Silt Fence & Sediment Control in Minneapolis, MN

Silt fence and sediment control are the pieces of an erosion control plan that catch soil after it starts moving. In Minneapolis they show up on teardowns, additions, garage rebuilds, utility trenches, commercial sites and new subdivisions. Our crews handle silt fence installation, inlet protection on storm drains, maintenance through the job and removal once the ground has grass. Builders and homeowners looking for silt fence contractors usually need us before any digging starts, because that is when the permit expects the fence to be in.

Why it is required

Minneapolis enforces Chapter 52 of its code to keep sand and dirt from leaving construction sites. Any disturbance over 500 square feet or 5 cubic yards needs an erosion and sediment control permit, and that includes demolition and utility excavation. Above 5,000 square feet, the city requires an approved erosion control plan first. On sites of an acre or more, the state construction stormwater permit applies as well, and it requires sediment control on all downgradient perimeters before land disturbance begins and protection on all storm drain inlets until the areas draining to them have permanent cover.

Silt fence done properly

Silt fence is geotextile fabric on stakes, set across the slope on the downhill side of bare soil. It slows runoff so sediment settles out behind it. It only works if the bottom of the fabric is buried in a trench so water cannot run underneath, the posts are on the downhill side, and the line follows the contour instead of running straight down a slope where it becomes a channel. Ends are turned uphill so water does not just go around. Most failures we see are fences that were stapled to the surface or run across a concentrated flow path they could never hold.

Inlet protection

Street catch basins and yard drains carry runoff straight to lakes, creeks and the Mississippi. Inlet protection traps sediment before it gets there. Depending on the inlet and traffic, that may be a filter bag under the grate, a fabric or sandbag barrier around a yard drain, or a gravel and mesh barrier. On city streets the device has to keep sediment out without flooding the road during a storm, so we pick and set them with that in mind.

Maintenance and the half-height rule

A silt fence is not install-and-forget. The state permit requires perimeter controls to be repaired, replaced or supplemented when they stop working or when sediment reaches half the height of the device, by the end of the next business day after it is found. It also calls for inspection after any rain over half an inch in 24 hours. We offer maintenance visits to clean out sediment, restake sagging sections and replace torn fabric, so the fence passes inspection after every storm. The permit also expects all inspections and maintenance to be written down, and the records kept on site during working hours. When we do maintenance, we send the date, what we found and what we fixed, so the permit holder has it for the log.

Coming down at the end

The fence stays until the ground behind it has permanent cover. Pulling it early lets the next storm carry soil off a site that was nearly done. When the grass is established, we pull the fence, smooth the trench, and seed the strip where it stood. Many of our silt fence jobs end the same way they started: with hydroseed.

Small residential jobs

Silt fence is not just for subdivisions. A garage teardown and rebuild, a basement walkout, a new driveway or a sewer line replacement on a city lot can cross the 500 square foot threshold quickly, and the permit then expects perimeter control and protection for the nearest catch basin. On those jobs we often install a single run of fence along the alley or street side, protect the inlet at the curb, and set a rock pad or other tracking control where trucks go in and out. The state permit asks for a vehicle tracking control on larger sites before work starts, and the same idea keeps mud off city streets on small ones.

Stockpiles and winter

Topsoil and spoil piles are a common source of sediment. The state permit calls for sediment control at the base of stockpiles, and we ring them with fence or other barriers the same way we protect a perimeter. Winter adds its own problem. When a site shuts down for frozen conditions, the permit requires an inspection after runoff occurs in spring, and the first thaw often finds fence pushed over by plowed snow or buried under it. We can check and repair fence at thaw, before the first spring rain, so the site starts the season with its controls working.