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Bioretention Technology

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Presentation on theme: "Bioretention Technology"— Presentation transcript:

1 Bioretention Technology
Presented by: The Low Impact Development Center, Inc. A non-profit water resources and sustainable design organization Presented by: The Low Impact Development Center, Inc. A non-profit water resources and sustainable design organization

2 The Low Impact Development Center, Inc
The Low Impact Development Center, Inc. has met the standards and requirements of the Registered Continuing Education Program. Credit earned on completion of this program will be reported to RCEP at RCEP.net. A certificate of completion will be issued to each participant. As such, it does not include content that may be deemed or construed to be an approval or endorsement by RCEP.

3 © Low Impact Development Center, 2012
COPYRIGHT MATERIALS This educational activity is protected by U.S. and International copyright laws. Reproduction, distribution, display, and use of the educational activity without written permission of the presenter is prohibited. © Low Impact Development Center, 2012

4 Purpose and Learning Objectives
The purpose of this presentation is to provide detailed information on bioretention pollutant removal, design variations, and sizing methods At the end of this presentation, you will be able to: Describe how bioretention works physically and chemically Design bioretention systems Why is LID an Important tool for the Navy? Because LID Meets Policy and Regulatory Requirements, Helps the Installation get “points” for Sustainable Design AND Meets Regulator Guidance for implementing Better Site Design into Navy Stormwater Projects. UFC Manual was completed in October 2004, and is a complete guide to the inclusion of LID features in DoD construction and retrofit projects. “Getting Points” Following regulator guidance for using “Better Site Design” techniques will help Navy installations get “points” with regulators, can reduce regulatory requirements and allow precious Navy funding to be directed to other needed facility and environmental projects. Meeting Navy policy and EO requirements will help Navy installations get “points” with HQ Navy and DOD. This can help in situations where installations are being considered for BRAC. Good News stories from a Navy Installation that used innovative methods to reduce requirements is more likely to be considered for future funding and future missions.

5 Overview Performance research State-of-the-art in bioretention design
Design tools

6 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

7 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”

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

9 Nitrogen Removal Step 1: Nitrification Step 2: Denitrification
Ammonia/urea → nitrate Aerobic process Nitrate is highly mobile, and tends to be exported Step 2: Denitrification Nitrate → nitrogen gas Anaerobic process May occur in gravel storage layer beneath underdrain

10 Phosphorus Removal Dependent on the amount of phosphorus present in the BSM Measured by the p-index of the topsoil used to mix BSM High p-index soils export phosphorus

11 Other Pollutants Heavy metals
Adsorb to clay and humus in BSM May be taken up by plants Organics (oil and grease, pathogens, PAHs, etc) Filtered by mulch and BSM Digested by microbes Taken up by plants TSS Bioturbation by earthworms may prevent clogging

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

13 Pollutant Mass Removal University of Maryland
Field experiments Small events produced zero effluent, so comparing inflow/outflow EMC underestimates removal Mass removal is a better metric, but produces misleadingly low removal rates for pollutants occurring at low concentrations (e.g. Cu, Pb, and Zn) Pollutant Mass removal TSS 57 % TP 78 % Cu 80 % Pb 86 % Zn 62 % NO3-N 93 %

14 Volume Reduction University of Maryland
Allen Davis at the University of Maryland has found that even lined bioretention cells with underdrains reduced runoff volume by at least 33% for 55-62% of events 18% of storm events had no outflow

15 Louisburg Bioretention Dr. Bill Hunt North Carolina State Research

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

17 Inflow vs. Outflow Rates

18 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)

19 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)

20 Infiltration System 2” Mulch Existing Ground 2’ Highly Pervious Soils

21 Combination Filtration / Infiltration
2” Mulch Existing Ground 2’ Sandy Organic Soil Drain Pipe Gravel

22 Bioretention Shallow Ponding - 4” to 6” Mulch 3” BSM Depth 2’ - 2.5’
50% Sand 30% Sandy Loam 20% Shredded Hardwood/ Compost Underdrain System Plants X 2’ Under Drain

23 Bioretention Soil Medium
Final proportion Component Properties 50% by volume Sand Conforms to ASTM C33 Fine Aggregate 20% by volume Organic Material Compost or shredded hardwood mulch 30% by volume Topsoil Sand (2.0 – mm) 50 – 85% by weight Silt (0.050 – mm) 0 – 50% by weight Clay (less than mm) 10 – 20% by weight * Organic Matter 1.5 – 10% by weight pH 5.5 – 7.5 (NOTE: pH can be corrected with soil amendments if outside acceptable range) Magnesium Minimum 32 ppm (NOTE: magnesium sulfate can be added to increase Mg) Phosphorus (Phosphate - P2O5) Not to exceed 69 ppm P-index should be less than 25 Potassium (K2O) Minimum 78 ppm (NOTE: potash can be added to increase K) Soluble Salts Not to exceed 500 ppm * If the proposed topsoil is known to contain expansive clays, clay content should not exceed 10% by weight.

24 Other Media Considerations
Homogenous Mixture Peat / Clays / Silts slow flows Test and standardize the media! But performance varies with source! Min 1.0’ depth of media Max depth varies with vegetation. Organic Component (Shredded Hardwood vs. Compost)

25 Underdrain System Needed for subsoils with percolation rates less than ½” per hour Filter fabric vs pea gravel diaphragm 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; or corrugated perforated HDPE Observation wells

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

27 Off-line 2005 Lake County, OH

28 Flow-through 2005 Lake County, OH

29 Plant 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

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

31 “Kerplunk” Method Bioretention cell is sized to store a target runoff volume within the ponded area and soil/gravel pore space. This method makes several simplifying assumptions, but works reasonably well (see Reese, Stormwater Magazine, September 2011)

32 “Kerplunk” Method 𝐴𝑟𝑒𝑎= 𝑅𝑢𝑛𝑜𝑓𝑓 𝑣𝑜𝑙𝑢𝑚𝑒 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝑑𝑒𝑝𝑡ℎ
𝐴𝑟𝑒𝑎= 𝑅𝑢𝑛𝑜𝑓𝑓 𝑣𝑜𝑙𝑢𝑚𝑒 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝑑𝑒𝑝𝑡ℎ 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒 𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝑑𝑒𝑝𝑡ℎ=𝑝𝑜𝑛𝑑𝑖𝑛𝑔 𝑑𝑒𝑝𝑡ℎ+ 𝐵𝑆𝑀 𝑑𝑒𝑝𝑡ℎ ∗𝐵𝑆𝑀 𝑝𝑜𝑟𝑜𝑠𝑖𝑡𝑦 +(𝑔𝑟𝑎𝑣𝑒𝑙 𝑑𝑒𝑝𝑡ℎ ∗𝑔𝑟𝑎𝑣𝑒𝑙 𝑝𝑜𝑟𝑜𝑠𝑖𝑡𝑦) BSM porosity ≈ 0.35 Gravel porosity ≈ 0.4

33 RECARGA Developed by the University of Wisconsin-Madison Department of Civil Engineering Capable of single event or continuous simulation Incorporates infiltration, evapotranspiration, overflow, and underdrain flow

34 RECARGA

35 Low Impact Development Center, Inc.
Thank you for your time. QUESTIONS? Low Impact Development Center, Inc.


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