Tom Ballestero, Rob Roseen, James Houle, Tim Puls, Federico Uribe, Josh Briggs

Transcription

1 Porous Pavement Hydrology Tom Ballestero, Rob Roseen, James Houle, Tim Puls, Federico Uribe, Josh Briggs University of New Hampshire Stormwater Center 22 nd Annual NEIWPCC Nonpoint Source Pollution Conference May Saratoga Springs, NY 1

2 Acknowledgements Funding by CICEET/NOAA Graduate and undergraduate students 2

3 Objective What are the runoff characteristics of permeable pavements? 3

4 Overview UNHSC Monitored Sites Infiltration Capacity (the surface) Moisture Content (filtration layer) Runoff Hydrographs (what comes out the bottom) Volume Reduction Freezing Curve Number 4

5 Permeable Pavement Sites UNHSC Porous Asphalt Lot UNHSC Porous Concrete Lot 5

6 Alumni Center and Hood House 6

7 Infiltration Capacity 7

8 New England Sites 8

9 Infiltration Capacity by Age 100,000 (cm/hr) IC via SI test 10,000 1, ,365 2,598 2,905 2, ,013 7, URI- UNH- URI- Grswld- Frpt- Sski- SlvrLk- StoYo- UNH- PA-02 PA-04 PA-04 PC-05 PA-06 PA-06 PA-06 PA-06 PC-07 9

10 Porous Asphalt Surface Infiltration Rates Even with 99% clogging the IR=10 in/hr > most sands & soils Worst case scenario, no maintenance performed for 3 yrs Certain areas have reduced IC (drive lanes) while parking areas remain unchanged Low maintenance sensitivity due to excess infiltration capacity Clogged areas can drain to adjacent unclogged areas 10

11 Moisture Content 11

12 Port 1 Port 2 Port 3 12

13 Moisture Content Profile 13

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16 Runoff Hydrographs Section with Filter Course for Water Quality Pervious pavement: 4-6 (10-15 cm) of porous asphalt Choker Course: 4-8 (10 20 cm) minimum i Filter Course: 8-12 (20-30 cm) minimum thickness of subbase (aka. bank run gravel or modified 304.1) Filter Blanket: intermediate setting bed: 3 (8 cm) thickness of 3 / 8 (1 cm) pea gravel Reservoir Course: 4 (10 cm) minimum thickness of 3 / 4 (2 cm) crushed stone for frost protection, 4-6 (10-15 cm) diameter perforated subdrains with 2 cover Optional-Liner for land uses where infiltration is undesirable (e.g., hazardous materials handling, sole-source aquifer protection) ti Native materials 16

17 REFERENCE LOT POROUS ASPHALT Tree Filter 17

18 UNHSC Porous Pavement Monitoring Compound weir Pressure transducer Datalogger 18

19 UNHSC Porous Pavement Hydrologic Data Real time flow monitoring 5-minute time step Real time rainfall monitoring 5- minute time step 19

20 Pervious Concrete Runoff Rational Q peak = 235 gpm 20

21 Pervious Concrete Flow Attenuation Volume (g gal.) ) Volume (gal Influent Effluent 4/1/08 1/1/08-6/30/08 3/31/08 Influent Effluent Total Volume (liters) 446,034 78,192 25,585 # of Flow Events t Influent Effluent /1/08 1/8/08 1/15/08 1/22/08 1/29/08 2/5/08 2/12/08 2/19/08 2/26/08 3/4/08 3/11/08 3/18/08 3/25/08 21

22 PC Pollutant Removal 82% RE 94% RE 22

23 Porous Asphalt Rational Q peak = 200 gpm 23

24 Porous Asphalt Rational Q peak = 433 gpm 24

25 Hydrologic Performance of Porous Pavements Porous Asphalt (HSG-C) Pervious Concrete (HSG-B) 25

26 PA Flow Attenuation Flo ow (gpm) in depth Flow (gpm) in depth D-Box Flow 0.09 Effluent D-Box DBox Flow Flow 0.09 Effluent Flow Precip 0.12 Precip , ,000 Time 1,500 (min) 2,000 2,500 3,000 Time (min) 5-Min 5-Min Preci cip (in) (in) 26

27 Hydraulic Efficiency P k E 1 1 p P k L T T I E I 1 27

28 Hydraulic Performance of Porous Pavements Device Porous Asphalt Surface Sand Filter Retention Pond Bioretention Gravel Wetland Stone-Lined Swale Measure Annual winter(6) summer(6) k L k p p k L k p k L k p k L k p k L k p k L k p

29 Hydraulic Performance Lag Time (k L ) Peak Reduction (k P ) /3/

30 Porous Asphalt Frost Penetration 30

31 Temperature Profile 31

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33 Frost Penetration does not mean or imply impermeable 33

34 What is the Curve Number For Porous Pavement? Who wants to know?!? (What is your OBJECTIVE?) 34

35 The SCS (NRCS) Curve Number Originally conceived to translate rainfall depth into runoff depth on agricultural watersheds method worked best for large storms This was then translated into a runoff hydrograph 35

36 SCS Dimensionless Unit Hydrograph Area under hydrograph is the runoff volume Divide runoff volume by watershed area = runoff depth 36

37 Methods of Teasing CN from the Data Measure P and Q, invert basic SCS equation Measure P and outflow hydrograph h (q), measure lag, estimate CN from lag equations Measure Q and q p, estimate CN from peak discharge equations 37

