1 Overview of Unit Processes Approach for BMP Selection and Design Overview of Unit Processes Approach for BMP Selection and Design 1 Eric W. Strecker, P.E. [email protected]Design Design Understanding and Applying Knowledge of Performance of Best Management Practices 2 We have a long way to go! But, we have learned a lot! Stormwater BMP Selection and Design and Design Standards Stormwater BMP Selection and Design and Design Standards 6 Should be targeted to “solving the problem's”; not just meet NPDES requirements 6 Should be targeted to “solving the problem's”; not just meet NPDES requirements 3 Design Standards Design Standards 6 Typically have focused almost entirely on “Size of Storm” for runoff treatment with no or little requirements for specifically addressing pollutants/parameters of concern 6 Typically have focused almost entirely on “Size of Storm” for runoff treatment with no or little requirements for specifically addressing pollutants/parameters of concern 4 6 Rarely have design standards development efforts started with the questions: 6 What are the pollutants and parameters of concern? 6 Will/can/how will my design standards for new and re-development address those parameters? 6 Rarely have design standards development efforts started with the questions: 6 What are the pollutants and parameters of concern? 6 Will/can/how will my design standards for new and re-development address those parameters? Setting Design Standards Setting Design Standards 1. Identify Pollutants and Parameters of Concern and Goals 6 303d listings 6 TMDLs 6 Other Typical Pollutants of Concern 1. Identify Pollutants and Parameters of Concern and Goals 6 303d listings 6 TMDLs 6 Other Typical Pollutants of Concern 5 o The usual “suspects” 6 Other Parameters of Concern: o Flow increases and resulting stream erosion o Temperature o Select a list that represents most of the issues/problems that need to be addressed and develop goals o The usual “suspects” 6 Other Parameters of Concern: o Flow increases and resulting stream erosion o Temperature o Select a list that represents most of the issues/problems that need to be addressed and develop goals Setting Design Standards Setting Design Standards 2. Identify Unit Processes Required to Address Pollutants/Parameters of Concern: 6 Physical 2. Identify Unit Processes Required to Address Pollutants/Parameters of Concern: 6 Physical 6 6 Physical 6 Biological 6 Chemical 6 Physical 6 Biological 6 Chemical
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1
Overview of Unit Processes Approach for BMP Selection and
Design
Overview of Unit Processes Approach for BMP Selection and
Understanding and Applying Knowledge of Performance of Best Management Practices
2We have a long way to go!But, we have learned a lot!
Stormwater BMP Selection and Design and Design Standards
Stormwater BMP Selection and Design and Design Standards
Should be targeted to “solving the problem's”; not just meet NPDES requirements
Should be targeted to “solving the problem's”; not just meet NPDES requirements
3
Design StandardsDesign Standards
Typically have focused almost entirely on “Size of Storm” for runoff treatment with no or little requirements for specifically addressing pollutants/parameters of concern
Typically have focused almost entirely on “Size of Storm” for runoff treatment with no or little requirements for specifically addressing pollutants/parameters of concern
4
Rarely have design standards development efforts started with the questions:
What are the pollutants and parameters of concern?Will/can/how will my design standards for new and re-development address those parameters?
Rarely have design standards development efforts started with the questions:
What are the pollutants and parameters of concern?Will/can/how will my design standards for new and re-development address those parameters?
Setting Design StandardsSetting Design Standards1. Identify Pollutants and Parameters of Concern and
Goals303d listingsTMDLs
Other Typical Pollutants of Concern
1. Identify Pollutants and Parameters of Concern and Goals
303d listingsTMDLs
Other Typical Pollutants of Concern
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o The usual “suspects”
Other Parameters of Concern:o Flow increases and resulting stream erosiono Temperature
o Select a list that represents most of the issues/problems that need to be addressed and develop goals
o The usual “suspects”
Other Parameters of Concern:o Flow increases and resulting stream erosiono Temperature
o Select a list that represents most of the issues/problems that need to be addressed and develop goals
Setting Design StandardsSetting Design Standards
2. Identify Unit Processes Required to Address Pollutants/Parameters of Concern:
Physical
2. Identify Unit Processes Required to Address Pollutants/Parameters of Concern:
Physical
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Physical
Biological
Chemical
Physical
Biological
Chemical
2
Design StandardsDesign Standards
3. Apply unit processes and empirical data to set design criteria/standards (or selection and design BMPs)
Hydrologic/Hydraulic Long-term simulations of precipitation/runoff/BMP hydraulicsA h h ff i d d d
3. Apply unit processes and empirical data to set design criteria/standards (or selection and design BMPs)
Hydrologic/Hydraulic Long-term simulations of precipitation/runoff/BMP hydraulicsA h h ff i d d d
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Assess how much runoff is prevented, treated and not treated
Assess effects of BMPs on flow-durationLong-term simulations of particle settling (using particle settling theory)Apply empirical data for other constituents to predict treated effluent quality
Assess how much runoff is prevented, treated and not treated
Assess effects of BMPs on flow-durationLong-term simulations of particle settling (using particle settling theory)Apply empirical data for other constituents to predict treated effluent quality
Design StandardsDesign Standards
4. Evaluate various potential options and conduct cost/effectiveness
Select example sites/land usesDevelop potential BMP options
l i l i f
4. Evaluate various potential options and conduct cost/effectiveness
Select example sites/land usesDevelop potential BMP options
l i l i f
8
Run long-term simulations for various sizing and hydraulicsEvaluate cost implications and effectiveness looking at “real sites”
5. Select design standards6. Provide for both prescriptive and
performance options
Run long-term simulations for various sizing and hydraulicsEvaluate cost implications and effectiveness looking at “real sites”
5. Select design standards6. Provide for both prescriptive and
performance options
Background and Context Background and Context
Projects:National Cooperative Highway Research Program Project 25-20(01)
“Development of a BMP Evaluation Methodology for Highway Applications”
Chris Hedges PO, Ed Herricks Chair of PSC
Projects:National Cooperative Highway Research Program Project 25-20(01)
“Development of a BMP Evaluation Methodology for Highway Applications”
Chris Hedges PO, Ed Herricks Chair of PSC
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Water Environment Research Federation Project 02-SW-1:
Critical Assessment of Stormwater Control Selection Issues
Jeff Moeller PO, Bob Pitt Chair of PSC
Primary DeliverablesGuidance Manuals on BMP Selection and Design
Water Environment Research Federation Project 02-SW-1:
Critical Assessment of Stormwater Control Selection Issues
Jeff Moeller PO, Bob Pitt Chair of PSC
