Report: Septic systems big contributor to Great Bay pollution

Source:, May 16, 2013
By: Aaron Sanborn

Sources of nonpoint nitrogen pollution in the Great Bay estuary is spread out almost equally between septic systems, fertilizers and atmospheric pollution, according to a new report.
The N.H. Department of Environmental Services unveiled its draft report, Great Bay Nitrogen Non-Point Source Study, during a two-hour presentation Thursday at its Portsmouth field office. Release of the report was highly anticipated given the long fight between local communities and the federal Environmental Protection Agency over more stringent regulation of area wastewater treatment plants.
Nonpoint sources have been identified as contributing to 68 percent of the bay’s nitrogen load with the remaining 32 percent from sewer plants along the Great Bay estuary that release nitrogen into the waterways during the treatment process
Until the release of Thursday’s report, no study had been done on the breakdown of these sources into the estuary. Ted Diers, watershed management bureau administrator for DES, described these sources as being hidden within a “black box” until now.
“We knew it was there, but we didn’t know what was inside,” he said. “My hope for the study is that it generates much discussion and planning for a future that includes a Great Bay with less nitrogen input.”
The report indicates 33 percent of nonpoint nitrogen pollution in the estuary comes from atmospheric deposition, while human waste from septic systems and chemical fertilizer each contributed 27 percent. Animal waste was cited for 13 percent.
Atmospheric deposition of nitrogen comes largely from pollution, such as reactive nitrogen from fossil fuel combustion for power generation or automobiles, that enters the watershed in the form of air pollution that settles onto land surface. The report determined 62 percent of the nitrogen pollution from atmospheric deposition comes from out-of-state sources.
For chemical fertilizers, the report determined fertilizers on crops and residential lawns contributed equally to the Great Bay’s pollution at 48 percent each, with the other 4 percent of fertilizer pollution coming from managed turf, such as golf courses and athletic fields. Diers said several fertilizer companies have agreed to remove phosphorus from their fertilizers and there’s state legislation supported by the House and Senate that also seeks to limit phosphorus in fertilizers.
“It means a reduction (of pollution to the bay) but we don’t know how much at this point,” he said.
There was some variance in nonpoint contributors among all of the waterways that make up the estuary, but for the most part the contributors in the individual waterways were consistent with the overall results, Diers said. As expected, highly populated areas such as Dover, Portsmouth and Rochester contributed the most nonpoint pollution to the estuary. Diers said a combination of development and a steady mixture of both septic and sewer systems contributed to this.
The report also notes that nonpoint nitrogen pollution gets into the estuary in a number of different ways, with stormwater accounting for 25 percent of pollution transport.
While the draft report provided communities with new data, no specific policies for remediation were discussed in it.
Stratham Town Administrator Paul Deschaine said the report is a lot to digest. “I didn’t see any great surprises in it,” he said. “But it’s good to have more documentation to validate some of our normal presumptions.”
Deschaine said the next step should be to discuss strategies for cutting down on the pollution and the potential costs associated with those strategies.
Exeter Public Works Director Jennifer Perry agreed, saying the report is a good starting point for those discussions. “We can start to get a sense of what we can focus on and reasonable efforts we can make,” she said.
Diers stressed the report is just a draft and open for public comment until June 17. Once a final report is prepared, next steps could include discussions on remediation strategies and costs. “We hope this helps to frame the start of the discussion, but at the end of the day there are two things people will probably consider and that’s money and money,” he said.
Increased nitrogen in the estuary has been blamed for the loss of eelgrass, a critical habitat for fish and other marine species.
Nitrogen pollution from wastewater treatment facilities along the Great Bay estuary have dominated discussion to date in efforts to clean up the bay, largely because of high cost estimates to upgrade and build new sewer plants to meet the EPA’s new mandates to reduce nitrogen emissions.
Exeter and Newmarket have committed to EPA permits that give them a certain amount of time to build new wastewater treatment plants and up to 15 years to reduce to 3 milligrams per liter the amount of nitrogen they release into the estuary during the treatment process. While those towns accepted the EPA permits, Portsmouth, Dover and Rochester are advocating for a less stringent nitrogen release limit of 8 milligrams per liter, and filed litigation against the EPA, challenging the science behind the permits.
To view the full report and supporting documents, visit

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