6 Why are Storm Water facilities necessary? Flood ControlChannel Stability of Creeks and RiversWater QualityPotential Re-use of rain water
7 Storm water Engineering Pipe sizing and typesBasin LocationBasin sizingSlope requirementsCalculation formatsCOB Runoff CoefficientsRainfall CurvesFloodplain Regulations
8 Types 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.
9 Retention 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
10 Detention 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
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 QualityThe 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.
19 Montana Cities implementing Phase II Billings & Yellowstone CountyMissoula & Missoula CountyGreat Falls and Cascade CountyButteBozemanHelenaKalispell
20 Phase 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
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 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
23 Estimated 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
24 Where 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
25 Storm Water Masterplan Adopted by City Commission late 2008Is available for public review and use
26 Masterplan Breakdown Existing System Inventory System Analysis Policy EvaluationNPDES Phase II Permit ComplianceFinancial Management EvaluationRecommended 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 LimitsAbove KagyBelow TamarackStorm LanghorStorm Tamarack(mg/l)TSS125121360322Oil and Grease10ND4.514Nitrogen (Total)20.8Phosphorus0.410.090.070.40.91Zinc0.210.010.080.18Lead0.1650.03Copper0.04COD80118627
30 Nutrients 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
31 Going forward from here… Actively working with MSU and other organizations to explore new options regarding storm water and storm water education.
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