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Oregon Department of Transportation Oregon Department of Transportation
Stormwater Management Initiative:Stormwater Management Initiative:Meeting New ChallengesMeeting New Challenges
Presented by:Presented by:Jennifer Sellers, ODOTJennifer Sellers, ODOT
andandRonan Igloria, HDRRonan Igloria, HDR
ACWA Stormwater Committee MeetingACWA Stormwater Committee MeetingNovember 27, 2007November 27, 2007
ODOT’s GoalsODOT’s Goals Develop a streamlined stormwater Develop a streamlined stormwater
treatment program to: treatment program to: Meet all regulatory needsMeet all regulatory needs
Provide ODOT with certainty Provide ODOT with certainty regarding scope, schedule, and regarding scope, schedule, and budget budget
Result in an overall environmental Result in an overall environmental benefit and promote species benefit and promote species recoveryrecovery
Components of the Stormwater Components of the Stormwater Initiative Work PlanInitiative Work Plan
Streamline DEQ Stormwater Streamline DEQ Stormwater Management Plan Approval Management Plan Approval ProcessProcess
Develop Process for ODOT Develop Process for ODOT Projects with T&E Species Projects with T&E Species and Stormwater Effectsand Stormwater Effects
Develop a watershed-based Develop a watershed-based mitigation program to offset mitigation program to offset stormwater effects that stormwater effects that cannot be treated “on-site” cannot be treated “on-site” with reasonable effortswith reasonable efforts
Develop Process for ODOT Projects with Develop Process for ODOT Projects with Stormwater EffectsStormwater Effects
Problem StatementProblem Statement
Stormwater has become a major impediment to Stormwater has become a major impediment to efficient ESA consultation process due to:efficient ESA consultation process due to:
Lack of congruence in water quality requirements Lack of congruence in water quality requirements between DEQ and NMFSbetween DEQ and NMFS
Changing thresholds for effects determinations in Changing thresholds for effects determinations in ESA Section 7 consultations ESA Section 7 consultations
Changing science regarding the action area for Changing science regarding the action area for dissolved metals (e.g. copper)dissolved metals (e.g. copper)
Lack of early coordination to identify emerging Lack of early coordination to identify emerging issues (i.e., new pollutants of concern)issues (i.e., new pollutants of concern)
Proposed Strategy/ProcessProposed Strategy/Process
Compile and synthesize literature Compile and synthesize literature on BMPs for stormwater treatmenton BMPs for stormwater treatment
Define water quality design stormDefine water quality design storm
Develop water quantity guidanceDevelop water quantity guidance
Develop Process for ODOT Projects with Develop Process for ODOT Projects with Stormwater EffectsStormwater Effects
Develop Strategy/Process for ODOT Develop Strategy/Process for ODOT Projects with Stormwater EffectsProjects with Stormwater Effects
Proposed Strategy/Process (cont.)Proposed Strategy/Process (cont.)
Incorporate minimization of stormwater impacts Incorporate minimization of stormwater impacts into project design (Low Impact Development into project design (Low Impact Development techniques)techniques)
Select most appropriate stormwater treatment Select most appropriate stormwater treatment BMPs for each project BMPs for each project
Develop a BMP Selection Tool and User’s GuideDevelop a BMP Selection Tool and User’s Guide
Proposed Strategy/Process (cont.)Proposed Strategy/Process (cont.)
Developing ESA Effects Determination GuidanceDeveloping ESA Effects Determination Guidance
Exploring expanding SLOPES IV and/or ESA Exploring expanding SLOPES IV and/or ESA programmatic consultation programmatic consultation
Will develop a performance measurement and Will develop a performance measurement and reporting methodreporting method
Develop Strategy/Process for ODOT Develop Strategy/Process for ODOT Projects with Stormwater EffectsProjects with Stormwater Effects
Develop Strategy/Process for ODOT Develop Strategy/Process for ODOT Projects with Stormwater EffectsProjects with Stormwater Effects
Anticipated Benefits for Anticipated Benefits for Regulatory AgenciesRegulatory Agencies
Meet regulatory requirementsMeet regulatory requirements
Well-defined terms and conditions that allow Well-defined terms and conditions that allow for flexibility in applicationfor flexibility in application
Protect ESA-listed fishProtect ESA-listed fish
Protect Oregon’s water quality and wetland Protect Oregon’s water quality and wetland resourcesresources
Develop Strategy/Process for ODOT Develop Strategy/Process for ODOT Projects with Stormwater EffectsProjects with Stormwater Effects
Anticipated Benefits for ODOTAnticipated Benefits for ODOT
Certainty in project development and constructionCertainty in project development and construction
Reduction in project delaysReduction in project delays
Support ODOT’s sustainability goalsSupport ODOT’s sustainability goals
Develop Strategy/Process for ODOT Develop Strategy/Process for ODOT Projects with Stormwater EffectsProjects with Stormwater Effects
Where are we now?Where are we now?
