Rain Gardens at Vassar College: A Water Quality Assessment

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

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

13. 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. 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

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