2012 overview
Massachusetts Water Resources Authority · from the MWRA · 84 pages · 8.3 MB
open the file ↗ · original at the source ↗
2012 Outfall Monitoring Overview Massachusetts Water Resources Authority Environmental Quality Department Report 2013-14 Citation: Werme C, Keay KE, Hall MP, Leo WS, Mickelson MJ, Taylor DI, Rex AC, Libby, PS. 2013. 2012 outfall monitoring overview . Boston: Massachusetts Water Resources Authority. Report 2013-14. 68 p. 2012 Outfall Monitoring Overview prepared by Christine Werme Independent Consultant Berkeley, CA 94705 and Kenneth E. Keay, Maurice P. Hall, Wendy S. Leo, Michael J. Mickelson, David I. Taylor, Andrea C. Rex Massachusetts Water Resources Authority Environmental Quality Department 100 First Avenue Charlestown Navy Yard Boston, MA 02129 and P. Scott Libby Battelle 397 Washington Street Duxbury, MA 02332 October 10, 2013 2012 Outfall Monitoring Panel and Committees Outfall Monitoring Science Advisory Panel (OMSAP) Andrew Solow (chair), Woods Hole Oceanographic Institution Robert Beardsley, Woods Hole Oceanographic Institution Norbert Jaworski, retired (Environmental Protection Agency) Robert Kenney, University of Rhode Island Scott Nixon, University of Rhode Island Judy Pederson, Massachusetts Institute of Technology Sea Grant Michael Shiaris, University of Massachusetts, Boston James Shine, Harvard School of Public Health Juanita Urban-Rich, University of Massachusetts, Boston Inter-Agency Advisory Committee (IAAC) US Geological Survey: Michael Bothner Massachusetts Coastal Zone Management: Todd Callaghan, Jan Smith US Army Corps of Engineers: Thomas Fredette Stellwagen Bank National Marine Sanctuary: Benjamin Cowie-Haskell US Environmental Protection Agency: Matthew Liebman Massachusetts Division of Marine Fisheries: Jack Schwartz Massachusetts Department of Environmental Protection: Catherine Vakalopoulos Public Interest Advisory Committee (PIAC) Save the Harbor/Save the Bay: Patty Foley (chair), Bruce Berman MWRA Wastewater Advisory Committee: Edward Bretschneider Conservation Law Foundation: Priscilla Brooks Massachusetts Audubon Society: Robert Buchsbaum MWRA Advisory Board: Joseph Favaloro Association to Preserve Cape Cod: Maggie Geist, Tara Nye Safer Waters in Massachusetts: Sal Genovese The Boston Harbor Association: Vivi en Li i Table of Contents Summary ....................................................................................................................... v 1. Introduction ............................................................................................................... 1 2. Effluent ..................................................................................................................... 2 2012 Characterization ............................................................................................... 2 Contingency Plan Thresholds ................................................................................... 9 3. Water Column ......................................................................................................... 10 Physical Conditions ................................................................................................ 11 Water Quality .......................................................................................................... 16 Phytoplankton Communities ................................................................................... 23 Zooplankton Communities...................................................................................... 26 Stellwagen Bank National Marine Sanctuary ......................................................... 30 Contingency Plan Thresholds ................................................................................. 37 4. Sea Floor ................................................................................................................. 39 Sediment Characteristics and Tracers ..................................................................... 41 Soft-bottom Communities ....................................................................................... 43 Sediment-profile Imaging ....................................................................................... 45 Stellwagen Bank National Marine Sanctuary ......................................................... 46 Contingency Plan Thresholds ................................................................................. 48 5. Fish and Shellfish .................................................................................................... 50 Flounder Health ...................................................................................................... 51 Fish and Shellfish Chemistry .................................................................................. 52 Contingency Plan Thresholds ................................................................................. 56 6. Special Studies ........................................................................................................ 57 Marine Debris Observations ................................................................................... 57 Continuous Monitoring Data .................................................................................. 59 Primary Productivity Model Evaluations................................................................ 61 Cape Cod Bay Studies ............................................................................................ 63 Eutrophication Studies in Boston Harbor ............................................................... 64 References ................................................................................................................... 66 List of Acronyms ........................................................................................................ 68 ii List of Figures Figure 2-1. Annual rainfall in Boston in 1950–2012 and mean for the period ............. 2 Figure 2-2. Annual primary-blended and full secondary effluent flows ...................... 3 Figure 2-3. Monthly primary-blended and full secondary effluent flows during 2012 3 Figure 2-4. Annual solids discharges ............................................................................ 4 Figure 2-5. Annual biochemical oxygen demand ......................................................... 5 Figure 2-6. Annual nitrogen discharges ........................................................................ 6 Figure 2-7. Annual metals discharges ........................................................................... 7 Figure 2-8. Annual mercury discharges ........................................................................ 7 Figure 2-9. Annual PCBs and pesticides discharges .................................................... 8 Figure 3-1. Water-column monitoring stations ........................................................... 10 Figure 3-2. Flows of the Merrimack and Charles rivers were low throughout much of the year, reflecting the relatively dry year .................................................................. 12 Figure 3-3. Average wind stress at NDCB Buoy 44013 ............................................. 12 Figure 3-4. Nearfield surface- and bottom-water temperature ................................... 13 Figure 3-5. Nearfield surface- and bottom-water salinity........................................... 14 Figure 3-6. Nearfield surface- and bottom-water dissolved oxygen concentrations .. 14 Figure 3-7. Bottom-water dissolved oxygen concentration at stations in Massachusetts and Cape Cod bays during the nine surveys conducted in 2012................................. 15 Figure 3-8. Bottom-water dissolved oxygen concentrations at NERACOOS Buoy A01 near Cape Ann and nearby MWRA stations, 2010–2012 ................................... 16 Figure 3-9. Mean nutrient concentrations at Station N18 in 2012, compared to 2011 and other prior years ................................................................................................... 17 Figure 3-10. Depth-averaged ammonium by station in Massachusetts and Cape Cod bays ............................................................................................................................. 18 Figure 3-11. (Top) Surface- and bottom-water ammonium on March 20, 2012 at the monitoring stations during mixed conditions. (Bottom) Cross-sections of concentrations at other depths along transects connecting selected stations, showing that the plume reached surface waters ........................................................................ 19 Figure 3-12. (Top) Surface- and bottom-water ammonium on May 15, 2012 at the monitoring stations during stratified conditions. (Bottom) Cross-sections of concentrations at other depths along transects connecting selected stations .............. 20 Figure 3-13. Surface-water chlorophyll fluorescence by station in Massachusetts and Cape Cod bays ............................................................................................................ 21 Figure 3-14. Moderate Resolution Imaging Spectroradiometer satellite imagery of surface chlorophyll concentrations in 2012 ................................................................ 22 Figure 3-15. Phaeocystis pouchetii abundance during the 2012 bloom ..................... 23 Figure 3-16. Mean nearfield abundance of Phaeocystis pouchetii, 1992–2012 ......... 24 Figure 3-17. Alexandrium fundyense bloom in 2012 .................................................. 25 Figure 3-18. Nearfield abundance of Alexandrium fundyense, 1992–2012................ 25 Figure 3-19. Total zooplankton abundance in 2012 ................................................... 27 iii Figure 3-20. Nearfield abundance of total zooplankton, Oithona similis , and Calanus finmarchicus in 2011 and 2012 compared to past years ............................................. 28 Figure 3-21. Long-term trend in zooplankton abundance and multi-year mean derived from a time-series analysis.......................................................................................... 29 Figure 3-22. Bottom water dissolved oxygen concentrations in Stellwagen Basin in 2012 compared to the previous years of monitoring .................................................. 30 Figure 3-23. Location of west-east transect from Deer Island, across MWRA outfall, through Stellwagen Bank, for modeled water-quality parameters presented in Figures 3-24 through 3-27 ....................................................................................................... 31 Figure 3-24. Modeled dissolved oxygen concentration on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December 2012 .................................................... 32 Figure 3-25. Modeled percent dissolved oxygen saturation on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December in 2012 ........................................... 33 Figure 3-26. Modeled dissolved inorganic nitrogen concentrations on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December in 2012 ............................... 34 Figure 3-27. Modeled chlorophyll concentrations on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December in 2012 ........................................................ 35 Figure 3-28. Surface-water phytoplankton abundance and composition at MWRA Cape Cod Bay stations, including Station F29 near Stellwagen Bank National Marine Sanctuary..................................................................................................................... 36 Figure 3-29. Zooplankton abundance and composition at MWRA Cape Cod Bay stations, including Station F29 near Stellwagen Bank National Marine Sanctuary. .. 37 Figure 4-1. Soft-bottom monitoring stations .............................................................. 39 Figure 4-2. Sediment-profile imaging stations ........................................................... 40 Figure 4-3. Concentrations of Clostridium perfringens spores, normaled for sediment grain size, in 2012 ....................................................................................................... 42 Figure 4-4. Mean concentrations of Clostridium perfringens spores during the baseline and outfall-discharge years ........................................................................... 42 Figure 4-5. Mean infaunal abundance per sample in four areas of Massachusetts Bay, 1992–2012................................................................................................................... 43 Figure 4-6. Mean abundance per sample of five dominant species and total abundance at nearfield stations, 1992–2012 ................................................................................. 44 Figure 4-7. Annual apparent color RPD depth for data from nearfield stations ......... 45 Figure 4-8. Thumbnail images from Station NF24, located within two kilometers of the outfall .................................................................................................................... 46 Figure 4-9. Soft-bottom community data superimposed on a non-metric multidimensional scaling plot, a multivariate analyses tool ....................................... 47 Figure 4-10. Annual community parameters with nearfield Contingency Plan thresholds .................................................................................................................... 