How do you stop erosion on a graded lot?
Cover bare ground quickly and slow the water down. Silt fence on the downhill edge catches mud, erosion blankets hold seeded slopes, rip rap protects the ground where a pipe empties, and seed builds the permanent cover. On any slope steeper than 3:1 (3 feet across for every 1 foot of rise), seed alone is not enough in Missouri; it needs a blanket over it.
| Method | Where it goes | What it does | Lasts |
|---|---|---|---|
| Silt fence | Perimeter or downhill edge of the work area | Slows sheet flow and catches sediment | Temporary |
| Erosion control blanket | Seeded slopes; needed on any slope steeper than 3:1 | Holds the surface and keeps seed moist | Temporary |
| Rip rap apron | Culvert, pipe, and concentrated flow outlets | Absorbs outlet energy and prevents scour | Permanent |
| Seeding and mulching | All disturbed ground | Builds vegetative cover | Permanent once established |
| Check dams | Drainage channels and swales | Slow water so sediment drops out | Temporary |
The cheapest erosion control: disturb as little ground as possible, for as short a time as possible. Grade one area, stabilize it, then move to the next. That beats any temporary measure on a fully stripped lot.
Why does Jefferson County erode so fast?
Clay soaks up water slowly, so rain runs off it. On a graded lot there are no roots or organic matter to slow that runoff, and the terrain at the northern edge of the Ozark plateau speeds it up. Missouri averages over 40 inches of rain a year, and a large share falls in spring and early summer, when most grading happens. Winter freeze-thaw cycles loosen the surface too, so anything put down in October has to hold until March.
What makes each method work?
Silt fence is a fabric barrier staked along the downhill edge. Its bottom edge has to be trenched into the ground; fabric pinned to the surface lets water run under it in the first storm. It also has to be cleaned out and repaired after rain, or it fills and fails.
Erosion control blankets are jute or coconut fiber mats pinned over seeded slopes. They hold the soil, keep the seed moist, and rot away as the grass takes over. Pin them closely: wet clay is slippery, and a blanket that slides off position protects nothing.
Rip rap aprons are pads of large stone where a culvert or drain pipe empties. Fast water leaving a pipe digs a hole that eventually undermines the pipe. Aprons are often skipped on homes, and the missing apron is one of the more common failures J1S sees. See what rip rap is.
Check dams are small rock or log barriers set across a ditch or swale at intervals. They slow the water so mud drops out before it leaves the property.
What does not work in Missouri clay?
- Straw wattles alone on steep grades. They help where water moves slowly. On a steep slope they add to a blanket; they do not replace it.
- Seeding a slope in spring with no blanket. Seed takes weeks to grow, and the first half-inch rain can carry off the topsoil and the seed with it.
Do I need an erosion control permit?
If the disturbance is under one acre, a state NPDES permit isn't required. Jefferson County and individual municipalities may have local stormwater requirements regardless of project size. J1S pulls the applicable permits for all work requiring them.
At one acre or more, Missouri DNR requires a land disturbance permit and a stormwater pollution prevention plan (SWPPP) before ground is broken. The plan lists the erosion measures to install, maintain, and inspect. On larger projects an engineer usually prepares it.
How J1S handles erosion control
Erosion control is part of the grading scope, and on residential projects it is included in the base quote. Silt fence goes in on day one. Graded areas get erosion blankets and temporary seed before the job closes, and permanent drainage outlets get rip rap. On permitted commercial or subdivision work, we install and inspect the measures in the engineer's SWPPP. See the land grading cost guide for pricing.
Frequently asked questions
How long does erosion control last?
Silt fence and erosion blankets stay in place through construction and until grass is established, usually one full growing season. Rip rap and established, planted slopes are permanent.
What if mud washes into my yard?
Document it with photos and timestamps. For projects over one acre that should have a land disturbance permit, contact Missouri DNR's stormwater program. For smaller projects, Jefferson County Public Works is the first call.
What is the best grass for a slope?
For fast cover during construction, annual ryegrass; it germinates in ten to fourteen days. For permanent cover, tall fescue, which suits Missouri clay, blended with native grasses and legumes. Slopes steeper than 3:1 do well with native warm-season grasses such as big bluestem and switchgrass, whose deep roots hold clay long-term.
Sources
- Missouri Department of Natural Resources, Construction Land Disturbance Permits: a land disturbance permit for construction disturbing one acre or more, with a stormwater pollution prevention plan as its main requirement.
- EPA, Stormwater Discharges from Construction Activities: the Clean Water Act permit requirement for construction disturbing one acre or more.