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Stormwater Green Infrastructure Research Needs

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Title: Stormwater Green Infrastructure Research Needs


1
Stormwater Green Infrastructure Research Needs
Results from the 319 NMP
Robert G. Traver, Ph.D., PE ProfessorDepartment
of Civil and Environmental EngineeringVillanova
University Director, Villanova Urban Stormwater
Partnership
2
Mission Statement
  • The mission of the Villanova Urban Stormwater
    Partnership is to advance sustainable stormwater
    management and to foster the development of
    public and private Partnerships through research
    on innovative SWM Best Management Practices,
    Directed Studies, Technology Transfer and
    Education.
  • Research and directed studies will emphasize
    sustainable stormwater management planning,
    implementation, and evaluation.
  • Technology transfer will provide tools, guidance
    and education for the professional.
  • Partnership Goal is to promote cooperation
    amongst the private, public and academic sectors.

3
1998 Sustainable Stormwater
  • Watershed Goals
  • Flooding
  • Water Quality
  • Surface Water
  • Tools
  • Detention

4
2008 Sustainable Stormwater
  • Watershed Goals
  • Flooding
  • Water Quality
  • Surface Water
  • Groundwater
  • Stream Channel Geomorphology
  • Base Flow
  • Tools
  • Problem Minimization
  • LID
  • Product Substitution
  • Volume Control
  • Infiltration
  • Evapotranspiration
  • Reuse
  • Extended Detention
  • Water Quality Treatment
  • Manufactured

5
from detention basins ? stormwater wetlands
? LID and Volume Reductionfrom an extreme
event flooding ? sustainable focus
Regulations have been enacted at the municipal,
state, and federal level to address stormwater,
focusing on flooding, recharge, water quality,
stream geomorphology and temperature effects (MDE
2000, PaDEP 2006, USEPA 2002, PWD 2008).
Stormwater Management has changed dramatically in
the last decade, as it has moved away from a
flood control perspective toward sustainability
of our rivers and watersheds.
6
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7
Generic Stormwater Management
  • Good Idea
  • Specifications General tied to processes?
  • Expected Results General Wide Range of error

8
Infiltration Trench
Permeable Pavement
Bioretention
9
Porous Pavement
Not a lot of data available!
Cost 23 / Square foot (instead of 1)
From CWP Webpage
10
Bioretention Guidelines
11
Bioretention BMPs Can Be Used On-line or Off-line
  • Advantages
  • Reduce the need for pipes
  • Control runoff at its source
  • Good use of space
  • Disadvantages
  • Controls only small storms
  • No definitive data available

12
Bioretention
Cost 7.3 V 0.99 V Vol Water Treated Cubic
Feet Cost Construction, Design and
Permitting May be less as these are areas that
would be landscaped anyway!
From CWP Webpage
13
  •  
  •  

Pa Design Manual 2005
14
  • Sizing criteria
  • a. Surface area is dependent upon storage volume
    requirements but should generally not exceed a
    maximum loading ratio of 51 (impervious drainage
    area to infiltration area see Protocol 2.
    Infiltration Systems Guidelines (Appendix C) for
    additional guidance on loading rates.)
  • b. Surface Side slopes should be gradual. For
    most areas, maximum 31 side slopes are
    recommended, however where space is limited, 21
    side slopes may be acceptable.
  • c. Surface Ponding depth should not exceed 6
    inches in most cases and should empty within 72
    hours.
  • d. Ponding area should provide sufficient surface
    area to meet required storage volume without
    exceeding the design ponding depth. The
    subsurface storage/infiltration bed is used to
    supplement surface storage where feasible.
  • e. Planting soil depth should generally be at
    least 18 where only herbaceous plant species
    will be utilized. If trees and woody shrubs will
    be used, soil media depth may be increased,
    depending on plant species.
  • 2. Planting Soil should be a loam soil capable of
    supporting a healthy vegetative cover. Soils
    should be amended with a composted organic
    material. A typical organic amended soil is
    combined with 20-30 organic material (compost),
    and 70-80 soil base (preferably topsoil).
    Planting soil should be approximately 4 inches
    deeper than the bottom of the largest root ball.

