Stormwater Utility Components

The City's Stormwater Utility collects $1.7 million per year from utility rate payers to fund three program components.  They include:

1. Deferred Maintenance - $650,000 per year to fix stormwater system issues that have existed for decades.  Expenses include fixing failed pipes, cleaning clogged infrastructure, and upgrading aged system components.  
2. Utility Operations - $800,000 per year to pay for daily costs required to keep the utility functioning. Expenses include funding 8 full-time positions, reoccurring system maintenance, supplies, permit fees, contracted services, and equipment.
3. System Enhancements - $250,000 per year to pay for expenses associated with infrastructure projects that clean stormwater by capturing sediments, trash, oil, and other pollutants before it is dumped into local waterways.   

Stormwater Utility Rate Model Structure

The City's stormwater rate model is based on two seperate charges. They include:

1. Flat Charge - Charged evenly across the service area and pays for deferred maintenance costs.  Properties with a water meter receive a monthly flat charge of $4.67 per meter.  Properties that do not have a water meter, but do have impervious area, also receive a monthly flat charge.
2. Variable Charge - Charged proportional to the amount of impervious area individual properties have and pays for utility operation and system enhancement costs. Impervious area does not allow water to soak into the ground during rain events creating stormwater runoff.  Larger impervious areas result in an increased impact on public infrastructure and local waterways.

Impervious area data is used to calculate the Variable Charge using an Equivalent Residential Unit (ERU) approach. An ERU is the average impervious area for all single-family residential properties (2,700ft²). The ERU becomes a standard billing unit that is applied towards all properties.  All single-family residential properties are billed for one ERU each month.  Multi-family and commercial properties are billed for multiple ERUs each month depending on their total impervious area.  The monthly charge for one ERU is $3.76

• Single-Family Residential: (2,700ft² of impervious area)/(2,700ft²) = 1 ERU billed monthly
• Multi-Family/Commercial: (18,900ft² of impervious area)/(2,700ft²) = 7 ERUs billed monthly

Stormwater Utility Credit

In 1980, the City implemented a new engineering standard that requires stormwater quantity and quality control infrastructure to be installed with any new development.  Quantity infrastructure temporarily captures stormwater on site and then releases it slowly to waterways at predetermined rates.  Quality infrastructure permanently captures stormwater on the site where it then sits until it infiltrates into the ground. Infrastructure used to achieve these standards often includes detention ponds, retention ponds, bioretention swales, mechanical treatment systems, and permeable pavers.

The City has developed a utility credit for properties that have made investments in these infrastructures. All properties were analyzed to determine if they should receive a credit based on historical aerial photography, record drawings, and inventoried stormwater infrastructure.  A 45% utility credit has been automatically applied to a property's variable charge if their existing infrastructure has been determined to meet the City's engineering standards at the time of development. There are two additional levels of credit available for properties exceeding City’s standard. 

The Stormwater Program Manager will review the original determination decision if a property owner feels that their Stormwater Utility Fee is incorrect or they feel they should receive more credit.  Documentation prepared by a qualified professional may be required to verify that the eligibility criteria outlined in the table below has been met. The City reserves the right to suspend credits if infrastructure is not being maintained.

Example Rate Calculations

Single-family residence without HOA detention pond

• Flat Charge: 1 water meter x $4.67 per water meter = $4.67
• Variable Charge: 1 ERU x $3.87 per ERU = $3.87
• Credit: none - no HOA detention pond
• Total: $4.67 + $3.87 = $8.54/month

Single-family residence with HOA detention pond

• Flat Charge: 1 water meter x $4.67 per water meter = $4.67 
• Variable Charge: 1 ERU x $3.87 per ERU = $3.87 
• Credit: 1 ERU x $1.75 credit per ERU = ($1.75)
• Total: $4.67 + $3.87 – $1.75 = $6.79/month

16,200ft² impervious area multi-family or commercial property without on site stormwater infrastructure

• Flat Charge: 1 water meter x $4.67 per water meter = $4.67
• ERU Calculation: 16,200ft² impervious area/2,700ft² (1 ERU) = 6 ERUs
• Variable Charge: 6 ERUs x $3.87 per ERU = $23.22
• Credit: none – no on site stormwater infrastructure
• Total: $4.67 + $23.22 = $27.89/month

16,200ft² impervious area multi-family or commercial property with on site stormwater infrastructure

• Flat Charge: 1 water meter x $4.67 per water meter = $4.67
• ERU Calculation: 16,200ft² impervious area / 2,700ft² (1 ERU) = 6 ERUs
• Variable Charge: 6 ERUs x $3.87 per ERU = $23.22
• Credit: 6 ERUs x $1.75 credit per ERU = ($10.50)
• Total: $4.67 + $23.22 – $10.50 = $17.39/month

Public Record

• Stormwater Utility Resolution
• Current Stormwater Service Billing Rates
• Municipal Code
• State of Montana Code