BMP Summary Reports BMP Summary Reports CompletedCompleted
BMP Selection Tool in BMP Selection Tool in developmentdevelopment
BMP Selection Tool Users’ BMP Selection Tool Users’ Guide to be developedGuide to be developed
Develop Strategy/Process for ODOT Develop Strategy/Process for ODOT Projects with Stormwater EffectsProjects with Stormwater Effects
Where are we now (cont.)Where are we now (cont.) Draft Water Quality Design Storms near Draft Water Quality Design Storms near
completioncompletion Water Quantity Guidance near completionWater Quantity Guidance near completion ESA Effects Determination Guidance for Water ESA Effects Determination Guidance for Water
Quality near completionQuality near completion
Design Storm EvaluationDesign Storm Evaluation
Water QualityWater Quality (and Water Quantity) (and Water Quantity)
Science-basedScience-based
– Geography-specific (hydrologic zones)Geography-specific (hydrologic zones)
Economics (cost-benefit)Economics (cost-benefit)
– Effects on facility sizeEffects on facility size
Ultimately a “Policy” decisionUltimately a “Policy” decision
Water Quality Design StormWater Quality Design Storm
Based on analysis of rainfall data from >50 Based on analysis of rainfall data from >50 precipitation stations across the state’s nine precipitation stations across the state’s nine climate zonesclimate zones
– Cumulative percent of total rainfall vs. storm Cumulative percent of total rainfall vs. storm sizesize
– Percentile of storm size Percentile of storm size
– Percent rainfall treatedPercent rainfall treated
– ““Sensitivity Analysis” for sizing treatment Sensitivity Analysis” for sizing treatment facilitiesfacilities
Water Quality Design StormWater Quality Design Storm
Oregon Climate Zones
Water Quality Design StormWater Quality Design Storm
Cumulative Percent of Rainfall by Storm Size
Water Quality Design Storm Analysis
0%
20%
40%
60%
80%
100%
0 0.5 1 1.5 2 2.5 3 3.5 4
Storm Size (depth, in.)
Per
cen
t o
f T
ota
l Rai
nfa
ll
Astoria Portland Corvallis Medfiord Pendleton Bend (View in Color)
Pendleton
Bend Astoria
Corvallis
Portland
Medford
Water Quality Design StormWater Quality Design Storm
Portland - Station 356751Percent Rainfall Volume Treated for Different Design Storm
85%
90%
95%
100%
105%
0 0.5 1 1.5 2 2.5 3 3.5
Storm depth, in
Per
cen
t T
rea
ted
% Treated (70% storm) % Treated (75% storm) % Treated (80% storm)
% Treated (85% storm) % Treated (90% storm) % Treated (95% storm)
70% Storm
75% Storm
80% Storm
85% Storm
90% Storm
95% Storm
Water Quality Design StormWater Quality Design Storm
Portland - Station 356751Percent Rainfall Volume Treated for Different Design Storm
85%
90%
95%
100%
105%
0 0.5 1 1.5 2 2.5 3 3.5
Storm depth, in
Per
cen
t T
rea
ted
% Treated (70% storm) % Treated (75% storm) % Treated (80% storm)
% Treated (85% storm) % Treated (90% storm) % Treated (95% storm)
70% Storm
75% Storm
80% Storm
85% Storm
90% Storm
95% Storm
Water Quality Design StormWater Quality Design Storm
Facility Size Sensitivity to Design StormGrassy Swale
0.00%
50.00%
100.00%
150.00%
200.00%
250.00%
70% 75% 80% 85% 90% 95%
Design Storm
Cu
mu
lati
ve
Pe
rce
nt
Inc
rea
se
in
To
p W
idth
Ashland
Astoria
Bend
Corvallis
Detroit Dam
La Grande
Medford
Newport
Pendleton
Portland
Sheaville
Silver Lake
Water Quality Design StormWater Quality Design Storm
ANOVA Analysis was used to group similar climate ANOVA Analysis was used to group similar climate zoneszones
Design storm corresponding to 85% cumulative Design storm corresponding to 85% cumulative rainfall results in:rainfall results in:
– >95% of rainfall treated>95% of rainfall treated
– >97>97thth percentile storm size percentile storm size
Facility size is most “sensitive” to design storms Facility size is most “sensitive” to design storms when increasing from 90% to 95% cumulative when increasing from 90% to 95% cumulative rainfall design stormrainfall design storm
Water Quality Design StormWater Quality Design Storm
Use the mean storm size corresponding to 85% Use the mean storm size corresponding to 85% cumulative rainfall for each station in the climate cumulative rainfall for each station in the climate zones.zones.
