Massachusetts Water Resources Authority

1

Massachusetts Water Resources Authority

Proposed Revisions to MWRA’s Ambient Monitoring Plan: Effluent and Water Column

Andrea Rex, MWRAto

Outfall 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.

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U

1

N20

N18

N16

N10

N07

N04

N01

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

! Nearfield stations

U GOMOOS mooring

? USGS mooring

1 NOAA mooring

Outfall diffuser0 2.5 5

Kilometers ±

Water Column Monitoring

7

2004 changes and current design: surveys

Five Nearfield-only surveys were dropped

Survey Month

Season (for threshold

calculation)

1 Nearfield + Farfield February Spring

2 Nearfield + Farfield February/Mar Spring

3 Nearfield March Spring

4 Nearfield + Farfield April Spring

5 Nearfield April/May Spring/Summer

6 Nearfield May Summer

7 Nearfield + Farfield June Summer

8 Nearfield July Summer


10 Nearfield August Summer

11 Nearfield + Farfield August Summer

12 Nearfield September Fall


14 Nearfield + Farfield October Fall

15 Nearfield October Fall

16 Nearfield November Fall

17 Nearfield December Fall

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.

F33

F32

F19

F18

F17F16

F15F14

F12

F10

F07

F05

N20

N10

N07

N01

F29

F28

F03

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

F33

F32

F19

F18

F17F16

F15F14

F12

F10

F07

F05

N20

N10

N07

N01

F29

F28

F03

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

Cape Cod Bay

BostonHarbor Massachusetts Bay

0 10 20 30 40 505Kilometers

northern boundary region

offshore region

MWRA stations (BWQM)

GoMOOS Buoy A

NOAA Buoy 44013

MWRA outfall diffuser

Regions

Stellwagen Bank Sanctuary

High : 0

Low : -125

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.

Station Type Code Sample depths per analysis per station

ANALYSIS BBR E H M

MRP Z

Dissolved Inorganic Nutrients 5 5 5 3 5 5

Organic and Particulate

Nutrients 3 3 3 3 3

Chlorophyll a and phaeophytin 5 5 5 3 5 5

Total suspended solids 3 3 3 3 3

Zooplankton 1 1 1 1

Phytoplankton 2 2 2

Respiration 3 3

Primary Production 5

Stations per station type

Station Type Code

BBR E H M

MRP Z

Nearfield 5 2

Farfield 112 2

10 1 2

F33

F32

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W42

°30'

N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

F33

F32

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W42

°30'

N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

Cape Cod Bay


0 10 20 30 40 505Kilometers


offshore region

coastal region

nearfield region

Phytoplankton and zooplankton station

Zooplankton-only station

GoMOOS Buoy A

NOAA Buoy 44013


Regions

High : 0

Low : -125

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.

F33

F32

F19

F18

F17F16

F15F14

F12

F10

F07

F05

N20

N10

N07

N01

F29

F28

F03

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

F33

F32

F19

F18

F17F16

F15F14

F12

F10

F07

F05

N20

N10

N07

N01

F29

F28

F03

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

Cape Cod Bay


0 10 20 30 40 505Kilometers


offshore region


GoMOOS Buoy A

NOAA Buoy 44013


Regions


High : 0

Low : -125

Proposed stations

11

Changes proposed: Stations retained

STATION ID

WATER DEPTH

(M)

LOCATION RELATIVE TO

OUTFALLPURPOSE

F06 33 29 km S Southern reference station

F10 33 20 km SFurthest expected southern expression of effluent plume

F13 25 14 km S Near coastal (model, Alexandrium)

F15 38 9 km S Evaluate extent of plume southeast

F22 80 17 km NE

Northern reference stationGulf of Maine influenceRegional physical forcing relates to nearfield DOLink between buoy and sampling data“Upstream” sentinel station in winter-spring

F23 25 12 km E Boston Harbor

N01 31 6.3 km NW Evaluate extent of plume northwest

N04 50 7.1 km NE Evaluate extent of plume northeast

N07 50 7.1 km SENear NOAA buoy MWRA instruments-data comparison

N18 27 2.5 km S

Closest station to outfallHighest ammoniumPrimary “impact” station for comparison to other stations

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GOMOOS-A

BUOY-44013

N18 N07

N04

N01

F23

F22

F15

F13

F10

F06

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

! Water Column Station

P GOMOOS-A Mooring Station

NWS Buoy

) MWRA Outfall Diffusers

Stellwagen Bank National Marine Sanctuary

Water Depth(meters) > 70 40 - 70 < 40

Cape Cod Bay


0 10 20 Kilometers

±

12

Proposed design: stations

STATION ID

WATER DEPTH

(M)

