What Are Those Black Fences Around New Construction? A Quick Guide.

You've seen them on every construction site in Austin. Short black fabric fences staked into the dirt around the perimeter of a lot. Little black tubes wrapped around storm drains. Orange plastic fencing separating one lot from the next.

Most people assume they're there to keep people out. They're not.

Those are erosion and sediment controls, and they're required by law. They exist to keep dirt from leaving the construction site and ending up in the storm drain, the creek, and eventually the water supply. Every construction project in Texas that disturbs more than an acre of ground is required to install and maintain them under a state permit.

Here's what each one actually does.

What is the black fence called and what does it do?

That's silt fence. It's woven geotextile fabric, usually backed with wire mesh, stretched between steel posts and buried several inches into the ground.

When it rains, water carrying loose soil runs downhill and hits the fabric. The water slowly passes through and ponds behind it, and the sediment settles out instead of continuing downstream. It's not filtering the water so much as slowing it down long enough for the dirt to drop out.

That's why silt fence is always installed along the low side of a site. Water goes downhill and the fence has to be where the water is going.

What are the black tubes around storm drains?

Those are inlet protection devices. They wrap or sit over the storm drain opening and catch sediment before it enters the drainage system.

If sediment gets into a storm drain it goes straight into the nearest creek or waterway. That's exactly what the permit is designed to prevent, which is why you'll see inlet protection on every drain within or downstream of an active construction site.

Why is there orange plastic fencing between lots?

That's usually construction fence separating an active build from a completed home or a protected area.

It marks a boundary so equipment operators know where they can and can't drive, and it keeps construction traffic off finished lawns, driveways, and landscaping. On sites with protected trees you'll also see orange or chain link fencing around the tree canopy — that's tree protection fencing, and it keeps equipment from compacting soil over the root zone.

What are the rock pads at construction site entrances?

Stabilized construction entrances. A layer of large crushed rock over geotextile fabric, usually fifty feet long, at every point where vehicles enter and exit the site.

The rock knocks mud off tires before trucks reach the public road. Without it, every vehicle leaving the site tracks dirt onto the street, where it washes into the storm drain the next time it rains. Tracking mud onto a public roadway is a violation, and the contractor has to clean it up immediately.

Why are these still here after the house is finished?

They shouldn't be, and this is where a lot of sites fall short.

Erosion controls are temporary. Once the site reaches final grade and permanent ground cover is established, they're supposed to be removed. Leaving silt fence in place after construction is done means someone stopped paying attention.

You'll sometimes see silt fence half buried, falling over, or full of accumulated sediment on lots where homes were finished months ago. That's a sign that either nobody was maintaining them during construction or nobody came back to remove them at close-out.

Do these things actually matter?

Yes, and the consequences are real.

Construction sites in Texas operate under a stormwater permit issued by the state. That permit requires controls to be installed before ground is disturbed, inspected regularly, repaired promptly, and removed only after the site is permanently stabilized with vegetation.

Sites that don't comply face fines that climb into serious money fast. More practically for the builder, the permit can't be closed until the site is stabilized — which means the project isn't actually finished, the paperwork stays open, and the liability stays with them.

What does "permanently stabilized" mean?

It means the disturbed ground is covered with established vegetation — typically seventy percent uniform cover — so soil isn't washing away anymore.

That's usually accomplished with hydroseeding or sod. Once the ground cover is established and the inspector signs off, the temporary controls come out and the permit closes.

This is the part of the process most homeowners never think about, but it's the reason you sometimes see a finished house sitting on bare dirt for months. The builder is either waiting for the right season, waiting for a sub, or hasn't gotten to it yet.

If you're staring at a site that isn't finished

Whether you're a homeowner wondering why the dirt around your new house still looks like a construction zone, or a builder who needs a site closed out, that's exactly what we do.

We're based in Southwest Austin and we handle erosion control and hydroseeding across Travis, Hays, and Blanco Counties. We install the controls, maintain them through construction, and get the ground covered so the permit can close.

Give us a call or send an email if you've got questions about a site. Happy to help.