15
Mis? Perceptions
  • PGC Md, Galli 1993
  • gt 60 Infiltration (mostly trenches)
  • Most not working as designed
  • Listed sediment in pre treatment, location,
    construction and maintenance
  • (used 72 hour rule to evaluate)
  • Suburban Md Lindsey, Roberts et al. 1992
  • 188 basins (repeat of earlier study)
  • gt ½ failed gt1/3 sediment buildup

16
Mis? Perceptions
  • Washington State Hilding 1996
  • Majority working
  • 1/3 had sediment buildup
  • NJ Pine Barrens Princeton Hydro, LLC 2005
  • 47 basins - 70 failed the 72 hour test
  • Two investigated
  • Poor maintenance
  • Designers missed restrictive soil layer

So, if you design, locate, construct, and
maintain poorly.. It will fail 50 of the
time..
17
Villanova Seepage Pit
18
Villanova Seepage Pit
19
  • Stormwater Control Level How do I design a
    stormwater control measure tailored to meet a
    specific goal based upon the climate, landuse,
    soils and geology for a specific site? What
    maintenance measures are needed to sustain its
    performance, and what is the life cycle
    expectation in longevity and cost?
  • Site Level How do I simulate for a site the
    overall performance of multiple stormwater
    controls for both the surface and groundwater
    systems.
  • Watershed Level How for a watershed do I first
    set a measurable goal, and how do we measure and
    or project the results of implementation. This
    addresses the issue of how does the benefits of
    each control measure translate to the watershed
    scale as measured by the impact on the water
    body.

20
Inherent Variability
  • Inflow
  • Pollutant loadings
  • Rainfall patterns
  • Climate
  • Performance of the BMP
  • Hydrologic Processes
  • Environmental Chemistry
  • Biology
  • Temperature
  • Back to Back storms
  • Construction
  • Maintenance / Replacement

21
  • .all components of the physical processes and
    tools to include landplaning, and that we are
    just beginning to understand the linkages and
    unit processes needed.

Thanks A. Davis
Thanks A. Davis
22
BioInfiltration
  • Contributing Watershed
  • Question How can we predict for the watershed,
    the hydrologic, pollutant, and thermal imputs to
    the Bioinfiltration Traffic Island?
  • Need To enable the design to be tailored to
    landuse, climate and storm size to the incoming
    increased flows and pollutants.
  •  
  • Pretreatment
  • Question How can we design to remove TSS, or
    other pollutants that are not treated by the
    control measure?
  • Need To enable the design to be sustainable,
    long lasting, and to treat pollutants (chlorides
    for example) that are not be addressed by the
    other components of the control measure.

23
BioInfiltration
  • Bioinfiltration - Bowl
  • Question What is the hydrological and
    sedimentation processes in the surface bowl?
  • Need To enable the design to address both volume
    and erosive flow reduction across the seasons.
  •  
  • Bioinfiltration - Vegetation
  • Question What are the vegetation processes to
    include maximization of evapotranspiration,
    maintenance of flow paths, and nutrient and
    pollutant reduction?
  • Need To enable the design to be tailored to
    individual pollutants, to select plants, and set
    maintenance and possible harvesting programs.

24
BioInfiltration
  • Bioinfiltration Soil Surface Layer
  • Made Soil
  • Existing Soil
  • Question What is the role of the surface layer,
    made soil, and existing soil, to include
    hydraulic, soil, chemical, and biological
    process?
  • Need To again enable the design to be tailored
    to individual pollutants, to set a geometry, and
    maintenance cycle. Which limits the infiltration
    or pollutant removal process? Does the gradation
    of the made soil change over time thus requiring
    replacement? Does the pollutant capture of the
    surface layer require regular replacement? What
    pollutant removal is expected in the existing
    soil after the runoff leaves the control measure?

25
Thanks A. Davis
26
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27
Per Year 28 events gt 0.5 in 12 events gt 1.0 in
6 events gt 1.5 in (1948 2001)
28
Brandywine River
Runoff
6.5 15
ET
24.6- (1.25) 55
Base Flow
14 (.25) 30
29
INFILTRATION BMPs
BioInfiltration Traffic Island (BTI)
  • Shallow (18), open, vegetated depression,
    sandsoil mixture, with initial mulch layer
  • Depth measured using an ultrasonic level detector
  • Quality, Rainfall, Depth and temperature
    measurements

30
INFILTRATION BMPs
BioInfiltration Traffic Island (BTI)
  • 1.3 Ac
  • 46 Impervious
  • 101 DCIA to BMP
  • 450 in/yr

31
INFILTRATION BMPs
BioInfiltration Traffic Island (BTI)
  • Constructed in 2001
  • 4 ft excavation, filled with a 11 sand/soil
    mixture
  • Planted with vegetation typically found along the
    eastern seaboard

