Storm Water System

Stormwater runoff is a major cause of water pollution in urban areas. When rain falls on our roofs, streets, and parking lots in cities and their suburbs, the water cannot soak into the ground as it should. Stormwater drains through gutters, storm sewers, and other engineered collection systems and is discharged into nearby water bodies. The stormwater runoff carries trash, bacteria, heavy metals, and other pollutants from the urban landscape into those water bodies.  Today cities and urban areas regulate storm water systems to help improve water quality by using various methods to remove pollutants from storm water before it enters our water bodies.  These methods include Best Management Practices, Low Impact Development and Green Infrastructure.

Due to the size of the City of Helena, our storm water system is regulated under the Montana Pollution Discharge Elimination System General Permit for Storm Water Discharges Associated with Small Municipal Separate Storm Sewer Systems (General Permit) issued by Montana Department of Environmental Quality. The City has developed a Storm Water Management Plan in accordance with the General Permit requirements.  New additions of infrastructure to the system and new connections that will discharge to the storm sewer system must be developed to meet the requirements in the General Permit, the Storm Water Ordinance under City Code 6-6-1, the Engineering and Design Standards, and the system must be operated to apply Best Management Practices to protect storm water quality.

The Utility Maintenance Division maintains and operates the storm sewer system.  The storm sewer system consists of approximately:

  • 70 miles of storm pipe, which range from 8 inch to 90 inch pipes
  • 30 miles of open storm drainage channels
  • 700 manholes
  • 1,800 storm inlets

If you see any maintenance needs, such as clogged inlets, eroding channels or poor drainage, please report them to:  Utility Maintenance Division at 447-8567 or the Engineering Division at 447-8431.

Storm Water Management Program

Storm Water Management Program

Federal regulations require municipalities and other operators of storm water systems to obtain authorization to discharge storm water under the National Pollution Discharge Elimination System.  Due to Helena's size, we are required to obtain authorization to discharge storm water as a Phase II community (See EPA Storm Water Phase II Final Rule, Fact Sheet 1.0.)

The General Permit for Storm Water Discharges Associated with Small Municipal Separate Storm Sewer Systems requires permittees to develop, implement, and enforce a Stormwater Management Program (SWMP). The SWMP is designed to reduce the discharge of pollutants from the permitted Municipal Separate Storm Sewer System (MS4) to the Maximum Extent Practicable (MEP), to protect water quality, and satisfy the appropriate water quality requirements of the Montana Water Quality Act.

The Storm Water Management Program consists of Best Management Practices (BMPs) for each of the six Minimum Control Measures (MCMs) as identified in the Permit:

  • Public Education and Outreach
  • Public Participation and Involvement
  • Illicit Discharge Detection and Elimination
  • Construction Site Storm Water Runoff Control
  • Post Construction Storm Water Management for New Development and Redevelopment
  • Pollution Prevention/Good Housekeeping for Municipal Operations

The Storm Water Management Program is available here.  The public is encouraged to review and comment on the SWMP at anytime.  If you have any comments please contact:

Matt Culpo - Stormwater Engineer
(406) 447-8073

Each year, the City of Helena prepares a Storm Water Small MS4 Annual Report which is submitted to the Department of Environmental Quality.  Last year’s annual report may be accessed at the following link: Small MS4 Annual Report.

The City of Helena also partners with the Lewis and Clark County Water Protection District (District). The District was formed in 1992.  Its mission is to preserve, protect and improve water quality within District boundaries which includes the City of Helena and the Lake Helena Watershed.  The District also provides outreach and education opportunities to the public. More information can be found at the Lewis and Clark County Water Quality Protection website:

For additional information related to storm water protection at home and to see how you can take part, please see our Storm Water Runoff Pollution and Clean Water Begins at Home flyers.

Illicit Discharges

Illicit Discharges

In general, only stormwater and water from the City water distribution system are allowed to be discharged into the storm drainage system.  Illicit discharges are defined as a storm drain that has measurable flow during dry weather containing pollutants and/or pathogens and any discharge to the storm sewer system that is not composed entirely of storm water, with exceptions for discharges allowed under the General permit, for example: waters used for firefighting operations, hydrant flushing or car washing.  A storm sewer with measurable flow but containing no pollutants is simply considered a normal storm water discharge and generally consists of storm water runoff or groundwater infiltration.  The Environmental Protection Agency’s, Storm Water Phase II Final Rule for Illicit Discharge Detection and Elimination Minimum Control Measure can be found here: IDDE Rule.

To report any suspected discharges or dumping of pollutants into the stormwater system, referred to as illicit discharges, please immediately contact:

Matt Culpo - Stormwater Engineer
(406) 447-8073

Low Impact Development and Green Infrastructure

Low Impact Development and Green Infrastructure

The term Low Impact Development (LID) refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat. Green infrastructure (GI) is the patchwork of natural areas that provide habitat, flood protection and cleaner water.  At both the site and regional scale, LID/GI practices aim to preserve, restore and create green space using soils, vegetation, and rainwater harvest techniques. LID is an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. LID employs principles such as preserving and recreating natural landscape features, minimizing effective imperviousness to create functional and appealing site drainage that treat stormwater as a resource rather than a waste product. There are many practices that have been used to adhere to these principles such as bioretention facilities, rain gardens, vegetated rooftops, rain barrels, bioswales and water quality ponds. By implementing LID principles and practices, water can be managed in a way that reduces the impact of development and promotes the natural movement of water within an ecosystem or watershed. Applied on a broad scale, LID can maintain or restore a watershed's hydrologic and ecological functions. 

The City of Helena, as part of a MS4 working group and in cooperation with the Montana Department of Environmental Quality, has prepared the Montana Post-Construction Storm Water Best Management Practices Design Guidance Manual (BMP Manual).  These best management practices identified in the BMP Manual represent green infrastructure that can be applied individually or in combination to a development or redevelopment to provide a LID system.  The BMP Manual provides design guidance for achieving the storm water quality requirement in the Engineering and Design Standards for treatment of runoff from the 0.5 inch precipitation event. 

Rain Gardens

The City of Helena encourages property owners to use Rain Gardens wherever possible to improve water quality and your property.  The City of Helena has prepared the following Rain Garden flyer related to design and construction of Rain Gardens in the Helena area.

Construction Storm Water

Construction Storm Water

An owner or operator of a construction activity is required to obtain authorization under the General Permit for Stormwater Discharges Associated with Construction Activity for construction activities that include clearing, excavating, grading, grubbing, or placement/removal of earth material with a total area of one or more acres.  An owner or operator is a person who owns, leases, operates, controls, or supervises the construction activity.  To apply for an authorization under the General Permit within the City of Helena submit a complete Notice of Intent Application Package including Storm Water Pollution Prevention Plan forms to the Building Department with your building permit application and to DEQ.  Go to the following link for information related to the General Permit requirements and to obtain the application package and forms:

For additional information please see our Storm Water and Construction Flyer.