Evaluating the Hydrologic and Water Quality Performance of Infiltrating Wet Retention Ponds

Transcription

1 Evaluating the Hydrologic and Water Quality Performance of Infiltrating Wet Retention Ponds Joshua Baird, E.I. Town of Morrisville Bill Hunt, Ph.D., PE Ryan Winston, PE North Carolina State University

2 Forested Watershed (Swift et al., 1987) ET = 50% Runoff = 5% Infiltration = 45%

3 Developed Watershed (US EPA, 1993) ET = 30% Runoff = 55% Infiltration = 15%

4 Why is increased runoff (stormwater) bad? Decreased groundwater recharge Increased flooding Increased peak flow rates Increased nutrients, metals, sediment, and pathogens to receiving bodies Thermal pollution Photo Credit: Bill Lord

5 Hydrograph

6 Stormwater Regulations Clean Water Act 1972 National Pollution Discharge Elimination System (NPDES) Phase NPDES Phase Energy Independence and Security Act 2007 Specific State regulations to protect certain water resources

7 Stormwater Control Measures (SCM) Stormwater Wetland Permeable Pavement Bioretention Dry Detention Basin Wet Retention Pond Grassed Swale Images from NC DEMLR BMP Manual (2009)

8 Wet Retention Pond Permanent pool of water for removing pollutants Additional capacity above permanent pool for detaining runoff Vegetated Side Forebay Forebay berm Temporary pool elevation Main pond Permanent pool elevation Outlet Structure Vegetated Shelf

9 Typical Wet Pond

10 Adsorption Wet Retention Pond Plant Uptake Sedimentation Dilution

11 Regulatory Credits Pollutant Removal - 85% Total Suspended Solids - 25% Total Nitrogen - 40% Total Phosphorous Water Quantity - Peak runoff attenuation - No runoff volume reduction

12 Wet Ponds Over Hydrologic Soil Group A Requires an impermeable liner to comply with state guidelines Water Bentonite/clay liner Permeable Soil

13 Regions of North Carolina

14 Infiltrating Wet Pond

15 Objectives Quantify the effects of infiltration on wet pond hydrology Assess the water quality performance of wet ponds that infiltrate Determine if infiltrating wet ponds are acceptable practices, and if so, develop supplemental design guidance and plant selection

16 Sites Bingham Station

17 Sites Bingham Station

18 Date construction was completed Surface area at permanent pool (ha) Sites Bingham pond Mar-11 Raeford pond Jun Underlying Soil/HSG Autryville loamy sand/a Drainage Area (ha) Impervious Area (ha) % Impervious Loading Ratio (area) 20:1 24:1 Depth to SHWT (m) >1 <1 Temp. water quality ponding depth (m) Candor sand/a

19 Bingham Station Raeford Crossing Apartments Inlet Inlet 1 Outlet Outlet Inlet 2 Images from Google Earth

20 Methods Influent/Effluent Flow Rates and Volumes - ISCO 6712 Automated samplers with Area Velocity Meter or compound weirs Rainfall and Intensity manual and tipping bucket rain gauge Evaporation - ET gage atmometer model E with #30 turfgrass reference ET cover (Allen et al., 1998) Storage Volume - Hobo U20 - water level logger

21 Water Budget = V f V i = Initial volume V in = Inflow volume P = Rainfall on pond V Out = Outflow volume E = Evaporation F = Infiltration V f = Final volume

22 Flow-proportional, composite samples using ISCO samplers Nutrients (TKN, TAN, NO x, TN, OrthoP, and TP) and Total Suspended Solids (TSS) Water Quality

23 Results Bingham Raeford Number of hydrologic events Minimum storm rainfall (mm) 3 3 Maximum storm rainfall (mm) Bingham Raeford Number of water quality events Minimum storm rainfall (mm) 4 5 Maximum storm rainfall (mm) Minimum - 5-min peak rainfall intensity (mm/hr) 3 7 Maximum - 5-min peak rainfall intensity (mm/hr)

24 Precipitation Month 30-yr Normal* Bingham Raeford Jan Feb Mar Apr May Jun** Jul** Aug Sep Oct Nov Dec Year *(State Climate Office of North Carolina, 2014) **Rainfall totals at Bingham site from 2013 and rainfall totals from Raeford site from 2014

25 44 mm Event - Bingham Flow rate (m 3 /s) % Volume Reduction Rainfall (mm) 0 11/26/13 8:24 11/26/13 18:00 11/27/13 3:36 11/27/13 13:12 11/27/13 22:48 11/28/13 8:24 Influent Effluent Rainfall 4

26 Volume Reduction - Bingham Volume Reduction (%) Rainfall (mm) Volume Reduction Rainfall

27 Bingham Water Budget Influent Vol (m 3 ) Effluent Vol (m 3 ) Infiltrat Vol (m 3 ) Vol Reduction (%) Month Rainfall (mm) Initial WL (m) Evap (m 3 ) Final WL (m) June July August September October November December January February March April May

