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 Preliminary Design City Board Review – DRC, DRB, Planning Board, City Commission, etc. Infrastructure Review – City Engineering, DEQ Approval

Review Criteria Zoning Growth Plan Transportation

Engineering Review

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

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

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.

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

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

In a perfect world…

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

When things start to go wrong…

Local Examples of Storm Water Management The Good

Local Examples of Storm Water Management The Bad

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.

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

Storm Water Hierarchy

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

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

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

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

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

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

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

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

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.

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.

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

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

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

Questions/Discussion