49 Figure 5-1. Fish-and-shellfish monitoring stations ..................................................... 50 iv Figure 5-2. Annual prevalence of centrotubular hydropic vacuolation, corrected for age ............................................................................................................................... 52 Figure 5-3. PCBs in flounder fillets, 1995–2012 ........................................................ 53 Figure 5-4. PCBs in flounder livers, 1995–2012 ........................................................ 53 Figure 5-5. PCBs in lobster meat, 1994–2012 ............................................................ 54 Figure 5-6. PCBs in deployed mussels, 1991–2012 ................................................... 55 Figure 5-7. Lead in deployed mussels, 2012 .............................................................. 55 Figure 6-1. Net used for sampling floatable marine debris ........................................ 57 Figure 6-2. Marine debris in net tow samples, 2000–2012......................................... 58 Figure 6-3. Temperature and dissolved oxygen at the NERACOOS Buoy A01, NDBC Buoy 44013, and during water quality surveys, June 2009 – December 2012 ........... 60 Figure 6-4. Areal productivity and BZpI0 for individual stations ............................... 62 Figure 6-5. Areal productivity and BZpI0 for monitoring seasons .............................. 62 Figure 6-6. The Center for Coastal Studies monitors its own eight stations and three MWRA stations in and near Cape Cod Bay ............................................................... 63 Figure 6-7. Right whale sightings in Cape Cod Bay, 1998–2012 .............................. 64 Figure 6-8. Time series plots of Boston Harbor water quality, 1994–2012 ............... 65 List of Tables Table i. Effluent Contingency Plan thresholds and exceedances ................................. v Table ii. Water column Contingency Plan thresholds and exceedances ..................... vii Table iii. Sea floor Contingency Plan thresholds and exceedances ........................... viii Table iv. Fish and shellfish Contingency Plan thresholds and exceedances ............... ix Table 2-1. Contingency Plan threshold values and 2012 results for effluent monitoring ..................................................................................................................... 9 Table 3-1. Contingency Plan threshold values and 2012 results for water-column monitoring ................................................................................................................... 38 Table 4-1. Contingency Plan threshold values and 2012 results for sea-floor monitoring ................................................................................................................... 48 Table 5-1. Contingency Plan threshold values and 2012 results for fish-and-shellfish monitoring ................................................................................................................... 56 v Summary Each year, the Massachusetts Water Resources Authority (MWRA) prepares this report, an overview of environmental monitoring related to the discharge of municipal effluent from the Deer Island Treatment Plant through its Massachusetts Bay outfall. The report presents monitoring results and information relevant to the MWRA’s permit-required Contingency Plan, including threshold exceedances and permit violations, responses, and corrective actions. The overview also includes monitoring results relevant to the Stellwagen Bank National Marine Sanctuary and information on special studies. The 2012 report marks the twenty-first year of MWRA’s monitoring program, including almost nine years of baseline monitoring and more than twelve years of “outfall- discharge” monitoring, covering the years since MWRA ceased discharge of sewage effluent to the relatively confined waters of Boston Harbor and began to discharge into deeper water in Massachusetts Bay. The monitoring program reports on results from effluent, water-column, sea-floor, and fish-and-shellfish monitoring in the outfall nearfield and at reference stations and on results from special studies. Operations at the Deer Island Treatment Plant continued to be exceptional in 2012, earning MWRA a second consecutive National Association of Clean Water Agencies (NACWA) Platinum Peak Performance Award. This NACWA award recognizes facilities with 100% permit compliance for five consecutive years. Ambient monitoring results from 2012 were consistent with predictions and past results. There were exceedances of Contingency Plan “caution level” thresholds 1 (Tables i through iv) for presence of Phaeocystis pouchetii , a nuisance algal species that is poor food for zooplankton; Alexandrium fundyense , a nuisance algal species that can cause paralytic shellfish poisoning; and for two soft-bottom benthic community parameters, Shannon-Wiener diversity and Pielou’s evenness. No “warning level” exceedances were observed in 2012 These exceedances have been reviewed for evidence of whether they were or were not caused or exacerbated by the outfall discharge. Blooms of Phaeocystis pouchetii are greatly influenced by temperature patterns and have not been found to be influenced by the outfall. Presence and abundance of Alexandrium fundyense is controlled by the presence and extent of seed beds to the northeast of Massachusetts Bay and on 1 MWRA’s NPDES permit includes Contingency Plan threshold indicators that may indicate a need for action. The thresholds are based on permit limits, state water quality standards, and expert judgment. “Caution level” thresholds generally indicate a need for a closer look at the data to determine the reason for an observed change. “Warning level” thresholds are a higher level of concern, and the permit requires a series of steps to evaluate whether adverse impacts occurred and if so, whether they were related to the discharge. If caused by the discharge, MWRA may need to implement corrective action. Thresholds based on effluent discharge permit limits are only “warning level.” Some ambient parameters have both “caution” and “warning” level thresholds, and others have only “caution level” thresholds. vi temperature, wind, and current patterns in the spring. The pattern of Alexandrium abundance in 2012 was unusual. In 2012 highest cell abundances were observed in Boston Harbor, the western portions of the nearfield, and along the Boston south shore, while counts in northern Massachusetts Bay were consistently much lower (i.e. the bloom did not begin in the north and move south as previous blooms have). Evaluation of the 2012 Alexandrium bloom found no evidence effluent nutrients played a major role, and indicates the unusual pattern may have resulted from the mild wind and weak currents that occurred during the bloom. However, the available data do not allow conclusions to be drawn as to the causes of the bloom. The exceedances in the benthic community parameter thresholds, which occurred for a third consecutive year, were indications of a somewhat more diverse community, resulting from normal cycles of relative abundance in the animal populations. Increased diversity is not considered to be environmentally adverse, and the changes are not thought to be related to the outfall. Table i. Effluent Contingency Plan thresholds and exceedances. = no exceedance, NA = not applicable, W = warning level exceedance Effluent Parameter 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 pH W Fecal coliform bacteria, monthly Fecal coliform bacteria, weekly Fecal coliform bacteria, daily W W Fecal coliform bacteria, 3 consecutive days Chlorine residual, daily W Chlorine residual, monthly Total suspended solids, weekly W Total suspended solids, monthly W cBOD, weekly cBOD, monthly Acute toxicity, mysid shrimp Acute toxicity, fish Chronic toxicity, fish W W Chronic toxicity, sea urchin W W PCBs Plant performance Flow NA Total nitrogen load NA Floatables NA NA NA NA NA NA NA NA NA NA NA NA NA Oil and grease vii Table ii. Water column Contingency Plan thresholds and exceedances. = no exceedance, NA = not applicable, C = caution level exceedance Water Column Parameter 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Nearfield bottom water Dissolved oxygen concentration Dissolved oxygen saturation C Dissolved oxygen depletion rate NA Stellwagen Basin bottom water Dissolved oxygen concentration Dissolved oxygen saturation C Nearfield chlorophyll Annual NA Winter/spring NA Summer NA C Autumn C Nearfield nuisance algae Phaeocystis pouchetii Winter/spring NA C C Summer NA C C C C C C Autumn Nearfield nuisance algae Pseudonitzchia Winter/spring NA Summer NA Autumn Nearfield nuisance algae Alexandrium Any sample C C C C C C Farfield shellfish PSP toxin extent Plume Initial dilution NA Complete viii Table iii. Sea floor Contingency Plan thresholds and exceedances. = no exceedance, NA = not applicable, C = caution level exceedance Sea Floor Parameter 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Nearfield sediment Acenaphthene NA NA NA NA NA NA NA NA Acenaphylene NA NA NA NA NA NA NA NA Anthracene NA NA NA NA NA NA NA NA Benzo(a)anthracene NA NA NA NA NA NA NA NA Benzo(a)pyrene NA NA NA NA NA NA NA NA Cadmium NA NA NA NA NA NA NA NA Chromium NA NA NA NA NA NA NA NA Chrysene NA NA NA NA NA NA NA NA Copper NA NA NA NA NA NA NA NA Dibenzo(a,h)anthracene NA NA NA NA NA NA NA NA Fluoranthene NA NA NA NA NA NA NA NA Fluorene NA NA NA NA NA NA NA NA Lead NA NA NA NA NA NA NA NA Mercury NA NA NA NA NA NA NA NA Naphthalene NA NA NA NA NA NA NA NA Nickel NA NA NA NA NA NA NA NA p,p’-DDE NA NA NA NA NA NA NA NA Phenanthrene NA NA NA NA NA NA NA NA Pyrene NA NA NA NA NA NA NA NA Silver NA NA NA NA NA NA NA NA Total DDTs NA NA NA NA NA NA NA NA Total HMW PAH NA NA NA NA NA NA NA NA Total LMW PAH NA NA NA NA NA NA NA NA Total PAHs NA NA NA NA NA NA NA NA Total PCBs NA NA NA NA NA NA NA NA Zinc NA NA NA NA NA NA NA NA Sediment RPD depth NA Nearfield soft-bottom benthic diversity Species per sample NA Fisher’s log-series alpha NA Shannon diversity NA C C C Pielou’s evenness NA C C C Nearfield soft-bottom species composition Percent opportunists NA ix Table iv. Fish and shellfish Contingency Plan thresholds and exceedances. = no exceedance, NA = not applicable, C = caution level exceedance Fish and Shellfish 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Nearfield flounder tissue Total PCBs NA NA NA NA NA NA NA Mercury NA NA NA NA NA NA Chlordane NA NA NA NA NA NA NA Dieldrin NA NA NA NA NA NA NA Total DDTs NA NA NA NA NA NA NA Nearfield flounder disease Liver disease (CHV) NA Nearfield lobster tissue Total PCBs NA NA NA NA NA NA NA Mercury NA NA NA NA NA NA NA Chlordane NA NA NA NA NA NA NA Dieldrin NA NA NA NA NA NA NA Total DDTs NA NA NA NA NA NA NA Nearfield mussel tissue Total PCBs NA NA NA NA NA NA NA Lead NA NA NA NA NA NA NA Mercury NA NA NA NA NA NA NA Chlordane NA C C NA NA NA NA NA NA Dieldrin NA NA NA NA NA NA NA Total DDTs NA NA NA NA NA NA NA Total PAHs NA C C C NA NA NA NA NA NA x 1 1. Introduction Since its creation by the Massachusetts state legislature in 1984, the Massachusetts Water Resources Authority (MWRA) has worked to minimize the effects of wastewater discharge on the marine environment. The mission of what became known as MWRA’s Boston Harbor Project included reducing inflow of contaminants into the waste stream, ending biosolids discharge, improving wastewater treatment facilities, and providing better dilution of the sewage effluent discharge. Throughout MWRA’s early years, scientists conducted environmental monitoring in Boston Harbor and also in Massachusetts Bay, at the (then future) location of a relocated sewage effluent discharge. In 2000, most of the Boston Harbor Project had been completed, including the relocated effluent outfall, which diverted sewage effluent from Boston Harbor to the deeper, less confined waters of Massachusetts Bay. The outfall operates under a National Pollutant Discharge Elimination System (NPDES) permit for the Deer Island Treatment Plant (DITP) constructed as part of Boston Harbor Project. The permit was issued jointly by the U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (MADEP). The NPDES permit includes requirements for ongoing monitoring of the sewage effluent and for ambient monitoring of the receiving waters. Monitoring assesses compliance with specific permit conditions and additional conditions specified by a permit-required Contingency Plan. Background information on the monitoring program can be found in Werme et al. (2012), an updated document that describes monitoring revisions implemented in 2011. The background document, monitoring plans (MWRA 1991, 1997a, 2004, 2010), the Contingency Plan (MWRA 1997b, 2001), and area-specific technical reports are available on the technical report list at MWRA’s website, http://www.mwra.state.ma.us/harbor/enquad/trlist.html. Results from most baseline years and for each year since the outfall began to discharge have been documented in reports such as this one, the annual outfall monitoring overview. Since the Massachusetts Bay outfall came on line in 2000, the reports have included information relevant to permit requirements, including Contingency Plan threshold exceedances, responses, and corrective actions. Reports also include information relevant to the Stellwagen Bank National Marine Sanctuary. This year’s outfall monitoring overview presents results for 2012, marking the twenty-first year of MWRA’s monitoring program, including more than twelve years of outfall-discharge monitoring. Measurements include effluent, water-column, sea- floor, and fish-and-shellfish parameters, as well as special studies conducted in response to permit conditions and environmental concerns. Data specifically related to the Stellwagen Bank National Marine Sanctuary are included in the overview’s water-column and sea-floor sections. 