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2009 City of Bozeman Storm Water Update

2009 City of Bozeman Storm Water Update. Dustin Johnson, P.E. Project Engineer City of Bozeman . 2009 City of Bozeman Storm Water management update. Design and Development Phase II and related expenses Storm Water Masterplan Storm Water Sampling. City of Bozeman Review Process.

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2009 City of Bozeman Storm Water Update

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  1. 2009 City of Bozeman Storm Water Update Dustin Johnson, P.E. Project Engineer City of Bozeman

  2. 2009 City of Bozeman Storm Water management update • Design and Development • Phase II and related expenses • Storm Water Masterplan • Storm Water Sampling

  3. City of Bozeman Review Process • Preliminary Design • City Board Review – DRC, DRB, Planning Board, City Commission, etc. • Infrastructure Review – City Engineering, DEQ • Approval

  4. Review Criteria Zoning Growth Plan Transportation

  5. Engineering Review

  6. Why are Storm Water facilities necessary? • Flood Control • Channel Stability of Creeks and Rivers • Water Quality • Potential Re-use of rain water

  7. Storm water Engineering Pipe sizing and types Basin Location Basin sizing Slope requirements Calculation formats COB Runoff Coefficients Rainfall Curves Floodplain Regulations

  8. Types of Storage/Treatment Facilities • Retention Basins • Designed to retain all runoff from a 10 year, 2 hour storm. • Detention Basins • Release water through controlled outlet structure, at no greater than pre-development runoff.

  9. Retention Basins Calculations based on the Rational Formula Q = CiA (cfs) V = 7200Q (cubic feet) i for Bozeman 10 year, 2 hour storm always = .41 in/hr

  10. Detention Basins • More complicated than Retention Basins • Determine Tc, i @ Tc, and Q of pre-development runoff • Determine Tc and i @ Tc of post-development runoff • Determine maximum storage volume at various storm lengths for 10 year storm • Determine size of discharge structure

  11. In a perfect world…

  12. Other considerations • Depth of groundwater • Other surrounding infrastructure • Historic Drainage Patterns • Limited Space • Facilities not built to specifications • Aesthetics • Easements

  13. When things start to go wrong…

  14. Local Examples of Storm Water Management The Good

  15. Local Examples of Storm Water Management The Bad

  16. NPDES Phase II • National Pollutant Discharge Elimination System • Federal EPA regulated by Montana Department of Environmental Quality The purpose is to reduce or eliminate potential storm water pollutants from reaching water resources such as streams and lakes.

  17. Who is permitted for Phase II in Bozeman? • Continued partnership with MSU and MDT as co-permittees on MS4 Phase II.

  18. Storm Water Hierarchy

  19. Montana Cities implementing Phase II • Billings & Yellowstone County • Missoula & Missoula County • Great Falls and Cascade County • Butte • Bozeman • Helena • Kalispell

  20. Phase II 6 Minimum Control Measures (MCM) • Public Education and Outreach • Public Involvement/Participation • Illicit Discharge Detection and Elimination • Construction Site Runoff Control • Post Construction Storm Water Management • Pollution Prevention and BMP’s

  21. Total Minimum 5 year Direct Costs for Phase II Total cost of $424,000 for 5 years

  22. Summary of Direct costs for Storm Water Maintenance All costs based on 2005 estimates taken from COB Storm Water Masterplan

  23. Estimated Total Future Storm Water Costs All costs based on 2005 estimates taken from COB Storm Water Masterplan

  24. Where are we today with Phase II • Completed year four of a five year permit • Required semi-annual storm water sampling • Continue working with our co-permitees MSU and MDT • New engineering standards • Updated public information • Completed Storm Water Masterplan

  25. Storm Water Masterplan • Adopted by City Commission late 2008 • Is available for public review and use

  26. Masterplan Breakdown • Existing System Inventory • System Analysis • Policy Evaluation • NPDES Phase II Permit Compliance • Financial Management Evaluation • Recommended Plan

  27. Significant Recommendations of the Masterplan • Move forward in establishing funding source for storm water. • Establish uniform approach to development submittals. • Continue relying on development-based storm water management until Phase II guidelines are more advanced.

  28. Storm Water Sampling • Started sampling storm water in Bozeman in 2007. • As with all Cities in Montana, the results were mixed. • Too early to get anything definitive from one sampling.

  29. Most Recent Sample Results(Taken 11/13/08)

  30. Nutrients in Storm water vs. Waste water effluent

  31. Going forward from here… • Actively working with MSU and other organizations to explore new options regarding storm water and storm water education.

  32. Questions/Discussion

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