Class I Injection Wells in Southeast Florida: Evaluation and Preliminary Modeling

Regulatory, political and economic constraints have shaped wastewater management strategies in Southeast Florida. Three options are currently available: Class I injection wells, ocean outfalls and reclaimed water. Class I injection wells have been used extensively for the disposal of secondary treated wastewater and concentrate in southeast Florida. Injection wells have been found to be the option with the lowest relative risk of impact to water consumers in the southeast coast. A prior study by the authors found that all the injection wells were over 2,400 feet deep, and typically over 3000 feet deep. Only two sets of wells indicated any migration in the lower monitoring zone, and in both cases there were injection well construction issues that have long-standing relevance to the findings. None of the upper monitor wells showed migration. Water quality was stable in most of the wells with periodic fluctuations that have no apparent relationship to injection rates or well use. The data gathered for this project was used to valuate modeling of individual wells. The intent was to determine the real likelihood of there being migration, and what might stop that migration. Density differential and diffusion were likely causes. The modeling is intended to initiate modeling discussions — that more calibration and comparisons are required.