Linear, anionic polyacrylamide (LA-PAM) has been examined in laboratory, field and numerical environments to evaluate its efficacy in reducing seepage in unlined water delivery canals and potential environmental impacts from its use. This report describes the laboratory-based research conducted on LA-PAM. The report is divided into chapters that present specific research experiments and findings. The final chapter is a synopsis that attempts to tie together the project findings into three categories: LA-PAM hydration and reactivity, acrylamide (AMD) fate and transport, and LA-PAM transport. The results show the following:

• LA-PAM will begin to hydrate within about 5 minutes of introduction into water and continue hydrating for about 20 minutes, depending on field conditions. Reduction in seepage in laboratory columns was shown to progress along these time periods; of course, field conditions with variable temperature, suspended sediment concentration and flow rates will affect the hydration period and subsequent sealing of the canal bottom.

• AMD fate was found to be influenced by sorption onto (primarily) fine-grained sediments, biodegradation and UV degradation. Taken together, it appears that AMD longevity would be on the order of 3 to 5 days in the environment, so that AMD accumulation is unlikely to occur.

• Numerical developments have proceeded such that model predictions of LA-PAM concentrations in downstream canal water can be made with good accuracy. Parameters that affect the transport rates in the model can be obtained through site-specific characterization of the geometry of the canal prism (e.g., wetted perimeter), and/or knowledge of water properties (e.g., water chemistry and velocity).
  On-going field and laboratory experiments will further clarify questions regarding LA-PAM efficacy and potential environmental risks.

Download full document: 41237_PAM_Lab_Experiments_July_2007.pdf

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