NJ: Rain Garden Research
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NJ: Rain Garden Research

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Rain Garden Research

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  • 1. Rain Garden Research and  Current Issues Michael Dietz, Ph.D. CT NEMO | Cooperative Extension  Univ. of ConnecticutManaging Stormwater from Impervious Surfaces: Green Infrastructure  Solutions for New Jersey The Heldrich | New Brunswick, NJ January 27, 2011
  • 2. Monitoring-Began November 2002
  • 3. Installation: 9‐19‐02
  • 4. Rain Garden Materials Detail (Based on PGC RG Manual, 2001)• Three native shrub species: – Chokeberry (Aronia prunifolia) – Winterberry (Ilex verticillata) – Compact inkberry (Ilex glabra compacta)• Native soil mix – Loamy sand• Roughly 5 cm of bark mulch
  • 5. Monitoring Equipment
  • 6. Methods•Lab analysis of water samples for: •Nitrate‐N, ammonia‐N, total Kjeldahl‐N, total  phosphorus, copper, lead, zinc•Water level in each garden measured•Temperature measured at inlet and outlet (underdrains)•Weekly measurements of soil moisture, redox potential (Eh), and frost depth
  • 7. Flow balance cm % of InflowInflow Roof Runoff 1202 79.7 Precipitation 306 20.3 Total 1507Outflow Underdrain 1438 95.4 Overflow 13 0.8 Total 1451Residual 56 3.7 99% of inflow  retained!
  • 8. Percent retention NO3-N NH3-N TKN TP TN ON gTotal In 388 30 250 9 647 211Total Out 128 5 186 20 316 181% Retention 67 82 26 -108 51 14 -Two years of results (year 1 much less) -Remember: 99% of inflow was retained
  • 9. Total Phosphorus 0.25 Roof runoff Underdrain average Exponential (Underdrain average) 0.2 Linear (Roof runoff)Total Phosphorus (mg/L) 0.15 0.1 0.05 R2 = 0.47 R2 = 0.06 0 Sep-02 Dec-02 Mar-03 Jun-03 Oct-03 Jan-04 Apr-04 Aug-04 Nov-04 Feb-05 Date
  • 10. Comparison with other research• Consistent with North Carolina – Hunt et al., 2006. Evaluating bioretention hydrology and nutrient removal at three field  sites in North Carolina. Journal of Irrigation and Drainage Engineering, Vol. 132(6), pp.  600‐608.• Consistent (N) & inconsistent (P) with  Maryland – Davis et al., 2006. Water quality improvement through bioretention media: nitrogen and  phosphorus removal. Water Environment Research, Vol. 78(3), pp. 284‐293.• Consistent with New Hampshire – Roseen, et al., 2009. Seasonal performance variations for storm‐water management  systems in cold climate conditions. Journal of Environmental Engineering, Vol. 135 (3),  pp. 128‐137.• Lots of variability in results!
  • 11. Second year• Modification to encourage denitrification and  increase treatment of NO3‐N• Saturated zone created in bottom of rain  garden (after Kim, et al., 2004)
  • 12. ModificationPonding depth
  • 13. Saturated zone Monitoring  tank1m Underdrain
  • 14. Impact on NO3‐N• No statistically significant reduction in NO3‐N  concentrations – Lots of samples below detection limit• Percent of outflow samples below detection  before/after change: – Before = 19% – After   = 56% – Significant using chi‐square statistic
  • 15. What happens in the winter?
  • 16. Frost TubeAfter Ricard, et al. (1976)
  • 17. Frost Tube Detail
  • 18. Winter performance• Measured frost depth• Did not impact annual performance• http://www.youtube.com/watch?v=cq6WB6VKeac• Similar findings at UNH Stormwater Center – Roseen, et al., 2009. Seasonal performance variations for storm‐water management  systems in cold climate conditions. Journal of Environmental Engineering, Vol. 135 (3),  pp. 128‐137.
  • 19. Some Current Issues• Filter fabric use – DON’T USE IN BIORETENTION! – Prone to clogging• Sizing – Water quality volume vs. curve number vs. ?
  • 20. Thank You!! Questions??michael.dietz@uconn.edu
  • 21. Two year ANOVA/mean separation Bulk Underdrain Overflow1Variable n Unit Deposition Roof Runoff Treatment Control Treatment Control *** -1NO3-N 73 mg L 0.7 bcd 0.9 abc 0.2 d 0.4 cd 2.0 ab 2.1 a -1NH3-N*** 78 mg L 0.04 a 0.04 a 0.01 b 0.01 b 0.08 a 0.04 aTKNns 79 mg L -1 0.5 a 0.6 a 0.4 a 0.5 a 0.6 a 0.3 aTN*** 72 mg L -1 1.3 abc 1.6 ab 0.7 c 0.9 bc 2.7 a 2.4 aONns 77 mg L -1 0.4 a 0.5 a 0.4 a 0.5 a 0.5 a 0.2 aTP*** 80 mg L -1 0.009 b 0.015 b 0.039 a 0.043 a 0.009 b 0.016 b -1Cutotal ns 26 µg L 3a 5a 3a 4a 3a - -1Pbtotal ns 26 µg L 3a 3a 3a 3a 3a - -1Zntotal ns 26 µg L 11 a 9a 10 a 5a 8a -*** p=0.001ns=ANOVA comparison non significant1 n=4 for overflow samples Means followed by the same letter are not significantly different at p=0.05