2010 water quality supplement mccabe’s brook watershed

8/6/2019 2010 Water Quality Supplement McCabes Brook Watershed

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Up-date: 2011-04-17

LaPlatte Watershed Partnership

Water Quality SupplementMcCabes Brook Watershed

2010 Data in Context and Pilot Flow Study

Introduction .. . 1Results .....1

Chlorides .... ... 1 Suspended Sediment ..2Phosphorus .. ...4Nitrogen ....... .. 9Episodic Events ....11 Nutrient loads . ..13

Conclusions and Recommendations ..... 17Data Management and Quality Assurance .. .17 Suspended Sediments ...18 Nutrients ...19 Land Use and Basin Planning ..21

Attachments . 23 Attachment a. Sampling Stations . .. 24Attachment b. Water Quality Data .... 25 Attachment c. Quality Assurance ... 27 Attachment d. Gaging Station Rating Curves ... 28

Prepared for

Water Quality SectionVermont Department of Environmental Conservation

and

The Town of Shelburne, VermontApril, 2011


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I. INTRODUCTION

The LaPlatte Watershed Partnership has implemented a volunteer water qualitymonitoring program in the LaPlatte watershed, including its tributary, McCabes Brook, on abi-weekly or monthly basis during the summer and fall seasons since 2004. The monitoringeffort has been provided laboratory support through the State of Vermonts LaRosa Volunteer Water Quality Monitoring Analytical Partnerships program, and financial support from theTown of Shelburne for laboratory supplies, establishment of flow gaging stations, data analysisand review, and public education under special environmental projects. Quality assuranceunder the monitoring program is carried out following the protocols contained in the StatesEPA approved Vermont General Quality Assurance Project Plan for Volunteer, Educationaland Local Community Monitoring and Reporting .

The LaPlatte Watershed Partnership prepared a review of the first four years of waterquality monitoring in the watershed in 2008, and a supplemental report of 2008 results in 2010.The present report discusses results of water quality monitoring carried out in 2010 in thecontext of results obtained from 2004-2007 and in 2008 1. The present report also includes theresults and interpretation of a pilot flow measurement initiative carried out in 2010.

II. RESULTS

a. Chlorides

Results of chloride analyses were in general typical of results reported during previoussampling years, generally low, and increasing steadily downstream between Lime Kiln Road(MB 05) and Bostwick Road (MB 03) as the stream receives runoff from roads, then decreasingbetween Bostwick Road and Falls Road (MB 02) as a result of dilution. The highest maximumconcentration which occurred at Route 7 (MB 04) was well below levels harmful to aquaticorganisms.

1 The monitoring program was suspended in 2009 as a result of a loss of funding for theLaRosa program during that year.


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b. Suspended Sediment

Both turbidity and total suspended solids were determined during 2010. The relationbetween the two parameters was identical to that observed in the LaPlatte watershed includingMcCabes Brook in 2004 and 2005 .

Levels of turbidity were similar to those observed over the period 2004-2007, althoughmaximum values were generally lower except on August 4, 2010 when they exceeded 1,000NTU at Route 7 (see discussion under Section II.e below). Although turbidity levels in mostsamples fell below the State standard, they did exceed the standard during 2010 in about 10%of all samples, mainly at Route 7 and downstream to Harbor Road.

0

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20

30

40

50

60

70

80

90

MB 02 MB 03 MB 04 MB 04a MB 05

C h l o r i

d e C o n c e n t r a t i o n ( m g

/ l )

Sampling Station

Chloride Concentrations in McCabe's Brook - 2010

Median Maximum Minimum

y = 1.2279x -0.6199R = 0.9995

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 200 400 600 800 1000 1200 1400 1600

T u r b i d i t y

( N T U

)

TSS Conc. (mg/l)

Turbidity vs. Total Suspended Solids Concentrations in McCabe's Brook,2010


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The decline in turbidity between Lime Kiln Road (MB 05) and the Vermont Teddy Bearaccess road (MB 04a) was less than in 2008, and is discussed below.

The Champlain Water District collected data on the distribution of particle sizes in watersamples from McCabes Brook before it discharges into the backwater from Lake Champlainbetween 2007 and 2010. The results confirm the predominance of clay and fine silt (5 0 N TU)


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turbidity levels (and flow) are low that have been observed in the LaPlatte River. As thesediment load reflected in turbidity levels increases, larger particles predominate. This may haveimplications related to phosphorus loadings and the fate of phosphorus in the lake (see discussionbelow).

Total suspended solids concentrations generally followed the pattern observed forturbidity, although the ratios of the two parameters (specific turbidity) were identical toobservations in the LaPlatte watershed in 2004 and 2005, but tended to increase downstream toRoute 7 or Bostwick Road, and when flow was relatively high on November 11, were very high(see Attachment b).

