The construction industry is a critical participant in our efforts to protect streams, rivers, lakes, and wetlands. As stormwater flows over a construction site, it picks up pollutants like sediment, debris, and chemicals.

Soil disturbance associated with a construction site can increase the potential for excess erosion if not properly addressed and erosion controls that aren’t maintained can cause excessive amounts of sediment and debris to be carried into the stormwater system. Preventing soil erosion and sedimentation is an important consideration at all construction sites. Through the use of Best Management Practices (BMPs), construction site operators are the key defense against erosion and sedimentation.

Do you know?

  • Excess soil erosion from construction projects removes the soil surface layer, rich in nutrients, and transports the sediments into surface waters contributing to sediment loading and pollution transported with the sediments.
  • The excess sediment collects in reservoirs, lakes, rivers, and streams reducing their water holding capacity and quality; and is detrimental to aquatic life.
  • While erosion and sedimentation are natural processes that help shape Montana's rivers and valleys, activities such as highway construction can greatly accelerate these natural processes causing serious and costly problems.
  • High volumes of stormwater can also cause stream bank erosion and destroy downstream aquatic habitat.
  • The implementation of BMPs to prevent soil erosion and the resulting sedimentation from entering the waterways can significantly reduce serious and costly problems in the future.
  • In addition to the environmental impact, uncontrolled erosion can have a considerable financial impact on a construction project. It costs money and time to repair gullies, replace vegetation, clean sediment-clogged storm drains, replace poorly installed BMPs, and mitigate damage to other people's property or to natural resources.

MDT’s Construction Erosion and Sediment Control BMP Manual

The Erosion and Sediment Control BMP Manual is intended to assist Contractors in identifying appropriate pollution prevention and temporary erosion and sediment control measures (or BMPs) for use during construction activities for projects administered by MDT. This manual is also intended to assist MDT personnel in inspecting, maintaining, replacing, and removing BMPs on MDT projects following completion of Contractor operations. Ultimately, these efforts are intended to prevent release of pollutants from construction sites into water resources.

Silt Fence

Source MDT

Erosion Control Blanket and Silt Fence

Source MDT

Check Dams

Source MDT

Bridge Repair

Source MDT

Some Soil Erosion Control Tips

  • Design the site to infiltrate stormwater into the ground and to keep it out of storm drains. Eliminate or minimize the use of stormwater collection and conveyance systems while maximizing the use of stormwater infiltration and bio-retention techniques.
  • Minimize the amount of exposed soil on site. To the extent possible, plan the project in stages to minimize the amount of area that is bare and subject to erosion. The less soil exposed, the easier and cheaper it will be to control erosion.
  • Vegetate disturbed areas with permanent or temporary seeding immediately upon reaching final grade.
  • Vegetate or cover stockpiles that will not be used immediately.
  • Reduce the velocity of stormwater both onto and away from the project area. Silt fences and other types of perimeter filters should never be used to reduce the velocity of runoff.
  • Keep sediment on site.
  • Maintain BMPs to ensure their effectiveness during the life of the project.

DEQ Stormwater Construction General Permit

Any construction activity that results in disturbance of one acre or greater total land area requires Storm Water Construction permit coverage from Montana DEQ. Disturbance is defined as clearing, excavating, grading, grubbing, or placement/removal of earthen material, so the total disturbed area should be accounted for. To apply for coverage, submit a complete application package to DEQ as described in the link above. A Stormwater Pollution Prevention Plan (SWPPP) must be included as part of the application package. See EPA’s guidance for developing your SWPPP.

In addition, if you are located in an MS4, you will need to look at the construction requirements specified by the MS4, as the city or county may require demonstration of coverage under DEQ’s Stormwater Construction General Permit and may require additional permits, plans, forms, and/or fees.

Links to additional MS4-specific stormwater construction requirements that are available are included in the table below.

MS4 Stormwater Construction Requirements
City of Billings Construction Permitting
City of Bozeman Apply for A Construction Permit
City-County of Butte-Silver Bow Stormwater Management: Construction
City of Great Falls Construction Site Storm Water Management
City of Helena Construction Storm Water
City of Kalispell Construction Stormwater Permit
City of Missoula Construction BMP’s & Permits
Cascade County Municipal Separate Storm Sewer System | Cascade County, MT (
Missoula County Missoula County Storm Water Requirements
Yellowstone County Yellowstone County, Montana (

MDT’s Permanent Erosion and Sediment Control Design Guidelines

The Permanent Erosion and Sediment Control Design Guidelines manual describes procedures and methods to address long-term erosion from highway construction and sedimentation from highway-related stormwater runoff. These guidelines include procedures for evaluating the need for permanent erosion and sediment control (PESC) measures during project development and determining which PESC measures can practicably be incorporated into the design. The PESC measures would be intended to reduce soil erosion and sediment deposition into adjacent waterways and to protect the highway facility.

MDT’s Low-Impact Development Practice Analysis

When an MDT design project is located within a regulated MS4 Area, the project will be evaluated for the applicability of the requirement to incorporate Low Impact Development (LID) practices. LID Practices must be evaluated for development or redevelopment projects that disturb a certain amount of area. According to the current MS4 permit, those LID practices will need to infiltrate, evapo-transpire, or capture for reuse, the runoff generated from the first 0.5 inches of rainfall from a 24-hour storm preceded by 48 hours of no measurable precipitation, when practicable. MDT had developed a LID Practice Analysis form that is intended to summarize the LID practice analysis findings for the subject project.