Define a water quality design storm for 5 zonesDefine a water quality design storm for 5 zones
ZoneZone Current Current DefinitionDefinition
85% Cumulative 85% Cumulative RainfallRainfall
11 1.61.6 2.32.3
2 and 32 and 3 1.01.0 1.41.4
44 1.51.5 2.32.3
55 0.60.6 1.31.3
6,7,8, and 96,7,8, and 9 0.50.5 0.70.7
BMP SelectionBMP Selection
Best Available TechnologyBest Available Technology– BMPs included in ODOT Hydraulics ManualBMPs included in ODOT Hydraulics Manual– Emerging and LID-type BMPs (e.g. bioslope, Emerging and LID-type BMPs (e.g. bioslope,
soil amendments)soil amendments) Key selection criteria (metrics)Key selection criteria (metrics)
– Treatment suitabilityTreatment suitability– Physical site suitabilityPhysical site suitability– MaintenanceMaintenance– CostCost– Resources, risk and public perceptionResources, risk and public perception
BMP SelectionBMP Selection
Conceptual Stormwater Treatment Design Conceptual Stormwater Treatment Design StrategyStrategy– SW Strategy SW Strategy Figure.pdfFigure.pdf
Schematic of BMP Selection ToolSchematic of BMP Selection Tool– Selection Tool Selection Tool Schematic.pdfSchematic.pdf
BMP SelectionBMP Selection
Treatment SuitabilityTreatment Suitability High variability with “effectiveness” dataHigh variability with “effectiveness” data Based on treatment mechanismsBased on treatment mechanisms
– Hydrologic attenuationHydrologic attenuation– Sedimentation/density separationSedimentation/density separation– SorptionSorption– FiltrationFiltration– Uptake/storageUptake/storage– Microbially-mediated transformationMicrobially-mediated transformation
BMP SelectionBMP Selection
Hydr
olog
ic At
tenu
atio
n (1
)
Dens
ity S
epar
atio
n
Sorp
tion
(che
mica
l act
ivity
)
Filtr
atio
n
Upta
ke/S
tora
ge(2
)
Micr
obia
l Tra
nsfo
rmat
ion(3
)
Sediment/Particulate (suspended solids) ■ ■ ■Nutrients(4) ■ ■ ■ ■Oil and Grease ■ ■ ■ ■ ■Polycyclic Aromatic Hydrocarbons (PAH) ■ ■ ■ ■Metals (particulate) ■ ■ ■Metals (dissolved) ■ □ □ ■ ■
□ = Depending on chemical activity of filter media(1) Refers to infiltration which is credited for overall pollutant mass load reduction of all
target pollutants primarily through volume reduction; pollutant removal is
also achived through filtering, sorption, and microbial transformation in the soil column.(2) Dependent on plant species(3) Dependent on types of microbes present (in soil or water column)(4) May not be considered a highway target pollutant, but included for completeness
Table 2. Treatment Mechanism - Target Pollutant Matrix
Targ
et P
ollu
tant
Mechanism
BMP SelectionBMP Selection
Oil C
ontro
l Fac
ilitie
s (p
retre
atm
ent)
Sedi
men
t Con
trol (
pret
reat
men
t)
Infilt
ratio
n tre
nch/
pond
Bior
eten
tion
Bios
lope
Poro
us P
avem
ent (
not s
tand
-alo
ne)
Gra
ss S
wale
(soi
l am
ende
d)
Filte
r Stri
p (s
oil a
men
ded)
Cons
truct
ed W
etla
nds
Exte
nded
Det
entio
n Dr
y Po
nd
Wet
Pon
ds
Wet
Vau
lts
Med
ia F
ilters
(non
-pro
prie
tary
)
Prop
rieta
ry S
epar
atio
n (p
retre
atm
ent)
Prop
rieta
ry F
iltrat
ion
Facil
ities
Hydrologic Attenuation ■ ■ ■ ■ □ □ □ ■ □Density Separation (Sedimentation/Flotation) ■ ■ □ ■ □ □ □ ■ ■ ■ ■ ■Sorption □ □ ■ ■ ■ ■ ■ □ □ □ □ □ ■Filtration □ □ ■ ■ ■ ■ ■ ■ □ □ □ ■ □ ■Uptake/Storage(1)
□ ■ □ □ □ ■ □ □Microbial Transformation(1)
□ ■ □ □ □ ■ □ □ □ □
Sediment/Particulate (suspended solids) ○ ● ● ● ● ● ● ● ● ● ● ● ● ● ●Nutrients ● ● ● ● ○ ○ ● ○ ○ -Oil and Grease ● ○ ● ● ● ● ● ● ● ○ ○ ○ ● ● ●Polycyclic Aromatic Hydrocarbons (PAH) ● ● ● ● - - ● ○ ○ -Metals (particulate) ○ ○ ● ● ● ● ● ● ● ● ● ● ● ● ●Metals (dissolved) ● ● ● ● ○ ○ ● ○ ○ ○ ○
■ = Key treatment mechanism for BMP
□ = Associated treatment mechanism for BMP; dependent on plant species/microbes present