McCabes Brook is listed under Part C of the State of Vermonts list of priority surfacewaters outside the scope of Section 303(d) of the Clean Water Act which identifies waters inneed of further assessment based on elevated turbidity affecting aquatic life.

c. Phosphorus

Phosphorus concentrations in McCabes Brook follow a pattern downstream from theVermont Teddy Bear access road (MB 04a) which has been consistent since the volunteermonitoring program was initiated in 2004, although some variability has been seen to occur fromyear to year. Total phosphorus levels observed throughout this portion of the stream in 2010were consistent with those observed in 2008, but slightly higher than those observed from 2004-2007. Total phosphorus concentrations also generally follow levels of suspended sediment in

1

10

100

1,000

10,000

MB 02 MB 03 MB 04 MB 04a MB 05

T S S C o n c .

( m g

/ l )

Sampling Station

Total Suspended Solids Concentrations in McCabe's Brook - 2010

M edi an Max imum Mi ni mum

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

MB 02 MB 03 MB 04 MB 04a MB 05

S p e c i f i c T u r b i d i t y

( N T U

/ T S S

)

Sampling Station

Specific Turbidity in McCabe's Brook - 2010

M edi an Ma xi mum M ini mum


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McCabes Brook reflected in turbidity level s and total suspended solids concentrations discussedabove, whereas particulate phosphorus concentrations were strongly correlated with total

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250

300

350

400

MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s C o n c .

( g

/ l a s P

)

Sampling Station

Median Total Phosphorus Concentrations in McCabe's Brook,2004-2007

500 Proposed State In-Stream TP Criterion

0

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100

150

200

250

300

350

MB 02 MB 03 MB 04 MB 04a MB 05

T o t a

l P h o s p

h o r u s C o n c .

( g

/ l a s P

)

Sampling Station

Total Phosphorus Concentrations in McCabe's Brook - 2008

Median High Low

F i e

l d s - n

o t c u

l t i v a t e

d

Proposed Effective Criterion for Streams

10

100

1,000

MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s C o n c .

( g

/ l a s P

)

Sampling Station

Total Phosphorus Concentrations in McCabe's Brook - 2010


Proposed State In-Stream TP Criterion

y = 14.188ln(x) + 54.126R = 0.563

y = 17.292ln(x) + 3.9669R = 0.9002

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40

60

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120

0 5 10 15 20 25

P h o s p

h o r u s C o n c .

( g

/ l a s P

)

TSS Conc. (mg/l)

Median Phosphorus Concentrations vs Total Suspended SolidsConcentrations in McCabe's Brook - 2010

Total Phosphorus Particulate Phosphorus Dissolved Phosphorus

Log. (Total Phosphorus) Log. (Particulate Phosphorus)


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suspended solids concentrations. The importance of the particulate fraction of the phosphorustransported by the stream is illustrated also in data for individual sampling stations:

Of interest is a consistent increase in the total phosphorus concentration betweenBostwick Road (MB 03) and Harbor Road (MB 02) in Shelburne, attributable to (at time verylarge) increases in particulate phosphorus levels. The stream between MB 03 and MB 02 flowsthrough wetlands behind the Shelburne Museum and the School Street neighborhood inShelburne to Harbor Road. Samples are taken at MB 02 downstream from the bridge at HarborRoad and a storm water outfall which discharges drainage from much of Shelburnes centraltown area. Other storm drains serving the School Street neighborhood discharge to wetlands

between the developed area and McCabes Brook.

0

20

40

60

80

100

120

MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s C o n c .

( u g

/ l a s P

)

Sampling Station

Median Phosphorus Concentrations in McCabe's Brook,

2006-2007

Particulate Phosphorus Dissolved Phosphorus

2 9

. 6

4 8

. 8 3 1

. 2 5

1 4

. 6 2 2

. 5

4 1

. 8

6 4

3 3

. 6

3 8

. 0 5

2 9

. 0 5

6 7

. 0 0

7 . 6

5 2 0

. 5 0 3

6 . 6

5

6 3

. 0 0

2 7

. 1 5

3 3

. 8 5

4 1

. 2 0

4 1

. 6 5

2 8

. 9 0

0

20

40

60

80

100

120

MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s

C o n c . (

g

/ l a s

P )

Sampling Station

Median Phosphorus Concentrations in McCabe's Brook, 2008


F i e

l d s -

n o t c u

l t i v a t e d

0

20

40

60

80

100

120

MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s C o n c .

( g

/ l a s P

)

Sampling Station

Median Phosphorus Concentrations in McCabe's Brook - 2010


3 7

. 9

5 1

. 3

4 2

. 2

5 0

. 0

5 5

. 9

3 1

. 6

2 1

. 9 4 0

. 7

3 8

. 6

7.7


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Of particular note, however, were results at Lime Kiln Road (MB 05) and at the Vermont

Teddy Bear access road (MB 04a). During the years 2004-2007, phosphorus concentrationstended to increase over this reach of the stream. During 2008, they tended to decrease, butincreased again in 2010. The changing pattern between MB 05 and MB 04a appeared to reflectchanging patterns of cropping in three fields wit h drainage to this section of McCabes Brook and shown in the orthophoto below:


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The coincidence of cultivation with increases in phosphorus concentrations in McCabesBrook over the section of the stream receiving drainage from the fields, together with theapparent rapid response of nutrient levels to an event on July 10, 2007 (see discussion below),strongly suggests that nutrient levels, and in particular those of phosphorus in streams may behighly sensitive and rapidly responsive to current land management and cover within theadjacent watershed.


