12/19/2007. Due to limited land area, many coastal towns discharge stormwater into the ocean or into sounds/bays

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1 2/9/27 An Examination of a Dune Infiltration System s Impact on Coastal Hydrology and Bacteria Removal Tiffany Bright, Mike Burchell & Bill Hunt Biological & Agricultural Engineering N.C. State University Stormwater Engineering Stormwater Discharge to Oceans/Beaches Due to limited land area, many coastal towns discharge stormwater into the ocean or into sounds/bays Coastal populations grew by 37 million people between 97 and 2, projected to increase by another 2 million by 25 (EPA 2). EPA Coastal Standards October 2 Beach Environment Assessment and Coastal Health Act Bacteria Standards Fecal Coliform standard Tier Beach > 2 CFU / ml single sample Enterococcus standard Tier Beach > 4 CFU / ml single sample Indicator Organisms present when pathogens present in water absent in uncontaminated water present in higher numbers than pathogens in contaminated water better survival in water than pathogens easy to analyze 26 of 35 coastal states adopted the EPA standards

2 2/9/27 Enterococcus Facultative Anaerobic Fecal Coliform North Carolina Advisories Spherical, Gram-Positive Phylum- Firmircutes Genus- Enterococcus Species- E. faecalis E. faecium Rod, Gram-Negative Phylum- Proteobacteria Genus- Escherichia Species- E. coli 25: 3 Bacteria Caused Advisories in Kure Beach, NC Kure Beach, North Carolina Kure Beach Stormwater BMP Goal Kure Beach, NC (Tier I beach) 7 Ocean Outfalls Kure Beach Reduce the frequency stormwater enters the ocean directly Reduce the potential for human contact with bacteria and pathogens Improve water quality (nutrients, sediment, oils/grease etc.) Flow reduction from outfalls reduces sign postings 2

3 2/9/27 Kure Beach: Site L and Site M Background Monitoring Site L Outfall Pipe.8 ha (4.5 acres) C =.8 Site M 4-ft MW 2-ft MW -ft MW 8-ft MW 6-ft MW 4-ft MW 3.3 ha (8.acres) WT Well C =.7 Outfall Pipe Site M: Water Table Data Design Considerations Capture.27 cm to 2.54 cm storms (78% of storms) Flow from larger storms bypass Minimize i i disturbance to dune vegetation and surrounding beach 3

4 2/9/27 Design Calculations Watershed Runoff Rate and Volume Design Storm = 2.5 mm/hr Rational Method Runoff Rate Natural Resources Conservation Service Method (NRCS) Method Runoff Volume Malcom (989) Inflow Hydrograph Outflow (m3/s) Site L Site M Design Calculations Cont.. Darcy s Equation Hydraulic Conductivity (K) Single Ring Infilitrometer test ~ 372 cm/hr (2.2 ft/hr) NRCS (25) Newhan Fine Sand, 99.4 % sand and.6% silt, K =39 cm/hr (2.8 ft/hr) Time (min) WT Observation WQ Wells WT Observation WQ Wells Installation Maintenance/Access point Continuous Internal Water Level Recorder Sediment Trap Float-Pulley System Inflow Overflow Isco 672 Portable Sampler Weir Sample tube Isco 73 Bubbler Module Dune Infiltration System (DIS) 36 cm (4 in) Diameter pipe to Chambers Site L (.9 ha watershed) = 2 Chambers Site M (3.2 ha watershed) = 22 Chambers 4

5 Weir Sample tube 2/9/27 Monitor Vault Finished DIS System WT Observation WQ Wells WT Observation WQ Wells Cleanout Pipes Groundwater Wells INFINITY Maintenance/Access point Continuous Internal Water Level Recorder Overflow Isco 672 Portable Sampler Monitoring Vault Rain Gauge Sediment Trap Float-Pulley System Inflow Isco 73 Bubbler Module JOBOX with ISCO Before and After July 25 October 27 Results 25 Storms Captured: March-October 26 Rainfall ranging from 6 mm to 5 mm Rainfall Intensity (mm/hr r) Rainfall Amount (mm) Under 2.5 mm/hr Over 2. 5mm/hr 5

