Massachusetts Water Resources Authority

1. Massachusetts Water Resources Authority Proposed Revisions to MWRA’s Ambient Monitoring Plan: Effluent and Water ColumnAndrea Rex, MWRAtoOutfall Monitoring Science Advisory PanelJune 29, 2009

2. Effluent: end floatables sampling • Extremely unusual (probably unique in country) requirement: MWRA had to design and build a one-of-a kind sampler; no way to compare data to other facilities, no standards • Requirement added because of concern about plastics (condoms, tampon applicators, plastic bags, etc.) • Floatables of concern extremely rare in samples • “Floatables” detected are generally extremely small, and are found at the parts per billion range. • No aesthetic problem at outfall, no sewage-related plastics found in net tows

3. Effluent: change toxic contaminant sampling frequency from weekly to 4/month • Overlapping studies sometimes result in several samples taken in a week, and 6 or more per month • Eliminates redundant sampling

4. Water Column: Original discharge monitoring design: farfield • 26 farfield stations, 8-70 km from outfall. • Sampled during 6 surveys/year, Feb-Oct. • Unchanged by 2004 revisions

5. Original discharge monitoring design: nearfield • 21 nearfield stations, 1-7 km from the outfall • Sampled during 17 surveys/year, Feb-Dec. • Most stations had only dissolved inorganic nutrient (DIN) analyses and hydrographic data collected • 26 farfield stations, 8-70 km from outfall. • Sampled during 6 surveys/year, Feb-Oct. • Revisions approved in 2004 affected ONLY nearfield stations and surveys.

6. Changes approved in 2004, stations • 14 nearfield (DIN-only) stations dropped. • Monitoring at retained stations included particulate, organic and inorganic nutrient samples . • Two of the retained stations (N04 and N18) included sampling for plankton, productivity, and respiration.

7. 2004 changes and current design: surveys Five Nearfield-only surveys were dropped 12 surveys were retained, including all 6 combined Nearfield + Farfield surveys.

8. Current Monitoring • Seven nearfield stations sampled during 12 surveys/year, Feb-Nov • 28 farfield stations sampled during six surveys/year, Feb-Oct • Farfield surveys require 3-4 field days, depending on season and weather. • Frequently, farfield surveys are interrupted by weather, often extending the sampling time period for many days, complicating interpretation. • No regional data are available for the 6 nearfield-only surveys, complicating the interpretation of findings.

9. Current monitoring design is very complex • Carrying out all analyses at all 35 stations would be prohibitively expensive. • Currently eight different unique combinations of sampling depths and analytes, complicates data interpretation. • Plankton at about half the stations.

10. Changes proposed: Stations • Focus on area plausibly affected by discharge, plus reference stations • Nearfield sampling at 4 of current 7 stations, including two of three current plankton stations. • End monitoring in reference areas unaffected by discharge • Cape Cod Bay • Boundary stations (including Stellwagen) • Sentinel reference stations in Offshore and Coastal regions. • All parameters measured at all stations. • Enable “synoptic” sampling to improve data interpretation.

11. Changes proposed: Stations retained

12. Proposed design: stations

13. Survey changes proposed 2010 2004 Five Nearfield-only surveys were dropped 2010 proposed three surveys dropped. 2010 proposed 9 surveys all nearfield plus reference

14. Changes proposed: Surveys • Reduce Nearfield surveys from twelve to nine per year. • Increase reference-farfield sampling from six to nine surveys per year • Improve ability to identify and distinguish regional events from localized nearfield events that could be outfall-related. • Sample important events in seasonal cycle

15. Changes Proposed: Surveys

16. Changes Proposed: Measurements • Drop direct measurements of water column primary production • Drop floatables tows in nearfield • Drop measurements of little-used parameters • Dissolved Organic Carbon • Particulate Biogenic Silica • Total Suspended Solids • Respiration • Add gene probe analyses for Alexandrium fundyense during bloom season • Retain all other measurements