2 2. Effluent 2012 Characterization As in past years, DITP continued to operate as designed through 2012, earning MWRA the National Association of Clean Water Agencies (NACWA) Platinum Peak Performance Award for a second consecutive year. The Platinum Award is NACWA’s highest award recognizing compliance with NPDES permit limits and is reserved for facilities that have had no permit violations for five consecutive years. It was a relatively dry year in the Boston area in comparison to other years since the outfall came on line in 2000, with precipitation about 20% below the long-term average (Figure 2-1). Total effluent flow was lower in 2012 than in any year since the outfall came on line, and virtually all the flow, 99.6%, received full primary and secondary treatment (Figure 2-2). There were no extreme or protracted storms, and consequently, storm-related discharges of primary-only effluent blended with effluent receiving full secondary treatment were relatively small and brief (Figure 2-3). Figure 2-1. Annual rainfall in Boston in 1950–2012 (black line) and mean (red line) for the period. Rainfall in 2012 was about 20% below the long-term average (red line). 0 10 20 30 40 50 60 70 Inches 3 Figure 2-2. Annual primary-blended and full secondary effluent flows. In 2012, 99.6% of effluent flow received full secondary treatment. (During large storms, flow exceeding the secondary capacity of the plant is diverted around the secondary process to prevent washing out the essential microbes that carry out secondary treatment. These diverted flows are combined with full-secondary flows before disinfection; all discharges meet permit limits.) Figure 2-3. Monthly primary-blended and full secondary effluent flows during 2012. Total flow was below average (about 350 million gallons per day) in every month throughout 2012, and there were only small amounts of primary-blended flow. 0 50 100 150 200 250 300 350 400 450 500 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Million gallons per day Primary-blended f lows Secondary f lows 0 50 100 150 200 250 300 350 400 450 500 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Million gallons per day Primary-blended f lows Secondary f lows 4 The total suspended solids load to Massachusetts Bay was just less than 10 tons per day, the lowest level recorded (Figure 2-4). Carbonaceous biochemical oxygen demand (BOD) was also at a record low in 2012, remaining well below levels that might be expected to affect ambient waters at the discharge site (Figure 2-5). Nitrogenous BOD (also shown in Figure 2-5), which is a result of the biological processes in secondary treatment and not a permit limit or Contingency Plan parameter, was lower than any level measured since 2001. Figure 2-4. Annual solids discharges . Solids discharges reached a record low in 2012. 0 5 10 15 20 25 30 35 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Tons per day 5 Figure 2-5. Annual biochemical oxygen demand (BOD). MWRA’s permit limits carbonaceous BOD, which reached a record low in 2012. Nitrogenous BOD is the result of microbiological breakdown that occurs during secondary treatment and is not regulated by the permit. Total nitrogen loads were also lower in 2012, remaining below the permit limits (Figure 2-6). The portion of the load made up of ammonium increased slightly. About 10% of the ammonium in the sewage influent is removed by secondary treatment, but the biological treatment process converts some organic forms of nitrogen to ammonium. Also, ammonium-rich liquids from the biosolids pelletizing (fertilizer) plant, built as part of the Boston Harbor Project, are reintroduced to DITP for treatment, adding to the ammonium load. As required by its permit, MWRA continually evaluates nitrogen-removal technologies, so that it could be quickly implemented, should a need arise (Bigornia-Vitale and Wu 2012). Because nitrogen loads have remained below the Contingency Plan caution threshold, and there have not been nitrogen-related adverse environmental impacts, nitrogen removal has not been required or implemented. 0 5 10 15 20 25 30 35 1998 2000 2002 2004 2006 2008 2010 2012 2014 Tons per day Carbonaceous BOD Nitrogenous BOD 6 Figure 2-6. Annual nitrogen discharges. Most of the nitrogen in the effluent is in the form of ammonium. Metals loads also decreased to record low levels in 2012 (Figure 2-7). Metals discharges are now only a small fraction of what they were before the Boston Harbor Project, when more than seven hundred fifty pounds of metals were discharged to Boston Harbor each day. Most metals meet water quality criteria in the effluent itself, while copper meets the criteria after initial dilution at the Massachusetts Bay outfall. Mercury loads were also low (Figure 2-8). Although sensitive methods have been adopted for mercury analysis, mercury is now only rarely detected in effluent samples, the consequence of efforts on the part of MWRA and the New England states and New York to reduce mercury use, handle workplace spills, and discourage disposal practices that introduce mercury into the sewer system. Most mercury entering New England waters is from atmospheric deposition. 0 3000 6000 9000 12000 15000 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Metric tons per year Caution Threshold Other Nitrogen Species Nitrite/Nitrate Ammonium 7 Figure 2-7. Annual metals discharges. Except for copper, the metals meet receiving water quality criteria in the effluent, even without the dilution provided by the outfall. Figure 2-8. Annual mercury discharges. Mercury is only rarely detected in the effluent, and fewer than ten pounds were discharged in 2012. (Note that prior years’ outfall monitoring overviews reported loads in pounds per day.) 0 50 100 150 200 250 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Average pounds per day Silver Nickel Chromium Lead Copper Zinc 0 10 20 30 40 50 60 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 Pounds per year 8 Polychlorinated biphenyl (PCB) and pesticide loads also decreased in 2012 and were similar to loads discharged in 2007 and 2009 (Figure 2-9). About two pounds of PCBs and two pounds of pesticides were discharged. All contaminant loads remained well below those that had been anticipated during the planning process for the relocated outfall. Those predictions had been that more than 10 pounds of the pesticide DDT and its breakdown products and more than 100 pounds of PCBs would be discharged each year. Figure 2-9. Annual PCBs and pesticides discharges. New methods were implemented in 2006 to detect these compounds, which are present at very low levels. PCBs and the pesticides DDT and chlordane were banned in the 1970s and 1980s but persist in the environment (4-4’ DDE is a DDT breakdown product and the only form detected in the effluent). (Note that prior years’ outfall monitoring overviews reported loads in pounds per day.) 0 1 2 3 4 5 6 7 2006 2007 2008 2009 2010 2011 2012 Pounds per year PCB congeners 4-4' DDE Chlordane 9 Contingency Plan Thresholds DITP had no permit violations, and there were no exceedances of the Contingency Plan effluent thresholds in 2012 (Table 2-1). For a second consecutive year, DITP achieved the NACWA Platinum Award for facilities having five consecutive years with 100% permit compliance. Table 2-1. Contingency Plan threshold values and 2012 results for effluent monitoring. cBOD = carbonaceous biological oxygen demand, NOEC = no observable effect concentration, LC50 = 50% mortality concentration, NA = not applicable Parameter Caution Level Warning Level 2012 Results pH None <6 or >9 Not exceeded Fecal coliform bacteria None 14,000 fecal coliforms/100 ml (monthly 90 th percentile, weekly geometric mean, maximum daily geometric mean, and minimum of 3 consecutive samples) Not exceeded Chlorine, residual None 631 μg/L daily, 456 μg/L monthly Not exceeded Total suspended solids None 45 mg/L weekly 30 mg/L monthly Not exceeded cBOD None 40 mg/L weekly, 25 mg/L monthly Not exceeded Toxicity None Acute: effluent LC50<50% for shrimp and fish Chronic: effluent NOEC for fish survival and growth and sea urchin fertilization <1.5% effluent Not exceeded PCBs Aroclor=0.045 ng/L None Not exceeded Plant performance 5 violations/year Noncompliance >5% of the time Not exceeded Flow None Flow >436 mgd for annual average of dry days Not exceeded Total nitrogen load 12,500 mtons/year 14,000 mtons/year Not exceeded Floatables NA Oil and grease None 15 mg/L weekly Not exceeded 10 3. Water Column The water-column monitoring program measures physical processes and water quality and studies phytoplankton and zooplankton at stations at the mouth of Boston Harbor, in Massachusetts Bay, and in Cape Cod Bay (Figure 3-1). Figure 3-1. Water-column monitoring stations. Also shown are two instrumented buoys, one operated by the Northeastern Regional Association of Coastal and Ocean Observing Systems (NERACOOS) and the other by the National Data Buoy Center (NDBC); the MWRA outfall diffuser; and the Stellwagen Bank National Marine Sanctuary. 11 The revised water-column monitoring plan implemented in 2011 (MWRA 2010, Werme et al. 2012) includes nine annual surveys at fourteen stations. Monitoring includes sampling for vertical profiles of physical, chemical, and biological characteristics in the area around the outfall (the nearfield), where some effects of the effluent were expected and have been observed. Similar measurements are carried out at farfield reference stations, including stations in Cape Cod Bay and near the Stellwagen Bank National Marine Sanctuary. Additional surveys are conducted and stations sampled in response to Alexandrium fundyense red tide blooms. The field monitoring program is augmented by measurements on two instrumented buoys, the Northeastern Regional Association of Coastal and Ocean Observing Systems (NERACOOS) Buoy A01 and the National Oceanic and Atmospheric Administration’s National Data Buoy Center (NDBC) Buoy 44013, and by satellite imagery. The program also benefits from collaboration with the Center for Coastal Studies at Provincetown, which conducts a monitoring program in Cape Cod Bay (see Section 6, Special Studies). The Center for Coastal Studies also conducts MWRA’s monitoring at stations in Cape Cod Bay and the Stellwagen Bank National Marine Sanctuary. Regulators have set a target that, whenever possible, sampling in Cape Cod Bay should occur within 48 hours of MWRA Massachusetts Bay sampling and that any failure to meet that schedule should be reported in the annual outfall monitoring overview. Except for one survey, in the first two years of sampling under the new monitoring plan, sampling in Cape Cod Bay was completed within 24 hours of sampling in Massachusetts Bay. For that one survey (May 14–20, 2011), inclement weather delayed sampling in Massachusetts Bay until six days after the Cape Cod Bay survey had been completed. All 2012 sampling was completed within the regulatory schedule. Physical Conditions Monitoring has shown that the water column in the vicinity of the outfall and throughout Massachusetts and Cape Cod bays is heavily influenced by river inflows, weather, and other physical factors. Information about physical conditions has proven key to interpreting the annual monitoring data. The year 2012 was notably drier than other recent years (noted in Section 2, Effluent), with an unusually warm winter, a mixing event in June, and Hurricane Sandy in the fall. The relatively dry conditions followed a period of wetter years in the Boston area and resulted in river discharges that were below average compared to 1992–2011 (Libby et al. 2013). Flows from both the Merrimack and Charles rivers were below average in every season and especially lower than average during the spring months (Figure 3-2). 12 Figure 3-2. Flows of the Merrimack (top) and Charles (bottom) rivers were low throughout much of the year, reflecting the relatively dry year. Flows from both rivers were low, especially during April–June, with flows translating to only the 12 th percentile for flows throughout the period. Even lower flows translated to higher percentiles during July–August, because flows are more typically low in the summer. Wind conditions promoted strong upwelling conditions in May, July, August, and September (Figure 3-3). In early June, a storm with winds from the northeast broke that pattern. Strong downwelling conditions late October and early November were caused by Hurricane Sandy, which reached the region on October 29. Figure 3-3. Average wind stress at NDBC Buoy 44013. Positive values indicate winds from the south or southwest, which result in upwelling-favorable conditions; negative values indicate winds from the north or northeast, which favor downwelling. The dip in June corresponds to a storm with winds from the northeast, and the strong decline in the fall corresponds to Hurricane Sandy. 