STORMWATER BMPS FOR HIGHWAYS

1. STORMWATER BMPS FOR HIGHWAYS

2. CHALLENGES • Stormwater Mgt. Vs Highway Safety • Limited Right-of-way • Highly Impervious Drainage Areas • Extensive Cuts and Fills • Spill Potential • Use of Deicing & Anti-skid Materials • Higher Concentrations of Pollutants • Thermal Impacts in Summer & Winter

3. TYPICAL POLLUTANTS IN HIGHWAY RUNOFF

4. TYPICAL POLLUTANTS IN HIGHWAY RUNOFF

5. BMP CONSIDERATIONS • Higher levels of Suspended Solids • Vegetated Systems • Grassed Swales • Filter Strips • Bioretention • Structural Elements • Catch Basin Inserts • Filters • Manufactured Treatment Units • Maintenance Measures • Street Sweeping • Vacuuming

6. BMP CONSIDERATIONS • Vegetated BMPs effective in removing pollutant loads if properly designed • Spill Containment • Subsurface, infiltration, or vegetative systems may have to be replaced • Deicing & Antiskid application may adversely affect BMPs

7. BMP CONSIDERATIONS • Temperature Impacts on aquatic life in receiving waters • Vegetated Systems replace Concrete • Discharge from Extended Detention through Vegetated Swales or Buffers • Extended Detention Design • Minimize Permanent Pool • Preserve existing Shade Trees • Align Pond in North-South Direction if possible • Avoid excessive Riprap & Concrete

8. HIGHWAY/ROAD STRATEGIES • Utilize sod-forming grasses adjacent to Roadway Shoulders & for Vegetated Swales to serve as Filters for Suspended Solids and Metals

9. HIGHWAY/ROAD STRATEGIES • Utilize non-invasive native species vegetation in lawn areas, on slopes and within wetland reconstruction/ banking areas to enhance Water Uptake and the storage of certain pollutants in plant tissue.

10. HIGHWAY/ROAD STRATEGIES • Limit use of curb-gutter sections as much as practical for Filtering and Temperature considerations

11. HIGHWAY/ROAD STRATEGIES • Limit use of storm sewers as much as practical for Filtering and Temperature considerations.

12. HIGHWAY/ROAD STRATEGIES • Consider Bioretention capability in the design of new detention basins (Dry Extended Detention Basin design)

13. HIGHWAY/ROAD STRATEGIES • Monitor the effectiveness of existing Constructed Wetlands, updating the current design practices as necessary

14. HIGHWAY/ROAD STRATEGIES • Consider alternative methods of energy dissipation (in lieu of rock aprons) at culvert and storm sewer outfalls for Temperature considerations Perforated Pipe in an Aggregate Trench Aggregate Trench Spreader with Filter Strip

15. HIGHWAY/ROAD STRATEGIES • Where practical, discharge storm sewers into wetland areas or vegetated swales for Filtering & Temperature considerations

16. HIGHWAY/ROAD STRATEGIES • Consider vegetated islands in lieu of concrete islands for Filtering and Temperature considerations

17. HIGHWAY/ROAD STRATEGIES • Consider use of Infiltration Berms and Retentive Grading in areas downslope of the roadway Infiltration Berm Cross-section Series of Woodland Infiltration Berms

18. HIGHWAY/ROAD STRATEGIES • Continue to monitor & minimize volume of winter maintenance materials to Minimize Pollutant Loadings

19. HIGHWAY/ROAD STRATEGIES • Continue to protect all salt storage & loading areas from weather influences to Minimize Pollutant Loadings

20. HIGHWAY/ROAD STRATEGIES • Consider practices to dilute flows where high concentrations of salts are anticipated to Minimize Pollutant Loadings

21. HIGHWAY/ROAD STRATEGIES • Consider Porous Pavement on Park-and-Ride sites and for Department building site parking lots

22. HIGHWAY/ROAD STRATEGIES • Consider Dry Wells and other Subsurface Infiltration for Department building roof drains