2009 City of Bozeman Storm Water Update

Dustin Johnson, P.E.Project EngineerCity 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

Transportation

Growth Plan

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 EngineeringPipe sizing and types

Basin sizing

Basin Location

Slope requirements

Calculation formats

COB Runoff CoefficientsRainfall 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

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

$28,000 $3,100

$203,500 $120,000

$20,000 $49,400 Public Outreach and Ed-ucation

Public Involvement and Participation

Illicit Discharge Detection and Elimination

Construction Site Storm Water Runoff Control

Post-Construction Storm Water Management

Pollution Prevention and Good Housekeeping for Municipal Operation

Total cost of $424,000 for 5 years

Summary of Direct costs for Storm Water Maintenance

Activity CostClean 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 CostDirect 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) (mg/l) (mg/l) (mg/l) (mg/l)

TSS 125 12 13 60 322

Oil and Grease 10 ND ND 4.5 14

Nitrogen (Total) 2 0.8 0.8 0.8 ND

Phosphorus 0.41 0.09 0.07 0.4 0.91

Zinc 0.21 0.01 ND 0.08 0.18

Lead 0.165 ND ND ND 0.03

Copper 0.04 ND ND ND 0.03

COD 80 14 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 0.07 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