Page 6 - USDA Compost sock use

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Utilization of Compost Filter Socks

(Agronomy Technical Note 4, January 2011)

Siting and design

Compost flter socks should be placed on contours, perpendicular to stormwater fow, and on prepared ground surfaces.

Compost flter socks, used as a sediment control bar-rier, should be placed 5 feet (1.5 m) beyond the toe of the slope to allow runoff accumulation, sediment deposition, and maximum sediment storage. The ends of the compost flter socks should be pointed upslope to prevent untreated stormwater fow around the treat-ment. See table 2 for recommended spacing and diam-eter requirements of compost flter socks for a range of slopes (Keener, Faucette, and Klingman 2007).

When used as a slope interruption management prac-tice, compost flter socks should be placed horizon-tally on slopes with the ends of the compost flter sock pointing upslope. This practice will reduce sheet fow velocity, dissipate sheet fow energy, and reduce soil erosion. Slope interruption practices can be used to reduce slope lengths for LS factors when predicting site soil loss with RUSLE 2.

Compost flter socks, used as a check dam (fg. 3) man-agement practice, in swales, channels, and ditches, should have the center of the check dam at least 6 inches (150 mm) lower than the banks. Spacing check dams closer together will reduce fow velocity and bed

erosion and increase pollutant removal. Compost flter socks used as check dams may be placed in a straight line across the channel, in a V formation or an inverted V formation, as determined by the designer.

When used as a drain inlet protection practice, the compost flter sock should be placed entirely in the sump, fully envelop the drain, and be placed on level ground to allow maximum runoff and sediment stor-age capacity. When used for curb inlet protection, the compost flter sock should not exceed the height of the intake opening or curb (fg. 4).

If used as a biofltration enclosure (fg. 5), cell, or ring, the compost flter sock should be placed on level ground and should not be flled beyond 50 percent of its volumetric capacity. Compost flter socks may be stacked to increase volumetric design capacity.

Figure 3 Compost flter sock check dam

Figure 4 Compost flter sock curb inlet

Maximum slope length above compost flter sock in ft (m)

Slope %

Diameter of compost flter sock required 8-inch (200-mm)

12-inch (300-mm)

18-inch (450-mm)

24-inch (600-mm)

 2 (or less) 300 (90) 375 (110) 500 (150) 650 (200)  5 200 (60) 250 (75) 275 (85) 325 (100) 10 100 (30) 125 (35) 150 (45) 200 (60) 15 70 (20) 85 (25) 100 (30) 160 (50) 20 50 (15) 65 (20) 70 (20) 130 (40) 25 40 (12) 50 (15) 55 (16) 100 (30) 30 30 (9) 40 (12) 45 (13) 65 (20) 35 30 (9) 40 (12) 45 (13) 55 (18) 40 30 (9) 40 (12) 45 (13) 50 (15) 45 20 (6) 25 (8) 30 (9) 40 (12) 50 20 (6) 25 (8) 30 (9) 35 (10)

Table 2 Recommended spacing and diameter require-

ments