28 Volume Reductions - Raeford Volume Reduction (%) Rainfall (mm) Volume Reduction Rainfall

29 Raeford Water Budget Initial WL (m) Final WL (m) Vol Reduction (%) Month Rainfall (mm) Influent Vol (m 3 ) Effluent Vol (m 3 ) Evap (m 3 ) Infiltrat Vol (m 3 ) August September October November December January February March April May June July

30 Fate of Runoff - Bingham Volume (m 3 ) Rainfall (mm) Outflow Infiltration Evaporation Rainfall

31 Fate of Runoff - Raeford Volume (m 3 ) Rainfall (mm) Outflow Infiltration Evaporation Rainfall

32 Fate of Runoff Bingham Pond Outflow Evaporation Infiltration Raeford Pond Outflow Evaporation Infiltration 54% 40% 46% 49% 6% 5%

33 Fate of Runoff Total inflow (m 3 ) % 54% 5% 46% 40% 49% Evaporation Infiltration Outflow 0 Bingham Raeford

34 Summary of Hydrology Bingham Raeford Median Peak Flow Reduction* 99.2% 98.7% Median Volume Reduction** 100.0% 100.0% Median Antecedent Dry Period (days) *Values include storm events with no outflow that have a volume reduction and peak flow rate reduction of 100%. ** Only solo storms (Bingham n=52, Raeford n=40) solo storms considered those that began when the stage was below the draw-down orifice and the pond had time to de-water prior to the following event

35 Bingham - 49 mm Event Flow Rate (cfs) /19/2013 0:00 8/20/2013 0:00 8/21/2013 0:00-97% Peak Flow Reduction -53% Volume Reduction Influent Effluent Rainfall Rainfall (mm)

36 Bingham Site Date Rain (mm) Peak Flow Reduction (%) Volume Reduction (%) 08/19/ /26/ /29/ /15/

37 Raeford Site Date Rain (mm) Peak Flow Reduction (%) Volume Reduction (%) 12/14/ /29/ /16/ /28/

38 Draw down curves post storm event Water Level (m) Bingham pond 2.38 days Raeford pond 4.81 days 0 5/16/14 5/17/14 5/18/14 5/19/14 5/20/14 5/21/14 Bingham Raeford

39 Average Water Level Water Level (m) Bingham Raeford Month

40 Volume Reduction Volume Reduction (%) Month Bingham Raeford

41 Bingham Water Level Stage Relative to Drawdown Orifice (m) 0 18 Oct 19 Oct 20 Oct 21 Oct 22 Oct 23 Oct 24 Oct 25 Oct 26 Oct 27 Oct 28 Oct Date

42 Bingham Water Level Stage Relative to Drawdown Orifice (m) 0 18 Oct 19 Oct 20 Oct 21 Oct 22 Oct 23 Oct 24 Oct 25 Oct 26 Oct 27 Oct 28 Oct Date

43 Bingham Water Level Stage Relative to Drawdown Orifice (m) 0 18 Oct 19 Oct 20 Oct 21 Oct 22 Oct 23 Oct 24 Oct 25 Oct 26 Oct 27 Oct 28 Oct y = x R² = Date

44 Bingham Infiltration Rate (October) m/day 0.56 mm/hr Infiltrated Volume = 390 m 3 Surface Area of pond = 1212 m 2 Number of Days = m/day 0.43 mm/hr Evaporation = 6.3 cm Number of days = 31 days m/day 0.09 mm/hr

45 Raeford Water Level Oct 19 Oct 21 Oct 23 Oct 25 Oct 27 Oct 29 Oct 31 Oct 2 Nov 4 Nov Water Level (m) y = x R² = Date

46 Median Nutrient Concentrations Raeford Median Nutrient Concentrations (mg/l) TKN NO3+NO2 TN TAN OP TP Influent n=11 n=9 Effluent TSS

47 Median Nutrient Concentrations Bingham Median Nutrient Concentrations (mg/l) TKN NO3+NO2 TN TAN OP TP Influent Effluent n=20 n= TSS

48 Median Concentration Reductions Concentration Reduction (%) n=17 n=9 20 TKN NO3+NO2 TN TAN OP TP TSS Bingham Raeford

49 Water Quality

50 Water Quality

51 Bingham WQ Concentrations Median Values Variable Inlet (mg/l) Outlet (mg/l) Percent median conc. reduction (%) TKN NO 2, * TN TAN * ON * OP * PBP TP * TSS * (n=23 inlet, n=19 outlet, n=22 inlet TSS, n=18 outlet TSS) *Significant difference between inlet and outlet at α=0.05 sig level