12 th 36 th percentile 26 th 45 th 12 th 21 st percentile 31 st 21 st 13 Nearfield surface- and bottom-water temperatures were higher than average throughout the late winter and spring, setting record highs for some surveys (Figure 3-4). Warm, calm weather heated surface waters in late May. Then in early June, a storm mixed warm surface waters down to the bottom, causing a strong spike in the temperature of bottom waters. The persistent upwelling following that event kept temperatures lower through the rest of the year, within the range for the monitoring program. Figure 3-4. Nearfield surface- and bottom-water temperature. Water temperatures were particularly warm, during the early part of the year, reaching record highs for the monitoring program during some surveys . Surface- and bottom-water salinities began the year within normal ranges but, because of the dry conditions, did not show the typical drop during the spring, when runoff usually introduces fresh water to the bays (Figure 3-5). Record high salinities were recorded for May, and relatively high levels persisted throughout the duration of field sampling for the year. Dissolved oxygen concentrations were lower than normal in the winter, and in May, bottom water dissolved oxygen levels reached record lows for that month (Figure 3-6, 3-7). Upwelling in late May and the mixing event in June may have prevented further drops, and through the rest of the summer and fall, concentrations were low but falling at a typical rate. The time-series data from the NERACOOS A01 buoy located off Cape Ann corresponded well with the survey data and documented the continued decline in bottom-water levels through mid-October (Figure 3-8). For much of Massachusetts Bay, stratification persisted until Hurricane Sandy reached the area on October 29. Another storm, with winds from the northeast, followed the hurricane, and by early November, the water column was well-mixed. 14 Figure 3-5. Nearfield surface- and bottom-water salinity . Salinity was high due to the relatively dry conditions throughout the year. Figure 3-6. Nearfield surface- and bottom-water dissolved oxygen concentrations. Dissolved oxygen concentrations were relatively low, although even lower values would be expected based on the warmer than average bottom temperatures and higher than average bottom salinity measurements. 15 Figure 3-7. Bottom-water dissolved oxygen concentration (mg/L) at stations in Massachusetts and Cape Cod bays during the nine surveys conducted in 2012. Several panels show additional data from MWRA’s in-house Boston Harbor monitoring surveys when those surveys were within a few days of the outfall monitoring surveys. Feb 06 Mar 20 Apr 10 May 15 Jun 19 Jul 26 Aug 21 Sep 06 Oct 23 4 5 6 7 8 9 mg/L 16 Figure 3-8. Bottom-water dissolved oxygen (DO) concentrations at NERACOOS Buoy A01 near Cape Ann and nearby MWRA stations, 2010–2012. Buoy and survey data were in good agreement during all three years. In 2012, the buoy data showed a continual decline in bottom water dissolved oxygen concentrations until mid-October and a return to mixed conditions by early November. Water Quality Water quality measurements for 2012, including quantification of nutrients and phytoplankton biomass (measured as chlorophyll), followed typical annual cycles and continued to confirm predictions that although there would be a measureable increase in levels of some parameters at stations very near the outfall, there would be no unexpected adverse effects (Libby et al. 2013). Nutrient concentrations were somewhat lower than most years during the February and March surveys, possibly due to the dry year with limited runoff, but overall, concentrations of the major nutrients important to phytoplankton growth fell into the ranges observed throughout the monitoring program (Figure 3-9). 5 6 7 8 9 10 11 12 Oxygen concentration (mg/l) Cape Ann (NERACOOS A01, 50 m) Survey deep DO (stations near Cape Ann buoy, 40-60 m) 17 Figure 3-9. Mean nutrient concentrations at Station N18 in 2012 (black ), compared to 2011 (red) and other prior years. Spring concentrations of nitrate and silicate were low compared to 2011 and other years, probably largely because it was a much drier year, with low runoff from rivers. and possibly also due to phytoplankton blooms prior to the first MWRA survey in March. Elevated ammonium levels were apparent at the outfall in most surveys (Figure 3-10), consistent with the results from prior years. The furthest southern extent that plume- related elevated ammonium concentrations were detected was Station F15 in May. Elevated levels were seen at Station N01, to the northwest of the outfall, in September and October. As has been typical since the outfall began to discharge, the plume was found in surface waters during the winter and spring (Figure 3-11) but was confined beneath the pycnocline during the summer, stratified season (Figure 3-12). The upwelling conditions present in May brought nutrients into the upper portions of the water column, although surface nutrient levels remained low. The detectable ammonium plume did not reach the surface, but it was apparent in the nearfield. Jan Mar May Jul Sep Nov Jan 0 5 10 15 μ M Jan Mar May Jul Sep Nov Jan 0 5 10 15 μ M Jan Mar May Jul Sep Nov Jan 0 5 10 15 μ M SIO4 Jan Mar May Jul Sep Nov Jan 0 0.5 1 1.5 μ M PO4 nitrate ammonium silicate phosphate 18 Figure 3-10. Depth-averaged ammonium (μM) by station in Massachusetts and Cape Cod bays. Several panels show additional data from MWRA’s in-house Boston Harbor monitoring surveys when those surveys were within a few days of the outfall monitoring surveys. Feb 06 Mar 20 Apr 10 May 15 Jun 19 Jul 26 Aug 21 Sep 06 Oct 23 0 2 4 6 8 10 μM 19 Figure 3-11. (Top) Surface- and bottom-water ammonium on March 20, 2012 at the monitoring stations during mixed conditions. (Bottom) Cross-sections of concentrations at other depths along transects connecting selected stations, showing that the plume reached surface waters. Mar 20 Mar 20 N N S S W W E E Mar 20 surface Mar 20 bottom Distance (km) Depth (m) 0 5 10 15 20 25 30 -70 -60 -50 -40 -30 -20 -10 0 F23 N21 N04 F22 Parameter: NH4 Survey: WN122 Date: 20-Mar-2012 Distance (km) Depth (m) 0 5 10 15 20 25 30 35 -35 -30 -25 -20 -15 -10 -5 0 N01 N21 N18 F15 F10 F06 W E N S 0 2 4 6 8 10 μM 20 Figure 3-12. (Top) Surface- and bottom-water ammonium on May 15, 2012 at the monitoring stations during stratified conditions. (Bottom) Cross-sections of concentrations at other depths along transects connecting selected stations. May 15 May 15 N N S S W W E E May 15 surface May 15 bottom Distance (km) Depth (m) 0 5 10 15 20 25 30 -70 -60 -50 -40 -30 -20 -10 0 F23 N21 N04 F22 Parameter: NH4 Survey: WN124 Date: 15-May-2012 Distance (km) Depth (m) 0 5 10 15 20 25 30 35 -35 -30 -25 -20 -15 -10 -5 0 N01 N21 N18 F15 F10 F06 W E N S 0 2 4 6 8 10 μM 21 Survey surface-water chlorophyll levels peaked on March 20 (Figure 3-13). High chlorophyll levels were observed two weeks before the survey date in satellite imagery from early March (Figure 3-14), suggesting that a winter-spring bloom began before the March 7 image was made. Chlorophyll fluorescence data from the NERACOOS Buoy A01 near station F22 off Cape Ann suggested that there could have been two early chlorophyll peaks. Chlorophyll levels were also elevated in the late summer and early fall, consistent with typical fall phytoplankton bloom patterns. The satellite imagery suggests an early fall bloom, which ended by mid September, and a later bloom in late September and October. The imagery also shows high chlorophyll levels later in the year, after the survey season was complete, particularly in the shallow waters of Cape Cod Bay. Figure 3-13. Surface-water chlorophyll fluorescence by station in Massachusetts and Cape Cod bays. The highest chlorophyll concentrations were recorded during the March 20, 2012 survey, when concentrations of particulate organic carbon were also high. Feb 06 Mar 20 Apr 10 May 15 Jun 19 Jul 26 Aug 21 Sep 06 Oct 23 0 2 4 6 8 10 μg/L 22 Figure 3-14. Moderate Resolution Imaging Spectroradiometer satellite imagery of surface chlorophyll concentrations in 2012. The stars show the timing of the nine MWRA surveys, and the circles highlight blooms. The imagery shows that the spring bloom detected during the March survey began before March 7. Chlorophyll levels were high throughout the bays in late August and much of the fall. Note that these images are heavily weather dependent and do not represent consistent intervals of time. Jan 05 Jan 18 Jan 24 Feb 09 Feb 18 Feb 20 Mar 07 Mar 18 Mar 21 Mar 30 Apr 07 Apr 16 Apr 25 May 07 No Data Jul 22 Jul 30 Aug 13 Aug 26 Aug 30 Sep 03 Sep 16 Sep 24 Sep 27 Oct 13 Oct 25 Nov 04 Nov 10 Nov 22 Dec 06 Dec 24 23 Phytoplankton Communities Total abundance of phytoplankton in 2012 was near the long-term mean for the monitoring program (Libby et al. 2013). The phytoplankton communities followed typical progressions throughout the year, with two notable pulses: a predominantly offshore bloom of Phaeocystis pouchetii in March and a coastal pulse of centric diatoms ( Skeletonema spp.) in September. As in other years, microflagellates comprised the numerically dominant group. Spring blooms of the colonial flagellate Phaeocystis pouchetii have occurred every year in Massachusetts Bay over the past decade, but the 2012 bloom was unique in its early start and early peak abundance, in March rather than in April (Figure 3-15). The bloom persisted, at a low level, into the early summer. Total microflagellate abundance also peaked earlier than usual, and it is possible that both these groups were affected by the unusually warm winter. Overall, Phaeocystis abundance was somewhat high in comparison to past years (Figure 3-16). Figure 3-15. Phaeocystis pouchetii abundance during the 2012 bloom . The bloom began earlier than in some past years, in March rather than in April, and it persisted into May. Note difference in scale for May survey . Mar 20 Apr 10 May 15 0 2 4 6 8 10 0 5 10 15 20 25 Million cells L -1 Thousands cells L -1 24 Figure 3-16. Mean nearfield abundance of Phaeocystis pouchetii, 1992–2012 . (Top) winter-spring. (Bottom) summer. Centric diatom abundance peaked in September or October in all regions except the northern, offshore stations, where abundance was highest in June. No large winter- spring diatom bloom occurred in any region, but the September bloom, dominated by Skeletonema spp., was large enough that annual centric diatom abundance was near the long-term mean. The June bloom in northern waters was dominated by Thalassiosira spp. and Chaetoceros spp., primarily Chaetoceros socialis . That bloom exceeded past Chaetoceros abundances in that region. Dinoflagellate abundances in 2012 were also approximately equal to the long-term mean. The toxic dinoflagellate Alexandrium fundyense occurred at low levels in April and June, but bloomed in May (Figure 3-17). Alexandrium fundyense blooms have occurred regularly in Massachusetts Bay since 2005 (Figure 3-18). Levels in 2012 reached above the 100 cells/L limit that triggers Alexandrium rapid-response surveys. 1 10 100 1,000 10,000 100,000 1,000,000 10,000,000 Winter-spring Phaeocystis (cells/l) 1 10 100 1,000 10,000 100,000 1,000,000 Summer Phaeocystis (cells/l) baseline outfall discharge caution threshold 25 Figure 3-17. Alexandrium fundyense bloom in 2012. The late spring storm ended the bloom rather than bringing cells in from the Gulf of Maine. Figure 3-18. Nearfield abundance of Alexandrium fundyense, 1992–2012. 