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The above discussion highlights the importance of suspended sediment as a factordetermining levels of phosphorus transported by McCabes Brook. It is noted also that theburden of particulate phosphorus associated with suspended sediment in McCabes Brook tendsto increase between Lime Kiln Road and the Vermont Teddy Bear access road, and decreases

downstream to Falls Road. But maximum values, which occurred mainly on May 15, 2010,increased to very high levels, especially at Route 7 and Bostwick Road, but also at Harbor Road

on September 1, 2010. The flow on September 1 was very low in the stream, suggesting that thesuspended solids consisted mainly of clay and very fine silt which potentially could persist insuspension into the open water of Shelburne Bay (see also discussion of suspended sedimentabove). Increases in particulate phosphorus concentrations coincident with decreases in solidsconcentrations from 2004-2007 can be attributed to increasing phosphorus burdens associatedwith solids.

d. Nitrogen

The patterns and levels of median total nitrogen concentrations have remained nearlyidentical and consistently below the proposed Vermont State criterion for Class B warm waterstreams from year to year, including 2010. On the other hand, concentrations within the stream

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MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s B u r d e n

( g m s P / K g T S S )

Sampling Station

Phosphorus Burden of Solids in McCabe's Brook - 2010



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exceeded the criterion in 21% of samples from 2004-2008, and in 35% of samples in 2010.From Lime Kiln Road (MB 05) to Route 7 (MB 04), the criterion was exceeded in about 50% of samples in 2010.

Concentrations of total nitrogen seldom exceeded 1.25 mg/l except at times whenextreme events occur (see discussion below).

Nitrate plus nitrite concentrations generally fall below the limit of detection of 0.05 mg/las N from Route 7 upstream, but are often detected at downstream locations, although stillgenerally at low concentrations. Significant nitrate concentrations may occur during extreme

events and can be of use in assessing sources of nutrients reaching by the stream.

Molar ratios of total nitrogen to total phosphorus were low, median values falling below10 at all locations and a maximum value at Bostwick Road of about 15, which resembled closelyobserved values during previous years and which indicates an excess of phosphorus in thedischarge from the stream.

0.10

1.00

10.00

MB 02 MB 03 MB 04 MB 04a MB 05

T o t a

l N i t r o g e n C o n c .

( m g

/ l a s N

)

Sampling Station

Total Nitrogen Concentrations in McCabe's Brook, 2004-2007

Me dian Maximum Minimum

Proposed State In-StreamTN Criterion

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

MB 02 MB 03 MB 04 MB 04a MB 05

T o t a

l N i t r o g e n C o n c .

( m g

/ l a s N

)

Sampling Station

Total Nitrogen Concentrations in McCabe's Brook, 2008

Median High Low

Proposed Effective Criterion for Streams

0.0

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1.0

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2.0

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MB 02 MB 03 MB 04 MB 04a MB 05

T N C o n c .

( m g

/ l a s N

)

Sampling Station

Total Nitrogen Concentrations in McCabe's Brook - 2010


Proposed State In-Stream TN Criterion


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e. Episodic Events

The volunteer water quality monitoring program in the LaPlatte River- McCabes Brook watershed was undertaken to provide baseline information on water quality and identify waterquality issues and hot spots for future investigation. It was not designed to identify unusualevents impacting on water quality in the stream. However, two such events have been identifiedwhich are instructive and suggest i) a need for further investigation, ii) a need to clarifymechanisms by which to identify quickly, respond to, and learn from events which may bereflected in the routine monitoring data, and iii) a need to assure that data available throughvolunteer monitoring programs are utilized by the State, Regional Planning Commissions, andtowns for establishing needs for TMDLs and for preparing land use and river basin plans.

July 10, 2007 . Water quality samples collected from McCabes Brook on July 10, 2010following several days of rain revealed an increase in the turbidity level between Lime Kiln

Road (MB 05) and the Vermont Teddy Bear access road (MB 04a). The increase in turbiditywas accompanied by a dramatic increase in the total phosphorus concentration caused primarilyby an increase in the particulate phosphorus concentration.

Of particular note was a dramatic and unusual increase in the total nitrogen concentrationto more than almost 11 mg/l attributable to an increase in the NO 3 + NO 2 concentration. TheNO3 + NO2 concentration, which rarely exceeds 1 mg/l, increased to more than 8 mg/l, farexceeding the Vermont State nitrate standard. Both concentrations of nutrients and turbidityremained high downstream from MB 04a.

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350

Bostwick Road(MB 3)

Route 7 (MB 4) Vermont TeddyBear acces road

(MB 4a)

Lime Kiln Road(MB 5)

T u r b

i d i t y

( N T U )

Sampling Station

Turbidity in McCabe's Brook - July 10, 2007

M ed ia n 2 00 8 J uly 10 , 20 08

Turbidity Standard = 25 NTU

F a r m

D r a i n a g e

Direction of Flow

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50100

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Bostwick Road(MB 3)


(MB 4a)


P h o s p h o r u s

C o n c .

