Biofiltration and Downspout Filter Media Evaluation for BMP Decision-Making at the Port of Vancouver, WA

Transcription

1 Biofiltration and Downspout Filter Media Evaluation for BMP Decision-Making at the Port of Vancouver, WA StormCon August 30 th, 2017 Sheila Sahu, Kennedy/Jenks Consultants Portland, OR Matt Graves, Port of Vancouver Vancouver, WA

2 Presentation Outline Introduction to Treatment Systems Stormwater Challenges, Goals, and Limitations Design and Performance (Overview) Infiltration Testing and Sampling Results (In-Depth): Terminal 2 (T2) System Grattix Box Summary of Findings Annual Maintenance Recommendations

3 Two Successful Treatment Systems at the Port T2 System Large Biofiltration System Installed 2009 Grattix Box Biofiltration in a Tote First installed 2008 Name derived from (Matt) Graves/ (Mary) Mattix combo

4 Stormwater Pollutant Challenges Sources everywhere (both municipal & industrial issues): TSS dirt, tires, worn pavement O&G motor oil & hydraulic fluids Metals zinc, copper, lead from galvanized materials, paint, dirt, roofs, fences, tires, shipping containers, etc. Pollutants fall from the sky through atmospheric deposition BMPs only help so much

5 Our Goals = WA ISGP Permit Benchmarks Quarterly Stormwater Sampling - Benchmarks Turbidity: 25 NTU ph: Oil Sheen: none visible Petroleum Hydrocarbons: 10 mg/l Total Copper: 14 µg/l Total Zinc: 117 µg/l Port discharge routed to Columbia River

6 Limitations of Conventional Methods E.g., ponds, vaults, swales, engineered wetlands Proprietary systems can be expensive Large footprint= $$ Most focus on particle settling, residence time Ineffective for dissolved metals & colloids

7 Why Natural Systems? Capital cost, O&M, sustainability More removal processes They work Mike Siegel / The Seattle Times

8 T2 System Large Biofiltration System 23,650 square feet (0.54 ac) Treats 60 ac impervious Peak inflow rate= 18.2 cfs (~5-yr, 24-hr storm event, 2.8 ) Design includes: Sedimentation basin Underdrains Collector line CBs (1-ft max. ponding) Sampling port Collector Line CBs Sampling Port Underdrain (typical) Sedimentation Basin

9 T2 System Performance Port achieved consistent attainment (8 consecutive quarterly sampling events meeting ISGP benchmarks) 4 years after install Allows for 3-year sampling suspension; will resume sampling in 2017 Discharge Monitoring Report (DMR)

10 T2 System 2016 Performance Evaluation Samples collected in each profile depth (red, pink, blue dots): 0-4 surface deposition 8-14 middle of soil mix bottom of soil mix Infiltration Testing (blue dots; Ecology Pilot Infiltration Test)

11 T2 System 2016 Performance Evaluation Invasive Plants Cirsium arvense (Canada thistle) Surface Deposition Equisetum arvense (Field horsetail)

12 Grattix Box Biofiltration in a Tote One box treats max. 5,000 sq. ft.

13 Grattix Box 2008 Pilot Study Performance Downspout Influent Downspout Effluent Total Zn (μg/l) Total Zn (μg/l) Benchmark 117 μg/l 11/20/ /25/ /12/ ND (<5) 12/29/ ND (<20)

14 Grattix Box 2016 Performance Evaluation Samples collected in each profile depth (3 boxes): 0-4 surface deposition 6-10 middle of soil mix bottom of soil mix/sand Infiltration Testing (single-ring infiltrometer)

15 T2 System and Grattix Box Results Infiltration Testing Laboratory analyses for: RCRA 8 metals plus Copper and Zinc Cation Exchange Capacity (CEC) Organic Content (OC) Sieve and Hydrometer (Particle Size)

16 Infiltration Testing Results BMPs had high infiltration rates compared with recommended (2-12 in/hr) Higher T2 System rates likely due to larger testing area, no ring restriction >Gravel surface samples = high constant head rate >Sand bottom samples = high falling head

17 Media Sampling Results (Metals) Number of Samples Range (mg/kg) Median (mg/kg) Metal Copper Top Middle Bottom Lead Top Middle Bottom Zinc Top Middle Bottom T2 System Sample T2 System ProUCL Box Plot Grattix Boxes

18 Media Sampling Results (CEC & OC) Soil mix is 40% compost, 60% sand by volume Highest Metals Capture (top samples >CEC & OC)

19 Particle Size Distribution Uniformity Coefficient (Uc) = (D60) / (D10) Uc= 4 or less recommended BUT higher Uc = higher metals capture Conclusion: Widely graded with fines is more effective than narrowly graded Assumption: Origination of fines is not runoff Highest Metals Capture

20 Summary of Findings T2 System and Grattix Boxes are successfully treating stormwater metals Primary processes are sedimentation, filtration, and adsorption 2016 sampling shows Grattix Boxes <benchmarks and T2 System slightly >Cu benchmark; maintenance can restore performance Filter media: has high but effective infiltration rates can be max inches deep; top 4-inch layer with >OC is key is predicted have a 30-year lifespan prior to breakthrough (defined as effluent= 10% influent concentrations) based on top sample OC is under Toxic Characteristic Leaching Procedure (TCLP) regulatory levels, but high total Cu levels may fail WA state book designation and be characterized as dangerous waste without bioassay results

21 Annual Maintenance Recommendations Daucus carota (Queen Anne s lace) Remove surface sediments and revegetate Till in compost to top 4 inches Clean catch basins Clean basin, pipes & downspouts Remove invasive plants/replace with plants with deeper root structure

22 Questions?