Primary DeliverablesGuidance Manuals on BMP Selection and Design
Background and Context WERF - Publication
Background and Context WERF - Publication
Available to WERF Subscribers now;Available to others IWA
Available to WERF Subscribers now;Available to others IWA
Overall Goal For ProjectsOverall Goal For Projects
Use the “best information” available to provide guidance on the selection and use of stormwater water quality controls
Unit Processes
Use the “best information” available to provide guidance on the selection and use of stormwater water quality controls
Unit Processes
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Observed BMP Performance
Develop stormwater controls selection and evaluation methodology for use by practitioners
NCHRP – Highway Specific
WERF – Urban Environment
Observed BMP Performance
Develop stormwater controls selection and evaluation methodology for use by practitioners
NCHRP – Highway Specific
WERF – Urban Environment
Achieving Project Goals Achieving Project Goals
Emphasize
Treatabilty
Evaluation and design by examination of fundamental unit processes
Emphasize
Treatabilty
Evaluation and design by examination of fundamental unit processes
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Include criteria of practicability, performance, and hydrologic assessment on a control-specific and regional basis
Provide technical guidance documents and related reports/research findings
Include criteria of practicability, performance, and hydrologic assessment on a control-specific and regional basis
Provide technical guidance documents and related reports/research findings
3
Definition-Fundamental Unit Process
Definition-Fundamental Unit Process
Underlying Hydrologic, Hydraulic, Physical, Chemical, and Biological Treatment Mechanisms
Underlying Hydrologic, Hydraulic, Physical, Chemical, and Biological Treatment Mechanisms
13
Treatment MechanismsTreatment Mechanisms
Definition-Treatment System Component (TSC)
Definition-Treatment System Component (TSC)
Design element or feature of a stormwater control or treatment system that includes one or more
Design element or feature of a stormwater control or treatment system that includes one or more
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system that includes one or more fundamental unit processes or operations
system that includes one or more fundamental unit processes or operations
Definition-Treatment System
“Best Management Practice (BMP)”
Definition-Treatment System
“Best Management Practice (BMP)”
A complete structure or device for removing, reducing, retarding, or A complete structure or device for removing, reducing, retarding, or
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preventing targeted stormwater runoff, runoff constituents, pollutants, and contaminants from reaching receiving waters.
preventing targeted stormwater runoff, runoff constituents, pollutants, and contaminants from reaching receiving waters.
Definition-Treatment Train
Definition-Treatment Train
More than one stormwater control or treatment system in series
i ibl h h
More than one stormwater control or treatment system in series
i ibl h h
16
It is possible to have more than one treatment train at a siteIt is possible to have more than one treatment train at a site
17
How to apply research to real problems?
How to apply research to real problems?
What approach best incorporates the state of the practice?Focus on selecting treatment trains that
What approach best incorporates the state of the practice?Focus on selecting treatment trains that
18
gmeet specific project goals (e.g. address specific pollutants of concern, etc.)
Integrated Unit Process Design Approach
gmeet specific project goals (e.g. address specific pollutants of concern, etc.)
Integrated Unit Process Design Approach
4
BMP Selection
and D i
BMP Selection
and D i
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Design ProcessDesign
Process
Step 1. Problem DefinitionStep 1. Problem Definition
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Key Concepts:What is the overall project scope and what are the regulatory drivers of stormwater management? How do stormwater management objectives relate to or conflict with other project objectives? What site conditions should be evaluated to properly define the problem?
Key Concepts:What is the overall project scope and what are the regulatory drivers of stormwater management? How do stormwater management objectives relate to or conflict with other project objectives? What site conditions should be evaluated to properly define the problem?
Hydraulics Manage flow characteristics upstream, within, and/or downstream of treatment system components
Hydrology Mitigate floods; improve runoff characteristics (peak shaving) Reduce downstream pollutant loads and concentrations of pollutants Improve/minimize downstream temperature impact Achieve desired pollutant concentration in outflow
Water Quality
Remove litter and debris Reduce acute toxicity of runoff Toxicity Reduce chronic toxicity of runoff Comply with NPDES permit Regulatory Meet local, state, or federal water quality criteria
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Meet local, state, or federal water quality criteria Implementation Function within management and oversight structure Cost Minimize capital, operation, and maintenance (life-cycle) costs Aesthetic Improve appearance of site and avoid odor or nuisance
Operate within maintenance and repair schedule and requirements Maintenance Design system to allow for retrofit, modification, or expansion
Longevity Achieve long-term functionality Improve downstream aquatic environment/erosion control Improve wildlife habitat Resources Achieve multiple use functionality Function without significant risk or liability Function with minimal environmental risk downstream Safety, Risk and
Liability Contain spills
Public Perception Clarify public understanding of runoff quality, quantity and impacts on receiving waters * Objectives adapted from ASCE/EPA, 2002.
Step 2. Characterize Site Conditions and Constraints Step 2. Characterize Site Conditions and Constraints
22
Key Concepts:What watershed characteristics should be evaluated during the data collection stageWhat site characteristics should be evaluated to identify site constraints?What water quality data should be collected for subsequent stages of the project?
Key Concepts:What watershed characteristics should be evaluated during the data collection stageWhat site characteristics should be evaluated to identify site constraints?What water quality data should be collected for subsequent stages of the project?
Step 3. Identify Fundamental Operation and Process Categories
Step 3. Identify Fundamental Operation and Process CategoriesSTEP 3
Identification of Applicable Fundamental Process Categories
(FPCs)
Select Applicable Physical Treatment Operations
(Particle Size Alteration, Size Separation, Density Separation, Aeration, Volatilization,
Physical Agent Disinfection)
Select Applicable Hydrologic Operations
(Peak Attenuation, Volume Reduction)
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Key Concepts:What hydrologic controls may be potentially applicable for your project?What physical unit operations may be of use in your design?What chemical and biological processes may be applicable for water quality treatment?
Key Concepts:What hydrologic controls may be potentially applicable for your project?What physical unit operations may be of use in your design?What chemical and biological processes may be applicable for water quality treatment?
