An Evaluation of BMP Removal Efficiency in the Kensico Reservoir WatershedAn Evaluation of BMP Removal Efficiency in the Kensico Reservoir Watershed

New York City New York City Department of Department of Environmental Environmental ProtectionProtection

16-17 September 200816-17 September 2008

Prepared by

Prepared for

2008 NYWEA Watershed 2008 NYWEA Watershed Science and Technical Science and Technical ConferenceConference

and

2Presenters:Presenters:

Paul Muessig, Michael Powell, and Jon TrombinoPaul Muessig, Michael Powell, and Jon TrombinoEA Science and TechnologyEA Science and Technology3 Washington Center3 Washington CenterNewburgh, New YorkNewburgh, New York

John CanningJohn CanningNew York City Department of Environmental ProtectionNew York City Department of Environmental ProtectionDivision of Drinking Water QualityDivision of Drinking Water QualitySutton Park OfficeSutton Park Office465 Columbus Avenue465 Columbus AvenueValhalla, New YorkValhalla, New York

3IntroductionIntroduction

● Acknowledgements – NYCDEP staffAcknowledgements – NYCDEP staff● 45 BMP structures in Kensico Reservoir watershed to 45 BMP structures in Kensico Reservoir watershed to

improve and maintain water qualityimprove and maintain water quality● Monitoring Plan and Quality Assurance Project PlanMonitoring Plan and Quality Assurance Project Plan● 5 BMPs selected for intensive monitoring5 BMPs selected for intensive monitoring● 4 on perennial tributaries to Kensico Reservoir4 on perennial tributaries to Kensico Reservoir● NYCDEP Kensico Laboratory processed all samples NYCDEP Kensico Laboratory processed all samples

(turbidity, total suspended solids [TSS], total (turbidity, total suspended solids [TSS], total phosphorus, and fecal coliform)phosphorus, and fecal coliform)

4TasksTasks

● Monitoring a minimum of 10 storm events at 5 Monitoring a minimum of 10 storm events at 5 selected BMPs, 2000-2007selected BMPs, 2000-2007

● Precipitation, hydrologic, and water quality data Precipitation, hydrologic, and water quality data compiled to Microsoft ACCESScompiled to Microsoft ACCESS

● Formatted and submitted to EPA/ASCE Formatted and submitted to EPA/ASCE International BMP DatabaseInternational BMP Database

● Evaluate removal efficiency of BMPs Evaluate removal efficiency of BMPs

5

6

BMP No. BMP TypeTributary

NameMonitoring

Period Sampling Locations

12 Retention Pond (Wet) - Surface Pond with Permanent Pool

Malcolm Brook

2000-2002 Inlets: MB-3, MB-4Outlet: MB-1

37 Retention Pond (Wet) - Surface Pond with Permanent Pool

N5 2004 Inlet: N51MAINOutlet: N5-1

13 Wetland - Basin without Open Water (Wetland Meadow Type)

N1 2005-2006 Inlet: BMP13INOutlet: BMP13OUT

57 Sand filter with Layered Media

None 2005-2006 Inlet: BMP57INOutlet: BMP57OUT

74 Retention Pond (Wet) - Surface Pond with Permanent Pool

E11 2007 Inlets: E11N1, E11S1Outlet: E11

7BMP 12—Retention PondBMP 12—Retention Pond● Wet retention with 2 inlets, forebay, and permanent Wet retention with 2 inlets, forebay, and permanent

micro-poolmicro-pool● Design WSE 370 ft MSL; extended detention 380 ft MSLDesign WSE 370 ft MSL; extended detention 380 ft MSL● Perennial tributary to Kensico ReservoirPerennial tributary to Kensico Reservoir● Watershed – 91.4 acresWatershed – 91.4 acres● Forested – 15.5 acresForested – 15.5 acres● Residential – 32.2 acresResidential – 32.2 acres● Office park – 43.7 acresOffice park – 43.7 acres● Slopes – generally < 8%Slopes – generally < 8%

8

9

10

11

12

13BMP 13—Wet MeadowBMP 13—Wet Meadow

● Wet meadow extended detention, 1 inlet with 2 ft deep Wet meadow extended detention, 1 inlet with 2 ft deep micro-poolmicro-pool

