Polyacrylamide use for erosion and turbidity control on construction sites

ABSTRACT:

Streams and lakes adjacent to construction sites are often heavily impaired by sediment and turbidity coming from areas of exposed soil. A study was conducted to determine if the application of polyacrylamide (PAM) can reduce erosion and runoff turbidity on moderate to steep slopes at construction sites. The test sites were three North Carolina Department of Transportation construction sites in the Piedmont and Coastal Plain. Two PAM products were applied at recommended rates (10.5 and 1.5 kg ha⁻¹; 9.3 and 1.3 lb ac⁻¹) and one half the recommended rates (5.2 and 0.76 kg ha⁻¹; 4.6 and 0.68 lb ac⁻¹) with and without grass seeding and straw mulching. Runoff volumes, turbidity levels, and eroded sediment data were collected after natural rain events. On a 50 percent fill slope, turbidity and sediment loss were significantly decreased with application of seed/mulch but not PAM alone. PAM applied on the seed/mulch treatment did not have statistical effects compared to the seed/mulch alone. Erosion rates of up to 43 t ha⁻¹ were recorded for one storm on bare soil; seed/mulch reduced this by 83 percent. On a 20 percent cut slope, PAM significantly (P < 0.10) reduced turbidity only during one of six storms but did reduce the average turbidity over all storms. No other PAM effects were found. The third site was comprised of a sandy soil on a 20 percent slope and PAM did not have any effect on any parameters, probably due to the low runoff rates on that soil. Overall, the results suggest that PAM application rates of 10.5 kg ha⁻¹ (9.3 lbs ac_-1) or less may not have significant benefits on moderate to steep slopes in the Piedmont. This may be at variance with state requirements or manufacturer recommendations, which can be as low as 0.56 kg ha⁻¹ (0.5 lb ac⁻¹).