PRELIMINARY ASSESSMENT OF THE IMPACTS OF CLASS V NON-ASR INJECTION WELLS ON THE WATER TABLE AND SALTWATER WEDGE IN SOUTHEAST FLORIDA

The heavily developed coast of Southeast Florida relies on Class V Non-ASR Injection Wells to discharge rooftop drainage. Recent work has developed a database of these wells, their cased depths, the salinity at the cased depth, and their specific capacities.

The potential impacts of approximately 10,000 wells within a kilometer of the shore on groundwater levels and saltwater intrusion have not been previously assessed or considered in models.

As part of a new project focused on near-shore saltwater intrusion, we estimate the geometry of the regional saltwater wedge based on data from an extensive monitoring system designed to provide early warning of threats to water supply wells.

A simplified preliminary 2-D model was populated using parameters from the USGS Urban Miami-Dade Model and generally calibrated to the observed saltwater wedge.

Incorporation of injection wells into the preliminary model shows that the more buoyant injected freshwater has a strong tendency to rise upward and that injection affects the water table. Rapid expulsion of water from surface storm drains --- including lifting of manhole covers --- in response to recent storms, suggests an interesting phenomenon wherein impermeable surfaces may be acting as confining layers when the usually unconfined aquifer beneath the impermeable surfaces completely fills, in part due to the deeper injection of roof drainage. Under such conditions, the surface drains may effectively become short-lived flowing artesian wells.