32
Rain Gage
Ultrasonic Level Detector
Invert (El 444.25)
Weir El 445.20
Lysimeters
Soil Moisture Meters
33
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Measurement
38
Hydrologic Performance
39
Hydrologic Performance
40
Hydrologic Performance
41
Output from SlopeFinder program
BTI (4.25 years of data)
EMERSON
42
William Heasom
43
Example 2005 TI
  • 77 Events
  • 48 Rainfall
  • (not all snow included)
  • 7 Events Overflowed
  • Yearly Summary
  • 5.5 - Overflow
  • 2.5 Pre (Meadow B)

44
October 6-8th BioInfiltration TI
6.02
Bill Heasom
45
Bill Heasom
46
GW Mounding?
Machusick
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PERFORMANCE INDICATOR
How should the performance of an infiltration
BMP be assessed?
  • Annual runoff capture efficiency
  • - Influenced by drainage area characteristics
  • Post storm ponded time
  • Most regulations include ponded time
  • 72 hr failure
  • Ponded recession rate
  • Can be related to physical properties
  • Direct indication of the infiltration process

54
PERFORMANCE INDICATOR
Ponded Recession Rate
  • Not always constant with depth
  • Each BMP has its own characteristic recession
    limb (shape) from storm to storm
  • Can be compared over time (longevity)

55
SEASONAL VARIATION
Summary of Regressions
  • All obs. regressions are significant at the gt95
    level
  • Predicted variations (viscosity correction) all
    lie well within the 95 CI of the regressions

56
LONGEVITY
PCIB
Low (3-61) ratio of DCIA to BMP area Inflow with
characteristically low TSS concentrations Shallow
bed Maintenance Vacuum Closed bed, no
vegetation, mulch, organic matter, or freeze-thaw.
57
LONGEVITY
IT
Extremely high (1301) ratio of DCIA to BMP
area Inflow with characteristically high TSS
concentrations Closed bed, no vegetation, mulch,
organic matter, or freeze-thaw Deep No Maintenance
58
LONGEVITY
Points to Ponder Re IT
  • PA BMP Manual(51 DCIA to BMP ratio)
  • IT (1301) 130 / 5 2626 times the annual
    sediment load
  • 80 equivalent years of operation

59
LONGEVITY
BTI
Heavily vegetated, Protective mulch layer, High
organic matter content in surficial soil Some
level of TSS pretreatment Shallow bed Freeze-thaw
action Can be maintained Moderate (101) DCIA to
BMP ratio
60
Design recommendations Need to understand the
unit processes!
  • CHOOSE your BMP based upon..
  • How dirty is runoff?
  • Look for clean sources!
  • Is pretreatment practical?
  • What is in it?
  • How much rain falls?
  • What Level of Maintenance?
  • RISK

61
Infiltration Risk Idea
Manhole
Storage
1 Runoff goes to Raingarden Pretreatment
Larger Storms 1 goes to UG Storage
62
WWW.VILLANOVA.EDU/VUSP
63
PERFORMANCE INDICATOR
Incremental Slopes (PCIB and IT)
64
PERFORMANCE INDICATOR
  • Each BMP has been the subject of continuous
    monitoring in total, approximately ten years
  • Needed an impartial, quantitative, and efficient
    method to find and calculate hundreds of slopes
  • Visual Basic program created to find and
    calculate the recession rates or slopes
    (SlopeFinder)

65
LONGEVITY
BioInfiltration Traffic Island (BTI)
66
LONGEVITY
Pervious Concrete Infiltration Basin (PCIB)
67
LONGEVITY
Infiltration Trench (IT)
(log scale)
68
LONGEVITY
  • Only the IT shows visual evidence of a systematic
    change (decrease) in performance
  • All three BMPs show significant (two-fold)
    seasonal variation

What is the origin of seasonal variation in
infiltration BMP performance? Why does only one
(IT) show a systematic decrease?
69
SEASONAL VARIATION
What is the origin of seasonal variation?
BioInfiltration Traffic Island
70
SEASONAL VARIATION
What is the origin of seasonal variation?
Infiltration Trench
71
SEASONAL VARIATION
  • The viscosity of water varies two-fold over
    average annual temp. ranges

Where K hydraulic conductivity LT-1 k
intrinsic permeability L2 ? fluid density
L-1T-1 g gravitational acc. LT-2 µ
fluid dynamic viscosity ML-1T-1
72
INFILTRATION TESTING
Soil texture-based classification
73
INFILTRATION
Assumptions
  • One dimensional flow
  • Homogeneous (area averaged)
  • Negligible influence of ponded depth
  • Saturated conditions, no influence of soil
    moisture potential

Except Infiltration Trench
74
INFILTRATION
Infiltration Trench (IT)
  • Trench Infiltration Model (McKsat)
  • Conceptually broken into two parts (bottom and
    sides)
  • Accounts for the head of ponded water
  • Accounts for the Trench geometry (infiltrating
    area)
  • Based on Darcys law
  • Monte Carlo method used to select best fit
  • Flow-weighted sum of squares

