitat quality that lowers shellfish populations and by causing chemical reactions in the bottom sediment that release even more nutrients stored there. Finally, the pond’s ecosystem shifts to one where filter feeders (clams, oysters and scallops) are replaced by organisms that eat decaying plants (worms and snails), destroying recreational and shell fishing opportunities.
Eelgrass beds provide an essential habitat for young fish and shellfish, and their presence is an excellent indicator of good water quality. In high quality systems, eelgrass beds should be found throughout wherever water depth is less than about 8 feet. Presently, eelgrass beds cover about half the 3,000 acres of potential eelgrass habitat area. In the past twenty years, eelgrass beds have declined significantly in Edgartown Great Pond (with a modest return in the last two years) and Sengekontacket Pond, and have decreased by over 50% in Tashmoo and Lagoon Ponds. Eelgrass coverage is the primary indicator of water quality and its health should be the goal of our actions in both the watersheds and in the surface waters themselves.
Water quality is adversely affected by nitrogen when the amount reaching a pond exceeds a threshold called the nitrogen load limit. Existing health code regulations for wastewater are designed to protect human health, but do not adequately protect coastal ponds. Wastewater coming out of a septic tank may have a nitrogen level of 35 parts per million (ppm) or more that is diluted on site to the point that it meets DEP Drinking Water Standards (10 ppm), yet still exceeds the lower limit required to protect the health of coastal ponds as the watershed builds out.
The Martha’s Vineyard Commission has calculated interim nitrogen-loading limits for most coastal ponds and watersheds, based on factors such as the area of the watershed, the volume of the pond, and the tidal circulation. These indicate that for many coastal ponds, the annual nitrogen produced by the current development already exceeds, and in some cases is double or triple, the acceptable nitrogen-loading limits. With projected future development, the problem will be even worse.
The MVC has also categorized the ponds, based on water quality data, eelgrass bed coverage trends, and other factors.
· Good means that the water quality indicators are almost always in the acceptable range and eelgrass beds have suffered only small losses.
· Somewhat Impaired means that water quality indicators are not acceptable some of the time or only in some parts of the system or that eelgrass coverage loss has exceeded 50%.
· Impaired means that the water quality indicators are almost always unacceptable in a substantial part of the system, nitrogen loading significantly exceeds the limit or eelgrass is no longer found in the system.
This deteriorated condition does not include the impacts of nitrogen from development that occurred in the last twenty to thirty years in more distant parts of pond watersheds since their nitrogen plumes have not yet reached the ponds. For those ponds that have surpassed their natural ability to deal with nitrogen, water quality deterioration will be even more rapid in the future, as the nitrogen from each new house must be offset by costly treatment.
In many ponds, the nitrogen load is already at or over the acceptable limit to maintain good water quality, and there are many acres of open, developable land available for even more development. Some ponds with very good tidal circulation (e.g. Cape Poge, Menemsha, Katama Bay) have very large limits to nitrogen loading. Others (e.g. Squibnocket and James Ponds) are over their limits even before nitrogen from wastewater is entered into the budget. For some coastal ponds where the tides are severely restricted (e.g. Farm Pond, Trapp’s Pond, south shore great ponds), the nitrogen limit may be substantially increased by improving tidal flow to flush out the nitrogen. However, in most cases, where a pond surpasses its limit, some other means of reducing the nitrogen must be found and, as the main substantial source manageable at the local level, wastewater is the prime candidate.
The cost of dealing with this excess nitrogen to clean up our coastal ponds – as will likely be required to comply with the federal Clean Water Act – will be staggering, likely in the hundreds of millions of dollars. There are already an estimated 3,600 houses beyond the number which would maintain clean water in ponds, and with present zoning and available land, there could be an additional 4,600 houses (based on interim nitrogen load limits). If it ends up costing an average of $50,000 do deal with the excess nitrogen from each house, including capital and operating costs, this would translate into $130 million just to deal with the excess nitrogen from existing development, and an additional $230 million to deal with the possible additional development. (Note: A Wastewater Management Study currently underway will help clarify this analysis, and its results will be included in the final version of the plan.)
After wastewater, the second most significant source of nitrogen pollution that we can control is fertilizers used in farming and landscaping. Unfortunately, we have little local control over one serious source of nitrogen pollution to our coastal ponds – acid rain (from gases produced when fossil fuels are burned by automobiles, power plants and industries, often hundreds of miles to our west). Water quality is also affected by limited tidal circulation and by pond management activities. The periodic breaching of the great ponds brings clean ocean water to flush nitrogen and other pollutants from the pond, or at least dilute them. Summer inlets are vital to water quality in the great ponds.
Objective W5: Ensure appropriate management of coastal ponds and their watersheds, including improvements to water circulation.
The target is to restore eelgrass to 75% of suitable habitat (as indicated by the 1951 eelgrass coverage), a clear indicator of improving water quality and restoration of pond habitat. The return of eelgrass to Katama Bay following the huge increase in tidal circulation that came with the breach across South Beach in 2007 demonstrates how quickly eelgrass can return with improved water quality. On-going monitoring of surface water quality is vital to responsive management.
· Strategy W5-1: Complete the Mass Estuaries Project (MEP) studies of coastal ponds. We need strong scientific support to minimize, and win support for, the significant expenditure of funds that will be needed to solve these problems. The MEP uses a rigorous scientific approach to determine each pond system’s tolerance limit for nitrogen, using computer models of pond system water quality, circulation, and watershed land use. The model allows Towns to project the pond response to various nitrogen-reducing solutions. At this time, Edgartown Great, Lagoon, Sengekontacket, Farm, and Tisbury Great Pond are in the program. We need to build community support to get the local cost share for the other eight pond systems.
