biofiltration for stormwater treatment port of … for stormwater treatment port of vancouver, wa...
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Biofiltration for Stormwater Treatment Port of Vancouver, WA
Sheila Sahu, Senior Project Manager, Kennedy/Jenks Consultants Portland, Oregon
Presentation Outline
►Introduction to Port’s Biofiltration Systems ►Stormwater Challenges, Goals, and Limitations ►Grattix Box Design, Performance, and Sampling
Results ►Terminal 2 (T2) System Design, Performance,
Infiltration Testing and Sampling Results ►Maintenance Recommendations ►Summary of Findings
Two Successful Systems at the Port
■ Grattix Box– Biofiltration in a Tote (first installed 2008)
■ T2 System– Biofiltration System (installed 2009)
2016 Goals: Determine life span and maintenance needs
Stormwater Pollutant Challenges
► Sources everywhere (both municipal & industrial issues): ■ TSS - dirt, tires, worn asphalt ■ O&G - motor oil & hydraulic fluids ■ Metals – Zinc, Copper, Lead - from galvanized materials,
dirt, roofs, fences, tires, shipping containers, etc. ► Pollutants fall from the sky through atmospheric deposition ► BMPs only help so much
Our Goals = WA ISGP Permit Benchmarks
► Quarterly Stormwater Sampling - Benchmarks ■ Turbidity: 25 NTU (OR = 100 mg/L TSS) ■ pH: 5.0-9.0 ■ Oil Sheen: none visible ■ Petroleum Hydrocarbons: 10 mg/L ■ Total Copper: 14 µg/L (OR = 20 µg/L) ■ Total Zinc: 117 µg/L (OR = 120 µg/L)
Limitations of Conventional Methods
► Ponds, vaults, swales, engineered wetlands ► Proprietary systems can be expensive ► Large footprint= $$ ► Most focus on particle settling, residence time ► Ineffective for dissolved
metals & colloids
Why Natural Systems?
► Capital Cost, O&M, sustainability ► More removal processes ► They work
Mike Siegel / The Seattle Times
Grattix Box – Biofiltration in a Tote
► http://www.portvanusa.com/assets/Grattix-how-to-flyer.pdf
Grattix Box – 2008 Pilot Study Performance
Downspout Influent Downspout Effluent
Total Zn (μg/L) Total Zn (μg/L)
11/20/08 295 21.3 11/25/08 947 14.7 12/12/08 278 ND (<5) 12/29/08 213 ND (<20)
Benchmark ≤117 μg/L
Grattix Box – 2016 Performance Evaluation
► Three samples collected in each profile depth ■0-4” surface deposition ■6-10” middle of soil mix ■12-16” sand
► Laboratory analyses for: ■RCRA 8 metals plus Copper and Zinc ■Sieve and Hydrometer
Grattix Box – 2016 Media Sampling Results
Filter Media Sampling Results
T2 System – Biofiltration in a Bigger Box
► 23,650 square feet (0.54 acres)
► Receives untreated stormwater from 60 acres of impervious area Previous bioswale
Current configuration
T2 System – 2009-2013 Performance
► 4 years after install, port achieved consistent attainment (8 consecutive quarterly sampling events meeting ISGP benchmarks)
► Allows for 3-year sampling suspension; need to resume sampling in 2017
T2 System – 2016 Performance Evaluation
► Three samples collected in each profile depth ■0-4” surface deposition ■8-14” middle of soil mix ■23-36” bottom of soil mix
► Laboratory analyses for: ■RCRA 8 metals plus Copper and Zinc ■Sieve and Hydrometer ■Organic Content
■Cation Exchange Capacity (CEC)
► Infiltration Testing
T2 System – 2016 Performance Evaluation
Invasive Weeds
Surface Deposition
T2 System Infiltration Testing and Sampling
T2 System – Infiltration Testing Results
2016 Measured Infiltration Rates
T2 System – Media Sampling Results (Metals)
Metal Number of Samples
Range (mg/kg)
Median (mg/kg)
Copper Top 9 26.5-83.7 58.5
Middle 9 12.7-33.5 15.5 Bottom 3 5.82-7.34 6.63
Lead Top 9 15.7-45.5 21.2
Middle 9 8.69-18.3 10.7 Bottom 3 5.36-7.09 5.55
Zinc Top 9 277-556 346
Middle 9 153-283 202 Bottom 3 50.2-72.6 67.2
2009 Grattix Box (comparison)
T2 System –Media Sampling Results (CEC & OC)
Highest Metals Capture
T2 System and Grattix – Particle Size Distribution
► Uniformity Coefficient (Uc) = (D60) / (D10)
► Uc= 4 or less recommended
► BUT higher Uc= higher metals capture
► Wide media grading with fines is more effective than narrow grading
Final Maintenance Recommendations
Annual Maintenance
Remove surface sediments and replant Remove invasive weeds
Till in compost to top 4 inches
Summary
► The T2 System and Grattix Boxes are currently effectively treating stormwater:
■ Metals removal through sedimentation, filtration, and adsorption ■ Filter media has high infiltration rates and is predicted to last a total
of 35 years based on current organic content ► Maintenance activities:
■ Revegetation ■ Amendments to the filter media ■ Flow routing management
► Current data gaps: ■ Effluent sampling from T2 System and Grattix boxes to identify
breakthrough ■ Organic content in Grattix boxes to more accurately predict filter
media life
Successful Construction Methods
