Site Evaluation and Considerations for Design and Review of Bioretention Jay Dorsey & John Mathews ODNR-DSWR June 18, 2014
Goals for Presentation Understanding Why Bioretention Practices Fail Site Considerations Right BMP? Site Limitations Site Properties for Design Giving Bioretention Practices the Best Chance to Function Over the Long Haul
Why Do Bioretention Practices Fail? Undersized Bioretention Cell Based on Overestimate of Infiltration Capacity
Why Do Bioretention Practices Fail? Undersized Bioretention Cell Based on Overestimate of Infiltration Capacity
Why Do Bioretention Practices Fail? Undersized Bioretention Cell Based on Overestimate of Infiltration Capacity Sediment Clogging of Geotextile Filter Between Soil and Aggregate Layers
Why Do Bioretention Practices Fail? Undersized Bioretention Cell Based on Overestimate of Infiltration Capacity Sediment Clogging of Geotextile Filter Between Soil and Aggregate Layers
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface
Clogging of Filter Surface
Clogging of Filter Surface Source: Bill Hunt, NCSU-BAE
Source: Bill Hunt, NCSU-BAE
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface 2. Eroding Sideslopes - Unstable Sideslopes and/or Concentrated Flow
Source: Brad Wardynski, NCSU-BAE Source: Amy Dutt, Urban Wild
Source: Brad Wardynski, NCSU-BAE
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface 2. Eroding Sideslopes 3. Undersized Surface Ponding Volume
Storage Volume Source: Brad Wardynski, NCSU-BAE
Storage Volume Severely Undersized (>25%) 35% Source: Brad Wardynski, NCSU-BAE
Results: Storage Volume Need to inspect average ponding depth (not height of outlet structure) Source: Brad Wardynski, NCSU-BAE
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface 2. Eroding Sideslopes 3. Undersized Surface Ponding Volume 4. Construction Issues/Lack of Construction Oversight
Construction Issues/Lack of Construction Oversight Loss of Exfiltration/Infiltration Capacity smearing or compaction of subgrade soils during excavation compaction of filter bed soils during construction
Construction Issues/Lack of Construction Oversight Loss of Exfiltration/Infiltration Capacity smearing or compaction of subgrade soils during excavation compaction of filter bed soils during construction Materials esp. filter sand and planting media
Photo: Geo Growers
Construction Issues/Lack of Construction Oversight Loss of Exfiltration/Infiltration Capacity smearing or compaction of subgrade soils during excavation compaction of filter bed soils during construction Materials esp. filter sand and planting media Elevations filter bed surface, overflow
Construction Issues/Lack of Construction Oversight Loss of Exfiltration/Infiltration Capacity smearing or compaction of subgrade soils during excavation compaction of filter bed soils during construction Materials esp. filter sand and planting media Elevations filter bed surface, overflow Existing or Hidden Infrastructure
Construction Issues/Lack of Construction Oversight Loss of Exfiltration/Infiltration Capacity smearing or compaction of subgrade soils during excavation compaction of filter bed soils during construction Materials esp. filter sand and planting media Elevations filter bed surface, overflow Existing or Hidden Infrastructure Keeping Sediment Out of BRC During Construction staging, site drainage and erosion control during construction, site stabilization
Source: Amy Dutt, Urban Wild
Bioretention Construction Construction season/ construction timing Excavation in fill material
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface 2. Eroding Sideslopes 3. Undersized Surface Ponding Volume 4. Construction Issues/Lack of Construction Oversight 5. Plant Selection and Management
Plant Selection and Management Plants: Plant selection tolerant to range of soil moisture involve landscape architect or horticulturalist familiar with bioretention Avoid visual clearance issues Minimize maintenance Year-round aesthetic appeal Commercially available
Plant Selection and Management - Resources - Horticulturalist or Landscape Architect (esp. ones with stormwater background) Local Rain Garden Alliance (e.g. CincyRain.org) Rain Garden and Stormwater Plant Guides
Grassed Bioretention VaDCR Independence, OH Orange Village, OH
Landscape Plants vs Grass Conrad St, Toledo
Landscape Plants vs Grass
Landscape Plants vs Grass
Third Federal Bank, North Olmstead Source: Dan Bogoevski, Ohio EPA Grassed Bioretention
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface 2. Eroding Sideslopes 3. Undersized Surface Ponding Volume 4. Construction Issues/Lack of Construction Oversight 5. Plant Selection and Management 6. Lack of Maintenance
