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Nahant, MA |
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History |
Throughout its history, Nahant has been a summer resort town. It is located less than 9 miles away from Boston, on the rocky shores of Essex County in Massachusetts.
During Colonial times, Nahant was an agricultural town, providing grazing lands for cattle, sheep and goats. However, it quickly became a small maritime village with most, if not all of its residents heavily reliant on the fishing industry. 1803 marked the new resort town trend for Nahant with the building of its first hotel. By 1826, there was a daily steamboat trip, and a bi-daily stagecoach trip between Nahant and Boston. At this time, fishing along with shoe shops were the main businesses in the town, simply because Nahant did not have a large permanent population. In the 1840's, Nahant was celebrated as, "the summer resort of Boston's elite," (Nahant). By the end of the 19th century, Nahant began to settle down, and became a small town with a current population of around 4,000. Today, Nahant has a 3.0% unemployment rate, with an average per capita income of about $22,700. It is also the home of the Northeastern University Research Station, where our class performed research, and I collected several water samples.
History of the Sewerage System in Boston Boston and its surrounding waters have had a long history of wastewater problems. In the 17th century, dirty water from homes either flowed downhill, or was piped into the tide water in the bay. Outhouse effluent was simply buried, where it then seeped into groundwater, and contaminated several drinking wells, and spread diseases such as cholera. By the late 1800's, people thought something ought to be done about the disease ridden water, and so it was recommended that it be pumped off-shore. The two locations that would receive the waste were near Deer Island and Moon Island. The formation of the Metropolitan Sewerage Commission occurred in 1889, and their job was to manage the Boston and Cambridge sewers. Not until 1939, when 250 million gallons of sewage per day were being dumped into the harbor, was there and discussion of a primary wastewater treatment plant. It took another 13 years for the plant to officially open in 1952 on Nut Island. The Deer Island plant opened in 1968. 15-20% of the sludge discharged from the plants returned with the tides, heavily polluting the harbor. In 1984, the city of Quincy decided enough was enough, and sued the Metropolitan District Commission because of the vast amounts of pollution in the harbor. The outcome of this suit was the formation of the Massachusetts Water Resources Authority (MWRA). The MWRA then took on the huge responsibility of cleaning up Boston Harbor with the help of a $3.8 billion dollar treatment plan. Beginning with the stoppage of sludge discharge into the harbor (thanks to a new sludge-to-fertilizer facility) in 1991, clean-up actions occurred quite rapidly. The Primary treatment plant on Deer Island was completed in 1995, followed by the first phase of the secondary treatment in 1997. "For the first time, the plant met the requirements of the federal Clean Water Act," (Timeline). In 1998, the Nut Island plant was closed, and the second phase of Deer Island's secondary treatment was opened. The last step was the development of a new wastewater outfall tunnel that discharges 9.5 miles off the coast into deeper waters, and the completion of the third phase of the secondary treatment plant in 2000. How Does All of This Affect Nahant? Where the Outflow Goes:
Prior to 2000, all of the effluent was pumped directly into Boston Harbor. The effects of this were felt at Nahant, especially on the southern coast of the peninsula. Now that the wastewater is being piped 9.5 miles off the coast, into deeper waters, the harbor and Nahant are not as greatly affected, but there is some discharge that reaches the shores, and has the potential to cause some damage. "There is concern that the new outfall... might turn Massachusetts Bay into the next Boston Harbor," (Predictions). This time, the waste has the potential to not only harm the human population, but the marine ecosystem as well. Models of the Discharge Site: Two different computer simulations of what would happen to the bay when the wastewater was discharged were carried out. The first was done by the Estuarine and Coastal Ocean Model (ECOM), which was designed at Princeton University, and has been used and refined over the past 10 years. This model has been deemed very precise, and therefore, the models which it has produced for Boston Harbor can be seen as accurate representations of what may occur. The third model is a time-variable, water quality model named the Bays Eutrophication Model. Developed by the USGS, and Hydroqual Inc., it is another reliable source for predictions about the health of the bay. You can see that in each of these models, the discharge plume does reach the southern coast of Nahant. These models are from March of 1998, so where it reads current outflow, that is where the effluent was being pumped prior to the off-shore pumping that is happening today.
What is Causing the Concern? Anytime that wastewater is being dumped into open water, there will be concern about the potential health problems. There are several contaminants that have been tested for in the bay. Modeling for three of them has been done by scientists assisting the MWRA. The three that were tested were Chlorophyll a, dissolved oxygen in bottom water, and particulate organic carbon flux. I have discussed the chlorophyll a and DO models here. There are several other possible contaminants, such as iron, copper, and aluminum, which I have tested for. The full list of tests, results, and discussion of results is located on the data pages for both Nahant and Bermuda. Chlorophyll a is of concern because, if the primary and secondary treatments do little to remove nutrients such as this, the phytoplankton may grow at an unrestricted pace, causing an overgrowth of alga in the bay. The models show that there is a significant decrease in the amount of chlorophyll a for a few reasons. A greater level of dilution in the deeper waters decreases the concentrations of the nutrient. Also, "because at the new, deeper location, discharged nutrients will mostly be below the summer pycnocline in the bay," (the health).
Dissolved oxygen in water allows for marine animals, like marine vertebrates (fish), to carry out respiration underwater. The deeper you go underwater, the lower the amounts of dissolved oxygen. Outflow from the treatment plants, when it is pumped into the water, requires oxygen from the water to be degraded further. The concern is that the bottom dwelling organisms may not be getting enough oxygen to survive. "Monitoring has shown that bottom water DO [dissolved oxygen] has occasionally fallen below the standard that the new outfall site," (the health). However, thanks to the secondary treatment that has been recently implemented at Deer Island, there has been a slight, overall improvement in the amount of deep water DO in Boston Harbor and Massachusetts Bay.
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