Page 3 - USDA Compost sock use

(Agronomy Technical Note 4, January 2011)

Utilization of Compost Filter Socks

Introduction

According to a national water quality assessment, 35 percent of the United States streams are severely im-paired and 75 percent of the population lives within 10 miles of an impaired water body (U.S. Environmental Protection Agency 2007). Sediment from stormwater runoff is the leading pollutant of surface waters in the United States; however, under stable soil condi-tions nearly 80 percent of stormwater pollutants can be in soluble or dissolved forms (Berg and Carter 1980). Typical stormwater runoff pollutants include sediment, nutrients, harmful bacteria, heavy metals, and petroleum hydrocarbons. Since 1995, nutrients, pathogens, and heavy metals have accounted for more than 21,000 cases of water quality impairment (U.S. Environmental Protection Agency 2007). Figure 1 is an aerial photo (taken in 2008) of high turbidity in Tom-A-Lex Lake after a rainfall-runoff event. This lake is located 7 to 14 miles southwest of Thomasville and High Point, North Carolina (combined population of 122,000). Soil erosion, sedimentation, and surface water turbidity are increased by soil disturbance from agricultural tillage and urbanization. These human activities are the leading contributors to sedimentation in our Nation’s waters.

Figure 1 Sediment contributing to high turbidity in Tom-

A-Lex Lake after storm event (Photo by Ray Archuleta, NRCS, 2008)

A major function of soil organic matter is fltration of pollutants introduced through natural infltration and subsurface hydrologic fow patterns, prior to ground and surface water recharge.

Organic matter in compost has been shown to provide stormwater fltration benefts in overland sheet and concentrated fow situations (Faucette et al. 2009a; Keener, Faucette, and Klingman 2007). Bio-based man-agement practices used for stormwater pollution pre-vention should be designed to reduce runoff sediment and soluble pollutants to protect and preserve natural ecosystems and the valuable services provided.

This technical note illustrates the effectiveness of compost flter socks as a stormwater fltration practice and provides guidance on proper use.

Compost filter socks

The compost flter sock is a tubular mesh sleeve that contains compost of a particular specifcation suitable for stormwater fltration applications. The compost fl-ter sock is a linear, land-based treatment that removes stormwater pollutants through fltration of soluble pol-lutants and sediments and by deposition of suspended solids (fg. 2). The compost flter sock is typically avail-able in 8-inch (200 mm), 12-inch (300 mm), 18-inch (450 mm), and 24-inch (600 mm) diameters.

Applications

Compost flter socks can be used in a variety of storm-water management applications. Recommended ap-plications include the following: • perimeter sediment control

• as a check dam to reduce soil erosion in swales, ditches, channels, and gullies

• storm drain and curb storm inlet protection • reduction of fecal coliform, E. coli., nitrogen, phosphorus, heavy metals, and petroleum hydro-carbons from stormwater

• reduction of suspended solids and turbidity in effuents