( g

/ l )

Sampling Station

Phosphorus Concentrations in McCabe's Brook -July 10,2007

Median Total P Median Particulate PMedian Dissolved P Tota P 7/10/2007Particulate P 7/10/2007 Dissolved P 7/10/2007

F a r m

D r a i n a g e

Direction of Flow

Proposed Total Phosphorus Criterion = 44 g/l


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It is noteworthy also that chloride concentrations, while lower than normal as a result of dilution, followed a typical pattern of steady increase downstream, and increased as normalbelow Lime Kiln Road.

The data strongly suggest that the dramatic increase in phosphorus associated withsuspended sediment, and of nitrate, were associated with runoff from a cornfield located to thenorth of Lime Kiln Road (see discussion above).

The Water Quality Section was eventually alerted, and in turn informed the Agency of Agriculture. Follow-up prevention and mitigation plans have not been provided.

August 4, 2010 . Water quality samples collected from McCabes Brook on August 4,2010 during a period of rainfall revealed an increase in turbidity and total suspended solidsconcentrations to very high levels between the Vermont Teddy Bear access road (MB 04a) andRoute 7 (MB 04). The increase in solids concentration was accompanied by an increase in thetotal phosphorus concentration to an equally high level caused by an increase in the particulatephosphorus concentration.

0

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4

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8

10

12

Bostwick Road(MB 3)


(MB 4a)


N i t r o g e n

C o n c .

( m g

/ l a s

N )

Sampling Station

Nitrogen Concentrations in McCabe's Brook -July 10, 2007

2007 Median Total N itrogen 2007 Median NO3+N O2Total N itrogen (7-10-2007) N O3+N O2 (7-10-2007)

F a r m

D r a

i n a g

e

Nitrate Standard = 5 mg/l

Direction of Flow

Proposed Total Nitrogen Criterion = 0.75 mg/l

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45

MB 03 MB 04 MB 04a MB 05

C h l o r i

d e C o n c .

( m g

/ l )

Sampling Station

Chloride Concentrations in McCabe's Brook - July 10, 2007

M edian 10 -Jul-10

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MB 02 MB 03 MB 04 MB 04a MB 05

T u r b i d i t y

( N T U

) / T S S C o n c .

( m g

/ l )

Sampling Station

Turbidity and Total Suspended Solids Concentrations in McCabe's Brook- August 4, 2010

Turbidity Total Suspended Solids

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MB 02 MB 03 MB 04 MB 04a MB 05

P h o s p

h o r u s C o n c .

( g /

l a s P

)

Sampling Station

Phosphorus Concentrations in McCabe's Brook, August 4, 2010

Part iculate P Dissolved P

8 6 8

1 7 5

2 0 5

. 7

84

39.7

88.3

119

2 2 4

60.349


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A simultaneous peak in the total nitrogen and NO 3 + NO 2 concentrations coincided withthe peaks in solids and total phosphorus concentrations. The peaks in solids and nutrient levelswere accompanied by a dip in the chloride concentration.

That the high levels of solids and nutrients, and the decreased concentration of chlorides,were not observed at downstream locations suggests an event which had taken place within avery short reach of McCabes Brook immediately prior to the time the sample was taken.

There exist two potential sources of change in water quality within this reach: overflowfrom a stormwater treatment and equalization pond receiving drainage from the Vermont TeddyBear Company buildings and parking lots, and a high embankment subject to failure. The

absence of an increase in the chloride concentration and the sudden onset of the event suggestthat drainage from the pond was not responsible, and that bank failure may have been, althoughthe peak in the total nitrogen and NO 3 + NO 2 concentrations would not be expected from such afailure.

f. Nutrient Loads

It has for several years been a vision of the LaPlatte Watershed Partnership to establishflow gaging stations on McCabes Brook to i) assess the practicality of incorporating flowmeasurement into volunteer water quality monitoring programs, ii) replace subjective assessment

of flow conditions with more a accurate measurement of flow, iii) provide greater understandingof flows in small Champlain Valley streams, and iv) provide an information base required todetermine nutrient and sediment loadings transported by the stream, assess their relativesignificance, and determine where the major sources impacting on loadings discharged toShelburne Bay are located. The incorporation of flow measurements on a pilot basis was madepossible in 2010 through financial support from the Town of Shelburne under a Special

0

0.5

1

1.5

2

2.5

3

MB 02 MB 03 MB 04 MB 04a MB 05

N i t r o g e n C o n c .

( m g

/ l a s N

)

Sampling Station

Phosphorus Concentrations in McCabe's Brook - August 4, 2010

NOx TN - NOx

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MB 02 MB 03 MB 04 MB 04a MB 05

C h l o r i

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( m g

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Sampling Station

Chloride Concentrations in McCabe's Brook - August 4,2010

8/4/20 10 Median


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Environmental Project, and assistance from Roy Schiff and Jessica Clark of Milone &MacBroom, Inc. to establish two gaging stations on McCabes Brook.

