Mitigating the Effects

of Urbanization with

Bioretention Rain Gardens

Amanda Cording, PhD Candidate

WRRC Seminar Series

February 5, 2015

Global Population will Reach 9.6 Billion by 2050

Image source: www.nasa.gov Source: U.N. Report (2013)

Increased Development Causes Water Quality Impairment

86 Square Miles of Bays and Estuaries are Impaired In Hawaii

Source: EPA (2010) Hawaii Water Quality Assessment Report

Proposed Management Strategies

Penn (2013) Valuation of Recreational Beach Quality and Water Quality Management Strategies in Oahu, Thesis

Low Impact Development

Low Impact Development

Green Roofs

Porous Pavement

Vegetated Swales Constructed Wetlands

Rain Gardens

LID is an approach to land development (or re-development) that works with nature to manage stormwater

as close to its source as possible.

Goals of LID & Bioretention

Volume Reduction

Pollutant Removal

Peak Flow Retention

Aesthetics

Sustainability

What is Bioretention?

Source: northfield.org

Pollutant Removal Mechanisms:

1. Physical 2. Biological 3. Chemical

What is Bioretention? Reference Definition

Davis, A. P., Shokouhian, M., Sharma, H., &

Minami, C. (2001). Laboratory Study of

Biological Retention of Urban Stormwater.

Water Environment Research, 73(1), 5–14.

• Layers of soil, mulch, and a variety of plant species.

• Soil: high sand content to provide rapid infiltration

but with low levels of silt and clay

Vermont Agency of Natural Resources. (2002).

The Vermont Stormwater Management

Manual Volume I - Stormwater Treatment

Standards (Vol. I).

• Shallow depression that treats stormwater as it

flows through a soil matrix, and is returned to the

storm drain system

Washington State University Pierce County Extension. (2012). Low Impact Development Technical Guidance Manual for Puget Sound.

• Soil is a highly permeable sandy mineral aggregate

mixed with compost.

Simple

Complex

Residential Scale

Neighborhood Scale

City Scale

Hydrologic Performance

Attenuated Peak Flow > 95% Reduced Volume > 97%

Hunt et al. (2008); Debusk et al. (2011)

Image Source: Liu et al. (2014)

Sediment Removal Performance

Removal of Total Suspended Solids

70%-99%

Brown and Hunt (2011); Bratieres et al. (2008); Hatt et al. (2008)

Nutrient Removal Performance

• Nutrient removal is variable • Phosphorus export is common • Nitrate is often exported unless

systems are designed to promote denitrification

Davis et al. (2001); Hunt et al. (2006); Debusk et al. (2011)

Image Credit: Amanda Cording

Phosphorus Removal Mechanisms

Tanner (1996); Arias et al. (2001); Lucas and Greenway (2011); Liping et al. (2012)

1. Soil Sorption Fe, Ca and Al > 90%

2. Plant Uptake (3% - 30%)

Nitrogen Removal Mechanisms

Davis et al. (2006); Bratieres et al. (2008); Kim et al. (2003)

Nitrogen Chemistry

Nitrification (aerobic bacteria) NH4

+ + 2 O2 -> NO3- + H2O + 2H+

NH4+ + H2O -> NH3

+ H3O+

Denitrification (anoxic bacteria) 2 NO3

- + organic matter -> N2 (N2O) + CO2 + H2O

Amanda Cording, PhD Candidate amanda.cording@uvm.edu UVM Department of Plant and Soil Science 230 Jeffords Hall Burlington, VT 05405 774.262.6256 Dr. Stephanie Hurley, Advisor and PI UVM Department of Plant and Soil Science Dr. Carol Adair, Committee Member and Co-PI UVM Rubenstein School of the Environment and Natural Resources Project Website: http://www.uvm.edu/~pss/?Page=bioretentionproject.html

University of Vermont

Bioretention Laboratory:

Partners

Research Questions

1. What are the characteristics of first flush pollutants from road-side watersheds? How do their mobilization thresholds compare?