Chemical Sorption ProcessesMetals, nutrients, organic
ll t t
Subsurface wetlandsEngineered media/sand/compost filtersI filt ti / filt ti t h d b i
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Processes pollutants Infiltration/exfiltration trenches and basins
Coagulation/FlocculationFine sediment, nutrients
Detention/retention pondsCoagulant/flocculant injection systems
Ion ExchangeMetals, nutrients
Engineered media, zeolites, peats, surface complexation media
Chemical DisinfectionPathogens
Custom devices for mixing chlorine or aerating with ozone
Advanced treatment systems
Step 4. Select Treatment System Components Step 4. Select Treatment System Components
29
Key Concepts:How should the treatment train approach be used in system design?What hydrologic controls are available?What pretreatment options are applicable?What conventional treatment system components can be used for the core design?What tertiary enhancements can be incorporated?
Key Concepts:How should the treatment train approach be used in system design?What hydrologic controls are available?What pretreatment options are applicable?What conventional treatment system components can be used for the core design?What tertiary enhancements can be incorporated?
Ranking of Conventional TSCs According to the UOP (unit
operations and processes) Effectiveness Level Ranking of Conventional TSCs According to the UOP (unit
operations and processes) Effectiveness Level Conventional TSCs
Fundamental Process Category
Unit Operations or Processes
Hydr
o-dy
nami
c De
vices
Settli
ng B
asins
Tank
s and
Vau
lts
Fine M
esh S
creen
s
Filter
Fab
ric
Biofi
lters
Media
Filte
rs
Exten
ded D
etenti
on
Pond
s
Reten
tion P
onds
Infiltr
ation
Bas
ins
Typical Location in Treatment Train P P P P P P/S P/S S S S
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Flow attenuation (hydrograph matching) 0 2 3 0 0 1 0 5 4 to 5 3 to 5
Reduce total volume of runoff 0 0 0 0 0 3 to 5 0 2 to 3 1 5 Hydrology / Hydraulics
Flow-duration control and design 0 1 3 0 0 1 0 4 to 5 4 to 5 4 to 5
P - Primary treatment, S - Secondary treatment 0 - TSC does not include unit process OR is not recommended for that process due to operations and maintenance issues (e.g., a filter should not be used to screen) 1 - TSC includes unit process, but likely provides poor effectiveness 2 - TSC includes process, but likely provides marginal effectiveness 3 - TSC designed to include unit process, but other TSCs may be more effective 4 - TSC is specifically designed to include unit process, but design not optimal 5 - TSC is specifically designed to include unit process and is among the best alternatives available
6
Ranking of Conventional TSCs According to the UOP Effectiveness Level
Ranking of Conventional TSCs According to the UOP Effectiveness Level
Conventional TSCs
Fundamental Process Category
Unit Operations or Processes
Hydr
o-dy
nami
c De
vices
Settli
ng B
asins
Tank
s and
Vau
lts
Fine M
esh S
creen
s
Filter
Fab
ric
Biofi
lters
Media
Filte
rs
Exten
ded D
etenti
on
Pond
s
Reten
tion P
onds
Infiltr
ation
Bas
ins
Typical Location in Treatment Train P P P P P P/S P/S S S S Screening 3 to 5 0 0 5 0 1 to 5 0 to 5 0 0 0 Filtration 0 0 0 3 3 3 to 5 5 0 0 4
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Settling 2 to 3 3 3 0 0 3 to 5 0 3 5 2 Flotation and Skimming 3 to 5 0 2 0 0 0 0 0 0 0 Sorption processes (absorption) 0 0 0 0 2 3 to 5 4 to 5 0 0 2
P - Primary treatment, S - Secondary treatment 0 - TSC does not include unit process OR is not recommended for that process due to operations and maintenance issues (e.g., a filter should not be used to screen) 1 - TSC includes unit process, but likely provides poor effectiveness 2 - TSC includes process, but likely provides marginal effectiveness 3 - TSC designed to include unit process, but other TSCs may be more effective 4 - TSC is specifically designed to include unit process, but design not optimal 5 - TSC is specifically designed to include unit process and is among the best alternatives available
Ranking of Conventional TSCs According to the UOP Effectiveness Level
Ranking of Conventional TSCs According to the UOP Effectiveness Level
Conventional TSCs
Fundamental Process Category
Unit Operations or Processes
Hydr
o-dy
nami
c De
vices
Settli
ng B
asins
Tank
s and
Vau
lts
Fine M
esh S
creen
s
Filter
Fab
ric
Biofi
lters
Media
Filte
rs
Exten
ded D
etenti
on
Pond
s
Reten
tion P
onds
Infiltr
ation
Bas
ins
Typical Location in Treatment Train P P P P P P/S P/S S S S Microbially-mediated transformations 0 0 0 0 0 0 to 2 2 3 4 2 Biological
32
transformations Biological Processes Uptake and storage 0 0 0 0 0 0 to 2 1 2 3 1
Sorption processes (adsorption) 0 0 0 0 2 3 4 to 5 1 to 2 2 4
Flocculation / Precipitation 0 0 0 0 0 0 0 0 to 2 2 0 Chemical Processes Chemical agent disinfection
(ozone, chlorine and chlorine compounds)
0 0 0 0 0 0 0 0 0 0
P - Primary treatment, S - Secondary treatment 0 - TSC does not include unit process OR is not recommended for that process due to operations and maintenance issues (e.g., a filter should not be used to screen) 1 - TSC includes unit process, but likely provides poor effectiveness 2 - TSC includes process, but likely provides marginal effectiveness 3 - TSC designed to include unit process, but other TSCs may be more effective 4 - TSC is specifically designed to include unit process, but design not optimal 5 - TSC is specifically designed to include unit process and is among the best alternatives available
Ranking of Tertiary
Enhancements According to the
UOP Effectiveness
Level
Ranking of Tertiary
Enhancements According to the
UOP Effectiveness
Level
Tertiary Enhancements Category Unit Operations and Processes
Soils
/ So
il Am
endm
ents
Micr
obial
Co
mmun
ities
Vege
tatio
n
Disin
fecti
on
Syste
m
Sprin
klers
Aera
tors
Floc
culan
t / Pr
ecipi
tant
Injec
tion S
ys.