Establishment of Gaging Stations . Suitable sites for location of staff gages on McCabesBrook were limited by the morphometry of the stream which includes wetlands, riffles, and otherstructures. Staff gages were installed in late June at two locations, one just upstream from theVermont Teddy Bear access road (MB 04a), the other downstream from Harbor Road (MB 02) asampling station MB 01a (not sampled during 2010).

The upstream gage captures flow from the stream upstream from Lime Kiln Road as wellas drainage from cultivated fields and pasture north of Lime Kiln Road. The downstream gagecaptures stream flow at Harbor Road plus intermittent discharges from Shelburnes sewagetreatment plant no.2.

Calibration of staff gages and discharge rating curves were prepared by Milone &MacBroom (Attachment d).

Samplers were provided with instructions for reading staff gages, and readings wereentered on field data forms at the time samples were taken. Results indicate that readings wereperformed accurately, but problems were encountered on several occasions. In the future,additional training will be provided to assure that reading of staff gages is performed accurately.

It is noted that discharges from Shelburne sewage treatment plant no. 2 were not likely toinfluence the downstream gage as no discharges took place for at least 2 hour and 30 minutes

prior to the times samples were taken on any of the sampling dates.

Results . Flows measured during the calibration of staff gages and, for the most part,those measured at the time samples were taken, in general revealed consistency of flowsupstream from the Vermont Teddy Bear access road (MB 04a) relative to those downstreamfrom Harbor Road (MB 01a) as shown in the following table:

Comparison of Flows at Vermont Teddy Bear and Harbor Road

Flow at Ratio of

Data Series Date MB 01a MB 04a Flow MB04a :Flow MB 01a

Calibration 7/8/2010 0.3 0.2 1.506/3/2010 0.6 0.2 3.00

10/18/2010 8 6 1.336/11/2010 8.1 3.6 2.2510/1/2010 46.3 38.6 1.20

WQ Sampling 9/1/2010 0.41 0.13 3.027/7/2010 0.41 0.23 1.80

10/6/2010 1.23 0.77 1.598/4/2010 14.44


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Flows measured coincident with the taking of samples varied from lows of 0.13 cfs atMB 04a and 0.41 cfs at MB 01a, to highs of 0.77 cfs at MB 04a on October 6, and 14.44 cfs atMB 01a on August 4 during a period of moderate rain. The results observed during thecalibration of staff gages indicate that even higher flows may occur at MB 01a following periodsof heavy rainfall. But the results also suggest that the staff gage reading at Vermont Teddy Bearon August 4 may have been erroneous, and that the actual flow could have been as much as 20times that recorded.

Nutrient and Total Suspended Solids Loadings in McCabe's Brook, 2010

Total Nitrogen Total PhosphorusParticulatePhosphorus

TotalSuspended Solids

DateSamplingStation

Flow(cfs)

Conc.(mg/l)

Load(Kg/day)*

Conc.(mg/l)

Load(Kg/day)*

Conc.(mg/l)

Load(Kg/day)*

Conc.(mg/l)

Load(Kg/day)*

7/7/2010 MB 01a 0.41 0.67 0.67 0.959 0.95 28.7 28.54

MB 04a 0.23 0.99 0.55 0.165 0.09 0.084 0.05 26.1 14.46

8/4/2010 MB 01a 14.44 0.83 29.32 0.224 7.91 0.175 6.18 117 4,133.54MB 04a 5.73** 0.8 11.22** 0.308 4.32** 0.084 1.18** 14.9 208.1**

9/1/2010 MB 01a 0.41 0.5 0.50 0.102 0.10 0.064 0.06 20.8 20.69

MB 04a 0.13 0.77 0.25 0.117 0.04 0.068 0.02 3.15 1.04

10/6/2010 MB 01a 1.23 0.63 1.90 0.0741 0.22 0.035 0.11 18 54.23

MB 04a 0.77 0.76 1.44 0.0799 0.15 0.02 0.04 6.23 11.79

11/4/2010 MB 01a 3.20 0.41 3.21 0.0407 0.32 0.02 0.16 9.17 71.77

MB 04a 0.48 0.0452 0.008 2.22* Loading in Kg/Day = (Flow in cfs)x(Conc. in mg/l)x(2.446848)**Estimated flow

Thus, base flows during dry periods at the downstream gage were 1.5 to 3 times those atthe upstream gage. It is noted that the catchment area upstream from MB 04a is about 3.13 mi. 2,and that draining the watershed between MB 04a and MB 02 is about 1.44 mi. 2.

Loadings of nutrients and of suspended solids calculated as the product of discharge andconcentrations expressed as Kg/Day provide important insights into sources of these pollutantstransported to the Laplatte estuary and Shelburne Bay and their relative importance.

In general, concentrations of total nitrogen varied little along McCabes Brook. As aresult, loading rates increased in proportion to flow. In terms of the important periods of highflow, by far the major source of nitrogen in the dis charge from McCabes Brook at Harbor Roadappears to originate downstream from the Vermont Teddy Bear access road and the upstreamfarm fields discussed above.

