Stormwater Management for Highway Projects Rules, Expectations, and Tools

1. Stormwater Management for Highway Projects Rules, Expectations, and Tools William Fletcher Water Resources Program Coordinator ODOT

2. When is Highway Runoff an Issue? • Adding Impervious Surface • Modifying the drainage system • Relocation of the drainage system • Change in the type of the drainage system • Completely reconstructing the roadway from the base grade up

3. When is Highway Runoff an Issue? • Replacement, Enlargement or Construction of a Bridge or a Culvert • Projects requiring Clean Water Act Section 404 permits that “involve” impervious surface.

4. Regulations and PermitsClean Water Act Project level review 401 Water Quality Certification for projects with 404 permits • Individual Permits: Full review by DEQ of a project’s impacts on water quality, including the Stormwater Management Plan • Nationwide Permits: Pre-certified, EXCEPT projects with impervious surface need a Stormwater Management Plan

5. Regulations and PermitsClean Water Act Mandate to protect “Beneficial Uses” means DEQ has the responsibility to evaluate a project’s impacts to more than simple water quality: • Riparian impacts • Channel modification • In-water work windows • Wetland impacts • Hydrologic impacts

6. Regulations and PermitsClean Water Act Focus on providing stormwater treatment “To the Maximum Extent Practicable”

7. Regulations and PermitsClean Water Act Programmatic TMDL/303(d) listings (Water Quality Limited Water Bodies) NPDES MS4 Permits

8. Regulations and PermitsSafe Drinking Water Act Covers discharges to groundwater through Underground Injection Control Systems • Permit required from DEQ • Discharges must meet drinking water standards (set by OHD, not DEQ)

9. Regulatory and PermitsEndangered Species Act The discharge of highway runoff to T&E species bearing streams is considered to be a “take”.

10. Regulatory and PermitsEndangered Species Act SLOPES IV • Covers many Transportation projects • Includes stringent stormwater management requirements Individual Biological Opinions • Provides opportunity to negotiate, but • Same base expectations as SLOPES IV

11. Regulations and Permits DEQ and NMFS expectations for stormwater treatment are in close alignment Satisfy one agency and both will be happy and the project can move forward

12. Water Resources Goals Treat All the stormwater from the Contributing Impervious Area Generated by the Water Quality Design Storm Using Preferred Best Management Practices

13. Contributing Impervious Area (CIA) The Contributing Impervious Area“ (CIA) consists of all impervious surface within the strict project limits, plus impervious surface owned or operated by ODOT outside the project limits that drain to the project via direct flow or discrete conveyance

14. Example Graphic: CIA

15. CIA Boundaries project limits

16. Water Quality Design Storm • Used to determine the volume and peak flow rate of highway runoff that is to be treated • Defined as a frequency and duration, specifically a percentage of the 2 year, 24 hour storm • Consistent as a percentage of the annual average rainfall across the state

17. Water QualityDesign Storm Defined for each Climate Region Percentage of the 2 year 24 hour storm: 50% 67% 75%

18. ODOT Flow Control Design Storm • These are the smallest and largest storms that are subject to hydrologic modification • Hydrologic modification has two goals: • Protection and maintenance of channel processes • Flood control

19. Flow Control Design Storm Lower Discharge Endpoint • Western OR - 42 percent of the 2-year, 24 hour event • Southeast, Northeast, North Central Regions: 48 percent of the 2-year, 24 hour event • Eastern Cascades Region: 56 percent of the 2-year, 24 hour event Upper Discharge Endpoint • Minimally incised streams -Channel bank overtopping event • Incised Streams -10-year/24-hour storm event

20. USGS Flood Frequency Regions

21. Flow Control Design Storm Flow control is not needed if: • The project increases the 10 year 24 hour storm discharge by less than 0.5 cfs • The project discharges to a major river, lake, reservoir or estuary

22. Preferred BMPS • Stormwater Treatment Techniques that are effective at treating a range of pollutants • They utilize infiltration into the soil and/or filtration through a media such as amended soil

23. Preferred BMPS • Infiltration techniques • Bioretention facilities • Bioslope (“Ecology Embankment”) • Amended Soil Swales and Filter Strips • Treatment wetlands

24. BMP Selection Tool • The selection of treatment techniques and strategies is supported by the BMP Selection Tool • The Selection Tool is to help designers find the most effective treatment that is suitable for an individual project

25. BMP Selection • Key selection criteria (metrics) • Treatment capability • Physical site suitability • Maintenance • Resources, risk and public perception • Cost

27. Infiltration • Infiltration ranks on the top because it reduces both the volume of runoff and the pollutant load delivered to the receiving waters. • Use of UICs involves additional permitting

28. Low Impact Development Water quality features in the linear right- of-way that emphasis infiltration and filtration through media and vegetation

29. Options if Things aren’t Perfect • Use the BMP Selection Tool to help assemble a treatment train of equivalent effectiveness as a Preferred BMP • Use the most effective BMPs you can, then: • For ESA compliance, do off-project mitigation • For 401 compliance, document that the project is doing the best it can (Maximum Extent Practicable)

30. Resources • ODOT Stormwater Management Program: http://www.oregon.gov/ODOT/HWY/GEOENVIRONMENTAL/Storm_Management_Program.shtml • DEQ 401 Certification: http://www.deq.state.or.us/WQ/sec401cert/sec401cert.htm • Training on developing SWMPs for DEQ: Upcoming for Local Agencies and Consultants, but not yet scheduled

31. Questions?