Laboratory-Scale Evaluation of Anionic Polyacrylamide as an Erosion and Sediment Control Measure on Steep-Sloped Construction Sites
Suspended sediment is the primary pollutant prevalent in runoff waters exiting construction sites with exposed and disturbed land. In this research, the effectiveness of a chemical stabilizer, known as anionic polyacrylamide (PAM), to prevent erosion and promote sedimentation was examined using different application methods (i.e., dry granular vs. semi-dissolved solution). In this study, the effectiveness of Silt Stop 712, a proprietary PAM product, was tested using different application methods at three different rates, i.e., 16.8, 28, and 39.2 kg ha-1 (15, 25, and 35 lbs acre-1), on bare, unseeded, unprotected 1.2 m × 0.6 m × 0.08 m (4 ft × 2 ft × 0.25 ft) laboratory-scale soil test plots. Laboratory-scale testing procedures using simulated rainfall were applied to mimic interrill erosion and sediment detachment scenarios similar to a highway embankment with a compacted 3H:1V fill slope. Our results showed that dry PAM treatments applied at the recommended rate of 39.2 kg ha-1 (35 lbs acre-1) were capable of reducing turbidity by 97% and net soil loss by approximately 50% in comparison to the bare soil control. Conversely, semi-dissolved PAM treatments applied at the same rate, i.e., 39.2 kg ha-1 (35 lbs acre-1), followed by a drying period of 48 h prior to the experiment, reduced turbidity by approximately 69% and soil loss by 76%. The lower application rates, i.e., 16.8 and 28 kg ha-1 (15 and 25 lbs acre-1), of semi-dissolved PAM without a drying time were observed to lose effectiveness after about 40 min; however, the higher application rate of 39.2 kg ha-1 (35 lbs acre-1) of semi-dissolved PAM provided consistent turbidity reductions throughout the entire experiment. Based on these results: (1) dry PAM applied directly to the surface at the manufacturer’s recommended rate was more effective as a sediment control (i.e., turbidity reduction) measure, and (2) semi-dissolved PAM applied directly to the surface at the manufacturer’s recommended rate and allowed to dry for 48 h prior to rainfall was a more effective erosion control (i.e., soil loss reduction) measure.