Oregon Department of Oregon Department of Transportation Transportation Stormwater Management Stormwater Management Initiative: Initiative: Meeting New Challenges Meeting New Challenges Presented by: Presented by: Jennifer Sellers, ODOT Jennifer Sellers, ODOT and and Ronan Igloria, HDR Ronan Igloria, HDR ACWA Stormwater Committee Meeting ACWA Stormwater Committee Meeting November 27, 2007 November 27, 2007
32
Embed
Oregon Department of Transportation Stormwater Management Initiative: Meeting New Challenges Presented by: Jennifer Sellers, ODOT and Ronan Igloria, HDR.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Oregon Department of Transportation Oregon Department of Transportation
Stormwater Management Initiative:Stormwater Management Initiative:Meeting New ChallengesMeeting New Challenges
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)
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
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)
– 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
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,
– Treatment suitabilityTreatment suitability– Physical site suitabilityPhysical site suitability– MaintenanceMaintenance– CostCost– Resources, risk and public perceptionResources, risk and public perception
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
□ = 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
– 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