Bioretention Rain Garden Technical Seminar

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1 Bioretention Rain Garden Technical Seminar Larry S. Coffman, President Stormwater Services, LLLP Phone: att.net

2 What is Bioretention? Filtering stormwater runoff through a terrestrial aerobic (upland) plant / soil / microbe complex to remove pollutants through a variety of physical, chemical and biological processes. The word bioretention was derived from the fact that the biomass of the plant / microbe (flora and fauna) complex retains or uptakes many of the pollutants of concern such as N, P and heavy metals. It is the optimization and combination of bioretention, biodegradation, physical and chemical that makes this system the most efficient of all BMP s

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4 Pollutant Removal Mechanisms Physical / Chemical / Biological Processes Sedimentation Filtration Adsorption Absorption Cation Exchange Capacity Polar / Non-polar Sorption Microbial Action (aerobic / anaerobic) decomposition / nitrification / denitrification Plant Uptake Cycling Nutrients / Carbon / Metals Biomass Retention (Microbes / Plant) Evaporation / Volatilization System Components Mulch Course Sand Pore Space Surface Area Complex Organics Microbes Biofilm Plants Ecological Structure

5 Bioretention Pollutant Removal University of Maryland Dr. Allen Davis, University of Maryland

6 Interesting Study Findings Mulch and Metals Plants and Metals P Uptake Capacity / Longevity Residence Time Oil and Grease 95% Removal 90% Bacteria Removal Flow rate varies with moisture content

7 Time Independent Processes Capturing Particle Bound Pollutants Sedimentation (Settling on top) Straining (Particles larger that pore space trapped) Chance contact (Smaller particles trap) Impaction (Heavy particles do not follow flow path) Interception (Particles trapped on contact) Microbe Adhesion (particles stick to slime) Small Decentralized Wastewater Management Systems,Crites Tchobanoglous, 1998

8 Roots, Fungi & Bacteria Capturing Particle Bound Pollutants Bacteria dot the surface of strands of fungal hyphae. Credit: R. Campbell. Fibrous Roots Fungi Bacteria Particles are captured in first 2 to 8 inches in bioretention bed depths.

9 Time Dependent Processes Reactive Filtration Capturing and Transforming Very Small Particles and Dissolved Pollutants Chemical Adsorption - bonding and chemical interaction. Physical Adsorption electrostatic, electrokinetic and van der Waals forces. Biological Growth * transformation and uptake. Volatilization - vaporized gas and transpiration. Highly Variable: Pollutant type / Temperature / ph / concentration / affinity / CEC / bulk density / wind / sunlight /

10 Pollutant Removal - Plant Microbe Phytoremediation Translocate Accumulate Metabolize Volatilize Detoxify Degrade Exudates Bioremediation Soils Capture / Immobilize Pollutants

11 Louisburg Bioretention Dr. Bill Hunt North Carolina State Research

12 Load Reductions: Louisburg Removal vs. PI Cell TN TP PI L-1 (unlined) L-2 (lined) 64% 66% 68% 22% 1 to 2 85 to 100 June February 2005

13 Inflow V. Outflow Rates Inflow Discharge (cfs) Outflow Cumulative Rainfall Depth (in) /13/ :00 1/14/2005 0:00 1/14/ :00 1/15/2005 0:00 1/15/ :00 1/16/2005 0:00 0

14 NC Shellfish Closures 100,000 acres of shellfish waters are permanently or temporarily closed to harvesting.

15 Hal Marshall Bioretention: Fecal Coliform Concentrations 100,000 10,000 1, FC- In FC- Out Concentration in Col/100 ml Min. Detect 8/1/ /1/ /1/2004 1/31/2005 4/2/2005 6/2/2005

16 Bacteria Removal Laboratory Testing Date Maturation period with removal rates above 95%

17 High Flow Rate Media Field Test So CA (Marina del Rey) installation Installed to meet bacteria TMDL Testing began in spring of 2007 Collection third party lab Analysis Method Bacteria: SM 9221 EPA ORD Possible CSO & SSO Design Solutions