· Strategy W5-2: Set up management committees to prepare plans for each coastal pond. The selectmen in each town should appoint committees or designate existing committees for each coastal pond – similar to the Edgartown Ponds Advisory Committee, the Joint Sengekontacket Pond Committee or the Tashmoo Management Committee -- tasked with evaluating the needs of each pond system in light of the Massachusetts Estuaries Report and preparing a plan to ensure the long-term sustainability of each pond. This will likely include measures to improve circulation, to increase wastewater treatment, to set nitrogen-loading limits on new developments, to manage boating and fishing, and possibly to limit growth. Implementation is crucial and each pond needs an on-going water quality monitoring program to track water quality changes. The creation of zoning overlay (Town or DCPC “water sheet” zoning) for water bodies is an option to provide an added layer of protection.
· Strategy W5-3: Improve pond circulation through dredging, removal of tidal restrictions and carefully managed openings to the sea. The MEP should help identify potential to achieve required nitrogen reduction through improving tidal circulation by dredging. Measures to optimize tidal flow into coastal ponds might include: maintenance dredging to remove shoals and channel fill; removal of culverts currently restricting tidal flow (Trapp’s Pond, Farm Pond under Beach Road); identification of other possibly restrictive structures under roads (e.g. Hariph’s Bridge, north inlet into Sengekontacket Pond). If indicated by the circulation computer model, permits should be put in place to allow maintenance dredging to remove tidal flats that obstruct or impair tidal flow both at the entrance to the system and within the system. If economically feasible, acquisition of dredging equipment would allow timely dredging and minimize costs. The opening of the great ponds should be managed to maximize shellfish production by improving overall water quality while retaining oyster spat when they are in the water column in July; a summer opening is critical to overall pond system health.
· Strategy W5-4 Set regulations limiting nitrogen from new projects in sensitive watersheds: New projects in impaired coastal salt ponds (see section 10.4) should be required to comply with nitrogen-loading limits, using the MVC’s interim limits until the definitive limits are calculated by the Mass Estuaries Project. The MVC already requires this for projects reviewed as Developments of Regional Impact. The Towns should set up procedures to enact this for all projects within these watersheds. Similar review should take place with respect to phosphorus in fresh-water ponds, and could include mandatory review by Conservation Commissions of all projects within 300’ of wetlands. It would be desirable to set up a system of impact fees, so that projects that are unable to adequately mitigate their impact on their property, could pay a fee that would then be used to help finance an appropriate project that offsets at least an equivalent amount of nitrogen, elsewhere in the watershed. In addition, broader watershed based growth control may be needed to limit the addition of future new nitrogen loads from presently vacant land by rezoning to limit density and intensity of use, or by focusing growth within the reach of sewage collection systems.
· Strategy W5-5: Increase shellfishing in coastal ponds by increasing habitat area and quality. The presence of shellfish, particularly oysters, quahogs and mussels, in a pond improves water quality by filtering water and removing nitrogen. Oysters remove nitrogen from the water and deposit it in the bottom sediments. When harvested, even more nitrogen is removed in their tissues and shells. To take advantage of these services, we need to improve habitat for wild populations and increase the opportunities for private shellfish aquaculture ventures. An expanded shellfishery will further improve water quality immediately, unlike a sewering project back in the watershed that might take years to have a positive impact. Growing techniques that minimize the visual and recreational impacts – such as bottom-culture and suspended mid-water column culture – are preferred. Adequate financial support is needed for public shellfish management and propagation efforts. The possibility should be explored of developing a system of nitrogen trading rights that would allow developers to purchase rights from aquaculture operations that remove nitrogen from the water column.
· Strategy W5-6: Identify sources and reduce bacterial contamination that closes shellfish beds: Bacterial closures of shellfishing beds may reduce the potential for aquaculture, compounding the nitrogen loading impact. Sources of bacterial contamination include stormwater runoff and waterfowl. Septic systems are a potential limited source due to active enforcement of the Title 5 health code. In all cases, the sources of bacteria should be identified and plans devised to reduce the sources. The non-migratory goose population and the recent invasive double-crested cormorant are primary candidates for the Sengekontacket Pond bacterial closures based on source identification technology. It is highly likely that fecal bacterial contamination in other systems has a similar source. A comprehensive, humane approach to addressing the waterfowl source is needed. Stormwater runoff reduction is discussed in Section 10. 3. More frequent testing is needed by DMF or by other certified labs to acquire more data and to seek out a test that will identify truly pathogenic problems that require closure to protect public health.
· Strategy W5-7: Manage boating and fishing to limit the impact on water quality. The Committees should work with existing Town committees, Shellfish Departments and Harbor Masters to map piers and mooring fields relative to shellfish and eelgrass beds to identify reasonable limits to their expansion based on knowledge of shellfish habitat, presence of eelgrass beds (now or historical) and capacity of systems such as water, wastewater, dock space etc. The goal should be to limit the scale of mooring fields, pier construction and recreational boating use to support high quality shellfish habitat. Utilize environmentally sound mooring systems that do not impact eelgrass beds such as elastic moorings. Limit recreational use of motorboats and personal watercraft in fragile areas. Public education on appropriate boat maintenance practices (e.g. safe bottom paints) will help limit impacts on resources.
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