● Micro-pool WSE 420 ft MSL; extended detention 425 ft Micro-pool WSE 420 ft MSL; extended detention 425 ft MSLMSL

● Perennial tributary to Kensico ReservoirPerennial tributary to Kensico Reservoir● Watershed – 20 acresWatershed – 20 acres● Forested – 3 acresForested – 3 acres● Residential (1/3-acre lots) – 17 acresResidential (1/3-acre lots) – 17 acres● Slopes – 8-15 %Slopes – 8-15 %

14

15

16

17BMP 37—Retention PondBMP 37—Retention Pond● Wet retention basin, 1 inlet with permanent micro-pool and Wet retention basin, 1 inlet with permanent micro-pool and

wet forebaywet forebay● Permanent pool 396 ft MSL; extended detention 398 ft MSLPermanent pool 396 ft MSL; extended detention 398 ft MSL● Watershed – 249 acresWatershed – 249 acres● Low density residential – 180.5 acresLow density residential – 180.5 acres● Medium density residential – 12.6 acresMedium density residential – 12.6 acres● Office park – 29 acresOffice park – 29 acres● Institutional – 23.5 acresInstitutional – 23.5 acres● Forested – 3.4 acresForested – 3.4 acres● Slopes – <8%Slopes – <8%

18

19

20

21

22BMP 57—Sand FilterBMP 57—Sand Filter● Multi-media layered sand filterMulti-media layered sand filter● Capture and treat runoff from 550 to 600 ft along Capture and treat runoff from 550 to 600 ft along

Nannyhaggen RoadNannyhaggen Road● Sedimentation chamber, filtration chamber (2 ft x 28.5 ft), Sedimentation chamber, filtration chamber (2 ft x 28.5 ft),

overflow bypass weiroverflow bypass weir● Temporary storage, 5 ft over filtration bedTemporary storage, 5 ft over filtration bed● Watershed – 2.3 acresWatershed – 2.3 acres● Forested – 2 acresForested – 2 acres● Paved road surface – 0.3 acresPaved road surface – 0.3 acres● Slope – < 8%Slope – < 8%

23

24

25Summary of Monitored Storm EventsSummary of Monitored Storm EventsSummary of Monitored Storm EventsSummary of Monitored Storm Events

BMPMonitoring

Period

Number of Events

MonitoredDuration of

Precipitation (hrs)Event

Precipitation (in.)

Events Exceeding Extended Detention

Design Event

BMP 12—Retention Pond

Feb-2000 - Sep-2001

17 1-30 0.23 - 3.36 7

BMP 13—Wet Meadow

Apr-2005 - Oct-2006

14 1-70 0.24 - 6.85 6

BMP 37—Retention Pond

Sep-2002 - Sep-2004

19 1-43 0.50 - 5.01 12

BMP 57—Sand Filter

Apr-2005 - Oct-2006

11 1-50 0.24 - 2.31 8

26Field MethodsField Methods

● ISCO 6700 Autosampler – timed and flow-ISCO 6700 Autosampler – timed and flow-weighted grab samples over duration of storm weighted grab samples over duration of storm event at inlet and outlet weirsevent at inlet and outlet weirs

● Continuous stage and discharge recordingContinuous stage and discharge recording● Precipitation record at Kensico ReservoirPrecipitation record at Kensico Reservoir● Hydrology staff selected 10 samples for Hydrology staff selected 10 samples for

analysis—4 each on rising and falling limb of analysis—4 each on rising and falling limb of hydrograph and 2 around peakhydrograph and 2 around peak

27Statistical MethodsStatistical Methods

● Paired comparisons between influent and Paired comparisons between influent and effluent concentrationseffluent concentrations

● Efficiency ratiosEfficiency ratios● Comparison of influent and effluent Comparison of influent and effluent

probability curvesprobability curves

28Paired Comparisons of Influent and Effluent Event Mean ConcentrationsPaired Comparisons of Influent and Effluent Event Mean Concentrations

BMP NMethod of

ComparisonSignificant Reduction?

BMP 12-Retention Pond

TSS 15 t-test Yes

Turbidity 17 t-test Yes

Total phosphorus

15 t-test Yes

Fecal coliform

16 Wilcox Signed Rank

Yes

BMP 13- Wetland Meadow

TSS 13 t-test on log-transforms

No

Turbidity 13 t-test Yes

Total phosphorus

13 t-test Yes

Fecal coliform

13 t-test on log-transforms

Yes

BMP NMethod of

ComparisonSignificant Reduction?