LOCATION RELATIVE TO OUTFALL PURPOSE

N01 31 6.3 km NW NEARFIELD Evaluate extent of plume northwest

N04 50 7.1 km NE NEARFIELD Evaluate extent of plume northeast

N18 27 2.5 km S

NEARFIELDClosest station to outfallHighest ammoniumPrimary “impact” station for comparison to other stations

N07 50 7.1 km SE NEARFIELD Near NOAA buoy MWRA instruments-data comparison

F22 80 17 km NE

REFERENCENorthern reference stationGulf of Maine influenceRegional physical forcing relates to nearfield DOLink between GoMOOS A buoy and sampling data“Upstream” sentinel station in winter-spring

F23 25 12 km E REFERENCE Boston Harbor

F15 38 9 km S REFERENCE Evaluate extent of plume southeast

F13 25 14 km S REFERENCE Near coastal (model, Alexandrium)

F10 33 20 km S REFERENCE Furthest expected southern expression of effluent plume

F06 33 29 km S REFERENCE Southern reference station

13

Survey changes proposed 2010

Survey MonthSeason (for threshold

calculation)

1 Nearfield + Farfield February Spring

2 Nearfield + Farfield February/Mar Spring

3 Nearfield March Spring

4 Nearfield + Farfield April Spring

5 Nearfield April/May Spring/Summer

6 Nearfield May Summer

7 Nearfield + Farfield June Summer



10 Nearfield August Summer

11 Nearfield + Farfield August Summer



14 Nearfield + Farfield October Fall

15 Nearfield October Fall

16 Nearfield November Fall

17 Nearfield December Fall

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

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GOMOOS-A

BUOY-44013

N18 N07

N04

N01

F23

F22

F15

F13

F10

F06

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

! Water Column Station

P GOMOOS-A Mooring Station

NWS Buoy

) MWRA Outfall Diffusers

Stellwagen Bank National Marine Sanctuary

Water Depth(meters) > 70 40 - 70 < 40

Cape Cod Bay


0 10 20 Kilometers

±

15

Changes Proposed: Surveys

WHEN PURPOSE

Early February Nutrient conditions near start of spring bloom

March Spring bloom

Early April Capture Phaeocystis bloom. Late winter/spring bloom nutrients

Mid-May Nutrient/water column conditions at end of winter-spring, Alexandrium

Mid-June Early summer stratification and nutrients. Mid-late red tide season.

Mid-July Mid-summer stratification and nutrients

Mid-August Mid-summer stratification and nutrients

Late September Nutrients, etc. prior to overturn.

Late October Mid-fall bloom nutrients, DO minima, etc.

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

ANALYTE DEPTH PARAMETER

Hydro profile

No change. Downcast data continuous, with upcast data at any sampled depths

Temperature SalinityDissolved oxygen Chlorophyll fluorescence Transmissometry IrradianceDepth of sensors

Water chemistry

No change. Five depths. Surface, bottom, and three intermediate depths which includes the chlorophyll maximum

AmmoniumNitrateNitriteTotal dissolved nitrogenParticulate nitrogenPhosphateTotal dissolved phosphorusParticulate phosphorusSilicateParticulate carbonChlorophyll

AlexandriumTwo depths, including chlorophyll maximum "C" depth

Gene probe

Phytoplankton Zooplankton

No change, net tow Identification, enumeration

18

Rationale for nearfield station selection: Bottom water dissolved oxygen nearfield averageR2 = 0.99

Nearfield Bottom DO, 1992-2008

y = 0.9778x + 0.2057

R2 = 0.9915

6

7

8

9

10

11

12

13

6 7 8 9 10 11 12 13

Current 7 stations

Pro

po

sed

4 s

tati

on

s

Dissolved Oxygen

Linear (Dissolved Oxygen)

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

Nearfield areal chlorophyll, 1992-2008

y = 1.0796x - 4.2291

R2 = 0.9796

0

100

200

300

400

500

0 100 200 300 400 500

Current 7 stations

Pro

po

sed

4 s

tati

on

s

Chlorophyll

Linear (Chlorophyll)

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.