18 Initial Start Up = 4 storm events

19 Removal Mechanisms Sorption 1 Filtration 1 Organic Matter 1 Biofilm 1 Temperature 1 ph 1 Flow Rate 1 Predators 2 CEC Slime on bacteria Combination of all Ciliate Flagellate Amoeba Rusciano and Obrupta research Rutgers University, NJ Dr. Allen Davis 2007 LID Conference proceedings Photos: Nematode Rotifer

20 Media Filtration Bacteria Removal Comparison High Flow Rate Media Blend: 98%-99% fecal/e.coli and 96% Enterococcus Peat-Sand Filter - Fecal Coliform: 90% (Galli, 1990) Bioretention Fecal Coliform: 90% (Davis 1993) Bioretention Fecal Coliform: 71% (Hunt 2006) Bioretention Fecal Coliform: 88% (Rusciano & Obropta 2006)

21 Bioretention Construction Costs Excavation (assume no hauling) Fill Media Vegetation/ Mulch Underdrains /Gravel & Outlet Total $3 - $5 / cy $15 - $20 / cy $ $1.50 / sf $ $1.50 / sf $10 - $14 / sf

22 Design Considerations Design Objectives (Quality / Volume / Flow / Recharge) Media Specifications / Consistency Sizing Offline / Flow Through Systems Pretreatment Unique configurations / designs (costs) Custom Application (Bacteria / Metals / Oil and Grease)

23 Bioretention Design Objectives Peak Discharge Control 1-, 2-, 10-, 15-, 100-year storms Bioretention may provide part or all of this control Water Quality Control ½, 1 or 2 rainfall most frequently used Bioretention can provide 100% control Ground water recharge Many jurisdictions now require recharge ( e.g., MD, PA, NJ, VA)

24 Infiltration System 2 Mulch 2 Existing Ground Highly Pervious Soils

25 Highly Pervious Soils Filtration System 2 Mulch Existing Ground 2 Drain Pipe

26 Combination Filtration / Infiltration 2 Mulch Existing Ground 2 Sandy Organic Soil Drain Pipe Gravel Moderately Pervious Soils

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28 Bioretention Shallow Ponding - 4 to 6 Mulch 3 Soil Depth Sandy Top Soil 65% Sand 20% Sandy Loam X 2 Under Drain 15% Compost Under Drain System Plants

29 Bioretention Planter Box Soaker

30 City of Portland, OR Low Flow - 1 to 3 / Hour Soaker Sand / Municipal Compost Ocean City, MD High Flow / Hour Filterra Corse Sand / Peat

31 Flow Rate and Annual Volume

32 Low Flow Media 2 to 10 inches / hour Peat / Sand / Aggregate Matrix - PSD Peat 15 to 20% by volume Clay <5% (<0.002 mm) Silt <5% ( mm) Very Fine Sand 5-10% ( mm) Fine Sand 15-20% ( mm) Medium to Coarse Sand 60-70% ( mm) Coarse Sand 5-10% ( mm) Fine Gravel <5% ( mm)

33 High Flow Media 10 to 50 inches / hour Peat Sand / Aggregate Matrix - PSD Peat 5 to 10% by volume Clay <2% (<0.002 mm) Silt <2% ( mm) Very Fine Sand 5% ( mm) Fine Sand 10% ( mm) Medium to Coarse Sand 70% ( mm) Coarse Sand 10-15% ( mm) Fine Gravel 5-10% ( mm)

34 Other Media Considerations Homogenous Mixture Peat / Clays / Silts slow flows Test and standardize the media! But performance varies with source! Min depth of media Max depth varies with vegetation. Organic Component (Peat vs. Compost)

35 Media Components Properties Sand Silt Loam Compost Peat Permeability (cm/hr) Water holding capacity (cm/cm) Bulk density (g/cm) < ph Organic matter (%) <1 < Cation exchange capacity Total phosphorus (%) <0.1 <0.1 Total nitrogen (%) <1.0 <2.5 Filtration efficiency after 18 in. (%)