17. Measurements Proposed

18. Rationale for nearfield station selection: Bottom water dissolved oxygen nearfield averageR2 = 0.99 2003 monitoring revision analyses showed strong spatial redundancy in nearfield, analyses show that the proposed 4 stations are very highly correlated to the existing 7 stations

19. Areal chlorophyll nearfield survey means R2 = -.98

20. Rationale: Regional reductions • Cape Cod Bay • Five stations, two sampled February through April, three sampled February through October • No indications of discharge impact • Boundary stations • Five stations, sampled February through October • Originally to characterize cross-boundary transport • No indications of discharge impact • Well-calibrated regional circulation models, supplemented by moorings, now better address circulation questions, support Bays Eutrophication Model • Data from remaining reference stations will continue to allow estimation of nutrient and plankton inputs for water quality modeling, with better temporal resolution than at present.

21. Rationale: Regional reductions • No outfall-related impacts have been observed in distant regions in almost 9 years of discharge monitoring. • Coastal stations helped define the plume of nutrients coming from Boston Harbor discharges. With the offshore outfall, coastal stations are less important. One off Cohasset is retained in the proposed monitoring. • Offshore stations retained in the proposed plan will be sufficient to help determine input loads for water quality modeling and the regional extent of blooms.

22. Rationale: End productivity special study • Significant decreases (improvements) seen in Boston Harbor. • NO changes observed in nearfield over 8 years of monitoring, monitoring question answered. • Special study is very expensive and labor-intensive • Measurements impose severe logistical constraints on survey track and schedule. • Study generates low-level radioactive waste.

23. Rationale: End Floatables tows • Debris tows have identified no anthropogenic plastics associated with the discharge • Fat particles observed are quite small (1-2 mm) and can only be detected after they are concentrated by the net. • Fat particles are not made up of petroleum hydrocarbons • Tows add to the time on station

24. Rationale, end other measurements • Total Solids • Much baseline data biased high by salt retention on filters • Not used in data evaluation • Biogenic Silica and Dissolved Organic Carbon data rarely used

25. Rationale: Survey schedule Nine remaining surveys chosen to provide sentinel seasonal information: • Important events observed in results to date would be captured: • Red tide blooms • Phaeocystisblooms • July 2006 Dactyliosolen fragilissimus bloom • Seasonal and annual averages used in threshold testing are very similar under both the existing and proposed monitoring

26. Comparisons of threshold parameters In all plots, averages for “current 7 stations” are means for all current stations, 12 surveys per year. Averages for “proposed 4 stations” are means for the 4 nearfield stations proposed for the 9 surveys/year proposed. For time series plots, current design in red, proposed in black.

27. Annual Chlorophyll Time series 1992-2008

28. Annual Chlorophyll values, correlation R2 = 0.95

29. Seasonal Chlorophyll (all seasons) 1992-2009

30. Seasonal Chlorophyll (Winter-spring) R2 = 0.81

31. Seasonal Chlorophyll (Summer) R2 = 0.97

32. Seasonal Chlorophyll (Fall) R2 = 0.79

33. Bottom water Dissolved Oxygen 1992-2009

34. Bottom Dissolved Oxygen

35. Contingency Plan testing preserved; some “borderline” exceedances would change Rev2 would pick up two new exceedances spring 2008 Phaeocystis, slightly over the threshold (2,080,000 cells/l compared to 2,020,000 cells/l – 2008 benthic infauna log-series alpha, where the value (15.6, based on EVEN station set that was sampled) is just over the upper threshold based on ALL "Rev2" stations, 15.39.

36. Contingency plan threshold tests • SEE HANDOUT • Thresholds recalculated from baseline using proposed station/survey set • Exception: Phaeocystis and Pseudonitzschia threshold levels left provisionally unchanged because the new station/survey set resulted in substantially higher threshold levels which then did not capture all the previous exceedances. Thus the new sample design would be more conservative than at present for these algae and (conceivably resulting in more exceedances). • Threshold tests yield very similar results with new survey design.