Flow attenuation (hydrograph matching)
0 0 1 0 0 0 0 Hydrology / Hydraulics Operations Reduce total volume of
5 5 3 0 0 0 0 Biological Process Uptake and storage 3 4 2 to 5 0 0 0 0
Sorption processes (adsorption)
4 to 5 0 3 to 4 0 0 0 0
Flocculation / Precipitation 0 0 0 0 0 0 5 Chemical Processes Chemical agent disinfection
(ozone, chlorine and chlorine compounds)
0 0 0 5 0 0 0
0 - TSC does not include UOP or is not recommended due to operations and maintenance issues (e.g., a filter should not be used to screen) 1 - TSC includes UOP, but likely provides poor effectiveness 2 - TSC includes UOP, but likely provides marginal effectiveness 3 - TSC designed to include UOP, but other TSCs may be more effective 4 - TSC is specifically designed to include UOP, but design not optimal 5 - TSC is specifically designed to include UOP and is among the best alternatives available
Conceptual Framework for Selecting TSCs Based on Particle Size.
Conceptual Framework for Selecting TSCs Based on Particle Size.
34
Step 5. Practicability Assessment of Candidate Treatment Systems
Step 5. Practicability Assessment of Candidate Treatment Systems
35
Key Concepts:How can you identify the best treatment system option based on hydrologic and hydraulic performance?What resources are available to help select the best treatment option from the candidate TSCs based on treatability data and water quality performance?
Key Concepts:How can you identify the best treatment system option based on hydrologic and hydraulic performance?What resources are available to help select the best treatment option from the candidate TSCs based on treatability data and water quality performance?
Recommended Measures of BMP Performance
Recommended Measures of BMP Performance
How much stormwater runoff is prevented? (“hydrological source control”)
How much of the runoff that occurs is treated by the BMP or not (“hydraulic performance”)?
Of the runoff treated, what is the effluent quality?
How much stormwater runoff is prevented? (“hydrological source control”)
How much of the runoff that occurs is treated by the BMP or not (“hydraulic performance”)?
Of the runoff treated, what is the effluent quality?
36
Of the runoff treated, what is the effluent quality? (“concentration characteristics achieved”)
Does the BMP address downstream erosion impacts?
Of the runoff treated, what is the effluent quality? (“concentration characteristics achieved”)
Does the BMP address downstream erosion impacts?
Percent Removal is Very Problematic and SHOULD NOT be used as a performance measure for BMPs.
Box plots of the fractions of Total Suspended Solids (TSS) removed and of effluent quality of
selected BMP types
Box plots of the fractions of Total Suspended Solids (TSS) removed and of effluent quality of
selected BMP types
0 6
0.8
1.0
0 6
0.8
1.0
Rem
oved
10 00
100.00
mg/
l)
3rdQuartile
1st Quartile
MedianLower 95% CL
Upper 95% CL
Upper Inner Fence
Lower Inner FenceOutside Value
90 % 11 to 18 mg/l
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0.0
0.2
0.4
0.6
- 0.0
0.2
0.4
0.6
Frac
tion
of T
SS
BMP Type BMP Type
0.10
1.00
10.00
TSS
(
Detention Basins
Hydro Dynamic Devices
Bioswales Media Filters
Retention Basins
Wetlands Detention Basins
Hydro Dynamic Devices
Bioswales
Retention Basins
Wetlands
50 %
Box plots of effluent quality of selected BMP types for Total Phosphorus and Total CopperBox plots of effluent quality of selected BMP types for Total Phosphorus and Total Copper
1 0
10.0
us (m
g/l) 100.0
(mg/
l)
3rd Quartile
1st Quartile
MedianLower 95% CL
Upper 95% CL
Upper Inner Fence
Lower Inner FenceOutside Value
r (ug
/l)
40
BioswalesDetentionBasins
MediaFilters
Hydro-DynamicDevices
RetentionBasins
Wetlands
BMP Type
0.001
0.010
0.10
1.0
Tota
l Pho
spho
ru 10.0
Tota
l Cop
per (
1.0
0.1 Bioswales Detention Basins Media
FiltersHydro-DynamicDevices
RetentionBasins
Wetlands
BMP Type
Tota
l Cop
per
Box plots of effluent quality of selected BMP types for Fecal Coliform and Fecal Coliform inflow and outflow
by event.
Box plots of effluent quality of selected BMP types for Fecal Coliform and Fecal Coliform inflow and outflow
by event.
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Lake George Field Study Evaluation Vortechs model 11000
Lake George Field Study Evaluation Vortechs model 11000
(Winkler and Guswa 2002)Is an average of 100+ mg/l TSS acceptable performance?Is an average of 100+ mg/l TSS acceptable performance?
8
Percent Removal Use ResultsPercent Removal Use Results
BMPs improperly “rejected”
BMPs improperly “accepted”
“Daisy-Chaining” BMPs and applied % removals at each t th t hi hl di t
BMPs improperly “rejected”
BMPs improperly “accepted”
“Daisy-Chaining” BMPs and applied % removals at each t th t hi hl di t
43
step that highly over predicts performance
Improper use of TSS as the sole indicator of performance
Etc. Etc.
step that highly over predicts performance
Improper use of TSS as the sole indicator of performance
Etc. Etc.
Our data coincides with the BMP Database publications advocating effluent quality as a performance measure. Our data coincides with the BMP Database publications advocating effluent quality as a performance measure.
Key Concepts:What level of analysis is needed to adequately size and conceptually design treatment system options?How do you optimize the design and verify that project goals will be met?
Key Concepts:What level of analysis is needed to adequately size and conceptually design treatment system options?How do you optimize the design and verify that project goals will be met?
Preliminary Design of Treatment System
Adaptive Management and Design Flexibility(Design Elements, Inherently Safe and Functional)
Typical Outlet Structures Used in Detention Basins.Typical Outlet Structures Used in Detention Basins.
47
Integrating Multiple Functions/Outlet Structures
Integrating Multiple Functions/Outlet Structures
48
9
Effective Work Index (W)
Range of Geomorphically Significant flows
49
Characteristics of Bed and Bank
Materials
τc τbi
Stream Flow
( ) tWn
icbi Δ⋅−=∑
=
5.1
1ττ
τc
Normal Dry Weather Flow Level
Illustration of the Flow-Duration Methodology.Source: Santa Clara Valley Urban Runoff Pollution Prevention Program
(SCVURPPP, 2004).
Illustration of the Flow-Duration Methodology.Source: Santa Clara Valley Urban Runoff Pollution Prevention Program
(SCVURPPP, 2004).
50
Erosion Potential (Ep)Erosion Potential (Ep)
ShearShear
pre
post
WW
Ep =( ) tWn
icbi Δ⋅−=∑
=
5.1
1ττ
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PostPost--UrbanUrban
PrePre--UrbanUrban
Work DoneWork Done
TimeTime
Shear Shear StressStress
τc
Example Comparison of Flow-Duration Control Design.Source: Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP,
2004).
