Groundwater Modeling / Chemical Fate & Transport Modeling

Chemical Storage Facility
San Francisco Bay Area, California

The Source Group recently developed a state-of-the-art groundwater flow and chemical fate and transport model for a 3,000 foot dissolved chlorinated volatile organic plume in a complex heterogeneous aquifer.

Data gathered through investigation efforts were used in development of the three-dimensional (3-D) groundwater flow simulation and chemical fate and transport model using MODFLOW™/RT3D™.

The MODFLOW™/RT3D™ model incorporates aquifer heterogeneities, hydraulic influence from local pumping wells, and degradation from natural attenuation and chemical speciation reactions to predict contaminant fate and transport.

The model was a key design tool to develop the most cost effective design for remedial actions including design and placement of a permeable reactive barrier, effectively targeting injection locations for hydrogen releasing compounds and negotiating a program of monitored natural attenuation with the CRWQCB (in lieu of extensive active remedial actions) for the distal portions of the dissolved VOC plume.

Results: By simulating plume behavior under various remedial action scenarios, optimum concentration of the effluent of the permeable reactive barrier required to meet cleanup objectives at points downgradient were determined. This resulted in reducing the thickness of the barrier and the amount of reactive media required yielding a savings of more than $500,000 to our client.

In addition, fate and transport modeling indicated that active remediation of the 2,000 foot dissolved plume downgradient of the PRB was unnecessary and that natural attenuation, coupled with the passive PRB plume containment action, would achieve cleanup objectives within seven years.