1 10 100 1,000 10,000 100,000 Alexandrium per sample (cells/l +1 ) baseline outfall discharge caution threshold 26 While the timing and relatively low magnitude of the 2012 bloom on a New England- wide scale had been forecast by Woods Hole researchers (based on measurements of cyst abundance in the fall of 2011), the spatial pattern in Alexandrium abundance and in paralytic shellfish poisoning (PSP) toxicity in Massachusetts Bay was unusual. The normal progression for Alexandrium blooms is that they develop in coastal Maine waters when cysts germinate and begin to multiply. The bloom then follows coastal currents south to New Hampshire and Cape Ann. If wind conditions are right, a bloom in those coastal waters can be swept into Massachusetts Bay. In 2012 the highest cell abundances were observed in Boston Harbor, the western portions of the nearfield, and along the Boston south shore, while counts in northern Massachusetts Bay were consistently much lower (i.e. the bloom did not begin in the north and move south). Also, while the bloom caused PSP toxicity and closed beds from Salem to Duxbury, there were no closures on the north shore. When MWRA discussed the bloom and the Contingency Plan threshold exceedance with regulators and OMSAP at its April 1, 2013 meeting, Panel members requested MWRA review the available data further to address whether effluent nutrients might have contributed to the unusual spatial pattern of the bloom. That review found no evidence effluent nutrients played a major role in causing the bloom. Effluent nutrient loading before and during the bloom were well within historic ranges for that time of year including the loading of ammonium, the effluent nutrient most immediately available to stimulate phytoplankton growth. The temporal and spatial patterns of nutrients before and during the 2012 Alexandrium bloom were well within the ranges observed during previous years, including years in which Alexandrium bloomed in Massachusetts Bay and years when it did not. High concentrations of nutrients did not extend further south from the outfall than is normally observed (~10- 20 km). As noted previously, 2012 was a dry year, with lower river discharges during the spring than occurs most years. Coupled with the weak and upwelling favorable winds experienced around the time of the bloom, this may have slowed circulation and increased residence times of the early season pulse of cells within Massachusetts Bay, allowing time for the small population of cells to grow to bloom levels. These weak winds also prevented transportation south of elevated cell abundances seen off the coast of Maine in late May. Unfortunately, the available data do not allow conclusions to be drawn as to the causes of this unusual bloom. It is important to note that even for an organism like Alexandrium , which has been extensively studied for decades because of its impacts on the shellfish industry, gaps remain in our understanding of all the factors involved in a bloom. Zooplankton Communities The 2012 abundances, species composition, and seasonal progressions of the zooplankton communities fell within the general patterns of past years, with highest abundances in June, July, and August (Figure 3-19) (Libby et al. 2013). Total abundance during the first survey in February was somewhat higher than typical, 27 possibly due to the warm, dry winter and possibly also an end result of an early, undetected diatom bloom (Figure 3-20). Total zooplankton abundance in February and continuing through the year was dominated by the small copepod Oithona similis and by total copepod nauplii, copepodites, and adults. Oithona feeds primarily upon microzooplankton, mostly protozoans, rather than on phytoplankton. The dominant abundance of this species in Massachusetts Bay and in other ecosystems around the world has been recognized only recently, because it is too small to be sampled by many conventional protocols. Figure 3-19. Total zooplankton abundance in 2012. Feb 06 Mar 20 Apr 10 May 15 Jun 19 Jul 26 Aug 21 Sep 06 Oct 23 0 30000 60000 90000 120000 150000 Individuals m -3 28 Figure 3-20. Nearfield abundance of total zooplankton, Oithona similis , and Calanus finmarchicus in 2011 (dashed red line) and 2012 (solid black line) compared to past years . Total zooplankton, dominated by Oithona similis , were relatively abundant in 2012. Calanus finmarchicus was almost absent in 2012, following a relatively abundant year in 2011. Jan Mar May Jul Sep Nov Jan 0 2 4 6 8 10 12 14 16 10,000 individuals/m3 TOTAL ZOOPLANKTON Jan Mar May Jul Sep Nov Jan 0 1 2 3 4 5 6 7 8 10,000 individuals/m3 Oithona Jan Mar May Jul Sep Nov Jan 0 0.5 1 1.5 2 10,000 individuals/m3 Calanus finmarchicus Total zooplankton Oithona similis Calanus finmarchicus 29 Larger abundant zooplankton taxa typically include Calanus finmarchicus , Acartia spp., and barnacle nauplii. Calanus finmarchicus and Acartia spp. were almost absent in the nearfield in 2012, following a year in which they were relatively abundant. Acartia spp. were abundant only in Boston Harbor. The dearth of Calanus finmarchicus , a known food for right whales, did not appear to affect whale abundance, as sightings by the Center for Coastal Studies remained relatively high (see Section 6, Special Studies). Time-series analysis of the zooplankton abundance data have shown that there was a decline throughout the bays during 2001–2006, but populations have rebounded since that period (Figure 3-18). Total abundance is now greater than the long-term mean. The 2001–2006 decline in total zooplankton largely reflected lower numbers of copepods during those years. Total copepod abundance has rebounded along with total zooplankton abundance. Reasons for such long-term trends are not well understood but occur on broad regional scales. There is no suggestion that the outfall discharge has affected zooplankton abundance or species composition in Massachusetts Bay. Figure 3-21. Long-term trend in zooplankton abundance and multi-year mean derived from a time-series analysis. Data are from Stations N04 and N18. 0 10000 20000 30000 40000 50000 60000 70000 1995 2000 2005 2010 2015 Total zooplankton (animals m -3 ) Trend Multi-year mean 30 Stellwagen Bank National Marine Sanctuary The NPDES permit to discharge from DITP into Massachusetts Bay requires annual reporting on results that are relevant to the Stellwagen Bank National Marine Sanctuary. Two stations are most relevant to the sanctuary, Station F22 in Stellwagen Basin to the northwest of the sanctuary and Station F29 on the sanctuary’s southern boundary. MWRA monitors dissolved oxygen concentration and saturation in Stellwagen Basin as Contingency Plan requirements. Bottom dissolved oxygen concentrations were low throughout 2012, the lowest measured during the monitoring program in late spring and early summer (Figure 3-22) (Libby et al. 2013). These levels reflected the warm, saline conditions found throughout the region in 2012. Figure 3-22. Bottom water dissolved oxygen concentrations in Stellwagen Basin in 2012 compared to the previous years of monitoring. Besides survey data, buoy data and model outputs are useful in determining water quality conditions throughout Massachusetts Bay, including the sanctuary. Data from the deep oxygen sensor on the NERACOOS Buoy A01, within the sanctuary, documented the return to oxygenated conditions with fall mixing (see Figure 3-8 and Section 6, Special Studies). Figure 3-23 shows the location of a transect running west to east across the Massachusetts Bay outfall and Stellwagen Bank, and Figures 3-24 through 3-27 depict modeled water quality parameters, including dissolved oxygen, dissolved oxygen saturation, dissolved inorganic nitrogen, and chlorophyll, along that transect. 31 Figure 3-23. Location of west-east transect from Deer Island, across MWRA outfall, through Stellwagen Bank, for modeled water-quality parameters presented in Figures 3-24 through 3-27. The model outputs supported predictions that there would be no indication of any effect of the outfall for most parameters, even in the nearfield, and no evidence of effects on the sanctuary. The model projects no effects of the outfall on dissolved oxygen concentration or saturation in any month. Elevated levels of dissolved inorganic nitrogen can be detected but only in the immediate vicinity of the outfall, with no influence on the sanctuary. Modeled chlorophyll levels show increased levels across the region in March at the time of the Phaeocystis bloom but no relation with the outfall. Note that the model tends to show less variation in chlorophyll values (such as a lower peak during the spring bloom and less difference from surface to bottom) than the field observations, but it generally captures the seasonal and geographic patterns. 32 Figure 3-24. Modeled dissolved oxygen concentration (mg/L) on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December 2012. 33 Figure 3-25. Modeled percent dissolved oxygen saturation on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December in 2012. 34 Figure 3-26. Modeled dissolved inorganic nitrogen concentrations ( μ M) on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December in 2012. 35 Figure 3-27. Modeled chlorophyll concentrations (μg/L) on the west-east transect across the MWRA outfall and Stellwagen Bank National Marine Sanctuary at the end of each month from January through December in 2012. 36 The Center for Coastal Studies monitoring program in Cape Cod Bay includes MWRA Station F29, on the southern boundary of the sanctuary as well as MWRA stations F01 and F02 in Cape Cod Bay. Major groups of phytoplankton and zooplankton followed similar abundance patterns at all three stations throughout the year (Figures 3-28 and 3-29). Phytoplankton samples showed dominance of microflagellates at all three stations during much of the year. Samples also confirmed the fall diatom bloom. Cape Cod Bay zooplankton sampling focuses on larger species than targeted by Massachusetts Bay sampling. The sampling techniques do not capture smaller copepods, such as the Oithona similis seen in MWRA’s Massachusetts Bay samples, but focuses on larger species, which are favored whale prey. Abundances of several larger species were lower than in 2011. Similar to the MWRA program, the large species Calanus finmarchicus was not abundant in any month. Figure 3-28. Surface-water phytoplankton abundance and composition at MWRA Cape Cod Bay stations, including Station F29 near Stellwagen Bank National Marine Sanctuary. (Data from the Center for Coastal Studies) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 Million cells per liter Microf lagellate Dinof lagellate Cryptophyte Pennate Diatom Centric Diatom Feb Mar Apr May Jun Jul Aug Sep Oct 37 Figure 3-29. Zooplankton abundance and composition at MWRA Cape Cod Bay stations, including Station F29 near Stellwagen Bank National Marine Sanctuary. ( Data from the Center for Coastal Studies) Contingency Plan Thresholds Most water-quality parameters were within normal ranges throughout 2012. Bottom water dissolved oxygen concentrations were consistent with the normal seasonal pattern but were low in comparison to past years, reaching minima that were only slightly above the Contingency Plan threshold baselines (Table 3-1). The low levels were due to the warm, dry conditions found in 2012 and not affected by the outfall. There were two exceedances of nuisance phytoplankton species thresholds, when samples collected in May exceeded the Phaeocystis pouchetii summer and Alexandrium fundyense caution levels. The Phaeocystis exceedance resulted from the early bloom lingering into May (which is considered summer for threshold calculation). The Alexandrium exceedance had been anticipated, based on information on overwintering Alexandrium cysts in the sediments off the coast of Maine and spring measurements of Alexandrium cells in coastal waters of Maine and New Hampshire. Results from rapid-response surveys indicated that the bloom proceeded in a pattern that was different from historic progressions, but the available data do not allow conclusions to be drawn as to the causes of this unusual bloom. 0 1000 2000 3000 4000 5000 6000 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 F01 F02 F29 Individuals per m3 Acartia Temora Pseudocalanus Centropages Calanus Feb Mar Apr May Jun Jul Aug Sep Oct 38 Table 3-1. Contingency Plan threshold values and 2012 results for water-column monitoring . DO = dissolved oxygen Location/ Parameter Specific Parameter Baseline Caution Level Warning Level 2012 Results Bottom water nearfield Dissolved oxygen concentration Background 5 th percentile 6.05 mg/L Lower than 6.5 mg/L for any survey (June- October) unless background conditions are lower Lower than 6.0 mg/L for any survey (June- October) unless background conditions are lower Lowest survey mean = 6.19 mg/L Dissolved oxygen percent saturation Background 5 th percentile 65.3% Lower than 80% for any survey (June-October) unless background conditions are lower Lower than 75% for any survey (June-October) unless background conditions are lower Lowest survey mean = 67.5% Bottom water Stellwagen Basin Dissolved oxygen concentration Background 5 th percentile 6.23 mg/L 6.5 mg/L for any survey (June- October) unless background conditions lower Lower than 6.0 mg/L for any survey (June- October) unless background conditions are lower Lowest survey mean = 6.6 mg/L Dissolved oxygen percent saturation Background 5 th percentile 67.2% Lower than 80% for any survey (June-October) unless background conditions Lower than 75% for any survey (June-October) unless background conditions are lower Lowest survey mean = 70.4% Bottom water nearfield DO depletion rate (June- October) 0.024 mg/L/d 0.037 mg/L/d 0.049 mg/L/d 0.022 mg/L/d Chlorophyll nearfield Annual 72 mg/m 2 108 mg/m 2 144 mg/m 2 96 mg/m 2 Winter/spring 50 mg/m 2 199 mg/m 2 None 144 mg/m 2 Summer 51 mg/m 2 89 mg/m 2 None 69 mg/m 2 Autumn 90 mg/m 2 239 mg/m 2 None 78 mg/m 2 Nuisance algae nearfield Phaeocystis pouchetii Winter/spring 622,000 cells/L 2,860,000 cells/L None 1,690,000 cells/L, Summer 72 cells/L 357 cells/L None 1,120 cells/L, caution level exceedance Autumn 370 cells/L 2,960 cells/L None Absent Nuisance algae nearfield Pseudo- nitzschia Winter/spring 6,735 cells/L 17,900 cells/L None 526 cells/L Summer 14,635 cells/L 43,100 cells/L None 388 cells/L Autumn 10,050 cells/L 27,500 cells/L None 2,820 cells/L Nuisance algae nearfield Alexandrium fundyense Any nearfield sample Baseline maximum = 163 cells/L 100 cells/L None 3,731 cells/L, caution level exceedance Farfield PSP toxin extent Not applicable New incidence None No new incidence 39 4. Sea Floor Sea-floor monitoring in 2012 included soft-bottom sampling for sediment conditions and infauna at 14 stations and sediment-profile imaging at 23 stations (Figures 4-1 and 4-2). Figure 4-1. Soft-bottom monitoring stations. Fourteen stations were sampled for benthic community parameters and sediment characteristics. Also shown are the instrumented buoys, the MWRA outfall diffuser, and the Stellwagen Bank National Marine Sanctuary. 