1. Stormwater Water Quality Treatment Options Alvin Shoblom, P.E. Hydraulics Engineer

2. Options Low Impact Development (LIDs) Engineered

3. Low Impact Development (LIDs) Definition: LID is the concept of designing projects to minimize the effect of natural hydrology and water quality. This is primarily accomplished by minimizing impervious surface area and providing opportunities for filtration of stormwater by vegetation and infiltration into the soil. For highway projects, LID refers to the treatment of highway runoff within the linear highway right of way using techniques and facilities that generally require minimal hydraulic engineering.

4. LID Options Minimizing impervious area Preserving or restoring adjacent roadside landscaping Mimicking natural drainage patterns (e.g. using sheet flow, dispersion, infiltration, and existing open channels) Incorporating/retrofitting vegetated shoulders and drainage channels with soil amendments

5. Soil Amendment

6. Example of maintaining existing vegetated shoulder (sheet flow)

7. Engineered Treatment Facilities Stormwater Ponds Biofiltration Swales Filter Strips Bioslopes Proprietary Structures

8. Bioretention Pond

11. Bioretention Pond Sizing Example Given: Salem Oregon Project Contributing ODOT impervious area (CIA) for project is 1 acre Determine: Water Quality Design Storm to size the pond. The design storm is a percentage of the 2-year, 24 hour event for the project site.

14. Bioretention Pond Sizing Example (Cont.) Results: Volume calculated is 3755 cubic feet using an appropriate hydrology method. Therefore, the volume in the pond would need to be 3755 cubic feet or greater.

15. Bioretention Pond

16. Biofiltration Swale (with soil amendment)

17. Biofiltration Swale

18. Filter Strip

19. Filter Strip

20. Bioslope

22. Downstream Defender (Separation unit)

23. Stormwater Management Stormfilter (Filtration unit)

24. Treatment Solution Selection For project with identified water Issues and treatment goals Incorporate LID techniques such as soil amendments, impervious surface reduction, preserving or restoring adjacent roadway landscaping Submit hydraulic Design Deviation for other BMP not listed in Water Quality Guidance/Tech Bulletin with supporting documentation Select appropriate treatment based on: BMP removal capabilities Constructability Cost and maintenance Site constraints (steep Slopes, high groundwater, Bedrock, etc) Go to Stormwater Management Tech Bulletin and attached Water Quality Guidance Sufficient LIDs Incorporated? Water Quality Selection Complete Y N BMP selected from Recommended list From Water Quality Guidance/Tech Bulletin? N Y LIDs and/or Engineered Treatment option used To meet treatment goals Sufficient design? Y Re-Submit deviation for for other BMP not listed in Water Quality Guidance/Tech Bulletin with supporting documentation N

25. Design Guidance Stormwater Management Program Technical Bulletin  Provides Selection and Design Guidance  Technical Bulletin #GE09-02B  Available online Hydraulic Design Deviation Requests Directive  Process for design not adhering to ODOT guidance  Directive #TSB08-01(D)  Available online