New York; Rain Garden - Vassar College

8/3/2019 New York; Rain Garden - Vassar College

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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



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

Stormwater and Water Quantity



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, Groffman

et al. 2003, National Research Council 2008)

- Water treatment is expensive



Rain gardens?

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



Town House Apartments Site



Redevelopment - 2008

Rain Garden 2

Rain Garden 1


http://slidepdf.com/reader/full/new-york-rain-garden-vassar-college 7/29Rain Garden 2 Rain Garden 1



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)



Site Map



Rain Garden Catch Basin Unfiltered Catch Basin



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

C o n c e n t r a t i o n ( m g / L )




Mean Dissolved Nutrient Concentrations in Catch Basins

0

0.2

0.4

0.6

0.8

1

1.2


C o n c e n t r a t i o n

( m g / L )

Ammonium

Nitrate

Phosphate




Mean Total Heavy Metal Concentrations in Catch Basins

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35



( m g / L )

Copper

Lead

Zinc



Rain Garden 2 inlet Rain Garden 1 inlet



Mean Total Heavy Metal Concentrations in Catch Basins

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35



( m g / L )

Copper

Lead

Zinc




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)



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)



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



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



Monitoring water quality for the

duration of a storm event



TSS in Rain Garden 1 Catch Basin on 10/14

y = -0.2302x + 7.254

R2

= 0.4652

0.00

2.00

4.00

6.00

8.00

10.00

12.00

1 7 : 3 1

1 7 : 4 6

1 8 : 0 1

1 8 : 1 6

1 8 : 3 1

1 8 : 4 6

1 9 : 0 1

1 9 : 1 6

1 9 : 3 1

1 9 : 4 6

2 0 : 0 1

2 0 : 1 6

2 0 : 3 1

2 0 : 4 6

2 1 : 0 1

2 1 : 1 6

2 1 : 3 1

2 1 : 4 6

2 2 : 0 1

2 2 : 1 6

2 2 : 3 1

2 2 : 4 6

2 3 : 0 1

2 3 : 1 6

Time

TSS in Rain Garden 1 Catch Basin and

Unfiltered Catch Basin on 10/14

0.00

5.00

10.00

15.00

20.00

25.00

30.00

1 7 : 3 1

1 7 :

4 6

1 8 : 0 1

1 8 : 1 6

1 8 : 3 1

1 8 :

4 6

1 9 : 0 1

1 9 : 1 6

1 9 : 3 1

1 9 :

4 6

2 0 : 0 1

2 0 : 1 6

2 0 : 3 1

2 0 :

4 6

2 1 : 0 1

2 1 : 1 6

2 1 : 3 1

2 1 :

4 6

2 2 : 0 1

2 2 : 1 6

2 2 : 3 1

2 2 :

4 6

2 3 : 0 1

2 3 : 1 6

Time

Rain Garden 1

Unfiltered Catch Basin



Total Heavy Metal Concentration and Water Depth i

Rain Garden 1 Catch Basin, 10/14

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1 7 : 3 1

1 7 : 4 6

1 8 : 0 1

1 8 : 1 6

1 8 : 3 1

1 8 : 4 6

1 9 : 0 1

1 9 : 1 6

1 9 : 3 1

1 9 : 4 6

2 0 : 0 1

2 0 : 1 6

2 0 : 3 1

2 0 : 4 6

2 1 : 0 1

2 1 : 1 6

2 1 : 3 1

2 1 : 4 6

2 2 : 0 1

2 2 : 1 6

2 2 : 3 1

2 2 : 4 6

2 3 : 0 1

2 3 : 1 6

Time

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

W a t e r D e p t h ( m )

Total heavy metals

Water depth



Water Depth in Rain Garden 1 Catch Basin and

Unfiltered Catch Basin and Precipitation on 10/14

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

1 7 : 0 0

1 7 : 1 5

1 7 : 3 0

1 7 : 4 5

1 8 : 0 0

1 8 : 1 5

1 8 : 3 0

1 8 : 4 5

1 9 : 0 0

1 9 : 1 5

1 9 : 3 0

1 9 : 4 5

2 0 : 0 0

2 0 : 1 5

2 0 : 3 0

2 0 : 4 5

2 1 : 0 0

2 1 : 1 5

2 1 : 3 0

2 1 : 4 5

2 2 : 0 0

2 2 : 1 5

2 2 : 3 0

2 2 : 4 5

2 3 : 0 0

2 3 : 1 5

2 3 : 3 0

2 3 : 4 5

0 : 0 0

Time

0

0.0005

0.001

0.0015

P r e c i p i t a t i o n

( m )

Unfiltered Catch Basin

Rain Garden 1

Precipitation



Assessing Flow Patterns



Identifying maintenance concerns

• Visual observation and

data collection

• Sediment build-up ininlets

• Water flow through soil

• Plant growth

• Establishment of weeds



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



Mean Nutrient Concentrations

0

5

10

15

20

25

30

Precipitation Runoff Soil Water Rain Garden CatchBasins

Unfiltered CatchBasin


( m g / L )

Ammonium

Nitrate

Phosphate



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

C o n c e n t r a t i o n ( m g / L )

Copper

Lead

Zinc

New York; Rain Garden - Vassar College

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