2. How will bioretention performance be affected by increased precipitation predicted as a result of climate change?

3. How do two soil media mixes compare with regards to nutrient and sediment removal?

4. How do two common planting designs compare with regards to nutrient and sediment removal?

5. How do greenhouse gas emissions from the soil profile compare among the different treatments?

Experimental Design: 3 Treatments

1. Precipitation: Ambient vs. Increased

2. Soil Media: Traditional vs. Sorbtive Media™

3. Vegetation: Low Diversity vs. High Diversity

Experimental Design Layout

Cell with Rain Pan

5

2

7 6

1

434 357 674

576 320 658

3

7 8

2 6

3

1

4

5

LOW DIV

HIGH DIV

AMB INCREASED INCREASED AMB

SORBTIVE MEDIA ™

Legend

AMB Ambient Rainfall

Precipitation Treatment

Vegetative Treatment

Sorbtive Media ™ Treatment

* Cell Area is listed in the watershed as ft2

Precipitation

Vegetation

Soil Media

Methods: Measuring Flow Rate (Q)

Inflow 90o Weir Box Outflow Thel-Mar™ Weir

Where:

Q = flow rate over the weir (L/s)

H= depth of water (head) behind the weir (pressure transducer)

n = an empirical exponent (dimensionless)

C= coefficient of discharge, or weir coefficient

Q=CHn

Methods: Water Quality Monitoring

Equipment Parameter

• ISCO 6712 Automatic Samplers • Model 720 Pressure Transducer

24 Samples Inflow and Outflow

8 Bioretention Cells (2-4 min for 24 to 48 min)

1. Total Nitrogen (TN) 2. Total Phosphorus (TP) 3. Nitrite+Nitrate-N (NO3

-) 4. Soluble Reactive Phosphorus (SRP) 5. Total Suspended Solids (TSS) 6. Flow Rate (Q)

*units: μg/L, mg/L, L/s or ft3/s (cfs)

Methods: Soil Conditions Equipment Parameter

• Soil Probes at Two Depths • High Resolution Rain Gauge

1. Soil Temperature 2. Volumetric Water Content 3. Electrical Conductivity 4. Rainfall

Inflow Monitoring Using 90o V-notch Weir Box

Outflow Monitoring Using 6” In-Pipe Thel-Mar ™ Weir

Installing Outflow Monitoring Equipment

Vegetation Planted: May 2013

Low Diversity (2 species) vs. High Diversity (7 species)

Results: Inflow Flow Rate (June 2013 – October 2014)

Mean = 0.185 L/s SEM = 0.038 SD = 0.285 N = 57

Inflow Flow Rate

(L/s)

Results: Outflow Flow Rate (June 2013 – October 2014)

Mean = 0.033 L/s SEM = 0.005 SD = 0.039 N = 58

Outflow Flow Rate

L/s

Flow Rate Reduction Performance

Inflow Outflow

Average Flow Rate

(L/s)

Average Flow Rate Reduction:

82%

Average of all cells, all storms (L/s):

Inflow Flow Rate = 0.185

Outflow Flow Rate = 0.033

N = 57

N = 58

Sediment Reduction Performance

TSS Load (mg)

Inflow Outflow

Average TSS Load (mg):

Inflow Load = 1,590 Outflow Load = 110

N= 54

N = 49

Average

TSS Reduction: 93%

Inflow Phosphorus Characteristics

Inflow Mass Load

(μg)

2,137 μg

5,881 μg

SRP TP

Average Inflow

Phosphorus Characteristics:

36% Soluble

64% Particulate

N = 55

Outflow Phosphorus Characteristics

Outflow Mass Load

(μg)

N= 54 SRP TP

Average Outflow

Phosphorus Characteristics:

87% Soluble

13% Particulate

10,629 μg

12,208 μg

Particulate Phosphorus Inflow vs Outflow

Mass Load (μg)

N = 55

N = 54

Inflow Outflow

Average

Particulate P Reduction:

48%

Average Particulate

Phosphorus Mass (μg):

Inflow = 3,744 Outflow = 1,939

Soluble Reactive Phosphorus (SRP) Inflow vs. Outflow

SRP Load (μg)

Inflow Outflow

Average SRP Mass Load (μg):