40 Figure 4-2. Sediment-profile imaging stations. Twenty-three stations are monitored. Also shown are the NDBC buoy and the MWRA outfall diffuser. 41 Sampling for grain-size composition, total organic carbon, the effluent tracer Clostridium perfringens spores, and benthic infauna was completed during August, following the revised monitoring plan implemented in 2011 (MWRA 2010, Werme et al. 2012). Sediment and infauna sampling included one station in the “transition” area, located between Boston Harbor and the nearfield stations (FF12); four nearfield stations located within two kilometers of the outfall (NF13, NF14, NF17, NF24); six nearfield stations located within Massachusetts Bay but farther than two kilometers from the outfall (NF04, NF10, NF12, NF20, NF21, NF22); and three farfield reference stations located in Massachusetts Bay and Cape Cod Bay (FF01A, FF04, and FF09). For the purposes of threshold testing, “nearfield” includes the transition station, as well as both groups of nearfield stations, for a total of eleven stations. The new design provides greater consistency than the one it replaced, in which different sets of soft-bottom stations were sampled in alternate years. Sediment-profile images were made on August 12. The images were used to measure the apparent reduction-oxidation (redox) potential discontinuity (RPD) depth, apparent successional stage of the community, and an organism sediment index which is derived from the RPD depth and the successional stage. Sediment Characteristics and Tracers Grain-size distributions of sediment samples in 2012 remained consistent with results from past years, ranging from silt and clay at some stations to mostly sand at others (Nestler et al. 2013). Percent organic carbon content in the samples was also consistent with past results at most stations, with higher mean total organic carbon concentrations at stations with finer sediments. Total organic carbon concentrations showed no signs of organic enrichment from the effluent discharge, even at stations closest to the outfall. As in past years since the outfall came on line (except 2006), it was possible to detect elevated levels of the effluent tracer, Clostridium perfringens spores, at the stations located closest to the outfall, although even at these stations, concentrations fell within the baseline range (Figures 4-3 and 4-4). Concentrations of Clostridium perfringens spores were highest at Stations NF13 and NF24, both located within two kilometers of the outfall. Overall, there has been a large decline in Clostridium perfringens spores at the transition station FF12 since the baseline period. A smaller decline may also be apparent in the nearfield samples farther from the outfall, while concentrations at farfield locations have remained stable. A concurrent monitoring program for Boston Harbor has documented declines in Clostridium spore counts throughout the Boston Harbor Project, with 2012 spore counts remaining consistently below historic levels (Pembroke et al. 2013). 42 Figure 4-3. Concentrations of Clostridium perfringens spores, normalized for sediment grain size, in 2012. Figure 4-4. Mean concentrations of Clostridium perfringens spores during the baseline and outfall-discharge years. Tran = transition area, stations located between Boston Harbor and the nearfield; NF<2km = stations within 2 km of the outfall; NF>2km = nearfield stations greater than 2 km from the outfall; FF = farfield stations offshore from the outfall 43 Soft-bottom Communities The soft-bottom communities continued to show no response to the outfall relocation (Nestler et al. 2013). Monitoring has shown that community structure is determined primarily by grain-size distribution of the sediments and by natural fluctuations in populations. Data from 2012 were consistent with past years’ results. Sampling and analysis of the 14 samples taken in 2012 yielded 27,114 organisms, classified into 210 species and 30 other taxonomic groups. The numbers of organisms per sample were higher than found in 2010 and 2011 in all regions and comparable to the historic means (Figure 4-5). Relative abundances of the five dominant species in the samples, those contributing at least 5% to total abundance numbers, were low in 2012, as they has been for several years (Figure 4-6). In particular, the polychaete Prionospio steenstrupi , which was the numerically dominant species during much of the 1990s and 2000s, was present in low numbers. Figure 4-5. Mean infaunal abundance per sample in four areas of Massachusetts Bay, 1992–2012. Tran = transition area, stations located between Boston Harbor and the nearfield; NF<2km = stations within 2 km of the outfall; NF>2km = nearfield stations greater than 2 km from the outfall; FF = farfield stations offshore from the outfall Total Abundance 0 500 1000 1500 2000 2500 3000 3500 4000 4500 Outfall Startup 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 Tran NF <2km NF >2km FF 44 Figure 4-6. Mean abundance per sample of five dominant species and total abundance at nearfield stations, 1992–2012. A series of multivariate analyses assessed spatial and temporal patterns in the communities and found no particular species or type of community that could be specifically associated with the outfall. A cluster analysis, which identified six separate faunal assemblages in the region, found that three of those species groups occurred at stations within two kilometers of the outfall but also at stations farther away. Species distributions were largely determined by sediment types. Temporal analyses suggested that species assemblages have varied little since 1992 and that samples were most similar to others collected from the same station over time. These analyses are discussed further under in the subsection addressing Stellwagen Bank National Marine Sanctuary below. 45 Sediment-profile Imaging Sediment-profile imaging measurements continued to show no adverse effects of the outfall (Nestler et al. 2013). Monitoring has shown that physical processes, such as storms and storm-induced sediment transport, are the primary stressors on the sea floor. The dominance of physical forces may be considered typical of outfalls that have been located in high-energy areas that promote rapid dispersion of effluent. The RPD depth (the depth to which oxygen penetrates into sediments as determined by color changes) remained deeper than the baseline mean, as it has been during most outfall-discharge years (Figure 4-7). The environmental concern before the outfall came on line was that the RPD depth would become shallower, so a deeper RPD depth continues to indicate that there has been no adverse effect from the discharge. Figure 4-7. Annual apparent color RPD depth for data from nearfield stations. The mean RPD for the outfall-discharge years is slightly deeper than the baseline mean, indicating that there has been no adverse effect from the discharge. SD = standard deviation The sediment-profile images also found no indications of organic carbon accumulation and no adverse effects on the types of organisms inhabiting the sediments. There is no evidence of organic carbon accumulation, even at stations located close to the outfall (Figure 4-8). If organic carbon concentrations were increasing in the sediments, the images would show increased darkening at the sediment surface, but the images continue to show light-colored, oxygenated surface sediment. -6 -5 -4 -3 -2 -1 0 RPD (cm) Mean RPD Depth +/- 1SD Outf all Startup Threshold 46 Figure 4-8. Thumbnail images from Station NF24, located within two kilometers of the outfall. There are no indications of increased organic carbon content or other outfall effects. Black hash marks are at five-centimeter intervals in images made prior to 2006 (many are quite faint). Hash marks in recent images are at one-centimeter intervals. Stellwagen Bank National Marine Sanctuary The NPDES permit to discharge from DITP into Massachusetts Bay requires annual reports on results that are relevant to the Stellwagen Bank National Marine Sanctuary. One MWRA sea-floor station lies within the sanctuary, in Stellwagen Basin, which is a long-term sediment sink (FF04, see Figure 4-1). Station FF09 is adjacent to the basin, southeast of the outfall diffusers. A third sea-floor station (FF01A) is just northwest of the sanctuary boundary. No large or unexpected changes in bottom- community parameters have been measured within or near the sanctuary since the outfall came on line. 47 Sediment conditions have not changed at Station FF04, and the deep-water station continued to support infaunal communities typical of the monitoring program (Nestler et al. 2013). As would be expected because of its depth, there are some differences from the shallower communities in the nearfield and elsewhere in Massachusetts Bay. Multivariate analyses of soft-bottom fauna showed that Station FF04 has consistently contained a somewhat distinct infaunal community, in that its samples group together, apart from samples from other stations (Figure 4-9). Community differences at Station FF04 in 2010, 2011, and 2012 compared to earlier years may reflect the decreases in the abundant polychaete Prionospio steenstrupi , which has decreased in numbers throughout the region. The separate grouping reflects Station FF04’s deepwater, silty sediment, typical for Stellwagen Basin, whereas many shallower stations are sandier. Monitoring during 1992–2010 showed the faunal community currently found at Station FF04 to be widespread throughout deeper waters, with similar faunal assemblages occurring at all stations with water depths greater than 70 meters. Figure 4-9. Soft-bottom community data superimposed on a non-metric multidimensional scaling plot, a multivariate analyses tool. Each point represents one sample collected during 1992–2012. Similarity of species composition is indicated by proximity of the points on the plot. Station FF04 (located within Stellwagen Basin and almost 30 km southeast of the outfall), has consistently maintained a unique fauna in comparison to sandier stations NF13 (about 2 km north of the outfall), NF24 (less than 2 km south of the outfall), and FF01A (more than 20 km northeast of the outfall). 48 Contingency Plan Thresholds RPD depth was more than twice as deep as the caution level, and percent opportunists among the soft-bottom community remained far below caution and warning levels. However, for a third consecutive year, there were Contingency Plan threshold exceedances for sea-floor community parameters (Table 4-1). Values for two threshold parameters, Shannon-Wiener diversity and Pielou’s evenness, were higher than the caution-level ranges (Figure 4-10). Two other community threshold parameters, total number of species per sample and Fisher’s log-series alpha, were within the caution-level ranges. Similar exceedances of Shannon-Wiener diversity and Pielou’s evenness thresholds were observed in 2010 and 2011 and evaluated in consultation with the Outfall Monitoring Science Advisory Panel (OMSAP). Those evaluations found that the 2010 and 2011 exceedances probably resulted from natural fluctuations in the communities and that they were not related to any outfall effect. Spatial and temporal analyses showed that the increases in Shannon-Wiener diversity and Pielou’s evenness did not result from changes at the stations closest to the outfall. Instead, the threshold exceedances were driven by data from nearfield stations that are farther away, more than two kilometers from the outfall and less likely to be influenced by the discharge. Region-wide declines in the abundance of the numerically dominant species, particularly the spionid polychaete Prionospio steenstrupi , are likely important factors in the recent increases. Increases in Shannon-Wiener diversity and Pielou’s evenness can be a signal of improvements rather than degradation in environmental conditions. However, the Contingency Plan community measures thresholds were selected to be triggered by any results that would indicate a change from baseline conditions, and consequently, they have upper as well as lower bounds. Table 4-1. Contingency Plan threshold values and 2012 results for sea-floor monitoring. Location/ Parameter Type Parameter Caution Level Warning Level 2012 Results Nearfield RPD depth <1.18 cm None 3.441 cm Even years, benthic diversity, nearfield Species per sample 442.99 or >81.85 None 73.45 Fisher’s log-series alpha <9.42 or >15.8 None 15.68 Shannon-Wiener diversity <3.37 or >3.99 None 4.36, caution level exceedance Pielou’s evenness <0.57 or >0.67 None 0.70, caution level exceedance Benthic opportunists % opportunists >10% >25% 0.16 % 49 Figure 4-10. Annual community parameters with nearfield Contingency Plan thresholds. The varied symbols represent differences in the stations sampled over the years of the program. Results were tested against thresholds calculated for each sampling design, but only the current threshold values are shown. Except for the percent opportunists threshold, which is based on levels in Boston Harbor, thresholds have both upper and lower bounds show potentially meaningful changes from the baseline. SD = standard deviation 30 50 70 90 Species per sample 6 10 14 18 Fisher's log-series alpha 2.5 3.0 3.5 4.0 4.5 5.0 Shannon-Wiener diversity 0.4 0.5 0.6 0.7 0.8 Pielou's evenness 0 3 6 9 12 Percent opportunists Baseline mean Thresholds Mean +/-1SD Outfall startup 50 5. Fish and Shellfish Each year MWRA monitors the health of winter flounder from Deer Island Flats in Boston Harbor, off Nantasket Beach just outside the harbor, the Massachusetts Bay outfall site, and eastern Cape Cod Bay. Every three years, including 2012, monitoring includes chemistry measurements in flounder fillets and liver, lobster meat and hepatopancreas, and blue mussel tissue. Lobsters are sampled from Deer Island Flats, the outfall site, and Cape Cod Bay. Mussels are deployed at two sites near the outfall, at Deer Island Light, and in Boston’s inner harbor (Figure 5-1). Figure 5-1. Fish-and-shellfish monitoring stations. Also shown are the two instrumented buoys, the MWRA outfall diffuser, and the boundaries of the Stellwagen Bank National Marine Sanctuary. 