Decentralized Wastewater System

Nutter and Associates personnel completed a hydrogeologic assessment, MODFLOW model, and detailed soil investigation, including the design of hydraulic loading parameters, for a 20-acre decentralized wastewater system site in Mobile County, Alabama.

The project site was uniquely suitable for high wastewater loadings based on the deep sands present throughout the site vadose zone and surficial aquifer. With the use of high loading rates concerns arose related to the potential for groundwater mounding, lateral flow, and offsite exfiltration which required greater assessment prior to permitting.

Using the results of the field investigation, a groundwater model was constructed using Visual MODFLOW to predict the groundwater table response to the hydrologic inputs of wastewater applications. The groundwater model was calibrated using water level data collected from the site piezometer network. Upon completion of the soil investigation report, hydrogeologic assessment, and Visual MODFLOW modeling the site was permitted using an Alabama Department of Environmental Management (ADEM) Class V Underground Injection Control (UIC) permit.