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 Q = CiA (cfs) V = 7200Q (cubic feet)
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, Tc, and Q of pre-development runoff
Determine Tc and 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
Activity
Cost
Clean Storm Sewer Facilities and Ditches
$30,731
Repair Storm Sewer System
$8,860
Leaf Cleanup
$32,650
Street Sweeping
$108,624
Miscellaneous
$9,739
TOTAL
$190,604
All costs based on 2005 estimates taken from COB Storm Water Masterplan

23. Estimated Total Future Storm Water Costs
Item
Cost
Direct Operational Cost
$191,000
Phase II Implementation
$100,000
Capital Improvements
$200,000
Indirect Costs (20% of total)
$98,000
Total Cost per Year
$589,000
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)
Permit Limits
Above Kagy
Below Tamarack
Storm Langhor
Storm Tamarack
(mg/l)
TSS
125 12 13 60
322
Oil and Grease 10 ND
4.5 14
Nitrogen (Total) 2
0.8
Phosphorus
0.41
0.09
0.07
0.4
0.91
Zinc
0.21
0.01
0.08
0.18
Lead
0.165
0.03
Copper
0.04
COD 80 11 86 27

30. Nutrients in Storm water vs. Waste water effluent
Total Nitrogen
Total Phosphorus
Estimated current effluent removal Quality for WWTP
9 mg/L
3 mg/L
Estimated effluent removal Quality for WRF expansion (phase I)
7.5 mg/L
1 mg/L
Sample taken 7/25/08 at storm drain in Tamarack
1.4 mg/L
2.14 mg/L
Sample taken 7/25/08 in Boz. Creek upstream from Kagy
0.6 mg/L
0.07 mg/L
Sample taken 11/13/08 in Boz. Creek below Tamarack
0.8 mg/L

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