biofiltration and downspout filter media … and downspout filter media evaluation for ......
TRANSCRIPT
Biofiltration and Downspout Filter Media Evaluation for BMP Decision-Making at the Port of Vancouver, WA
Sheila Sahu, Kennedy/Jenks ConsultantsPortland, OR
Matt Graves, Port of VancouverVancouver, WA
StormCon
August 30th, 2017
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
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
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
Our Goals = WA ISGP Permit Benchmarks
► Quarterly Stormwater Sampling - Benchmarks
■ Turbidity: 25 NTU
■ pH: 5.0-9.0
■ 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
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
Why Natural Systems?
► Capital cost, O&M, sustainability
► More removal processes
► They work
Mike Siegel / The Seattle Times
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
Sedimentation Basin
Underdrain (typical)
Collector Line
Sampling Port
CBs
T2 System – 2009-2013 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)
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
■ 23-36” bottom of soil mix
► Infiltration Testing (blue dots; Ecology Pilot Infiltration Test)
T2 System – 2016 Performance Evaluation
Invasive Plants Surface Deposition
Cirsium arvense
(Canada thistle)
Equisetum arvense
(Field horsetail)
Grattix Box – Biofiltration in a Tote
► http://www.portvanusa.com/assets/Grattix-how-to-flyer.pdf
One box
treats max.
5,000 sq. ft.
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
► Samples collected in each profile depth (3 boxes):
■ 0-4” surface deposition
■ 6-10” middle of soil mix
■ 10-16” bottom of soil mix/sand
► Infiltration Testing (single-ring infiltrometer)
2009
20122016
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)
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
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
T2 System
Grattix Boxes
Sample T2 System ProUCL Box Plot
Media Sampling Results (CEC & OC)
Highest
Metals
Capture
(top samples
>CEC & OC)
► Soil mix is 40% compost, 60% sand by volume
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
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. 16-20 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
Annual Maintenance Recommendations
Remove surface sediments
and revegetate
Remove invasive
plants/replace with plants
with deeper root structure
Till in compost to top 4 inches
Clean catch basins Clean basin, pipes & downspouts
Daucus carota
(Queen Anne’s lace)