Know Your Roll: How to choose between compost socks and straw wattles

Of the seeming thousands of options for erosion and sediment control on construction sites, a few methods jump to the forefront as consistent, tried-and-true ways that can be used in a wide variety of projects: silt fences, check dams, rock roads, temporary grass (of course), compost socks, straw wattles… but wait for a second, those last two are basically the same thing, right? No indeed. Both are effective Best Management Practices (BMPs) for slowing water and causing sediment to settle out, but the situations in which they should be used can be very different.

Straw wattles protecting a sidewalk

Straw wattles are versatile, relatively inexpensive, and easily replaced or disposed of. They provide filtration, help establish vegetation, reduce water velocity, and some are biodegradable or photodegradable. They’re good for slowing flows on slopes, for curbside applications to keep sediment from going to paved roads (see picture above), to prevent sheet and rill flow on broad strips of land, and many other uses. Because of their lightweight, straw wattles need to be placed in a small trench dug beforehand, and then secured with stakes.

Compost socks on a paved surface.

Compost socks are an excellent option for flat surfaces, especially perimeters. Due to their weight, they do not need to be keyed into a trench-like straw wattle, nor do they always need to be staked (unless they are indeed installed on a slope). They form a nice barrier to settle out water, contouring themselves to the surface on which they are placed. Installation can be done with a blower, or the socks can be purchased in premeasured lengths. As a slightly heavier-duty option, compost socks can handle larger volumes of water and are a better option as a barrier on the perimeter, while a series of straw wattles used more toward the center of a site is generally sufficient—of course, all projects are different, so this is by no means a broad and unbreakable rule.

Both compost socks and straw wattles are delicate, and cannot stand up to vehicles driving over them. Once they fill with sediment, they need to be dug out and replaced, so on sites where erosion control is lacking and sediment-laden water consistently runs against these BMPs, they will need to be replaced regularly.