Example Comparison of Flow-Duration Control Design.Source: Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP,
2004).
52
Recommended Process ModelingRecommended Process ModelingContinuous simulation, using a model suited to the task
Continuous simulation models can be used to simulate the effects of use of simpler methods for sizing treatment systems.
Event models of “classical” hydrology, using site-specific data.
These models should only be used when verified with a ti i l ti h i ll iti l f
Continuous simulation, using a model suited to the taskContinuous simulation models can be used to simulate the effects of use of simpler methods for sizing treatment systems.
Event models of “classical” hydrology, using site-specific data.
These models should only be used when verified with a ti i l ti h i ll iti l f
53
continuous simulation approach; especially critical for design of systems for reducing downstream erosion.
Generalized regional guidelinesThese can include simplified methods provided by WEF and ASCE (1998), BUT should be adapted/confirmed for local conditions
These regional guidelines might provide a starting point for event and continuous models.
continuous simulation approach; especially critical for design of systems for reducing downstream erosion.
Generalized regional guidelinesThese can include simplified methods provided by WEF and ASCE (1998), BUT should be adapted/confirmed for local conditions
These regional guidelines might provide a starting point for event and continuous models.
Step 7. Performance Monitoring and EvaluationStep 7. Performance Monitoring and Evaluation
54
Key Concepts:What monitoring is needed or required to demonstrate long-term project success
How will the monitoring program be implemented?
Key Concepts:What monitoring is needed or required to demonstrate long-term project success
How will the monitoring program be implemented?
10
Example Conceptual Design Using the Integrated Treatment Process
Approach
Example Conceptual Design Using the Integrated Treatment Process
Approach
Characterize site conditions and identify constraints
Id tif F d t l U it P
Characterize site conditions and identify constraints
Id tif F d t l U it P
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Identify Fundamental Unit Process Categories (FPCs) and associated Treatment System Components (TSCs)
Formulate design alternatives
Critically assess alternatives and select most feasible alternative
Size/configure the facility
Identify Fundamental Unit Process Categories (FPCs) and associated Treatment System Components (TSCs)
Formulate design alternatives
Critically assess alternatives and select most feasible alternative
Size/configure the facility
Example Site Characterization and Constraint Identification
New highway in an urban setting in warm arid region
Type B soils and groundwater is deep, but sole-if
New highway in an urban setting in warm arid region
Type B soils and groundwater is deep, but sole-if
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source aquifer
Receiving waters with TSS and dissolved copper TMDLs established
Concern about erosive discharges and a requirement to reduce post-const runoff
Need a BMP with low land requirements or multi-use functionality
source aquifer
Receiving waters with TSS and dissolved copper TMDLs established
Concern about erosive discharges and a requirement to reduce post-const runoff
Need a BMP with low land requirements or multi-use functionality
Consider each of the Fundamental Process Categories (FPCs)
Consider each of the Fundamental Process Categories (FPCs)
Emphasis on BMPs that reduce runoff volumes by evapotranspiration and infiltrationManage runoff rates and/or volumes and/or instream measures to reduce
Emphasis on BMPs that reduce runoff volumes by evapotranspiration and infiltrationManage runoff rates and/or volumes and/or instream measures to reduce
58
and/or instream measures to reduce stream erosionand/or instream measures to reduce stream erosion
to remove suspended particulates and attached pollutants (TSCs: screens, biofilters media filters infiltration
Particle/Material Size SeparationFiltration
to remove suspended particulates and attached pollutants (TSCs: screens, biofilters media filters infiltration
60
biofilters, media filters, infiltration facilities)
Particle/Material Density SeparationSedimentation
to remove settable solids and attached pollutants (TSCs: sedimentation basin/forebay, detention facilities, hydrodynamic devices)
biofilters, media filters, infiltration facilities)
Particle/Material Density SeparationSedimentation
to remove settable solids and attached pollutants (TSCs: sedimentation basin/forebay, detention facilities, hydrodynamic devices)
11
Types of DevicesTypes of Devices
FilteringCB Inserts
ScreeningLarger In-conveyance Devices
“Hydrodynamic Devices”In-ground “swirlly” devices
FilteringCB Inserts
ScreeningLarger In-conveyance Devices
“Hydrodynamic Devices”In-ground “swirlly” devices
61
g ySettling
Rapid Settlement for Dense Gross SolidsSeparation and Baffle Devices
Boxes with baffles, plates, hoods, etc.Maceration
Not useful in StormwaterCombination
CDS Unit – Fluid/particle separation and screening
g ySettling
Rapid Settlement for Dense Gross SolidsSeparation and Baffle Devices
Boxes with baffles, plates, hoods, etc.Maceration
Not useful in StormwaterCombination
CDS Unit – Fluid/particle separation and screening
Pollutant Fact Sheets
www.bmpdatabase.org
Pollutant Fact Sheets
www.bmpdatabase.org
Copper (Cu) Treatability and available unit operations and processes
Treatability is a function of partitioning (particulate vs. aqueous); if aqueous, treatability is a function of concentration and speciation, and if particulate-bound, treatability is a function of distribution across the gradation. Once complexed in aqueous solution, uncharged aqueous complexes (i.e. CuCO3) are very difficult to remove unless precipitated or advanced unit operations such as reverse osmosis are applied. Complexation or partitioning can be reversible; particulate-bound Cu can be a chronic threat especially in a cyclic redox environment. Cu can partition to both the aqueous and particulate phases as a function of rainfall-runoff chemistry, hydrodynamics and residence time. The important forms of copper from a treatability and regulatory perspective are total, dissolved, and particulate-bound copper. If bound to organic or inorganic particles, viable unit operations include sedimentation and filtration either as separate unit operations or in combination with coagulation/flocculation as pre-treatment to these operations. If present as a complex, precipitation can be effective. If present as an ionic species such as Cu2+, then surface complexation (including adsorption) can be effective.
Form Unit Operation or Process Particulate-bound Sedimentation, filtration, coagulation-flocculation Dissolved Adsorption, surface complexation, ion exchange, precipitation
Description and properties
Copper is a reddish-brown, odorless metal which becomes dull when exposed to air. It is malleable, ductile, and an excellent conductor of heat and electricity, being second only to silver in terms of its high conductivity. Common forms in surface waters include complexes with organics (CuDOM), carbonate (CuCO3), hydroxide (CuOH+), sulfates (CuSO4), , and dissolved ionic forms (Cu2+), and (and to lesser degrees, Cu+ and depending on Cl- levels, CuCl where this species can become significant in coastal areas and areas subject to road de-icing salts containing chlorides). The relative percentages of these species are a function of rainfall-runoff chemistry and to a lesser degree hydrology. Of these, complexes with organics (CuDOM) and carbonate (CuCO3) are predominant in urban rainfall-runoff.