Why Do Bioretention Practices Fail? 1. Sediment Clogging of Filter Bed Surface 2. Eroding Sideslopes 3. Undersized Surface Ponding Volume 4. Construction Issues/Lack of Construction Oversight 5. Plant Selection and Management 6. Lack of Maintenance 7. Bioretention BMP or Design Poor Fit for Site
Design for Constructability Specify sod for grassed sideslopes Specify approach/equipment to be used for media placement B. Prunty Photo B. Prunty Photo B. Prunty Photo
Design for Maintainability Specify sod for grassed sideslopes Access for maintenance activities Create separate snow storage area w/pretreatment before bioretention NCSU Photo
Planning Considerations Drainage Area < 2 Acres Existing Infrastructure Setbacks from Property Lines, Building Foundations, Wells, Septic Systems
Planning Considerations Drainage Area < 2 Acres Existing Infrastructure Setbacks from Property Lines, Building Foundations, Wells, Septic Systems Commitment/Resources to Maintain Practice
Site Evaluation Groundwater Pollution Concerns Karst or Shallow Sand/Gravel Aquifer Areas
Groundwater Pollution Potential Maps Search on ODNR groundwater program
Site Evaluation Groundwater Pollution Concerns Karst or Shallow Sand/Gravel Aquifer Areas Shallow Depth to Bedrock Shallow Depth to Water Table 2 ft separation recommended, 1 ft required
Site Evaluation Groundwater Pollution Concerns Karst or Shallow Sand/Gravel Aquifer Areas Shallow Depth to Bedrock Shallow Depth to Water Table 2 ft separation recommended, 1 ft required Soil Limitations/Hydrologic Soil Group (HSG)
Soil Survey Information Search on ODNR soils data
Planning and Design Considerations HSG Shorthand HSG-A Shallow aquifer? Avoid short circuiting from pollutant hot spots HSG-B Easy to work with Maintain infiltration capacity of soils Drainage usually recommended HSG-C Oftentimes in optimal landscape position Maintain infiltration capacity of soils Drainage required HSG-D Must identify limitations and design accordingly Drainage required
Site Evaluation Groundwater Pollution Concerns Karst or Shallow Sand/Gravel Aquifer Areas Shallow Depth to Bedrock Shallow Depth to Water Table 2 ft separation recommended, 1 ft required Soil Infiltration Capacity
BMP Hydrology P Precipitation (Rainfall & Snowmelt) ET Evaporation & Transpiration S1 Temporary Surface Storage S2 Temporary Subsurface Storage F1 Infiltration F2 Exfiltration Qin Runon/Lateral Inflow Qout - Runoff P ET S1 Qoverflow Qin Qin-leak F1 Qout-leak Qtile S2 F2 Qout
Infiltration Test for BMP Design? Bore Hole/ Perc Test (v1)? Ponded Ring Infiltrometer Test 3-Dimensional Flow ~1-Dimensional Flow
Single Ring Infiltrometer
Single Ring Infiltrometer
Estimating Infiltration Rates for BMPs for Site Planning
Soil Water Characteristics Calculator
Subgrade Kfs Estimates Subgrade USDA Soil Texture Clay Content % Ksat (in/hr) Sand < 8 2.8 Loamy Sand < 15 2.0 Sandy Loam < 20 0.80 Loam 7 27 0.16 Silt Loam < 27 0.05 Silt < 12 0.05 Sandy Clay Loam 20 35 0.07 Clay Loam 27 40 0.02 Silty Clay Loam 27 40 0.02 Silty Clay 40 50 0.01 Sandy Clay 35 55 <0.005 Clay > 40 <0.005
Pretreatment Realities For the bioretention practice to function: 1. The system must remove most sediment from runoff before it enters the filter bed area The bioretention system necessarily includes pretreatment components 2. The runoff must be introduced to the filter bed area with little or no erosive energy The design must address elevation change and concentrated flow
Pretreatment Requirements Some form of pretreatment is required Grass Filter Strip Gravel Verge plus Grass Filter Strip Grass Swale Sediment Forebay
Pretreatment Forebay Source: Brad Wardynski, NCSU-BAE
Pretreatment
Source: Bill Hunt, NCSU-BAE
Grass Filter Strip Source: Matt Repasky, ODNR
Grass Filter Strip and Grass Swale Sterncrest Road, Orange Village
flow too concentrated, flowpath too short
too steep? add grass filter? flow too concentrated, flowpath too short
Okay
Much Better Alternative Okay
Good Enough?
Education Center, Zanesville
References ODNR. Rainwater and Land Development Manual. Wardynski and Hunt. 2012. Are Bioretention Cells Being Installed per Design Standards in North Carolina? A Field Assessment. J. Env. Eng. 138(12): 1210-1217. Hunt, Davis, and Traver. 2012. Meeting Hydrologic and Water Quality Goals through Targeted Bioretention Design. J. Env. Eng. 138(6): 698-707. Brown, Hunt, and Kennedy. 2009. Designing Bioretention with an Internal Water Storage (IWS) Layer. NCSU-CE. CWP. 2012. West Virginia Stormwater Management and Design Guidance Manual.
Questions: Jay Dorsey Water Resources Engineer ODNR, Soil & Water Resources (614) 265-6647 jay.dorsey@dnr.state.oh.us