Erosion And Sediment Control Inspections

Driving along Snelling Avenue, you feel the warmth of the rising sun on your face as you commute to work. You glance around, noticing dozens of construction projects underway, taking advantage of good weather before the Minnesota winter comes back around. At one of the sites, you see us, Capitol Region Watershed District (CRWD)’s Regulatory staff, wearing our signature blue hard hats during an active construction site inspection.

Water and Construction

Imagine a construction site where workers dig up and move soil, bulldozers roll across the area, and trucks pour concrete. Have you ever considered what happens to a construction site when it rains? Water carries exposed soil, which may be contaminated with onsite chemicals or concrete waste, to the nearest storm drain. Unlike sanitary sewers, storm sewers carry runoff directly to our local water bodies without treatment, meaning any sediment or pollutants the water picks up on its journey from the construction site to the storm sewer system can negatively impact water quality in lakes, wetlands, and the Mississippi River.

So, how does CRWD help prevent water pollution from construction sites?

CRWD’s Role

CRWD’s Regulatory division helps prevent water pollution from construction sites by:

  • Requiring a permit for all sites that disturb more than one acre of land,
  • Monitoring active construction sites for erosion and sediment control through weekly inspections to prevent stormwater pollution and
  • Enforcing the use of erosion and sediment control practices.

Erosion and Sediment Control Practices

What are the differences between erosion control and sediment control, and why are they essential to water quality?

Picture a large pile of soil on a construction site. What will happen if you take a cup of water and pour it on the pile? The water will carve a path down the side, carrying some sediment from the upper slopes down towards the bottom, where it fans out. Erosion control practices stabilize exposed soil and prevent this carving action by reducing the surface area of bare soil, either temporarily with blankets or mulch, or more permanently by establishing grass and/or plants.

Sediment control, on the other hand, focuses on preventing any eroded soil from moving offsite. Sediment control best management practices (BMPs) often fall into three different categories:

  • Perimeter control
  • Sediment tracking, and
  • Inlet protection.

Perimeter controls are barriers to prevent sediment movement from a particular location. The different types of barriers include biologs, silt fencing, and soil berms, which can vary in use depending on the specific situation. As the name suggests, perimeter controls typically encircle the outside of an active work zone and any large piles to prevent sediment from leaving the area when it rains.

Sediment tracking BMPs control the sediment that exits a construction site on the wheels of equipment. The tires and tracks of construction machinery can get extremely muddy when it rains. Even under dry conditions, tires and tracks can pick up a lot of soil and other pollutants. Without sediment tracking BMPs, sediment on tires is carried off the work site and onto nearby roads. Sediment on roads poses a hazard to pedestrians and drivers, and it pollutes nearby lakes and the Mississippi River when carried into storm drains. Sediment tracking BMPs, such as tracking mats or rock construction exits, in combination with street sweeping, help reduce sediment on the road.

Inlet protection is the last line of defense against sediment pollution from construction sites. Inlet protection involves covering or adding bags to storm drains near construction sites to prevent sediment from entering the storm sewers.

These erosion and sediment control BMPs at active construction sites work together to stabilize disturbed soils, prevent sediment movement offsite, and protect clean water. The Minnesota Pollution Control Agency (MPCA) has a graphic that illustrates the 10 Steps to Stormwater Pollution Prevention PDF.

Inspection Walkthroughs

Now that you understand erosion and sediment control, how do we apply these principles during our active construction site inspections?

Construction projects that disturb an acre or more of land within CRWD’s boundaries, require a permit. CRWD Rules outline how to manage erosion and sediment control on active construction sites, along with guidelines for permanent stormwater management BMPs. We track the permits and divide them among our division’s staff, so each person has a dedicated list of sites to visit for ongoing inspections during active construction.

When we visit a site for an erosion and sediment control inspection, we start with a site walkthrough. The walkthrough involves wearing proper safety equipment and touring the site to note the erosion and sediment control BMPs. We examine the exterior of the site to look at the construction exit and the perimeter control, making sure the BMPs are present, not damaged, overlapping sufficiently, and flush with the ground. We also look at adjacent roads to note any sediment tracking from the site and to locate storm drains, checking for inlet protection and ensuring they are clear of sediment, trash, and vegetation residue.

For erosion control, we look for gullying and rutting, or the formation of valleys in any piles or slopes of soil, and make sure erosion control blankets are laid flat on the ground with a uniform slope. Erosion control practices also apply beyond active construction and may involve a classic case of watching grass grow until the site reaches at least 70% coverage on disturbed soils, at which point their CRWD permit can be closed. Other key aspects of erosion and sediment control inspections include monitoring the construction site for washout of concrete or other hazardous materials and for dewatering, the process of removing excess or accumulated water from a site.

