Vassar College NY: Rain Garden

1. 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

2. Stormwater and Water Quantity
National Research Council, “Stormwater Management in the United States” (2008)

3. Stormwater and Water Quality
• Sediment - erosion, bound to other
pollutants
• 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

4. Rain gardens?
NYS DEC, “New York State Stormwater Design Manual” (2008)

5. Town House Apartments Site

6. Redevelopment - 2008
Rain Garden 1
Rain Garden 2

7. Rain Garden 2 Rain Garden 1

8. 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)

9. Site Map

10. Rain Garden Catch Basin Unfiltered Catch Basin

11. Mean TSS in Catch Basins
25
20
Concentration (mg/L)
15
10
5
0
Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin
n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

12. Mean Dissolved Nutrient Concentrations in Catch Basins
1.2
Ammonium
Nitrate
1 Phosphate
Concentration (mg/L)
0.8
0.6
0.4
0.2
0
Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin
n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

13. Mean Total Heavy Metal Concentrations in Catch Basins
0.35
Copper
0.3
Lead
Zinc
Concentration (mg/L)
0.25
0.2
0.15
0.1
0.05
0
Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin
n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

14. Rain Garden 2 inlet Rain Garden 1 inlet

15. Mean Total Heavy Metal Concentrations in Catch Basins
0.35
Copper
0.3
Lead
Zinc
Concentration (mg/L)
0.25
0.2
0.15
0.1
0.05
0
Rain Garden 2 Rain Garden 1 Unfiltered Catch Basin
n = 6, samples from December 2008, March 2009, April 2009, August 2010, and October 2010

16. 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 by
the growing season)
– Some studies found that although total N and P
reduced, 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)

17. 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 stormwater
quantity (Davis et al. 2009, Davis 2007, Hood et al.
2007, Hatt et al. 2009)

18. 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

19. Next steps
• Do rain gardens continue to function the same
way over the duration of a storm event?
– Monitoring water quality
– Assess flow patterns on site
• What kind of maintenance is required? Is the
design functioning as it was intended?
– Visual observations and considerations for
maintenance and potential design modifications

20. Monitoring water quality for the
duration of a storm event

21. Concentration (mg/L) Concentration (mg/L)
17
0.00
2.00
4.00
6.00
8.00
10.00
12.00
10.00
15.00
20.00
25.00
30.00
0.00
5.00
17
:3 :3
17 1 17 1
:4 :4
18 6 18 6
:0 :0
18 1 18 1
:1 :1
18 6 18 6
:3 :3
18 1 18 1
:4 :4
19 6 19 6
:0 :0
19 1 19 1
:1 :1
19 6 19 6
:3 :3
19 1 19 1
:4 :4
20 6 20 6
:0 :0
20 1 20 1
:1 :1
20 6 20 6
:3 :3
Time
20 1 20 1
Time
:4 :4
21 6 21 6
:0 :0
21 1 21 1
:1 :1
21 6 21 6
Unfiltered Catch Basin on 10/14
:3 :3
TSS in Rain Garden 1 Catch Basin on 10/14
21 1 21 1
TSS in Rain Garden 1 Catch Basin and
:4 :4
22 6 22 6
:0 :0
22 1 22 1
:1 :1
22 6 22 6
:3 :3
22 1 22 1
:4
Rain Garden 1
:4
23 6 23 6
:0 :0
R2 = 0.4652
23 1 23 1
:1
Unfiltered Catch Basin
:1
6 6
y = -0.2302x + 7.2547

22. Total Heavy Metal Concentration and Water Depth in
Rain Garden 1 Catch Basin, 10/14
1.4 0.45
0.4
Concentration
1.2
Heavy Metal
0.35
Water Depth (m)
1
0.3
Total heavy metals
0.8 0.25
Water depth
0.6 0.2
0.15
0.4
0.1
0.2
0.05
0 0
17 1
6
1
6
1
6
19 1
6
19 1
6
1
6
1
6
1
6
1
22 6
1
22 6
1
23 6
1
6
:3
:4
:0
:1
:3
:4
:0
:1
:3
:4
:0
:1
:3
:4
:0
:1
:3
:4
:0
:1
:3
:4
:0
:1
17
18
18
18
18
19
19
20
20
20
20
21
21
21
21
22
22
23
Time

23. Water Depth (m)
17
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
:0
17 0
:
17 15
:3
17 0
:4
18 5
:
18 00
:1
18 5
:3
18 0
:
19 45
:0
19 0
:1
19 5
:
19 30
:4
20 5
:0
20 0
:1
20 5
:
20 30
:4
Time
21 5
:0
21 0
:
21 15
:3
21 0
:4
22 5
:
22 00
:1
22 5
:3
22 0
:
23 45
:0
23 0
:1
Precipitation
23 5
Water Depth in Rain Garden 1 Catch Basin and
:
Rain Garden 1
Unfiltered Catch Basin and Precipitation on 10/14
23 30
:4
5
0:
00
Unfiltered Catch Basin
0
0.001
0.0005
0.0015
Precipitation (m)

24. Assessing Flow Patterns

25. Identifying maintenance concerns
• Visual observation and
data collection
• Sediment build-up in
inlets
• Water flow through soil
• Plant growth
• Establishment of weeds

26. 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

28. Mean Nutrient Concentrations
30
Ammonium
25
Nitrate
Phosphate
Concentration (mg/L)
20
15
10
5
0
Precipitation Runoff Soil Water Rain Garden Catch Unfiltered Catch
Basins Basin

29. Mean Heavy Metal Concentrations
3
Copper
2.5 Lead
Zinc
Concentration (mg/L)
2
1.5
1
0.5
0
Precipitation Runoff Soil Water Rain Garden Catch Unfiltered Catch
Basins Basin