Inflow Load = 2,099

Outflow Load = 10,629 N= 56

N = 58

Exporting SRP (5x)

Baseline Conditions: 60:40 Sand Compost Mix

0

50

100

150

200

250

300

350

60:40 Compost Mix (Top 12")

mg/kg

K

Mg

Available Phosphorus

Na

S

Mn

Al

Fe

Zn

B

Cu

190 mg/kg

Total Available Phosphorus in Top 15 cm of Bioretention Soil

Available Phosphorus

mg/kg

Inflow Nitrogen Characteristics

Inflow Mass Load

(μg) 8,127 μg

26,595 μg

NO3- TN

Average Inflow

Nitrogen Characteristics:

31% Nitrite + Nitrate 69% Organic N + NH4

+

N = 48

Outflow Nitrogen Characteristics

Outflow Mass Load

(μg)

12,225 μg

N = 52 NO3- TN

Average Outflow

Nitrogen Characteristics:

55% Nitrite + Nitrate 44% Organic N + NH4

+

22,051 μg

Mahalo! Questions?

Amanda Cording, PhD Candidate

acording@uvm.edu

References 1. Blecken, G.-T., Zinger, Y., Deletić, A., Fletcher, T. D., Hedström, A., and Viklander, M. (2010). “Laboratory study on stormwater

biofiltration: Nutrient and sediment removal in cold temperatures.” Journal of Hydrology, 394(3-4), 507–514.

2. Claytor, R. A., & Schueler, T. R. (1996). Design of Stormwater Filtering Systems (pp. 1–220).

3. Collins, K. a., Lawrence, T. J., Stander, E. K., Jontos, R. J., Kaushal, S. S., Newcomer, T. a., Grimm, N. B., and Cole Ekberg, M. L. (2010). “Opportunities and challenges for managing nitrogen in urban stormwater: A review and synthesis.” Ecological Engineering, Elsevier B.V., 36(11), 1507–1519.

4. Davis, A. P., Shokouhian, M., Sharma, H., and Minami, C. (2006). “Water quality improvement through bioretention media: nitrogen and phosphorus removal.” Water environment research, Water Environment Federation, 78(3), 284–93.

5. Dietz, M. E., & Clausen, J. C. (2005). A Field Evaluation of Rain Garden Flow and Pollutant Treatment. Water, Air, and Soil Pollution, 167, 123–138.

6. Dietz, M. E., & Clausen, J. C. (2006). Saturation to improve pollutant retention in a rain garden. Environmental Science & Technology, 40(4), 1335–40. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/16572794

7. Harper, C. W., Blair, J. M., Fay, P. A., Knapp, A. K. and Carlisle, J. D. 2005. “Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystem.” Global Change Biol. 11, 322-334.

8. Hatt, B. E., Fletcher, T. D., and Deletic, A. (2008). “Hydraulic and pollutant removal performance of fine media stormwater filtration systems.” Environmental Science & Technology, 42(7), 2535–41.

9. Hsieh, C. & Davis, A. P. Evaluation and Optimization of Bioretention Media for Treatment of Urban Storm Water Runoff. 131, 1521–1531 (2006).

10. Hunt, W. F., Jarrett, A. R., Smith, J. T., and Sharkey, L. J. (2007). “Evaluating Bioretention Hydrology and Nutrient Removal at Three Field Sites in North Carolina.” Journal of Irrigation and Drainage Engineering, 132(6), 600–608.

11. Kim, H., Seagren, E. A., Davis, A. P., and Davis, P. (2003). “Engineered Bioretention for Removal of Nitrate from Stormwater Runoff.” Water Environment Federation, 75(4), 355–367.

12. Ventera, R. & Parkin, T. USDA-ARS GRACEnet Project Protocols Chapter 3. Chamber-Based Trace Gas Flux Measurements 4. 2010, 1–39 (2010).

13. Vermont Agency of Natural Resources. (2002). The Vermont Stormwater Management Manual Volume I - Stormwater Treatment Standards (Vol. I).

14. Washington State University Pierce County Extension. (2012). Low Impact Development Technical Guidance Manual for Puget Sound.