Polyacrylamide Use for Erosion and Turbidity Control on Construction Sites

Abstract

Sediment is the most widespread pollutant of streams and rivers in North Carolina. Construction sites are a source of accelerated erosion contributing to the sediment problem. This study was conducted to determine if the application of polyacrylamide (PAM) to soil surfaces on construction sites reduces erosion and turbidity. Polyacrylamide has been demonstrated to greatly reduce erosion in furrow irrigation, and there is limited evidence it controls erosion when applied to bare soil. Two PAM products applied at manufacturers recommended rates (11.2 and 1.68 kg ha-1) and one half the recommended rates (5.6 and 0.84 kg ha-1) with and without grass seeding and mulching were tested on three North Carolina Department of Transportation construction sites in Raleigh and near Fayetteville. Runoff volumes, turbidity levels, and eroded sediment data were collected after natural rain events. On a 2:1 cut slope, turbidity and sediment loss were significantly decreased with application of seed/mulch. Erosion rates were 20 times greater on bare soil after seven rain events, with or without PAM, compared to treatments receiving seed/mulch. Polyacrylamide applied with seed/mulch produced slight reductions in turbidity and sediment loss in early rain events. At the higher rate, PAM applied directly on a more moderate, 4:1 fill slope decreased sediment loss and turbidity in the first few rain events following application compared to bare soil, with decreases diminishing over time. A sandy fill slope had inconsistent results between PAM treatments but reductions in turbidity and sediment from seed/mulch applications.