51 Flounder Health Annual flounder monitoring focuses on the presence of early liver disease and liver neoplasms (tumors). Other indications of health are also documented. In April 2012, 50 sexually mature flounder were collected from each site (Moore et al. 2012). Catch per unit effort remained low near the outfall and off Nantasket Beach, as has been typical, and there was a small decrease in eastern Cape Cod Bay, although the catches there remained the highest of the regions. Catch per unit effort increased at Deer Island Flats to the highest levels observed since 2005. Abandoned fishing gear continued to interfere with catches at the outfall site and Deer Island Flats. Average ages, lengths, and weights of the winter flounder collected from near the outfall site in 2012 were lower than in most years. Average age fell at all locations except Deer Island Flats, but remained within the historic range for the monitoring program. As they have been throughout most of the monitoring program, the catches continued to be dominated by females. The percent females increased at all sites, to more than 95% at Nantasket Beach and eastern Cape Cod Bay. External condition measures also fell within historic ranges. Prevalence of fin erosion, a condition that can be indicative of elevated concentrations of ammonium and other pollutants, was highest at Deer Island Flats and within the historic range of the monitoring program, continuing to be much lower than had been observed in other studies during the 1980s. The greatest percentage of another common condition, bent fin ray, also occurred at Deer Island Flats. Incidence of blind-side ulcers, which were first noted in 2003, decreased substantially from 2011 and were present only at Nantasket Beach and the outfall site. No neoplasms were observed in any fish from any site. Incidence of neoplasia has been rare throughout the area since routine monitoring started in 1991, although levels were as high as 12% in flounder taken from Boston Harbor for studies during the 1980s. Neoplasia has never been observed in a fish taken from the outfall site. The incidence of centrotubular hydropic vacuolation (CHV), a mild condition associated with exposure to contaminants, remained lower than the baseline observations. Incidence of CHV, corrected for age, continued to drop in fish taken near the outfall site after a gradual increase observed during 2005–2010 (Figure 5-2). CHV incidence in fish from Deer Island Flats remained lower than the relatively high baseline levels and about the same as was measured in 2011. Average severity of CHV also remained lower than baseline levels. 52 Figure 5-2. Annual prevalence of centrotubular hydropic vacuolation (CHV), corrected for age. DIF = Deer Island Flats, NB = Nantasket Beach, OS = Outfall site, ECCB = Eastern Cape Cod Bay Fish and Shellfish Chemistry Samples for chemical analyses of winter flounder tissues were taken from the same April collections made for the health assessments (Hall et al. 2013). Three replicates of winter flounder fillets and livers, each composed of tissue from five fish, were analyzed for PCBs, pesticides, and mercury. Liver samples were also analyzed for selected metals and polycyclic aromatic hydrocarbons (PAHs). Lobsters were collected by local lobstermen in August and October. Three replicates of lobster meat and hepatopancreas were composed of tissues from seven lobsters from each site and were analyzed for PCBs, pesticides, and mercury. Hepatopancreas samples were also analyzed for metals and PAHs. Mussels were collected in June from a reference location at Pemaquid Point, Maine, and deployed in cages for 60 days, ending in late August. Mussel tissues were analyzed for PCBs, pesticides, PAHs, mercury, and lead. Concentrations of organic compounds in flounder fillets and livers remained low, as they have been throughout the monitoring program. Concentrations of the banned organochlorine pesticides, DDT and chlordane, and their breakdown products continued to show long, slow, region-wide declines in most samples. Concentrations of PCBs in fillet samples from Deer Island Flats, Nantasket Beach, and the outfall site were higher than in most past years, but within the range for the monitoring program (Figure 5-3). PCB levels also increased in liver samples but were lower than those measured in 1995 at all sites (Figure 5-4). 0% 2% 4% 6% 8% 10% 12% 14% 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 %CHV/mean age DIF NB OS ECCB outf all startup 53 Figure 5-3. PCBs in flounder fillets, 1995–2012. DIF = Deer Island Flats, NB = Nantasket Beach, OS = Outfall site, ECCB = Eastern Cape Cod Bay Figure 5-4. PCBs in flounder livers, 1995–2012. DIF = Deer Island Flats, NB = Nantasket Beach, OS = Outfall site, ECCB = Eastern Cape Cod Bay 0 200 400 600 800 1,000 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 ng/g dry wt DIF NB OS ECCB outf all startup 0 2,000 4,000 6,000 8,000 10,000 12,000 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 ng/g dry wt DIF NB OS ECCB outf all startup 54 In contrast, PCB levels in lobster tissues were among the lowest measured throughout the monitoring program. PCB concentrations in lobster meat samples were low at all three sites (Figure 5-5). Concentrations in hepatopancreas samples were similarly low. Concentrations of other organic contaminants in lobster samples were also very low, continuing to reflect long, slow declines, while metals levels continued to have less predictable spatial and temporal patterns. Figure 5-5. PCBs in lobster meat, 1994–2012. DIF = Deer Island Flats, OS = Outfall site, ECCB = Eastern Cape Cod Bay Deployed mussels also showed historically low levels of PCBs (Figure 5-6). Concentrations of other organic compounds were also low. Total chlordane, which was not detected in the source mussels, bioaccumulated at all sites, but to similarly low levels except the Boston inner harbor. Mussels from the inner harbor also accumulated higher levels of DDT, PAHs, mercury, and lead. Lead levels at all sites except the inner harbor were very low, even lower than detected in the source mussels (Figure 5-7). 0 200 400 600 800 1,000 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 ng/g dry wt DIF OS ECCB outf all startup 55 Figure 5-6. PCBs in deployed mussels, 1991–2012. DIL = Deer Island Light; OSM = Outfall site, four locations just south of the diffuser heads; LNB = Buoy B, one kilometer south of the outfall Figure 5-7. Lead in deployed mussels, 2012. Levels at the outfall site were lower than those found at the reference site. PE = reference site at Pemaquid Point, Maine; LNB = Buoy B, one kilometer south of the outfall; OSM = Outfall site, four locations at the edge of the mixing zone; DIF = Deer Island Flats; IH = Boston inner harbor 0 100 200 300 400 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 ng/g dry wt DIL OSM LNB outf all startup 0 1 2 3 4 PE LNB OSM DIF IH μg/g dry wt 56 Contingency Plan Thresholds There were no Contingency Plan threshold exceedances for fish and shellfish in 2012 (Table 5-1). Incidence of CHV, the most common indicator of liver disease in the winter flounder of the region, was 12% in fish taken from the vicinity of the outfall site, lower than the caution threshold and less than half the baseline average. Chemistry threshold parameters values were lower than the thresholds for every parameter and also lower than baseline averages for every parameter except for PCBs in flounder fillets. Table 5-1. Contingency Plan threshold values and 2012 results for fish-and-shellfish monitoring. Parameter Type/ Nearfield Parameter Baseline Caution Level Warning Level 2012 Results Flounder disease Liver disease (CHV) 24.4% 44.9% None 12% Flounder meat PCB 0.033 ppm 1 ppm wet weight 1.6 ppm wet weight 0.0413 ppm Mercury 0.074 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.0646 ppm Flounder liver lipid normalized Chlordane 242 ppb 484 ppb None 73.6 ppb Dieldrin 63.7 ppb 127 ppb None 0 ppb DDT 775.9 ppb 1552 ppb None 369 ppb Lobster meat PCB 0.015 ppm 1 ppm wet weight 1.6 ppm wet weight 0.0086 ppm Mercury 0.148 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.115 ppm Lobster hepatopancreas lipid normalized Chlordane 75 ppb 150 ppb None 0 ppb Dieldrin 161 ppb 322 ppb None 0 ppb DDT 341.3 ppb 683 ppb None 45.1 ppb Mussel tissue PCB 0.011 ppm 1 ppm wet weight 1.6 ppm wet weight 0.0024 ppm Lead 0.415 ppm 2 ppm wet weight 3 ppm wet weight 0.216 ppm Mercury 0.019 ppm 0.5 ppm wet weight 0.8 ppm wet weight 0.0161 ppm Mussel tissue lipid normalized Chlordane 102.3 ppb 205 ppb None 40.5 ppb Dieldrin 25 ppb 50 ppb None 0 ppb DDT 241.7 ppb 483 ppb None 33 ppb PAH 1080 ppb 2160 ppb None 1020 ppb 57 6. Special Studies Besides monitoring the effluent and the water column, sea floor, and fish and shellfish in Massachusetts Bay and the surrounding area, MWRA conducts special studies in response to specific permit requirements, scientific questions, and public concerns. Special studies in 2012 included evaluation of marine debris observations at the outfall site in 2000–2012; continuous monitoring results from instrumented buoys; evaluation of primary productivity models; Center for Coastal Studies monitoring in Cape Cod Bay; and changes in eutrophication indicators in Boston Harbor. Marine Debris Observations One environmental concern for the outfall was aesthetics, specifically that the outfall would discharge unsightly, floating debris. After the outfall came on line in September 2000 and through 2010, MWRA conducted visual observations and sampled debris at the outfall and a reference site during all water-column surveys. Sampling was made by net tows (Figure 6-1). Figure 6-1. Net used for sampling floatable marine debris. The net measures 1 x 2 meters, with 500-μm mesh. 58 Routine sampling by nets ended with revisions to the monitoring plan in 2010. The revised plan called for net tows following events in which some primary-only treated effluent is blended with effluent that received full primary and secondary treatment before discharge. The new plan also called for analyzing debris captured by the net for organochlorine pesticides, PCBs, PAHs, and mercury. Four tows were conducted in response to blending events in March 2011 and May and July 2012. From September 2000 through July 2012, MWRA conducted 136 marine debris surveys, collecting 135 samples at a reference site and 134 samples at the outfall (Rex and Delaney 2013). Debris was found at both the reference site and the outfall but was detected in more samples from the outfall (Figure 6-2). In particular, fat particles were more frequently detected at the outfall, with 49% of the samples from the outfall having fat particles compared to only 5% at the reference site. Other types of debris were found in more similar numbers in both the outfall and the reference tows. Sightings of sewage-related floatable debris, such as tampon applicators and condoms, were rare. Figure 6-2. Marine debris in net tow samples, 2000–2012. Different types of debris were sometimes present in the same sample. “Plastic” includes plastic and latex-like material; “Paper” includes paper, cellophane, string, and fabric. Chemical analyses of the fat particles did not detect significant quantities of pesticides, PCBs, PAHs, or mercury. Even using conservative assumptions and calculations, MWRA estimated that only small fractions of the already low total effluent loadings of these contaminants to the bay could have come from the fat particles. 