EPA's Region 6 Office
Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations
The shallow aquifer beneath the Popile site occurs within the sand unit of the Cockfield formation. The direction of groundwater flow is east and northeast with a horizontal gradient on the order of 0.015 feet/feet. Groundwater is under unconfined to confined conditions, as the sand aquifer is recharged in the higher elevation area and the upper layer acts as the confining layer in the lower elevation area. Unconfined conditions exist along the western boundary but change to confined conditions eastward across the site. The degree of confinement increases toward the Bayou de Loutre as the proportion of silt and clay increases in the upper layer. Hydraulic communication between the shallow aquifer and the Bayou is weak, and groundwater flow tends to pass beneath the Bayou in this reach.
Hydraulic conductivities across the site vary with depth. The greatest hydraulic conductivity contrast occurs on the interface between the upper layer and the sand layer. Hydraulic conductivity values tend to be within the 1x10-5 to 1x10-4 cm/sec range within the upper layer, and 5x10-4 to 5x10-3 cm/sec range within the shallow aquifer. Contaminant transport is predominantly horizontal in the sand layer.