Contribution of ocean wastewater disposal to contamination in a coastal city during storms

Flood risk modeling and management have become critical because of sea level rise and increasingly strong storms, especially near coastal areas. These areas are at risk of inundation from several sources, including river, tidal, and coastal flooding. Floods can mobilize contaminants from sources such as wastewater, and those contaminants cause both physical and psychological harm to humans. Puerto Rico is vulnerable to floods and hurricanes; as a result, exposure to wastewater contaminants from flooding is of particular concern, especially for older adults. In Loíza, Puerto Rico the contamination comes from municipal sources such as wastewater treatment plants as well as informal wastewater containment built after hurricanes. We focus on storm conditions needed for wastewater contaminants discharged into the ocean to threaten the people of Loíza. Numerical simulations of depth-averaged hydrodynamics and transport of a conservative tracer were used to study the effects of coastal storm surges in Loíza resulting from storms that lasted 3 days. Only storms in Category 3 or above (wind speeds greater than 49.4 m/s) resulted in wastewater contaminants reaching houses in Loíza. For these storms, contaminants reached the shore within 1 hour. The simulations allow the concentrations of contaminants in the flooded areas to be determined and possible risks to public health to be discussed.