Low Impact Development in the Transportation Environment: Lessons Learned in North Carolina Ryan Winston, M.S., P.E. Extension Associate Biological and Agricultural Engineering North Carolina State University ODOT Stormwater Workshop Columbus, Ohio December 12, 2014
Appalachian State University
Presentation Outline Case Studies: Highway Runoff Treatment Bioretention Enhanced (bio)swales Check Dams Main Street SCMs Street retrofits Street tree stormwater filters Maintenance of Highway SCMs
NCDOT Bioretention Cells BR Cells with 3 ft+ deep ponding Grassed systems Plant health has Suffered 3.5 ft Benefit for peak flow reduction
Plant Health with Deep Ponding?
NCDOT Interchange Bioretention Cells
Carolina Stalite(Expanded Shale)
Stalite Expanded slate aggregate Fired in kiln at 2000 F, creates porous, lightweight, high strength material Used in ROW when structural support is needed (within clear recovery zone and in medians)
Other Swale Retrofits Check dams Wetland swales Underdrained or Bioswales Regenerative Stormwater Conveyance
Grassed vs. Wetland Swale Dry Swale Wetland Swale Grassy (sites A/D) Vegetated (sites B/C)
Study Site Locations
Swale TN Concentrations Winston et al. 2012, Journal of Environmental Engineering
Winston et al. 2012 Effluent Type Comparing Dry and Wetland Swales Nitrogen Concentrations Wetland- Swale B Wetland Swale C Dry Swale A Dry Swale D TN 1.22 1.15 1.65 1.62 TAN 0.07 0.09 0.14 0.14 ON 1.05 0.81 1.11 1.26
Some Wet(land) Swale Guidance
Manning s Roughness Coefficient (n) Liner n Grass/ Turf 0.030 Fully Vegetated Wetland Swale 0.070 Moderately Veg. Wetland 0.050 Swale http://www.humboldt.edu/geology/for_download/fl uvial/arcement_wsp_2339_netvers.pdf
What Else Can We do to Improve Performance? Check Dams!
Lake Taupo New Zealand
Fancy Check Dam to Improve Hydrology
Check Dam Material Metal Wood Grass Concrete
Staggeet al. (2012) Water Research Highway runoff study looking at swale performance w/ & w/o filter strips and check dams No Filter Strip (No-FS) site
Staggeet al. (2012) Water Research Highway runoff study looking at swale performance w/ & w/o filter strips and check dams Filter Strip (FS) site
Check Dam Retrofit Swales monitored from Nov 2004-May 2006 for total of 18 events Retrofitted with 2 sets of 3 ft wide Panicum Virgatum check dams. Each check dam had three rows 1 ft apart (2007-2009, 27 storms) Designated FS-CD and No-FS-CD
TSS Performance No significant improvement in TSS concentration with check dam Similar results observed for heavy metals
Phosphorus Performance Swales in this study showed little capability for decreasing total phosphorus (TP) levels Inclusion of a check dam had negligible effect on TP concentrations
Check Dam Hydraulic Performance For smallest and largest events no impact of check dams
Performance of CDs Varies By storm event size: Complete capture (smallest events) Reducing runoff volume (mid-size events) Negligible volume attenuation (largest events) Complete Capture 0 0.9 Runoff Reduced 0.9 1.3 Flow Conveyance 1.3 +
Check Dam Studies for NCDOT Two studies are ongoing: Standard rock check composed of class B riprap and #57 stone (Mango Creek) Straw wattle check dams (I-40) Incorporated virophos-amended check dams into study
Mango Creek Swale Monitoring Schematic Rock Check Dam #1 Inlet Sampling Point Rock Check Dam #2 Outlet Sampling Point Forebay
Mango Creek: Installation Before Retrofit After Retrofit
I-40 Swale Monitoring Schematic Inlet Sampling Point Middle Sampling Point Standard Wattle Check Dam #1 Road Runoff Sampling Point Outlet Sampling Point P-Sorb Media Standard Wattle Check Dam #2 P-Sorb Media Standard Wattle Check Dam #3
I-40 Swale: Check Dam Photos CD #2 May 2014 CD #1 CD #3
Mango Creek Post-Retrofit Data Constituent Median Inlet Median Outlet % Reduction (mg/l) (mg/l) TKN 0.49 0.85-73 NO 2,3 -N 0.17 0.36-111 TN 0.68 1.25-84 NH 3 -N 0.02 0.10-400 TP 0.10 0.15-50 TSS 55.5 23.6 57.4 Extremely low influent nutrient concentrations affected swale performance TSS reduction did improve slightly from 45.7% to 57.4%. Median effluent concentration pre- vs. post-retroft (25.5 vs. 23.6 mg/l) also improved
Bioswales Typically have an underdrain and designer soil media mix
Introducing Bioswales Ingvertsen et al. (2012). Journal of Environmental Quality
Bioswalesin Charlotte, NC
ARC Guidance for Bio-Swale
Brunswick County Bioswale Lockwoods Folly River TMDL for Bacteria and closed shellfishing waters
Outlet Structure High Flow Media Bioswale Concrete Channel
Construction of Bioswale
Construction of Bioswale
Construction of Bioswale
Construction of Bioswale
Construction of Bioswale
Construction of Bioswale
Design Specifications Parameter Value Drainage Area 1.83 ac % Impervious 44% Surface Storage Volume 500 ft3 Media Void Storage 800 ft3 Media Infiltration Rate 100 in/hr Underdrain Diameter 8 in
Design Specifications Bacterra-type media
Data Collection Through the end of November (2014), ten storm event samples have been collected 5 of 10 storms produced overflow (>1.5 RF) Typically 1-2 log reductions in indicator bacteria (fecal coliform and enterococcus) Complete monitoring in April 2015, full data analysis & final report
Enterococci Probability Plot Most Probable Number 60000 50000 40000 30000 20000 10000 0 Inlet Underdrain Overflow 0 0.2 0.4 0.6 0.8 1 Cumulative Probability
Fecal coliform Probability Plot Most Probable Number 6000 5000 4000 3000 2000 1000 0 Inlet Underdrain Overflow 0 0.2 0.4 0.6 0.8 1 Cumulative Probability
Comparing Against Human Health Thresholds Geometric Mean Sampling Location enterococci (MPN/100 ml) fecal coliform (MPN/100 ml) IN 11258 1168 UD 3619 190 OF 5322 150 Swimming Limit 35 126
Future Research on Bioswales Look at nutrient/sediment load reduction on DOT right-of-ways Studies needed in Piedmont (tight soils) Difficult to cite other SCMs in the typical section Source: CALTRANS
Conclusions Wetland swales perform better for nutrient removal than dry swales Maintenance is key to prevent swales from eroding and forming head cuts Water quality studies to be completed in 2015 on check dams and bioswalesin NC Additional design guidance is expected from these studies