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ACWA Stormwater Committee Meeting

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Presentation on theme: "ACWA Stormwater Committee Meeting"— Presentation transcript:

1 ACWA Stormwater Committee Meeting
Oregon Department of Transportation Stormwater Management Initiative: Meeting New Challenges Presented by: Jennifer Sellers, ODOT and Ronan Igloria, HDR ACWA Stormwater Committee Meeting November 27, 2007 When 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.

2 ODOT’s Goals Develop a streamlined stormwater treatment program to:
Meet all regulatory needs Provide ODOT with certainty regarding scope, schedule, and budget Result in an overall environmental benefit and promote species recovery We identified several goals in relation stormwater management

3 Components of the Stormwater Initiative Work Plan
Streamline DEQ Stormwater Management Plan Approval Process Develop Process for ODOT Projects with T&E Species and Stormwater Effects Develop a watershed-based mitigation program to offset stormwater effects that cannot be treated “on-site” with reasonable efforts We identified three areas in relation to stormwater that needed work The 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 taken As I only have 20 minutes and we have not begun work on that component, I am omitting it from this presentation.

4 Develop Process for ODOT Projects with Stormwater Effects
Problem Statement Stormwater has become a major impediment to efficient ESA consultation process due to: Lack of congruence in water quality requirements between DEQ and NMFS Changing thresholds for effects determinations in ESA Section 7 consultations Changing 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 present New scientific literature regarding the effects of dissolved metals, especially copper, on juvenile salmonids has concluded that concentrations as low as 5 ppb have sublethal effects New 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.

5 Develop Process for ODOT Projects with Stormwater Effects
Proposed Strategy/Process Compile and synthesize literature on BMPs for stormwater treatment Define water quality design storm Develop water quantity guidance A 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 process This team has been working for over a year on the following topics

6 Develop 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 project Develop a BMP Selection Tool and User’s Guide Low 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 facility The 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

7 Develop Strategy/Process for ODOT Projects with Stormwater Effects
Proposed Strategy/Process (cont.) Developing ESA Effects Determination Guidance Exploring expanding SLOPES IV and/or ESA programmatic consultation Will develop a performance measurement and reporting method A 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 in We are working with NMFS to have the products of this team’s efforts in SLOPES IV (design storms, BMP Selection Tool

8 Develop Strategy/Process for ODOT Projects with Stormwater Effects
Anticipated Benefits for Regulatory Agencies Meet regulatory requirements Well-defined terms and conditions that allow for flexibility in application Protect ESA-listed fish Protect Oregon’s water quality and wetland resources Certainty 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

9 Develop Strategy/Process for ODOT Projects with Stormwater Effects
Anticipated Benefits for ODOT Certainty in project development and construction Reduction in project delays Support ODOT’s sustainability goals

10 Develop Strategy/Process for ODOT Projects with Stormwater Effects
Where are we now? BMP Summary Reports Completed BMP Selection Tool in development BMP Selection Tool Users’ Guide to be developed

11 Develop Strategy/Process for ODOT Projects with Stormwater Effects
Where are we now (cont.) Draft Water Quality Design Storms near completion Water Quantity Guidance near completion ESA Effects Determination Guidance for Water Quality near completion A 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 regions Janine 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.

12 Design Storm Evaluation
Water Quality (and Water Quantity) Science-based Geography-specific (hydrologic zones) Economics (cost-benefit) Effects on facility size Ultimately a “Policy” decision

13 Water Quality Design Storm
Based on analysis of rainfall data from >50 precipitation stations across the state’s nine climate zones Cumulative percent of total rainfall vs. storm size Percentile of storm size Percent rainfall treated “Sensitivity Analysis” for sizing treatment facilities

14 Water Quality Design Storm

15 Water Quality Design Storm

16 Water Quality Design Storm

17 Water Quality Design Storm

18 Water Quality Design Storm

19 Water Quality Design Storm
ANOVA Analysis was used to group similar climate zones Design storm corresponding to 85% cumulative rainfall results in: >95% of rainfall treated >97th percentile storm size Facility size is most “sensitive” to design storms when increasing from 90% to 95% cumulative rainfall design storm

20 Water 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 zones Zone Current Definition 85% Cumulative Rainfall 1 1.6 2.3 2 and 3 1.0 1.4 4 1.5 5 0.6 1.3 6,7,8, and 9 0.5 0.7

21 BMP Selection Best Available Technology
BMPs included in ODOT Hydraulics Manual Emerging and LID-type BMPs (e.g. bioslope, soil amendments) Key selection criteria (metrics) Treatment suitability Physical site suitability Maintenance Cost Resources, risk and public perception

22 BMP Selection Conceptual Stormwater Treatment Design Strategy
SW Strategy Figure.pdf Schematic of BMP Selection Tool Selection Tool Schematic.pdf

23 BMP Selection Treatment Suitability
High variability with “effectiveness” data Based on treatment mechanisms Hydrologic attenuation Sedimentation/density separation Sorption Filtration Uptake/storage Microbially-mediated transformation

24 BMP Selection

25 BMP Selection

26 BMP Selection Priority BMPs for Treating Dissolved Metals
Treatment Mechanisms Hydrologic Attenuation (infiltration) – preferred Sorption, uptake, microbial transformation “Preferred” BMPs Infiltration trench Bioretention Bioslope (“Ecology Embankment”) Amended Swale and Filter Strip

27 BMP Selection Next Steps Finalize Metric Ratings
Apply to Pilot Projects Integrate into an “Electronic Tool” Develop Users’ Guide

28 Questions?

29 Water Quantity Design Storm
Match pre-project hydrology from a low-discharge, high frequency event to a high-discharge, low-frequency event Low discharge event: when substantial bed-load begins to occur High discharge event: bank over-topping event; or when amount of impervious area has little effect on stream discharge (10-year/24-hour event)

30 Water Quantity Design Storm
Low discharge event: when substantial bed-load begins to occur; Studies have shown: 2/3 of bankfull discharge 50% of 2-year/24-hour event Average bankfull discharge event: Eastern OR = 1.5-year/24 hour event Western OR = 1.2-year/24 hour event 64 streamflow gauges were analyzed from 8 flood frequency regions defined by USGS

31 Water Quantity Design Storm
Low Discharge End Point: West Region: 42% of 2-year,24 hour event SE, NE, NC Regions: 48% of 2-year, 24-hour event E-Cascades: 56% of 2-year, 24 hour event High Discharge End Point: 10-year, 24-hour event for incised streams; or Event corresponding to bank overtopping recurrence interval for minimally incised streams

32 Water Quantity Design Storm
Design Criteria: Minimum ¼ acre or 0.5 cfs increase in discharge from project site Considerations for Minimum orifice size

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