0 10 20 30 40 50 60 70 80 90 100 Plastic Paper Fat Particles Total with debris Total no debris Number of samples Control Outfall 59 Based on the results from these studies, EPA and MADEP agreed to end net tows and chemical analyses. Visual observations of floating debris continue. Continuous Monitoring Data In 2007, MWRA partnered with the National Data Buoy Center (NDBC) to add water quality and oceanographic sensors to the NDBC Buoy 44013, a weather buoy located seven kilometers southeast of the outfall, just east of MWRA’s water-column station N07 (see Figure 3-1 in Section 3, Water Column). MWRA’s regulators, EPA and MADEP, wanted continuous data from moored sensors communicated or “telemetered” back to shore in real time as a method of “filling the gaps” between surveys. The active shipping lanes into Boston Harbor pass right over the outfall, making ship strikes a possibility for the surface buoy and antenna required for telemetered data. However, the weather buoy is in a protected traffic-separation corridor and well- known to ship operators. At the time of partnering with MWRA, NDBC was already conducting a pilot study to add water quality and oceanographic sensors to selected buoys nationwide, so adding sensors to Buoy 44013 met needs of both groups. Deployment of new sensors was completed in June 2009. During the spring through fall months of 2009–2012, hourly temperature, salinity, water clarity, dissolved oxygen, and chlorophyll fluorescence data were telemetered to NDBC. The water quality sensors were not designed to survive freezing temperatures and were removed in the winter. A subset of parameters was measured through the winter using submerged sensors, but those data were not telemetered to shore. Despite its protected location, a ship strike disabled NDBC Buoy 44013 for much of 2012. Comparisons of data from the NDBC Buoy 44013, from the other instrumented buoy in the region (NERACOOS Buoy A01 off Cape Ann), and from surveys generally showed good correspondence. Temperature (Figure 6-3, top) and salinity (not shown) data from the buoys corresponded well with survey data. Dissolved oxygen measurements from the NDBC buoy through 2011 tended to be slightly lower than the shipboard survey data but showed the typical seasonal cycle (Figure 6-3, bottom). Correspondence between the NERACOOS Buoy A01, which added dissolved oxygen sensors at the end of 2011, and the survey data was relatively good. The limited available 2012 data from both buoys compared relatively well with survey data. Except for their collaboration with MWRA, NDBC’s pilot study for adding instruments to weather buoys ended in 2009. Their support for the MWRA partnership ended in December 2012. MWRA, its regulators, and OMSAP are determining the need for continuous monitoring data closer to the outfall. Meanwhile, measurements at the NERACOOS Buoy A01 continue. 60 Figure 6-3. Temperature (top) and dissolved oxygen (bottom) at the NERACOOS Buoy A01, NDBC Buoy 44013, and during water quality surveys, June 2009 – December 2012. WC = water column 0 4 8 12 16 20 24 Temperature (ºC) 7 8 9 10 11 12 13 Oxygen concentration (mg/l) NERACOOS Buoy A (2 m) WC stations (near Buoy A) NDBC Buoy 44013 (0.5 m) WC stations (near Buoy 44013) NDBC Buoy 44013 (2.4 m) 61 Primary Productivity Model Evaluations Through 2010, MWRA measured primary productivity at three stations, one at the mouth of Boston Harbor (F23), one several kilometers to the northeast of the outfall (N04), and one a kilometer to the south of the outfall (N18). (See Figure 3-1 in Section 3, Water Column, for station locations.) In 2009, MWRA proposed ending that special study, because the measurements were costly and results had found that the relocated discharge did not result in detectable increased productivity near the outfall. Regulators and their science advisory panel (OMSAP) concurred, but requested that MWRA evaluate other, less costly approaches to assessing primary productivity in marine waters. One alternative approach was to use a simple light-biomass model, known as BZpI0, which had been developed for estuaries. BZpI0 multiplies the chlorophyll biomass present in the photic zone (the BZp term) by the intensity of the sunlight hitting the ocean surface (the I0 term). BZpI0 has been found to be a suitable replacement for direct productivity measurements in many well-mixed coastal systems where the amount of available light limits algal growth. Comparisons between BZpI0 and productivity measurements had already been included in MWRA reports for 1992–2000. Those results were mixed, with good correlations for some stations in some years but poor correlations for other stations and years. A new evaluation of data from 2001–2010 found similar mixed results (Keay et al. 2013). Comparison of annual results found that some years showed a good correlation between BZpI0 and field measurements, but others did not. Spatially, the correlation was better for data from the station at the mouth of Boston Harbor than it was for the offshore stations (Figure 6-4). Spring and fall data correlated better than summer data (Figure 6-5). Overall, BZpI0 did not reflect the measured primary productivity well enough to consider its use as a replacement for direct measurements. The variability in results was not surprising, because BZpI0 is a simple model with assumptions that are sometimes not met in Boston Harbor or Massachusetts Bay. 62 Figure 6-4. Areal productivity and BZpI0 for individual stations. (a) F23, (b) N04, (c) N18 Figure 6-5. A real productivity and BZpI0 for monitoring seasons. (a) Winter-spring: February – April, (b) Summer: May – August, (c) Autumn: September – December R² = 0.4906 0 3000 6000 9000 12000 15000 0 1000 2000 3000 4000 5000 BZpI0 Areal productivity a R² = 0.462 0 3000 6000 9000 12000 15000 0 1000 2000 3000 4000 5000 BZpI0 Areal productivity c R² = 0.2037 0 3000 6000 9000 12000 15000 0 1000 2000 3000 4000 5000 BZpI0 Areal productivity b R² = 0.5251 0 3000 6000 9000 12000 15000 0 1000 2000 3000 4000 5000 BZpI0 Areal productivity a R² = 0.1061 0 3000 6000 9000 12000 15000 0 1000 2000 3000 4000 5000 BZpI0 Areal productivity b R² = 0.3881 0 3000 6000 9000 12000 15000 0 1000 2000 3000 4000 5000 BZpI0 Areal productivity c 63 Cape Cod Bay Studies Since 2011, MWRA has collaborated with the Center for Coastal Studies at Provincetown, which has had an extensive program to monitor Cape Cod Bay and its shorelines since 2006. MWRA’s focus is on the portion of the program that provides offshore water quality and plankton measurements. The Center for Coastal Studies also has an inshore measurement component, which employs citizen volunteers to monitor areas not accessible by boat. Overall, the program provides additional detail for the region, with a focus on information relevant to the whale populations that visit the area each year. The Center for Coastal Studies also makes observations of whales in the region, including aerial surveys and shipboard observations. Some of the Cape Cod Bay program results have been reported on in Section 3, Water Column. In 2012, the Center for Coastal Studies completed 16 surveys of eleven stations in Cape Cod Bay and the southwestern corner of Stellwagen Bank, including three MWRA stations (F01, F02, F29) (Figure 6-6). Those surveys found typical hydrographic and water quality patterns. Phytoplankton communities were dominated by microflagellates. The zooplankton community was somewhat different from past years, including unusual free-swimming gastropods (pteropods), possibly due to intrusion of water from offshore. Figure 6-6. The Center for Coastal Studies monitors its own eight stations and three MWRA stations (F01, F02, and F29) in and near Cape Cod Bay. (Figure from the Center for Coastal Studies) 64 Numbers of Center for Coastal Studies whale sightings have been relatively high since 2007, with 2012 numbers lower than 2011 but greater than 2010 (Figure 6-7). In 2012, whales entered the bay and reached peak abundance earlier than is typical of most years, with the last whales sighted in April. The early arrival may have been related to warm water temperatures. Figure 6-7. Right whale sightings in Cape Cod Bay, 1998–2012. IPUE = individuals per unit effort (Figure from the Center for Coastal Studies) In March 2012, a bowhead whale was sighted off Cape Cod, the first such recorded sighting. Bowhead whales typically live farther north in the Atlantic, Pacific, and Arctic oceans and had never been sighted so far south. Eutrophication Studies in Boston Harbor While studies in Massachusetts Bay have confirmed predictions that any outfall- related changes would be minor and localized, comparable measurements in Boston Harbor have documented improvements resulting from the Boston Harbor Project (Figure 6-8). Average 2012 summer and winter levels of dissolved inorganic nitrogen, chlorophyll, and transparency (measured as a light-attenuation coefficient), were similar to those in 2011, continuing conditions observed in recent years. Minimum dissolved oxygen concentrations in the inner and outer regions of the harbor were also similar to previous years. Over the course of the Boston Harbor Project, inputs of nitrogen, phosphorus, and organic carbon declined by 65–90%, most of which was due to the ending of sewage effluent discharge to the harbor. A recent report (Taylor 2013) documents the improvements through 2009, changes that reversed the historic eutrophic conditions. These improvements have been maintained since the diversion of discharge to Massachusetts Bay. 0 1 2 3 4 5 6 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 IPUE 65 Figure 6-8. Time series plots of Boston Harbor water quality, 1994–2012 . DIN=dissolved inorganic nitrogen, CHL-A=chlorophyll 66 References Bigornia-Vitale G, Wu D. 2012. Technical survey of nitrogen removal alternatives of the Deer Island Treatment Plant. Boston: Massachusetts Water Resources Authority. Report 2012-01. 35 p. Hall M, Lao Y, Moore M. 2013. 2012 fish and shellfish report. Boston: Massachusetts Water Resources Authority. Report 2013-08. 47 p. Keay KE, Taylor, DI, Hall MP, Leo WS, Libby PS. 2013. Comparisons of measured productivity and the composite parameter BZpI0 in Massachusetts Bay: 2001–2010. Boston: Massachusetts Water Resources Authority. Report 2013-10. 15 p. Libby PS, Borkman DG, Geyer WR, Turner JT, Costa AS. 2013. 2012 water column monitoring results. Boston: Massachusetts Water Resources Authority. Report 2013- 15. 50 p. MWRA. 1991. Massachusetts Water Resources Authority effluent outfall monitoring plan: Phase I baseline studies. Boston: Massachusetts Water Resources Authority. Report 1991-ms-02. 95 p. MWRA. 1997a. Massachusetts Water Resources Authority effluent outfall monitoring plan: Phase II post discharge monitoring. Boston: Massachusetts Water Resources Authority. Report 1997-ms-44. 61 p. MWRA. 1997b. Massachusetts Water Resources Authority Contingency Plan. Boston: Massachusetts Water Resources Authority. Report 1997-ms-069. 41 p. MWRA. 2001. Massachusetts Water Resources Authority Contingency Plan revision 1. Boston: Massachusetts Water Resources Authority. Report 2001-ms-071. 47 p. MWRA. 2004. Massachusetts Water Resources Authority effluent outfall ambient monitoring plan Revision 1, March 2004. Boston: Massachusetts Water Resources Authority. Report 2004-ms-092. 65 p. MWRA. 2010. Ambient monitoring plan for the Massachusetts Water Resources Authority effluent outfall Revision 2, July 2010. Boston: Massachusetts Water Resources Authority. Report 2010-04. 107 p. Moore MJ, Nestler EC, Pembroke AE. 2012. Flounder monitoring report: 2012 results. Boston: Massachusetts Water Resources Authority. Report 2012-12. 17 p. Nestler EC, Diaz RJ, Hecker B, Pembroke AE. 2013. Outfall benthic monitoring report: 2012 results. Boston: Massachusetts Water Resources Authority. Report 2013- 12. 36 p. 67 Pembroke AE, Diaz RJ, Nestler EC. 2013. Harbor benthic monitoring report: 2012 results. Boston: Massachusetts Water Resources Authority. Report 2013-13. 41 p. Rex A, Delaney M. 2013. Summary of marine debris observations at MWRA’s Deer Island Treatment Plant effluent discharge site in Massachusetts Bay, 200–2012. Boston: Massachusetts Water Resources Authority. Report 2013-01. 10 p. Taylor DI. 2013. The Boston Harbor Project and the reversal of eutrophication of Boston Harbor. Boston: Massachusetts Water Resources Authority. Report 2013-07. 33 p. Werme C, Rex AC, Hunt, C. 2012. Outfall monitoring overview background: 2012 update. Boston: Massachusetts Water Resources Authority. Report 2012-02. 59 p. 68 List of Acronyms BOD Biochemical oxygen demand cBOD Carbonaceous biochemical oxygen demand CHL-A Chlorophyll CHV Centrotubular hydropic vacuolation DDE Dichlorodiphenyldichloroethylene DDT Dichlorodiphenyltrichloroethane DIF Deer Island Flats DIN Dissolved inorganic nitrogen DITP Deer Island Treatment Plant ECCB Eastern Cape Cod Bay EPA U.S. Environmental Protection Agency FF Farfield HMW High molecular weight IAAC Inter-Agency Advisory Committee IH Inner Harbor IPUE Individuals per unit effort LC50 50% mortality concentration LMW Low molecular weight LNB Outfall site B MADEP Massachusetts Department of Environmental Protection MWRA Massachusetts Water Resources Authority NA Not analyzed/not applicable NACWA National Association of Clean Water Agencies NB Nantasket Beach NERACOOS Northeastern Regional Association of Coastal Ocean Observing Systems NDBC National Data Buoy Center NF Nearfield NOEC No observed effects concentration NPDES National Pollutant Discharge Elimination System OMSAP Outfall Monitoring Science Advisory Panel OS Outfall site OSM Outfall site PAH Polycyclic aromatic hydrocarbon PCB Polychlorinated biphenyl PE Pemaquid Point, Maine PIAC Public Interest Advisory Committee PSP Paralytic shellfish poisoning RPD Redox potential discontinuity T Temperature WC Water column Massachusetts Water Resources Authority Charlestown Navy Yard 100 First Avenue Boston, MA 02129 (617) 242-6000 www.mwra.com
related records
Records whose documents say similar things, nearest first.
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2006
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2014
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2007
- Environmental permitU.S. Environmental Protection AgencyDeer Island treatment plant discharge permit (MA0103284), 2023 draft
- Water & harborMassachusetts Water Resources AuthorityDeer Island outfall monitoring overview, 2001