Stevens-Rugg Brook: Diversion Structure Improvement Alternatives St Albans, Vermont

1. Stevens-Rugg Brook:Diversion Structure Improvement AlternativesSt Albans, Vermont

2. Background • Flood damage to homes, businesses, rec areas, and ag areas led to need for detention structure between Stevens and Rugg Brooks • Water quality, sediment and erosion concerns • Three proposed initial routes: railroad, power line, trailer park

3. Many problems existed between the city and landowners leading to the selection and implementation of the power line alternative. • 1974 construction began on structure • Stevens Brook diverts water to Rugg Brook

4. Map of Jewett Brook and Mill River Watersheds • Two streams are Stevens (N) and Rugg (S) • City of St Albans in orange/teal Detention Structure

5. Problem • The existing St. Albans diversion structure is not effective at preventing floods during high water flow events and does not produce effluent that meets water quality standards.

6. Culvert holds 70 cfs when full Base flow is 2 cfs When flow exceeds 70 cfs, pooling occurs which leads to diversion structure Stevens Brook and existing Culvert

8. Diversion Structure: Sediment Basin

9. Diversion Structure: Outlet weir

10. Diversion Structure: Outlet

11. Diversion Structure: Rugg Brook

12. Problem: Sedimentation

13. Problem: Debris Accumulation

14. Problem: Water Quality

15. Problem: Erosion-Stevens

16. Improvement Measures: 1 Construct Sediment Traps in Existing Basin • Excavate permanent deep pools for sediment • revegetation for aquatic habitat • Removal of pollutants bound to sediments

17. Measure 1: Engineer Drawing

18. Improvement Measures: 2Construct Detention Basin by Excavating Diversion Channel • Excavate 2-3 ft deep basin at downstream end • Low flow outlet in existing weir • Sediment forebay at head of basin • Revege for aquatic habitat

20. Improvement Measures: 3Construct Detention Basin by Raising Outlet Structure • Low flow outlet at current elevation, raise weir 1-2 feet • Sediment forebay at head of basin • Revege for aquatic habitat

22. Improvement Measures: 4Construct Enhanced Wetland in Diversion Channel • Enhance habitat • Sinuous low flow channel for settling • Shallow and deep pools • Sediment forebay • Revegetation for aquatic habitat

23. Alternative Constructed Wetlands • Flood attenuation • Pollutant removal • Aquatic habitat Extended detention wetland Pond/wetland system Pocket wetland

24. Findings: Multiple Criteria Decision Analysis

25. Pollutant Removal Flood Water Detention Geomorphology of Rugg Brook Total Measure 1 3 0 1 4 Measure 2 1 3 3 7 Measure 3 1 1 2 4 Measure 4 3 0 1 4 • From MCDA most important criteria are: pollutant removal, flood water detention and stream geomorphology

26. Recommendations: MCDA • Measure 2: sediment forebay and detention pond • Constructed wetland close to outlet including native plant stock • Reduction and development of effective impervious surfaces in the city of St Albans. • Riparian buffers

27. Recommendations: Buffer • Stevens Brook • Bank stability • Reduce sedimentation

28. Buffer • Along sides of detention pond and constructed wetland • Increase bank stability • Habitat • Aesthetics

29. Recommendations: Monitoring and Maintenance • Are the improvements functioning as designed? • Future sediment removal and disposal • Testing effluent against water quality standards • Geomorphologic assessment of Rugg

30. Acknowledgments • Erica Gaddis • Breck Bowden • Dan Lindly: Town administrator • Bonnie Wagner: Northwest Regional planning Commission