6Why are Storm Water facilities necessary? Flood ControlChannel Stability of Creeks and RiversWater QualityPotential Re-use of rain water
7Storm water Engineering Pipe sizing and typesBasin LocationBasin sizingSlope requirementsCalculation formatsCOB Runoff CoefficientsRainfall CurvesFloodplain Regulations
8Types of Storage/Treatment Facilities Retention BasinsDesigned to retain all runoff from a 10 year, 2 hour storm.Detention BasinsRelease water through controlled outlet structure, at no greater than pre-development runoff.
9Retention Basins Q = CiA (cfs) V = 7200Q (cubic feet) Calculations based on the Rational FormulaQ = CiA (cfs)V = 7200Q (cubic feet)i for Bozeman 10 year, 2 hour storm always = .41 in/hr
10Detention Basins More complicated than Retention Basins Determine Tc, Tc, and Q of pre-development runoffDetermine Tc and Tc of post-development runoffDetermine maximum storage volume at various storm lengths for 10 year stormDetermine size of discharge structure
14Local Examples of Storm Water Management The Good
15Local Examples of Storm Water Management The Bad
16NPDES Phase II National Pollutant Discharge Elimination System Federal EPA regulated by Montana Department of Environmental QualityThe purpose is to reduce or eliminate potential storm water pollutants from reaching water resources such as streams and lakes.
17Who is permitted for Phase II in Bozeman? Continued partnership with MSU and MDT as co-permittees on MS4 Phase II.
19Montana Cities implementing Phase II Billings & Yellowstone CountyMissoula & Missoula CountyGreat Falls and Cascade CountyButteBozemanHelenaKalispell
20Phase II 6 Minimum Control Measures (MCM) Public Education and OutreachPublic Involvement/ParticipationIllicit Discharge Detection and EliminationConstruction Site Runoff ControlPost Construction Storm Water ManagementPollution Prevention and BMP’s
21Total Minimum 5 year Direct Costs for Phase II Total cost of $424,000 for 5 years
22Summary of Direct costs for Storm Water Maintenance ActivityCostClean Storm Sewer Facilities and Ditches$30,731Repair Storm Sewer System$8,860Leaf Cleanup$32,650Street Sweeping$108,624Miscellaneous$9,739TOTAL$190,604All costs based on 2005 estimates taken from COB Storm Water Masterplan
23Estimated Total Future Storm Water Costs ItemCostDirect Operational Cost$191,000Phase II Implementation$100,000Capital Improvements$200,000Indirect Costs (20% of total)$98,000Total Cost per Year$589,000All costs based on 2005 estimates taken from COB Storm Water Masterplan
24Where are we today with Phase II Completed year four of a five year permitRequired semi-annual storm water samplingContinue working with our co-permitees MSU and MDTNew engineering standardsUpdated public informationCompleted Storm Water Masterplan
25Storm Water Masterplan Adopted by City Commission late 2008Is available for public review and use
26Masterplan Breakdown Existing System Inventory System Analysis Policy EvaluationNPDES Phase II Permit ComplianceFinancial Management EvaluationRecommended Plan
27Significant 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.
28Storm 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.
30Nutrients in Storm water vs. Waste water effluent Total NitrogenTotal PhosphorusEstimated current effluent removal Quality for WWTP9 mg/L3 mg/LEstimated effluent removal Quality for WRF expansion (phase I)7.5 mg/L1 mg/LSample taken 7/25/08 at storm drain in Tamarack1.4 mg/L2.14 mg/LSample taken 7/25/08 in Boz. Creek upstream from Kagy0.6 mg/L0.07 mg/LSample taken 11/13/08 in Boz. Creek below Tamarack0.8 mg/L
31Going forward from here… Actively working with MSU and other organizations to explore new options regarding storm water and storm water education.