A similar, but generally less pronounced, pattern of increase in the total phosphorusloading rate at low flows, and lower, but dramatic increase by a factor of 18 occurred during theperiod of high flow on August 4. As indicated above, however, this observation should be


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viewed with caution. Increases in dissolved phosphorus loading rates were consistent at lowerflows, but very much lower during the period of high flow when they increased by a factor of 5.4. Particulate phosphorus loadings, by contrast, increased by a factor of 51.5, highlighting therelative importance of sediment entering downstream from the Vermont Teddy Bear access roadand the upstream farm fields.

Increases in sediment load downstream from the Vermont Teddy Bear access road werein general greater than those of nutrients, and during the period of high flow of August 4,increased by a factor of about 200, again highlighting the importance of sediments entering thestream downstream from MB 04a and impacting on the stream and discharging into ShelburneBay as seen in the following orthophoto.

Overall, the results of the pilot flow measuring effort during the summer of 2010confirmed both the practicality of flow measurement by volunteer water quality samplers and thevalue of flow data to putting sources of pollutants in McCabes Brook into perspective. However, they also highlighted the need for increased training.

Shelburne Bay

McCabes Brook LaPlatte River


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III. CONCLUSIONS AND RECOMMENDATIONS

The volunteer monitoring effort in the McCabes Brook watershed has provided manyinsights into factors impacting on water quality within the watershed, identified issues relatingwater quality within the watershed and impacting on Shelburne Bay, and highlighted specificneeds and directions for further clarification, as well as application of findings. These aresummarized below, together with recommendations applicable to all volunteer water qualitymonitoring programs based on lessons learned, as well as specific recommendations relating tosediment and nutrients in McCabes Brook. In addition, results of water quality monitoring havea broader value to overall planning activities within the Lake Champlain Basin.

a. Data Management and Quality Assurance

Laboratory results are available to volunteer monitoring programs between three and four

weeks following delivery to the LaRosa Laboratory after all tests have been completed andresults have been reviewed for quality control purposes in the laboratory. The delay in receivingresults has several consequences. First, while it is not the purpose of volunteer monitoringprograms to identify violations or events requiring remediation, in the event that results dohighlight such events, they can be useful to identify problems or opportunities to learn andimprove practices. Several such events have been identified as a result of monitoring in theMcCabes Brook watershed. Secondly, the delay leaves little time to review quality controlissues and to respond to them in advance of the next sample collection. Possible improvementsmay be possible involving both procedures in the laboratory and on the part of watershedcoordinators.


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RECOMMENDATIONS

The Water Quality Division and the LaRosa laboratory should considerthe feasibility of flagging exceptional results based on historical results orexperience of the laboratory and identify steps by which to notify programcoordinators.

The LaRosa Laboratory should determine the feasibility of notifyingprogram coordinators when results are posted.

Program coordinators need to monitor the Water Quality Divisionswebsite on a daily basis and download results as soon as they are posted.

Program coordinators need to review results immediately for unusualresults or emerging issues requiring follow-up and immediately notify theWater Quality Division.

The Water Quality Division must respond according to Agencyprocedures. Interagency agreements need to be reviewed to assureresponse where needed.

Program coordinators need to review sample and duplicate data as well asfield blanks for inconsistencies and respond to correct quality controlissues identified. Procedures should be included in training of coordinators.

b. Suspended SedimentsMcCabes Brook is listed under Part C of the State of Vermonts list of priority surface

waters outside the scope of Section 303(d) of the Clean Water Act which identifies waters inneed of further assessment based on elevated turbidity affecting aquatic life. Results of volunteer water quality monitoring indicate that turbidity levels exceeded the Vermont Statestandard in about 15.5% of all samples from Lime Kiln Road to Harbor Road analyzed from2004 through 2010. Sources appear to be erosion, bank failures, and runoff from cultivatedfields draining into McCabes Brook between Lime Kiln Road and the Vermont Teddy Bear access road in the upstream areas. Sources in the lower reaches of the stream from Route 7

downstream require further investigation.

The greatest increases in turbidity levels occurred between Bostwick Road and HarborRoad where the Vermont State standards have been exceeded in nearly half the samplesanalyzed. The importance of the increase in turbidity levels and concentrations of suspendedsolids becomes even more evident when increases in suspended sediment loadings, which canreach very high levels during high flows, are considered. Suspended sediment can impact not


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only directly on aquatic life in McCabes Brook, but on phosphorus levels uin the stream, andphosphorus and sediment loads discharged to Shelburne Bay.

RECOMMENDATIONS

Undertake further investigation of sources of suspended sediments in thereaches between Lime Kiln Road and the Vermont Teddy Bear accessroad, particularly as they relate to land management practices and landcover.

Undertake further investigation of sources of suspended sediment betweenBostwick and Harbor Roads.

Develop a methodology for Phase II fluvial geomorphology of lowgradient streams including reaches associated with wetlands.