BMP 37 Retention Pond

TSS 18 Wilcox Signed Rank

Yes

Turbidity 18 Wilcox Signed Rank

Yes

Total phosphorus

17 t-test on log-transforms

Yes

Fecal coliform

17 t-test Yes

BMP 57 Sand Filter

TSS 10 t-test Yes

Turbidity 10 t-test on log-transforms

Yes

Total phosphorus

8 t-test Yes

Fecal coliform

10 t-test on log-transforms

No

29BMP Removal EfficienciesBMP Removal EfficienciesBMP Parameter ER

BMP 12-Retention Pond

TSS 71%

Turbidity 55%

Total phosphorus 57%

Fecal coliform 52%

BMP 13- Wetland Meadow

TSS Not statistically significant

Turbidity 35%

Total phosphorus 29%

Fecal coliform 55%

BMP 37 Retention Pond

TSS 78%

Turbidity 59%

Total phosphorus 50%

Fecal coliform 40%

BMP 57 Sand Filter

TSS 79%

Turbidity 31%

Total phosphorus 73%

Fecal coliform Not statistically significant

30BMP 12 Retention Pond Effluent Probability Plot for TSSBMP 12 Retention Pond Effluent Probability Plot for TSS

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 10 100 1,000

Concentration (mg/L)

Influent

Effluent

Significant Removal (p < 0.01)

Concentration (mg/L)

• Good removal over influent concentrations >30 mg/L.

• Estimated irreducible concentration is 2 mg/L.

31

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 10 100 1,000 10,000

Influent

Effluent

Significant Removal (p < 0.01)

BMP 37 – Retention Pond Effluent Probability Plot for TSSBMP 37 – Retention Pond Effluent Probability Plot for TSS

Concentration (mg/L)

Good removal with influent >10 mg/L.

Irreducible Concentration = 10 mg/L

32BMP 57 - Sand Filter Effluent Probability Plot for TSSBMP 57 - Sand Filter Effluent Probability Plot for TSS

Concentration (mg/L)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 10 100 1000

Influent

Effluent

Significant Removal (p < 0.01)

Good removal over range of influent concentrations.

33BMP 12 - Retention Pond Effluent Probability Plot for Fecal ColiformBMP 12 - Retention Pond Effluent Probability Plot for Fecal Coliform

Concentration (cfu/100mL)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 10 100 1,000 10,000 100,000

Influent

Effluent

Significant Removal (p = 0.02)

For small storm events, BMP is actually a contributor.

Some removal with influent concentrations >1,000 cfu/100mL.

34BMP 13 – Wet Meadow Effluent Probability Plot for Fecal ColiformBMP 13 – Wet Meadow Effluent Probability Plot for Fecal Coliform

Concentration (cfu/100mL)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

10 100 1,000 10,000 100,000 1,000,000

Influent

Effluent

Significant Removal (p < 0.01)

Consistent removal (50%) over range of influent concentrations.

35

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

100 1,000 10,000 100,000 1,000,000

Concentration (cfu/100mL)

Influent

Effluent

Significant Removal (p < 0.01)

BMP 37 – Retention Pond Effluent Probability Plot for Fecal ColiformBMP 37 – Retention Pond Effluent Probability Plot for Fecal Coliform

Concentration (cfu/100mL)

Removal with influent >20,000 cfu/100mL.

36ConclusionsConclusions

● TSSTSS Consistent 70-80% removal (with exception of BMP Consistent 70-80% removal (with exception of BMP

13 – Wet Meadow)13 – Wet Meadow) Removal of turbidity and total phosphorus is similar Removal of turbidity and total phosphorus is similar

to TSSto TSS● Fecal ColiformFecal Coliform

Sand filter is ineffectiveSand filter is ineffective Retention ponds and wetland meadow remove Retention ponds and wetland meadow remove

50% at high influent concentrations50% at high influent concentrations Residual in retention ponds and wetland meadow Residual in retention ponds and wetland meadow

may contribute at low influent concentrationsmay contribute at low influent concentrations