6 2/9/27 Site L Hydrologic Results Storms Overflowed- 659 m 3 Capture Runoff Volume Captured m 3, average 26.4 m 3 Total Runoff Volume (m 3 ) ` Site M Hydrologic Results 5 Storms Overflowed- 99 m 3 Bypass total Runoff Volume Captured m 3, average 78 m 3 Total Runoff Captured= 2,958 m 3 Runoff Volume (m 3 ) Mar 26-Apr 4-May 2-May 2-Jun 25-Jun 27-Jun 6-Jul 25-Jul 2-Aug -Sep 3-Sep 7-Oct, 2-Mar 6-Apr 26-Apr 7-May 4-May 5-May 2-May 5-Jun 2-Jun 4-Jun 25-Jun 26-Jun 27-Jun 6-Jul 6-Jul 23-Jul 25-Jul 3-Jul 2-Aug 22-Aug -Sep 6-Sep 3-Sep 8-Oct 7-Oct, Storm Volume Captured Volume Overflowed Site L: Ground Water Elevation Hydrology Results Elevation (m) Jul 8-Jul 5-Jul 22-Jul 29-Jul 5-Aug 2-Aug 9-Aug 26-Aug 2-Sep 9-Sep 6-Sep 23-Sep 3-Sep 7-Oct 4-Oct Tropical Storm Tammy October 6, 25, Rain ~3 cm Water Table Rise ~. m Tropical Storm Ernesto Sept, 26 Rain = 3 cm Water Table Rise ~.7 m Oct The amount of stormwater runoff directly discharged onto the beach is significantly less than the amount of stormwater captured in the DIS (p<.). ) The peak rate of stormwater runoff directly discharged onto the beach is significantly less than the peak rate overflowing the DIS (p<.). 6

7 2/9/27 Site L Bacteria Results Fecal Enterococcus Coliform (CFU/ml) Inflow= =8 - >25 47,662 Median Medium =7 =3 Groundwater = < Median Medium = = < Fecal Enterococcus concentration concentration (CFU/ml) (CFU/ml).. 2-Mar 6-Apr 7-May 26-Apr 5-May 4-May 2-May 5-Jun 4-Jun 2-Jun 26-Jun 25-Jun 6-Jul 27-Jun 25-Jul 6-Jul 2-Aug 25-Jul 6-Sep 2-Aug 8-Oct -Sep 3-Sep 7-Oct, NC's Standard NC's Standard 2 4 Stormwater Runoff Stormwater Runoff Groundwater Groundwater Site M Bacteria Results Enterococcus Fecal Coliform (CFU/ml) Inflow= =76 <- <25-94 Median 725 =9, Groundwater =<-25 = - TNTC Median =26 = 3 62 samples over standard Fecal Enterococcus concentration concentration (CFU/ml) (CFU/ml).. 2-Mar 6-Apr 26-Apr 7-May 4-May 5-May 2-May 2-Jun 5-Jun 4-Jun 25-Jun 27-Jun 26-Jun 6-Jul 6-Jul 25-Jul 25-Jul 2-Aug 2-Aug -Sep 6-Sep 3-Sep 8-Oct 7-Oct, NC's Standard NC's 4 Standard 2 Stormwater Runoff Groundwater Site M Bacteria Results Bacteria Results Seasonal Variation Bacteria Loading Volume of Runoff (m 3 ) Enterococcus Concentration n (CFU/ml) State Standard =4 CFU/ ml 7- May 5- Jun 6- Apr 5- May 4- Jun 26- Jun 6- Jul 25- Jul 2- Aug 6- Sep 8- Oct The fecal coliform concentration in the inflowing stormwater runoff is significantly greater than in the ground water samples (p<.). The enterococcus concentration in the inflowing stormwater runoff is significantly greater than the in ground water samples (p<.). Volume of Runoff Enterococcus in Gorundwater 7

8 I 2/9/27 Conclusions Captured 97% of the stormwater runoff Questions or Comments No significant increase in groundwater fecal coliform concentration Dune Infiltration Systems should continue to be evaluated & potentially implemented at other ocean outfalls Special Thanks Dr. Bob Holman NCDOT Public Works Department Kure Beach, NC Bob Maestro HydroLogic Solutions Dr. Michael Burchell Dr. Bill Hunt Site M Hydrologic Results 5 Storms Peak flow Rate =.53.8 m 3 /s June 4, 26 Peak Runoff Rate Captured.2.54 m September 3, 26 /s,.5.4 average.2 m /s nflow ( m 3 /s ) /4/6 : 6/4/6 2:24 6/4/6 4:48 6/4/6 7:2 6/4/6 9:36 6/4/6 2:.4.2 Peak Inf low Flow Stage in Vault. (m 3 /s) Stag e ( m ) (m 3 /s) In flo w /4/26 : 9/4/26 2:24 9/4/26 9/4/26 4:48 7:2 2-Mar 6-Apr 26-Apr 7-May 4-May 5-May 2-May 5-Jun 2-Jun 4-Jun 25-Jun 26-Jun 27-Jun 6-Jul 6-Jul 23-Jul 25-Jul 3-Jul 2-Aug 22-Aug -Sep 6-Sep 3-Sep 8-Oct 7-Oct, Inflow Stage 9/4/26 9: /4/26 2: Staag e (m) Peak Inf low Peak Outf low 8

9 2/9/27 Tidal Effect on Water Table Watertable Elevation (m) Jun 7-Jul 6-Aug 26-Aug 5-Sep 5-Oct 25-Oct Site L Site M Tide Data Tide elevations varied from -.36 m to 2. m 2.5 m difference. Site L water table range.73 m m Site M water table range.7 m m Tidal fluctuation (m) 9