Microbial induced calcite precipitation of dune sand using a surface spray technique

Hurricanes Irma and Matthew caused significant damage to the coastal dune systems in northeast Florida. Dunes are the first line of protection in storm events for the prevention of beach erosion and inland floods. It would be beneficial if a sustainable, rapidly-deployable strengthening mechanism could be used to fortify the dunes prior to hurricanes to help mitigate damage. One potential technology for dune protection is microbial induced calcite precipitation (MICP). Dune sand was collected from Neptune Beach, FL, and the feasibility of treating the sand using a surface-spray technique was investigated. Specifically, microbes, urea solution, and calcium chloride were applied to a bench-scale synthetic dune surfaces using a garden hose attachment. The treated dunes were allowed to cure for 48 hours. Results showed this application technique may provide erosion protection via three mechanisms. An erosion resistant crust formed along the outer surface of the dune; large blocks of cemented material are formed on the interior of the dune; and treatment appears to increase median grain size diameter. However, the increase in grain-size diameter may have a relatively small effect on erosion mitigation.