Presentation on theme: "ACWA Stormwater Committee Meeting"— Presentation transcript:
1ACWA Stormwater Committee Meeting Oregon Department of Transportation Stormwater Management Initiative: Meeting New ChallengesPresented by:Jennifer Sellers, ODOTandRonan Igloria, HDRACWA Stormwater Committee MeetingNovember 27, 2007When I started at ODOT in Feb 2006, one of my first tasks was to help with the stormwater problem.William Fletcher and I worked diligently to develop a work plan that identified the problems that ODOT project teams were facing with stormwater management and to work toward development of a solution.
2ODOT’s Goals Develop a streamlined stormwater treatment program to: Meet all regulatory needsProvide ODOT with certainty regarding scope, schedule, and budgetResult in an overall environmental benefit and promote species recoveryWe identified several goals in relation stormwater management
3Components of the Stormwater Initiative Work Plan Streamline DEQ Stormwater Management Plan Approval ProcessDevelop Process for ODOT Projects with T&E Species and Stormwater EffectsDevelop a watershed-based mitigation program to offset stormwater effects that cannot be treated “on-site” with reasonable effortsWe identified three areas in relation to stormwater that needed workThe third component of the work plan is to develop a watershed-based mitigation program to offset stormwater effects from stormwater that cannot be treated after all reasonable efforts have been takenAs I only have 20 minutes and we have not begun work on that component, I am omitting it from this presentation.
4Develop Process for ODOT Projects with Stormwater Effects Problem StatementStormwater has become a major impediment to efficient ESA consultation process due to:Lack of congruence in water quality requirements between DEQ and NMFSChanging thresholds for effects determinations in ESA Section 7 consultationsChanging science regarding the action area for dissolved metals (e.g. copper)Lack of early coordination to identify emerging issues (i.e., new pollutants of concern)The second component of the work plan deals with stormwater when ESA listed fish are presentNew scientific literature regarding the effects of dissolved metals, especially copper, on juvenile salmonids has concluded that concentrations as low as 5 ppb have sublethal effectsNew literature that was cited by NMFS also concludes that the fate and transport of dissolved metals is different than that of sediment. This research has shown that dissolved metals do not settle out of the water column, rather they are resuspended and travel to the ocean or estuary. Beyond that the fate is not really known.
5Develop Process for ODOT Projects with Stormwater Effects Proposed Strategy/ProcessCompile and synthesize literature on BMPs for stormwater treatmentDefine water quality design stormDevelop water quantity guidanceA task force comprised of agency representatives from DEQ, NMFS, USFWS, EPA, FHWA, and ODOT has been meeting to work toward resolution and toward development of a program and processThis team has been working for over a year on the following topics
6Develop Strategy/Process for ODOT Projects with Stormwater Effects Proposed Strategy/Process (cont.)Incorporate minimization of stormwater impacts into project design (Low Impact Development techniques)Select most appropriate stormwater treatment BMPs for each projectDevelop a BMP Selection Tool and User’s GuideLow impact development for highway projects refers to treatment of stormwater close to the source (such as retaining vegetation) and prior to conveyance – which can result in a minimization of stormwater that needs to be conveyed and/or treated by a facilityThe BMP selection tool is a way to provide guidance to choose BMPs that most effectively treat stormwater for a particular PoC and the regulators want the certainty that these more effective BMPs are the output of use of the tool if site conditions permit
7Develop Strategy/Process for ODOT Projects with Stormwater Effects Proposed Strategy/Process (cont.)Developing ESA Effects Determination GuidanceExploring expanding SLOPES IV and/or ESA programmatic consultationWill develop a performance measurement and reporting methodA subgroup comprised of reps from NMFS, USFWS, ODWF and ODOT have been meeting to develop ESA effects determination guidance. We are very close to providing guidance regarding what constitutes a NE, NLAA, and LAA. We are working to obtain FHWA input and buy inWe are working with NMFS to have the products of this team’s efforts in SLOPES IV (design storms, BMP Selection Tool
