Evaluation of Anionic Polyacrylamide as an Erosion Control Measure Using Intermediate-Scale Experimental Procedures

Abstract

The United States Environmental Protection Agency (EPA) has been working to establish stricter guidelines and limitations pertaining to stormwater and the various pollutants transported by runoff. This transport is primarily prevalent in runoff exiting exposed and disturbed land common to construction sites. Therefore, understanding the effectiveness of many different erosion and sediment control technologies is becoming a high priority to the construction industry. In this research, the effectiveness of a chemical stabilizer known as anionic polyacrylamide (PAM) was examined using intermediate-scale testing procedures that mimic conditions similar to a highway embankment with a compacted 3:1 fill slope. The first phase of this research focused on intermediate-scale testing procedures that were developed from previous research efforts and further modified to enable researchers to rapidly generate large quantities of valuable data. The rain regime selected for this research consisted of a 2-year, 24-hour storm event for Montgomery, AL which was divided into four 15 minutes rain events with 15 minute breaks in between that produced 1.10 in. of rainfall per event and a total cumulative amount of 4.4 in. The second phase of research focused on conducting intermediate-scale experiments to examine the effectiveness of PAM with different application rates and application methods. These different application methods included: (1) dry granular PAM applied directly to test plots and (2) dry PAM mixed with water to form a liquid spray application. Application rates were determined through manufacturer recommendations (i.e. 25 to 35 lbs/acre) and this research conducted additional experiments to examine the performance at PAM at rates lower than the recommended rate (i.e. 15 lbs/acre). Liquid PAM applications were not allowed to dry prior to being subjected to rainfall to simulate a ‘worst-case scenario’ for treatments. The results from this phase of research showed that dry PAM applied at the recommended rate of 35 lbs/acre performed the best out of the various PAM treatments by significantly reducing initial turbidity levels by 97% and eroded soil by 50% when compared to the bare soil control condition. Collected runoff samples indicated that runoff from test plots treated with dry PAM applied at 35 lbs/acre reduced turbidity to the proposed EPA effluent limits of 13 NTU within 20 seconds.