To supplement CRWD’s inspections, contractors are also expected to conduct their own sediment and erosion control inspections weekly and after every half-inch rainfall. They are required to have a Stormwater Pollution Prevention Plan (SWPPP) for the site to outline the site-specific details of how to manage stormwater and erosion and sediment control, often including a map of BMP locations and key reminders regarding stormwater structure installation.

Basics of Inspection Reports

Construction sites vary in size and extent, ranging from a single lot to an entire establishment, and no two are entirely alike. We often gather dozens of photos and notes during an inspection. When we return to the office after an inspection, we process our observations into a digestible report. Our inspection reports serve as a key form of communication with the site crew to identify areas for improvement in erosion and sediment control onsite.

Inspection reports categorize erosion and sediment control BMPs into nine sections:

  1. Perimeter Control,
  2. Inlet Protection,
  3. Stabilized Construction Exit,
  4. Sediment Tracking/Accumulation,
  5. Soil Stabilization,
  6. Concrete and Other Washout Waste,
  7. Inspections and SWPPP Updates,
  8. Dewatering, and
  9. Other

Each category addresses different CRWD and MPCA rules. We include pictures of any problematic areas we observed for each section and provide detailed captions describing the necessary actions. We summarize our conclusions in the main body of the report and rate each section into four categories:

  • Compliant: There are no issues with BMP use in a specific section.
  • Action Required: There is a lack of or misuse of proper BMPs.
  • Non-Compliant: We flagged this category as ‘Action Required’ during a previous inspection, and the contractor has yet to resolve the issue.
  • Not Applicable.

The collective characterization of each section contributes to an overall site grade of ‘A’ through ‘F.’ The most common grades are ‘B’ and ‘C,’ depending on the level of compliance. We send completed inspection reports to onsite supervisors, city, county, or state partners, and/or company leaders so they can use the report to identify and tackle erosion and sediment control problems around their site before the next CRWD inspection. When we return to a site after a week or two, we expect that the contractors have addressed the issues identified in the previous inspection. We conduct inspections throughout the entirety of the construction project, from the moment erosion and sediment control BMPs are in place through the end of construction and permanent restoration, to prevent continual erosion and sediment loss onsite and to protect local water resources.

Understanding Construction Plans and Communication

Although erosion and sediment control inspections are our primary focus, we must also understand construction plans and how to communicate with contractors. We spend hours before inspections reviewing construction plans to understand the existing and future site layout, the locations of storm and sanitary sewer lines and utilities, and the planned erosion and sediment control BMPs. Reviewing the construction plans helps us achieve our goal of understanding the project as a whole and how construction will contribute to water flowing to storm sewers.

Onsite, we also often conduct inspection walkthroughs with the site superintendents, so that the contractors have a better understanding of where BMP issues are located on their site and can ask questions. We must develop strong professional relationships with the contractors to ensure proper BMP use. A level of trust is necessary for us to have civil, proactive conversations and action to quickly address any erosion and sediment control issues.

2025 Inspection Season

We are improving and maintaining local water quality throughout another busy construction season. So far this year, we have 25 new inspection sites, with more to come, in addition to ongoing projects from previous years. For context, in 2024, we received 42 permit applications!

To assist with the influx of active construction site inspections, our division hires a current student or recent graduate to fill the role of seasonal Permit Inspector every summer. As the newest hire for this position, I have become immersed in the world of erosion and sediment control. I’m using my position to not only apply what I learned in school but also to continue exploring and honing my professional interests, all while refining my understanding of BMPs and stormwater systems. The permit inspector role also provides a key introduction to local government operations and environmentally focused regulatory work. The work I do in this position has visible impacts, and I know that each day I go to work, I am making a difference.

Do-It-Yourself Erosion and Sediment Control

Now that you understand the basics of erosion and sediment control, how can you make a difference? Although you likely have little control over construction sites, you can take note of potential erosion and sediment control concerns in your yard. Do you have bare patches of soil? Are there areas where water has carved a path into the ground? If these are present in your yard, consider taking action to stabilize the soil by filling in holes, reseeding bare spots, and protecting the area with mats, mesh, or other soil stabilization methods until you achieve at least 70% vegetation coverage. Even your small-scale action goes a long way toward protecting clean water in our lakes and the Mississippi River.

About the Guest Author

Erin Hudson (she/her) is the seasonal Permit Inspector for the summer 2025 season. She recently graduated from the University of Minnesota with degrees in Environmental Geosciences and Spanish Studies. Erin will begin graduate studies at the University of Arizona in the fall, where she will research remediation methods for heavy metals in water.