Suitability of Recycled Glass Cullet as Artificial Dune Fill along Coastal Environments

Abstract

Makowski, C.; Finkl, C.W., and Rusenko, K., 2013. Suitability of recycled glass cullet as artificial dune fill along coastal environments.Coastal dune systems are an integral component of maintaining a sustainable, well-performing beach. With the aid of dune-stabilizing vegetation, constructed foredunes provide a “natural” armorment behind the dry berm to help protect the backshore from storm surge and intense overwash. However, as the costs of beach nourishment continue to inflate, the urgency to construct or restabilize the foredune area of the beach is often overlooked. Furthermore, to compound the problem, suitable sand resources are becoming unobtainable because of regulatory restrictions, prompting engineers and coastal zone managers to use all available dredged sediments for berm and beach face replenishment. In order to provide an alternative method for dune construction, this study examined the suitability of recycled glass cullet as an artificial dune fill material. After construction of an artificial dune was completed, recycled (silica) glass cullet and natural beach sand were provided as growth mediums for dune-stabilizing vegetation. Immature transplants of sea oats (Uniola paniculata) and panic grass (Panicum amarum) were planted in the artificial dune and evaluated over a 1-year growing period. Suitability of the recycled glass cullet was determined through the overall performance of the salt-tolerant plants, which included fresh and dry weight measurements, new shoot development, and root and stalk length. It was determined that both species of dune-stabilizing vegetation planted in a recycled glass medium outperformed those specimens growing in the natural beach sediment controls. We postulate that the results may stem from a slight increase in the angularity of the recycled cullet vs. the natural sand grains. This minuscule planar difference in the surface area of the grains may contribute to more aggregated moisture content within a recycled glass cullet dune, allowing for optimal growing conditions for dune vegetation. By showing this positive suitability of recycled glass cullet as artificial dune fill, a new, innovative method for dune protection may now be considered.