Nutrient Retention Time in High-Permeability, Oil-Fouled Beach

Following the grounding of the Exxon Valdez in March 1989, many beaches in the Alaskan waters were fouled with oil. One of these was Kittiwake Beach of Knight Island in Prince William Sound. The U.S. Environmental Protection Agency initiated a research project to evaluate the application of nutrients to the surface of the beach to stimulate biodegradation of the surficial and infiltrated oil by indigenous microbial populations. Nutrients were dissolved in seawater and applied by sprinklers to study plots along the beach. As part of this project, a preliminary, simplified model of the beach hydraulics is developed to describe the advective fate of the applied nutrients. The retention time of nutrients in the beach is estimated to be on the order of 12 h (one tidal cycle) for the application method used. Simulations indicate that application of nutrients through a trench or subsurface drain placed above the high-tide level, rather than directly on the beach by sprinklers, would result in significantly longer retention times. Design guidance for future remediation is provided to ensure nutrient coverage of the entire oiled profile of a permeable beach.