● = High capability to remove target pollutant
○ = Moderate capability to remove target pollutant
- = Low capability to remove target pollutant(1) Dependent on types of plant species or microbes (in soil or water column) present
Targ
et P
ollu
tant
Table 3. Treatment Mechanism - BMP Matrix
Trea
tmen
t Mec
hani
smBest Management Practice
Pretreatment Infiltration Filtration Pool-Ponds
Space-constrained or Urban Application
BMP SelectionBMP Selection
Priority BMPs for Treating Dissolved MetalsPriority BMPs for Treating Dissolved Metals
Treatment MechanismsTreatment Mechanisms
– Hydrologic Attenuation (infiltration) – preferredHydrologic Attenuation (infiltration) – preferred
– Sorption, uptake, microbial transformationSorption, uptake, microbial transformation
““Preferred” BMPsPreferred” BMPs
– Infiltration trenchInfiltration trench
– BioretentionBioretention
– Bioslope (“Ecology Embankment”)Bioslope (“Ecology Embankment”)
– Amended Swale and Filter StripAmended Swale and Filter Strip
BMP SelectionBMP Selection
Next StepsNext Steps Finalize Metric RatingsFinalize Metric Ratings Apply to Pilot ProjectsApply to Pilot Projects Integrate into an “Electronic Tool”Integrate into an “Electronic Tool” Develop Users’ GuideDevelop Users’ Guide
Questions?Questions?
Water Quantity Design StormWater Quantity Design Storm
Match pre-project hydrology from a low-Match pre-project hydrology from a low-discharge, high frequency event to a high-discharge, high frequency event to a high-discharge, low-frequency eventdischarge, low-frequency event
Low discharge eventLow discharge event: when substantial bed-: when substantial bed-load begins to occurload begins to occur
High discharge eventHigh discharge event: bank over-topping : bank over-topping event; or when amount of impervious area has event; or when amount of impervious area has little effect on stream discharge (10-year/24-hour little effect on stream discharge (10-year/24-hour event)event)
Water Quantity Design StormWater Quantity Design Storm
Low discharge eventLow discharge event: when substantial bed-: when substantial bed-load begins to occur; Studies have shown:load begins to occur; Studies have shown:
– 2/3 of bankfull discharge 2/3 of bankfull discharge
– 50% of 2-year/24-hour event50% of 2-year/24-hour event
Average bankfull discharge event:Average bankfull discharge event:
– Eastern OR = 1.5-year/24 hour eventEastern OR = 1.5-year/24 hour event
– Western OR = 1.2-year/24 hour eventWestern OR = 1.2-year/24 hour event
64 streamflow gauges were analyzed from 8 flood 64 streamflow gauges were analyzed from 8 flood frequency regions defined by USGSfrequency regions defined by USGS
Water Quantity Design StormWater Quantity Design Storm
Low Discharge End PointLow Discharge End Point::
– West Region: 42% of 2-year,24 hour eventWest Region: 42% of 2-year,24 hour event
– SE, NE, NC Regions: 48% of 2-year, 24-hour SE, NE, NC Regions: 48% of 2-year, 24-hour eventevent
– E-Cascades: 56% of 2-year, 24 hour eventE-Cascades: 56% of 2-year, 24 hour event
High Discharge End Point:High Discharge End Point:
– 10-year, 24-hour event for incised streams; or10-year, 24-hour event for incised streams; or
– Event corresponding to bank overtopping Event corresponding to bank overtopping recurrence interval for minimally incised recurrence interval for minimally incised streamsstreams
Water Quantity Design StormWater Quantity Design Storm
Design CriteriaDesign Criteria::
– Minimum ¼ acre or 0.5 cfs increase in Minimum ¼ acre or 0.5 cfs increase in discharge from project sitedischarge from project site
– Considerations for Minimum orifice sizeConsiderations for Minimum orifice size
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