Presentation on theme: "Vegetated Filter Strip Performance for Cost- Effective Roadway Runoff treatment in Alabama An evaluation of vegetated filter strips capacity to effectively."— Presentation transcript:
Vegetated Filter Strip Performance for Cost- Effective Roadway Runoff treatment in Alabama An evaluation of vegetated filter strips capacity to effectively treat roadway stormwater runoff Kevin White, Ph. D., P.E. Cecil Bernhard
Outline Background Roadway Runoff ALDOT Vegetated Filter Strip Study Data Collected to-date Similar Studies and Results
Non-point source constituents Stormwater Runoff BOD (oxygen demand) Nutrients (increases oxygen demand) Suspended Solids Metals Oil and Grease
Stormwater Design: Conveyance only vs. Conveyance +Treatment Traditional Design—Conveyance only Large water volumes due to extensive use of impervious surfaces No treatment of stormwater Primary purpose to eliminate flooding Improved Design—Conveyance + Treatment Mimic natural processes to treat runoff Slows velocity and reduces stormwater runoff constituents thus promoting healthy water bodies. Promotes infiltration
NPDES NPDES Permits Regulates non-point source discharges through MS4 regulations 40% of water bodies do not meet water quality standards (EPA) Post Construction Runoff Control is important Best Management Practices (BMPs)
BMP Design Stormwater BMPs Engineered Systems which transport, store, and treat stormwater runoff Often Relying on Natural Processes For example, the use of vegetation to absorb or biologically assimilate nutrients or metals Incorporating permeable surfaces to enhance infiltration and reduce runoff volume
Examples of BMPs Taken From
Stormwater Wetland BMP, Provides both Storage and Treatment of Stormwater
Vegetated Filter Strips Filter strips are vegetated slopes that treat sheet and overland flow from adjacent surfaces. Design criteria include: Slope Length Vegetation density Documented to significantly increase runoff quality Uniquely applicable to roadway systems Medians Side slopes
Common Constituents of Roadway Runoff Nutrients Nitrogen Phosphorus Metals Zinc Nickel Copper Lead Chromium Cadmium COD (oxygen demand) BOD (oxygen demand) Suspended Solids Oil and Grease The most common sources of pollution are: - vehicle traffic - emissions - dustfall - precipitation This is affected by: - traffic density - local land use - weather - other…spills,etc.
First Flush Effect Greater concentrations (or mass) occur at the onset of rainfall Materials are washed off the road Important to sample the “first flush”
Design and Construction of Sampling Stations 2 Roadway Locations in Mobile, AL Rangeline Road (state Hwy 193 to Dauphin Island, suburban/industrial) I-10/I-65 Each location evaluates: 2 slope conditions (~8% and ~12%) 4 lengths from the edge of pavement 0 meters 2 meters 4 meters 6 meters An in-ground sampler collects first flush runoff at each length
Site Locations Site I Site R
Rangeline Road (AL 193)
Sample Methods Antecedent Conditions > 0.10 inch of rainfall RainWave alert and quantification Doppler radar Intensity Incremental rainfall quantity WQ analysis Hach Std methods Data compared to: - background river WQ in Alabama (USGS) - National Atmospheric Deposition Program (USGS)
Similar Studies and Results Barrett et al. (UT, CalTrans) TSS and Total Metals were reduced Nutrient Concentrations were statistically unchanged Best reduction….length > 4.5 meters (~15 feet) Ming- Han et al. (UT, TxDot) TSS and Heavy Metals were greatly reduced Nutrient Concentrations were unchanged Best Reduction….length > 4 meters (~13 feet)
Copper Reduction of Copper w/ length at both sites Reduction to or below background levels
Nitrate NO3 Concentrations similar to atmospheric deposition Background levels
Suspended Solids Removal No observable effect on TSS Concentrations w/ length
Biochemical Oxygen Demand
What we’ve learned....to date ( December 2012 – present) Effective removal of metals (especially Cu, Cr) > 85% Cu removal No nitrogen removal observed Effective removal of Phosphorus Less than or equal to background stream concentrations Background concentrations reached at ~ 4 m (for most) No correlation between TSS removal and length. No correlation between treatment and slope
On going Evaluations Important Factors to Consider Rain Intensity Traffic Density Antecedent Conditions Increased Length of Filter Strip?
Works Cited 1. Davis, Mackenzie L. and Cornwell, David A. “Introduction to Environmental Engineering” 5 th Edition McGraw Hill, Copyright 2013, New York, United States Environmental Protection Agency (USEPA). (2009) “Incorporating Low Impact Development into Municipal Stormwater Programs” EPA 901-F April United States Environmental Protection Agency (USEPA). (2000) “Stormwater Phase II Final Rule. An Overview” EPA 833-F January 2000 (revised December 2005) 4. Li, Ming-Han, Barrett, Michael E., Rammohan, Pavitra Olivera, Francisco, and Landphair Harlow C. (2008) “Documenting Stormwater Quality on Texas Highways and Adjacent Vegetated Roadsides” J. Environ. Eng. 134: Barrett, Michael E., Zuber, Robert D., Collins, E.R. III (1995) “ A Review and Evaluation of Literature Pertaining to the Quality and Control of Pollution from Highway Runoff and Construction.” Center for Research in Water Resources Bureau of Engineering Research, The University of Texas at Austin. Austin, Texas. 6. Stenstrom, M.K., Lau S-L., Lee, H-H. Ma, J-S,. H. Ha, Kim, L-H, Khan, S. and Kayhanian, M. (2001) “First Flush Stormwater Runoff from Highways” World Water Congress 2001, Civil and Environmental Engineering Dept., UCLA. Copyright ASCE Barrett, Michael, Lantin, Anna, Austheim-Smith, Steve (2003) “Stormwater Pollutant Removal in Roadside Vegetated Buffer Strips.” Report for California Department of Transportation, Contract No. 43A0051. RBF Consulting, San Diego.