Species Molecular weight Specific gravity Solubility (g/100ml) Cu (metal) 63.6 9.0 Solid metal CuCO3 187.1 4.4 Variable CuSO4 159.6 3.6 75.4
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CuCl 99.0 4.1 0.0062 Natural sources
Copper is a common element, naturally occurring in rocks, soil, waters, plants, animals, and humans. Besides small amounts of metallic copper, copper is found as sulfide or oxide ores.
Point sources Emissions to air, soil and water may result from mining and primary extraction processes (mineral processing, smelting, electrolytic processing, leaching and solvent extraction), and from manufacturing of products using and/or containing copper (electrical goods, pipes, alloys, etc.).
Diffuse sources and consumer products containing copper Diffuse sources include agricultural and commercial applications, gardening applications, leaching from paint on vessels and infrastructure. Automobile brakes generate abraded copper metal or alloyed copper during their normal use, contributing to copper metal in dry or wet deposition. Consumer products containing copper include coins, cigarettes, jewelry, electrical appliances, cookware, some unwashed agricultural products, some commercial gardening products, some vitamin / mineral dietary supplements, and treated wood products.
Environmental fate and transport Copper can partition to particles and organic matter, but can also be largely dissolved (ionic and complexed) in urban rainfall-runoff depending on rainfall-runoff chemistry, other species and residence time. Re-partitioned particulate-bound copper is distributed across the particle-size gradation. Copper can be transported as particles released into the atmosphere or as dissolved compounds in natural waters. Soluble and free ionic copper are easily taken up by plants. Finely-abraded metallic Cu or Cu-alloy particles are subject to aerodynamic and waterborne transport. Once contacted by poorly-buffered and acidic rainfall or runoff these finely-abraded particles undergo leaching and dissolution. Copper in soils can precipitate with hydroxide, phosphate, carbonate, and silicate to become a component of the amorphous fraction of soil. It can also be adsorbed on the negatively charged sorption sites of clay minerals and Cu can form both soluble and insoluble complexes with components of soil organic matter.
Aquatic toxicity Low pH, soft water, and high temperatures are known to increase toxicity of copper. Mixtures of copper and zinc are known to be additive or synergistic in toxicity to many aquatic organisms. The freshwater and saltwater criteria for dissolved copper are shown below.
Alternative 1 – Flow Management, TSS, Trash and Debris and Dissolved Copper
Alternative 1 – Flow Management, TSS, Trash and Debris and Dissolved Copper
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c
12
Critically Assess BMP Options
Expected PerformanceRequired Surface and Subsurface AreaCost
Expected PerformanceRequired Surface and Subsurface AreaCost
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CostMaintenanceAesthetics
CostMaintenanceAesthetics
Low Impact Development (LID) in the Treatment Train
Low Impact Development (LID) in the Treatment Train
On-site/micro scale distributed controlsMany highways are already designed this way
On-site/micro scale distributed controlsMany highways are already designed this way
68
wayLID by accidentMany natural drainage (country drainage) designs are easily adapted/retrofit for improved WQ performance
wayLID by accidentMany natural drainage (country drainage) designs are easily adapted/retrofit for improved WQ performance
LID Center Photo
Recommendations for Setting of BMP Design Requirements
Recommendations for Setting of BMP Design Requirements
Recommended BMP Performance requirements should not use percent removal
Design standards should account for the hydrologic losses (HSC) that can occur with
Recommended BMP Performance requirements should not use percent removal
Design standards should account for the hydrologic losses (HSC) that can occur with
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y g ( )some BMP types to encourage their use. o Both biofiltration systems and dry extended
detention ponds appear to show significant reductions in runoff that is routed through them.
o Much of this “loss” is likely evapotranspiration losses.
y g ( )some BMP types to encourage their use. o Both biofiltration systems and dry extended
detention ponds appear to show significant reductions in runoff that is routed through them.
o Much of this “loss” is likely evapotranspiration losses.
Recommendations for Setting of BMP Design Requirements
Recommendations for Setting of BMP Design Requirements
Continuous simulation techniques with local rainfall data and local conditions should be employed in developing design requirements to assess potential BMP design sizing vs. “percent capture” to ascertain hydrologic/hydraulic performance
Continuous simulation techniques with local rainfall data and local conditions should be employed in developing design requirements to assess potential BMP design sizing vs. “percent capture” to ascertain hydrologic/hydraulic performance
70
performanceo Expenditures of resources by the private
and public sector on BMPs
performanceo Expenditures of resources by the private
and public sector on BMPs
Example ApplicationExample Application
Lake Tahoe: Factoring potential BMP performance
TMDL Development TMDL “crediting”
Lake Tahoe: Factoring potential BMP performance
TMDL Development TMDL “crediting”
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TMDL “crediting”TMDL “crediting”
Continuous SWMM modeling Together with BMP Effluent Performance to Assess BMP Performance at a Project Scale
How much runoff is evapotranspirated or infiltrated? Hydrological Source Control
How much runoff is treated (and not)?
What is effluent quality of
How much runoff is evapotranspirated or infiltrated? Hydrological Source Control
How much runoff is treated (and not)?
What is effluent quality of
72
treated runoff?
Evaluations included:Assessed effects of residence time
Evaluated 20 alternate sizing criteria (0.1” to 2”)
Generated performance curves for percent runoff captured as well as percent particle treated
treated runoff?
