A weight of evidence has made clear that excessive nitrogen is detrimental to the health of Great Bay, with vast acreages of eelgrass – the cornerstone of the ecosystem – having disappeared. In fact, it would be highly unlikely to find any eelgrass at all from New Castle all the way upriver and to Adams Point in Durham – a distance of more than 10 miles. All of Great Bay and the Piscataqua River have been officially designated as impaired for the loss of eelgrass by the U.S. Environmental Protection Agency and the New Hampshire Department of Environmental Services.
Watch the brief video above, where I explain more about why eelgrass is so critical to the Great Bay ecosystem.
To correct the problem of eelgrass loss in the estuary, sewage treatment plants – the largest controllable source of nitrogen pollution – are being required to reduce their discharges of nitrogen. So, just how much progress are Seacoast communities making to address this important issue?
Several Seacoast-area communities – including Dover, Rochester, Somersworth, and Kittery, Maine – are doing quite well. All are already recording lower levels of nitrogen waste, or will be, by summer’s end. Newington, Newmarket, Durham, and Exeter are all working on either facility upgrades or new plant construction, which will allow these towns to dramatically lower their nitrogen contributions to the estuary.
The City of Portsmouth’s Peirce Island sewage treatment plant – the largest and most antiquated plant in the region, with only “primary” treatment – is finally moving in a positive direction. The City Council reaffirmed a decision to upgrade the plant to secondary treatment, which will reduce the plant’s annual discharge of total suspended solids into the Piscataqua River by hundreds of tons per year. City staff are recommending that nitrogen controls be included in the upgrade now, to save money that would be spent on retrofitting later. The exact date of these upgrades is still up in the air, but CLF will continue to monitor these developments.
With treatment plants accounting for about a third of the nitrogen pollution in the estuary, and with upgrades reducing that load significantly, there should be dramatic relief by the end of the decade. Of course, sewage treatment plants are not the only source. Stormwater runoff, septic systems, and fertilizers all contribute to the problem. It’s heartening to see some communities coming to grips with these issues; it’s imperative if we want clean water and healthy ecosystems in our Great Bay backyard.