Full-Scale Performance Evaluations of Various Wire-Backed Nonwoven Silt Fence Installation Configurations

Abstract

Silt fences have long been a key component for controlling construction stormwater runoff; nonetheless, many silt fence installations fail to perform in the field as intended. Silt fences are temporary sediment control measures used to retain sediment by impounding runoff and allowing for sedimentation on-site, while simultaneously discharging stormwater runoff at a controlled rate. This study evaluated the performance of eight alternative configurations of the Alabama Department of Transportation (ALDOT) standard wire-backed, nonwoven silt fence. Standard installation parameters associated with the ALDOT silt fence include (1) 32-in. (81.3-cm) high fence, (2) 0.95 lb/ft (1.4 kg/m) support T-post, and (3) 10 ft (3.0 m) T-post spacing. Throughout the series of configurations tested, these standard parameters were varied individually and jointly in efforts to improve overall performance. Variations to the standard parameters include (1) 24-in. (61.0-cm) high fence, (2) 1.25 lb/ft (1.9 kg/m) support T-post, (3) 5 ft (1.5 m) T-post spacing, and (4) trench offsetting. Performance analyses were conducted on each configuration and results were evaluated to determine the best overall configuration to enhance the in-field performance of the ALDOT silt fence. Ultimately, the offset 24 in. (61.0 cm) fence with 1.25 lb/ft (1.9 kg/m) T-post spaced 5 ft (1.5 m) on-center resulted in the best overall improvement, retaining an average of 93% of sediment and deflection of only 0.18 ft (0.004 m) over the course of three simulated storm events.

Full-Scale Performance Evaluations of Innovative and Manufactured Sediment Barrier Practices

“…This data was used to assess the overall performance of each SB practice to evaluate their structural performance, sediment retention capabilities, and impacts on water quality. Additionally, findings from this study were compared with results reported by Whitman et al (15) for the most effective nonproprietary, wire-backed nonwoven silt fence installation configuration, which will be referred to as the heavy-duty silt fence (HDSF).…”

“…(15 cm) downstream of the trench, thus eliminating downstream post voids. This installation method has been proven to be effective means for improving structural stability and minimizing undermining on common silt fence installations ( 15 ).…”

“…A comprehensive summary of structural failures and associated times of observed failure for each innovative and manufactured SB practice is provided in Table 1. For comparison, structural observations made by Whitman et al ( 15 ) for the most effective silt fence installation modification (i.e., HDSF) are included.…”

“…Due to the wide acceptance of silt fence within the construction industry, most studies have evaluated the performance of silt fence geotextiles (9)(10)(11)(12)(13)(14). Recently, Whitman et al (15) concluded a fullscale study on the performance of various silt fence installation configurations. Results indicated that the best overall installation configuration for a nonproprietary silt fence consisted of a 24 in.…”

State-of-the-Practice Review on the Use of Flocculants for Construction Stormwater Management in the United States

“…Sediment barriers, sediment basins, construction exit pads, surface roughening, temporary mulching, seeding, erosion control blankets, check dams, and inlet protection practices are some examples of common E&SC practices. However, traditional E&SC practices are not sufficient in removing fine-sized particles, which are difficult to remove from suspension and contribute to turbidity plumes (10)(11)(12)(13). Typically, detention-based practices such as sediment basins and traps are used to capture these fine-graded particles.…”