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Rain Gardens at Vassar College:  A Water Quality Assessment Emily Vail Collins Research Fellow Vassar College Environmental Research Institute Community Educator Environment Program Cornell Cooperative Extension Dutchess County

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    Rain Gardens at Vassar College:

    A Water Quality Assessment

    Emily VailCollins Research Fellow

    Vassar College Environmental Research Institute

    Community Educator

    Environment Program

    Cornell Cooperative Extension Dutchess County

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    National Research Council, Stormwater Management in the United States (2008)

    Stormwater and Water Quantity

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    Stormwater and Water Quality

    Sediment - erosion, bound to otherpollutants

    Nutrients - eutrophication

    Heavy metals - toxicity

    Other contaminants

    - Ecological problems in streams(Walsh et al. 2005, Paul & Meyer 2001, Groffmanet al. 2003, National Research Council 2008)

    - Water treatment is expensive

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    Rain gardens?

    NYS DEC, New York State Stormwater Design Manual (2008)

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    Town House Apartments Site

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    Redevelopment - 2008

    Rain Garden 2

    Rain Garden 1

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    Water samples collected:

    Precipitation

    Stormwater runoff

    Soil water

    Catch basins

    Analyzed for:

    Total suspended solids (TSS)

    Dissolved inorganic nutrients (N, P)

    Heavy metals (Cu, Pb, Zn)

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    Site Map

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    Rain Garden Catch Basin Unfiltered Catch Basin

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    n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

    Mean TSS in Catch Basins

    0

    5

    10

    15

    20

    25

    Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin

    Concentration(mg/L)

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    n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

    Mean Dissolved Nutrient Concentrations in Catch Basins

    0

    0.2

    0.4

    0.6

    0.8

    1

    1.2

    Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin

    Concentration

    (mg/L)

    Ammonium

    Nitrate

    Phosphate

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    n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

    Mean Total Heavy Metal Concentrations in Catch Basins

    0

    0.05

    0.1

    0.15

    0.2

    0.25

    0.3

    0.35

    Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin

    Concentration

    (mg/L)

    Copper

    Lead

    Zinc

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    Rain Garden 2 inlet Rain Garden 1 inlet

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    Mean Total Heavy Metal Concentrations in Catch Basins

    0

    0.05

    0.1

    0.15

    0.2

    0.25

    0.3

    0.35

    Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin

    Concentration

    (mg/L)

    Copper

    Lead

    Zinc

    n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

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    Summary

    Rain gardens are effective at removing TSS

    Consistent with other studies (Davis 2007, Davis 2009,Bratieres et al. 2008)

    May be net exporters of nutrients (affected bythe growing season)

    Some studies found that although total N and Preduced, inorganic nutrients increased (Davis et al.

    2009, Davis et al. 2006, US EPA 1999, Davis et al. 2007, Dietz &Clausen 2006, Kim et al. 2003)

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    Summary

    Do not appear to moderate heavy metal loads(further studies needed)

    Laboratory studies show 88-97% removal of Cd, Cu,

    Pb, Zn from synthetic stormwater (Sun & Davis 2006,Davis et al. 2001, Davis et al. 2003)

    Field studies - slightly lower removal rates for

    metals (Davis 2007)

    Increased retention time for stormwaterquantity (Davis et al. 2009, Davis 2007, Hood et al.2007, Hatt et al. 2009)

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    Conclusion Rain gardens - an important aspect of Low Impact Design

    Maintain pre-development hydrology

    Local BMPs to address ecosystem-wide problems

    Need for assessment

    Aesthetics and function

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    Next steps

    Do rain gardens continue to function the sameway over the duration of a storm event?

    Monitoring water quality

    Assess flow patterns on site

    What kind of maintenance is required? Is thedesign functioning as it was intended?

    Visual observations and considerations formaintenance and potential design modifications

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    Monitoring water quality for the

    duration of a storm event

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    TSS in Rain Garden 1 Catch Basin on 10/14

    y = -0.2302x + 7.254

    R2

    = 0.4652

    0.00

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    Time

    TSS in Rain Garden 1 Catch Basin and

    Unfiltered Catch Basin on 10/14

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    Time

    Rain Garden 1

    Unfiltered Catch Basin

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    Total Heavy Metal Concentration and Water Depth i

    Rain Garden 1 Catch Basin, 10/14

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    Time

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    WaterDepth(m)

    Total heavy metals

    Water depth

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    Water Depth in Rain Garden 1 Catch Basin and

    Unfiltered Catch Basin and Precipitation on 10/14

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    Precipitation

    (m)

    Unfiltered Catch Basin

    Rain Garden 1

    Precipitation

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    Assessing Flow Patterns

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    Identifying maintenance concerns

    Visual observation and

    data collection

    Sediment build-up ininlets

    Water flow through soil

    Plant growth

    Establishment of weeds

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    Acknowledgements

    Dr. Lynn Christenson, Dr. Mary Ann Cunningham,

    Dr. Stuart Belli, Dr. Kirsten Menking, Dr. David Gillikin,

    Dr. Jill Schneiderman, Dr. Mark Schlessman, Rick Jones,

    Keri VanCamp, Seth Stickle, Danielle Goldie, Cat Foley,Sandy Alles, & Will Jobs

    Vassar College Environmental Research Institute

    Vassar College Environmental Studies Program

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    Mean Nutrient Concentrations

    0

    5

    10

    15

    20

    25

    30

    Precipitation Runoff Soil Water Rain Garden CatchBasins

    Unfiltered CatchBasin

    Concentration

    (mg/L)

    Ammonium

    Nitrate

    Phosphate

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    Mean Heavy Metal Concentrations

    0

    0.5

    1

    1.5

    2

    2.5

    3

    Precipitation Runoff Soil Water Rain Garden Catch

    Basins

    Unfiltered Catch

    Basin

    Concentration(mg/L)

    Copper

    Lead

    Zinc