Three-Dimensional Multifluid Flow and Transport at the Brooklawn Site near Baton Rouge, LA: A Case Study

Abstract

Disposal quantities of organic wastes at the Brooklawn Site in Louisiana are suspected to equal nearly 1.45 × 108Kg, making this site one of the most contaminated dense nonaqueous phase liquid (DNAPL) sites in the world. Remedial activities at the site include groundwater and DNAPL extraction from recovery wells. DNAPL recovery has markedly declined in recent years, with many of the peripheral wells showing negligible recovery of organic liquids. Three-dimensional simulations of DNAPL movement in the subsurface were conducted using the STOMP simulator, including a new coupled-well model. The objectives of this modeling effort were to (1) determine the fate and transport of infiltrated DNAPL, and (2) measure the effects of active recovery through DNAPL pumping. A detailed three-dimensional geologic model of the Brooklawn primary DNAPL disposal area was developed and used as the framework for DNAPL simulations. Additionally, site-specific data were obtained to determine the most important hydraulic properties of the subsurface related to DNAPL movement and formation of entrapped DNAPL in the laboratory. In addition to a simulation using the best available subsurface information, several sensitivity simulations were conducted to assess the effects on DNAPL migration. These simulations include DNAPL pumping, well screen extension, an alternative geology, increased DNAPL density, lower DNAPL viscosity, and more-permeable sand and silt deposits. Results of the simulations were compared to field data that define the extent of DNAPL movement based on where DNAPL has been extracted in the site recovery wells. The model simulations show that pumping has a negligible effect on subsurface DNAPL saturations and movement. Pumped DNAPL volumes diminish rapidly due to the limited radius of influence of the wells and movement of the DNAPL out of the zone of influence of the wells with a maximum radius of influence of about 6 m. The numerical analysis also demonstrates that it is impractical to extend existing wells or install new wells to retrieve enough DNAPL to affect the overall extent of DNAPL movement.