Utilize results and findings of volunteer water quality monitoring in thefollow-up to needs identified in the 303(d) list of waters in need of furtherassessment based on the effects of turbidity on aquatic life.

c. Nutrients

Nitrogen . Total nitrogen concentrations have tended to remain relatively constant within

McCabes Brook, although decreasing slightly downstream from Route 7, at a medianconcentration slightly below the proposed Vermont State criterion for Class B warm waterstreams. On the other hand, they frequently have exceeded the criterion at all locations sampled.On one sampling date, the total nitrogen rose to a level in excess of 10 mg/l, and the nitrate tomore than 8 mg/l, far in excess of the State nitrate standard of 5 mg/l, apparently related to runoff from cultivated fields reaching the McCabes Brook between Lime Kiln Road and the VermontTeddy Bear access road. Because total nitrogen concentrations remain relatively constant alongthe stream, nitrogen loadings tend to be proportional to stream flow, and save for unusual events,do not suggest any hot spots.

Nitrogen concentrations in McCabes Brook have been consistently very low relative tophosphorus concentrations, indicating that phosphorus in the stream is present in excess.

Phosphorus . Phosphorus occurs in McCabes Brook primarily in association withparticulate matter, as it is in most (but not all) streams in the Champlain Valley, and totalphosphorus concentrations exceed the proposed Vermont State criterion for Class B warm waterstreams in most samples.


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There are two areas of particular interest related to phosphorus in McCabes Brook. Thefirst is the reach extending from Lime Kiln Road to the Vermont Teddy Bear access road. Thisreach of the stream receives drainage from agricultural fields in cultivation, pasture, or grass atdifferent times during the years that water quality sampling has been carried out. The trendsobserved between the two locations, increasing during years that fields were cultivated, anddecreasing during 2008 when none of the fields were cultivated, strongly suggest a link betweencultivation of the field, as well as drainage configurations, influence phosphorus concentrationsin the stream. This suggestion is strengthened by observation of greatly increased phosphorusconcentrations in the stream over this reach associated with exceptional increases in totalnitrogen and nitrate discussed above.

Unusual or extreme events may provide insights into sources of nutrients and factorsaffecting water quality and loadings, and may provide opportunities to improve land

management practices to reduce nutrient loadings on Lake Champlain.

A second area of interest is the reach of McCabes Brook extending from Bostwick Roadto Harbor Road in Shelburne. Concentrations of phosphorus, primarily associated withparticulate matter, consistently increase, and frequently double, over this reach of the stream.This increase may have a very large impact on the total load of solids and phosphorustransported by the stream as it flows to its confluence with the LaPlatte River and ShelburneBay, especially when flows are high.


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RECOMMENDATIONS

Management of agricultural fields and their drainage should beinvestigated with a view to reducing discharge of nutrients to McCabesBrook and improving best management practices generally.

Sources of increases in concentrations and loadings of sediment andphosphorus associated with it between Bostwick and Harbor Roads shouldbe investigated with a view to reducing loads in McCabes Brook anddischarges to Shelburne Bay.

Develop a methodology for Phase II fluvial geomorphology of lowgradient streams including reaches associated with wetlands.

Results of water quality monitoring and findings relating to factorsaffecting water quality in McCabes Brook may provide insights which

can benefit further assessment of the impacts of small direct to lakedrainages.

Unusual or extreme events should be identified as soon as monitoring databecome available and followed-up with the Department of EnvironmentalConservation.

d. Land Use and Basin Planning

The water quality data provided through the LaRosa Volunteer Water Quality MonitoringAnalytical Partnerships program constitute a valuable resource which should be utilized to thegreatest extent possible. Furthermore, volunteer sampling programs can be designed to improvetheir utility for identifying areas of interest, improving water quality, and planning at State,County, and local levels.


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RECOMMENDATIONS

The program should encourage the organization of more programs focusedon small direct to lake streams.

Volunteer monitoring programs should be reviewed periodically to assurethat they are providing optimally useful information and that they have thecapacity to assess, interpret, and follow up on findings.

Results from all volunteer monitoring programs should be reviewed toidentify common lessons learned and common themes that can inform theStates overall water quality program.

Guidance should be provided to facilitate and guide volunteer waterquality monitoring groups in the analysis and interpretation of data, aswell as follow-up procedures.

Results from volunteer water quality monitoring programs, as well asfluvial geomorphologic studies, should be utilized more effectively as abasis for formulating policies relating to land management and protectingwatersheds and Lake Champlain, as well as for drafting land use and basinplans.

Results from volunteer water quality monitoring programs, as well asfluvial geomorphologic studies, should be utilized more effectively as abasis for planning by Regional Planning Commissions and towns.


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IV. ATTACHMENTS


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a. Sampling Stations

Site LocationSite

LatitudeSite

Longitude

Parameter

Flow Temp. TSS Turbidity ChlorideTotal

PDiss.