Evaluations included:Assessed effects of residence time
Evaluated 20 alternate sizing criteria (0.1” to 2”)
Generated performance curves for percent runoff captured as well as percent particle treated
13
BMP Performance Curves for Various Design Sizes and Draw Down times (Scenario Site, Met Grid 42)
BMP Performance Curves for Various Design Sizes and Draw Down times (Scenario Site, Met Grid 42)
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85 to 95% “Capture” for 1” Depth Design depending on draw-down time
Effect of Sizing and Residence Time on Fine Particle Removal Efficiency
Effect of Sizing and Residence Time on Fine Particle Removal Efficiency
0102030405060708090
100
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2U it B i Si (i h )
Methodology Development toEstimate Pollutant Load Reductions
For Lake Tahoe
Methodology Development toEstimate Pollutant Load Reductions
For Lake Tahoe
Goals and Objectives of Methodology
Focus on stormwater and BMPs in urbanized
Goals and Objectives of Methodology
Focus on stormwater and BMPs in urbanized
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areasPractical for application by implementers
Include flexibility to modify in the future based on monitoring data or new research
areasPractical for application by implementers
Include flexibility to modify in the future based on monitoring data or new research
Overview – What’s been doneOverview – What’s been done
Summarize Local Practices Literature Review Summarize National
Practices
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Screening CriteriaAnd Analysis
Develop Initial Methodology and Begin Testing
Overview – What’s been done (cont.)Overview – What’s been done (cont.)
Develop Initial Methodology and Begin Testing
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Prepare Examples
Develop Working Tool
Present to PAC and Public for Comment
What we learned?What we learned?
Limited examples of similar work/methods developed for other areasExisting examples have typically not applied the latest findings regarding BMP performanceE i ti l f t l
Limited examples of similar work/methods developed for other areasExisting examples have typically not applied the latest findings regarding BMP performanceE i ti l f t l
78
Existing examples for source controls are essentially non-existentThere is limited performance data for many if not most BMPs
Existing examples for source controls are essentially non-existentThere is limited performance data for many if not most BMPs
Potential Scenarios Include:Swales, media filters, detention basins, wet ponds, wetlands, and user-defined BMPsUp to three BMPs in series, in parallel, or combination of both
Potential Scenarios Include:Swales, media filters, detention basins, wet ponds, wetlands, and user-defined BMPsUp to three BMPs in series, in parallel, or combination of both
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or combination of bothInfiltration an evapotranspiration simulated in each BMPSedimentation by particle size
or combination of bothInfiltration an evapotranspiration simulated in each BMPSedimentation by particle size
SummarySummary
Hydrologic Simulation
User Input
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Pollutant Load Generation
Pollutant Load Reduction
Pollutant Load
CCSD#1 Rules & Regs for Stormwater QualityCCSD#1 Rules & Regs for Stormwater QualityCCSD#1 Rules & Regs for Stormwater QualityCCSD#1 Rules & Regs for Stormwater Quality
Stormwater treatment requiredVegetated treatment required for all new development (swales, filter strips, wetlands, wet ponds, and detention basins)Recommendation: Allow additional types: bioretention, green roofs, planters, etc.
Proprietary mechanical devices are acceptable with pre-approval
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ppRecommendation: Limit use where surface facilities are feasible.
Infiltration required for new development (½-inch in 24-hrs). Treatment required (prior or concurrent with infiltration).
Often implemented in conjunction with treatment, e.g. dead pool within detention basins.Recommendation: Allow compliance through hydrologic source control measures such as roof runoff disconnects, permeable pavement, stormwater planters, etc.
Burgundy Rose DevelopmentBurgundy Rose DevelopmentBurgundy Rose DevelopmentBurgundy Rose Development
150 lots SFR on 35 acres52% impervious coverModerate to
150 lots SFR on 35 acres52% impervious coverModerate to
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Moderate to steep slopesSoils –Cascade Silt Loam
Moderate to steep slopesSoils –Cascade Silt Loam
Design Standards for WQ facilitiesDesign Standards for WQ facilitiesDesign Standards for WQ facilitiesDesign Standards for WQ facilities
WQ Treatment Volume: Sized by SBUH in accordance with regs. Only considered on-site runoff.
WQ treatment volume = 130,000 ft3
WQ Discharge Rate (based on Regs):Average Rate calculated as: 130,000 ft3 / 24 hrs = 1.5 cfsWQ orifice sized for this outlet for entire 130,000 ft3
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WQ orifice sized for this outlet for entire 130,000 ft
Detention Basin Sizing: Basin was sized by routing “WQ event” through the basin.
i.e. Pond was draining at the average 1.5 cfs while filling. Therefore 130,000 ft3 could be processed without overtopping weir with small basin size As-built WQ pool volume = 35,000 ft3
Continuous Simulation Analyses to Assess PerformanceContinuous Simulation Analyses to Assess PerformanceContinuous Simulation Analyses to Assess PerformanceContinuous Simulation Analyses to Assess Performance
Hydrologic Processes SWMM Representation
precipitation
evapotranspirationPrecipitation
(hourly)
ETET
Impervious areas(runoff block)
Precipitation (hourly)
Pervious areas(runoff block)
Disconnected runoff
Hydrologic Processes SWMM Representation
precipitation
evapotranspiration
precipitation
evapotranspirationPrecipitation
(hourly)
ETET
Impervious areas(runoff block)
Precipitation (hourly)
Pervious areas(runoff block)
Disconnected runoffPrecipitation (hourly)
ETET
Impervious areas(runoff block)
Precipitation (hourly)
Pervious areas(runoff block)
Disconnected runoff
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runoff
infiltration
BMP
Development areaSurface runoff hydrograph
ETInfiltration
GW recharge
Stormwater runoff
hydrograph
BMP (Storage treatment block)
Outflow hydrograph (to receiving waters)
Base flows (not considered for Burgundy Rose)
runoff
infiltration
BMP
Development area
runoff
infiltration
BMP
Development areaSurface runoff hydrograph
ETInfiltration
GW recharge
Stormwater runoff
hydrograph
BMP (Storage treatment block)
Outflow hydrograph (to receiving waters)
Base flows (not considered for Burgundy Rose)
Surface runoff hydrograph
ETInfiltration
GW recharge
Stormwater runoff
hydrograph
BMP (Storage treatment block)
Outflow hydrograph (to receiving waters)
Base flows (not considered for Burgundy Rose)
Stage Discharge Relationships for the Burgundy Rose Detention Basin
Stage Discharge Relationships for the Burgundy Rose Detention Basin
Average Detention Time Estimates from SWMM ModelAverage Detention Time Estimates from SWMM ModelAverage Detention Time Estimates from SWMM ModelAverage Detention Time Estimates from SWMM Model
Average detention time in WQ pool (hrs)
Basin design As-built Single
orifice outlet Riser outlet
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24-hr drain time 1.3 6.4 18.2
36-hr drain time 11.6 23.2
48-hr drain time 17.0 27.6
72-hr drain time 27.7 35.0
Percent Sediment Removed by Particle RangePercent Sediment Removed by Particle RangePercent Sediment Removed by Particle RangePercent Sediment Removed by Particle Range
50%
60%
70%
80%
90%
100%
Trea
ted
As-Built24-hr single orfice24-hr riser outlet
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0%
10%
20%
30%
40%
50%
2 to 4 4 to 8 8 to 12 12 to 24 24 to 48 48 to 100
Particle Size Range (um)
Perc
ent
17
Effect of Design Rainfall Depth and Drawdown Time on Sediment Effect of Design Rainfall Depth and Drawdown Time on Sediment Trapping Efficiency and Percent CaptureTrapping Efficiency and Percent Capture
Effect of Design Rainfall Depth and Drawdown Time on Sediment Effect of Design Rainfall Depth and Drawdown Time on Sediment Trapping Efficiency and Percent CaptureTrapping Efficiency and Percent Capture
Basin Size Vs Particle Removal Performance24-hours
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%%
Par
ticle
Tre
ated
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
% R
unof
f Cap
ture
32-64 Particle Size (um)16-32 Particle Size (um)
%Runoff Capture
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0%0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Design Storm Depth (in)
0%
Basin Size Vs Particle Removal Performance48-hours
Evapotranspiration (ET) is often upwards of 70 to almost 90 percent of precipitationPre-development deep infiltration is often very smallRunoff is also small (except this last few weeks!)