75
INFILTRATION
Infiltration Trench (IT)
76
INFILTRATION
Infiltration Trench (IT)
  • Inputs
  • Trench geometrystage storage wetted area
  • Bounds for K in/hr estimation
  • No. of iterations
  • Specific storm hydrograph inf. vs. time
  • Outputs
  • Best fit Ks in/hr
  • Error flow-weighted sum of squares
  • Simulated hydrograph

Kbottom 0.026 in/hr
Ktop 0.73 in/hr
77
SEASONAL VARIATION
  • Linear Regressions
  • How does the performance change with temperature?
  • What portion of this variation might be caused by
    temperature induced viscosity effects?
  • Which BMPs are more or less dependant on
    temperature, and why?

78
SEASONAL VARIATION
  • Assumptions of Linear Regression Model
  • Linear relationship is expected
  • Normal distribution of residuals around the
    regression
  • Constant standard deviation over range of
    independent variable
  • Independent observations (autocorrelation)

79
SEASONAL VARIATION
What portion of the variation can be attributed
to temperature-induced viscosity effects?
Method
  • Determine the average Temp and corresponding K
    in/hr for each regression.
  • Based on the average Temp, calculate the
    resulting fluidity
  • Solve for k in2
  • Using this k in2 vary Temp (f) and fluid
    properties and solve for K in/hr

Where K LT-1 hydraulic conductivity k L2
intrinsic permeability f L-1T-1 fluidity
f (temp.)
80
SEASONAL VARIATION
Pervious Concrete Infiltration Basin (PCIB)
81
SEASONAL VARIATION
Pervious Concrete Infiltration Basin (PCIB)
82
SEASONAL VARIATION
Summary of Regressions
  • All obs. regressions are significant at the gt95
    level
  • Predicted variations (viscosity correction) all
    lie well within the 95 CI of the regressions

83
LONGEVITY
Do the PCIB or BTI show any signs of a systematic
decrease over time?
  • Multiple linear regressions (temperature age)

84
LONGEVITY
  • The IT data show undeniable evidence of a
    decrease over time.
  • To be fair, the IT data includes first 1.5 yr of
    operation (PCIB and BTI do not)

85
?So.. Mechanisms?
  • CONSTRUCTION!
  • DESIGN
  • How Dirty is the Runoff?
  • Can you pretreat?
  • Soil infiltration capacity?
  • Clogging of Surface Layer / Geotextile
  • pretreatment?
  • ability to maintain?
  • Depth impact?
  • Impact of Rain / Soil protection?

86
LONGEVITY
What impacts the longevity of infiltration BMPs?
  • There are many processes that tend to decrease
    the rate of infiltration.
  • There are also many processes and soil
    characteristics that resist degradation and can
    improve the overall rate of infiltration.
  • not including native soil profile, depth to
    groundwater, and construction techniques.

Not so good
Bad
Good
87
LONGEVITY
PCIB
Low (3-61) ratio of DCIA to BMP area Inflow with
characteristically low TSS concentrations Shallow
bed Maintenance Vacuum Closed bed, no
vegetation, mulch, organic matter, or freeze-thaw.
88
LONGEVITY
IT
Extremely high (1301) ratio of DCIA to BMP
area Inflow with characteristically high TSS
concentrations Closed bed, no vegetation, mulch,
organic matter, or freeze-thaw Deep No Maintenance
89
LONGEVITY
Points to Ponder Re IT
  • PA BMP Manual(51 DCIA to BMP ratio)
  • IT (1301) 130 / 5 2626 times the annual
    sediment load
  • 80 equivalent years of operation

90
LONGEVITY
BTI
Heavily vegetated, Protective mulch layer, High
organic matter content in surficial soil Some
level of TSS pretreatment Shallow bed Freeze-thaw
action Can be maintained Moderate (101) DCIA to
BMP ratio
91
Design recommendations
  • CHOOSE your BMP based upon..
  • How dirty is runoff?
  • Look for clean sources!
  • Is pretreatment practical?
  • What is in it?
  • How much rain falls?
  • What Level of Maintenance?
  • RISK

92
Infiltration Risk Idea
Manhole
Storage
1 Runoff goes to Raingarden Pretreatment
Larger Storms 1 goes to UG Storage
93
Per Year 28 events gt 0.5 in 12 events gt 1.0 in
6 events gt 1.5 in (1948 2001)
94
WWW.VILLANOVA.EDU/VUSP
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