38 Method 1 - Depth of Runoff (Q)Method Q I a 0.2S P I a 2 P I a S Eq.2. Eq P I P 0.2S a Q P 0.8S P 0.8S 2 Q: Total Runoff Depth (in) measured from hydrographs P: Total Precipitation Depth (in) measured Eq.3. Calculate I a : Initial Abstraction (in) S: Storage Parameter (in) S 1000 CN 10 Eq.4. CN: Curve Number 38

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40 Method 2 -Lag Methods Study how the timing of the runoff is transformed Time of concentration Lag time Time base Peak time 40

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42 Method 2 Lag Methods T lag L S 1 Eq Y 0.5 T c 5 3 T lag Eq. 6. T lag : Lag Time (hr) measured on hydrographs T c : Concentration Time (hr) measured on hydrographs Y: Surface Slope (%) measured in field Compute S 1000 CN 10 Eq. 7. S: Storage Parameter (in) CN: Curve Number 42

43 Lag Methods 3 APPROACHES LAG METHOD (1) 1. T base (Sánchez San Román [2009]) In. Abs. T base T precip Recession curve T base = T precip + T conc T conc = T base T precip Using Eq. 5 and Eq. 6 used into Eq.7., solve for CN l [in] Rainfal [gpm] Runoff

44 Lag Methods LAG METHOD (2) 2. T peak (Sánchez San Román [2009], Folmar, Miller and Woodward [2007]) In. Abs. T peak T precip T lag T peak = T lag + T precip/2 T lag = T peak T precip/2 Insert Eq. 1 into Eq.3 and solve for CN: 1000 CN 1900 T LAG Y 0.5 L l [in] Rainfal [gpm] Runoff 44

45 Lag Methods LAG METHOD (3) 3. T centroid (NRCS [2009], Folmar, Miller and Woodward [2009]) T lag: time from the centroid of excess precipitation to the peak of the hydrograph. CN T LAG Y 0.5 L In. Abs. T lag l [in] Rainfal [gpm] Runoff 45

46 Method 3 GRAPHICAL PEAK DISCHARGE METHOD q p : Peak Discharge (cfs) q u : Unit Peak Discharge (csm/in) A m : Drainage area (mi 2 ) Q: NRCS Storm Runoff (in) Folmar, et. al Excess precip. prior to peak. q q A Q q u g ( / ) p u m pm] 3 Runoff [g

47 GRAPHICAL PEAK DISCHARGE METHOD q p q u A m Q Eq.8. Runof ff [gpm] q u q p Eq. 9. QA m Area = mi 2 (5600 ft 2 )

48 Method 3 Graphical Peak kdi Discharge Unit Peak discharge for NRCS type III rainfall distribution chart. Measure q p, Am, Q Compute q u Ia/P = 0.1 Determine Tc Compute S, CN If Ia/P < 0.1 then Ia/P=0.1 If Ia/P > 0.5 then Ia/P=0.5 Check Ia/P 48

49 Method 3 Graphical Peak Discharge q q A Q p u m Tc f ( q ) u CN T LAG Y L

50 Storm Date Rainfall [in] CN (Clean Data) Runoff [in] Method 1 Q-P Method 2 Lag Method 3 Q peak Method 3 Q peak Tbase Tpeak Tcentroid NRCS Folmar 1 10/8/ R>P R>P /15/ R>P R>P /11/ R>P R>P /2/ R>P R>P /20/ R>P R>P /3/ R>P R>P /16/ /12/ /19/ /23/ /11/ /8/ /10/ /16/ /15/ /16/ /4/ /9/ /19/ /28/ /3/ /23/ /26/ /9/ /4/ /27/ R>P: The rainfall center of mass exceeds hygrograph peak timing 50

51 RESULTS Mean Median Standar Deviation Method 1 Method 2 Method 3 Method 3 Q-P Lag Q p Q p Tbase Tpeak Tcentroid NRCS Folmar

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53 Long Term Water Balance -PA 350, , ,000 Precipitation Effluent Net Inflow (gal)_ Cum. Vol 200, , ,000 50, ,000 4/1/05 7/1/05 9/30/05 12/30/05 4/1/06 7/1/06 9/30/06 Date 53

54 Long Term Mass Balance (Q vs P) Curve Numbers A soil system C soil system Winter 8 85 Spring Summer 0 63 Fall

55 So.Which to Use? Events Peak Outflow from Drain Peak flow method No net increase in benchmark storms Lag method Long Term Simulation Lag method Runoff depth method Watershed Simulation Seasonal CN Lag method 55

56 Philosophically Speaking.. What is the CN for a detention pond? flow watershed hydrograph pond hydrograph time 56

57 REFERENCES FOLMAR,N.D; MILLER, A.C.; AND WOODWARD, W.E; HISTORY AND DEVELOPMENT OF THE NRSC LAG TIME EQUATION. JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION. VOL. 43(3): LEMAY, G; DETERMINING THE CURVE NUMBER (CN) FOR POROUS ASPHALT SYSTEMS INDIVIDUAL STORM VOLUMES. HONORS THESIS INDEPENDENT SANCHEZ SAN ROMAN, F.J HIDROLOGIA SUPERFICIAL III. ONLINE UNITED STATES DEPARTMENT OF AGRICULTURE. NATIONAL RESOURCES CONVERSATION SERVICE URBAN HYDROLOGY FOR SMALL WATERSHEDS TR 55. ONLINE 57

58 Acknowledgements Funding Source: 58

59 Questions? or Simply Search for UNHSC 59

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