8Develop Strategy/Process for ODOT Projects with Stormwater Effects Anticipated Benefits forRegulatory AgenciesMeet regulatory requirementsWell-defined terms and conditions that allow for flexibility in applicationProtect ESA-listed fishProtect Oregon’s water quality and wetland resourcesCertainty in project development and construction would result, thus leading to reduction in project delays and project cost, thereby saving time and money while protecting ESA-listed fish
9Develop Strategy/Process for ODOT Projects with Stormwater Effects Anticipated Benefits for ODOTCertainty in project development and constructionReduction in project delaysSupport ODOT’s sustainability goals
10Develop Strategy/Process for ODOT Projects with Stormwater Effects Where are we now?BMP Summary Reports CompletedBMP Selection Tool in developmentBMP Selection Tool Users’ Guide to be developed
11Develop Strategy/Process for ODOT Projects with Stormwater Effects Where are we now (cont.)Draft Water Quality Design Storms near completionWater Quantity Guidance near completionESA Effects Determination Guidance for Water Quality near completionA NATIONAL survey of water quality design storms used was conducted – most could not recall the rationale for use or it was based upon cost. We have worked to develop the design storms on based upon science and climate. The data show that Oregon can be divided into 5 climatic regions. We are working on further analysis to determine what the design storms should be in these 5 regionsJanine Castro, a fluvial geomorphologist with USFWS, has been working with us to develop water quantity guidance. We have an upper end point – the 10 year storm and are working on the lower end point – 42% of the 2 year event.
12Design Storm Evaluation Water Quality (and Water Quantity)Science-basedGeography-specific (hydrologic zones)Economics (cost-benefit)Effects on facility sizeUltimately a “Policy” decision
13Water Quality Design Storm Based on analysis of rainfall data from >50 precipitation stations across the state’s nine climate zonesCumulative percent of total rainfall vs. storm sizePercentile of storm sizePercent rainfall treated“Sensitivity Analysis” for sizing treatment facilities
19Water Quality Design Storm ANOVA Analysis was used to group similar climate zonesDesign storm corresponding to 85% cumulative rainfall results in:>95% of rainfall treated>97th percentile storm sizeFacility size is most “sensitive” to design storms when increasing from 90% to 95% cumulative rainfall design storm
20Water Quality Design Storm Use the mean storm size corresponding to 85% cumulative rainfall for each station in the climate zones.Define a water quality design storm for 5 zonesZoneCurrent Definition85% Cumulative Rainfall11.62.32 and 31.01.441.550.61.36,7,8, and 90.50.7
21BMP Selection Best Available Technology BMPs included in ODOT Hydraulics ManualEmerging and LID-type BMPs (e.g. bioslope, soil amendments)Key selection criteria (metrics)Treatment suitabilityPhysical site suitabilityMaintenanceCostResources, risk and public perception
23BMP Selection Treatment Suitability High variability with “effectiveness” dataBased on treatment mechanismsHydrologic attenuationSedimentation/density separationSorptionFiltrationUptake/storageMicrobially-mediated transformation
29Water Quantity Design Storm Match pre-project hydrology from a low-discharge, high frequency event to a high-discharge, low-frequency eventLow discharge event: when substantial bed-load begins to occurHigh discharge event: bank over-topping event; or when amount of impervious area has little effect on stream discharge (10-year/24-hour event)
30Water Quantity Design Storm Low discharge event: when substantial bed-load begins to occur; Studies have shown:2/3 of bankfull discharge50% of 2-year/24-hour eventAverage bankfull discharge event:Eastern OR = 1.5-year/24 hour eventWestern OR = 1.2-year/24 hour event64 streamflow gauges were analyzed from 8 flood frequency regions defined by USGS
31Water Quantity Design Storm Low Discharge End Point:West Region: 42% of 2-year,24 hour eventSE, NE, NC Regions: 48% of 2-year, 24-hour eventE-Cascades: 56% of 2-year, 24 hour eventHigh Discharge End Point:10-year, 24-hour event for incised streams; orEvent corresponding to bank overtopping recurrence interval for minimally incised streams
32Water Quantity Design Storm Design Criteria:Minimum ¼ acre or 0.5 cfs increase in discharge from project siteConsiderations for Minimum orifice size