PTotal

N N

B02 - McCabes Brook at Harbor Road44.38305 -73.23853 X

X X X X X X X X

B03 - McCabes Brook at Bostwick Road44.36892 -73.23586

X X X X X X X X

B04 - McCabes Brook at Route 744.36230 -73.23461

X X X X X X X X

B04a - McCabes Brook at Teddy Bear Access Road

44.36086 -73.23405

X X X X X X X X X

B05 - McCabes Brook at Lime Kiln Road44.34582 -73.22868

X X X X X X X X


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b. Water Quality Data

Solids Concentrations in McCabe's Brook - 2010Station

No. 5/5/2010 6/2/2010 7/7/2010 8/4/2010 9/1/2010 10/6/2010 11/3/2010 Median Minimum Maximum

TSS MB 02 3.91 22 28.7 117 20.8 18 9.71 20.8 3.91 117

MB 03 1.79 1.61 162


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Chloride Concentrations in McCabe's Brook - 2010Station


MB 02 27.1 38.8 46.2 18.3 41.2 32.8 33.1 33.1 18.3 46.2

MB 03 23 45.4 38.7 43.6 72.4 30.7 30.3 38.7 23 72.4MB 04 20.9 49 40.3 14.4 82.9 26.7 27.9 27.9 14.4 82.9

MB 04a 20.5 25.8 27.9 23.4 56.1 22.7 25.9 25.8 20.5 56.1

MB 05 15.5 13.7 18.9 6.22 19.9 17.3 21.1 17.3 6.22 21.1

Nitrogen Concentrations in McCabe's Brook - 2010Station


TN MB 02 0.43 0.49 0.67 0.83 0.5 0.63 0.41 0.58 0.41 0.83

MB 03 0.42 0.43 0.65 1.13 0.47 0.62 0.46 0.54 0.42 1.13

MB 04 0.44 0.64 0.78 2.54 0.49 0.75 0.5 0.71 0.44 2.54MB04a 0.45 0.68 0.99 0.8 0.77 0.76 0.48 0.74 0.45 0.99

MB 05 0.43 0.83 1.01 0.73 0.79 0.69 0.45 0.78 0.43 1.01

Nox MB 02 < 0.05


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c. Quality Assurance

Completeness of Sampling and Field Duplicates

No. of No. of Stations

Stations Date Sampled Chloride Turbidity TSS Total P Diss. P Total N NOx

5 5/5/2010 5 5 5 5 5 5 5 5 6/2/2010 5 5 5 4 5 5 5 5 7/7/2010 5 5 5 5 5 4 5 5 8/4/2010 5 5 4 5 5 5 5 5 9/1/2010 5 5 5 5 5 5 5 5 10/6/2010 5 5 5 5 5 5 5 5 11/3/2010 5 5 5 5 5 5 5

otal No. of Stations 35 35 35 34 34 35 34 35 35

ercent 100 97.1 97.1 100 97.1 100 100

arget Percent 80% 80% 80% 80% 80% 80% 80

umber of Duplicates 8 7 7 7 7 7 ercent of Total 22.9 20.6 20.6 20.0 20.6 20.0 20.0

arget Percent 10% 10% 10% 10% 10% 10% 10%

Summary of Percent Differences

ParameterTarget

PrecisionMeanRPD

Chloride 10% 1.66Turbidity 15% 4.00TSS 15% 18.53

Total P 15% 5.09Diss. P 15% 1.31Total N 15% 1.87

NOx 10% 0


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Attachment d. Gaging Station Rating Curves


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Analysis of Flows in McCabes Brook 2010

Flows at Vermont Teddy Bear and Harbor RoadHarbor Road Vermont Teddy Bear

DateTotal

Flow (cfs)Total

Flow/mi. 2

ReachFlow/mi. 2

(RF2)

TotalFlow(cfs)

TotalFlow/Mi. 2

(TF4a) TF4a :RF

Calibration 7/8/2010 0.3 0.066 0.069 0.2 0.064 0.926/3/2010 0.6 0.131 0.278 0.2 0.064 0.23

10/18/2010 8 1.751 1.389 6 1.917 1.386/11/2010 8.1 1.772 3.125 3.6 1.150 0.3710/1/2010 46.3 10.131 5.347 38.6 12.332 2.31

Sampling 9/1/2010 0.41 0.089 0.189 0.13 0.043 0.237/7/2010 0.41 0.089 0.125 0.23 0.072 0.58

10/6/2010 1.23 0.269 0.318 0.77 0.247 0.788/4/2010 14.44 3.159 - - -

0

5

10

15

20

25

30

35

40

45

50

Harbor Road Vermont Teddy Bear

F l o w

( c f s )

Flows in McCabe's Brook, 2010 Calibration

Oc tobe r 1 , 2 01 0 Oct obe r 1 8, 2 01 0 June 11 , 2 01 0 June 3, 2 01 0 Jul y 8 , 2 01 0

0

5

10

15

20

25

30

35

40

45

50

Harbor Road Vermont Teddy Bear

F l o w

( c f s )

Flows in McCabe's Brook - 2010 Monitioring

A ug us t 4 , 2 01 0 O ct obe r 6 , 2 01 0 Jul y 7 , 2 01 0 Se pt embe r 1 , 2 01 0

2010 water quality supplement mccabe’s brook watershed

Documents