Evapotranspiration (ET) is often upwards of 70 to almost 90 percent of precipitationPre-development deep infiltration is often very smallRunoff is also small (except this last few weeks!)
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Importance of “Managing the ET Sponge”Loss of CanopyLoss of “Duff” layer
Reliance on Infiltration in many cases results in increased infiltration
Importance of “Managing the ET Sponge”Loss of CanopyLoss of “Duff” layer
Reliance on Infiltration in many cases results in increased infiltration
BMP PrioritiesBMP Priorities
More focus on maximizing “hydrological More focus on maximizing “hydrological source control”:source control”:
Evapotranspiration firstEvapotranspiration firstInfiltration nextInfiltration next
City and County of Honolulu-Factors Considered in Selecting Standards
Reduce pollutants to “Maximum Extent Practicable”Pollutants of concern - NPDES SamplingWater Quality Limited water bodiesRainfall - Point of diminishing returnRainfall/runoff analysis to ascertain what proposed
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Rainfall/runoff analysis to ascertain what proposed requirements would achieve for different BMP typesWe have a lot more to learn about stormwater BMP effectivenessHawaii development site conditionsThis is an initial start
20002000
Technical ApproachesTechnical Approaches
Setting water quality facility sizing requirements
Assess rainfall, runoff, and BMP functioning to ascertain what will be achieved
Setting water quality facility sizing requirements
Assess rainfall, runoff, and BMP functioning to ascertain what will be achieved
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Volume vs. flow-through BMPs need separate approachesMake requirements simpleEncourage “treatment trains”Recognize that standards will need to evolve as we learn more
Volume vs. flow-through BMPs need separate approachesMake requirements simpleEncourage “treatment trains”Recognize that standards will need to evolve as we learn more
Example Site Analyses Approach/Results - Simulation of
the Results of Requirements Performed
Selected Actual Site ExamplesD l d Sit R d i f h i i
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Developed Site Re-designs for each sizing requirementPredicted Results - Hydrologic, Hydraulic and Pollutant Removal PerformanceDeveloped Cost Implications/EvaluationAssessed Land use/aesthetics
19
COMPARISON OF ON-SITE WATER QUALITY DESIGN STORMS FOR TYPICAL COMMERCIAL
OFFICE BUILDING DEVELOPMENT
COMPARISON OF ON-SITE WATER QUALITY DESIGN STORMS FOR TYPICAL COMMERCIAL
OFFICE BUILDING DEVELOPMENT
WaterQuality
Water Quality Site Design Estimated Annual Pollutant Loadof Total Suspended Solids (TSS)
EstimatedReduction
DesignStorm
Potential WaterQuality BMP
Estimated Percentage ofAnnual Runoff Volume
Treated
Cost Implications1
TraditionalSite
Site WithWater
QualityPercent
Reduction
in AnnualPollutant
Load of TotalRainfallAnalysis
SWMMModeling
Capital Maintenance Design Facilities Copper (Cu)
0 30 i /h t t d l 65% $25 000 $3 000 710 lb 327 lb 54% 45%
NOTES:1. “Cost Implications” based on comparison to construction and maintenance of conventional storm drainage system.2. Pollutant loads based on stormwater quality data collected on Oahu between 1992 and 1996.3. Pollutant removal based on performance data reported in Portland Stormwater Quality Facilities Design Guidance Manual.
Detention Based Water Quality Control -Design Sizing/Detention Time
Detention Based Water Quality Control -Design Sizing/Detention Time
Figure 1Required Water Quality Design Volume for Detention
Based Systems
2000250030003500
Wat
er Q
ualit
yum
e (c
ubic
ac
re)
Figure 2: Required Average Outlet Discharge Rates for Extended Detention Volume
0.030
0.035
0.040
0.045
Rat
e (c
ubic
p
er a
cre)
full to half fullhalf full to empty
110
0500
10001500
0 10 20 30 40 50 60 70 80 90 100
Impervious Area Percentage
Req
uire
d W
Des
ign
Vol
feet
/a
0.000
0.005
0.010
0.015
0.020
0.025
0 500 1000 1500 2000 2500 3000 3500
Storage Volume Per Acre (cubic feet/acre)
Ave
rage
Out
let R
feet
per
sec
ond p y
Approach Approach --Provided simple charts for sizing of facilitiesProvided simple charts for sizing of facilities
RecommendationsRecommendations
Communities should commit sufficient resources into developing design standards for stormwater that actually “work”
Communities should commit sufficient resources into developing design standards for stormwater that actually “work”
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“work”
BMP Manuals need to be significantly updated to emphasize unit processes based BMP Selection and Design
“work”
BMP Manuals need to be significantly updated to emphasize unit processes based BMP Selection and Design
BMP PrioritiesBMP PrioritiesMore focus on maximizing “hydrological More focus on maximizing “hydrological source control”:source control”:
Maximize Evapotranspiration firstMaximize Evapotranspiration first
Infiltration nextInfiltration next
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Pollutant Source ControlPollutant Source Control
TreatmentTreatment
Traditional vs. Integrated Landscape Stormwater Design Approaches – Getting Costs “Right”
Traditional vs. Integrated Landscape Stormwater Design Approaches – Getting Costs “Right”