36 Louisburg Bioretention Cells Soil Media: Nominally 0.75 m Deep 60% Sand 40% Ballfield Mix Low PI (1-2) fill 85% Sand 10% Fines 5% Organics Constructed Spring 2004

37 Other Media Considerations Mulch Hardwood / Pine bark Use as pretreatment Water retention Pollutant removal Maintenance

38 Underdrain System Avoid Filter Fabric use bridging stone (pea gravel around pipe) Minimum of 3" of gravel over pipes; not necessary underneath pipes Underdrain Piping ASTM D-1785 or AASHTO M-2786" rigid schedule 40 PVC 3/8" 6" on center, 4 holes per row; Observation wells

39 New York Design Manual, Appendix C Pretreatment NOT NECESSARY! Little additional benefit Additional Maintenance issues Requires additional space Restricts use

40 Design Configuration Considerations Off line vs. Flow-through Inlet Surface Storage Underdrain Dewater media

41 2005 Lake County, OH Off-line

42 Flow-through 2005 lake County, OH

43 Plants Considerations Pollutant uptake Evapotranspiration Soil ecology / structure / function Number & type of plantings may vary, Aesthetics Morphology (root structure trees, shrubs and herbaceous) Native plants materials Trees 2 in. caliper / shrubs 2 gal. size / herbaceous 1 gal size. landscape plan will be required as part of the plan. Sealed by a registered landscape architect. Plants are an integral part no changes unless approved Plant survival Irrigation Typical / customary

44 Bioretention: Site Analysis Map site soils by soil series, hydrologic soil type (A, B,C, D), textural classification and engineering properties If possible, avoid laying impervious surfaces (roads, parking lots, driveways) over HSG A and B soils Minimize cut and fill in A & B soils (site fingerprinting) Infiltration facilities in C & D soils require underdrains.

45 Sizing Flow rate Infiltration rate Volume Intensity Void space Drainage area (Smaller the Better)

46 Construction / Inspection Preconstruction meeting with the contractor / owner / architect / engineer Geotechnical Report Ensure sediment control measures in place Sub grade soils and preparation. Presence of Ground water Under drain and filter media installation. Soil certifications for back fill. Topsoil layers should be thoroughly wetted achieve settlement. Plant placement / warrantee / type Proper site grading Site stabilization before planting. U&O

47 Inspection / Maintenance Require a long term maintenance plan. Periodic flow testing. Non Erosive Designs Inlet / Outlet / Flowthrough. Sediment build-up. Annual inspection / plant care. Excessive ponding (Longer than 8 hours). Use underdrains. Right Vegetation. Spills.

48 Enforcement Site Inspectors field adjustments Site restoration or construction bonds Site Inspection fees Individual property owner agreement Home Owner Association Easements / Rights-of-way Enable local government actions Fees / Fines / Penalties Administrative and Court actions Community standards U&O

49 Lessons Learned High Failure Rates Due to: Use of Old Design Standards - clay / organic / K factor Poor Drainage - Under drain design / Geo-fabrics / Saturated soils Media Variability - Reliable Sources Contractor Substitutes Contamination - P, N and Heavy Metals Sizing / Space Maintenance - Can be high as system become larger

50 Bioretention Applications

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54 Rain Garden in an office building.

55 Residential Rain Gardens

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61 Bioretention Types Fieldstone weep garden design

62 Weep Wall Filter

63 Rain Garden with turf grass treating the rooftop runoff (sheet-flows across lawn) of a hospital facility.

64 The first Rain Garden in Virginia, located in a turning circle in front of St. Stephens School, Alexandria.

65 St. Stephens Rain Garden- 5 years later.

66 Rain Gardens used through-out the Alexandria Central Library to treat all impervious runoff

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68 All green space can be designed to be hydrologically functional and treat runoff.

69 Port Towns Shopping Center Flow

70 0.94 $29,000 $30,000 / Ac.

71 Buckman Heights courtyard with infiltration garden

72 Buckman Heights Apartments Infiltration garden

73 Division Street Planters

74 Tree Box Filter

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76 Maintenance

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