52 Raeford WQ Concentrations Median Values Variable Inlet (mg/l) Outlet (mg/l) Percent median conc. reduction (%) TKN NO 2, * TN * TAN * ON OP * PBP TP * TSS * (n=20 inlet, n=16 outlet) *Significant difference between inlet and outlet at α=0.05 sig level

53 Median Effluent Concentrations Median Effluent Concentratoins (mg/l) TKN NOx TN TAN OP TP Bingham Raeford DOT Museum TSS Winston, R. J., Hunt, W. F., Kennedy, S. G., Merriman, L. S., Chandler, J., & Brown, D. (2013). Evaluation of floating treatment wetlands as retrofits to existing stormwater retention ponds. Ecological Engineering, 54(0),

54 Median Effluent Concentrations Median Effluent Conc. (mg/l) TKN NOx TN TAN Bingham Raeford DOT Museum Winston, R. J., Hunt, W. F., Kennedy, S. G., Merriman, L. S., Chandler, J., & Brown, D. (2013). Evaluation of floating treatment wetlands as retrofits to existing stormwater retention ponds. Ecological Engineering, 54(0),

55 Median Effluent Concentrations Median Effluent Conc. (mg/l) OP TP 0 TSS Bingham Raeford DOT Museum Winston, R. J., Hunt, W. F., Kennedy, S. G., Merriman, L. S., Chandler, J., & Brown, D. (2013). Evaluation of floating treatment wetlands as retrofits to existing stormwater retention ponds. Ecological Engineering, 54(0),

56 Mean Effluent Conc. (mg/l) Mean Effluent Concentrations TKN TN TAN Bingham Ann McCrary Echo Farms Golf Course Waterford Raeford Silver Stream Lakeside Runaway Bay (Mallin et al., 2002) and (Wu et al., 1996)

57 Mean Effluent Concentrations Mean Effluent Conc. (mg/l) OP Bingham Pond A Ann McCrary Echo Farms Golf Course TP Raeford Pond C Silver Stream Lakeside Waterford Runaway Bay (Comings et al., 2000), (Mallin et al., 2002) and (Wu et al., 1996) TSS

58 Bingham Load Reductions Variable Inlet Loading (kg) Outlet Loading (kg) Percent Reduction (%) TKN * NO2, * TN * TAN * ON * OP * PBP * TP * TSS * Nutrients n=19, TSS n=17 -only the storms with both inflow and outflow sampled * Significant difference between inlet and outlet at α=0.05 sig level on a storm-by-storm basis

59 Raeford Load Reductions Variable Inlet Loading (kg) Outlet Loading (kg) Percent Reduction (%) TKN * NO2, * TN * TAN * ON * OP * PBP * TP * TSS * n=16 only the storms with both inflow and outflow sampled * Significant difference between inlet and outlet at α=0.05 sig level on a storm-bystorm basis

60 Bingham Yearly Loadings Annual Influent loading (kg/yr) Annual Effluent loading (kg/yr) Annual Influent loading (kg/ha/yr) Annual Effluent loading (kg/ha/yr) Percent Reduction (%) NC undeveloped* (kg/ha/yr) Variable TKN NO 2, TN TAN ON OP TP TSS *(Line & White, 2007)

61 Raeford Yearly Loadings Annual Influent loading (kg/yr) *(Line & White, 2007) Annual Effluent loading (kg/yr) Annual Influent loading (kg/ha/yr) Annual Effluent loading (kg/ha/yr) Percent Reduction (%) NC undeveloped* (kg/ha/yr) Variable TKN NO 2, TN TAN ON OP TP TSS

62 Inlet Forebay Berm Outlet Basin Lined Un-lined

63 Restrict or Allow Infiltration Inlet Forebay Berm Basin Outlet

64 25000 Restrict or Allow Infiltration? Outflow Volume (m 3 ) % 93% 0 Bingham Location Raeford Infiltration Allowed Infiltration Restricted

65 Research Implications Inlet Forebay Berm Outlet Basin Lined Un-lined

66 BMP Manual Errata Sheet

67 Plant Selection for Infiltrating Wet Ponds ming_soon.html

68 Conclusions Substantial volume reductions when unlined and located over hydrologic group A soils Both ponds able to reduce peak flows from small and large events With both reduced EMCs and volume reductions, nutrient and TSS loading were significantly reduced Effluent EMCs appear to be on par with other non-infiltrating wet ponds.

69 Next Steps Complete one year of monitoring at each pond Statistical analysis Design guidelines for purpose built infiltrating wet ponds Plant selection recommendations Assign pollutant removal credits to infiltrating wet ponds

70 Acknowledgements Dr. Bill Hunt Ryan Winston Shawn Kennedy City of Fayetteville (Giselle Rodriguez) Home Builders Association of Fayetteville Linda McKenzie and Jenny James, Center for Applied Aquatic Ecology

71 More information Joshua Baird