An Analysis of Groundwater Flow Patterns in a Constructed Treatment Wetland Cell

This research effort analyzed groundwater flow paths within a treatment wetland constructed to degrade tetrachloroethylene (PCE) in groundwater. The treatment cell is a vertical flow wetland that allows the water to flow from the bottom to the surface breaking down PCE and daughter products. The method of conducting this research included collecting field data of hydraulic head contours nested piezometers and collecting data from sampling wells to determine hydraulic conductivities in the wetland. The field data was used to create a numerical computer model to determine groundwater flow patterns. The field data and the model demonstrate that there are areas in the wetland with flow velocities as low as 0.0019 m/day and as high as 2.779 m/day. The computer model also shows residence times of water particles traveling from the bottom of the wetland cell to the surface water varying from < 1 day, to over 1000 days. Groundwater flow patterns occurring in the wetland today were compared to a study five years ago. The hydraulic head contours and hydraulic parameters measured in the field were similar in both studies. The results of both studies show the residence times and the desired uniform flow across the wetland is being short circuited.