Rain Gardens at Vassar College: A Water Quality Assessment

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

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

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

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

Town House Apartments Site

Redevelopment - 2008 Rain Garden 2 Rain Garden 1

Rain 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

Concentration (mg/l) Mean TSS in Catch Basins 25 20 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

Concentration (mg/l) Mean Dissolved Nutrient Concentrations in Catch Basins 1.2 1 Ammonium Nitrate Phosphate 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

Concentration (mg/l) Mean Total Heavy Metal Concentrations in Catch Basins 0.35 0.3 0.25 Copper Lead Zinc 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

Rain Garden 2 inlet Rain Garden 1 inlet

Concentration (mg/l) Mean Total Heavy Metal Concentrations in Catch Basins 0.35 0.3 0.25 Copper Lead Zinc 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

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)

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)

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 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

Monitoring water quality for the duration of a storm event

TSS in Rain Garden 1 Catch Basin on 10/14 12.00 10.00 8.00 6.00 4.00 2.00 0.00 30.00 25.00 20.00 15.00 10.00 5.00 0.00 17:31 17:46 18:01 18:16 18:31 18:46 19:01 19:16 19:31 19:46 20:01 20:16 20:31 Time TSS in Rain Garden 1 Catch Basin and Unfiltered Catch Basin on 10/14 17:31 17:46 18:01 18:16 18:31 18:46 19:01 19:16 19:31 19:46 20:01 20:16 20:31 Time y = -0.2302x + 7.2547 R 2 = 0.4652 20:46 21:01 21:16 21:31 21:46 22:01 22:16 22:31 22:46 23:01 23:16 Rain Garden 1 Unfiltered Catch Basin 20:46 21:01 21:16 21:31 21:46 22:01 22:16 22:31 22:46 23:01 23:16

Water Depth (m) Total Heavy Metal Concentration and Water Depth in Rain Garden 1 Catch Basin, 10/14 1.4 0.45 1.2 0.4 1 0.8 0.6 0.4 0.2 0 17:31 17:46 18:01 18:16 18:31 18:46 19:01 19:16 19:31 19:46 20:01 20:16 20:31 Time Total heavy metals Water depth 20:46 21:01 21:16 21:31 21:46 22:01 22:16 22:31 22:46 23:01 23:16 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

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

Assessing Flow Patterns

Identifying maintenance concerns Visual observation and data collection Sediment build-up in inlets 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

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

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