F33

F32

F19

F18

F17F16

F15F14

F12

F10

F07

F05

N20

N10

N07

N01

F29

F28

F03

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

F33

F32

F19

F18

F17F16

F15F14

F12

F10

F07

F05

N20

N10

N07

N01

F29

F28

F03

F23

F22

F13

F06

N18

N16

N04

F31

F30

F27

F26

F25

F24

F02

F01

70°15'W

70°15'W

70°30'W

70°30'W

70°45'W

70°45'W

71°0'W

71°0'W

42°3

0'N

42°3

0'N

42°1

5'N

42°1

5'N

42°0

'N

42°0

'N

41°4

5'N

41°4

5'N

Cape Cod Bay


0 10 20 30 40 505Kilometers


offshore region


GoMOOS Buoy A

NOAA Buoy 44013


Regions


High : 0

Low : -125

Proposed stations

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.

Annual Production

0

200

400

600

800

F23 N16/N18 N04

g C

m-2

y-1

Harbor Nearfield at outfall

Nearfield northeast corner

23

Rationale: End Floatables tows

• 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

0

5

10

15

20

25

30

35

40

45

Papercontrol

site

Paperoutfall site

Plasticcontrol

site

Plasticoutfall site

Fatparticlescontrol

site

Fatparticles

outfall site

Pe

rce

nt

Po

siti

ve

Before outfall on-line After outfall on-line

00

• Debris tows have identified no anthropogenic plastics associated with the discharge

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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– Phaeocystis blooms– 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

Annual Mean Chlorophyll

0

20

40

60

80

100

120

140

160

180

200

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Year

Ann

ual m

ean

chlo

roph

yll m

g/m

2

Current 7 Stations

Proposed 4 stations

28

Annual Chlorophyll values, correlation R2 = 0.95

Nearfield chlorophyll

y = 0.9247x + 3.3806

R2 = 0.9051

0

20

40

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120 140 160 180 200

Current 7 stations (mg/m2)

Pro

po

sed

4 s

tati

on

s(m

g/m

2)

Annual Mean

Linear (Annual Mean)

29

Seasonal Chlorophyll (all seasons) 1992-2009

Nearfield Chlorophyll Seasonal Means

0

50

100

150

200

250

300

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Are

al C

hlo

rop

hyl

l

Current

Proposed

30

Seasonal Chlorophyll (Winter-spring) R2 = 0.81

Winter-Spring

y = 1.1494x - 2.3668

R2 = 0.8089

0

50

100

150

200

250

300

0 50 100 150 200 250


Pro

po

sed

4 s

tati

on

s (m

g/m

2)

Chlorophyll

Linear(Chlorophyll)

31

Seasonal Chlorophyll (Summer) R2 = 0.97

Summer

y = 1.0712x - 6.3939

R2 = 0.9674

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Current 7 Stations (mg/m2)

Pro

po

sed

4 s

tati

on

s (m

g/m

2 )

Chlorophyll


32

Seasonal Chlorophyll (Fall) R2 = 0.79

Fall

y = 0.819x + 11.851

R2 = 0.7947

0

50

100

150

200

250

0 50 100 150 200 250 300


Pro

po

sed

4 s

tati

on

s (m

g/m

2)

Chlorophyll


33

Bottom water Dissolved Oxygen 1992-2009

Bottom DO

4

5

6

7

8

9

10

11

12

13

1990 1993 1995 1998 2001 2004 2006 2009 2012

Year

Bo

tto

m W

ater

DO

(m

g/L

)

Current

Proposed

34

Bottom Dissolved Oxygen

Nearfield Bottom Water Annual Minima

4

5

6

7

8

9

1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

DO

(m

g/L

)

Current

Proposed

35

Contingency Plan testing preserved; some “borderline” exceedances would change

Caution and Warning Level Exceedances still exceeds with Rev2 stations/surveys?

May 18, 2009 Alexandrium yes May 16, 2008 Alexandrium yes

Winter/Spring 2007 Phaeocystis yes Summer 2006 Phaeocystis yes

Summer 2006 Chlorophyll no.

Value changes from 97 to 91 mg/m2, while caution level changes from 93 to 96.

May 17, 2006 Alexandrium yes Summer 2005 Phaeocystis pouchetii yes May 11, 2005 Alexandrium yes

Spring and Summer 2004

Phaeocystis pouchetii yes (spring) and yes (summer)

Summer 2003 Phaeocystis pouchetii yes

May-August 2002 Phaeocystis pouchetii no,

since due solely to early May survey 2002 - that survey was dropped in 2004 already.

Fall 2000 chlorophyll yes

October 1, 2000 Dissolved oxygen percent saturation

N/A since we went to using background

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.

Documents

Massachusetts Water Resources Authority