Sediment Control on Oregon Job Sites: Silt Fence, Wattles & Basins

Keeping Dirt Where It Belongs

The moment you strip vegetation and break ground, soil becomes mobile. Rain hits bare earth, picks up sediment, and carries it off the site — into streets, storm drains, ditches, and ultimately Oregon's streams and rivers. That muddy runoff is a real environmental problem and a regulated one. Sediment control is the set of practices that keep disturbed soil on the job site until the ground is stabilized again.

These practices are called BMPs — best management practices — and on Oregon construction sites they aren't optional. This guide walks through the common ones and when each applies. For the broader picture, see our Oregon drainage guide and the related erosion control excavation guide.

Erosion Control vs. Sediment Control

A quick distinction worth understanding: erosion control prevents soil from being dislodged in the first place — cover, mulch, seeding, blankets. Sediment control catches soil that has already started moving, before it leaves the site. A good plan uses both: stop erosion where you can, and trap whatever still gets loose. The BMPs below are mostly sediment control, the second line of defense.

Silt Fence

Silt fence is the most recognizable sediment BMP — that line of black fabric on wooden or metal stakes around the downhill edge of a site. It works as a perimeter barrier: runoff hits the fence, water slowly passes through or ponds behind it, and the sediment drops out instead of leaving the site.

Silt fence works best on the down-slope perimeter where sheet flow (shallow, spread-out runoff) reaches it. Its key requirements: the bottom edge has to be trenched into the ground so water can't undercut it, and it has to be maintained — sediment removed before it overtops, tears repaired, undermined sections re-set. Silt fence is for sheet flow, not concentrated channel flow, which will overwhelm and breach it.

Wattles (Fiber Rolls)

Wattles are tubes of straw, coir, or other fiber, staked along contours or in channels. They're the flexible cousin of silt fence. A wattle slows runoff, spreads it out, and traps sediment as water filters through or ponds behind the roll.

Silt fence vs. wattle comes down to placement and flow:

• Silt fence for the site perimeter and sheet flow, where you want a continuous barrier.
• Wattles along slopes to break up flow length, in small channels and swales, and around inlets, where their flexibility and ability to follow the ground shine.

Wattles are quick to install, conform to uneven ground, and are easy to reposition as the site changes — which is why they often supplement silt fence rather than replace it.

Inlet Protection

Storm drain inlets are the express lane for sediment to leave a site. Inlet protection — fabric wraps, gravel bags, or manufactured inserts around and over catch basins and drop inlets — filters runoff before it enters the storm system. Every active inlet receiving site runoff needs protection, and it needs cleaning out as sediment collects so it doesn't clog and cause flooding.

Sediment Basins and Traps

For larger sites or where a lot of runoff concentrates, a sediment basin or sediment trap is an excavated pond that holds runoff long enough for sediment to settle out before the cleaner water is released. Basins are sized to the drainage area and the expected sediment load, and they need periodic cleanout as they fill. They're the heavy-duty option for sites where perimeter BMPs alone can't handle the volume.

Stabilized Construction Entrance

Trucks track mud onto public roads, and that tracked sediment washes into storm drains. A stabilized construction entrance — a pad of large, clean rock where vehicles enter and exit — knocks mud off tires before they reach pavement. It's a simple BMP that addresses a sediment path many people overlook, and it's commonly required.

The BMPs Work as a System

No single BMP handles a site alone. A typical Oregon plan layers them: stabilized entrance at the access point, silt fence and wattles around the perimeter and slopes, inlet protection on every drain, and a sediment basin where runoff concentrates — all backed by erosion control like cover and seeding on disturbed areas. Together they keep soil on site through Oregon's wet season.

And maintenance is half the job. BMPs that aren't inspected and cleaned fail — silt fence overtops, inlets clog, wattles get buried. On permitted sites, regular inspection (especially after storms) isn't just good practice, it's required.

Permits Tie It Together

Sediment control isn't freelance. On sites disturbing an acre or more, the Oregon DEQ 1200-C construction stormwater permit requires an erosion and sediment control plan specifying which BMPs go where, plus inspection and recordkeeping. Our DEQ 1200-C stormwater permit guide covers when it applies and what it demands.